Welding Electrodes

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Welding Electrodes
Welding Electrodes

Video: Welding Electrodes

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Video: Stick Welding Electrodes Explained: Stick Welding Basics for Beginners 2023, February
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  • Purpose of the electrode, its characteristics
  • How electrodes work
  • How is the type of electrode coating related to their welding and technological properties?
  • Consumable and non-consumable electrodes - what is the difference between them
  • Electrodes are divided into several groups

    • Group of electrodes for welding work with carbon and low alloy steels
    • Group of electrodes for welding with high-alloy steels and alloys
    • Group of electrodes for welding work on alloyed structural steels (high and high strength)
    • Welding electrodes
    • A group of electrodes used to perform cold welding and surfacing of cast iron products
  • Welding of heat-resistant steels - used electrodes
  • Welding of non-ferrous metals - some details
How electrodes work
How electrodes work

For better welding of metals and alloys, it is necessary to select a specific brand of welding electrodes for each of them. And in order not to be mistaken in the choice, you need to know what types of electrodes exist, how to recognize their markings and areas of application - the answers are in this article.

Purpose of the electrode, its characteristics

The electrode is an important link in the technology of electric arc welding - it is designed to supply electric current to the welding object. Today there are many types and brands of welding electrodes that have their own narrow specialization.

The electrodes must meet the following conditions:

  • supply of a constant burning arc, the formation of a high-quality seam;
  • the metal in the weld must have a certain chemical composition;
  • the electrode rod and its coating melt evenly;
  • welding with high productivity with the least spatter of electrode metal;
  • the slag obtained during welding is easily separable;
  • preservation of technological and physicochemical characteristics during a certain period (during storage);
  • low toxicity during production and during welding.

How electrodes work

For their manufacture, electric current-carrying welding wire or metal rods are used, the chemical composition of which determines the quality of the electrodes. The electrodes can only consist of a metal rod (wire) - such welding electrodes are called uncoated. If the electrode rod is coated with a special compound designed to improve the quality of welding, the electrodes are called coated. Several types of coating are used: acidic, basic, rutile, cellulose and mixed.

How electrodes work
How electrodes work

According to its purpose, the coating is divided into two types: protective (thick-coated electrodes) and ionizing (thin-coated electrodes). For a better understanding of the difference between these types of coatings, it should be noted that the quality of welding with electrodes with an ionizing coating is inferior to welding with electrodes with a protective coating - the first type of coating is not able to protect the weld from nitriding and oxidation.

How is the type of electrode coating related to their welding and technological properties?

The ability to weld in any position, the performance of electric welding, the required welding current, the tendency to pore formation, as well as (in some cases) the tendency to form cracks in the weld and the hydrogen content in the deposited metal - all these factors directly depend on the type of coating of the welding electrodes …

The acidic coating consists of silicon, manganese and iron oxides. Acid-coated electrodes (SM-5, ANO-1), according to the properties of the welded joint and the weld metal, are types E38 and E42. When welding with electrodes with an acidic coating of metals covered with rust or scale, pores will not form (the same - when the arc is lengthened). The welding current for such electrodes can be alternating or constant. A negative factor when welding with acid-coated electrodes is a high tendency to hot cracks in the weld metal.

The main coating of the electrodes (UONII-13, DSK-50) is formed by fluoride compounds and carbonates. The chemical composition of the metal directed by such electrodes is identical to that of quiet steel. The low content of inclusions of non-metals, gases and harmful impurities provides the weld metal with high impact strength (at normal and low temperatures) and ductility, it is characterized by increased resistance to hot cracks. According to their characteristics, electrodes with basic coating belong to the types E42A and E46A, E50A and E60.

However, electrodes with a basic coating are inferior in their technological characteristics to some types of electrodes due to their drawbacks - in the case of wetting the coating and lengthening the arc in working with them, the sensitivity to pore formation in the weld metal is high. Welding with such electrodes is carried out under direct current with reverse polarity, the electrodes require calcination before starting welding (at t 250-420 ° C).

Rutile coated electrodes
Rutile coated electrodes

Rutile-coated electrodes (MP-3, ANO-3, ANO-4, OZS-4) bypass all other types of electrodes in a number of technological qualities. When performing AC welding, the arc burning of such electrodes is powerful and stable, with minimal metal spatter - a high-quality seam is formed, and the slag crust is easily separable. Changing the arc length, welding wet or rusty metal, welding on the surface with oxides - all this has little effect on the pore formation of rutile electrodes.

However, the weld metal formed by them also has negative qualities - reduced toughness and plasticity caused by inclusions of silicon oxide.

