How to choose the right welding current

How to correctly set the welding current?

Welding current is the main parameter of electric arc welding. The quality of the connection and its service life depend on it. Electric current is adjustable over a wide range. Its value is established based on the characteristics and properties of the base metal.

Basic Concepts

The unit of measurement for electrical current is ampere. According to its properties it happens:

1. Constant . In this case, the energy does not change its parameters. Direct welding current is used in semiconductor inverters and welding rectifiers.
2. Variable . Characterized by a constant change in the direction of electron movement. This type is used in the power supply of apartment buildings and private houses. The principle of using variable energy is implemented in step-down welding transformers, the primary winding of which is connected to a 220 or 380 V network.

The principle of operation of a transformer.

In addition to the type of welding current, the quality of the future connection is affected by the following parameters:

• Thickness of welded elements.
• The type of metal or alloy to be worked with.
• Parameters and cross-sectional area of ​​the electrode element.
• Welding equipment used and current value.

The last point should be discussed in more detail. The relationship between current strength and amount of heat is direct . The higher the first indicator, the more heat is released when an electric arc burns; accordingly, the base surface heats up faster, increasing productivity.

Based on this, the higher the thickness of the workpiece, the stronger the current must be for complete penetration of the metal.

How does an experienced welder choose?

Correct selection of operating parameters depends on the qualifications of the specialist. Special welder tables have been developed for beginners . They indicate all the necessary operating parameters. The reference point is the diameter of the electrode.

An experienced welder does not wonder how to select the current for welding with an inverter or other machine. Let's consider based on what indicators we can select optimal welding indicators.

During the joining of parts, specific chemical and physical processes occur, which are accompanied by characteristic sound and visual effects. These include:

• Stability and intensity of electric arc combustion.
• The size of the melt zone.
• Metal fluidity.
• Crystallization rate.
• Seam shape.

By analyzing the combination of the above factors, a specialist can correctly select, and, if necessary, adjust welding parameters during work.

An important indicator is the size of the cross-section of the filler material , the features of the choice of which will be discussed below.

Dependence on electrode thickness

Technical documentation and training manuals contain tables that allow you to select the optimal type and cross-sectional area of ​​the electrode, depending on the properties of the material being welded.

So, how do you choose the diameter of the electrode depending on the thickness of the metal? Before addressing this issue, it is necessary to study the changes that the surface and filler material undergo with increasing energy. First of all, as the current increases, the thermal effect increases, which accelerates the melting processes of the electrodes and the plane. For example, the optimal current for a 3 mm electrode will be 65-100 A, depending on the type of base metal.

As an example, see the table for selecting the diameter of the electrode for welding.

The process of seam formation depends on the density. Using a large diameter rod, the density will decrease, while the number of amps involved remains the same. Thus, the thickness of the electrode must be increased depending on the change in the thickness of the metal.

Practical definition

A qualified specialist will easily select the optimal connection mode, regardless of the welding mode, MMA or MIG. Beginners often have to turn to reference books.

Manufacturers of welding equipment and consumables provide their products with operating instructions containing recommendations for choosing a mode . Such information should be considered priority.

When working at production sites, there is no opportunity to study technical literature. To select parameters, simple formulas have been developed that allow you to select indicators in a matter of seconds.

Location and nature of the seam

The influence of electrode speed on the type of seam.

In addition to the characteristics of the welding arc, the following parameters influence the shape and quality of the future weld:

1. Preliminary surface preparation, namely edge preparation.
2. Electrode movement speed.
3. Seam type. It can be one- or two-sided.
4. Welding angle of elements.

The horizontal welding method is considered the most comfortable . It allows you to immediately set the optimal parameters of the device, which cannot be said about vertical or ceiling seams.

This is due to the fact that the molten metal, being in a horizontal plane, will not spread. You can immediately start working at high parameters, which will allow you to heat up the metal faster, increasing the connection speed.

Due to the complexity of the location, welding ceiling seams is considered the most difficult job . The work is carried out only at low parameters, which does not always allow for deep heating of the workpiece. Otherwise, the molten metal will quickly drain from the surface under the influence of gravity.

Only qualified welders who are able to control the degree of heating of the parts are allowed to work with ceiling connections. In some cases, an alternative method of working with a ceiling seam is used - instead of reducing the current, they increase the speed of the electrode. As a result, the metal does not have time to acquire strong fluidity, and the speed of work increases.

When chamfering a surface, experienced specialists recommend slightly reducing the current parameters, since the shape of the prepared part provides deeper penetration without increasing the power of the electric arc. At the same time, the speed of movement of the filler material must be increased in order to avoid burn-through of the products.

How does the welding current change as the arc length increases?

An electric arc is a welder’s working tool, regardless of the work parameters and power source . Combustion is accompanied by the release of a large amount of heat, which acts on the base surface and filler material, creating a melt zone. The following types of work are performed using an arc:

1. Manual arc welding. The discharge acts directly on the surface, melting the metal and electrode. When the state of aggregation changes, the flux coating releases gases that protect the melt zone from contact with the atmosphere.
2. Semi-automatic. In this case, an electrode made of a refractory material is used. The filler material is the wire fed to the arc. The melt zone is protected by inert gases.
3. Automatic. Used in large industrial enterprises. Based on the name, work on such installations does not require a large number of maintenance personnel. Despite the fact that work can be carried out simultaneously at several positions, one operator is sufficient for control.

The intensity of surface heating and other quality indicators depend on the arc parameters. Its formation is influenced by the cross-sectional diameter of the electrode - the larger it is, the thicker the electric arc will be. The properties of the seam are influenced not only by the thickness, but also by the length of the arc. Let's consider how the value of the welding current changes with increasing arc length.

The increase in arc is caused by a change in the distance between the tip of the rod and the surface to be welded . The electrical discharge begins to lengthen, losing its density. In this case, the temperature effect on the workpiece is reduced.

Upon reaching the critical point, the discharge will lose its stability and go out. The maximum possible distance between points depends on the welding parameters.

How to choose the right one on the inverter?

The inverter is a product of semiconductor technology. The main advantages of this device are its small dimensions compared to welding transformers and high efficiency, reaching 95%. Modern inverter units are capable of operating in the range from 20 to 500 A. There are a number of useful functions designed to make life easier for the master:

• Fast start;
• Arc Force;
• Anti-stick electrode.

Many devices are equipped with thermal protection devices. Professional models have a dust- and moisture-proof design that can function in difficult conditions.

All this makes the devices an ideal choice for home use. After the purchase, the novice specialist does not know which current to choose for welding with an inverter. To solve this problem, you should follow the manufacturer's recommendations. If they are missing, use reference books.

The welder encounters the main difficulties when working with thin sheet metal, which is very easy to burn through. This process should be approached with extreme caution. For example, to weld a steel sheet 0.8 millimeters thick, the required current will be 35 A. The recommended electrode thickness is no more than 1.8 mm.

When working with electrodes with a diameter of 3-4 mm, which are considered the most popular for household work, to calculate the required ampere characteristics, there is the following formula:

I = d*40 – 10%

Where I is the current strength, and d is the cross-sectional area of ​​the electrode.

