US3777044A - Plasma-arc furnace - Google Patents

Abstract

A plasma-arc furnace for remelting of sheet-waste material of high reactivity metals and their alloys has a furnace chamber containing a mould, plasmatrons mounted on a roof of the chamber, and a charging device for feeding sheet-waste material into a melting zone. The charging device has a hopper arranged to contain the sheet-waste material, a water-cooled base plate, guide troughs along which the sheet-waste material is fed, and controlling means to control the feed of the sheet-waste into the melting zone. The furnace expediently employs a stripping and conveying gear to deliver remelted sheet-waste material in any desired form such as a bar or a slab.

Description

United States Patent [191 Nautny et a].

[ PLASMA-ARC FURNACE [76] Inventors: Konstantin Troiimovich Nautny,

ultisa Krasitskogo, 17, kv. 2; Viktor Iosifovich Lakomsky, ulitsa Bastionnaya, 10, kv. 30; Anatoly Ivanovich Chvertko, bulvar Lasi Ukrainki, 2, kv. 36, all of Kiev; Anatoly Vasilievich Zherdev, ulitsa Zhdanova, 3-a; Alexandr Petrovich Voropaev, ulitsa Gorkogo, 49, kv. 71, both of Kommunarsk Voroshilovgradskoi oblasti; Viktor Romanovich Pillipchuk, ulitsa Mashinostroitelnaya, 12, kv. 4, Kiev; Semen Yakovlevich Shekhter, ulitsa Brestkaya, l5, kv. 18, Kommunarsk Voroshilovgradskoi oblasti; Alexandr Mikhailovich Reznitsky, ulitsa Kirova, 2, kv. 18, Kommunarsk Voroshilovgradskoi oblasti; Leonid Nikolaevich Tsipura, ulitsa Gagarina, 23, kv. 24, Kommunarsk Voroshilovgradskoi oblasti; Oleg Semenovich Zabarilo, ulitsa Chapaeva, 2/10, kv. 3, Kiev, all of USSR.

[22] Filed: Oct. 1, 1971 [21] Appl. No.1 186,267

Oct. 1, 1970 [52] US. Cl 13/33, 13/9, 214/23 [5l] Int. Cl H051) 7/00, F27d 3/00 [58] Field of Search 13/]. 9, 33, 31;

Primary ExaminerRoy N. Envall, .l r. AttorneyHolman & Stern [5 7 ABSTRACT A plasma-arc furnace for remelting of sheet-waste material of high reactivity metals and their alloys has a furnace chamber containing a mould, plasmatrons mounted on a roof of the chamber, and a charging device for feeding sheet-waste material into a melting zone. The charging device has a hopper arranged to contain the sheet-waste material, a water-cooled base plate, guide troughs along which the sheet-waste material is fed, and controlling means to control the feed of the sheet-waste into the melting zone. The furnace expediently employs a stripping and conveying gear to deliver remelted sheet-waste material in any desired from such as a bar or slab.

4 Claims, 5 Drawing Figures SHEET 2 BF 4 PATENTED DEC 4 I975 PLASMA-ARC FURNACE BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to electrometallurgy and more particularly to devices for plasma-arc remelting of wastes produced in sheet rolling high-reactivity metals (titanium, zirconium, etc.) and their alloys.

2. Description of Prior Art Widely known are plasma-arc furnaces for the remelting of a consumable blank, comprising a chamber with a blank feed gear, fitted with plasmatrons, and a mould butting against said chamber.

The use of these furnaces for the production of slabs (ingots) of high-reactivity metals and their alloys from their wastes necessitates for the manufacture of a consumable electrode a double remelting process since single melting does not ensure the requisite quality of blank surface.

Consumable electrodes for plasma-arc furnaces can be manufactured either from sheet wastes of highreactivity metals and alloys or from a major charge component (sponge) to which said wastes are added.

For producing the electrodes from the sheet wastes diversified methods can be utilized, such as for exam ple, pressing, welding, joining sheet wastes together by means of special fittings, etc.

