Stainless Steel Fasteners

Austenitic steel (steel grades A1, A2, A3, A4, A5, and A8), with high amounts of chromium and nickel, cannot be hardened by heat treatment. It has excellent corrosion resistance, good ductility, and is usually only slightly magnetizable.

Ferritic steel (steel grade F1) contains less than 0.1% carbon, and usually 11% to 18% chromium, cannot be hardened by heat treatment, and is significantly magnetizable. If a lower corrosion resistance than that of the austenitic grades A2 or A3 is suitable for the planned application, stainless steel grade F1 may be a good economic compromise.

Martensitic steel (steel grades C1, C3, and C4) has high amounts of chromium but a very low nickel content and it can be hardened by heat treatment to increase strength. However, it has reduced ductility and is significantly magnetizable. Martensitic grades C1 and C4 have a lower corrosion resistance than austenitic grades.

Duplex steel (steel grades D2, D4, D6, and D8) has a microstructure with both austenitic and ferritic phases (typically 40% to 60%), which has a higher content of chromium and a lower content of nickel compared to austenitic steel. It is high-strength and highly magnetizable. Duplex stainless steels also have excellent corrosion resistance and, compared to austenitic stainless steels A1 to A5, a much better resistance to stress cracking corrosion.

With regard to pitting and crevice corrosion, D2 has at least equivalent corrosion resistance to A2; D4 is equivalent to A4. D6 has an improved corrosion resistance over A4 and D4. D8 has a corrosion resistance that is comparable to A8.