What are the high-strength bolts made of
Writer： admin Time：2019-10-12 22:00
1.Maximum tensile strength and the material of high strength bolt quenching process has much to do, 40 cr after quenching process is generally difficult to meet the requirements of the material of high strength bolts 10.9 S level, in is not very strict inspection, can according to judging the surface hardness of the material after quenching treatment of the maximum tensile strength. In addition to the performance of the process, the high-strength bolts of different materials are different in the high stress state.
2.The 40Cr high-strength bolt is mainly used in bolt-bulb nodal frame, which is designed to be 390MPa (d > = 30mm) or 430MPa (d < 30mm), which is not very high in pre-tensile stress. When used for high pretension, be aware of and guarantee its delayed fracture performance. The delayed fracture of 20MnTiB is better than the 40B.
According to GB/t1231-91, 10.9 S bolts are recommended for 20MnTiB (applicable specifications < = M24) and 35VB (applicable specifications < = M30). In quenching process, the large diameter high strength bolts is not easy to hardening, so usually don't use up too much of the diameter of the high strength bolt, if you want to use, should reduce the working stress.
The mechanical properties of carbon steel and alloy steel bolts, screws and studs:
(1) carbon steel and alloy steel bolts, screws and stud (screw thread is 1.6-39 mm in diameter, working temperature was 50 300 of the performance level markup code with a total of 10, 3.6, 4.6, 4.8, 5.6, 5.8, 6.8, 8.8, 9.8, 10.9, and 12.9 (made of free cutting steel bolts, screws and stud working temperature should not exceed 250 Of magnitude 8.8 and above bolt is made of low carbon alloy steel and medium carbon steel and the heat treatment (quenching and tempering), known as high strength bolts, the rest of the known as ordinary bolts.
(2) there are two parts of the bolt performance level label, which are the nominal tensile strength and the ratio of the strength of the bolt.
For example, a performance rating of 4.6, which me