Which steel is best for welding? Welded steel grades. Weldability of steels. Groups. Welding current, technical characteristics, diagrams

Heat-resistant (scale-resistant) steels are considered to be capable of withstanding chemical destruction of the surface in air or in another gaseous environment at temperatures above 850 ° C in an unloaded or lightly loaded state. They contain up to 20-25% chromium and operate at temperatures up to 1050 ° C and above.

Heat resistance of the deposited metal up to 1000 ° C on steels 20Kh23N13, 20Kh23N18, etc. is achieved by electrodes of the E-10Kh25N13G2 type, grades SL-25, OZL-4, OZL-6, TsL-25.

For welding heat-resistant steels that operate for a long time at temperatures above 1000 ° C, electrodes of the E-12X24N14C2 type of OZL-5, TsT-17, etc. should be used, as well as electrodes of the E-10X17N13C4 type of OZL-29, providing heat resistance up to a temperature of 1100 ° C in oxidizing and carburizing environments. For structures operating in sulfur-containing environments, nickel-free high-chromium heat-resistant steels 15X25T, 15X28, etc. are used, which are welded with electrodes of the E-08X24N6TAFM type.

Characteristics of electrodes for welding heat-resistant (scale-resistant) steels

Type Э-10Х25Н13Г2
Electrode / wire brand Code designation in accordance with GOST Application area Technological features	Coating	Rod, current polarity	Surfacing coefficient, g / A × h	Position in space
UONI-13 / NZh-2 / 07H25N13 E - 2075 - B20
ZIO-8 / 07H25N13 E-0053-RB20
TsL-25 / 07H25N13 E - 0075 - B20
OZL-6 / 07H25N13 E - 2275 - B20
For 10Х23Н18, 20Х23Н13, 20Х23Н18, etc., operating in environments without sulfur compounds at temperatures up to 1000 ° С, as well as for two-layer steels from the side of the alloyed layer without requirements for resistance to intergranular corrosion. Seams are prone to embrittlement at 600-800 ° C. Short arc. Thermal preparation of edges is not allowed
SL-25 1 07H25N12G2T E - 0075 - B30
The same for heat-resistant steels
Type Э-12Х24Н14С2
OZL-5 / 10H20N15 E - 0085 - B20
TsT-17 / 10H20N15 E - 0085 - B20
For steels 20Х25Н20С2, 20Х20Н14С2, etc., operating at temperatures up to 1100 ° С in oxidizing and carburizing environments. Narrow bead welding
Type Э-10Х17Н13С4
03L-29 / 02H17N14S4 E - 0085 - B20
OZL-Z / 15H18N12S4TYu E - 5087 - B20
For steels 20Х20Н14С2, 20Х25Н20С2, 45Х25Н20С2, etc., operating at temperatures up to 1100 ° С in oxidizing and carburizing environments, as well as for steel 15Х18Н12С4ТЮ, operating in corrosive media without high requirements for resistance to intergranular corrosion

