What material is generally used for high-strength bolts?
2024-05-22
1. The upper limit of the tensile strength of the material used in high-strength bolts has a lot to do with the quenching treatment. After 40Cr quenching treatment, it is generally more difficult to meet the material requirements of 10.9S-grade high-strength bolts. In the not very strict inspection, the upper limit of the tensile strength of the material can be judged based on the surface hardness after quenching treatment.In addition to the different properties in the processing process, the delayed fracture properties of high-strength bolts with different materials under high stress are also different.
2. 40Cr high-strength bolts are mainly used in bolt ball node grid frames. Their design strength is generally 390MPa (d>=30mm) or 430MPa (d<30mm), and there is no high pre-tensile stress in use.When used in situations where high pre-tension is to be applied, care should be taken to understand and ensure its delayed fracture performance.The delayed fracture performance of 20MnTiB high-strength bolts is better than that of 40B.
3. According to GB/T1231-91, the recommended materials for 10.9S bolts are 20MnTiB (applicable specifications <=M24) and 35VB (applicable specifications<=M30).In the quenching process, large-diameter high-strength bolts are not easy to harden, so under normal circumstances, high-strength bolts with excessive diameters should not be used. If they are to be used, their working stress should be reduced.
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