US3834587A

US3834587A - Means for automatic control of batching when casting from a heat-retaining of casting furnace or ladle (crucible)

Info

Publication number: US3834587A
Application number: US00305684A
Authority: US
Inventors: F Bengt; B Kjell
Original assignee: ASEA AB
Current assignee: ABB Norden Holding AB
Priority date: 1971-11-18
Filing date: 1972-11-13
Publication date: 1974-09-10
Anticipated expiration: 1991-09-10
Also published as: SE364654B; DE2254946A1

Abstract

For the automatic control of batching when casting from a heatretaining furnace or ladle, an arrangement is provided for tapping the ladle in batches into a batching ladle. An arrangement is provided for weighing the batching ladle and the output signal of the weighing arrangement is fed to a deriving device which gives an output signal dependent on the melt flow. The output signal of the deriving device is fed to a comparison device along with a signal representing a desired value. A control device for the tapping of the furnace is combined with the output signal of the comparison device to terminate tapping when a predetermined quantity of melt has been tapped.

Description

Umted States Patent 11 1 1111 3,834,587 Bengt et a1. Sept. 10, 1974 [54] MEANS FOR AUTOMATIC CONTROL OF 2,772,455 12/1956 Easton et a1. .1 164/155 BATCHING WHE CASTING FROM A 2,882,567 4/1959 Deakins et a1. 222/166 X HEAT-RETAINING 0F CASTING FURNACE 232331323 3/1323 33123235219133: "61111333112 OR LADLE (CRUCIBLE) 3,457,985 7/1969 Wilson 164/155 [75 Inventors: Fredrikson B Bergman Kiel], 3,537,505 11/1970 Thalmann 164/155 X both of Vasteras, Sweden Primary Examiner-Robert B. Reeves Asslgnee: Aumanna Sven-Ska Elekmska Assistant Examiner-David A, Scherbel Aktiebolaget, Vasteras, Sweden 22 Filed: Nov. 13, 1972 [57] ABSTRACT [21] AppL NO: 305 684 For the automatic control of batching when casting from a heat-retaining furnace or ladle, an arrangement is provided for tapping the ladle in batches into a Forelgn Apphcatlon Priority t batching ladle. An arrangement is provided for weigh- Dec. 18, 1971 Sweden [4738/71 ing the batching ladle and the output signal of the weighing arrangement is fed to'a deriving device [52] US. Cl ..-222/56, 164/155, 222/77 which gives an output signal dependent on the melt [51] Int. Cl B22d 37/00 flow. The output signal of the deriving device is fed to [58] Field of Search 222/ 166, 14, 16, 56, 77, a comparison device along with a signal representing a 222/DIG. l5, DIG. 12; 164/4, 154, 155 desired value. A control device for the tapping of the furnace is combined with the output signal of the com- [56] References Cited parison device to terminate tapping when a predeter- UNITED STATES PATENTS mined quantity of melt has been tapped.

2,768,413 10/1956 Alexanderson 164/155 4 Claims, 9 Drawing Figures 3/ 25 32 27 33 26 1 tai ng" 47 -1? {j W5 v I 37. "8

48 I 1 7 517 78" I W 1 l //l l 36 .,&L L

\ -1 I 12 1 4 P M W 20 22 PATENIE SEH 01914 834,587

SHEET 2 [If 3 Fig2 I MEANS FOR AUTOMATIC CONTROL OF BATCI'IING WHEN CASTING FROM A HEAT-RETAINING OF CASTING FURNACE OR LADLE (CRUCIBLE) BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a means for automatic control of batching or proportioning when casting from a heat-retaining or casting furnace or ladle (crucible).

A pressure casting method of this kind is shown in ASEAs brochure AUl0-103 PRESSPOUR casting m -J a.

2. Description of the PrioFArt For control of the flow from the furnace or the ladle during automatic batching, previously among other things level indicators for the melt have been used, placed in the tapping spout of the furnace and/or in the moulding box or the casting device. Such level indicators, for example those which are placed on the moulding box, involve the disadvantage that a rising gate has to be arranged which, among other things, causes expense for exchange of deteriorated material. In other words, certain parts of the casting body have to be cast, and these must be removed later on in order to obtain a signal from the level indicator. Such level indicators of on-off type also involve a problem concerning the accuracy when casting, and also their reliability in operation has been a problem. Indicators with a proportional signal have also been a problem.

It has also been tried to cast on the basis of time. In these cases an approximately constant flow has been used and the time has been measured. After a certain tapping time, the tapping has been interrupted, and then it has been possible to count on there being a certain fixed batch in the pouring ladle or casting device. Also this has involved certain drawbacks, and often a bad material exchange. Weight control at the casting ladle has also been used, and at a certain signal the casting has been interrupted, but a disadvantage of these devices is that after the interruption an extra amount has been obtained in the pouring ladle, corresponding to the time constant and the melt quantity in the spray. Furthermore, the stoppage in casting has taken place quite abruptly, causing overproportioning and wastage and other inconvenience. All these previously known devices have therefore as a rule required supervision by an operator. It is desirable that the conditions should be constant during the batching, independent of the filling degree of the furnace, but so far this has been difficult to achieve.