In order to convey the electrodes manufactured using the wastes by the aforesaid procedures into the remelting zone, use is made of furnaces having feed gears, providing with both vertical movement and rotation (oscillation).

However, peculiar to the furnaces equipped with such gears is a sophisticated construction. As for the manufacture of electrodes from rolled sheet wastes, it necessitates intricate production equipment. All this is labour-consuming, and is associated with large expediture and low production rate; in some cases, particularly in producing heavy ingots, the above technique is not suitable at all for the fabrication of electrodes. It restricts potential uses of sheet wastes for manufacturing ingots of the requisite dimensions and cross-section.

SUMMARY OF THE INVENTION It is an object of the present invention to increase the efficiency of a waste-remelting furnace by charging it with rolled sheet wastes cut in specified lengths. Another object of this invention is to reduce both the process labour input and expenditure on preparation of consumable electrodes for remelting. Still another object of the invention is to simplify the furnace construction and to ensure the melting in this furnace of the ingots of the requisite size and weight.

According to the specified and other objects in a plasma-arc furnace for remelting sheet-wastes of highreactivity metals incorporating a chamber with a charging device and plasmatrons mounted in its roof, and a mould butting against the lower part of said chamber, conforming to the invention, the charging device has an air-tight hopper arranged in the upper part of the chamber together with a sheet-waste container, a water-cooled base-plate with guide troughs set up between the container and the mould and a gear located under the container and intended for feeding sheetwastes along the troughs of the said baseplate into the remelting zone which will permit reducing. time and labour requirements for the remelting of sheet trimmings.

The'sheet-waste feed gear has a mobile carriage including pushers and said container hinged thereto and further comprising several compartments slotted in their lower portion to let said pushers pass. Provided in the lower portion of the container front wall are ports with slides-uncovering to pass sheet-wastes. With the above construction the remelting of sheet-wastes can be accomplished without packing them into electrodes thus simplifying substantially the production process.

The furnace can be equipped with at least two identical charging devices set up around the mould which enables sheet-wastes to be fed into the remelting zone in several flows at one and the same time.

All the gears and assemblies of the charging device are mounted in the furnace in succession ensuring a continuous technological process of feeding the wastes, cut in specified lengths, into the remelting zone with the ensuing production at the end of this process of ingots having the requisite weight.

BRIEF DESCRIPTION OF THE DRAWINGS Described below is an exemplary embodiment of the invention to be considered with reference to the accompanying drawings, in which:

FIG. 1 is a fragmentary longitudinal sectional view of a plasma-arc furnace, conforming to the invention;

FIG. 2 shows a general view (with a fragmentary cutaway) of a furnace container of the plasma-arc furnace of FIG. 1;

FIG. 3 section II-II of FIG. 1;

FIG. 4 section III-III of FIG. 1;

FIG. 5 section IV--IV of FIG. 2.

A plasma-arc furnace has a welded flat box-type chamber 1 (FIG. 1) which serves for erecting main asse'mblies. The chamber 1 has in its medium portion a through opening (not shown in the drawing) above which a collapsable roof (not shown in the drawing) is placed. The roof is made in the form of a rectangular box enclosed in a water jacket extending throughout its surface. The upper portion of the roof is fitted with holes through which pass plasmatrons 2 arranged so that they are free to move vertically and radially. The furnace roof is hinged to chamber 1. Fastened on the opposite side of the hinged portion of the roof are two rollers through which passes a rope associated with a roof lifting gear. Under the roof secured to the base of chamber 1 is a casing constituting a mould 3. The casing of mould 3 is a welded rectangular construction open at the top. At its bottom there are: a rectangular opening to receive an ingot, a dummy bar of an ingot withdrawing device (not shown in the drawing) and six circular holes through which run pipes for cooling the mould 3'. The entire surface of the casing of mould 3 is enclosed in the a water jacket and the upper part of the casing is fitted with a flange (not shown in the drawing) intended for bolting the casing of mould 3 to the furnace chamber 1; Mould 3 is mounted on internal projecting parts of the flange being separated from it by means of insulating straps. Located below the casing of mould 3 along its perimeter are special grippers (not shown inthe drawing) through which it is coupled to the ingot withdrawing device. Mould 3 is of a composite copper-steel construction with water cooling. Water is supplied and discharged via six copper pipes passing through the holes in the bottom of the casing of mould 3.

