U.S. patent application number 15/875042 was filed with the patent office on 2018-08-16 for methods of forming components utilizing ultra-high strength steel and components formed thereby.
The applicant listed for this patent is Magna Powertrain, Inc.. Invention is credited to David Dorigo, John Sabo, Sokol Sulaj.
Application Number | 20180230563 15/875042 |
Document ID | / |
Family ID | 63106754 |
Filed Date | 2018-08-16 |
United States Patent
Application |
20180230563 |
Kind Code |
A1 |
Sabo; John ; et al. |
August 16, 2018 |
METHODS OF FORMING COMPONENTS UTILIZING ULTRA-HIGH STRENGTH STEEL
AND COMPONENTS FORMED THEREBY
Abstract
Components and methods for forming components utilizing
ultra-high strength steel are provided. A first method includes the
steps of providing a blank of ultra-high strength steel, cold
forming the blank into an unfinished component, and applying a
coating to the outer surface of the unfinished component that is
adapted to inhibit the formation of a ferrite soft layer on the
component during heating thereof. A second method includes the
steps of providing a blank of heavy gauge thickness ultra-high
strength steel, cold forming the blank into a finished component,
heating the finished component and quenching the component without
the use of tooling.
Inventors: |
Sabo; John; (Caledon,
CA) ; Sulaj; Sokol; (Etobicoke, CA) ; Dorigo;
David; (Oakville, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Magna Powertrain, Inc. |
Concord |
|
CA |
|
|
Family ID: |
63106754 |
Appl. No.: |
15/875042 |
Filed: |
January 19, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62459262 |
Feb 15, 2017 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C21D 2201/00 20130101;
C21D 1/70 20130101; C21D 8/005 20130101; C21D 7/02 20130101; C21D
9/0068 20130101; C21D 1/673 20130101; C22C 2202/00 20130101; C21D
6/00 20130101; C22C 38/32 20130101 |
International
Class: |
C21D 1/70 20060101
C21D001/70; C21D 1/673 20060101 C21D001/673; C21D 6/00 20060101
C21D006/00; C21D 7/02 20060101 C21D007/02; C21D 8/00 20060101
C21D008/00; C21D 9/00 20060101 C21D009/00; C22C 38/32 20060101
C22C038/32 |
Claims
1. A method of forming a component utilizing ultra-high strength
steel including the steps of: providing a blank of ultra-high
strength steel; cold forming the blank into an unfinished
component; applying a coating to the outer surface of the
unfinished component, wherein the coating is adapted to inhibit the
formation of a ferrite soft layer on the unfinished component
during heating of the component; heating the unfinished component;
and quenching the unfinished component.
2. The method as set forth in claim 1 wherein the outer surface of
the unfinished component includes at least a first portion and a
second portion, and wherein applying a coating to the outer surface
of the unfinished component includes applying the coating to only
the first portion of the outer surface of the component.
3. The method as set forth in claim 2 wherein the first portion of
the outer surface of the unfinished component extends about an
opening defined by the outer surface such that the coating is
applied about the opening.
4. The method as set forth in claim 1 wherein the coating is
applied to at least substantially the entire outer surface of the
unfinished component.
5. The method as set forth in claim 1 wherein the coating includes
at least one of a nickel electrolyte coating, a high-temperature
graphite oil, or a water-based ceramic coating.
6. The method as set forth in claim 1 wherein the component is at
least one of a differential housing, a CVT plunger, inner diameter
splines of a clutch housing, and external gears.
7. A method of forming a component utilizing ultra-high strength
steel including the steps of: providing a blank of heavy gauge
thickness ultra-high strength steel; cold forming the blank into a
finished component; heating the finished component; and quenching
the finished component without the use of tooling.
8. The method as set forth in claim 7 wherein a thickness of the
blank is between approximately 3.5 and 6.5 mm.
9. The method as set forth in claim 7 wherein the blank has the
composition of: carbon 0.08 to 0.33 wt %; manganese 0.8 to 1.50 wt
%; boron 0.0005 to 0.005 wt %; silicon less than or equal to 0.50
wt %; phosphorous less than or equal to 0.030 wt %; sulfar less
than or equal to 0.0025 wt %; and chromium less than or equal to
0.35 wt %.
10. The method as set forth in claim 7 wherein the component is at
least one of a differential housing, a CVT plunger, inner diameter
splines of a clutch housing, and external gears.
11. The method as set forth in claim 7 wherein heating the finished
component includes heating the component with one of an electric
furnace, a gas furnace, or an induction heat source.
12. The method as set forth in claim 7 wherein heating the finished
component includes heating the finished component to 930 degrees
Celsius.
13. The method as set forth in claim 7 wherein quenching the
finished component includes quenching only a portion of the
finished component.
