U.S. patent application number 12/846156 was filed with the patent office on 2012-02-02 for aluminum alloy for die casting.
This patent application is currently assigned to GIBBS DIE CASTING CORPORATION. Invention is credited to James M. Evans.
Application Number | 20120027639 12/846156 |
Document ID | / |
Family ID | 45526944 |
Filed Date | 2012-02-02 |
United States Patent
Application |
20120027639 |
Kind Code |
A1 |
Evans; James M. |
February 2, 2012 |
ALUMINUM ALLOY FOR DIE CASTING
Abstract
An alloy for use in die casting having improved thermal
conductivity and strength includes at least about 86.0 percent
aluminum by weight, from about 9.70 to about 10.70 percent silicon,
by weight, from about 0.40 to about 0.70 percent iron, by weight,
about 0.25 percent copper, by weight, about 0.50 percent manganese,
by weight, from about 0.10 to about 0.20 percent titanium, by
weight; and from about 0.010 to about 0.025 percent strontium, by
weight.
Inventors: |
Evans; James M.;
(Evansville, IN) |
Assignee: |
GIBBS DIE CASTING
CORPORATION
Henderson
KY
|
Family ID: |
45526944 |
Appl. No.: |
12/846156 |
Filed: |
July 29, 2010 |
Current U.S.
Class: |
420/532 ;
420/530 |
Current CPC
Class: |
C22C 21/04 20130101;
C22F 1/043 20130101 |
Class at
Publication: |
420/532 ;
420/530 |
International
Class: |
C22C 21/02 20060101
C22C021/02 |
Claims
1. An alloy for use in die casting comprising at least about 86.0
percent aluminum by weight; from about 9.70 to about 10.70 percent
silicon, by weight; from about 0.40 to about 0.70 percent iron, by
weight; up to about 0.25 percent copper, by weight; up to about
0.50 percent manganese, by weight; from about 0.10 to about 0.20
percent titanium, by weight; and from about 0.010 to about 0.025
percent strontium, by weight.
2. The alloy of claim 1, further comprising up to about 0.25
percent nickel, by weight.
3. The alloy of claim 2, further comprising up to about 0.50
percent zinc, by weight.
4. The alloy of claim 3, further comprising up to about 0.15
percent tin, by weight.
5. The alloy of claim 2, further comprising up to about 0.15
percent tin, by weight.
6. The alloy of claim 1, further comprising up to about 0.15
percent tin, by weight.
7. The alloy of claim 6, further comprising up to about 0.50
percent zinc, by weight.
8. The alloy of claim 1, further comprising between about 86.0 to
about 90.0 percent aluminum, by weight.
9. The alloy of claim 8, further comprising up to about 0.25
percent nickel, by weight.
10. The alloy of claim 9, further comprising up to about 0.50
percent zinc, by weight.
11. The alloy of claim 10, further comprising up to about 0.15
percent tin, by weight.
12. The alloy of claim 9, further comprising up to about 0.15
percent tin, by weight.
13. The alloy of claim 8, further comprising up to about 0.15
percent tin, by weight.
14. The alloy of claim 6, further comprising up to about 0.50
percent zinc, by weight.
15. An article of manufacturing comprising between about 86.0 to
about 90.0 percent aluminum, by weight; from about 9.70 to about
10.70 percent silicon, by weight; from about 0.40 to about 0.70
percent iron, by weight; about 0.25 percent copper, by weight;
about 0.50 percent manganese, by weight; from about 0.10 to about
0.20 percent titanium, by weight; and from about 0.010 to about
0.025 percent strontium, by weight.
16. The alloy of claim 15, further comprising up to about 0.25
percent nickel, by weight.
17. The alloy of claim 16, further comprising up to about 0.50
percent zinc, by weight.
18. The alloy of claim 17, further comprising up to about 0.15
percent tin, by weight.
19. The alloy of claim 16, further comprising up to about 0.15
percent tin, by weight.
20. The alloy of claim 15, further comprising up to about 0.15
percent tin, by weight.
21. The alloy of claim 6, further comprising up to about 0.50
percent zinc, by weight.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates generally to aluminum alloys
and more specifically aluminum alloys for casting such as for
pressure die-casting.
