U.S. patent application number 16/021251 was filed with the patent office on 2019-01-03 for retention of mechanical properties in steel alloys after processing and in the presence of stress concentration sites.
This patent application is currently assigned to The NanoSteel Company, Inc.. The applicant listed for this patent is The NanoSteel Company, Inc.. Invention is credited to Scott T. ANDERSON, Andrew T. BALL, Daniel James BRANAGAN, Sheng CHENG, Kurtis R. CLARK, Andrew E. FRERICHS, Taylor L. GIDDENS, Grant G. JUSTICE, Scott T. LARISH, Brian E. MEACHAM, Alla V. SERGUEEVA, Logan J. TEW, Jason K. WALLESER.
Application Number | 20190003003 16/021251 |
Document ID | / |
Family ID | 64738558 |
Filed Date | 2019-01-03 |
![](/patent/app/20190003003/US20190003003A1-20190103-D00000.png)
![](/patent/app/20190003003/US20190003003A1-20190103-D00001.png)
![](/patent/app/20190003003/US20190003003A1-20190103-D00002.png)
![](/patent/app/20190003003/US20190003003A1-20190103-D00003.png)
![](/patent/app/20190003003/US20190003003A1-20190103-D00004.png)
![](/patent/app/20190003003/US20190003003A1-20190103-D00005.png)
![](/patent/app/20190003003/US20190003003A1-20190103-D00006.png)
![](/patent/app/20190003003/US20190003003A1-20190103-D00007.png)
![](/patent/app/20190003003/US20190003003A1-20190103-D00008.png)
![](/patent/app/20190003003/US20190003003A1-20190103-D00009.png)
![](/patent/app/20190003003/US20190003003A1-20190103-D00010.png)
View All Diagrams
United States Patent
Application |
20190003003 |
Kind Code |
A1 |
BRANAGAN; Daniel James ; et
al. |
January 3, 2019 |
Retention Of Mechanical Properties In Steel Alloys After Processing
And In The Presence Of Stress Concentration Sites
Abstract
This invention is related to retention of mechanical properties
in high strength steel at reduced thicknesses and which mechanical
property performance is also retained at relatively high strain
rates. These new steels can offer advantages for a myriad of
applications where reduced sheet thickness is desirable. In
addition, the alloys herein are those that retain useful mechanical
properties after introduction of a geometric discontinuity and an
accompanying stress concentration.
Inventors: |
BRANAGAN; Daniel James;
(Idaho Falls, ID) ; SERGUEEVA; Alla V.; (Idaho
Falls, ID) ; MEACHAM; Brian E.; (Idaho Falls, ID)
; FRERICHS; Andrew E.; (Idaho Falls, ID) ; CHENG;
Sheng; (Idaho Falls, ID) ; LARISH; Scott T.;
(Idaho Falls, ID) ; JUSTICE; Grant G.; (Idaho
Falls, ID) ; BALL; Andrew T.; (Reno, NV) ;
WALLESER; Jason K.; (Idaho Falls, ID) ; TEW; Logan
J.; (Idaho Falls, ID) ; ANDERSON; Scott T.;
(Idaho Falls, ID) ; CLARK; Kurtis R.; (Idaho
Falls, ID) ; GIDDENS; Taylor L.; (Idaho Falls,
ID) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
The NanoSteel Company, Inc. |
Providence |
RI |
US |
|
|
Assignee: |
The NanoSteel Company, Inc.
Providence
RI
|
Family ID: |
64738558 |
Appl. No.: |
16/021251 |
Filed: |
June 28, 2018 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
62527400 |
Jun 30, 2017 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C21D 6/005 20130101;
C22C 38/42 20130101; B21B 3/00 20130101; B21B 1/22 20130101; C22C
38/58 20130101; C21D 8/0205 20130101; C22C 38/34 20130101; C21D
6/004 20130101; C21D 9/46 20130101; C21D 8/0226 20130101; C21D
6/008 20130101; B21B 2001/225 20130101 |
International
Class: |
C21D 9/46 20060101
C21D009/46; C22C 38/58 20060101 C22C038/58; C22C 38/42 20060101
C22C038/42; C22C 38/34 20060101 C22C038/34; C21D 8/02 20060101
C21D008/02; C21D 6/00 20060101 C21D006/00; B21B 1/22 20060101
B21B001/22; B21B 3/00 20060101 B21B003/00 |
Claims
1. A method to retain mechanical properties in a metallic sheet
alloy at reduced thickness comprising: a. supplying a metal alloy
comprising at least 70 atomic % iron and at least four or more
elements selected from Si, Mn, Cr, Ni, Cu, or C, melting said
alloy, cooling at a rate of <250 K/s, and solidifying to a
thickness of 25.0 mm up to 500 mm; b. processing said alloy into
sheet form with thickness T.sub.1 with the sheet having a total
elongation of X.sub.1 (%), an ultimate tensile strength of Y.sub.1
(MPa), and a yield strength of Z.sub.1 (MPa); c. further processing
said alloy into a second sheet with reduction in thickness
T.sub.2<T.sub.1 with the second sheet having a total elongation
of X.sub.2=X.sub.1.+-.10%, an ultimate tensile strength of
Y.sub.2=Y.sub.1.+-.50 MPa, and a yield strength of
Z.sub.2=Z.sub.1.+-.100 MPa.
2. The method of claim 1 wherein said at least 70 atomic percent
iron is combined with five or more elements that are selected from
Si, Mn, Cr, Ni, Cu, or C.
3. The method of claim 1 wherein said at least 70 atomic percent
iron is combined with all six elements: Si, Mn, Cr, Ni, Cu, and
C.
4. The method of claim 1 wherein the levels of the four elements
that are selected are as follows: Si (1.14 to 6.13 atomic percent),
Mn (3.19 to 15.17 atomic percent), Cr (0.78 to 8.64 atomic
percent); Ni (0.9 to 11.44 atomic percent), Cu (0.37 to 1.87 atomic
percent).
5. The method of claim 1 wherein said alloy formed in step (b),
exhibits X.sub.1 (12% to 80%), Y.sub.1 (700 MPa to 2100 MPa), and
Z.sub.1 (250 MPa to 1500 MPa).
6. The method of claim 1 wherein said alloy formed in step (b),
exhibits a thickness from 1.2 mm to 10.0 mm.
7. The method of claim 1 wherein said alloy formed in step (c),
exhibits X.sub.2 (2 to 90%), Y.sub.2 (650 MPa to 2150 MPa), and
Z.sub.2 (150 MPa to 1600 MPa).
8. The method of claim 1 wherein said alloy formed in step (c),
exhibits a thickness from 0.2 mm to <1.2 mm.
9. The method of claim 1 wherein said alloy formed in step (c) is
positioned in a vehicular frame, vehicular chassis, or vehicular
panel.
10. The method of claim 1 wherein said alloy formed in step (c) is
positioned in a storage tank, freight car, or railway tank car.
11. A method to retain mechanical properties in a metallic sheet
alloy at relatively high strain rates comprising: a. supplying a
metal alloy comprising at least 70 atomic % iron and at least four
or more elements selected from Si, Mn, Cr, Ni, Cu, or C and melting
said alloy and cooling at a rate of <250 K/s and solidifying to
a thickness of 25.0 mm up to 500 mm; b. processing said alloy into
sheet form with thickness from 1.2 mm to 10.0 mm with the sheet
having a total elongation of X.sub.1 (%), an ultimate tensile
strength of Y.sub.1 (MPa), and a yield strength of Z.sub.1 (MPa)
when tested at a strain rate S.sub.1; c. deforming the sheet from
said alloy at a strain rate S.sub.2>S.sub.1 with the sheet
having a total elongation of X.sub.3=X.sub.1.+-.7%, ultimate
tensile strength Y.sub.3=Y.sub.1.+-.200 MPa, and yield strength
Z.sub.3=Z.sub.1.+-.50 MPa.
12. The method of claim 11 wherein said at least 70 atomic percent
iron is combined with five or more elements that are selected from
Si, Mn, Cr, Ni, Cu, or C.
13. The method of claim 11 wherein said at least 70 atomic percent
iron is combined with all six elements: Si, Mn, Cr, Ni, Cu, and
C.
14. The method of claim 11 wherein the levels of the four elements
that are selected are as follows: Si (1.14 to 6.13 atomic percent),
Mn (3.19 to 15.17 atomic percent), Cr (0.78 to 8.64 atomic
percent); Ni (0.9 to 11.44 atomic percent), Cu (0.37 to 1.87 atomic
percent).
15. The method of claim 11 wherein said alloy formed in step (b),
exhibits X.sub.1 (12% to 80%), Y.sub.1 (700 MPa to 2100 MPa), and
Z.sub.1 (250 MPa to 1500 MPa).
16. The method of claim 11 wherein the strain rate S.sub.1 is 0.007
s.sup.-1 to 0.0001 s.sup.-1.
17. The method of claim 11 wherein said alloy formed in step (c),
exhibits X.sub.3 (5% to 87%), Y.sub.3 (500 MPa to 2300 MPa), and
Z.sub.3 (200 MPa to 1550 MPa).
18. The method of claim 11 wherein the strain rate S.sub.2 is
>0.007 s.sup.-1 to 1200 s.sup.-1.
19. The method of claim 11 wherein said processing in step (c)
comprises roll forming, metal stamping or hydroforming.
20. The method of claim 11 wherein said alloy formed in step (c) is
positioned in a vehicular frame, vehicular chassis, or vehicular
panel.
21. The method of claim 11 wherein said alloy formed in step (c) is
positioned in a storage tank, freight car, or railway tank car.
22. The method of claim 11 wherein said alloy formed in step (c) is
positioned in body armor, shield, military vehicle, or armored
vehicle.
23. A method to retain mechanical properties in a metallic sheet
alloy comprising: a. supplying a metal alloy comprising at least 70
atomic % iron and at least four or more elements selected from Si,
Mn, Cr, Ni, Cu, or C and melting said alloy and cooling at a rate
of <250 K/s and solidifying to a thickness of 25.0 mm up to 500
mm; b. processing said alloy into sheet form with thickness from
1.2 mm to 10.0 mm with the sheet having a total elongation of
X.sub.1 (%), an ultimate tensile strength of Y.sub.1 (MPa), and a
yield strength of Z.sub.1 (MPa); c. introducing stress
concentration sites and then deforming the sheet from said alloy
with the sheet having a total elongation of
X.sub.4.gtoreq.0.2X.sub.1 (%), an ultimate tensile strength
Y.sub.4.gtoreq.0.5Y.sub.1 (MPa), and a yield strength
Z.sub.4.gtoreq.0.6Z.sub.1 (MPa).
24. The method of claim 23 wherein said at least 70 atomic percent
iron is combined with five or more elements that are selected from
Si, Mn, Cr, Ni, Cu, or C.
25. The method of claim 23 wherein said at least 70 atomic percent
iron is combined with all six elements: Si, Mn, Cr, Ni, Cu, and
C.
26. The method of claim 23 wherein the levels of the four elements
that are selected are as follows: Si (1.14 to 6.13 atomic percent),
Mn (3.19 to 15.17 atomic percent), Cr (0.78 to 8.64 atomic
percent); Ni (0.9 to 11.44 atomic percent), Cu (0.37 to 1.87 atomic
percent).
27. The method of claim 23 wherein said alloy formed in step (b),
exhibits X.sub.1 (12% to 80%), Y.sub.1 (700 MPa to 2100 MPa), and
Z.sub.1 (250 MPa to 1500 MPa).
28. The method of claim 23 wherein said processing in step (c)
comprises roll forming, metal stamping or hydroforming.
29. The method of claim 23 wherein said alloy formed in step (c) is
positioned in a vehicular frame, vehicular chassis, or vehicular
panel.
30. The method of claim 23 wherein said alloy formed in step (c) is
positioned in a storage tank, freight car, or railway tank car.
31. The method of claim 23 wherein said alloy formed in step (c) is
positioned in body armor, shield, military vehicle, or armored
vehicle.
Description
FIELD OF INVENTION
[0001] This disclosure is related to retention of mechanical
properties in high strength steel at reduced thicknesses and which
mechanical property performance is also retained at relatively high
strain rates. These new steels can offer advantages for a myriad of
applications where reduced sheet thickness is desirable. In
addition, the alloys herein are those that retain useful mechanical
properties after introduction of a geometric discontinuity and an
accompanying stress concentration.
