In addition to the performance of the treatment process is different, the high strength bolts of different raw materials, its high pressure in the state of the delay, the fracture performance is also different. In the first place, the tensile strength of high strength bolts has a great relationship with the quenching process. Usually, after 40 degree quenching treatment, the raw material requirements of the 10.9 stage high strength bolts are difficult to achieve. If it is not strictly normal, we can determine the tensile strength of the products according to the surface hardness after quenching.
Secondly, 40Cr quenching process for the high strength bolts mainly used in the bolt ball node network, which is generally designed to 390MPa (d>=30mm) or 430MPa (d<30mm). There is no high tension in the use of pre tension, if you want to add a high pre tension, but also pay attention to understand and ensure the performance of its delayed fracture. High strength bolt product quality is the key, strictly according to the requirements to do is necessary.