What are the types of electrodes? Types and types of electrodes

Welding is a technological process for obtaining reliable joints by heating the edges of parts to the melting point. Manual arc is the most common form of it. This method is highly productive, universal, technologically simple and accessible at home.

The essence of RDS

The edges of the connected parts are melted due to the released heat by the ionized stream of particles between the cathode and the anode - the electric arc. Ionization occurs due to the presence of a current and a short circuit between two poles with constant or variable characteristics.

The tool used to create and burn the arc is an electrode - a rod of metallic or non-metallic origin. The work can be performed by either one or several rods with the possibility of creating an additional arc between them (welding with a three-phase arc). The ionized flow of electrons is surrounded by evaporation from the tool and its coating, the melting metal of the parts being connected, the results of their interaction with air. The types of welding electrodes are determined taking into account all the characteristics inherent in a particular material.

Classification of rods by material of manufacture

At its core, all welding tools for RDS are divided into melting and non-melting.

• Melting: metal tools made of cast iron, steel, aluminum, copper (depending on the type of metal to be welded). The rod acts as a cathode or anode, and also functions as a filler material to fill the weld pool and form a seam.
• Non-melting: rods of coal, graphite, of tungsten; Perform only the primary function; Additive metal wire is used; Tungsten are needed for argon-arc welding.

Among the first group, the main types of electrodes are:

• Without cover. This type of tool is not used for RDS.
• Covered. The appropriate coating is used to maintain arc stability, protect the metal from burning out, from the influence of gases, increase the mechanical characteristics of the seam by natural alloying (ingress of alloying elements from the melting rod into the weld pool).

Application by type of work

Types of electrodes for manual arc welding, listed above, have individual application, depending on the method of work.

Coal uncovered electrodes - the primary welding invention, which belongs to NN Benardos and refers to 1882 - are used in modern times. Features: direct current, direct polarity, additional feeding of filler wire, stable arc, rod burns slowly, carburization does not occur. The use of reverse polarity reduces the characteristics of the arc and the seam (it is carburized).

Metal electrodes - the next invention in the field of welding technology, which belongs to NG Slavyanov (1888). Together with them, prototypes of modern welding machines were born. Welding with the help of melting rods has found wider application in industry and has been actively developed. For today it is used in manual arc, automatic and semiautomatic (under flux) welding.

The tungsten electrode, due to the high melting point of 3422 ° C, is used as a non-melting electrode for argon-arc welding. Thus, different types of electrodes correspond to different welding technologies.

Distribution according to purpose

Purpose - this is the characteristic in accordance with which all the known electrodes are distributed. The types and use of rods are denoted by one letter (GOST 9466-75):

• Structural steels, including low-alloyed ones with a strength of 60 kgf / mm ² (600 MPa) are marked in the marking with the letter "U" - carbon;
• Alloyed structural steels having a strength of 600 MPa - "L";
• High-alloy structural steel - "B";
• Heat-resistant alloyed steel - "T";
• Alloys with special properties, which are characterized by surfacing - "H".

The appointment is indicated in the expanded stamp.

Coatings of rods

Various coatings and origin are used in individual cases for different materials. The following types of electrode coatings are used:

• Sour "A". Contain ferromanganese and ferrosilicon. They are used for direct or direct current. Characterized by high melting rates. It is better to use for lower seams.
• Rutile "R". Contain rutile (titanium dioxide), carbonates, aluminosilicates, ferromanganese, liquid glass. Welding seams of any position and type with direct or direct current. As a result of successive chemical reactions, a protective slag is formed, which prevents burnout of the elements. Good quality of welded joints, low toxicity.
• Cellulose "C". The composition includes cellulose, manganese ore, talc, rutile, ferromanganese. Protective gases are formed around the arc and weld pool. For all seams; High speed of work execution; good quality; Do not overheat; Large losses during spraying. Used for non-detachable pipe connections .

• Basic "B". In the composition of carbonates and fluorides of calcium. The formation of protective carbon dioxide occurs as a result of the reaction of carbon from carbonates with oxygen from the burning of the arc. It is desirable to perform work under direct current with polarity in the opposite direction. During welding under variable, a low-quality seam is obtained, additional technologies are required to increase its mechanical characteristics.
• Other "P". Contain alloying elements. The quality of the seam is enhanced by introducing a certain amount of alloying elements from the melting electrode into it.
• Special. Contain liquid glass with resinous substances. Protect from penetration of moisture. They are used for welding under water.