14. The method as set forth in claim 7 wherein quenching the
finished component includes quenching the entire finished
component.
15. A method of forming a powertrain component for a vehicle
utilizing ultra-high strength steel including the steps of:
providing a blank of ultra-high strength steel; cold forming the
blank into an unfinished powertrain component; applying a coating
to the outer surface of the unfinished powertrain component,
wherein the coating is adapted to inhibit the formation of a
ferrite soft layer on the unfinished component during heating of
the component; heating the unfinished powertrain component; and
quenching the unfinished powertrain component.
16. The method as set forth in claim 15 wherein the outer surface
of the unfinished powertrain component includes at least a first
portion and a second portion, and wherein applying a coating to the
outer surface of the unfinished powertrain component includes
applying the coating to only the first portion of the outer surface
of the component.
17. The method as set forth in claim 6 wherein the first portion of
the outer surface of the unfinished powertrain component extends
about an opening defined by the outer surface such that the coating
is applied about the opening.
18. The method as set forth in claim 15 wherein the coating is
applied to at least substantially the entire outer surface of the
unfinished powertrain component.
19. The method as set forth in claim 15 wherein the coating
includes at least one of a nickel electrolyte coating, a
high-temperature graphite oil, or a water-based ceramic
coating.
20. The method as set forth in claim 15 wherein the unfinished
powertrain component is at least one of a differential housing, a
CVT plunger, inner diameter splines of a clutch housing, and
external gears.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Patent Application Ser. No. 62/459,262 filed on Feb. 15, 2017, and
titled "Methods of Forming Components Utilizing Ultra-High Strength
Steel and Components Formed Thereby", the entire disclosure of
which is hereby incorporated by reference.
FIELD
[0002] The present disclosure relates generally to methods of
forming components from ultra-high strength steel, such as boron
steel, and to components formed by such methods.
BACKGROUND
[0003] Ultra-high strength steel is currently used in building
construction and static automotive structures, e.g., vehicle bodies
and frames. The use of ultra-high strength steel generally allows
the weights of these structures to be reduced. Additionally, in
automotive structures, the ultra-high strength steel enables the
absorption of impact energy and minimizes intrusion into occupant
seating areas. Although ultra-high strength steel can be made
extremely strong, other properties such as formability,
weldability, and impact toughness may be negatively affected,
resulting in structures which may be more prone to cracking and
fracture.
[0004] Power transmission components for automotive vehicles, such
as clutch assemblies having clutch plates within a clutch housing
and clutch hub are well-known. Such clutch housings have a
generally cylindrical or cup-shaped body and an open end. The
cylindrical or cup-shaped body is formed from a sheet metal blank
and has a plurality of spline teeth formed thereon. The clutch
plates fit within the clutch housing and engage the spline teeth.
The clutch hub can also be a formed sheet metal component and is
typically connected to a transmission shaft.
[0005] Powertrain components including clutch housings and hubs are
commonly made of aluminum or high strength low alloy steel (HSLA)
rather than ultra-high strength steel, such as boron steel.
Aluminum or HSLA steel is used primarily because of its
formability. Specifically, these types of materials are high
strength materials which can achieve a specific geometric dimension
or shape and have a specific tolerance required. Consequently,
aluminum or HSLA may be used in powertrain components including
parts of an automatic transmission easily, efficiently, and at a
low-cost.
[0006] Typically, components such as reaction shells, clutch
housings, and hubs made of aluminum or HSLA are formed using one or
a combination of cold-forming or stamping processes and thermal
heat treatments to obtain the desired shape, performance, and
strength characteristics. Additionally, the structures such as the
plurality of spline teeth of the clutch housing may be formed
easily by using a series of rollers. Similar processes also may be
used to form other powertrain components such as planetary carriers
used in differentials and various covers used in a vehicle
powertrain.
[0007] Ultra-high strength steel lacks formability using the
conventional cold-forming technologies discussed above. Use of
conventional cold-forming technologies with ultra-high strength
steel typically does not result in the formation of required
geometric dimensions and tolerances. However, there is a desire by
manufacturers and suppliers to utilize ultra-high strength steel in
forming automotive components such as power transmission components
for similar reasons as those discussed above when used in static
applications of automotive structures (e.g. reduced component
weight and improved absorption of impact energy).
[0008] As such, a need exists for components, such as clutch
housings and hubs, to be formed from ultra-high strength steel,
such as boron steel. Additionally, there is a need for an improved
method for forming the same.
SUMMARY
[0009] This section provides a general summary of the inventive
concepts associated with the present disclosure and is not intended
to represent a comprehensive disclosure of its full scope or all of
its features, object, aspects and advantages. Components formed
with ultra-high strength steel and methods of forming these
components from ultra-high strength steel are provided.
