The effects of post weld heat treatment on the mechani̇cal properti̇es of tempered martensi̇te and hi̇gh strength steel welded joi̇nts

In this study, it was aimed to investigate post weld heat effects on the mechanical properties of tempered martensite steel and high strength steel welded joints. These welded joints were designed in accordance with related standards which were EN 15609, EN 15614 etc. In terms of welding process, Hardox450 and Optim700MC were chosen due to their partially high carbon equivalent. Chemical analysis, hardness tests and microscopic examination were implemented to validate the mechanical properties of experiment parts before the welding process. Test pieces were joined with MAG welding method applied in PB position. In pursuit of the welding operation, post weld heat treatments were applied on same duration and different temperatures for each specimen. 150oC, 300oC and 450oC were determined as post weld heat treatment temperatures. After the post weld heat treatment, cross sections were taken from the area exposed to post weld heat. Specimens were subjected to microscopic examination, hardness test and non-destructive testing. As a consequence, it was determined that hardness values in heat affected zones of tempered martensite steel were decreased with increasing post weld temperatures.