NationMaster - Encyclopedia: Spot welding

Spot welding is a type of resistance welding used to weld various sheet metals. Typically the sheets are in the 0.5-3.0 mm thickness range. The process uses two shaped copper alloy electrodes to concentrate welding current and force between the materials to be welded. The result is a small "spot" that is quickly heated to the melting point, this forms a nugget of welded metal after the current is removed. The amount of heat released in the spot is determined by the amplitude and duration of the current. The current and duration are chosen to match the material, the sheet thickness and type of electrodes. Applying the current for too long can result in molten metal being expelled as weld splash, or can even burn a hole right through the materials being welded. Download high resolution version (2103x1289, 698 KB) A Miller spot welder. ... Download high resolution version (2103x1289, 698 KB) A Miller spot welder. ... Resistance welding refers to a group of welding processes that produce coalescence of the faying surfaces with the heat obtained from resistance of the workpieces to the flow of the welding current in a circuit of which the workpieces are part, and by the application of pressure. ... Hot metal work from a blacksmith In chemistry, a metal (Greek: Metallon) is an element that readily loses electrons to form positive ions (cations) and has metallic bonds between metal atoms. ... General Name, Symbol, Number copper, Cu, 29 Chemical series transition metals Group, Period, Block 11, 4, d Appearance metallic pinkish red Standard atomic weight 63. ... An alloy is a homogeneous mixture of two or more elements, at least one of which is a metal, and where the resulting material has metallic properties. ... An electrode is an electrical conductor used to make contact with a metallic part of a circuit (e. ... The melting point of a crystalline solid is the temperature at which it changes state from solid to liquid. ...

Applications

Spot welding is typically used when welding particular types of metal steel sheet metal. Thicker stock is difficult to heat up from a single spot, as the heat can flow into the surrounding metal too easily. Spot welding can be easily identified on many sheet metal goods, such as metal pails (buckets). Aluminum alloys can also be spot welded. However, their much higher thermal conductivity and electrical conductivity mean that up to three times higher welding currents are needed. This requires larger, more powerful, and more expensive welding transformers. The steel cable of a colliery winding tower. ... Sheets of stainless steel cover the Chrysler Building Thin sheets of gold leaf Sheet metal is simply metal formed into thin and flat pieces. ... // Look up stock in Wiktionary, the free dictionary. ... An alloy is a homogeneous mixture of two or more elements, at least one of which is a metal, and where the resulting material has metallic properties. ... In physics, thermal conductivity, k, is the intensive property of a material that indicates its ability to conduct heat. ... Electrical conductivity or specific conductivity is a measure of a materials ability to conduct an electric current. ... Three-phase pole-mounted step-down transformer. ...

Perhaps the most common application of spot welding is in the automobile car manufacturing industry, where it is used almost universally to weld the sheet metal to form a car. Spot welders can also be completely automated, and many of the industrial robots found on assembly lines are spot welders (the other major use for robots being painting). Image File history File links KUKA_robots_in_car_production. ... KUKA industrial robots welding a car body in the white section of a production line. ... Automakers are companies that produce automobiles. ... Spot welding: KUKA industrial robots welding a car body in the white section of a production line. ... ASIMO, a humanoid robot manufactured by Honda. ... Modern car assembly line. ...

A further place where spot welding is used is in the orthodontist's clinic, where small scale spot welding equipment is used when resizing metal "molar bands" used in orthodontics (dentistry).

Electrical notes

The voltage needed for the welding depends on the resistance of the material to be welded, the sheet thickness and desired size of the nugget. When welding a common combination like 1.0 + 1.0 mm sheet steel, the voltage between the electrodes is only about 1.5 V at the start of the weld but can fall as low as 1 V at the end of the weld. This drop in voltage stems from the resistance reduction caused by the steel melting. The open circuit voltage from the transformer is much higher than this, typically in the 5-10 V range, but there is a very large voltage drop in the electrodes and secondary side of the transformer when the circuit is closed.

Due to changes in the resistance of the metal as it starts to liquefy, the welding process can be monitored in real-time to ensure a perfect weld every time, using the most recent advances in monitoring/feedback control equipment. The resistance is measured indirectly, by measuring the voltage at and current through the electrodes. Electrical resistance is a measure of the degree to which an electrical component opposes the passage of current. ... Wikipedia does not have an article with this exact name. ...

