What are the general materials for high-strength bolts?

What are the general materials for high-strength bolts?

1. The maximum tensile strength of materials used for high-strength bolts is closely related to quenching treatment. After 40Cr quenching treatment, it is generally difficult to meet the material requirements of 10.9s grade high-strength bolts. In less stringent inspections, the maximum tensile strength of the material can be determined based on the surface hardness after quenching treatment. High strength bolts made of different materials exhibit different delayed fracture properties under high stress conditions, in addition to their performance during treatment.

2. 40Cr high-strength bolts are mainly used for bolted ball node grid structures, with a design strength of 390mpa (d>=30mm) or 430mpa (d<30mm), and there is no high prestressing force during use. When using under high pre tension, attention should be paid to understanding and ensuring 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 specification<=M24) and 35VB (applicable specification<=M30). In quenching treatment, large-diameter high-strength bolts are not easy to harden, so generally, large-diameter high-strength bolts should not be used. If they are to be used, their working stress should be reduced. GB 799, L-shaped bolts, etc., can produce thread diameter 6-120mm, length is not limited, material: Q235, 45 × Q. Q345B, 40Cr, 35CrMoA, etc. Anchor bolts can be divided into straight hook type, arc hook type, anchor melon type, reinforced anchor plate type, Q235 type, and 35 type according to their types × Steel feet, including 24000 sets of high-strength bolts, material 40, and 0 sets of high-strength bolts (210 "), consisting of two open channels of Tongjiezi Project. The steel beams of the concrete construction trestle have been installed and put into use. 1. The steel structure is connected with high-strength bolts

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Mechanical property marking of carbon steel and alloy steel bolts, screws, and studs:

(1) Carbon steel and alloy steel bolts, screws, and studs have 10 performance level codes (thread diameter 1.6-39mm, working temperature -50 ℃ -300 ℃), including 3.6, 4.6, 4.8, 5.6, 5.8, 6.8, 8.8, 9.8, 10.9, and 12.9 (working temperature of free cutting steel bolts, screws, and studs shall not exceed 250 ℃). Among them, bolts of grade 8.8 and above are made of low-carbon alloy steel or medium carbon steel, which are generally referred to as high-strength bolts after heat treatment (quenching and tempering), while other bolts are generally referred to as ordinary bolts.

(2) The bolt performance grade symbol consists of two parts of numbers, representing the nominal tensile strength value and yield strength ratio of the bolt material.

For example, a bolt with a performance level of 4.6 represents:

1. The nominal tensile strength of the bolt material reaches 400MPa;

2. The yield strength ratio of bolt material is 0.6;

3. The nominal yield strength of bolt material reaches 400 × 0.6=240mpa

The performance level is 10.9 grade high-strength bolts, and the material can reach:

4. The nominal tensile strength of bolt material can reach 1000MPa

5. The yield strength ratio of bolt material is 0.9;

6. The nominal yield strength of the bolt material is 1000 × 0.9=900MPa.

The meaning of bolt performance level is an international standard. For bolts of the same performance level, regardless of material and origin, their performance is the same, and only the performance level can be selected in the design

The company's main products include high-strength bolts, high-strength nuts, steel structural bolts, steel structural nuts, grid sealing plates, grid bolts, etc.