New Aluminum alloy for making molds?

[Firebird]

MSFC-398 (http://www.sciencedaily.com/releases/2002/08/020801081009.htm) is a new aluminum-silicon alloy developed at NASA for engine pistons. Described as having 3-4 times the strength of conventional alloys at 600 degrees F, and is harder and more wear resistant.
Sounds like just what we need for mold making, and is low cost and must not be too bad to machine or they wouldn't be using it for pistons.

[Red River Rick]

Interesting. Problem is, when will it be available, and if it's ever produced in large enough quantities. This is probably just another alloy that's been stumbled upon. And may or may not make it onto the market, like there isn't enough "Aluminum Alloys" out there already.

RRR

[badgeredd]

MSFC-398 (http://www.sciencedaily.com/releases/2002/08/020801081009.htm) is a new aluminum-silicon alloy developed at NASA for engine pistons. Described as having 3-4 times the strength of conventional alloys at 600 degrees F, and is harder and more wear resistant.
Sounds like just what we need for mold making, and is low cost and must not be too bad to machine or they wouldn't be using it for pistons.

Firebird,

I read the article and see no mention of the actual hardness in on a standard scale. I guess I would like to know that piece of info first before I further commented. I suspect that Lee uses an alloy sinilar to 6061 'cause it seems softer to me than 7075 which is a hard (for aluminum) alloy. Increase silicon does add some hardness and wear resistance to a recipricating load but may not be worth beans for a mold due to poracity. I'm sure others have opinions too and likely some here have more metalugical knowledge than I do. Just my nickels worth.

Edd

[BABore]

The first time I cut aluminum molds, I went with what all the other mold makers use, 2024-T351 alloy. I think I paid over $75 for a 3/4 x 1 1/2 x 144" bar. When I ran out, I tried some of the 6061 alloy that we use for most of our non-contact, weld tooling. It costs about one third that of the 2024. I could not see a lick of difference in how the block sets held up. If anything, it cut better. I've also used random pieces of MIC 6, type 300, cast tool and jig plate. It's cast, stress relieved, and machined to final thickness. It holds up well and machines well. About the biggest diference I've seen is how one type of aluminum will absorb the WD-40, we use for cutting fluid, over another type. If you look up the physical properties of the different (common) aluminum alloys, there's just not that much of a difference in hot strength/hardness.

I guess it also helps that I don't use a mold as a hammer nor slam blocks together just to see how fast I can go.

[TAWILDCATT]

BaBore:naughty,naughty.you mean there are people that think the molds are hammers and use them as such like throw at the wall.:coffee:[smilie=1::drinks:

[Firebird]

I don't know about porosity of the alloy, but what caught my attention was the claim of 3-4 times the strength at 600 degrees. I know one of the big problems with our aluminum molds is the lack of strength at temperature and this alloy would hopefully solve it.
I did go back and re-read the article again, and realized that they only talked about investment casting of this alloy, nothing about machining the pistons after they are cast; so the machinablility may not be as good as I assumed. If this alloy does become popular in the auto industry for pistons, I would think that it would become available outside of the auto industry also, though maybe only in ingots, not in bar form, if all it is used for is castings.

[felix]

That is the aluminum I can get from Noranda. I've discussed this before. All we need are some bonifide mold makers. I tried to get Dan at Mountain Molds to try it, and he refused. ... felix

[Frank46]

Just a thought, has anyone ever tried the aluminum bronze rod that enco sells?. I think (here we go again) that with the addition of the bronze in the alloy it just might
be a bit better at higher temps. Maybe someone with more metalurgical knowledge than me might be able to chime in and say something. Frank

[Buckshot]

BaBore:naughty,naughty.you mean there are people that think the molds are hammers and use them as such like throw at the wall.:coffee:[smilie=1::drinks:

..............HA! Ole 9.3x62AL had an extra special Lee 457-405F mould he cared a great deal about. He cared enough to drive 70 miles just to throw it into the Salton Sea :-)

Frank46, Aluminum Bronze is a Bronze alloy that some small amount of Aluminum has been added to, and not Aluminum that has a bit of bronze added to it. Small percentages of other metals added can change certain properties significantly. Its been sometime since I looked at the list but alloys of Aluminum all melt in the same relative region, which isn't a whole lot hotter (maybe 300*?) then an electric lead melting furnace can reach.

