Meaning of screw and bolt performance level

Update:14 Oct 2020
Summary:

The performance grades of bolts for steel structure con […]

The performance grades of bolts for steel structure connection 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, 12.9, among which bolts of grade 8.8 and above are made of low carbon alloy steel or medium carbon steel and are heat treated (Quenching, tempering), commonly known as high-strength bolts, the rest are commonly known as ordinary bolts. The bolt performance grade label consists of two parts of numbers, which respectively indicate the nominal tensile strength value and the yield ratio of the bolt material.

E.g:
The meaning of bolts of performance class 4.6 is:
1. The nominal tensile strength of the bolt material reaches 400MPa;
2. The yield ratio of bolt material is 0.6;
3. The nominal yield strength of the bolt material reaches 400×0.6=240MPa
Performance grade 10.9 high-strength bolts, after heat treatment, can reach:
1. The nominal tensile strength of bolt material reaches 1000MPa;
2. The yield ratio of bolt material is 0.9;
3. The nominal yield strength of the bolt material reaches 1000×0.9=900MPa
The meaning of bolt performance grade is an international standard. The performance of bolts of the same performance grade is the same regardless of the difference in material and origin. Only the performance grade can be selected in the design.
The so-called 8.8 grade and 10.9 grade of strength refers to the bolt's shear stress resistance grade of 8.8GPa and 10.9GPa
8.8 Nominal tensile strength 800N/MM2 Nominal yield strength 640N/MM2
General bolts use "XY" to indicate the strength, X*100=the tensile strength of the bolt, X*100*(Y/10)=the yield strength of the bolt (because according to the label: yield strength/tensile strength =Y/10)
Such as level 4.8
The tensile strength of this bolt is: 400MPa; the yield strength is: 400*8/10=320MPa.
Another: stainless steel bolts are usually marked as A4-70, A2-70, the meaning is explained otherwise
Measurement: There are two main length measurement units in the world today, one is the metric system, the measurement units are meters (m), centimeters (cm), millimeters (mm), etc., which are more commonly used in Southeast Asia such as Europe, my country and Japan. The other is the imperial system, and the unit of measurement is mainly inches (inch), which is equivalent to the market inch of my country's old system, and is used more in the United States, Britain and other European and American countries.
1. Metric measurement: (decimal system) 1m =100 cm=1000 mm
2. Imperial measurement: (octal system) 1 inch = 8 inch minutes 1 inch = 25.4 mm 3/8¢¢×25.4 =9.52
3. Products below 1/4¢¢ are designated by designations, such as: 4#, 5#, 6#, 7#, 8#, 10#, 12#

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