U.S. patent application number 11/238383 was filed with the patent office on 2007-03-29 for method for repairing die cast dies.
This patent application is currently assigned to Honeywell International, Inc.. Invention is credited to William F. Hehmann, Yiping Hu, Clyde R. Taylor.
Application Number | 20070068648 11/238383 |
Document ID | / |
Family ID | 37892446 |
Filed Date | 2007-03-29 |
United States Patent
Application |
20070068648 |
Kind Code |
A1 |
Hu; Yiping ; et al. |
March 29, 2007 |
Method for repairing die cast dies
Abstract
Methods are provided for repairing a worn surface of a steel
die-cast die. The method includes heating an amorphous material to
a predetermined temperature with a laser beam and allowing the
melted amorphous material to solidify to thereby form an amorphous
layer over the worn surface. These processes are useful for
eliminating or minimizing cracking and/or part distortion and
minimize heat-affected zone during welding. In addition, the
formation of an amorphous layer over the worn surface allows the
repaired die-cast die to better withstand typical operating
environments than previous repair materials. These methods combine
low heat input welding with amorphous alloys to effectively repair
die-cast dies.
Inventors: |
Hu; Yiping; (Greer, SC)
; Hehmann; William F.; (Greer, SC) ; Taylor; Clyde
R.; (Laurens, SC) |
Correspondence
Address: |
HONEYWELL INTERNATIONAL INC.
101 COLUMBIA ROAD
P O BOX 2245
MORRISTOWN
NJ
07962-2245
US
|
Assignee: |
Honeywell International,
Inc.
|
Family ID: |
37892446 |
Appl. No.: |
11/238383 |
Filed: |
September 28, 2005 |
Current U.S.
Class: |
164/92.1 ;
164/113 |
Current CPC
Class: |
B22D 17/2209 20130101;
B22D 7/068 20130101 |
Class at
Publication: |
164/092.1 ;
164/113 |
International
Class: |
B22D 19/10 20060101
B22D019/10 |
Claims
1. A method for repairing a worn surface of a steel die-cast die,
the method comprising the steps of: depositing an amorphous
material onto the worn surface, the amorphous material formulated
to form an amorphous layer after being heated to a predetermined
temperature and cooled; heating the amorphous material to the
predetermined temperature with a laser beam, and without
compressing the amorphous material, to form a repair layer over the
worn surface; and allowing the heated amorphous material to
solidify to thereby form the amorphous layer.
2. The method of claim 1, wherein the amorphous material comprises
chromium, boron, silicon, carbon and iron.
3. The method of claim 2, wherein the chemical compositions of the
amorphous material (by weight percent) comprises between about 50%
and about 50% chromium, between about 5% and about 7% boron,
between about 1% and about 3% silicon, up to about 1% carbon, and
balance iron.
4. The method of claim 1, wherein the amorphous material is a
powder.
5. The method of claim 1, wherein the amorphous layer has a
Rockwell hardness of between about Rc65 and about Rc73.
6. The method of claim 1, wherein the laser used for heating
comprises one of a Nd:YAG laser, a fiber laser, a diode laser and a
CO.sub.2 laser generator.
7. The method of claim 1, wherein the step of heating comprises
supplying a laser power output of about 50 watts or higher.
8. The method of claim 1, further comprising machining the repair
layer.
9. The method of claim 1, further comprising the step of
pre-treating the worn surface to receive the amorphous
material.
10. The method of claim 9, wherein the step of pre-treating
comprises a treatment selected from the group consisting of
machining, degreasing, and grit blasting.
11. The method of claim 1, further comprising the step of heat
treating the die.
12. A method for repairing a worn surface of a steel die-cast die,
the method comprising the steps of: heating a solid amorphous
material with a laser beam to a predetermined temperature to form a
liquid, which solidifies to form an amorphous layer after cooling;
depositing the liquefied amorphous material onto the worn surface,
without compressing the liquefied amorphous material, to form a
repair layer thereover; and allowing the amorphous material to cool
to form the amorphous layer.
13. The method of claim 12, wherein the amorphous alloy has a
Rockwell hardness of between about Rc65 and about Rc73.
14. The method of claim 12, wherein the step of heating comprises
supplying a laser power input of about 50 watts or greater to the
laser.
15. The method of claim 12, further comprising the step of
pre-treating the worn surface to receive the amorphous
material.
16. The method of claim 15, wherein the step of pre-treating
comprises a treatment selected from the group consisting of
machining, degreasing, and grit blasting.
17. The method of claim 12, wherein the amorphous material
comprises chromium, boron, silicon, carbon and iron.
18. The method of claim 17, wherein the chemical compositions of
the amorphous material (by weight percent) comprises between about
40% and about 50% chromium, between about 5% and about 6% boron,
between about 1% and about 3% silicon, up to 1% carbon, and balance
iron.
19. (canceled)
20. (canceled)
Description
FIELD OF THE INVENTION
[0001] The present invention relates to the repair of die-cast
dies, and more particularly, to methods of using amorphous alloys
to repair die-cast dies and/or injection molds.