[0010] In accordance with one aspect of the present disclosure, a
method for forming a component from ultra-high strength steel
includes pre-forming, such as via cold-forming, a blank of
ultra-high strength steel, such as a flat blank of ultra-high
strength steel, into a predetermined shape. The method also
includes applying a coating to the outer surface and/or other
exposed areas of the component, wherein the coating is configured
to eliminate or reduce the formation of a ferrite soft layer that
can be formed as a result of scale/decarburization during heat
treatments of the component. The application of the coating
therefore increases the strength of the component by preventing the
formation of the ferrite soft layer.
[0011] In accordance with another aspect of present disclosure, a
further method for forming a component utilizing ultra-high
strength steel is provided. The method includes the step of
providing a blank of heavy gauge, ultra-high strength steel and
forming the blank into a component. Next, the method includes the
steps of heating the component. The method proceeds with quenching
the component without the use of tooling. The use of tooling is not
required for thicker walled components according to the subject
method because the thicker material undergoes minimal distortion
during cooling and such components are typically machined to final
critical tolerances. Utilizing the subject method provides a
quicker quenching process which leads to decreased overall cycle
time
DRAWINGS
[0012] Other advantages of the present disclosure will be readily
appreciated, as the same becomes better understood by reference to
the following detailed description when considered in connection
with the accompanying drawings wherein:
[0013] FIG. 1 is a perspective view of a clutch housing and a
clutch hub in accordance with an exemplary embodiment of the
present disclosure;
[0014] FIG. 2 is a cross-sectional view along 2-2 of FIG. 1;
[0015] FIG. 3 is a perspective view of a clutch housing having a
plurality of spline teeth for engaging a clutch plate in accordance
with the exemplary embodiment of the present disclosure;
[0016] FIG. 4 is a flowchart of a method for forming a power
transmission component utilizing ultra-high strength steel in
accordance with the exemplary embodiment of the present
disclosure;
[0017] FIG. 5 is a flowchart of a method for forming a power
transmission component utilizing ultra-high strength steel in
accordance with the exemplary embodiment of the present
disclosure;
[0018] FIG. 6 is a flowchart of a method for forming a power
transmission component utilizing ultra-high strength steel in
accordance with an exemplary embodiment of the present
disclosure;
[0019] FIG. 7 is a flowchart of a method for forming a power
transmission component utilizing ultra-high strength steel in
accordance with an exemplary embodiment of the present
disclosure;
[0020] FIG. 8 is a perspective view of a clutch hub in accordance
with a second embodiment of the present disclosure;
[0021] FIG. 9 is a perspective view of a continuously variable
transmission (CVT) plunger in accordance with a third embodiment of
the present disclosure;
[0022] FIG. 10 is a perspective view of a CVT cylinder in
accordance with a fourth embodiment of the present disclosure;
[0023] FIG. 11 is a perspective view of a planetary carrier in
accordance with a fifth embodiment of the present disclosure;
[0024] FIG. 12A is a perspective view of a reaction shell in
accordance with a sixth embodiment of the present disclosure;
[0025] FIG. 12B is a perspective view of a reaction shell in
accordance with the sixth embodiment of the present disclosure;
[0026] FIG. 13A is a perspective view of a differential housing in
accordance with a seventh embodiment of the present disclosure;
[0027] FIG. 13B is a cross-sectional view along 13B-13B of FIG.
13A;
[0028] FIG. 13C is a cross-sectional view along 13C-13C of FIG.
13A;
[0029] FIG. 14 is a perspective view of a differential cover in
accordance with a eighth embodiment of the present disclosure;
[0030] FIG. 15A is a perspective view of a torque converter cover
in accordance with a ninth embodiment of the present
disclosure;
[0031] FIG. 15B is a front view of a front portion of the torque
converter cover shown in FIG. 15A;
[0032] FIG. 15C is a front view of a back portion of the torque
converter cover shown in FIG. 15A;
[0033] FIG. 16 is a perspective view of an oil pan in accordance
with an eleventh embodiment of the present disclosure;
[0034] FIG. 17 is a perspective view of a CVT plunger in accordance
with an eleventh embodiment of the present disclosure;
[0035] FIG. 18 is a perspective view of a housing of a differential
in accordance with a twelth embodiment of the present
disclosure;
[0036] FIG. 19 is a perspective view of a reaction shell in
accordance with a thirteenth embodiment of the present
disclosure;
[0037] FIG. 20 is a flowchart of a method for forming a power
transmission component utilizing ultra-high strength steel wherein
a coating is applied to the component prior to heat treating in
accordance with an exemplary embodiment of the present
disclosure;
[0038] FIG. 21 is a magnified view of a component that was
partially coated in accordance with the method illustrated in FIG.
