Abstract: Provided is steel for a wind power gear with improved purity and reliability. The chemical components thereof comprise, in percentages by mass: 0.15-0.19% of C, ?0.4% of Si, 0.5-0.7% of Mn, ?0.012% of P, ?0.006% of S, 1.5-1.8% of Cr, 0.28-0.35% of Mo, 1.4-1.7% of Ni, and 0.02-0.04% of Al, with the balance being Fe and inevitable impurities. A smelting method therefor comprises adding raw materials to a converter for primary melting, transferring same to a refining furnace for refining, carrying out continuous casting after vacuum degassing, and transferring same to a gas protection furnace for electroslag remelting.

Abstract: A method for rapidly measuring the roller pass major semi-axis of a three-roller reducing mill to improve the outer-diameter precision and surface quality of a steel pipe includes selecting a corresponding value of the average diameter of an elliptical pass, a value of a first major semi-axis, and a value of a minor semi-axis according to a rack station number of a special numerical control lathe; calculating a value of a first line segment according to an elliptic equation, the obtained value of the first major semi-axis, and the obtained value of the minor semi-axis; calculating a value of a second major semi-axis according to the right-angle triangle theorem and the value of the first line segment; and measuring a value of the first dimension by attaching three claws of a three-claw internal micrometer to three roller gaps.