Heating method for refining austenite grains of 45 steel

The invention discloses a heating method for refining austenite grains of 45 steel. The heating method comprises the following steps: (1) by virtue of an electrical contact heating, a power frequency induction heating or electrochromic rapid heating method, rapidly heating the 45# steel to 1000-1100 DEG C at a heating rate of 5-1000 DEG C/s and carrying out heat preservation for 1-5 seconds; (2) carrying out grading cooling and short-term heat preservation on the 45# steel, namely, firstly rapidly cooling to 950-1000 DEG C and carrying out heat preservation for 1-5 seconds, then rapidly cooling to 900-950 DEG C and carrying out heat preservation for 1-5 seconds, further rapidly cooling to 850-900 DEG C and carrying out heat preservation for 1-5 seconds, and finally rapidly cooling to 800-840 DEG C and carrying out heat preservation for 5-20 seconds, wherein the cooling rate is greater than or equal to 10 DEG C/sec; and (3) quenching the 45# steel or rapidly transferring the 45# steel to a pit furnace or a bench-type furnace of which the furnace temperature is 800-840 DEG C, carrying out heat preservation for 5-60 minutes and carrying out air cooling or quenching to obtain the 45# steel of which the austenite grain size can reach level 10-15. The heating method is simple in process, low in cost and small in production process flow influence, no complex device needs to be added, and the heating method can be used for the heat treatment of the 45# steel and heating process before heat processing.