RU2536314C1 - Flux cord wire underwater steels welding - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: charge in wire steel cover contains the following component ratio, wt %: rutile concentrate 25-37; calcium fluoride 8-17; iron powder 32-45; ferromanganese 5-9; nickel 1-3; alkaline metal carbonate 3-7, alkaline metal complex fluoride 3-13.

EFFECT: wire has good welding processing characteristics, it provides microdrop transfer of molten metal, arc stability and better formation of welded seal and quality of welded joints due to active metallurgic reactions on binding of water with hydrogen.

3 cl, 1 tbl

Description

The present invention relates to mechanical engineering and can be applied in mechanized and automatic underwater welding and surfacing of metal parts.

Known flux-cored wire for welding steels (see Grishanov A.A., Pankov V.I. Flux cored wire for welding steels. RF patent №2012469, V23K 35/368 dated 12/29/1991, published on 05/15/1994), which contains a mixture, with the following components, wt.%: calcium fluoride 40-49; lithium fluoride 5-11; cobalt fluoride 0.5-2; calcium carbonate 5-8; silicon dioxide 4-6; aluminum 9-11; molybdenum 7-10; iron powder 13-15; Nickel 1.5-3.

The specified flux-cored wire can improve the quality of the welded joint due to intense metallurgical reactions for the binding of water and hydrogen. However, cobalt difluoride, which has a high reactivity and is a toxic compound, is introduced into the charge, which is unacceptable when welding under water. In addition, the slag system based on calcium fluoride with the introduction of silicon dioxide has a reduced density (see Lepinsky BM, Manakov AI Physical chemistry of oxide and oxyfluoride melts. M: Nauka, 1977. - 192 p.), which worsens the conditions of the slag protection of the weld pool during underwater welding. The introduction of aluminum together with nickel leads to the formation of a low-melting eutectic NiAl and brittle intermetallic Ni ₃ Al, which reduces the ductility and toughness of welds at dynamic loads typical of underwater structures.

Known electrode for underwater welding of metal structures (see I. Lyakhovskaya, S.Yu. Maksimov, BC But and others. Underwater welding electrode. RF patent №2364483, V23K 35/365 from 05/11/2006 Bull. No. 23 Published on August 20, 2009). The specified electrode contains a rod brand Sv-08, which is coated with the following components, wt.%: Fluorite 19.5-28; rutile concentrate 18-33.5; iron oxide 13-28; feldspar 8-12; magnesite 4-8; manganese 5-10; nickel 0.5-3.5; carbomethyl cellulose 1.5-2.

The electrode allows you to perform arc welding under water of parts in any spatial positions with the formation of welds with a low hydrogen content. However, this electrode can be used only for manual arc welding, which significantly increases the complexity and reduces the performance of welding underwater operations. In addition, the electrode coating contains a significant amount of gas-forming and deoxidizing components, which contributes to turbidity of the water due to the release of aerosols. This complicates the visual control of the welder-diver over the formation of the seam and contributes to the formation of defects in the form of imperfections, undercuts, and slag inclusions.

Known flux-cored wire for welding under water during the repair of hulls, restoration of pipelines and other hydraulic structures (see Grishanov A.A., Pankov V.I. Flux cored wire for welding steels. RF patent №2012471, V23K 35/368 from 02.20. 1992 Published May 15, 1994), which is taken as a prototype. The specified wire contains a steel sheath and a powder mixture with the following components, wt.%: Rutile concentrate 28-35; hematite 16-25; iron powder 30-40; potassium dichromate 0.5-2; manganese 5-7; silicocalcium 1-2; nickel 3.5-5.

The invention improves the quality of welded joints by improving its mechanical properties. However, the composition of the charge according to the prototype contains an increased amount of deoxidizing agents - manganese and silicocalcium. When welding, these components form finely dispersed oxides of manganese and calcium, which are released in the zone of arc burning and the formation of the weld. The release of aerosols causes turbidity of the water in the welding zone and the welder under water cannot visually monitor the melting of the metal and the formation of the weld. In addition, when welding with the indicated wire, toxic manganese oxides and chromium oxides are released, which harm the ecology of the aquatic environment. Another significant disadvantage of the prototype is the absence in the composition of the mixture of active components for binding water vapor and hydrogen. The welding arc under water burns in a gas-vapor bubble, which mainly consists of water vapor, molecules, atoms and hydrogen ions. Hydrogen can saturate the weld and cause the formation of defects in the form of gas pores and cracks.

