The selection of materials under low temperature conditions should comply with the following regulations:
(1) The minimum operating temperatures and low-temperature impact test exemption conditions for carbon steel, low-temperature carbon steel, chromium-molybdenum alloy steel, and stainless steel should comply with the relevant provisions of current national standards;
(2) The steel used for low-temperature pipelines should be killed steel;
(3) For carbon steel, low-temperature carbon steel, low alloy steel, medium alloy steel and ferritic high alloy steel with a pipeline design temperature lower than or equal to -20°C, the base metal and its weld metal and heat-affected zone shall be determined according to national regulations. Low temperature impact test is carried out according to the relevant provisions of the standard;
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(4) Chromium-nickel austenitic stainless steel base metal is exempted from low-temperature impact testing when the design temperature is higher than or equal to -196°C and meets the following requirements:
1) The carbon content of the material is less than or equal to 0.10%;
2) The material should be in solution heat treatment state.
(5) The weld metal and heat-affected zone of chromium-nickel austenitic stainless steel can be exempted from low-temperature impact testing when they meet the following requirements:
1) For austenitic stainless steel base metal with a carbon content of less than or equal to 0.10%, welded without filler metal, the design temperature should not be less than -101°C;
2) If the carbon content of the weld metal is less than or equal to 0.10%, the filler metal used for welding meets the corresponding standards, and the design temperature should not be lower than -101°C; if the carbon content of the weld metal is greater than 0.10%, the filler metal used for welding meets the corresponding standards Standard, the design temperature should not be less than -48℃.
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