Electrodes for welding thick-walled high-pressure pipes. What electrodes are needed for welding pipes, profiles and other metal structures. Electrode selection criteria

There is a misconception that the quality of the weld depends only on the performer, but this is far from the case, and any good welder understands this - electrodes for welding heating and water pipes play an important role in such work.

First of all, it should be noted that such conductive rods can be either metallic or non-metallic, that is, carbon or graphite, but in in this case, the second type does not interest us.

Let's look at what signs can be used to distinguish consumables of this type, how best to choose them, and the video in this article will demonstrate visual information on our topic.

How are they distinguished?

Electrodes made of metal can be consumable or non-consumable. The first type can be coated, with a steel, cast iron, bronze, copper or aluminum rod, but uncoated ones are currently used only in the form of wire (see photo above) when welding work is carried out in a gas protective environment.

The non-melting type includes intruded, thoriated, lanthanum, and tungsten, therefore, it is quite natural that their price is much higher.

In addition, electrodes are classified according to their purpose, that is, according to the type of material to be processed. For high-carbon steel according to GOST 9467-75, the material is marked with the letter U, for alloy and heat-resistant steels - with the letter T, but for deposition of the surface layer - with the letter T.

Tungsten – TIGWIG

In most cases, there is a coating on the rods, but it also varies and has its own marking according to GOST 9466-75.

For example:

• thin coating is marked with the letter A (international format - A);
• middle – letter C (international format – B);
• thick - letter D (international format - R);
• and especially thick - with the letter G (international format - C).

In addition to the thickness of the coating layer, it is classified according to its type:

• A – sour;
• B – basic;
• C – cellulose;
• R – rutile;
• P – mixed.

In addition, the mixed layer can be:

• AR – acid-rutile;
• RB – rutile-basic;
• RP – rutile-cellulose;
• RZh – rutile, with an admixture of iron powder.

Note. Due to the fact that welding work can be carried out in different positions, electrodes here are classified into different types.
So, they can be for the lower position, vertical from bottom to top, horizontal and lower in a boat.
The instructions also include rods for any position.

By appointment. Types of materials

• Carbon and low alloy structural steels. In this case, the temporary tensile strength can be up to 60 kgf/mm or 600 MPa.
• High alloy steel types, which are endowed with special properties.
• Structural steels, where applicable arc welding. Here the temporary tensile strength will already be more than 60 kgf/mm or 600 MPa.
• Surfacing of the surface layer of metal, which has special properties.
• Cast iron.
• Non-ferrous metals. (See also article.)

More about coverage

• A – acid or sour coating. It contains oxides of iron, manganese and silicon.
• B – basic. It contains calcium fluoride and calcium carbonate. Welding work using such electrodes is carried out with direct current of alternating polarity.
• C – cellulose. It contains flour and other organic components, which are intended to create a gas protective shell during production welding work.
• R – rutile. It contains rutile as the main component, as well as other mineral and organic components. Besides gas protection Such components can significantly reduce spattering during seam production.

Note. IN household use(heating, frames) everything is somewhat simpler, since for all cases they usually use electrodes with a main (B) coating, the diameter of which depends on the thickness of the metal.
For example, if you are interested in which electrodes to cook profile pipe, then given the thin profile wall (1.0-1.5 mm), you are better off using a rod with a cross-section of 2 mm.
Depending on the welding (transformer or inverter), you will select the consumables itself (for alternating or direct current).

Consumption rates

For heating installation, the consumption rates of electrodes when welding pipes may be different, depending on the type of seam, but we will consider only a vertical connection without beveled edges, as the most commonly used.

Consumption of electrodes when welding pipes per meter of seam

Consumption of electrodes when welding pipes per joint

Note. By by and large Electrodes of any type are classified as one of the groups of welding materials.
In addition to them, this includes filler rods, wire, shielding gases and filler fluxes.

Conclusion

As you noticed, there are quite a few brands of electrodes, but if you want to heat your home with your own hands, then you immediately need to select materials for high-alloy and non-ferrous steels, as well as cast iron.

In addition, the thickness of the walls of heating pipes is usually at least 2 mm, then a 3 mm rod is needed. In addition, you will need an electrode for all positions, with a medium coating (C) type, acid (A) or basic (B), for carbon and low-carbon steels.

