Weldability of welding materials and surfacing process evaluation
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The weldability of welding materials refers, in addition to the metallurgical weldability of the droplets and molten pool as well as the thermal weldability of the heat-affected zone, primarily to the weldability of the weld metal or surfacing layer formed after the fusion of the welding material and the base material. Both the weld metal and the surfacing layer are new materials different from the base material and the deposited metal, and require a fresh understanding. Weldability is the basis for evaluating welding processes. Only through weldability tests can one understand the influence of factors such as welding methods, welding materials, and welding processes on the weld metal and the surfacing layer, as well as determine the appropriate range of welding process parameters. During the weldability testing for corrosion-resistant surfacing under various corrosion requirements, it is necessary to compare the corrosion resistance with the chemical composition of the deposited metal from the surfacing welding material, in order to identify patterns and select welding materials and welding procedures with appropriate chemical compositions. The purpose of evaluating the corrosion-resistant surfacing welding process is to achieve corrosion resistance, whereas the purpose of the evaluation criteria for such processes is to ensure that the chemical composition meets the required standards. At present, there are no evaluation standards for surfacing processes in the world that use corrosion resistance as a criterion; instead, ISO, ASME IX, and national standards all use the chemical composition of the surfacing layer as the basis for re-evaluating such processes. In the terminology of \"welding procedure qualification,\" arbitrarily adding \"corrosion resistance\" and, at the same time, stipulating in the standard provisions that after the evaluation of corrosion-resistant surfacing, \"corrosion-resistant specimens\" must be prepared for testing is redundant. This ignores the foundation of welding procedure qualification, which is weldability, and completely alters the criteria for re-evaluating corrosion-resistant surfacing, leading to confusion in the guiding principles of welding procedure qualification. Even the terminology related to \"welding procedure qualification\" is incorrect, which also casts doubt on the standard provisions! Some companies have revealed that corrosion resistance tests are carried out only as a last resort when the weldability of the surfacing welding material has not been thoroughly tested, or when inferior welding materials are used or when welders proceed with welding in violation of the prescribed procedures. However, this test cannot replace the weldability tests for surfacing welding materials. If the officially published standard text contains provisions regarding the inspection of corrosion-resistant specimens from the surfacing layer, is it still necessary to add a requirement for \"preparing corrosion-resistant specimens\" when conducting the evaluation of corrosion-resistant surfacing processes in accordance with NB/T 47014-2011, which has been in use for over 10 years? !
The weldability of welding materials is an important indicator for assessing the quality of the bond between the welding material and the base metal; it relates to the metallurgical weldability of the droplets and molten pool, as well as the thermal weldability of the heat-affected zone. In the surfacing process, the weld metal and the surfacing layer are new materials formed by the fusion of welding material and the base material; this means that their properties may differ from those of the original base material and the deposited metal. Therefore, weldability tests are required to re-evaluate and understand them. The surfacing process qualification is used to determine whether the surfacing layer can achieve the desired performance, especially in terms of corrosion resistance. Since corrosion resistance is a key performance indicator for many industrial applications, the chemical composition of the welding material and the welding process parameters are carefully considered and selected when evaluating the surfacing process. In the process evaluation of corrosion-resistant surfacing, certain standards are typically used to guide this evaluation, such as ISO, ASME IX, and the international standard GB. These standards are primarily based on the chemical composition of the surfacing layer as the basis for evaluation. Corrosion resistance is usually not used as a direct evaluation criterion, which may lead to confusion in the implementation of certain standards. Based on your description, it seems that someone has suggested including considerations of corrosion resistance in the process evaluation for surfacing, but this suggestion may not be appropriate, as it could deviate from the original objectives related to weldability and process evaluation. Furthermore, the testing of corrosion resistance specimens should be supplementary rather than a replacement for weldability tests. As for whether the requirement to \"produce corrosion-resistant specimens\" should be added to the existing standards for evaluating corrosion-resistant surfacing processes, this needs to be determined by considering the specific provisions of those standards as well as the actual needs of the industry. If the standards already contain clear requirements, then the existing standards should be followed during implementation. If there are doubts regarding the standards themselves or if updates are required, it should be the relevant standard committees or professional organizations that carry out the revisions and improvements. .