What is straight polarity current welding - Metals and their processing

Reverse polarity when welding and direct polarity: differences and how to choose for an inverter

All articles and reviews related to welding have an electrical theme. Be it devices, be it electrodes, be it types of seams – in any welding question the type of current is mentioned and specified. In some places it is constant, in others it is variable, and it also has two options - direct and reverse polarity when welding.

It's time to figure out what's what in order to choose the right materials, devices, electrodes and welding methods. Knowledge of the nuances of electricity in welding will help you quickly and correctly configure the inverter, on which the quality of welding seams depends to a large extent.

Anodic spots, cathodic spots

Of course, you can work all your life on your inverter machine, in which by default the direct current is set to straight polarity: you do not have any hassle or problems with adjustments to the welding electricity.

This wonderful idyll is possible only on the condition that the type of work you do is the same, you don’t change, you still don’t know all the capabilities of your device, and in general why talk about electricity, everything is fine as it is, there’s no need to complicate it

It’s not necessary, it’s not necessary, but if you need to weld, for example, high-quality high-alloy steel, then your idyll will immediately be disrupted: you won’t be able to produce a high-quality weld with the old electrical settings. You will have to understand the concept of reverse or forward polarity when welding, which we will help you with right now.

Firstly, working on an inverter device involves direct current. And it, in turn, implies two sockets for connecting the positive and negative terminals. Let's remember the polarity when welding with an inverter by connecting the electrode, it’s easier. If the electrode is connected to the negative socket, then this is straight polarity when welding. If it’s positive, it’s the opposite.

Direct and reverse polarity.

In principle, with the direct version, the electrode that is connected to the negative terminal itself becomes the cathode. And our metal blank becomes the anode. In the opposite case, the electrode begins to work as an anode, because it is connected to the positive pole. Well, the workpiece, accordingly, turns into a cathode.

In both cases, anodic and cathodic spots are formed. The anode cloud is hotter, and significantly: the difference in the temperatures of the anode and cathode regions reaches 800°C.

Let us not lose sight of an important detail: if we are talking about two options - forward and reverse, this always relates only to direct current. The fact is that with alternating current the polarity itself changes from direct to reverse with a high frequency.

Once again: switching direct and reverse polarities makes sense and is only possible with direct current, this is direct current welding. With alternating current, such switching makes no sense or is possible. Friends, this is physics.

Straight polarity

So, the electrode is connected to the minus, the metal workpiece is connected to the plus. This is the classic polarity when welding with an inverter. On the plus side, a wonderful anode cloud spreads its heat.

Direct DC connection has some features that must be taken into account:

with direct connection, a stable and even arc is obtained with all the ensuing consequences in the form of high-quality seams;
the welding seam is narrow and deep;
shall not be used in any case if the electrodes indicate that they are intended for alternating current technology;
with some metals, when working in inert gases, the deposition rate increases;
the composition of the metal in the weld with direct polarity has its own characteristics: there is practically no carbon in it, but silicon and manganese are present;
quite high degree of metal spattering;
quick melting of the consumable with its frequent replacement.

Reverse polarity

Reverse polarity when welding.

We remember that with reverse polarity when welding with direct current, the positive anode warm spot is on the electrode. Thus, we eliminate additional heating of the metal to which the negative terminal is connected. The main type of welding for reverse connection is electric arc with flux and the method in a shielding gas environment, in particular in argon.

The main metal “consumers” of reverse connection are high-alloy steels and thin workpieces made of any metal: what matters here is the thinness of the edge, which is easy to burn through at the slightest overheating. So the work on the reverse connection can be called quite delicate. And where there is delicacy, there are performance features and professional advice.