What effect does polarity have?

Regardless of the type of welding equipment, the operating mode is closely related to polarity. It comes in two types:

With direct polarity, the anode is connected to the part being welded, and the cathode is connected to the electrode of the apparatus . The process is characterized by accelerated melting of the filler material, the speed of which exceeds the intensity of the workpiece melt.

The use of straight polarity leads to increased consumption of electrode material. This is justified when working with thin sheet metal, or when welding a thin element with a massive part.

Reverse polarity is characterized by connecting the anode to the electrode, and the cathode to the base metal . In this case, the process acquires the opposite qualities - intensive melting of the workpiece with economical consumption of electrodes. Reverse polarity helps to work with thick products.

Conclusion

The main parameters that affect the quality of the connection are: welding current, type of electrodes and arc parameters. In addition, it should be remembered that the properties of different metals require an individual approach. An experienced specialist will easily select the optimal mode without additional help. We recommend that beginners use reference books to avoid getting poor-quality seams.

Source: https://svarka.guru/vidy/thermo/dugovaya/tok.html

How to choose the right current when welding with an inverter

Welding of metal products is used when it is necessary to obtain a high-quality permanent connection characterized by increased strength.

In this case, metals are connected to each other at the molecular level; electrodes are used to perform such welding, which directly affect the quality of the connection made.

When performing welding work, you should correctly select the welding current indicators depending on the electrode used and its diameter. The quality of the work performed largely depends on this, so the welder needs to correctly calculate the ratio of power and electrode diameter.

Welding modes

Modern inverter welding machines allow you to change the current strength, which in turn makes it possible to work with metals of different fusibility characteristics. When choosing a specific welding mode, the following factors should be considered:

• Electrode brand.
• Its diameter.
• Electrode position during welding.
• Type and strength of current.
• Number of layers in a seam.
• Current polarity.

Simply put, current indicators are selected based on the diameter of the electrode. Such a rod, in turn, should be selected for a specific brand of metal elements that are used in the work. It is also necessary to take into account the position when performing welding.

So, for example, if work is performed in a vertical position, it is necessary to reduce the number of Amperes from the nominal by 20%. This will prevent molten metal from draining from the seam.

Remember that the maximum rod diameter for ceiling welding is 4 millimeters.

Selecting the correct current for welding

The diameter of the rods for working with an inverter or classic welding machines is selected depending on the thickness of the parts being welded. If you need to weld a surface of 3-5 millimeters, then you should choose a rod diameter of no more than 4 millimeters. For an 8 mm working seam, an electrode with a thickness of 5 mm will be sufficient. In this case, for each of these rods it is necessary to select the correct current strength.

When working with a 3 mm electrode, the current indicators are in the range of 65-100 Amperes. The choice of a specific current indicator in this case depends on the welding position and the type of metal. Experienced welders advise using an average value of 80 Amps.

When working with 4 mm electrodes, it is necessary to set the current strength to 120-200 Amperes. It should be said that 4 mm rods are most widely used today, as they are suitable for working with small and medium-sized seams.

Varieties of electrodes with a thickness of 5 millimeters will require the use of a current of 160-250 Amperes. It should be said that inverters capable of operating with such voltage are classified as professional. They guarantee deep welding and excellent joint quality.

Electrodes 6-8 millimeters thick require a current of 250 Amperes. In some cases, when working with refractory metal alloys, it is necessary to use a current value of 350 Amperes.

It must be said that the use of inverters made it possible to perform high-quality welding even with the use of thin electrodes. That is why today rods with a thickness of 1 to 2 millimeters are increasingly used.

To work with them, a current of 45 Amps will be sufficient.

Note that for high-quality performance of such welding, the inverter must have the function of smoothly adjusting the current, since sharp jumps and minimal errors can have a significant impact on the quality of the weld.

Recommendations

Modern welding inverters allow you to set the voltage completely automatically. You will only need to indicate the thickness of the electrode used, and the inverter automation will set the current indicators automatically. All this allows us to significantly simplify welding, while simultaneously improving the quality of such work.

Source: https://steelfactoryrus.com/kak-pravilno-vybrat-tok-pri-svarke-invertorom/

Choosing a welding machine for home

How to choose a welding machine for home use? How to avoid mistakes when choosing a welding machine and not overpay when purchasing. Periodic car repairs in the garage, housekeeping activities at a summer cottage, building a house - these and other works are difficult to carry out without welding equipment. In this article we will try to help in choosing a good welding machine.

Before purchasing welding equipment, you need to answer a number of questions:

• knowledge and experience in the field of welding;
• types of work, volume of processed material;
• types of metals to be welded;
• frequency of equipment operation;
• availability of the amount necessary to purchase a welding machine, components, electrodes, personal protective equipment.

The answers influence the choice of the type of apparatus and the welding methods used.

Welding type

Three modes are most suitable for housework and small businesses:

Each method has its own advantages and disadvantages.

MMA welding

The abbreviation means manual electric arc welding using electrodes coated with a layer of protective flux. The essence of the process:

• The mains voltage is supplied to the power step-down transformer. The voltage decreases with a simultaneous increase in the current value.
• Next, the electrical circuit is closed: one power cable is connected to the working conductive table or directly to the workpiece; the other to the electrode holder.
• An electric arc is formed at the point of contact between the electrode and the workpiece, and significant local heat generation occurs. The metal begins to melt, forming a weld pool. When cooling, a connecting seam is formed in this place.  

Flux on the electrode is necessary to create a protective layer that protects the molten metal from oxidation.

The MMA mode is the most popular due to its ease of use. The welding machine is not complicated in design and is cheaper than machines for other types of welding.

TIG welding

It is the process of joining metal by creating an arc using a non-consumable electrode. The latter uses a graphite or tungsten rod. To protect the weld pool from exposure to ambient air, a protective gas environment (argon, helium, carbon dioxide) is used.

Welding occurs on a direct or indirect arc. For the first case, heat is transferred directly to the metal, which is melted, creating a connecting seam. In the second case, additional filler wire is used.

MIG/MAG welding

The second most widely used method of joining metals. A common name is semi-automatic gas shielded welding. A wire is used as an electrode, fed by a special mechanism into the connection area. Protection from the external atmosphere is created by a cloud of gases supplied to the place where the weld pool is formed.

If it is not possible to use a gas component, a special flux-cored wire is used. It is a tubular structure. The outer layer is the working metal for the melt. The inner layer is powder protective flux.

Types of welding machines

For each welding method, specific equipment is used. Common to all types of welding is the presence of a current source. Additionally - wire feed mechanism and equipment for the gas component. Basic:

• welding transformer;
• welding rectifier;
• welding inverter;
• semi-automatic welding.

Welding transformer

The very first welding machine that operates using a voltage reduction circuit and produces alternating current. The mains voltage is 220V or 380V. Works in MMA mode.

Advantages

• simplicity of design;
• ease of use and maintenance;
• inexpensive;
• long service life;
• maintainability, availability of spare parts.