BACKGROUND
[0002] Steel is the engineering material of choice where cost,
strength, and ductility are major factors. Accordingly, steel
continues to be used in a myriad of applications in our daily
lives, including in the construction of buildings, appliances, and
automobiles. A large variety of steel alloys exist to achieve this
range of needs, with targeted property ranges used for these wide
ranging applications. Designations are provided for ranges of
steel, which fit three distinct classes based upon measured
properties, in particular maximum tensile strain and tensile stress
prior to failure. These three classes are: Low Strength Steels
(LSS), High Strength Steels (HSS), and Advanced High Strength
Steels (AHSS). Advanced High Strength Steels (AHSS) are of primary
interest for advanced engineering applications, and are classified
by tensile strengths greater than 700 MPa and include such types as
martensitic steels (MS), dual phase (DP) steels, transformation
induced plasticity (TRIP) steels, and complex phase (CP) steels. As
the strength level increases the trend in maximum tensile
elongation (ductility) of the steel is negative, with decreasing
elongation at high tensile strengths. For example, tensile
elongation of LSS, HSS and AHSS ranges from 25% to 55%, 10% to 45%,
and 4% to 30%, respectively.
[0003] An area where steel provides particular engineering
advantages is in automobiles, with many different types of steels
utilized throughout the car in various locations. Current consumer
desires and governmental regulations are pushing automobile
manufacturers to design vehicles that attain ever greater fuel
efficiency. Automobile designers have identified weight reduction,
particularly in the body-in-white structure, to have the greatest
potential impact on improving fuel efficiency. The process of
reducing automobile weight, known as lightweighting, can be
accomplished through reducing the thickness of the body-in-white
structure and increasing the geometric complexity of the various
parts using high strength, high formability materials. Accordingly,
increasingly high strength steels are desired throughout the
automobile assembly in order to enable the thickness reduction and
weight savings.
[0004] Safety must be kept constant or improved during the
lightweighting process as well. Automobile highway speed limits are
regularly increasing, and consumers expect safety performance to be
a major part of automobile design. The body-in-white structure of
an automobile is designed to provide a rigid structure that will
protect the passenger while traveling at speed and in the case of a
collision. During an automobile collision, dynamic loading, rapid
deformation, and energy dissipation occurs throughout the
automobile and body-in-white structure in particular. The time
frame over which this occurs can be 100 ms. High strain rates are
observed throughout the body-in-white structure during this time,
and materials need to be able to withstand complex loads across a
range of strain rates. For instance, a low speed collision that
occurs in a parking lot would result in a lower strain rate for
body-in-white than would a collision at highway speeds. The
mechanical properties of materials for the body-in-white structure
are measured by many means, including uniaxial tensile testing,
across this range of strain rates such that their response during a
collision can be predicted and design considerations taken into
account. High strain rates can result in a change in mechanical
properties, limiting the maximum lightweighting that automobile
designers are able to achieve by requiring additional thickness to
maintain safety under high strain rate conditions.
[0005] As advances in engineering and technology occur, there is an
increasing drive to the small scale. Consumers, and by extension
engineers/designers, are regularly searching for products that are
size efficient. Consumers seek out products that accomplish the
needed task while occupying the smallest volume possible. A good
example of this phenomenon can be found in the electronics
industry, where cell phones, tablets, and other devices are
regularly reduced in size with consecutive design iterations. With
the drive of products to smaller and smaller sizes, the demands on
engineering materials that the products are made from increase
dramatically. As the overall size of a part decreases, defects that
are inherent in everyday manufacturing processes can result in
significant reductions in material properties. High strength
materials are particularly impacted by the reduction of part size
to the small or very small due to the complex and often specialized
processing required to achieve those properties.
[0006] Martensitic steels, for example, provide excellent strength
yet require a quench as a final processing step to create the
necessary microstructure. Quenching is difficult to control at a
small scale and may potentially cause unacceptable distortion in
small parts. Final processing may not be performed on the final
part geometry but rather on sheet or foils in some applications.
For thermally sensitive materials such as martensitic steels,
thermal exposure during cutting to produce the final part may
detrimentally alter the microstructure and compromise properties.
Geometry effects also play a greater role in mechanical properties
of ductile materials at the small scale, with the effects of stress
concentrators, grain size, and thickness adversely changing the
material's mechanical response to stress. Due to these facts,
expensive engineering materials are often required for uses on
small scale that are either thermally insensitive or have simple
processing such as low alloyed or pure materials. Engineers would
prefer to not use exotic materials for these applications; however
everyday engineering materials are often unavailable for use at
reduced thicknesses resulting in the slow adoption of smaller
devices due to prohibitive cost and processing requirements.
SUMMARY
[0007] In one embodiment, the present invention is directed at a
method to retain mechanical properties in a metallic sheet alloy at
reduced thickness comprising supplying a metal alloy comprising at
least 70 atomic % iron and at least four or more elements selected
from Si, Mn, Cr, Ni, Cu, or C, melting said alloy, cooling at a
rate of <250 K/s, and solidifying to a thickness of 25.0 mm up
to 500 mm. This is followed by processing the alloy into sheet form
with thickness T.sub.1 with the sheet having a total elongation of
X.sub.1 (%), an ultimate tensile strength of Y.sub.1 (MPa), and a
yield strength of Z.sub.1 (MPa). This is then followed by further
processing the alloy into a second sheet with reduction in
thickness T.sub.2<T.sub.1 with the second sheet having a total
elongation of X.sub.2=X.sub.1.+-.10%, an ultimate tensile strength
of Y.sub.2=Y.sub.1.+-.50 MPa, and a yield strength of
Z.sub.2=Z.sub.1.+-.100 MPa.
[0008] In another embodiment the present invention relates to a
method to retain mechanical properties in a metallic sheet alloy at
relatively high strain rates comprising supplying a metal alloy
comprising at least 70 atomic % iron and at least four or more
elements selected from Si, Mn, Cr, Ni, Cu, or C and melting said
alloy and cooling at a rate of <250 K/s and solidifying to a
thickness of 25.0 mm up to 500 mm. This is then followed by
processing the alloy into sheet form with thickness from 1.2 mm to
10.0 mm with the sheet having a total elongation of X.sub.1 (%), an
ultimate tensile strength of Y.sub.1 (MPa), and a yield strength of
Z.sub.1 (MPa) when tested at a strain rate S.sub.1. This is then
followed by deforming the sheet from the alloy at a strain rate
S.sub.2>S.sub.1 with the sheet having a total elongation of
X.sub.3=X.sub.1.+-.7%, ultimate tensile strength
Y.sub.3=Y.sub.1.+-.200 MPa, and yield strength
Z.sub.3=Z.sub.1.+-.50 MPa.
[0009] In yet another embodiment the present invention is directed
at A method to retain mechanical properties in a metallic sheet
alloy comprising supplying a metal alloy comprising at least 70
atomic % iron and at least four or more elements selected from Si,
Mn, Cr, Ni, Cu, or C and melting said alloy and cooling at a rate
of <250 K/s and solidifying to a thickness of 25.0 mm up to 500
mm. This is then followed by processing the alloy into sheet form
with thickness from 1.2 mm to 10.0 mm with the sheet having a total
elongation of X.sub.1 (%), an ultimate tensile strength of Y.sub.1
(MPa), and a yield strength of Z.sub.1 (MPa). Then, one may
introduce stress concentration sites and then deform the sheet from
the alloy with the sheet having a total elongation of
X.sub.4.ltoreq.0.2X.sub.1 (%), an ultimate tensile strength
Y.sub.4.ltoreq.0.5Y.sub.1 (MPa), and a yield strength
Z.sub.4.gtoreq.0.6Z.sub.1 (MPa).
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] The detailed description below may be better understood with
reference to the accompanying FIG.s which are provided for
illustrative purposes and are not to be considered as limiting any
aspect of this invention.
[0011] FIG. 1 Summary of novel ductility achievement in alloys
herein at reduced length scales.
[0012] FIG. 2 Summary of novel ductility achievement in the alloys
herein at high strain rates.
[0013] FIG. 3 Summary of maintained ductility in the alloys herein
with introduced stress concentration sites such as edge
notches.
[0014] FIG. 4 Yield strength and ultimate tensile strength as a
function of Alloy 2 sheet thickness.
[0015] FIG. 5 Tensile elongation as a function of Alloy 2 sheet
thickness.
[0016] FIG. 6 Comparison of stress-strain curves for Alloy 2 sheet
with different thicknesses.
[0017] FIG. 7 Effect of sheet thickness on tensile elongation of
samples from various alloys.
[0018] FIG. 8 Effect of sheet thickness on yield strength in
samples from various alloys.
[0019] FIG. 9 Effect of sheet thickness on ultimate tensile
strength in samples from various alloys.
[0020] FIG. 10 SEM images of the microstructure in the center of
Alloy 1 sheet samples with various thicknesses; a) 0.7 mm thick
cold rolled sheet, b) 0.7 mm thick cold rolled and annealed sheet,
c) 0.5 mm thick cold rolled sheet, and d) 0.5 mm thick cold rolled
and annealed sheet.
[0021] FIG. 11 SEM images of the microstructure in the center of
Alloy 2 sheet samples with various thicknesses; a) 1.0 mm thick
cold rolled sheet, b) 1.0 mm thick cold rolled and annealed sheet,
c) 0.5 mm thick cold rolled sheet, d) 0.5 mm thick cold rolled and
annealed sheet, e) 0.2 mm thick cold rolled sheet, and f) 0.2 mm
thick cold rolled and annealed sheet.
[0022] FIG. 12 SEM images of the microstructure in the center of
Alloy 27 sheet samples with various thicknesses; a) 0.8 mm thick
cold rolled sheet, b) 0.8 mm thick cold rolled and annealed sheet,
c) 0.5 mm thick cold rolled sheet, d) 0.5 mm thick cold rolled and
annealed sheet, e) 0.4 mm thick cold rolled sheet, and f) 0.4 mm
thick cold rolled and annealed sheet.
[0023] FIG. 13 SEM images of the microstructure in the center of
Alloy 37 sheet samples with various thicknesses; a) 1.4 mm thick
cold rolled sheet, b) 1.4 mm thick cold rolled and annealed sheet,
c) 0.5 mm thick cold rolled sheet, d) 0.5 mm thick cold rolled and
annealed sheet, e) 0.3 mm thick cold rolled sheet, and f) 0.3 mm
thick cold rolled and annealed sheet.
[0024] FIG. 14 Schematic illustration of the ASTM D 638 Type V
tensile specimen geometry; all dimensions are in millimeters.
[0025] FIG. 15 Schematic diagram of the direct tension split
Hopkinson bar (SHB) device.
[0026] FIG. 16 Effect of strain rate on the tensile elongation at
fracture for Alloy 2 sheet.
[0027] FIG. 17 Bright-field TEM micrographs of microstructure in
gauge section of the sample from Alloy 2 sheet tested at strain
rate of 1200 s.sup.-1; a) lower magnification image, b) higher
magnification image.
[0028] FIG. 18 Bright-field TEM micrographs of microstructure in
gauge section of the sample from Alloy 2 sheet tested at strain
rate of 500 s.sup.-1; a) lower magnification image, b) higher
magnification image.
[0029] FIG. 19 Bright-field TEM micrographs of microstructure in
gauge section of the sample from Alloy 2 sheet tested at strain
rate of 100 s.sup.-1; a) lower magnification image, b) higher
magnification image.
[0030] FIG. 20 Bright-field TEM micrographs of microstructure in
gauge section of the sample from Alloy 2 sheet tested at strain
rate of 10 s.sup.-1; a) lower magnification image, b) higher
magnification image.
[0031] FIG. 21 Bright-field TEM micrographs of microstructure in
gauge section of the sample from Alloy 2 sheet tested strain rate
of 0.7 s.sup.-1; a) lower magnification image, b) higher
magnification image.
[0032] FIG. 22 Bright-field TEM micrographs of microstructure in
gauge section of the sample from Alloy 2 sheet tested at strain
rate of 0.0007 s.sup.-1; a) lower magnification image, b) higher
magnification image.
[0033] FIG. 23 Feritscope measurements at the gauge section of the
samples from Alloy 2 sheet tested at different strain rates.