Chamber 1 is equipped with two charging devices (not shown in the drawing) located symmetrically relative to mould 3.

Each charging device comprises a hopper 4 which serves for accommodating container 5.

Each of the two hoppers 4 is made in the form of a hollow box flanged at the top and underneath and open at both ends. The lower flange of each hopper 4 is secured at the top of chamber 1 under a hole for container S by means of a hermetic connection, while the upper flange carries swivelling cover 6 hinged to it. Lateral faces of both hoppers 4 have flanges in their upper portions whose purpose is to couple piping of a gas circulating and recovery system. In addition oneof the hoppers 4 is fitted with a safety valve which connects the furnace interior with atmosphere and cuts off all feed sources if pressure within the furnace builds up.

The container serves for accommodating wastes 7 and loading them into the furnace for remelting. Container 5 comprises housing 8 (FIG. 2) subdivided into several compartments 9 in which is placed sheet-waste 7 cut in specified lengths and piled to be remelted. The bottom of each compartment 9 has longitudinal through slots 10 located centrally. The lower portion of the front wall of container 5 is fitted with ports through which the sheet-waste 7 to be remelted pass into the remelting zone. Guides 11 cater for positioning container 5 in chambr l of the furnace.

Two eyebolts 12 are employed for handling container 5 with the aid of hoisting gears (not shown in the drawing), the eye bolts being secured'to an upper partition of container 5 from above.

Disposed between container 5 and mould 3 is watercooled base-plate 13.

Base-plate 13 is of welded construction is made up of copper sheets; it is intended to direct sheet-waste 7 to be remelted ontheir way from container 5 to the melting zone. Its upper portion is provided with guide troughs 14 whose number depends on the number of compartments 9 of container 5. The base plate is fastened to chamber 1 in a horizontal position.

Located under container 5 in the furnace chamber 1 is gear 15 for pushing sheet-wastes 7 one after another from container 5 and feeding them along guide troughs 14 into the melting zone.

Sheet-waste feed gear 15 comprises a carriage 16 whose upper portion is fitted with a nut 17 which has a through hole extending over its length and intended for a drive screw 18; four rollers 19 with shaped grooves, are secured in bearing assemblies on either side along carriage 16 on shafts 20 (FIG. 3) and are coupled thereto by means of a rigid joint; two guide rods 21 are fastened on brackets 22 (FIG. 4) of chamber l with the internal sides of the rods having doublesided bevels extending along their length and receiving the shaped grooves of rollers 19', pushers 23 are provided whose height is adjusted by replaceable carns attached in the front portion of carriage 16 on pivots 24 the pushers being free to rotate on the pivots (the rear part of the pushers is chamfered); springs 25 (two per each pusher) are provided forcing pushers 23 against resets 26 (one end of springs 25 is inserted into the apertures in pushers 23 and their other end in the openings in screw 27 driven into carriage 16); a drive screw 18 is driven in nut 17 with the screw front end fastened in a bearing block mounted in stand 28 connected by means of a rigid joint to the bottom of chamber 1 with the other end secured in a bearing block arranged in cover 29 which is attached to the rear wall of chamber 1. Screw 18 projects through vacuum seal 30 and its tail carries a rigidly fitted gear wheel 31 through which feeding gear 15 is coupled to drive 32.

Drive 32 serves for imparting to the pushers 23, a translatory motion with a requisite speed in the direction of base-plate l3 and returns the pushers with a high speed into an initial extreme rear position. Drive 32 is attahced to the exterior of chamber 1 above sheetwaste feeding gear 15. v

Fastened by bolts 33, to the front wall of container 5 near the waste outlet (FIG. 5) is a slide 34 shifted verticallyby means of a special bolt 35.

