GB2217637A

GB2217637A - Apparatus for removing slag from the surface of molten metal in pig-casting moulds

Info

Publication number: GB2217637A
Application number: GB8906439A
Authority: GB
Inventors: Heinz Brand; Wilfried Hampe; Rudolf Schima; Rudolf Prussak; Bernd Schliessen
Original assignee: Mansfeld Kombinat Wilhelm Pieck VEB
Current assignee: Mansfeld Kombinat Wilhelm Pieck VEB
Priority date: 1988-03-21
Filing date: 1989-03-21
Publication date: 1989-11-01
Also published as: FR2628663A1; SE8900983D0; DE3905127A1; GB8906439D0; DD275990A3; SE8900983L; PL278369A1

Description

An apparatus for removing slag from the surface of molten metals The invention relates to an apparatus for removing slag from the surface of molten metals in the moulds in pig-casting belts.

Pigs or ingots of various metals are often cast on so-called pig-casting belts. With such processes, it becomes necessary to remove the layer of slag which forms on the molten metal in the individual moulds in the pig-casting belt before the metal solidifies.

Apparatuses have become known which use scraper elements for removing such layers of slag from the surface of the metal.

For example, SU-PS 455 804 describes an arrangement in which spatula-like scraper blades of the width of a mould and set at right-angles to the direction of movement of a pig-casting belt are propelled by a chain transmission at an acute angle to the surface of the liquid metal in a box-like frame which is situated above the pig-casting belt, the blades scraping off the layer of slag, the quantity of slag which is present on the scraper blades being dumped into a container fixed on the frame as. they run back over the reversal point on the frame. The box-like frame is fixed on guide elements disposed on both sides of the pig-casting belt and parallel with its direction of movement. They make it possible for the box-like frame, sliding on them, to be carried a short distance over the moving pigcasting belt.

This solution does not permit of careful slag removal and encourages losses of metal due to splashing. Use on high speed pig-casting belts or variable-speed installations is impossible since the necessary synchronism of the slag removing apparatus with the pig-casting belt cannot be adequately established during the removal of the slag from a mould. In addition, the problem of carrying away the quantity of slag which has collected in the aforesaid container remains unsolved.

Another apparatus is disclosed in DD-PS 211 728, in which a movable scraper blade is drawn over the entire surface of the liquid metal until, at the end of the mould, it closes with a fixed scraper blade, the slag being picked up and lifted off between them. This lifting off is brought about by a system of articulated arms and operating cylinders. Driven by operating cylinders, the system runs axially parallel with the pig-casting belt until the slag removal from a mould is completed and, after the slag has been ejected, it returns to the starting point, in other words back to the next mould from which the slag is to be re-moved.Synchronism of movement between the scraper apparatus and the relevant mould is interrupted by complicated and spatially controlled movement phases during which there is entrainment and splashing of metal due to highly accelerated movement processes, because the scrapers leave the work site from time to time. Furthermore, the apparatus is of complicated construction and is therefore susceptible to breakdown; the time phase for removing the slag from a mould is relatively long since only one scraper blade per mould is drawn over the entire length of the surface of the molten metal.

An object of the invention is a careful but very rapid scraping of the slag from molten metals which are contained in moulds in pig-casting belts which operate at high and variable speeds in continuous casting operations.

The invention is based on the problem of providing an apparatus for removing the slag from the surface of molten metals in the moulds of pig-casting belts which during continuous casting at high and variable speeds guarantees synchronism between the particular mould from which the slag is to be removed and the scraper elements for the period of slag removal; with the scraping process requiring minimal time, the apparatus is not readily susceptibel to breakdown; entrainment or splashing of molten metal is avoided; setting of the scraper elements in the solidified metal during breakdowns in the plant cannot occur, while simple and expedient removal of the slag taken from the moulds is assured.

According to the invention, the problem was resolved in that a double-cheeked frame formed as an irregular polygon with more than four sides is disposed above and parallel with a pigcasting belt. The distance between the two cheeks of the frame amounts to at least the width of the moulds in the pig-casting belt. The sides of the polygonally formed cheeks of the frame are hereinafter also referred to as the working portions of the polygon.

