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Stock 440 Exhaust Manifold Nuts in Stainless?

I never said 304 had lead in it. There is a stainless that is "free machining" stainless. I have cut it for many years. It's been years since machining but I had been told it was because it contained lead. I know in order to cut it "free machining" it contains sulfur and maybe some lead content.
As a machinist I didn't go into the engineering aspects. I just make setups and make the parts according to what's needed. I know it cut easier, cut down quite a bit of machine time and saved cost to the customer if it was acceptable to engineering. When I requested an engineer this suggestion once for of using it for test chamber parts he said "No -because it wouldn't satisfy extreme environmental conditions." So back to 304 and timely machining.

From this article which is pretty interesting reading:

"Stainless steels are known for their corrosion-resistant qualities given by a complex oxide protective film on the alloy surface. Chromium and nickel are the most important elements which form passive film. On the other hand, most grades of stainless steels are more or less difficult to machine in end-use conditions and are substantially different from that of carbon or alloy steels and other alloys. One procedure for improving machinability of stainless steels is the result of changes in composition by adding sulfur, selenium, lead, copper, etc. Alloying elements serve to reduce the friction forces, transverse ductility and the tendency of the chips to weld to the tool, but they affect functional (corrosion resistance, transverese ductility) and technological properties (machinability, weldability) in a free-machining stainless steel."

May I suggest looking at this article:

Free-Machining of Stainless Steels :: Total Materia Article
I use to purchase materials and design high temperature gas to gas heat exchangers using plate, structural shapes and pipe in all the aforementioned alloys using the ASME and ASTM requirements for the service that was intended. I'm very much aware of the fundamental differences between the different alloys and their use in both machining, forming, and welding and the ease and difficulties in their use, as it applies to both ferritic (basically iron and chrome no nickel) and austinetic alloys and pure nickel alloys. There are many aspects to producing a product with machining as one of several criteria, but not the only aspect. Functionality of the final product being the driving factor.
BOB RENTON
 
I use to purchase materials and design high temperature gas to gas heat exchangers using plate, structural shapes and pipe in all the aforementioned alloys using the ASME and ASTM requirements for the service that was intended. I'm very much aware of the fundamental differences between the different alloys and their use in both machining, forming, and welding and the ease and difficulties in their use, as it applies to both ferritic (basically iron and chrome no nickel) and austinetic alloys and pure nickel alloys. There are many aspects to producing a product with machining as one of several criteria, but not the only aspect. Functionality of the final product being the driving factor.
BOB RENTON

This company was called SES - Standard Environmental Systems. Maybe you heard of them?

Thanks for the replies and the details
 
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