Welding Wiki Welding technology by Fronius

AC balance

AC balance is a function on the welding system. It refers to the sine wave of the alternating current represented on a graph. The positive section of the curve is called the “cleaning half cycle”: opposite the parent material, the zone at the edge of the weld seam is cleaned. The “cooling half cycle” on the other hand, which describes the negative area of the curve, protects the tungsten electrode by preventing it from melting. The longer the cooling half cycle lasts, the better the penetration conditions are.

AC frequency

Function to change the frequency of the alternating current in AC TIG welding. This setting determines the number of cycles per second.

AC wave shape

In AC welding, different wave shapes can be selected: sine, rectangle, and triangle, as well as mixed waves. This changes the arc properties accordingly, which is reflected in the noise level, for example.

Additive manufacturing

Additive manufacturing processes are all based on the same basic principle: a component is created by joining volume elements on top of one another or together in layers (filler metal). The parent material, which can either be in powder form, a fluid, or also a solid material (wire), is hardened by introducing energy. Complex geometries and components can therefore be manufactured without the need for tools. Conventional production would otherwise not be possible or would be very costly.

Air gap

This is the technical term for the distance between two sheets.

Anode

By definition, an anode is the pole that receives electrons or the pole to which the electrons flow. For welding, this is therefore always the positive pole.

Arc

The arc burns during welding between the electrode and workpiece. Due to its high plasma temperatures, it fuses the parent material and melts away the filler metal.

Arc blow

The arc blow describes the irregular fluttering of the electric arc in an undesirable direction.

Arc break voltage

Refers to TIG welding torches without a torch trigger and stick electrodes: In both processes, the welding process is ended by lifting the welding torch or electrode off the workpiece. The required distance to the workpiece is defined in volts in advance by the arc break voltage.

Arc characteristic

The arc characteristic indicates the relationship between the arc voltage and the arc current.

Arc length

The arc length refers to the distance between the point where the arc touches the wire electrode until the point of reaching the workpiece. The voltage is a characteristic dimension for the arc length.

Cap-shaping mode

Cap-shaping mode is the function on the welding system that prepares the tungsten electrode for AC welding. Instead of the usual tip, the electrode is melted into a hemispherical cap.

Cathode

The cathode is the negative pole in the welding circuit.

Characteristic

The characteristic of a power source is a material and shielding gas dependent combination of current and voltage across the entire power range.

Cleaning effect

The cleaning effect in aluminum welding means the destruction of the aluminum oxide layer. This process is caused by the positive polarity of the tungsten electrode (during TIG welding).

Corrosion

Corrosion describes a reaction of a material with its environment, which causes a measurable change in the material and can impair the function of a component or system. In metals, chemical corrosion is particularly significant. The best-known type of chemical corrosion in metals is rust, that is, the oxidation of iron.

Cracks

Cracks are weld seam faults that occur under tensile stresses. The two main groups are cold and heat cracks.

Crater crack

Crater cracks occur when a crater is not filled before the welding arc goes out. This causes the outer edges of the crater to cool down faster than the crater. This creates stresses, which can result in longitudinal splits, or transverse or radial cracks.

Crater shrink hole

The crater shrink hole is a hemispherical opening at the end of a weld seam. It occurs when the end-crater is not properly filled.

Efficiency

The efficiency describes the relationship between the power input and power output. Examples include the electrical efficiency of a welding system or the thermal efficiency of the arc.

Electrical current

Electrical current is the directed movement of negatively charged charge carriers (electrons). The unit of measurement is an ampere (A). The formula symbol I describes the quantity of current that flows through a line within a given time period. In order for current to be able to flow, it requires an electrical voltage.

Electrical resistance

The electrical resistance indicates how much the electrons are slowed down while the electrical current is flowing. Its formula symbol is R and the unit of measurement is ohm (Ω).

Electrical voltage

The electrical potential difference is referred to as voltage and is between the positive and negative pole. The formula symbol for electrical voltage is U and the unit is volt (V).

Electrode holder

Secures the rod electrode during manual welding and allows the current to be transferred to the electrode.

End-crater

At the end of the welding process, the welding power is reduced rapidly. The weld pool cools down from the edge to the center. The molten mass that is still liquid has no strength to speak of and is distributed between the solidification fronts.
Result: A so-called end-crater forms in the middle.
Practical tip: At the end of the welding process, reduce the welding current slowly, move the welding torch back and forth or in a circle until the end-crater is completely filled.