Flaws

• arc instability;
• difficulty with arc ignition and subsequent maintenance, especially for novice welders;
• greater sensitivity to voltage surges and drops;
• instability of the welding mode causes lack of penetration of the metal and the formation of a low-quality connecting seam;
• the process is accompanied by intense splashing of molten material, which necessitates subsequent cleaning of the seam and the surrounding surface;
• there is an effect of “sticking” of the electrode to the workpiece.

Welding rectifier

Consists of a power step-down transformer, a rectifying device and a control unit. Converts alternating voltage to direct voltage. Powered by 220V or 380V mains. Used to work in MMA mode.

Advantages

• simplicity of design;
• improved arc stability;
• high quality connecting seam;
• ability to work with all types of electrodes;
• work with various types of metals: ferrous, alloyed, non-ferrous and alloys based on them;
• low noise level during operation.

Flaws

• costs 2–3 times more than a welding transformer;
• difficult to repair;
• sensitive to changes in network voltage;
• may overheat at peak loads.

Welding inverter

The design includes primary and secondary rectifiers, an electronic transistor unit, and a high-frequency transformer. Generates pulsation-stabilized unidirectional direct current. Works in MMA mode. Power supply 220V or 380V. The most used welding machine of the early 21st century.

Advantages

• provides high stability of the electric arc during mains voltage fluctuations (170V–240V);
• possibility of smooth adjustment of output parameters in an extended range of voltage and current values;
• easy process of ignition and maintenance of the electric arc;
• protective functions during peak or long-term loads;
• possibility of process automation;
• welding with all types of coated electrodes on alternating or direct current;
• formation of a seam in horizontal and vertical, including ceiling planes;
• work with an expanded list of metals; ferrous, ordinary and alloy steels, non-ferrous metals and alloys based on them, difficult-to-weld materials;
• no “sticking” effect of the electrode.

Flaws

• a more expensive device among those presented above;
• requires careful care due to the presence of electronic power units and control systems.

Semi-automatic welding

A unit with automatic supply of welding wire to the weld area. The wire simultaneously acts as a conductor that ignites and maintains the arc. Protection from the environment is provided by a cloud of inert or active gas. Operates in MIG/MAG mode.

The semi-automatic device operates using an inverter circuit or as a rectifier. Additionally subdivided:

Source: https://meot.ru/article/kak-vybrat-svarochnyy-apparat/

Welding modes - selection and parameters

When the conversation turns to such a concept as welding modes, it is necessary to realize that this is a fairly large set of various parameters, which in turn determine the conditions of the welding process. And in order for the quality of the final result to be only positive, you need to choose these same parameters correctly. And although experts conditionally divide them into primary and secondary, all of them, without exception, affect the quality of the weld.

The main parameters of the welding mode include:

• The amount of current installed on the welding machine.
• Its gender (fixed or variable) and polarity (direct or reverse).
• Welding arc voltage.
• Diameter of the electrode used.
• Speed ​​of the welding process.
• Number of passes to fill the weld.

The secondary ones include:

• The quality of cleaning of welded workpieces.
• The shape of the joined edges.
• Type of electrode: its brand, type of coating, coating thickness.
• The angle of inclination of the electrode relative to the welding surface.
• Its position (top, bottom or side).
• How the joint is located (horizontally, vertically, at an angle).

Welding mode parameters

It should be noted that most often welders pay attention to the main parameters and their mutual relationship, but at the same time they do not lose sight of the secondary ones.

For example, the diameter of the electrodes is selected depending on the thickness of the metal parts being welded, the position of the joint, as well as the shape of the prepared edges.

And although there are tables that determine the diameter of the consumable relative to the thickness of the workpieces, it is very important to take into account the position of the electrode itself during the welding process.

Electrodes with a diameter larger than 4 mm cannot be used for ceiling welding. The same applies to the multi-pass process, because it is in this case that the root weld may not penetrate properly.

Welding current

As for the current strength, here too there are several provisions regarding the choice of welding parameters. The thing is that the more intense the current, the higher the temperature inside the weld pool. And this affects the rate of metal melting and the productivity of the welding process itself. And this is correct, but with some reservations.

• With increased current and a small diameter of the electrode, overheating occurs in the welding zone of the workpieces. This is already a decrease in the quality of the seam. Plus intense splashing of metal inside the bathtub. Often this mode leads to burnout.
• If the current strength is reduced, then this is a guarantee of lack of penetration, because at low current the arc becomes unstable. And with such an arc, the welding process often breaks down. This is the reduction in connection quality.
• If an electrode with a large diameter is selected without taking into account the thickness of the workpieces, the current density deteriorates. The reason is low cooling of the metal in the welding zone.

Not the last word in such a concept as the choice of welding mode is the polarity of direct current. With reverse polarity of the current, the penetration depth is 40% greater than with direct polarity. When using alternating current for welding, it must be taken into account that the penetration depth when using it is 15% less than when using constant current. And this is at the same current value.

Welders themselves with extensive experience set the welding current experimentally. They simply pay attention to the stable state of the arc, to its stable combustion. Beginners can use various tables or formulas. For example, one of the formulas that determines the current strength depending on the diameter of the consumable. It can be used if welding uses an electrode with a diameter of less than 3 mm.

I=30d

Welding process speed

The choice of arc welding mode also depends on the speed of movement of the electrode. This parameter is directly related to the thickness of the parts and the thickness of the seam. Its ideal value can only be considered when the area where the molten metal joins the edges of the parts is free of undercuts, burns and lack of penetration. The seam itself is a transition of a uniform shape without sagging or undercuts.

The higher the speed, less metal will get into the bath, the edges will not heat up to the required temperature, hence the lack of fusion of the seam, which will quickly crack. If the speed is lower, nodules are formed that interfere with penetration. The optimal mode is when the width of the seam is twice the diameter of the consumable.

Arc length

Another parameter that affects arc welding modes. Arc length is the distance from the end of the electrode to the top surface of the edge being welded. The ideal option is if this distance is the same along the entire length of the weld. But that's not all. It is important to choose this distance correctly.

Experts believe that the length of the arc should be equal to the diameter of the consumable used. Unfortunately, only experienced welders can withstand such a distance. Therefore, there are certain deviations. For example, for an electrode with a diameter of 3 mm, it is better to keep the distance to the edge within 3.5 mm.

Electrode angle

The position of the electrode relative to the welding plane affects the width of the weld and its penetration depth. It is considered optimal if the rod should be located perpendicular to the connection of the workpieces. But this is practically impossible, because the welding tool of the welding machine moves along the joint. Therefore, the electrode is positioned either tilted forward or tilted backward.

In the first case, the seam becomes wide, and the penetration depth decreases. This happens because the molten metal is forced out to the front of the weld pool. In the second case, on the contrary, the molten metal is pushed to the rear of the bath. Therefore, the depth of the joint is well welded in this way, but the width of the seam is noticeably reduced.

By the way, the angle of inclination of the workpieces being welded has exactly the same effect on the quality of the seam.

If welding is performed on parts that are located at a certain angle, and the electrode itself moves from top to bottom, then a thickened layer of molten metal forms under the consumable. And this is an increase in the width of the seam and a decrease in the depth of penetration.