weldering.com

Electrodes for welding carbon and low alloy steels

Skip to Main Content Area

Diameter, mm	Current type	Purpose and scope
ANO-4
3,0; 4,0; 5,0		For welding structures made of low-carbon steels of grades St3,10, 20, etc. ANO-4 electrodes provide a defect-free weld during welding at elevated conditions. The electrodes provide good formation of the weld metal, high resistance of the weld metal against the formation of porosity and hot cracks.
ANO-6
3,0; 4,0; 5,0	Variable from a transformer with an open-circuit voltage of less than 50 V; direct current of any polarity.	For welding structures made of low-carbon steels of grades St3, 10, 20, etc. ANO-6 electrodes provide high resistance of the weld metal against the formation of defects during welding by rust. The electrodes provide good formation of the weld metal, high resistance of the weld metal against the formation of porosity and hot cracks.
ANO-13
3,0; 4,0; 5,0	Variable from a transformer with an open-circuit voltage of less than 50 V; direct current of any polarity.	For welding structures made of low-carbon steel grades St3, 10, 20, etc. ANO-13 electrodes allow welding at extremely low current values, welding vertical seams in a top-down manner, and are effective in welding short seams. The electrodes provide good formation of the weld metal, high resistance of the weld metal against the formation of porosity and hot cracks.
ANO-21
2,0; 2,5; 3,0		For welding structures made of low-carbon steels of small thickness, grades St3, 10, 20, etc. They can be used for welding water pipes, low pressure gas pipelines. ANO-21 electrodes provide good welding and technological properties when welding from small-sized (household) transformers: easy arc ignition, fine-flake formation of the weld metal, easy or spontaneous separation of the slag crust.
ANO-24
3,0; 4,0; 5,0	Variable from a transformer with an open circuit voltage of at least 50 V; direct current of any polarity.	For welding structures made of low-carbon steels of grades St3, 10, 20, etc. ANO-24 electrodes allow welding at extremely low current values, are effective when welding short-length seams, when welding on a vertical plane. The electrodes ensure good formation of the weld metal against porosity and hot cracking.
MP-3
3,0; 4,0; 5,0	Variable from a transformer with an open circuit voltage of at least 60 V;	For welding structures made of low-carbon steels of grades St3, 10, 20, etc. When welding with MP-3 electrodes at high conditions, the formation of pores in the seam is possible. The electrodes ensure good formation of the weld metal against porosity and hot cracking.
UONI-13/45
3,0; 4,0; 5,0	Direct current reverse polarity.	For welding critical structures made of carbon (type 08, 20, 20L, St3) and low-alloy (type 09G2, 14G2) steels, when increased requirements for ductility and impact toughness are imposed on the weld metal, in particular, when working at low temperatures. UONI-13/45 electrodes are sensitive to the formation of porosity in the presence of rust and oil on the edges of the parts being welded, as well as when the arc length is lengthened.
UONI-13/55
3,0; 4,0; 5,0	Direct current reverse polarity.	For welding critical structures made of carbon (type 08, 20, 20L, St3) and low-alloy (type 16GS, 09G2S) steels, when increased requirements for ductility and impact toughness are imposed on the weld metal, in particular, when operating at low temperatures. UONI-13/55 electrodes are sensitive to the formation of porosity in the presence of rust and oil on the edges of the parts being welded, as well as when the arc length is lengthened.
ANO-TM / CX
3,0; 4,0; 5,0		For welding butt joints of main pipelines made of carbon and low-alloy steels with a tensile strength of 490-590 MPa (root layers) and 490-540 MPa (filling and facing passages). ANO-TM / CX electrodes ensure high-quality formation of a reverse bead of the root layer of the weld with a smooth transition to the base metal, and therefore no welding of the pipe root from the inside is required. ANO-TM / CX electrodes have a permit from the Center for Certification and Quality Control of Construction of Oil and Gas Facilities of Ukraine to be used for welding pipes, fittings and valves at oil and gas facilities.
ANO-TM60
3,0; 4,0; 5,0	Direct current reverse polarity; alternating current from a transformer with an open circuit voltage of at least 70V.	For welding butt joints of main pipelines made of carbon and low-alloy steels with a tensile strength of more than 588 MPa (root layers) and 540–650 MPa (filling and facing passages). ANO-TM60 electrodes provide high-quality formation of a reverse bead of the root layer of the weld with a smooth transition to the base metal, and therefore no welding of the pipe root from the inside is required. ANO-TM60 electrodes have a permit from the Center for Certification and Quality Control of Construction of Oil and Gas Facilities of Ukraine to be used for welding pipes, fittings and valves at oil and gas facilities.
ANO-TM70
3,0; 4,0; 5,0	Direct current reverse polarity; alternating current from a transformer with an open circuit voltage of at least 70V.	For welding butt joints of main pipelines made of low-alloy steels with a tensile strength of more than 685 MPa. ANO-TM70 electrodes ensure high-quality formation of a reverse bead of the root layer of the weld with a smooth transition to the base metal, and therefore no welding of the pipe root from the inside is required. ANO-TM70 electrodes have a permit from the Center for Certification and Quality Control of Construction of Oil and Gas Facilities of Ukraine to be used for welding pipes, fittings and valves at oil and gas facilities.

back upstairs

www.metalika.ua

Welding electrodes for steel

Back in the 19th century, the Russian scientist Nikolai Nikolaevich Bernardos, while studying the possibilities of an electric arc, made a connection of several metal elements. With the advent of new types of steels, it became necessary to expand the list of electrodes for welding such steels. Nikolai Gavriilovich Slavyanov carried out a large amount of research at the end of the 19th century aimed at creating a rod electrode close to the metals being welded in its chemical composition.

Nowadays there are a very large number of electrodes designed for welding a specific steel grade.

The most widespread are electrodes for welding carbon steels, since it is these steels that are most widely used. Manufacturers produce a lot of types of electrodes that correspond to specific types of carbon steels. By the number of consumed and produced units, the most common brands are: MR, ANO, UONI and OZS. These electrodes provide excellent weldability, they prevent overheating, hot cracking, splashing and boiling of the bath.

Each of these brands has its own characteristics:

SSSI 13/45 and SSSI 13/55 electrodes have low metal spatter and good slag separation;

The MP-3 and MP-3S electrodes have high welding and technological properties, namely: ease of use, good separation of the slag crust, easy arc reignition, and minimal metal spatter. These grades of electrodes do not require high qualifications of the welder when working.

The electrodes OZS-4, OZS-6, OZS-12 can be used on a separate surface, which makes it possible to create seams with a high marketable appearance and a self-separating slag crust.

ANO-21 electrodes have the ability to lightly re-ignite the arc, which greatly facilitates the welding process. They have good slag separation and minimal metal spatter.

There are also electrodes for other types of steels:

For welding mild steels. - for welding low-alloy steels. - for welding alloy steels. - for welding stainless steels. - for welding high-alloy steels.

Each of these types of electrodes includes several brands. Some brands of electrodes are universal, i.e. can be used for several types of steel.