Here are the technological features of using reverse polarity that need to be taken into account:

the seam with reverse connection is wider and shallower than with direct connection;
copes excellently with joining thin and medium-thick edges of metal workpieces;
the welding arc is not as stable as with direct polarity; if the voltage is low, the arc begins to jump and be interrupted;
if you are welding high-alloy steel, then in addition to the reverse connection, you must comply with additional requirements for the operating cycle and cooling temperature of steel workpieces;
Never cook with electrodes that are sensitive to overheating;
an additional reduction in temperature on the workpiece can be achieved by reducing the voltage potential;
the fact that the arc is not very stable can be used for good: it is better to weld very thin edges with intermittent seams - interrupting the arc;
if in reverse polarity direct current welding you make a butt seam, the gap between the surfaces should be minimal, but if the seam is overlapping, the surfaces should fit together hermetically. Otherwise you will get a burn;
flanging the edges of the surfaces to be welded will help greatly to reduce the risk of burn-through.

How to choose the correct polarity

But if you work with different metals and metal workpieces of different thicknesses, you will have to independently adjust the parameters of the welding current and, in particular, the polarity. It's not difficult, let's go.

It's all about moving the warm anode spot, that is, the concentration of heating. With direct polarity, the plus goes to the metal workpiece, which is what heats up. The choice of connection option when working with different workpieces made of different metals depends on this factor. Everything is logical and simple, here are the criteria for decisions regarding connecting direct welding current:

Edge thickness of metal workpiece

Direct and alternating current welding.

Thick surface edges? Of course, welding with direct polarity current! Additional concentration of heat at the melting points in thick parts will contribute to deep testing and, therefore, obtaining a high-quality, durable seam. If the edges of the surfaces being welded are thin, then you need to reason and then act quite the opposite.

It is important not to overheat the thin edges to prevent burn-through. So we send the warm anode spot out of harm’s way to the other side – to the electrode. So we cook the thin parts when connecting them back.

Type of metal

Here, moving the thermal anode spot will help us: what metals will it not harm, but, on the contrary, will help? The correct thing to do would be to carefully read the instructions for electrical settings of the welding machine, which accompany any modern alloy.

But now you can remember the fact that aluminum, along with alloys, welcomes heat; it helps reduce the amount of oxides formed during the process. So welding of aluminum with direct current is carried out only with a direct connection. Officially, this will be called DC welding of aluminum in an argon environment.

Non-ferrous metals, like aluminum, are welded with non-consumable tungsten electrodes only when directly connected, without any exceptions.

Type of electrode

You know that modern electrodes are divided according to a huge number of criteria; they are produced in an incredible variety. Electrical parameters are also included in the description of each type of electrode. It never hurt anyone to read the instructions most carefully.

But here we can very well reason logically to choose the correct polarity for each type of electrode. The choice depends on the same thing - the warm anode spot, that is, the temperature regime. And such modes of electrodes depend on the type of flux and many other factors.

It is impossible to give short recommendations on current polarity for different welding consumables - there are too many of them. The only practical advice in this case is to read the instructions and not neglect them.

But what should you do if the instructions for the metal or alloy require the same electrical parameters, but the selected electrode requires completely different welding current settings? This happens, in this case there is only one answer: try and look for the best option experimentally.

Current strength, duty cycles, connection to poles - everything will have to be adjusted manually. But we are given a head to think, right?

Source: https://tutsvarka.ru/vidy/obratnaya-polyarnost

Direct and reverse polarity when welding with an inverter - Metalworker's Handbook

The advent of inverter welding machines has helped to open up new areas of application. Thanks to this, every home master can use it for their own purposes. But not all owners know the features of such tools. Particularly relevant is the question of what reverse and direct polarity are when welding with an inverter. It is this topic that will be discussed in the article.

Why do you need this type of welding machine? Most often, a welding inverter is used for electric arc welding. It is this that allows you to connect or separate workpieces made of steel of various types. Before using such a device, it is necessary to select two main parameters - welding current and type of electrodes. After this, you can safely begin working with this unit.

How to use the inverter

Having learned about the basics of using this device, you need to consider how to operate it. This includes the following stages:

The surface of the material is separated from dirt and rust. This will be needed in order to form a reliable seam;
Select the welding current mode and electrode type. Here it is important to consider both the material and the parameters of the weld;
Connect the positive terminal to a metal surface to carry out the necessary operations;
We connect the minus to the electrode holder;
We form an arc, then use a hammer to remove scale from the resulting seam.