If the movement is made from bottom to top, then there is much less molten metal under the arc, which makes it possible to deepen the welding, but at the same time obtain a small seam width.

Experts recommend installing the workpieces at a slight angle, no more than 10°. In this way, metal spreading along the seam can be avoided, which will ensure the quality of welding. In this way, lack of penetration and undercuts can be avoided.

As you can see, manual arc welding modes are a set of measures based on the correct selection of certain parameters. Even the slightest deviation can lead to a decrease in the quality of the connection between two metal workpieces.

Source: https://svarkalegko.com/tehonology/rezhimy-svarki.html

Choosing a good welding wire: 2018 rating and tips for assessing quality

The purpose of a welding cable is to supply electrical energy to the parts that are welded together, the electricity is converted into heat and the metal is melted.

Device

The wires for the welding machine have two conductors; they contain an electrode holder with terminals; in general, the cable structure is the same as that of welding inverters used in everyday life.

Product requirements

A cable intended for welding must ensure the delivery of operating current to the welding site with minimal losses. It is made of copper: this metal has maximum conductivity, the wire is made thick enough to prevent it from heating up.

Metal structures have different shapes, so it is important to be able to weld in different positions. The copper welding wire should allow the welder to reach any place; it is important that it is flexible and does not interfere with the welder’s work.

Reliable cable insulation allows you to weld metal parts, even if they are in close proximity to conductive structures. The insulating layer must withstand any external influences: heat, frost, lubricant.

It is equally important that the insulated conductor withstand exposure to aggressive chemicals; they must be immune to sudden movements or shocks.

The cable is often wound and unwound; a stranded copper wire with a large cross-section meets all the necessary requirements; it is enclosed in a special sheath of soft rubber, which is oil-resistant.

The length of the welding wires is calculated according to ISO; it is important that during welding work the voltage in the cable does not drop by more than 6%. When calculating the total length, the current strength, wire material and its cross-section are taken into account.

The following formula is used: Cross-sectional area of ​​the copper wire = Maximum length *Multiplier, where the Multiplier for a current value of 200 - 500 Amperes is 2, if the current value is less than 200, then the current is divided by 100.

Performance characteristics

Today, manufacturers do not produce cables suitable for operation in any production and climatic conditions. In the photo of the welding wire you can see the entire line of products, despite the different characteristics, they are all flexible and with minimal resistance.

The KG brand on products from Russian manufacturers means that this is a flexible copper wire; it is used to connect the power elements of mobile devices; if the KS brand is used, the performance properties are almost completely identical to KG.

An example of decoding can be presented as follows: KG 1x16, in front of you is a special single-core cable, the product has the necessary flexibility, its cross-section is 16 mm2, and the permissible operating current is 189 A.

The number of cores is put in front, and the remaining numbers are the cross-section, 2 letters HL indicate that the wire is intended for use at low temperatures, thanks to the additional coating it can withstand frost of -60 degrees.

The letter T denotes other characteristics of the wire; it is suitable for welding in damp places where it is constantly hot and the temperature can rise to +85 degrees. Thanks to its good antiseptic properties, the product is not afraid of mold and fungi.

The letters KOG indicate that the conductors are particularly flexible, the conductor is suitable for use in the most inconvenient places, while all working qualities are fully preserved.

The abbreviation KGN serves to denote non-flammability; the KG wire has excellent tightness and is used under water.

Types of conductors

The following main types are distinguished:

• Single-core. They are used in an inverter; the copper core is made of thin wires.
• Twin-core. They provide an anode and a cathode to ensure the application of high frequency current. Current with these characteristics is excellent for pulse welding or metal cutting.
• Three-core. The conductors are intended for use in welding machines that are capable of producing high-quality seams; they are used when installing pipelines.

Is extension allowed?

It is important to know how to connect welding leads correctly and when to extend them. The wire for ground power is connected to the “-” connector, and the cable with the electrical holder is connected to the “+” connector.

A long wire is convenient to use, but at the same time the resistance of the conductor increases, which means that the voltage will drop additionally.

When a welding lead extension is required, it must be thicker than the cable connected to the welding machine and have a large cross-section. In this case, it will be possible to avoid losses on the conductor, but the mass of the cable will inevitably increase too.

Photo of a good welding wire

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Source: https://instrumentgid.ru/vybor-xoroshego-svarochnogo-provoda/

How to choose the right current when welding with an inverter - Machine tools, welding, metalworking

In a private house, in a country house, in a garage and even in an apartment - everywhere there are many jobs that require metal welding. This need is especially acute during the construction process. Here, especially often, something needs to be cooked or cut off.

And if you can still cut it with a grinder, then there is nothing to reliably connect the metal parts with except welding. And if the construction is carried out with your own hands, then the welding work can be done independently. Especially in places where the beauty of the seam is not required.

We will tell you how to properly weld by welding in this article.

Basics of electric welding

Welded metal joints are the most reliable today: pieces or parts are fused into a single whole. This happens as a result of exposure to high temperatures.

Most modern welding machines use an electric arc to melt metal. It heats the metal in the affected area to the melting temperature, and this happens over a small area.

Since an electric arc is used, welding is called electric arc welding.

This is not a completely correct way of welding)) At a minimum, you need a mask

Types of electric welding

An electric arc can be formed by both direct and alternating current. Welding transformers use alternating current, and inverters use direct current.

Working with a transformer is more complicated: the current is alternating, so the welding arc “jumps”, the device itself is heavy and bulky. The noise that both the arc and the transformer itself makes during operation is also quite annoying. There is one more problem: the transformer greatly “stresses” the network. Moreover, significant voltage surges are observed. The neighbors are not very happy about this fact, and your household appliances may suffer.

Inverters mainly operate from a 220 V network. At the same time, they are small in size and weight (about 3-8 kilograms), operate quietly, and have almost no effect on voltage.

The neighbors won't even know you started using the welding machine unless they see you. In addition, since the arc is caused by direct current, it does not jump and is easier to stir and control.

So if you decide to learn how to weld metal, start with a welding inverter. Read about choosing an inverter welding machine here.  

Welding technology

For an electric arc to occur, two conductive elements with opposite charges are required. One is a metal part, and the second is an electrode.

The electrodes used for manual arc welding consist of a metal core coated with a special protective compound. There are also graphite and carbon non-metallic welding electrodes, but they are used for special work and are unlikely to be useful to a novice welder.

When an electrode and metal of opposite polarity touch, an electric arc occurs. After its appearance, in the place where it is directed, the metal of the part begins to melt. At the same time, the metal of the electrode rod melts, being transferred with the electric arc to the melting zone: the weld pool.

How a weld pool is formed. Without understanding this process, you will not understand how to weld metal correctly (To enlarge the size of the picture, right-click on it)

During the process, the protective coating also burns, partially melting, partially evaporating and releasing a certain amount of hot gases. Gases surround the weld pool, protecting the metal from interaction with oxygen. Their composition depends on the type of protective coating. The molten slag also coats the metal, also helping to maintain its temperature. To weld properly, you must ensure that the slag covers the weld pool.

