What it is?
When working with direct electric current, the electric welding process can be carried out using electric current with direct or reverse polarity.
When performing electric welding, the term “straight polarity” means that the electric current passes from the rectifier of the welding device to the surface of the workpiece with a positive charge. The positive terminal of the welding device is connected to the workpiece via a special electrical cable, and a negative electric charge passes through the electrode holder, which is connected to the negative terminal. Features of the electric welding process in this version are that the positive pole of the anode has a temperature significantly higher than the cathode, which serves as the negative pole. For this reason, the use of electric current with straight polarity is widespread when performing welding work on parts with thick walls. In addition, this method is also used for cutting metal, as well as in cases where the generation of a large volume of thermal energy is necessary to perform a particular process. As for performing the welding process using electric current of reverse polarity, to carry out welding work it will be necessary to change the connection order in the opposite direction. In this case, the negative charge of the terminal with the “-” sign will be applied to the working surface of the workpiece, and the positive charge from the terminal with the “+” sign will be directed to the welding electrode.
A feature of the reverse polarity of the welding electric current is that the entire potential of thermal energy falls on the electrode end of the rod, while the workpiece itself heats up much less. This version of electric welding allows you to carefully align the edges of the workpieces, minimizing the risk of through burning. Reverse polarity electric welding is used to work with alloyed or stainless steel grades of metal, with thin-walled parts, and in addition, it is suitable for those metals whose overheating during welding is extremely undesirable. Making a weld with electric current of reverse polarity is also effective for welding using flux or shielding gases.
Process Features
In direct direction, the welding cable connects the element being welded to the positive terminal of the machine. Thus, the positive charge reaches the workpiece from the inverter; the negative is supplied through an electrode holder.
This type of connection causes an increase in temperature at the anode (pole “+”) compared to the cathode (“-”). This determines the scope of use of direct polarity when welding. It is applicable for cutting metal structures, workpieces with thick walls, as well as in cases where it is necessary to generate a large amount of heat or create a high process temperature.
Reverse polarity when welding with an inverter is the supply of a negative charge to the metal being processed, and a positive charge to the electrode. The situation with heat release is the opposite - there is excessive heating on the consumable element, and insufficient heating on the workpiece being welded. Therefore, reverse polarity when welding is used if it is necessary to minimize damage to the workpiece during work, as well as for delicate work. It is used for permanent connections of materials such as:
- stainless steel;
- sheet metal;
- high-carbon or alloy steel;
- alloys susceptible to overheating.
The most well-known types of welding that use reverse current supply are flux-cored arc and gas-shielded welding.
Battery polarity
Polarity refers to the arrangement of current-carrying elements on the top cover or front side of the battery. In other words, this is the position of the plus and minus. The current leads are also made of lead, as are the plates inside.
Direct and reverse polarity
There are two common layouts:
- straight polarity;
- reverse polarity.
Straight
During the Soviet period, all domestically produced batteries were with straight polarity. The pole terminals are arranged according to the diagram - plus (+) on the left and minus (-) on the right. Batteries with the same circuit are still produced in Russia and the post-Soviet space. Foreign-made batteries that are made in Russia also have this terminal arrangement.
Reverse
On such batteries, the minus is located on the left and the plus on the right. This arrangement is typical for European-made batteries and therefore this polarity is often called “Europolarity”.
Accumulator battery
The different position schemes do not provide any special advantages. It does not affect the design and operational features. Problems may arise when installing a new battery. A different polarity will force the battery to change position and the wire may not be long enough. Also, the driver can simply mix up the contacts, which will lead to a short circuit. Therefore, it is important to decide on the type of battery for your car when purchasing.
Alternative option
Many drivers are not satisfied with a tablet constantly looming before their eyes, on a bulky design and with a charging cord. To avoid this situation, you can directly mount the tablet into the front panel.
Craftsmen will do absolutely anything for your money, the main thing is that there is enough free space and the will of the car owner. This option eliminates constant charging, since the device will be directly connected to the machine’s power supply.
But you need to take care of a normal charging adapter, because the voltage for the tablet and the general system may differ - this needs to be taken into account.
