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For a novice welder, choosing an electrode can be a problem: there are more than two hundred brands with different properties, purposes and characteristics. Moreover, about 100 brands are suitable for manual arc electric welding with inverter devices. It is impossible to tell about everyone, yes, for a start, and it is not necessary. Let’s just briefly describe the main types and which electrodes for inverter welding are more suitable for beginners than others. We will also talk about what diameter to take and what current to set for welding metal of different thicknesses.
What is an electrode and what is the coating for?
An electrode is a piece of metal wire coated with a special coating. During welding, the core melts from the temperature of the arc. At the same time, the coating burns and melts, creating a protective gas cloud around the welding area – the weld pool. It blocks the access of oxygen contained in the air. During the combustion of the coating, part of it passes into a liquid state and covers the molten metal with a thin layer, also protecting it from interaction with oxygen. So the coating ensures a good quality of the seam.
Any electrode is inspected before welding: the coating should not have chips. Otherwise, you will not achieve uniform heating and a high-quality seam. Also pay attention to the tip of the electrode: the thickness of the coating should be the same on all sides. Then the arc will come out in the center. Otherwise, it will be moved. For experienced welders, this is not scary, but for beginners it can create tangible problems.
It is necessary to monitor the humidity of the coating. Some of them ignite very poorly at high humidity (for example, SSSI). In connection with such a “capriciousness” of the coating, they must be stored in a dry place, providing, if possible, airtight packaging. You can put the box in a bag, and put a few bags of salt there, which are in shoe boxes.
Buying wet electrodes is not worth it: they can, of course, be dried, but their performance will decrease. If, nevertheless, it happened that the electrodes got damp, they can be dried in a conventional household oven at low temperatures (they are usually indicated on the packaging). The second way is to put it in a dry, well-ventilated area for a long time.
Types of coating and their characteristics
There are only four types of coatings:
- The main thing.
- Rutile.
- Sour.
- Pulp.
Basic (SSSI) and cellulosic coatings are only suitable for DC welding. They can be used on critical seams: they create a strong, elastic seam that is resistant to shock loads.
The other two (rutile and acidic) can work with both AC and DC welding. But the acidic coating is very toxic: you can work indoors only if the workplace is equipped with a forced exhaust.
Rutile coating has a greenish or blue tint, the electrodes are distinguished by easy ignition. They ignite well even if the inverter has a low open-circuit voltage (for reliable ignition of the main coating, a good volt-ampere characteristic is required, how to choose an inverter welding machine, read here.). When welding with rutile electrodes (MP-3), the metal almost does not spatter, but there is a lot of slag and it does not come off easily: you have to work with a hammer.
You may be interested in how to weld a gazebo from a metal pipe or how to make a shed on a pipe frame.
How to choose electrodes for inverter welding
First of all, the composition of the core is selected: it must be similar to the type of metal being welded. Structural steels are most often used in the household. The electrodes should be from the same wire. Sometimes you still have to cook stainless steel. Then the core must also be made of stainless steel, and for highly alloyed and heat-resistant ones they are made of metal with the same characteristics.
You can perform all the work around the house or at a construction site using just a few brands of electrodes:
- MR-3
- UONI 13/55
- ANO 21
- OK 63.34
They are recognized by many as the best electrodes for beginners who work with inverter welders: they are easier to work with, at the same time, they allow you to weld quality seams even without significant experience. Below are the characteristics and general application of those consumables that many experts consider good electrodes for the inverter. In any case, they are often recommended to novice welders to gain experience.
Rutile coated electrodes MP 3
Most often, beginners are advised to start mastering welds with MP-3 electrodes. They are easily ignited, even with a not very good current-voltage characteristic of the welding machine, they provide good protection for the weld pool, and make it quite easy to control its position. If the electrode does not ignite, bake it at a temperature of 150-180° for 40 minutes.
They are used in devices with alternating current (welding transformers) and direct current (welding rectifiers and inverters). Inverters are usually connected with reverse polarity (+ on the electrode). Suitable for any type of seam, except vertical top-down.
