The Heat Treatment Process Of Super Martensitic Stainless Organizations And The Performance

In this work, a new type of Cr13 super martensitic stainless steel was designed in order to achieve localization. The steel was designed through adjusting the composition of alloy elements on the basis of super martensitic stainless steel which was used in Japan. The effect of heat treatment on microstructure and property of the tesed steel has been systematiclly studied by transmission electron microanalysis and x-ray diffraction analysis, and the following major results have been obtained:The microstructure of the tested steel quenched at 800～1150℃is quenched martensite and the martensite platelet coarsens with the rising quenching temperature. Original austenite crystal grain sizes of the tested steel increase with the rising quenching temperature from 900℃to 1150℃. And crystal grain sizes of the steel without tungsten and copper are increased from 8.99μm to 44.11μm, while that of the steel with tungsten and copper are increased from 8.32μm to 50.94μm. The HRC increases when the tested steel are qhenched at 800～850℃and then decreases when quenching temperatures are 900～1150℃0.The microstructures of tested steel tempered at 550～750℃after quenching at 1050℃are the tempered martensites which become fine with the rising temepring temperature. The results of mechanical properties show that the HRC and tensile strength (σb) decrease when tempering temperature is between 550～650℃and then increase with elevated temperature. The elongation increases with raised temperature and displays a maximum at a temperature of 650℃and then decreases. The amount of reversed austenite increases first and then decreases with raised tempering temperature and displays a maximum value at the temperature of 650℃.When the tested steel are tempered at 650℃after quenching at 900～1100℃, the tensile strength of steel decreases with increased quenching temperature and decreases slightly when quenching temperatures are 1050～1100℃. While the elongation and hardness of the steels change in a certain range and display the maximum value when the quenching temperature is 1050℃. Thus, the integrated analysis of mechanical properties shows that the strength of steel assorts with toughness best when samples are tempered at 650℃after quenching at 1050℃. The mechanical properties of steel with tungsten and copper are always better than the steel without them in the same heat treatment condition.TEM observations indicate that the lath martensite with a high dislocation density is very fine. Reversed austenites with strip and diamond shape are observed along the boundaries of original austenite crystals and lath boundaries after tempering. The length of them is measured about 102-103nm and the width is about 100nm. There are also M23C6 carbides precipitating along the boundaries of lath martensite.