[0034] FIG. 24 Schematic illustration of the notched tensile
sample.
[0035] FIG. 25 Notch diameter with a constant depth of 0.5 mm
effect; a) on tensile elongation and b) on ultimate tensile
strength of the sheet from Alloy 2.
[0036] FIG. 26 Half circle notch diameter effect; a) on tensile
elongation and b) on ultimate tensile strength of the sheet from
Alloy 2.
[0037] FIG. 27 SEM images of the fracture surface in the Sample 1
from Alloy 2 with a notch of 1 mm in diameter; a) in the center of
the fracture cross section, b) near the edge of the fracture cross
section.
[0038] FIG. 28 SEM images of the fracture surface in the Sample 2
from Alloy 2 with a notch of 6 mm in diameter; a) in the center of
the fracture cross section, b) near the edge of the fracture cross
section.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0039] The retention of mechanical properties in the alloys herein
at reduced thickness and relatively high strain rates is
illustrated in FIG. 1 and FIG. 2. FIG. 1 represents a summary on
mechanical property retention in the alloys herein when reduced in
thickness. In Step 1 in FIG. 1, the starting condition is to supply
a metal alloy. This metal alloy will preferably comprise at least
70 atomic % iron and at least four or more elements selected from
Si, Mn, Cr, Ni, Cu, or C. The alloy chemistry is melted, cooled at
a rate of <250 K/s, and solidified to a thickness of 25.0 mm and
up to and including 500 mm. The casting process can be done in a
wide variety of processes including ingot casting, bloom casting,
continuous casting, thin slab casting, thick slab casting, thin
strip casting, belt casting etc. Preferred methods would be
continuous casting in sheet form by thin slab casting, thick slab
casting, and thin strip casting. Preferred alloys exhibit a
fraction of austenite (y-Fe) at least 10 volume percent up to 100
volume percent and all increments in between. The alloy is then
processed into sheet form with a thickness T.sub.1 that is in the
range of 1.2 mm to 10.0 mm, and therefore includes thicknesses of
1.2 mm, 1.3 mm. 1.4 mm 1.5 mm. 1.6 mm, 1.7 mm, 1.8 mm, 1.9 mm, 2.0
mm, 2.1 mm, 2.2 mm, 2.3 mm, 2.4 mm, 2.5 mm, 2.6 mm, 2.7 mm, 2.8 mm,
2.9 mm, 3.0 mm, 3.1 mm, 3.2 mm, 3.3 mm, 3.4 mm, 3.5 mm, 3.6 mm, 3.7
mm, 3.8 mm, 3.9 mm, 4.0 mm, 4.1 mm, 4.2 mm, 4.3 mm, 4.4 mm, 4.5 mm,
4.6 mm, 4.7 mm, 4.8 mm, 4.9 mm and 5.0 mm, 5.1 mm, 5.2 mm, 5.3 mm.
5.4 mm. 5.5 mm, 5.6 mm, 5.7 mm, 5.8 mm, 5.9 mm, 6.0 mm, 6.1 mm, 6.2
mm, 6.3 mm, 6.4 mm, 6.5 mm, 6.6 mm, 6.7 mm, 6.8 mm, 6.9 mm, 7.0 mm,
7.1 mm, 7.2 mm, 7.3 mm, 7.4 mm, 7.5 mm, 7.6 mm, 7.7 mm, 7.8 mm, 7.9
mm, 8.0 mm, 8.1 mm, 8.2 mm, 8.3 mm, 8.4 mm, 8.5 mm, 8.6 mm, 8.7 mm,
8.8 mm, 8.9 mm, 9.0 mm, 9.1 mm, 9.2 mm, 9.3 mm, 9.4 mm, 9.5 mm, 9.6
mm, 9.7 mm, 9.8 mm, 9.9 mm and 10.0 mm.
[0040] The steps to produce this sheet at thickness T.sub.1 from
the cast product can vary depending on specific manufacturing
routes and specific targeted goals. As an example, consider thick
slab casting as one process route to get to sheet of this targeted
thickness. The alloy would be cast going through a water cooled
mold typically in a thickness range of 150 to 300 mm in thickness.
The cast ingot after cooling would then be preferably prepared for
hot rolling which may involve some surface treatment to remove
surface defects including oxides. The ingot would then go through a
roughing mill hot roller which may involve several passes resulting
in a transfer bar slab typically from 15 to 100 mm in thickness.
This transfer bar would then go through successive/tandem hot
rolling finishing stands to produce hot band coils which have a
thickness T.sub.1 in the above referenced range from 1.2 mm to 10.0
mm.
[0041] Another example would be to preferably process the cast
material through a thin slab casting process. In this case, after
casting typically forms 35 to 150 mm in thickness by going through
a water cooled mold, the newly formed slab goes directly to hot
rolling without cooling down with auxiliary tunnel furnace or
induction heating applied to bring the slab directly up to targeted
temperature. The slab is then hot rolled directly in multi-stand
finishing mills which are preferably from 1 to 7 in number. After
hot rolling, the strip is rolled into hot band coils with thickness
T.sub.1 in the above referenced range of 1.2 mm to 10.0 mm in
thickness. Note that bloom casting would be similar to the examples
above but higher thickness might be cast typically from 200 to 500
mm thick and initial breaker steps would be needed to reduce
initial cast thickness to allow it to go through a hot rolling
roughing mill. Strip casting would be similar but lower thickness
might be cast of T.sub.1 having a value of 1.2 mm to 10.0 mm in
thickness with preferably only one hot rolling stand directly after
casting.
[0042] Accordingly, the specific process in going from the slab
material in Step 1 to a preferred thickness T.sub.1 of 1.2 mm to 10
mm and then in Step 2 to a preferred thickness in the range of 0.2
mm to less than 1.2 mm may include hot rolling, cold rolling,
and/or cold rolling followed by annealing. Accordingly, in Step 2,
the alloy thickness may preferably be 0.2 mm, 0.3 mm, 0.4 mm. 0.5
mm. 0.6 mm. 0.7 mm. 0.8 mm. 0.9 mm, 1.0 mm 1.1 mm up to by not
including 1.2 mm. Hot rolling is generally used to provide a
preferred thickness from 1.2 mm to 10.0 mm and is typically done in
roughing mills, finishing mills, and/or Steckel mills. Cold rolling
is preferred in Steps 1 and/or Step 2 and is generally done using
tandem mills, Z-mills, and/or reversing mills. The cold rolled
material depending on property targets may be annealed to restore
the ductility lost from the cold rolling process either partially
or with restoration of ductility. Typically as cold rolling
proceeds and higher amounts of gauge reduction occurs, ductility is
reduced and cold rolling will continue until or just before
cracking is observed. Restoration of the tensile ductility of the
cold rolled sheet generally occurs with heat treatments at
700.degree. C. and above. Once the sheet is formed with thickness
T.sub.1 specified in Step 2, the sheet will then exhibit a total
elongation of X.sub.1 (%), an ultimate tensile strength of Y.sub.1
(MPa), and a yield strength of Z.sub.1 (MPa). Preferred properties
for alloys herein in Step 2 would be tensile elongation from 12 to
80%, ultimate tensile strength values from 700 to 2100 MPa, and
yield strength is in a range from 250 to 1500 MPa.
[0043] In Step 3, the alloy is preferably cold rolled and annealed
in similar manner as in Step 2 to thickness T.sub.2<T.sub.1. In
Step 3, comparing said alloy in Step 1 and after Step 2, the total
elongation is maintained at the level where the total elongation
X.sub.2=X.sub.1.+-.10%, Y.sub.2=Y.sub.1.+-.50 MPa, and
Z.sub.2=Z.sub.1.+-.100 MPa. The thickness of the alloy in Step 3 is
identified as T.sub.2 and is less than the thickness T.sub.1 in
Step 2. The preferred properties of the alloy in Step 3 are as
follows: X.sub.2=2 to 90%; Y.sub.2=650 MPa to 2150 MPa and
Z.sub.2=150 MPa to 1600 MPa.
[0044] FIG. 2 shows a summary on ductility retention of the present
disclosure in the alloys herein at relatively high strain rates,
that is where the alloys experience a strain rate of S.sub.2 of
>0.007 to 1200 s.sup.-1. Step 1 and Step 2 are identical to that
described above in relation to FIG. 1. Once the sheet is formed
with thickness from 1.2 mm to 10.0 mm, the sheet will then exhibit
a total elongation of X.sub.1 (%), an ultimate tensile strength of
Y.sub.1 (MPa), and a yield strength of Z.sub.1 (MPa) when tested at
strain rate S.sub.1, which is preferably at or below 0.007 s.sup.-1
and in the range from 0.007 to 0.0001 s.sup.-1 Preferred properties
for this alloy would be tensile elongation from 12 to 80%, ultimate
tensile strength values from 700 to 2100 MPa, and yield strength is
in a range from 250 to 1500 MPa. In Step 3, the sheet with
thickness from 0.2 mm to less than 1.2 mm is such that when
deformed at an engineering strain rate S.sub.2>S.sub.1 and the
alloy exhibits X.sub.3=X.sub.1.+-.7%, ultimate tensile strength
Y.sub.3=Y.sub.1.+-.200 MPa, and yield strength
Z.sub.3=Z.sub.1.+-.50 MPa. The preferred properties of the alloy in
Step 3 are as follows: X.sub.3=5 to 87%; Y.sub.3=500 MPa to 2300
MPa, and Z.sub.3=200 MPa to 1550 MPa.
[0045] Alloys herein are also shown to avoid brittle fracture when
stress concentration sites are introduced such as notches at the
sheet edge. A stress concentration site herein is a location on the
alloy sheet where stress can be concentrated, including but not
limited to geometric discontinuities, such as a notch, hole, cut in
the surface, crack, chipped portion, dent, etc. FIG. 3 shows a
summary on how changes in mechanical properties are retained in the
alloys herein with the introduction of stress concentration sites
such as edge notches. Once the sheet is formed with thickness from
1.2 mm to 10.0 mm in Step 2, the sheet will then exhibit a total
elongation of X.sub.1 (%), an ultimate tensile strength of Y.sub.1
(MPa), and a yield strength of Z.sub.1 (MPa). Preferred properties
for this alloy would again be tensile elongation from 12 to 80%,
ultimate tensile strength values from 700 to 2100 MPa, and yield
strength is in a range from 250 to 1500 MPa. In Step 3, the sheet
that experiences a stress concentration is capable of exhibiting
the following in response to a deformation:
X.sub.4.gtoreq.0.2X.sub.1 (%), an ultimate tensile strength
Y.sub.4.gtoreq.0.5Y.sub.1 (MPa), and a yield strength
Z.sub.4.gtoreq.0.6Z.sub.1 (MPa). The preferred properties of the
alloy in Step 3 are as follows: X.sub.4.gtoreq.2.4%;
Y.sub.4.gtoreq.350 MPa, and Z.sub.4.gtoreq.150 MPa.
Alloys
[0046] The chemical composition of the alloys herein is shown in
Table 1 which provides the preferred atomic ratios utilized.
