Abstract: The 20mm hot-rolled GCr15 bearing steels were obtained through four kinds through-water cooling processes. The effects of through-water cooling on microstructure and mechanical properties of the hot-rolled bearing steels and heat-treated bearing steels after spheroidizing annealing and quenching-tempering processes， respectively were investigated. The results showed that when the through-water cooling was carried out both before and after finish rolling and the finish-rolling and re-reddening temperature was 800~860℃ and 620℃， respectively， the temperature of phase transformation for the proeutectoid carbide and the pearlite went down， and the thickness and continuity of the proeutectoid carbide， the pearlite interlamellar spacing and the pearlitic colony size in the hot-rolled bearing steels were decreased. Accordingly， the thickness of carbide in the annealed and tempered microstructure was decreased while the homogeneity was enhanced. Moreover， the thick undissolved carbide networks were prevented. Eventually， the tensile strength and percentage of area reduction of the hot-rolled and heat-treated bearing steels were increased.

Key words: GCr15 bearing steel, through-water cooling, hot-rolling, spheroidizing annealing, quenching-tempering, microstructure, mechanical property