科研之友
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摘要
To reveal the influence mechanism of linear heat input (LHI) on the mechanical properties and corrosion behaviors of SUS304 weldments manufactured by local dry underwater pulsed metal inert-gas welding (LDU-PMIG), phase structure, grain structure, grain preferred orientation, and grain type of weld metal (WM) were investigated in this paper. With LHI increasing, ferrite phase morphology transformed from lath to skeleton, and grain size was enlarged. The content of equiaxed grains was increased, and that of columnar grains was reduced remarkably. The mechanical performance ascended first and then reduced with the increase of LHI. The increase of equiaxed grain content and the diversification of grain preferred orientation were beneficial to the improvement of mechanical performance, then, grain coarsening led to mechanical performance decreasing. Besides, the corrosion potential, corrosion current and pitting potential of WM were detected through electrochemical corrosion tests. The results illustrated that the corrosion resistance of WM was lower than that of base metal (BM), and the corrosion rate was enlarged with LHI enhancing, which meant the corrosion resistance declining. The corrosion resistance was mainly determined by Cr precipitates, ferrite phase and grain size. The microhardness, tensile strength, and elongation reached their maxima in the LHI of 336.7 J/mm. The greatest corrosion resistance of WM was obtained in the LHI of 256.2 J/mm and reached 69.9% of BM. This study is meaningful to promote the further development and application of LDU-PMIG in marine underwater welding field.
