# welding

Joining two pipes by oxy-fuel welding with filler wire, 1942

The welding is a group of joining methods for permanently joining (bonding) of two or more workpieces. Welding is the most important group of joining processes. According to DIN 8580 main group 4 part 6, it is defined as joining by welding . Most welding processes are also suitable for coating , which is referred to in practice and in specialist literature as surfacing - defined in DIN 8580 main group 5, part 6, as coating by welding .

According to EN 14610 and DIN 1910-100, welding is understood to mean “the permanent joining of components using heat and / or pressure , with or without filler metals ”. The filler materials are usually supplied in the form of rods or wires, melted and solidified in the joint between the parts to be joined in order to create the connection. They therefore correspond to the solder used for soldering or the adhesive used for gluing . The required welding energy is supplied from outside. Welding auxiliaries such as shielding gases , welding powder , flux , vacuum (in electron beam welding) or pastes can make welding easier or even possible in the first place. Welding can be carried out by supplying heat until the material melts or by supplying heat and applying additional force (pressure) to the workpiece.

Welding is one of the cohesive connection methods together with soldering and gluing. When welding, connections with high strength are created; during fusion welding due to the local melting of the components to be connected. With related soldering, on the other hand, only the solder becomes liquid, while the components are heated but not melted. Soldered connections therefore have a lower strength, but are also suitable for connections between materials with very different melting points. Such material pairings can, however, also be produced by pressure welding.

Welding is one of the most important and most widespread joining processes, as it is significantly more cost-effective than screwing or riveting and enables significantly stronger connections than soldering or gluing.

## Structure of the welding process

Classification of metal welding processes according to DIN 1910-100 with serial numbers according to DIN EN ISO 4063

The welding process can be classified according to

Type of energy acting on the workpiece
Type of base material
Purpose of welding
• Joint welding is used to join workpieces
• Overlay welding is used to coat a workpiece; if the base material and the overlay material are different, a further distinction is made between overlay welding
• Armor
• Plating
• Buffer layers
physical process of welding
• Fusion welding is welding with a localized melt flow, without the use of force, with or without a similar filler material (ISO 857-1). In contrast to soldering , the liquidus temperature of the base materials is exceeded. In principle, all materials that can be converted into the molten phase can be joined by fusion welding. In many processes, additional material is added, for example in the form of a welding wire .
• Pressure welding brings the materials to be connected to the required welding temperature using different forms of energy, whereupon the connection is made under the action of a force. Pressure welding does not require the addition of additional material such as welding wire.
Degree of mechanization
• Hand welding
• than purely manual welding
• as partially mechanized welding, in which the filler material and the auxiliary materials (shielding gases) are fed mechanically, but the torch is moved by hand,
• fully mechanical welding
• (fully) automated welding

## Weldability of a component

In order to be able to weld a component, it must be weldable. This means that through the interaction of the suitability of the material for welding ( weldability ), a weldable construction ( welding safety ) and a suitable production organization (welding option), individual parts can be welded together to form components with the desired quality. If this is not observed, the component can become unusable.

## Weldability of a material

As a result of the thermal effect on the welded parts during welding, their metallurgical properties change. Depending on the material composition and the type of temperature cycle, structures can arise that have negative quality influences. Weldability describes the extent to which a material can be welded to a satisfactory quality under certain conditions.

## Selection of a welding process

There are numerous welding processes available for joining individual parts to the workpiece, one of which must be selected in a specific case. When making the selection, the following aspects should be taken into account: From a process-technological point of view, the material, the component geometry, the accessibility to the welding point and the possible welding position play a role, as do the quality requirements for the welded product. From an economic point of view, the number of workpieces to be produced, the costs for the required welding equipment and those for carrying out the production work must be taken into account when choosing the method.

## Welded joint quality

Welding is used to connect components to one another in such a way that they can meet the requirements placed on them over an expected service life. For this purpose, the connections must meet quality criteria or quality features that meet the requirements. General specifications for the quality characteristics cannot be made, because these are always closely linked to the respective component requirements in use.

Sufficient quality can be expected if irregularities in the weld seam that occur during or after welding can be tolerated for the use of the welded component. If they are no longer acceptable, the irregularities are referred to as connection errors.

## Fusion welding process

### Preparation - weld joint

Welded parts are connected by so-called welded joints, which often require special joint preparation. The area where weldments join together is called the weld joint. The types of joints differ depending on the structural arrangement of the parts and the preparation of the joint, which enables a professional execution and inspection of the weld seam.

### Execution - welding position

Depending on the arrangement of the welding parts and the accessibility of the torch and the welding electrode to the seam, welding positions defined in the DIN EN ISO 6947: 2011-08 standard result.

