What is the difference between direct polarity and reverse polarity when welding

What is direct and reverse polarity when welding?

22.08.2019

For installation of metal products and repair work, DC welding is often used. Using rectifiers and inverters, you can change the polarity when welding and regulate the zone of maximum heating of the arc. It is worth talking about the nuances of direct and reverse connection of poles in detail: how the poles are connected, in which cases the minus is brought out to the electrode, what is the peculiarity of the seam with direct and reverse polarity.

Connectivity differences

Anyone who has used electric arc welding machines understands that we are talking about the distribution of poles between the holder and the workpiece. There are two types of polarity when welding:

Direct, when electrons move towards the workpiece (minus on the electrode). The arc turns out compact and dense.
Reverse, when a plus is connected to the holder. A diffuse area of contact between the arc and the metal is formed.

The main difference between direct and reverse polarity welding is the localization of the point of maximum heating. With direct heat, the metal heats up more, and with reverse heat, the consumables heat up more. The method of connecting the poles depends on the thickness and physical properties of the metal.

Differences in connecting direct and reverse polarity

Features of straight polarity when welding

First, a few words about the scope of application of straight polarity in welding. It is extensive and is used:

When installing rolled steel from carbon, low-alloy, special steels using consumable electrodes.
When welding is performed with a tungsten non-consumable electrode using a surfacing wire. A refractory rod is needed for butt joints of thin parts and non-ferrous metals; it is used when working with fluid alloys.
For cutting workpieces using welding equipment.

Advantages of current standard terminal connection:

a narrow suture bead is formed;
due to the high plasma density, the workpiece is boiled deeply;
a wide range of surfacing electrodes with various types of coatings is produced;
a stable arc is maintained.

Disadvantages of direct connection:

the metal is strongly sprayed (a dense stream of plasma hits the melt pool with force);
there is a high risk of burning through thin parts;
residual stresses arise in the heat-affected zone.

So, with a direct connection, the cable from the positive terminal is connected to the workpiece, and from the negative socket it is led out to the electrode holder.

Features of reverse polarity when welding

Self-taught welders sometimes involuntarily change the polarity of the current if they do not handle the device carefully. In such cases, it takes a long time to weld the metal, the seam is wide, and consumables burn out quickly. The reason is that the point of maximum arc heating is focused at the tip of the electrode. When welding with reverse polarity, the melting rate is one and a half times lower.

Source: https://svarkaprosto.ru/tehnologii/pryamaya-i-obratnaya-polyarnost-pri-svarke

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

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.

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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.

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

Direct and reverse polarity when welding with an inverter

23.12.2019

Correct performance of welding work largely depends on the selected equipment settings. When working with semi-automatic installations, it is important not only to select the correct current strength, but also to set the desired polarity.

The factory setting (default) is not suitable for many tasks. Especially when it comes to joining high-alloy steel, non-ferrous or rare metals.

Therefore, to obtain a good quality weld, the equipment must be properly configured.

How does polarity affect welding?

The concept of polarity implies a certain option for connecting equipment, which is dictated by the task at hand and the characteristics of connecting certain materials. To change the polarity, simply “switch” the terminals. After this, the direction of current movement will change and, accordingly, the physical processes of welding will change.

There are only two polarity options, which are adjusted before operation:

Direct . It is chosen in cases where it is necessary to connect two thick parts, and the seams must be deep. In this case, the workpieces are connected to the positive terminal, and the electrode to the negative terminal. Connecting with straight polarity leads to the formation of cathode and anode spots during operation. The hotter of them - the anode - appears on the workpiece: it is to it that the positive terminal is connected. Because of this, the metal warms up (and, therefore, melts) to a greater depth. This makes it possible to work with aluminum, cast iron and other parts made of complex alloys.
Reverse . In this case, it’s the other way around: the electrode is connected to the positive terminal, and the workpiece is connected to the negative terminal. An anodic hot spot can only form on the consumable. This connection option is good because it makes it possible to work with thin-walled and low-melting metals.

Depending on the goals and materials, the welder selects one or another polarity option on the inverter. Young specialists who have not studied the theoretical part often experience problems when working with metals of small or large thickness. Therefore, it is very important to carefully study the technical documentation that comes with the inverter. And only after that you can begin the practical part.