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Advantages and disadvantages of methods
Varying the polarity has different effects on the activity of the electrode. Thus, reverse polarity during welding has the following features:
- increased heat input to the workpiece;
- high-quality, deep penetration of the welded part;
- the electrode works longer (melts slowly);
- splashing of liquid metal from the workpiece is minimized.
Forward current has the following features:
- the heat flow to the workpiece is minimal;
- the penetration of the part is high, but lower than with reverse polarity;
- the working element quickly melts, requiring replacement;
- metal splashes with maximum probability.
Can we say with certainty that one method is preferable to the other? Welding with reverse polarity current has more obvious advantages, but the choice is not determined solely by the advantages. For most electrodes, the recommended polarity is indicated on the label.
How to determine?
It's not that hard to find out. First you need to turn the battery with the front side facing you. It is located on the side where the stickers with characteristics and logo are located. Also, the pole terminals are located closer to the front side.
On many batteries you can immediately see the “+” and “−” signs, which accurately indicate the polarity of the contacts. Other manufacturers indicate information in the markings or highlight the current leads in color. Usually the plus is red and the minus is blue or black.
In the marking, reverse polarity is indicated by the letter “R” or “0”, and direct polarity by the letter “L” or “1”.
Which one should I use?
One of the important criteria on which the choice of electric welding polarity is based is the composition of the welding electrode coating. Depending on the electrode material, the electric welding mode is selected. For example, black carbon rods, which tend to heat up quickly, are not suitable for reverse polarity welding. Such electrodes will quickly collapse, and the electric welding process will be constantly interrupted; in addition, they are not suitable for thin metal.
The correct selection of the electrode in this case depends on the composition of the workpiece material. If you take an uncoated electrode, then when electric welding under conditions of direct polarity it will melt and burn well, but if you work with such wire under alternating electric current conditions, the uncoated electrode will not burn. The strength and appearance of the weld depends on the polarity of the poles. To obtain the deepest penetration of metal, you will need to use technology using direct current with reverse direction. With this arrangement of poles, the maximum gain of thermal energy will be in the anode region.
The use of electric welding with reverse current direction is considered the most popular. The welding machine can feed welding wire at a certain speed, which will determine the choice of certain welding technology options. Reverse polarity electric current is used for working in shielding gases, and forward polarity welding is used when working with flux-cored welding wire.
The direct direction of electric current is used to work with non-ferrous metals, when a tungsten electrode is used for welding metal.
The forward and reverse direction of the electric current is selected based on a number of factors, the main ones being the composition of consumables, the equipment used, the type of metal of the workpiece and its thickness. Regardless of which polarity of electric current is selected, there are certain nuances that are important to consider.
It is known that using constant electric current, it is possible to obtain a welded joint without the presence of large scale formation due to spatter. The cooled seam is neat and durable. Such characteristics of the seam are explained by the fact that when working with direct current, there is no frequent change of polarities, in contrast to working with an alternating type of electric current supply.
In the case when consumable-type electrodes are used for the welding process, due to the difference in heating between the cathode and anode, burn-through of the surfaces of the workpieces is possible. To avoid burning through the workpiece in the area where it is connected to the electrical cable, use a clamping clamp.
The charge carried by the cable does not play a role - in both cases, the clamp acts as additional protection for the workpiece.
Rules for choosing polarity
The main criterion for choosing direct or reverse polarity when welding is the electrode coating material. For example, carbon consumables heat up very quickly when the elements are connected in the opposite way and, as a result, are destroyed. A wire that does not have any coating burns well with straight polarity, but does not burn at all when using alternating current.
The dimensions and shape of the resulting seam also depend on the location of the poles. For example, deeper penetration is possible with a constant reverse current, which is due to increased heat generation at the anode and cathode.
It is important to remember that the faster the welding process is carried out, the smaller the width of the seam and the depth of penetration become.
Sheet metal thickness
Parts whose thickness does not exceed 3 mm are often burned through. To weld such workpieces, a reverse-polar scheme is used, providing an anode thermal spot at the edge of the electrode. This approach is appropriate when processing non-ferrous, alloyed materials.
Types of metals
The positive terminal is responsible for the final heating of the products and the holder. The cathode generates less heat than the anode. When machining refractory steels, it is better to use direct connection when the temperature reaches 4000 °C. For metals that change characteristics when overheated, connect the negative terminal. With direct-polar processing, the seam deepens; with “reverse” processing, it concentrates on the surface.
