RU2356708C1 - Method for high speed argon-arc welding of cylindrical parts - Google Patents

Abstract

FIELD: machine building.

SUBSTANCE: invention may be used in manufacture and repair of machine cylindrical parts, for instance in worn out shafts, for instance for application of special alloys on shaft journals. Surface of rotary part is heated by electric arc to condition close to melting. Filler wire, end of which has shape of cone, is oriented with its longitudinal axis relative to axis of part rotation at the angle and is supplied to zone of arc burning with permanent axial force. Filler is rotated under condition of match between vector of cone base circular speed and vector of part generatrix circular speed. Filler wire is supplied with the speed that is 1.15…1.25 times more than the rate of its melting. Tungsten electrode relative to axis of wire rotation is diverged in plane that is perpendicular to axis of rotation for 24…28° to the side that is opposite to part rotation, and also for 16…18° in direction of welding. Arc capacity is increased simultaneously with connection of line feed.

EFFECT: invention makes it possible to produce welded layers with thickness of 0,3…0,6 mm, allowance for further treatment within the limits of 0,1…0,12 mm per side, at that savings of filler material make 30…40%.

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Description

The invention relates to the manufacture and repair of machine parts, and in particular to methods of automatic argon-arc surfacing of the surface of parts, and can be used to restore worn surfaces of cylindrical parts, as well as to give the surface of the part special physical and mechanical properties in their manufacture.

Most parts of internal combustion engines and transmissions of modern agricultural machines have wear within 0.1 ... 0.3 mm, their share reaches up to 64%. To repair these parts, various methods of electric arc surfacing are used, which in real production conditions do not allow to obtain a surfacing thickness of less than 1 mm per side. With further machining, up to 80% of the deposited metal is converted to shavings. For economical consumption of the deposited metal, taking into account subsequent mechanical processing, it is necessary to deposit a layer with a thickness of 0.3 ... 0.6 mm.

A known method of surfacing, for example, in a protective gas environment non-consumable electrode [Petrov G.L., Tumarev A.S. Theory of welding processes. - M .: Higher school, 1977, p. 28, fig. 1.13b], in which the arc between the non-consumable electrode and the part is ignited, and the filler wire is fed into the arc or weld pool formed on the part.

The disadvantage of this method is that the thickness of the surfacing is more than 1 mm, in addition, the process has a very low productivity on the surface area deposited per unit time (about 20 ... 30 mm ² / s).

A known method of electric arc welding of cylindrical parts [A.S. No. 599935. M. Cl. ² B23K 9/04. The method of electric arc surfacing. Publ. in BI, 1978, No. 12], in which the deposited part rotates at an increased speed of 150 ... 300 mm / s, and the electrode wire is automatically fed along the tangent to the surface. Directly behind the arc burning zone, a forming roller is pressed against the part with little effort, rotating from friction against the part. Drops of metal formed at the end of the electrode during arc burning are dumped onto the roller, which are transferred to the surface of the part and are formed into a thin layer by the roller. The method provides increased productivity relative to analogs, a small zone of thermal influence on the part (about 0.3 mm) and a surfacing thickness satisfying production of 0.5 mm.

This method has the following disadvantages. The deposited rollers have an undercut (a sharp transition of the deposited roller to the surface of the part), which leads to the formation of a large number of pores and shells in the fusion zone of adjacent rollers.

Closest to the technical nature of the proposed method is a method [Pat. No. 2211123, IPC ⁷ V23K 9/04, 9/167. Method for high-speed argon-arc surfacing of cylindrical parts. Bull. No. 24, 2003], in which the surface of the rotating part is heated by an electric arc to a state close to melting, while an additive is brought into contact with the surface of the part, which is fed with constant axial force into the arc burning zone, rotating the additive around its axis, and the end additives pre-shape the cone with an angle at the apex equal to 150 ... 176 °, the additive is oriented with the longitudinal axis relative to the axis of rotation of the part at an angle of 75 ... 88 °, combining the generatrix of the latter with the generatrix of the additive cone, and heat up the end of the additive to p of the elastic state, and the additive is rotated with the condition that the vector of the peripheral velocity of the base of the cone coincides in magnitude and direction with the vector of the peripheral speed of the forming part, and the line of action of the vectors of the peripheral velocities of the additive and the part at the point of coincidence is combined with a plane perpendicular to the axis of the part and passing through the tungsten generatrix electrode from the side of the deposited layer.

The disadvantage of this method is that with a small thickness of surfacing, high speed and productivity, the combing remains high.

The aim of the invention is to increase the efficiency of the surfacing process by ensuring the optimal thickness of the surfacing, reducing the combing of the deposited layer while maintaining high productivity and high quality layer.