What is direct and reverse polarity: technical conditions for selection

The basis for a balanced choice of polarity type is the technical conditions that must be adhered to during welding. Due to the specific type of connection, a higher temperature regime is located on the workpiece or on the electrode itself. Several important factors influence the final decision.

Workpiece thickness

Direct connection is best suited for small to thick workpieces. In this case, the workpiece heats up better compared to the electrode, which makes it possible to obtain a deeper seam. This mode is also great for cutting metal. For thin sheets, it is better to choose reverse polarity. Then the main heat is concentrated on the electrode and overheating of the workpiece can be prevented.

Metal type

Changing the location of the heat spot allows you to select the most suitable operating mode for a specific part. For example, stainless steel or cast iron is quite easy to overheat. In this case, a connection with reverse polarity is better suited, which makes it possible to form a strong and reliable seam. But aluminum alloys need to be welded with straight polarity. In this case, it is possible to overcome the oxidizing film faster.

Type of consumables

Conditions depend on the type of consumable flux. Reverse polarity is not suitable for carbon electrodes. In this situation, the flux will overheat and the rod will become unsuitable for further use. There are cases when the flux material and the workpiece have mutually exclusive requirements. The welder has to use a lot of creativity to find the optimal current offset and select the appropriate duty cycle.

Source: https://vtmstol.ru/blog/pryamaya-i-obratnaya-polyarnost-pri-svarke-invertorom

Polarity when welding with an inverter

When performing welding work, the main attention is paid to connecting the parts being joined. This factor largely depends on the correct settings of the welding equipment.

When working with semi-automatic machines, you should adjust not only the current strength, but also set the desired polarity when welding with an inverter.

The default settings do not allow you to fully solve the assigned tasks, especially when it comes to rare materials or high-alloy steels. Nevertheless, any inverter can be configured in the desired mode and get a high-quality seam.

How does forward and reverse polarity affect welding?

The very concept of polarity, in relation to welding equipment, means one or another connection option associated with current processes and the need to solve a specific problem. In order to change the polarity, you just need to swap the connection terminals. The current will change its direction and the physical processes, and the welding itself will proceed differently in each case.

There are two types of polarity that can be adjusted before performing work:

Straight polarity. Installed on the equipment before joining thick workpieces with deep seams. In this case, the electrode is connected to the negative terminal, and the metal being welded is connected to the positive terminal. Due to straight polarity, so-called anodic and cathode spots appear during the welding process. A hotter anode spot appears on the workpiece side. Due to this, the base metal is melted to a great depth, making it possible to weld cast iron, aluminum and other workpieces made of complex metals.
Reverse polarity. With this connection, the plus is connected to the electrode, and the minus is connected to the metal workpiece. An anode spot with an increased temperature appears on the opposite side, that is, on the electrode. The metal remains relatively cold, but the electrode heats up. This joining method allows you to weld thin-walled workpieces.

In accordance with specific tasks, the welder adjusts the forward and reverse polarity when welding with an inverter. Some young specialists do not know all the specifics of setting, so they sometimes have difficulty heating and melting workpieces made of different materials. It is recommended to first study the technical documentation of inverter welding and test the theory with practical actions.

Specifications for polarity selection

The polarity of the connection is selected based on the technical conditions necessary to solve a specific problem. By changing the connection type, it is possible to obtain a concentration of the anode hot spot either on the workpiece itself or on the electrode. Direct heating is carried out due to the positive terminal, so direct connection to it leads to heating of this area.

This connection feature makes it possible to select the operating mode taking into account the following factors.

Thickness of metal workpiece

When welding parts with medium and large thickness, you should use a direct connection. In this case, thermal energy is concentrated on the product itself, helping to obtain a deep weld.

In the same mode, it is possible to cut metals, regardless of their thickness. For welding thin sheet metals, it is recommended to use reverse polarity, where the main heat is concentrated on the electrode.

Due to this, it is possible to avoid overheating of the workpieces, and the melting of the electrode will occur much faster.

