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Factors Affecting the Quality of 40Cr Steel

The level of operators is an important factor affecting the quality of 40Cr steel. At the same time, there are many reasons such as equipment, materials and processing before quenching and tempering:
(1)The transfer of 40Cr steel from the heating furnace to the cooling tank is slow, and the temperature of the workpiece entering the water has dropped below the Ar3 critical point, resulting in partial decomposition. 40Cr steel has an incompletely quenched structure and cannot meet the hardness requirements. Therefore, the cooling liquid of small parts for 40Cr steel should pay attention to the speed, and the cooling time of large workpieces should be mastered.

(2)The charging amount of 40Cr steel should be reasonable, preferably 1~2 layers. The overlapping of workpieces will cause uneven heating and uneven hardness.

(3)The arrangement of 40Cr steel into the water should keep a certain distance. If it is too dense, the rupture of the steam film near the workpiece will be hindered, resulting in low hardness of the surface of 40Cr steel.

(4)Quenching in the furnace should not be completed at once. Depending on the degree of furnace temperature drop to close the furnace halfway and reheat, So that the hardness of 40Cr steel is consistent before and after quenching.

(5)Pay attention to the temperature of the cooling liquid. The coolant should not have oil, mud and other impurities, otherwise, the hardness of 40Cr steel will be insufficient or uneven.

(6)The hardness of the unprocessed rough is not uniform. The rough should be turned and the bar should be forged to obtain good conditioning quality.

(7) Strictly control the quality, the hardness after quenching is 1~3 units lower, and the tempering temperature can be adjusted to meet the hardness requirements of 40Cr steel.