Study On The Effect Of C Content And Cooling Rate On The Microstructure And The Properties Of ZCr25Ni13 Heatresistant Steel

This paper studies the C content and cooling rate on microstructure and properties of the ZCr25Ni13 heat-resistant steel. According to the C content is 0.050 %, 0.075 % and 0.100 %, respectively melting ingredients to prepare a sample, after the solution were then incubated with brine cooling, water cooling, oil cooling, air cooling, furnace cooling five ways to cool to room temperature, compared with the cast specimens, then using optical microscopy, tensile testing machine, hardness tester explore organizational performance variation of each group. Using scanning electron microscopy, energy dispersive spectroscopy, Xray diffraction analysis to explore the C content and cooling rate on the microstructure and properties. The results showed that:The matrix of different carbon content of ZCr25Ni13 heat-resistant steel cast microstructure is austenitic. Different C content of ZCr25Ni13 heat-resistant steel after heat treatment of tissue remains austenitic. But its grain boundaries, grain and composition change. Respectively ZCr25Ni13 heat-resistant steel cast and heat treated specimen tensile and hardness testing. That either after the heat treatment of ZCr25Ni13 heat-resistant steel which exhibits its yield strength, tensile strength, elongation, percentage shrinkage, hardness values as the carbon content of the change has changed to varying degrees.Elongation at different C content of ZCr25Ni13 heat-resistant steel cooling rate increases with an increasing trend, the tensile strength varies with the cooling rate is not obvious. Oil cooling and air cooling have worse plasticity. Furnace cooling and the cast specimen have the worst plasticity. After the incubation solution by saline or water cooled markedly improved plasticity. With the increase of the C content, the influence of cooling rate on the tensile strength and elongation of ZCr25Ni13 heat-resistant steel is weakened. The tensile strength of the furnace cooling and elongation is minimum of three groups. The matrix organization of ZCr25Ni13 heat-resistant steel is austenitic. The faster of cooling rate the more uniform of matrix. Slower cooling the tissue along the grain boundary precipitates, and the slower the cooling rate precipitates more. Cold saline, water-cooled sample of island-shaped areas and the matrix structure is a phase, which is slightly lower than the amount of C content of matrix.The precipitates of ZCr25Ni13 heat-resistant steel is mainly carbide M16C(Cr2Fe14C). M16 C appears in organization after heat treatment. The faster the cooling rate, the less the precipitates. The slower the cooling rate, the more the precipitates. With a lower cooling rate, the grain becomes large, the grain boundary becomes small. When cooling rater is fast only a small amount of M16 C carbide dispersed in the matrix, while the cooling rate is slow, M16 C carbide reticular distributed along the grain boundaries and a lot of precipitation.Due to the lower tensile strength and ductility, ZCr25Ni13 heat-resistant cast steel is not suitable for inner and external pipe manufacturing boilers. But after solution treatment and the use of saline or water cooling, its tensile strength and ductility achieve using standard, suitable for inner and external pipes manufactured boilers.