Glossary

A

• Alternating current, power source (AC) – the output current from the power source takes the form of a sine wave, which changes polarity at regular intervals, with a frequency of 50 or 60 cycles per second (Hertz).
• Anti stick [MMA] – a device that automatically switches off the welding power source if the electrode sticks to the material being welded, so that it can be removed manually.
• Arc force [MMA] – a device that facilitates the transfer of drops of melted material from the electrode to the material being welded, thus preventing the arc from extinguishing when the drops make a contact between the electrode and the weld pool.

C

• Chopper, power source – constructive technology, typified by specific electronic circuits, that is able to make considerable improvements to power source performance compared to conventional models.
• Coated electrode [MMA] – a metal rod consisting of a core (the purpose of which is to conduct the current and supply the welding material that will fill the joint), and a coating (the primary purpose of which is to protect the weld pool and stabilise the electric arc).
• Current, adjustment field – the indication of the minimum and maximum current that a power source is able to supply.

D

• Direct current, power source (DC) – the output current from the power source takes the form of a continuous wave, which is obtained by a rectifier device, situated downstream of the transformer, that is able to convert alternating current to direct current. This output is typical of 3-phase conventional electromechanical, SCR electronic and inverter power sources.
• Duty Cycle – power source usage time, expressed as a percentage, without causing excessive overheating or general interruptions due to activation of the thermostatic protection devices (e.g. 170 A @ 40 % - periods of 4 minutes' work and 6 minutes' pause).

E

• Electric arc – this is the zone, when welding, delimited by the tip of the electrode and the material being welded, through which the current flows to create the heat that melts the welding material and the base material.

F

• Flux core [MIG-MAG] – welding material for wire welding with inert or active gas bottle (also called GAS welding); the material usually has the same composition as the base material.
• FLUX – welding process in which the heat required to make the weld is supplied by an electric arc that is maintained between the piece being welded and the wire-electrode. The welding zone is constantly fed, by means of a special torch, by a wire electrode whose core is filled with granular powder (flux) that has the same function as the coating on coated electrodes. The main features are the absence of the gas bottle in the welding circuit together with the use of tubular wire-electrodes.

H

• HF strike [TIG] - an electric arc-striking method. The pilot spark is supplied by a high frequency power source that superimposes a high voltage impulse on the welding voltage. The HF strike requires the use of a welding torch equipped with a button able to control its activation.
• Hot start – a device that aids electric arc strike by supplying an overcurrent whenever welding restarts.

I

• Inverter, power source - constructive technology, characterised by specific electronic circuits and allowing considerable size and weight reductions in the power sources, hence increasing their performance.

L

• LIFT strike [TIG] – an electric arc-striking method. This is obtained by means of a special device that supplies a low current so as not to damage the tip of the tungsten electrode when it is in contact with the material being welded. At the instant when the electrode is moved away from the piece, a spark is created causing the arc to strike; the power source then increases the welding current until it reaches the preset value. Since high frequencies are not present, LIFT start has the property of not creating electromagnetic interference.

M

• Mains fuse – a device that is used to cut off the mains power supply if excessive power absorption occurs.
• Microprocessor – small sized electronic device, which can be programmed to carry out a numerous functions; it is inserted into high performance products.
• MIG-MAG (GMAW) – welding process in which the heat required to make the weld is supplied by an electric arc that is maintained between the piece to be welded and the wire-electrode. The welding zone is constantly fed with welding material (the wire electrode) by a special torch which is also able to supply the gas flow (or gas mixture). The purpose of the gas is to protect the wire-electrode, the weld pool, the arc and the surrounding area of base material from atmospheric contamination. The distinctive features are the presence of the gas bottle (inert or active gas or a mixture) together with the use of flux core wire-electrodes.
• MMA (SMAW) – welding process in which the heat source consists of the electric arc which strikes between the coated electrode and the piece being welded (base material), developing the heat that causes rapid melting of both the base material and the electrode (welding material).

O

• Open circuit voltage – this is the voltage, expressed in Volts, measured at the power source power outlets when the circuit is open i.e. there is no current circulation.

P

• Pilot arc strike [TIG] – an electric arc-striking method. The arc is struck between the tungsten electrode and an auxiliary electrode. The pilot arc is struck by a high frequency spark which is subsequently disconnected. It is mostly used in automatic systems.
• Pulsed arc, transfer [MIG-MAG] – obtainable with pulsed current power sources, where the pulses cause small-sized drops to detach and thus achieving the characteristic spray arc, even with low currents. This procedure is used extensively for materials such as aluminium and stainless steel.
• Pulsed current, power source – direct current power sources equipped with special devices that are used to change welding current amplitude. They give excellent results when welding thin materials.

S

• Scratch strike [TIG] – an electric arc-striking method, which is achieved by scratching the tungsten electrode along the piece to be welded. Because of the contact between the electrode and the piece, the start of the seam will contain tungsten inclusions.
• Short arc, transfer [MIG-MAG] – the welding material is transferred to the weld pool in the form of drops that are submersed in the pool itself, creating continual short circuits. It is obtained by direct current power sources and makes it possible to weld thin pieces and in all positions.
• Single-phase power supply voltage – this is typical of the domestic distribution network, where an apparatus is connected to the power supply using 2-pin or 2-pin + earth connectors.
• Synergic, power source [MIG-MAG] – welding parameter adjustment is achieved using at most only two control knobs. In fact, the manufacturer stores the optimal welding parameter values in the power source and these can be recalled and/or corrected by the operator, depending on the requirements of the work on hand.
• Spray arc, transfer [MIG-MAG] – The high current being used causes drops of welding material to be sprayed into the pool, creating a continuous flow of material. An extremely fluid weld pool is generated, with considerable penetration. This is primarily suitable for horizontal welding on medium and thick materials.

T

• TIG (GTAW) – welding process in which the heat required to make the weld is supplied by and electric arc that is maintained between a non-consumable electrode and the piece being welded; a tungsten or tungsten alloy electrode is used. The welding zone, the melted metal and the non-consumable electrode are protected from atmospheric agent contamination by inert gas that is supplied by the electrode-holder torch.
• Tubular wire [FLUX] – welding material for wire welding without a gas bottle (also called NO GAS welding). The inner core of the wire is filled with granular powder (flux) with the same purpose as the coating on electrodes used for MMA welding.
• Three- phase power supply voltage – this is typical of the industrial distribution network, where an apparatus is connected to the power supply using 3-pin + earth or 3-pin + earth + neutral connectors.