Essential: the principle of stainless steel wire for the manufacture of fasteners

January 20, 2024

　　 Material selection principle
The choice of stainless steel materials is mainly considered from the following five aspects.
1. Requirements for mechanical properties, especially strength, of fastener materials.
2. Requirements for the corrosion resistance of the material under working conditions.
3, the working temperature on the material's heat resistance (high temperature strength, oxidation resistance) requirements.
4. Requirements for material processing performance in terms of production process.
5, other aspects, such as weight, price, procurement factors must be considered.
After comprehensive and comprehensive consideration of these five aspects, the brand, variety, specifications and material standards of the selected fasteners are finally determined.
Austenitic stainless steel
Commonly used grades are four grades of 302, 303, 304, and 305, the so-called "18-8" austenitic stainless steel grades. Both corrosion resistance and mechanical properties are similar. The starting point for the selection is the production process of the fasteners, which in turn depends on the size and shape of the fasteners, 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 use in the processing of fasteners using the enthalpy process, such as longer gauge bolts, large diameter bolts, which may exceed the range of the cold heading process.
Type 305 is suitable for use in the processing of fasteners using the cold heading process, such as cold formed nuts, hex bolts.
Types 309 and 310, which have higher Cr content and Ni content than 18-8 stainless steel, are suitable for fasteners 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 fasteners that do not anneal after welding or service at 420 to 1013 °C.
Ferritic stainless steel type 430 ordinary chrome steel, its corrosion resistance and heat resistance are better than 410 type, magnetic, but it can not be heat-treated and strengthened, it is suitable for the corrosion resistance and heat resistance slightly higher strength requirements General stainless steel fasteners.
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 and corrosion resistant fasteners. Type 416 is slightly high in sulfur and is a free-cutting stainless steel.
Type 420, sulphur content ≧0.15%, improved mechanical properties, heat treatment strengthening, maximum hardness value 53 ~ 58HRC, for fasteners requiring higher strength.
Precipitation hardening stainless steel 17-4PH, PH15-7Mo, which can achieve higher strength than the usual 18-8 type stainless steel, is used for high strength, corrosion resistant stainless steel fasteners.
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 and corrosion-resistant fastener, it can be used up to 650-700 °C. (Source: Mechanical Expert)

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Mr. tiloo

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