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1. Introduction: Alkalis such as sodium hydroxide, potassium hydroxide, and ammonia can all cause stress corrosion cracking in steel. Taking NaOH as an example, stress corrosion failure occurs frequently in industrial production; it can affect carbon steel, low-alloy steel, ferritic stainless steel, and austenitic stainless steel. In industry, this phenomenon is referred to as \"alkali embrittlement\" or \"caustic embrittlement\". In a NaOH environment, the corrosion resistance of austenitic stainless steel is only slightly higher than that of cast iron and carbon steel. Generally, type 18-8 stainless steel can only be used in very dilute alkaline solutions at temperatures below 90°C. When the concentration of the alkaline solution exceeds 0.1%, austenitic stainless steel may develop a tendency to stress corrosion, and it becomes more prone to cracking as stress and temperature increase. When the temperature is above 300°C, 18-8 stainless steel will experience stress corrosion cracking within a day in alkaline solutions with very low concentrations. The convection chambers of converter furnaces, cracking furnaces, and continuous reforming heaters all contain waste heat boilers. If care is not taken during the startup heating process, the alkali solution used for heating may spill into the steam superheating section; as this alkali solution heats up and concentrates, it can cause stress corrosion cracking in the tubes of the steam superheating section. Additionally, there have been cases of stress corrosion cracking in furnace tubes caused by the injection of alkali into the process medium. 2. Example: During the alkali boiling treatment of the steam superheating section tubes in the convection chamber of a certain converter, multiple fractures occurred in those tubes. The tubes in the steam superheating section and the elbows are both made of 304 steel, while the outlet header is made of 321 steel. On-site inspections revealed that the fractures occurred in the furnace tube sections connected to the collectors, the furnace tube sections connected to the sharp bends, as well as on the sharp bends themselves. Most cracks are located in the weld heat-affected zone; they are circumferential cracks, and there is considerable alkali deposition on the outer surface of the pipe surrounding the cracks. The analysis indicates that the loss of control over the drum liquid level during boiler operation led to alkali solution leaking into the steam superheating section, thereby causing stress corrosion cracking.