When fusion arc welding, consumable electrodes are used, made of cold-drawn calibrated or hot-rolled wire with a diameter of 0.3-12 mm, or flux-cored wire. Electrode strips and plates are also used as electrodes. Electrodes are classified according to material, purpose for welding certain steels, thickness of the coating applied to the rod, type of coating, nature of the slag formed during melting, technical properties weld metal, etc. A certain composition is applied to all electrodes - a coating.

The general purpose of electrode coatings is to ensure stability of the welding arc and obtain weld metal with predetermined properties. The most important properties are ductility, strength, impact strength, and corrosion resistance. The coating performs many important functions.

Firstly, this gas protection welding zone and molten metal, which is formed during the combustion of gas-forming substances. It protects the molten metal from exposure to oxygen and nitrogen. Such substances are introduced into the coating in the form of wood flour, cellulose, and cotton fabric.

Secondly, deoxidation of the weld pool metal by elements that have a greater affinity for oxygen than iron. These elements include manganese, titanium, molybdenum, chromium, silicon, aluminum, and graphite. Deoxidizers are not included in the coating pure form, but in the form of ferroalloys.

Thirdly, slag protection. The slag coating reduces the rate of cooling and hardening of the weld metal, thereby facilitating the release of gas and non-metallic inclusions. The slag-forming components of coatings are titanium and manganese ores, kaolin, marble, quartz sand, dolomite, feldspar, etc.

Fourthly, alloying the weld metal to give it special properties (increasing mechanical properties, wear resistance, heat resistance, corrosion resistance). Chromium, nickel, molybdenum, tungsten, manganese, and titanium are used as alloying components.

In addition, to increase welding productivity, iron powder is introduced into the electrode coatings. Such a powder facilitates re-ignition of the arc, reduces the cooling rate of the deposited metal, which has a beneficial effect on welding under conditions low temperatures. The powder content can reach up to 60% of the coating mass. To secure the coating on the electrode rod, binders are used, such as liquid glass. To give the coating better plastic properties, forming additives such as bentonite, kaolin, dextrin, mica, etc. are introduced into it.

Depending on the materials being welded, all electrodes are divided into the following groups: L - for welding alloyed structural steels with a tensile strength of over 600 MPa - five types (E70, E85, E100, E125, E150); U - for welding carbon and low-carbon structural steels; B - for welding high-alloy steels with special properties; T - for welding alloyed heat-resistant steels - 9 types; N - for surfacing surface layers with special properties - 44 types. The guaranteed tensile strength of the weld metal is indicated by numbers in the electrode brand. For example, the name of the electrode, designated E42, indicates that it is intended for arc welding; the minimum tensile strength of the weld metal is 42 kgf/mm 2 .

The choice of the diameter of the electrode for welding is carried out depending on the thickness of the metal being welded, its grade and chemical composition, edge shapes, welding positions, types of connections. To the main features various diameters electrodes include:

1. Welding electrodes 1 mm - designed to work with metal whose thickness is 1-1.5 mm, with a current strength of 20-25A;

2. Welding electrodes 1.6 mm - in accordance with GOST 9466-75 for low-carbon and alloy steel, are available in two sizes 200 or 250 mm, used for working with metals whose thickness is from 1 to 2 mm with a current strength of 25-50A;

3. Welding electrodes 2 mm - according to GOST 9466-75 for low-carbon and alloy steel, they are made 250 mm long, a length of 300 mm is also allowed, the thickness of the metals being welded is from 1 to 2 mm, the current strength is 50-70A;

4. Welding electrodes 2.5 mm - according to GOST 9466-75 for low-carbon and alloy steel are produced in lengths of 250-300 mm, a length of 350 mm is also allowed, the thickness of the metals being welded is from 1 to 3 mm, the current strength is 70-100A;

5. Welding electrodes 3 mm - the most widely used electrode diameter, in accordance with GOST 9466-75 for low-carbon and alloy steel, are available in three sizes 300, 350 and 450 mm, designed to work with metals whose thickness is from 2 to 5 mm with current strength 70-140A;

6. Welding electrodes 4 mm - a widely used diameter suitable for work on both professional and household equipment. Produced in accordance with GOST9466-75 in two sizes 350 and 450 mm for any types of steel, for metals whose thickness is from 2 to 10 mm with a current strength of 100-220A;

7. Welding electrodes 5 mm - electrodes of this diameter require fairly powerful welding equipment. In accordance with GOST 9466-75, they are manufactured with a length of 450 mm for low-carbon and alloy steel, and a length of 350 mm is also allowed for high-alloy steel. Designed to work with metals whose thickness is from 4 to 15 mm with a current of 150-280A;

8. Welding electrodes 6 mm - designed to work on professional equipment. According to GOST9466-75, it is produced in a length of 450 mm for low-carbon and alloy steel, and for high-alloy steel, a length of 350 mm is also allowed. Designed to work with metals whose thickness is from 4 to 15 mm with a current strength of 230-370A;

9. Welding electrodes 8-12 mm - for working on high-performance industrial equipment. In accordance with GOST 9466-75, it is produced in a length of 450 mm for low-carbon and alloy steel, and for high-alloy steel, a length of 350 mm is also allowed. Designed to work with metals whose thickness is over 8 mm with a current strength of 450A;

It should be noted that for a certain electrode diameter, the current range for each brand of electrode is different. For example, with an electrode diameter of 3 mm for UONI 13/55 the current is 70-100A, and for MP-3 the current is 80-140A.

