Research For Controlling Parameter Of Microstructure And Mechanical Properties Of Bogie Steel Of High-speed Railway

As china increases the railway speed the sixth time, we enter into the era of high-speed railway. Bogie is one of the most important carrying structures in locomotive, facing a severe test. Steel used for high-speed railway bogie should not only have a certain strength and toughness, but also have a good welding performance, fatigue resistance and corrosion resistance. At present, there exists large gap between the bogie steel of china such as Q345 series and that of foreign advanced countries. So development of the new high-speed railway bogie steel is very significant combining microalloying with TMCP. So this paper is about a new kind of steel used for high-speed railway bogie, researching into the microstructure change in the rolling and the effect of microalloy elements on the microstructure and mechaincal property.The contents of this paper are shown as follows:(1) The No.1 steel containing 0.025% Nb,0.02%Ti is investigated through single-pass compression test. The influence of the deforming temperature, deforming degree and deforming rate to the stress of the steel are researched, and the mathematical model of resistance of deformation is established.(2) The No.1 steel containing 0.025% Nb,0.02%Ti and No.2 steel containing 0.032% Ti are investigated through double-pass compression test. The behavior of static recrystallization during constant temperature after the hot deformation of the steel to be tested in austenitic area is researched. The activation energy of static recrystallization of No.1 steel is 250.61 kJ/mol and that of No.2 steel is 203.41 kJ/mol. The dynamic model of static recrystallization of No.1 steel is set up.(3) The thermal dilatation method is taken to test the CCT curves on both different austenitizing temperature and deformation condition. The influence of austenitizing temperature, deformation and cooling rate in microstructure of No.1 steel and microalloy precipitation have been researched from the metallographic. The result shows the lower austenitizing temperature and deformation make CCT diagram move leftward and upward, promoting the transformation from austenite to ferrite. And deformation makes more precipitation containing Nb, Ti..(4) Through the hot rolling test in the laboratory, the influence of the parameters (finish rolling temperature, finish cooling temperature, cooling rate and microalloy) on the structure and property of the steel tested is shown. And the proper rolling and cooling technology is made. The experiment results indicate that the strength of No.l steel is increased and then decreased with the decrease of finish rolling temperature and finish cooling temperature. It also shows the strength is higher as the cooling rate increases. And the steel with microalloy Nb, Ti gets higher strength and toughness.