RU2478029C2 - Composite wire for arc welding and building up - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention may be used for electric arc welding and building up of complex-alloyed refractory alloys based of nickel aluminide Ni₃Al. Composite wire consists of two-layer shell, outer nickel and inner aluminium layers shell to accommodate fusion alloying components, and wire components and tapes. Interlayer of the mix of ultrafine refractory compounds with binder is arranged between shell layers.

EFFECT: guaranteed transfer of refractory components into molten pool via low temperature region of reaction area.

3 cl, 4 dwg, 1 tbl, 1 ex

Description

The invention relates to welding and surfacing materials, in particular to composite wires used in metallurgical, petrochemical, nuclear power and general engineering, as well as in the manufacture of aircraft and can be used for electric arc welding of complex alloyed heat-resistant alloys based on nickel aluminide Ni ₃ Al .

Known flux-cored wire (USSR author's certificate No. 1722756, B23K 35/40, publ. Bull. No. 12, 1992), the design of which contains at least two sheaths with a given ratio (0.12-0.30) between their thicknesses and the charge located in the inner shell.

To obtain a deposited metal based on Ni ₃ Al using a wire of this design, the shell layers can be made of nickel and aluminum. But to ensure a stoichiometric ratio between the masses of nickel and aluminum, it is necessary to go beyond the permissible limits of the thicknesses of the layers of the wire sheath specified in A.S. No. 1722756.

In addition, if aluminum and nickel powders are introduced into the composition of the wire charge, then the oxygen contained in the minerals will cause a significant decrease in the properties of the deposited metal.

Known electrode wire (patent of Russia, No. 2355543, B23K 35/368), B23K 35/10, publ. May 20, 2009), consisting of a metal tube and a filler. On the outer and inner surfaces of the tube there are layers of a composite coating up to 100 microns thick, which is a mixture of one of the metals (nickel, copper, titanium, chromium, aluminum, molybdenum) with particles of activating flux (oxides and salts). The metal tube filler contains a mixture of slag and gas-forming components. This design through the use of components of the activating flux allows you to counteract the welding arc, which helps to increase its penetrating ability. In addition, the slag melt formed during melting of the coating reduces interfacial tension, which leads to an improvement in the droplet transfer of electrode metal into the weld pool.

Using this design to produce Ni ₃ Al-based alloys in weld metal and welds requires the manufacture of a tube from components of an intermetallic compound (for example, nickel as the element having the largest mass fraction in the joint). In this case, it is necessary that the mass of the tube be in a stoichiometric ratio with the mass of the second component (aluminum), which can be introduced through the composite coating or charge of the filler. However, in the process of melting the wire, this will lead to the intense oxidation of aluminum by slag and gas-forming components contained both in the activating flux and in the charge of the wire. In addition, the use of only slag and gas-forming components in the wire filler results in a lower value of the deposition coefficient.

Closest to the proposed object is the construction of a composite wire for surfacing an alloy based on nickel aluminide Ni ₃ Al (RF patent No. 2274536, IPC B23K 35/40, publ. 04/20/2006), having a two-layer sheath, the outer layer of which is made of nickel and the inside is aluminum. The inner volume of the wire contains a mixture of nickel and aluminum, as well as the wire components of tantalum, tungsten and molybdenum located coaxially to the sheath. The stoichiometric ratio between the masses of nickel and aluminum in the composite wire is regulated by the ratio of the thicknesses of the outer and inner layers of the sheath within (mm): 0.4 ... 0.8 and 0.076 ... 0.185, respectively. A decrease in the thickness of the shell layers is compensated by an increase in the content of aluminum and nickel in the charge.

This design reduces the separation of the charge while maintaining the technological reliability of the wire.

However, the use of such a composite wire design as an electrode material for welding and surfacing alloys based on doped nickel aluminide is not rational. The introduction of nickel and aluminum into the filler of the composite wire in the form of metal powders, which, in comparison with wire components, has an increased specific surface area and, consequently, oxidation, leads to a deterioration in the plastic properties of the deposited metal.

In addition, the amount of nickel and aluminum in the charge is regulated by specified ranges of shell thicknesses, which reduces the possibility of varying the contents of aluminum and nickel in the composite wire.