If manual arc welding is carried out, then it is performed in 2-3 layers, since multilayer welding provides deep penetration of the root and increases the density of the welded joint. This method is used with and without rotation of the welded joints. To avoid metal burn-through, it is recommended to weld the first layer with electrodes with a diameter of 4 mm at a welding current of 120-140 A. The layers should be welded in one direction with a gradual rotation of the welded section. If a non-rotating joint is welded, then welding is carried out when connecting the sections into one string and the final installation of the pipeline. The order of applying welds is as follows: the first layers are welded from bottom to top; subsequent seams - from top to bottom. Locks, or closing areas in adjacent layers of the seam, should be spaced from each other at a distance of approximately 60-100 mm; in the ceiling part of the seam it is convenient to finish welding at a distance of 50-70 mm from the bottom point of the pipe. If it is impossible to weld non-rotating joints, then a combined method is used. With this method, the joint is welded with the insert, while the lower part of the seam is welded with inside; upper part The seam is welded from the outside. The type of electrodes used is the same as when welding rotary joints. If main pipelines are being laid, then manual welding is carried out only when applying the first layer of seam.

Welding mode refers to the main indicators that determine the welding process, which are established on the basis of initial data and must be performed to obtain a welded joint of the required quality, size and shape established by the project. These indicators for manual arc welding include: brand of electrode, its diameter, strength and type of welding current, polarity with direct current, number of layers in the seam. For a multilayer seam - the diameter of the electrode and the current strength for the first and subsequent layers, as well as other characteristics. To determine the welding mode, initial data are used, for example, the grade and thickness of the base metal, the length and shape of the welds, design requirements for the quality of the welds (electrode type), and the position of the seams in space.

Depending on the brand of metal being welded and its thickness, the type and brand of electrodes are selected. The diameter of the electrode is selected depending on the welding position and the thickness of the metal. In the lower welding position, the diameter of the electrode can be determined based on the relationship between the diameter of the electrode and the thickness of the metal being welded

The cross-sectional area of multi-layer seams is usually given in the Unified Standards and Prices for welding work, from which you can easily determine the number of layers (passes) of a multilayer seam.

Welding mode. In this work we use the electrode brand UONI 13/55, the electrode diameter is 3 mm. The position of the seam in space is vertical, bottom and ceiling. Current 75 - 100 A (depending on the position of the seam in space)

When welding in a vertical position, the current decreases by 10-20%, when welding horizontal seams - by 15-20% and when welding ceiling seams - by 20-25%. When welding in the lower position, the current strength will be equal to 100A, in the vertical position 80 - 100A, and when welding in the ceiling position, the current strength will be equal to 75 -80A.

The welding speed (arc movement) largely depends on the qualifications of the welder and his ability to conduct the welding process with breaks only for changing the electrode. In addition, the welding speed is influenced by the deposition rate of the electrodes used and the strength of the welding current. The higher the deposition rate and the higher the current, the faster the arc moves and, consequently, the welding speed increases. It should be borne in mind that an arbitrary increase in current may cause overheating of the electrode.

steel electrode welding door

How to set the welding current and select the electrode diameter? Selecting electrodes and welding mode

Dear novice welders, in this article we will briefly talk about electrodes and give practical recommendations on their use.

To select an electrode, you need to determine:

Metal thickness - (the thicker the metal, the larger the diameter of the electrode).
Steel grade - (ferrous metal, stainless steel, heat-resistant, etc.).
We determine the current by the electrode!
Welding position - (lower, horizontal, lower tee, vertical - welding from bottom to top, ceiling, ceiling tee).

As for the welding current that you will supply to the electrode. Each electrode manufacturer makes different claims. welding current. Below we present the classic parameters; welders who have been working in the profession for more than one year agreed with these parameters.

The choice of current also depends on the spatial position and size of the gap. For example: for a diameter of 3 mm, a current of 70-80 A is recommended. This is the current for welding in a ceiling position or a vertical lift, and also if the gap is equal to or greater than the diameter of the electrode. If you cook in the lower position, there is no gap and the thickness of the metal allows, then you can give 120 A on a simple electrode.

Experienced welders advise using the following formula. You can try following this formula.