Welding Electrodes

OK 96.10 for aluminum

elektrod-3g.ru

Electrodes for heat-resistant and heat-resistant steels

Heat-resistant steels are considered that retain the ability to resist oxidation, or the appearance of scale at temperatures above 550 ° C. Heat-resistant steels operate at temperatures up to 900 ° C under load for a given period of time, without changing their physical and mechanical properties. To achieve such properties, special alloying additives are used in the production of steels - Cr, Si, Al, for heat-resistant steels. Ti, Al, Mo, B, Nb for heat resistant. And also special modes of hardening and aging are used. All these factors create certain difficulties in welding.

When the weld is formed, heat-resistant steels form a protective oxide film in the welding zone, which leads to weakening of the seam. And when it cools down due to the crystal structure of the steel around the weld zone, there is a high probability of the formation of microcracks. In this case, preheating does not reduce the cooling rate of the metal below the critical one, but only increases the grain of the metal in the weld area, which leads to the appearance of cracks already in the cold state. To combat this phenomenon is obtained only by using special techniques when carrying out welding work. According to GOST 10052-75, it is documented with which electrodes to cook heat-resistant and heat-resistant steel, and it is for these steels that about 30 types of electrodes have been allocated. Let's list some specific varieties.

OZL-25B, TsT-28 - welding of heat-resistant nickel-based alloys, KhN78T;

TsT-15 - Welding of heat-resistant structures from steels 12Х18Н9Т, 12Х18Н12Т and Х16Н13Б;

OZL-6 - welding of heat-resistant steels operating in oxidizing environments 20X23H18 and 20X23H13;

GS -1 - welding of thin-sheet steels operating in carburized environments, such as 20X25H20S2, 45X25H20S2;

OZL-35 - welding of heat-resistant nickel-based steels withstanding up to 1200 ° С, type ХН70Ю and ХН45Ю;

INOX B 25/20, E6018, AWS E505-15 - foreign counterparts for welding heat-resistant chromium-nickel steels.

In general, they can be grouped according to the type of coating - basic, rutile and rutile-basic. The rutile coating consists mainly of titanium dioxide in mineral or synthetic form. Melting occurs in small droplets, spatter is minimal, the seam comes out neat and thin, and the slag is easy to clean. The main type of coating contains mainly oxides of calcium, magnesium and a certain proportion of fluorspar. Some sluggishness of the welded pool is formed, in connection with this, the weld seam is formed by more convex and larger beads. Electrodes with this coating are well suited for welding in any position.

In this case, high-alloy steel is used for the electrode rod. Its thermal conductivity is much lower, and its electrical resistance is much higher, which leads to its rapid melting. And at the output we get a much higher deposition rate than electrodes for carbon and low alloy steels. But at the same time it is necessary to adhere to sufficiently low values ​​of the welding current, and use electrodes of short length. Otherwise, you can get overheating of the electrode itself, and the wrong nature of the melting of the latter, up to the pieces falling off the electrode.

Good results in welding heat-resistant and heat-resistant steels are obtained by argon-arc welding with a non-consumable tungsten electrode. Automatic submerged-arc welding with the use of alloy steel filler wire has also become quite widespread.

ANO-21 electrodes

Welding electrode composition

Weldability is understood as the ability of a steel of a given chemical composition to produce a high-quality welded joint without cracks, pores and other defects when welding in one way or another. The chemical composition of steel determines its structure and physical properties, which can change under the influence of heating and cooling of the metal during welding. The weldability of steel is affected by the content of carbon and alloying elements in it. For a preliminary judgment about the weldability of steel of known chemical composition, the equivalent carbon content can be calculated using the formula

On the basis of weldability, all steels can be conditionally divided into four groups:

1. Well-welded, in which the equivalent is not more than 0.25. These steels do not give cracks when welding in the usual way, that is, without preliminary and concomitant heating and subsequent heat treatment.

2. Satisfactory weldable, in which C equiv in the range of 0.25-0.35; they allow welding without the appearance of cracks, only under normal production conditions, that is, at an ambient temperature above 0 ° C, no wind, etc.

This group also includes steels that need preheating or preliminary and subsequent heat treatment to prevent the formation of cracks during welding under conditions that differ from normal (at temperatures below 0 ° C, wind, etc.).

3. Limited weldable, in which C eq is in the range of 0.35-0.45; they are prone to cracking when welded under normal conditions. When welding such steels, preliminary heat treatment and heating are required. Most of the steels in this group are also heat treated after welding.

4. Poorly welded, in which C eq is higher than 0.45; such steels are prone to weld cracking.

They can only be connected with preliminary heat treatment, heating during welding and subsequent heat treatment. For metal of small thickness, the limiting value of C eq can be increased to 0.55. The preheating temperature for low-alloy steels, depending on the value of C equiv, is taken as follows:

Preheating slows down cooling and prevents cold cracking during welding.

The weldability of steel is also determined by various tests. With the help of tests, it is established whether brittle structures appear in the weld metal and the near-weld zone during welding of this steel, which contribute to the formation of cracks.

