| With the rapid development of China's industry,the application of pressure vessels is more and more widespread.However,due to the pressure vessel in high pressure,high temperature,corrosive medium in service,prone to burning,explosion accidents,resulting in heavy losses to the lives of the people.Therefore,the production of high-performance pressure vessel steel is particularly important.In this paper,a steel company based on the production line to pressure vessel steel 15CrMoR as the research object,the use of four different rolling process to study the heat treatment process and organizational performance.The main research work and results of this paper are as follows:(1)Combined with the working environment of the pressure vessel and the required performance,as well as the compounding ratio of each element within the allowable content of the national standard,the chemical composition of the steel 15CrMoR is designed:0.16C-0.3Si-0.5Mn-0.9Cr-0.47Mo;(2)The phase transition of undercooled austenite was studied by DIL805A/D thermal expansion phase changer and Formastor-F ?.The experimental results show that Ac3=856?,Ac1=726?,Ar3=806? and Ar1=669? for 15CrMoR steel.The dynamic CCT curve moves to the upper left and upward and the transition temperature starts from high temperature,expanding the area of high-temperature transformation products.(3)Based on the study of the continuous cooling transformation of undercooled austenite in 15CrMoR steel,the hot rolling process parameters were designed by four different rolling processes.The rolling temperature was 1100?,the finishing temperature was 860?,the cooling rate control at 0?20?/s;(4)The box-type resistance furnace heat treatment of hot-rolled steel to study the heat treatment on the mechanical properties.The results show that with the increase of normalizing temperature,the banded structure of the experimental steel gradually disappears,the strength gradually decreases,the impact toughness increases first and then decreases,the mechanical properties are better when the normalizing temperature is 900?,and the four different rolling processes mechanical properties after heat treatment is not much difference after rolling slow cooling slightly better overall performance.15CrMoR steel is not sensitive to tempering temperature,tempering temperature at 680? when the strength and toughness match better.The research on the mechanical properties of 15CrMoR steel shows that the properties of the material are better when the normalizing temperature is 900?,the holding time is 3min/mm,the tempering temperature is 680? and the holding time is 3min/mm.(5)15CrMoR steel after heat treatment at high temperature tensile test.The experimental results show that with the increase of the experimental temperature,the yield strength decreases gradually and the elongation at break decreases firstly and then increases.The tensile strength gradually increases in the temperature range from 150?to 300?.After this temperature range,the tensile strength gradually increases decline,analysis that is due to the impact of blue-brittle phenomenon;(6)Using the tensile strength data measured by the instantaneous high temperature tensile test,the high temperature lasting strength was predicted,the post-rolling air cooling and the post-rolling rapid cooling experimental steel were heat treated,and the working steel was heated at 500? for 100,000 hours strength are close to 150MPa,showing that the heat treatment of the rolling process has little effect on the organizational performance;(7)High-temperature creep experiment after heat treatment of the experimental steel after the air-cooling rolling process.The experimental results show that the 15CrMoR steel meets the creep regularity of steel at 500? under different stress.The relationship between the steady creep rate and stress of 15CrMoR steel is obtained by least squares fitting. |
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