Steel group C in ISO 3506-1

[CoryPad]

Why is the letter C used as the designation for the martensitic steel group in ISO 3506-1 Mechanical properties of corrosion-resistant stainless steel fasteners -- Part 1: Bolts, screws and studs? The letters A and F are used for austenitic and ferritic, respectively, which is logical. Why not M for martensitic?

 

[metengr]

Good question. Being involved with code and standards over the years I would guess not to confuse the M with ISO standard metric screw size designation.

 

[CoryPad]

That makes sense, it could be confusing to have class M1, M3 and M4 since that also could be thread size.

I way suppose the C comes from higher carbon in those alloys to promote martensite microstructure.

Thanks.