For manual electric arc welding For joints of pipelines and boiler pipes made of carbon, low-alloy and high-alloy steels, it is necessary to use electrodes that meet the requirements of GOST 9466-75, 9467-75 and 10052-75. The brand of electrodes for welding pipe joints should be selected depending on the grade of steel being welded (Table 10.24).

Electrodes for welding fastening parts made of high-alloy steels to superheater pipes and other boiler or pipeline elements made of low-alloy pearlitic steels, as well as for welding fastening parts to each other, must be selected according to table. 10.25. To weld fasteners (made of steel of any grade) to pipes made of austenitic steel, austenitic electrodes OZL-6, TsL-25, ZIO-8 and other types E-10Х25Н13Г2 or electrodes EA-400/10у and EA-400/10t should be used. The fasteners must be welded to pipes made of EI 756 steel (regardless of the steel grade of the fastenings) using ZIO-8, EA-400/10u or EA-400/10t electrodes.

The technological properties of the electrodes of each batch must be checked before their use, regardless of the presence of a certificate. This inspection must be performed by a certified welder. Alloy electrodes intended for welding boiler tube systems and pipelines made of alloy steels must be checked for compliance with the grade composition by styloscopy of the deposited metal. Electrodes TsT-15 and TsT-26 are also checked for ferrite content in the deposited metal. This check should precede all other electrode tests.

Before welding production joints and testing, electrodes must be calcined (dried) under the following conditions:

• electrodes with basic coating for welding pearlitic (carbon and low-alloy) steels (UONI-13/55, TsU-5, TMU-21, TML, TsL-39, TsL-20, etc.) – at 380–420 °C for 1 hour; if after this the electrode coating noticeably loses strength (the coating crumbles), the temperature should be reduced to 350 °C and the holding time to 0.5 hours;
• electrodes with basic coating for welding austenitic steels – at 200–250 °C for 1 hour;
• electrodes with rutile coating, as well as mixed coating, for example, rutile-basic or ilmenite (MR-3, OZS-6, OZS-4, etc.) - at 150–200 °C for 1 hour;
• electrodes with cellulose coating (VSC-4) – at 100–110 °C for 1 hour.

electrodes with a basic coating intended for welding pearlitic steels should be used within 3 days after calcination, other electrodes - within 15 days. After specified period Electrodes must be calcined before use.

The technological properties of electrodes intended for installation welding of pipelines and boiler pipes made of carbon and low-alloy steels (except for boiler heating surface pipes) must be determined in the process of melting the electrodes when welding in the ceiling position of a one-sided T-joint of two shoulder straps in one layer 150 mm long, cut from pipes, or two plates measuring 180x140 mm (Fig. 10.2).

Fig. 10.2. Welding T-joints of plates (pipe straps) to determine the technological properties of electrodes

The technological properties of electrodes can also be checked when welding the ceiling section of pipes of appropriate diameters or when welding a vertical joint of pipes with a diameter of 133–159 mm, a thickness of 10–18 mm, made of the appropriate steel. Welding must be carried out with preliminary and accompanying heating, if it is provided for a given grade of steel. After welding the T-joint, the weld and fracture are inspected. After welding the pipe joint, the seam is ground to lathe with removal of a layer up to 0.5 mm thick or illuminated with gamma or x-rays to determine the continuity of the deposited metal. To facilitate the destruction of the sample, it is allowed to make a cut in the middle of the seam on the reinforcement side with a depth of no more than 20% of the thickness of the plates being welded.

Note.

Technological properties of electrodes intended for welding pipelines in factory conditions in the lower or vertical position, can be determined when welding in a vertical position.

* Electrodes ANO-6M, MR-3, OZS-4, OZS-6, ANO-12, ANO-14 are intended for welding on both alternating and DC reverse polarity (+ on the electrode), VSC-4 electrodes on direct current of any polarity, other brands of electrodes - on direct current of reverse polarity.

** Can be used for welding the following products made of carbon steels: steam and hot water pipelines of categories 3 and 4; pipelines within the boiler and turbine with a working pressure of no more than 3.9 MPa (39 kgf/cm2) and a temperature of no more than 350 °C; pipes of heating surfaces of boilers with operating pressure up to 5 MPa (50 kgf/cm2); pipelines that are not subject to the rules of Gosgortekhnadzor, except for turbine control pipelines, oil pipelines and fuel oil pipelines.

