Don't hurry to quench, because there will be internal stress after steel processing, which is easy to deform. Try stress relief annealing first. Heat the steel to a temperature slightly higher than Ac 1, keep the temperature for a certain time, then cool it with the furnace to 550~600℃, and take it out for air cooling. And then quenching, carburizing or quenching and tempering as required. Taking 45 # steel as an example, gears and shafts are usually treated by quenching and tempering, stress relief annealing or normalizing (fine grain structure, balance)-rough machining-quenching-finishing-tempering (high, medium and low temperature).

Box furnace: 830 to 850 degrees, heat preservation for 50 minutes, quenching method: 5% to 10% salt water; Quenching hardness: greater than HRC52；; Tempering temperature is 400 degrees, and hardness is between HRC 38 and HRC 42.