EN ISO 1090

EN ISO 1090 is a European standard for structural steel and aluminum components, and affects all manufacturers, distributors, and suppliers. Since 07/01/2014, structural steel and aluminum constructions can only be brought onto the market in Europe if they comply with this series of standards and carry CE marking. Before CE marking, components were subject to self-monitoring by the manufacturer (factory production control), who then had to complete a declaration of performance for the guaranteed component properties.

Gas post-flow

Controls the time of gas flow after welding is completed. This prevents tarnishing and oxidation in the end crater area.

Gas pre-flow

The gas pre-flow is a way to obtain better shielding gas cover at the start of welding. A fixed period of time is defined here during which the gas solenoid valve should open before welding starts.

GMAW overlay welding

Gas metal arc overlay welding is used for cladding. A wear protection layer is applied over the base body using the MIG welding process. A characteristic of this is low penetration, low fusion, and a low ferrite content in the first weld layer.

Gouging

In gouging, the metal is melted with a special carbon electrode. The liquid material is purged by a stream of compressed air. Joins can be produced, defective weld seams removed, weld backups cut off, or very thick pieces of metal cut through. A special electrode holder is needed here with an integrated compressed air supply (see figure).

Grounding cable

The grounding cable is the current return cable in the welding circuit. It is secured to the component.

Grounding clamp

The grounding clamp is a quick-release mechanical connection between the workpiece and the current-return cable in the welding circuit.

Inner control

For the inner control, constant-voltage characteristics or slightly drooping characteristics are used. The result is that when the welding amperage is changed, the voltage barely changes or does not change at all. Inner control improves process stability, even if the distance between the welding torch and the workpiece changes.

Intermediate arc

The intermediate arc is characterized by a coarse droplet, short-circuited droplet transfer. The advantages include positional freedom and relatively deep penetration. In contrast, however, is the increased spattering.

Interval mode

In interval mode, both the arc time and pause time can be set.

Inverter

Inverting means transforming. This concerns converting DC into AC current and vice versa. In the case of the inverter power source, the transformer is driven by a very high frequency, whereby the volume of the transformer can be kept extremely low. This reduces the weight and the power source is mobile. In addition to direct current, inverters can also generate sinusoidal and square wave alternating current for special requirements.

IP rating

The abbreviation IP stands for International Protection and is also called protection class. It defines the protection of electrical equipment against the penetration of foreign objects and water, and their impact resistance.

Lack of fusion

Lack of fusion occurs if there is no secure join between the weld metal and the parent material, or in multirun welding.

Lines of force

Components that are mainly subject to dynamic loads need homogeneous weld seam transitions (line of force progressions) to avoid a notch effect.

Lowering/intermediate current

Temporary higher/lower welding current by means of a controlled change on the torch button to the set value.

Open circuit voltage

This is the voltage that is applied to the welding sockets prior to welding, for example from the ignition of the rod electrode.

Operating point

The operating point is the intersection between the power source characteristics and the physical arc characteristics.

Outgassing

Outgassing refers to the escape of gases from liquid or solid material during the welding process.

Oxide film

Aluminum forms a protective layer that is called an oxide film. The oxide film has a destructive effect during welding and must be broken up. This is done during TIG welding with alternating current (AC). The melting point of the oxide film is approximately 2100°C, in contrast to aluminum that has a melting point of approximately 660°C depending on the alloy.

Oxide formation

Surface scaling is called oxide formation. This occurs especially during the manufacturing of steel or slightly in the case of poor shielding gas cover.

Reversed polarity ignition (RPI)

A reversed polarity ignition is a polarity reversal of the tungsten electrode to the positive pole in the ignition phase, in order to achieve a more accurate and stable ignition.

R/L alignment

R stands for resistance in mΩ (milliohms), L for inductivity in µH (microhenrys). Aligning the welding circuit resistance and the welding circuit inductivity is a function on the welding system. This compensates for losses with long hosepacks or grounding cables. It enables consistent, optimal welding results to be achieved.

Root pass

The root pass refers to the first bead that is introduced into the join during multirun welding. Fronius offers special characteristics with the ROOT characteristic for this purpose.