The current strength is calculated according to the formula 30-40 A per 1 mm electrode, i.e. per electrode d 3 mm. set the current to 90-120 A., set the current to 120-160 A on the electrode d 4mm, etc. When welding in vertical position reduce the current by 15%.

Diameter 2 mm. – 40 – 80 Ampere. “Two” is perhaps the most capricious electrode. Many people think that the smaller the diameter of the electrode, the easier it is to work. But this is not entirely true. For example: “two” requires certain skills and dexterity, it burns quickly and gets very hot if you set a high current. “Two” is good because it requires little current and welds thin metals. But it takes skill and patience.

Diameter 3mm or 3.2mm. – 70-80 Ampere. UNDER CONDITIONS OF WELDING WITH DC CURRENT. Everyone agrees that 80 Amps is the maximum current value; anything higher is no longer welding, but cutting. Try to start welding with 70 Amps, you will understand that it does not weld - add 5-10 Amps, if 80 Amps is not enough - turn the welding current adjustment knob to 120 A, but no more. If you cook on AC current, you should set it to 110-130 amperes. Sometimes even up to 150 Amps. But most likely you don’t need this, since you have an inverter welding machine, not a transformer one.

Diameters from 5 mm and above– these are already professional electrodes; as a rule, they are used by professional welders. We will not give them recommendations; they already know how to work with them, and novice welders simply do not need them. Let’s just say that such diameters are often used not for welding, but for surfacing.

Which welding electrode to choose?

We will now talk about the main types of welding electrodes.

MP-3 and ANO– these electrodes are best used on alternating current. They are not picky about dampness. These electrodes are not for critical structures; they are never used to weld bridges and load-bearing beams roofs, they are used to make fences, gates and greenhouses in the country, fencing, small metal structures household use. If there is no overload, these are the electrodes for you. The most popular brands among amateur welders and summer residents.

UONII 13/55– these are excellent electrodes, but very “specific”. UONII 13/55 is brewed by professionals. You have to cook on a short arc! These are electrodes for critical structures. They only light up DC, love a stable arc and do not like voltage surges. Start working with UONII 13/55 only when you learn how to cook MP-3 and ANO.

LB-52U– we recommend buying these electrodes from the Japanese company KOBELCO. These electrodes are used for welding pipes under high pressure. Very high quality seam. LB-52U electrodes are one of the most expensive; as a rule, they are purchased by enterprises and structures involved in the repair of urban heating/water networks.

We introduced you to the most popular electrodes. Below we will briefly describe the electrodes of the ESAB Concern (Sweden), perhaps you will find exactly what you need. All ESAB electrodes begin with the letters OK - in honor of the founder of the Concern, Oskar Kelberg.

OK 46.00 ESAB (Russia)– metals can be welded with these electrodes using direct and alternating currents. Often these electrodes are called UNIVERSAL or ELECTRODE FOR STEEL. If you don’t know what to choose, take these electrodes – you won’t go wrong. Electrodes are good because they have a wide range of diameters. You can always choose the one you need.

OK 48.00 ESAB (Sweden)- direct current only. Ideal for critical structures.

Special electrodes.

OK 61.30 ESAB– stainless steel/stainless steel welding (steel grades 304, 308L, 03Х18Н11, 06Х18Н11, 08Х18Н10, 08Х18Н10Т, 12Х18Н10).

OK 67.60, OK 67.62 ESAB- stainless steel/steel welding.

OK 63.30 ESAB ( Russian analogues ANV-26)– (steel grade 316 , 03Х17Н14М2, 10Х17Н13М3Т, 06Х19Н11Г2М2) are ideal for welding thin-walled pipes and thin-sheet products.

If you don’t understand what kind of steel is in front of you, you don’t know its composition - your choice OK 68.81, OK 68.82– these electrodes can be used to weld dissimilar steel products and steels of unknown composition.

There are many nuances when welding cast iron!

Welding cast iron\steel ESAB OK 92.18 (new name OK Ni-Cl)- designed for welding thin cast iron (no more than 3 layers).

Welding cast iron\cast iron; cast iron\steel ESAB OK 92.60. (new name OK NiFe-Cl)-they can just cook cast iron of any thickness and cast iron with steel

Aluminum welding. Aluminum is a very complex metal, it requires heating before welding, it melts quickly and hardens quickly. Typically aluminum is welded using TIG or MIG welding. It is very difficult to weld aluminum with an electrode, but if you succeed, you can consider yourself a master!

OK 96.20 ESAB- it can be used to cook a very limited number of grades of aluminum. Study the composition carefully.

The most universal electrode for aluminum is OK 96.40. IMPORTANT that the aluminum electrode must be used in one ignition. An unfinished electrode must be replaced with a new one. Plus, unlike steels, you need to make circular movements with the end of the electrode.

Why do you need to calcinate the electrodes?