### Gas fusion welding

In gas fusion welding or autogenous welding, the metal is heated by the combustion of fuel gases. The fuel gas that is usually used is acetylene (ethyne), which, together with oxygen in an acetylene-oxygen mixture, creates the welding flame. The temperature of the flame is around 3200 ° C. A welding wire is usually used as a filler material.

The gas melting process is suitable for both welding work in the factory and on the construction site. The slow process is primarily suitable for welding thin sheets and some non-ferrous metals as well as for repair and surfacing. This method is used particularly in heating, plumbing and pipeline construction, but is only of minor importance.

### Arc welding

In arc welding, an electric arc ( welding arc ) burns between the workpiece and an electrode, which, depending on the process, can melt and then at the same time serve as a filler material or is non-melting.

The main procedures are

• manual arc welding
• gas shielded welding with numerous sub-variants
• and submerged arc welding.

The electron bombardment causes the anode (positive pole) to heat up more. In most welding processes, consuming electrodes are operated as anodes, i.e. the workpiece as a cathode (negative pole). In the case of covered electrodes, the polarity depends on the electrode cover. If the cover consists of poorly ionizable components, as is the case with basic electrodes, the electrode is welded to the hotter positive pole, otherwise because of the lower current load on the negative pole.

#### Manual arc welding

Manual arc welding: 1 wire electrode with coating, 2 core wire, 3 shielding gas, 4 molten bath, 5 base material, 6 weld metal, 7 slag. The sweat drops are drawn by the polarization from 2 to 4.

Manual arc welding or electrode welding is a purely manual process ( manual welding) with a consumable electrode. These stick electrodes have a covering that also melts and partially evaporates, thereby forming protective gases and slag, both of which protect the melt from unwanted environmental influences. The slag can also change the metallurgical composition of the melt, so that the process can be adapted to many applications. It is very simple and requires little investment in equipment, but it is not particularly productive, so it is mainly used for repair work, in workshops and on construction sites.

#### Inert gas welding (SG)

TIG welding, a variant of inert gas welding

In inert gas welding, shielding gases are used that flow around the electrode and the melt. The supply of the protective gases is integrated in the burner. Gas-shielded welding processes are more productive than manual electric welding and can also be mechanized, some even completely automated. The costs are still low and the flexibility in use is significantly better than the more productive beam processes (laser / electron beam welding). In terms of frequency of use, inert gas welding is therefore the most important group of welding processes.

• Gas-shielded metal arc welding (MSG): Here the electrode melts and consists of the same or a similar material as the workpiece (as in manual electric welding)
• Metal inert gas welding (MIG): Inert gases are used here, i.e. those that do not enter into any chemical reactions with the melt. It is mainly used for non-ferrous metals and high-alloy steels.
• Metal active gas welding (MAG): Here, reactive gases are used to consciously change the composition of the melt. It is used for unalloyed and low-alloy steels.
• Tungsten inert gas welding (TIG): Uses a non-consumable electrode made of tungsten. High seam quality can be achieved, but it is slower than MIG / MAG welding.
• Plasma welding: related to TIG. The arc generates a plasma that has a higher power density than the simple arc. It is very productive, but also less flexible than the other inert gas processes and in this respect represents the transition to the blasting process.

#### Submerged arc welding

Submerged arc welding of a pipe longitudinal seam in the 3-wire process
Solidified pieces of slag from a UP welding bead

The submerged arc welding (submerged arc welding, EN ISO 4063: Process 12) is an arc welding method with a consumable wire (Process 121) or tape electrode (process 122), can be achieved in which high deposition rates. It is mainly used industrially for welding long seams and is not suitable for manual execution.

In submerged arc welding, the weld pool is covered by a layer of coarse-grained mineral welding powder. This melts due to the heat emitted by the arc and forms a liquid slag which, due to its lower density, floats on the metallic weld pool. The slag layer protects the liquid metal from exposure to the atmosphere. The arc burns in a gas-filled cavern under slag and powder. After the welding process, the slag layer often comes off by itself; the unmelted powder can be reused.

Particularly noteworthy is the fact that this process is largely emission-free, since the arc burns under the powder layer and only small amounts of smoke are released. No privacy protection is necessary. Because the process is covered, the method has a high thermal efficiency, which, however, limits its use to large sheet metal thicknesses. At the same time, this means that no direct visual inspection of the process is possible. However, in general, splatter-free seams of very high quality are achieved provided that suitable welding parameters are used.

