RU2231725C2 - A cool smelting hearth - Google Patents

Abstract

FIELD: metallurgy; smelting equipment.

SUBSTANCE: the invention is dealt with the melting equipment, namely with design members of the plasma-arc and cathode-ray furnaces with a cool hearth and may be used for production of ingots and slabs of high-reaction metals of commercial purity. The technical result is creation of a large-size technologically effective cool smelting hearth with an increased duration of its service life. The cool smelting hearth consists of devices in series mounted on a frame including a melting and a refining crucibles, a crystallizer and overflow thresholds. The crystallizer is rigidly fixed on the frame and all devices are connected to each other by elastic external relations links. The design of the hearth at its thermal expansion ensures a shift of crucibles and the overflow thresholds on a longitudinal axis of the frame relative to the rigidly fixed on the frame crystallizer, so preventing excessive thermal strains.

EFFECT: the invention allows to create a large-size technologically effective cool smelting hearth cool smelting hearth with an increased duration of its service life.

2 cl, 2 dwg, 1 ex

Description

The invention relates to smelting equipment, in particular to structural elements of plasma-arc and electron-beam furnaces with a cold hearth, and may find application for the production of ingots and slabs of highly reactive metals of commercial purity.

The melting process in plasma and electron-beam furnaces is characterized by heating the cold hearth, the effect of thermal loading on the structure for a fixed time and subsequent cooling. During the considered time, a change in temperature fields occurs in the hearth structure, which leads to a cyclic change in the stress-strain state. The duration of one cycle is several hours. With an increase in the number of loading cycles, plastic deformations increase up to the formation of cracks.

A known method of electron beam remelting of titanium sponge and installation for its implementation (RF patent No. 94037492, publ. 07.20.97), containing electronic guns with deflecting systems, consumable container, an intermediate container and a mold.

The disadvantages of the installation are:

- large-sized units made of monolithic billets require complex structural solutions to compensate for their significant thermal expansions;

- irrational layout, requiring accurate installation of nodes with minimal gaps and constant monitoring of them in the process;

- the complexity of organizing rational metal flows in the direction and height of the overflow.

A known design of a cold hearth melting crucible in an electronic melting furnace patented in the USA in 1965 by Temescal Metallurgical Corp. (M.Ya. Smelyansky. Electronic furnaces. - M .: Energy, 1971, p. 34) - prototype.

The disadvantage of this design is the difficulty in manufacturing a cold, monolithic hearth of large size consisting of several crucibles located at different levels. The dimensions of the hearth are limited by the maximum dimensions of the blank of the copper plate, as with existing technological processes, the production of a copper ingot with a mass of more than 10 tons becomes economically unjustified. With this limitation, and also taking into account machining allowances, the possible maximum working area of the hearth does not exceed 4 m ² .

In addition, the design works under conditions of cyclic heating at large temperature gradients, leading to uneven thermal expansion of its elements. Emerging temperature stresses become one of the main factors that reduce the resistance of the cold hearth, and a prerequisite for creating an emergency.

The problem to which this invention is directed, is the creation of a large-sized, technologically advanced in the manufacture of a cold hearth melting furnace with an extended service life.

The technical result of the invention is:

- creation of a cold hearth of the furnace from successively assembled structures, the dimensions of each of which allow their manufacture on standard equipment;

- development of the design of the cold hearth, in which the temperature stresses arising during the work of the hearth do not exceed the yield strength of the material at operating temperatures;

- manufacturability of the hearth design, its high durability, ease of installation, operation and repair.

The technical result is achieved by the fact that in the cold hearth of the melting furnace, consisting of devices sequentially mounted on the frame comprising melting and refining crucibles, a mold and overflow thresholds, only the mold is rigidly fixed to the frame, and all devices are connected in series by elastic external connections.

Cold under can be equipped with several refining crucibles, sequentially interconnected by elastic external bonds. This greatly expands its functionality.

The invention is illustrated by drawings, figure 1 shows a cold under, side view; figure 2 is a top view.

The sub contains a melting crucible 1, refining crucibles 2 and 3, dividing thresholds 4, 5 and 6, a mold 7, rigidly fixed to the frame 8 with bolts 9. On the upper flange of the mold 7, a rocker 10 is fixed to which, using pins 11 and elastic elements 12 thresholds, refining and melting crucibles are connected, which, in turn, are freely supported on frame 8 by means of mounting gaskets 13. Refining crucibles are shifted relative to the central axis in order to better mix the metal, and in order to save copper and maintain symmetry stainless steel frames 14 and 15.

Melting and refining crucibles are trough-like copper water-cooled plates. Overflow thresholds, with the aim of creating a stream of overflowing metal and cleaning it from heavy inclusions, are made of different heights.

The charge is melted in a melting crucible. As the crucible is filled, the liquid metal through the overflow threshold enters the refining crucibles, and then into the mold, where it is formed into an ingot. Melting and maintaining the temperature in the furnace are carried out using independent heating devices.

The melting and refining crucibles are arranged so that the channel of the liquid metal gives a serpentine path in plan and a different depth throughout depending on the requirements of the technology.

As the metal fills, a skull forms on the surface of the hearth. The crucibles warm up, their linear sizes increase. The hearth design during its thermal expansion provides the displacement of crucibles and overflow thresholds along the longitudinal axis of the frame relative to the mold rigidly fixed on the frame. The elastic elements fastening the hearth devices limit these displacements in such a way as to prevent stresses in the hearth structure material from exceeding the yield strength on the one hand and to prevent gaps at the joints on the other.

Example. A water-cooled, cold underneath was made for the RETECH plasma furnace used for smelting titanium alloys.

Overall dimensions of the cold hearth: length - 4800 mm, width - 1700 mm. Weight - 8760 kg. The hearth bath is made of M1 brand copper. The design includes a melting and two refining crucibles, three overflow thresholds and a crystallizer, which are connected in series by elastic bonds. The mold is rigidly fixed to the frame. After 5 experimental swimming trunks, violations of the hearth design were not observed. The rated resistance of the hearth is 1000 heats.

The proposed prefabricated design of the cold hearth allows the manufacture of its components on standard equipment, reduce heat loads, increase durability and maintainability.

Claims (2)

1. Cold under the melting furnace, consisting of devices sequentially installed on the frame comprising melting and refining crucibles, a mold and overflow thresholds, characterized in that only the mold is rigidly fixed to the frame, and all devices are connected in series with elastic external connections. 2. Cold under the melting furnace according to claim 1, characterized in that it contains two refining crucibles interconnected by elastic external bonds.

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