This is the standard sequence of actions. However, it does not take into account the shape of the connection and the orientation of the electrode. Such subtleties are necessary to form special types of seams for welding. The latter are used for cylindrical containers (separators in the oil and gas industry, construction tanks).

Choosing the right model

For all units, both direct and reverse polarity are available when welding with an inverter. But such inverters must have additional characteristics, which determine the scope of application, speed and comfort of the work performed. And therefore it is necessary to take a professional approach to choosing a welding inverter. The recommended functionality of such a unit is as follows:

Hot start for rapid arc formation;
Anti-stick allows you to form a seam of the correct shape (as smooth as possible);
Automatically activated when there is molten metal at the end of the electrode. A short increase in current will avoid sticking;
Alternating current for working with aluminum workpieces;
To work in rooms with high humidity or a small area, a reduced idle value is required;
The type of indication is also important, ideally digital symbols of the parameter.

In addition, you need to clearly select the welding current, since it directly depends on the diameter of the electrode used and the thickness of the material. The most commonly used electrodes are the ANO and MR brands, which are suitable for creating a seam on metal surfaces. If you need to weld aluminum structures or several alloys, you will need special materials, including additives.

Application of direct and reverse polarity

The change in polarity occurs due to ongoing processes. In addition to selecting the basic parameters, you can swap the connected terminals. As a result, current will flow from the negative element to the positive one and the first one will heat up to the required values.

Direct polarity is needed in cases where deep seams are processed on thick workpieces. Here the minus is connected to the electrode, the metal has a plus. It is also good to use this polarity when welding cast iron and deep penetration of the main metal (aluminum, iron, and so on).

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Reverse polarity (plus to the electrode, minus to the metal) . The metal is cold, the electrode heats up. It is used only for thin-walled workpieces, since the electrode fails very quickly. Depending on the goals of the process, the wizard applies one of the operating modes.

It should also be taken into account that with alternating current low-carbon steels are welded with rutile-coated electrodes, in the presence of magnetic blast of thick-sheet structures made of low-carbon steels.

There is no dependence on the type of polarity; you can use any one that is convenient for a novice specialist.

Summarize. We looked at what a welding inverter is and why you need to know about direct and reverse polarity.

Often, novice craftsmen do not know the specifics of the work, which is why difficulties arise when melting metal or welding structures made of various alloys. However, changing polarities is quite simple.

By changing the terminals with each other, you can achieve the necessary parameters for working with different products. Study welding inverters carefully, and your work will become noticeably more comfortable!

Source: https://ssk2121.com/pryamaya-i-obratnaya-polyarnost-pri-svarke-invertorom/

How to determine the polarity of the electrodes?

Welding is a manual labor, but welders must have a sufficient amount of technical knowledge, even if physics was something supernatural for them at school.

One of the mandatory concepts that you need to know is “welding current” . The welder must have a good understanding of polarity and the impact it has on the welding process.

On welding machines and electrodes you can see the designations AC or DC, which describe the polarity of the current. Why do electric currents and polarities occur during welding? Let's look at these concepts carefully.

What is alternating (AC) and direct (DC) current?

AC from English “alternating current” means alternating current , and DC “direct current” means direct current .

AC alternates the direction of current, but DC flows in only one direction.

Welding machines and electrodes marked DC have a constant polarity, while those marked AC change polarity 120 times per second with a current frequency of 60 hertz.

How do alternating and direct current differ in welding?

Direct current (DC) welding creates smoother, more stable arcs and produces less spatter. It is easier to weld in the vertical and upper positions.

However, alternating current (AC) may be the preferred choice of new welders as it is often used in low-cost, entry-level welders. AC is also common in shipbuilding welding or any environment where the arc may float from side to side.

What is polarity?

The electrical circuit that occurs when the welding machine is turned on has a negative and a positive pole - this property is called polarity . Polarity is important in welding because choosing the correct polarity affects the strength and quality of the weld. Using the wrong polarity can result in a lot of spatter, poor fusion and loss of control of the welding arc.