The chemical composition of the weld metal can be influenced by the selection of a certain combination of wire and powder, since the reactions of metallic melt and slag in the cavern can cause alloy elements to burn up or burn over.

Because of the large weld pools, the UP process can only be used in a trough position or, with powder support, also in a transverse position.

### Laser welding

The laser welding (EN ISO 4063: Process 52) is mainly used for welding of components with high welding speed, narrow and slender weld form and must be fitted with low thermal distortion. The laser welding or laser beam welding is usually carried out without the addition of an additional material. The laser radiation is focused using optics. The workpiece surface of the joint edge, i.e. the joint joint of the components to be welded, is in the immediate vicinity of the focus of the optics (in the focal point). The position of the focus relative to the workpiece surface (above or below) is an important welding parameter and also determines the welding depth. The focal spot has a typical diameter of a few tenths of a millimeter, which results in very high energy concentrations if the laser used has the typical power of a few kilowatts of laser power. The absorption of the laser power causes an extremely rapid rise in temperature on the workpiece surface beyond the melting temperature of metal, so that a melt is formed. Due to the high cooling speed of the weld seam, it becomes very hard, depending on the material, and usually loses its toughness.

### Electron beam welding

In electron beam welding (EN ISO 4063: Process 51), the required energy is brought into the process zone by electrons accelerated by high voltage (60–150  kV ) . The jet formation takes place in a high vacuum (<10 −4 mbar). The welding process usually takes place in a vacuum, but can also be carried out under normal pressure. A beam power of up to 30 kW is used here, whereby the working distance between the beam outlet and the workpiece should be between 6 and 30 mm.

Electron beam welding offers about the same power flux density as laser beam welding with a higher efficiency of beam generation (laser: 3 to 40%, electron beam: about 70%). In addition, there is no need for shielding gases with electron beam welding in a vacuum. Both have a direct effect on the operating costs, so that an electron beam system can be cheaper than a comparable laser system in total and over its service life.

Electron beam welding allows high welding speeds with extremely deep, narrow and parallel seams. Due to the small seam widths and the high parallelism, the distortion can be kept extremely small. This process can therefore also be used at the end of the production chain. The process is also suitable for small, complex weld seams, since the electron beam can be deflected precisely and quickly by electrical or magnetic fields. This means that there is no need to move the component; the electron beam performs the movement itself. The spectrum of possible seam depths is between 0.1 mm and 300 mm ( aluminum ), ( steel ) 150 mm, ( copper ) 100 mm, ( titanium ): 100 mm.

Electron beam welding systems are often used in the mass production of gear components in the automotive industry (especially Japan and Germany). In addition to simple and inexpensive subcontracting, components for the aerospace industry, rail transport, medical technology and the food industry are electron beam welded.

### Aluminothermic welding

Aluminothermic welding is also known under the name Thermit welding and is mainly used for welding railway tracks . A mixture of iron oxide powder and aluminum powder is ignited (with the help of a magnesium chip) in a crucible with a hole on the underside, which is located on the connection point, from which liquid iron and aluminum oxide slag floating on it form at a temperature of around 2450 ° C .

${\ displaystyle \ mathrm {Fe_ {2} O_ {3} +2 \ Al \ longrightarrow 2 \ Fe + Al_ {2} O_ {3}}}$

### Fiber optic splicing

Welding device for splicing glass fibers

Optical fibers used for data transmission are connected to one another by means of arc welding without filler material. The process is known as splicing. The core diameters of the glass fibers to be connected are between 3.5 and 1500 µm, the jacket diameters between 125 and 1550 µm. Devices used for the welded connection position the glass fibers either automatically or manually using a microscope and micrometer screw before the connection, then an arc is used to heat the glass up to the melting temperature of the glass and the two fibers to fuse. Signal attenuation below 0.1 dB is achieved at the connection point.

### Fusion welding of plastics

Thermoplastic plastics can be joined using the following fusion welding processes:

## Pressure welding process

### Fire welding

Fire welding: Glowing sheet metal package with melting borax

In the case of fire welding, the metals to be joined are brought into a doughy state in the fire with the exclusion of air and then joined together with great pressure, for example with hammer blows. These must not be too strong at the beginning, otherwise the parts to be connected will be bounced apart again. Unlike most other welding methods of steel this is not melted, but at welding temperature (1200 to 1300 ° C) together . In preparation for the welding process in the forge, attention must be paid to the absence of air on the workpieces to be joined so that the surfaces do not oxidize . Originally, the exclusion of air was achieved by a strongly reducing flame and fine-grained river sand, whereby it was difficult to find such a sand with the correct melting point. Nowadays, borax is mostly used , which, like sand, forms a liquid, glassy skin over the steel parts and seals it. This protects them from oxide attack.