The purpose of slide 34 is to restrict the amount of sheet-waste material supplied from container 5 and delivered by pushers 23 into the remelting zone.

The number of pushers 23 in sheet-waste feeding gear 15, and the number of compartments 9 in container 5 and troughs 14in base-plate 13 are accordingly equal. The spacings between the axes of symmetry of these elements are also equal.

The furnace is fitted with a discharge gear (not shown in the drawing) intended for withdrawing an ingot from mould 3 and conveying it to a storage. The discharge gear is made up of: an ingot withdrawing gear, power feeders, a frame and a car (not shown in the drawing).

The furnace feeders can be made in the form of brushes mounted on the ingot withdrawing gear.

The discharge gear frame is arranged on a car. It can be made in the form of a truncated cone, made from angles with flat sides from above and underneath having rectangular holes through which the ingot withdrawing gear passes. The car moves on a rail track and has mounted thereon all the assemblies of the discharge gear, a hydraulic cabinet and a pumping plant. The car is also intended for conveying the melted ingot to the storage.

Incorporated in the furnace is also a gear (not shown in the drawing) for roof lifting for cleaning and for inspecting base-plate 13 and mould 3.

For cooling the furnace assemblies, arranged to cool the high temperature zone is provided a cooling system which consists of a hydraulic unit, a pumping plant, elements for distributing water among the units to be cooled, a reservoir and water flow and temperature controls. The furnace components to be cooled are subdivided into two groups: those cooled by conventional water flow and those cooled by comparitively soft water which does not produce scale. Soft water is used for cooling mould 3, the dummy bar (not shown in the drawing) and plasmatrons 2. Flow relays are set up at the conduit outlet of all these component cooling assemblies. In addition, each conduit is controlled by a temperature relay. The furnace is equipped with a hydraulic system whose purpose is to tighten and to secure the ingot withdrawing gear to the casing of mould 3 prior to melting as well as to displace the ingot discharge gear (not shown in the drawing) to the discharge and return to'its initial position under mould 3.

For feeding plasmatrons 2 the furnace has a gas recovery and circulation system.

The. furnace operates in the following manner.

In the initial position container 5 (FIG. 1) accommodating piled wastes to be remelted is placed in hopper 4. Its lower part passes through the opening in chamber 1. Container 5 rests on stand 36 welded to the walls of chamber 1.

The upper edge of the bottom of container 5 on which sheet-wastes 7 to be remelted are lying rises slightly above the bottom of troughs 14 of base-plate 13. Pushers 23 with carriage 16 are set up in the extreme rear position and are drawn out of slots (FIG. 2) provided in the bottom of compartments 9 of container 5. As pushers 23 advance forward their height provides for gripping and ejecting from container 5 the requisite amount of sheet-waste 7 to be remelted.

Slide 34 (FIG. 5) is arranged at a level ensuring free passage of material 7 (to be remelted), pulled by pushers 23 from container 5, through the ports in the front wall of container 5.

In the initial position the axes of symmetry of pushers 23, compartments 9 and troughs 14 of base-plate 13 are made to coincide.

When in the initial position the dummy bar (not shown in the drawing) is inserted into the interior of mould 3 up to its upper chamfered region.

The furnace roof (not shown in the drawing) is lowered. Next the gas recovery and circulation system is turned on. The requisite pressure is maintained in the chamber 1 of the furnace. Supply sources are coupled to the ingot withdrawing gear. Then the water cooling system is cut in and all plasmatrons 2 of the furnace are actuated alternately to accomplish the remelting process. The unit is started by bringing a glowing torch near to the metal charge in mould 3 whereupon the system operates for returning plasmatrons 2 into initial operating position.

For feeding the sheet-waste to be remelted into the remelting zone, drive 32 whose shaft is automatically reversed after the requisite number of revolutions, imparts a reciprocating motion to pushers 23 fastened on carriage 16 (FIGS. 3 and 4) of sheet waste feeding gear via gear train 31, drive screw 18 and nut 17. The rate at which pushers 23 move forward (operating speed) can be adjusted within a wide range, with that of the reverse motion (operating speed) being constant and maximum.

