What are the principles of selecting stainless ste

2022-09-25
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What are the principles of selecting stainless steel wire for fasteners?

fasteners are mechanical basic parts, which are in great demand. Generally, bolts, screws, rivets, etc. in order to ensure safety or glass fiber reinforcement, the impact of temperature, harsh environment or other dangerous working conditions are generally not considered. Commonly used materials are carbon steel, low alloy steel and non-ferrous metals. However, in certain occasions, fastener materials need to meet the conditions of severe corrosion or high strength, and many stainless steels and ultra-high strength stainless steels came into being

this paper briefly introduces the excellent stainless steel used in fastener production. Most stainless steel materials can be made into steel wires or bars for fastener production, including austenitic stainless steel, ferritic stainless steel, martensitic stainless steel, precipitation hardening stainless steel

selection principle

the selection of stainless steel materials is mainly considered from the following five aspects

1. Requirements for fastener materials in terms of mechanical properties, especially strength

2. Requirements of working conditions on corrosion resistance of materials

3. Requirements of working temperature on heat resistance (high temperature strength, oxidation resistance) of materials

4. Requirements of production process on material processing performance

5. Other factors, such as weight, price and purchase, should be considered

through the comprehensive tensile testing of these five aspects, the machine, also known as the universal material testing machine, is used to carry out mechanical stress testing for various materials, such as static load, tension, contraction, bending, shearing, peeling and other mechanical properties. After comprehensive consideration, the brand, variety, specification and material standard of the selected fasteners are finally determined

austenitic stainless steel

the commonly used grades are 302, 303, 304 and 305, which are the so-called austenitic stainless steel. Both corrosion resistance and mechanical properties are similar. The starting point of selection is the production process of fasteners, and the method depends on the size and shape of fasteners, as well as the quantity of production

302 type is used for machined screws and self tapping bolts

303 type in order to improve the cutting performance, 303 type stainless steel is added with a small amount of sulfur, which is used to process nuts with bars

304 type is applicable to fasteners processed by hot heading process, such as bolts with longer specifications and bolts with large diameter, which may exceed the scope of cold heading process

305 is suitable for processing fasteners by cold heading process, such as cold formed nuts and hexagon bolts

309 and 310, their Cr content and Ni content are higher than that of type stainless steel, which are suitable for fasteners working at high temperature

316 and 317, both of which contain the alloying element Mo, so their high temperature strength and corrosion resistance are higher than that of type stainless steel. Wear resistant electrode

321 and 347. 321 contains relatively stable alloy element Ti and 347 contains Nb, which improves the intergranular corrosion resistance of the material. It is applicable to fasteners that are not annealed after welding or that are in service at 420 ~ 1013 ℃

ferritic stainless steel

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

martensitic stainless steel

Zhou Yi, chief designer of China Aerospace Sanjiang group technology center, type 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 is a free cutting stainless steel with slightly higher sulfur content

420 type, sulfur content ≥ 0.15%, improved mechanical properties, can be strengthened by heat treatment, and the maximum hardness value is 53 ~ 58hr. It is used for fasteners requiring higher strength in consideration stage C

precipitation hardening stainless steel

ph, phmo, they can obtain higher strength than the usual 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 commonly used type stainless steel, and still has good mechanical properties when the temperature increases. Used as high-strength, heat-resistant and corrosion-resistant fasteners, it can be used to 650 ~ 700 ℃

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