### Resistance welding

Principle of resistance spot welding

In resistance welding, the electrical resistance of the joint partners is used. They are compressed and electricity flows through them. The resistance is greatest at the contact points, so that is where most of the heat is released and the materials are heated the most.

• In resistance spot welding (also known as spot welding for short), mainly sheet metal is welded. They are pressed together at one point by two opposing electrodes. A welding current is introduced into the sheet metal through the electrodes. Spot welding is used particularly frequently for welding car bodies in the automotive industry
• In the case of roller seam welding , the electrodes are disk-shaped and roll off the joining partners conveyed through between the disks. This enables continuous seams to be produced. An example of application of the method is the production of the cylindrical part of food cans.
• Resistance projection welding corresponds in principle to spot welding, but one or more elevations (welding projection) are made in one of the components to be connected. Only these bosses now rest on the other component to be welded. The area of ​​the current transfer is precisely defined by the geometry of the boss, and flat copper electrodes are used as electrodes (in contrast to spot welding). During the flow of current, the hump partially melts, partially presses the material of the hump into the other component and forms a connection with it.
• The pressure butt welding processes and flash butt welding are easy to automate and are used to join tubular structures, rollers, rings, chain links, rails, concrete rebars, window frames, foils and hoses. The components are pressed against each other with two clamping jaws to which an electrical voltage is applied. A high current flows through the components, so that the joint briefly melts.

### Cold pressure welding

Connections using cold pressure welding (EN ISO 4063: Process 48) are made under high pressure and below the recrystallization temperature of the individual parts. Here the partners remain in a solid state, but plastic deformation with a strong approach of the contact surfaces is necessary. The extremely close contact between the two contact surfaces results in the destruction of interfering surface layers and a stable connection between the workpieces due to the interatomic bonding forces that are now acting. In order to obtain a good connection, minimum deformations of materials with sufficient cold formability are necessary (example: copper and aluminum with each other and with each other). Like other welding processes, cold pressure welding is also suitable for electrically conductive connections. In the case of aluminum, degreasing beforehand and tearing open the surface oxide layer is helpful (example: aluminum contact lugs in electrolytic capacitors ). Metals can also be cold-press welded to ceramics under high vacuum .

### Friction welding

In friction welding (EN ISO 4063: Process 42), two parts are moved relative to one another under pressure, with the parts touching on the contact surfaces. The resulting friction causes the material to heat up and plasticize. At the end of the rubbing process, it is of crucial importance to correctly position the parts in relation to one another and to exert high pressure. The advantages of this process are that the so-called heat-affected zone is significantly smaller than with other welding processes and that there is no formation of melt in the joining zone. A variety of materials, such as aluminum and steel, can be welded together. The connection of metallic materials that do not form alloys is also possible in many cases.

Process variants are:

### Ultrasonic welding

Sonotrode with catenoid shape for ultrasonic welding

The ultrasonic welding (EN ISO 4063: Process 41) is a method for joining of thermoplastic plastics and metal materials. The process is used in many areas of industry. So z. B. in the packaging industry plastic packaging or in the automotive industry cable harnesses are welded using ultrasound. In the case of metallic materials, it is mainly used for aluminum, copper and their alloys. The weld is caused by a high-frequency mechanical vibration in the range of i. d. Usually 20 to 35 kHz is reached, which leads to heating between the components due to molecular and interface friction, and in the case of metals also to the interlocking and entanglement of the parts to be joined. Ultrasonic welding therefore belongs to the group of friction welding.

With the help of a generator , high-frequency alternating current is generated and transmitted via a coaxial cable to an ultrasonic transducer, the so-called converter , which uses the piezoelectric or magnetostrictive effect to generate a mechanical ultrasonic vibration . These vibrations are transmitted to the sonotrode via an amplitude transformation piece . Different applications require different types of sonotrode, which are usually made of steel, aluminum or titanium. The amplitude of the oscillation and the impedance matching is influenced by the shape and mass of the amplitude transformation piece. The vibrations are transmitted under pressure via the structured, often corrugated work surface of the sonotrode to the workpieces to be connected.

When welding plastic, the vibration is usually introduced vertically to the joint partners. These heat up and begin to soften, which increases the damping coefficient . The increase in the damping coefficient leads to higher internal friction, which further accelerates the increase in temperature. The melted materials combine and are welded together after cooling and solidification.

When welding metals with ultrasound, the vibration is introduced horizontally to the joining partners so that they rub against each other. The connection is created after the roughness peaks have been sheared off and the oxide layer has broken open, essentially through the interlocking and interlocking of the parts to be joined. This takes place through plastic flow without the materials melting, which is particularly advantageous in the case of foils, thin sheets or wires, such as wire bonding .