The technical result of the invention is to improve the welding and technological properties of cored wire and the quality of welded joints by changing the chemical composition of the charge, optimizing the slag system, changing the atmosphere of a gas-vapor bubble and active metallurgical reactions to bind water and hydrogen.

The essence of the invention lies in the fact that the flux-cored wire is made of a steel sheath, inside which a powdery mixture is placed at the following content of components, wt.%: Rutile concentrate 25-37; fluorspar 8-17; iron powder 32-45; ferromanganese 5-9; nickel 1-3; alkali metal carbonate 3-7, complex alkali metal fluoride 3-13.

Unlike the prototype, the proposed wire allows to reduce the amount of emissions of insoluble toxic aerosols, which preserves the transparency of the water and improves visual control of the diver welder over the formation of the seam.

The mixture according to the invention has a high total content of calcium fluoride and complex alkali metal fluoride, for example sodium hexafluoroaluminate Na ₃ AlF ₆ , which contributes to intense metallurgical reactions and decomposes during welding with the release of a significant amount of sodium and fluorine. Sodium is an element with a low ionization potential, which improves the stability of arc burning under water and reduces the arc voltage. Fluorides bind hydrogen molecules, atoms and ions in a gas-vapor bubble with the formation of gaseous hydrogen fluoride HF, which reduces the formation of defects and improves the quality of welded joints. A similar effect is exerted by hexafluoroaluminates Li ₃ AlF ₆ , K ₃ AlF ₆ , hexafluorotitanates Na ₂ TiF _6, Li ₂ TiF ₆ , K ₂ TiF ₆ , hexafluorosilicates Na ₂ SiF _6, Li ₂ SiF ₆ , K ₂ SiF ₆ , hexafluorozirconates Na ₂ ZrF _6, Li ₂ ZrF ₆ , K ₂ ZrF ₆ .

Sodium hexafluoroaluminate Na ₃ AlF ₆ has a low melting point of 1000 ° C and a low surface tension of about 130 mJ / m ² , which contributes to the wetting of the metal by slag and reduces the interfacial tension of the molten metal of the steel shell of the wire. This improves the process of dropping the metal into the weld pool during the melting of the flux-cored wire, the stability of arc burning and the formation of the weld. A similar effect is exerted by hexafluoroaluminates, Li ₃ AlF ₆ , K ₃ AlF ₆ , hexafluorotitanates Na ₂ TiF ₆ , Li ₂ TiF ₆ , K ₂ TiF ₆ , hexafluorosilicates Na ₂ SiF _6, Li ₂ SiF ₆ , K ₂ SiF ₆ , hexafluorozirconates Na ₂ ZrF _6, Li ₂ ZrF ₆ , K ₂ ZrF ₆ .

This combination of well-known and new features allows to improve the welding and technological properties of cored wire and the quality of welded joints during underwater welding of metal products. This becomes possible because the composition of the charge has an ore-acid slag system, which has low moisture permeability (see Petrov GL, Welding materials. M.: Mechanical Engineering, 1972 - 280 p.). The basis of ore-acid slag consists of TiO ₂ with a density of 4.2 g / cm ³ and CaF ₂ with a density of 2.5 g / cm ³ , therefore it has a glassy dense structure with a reduced viscosity and a surface tension of about 240 mJ / m ² .

This allows the slag in the molten state to close the surface of the weld pool and prevent the penetration of water and hydrogen into the weld metal, which improves the formation of the weld and reduces the formation of defects in the weld metal. Wetting of the weld pool at high cooling rates under water is facilitated by the low viscosity of the acidic slag of the TiO ₂ -CaF _{2 system of} about 0.08 N · s / m ² , which is further reduced by the introduction of complex alkali metal fluoride.

The optimal content of rutile concentrate in the charge is, mass.,%: 25-37, fluorspar: 8-17. The specified ratio of slag-forming components is selected from the condition of achieving the minimum viscosity and surface tension of the TiO ₂ -CaF _{2 system} in order to improve the drip transition and the formation of a weld under water. In addition, the specified ratio of TiO ₂ -CaF ₂ ensures the uniformity of the slag, reduces the likelihood of delamination and has a minimum melting temperature (see Toropov N.A., Barzakovsky V.P. et al. State diagrams of silicate systems. Handbook. Issue 1. Binary Systems.Leningrad: Nauka, 1969 .-- 822 p.).

If the content of slag-forming components is reduced below the optimum value, the volume of slag formed is insufficient to protect the weld pool from the ingress of water, hydrogen and oxygen, which affects the formation and quality of the weld. With an increase in the content of slag-forming components above the optimum value, the deposition coefficient and heat input efficiency decrease, which reduces the productivity of the welding process.

