Welding processes in industrial production: an in-depth analysis

Welding is an indispensable technique in the field of industrial production, particularly metalworking. In this article, we will explore the main welding processes used in industries and their applications in various sectors.

The role of welding in industry

Welding is a process that allows two or more pieces of metal to be joined by the addition of heat and, sometimes, addition materials. This process is essential in a variety of industries, including:

•   Construction of infrastructure such as bridges, skyscrapers, dams;
•  Manufacture of vehicles, means of transport and mechanical components;
•  Assembly of electrical and electronic systems;
•  Manufacture of consumer goods such as household appliances;
•  Maintenance of structures and plants.
   

Types of welding processes

There are various welding techniques that can be classified according to the method of heat input, the presence or absence of filler material and the use of shielding gas. Some of the most common welding processes in industries are the following:
 

Electric arc welding

Electric arc welding uses an electric arc between the workpiece and the electrode to generate the necessary heat. This type of welding can be divided into several variants, including:

•  Coated electrode welding (SMAW): uses a coated electrode that is consumed during welding and provides the filler material at the same time.
•  MIG/MAG welding (GMAW): uses a continuous wire as electrode and filler material, with the use of inert (MIG) or active (MAG) gas as protection against oxidation.
•  TIG welding (GTAW): involves the use of a non-consumable tungsten electrode and requires the separate addition of filler material; it is one of the most precise and cleanest processes due to the use of inert gas.

Resistance welding

Resistance welding uses electric current to locally heat the contact areas between the parts to be joined, causing the metal to melt and consolidate. Resistance welding techniques include:

•  Spot Welding (RSW): involves applying pressure and an electric current to the surfaces to be welded in order to create small fusion ‘spots’.
•  Projection welding: involves the use of a sensing element on the surface of the workpiece to be welded, which melts due to the electric current and bonds with the underlying material under the action of pressure.
   

Friction welding

Friction welding uses the mechanical force and heat generated by friction between relative moving parts to reach fusion temperature and join the parts. This process includes:
 

•  Stretch friction welding (FSW): uses a non-consumable rotating tool inserted into the joint between two metal parts; the heating produced by the friction and the plastic mixture of the tool allow the formation of a solid, flawless joint when it cools.
•  Ultrasonic welding: this is a fast and precise method that uses high-frequency vibrations to generate heat and weld metal or plastic parts.
   

Considerations on the choice of industrial welding process

The choice of the most suitable welding process for a specific industrial application depends on several factors, including:

•  Type and thickness of the material to be welded;
•  Size and geometry of the joint;
•  Accuracy and quality required for the joint;
•  Production speed and cycle cost;
•  Safety and environmental impact of the process.

In general, electric arc welding is preferred for machining ferrous metals and aluminium alloys due to its versatility, speed and ease of use. TIG welding is particularly suitable for high-precision joints and in the presence of materials sensitive to high temperatures, such as aircraft alloys or refractory metals. Resistance welding is mainly used in the manufacture of small components such as brackets, clips and frames, while friction welding is ideal for the assembly of pipes, fasteners and complex structures without the addition of foreign materials.