SU1700073A1 - Method of electroslag melting of bulk materials - Google Patents

Abstract

The invention relates to special electrometallurgy and is intended for electroslag remelting of chips, metal dust, sludge and other non-compact detours. The aim of the invention is to reduce heat loss and improve remelting performance. The method consists in that non-compact materials load at a rate of 1.05-1.5 their melting speed, and the temperature W; the pack in the upper volumes of the slag bath is maintained at 1750-1800 ° C. The method allows to reduce heat loss from 15% to zero Gu to increase productivity by 30%. 2 tab. with

Description

The invention relates to special electrometallurgy and is intended for electroslag remelting of chips, metal dust, sludge and other non-compact materials.

The rational use and return to the production of the products, both at the stage of metallurgical processing and at the subsequent processing of various types of waste metals and alloys, represents an important national economic task. The disposal of chips, metal dust, sludge from heat-resistant nickel alloys, which are formed in large quantities in aircraft manufacturing enterprises, is in a special position.

The existing methods for remelting chips in arc and open induction furnaces do not provide the required quality of the metal in terms of the content of impurities entering the metal from the lining of furnaces and electrodes resulting from the interaction of the metal with the atmosphere. Moreover, with such methods of remelting, the alloy dangers are high (from 10 to 20%).

The disposal of waste from expensive nickel-resistant alloys can be successfully solved on the basis of the electroslag process. Electroslag remelting of non-compact waste heat-resistant alloys can be carried out according to various schemes.

Conventionally, the methods of electroslag remelting of non-compact wastes can be divided into three types: the manufacture and remelting of a consumable electrode in a slag layer (provides for the formation of ingot in a cooled copper mold,

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due to the melting of the tubular electrode rolled up by the metal charge); remelting of waste fed by screw devices, where the waste column enclosed in a pipe is also an electrode; remelting with heating of the slag bath with non-consumable electrodes and the gradual loading of chips.

The method of heating the slag bath with non-consumable electrodes is more promising and can be implemented in industry.

With the development of non-consumable metal electrodes, it became possible to implement this technology for high-temperature alloys. Earlier, when conducting the electroslag process with graphite electrodes, this could not be done due to the danger of carbonization of the metal.

However, the methods of electroslag remelting of non-compact waste have disadvantages. The option of remelting a pressed consumable electrode is not rational, since the operation of pressing chips and other waste heat-resistant alloys is extremely time-consuming and complex.

The difficulties of remelting waste with a screw pusher consist in the supply of chips, especially twisted, auger pushers and the transfer of large currents through a column of chips.

Remelting with non-consumable electrodes is devoid of the listed disadvantages and has several advantages. The basis of its advantages lies in the possibility of separate control of the power supplied to the slag bath and the waste loading rate, which allows a wide range to vary the temperature, the quantity and composition of the slag, and also to regulate the energy parameters of the process and heat exchange parameters.

The disadvantages of this method include high heat loss by radiation from the surface of the slag bath (up to 20%) and the possibility of the non-smelted charge in the metal bath to fall into the metal bath.

The aim of the invention is to reduce heat loss and increase the productivity of the propeal mixture.

This goal is achieved by the fact that non-compact materials are loaded at a rate of 1.0-1.5 their melting speed, and the slag temperature in the upper volumes of the slag bath is maintained at 1750-1800 ° C.

The essence of the method is as follows.

When charging the metal charge on top of the slag, the slag on its particles is frozen in the slag and they are in the upper layers of the slag.

baths. As the slag that fills the slag is heated and melted, the metal particles sink deeper and deeper into the slag bath, where, as well,

melted down. If the charge loading rate is maintained above the melting rate, then a layer of metal charge is formed on the surface of the slag bath. Thus the mirror of the slag bath will be closed and there will be no heat loss by radiation. If, moreover, the heat generation in the slag bath is shifted to the upper volumes, then the productivity of the fusion increases. Melting chips or other

5, the charge will occur over the entire area of the slag bath, as is the case with the traditional ESR consumable electrode, increasing the fill factor of the mold.