*** For welding only the root layer of gas pipeline joints with a diameter of 219 mm or more without backing rings.

Notes:

1. If the project provides for pipes made of carbon steel, and pipes made of low-alloy steel of the same dimensions (diameter and wall thickness) are installed, then it is allowed to use carbon electrodes with a basic (calcium fluoride) coating.

1 For DC welding with reverse polarity.

Welding wire

For manual and automatic argon-arc welding with a non-consumable electrode, gas (acetylene-oxygen) welding, semi-automatic in carbon dioxide and automatic welding Submerged arc welding wire must be used that meets the requirements of GOST 2246-70. The brand of welding wire should be selected according to the table. 10.26. For manual and automatic argon-arc welding of joints of steam superheating pipes made of steels 12Х2МФБ and 12Х2МФСС, wire grades Sv-08МХ, Sv-08ХМ, Sv-08ХМФА or Sv-08ХГSMFA should be used, from steel 12Х11В2МФ - Sv-07Х25Н13 or Sv-04Х19Н11МЗ; from steels 12Х18Н10Т, 08Х18Н10Т, 12Х18Н12Т and 08Х18Н12Т – Sv-04Х19Н11МЗ or Sv-04Х19Н9.

Each batch of wire must have a certificate indicating the manufacturer, its brand, diameter, heat number and chemical composition. Each coil (coil) of wire must have a tag attached to it indicating the manufacturer, its heat number, the grade and diameter of the wire in accordance with GOST 2246-70.

If there is no certificate or tag, or if there is any doubt about the quality of the wire, it is necessary to check its chemical composition. If results are unsatisfactory chemical analysis repeat the analysis on twice the number of samples. If the results of the repeated analysis are unsatisfactory, the wire is rejected.

The surface of the wire must be clean, free of scale, rust, oil and dirt. If necessary, it is cleaned of rust and dirt. sandblaster or by etching in a 5% solution of hydrochloric or inhibited acid (3% solution of hexamine in hydrochloric acid). You can clean the wire by passing it through special mechanical devices(including through devices filled with welding flux, bricks, fragments of emery wheels and felt filters). Before cleaning, it is recommended to anneal the coil of wire at 150–200 °C for 1.5–2 hours. It is also allowed to clean the wire with emery cloth or another method until it has a metallic shine. When cleaning wire intended for automatic welding, do not allow it to be sharply bent (fractured). In all cases, after cleaning, the wire must first be washed in a 12–15% aqueous solution soda ash at 70–90 °C, then at hot water and air dry.

Each coil (hank, coil) of alloyed wire before welding (regardless of the welding method) must be checked by steeloscopy to determine the main alloying elements. The ends of each coil (skein, reel) are steeloscoped. If the steeloscopy results are unsatisfactory, this coil cannot be used for welding until the exact chemical composition of the wire is determined by quantitative chemical analysis.

Flat consumable rings, used as an additive for the root layer during automatic argon-arc welding of pipeline joints with a non-consumable electrode without remaining backing rings, are made from wire with a diameter of 3 or 4 mm. The grade of wire is selected depending on the grade of steel of the pipes being welded according to the table. 10.26. The cross section of the melting ring is shown in Fig. 10.3.

Rice. 10.3 Section of a melting flat ring Table 10.26. Application areas of welding wire

* For manual and automatic argon arc welding of the root layer of pipelines with a thickness of more than 10 mm made of chrome-molybdenum and chrome-molybdenum-vanadium steels, Sv-08G2S or Sv-08GS wire should be used.

Flux for automatic welding

For automatic submerged arc welding of rotary joints of pipes made of carbon and low-alloy structural steel, AN-348A or OSTS-45 flux should be used.

The flux must be stored in a dry place at relative humidity no more than 50% and a temperature not lower than 15 °C.

Before use, the flux must be calcined at 300–400 °C for 5 hours, after which it can be used for 15 days. After the specified period, the flux should be calcined again before use.

