Aluminum alloy modifier to reduce leaks on permanent mold castings
Aluminum alloy modifier to reduce leaks on permanent mold castings
(OP)
Hi there.
Would anybody in this forum know of a alloy modifier that will modify aluminum alloys (in our case, 356) so that the castings will have less chances to leak under pressure? We are developing a casting that needs to resist up to 70 psi pressures.
emilio
Would anybody in this forum know of a alloy modifier that will modify aluminum alloys (in our case, 356) so that the castings will have less chances to leak under pressure? We are developing a casting that needs to resist up to 70 psi pressures.
emilio





RE: Aluminum alloy modifier to reduce leaks on permanent mold castings
one, degass thouroughly
two, modify with suitable grain refiner. Ti-B. this will give smaler grains that should help pressure tightness
three, modify with sodium or strontium, this can be hit or miss., but cn have spectacular results.
RE: Aluminum alloy modifier to reduce leaks on permanent mold castings
Bob Pajak
RE: Aluminum alloy modifier to reduce leaks on permanent mold castings
RE: Aluminum alloy modifier to reduce leaks on permanent mold castings
In addition to the above, there may be other issues related to melt cleanliness, i.e., inclusions and excessive hydrogen gas. Again, AFS should be able to help. Here is a link to their site:
http://www.afsinc.org/Directory.htm
RE: Aluminum alloy modifier to reduce leaks on permanent mold castings
Here is one website among many
http://www.magnatechmfg.com/mt_vacuum.asp
RE: Aluminum alloy modifier to reduce leaks on permanent mold castings
The results with the current runs will be out soon, and I will post them right away.
Emilio
RE: Aluminum alloy modifier to reduce leaks on permanent mold castings
You may call me at 610-693-5822 for discussion if you wish.
Gary Boone
RE: Aluminum alloy modifier to reduce leaks on permanent mold castings
Emilio
RE: Aluminum alloy modifier to reduce leaks on permanent mold castings
Regards,
Cory
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: Aluminum alloy modifier to reduce leaks on permanent mold castings
- degassed castings
- Tibor grain refined
- Strontium moodified
and a combination of degassed+tibor refined
Our scrap rate after pressure test was about 10% in all cases, except for that without the grain refiner, which was out worst case scenario (0ver 20%).
With regards to fluidity, we didnt notice that much of a diference on this specific die with which we ran the experiment.
Emilio
RE: Aluminum alloy modifier to reduce leaks on permanent mold castings
Strontium seems good for turning macro shrinkage into micro shrinkage, whereas sodium can have effect of eliminating it completely.
RE: Aluminum alloy modifier to reduce leaks on permanent mold castings
What type of porosity you have in the leaks? microshrink, gas porosity, Al oxides, inclusions?
Here you have some facts about refiner and modifier (AFS has several technical informations about these facts).
Ti-B is an excellent grain refiner (give smaller DAS secondary dendritic arm spacing) helps to reduce shrink and microshrink. Improve mechanical properties and soundness.
Al-Sr (better than Na) is a modifier of silicon (Si). Al-Sr modified Si from large plates acicular particles to fine fibrous Si particles (improve mechanical properties). But it increases the size of the microshrink and gas porosity, so be careful to add Al-Sr. Al-Sr has not effect in fluidity.
The RPT (reduce pressure test) specific gravity needs to be equal or more than 2.59 to eliminate gas porosity due to hydrogen.
In permanent mold when you have 12 mm or less of thickness you will reduce dramatically the microshrink.
If you want I can help to determine the anomaly type that you have in your leakers (free of charge). Just let me know and I will send you my address.
I used to work in gravity permanent mold making master cylinder (60,000 pieces per week) and we reached 300 ppm rejections (included leakers and other anomalies).