Los parámetros variables de soldadura son los factores que pueden ser ajustados para controlar una soldadura.

Para obtener los mejores resultados en el proceso, es necesario conocer el efecto de cada variable sobre las diversas características o propiedades del proceso de soldadura. Algunas de estas variables, a las que se denominan variables preseleccionadas, son:.

Por otra parte también hay que definir otras variables denominadas variables primarias que son las que controlan el proceso después que las variables preseleccionadas son seleccionadas. Estas controlan la estabilidad del arco, el régimen de soldadura y la calidad de la misma:.

Otras variables a tener en cuenta son las denominadas variables secundarias, que pueden ser modificadas de manera continua. Son a veces difíciles de medir con precisión y especialmente en soldadura automática. Estas no afectan directamente la forma del cordón, pero actúan sobre una variable primaria que a su vez influye en el mismo. Estas variables son:.

Los parámetros regulables que podemos considerar como más importantes y que más afectan a la soldadura son:.

Polarity

The most normal thing is that today's machines work with reverse or positive polarity (the piece to the negative and the welding wire to the positive). In cases where a higher temperature is required in the piece than in the wire, direct or negative polarity is used, since the electrons always go from the negative to the positive pole, producing a greater increase in temperature in the latter.

Arc voltage

This parameter is one of the most important when transferring the material provided to the part. It can be adjusted in most machines by the operator and allows the tension applied to the arc to be increased or decreased, but it will not always modify the work intensity.

Thread speed

In this type of welding, it is not the intensity that is previously regulated, but rather the variation in wire speed that causes the appearance of different intensities thanks to the self-regulation phenomenon.

Nature of the gas

The type of gas used for welding influences material transfer, penetration, bead shape, projections, etc.

En la soldadura MIG/MAG podemos encontrar tres tipos de transferencia del metal aportado, los cuales dependen directamente de la tensión e intensidad con los que se trabaje.

Short circuit transfer

In this type of transfer, the most used by the MAG application, the supplied material melts in droplets between 50 and 200 times per second when the tip of the electrode touches the molten weld metal and makes a short circuit. Low currents and voltages are used, the gases are rich in carbon dioxide and the electrodes are made of small diameter wire. Due to its low heat input characteristics, the method produces small zones of rapidly cooling molten solder, making it ideal for welding in all positions. Short circuit transfer is also especially adaptable to welding sheet metal with minimal distortion and for filling voids or tighter fitting parts with less tendency to overheat the part being welded.

With this type of transfer, small thickness pieces are welded since the applied tension is low compared to other types.

globular transfer

It is frequently used in MAG application and sometimes in MIG. When working with this transfer, the thread melts into thick drops that can reach all the gaps. The metal is transferred in large droplets and occurs by gravity when their weight exceeds the surface tension. Gases rich in carbon dioxide and argon are used, and also produces high currents that allow greater weld penetration and higher speeds than those achieved with short circuit and spray transfers. Also, a lot of splashes are produced and therefore it is not advisable to weld overhead (tubular), and it is advisable to perform it in a horizontal position. Heavier pieces are usually joined using this method.

This type of transfer is not used in any work, but can be seen in machine set-up operations.

Spray arc transfer

It is the classic method used in MIG application. The filler metal is transported at high speed in very fine particles through the arc, between 500 and 2000 times per second. The electromagnetic force is high, allowing the droplets to be atomized from the tip of the electrode in a linear manner towards the welding area. It can be welded at high temperatures. Additionally, it is necessary to use direct current and a positive electrode to guarantee that the drops form and are released at a rate of hundreds per second. The shielding gas is argon or an argon-rich mixture.

This type is recommended for welding thick pieces thanks to its great penetration into the material.

welding wires

The most common diameters in this type of welding are 0.8; 1.0; 1,2; 1.6 and in some cases 2.4 mm. Choosing one of these diameters when working is very important since for large diameters, high intensities are used and large penetrations are produced, possibly causing perforations in the pieces. On the other hand, for small diameters, low intensities are applied and low penetrations are achieved, and it may occur that the penetration into the piece is too small.

The standard format of the thread is spools of different sizes. The wires are usually covered with copper so that the conductivity of the wire with the contact tube is good, in addition to reducing friction and so that oxidation does not appear.

Shielding gases

In the MIG (Metal Inert Gas) variant, the shielding gas is inert (it does not act actively in the welding process) and is very stable. On the other hand, in MAG (Metal Active Gas) welding, the protection gas behaves inertly in the contamination of the weld but on the other hand intervenes thermodynamically in it.

Among the inert gases available in Europe, the most used is argon, and in the United States it is helium that is most used.

