What is manual arc welding with coated electrodes

What is manual arc welding with coated electrodes?

One type of permanent connection of materials carried out manually is manual arc welding. It is based on the action of an electric arc that occurs during a controlled short circuit.

The welder manually controls the electrode and, if necessary, supplies filler material. Although the productivity of the manual method is not high, it is often used at home. The equipment for it is quite accessible, and anyone can learn manual welding if they wish.

Technology Brief

When manual electric arc welding is used, the metal is quickly heated to its melting temperature by the action of an electric arc, which occurs as the effect of air breakdown between the electrode and the mass (parts being welded). Additional material is introduced into the weld, which allows you to fill the gap between the parts being welded.

At the heating point, a so-called weld pool is formed, which is a zone of mixing of the molten metal of the part with the additive material.

Light molten slag floats up - this is the burnt coating of a consumable electrode or the remains of a non-consumable rod. The slag protects the hot metal from the harmful effects of gases in the atmosphere.

https://www.youtube.com/watch?v=uRA3__KgGx8

This influence can lead to oxidation of the seam and the penetration of gas atoms into its structure, as a result of which the seam will not acquire the required strength.

Manual arc welding is performed with a consumable or non-consumable electrode. The first is itself a filler material, the second requires the introduction of filler wire into the melt.

There are various hand welding technologies. The least complex and costly of them requires only an AC or DC welding machine and the necessary equipment for the welder, but this method is suitable, as a rule, only for ferrous metals that normally tolerate contact with oxygen. To protect the weld pool, where steel and iron are melted, only the environment generated by the protective coating of the electrode is sufficient.

More complex methods, such as argon arc welding, require a special torch with a nozzle through which argon or other shielding gas is supplied.

The welding arc is initiated by a short circuit when the electrode contacts the ground. The arc temperature can reach 5000 °C.

Purpose

The use of manual arc welding is very wide - from everyday work around the house and country house to industry, including high-tech. Among the main industries and national economy where it is used are:

• various service and repair work, for example, automotive equipment;
• welding of pipes for water, gas, oil products.;
• shipbuilding (welding of hull plates);
• many types of mechanical engineering.

The principle of manual welding is often used for surfacing another metal onto the surface of a part. In everyday life, gazebos, benches, barbecues, swings are welded using the manual arc method, and metal products are repaired.

Technical capabilities

Manual welding has significant limitations on the thickness of the parts being welded; this is its main disadvantage. As a rule, sheets thicker than 10 mm are not welded using this method.

Others include the relatively low speed of the process and the direct dependence of the result on the skill of the welder. The manual welding process, like any manual process, is difficult to standardize: the result depends on many factors. Among them:

• type of current source;
• the power of the source;
• characteristics and properties of the processed alloy;
• edge thickness;
• compliance of the electrodes with the task assigned to them;
• well-chosen welding mode.

The peculiarities of arc welding are that a relatively low voltage and a very high current are used to produce it. The arc voltage ranges from 30 to 90 V (many welding machines for home use are rated at an average value of 48 V), but the current is very high - from 90 to 350 A.

Selection of welding parameters

The main parameters of arc welding are current and voltage (but it is fixed). Frequency is less important, since nowadays, as a rule, installations for DC welding are used - inverters.

For welding using electricity, regardless of the method, a direct proportional relationship applies: the thicker the metal, the greater the current should be at a fixed voltage. For comparison: sheets 3 mm thick are cooked with a current of 175-185 A, 5 mm - at least 200 A, 10 mm - 300-330 A.

It is strongly recommended that, in order to avoid burning and severe spattering of the metal, weld with the minimum current possible.

But at the same time, the thickness of the welding electrode and its correspondence in chemical composition to the metal that is supposed to be processed is also very important.

A standard arc welding electrode has a thickness of 3 mm. It is suitable for welding parts with an edge thickness of 2-3 mm. For thicker metal, you can follow the rule that the diameter of the electrode should be 1-2 millimeters less than the thickness of the metal plates that are supposed to be connected with it.

The maximum thickness of electrodes produced by industry is 6 mm. They are suitable for welding ten-millimeter steel sheets.

Each pack of electrodes has its own marking, indicating for what purpose they are intended.

What does marking mean?

It is impossible to imagine manual arc welding without electrodes. Their marking determines what metals they are intended for, what thickness and composition of the coating they have, in what position they should be held when welding (vertically, horizontally, at an angle), what metals they are intended for. The nature of the marking is alphanumeric.

The first letter after the name and brand of the electrode is the letter that determines its purpose. U - for low-alloy and medium-carbon steels, T - for heat-resistant alloy steels. The letter N is for surfacing, A is for ductile metals.

Next comes a letter indicating the thickness of the coating. M - thin coating, C - medium, D - thick, G - extra thick.

The thickness of the coating is determined as a percentage relative to the rod itself.

The next letter of the code indicates the type of electrode. If it is the letter E, then the electrode is consumable.

This is followed by numbers that characterize tensile strength, relative elongation and impact strength retention temperature. They are important only for professional welders working in particularly critical production.

They are followed by one or two letters indicating the coating material of the electrode. A means acidic compound, B - alkaline, C - cellulose, R - rutile, P - other types. Mixed types of coating are possible, such as RC.

The last two digits of the code indicate one of the most important parameters - the position in space in which manual arc welding can be performed, and the current characteristics for welding.

For example, code “13” should be read as 1 and 3. 1 - you can cook in any spatial position, 3 - you must use a current of reverse polarity or an alternating voltage of 50 V.

Types of equipment

Equipment for manual arc welding, as a rule, is a welding machine of a transformer or inverter type, equipped with a cord for connecting to a power source and two contact cords with holders for the electrode and for ground.

The difference between the devices is that the transformer welds only with alternating current, and the inverter or semi-automatic device has a current rectification function for better arc welding quality and the ability to work in direct or reverse polarity.

With direct polarity, the conductive rod is connected to the minus, and the part to the plus. The opposite is the opposite. Different types of metals and alloys require either forward or reverse welding.

GOST requirements

Manual arc welding is subject to the requirements of GOST 5264 80 and GOST 11534 75. These are the main standards that must be followed when welding.

The first - GOST 5264 80 - regulates the technology for creating welded joints of various configurations from steels, pure nickel and nickel-iron alloys.

It consists of a large number of tables that provide drawings of the types of connections that must be met. GOST also indicates the limits of permissible errors and other important numerical parameters.

GOST 11534 75 describes the main types, sizes and design features of products made of low-alloy and carbon steels that can be bonded by manual arc welding with a consumable electrode.

It does not apply to the non-consumable electrode welding methodology. The document also consists of tables containing examples of connections, permissible error limits, thicknesses and angles of connected parts.

Source: https://rem-serv.com/chto-takoe-ruchnaya-dugovaya-svarka-pokrytymi-elektrodami/

Manual arc welding with coated electrodes: features, technique, where it is used

Of all the welding options, coated manual arc electrodes stand out. This is the most popular way to weld metal parts without the help of specialists.

Rods with a special coating will replace flux and gas. With them, it is possible to weld metal firmly, efficiently, without a special expensive apparatus, without the training of a welder.