The weld is formed by moving the bath. And it moves when the electrode moves. This is the whole secret of welding: you need to move the electrode at a certain speed. It is also important, depending on the required type of connection, to correctly select its angle of inclination and current parameters.

As the metal cools, a slag crust forms on it - the result of the combustion of protective gases. It also protects the metal from contact with oxygen in the air. After cooling, it is beaten with a hammer. In this case, hot fragments fly away, so eye protection is required (wear special glasses).

You can read about how to make a barbecue out of a cylinder or barrel here. Just get some practice.

How to learn to cook by welding

It all starts with preparing the workplace. Safety when working with electric welding must be given increased attention: there is a possibility of injury from both electricity and high temperatures. Therefore, take your preparation seriously.

It is more convenient to learn to weld with electric welding on a thick piece of metal: it is better to practice on it. In addition to it and the welding machine, you will need gaiters (thick gloves) and a welder’s mask. You also need thick clothing that protects the entire body, and durable shoes with thick leather. They must withstand sparks and scale. You will also need a hammer and a wire brush to knock off the slag. You will need glasses to protect your eyes.

How to connect the electrode

It will be easier for beginners to carry out welding work if they take a universal electrode with a diameter of 3 mm (3.2 mm, to be precise). They are more expensive, but easier to work with. After you learn how to weld metal, you can try using cheaper ones, but it’s better to start with these.

The electrode is inserted into a holder attached to one of the welding cables. There are two types of clamps - spring and screw. If the electrode holder is spring-loaded, press the button on the handle and insert the electrode into the socket that appears. When screw clamped, the handle rotates. Unscrew it, insert the electrode and clamp it. In any case, it should not wobble. After installing the electrode, you can connect the cables.

There are two outputs on a DC welder: positive and negative. There are also two welding cables:

• one ends with a metal clamp-retainer - it is connected to the part;
• the other is a holder for the electrode.

Which polarity to connect for welding depends on the type of work. If we talk about inverters, then more often the plus is connected to the part, and the minus is supplied to the electrode. This connection option is called direct polarity. But there is a list of works in which reverse polarity is applied: minus to the part, plus to the electrode (for example, for welding stainless steel).

Direct and reverse polarity of connection on the welding inverter

Straight polarity provides better heating of the metal, which is necessary for most connections. This is explained by the fact that electrons move from the negatively charged pole - with straight polarity, this is the electrode - to the positive - part. At the same time, they additionally transfer their energy to the metal, increasing its temperature.

We figured out how to connect the electrode to the inverter. Now about how to light an arc. It occurs when there is direct contact between the electrode and the part. There are two ways:

• chirping;
• tapping.

Everything is clear from the name: in one case, you need to run the electrode along the seam (so that there are no marks left), in the second, you need to hit the part with the tip of the electrode several times.

When the electrode is new, its tip is exposed, ignition occurs easily. If it was already in use, a wall of several millimeters of protective coating would form around the rod. This coating needs to be knocked off by hitting the part with the tip several times.

Both methods of ignition are used, here everyone chooses what is convenient for them. This skill is the first one you will have to master if you want to learn how to use electric welding.

Therefore, you take several electrodes, a thick piece of metal, and try to strike an arc. Once you have succeeded, you can proceed to the next stage of training.

Electrode tilt

The main position of the electrode is tilted slightly towards you - at an angle from 30° to 60° (see figure). The amount of inclination is selected depending on the required weld and the set current. Focus on the condition of the weld pool.

The first position is called the “backward angle.” In this case, the bath and molten slag moves behind the tip of the electrode. Its angle of inclination and speed of movement must be such that the slag has time to cover the molten metal. In this position, we obtain heating of the metal to a greater depth.

Manual arc welding technique: positioning the electrode at an angle forward and at an angle backward

There are situations when the metal does not need to be heated very much. Then the angle of inclination changes to the opposite, the seam and the bathtub “stretch” behind the electrode. In this case, the heating depth is minimal.

Electrode movements

The answer to the question “how to properly weld with electric welding” is simple: you need to control the weld pool. To do this, it is necessary to hold the electrode at a distance of 2-3 mm from the metal surface and control the condition and size of the weld pool. This is where the skill of a welder lies.

  Eye drops after welding

The difficulty lies in the fact that several parameters have to be controlled simultaneously:

• move the electrode along one of the trajectories shown in the photo,
• as it burns, lower it a little lower, maintaining a constant distance of 2-3 mm;
• monitor the size and condition of the weld pool, accelerating or slowing down the movement of the electrode;
• follow the direction of the seam.

The movements of the electrode tip are shown in the figure. Those who want to learn electric welding for home use do not need to master all of them, but you will need two or three movements: for different situations, seams and metals.

Another element of manual arc welding technique: the tip of the electrode must move along one of these trajectories (or something similar)

How to learn to cook with electric welding? Practice movements on a thick piece of metal. Then you get not seams, but rollers. This stage is the initial one. On it you will master the basic skills of a welder: learn to control the distance from the tip of the electrode to the part, and at the same time, move it along a given path, monitor the weld pool and the slag in it.

You won’t succeed the first time, or even the tenth time. You will probably use a dozen electrodes.

When the manual arc welding technique has been mastered: the bead is uniform, its width and height are constant (or almost), you can try to connect the parts.

You should get similar rollers. This way you can learn how to weld using electrodes correctly.

Read how to make a gazebo on a metal frame in this article, and here the construction of a shed on a metal frame is described.

How to weld metal correctly

Learning to hold the electrode correctly and move the bath is not enough for a good result. It is necessary to know some of the subtleties of the behavior of the metals being joined. The peculiarity is that the seam “pulls” the parts, which can cause them to warp. As a result, the shape of the product may differ greatly from what was intended.

https://www.youtube.com/watch?v=PFhXTomXXSw

Electric welding technology: before starting to apply a seam, the parts are connected using tack welds - short seams located at a distance of 80-250 mm from each other

Therefore, before work, parts are secured with clamps, ties and other devices. In addition, tacks are made - short transverse seams laid every few tens of centimeters. They hold the parts together, giving the product its shape. When welding joints, they are applied on both sides: this way the resulting stresses are compensated. Only after these preparatory measures do welding begin.

Read about the types of welds and joints (horizontal, vertical, ceiling) and how to weld them correctly here.

How to choose a current for welding

It is impossible to learn how to weld using electric welding if you do not know what current to set. It depends on the thickness of the parts being welded and the electrodes used. Their dependence is presented in the table.

But with manual arc welding, everything is interconnected. For example, the voltage in the network has dropped. The inverter simply cannot produce the required current.

But even under these conditions you can work: you can move the electrode more slowly, achieving good heating. If this does not help, change the type of movement of the electrode - passing over one place several times.

Another way is to use a thinner electrode. By combining all these methods you can achieve a good weld even in such conditions.

Now you know how to weld properly. All that remains is to practice the skills. Choose a welding machine, buy electrodes and a welding helmet and start practicing.

To reinforce the information, watch the video lesson on welding.

Source: https://stanki-info.com/kak-pravilno-vybrat-tok-pri-svarke-invertorom/

How to choose an inverter welding machine - Forging, welding, blacksmithing

Before you go to the store, choose and buy welding equipment “for the home - for the family,” you need to prepare for this serious event.