The simplest is the technological test, in which a rectangular plate is welded to a sheet of the tested steel with a one-sided fillet weld (Fig. 127, a). After cooling in calm air, the plate is knocked down with a hammer, destroying the seam from the side of its top. If traces of previously formed cracks or fractures are found in the form of breaks in the base metal near the weld, then the steel is limited weldable and requires preliminary heating and subsequent heat treatment.

The tendency to the formation of cold cracks in thicker steel can be checked by a breakdown by the method of the Kirovsky plant (Fig. 127, b, cc). In the middle of a square (130x130 mm) specimen, a groove with a diameter of 80 mm is made. The thickness a of the rest of the sample is 2, 4, 6 mm. One or two rollers are fused into the groove (see Fig. 127, whig), cooling the bottom from the outside with air or water. If the specimen does not crack when surfacing the bead and cooling with water, the steel is considered to be weldable. If cracks appear when cooled with water, but do not occur when cooled in air, then the steel is considered to be weldable satisfactorily. Steel is considered to be limited weldable if

Steel is the main structural material, which is an alloy of iron with carbon and various impurities. All elements that make up steel products affect its characteristics (in particular, the weldability of steels).

The main indicator of weldability is carbon equivalent, which is designated as Ceq. This conditional factor takes into account the level of influence on the properties of the welded seam of carbon, alloying components.

Factors affecting the weldability of steels:

• Thickness of metal sample
• The volume of harmful impurities
• Environmental conditions
• Carbon capacity
• Doping level
• Microstructure

The main parameter for information is the chemical composition of the material.

Weldability groups

Considering all of the above criteria, weldability can be divided into groups with different properties.

Classification of metals by weldability:

• Good - the Ceq coefficient is at least 0.25% - for products made of low-carbon steels, regardless of weather conditions, product thickness, preliminary preparation.

• Satisfactory - the Ceq coefficient is in the range of 0.25-0.35%. Limitations: on the diameter of the welded product, environmental conditions. The thickness of the material is allowed no more than 2 cm, the air temperature should be at least minus 5 degrees, calm weather.
• Limited - the Ceq coefficient is in the range of 0.350-0.45%. Preheating the material is required to form a high quality welded joint. This procedure is needed for a "smooth" austenitic transformation, the creation of stable structures (bainitic, ferrite-pearlite).
• The bad one is the Ceq coefficient of about 45% (steel 45). In this case, it is impossible to ensure the stability of the welded joint without preheating the metal edges, heat treatment of the finished structure. To create the required microstructure, it is necessary to additionally carry out heating and cooling.

Weldability groups provide an opportunity to understand the technological specifics of welding of specific grades of iron-carbon alloys.

Depending on the category, technological parameters, the properties of welded joints can be corrected by successive temperature effects. Heat treatment can be carried out in several ways: tempering, hardening, normalizing, annealing. Quenching and tempering are most in demand. Such procedures increase the hardness, respectively, the strength of the welded joint, prevent the formation of cracks in the material, and relieve stress. The tempering rate will depend on the desired material characteristics.

How do alloying impurities affect weldability?

Influence of the main alloying elements on the weldability of steel

• Phosphorus, sulfur are harmful impurities. The content of these chemical elements for low-carbon steels is 0.4-0.5%.

• Carbon is an important component in the composition of alloys, which determines such indicators as hardenability, ductility, strength, and other properties of the material. Carbon content in the range of 0.25% does not affect the weld quality. The presence of more than 0.25% of this chemical. element promotes the formation of hardened joints, heat-affected zones, cracks are formed.

• Copper. The content of copper as an impurity is not more than 0.3%, as an additive for low-alloy steels - within 0.15-0.50%, as an alloying component - not more than one percent. Copper improves the corrosion resistance of the metal without impairing the quality of welding.

• Manganese. Manganese content up to one percent does not hinder the welding process. If manganese is 1.8-2.5%, then the formation of hardening structures, cracks, heat-affected zones is not excluded.

• Silicon. This chemical element is present in the metal as an impurity - 0.30 percent. This amount of silicon does not affect the quality index of the metal compound. In the presence of silicon in the range of 0.8-1.5%, it acts as an alloying component. In this case, there is a possibility of the formation of refractory oxides, which worsen the quality of the metal compound.

• Nickel, like chromium, is present in low-carbon steels, its content is up to 0.3%. In low-alloyed metals, nickel can be about 5%, high-alloyed - about 35%. The chemical component increases the ductility, strength characteristics of the metal, improves the quality of welded joints.

• Chromium. The amount of this component in low-carbon steels is limited to 0.3 percent, its content in low-alloy metals can be in the range of 0.7-3.5%, alloyed - 12-18 percent, high-alloyed about 35%. At the time of welding, chromium contributes to the formation of carbides, which significantly impair the corrosion resistance of the metal. Chromium promotes the formation of refractory oxides, which negatively affect the quality of welding.

• Molybdenum. The presence of this chemical element in the metal is limited to 0.8 percent. Such an amount of molybdenum has a positive effect on the strength characteristics of the alloy, but during the welding process the element burns out, as a result of which cracks form on the weld section of the product.