High purity argon is only used in welding titanium, aluminum, copper and nickel. For steel welding, it must be applied with quantities less than 5% mixed with oxygen since pure argon produces irregular bites and beads. This improves the penetration and widening of the lower part of the cord.

The use of helium produces wider beads and shallower penetration than that produced by argon.

Although there are tables with intensity values ​​for each thickness of iron to be welded, the practice of the experienced welder is the most commonly used way to proceed.

Carbon dioxide (CO2) is one of the gases used in this type of welding. It is an odorless, colorless gas with a pungent taste. It has a weight one and a half times greater than air, and it is an oxidizing gas that at high temperatures dissociates in a reaction in the arc of 2CO2-2CO2+O, absorbing heat and in the re-composition in the base 2CO2+O, giving up heat.

Its drawbacks are that it produces very energetic arcs, which also produces a large number of projections.

On the other hand, it is a much cheaper gas than argon, capable of producing much deeper and wider penetrations than argon. It also has the advantage of reducing the risk of bites and lack of fusion.

The mixture of carbon dioxide and argon is usually used with parts between 15% and 25% CO2. The gains from working with this mixture are better visibility of the bath, a smoother arc, with less turbulence, a colder melt pool, a better appearance and presentation of the bead, fewer projections and better arc stability. Its biggest drawback is economic.

Las máquinas del tipo estándar están formadas por diferentes elementos para poder llevar a cabo la soldadura MIG/MAG.

Transformer

It is the source of electrical power that is responsible for supplying enough energy to melt the electrode into the workpiece. They are direct current with constant voltage (CV) output.

Its function is to reduce the alternating voltage of the consumer network to another suitable for welding.

Mainly, a transformer is made up of a core made up of stacked magnetic sheets in whose columns two coils are wound. In the first of them it consists of the primary circuit formed by a number of turns greater than the second and with a section smaller than this. In the second, the secondary circuit is formed, thus formed with a smaller number of turns and a larger section.

Rectifier

This element converts alternating current into direct current, which is very necessary to be able to perform MIG/MAG welding.

The rectifier is made up of power semiconductors (silicon diodes), normally placed on fins in order to increase their cooling.

Inductance

The mission of the inductance is the isolation of the welding current, which produces greater welding stability. If the machine is equipped with an inductance with a high inductive value, it will also be equipped with a system that eliminates this effect during arc striking, since if the arc is struck with a high inductance, the arc will not be produced.

This element is formed by a core in which some turns are wound through which the direct welding current circulates.

Wire feeder unit

This unit advances the wire necessary to carry out the welding at a constant speed using a motor, generally direct current.

The speed can be regulated between values ​​ranging from 0 to 25 m/min. This regulation can normally be achieved through an electrical control that acts on a feed motor.

The drive system consists of one or two drive rollers that work against other pressure rollers. The pressure roller must be adjusted correctly, since excessive pressure can cause crushing of the thread, causing it to not slide well. On the contrary, when there is not enough pressure on the wire, feeding at irregular speeds can occur.

Shielding gas circuit

The bottle outlet is equipped with a pressure reducer-flow meter that allows regulation by the operator to provide the necessary flow rate for welding. The passage of gas towards the welding is produced by an electrically activated valve using a button equipped on the torch.

As a standard rule, a flow rate in l/m ten times greater than the diameter of the wire should be used.

welding torch

Through this element the wire is guided, the electric current is activated and the protective gas is activated in the welding arc area.

All the ducts are covered by a rubber tube and the entire assembly forms the hose that connects the machine to the gun. An external nozzle is mounted at the tip of the torch that channels the gas to the welding area. Inside there is a contact tube that provides the wire with the necessary current to make the welding arc. This contact tube has its inner hole calibrated for each wire diameter.

The distance between the tip of the contact tube and the arc is controlled by the operator, but the length of the arc is automatically controlled by the parameters set on the machine.

gear factor

Welding equipment is designed to work at a nominal intensity continuously. Las máquinas al cabo de un tiempo de trabajo tienen que estabilizar la temperatura de sus componentes a la intensidad nominal de trabajo, pero en la soldadura MIG/MAG estándar no es posible trabajar de forma continua, ya que existen tiempos de preparación, cambios de hilo, de botellas de gas, de descansos del operario, etc. A causa de no poder trabajar de forma continua, las temperaturas disminuyen gracias a los espacios de tiempo que no se está trabajando, por lo que se hace necesario hablar del factor de marcha.

The duty factor is the ratio between the welding time and the total working time. During welding stops, the equipment components cool down, stabilizing their temperature in a small range of values, lower than their maximum working temperature.

To determine the intensity for a given gear factor, the following expression is used:.

