Production method of steel for transmission gear

The invention discloses a production method of steel for a transmission gear. The steel comprises the following chemical components in percentage by weight: 0.18%-0.21% of C, 0.12%-0.20% of Si, 1.05%-1.12% of Mn, 0.018%-0.032% of S, 1.20%-1.30% of Cr, 0.01%-0.03% of Ti, 0.025%-0.040% of Al, 0.020%-0.035% of Nb, 0.011%-0.016% of N, less than or equal to 0.0003% of B, less than or equal to 0.0010% of O and the balance of Fe and inevitable residual elements. The rolled round steel for the transmission gear produced through the method is moderate in rolling state hardness, uniform and compact in macrostructure and low in content of harmful elements and non-metallic inclusions, the total oxygen content can reach 10 ppm or below, the grain size is 7.5-8.5 grades, the banded structure is smaller than or equal to 2.0 grades, the hardenability bandwidth is smaller than or equal to 4 HRC, and the component deviation of the section of the rolled round steel can be controlled within 0.015%; and the produced transmission