Heating method for refined No.35 steel austenite grains

The invention discloses a heating method for refined No.35 steel austenite grains. The heating method comprises the following steps: (1) rapidly heating No.35 steel to 1000-1100 DEG C at a heating speed of 5-1000 DEG C/second by virtue of electric contact heating, line-frequency induction heating or rapid electro-heating, and preserving the heat for 1-5s; (2) carrying out classified cooling and short-time heat preservation on the No.35 steel obtained from the step (1), namely rapidly cooling the steel to 950-1000 DEG C and preserving heat for 1-5s firstly, then rapidly cooling to 900-950 DEG C and preserving heat for 1-5s, subsequently rapidly cooling to 850-900 DEG C and preserving heat for 1-5s, and finally rapidly cooling to 820-850 DEG C and preserving heat for 5-20s, wherein the cooling rate is more than or equal to 10 DEG C/s; and (3) quenching the No.35 steel obtained from the step (2) or transferring the No.35 steel to a pit furnace or a desktop furnace with furnace box temperature at 820-850 DEG C, preserving heat for 5-60min and air-cooling or quenching, wherein the granularity of the austenite can reach 10th-15th grade. The heating method disclosed by the invention is simple in process, unnecessary to add complex equipment, relatively low in cost, not high in influence on production technological process and is applicable to the heat treatment or heating processing heating process of the No.35 steel.