These days there are a great variety of coated models. It's not easy to navigate this assortment. Here we will briefly explain what nuances need to be taken into account to choose the right option.

We'll show you how to use them in everyday life. We'll tell you what a beginner needs to know.

General information about labeling

A - acidic electrodes. They contain manganese, silicon, titanium, and iron oxide. Different manufacturers have several options for the composition and purpose of such models. During such work, “hot cracks” may form, so they are used with caution.

B – main coating of electrodes. Options coated with bases, like rutile, are more commonly used. Similar models are made from calcium fluoride and calcium carbonate. To obtain a reliable connection, you need to set the equipment to direct current and cook with reverse polarity. Such rods practically prevent cracks from forming - exactly what is suitable for beginners.

C – electrodes with cellulose coating. Their basis is cellulose. Some manufacturers use flour or similar organic substances. When such a coating melts, a cloud of gas is formed, which protects the connection from the formation of slag and improves specialized characteristics. Cellulose-coated rods are suitable for welding thin metal parts.

R – electrodes with rutile coating. This coating option is the most common. Rutile is the basis of the rod, containing other materials of organic origin, which ensure freedom from toxins. The process can be carried out with direct or alternating current. Moreover, the material produces almost no splashes at all, the arc behaves stably and is easier to ignite. The connection will be strong even for novice welders.

P - others.

Mixed coatings may occur. Such options are indicated by the first letters. Example - rutile-cellulose coating - RC.

Brand

The brand of coated electrode is what determines the quality of welding; it is very important. Below are the grades used to join carbon or low alloy steels.

When welding other types of metals, there are different brands, but the most popular are: ANO-1, OZS-6, MR-3, UONI 13/45. These options are quite versatile and are suitable for welding most metals.

Still, we recommend that you take an interest in other brands; this will help you apply your knowledge in your work.

Peculiarities

Selecting the correct diameter of the coated electrode is a priority task. As well as choosing the optimal current strength on the equipment.

By choosing the correct current strength and rod thickness, you will significantly improve the quality of the connection and make the welding process easier for yourself. Below you see a table with recommended sizes. They are true for rutile coated models.

Next, we ignite the arc. There are two options to do this. Let's call them "A" and "B".

"A" is the most popular method. We touch the surface of the material with the electrode and raise it a few centimeters. Sometimes touching is replaced by light tapping.

Method B is less known, but it's worth learning. We touch the welding zone with the electrode and move it to the side - as if we were lighting a match. This method is called "strike". It is very important to learn how to choose the correct diameter of the welding arc.

Welding experts say that it should be within no more than 0.7-1.0 from the cross-section of the metal end of the rod.

Naturally, small deviations can be allowed, but it is better to follow the recommended indicators.

This option ensures the formation of strong seams.

The position of the rod is very important. It depends on the position in space of the welding process - horizontally, vertically, etc.

When welding vertical joints, the coated electrode is parallel to the welding surface and moves in different directions at the discretion of the welder. In the lower position, the rod is guided away from itself. Self-movement is used when other options are impossible.

When welding on a ceiling or a vertical seam at height, reduce the current on the equipment to a minimum. This will make it possible to control the melting of the rod, the seam will form before the coated electrode melts and drips down.

We must not forget about welding seams. Basically, the width of the joints should be compared with the diameter of the rod. Of course, there are also unique cases when the seam is very wide, but these options are not applicable in manual welding.

There are several popular options for creating a seam. For a novice welder, they are more than enough.

Seams can be multi-layered or single-layered. This depends on the number of layers of fused metal. Single-layer ones have one layer, multi-layer ones have several layers. For multi-layer seams, a distinction is made between the bottom and middle layers (or seams).

The reliability of welds directly depends on the quality of the bottom seam. Provided that the middle seam is of high quality, and the bottom one is less strong, corrosion will certainly appear and destroy the connection.

Experts debate a lot about which seam is better. Single-layer ones cook much faster. Multilayer – more durable and elastic. You need to choose the option you need based on the work ahead.

To weld shelves for your dacha, you shouldn’t waste time on multi-layer welding.

Conclusion

Manual arc welding with coated electrodes is a fairly simple and inexpensive option for carrying out work at home. You can buy coated rods almost everywhere, there are many models.

It is necessary to purchase rods based on the work plan and financial capabilities. We recommend purchasing products from well-known brands; frankly cheap models can ruin the material and mood. There is a risk of wasting time, money and not achieving the goal.

We have shared with you the basic information about coated electrodes. Find an opportunity to study as much information as possible - this will help you learn the nuances of manual arc welding and achieve better results.

If you have something to tell us about this, write comments. Good luck with your work!

Source: https://prosvarku.info/tehnika-svarki/svarka-pokrytymi-ehlektrodami

Features of manual arc welding with coated electrodes

There are many types of welding, but among them, manual arc welding using coated electrodes stands out. Manual arc welding with coated electrodes is one of the most popular ways to join metal structures in small-scale production or home welding. Coated electrodes replace flux and gas; with their help, you can make a high-quality and reliable seam without using expensive equipment or professional welding skills.

The modern market offers different types of coated electrodes, and it is quite difficult for a novice welder to understand such a variety. We will simplify your task and briefly tell you everything you need to know about coated electrodes, teach you how to use them at home, and tell you about all the features that are worth considering.

Types of coating

Types of electrode coating:

• A - acidic electrodes. Acidic electrodes contain iron oxide, manganese, silicon and titanium. The composition may vary depending on the manufacturer and purpose of the electrode. Please note that acid-coated electrodes promote hot cracking, so they must be used with caution.
• B - main coating of electrodes. Electrodes with a basic coating (along with rutile) are the most popular on the market. This coating consists of calcium fluoride and calcium carbonate. To ensure a high-quality and reliable seam, set the welding machine to direct current and work in reverse polarity. By the way, electrodes with a basic coating almost do not contribute to the formation of cracks, so we recommend that beginners use such rods.
• C - electrodes with cellulose coating. As you might guess, the basis of such rods is cellulose. Sometimes flour or other organic substances are used. When the coating melts, a gas cloud is formed, protecting the seam from the formation of slag and improving its mechanical properties. Cellulose-coated electrodes are most often used for welding thin metals.
• R - electrodes with rutile coating. This is the most popular type of coating and the most versatile. The basis of the rod is rutile, as well as various organic substances that guarantee the absence of slag. You can cook with both alternating and direct current. In this case, the metal practically does not spatter, the arc is stable and ignites easily. The seams are of high quality even for novice welders.
• P - others.

Sometimes there are mixed coatings; they are designated by several letters. For example, rutile-cellulose coating is RC, and so on by analogy.

Electrode marking

The brand of electrode plays an important role; the quality of work largely depends on its choice. In the picture below you can see the grades of coated electrodes used when welding carbon and low alloy steels.

There are different brands for welding other types of metals, but in general the most common ones can be identified: ANO-1, OZS-6, MR-3, UONI 13/45. They are quite versatile and suitable for welding most metals. But despite this, we still recommend that you familiarize yourself with other brands in order to further rely on your experience and knowledge.

