Following are some important welding related processes used in industries.
- Oxy-acetylene cutting
- Arc cutting
- Hard facing
Plates made of iron and steel are cut by oxygen, acetylene cutting torch. Oxygen and acetylene are mixed in the cutting torch and a gas flame is generated. The flame heats the sheets to bring them to red hot condition. High pressure oxygen is supplied on the red hot metal through a separate central hole of the cutting torch. Iron and steel sheets are thus cut by the jet of oxygen.
In this process, the metal parts are heated by means of carbon or metal electrodes. High pressure air is supplied on the molten metal to remove it and cut the metal parts. Oxygen jet is supplied along with the electrode instead of air nowadays. Arc cutting is not suitable for accurate work.
Hard facing is a process of coating a hard matrial on soft metal parts. Powdered coating metal is filled in the welding gun. The metal powder is melted by the oxy-acetylene gas flame. The supply of inert gas at pressure makes the powdered metal to split into small particles. These particles are sprayed on the surfaces of the soft metal. Coatings of Tungsten carbide, Chromium carbide and Aluminium oxide can be made on the surfaces of different cutting tools and cutters.
Two parts made of similar or dissimilar metals are joined by a solder made of a fusible alloy. Solder is an alloy made of Tin and Lead. The melting temperature of the solder is in the range of 150°C to 350°C. The surfaces of the two metal parts are cleaned and held in correct positions. Flux paste made of Zinc chloride is applied on the parts by soldering iron. Application of flux prevents oxidation. The solder is melted by the heat provided by the soldering iron and filled between the metal parts. The solder solidifies and joins the metal parts.
In brazing, filler metal in molten state is filled between the metal parts of the joint. The filler rod is heated upto 450°C. The parts to be joined are cleaned and the molten filler metal is applied between the parts to make the joint. In this method, the metal parts are not melted.