• Vanadium. The content of this element in alloy steels can be from 0.2 to 0.8 percent. Vanadium contributes to an increase in the plasticity, toughness of the metal, improves its structure, and increases the hardenability index.

• Niobium, titanium. These chemical components are contained in heat-resistant, corrosion-resistant metals, their concentration is no more than one percent. Niobium and titanium reduce the sensitivity of the metal alloy to intergranular corrosion.

Outcome

The weldability of steel is considered a comparative indicator, depending on the chemical composition, physical characteristics, microstructure of the material. At the same time, the ability to create high-quality welded joints can be adjusted due to a well-thought-out technological approach, meeting the requirements for welding, and the availability of modern special equipment.

When assessing the weldability, the role of the chemical composition of steel is prevalent. According to this indicator, in the first approximation, the weldability is assessed.

The influence of the main dopants on are given below.

Carbon (C) is one of the most important impurities that determines the strength, ductility, hardenability, and other characteristics of steel. Carbon content in steels up to 0.25% does not reduce weldability. A higher content of "C" leads to the formation of quenching structures in the metal of the heat-affected zone (hereinafter referred to as HAZ) and the appearance of cracks.

Sulfur (S) and phosphorus (P) are harmful impurities. The increased content of "S" leads to - red brittleness, and "P" causes cold brittleness. Therefore, the content of "S" and "P" in low carbon steels is limited to 0.4-0.5%.

Silicon (Si) is present in steels as an impurity in an amount of up to 0.3% as a deoxidizing agent. With this "Si" content, the weldability of the steels does not deteriorate. As an alloying element with a content of "Si" - up to 0.8-1.0% (especially up to 1.5%), the formation of refractory oxides "Si" is possible, which worsen the weldability of steel.

Manganese (Mn) with a content of up to 1.0% in steel - the welding process is not difficult. When welding steels with "Mn" content in the amount of 1.8-2.5%, hardening structures and cracks may appear in the HAZ metal.

Chromium (Cr) in low carbon steels is limited as an impurity up to 0.3%. In low-alloy steels, chromium content is possible in the range of 0.7-3.5%. In alloyed steels, its content ranges from 12% to 18%, and in high-alloyed steels it reaches 35%. When welded, chromium forms carbides that impair the corrosion resistance of the steel. Chromium promotes the formation of refractory oxides, which hinder the welding process.

Nickel (Ni), similar to chromium, is contained in low-carbon steels in an amount of up to 0.3%. In low-alloy steels, its content increases to 5%, and in high-alloy steels - up to 35%. In nickel-based alloys, its content is prevalent. Nickel increases the strength and plastic properties of steel, has a positive effect on weldability.

Vanadium (V) in alloy steels is contained in an amount of 0.2-0.8%. It increases the toughness and ductility of steel, improves its structure, and improves hardenability.

Molybdenum (Mo) in steels is limited to 0.8%. With such a content, it has a positive effect on the strength characteristics of steels and refines its structure. However, during welding, it burns out and contributes to the formation of cracks in the weld metal.

Titanium and niobium (Ti and Nb) in corrosion-resistant and heat-resistant steels contain up to 1%. They reduce the sensitivity of steel to intergranular corrosion; at the same time, niobium in steels of type 18-8 promotes the formation of hot cracks.

Copper (Cu) is contained in steels as an impurity (up to 0.3% inclusive), as an additive in low-alloy steels (0.15 to 0.5%) and as an alloying element (up to 0.8-1%). It enhances the corrosion properties of steel without compromising weldability.

When assessing the effect of chemical composition on in addition to the carbon content, the content of other alloying elements that increase the tendency of steel to hardening is also taken into account. This is achieved by recalculating the content of each alloying element of steel in equivalent for the effect on its hardenability using conversion factors determined experimentally. The total content of carbon in steel and the recalculated equivalent amounts of alloying elements is called the carbon equivalent. To calculate it, there are a number of formulas drawn up according to various methods, which make it possible to assess the effect of the chemical composition of low-alloy steels on their weldability:

SEKV = C + Mn / 6 + Cr / 5 + Mo / 5 + V / 5 + Ni / 15 + Cu / 15 (MIS method);

SEKV = C + Mn / 6 + Si / 24 + Ni / 40 + Cr / 5 + Mo / 4 (Japanese method);

[C] X = C + Mn / 9 + Cr / 9 + Ni / 18 + 7Mo / 90 (Seferian's method),

where the numbers indicate the content in the steel in mass percentages of the corresponding elements.

Each of these formulas is acceptable only for a certain group of steels, but the value of the carbon equivalent can be used in solving practical issues related to development. Quite often, calculations of the chemical carbon equivalent for carbon and low-alloy structural steels of the pearlite class are performed using the Seferian formula.

According to the weldability, steels are conventionally divided into four groups: well weldable, satisfactory weldable, limited weldable, poorly welded (Table 1.1).

