Study On CCT Curve And Contact Fatigue Properties Of The New Type Of Bainitic Steel

With the development of the railway’s speed-up and overloading of our country, therailway contact stress become bigger and bigger,the condition of railway became progressivelyworse,the working stability and security of railway was influenced. It has a great significance toresearch the high strength steel in preventing and slowing down damage, and prolonging theperiod of railway. The bainite steel material has good comprehensive mechanical properties asit has low carbon,high strength and high toughness. It was widely used in many fields.Nowadays the applied research of the railway is not enough yet, it is necessary tosystematically carry out the research of bainite materials applied in railway and it is significantto the development of railway heavy-load transportation in China.By the method of dilatometric change, combining with expansion method and hardnessmethod，the CCT curve of the new type of self-manufactured bainitic steel is determed,themicrostructures in different cooling rates are observed and the microhardness and the effect ofalloy elements are analysed.The starting temperature of bainite transformation of the new typeof bainitic steel are obviously reduced, Ferrite is obtained when the cooling rate ranges between0.011℃/S and0.03℃/S,Fainite is obtained when the cooling rate ranges between0.011℃/Sand1℃/S,Martensite is obtained when the cooling rate ranges between0.03℃/S and70℃/S.Because of the effect of alloying elements, the new type of bainitic steel is provided with goodhardenability, bainite structure can be obtained under air cooling condition,and the bainitetransformation zone become flat.To study the contact fatigue properties of new type of bainitic steel, ordinary process andelectroslag remelting process to new type bainite steel contact fatigue tests have been carriedout. The metallographic and SEM of the spalling concave pit is analysised. The results showthat when the test load is918kg, the contact fatigue life of ordinary process is better than that ofelectroslag remelting process. When the test load is1000kg,1183kg,1265kg separatly, thefatigue life of electroslag remelting process is better than that of the ordinary process."pitting"and "flake"appered in both of the damages of two kinds process, and the concrete form andthe process which has no obvious relation. But the electroslag remelting process peeling pits issmaller and shallower than that of the ordinary process.