Features of welding with coated electrodes

The first thing you need to do is to choose the right electrode diameter (according to the type and thickness of the metal), and also set the optimal current strength on the welding machine. By doing this, you will significantly simplify further work and the result will be noticeably better. Below you can see a table with recommended values ​​for rutile electrodes.

Then you need to ignite the arc. There are two methods, in the picture on the right they are labeled “A” and “B”.

Method "A" is the most popular. You need to touch the surface of the metal with the electrode and then lift it a few centimeters. You can also replace touching with light tapping. Method “B” is used less often, but you also need to be able to use it. You need to touch the welding zone with the electrode and move it to the side, similar to how you light a match.

This method is also called "strike". It is also important to be able to determine the correct arc diameter. Experienced craftsmen believe that the diameter should not exceed 0.7 - 1.0 from the cross-section of the metal end of the electrode. And we agree with this. Of course, small deviations are acceptable, but we still recommend sticking to this indicator.

This will contribute to the formation of a high-quality, durable seam.

Pay attention to the position of the electrode. It directly depends on the spatial orientation in which you are welding: horizontal, vertical, bottom, ceiling, corner, and so on.

If you need to weld a vertical seam, the electrode can be positioned parallel to the surface being welded and moved in any direction, at the discretion of the welder. If you cook in the lower position, the electrode should move away from you.

Self-pull is allowed, but only if no other option is available.

Helpful advice! If you have to weld a ceiling or vertical seam at height, then reduce the amperage on your welding machine to the minimum value. This way you can control the melting of the electrode and form a seam before the molten rod begins to drip down.

Also don't forget about the seams themselves. In most cases, their width should be comparable to the diameter of the electrode. Yes, there are specific jobs where the seam is very wide, but this does not apply to manual welding. In the figure below you can see the most common seam trajectories. They are not the only correct ones, but they will be enough for a novice welder.

Seams can also be single-layer or multi-layer. Single-layer ones consist, as you might guess, of one layer of deposited metal, while multi-layer ones consist of several. In multi-layer joints there is a so-called bottom layer (or seam) and a middle layer. The durability of the welded joint directly depends on the quality of the bottom seam. Even if you cover a poor-quality bottom seam with a better-quality middle one, after a while corrosion will still appear and the connection will begin to deteriorate.

Welders often argue about which type of weld is best. Of course, single-layer seams are made much faster than multi-layer ones, but they do not have the proper elasticity and durability. Choose the type of seam based on the task at hand. If you need to weld a garage rack, then multi-layer seams are unnecessary.

Instead of a conclusion

Manual arc welding with coated electrodes is a relatively inexpensive and easy way to perform most welding jobs at home. Coated electrodes are sold in any welding shop and their range is very wide. You can purchase rods based on your needs and budget. We recommend buying components from trusted manufacturers, not chasing the lowest price and not buying outright counterfeit products.

We have told you all the basic information about coated electrodes. Don’t be lazy and study additional materials, for example, welding regulations. In them you can learn additional features of arc welding using coated electrodes and welding rules in general. Share this article on social networks and describe your experience using coated rods in the comments. Good luck!


Source: https://svarkaed.ru/rashodnye-materialy/elektrody/osobennosti-ruchnoj-dugovoj-svarki-pokrytymi-elektrodami.html

Manual arc welding | Welding and Control

Manual arc welding of pipelines with coated electrodes

Manual arc welding with a coated electrode is an arc welding in which the initiation of the arc, the supply of the electrode and its movement are carried out manually, the protection of the weld pool is ensured by the melting and decomposition of the coating components.

Welding with coated electrodes is the most widely used welding method in Russia and occupies the largest volume in comparison with other welding methods. The method allows welding of almost any structures and parts of varying complexity, in hard-to-reach places, in different spatial positions of the weld.

The quality of welded joints made by manual arc welding cannot be guaranteed without strict adherence to welding technology and operational control of all processes. Starting from incoming inspection of welding and basic materials, checking the qualifications of welders, compliance with welding regimes and final inspection of the finished welded joint.

Common designations:

RD – manual arc welding;

MMA – Manual Metal Arc (Welding) – manual metal arc welding;

SMAW – Shielded Metal Arc Welding – metal arc welding in a protective atmosphere;

E is the international symbol for manual arc welding.

The essence of manual arc welding with coated electrodes

In manual arc welding with coated electrodes, the arc is excited when the electrode touches the part being welded, as a result of the closure of the electrical welding circuit.

During the welding process, the coated electrode is applied to the part being welded as the electrode melts and is mixed along the joint with transverse vibrations to give the desired shape and size of the weld.

Movements of a coated electrode during welding

During the manual arc welding process, the coating and the electrode metal wire melt. The expanding coating forms slag and gases are released. The slag envelops drops of molten metal that appear when the electrode rod melts.

In the bath, the slag floats to its surface and forms a protective layer that protects the metal from interaction with atmospheric air. In addition, rising to the surface of the weld pool, the slag cleanses the molten metal of harmful impurities.

The welding gases formed when the coating melts displace air from the welding zone and, thereby, protect the weld pool from interaction with oxygen and nitrogen.

The liquid slag hardens and forms a hard slag crust on the surface of the weld, which is removed after welding. That is, the components included in the coating of the welding electrode protect the weld pool and the solidifying metal of the welded joint from reactions with atmospheric gases and clean the metal during the chemical reactions occurring in the weld pool.

Covered electrodes are used for welding steels, cast irons and non-ferrous metals of various thicknesses. Coated electrodes are also used for surfacing to restore worn parts and obtain coatings with special properties, mainly anti-corrosion and wear-resistant.  

The welder moves the welding electrode along the weld and feeds it into the welding zone as it melts.

  In this regard, the stability of the process and the quality of welding depend on the qualifications of the welder and his visual-motor coordination, since the length of the arc, the inclination of the electrode, and the speed of its movement will change, which leads to a change in the mode parameters - arc voltage and welding current.

When manual arc welding with coated electrodes, to ensure stability of welding modes, welding current sources with steeply falling current-voltage characteristics are used.

Schematic diagram of manual arc welding with coated electrodes

Advantages of manual arc welding:

• manual use is possible in various, most inconvenient spatial positions;
• welding can be performed in hard-to-reach places;
• versatility of the method, the ability to weld products of various configurations;
• applicability to a wide range of different steel grades;
• high mobility.

Disadvantages of this method:

• few highly qualified welders;
• it is impossible to guarantee the quality of the welded joint;
• low welding productivity;
• unfavorable working conditions.

Reasonable applications:

• welding of metal structures, pipelines;
• It is rational to use when welding short seams.

Technology of manual arc welding with coated electrodes

Manual arc welding technology includes the following operations: cutting and preparing welding edges, exciting the welding arc, moving the electrode during welding, the order of applying welds depending on the grade of materials and the design of welded joints.

Manual arc welding requires high-quality preparation of the edges and adjacent surfaces of the parts being welded. Mechanical processing and cleaning of welded parts is performed on machines or manually.

The welded edges are cleaned to a metallic shine; there should be no traces of rust, a loose layer of scale, dirt, or oil stains, because insufficient preparation will lead to defects and, as a result, a decrease in the strength characteristics of the welded joint.

