U.S. patent application number 16/174443 was filed with the patent office on 2020-04-30 for high-strength nodular iron with good weldability and machinability.
The applicant listed for this patent is GM GLOBAL TECHNOLOGY OPERATIONS LLC. Invention is credited to Dale A. Gerard, Huaxin Li, Daniel J. Wilson, Jianghuai Yang, David M. Zini.
Application Number | 20200131606 16/174443 |
Document ID | / |
Family ID | 70327931 |
Filed Date | 2020-04-30 |
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United States Patent
Application |
20200131606 |
Kind Code |
A1 |
Li; Huaxin ; et al. |
April 30, 2020 |
HIGH-STRENGTH NODULAR IRON WITH GOOD WELDABILITY AND
MACHINABILITY
Abstract
A nodular iron alloy and automotive components, such as
differential and drive axle components, are provided. The nodular
iron alloy may include iron, about 3.1-3.3 wt % carbon, about
2.7-4.3 wt % silicon, about 0.15-0.40 wt % manganese, about 0-0.10
wt % magnesium, about 0-0.2 wt % nickel, about 0-0.4 wt % copper,
about 0-0.30 wt % chromium, about 0-0.03 wt % phosphorus, and about
0-0.02 wt % sulfur. The nodular iron alloy may have an ultimate
tensile strength of at least 620 MPa as-cast. This alloy possesses
favorable weldability to weld with steel components without
substantial preheating or post heat treatment for a strong and
tough weldment, and it has good machinability to facility
comprehensive machining operations.
Inventors: |
Li; Huaxin; (Rochester
Hills, MI) ; Yang; Jianghuai; (Rochester Hills,
MI) ; Wilson; Daniel J.; (Novi, MI) ; Gerard;
Dale A.; (Bloomfield Hills, MI) ; Zini; David M.;
(Novi, MI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
GM GLOBAL TECHNOLOGY OPERATIONS LLC |
Detroit |
MI |
US |
|
|
Family ID: |
70327931 |
Appl. No.: |
16/174443 |
Filed: |
October 30, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C22C 37/04 20130101;
C22C 37/10 20130101; C22C 37/08 20130101 |
International
Class: |
C22C 37/10 20060101
C22C037/10; C22C 37/04 20060101 C22C037/04; C22C 37/08 20060101
C22C037/08 |
Claims
1. A nodular iron alloy comprising: iron; about 3.1 to about 3.3
weight percent carbon; about 2.7 to about 4.3 weight percent
silicon; and about 0.15 to about 0.40 weight percent manganese.
2. The nodular iron alloy of claim 1, wherein the silicon is
provided in an amount of about 3.5 to about 4.1 weight percent.
3. The nodular iron alloy of claim 2, wherein the iron is provided
in an amount of at least 86.55 weight percent.
4. The nodular iron alloy of claim 3, further comprising magnesium
in an amount not exceeding 0.10 weight percent.
5. The nodular iron alloy of claim 4, further comprising nickel in
an amount not exceeding 0.2 weight percent.
6. The nodular iron alloy of claim 5, further comprising copper in
an amount not exceeding 0.4 weight percent.
7. The nodular iron alloy of claim 6, further comprising chromium
in an amount not exceeding 0.30 weight percent.
8. The nodular iron alloy of claim 7, further comprising sulfur in
an amount not exceeding 0.02 weight percent.
9. The nodular iron alloy of claim 8, further comprising phosphorus
in an amount not exceeding 0.03 weight percent.
10. The nodular iron alloy of claim 3, wherein the nodular iron
alloy has an ultimate tensile strength greater than 620 MPa
as-cast.
11. The nodular iron alloy of claim 10, having an elongation of
greater than 6%.
12. The nodular iron alloy of claim 3, wherein the nodular iron
alloy is substantially free of cobalt and molybdenum.
13. The nodular iron alloy of claim 11, wherein the iron is present
in an amount of 65-85% of a ferrite microstructure and in an amount
of 15-35% of a pearlite microstructure, wherein the iron surrounds
a plurality of graphite nodules.
14. An automotive component created from a nodular alloy according
to claim 3.
15. The automotive component of claim 14, wherein the automotive
component is one of a differential component and a drive axle
component.
