RU2520881C1 - Non-consumable electrode for arc welding - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: this non-consumable electrode consists of cylindrical body and working section. Radial slot is made at α<90° to the axis terminating at electrode end surface in diametral plane of working section in generatrix.

EFFECT: higher efficiency of welding, ruled out arc burns, better seam formation.

1 tbl, 6 dwg

Description

The invention relates to welding equipment, namely, to designs of non-consumable electrodes for arc welding and high-temperature processing of materials and can be used in mechanical engineering.

A non-consumable electrode for arc processes is known (AS No. 5889102 MKI B23K 35/02, published January 25, 1978), in which the apex of the conical working part is displaced relative to the axis of the electrode, and the axis of the conical part can be parallel or cross the axis of the cylindrical parts, resulting in a displacement of the vector of the force of the arc in the direction of deviation or displacement of the axis of the cone. When the axis of the conical part of the working section deviates in the direction of the welding speed vector, compensation is made for the natural lag of the arc discharge at high speeds and an improvement in weld formation.

However, this design provides arc burning only with a compressed (contracted) cathode spot, which leads to a high concentration of arc pressure on the axis of the weld, which negatively affects its formation. Since the pressure value is proportional to the square of the arc current, this does not allow to achieve high-quality formation of welds when welding at high speeds and high values of the welding current. This is especially evident when performing welded joints of thick-walled metal structures.

In addition, for the implementation of this sharpening requires a special mechanism that provides rotational and oscillatory motion of the electrode. The presence of cone sharpening does not allow long-term use of the electrode at high currents due to the rapid destruction of the working section.

Also known is an electrode in a torch for arc welding (AS No. 663512 MKI B23K 9/16 published on 05/25/1979), consisting of a nozzle with a side current supply and an electrode, the tip of which is formed by two planes located at different sharp angles to the axis of the electrode, moreover, on the side of the side current supply there is a plane inclined to the axis of the electrode at a smaller angle.

The advantage of this design is that when the current supply is located in the opposite direction to the welding direction, due to the magnetic field generated by the welding current flowing through it, the arc deflects in the welding direction, and the cathode spot of the deflected welding arc stabilizes on a plane located at an angle α to the axis of the electrode. This makes it possible to improve the formation of welds when welding with a non-consumable electrode at higher speeds in the environment of shielding gases. However, this design also excludes the possibility of operating in modes with a diffuse (diffuse) cathode spot at high currents, which leads to disruption of the formation of welds. In addition, the use of a one-sided side current supply worsens the heat sink from the non-consumable electrode and interferes with the laminar flow of the protective gas. The effect of deflection of the arc discharge in this design is associated with the position of the contact of the return cable, which is a technological limitation in use and reduces the welding performance.

Closest to the invention in technical essence is a non-consumable electrode for arc processes (patent No. 88308 MKP B23K 35/02 published 10.11.2009), consisting of a cylindrical body and a working section, along the axis of which one or more longitudinal slots are made, the working section has the form a cylinder with a diameter equal to or less than the diameter of the body, and the depth of the slot is not less than the diameter of the working section. Due to the uniform heating of the working section by Joule heat, the forces of the electromagnetic field and cooling of the outer layer by means of radiation, a diffuse (diffuse) cathode spot of the arc is formed, which is shifted to the internal surfaces of the slot. This mode of combustion allows to increase the productivity of welding, as well as reduce the likelihood of burnout during welding and improve the formation of the weld. However, when welding at high speeds, the arc deviates from the axis of the electrode in the direction opposite to the direction of welding, which leads to defects in the formation of the weld and reduces welding performance.

The objective of the invention is to expand the range of operating currents and welding speeds of non-consumable electrode in the direction of large values.

The technical result of the present invention is to increase the welding productivity by increasing the maximum allowable current and speed, as well as reducing the likelihood of burn-through and improving the formation of the weld by reducing pressure and increasing the spatial stability of the arc.

This is achieved by the fact that in a non-consumable electrode for arc welding, consisting of a cylindrical body and a working section, a radial groove is made along the generatrix in the diametrical plane of the working section at an angle α <90 ° to the axis, facing the end surface of the electrode.

A distinctive feature of the device is the presence of a radial groove formed along the generatrix at an angle α <90 ° to the axis that extends to the end surface of the electrode. The flow of the welding current through such a working section ensures the formation of an asymmetric magnetic field around it. The presence of a low magnetic field in the groove region leads to the formation of the cathode spot of the arc on the electrode planes, formed by a radial groove. This, in turn, deflects the axis of the arc in the direction of the groove, which is used to compensate for the natural deviation (lag) of the arc at high values of the speed of its movement.

