The Change of Character in high temperature enviroment

Change (1) the performance of metal materials in high temperature creep at high temperature steel subjected to external forces, with the extension of time, slowly and continuously produce plastic deformation phenomenon, known as creep. Creep characteristics of steel has a great relationship with the temperature and stress. Temperature or stress increases, creep speed. The operating temperature of the carbon steel, for example, more than 300 ~ 350 ℃, alloy steel working temperature more than 300 ~ 400 ℃ will creep. The needed to generate creep stress below test temperature steel yield strength. Therefore, for long-term work under high temperature of boiler, steam pipe, pressure vessel steel should be used with good creep resistance, in order to prevent the large deformation caused by creep structure fracture and the malignant accident such as blast. (2) the spheroidizing and graphitization Under the effect of high temperature, the carbon steel cementite due to gain energy will take place in the migration and accumulation, the formation of coarse grains of cementite and inclusions in ferrite, the carburizing experience from flake gradually into a ball, called the ball. Due to the low intensity of graphite and flake, make the material strength greatly reduced, increased brittleness, referred to as the material of graphitization. Carbon steel is to work for a long time in more than 425 ℃ environment, graphitization occurs, the more obvious in higher than 475 ℃. Highest SH3059 regulation of carbon steel using temperature is 425 ℃, GB150 regulation of carbon steel using highest temperature is 450 ℃. (3) thermal fatigue performance If steel heating and work for a long time, so material under the action of internal thermal stress caused by changes in temperature, will produce tiny crack and expanding, finally lead to fracture. Therefore, changes in temperature and work structure, the pipe should be considered under the condition of the thermal fatigue properties of steel. (4) the material of high temperature oxidation of metal materials in high temperature oxidizing medium environment, such as flue will be oxidized and produce scale, crisp fall easily. Carbon steel at 570 ℃ high temperature gas variation in scale and make the metal thinning. Therefore, gas, flue pipe should be limited work under 560 ℃.

If you would like to know more about ERW steel pipe,pls contact:hunan great steel pipe co.,ltd