What are the grades of screws?

1. Bolt functional level, that is, the functional level of bolts used for steel structure connection, is divided into more than 10 levels, including 3.6, 4.6, 4.8, 5.6, 5.8, 6.8, 8.8, 9.8, 10.9 and 12.9. Screw customization introduction The functional grades of steel structure connecting bolts are divided into more than 10 grades such as 3.6, 4.6, 4.8, 5.6, 6.8, 8.8, 9.8, 10.9 and 12.9, among which the raw materials of bolts above 8.8 are low carbon alloy steel or medium carbon Steel, and after heat treatment, they are collectively called high-strength bolts, and the others are collectively called ordinary bolts. The bolt function grade mark is composed of two parts of numbers, which respectively indicate the nominal tensile strength value and the yield strength ratio of the bolt data.
2. The functional grade of steel structure connecting bolts exceeds 10 grades, including 3.6, 4.6, 4.8, 5.6, 6.8, 8.8, 9.8, 10.9 and 12.9. Among them, the raw materials of bolts of grade 8.8 and above are low-carbon alloy steel or medium-carbon steel, usually called high-strength bolts, and others are called ordinary bolts. The bolt function grade mark is composed of two parts of numbers, which respectively indicate the nominal tensile strength value and the yield strength ratio of the bolt data. For example: a bolt with a function level of 4.6 means:
1. The nominal tensile strength of the bolt material reaches 400MPa;
2. The yield strength ratio of the bolt material is 0.6;
3. The nominal yield strength of the bolt raw material is as high as 400×0.6 = 240mpa
After heat treatment, the data of high-strength bolts with a functional level of 10.9 can reach:
1. The nominal tensile strength of the bolt material reaches 1000MPa;
2. The yield strength ratio of the bolt material is 0.9;
3. The nominal yield strength of the bolt material is 1000×0.9 = 900MPa.

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