The welded edges and the adjacent metal surface with a width of at least 20 mm are subject to mandatory cleaning;

The form of edge preparation for manual arc welding with coated electrodes is established by the standards for structural elements of welded joints, depending on the thickness of the parts. The bevel angle of the edges, the bluntness and the gap between the parts to be joined must be uniform and not exceed the established tolerances.

Structural elements of welded joints

Assembly and preparatory work should be carried out in such an order that the structure is located conveniently for work and welding in the lower position. All products received for assembly must be checked for compliance with the drawings and the correct preparation of edges for welding.

To prevent deformations during the welding process, assembly should be carried out using tacks or rigidly fixed jigs. For tack welding, the same electrodes are used as for welding, unless otherwise specified in the technical documentation. The length of the tacks must be at least 50 mm in increments of at least 500 mm.

To avoid defects at the end of welding, it is necessary to use lead strips.

The welding arc is ignited in two ways: the welder touches the end of the coated electrode to the surface of the work being welded, or strikes the end of the electrode along the surface of the metal and quickly moves it to the side by about 2-4 mm. This is how the arc is excited. When welding, the arc length should be kept constant, as short as possible, for which the welder feeds the coated electrode as it melts.

An arc that is too long does not provide the required depth of penetration of the base metal, there is excessive spattering of the metal, and poor protection from atmospheric air, as a result of which unacceptable defects may form. A short welding arc provides fine droplet transfer of metal, the coated electrode melts evenly, the welding process is more stable than with a long arc.

If the welding arc breaks, the breakage area should be cleaned. Welding should be resumed by moving 5 - 10 mm away from the break point onto the previously deposited bead, and carefully weld the crater formed at the break point.

When welding, the electrode must be held at a certain angle to the parts being welded. The inclination of the electrode depends on the spatial position, thickness and grade of the base metal, the diameter of the electrode of its type and the thickness of the coating. Welding can be carried out from left to right, right to left,

from yourself and to yourself. Regardless of the direction of welding, the electrode must be inclined to the axis of the seam so that the base metal is melted to the greatest depth and the seam is formed correctly.

Source: https://svarkka.ru/%D1%80%D1%83%D1%87%D0%BD%D0%B0%D1%8F-%D0%B4%D1%83%D0%B3%D0% BE%D0%B2%D0%B0%D1%8F-%D1%81%D0%B2%D0%B0%D1%80%D0%BA%D0%B0-%D0%BF%D0%BE%D0% BA%D1%80%D1%8B%D1%82%D1%8B%D0%BC%D0%B8-%D1%8D%D0%BB%D0%B5%D0%BA/

Technique and technology of manual arc welding with coated electrodes

Manual arc welding (MAW) is not losing ground. Productivity, penetration depth is lower, process stability is poor. But it is not yet possible to displace the melting electrode in the coating. RDS kindly offers space for progressive technologies that make work easier and speed up welding work while staying afloat.

RDS welding is

Manual arc welding is used for installation and assembly work, where modern methods are not used. The method has been used since 1888. The essence of the method is to initiate the excitation of an electric arc between polar sources, one of which is an electrode, the other is a part.

The electrical holder (cathode) transfers charge to the electrode core. Brief contact with the workpiece (anode) initiates an arc, the only source of heat for melting. Localization of heating in the arc combustion zone leads the surface of the metal of the product to a liquid state.

The weld pool at the base of the arc column is filled with molten metal of the product and drops of deposited metal of the electrode rod. The uniform mixing of 2 substances forms a homogeneous alloy.

Liquid slag from the coating material covers the bath and prevents oxidation processes. The frozen glassy mass of slag is removed mechanically after each pass. Otherwise, the integrity of the seam with uniform penetration will be compromised.

The entire process is controlled by an electric welder . Maintaining the size of the arc and smooth movement along the seam boundary to avoid lack of penetration and undercuts are carried out by eye: only visual control is available.

The level of professionalism of the performer determines the quality of the connection. What is a qualified RDS welder: reliable sealing of joints of elements of pressure vessels, production of load-handling devices. He masters the technique of controlling direct and alternating current devices, and cooks with consumable and non-consumable electrodes.

Types of consumable electrodes

There are multi-place electrode holders: 2 or more electrodes involved in filling a deep groove, a three-dimensional seam leg, speed up the process. And the rod electrodes themselves differ in chemical composition to ensure the identity of the connection with the material and the protective components of the coating.

Types of electrodes by application:

• U – low-alloy steels with a tensile strength of 600 MPa;
• T – heat-resistant steels;
• N – floating electrodes;
• A – Plastic metals.

Limitations on the spatial application of the seam are associated with the fluidity of the melt of the rod. Regulations for the use of vertical, ceiling one and two-sided seams, welding at an angle contain GOST 5264-80, for joints welded at acute and obtuse angles GOST 11534 75 is responsible. Additional digital indexing on the marking indicates the scope of application of consumable electrodes:

• 1 – without position restrictions;
• 2 – except vertical from top to bottom;
• 3 – ceiling seams are excluded;
• 4 – only horizontal.

Directories are full of recommendations for the use of electrodes with a certain range of alloys similar in composition to the melting rod. The complex of alloying elements of the melt of the connecting seam in this case creates an almost monolithic connection.

An example of electrode type matching for alloyed structural, high-alloy and heat-resistant steels:

• Art. 14Kh2GMSSH, 14KhMNDFR – electrode ANP2, E70;
• Art. 12Kh2NVFA, 30KhGSA – NIAT 3M;
• 30KhG2S – UONI-13/85;
• 15Х1М1Ф, 12ХМФ – OZS-11;
• 15Х1М1ФЛ, 20ХМФЛ – ТМЛЗУ;
• 12Х1МФ – ЦЛ45.

Generalized table of purpose by area of ​​application, types and brands of consumable electrodes

coatings

The thickness of the coating is not a universal value. Regarding the diameter of the rod, standard ratios are distinguished:

• M – 20%;
• WITH – 40%;
• D – 80%;
• G – more than 80%.

The compositions of the coatings are predominantly mixed in properties, taking into account the multicomponent nature of the alloys. Basics and purpose of types :

• A – Mg, Ti, Si, FeO3. Porosity of the seam is excluded, but hot cracking of the upper part of the seam is possible. Example - E-08Х19Н10Г2Б, used for high-alloy alloys;
• C – 50% organic filler, mainly cellulose, flour, spar. The melt corresponds to semi-quiet and calm steels with a high hydrogen content. Electrodes E50, E46 are good for vertical seams;
• P – mineralization with rutile (TiO2) up to 50%, organic matter. Hot cracking is excluded. Impact strength is high. Requires calcination to remove moisture. The spatial position of the seam is without restrictions;
• B – CaCO3, KF, minerals. Active slag formation, non-susceptibility to hydrogen sulfide cracking. Dominate in pipeline welding;
• P - RC , AB , others - double types, are classified separately.

RDS welding of non-ferrous metals

Arc welding of aluminum is complicated by a refractory oxide film on the surface of the metal, which must be removed by leaching . Alkali metal chlorides and fluorides included in the coating neutralize the film. Parts with a thickness of less than 4.5 mm are not recommended for arc welding.

