U.S. patent application number 16/078447 was filed with the patent office on 2019-01-24 for high fluidity iron alloy forming process and articles therefrom.
The applicant listed for this patent is DETROIT MATERIALS INC.. Invention is credited to Pedro GUILLEN, Nicholas Anton MOROZ.
Application Number | 20190022736 16/078447 |
Document ID | / |
Family ID | 59685700 |
Filed Date | 2019-01-24 |
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United States Patent
Application |
20190022736 |
Kind Code |
A1 |
MOROZ; Nicholas Anton ; et
al. |
January 24, 2019 |
HIGH FLUIDITY IRON ALLOY FORMING PROCESS AND ARTICLES THEREFROM
Abstract
A process of casting an article includes an iron alloy being
heated to a pour temperature of between 1460.degree. C. and
1650.degree. C. and a fluidity length of greater than 23
millimeters to form a melt. The melt is poured into a mold and
allowed to solidify to the article. The article is then removed
from the mold. A process of forging an article is also provided
that includes an iron alloy workpiece being heated to a temperature
of between 600.degree. C. and 1200.degree. C. The heated workpiece
is then placed into a die set and repeatedly struck with a forging
die. The workpiece flows into the die cavity in response to the
striking. The workpiece is then removed from the die cavity. The
resulting articles and the alloy from which such articles are
formed are also provided.
Inventors: |
MOROZ; Nicholas Anton;
(Wixom, MI) ; GUILLEN; Pedro; (Wixom, MI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
DETROIT MATERIALS INC. |
Wixom |
MI |
US |
|
|
Family ID: |
59685700 |
Appl. No.: |
16/078447 |
Filed: |
February 24, 2017 |
PCT Filed: |
February 24, 2017 |
PCT NO: |
PCT/US2017/019473 |
371 Date: |
August 21, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62299325 |
Feb 24, 2016 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C22C 38/16 20130101;
B22C 9/06 20130101; C22C 38/02 20130101; C22C 38/04 20130101; C22C
38/06 20130101; B22D 11/001 20130101; B21J 5/02 20130101; B21J
13/02 20130101; B22D 23/00 20130101; C22C 38/12 20130101; C22C
38/08 20130101; B21J 1/003 20130101 |
International
Class: |
B21J 5/02 20060101
B21J005/02; B22D 11/00 20060101 B22D011/00; C22C 38/02 20060101
C22C038/02; C22C 38/04 20060101 C22C038/04; C22C 38/06 20060101
C22C038/06; C22C 38/08 20060101 C22C038/08; C22C 38/12 20060101
C22C038/12; C22C 38/16 20060101 C22C038/16 |
Claims
1. A process of casting an article comprising: heating an iron
alloy to a pour temperature of between 1460.degree. C. and
1650.degree. C. and a fluidity length of greater than 23
millimeters to form a melt; pouring the melt into a mold; allowing
the melt to solidify to the article; and removing the article from
the mold.
2. A process of forging an article comprising: heating an iron
alloy workpiece to a temperature of between 600.degree. C. and
1200.degree. C.; inserting the heated workpiece into a die set;
repeatedly striking the workpiece with a forging die; allowing the
workpiece flow into the die cavity; and removing the workpiece from
the die cavity.
3. The process of claim 1 wherein the mold has a minimal interior
dimension reflected in the article of between 1 and 5
millimeters.
4. (canceled)
5. (canceled)
6. The process of claim 1 wherein the pour temperature is between
1460.degree. C. and 1650.degree. C.
7. The process of claim 1 wherein the alloy composition is about
90% Fe, 0.1-2.0% C, 1.5-5% Si, 0.1-0.6% Mn, 0.1-2% Cu, 0.5-5% Ni,
0.01-1% Mo, with the remainder being trace elements and a liquidus
temperature (T.sub.liquidus) of less than 1515.degree. C.