Types of electrodes
When choosing the brand of electrodes, take into account the type of current. Any variety is suitable for alternating voltage, since polarity does not play any role in this case. For varieties OK, OZS, MR, reverse connection is recommended. UONII and similar modifications are designed for a direct circuit. Manufacturers' recommendations are indicated on the packaging. Many welders prefer universal analogs to other options.
Additives and other consumables
Refractory electrodes used to create an arc are often used with straight polarity. Working with surfacing wire involves the use of only tungsten elements. Coal analogues are unstable to high temperatures, become brittle and crumble.
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.
But steel, cast iron with various steel alloys require reverse connection of direct welding current: they do not need any additional heat due to the risk of the formation of refractory compounds.
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?
Selecting an inverter and its operation
To quickly switch polarity when working with thin and thick metals, the inverter must have reliable power cable connectors. The flimsy thin pins in the connector and the low rim for fixing quickly wear out from frequent rearrangements. Then there will be a backlash, the cable sockets will dangle, increased resistance and overheating will form. The welding current will drop, and an electric arc may even form between the connector and socket.
Select reliable MMA inverters with durable sockets so that when changing polarity, nothing wears out or dangles. If you already have an inverter and its connectors are worn out, you can replace them with stronger ones by choosing from a catalog of connecting cable connectors.
Welding thin metal with a 1.0-1.5 mm coated electrode is a difficult task for a beginner. RDS inverters with the “Anti-stick” function will help you cope with it without burns. When the tip of the electrode is immersed in the weld pool, the machine “feels” this and turns off the welding current. As a result, there is no holding force; you do not need to tilt the holder left or right to lift the electrode from the surface. The coating of the consumable does not crumble in this case.
The Arc Force function also helps when welding thin metal with reverse polarity. When the electrode is about to stick, the inverter automatically increases the current by 10A, maintaining the electric arc. As soon as you have restored the air gap, the device itself reduces the current strength to its previous value, eliminating burn-through.
What equipment to use
The reverse direction is required in work with special installations. The specificity is that the machine feeds the wire at a certain speed to the workpiece, so several types of welding can be selected.
For example, in a protective gas environment (when argon or carbon dioxide is used), or using powder-treated wire. Reverse direction of current is applicable when working with gases, direct - when the process is performed with cored wire (also known as flux-cored wire).
Semi-automatic welding involves a number of process changes. Firstly, the connection of the “holder” and “ground” changes - on the first “plus”, on the second “minus” (reverse). This is done so that the flux burns out completely, and the welding process occurs inside the resulting gaseous cloud. The metal will heat up less, and the splashing of droplets will be minimized.
The straight line is used for welding non-ferrous metals, when the working consumable element is a tungsten electrode. In this way, an increase in temperature in the heating zone is achieved, which can be critical for, for example, aluminum.
When working with alternating current, the user’s task is to change consumables in a timely manner. Professionals or advanced amateurs prefer direct current as a reliable guarantee of high-quality welding. Working with an inverter allows you to choose one of two known options. Direct and reverse polarity when welding are used in methods, each of which has its own advantages and disadvantages. The choice of direction is dictated by a number of factors, the main of which are the material of consumables and the equipment used.
Patterns of choice
Why is reverse polarity chosen for some jobs, and direct polarity for others when welding?
Let's answer this question by considering the thermal features of the process using reverse direction. When a welding arc burns on a workpiece, a pair of areas called anode and cathode spots appear at the end of the electrode. The difference in their temperatures sometimes reaches 800 degrees Celsius (in favor of the anode). That is, the amount of heat generated on the workpiece during operation is quite large, and the method is more suitable for high-quality welding of seams.
It is noteworthy that when operating with direct current of straight polarity, the combustion rate of the electrode metal is 20-40% lower. But for alternating current, observing polarity is not relevant at all - its peculiarity is that the direction of the current changes 100 times per unit of time.
What does direct and reverse polarity give when welding with an inverter?