The electrodes are calcined in order to remove moisture from them. If the electrode is damp, during welding, defects may occur in the weld seam or the electrode will constantly stick to the product.

Please note that in our online store all the electrodes are “fresh”, we purchase them from suppliers who have special heated warehouses, the electrodes are not stored in warehouses for more than a month, all packs are sealed.

Construction companies have special equipment for calcining electrodes, amateur welders, as a rule, do not have such installations. If you have opened a new pack, we recommend that you either use it completely, or remove the remaining unused electrodes from the pack in a dry, warm place. Do not store electrodes in open spaces, attics or basements.

Useful information.

Forward polarity and reverse polarity.

If the electrode is on “+” and the terminal is on “-”, then the electrode melts more. - this is called reverse polarity.

If the electrode is on “-” and the terminal is on “+”, then the metal being welded melts more. - this is called direct polarity.

Direct current is DC, alternating current is AC. As a rule, all manual arc welding machines are welded on DC (direct current).

When welding with direct polarity, penetration is less (welding of thin-sheet products), and, accordingly, with reverse polarity it is greater (thick-walled products).

The ease of use of the inverter has made welding accessible to many craftsmen. This welding equipment has a control system, rectifier, filter, converter that supplies the required current.

The inverter provides direct current, the polarity of which can be changed during welding. A guarantee of a high-quality seam is the correctly selected operating mode of the unit and suitable electrodes for the inverter. There are a great variety of products.

Characteristics and sizes vary. In order to successfully buy electrodes for welding with an inverter, to determine which ones are best suited to each specific case, you need to delve into the essence of the process.

There are several types of inverter. Main sign, which should be taken as a basis, is the ability to melt. Rods that do not melt during welding are used to work in an atmosphere of shielding gas, such as argon.

Melting rods are used in manual arc welding with an inverter, which in practice is most often carried out at home. It is not the metal core that melts, but the coating applied on top. The components of the outer layer improve the properties of the arc and form a protective cloud over the working area.

When choosing a specific brand for an inverter, the amount of work, requirements for seam quality and advice from professionals are taken into account. You can look at specialized magazines to find out brand ratings.

But for home use It is quite enough to carefully read the description on the packaging in order to understand what current and what materials the electrode is intended for welding. It is best to purchase products from a trusted supplier. For experts, they recommend rutile or basic brands.

Coating

When choosing electrodes for an inverter, the welding mode and the chemical composition of the consumable material are of decisive importance:

electrodes coated with alkaline (basic) components are used if it is necessary to cook with an inverter at a constant current of reverse polarity. They are used to cook high-alloy steels;
Rutile coatings can be used when welding with alternating and direct current of both direct and reverse polarity. Titanium dioxide (rutile) ensures easy ignition of the arc, and there is no spattering of metals during operation. This best option, which can be selected;
for direct current (that is, an inverter), cellulose coating is suitable, which creates a good protective gas environment;
rutile acid coating is suitable for welding metal with alternating current or an inverter (any polarity). Arc ignition occurs even at low voltage. It is important to note that when working with acidic compounds, dangerous fumes are released. Welding must be carried out with good forced ventilation.

The alloys from which the parts are made determines the type of core. The compositions must match each other.

The choice of electrodes is regulated by GOST. The standard stipulates not only the composition of rods and coatings, but also appearance, eliminating the presence of swelling, porous areas, and sagging.

Kernel

Electrodes for inverter welding made from three types of materials: high-alloy wire, ordinary alloy or carbon raw materials.

A novice master can navigate products by labeling. The more letters and numbers it contains, the higher the degree of doping. Each letter represents a certain additive, and the number next to it indicates its percentage.

For example, a product made of carbon steel is designated Sv-10G2, and a product made of high-alloy steel is designated Sv-30Х15Н35В3Б3Т. The difference is obvious.

Popular brands

Over the years of intensive work with inverters, a rating of the popularity of electrodes has been formed in the circles of welding specialists and home craftsmen.

The ANO brand is considered the most universal. Electrodes of this group allow you to make any welding joints: corner, butt, overlap. With this electrode product you can weld parts with a thickness of no more than 5 mm in any position, even in the vertical direction from top to bottom.

There is no need to thoroughly clean surfaces from oxidation products. These electrodes can be used for root welding of thick parts. If there is a rutile, cellulose coating, then connecting any polarity of the inverter is allowed.

The products of the MR line are presented in two categories. MP-3 works effectively with parts with to varying degrees pollution. Electrodes coated with a rutile layer are used for direct and alternating currents, for any type of inverter connection.

You need to choose a position for work, taking into account the diameter of the electrode. MP-3S products are convenient for welding in various positions. These electrodes can be used to connect parts with residual moisture.

The UONI category is represented by electrodes for welding parts made of carbon and low-alloy steel alloys. The resulting seams are plastic, have high impact strength, and firmly connect structures for special purposes.