8. The process of claim 1 wherein T.sub.liquidus is 1536-K(% C)-8(%
Si)-5(% Mn)-30(% P)-25(% S)-1.7(% Al)-5(% Cu)-1.5(% Cr)-4(% Ni)-2(%
V)-1(% W)-1.7(% Co)-12.8(% Zr)-7(% Nb)-3(% Ta)-14(% Ti) where K is
a coefficient of 88 for % C greater than 0.5% and is 65 for % C
less than or equal to 0.5%.
9. (canceled)
10. (canceled)
11. (canceled)
12. (canceled)
13. (canceled)
14. (canceled)
15. A steel alloy for a low alloy, medium carbon, for the
production of cast and forged products with a chemical composition
(in weight %) comprising: about 90% Fe, 0.1-2.0% C, 1.5-5% Si,
0.1-0.6% Mn, 0.1-2% Cu, 0.5-5% Ni, 0.01-1% Mo, with the remainder
being trace elements, having a liquidus temperature that is less
than 1515.degree. C.
16. The steel alloy of claim 15 further comprising an additional
0.05-5% Al content by weight percentage.
17. The steel alloy of claim 15 further comprising an additional
0.05-5% Al content by weight percent, and less than 0.01% Si by
weight.
18. The process of claim 2 wherein the mold has a minimal interior
dimension reflected in the article of between 1 and 5
millimeters.
19. The process of claim 2 wherein the pour temperature is between
1460.degree. C. and 1650.degree. C.
20. The process of claim 2 wherein the alloy composition is about
90% Fe, 0.1-2.0% C, 1.5-5% Si, 0.1-0.6% Mn, 0.1-2% Cu, 0.5-5% Ni,
0.01-1% Mo, with the remainder being trace elements and a liquidus
temperature (T.sub.liquidus) of less than 1515.degree. C.
21. The process of claim 2 wherein T.sub.liquidus is 1536-K(%
C)-8(% Si)-5(% Mn)-30(% P)-25(% S)-1.7(% Al)-5(% Cu)-1.5(% Cr)-4(%
Ni)-2(% V)-1(% W)-1.7(% Co)-12.8(% Zr)-7(% Nb)-3(% Ta)-14(% Ti)
where K is a coefficient of 88 for % C greater than 0.5% and is 65
for % C less than or equal to 0.5%.
22. The steel alloy of claim 15 having a tensile strength of at
least 750 MPa.
23. The steel alloy of claim 15 formed to a minimum thickness of
between 1 and 5 millimeters.
24. The steel alloy of claim 15 formed having a surface area to
volume ratio of between 2 and 20.
Description
RELATED APPLICATIONS
[0001] This application claims priority benefit of U.S. Provisional
Application Ser. No. 62/299,325 filed 24 Feb. 2015.
FIELD OF THE INVENTION
[0002] The present invention in general relates to metallurgy and
in particular to process of casting or forging with an iron alloy
composition that can be heated to a low viscosity melt that
facilitates complex shape castings shapes with feature thicknesses
as thin as 1 mm
BACKGROUND OF THE INVENTION
[0003] There is an on-going need for steel components that are both
high strength and easily cast into complex shapes. Traditionally,
low viscosity steel melts suitable for complex casting have been
low strength while high strength steels had melt properties that
precluded complex castings resulting in crude form castings that
needed extensive machining to form complex shapes. As a result, the
cost of high strength steel components has remained high.
[0004] Recent developments in advanced high strength (AHSS) and
ultra-high strength steels (UHSS) have relied heavily on extensive
alloying using high-melting point elements such as vanadium,
nickel, molybdenum, cobalt, tungsten, tantalum, niobium, and
cobalt. These efforts have produced a third generation of advanced
and ultra-high strength steels such as TRIP steel, maraging steel,
and other heat treated steels with exceptional strength and
ductility, focused on lightweighting structural applications. Owing
to the high melt viscosity of these steels, efforts have been
focused on manufacturing steel components through continuous
casting, forgings, and machining parts from billet, as the high
alloy content of these alloys cannot readily be poured to form
geometrically complex net-shape castings.
