Study Of Remanufacturing Technology Of Austenite Stainless Steel Service At High Temperature

In order to alleviate the contradiction of wastes and shortages of resources, reduce the harm of failure products to environment and make use of failure products at the maximum limit, remanufacturing engineering as a new kind of development mode arises at the historic moment. As aging at high temperature the precipitation of a phase from austenitic stainless steel due to its chemical composition is inevitable, while different processing technology and adding the elements only delay the precipitation time of a phase. The precipitation of a phase reduces seriously the properties and corrosion resistance of stainless steel, and then influences its service life. In order to improve its service life and its efficiency at high temperature, re-manufacturing engineering of austenitic stainless steel with the micro structure degradation needs to be developed as soon as possible.In this paper the possibility of the remanufacturing mainly for austenitic stainless steel service at high temperature for a long time with the degradation of the micro-structures was researched, AISI 321 stainless steel service for 80000 hours at 700℃as the research object, and solution treatment as the method of remanufacturing technol-ogy. In this paper, the tests of microstructure and properties of AISI 321 stainless steel service for 80000 hours at 700℃was carried out, and the influence of solution treat-ment with AISI 321 stainless steel service for 80000 hours at 700℃on the microstruc-ture, properties at room temperature and high temperature was discussed.The main conclusions are summarized as follows:1. After service for 80000 hours at 700℃, the parent, HAZ and weld precipitated a large number of a phase, and the degradation of micro structures was seriously. The precipita-tion of a phase made austenite stainless steel brittle, and the capacity to stand strain was reduced to a great extent.2. After solution treatment, a phase in all areas gradually dissolved. The higher temperature of solution treatment is, the fasterσphase dissolved. Austenitic grains obviously grew up and the growth of grains was the reason for the relative size ofσphase from intergranular to intragranular.3. After solution treatment, the micro hardness was obviously reduced; the impact tough-ness was drastically increased compared to AISI 321 service for 80000 hours at 700℃, about 10 times. The difference in impact toughness between 2-10 hours was small; the tensile strength at room temperature was obviously reduced after solution treatment, the fracture was changed from the obvious brittle after service to ductile after solution treat-ment and percentage elongation was raised after solution treatment.4. The tensile strength at the temperature of 700℃was increased with solution treatment time. Percentage elongation was raised with of solution time before two hours, after that it was reduced with the solution time.In all, solution treatment was capable to mend the microstructure and improve the me-chanical properties of AISI 321 service for 80000 hours at 700℃.So austenitic stainless steel with the microstructure degradation due to serve at high temperature for a long time is able to be reproduced, and solution treatment is able to be as the process of remanufacturing tech-nology of AISI 321 stainless steel service.