In the USA, It is the steel mill that "certifies" the heat ( melt) . You know 4140 is not 4140 ?Greg_Lewis wrote: ↑Thu Dec 08, 2022 12:16 pm A question that then comes to mind is any impurities in the steel. What is the allowance for impurities and how can that be checked? If a particular alloy is marketed as, say, M35, what is the level of permitted impurities and how can that be checked after the alloy has been created? And who does that checking?
Well, it is , but it has variations that many are not aware of . For example :
The Die shop I worked at did some very large dies , like 50,000 pounds net in our big dies .
But even our small dies ( 800 pounds) all had "AQ" steel. So we ordered 4140 AQ which is superior to 4140 you buy at a steel supplier.
The "AQ' Rating meant several things, first it was Aircraft Quality ( dig the name) and that meant good enough for aircraft components.
How does that come about ? well they Xray/ultrasound the steel and not only does it have Chemical certs ( we got) , but "inclusions" could not
exceed a size or quantity as the number was restricted . When the steel passed that level, it was AQ rated. I have horror stories about inclusions in steel we got from false vendors .
I have nothing to do with this mill nor did we buy from them , but in my experience , Carpenter Steel has some of the finest steel
I have ever worked with .. extremely consistent and reliable !
if that M 35 steel is made elsewhere, good luck, you have no guarantees . If you got it from Carpenter, i would no qualms !
Rich