When welding metal with direct current, the temperature at the end of the electrode depends entirely on which pole will be connected to it. With reverse polarity, when a plus is connected to the electrode, the temperature at the end of the electrode reaches 4000 degrees. When the inverter is switched to direct polarity, when minus is applied to the electrode, this temperature is significantly lower, almost 1000 degrees.
Thus, by changing the forward and reverse polarity of the inverter, you can more finely control the welding process.
First of all, this applies to welding thin and thick metals, when it is necessary either not to burn through the metal, or, on the contrary, to achieve a high-quality and reliable connection.
What does changing the polarity on the inverter give?
From all of the above, it becomes clear what welding in direct and reverse sequence gives:
In general, welding in reverse polarity with an inverter is recommended when welding thin metals and stainless steel. In other words, those types of metal that are very sensitive to overheating.
In this case, it is worth considering one important nuance, which is associated with the consumption of electrodes. When welding with an inverter on direct and reverse polarity, the rate of electrode combustion will be different. When welding with an inverter at reverse polarity, due to strong heating, the consumption of electrodes will be much higher than at direct polarity.
Why do you need a holder?
For most, the answer will seem obvious, but there are car owners who really do not understand why such a device is needed. Firstly, you can attach not only a smartphone to it, but also a navigator and other similar devices, whose display must be in front of your eyes without losing sight of the road. Secondly, this allows you to conveniently position the device for charging.
How to properly connect a welding inverter
Many novice welders do not know that an inverter can be used to weld in different ways. They still use it this way, the standard connection is positive to the electrode and negative to the metal.
However, if you connect the inverter differently, the electrode to the minus, and the metal to the plus, you can achieve better deepening of the weld. In simple words, with this connection of the inverter, the main temperature will fall on the metal, as a result of which the workpiece will warm up better.
Well, and, on the contrary, with a “standard” connection of the inverter, when the electrode is connected to the plus and the metal to the minus, it will be possible not to burn through the thin workpiece. How does it work and what is the point? How to connect the inverter correctly, positive to electrode or negative? Read in this review.
Features of welding with reverse polarity current
When carrying out welding work to connect metal products of small thickness, there is always a high probability of so-called burn-throughs. Therefore, to perform such complex, labor-intensive work, as a rule, the welding machine holder is connected to the plus, and the product being welded to the minus. When using this mode, welding of metal structures, as well as workpieces, is carried out using an intermittent seam. Simply put, when joining them, first a small section is welded at the beginning of the seam, and then its central part is welded.
For correct, reliable welding of products made of thin metal, during welding work, the arc must be periodically interrupted. Simply put, the welding electrode needs to be pulled out of the welding area, and then quickly ignited again.
If it is necessary to do overlap welding, then the metal parts to be joined should be securely, hermetically and tightly pressed against each other. Otherwise, even if there is a small air gap, a burn will appear on the top of the part being welded. In order to securely secure the workpieces together, it is recommended to use clamps or a large load before performing overlap welding.
The choice of welding mode primarily depends on the tasks assigned to the welder. When it is necessary to weld non-ferrous metals together, as a rule, direct polarity is used. In addition, it is more expedient to use it for working with massive, thick workpieces, since the metal will be melted much deeper, which will ensure good quality of the seam. It is also more suitable for cutting metal structures. Reverse polarity is recommended for use in cases where it is necessary to weld high-alloy steel or thin sheet metal.
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.
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.
Is it possible to install a battery of a different polarity?
This question often arises among those who inadvertently bought a battery of a different type. Theoretically, this is possible, but it will require costs and unnecessary red tape with installation. The fact is that if you buy a battery with reverse polarity for a domestic car, then the length of the wires may simply not be enough. You can't just lengthen the wire. It is necessary to take into account the cross-section and diameter of the terminals. This may also affect the quality of current transmission from the battery.
The best option would be to replace the battery with another one with a suitable contact arrangement. You can try to sell the purchased battery so as not to be at a loss.
Connecting a welding inverter - plus and minus
As mentioned above, many novice welders do not pay enough attention to polarity when welding with an inverter. And to be more precise, some have never heard anything about it.
As a result, a lot of problems arise - thin metal is quickly burned through, while thick metal, on the contrary, is not sufficiently fused. Just try experimenting when connecting the inverter.