The frame carries a chain conveyor, the sprockets of which are fixed at the corners of the frame cheeks, referred to as polygon points. Disposed on the chains of the chain conveyor, and equidistant between the chains, are a number of swivel joints on which freely suspended scraper modules are mounted by means of hinge pins and fixing elements.

The chain conveyor is driven by the pig-casting belt drive.

Therefore, it always runs in synchronism with the pig-casting belt. One side or one working portion of the polygon has the same pitch angle as the pig-casting belt. At.the same time, the chain conveyor is disposed at such a height above the pigcasting belt with its moulds that the scraper modules, which rotate in a polygonal pattern, carrying their scraper blades are in this working portion slightly immersed in the molten metal in the moulds so that in other words they pierce the layer of slag which is on the molten metal. The working portion which follows this working portion which extends at the same pitch angle as that of the pig-casting belt has a 13 to 15 steeper pitch angle than the previous one. Consequently, the scraper modules are gently and gradually lifted off the surfaces of the metal in the moulds.On the front vertical side of the polygonal frame which is in the direction of conyeyance of the pig-casting belt there is a horizontal fixed hingeing point at which the frame is pivotally mounted. On the likewise vertical side of the polygon opposite the frame side with the fixed hingeing point there is a joint on which the piston rod of a lifting element is articulated. By means of this lifting joint, the entire frame can if necessary be tipped upwards about the fixed hingeing point. In this respect, the lifting travel of the lifting element is always greater than the depth of immersion of the scraper blades of the scraper modules into the slag and the molten metal in the moulds.

The part of the polygon where are disposed the sprockets of the chain conveyor on the frame constitutes a clear space in which, at right-angles to the pig-casting belt, there is an endless slag conveyor which is constructed as a pig belt and around which the scraper modules travel, the working portion of the polygon extending horizontally above the slag conveyor.

At regular intervals on the chains of the chain conveyor, in each case opposite one another, there are fixed swivel joints from which scraper modules are freely suspended by means of hinge pins through fixing elements and in each case between two oppositely disposed rotating elements. By the force of gravity, therefore, these scraper modules are always vertically suspended regardless of the different pitch angles of the polygon of the chain conveyor.

In the housings of the slag removing modules, horizontally beside one another and in each case extending as far as the centre of the housing, there are working in opposite directions two working cylinders and, in the extension of the longitudinal axes, guide columns which serve to mount sliding members which are connected to the piston rods of the working cylinders.

Fixed on the sliding members are inwardly angled over-supports which project downwardly beyond the housing, and on the angledover parts of which there are scraper blades which, in the grouped-together condition, in other words when the process of scraping each mould on the pig-casting belt is completed, form a wedge-shaped space to receive the quantity of scraped-off slag. The width of the scraper blades corresponds to the width of the moulds. Also accommodated in the scraper modules are, in each case, a controllable group of multi-way valves, a signal transmission system for control commands, operating on a noncontacting and wireless basis, and an energy transmitting module for compressed air and an inbuilt electrical supply voltage.

The supply of working energy for the working cylinders is effected via a rotatable compressed air distributor disposed on the frame, substantially in the centre of rotation of the slag removing modules. At specific positions on the frame tehre are command transmitters for the contactless transmission of signals for controlling the multi-way valves in the scraper modules.

A feature of the invention, therefore, is the polygonal rotation of the scraper modules in working portions of clearly defined pitch, such as the working portion of the slag removal process, in which the pitch of the chain conveyor corresponds to the pitch of the pig-casting belt; the working portion concerned with lifting the scraper modules has a slightly steeper pitch than the pig-casting belt, the working portion concerned with the lifting work, in which the change of direction of rotation of the chain conveyor is initiated, the working portion concerned with ejection of the slag onto the slag conveyor, during which the movement of the chain conveyor is horizontal, and the working portion concerned with lowering to the working level and immersion of the scraper blades into the molten metal in the moulds in synchronism with the pig-casting belt.

