RU98165U1 - COMPOSITION WIRE FOR Fusing ALLOYS ON THE BASIS OF TITANIUM ALUMINIDES - Google Patents

Abstract

 Composite wire for electroslag and arc surfacing, containing a tubular sheath, inside which a cylindrical titanium core is installed in contact with it, characterized in that the core diameter is 1.5 ... 3.5 mm, and the sheath is made of aluminum, and the outer diameter of the sheath determined from the relation DAl = kdTi [mm],! where DAl is the outer diameter of the shell; ! dTi is the core diameter; ! k is the coefficient determining the stoichiometric ratio between the masses of the titanium core and the aluminum shell, with k = 1.14 ... 1.26 to obtain Ti3Al titanium aluminide in the deposited metal; k = 1.41 ... 1.59 to obtain titanium aluminide TiAl in the deposited metal.

Description

Composite wire refers to surfacing materials used in metallurgical, petrochemical, nuclear energy and general engineering and can be used for electroslag and arc surfacing and welding, as well as electron beam and laser welding and surfacing, alloys based on titanium aluminides Ti ₃ Al and TiAl .

Known flux-cored wire for welding (patent of European Patent Office No. 1277538, IPC B23K 35/02, publ. 2003) in which the sheath can be made in the form of a seamless tube of nickel alloy inside of which is a filler containing a powder mixture of rutile and alumina minerals, and located coaxially conductive wire that does not have contact with the sheath.

The design feature of this flux-cored wire for welding is the central location of the conductive core, which ensures stable arc burning and increased melting ability, which is unacceptable in surfacing processes. In the case of using this design in the welding and surfacing of products from alloys based on titanium aluminides, the oxides contained in the titanium and aluminum minerals will cause an increased oxygen content in the deposited metal, which will significantly reduce its plastic properties.

Known composite wire (see patent No. 3169495, Japan, IPC B23K 35/02, publ. 07.23.1991), consisting of a tubular sheath made of aluminum, inside of which is placed a cylindrical aluminum core and thin wires of equal diameter of magnesium, zirconium , titanium and boron are located concentrically to the core and located between it and the surface of the tubular shell. This design helps to increase the fill factor of the composite fiber, eliminates the separation of components in it and obtain aluminum-magnesium alloy in the weld metal. Also, the use of such a design allows you to roll the composite wire, due to the manufacture of the sheath and core of a homogeneous, plastic and well-deformed material.

The use of this design for producing in the weld form alloys based on TiAl and Ti ₃ Al intermetallic compounds requires the manufacture of titanium and aluminum wire components, the mass ratio of which in the composite wire must be in the required (according to the Ti-Al state diagram) stoichiometry. But the introduction of titanium and aluminum in the structure under consideration is possible only due to wires of a constant and equal diameter or core, which also has a constant diameter, which does not allow varying the content of titanium and aluminum to ensure their stoichiometric ratio.

Known composite flux-cored wire for surfacing an alloy based on nickel aluminide (RF patent No. 2274536, IPC B23K 35/40, publ. Bull. No. 11, 2006), consisting of two sheaths in contact with each other, nickel outer and aluminum inner, coaxially which introduced wire components from tantalum, tungsten, molybdenum, and the mixture contains aluminum and nickel. This design reduces the separation of the charge while maintaining the technological reliability of the wire. However, for the deposition of alloys based on titanium aluminides, this design is not rational, since the amount of charge is regulated by the specified thicknesses of the shells, which does not allow varying the content of aluminum and titanium in the charge. In addition, in the case of the introduction of titanium in the form of a metal powder, which has a higher specific surface area in comparison with the wire component, the degree of titanium oxidation by atmospheric oxygen increases significantly, which worsens its plastic properties. In the case of the introduction of aluminum and titanium through wire components, their number is limited by the fill factor of the cored wire.

Closest to the proposed object is the design of the consumable electrode for electric arc welding and surfacing in protective gases (RF patent No. 2082577, IPC B23K 35/02, publ. Bull. 1997), having a composite structure - a steel rod inside which is in contact with it placed a core of titanium or zirconium, the diameter of which is 0.07 ... 0.5 of the diameter of the rod. This ratio of diameters contributes to the alignment of the melting rates of the core and rod during the welding process with the formation of a conical shape of the electrode end, which determines the effect of jet transfer of metal droplets.

A similar design of the electrode can be implemented in the form of a composite wire used in welding and surfacing processes as filler material. In this case, the steel rod of the electrode performs the function of a tubular shell, inside of which there is a titanium core having good electrical contact with the surface of the shell. This design in comparison with analogues is the most technologically advanced in manufacture, since it contains fewer structural elements.

