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 the bolts of grade 8.8 and above are made of low-carbon alloy steel or medium-carbon steel and have been heat-treated (quenching, tempering), commonly known as high-strength bolts, and the rest are commonly referred to as ordinary bolts.
picture
The bolt performance grade label consists of two parts of numbers, which respectively represent the nominal tensile strength value and yield strength ratio of the bolt material. 48 is 4.8.
For example: bolts with performance grade 4.8, its meaning is:
1. The nominal tensile strength of the bolt material reaches 400MPa;
2. The yield strength ratio of the bolt material is 0.8;
3. The nominal yield strength of the bolt material reaches 400×0.8=320MPa
Performance grade 10.9 high-strength bolts, after heat treatment, 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 reaches 1000×0.9=900MPa level
The meaning of bolt performance grade is an international standard. Bolts of the same performance grade have the same performance regardless of the difference in their materials and origins. Only the performance grade can be selected for design.
The so-called strength grades of 8.8 and 10.9 mean that the shear stress grades of the bolts are 8.8GPa and 10.9GPa. The 8.8 nominal tensile strength is 800N/MM2 and the nominal yield strength is 640N/MM2. Generally, the bolts use "X.Y" to indicate the strength, and X *100=tensile strength of this bolt, X*100*(Y/10)=yield strength of this bolt (because according to the label: yield strength/tensile strength=Y/10, that is, 0.Y is the yield strength ratio ) Such as grade 4.8, the tensile strength of this bolt is: 400MPa; the yield strength is: 400*8/10=320MPa.
In addition: stainless steel bolts are usually marked as A4-70, A2-70, and the meaning is explained otherwise. ), millimeter (mm), etc., which are widely used in Southeast Asia such as Europe, my country, and Japan.
1. Metric measurement: (decimal system) 1m =100 cm=1000 mm
2. Inch measurement: (octal system) 1 inch=8 inches 1 inch=25.4 mm 3/8¢¢×25.4 =9.523, 1/4¢¢
The following products use serial numbers to indicate their appellation
Such as: 4#, 5#, 6#, 7#, 8#, 10#, 12#.
