Which welding methods are there? An overview
There are various methods available for welding metals. Depending on the material and application, the welding company will choose the appropriate method:
- Manual arc welding
- MIG / MAG welding
- TIG / TIG welding
- plasma welding
- gas welding
- spot welding
- robot welding
- Seam welding
- friction welding
- orbital welding
- laser welding
Manual arc welding
Arc welding is a type of welding in which two metals are melted to fuse together through an arc. An arc is a current flow through a gap in the circuit facilitated by localized thermally ionized gas particles. This arc is triggered by bringing an electrode into contact with the workpiece. The circuit is short-circuited and then separated with a small distance. The resulting temperature due to this arc is on the order of 4500 ° C or higher, allowing any metal to be melted.
MIG / MAG welding
MIG and MAG welding are types of gas-metal arc welding processes. Metal-gas arc welding is an arc welding method in which a consumable bare metal wire serves as an electrode. The bare metal wire is continuously guided by a coil through a welding tongs. In addition to the wire, the nozzles of the welding gun direct the shielding gas to the welding area to protect it from contamination. The type of gas used for shielding results in the two types MIG and MAG. When a mixture of helium and argon gas is used, this is called metal inert gas welding. The main applications include the welding of non-ferrous metals. However, if the shielding gas consists of carbon dioxide, oxygen and argon, welding is referred to as metal-active gas welding, which is used for welding low and medium carbon steels.
TIG / TIG welding
TIG welding (tungsten inert gas) is a widespread welding technique. In English, tungsten is called Tungsten, so it is known as TIG welding. It is a type of arc welding process that uses a non-consumable tungsten electrode. The high melting point of tungsten makes it a good electrode material and allows the welding of dissimilar metals. It can work both with and without cored wire. As can be seen from the name, argon, helium or their mixture is used as a protective gas. When filler wire is used, the arc is not introduced through the flux-cored wire but through the electrode into the weldment. This makes TIG welding a high-quality welding process without spatter. However, it is an expensive process when used for steels or high melting metals. Therefore, TIG welding is often used for welding aluminum and stainless steels or for welding thin profiles.
Plasma welding is a modified form of TIG welding. It uses a tungsten electrode as in TIG welding, but it is housed in a special nozzle that directs shielding gas into the arc region. These inert gases, which are applied at high speed, produce a plasma arc current with temperatures of up to 17000 ° C. The higher temperatures in plasma welding are mainly due to the narrowing of the arc in the production of plasma, which increases the power density of the arc. These higher temperatures can easily melt any metal. Therefore, plasma welding can hitherto easily weld hard-to-weld metals such as tungsten. Plasma welding produces high-quality welds, enabling high cutting speeds and low distortion. This makes it ideal for welding high-quality assemblies in automotive or aerospace applications.
Gas welding is a common term for gas welding. In reality, however, gas welding involves a group of autogenous welding processes. In each of these processes, fuel is combined with oxygen to create a flame for welding. The leading fuel is acetylene, which makes gas welding a synonym for gas welding. Oxy-acetylene combines oxygen and oxygen from separate cylinders in the torch to create a flame and maintain temperatures of up to 3500 ° C. There are also cheap, small and portable devices that usually reach lower temperatures. Autogenous welding is economical and ideal procedure for repair work and small series. Common welding applications are sheets and plates thinner than 6 mm.
Spot welding or resistance spot welding is a resistance welding process for bonding metal surfaces. It is a crucial process in the manufacture of automobiles, metal furniture, appliances and a variety of other sheet-based products. In a spot welding process, two metal surfaces to be joined are first pressed together by opposing electrodes and briefly supplied with power. The current melts the metal where the two surfaces touch and fuses it. Due to the nature of this welding process, it is ideal for welding sheet metal parts with a thickness of less than 3 mm.