TABLE-US-00001 TABLE 1 Chemical Composition of Alloys (Atomic %)
Alloy Fe Cr Ni Mn Si Cu C Alloy 1 75.75 2.63 1.19 13.86 5.13 0.65
0.79 Alloy 2 74.75 2.63 1.19 14.86 5.13 0.65 0.79 Alloy 3 77.31
2.63 8.49 5.00 5.13 0.65 0.79 Alloy 4 77.14 2.63 6.49 7.17 5.13
0.65 0.79 Alloy 5 76.24 2.63 4.49 10.07 5.13 0.65 0.79 Alloy 6
75.34 2.63 2.49 12.97 5.13 0.65 0.79 Alloy 7 78.92 2.63 6.49 5.39
5.13 0.65 0.79 Alloy 8 77.34 2.63 4.49 8.97 5.13 0.65 0.79 Alloy 9
75.77 2.63 2.49 12.54 5.13 0.65 0.79 Alloy 10 75.90 2.63 3.74 11.16
5.13 0.65 0.79 Alloy 11 77.73 2.63 3.74 9.33 5.13 0.65 0.79 Alloy
12 79.57 2.63 3.74 7.49 5.13 0.65 0.79 Alloy 13 75.97 2.63 3.74
10.09 5.13 1.65 0.79 Alloy 14 77.80 2.63 3.74 8.26 5.13 1.65 0.79
Alloy 15 79.64 2.63 3.74 6.42 5.13 1.65 0.79 Alloy 16 76.88 2.63
3.74 9.18 5.13 1.65 0.79 Alloy 17 76.83 2.63 3.74 9.85 5.13 1.03
0.79 Alloy 18 76.57 2.63 3.06 10.17 5.13 1.65 0.79 Alloy 19 76.52
2.63 3.06 10.84 5.13 1.03 0.79 Alloy 20 78.02 1.13 3.06 10.84 5.13
1.03 0.79 Alloy 21 80.02 1.13 3.06 10.84 3.13 1.03 0.79 Alloy 22
76.70 2.63 3.40 10.01 5.13 1.34 0.79 Alloy 23 76.20 3.13 3.40 10.01
5.13 1.34 0.79 Alloy 24 75.70 3.63 3.40 10.01 5.13 1.34 0.79 Alloy
25 77.70 2.63 3.40 10.01 4.13 1.34 0.79 Alloy 26 75.70 2.63 3.40
10.01 6.13 1.34 0.79 Alloy 27 77.20 2.63 3.40 10.01 4.13 1.34 1.29
Alloy 28 75.20 2.63 3.40 10.01 6.13 1.34 1.29 Alloy 29 76.98 2.88
3.40 10.01 4.63 1.34 0.76 Alloy 30 77.23 2.88 3.15 10.01 4.63 1.34
0.76 Alloy 31 77.48 2.88 2.90 10.01 4.63 1.34 0.76 Alloy 32 77.73
2.88 2.65 10.01 4.63 1.34 0.76 Alloy 33 77.98 2.88 2.40 10.01 4.63
1.34 0.76 Alloy 34 74.59 2.61 0.00 15.17 3.59 1.86 2.18 Alloy 35
82.22 3.69 9.94 0.00 2.26 0.37 1.52 Alloy 36 76.17 8.64 0.90 11.77
0.00 1.68 0.84 Alloy 37 82.77 4.41 6.66 3.19 1.14 1.16 0.67 Alloy
38 76.55 0.78 0.72 14.43 3.42 0.42 3.68 Alloy 39 81.44 0.00 4.42
10.33 2.87 0.00 0.94 Alloy 40 81.00 1.22 0.89 13.45 2.66 0.78 0.00
Alloy 41 81.68 2.24 3.25 9.87 0.00 1.55 1.41 Alloy 42 78.47 3.16
5.57 7.43 3.70 0.51 1.16 Alloy 43 79.73 3.34 7.02 4.95 3.22 0.46
1.28 Alloy 44 81.47 3.69 10.69 0.00 2.26 0.37 1.52 Alloy 45 80.72
3.69 11.44 0.00 2.26 0.37 1.52 Alloy 46 81.47 3.69 9.94 0.00 2.26
1.12 1.52 Alloy 47 80.72 3.69 9.94 0.00 2.26 1.87 1.52 Alloy 48
81.00 3.69 9.94 0.00 3.70 0.51 1.16 Alloy 49 82.84 1.85 9.94 0.00
3.70 0.51 1.16 Alloy 50 84.69 0.00 9.94 0.00 3.70 0.51 1.16 Alloy
51 82.30 3.69 4.97 3.67 3.70 0.51 1.16 Alloy 52 81.00 3.69 4.97
4.97 3.70 0.51 1.16 Alloy 53 79.70 3.69 4.97 6.27 3.70 0.51 1.16
Alloy 54 83.52 3.69 4.97 3.67 2.26 0.37 1.52 Alloy 55 82.22 3.69
4.97 4.97 2.26 0.37 1.52 Alloy 56 80.92 3.69 4.97 6.27 2.26 0.37
1.52
[0047] As can be seen from Table 1, the alloys herein comprise,
consist essentially of, or consist of iron based metal alloys,
having greater than 70 at. % Fe, and at least four or more elements
selected from the following six (6) elements: Si, Mn, Cr, Ni, Cu,
and C. The level of impurities of other elements are in the range
of 0 to 5000 ppm. Accordingly, if there is 5000 ppm of an element
other than the selected elements identified, the level of such
selected elements may then in combination be present at a lower
level to account for the 5000 ppm impurity, such that the total of
all elements present (selected elements and impurities) is 100
atomic percent.
[0048] With regards to the above, and as can be further seen from
Table 1, preferably, when Fe is present at a level of greater than
70 at. %, and one then selects the four or more elements from the
indicated six (6) elements, or selects five or more elements, or
selects all six elements to provide a formulation of elements that
totals 100 atomic percent. The preferred levels of the elements, if
selected, may fall in the following ranges: Si (1.14 to 6.13), Mn
(3.19 to 15.17), Cr (0.78 to 8.64); Ni (0.9 to 11.44), Cu (0.37 to
1.87), and C (0.67 to 3.68). Accordingly, it can be appreciated
that if four (4) elements are selected, two of the six elements are
not selected and may be excluded. If five (5) elements are
selected, one of the elements of the six can be excluded. Moreover,
a particularly preferred level of Fe is in the range of 73.95 to
84.69 at. %. Again, the level of impurities of other elements are
preferably controlled in the range of 0 to 5000 ppm (0 to 0.5 wt
%).
Laboratory Slab Casting
[0049] Alloys were weighed out into 3,000 to 3,400 gram charges
according to the atomic ratios in Table 1 using commercially
available ferroadditive powders and a base steel feedstock with
known chemistry. As alluded to above, impurities can be present at
various levels depending on the feedstock used. Impurity elements
would commonly include the following elements; Al, Co, N, P, Ti,
Mo, W, Ga, Ge, Sb, Nb, Zr, O, Sn, Ca, and S which if present would
be in the range from 0 to 5000 ppm (parts per million) (0 to 0.5 wt
%) at the expense of the desired elements noted above. Preferably,
the level of impurities is controlled to fall in the range of 0 to
3000 ppm (0.3 wt %).
[0050] Charges were loaded into a zirconia coated silica crucible
which was placed into an Indutherm VTC800V vacuum tilt casting
machine. The machine then evacuated the casting and melting
chambers and flushed with argon to atmospheric pressure twice prior
to casting to prevent oxidation of the melt. The melt was heated
with a 14 kHz RF induction coil until fully molten, approximately
from 5 to 7 minutes depending on the alloy composition and charge
mass. After the last solids were observed to melt it was allowed to
heat for an additional 30 to 45 seconds to provide superheat and
ensure melt homogeneity. The casting machine then evacuated the
chamber and tilted the crucible and poured the melt into a water
cooled copper die. The melt was allowed to cool under vacuum for
200 seconds before the chamber was filled with argon to atmospheric
pressure.
[0051] Laboratory casting corresponds to Step 1 in FIG. 1, FIG. 2
and FIG. 3 and provides slabs with thickness of 50 mm. Depending on
equipment capability, slab thickness in Step 1 can vary from 25.0
to 500 mm.
Thermal Analysis
[0052] A sample of between 50 and 150 mg from each alloy herein was
taken in the as-cast condition. This sample was heated to an
initial ramp temperature between 900.degree. C. and 1300.degree. C.
depending on alloy chemistry, at a rate of 40.degree. C./min.
Temperature was then increased at 10.degree. C./min to a max
temperature between 1425.degree. C. and 1515.degree. C. depending
on alloy chemistry. Once this maximum temperature was achieved, the
sample was cooled at a rate of 10.degree. C./min back to the
initial ramp temperature before being reheated at 10.degree. C./min
to the maximum temperature. Differential Scanning calorimetry (DSC)
measurements were taken using a Netzsch Pegasus 404 DSC through all
four stages of the experiment, and this data was used to determine
the solidus and liquidus temperatures of each alloy, which are in a
range from 1102 to 1505.degree. C. (Table 2). Depending on alloys
chemistry, liquidus-solidus gap varies from 31 to 138.degree. C.
Thermal analysis provides information on maximum temperature for
the following hot rolling processes that varies depending on alloy
chemistry.
TABLE-US-00002 TABLE 2 Thermal Analysis of Selected Alloys Solidus
Liquidus Melting Gap Alloy (.degree. C.) (.degree. C.) (.degree.
C.) Alloy 1 1390 1448 58 Alloy 2 1398 1446 49 Alloy 3 1403 1456 53
Alloy 4 1411 1456 45 Alloy 5 1391 1448 57 Alloy 6 1384 1442 58
Alloy 7 1407 1462 55 Alloy 8 1400 1452 52 Alloy 9 1386 1444 59
Alloy 10 1375 1444 70 Alloy 11 1392 1453 61 Alloy 12 1393 1459 67
Alloy 13 1374 1441 67 Alloy 14 1386 1453 67 Alloy 15 1401 1459 57
Alloy 16 1400 1453 53 Alloy 17 1397 1453 56 Alloy 18 1399 1452 53
Alloy 19 1400 1452 52 Alloy 20 1401 1454 53 Alloy 21 1409 1467 57
Alloy 22 1396 1452 56 Alloy 23 1394 1450 56 Alloy 24 1404 1454 49
Alloy 25 1405 1460 55 Alloy 26 1372 1440 68 Alloy 27 1383 1454 70
Alloy 28 1369 1430 61 Alloy 29 1420 1458 38 Alloy 30 1412 1459 47
Alloy 31 1431 1462 31 Alloy 32 1408 1460 52 Alloy 33 1415 1462 48
Alloy 34 1358 1445 88 Alloy 35 1458 1496 39 Alloy 36 1406 1488 82
Alloy 37 1462 1502 41 Alloy 38 1294 1432 138 Alloy 39 1438 1491 53
Alloy 40 1425 1481 56 Alloy 41 1438 1494 56 Alloy 42 1442 1481 39
Alloy 43 1460 1493 33 Alloy 44 1458 1500 42 Alloy 45 1465 1505 39
Alloy 46 1456 1498 42 Alloy 47 1453 1492 39 Alloy 48 1456 1496 40
Alloy 49 1472 1504 32 Alloy 50 1456 1500 43 Alloy 51 1451 1491 40
Alloy 52 1430 1480 51 Alloy 53 1442 1482 40 Alloy 54 1447 1489 42
Alloy 55 1450 1490 40 Alloy 56 1447 1488 41
Laboratory Hot Rolling
[0053] The alloys herein were preferably processed into a
laboratory hot band by hot rolling of laboratory slabs at high
temperatures. Laboratory alloy processing is developed to simulate
the hot band production from slabs produced by continuous casting.
Industrial hot rolling is performed by heating a slab in a tunnel
furnace to a target temperature, then passing it through either a
reversing mill or a multi-stand mill or a combination of both to
reach the target gauge. During rolling on either mill type, the
temperature of the slab is steadily decreasing due to heat loss to
the air and to the work rolls so the final hot band is formed at a
reduced temperature. This is simulated in the laboratory by heating
in a tunnel furnace to between 1100.degree. C. and 1250.degree. C.,
then hot rolling. The laboratory mill is slower than industrial
mills causing greater loss of heat during each hot rolling pass so
the slab is reheated for 4 minutes between passes to reduce the
drop in temperature, the final temperature at target gauge when
exiting the laboratory mill commonly is in the range from
800.degree. C. to 1000.degree. C., depending on furnace temperature
and final thickness.
[0054] Prior to hot rolling, laboratory slabs were preheated in a
Lucifer EHS3GT-B18 furnace. The furnace set point varies between
1100.degree. C. to 1250.degree. C., depending on alloy melting
point and point in the hot rolling process, with the initial
temperatures set higher to facilitate higher reductions, and later
temperatures set lower to minimize surface oxidation on the hot
band. The slabs were allowed to soak for 40 minutes prior to hot
rolling to ensure they reach the target temperature and then pushed
out of the tunnel furnace into a Fenn Model 061 2 high rolling
mill. The 50 mm casts are hot rolled for 5 to 10 passes though the
mill before being allowed to air cool. Final thickness ranges after
hot rolling are preferably from 1.8 mm to 4.0 mm with variable
reduction per pass ranging from 20% to 50%.