Electrodes coated with a base layer can be used with direct current, reverse polarity of the connection.

Electrodes marked OK 63.34 show good performance. They can weld thermally strong steels and alloys that are resistant to corrosion. It is possible to weld vertically structures of small thickness, make butt and overlap joints.

For welding structures that require high strength and reliability of the seam, electrodes of the OZS-12 brand are used. They operate on direct current of an inverter of direct polarity, as well as on alternating current.

It is also worth mentioning the brands ESAB, Lincoln, Electric, Resanta, Kobelco, which offer high quality products with rutile, basic and combined coatings. The price range here is different, and each buyer decides for himself which option is best.

Diameter selection

When choosing a product, you should pay attention to its diameter. The thinner the design, the smaller the possible electrode diameter. For welding profiles, products with a diameter of up to 2 mm are sufficient.

By the way, you need to learn how to work with delicate products. Such electrodes quickly melt and are consumed. To work with them you must have special skills.

Depending on the diameter of the electrode, the current strength for welding with an inverter is determined. Recommended values are often indicated on the top of the packaging. In general, the pattern is as follows: the larger the diameter of the electrode product, the higher the required current value.

Inconsistency between material thickness, electrode diameter and current may degrade quality welded joint, lead to the formation of pores in it.

Advantages

Difficulties in forming a seam can only arise due to wrong choice grades for a specific metal or alloy. When the work is carried out correctly, high-quality connections of any shape and location are formed.

Consumable electrodes of the indicated brands form slag, which, after completing its protective functions easy to separate. There is no need to beat him for a long time and painfully. The quality of the seam will be immediately visible.

The presented types of electrodes allow you to work even with parts that have rust residues. Sometimes this feature is very important. When working in extreme conditions, there may not be time or opportunity to thoroughly clean surfaces.

Electric arc welding is performed using a transformer or. The second option is more popular in everyday life due to its compact size and low weight. Any of these units works using electrodes.

What does a welding electrode consist of?

The basis is a metal rod. Depending on, it can be:

Melting. It is made of steel electrode wire or a special alloy. A special paste is applied over the metal rod - coating (coating).

The composition of the coating includes various chemical elements and additives, with the help of which the correct configuration of the welding seam is formed. In addition, thanks to the coating, a stable burning of the welding arc is maintained.

Non-melting. Electrodes of this type do not participate in the formation of a seam, but serve only as a source for the occurrence of a welding arc. Made from refractory materials. The most common is tungsten rod.

The non-consumable electrode itself (as its name suggests) remains intact during work. To form a weld, a filler material is supplied to the melt zone in the form of a wire made of the same metal as the workpiece.

Tungsten rods are used for inverter welding of aluminum. The work is carried out in an environment of neutral gases, for example argon.

Both considered options refer to piece electrodes, that is, each of them is a separate element of a certain length. There are also continuous feed electrodes - the so-called welding wire.

It is fed into the contact zone with the workpiece, mechanically. The seam is formed due to its melting and flowing into the bath. Since the wire is a conductor, it ensures the operation of the welding arc. There is no coating for such an electrode, so all elements to create the correct weld are embedded in the alloy.

To saturate the welding zone with the necessary additives and chemical elements, a flux-cored wire has been created, which is a thin tube with the required composition in the middle.

This wire is used in welding machines for inverter welding of the “semi-automatic” type. An electrode in the form of a wire (monolithic or filled with flux-cored wire) is located inside and is fed into the welding zone automatically; the operator only gives a command to turn it on.

Operating principle of the inverter

To obtain a large welding current, a huge transformer is required. It is inconvenient to transport and maintain. Unlike welding transformer– the inverter works as pulse block high power supply.

Rutile electrodes MP-3

Ask any welder what consumables he started training with - and you will get the answer: “MR-3”. This brand is ideal for a beginner. Ignition occurs instantly, even if you made a slight mistake with the inverter parameter settings.

The bath is protected by additives from the coating; special effort is not required to control its position. If you can’t “catch the arc” the first time, just calcinate the electrodes at a temperature of 160°-190° for 30-50 minutes. You can weld in any position of the welding seam, except vertical from top to bottom.

Despite the versatility of the current (you can cook both alternating and constant) - best seam It turns out precisely on inverters with direct current.

The quality of the surface does not matter; corrosion or moisture on the surface is not a problem. If you picked up an electrode holder for the first time, it should contain an MP3.

Basic coating UONI 13/55

Most common consumables welder Manufacturers recommend them for working on metals with high content carbon. The durable seam resists impact loads well and has a high tensile strength coefficient. In Russia, these electrodes are also popular because the seams tolerate low temperatures well.

UONI 13/55 operate on direct current with reverse polarity, full compatibility with inverters.