................Buckshot

[montana_charlie]

I don't know about porosity of the alloy, but what caught my attention was the claim of 3-4 times the strength at 600 degrees. I know one of the big problems with our aluminum molds is the lack of strength at temperature and this alloy would hopefully solve it.
I thought the 'strength problem' with aluminum came into play when trying to hold 50 pounds of molten alloy in an aluminum pot.

Never heard of a mould breaking from the weight of the bullet.
CM

[Firebird]

Breaking, no but how many molds (and how many times for each mold) have you had to go back and reset the alignment pins? Or accidentally drop a hot mold and have a big ding in a corner, then realize the whole block is now bent? It isn't just heat expansion that's moving things, it's that hot aluminum just isn't very strong. Mountain Molds has a chart up on his mold construction page showing the 2024 aluminum he uses has a yield strength at room temp of 45,000 psi, but at 500 degrees F. the yield strength is only 9500 psi, and it melts at 935 degrees F. And this drop in strength when hot to about 20% of room temperature strength is described as "better than most aluminum alloys". If this new alloy has 3-4 times the strength when hot compared to other aluminum, that's a very good thing for our molds.

[Southron Sanders]

Besides machineability, the next question is: How well does this new aluminum alloy transfer heat? A good mould alloy must transfer heat to the air so the cavity dosen't get too hot during a long casting session.

Someone needs to get a hold of some of this new alloy, make a mould out of it, cast some boolits and then report back on this BB how good or bad this new alloy is for making bullet moulds!

Any takers out there?

[Frank46]

Rick, thanks for the explanation. Frank

[BABore]

Breaking, no but how many molds (and how many times for each mold) have you had to go back and reset the alignment pins? Or accidentally drop a hot mold and have a big ding in a corner, then realize the whole block is now bent? It isn't just heat expansion that's moving things, it's that hot aluminum just isn't very strong. Mountain Molds has a chart up on his mold construction page showing the 2024 aluminum he uses has a yield strength at room temp of 45,000 psi, but at 500 degrees F. the yield strength is only 9500 psi, and it melts at 935 degrees F. And this drop in strength when hot to about 20% of room temperature strength is described as "better than most aluminum alloys". If this new alloy has 3-4 times the strength when hot compared to other aluminum, that's a very good thing for our molds.

The answer is none? I use stainless liners and bushings. I wouldn't use any aluminum alloy without them. Even iron molds benefit from the same setup. All contact and wear is on them. How you treat the rest of the mold is up to you. I've made bunches of aluminum molds the show no wear after 1,000's of cycles.

[windrider919]

Honestly.....I think the whole debate is much adu about nothing. I have used Lee moulds for years and thousands of bullets per mould. Given the SAME care spent with cast iron moulds they last and produce just fine. I have seen Lee moulds fail but invariably if asked to demonstrate their casting technique the guys that had damaged moulds had poor procedures and improper handling care.

It does not matter that Al looses so much strength because that strength IS NOT BEING CALLED ON as a mould. It certainly applies in a pressure situation such as a rocket motor case or gas lines in a high temp environment but not for moulding lead.

I have a Lee 457 conical mould that I use for my Ruger Old Army [and size for 45ACP too]. I bought this mould in 1982 and by my notes this mould has produced over 5000 bullets that are just as perfect of finish and size as when new. If I remember correctly I paid less than $15.00 for it. Why would I need a "Stronger tensile strength" mould material? It has what we need: Heat transfer at a good rate for manual casting.

Further, I have encountered iron blocks that have warped or have alignment pins that failed too. And again, it was usually traced to misuse. My take is dont try to fix whats not broken.