[0055] Tensile specimens were cut from laboratory hot band using
wire EDM. Tensile properties were measured on an Instron mechanical
testing frame (Model 3369), utilizing Instron's Bluehill control
and analysis software. Samples were tested under displacement
control at a constant displacement rate of 0.036 mm/s, which
resulted in sample strain rates, calculated from video strain
measurements, ranging from 4.4.times.10.sup.-4 s.sup.-1 to
6.8.times.10.sup.-3 s.sup.-1, depending on several factors
including, but not always limited to mechanical compliance, sample
slippage, and settling of the wedge action grips used.
[0056] Tensile properties of the alloys in the hot rolled condition
with a thickness from 1.8 to 2.3 mm are listed in Table 3 including
magnetic phases volume percent (Fe %) that was measured by
Feritscope. The ultimate tensile strength values may vary from 913
to 2011 MPa with tensile elongation from 13.0 to 69.5%. The yield
strength is in a range from 250 to 1313 MPa. Mechanical properties
of the hot band from steel alloys herein depend on alloy chemistry,
processing conditions, and material mechanistic response to the
processing conditions. The relative magnetic phases volume percent
was measured by Feritscope with the magnetic phases volume percent
of 0.1 to 64.9 Fe % in a hot band depending on alloy chemistry.
Note that the Table 3 properties correspond to Step 2 of FIG. 1,
FIG. 2, and FIG. 3. Further processing of the hot band can
additionally occur through cold rolling and annealing as shown for
example in Case Example 1.
TABLE-US-00003 TABLE 3 Hot Band Tensile Properties of Alloys
Ultimate Average Magnetic Tensile Tensile Yield Phases Volume
Elongation Strength Strength Percent Alloy (%) (MPa) (MPa) (Fe %)
Alloy 1 51.4 1248 294 1.7 49.2 1253 310 31.2 1093 396 Alloy 2 57.6
1175 311 1.3 58.6 1209 294 56.6 1167 302 Alloy 3 55.4 1163 330 3.2
59.5 1154 373 58.1 1165 347 Alloy 4 59.8 1220 342 0.3 51.6 1241 338
55.5 1245 375 54.6 1324 377 Alloy 5 54.3 1248 325 0.5 53.1 1218 313
50.6 1258 304 54.1 1242 331 Alloy 6 58.3 1212 330 0.4 53.7 1212 283
58.7 1193 315 Alloy 7 28.1 1508 333 10.4 28.5 1516 331 26.0 1520
317 Alloy 8 41.2 1343 330 0.9 32.8 1281 328 45.7 1387 336 41.4 1375
328 Alloy 9 48.1 1248 300 1.4 50.5 1293 304 52.0 1280 303 Alloy 10
58.5 1229 379 2.7 57.8 1223 384 59.0 1220 389 Alloy 11 45.3 1411
360 0.8 40.2 1460 359 41.3 1429 325 47.1 1448 347 Alloy 12 31.3
1624 250 1.5 31.7 1581 304 28.7 1610 319 Alloy 13 57.1 1101 358 0.1
66.1 1120 362 68.5 1114 362 60.1 1120 350 Alloy 14 45.1 1371 354
0.4 40.6 1403 363 42.3 1403 364 46.9 1379 341 Alloy 15 26.2 1579
295 1.6 25.2 1593 264 24.6 1588 302 Alloy 16 54.8 1239 379 0.2 58.5
1207 341 55.8 1207 359 Alloy 17 51.3 1270 354 0.6 50.1 1328 384
Alloy 18 58.8 1224 384 0.3 56.1 1245 390 50.7 1190 365 Alloy 19
47.4 1263 348 0.4 50.7 1260 362 51.8 1277 363 Alloy 20 40.1 1337
376 0.3 43.9 1343 375 44.7 1328 394 Alloy 21 45.2 1277 327 0.5 46.1
1318 340 54.2 1310 325 Alloy 22 49.6 1272 369 0.3 54.9 1275 354
54.8 1271 319 52.4 1297 340 Alloy 23 53.5 1246 344 0.3 55.9 1226
359 51.2 1232 346 52.7 1228 375 Alloy 24 57.0 1209 356 0.2 54.6
1202 348 55.1 1207 363 56.9 1225 338 Alloy 25 53.4 1227 357 0.4
56.5 1249 325 54.5 1214 345 49.5 1220 343 Alloy 26 49.0 1319 340
0.5 48.4 1320 344 50.5 1304 331 51.1 1296 346 Alloy 27 56.5 967 404
0.1 54.5 956 421 67.6 979 417 52.0 942 390 Alloy 28 50.4 1121 442
0.4 49.8 1088 407 51.8 1116 423 Alloy 29 56.0 1229 422 4.2 56.3
1247 409 54.6 1226 405 50.0 1196 421 56.3 1199 412 53.3 1205 402
Alloy 30 52.1 1271 421 5.5 51.4 1284 416 50.6 1269 407 53.9 1248
418 49.9 1237 399 54.8 1241 407 Alloy 31 48.6 1326 379 6.5 51.3
1323 390 51.6 1293 372 51.4 1314 374 Alloy 32 49.5 1347 383 5.7
47.0 1367 388 47.9 1341 381 47.8 1391 431 Alloy 33 44.8 1373 372
7.3 42.3 1392 381 40.7 1388 381 Alloy 34 65.9 963 515 0.3 58.7 954
485 62.1 970 545 Alloy 35 19.6 2000 533 43.3 22.3 1976 511 19.8
1995 526 Alloy 36 60.1 1091 439 2.0 61.0 1114 469 59.4 1137 481
Alloy 37 13.8 1572 649 56.4 14.1 1619 711 14.6 1610 692 Alloy 38
58.9 1105 531 0.7 61.4 1108 524 58.6 1106 511 Alloy 39 51.0 1317
354 8.2 50.5 1334 370 50.5 1325 368 Alloy 40 47.9 1374 330 5.8 48.8
1336 317 41.5 1362 321 Alloy 41 51.1 963 472 5.2 48.4 913 463 Alloy
42 61.6 1081 440 7.0 69.5 1098 450 64.3 1070 440 67.2 1081 438 62.2
1082 439 Alloy 43 44.5 1176 440 16.6 35.0 1073 447 38.4 1136 447
36.8 1140 454 Alloy 44 23.9 1858 577 40.5 24.5 1852 624 24.9 1866
685 23.1 1841 672 Alloy 45 32.5 1758 439 32.4 28.9 1733 408 26.9
1746 442 26.6 1725 417 Alloy 46 21.9 1917 826 46.0 21.4 1898 753
21.0 1907 748 22.2 1911 698 Alloy 47 24.8 1765 526 40.1 24.6 1787
492 23.7 1781 463 24.2 1771 478 Alloy 48 16.2 1890 1108 55.0 17.0
1926 1093 15.9 1920 1139 16.4 1899 1073 Alloy 49 16.4 2002 1247
61.5 15.4 1961 1225 16.0 2011 1276 16.3 1990 1275 Alloy 50 16.9
1853 1259 64.9 15.4 1859 1265 15.7 1816 1195 14.6 1833 1313 Alloy
51 18.8 1960 944 51.8 17.8 1963 911 18.1 1947 994 17.3 1915 927
Alloy 52 23.3 1598 366 24.5 20.1 1522 369 25.4 1627 364 25.6 1624
383 Alloy 53 40.3 1407 447 13.1 37.6 1375 441 37.6 1310 437 41.2
1393 444 Alloy 54 19.0 1834 416 36.4 17.8 1827 420 13.0 1720 423
15.4 1811 462 Alloy 55 23.0 1237 462 24.9 18.3 1088 443 21.6 1212
468 22.9 1302 470 Alloy 56 36.8 1039 473 13.2 36.0 1051 497 36.4
1026 480 34.9 1068 514
CASE EXAMPLES
Case Example #1 Tensile Properties of the Sheet at 1.2 mm
Thickness
[0057] The hot band from alloys herein listed in Table 1 was cold
rolled to final target gauge thickness of 1.2 mm through multiple
cold rolling passes. Cold rolling is defined as rolling at ambient
temperature. Hot band material was media blasted prior to cold
rolling to remove surface oxides which could become embedded during
the rolling process. The resultant cleaned sheet material was
rolled using a Fenn Model 061 2 high rolling mill. Sheet was fed
through the rolls, and the roll gap is reduced for each subsequent
pass until the desired thickness is achieved or the material
hardens to the point where additional rolling does not achieve
significant reduction in thickness. Annealing was applied before
next rolling to recover ductility. Multiple cycles of cold rolling
and annealing might be applied. Once the final gauge thickness was
reached, samples were cut from each cold rolled sheet by wire EDM.
Tensile properties were measured on an Instron mechanical testing
frame (Model 3369), utilizing Instron's Bluehill control and
analysis software. All tests were run at ambient temperature in
displacement control. Samples were tested under displacement
control at a constant displacement rate of 0.036 mm/s, which
resulted in sample strain rates, calculated from video strain
measurements, ranging from 4.4.times.10.sup.-4 s.sup.-1 to
6.8.times.10.sup.-3 s.sup.-1, depending on several factors
including, but not always limited to mechanical compliance, sample
slippage, and settling of the wedge action grips used.
[0058] Tensile properties of 1.2 mm thick sheet from alloys herein
after cold rolling are listed in Table 4. The ultimate tensile
strength values after cold rolling is in a range from 1360 to 2222
MPa; yield strength varies from 1006 to 2073 MPa and tensile
elongation is recorded in the range from 4.2 to 37.2%. The magnetic
phases volume percent was measured by Feritscope in a range from
1.6 to 84.9 Fe % in a cold rolled sheet depending on alloy
chemistry.