Organic components in large quantities (up to 50%) make up the cellulose type of electrode coating (VSC-1, VSC-2, OMA-2). The metal deposited by them is identical to calm or semi-calm steel (in chemical composition). According to their characteristics, electrodes with cellulose coating belong to types E50, E46 and E42.

One-sided welding with cellulose electrodes by weight allows you to get a uniform reverse seam bead, you can also weld vertical seams - using the top-down method. However, the seam metal obtained by welding with cellulose electrodes has a high hydrogen content and this is a big minus.

Mixed coating allows you to combine the quality characteristics of different types of electrode coatings. Mixed coatings are sour-rutile, rutile-cellulose, rutile-basic, etc.

Cover type Marking according to GOST 9466-75 International ISO mark Marking according to the old GOST 9467-60 sour AND AND P (ore) the main B AT F (calcium fluoride) rutile P R T (rutile (titanium)) cellulosic C FROM Oh (organic) mixed coating types acid-rutile AR AR rutile basic RB RC mixed other P S rutile with iron powder RJ RR

Consumable and non-consumable electrodes - what is the difference between them

A metal rod of consumable electrodes is used in welding as a forming material for a seam; the material for such electrodes is steel or copper. Non-consumable electrodes are made from coal or tungsten - their purpose is to supply electric current to the welding site, and a filler wire or rod is used to fasten the welded elements (connected primarily by their own metal). The material for the production of carbon electrodes is a special electrotechnical amorphous coal, which is given the appearance of rods of a rounded cross-section. Carbon electrodes are used in two ways: to obtain neat welds from an aesthetic point of view - if the appearance of the final product is especially important; they can be used to cut extra thick metal (air-arc cutting).

The length of the electrode depends on its diameter:

Electrode diameter, mm Electrode length, mm Electrode diameter, mm Electrode length, mm alloyed or carbon highly doped alloyed or carbon highly doped 1.6 220

250

150

200

4.0 350

450

350 2.0 250 200

250

5.0

6.0

8.0

10.0

12.0

450 350

450

2.5 250

300

250 3.0 300

350

300

350

The marking of the electrodes is carried out according to the following scheme:

Electrode marking
Electrode marking

1st value corresponds to the type of electrode;

2nd - brand of electrode;

3rd - diameter (mm);

4th - describes the purpose of the electrodes;

5th - coating thickness;

6th - an index informing about the characteristics of the weld metal and weld metal (GOST 9467-75, GOST 10051-75 or GOST 10052-75);

7th - type of coverage;

8th - types of spatial positions of surfacing or welding, permissible for these electrodes;

9th - polarity and type of current, rated voltage for an alternating current source at no load.

A prerequisite for the structure of electrode marking is an indication of the technical requirements (GOST), according to which these electrodes were performed (according to the conditions of GOST 9466-75, TU 14-4-644-65, TU 14-4-321-73, TU 14-4 -831-77, TU 32-TsTVR-611-88).

Example of electrode marking:

E46A - UONI - 13/45 - 3.0 - UD2 GOST 9466-75, GOST 9467-75 E432 (5) - B10

The proposed example contains the marking of electrodes of the E46A type, let us consider its meaning in more detail.

Divider designation:

  • E - electrode intended for arc welding;
  • 46 - guaranteed minimum ultimate tensile strength (according to GOST 9467-75);
  • A - improved type electrodes;
  • U - electrodes are applicable for welding structural steels (carbon and low-alloyed) with ultimate tensile strength up to 600 MPa;
  • D2 - coating thickness corresponds to the 2nd group;

Denominator designations:

  • 43 2 (5) - characteristics of weld and weld metal;
  • B - according to the above table of types of coatings, corresponds to the main type;
  • 1 - spatial position, admissible during welding;
  • 0 - reverse polarity direct current.

When marking electrodes suitable for welding structural steels (carbon and low-alloyed) with ultimate tensile strength up to 600 MPa, the dash after the letter “E” (in the denominator) is not put.

According to GOST 9466-75, metal electrodes produced by the crimping method for performing manual arc welding of steels and surfacing the outer (surface) layers with special properties are marked with the appropriate letter designation and are divided into classes:

  • for welding carbon and low-alloy steels (with ultimate tensile strength up to 600 MPa) - “U” marking;
  • for welding alloy steels (ultimate strength over 600 MPa) - marking "L";
  • for welding alloy steels of high heat resistance - marking "T";
  • for welding high-alloy steels with special properties - marking "B";
  • For surfacing of surface layers with special properties - marking "H".