BACKGROUND OF THE INVENTION
[0002] Die-cast dies have been widely used to manufacture a variety
of machine parts. For example, automobile parts, such as
transmission housings, are typically cast from die-cast dies.
Generally, these types of dies are made of a tool steel, such as
H-13 tool steel, or comparable material, and are used in a number
of casting operations.
[0003] Over time, the die-cast die may become worn from repeated
exposure to mechanical erosion and/or chemical attack.
Additionally, the die cast-die may experience physical and thermal
stresses, which may cause surface cracking. Consequently, the
die-cast die may need to undergo a repair process to restore its
original configuration and dimension, and to improve its
metallurgical integrity.
[0004] Several die-cast die repair techniques exist. For example,
Tungsten-Inert-Gas ("TIG") welding and Plasma-Arc welding ("PAW")
techniques have conventionally been used to repair die-cast dies.
However, these conventional welding repair processes typically
expose the die-cast dies to high temperatures, which may cause the
dies to crack in and/or near repaired areas or to be distorted.
Additionally, a large area of the dies under welding zone may be
unnecessarily exposed to the heat. Thus, die-cast dies that have
been repaired using conventional welding techniques may not retain
their original functionality and may need to be serviced more often
after repair.
[0005] Hence, there is an ongoing need to provide improved methods
for repairing die-cast dies. It is desirable for the method to be
compatible with existing manufacturing methods and to be relatively
inexpensive to perform. It is also desirable for the repair method
to have cost and performance advantages over existing repair
methods and over the option of replacing worn parts with new ones.
The present invention addresses one or more of these needs.
SUMMARY OF THE INVENTION
[0006] Methods are provided for repairing a worn surface of a steel
die-cast die. In one embodiment, and by way of example only, the
method comprises depositing an amorphous material onto the worn
surface, where the amorphous material formulated to form an
amorphous layer after being heated to a predetermined temperature
and cooled. The method also includes heating the amorphous material
to the predetermined temperature with a laser beam to form a repair
layer of the amorphous alloy over the worn surface. Additionally,
the method includes allowing the heated amorphous material to
solidify to thereby form the amorphous layer.
[0007] In another embodiment, and by way of example only, the
method includes heating a solid amorphous material with a laser
beam to a predetermined temperature to form a liquid, where the
amorphous material formulated to form an amorphous layer after
being heated to the predetermined temperature and cooled.
Additionally, the method includes the step of depositing the
amorphous material onto the worn surface to form a repair layer of
the amorphous layer thereover. The method also includes allowing
the liquid to cool to form the amorphous layer.
[0008] In still another embodiment, and by way of example only, a
die-cast die having a repaired area is provided. The die-cast die
includes a matrix layer comprising steel and a repair layer
disposed over the matrix layer, wherein the repair layer comprises
an amorphous alloy.
[0009] Other independent features and advantages of the method for
repairing die cast dies will become apparent from the following
detailed description, taken in conjunction with the accompanying
drawings which illustrate, by way of example, the principles of the
invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is a cross-sectional view of a portion of an
exemplary repaired workpiece;
[0011] FIG. 2 is a flow diagram showing steps in an exemplary
method for repairing the workpiece;
[0012] FIG. 3 is a perspective view of a portion of an exemplary
workpiece to be repaired; and
[0013] FIG. 4 is a perspective view of the workpiece shown in FIG.
3 after repair.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
[0014] The following detailed description of the invention is
merely exemplary in nature and is not intended to limit the
invention or the application and uses of the invention.
Furthermore, there is no intention to be bound by any theory
presented in the preceding background of the invention or the
following detailed description of the invention. Reference will now
be made in detail to exemplary embodiments of the invention,
examples of which are illustrated in the accompanying drawings.
Wherever possible, the same reference numbers will be used
throughout the drawings to refer to the same or like parts.
[0015] Referring now to FIG. 1, a workpiece 100 having a repaired
area 102 is shown. The workpiece 100 includes a matrix section 104
and a repair layer 106. The matrix section 104 comprises workpiece
material, which may be a die grade steel, such as H-13 steel. The
repair layer 106 comprises an amorphous alloy having an absence of
grain boundaries, which provides better corrosion resistance and
wear resistance than polycrystalline materials.
[0016] FIG. 2 is a functional block diagram of an exemplary method
for producing the repaired part 200. In one exemplary embodiment of
the method, a suitable workpiece having a worn surface is first
identified, step 202. In this regard, the workpiece is inspected to
confirm that it is capable of being repaired. For example, the
workpiece should have a minimal number of mechanical defects or
other damage that would prevent it from undergoing further service
after repair. One exemplary workpiece 300 is depicted in FIG. 3.
Here, the workpiece 300 is a ring-shaped die that includes a worn
surface 302. The worn surface 302 is missing a lug 304, an outline
of which is shown, which exposes die grade steel 306.
[0017] In some cases, the workpiece has a surface that is corroded
or eroded, and includes an impurity buildup or other contamination
that may interfere with laser welding. Thus, the workpiece is
preprocessed and prepared for welding repair thereon, step 204. In
one exemplary embodiment, the work piece is machined and degreased
to remove the contamination. In another example, the workpiece is
grit blasted with an abrasive material such as aluminum oxide.
