AU699470B2

AU699470B2 - Method and device for directly charging an electric furnace with liquid metal from a ladle

Info

Publication number: AU699470B2
Application number: AU21348/95A
Authority: AU
Inventors: Norbert Kaell; Rudy Petry
Original assignee: Paul Wurth SA
Current assignee: Paul Wurth SA
Priority date: 1994-06-29
Filing date: 1995-03-21
Publication date: 1998-12-03
Anticipated expiration: 2015-03-21
Also published as: JPH10502128A; ES2124541T3; FI965235A0; LU88505A1; CN1151764A; AU2134895A; FI965235A; CN1042956C; RU2149904C1; CA2193472A1; EP0767843B1; EP0767843A1; ATE172751T1; WO1996000799A1; DE69505670D1; BR9508705A; DE69505670T2; CZ382096A3

Abstract

A method and a device for directly feeding liquid metal into an electric furnace. A carriage carrying a ladle filled with molten metal is moved forward into a starting position adjacent the electric furnace then lowered and horizontally translated until the upper rim of the ladle is located over the electric furnace. The ladle is then tipped and gradually raised and translated to keep the upper ladle rim in a position in which the liquid metal can be poured into the furnace. The ladle is tilted back, lowered and horizontally translated to return it to the starting position.

Description

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i x~ I r PCT/EP95/01052 P-PWU-308/WO International patent application no. PCT/EP95/01052 Date of application: 21 March 1995 Applicant: PAUL WURTH S.A.

METHOD AND DEVICE FOR DIRECTLY CHARGING AN ELECTRIC FURNACE WITH LIQUID METAL FROM A LADLE The present invention describes a method and a device for directly charging an electric furnace with liquid metal from a ladle.

A large part of the recycling of scrap iron is achieved using electric furnaces such as arc furnaces. These furnaces make it possible to melt and reuse the scrap iron treated in this way in order to make new steel products.

Some of the residual elements contained in the scrap iron, such as copper, nickel, etc., cannot be separated from the steel and are therefore present in the finished products. The more the scrap iron has been subjected to recycling operations, the higher will be the concentration of these residual elements. The latter are a nuisance in the manufacture of certain products such as steel s.ieets, etc.

One way of reducing the concentration of residual elements in the steel obtained from scrap iron is to add some liquid pig iron directly to the electric furnace.

However, when the liquid metal is poured from a ladle into an electric furnace using a crane or an overhead traveller, it is very difficult to control the rate at which the pig iron flows from the ladle. In fact, the rate of flow is not constant and varies as a function of the angle of inclination of the ladle.

Moreover, it is very difficult to control the angle of inclination of a ladle suspended from an overhead traveller or a crane. During uncontrolled pouring f the liquid metal into the furnace, part of this. .jid metal or of the partially |p j 2 melted steel contained in the furnace is ejected out of the furnace and the impact of the liquid pig iron risks damaging the cooling panels lining the inside of the furnace.

The document DE-B-1 284576 describes a carriage comprising a frame for the transport of a ladle containing liquid metal. The ladle may be raised and lowered by a first actuator and may be tilted laterally by means of a second actuator independent of the first in order to pour liquid metal from the ladle into an electric furnace.

The aim of the present invention is to find a method and a device making it possible to pour the liquid metal into an electric furnace in a controlled manner.

In accordance with a first aspect of the present invention, therefore, there S is provided a method for directly charging an electric fun ,ace with liquid metal H from a ladle, said method including: moving a carriage carrying a ladle having an upper end and a lower 16 end and filled with molten metal to an initial position near said electric furnace; co-ordinated lowering and horizontal translation of said ladle until the upper end of the ladle is positioned above said electric furnace; co-ordinated tilting, progressive raising and gradual horizontal translation of said ladle in such a way that said upper end of said ladle is held in 6:"23: a position enabling said liquid metal to be poured into said furnace; pouring of said liquid metal into said furnace; and I co-ordinated tilting, lowering and horizontal translation of said ladle in order to return it to its initial position.

The liquid metal is no longer poured into the furnace by means of a crane or an overhead traveller, but the ladle is manipulated using a carriage allowing it to perform a complex and controlled movement. The upper end of the ladle, which is preferably fitted with a pouring lip, is held permanently at a small distance above the edge of the furnace. The height through which the liquid metal falls is thus i| |i considerably reduced in comparison with pouring the liquid 1310OI98GC89a.SPE,2

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4, 3 metal from a ladle using a crane or overhead traveller. As a result, the risk of damage to the cooling panels and/or the refractory material is low.

