The invention relates to steel for ball screws. The steel for ball screws comprises, by
mass: 0.45%-0.60% of C, 0.15-0.40% of Si, 0.90-1.10% of Mn, 0.70-1.20% of Cr, less than or equal to 0.015% of S,less than or equal to 0.025% of P, less than or equal to 0.25% of Ni, 0.15-0.40% of Mo, less than or equal to 0.30% of Cu, less than or equal to 0.05% of Al, less than or equal to 0.0010% of Ca, lessthan or equal to 0.003% of Ti, less than or equal to 0.0010% of O, 0.0050-0.0090% of N, less than or equal to 0.04% of As, less than or equal to 0.03% of Sn, less than or equal to 0.005% of Sb, lessthan or equal to 0.002% of Pb, and the balance Fe and inevitable impurities. The delivery state of the steel is as follows: high-temperature
quenching and
tempering are carried out, and the
hardness meets 220-280 HBW, and the microscopic structure is of a sorbite and
bainite structure, and is subjected to SEP 1927
water immersion high-frequency flaw detection, so that the defect length is requirednot to exceed 5 mm. The manufacturing process comprises the steps of electric furnace or converter, external refining, VD or RH vacuum degassing,
continuous casting,
continuous casting blank squaringto form an intermediate billet (a square billet), intermediate billet heating and rolling, finishing, quenched-tempered heat treatment (including high temperature
quenching and
tempering), surface lathing and warehousing.