The current increases up to 1.5 times. Pre-heating of parts and heat-dissipating pads during welding are used to minimize spreading. The welder's scourge is crystallization cracking and post-welding deformation . Filling the groove continuously until the electrode burns out completely.

The electrodes are oriented towards pure metal without impurities, technical alloys:

• Refined aluminum grade AO-A3 - electrode OZA1, OZANA-1. Careful preparation of edges. Horizontal and vertical seam guidance is available. Alternating current, reverse polarity;
• Silicon alloys (silumins) – OZA2, OZANA-2. The coating is hygroscopic, filled with fluoride and chloride salts;
• Surfacing of wrought alloys – UANA.

The high cost is justified by ESAB OK Almn1 alkaline salt electrodes for assembling a structure from pure metal. High-quality seam, easy removal of slag crust.

For alloys with magnesium and manganese, duralumin – Alsi12. UTR 48 with a silicon content of up to 12%, giving an even scaly seam.

According to rough estimates, the current strength is correlated with the thickness of the base metal. For 1 mm take 20 - 30 A, without going beyond 200 A.

For RDS welding of copper and alloys, the choice of consumable electrodes is wide: Komsomolets 100, ANTs/OZM2, (OZM3, OZM4).

Modes

A beginner has a question: what electrode should be used to weld 2 mm metal? A maximum of three, optimally – not to exceed the thickness of the metal. We won’t find a rod thinner than Ø 1.6 mm; all that remains is to adjust the welding current to the optimum.

Welding mode – a combination of the sum of parameters:

• Arc current and voltage;
• Diameter and speed of movement of the electrode;
• Polarity, type of current;
• The position of the seam in space.

Practice shows that it is advisable to use the maximum permissible current, and the speed determines the cross-section of the seam . The arc is ignited in 2 ways: by a short touch with a tear off (butt-to-end) or by a longitudinal movement along the workpiece (with a match).

Vertical and ceiling seams are carried out with current correction down to 20%, voltage - up to 30 V, electrode diameter does not exceed 4 mm. Under standard conditions, the penetration depth reaches 1 – 2 mm.

Maintaining the arc at a distance of 0.5 - 1 diameter to the crater funnel is ensured by the uniform supply of the consumable fuse element. Increasing the arc length increases the flow of air into the melt, reducing quality. Metal waste and spattering increase.

Interruption of the arc is fraught with the formation of a crater where slag accumulates, and cracks may form. The crater is welded until it is filled. The reason for the formation of a crater cannot be the completion of the seam - this is a defect.

Extended seams are made in separate sections. On thick metal, where there is no risk of warping, the passage length is 200 - 300 mm. On thin sheet - short in a checkerboard pattern.

Equipment

DC and AC welding machines are sources of energy supply. AC units are simpler, cheap, compact, easy to maintain, and consume less energy.

Direct current equipment ensures arc stability, the process is simplified and does not require highly qualified welders. Mechanization and automation are available.

Source: https://svarka.guru/vidy/thermo/dugovaya/ruchnaya-pokrytymi-elektrodami.html

Manual arc welding with coated electrodes - description of technology and methods

There are various methods for obtaining permanent connections. Manual arc welding is considered the most rational and universal. Whether this corresponds to reality, how it is carried out with coated electrodes, the features of the technology, ways to increase its efficiency - all this will be the subject of conversation.

When is it best to use

• When changing the electrode position frequently. Using arc welding, you can get a high-quality seam in various directions - horizontal, vertical, at any angle.
• When work is carried out in difficult conditions, including hard-to-reach places.
• If you need to create a permanent connection between dissimilar metals (alloys), or quickly switch from one to another, which often happens during the installation process.
• For producing short seams.

Arc welding technology

Any coated electrode is a metal rod, the outer layer of which (silicate, flux, glass coating) upon combustion forms either a gas cloud or slag. They are the protective environment that prevents air from entering the work area.

By type of slag

• Alloying.
• Refining.
• Deoxidizers.
• Protective, creating a “crust”.

Depending on the type of electrodes, slags can also be plasticizing and binding.

There are several types of welding - direct current, pulsed (m/h), alternating. When voltage is applied, it follows the “electrode – workpiece” circuit, but only at the moment of contact with the part. This leads to the formation of an arc. In the high temperature zone (up to 6,800 – 7,000 ºС) both the edges of the sample and the rod melt. As a result of further crystallization of metals, which occurs when it decreases (as the electrode moves along the intended line), a seam is obtained.

In manual mode, welding is carried out with alternating or direct current. Professionals prefer the latter option, with direct polarity. As a result, the electrode remains cold, but the metal in the working area heats up.

What to consider? For different types of welding, different electrodes are used for “=” or “~” current.

Conditions for high-quality arc welding

• Dry sections of samples and electrode.
• Uninterrupted power supply.
• Integrity of grounding conductor insulation. Its defects often cause damage to the seam, “sticking” of the electrode in the working area due to “leakage” of current.

Necessary equipment

• Balanced rheostat. With its help, by changing the current strength, you can perform not only welding work, but also a number of others - cutting, surfacing, tightening.
• Grounding cable. It is an element of an electrical circuit and forms a closed circuit through which current flows.
• "Derzhak."

Arc ignition

The current strength is set based on the type of seam, its spatial orientation, the brand of the coated electrode, the type of metal and a number of other operating features. The table shows the most commonly used values.

Methods of “ignition”

No. 1 - lightly touch the metal, followed by raising the electrode by 20 - 25 mm.

No. 2 – used when the arc breaks. Touching in front of the crater, with retraction in the opposite direction, to the fusion zone. At the same time, waste is removed from it.

The optimal arc diameter is considered to be within 0.7 - 1.0 of the cross-section of the metal electrode rod. During welding, it is advisable to maintain this parameter within the specified limits. Then the seam will be high-quality and even.

Covered Electrode Position

Depends on the spatial orientation of the seam: ceiling, vertical or horizontal, bottom. When laying vertical seams, the electrode can move in both directions, as is more convenient for the welder. In the lower position – tilt in the direction of welding. Movement - either “from oneself”, “or towards oneself”.

Seam characteristics

The width of the roller depends on the specifics of the operation being performed and correlates with the diameter of the coated electrode.

• From 0.8 to 1.5 d – a “thread” (narrow) seam is applied if it is the primary one in a multilayered one. It is also used if the thickness of the samples being welded is relatively small (thin rolled products).
• 2.2 – 4.0 d – the most common (medium) seam. The most commonly practiced (but not the only possible) electrode movements are shown in the figure.

 Length - depends on the specifics of welding. Seams: short - up to 30 cm, medium - from 0.35 to 1 m and long - more than 100 cm.

 Thickness – depends on the depth of “cutting”. Based on this, the seams are made single- or multi-pass, in several layers or in one.

Less time is spent on obtaining a seam made in 1 pass. Consequently, productivity increases. A significant disadvantage is the insufficient elasticity of the connection, possible overheating of the metal in certain areas.

A multilayer seam is more durable, since when repeated penetration, the underlying level is subjected to additional thermal effects. The structure of the connection becomes homogeneous, which directly affects its reliability.