Types of metals to be welded

The ability to change the location of the anode heat spot allows you to select the operating mode that is most effective for a specific part.

For example, when welding cast iron or stainless steel, reverse polarity is used when welding with an inverter so as not to overheat the alloy and form a reliable connection. Aluminum, on the contrary, needs to be welded in direct connection mode in order to overcome the oxidative film as quickly as possible.

There are recommendations for setting up equipment for specific alloys, which should be carefully studied and used in practice.

Type of welding wire or electrode

These components also differ in their individual temperature regimes, which largely depend on the fluxes used. If welding is performed with carbon electrodes, then connecting in reverse polarity mode is not suitable, since the flux will be subject to severe overheating and the electrode will become unsuitable for work. In such cases, choosing the most appropriate settings depends entirely on the type of flux and wire.

Sometimes the metal and electrodes require completely different settings, and the welder has to select the most optimal combination of work cycles and amperage. In addition, it is necessary to take into account the manufacturer’s recommendations reflected in the technical documentation.

Features of welding with direct and reverse polarity

The direct and reverse polarity of the inverter have individual properties that must be taken into account when performing welding work.

Features of welding when connecting an inverter with direct polarity:

Electrodes and filler materials melt during operation and are transferred into the weld pool in the form of large metal drops. This leads to increased metal spattering and an increase in the penetration coefficient.
The direct connection mode is characterized by instability of the electric arc.
On one side of the workpiece, the depth of welding is reduced, and on the other, the amount of carbon introduced into the metal mass of the part is reduced.
The metal is heated correctly, its structure is not damaged and remains unchanged.
The welding wire or electrode heats up less, which makes it possible to increase the current if necessary.
Certain welding materials are characterized by an increased deposition rate, especially when consumable electrodes are used in active and inert gases. The same effect is obtained when additives interact with certain types of fluxes.
Straight polarity during welding affects the structure of the material remaining inside the seam between the welded metal parts. The result is a composition containing manganese and silicon in the complete absence of carbon.

Reverse polarity when welding with an inverter is necessarily used when workpieces made of thin sheet metals are welded. This process requires attention and caution, since there is a high probability of burning and damaging the material. This connection mode is complemented by other methods to avoid inadvertent damage.

Among them are the following:

A decrease in current strength, causing a decrease in temperature on the surface of the workpiece.
It is recommended to use an intermittent weld during the welding process. First, several sections are welded in different places, after which they are connected to each other into a single whole. This scheme may vary depending on the specific conditions of the metal connection. In this way, it is possible to prevent deformation of metal workpieces, especially if their length exceeds 20 cm. A larger number of segments makes each section shorter, and the metal warps much less due to this.
Welding of workpieces that are too thin is carried out with a periodically interrupted electric arc. The electrode quickly leaves the working area and immediately returns to its place and is ignited. The process runs almost continuously.
When joining with an overlap, the pressure of the workpieces against each other should be as tight and airtight as possible. The presence of even a slight air gap can cause burning of the part located on top. You can create a tight fit using some kind of weight or clamps.
When making butt joints, it is necessary to ensure a minimum gap between the products being welded. Ideally, there should be no gap at all.
If thin sheet workpieces have too uneven edges, then a material is placed under the welding joint in this place to compensate for excess heat. Copper or steel plates are best suited for these purposes, the thickness of which should preferably be chosen as large as possible.

For beginners who have just begun to master this type of connection, we recommend training welding with reverse polarity on damaged metal sheets. This will make it possible to feel all the features of the process and in the future avoid burns and other defects.

Source: https://electric-220.ru/news/poljarnost_pri_svarke_invertorom/2019-05-17-1690

Welding with direct and reverse polarity current

Depending on the conditions of welding work, various methods are used to connect the current circuit of the welding unit.

Direct polarity when welding involves connecting the positive bus to the workpiece being welded, and the negative bus to the working electrode. In the case of reverse supply of the supply current, the connection is made “exactly the opposite”.

The main difference is the connection

In the case of straight polarity, the welding cable is connected to the positive terminal of the machine, so that electrical charge carriers flow to it through the workpiece. The negative pole of the influx of charges is formed in the area of the welder’s main tool – the holder with the electrode.