The introduction of iron powder into the mixture contributes to an increase in the deposition coefficient and heat input efficiency, which increases the penetration depth and productivity of the welding process. The optimal content of iron powder in the mixture is, mass.,%: 32-45. When the content of iron powder decreases below the optimum value, the deposition coefficient and heat input efficiency decrease, which causes a decrease in the penetration depth and productivity of the welding process. With an increase in the iron powder content above the optimum value, the slag protection of the weld pool deteriorates, which affects the formation of the weld, the density of the weld metal and the welding and technological properties of the flux-cored wire.

The introduction of ferromanganese into the mixture at the optimum content, wt.%: 5–9, promotes the reduction of iron through metallurgical reactions of the oxidation of iron oxides, the binding of sulfur contaminants to refractory manganese sulfides MnS. This improves the density of the weld metal and its mechanical characteristics. If the ferromanganese content decreases below the optimum value, the mechanical characteristics of the weld deteriorate, and when the ferromanganese content increases above the optimum value, the transparency of the aqueous medium decreases due to an increase in the number of aerosol emissions.

The introduction of the mixture of Nickel at the optimum content, wt.,%: 1-3 improves the mechanical characteristics of the weld, increases the ductility of the weld and the growth of the deposition coefficient. With a decrease in the nickel content below the optimum value, there is no effect of improving the ductility of the weld metal, and with an increase in nickel content above the optimum value, the formation of the weld and the density of the weld metal deteriorate.

The introduction of the mixture of alkali metal carbonate, for example Li ₂ CO ₃ at the optimum content, wt.%: 3-7, improves the stability of arc burning by increasing the degree of plasma ionization and increasing the partial pressure of carbon dioxide in a gas-vapor bubble, which reduces the concentration water and hydrogen over the weld pool. A similar effect is exerted by potassium carbonates K ₂ CO ₃ and sodium Na ₂ CO ₃ . With a decrease in the alkali metal carbonate content, the stability of arc burning decreases, and with an increase in the content, the heat input efficiency and the deposition coefficient decrease.

The introduction of a mixture of complex alkali metal fluoride, such as sodium hexafluoroaluminate Na ₃ AlF ₆ with a low surface tension of about 130 mJ / m ² provides a small drop transfer of metal. This effect occurs as a result of partial dissociation of the compound by the reaction: Na ₃ AlF ₆ = 2NaF + NaAlF ₄ . Sodium tetrafluoroaluminate NaAlF ₄ has a low melting point and low surface tension of about 86.6 mJ / m ² , it is concentrated in the surface slag layer and helps to reduce the interfacial tension of the molten metal (see Lepinsky B.M., Manakov A.I. Physical chemistry oxide and oxyfluoride melts. M: Nauka, 1977. - 192 p.). As a result, the diameter of the droplets decreases and the frequency of the droplet transition increases.

As a result of the decomposition and evaporation of Na ₃ AlF ₆ , gaseous compounds of NaF, AlF ₃ , AlF ₂ , AlF are formed around the welding arc, which change the chemical composition of the atmosphere of the vapor-gas bubble formed during the decomposition of water by the welding arc. The pressure of gaseous fluorides in a vapor-gas bubble increases with increasing concentration of AlF ₃ , which has the highest vapor pressure. The saturation of the vapor-gas bubble with fluorides is facilitated by the reactions of the compounds NaF, AlF ₃ , AlF ₂ , AlF with titanium dioxide TiO ₂ . In this case, titanium fluorides TiF ₄ , TiF ₃ , TiF _{2 are formed} , which have high chemical activity in hydrogen bonding reactions. A similar effect is exerted by introducing lithium hexafluoroaluminate Li ₃ AlF _{6 into the} mixture, which during welding dissociates into LiF, AlF ₃ , AlF ₂ , AlF compounds, as well as potassium hexafluoroaluminate K ₃ AlF ₆ , which when welding dissociates into KF, AlF ₃ , AlF ₂ , AlF. A similar effect on the binding of water and hydrogen is exerted by hexafluorotitanates Na ₂ TiF _6, Li ₂ TiF ₆ , K ₂ TiF ₆ , hexafluorosilicates Na ₂ SiF _6, Li ₂ SiF ₆ , K ₂ SiF ₆ , hexafluorozirconates Na ₂ ZrF _6, Li ₂ ZrF ₆ K ₂ ZrF ₆ .

An increase in the concentration of active fluorine in the atmosphere of a gas-vapor bubble allows efficient bonding of water, molecules and hydrogen atoms into gaseous compounds of hydrogen fluoride HF insoluble in the weld pool.

