Study On Process And Microstructure Of Hydrogen Pressure Vessel Steel Heavy Plate

Along with the development of petroleum and chemical industry to large-scaledevelopment, put forward more and more strict requirements of pressure vessel steelsused in key parts of petroleum and chemical vessels. But in the production process ofcasting, segregation of elements inevitably affects the steel quality. In order tooptimize the micorstucture and performance of the14Cr1MoR hydrogen pressurevessel heavy steel plates, and to meet the demand of steel manufacturing enterprises,this thesis has carried out the following research work.First of all, the14Cr1MoR hydrogen pressure vessel steel heavy plates were usedto study the microstructure and mechanical properties. The production route andchemical composition was designed. Lower silicon was adopted to prevent carbidecoarsening in order to obtain good mechanical properties.Secondly, the influence of microstructure and mechanical properties was analyzedby heat treatments. Results showed that the microstructure was ferrite and a largenumber of irregular carbides when the steel sample was quenched at930C for40minand then tempered at660C for100min. This heat treatment was the optimized onefor superior mechanical properties.Thirdly, the investigation was conducted on the microstructure and mechanicalproperties of14Cr1MoR heavy plates at different places along thickness. Macrosegregation occurred in the solidification process of big ingots due to selectivecrystallization of chemical elements, the heavy plates inherted the castingmicrostructure and resulted in inhomgenity of microstructure and mechanicalproperties along heavy plate thickness.Finally, in order to improve the uniformity of microstructure and mechanicalproperties of heavy plate, steel bands were fed into big ingots in order to improve the carbon segregation. By adding1.0%cold steel bands into liquid steels during casting,carbon segregation in the center of ingots was greatly improved, which provided aneffective way to improve the uniformity of microstructure and mechanical propertiesof heavy plates.