The metal charge will melt in the upper layers of the slag bath and the metal droplets will pass through the slag. At the same time, the number of drop cages increases dramatically, which, on the one hand, reduces

5 overheating of the metal, on the other hand, provides a shallow flat metal bath, which prevents the non-smelting charge from entering the liquid metal and good removal of impurity1; metal bath.

0 The proposed method is simple and easy to implement in industry. The feed rate of the charge can be controlled by the dimensions of the gate on the bunker with a charge or amplitude and vibration frequency of the vibrating plate, and the displacement of the heat release zone into the upper volumes of the slag bath is due to the increase in voltage on the electrodes and their operation in the upper layers of slag.

Dependence of process indicators on

0 download speed charge listed in the table. one.

As can be seen from the table. 1, with a loading rate equal to the melting rate (i.e., 1.0), a decrease in heat loss is observed. The productivity of the propell is increasing at the same time. It is not expedient to increase the loading speed of more than 1.5 propellon speeds, since there is no heat loss and no increase in propellant productivity.

0 Moreover, it is possible under the action of the weight of the charge mixture poured onto the slag to squeeze the slag up to the top of the mold and to break or stop the electroslag process.5 The dependence of the process indicators on the slag bath temperature in the upper volumes is given in Table. 2

Presented in table. 2 data shows that with increasing temperature and productivity increases, however

at temperatures above 1800 ° C, an abundant emission of smoke and fluoride begins, the content of which exceeds the maximum permissible limits. This is due to the decomposition of components — components of the slag — at such temperatures. For remelting, mainly CaF2 - CaO - system slags are used, which ensure the stability of the electroslag process, high heat generation in the slag and process efficiency, as well as purity of the remelted mixture and refining from metal impurities.

When using the proposed method, heat loss by radiation from the surface of the slag bath is reduced, remelting performance is increased, the unmelted mixture is prevented from entering the metal bath, the number of melting points and the formation of metal drops is increased, the metal overheating in the drop is reduced, a flat shallow metal bath is provided for floating inclusions.

The distinctive features of the proposed method in comparison with the known ones are the following: due to the loading rate higher than the rate of smelting of the charge on the surface of the slag bath, it maintains a layer of the charge; the heat release zone is shifted to the upper volumes of the slag bath.

Example. The method was tested on crystallizers of 100.170 and 270 mm, and also on installation 90-105 in a crystallizer with a diameter of 400 mm.

The weight of the weld ingots of chips, dust and slag is 450-500 kg

Experiments have shown that when the charge loading rate is higher than its melting rate, the heat loss by radiation decreases from 15% to zero, and the remelting capacity increases by 30% (from 180 to 250 kg / h).

The power supplied to the slag bath is constant (on the order of 250 kW), the voltage rises to 60 V, and the voltage drops from 5000 to 4000 A. At the same time, cooled metal electrodes instead of 100 mm are buried in the slag by 40 mm. The slag temperature in the upper layers (about 50 mm, with a total slag bath depth of 150 mm) is almost 100 ° C higher and is 1800 ° C.

The electroslag process is stable and stable. The charge is scattered on the surface of the slag bath almost evenly. At certain moments during remelting of chips, small arc discharges from the electrodes to the chips occur. However, this disadvantage is eliminated by electrically insulating the electrode above the level of the slag bath. One of the most effective ways is to protect the electrode with a slag skull.

Claims (1)

Invention Formula The method of electroslag remelting of non-compact materials, predominantly metal dust and sludge, including their gradual loading and melting in a shpak heated with non-consumable metal cooled electrodes, characterized in that, in order to reduce heat loss and improve the performance of the melting, non-compact slag materials in the upper volumes of the slag bath support 1750-1800 ° C. Note. Vmt. - the rate of melting of the charge. Table 1 table 2