Los parámetros variables de soldadura son los factores que pueden ser ajustados para controlar una soldadura.

Para obtener los mejores resultados en el proceso, es necesario conocer el efecto de cada variable sobre las diversas características o propiedades del proceso de soldadura. Algunas de estas variables, a las que se denominan variables preseleccionadas, son:.

Por otra parte también hay que definir otras variables denominadas variables primarias que son las que controlan el proceso después que las variables preseleccionadas son seleccionadas. Estas controlan la estabilidad del arco, el régimen de soldadura y la calidad de la misma:.

Otras variables a tener en cuenta son las denominadas variables secundarias, que pueden ser modificadas de manera continua. Son a veces difíciles de medir con precisión y especialmente en soldadura automática. Estas no afectan directamente la forma del cordón, pero actúan sobre una variable primaria que a su vez influye en el mismo. Estas variables son:.

Los parámetros regulables que podemos considerar como más importantes y que más afectan a la soldadura son:.

Polarity

The most normal thing is that today's machines work with reverse or positive polarity (the piece to the negative and the welding wire to the positive). In cases where a higher temperature is required in the piece than in the wire, direct or negative polarity is used, since the electrons always go from the negative to the positive pole, producing a greater increase in temperature in the latter.

Arc voltage

This parameter is one of the most important when transferring the material provided to the part. It can be adjusted in most machines by the operator and allows the tension applied to the arc to be increased or decreased, but it will not always modify the work intensity.

Thread speed

In this type of welding, it is not the intensity that is previously regulated, but rather the variation in wire speed that causes the appearance of different intensities thanks to the self-regulation phenomenon.

Nature of the gas

The type of gas used for welding influences material transfer, penetration, bead shape, projections, etc.

En la soldadura MIG/MAG podemos encontrar tres tipos de transferencia del metal aportado, los cuales dependen directamente de la tensión e intensidad con los que se trabaje.

Short circuit transfer

In this type of transfer, the most used by the MAG application, the supplied material melts in droplets between 50 and 200 times per second when the tip of the electrode touches the molten weld metal and makes a short circuit. Low currents and voltages are used, the gases are rich in carbon dioxide and the electrodes are made of small diameter wire. Due to its low heat input characteristics, the method produces small zones of rapidly cooling molten solder, making it ideal for welding in all positions. Short circuit transfer is also especially adaptable to welding sheet metal with minimal distortion and for filling voids or tighter fitting parts with less tendency to overheat the part being welded.

With this type of transfer, small thickness pieces are welded since the applied tension is low compared to other types.

globular transfer

It is frequently used in MAG application and sometimes in MIG. When working with this transfer, the thread melts into thick drops that can reach all the gaps. The metal is transferred in large droplets and occurs by gravity when their weight exceeds the surface tension. Gases rich in carbon dioxide and argon are used, and also produces high currents that allow greater weld penetration and higher speeds than those achieved with short circuit and spray transfers. Also, a lot of splashes are produced and therefore it is not advisable to weld overhead (tubular), and it is advisable to perform it in a horizontal position. Heavier pieces are usually joined using this method.

This type of transfer is not used in any work, but can be seen in machine set-up operations.

Spray arc transfer

It is the classic method used in MIG application. The filler metal is transported at high speed in very fine particles through the arc, between 500 and 2000 times per second. The electromagnetic force is high, allowing the droplets to be atomized from the tip of the electrode in a linear manner towards the welding area. It can be welded at high temperatures. Additionally, it is necessary to use direct current and a positive electrode to guarantee that the drops form and are released at a rate of hundreds per second. The shielding gas is argon or an argon-rich mixture.

This type is recommended for welding thick pieces thanks to its great penetration into the material.

welding wires

The most common diameters in this type of welding are 0.8; 1.0; 1,2; 1.6 and in some cases 2.4 mm. Choosing one of these diameters when working is very important since for large diameters, high intensities are used and large penetrations are produced, possibly causing perforations in the pieces. On the other hand, for small diameters, low intensities are applied and low penetrations are achieved, and it may occur that the penetration into the piece is too small.

The standard format of the thread is spools of different sizes. The wires are usually covered with copper so that the conductivity of the wire with the contact tube is good, in addition to reducing friction and so that oxidation does not appear.

Shielding gases

In the MIG (Metal Inert Gas) variant, the shielding gas is inert (it does not act actively in the welding process) and is very stable. On the other hand, in MAG (Metal Active Gas) welding, the protection gas behaves inertly in the contamination of the weld but on the other hand intervenes thermodynamically in it.

Among the inert gases available in Europe, the most used is argon, and in the United States it is helium that is most used.

