Application Investigation On Controlled Rolling And Controlled Cooling For GCr15 Stell

The theory of controlled rolling and controlled cooling conditions to improve the carbide network on grain boundary in GCr15 bearing steel has been studied very well, yet it hasn't been fully applied in some industrial organizations like ours .This subject is a successful trial about using present theory on guiding and operation in practice under our plant's condition.In order to amend the carbide network, Co-operating with our practice, the method taken in this subject is finishing rolling on hot recrystallization zone followed by fast cooling and analyzing the data collected between 780℃ and 830℃ .The results are:① That rapidly quenching the hot rolled steel with the diameter between 12mm and 14mm by high-pressure turbulent water to the range of 780 ℃~ 830 ℃ is effective to reduce the grade of carbide network. But it doesn't present that the hydrocooling finishing temperature influence obviously the grade of carbide network.② There is no direct relation between the grade of carbide network and individual carbon content ,neither is individual chrome content, because the conditions for strictly controlling contrast processing parameter is imperfect. But lots of statistical comparison under the approximately identical technological conditions indicates that the grade of carbide network rises when the total content of carbon and chrome increases, which followings approximately the rule that if the total content of carbon and chrome increases 0.02%, the grade of carbide network will increases 0.07. According above stated, the content of carbon and chrome should be controlled at the lower limit of critical field.③ That GCr15 bearing steel is rapidly quenched after it has been rolled ,on the one hand inhibit recrystal grain coarsening ,on the other hand reserve intracrystalline defect caused by roll forming, which lead to finer grains and more dispersed carbide and improve the grade of carbon network before annealing treatment . Meanwhile, such structure makes a large number of point particles retain during the annealing treatment. The particles are existing core of spheroidization, that's to say which takes advantage of carbide spheroidization. It is the real reason that our subject can gain success.④ The present sampling taking rule is between splat cooling area and non splat cooling area, which is an important reason that the examination result is not stable .