The first group includes the most common grades of low-carbon and alloy steels ([C] X≤0.38), which can be welded using conventional technology, i.e. without heating before welding and during welding, as well as without subsequent heat treatment. It is recommended to weld cast parts with a large amount of weld metal with an intermediate heat treatment. For structures operating under static loads, post-weld heat treatment is not performed. For critical structures operating under dynamic loads or high temperatures, heat treatment is recommended

The second group includes carbon and alloy steels ([C] x = 0.39-0.45), during welding of which cracks do not form under normal production conditions. This group includes steels that must be preheated to prevent the formation of cracks, as well as subjected to subsequent heat treatment. Heat treatment before welding is different and depends on the grade of steel and the design of the part. Annealing is required for 30L steel castings. Machine parts made of rolled products or forgings that do not have rigid contours can be welded in a heat-treated state (quenching and tempering). Welding at ambient temperatures below 0 ° C is not recommended. Welding of parts with a large volume of deposited metal is recommended to be carried out with intermediate heat treatment (annealing or high tempering)

Table 1. Classification of steels by weldability.

Weldability group		steel grade
Well weldable		Low-carbon St1-St4 (kp, ps, cn)
		08-25 (kn, ps)
Well weldable		15K, 16K, 18K, 20K, 22K
		A, A32, A36, A40, B, D, D32, D36, D40, E, E32, E36, E40
		15L, 20L, 25L
		Low-alloyed 15G, 20G, 25G, 10G2, 12XN, 12XH2, 15H2M, 15X, 15XA, 20X, 15HF, 20N2M
		09G2, 09G2S, 09G2D, 10G2B, 10G2BD, 12GS, 16GS, 17GS, 17G1S, 10G2S1,09G2SD, 10G2S1D, YUHSND, YUKHNDP, 14G2AF, 14G2AFD, 15GFD, 15HSND
		08GDNFL, 12DN2FL, 13HDNFTL
Satisfactory weldable
		Alloyed 16HG, 18HGT, 14HGN, 19HGN, 20HGSA, 20HGR, 20HN, 20HNR, 12HN3A, 20HN2M
		15G2AFDps, 16G2AFD, 15G2SF, 15G2SFD
		18G2S, 25G2S
		20GL, 20GSL, 20FL, 20G1FL, 20DHL, 12DHN1MFL
Limited weldable		Carbonaceous St5 (ps, cn), St5Gps
		Alloyed 25ХГСА, 29ХН3А, 12Х2Н4А, 20Х2Н4А, 20ХН4А, 25ХГМ, 35Г, 35Г2, 35Х, 40Х, 33ХС, 38ХС, 30ХГТ, 30ХРА, 30ХГС, 30ХГСА, 35ХГСА, 25ХГНМТ, 30Х2Н4А, 20
		35GL, 32H06L, 45FL, 40HL, 35HGSL, 35NGML, 20HGSNDML, 30HGSFL, 23HGS2MFL
Poorly weldable		Carbon 50, 55
		Alloyed 50Г, 45Г2, 50Г2, 45Х, 40ХС, 50ХГ, 50ХГА, 50ХН, 55С2, 55С2А, 30ХГСН2А, etc.
		30HNML, 25H2G2FL
* DSTU 2651-94 (GOST 380-94). ** Canceled in Ukraine.

In the case when subsequent tempering is impossible, the welded part is subjected to local heating. The post-weld heat treatment is different for different steel grades. When welding small defects in steel containing more than 0.35% carbon, heat treatment (annealing or high tempering for a given steel) is necessary to improve the mechanical properties and machinability.

The third group includes carbon and alloy steels ([C] X = 0.46-0.59) of the pearlite class, which are prone to cracking under normal welding conditions. Weldability of steels this group is ensured by using special technological measures, consisting in their preliminary heat treatment and heating. In addition, most products from this group of steels are subjected to heat treatment after welding. For parts and castings from rolled products or forgings that do not have particularly rigid contours and rigid assemblies, welding in a heat-treated state (quenching and tempering) is allowed.

Without preheating, such steels can be welded in cases where the joints do not have rigid contours, the metal thickness is not more than 14 mm, the ambient temperature is not lower than + 5 ° C and the welded joints are of an auxiliary nature. In all other cases, preheating to a temperature of 200 ° C is required.

Heat treatment of this group of steels is assigned according to the mode selected for a particular steel.

The fourth group includes carbon and alloy steels ([C] x≥0.60) of the pearlite class, the most difficult to weld and prone to cracking. When welding this group of steels using rational technologies, the required performance properties of welded joints are not always achieved. These steels are welded to a limited extent, therefore, they are welded with mandatory preliminary heat treatment, with heating during welding and subsequent heat treatment. Such steel must be annealed before welding. Regardless of the thickness and type of joint, the steel must be preheated to a temperature of at least 200 ° C. Heat treatment of the product after welding is carried out depending on the steel grade and its purpose.