When welding with alternating current, polarity is not required!

In turn, welding using direct current is of two types:

— welding with direct polarity

— welding with reverse polarity

Polarity

straight reverse

negative positive

(–) (+)

The welding process will vary depending on the direction, polarity of the current: positive (+) or negative (–) .

Positive DC polarity (DC+) will provide high penetration rates, while negative DC polarity (DC–) will give less penetration but higher deposition rates (eg on thin sheet metal). Various shielding gases can further influence the welding process.

Welding with straight polarity current

Direct polarity welding is usually understood as welding, during which a positive charge the part (product) being from the welding machine, i.e. The welding cable connects the workpiece being welded to the (+) terminal of the welding machine. A negative charge is supplied to the electrode through an electrode holder connected by a cable to the (–) terminal.

When welding with direct polarity current, the main temperature load falls on the metal part being welded . That is, it heats up more, which allows the root of the weld to be deepened.

Direct polarity current is recommended to be used when it is necessary to cut metal structures and weld thick-walled parts, as well as in other cases when it is necessary to achieve a large heat release, which is precisely a characteristic feature of this type of connection.

Reverse polarity current welding

Reverse polarity welding is usually understood as welding, during which a negative charge is the part (product) being welded from the welding machine, i.e. The welding cable connects the workpiece being welded to the (–) terminal of the welding machine. A positive charge is supplied to the electrode through an electrode holder connected by a cable to the (+) terminal.

When welding with reverse polarity current, more heat is released at the electrode , and heating of the part comparatively reduced . This allows for more “delicate” welding and reduces the likelihood of burning through the part.

Welding with reverse polarity current is recommended for use when it is necessary to weld thin sheets of metal, stainless steel, alloy steel, and other steels and alloys that are sensitive to overheating.

Since alternating current (AC) is half positive and half negative, its welding properties are right in the middle of the positive and negative polarity of direct current (DC). Some welders choose alternating current (AC) if they want to avoid deep penetration. For example, during repair work on rusty metals.

Although alternating current itself has no polarity, if alternating current welding electrodes are used with direct current, they will show poorer results. Therefore, electrode manufacturers usually indicate the most appropriate polarity on the electrode coating and packaging.

Understanding the direction and polarity of welding current is important for proper welding. Knowing how these factors affect your weld will make your job easier.

Source: https://rem-serv.com/kak-opredelit-polyarnost-elektrodov/

What is reverse polarity welding?

There are two main types of welding using direct current:

straight polarity welding process; reverse polarity welding process.

In the first case, a minus is connected to the electrode, while a plus is connected to the product. Welding with direct current of reverse polarity implies a situation where the product receives a minus, and the electrode receives a plus.

Influence of polarity during welding

What is the effect of DC polarity?

Welding with direct and reverse polarity forms a cathode and anode spot at the tip of the electrode. During the welding process, the cathode spot is formed on the minus, while the anodic spot is on the plus.

In the area of the anode spot the temperature is much higher (up to 3900 o C) than in the area of the cathode spot (up to 3200 o C). When welding with direct polarity, most of the heat is concentrated on the product itself, which causes the root of the weld to deepen.

That is why reverse polarity welding is used mainly on products made of thin sheet steel or when it is necessary to weld low-melting metals. Reverse polarity welding is also practiced when working with stainless, alloy and high-carbon steels, which are very sensitive to overheating.

IMPORTANT: during welding with alternating current, the polarity can change very sharply (up to 100 times per second), so there is no rule for observing polarity during this process.

Features of DC welding (general provisions)

Regardless of what polarity of welding electrodes is used in the work, welding with direct and reverse polarity has some features:

It is recommended to use a clamping clamp (it will not allow damage to the part being welded in the place where a cable with a negative or positive charge is connected due to the appearance of microcharges);
in comparison with the process using alternating current, welding using direct current is recognized as more “accurate”, that is, during operation there is no such amount of metal splashes, and the welding seam itself is more even;
due to the fact that the cathode and anode are always heated differently, the connection method will determine how much metal will be transferred from the melting electrode to the workpiece.

