What are red welding rods for?
The only process for welding was forge welding. This was the method blacksmiths used for many millennia for joining iron and steel through heating and hammering. Arc welding, oxy-fuel welding, and electric resistance welding were some of the first to be developed in the latter part of the century. As world wars created a need for reliable, inexpensive joining methods, welding technology developed quickly in the 20th century. Many modern welding techniques were created after the wars. These included manual methods such as shielded-metal arc weld, which is still the most popular method of welding. Semi-automatic and automated processes like gas metal arc weld, submerged arc weld, flux-cored and electroslag welding were also developed. In the second half of the 20th century, laser beam welding was invented. Robot welding is now commonplace in industrial settings as science advances. Researchers continue to develop new welding techniques and improve our understanding of weld quality.
Crystalline solids cohesion can be achieved by a chemical or metallic bond between constituent atoms. There are two types of chemical bonds: covalent and ionic. A valence electron or bonding electron is required to separate from an atom in order to form an ionic bonded. Once attached to another atom, the valence electron can be detached to form opposingly charged ions. When the ions are in an equilibrium position, the force between them is equal to zero, then they bond in the static position. The inter-ionic spacing between ions increases when they are subject to tension force. A repulsing force is created under compressive force between atomic nuclei.
The body-centred hexagonal, face centred cubic, and close packed hexagonal are the three most used crystallitice structures in metals. Austenitic steel has the body-centred hexagonal structure while ferritic iron has the body-centred cylindrical structure. Non-ferrous materials like nickel, copper, and aluminium have the face centred cubic structures. Ductility plays an important role in the stability of structures. It allows them to withstand local stress levels without breaking. A structure must have acceptable strength. This is a function of a material’s yield strengths. As a general rule, fracture toughness decreases as a material's yield strength increases.
In the last decades of the 19th Century, resistance welding was also developed. The first patents went to Elihu Thompson in 1885. He continued making further improvements over the next 15-years. In 1893, thermite welding was developed. Around that time, another process, called oxyfuel welding became popular. Edmund Davy discovered acetylene in 1836. However, it was not practical for welding until 1900 when a torch was invented. Because of its portability and low cost, oxyfuel welding was initially a popular method for welding. However, oxyfuel welding became less popular for industrial applications as the 20th century progressed. As advances in metal coatings (known simply as flux) became available, they were largely replaced by arc welding. Flux covers the electrode not only protects the base material against impurities but can also stabilize the arc and add alloying components.
Energy beam welding methods, namely laser beam welding and electron beam welding, are relatively new processes that have become quite popular in high production applications. The two processes are quite similar, differing most notably in their source of power. Laser beam welding employs a highly focused laser beam, while electron beam welding is done in a vacuum and uses an electron beam. Both have a very high energy density, making deep weld penetration possible and minimizing the size of the weld area. Both processes are extremely fast, and are easily automated, making them highly productive. The primary disadvantages are their very high equipment costs (though these are decreasing) and a susceptibility to thermal cracking. Developments in this area include laser-hybrid welding, which uses principles from both laser beam welding and arc welding for even better weld properties, laser cladding, and x-ray welding.
Gas metal arc welding (GMAW), also known as metal inert gas or MIG welding, is a semi-automatic or automatic process that uses a continuous wire feed as an electrode and an inert or semi-inert gas mixture to protect the weld from contamination. Since the electrode is continuous, welding speeds are greater for GMAW than for SMAW. A related process, flux-cored arc welding (FCAW), uses similar equipment but uses wire consisting of a steel electrode surrounding a powder fill material. This cored wire is more expensive than the standard solid wire and can generate fumes and/or slag, but it permits even higher welding speed and greater metal penetration. Gas tungsten arc welding (GTAW), or tungsten inert gas (TIG) welding, is a manual welding process that uses a non-consumable tungsten electrode, an inert or semi-inert gas mixture, and a separate filler material. Especially useful for welding thin materials, this method is characterized by a stable arc and high-quality welds, but it requires significant operator skill and can only be accomplished at relatively low speeds.
Gas metal arc welding (GMAW), also known by metal inert gases or MIG welding is a semi-automatic, or automatic process that uses a continuous feed of wire as an electrode and an inert/semi-inert gas mixture as a protection gas to prevent contamination. GMAW welding speeds are faster than SMAW because the electrode is continuous. Flux-cored arc welding, which uses similar equipment, uses a wire made of a steel electrode and a powder fill. Cored wire can be more expensive than standard solid wire, and may produce fumes or slag. However, it allows for faster welding speeds and better metal penetration. Gas tungsten welding (GTAW) or tungsten inert gases (TIG), is a manual welding method that employs a non-consumable, non-renewable tungsten electrode, a semi-inert gas mixture and a separate filler. This method is especially useful for welding thin materials. However, it requires considerable operator skill and can only work at low speeds.