The ejections of liquid metal and molten steel are reduced because the rate at which the liquid metal is poured can be chosen so as to minimise such ejections.

Preferably, the carriage and/or the ladle are continuously weighed before the ladle is filled and during the whole time the liquid metal is being poured from the ladle. In this way, it is possible to determine and possibly to record the flow rate of the liquid metal poured during each operation. This allows a continuous adaptation of the complex movement made by the ladle during the pouring. An optimum movement to be made by the ladle can thus be calculated.

It -vas found, during the work which culminated in this invention, that the flow rates of liquid metal may vary significantly from one ladle to another, depending on, for example, the shape of the pouring lip and the wear of the .15 refractory lining of the ladles, etc. By marking the different ladles, it is possible to establish an optimum pouring movement for each ladle by measuring the flow rate using a continuous weighing of the ladle while the liquid metal is being poured into K: the furnace.

If the flow rate should at times become too great, the tilting speed or even the angle of inclination could be temporarily reduced until the flow rate has once again stabilised. Automation of the control and the adaptation enables the regulation of the flow rate to be achieved in real time.

In accordance with a further aspect of the present invention, therefore, there is provided a device for directly charging an electric furnace with liquid metal from a ladle, said device including: a carriage with a supporting frame; two arms with jaws, manoeuvrable around a first axis, making it possible to raise and lower a ladle placed by suspension arms into seid arms with jaws; a double arm manoeuvrable around a second axis whose centre of rotation coincides with an axis passing through journals mounted on said suspension arms and making it possible to give a rotational movement to said ladle; and means for actuating said arms with jaws and said double arm.

1 aAc 1311 98GC89GC8s8.PE,3 I i r rw:: 4 One of the advantages of this carriage is that the ladle may be raised or lowered and tilted at the same time or independently. It is therefore possible respectively to raise or lower the ladle without necessarily having to change its angle of inclination.

The respective raising or lowering and the tilting of the ladle may be achieved by hydraulic means such as actuators or by electro-mechanical means.

It is to be noted that one of the movements may be achieved by hydraulic means while the other movement may be achieved by electro-mechanical means.

The weight of the ladle may be continuously determined by the hydraulic means and/or by the electro-mechanical means used to produce the movements of the ladle.

With advantage, the ladle is closed by a cover, preferably a cover made of Ia refractory material, during its transport in order to limit heat losses. This cover is removed before the carriage reaches its initial position prior to the pouring of the liquid metal.

This method and this device may be used with all types of electric furnace.

It is, however, particularly advantageous to use them in combination with an electric furnace having a lateral charging platform. In effect, this charging method and device enable the dimensions of such a charging platform to be reduced, since it is possible to pour the liquid metal into the furnace from a ladle with very great accuracy. Since the flow rate can be maintained at a predetermined value, the dimensions of the lateral charging platform can be adapted to the flow rate from the ladle. If this method and device were not used, the lateral charging platform would have to be oversized. As a result, the Gr 13/10/98GC898S.SPE,4 I I whole construction of the furnace would therefore have to be adapted. This is particularly the case when the furnace involved is of the EBT type (having an eccentric tap hole), which is pivotable on a tilting seat; it is then necessary to attach counterweights to the side of the furnace opposite the platform in order to allow the furnace to resume its horizontal position automatically after having been tilted during the casting of the liquid steel. If the size of the lateral charging platform can be reduced through the use of the present invention, the counterweights will be able to be smaller and it will be cheaper to build the electric furnace.

Additional advantages and characteristics will emerge from the detailed description of advantageous embodiments of the invention given below, solely for the purposes of illustration, by referring to the appended drawings, in which: -Figure 1 shows a graph of the variation in the weight of a ladle containing liquid metal as a function of its angle of inclination; Figures 2A, 2B and 2C show a side view of the carriage for charging an electric furnace with liquid metal together with the means supporting the ladle in the carriage; Figures 3A, 3B and 3C show a sequence in the charging of an electric furnace with liquid metal; Figure 3A shows the carriage in its initial position near an electric furnace; Figure 3B shows the carriage and the ladle at the start of pouring; Figure 3C shows the carriage in the position it occupies at the end of at the pouring proper.

