Overview
Eastern Alloys manufactures the complete range of zinc die casting
alloys. ZAMAK alloys were first developed during the 1920's by The New Jersey
Zinc Company. The name ZAMAK draws upon the basic metallurgy of the alloy
group: Z-Zinc, A-Aluminum, MA-Magnesium, and K-Kopper (e.g., German). In the
United States, ZAMAK 3 is the most common alloy for hot chamber die casting.
With a combination of superior mechanical properties and low
melting/manufacturing costs, it fulfills the needs for most die casting
applications. Other ZAMAK alloys include ZAMAK 2, ZAMAK 5, and ZAMAK 7. Common
to each alloy is a consistent Aluminum content range, however, the alloys
differ in specification by varying amounts of copper, magnesium, and nickel -
resulting in different mechanical and physical properties.
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#3 Ingots stacked on alloy feet.
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Eastern Alloys is the global leader in ZA alloy manufacturing and
process technology. High strength ZA alloys were originally engineered for
gravity casting, but now own an increasing percentage of the die casting
market. Today, there are three ZA alloys: ZA8, ZA12, ZA27. ZA8 is the only ZA
alloy that can be HOT chamber die cast due to the relatively low melting
temperature (708-759 F). ZA12 and ZA27 can be COLD chamber die cast at higher
melting temperatures (875-1050 F).
The ACuZinc is another zinc die casting alloy-, developed by General Motors
Research and Development engineers. At the outset ACuZinc alloys were limited
to production of GM-specific parts. More recently, however, the GM licensing
agreement allows for a broader scope of applications. With the addition of high
percentages of copper, ACuZinc alloys were developed to improve the wear
resistance and creep properties in the zinc alloy family. Today there are two
ACuZinc alloys: ACuZinc 5 (5% Copper), and ACuZinc 10 (10% Copper), and are
used in a variety of automotive applications. ACuZinc 5 is HOT chamber die cast
due to its lower melting temperature, whereas ACuZinc 10 is COLD chamber die
cast.
The process of casting these zinc die casting alloys utilize an
hydraulic press that allows metal to be injected into a cavity at extremely
high pressures. The term "HOT" (as in HOT chamber) refers to the fact the metal
pump (gooseneck) is immersed in the hot metal. In COLD chamber die casting, the
metal is ladled into a holding sleeve until a plunger forces the metal into the
cavity. These processes are designed for high volume applications, and are cast
at "net-shaped" precision.
For more information about Eastern Alloys and its selection of
die-casting alloys, contact the Eastern Alloys
sales engineer nearest you , or send inquiries to
rwinter@eazall.com.
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Alloy Description
| #3 |
No. 3 alloy is usually the first choice when considering zinc die casting. Its
excellent balance of desirable physical and mechanical properties, superb
castability and long-term dimensional stability are the reasons why over 70% of
all North American zinc die castings are in No. 3 alloy. It is, therefore, the
most widely available alloy from die casting sources. ZAMAK No. 3 also offers
excellent finishing characteristics for plating, painting and chromate
treatments. It is the "standard" by which other zinc alloys are rated in terms
of die casting. |
| #5 |
No. 5
alloy castings are marginally stronger and harder than No. 3. However, these
improvements are tempered with a reduction in ductility which can affect
formability during secondary bending, riveting, swaging or crimping operations.
No. 5 contains an addition of 1% copper which accounts for these property
changes. The alloy is widely die cast in Europe and does exhibit excellent
castability characteristics, as well as, improved creep performance over No. 3.
Because of No. 3's wide availability, material specifiers often strengthen
components by design modifications instead of using No. 5. However, when an
extra measure of tensile performance is needed, No. 5 alloy castings are
recommended. The alloy is readily plated, finished and machined, comparable to
No. 3 alloy.
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| #7 |
No. 7 alloy is
a modification of #3 alloy in which lower magnesium content is specified in
order to increase the fluidity. To avoid problems with inter-granular corrosion
lower levels of impurities are called for and a small quantity of nickel is
specified. Alloy #7 has slightly better ductility than #3 with other properties
remaining at the same level.
The alloy is therefore popular for those special cases where the die caster is
making thin walled components requiring a good surface finish. However,
research testing has shown that metal and die temperatures have a bigger effect
than changing alloys. Close attention to control of the die casting process
parameters is important so as to eliminate defects and achieve consistent
quality.
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| #2 |
No. 2 is
the only ZAMAK alloy which is used for gravity casting; mainly for metal
forming dies or plastic injection tools. This alloy is sometimes referred to as
Kirksite.
