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Zinc Plated Partially Threaded Mushroom Head Square Neck Carriage Bolt Grade 6.8 DIN603,M 10 /12
Diameter range (mm)：M5-M24，3/16-1'Length range (mm)：16-600，1''-2'
1. The compressive strength limit of common raw materials for high-strength bolts is closely related to the heat treatment solution. After 40Cr heat treatment is solved, it is generally difficult to achieve the material requirements of 10.9S grade high-strength bolts. The resolved surface strength is used to identify the compressive strength limit of the raw material. In addition to the different properties in the process, high-strength bolts with different materials have different delayed time rupture properties under high pressure.
2. 40Cr high-strength bolts are mainly used in spherical grids with bolt ball connection points. The compressive strength of the design scheme is generally 390MPa (d>=30mm) or 430MPa (d<30mm), and no high pre- tensile stress. When it is used to increase the condition of very high tensile strength, attention should be paid to grasp and ensure its delayed time rupture performance. The delayed time rupture 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 (available specifications <= M24) and 35VB (available specifications <= M30). In the heat treatment solution, large-diameter high-strength bolts are not easy to be hardened, so under normal conditions, it is not necessary to adopt high-strength bolts of excessive size. If they are to be used, the internal stress in their work should be reduced.
Carbon steel and carbon steel bolts. Identification of mechanical properties of screws and studs:
Carbon steel and carbon steel bolts, screws and studs (diameter of external thread 1.6-39mm, operating temperature -50℃-300℃) have a total of 10 performance level identification numbers, namely 3.6.4.6.4.8.5.6. 5.8.6.8.8.8.9.8.10.9 and 12.9 (bolts made of free-cutting steel. The operating temperature of screws and studs shall not exceed 250°C). Among them, the bolts of grade 8.8 and above are made of low-carbon environmental protection carbon steel or medium carbon steel and undergo heat treatment (heat treatment. quenching), which are collectively referred to as high-toughness bolts, and others are collectively referred to as general bolts.
