A good "exothermic welding" solder joint should have a full and bright surface and no pore. The section of the joint should be cut and observed as a whole without pore and defect. The most important factor affecting the welding effect of exothermic welding is temperature or water gas, because moisture may be absorbed in the mould, welding powder and the welded object. Therefore, how to prevent or remove water vapor is the most important step to be taken in exothermic welding.
Another factor affecting the welding effect of exothermic welding is the cleanliness of the mould and the welded object, such as dust, grease, oxide (rust) or other attachments on the surface of the welded object must be completely removed so that the welding operation can be carried out only after it is clean and bright. Otherwise, the electrical conductivity and mechanical properties of the welded joint will be affected. If the residue left behind in the die is not completely removed, the welded surface will be not smooth and bright.
Points: 1. Remove moisture, 2. Clean solders, 3. Clean moulds.