Read about the types of welding machines here.
MP 3 electrodes are not capricious to the quality of the welded surfaces. They can even be used on unfinished, rusty and wet parts. Welding is carried out with a medium (2-3 mm) or short arc.
The MP 3 feature is very important for beginner welders: they “hold” the arc well, it’s easy to work with them. For this, not all professionals love this brand: they call them sparklers. They cook too softly: slow movements are necessary for good warming up. What the pros do not like, beginners – what they need. Try to start learning welding with MP3. You should be able to do everything.
| Electrode diameter LEZ MR-3, mm | Length, mm | Recommended welding current, A | Pack weight, kg | Price, rub |
|---|---|---|---|---|
| 2,0 | 250 | 40-60 A | 1,0 | 146 |
| 2,5 | 300 | 60-100 A | 1,0 | 120 |
| 3 | 350 | 70-100 A | 1,0 | 95 |
| 4 | 450 | 80-170 A | 1,0 | 91 |
| 5 | 450 | 130-210 A | 1,0 | 91 |
UONI 13/55 with basic coating
These are, perhaps, the most widespread and popular electrodes with a basic coating. They are recommended for welding carbon and low alloy steels. Suitable for connections of critical structures. The seams are durable to shock loads and plastic, they tolerate the effects of low temperatures well.
The disadvantage of these electrodes is that they are well ignited only with a sufficiently large idle value of the inverter (above 70 V). The second significant drawback: high requirements for cleaning and processing of welded metals. If rust, dust, oil or other contaminants remain on the edge, the seam will be porous.
It is possible to work with UONI 13/55 only on DC welding machines, including those with inverters, with reverse polarity (+ is applied to the electrode), and with a short arc (keep the tip of the electrode closer to the surface to be welded). Minimum open circuit voltage 65 V.
| Electrode diameter UONI 13/55 (manufactured by Mezhgosmetiz) | Electrode length, mm | Recommended welding current, A | Retail price of a pack, rub |
|---|---|---|---|
| 2,0 | 250 | 30-60 A | |
| 2,5 | 300 | 40-70 A | 127 rub |
| 3 | 350 | 80-100 A | 116 rub |
| 4 | 450 | 130-160 A | 111 rub |
| 5 | 450 | 180-210 A | 110 rub |
ANO 21
This type of rutile coated electrode is designed to work with thin carbon steels. (Read about welding thin metals here.) When using them, the arc ignites easily (including when re-igniting), the seam turns out to be finely flaky (from small waves), and the slag is easily separated. Electrodes ANO 21 can be used for welding water or gas pipes.
They work with both alternating and direct current of any polarity. Before welding, heat treatment is necessary: they are calcined at a temperature of 120 ° C for 40 minutes.
| Diameter, mm | Lower electrode position | Vertical electrode position | Ceiling position of the electrode |
|---|---|---|---|
| 2 | current strength 50-90 A | current strength 50-70 A | current strength 70-90 A |
| 2,5 | current strength 60-110 A | current strength 60-90 A | current strength 80100 A |
| 3 | current strength 90-140 A | current strength 80-100 A | current strength 100-130 A |
Stainless steel electrodes OK 63.34
If you need to weld stainless steel, try OK 63.34. They can also weld structural steels. This results in a seam with a fine wave with a smooth transition to the main surface of the metal. The amount of slag is small, it fights off easily.
With this electrode, it is good to weld vertical seams in metal 6-8 mm, passing from top to bottom. Suitable for multi-pass welding of butt and lap joints. Works with direct and alternating current of any polarity, the minimum open circuit voltage is 60 V.
You will also need a mask for welding. To make it easier to work, take a chameleon welding mask.
How to choose the diameter of the electrode, how to connect it and what current strength to set
Choosing the brand of electrodes for the inverter is not all. Even if you have made up your mind, at least three questions remain:
- what electrode diameter to use when welding;
- what current to set;
- to which output “+” or “-” to connect the electrode.
