How to Avoid Common Welding Defects

Spatter and welding slag shall not be cleaned after welding

Phenomenon: This is a common problem, which is not beautiful and harmful. Splashes will increase the hardened structure on the surface of the material and produce hardening and other defects.

Cause: the welding material is damped and deteriorated when it is stored, or the welding rod does not match the substrate, the welding equipment does not meet the requirements, the current is large, there are sundries and oil dirt pollution at the edge of the weld groove, and the welding environment does not meet the requirements.

Precautions:

Appropriate welding equipment shall be selected according to the welding base metal. The welding rod shall be equipped with dry and constant temperature equipment to clean the edge of the joint and discharge water, oil and sundries. The overlapping protective shed shall be constructed in winter and rainy season to ensure the welding environment. Before welding non-ferrous metals and stainless steel, the base metal on both sides of the weld can be coated for protection, and welding rod and argon protection can be selected, Eliminate spatter and reduce slag.

Arc scar

Phenomenon: improper operation causes the welding rod to contact with the weldment, or the ground wire to contact with the workpiece poorly.

Regularly check the insulation of the welding handle wire and the grounding wire. If any damage is found, it shall be wrapped up in time. The grounding wire shall be installed firmly and reliably. During welding, do not strike an arc outside the weld bead. The welding clamp shall be placed in isolation from the base metal or hung properly. When not welding, cut off the power supply. If there is any scratch, polish it with an electric grinding wheel in time and put it on the workpiece with corrosion resistance requirements, The arc scar will reduce the performance of the material.

Incomplete penetration

Phenomenon: during welding, the root of the weld is not fully fused with the base metal, or there is partial incomplete penetration between the base metal and the base metal. This defect is called incomplete penetration, also known as incomplete fusion. It reduces the mechanical properties of the joint and will produce stress concentration and cracks in this part. Incomplete penetration is not allowed for any weld during welding.

Cause: the groove is not processed as required, the blunt edge is thick, the groove angle gap is too small, and the root is not completely cleaned during double-sided welding, resulting in oxides, slag, etc., which hinder the fusion between metals.

If the welding current is too high, the base metal has not melted, the welding rod has melted and cannot be fused together, the current is too small, the speed of electrode transportation is too fast, so that the base metal and welding rod cannot be fused, the electrode angle is incorrect, the melting is biased to one side or partial blowing will form incomplete penetration.

Precautions:

According to the design drawing or the specified groove size, carry out processing and assembly clearance, carefully clean the rust and oil stain at the root of the weld groove. During multi-layer weld welding, grind and clean the oxide between the welding layers with angular grinding wheel, select appropriate current and welding speed, pay attention to the correct angle of the welding rod, and for the weldments with thick thickness, high thermal conductivity and fast heat dissipation, Preheat before welding or heat during welding to fuse the base metal and electrode metal.