Flange bolt is an integral bolt composed of hexagon head and flange plate (the gasket under the hexagon is fixed with the hexagon) and the screw (cylinder with external thread), which needs to be matched with the nut for fastening. Parts connecting flange bolts with two through holes.

1. High carbon steel C%>0.45%. Hexagon flange bolt product materials are basically not used in the market at present;

2. Medium carbon steel 0.25% hexagon head bolts Medium carbon steel materials are usually called No. 35 and No. 45 steel in China, and are basically called 1035, CH38F, 1039, 40ACR, etc. abroad. Mainly used for grade 8 nuts, grade 8.8 bolts and grade 8.8 hexagon socket products;

3. Low carbon steel C%≤0.25% is usually called A3 steel in China. Foreign countries are basically called 1008, 1015, 1018, 1022, etc. Mainly used for grade 4.8 bolts, grade 4 nuts, small screws and other products without hardness requirements. (Note: The drill tail screw is mainly made of 1022 material.)

4. Alloy steel: Add alloying elements to ordinary carbon steel to increase some special properties of steel: such as 35, 40 chromium molybdenum, SCM435, 10B38. Hexagon flange bolts mainly use SCM435 chromium molybdenum alloy steel, the main components are C, Si, Mn, P, S, Cr, Mo.

Flange is the connection device of two large-diameter pipes, usually two flanges and several fastening bolts. Carbon steel flanges are flanges made of carbon. Low carbon steel has good plasticity and low strength. After adding an appropriate amount of carbon, it will become hard, and the plasticity will decrease and the strength will increase.

Flange connections may need to withstand high tensile, compressive, torsional, and shear strengths, and carbon steel flanges are a better choice. The determination of the nominal pressure should be based not only on the maximum working pressure, but also on the maximum working temperature and material properties, not just the fact that the nominal pressure is greater than the working pressure.

Bolted connection is a fastener connection. Compared with other connection methods, it has advantages. It is easy to assemble and disassemble, which is convenient for maintenance. It can increase the pre-tightening force to prevent loosening, and will not cause the phase change of the material composition of the connection, but it also has disadvantages. It increases the weight, and is prone to corrosion at the cracks of the bolted connection, resulting in the failure of the connection. The hexagonal flange face bolts have a large contact surface and are used in combination with conical and spherical gaskets, mainly for fixing two non-parallel parts.
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