Permitted residual elements in steel.

[Jeff37]

Hi,
Does anyone know of any specifications that define permitted levels of residual elements that aren't included in the material spec, for AMS steel specs?
Thanks,

 

[EdStainless]

It depends.
In AMS there are some specs that limit some residuals.
In general if it does not change the grade or properties there are no limits.
What is your specific question?

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P.E. Metallurgy, Plymouth Tube

 

It helps to define 'residual', because there are many different understandings of this, and not just among non-metallogists.

There are the normal 'alloy' elements that are carried into carbon steels, such as Cr, Mo, Ni, and Cu. Numerous ASTM standards specify permissible limits on these (although the adequacy of these limits is debatable). This reflects the reality that many products are made by electric furnace remelting, which uses a high fraction of recycled scrap. Incidentally, this trend is a growing risk for certain sectors, primarily oil & gas.

There are 'impurity' elements, classically understood as S and P, which are reduced to acceptably low levels during steelmaking.

Then there are 'tramp' elements, understood to be those obscure elements that can enhance temper embrittlement, which afflicts Cr-Mo steels after long times at very high service temperature. These include Sn and As.

At the end of the day, ASTM standards do not guarantee that you will be supplied metal with composition that meets the requirements of your equipment. Their main function is not to put too many companies out of business. Your tech spec can specify your own limits that are tighter than ASTM.

Buyer beware.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."