To begin, connect the holder to the plus of the device, and start cooking, and then connect the inverter, on the contrary, with the holder to the minus. You will definitely feel the difference.
It's all about polarity, since a welding inverter, unlike an AC transformer, produces direct current. And if on transformer machines there is no such difference in connecting cables, then when welding on direct current, it is still the same, and, moreover, significant.
What does polarity mean when welding?
In inverter welding machines, inscriptions are used to indicate polarity
. Considering the issue of polarity, it is clear that welding in this case is carried out with a constant voltage current. The welding inverter terminals, where the power cables of the electrode holder and ground are connected, are marked with “+” and “-”. Usually, when connecting such a device and starting to operate it, many, guided by the instructions or recommendations of a familiar specialist, do not think about why they hang this particular wire and not another wire on a specific terminal.
But there is still a difference, and here lies the unambiguous physical law of motion of charged particles - electrons. Electrons, having a negative charge, always move from minus to plus in any circuit, including an inverter. When welding, you can connect the electrode to both the positive and negative terminals - everything will work. But the electrons in both cases will move in different directions along the circuit, this will affect the process and the final result.
Direct polarity connection
If the circuit is assembled in such a way that the plus from the inverter goes to the steel workpiece (the part being welded), then through the arc gap, the welding electrode to the minus of the inverter, then such a connection is called direct polarity when welding. In this case, the anode is the part, and the cathode is the electrode. The connection point on the part will heat up more than the tip of the electrode, approximately 700 degrees Celsius.
Reverse polarity connection
The connection diagram for the cables of the welding machine, when the plus from the inverter comes to the welding electrode, then through the arc gap hits the work piece and the minus of the inverter, is called reverse polarity during welding. Here the electrode will heat up more strongly, since the anode spot will be on it, and the cathode spot will be in the area where the steel workpieces are connected.
Direct and reverse polarity when welding
Thus, when connecting a DC welding machine, you can connect the electrode holder to the positive or negative terminal. If the holder with the electrode is connected to the positive terminal of the welding arc source, then we get reverse polarity.
Reverse polarity is characterized by greater heating of the electrode, since where there is plus, the temperature will always be higher. This connection will make it possible not to burn through metal of small thickness, since the main concentration of temperature during welding will be on the electrode, and not on the metal being welded.
And vice versa, if the holder with the electrode is connected to the negative terminal, and the ground holder to the positive terminal, then the metal will heat up the most. Straight polarity is used when welding metal workpieces of significant thickness. When welding, this mode allows the metal to melt well and sufficiently deepen the root of the weld.
Types of welds
Differences in welding modes
When welding with constant current, a thermal spot with a high temperature appears at the tip of the consumable. Depending on the pole connected to the electrode, the welding mode is selected. For example, if a positive terminal is connected to the electrode, an anode spot with a temperature of 3900 degrees Celsius will form at its end; if a negative terminal is connected, the spot will be cathode, and its temperature will reach 3200 degrees Celsius. This is the main difference between the two methods.
Connecting welding cables with different polarities.
When welding with direct polarity is used, the main part of the temperature load is received by the metal part. As a result, it is easy to deepen the weld seam. In the case of reverse polarity, the heat is concentrated at the end of the electrode. In this case, the parts at the joints heat up less, which is advisable for welding workpieces of small thickness.
The work involves heating the metal until it melts, that is, the formation of a weld pool, the state of which is influenced by the choice of welding mode with reverse or direct polarity:
- If the current is too high, the electric arc will begin to push away the heated metal. In this case, the parts cannot be connected;
- if the voltage is insufficient, the metal will not heat up to the desired state.
With straight polarity, a spreading medium is created in the bath, where you can guide the electrode, directing the weld and controlling its depth. The final result depends on the speed of the electrode. The smaller it is, the more heat enters the welding zone and the better the metal warms up. The depth and width of the weld depend on the mode used.
Diagram for connecting poles with reverse polarity.
Important! The higher the current and driving energy on the arc, the deeper the penetration. The greatest penetration depth can be achieved using the reverse polarity welding mode.
As for the choice of consumables, it is recommended to use clean uncoated metal rods for welding in reverse polarity mode, and carbon electrodes for direct welding.
Some features of welding with direct polarity
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.
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.