Along with this, the presence of a radial groove does not violate the constancy of the cross-sectional area of the working section of the electrode along its length and makes it possible to enter welding modes when the Joule heat release at the exit of the working section plays a significant part in the thermal balance of the electrode. This contributes to the transition to the regime of arc burning with a diffuse (diffuse) cathode spot, which ensures high-quality weld formation during welding at high speeds of both thin-sheet metals and thick-walled structures.

Figure 1 presents a General view of a non-consumable electrode, Figure 2 is a General view of the electrode with a groove made at an angle α <90 ° to the axis of the electrode, and Figures 3, 4, 5, 6 show possible cross-sectional variations of electrodes with different shape of the groove.

Non-consumable electrode for arc welding is a monolithic body 1 (figure 1) made of tungsten or other refractory material. In the working section 2, a radial groove 3 is made. Possible forms of the radial groove 3 are presented in FIGS. 2, 3, 4, 5, 6. The use of the radial groove 3 on the working section 2 of the electrode when an electric current flows causes a change in the nature of the magnetic field created by it . As a result, an asymmetric magnetic field is formed, the intensity of which is minimal in the groove cavity. Thus, the arc discharge, shifting to a region with a low magnetic field strength, burns with a deviation from the axis of the electrode. This deviation is caused by a specific shape of the magnetic field due to the design of the working section of the non-consumable electrode and does not depend on the position of the current lead to the product.

When welding at certain currents shown in the table, due to uniform heating of the working section by Joule heat, electromagnetic field forces and cooling of the outer layer by means of radiation, a diffuse cathode spot of the arc is formed, which is shifted to the internal surfaces formed by the groove. This mode, due to the peculiarities of the heat balance, is achieved with a groove depth of at least half the electrode radius. At lower depths, the stability of the cathode spot binding is violated, which causes an uneven heating of the internal faces and a transition to an arc with a cathode spot moving along the working section of the electrode.

When welding at low current values, it is difficult to ensure the mode of combustion of an arc with a diffuse cathode spot, which is explained by a high temperature gradient along the length of the working section of the electrode and the predominant localization of the active spot of the arc on the outer edges of the electrode formed by the groove.

Table Ranges of permissible currents for the proposed electrode The diameter of the working section of the electrode, mm Groove thickness mm Groove length mm Range of working currents, A 2 0.4 ÷ 0.6 2.0 ÷ 4.2 50 ÷ 230 3 0.7 ÷ 0.9 3.0 ÷ 5.2 90 ÷ 400 four 1,0 ÷ 1,2 4.0 ÷ 8.2 210 ÷ 600 5 1.3 ÷ 1.5 5.0 ÷ 10.2 250 ÷ 750 6 1.6 ÷ 1.8 6.0 ÷ 12.2 300 ÷ 900

Orientation of the electrode so that the discharge axis deviates in the welding direction (groove edges are oriented in the direction of the welding vector) provides effective compensation for the natural arc deviation from the electrode axis (lag) when welding at high speeds. Arc burning with a dispersed cathode spot leads to a decrease in the force of the arc at the front of the weld pool and a decrease in the thickness of the liquid metal layer, which ensures high-quality formation of welds at high values of the welding current. For better stabilization of the cathode spot on the edges of the radial groove 3, the latter can be made at an angle α <90 ° to the axis of the electrode (figure 2). In order to increase or decrease the value of the transition current to the burning of an arc with a diffuse cathode spot, the radial groove 3 can be made in the form of a wedge (Figs. 4, 6). A radial groove 3 in the form of a reverse wedge (Fig.6) forms a sharper edge at the end of the working section 2, which contributes to an increase in the stability of the cathode spot binding on it at low current strengths.

Thus, the proposed design allows the axis of the arc discharge to be deflected in the right direction, thereby controlling the thermo-force effect of the arc on the weld pool, and the burning of an arc with a diffuse cathode spot allows welding to be performed at high values of the welding current without disturbing the formation of the weld. In practice, the design of the electrode provides arc burning with a diffuse cathode spot and high-quality formation of welds in the current range from 50 to 900 A at welding speeds of more than 20 m / h. All this helps to increase the productivity of welding with a non-consumable electrode in inert gases by 1.5-2.0 times.

Claims (1)

Non-consumable electrode for arc welding, consisting of a cylindrical body and a working section, characterized in that in the diametrical plane of the working section a radial groove is made along the generatrix at an angle α <90º to the axis of the electrode with access to its end surface.

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