First, ferritic stainless steel
Type 430 ordinary chrome steel, its corrosion resistance and heat resistance are better than 410 type, it is magnetic, but it can not be heat-treated and strengthened. It is suitable for stainless steel stainless steel with high strength and corrosion resistance. Screw.
Second, martensitic stainless steel
Types 410 and 416 can be heat-treated and reinforced with a hardness of 35 to 45 HRC. They have good machinability and are used for general purpose heat-resistant and corrosion-resistant stainless steel screws. The Type 416 has a slightly higher sulfur content and is a free-cutting stainless steel. Type 420, sulfur content R0.15%, improved mechanical properties, heat treatment strengthening, maximum hardness value 53 ~ 58HRC, for stainless steel screws requiring higher strength.
Third, precipitation hardening stainless steel
17-4PH, PH15-7Mo, they can be used with higher strength than the usual 18-8 type stainless steel, and are therefore used for high strength, corrosion resistant stainless steel stainless steel screws.
A-286, a non-standard stainless steel, has higher corrosion resistance than the commonly used 18-8 stainless steel and good mechanical properties at elevated temperatures. Used as a high-strength, heat-resistant, corrosion-resistant stainless steel screw, it can be used up to 650 ~ 700 °C.
Fourth, austenitic stainless steel
Commonly used grades are four grades of 302, 303, 304, and 305, the so-called "18-8" type austenitic stainless steel. Both corrosion resistance and mechanical properties are similar. The starting point for the selection is the production process of stainless steel screws, which in turn depends on the size and shape of the stainless steel screws, and also on the quantity produced.
Type 302 is used for machined screws and self-tapping bolts.
Model 303 In order to improve the cutting performance, a small amount of sulfur is added to the Type 303 stainless steel for the processing of nuts with bar stock.
Type 304 is suitable for machining stainless steel screws with a hot boring process, such as longer gauge bolts and larger diameter bolts, which may exceed the range of the cold heading process.
Type 305 is suitable for machining stainless steel screws with cold heading, such as cold formed nuts and hexagon bolts.
Types 309 and 310, which have higher Cr content and Ni content than 18-8 stainless steel, are suitable for stainless steel screws working at high temperatures.
Types 316 and 317, both of which contain the alloying element Mo, are therefore higher in strength and corrosion resistance than 18-8 stainless steel.
Types 321 and 347, Type 321 contains a relatively stable alloying element Ti, and Type 347 contains Nb, which improves the intergranular corrosion resistance of the material. Suitable for stainless steel standard parts that are not annealed after welding or serviced at 420 to 1013 °C
The grades of stainless steel bolts are divided into 45, 50, 60, 70, 80 materials mainly divided into austenite A1, A2, A4, martensite and ferrite C1, C2, C4, which are represented by methods such as A2-70, "- - "The bolt material and strength level are indicated before and after respectively.