However, with the known ratio of the diameters of the core and the rod, it is impossible to design a composite wire for surfacing an alloy with a given stoichiometric mass ratio of titanium and aluminum. In addition, the use of aluminum and titanium significantly differing in strength and plastic properties requires ensuring the technological reliability of the composite wire, which consists in its good ductility to ensure a high-quality roll process without the formation of discontinuities between the core and the sheath.

The technical result consists in creating a technologically reliable design of a composite wire for electroslag and arc surfacing and welding of heat-resistant alloys and in guaranteed receipt of a deposited metal and a weld metal based on titanium aluminides Ti ₃ Al and TiAl when melting the wire.

The technical result is achieved by the fact that the composite wire for electroslag and arc welding and surfacing contains a sheath, inside which a cylindrical core of titanium is installed in contact with it, the sheath is made of aluminum, the core diameter being 1.5 ... 3.5 mm, and the outer diameter of the shell is determined from the ratio D _Al = kd _Ti [mm], where D _Al is the outer diameter of the shell; d _Ti is the diameter of the core; k is a coefficient that determines the stoichiometric ratio between the masses of the titanium core and the aluminum shell and is in the ranges 1.14 ... 1.26 and 1.41 ... 1.59 to obtain titanium aluminides Ti ₃ Al and TiAl in the weld metal, respectively.

The execution of the sheath of a composite wire made of aluminum with increased ductility improves the deformation ability of the wire, which contributes to the high manufacturability of its drawing, which consists in reducing the complexity of obtaining the required wire diameter.

The diameters d _{Ti of the} titanium cores are selected in the range of 1.5 ... 3.5 mm, which allows the ratio D _Al = kd _{Ti to} determine the diameter of the composite rod in the range of 2 ... 5 mm and obtain a technologically reliable composite wire. The condition under which d _Ti <1.5 mm corresponds to an increase in the probability of wire breaks when it is drawn due to the low deformation ability of a high-strength titanium core, as well as to peeling of a thinned (thickness less than 0.1 mm) aluminum shell and its further destruction. An increase in the diameter of the titanium core over 3.5 mm leads to an increase in the diameter of the composite wire over 5 mm, which makes it difficult to roll. Small (within current standards) 2 ... 5 mm wire diameters allow it to be used both in arc, plasma, beam, and in ESH and ESW processes with a small-sized slag bath.

The outer diameter of the shell is determined from the relation D _Al = kd _Ti . The coefficient k, which determines the stoichiometric ratio, according to the Ti-Al state diagram, between the content of titanium and aluminum in the composite wire, is selected from the condition of guaranteed production of deposited metal based on titanium aluminides Ti ₃ Al k = 1.14 ... 1.26 and TiAl k = 1.41 ... 1.59. Finding the coefficient k in the declared intervals ensures the fulfillment of the stoichiometric ratio between the masses of the aluminum shell and the titanium core, as well as in any cross section of the wire.

The lower values of these ranges correspond to a minimum aluminum content of at least 15 and 34 wt.%, Respectively, in which the deposited metal has a solid solution structure based on α ₂ -Ti ₃ Al and γ-TiAl. The upper values of the limits of the coefficient k correspond to the maximum content of aluminum in the deposited metal, which is 25 and 48 wt.%, Respectively. Exceeding the upper limit of doping with aluminum in the case k> 1.59 leads to the formation of TiAl ₂ and TiAl ₃ intermetallic phases in the deposited metal, which have a low ordering temperature of the crystal structure, which reduces the heat resistance of the metal. At k> 1.26, two types of intermetallic compounds are immediately formed in the structure of the deposited metal: α ₂ and γ, which does not provide a technical result.

The invention is illustrated in the drawing.

Figure 1 shows a cross section of a composite wire for surfacing and welding of an alloy based on Ti ₃ Al.

Figure 2 shows a cross section of a composite wire for welding and welding of an alloy based on TiAl.

The composite wire consists of an aluminum shell 1, which is a tube, inside of which a cylindrical core 2 made of titanium is located in contact with the shell. Finding the core diameter d _Ti in the range of 1.5 ... 3.5 mm determines, when the ratio D _Al = kd _{Ti is} fulfilled, the maximum outer diameter of the composite wire is up to 5.5 mm, which allows it to be rolled. Also, the small diameter of the wire provides better handling if it is fed into a welding arc or other small-sized heat source.

Composite wire is used as follows.

