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Analysis of Defects in Crane Welding Slag

Mar 26, 2020
Slag inclusion refers to the slag remaining in the weld metal, that is, some non-metallic inclusions in the molten pool during the welding metallurgy process are too late to float during the crystallization process and remain inside the weld. Flux-cored welding and submerged arc welding are prone to slag inclusion.
 
The generation of slag is related to the welding method, the composition of the welding materials (wires, fluxes) and the base material to be welded. Slag inclusion is mainly divided into root slag inclusion, welding layer and grain boundary slag inclusion, seam welding slag inclusion.
 
Harm
Not only reduces the mechanical properties, but also increases the tendency to generate thermal cracks, which induces layered tearing of the sheet.
 
Reason
A. The welding current is too small, and the liquid metal and slag cannot be separated.
B. The welding speed is too fast, and the slag does not have time to float out.
C. The edges of the workpiece and the weld are not cleaned.
D. The electrode welding angle is incorrect.
 
Preventive measures
1. Welding materials (wire purity, flux) should be selected properly, the content of sulfur and phosphorus in the base metal should be controlled, 
2. Should selected the appropriate welding parameters. 
3. The existence of the molten pool should not be too short.
4. In multi-layer welding, pay attention to removing the previous welding slag and welding correctly to facilitate the slag floating.
 
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