As pushers 23 move forward from their extreme rear position, they enter through slots 10 provided in the bottom of compartments 9 of container 5 (with the direction of movement of the pushers coinciding with that of slots 10 in compartments 9), approach the lower strips of the material 7 to be melted, and striking against their butt ends eject them through the ports in the front wall of container 5 into troughs 14 in baseplate 13 and then into the remelting zone.

Molten material from the blanks being fused flows into mould 3 and the ingot being performed is drawn out by the withdrawing gear. The number of the waste strips pushed out of container 5 is controlled by slide 34. When the lower strips are pushed out, the upper ones descend by gravity to take their place and pushers 23 coming out of the limits of container 5 reach their extreme front position.

As pushers 23 (FIG. 3) move from the extreme front into rear position their chamfers run into wastes 7 lying in container 5, revolve about pivots 24 in an opposite direction relative to the movement of carriage 16, expanding springs 25, which force them against rests 26 and ensuring thereby slippage of pushers 23 with regard to wastes 7 being remelted. On coming out of contact with the sheet-waste, pushers 23 return into their initial position under the action of springs 25 and lean against rests 26. The cycle described above is reiterated.

The plasma-arc furnace, proposed herewith, allows remelting sheet-wastes of high-reactivity metals and alloys to produce from them directly slabs of any desired section and a high quality, thereby providing for a reduction in time and labour requirements when rolling slabs into sheets, the invention also ensures an increase in the yield of rolled products and reduces the cost of rolled sheets.

What is claimed is:

l. A plasma-arc furnace for the remelting of sheetwaste material of high-reactivity metals and their alloys, comprising: a chamber for remelting the said sheet-waste material, said chamber having a roof and a melting zone; plasmatrons mounted on the roof of the said chamber; a mould means disposed in a lower part of the said chamber and designed for forming an ingot out of molten sheet-waste material; at least one charging device enclosed in the said chamber and including: an air-tight hopper having a container to accommodate said sheet-waste material arranged in an upper portion of the said chamber, a water-cooled base-plate having guide troughs mounted between the said container and the mould, and means for feeding said sheet-waste material along the guide troughs of the said base-plate into said melting zone, said means for feeding being located in said chamber substantially under said container.

2. A plasma-arc furnace as claimed in Claim 1, in which said means for feeding includes a carriage having pusher means for pushing the sheet-waste material.

3. A plasma-arc furnace as claimed in claim 2, in which the said container has a front wall, and compartments whose lower part is provided with longitudinal through slots formed to let pass said pushers and wherein in a lower part of the front wall of said container there are ports with slides uncovering to let said sheet-waste pass through.

4. A plasma-arc furnace of as claimed in Claim 1 in which at least two identical charging devices located around said mould are provided.

Claims (4)

1. A plasma-arc furnace for the remelting of sheet-waste material of high-reactivity metals and their alloys, comprising: a chamber for remelting the said sheet-waste material, said chamber having a roof and a melting zone; plasmatrons mounted on the roof of the said chamber; a mould means disposed in a lower part of the said chamber and designed for forming an ingot out of molten sheet-waste material; at least one charging device enclosed in the said chamber and including: an air-tight hopper having a container to accommodate said Sheet-waste material arranged in an upper portion of the said chamber, a water-cooled base-plate having guide troughs mounted between the said container and the mould, and means for feeding said sheet-waste material along the guide troughs of the said base-plate into said melting zone, said means for feeding being located in said chamber substantially under said container.

2. A plasma-arc furnace as claimed in Claim 1, in which said means for feeding includes a carriage having pusher means for pushing the sheet-waste material.

3. A plasma-arc furnace as claimed in claim 2, in which the said container has a front wall, and compartments whose lower part is provided with longitudinal through slots formed to let pass said pushers and wherein in a lower part of the front wall of said container there are ports with slides uncovering to let said sheet-waste pass through.

4. A plasma-arc furnace of as claimed in Claim 1 in which at least two identical charging devices located around said mould are provided.

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