By means of the the invention, it is possible carefully and rapidly to scrape the slag from molten metals which are contained in moulds of upwardly travelling pigcasting belts, even under conditions of continuous casting and at high and variable pig-casting belt speeds. For the period required to scrape the slag from the metal surface, the apparatus guarantees exact synchronism between the scraper elements and the mould from which the slag is to be removed. Entrainment or splashing of molten metal is substantially avoided. Setting of the scraper elements in the solidifying metal during breakdowns of the casting plant cannot occur. The quantities of slag scraped from the moulds can be carried away easily and yet in a very expedient manner. The apparatus works in a trouble-free fashion. Its design is relatively uncomplicated and it is simple to produce.

It is intended to explain the invention in greater detail hereinafter with reference to an example of embodiment shown in the accompanying drawings, in which: Fig. 1 is a diagrammatic side view of the apparatus; Fig. 2 is a view of a scraper module; Fig. 3 is a plan view of a scraper module; Fig. 4 is a section taken on the line A-A in Fig. 1; Fig. 5 is a view of the working range of the scraper modules in the polygon; Fig. 6 is a longitudinal section through the apparatus without the double-cheeked frame.

A double-cheeked frame 6 is shaped like an irregular polygon and in the present example it has nine sides, its cheeks being disposed parallel with and situated above a pig-casting belt 1.

The distance between the cheeks of the frame 6 is somewhat greater than the width of the moulds 2 in the pig-casting belt 1.

The individual sides of the cheeks which are shaped like a polygon are also referred to hereinafter as working portions.

The frame 6 carries a chain conveyor 8, the sprockets 7 of which are fixed at the corners of the cheeks of the frame 6, also designated polygon points.

Equidistantly between the chains 20 of the chain conveyor 8 there are seven scraper modules 10 which are freely suspended via swivel joints 21, hinge pins 9 and fixing elements 23.

The chain conveyor 8 is driven by the same drive 5 as the pig casting belt 1, in other words it always runs in synchronism with the speed of that belt. One working portion of the polygon has the same pitch angle as the pig-casting belt and in the present example this is 70.

In this working portion which has the same pitch angles of pigcasting belt 1 and chain conveyor 8, the vertical distance of the chain conveyor 8 above the pig-casting belt 1 is so dimensioned that the scraper modules 10 which are rotating in a polygonal fashion in this case have their scraper blades 11 dipping slightly into the molten metal 3 in the moulds 2. The working portion which follows this one has a pitch angle of 200, so that the scraper modules 10 are gradually lifted from the surfaces of the metals in the moulds 2. The polygonal section of the chain conveyor 8 forms a free space 15 in which, disposed at a right-angle to the pig-casting belt 1, there is an endless slag conveyor 14 around which the scraper modules 10 travel. It is constructed as a pig belt.As soon as one scraper module 10 with the quantity of slag disposed between its closed scraper blades 11 is disposed on the horizontal part of the polygonal section, above the slag conveyor 14, the scraper blades 11 are drawn apart and the slag 4 falls into a mould 26 in the slag conveyor 14. Attuning the speed of the slag conveyor 14 with that of the chain conveyor 8 makes it possible for the quantities of slag from several moulds 2 in the pig-casting belt 1 to fall into one mould 26 in the slag conveyor 14, where it sinters together and can subsequently be easily conveyed to further use.

Equidistantly and in each case opposite one another, there are on the two chains 20 of the chain conveyor 8 swivel joints 21 on which through fixing elements 23 and by means of hinge pins 9, scraper modules 10 are disposed between the oppositely positioned swivel joints 21.

By reason of their being freely suspended and due to the action of gravity the (in the present example) seven scraper modules 10 align themselves automatically so that regardless of the different pitch angles of the chain run 25, their scraper blades 11 are parallel with the surface of the molten metal 3 in the @@@@@@@ 2 in the pig-casting belt 1. The diagrammatic side view in Fig 1 and in particular Fig. 5 clearly show this process.

In the housings of the slag removing modules 10 and extending each case as far as the middle of the housing, there are, work ing in opposite directions, two working cylinders 12 and iiir.

extension of the longitudinal axes of the working cylindersel2F, guide columns 28 which occupy the other half of the housing,.