20, illustrating the fatigue strength of the coated and uncoated
regions;
[0039] FIG. 22 is a magnified view of a component that was
partially coated in accordance with the method illustrated in FIG.
20, illustrating the fatigue strength of the coated and uncoated
regions;
[0040] FIG. 23 is a perspective view of a cylinder of a CVT
transmission in accordance with a fourteenth embodiment of the
present disclosure;
[0041] FIG. 24 is a perspective view of a housing of a CVT
transmission in accordance with a fifteenth embodiment of the
present disclosure;
[0042] FIG. 25 is a perspective view of a planetary carrier in
accordance with a sixteenth embodiment of the present
disclosure;
[0043] FIG. 26 is a perspective view of a rotary carrier in
accordance with a seventeenth embodiment of the present
disclosure;
[0044] FIG. 27 is a flowchart of a method for forming a power
transmission component utilizing ultra-high strength steel wherein
no tooling is used during quenching in accordance with an exemplary
embodiment of the present disclosure;
[0045] FIG. 28 is a chart illustrating temperature vs carbon
content of parts made in accordance with an exemplary method of the
present disclosure;
[0046] FIG. 29 a top view of a component made in accordance with an
exemplary method of the present disclosure, wherein testing points
are labeled; and
[0047] FIG. 30 is a chart illustrating testing data for hardness vs
distance at the testing points labeled in FIG. 29.
DETAILED DESCRIPTION
[0048] Detailed examples of the present disclosure are disclosed
herein; however, it is to be understood that the disclosed examples
are merely exemplary and may be embodied in various and alternative
forms. It is not intended that these examples illustrate and
describe all possible forms of the disclosure. Rather, the words
used in the specification are words of description rather than
limitation, and it is understood that various changes may be made
without departing from the spirit and scope of the disclosure.
[0049] As those of ordinary skill in the art will understand
various features of the present disclosure as illustrated and
described with reference to any of the Figures may be combined with
features illustrated in one or more other Figures to produce
examples of the present disclosure that are not explicitly
illustrated or described. The combinations of features illustrated
provide representative examples for typical applications. However,
various combinations and modifications of the features consistent
with the teachings of the present disclosure may be desired for
particular applications or implementations.
[0050] Example embodiments of components formed from ultra-high
strength steel constructed in accordance with the present
disclosure will now be more fully described. These example
embodiments are primarily directed to powertrain components.
Moreover, each of the exemplary embodiments is provided so that
this disclosure is thorough and fully conveys the scope of the
inventive concepts, features and advantages to those skilled in the
art. To this end, numerous specific details are set forth to
provide a thorough understanding of each of the embodiments
associated with the present disclosure. However, as will be
apparent to those skilled in the art, not all specific details
described herein need to be employed, the example embodiments may
be embodied in many different forms, and that neither should be
construed or interpreted to limit the scope of the disclosure.
[0051] FIGS. 1-3 show various views of a clutch housing 10 in
accordance with an exemplary embodiment of the present disclosure.
In particular, FIG. 1 shows a perspective view of a clutch housing
10, FIG. 2 shows a cross-sectional view of the clutch housing 10
and hub 12, and FIG. 3 shows a perspective view of the clutch
housing 10 having a plurality of spline teeth 16 disposed thereon.
In FIGS. 1 and 2, the clutch housing 10 is shown without the
plurality of spline teeth 16. The clutch housing 10 has a generally
cylindrical or cup-like shape having a radial ring portion 12 and a
cylindrical drum portion 15. Housing 10 is formed from a strip
(i.e. blank) of ultra-high strength steel 14, one preferred type of
ultra-high strength steel 14 includes 22MnB5 boron steel. The
ultra-high strength steel may be pre-coated with aluminum silicon
(AlSi) or other material to prevent corrosion and decarburization
during the heating and quenching steps. The clutch housing 10 may
be a single piece or may be two pieces joined together by a weld or
may be pressed-formed. To form the clutch housing 10, a blank of
boron steel 14 is preformed, specifically cold-formed, into a
predetermined shape. The predetermined shape may be a cylindrical
shape or any shape known in the art related for clutch housings.
After the blank 14 is cold-formed into a predetermined shape, the
predetermined shape is heat treated in an inert environment. The
inert environment may be an induction oven or induction chamber.
Heat treatment may include, but is not limited to, any or a
combination of annealing, case hardening, tempering, quenching, hot
forming, or welding. Next, the clutch housing 10 is exposed to a
water cooled quenching tool die to form a plurality of spline teeth
16 thereon, as shown in FIG. 3. Alternatively, the water cooled
quenching die may form a second predetermined shape instead of a
plurality of spline teeth 16, as shown in FIGS. 1-2 where the
clutch housing 10 is smooth. It is important to note in FIG. 2 that
the cross-sectional view shows a reduction in materials used
compared to conventional methods using HSLA steel. A clutch hub may
be formed in the same manner as will be described further
below.