Welding process control

DC welding (polarity) is the task of heating the base metal as best as possible until it melts, so that a weld pool is formed. If, for example, the current is too low, the welding surface of the metal will not be heated properly. If the current is too high, the metal will heat up so well that the arc will penetrate inside, pushing the metal back.

Direct polarity of welding helps to organize an environment in which the weld pool will spread, and the movement of the electrode can easily control the entire welding process.

The faster the electrode moves, the less heat will flow to the surface of the base metal, so it will not warm up as well. If you move the electrode more slowly, more heat will flow, therefore, the metal will warm up much better.

IMPORTANT: professional welders immediately set a little more current, and simply regulate the welding speed with the electrode (by the speed of its movement along the surface of the product being welded). When finishing the weld, it is recommended to deposit a little more metal to avoid the formation of a crater.

Source: https://ostwest.su/instrumenty/chto-takoe-svarka-tokom-obratnoj-poljarnosti.php/

How to quickly learn to weld with a welding inverter

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.

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

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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.

Watch a useful video on how to learn how to weld with electric welding for beginners:

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.

To facilitate arc ignition, inverter devices have a built-in Hot Start function.
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.
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.

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.
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?

When cutting with electric welding, straight polarity is preferable. The melting zone is narrow but deep.
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://plavitmetall.ru/svarka/invertorom-dlya-nachinayushhix.html

ACϟDC. Understanding Welding Current and Polarity

Welding is a manual labor, but welders must have a sufficient amount of technical knowledge, even if physics was something supernatural for them at school.

One of the mandatory concepts that you need to know is “welding current” . The welder must have a good understanding of polarity and the impact it has on the welding process.

Features of welding with direct polarity current: differences from reverse polarity

What is welding with direct polarity current? It is connecting the positive wire from the equipment to the parts being connected, and the negative wire goes to the negative wire from the holder on which the electrode is fixed. With mirroring, we obtain reverse polarity at the output. Different connections contribute to changes in the temperature of the welding crater.

Reverse type

A similar polarity when welding is used when it is necessary to reduce the risk of defects on parts to a minimum, as well as during the performance of important tasks, so that welding is carried out with high accuracy. With this technique, the high temperature is concentrated on the conductive rod, and the heat level is much lower on the structure being connected.

Therefore, the reverse type of polarity is used for high-quality welding of thin metal , in order to eliminate the possibility of warping from excessive heat, as well as when connecting steel parts of varying degrees of alloying, because such workpieces are especially sensitive to possible overheating. A similar connection is used to connect metals protected by flux or inert gases, such as argon.

To avoid mistakes when welding, you need to know the following differences:

the choice of reverse polarity when welding with direct current makes the seam joint small in depth, but voluminous in width;
when joining thick metals, the quality of the seam decreases;
Do not use electrodes that are sensitive to overheating;
when the current decreases, arc surges are formed, which negatively affects the strength and quality of the seam;
When connecting high-alloy steels, it is necessary to strictly maintain the work cycle and cooling time of the connected workpieces.

In the case of connection from an alternating current network, welding of metals with a low carbon content is carried out with rutile conductive rods, which do not depend on polarity, so any technique that is most convenient for the performer is used.

Selection criterion

Experienced welders independently decide where to connect the wires to the plus or minus when connecting the mass to the welding machine in order to concentrate more heat on the structure or the melting rod with coating. Sometimes you have to choose the polarity several times - this directly depends on the complexity of the design or the thickness of the metal being connected, for example, with medium or large thickness, choose the straight polarity option.

Strong heating of the workpiece allows you to make a deeper seam, which greatly increases the strength and quality of the connection; a similar polarity is chosen when it is necessary to cut off any element from the overall structure. Reverse polarity is selected when working with thin-walled parts; the parts do not overheat, but the electrode melts faster.