For die casting, No. 2 offers the highest strength and hardness of the ZAMAK
family. However, its high copper content (3%) results in property changes upon
long term aging. These changes include slight dimensional growth (0.0014
in/in/after 20 yrs.), lower elongation and reduced impact performance (to
levels similar to aluminum alloys) for die cast products.
Although No. 2 alloy exhibits excellent castability, it has seen limited use by
die casters in North America. It does, however, provide some interesting
characteristics which may assist designers. Its creep performance is rated
higher than the other ZAMAKs and No. 2 maintains higher strength and hardness
levels after long term aging. Also, preliminary investigations suggest No. 2
alloy is a good bearing material, and may eliminate bushings and wear inserts
in die cast designs.
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| ZA-8 |
A good gravity
casting alloy, ZA-8 is rapidly growing for pressure die casting. ZA-8 can be
hot chamber die cast, with improved strength, hardness and creep properties
over ZAMAK's, with the exception of a No. 2 alloy which is very similar in
performance. ZA-8 is readily plated and finished using standard procedures for
ZAMAK. When the performance of standard No. 3 or No. 5 is in question, ZA-8 is
often the die casting choice because of high strength and creep properties and
efficient hot chamber castability. |
| ZA-12 |
ZA-12 is
the most versatile zinc alloy in terms of combining high performance properties
and ease of fabrication using either gravity or pressure die casting. ZA-12 is
the best gravity casting alloy for sand, permanent mold and the new graphite
mold casting process. It is also a good pressure die casting alloy (cold
chamber) which provides a sounder structure than ZA-27, as well as higher die
cast elongation and impact properties. For these reasons, die cast ZA-12 often
competes with ZA-27 for strength application. An excellent bearing alloy, ZA-12
is also platable, although plating adhesion is reduced compared to the ZAMAK
alloys. |
| ZA-27 |
ZA-27 is the
high strength performer of the zinc alloys whether for gravity or pressure die
casting (cold chamber). It is also the lightest alloy and offers excellent
bearing and wear resistance properties. ZA-27, however, requires care during
melting and casting to assure sound internal structure, particularly for heavy
wall sections. It may also need a stabilization heat treatment when tight
dimensional tolerances are required. ZA-27 is not recommended for plating.
However, when brute strength or wear resistant properties are needed, ZA-27 has
demonstrated extraordinary performance. |
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Mechanical Properties
| Ultimate Tensile Strength:
psi x 103 (MPa) |
41 (283) |
48 (328) |
41 (283) |
52 (359) |
54 (374) |
58 (400) |
61 (421) |
| Yield Strength - 0.2%
Offset: psi x 103 (MPa) |
32 (221) |
39 (269) |
32 (221) |
41 (283) |
42 (290) |
46 (317) |
55 (379) |
| Elongation:
% in 2" |
10 |
7 |
13 |
7 |
6-10 |
4-7 |
1-3 |
| Shear Strength:
psi x 103 (MPa) |
31 (214) |
38 (262) |
31 (214) |
46 (317) |
40 (275) |
43 (296) |
47 (325) |
| Hardness: Brinell |
82 |
91 |
80 |
100 |
95-110 |
95-115 |
105-125 |
| Impact Strength:
ft-lb (J) |
432 (58) |
482 (65) |
432 (58) |
352 (48) |
313 (42) |
213 (29) |
93
(5) |
| Fatigue Strength Rotary Bend
- 5x108 cycles: psi x 103 (MPa) |
6.9 (48) |
8.2 (57) |
6.8 (47) |
8.5 (59) |
15 (103) |
17 (117) |
21 (145) |
Compressive Yield
Strength 0.1% Offset:
psi x 103 (MPa) |
604 (414) |
874 (600) |
604 (414) |
934 (641) |
37 (252) |
39 (269) |
52 (385) |
Modulus of Elasticity - psi x
106
(MPa x 103) |
12.46 (85.5) |
12.46 (85.5) |
