Abstract
When designing piping systems for various industrial facilities, carbon steel and stainless steel are widely being used. In order to satisfy design requirements in the piping systems, the two different materials are often welded in various cases. Therefore, for quality assurance, it is necessary to understand mechanical and metallurgical properties of dissimilar metal welds thoroughly. In this study, dissimilar metal welds of stainless and carbon steels were produced through the gas tungsten arc welding (GTAW) process. In the middle of the dissimilar weld, buttering welding and butt welding were manufactured using filler wires of ERNiCr-3 and ER316L. The chemical composition of the dissimilar metal weld was analyzed. Tensile test, bending test, and hardness test were additionally performed. The microstructures of the dissimilar metal weld were investigated to analyze the cracks found during the tensile test and the bending test. The metallographic behavior was analyzed in the vicinity of the cracks. The mechanism and cause of the cracks in the dissimilar metal weld were identified. As a result, the precipitates of complex carbide types were observed in segregation bands.
Highlights
When designing piping systems for various industrial facilities, materials that satisfy optimal performance are selected in consideration of design conditions such as durability, corrosion resistance, economy, and productivity [1,2,3,4]
Stainless steel is usually used in the part where corrosion resistance is required, and carbon steel is used in the part where corrosion resistance is not required, depending on the operational environment
If a piping system is composed of different steel types depending on operational environment and design conditions, the joints of dissimilar metals are essential for the fabrication of the piping system
Summary
When designing piping systems for various industrial facilities, materials that satisfy optimal performance are selected in consideration of design conditions such as durability, corrosion resistance, economy, and productivity [1,2,3,4]. Stainless steel is usually used in the part where corrosion resistance is required, and carbon steel is used in the part where corrosion resistance is not required, depending on the operational environment. If a piping system is composed of different steel types depending on operational environment and design conditions, the joints of dissimilar metals are essential for the fabrication of the piping system. Compared to the weld between same materials, the dissimilar metal weld of carbon and stainless steels can cause weld defects and corrosion, due to difference in stress, carbon migration, and weld discontinuities [5]. In order to prevent weld defects and corrosion for the sound welds of dissimilar metal, it is important to optimize welding conditions and to select proper filler materials based on the metallurgical understanding
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