With this welding technology, seams are made in different ways: “slide”, “cascades”, sequential application of each successive layer along the entire length of the joint line.

The last option is the most common, and the first two are used mainly when welding samples of large thickness (or for deep sections).

The quality of the bottom layer is a guarantee of the strength of the entire connection. It is the first penetration that should be given special attention.

Useful tips

• It is advisable to master arc welding technology using the same type of machine with which you plan to work in the future.
• Protective filters have different numbers. For a particular welder, it is selected individually, taking into account the characteristics of his vision (diopters, sensitivity). There is only one criterion: the worker must see the weld pool clearly.
• The quality of the connection depends on the correctly selected part-electrode gap. If it is too small, you will get a convex seam, since the heating of the metal will be insufficient. If its value is greater than the recommended one, the placement of the melt will be uneven due to the fact that the arc will “jump” (deviate from the welding line).

Basic rules of TB

• When manual arc welding, it is prohibited to lay a grounding conductor over a damp base, especially puddles, melted snow, and the like.
• All operations are carried out only with rubber gloves. Before starting work, their integrity must be checked.
• The master’s face must be protected from hot splashes of metal, and his eyes must also be protected from bright light.

It remains to add that the article only gives the “basics” of the technology and methods of manual arc welding. All its advantages can be realized only if the employee has the necessary knowledge and practical skills. Only in this case will the high quality of the seam joint be ensured.

Good luck in mastering your welding skills!

Source: https://ismith.ru/welding/ruchnaya-dugovaya-svarka-pokrytymi-elektrodami/

Manual arc welding with coated electrodes. Essence of the method, characteristics of coatings, technology

Manual arc welding with coated electrodes is an arc welding using coated electrodes, with the welder manually feeding them into the welding zone and moving the arc along the edges being joined. As a result of the melting of the metal edges and the melting of the electrode rod, a weld is formed.

The heating source is an electric discharge (welding arc) between the workpiece and the electrode, which occurs when an electric current passes through an environment filled with air or gas.

The process requires protecting the weld pool from external influences of air gases in order to avoid their penetration into the molten metal, which can lead to deterioration in the quality of the weld. One type of arc zone protection is the use of coated electrodes.

Advantages of the method:

• versatility;
• simplicity;
• possibility of welding in any position in space and hard-to-reach places.

Disadvantages include the dependence of the quality of work on the qualifications of the welder and the low productivity of the process.

Where is it used?

The method is used for the manufacture of metal structures in the following areas:

• automotive industry;
• energy;
• construction;
• petrochemicals.

The method is common when repairing various products and elements.

Types and characteristics of coated electrodes

The element has the form of a coated metal rod. To coat its surface, a powder from a mixture of different components is used. The technological qualities of the coated electrode depend on the composition of the coating and the quality of its application.

Rods are classified according to several criteria.

By purpose:

1. U – for joining carbon and low-alloy steels.
2. L – structural steels with alloying additives.
3. T – alloyed heat-resistant steels.
4. B – high-alloy steels with specific properties.

By coating thickness : thin, medium, thick and extra thick.

By type of coverage:

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

Sour (A)

Contain:

• ores and materials with a high oxygen content (granite, hematite) - provide slag protection;
• ferroalloys – reduce iron from oxides and remove oxygen;
• organic impurities (dextrin, starch) – gas protection.

Welding with such electrodes can be carried out in all positions with constant and variable power sources.

Not suitable for cramped conditions.

Basic (B)

The composition of the coating includes:

• ferroalloys;
• calcium fluoride compounds.

Purpose – welding in any position with direct current. The use of alternating current requires the addition of stabilizers to the coating.

Basic electrodes are used for welding critical structures made of alloy and low-carbon steels and parts with large cross-sections.

Cellulose coated (C)

Contain:

• oxycellulose;
• ferroalloys;
• rutile.

The electrodes are suitable for DC welding in any spatial arrangement.

They are often used to connect pipeline joints.

Rutile (R)

Includes:

• rutile concentrate (titanium oxide);
• calcium carbonates (muscovite, marble, talc, magnesite, cellulose, ferroalloys).

Electrodes are used to connect low-carbon steels with alternating and direct current in any location in space.

Welding technology

According to their position in space, seams are of the following types:

• lower;
• vertical;
• ceiling;
• horizontal.

They differ from each other in the angles at which the surface of the welded element is located. The quality of seam formation depends on the angle of inclination of the electrode to the welding direction and the product being welded.

Bottom seams

The butt weld, performed in the lower position, is of high quality. The technology for its implementation is simple.

In order for the welder to clearly see the joint area, it is recommended to apply the bead towards you or from left to right. The width of the roller corresponding to 3-4 electrode diameters is considered normal.

Single-pass welding with a v-shaped edge groove is carried out by transverse oscillation of the electrode over the full width . The arc must move from the bevel of the edges to the area of ​​​​the untreated metal plane. The difficulty may lie in ensuring uniform welding of the seam along the entire length. Welding such a seam in several passes better ensures penetration of the first layer.

Seams with x- or u-shaped edges are made in the same way . The difference is that each subsequent seam is applied towards the previous one. Bottom butt joint welding is preferably done on a removable copper or steel backing. At the turning points, the seam is welded without breaking the arc.

The corner connection in the lower position is performed using the “symmetrical” or “asymmetrical boat” methods . To perform the work efficiently, welding is carried out using a rod with the visor resting on the edges. When making a corner connection with an inclined electrode, it is recommended to use the “back angle” technique.

The connection without bevel of the edges is made in one layer by transverse movements of the rod in a “triangle”. The fillet weld of an overlap joint is made in one layer using an electrode with a diameter of up to 5 mm.

Vertical

The technique for forming butt and fillet welds is from bottom to top. First, a metal horizontal platform is created, the cross-section of which is equal to the cross-section of the seam material. Electrode movements are transverse, in a triangle. When welding the root of the weld, it is recommended to delay the burning of the arc. The greatest penetration of the root is achieved when the rod is perpendicular to the vertical axis.

Welding using large-diameter electrodes and high current values ​​is difficult due to metal dripping and poor weld formation. In this regard, electrodes up to 4-5 mm in diameter are used. The welding current is reduced by 10% compared to bottom welding.

Vertical welding in the top-down direction is performed with electrodes that produce a thin layer of slag (cellulose, organic plastic coatings).

Ceiling

Due to the possible leakage of liquid metal from the bath, welding ceiling seams is labor-intensive. For this reason, work is performed with a short arc. Characteristic points of ceiling welding:

• 15-20% reduction in welding current compared to the lower position;
• for welding metal with a thickness of 8 mm or more, multi-pass welds are used;
• the diameter of the electrodes is 3-4 mm;
• it is possible to use the method based on the coating of the rod.

Horizontal

Making horizontal butt seams is more difficult than vertical ones.

During operation, liquid metal from the bath flows onto the lower edge. Therefore, a bevel of the top edge is required. An arc is excited at the lower edge, after which the electrode is redirected to the upper edge.

Such seams can be made with a rod located vertically, and an angle back, an angle forward.

