| In recent years, the precipitation sclerosis stainless steel has been used more widelybecause of its good obdurability. In order to satisfy the performance requirements inautomobile sensor parts for an enterprise, chose15-5PH stainless steel which is a new typeof precipitation hardened stainless steel as the material of parts for an enterprise. Bychanging the quenching temperature(1000℃~1050℃), solid solution holding time(20min~100min) and aging temperature (450℃~620℃) for heat treatment, than observethe microstructure of the material through the depth of field microscope, X-raydiffractometer(XRD), transmission electron microscopy(TEM), and analysis themechanical property by tensile test, Rockwell hardness test and fracture test, to determinethe best heat treatment process of15-5PH stainless steel.The results of different solution temperature experiment show that: when the solutiontemperature below1050℃, themicrostructure is uneven and contains some undissolvedδ-ferrite, there are many uneven ferrites after quenching, it makes lower hardness. Andthere are little intermetallic compound (IMC) occurring after aging. When the solutiontemperature higher than1050℃, the microstructure tends to be even, but the hardness islower because of the size of grains grow up sharply and austenitic has been occurring.When the solution temperature is1050℃, themicrostructure is uniform, size of grain issmall, saturation of martensite is higher, and has the maximum hardness of39.1HRC.The results of different solution holding time experiment show that: when the holdingtime less than60min, size of grains are small, but the hardness is lower, it due to thesaturation of martensite is lower. When the holding time more than60min, the size ofgrains grow bigger, and more austenite occur, it causes lower hardness. When the holdingtime is60min, the microstructure is uniform, size of grain is small, saturation of martensiteis higher, and has the maximum hardness of39.1HRC.The results of different aging temperature experiment show that: the microstructure of15-5PH not only contains martensite, but also austenite, ferrite and precipitated phases.When the aging temperature is450℃, there are many quenched martensite in themicrostructure and little carbide and intermetallic compound (IMC) has been occurringfrom martensitic matrix. It causes higher strength and lower plasticity. With the increase ofaging temperature, quenched martensite has been decomposed gradually, the tempered martensite inceasing, the size of quadratic phase becomes bigger. When the temperaturereaches620℃, the exhalation phase has grown up and aggregated, and the revertedaustenite has been occurring, it causes strength decreases and plastic increases.Compared comprehensively, the15-5PH stainless steel with the solution temperatureof1050℃, the solution holding time of60min, the aging temperature of550℃, has the bestmicrostructure and mechanical property. |
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