SU1371827A1 - Apparatus for thermit cutting of metal parts - Google Patents

Abstract

The invention relates to the field of metal arc processing and is used for thermal cutting of metal parts. The device provides improved cutting accuracy by fixing the heating point. The device contains two main contact electrodes, covering the part, and a third additional one. The part is cut between the main electrodes by heating the main rectifier connected to the primary windings of the four-rod transformer with current. The multiphase voltage on the latter is created by controlled valves (keys) connected to a three-phase rectifier input connected to the AC mains. The valves of the main rectifier, connected to the secondary windings of the transformer, operate with three valves each and provide the current flowing through the main electrodes necessary to melt the part. An additional high voltage rectifier with a current limited by a resistor through the third electrode provides initial heating in the cross section of the cut, thereby improving cutting accuracy. 2 Il. 1C (L

Description

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The invention relates to co-tact cutting and can be used in flexible, automated production for cutting metal pipes, rods, and other shaped steel.

The aim of the invention is to improve the accuracy.

FIG. 1 shows a circuit diagram of the device; in fig. 2 - diagrams of instantaneous values of voltages and currents, explaining the operation of the device.

The device contains two detachable electrodes 1 and 1 with a drive 2, which provides a clamp of the part being cut 3. Parts of the detachable electrodes are connected by cable 4. The input rectifier 5 is connected to an AC network. Key management 6 is carried out by a control system 7 generating a four-phase voltage. The output of each control key 6 is connected to one of the branches of the primary winding 8 of the transformer 9. The secondary windings 10 are connected in a star, to the neutral of which is connected the first plug electrode 1. The second rectifier is made on the gates 11, the cathodes of which are combined and connected to the second plug electrode 1. The third rectifier is made on the valves. 1ЫХ 12, the anodes of which are combined and connected to a resistor 13, which is connected to the third electrode 14, installed in an insulated holder, which has a common drive with a moving part second detachable electrode G.

The control system 7 comprises a master oscillator, a pulse distributor, amplifiers, pulse shapers and isolating pulse transformers, the output windings of which are connected to the control circuits of the valves 6.

FIG. Figure 2 shows diagrams of instantaneous values: the current in four controlled keys 6 (diagram 15-18), for example - on the secondary winding 10 of the first phase A (diagram 19), the voltage at the output of the second rectifier at the cathodes of the valves 11 (diagram 20); voltages at the output of the third rectifier at the anodes of the valves 12 (diagram 21); current in the valve 11 of the first phase A (diagram 22), the current in the valve 12 of the first phase A (diagram 23).

The device works as follows.

The input rectifier 5 provides a positive voltage on the anodes of the keys 6. When actuator 2 triggers, detachable electrodes 1 and G compress the cut part 3. The third electrode 14 is pressed with the help of drive 2 to the cut part 3 at the point where the cut is to be made. The alternate operation of the keys 6, controlled from the control system 7, provides a positive half-wave voltage on the windings 10 in the interval equal to 3/4 of the current pulse repetition period in the valves. Each switch 6 operates 1/4 of a period and at the same time ensures the operation of three valves 11, allows increasing the load, receives power from its winding 10. High

and a uniform loading of the valves 11 makes it possible to obtain a current in the part 3 being cut between the electrodes 1 and G, which is necessary to melt the metal of the part 3.

When key 6 is in operation, the current passes through three sections located on the three rods of the transformer 9 magnetic core, and the magnetic fluxes in these rods have the same positive increments. The magnetic fluxes of these three rods are summed in the winding 10 of the fourth rod.

5 creates a negative voltage on the second rectifier Ud (diagram 20) and the voltage on the third rectifier Udz (diagram 21). The voltage from the third rectifier through the resistor 13 is supplied to the electrode 14. The resistor 13 limits

0 the amount of current through the electrode 14. The working interval of the valves 11 is equal to 3/4 of the period (chart 22). The working interval of the valves 12 is equal to 1/4 of the period (figure 23). The working currents of the valves 12 are many times less,

5 than the operating currents of the valves 11. Due to the higher voltage on the third rectifier, which feeds the third electrode 14, the output power increases the temperature of the part 3 at the point of contact of the electrode 14. Local temperature increase

0 causes a local increase in resistance, which in turn causes a change in current density across the section of part 3. An increase in current density causes an increase in power output in this area, which causes the part 3 to melt in the section where the point of contact of the electrode 14 is located.

When the metal of the part 3 melts throughout the cross section, the current through the valves 11 of the second rectifier decreases, and after the interval specified by the control system 7, control pulses on the keys 6 cease to flow.

The device allows the use of a high valve switching frequency. Frequency is large enough to

5 reduce the size of the transformer 9. The frequency is limited at the level of 400-500 Hz by the frequency properties of the valves 11 and the conditions for matching the linear dimensions of the power valves 11 and the transformer coils 9. The presence of the input rectifier

0 ensures a uniform load of the phases of the supplying AC network and a high power factor (not less than 0.9). The operation of a power transformer with an asymmetrical voltage form allows two output voltages to be obtained, which

5 differ in value by three times. A lower voltage allows you to obtain the necessary currents for cutting the part. A higher voltage allows you to create an initial heating in the section of the part where it is necessary to cut. The use of initial heating of the part improves the cutting accuracy. The cutting accuracy is 1-2 mm with a cutting width of 5-8 mm.

Claims (1)

Invention Formula A device for thermal cutting of metal parts containing two detachable electrodes arranged along the length of the parts being cut, consisting of moving and stationary parts installed with a gap within which the cutting is performed, the first straightener connected to the AC network, four controllable keys with a key management system, a transformer having primary and secondary windings, a second rectifier, characterized in that, in order to improve cutting accuracy, a third rectifier, a resistor and rety electron the transformer is four-rod, with the positive pole of the first rectifier connected to the anodes of controlled keys, each cathode of which is connected to the negative pole of the first rectifier through primary winding branches made of three sections connected in series and located on three transformer magnetic cores alternately in each branch, with a secondary winding placed on each magnetic core, the first terminals of the secondary windings are combined and connected to the first connector mnomu electrode and the second terminals of each secondary winding 5 are connected to the anodes of the second valve and the cathodes of the third rectifier valves, the cathodes of the second rectifier valves are connected and connected to the second detachable electrode, and the anodes of the third rectifier valves are connected and connected 0 through a resistor to the third electrode, attached to the moving part of one of the pa; vi. Emery electrodes, and electrically isolated from it. / 7/2 IJ2 FIG. / five p p p p p p g A (J2S 23 ggpp p n Fi .. 2