Robot welding is a process for automating welding. It is characterized by the use of programmable robots that not only move the welding head, but also position the workpiece as needed. The robots can be programmed according to the requirements of the facility, which makes the automation flexible and suitable for the production of complex products. Arc welding and spot welding are the most common welding processes in robot welding. Spot welding robots are used in almost every final assembly in the automotive sector.
Roll seam welding is also a resistance welding process and is very similar to spot welding. It involves the use of electrodes in the form of rotating wheels. During roll seam welding, the wheel-shaped electrodes exert pressure on the metal surfaces to be joined. When powered, the intervening metal melts and creates a weld nugget. While the pressure is applied constantly, the current application can vary, which can lead to different types of weldment. If the current is constant, there is a continuous weld. When turned on and off at a certain frequency, overlapping welds are detected. A further reduction in frequency leads to weld bodies with small regular intervals in between. Roll seam welding enables the production of airtight connections. Exhaust systems for automobiles, fuel tanks and similar metal containers are some of the most common applications.
Friction welding is a type of solid-state welding. Solid Welding means that welding takes place without melting the machined parts and only by applying heat and pressure. Friction welding uses friction between parts as a heat source. For this purpose, the two parts to be welded are moved relatively zueinaner. The resulting friction generates heat and raises the temperature of both parts. Once the interface temperature has reached the hot zone of the metals to be machined, the rotation is stopped and pressure applied to drive the parts toward each other. This creates a metallurgical connection. The pressure disturbs the part geometry and pushes out some material that needs to be trimmed. Friction welding is typically used in the automotive, petroleum, natural gas and aircraft industries.
Orbital welding is a technique for welding pipes. Hand welding fulfills a reasonable task for larger pipes and various applications in pipeline construction. However, in the case of increased safety requirements, such as high pressure and to avoid contamination, orbital welding is more suitable. In orbital welding, a welding head is rotated around a pipe with complete control of a computer to perform the welding operation. For each new order, the controller must be configured to be able to be repeated again and again without loss of quality. In the first place, tungsten inert gas welding is used. Both inside and outside the tube shielding gas to shield against oxidation is present. It creates a high-quality connection, but is an expensive process that is only suitable for high-end applications in the aerospace, pharmaceutical and semiconductor industries.
Submerged arc welding is an automatic arc welding technique. It is a melting bare wire electrode that is fed from a coil. Instead of shielding gases around the arch, a powder flow covers the arch and forms a shielding blanket. The flux is supplied continuously along with the wire. It encloses the arc and prevents spatter and sparking. Thus, submerged arc welding can be observed without a welding helmet. Safety glasses and gloves are still recommended. As a more user-friendly automatic technique, it is well suited for high volume industries. It is often used for welding pipes and plates with a thickness of about two centimeters.
Laser welding or laser welding is characterized by the use of a laser for joining metal parts. It is a fusion welding process in which the heat generated by the laser performs the welding process. The resulting heat can lead to oxidation of the weld metal, which is why protective gases such as nitrogen, argon, carbon dioxide and helium are used to prevent this. Laser welding usually requires no filler material, but the melt combines by itself. The heat-affected areas of laser-welded parts are small, but due to the nature of the laser, they can only be used to weld small parts. Laser welding is widely used in the automotive industry, where it is performed either by robots or manually.
Soldering is one of the most popular joining techniques for metals. The soldering is characterized by the melting of a solder, its distribution on the abutting surfaces of the parts to be joined and its solidification. The working temperature during soldering is below the melting point of the base materials, therefore only the filler melts. The filler material has a melting point below the melting point of the parent metals and above 450 ° C. A properly brazed joint has higher strength than the braze because of the metallurgical bond between the braze and the base material. However, it is weaker than a welded joint. Due to the ease of use, the faster cycle times, the possibility of joining different metals and the lower power requirement, it is used as an alternative to welding in various applications. It is widely used in the repair and maintenance industry and in piping construction. Apart from that it finds use in the manufacture of automobiles, electrical appliances and jewelery.