Electrodes intended for welding high-alloy steels are subdivided into classes depending on the chemical composition and mechanical properties of the deposited metal: there are 49 types of such electrodes (according to GOST 10052-75), designated by the index "E", followed by numbers and letters. The numbers behind the index (two) inform about the carbon content (average, in hundredths of a percent) in the deposited metal. The following letter designations of chemical elements are given (no quotation marks are put on the marking): nitrogen - "A", niobium - "B", tungsten - "B", manganese - "G", copper - "D", molybdenum - "M", nickel - "N", titanium - "T", vanadium - "F" and chrome - "X". If the average content of chemical elements in the deposited metal is less than 1.5%, the numbers after the letter designation are not set.

Possible spatial positions during welding are indicated as follows:

  • if welding in all positions is permissible for this type of electrodes - "1";
  • all positions, except for welding in the top-down position - "2";
  • only for a horizontal position on a plane located vertically, for a vertical position from bottom to top and for a bottom position - "3";
  • only for the bottom position and the bottom in the boat - "4".

Electrodes are divided into several groups

Group of electrodes for welding work with carbon and low alloy steels

The electrodes included in this group are used for welding carbon steels (carbon content up to 0.25%) and low-alloy steels with a ultimate tensile strength of no more than 590 MPa. This group of electrodes is united by the following properties of the welded joint and the mechanical characteristics of the weld metal: impact strength and elongation, bending angle and ultimate tensile strength.

These properties of electrodes determine their classification within the group (when marking the numbers following the letter designation "E", they inform about the smallest ultimate tensile strength of the welded joint or weld metal, in kgf / mm2):

  • welded work on steels with ultimate tensile strength less than 490 MPa (E38, E42, E46 and E50);
  • welded work on steels with high requirements for impact toughness and relative elongation of the weld metal (E42A, E46A and E50A);
  • welded works on steels with ultimate tensile strength of more than 490 MPa, but not higher than 590 MPa (E55 and E60).

Group of electrodes for welding with high-alloy steels and alloys

Within the group, electrodes, the purpose of which is to weld alloys based on nickel and iron-nickel, as well as high-alloy steels, are divided into:

  • intended for welding heat-resistant (heat-resistant) steels and alloys;
  • designed for welding corrosion-resistant steels and alloys.

According to the conditions of GOST 10052-75, electrodes intended for welding high-alloy steels and alloys with corrosion resistance, heat resistance and heat resistance are classified according to the mechanical properties of the weld metal and the chemical composition of the deposited metal into 49 types. For most industrial electrodes, the characteristics of the weld metal are determined by the manufacturer's specifications.

Electrodes for welding high-alloyed alloys and steels
Electrodes for welding high-alloyed alloys and steels

Electrodes intended for welding high-alloyed alloys and steels have significant differences in the characteristics of the deposited metal and chemical composition from the characteristics and composition of the metals welded by them. In order to make the best choice, it is necessary to achieve the basic operational parameters for welded joints (corrosion resistance and mechanical properties, heat resistance and heat resistance) and resistance of the weld metal to cracking.

Welding of high-alloy steels and alloys is performed with electrodes with rutile, basic and rutile-basic types of coatings. Such electrodes have a high melting rate and deposition rate due to rods made of high-alloy alloys and steels, compared to electrodes intended for welding low-alloy, alloy and carbon steels - the thing is that electrodes for welding high-alloy alloys and steels have high electrical resistance and low thermal conductivity. The same properties require welding under welding currents of reduced values ​​and shortening the length of the electrodes, the welding itself is performed mainly under reverse polarity direct current.

Group of electrodes for welding work on alloyed structural steels (high and high strength)

The electrodes of this group are used for welding with a ultimate tensile strength of more than 590 MPa. Welding of such grades of steels is carried out in two ways: after welding, the seams are subjected to heat treatment or it is not carried out.

Heat treatment of welded seams allows to obtain welded joints of equal strength. There are five types of electrodes (according to GOST 9467-75) designed for welding these types of steels (E70, E85, E100, E125 and E150). According to GOST, the deposited metal cannot contain more than 0.030% sulfur and 0.035% phosphorus.

Important note: before performing welding work on structures, the operation of which assumes the presence of extreme conditions, it is necessary to pay close attention to the chemical composition of the electrode and the metal that will be welded by it (you can determine the chemical composition using the regulatory documentation, or use general data from the complete marking of electrodes).

In the case when there is no special need for equal-strength joints during welding, electrodes can be used that can provide the austenitic structure of the seam metal. The welded joints obtained in this way have increased resistance to cracking, and the distinctive characteristics of the weld metal will be toughness and ductility. This type of electrodes can be used for welding dissimilar and high-alloy steels, taking into account during welding all the features of such electrodes, created for welding high-alloy steels.

Welding electrodes

For the formation of surface layers by arc surfacing (except for surfacing layers on non-ferrous metals), there is a specialized group of electrodes produced in accordance with GOST 10051-75 and GOST 9466-75.