Source: https://elsvarkin.ru/texnologiya/ruchnaya-dugovaya/

Manual arc welding with coated electrode

Among other types of joining two metal surfaces, the most popular is manual arc welding using protective electrodes. It is used for household and small industrial work. The coating that protects the electrodes does not require the use of flux or gas. The seam is reliable, and the welding process does not require the purchase of expensive equipment. A master's skills can be mediocre, everything comes with experience.

And the variety of electrodes for welding is even greater than that of welding machines. We decided to help beginners understand all the nuances of welding technology with a consumable coated electrode. We will tell you in detail about the types, types of coatings and for what work certain elements are used.

What types of coating are there and their features?

Coated metal electrodes are designated by established letters and are divided into five types:

• acidic electrodes are designated “A”. This means that the rod shell contains manganese, iron oxide, titanium and silicon. The percentage of substances may vary depending on the manufacturer and application of the electrode. The disadvantage of the acidic type is excessive spattering and a tendency to form hot cracks in the seams;
• Basic coating “B” is most suitable for beginners in welding. The protective shell is based on calcium fluoride and calcium carbonate. The seam turns out to be of high quality if you set the necessary settings: direct current and reverse polarity. Welding with such an electrode does not form cracks, which will be an incentive for beginners;
• "C" - cellulose coating. Sometimes organic substances such as flour are added to cellulose. When heated, the coating melts, forming a protective haze that protects the seam from the appearance of slag. It is preferable to work with metals that are not very thick;
• rutile coating "P" is universal in all respects. The basis of the powder, as you might guess, is rutile and a small admixture of organic compounds, which help to obtain a clean seam. Direct and alternating current are used, there is no splashing of droplets. The arc with rutile electrodes ignites quickly and burns stably. Even the inexperience of the technician does not affect the quality of the connection.

There are combined types of coatings, as indicated by the corresponding abbreviation. If the letter “F” appears, it means that the composition contains iron.

Electrode marking

All necessary information is contained on the packaging. Without using the electrode in practice, you can understand whether it is worth buying it for your purposes or not. But first things first. Let's talk briefly about the purpose of the electrodes:

• low-alloy and carbon materials should be welded with electrodes marked on the packaging with the letter “U”;
• work with alloyed alloys is indicated by the letter “L”;
• processing of heat-resistant metals with the abbreviation “T”;
• highly alloyed - “B”;
• when surfacing an additional layer of metal, electrodes marked “H” are required.

Electrodes also have a coating thickness, where:

• M – small thin shell;
• C – middle protective layer;
• D – thickened coating;
• G – maximum permissible.

The spatial position of the seam also has its own designations:

• 1 – all types of seam location;
• 2 – except vertical:
• 3 – except vertical and ceiling;
• 4 – for the bottom seam.

Abbreviation of welding current

0 – indicates only operation on reverse polarity without idle control.

Open circuit voltage within 45-55 V:

• 1 – work with any polarity;
• 2 – work with straight polarity;
• 3 – work with reverse polarity.

Open circuit voltage within 60-80 V:

• 4 – work with any polarity;
• 5 – work with straight polarity;
• 6 – work with reverse polarity.

Open circuit voltage within 85-95 V:

• 7 – work with any polarity;
• 8 – work with straight polarity;
• 9 – work with reverse polarity.

Let's look at an example of a separate marking, let it be E46-LEZMR-3S-O-UD E 43 1(3)-RTs 13, where:

• E – stands for the word “electrode”;
• 46 is the load per mm2, in other words, how much weight the product can withstand after welding with this electrode. That is, 1 square millimeter should be subject to a force of no more than 46 kilograms and the finished product will not burst;
• LEZ is a manufacturing plant, literally – Losinoostrovsky Electronic Plant;
• MP-3S is the brand of electrode itself, it means that the electrode has a thin coating (M), has the appropriate standards (P), the name of the electrode from a specific manufacturer (3), the blue color of the coating (C);
• About the diameter of the electrode, if the number is not indicated, it means it can be printed;
• UD - the purpose of the electrode and the coating layer, in our case it is the ability to weld low-alloy steels and carbon metals, the electrode has a thick layer of melting coating;
• E - indicates that after it comes the index of the electrode, its characteristics should be looked for in GOST;
• 43 1(3) – the index itself;
• RC is a type of coating, we have rutile-cellulose;
• 1 – indicates that this electrode can be used to weld in all positions of the seam;
• 3 – means that when the welding machine is idling at 50V, the reverse polarity of the welding current is used.

We hope that our detailed instructions have revealed the secret of writing strange signs on a box with electrodes.

Some features when working with coated electrodes

To make the welding process easier for yourself, you need to choose the correct electrode diameter, comparable to the thickness of the metal and its type. And also choose the correct current settings.

The thicker the metal, the larger the diameter of the electrode means, and accordingly the higher the current setting. For example, if you are welding the bottom seam of a one and a half millimeter coating, then the diameter of the rutile electrode should be 2 mm, and the welding current power should be within 35-50 Amps.

With a metal thickness of 5 mm, take an electrode with a diameter of 4 mm and a current strength of 130-180 Amperes.

The next step is to ignite the arc. This can be done in two ways:

• tap the electrode on the metal;
• Scratch with an electrode at the place where the seam is created.

The first method is more common and simple, the second requires some skill.

The position of the electrode during welding plays an important role. Depending on the spatial position of the parts, the movement of the electrode is different. When welding a vertical seam, the torch and electrode must be held parallel to the seam; when welding the lower positions of the seam, move the electrode away from you. If you have to make a ceiling seam, then reduce the welding current to a minimum. Thus, a seam will form before the molten electrode begins to flow down.

The width of the seam should not be greater than the diameter of the electrode. There are exceptions, then another type of welding is used, not manual electric arc.

Seams can be multi-layered or single-layered. The first layer affects all subsequent ones. If another thickness of molten metal is applied to the first low-quality seam, then over time the structure will still begin to corrode. Therefore, try to perform all seams at the highest level.

Experienced welders say that single-layer joints are fragile and short-lived. But you need to start from the goals you are pursuing. If you need to weld a greenhouse for cucumbers, then using multi-layer welding is not advisable.

conclusions

RDS is not only a budget option for home use, but also provides a reliable connection between two metal parts. It’s not difficult to master, and thanks to practical advice, it’s quick.

All necessary equipment is sold in any specialized welding equipment department. You can also find all types of coated electrodes there. The only caveat: do not buy equipment that is frankly cheap or of unknown brands.

First, inquire about the availability of service centers for a specific model and the cost of their services.

Source: https://svarka-weld.ru/ruchnaya-dugovaya-svarka-pokrytym-elektrodom

Manual arc welding with coated electrodes

Nowadays, there are a large number of different ways to join metal using welding. Many techniques have been developed, but one of the earliest and simplest is still the most common.

Manual arc welding with coated electrodes is carried out using a welding transformer or inverter. There are many models of this technique, as well as brands of coated electrodes that can be used in this process.

Each of them has its own characteristics, as they are produced for certain grades of metal.

Manual arc welding with coated electrodes

Application area

MMA welding can be used in almost any field. It is mainly used for joining low-carbon steels. This is most often used in the private sector, in small construction work, in the repair of various parts, as well as in production.