[0005] Ausferritic alloys with high silicon content (greater than
1% by weight) offer an outstanding combination of strength and
ductility without the need for large amounts of heavy alloying
elements. The application of these ausferritic alloyed steels has
been toward products in sheet form, typically as hot-rolled
products providing high tensile strength with high formability.
However, these ausferritic alloys currently do not offer the low
liquidus temperature and low melt viscosity required to produce
complex castings. As a result, castings with ausferritic alloys
still require considerable amounts of machining to impart desired
complex shapes. Additionally, low melt viscosity castings are prone
to defects such as hot tearing and porosity that reduces
manufacturing throughput.
[0006] Therefore, there exists a need for a process of casting with
an iron alloy chemistry that provides a low liquidus temperature,
which will offer low pour viscosity that allows for the forming of
geometrically complex net-shape castings that are also high
strength and high ductility through subsequent heat treatments of
the cast article. There further exists a need for articles formed
from such a composition with cast thicknesses in areas of as thin
as 1 millimeter.
SUMMARY OF THE INVENTION
[0007] A process of casting an article includes an iron alloy being
heated to a pour temperature of between 1460.degree. C. and
1650.degree. C. and a fluidity length of greater than 23
millimeters to form a melt. The melt is poured into a mold and
allowed to solidify to the article. The article is then removed
from the mold. A process of forging an article is also provided
that includes an iron alloy workpiece being heated to a temperature
of between 600.degree. C. and 1200.degree. C. The heated workpiece
is then placed into a die set and repeatedly struck with a forging
die. The workpiece flows into the die cavity in response to the
striking. The workpiece is then removed from the die cavity. The
resulting articles and the alloy from which such articles are
formed are also provided.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIGS. 1A and 1B are front and rear perspective views,
respectively, of a net-shape casting produced with low-alloy high
fluidity steel in accordance with embodiments of the invention;
[0009] FIG. 1C is a cross-sectional view of the casting that shows
no macroporosity in the casting;
[0010] FIG. 2 is a top perspective view of a fluidity spiral design
used to determine the fluidity lengths of embodiments of inventive
alloys simulated during gravity feeding in a sand mold; and
[0011] FIG. 3 is a graph of fluidity length versus pouring
temperature as measured along the fluidity spiral of FIG. 2 as
simulated using finite element analysis method that shows superior
fluidity of low-alloy high silicon steel of embodiments of the
invention.
DESCRIPTION OF THE INVENTION
[0012] The present invention has utility as an iron alloy
composition that can be heated to a low viscosity pour melt (as
measured by the length of spiral fill) that allows for a casting to
be made with features as thin as 1 mm As a result, a process is
provided by which complex castings are achieved with article with
features as thin as 1 mm and in some inventive embodiments having a
surface area to volume ration (SA/V) of greater than 3 and in other
instance SA/V of between 2.25 and 3.75. The low viscosity pour melt
of the inventive iron alloy compositions allows for complex
castings that could not previously be made, saving on machining and
making cast iron available for parts that were not previously
attainable. The resulting complex-shaped articles are amenable to
subsequent heating, chemical, and hammering treatments to further
modify the article properties. Higher strength and higher ductility
are routinely obtained through subsequent heat treatments.
[0013] It is to be understood that in instances where a range of
values are provided that the range is intended to encompass not
only the end point values of the range but also intermediate values
of the range as explicitly being included within the range and
varying by the last significant figure of the range. By way of
example, a recited range of from 1 to 4 is intended to include 1-2,
1-3, 2-4, 3-4, and 1-4.
[0014] As used herein, "high strength" with respect is defined as
an alloy with a tensile strength of at least 450 MPa. An alloy that
is not high strength is termed comparatively as "low strength".