Arc welding modes are a set of controlled parameters that determine the conditions of the welding process. Correctly selected and maintained parameters throughout the welding process are the key to a high-quality welded joint. Conventionally, the parameters can be divided into basic and additional.
Basic parameters of arc welding mode: electrode diameter, magnitude, type and polarity of current, arc voltage, welding speed, number of passes.
Additional parameters: the amount of electrode stickout, the composition and thickness of the electrode coating, the position of the electrode, the position of the product during welding, the shape of the prepared edges and the quality of their cleaning.
Selecting the electrode diameter
The diameter of the electrode is selected depending on the thickness of the metal being welded, the position in which welding is performed, the leg of the weld, as well as the type of connection and the shape of the edges prepared for welding. In order to choose the correct electrode diameter, you can use Table 1:

Table 1. Approximate ratio of the diameter of the electrode and the thickness of the parts being welded

However, this ratio is approximate, since this factor is influenced by the placement of the seam in space and the number of welding passes. For example, when the seam is in a ceiling position, it is not recommended to use electrodes with a diameter of more than 4 m. Do not use electrodes of large diameters for multi-pass welding, as this can lead to lack of penetration of the root of the seam.
Current strength is selected depending on the diameter of the seam, the length of its working part, the composition of the coating, the welding position, etc. The greater the current, the more intensely its working part melts and the higher the welding performance. But this rule can be accepted with some reservations. If the current is excessive for the selected electrode diameter, the working part overheats, which can lead to deterioration in the quality of the seam, splashing of droplets of liquid metal, and can even lead to burnout of parts. If the current is insufficient, the arc will be unstable and will often break, which can lead to lack of penetration, not to mention the quality of the seam. The larger the diameter of the electrode, the lower the permissible current density, since the cooling conditions of the weld worsen.
Experienced welders determine the current strength experimentally, focusing on the stability of the arc. For those who do not yet have sufficient experience, the following calculation formulas have been developed: For the most common electrode diameters (3 -6 mm):
- I St = (20 + 6d e)d e
- where I St - current strength in A, d e - electrode diameter in mm
For electrodes with a diameter of less than 3 mm, the current is selected according to the formula:
- Icv = 30dе
- For welding ceiling seams The current strength should be 10 - 20% less than with the lower position of the seam.
- Besides, The current strength is influenced by the polarity and type of current. For example, when welding with direct current with reverse polarity, the cathode and anode change places and the penetration depth increases to 40%. The penetration depth when welding with alternating current is 15 - 20% less than when welding with direct current. These circumstances should be taken into account when choosing welding modes.

Selecting arc welding mode

When choosing welding modes, the presence of a bevel of the welded edges should also be taken into account. All these circumstances are taken into account and summarized in tables 2 and 3. The features of burning a welding arc on direct and alternating current are different. The arc, which is a gas conductor, can be deflected by magnetic fields created in the welding zone. The process of deflection of the welding arc under the influence of magnetic fields is called magnetic blast, which complicates welding and stabilization of the arc.

Table 2. Mode for welding butt joints without beveled edges

Character of the seam	Electrode diameter, mm	Current, A	Metal thickness, mm	Gap, mm
Unilateral	3	180	3	1,0
Double sided	4	220	5	1,5
Double sided	5	260	7-8	1,5-2,0
Double sided	b	330	10	2,0

Note: the maximum current value must be specified in the electrode data sheet.

Table 3. Welding modes of butt joints with beveled edges

Electrode diameter, mm		Current, A	Metal thickness, mm	Gap, mm	Number of layers of cooked and decorative cream
First	Subsequent	Current, A	Metal thickness, mm	Gap, mm	Number of layers of cooked and decorative cream
4	5	180-260	10 .	1,5	2
4	5	180-260	12	2,0	3
4	5	180-260	14	2,5	4
4	5	180-260	16	3,0	5
5	6	220-320	18	3,5	6

Note: the value of the current value is specified according to the passport data of the electrode.

Magnetic blast is especially pronounced when welding on a direct current source. Magnetic blast impairs arc stabilization and complicates the welding process. To reduce the influence of magnetic blast, protective measures are used, which include: short-arc welding, tilting the electrode in the direction of the magnetic blast, supplying welding current to a point as close as possible to the arc, etc. If it is not possible to completely get rid of the effect of magnetic blast, then change the power source to an alternating one, in which the influence of magnetic blast is noticeably reduced. Low-carbon and low-alloy steels are usually welded using alternating current.