In the process of electroslag surfacing, the composite wire is fed into the slag bath. When using the composite wire of the structure of FIG. 1, the thin-walled shell 1 is melted with some lead, which exposes the core 2 in the slag. Slow melting of the refractory titanium core in the slag leads to supercooling of the molten metal bath, contributing to the fine-grained structure of the deposited metal, which therefore has enhanced operational and technological properties. Averaging the chemical composition of metal droplets occurs in a bath of molten metal. Taking into account the close transfer coefficients (k _{per Al} = k _{per Ti} = 0.4) of aluminum and titanium to slag, the stoichiometric ratio of their masses in the deposited metal is not violated. When used in the ESH design (Fig. 2), the sheath 1 of the composite wire melts and covers the surface of the titanium rod 2. At the time of formation of the melt containing aluminum and titanium, the drop separates.

In the case of arc surfacing, the composite wire is fed into the peripheral region of the arc in order to reduce its melting rate. Helium, argon, or mixtures thereof are used as a protective medium. The melting of a thin-walled shell occurs with a certain lead, which exposes the titanium rod, in connection with which the formation of the melt occurs in the weld pool.

Example 1

The initial component for the manufacture of the core of the composite wire (Fig. 1) was a titanium wire of grade VT1-00 GOST 19807 with a diameter of 2 mm. To determine the outer diameter of the wire D _{Al, the} coefficient k was chosen from the range 1.41 ... 1.59 in which the mass ratio of the titanium core and the aluminum shell are in stoichiometry, which ensures the TiAl-based alloy in the state diagram. At k = 1.50, the diameter of the composite wire should be 3.0 mm. In order to accommodate the titanium core, an aluminum tube with an inner diameter of 2.1 mm and a wall thickness of 0.5 mm made of aluminum of grade AD00 GOST 4784 was used. To ensure contact between the inner surface of the aluminum tube and the titanium core, they were pressed together in a die with a working diameter of 3.0 mm with the formation in the cross section of a solid wire.

A tube made of aluminum of the grade AD00 GOST 4784 manufactured according to the requirements of GOST 18475 was also used. To obtain a composite wire with a diameter of 3 mm, the closest tube diameter according to GOST 18475 is 6 mm. A tube with a diameter of 6 mm and a wall thickness of 0.75 mm was used. The tube was preliminarily squeezed in the dies by triple drawing to ensure that the inner diameter of the tube is sufficient to accommodate a titanium core and a wall thickness of 0.5 mm. Then, the aluminum tube and the titanium core were jointly crimped in a die with a working diameter of 3.0 mm.

The resulting composite wires in the state after roll-up provided tight contact between the aluminum shell and the titanium core, and also had a constant shell wall thickness along the perimeter of the cross section and the length of the wire.

Industrial production of composite wire is possible on existing technological equipment for the manufacture of flux-cored wires with a slight readjustment.

Electroslag surfacing in a current-conducting mold using low-oxygen flux ANF-6 was conducted with direct current of direct polarity with a power of 180-200 A and a voltage on the slag bath of 21-23 V. The surface of the slag bath was protected from the atmosphere by argon. After the formation of a slag bath, a composite wire was immersed into it at a speed of 5 ... 7 mm / s. During the melting of the composite wire, an advance was observed in the melting of the thin-walled aluminum sheath relative to the refractory titanium rod. The deposited metal had a single-phase structure of titanium aluminide α ₂ -Ti ₃ Al.

Example 2

An arc surfacing was performed with a non-consumable tungsten electrode with a direct current of reverse polarity of 150 A at a voltage of 30 V on an arc. A composite wire 3 mm in diameter similar to Example 1 was used. The wire was fed into the peripheral region of the arc in order to reduce its melting rate. Helium was used as a protective medium, the flow rate of which was 5 l / min. In the process of melting the composite wire of the structure, a small acceleration of shell melting in the peripheral zone of the arc was observed, in comparison with ESH, with satisfactory formation of the deposited metal and minimal (0.5 ... 1%) penetration of the steel substrate.

Using the proposed composite wire design in the welding and welding processes: electroslag, arc in argon, helium and their mixtures, in comparison with the known models of filler materials gives the technical result:

- allows to obtain heat-resistant alloys based on titanium aluminides Ti ₃ Al and TiAl when melting the wire;

- provides a technologically reliable and universal design for use in the processes of arc and electroslag surfacing and welding.

Claims (1)

Composite wire for electroslag and arc surfacing, containing a tubular sheath, inside which a cylindrical titanium core is installed in contact with it, characterized in that the core diameter is 1.5 ... 3.5 mm, and the sheath is made of aluminum, and the outer diameter of the sheath determined from the relation D _Al = kd _Ti [mm], where D _Al is the outer diameter of the shell; d _Ti is the diameter of the core; k is the coefficient that determines the stoichiometric ratio between the masses of the titanium core and the aluminum shell, with k = 1.14 ... 1.26 to obtain titanium aluminide Ti ₃ Al in the deposited metal; k = 1.41 ... 1.59 to obtain titanium aluminide TiAl in the deposited metal.