Selection of welding materials for 304 steel in low-temperature applications
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Some pipelines for desulfurization and decarbonization are made of S30408 material, with a design temperature of -196°. According to SHT 3525-2015, the welding specifications for low-temperature steels in the petrochemical industry, section 4.2.2 states that when austenitic stainless steel is used and its design temperature is above -196°, the low-temperature impact test can be waived. Therefore, the base material does not have a low-temperature impact test. The question now is, what to do with the welding material? Are there any special requests? Will ordinary ER308 welding wire work? Does the welding wire need to undergo low-temperature impact testing? And how to conduct welding procedure qualification.
Add impact and hardness tests on top of the original welding process evaluation
The selection of welding materials is determined by the requirements of the base metal to be welded; whatever is needed for the base metal determines what welding materials should be used. In many cases, for materials used under special operating conditions, design requirements call for a \"retest\" of their performance on-site; however, according to standards, many manufacturers already conduct relevant performance tests before the products leave the factory ； The base material is 304, and the welding material is ER308 ； Many welding materials undergo relevant performance tests before leaving the factory; all that’s needed is to check whether the test results meet your requirements. If they don’t, ask the manufacturer to provide the data required to meet those standards. That’s all there is to it.
The base material is exempt from low-temperature impact testing; is the welding material also exempt or does it still need to be tested? dizzy:
By referring to SHT3525, clause 4.4.2 specifies that low-hydrogen electrodes require retesting for moisture content and diffused hydrogen. Clause 4.4.4 states that \"the chemical composition and mechanical properties of the deposited metal should be similar to those of the base material, and its low-temperature impact toughness value should not be lower than the standard for the base material.\" This clause specifies the required chemical composition and mechanical properties for solid wire billets; technical requirements must be defined at the time of purchasing the wire, and relevant tests must be conducted on the wire before it leaves the factory! Personal opinion: 1. Seek the opinion of the design firm. 2. There are no mandatory provisions requiring retesting; it is not necessary to conduct another test, but doing so provides greater peace of mind when using it. Purely a personal opinion, for reference only! However, the welding procedure qualification must involve relevant physical and chemical tests at the design temperature