Therefore, there is always one working cylinder 12 and one-gpi-Xde column 28 disposed horizontally and opposite each other. Seated on the guide columns 28 are displaceable sliding members 133 which are connected to the piston rods of the working cylinders 12. Each sliding member 13 carries, projecting downwardly beyond the housing. an inwardly angled-over support 29. Mounted on the angled-over parts are scraper blades 11. So long asth scraper blades 11 have been moved towards one another by the working cylinders 12, they form a wedge-shaped space to accomar > ,.^ date the slag 4 scraped from the surface of the mould 2 (Fig.12) The width of the scraper blades 11 corresponds to the width ot the moulds 2 of the pig-casting belt 1.In the moved-apart con- dition (upper scraper module 10 in Fig. 4), the distance between the scraper blades 11 is equal to the length of the moulds 2.

In order to be able to counteract setting of the scraper blade 11 in the solidified metal 3 during breakdowns in the casting operations, there is a joint 17 on that part of the polygonal frame 6 which is opposite the fixed hingeing point 19. Articu lated on it is the piston rod of a lifting element 16. In the event of a breakdown, if the pig-casting belt 1 and thus also the chain conveyor 8 with the scraper modules 10 mounted on it become immobilised, then the lifting element 6 which is -constructed as a working cylinder 12 is acted upon and tips the frame 6 with the chain conveyor 9 and the scraper modules 10 on it upwardly about the fixed hingeing point 19, so lifting the scraper blades 11 out of the slag 4 or molten metal 3 (see the broken-lined part of the frame 6 in Fig. 1).The amount of lift 18 of the lifting element 16 corresponds at least to the depth of immersion of the scraper blades 11. into the slag 4 and the molten metal 3.

The supply of the compressed air used as the operating energy for the working cylinder 12 is effected via a rotatably constructed compressed air distributor 24 mounted on the outside of the frame 6, substantially in the centre of the rotation of the scraper modules 10 (see Fig. 4). This rotatable compressed air distributor 24 feeds the compressed air through compressed air supply lines 22 to the scraper modules 10 and thus to the multiway valves 30 of the working cylinders 12. At the same time, the multi-way valves 30 are disposed in groups and are constructed so that they can be controlled. In each of the scraper modules 10 there is, apart from the controllable group of multi-way valves 30, a signal transmission system for control commands, operating on a wireless and non-contacting basis, and also an energy transmitting module for compressed air and built-in electrical supply.Mounted on the frame 6 are command transmitters 27 by means of which the multi-way valves 30 are operated via the wireless and non-contacting signal transmission system, so that opening and closing of the scraper blades 11 of the scraper modules 10 occur in specific positions of the polygonal rotation of the chain conveyor 8.

The mode of operation of the apparatus will be explained in principle once again hereinafter.

By reason of the adjustable-speed drive 5 of the pig-casting belt 1, the chain conveyor 8 guided via sprockets 7 in the double-cheeked frame 6 is moved at a speed which is in synchronism with that of the pig-casting belt 1 and the seven slag removing modules 10 suspended from the swivel joints 9 are transported into their relevant working positions. Over the third mould 2 after casting, the scraper blades 11, while in the open state, dip into the layer of slag and slightly into the molten metal 3 and, at a signal from one of the command transmitters 27, are pushed by the pneumatic working cylinders 12 into the midway position, the slag 4 collecting in the wedgeshaped space between the closed scraper blades 11.

After the pitch portion of 70 which runs in synchronism with the pig-casting belt 1, the chain conveyor 8, in the following pitch portion, which is at 200 to the horizontal, is deflected somewhat upwardly in the frame 6, so that the closed scraper blades 11 are lifted out of the molten metal 3 by the raising-of the relevant scraper module 10, the slag 4 remaining between the closed scraper blades 11. Molten residues of the metal 3 can drop off the scraper blades 11 and from the wedge-shaped space which they have formed into the still-moving moulds 2 without being entrained.

By further deflections of the chain conveyor 8, the closed scraper modules 10 reach the horizontal portion above the slag conveyor 14 where, at a signal from a command transmitter 27, the scraper blades open and the slag 4 between them drops into one of the moulds 26 in the slag conveyor 14. With the scraper blades 11 open, the scraper modules 10 are transported onwardly to that portion of the chain conveyor 8 which rises at the same angle as the pig-casting belt 1, and the slag removing process begins again.