The main reason for the formation of gas pores is the absorption of hydrogen by molten metal [I. Pokhodnya Gases in the welds. M., Engineering, 1972, 256 S.]. Sources of hydrogen during welding are water, the vapor of which is contained in the atmosphere of a gas-vapor bubble and in the plasma of an arc. Water Н ₂ О and a hydrogen molecule at the temperature of the welding arc dissociate according to the reactions:

H ₂ O ↑ = H ₂ ↑ + 1 / 2O ₂ ↑ and H ₂ ↑ = H ↑ + H ↑.

The equilibrium constant of dissociation reactions increases with increasing plasma temperature, which is maximum in the center of the arc and minimum at its boundary. The removal of moisture and hydrogen is based on the chemical bonding of water molecules H ₂ O, hydrogen molecules H ₂ , hydrogen atoms H to gaseous compounds insoluble in the weld pool, according to the following types of chemical reactions:

$$2Me{F}_{\mathrm{to}}+H_2{O}_g\uparrow =2H{F}_g\uparrow +M{e}_2{O}_{\mathrm{to}}\text{I}$$

$$2Me{F}_{\mathrm{to}}+H_2{O}_g\uparrow =2H{F}_g\uparrow +M{e}_2{O}_g\uparrow \text{II}$$

$$Me{F}_g+H_2{O}_g\uparrow =H{F}_g\uparrow +M{e}_2{O}_{\mathrm{to}}\text{III}$$

$$Me{F}_g+H_2{O}_g\uparrow =H{F}_g\uparrow +M{e}_2{O}_g\uparrow \text{IV}$$

$$2Me{F}_{\mathrm{to}}+H_{2g}\uparrow =2H{F}_g\uparrow +M{e}_g\uparrow \text{V}$$

$$2Me{F}_g+H_{2g}\uparrow =2H{F}_g\uparrow +M{e}_g\uparrow \text{VI}$$

$$Me{F}_{\mathrm{to}}+H_g\uparrow =H{F}_g\uparrow +M{e}_g\uparrow \text{VII}$$

$$Me{F}_g\uparrow +H_g\uparrow =H{F}_g\uparrow +M{e}_g\uparrow ,\text{VIII}$$

where Me is an alkali metal; k - condensed (liquid or solid) phase; g is the gaseous phase. In welding, fluorides can exist in two separate phases, which have different values of enthalpy, entropy and reduced Gibbs energy.

Similar reactions to bind water, a molecule and a hydrogen atom occur with aluminum fluoride AlF ₃ :

$$2Al{F}_{3\mathrm{to}}+3H_2{O}_g\uparrow =6H{F}_g\uparrow +A{l}_2{O}_{3\mathrm{to}}\text{I}$$

$$2Al{F}_{3\mathrm{to}}+3H_2{O}_g\uparrow =6H{F}_g\uparrow +A{l}_2{O}_{3g}\uparrow \text{II}$$

$$2Al{F}_{3g}+3H_2{O}_g\uparrow =6H{F}_g\uparrow +A{l}_2{O}_{3\mathrm{to}}\text{III}$$

$$2Al{F}_{3g}+3H_2{O}_g\uparrow =6H{F}_g\uparrow +A{l}_2{O}_{3g}\uparrow \text{IV}$$

$$2Al{F}_{3\mathrm{to}}+3H_2{}_g\uparrow =6H{F}_g\uparrow +2A{l}_g\uparrow \text{V}$$

$$2Al{F}_{3g}+3H_2{}_g\uparrow =6H{F}_g\uparrow +2A{l}_g\uparrow \text{VI}$$

$$Al{F}_{3\mathrm{to}}+3H_g\uparrow =3H{F}_g\uparrow +A{l}_g\uparrow \text{VII}$$

$$Al{F}_{3g}+3H_g\uparrow =3H{F}_g\uparrow +A{l}_g\uparrow \text{VIII}$$

As a result of all types of reactions I ... VIII, the amount of water and hydrogen in the arc burning zone and in the molten metal decreases sharply, which prevents the formation of gas pores and improves the quality of the welded joint.