The described difference in direct and reverse polarity of connection to inverters has a significant impact on the temperature regime in the welding zone.

Thus, direct connection increases the temperature at the anode pole of the arc discharge ("+" sign) compared to the cathode contact ("-" sign). This effect determines the possible scope of application of direct polarity when carrying out welding work.

The direct direction of the current ensures the release of significant amounts of thermal energy from the workpiece. As a result, direct polarity can be used for cutting large metal structures and massive steel products with thick walls.

When turned back on, the picture of the distribution of the released thermal energy is completely different. In this case, excess heat is observed on the electrode of the welding inverter, and on the side of the workpiece being processed, its level noticeably decreases.

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That is why reverse polarity is used in cases where it is necessary to minimize the risk of workpieces being rejected, as well as when carrying out jewelry-calibrated, precise work.

Reverse polarity is also used when welding thin-sheet materials and steels of varying degrees of alloying that are sensitive to overheating. The most widespread is the use of reverse switching current when working under submerged arcs, as well as in an environment of inert gases.

Direct and alternating current

In addition to the direct and reverse polarity of the voltage supply, the type of current (direct or alternating) has a great influence on welding. The dependence of the welding process in this case is manifested in the fact that when welding with direct direct current, the electrode burns out much longer.

The type and polarity of the current, as factors that jointly influence the characteristics of welding, makes sense to consider only for constant voltage.

When an electric arc is formed in alternating current mode, the concept of polarity is automatically excluded from consideration.

The influence of the type of supply voltage (DC or AC) affects the selection of welding equipment. It is expressed in the following contradictory factors:

when working with an inverter on direct current, it is possible to obtain a better and more reliable seam;
the same result is obtained when working with a semi-automatic machine;
on the other hand, most electronic and automated welding systems are sensitive to the supply voltage and require a stabilizer;
A conventional transformer converter does not have strict limitations in terms of supply voltage and can be started even with very low readings.

For this reason, if the operating network is highly unstable, it is best to purchase a conventional transformer unit operating in alternating current mode (sacrificing quality to some extent).

Otherwise, the electronic systems built into the inverters will automatically turn off at the most inopportune moment.

Influence on the choice of electrodes

The type of current also affects the choice of electrodes for welding. Thus, a unit operating on alternating current will be able to weld products only with electrodes specially designed for this purpose.

When working with such equipment, it is also possible to use universal consumables.

But this device cannot work with electrodes intended for use in direct current mode (UONII, for example). Note also that the inverter can cook with almost any consumables, but preference is usually given to universal rods.

Thus, the type of current, as a factor influencing welding procedures, determines the choice of a suitable apparatus and electrodes used in welding.

Features of each connection

Changing the polarity of the unit connection primarily affects the quality of the weld and the condition of the electrode. The use of reverse polarity when welding is characterized by the following positive features:

increased amount of thermal energy consumed from the electrode;
high-quality and deep penetration of the workpiece being processed;
minimal splashing from the side of the fused product.

In turn, the direct current limits the flow of heat to the workpiece from the electrode side and reduces its melting compared to reverse polarity. However, the electrode rod still melts quickly and requires frequent replacement.

When evaluating each of these modes, it cannot be guaranteed that one is preferable to the other.

At first glance, reverse current welding has a clear advantage, but other factors of the welding process must also be taken into account.

For this purpose, for most electrodes used in welding, the recommended polarity is indicated on their packaging (on a special label).

Working with a semi-automatic machine

The specific operation of semi-automatic units presupposes a certain speed of wire feeding to the junction of the workpieces and, accordingly, several welding modes.

This can be work either in an environment of protective gases (argon or carbon dioxide), or with a special powdered wire. In this case, the switching polarity depends on the specifically selected mode and is determined by the requirements for the efficiency of welding operations and their economy.

Reverse polarity is in demand when welding in a shielded gas environment, while direct polarity is most often used when working with flux-cored (flux-cored) wire.

Due to the correctly selected polarity of the current supply in semi-automatic mode, complete burnout of the flux and the formation of the required protective environment in the welding zone are ensured. In this case, the metal heats up noticeably less, and its splashing is reduced to the minimum possible for the given conditions.