As in the prototype method, the surface of a part rotating at an increased speed is heated by an electric arc to a state close to melting, while an additive is brought into contact with the surface of the part, which is fed with constant axial force into the arc burning zone, rotating the additive around its axis, and the end face of the additive is preliminarily shaped into a cone with an apex angle of 150 ... 176 °, the additive is oriented with its longitudinal axis relative to the axis of rotation of the part at an angle of 75 ... 88 °, combining the generatrix of the latter with the generatrix of the additive cone, and heating the end of the additive to a plastic state, and the additive is rotated with the condition that the vector of the peripheral velocity of the base of the cone coincides in magnitude and direction with the vector of the peripheral speed of the forming part, and the line of action of the vectors of the peripheral velocities of the additive and the part at the point of coincidence is combined with a plane perpendicular to the axis of the part and passing through the generatrix of the tungsten electrode from the side of the deposited layer.

According to the invention, in the inventive welding method, the goal is achieved in that the wire is fed at a speed of 1.15 ... 1.25 times its melting speed, the electrode relative to the axis of rotation of the wire is deflected in a plane perpendicular to the axis of rotation, 24 ... 28 ° to the side , opposite to the rotation of the part, as well as 16 ... 18 ° in the direction of surfacing, simultaneously with the inclusion of the longitudinal feed increase the arc power.

Comparative analysis with the prototype shows that the inventive method of high-speed argon-arc surfacing of cylindrical parts is characterized by the presence of new features:

- the wire is fed at a speed of 1.15 ... 1.25 times the speed of its melting,

- the electrode relative to the axis of rotation of the wire is deflected in a plane perpendicular to the axis of rotation, 24 ... 28 ° in the direction opposite to the rotation of the part, as well as 16 ... 18 ° in the direction of surfacing;

- simultaneously with the inclusion of the longitudinal feed increase the power of the arc.

When analyzing the patent and technical literature, the applicant did not find another identical and equivalent to the claimed method of technical solution and, therefore, believes that the invention meets the eligibility criteria of "novelty." In addition, the set of essential features and the achieved result do not explicitly follow from the prior art, which allows us to conclude that the solution meets the criterion of "inventive step".

The inventive method of high-speed argon-arc surfacing of cylindrical parts is illustrated in figures 1, 2, 3, 4.

The first distinguishing feature of the invention is that the wire feed speed is greater than its melting speed. In the technical requirements for the manufacture and restoration of parts, allowable values of ovality, taper, deflection on worn parts are given, these data increase several times, and also, given the large linear speed of the process, an increase in the filing speed of the filler wire increases speed, therefore, the wire is constantly in contact with surface of the deposited part, which is one of the main conditions for the stable process of high-speed argon-arc surfacing (VAN). When the wire feed speed is less than its melting speed, the process does not go when they are equal - the process is unstable, the layer is obtained with gaps and spaces, which leads to large combing. The wire feed speed is 1.15 ... 1.25 times its melting speed, these limits are established experimentally. When the feed rate is less than 1.15 times, there is a deterioration in the quality of the deposited surface. At more than 1.25 times, the formation of the roller also deteriorates - its crestiness increases, and the longitudinal stability of the filler wire at the outset is violated and the process stability is impaired, and on the other hand, the service life of the channel for feeding the mouthpiece wire and the wire feeding device as a whole is reduced. At such a feed speed, the feed rollers of the device begin to heat up very much, since there is intense slipping of the rotating wire at the contact point with the surface of the rollers.

The second distinguishing feature of the method of surfacing a part is that the electrode relative to the axis of rotation of the wire deviates in a plane perpendicular to the axis of rotation, 24 ... 28 ° in the direction opposite to the rotation of the part, as well as 16 ... 18 ° in the direction of surfacing (figure 1) .

Using a standard torch for argon welding during surfacing, it was possible to obtain some qualitative and quantitative process parameters. We found that the deviation of the electrode in 2 ^x planes significantly affects the process. At the beginning, experiments were carried out and evaluated on the basis of the “better-worse” principle. When the angle γ is set equal to 45 ° or more, the surfacing process does not proceed, since the arc is pulled in the direction of rotation of the part and in this case it lights up between the electrode and filler wire, as a result of which the base of the part is not fused. When reducing the angle γ to 32 °, the surfacing process is unstable, since the use of a standard torch does not allow reducing the angle less than 32 °, therefore, three mouthpiece assemblies of the original design were designed (before working drawings) (Fig. 2), allowing changing the inclination angle γ by 4 ... 6 °, i.e. with an initial angle of respectively 1 ^st - 28 °, ^2nd - 24 ° and 3 ^rd - 18 °.

