Study On The Heat-treatment Parameters, Microstructures And Properties Of ZDPH Highly Purified Forging Steels For Brake Discs

Express train is a promising way to the development of railway transportation in chian,in which brake disc is a kind of basal device crucial to the security of train movements.ZDPH Highly Purified Forging Steels were developed for Brake Discs of 300 km/h Express Trains.As a new steel,studying heat-treatment process,analyzing its properties and standard its maps is very important to the popularization and application in the brake disc.On the basis of summarising the basic types of heat treatment and the development of new technologies on heat-treatment,this paper conducts in-depth studies on the heat-treatment process,microstructures and mechmical properties of a newly developed high-speed train brake disc material(ZDHP highly purefied forging steels).And Monte Carlo-complex optimizing method was employed to optimize the heat-treatment process. The influence on the mechnical properties of the material from the heat-treatment parameters was studided and mechnical properties as well as microstructures of the material were tested.1.The heat-treatment parameters are optimized by Monte Carlo-complex optimizing method.The best quenchinig temperature ranges between 860±5℃and the tempering temperature is 655±5℃.These heat-treatment parameters are contributive to the excellent mechanical properties of the material.2.The critical temperature range of ZDPH steel was determined by probe quenching method:Ac1 is between 760℃and 780℃,Ac3 is between 820℃and 840℃.3.The organizational characteristics of the material after heat treatment were studied by modern microstructure analysis techniques such as quantitative metallography,x-ray diffraction method and so on.The results show that organizations contain high pro-eutectoid ferrite when quenched below 860℃,and quenched above 900℃the content of Rretained Austenite increase.4.The ZDPH highly purified steel has good mechanical and physical properties under the heat-treatment parameters,such as ultimate tensile strength,yield strength, elongation,impact energy and anti-thermal fatigue.5.Heat-treatment process studied in this paper can guide actual factory production. The heat-treated experiments on samples were done in the factory.The results showed that the various parts of samples were in good condition through hardening,the haat-treatment process studied in this paper was applicable and can guide actual factory production.