Silicon content in 4370 Investment Castings
Silicon content in 4370 Investment Castings
(OP)
We use some small 4370 investment castings that have been having problems with non-metallic inclusions. The foundry wants to raise the silicon content from 0.3% to 1.0% in an effort to help with the inclusions.
What would be the effect in raising the silicon content?
The castings are heat treated to 60 HRC and are subject to impact and wear during service.
TIA
What would be the effect in raising the silicon content?
The castings are heat treated to 60 HRC and are subject to impact and wear during service.
TIA





RE: Silicon content in 4370 Investment Castings
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RE: Silicon content in 4370 Investment Castings
They are showing up in a WEDM step. The wire deflects around the inclusions.
I am not getting very good help from the foundry........they have been doing these castings for 5 years without trouble. Now there is an issue and they do not want to look at their process........
RE: Silicon content in 4370 Investment Castings
I am providing a few references for further reading. however, if it is macro defect I feel that the problem lies with process controls and chemistry might have no major role to play.
http://neon.mems.cmu.edu/afs/afs2/intro.html
http://www.p2pays.org/ref/08/07546.pdf
Castings : Author John Campbell isbn=0750647906
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RE: Silicon content in 4370 Investment Castings
You need to get these guys to keep them out in the first place. My hunch is that it is related to the raw material supply.
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RE: Silicon content in 4370 Investment Castings
I think this is how they can offer us 4370. Its really a non-standard alloy. We may have to switch foundries and use S7 but I don't think S7 can be hardened to 60 HRC with a decent temper.
When I say you can see the inclusions with the naked eye.....some of them are easily 1mm.
RE: Silicon content in 4370 Investment Castings
RE: Silicon content in 4370 Investment Castings
I'd ask the foundry what the intent of the Si additions would be and why they feel it would solve the problem. They may actually know more than someone on an internet message board.
I am not sure I agree with arunmrao that the increased silicon will be detrimental. AMS 6257 (300M) is a modified 4340 (with 0.35-0.45 Mo, 1.45-1.80 Si and 0.05-0.10 V) and is used in applications where higher strength and toughness than can be obtained with 4340 is needed. I'm not saying that for your application that the higher Si content would be beneficial, but rather that there are cases where higher Si is used successfully.
rp
RE: Silicon content in 4370 Investment Castings
High Si content causing brittleness is a practical observation made. Instead of using steel scrap there was a mixup and high silicon steel was used instead. The castings were found to break like biscuits .
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RE: Silicon content in 4370 Investment Castings
Regards,
Cory
Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips Fora.
RE: Silicon content in 4370 Investment Castings
Cory, I was not trying to compare 4340 to a casting with 1% Si (I agree, that would be an unfair comparison). I was comparing 4340 to 300M, where one of the major differences is a 5 to 6 times increase in the silicon content. That is, to provide an example where the higher silicon content does not result in unacceptable toughness. Are you trying to say that an as-cast steel with 0.7 % C and 0.3% silicon will not have "ductility problems"?
My advice to the OP was that if he had questions on what the vendor proposed, to dicuss it with them. Most likely, this isn't the first time they have run across this problem and they might have some practical experience in the matter. As to what the effect of raising the silicon content in the material would be, they might just be able to answer that, too.
rp
RE: Silicon content in 4370 Investment Castings
I think an as-cast steel with 1 % Si will have worse ductility than if it had 0.3 % Si.
I think you are giving the vendor too much credit - this is a HUGE change that is proposed, and if the casting contains 1 mm sized inclusions, then there is a fundamental problem with the entire process.
Regards,
Cory
Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips Fora.
RE: Silicon content in 4370 Investment Castings
I have discussed this with the foundry and actually people on a message board know more then them. They do not want to help with these problems and are basically blowing me off.
We are currently looking for another foundry.
Thanks all for the comments.....................
RE: Silicon content in 4370 Investment Castings
I had suspected a similar situation. For business reasons or technical incapabilities,whenever situations arise this is the common ploy adopted by foundries here. Since it was a technical forum I did not discuss this aspect.
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RE: Silicon content in 4370 Investment Castings
Could you make an exception in this case and discuss the business aspects? This is actually very important to my company. Understanding the underlying reason behind this request from the foundry, does....in some way....relate to the technical aspect of the forum.
many thanks.........
RE: Silicon content in 4370 Investment Castings
you may contact handlename @ hotmail.com with more details.
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