Figure 1 represents a graph of the variation in the contents of a ladle plotted against its angle of inclination. This graph shows that the quantity poured is not constant as the angle of inclination of the ladle varies, but that it passes through a maximum at a well-defined angle. It can be seen that this maximum also depends on the variation in the angle of inclination of the ladle. If I Z- \i3,0 the variation in the angle is lower, as represented in the lower curve instead I;

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1 i INTERNATIONAL SEARCH REPORT Inu amCE ,ppiheaion No f PCT/EP 95/01052 -own 6 of 50), the maximum is less pronounced. It is clear that this graph was plotted for a ladle with a particular shape. This graph varies considerably with the geometry of the ladle and also varies, for the same ladle, as a function of the progressive wear of the refractory lining inside the ladle.

Figures 2A, 2B and 2C show a device for directly charging an electric furnace with liquid metal from a ladle. The carriage 10 comprises a supporting frame 12 fitted with three axles 14, 16, 18.

Figure 2B clearly shows one of the two arms with jaws 20 hinged about a shaft 21 located on the supporting frame 20 outside the ladle 22. The arm can be manoeuvred by a piston 23 fixed in a pivotable manner by a first end to the frame 20 and by a second end to the arm 20, thus making it possible to raise and lower the ladle 22 which is placed by suspension arms 26 into the arms with jaws 20. The ladle 22 is fixed to the frame 12 by an anchoring -device 19. This device prevents the ladle 22 from pivoting in the arms with jaws during transport.

Figure 2C shows a second manoeuvrable double arm 30 whose centre of rotation coincides with the axis of journals 24 enabling the ladle 22 to perform a rotational movement. One end of the double arm 30 is fixed to journals 24 on the ladle 22. At its base, the ladle 22 is equipped with a lug which fits into a groove 27 made in the other end of the double arm 30. A piston 29, fixed in such a way that it can pivot by one end on the arm with jaw 20 and by the other end on the double arm 30, enables the ladle 22 to be tilted about an axis passing through the journals 24.

Figures 3A, 3B and 3C show a sequence in the pouring of liquid pig iron 25 into an electric furnace. Figure 3A shows a device 12 for directly pouring liquid metal mounted on a carriage 10 in the initial position near an electric furnace 130. The furnace 30, in this example, has a lateral charging platform 32 by which the liquid metal is introduced into the furnace 30. The platform 32 is covered inside by a thick layer of refractory material 34. An impact plate 36 made of a S% special refractory material is built on to the bottom of the said platform 32 in INTERNATIONAL SEARCH REPORT [WM& ,pikrionNo PCT/EP 95/01052 n Tn BE RELEV' 1 order to protect the refractory material 34 from shocks due to the impact of the liquid pig iron. A ladle 22, with a pouring lip 38 and filled with liquid pig iron, is placed on the carriage Figure 3B shows the second stage of the pouring just before the beginning of the pouring of the liquid pig iron into the charging platform. The ladle 22 has been lowered by a movement of the piston 23 and tilted so that the pouring lip 38 is located above the platform 32. Since the ladle 22 is fixed by its lower end to the frame 12 by the anchoring device the ladle is tilted without direct involvement of the double arm 30. The small distance between the pouring lip 38 and the platform 32 should be pointed out, a factor that reduces the energy of impact of the liquid pig iron in the platform 32 on the refractory material 34, 36, Because of this small drop height, the projections of liquid pig iron are limited, thus increasing the safety of personnel working near the electric furnace.

Figure 3C shows the ladle in position during the end of pouring the liquid pig iron into the electric furnace 30. The ladle 32 is now in a horizontal position and all the pig iron is able to flow from the ladle 22. It is important to stress that the ladle 22 does not necessarily have to be completely emptied. The situation may in fact be that, if it is required to pour only a well-defined quantity of pig iron into the furnace 30, the ladle 22 only has to be half emptied, for example.

position.

