The Effect of Post Weld Heat Treatment (PWHT) Temperature on 316L Stainless Steel with Gas Metal Arc Welding (GMAW)/ Metal Inert Gas (MIG)

The effect of post-weld heat treatment temperature on 316L stainless steel using metal inert gas (MIG) as welding method is studied. During welding processes, the temperature of molten weld pool is high meanwhile the rest of steel is almost at ambient temperature. This will lead to the changes the microstructure of steel and resulting in property changes that make steel weaker and brittle. Post Weld Heat Treatment (PWHT) able to eliminate these effects by heating the weld area in a controlled manner using optimum temperature. The present work involves the dissimilarities of microstructure and physical properties on welded steel. Steel plates of 5mm thickness were welded by MIG process. After welding processes, the steel plates will be cut into four pieces according to the standard of testing that been decided for each plate; microstructure test, hardness test and tensile test. For tensile testing, the specimens were cut into four dogbone shape according to ASTM E8. This study uses common standards to make sure all results are valid. Heat treatment consisted annealing at 300ᵒC, 600ᵒC and 900ᵒC for half an hour and cooled by ambient air. One specimen is left without heat treatment to see the difference between before and after heat treatment. For microstructure testing, scanning electron microscope (SEM) was used. The relevant microstructural test was done in the interpretation of changes before and after welding structure. The hardness values are rising with the increasing of annealing temperature. However, when a hardness test was done on 900ᵒC heat treatment specimen, it shows decreasing. This is due t