The operational reliability and durability of welded structures made of low-alloy heat-resistant steels depends on the maximum permissible operating temperature and the long-term strength of welded joints at this temperature. These indicators are determined by the alloying system of heat-resistant steels. According to the alloying system, steels can be divided into chromium-molybdenum, chromium-molybdenum-vanadium and chromium-molybdenum-tungsten (Table 1.2). In these steels, the value of the carbon equivalent varies over a wide range and the assessment of the weldability of steels by its value is impractical. The calculation of the preheating temperature is carried out for each specific steel grade.

The division of high-alloy steels into groups (stainless, acid-resistant, heat-resistant and heat-resistant) within the framework of GOST 5632-72 is made conditionally in accordance with their main service characteristics, since heat-resistant and heat-resistant steels are both acid-resistant in certain aggressive environments, and acid-resistant steels have both heat resistance and heat resistance at certain temperatures.

For well-welded high-alloy steels, heat treatment before and after welding is not carried out. With significant work hardening, the metal must be hardened from 1050-1100 ° C. Thermal normal. This group of steels includes a number of acid-resistant and heat-resistant steels with austenitic and austenitic-ferritic structure.

For satisfactorily weldable high-alloy steels, a preliminary tempering at 650-710 ° C with air cooling is recommended before welding. The heat condition of welding is normal. Welding is not allowed at negative temperatures. Preheating up to 150-200 ° C is necessary when welding structural elements with a wall thickness of more than 10 mm. After welding, to relieve stress, it is recommended to temper at 650-710 ° C. This group primarily includes most of some chromium-nickel steels.

Table 2. Grades of heat-resistant and high-alloy steels and alloys based on iron-nickel and nickel.

	GOST or TU	steel grade
Pearlite or martensitic		Heat-resistant chromolybdenum 15XM, 20XM, 30XM, 30XMA, 35XM, 38XM, 38X2MYUA
	GOST20072-74	12MX, 15X5M, 15X5
		12XM, 10X2M, 10X2M-VD
	TU5.961-11.151-80
		Heat-resistant chromium-molybdenum-vanadium and chromium-molybdenum-tungsten 40KhMFA, 30KhZMF
	GOST20072-74	20H1M1F1BR, 12H1MF, 25H1MF, 25H2M1F, 20H1M1F1TR, 18HZMV, 20HZIVF, 15H5VF
	TU14-1-1529-76	15H1M1F TU14-1-3238-81, 35HMFA
		12X2MFA, 18X2MFA, 25X2MFA
	TU14-1-1703-76
	TU5.961-11151-80	20HMFL, 15H1M1FL
Ferritic, martensitic-ferritic and martensitic		High chromium stainless 08X13, 12X13, 20X13, 30X13, 40X13, 25X13H2
		High-chromium acid-resistant and heat-resistant 12X17, 08X17T, 09X16N4B, 30X13N7S2, 08X18T1, 15X18XYu, 15X25T, 15X28, 14X17H2, 20X17H2, 10X13XYu, 40X9S2, 40X10S2M
	TU 14-1-2889-80
	TU14-1-1958-77
	TU14-1-2533-78
		High-chromium heat-resistant 15H11MF, 18H11MNFB, 20H12VNMF, 11H11N2V2MF, 13H11N2V2MF, 13H14NZV2FR, 15H12VNMF, 18H12VMBFR
Austenitic and austenitic-ferritic		Acid 04H18N10, 08H18N10, 08Cr18Ni10Ti, 12H18N9, 12X18H9T, 17H18N9, 12X18H10T, 12H18N10B, 03H18N11, 08H18N12B, 03H17N14M2, E8H17N13M2T, 10X17H13M2T, 10H13MZT, 08H17N15MZT, 08H18N12T, 08H10N20T2, 10H14G14NZ, 10H14G14N4T, 10H14AG15, 15H17AG14, 07H21G7AN5, 03H21N21M4GB, 12H17G9AN4, 08H18G8N2T , 15Х18Н12С4ТЮ
	TU108.11.595-87
Austenitic-martensitic		07Х16Н6, 09Х17Н7Ю, 09Х17Н7ЮТ, 08Х17Н5МЗ, 08Х17Н6Т, 09Х15Н8Ю, 20Х13Н4Г9
Ferritic-austenitic		High-strength acid-resistant 08Х22Н6Т, 12Х21Н5Т.08Х21Н6
	TU14-1-1958-77	10X25N6ATMF
Ferritic-austenitic		12Х25Н5ТМФЛ
	TU14-1-1541-75	03Х23Н6, 03Х22Н6М2
Austenitic		Heat-resistant 20Х23Н13, 10Х23Н18, 20Х23Н18, 08Х20Н14С2, 20Х20Н14С2, 20Х25Н20С2, 12Х25Н16Г7АР, 36Х18Н25С2, 45Х22Н4МЗ, 55Х20Г9АН4
		KhN38VT, KhN60Yu, KhN70Yu, KhN78T
Austenitic		Heat-resistant 10Х11Н20ТЗР, 10Х11Н23ТЗМР, 08Х16Н13М2Б, 09Х16Н15МЗБ, 08Х15Н24В4ТР, 31Х19Н9МВБТ, 10Х11Н20ТЗР, 37Х12Н8Г8МФБ, 45Х14Н14В2М, 09Х16Н13М2В
Iron-nickel and nickel-based alloys		KhN35VT, KhN35VTYu, KhN32T, KhN38VT, KhN80TBYu, KhN67MVTYu

For limited weldable high-alloy steels, the heat treatment before welding is different (tempering at 650-710 ° C with air cooling or quenching in water from 1050-1100 ° C). When welding most steels of this group, preheating to 200-300 ° C is required.