The technical result of the invention is to create an electrode composite wire that provides a high-quality weld based on doped nickel aluminide by placing refractory ultrafine alloying elements in the peripheral section of the composite wire, which, when melted, ensures a guaranteed transition of these components to the weld pool through the low-temperature region of the reaction zone welding.

The technical result is achieved by the fact that in a composite wire for arc welding and surfacing, consisting of a two-layer sheath - the outer nickel and inner aluminum, inside of which there are wire components and a charge in contact with it, between the layers of the sheath is a layer of a powder mixture of ultrafine refractory components with binder, thickness & pr which is determined by the ratio

,

,

where b _CR - the thickness of the layer, mm; K ₂ is a coefficient that determines the content of refractory ultrafine components introduced into the metal, with K ₂ = 0.01-1.0; D _KP - the diameter of the composite wire, mm, and the sheath of aluminum is a layer, the cross-sectional area S _{A1 of} which is determined by the ratio

where ρ _Ni , ρ _al is the specific gravity of the elements of the intermetallic compound Ni ₃ Al; m _i , ρ _i - mass fraction and specific gravity of alloying elements, n - number of alloying elements; D _KP is the diameter of the composite wire, mm, k _c is the stoichiometric ratio between the masses of nickel and aluminum included in the intermetallic compound Ni ₃ Al:

where Ni _l , Al _l , Ni _about , Al _sl - the mass of Nickel and aluminum contained in the alloying components, as well as in the Nickel and aluminum layers of the shell, respectively.

As refractory components, it contains elements of transition metals of groups IV, V, and VI, as well as their refractory compounds with carbon or nitrogen, or oxygen, or boron.

Inside the aluminum layer of the shell there are additionally metal bands.

Placing the interlayer between the layers of the shell (Fig. 1) ensures the formation of a low-temperature nickel-aluminum melt containing refractory ultrafine compounds during its melting, which contributes to their reliable transition to the weld pool through the peripheral region of the reaction zone of the weld.

Ultrafine refractory compounds, being crystallization centers, intensify the release of ultrafine secondary phases γ _W '-Ni ₃ Al, which leads to an increase in the high-temperature properties of the deposited metal based on nickel aluminide. As refractory components, elements of transition metals of groups IV, V, and VI are used, as well as their refractory compounds with carbon or nitrogen, or oxygen, or boron, which have a high melting point and thermodynamic stability in the melt of nickel aluminide.

The placement of refractory elements in the form of wire components and tapes coaxially with the composite wire in its central volume (Fig. 2) in contact with a relatively low-melting layer of aluminum, allows you to evenly distribute the arc over the cross section of the wire. This increases the stability of arc burning from the composite wire and contributes to a more uniform melting of the wire components at a speed close to the melting speed of the charge and shell. At the same time, a melt of doped nickel aluminide is formed on the melting end of the composite wire (Fig. 3).

The thickness of the layer is determined from the ratio

where K ₂ = 0.01-1.0 is a coefficient that determines the content of refractory ultrafine components introduced into the metal.

The proposed intervals of the coefficient K ₂ provide the transition of ultrafine particles of refractory components to the low-temperature region of the reaction zone of welding and the modification of the structure of the deposited metal based on Ni ₃ Al. The condition under which K ₂ <0.01, causes a significant decrease in the amount of refractory components introduced into the metal, which does not allow modification of the alloy based on nickel aluminide. At K ₂ > 1.0, the number of refractory components introduced into the metal increases significantly, which leads to the formation of cracks in the deposited metal due to the excessive content of refractory components along the grain boundaries of nickel aluminide.

An aluminum sheath represents a layer, the cross-sectional area S _A1 , which depends on the amount of alloying components and the stoichiometric ratio between the masses of aluminum and nickel in the composite wire and is determined by relation (1).

where D _KP - the diameter of the composite wire; ρ _Ni , ρ _Al is the specific gravity of the elements of the intermetallic compound Ni ₃ Al; m _i , ρ _i - mass fraction and specific gravity of alloying elements, n - number of alloying elements; k _c is the stoichiometric ratio between the masses of nickel and aluminum included in the intermetallic compound Ni ₃ Al:

where Ni _l , Al _l , Ni _r , Al _sl are the masses of nickel and aluminum contained in the alloying components, as well as in the nickel and aluminum layers of the shell, respectively.

