Study On Stress Corrosion Cracking Of 304L Stainless Steel In Caustic Solution At High Temperature

The present paper focuses on the problem of the SCC on the nozzle of hydrogenation reactor of PTA installation which is due to on-line alkali cleaning. According to the actual conditions of on-line alkali cleaning, SCC behavior of 304L stainless steel in low concentration sodium hydroxide solution at high temperature was studied by Slow Strain Rate Tests (SSRT). Corrosion resistance performance of the sensitized 304L was also studied under the above test conditions because austenitic stainless steel may be sensitized in equipment processing. Meanwhile, SSRT tests were conducted in the environment of high temperature pure water. By compared with this, the SCC susceptibility and its factors of 304L stainless steel in low concentration sodium hydroxide solution at high temperature were evaluated. From above experimental research, SCC susceptibility of 304L stainless steel in low concentration sodium hydroxide solution at high temperature is understood, which is helpful to ascertain appropriate processing conditions of on-line alkali cleaning, such as temperature and concentration of sodium hydroxide, and is very significant to extending service life of the hydrogenation reactor.The main research contents and conclusions are summarized as follows:(1)As known from the SSRT results in high temperature pure water, ductile rupture of 304L stainless steel is dominant in the scope of the strain rates from 1×10-6 to 1×10-5s-1. Brittle rupture occurs from outer surface of specimens with the increase in temperature and the decrease in strain rate. At the strain rate of 1×10-6s-1, absorbed energy in the process of 304L stainless steel's rupture decreases with increasing temperature, which indicates that SCC has slightly occurred. Therefore, it is feasible to evaluate SCC susceptibility by use of SSRT at the strain rate of 1×10-6s-1.(2)For 304L stainless steel, SSRT in low concentration sodium hydroxide solution at high temperature was carried out. Effects of the different temperatures and concentration on SCC were also studied. The research results show that ultimate tensile strength (UTS),...