[0015] As used herein, "high ductility" with respect is defined as
an alloy with percent elongation in tensile fracture of at least
10% for an alloy with tensile strength less than 750 and an
elongation in tensile fracture of at least 5% for an alloy with
tensile strength greater than 750.
[0016] An alloy that is not high ductility is termed comparatively
as "low ductility".
[0017] Embodiments of the inventive steel alloys utilize an iron
alloy composition which exhibits high pour fluidity and high
strength for the production of cast and forged products. Articles
formed according to the present invention have applications in a
variety of fields and articles such as transportation to form
suspension components illustratively including knuckles, gears,
housings, and control arms; agricultural to form ground engagement
tools illustratively including plows, disk harrows, hillers,
furrowers, cultivators, and aerators; defense to form armor and
shielding; seafaring to form hull components; and oil and gas and
industrial fluid management to form pump components and fluid
heads. An exemplary casting produced by an inventive process is
shown in FIGS. 1A-C. The casting 10 in FIGS. 1A and 1B is a
differential housing with sharp transitions from bulk sections
(greater than 25 millimeters (mm)) to thin features (less than 3
mm), without macroporosity, shown in the cut section of the wall 15
in FIG. 1C. The casting 10 is gravity fed cast in a sand mold under
ambient atmosphere. The vane feature 14, channel 16, and fastener
engagement region 12 as shown illustrate thin features formed
according to the present invention that are either thinner than in
conventional steel castings and as such require less or no
machining than conventional castings. Additionally, inventive
castings are formed of high strength materials. The article
depicted in FIGS. 1A and 1B has a SA/V of 3. An inventive casting
is readily formed with thin features as small as 1 mm It is
appreciated that the ability to form high aspect ratio vanes 14 as
depicted in FIG. 1A are particularly advantageous in promoting
radiative cooling of an article during operation.
[0018] A measure of the complex shape casting according to the
present invention is that components with SA/V of greater than 3
are obtained. In still other embodiments articles with SA/V of
between 2 and 20 are obtained. The application to form thinned
walled articles from iron alloys that can have high strength allows
for a considered weight reduction, material savings, and ease of
manufacturing for a number of conventional articles including the
aforementioned.
[0019] To illustrate the differential in SA/V associated with the
present invention, Table 1 provides SA/V values for simple
geometric shapes of a hollow cylinder, hollow sphere, and a square
sheet as a function of thickness.
TABLE-US-00001 TABLE 1 SA/V for a hollow cylinder, hollow sphere
and square sheet Wall thickness SA/V hollow SA/V hollow SA/V square
(mm) cylinder* sphere** sheet*** 1 22.2 20.00 21.3 3 6.9 6.7 8.0 5
4.2 4.1 5.3 10 2.2 2.1 3.3 *.DELTA.radius is wall thickness, height
= 90 mm; **inner radius = 30 mm; ***side = 30 mm
[0020] In comparison to the present invention, a conventional
casting corresponding to that depicted in FIGS. 1A and 1B has a
SA/V of 2.9Iron alloys suitable for use in the present invention
are formulated with a liquidus temperature of less than
1515.degree. C. that also provides an ultimate tensile strength of
at least 750 MPa. It is appreciated that the ultimate tensile
strength is obtained by subjecting an article cast according to the
present invention to subsequent heating protocols.
[0021] It is appreciated that the ultimate tensile strength is
obtained by subjecting an article cast according to the present
invention to subsequent heating protocols. These protocols can
include, but are not limited to, heat treatments detailed in
MIL-H-6875H, which include normalizing, annealing, stress
relieving, austenitizing, quenching, tempering, and hardening for
class A, B, C, and D steels.
[0022] The liquidus temperature, high fluidity, and high strength
of the alloy allows for the creation of cast and, or, forged
articles with complex geometry that are not readily formed with
conventional steels. The tensile strength of the material upon
casting is at least 750 MPa and can even be as high as 924 MPa, as
the effect of small variations in chemical composition and casting
quality a this number.
