| The topic of this thesis comes from Shenhua Group Corporation Limited’s scientific and technological innovation and technology project ―preparing post welding heat treatment specification of stainless steel pipelines with stabilizing elements, intending to formulate suitable for energy industries coal fuel and chemical enterprises with stabilizing elements of stainless steel pipeline post welding heat treatment norms,‖ Our school is a member of the project. In the construction of the project of direct liquefaction of Shenhua coal in Ordos, the stainless steel thick wall tube of the device was found to have serious cracking after the stabilizing heat treatment, which led to the question of the traditional heat treatment process. Austenitic stainless steel has good high temperature oxidation resistance, wear resistance, corrosion resistance and thermal stability, and is widely used in all walks of life. Stabilizing heat treatment is a kind of heat treatment method to improve the intergranular corrosion resistance of austenitic stainless steel containing stabilizing elements. But in the process of stabilizing heat treatment, after sensitization temperature, the stainless steel becomes prone to reheat cracks. And stabilizing heat treatment can easily cause the decline of the materials mechanical properties and stress corrosion resistance decline.In view of the above problems,TP321 and TP347 austenitic stainless steel were selected as the research object. To comprehensively evaluate the effect of stabilizing heat treatment of austenitic stainless steel material, we analyze the mechanical properties, stress corrosion performance, intergranular corrosion performance and microstructure changes of before and after stabilizing heat treatment. The actual evaluation basis is given whether takeing stabilizing heat treatment in engineering.As to the TP321 and TP347 materials before and after the stabilizing heat treatment of weld samples, mechanical properties testing was done firstly, to obtain the mechanical properties. Then, the stress corrosion test was carried out under constant load tensile stress. The stress life relationship of each material at each stress and strain level was obtained, and the stress corrosion threshold value was obtained. Secondly, the intergranular corrosion test of intergranular corrosion properties were analyzed. Finally, the lateral bending test and microstructure analysis, metallographic analysis, SEM, XRD and other means are taken to analyze the microstructure change and component change of stabilizing heat treatment.The main results of this paper are as follows:The establishment of stress- life mathematical model in saturated hydrogen sulfide environment of TP321 and TP347 before and after the stabilizing heat treatment, and corresponding threshold σth Was given.The sensitivity of the 2 materials to stabilizing heat treatment was given. After stabilizing heat treatment, the mechanical properties of TP321 materials and the corrosion resistance of hydrogen sulfide were decreased, and the TP347 materials were not affected.The intergranular corrosion characteristics of 4 kinds of two kinds of materials were presented. The effects of stabilizing heat treatment and sensitization treatment on microstructure were obtained. |
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