Welders use straight polarity when handling such equipment when working with tungsten electrodes, most often used for fusing products made of non-ferrous metals.

Thanks to their use, it is possible to increase the temperature in the heating zone, which is very important for such a difficult-to-process metal as aluminum.

We can conclude that the choice of one or another polarity for connecting the supply voltage is determined by a number of factors, sometimes not related to the class of equipment used.

The main influence is exerted by the type of consumable (electrode) used, the material of the workpiece being welded and the operating mode of a particular welding unit.

Source: https://svaring.com/welding/teorija/prjamaja-i-obratnaja-poljarnost-pri-svarke

Reverse and direct polarity when welding with an inverter: direct and alternating current, model selection

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).

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).

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://tokar.guru/svarka/obratnaya-i-pryamaya-polyarnost-pri-svarke-invertorom.html

Reverse and direct polarity when welding with an inverter - features, pros and cons

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.

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.

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.

Change of polarities

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:

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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.

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

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.

Conclusion

To summarize all of the above, then using an inverter or semi-automatic welding machine for welding at home is a very common thing. But the correct choice of connection for direct current, as well as knowledge of what material needs to be cooked in what way, is the basic information necessary for the successful completion of the work. If this knowledge is available, then using these tools will not be a problem.

Source: https://FB.ru/article/348073/obratnaya-i-pryamaya-polyarnost-pri-svarke-invertorom---osobennosti-plyusyi-i-minusyi

Why is all this needed?

When welding with direct current, a thermal spot is formed at the tip of the electrode, which has a high temperature. Depending on which pole is connected to the electrode, the temperature at its tip will depend, and accordingly the mode of the welding process will depend. For example, if a plus is connected to a consumable, then an anode spot forms at its end, the temperature of which is 3900C. If it is minus, then you get a cathode spot with a temperature of 3200C. The difference is significant.

What does it give?

When welding with direct polarity current, the main temperature load falls on the metal workpiece. That is, it heats up more, which allows the root of the weld to be deepened.
When welding with reverse polarity current, the temperature concentration occurs at the tip of the electrode. That is, the base metal heats up less. Therefore, this mode is mainly used when joining workpieces with small thickness.

It should be added that the reverse polarity mode is also used when joining high-carbon and alloy steels and stainless steel. That is, those types of metals that are sensitive to overheating.

Attention! Since the temperatures at the anode and cathode spots are different, the consumption of the electrode itself will depend on the correct connection of the welding machine. That is, reverse polarity when welding with an inverter means excessive consumption of electrodes.

In the process of welding with direct current, it is necessary to ensure that the metal of the workpieces warms up well, almost to a molten state. That is, a weld pool should form. It is the direct and reverse polarity of the welding mode that affects the quality of the bath.

If the current strength is high, and therefore the heating temperature is also high, then the metal will heat up to such a state that the electric arc will simply repel it. There is no need to talk about any connection here.
If the current, on the contrary, is too small, then the metal will not heat up to the required state. And this is also a minus.

With straight polarity, an environment will be created inside the bath that is easy to control with the electrode. It spreads, so one movement of the rod creates the direction of the weld. At the same time, the welding depth can be easily controlled.

By the way, the speed of the electrode directly affects the quality of the final result. The higher the speed, the less heat enters the welding zone, the less the base metal of the workpiece warms up. By decreasing the speed, the temperature inside the weld pool increases. That is, the metal warms up well. Therefore, experienced welders set the current on the inverter to more than necessary. But the quality of the weld is controlled precisely by the speed of movement of the electrode.

As for the electrodes themselves, the choice of polarity is determined by the material from which it is made or the type of coating.

For example, using reverse polarity in DC welding, which uses a carbon electrode, leads to rapid consumption of weld rods. Because at high temperatures the carbon electrode begins to deteriorate.

Therefore, this type is used only in straight polarity mode. A clean, uncoated metal rod, on the other hand, fills the weld seam well when the polarity is reversed.

The depth and width of the weld also depends on the mode used. The higher the current, the greater the penetration. That is, the depth of the weld increases. It's all about the heat input on the arc. Essentially, it is the amount of thermal energy passing through a unit length of the weld.

