Steel for high-strength speed reducer gear of new energy automobile and manufacturing method of steel

The invention relates to steel for a high-strength speed reducer gear of a new energy automobile and a manufacturing method of the steel. The steel for the gear comprises the following chemical components in percentage by mass: 0.13 to 0.18 percent of C, less than or equal to 0.15 percent of Si, 1.10 to 1.35 percent of Mn, 1.20 to 1.45 percent of Cr, less than or equal to 0.012 percent of P, less than or equal to 0.003 percent of S, 0.15 to 0.35 percent of Ni, 0.05 to 0.20 percent of Mo, 0.015 to 0.050 percent of Al, 0.015 to 0.050 percent of Nb, 0.0085 to 0.0225 percent of N, 0.0015 to 0.0035 percent of B and the balance of Fe and inevitable impurities. The steel for the high-strength speed reducer gear of the new energy automobile is manufactured through the technological steps of primary smelting, refining, vacuum degassing, continuous casting, hot delivery, rolling, isothermal heat treatment and the like, the banded structure of the steel is smaller than or equal to 1.5 grades, the hardness of the steel i