Metal thickness

The specifics of welding thick metal are quite simple: we connect the ground to the plus on the unit, and the electrode to the minus . The presence of a high temperature on the workpiece contributes to greater heating of the metal, which will increase the depth of welding, and as a result the weld will be of higher quality and strength.

When welding thin-walled metal, reverse polarity is used, since the anode spot moves to the electrode and the threat of burning out the structure is completely eliminated.

View

Polarity largely depends on the type of metal that makes up the structure being connected or the individual parts prepared for welding. For example, to firmly connect products made of stainless steel or cast iron, reverse polarity is used to avoid overheating of the workpieces and to get rid of the appearance of a refractory welded joint, which requires special processing.

When welding aluminum, a direct connection method is used - a durable film covering the non-ferrous metal melts when heated strongly and does not interfere with the formation of a seam joint. Experienced welders know how and by what methods it is necessary to weld metals of different chemical compositions, and novice performers consult a reference book or study the accompanying documentation, which describes in detail the welding technique, as well as what polarity should be used.

The influence of the thickness of the parts to be connected on the choice of connection.

Briefly about electrodes

If an inverter is used for welding, then when connecting the direct or reverse option, the type of electrode used must be taken into account, since these products have individual parameters that depend on temperature changes.

The chemical composition of the coating or spraying has a special impact on the quality of the welding process , for example, when using reverse polarity, a carbon electrode cannot be used, because due to the influence of high temperature, the flux overheats and loses the necessary properties - the product will be unsuitable for further use.

It is necessary to use a direct connection option, and on each type of electrode there is a marking indicating the mode of use, and the packaging contains similar recommendations from the manufacturer, so it is extremely difficult to confuse them.

Semi-automatic operation

This type of welding is typical for production processes, and it is necessary to correctly set the polarity of this semi-automatic device, for example, to connect parts made of stainless metal, a shielding gas is used and a reverse connection is selected, and when a flux-cored filler wire is used when welding aluminum products, a direct connection is used.

How to manage the process?

The main thing for the performer is to heat the parts being welded until the edges are completely melted, so that a welding crater is formed. We list the negative processes that may appear in this case:

if a low current is set, then the metal of the workpieces does not have time to completely warm up, so the weld pool moves behind the electrode;
when the current is excessive, strong heating occurs, the arc begins to penetrate into the metal and push the molten substance back.

With normal use of current, the liquid metal in the crater does not spread much, and the outer edges are thin and the welder has full control of the process.

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

When welding parts with a large thickness of metal, it is necessary to increase the current strength in order to completely heat the part, and thin-walled structures heat up quickly, so you need to work at a low current strength. During the welding process using coated or sprayed electrodes, the wire speed must also be taken into account.

External condition of the seam joint.

Advantages and disadvantages of methods

Changing the connection affects the operation of the conductive rod in different ways, for example, with the reverse method, the following processes are observed:

more thermal energy is supplied to the structure than to the coated rod;
good heating ensures high-quality and deep fusion;
the electrode melts slowly, so frequent replacement is not necessary;
There is practically no spattering of metal during welding.

Straight polarity when welding is characterized by the following nuances:

heating of the workpieces is minimal;
melting of the electrode occurs much faster, so frequent replacement of rods is required;
liquid metal splashes heavily.

The conclusion is simple - the reverse method has more obvious advantages, but not only the advantages determine the choice, since for most electrodes, recommendations for choosing a connection are written on the label by the manufacturer.

conclusions

Inverter or semi-automatic welding equipment is characterized by simple operation, therefore it is often used in a home environment, for example, in a country house or during repairs in private housing construction, and it is easier for inexperienced performers to connect metal structures using a regular standard network connection. To obtain high-quality connections, you need to know exactly how and when to use the reverse or direct connection method.

Source: https://svarka.guru/sertifikatsiya-i-obuchenie/osobennosti-pryamoy-polyarnosti.html

What is direct and reverse polarity when welding with direct current

A high-quality welded connection when working with DC devices largely depends on their settings. Even the simplest inverter has not only current settings, but also polarity.

