Welding is generally used to bond two pieces of metal together. Welding services Manteca CA can also be used to disjoin to metal pieces that were previously welded together or make holes in metal. Welding is typically understood to involve metals, especially cast iron, steel, copper, nickel, titanium, and aluminum, as well as alloys of each. Joining other materials, such as plastics, may be referred to as welding, but the process is different. Sometimes something goes wrong during welding, and the following imperfections can occur.
- Hydrogen Cracking
Hydrogen gas is a byproduct of the welding process. If the hydrogen level is too high, the heat-affected zone adjacent to the weld may crack as it cools down. This may be prevented by using a process that produces lower levels of hydrogen or by maintaining the heating for a given hold time to allow diffusion of the hydrogen. The thickness of the metal determines the length of the hold time.
- Solidification Cracking
As the metal expands and retracts with changes in temperature, sometimes the strength of the weld bead is insufficient to withstand the resulting stresses. The solidification crack that occurs is oriented longitudinally and may be prevented with high silicon and manganese content in the consumables while keeping impurity and carbon levels low.
Porosity refers to holes in the weld pool after it solidifies. This occurs because of pockets of gas that get trapped in the material. It can range in severity, with “wormholes” being a particularly serious form of porosity. Porosity can occur because of insufficient deoxidants in the parent metal, contaminants on the surface, or poor gas shielding. Porosity may be prevented by removing primer coatings and cleaning and degreasing the joint area. Manganese and silicon can form slag by combining with the trapped air, which is beneficial in preventing porosity. It can also help to add aluminum to the weld pool depending on the oxygen content of the material to be welded.