The use of metal tapes will make it possible to increase the fill factor of the composite wire if it is limited by the number of wire components, and also to perform additional alloying of the deposited metal.

The invention is illustrated by drawings.

Figure 1 shows a cross section of a composite wire for welding and surfacing alloys based on Ni ₃ Al.

Figure 2 shows a cross section of a filler composite wire.

Figure 3 shows a diagram of the process of melting a composite wire in a welding arc.

Figure 4 shows the microstructure of the weld metal based on nickel aluminide (× 1000).

The proposed composite wire for arc welding and surfacing contains a two-layer sheath with an outer nickel 1 and an inner aluminum 2 layers (figure 1). Between the layers of the shell is a layer 3 of a mixture of powders of ultrafine refractory components with a binder. The thickness of the interlayer b _pr is determined from the product K ₂ к D _kp . Coefficient K ₂ determines the content of ultrafine refractory components introduced into the metal and is in the range of 0.01-1.0. As these components, elements of transition metals of groups IV, V, and VI are used, as well as their refractory compounds with carbon or nitrogen, or oxygen, or boron. The aluminum layer 2 of the sheath is a layer whose cross-sectional area S _{A1 of} which depends on the diameter of the composite wire D _kn , the number of alloying components and the stoichiometric ratio between the masses of aluminum and nickel in the composite wire. For its determination using formulas (1) and (2). In the Central volume of the composite wire (figure 2) in contact with the inner layer of the sheath 2, there are components in the form of wires 4 and tape 5, as well as the charge 6.

Composite wire is used as follows. Welding using composite wire is carried out at constant current (plus on the electrode). Depending on the diameter of the wire (1.6-4 mm), the magnitude of the electrode extension from the current-carrying mouthpiece is set in the range of 30-50 mm. As a protective medium 7 use helium, argon or mixtures thereof. In the process of arc welding and surfacing, the melting of the layers 1 and 2 of the shell occurs with a certain lead, as a result of which the formed nickel-aluminum melt 8 covers the surface of the refractory wire components 4 (Fig. 3). After melting the most refractory wire component in the nickel-aluminum melt 8, a drop 9 is separated from the end of the composite wire, which is transferred to the weld pool 10.

Example

A composite wire of 3 mm diameter was made. The outer layer of the composite wire sheath was formed from nickel tape grade NP-2 GOST 2170 8 mm wide and 0.6 mm thick. A mixture of a refractory component with a binder was applied to the inner surface of the nickel tape. The thickness of the formed layer for the selected diameter of the composite wire was b _CR = K ₂ · D _KP = 0.1 · 3 mm = 0.3 mm As an ultrafine component, tungsten carbide powder WC obtained by plasma chemical technology was used. The material transporting ultrafine WC particles was nickel micropowder (99.9% Ni) with a particle size of up to 60 μm. Nickel granules obtained as a result of joint processing of powders in a planetary mill contained up to 50 wt.% WC particles. A 96% solution of ethyl alcohol was used as a binder for applying granules on a metal surface.

The cross-sectional area S _{A1 of the} aluminum sheath was determined by the formula 1. The calculation was based on the known specific gravities of the elements and the composition of the composite wire, providing a weld metal based on doped nickel aluminide: (wt.%) 0.3 C; 3.0 W; 2.5 mo; 1.8 Zr; 4.2 Cr; 1.9 Ta; 11 Al; Ni is the rest. Since nickel and aluminum were only in the layers of the shell, formula 2 had the following form:

Substituting the obtained value into the formula (1), it was obtained that S _A1 = 0.235 · 3 ² = 2.12 mm ² — the cross-sectional area of the aluminum layer was obtained. In this example, the obtained value of S _{A1 was} equated to the area occupied by the cross section of the aluminum tube, from which its diameter and wall thickness were expressed. For S _A1 = 2.12, the outer diameter of the tube is 2 mm and the wall thickness is 0.46 mm.

After the formation of both layers of the shell, tungsten and molybdenum wire components with a diameter of 0.5 mm, a tantalum tape with a width of 1.5 mm and a thickness of 0.05 mm, as well as chromium aluminothermic and zirconium powders were placed and drawn. In the process of plastic deformation of the components a wire was formed, the appearance of the cross section of which corresponded to figure 1.

The study of the cross section of the finished composite wire showed good sealing of the joint of the sheath after a single crimp. The density of the butt joint of the edges of the sheath along the length of the wire is high.

