Abstract
Weldments inevitably shrink during cooling from the melt pool. Residual stresses then occur owing to surrounding constraints. Tensile residual stresses in weldments cause various problems, such as deformation and reduction of fatigue strength. Low-temperature transformation (LTT) welding consumables can reduce the tensile residual stress through volume expansion, which accompanies a phase transformation from austenite to martensite. In this study, the relationship between residual stress and net strain was examined, mainly by controlling the martensite start (Ms) temperature, and the result was related to the weld’s microstructure. The Ms temperature and the expansion accompanying the phase transformation were analyzed by the dilatometric method. A hole drilling test was carried out to measure the residual stress in the weldments. The highest compressive stress was observed in the most expanded weldment at room temperature, and a linear relationship between the net strain and residual stress was derived. This linear relationship was analyzed with a microstructural approach.
Highlights
(Ms) temperature, and the result was related to the weld’s microstructure
We examined the relationship between residual stress and deformation, considering the microstructure of the low-temperature transformation (LTT) weld
To determine the LTT material characteristics, the martensite start (Ms) temperature was calculated from the Cr and Ni content according to the following empirical equation [25]: Ms = 539 − 423C − 30.4Mn − 12.1Cr − 17.7Ni − 7.5Mo
Summary
(Ms) temperature, and the result was related to the weld’s microstructure. The Ms temperature and the expansion accompanying the phase transformation were analyzed by the dilatometric method. The highest compressive stress was observed in the most expanded weldment at room temperature, and a linear relationship between the net strain and residual stress was derived. This linear relationship was analyzed with a microstructural approach. Residual stresses that inevitably occur during this process cause deformation of the welded part, thereby reducing the integrity of the structure [6]. Because buckling deformation is caused by the tensile residual stress in the weld, it is essential to study this stress to control the strain. Low-temperature transformation (LTT) materials, which can reduce residual stress by controlling the martensite start (Ms) temperature, have been actively studied
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