TABLE-US-00004 TABLE 4 Tensile Properties of 1.2 mm Thick Sheet
from the Alloys After Cold Rolling Ultimate Magnetic Cold Tensile
Tensile Yield Phases Volume Rolling Elongation Strength Strength
Percent Reduction Alloy (%) (MPa) (MPa) (Fe %) (%) Alloy 1 20.5
1712 1114 31.4 38.0 20.4 1712 1131 15.0 1705 1073 Alloy 2 21.8 1603
1135 27.8 39.7 23.2 1612 1111 25.7 1589 1120 Alloy 3 29.9 1540 1140
34.6 36.9 28.9 1551 1118 29.5 1553 1234 Alloy 4 25.4 1645 1192 43.3
39.2 25.6 1650 1217 26.4 1639 1381 Alloy 5 17.1 1758 1335 44.9 38.3
18.5 1764 1321 17.8 1764 1285 Alloy 6 22.5 1686 1018 31.3 35.3 22.9
1685 1072 21.6 1687 1042 Alloy 7 16.9 1874 1666 66.5 35.7 14.8 1881
1680 13.3 1875 1360 Alloy 8 10.7 1835 1068 53.4 35.4 16.4 1859 1086
17.5 1860 1336 Alloy 9 19.7 1742 1014 37.0 36.0 17.5 1732 1104 18.2
1732 1120 Alloy 10 20.1 1715 1038 40.3 35.1 20.5 1716 1280 20.5
1729 1173 Alloy 11 13.9 1893 1320 69.9 32.7 15.0 1906 1467 15.6
1875 1536 Alloy 12 5.5 2125 1913 57.0 33.8 5.9 2116 1720 4.2 2114
1675 Alloy 13 22.8 1500 1182 25.6 36.5 24.0 1523 1204 23.9 1518
1098 Alloy 14 18.6 1790 1561 52.1 34.5 20.2 1793 1436 17.9 1726
1491 Alloy 15 5.0 2051 1784 58.9 37.3 6.2 2073 2000 6.3 2057 1957
Alloy 16 19.9 1700 1413 42.0 36.9 19.7 1689 1436 21.1 1704 1302
Alloy 17 20.1 1765 1379 45.9 36.0 20.2 1759 1306 17.2 1764 1374
Alloy 18 20.6 1708 1388 44.1 37.3 20.0 1721 1326 18.9 1709 1369
Alloy 19 18.9 1810 1213 44.8 38.0 19.3 1807 1324 19.2 1806 1260
Alloy 20 15.1 1864 1404 54.8 38.3 16.2 1884 1461 17.1 1879 1512
Alloy 21 18.6 1780 1374 54.9 34.1 18.0 1785 1414 18.6 1786 1006
Alloy 22 17.3 1759 1356 43.9 38.0 21.3 1736 1196 18.8 1757 1304
Alloy 23 19.3 1718 1240 41.3 37.4 20.4 1728 1283 19.0 1727 1271
Alloy 24 22.0 1709 1136 36.8 37.5 12.6 1695 1256 14.8 1706 1258
Alloy 25 19.8 1715 1326 42.6 33.5 20.2 1704 1320 21.0 1700 1316
Alloy 26 18.8 1822 1377 48.5 35.6 17.9 1816 1327 Alloy 27 30.7 1442
1146 12.6 34.5 29.9 1360 1108 24.2 1428 1164 Alloy 28 21.0 1625
1215 20.6 37.5 26.6 1646 1187 23.9 1602 1172 Alloy 29 18.1 1718
1483 58.3 38.8 18.6 1712 1454 19.4 1720 1407 Alloy 30 17.7 1770
1335 44.6 39.9 17.7 1764 1430 17.9 1765 1515 Alloy 31 17.5 1834
1524 49.4 40.5 16.9 1831 1707 16.0 1837 1578 Alloy 32 15.7 1890
1442 50.2 41.1 14.8 1897 1563 15.4 1886 1676 Alloy 33 15.4 1891
1533 56.3 38.2 16.3 1889 1604 15.8 1895 1419 Alloy 34 10.9 1519
1249 1.6 39.0 9.4 1515 1037 10.8 1519 1345 Alloy 35* 16.2 2222 1693
73.7 19.6 16.4 2216 1735 16.2 2217 1657 Alloy 36 16.4 1641 1116
29.6 36.7 20.6 1604 1187 19.1 1623 1295 Alloy 37 7.1 1949 1617 84.9
36.3 6.6 1977 1824 6.5 1975 1834 Alloy 38 7.0 1727 1539 3.8 43.0
9.7 1721 1373 10.0 1717 1490 Alloy 39 16.0 1869 1289 50.0 36.5 19.0
1840 1471 19.0 1837 1245 Alloy 40 15.6 1917 1238 45.8 37.4 17.2
1913 1361 17.7 1917 1192 Alloy 41 28.6 1452 1121 26.4 39.2 31.1
1445 1101 31.1 1431 1231 Alloy 42 21.4 1673 1516 35.5 44.9 23.1
1686 1519 22.9 1675 1509 Alloy 43 37.2 1656 1313 38.1 39.2 31.2
1650 1304 30.0 1667 1332 Alloy 44 19.6 2091 1623 57.8 37.1 20.4
2095 1653 20.1 2098 1656 Alloy 45 21.7 2028 1331 50.9 40.9 22.8
2014 1313 22.6 2017 1334 Alloy 46* 18.5 2095 1755 62.2 29.3 18.5
2100 1754 19.3 2106 1773 Alloy 47 14.7 2024 1482 57.8 36.2 21.3
2020 1496 19.4 2024 1473 Alloy 48* 11.7 2197 2029 72.6 20.7 11.6
2197 1993 10.6 2197 2010 Alloy 49 11.1 2138 1985 76.6 11.3 11.6
2137 1948 11.1 2138 1964 Alloy 50* 8.7 2166 2041 83.3 26.7 8.0 2168
2060 8.5 2170 2073 Alloy 51* 11.9 2197 1904 68.4 21.0 11.0 2194
1917 12.0 2190 1897 Alloy 52 15.2 2071 1788 55.1 34.6 16.4 2068
1764 13.8 2073 1781 Alloy 53 22.1 1908 1630 45.3 38.5 23.5 1911
1584 24.3 1908 1590 Alloy 54* 7.9 2104 1675 57.5 30.3 5.8 2032 1673
7.4 2083 1646 Alloy 55 8.2 1738 1479 44.5 38.1 11.0 1812 1497 11.5
1829 1486 Alloy 56 28.8 1705 1386 32.9 39.4 32.5 1703 1452 28.2
1747 1443 *Thickness of 1.2 mm was not achieved in these alloys due
to high strength and equipment limitations. Alloys are tested at
thickness from 1.3 to 1.4 mm.
[0059] The samples were annealed under conditions intended to
simulate the thermal exposure expected during an industrial
continuous annealing process representing final treatment of sheet
material in Step 2 in FIG. 1, FIG. 2 and FIG. 3. Samples were
loaded into a furnace preheated to 850.degree. C., and held at
temperature for 10 minutes, wrapped in foil and held under a steady
argon flow to minimize oxidation damage. Samples were removed at
temperature and allowed to air cool to ambient temperature before
testing. Tensile properties were measured on an Instron mechanical
testing frame (Model 3369), utilizing Instron's Bluehill control
and analysis software. All tests were run at ambient temperature in
displacement control at a constant displacement rate of 0.036 mm/s,
which resulted in sample strain rates, calculated from video strain
measurements, ranging from 4.4.times.10.sup.-4 s.sup.-1 to
6.8.times.10.sup.-3 s.sup.-1, depending on several factors
including, but not always limited to mechanical compliance, sample
slippage, and settling of the wedge action grips used.
[0060] Tensile properties of 1.2 mm sheet from alloys herein after
annealing are listed in Table 5. The ultimate tensile strength
values of the annealed sheet from alloys herein is in a range from
725 to 2072 MPa; yield strength varies from 267 to 1428 MPa and
tensile elongation is recorded in the range from 12.8 to 76.9%. The
relative magnetic phases volume percent was measured by Feritscope
with the magnetic phases volume percent of 0.2 to 68.2 Fe %
depending on alloy chemistry.
[0061] Properties of cold rolled and annealed sheet from Alloys
herein corresponds to Step 2 in FIG. 1, FIG. 2 and FIG. 3.
TABLE-US-00005 TABLE 5 Tensile Properties of 1.2 mm Thick Sheet
from the Alloys after Annealing Ultimate Average Tensile Tensile
Yield Magnetic Phases Elongation Strength Strength Volume Percent
Alloy (%) (MPa) (MPa) (Fe %) Alloy 1 55.7 1267 473 1.2 52.0 1242
451 56.1 1248 470 57.7 1277 463 Alloy 2 62.4 1162 491 1.3 59.4 1179
469 61.8 1193 477 62.6 1172 531 Alloy 3 61.2 1165 319 0.9 64.2 1153
320 63.2 1145 302 Alloy 4 61.9 1218 350 1.2 58.6 1201 344 51.4 1223
341 64.1 1208 337 Alloy 5 52.0 1239 393 0.7 54.6 1235 398 53.9 1227
442 Alloy 6 61.3 1194 426 1.0 61.0 1238 450 53.9 1208 417 Alloy 7
31.5 1440 338 10.8 33.1 1475 322 32.7 1483 312 33.1 1481 347 31.3
1461 323 32.1 1472 332 Alloy 8 56.2 1269 430 0.9 61.3 1225 471 56.6
1277 421 Alloy 9 56.2 1269 430 1.0 61.3 1225 471 56.6 1277 421
Alloy 10 54.3 1238 412 0.7 56.9 1192 397 59.9 1238 412 Alloy 11
41.3 1437 420 0.9 44.3 1434 424 41.7 1464 412 43.5 1419 417 Alloy
12 29.9 1574 379 2.3 30.1 1571 374 29.7 1579 373 Alloy 13 62.9 1097
367 1.0 69.8 1121 375 68.9 1103 368 Alloy 14 47.1 1363 372 1.1 46.7
1384 376 43.8 1365 366 42.6 1386 370 Alloy 15 24.2 1528 305 20.0
24.8 1535 308 26.0 1534 315 Alloy 16 54.6 1243 376 0.9 55.0 1258
422 54.8 1237 376 55.9 1249 382 Alloy 17 53.3 1333 406 0.4 50.0
1304 410 53.6 1289 403 51.1 1323 392 Alloy 18 55.2 1238 420 0.6
58.7 1198 414 56.1 1235 425 53.2 1244 417 Alloy 19 50.4 1273 451
0.8 50.5 1278 416 51.0 1348 436 53.2 1299 414 Alloy 20 43.4 1378
408 1.0 44.7 1362 406 34.1 1308 429 28.7 1175 397 Alloy 21 52.7
1298 340 1.6 46.9 1326 348 35.4 1270 349 48.6 1324 350 Alloy 22
54.8 1273 399 0.9 54.1 1268 397 56.1 1297 408 Alloy 23 59.3 1239
403 0.3 59.5 1296 407 56.2 1255 409 Alloy 24 60.0 1235 423 0.7 60.1
1247 432 61.8 1237 428 Alloy 25 56.8 1255 376 0.3 51.6 1244 380
57.0 1217 382 Alloy 26 51.0 1305 417 0.7 50.0 1311 432 51.1 1319
433 Alloy 27 59.7 1033 387 0.5 53.8 975 368 63.0 1017 377 Alloy 28
41.3 1128 480 0.2 45.7 1168 482 47.2 1168 485 47.0 1168 492 Alloy
29 58.4 1218 370 1.1 50.7 1250 386 57.3 1251 378 55.1 1239 382
Alloy 30 49.0 1297 383 1.1 54.0 1318 445 53.3 1304 381 Alloy 31
45.0 1299 382 1.2 47.5 1328 383 52.3 1328 392 50.8 1328 397 Alloy
32 50.9 1380 420 1.1 43.1 1373 391 52.4 1371 390 Alloy 33 45.6 1399
388 1.1 36.3 1383 396 44.2 1418 398 34.4 1380 410 Alloy 34 64.7 993
484 0.3 66.1 997 491 66.2 994 481 66.3 994 491 Alloy 35* 14.0 2066
792 60.1 14.0 2072 775 14.5 2072 745 13.6 1971 775 Alloy 36 50.1
1175 483 0.9 50.9 1161 472 50.8 1190 471 Alloy 37 13.2 1621 635
68.2 13.2 1607 645 13.5 1586 574 13.4 1600 644 Alloy 38 60.3 1134
499 0.5 58.2 1141 500 60.4 1139 500 64.2 1138 490 Alloy 39 20.2 929
372 3.0 16.2 725 375 19.4 827 382 21.9 941 362 Alloy 40 15.6 759
379 0.6 17.9 888 420 17.0 839 368 18.0 849 431 Alloy 41 53.0 889
312 1.4 43.5 893 311 50.9 882 315 Alloy 42 68.5 1126 381 1.4 74.7
1105 370 75.2 1154 384 76.9 1141 375 Alloy 43 51.3 1285 344 3.0
50.6 1296 352 41.2 1132 341 62.4 1284 342 Alloy 44 12.8 1898 1269
57.5 14.0 1959 1272 14.1 1962 808 14.1 1961 1235 Alloy 45 16.1 1875
540 51.3 15.5 1888 517 16.0 1867 514 15.4 1878 546 Alloy 46* 14.2
2007 1125 59.0 14.3 2004 879 14.6 1998 866 13.5 2000 903 Alloy 47
13.3 1888 1217 53.6 14.6 1877 1240 13.0 1884 1237 14.2 1892 1253
Alloy 48* 15.2 1853 1128 59.1 15.0 1854 1130 15.4 1852 1131 Alloy
49 15.3 1982 1409 65.1 15.6 1998 1399 14.2 1964 1381 15.4 2008 1428
Alloy 50* 14.6 1833 1307 64.8 14.7 1846 1325 14.5 1844 1271 14.4
1844 1387 Alloy 51* 15.9 1940 1297 57.5 15.4 1937 1209 16.0 1929
1223 Alloy 52 25.4 1722 314 23.2 24.6 1719 267 23.8 1706 276 28.6
1717 319 Alloy 53 47.3 1492 421 5.0 44.1 1514 420 38.4 1478 401
48.9 1488 420 Alloy 54* 17.7 2012 569 50.8 17.1 2009 1053 17.0 2017
1158 16.8 2023 1140 Alloy 55 35.0 1627 351 20.6 39.6 1656 350 33.0
1657 358 Alloy 56 42.2 1265 388 6.4 41.2 1288 391 45.9 1345 395
47.7 1289 387 *Thickness of 1.2 mm was not achieved in these alloys
due to high strength and equipment limitations. Samples were tested
at thickness from 1.3 to 1.4 mm.
[0062] This Case Example demonstrates properties of the sheet
material from alloys herein with thickness of 1.2 to 1.4 mm and
tested at strain rates from 4.4.times.10.sup.-4 s.sup.-1 to
6.8.times.10.sup.-3 s.sup.-1.