In addition to spot welds, seam welds are also possible with rolling sonotrodes, e.g. B. in the manufacture of solar collectors .

The process is also characterized by very short welding times and high economic efficiency . Different materials can be connected to one another, the workpieces are only slightly heated in the welding area, so the surrounding material is not damaged.

### Explosion welding

Connection surface of an explosion weld (EN ISO 4063: Process 441) with the typical wave structures

With the help of the explosion welding process it is possible to join two non-fusion-weldable materials permanently and firmly. With the aid of explosives, the two welding surfaces collide at at least 100 m / s at an angle of 2 ° to 30 °. The collision energy brings the welding partners together down to the atomic level, so that the lattice forces (with metals) also act. Since the melting temperature is not reached, no intermetallic phases can form. In industrial applications, two metal partners that cannot be conventionally welded are usually joined in this way, for example titanium and copper. The main explosives used are highly explosive plastic PETN , RDX and HMX explosives such as Semtex with detonation speeds of more than 5000 m / s. The impact of the welding partners creates wave-like distortions at the interfaces, which create a material bond.

### Electromagnetic pulse welding

The electromagnetic pulse welding , short-EMP-welding or EMPW can without heat by the method of the magnetic reshaping (also Electromagnetic pulse technique, short-EMPT) material mixed compounds, but also similar materials, within about 25 microseconds to connect with each other by one of the joining partner by means of a magnetic field without contact a pulse experiences and collides with the other partner. The process is therefore related to explosion welding and cladding. Pipes, sheets and cylinders can be welded. In the process, the components are located near a coil through which a very high current pulse flows, which is obtained from a pulse generator . At least as one of the joining partners, only highly conductive materials such as aluminum can be processed. The high speed of the collision between the parts to be joined results in a material bond in the solid phase, as is the case with explosion welding.

Welding aluminum to steel with electromagnetic pulse technology

When joining sheets (plating), the impulse accelerates one of the two sheets to be joined over a distance of 0.3–2 mm to speeds of over 200 m / s. When this sheet hits a stationary counter sheet, the oxide layers adhering to both surfaces are loosened in the impact area and the air between the sheets is blown out. The clean surfaces created in this way are now highly reactive and are pressed together with high pressure. This causes a possibly helium-tight metallic bond through electron exchange.

The method hardly introduces any heat into the components. It is therefore possible to weld metallic materials with very different melting points. In addition, there is no structural influence from heat. Therefore, for example, connections between sheets made of aluminum alloys and high-strength steels can be made without changing their strength-determining structure.

### Diffusion welding

The diffusion welding (EN ISO 4063: Process 45) is an about 50-year-old welding, to connect to predominantly metallic workpieces. The quality of the welded joints is extremely high and can be in the range of the material used.

Diffusion welding takes place at high pressure (typical order of magnitude: flow limit ) and slightly below the solidus temperature . But metals can also tend to diffusion bonding below room temperature, provided their surfaces are extremely flat and smooth. Gauge blocks , for example, can cold welding together after a short time when they are wrung, so very are close together.

• In the predominantly in the powder metallurgy process used hot isostatic pressing (HIP) the work pieces to be welded into a steel can and then evacuated or disclosed in a pressure chamber. A protective gas with the appropriate pressure and temperature presses the components together. The force acts from all sides, i.e. isostatically.
• The second variant is also known as Uniaxial Diffusion Weld (UDW). Here, a uniaxial force is usually exerted perpendicular to the connecting surface by means of a hydraulic press. The press either has a vacuum container or a canister similar to the HIP process is used.

### MBP welding

Classification of arc pressure welding according to DIN 1910-100

The MBP-welding (pressure welding with a magnetically moved arc) is an arc pressure welding process according to DIN 1910-100: 2008-02, and has the serial number 185 in accordance with EN ISO 4063. The process is also referred to as MBL or Magnetarc welding. In the English language literature, it is known as MIAB Welding - magnetically impelled arc butt welding . With this process, profiles with a closed cross-section are butt connected to one another.

### Arc stud welding

Arc stud welding (short form: stud welding , serial number 78 EN ISO 4063) is one of the arc pressure welding processes. The process is used to permanently connect bolt-shaped elements (e.g. threaded bolts, pins, sockets, hooks, eyes) with larger components (e.g. body panels, housings, radiators).