[0018] The repair layer 104 is then formed, step 206. In one
exemplary embodiment of step 206, the repair layer 104 is formed by
depositing amorphous material over the worn surface. The amorphous
material is heated using a laser-welding process and transformed
into an amorphous layer. It will be appreciated that any one of
numerous materials may be used that are suitably formulated to
produce an amorphous layer which can better withstand environments
in which die-cast dies typically operate than materials previously
used to repair dies. The amorphous material may be a powder, or any
other form suitable for use in a laser welding technique. In an
example in which the amorphous material is a powder, the powder
material is laser deposited onto the worn surface. In another
exemplary embodiment of step 206, the repair layer 104 is formed by
heating a solid amorphous material into a liquid using a laser beam
and forming the amorphous layer onto the worn surface after
cooling.
[0019] In any case, the amorphous material is preferably selected
to yield an amorphous layer having a relatively high hardness, high
wear resistance and high corrosion resistance. For example, the
amorphous layer preferably has a Rockwell hardness value of between
about Rc 65 to about Rc 73. In another example, the amorphous alloy
is preferably more resistant to wear than polycrystalline
materials, due to high hardness and fine boride distributions. In
still another example, the amorphous alloy is more resistant to
corrosion than polycrystalline materials, due to an absence of
grain boundaries. Examples of suitable materials include LMC-C and
LMC-M both available from Liquidmetal Technologies of Lake Forest,
Calif. More preferably, the chemical compositions of the preferred
amorphous layer by weight percent includes between about 40 and
about 50% of chromium, between about 5% and about 7% of boron,
between about 1% and about 3% of silicon, up to about 1% of carbon,
and balance iron.
[0020] Next, the amorphous material is laser-welded and transformed
into an amorphous alloy. It will be appreciated that one of various
types of lasers suitable for welding may be used, such as, for
example, a welding torch described in U.S. Pat. No. 6,593,540,
which is commonly assigned to the assignee of the present
invention, Honeywell International, Inc., an Yttrium Aluminum
Garnet (YAG) laser that includes a doping material, such as
Neodymium (Nd), or a direct diode, a fiber, or a CO.sub.2 laser
generator.
[0021] During laser welding, the laser preferably has a power
output of about 50 watts or higher. The laser beam is directed onto
the amorphous material and energy from the laser beam melts the
material. It will be appreciated that welding parameters, such as
laser power output, powder feed rate, traverse speed and shield gas
flow rate, and the like may be manipulated to eliminate or minimize
hot cracking on the workpiece. After the melted material cools, it
solidifies to form an amorphous layer having a Rockwell hardness of
between approximately Rc 65 and Rc 73.
[0022] It will be appreciated that step 206 may be repeated several
times to achieve a desired thickness and dimension of the repair
layer 104, or to cover a desired surface area. After the repair
layer 104 is formed, the repair area may be machined to restore
original contour and dimension of the repaired workpiece 100, step
208. Any one of various conventional machining techniques may be
used. One suitable technique includes a CNC controlled milling
and/or grinding process that is used to machine the workpiece or
surface of the workpiece to a desired dimension or contour. FIG. 4
shows the workpiece depicted in FIG. 3 as a repaired workpiece 400.
The workpiece 400 includes a repaired lug 402 that was formed
thereon and subsequently machined.
[0023] Optionally, the repaired workpiece may be heat treated, step
210. In one exemplary embodiment, the heat treatment is performed
below the re-crystallization temperature to relieve welding stress
while avoiding crystal growth. In another exemplary embodiment, the
repaired workpiece is heat treated at a temperature of between
approximately 800 to approximately 1400 degrees F. for about 1
hour. Subsequently, the repaired workpiece may be inspected, for
example, by an FPI (fluorescent penetration inspection), to
determine whether it can be returned to service, step 212.
[0024] There has now been provided a method for repairing a
die-cast die that substantially eliminates cracking, reduces part
distortion, and minimizes the area of a heat-affected zone of the
dies by using a laser welding process. In the laser welding
process, the laser power output and welding parameters such as beam
spot size, powder feed rate, traverse speed and shield gas flow
rate, and the like are controlled. Also, the amorphous layer
provides excellent wear-resistance, while maintaining bulk hardness
at a level sufficient to provide a tough support structure. This
allows the welded material to withstand repeated thermal cycling
without spallation and prolongs the service lives of the repaired
die-cast dies thereof.
[0025] While the invention has been described with reference to a
preferred embodiment, it will be understood by those skilled in the
art that various changes may be made and equivalents may be
substituted for elements thereof without departing from the scope
of the invention. In addition, many modifications may be made to
adapt a particular situation or material to the teachings of the
invention without departing from the essential scope thereof.
Therefore, it is intended that the invention not be limited to the
particular embodiment disclosed as the best mode contemplated for
carrying out this invention, but that the invention will include
all embodiments falling within the scope of the appended
claims.
* * * * *