[0023] The material can be further refined with subsequent heating
protocols could include annealing, quenching and tempering,
quenching and partitioning, and cryogenic treatment. The tensile
strength upon these subsequent heating protocols can range from 770
to 2000 MPa.
[0024] Fluidity is determined using the spiral depicted in FIG. 2.
The measure of melt flow as used herein is detailed in Chapter 3 of
per John Campbell, Castings, 2.sup.nd ed., Butterworth Heineman,
2003. A casting spiral measurement device is detailed in this
reference with respect to FIG. 3.2.
[0025] A process of casting an article is provided according to the
present invention that includes heating an iron alloy to a pour
temperature of between 1475.degree. C. and 1650.degree. C. [PLEASE
CONFIRM] and a fluidity length of greater than 23 millimeters to
form a melt. It is appreciated that the melt temperature when the
molten alloy is poured is a parameter that controls the fluidity
length and therefore the ability to fill cavities in the mold
corresponding to thin features in the complementary article. The
mold used in an inventive process includes a variety of
conventional mold materials including sand and plaster. Resin
bonded sand molds are noted to be particularly well suited for the
complex castings that are formed by the present invention. The
molten material at the pour temperature is then poured into a mold
and allowed to solidify to form the article. The article is then
removed from the mold.
[0026] While the present invention is detailed above with respect
to cast, it is appreciated that the iron alloys of the present
invention are also amenable to hot forging, at or near temperature
above the recrystallization temperature of the alloy, to achieve
complex forgings as well. For the iron alloys detailed herein hot
forging occurs at temperature of between 600.degree. C. and
1200.degree. C. It is appreciated that forging at these
temperatures inhibits strain hardening of the metal during
deformation. In some embodiments of the present invention, hot
forging occurs in a controlled atmosphere as to either gas
composition, pressure, or both to control oxidation. This process
of commonly referred to in the art as isothermal forging. Typical
forging and hot forging are conducted in ambient air; however, it
is appreciated that one can utilize nitrogen, argon, or endothermic
gas mixture atmospheres in order to reduce the risk of surface
oxidation.
[0027] A mold or a forge die according to the present invention has
an interior cavity dimension of between 1 mm and 5 mm that is
imparted to the resulting article. In still other embodiments, such
as that shown in FIGS. 1A and 1B, article features of from 3 mm to
5 mm, or 2 mm to 4 mmm is imparted to an article. In still other
embodiments of the present invention, the thin features are
produced with an aspect ratio (height to thickness) above the other
portions of the articles of between 1 and 10, while in other
embodiments, the aspect ratio is between 1 and 6. The vane 14 and
channel 16 shown in FIGS. 1A and 1B, respectively are exemplary of
such aspect ratios.
[0028] In a specific embodiment of the steel alloy for a low alloy,
medium carbon, for the production of cast and forged products has a
chemical composition (in weight %) of approximately 90% Fe (iron)
with 0.1-2.0% C (carbon), 1.5-5% Si (silicon), 0.1-0.6% Mn
(manganese), 0.1-2% Cu, 0.5-5% Ni (nickel), 0.01-1% Mo
(molybdenum), the remainder being trace elements, where the alloy
composition follows the condition that the calculated liquidus
temperature is less than 1515.degree. C. using the formula as
disclosed by Dinami, Realnih, Jekel Z. Metodami, And Ne Analize. In
"Determination of the solidus and liquidus temperatures of the
real-steel grades with dynamic thermal-analysis methods." Materiali
in Tehnologije 47.5 (2013): pp 569-575: as follows:
T.sub.liquidus=1536-K(% C)-8(% Si)-5(% Mn)-30(% P)-25(% S)-1.7(%
Al)-5(% Cu)-1.5(% Cr)-4(% Ni)-2(% V)-1(% W)-1.7(% Co)-12.8(%
Zr)-7(% Nb)-3(% Ta)-14(% Ti) where the coefficient K is 88 for % C
greater than 0.5% and K is 65 for % C less than or equal to
0.5%.