There are electrodes that are designed for use in shipbuilding, metallurgy, work in the chemical industry, and so on.

For especially critical places, they try not to use it, since it is inferior to many other types, such as TIG welding.

Advantages

The main advantages of this technology include the following factors:

• Relatively low cost of the resulting seams;
• A lengthy process of setting up and preparing welding equipment and materials is not required;
• There is no great danger of explosion here, as when working with gas;
• Welding can be carried out with both thin and thick parts;
• The equipment for carrying out the work is compact and mobile;
• Inverters operate without problems from an ordinary household outlet;
• There is a wide selection of welding transformers and inverters of any price category and various parameters;
• All materials are widely available.

Flaws

But there are also a number of disadvantages, among which the following should be noted:

• Electrode coating provides a low level of protection when compared with other technologies, so the quality of the seam is inferior to them;
• The electrode coating may become damp, allowing hydrogen to enter the bath;
• The welding speed is fast, so inexperienced welders may make many careless mistakes;
• Non-ferrous metals, their alloys, stainless steel and other varieties that are difficult to weld turn out to be very problematic when processed using this method;
• The likelihood of a defect occurring strongly depends on external conditions;
• To create an acceptable level of welding quality, you need to use many additional materials and types of processing, such as fluxes and so on.

Source: https://svarkaipayka.ru/tehnologia/termicheskaya/ruchnaya-dugovaya-svarka-pokryityimi-elektrodami.html

Manual arc welding with coated MMA electrode

During manual arc welding with coated metal electrodes, the welding arc burns from the electrode to the product, melting the edges of the product being welded and melting the metal of the electrode rod and the coating of the electrode (Figure 1). The crystallization of the base metal and the electrode rod metal forms a weld.

Figure 1. Covered metal electrode welding diagram

The electrode consists of an electrode rod and an electrode coating (see Figure 1). Electrode rod – welding wire; electrode coating is a multicomponent mixture of metals and their oxides. Based on functional characteristics, the components of the electrode coating are divided into:

• Gas-forming:
  • shielding gas;
  • ionizing gas;
• Slag-forming:
  • for physical isolation of molten metal from active gases of atmospheric air;
  • deoxidizers;
• refining elements;
• Binders;
• Plasticizers.

Ignition of the welding arc

Before igniting (exciting) the arc, the required strength of the welding current should be set, which depends on the brand of electrode, type of welded joint, position of the seam in space, etc.

Ignition (excitation) is carried out in two ways. In the first method, the electrode is brought perpendicular to the place where welding begins and, after a relatively light touch to the product, the top is moved back to a distance of 25 mm.

The second method resembles the process of lighting matches. If the arc breaks, it is re-ignited in front of the crater on the base metal with a return to the deposited metal to bring contaminants accumulated in the crater to the surface.

After this, welding is carried out in the desired direction.

The use of one or another arc ignition method depends on the welding conditions and the skill of the welder.

Position and movement of the electrode during welding

The position of the electrode depends on the position of the seam in space. The following positions of the seams are distinguished: bottom, vertical and horizontal on a vertical plane, ceiling. Welding vertical seams can be done from top to bottom and bottom to top.

When welding in the lower position, the electrode is inclined from the vertical towards the direction of welding. The movement of the electrode during welding can be carried out in the “toward” and “away” ways.

In the absence of transverse oscillatory movements of the end of the electrode, the width of the roller is equal to (0.8 - 1.5) d electrode. Such seams (or rollers) are called narrow, or thread. They are used when welding thin metal and when applying the first layer in a multilayer weld.

Obtaining medium seams (or rollers), the width of which is usually no more than (2 - 4) d of the electrode, is possible due to the oscillatory movements of the end of the electrode. The main options for oscillatory movements of the electrode end are shown in Figure 2.

Figure 2. Main types of trajectories of transverse vibrations of the end of the electrode

The order of seams

Depending on the length, short (250-300 mm), medium (350-1000 mm) and long (more than 1000 mm) seams are distinguished.

Depending on the cross-sectional dimensions, the seams are made single-pass or single-layer, multi-pass or multi-layer.

Single-pass welding is productive and economical, but the weld metal is not ductile enough due to the rough columnar structure of the weld metal and an increased overheating zone.

In the case of multilayer welding, each underlying bead undergoes heat treatment when applying the subsequent bead, which makes it possible to obtain a crushed structure of the weld metal and, accordingly, increased mechanical properties of the seam and welding joint.

The arrangement of layers in multilayer welding comes in three types of overlay; sequentially each layer along the entire length of the seam, using the “cascade” method and the “slide” method. Both of the latter methods are used when welding metal of significant thickness (more than 20–25 mm). When making multi-layer seams, special attention should be paid to the quality of the first layer at the root of the seam. The penetration of the root of the seam determines the strength of the entire multi-layer seam.

Selection of current strength and electrode diameter

The strength of the welding current is selected depending on the brand and diameter of the electrode, taking into account the position of the seam in space, the type of connection, the thickness and chemical composition of the metal being welded, as well as the ambient temperature. Taking into account all these factors, it is necessary to strive to operate at the highest possible current strength.

Table 1 - Selecting the diameter of the electrode when welding butt joints

Part thickness Electrode diameter

1,5-2,0	3,0	4,0-8,0	9,0-12,0	13,0-15,0	16,0-20,0	more than 20
1,6-2,0	3,0	4,0	4,0-5,0	5,0	5,0-6,0	6,0-10,0

Table 2 - Selection of electrode diameter for corner and T-joints

Seam leg Electrode diameter

3,0	4,0-5,0	6,0-9,0
3,0	4,0	5,0

The strength of the welding current is determined by the formula

Isv=πde2*j/4,

where de is the diameter of the electrode (electrode rod), mm;

j is the permissible current density, A/mm2.

Table 3 — Values ​​of permissible current density in the electrode

Type of coating Allowable current density j in the electrode, A/mm2, with electrode diameter de, mm 3 4 5 6

Ore-acid, rutile	14,0-20,0	11,5-16,0	10,0-13,5	9,5-12,5
Calcium fluoride	13,0-18,5	10,0-14,5	9,0-12,5	8,5-12,0

With approximate calculations, the value of the welding current can be determined using one of the following formulas:

Iсв=k*de

Isv=k1*de1.5

Isv=de*(k2+α*de)

where de is the diameter of the electrode (electrode rod), mm;

k1, k2, α - coefficients determined experimentally:

k1=2025; k2=20; α=6.

Advantages of the method:

• Simplicity of equipment;
• Possibility of welding in all spatial positions;
• Possibility of welding in hard-to-reach places;
• Fast, time-consuming transition from one type of material to another;
• Large range of welded metals.

Disadvantages of this method:

• Large material and time costs for preparing a welder;
• The quality of the welded joint and its properties are largely determined by the subjective factor;
• Low productivity (proportional to the welding current, an increase in the welding current leads to destruction of the electrode coating);
• Harmful and difficult working conditions.

Reasonable applications:

• Welding during installation;
• Welding of short seams.

Source: https://www.rudetrans.ru/o-svarke/ruchnaya-dugovaya-svarka-pokrytym-elektrodom-mma/