[0052] With respect to FIG. 4, a flowchart of a method for forming
a component utilizing ultra-high strength steel in accordance with
an exemplary embodiment of the present disclosure is provided. As
illustrated by additional embodiments described in more detail
below, the component may be, but is not limited to, a clutch
housing, clutch hub, planetary gear carrier, or a torque converter
cover. In the exemplary embodiment, the component is the clutch
housing 10 described above. First, the method includes the 100
pre-forming a flat blank of steel into a predetermined shape having
a plurality of spline teeth 16. Specifically, the pre-forming of
the flat blank of steel is carried out by cold-forming techniques.
The predetermined or unfinished shape is based on the type of
component. For example, if the component is a clutch housing 10,
the steel may be cold-formed into a cylindrical or cup-like shape.
The flat blank of steel may be 22MnB5 boron steel and may be
pre-coated to prevent corrosion. After the flat blank of steel has
been pre-formed into a predetermined shape with the plurality of
spline teeth 16, the pre-formed predetermined shape is 102 heat
treated in an inert atmosphere to alter the properties of the
steel. The heat treated steel is then sized and calibrated using a
quenching tool 104. In particular, a water cooled quenching
die.
[0053] With respect to FIG. 5, a flowchart with a method for
forming a component utilizing ultra-high strength steel in
accordance with an exemplary embodiment of the present disclosure
is provided. The method includes 200 pre-forming a flat blank of
steel into a cup-shaped body. As discussed above, the flat blank of
steel may be a 22MnB5 boron steel blank. The cup-shaped body is
then 202 heat treated in an inert environment. The inert
environment may be an induction chamber or oven. Next, the method
includes 204 water cooled quenching the cup-shape body to form a
plurality of spline teeth thereon.
[0054] FIGS. 6-7 also show flowcharts of methods for forming a
component utilizing ultra-high strength steel in accordance with an
exemplary embodiment of the present disclosure. Like the methods
shown in FIGS. 4-5, the methods shown in FIGS. 6-7 utilize 22MnB5
boron steel. However, it is appreciated by one skilled in the art
that any type of ultra-high strength steel or any type of boron
steel may be used in conjunction with these methods. In FIG. 6, the
method includes 300 pre-forming or cold-forming the flat blank of
steel into a predetermined shape. The predetermined or unfinished
shape of the method shown in FIG. 6 does not include a plurality of
spline teeth 16. The cold-formed steel is then 302 heat treated in
an inert atmosphere. The heat treatment may be localized to a
certain portion of the steel. The method further includes 304
forming a plurality of spline teeth 16 within the heat treated
steel using a quenching tool. The quenching tool is a water-cooled
quenching die.
[0055] With respect to FIG. 7, the method for forming a component
utilizing ultra-high strength steel in accordance with an exemplary
embodiment of the present disclosure includes 400 heat treating a
flat blank of steel in an inert atmosphere and 402 quenching the
heat treated flat blank into a predetermined shape using a
quenching tool.
[0056] The method discussed above may also include, but is not
limited to cold-forming the clutch housing 10 without a plurality
of spline teeth 16, heat treating the unfinished shape of the
clutch housing 10 using localized induction heating, and forming
and sizing the plurality of spline teeth 16 using the quenching
die. Alternatively, the method may include pre-forming/cold-forming
the clutch housing 10 with a plurality of spline teeth 16, heating
the unfinished shape of the clutch housing 10 in an inert
environment, and sizing and finalizing the shape of the housing 10
in the quenching die. Similarly, planetary gear carriers and other
components may be partially or completely cold formed and then
heated using either localized or entire part heating.
[0057] In addition to the clutch housing 10 disclosed above, other
embodiments of components from ultra-high strength steel
constructed in accordance with the present disclosure are described
in more detail below. FIG. 8 shows a clutch hub 500 in accordance
with a second embodiment of the present disclosure. The clutch hub
500 has a cup-like shape having a radial ring portion 502 and a
cylindrical drum portion 504. A tubular neck 506 extends
longitudinally from the radial ring portion 502 and a drive gear
508 is attached to the tubular neck 506. Like the clutch housing
10, the clutch hub 500 may be formed from a strip (i.e. blank) of
ultra-high strength steel. The ultra-high strength steel may also
be pre-coated with aluminum silicon (AlSi) or other material to
prevent corrosion and decarburization during the heating and
quenching steps. The clutch hub 500 may be a single piece or may be
two pieces joined together by a weld or may be pressed-formed. To
form the clutch hub 500, a blank of boron steel can be cold-formed
into a predetermined or unfinished shape. A plurality of generally
triangular openings 510 can be formed in the radial ring portion
during cold forming for weight reduction. The predetermined shape
may then be heat treated in an inert environment. Next, the clutch
hub 500 may be exposed to a water cooled quenching tool die to form
a plurality of radially outwardly extending spline teeth 512
disposed about the cylindrical drum portion 504.
