Fasteners are mechanical foundation pieces that require a lot of pressure, usually bolts, screws, rivets, etc. in order to ensure safety or generally do not take into account the effects of temperature on harsh environments or other dangerous conditions. Commonly used materials are carbon steel, low alloy steel and nonferrous metals. However, in certain occasions, fastener materials need to meet the serious corrosion or high strength conditions, there are many stainless steel and ultra-high strength stainless steel came into being.

This article briefly describes the excellent stainless steel for fastener production. Most stainless steel materials can be made of steel wire or bar for fastener production, austenitic stainless steel, ferrite stainless steel, martensitic stainless steel, precipitation hardened stainless steel.

Selection principle:

The choice of stainless steel material mainly from the following five aspects to consider.

1, the fastener material in the mechanical properties, especially the strength requirements.

2, working conditions on the corrosion resistance of materials on the requirements.

3, the working temperature of the material heat resistance (high temperature strength, oxidation resistance) requirements.

4, the production process on the material processing performance requirements.

5, other aspects, such as weight, price, procurement factors should be considered.

Through the five aspects of a comprehensive, comprehensive consideration, the final selection of the choice of fasteners brand, variety, specifications, material standards.

Austenitic stainless steel

Commonly used grades for the 302,303,304,305 four grades, the so-called "18-8" type austenitic stainless steel these four grades. Whether it is corrosion resistance, or its mechanical properties are similar. The starting point of the selection is the method of production of the fastener, and the method depends on the size and shape of the fastener, as well as the quantity produced.

Type 302 for use with machined screws and tapping bolts.

303 In order to improve the cutting performance, 303 stainless steel added a small amount of sulfur, for the use of bar processing nuts.

Type 304 is suitable for use with hot forging processes for fasteners, such as longer bolts, large diameter bolts, which may exceed the scope of the cold heading process.

Type 305 is suitable for use with cold heading processes for fasteners, such as cold forming nuts, hex bolts.

309 and 310, their Cr content and Ni content are higher than 18-8 stainless steel, suitable for high temperature work fasteners.

Model 316 and Model 317, all of which contain alloying elements Mo, so their high temperature strength and corrosion resistance are higher than those of type 18-8 stainless steel.

321 type and 347 type, 321 type contains more stable alloying elements Ti, 347 type containing Nb, thus improving the material resistance to intergranular corrosion. Applicable to non-annealing after welding or service in the 420 ~ 1013 ℃ fasteners.

Ferritic stainless steel

430 type chrome steel, its corrosion resistance and heat resistance than the 410 type is good, magnetic, but it can not heat treatment to strengthen, suitable for corrosion resistance and heat resistance slightly higher, the strength requirements of the general stainless steel tight firmware.

Martensitic stainless steel

410 and 416 type can be heat-treated to strengthen the hardness of 35 ~ 45HRC, good machinability, for general-purpose heat-resistant corrosion-resistant fasteners. 416 type slightly higher sulfur content, is easy to cut stainless steel.

420 type, sulfur content ≥ 0.15%, mechanical properties, can be heat treatment to strengthen the maximum hardness of 53 ~ 58HRC, for the requirements of higher strength fasteners.

Precipitated hardened stainless steel

17-4PH, PH15-7Mo, they can be higher than the usual 18-8 stainless steel strength, which is used for high strength, corrosion-resistant stainless steel fasteners.

A-286, a non-standard stainless steel, has a higher corrosion resistance than conventional 18-8 stainless steel and has good mechanical properties at elevated temperatures. For high strength, heat resistance, corrosion-resistant fasteners, can be used to 650 ~ 700 ℃.