16. A nodular iron alloy consisting essentially of: about 3.1 to
about 3.3 weight percent carbon; about 2.7 to about 4.3 weight
percent silicon; about 0.15 to about 0.40 weight percent manganese;
0 to about 0.10 weight percent magnesium; 0 to about 0.2 weight
percent nickel; 0 to about 0.4 weight percent copper; 0 to about
0.30 weight percent chromium; 0 to about 0.03 weight percent
phosphorus; 0 to about 0.02 weight percent sulfur; and the balance
iron.
17. The nodular iron alloy of claim 16, wherein the silicon is
provided in an amount of about 3.5 to about 4.1 weight percent.
18. The nodular iron alloy of claim 17, wherein the nodular iron
alloy has an ultimate tensile strength greater than 620 MPa
as-cast.
19. The nodular iron alloy of claim 18, the nodular iron alloy
being substantially free of cobalt and molybdenum, wherein the iron
is present in an amount of 65-85% of a ferrite microstructure and
in an amount of 15-35% of a pearlite microstructure, and wherein
the iron surrounds a plurality of graphite nodules.
20. An automotive component created from a nodular iron alloy
according to claim 16.
Description
FIELD
[0001] The present disclosure relates generally to iron alloys, and
more particularly, to iron alloys that are nodular and have a
desired strength for weldability and machinability, as well as
components made therefrom, such as differential and drive axle
components.
INTRODUCTION
[0002] Welded front wheel drive differential carriers reduce both
weight and cost compared to conventional bolt-joined structures.
However, traditional high-strength ductile irons, such as SAE D5506
and D7003 have poor weldability to steel and poor machinability due
to a high percentage of pearlite in the matrix (e.g., about
70-100%). A high concentration of pearlite generally results in low
weldability, low machinability, and low fracture toughness. On the
other hand, for ductile irons, the more of the pearlite phase, the
higher the strength. High strength is generally desired in many
automotive components.
[0003] Low toughness of the weld heat affected zone (HAZ) in
ductile iron makes the weld very sensitive to welding cracking. For
example, because of a high pearlite volume in D7003, welding is
very difficult without complex welding procedures, such as those
involving preheating and post-welding heat treatment.
SUMMARY
[0004] This disclosure provides a new high-strength nodular iron
alloy that has desirable weldability and machinability. The new
nodular iron alloy may have, for example, an ultimate tensile
strength of at least 620 MPa and an elongation of at least 6%. The
high-strength nodular ductile iron alloy may have a
ferrite/pearlite matrix with the pearlite phase being no greater
than 35%. Weld heat affected zone (HAZ) toughness and fatigue
strength are enhanced, and machining costs may be lowered though
the use of this new ductile iron alloy.
[0005] In one example, which may be combined with or separate from
the other examples and features provided herein, a nodular iron
alloy is provided containing: iron, about 3.1 to about 3.3 weight
percent carbon, about 2.7 to about 4.3 weight percent silicon, and
about 0.15 to about 0.40 weight percent manganese.
[0006] In another example, which may be combined with or separate
from the other examples given herein, a nodular iron alloy is
provided that consists essentially of: about 3.1 to about 3.3
weight percent carbon, about 2.7 to about 4.3 weight percent
silicon, about 0.15 to about 0.40 weight percent manganese, 0 to
about 0.10 weight percent magnesium, 0 to about 0.2 weight percent
nickel, 0 to about 0.4 weight percent copper, 0 to about 0.30
weight percent chromium, 0 to about 0.03 weight percent phosphorus,
0 to about 0.02 weight percent sulfur, and the balance iron.