[0058] FIG. 9 shows a continuously variable transmission (CVT)
plunger 520 in accordance with a third embodiment of the present
disclosure. The CVT plunger 520 includes a generally bell-shaped
body defining a centrally disposed opening 522. The CVT plunger 520
is formed from a preformed flat blank of ultra-high strength steel,
preferably 22MnB5 boron steel. The blank of boron steel may be
cold-formed into a predetermined or unfinished shape with a thick
center and outer edge. The predetermined shape shape can then be
heat treated in an inert environment. Next, the CVT plunger 520 can
be exposed to a water cooled quenching tool die.
[0059] FIG. 10 shows a CVT cylinder 540 in accordance with a fourth
embodiment of the present disclosure. The CVT cylinder 540 includes
an annular or cylindrically shaped body having a first end 542 and
a second end 544 and including a shoulder 546 formed at the first
end 542. The body of the CVT cylinder 540 defines an opening 548
longitudinally extending from the first end 542 to the second end
544. The CVT cylinder 540 begins as a preformed flat blank of
ultra-high strength steel, preferably 22MnB5 boron steel, with the
centrally disposed material removed and discarded. Next, the
preformed blank or unfinished shape is heat treated in an inert
environment. Then, the CVT cylinder 540 is exposed to a water
cooled quenching tool die.
[0060] FIG. 11 shows a planetary carrier 560 in accordance with a
fifth embodiment of the present disclosure. The planetary carrier
560 comprises a first piece 562 and a second piece 564 joined
together by a weld. A plurality of apertures 566 are
circumferentially disposed in a spaced relationship to each other
about the perimeter of each piece 562, 564. The first piece 562
includes a plurality of legs 568 extending longitudinally. To form
the first piece 562 of the planetary carrier 560, a flat blank of
boron steel can be cold-formed into a predetermined or unfinished
shape with the plurality of apertures 566 and including the legs
568. To form the second piece 564 of the planetary carrier 560, a
flat blank of boron steel can be cold-formed into a an unfinished
shape with the plurality of apertures 566. The unfinished shapes of
the pieces 562, 564 are heat treated in an inert environment. Next,
each piece 562, 564 of the carrier 560 may be exposed to a water
cooled quenching tool die. The planetary carrier 560 is completed
by joining or welding the legs 568 of the first piece 562 to the
second piece 564.
[0061] FIGS. 12A and 12B show two reaction shells 580 in accordance
with a sixth embodiment of the present disclosure. Each reaction
shell 580 comprises a body including a cylindrical first portion
582 of a first diameter and a cylindrical second portion 584 of a
second diameter being larger than the first diameter. A plurality
of radially outwardly extending spline teeth 586 are disposed about
the cylindrical second portion 584. A plurality of bores 588 are
defined by the cylindrical first portion 582 and the cylindrical
second portion 584. To form the reaction shell 580, a flat blank of
boron steel is cold-formed into a predetermined tubular shape or
unfinished shape having the bores. The predetermined tubular shape
is then heat treated in an inert environment. Although the bores
588 are formed while cold-forming, it should be understood that the
bores 588 may also be formed while the predetermined tubular shape
is hot. Next, the reaction shell is exposed to a water cooled
quenching tool die to hold the geometry and form the radially
outwardly extending spline teeth 586 disposed about cylindrical
second portion 584.
[0062] FIG. 13A shows a differential housing 600 in accordance with
a seventh embodiment of the present disclosure. The differential
housing 600 is generally cup or drum shaped with a tubular neck
portion 602 defining a central opening 604 and including a
plurality of arms 606 extending radially and longitudinally from
the neck portion 602. The arms 606 alternate circumferentially
between the arm 606 including a radially inwardly extending
shoulder 608 (FIG. 13C) and the arm 606 having a generally L shaped
cross section (FIG. 13B). Each arm 606 also includes at least one
aperture 610. The differential housing 600 begins as a preformed
flat blank of ultra-high strength steel, preferably 22MnB5 boron
steel, with an extrusion forming the neck portion 602 and the
central opening 604. The preformed blank or unfinished shape is
heat treated in an inert environment. Then the differential housing
600 is exposed to a water cooled quenching tool die.
