What stainless steel materials are commonly used for fasteners?
1. Austenitic stainless steel
The commonly used grades are 302, 303, 304 and 305, namely the so-called "18-8" austenitic stainless steel. Both corrosion resistance and mechanical properties are similar. The starting point of selection is the production process of fasteners, which depends on the size and shape of fasteners, and also depends on the number of production.
Type 302 is used for machining screws and self tapping bolts.
In order to improve the cutting performance, 303 stainless steel is added with a small amount of sulfur, which is used to process nuts with bar stock.
Type 304 is suitable for the processing of fasteners by hot upsetting, such as long specification bolts and large diameter bolts, which may be beyond the scope of cold upsetting.
Model 305 is suitable for processing fasteners by cold heading process, such as cold formed nuts and hexagon bolts.
The Cr and Ni contents of 309 and 310 are higher than those of 18-8 stainless steel, which are suitable for fasteners working at high temperature.
Both types 316 and 317 contain Mo, so their high temperature strength and corrosion resistance are higher than those of 18-8 stainless steel.
321 and 347, 321 contain more stable alloy elements Ti, 347 contain Nb, so the intergranular corrosion resistance of the material is improved. It is suitable for fasteners not annealed after welding or in service in 420-1013c.

2. Ferritic stainless steel
430 type ordinary chromium steel has better corrosion resistance and heat resistance than 410 type. It is magnetic, but it can not be strengthened by heat treatment. It is suitable for stainless steel fasteners with slightly higher corrosion resistance and heat resistance, and its strength requirements are general.

3. Martensitic stainless steel
410 and 416 can be strengthened by heat treatment, with hardness of 35 ~ 45hrc and good machining performance. They are used as heat-resistant and corrosion-resistant fasteners for general purposes. Type 416 has a slightly higher sulfur content and is a free cutting stainless steel.
420 type, sulfur content ≥ 0.15%, improved mechanical properties, can be strengthened by heat treatment, the maximum hardness value is 53 ~ 58hrc, used for fasteners requiring higher strength.

4. Precipitation hardening stainless steel
17-4PH, ph15-7mo, they can obtain higher strength than the normal 18-8 type stainless steel, so they are used for high-strength, corrosion-resistant stainless steel fasteners.
A-286, a non-standard stainless steel, has higher corrosion resistance than the common 18-8 stainless steel, and still has good mechanical properties when the temperature increases. It can be used as high-strength, heat-resistant and corrosion-resistant fastener, and the service temperature can reach 650 ~ 700C.