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Liquid ammonia stress corrosion environment and material processing: I. The liquid ammonia medium in contact meets the following conditions to be considered a liquid ammonia stress corrosion environment: 2 E, o7 q2 t; c, C5 U1. The medium is liquid ammonia with a water content of no more than 0.2%, and it may be exposed to air (oxygen or carbon dioxide). ) C- k/ M' o# E( t8 e: }2 – The operating temperature should be above minus 5 degrees Celsius. II. Low-carbon steels and low-alloy high-strength steels (including welded joints) used in liquid ammonia stress corrosion environments must meet the following requirements: 1. The yield strength σs specified in the material standards must be ≤355 MPa. 2 |2 X$ B9 B$ W, f2; the actual measured tensile strength σb of the material is ≤630 MPa. 3. The material shall be in at least one of the following conditions: normalizing + tempering, annealing, or quenching and tempering. 2 l* ]- x0 g (Limits on P4 and carbon equivalent; when the carbon equivalent limit is exceeded, the frequency of checks on the hardness limit should be increased) ； a. Low-carbon steel and carbon-manganese alloys: CE≤0.40. b. Low-alloy steel: CE≤0.45. 5. For materials that are not welded or have been heat-treated after welding, the hardness limits are as follows: a. Low-carbon steel: HV(10)≤220 (single value). b. Low-alloy steel: HV(10)≤245 (single value). 6. All welds must undergo welding procedure qualification, including butt welding, repair welding, welding of pipes to tube sheets, cladding welding, fillet welding, etc ； 7. Where strength requirements are met, low-strength welding materials should be used as much as possible ； 8. The hardness limits for welded joints (including welds, heat-affected zones, and base metal) are the same as those specified in Article 5 ； / v+ B1 I; g, E) F* }8 D9: The start and arc-forming points at the welds (including those in temporary welds) must be ground to a depth of more than 0.3 mm before post-weld heat treatment, and magnetic particle or coloring inspections must be conducted ； ' S2 V6 t/ E- V8 t. Y+ b; p/ i& M" f0 S10: Heat treatment is required after welding, or a welding process that ensures a hardness of no more than HB185 should be used ； 11. Adding ≥0.2% water to ammonia as a buffer can also serve as an auxiliary measure to prevent stress corrosion cracking ；