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Most often, the default is straight polarity when welding and you can work with your inverter for years without knowing all its capabilities.

If you have a need to weld high-alloy steel or cannot achieve a high-quality seam, then knowledge of all the subtleties of the settings is simply necessary for you. We will talk about what polarity is and how it affects welding work.

What is forward and reverse polarity

DC welding implies the presence of a socket for connecting to the “+” and “–” of the welding machine. Depending on where the ground is connected and where the electrode is connected, the polarity is distinguished.

Direct polarity is a connection diagram in which ground is connected to the positive socket, and an electrode is connected to the negative socket. In this case, the type and polarity of the current determines the existence of anode and cathode spots. With this connection, the anodic (hotter) is formed on the workpiece side.
Reverse polarity - the mass is connected to the minus, and the electrode to the plus. In reverse polarity when welding with direct current, an anode spot with a higher temperature is formed on the opposite side, that is, the electrode.

Note! Welding with alternating current involves independently changing the polarity up to hundreds of times per second, so in such cases it makes no sense to follow the connection diagram.

What determines the choice of polarity

By changing the type of connection, you can concentrate the heat either on the part being welded or on the electrode (by moving the anode spot). The positive socket is responsible for heating, therefore, with a direct connection, when the plus is connected to the metal, the welded joint heats up more, and with reverse polarity, the electrode heats up more. We recommend! How to cook semi-automatically with carbon dioxide

Thanks to this feature, we can choose a connection diagram based on:

Metal thickness. If we are welding thick or medium-thick parts, then a direct connection is suitable, in which the heat concentrated on the product will help to obtain a deeper seam and high-quality penetration. This type of connection is also suitable for cutting metals of various thicknesses. Thin metals are best welded in reverse polarity, concentrating most of the heat on the electrode. This way the part will not succumb to overheating, and the electrode itself will melt faster.
Kind of metal. The ability to change the localization of the heat spot helps to select the most effective operating schemes for various metals. For example, if we are welding stainless steel or cast iron, then a reverse connection is necessary to help avoid overheating of the alloy and the formation of refractory compounds. For aluminum, a direct connection is necessary, otherwise it will be very difficult to break through the oxides. Before starting work, carefully study the recommendations for setting up the device for a specific alloy.
Type of electrode or wire. Like metals, electrodes have their own temperature regimes, which are largely related to the type of flux. For example, when working with carbon electrodes, you cannot use reverse polarity, otherwise the flux will overheat and the electrode will become unusable. To select the setting that suits your electrode, look at the type of wire and flux, or use the manufacturer's recommendations. Speaking about wires for semi-automatic machines, they also have recommendations regarding connecting the minus and plus of the device.

Now you know what can affect your connection settings. There are cases when the metal requires one setting, and the electrode requires completely different settings. In such cases, compromises must be made by adjusting the amperage and duty cycles.

Remember! The type of connection does not depend on the spatial position.

Features of welding with straight polarity current

Straight polarity when working with direct current has a number of features. We have already listed some of them, the rest are worth paying special attention to:

the weld seam is deep, but quite narrow.
Suitable for most steels with a thickness of 3 mm or more.
Non-ferrous metals using a tungsten rod are welded only with straight polarity.
characterized by a stable arc and, as a result, a better quality seam.
It is prohibited to use electrodes for AC welding machines.
better suited for cutting metal.

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Features of welding with reverse polarity current

Like direct polarity, reverse polarity when welding with an inverter has a number of features, knowing which you can avoid a number of mistakes common to beginners. It is worth highlighting the following features:

when welding with direct current with reverse polarity, the seam is less deep, but wider
Excellent for welding thin and medium thickness metals. When working with thick workpieces, the quality of the seam decreases sharply.
It is prohibited to work with reverse polarity with electrodes sensitive to overheating.
at low currents there is a significant decrease in the quality of the weld due to the jumping arc.
In addition to the reverse connection, when working with high-alloy steels, the recommendations regarding the work cycle and cooling of the workpiece must be strictly adhered to.

