Low High Strength Martensitic Stainless Steel Components, Organization And Performance Studies

00Cr12Nil0MoTi is martensite stainless steel used in low-temperature environment, except for the high strength and toughness in low temperature, its capacity of cold deformation and welding performance are excellent, which make it become the important material for the storage and transportation of Liquid Oxygen and Liquid Nitrogen. The 00Cr12Nil0MoTi cryogenic steel adopts solution treatment below the recrystallization temperature (750℃), its obdurability and corrosion stability are all better than adopting the solution treatment above the recrystallization temperature. The temperature 750℃is below the recrystallization, the microstructure inherits the structure of prior hot working during the solution treatment, therefore the structure before the final solution treatment has significantly effect on the final performance and structure. For this reason, the paper investigated how the pretreatment temperature effects the mechanical property and microstructure of the forging bar, hot rolled strip and cold rolled strip. This study has great significance of fully tapped the potentials of material obdurability and improve the stability of mechanical properties. Meanwhile the article investigated the evolution of the microstructure and the mechanism of strength and toughness with the technology of Light Microscopy, SEM, TEM and XRD, through which the study gets the following main conclusions:After the effect of pretreatment between 750℃～1100℃was studied on the microstructure of forging bar, the results show that the austenite which formed by non-diffusion reverse a'â†'y transformation below 950℃pretreatment inherits the forging structure, while it formed recrystallized austenite after pretreatment above 950℃. As the 750℃final solution treatment inherits the structure of the pretreatment, changing the pretreatment temperature has significantly effect on the mechanical properties:for 250℃tempered material, changing the pretreatment temperature mainly affects the strength, especially the yield strength. The experiment proves that the ultimate strength and yield strength reach the peak pretreatment at 850℃, and the content of residual austenite increased with the pretreatment temperature decreasing, instead it finally decreased the strength of the material; for 500℃tempered material, changing the pretreatment temperature mainly affects the content of residual/reverse austenite, which observably increased when the pretreatment temperature decreased, and then the low-temperature toughness was obviously improved. The low-temperature toughness of pretreatment at 750℃is even higher than it is in the low strength condition (250℃tempered).The study on hot rolled strip shows that it also formed recrystallized austenite after pretreatment above 950℃, and the strength value reached the peak at pretreatment 850℃; the temperature which formed recrystallized austenite reduced to 900℃for the distortion 25% cold rolled strip, and the distortion 50% reduced to 850℃, and accordingly reached the maximum strength at 800℃and 750℃respectively.