Quenching and Tempering Treatment of 42CrMo4 Steel

In the quenching and cooling process of normal quenching and tempering treatment of 42CrMo4 steel, oil cooling quenching or water quenching oil cooling quenching process is generally adopted. In order to prevent quenching crack defects in the ring gear, the following technical measures have been taken:
(1) After the 42CrMo4 steel is quenched and kept out of the furnace, it is pre-cooled in the air to reduce the surface temperature of the 42CrMo4 steel to about 780T, and then enters the quenching liquid to cool.

(2) After the 42CrMo4 steel is cooled in the quenching liquid for a certain period of time, the 42CrMo4 steel is air-cooled for 1.0 min to 1.5 min to reduce the temperature difference of the cross-section of the 42CrMo4 steel, and then enter the quenching liquid to continue cooling for a certain period of time.

(3) Control the final cooling surface temperature of the 42CrMo4 steel to about 230T during quenching and cooling.

(4) After the 42CrMo4 steel is quenched and cooled, it must be tempered in a furnace in time to eliminate the thermal stress and structural stress caused by quenching.

Low-temperature tempering and heat preservation are carried out near the Ms point temperature of 42CrMo4 steel, so that the outside of the 42CrMo4 steel is heated and tempered, and the inside continues to cool down and transform.