In addition to the different properties in the treatment process, the retardation and fracture properties of steel structural bolts with different raw materials under high pressure are also different. First of all, the tensile strength of the raw material of steel structure bolts has a lot to do with its quenching process. Generally, it is difficult to meet the raw material requirements of 10.9 high-strength bolts after 40-degree quenching treatment. If it is not in strict normal inspection, it can be quenched according to the product. After the surface hardness to judge the quality of its tensile strength. Apart from 
　

       Secondly, the high-strength bolts with 40Cr quenching treatment as raw materials are mainly used in the bolt spherical joint grid. The design strength is generally 390MPa (d>=30mm) or 430MPa (d<30mm). Tensile pressure, if you want to add a high pre-tension, but also pay attention to understand and ensure its delayed fracture performance. The quality of high-strength bolts is the key, and it is necessary to strictly follow the requirements.