[0063] FIG. 14 shows a differential cover 620 in accordance with an
eighth embodiment of the present disclosure. The differential cover
620 comprises a generally bell shaped body 622 extending between a
generally cylindrical first end 624 and an opposite annular second
end 626. A ring gear 628 is attached to the second end 626 of the
cover 620. The cover 620 is for enclosing a plurality of pinion
gears 630. The cover 620 is formed with a flat blank of boron steel
that is cold-formed into a unfinished flat or cup shape having an
extrusion extending longitudinally at its center. Next, the cover
620 is heat treated in an inert environment. Then the cover 620 is
exposed to a water cooled quenching tool die. The ring gear 628 may
initially be two pieces which are welded to the outer diameter of
the cover 620.
[0064] FIG. 15A shows a torque converter cover 640 in accordance
with a ninth embodiment of the present disclosure. The torque
converter cover 640 comprises a front portion 642 (FIG. 15B) and a
back portion 644 (FIG. 15C). The front portion 642 is generally
drum-shaped and includes a radial wall 646 having an outer
peripheral portion defining a lock-up surface. An integral
cylindrical portion 648 of the front portion 642 has an inner
surface that extends longitudinally from the radial wall 646. The
inner surface of the front portion may also define an internal
spline. The back portion 644 is ring shaped and has a center
opening 650 and a curved cross-section or half round shape. Each
portion 642, 644 begins as a flat blank of boron steel which is
cold-formed into a predetermined shape. The predetermined or
unfinished shapes may then be heat treated in an inert environment.
Next, each portion 642, 644 of the cover can be exposed to a water
cooled quenching tool die. Such torque converter covers 640 using
higher strength steel allow for a thinner wall which reduces weight
compared to covers made from other materials.
[0065] FIG. 16 shows an oil pan 660 in accordance with a tenth
embodiment of the present disclosure. The oil pan 660 comprises a
generally rectangular base 662 with a side wall 664 disposed around
the periphery of the base 662 and extending generally
perpendicularly from the base 662 to an upper continuous flange 668
adapted to be secured to a block of an engine. A plurality of
openings 670 are defined by the flange 668 and spaced from each
other circumferentially about the flange 668. The oil pan 660 may
be formed from a flat blank of boron steel which is cold-formed
into a predetermined shape. The predetermined or unfinished shape
may then be heat treated in an inert environment. Then the oil pan
660 can be exposed to a water cooled quenching tool die. The use of
high strength steel in this type of application allows for a
thinner base 662 and side wall 664 and can also allow for ribbing
features.
[0066] In each of the aforementioned embodiments, the components
may be formed from 22MnB5 steel, however, it should be understood
that the amount of boron (B5-B50) may be selected depending on the
type of component or strength desired. Additionally, the amount of
other materials which comprise the ultra-high strength steel, such
as carbon, may cause variation in the martensitic percentage and
hardness after quenching. During the heat treatment, the heating
temperature is approximately 850-950 degrees C. More specifically,
the target heating temperature for 22MnB5 steel is 900 degrees C.,
however, the heating temperature may be increased as the amount of
boron is increased. As described above, the heat treating may be
partially or completely localized. The heating method may be
induction or by other techniques. When it is desirable to localize
strength in one particular area of a component, the heat treatment
may be localized to that area. In other instances, localized heat
treatment may be used for sections of a component having a thicker
cross section.
[0067] During the quenching step that may be used in forming each
of the aforementioned embodiments, the quench press/die defines the
final shape of the part. The release temperature may range between
approximately 150-250 degrees C., with a preferred target
temperature of 200 degrees C. The components generally remain in
the quench press/die for approximately 6-20 seconds depending on
the cross sectional thickness and desired strength.
[0068] In general, materials having a strength of approximately
1000 Mpa will crack or spring back during cold forming, therefore
the aforementioned methods are advantageous when forming such high
strength materials. Additionally, due to a reduction of cross
section, the geometry of components formed with heat assisted
calibration (HAC) methods disclosed herein may be more complex
(i.e. ribs). Consequently, the manufacturing of some components
(e.g. planetary carrier described in the fifth embodiment above)
that is not possible using cold forming is made possible with HAC
processes.
[0069] According to another aspect of the present disclosure, a
method is provided for applying a coating to the outer surfaces and
other exposed areas of the components prior to heat treating.
Applying such a coating eliminates or reduces the formation of a
ferrite soft layer on the component that can be formed as a result
of scale/decarburization during heat treatments of the component
which is known to affect the strength of the component in its final
form.
[0070] More particularly, the coating is applied to areas such as
windows, holes or cutouts of components, such as those found on the
components illustrated in FIGS. 17-19. The coating may be comprised
of materials such as a nickel electrolyte coating, oils applied to
form an unfoliated oxide layer, high-temperature graphite oil,
water-based ceramic coatings, and other high-temperature protective
coatings that are adapted to control oxidation and decarburization.
