Correlation between fusion hole morphology and weld penetration in TIG welding
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One-side welding with back-formation technique is widely used in pressure vessels and the pressure piping industry. Welders attach immense importance to the role of the fusion hole in one-side welding with back-formation process. Fusion hole is beneficial for the transfer of liquid metal to the back of the weld, which has an important effect on the penetration and good weld formation of double sides. In contrast to other keyhole welding processes, the current understanding of the fusion hole is only at the experience level with nearly absent systematic research. Clear topside images of the fusion hole were captured in one-side welding with back-formation welding using a CCD camera with a narrow-band filter. An image processing algorithm was developed on the basis of image characters to extract the edge of the fusion hole and gap. The width of the fusion hole and the size of the gap were obtained. The experiment was conducted on 2-mm-thick low-carbon steel sheets. Findings show that the width ratio between the widths of the fusion hole and the gap increases with the welding current. In full penetration condition, the width ratio ranged between 1.80 and 1.90, whereas under partial penetration, this ratio reached below 1.70. When the welding current is extremely large, the workpiece is burnt through with a width ratio of 2.60–2.70. The difference of the width ratio in different penetration conditions provides a theoretical basis for the feedback control of the welding process.
KeywordsFusion hole behavior Vision-based sensing Image processing One-side welding with back-formation
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The authors would like to thank the National Natural Science Foundation of China for its financial support (No. 51675309).
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