Specific purposes have all coated electrodes. The main type of coating is rutile because of its versatility. Coatings perform protective functions by deoxidizing the alloy in a weld pool, adding alloying elements to it, forming a halo of protective gases or slag. This makes it possible to avoid a lower quality of the seam than that of the edge materials of the parts, to ensure the formation of good welded joints.

Requirements for instruments, established by GOST 9466-75

• Electrodes must be made of quality material.
• Coverage should be unbroken, not have significant defects (small dents and cracks are allowed without blistering and porosity).
• High mechanical resistance to accidental shock loads.
• Different types of electrodes coating should be evenly fused, do not crumble, do not form uneven islands, do not splash over the permissible characteristics.
• The rod should ensure the formation of a quality weld: without cracks, pores, local excess of welded metal.
• Rational choice in accordance with all the necessary parameters and compliance with technology - the key to the formation of a reliable and lasting connection.

The choice of the rod depending on the size

A novice welder is more familiar with the types of electrodes that are determined by their size. The diameter of the tool, with which the work will be carried out, is selected strictly in accordance with the thickness of the workpiece to be welded. It is not encrypted, it is clearly indicated in the marking of the instrument. The length of the electrode is also fixed according to its diameter. It is important to have an understanding of the length of the bare, uncovered end of the tool.

Thickness of prepared edges, mm	Electrode diameter, d, mm	Electrode length, mm	Length of stripped uncoated end, mm
Up to 2	2	200-250	20
From 3 to 5	3-4	300-450	25
From 6 to 8	4-5	350-450	25
From 9 to 12	5-6	350-450	thirty
From 13 to 15	6-7	450	thirty

For home welding, the most commonly used types of electrodes for arc welding with a diameter of 2-4 mm. Thick rods are applicable in repair shops and in production.

Coating Thickness

It has its designation in the marking of the instrument. Determined by the ratio of its ratio D (mm) to the thickness of the rod itself d (mm). It is divided into 4 groups:

• Thin "M" (coefficient up to 1.2);
• Average "C" (the coefficient has values ranging from 1.2 to 1.45);
• Thick "D" (coefficient - within the limits of 1.45-1.8);
• Especially thick "G" (the coefficient value is more than 1.8).

The results of the work are influenced not only by the types of coatings of the electrodes of manual arc welding, but also by the thickness of the coating layer itself, as well as the dimensions of the rod. Correct electrode size selection provides a good speed of work, qualitative parameters of the arc and the formed connection.

The choice of rods depending on the type of seam and its spatial position

Seams have several classifications:

• Depending on the action of the main forces: flank, frontal, oblique, end.
• In accordance with the position of the parts to be welded: butt, angled, T-joints, overlapping.
• Depending on the presence of bevels: with bevel, without bevel.
• In accordance with the position in space: bottom, top, horizontal, vertical.

The choice of the spatial location of the seam. Its type is indicated in the marking of the rod.

• 1 - for welding in all positions;
• 2 - exceptions apply only to vertical seams from top to bottom;
• 3 - for the lower seams, horizontal at the vertical plane, vertical from the bottom up;
• 4 - for the lower seams.

The type of the seam relative to the spatial position is taken into account when determining the current values.

Effect of electric arc parameters on the choice of welding tools

Welding can be carried out under direct or direct current, straight ("minus" on the electrode, "plus" on the product) or reverse polarity. The choice depends on the material to be welded and its properties. The type of current is determined by the power source.

As the main equipment that generates and (or) converts a current, transformers and oscillators (reduce the mains voltage to the required values), converters and rectifiers (convert the alternating current of the network into a direct current of the welding process) can be used.

The parameters necessary to ignite the arc are significantly different from those that are traced during its maintenance. The voltage required for rapid arc formation is called idling voltage. Consider the values of the stresses necessary to ignite the arc and to maintain its combustion.

Type of current	Idling voltage, V	Stresses to maintain the arc, V
Variable	50-80	20-30
Constant	45-50	16-25

The types of welding electrodes differ depending on the network characteristics and are indicated by the numbers from 0 to 9:

• 0 - only for direct current of reverse polarity;
• 1-9 - for any currents;
• 1, 4, 7 - any polarity;
• 2, 5, 8 - a straight line;
• 3, 6, 9 - the reverse;
• 1-3 - open circuit voltage of 50 V;
• 4-6 - 70 V;
• 7-9 - 90 V.