[0002] Die casting is a process in which molten metal is forced
into metal dies under pressure to form dimensioned components that
require little or no post processing. Aluminum is a widely used
base for alloys in the casting of dimensional components. For
example, aluminum alloys are used extensively in die-casting due to
the excellent flow characteristics and dimensional stability
achieved by aluminum alloys.
[0003] The use of various alloying agents to improve the strength,
ductility, wear resistance, corrosion resistance, and thermal
conductivity of aluminum may result in significant variations in
the physical properties of the resulting alloy. The alloying agents
also affect the ability of the resulting alloys to be die-cast
successfully and with maintenance of the dimensional stability of
the resulting parts. Various alloying agents are known to be used
with aluminum. For example, copper, manganese, silicon, magnesium,
zinc, and even iron, in some cases, may be used to form aluminum
alloys with varying properties.
[0004] In addition, the resulting structures may be treated after
the die casting process to modify physical characteristics.
Coatings such as paint or anodize may improve the strength, wear
resistance, and corrosion resistance of the final products. Various
heat treatments may also be used to modify the mechanical
properties of the parts after the die casting process has been
completed.
[0005] Strontium is an elemental metal that reacts with water and
burns in air. Strontium has been used in magnesium alloys which
also include relatively small amounts of aluminum to form creep
resistant magnesium based alloys. In such applications, the
strontium is used to refine eutectic silicon. For example, U.S.
Pat. No. 7,108,042 discloses that strontium, sodium, or calcium may
be used to refine the eutectic silicon.
SUMMARY
[0006] According to the present disclosure, an alloy for use in die
casting has improved thermal conductivity and strength. The alloy
includes at least about 86.0 percent aluminum by weight, from about
9.70 to about 10.70 percent silicon, by weight, from about 0.40 to
about 0.70 percent iron, by weight, up to about 0.25 percent
copper, by weight, up to about 0.50 percent manganese, by weight,
from about 0.10 to about 0.20 percent titanium, by weight; and from
about 0.010 to about 0.025 percent strontium, by weight.
[0007] The alloy may include up to about 90.0 percent aluminum. In
some embodiments, the alloy may include up to about 0.30 percent
magnesium, by weight. In some embodiments, the alloy may include
impurities. For example, the alloy may include up to about 0.25
percent nickel, up to about 0.50 percent zinc, by weight, and up to
about 0.15 percent tin by weight. The alloy may be used to produce
articles of manufacture.
[0008] Additional features and advantages of the invention will
become apparent to those skilled in the art upon consideration of
the following detailed description of illustrated embodiments
exemplifying the best mode of carrying out the invention as
presently perceived.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] The detailed description of the drawings particularly refers
to the accompanying figures in which:
[0010] FIG. 1 is a graph comparing the thermal conductivity of
alloy of the present disclosure to other alloys; and
[0011] FIG. 2 is a graph comparing the strength of the present
alloy to aluminum 365.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0012] The aluminum alloy of the present disclosure has been shown
to provide improved thermal conductivity and strength over the A413
such that the new alloy provides mechanical properties that compare
to the 365 alloy with a significantly lower cost. In the special
413 alloy of the present disclosure, hereinafter referred to as
SP413, strontium is added in amounts between about 0.01 and 0.02%
to modify silicon included in the alloy.
[0013] Strontium improves the tensile strength and the thermal
conductivity of the SP413 as compared to the A413. A comparison of
the thermal conductivity of several alloys is shown below in Table
1.
TABLE-US-00001 TABLE 1 THERMAL CONDUCTIVITY (W/K-m) Heat Die Cast
Die Cast Die Cast SP413 SP413 Treatment 356 380 A413 w/o Sr w/Sr As
cast 143 96.2 121 144 150 300 F. 144 97 124 147 150 400 F. 145 104
127 155 156 500 F. 148 116 130 158 165 600 F. 145 119 131 159
163
Referring to FIG. 1, the thermal conductivity of five different
alloys is shown with various heat treatments. It can be seen that
the SP413 without strontium shows improvement in thermal
conductivity as compared to A413, 356, and 380. The data also shows
that the addition of strontium further improves the thermal
conductivity of the SP413 alloy. SP413 without strontium has about
a 20% average improvement over A413 in thermal conductivity. SP413
with Strontium has about a 24% average improvement over A413 in
thermal conductivity.
