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  • Why pressiure die-cast in ZINC rather than ALUMINIUM?

    Discussion in 'Metal casting & moulding' started by kenny82, Jan 26, 2010.

    1. kenny82

      kenny82 Well-Known Member

      Aug 2009
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      i have been doing some recent die-casting component design and there's one thing I dont understand :? ......

      Why would some people choose Zinc over Aluminium as a material?????

      Is it only because it's cheaper, or is it somehow a tougher material? I have seen som zinc die-castings and theyre very heavy. Can anyone explain the relative advantages and disavantages of the two materials????

      Thx guys.
    3. ConnectUTS

      ConnectUTS Active Member

      Sep 2009
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      There are a number of reasons for choosing Zinc over aluminum.

      1. As you noted cost to produce a pressure cast zinc part is lower in a lot of application. I will not say all because there would be applications where the die cast zinc part would be more expensive.

      2. Zinc is much easier to process than aluminum.
      a. Aluminum can be difficult to process because it is very reactive, especially when in molten form.
      b. Liquid zinc flows much better than aluminum.
      c. Zinc's melting point is lower than aluminum 420C vs 660C
      d. Zinc does not require alloying to be used.

      3. Zinc has a much better surface finish it is both shinier and smoother than aluminum. This is important for high quality castings.

      Niel Leon
      Unicorn Technical Services
      Bringing your Vision to Reality
    4. mvalenti

      mvalenti Well-Known Member

      Nov 2009
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      when you say pressure die cast, are you refering to the method that they heat the metal to its plastic state and ram it into the mold?
    5. kinnavate

      kinnavate Member

      Sep 2010
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      I have produced many products (cast in the millions of parts per year) and are used outside and are exposed to the the elements. Zinc is vastly superior to aluminum in corrosion resistance. I have done 500 hour salt spray tests where the aluminum castings were so corroded they nearly crumbled when handling them. These were powder coated parts which were scratched to see how the scratch propagated into the base metal. The next big advantage is cost per lb. Zinc #3 is much less expensive than say A360 aluminum per pound. Zinc also has a higher flow rate than aluminum so the walls can usually be half as thick as aluminum and have less draft. Zinc reproduces finer detail than aluminum and usually has less casting porosity. Even know aluminum has less mass then the zinc #3 with the thicker wall section , the parts end up being similar in weight but the aluminum parts are much bulkier. The bulkier part leads to higher costs for packaging and transportation. This is especially critical when you are shipping product from Asia, you want as high a density as possible to avoid shipping air. Depending on your strength requirements you might need a zinc alloy with some aluminum content to improve ductility (i.e ZA-8, ZA-12, ZA-27). I would recommend you visit NADCA (North American Die Casting Association) website at www.diescasting.org. They have a great book called NADCA Product Specification Standards for Die Casting (among others).

      Hope this helps


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