This group contains 44 types of electrodes (for example, E-16G2XM, E-110X14V13F), classified by hardness (at normal temperature) and by the characteristics of the deposited metal (its chemical composition). The characteristics of the deposited metal of the electrodes are determined in a number of cases according to the technical specifications of each manufacturer.

Cladding electrodes
Cladding electrodes

According to the operational characteristics of the deposited metal and the selected alloying system, electrodes for surfacing can be divided (conditionally) into six groups that form the deposited metal:

  • low-carbon, low-alloy, with high resistance to shock loads and friction of two metals;
  • medium-carbon low-alloyed, having high resistance to shock loads, with friction of two metals at normal and elevated temperatures (up to 600-650 ° C);
  • carbon alloyed (high-alloyed), resistant to abrasive wear and shock loads;
  • high-alloy carbon, with increased resistance to high temperatures (650-850 ° C) and high pressures;
  • high-alloyed austenitic structure with high resistance to corrosion and erosion wear and friction of two metals at high temperatures (up to 570-600 ° C);
  • dispersion-hardened, high-alloyed, highly resistant to particularly difficult deformation and temperature conditions (910-1100 ° C).

Work on metal surfacing is carried out according to special technologies, which may include heating (preliminary and concomitant) heat treatment, etc. - based on the state and chemical composition of the metals (base and deposited). Strict adherence to technology allows to obtain weld metal surfaces with specified performance characteristics.

A group of electrodes used to perform cold welding and surfacing of cast iron products

Such electrodes make it possible to correct defects found in cast iron castings; the same group includes electrodes used in repair and restoration work on worn out equipment. It is possible to use electrodes for cold welding in the creation of structures by the welded-injection method.

Using electrodes from this group, it is possible to obtain a weld metal of certain properties - steel and nickel-based alloys, an alloy of iron and nickel, copper, etc.

Welding of heat-resistant steels - used electrodes

Heat-resistant steels (grades TsL-17, TsL-39, TML-1U, TML-3U, TsU-5, OZS-11, etc., capable of operating at high temperatures - up to 550-600 ° C) are welded with special electrodes, the main properties of which are chemical properties of deposited metal and mechanical characteristics of weld metal at normal temperature. Before starting welding, it is important to take into account the maximum size of the working temperature, its compliance with the calculated indicators of the long-term strength of the weld metal.

According to the conditions of GOST 9467-75, there are nine types of electrodes (E-09M, E-09MH, E-09x1M, E-05x2M1, E-09x1M1NFB, E-10x3M1BF, E-10x5MF) with a basic and rutile coating, the specialization of which (according to chemical characteristics and mechanical properties of weld metal and weld metal) consists in welding heat-resistant steels.

Also, welding of heat-resistant steels can be performed with electrodes that do not fall under GOST 9467-75 - provided that they are intended for welding with steels of other classes (for example, ANZhR-1 grade electrodes, the main purpose of which is to weld dissimilar steels).

When welding heat-resistant steels, as a rule, they are preheated, and upon completion of welding, heat treatment.

Welding of non-ferrous metals - some details

When welding copper and its alloys, it is important to take into account the high activity of this metal in interaction with gases (most of all with hydrogen and oxygen). The consequence of these reactions can be microcracks and pore formation in the weld metal, which can be prevented only by working with deoxidized copper. Before starting welding, the electrodes must be thoroughly calcined, and the areas for the seams on the welded elements must be cleaned until a metallic sheen appears, with the complete removal of oxides, grease, contamination, etc. The main difficulty in welding bronze parts is their high fragility and a decrease in strength characteristics when heated; when welding brass structures, zinc actively evaporates.

Non-ferrous metal welding
Non-ferrous metal welding

Aluminum and its alloys are highly oxidizable - the dense oxide film on the surface of the elements being welded is highly refractory. The surface of the weld pool can also be covered with a film of aluminum oxide, which interferes with the welding process - interfering with the formation of the weld, contributing to the appearance of non-welded areas and non-metallic inclusions in the weld metal. It is required to remove the oxide film - the solution to this problem in manual welding will be the introduction of fluoride and chloride salts of alkali (alkaline earth) metals into the coating composition of the electrodes, which, being in a molten state, will help to eliminate the film and maintain a stable arc.

The toughness and strength of nickel, especially its alloys, which (depending on their composition) have high corrosion resistance, heat resistance and heat resistance, make it an attractive structural material. However, when welding structural elements made of this metal (its alloys), difficulties arise due to the increased sensitivity of nickel to impurities, especially to dissolved gases (hydrogen, oxygen and, to a greater extent, to nitrogen), as well as to the appearance of hot cracks. It is possible to prevent pore formation and the appearance of cracks by using high-purity welding electrodes and welding elements made of nickel (its alloys), paying increased attention to preliminary preparation for welding.

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