When the angle γ varies within 28 ... 32 °, the surfacing process is stable, the deposited layer is uniform, but at the beginning of the process a drop of metal of a significant size is formed (up to 6 ... 8 mm in diameter), and when the power source is disconnected, the deposited metal bursts and a crater forms based on the details. When the angle γ varies within 24 ... 28 °, the surfacing process is stable, the surface of the deposited samples is uniform. At an angle γ = 18 ... 24 ° or less, the surfacing process is unstable, an increased electrode consumption is observed. The arc burns with a distinctive crack. Fusion with the base of the part is complete, but the surface of the deposited layer is of high combing.

The zone of action of the arc on the surface of the part has the shape of an ellipse, the large axis of which coincides with the direction of surfacing. At high speeds for moving the source, the width (the small axis of the ellipse) decreases, which leads to instability of the process. An increase in the inclination angle β to the side of surfacing leads to an increase in the small axis of the ellipse, more efficient heating of the surface before surfacing, i.e. compliance with the conditions of the wire in the arc zone, more precisely, on the heating spot. The values of this angle β = 16 ... 18 ° (Fig. 1) were established experimentally, while taking into account the design features of the mouthpiece, its cooling, supply of argon, etc. Thus, this feature gives optimal conditions for the formation of the roller and ensures the uniformity of the latter in thickness.

The third distinguishing feature of surfacing is that simultaneously with the inclusion of the longitudinal feed, the arc power is increased, this feature allows you to withstand optimal thermal conditions during surfacing, because when filler wire is fed into the arc zone, heat is drawn into the wire, the surface temperature in the contact zone decreases, which leads to a violation of the temperature regime of surfacing.

When carrying out the welding process according to the proposed method, the weld bead is obtained of a small thickness, solid, well fused with the base and the previous bead. The microvolumes of the deposited metal crystallize immediately after leaving the arc zone due to heat removal to the body of the part.

The surfacing process proceeds practically without formation of splashes with the correctly selected deposition mode, since there are no conditions for the formation of splashes. The liquid metal of the additive covers the base of the cone of the additive with a very thin layer and holds well on the additive due to surface tension forces. The transition of the liquid metal additive to the part occurs only in the micro-bath, where the metal is constantly in the liquid state. Spray occurs only when the process is interrupted, for example, with a significant runout of the surface of the part and when the additive periodically breaks away from the surface of the part due to non-compliance with the wire feed speed and surfacing.

The possibility of obtaining a layer of small thickness with high quality of the layer and full alloying with the metal of the part is explained by the action of the whole complex of features of the claims.

The method of high-speed argon-arc surfacing of cylindrical parts is carried out using the installation (Fig.3 and 4).

Installation for implementing the method of argon-arc surfacing of cylindrical parts created and works (Fig.3 and 4). The schematic diagram of which is shown in Fig.3. The surfacing unit of the device is shown in Fig.4. The installation includes the following main mechanisms: serial screw-cutting lathe 1, which serves to rotate part 17 and provide longitudinal feed 12, with a hydraulic speed controller 2; on the support 18 of the lathe 1, a surfacing strut 5 is installed. On the surfacing strut 5, an electric motor 9 is fixed with a cassette 8 of filler wire 4, a wire feed mechanism 7, the device of which is described in the patent [Pat. No. 2266180 MPK ⁷ V23K 9/12 Device for supplying a rotating surfacing wire. Bull. No. 35, 2004], a mouthpiece 6 with a guide channel for supplying filler wire and a non-consumable tungsten electrode installed on it 19. In addition, the installation kit includes an arc power source 3, control panels 10, 11, a transformer for heating the filler wire 14, a cylinder with argon 15 and a water pump 16 for cooling the mouthpiece 6.

When welding a shaft of steel 45 with a diameter of 40 mm, the following settings are used (Fig. 1): tungsten electrode with a diameter of 4 mm (EVL (GOST 23969-80), filler wire Np-65G, 2 mm in diameter, arc current 500 A, angle α = 80 °, offset 5 mm, interelectrode gap a = 2 mm, gap between electrode and wire B = 2 mm, displacement from zenith C = 2 mm, wire feed speed 1.2 times its melting speed, electrode relative to the axis of rotation of the wire is deflected in the plane perpendicular to the axis of rotation by γ = 24 ° in the direction opposite to the rotation of the part, and t kzhe at β = 18 ° in the direction of welding.

Surfacing mode.