Claims

1. An apparatus for removing slag from the surface of molten metals in moulds in a pig-casting belt, said apparatus comprising a double-checked polygonally shaped.

frame disposed above and parallel with the pig-casting belt carried on the cheeks, which are spaced apart by at least the width of the moulds, a chain conveyor with sprockets are mounted at the polygon points of the cheeks of the frame, the chains of the chain conveyor carrying a number of equidistant swivel joints between which, freely suspended via hinge pins and fixing elements there are scraper modules the chain conveyor being driven at a speed synchronous with that of the pig-casting belt by the drive used for this latter; the polygonal rotation of the slag removing modules comprises a working portion of the polygon which extends at the same pitch angle of the pig-casting belt and the scraper blades of the scraper modules guided over the moulds of the pig-casting belt are guided at such a height that they dip slightly into the molten metal while a subsequent working portion of the polygon comprises lifting of the scraper modules out of the moulds, the difference between the pitch angle of the pig-casting belt and the pitch angle of this working o portion of the polygon amounting to 13 to 15

2. An apparatus according to claim 1, wherein the cheeks of the frame form irregular polygons with more than four sides which are described as working portions.

3. An apparatus according to claim 1, wherein the frame is mounted to be pivotable about a horizontal fixed hinging point disposed on the front vertical side of the frame.

4. An apparatus according to claim 1, wherein a joint on which the piston rod of a lifting element is articulated opposite the fixed hinging point of the frame.

5. An apparatus according to claim 4, wherein the lifting travel of the lifting element is greater than the depth of penetration of the scraper blades into the slag and the molten metal.

6. An apparatus according to claim 1, wherein there is at right-angles to the pig-casting belt and endless slag conveyor around which the scraper modules travel positioned in the free space formed by the polygonal section of the sprockets of the chain conveyor which are disposed in the frame.

7. An apparatus according to claim 6, wherein the slag conveyor is constructed as a pig-casting belt.

8. An apparatus according to claim 6, wherein the working portion of the polygon is disposed horizontally above the slag conveyor.

9. An apparatus according to claim 1, wherein in the housing of the individual slag removing modules there are disposed horizontally besides each other and extending as far as the middle of the housing, two oppositely operating working cylinders and, in extension of their longitudinal axes, guide columns on which there are displaceable slide members connected to the piston rods of the working cylinders while on the sliding members and projecting downwardly beyond the housing there are inwardly angled-over supports on the angled-over part of which there are scraper blades which, in the groupedtogether state, form a wedge-shaped space.

10. An apparatus according to claim 1, wherein the width of the scraper blades corresponds to the width of the moulds.

11. An apparatus according to claim 1, wherein there are in the scraper modules on the frame command transmitters controlled by the chain conveyor for the contactless controlling of multi-way valves in the working cylinders.

12. An apparatus according to claim 1, wherein in the scraper modules there are in each case a controllable group of multi-way valves for the working cylinders a wireless and non-contacting signal transmission system for control commands and an energy transmitting module for compressed air and inboard electrical voltage.

13. Apparatus for removing slag from moulds in pigcasting belts, the apparatus comprising: i. first moving means for moving a belt of pig-casting moulds; ii. scraping means for scraping slag from metal contained in the moulds; and iii. second moving means for moving the scraping means in synchronisation with the pig-casting belt, the arrangement being such that-the scraping means is guided into a mould and then out of the mould.

14. Apparatus as claimed in claim 12 wherein the scraping means is guided along a path comprising linear portions.

15. Apparatus for. removing slag from surface of molten metals substantially as described herein with reference to the drawings.

16. A method of removing slag from moulds in pig-casting belts; the method comprising the steps of: i. moving a mould containing slag in a belt; ii. moving scraping means in synchrony with the mould; iii.guiding the scraping means into the mould; iv. scraping slag from metal contained in the mould; v. guiding the scraping means out of the mould;

17. A method of removing slag substantially as described herein with reference to the drawings.