### Pressure welding of plastics

Thermoplastic plastics can be joined using the following pressure welding processes:

## Welding simulation

The welding simulation is a tool for the clarification of welding-related questions, which is based on the numerical solution of a mathematical model. The aim is, on the one hand, to reduce costs in the company by replacing numerous practical tests and, on the other hand, to gain information that could not be obtained via measurements or only with a very high level of effort.

For welding training manufacturer Welding be some welding simulators available. These can simulate TIG, MAG and manual arc welding. With the simulator, various welding tasks can be trained in real time and under realistic conditions. Compared to normal welding, such devices for virtual welding training offer several advantages. Among other things, no material is consumed, no health and safety measures have to be observed, even rare work tasks or combinations of materials and materials can be used, through the variation of parameters an understanding of the dependencies of the welding results can be achieved and, depending on the torch position and management, the Results are analyzed immediately and errors corrected. Individual simulators also use real electric arcs.

## Service life extension through post-treatment methods

Example of a welded construction post-treated by means of high-frequency hammering

The durability and service life of dynamically loaded welded metal structures is in many cases by the welds - determined - in particular the weld transitions. Targeted post-treatment of the transitions by grinding , blasting , shot peening , high-frequency hammering, etc. can significantly increase the service life of many constructions with simple means. In the case of high-frequency hammering , the increase in service life is essentially based on a reduction in the notch effect , strengthening of the surface layer and the introduction of residual compressive stresses to increase the resistance against crack formation and crack propagation by superimposing the notch stresses with residual compressive stresses . After treatment, the weld seams must be protected by suitable measures such as coating with a corrosion-resistant, long-lasting material ( passive corrosion protection ). However, such a coating can be problematic in the event of repairs.

## Osh

### Danger from welding fumes and welding gases

Welding is associated with dangers that can result from the use of electricity, from pressurized gases, heat and from the release of optical radiation and hazardous substances. The hazards depend on which welding process is used.

Hazardous substances in the form of welding fumes and welding gases are released from the melt - especially from consumable welding consumables. Metal evaporates when the melt or the filler metal is overheated. The steam rises above the melt, cools down and forms metal particles through condensation. Airborne metal particles are known as welding fumes. The composition of the smoke depends on the composition of the materials to be welded. Fumes that are released when welding unalloyed and low-alloy steels consist mainly of iron and manganese or their oxides . When welding aluminum materials, the smoke consists primarily of aluminum or aluminum oxides; welding of corrosion-resistant chromium-nickel steels releases nickel and chromium compounds. Inhaled iron and aluminum compounds can burden the airways and impair lung function . Acute poisoning through inhalation of dusts with a very high manganese content can lead to inflammatory reactions in the lungs . This toxicity manifests as bronchitis and can develop into fibrous lung disease . Fumes containing manganese can also cause neurological disorders similar to Parkinson's disease ; hexavalent chromium compounds and nickel oxide are classified as carcinogenic. The International Agency for Cancer Research (IARC) even classifies welding fumes as generally carcinogenic.

Welding gases such as carbon monoxide , carbon dioxide , nitric oxide , nitrogen dioxide and ozone can also damage the respiratory tract. MIG / MAG welding only releases these gases in small quantities, so that the associated health risks are generally assessed as low. However, if welding is carried out in narrow, poorly ventilated rooms, the gases can displace the oxygen in the air, creating a risk of suffocation.

In order to protect employees, German legislation has stipulated limit values ​​for the air quality at workplaces . B. in the technical rule for hazardous substances (TRGS) 528 "Welding work" are listed. TRGS 528 also describes the procedure for determining process-related hazards and provides information on protective measures and preventive occupational health care.

As a technical protective measure, filter systems and devices for extracting and separating welding fumes should usually be used. If the air cleaned in this way is returned to the work area, special requirements are placed on the filter properties of the devices. This applies in particular to devices for the separation of carcinogenic fumes, which z. B. be free when welding chrome-nickel steels . In these cases, air return is only permitted for devices that have been positively tested in accordance with DIN EN ISO 15012-1 and -4 (in future DIN EN ISO 21904). The Institute for Occupational Safety and Health of the German Social Accident Insurance (IFA) offers equipment manufacturers and distributors tests according to these standards on a voluntary basis. The manufacturers of positively tested filter systems and devices receive a DGUV test certificate. Filter systems and devices that meet the safety requirements of the standard are listed in a positive list.

