Quenching and tempering of 40Cr steel

Quenching and tempering of 40Cr steel
Element Cr in 40Cr steel function 
Element Cr in 40Cr steel can increase the hardenability of steel, improve the strength and tempering stability of steel, and has excellent mechanical properties. Cr steel should be used for large or important quenched and tempered parts. But Cr steel has a second type of tempering brittleness.

Quenching and tempering of 40Cr steel

 The quenching and tempering of 40Cr steel products: This process is specified with strict requirement. In actual operation, we experience:
    (1) 40Cr steel should be oil-cooled after quenching. 40Cr steels have better hardenability, can be hardened by cooling in oil, and have a small tendency to deform and crack. However, in the case of tight oil supply, small enterprises can harden workpieces with uncomplicated shapes in water, and no cracks are found. The operator must strictly control the temperature of water entering and exiting from experience.
    (2) The hardness of the 40Cr workpiece is still high after quenching and tempering, and the second tempering temperature will increase by 20 ~ 50 ° C. Otherwise, it is difficult to reduce the hardness.
    (3) After the high temperature tempering of the 40Cr steel, the complex shape is cooled in oil and simply cooled in water, the purpose is to avoid the impact of the second type of tempering brittleness. After tempering and rapid cooling, if necessary, stress relief treatment should be applied.

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