It is recommended to do the following:

• Firstly, critically evaluate your knowledge and experience in the field of electric welding. This will help you choose a device with the options you need. It should be borne in mind that unnecessary options will lead to unnecessary material costs, and their lack will lead to poor welding quality;
• secondly, think (and “strongly”!) and decide:
  • what kind of work you expect to do. It is likely that you will only need a welding machine that allows you to perform manual arc welding (MMA), carried out with stick consumable electrodes;
  • how often this will happen;
  • under what conditions you will perform welding work;
  • what material do you intend to process, etc.

Proper preparation will help you avoid a situation in which you either purchase a cheap welder that cannot meet your “welding” expectations, or a very expensive, high-performance and “can-do-it-all” welder, but for which you will not have a job. In both cases, you will face extra material costs for equipment that will not be used.

In addition to technical training, it would be a good idea to consult with owners of welding inverters: what would they advise? The advice and recommendations of people you personally know well are especially valuable.

It will not be superfluous to visit the service center nearest to you, to which, in unfavorable circumstances, you will take your welding inverter. Listen to what the repairmen have to say and advise.

Before you go shopping, go to specialized stores and consult with sales consultants.

Read the article Repair of welding inverters.

Now let's discuss how to choose the right inverter welding machine. Let's start with the technical requirements that will be presented to your amateur inverter welding machine.

Welding inverter on a belt.

Requirements for an inverter welding machine

Let us note in passing that all inverter welding machines are divided into three classes:

• household or amateur;
• professional;
• industrial.

The last two classes are not of interest to us today, and we will not consider them here.

Amateur welding inverters are used for welding in domestic conditions:

• in the country;
• in the garage, etc.

The following technical requirements apply to this class of welders:

• welding quality is standard;
• operating mode: short-term;
• the amount of work is small or, in general, one-time work;
• rated welding current, A: 120200.

In addition, the inverter welding machine must be:

• highly mobile, lightweight and easy to transport (on a belt slung over the shoulder, or in another similar way);
• not whimsical:
  • operating with poor quality input power supply voltage:
    • low and spasmodic;
    • the shape is noticeably different from a sine wave and the frequency is not exactly 50 Hz;

“Bad” supply voltage.

• allowing power supply from mobile electric generators with internal combustion engines;
• not consuming a lot of electricity;
• not requiring special maintenance, etc.

Choosing a welding inverter

When choosing a welding inverter, you should pay attention to the following:

• welding current value;
• special options;
• layout.

How to choose the right welding current

The rated operating current for a welding device is that at which the inverter will operate without overload and, therefore, without overheating. The magnitude of this current is indicated in the following documents for the device:

• "Passport";
• "Operation Manual".

You can start your acquaintance with the advertising brochure. But the information in it may not always be up to date and correspond to reality.

During the preparation, you determined what maximum welding current you will need in your work. The welding inverter should be selected with a margin of 3050%. This must be done for the following reasons:

• operation of the welder in the mode of its maximum welding current values ​​will lead to overheating and rapid failure;
• you will be protected from troubles in case of a drop in input voltage. The fact is that the power of the inverter drops, and the welding current will be significantly lower than the rated current (with all the unpleasant consequences for you). Voltage drops are possible for a number of reasons:
  • poor-quality voltage in the electrical network (what is it - see above);
  • network cables longer than 15 m are used. This will be especially noticeable if they are of small cross-section. In this case, the voltage drop in the power circuits will increase, and the voltage at the inverter input will be too low.

If the network voltage is constantly low (for example, in gardening, at the dacha, in the garage, etc.), then choose a welding inverter model whose “Operation Manual” directly states the possibility of its operation under these conditions. Be sure to pay attention to the intermittency factor (IR).

It indicates how long the machine can operate continuously at maximum welding current. It is indicated as a percentage. For example, CP = 60% means that the welder must cool down every 10 minutes.

Its continuous operation is possible with a welding current that is significantly less than the declared maximum welding current.

Experience shows that for standard household welding inverters, a rated current of 160200 A is sufficient.

Special options for welding inverters

We recommend paying attention to welding inverters that have the following options:

• "HOT START". Provides easy ignition of the welding arc due to the fact that at the moment the electrode touches the part being welded, an additional electrical impulse is created;
• "ARC FORCE". Allows you to avoid sticking of the electrode to the product. This happens due to the increased current of the welding arc;
• "ANTI STICK". Automatically turns off the welding inverter at the slightest sticking of the electrode during the welding process.

They will be especially useful for beginning welders.

Welding inverter layout

It is known that the main enemy of any electronics is metal dust. Welding inverters are no exception. Getting on the printed circuit board, it closes the printed contact tracks on it, leading to a short circuit of metal particles and burnout of circuit elements.

To combat dust, different types of assembly arrangements are used. The most practical placement of printed circuit boards is the so-called tunnel one. With this layout option, the device is divided into two zones:

• "clean". It contains all the electronics;
• "dirty". Here are:
  • fan;
  • radiators;
  • transformer.

An example of tunnel technology.

Such a layout scheme is more complicated, but it allows you to increase the reliability of welding equipment and makes it possible to operate the device in very difficult climatic conditions.

You should pay attention to how many circuit boards are installed in the welder. Often, in order to save money, the entire structure is mounted on 2 boards (there are instances entirely assembled on one board).

The design itself, in which light and heavy elements are installed on one circuit board (cooling radiator, high-frequency and current transformers, etc.), is flawed, because it leads to an excessive load on its load-bearing part.

Strictly speaking, printed circuit boards, in general, are not intended for power loads and for attaching heavy parts to them.

In multi-module welding inverters, transformers and radiators, as a rule, have fastenings separate from the board and do not “hang” on it.

During prolonged operation, the board and everything on it heat up to a high temperature, and with sudden movements (for example, one section of a fence was welded, the inverter was moved to another and, with a tired hand, it was abruptly lowered to the ground), the components can loosen the electrical contacts on the board . Several such transitions from place to place and the welder, for no apparent reason, will stop working.

Dust and dirt inside the inverter.

Single- and double-board inverters have very low maintainability. A welder is a complex electronic device, and diagnosing one common board is much more difficult than diagnosing individual functional blocks.

If it is necessary to replace a burnt-out element, repairing or replacing the functional board will cost significantly less than the boards of the entire welder. Look at how the functional blocks are connected to each other.

This, for the reasons given above, should be flexible connections.

How can you find out how many boards are in a welding inverter without removing the casing from it? Firstly, you should pay attention to this when preparing: look on the Internet, advertising, etc. Next - in the store:

• ask a sales consultant;
• determine visually - by the appearance of the inverter. In a single- and double-board welding machine, the boards are arranged vertically and obliquely. They are rigidly attached to the front panel of the device using panel sockets. In this case, the latter are located vertically (one above the other) or obliquely, which should alert you. And the most radical way is to look into the ventilation louvers of the building. They will be very clearly visible there.

Fastening heavy components separately from the rest.

General Tips

We recommend purchasing inverter welding machines from well-known brands that have been on the market for at least five years, and from specialized welding stores.