The probability of chemical reactions increases with increasing equilibrium constants, which for most reactions at T = 3000-5000 K have positive values, see Table 1

Table 1 The values of the logarithm of the equilibrium constant of chemical reactions log K _p Reaction type The reaction temperature, K The value of log K _P for reactions with fluorides CaF ₂ NaF Alf ₃ Kf LiF I 3000 K 0.2 -1.1 5.1 -1.3 -0.5 4000 K 0.9 -0.4 5.5 -0.5 0 5000 K 1,2 -0.1 5,6 -0.2 0.04 II 3000 K -3.1 -0.3 1.3 -0.7 -0.2 4000 K 0.05 1.3 3,1 0.45 one 5000 K 1,5 2.2 3,7 1.3 1.9 III 3000 K 5.5 4.7 2.1 3.3 5.8 4000 K 4.6 3.9 1.8 2.80 4.8 5000 K 3.9 3.3 1,5 2,3 4.1 IV 3000 K -3.6 1.7 -1.8 -2.5 -1.8 4000 K -1.2 -1.1 -0.1 -1.90 -1.3 5000 K 0.2 -0.7 one -1.5 -1.1 V 3000 K -2.3 1.45 one 1.4 0.1 4000 K 0.3 2.2 3.8 1.97 one 5000 K 1.7 2,8 4.4 2.6 1,5 VI 3000 K -2.6 0.02 -2 -0.4 -1.4 4000 K -0.9 0.6 0.97 0.13 -0.4 5000 K 0,07 0.9 2.7 0.4 0.2 VII 3000 K -0.57 2.25 3.4 2.1 0.9 4000 K 0.5 2.28 3.9 2.30 1,5 5000 K 1,1 2,3 4.2 2,4 1,6 VIII 3000 K -one 0.8 0.3 0.4 -0.64 4000 K 1.3 0.3 0.35 -0.05 -0.63 5000 K 1.4 0 0.4 -0.3 -0.62

The optimal content of complex alkali metal fluoride is, wt.,%: 3-13. This range of values allows you to ensure the minimum viscosity of the slag system TiO ₂ -CaF ₂ and reduce the surface tension of the molten fluorspar to 160 mJ / m ² .

With a decrease in the content of complex alkali metal fluoride below the optimum value, the process of flux-cored wire melting and droplet transition, as well as the ability of the mixture to actively bind water and hydrogen, deteriorate, which leads to the appearance of defects in the weld metal deposited. With an increase in the content of complex alkali metal fluoride above the optimum value, the stability of arc burning, the slag protection of the weld pool, the formation of the seam and the density of the deposited metal are deteriorated.

As an example of the application of the proposed wire is a mechanized arc welding of samples of low carbon steel with a size of 300 × 200 mm and a thickness of 10 mm A particularly soft steel strip 0.2 mm thick 10 mm wide made of 08kp steel was placed in a rolling mill in which a 4.5 mm diameter steel sheath was formed. At the same time as molding, a finely ground mixture of the following composition was poured into the steel shell, mass.,%: Rutile concentrate 30; fluorspar 15; iron powder 35; ferromanganese 5; nickel 3; lithium carbonate 5; sodium hexafluoroaluminate 7. Then, the wire was reduced by a method of successive drawing to a diameter of 1.6 mm.

The obtained flux-cored wire was used in mechanized arc welding using a Magma-315U power source with immersion to a depth of 14 m in the Baltic Sea. The butt joint of the plates had two symmetrical bevel edges on both sides, the designation of the welded joint C25 according to GOST 14771-76. The filling of the weld was carried out in two passes on each side with an arc voltage of 37 V. The flux cored wire with a charge of the indicated composition had stable arc burning, stable small droplet transfer, ensured fine-scale smooth formation of welded beads, good slag protection of the weld pool. Mechanical tests of welded joints showed that the strength of welds is higher than the strength of the base metal by 22-26%.

Thus, the proposed flux-cored wire provides a technical effect, which is expressed in the improvement of the drip transition, the stability of the arc burning and the formation of the weld during underwater welding, can be manufactured and applied using methods known in the art, therefore, it has industrial applicability.

Claims (3)

1. A flux-cored wire for welding steels under water, consisting of a steel shell and a mixture containing rutile concentrate, iron powder, ferromanganese and nickel, characterized in that the mixture additionally contains fluorspar, alkali metal carbonate and complex alkali metal fluoride in the following components , wt.%:
rutile concentrate 25-37
fluorspar 8-17
iron powder 32-45
ferromanganese 5-9
nickel 1-3
alkali metal carbonate 3-7
complex alkali metal fluoride 3-13. 2. The flux cored wire according to claim 1, characterized in that, as an alkali metal carbonate, the mixture contains a compound or mixture of compounds selected from the group of lithium, potassium, sodium carbonates. 3. The flux cored wire according to claim 1 or 2, characterized in that, as a complex alkali metal fluoride, the mixture contains a compound or mixture of compounds selected from the group of hexafluoroaluminates, hexafluorotitanates, hexafluorosilicates, alkali metal hexafluorozirconates.