Case Example #2 Sheet Thickness Effect on Tensile Properties of
Alloy 2
[0063] The hot band from Alloy 2 was cold rolled into sheets with
different thicknesses through multiple cold rolling passes. Once
the targeted gauge thickness was reached, samples were cut from
each cold rolled sheet by wire EDM. The samples were annealed under
conditions intended to simulate the thermal exposure expected
during an industrial continuous annealing process. Samples were
wrapped in stainless steel foil to prevent oxidation and loaded
into a preheated furnace at 850.degree. C. Samples were left in the
furnace for 10 minutes while the furnace purged with argon before
being removed and allowed to air cool. The only exception was the
final anneal for the 4.8 mm material. This anneal was an
850.degree. C. 20 min air cooled anneal, as opposed to the 10
minute anneal used for every other thickness. The purpose of this
change was to allow more time for the material to heat up as it was
a much thicker sample. Tensile properties were measured on an
Instron mechanical testing frame (Model 5984), utilizing Instron's
Bluehill control and analysis software. All tests were run at
ambient temperature in displacement control. All samples were
tested at displacement rate of 0.125 mm/s, which resulted in sample
strain rates, calculated from video strain measurements, ranging
from 9.1.times.10.sup.-4 s.sup.-1 to 1.9.times.10.sup.-3 s.sup.-1
depending on several factors including, but not always limited to
mechanical compliance, sample slippage, and settling of the wedge
action grips used.
[0064] The results of tensile testing of the sheet from Alloy 2
processed to different thicknesses are listed in Table 6. In
samples with thickness less than 1.2 mm representing Step 3 in FIG.
1, tensile strength varies from 1100 to 1190 MPa and yield strength
is between 408 and 439 MPa. FIG. 4 and FIG. 5 show the tensile
properties of Alloy 2 sheet as a function of the thickness. Average
tensile elongation is 53.7% for Alloy 2 sheet with thickness
varying from 0.20 to 1.03 mm (as compared to average of 61.5% in
Alloy 2 sheet with thickness of 1.2 mm). Slightly higher elongation
is observed up to 66.4% in thicker sheet samples above 1.2 mm. The
stress-strain curves in FIG. 6 also demonstrate consistent
properties and stress-strain behavior in sheet samples with
different thicknesses.
TABLE-US-00006 TABLE 6 Sheet Thickness Effect on Tensile Properties
of Alloy 2 Ultimate Yield Sample Thickness Tensile Elongation
Tensile Strength Strength (mm) (%) (MPa) (MPa) 4.82 54.7 1164 377
4.81 60.2 1202 380 4.79 57.8 1203 350 3.05 57.5 1222 453 3.04 66.4
1183 462 3.01 65.8 1190 450 1.03 52.3 1190 411 1.03 53.8 1179 410
1.02 62.1 1170 408 1.00 57.6 1186 415 0.77 54.8 1184 432 0.77 53.8
1178 430 0.75 52.2 1180 428 0.53 55.3 1148 417 0.53 53.5 1106 423
0.53 51.7 1163 422 0.41 51.6 1111 438 0.41 53.9 1120 439 0.41 51.1
1100 439 0.21 51.2 1125 434 0.20 51.0 1124 434
[0065] This Case Example demonstrates that high ductility
maintained in the sheet with thickness in a wide range from 4.8 mm
down to as small as 0.2 mm. Reduction in sheet thickness below 1.2
mm results in an average total elongation that is no less than that
in the sheet with 1.2 mm thickness and above minus 7.8%. An average
ultimate tensile strength is 25 MPa less than that in the
corresponding sheet with 1.2 mm thickness and above and average
yield strength is 67 MPa less.
Case Example #3 Thickness Effect on Tensile Properties of Sheet
from Selected Alloys
[0066] The hot band from Alloy 1, Alloy 27, and Alloy 37 was cold
rolled in to sheets with different thicknesses less than 1.2 mm
through multiple cold rolling passes. Once the targeted gauge
thickness was reached, samples were cut from each cold rolled sheet
by wire EDM. The samples were annealed under conditions intended to
simulate the thermal exposure expected during an industrial
continuous annealing process representing final treatment at sheet
processing in Step 2 in FIG. 1. Samples were wrapped in stainless
steel foil to prevent oxidation and loaded into a preheated furnace
at 850.degree. C. Samples were left in the furnace to 10 minutes
while the furnace purged with argon before being removed and
allowed to air cool. Tensile properties were measured on an Instron
mechanical testing frame (Model 5984), utilizing Instron's Bluehill
control and analysis software. All tests were run at ambient
temperature in displacement control. All samples were tested at the
displacement rate of 0.125 mm/s, which resulted in sample strain
rates, calculated from video strain measurements, ranging from
9.1.times.10.sup.-4 s.sup.-1 to 1.9.times.10.sup.-3 s.sup.-1
depending on several factors including, but not always limited to
mechanical compliance, sample slippage, and settling of the wedge
action grips used.
[0067] The results of tensile testing of the sheet from the alloys
processed to different thicknesses are listed in Table 7
representing Step 3 in FIG. 1. For Alloy 1, tensile elongation is
measured in the range from 44.9 to 51.1%, for Alloy 27 in the range
from 63.8 to 73.8%, and for Alloy 37 in the range from 6.0 to 7.0%.
Tensile elongation as a function of the sheet thickness is
illustrated in FIG. 6 for the selected alloys. FIG. 8 and FIG. 9
show the yield strength and ultimate tensile strength of the sheet
with different thicknesses for the selected alloys. The ultimate
tensile strength is in a range from 1203 to 1269 MPa in Alloy 1
sheet, from 972 to 1067 MPa in Alloy 27 sheet, and from 1493 to
1614 MPa in Alloy 37 sheet. Yield strength varies from 375 to 444
MPa in Alloy 1 sheet, from 367 to 451 MPa in Alloy 27 sheet, and
from 612 to 820 MPa in Alloy 37 sheet.
TABLE-US-00007 TABLE 7 Tensile Properties of the Sheet from
Selected Alloys at Thickness < 1.2 mm Tensile Ultimate Tensile
Yield Thickness Elongation Strength Strength Alloy (mm) (%) (MPa)
(MPa) Alloy 1 0.52 49.2 1269 444 0.52 51.1 1247 440 0.52 48.1 1203
433 0.76 49.8 1241 406 0.76 50.7 1238 409 0.77 44.9 1247 413 0.99
46.8 1253 375 1.01 45.4 1262 381 1.01 46.7 1251 384 1.02 47.6 1255
396 1.03 50.3 1237 384 1.04 45.6 1246 396 Alloy 27 0.21 63.8 1067
440 0.21 64.9 1063 445 0.37 67.1 1039 429 0.38 68.6 1040 427 0.38
69.5 1022 425 0.51 68.2 1060 451 0.52 68.5 1056 449 0.75 71.8 1019
413 0.76 71.1 1012 412 1.02 72.9 972 367 1.03 73.8 1005 380 1.04
71.7 1001 369 Alloy 37 0.30 6.4 1579 727 0.32 6.0 1493 782 0.32 6.5
1523 790 0.50 6.6 1603 820 0.51 6.3 1614 754 0.51 6.0 1602 775 0.75
6.7 1602 710 0.77 6.6 1590 612 0.99 6.9 1589 659 1.01 6.8 1588 673
1.01 6.9 1596 648
[0068] This Case Example demonstrates that tensile ductility of
alloys herein is maintained even at sheet thickness as small as 0.2
mm demonstrating an average total elongation no less than that in
the corresponding sheet with 1.2 mm thickness and above minus 7.3%.
An average ultimate tensile strength is a range of .+-.35 MPa of
that in the corresponding sheet with 1.2 mm thickness and above
with the yield strength in a range of .+-.98 MPa.
Case Example #4 Microstructure in Sheet from Selected Alloys at
Different Thicknesses
[0069] The hot band from Alloy 1, Alloy 2, Alloy 27, and Alloy 37
was cold rolled in to sheets with different thicknesses less than
1.2 mm through multiple cold rolling passes. Once the targeted
gauge thickness was reached, samples were cut from each cold rolled
sheet by wire EDM. The samples were annealed under conditions
intended to simulate the thermal exposure expected during an
industrial continuous annealing process. Samples were wrapped in
stainless steel foil to prevent oxidation and loaded into a
preheated furnace at 850.degree. C. The microstructures of the cold
rolled and annealed state were studied by SEM to show the
structural change during processing. To prepare SEM samples, pieces
were cut by EDM from the sheet and mounted in epoxy, and the sheet
cross-sections were polished progressively with 9 .mu.m, 6 .mu.m
and 1 .mu.m diamond suspension solution, and finally with 0.02
.mu.m silica. The SEM study was conducted using an EVO-60 scanning
electron microscope manufactured by Carl Zeiss SMT Inc.
[0070] FIG. 10 shows microstructures in Alloy 1 sheet samples with
different thicknesses. Cold rolled structure is shown in FIG. 10a
and FIG. 10c in the center of the sheet with thickness of 0.7 and
0.5 mm, respectively. The cold rolled sample bears the highly
deformed microstructure in which grain boundaries are difficult to
see. The microstructure in these sheet samples after annealing is
shown in FIG. 10b and FIG. 10d represented by the recrystallized
structure with equiaxed grains and clear grain boundaries.
[0071] FIG. 11 shows microstructures in Alloy 2 sheet samples with
different thicknesses. Cold rolled structure is shown in FIG. 11a,
FIG. 11c and FIG. 11e in the center of the sheet with thickness of
1.0, 0.5 and 0.2 mm, respectively. The cold rolled sample bears the
highly deformed microstructure in which grain boundaries are
difficult to see. The microstructure in these sheet samples after
annealing is shown in FIG. 11b, FIG. 11d and FIG. 11f represented
by recrystallized structure with equiaxed grains and clear grain
boundaries.
[0072] The structure in the sheet samples from Alloy 27 is similar
to Alloy 1 and Alloy 2 and is shown in FIG. 12. The recrystallized
microstructure in the sheet from Alloy 27 has fewer twins as
compared to other studied alloys, as shown in FIG. 12b, FIG. 12d
and FIG. 12f.
[0073] Alloy 37 is a different type of the alloy in which the
annealing does not lead to the typical recrystallized structure
formation. FIG. 13 shows the structures at the center of the sheet
from Alloy 37 with different thicknesses after cold rolling and
after cold rolling and annealing. Only a small difference between
the cold rolled and the annealed structures is observed.
Corresponding samples at different thicknesses have effectively
identical structures.
[0074] This Case Example demonstrates that microstructure is
maintained in alloys herein after annealing of cold rolled sheet
independently from the final sheet thickness.
Case Example #5: Strain Rate Effect on Tensile Ductility of the
Sheet from Alloy 2
[0075] Slabs of Alloy 2 were cast according to the atomic
compositions provided in Table 1. Following casting, the slabs were
hot rolled through successively smaller roll gaps to produce hot
band coils in the range of 2 to 5 mm thick, which were subsequently
subjected to cold rolling and annealing cycles until the targeted
thickness of approximately 1.4 mm was achieved representing sheet
material in Step 2 in FIG. 2. Annealing was done in this case in
the temperature range from 950 to 1050.degree. C.
[0076] The tensile properties of the material were characterized as
a function of strain rate. Tensile samples were tested at 0.0007
s.sup.-1, 0.7 s.sup.-1, 10 s.sup.-1, 100 s.sup.-1, 500 s.sup.-1 and
1200 s.sup.-1 nominal strain rates in the ASTM D638 Type V tensile
geometry shown in FIG. 14. Tensile samples tested at strain rates
from 0.0007 s.sup.-1 to 500 s.sup.-1 were tested on an MTS
servo-hydraulic test frame. Samples were inserted into grips and
load was applied by raising the crosshead at speeds necessary to
produce the nominal strain rates. A slack adapter consisting of a
cup and cone rod assembly was used at strain rates greater than 1
s.sup.-1 to allow the test frame to achieve the targeted constant
strain rate prior to applying load to the specimen. An instrumented
bar was used at 500 s.sup.-1 to mitigate the effects of standing
waves in the test apparatus that occurred during high strain rate
testing. At 1200 s.sup.-1 strain rate, a split Hopkinson bar (SHB)
was used. The SHB device was composed of 25.4 mm diameter 7075 Al
incident and transmission bars, with the test specimen tightly
gripped between the Al bars. Strain gauges were used on the
transmission and incident bars to measure strain in the bars. A
striker tube was launched around the incident tube towards the
striker plate to generate the tensile strain pulse and the strain
within the sample was recorded. A schematic diagram of the SHB is
provided in FIG. 15.