Specialized stores, being official representatives of welding equipment manufacturers, always value their name and will not sell counterfeit equipment.

Even if the company at the beginning of its activities imported goods of poor quality (but cheaper), then within five years such devices were completely rejected. For that, now such a campaign will have a good developed service.

Go to the welding invectors section or the current models section.

Sections: Welding equipment

Source: https://kovka-svarka.net/2012/01/kak-vybrat-invertornyi-svarochnyi-apparat/

How to choose the right current when welding with an inverter - Metalworker's Handbook

You bought a welding machine and want to learn how to weld with an inverter for beginners.

There is no need to be afraid of difficulties! The inverter machine is easy to use; anyone without experience or knowledge can master the welding process in a short time.

Equipment, equipment, safety precautions

Safety precautions. Welding production is associated with electrical voltage, or in common parlance - current. The current is invisible, but can kill a person.

We check the welding cables for serviceability and connect them to the inverter equipment. Return cable with a clothespin on metal to the negative connector. Cable with electrode holder to connector +. We insert the electrode into the electrode holder.

When connecting the device to the network, visually evaluate the current-carrying cables for serviceability. After making sure that the cables are in good condition, we plug in the plug into the socket and the toggle switch on the device, having previously set the current regulator to the lowest value. If the cooling fan starts working smoothly, without crackling or noise, then everything is fine.

Metal weight. When connecting heavy structures, take precautions. If multi-ton products collapse, they can lead to death or disability.

Equipment. Welding production involves high temperatures. The welder must have:

• canvas mittens (gaiters);
• robe (special suit);
• mask with a light filter;
• respirator for work in confined spaces;
• boots with rubber soles.

Gaiters are used when welding at heights, when arms are raised up, and mittens in other cases.

Other accessories:

• welding machine;
• hammer;
• brush;
• electrodes.

Electrodes are selected according to the metal (carbon content, additives) and diameter, depending on the thickness of the metal and the technical characteristics of the inverter.

Inverter Welding Basics

For beginners, experienced welders advise attaching the holder cable to the body, pressing it with the elbow of the arm and wrapping it along the forearm (from the elbow to the hand), and taking the holder in your hand. This way the shoulder joint will pull the cable, and the arm and hand will remain free. The method will help you manipulate your hand with ease.

Correct placement of the cable on the forearm. You should not work with bare hands.

If you simply take the holder in your hand without wrapping the cable around your forearm, then during the welding process your hand will get tired and wrist movements will cause the cable to dangle. Which will affect the quality of the welded joint.

How to cook using inverter welding correctly? We set the welding current on the machine according to the diameter of the electrode, the type of connection and the welding position. Setup instructions are available on the device and the electrode pack. We take a stable stance, move our elbow away from the body (no pressing), put on a mask and begin the process.

For beginners, it is better to start welding with an inverter with metal workpieces larger than 20 cm.

It is known that a beginner, putting on a mask and lighting an arc, stops breathing, trying to boil the entire length of the workpiece in one breath. With short products, you will develop the habit of cooking in one go. Therefore, practice on long workpieces, learning to breathe properly when welding.

Workpieces (plates) on the work table can be placed in a horizontal plane - vertically towards you or horizontally, it makes no difference.

At the beginning of welding, place the electrode clamped in the holder at an angle of 90 degrees (perpendicular) and move it towards the seam by 30-45 degrees. Light the arc and start moving.

1. If welding is performed at an angle backwards, then the tilt of 30-45 degrees goes towards the seam.
2. If the connection occurs at an angle forward, then the electrode is tilted away from the seam.

The distance between the surface to be welded and the electrode is 2-3 mm, imagine that you are running a pencil along a sheet of paper.

Please note that when welding, the electrode decreases as it burns - gradually bring the melting rod closer to the surface at a distance of 2-3 mm and maintain an inclination angle of 30-45 degrees.

:

How can a beginner learn to weld with a welding inverter?

First we learn to light and hold an arc. Feel the edge when to bring the electrode closer to the surface to be welded during combustion so that the arc does not interrupt.

The electrode is ignited in two ways:

• tapping;
• chirping.

The new electrode ignites easily. A slag film appears on the working rod, preventing ignition. You just need to tap longer to break the film.

1. To facilitate arc ignition, inverter devices have a built-in Hot Start function.
2. If a beginner quickly brings the electrode closer to the surface, the Arc Force function (arc force, anti-sticking) is activated, increasing the welding current, preventing the electrode from sticking.
3. If the melting rod gets stuck, the Anti Stick function cuts off the current, preventing the inverter from overheating.

: What is arc force on a welding inverter and how to use it.

It is better for a beginner to first learn on a thread seam; the electrode is held smoothly, without oscillatory movements.

After mastering thread technology, proceed to welding metal with oscillatory movements. Which are used on thick metal for heating, holding the electrode at a certain point using movements - herringbone, zigzags, spiral or your own method.

Types of oscillatory movements

At the beginning of the connection, we carry out several movements from left to right, forming a weld pool and go along the seam making oscillatory movements. The angle of inclination of the electrode is 30-45 degrees. After passing, we beat off the slag with a hammer and clean it with a brush. Take care of your eyes, wear glasses.

Tip: at the end of the weld, make oscillatory movements to the sides and move the electrode towards the deposited metal. This trick will add beauty to the welded joint (get rid of the crater).

: how to weld corner joints, butt joints and overlap joints.

Seams are divided into:

• single-pass (one pass replenishes the thickness of the metal);
• multi-pass.

A single-pass weld is performed on metals up to 3 mm. Multi-pass seams are applied for large metal thicknesses.

Welders check the quality of the seam with a hammer - they strike next to the seam. If the seam is smooth, without irregularities, then after the impact the slag flies off completely, there is nothing for it to catch on. It is important to select the correct temperature regime: an overheated seam (hot) will break, an underheated one - there is a risk of lack of penetration.

The current is selected based on the diameter of the electrode, in theory 30 A per 1 mm of electrode diameter.

Direct and reverse polarity when welding with an inverter

Let's consider polarity when welding with an inverter. With a DC connection, the movement of electrons is constant, which reduces spattering of molten metal. The seam is of high quality and neat.

The device has a choice of polarity. What is polarity is the direction of movement of electrons depending on the connection of cables to equipment connectors.

1. Reverse polarity when welding with an inverter - minus on the workpiece, plus on the electrode. The current flows from minus to plus (from the workpiece to the electrode). The electrode heats up more. Used for welding thin metals, the risk of burn-through is reduced.
2. Straight polarity - minus on the electrode, plus on the workpiece. Current moves from the electrode to the workpiece. The metal heats up more than the electrode. Used for welding thick metals from 3 mm and cutting with an inverter.

The polarity is indicated on the pack of electrodes; these instructions will help you correctly connect the wires to the equipment.

Welding thin metal with an inverter

The essence of connecting thin plates comes down to selecting small-diameter electrodes and adjusting the welding current. For example, for metal with a thickness of 0.8 mm, electrodes with a diameter of 1.8 mm are used. The current on the inverter is set to 35 A.

Technology occurs in intermittent movements. Watch a video showing how to join thin plates in detail.