[0014] The addition of Strontium also improves the yield strength
of the SP413 alloy as shown in table 2.
TABLE-US-00002 TABLE 2 Tensile Strength Yield Strength Material
KSI(MPa) KSI(MPa) Elongation % 413 As-Cast 42.9(296) 21.0(145) 2.5
SP413 As-Cast 39.8(274) 15.6(108) 6.7 SP413 As-Cast w/Sr 44.6(308)
17.7(122) 9.9
The addition of strontium to SP413 improves the tensile strength of
the alloy by approximately 12%, yield strength by approximately 9%
and the elongation by approximately 48%. This improvement results
in the SP413 with strontium to be similar to 365 in mechanical
properties. As discussed below, the SP413 of the present disclosure
provides this performance with a higher tolerance for impurities,
thereby reducing the cost of the alloy. The relative mechanical
performance is shown in Table 3.
TABLE-US-00003 TABLE 3 Tensile Strength Yield Strength Material
KSI(MPa) KSI(MPa) Elongation % 365 As-Cast 47.6(328) 21.6(149) 8.2
SP413 As-Cast w/Sr 44.6(308) 17.7(122) 9.9
In one application, a test was performed to compare the performance
of the SP413 with 365. A test coupon was cast with each alloy and
the coupons were heat-treated under the same conditions. A
compression test was then performed with the results of the tests
being compared as shown on the graph in FIG. 2. As can be seen in
FIG. 2, the SP413 and 365 alloys have a similar stress-strain
profile until elongation. The 365 begins to elongate at a lower
stress then the SP413. Once the SP413 begins to elongate the
difference between the curves remains generally constant throughout
the remainder of the test. Ten castings from both alloys were
tested and no cracks were observed on any of the castings.
[0015] The chemistry of each of the A413, SP413, and 365 alloys is
presented in Table 4.
TABLE-US-00004 TABLE 4 ALLOY ELEMENT A413 SP413 365 Silicon (wt. %)
11.0-13.0 9.70-10.70 9.5-11.5 Iron (wt. %) 1.30 0.40-0.70 0.15
Copper (wt. %) 1.00 0.25 0.03 Manganese (wt. %) 0.35 0.50 0.5-0.8
Magnesium (wt. %) 0.10 0.30 0.1-0.5 Nickel (wt. %) 0.50 0.25 --
Zinc (wt. %) 0.50 0.50 0.07 Tin (wt. %) 0.15 0.15 -- Titanium (wt.
%) -- 0.10-0.20 0.04-0.15 Strontium (wt. %) -- 0.010-0.025
0.010-0.020 Aluminum (wt. %) 83.1-89.0 86.38-89.79 86.78-89.85
The use of silicon helps improve the fluidity of the alloys. The
iron improves hot tear resistance and reduces the occurrence of die
soldering. Copper improves the strength and hardness in the as-cast
and heat-treated conditions. Keeping the levels of copper
relatively low helps improve corrosion resistance. Manganese tends
to reduce die soldering as well. Magnesium improves strength and
hardness in the as-cast and heat-treated conditions. Titanium is
used to refine the aluminum grain structure in the alloy. Strontium
is used to modify and refine the silicon particles. Nickel, zinc,
and tin are considered impurities in the alloy, with the SP413
tolerating reasonable amounts of the nickel, zinc, and tin, thereby
reducing the costs of refining the alloy. After a review of the
test coupons, it was determined that the microstructures of the
SP413 and the 365 are similar.
[0016] Thus, it can be seen that the SP413 alloy of the present
disclosure provides an alloy having improved thermal conductivity
and strength at a lower cost than known alloys. The combination of
the improved thermal conductivity with improved strength provides a
new option for the preparation of structural components in
applications subjected to high thermal loads.
[0017] Although certain illustrative embodiments have been
described in detail above, variations and modifications exist
within the scope and spirit of this disclosure as described and as
defined in the following claims.
* * * * *