But it is impossible to increase the current indefinitely, even regardless of the thickness of the metal workpieces being welded. Because thermal energy creates pressure on the molten metal, which causes it to be displaced. The end result of such electric welding at high current is burning through the weld pool.

If we talk about the influence of direct and reverse polarity when welding with an inverter, then a greater penetration depth can be provided by the reverse polarity mode.

What is straight polarity is defined. Some qualities of welds are indicated when carrying out the joining process in direct polarity mode. But some subtle points remain.

Metal from electrodes or filler materials is transferred into the weld pool in large drops. Firstly, this is a large splash of metal. Secondly, an increase in the penetration coefficient.
In this mode, the electric arc is unstable.
On the one hand, there is a decrease in the depth of penetration, on the opposite, there is a decrease in the penetration of carbon into the mass of the metal of the workpiece.
Proper heating of the metal.
Less heating of the electrode rod or filler wire, allowing the welder to use higher currents.
With some welding consumables, an increase in deposition rate is observed. For example, when using consumable electrodes in inert and some active gases. Or when using filler materials that are applied under certain types of fluxes, for example, OSC-45 grade.
By the way, direct polarity also affects the composition of the material found in the seam between two metal workpieces. Usually there is practically no carbon in the metal, but silicon and manganese are present in large quantities.

Features of welding with reverse polarity current

Welding thin workpieces is a process with increased difficulty, because there is always the danger of burns. Therefore, they are connected in reverse polarity mode. But there are other methods to reduce the danger.

Reduce the current potential to reduce the temperature on the workpiece.
Welding is best done with an intermittent seam. For example, make a small section at the beginning, then move to the center, then start joining from the opposite side, then start cooking the intermediate sections. In general, the scheme can be changed. In this way, you can avoid warping of the metal, especially if the length of the joint is more than 20 cm. The more welded sections, the shorter each section, the lower the percentage of metal warping.
Very thin metal pieces are welded by periodically interrupting the electric arc. That is, the electrode is pulled out of the welding zone, then quickly ignited again, and the process continues.
If overlap welding is carried out, the two workpieces must be pressed tightly against each other. A small air gap leads to burnout of the upper part. To create a tight fit, you need to use clamps or any weight.
When connecting workpieces, it is better to minimize the gap between the parts, and ideally there would be no gap at all.
To weld very thin workpieces with uneven edges, it is necessary to place a material under the joint that would absorb the heat of the process well. Typically a copper plate is used for this. It can also be made of steel. In this case, the greater the thickness of the auxiliary layer, the better.
It is possible to flange the edges of the welded products. The flange angle is 180°.

Experts recommend that before you start welding thin workpieces with reverse polarity, it is better to practice a little on a defective sheet of metal. It's better to spend time training than patching burn holes.

Source: https://svarkalegko.com/tehonology/pryamaya-i-obratnaya-polyarnost.html

Reverse and direct polarity when welding with an inverter: direct and alternating current, model selection - Machine

Features of reverse polarity welding

Direct and reverse polarity when welding with an inverter (or any other welding machine) sets the tone for the entire work process and the correct choice of this parameter directly affects the quality of the welded joint. With reverse polarity, “minus” is applied to the metal parts, and “plus” is applied to the electrode. In the case of direct polarity, the opposite is true. And this is just one of several features that need to be taken into account when welding. But today we will focus on reverse polarity.

In this article we will talk in more detail about reverse polarity when welding. You will learn what reverse polarity is, under what conditions this type of current direction is selected, what equipment is used when working with reverse polarity, and how to set up the device to get the job done efficiently and quickly.

general information

What is reverse polarity in welding? Reversing current polarity is the process of applying a positive electrical charge to the electrode and a negative electrical charge to the metal part being welded.

In this case, the heat is distributed in the reverse order: the electrode significantly overheats, but the part, on the contrary, does not warm up at all.

For this reason, reverse polarity in arc welding is used in special cases when there is a high chance of deforming the metal at high temperatures or a very neat seam is required. Due to exposure to high temperatures, the metal easily warms up, the seam is formed quickly and evenly.