SUMMARY OF THE INVENTION The invention aims at a solution to these and related problems and is characterised in that the furnace is arranged to be tapped in batches into a batching ladle which is provided with weight equipment, the output signal of whichis fed to a deriving device in order to obtain an output signal dependent on the melt flow, said signal being arranged to be transmitted together with a signal for the desired value to a comparison device, the output signal of which is arranged to control the tapping from the furnace and other factors. In this way, a signal is obtained, acting as a control signal and being directly dependent on the flow, and it is possible,

for example, to slacken the tapping before the batching ladle is completely filled and stop the tapping just at the right moment. The melt content in the flow being tapped can also be taken into consideration. Thus, an exact batching control is obtained without appreciable wastage of material and without supervision being nec essary. Such a means is easily fitted into an automatic production line for such cast products.

BRIEF DESCRIPTION OF THE DRAWINGS The invention is exemplified in the accompany drawings, of which FIG. 1 shows a skeleton diagram used for a pressure casting furnace of channel type. FIG. 2 shows the filling and emptying conditions during batching with one batching ladle, FIG. 3 the corresponding condition when using two batching ladles and FIG. 4 the same for four batching ladles. FIG. 5 shows a gearing device for the tare in case of small tare weight, and FIG. 6 shows the same device seen from the side. FIG. 7 shows the devices for weighing the tare arranged in accordance with FIG. 5, and FIGS. 8 and 9 alternative solutions of the gearing of the tare.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a furnace of submerged resistor type (channel-type induction furnace) ll of tea-pot type having separate inlets 12 and outlets 13 and a furnace hearth closed by means of a liquid lock, said furnace being provided with one or several inductors of channel type. A tapping spout 15 is arranged at the outlet, through which melt from the furnace is to be supplied to a batching ladle 16 in suitable batches, and this batching ladle can be arranged together with other similar means on a rotatable base on a so-called turning head system (see the small figure to the left in FIG. 4). When more batching ladles are used, these can also be arranged on the turning head system. When the ladle 16 has been filled with a suitable quantity of melt, it can be teemed into a funnel or mould 17 which, in turn, is to be emptied into a flank or mould 27 on an automatic casting line or moulding machine, type DISAMATIC.

The weight of the batching ladle (W-l-tare) is arranged to be measured in a suitable manner, for example by means of a magnetostrictive measuring device of the type shown in Swedish patent specification 151,267, see detail .19 in the present FIG. I, and the tare (the weight of empty batching ladle 16) is arranged to be measured when the batching ladle after emptying returns to position for filling and affects a sensing device at 21, preferably in a similar way, and the measuring signal for the tare is transmitted to a calculating device or computer 20, where the tare signal is then subtracted from the gross weight in order to obtain a signal for the net weight (W), said signal being then derived in order to obtain a signal proportional to the flow (W the derivate of the net weight). The batching ladle 16 is tiltable by means of a suitable drive means, such as a hydraulic device 18, where the teeming rate can be controlled with a programming device in order to obtain a favorable flow at the beginning and end. At the batching ladle, inoculation with, for example, ferrosilicon is automatically carried out.

The computer 20 is connected to an indicating device 22 of digital or other type, and at the desk 23 the information to be indicated at 22 can be fed, such as batch weight, total weight, tare weight, flow, remaining melt in the furnace and so on. The furnace II can also be tiltable and possibly of crucible or of other type and provided with a heat-retaining member.

At the desk 23 the desired batch weight can be fed at a certain casting line, and the batch weight should be independent of the degree of filling of the furnace 11.

At 31 a ramp device is arranged, from which a suitable desired value for the flow (W) reference flow can be obtained, said value being transmitted to an addition device 25 together with the signal for actual value W for the flow. The signal for flow deviation (from 25) is transmitted to a flow regulator 32, preferably a control amplifier of proportional, integrating type. Output signals for this amplifier 32 will, as appears below, constitute a reference for the pressure control (the pressure tapping of the furnace 11), and this signal is transmitted to a second addition device 27, together with a signal corresponding to the pressure 28 measured above the melt in the furnace. The pressure signal is also transmitted over a motor driven potentiometer 34, constituting a memory circuit" for the pressure during the tapping which is not constant during the whole emptying process but varies according to a certain curve. The output signal from the potentiometer 34 is transmitted, after switching on at the end of the filling, to the same addition device 27, and error signals (deviations from desired pressure in the furnace degree of tapping) are transmitted to a pressure control amplifier 33, the output signal of which is transmitted to an adjusting device for the pressure in the furnace (air or inert gas, transmitted at 14).

It is desirable, as appears from FIG. 2, when using one batching ladle 16, to allow the flow rate W (F S) to increase first along a sloping curve, and then to be held constant until a certain directional signal W has been attained, after which the flow is to be slackened to a certain weight W where the tapping is to be discontinued. (At W the tapping is to be switched from W to W T shows then the emptying of the batching ladle and F the filling which again follows. W shows in FIG. 2 when the final weight is to be attained, and N is the level in the furnace and how this changes with the time t.

