Die casting questions: choice of Al-Zi-Mg alloys
Die casting questions: choice of Al-Zi-Mg alloys
(OP)
Hi,
I'm designing a part with a size and complexity comparable to a
standard retractable utility knive. These knives seem to be diecast
from whitemetal (some alloy of Al,Zi,Mg) but my spec on surface
hardness is tougher than the samples I've tested.
This app is cost sensitive, and my reading of past articles suggests
that 1) stainless can't be diecast and 2) other methods are a good bit
more expensive; I guess that's why I don't see any SS utility knives.
Still, I'd like to understand the tradeoffs between a soft stainless
steel (or at least rust resistant steel) and some whitemetal alloy.
Qs:
1) Steel can't be diecast the way whitemetal is, right ?
2) What's the cheapest unit cost process that can compete with diecasting
for steel?
3) Are there any references for a really tough whitemetal alloy
(diecastable)? Weight is not an issue, cost is.
Thank you,
I'm designing a part with a size and complexity comparable to a
standard retractable utility knive. These knives seem to be diecast
from whitemetal (some alloy of Al,Zi,Mg) but my spec on surface
hardness is tougher than the samples I've tested.
This app is cost sensitive, and my reading of past articles suggests
that 1) stainless can't be diecast and 2) other methods are a good bit
more expensive; I guess that's why I don't see any SS utility knives.
Still, I'd like to understand the tradeoffs between a soft stainless
steel (or at least rust resistant steel) and some whitemetal alloy.
Qs:
1) Steel can't be diecast the way whitemetal is, right ?
2) What's the cheapest unit cost process that can compete with diecasting
for steel?
3) Are there any references for a really tough whitemetal alloy
(diecastable)? Weight is not an issue, cost is.
Thank you,





RE: Die casting questions: choice of Al-Zi-Mg alloys
http://www.diecasting.org/faq/
One method of forming small, complex, high quality SS parts is “Metal Injection Molding. It is very similar to plastic injection molding but with metal powder blended with a binder...” The binder is then baked out, and the part is sintered at high temperature. The process is cost-effective for complex parts, where it may eliminate joining, machining & surface finishing operations. Perhaps reduce the cost by using less (thinner) of the higher strength SS vs. a typical die cast alloy. See
Metal Injection Molding Design Guidelines http://www.alberox.com/MIM_design_guide.pdf
RE: Die casting questions: choice of Al-Zi-Mg alloys
RE: Die casting questions: choice of Al-Zi-Mg alloys
It is nearly impossible for me to explain the limitations of die casting process and the intricacies involved.
RE: Die casting questions: choice of Al-Zi-Mg alloys
Hello,
I apologize for not being too clear in my initial description.
The required internal complexity (keys, lips & webbing) is equivalent
to those utility knives. Since, the outside surface can't be stamped
in, this part would require at least two stampings,so I think the best
candidates are
1) a hard Al/Zi alloy, possibly nickel plated surface
2) finding a cheap way to do investment casting in steel.
Thanks for the replies and references,
RE: Die casting questions: choice of Al-Zi-Mg alloys
RE: Die casting questions: choice of Al-Zi-Mg alloys
Steels can be die cast in expensive refractory metal (e.g., Mo, W) dies, but I don't know of much use commercially. The preheat temperatures needed are higher than can be reached by the usual method of flowing hot flowing through passages in the mold.
Intricate SS parts are often made by investment casting (aka. lost wax, lost foam). Slower & more expensive, though. Shell moulding is similar; less expensive at greater quantities. For a simplified overview of the various moulding & casting processes, see http://www.foundryonline.com/foundvpr.htm
Ken
RE: Die casting questions: choice of Al-Zi-Mg alloys
I'll review and let people know how it turns out...