### activities

Pictogram "Use welding mask" according to DIN EN ISO 7010

A risk assessment must be drawn up for welding workplaces. All of the constituents of the welding smoke must be taken into account here, including titanium dioxide , fluoride , magnesium oxide , calcium oxide , iron oxides and their alloy components such as nickel , cobalt , chromium and manganese . In the case of high-alloy steels , if possible, electrode welding should be avoided and gas-shielded welding or automated processes should be used, because fewer chromates are released due to the lack of a coating on the electrode .

information

Appropriate professional instruction is mandatory for all dependent employees according to the Occupational Safety and Health Act (ArbSchG); Proof of training (skilled worker certificate or course examination from a Chamber of Crafts) is also common. In many industrial sectors, in railway applications, welding supervision is required.

Eye protection
Robots during inert gas welding

With autogenous welding you need protective glasses so that no glowing parts or sparks get into the eyes. The glasses are colored so that you can observe the welding environment without glare.

Arc welding produces ultraviolet radiation that damages the skin, but especially the eyes . Furthermore, infrared radiation (thermal radiation) is generated , which not only causes burns on unprotected parts of the body, but can also damage the retina. For this reason, protective glasses must be used that shield these two types of radiation . The protection classes for such glasses are specified in the European standard EN 169. Protection classes 2 to 8 are provided for oxy-fuel welding, while classes 9 to 16 are provided for open arc welding. The protective glasses have a lettering that characterizes the properties of the glass. The information is as follows: protection class, manufacturer code, optical class 98, DIN standard . The modern replacement for protective glasses are automatic welding protection filters .

Since the UV radiation also damages the skin , a screen is used that covers the entire face . Before the actual, almost black glass, there is usually a normal glass that blocks sparks and is cheaper to replace. In order to have both hands free, the umbrella can be attached to a protective helmet or to a device that can be folded up on the head. In addition, special flame-retardant welding clothing must be worn that safely covers all skin surfaces. Many welding processes are very noisy, so appropriate hearing protection is required.

Central welding fume extraction with BGIA certification
Dust protection

During welding, the finest dust particles are also created, which have to be extracted so that they do not get into the welder's lungs and diffuse from there into the bloodstream. For this purpose, mobile or stationary welding smoke filters are used to extract and filter this fine dust. State-of-the-art technology are so-called ePTFE filters (surface filtration). If no effective extraction of the welding fumes can be ensured, the welder must be protected by personal protective equipment in the form of a blower filter device (PAPR). These devices do not protect against a lack of oxygen or harmful gases in shafts and containers. If adequate ventilation is not possible, self-contained breathing apparatus must be worn. Particular care should be taken when straightening the flame and preheating it with gas burners in insufficiently ventilated confined spaces, as the flame consumes part of the breathing oxygen.

Environmental protection

When welding, people in the vicinity must also be protected from radiation and noise. There are also welding lamella and welding curtains as well as soundproof partition systems. In manual arc welding, particular attention must be paid to the electrical hazard to the welder. Although the arc voltage is below the - in general - hazardous range, a number of precautionary measures must be observed, especially when working with particular electrical hazards, e.g. when working in narrow, electrically conductive spaces (boilers, pipes, etc.), including: in the leaflet BGI 553 of the metal trade association.

Measures for laser welding

In laser welding, the laser beam itself is an additional source of danger. He is usually invisible. While radiation in the near infrared range (solid-state laser, fiber laser, diode laser) penetrates the skin and the eye and causes retinal damage even at low intensities (scattered radiation), the radiation from the CO 2 laser (medium infrared) is transmitted to the surface (skin and cornea of ​​the Eye) absorbs and causes superficial burns. Skin burns caused by near-infrared lasers are also dangerous because the radiation is absorbed in deep areas under the skin where there are no temperature-sensitive nerves. Laser welding devices are usually safely housed (locked safety doors, laser safety windows), they then fall under laser class I and can be safely operated without laser safety goggles.

clothing

The welder is protected against sprayed-off slag and weld metal particles by means of suitable clothing that must be resistant to hot particles, e.g. B. a leather apron, and which must not form folds in which these particles can settle.

## Associations

National and international cooperation in training, certification, standardization and technical-scientific development in the field of welding and joining technology is coordinated in Germany by DVS , in Europe by EWF and worldwide by IIW .

## literature

• Specialist group for welding engineering training: joining technology welding technology. 6., revised. Edition. DVS Verlag, Düsseldorf 2004, ISBN 3-87155-786-2 .
• U. Dilthey, A. Brandenburg: Welding manufacturing processes. Volume 3: Design and strength of welded structures. 2nd Edition. Springer Verlag, 2001, ISBN 3-540-62661-1 .
• H. Huegel: Laser beam tool. (= Teubner study books mechanical engineering). Stuttgart 1992, ISBN 3-519-06134-1 .
• U. Dilthey (Ed.): Laser beam welding - processes, materials, production, testing. DVS-Verlag, Düsseldorf 2000, ISBN 3-87155-906-7 .
• H. Schultz: Electron beam welding. (= Welding technology series of books. Volume 93). DVS-Verlag, Düsseldorf 2000, ISBN 3-87155-192-9 .
• K.-J. Matthes, E. Richter: Welding technology. Fachbuchverlag Leipzig in Carl Hanser Verlag, 2002, ISBN 3-446-40568-2 .

