304L VIM/VAR 3

[dho]

what 304L VIM/VAR stands for ?
does it mean 304L went thru VacuumInductionMelt and then went thru VacuumArcRemelting ? double melting ?
I could not find a source.
thanks.

 

[dho]

from Carpenter web, double melt.
but what AMS spec?
thanks.

 

[EdStainless]

Yes, both melts, one after the other.
So you get VIM/VAR, AOD/ESR, and half dozen other combinations. These are done for internal cleanliness reasons.
This type of material is covered in a number of ASTM F specs for medical device applications.

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P.E. Metallurgy, Plymouth Tube

 

[dho]

did a lot search, google, global engineering doc, ... could not find a spec governing VAR 304L material.
anyone has a spec?
thanks.

 

[EdStainless]

I know of some 316L VIM/VAR specs off hand, but not 304L.
Why would you want it?
There are better alloys depending on what your concerns are.
And they are already produced as remelted.

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P.E. Metallurgy, Plymouth Tube

 

[dho]

i think it is the way the aerospace industry does. all material need to meet some specification. old days, the government QQ-S-XXX spec. now, AMS. 304L is under AMS5647 which does not distinguish VIM/VAR or not.
thanks.

 

[EdStainless]

Unless there are very tight restrictions on inclusions in the metal there is no need for remelt. For example the 21-6-9 (219) that is used for hydraulic tubing is required to be remelted.
Today's AOD material is much cleaner than steels 40 years ago

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P.E. Metallurgy, Plymouth Tube

 

[dho]

this is for K--de application. we found a source supplying 304L EAF/AOD/VAR. but the engineer at K--de would not accept as it is not VIM/VAR, but gave us a K--de spec 550021 specifying the inclusion size/quantity. seems we have to go thru a metallurgical examine to generate a report to satisfy the customer.

 

[EdStainless]

AOD/VAR or AOD/ESR will meet the tightst inclusion requirements. There is no need for VIM.
VIM is very expensive since all virgin feedstock is used. Since there is no way to remove carbon or adjust the chemistry. VIM heats also tend to be small and have greater chemistry variation from heat to heat.

I hope that their spec refers either to the ASTM or ISO inclusion rating specs. You can get any reputable testing lab to do this for you.

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P.E. Metallurgy, Plymouth Tube

 

[MagBen]

VIM/VAR, double vacuum, will give you super clean material, with least inclusions. some nuclear and medical applications specify it must be VIM/VAR.

Normally static cast, concast is sufficient. Arc+VAR or ARC+ESR is better. VIM/VAR is superior. Carpenter even uses triple melting VIM+ESR+VAR for lots of aerospace applications (not for 304L)

 

[dho]

question remains. is there a QQ, AMS, ASTM spec for such inclusion limits other than company specific spec ?
thanks.

 

[EdStainless]

E45 is the ASTM inclusion rating spec.

We have looked at heats melted various ways. We have no difference in inclusion ratings. The EAF-AOD/ESR material is as clean as any other. The triple melt was no better in the alloy that we were looking at. I will add that our alloy has a nitrogen content of 0.35-0.40% that is critical. This pretty much eliminates VAR as an option.

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P.E. Metallurgy, Plymouth Tube

 

[MagBen]

In most cases, VIM/VAR is driven by customers. There may have an AMS spec that specfies this requirement, but I personally never met/saw. ASTM is more general, even less likely to inlcude such a requirement.

 

[EdStainless]

The AMS specs that I am aware of require remelt, but give options, and then they state the required cleanliness rating.
There are ASTM F specs for high cleanliness 316L and a few Ni and Co alloys that are used for medical implants.

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P.E. Metallurgy, Plymouth Tube