[0029] In a specific embodiment, the iron alloy above may be formed
with an additional 0.05-5% Al (aluminum) content by weight %. In a
specific embodiment the iron alloy above may be formed with an
additional 0.05-5% Al content by weight %, and less than 0.01% Si
by weight.
[0030] Simulations utilizing finite element analysis methods to
model the solidification of alloys during casting procedures were
conducted, of a gravity fed sand casting of a fluidity spiral 20 as
shown in FIG. 2, to compare the fluidity length along the spiral of
embodiments of the low-alloy high silicon steel alloys compared to
other existing steels. The results of the simulation are shown in
FIG. 3., which show that the length along the spiral before the
alloy created a cold shut (the fluidity length) is longest for the
low-alloy high silicon content material as compared to stainless
steel and chromoly steel for the entire temperature range which
spans from the average liquidus temperature of the steels to the
average solidus temperature of the steels.
EXAMPLES
Example 1
[0031] A medium carbon iron alloy is formed with a chemical
composition (in weight %) of approximately 90% Fe, with 0.1-2.0% C,
1.5-5% Si, 0.1-0.6% Mn, 0.1-2% Cu, 0.5-5% Ni, 0.1-1% Mo
(molybdenum), the remainder being trace elements. This alloy is
cast at a pouring temperature of 1550.degree. C. exhibits a
Fluidity
[0032] Length (L.sub.f) using the Fluidity Test Spiral casting as
shown in FIG. 2 of at least 8.48 mm in a channel cross section of
10.0.times.5.0 mm.
Example 2
[0033] The process of Example 1 is repeated with an alloy with a
chemical composition (in weight %) of approximately 90% Fe, with
0.1-2.0% C, 1.5-5% Si, 0.1-0.6% Mn, 0.1-2% Cu, 0.5-5% Ni, 0.1-1% Mo
(molybdenum), the remainder being trace elements. This alloy cast
at a pouring temperature of 1475.degree. C. exhibits a Fluidity
Length (Lf) using the Fluidity Test Spiral casting shown in Error!
Reference source not found. of at least 1 mm in a channel cross
section of 10.0.times.5.0 mm
Example 3
[0034] The alloy of Example 1 is poured into a mold complementary
to the shape of FIGS. 1 1A and 1B at a pouring temperature of
1550.degree. C. The mold being formed of air set sand. After
allowing the casting to cool, the cast article is removed from the
mold as shown in FIGS. 1A and 1B. Casting gating and sprue were
removed from casting.
Example 4
[0035] A pair of impression die are produced having surfaces
complementary to those depicted in FIGS. 1A and 1B. A billet of the
metal of Example 1 is placed in the first die of the set at a
temperature of 900.degree. C. The first die is attached to an
anvil. A hammer die is shaped as the complement to the first die to
define a cavity corresponding to the article shown in FIGS. 1A and
1B. The hammer is then dropped on the workpiece, causing the metal
to flow and fill the die cavities. The hammer contact with the
workpiece being on the order of milliseconds per strike. The hammer
is dropped 1 to 10 times to complete the forming of the workpiece.
Excess metal is squeezed out of the die cavity as flash. In
contrast to conventional forging that involves successive edging,
blocking, and finish cavities, the article is formed with a single
forging owing to the plasticity of the alloy under forging
conditions. The resulting forging article is heat treated to impart
a final high tensile strength to the article as detailed in Example
1.
[0036] The foregoing description is illustrative of particular
embodiments of the invention, but is not meant to be a limitation
upon the practice thereof. The following claims, including all
equivalents thereof, are intended to define the scope of the
invention.
* * * * *