Manual arc welding technique

Electrode trajectory

Proper arc maintenance and movement is the key to quality welding. An arc that is too long promotes oxidation and nitriding of the molten metal, splashes droplets and creates a porous weld structure. A beautiful, even and high-quality seam is obtained when making the right choice arc and its uniform movement, which can occur in three main directions.
The forward movement of the welding arc occurs along the axis of the electrode. With this movement, the required arc length is maintained, which depends on the melting rate of the electrode. As the electrode melts, its length decreases, and the distance between the electrode and the weld pool increases. To prevent this from happening, the electrode should be moved along the axis, maintaining a constant arc. It is very important to maintain synchronicity. That is, the electrode moves towards the weld pool synchronously with its shortening.
The longitudinal movement of the electrode along the axis of the welded seam forms the so-called thread welding bead, the thickness of which depends on the thickness of the electrode and the speed of its movement. Typically, the width of the thread welding bead is 2 - 3 mm larger than the diameter of the electrode. Strictly speaking, this is already a welding seam, only a narrow one. For a strong welding joint, this seam is not enough. And therefore, as the electrode moves along the axis of the weld, a third movement is performed, directed across the weld.
The transverse movement of the electrode allows you to obtain the required seam width. It is committed oscillatory movements reciprocating nature. The width of the transverse vibrations of the electrode is determined in each case individually and largely depends on the properties of the materials being welded, the size and position of the seam, the shape of the groove and the requirements for the welded joint. Typically, the width of the seam lies in the range of 1.5 - 5.0 electrode diameters.
Thus, all three movements overlap each other, creating a complex trajectory of the electrode. Almost everyone experienced master has his own skills in choosing the trajectory of the electrode, drawing intricate shapes with its end. Classic trajectories of electrode movement during manual arc welding are shown in Fig. 1. But in any case, the arc movement trajectory should be chosen in such a way that the edges of the parts being welded are fused to form the required amount of deposited metal and the specified weld shape.
If the weld is not completed before the length of the electrode decreases so much that it requires replacement, then welding is stopped for a while. After replacing the electrode, remove the slag and resume welding. To complete a broken seam, strike an arc at a distance of 12 mm from the depression formed at the end of the seam, called a crater. The electrode is returned to the crater to form a fusion of the old and new electrodes, and then the electrode begins to move again along the originally chosen path.

Arc welding diagram

The order of filling the seam along the cross-section and length determines the ability of the welded joint to absorb given loads and affects the magnitude of internal stresses and deformations in the seam mass.
Seams are distinguished: short - the length of which does not exceed 300 mm, medium - 300 - 100 mm long and long - over 1000 mm. Depending on the length of the seam, it can be filled according to various schemes welding filling, which are shown in Fig. 2.
In this case, short seams are filled in one pass - from the beginning of the seam to its end. Seams medium length can be filled using the reverse-step method or from the middle to the ends. To perform the reverse-step filling method, the seam is divided into sections whose length is 100-300 mm. In each of these sections, the seam is filled in the direction opposite to the general welding direction.
If one pass of the welding arc is not enough to fill the seam normally, multilayer seams are applied. Moreover, if the number of applied layers is equal to the number of passes, the seam is called multilayer. If some layers are performed in several passes, such seams are called multi-layer-pass. Such seams are shown schematically in Fig. 3.


Rice. 2. Arc welding patterns: 1—through welding; 2 - welding from the middle to the edges; 3 - reverse-step welding; 4 - block welding; 5 - cascade welding; 6 - welding with a slide	Rice. 3. Species welds : 1 - single layer; 2 - multi-pass; 3 - multi-layer, multi-pass

From the point of view of labor productivity, the most appropriate are single-pass welds, which are preferred when welding metals of small (up to 8-10 mm) thicknesses with preliminary cutting of the edges.
But for critical structures (pressure vessels, load-bearing structures etc.) this is not enough. Internal stresses arising during the welding process can cause cracks to appear in the weld or in the heat-affected zone due to insufficient ductility of the weld and high rigidity of the base metal. When welding products with relatively low rigidity, internal stresses cause local or general warping (deformation) of the structure being welded. In addition, when welding metals with a thickness of more than 10 mm. volumetric stresses appear and the risk of cracks increases. In such cases, a number of measures are taken to reduce stress and deformation: welds are used minimum section, welding with multilayer seams, seams using “cascade methods” or “slide”, forced cooling or heating.
When welding “slide”, first a first layer is laid at the base of the cut edges, the length of which should be no more than 200 - 300 mm. After this, the first layer is covered with a second one, the length of which is 200 - 300 mm longer than the first. The third layer is applied in the same way, overlapping the second by 200 - 300 mm. In this way, filling is continued until the number of layers in the area of the first seam is sufficient for filling. The next layer is applied at the end of the first layer, overlapping the last one (if the length of the seam allows) by the same 200 - 300 mm. If the first seam was laid not at the beginning of the seam, but in its middle part, then the slide is formed sequentially in both directions (Fig. 2, e). So, forming a slide, the entire seam is sequentially filled. The advantage of this method is that the welding zone is in a heated state all the time, which helps to improve the physical and mechanical properties of the seam, since internal stresses are minimal and the appearance of cracks is prevented.
The “cascade method” of filling a seam is essentially the same “slide”, but it is performed in a slightly different sequence. To do this, the parts are connected to each other “on tacks” or in special devices. Lay the first layer, and then, stepping back from the first layer at a distance of 200 - 300 mm, lay the second layer, covering the area of the first (Fig. 2e). Continuing in the same sequence, fill the entire seam.
Fillet welds (Fig. 4) can be performed using two methods, each of which has its own advantages and disadvantages. When welding “in the corner”, a larger gap between parts is allowed (up to 3 mm), easier assembly, but the welding technique is more complicated. In addition, undercuts and sagging are possible, and productivity is reduced due to the need to weld small-section seams with a leg less than 8 mm in one pass. Boat welding allows for larger seam legs in one pass and is therefore more productive. However, such welding requires careful assembly.
The indicated arc welding techniques were considered at the lower positions of the seam, the implementation of which is the least labor-intensive. In practice, it is often necessary to perform horizontal seams on a vertical plane, vertical and ceiling welding. To perform these works, the same techniques are used as for seams with a lower position, but the labor intensity of the work and some technological features require a more detailed approach and changes in some methods.
When welding such seams, there is a possibility of molten metal leaking out, which leads to drops falling to areas unfilled by welding, molten metal flowing along horizontal planes, etc.