External links

Category: Welding Image File history File links This is a lossless scalable vector image. ... Turned chess pieces Metalworking is the craft and practice of working with metals to create structures or machine parts. ... Welding is a fabrication process that joins materials, usually metals or thermoplastics, by causing coalescence. ... Manual Metal Arc welding, also known as stick or MMA welding is one of the most common forms of welding. ... Shielded metal arc welding Shielded metal arc welding (SMAW), also known as manual metal arc (MMA) welding or informally as stick welding, is a manual arc welding process that uses a consumable electrode coated in flux to lay the weld. ... Gas metal arc welding Gas metal arc welding (GMAW), sometimes referred to by its subtypes, metal inert gas (MIG) welding or metal active gas (MAG) welding, is a semi-automatic or automatic arc welding process in which a continuous and consumable wire electrode and a shielding gas are fed through... A wire feeder configured for . ... A submerged arc welder used for training. ... Gas tungsten arc welding (GTAW), also known as tungsten inert gas (TIG) welding, is an arc welding process that uses a nonconsumable tungsten electrode to produce the weld. ... Plasma arc welding (PAW) is an extension of the gas tungsten arc welding (GTAW) process. ... This is a list of welding processes, separated into their respective categories. ... Oxyacetylene redirects here. ... Resistance welding refers to a group of welding processes that produce coalescence of the faying surfaces with the heat obtained from resistance of the workpieces to the flow of the welding current in a circuit of which the workpieces are part, and by the application of pressure. ... Forge welding is a welding process of heating two or more pieces of wrought iron or steel until their surfaces are malleable and then hammering them together. ... Ultrasonic welding is an industrial technique whereby high-frequency ultrasonic acoustic vibrations are used to weld objects together, usually plastics, and especially for joining dissimilar materials. ... Electron beam welding is a welding process where the energy to melt the material is applied by an electron beam. ... Laser beam welding is a technique in manufacturing whereby two or more pieces of material (usually metal) are joined by together through use of a laser beam. ... A high output constant current welding power supply for use with GTAW and SMAW A welding power supply is an electrical device that provides an electrical current to perform welding procedures which require electricity. ... An electrode is an electrical conductor used to make contact with a metallic part of a circuit (e. ... A filler metal is a metal added in the making of a joint through welding, brazing, or soldering. ... Shielding gases are inert or semi-inert gases that are commonly used in several welding processes, most notably gas metal arc welding and gas tungsten arc welding. ... Spot welding: KUKA industrial robots welding a car body in the white section of a production line. ... Welding helmets are typically worn when arc welding. ... The cross-section of a welded butt joint, with the darkest gray representing the weld or fusion zone, the medium gray the heat affected zone, and the lightest gray the base material. ... Welding is a fabrication process that joins materials, usually metals or thermoplastics, by causing coalescence. ... Residual stresses are stresses that remain after the original cause of the stresses (external forces, heat gradient) has been removed. ... Arc eye, also known as arc flash, welders flash, corneal flash burns, or flash burns, is a painful ocular condition sometimes experienced by welders who have failed to use adequate eye protection. ... Underwater welding Underwater welding refers to a number of distinct welding processes that are performed underwater. ... Brazing is a joining process whereby a non-ferrous filler metal or alloy is heated to melting temperature (above 450Â°C; 842Â°F) and distributed between two or more close-fitting parts by capillary action. ... (De)soldering a contact from a wire. ... Turned chess pieces Metalworking is the craft and practice of working with metals to create structures or machine parts. ... A typical steel fabrication shop Fabrication, when used chas an industrial term, applies to the building of machines and structures by cutting, shaping and assembling components made from raw materials. ... Casting may be used to create artistic sculptures Casting is a manufacturing process by which a molten material such as metal or plastic is introduced into a mold, allowed to solidify within the mold, and then ejected or broken out to make a fabricated part. ... A lathe is a common tool used in machining. ... Metallurgy is a domain of materials science and of materials engineering that studies the physical and chemical behavior of metallic elements, their intermetallic compounds, and their mixtures, which are called alloys. ... Jewelry (the American spelling; spelled jewellery in Commonwealth English) consists of ornamental devices worn by persons, typically made with gems and precious metals. ...