Part rotation frequency ω _d = 2.33 s ^-1 _, longitudinal feed 0.5 mm · rev, additive rotation frequency ω _pr = 46.7 s ^-1 , axial force F = 20 H, voltage U = 13 V, current J = 450 A, argon consumption 7 l / min, arc power source VDU-1201.

Part surfacing is performed in the following order.

The part is fixed to the centers of the lathe 1. The surfacing head (mouthpiece) 6 is fed to the neck of the part 17, and the mouthpiece 6 and the argon-arc torch are adjusted according to the settings given above. Before the start of the process, the end of the additive 4 is sharpened on a cone at an angle at the apex of 150 ... 176 °, and the additive is retracted from the part to a distance of 5 ... 6 mm.

The sequence of the process. The high-speed argon-arc surfacing is controlled by the operator using the remote control 10 and 11. The part 17 is turned on, argon is supplied to the mouthpiece 6, voltage is supplied to the electrode 17 and the part through current lead 13, and the arc between the tungsten electrode 19 and part 17 is ignited. the electrode relative to the axis of rotation of the wire is deflected in the plane perpendicular to the axis of rotation by γ = 24 ... 28 ° in the direction opposite to the rotation of the part, and also by β = 16 ... 18 ° in the direction of surfacing. The arc is ignited using an oscillating voltage [Pat. No. 39850, IPC ⁷ V23K 9/12, 9/167. A device for exciting a direct current electric arc during welding and surfacing in shielding gases. Bull.№23, 2004] or by short circuiting with a carbon rod of the interelectrode gap. The surface of the part is heated by an arc for 4 ... 6 s (more accurately set according to the developed calculation program "Calculation of temperature fields in a cylinder under the action of surface heat sources, Heat 4.0", Registration certificate No. 9776). Turns on the rotation of the additive and its supply. In this case, the wire feed speed is 1.15 ... 1.25 times the rate of its melting. When the additive is in contact with the component, the additive is pressed with constant force, and after heating the end of the additive, metal is extruded into the base of the cone and an initial roll is formed on the part. The feed of the machine support is turned on with a welding head fixed to the support with a simultaneous increase in the arc power, and the neck is fused to its entire length. The surfacing process is completed by the common stop button (turns off: arc voltage, argon supply, machine drive, rotation drive and wire feed).

The specified deposition mode gives complete fusion of the layer with the base with a layer thickness of 0.35 mm; a surfacing time of a neck length of 25 mm is approximately 24 s. If the additive is heated at the exit from an additional power source with a current of J ₁ = 180 A at U ₁ = 4 B, then the thickness of the deposit increases to 0.5 mm. By changing the values of U ₁ and J ₁ , intermediate values of the thickness of the surfacing can be obtained.

The proposed method of surfacing gives the minimum roughness of the deposited layer, which allows you to assign an allowance for subsequent processing (grinding) in the range of 0.1 ... 0.12 mm per side. When restoring parts with low wear, the proposed method of surfacing saves filler metal 30-40% compared with the method adopted for the prototype.

The proposed method of surfacing can be used in mechanical engineering, for example, in the manufacture of shafts, when the surface of the necks of the shafts requires imparting special properties (high wear resistance, chemical resistance, etc.). Moreover, the proposed method of surfacing is more cost-effective compared to the known methods of surfacing or spraying metal even when using expensive filler materials, since the proposed method of surfacing gives small thicknesses of surfacing with a relatively high productivity of the process.

Claims (1)

A method of high-speed argon-arc surfacing of cylindrical parts, in which the surface of the rotating part is heated by an electric arc to a state close to melting, while an additive is brought into contact with the surface of the part, which is fed with constant axial force into the arc burning zone, rotating the additive around its axis , the end face of the additive is pre-shaped as a cone with an angle at the apex of 150 ... 176 °, the additive is oriented with the longitudinal axis relative to the axis of rotation of the part at an angle of 75 ... 88 °, combining the generatrix of the latter with the sample of the additive cone, and the end of the additive is heated to a plastic state, while the additive is rotated with the condition that the circumferential velocity vector of the cone base coincides in magnitude and direction with the peripheral velocity vector of the forming part, and the line of action of the additive peripheral velocity vectors and the part at the point of their coincidence is combined with a plane perpendicular to the axis of the part and passing through the generatrix of the tungsten electrode from the side of the deposited layer, characterized in that the additive is fed at a speed of 1.15 ... 1.25 times greater higher than its melting rate, the tungsten electrode relative to the axis of rotation of the additive is deflected in the plane perpendicular to the axis of rotation, by 24 ... 28 ° in the direction opposite to the rotation of the part, as well as by 16 ... 18 ° in the direction of surfacing, and at the same time turning on the longitudinal feed, they increase the power arcs.

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