Nickel coatings may remain as a layer after final production of the
component, while oil or water-based ceramics may be washed off or
absorbed after heat treatment. It should be appreciated that the
coating may be applied by spraying or brushing. Furthermore, the
coating may be applied to only targeted portions, or to the entire
component. For example, a first portion that is coated may include
the areas around windows, while a second portion that is uncoated
may include the rest of the component.
[0071] With respect to FIG. 20, a flowchart of a method for forming
a component in accordance with an exemplary embodiment of the
present disclosure is provided. The method may include the step of
1000 providing a blank of ultra-high strength steel. The method
proceeds with 1002 cold forming the blank into an unfinished
component. The method continues with 1004 applying a coating to the
outer surface of the unfinished component, wherein the coating is
adapted to inhibit the formation of a ferrite soft layer on the
unfinished component during heating of the component. The method
continues with 1006 heating the unfinished component. Finally, the
method proceeds with 1008 quenching the unfinished component.
[0072] It should be appreciated that applying a coating in
accordance with the subject method allows the mechanical properties
of the component to be tailored by applying the coating to
predetermined regions. More particularly, the coating may be
applied to a first portion of the unfinished component, while a
second portion of the unfinished component remains uncoated. As
illustrated in FIGS. 21 and 22, tests were conducted on components
that were coated in accordance with the subject method at certain
regions, while other regions of the components were allowed to
remain uncoated. As illustrated in these figures, an optical
microscopy of the surface microstructure of the component can be
utilized to identify where a coating was applied. The tests
revealed a fatigue strength of approximately 475 Mpa in coated
regions, and only 305 Mpa in uncoated regions. The tests further
affirmed that components that are coated in accordance with the
subject method can meet strength requirements, and surface and core
hardness of minimum 400 HV requirements.
[0073] In view of the foregoing, it should be appreciated that an
advantage of utilizing the subject coating method include the
prevention of the formation of a ferrite soft layer on the
component, which reduces thickness and improves the fatigue
strength of the component.
[0074] According to a further aspect of the disclosure, a method is
provided wherein thicker walled, heavy gauge components are
directly quenched, i.e., without the use of tooling, after being
heat treated to provide a more cost effective process. More
particularly, as discussed in the foregoing, thinner walled
components can be held with tooling during quenching to reduce
distortion. Such tooling is not required for thicker walled
components according to the subject method because the thicker
material undergoes minimal distortion during cooling and because
thicker walled components are typically machined to final critical
tolerances. Utilizing the subject method provides a quicker
quenching process which leads to decreased overall cycle time.
[0075] Thicker walled, heavy gauge components according to the
subject method have a wall thickness between approximately 3.5 to
6.5 mm. Such components may include, but are not limited to, a CVT
plunger 520, 1520 such as that presented in FIGS. 9 and 17, a CVT
cylinder 540, 1540 such as that presented in FIGS. 10 and 23, a
differential housing 600, 1600 such as that presented in FIGS.
13A-13C, a differential cover 620 such as that presented in FIG.
14, a CVT housing 1542 such as that presented in FIG. 24, a
planetary carrier 1544 such as that that presented in FIG. 25, and
a rotary carrier 1546 such as that presented in FIG. 26.
Furthermore, such heavy gauge components may have the following
composition:
[0076] Carbon 0.08 to 0.33%;
[0077] Manganese 0.8 to 1.50%;
[0078] Boron 0.0005 to 0.005%;
[0079] Silicon 0.50% max;
[0080] Phosphorous 0.030% max;
[0081] Sulfar 0025% max; and
[0082] Chromium 0.35% max.
[0083] With respect to FIG. 26, a flowchart of a method for forming
a component in accordance with an exemplary embodiment of the
present disclosure is provided. The subject method may include step
2000 of pre-forming or cold-forming, such as with a roller or cam
die, a flat blank of steel into a final shape. The method continues
with step 2002 heating the formed blank such as with an electrical
or gas furnace or induction heating source. For example, the blank
may be heated up to 930 degrees Celsius. The method continues with
quickly transferring the component to a quenching media, and step
2004 quenching the component without the use of tooling. The
component may be fully or partially quenched. After quenching is
complete, the component is removed from the quenching media.
[0084] It should be appreciated that the subject method allows the
mechanical properties of components to be tailored for specific
purposes and for the overall weight of the component to be reduced.
As illustrated in FIGS. 27-29, by utilizing the subject method,
components were able to meet strength and hardness minimum
requirements of 400 HC, and core hardness minimum requirements of
200 HV.
[0085] While examples of the disclosure have been illustrated and
described, it is not intended that these examples illustrate and
describe all possible forms of the disclosure. Rather, the words
used in the specification are words of description rather than
limitation, and it is understood that various changes may be made
without departing from the spirit and scope of the disclosure.
Additionally, the features and various implementing embodiments may
be combined to form further examples of the disclosure.
* * * * *