Welding is a process widely used in all industries for fabrication and repair. This article introduces welding technology and procedures. Welding has advantages over other methods of joining metals as it weighs less and is stronger.
Welding and Types of Welding
Welding is a process by which two pieces are joined by increasing their temperature to the melting point so that they form pools of molten material at the ends where joining is to be done. If required a separate filler material having the same composition as that of the parent materials is added and the pool is allowed to solidify and form a weldment. The welding process described above is called fusion welding and is very popular in the form of gas welding, electric arc welding, TIG, MIG etc.
The other basic form of welding is known as pressure welding. In pressure welding the ends of the material to be joined are brought up to a plastic state and then joined by applying pressure as in forge welding.
Advantages of Welding over other methods of joining
- The structures are built lighter due to welding as over riveting and other methods of joining.
- Additional joint strength can be obtained by using smaller structural members.
- Welded joints are more corrosion resistant as compared to rivets and bolts.
- Welded joints can be made fluid tight for tanks, ships, and boats.
Classification of Welding
The welding processes are of three types: plastic welding, fusion welding, and solid-phase welding. Fusion welding and plastic welding have been discussed above. Solid phase welding is done by the creation of metallic bonds between two surfaces being joined. The fusion welding processes are of further types as follows:
- Oxy-fuel gas
- Shield metal arc
- Submerged arc
- Gas tungsten arc
- Gas metal arc
- Resistance welding
- Eletroslag welding
- Thermit welding
- Plasma arc
- Electron beam
- Laser beam
Another welding process is called cold welding, which is a pressure welding process in which the ductile materials can be welded without the application of heat or electric current. Welding is done in materials at room temperature by subjecting them to sufficient pressure.
Welding Caution Poster
Safety in Welding
Welding and the related thermal processes use gas or high electric current to melt metal, and hence proper safety precautions must be taken while working.
- Protection against electric shocks: Direct shocks can cause thermal burns with deep tissue damage and cardiac arrest. Indirect shocks can cause injuries by falling from heights.
- Protection against burns: Molten metal and sparks can burn and therefore proper attire is a must.
- Protection against ultraviolet light: It can cause sun burns and painful eyes. Use proper eyes and face shield.
- Protection against flying chips: When removing slag using a chipping hammer, the sharp chips can land in your eyes. In some kind of welding like stainless steel welding the slag starts coming out by itself on cooling.
- Protection against welding fumes: Alloying and surface treatment of metals may give off smoke that is poisonous and can cause long term health problems.
- Production Technology by R.K. Jain
- Workshop Technology by B.S. Raghuwanshi
- Handbook for Maritime Welders by Unitor
- Materials and Processes in Manufacturing by E. Paul DeGarmo, J.T. Black, and Ronald A. Kosher
Image of a Caution Poster by Mohit Sanguri, Chief Engineer