Method for improving metallographic structure level of 40Cr automobile half-axle quenched and tempered steel

The invention provides a method for improving the metallographic structure level of 40Cr automobile half-axle quenched and tempered steel, which comprises the following steps: sequentially carrying out pretreatment, quenching and tempering treatment, rough machining, rod part medium-frequency quenching and low-temperature tempering treatment on steel to obtain quenched and tempered steel; the pretreatment comprises medium-frequency heating, cross wedge rolling and grinding disc swinging which are carried out in sequence; the quenching and tempering treatment comprises afterheat quenching and high-temperature tempering which are carried out in sequence. According to the method, the reasonable heating temperature is selected, strict temperature control is implemented, the initial forging temperature is determined, meanwhile, the number of repeated heating times of the rod material is strictly controlled, rapid growth of the grain size of the rod material is avoided, the metallographic structure level of the 40C