SU841871A1 - Non-meltable electrode for arc processes - Google Patents

Description

(54) NON-MOLDING ELECTRODE FOR ARC PROCESSES

  , I

The invention relates to the field of electric arc processing and can be applied in plasma cutting, welding, surfacing of metals, their smelting in metallurgy.

Structures of a non-consumable electrode, predominantly a cathode made in the form of a rod (active insert) - cylindrical, fixed, for example, by soldering or pressing, in a copper water-cooled holder and designed for operation in various plasma-forming media 1 are known.

A common drawback of the known structures is the low resistance of the electrode at high heat loads to it, due to the fact that the heat removal from the working surface of the electrode and its cooling, mostly water, occurs only along a cylinder with a diameter j almost equal to the diameter of the active insert.

The electrode structure is also known with a cylindrical active insert, in which the water-cooled surface of the holder is filled with parabolic and equidistant with cooling pipe 2.

The disadvantage of this design is the need to increase the length of the active insert J, which. in its ocheoeed worsens heat from it.

A non-consumable electrode for arc processes is known, comprising a holder with a cooling phase tube located therein, and an active insert mounted on the topne of the holder, made into a truncated cone tapering to the working end of the electrode and having a cooling side

deepening s1.

 This design, although it increases the temperature resistance of the electrode, c. compared to the above is not optimal, especially with increasing thermal loads and in connection with overheating

3

the working surface of the active insert and its resulting burnout.

The purpose of the invention is to increase the life of the electrode by increasing its heat resistance during operation at higher thermal loads.

This goal is achieved by the fact that the electrode is provided with a housing and a tube placed inside it, mounted coaxially to the sleeve and forming annular cavities for additional cooling inserts, and the recess is made in the form of a spherical segment.

FIG. shows the proposed electrode, a general view; Fig. 2 shows the configuration of the active insert of a non-consumable electrode, made with deepening and with side cooling.

The non-consumable electrode (fig.) Consists of a water-cooled case 1 and a holder 2 fixed in it (there is no conical nozzle, etc.) on the thread, made of heat and electrically conductive metal, as a rule, high-frequency copper. The electrode also contains coaxial non-communicating internal cavities 3 and 4, which serve to supply coolant to the working section. In OBDAYDAY 2, insert 5 is tightly fastened by pressing or soldering, made in the form of a truncated cone tapering to the anchorage area of the arc on it. The insert surface 6 facing the cooling cavity is made with a recess, advantageously in the form of a spherical segment. Box 5 may be end-to-end, i.e. not ,.

contact with the cooling electrode and non-through liquid directly, and separate from this liquid by a layer 7 of heat-conducting material of the holder. The cavities 8 and 9 in the electrode are designed to remove the coolant after the heat from the working section of the electrode.

The present invention is based on the results of calculations on the computer-222 temperature fields in the cathode and experimental data obtained on

Ukrulnenno-laboratory installation of the Institute Gipronickel. These results show that at arc currents above 500 A, the heat sink from the active

An insert, made in the form of a truncated -cone into the holder, is not 14

sufficient: the insert overheats, burns out to a large extent and the electrode operation becomes impossible. An insert with a deepening according to the invention has a significantly lower thermal resistance, due to which its temperature, all other things being equal, is 50 ° C lower than that of an insert without a depth. Physically, this is due to the fact that in the presence of burial, the distance from the working surface of the insert is reduced, which perceives virtually the entire heat flux from

arc, to the cooling cathode fluid or a layer of heat-conducting metal between the insert and this fluid. The heat flux from the arc, initially directed along the axis of the cathode, is reflected from the side surfaces of the cone, and a significant part of it, regulated by the depth, is radially directed toward the periphery of the sleeve.

In this case, additional lateral cooling of the cathode, effective along with the central one due to the presence of two cooling cavities, becomes effective, while reducing the temperature of the water-cooled surface of the active insert or of the cage layer by another 30–60, and the heat flux removed through the central part

surfaces, by 15 - 25%.

The active insert is made of graphite C-1, pressed into a water-cooled copper ferrule. The dimensions of the conical inserts are the same with the angle

at the apex, about lying between 45-60 °, except for the fact that in the insert in Fig. 2, a depth is made in the form of a spherical segment with height I and a base diameter d.

,

The table shows the temperatures at various points of the active inserts of both types being compared, obtained using a non-melting electrode as the cathode of a DC arc burning at 1000 A in a mixture of natural and carbon dioxide gases, and a heat transfer coefficient to cooling water of 210 W / m . hail. Characteristic points are selected as follows: t.A. in the center of the working surface of the active insert, on which the near electrode electrode area is attached; TB - on the border of the working surface of the active insert with a copper winding; t, C - on the axis of the active insert at a distance H from its base, corresponding to the height of the spherical segment; T.O. - based on

The data obtained in the table is for a cathode with active inserts, the base diameters of which are 210 m and

-4-1b

4.5 10 m with height of SZW m and height H

ball segment for insertion

B

.fig. 2, equal to 1,540 m.

Similar dependences are preserved. And for cathodes having different dimensions to the materials of the inserts.

An analysis of the data in the table shows that, in the case of a known cathode, the temperature on the working surface of the active insert exceeds the melting temperature of graphite, which eliminates the possibility of its operation in the most favorable mode for the indicated plasma-forming mixture and leads to its burnout.

The operation of the proposed electrode is as follows.

After supplying the cooling electrode of the water through the central and lateral cavities, and through the central one with an intensity 2.3 times greater than through the side cavities, and supplying the arc-forming plasma-forming gas, the arc is ignited.

Due to the presence of deepening on the cooled side of the tapered active insert and the lateral (together with the central) cooling, the electrode works without burnout and without exceeding the preactive insert by. the distance from the axis corresponding to the radius of the base of the spherical segment; i.e., on the border of the base of the active insert with a copper clip.

5 effective heat loads and temperatures for the insert material.

Claims (3)

1.Esibn E.M. Plasma arc equipment. Publishing House of Technology, Kiev,, 1571, p.80-82. 2. USSR Author's Certificate No. 420222, cl. B 23 K 35/02, 1975. 3. Austria patent number 271653, cl. 21 K 38/01, 1969. i Water (pui.f