Argon, oxygen, acetylene and carbon dioxide

As shielding gas for manual and automatic argon-arc welding with a non-consumable electrode, argon of the highest, first and second grades with physical and chemical indicators in accordance with GOST 10157-79 is used (Table 10.27). Both gaseous and liquid argon can be used equally.

1 Corresponds to the indicators of argon gas obtained by complete evaporation of a sample of liquid argon.

For gas acetylene-oxygen welding, it is necessary to use gaseous oxygen that meets the requirements of GOST 5583-78 for the highest or first grade (with a volumetric oxygen content of at least 99.2%). Dissolved technical acetylene in accordance with GOST 5457-75, supplied to the consumer in cylinders or obtained locally from calcium carbide that meets the requirements of GOST 1460-81, should be used as a flammable gas.

For semi-automatic welding in carbon dioxide, welding carbon dioxide of the first and second grade or food grade according to GOST 8050-85 is used as a shielding gas. Use of technical carbon dioxide not allowed.

Before using gas from each cylinder, the quality of the gas should be checked by fusing a roller 100–150 mm long and appearance surfacing surfaces determine the reliability of gas protection. If there are pores in the weld metal, the gas in this cylinder is rejected.

Tungsten electrodes for argon arc welding

For manual and automatic welding in an argon environment, rods of lanthanum tungsten or yttriated tungsten brand SVI-1 with a diameter of D= 2÷4 mm (Fig. 10.4).

Rice. 10.4. Tungsten electrode sharpening shape

To easily excite the arc and increase the stability of its combustion, the end of the tungsten electrode is sharpened into a cone (Fig. 10.4). In this case, the length of the conical part l should be 6–10 mm, and the diameter of the blunting

During construction country house important proper planning engineering communications. At the project stage, heating, water supply and drainage schemes are laid out. Today there are a large number of technological solutions to these issues. There are tap and heating pipes PVC and classic metal pipes.

The choice of pipe type is influenced by a large number of factors. But despite the increased popularity polymer products, metal pipes remain popular and are often used when creating utility networks.

In order to finished design was strong and durable, it is necessary to connect all the joints correctly. The main connection method metal pipes is welding. And the quality of welding is influenced not only by the skill of the master, but also by the correctly selected brand of electrode suitable for connecting such products. If you have basic skills and necessary equipment welding heating pipes can be done by yourself.

Welding heating pipes can be divided into several stages.

1. Preparation of equipment and tools.
2. Preparation of the surface to be welded.
3. Welding process.

To perform welding work you will need a welding machine, an angle grinder, a hammer, a protective mask and gloves, as well as welding electrodes. The surface of the pipes that is planned to be welded must be clear out from rust, dirt and paint, as well as degrease. Cleaning must be done inside And outside to a depth of at least 1 cm. After this, you can begin the welding process.

For beginners, rutile electrodes of the OK46, ANO-21, MR-3 and OZS-4 brands are recommended for welding heating and water pipes. These electrodes are of the same type and have similar characteristics. Professionals can use electrodes of the UONI-13/45 brand. The choice of electrode diameter depends on the thickness of the pipe walls. For metal thickness up to 5 mm, electrodes with a diameter of 3 mm are suitable. To weld pipes with a wall thickness of up to 10 mm, you need to use electrodes with a diameter of 4 mm. In this case, surfacing is performed in several layers.

Force welding current for each diameter and brand is installed individually. Experienced welders rely on their feelings. Beginners are recommended to choose the welding modes indicated on the packaging with electrodes. The pack also indicates the calcination modes. And if electrodes with rutile coating at proper storage you don't have to ignite it, then main brands Necessarily subject to calcination. This is necessary to remove from the coating excess moisture, to ensure a high-quality and durable seam.

When performing welding work, remember safety precautions. Use special protection and ground the welding machine. Do not use shoes with metal inserts.

After completion of the work it is necessary check for leaks designs. Run water or gas through the pipes. There should be no leaks at the welding site. If everything was done correctly, the pipe connection was successful.

You can select welding electrodes and learn more about welding on the manufacturer’s website: https://goodel.ru/

Video: How to replace batteries yourself?

Metal pipeline and electric welding are inseparable concepts. When installing water supply, heating, high or high sewerage low pressure In everyday life or at work, pipes are joined by welding.