FIG. 3 shows how the emptying (T) and filling (F) scheme can be arranged when two ladles (1,2) are used, and FIG. 4 shows the same for four ladles (1,2,3,4). To the left in FIG. 4 is shown how the ladles are turned in the direction of the arrow for emptying (T) and filling (F) on the turning head system.

W and W (FIG. 1) are adjusted at the computer 20, and on attaining W for one batch the relay coil 29 receives current and its contact 29 closes the circuit W to the ramp device after W has been switched on previously. A filling scheme according to FIG. 2 is obtained until W has been attained, when the relay coil 48 receives current and, among other things, its contact 48 breaks and the flow control ceases. The reference device 34 is switched on by means of the contact 48" and takes over the control as well the pressure reduction reference A P.

The supervision now comprises a photocell device 49, the output signal of which is transmitted to an integrating amplifier 36 which, after coil 48 has received current, also causes contact 48" to feed the addition device 27. The integration time for the amplifier 36 is selected so that maximum filling rate is accomplished with no risk of running over. A P is the desired pressure reduction during tapping of a batch.

In order to avoid undesirable disturbances when starting up after a tapping process (see FIG. 2 the second time F occurs), a circuit 37 is switched on, arranged in such a way that the output signal from the flow control 32 corresponds to the current pressure during tapping (bump-less function).

The control amplifier 37 is arranged to transmit a signal to the addition device 25 over contact 48"" (closed when the coil 48 receives current), in this way affecting the output signal of the flow control so that it corresponds to the current pressure when starting up.

In FIG. 5 is shown how the taring control can be ar ranged for small tares. The ladle is located at the end of a lever 51, or supported at a point 54 and rotatable by means of a motor 53 for tapping through the gear drive 52. See also FIG. 6 where the same process is shown seen laterally. In FIG. 7 is shown how the shaft 51 is arranged on a fixedly supported revolving axle 54 in which the balance devices 19 are arranged. FIG. 8 shows how the balance device is arranged at 19, said balance device emitting a suitable signal corresponding to the tare, which signal can also be obtained in the case of very small tare weights. FIG. 9 shows an alternative, the balance device being located below a pivot for a shaft, at the end of which the ladle is positioned.

To sum up, the advantages of this invention can be said to be the following:

Controlled tapping rate, which means that a maximum proportioning rate can be maintained during the major part of the tapping process. The flow rate is determined by deriving the weight signal, and therefore no particular sensing member for the flow rate itself is needed. The demand on accuracy for the flow control is moderate, since the total weight finally decides when the tapping is to cease.

Controlled metal weight in the batching ladle prior to casting. Since close tolerances can be kept, essential savings as to material costs can be made.

When the tapping is finished, the level in the tapping channel is lowered to a position on a level with the dam for the tapping spout 15, independent of the degree of filling of the furnace 11. This means, aside from time saving, that the consumption of the pressure gas in the furnace hearth (the furnace tank) is reduced to a minimum. The latter is particularly advantageous when casting nodular iron.

Filling of the furnace can be made irrespective of whether tapping is going on or not.

The system can be fully automated.

The system makes possible continuous casting on a casting line. When applying the turning head system and/or oscillating batching ladle 16, casting can be carried out without having to stop the casting line.

The arrangements exemplified above can be varied in many ways within the scope of the following claims.

We claim:

1. Means for automatic control of batching when casting from a crucible including a batching ladle, means for tapping the crucible in batches into the batching ladle, means for weighing the batching ladle, a deriving device, means for feeding the output signal of the batching ladle weighing means to the deriving device, means in the deriving device to transform the output signal of the batching ladle weighing means, which output signal depends upon the weight of batches of the tapped melt, into the derivative of the output signal of the batching ladle weighing means, the derivative of the output signal of the weighing means representing the rate of the melt flow out of the crucible, a reference device providing signals representing the desired value of melt flow rate out of the crucible, means responsive to the output signal of the batching ladle weighing means to change the output signal of the reference device, a comparison device, means to feed to the comparison device the signal from the reference device and the output signal from the deriving means, a control device for the tapping of the crucible, and means to feed to the control device output signals from the comparison device to control the tapping rate to maintain it at different values in response to differences in the weight of the batching ladle.

2. Means according to claim 1, in which the crucible is a furnace of submerged resistor type provided with separate inlets and outlets and with an inflow for pressure medium at the hearth in order to control the tapping.

3. Means according to claim 2, in which a level measuring device is arranged at the outflow of the furnace and means responsive to the output signal of said level measuring device for controlling the pressure in the furnace.

4. Means according to claim 1, which includes means to measure the tare when the ladle is empty, a subtraction device, and means to feed the outputs of the tare measuring means to said subtraction device together with the output signalof the weighing means.

Claims

4. Means according to claim 1, which includes means to measure the tare when the ladle is empty, a subtraction device, and means to feed the outputs of the tare measuring means to said subtraction device together with the output signal of the weighing means.