Stress corrosion cracking (Stress Corrosion Cracking, SCC) refers to the phenomenon of delayed cracking or lagging fracture caused by the synergistic action of corrosion medium and stress in some specific medium, which is subjected to tensile stress. Common SCC include: "alkali brittleness" of boiler steel in hot alkali solution, "nitrite brittleness" of low carbon steel in nitrate, "chlorine brittleness" of austenitic stainless steel in chloride solution and "ammonia brittleness" in ammonia solution. It is generally believed that the occurrence of SCC requires three conditions at the same time, namely, sensitive materials, specific media and tensile stress. Specifically: (1) the material itself is sensitive to SCC. Almost all metals or alloys have certain SCC sensitivity in certain media, and alloys and metals containing impurities are more likely to produce SCC than pure metals. (2) There is a medium which can cause SCC of the metal. For each material, not any medium can cause SCC, only certain medium can produce SCC. (3) SCC must have a certain tensile stress. The tensile stress can be the working stress caused by the external load under the working state; it can also be the residual stress, such as thermal stress, deformation stress, etc., formed in the process of production, manufacture, processing and installation, or the additional stress caused by the surface corrosion product film (passivation film or dealloy loose layer), and the corrosion inside the crack. Tensile stress also occurs during wedging due to volume effect of the product. Table metals and alloys produce stress corrosion specific medium material medium low carbon steel NaOH solution, nitrate solution, H2S and HCl solution, CO-CO2-H2O, carbonate, phosphate high carbon steel various water medium, organic solvent containing trace water, HCN solution austenitic stainless steel chloride aqueous solution, high temperature and high oxygen content Pure water, even sulfuric acid, alkaline solution aluminum and aluminum alloy wet air, water, halogen containing water, organic solvent, molten NaCl copper and copper alloy containing NH4+ solution, ammonia vapor, mercury salt solution, SO2 atmosphere, vapour titanium and titanium alloy fuming nitric acid, methanol (steam), high temperature NaCl solution, HCl, H2SO4, wet. Cl2, N2O4 (including O2, NO, 24~74) magnesium and magnesium alloys wet air, high pure water, fluoride, KCl+K2CrO4 solution nickel and nickel alloy molten hydroxide, hot concentrated hydroxide solution, HF vapor and solution zirconium alloy chlorine ion water solution, organic solvent test method and standard ASTM G103 GB/T 10567.2 ASTM G13 9 GB/T 17898 ASTM G35 GB/T 1842 ASTM G36 GB/T 22640 ASTM G38 GB/T 25996 ASTM G41 6957. 1) thickness < 30mm: parallel sampling, the same product takes 1 groups of samples, the number is 3; 2) 30mm < 88mm > thickness < 88mm: the same product takes 1 sets of samples, the number is 3; the thickness is more than 88mm: the step sampling, the 1 sample thickness < 30mm, the maximum number of samples according to the actual thickness. >>SSC-A method - standard tensile sample CAD drawings and physical drawings (number of samples are 3 groups) >>SSC- four points bending ISO 7539 and ASTM G39 samples and physical drawings (number of samples are 3 groups) test equipment: stress ring laboratory strength, stress ring quantity sufficient, SSC hydrogen sulfide stress corrosion test can be the same 120 sets of tests were performed at the same time, and 200 sets of HIC tests were performed at the same time.