What are types of welding?

The heat-affected area (HAZ), which is the area around the weld, in which the temperature and stresses of uneven heating/cooling alter the alloy's heat-treatment properties, is known as the heat-affected circle. The effects of welding on the material surrounding the weld can be detrimental--depending on the materials used and the heat input of the welding process used, the HAZ can be of varying size and strength. The thermal diffusivity (or heat transfer) of the base material is important. If the diffusivity is high the material cooling rate will be high and the HAZ will be small. Low diffusivity results in slower cooling and a greater HAZ. A key factor in the process of welding is the amount of heat being injected. Processes like oxyacetylene weld have a high heat input, which increases the HAZ. Laser beam welding is a process that produces a high concentration of heat with a limited amount of heat. This results in a small HAZ. Arc welding lies between these two extremes. However, each process has a slightly different heat input. This formula can be used for calculating the heat input required to arc weld.

The history and practice of joining metals has been around for many millennia. This technique was first demonstrated in Europe and Middle East during the Bronze and Iron Ages. Herodotus an ancient Greek historian stated in The Histories of 2005 BC that Glaucus of Chios invented iron welding. Welding was used during the construction the Iron pillar Delhi. It was erected at Delhi, India, in around 310 AD. It weighed approximately 5.4 tonnes. A variety of energy sources are available for welding: a gas fire (chemical), an electricity arc (electrical), and a laser. An electron beam, friction, as well as ultrasound. While welding is often an industrial process it can also be done outdoors, in the open, in water, or in outer space. Welding can be dangerous and requires careful precautions to avoid burns and electric shocks, vision damage, inhalation and inhalation toxic gases and fumes, as well as exposure to ultraviolet radiation.

Submerged arc welding is a high-productivity method of welding. The arc is struck under a cover layer of flux. The flux blocks contaminants from the atmosphere, which increases the quality of the arc. With continuous wire feeding, the weld deposition rate can be high because the slag that forms on the welding process is usually removed by itself. The flux conceals the arc, so there is almost no smoke and much better working conditions. This process is used in many industries, including large-sized products and the production of welded pressure vessels. The process can also be used for electroslag welding (ESW), atom hydrogen welding, and stud-arc welding. ESW is a single-pass, highly productive welding process that can be used for thicker materials. It can be used in vertical or near vertical positions.

The durability and life of dynamically loaded, welded steel structures is determined in many cases by the welds, in particular the weld transitions. Through selective treatment of the transitions by grinding (abrasive cutting), shot peening, High-Frequency Impact Treatment, etc. the durability of many designs increases significantly. Most solids used are engineering materials consisting of crystalline solids in which the atoms or ions are arranged in a repetitive geometric pattern which is known as a lattice structure. The only exception is material that is made from glass which is a combination of a supercooled liquid and polymers which are aggregates of large organic molecules.