Commons : welding  - album with pictures, videos and audio files
Wiktionary: Welding  - explanations of meanings, word origins, synonyms, translations

## Individual evidence

1. DIN EN 14610: 2005-02 Welding and allied processes - Terms for metal welding processes.
2. DIN 1910-100: 2008-02: Welding and related processes - Terms - Part 100: Metal welding processes with supplements to DIN EN 14610: 2005.
3. a b c DIN EN ISO 4063: 2011-03 Welding and related processes - list of processes and serial numbers
4. Pressure welding process. Retrieved October 9, 2017 .
5. DIN EN ISO 6520-1: 2007-11 Welding and related processes - Classification of geometric irregularities in metallic materials - Part 1: Fusion welding , 2007.
6. DIN EN ISO 17659: 2005-09 Welding - Multilingual terms for welded joints with images
7. DIN EN ISO 6947: 2011-08 Welding and allied processes - welding positions
8. gas welding. In: Klaus-Jürgen Matthes, Erhardt Richter: Welding technology: Welding of metallic construction materials. Carl Hanser Verlag, 2008, ISBN 978-3-446-41422-8 , p. 290 ( limited preview in the Google book search).
9. Hans J. Fahrenwaldt, Volkmar Schuler: Practical knowledge of welding technology. Friedrich Vieweg & Sohn Verlag / DVS Verlag, 2007, ISBN 978-3-87155-970-9 , p. 42 (section: submerged arc welding. Limited preview in Google book search).
10. technolix.net ( Memento from January 15, 2008 in the Internet Archive ) (July 8, 2007)
11. Website of the RWTH Aachen, Institute for Welding and Joining Technology
12. Ulrich Dilthey: Welding Manufacturing Process 1: Welding and Cutting Technologies. Springer Verlag, 2006, ISBN 3-540-21673-1 (section: Metallschutzgasschweissen (MSG). Limited preview in the Google book search).
13. Gerd Witt among others: Pocket book of manufacturing technology. Carl Hanser Verlag, Munich 2006, ISBN 3-446-22540-4 ( limited preview in the Google book search).
14. Official website. soniKKs Ultrasonics Technology GmbH, accessed on December 3, 2013 .
15. a b c Basics and welding. Ultrasonics Steckmann GmbH, accessed on October 29, 2014 .
16. a b c d metal welding. Ultrasonics Steckmann GmbH, accessed on October 29, 2014 .
17. Christian Bonten: Product Development: Technology Management for Plastic Products. Carl Hanser-Verlag, Munich, ISBN 3-446-21696-0 ( limited preview in the Google book search).
18. dynaplat.de ( Memento of the original from November 10, 2013 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice.
19. Ralph Schäfer, Pablo Pasquale: The electromagnetic pulse technology in industrial use. (PDF; 949 kB).
20. Sheet metal welding really different. PSTproducts GmbH customer magazine (PDF; 4.09 MB).
21. DVS : Pressure welding with magnetically moving arc (MBP welding) DVS Merkblatt 2934, 2001.
22. Welding trainer systems - a "revolution" in joining technology training? In: DVS-Magazin 01/2012 pp. 5–8. (PDF; 1.6 MB)
23. Stéphane Itasse: Welding galvanized steel . Machine market. 11th August 2017.
24. Occupational safety welding: Manganese in welding fumes causes symptoms similar to Parkinson's. Retrieved April 21, 2020 .
25. Leibniz Institute for Prevention Research and Epidemiology: IARC intensifies risk assessment: welding fumes are carcinogenic in humans. Retrieved April 21, 2020 .
26. Technical rule for hazardous substances 528 (TRGS 528). Federal Institute for Occupational Safety and Health
27. IFA manual: Filter systems for separating welding fumes. Retrieved April 20, 2020 .
28. Institute for Occupational Safety and Health of the German Social Accident Insurance (IFA): Principles for the testing and certification of facilities for the collection and separation of welding fumes. Retrieved April 20, 2020 .
29. IFA manual: Welding fume extractors - positive list -. Retrieved April 20, 2020 .
30. Page no longer available , search in web archivesInfo: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice. Professional association for metal: Arc welder
 This version was added to the list of articles worth reading on December 19, 2005 .