Abstract
The present study utilized a metal inert gas welding (MIG) to make a dissimilar weld of stainless steel AISI 304, 314, 316L, 420 grades and a standard structural steel S355MC. It refers to a weld joining two materials from different alloy systems commonly used in heat exchangers, pressure vessels, and power plant systems. Obviously, maintaining the integrity of such welds is of paramount importance to the safety issues. Therefore, detailed microscopic and experimental studies were performed to evaluate the reliability of these welds. The microscopic analysis did not reveal any presence of weld defects such as porosity or cracks, which ensured that MIG process parameters were properly selected. The performance of dissimilar welds was assessed by hardness and tensile tests. The hardness profiles revealed differences between austenitic and martensitic steel welds that later showed extremely high values in the heat-affected zone (HAZ), which caused fractures in this zone during tensile test. The welds of all austenitic steel grades withstood the tensile test, showing an average tensile strength of 472 MPa with fractures observed in the base metal zone. It made clear that the use of a filler rod 308LSI is suitable only for the austenitic stainless and structural steel dissimilar welds and not appropriate for martensitic-structural steel welds. The achieved results revealed that the higher hardness of the martensitic phase in the HAZ of AISI 420 is closely related with the formation of untempered coarse martensitic structure and higher carbon content.
Highlights
Generation of hybrid structures of materials provides huge opportunities for constructors in creating and developing new products with the required properties and high reliability
The correlation of the fatigue strength, tensile properties, hardness, and microstructure of austenitic stainless and medium carbon steel dissimilar welds was reported [7] showing 40% lower fatigue strength of dissimilar welds compared to austenitic steel welds and 30% lower fatigue strength when compared to medium carbon steel welds
The results of the studies showed that the co Summarizing the results of the performed detailed research, it can be stated that metal inert gas welding (MIG) welding using the filler rod 308LSi is suitable to produce dissimilar 3xx and 4xx series steel to structural steel welds
Summary
Generation of hybrid structures of materials provides huge opportunities for constructors in creating and developing new products with the required properties and high reliability. Requirements related to the welding procedure of dissimilar steel welds cover the production of boilers, tanks, heat exchangers, and pressure vessels used in various industries Such a specific application requires different materials to be joined with high reliability and joint quality. The problems most commonly encountered in dissimilar weld joints are related to the formation of brittle phases and undesirable residual stress distributions across different zones of welds, which initiates formation of cracks or failures of the joint before the expected service life [1,2]. The majority of these negative consequences can be solved in principle by adjusting the microstructure while welding. Dimensions of the fatigue process zone and the peculiarities of its formation were determined [8] by the method of laser interferometry and the optical method, and a three-dimensional finite element sub-model of the near-crack tip region for stress–strain state analysis of metal alloys at normal tension was developed [9]
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