[0007] Additional features may be optionally provided, including
but not limited to the following: wherein the silicon is provided
in an amount of about 3.5 to about 4.1 weight percent; wherein the
iron is provided in an amount of at least 86.55 weight percent; the
nodular iron alloy further comprising magnesium in an amount not
exceeding 0.10 weight percent; the nodular iron alloy further
comprising nickel in an amount not exceeding 0.2 weight percent;
the nodular iron alloy further comprising copper in an amount not
exceeding 0.4 weight percent; the nodular iron alloy further
comprising chromium in an amount not exceeding 0.30 weight percent;
the nodular iron alloy further comprising sulfur in an amount not
exceeding 0.02 weight percent; the nodular iron alloy further
comprising phosphorus in an amount not exceeding 0.03 weight
percent; wherein the nodular iron alloy has an ultimate tensile
strength greater than 620 MPa as-cast; the nodular iron alloy
having an elongation of greater than 6%; wherein the nodular iron
alloy is substantially free of cobalt and molybdenum; wherein the
iron is present in an amount of 65-85% of a ferrite microstructure
and in an amount of 15-35% of a pearlite microstructure; and
wherein the iron surrounds a plurality of graphite nodules.
[0008] Further additional features may be included, including but
not limited to the following: an automotive component being created
from any variation of the nodular iron alloy; and the automotive
component being a differential component or a drive axle
component.
[0009] The above features and advantages, and other features and
advantages of the present disclosure, will be readily apparent from
the following detailed description of the many aspects of the
present disclosure when taken in connection with the accompanying
drawings and appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] The drawings are provided for illustration purposes only and
are not intended to limit this disclosure or the claims appended
hereto.
[0011] FIG. 1 is an enlarged view of a nodular iron alloy
illustrating the microstructure thereof, in accordance with the
principles of the present disclosure; and
[0012] FIG. 2 is a perspective view of a differential assembly
having components formed of a nodular iron alloy in accordance with
the principles of the present disclosure.
DETAILED DESCRIPTION
[0013] Nodular ductile iron alloys having desirable strength,
weldability, and machinability are provided. These nodular iron
alloys are particularly useful for cast automotive components that
undergo large loads, fatigue, and a significant amount of machining
operations, as well as being welded to another component. The
automotive components may be implemented as cast, which saves on
additional steps and costs. For example, components formed of the
disclosed nodular iron alloy may be laser-welded to steel without
preheating or post-welding heat treatments. Heat affected zone
hardness/brittleness may be lower than that of conventional iron
alloys, resulting in an improvement to the welded zone's fracture
toughness and fatigue properties.
[0014] The nodular iron alloys disclosed herein contain iron,
carbon, silicon, manganese, and the nodular iron alloys may also
contain phosphorus, sulfur, nickel, copper, chromium, and
magnesium.
[0015] The nodular iron alloys disclosed herein may include iron
and by weight about 3.1 to about 3.3 weight percent (or exactly
3.1-3.3 wt %) carbon, by weight about 3.5 to about 4.1 weight
percent (or exactly 3.5-4.1 wt %) silicon, by weight about 0.15 to
about 0.40 weight percent (or exactly 0.15-0.40 wt %) manganese. In
some cases, the silicon may be provided in amounts as low as about
2.7 weight percent or as high as about 4.3 weight percent, and a
carbon equivalent of about 4.2 to about 4.4 weight percent is
maintained.
[0016] The iron may be provided in an amount of at least 86.55
weight percent. The nodular iron alloys may also include one or
more of the following: magnesium in an amount not exceeding 0.10
weight percent; nickel in an amount not exceeding 0.2 weight
percent; copper in an amount not exceeding 0.4 weight percent;
chromium in an amount not exceeding 0.30 weight percent; phosphorus
in an amount not exceeding 0.03 weight percent; and sulfur in an
amount not exceeding 0.02 weight percent. For example, Table 1
shows a first example of the nodular iron alloy, which contains
iron, carbon, silicon, manganese, and which may also contain
phosphorus, sulfur, magnesium, nickel, copper, and chromium. The
iron may be provided in an amount of at least 86.55 weight
percent.
TABLE-US-00001 TABLE 1 First Example of a New Nodular Iron Alloy
Carbon C Si Mn P S Cu Ni Cr Mg Equivalent (wt %) (wt %) (wt %) (wt
%) (wt %) (wt %) (wt %) (wt %) (wt %) CE (wt %) Fe 3.1-3.3 2.7-4.3
0.15-0.40 0-0.03 0-0.02 0-0.4 0-0.2 0-0.30 0-0.10 4.2-4.4
Balance
[0017] In another example, Table 2 shows an example of the nodular
iron alloy, which contains iron, carbon, silicon, manganese, and
which may also contain phosphorus, sulfur, magnesium, nickel,
copper, and chromium. In this second example, the silicon has a
smaller range of possible amounts, by weight percent. As before,
the iron may be provided in an amount of at least 86.55 weight
percent.
