Welding or bonding is the process of joining two materials. To create a bond between two metal pieces, a weld must be created. Welds are bonds that use a third metal to form the bond. This third metal is heated up to the point at which it becomes molten. This molten metal can be directed to fill crevasses and cracks that separate the two materials to be bonded. Once the molten metal has been properly placed, the welding torch can be removed from the molten metal. The metal quickly cools and solidifies. A good weld will form a permanent bond between the two metals.
Welding can be used to create complex mechanical devices. Most modern machines use some form of metal bonding to attach the various components together. For example, the hull of a navy ship has many welds that connect the various bulkheads to the ships frame. Each of these welds must be capable of withstanding corrosion, impact, and they must be waterproof. Creating welds that meet all three of these criteria is not always easy. There are a few steps a welder can take to ensure that they create the best welds and bonds possible.
When preparing a part for welding, a welder should clean it as best they can. The material should be free of moisture and oil. Welding torches are either electrical or gas fired. With electrical torches, working on a wet piece of metal can be incredibly hazardous. With a gas fired torch, a material covered in oil can burst into flames. In addition to ensuring that the material is dry, the welder should also ensure that it is free of dirt and contamination. Any piece of contamination that makes its way in between the weld and the metal can serve as a weak spot in the weld. Consider a small piece of wax that the welder misses when cleaning the material. When welded over, the wax will evaporate and leave a void in the weld. This void may be below the surface, meaning that anyone who inspects the welds will not see any fault. However, this weld will be substantially weaker than a solid weld.