Welding and technological properties of the experimental composite wires were controlled by recording oscillograms of the welding current and arc voltage during the surfacing of control samples. Metallographic studies were performed using optical, electron (scanning double-beam electron microscope Quanta 3D FEG) and atomic force microscopy (scanning probe microscope Solver PRO-M).

The test results are shown in the table.

Table Composition
naya wire Koeffi
CENT K ₂ Arc Stability The nature of the structure of the weld metal The distribution and content of the γ'-phase in the structure of the deposited metal, volume. % Resistance of deposited metal to deformation at elevated temperature up to 1100 ° С, V _d × 10 ^-3 , mm ³ * Offered (D _KP = 3 mm) 0.005 electrical parameters of the mode (I _St and U _d ) stable, no short circuits γ'-Ni ₃ Al solid solution, carbide phases of various composition and origin, with a small amount of ultrafine precipitates of γ _W '-Ni ₃ Al uniform, 75-80 4.8 0.01 The same, but with numerous closely spaced ultrafine precipitates γ _W '-Ni _s Al 3.4 0.1 2.9 1,0 3.2 1,5 The same, but with a small amount of coarse precipitates γ _W '-Ni ₃ Al 4.0 Prototype - Intermittent short circuits, increased spatter γ'-Ni ₃ Al solid solution, numerous carbide phases of various composition and origin. not uniform, 50-60 5.2 * V _d - the volume of the deformed metal indenter, mm ³ . A lower value of V _d corresponds to a better metal resistance to plastic deformation.

The plastic strain metal resistance was evaluated using sclerometric tests of the surface of samples heated to a temperature of 1100 ° C with a load on the Rockwell indenter of 4.5 N. The criterion was the volume of metal deformed by the indenter in a 10 mm long section.

From the table it follows that the proposed composite wire in comparison with the prototype has the best welding and technological and high temperature properties.

In the process of arc surfacing using the developed composite wire, the electrical parameters of the mode (I _st and U _d ) are stable, there are no short circuits, which indicates a relatively uniform density of the welding current over its cross section. The structure of a well-formed deposited metal consists of a dendritic γ'-Ni ₃ Al solid solution, a disordered solid solution of aluminum in nickel, as well as numerous carbide phases of various composition and origin (Fig. 4). No welding defects were detected in the deposited metal, which indicates the high quality of the composite wire.

The use of the proposed composite wire for welding and surfacing in comparison with the known composite wires gives the following positive effect:

1. The possibility of using technologically flexible arc welding processes in shielding gases for the manufacture of new and repair of worn products from heat-resistant alloys based on Ni ₃ Al.

2. The ability to obtain high-quality complex alloyed weld and deposited metal with high-temperature properties.

Claims (3)

1. Composite wire for arc welding and surfacing, consisting of a two-layer sheath, an external nickel and an internal aluminum sheath, inside of which are in contact with it wire components and a charge, characterized in that between the layers of the sheath is a layer of a mixture of powders of ultrafine refractory components with a binder , the thickness b _CR which is determined by the ratio b _CR = K ₂ · D _KP , where
b _CR - the thickness of the layer, mm; K ₂ is a coefficient that determines the content of refractory ultrafine components introduced into the metal, with K ₂ = 0.01-1.0; D _KP - the diameter of the composite wire, mm, and the sheath of aluminum is a layer, the cross-sectional area S _{Al of} which is determined by the ratio

where ρ _Ni , ρ _Al is the specific gravity of the elements of the intermetallic compound Ni ₃ Al; m _i , ρ _i - mass fraction and specific gravity of alloying elements; n is the number of alloying elements; D _KP - the diameter of the composite wire; k _{c is the} stoichiometric ratio between the masses of nickel and aluminum included in the intermetallic compound Ni ₃ Al:

where Ni _l , Al _l , Ni _r , Al _sl are the masses of nickel and aluminum contained in the alloying components, as well as in the nickel and aluminum layers of the shell, respectively. 2. The composite wire according to claim 1, characterized in that as refractory components it contains elements of transition metals of groups IV, V and VI, as well as their refractory compounds with carbon, or nitrogen, or oxygen, or boron. 3. The composite wire according to claim 1, characterized in that the metal layer is additionally located inside the aluminum layer of the sheath.

Images