Reverse polarity is simply necessary when welding stainless steel, thin metal, alloy and high-carbon steel, aluminum and other alloys that are easily subject to overheating. For example, a current of reverse polarity is a mandatory satellite of electric arc welding using flux or welding in an inert gas environment. You simply won’t be able to deposit metal well if you use, say, argon arc welding and set straight polarity.

Many beginners still wonder why some jobs use reverse or direct polarity when welding with an inverter? We will try to explain in more detail. Reverse polarity is used in work, since when the arc burns, areas with a high concentration of anodes and cathodes are formed at the end of the welding rod. In this case, the temperatures differ significantly; the anode region can be hotter than the cathode region by 700 degrees Celsius!

Based on this, it is not difficult to guess that with reverse polarity, a huge amount of heat is released, which contributes to high-quality welding of the metal. If this indicator is important for welding a particular metal, then reverse polarity is used. Direct current direction is used in all other cases.

By the way, when working with direct current of reverse polarity, the electrode burns out much faster than when working with direct polarity. This is again due to excessive heating of the rod. So be prepared to overuse components. If you are using alternating current, then the choice of polarity is not relevant at all, since the direction of the current will constantly change during operation.

So, let us repeat: polarity is set only when working with direct current. Reverse polarity is used when welding special, easily deformable metals, when the seam needs to be formed quickly and efficiently.

Welding with reverse polarity current cannot affect the properties of the electrode used in the work. A large amount of heat passes through the rod, which means that the part itself heats up very quickly, the metal is easily and deeply boiled, and there is practically no spattering (especially when welding with flux).

Is it possible to change the polarity directly during operation if the welding inverter (or any other type of equipment) has such an option? You can, of course, try this method as an experiment, but we will not recommend it to you. This is simply not necessary.

But sometimes there are situations when you started working with the wrong polarity and suddenly discovered this, so you want to set other settings. Try to finish what you started without changing the polarity (unless the requirements for the weld are very high). Yes, the electrode will stick, but you have to live with it.

If the seam should turn out to be of high quality and beautiful, then it is better to start the work again, setting a different polarity.

Polarity selection

Let's spend a little more time choosing the correct polarity. In addition to the metal itself, it is important to consider the electrodes or wire that you use in your work. The choice of direct or reverse polarity when welding depends on the type of coating.

If you work with a carbon electrode, then connecting in the opposite way is undesirable, since such rods quickly collapse when overheated.

If you use a wire that does not have any coating at all, then it will melt without problems even with straight polarity, but when used with alternating current it will not even heat up.

The choice of polarity is also influenced by what kind of seam you want to make, what size and shape it should have. When working with constant and reverse direction, the seams are well fused, the welded joint is narrow and shallow, since the welding process does not last long due to high temperatures.

Equipment

Welding with reverse direct current is carried out only on welding machines designed for such work. Choosing a welding machine is a very important topic, so in this article we will tell you only the most important things.

First of all, your welding machine must be able to work with different modes and feed wire at different speeds.

So you can weld with argon or carbon dioxide (this is very important when welding stainless steel), but you cannot weld with flux-cored wire, since this requires straight polarity.

With the help of reverse polarity, it becomes possible to use semi-automatic welding equipment in your work. Here the holder and ground are connected to “plus” and “minus”, respectively. Due to this, the flux burns out gradually and completely, and the welding itself occurs in the resulting gas cloud.

Instead of a conclusion

Choosing polarity when welding with DC is not an easy task if you are a beginner welder.

You need to take into account all possible nuances related to the type and thickness of the metal, the electrode or filler wire used in the work, and also successfully select a welding machine with the set of functions you need.

All this seems like something very complicated, but believe me, with experience you will set up the device and select components without even thinking. Study a lot of theory and don't forget to put it into practice.

Tell us in the comments about your personal experience with reverse polarity welding if you are an experienced craftsman. This will be very useful for beginners. Also share this article on social networks. We wish you good luck in your work!

Source: https://svarkaed.ru/svarka/obuchenie-svarke/osobennosti-svarki-s-obratnoj-polyarnostyu.html