High purity argon is only used in welding titanium, aluminum, copper and nickel. For steel welding, it must be applied with quantities less than 5% mixed with oxygen since pure argon produces irregular bites and beads. This improves the penetration and widening of the lower part of the cord.

The use of helium produces wider beads and shallower penetration than that produced by argon.

Although there are tables with intensity values ​​for each thickness of iron to be welded, the practice of the experienced welder is the most commonly used way to proceed.

Carbon dioxide (CO2) is one of the gases used in this type of welding. It is an odorless, colorless gas with a pungent taste. It has a weight one and a half times greater than air, and it is an oxidizing gas that at high temperatures dissociates in a reaction in the arc of 2CO2-2CO2+O, absorbing heat and in the re-composition in the base 2CO2+O, giving up heat.

Its drawbacks are that it produces very energetic arcs, which also produces a large number of projections.

On the other hand, it is a much cheaper gas than argon, capable of producing much deeper and wider penetrations than argon. It also has the advantage of reducing the risk of bites and lack of fusion.

The mixture of carbon dioxide and argon is usually used with parts between 15% and 25% CO2. The gains from working with this mixture are better visibility of the bath, a smoother arc, with less turbulence, a colder melt pool, a better appearance and presentation of the bead, fewer projections and better arc stability. Its biggest drawback is economic.

Las máquinas del tipo estándar están formadas por diferentes elementos para poder llevar a cabo la soldadura MIG/MAG.

Transformer

It is the source of electrical power that is responsible for supplying enough energy to melt the electrode into the workpiece. They are direct current with constant voltage (CV) output.

Its function is to reduce the alternating voltage of the consumer network to another suitable for welding.

Mainly, a transformer is made up of a core made up of stacked magnetic sheets in whose columns two coils are wound. In the first of them it consists of the primary circuit formed by a number of turns greater than the second and with a section smaller than this. In the second, the secondary circuit is formed, thus formed with a smaller number of turns and a larger section.

Rectifier

This element converts alternating current into direct current, which is very necessary to be able to perform MIG/MAG welding.

The rectifier is made up of power semiconductors (silicon diodes), normally placed on fins in order to increase their cooling.

Inductance

The mission of the inductance is the isolation of the welding current, which produces greater welding stability. If the machine is equipped with an inductance with a high inductive value, it will also be equipped with a system that eliminates this effect during arc striking, since if the arc is struck with a high inductance, the arc will not be produced.

This element is formed by a core in which some turns are wound through which the direct welding current circulates.

Wire feeder unit

This unit advances the wire necessary to carry out the welding at a constant speed using a motor, generally direct current.

The speed can be regulated between values ​​ranging from 0 to 25 m/min. This regulation can normally be achieved through an electrical control that acts on a feed motor.

The drive system consists of one or two drive rollers that work against other pressure rollers. The pressure roller must be adjusted correctly, since excessive pressure can cause crushing of the thread, causing it to not slide well. On the contrary, when there is not enough pressure on the wire, feeding at irregular speeds can occur.

Shielding gas circuit

The bottle outlet is equipped with a pressure reducer-flow meter that allows regulation by the operator to provide the necessary flow rate for welding. The passage of gas towards the welding is produced by an electrically activated valve using a button equipped on the torch.

As a standard rule, a flow rate in l/m ten times greater than the diameter of the wire should be used.

welding torch

Through this element the wire is guided, the electric current is activated and the protective gas is activated in the welding arc area.

All the ducts are covered by a rubber tube and the entire assembly forms the hose that connects the machine to the gun. An external nozzle is mounted at the tip of the torch that channels the gas to the welding area. Inside there is a contact tube that provides the wire with the necessary current to make the welding arc. This contact tube has its inner hole calibrated for each wire diameter.

The distance between the tip of the contact tube and the arc is controlled by the operator, but the length of the arc is automatically controlled by the parameters set on the machine.

gear factor

Welding equipment is designed to work at a nominal intensity continuously. Las máquinas al cabo de un tiempo de trabajo tienen que estabilizar la temperatura de sus componentes a la intensidad nominal de trabajo, pero en la soldadura MIG/MAG estándar no es posible trabajar de forma continua, ya que existen tiempos de preparación, cambios de hilo, de botellas de gas, de descansos del operario, etc. A causa de no poder trabajar de forma continua, las temperaturas disminuyen gracias a los espacios de tiempo que no se está trabajando, por lo que se hace necesario hablar del factor de marcha.

The duty factor is the ratio between the welding time and the total working time. During welding stops, the equipment components cool down, stabilizing their temperature in a small range of values, lower than their maximum working temperature.

To determine the intensity for a given gear factor, the following expression is used:.