[0077] Strain in the tensile samples was measured by a mechanical
extensometer at 0.0007 s.sup.-1 and 0.7 s.sup.-1 strain rates.
Digital Image Correlation (DIC) was used to measure strain for
samples tested at 10 s.sup.-1, 100 s.sup.-1, and 500 s.sup.-1. Five
tensile samples were tested at all strain rates. In the case of one
sample at 0.0007 s.sup.-1 strain rate, a malfunction occurred that
resulted in the loss of the sample. Two samples tested at 1200
s.sup.-1 did not fail during testing.
[0078] Measured strain at failure is provided in Table 8. The
measured strain is plotted as function of strain rate in FIG. 16.
Table 9 provides the average ductility as measured by tensile
elongation at failure for each nominal strain rate. Note that the
average tensile elongation measured at all strain rates is close to
the overall average of 55.5% across all strain rates. At strain
rates from 0.0007 s.sup.-1 to 500 s.sup.-1, the average tensile
elongation at failure is within approximately .+-.3% of the total
average of all tests. Tests at 1200 s.sup.-1 were measured to
possess higher tensile elongation at failure than all other tests,
however due to the nature of this test methodology these values may
be measured slightly higher than actual values. Ultimate tensile
strength is measured in a range from 944 to 1187 MPa with yield
strength from 347 to 512 MPa (Table 10).
[0079] Tensile properties in Tables 8 through 10 represents sheet
material in Step 3 in FIG. 2.
TABLE-US-00008 TABLE 8 Tensile Elongation of Alloy 2 Sheet Samples
Tested at Different Strain Rates Nominal Strain Strain Elongation
at Rate Measurement Measured Strain Rate Failure (s.sup.-1)
Technique (s.sup.-1) (%) 0.0007 Extensometer 0.000803 62.4 0.0007
Extensometer 0.000768 44.6 0.0007 Extensometer 0.000713 44.9 0.0007
Extensometer 0.000749 59.2 0.7 Extensometer 0.644 57.1 0.7
Extensometer 0.682 53.7 0.7 Extensometer 0.632 54.4 0.7
Extensometer 0.634 54.5 0.7 Extensometer 0.650 52.5 10 DIC 5.83
49.5 10 DIC 6.03 50.4 10 DIC 6.07 54.6 10 DIC 6.02 49.5 10 DIC 5.78
54 100 DIC 65.7 55.7 100 DIC 87.9 52.7 100 DIC 88.5 56.2 100 DIC
86.2 54.5 100 DIC 85.4 57.1 500 DIC 438 57.0 500 DIC 442 57.3 500
DIC 440 56.2 500 DIC 414 57.5 500 DIC 425 56.1 1200 SHB 1169 64.9
1200 SHB 1222 67.7 1200 SHB 1152 63.1
TABLE-US-00009 TABLE 9 Average Tensile Elongation of Sheet from
Alloy 2 at Each Strain Rate Strain Nominal Strain Rate Measurement
Elongation at Failure (s.sup.-1) Technique (%) 0.0007 Extensometer
52.8 0.7 Extensometer 54.4 10 DIC 52.0 100 DIC 55.2 500 DIC 56.8
1200 SHB 65.2 Overall Average 56.0
TABLE-US-00010 TABLE 10 Strength Characteristics of Alloy 2 Sheet
Tested at Different Strain Rates Ultimate Nominal Strain Strain
Measured Yield Tensile Rate Measurement Strain Rate Strength
Strength (s.sup.-1) Technique (s.sup.-1) (MPa) (MPa) 0.0007
Extensometer 0.000803 375 1159 0.0007 Extensometer 0.000768 356
1151 0.0007 Extensometer 0.000713 365 1171 0.0007 Extensometer
0.000749 371 1187 0.7 Extensometer 0.644 354 1014 0.7 Extensometer
0.682 454 992 0.7 Extensometer 0.632 431 1017 0.7 Extensometer
0.634 416 1024 0.7 Extensometer 0.650 442 1006 10 DIC 5.83 455 989
10 DIC 6.03 422 979 10 DIC 6.07 424 980 10 DIC 6.02 450 975 10 DIC
5.78 347 977 100 DIC 65.7 483 956 100 DIC 87.9 499 944 100 DIC 88.5
488 953 100 DIC 86.2 505 956 100 DIC 85.4 459 948 500 DIC 438 425
1020 500 DIC 442 409 1030 500 DIC 440 500 1010 500 DIC 414 444 1030
500 DIC 425 512 1020 1200 SHB 1169 -- 946 1200 SHB 1222 -- 965 1200
SHB 1152 -- 972
[0080] This Case Example demonstrates that tensile ductility of
alloys herein is retained across a relatively large range of strain
rates of 0.007 to 1200 s.sup.-1. A measured average ultimate
tensile strength is 62 MPa lower at higher strain rates and average
yield strength is 59 MPa lower.
Case Example #6 Strain Rate Effect on Microstructure in the Sheet
from Alloy 2
[0081] The microstructures of the samples from sheet from Alloy 2
tested at five different strain rates ranging from 0.0007 s.sup.-1
to 1200 s.sup.-1 (see Case Example #5) were studied by TEM. For TEM
study, pieces are cut from the gauge section of deformed samples by
diamond saw. Grinding and polishing are then undertaken to make
thin foils from the cut pieces. The polishing was conducted
progressively with 9 .mu.m, 6 .mu.m and 1 .mu.m diamond suspension
solution, and finally with 0.02 .mu.m silica. Foils with thickness
of 70 to 80 .mu.m were obtained after the polishing. Discs of 3 mm
in diameter were punched from the foils and the final polishing was
fulfilled with electropolishing using a twin-jet polisher. The
chemical solution used was a 30% Nitric acid mixed in Methanol
base. In case of insufficient thin area for TEM observation, the
TEM specimens may be ion-milled using a Gatan Precision Ion
Polishing System (PIPS). The ion-milling usually is done at 4.5
keV, and the inclination angle is reduced from 4.degree. to
2.degree. to open up the thin area. The TEM studies were done using
a JEOL 2100 high-resolution microscope operated at 200 kV.
[0082] FIG. 17 shows the bright-field TEM images of the sample
tested at 1200 s.sup.-1. It can be seen that deformation twins are
prominent in the high rate deformed sample which are a forming of
twinning which does not occur through mechanical deformation but
during heat treatment. The twins are distinct and sharp, suggesting
that they are newly formed from the deformation. With twinning
being a deformation mode in the sample, phase transformation is
reduced since the deformation twins maintain austenitic structure.
Twinning as a method of deformation can be seen in the sample
deformed at strain rates of 500, 100, 10, and 0.7 s.sup.-1, as
shown in FIG. 18 through FIG. 21. The sample deformed at strain
rate of 0.0007 s.sup.-1 has different structure as can be seen in
FIG. 22 demonstrating a domination of dislocation with phase
transformation during deformation that is evident from the
Feritscope measurements in the sample gauges after deformation. As
shown in FIG. 23, the magnetic phases volume percent, which
correlates to the transformed product phases, is highest in the
case of deformation at low strain rate of 0.0007 s.sup.-1.
[0083] This Case Example demonstrates the alteration of deformation
mechanisms during deformation of the alloys herein with higher
occurrence of twinning with increasing strain rate. Deformation by
twinning at high strain rates suppresses the phase transformation
(i.e. means that the total amount of ferrite produced is reduced)
allowing to the retention of relatively high tensile ductility of
the sheet material in a wide range of strain rates.
Case Example #7 Notch Effect on Tensile Properties of Sheet from
Alloy 2
[0084] Slabs of Alloy 2 were cast according to the atomic
compositions provided in Table 1. Following casting, the slabs were
hot rolled through successively smaller roll gaps to produce hot
band coils, which were subsequently subjected to cold rolling and
annealing cycles until the targeted thickness of approximately 1.4
mm was achieved representing sheet in Step 2 in FIG. 3.
[0085] Tensile specimens were cut from the sheet via wire EDM. The
specimens had two notches, symmetric at about the center of the
width and the length as showed in FIG. 24. Samples were tested in
tension with one grip fixed and the other moving at a fixed rate of
0.125 mm/s displacement rate. Tensile properties were measured on
an Instron mechanical testing frame, utilizing Instron's Bluehill
control and analysis software. All tests were run at ambient
temperature in displacement control. A 50 mm gauge length was used
centered on the notch. Stresses were calculated based on the
nominal width not the notched width (FIG. 24).
[0086] Tensile properties of the Alloy 2 sheet samples as a
function of notch diameter and notch depth are listed in Table 11.
Tensile elongation of notched samples ranged from 12.4% to 40.7%,
yield strength ranged from 298 to 420 MPa, and ultimate tensile
strength ranged from 636 to 1123 MPa. Effect of notch diameter with
constant depth of 0.5 mm on tensile properties of the sheet from
Alloy 2 is illustrated in FIG. 25. Changes in tensile properties of
the sheet with half circle notches as a function of notch diameter
are shown in FIG. 26. This data represents sheet in Step 3 in FIG.
3.
TABLE-US-00011 TABLE 11 Tensile Properties of Notched Specimens
from Alloy 2 Sheet Notch Strain at Ultimate Tensile Diameter Notch
Depth Break Strength Yield Strength (mm) (mm) (%) (MPa) (MPa) 0.35
0.175 22.1 913 407 0.35 0.175 26.6 991 409 0.35 0.175 21.2 909 420
0.5 0.25 17.7 844 416 0.5 0.25 18.9 874 411 0.5 0.25 22.0 923 397 1
0.5 14.4 789 406 1 0.5 17.3 827 386 1 0.5 18.2 862 408 2 1 16.7 802
386 2 1 17.9 839 375 2 1 23.0 875 345 4 2 15.6 764 371 4 2 18.7 816
372 4 2 17.9 811 377 6 3 12.4 636 314 6 3 13.1 646 308 6 3 12.9 651
298 2 0.5 22.8 926 405 2 0.5 26.3 992 405 2 0.5 25.8 992 397 4 0.5
27.4 982 394 4 0.5 32.8 1054 391 4 0.5 31.7 1056 396 6 0.5 34.8
1071 383 6 0.5 40.7 1123 384
[0087] This Case Example demonstrates an increase in tensile
elongation of the notched samples from alloys herein with
increasing notch diameter at constant depth. In the case of
increasing depth, average elongation is shown to be independent of
the notch depth (half circle).
Case Example #8 Ductile Fracture Surface in Notched Sample after
Testing
[0088] SEM fracture analysis was performed on selected notched
specimens from Alloy 2 sheet after tensile testing (see Case
Example #7). Two samples with notch radius of 1.0 and 6.0 mm were
selected for examination (Table 12). The SEM study was conducted
using an EVO-60 scanning electron microscope manufactured by Carl
Zeiss SMT Inc.
TABLE-US-00012 TABLE 12 Samples for SEM Analysis Notch Diameter
Notch Depth Samples (mm) (mm) 1 1.0 0.5 2 6.0 0.5
[0089] In FIG. 27 and FIG. 28, SEM images of fracture surface after
tensile testing are shown for Sample 1 and Sample 2, respectively.
Images are taken from the center of the fracture cross section and
close to the edge. Both samples demonstrated ductile fracture.
There is no difference in fracture mode between the center and the
edge of the fracture cross section although finer structure is
found closer to the edge.
[0090] This Case Example demonstrates that notch introduction into
the sheet material from alloys herein does not cause brittle
catastrophic failure. Notched samples after testing have
demonstrated ductile fracture.
[0091] The alloys herein may be utilized in variety of
applications. For example, the alloys herein may be positioned in
vehicular frame, vehicle chassis or vehicle panel. In addition, the
alloys herein may be utilized for a storage tank, freight car, or
railway tank car. Railway tank cars may specifically include tanks,
jacketed tanks or tanks with a headshield. Other applications
include body armor, metallic shield, military vehicles, and armored
vehicle Such applications apply to the alloys produced according to
any one of FIG. 1, FIG. 2 and/or FIG. 3.
* * * * *