What are the common weld defects during welding?
2 Answers
Weld defects can be divided into surface defects and internal defects: 1. Surface defects of welds: Weld size not meeting requirements, undercut, burn-through or weld reinforcement, lack of penetration, incomplete filling, collapse, surface porosity or slag inclusion, surface cracks, and arc strikes; 2. Internal defects of welds: Porosity, slag inclusion, lack of fusion, lack of penetration, and internal cracks. The following are common methods for inspecting welding defects: 1. Visual inspection: Generally performed by visual observation, but the accuracy of inspection can be greatly improved with the help of some tools. Commonly used tools include weld inspection gauges, tape measures, steel rulers, and low-power magnifying glasses, which are used to inspect external defects of welds. 2. Air tightness test: (1) Water immersion test: A container filled with a certain pressure is submerged to a certain depth in a water tank and then slowly rotated to observe whether bubbles appear on the container to determine if there is leakage; (2) Soap water test: A brush dipped in soap solution is used to apply the solution to the welds on a container filled with pressurized gas. If no bubbles appear, the weld is qualified. 3. Kerosene test: Utilizing the strong permeability of kerosene to test the tightness of welds. Limewater is applied on one side of the weld (the outer side of the container), and after the limewater dries, kerosene is applied on the other side of the weld (the inner side of the container). The test checks whether oil spots appear on the white lime.
There are quite a few common weld defects in welding. I remember when I first started this job, I encountered several issues. The most common one is porosity - those tiny bubbles trapped in the weld bead are really annoying, usually caused by unclean surfaces or damp electrodes. Then there's slag inclusion; if the slag isn't properly removed and stays inside, it weakens the joint strength. Cracks are also frequent, especially cold cracks or hot cracks, which tend to occur when material stress is high. Lack of fusion is even more troublesome, where two parts don't truly bond together due to insufficient penetration. Undercut is another common problem where the weld edge doesn't melt adequately, resulting in irregular shapes. I always pay extra attention to these details during inspection, otherwise structural safety could be compromised - especially in large component welding where potential hazards are greater.