12.46 (85.5) |
12.46 (85.5) |
- |
- |
- |
| Poisson's Ratio |
0.27 |
0.27 |
0.27 |
0.27 |
0.29 |
0.30 |
0.32 |
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Physical Properties
| Density:
lb/cu in (g/cm3) |
.24 (6.6) |
.24 (6.6) |
.24 (6.6) |
.24 (6.6) |
.227 (6.3) |
.218 (6.0) |
.181 (5.0) |
| Melting Range:
°F (°C) |
718-728 (381-387) |
717-727 (380-386) |
718-728 (381-387) |
715-734 (379-390) |
707-759 (375-404) |
710-810 (377-432) |
708-903 (376-484) |
| Electrical Conductivity:
%IACS |
27 |
26 |
27 |
25 |
27.7 |
28.3 |
29.7 |
| Thermal Conductivity:
BTU/ft/hr/°F (W/m/hr/°C) |
65.3 (113.0) |
62.9 (108.9) |
65.3 (113.0) |
60.5 (104.7) |
66.3 (114.7) |
67.1 (116.1) |
72.5 (125.5) |
Coefficient of Thermal
Expansion:
68-212°F µin/in/°F (100-200°C µm/mm/°C) |
15.2 (27.4) |
15.2 (27.4) |
15.2 (27.4) |
15.4 (27.8) |
12.9 (23.3) |
13.4 (24.2) |
14.4 (26.0) |
| Specific Heat:
BTU/lb/°F (J/kg/°C) |
.10
(419) |
.10
(419) |
.10
(419) |
.10
(419) |
.104 (435) |
.107 (448) |
.125 (534) |
| Pattern of Die Shrinkage:
in/in |
.007 |
.007 |
.007 |
.007 |
.007 |
.0075 |
.008 |
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Compositions
| Al |
3.9-4.3 |
3.5-
4.3 |
3.9-4.3 |
3.5-
4.3 |
3.9-4.3
|
3.5-
4.3
|
3.9-4.3 |
3.5-
4.3 |
| Mg |
.025-.05 |
.020-.05 |
.03-.06 |
.03-
.08 |
.01-.020 |
.005-.020 |
.025-.05 |
.020-.050 |
| Cu |
.10 max |
.25 max9 |
.75-1.25 |
.75-1.25 |
.10 max |
.25 max |
2.6-2.9 |
2.5-
3.0 |
| Fe (max) |
.075 |
.10 |
.075 |
.10 |
.075 |
.075 |
.075 |
.10 |
| Pb (max) |
.004 |
.005 |
.004 |
.005 |
.0020 |
.003 |
.004 |
.005 |
| Cd (max) |
.003 |
.004 |
.003 |
.004 |
.0020 |
.002 |
. 003 |
.004 |
| Sn (max) |
.002 |
.003 |
.002 |
.003 |
.0010 |
.001 |
.002 |
.003 |
Ni
(other)x10
|
- |
- |
- |
- |
.005-.020 |
.005-.020 |
- |
- |
| Zn |
Bal. |
Bal. |
Bal. |
Bal. |
Bal. |
Bal. |
Bal. |
Bal. |
Color Code
ASTM B908 |
None |
Black |
Brown |
Green |
|
|
|
|
| Al |
8.2-8.8 |
8.0-
8.8 |
10.8-11.5 |
10.5-11.5 |
25.5-28.0 |
25.0-28.0 |
| Mg |
.020-.030 |
.015-.030 |
.020-.030 |
.015-.030 |
.012-.020 |
.010-.020 |
| Cu |
0.8-1.3 |
.8-
1.3 |
0.5-1.2 |
0.5-
1.2 |
2.0-2.5 |
2.0-
2.5 |
| Fe (max) |
.065 |
.075 |
.065 |
.075 |
.072 |
.075 |
| Pb (max) |
.005 |
.006 |
.005 |
.006 |
.005 |
.006 |
| Cd (max) |
.005 |
.006 |
.005 |
.006 |
.005 |
.006 |
| Sn (max) |
.002 |
.003 |
.002 |
.003 |
.002 |
.003 |
Ni
(other)x10
|
- |
- |
- |
- |
- |
- |
| Zn |
Bal. |
Bal. |
Bal. |
Bal. |
Bal. |
Bal. |
Color Code
ASTM B908 |
Blue |
Orange |
Purple |
|
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Shapes and Sizes
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Applications
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With ZA-27 alloy cast in the same dies
as its 380 aluminum counterparts,
Superwinch was able to cut project
development time for its medium-load
electric winch from 18 months to six months.
Die-casting supplier: Kennedy D.C., Inc.
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The zinc cover on the faucet - manufactured by
Delta Faucets - provides and excellent base
for plating and finishing.
Die-casting supplier: Gamco Products, Inc.
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The connector shield geometry is complex,
containing pin grooves, cored holes in two
directions and connector slots in both legs.
Die-casting supplier: Dynacast, Inc.
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Eastern Alloys, Inc. is a member of the London Metal Exchange, or LME, ILZRO,
Interzinc, NADCA, and DDC.
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Overview
Alloy Description
Mechanical Properties
Physical Properties
Compositions
Shapes and Sizes
Applications
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