Conclusion

DC welding machines, such as inverters or semi-automatic machines, are simple enough to use at home. That is why the demand and supply of these devices on the market is constantly growing. This is facilitated by their availability, low cost, and it is easier to cook with direct current than with alternating current.

However, in order to obtain a high-quality, beautiful and durable welded joint, you need to know a number of technological features, including the purpose and types of polarity. With the knowledge from this article and a DC source, you can do any welding work with your own hands.

The main thing is a careful approach to work and compliance with all protective measures.

Source: https://svarkagid.ru/tehnologii/pryamaya-i-obratnaya-polyarnost-pri-svarke-invertorom.html

DC welding of direct and reverse polarity

There are two main types of welding using direct current:

straight polarity welding process; reverse polarity welding process.

Reverse and direct polarity when welding with an inverter - Ice advice

Business October 10, 2017

When welding a structure using direct current, it is important to know that the quality of the seam will depend largely on the settings of the machine. An important nuance is that in addition to the current regulator, it is necessary to select the correct polarity. There can be only two types - direct and reverse polarity when welding with an inverter.

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.

Source: https://LEDsovet.ru/obratnaia-i-priamaia-poliarnost-pri-svarke-invertorom/

Welding current polarity - forward and reverse

The polarity of the welding current is one of the important parameters affecting the quality of the weld. After all, the direction of movement of the current, that is, electrons in the metal, depends on it, which affects the process of making the seam, the burning of the arc, the formation of the weld pool and, as a result, the quality of the welded joint.

I wrote a separate article earlier regarding the physical meaning, as well as the terms “direct” and “reverse”. And now I will tell you the basic principles of using direct and reverse polarities of welding current. And the main thing you need to know: where there is “+”, it heats up more. Accordingly, when welding on current with reverse polarity, when “+” is on the electrode, it heats up more than in the case of direct polarity. And the part, on the contrary, heats up more when welding with a current of direct polarity.

Subtleties and features

With detail, the situation is somewhat more tricky. When there is a “+” on the part, the penetration spot is wider, but the depth is no greater, or even less, than when the part is “-“. With a “minus”, the weld pool spot on the part is smaller, but its depth can be no less, or even greater, than when welding with direct polarity current. Thanks to this, when there is a “minus” on the part, it is possible to better control the movement of the weld pool.

How to use this in practice? There are many options. Usually, the default polarity of the welding current is used - especially when you need to strongly heat and weld parts. Reverse polarity is used in cases where it is necessary to more accurately control the movement of the weld pool.

For example, these are some types of vertical seams, especially from top to bottom.

Also, welding with reverse polarity current can help when making ceiling seams and welding thin metal - because in this case, the part heats up less, and this will minimize the flow of metal when making vertical and ceiling seams and through penetration of metal when welding thin sheets.

The polarity of the welding current also depends on the electrodes

Another important point is welding electrodes. Not all electrodes allow the use of welding current of any polarity. For example, with electrodes with the main type of coating, welding should be carried out only with a “minus” on the metal being welded. Such electrodes include, for example, UONI-13/55 electrodes. In any case, always check that the actual polarity of the welding current is correct for the specific electrodes being used.

Summary

So, it is important to understand that the choice of the direction of the welding current depends on the spatial position of the weld, the selected electrodes, the thickness of the metal and the personal skills of the welder. If all these conditions are met, then the seams will be of high quality, reliable and aesthetic.

And most importantly - experiment! I say this very often because in fact, only an experiment will give you the most accurate and correct answers to your questions!

Perhaps I covered this topic a little chaotically, so if you still have any questions, write them in the comments. And also be sure to tell us about your experience of using direct and reverse polarities!

More on the topic:

Which electrodes are best for an inverter?

Features of welding thin metal

Thin metal, vertical seam

courses:

How to cook with electric welding

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How to set up a chameleon mask correctly

How to choose a welding inverter

Source: http://www.elektrosvarka-blog.ru/polyarnost-svarochnogo-toka/

Direct and reverse polarity when welding with an inverter - Machine tools, welding, metalworking