| When the petrochemical pressure equipment suffered after the fire, they maybe deformed partially or wholly and the mechanical properties of materials would be degraded.However, it doesn’t necessarily mean losing the ability of fitness for service. The safety and reliability assessment of petrochemical pressure equipment suffered to the fire is therefore needed in practice. This research is based on inter-external experiences and API579 evaluation method after the fire, securely evaluated the aluminum parts of petrochemical equipment after fire. Heat treatment with different temperature,holding time and cooling rate was conducted for 3A21 aluminium alloy to simulate the fire process. The mechanical properties and microstructure were investigated afte r fire process and make a timely, accurate and rapid evaluation method. Main research results are:the cooling rate influenced obviously the impact toughness of 3A21 Al alloy when the fire exposure temperature was below 510℃. The charpy impact energy was improved by 65% at air cooling condition when fire temperature was 204 ℃, and it was improved by 57% at water cooling condition when fire temperature was 427 ℃. The mechanical properties decreased slightly with increasing fire temperature when the fire temperature was below 510℃, and the tensile strength is reduced by 30%, the yield strength is reduced by 45%, the hardness of the air cooling is decreased by 37%, and the water cooling is reduced by 28%when the fire temperature reached 657 ℃.The cooling rate influenced obviously the impact toughness of 3A21 Al alloy when the fire exposure temperature was below 510℃. the impact toughness is basically the same as that of the air cooling and water cooling when the fire exposure temperature was up 510 ℃. when the fire exposure temperature higher than 510℃the fine uniform texture microstructure was becoming gradually recrystallizing and precipitating hard phases, partly dissolving and precipitating hard phases again at the grain boundary and grain coarsening that lead to decreased mechanical properties. The critical temperature of the 3A21 aluminum alloy is 510 ℃ that grain coarsening, dissolution of second-phase particle.The critical value of hardness is 38 HB. The tensile strength decreased to 217 Mpa reduced by 15%,hardness decreased to 67 HB reduced by 13%, elongation reached 62% increase of 72%,contraction of area reached 83% that was stable in air cooling condition.When the pure copper in water cooling condition, the tensile strength decreased to 223 Mpa reduced by 13%,hardness decreased to 69 HB reduced by 10%,elongation reached 60% increase of 67%,contraction of area reached 83% that was stable. The critical temperature of the pure copper is 621 ℃that recrystallized grain grorth and grain coarsening, the critical value of hardness is 38 HB.The recrystallization grain growth at 621 ℃ after fire of pure copper that grain coarsening,appear bigger and deeper dimples.when the fire exposure temperature was below 621 ℃ that the mechanical properties of pure copper was stable.By comparing the surface color and hardness of the 3A2 1 aluminum alloy ã€pure copper with the fire judge the fire exposure zone of the component and make a rapid evaluation, based on API579. To screen for the damage severity of the damage pressure equipment. The maximum allowable working pressure(MAWP) of the material is calculated according to the change of the mechanical properties of the heat treatment, so that the evaluation result is more in line with the actual conditions of the pressure equipment. |