This is due to the fact that Weld in strength and structure it does not differ from the material of the pipeline elements. It provides a monolithic, in-place design with a guarantee of absolute sealing and durability.

Contents of the article

Pros and cons of pipe welding

Like any method in construction, electric welding steel pipes has its advantages and disadvantages.

The advantages of this method include:

• the ability to connect pipes of any diameter, regardless of wall thickness;
• Thanks to the weld, the initial outer and inner diameters of the pipe are preserved. In the case, for example, with couplings, the diameter of the joint increases significantly in comparison with the elements being joined;
• The same material is used for welding as for the pipeline itself. This makes it possible to ensure complete solidity of the structure without changing the properties of the material used;
• welding does not require the purchase of additional fittings, which are often quite expensive;
• This method is quite cheap and simple, provided that specialists get down to business.

In fact, there is only one drawback: only a specialist can weld pipes correctly.

If you take on such work yourself, you can end up with a poor-quality seam with significant cracks, slag accumulations, etc. In the future, this will lead to leaks and rotting of the pipe near the joint.

Briefly about the welding process

The process of connecting metal pipes by electric welding is to create electric arc between the electrode and the elements being welded.

Under the influence of an electric arc, two similar materials melt, mix and create a monolithic seam as the electrode is removed.

Thanks to the special coating of the electrode, special conditions, preventing oxygen from entering the melting point of metals and creating a protective film.

The width and thickness of the seam depend on the thickness of the electrode, the materials of the elements being welded, the welding mode, the speed of the arc, and the network voltage. The formation of slag on the surface depends on these same parameters, especially the last one. Slags formed during the welding process must be removed.

Before you start welding the system, you need to understand many nuances, prepare tools and equipment, purchase electrodes, and prepare the welded edges of the pipes.

The process of electric arc welding of steel pipes (video)

Welding Tools

To carry out welding work, first of all, electric welding will be required. There are two types of welding machines:

• The basis of the first type is a step-down transformer. The current of such welding is regulated by changing the magnetic gap or the position of the rheostat. Today, such a device is considered obsolete. It has significantly heavy weight and requires special skills;
• the second type is inverter welding. Thanks to the use of a much smaller transformer, the device has become compact and quite lightweight. It can be easily moved around the room or even hung on your shoulder. Current adjustment inverter welding carried out by regulators with high precision.

Besides welding machine we will need:

• electrodes. We'll talk about choosing electrodes later;
• mask. It is needed to protect the face and eyes from welding burns. The old versions of masks were quite inconvenient to use. It was necessary to tune in, attach the electrode and only then put on the mask, since they did not let in any light at all. Today the market offers so-called chameleon masks. They are able to automatically adjust the degree of glass darkness;
• workwear. During the welding process, splashes of hot metal fly from the joint. Therefore, it is better to protect yourself from burns with the help of welding overalls;
• a metal brush or other abrasive tool for cleaning the edges of the joined elements;
• hammer for beating slag.

Selecting Electrodes

Weld quality directly depends on the correct choice of electrodes. They are selected based on the material, diameter and wall thickness of the pipe. Welding thin-walled pipes is carried out with a 2-3 mm electrode; a thick-walled heating pipe must be welded with a 4-5 mm electrode.

In addition to the thickness of the metal rod, the electrodes also differ in the thickness of the coating and its material. The coating can range from 3 to 20% of the total mass.

Let us recall that the coating in the electrode is needed to create a special environment in which welding is carried out without access to oxygen. But, the larger the coating layer, the more slag is created, which negatively affects the quality of the seam and the integrity of the structure.

Therefore, when choosing electrodes, it is important to find a compromise between the thickness of the rod and the coating layer, taking into account the characteristics of the pipe.

Understanding which electrodes and at what current strength is it correct to cook? This or that pipe comes with experience. Such experience is usually obtained by the method of “scientific poking”. However, in order to prevent large quantity errors, you should first refer to the tables of correspondence between types of electrodes, types of pipes and electric welding current.

Preparation of joints

You can start welding heating pipes only after their joints are completely cleared of debris and deposits. If you are a beginner, you should not try to weld wet pipes, as the water will boil, evaporate and significantly complicate the process.

