Comprehensive analysis of bolt tensile strength Calculation of bolt tensile strength

Comprehensive analysis of bolt tensile strength
 The performance levels of bolts and studs are divided into 10 levels: from 3.6 to 12.9. The number before the decimal point represents 1/100 of the material's tensile strength limit, and the number after the decimal point represents 10 times the ratio of the material's yield limit to its tensile strength limit.
 The performance level of nuts is divided into 7 levels, from 4 to 12. The numbers roughly represent 1/100 of the minimum stress the nut is guaranteed to withstand.
For unified inch threads, there are three thread grades for external threads: 1A, 2A and 3A, and three grades for internal threads: 1B, 2B and 3B, all of which are clearance fits. The higher the level number, the tighter the fit.
 Classes 1, 1A and 1B, very loose tolerance classes, which are suitable for the tolerance fit of internal and external threads.
Levels 2, 2A and 2B are the most common thread tolerance levels specified for British series mechanical fasteners.
Grades 3, 3A and 3B, screw together to form the tightest fit, suitable for fasteners with tight tolerances and used in safety-critical designs.
 Metric thread, external thread has three thread grades: 4h, 6h and 6g, internal thread has three thread grades: 5H, 6H, 7H. The thread fit is best combined into H/g, H/h or G/h. For refined fastener threads such as bolts and nuts, the standard recommendation is to use a 6H/6g fit.
Carbon steel: The strength grade mark code consists of two parts of numbers separated by "?". The meaning of the number before "?" in the marking code indicates the nominal tensile strength. For example, "4" in grade 4.8 indicates 1/100 of the nominal tensile strength 400N/MM2. The meaning of "?" and the number after the dot in the mark code indicates the yield ratio, that is, the ratio of the nominal yield point or the nominal yield strength to the nominal tensile strength. For example, the yield point of grade 4.8 products is 320 N/mm2.
 The strength grade mark of stainless steel products consists of two parts separated by "-". The symbol before "-" in the mark code indicates the material. For example: A2, A4 and other marks followed by "-" indicate intensity, such as: A2-70
Carbon steel: Metric bolt mechanical performance grades can be divided into: 3.6, 4.6, 4.8, 5.6, 5.8, 6.8, 8.8, 9.8, 10.9, 12.9, a total of 10 performance grades
The performance grades of bolts for steel structure connections are divided into more than 10 grades, including 3.6, 4.6, 4.8, 5.6, 6.8, 8.8, 9.8, 10.9, and 12.9. Among them, 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 others are commonly known as ordinary bolts. The bolt performance grade label consists of two parts of numbers, which respectively represent the nominal tensile strength value and the yield strength ratio of the bolt material. For example, a bolt with performance level 4.6 means:
  1. The bolt material has a nominal tensile strength of 400MPa;
  2. The yield-strength ratio of the bolt material is 0.6;
ˆ 3. The nominal yield strength of the bolt material reaches 400×0.6=240MPa level
 Performance level 10.9 high-strength bolts, after heat treatment, can achieve:
  1. The nominal tensile strength of the bolt material reaches 1000MPa;
  2. The yield-strength ratio of the bolt material is 0.9;
ˆ 3. The nominal yield strength of the bolt material reaches 1000×0.9=900MPa level