:

How to cut metal with a welding inverter

To properly burn a hole in a pipe, we set the current on the device to 140 A for a 2.5 mm electrode. We light the electrode, placing it in one place to warm up the metal and press it in. We move the electrode to a new place, warm it up and press it in. Gradually, we cut a hole in the pipe.

Pipe cutting

When cutting, it is better to place the plate vertically so that the molten snot flows down. If you cut in a horizontal position, icicles will harden at the bottom of the cut. That's all the tricks!

Beginners are tormented by the question, which polarity of wires is better when cutting with an inverter?

1. When cutting with electric welding, straight polarity is preferable. The melting zone is narrow but deep.
2. With reverse polarity, the melting zone is wide but shallow.

It is not recommended to cut with electric welding (metal melts from the cut zone). It’s better to take a grinder and cut off the desired piece.

:

Source: https://ssk2121.com/kak-pravilno-vybrat-tok-pri-svarke-invertorom/

What does straight polarity mean?

In order to achieve a high-quality seam when welding various steels, it is important to know which polarity is suitable for the material that needs to be processed. The general essence of welding with an inverter is that the machine must have “+” and “-“ sockets. Depending on which socket the ground will be connected to and which the electrode will be connected to, the polarity will depend.

Direct polarity is connected in this way: a ground is added to the positive socket, and an electrode is added to the negative socket. It is important to know here that the type and polarity of the current will be determined by the existence of the anode and cathode spots. During straight polarity welding, an anodic spot, which is hotter, will form on the workpiece side.

What does reverse polarity mean?

With reverse polarity, it is logical that the connections of the ground and the electrode are swapped. That is, an electrode is connected to the positive socket, and ground is connected to the negative socket. Here you need to understand that when connecting the sockets in this way, an anode spot will also form, but it will appear not on the side of the workpiece, but on the opposite side from it, that is, on the electrode.

Important note! Connecting the polarity manually is carried out only when welding with an inverter, that is, in the presence of direct current. When carrying out the same process, but on alternating current, the polarity is changed up to hundreds of times per second independently. Therefore, the connection method does not matter.

As you can see, the difference between direct and reverse polarity when welding with an inverter is that the anode spot will form in different places.

Polarity selection criterion

When changing the connection, the specialist changes the location of the heat concentration, transferring it either to the workpiece or to the electrode itself. It is important to know here that the socket with a plus is responsible for heating, which means that with a direct connection, the maximum temperature will be observed at the welding seam. When connected in reverse, the maximum temperature is spent on heating the consumable element. Knowing this feature, you can independently choose the connection diagram based on such a parameter as the thickness of the material.

The choice between forward and reverse polarity when welding will greatly depend on the thickness of the metal product. If this parameter has a medium or high value, then it is best to resort to straight polarity. This is explained by the fact that strong heating of the workpiece will provide a deeper seam, which, in turn, will improve the quality of the weld. Straight polarity is also used when cutting pieces of metal.

And, on the contrary, when welding thinner metal workpieces, it is recommended to use a reverse connection, since the material will not overheat too much, but the electrode will melt much faster.

Metal type

Forward and reverse polarity when welding will also depend on the type of metal product that needs to be processed. It is important to understand that the ability to independently change the type of connection affects the efficiency of working with various types of workpieces. An example is welding stainless steel or cast iron.

When working with such materials, it is best to use reverse polarity, which will avoid severe overheating of the raw material, which will eliminate the need to create a refractory welded joint. But, for example, when working with a type of metal such as aluminum, it is best to use straight polarity when welding. Since with low heating it will be very, very difficult to break through the oxides of this raw material.

Most often, each material has a recommendation that states what type of polarity is best to process this workpiece.

Types of electrode and wire

Another very important detail that must be taken into account when welding with a direct or reverse polarity inverter is the type of electrode, which, like metal, has its own characteristics at different temperature conditions. Most often, the parameters are related to the type of flux used in the base of the consumable. Let's say we have a carbon-type electrode.

It is impossible to use a reverse connection to work with such an element, since too much heating of a consumable of this type will overheat the flux and the product will become completely unusable. You can only use DC welding with straight polarity.

Here, as in the case of metal blanks, in order not to make a mistake, it is best to study the markings and manufacturer’s recommendations for working with each type of consumable separately.

Properties of straight polarity

It is quite obvious that there are advantages to welding with direct and reverse polarity. If we talk about the first type of connection, we can highlight the following points:

• the resulting weld will be quite deep, but at the same time quite narrow;
• used when welding most metal workpieces whose thickness is higher than 3 mm;
• Welding, for example, non-ferrous steel is possible only with a tungsten electrode, as well as with a direct connection to the inverter;
• straight polarity when welding metals also has a more stable arc, which, in turn, ensures a higher quality weld;
• when using a direct connection, it is strictly prohibited to use electrodes that are suitable for welding with alternating current;
• straight polarity has also proven itself in cutting metal workpieces.

Reverse polarity properties

Just as direct polarity during welding has its strengths and weaknesses, reverse connection can also be characterized by certain properties:

• If you use DC welding, but make a reverse connection, the resulting seam will not be too deep, but very wide.
• The best weld quality is achieved only when working with thin metals; if reverse polarity is used to weld thick materials, the weld quality will be too unsatisfactory.
• When welding on a reverse connection, it is strictly forbidden to use electrodes that cannot be overheated.
• If the current strength decreases significantly, the quality of the seam will also deteriorate significantly due to the fact that the arc will begin to “jump”.
• Since reverse polarity is most often used for welding high-alloy steels, it is necessary to be guided not only by the rules of welding with an inverter, but also take into account the requirements of the metal for the duration of the working cycle, as well as for the cooling process of the metal.

After a person has studied in detail the features of welding with direct polarity, as well as with reverse polarity, it becomes quite simple to answer the question of why change it. To briefly summarize, we can say the following:

The use of direct polarity is justified in cases of large metal thickness. Also, this type of connection is justified if non-ferrous metal is welded: brass, copper, aluminum.

It is most important to pay attention to working with aluminum, since its oxide film has a huge melting temperature, which greatly exceeds the melting point of the raw material itself.

In other words, we can say that straight polarity welding is the rough processing and joining of the structure.

The reverse connection, in turn, is used to work with thin steels. In addition, it is used when processing high-alloy or stainless steel. These materials do not tolerate overheating well, and therefore it is impossible to use melting at high temperatures. That is, work on the reverse connection is considered more delicate.

From this we can conclude that the answer to the question of why change the polarity when welding with electrodes is that the quality of the weld depends on it, as well as the performance of the consumable itself, since not all electrodes can be connected in the reverse way.

We select the welding current depending on the specific diameter of the electrodes

Welding of metal products is used when it is necessary to obtain a high-quality permanent connection characterized by increased strength.

In this case, metals are connected to each other at the molecular level; electrodes are used to perform such welding, which directly affect the quality of the connection made.

When performing welding work, you should correctly select the welding current indicators depending on the electrode used and its diameter. The quality of the work performed largely depends on this, so the welder needs to correctly calculate the ratio of power and electrode diameter.