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The marking of fasteners can be simplified

Simplified marking of fasteners

The marking of fasteners can be simplified according to the following simplification principles:

1) The age of fastener names and standard numbers are allowed to be omitted;

2) When only one type, accuracy, performance level or material, heat treatment and surface treatment are specified in the fastener product standard, it may be omitted;

3) When the product standard specifies two or more types, accuracy, performance levels or materials, heat treatment and surface treatment, one of them may be omitted.

Classification of fasteners

At present, the standard parts on the market are mainly carbon steel, stainless steel, brass, and aluminum alloy.

1.Carbon steel

According to the carbon content of carbon steel materials, it is divided into: low carbon steel, medium carbon steel, high carbon steel and alloy steel

1) Low carbon steel C ≦ 0.25%, which is usually called A3 steel in China. Mainly used for 4.8 bolts, 4 nuts, small screws and other products without hardness requirements.

2) Medium carbon steel 0.25% <C ≦ 0.60%, generally referred to as 35 #, 45 # steel in China. It is mainly used for 8-level nuts and 8.8-level bolts.

3) High carbon steel C> 0.60%, which is basically not used in the market.

2.Stainless steel

Mainly divided into austenite (18% Cr, 8% Ni), advantages: good heat resistance, good corrosion resistance, good weldability


Common materials are brass and zinc-copper alloy

4.Alloy steel

Chromium molybdenum alloy steel