Building up Stainless 2

[magusinp]

Visited an investment casting foundry last week. The owner said that he 'built-up' 316SS from 304 by adding Mo to the melt. He explained that he could build up various different metals this way. He verified the composition using a spectrometer he has in-house. He would not do this if it were to be a code vessel or require some special certifications or we didn't like it. However he could provide certified MTRs of each heat with his spectrometer as it is NIST traceable.
I've never heard of a small foundry doing this. Is it acceptable? It seems as if it is based on my judgement alone.

 

[unclesyd]

This is how some small producers make different alloys in small lots and is a fairly common practice. We have had additional metals added for experimental work.

The caveats are:

Can they produce a homogeneous material?

Do they have a way to properly sample the material for the physical testing, if required?

Watch for tramp materials.

Carbon control is difficult.

I think that if you just need 316 S/S for corrosion resistance and not pressure containing parts that come under any code you are ok to use.

The bit about traceable is that he uses a NIST standard sample for calibration.

Be careful as I worked on the NIST Sample Program years ago.

 

[arunmrao]

To produce CF8M castings ,304 charge is the starting material and then add Mo,Ni and Cr(melting loss). The end melt is CF8M and there is no variation. C is not a concern as selection of 304 charge controls it.Achieving mechanical properties is no sweat and microstructure analysis is also satisfied. I have been doing this for 12 years. I also make higher alloys this way.

 

[mcguire]

Making any version of the austenitic stainless steels is simply adding ingredients until one reaches the right percentages for each required component. The only refining is done in the subtraction, i.e. the removal of unwanted ingredients, usually carbon, sulfur, oxygen. If there are excessive amounts of tramp metals such as copper or managanese they must be diluted. Some metals with high vapor pressures like lead, mercury, etc can be removed by blowing gasses through the molten metal.