Before starting work, you need to properly clean the edges of the joined elements. For this they use different abrasive tools, starting from sandpaper and ending with a circle on a grinder, depending on the thickness and quality of the pipe. You can start welding joints only after how there will be no burrs or sharp edges on them.

• Before starting welding work, you need to make sure that there are no flammable or explosive objects near the junction of the heating pipes. If they exist and it is not possible to remove them, you need to fence off the work area non-flammable material, for example, asbestos;
• You need to place a container of water near the welding site in case of an unexpected fire;
• make sure that the grounding is securely fastened and the integrity of the welding machine wire;
• check the network voltage. If the voltage is weak or changes are observed, increased slagging may occur during the welding process. To avoid this, it is better to use a straightener;
• clean and dry pipe joints. Experienced master can weld heating pipes at a wet joint, but this will seriously interfere with a beginner;
• put on a welding suit and mask;
• We set the required current on the transformer of the welding machine. As a rule, welding of heating pipes up to 5 mm, with an electrode thickness of 3 mm, at rotary joints is carried out with a current of 100 - 250 A, at fixed joints - 80 - 120 A;
• check if the voltage is selected correctly. To do this, we light the arc by moving the electrode at a distance of 5 mm until sparks appear. If sparks do not occur, adjust the current;
• Having completed all of the above steps, you can begin welding heating pipes.

Welding stages

After setting up the welding machine and achieving a stable arc, we begin to connect the pipeline elements.

There are three options for moving the welding arc:

1. The forward movement of the electrode along the weld seam, ensuring arc stability.
2. Along the junction. A continuous seam is provided, the height of which depends on the speed of movement of the electrode.
3. Across the joint oscillatory movements. This method provides not only the required height, but also the width of the seam.

Welding of small diameter pipes with wall thickness up to 5 mm made with a continuous seam. Similar products larger diameters are cooked intermittently.

Pipeline elements with a wall thickness of up to 6 mm need to be welded in two layers, from 6 to 7 mm - in three, over 7 mm 4 are laid welds.

Joints must be welded before full connection without interruptions in the seam.

It is better to weld the first layers in steps to connect the joints. All subsequent layers are made with a continuous seam. After welding the first continuous layer, you need to beat off all the slag and carefully inspect the joint for cracks and burns. If there are any, they need to be melted and boiled again.

There is an opinion that welding pipes is quite simple technological operation, which even a beginner can handle.

Indeed, it would seem that there is nothing complicated here. The parts are quite large, the connecting surfaces are well adjusted to each other and processed, the material is of high quality. At first glance, there is everything necessary to form an aesthetic and durable seam!

In practice, however, it turns out completely differently. This process is quite difficult, especially if we're talking about on the formation of a full-fledged pipeline operating under pressure. The best specialists are attracted to work with its segments.

Why is this happening? How to perform welding with high quality without having significant experience? What tips and tricks should you follow?

The most common and popular technique is electric arc welding.

Yes, she has alternatives in the form gas welding, but her undeniable advantages lies in simplicity minimum set equipment and results that meet the most stringent standards.

Even when designing main pipelines, this method is used. To achieve High Quality, it is necessary to treat the work with full responsibility.

Selecting Electrodes

The connection of steel pipeline segments must be carried out using high-quality consumables, otherwise it is unlikely that a good result will be achieved.

For example, when it comes to choosing electrodes, the following models are considered the best:

• , ANO-24 and. Operate on alternating currents. Work is allowed even with wet coating. The cost of the products is low, which explains their demand in everyday life; they are ideal for connecting structural elements gates, greenhouses and other structures of small mass that do not experience high loads. Work with pipelines in which the medium is transported under significant pressure is not permitted.
• . The quality of the cores deserves flattering reviews even from professional welders, but they have a disadvantage - work cannot be carried out with high speed. It is necessary to constantly monitor the stability of the arc; the weld is deposited gradually, so the worker must have some experience in interacting with classic ANO and MR electrodes.
• Excellent for metal pipes. This is a Japanese development. It is she who is given preference when implementing major projects. They form an even and stable arc, the resulting seam combines strength and aesthetics. Minus - quite high price, but they are suitable for both specialists and beginners.