In order to tilt the ladle ?2 to a predetermined position, the anchoring j device 19 is detached from the frame 13 and, actuating the piston 29, a tilting movement is imposed on the ladle 22 around the axis passing through the journals 24. By actuating the piston 23, it is possible to raise and lower the Sladle 22 independently of the angle of inclination of the ladle 22 in such a way as to minimise the height through which the pig iron falls.

nI AELA DMAND PCT/EP 95/01052 CI 6 C2C5-/52 F7n/1A 1 :t/lg DOOnOA1f,, I I 8 When the ladle 22 is empty or when the required amount of pig iron has been poured into the furnace 30, the ladle 22 is returned to its initial position by carrying out the same movements but in reverse order.

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Claims

1. A method for directly charging an electric furnace with liquid metal from a ladle, said method including: moving a carriage carrying a ladle having an upper end and a lower end and filled with molten metal to an initial position near said electric furnace; co-ordinated lowering and horizontal translation of said ladle until the upper end of the ladle is positioned above said electric furnace; co-ordinated tilting, progressive raising and gradual horizontal translation of said ladle in such a way that said upper end of said ladle is held in a position enabling said liquid metal to be poured into said furnace; pouring of said liquid metal into said furnace; and co-ordinated tilting, lowering and horizontal translation of said ladle in order to return it to its initial position.

2. The method according to Claim 1, wherein the flow rate of said liquid S *.1t metal is determined by continuously weighing said carriage during the whole Sl pouring operation and wherein the variation of the angle of inclination of said ladle is regulated as a function of the flow rate of said liquid metal. .9

3. The method according to Claim 1 or Claim 2, wherein said ladle is lowered by means of two arms with jaws in which said ladle is suspended and which are articulated around a first axis, said ladle is tilted by means of a double arm maroeuvrable around a second axis whose centre of rotation coincides with S" an axis passing through journals mounted on said suspension arms and enabling a rotational movement to be given to said ladle, and wherein said ladle is progressively raised by means of said two arms with jaws.

4. The method according to Claim 3, wherein said first rotation axis is located outside said ladle on a supporting frame.

A device for directly charging an electric furnace with liquid metal from a ladle, said device including a carriage with a supporting frame; two arms .vith jaws, manoeuvrable around a first axis, making it possible to raise and lower a ladle placed by suspension arms into said arms with jaws; a double arm manoeuvrable around a second axis whose centre of rotation coincides with an is passing through journals mounted on said suspension arms and making it 13110/98GC8988.SPE,9 f i possible to give a rotational movement to said ladle; and means for actuating said arms with ja,' and said double arm.

6. The device according to Claim 5, wherein said first axis of rotation is located outside said ladle on said supporting frame.

7. The device according to Claim 5 or Claim 6, including at least one Ifirst hydraulic actuator operating said two arms with jaws.

8. The device according to any one of Claims 5 to 7, including at least one hydraulic actuator operating said double arm.

9. The device according to Claim 5 or Claim 6, wherein said two arms with jaws are driven byelectro-mechanical means.

The device according to Claim 5 or Claim 6, wherein said double arm S is driven by electro-mechanical means.

11. The device according to any one of Claims 5 to 10, including means S for weighing said ladle continuously during the whole pouring operation. .6

12. The device according to any one of Claims 5 to 11, including a cover made of a refractory material which covers said ladle while it is being transported to its initial position.

13. A method for directly charging an electric furnace with liquid metal from a ladle, substantially as described herein with reference to the accompanying drawings. I

14. A device for directly charging an electric furnace with liquid metal from a ladle, substantially as described herein with reference to the accompanying drawings. DATED this' 13th day of October, 1998. PAUL WURTH S.A. By their Patent Attorneys: J i CALLINAN LAWRIE f 113/10/98GC8988.SPE,1 0 INTERNATIONAL SEARCH REPORT Informrnon on patent family manbe Intmrtien pliaion No Pnt PCT/EP 9t5/1i52on Pa t e document mernberls)I ABSTRACT Method and device for directly charging an electric furnace with liquid metal from a ladle. A carriage transporting a ladle filled with molten metal is moved forward to an initial position near the electric furnace, then lowered and traversed horizontally until the upper rim of the ladle is positioned above the electric furnace. The ladle is then given a tilt, a progressive raising and a gradual traversing motion in such a way that the upper rim of the ladle is held in a position enabling the liquid metal to be poured into the furnace. The ladle returns to its initial position by performing a tilt, a lowering and a horizontal traversing motion. Jt 7 gAL Ii N ok'i 1