Run-in and run-off plates

These are metal pieces that are attached directly to the workpiece before the start of the weld seam and at the end of the weld seam. This ensures full penetration is achieved from the start of the weld seam to the end, without resulting in restarts of welds and end-craters.

TAC

During tacking with TAC, a TIG pulsed arc causes the liquid weld pool to begin moving. This leads to accelerated merging of the elements and therefore to a shorter tacking process.

Tacking

Tacking refers to the joining of the components prior to the actual welding process.

Tandem welding

In tandem welding, two completely isolated wire electrodes are melted in a welding torch and a common weld pool. The process allows a particularly high deposition rate, which can be converted to welding speed or volume filling. This welding process is known at Fronius under the brand name TWIN.

Temper colors

Temper colors are superficial, bright colorings on metals, generally caused by thermal heat input and oxidation. These can be avoided by using various forming and shielding gases.

Thermal conductivity

Thermal conductivity is a material value that describes how well a material conducts heat. Materials with high thermal conductivity are difficult to weld and need a special welding start treatment (e.g., aluminum) or require a high preheating temperature (e.g., copper).

Thermal joining processes

Thermal joining processes refer to the connecting of materials by introducing heat and/or using force. They include press welding and fusion welding.

TIG AC

This is TIG welding using alternating current, whereby the polarity of the electrode changes quickly between positive and negative. It is mainly used in aluminum welding.

TIG Comfort Stop

Stopping the welding process without a torch trigger by briefly lifting and lowering the electrode.

TIG contact ignition

With conventional TIG contact ignition, the tungsten electrode is lifted off the workpiece. The preset welding start sequence then takes place.

TIG DC

TIG welding with direct current, where the polarity of the electrode is negative throughout the entire welding process. In exceptional cases, DC plus can also be used.

TIG overlay welding

Tungsten inert gas overlay welding is universally applicable and is ideal for surfacing high-alloy metals and steels. The welding process provides high-quality surfaces that are clean and exact, with little spatter.

TIG touchless ignition (HF ignition)

In TIG welding, the arc can be ignited touchlessly. Here a high-voltage source is used that is temporarily connected with high frequency and low power.

TIME process

TIME stands for Transferred Ionized Molten Energy. The TIME welding process is synonymous with MAG high performance welding with a wire.

Time Twin

With Time Twin, two digital power sources that can be controlled separately work in a single gas nozzle and in a common weld pool. Both wire electrodes are completely isolated. This shortens cycle times and increases weld quality and cost effectiveness in high-performance welding.

Tolerance

This is the technical term for the gap between two sheets in the longitudinal direction and/or the height of the plates.

Torch to workpiece distance

The torch to workpiece distance is the distance between the gas nozzle and workpiece. To achieve optimum results, the correct distance must be chosen and remain constant during welding.

Torch trigger logic

Two alternative operating modes can be set: 2-step and 4-step (the difference is the way the torch trigger works). Choosing between these two step modes allows the welder to decide whether they want to hold down the torch trigger permanently or only do so to start and stop welding. In 2-step mode, the torch trigger is held down during welding and released to end it. In 4-step mode, the trigger is pressed and released again (the same action is repeated to end welding). This makes torch guidance/handling more relaxed for the welder, which has a positive effect, especially when longer weld seams are involved.

TouchHF

Ignition via high-voltage pulses triggered by touching the workpiece.

Tungsten inclusions

If the tungsten electrode touches the weld pool during TIG welding, particles of the electrode can get into the molten mass and cause welding faults or tungsten inclusions.

Types of radiation in the electric arc

The electric arc emits visible radiation, invisible infrared or heat radiation, and invisible ultraviolet radiation.

VRD - Voltage Reduction Device

On MMA devices, there is a relatively high open circuit voltage at the sockets for igniting the electrode. To increase safety for the user the open circuit voltage is limited to 12 V by the VRD (Voltage Reduction Device) option. The welding system identifies whether welding is taking place or not by measuring the welding circuit resistance. If the welding circuit resistance is greater than 200 ohms, the welding system assumes that no welding is taking place (open welding circuit) and reduces the open circuit voltage to 12 V for safety reasons. If, however, the welding circuit resistance drops below 200 ohms (i.e., closed welding circuit), the welding system assumes that welding is to take place (electrode makes contact with the workpiece, and the welding circuit resistance of course drops). Detection takes the welding system just 0.3 seconds.