Watch a video on the topic of which electrodes to use for welding pipes:

Basic methods

The connection can be made in one of the following ways:

1. Butt joint, when the pipes to be connected are placed opposite each other. The most common option, characterized by relative ease of implementation. However, it is also characterized by certain difficulties. The first point is that it is better to work from below. The second point is that the metal must be thoroughly welded so that the depth of welding corresponds to the thickness of the wall.
2. Overlapping. This method is aimed at connecting elements that initially differ in diameter, or segments, one of which is flared, that is, its diameter is increased intentionally, using mechanical action.
3. The T-joint is made at a 90-degree angle.
4. A corner connection assumes that the angle between the connected segments is less than 90 degrees.

Before electric welding pipes, it is worth remembering a number of tips, following which will simplify the process and also improve the quality of the final result:

• If the connection is made using the butt or tee method, then electrodes whose diameter varies from 2 to 3 millimeters perform best.
• The recommended amperage is from 80 to 100 amperes, with the exception of overlap welding, when it is recommended to increase it to 120 amperes.
• When filling a welding seam, you need to ensure that the rise of the metal above the plane of the element reaches 2-3 millimeters.
• If the cross-section of the pipe is not the usual ovals or circles, but profiles, that is, rectangles and squares, then a point method of connecting it is used.

Its essence is that you first need to cook small area on one of the sides. Next - a similar section on the opposite side, then - on the remaining two planes. Only after this the pipe is finally welded.

This approach makes it possible to eliminate the possibility of warping of the product when the temperature rises; its geometry remains stable.

Preparatory operations

The final quality of the joint depends not only on the professionalism of the welder and the use of the “correct” electrodes, but also on how well the preliminary preparation is done.

It consists of the following operations:

• Checking the compliance of the geometry of the connected elements with the selected technology. It must be remembered that the wall thickness must be identical, otherwise it will not be possible to fully weld a thick-walled pipe, and in the case of working with a thin-walled product, on the contrary, the risk of burn-through increases.
• The presence of defects on the welded products, be it cracks, creases or deformations, is not allowed. During the process of thermal expansion, they can turn into areas of complete destruction of the structure.
• Geometric deviations of the cut are not allowed. Its angle must be 90 degrees, otherwise the welding seam will not be strong enough and problems will arise with its formation, which will pose a threat of destruction of the entire structure.
• The edges of the pipes to be connected must be cleaned until a shiny metal surface appears, for which a rough sandpaper or a special brush. The minimum length of the area to be cleaned is a centimeter from the edge.
• Grease and other contaminants, traces of paint and corrosion are removed. Most effective remedy removal - chemical solvent.

This video shows how to prepare the edges of a pipe for clearance using a grinder:

Process Features

Pipe welding technology requires following the following rules:

• The seam must be continuous, that is, end at the point of its beginning. Tearing of the electrode from the surface is not allowed. It is impossible to follow the rule if the pipe diameter is too large. In such a situation, multilayer welding is used. The number of layers must be correlated with the thickness of the walls.

2 layers correspond to a thickness of less than 6 millimeters, 3 - from 6 to 12, 4 - more than 12. Before applying subsequent layers, you need to make sure that the first one has cooled completely.

• Before welding two pipes, they need to be fixed. The tack will simplify the work, eliminate transverse and longitudinal movements, and allow you to form an even and strong seam without unnecessary effort.
• When the pipe wall thickness is more than 4 millimeters, it is possible to form a root seam, the main feature of which is to fill the area between adjacent edges to the full depth. An alternative to a root seam is a roller analogue, which is identified by a 3 mm bead on top of the seam.
• Checking the quality of the seam. It is tapped with a hammer, which allows you to remove slag inclusions. After this is carried out visual inspection, cracks, areas with insufficient penetration, chips, gouges, and burns are not allowed.

If a liquid or other medium under pressure will be transported through pipes, a test run is carried out to determine the tightness.

Useful video

Watch the video where an experienced welder shows how to easily and quickly weld pipes for beginners:

Video for beginner welders, welding pipes with a crescent:

Conclusion

So, welded joint pipes is a responsible task, but with the proper approach and careful attention, even beginners can cope with it. The main thing is to do everything according to the instructions, not to deviate from technology, to remember all the little things.