Rice. 4. Position of the electrode and the product when making fillet welds: A - symmetrical boat welding; B - in an asymmetrical “boat”; B - “in the corner” with an inclined electrode; G - with melted edges	Rice. 5. : As the speed increases, a noticeable decrease in the width of the weld is observed, while the penetration depth remains almost unchanged.

Considering the essence of the processes occurring in such seams, we said that surface tension forces can hold the metal in a molten bath. In order for these forces to be sufficient, the welder must master welding techniques masterfully. Here it is necessary to reduce the welding current and use electrodes of reduced cross-section. This ultimately affects productivity as the number of welding passes has to be increased. Therefore, in practice, they try to add a “surface tension film” in addition to surface tension forces. The essence of this method is that the arc is not held constantly, but at certain intervals, that is, pulses.
To do this, the arc is constantly interrupted, igniting it at certain intervals, allowing the molten metal to partially crystallize. It is here that the welder’s ability to choose such intervals is manifested when the welding leg does not have time to form and at the same time the metal would lose part of its fluidity.
The ceiling seam is the most difficult. Therefore, conducting it with continuous arc burning is a futile task. Welding is performed by short-circuiting the arc to the weld pool so that it does not have time to cool, replenishing it with new portions of molten metal.
When welding with this method, you should monitor the size of the arc, since its lengthening can cause unwanted undercuts. In addition, when welding such seams, unfavorable conditions to release slag from the molten metal, which can lead to porosity in the weld.
Vertical seams can be welded in two directions - from bottom to top and from top to bottom. Both methods have a right to exist, but uphill welding is always preferable. In this case, the metal located below holds the weld pool, preventing it from spreading.
When welding downhill, it is more difficult to hold the weld pool, and therefore it is much more difficult to achieve a high-quality seam. The essence of this method is practically no different from ceiling welding, and it is used when upward welding is technologically impossible.
Horizontal seams on a vertical plane also have their own characteristics. In these welds, it is especially difficult to retain the weld pool at both edges of the parts being welded. To facilitate this process, the bottom edge is not beveled. In this case, a shelf is obtained that helps to hold the molten weld pool in place. Pulse welding with short-term ignition of the arc is also appropriate here, as for ceiling seams.
Welding slag is removed with a chipping hammer. To do this, wait until the workpiece has cooled down enough that it can be picked up by hand, press it firmly to the table and, with hammer blows directed along the seam, remove the slag covering the weld seam. After this, the seam is forged to relieve internal stress. To do this, the hammer head is deployed along the seam and forged along its entire length. Finish the cleaning with a stiff wire brush, moving it with sharp movements, first along the seam and then across it to remove the last remnants of slag.


Rice. 6. The influence of the angle of inclination of the product on the shape of the weld: When welding uphill, a large penetration depth is observed, as well as a large bead height. When welding downhill, on the contrary, the depth of penetration decreases and the height of the weld decreases. In this case, the width of the seam practically does not change.	Rice. 7. Influence of electrode position on the shape of the weld: The figure shows that when welding with a backward angle, deeper penetration occurs, and when welding with a forward angle, the width of the seam increases and the height of the bead decreases.

Rice. 8. Influence of welding speed on the shape of the weld: The position of the weld pool when the workpiece, arc or electrode is tilted. Downhill welding, uphill welding, forward angle welding.	Rice. 9. The influence of preparing edges for welding in butt joints.

Rice. 10. Elements of a butt weld, fillet weld and bead on a plate: B - width of the weld; K - seam leg	Rice. 11. Influence of the welding current value during welding: If you change the welding current during welding, the parameters of the weld cross-section will change. At a lower current, the penetration depth increases and the weld bead increases.