| Recently, low-temperature steel is widely used in sets of low-temperature equipment inenergy industry and petrochemical industry. In coal gasification project, low-temperaturevessel for production, storage and transport of LPG and LNG and demethanizer and otherlow-temperature equipment and all kinds of ethylene unit low-temperature steel are widelyused. Among the low-temperature steel,3.5Ni steel has good impact toughness andmechanical property under the low temperature environment, which was usually used underlow temperature environment ranging from such as-70℃to-101℃.3.5Ni steel is widelyused to product the equipment in the area of cryogenic separation process, air separation andliquid gas storage. Recently, the low-temperature equipment in domestic coal chemicalprojects e.g. CO2absorption tower, H2S absorption tower, H2S concentration tower, methanolscrubbing column etc are made of this kind of material. And so far the maximum wallthickness is110mm.In this paper, the influence of welding, forming, heat treatment and other thermal processon microstructures and properties base metal SA203D/E（3.5Ni steel）and weld seam isinvestigated. On the basis of test results, the key issues has been resolved during the welding,hot forming and heat treatment of3.5Ni steel to meet the requirement of base metal andwelding material and relevant technology principle and thus provides processing parametersof GTAW(gas tungsten-arc welding), SMAW(shielded metal arc welding), SAW(submerged-arc welding), high-temperature hot forming and heat treatment with idea welding jointstrength, hardness and improved low-temperature impact toughness. |
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