The choice influences the features of the technology and the quality characteristics of the seams. So, the least depth of digestion is provided by working with variable network parameters. Used for unpretentious materials and simple designs. When welding with an arc with constant characteristics and reverse polarity, the depth of the weld pool and the mechanical properties of the weld are 50% higher than even with direct polarity. Used for non-conforming materials and responsible structures.

Determination of the current

In arc welding, the manual type, it can be different - from 30 to 600 A. The choice of the required value is carried out depending on the diameter of the working electrode and the type of seam relative to the spatial position. Calculated as follows:

• For the lower seams: I = d * k.
• For the upper ones, I = k * d * 0.8.
• For horizontal - I = k * d * 0.85.
• For vertical seams - I = k * d * 0,9.

Where I is the current, A;

D is the diameter, mm;

K is the coefficient, A / mm.

The coefficient depends on the diameter of the rod:

• For electrodes with a thickness of 1-2 mm - k = 25-30 A / mm;
• 3-4 mm - k = 30-45 A / mm;
• 5-6 mm - k = 45-60 A / mm.

Increasing the force speeds up the working welding process. Exaggerating the allowable values can lead to overheating of the edges, excessive burnout of components, deterioration of the quality of the welded seam.

Marking

In order to consider all the nuances of marking, it is important to give a standard example in accordance with GOST 9466-75 and 9467-75: (E42A-SSSI-13 / 45-3.0-UD) / (E432 (5) -B10).

• Brand: SSSI-13/45.
• Type: E42A - electrode for RDS, provides the strength of the weld 420 MPa of increased plasticity (A).
• 3,0 - diameter of 3 mm.
• U - for welding of carbon steels and low alloyed structures.
• D is a thick coating.
• E432 (5) - indices, in which the characteristics of the joint and the weld metal are encrypted.
• 43 - tensile strength not less than 430 MPa;
• 2 - the relative elongation is not less than 24%;
• 5 - welding is possible at temperatures up to -40 ° C; At the same time the minimum admissible value of the toughness of the metal is 34 J / cm ² .
• B - basic coverage.
• 1 - the spatial position of the seam: any.
• 0 - only arc welding with constant characteristics and direct polarity.

Using different types and brands of welding tools

Everything discussed above, refers more to the marking of electrodes for RDS steel. It is important to give examples of the rods used for a variety of ferrous and non-ferrous metals. Below are their most common types.

Types of electrodes are distributed depending on the metal to be welded and the specified typical mechanical characteristics of the joint.

Carbon low-alloy steels are welded by rods of types:

• E42: the brand ANO-6, ANO-17, WCC-4M.
• E42: SSSI-13/45, SSSI-13 / 45A.
• E46: ANO-4, ANO-34, OZS-6.
• E46A: SSSI-13 / 55K, ANO-8.
• E50: WCC-4A, 550-U.
• E50A: ANO-27, ANO-TM, ITS-4S.
• E55: SSSI-13 / 55U.
• E60: ANO-TM60, SSSI-13/65.

Alloyed alloys of increased strength:

• E70: ANP-1, ANP-2.
• E85: SSSI-13/85, SSSI-13 / 85U.
• Э100: АН-ХН7, ОЗШ-1.

High-strength alloyed steel: E125: NII-3M, E150: NIAT-3.

Surfacing of metal: OZN-400M / 15G4S, ЭН-60М / Э-70Х3СМТ, OZN-6 / 90Х4Г2С3Р, УОННИ-13 / Н1-БК / Э-09Х31Н8АМ2, ЦН-6Л / Э-08Х17Н8С6Г, ОЗШ-8 / 11Х31Н11ГСМ3ЮФ.

Cast iron: ОЗЧ-2 / Cu, ОЗЧ-3 / Ni, ОЗЧ-4 / Ni.

Aluminum and its alloys: OZA-1 / Al, OZANA-1 / Al.

Copper and its alloys: ANC / OZM-2 / Cu, OZB-2M / CuSn.

Nickel and its alloys: OZL-32.

From the above list, we can conclude that the marking system is very complex, while it is based on approximately the same principles of encryption of the characteristics of the rod, its coverage, diameter, the presence of alloying elements.

The quality of the welding joint depends on a rational technological scheme. The following factors influence which types of electrodes to choose:

• The material to be welded and its properties, the presence of alloying elements and the degree of alloying.
• Thickness of the product.
• Type and position of the seam.
• Specified mechanical properties of compound or weld metal.

It is important for a novice welder to be guided in the basic principles of selection and marking of tools for welding steel, and also to operate the distribution of bar stamps to their intended purpose, to know the main types of electrodes and to use them rationally during welding operations.