The properties and classification of stainless steel fasteners

Stainless steel fasteners are mainly made of stainless steel wire as raw materials, followed by a series of processes such as piercing according to the steps of producing standard parts, and the use of stainless steel to manufacture fastener products has become very popular. Stainless steel fasteners have the following properties:

1. High temperature resistance of stainless steel fasteners. Because the hardness of stainless steel itself is relatively strong, the fasteners after production have strong anti-oxidation ability, and they cannot work normally under high temperature, and will not be interfered by too much high temperature. Passivation, then the effect will become better.

Second, the physical properties of stainless steel fasteners have a relatively high electronegative rate. Compared with carbon steel wire, we can see that the cathode rate of stainless steel fasteners is five times higher than that of carbon steel. There is an expansion coefficient in the standard parts. After testing, we know that if the temperature is higher, the expansion coefficient of stainless steel fasteners will increase to a certain extent.

3. The force capacity of stainless steel fasteners. For stainless steel fasteners, the load that can be tolerated is relatively moderate. Although it cannot be compared with high-strength bolts, it also meets the needs of normal people.

Fourth, the mechanical properties of stainless steel fasteners. In the mechanical properties, we can know that many of them have a great relationship with the stainless steel wire. For example, no rust and high corrosion resistance are closely related to the properties of stainless steel. With the continuous development of standard parts, these mechanical properties also become stronger and stronger.

Fasteners are characterized by a wide variety of specifications, different performances and uses, and a high degree of standardization, serialization and generalization. Commonly used materials for manufacturing fasteners are carbon steel, low alloy steel and non-ferrous metals.

According to the material of stainless steel, it can be divided into (1) standard austenitic stainless steel (2) martensitic stainless steel (3) ferritic stainless steel (4) precipitation hardening stainless steel

Among them, the commonly used grades of the standard austenitic stainless steel we call are 302, 303, 304 and 305, namely the so-called "18-8" type austenitic stainless steel. Both corrosion resistance and mechanical properties are similar. The starting point for selection is the process method of the fastener, which in turn depends on the size and shape of the fastener, as well as on the quantity.

Type 302 is used for the manufacture of screws and self-tapping bolts.

Type 303 has a small amount of sulfur added to improve performance and is mainly used for standard nuts.

Type 304 is suitable for warm upsetting process, such as longer specification bolts and larger diameter bolts.

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

Types 309 and 310, which have higher chromium and nickel content than Type 18-8 stainless steel, are suitable for fasteners made at high temperatures.

Types 316 and 317, both of which contain the alloying element manganese, have higher high temperature strength and corrosion resistance than Type 18-8 stainless steel.

321 type and 347 type, 321 type contains more stable alloying element titanium, 347 type contains niobium, which improves the material's resistance to intergranular corrosion.