Fasteners are mechanical basic parts and are in great demand. Usually, bolts, screws, rivets, etc. are used to ensure safety or generally do not need to consider the influence of temperature in harsh environments or other dangerous working conditions. Commonly used materials are carbon steel, low alloy steel and non-ferrous metals. However, in certain occasions, fastener materials need to meet severe corrosion or high-strength conditions, and many stainless steels and ultra-high-strength stainless steels have emerged as the times require.
This article provides a brief introduction to the fine stainless steels used in fastener production. Most stainless steel materials can be made into wire or rod for fastener production, including austenitic stainless steel, ferritic stainless steel, martensitic stainless steel, and precipitation hardening stainless steel.
Material 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. The requirements of working conditions on the corrosion resistance of materials;
3. Requirements of working temperature on heat resistance (high temperature strength, oxidation resistance) of materials;
4. Requirements for material processing performance in terms of production technology;
5. Other aspects, such as weight, price, procurement and other factors must be considered.
After comprehensive and comprehensive consideration of these five aspects, the grade, 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 four grades of so-called "18-8" austenitic stainless steel. Whether it is corrosion resistance, or its mechanical properties are similar. The starting point for selection is the production process method of the fastener, and the method depends on the size and shape of the fastener, and also depends on the quantity produced.
Type 302 is used for machined screws and self-tapping bolts.
Type 303 In order to improve the cutting performance, a small amount of sulfur is added to Type 303 stainless steel, which is used to process nuts from bar stock.
Type 304 is suitable for processing fasteners by hot heading process, such as longer specification bolts and large diameter bolts, which may be beyond the scope of cold heading process.
Type 305 is suitable for processing fasteners by cold heading process, such as cold formed nuts and hexagonal bolts.
Type 309 and Type 310, which have higher Cr and Ni content than Type 18-8 stainless steel, are suitable for fasteners working at high temperatures.
316 and 317 types, they both contain alloying element Mo, so their high temperature strength and corrosion resistance are higher than those of 18-8 stainless steel.
Type 321 and Type 347, Type 321 contains Ti, a relatively stable alloying element, and Type 347 contains Nb, which improves the intergranular corrosion resistance of the material. It is suitable for fasteners that are not annealed after welding or that are in service at 420-1013°C.
Ferritic stainless steel
430 ordinary chromium steel, its corrosion resistance and heat resistance is better than 410, magnetic, but it can not be heat treatment strengthening, suitable for the corrosion resistance and heat resistance of slightly higher and general strength requirements of stainless steel fasteners.
Martensitic stainless steel
Type 410 and Type 416 can be strengthened by heat treatment, with a hardness of 35-45HRC, good machining performance, and are used for heat-resistant and corrosion-resistant fasteners for general purposes. Type 416 has a slightly higher sulfur content and is an easy-to-cut stainless steel.
Type 420, with sulfur content ≧0.15%, has improved mechanical properties and can be strengthened by heat treatment. The maximum hardness value is 53-58HRC. It is used for fasteners requiring higher strength.
Precipitation Hardened Stainless Steel
17-4PH, PH15-7Mo, they can get higher strength than the usual 18-8 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 18-8 type stainless steel, as well as good mechanical properties at elevated temperatures. Used as high-strength, heat-resistant and corrosion-resistant fasteners, it can be used up to 650-700 °C.
Chuangtuo Jinggong (Jiangsu) Co., LTD is profession manufacturer of various types of Hexagon Nuts, everything is customized in our factory, Should you have any questions please feel free to come back to us.
Contact: Lorena
Email: market@chtofastener.com
Mobile: 0086 153 6641 6606 (Wechat/Whatsapp ID)
LET'S GET IN TOUCH
Privacy statement: Your privacy is very important to Us. Our company promises not to disclose your personal information to any external company with out your explicit permission.
Fill in more information so that we can get in touch with you faster
Privacy statement: Your privacy is very important to Us. Our company promises not to disclose your personal information to any external company with out your explicit permission.