28.3. What are the causes of夹渣 defects?

During the welding process, the welding rod and steel plate produce a certain amount of slag, and this slag cannot be completely eliminated, resulting in some residue remaining in the weld seam. This residual slag in the weld seam ultimately leads to the slag inclusion defect in welding. The slag inclusion defect is also one of the more common defects in the welding process. There are many classification standards for slag inclusion, which explain the causes of slag inclusion from different perspectives. During the welding process, due to the use of alkaline welding rods, oxides are easily produced under high temperature conditions, especially under the influence of welding current. The oxides in the welding rod rapidly react with the oxides in the steel plate, and as the molten metal enters the welding gap, it easily forms slag inclusion defects during the cooling process.