TABLE-US-00002 TABLE 2 Second Example of a New Nodular Iron Alloy
Carbon C Si Mn P S Cu Ni Cr Mg Equivalent (wt %) (wt %) (wt %) (wt
%) (wt %) (wt %) (wt %) (wt %) (wt %) CE (wt %) Fe 3.1-3.3 3.5-4.1
0.15-0.40 0-0.03 0-0.02 0-0.4 0-0.2 0-0.30 0-0.10 4.2-4.4
Balance
As with Table 1, it should be understood that the new nodular iron
alloy can have any combination of the listed elements above in
Table 2, and need not include all of them.
[0018] Referring now to FIG. 1, a nodular iron alloy 10 is
illustrated, which may have a microstructure developed from a
composition such as that of Table 1. A plurality of graphite
nodules 12 are present, and iron 14 surrounds the graphite nodules
12. Of the iron 14 surrounding the graphite nodules 12, 65-85% of
the iron has a ferrite microstructure 16, and only 15-35% has a
pearlite microstructure 18. In one example, the iron 14 may be
provided with about 20% being pearlite and with about 80% being
ferrite. Generally, the pearlite microstructure 18 surrounds the
ferrite microstructure 16, and the ferrite microstructure 16 is
disposed directly adjacent to the nodules 12. The ferrite
microstructure 16 appears lighter than the pearlite microstructure
18 in FIG. 1, upon a regular etching procedure for metallographic
characterization.
[0019] The nodular iron alloy 10 may have an ultimate tensile
strength, for example, of at least 620 MPa, as-cast. In some
examples, the ultimate tensile strength of the as-cast nodular iron
alloy may be in the range of about 620 to about 700 MPa.
Accordingly, the nodular iron alloy 10 has sufficient strength for
use in high-load automotive components, such as differential and
drive axle components, but is also machinable and weldable. The
nodular iron alloy 10 may have, for example, at least 6%
elongation.
[0020] The nodular iron alloys described herein may be used to
manufacture an automotive component, which may be, in some cases, a
cast automotive propulsion system component. Therefore, it is
within the contemplation of the inventors herein that the
disclosure extends to automotive components, including but not
limited to differential components, drive axle components for both
front and rear axles, axle shafts, and the like. For example,
referring to FIG. 2, a differential assembly 200 is illustrated,
which may have components made of any variation of the nodular iron
alloy described herein, and which may be cast. For example, the
differential assembly 200 has a differential carrier 202 that may
be formed of a variation of the nodular iron alloy described
herein. As such, the differential carrier 202 may be effectively
welded via weld joints 204, 206 to adjacent components. More
specifically, the differential carrier 202 may be welded via an
axial weld joint 204 to an external ring gear 208 for further
connection to a transmission assembly. In the alternative, the
components could be arranged such that the weld joint 204 could be
a radial weld joint. Further, the differential carrier 202 may be
welded, for example, by a radial weld joint 206 to another
component, such as the cover 210. In this example, the external
ring gear 208 and the cover 210 are formed of steel, and the
differential carrier 202 formed of the nodular iron alloy disclosed
herein forms a good weld with these steel components.
[0021] The differential carrier 202 may house side gears 212, 214
that are connected to half shafts 216, 218 and differential pinion
gears 220, 222 that are connected to that may be connected to the
shaft 224. Any of the components of the differential assembly 200
may be formed of any variation of the nodular iron alloy disclosed
herein. Accordingly, the components of the differential assembly
200, such as the differential carrier 202, are machinable,
weldable, and of sufficient strength to be used in automotive
applications. The present iron alloys may also be useful in gas and
oil industry components and general industrial components.
[0022] Furthermore, while the above examples are described
individually, it will be understood by one of skill in the art
having the benefit of this disclosure that amounts of elements
described herein may be mixed and matched from the various examples
within the scope of the appended claims. It is further understood
that any of the above described concepts can be used alone or in
combination with any or all of the other above described
concepts.
* * * * *