Research And Development On Low-Temperature Pressure Vessel Steel09MnNiDR

With the rapid development of economic and the popularity of low-temperature technology, the application and demand of low-temperature vessels for the storage of low-temperature liquids such as liquid nitrogen, liquid oxygen, liquid argon,and so on is urgent.09MnNiDR is a low-temperature pressure vessel steel with0.5Ni at-70℃.It is widely used in ethylene, fertilizer, city gas carbon dioxide and other low-temperature devices. In this paper, the effect of processing parameters on microstructure and mechanical properties was studied by experiment of thermal simulation, hot rolling, normalizing and tempering. The09MnNiDR steel was successfully produced in the industrial trial.The chief original work and results are as follows:(1) By thermal simulation, the static CCT curve diagram was obtained, based on which the processing parameters of hot rolling and heat treatment can be tentatively given.(2) By thermal simulation, the influence of finish rolling temperature, finish cooling temperature, normalizing temperature and tempering temperature on microstructure was studied Results show that the higher the finish rolling temperature, the greater the grain size. The reasonable finishing temperature is ranged from800℃to850℃. As finish cooling temperature increase, the ferrite grain size becomes larger. The reasonable finish cooling temperature is400℃～650℃. Normalizing temperature has a great influence on the microstructure. As the normalizing temperature increase, the grain size increases obviously. Tempering temperature has a less influence on grain size.(3) Test steel was hot rolled followed by normalizing and tempering in the laboratory on the basis of the thermal simulation experiment. Two products thickness,12mm and20mm were chosen. The ordinary rolling and TMCP were used in the12mm steel. Their microstructure and mechanical properties were comparatively studied. The TMCP was used in the20mm size of steel. The influence of finish rolling temperature, finish cooling temperature, normalizing temperature and tempering temperature on microstructure and mechanical properties was studied. Results show that:with the decreasing of finish cooling temperature, the tensile strength and yield strength increases, but the impact energy decreases slightly. With the decreasing of the finish rolling temperature, toughness increases slightly, but strength changes little. Normalizing temperature had relatively large effect on properties. When the normalizing temperature increases, tensile strength and yield strength decreases, but impact toughness is obviously improved. After tempering treatment the strength of steel decreases, and the toughness increased significantly. Moreover, tempering temperature has little effect on properties.(4) The09MnNiDR steel was produced in the industrial trial and the properties were tested. Results show that the strength and low-temperature impact toughness of09MnNiDR steel is good, which well meets the required mechanical properties of GB3531-2008with a large amount of surplus.