After welding, to relieve stress and lower the hardness, the parts are tempered at 650-710 ° C. For welding a number of steels of the austenitic class, quenching in water from 1050-1100 ° C is required.

For poorly welded high-alloy steels, before welding, it is recommended to temper according to certain modes for various steels.

For the entire group of steels, preheating up to 200-300 ° C is required. Welding of steel 110G13L in the hardened state is carried out without heating. Post-weld heat treatment is performed according to special instructions, depending on the steel grade and purpose. Heat treatment is not required for 110G13L steel.

Weldability- the ability of the metal to form high-quality welded joints that meet the operational requirements for them.

The possibilities and conditions for the formation of a high-quality welded joint are determined by many factors, the most important of which are:

• characteristics and properties of the metals being welded;
• selection of electrode and filler metal;
• welding modes;
• heating temperature, etc.

The weldability is significantly influenced by the chemical composition of the steel, in particular, the content of carbon and alloying elements. The effects of individual elements are manifested in different ways - especially in combination with carbon.

Among the main characteristics of the weldability of steels, it is worth highlighting the tendency to form cracks and the mechanical properties of the welded joint. They can be determined by welding control samples.

Formula for determining the weldability of steel

If the chemical composition of the steel is known, its weldability can be determined from the equivalent carbon content. To do this, use the formula:

With equiv. = С + Mn / 20 + Ni / 15 + (Cr + Mo + V) / 10.

The numbers in this formula are constant values, and the symbols for each of the chemical elements denote its maximum inclusion in steel of a certain grade, expressed as a percentage.

The equivalent carbon content obtained from this formula is an indication of the weldability of steels, which can be roughly divided into four groups:

• well weldable (Ceq does not exceed 0.25%);
• satisfactorily weldable (Ceq = 0.25% - 0.35%);
• restrictedly weldable (Ceq = 0.35 - 0.45%);
• poorly weldable (Ceq exceeds 0.45%).

The good weldability of low-carbon steels can be judged by a strong welded joint with the base metal without cracks and a decrease in ductility in the heat-affected zone.

The weldability of alloy steels is assessed by the possibility of obtaining joints resistant to cracking and hardened structures, as well as by the decrease in strength, corrosion, and so on.

Homogeneous metals weld much easier than dissimilar ones. The weld metal and the heat affected zone metal are inhomogeneous. A sign of unsatisfactory weldability is the tendency to form cracks, which are categorically unacceptable in welded joints.

The characteristic of the weldability of heat-hardened steels is the tendency to decrease in strength in the heat-affected zone at a temperature of 400-720º C, depending on the tempering temperature of the steel during its manufacture at the plant. Thus, the manufacture of a strong welded structure is possible only under the condition of a detailed study and consideration of the weldability of steel.

Influence of basic elements on the weldability of steels

Carbon if it is less than 0.25% in steel, the weldability does not deteriorate, and with a higher content of it, the weldability deteriorates, since hardened structures are formed in the heat-affected zone, which leads to the formation of cracks. If an increased carbon content is noted in the filler material, this leads to porosity in the weld.

Manganese when its content is not more than 0.8%, the weldability does not worsen, but when this indicator is exceeded, the risks of cracking are high due to the fact that this element contributes to the hardening of steel.

Silicon within the range of 0.02–0.35% does not affect the quality of welding, and at a content of 0.8 to 1.5%, it significantly complicates welding due to increased fluidity and the formation of refractory silicon oxides.

Vanadium promotes hardening of the steel, which complicates the welding process. When welding, vanadium, actively oxidizing, burns out.

Tungsten increases the strength of the steel and makes it difficult to weld due to strong oxidation.

Nickel increases ductility and power without compromising the weldability of the steel.

Molybdenum during welding, it actively oxidizes and burns out, contributing to the formation of cracks.

Chromium, which forms refractory carbides, greatly complicates welding.

Niobium and titanium during the welding process, they combine with carbon and prevent the formation of chromium carbide, contributing to improved weldability.

Copper improves weldability, increasing the strength and ductility of steel, making it more resistant to corrosion.

Oxygen works to reduce the ductility and strength of steel, impairing its weldability.

Nitrogen has the ability to create nitrides, that is, chemical compounds with iron, which increase the hardness and strength, significantly reducing the ductility of steel.

Hydrogen negatively affects weldability as it builds up in the seam causing pores and small cracks to form.

Phosphorus- a harmful additive that increases the hardness of steel and makes it more brittle, which leads to the formation of cold cracks.

Sulfur highly undesirable as it promotes the rapid formation of hot cracks. When the sulfur content is exceeded, the weldability deteriorates sharply.