45# steel is a high-quality carbon structural steel, corresponding to Japanese standard S45C, American standard: 1045 and German standard C45. It is characterized by higher strength and deformation resistance than ordinary A3 steel.

Its chemical composition element ratio (%): carbon C: 0.42 ~ 0.50; Chromium Cr: ≤ 0.25; Manganese Mn: 0.50-0.80; Nickel Ni: ≤ 0.25; Phosphorus P: ≤ 0.035; Sulfur s: ≤ 0.035; Silicon Si: 0. 17 ~ 0.37

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mechanical properties

According to GB/T699- 1999 standard, the recommended heat treatment system of 45 steel is normalizing at 850℃, quenching at 840℃ and tempering at 600℃, and the achieved properties are yield strength ≥355MPa.

According to GB/T699- 1999 standard, the tensile strength of 45 steel is 600MPa, the yield strength is 355MPa, the elongation is 16%, and the area shrinkage is 40%. Tempering of hardness specification is a dual heat treatment of quenching and high temperature tempering, and its purpose is to make the workpiece have good comprehensive mechanical properties.

There are two kinds of quenched and tempered steel: carbon quenched and tempered steel and alloy quenched and tempered steel. Whether carbon steel or alloy steel, its carbon content is strictly controlled. If the carbon content is too high, the strength of quenched and tempered workpiece is high, but the toughness is not enough. For example, the carbon content is too low, the toughness is improved and the strength is not enough. In order to obtain good comprehensive properties of quenched and tempered parts, the carbon content is generally controlled at 0.30~0.50%.

When quenching and tempering, the workpiece is required to be quenched in full section, so that the microstructure of the workpiece is mainly fine needle-shaped quenched martensite. Homogeneous tempered sorbite structure was obtained by high temperature tempering. It is impossible for small factories to carry out metallographic analysis on each furnace, and generally only do hardness test, that is to say, the hardness after quenching must reach the quenching hardness of materials, and the hardness after tempering should be checked according to the requirements of drawings.

The operation of workpiece quenching and tempering treatment must be carried out in strict accordance with the process documents. We just put forward some views on how to implement the process in the operation process.

Baidu Encyclopedia -S45C