About everything in order. Let’s start with what diameter of the electrode is needed for welding. In general, it is recommended to proceed from the thickness of the metals being welded: for small thicknesses, the electrode is taken with a diameter of the same size as the metal. If you weld metal 3 mm thick, then take the electrodes of the same size. If you cook something thicker, take 4 mm accordingly. But it will be difficult for beginners to work with large electrodes. Start mastering welding with a metal thickness of 3-4 mm. To do this, use electrodes 3 mm, or as they say “troika”.
Regarding which output to connect the electrodes. The technical specifications on the pack most likely indicate which polarity the electrode is intended for. When connected back, an electrode is connected to the positive output, and a clip is connected to the negative output, which is attached to the part. With direct polarity, a plus is planted on the part, a minus is applied to the electrode. How it looks on a welding inverter is shown in the photo.
How are these two connection types different? The flow of electrons has a different direction. As you know, electrons move from “minus” to “plus”. Therefore, when welding, it turns out that the element that is connected to the “+” heats up more. By changing the connection modes, you can control the intensity of metal heating.
Let’s consider several situations. For example, you have a 3 mm electrode, 2 mm metal. If you apply a “+” to the part, burnout may result. Therefore, in this case it is better to use reverse polarity, at which the electrode will heat up more. If you want to weld 6 mm metal with the same trio, it is better to do it on direct polarity: this way the heating of the metal will be deeper and the seam will be more durable.
How to choose a welding inverter read here. You may be interested in building a fence from corrugated board.
Welding current
In general, when installing the electrode, the welding current for the inverter is set depending on the diameter of the electrode used. In general, there are recommendations on each pack, but you can do without them: 20-30 Amperes of current are taken for each millimeter of diameter. It turns out a fairly wide range, but then you also need to consider how you will put the seam: with or without a gap. For welding without separation, lower currents are set, with separation – higher currents.
For example, for an electrode with a diameter of 3 mm, the calculated current is from 60 A to 90 A. Actually, they work in the range from 30 Amperes to 140 Amperes. When welding without interruption, a current of the order of 70-90 A is set, with a separation – 90-120 A. These parameters can “walk” in both directions: it also depends on the speed of the electrode tip, on the brand and “fluidity” of the steel being welded, on the position of the seam (for a vertical and horizontal seam they put a little less, for a ceiling – even less).
In general, even the currents recommended by the manufacturer are far from being a requirement. Start with them, and then choose so that it is convenient for you to work and the seam is good. You should get a high-quality connection, and you will select the ratio of current strength and movement speed experimentally. In this case, be guided by the state of the weld pool. She is your main indicator of quality.
Read about how to cook with inverter welding here.
Now you know not only how to choose electrodes for inverter welding, but also how to connect them, what diameter you need for this job, and how to select the current for each type of electrode and seam. Now let’s talk a little about holders for electrodes.
Holders for electrodes
One of the welding cables has a holder (holder) into which the welding electrode is inserted. They are of two types:
- with a trigger key, the electrode is clamped in them automatically when the spring-loaded key is released, released when it is pressed;
- threaded – the handle twists and unwinds, releasing or clamping the inserted electrode core.
Which one is better? It’s up to you, but by accidentally pressing the key, you can drop the electrode during welding. Nothing bad happens, but it’s annoying…
When choosing an electrode holder, the main thing to pay attention to is the current strength for which it is designed. Choose by the maximum parameter that is available for your welding machine.
How to connect the cable to the welding electrode holder with threaded clamp is shown in the video.
The disadvantage of the clothespin holder is that over time, the spring that presses the electrode core is weakened, the contact deteriorates. You have to put in a new one. How to do it on a clothespin, see the video.
Connecting the electrode holder for welding is easy. There is only one caveat: with frequent work, the welding cable is frayed by its edge. You can, of course, shorten the cable and reseal it, but you don’t always want to cut off even 10-20 cm. To prevent this from happening, find a hose whose inner diameter is the same or slightly smaller than the outer diameter of the welded cable. Cut off a small piece of it – 15 centimeters – and cut along. Now you can put it on the cable, pull it up and fix it there.