US3536124A - Means for controlling teeming rate in continuous casting - Google Patents

Description

United States Patent [72] Inventors Bertil Hanas;

Rune Flinth, Vasteras, Sweden [21] Appl. No. 628,936 [22] Filed Apri16, 1967 [45] Patented Oct. 27, 1970 [73] Assignee Allmanna SVCIISkH'ElCkll'iSkH Aktiebolaget Vasteras, Sweden a corporation of Sweden [32] Priority April 7, 1966 [3 3 1 Sweden [3 I 1 4845/66 [54] MEANS FOR CONTROLLING TEEMING RATE 1N CONTINUOUS CASTING 3 Claims, 4 Drawing Figs.

[52] U.S.Cl 164/155, 164/281 [51] Int. Cl E22d 17/32 [50] Field ofSearch l64/l55.4, 154, I56, 281, 337

[56] References Cited UNITED STATES PATENTS 2,768,413 10/1956 Alexanderson 164/155 2,882,567 4/1959 Deakins etal. 164/155 2,905,989 9/1959 Black l64/28IX Primary Examiner-J. Spencer Overholser Assistant Examiner.lohn S. Brown Art0rneyBailey, Stephens & Huettig ABSTRACT: Mezins for controlling the teeming rate in continuous casting from a crucible or a furnce to a casting mould. The melt is tapped from the crucible to an intermediate casting box and from the box to the mould. The weight of the box and melt level in the casting mould are indicated and said signals are combined and amplified and the output signal from the amplifier is transmitted to a stop valve in the crucible.

MEANS FOR CONTROLLING TEEMING RATE IN CONTINUOUS CASTING BACKGROUND OF THE INVENTION l Field of the Invention The present invention relates to a means for controlling the teeming rate in continuous casting.

2. The Prior Art A conventional means for continuous casting includes a transport ladle with pourer and stop means. which is tapped into a casting box or intermediate ladle which is also provided with pourer and stop means. The last-mentioned container is tapped into a casting mould provided with a cooled form and transport rolls situated under this to carry the solidified substance for further cooling and cutting into suitable lengths. etc. The level in the casting mould is often tested to prevent cracks and other faults arising in texture and shape which might otherwise easily occur if the level were faulty. It is also desirable to check that the casting box has constant weight, for which the pouring from both casting box and ladle must be controlled. For manual control of this step two men are necessary and for automatic control there is a relatively great demand for control stability.

It has also been tried to tap a ladle or furnace directly into the casting mould. but this is not very satisfactory due to variations in the speed of the flow of melt at different levels in the ladle which incurs considerable control problems Furthermore. the space near a furnace or transport ladle is often insufficient and for other reasons unsuitable for casting so that it is preferable to use an intermediate casting box.

SUMMARY OF THE INVENTION The invention is intended to solve these and other similar problems. It relates to a device containing a ladle, furnace or other container for melt having a pourer, a casting box or intermediate ladle for melt from the first mentioned container. etc. and a casting mould having a level indicator for the melt from the casting box. The invention is characterised in that a signal obtained from the level indicator and a signal from a weight indicator weighing the casting box with its contents or measuring the melt level in this box, are transmitted to a control means such as a control amplifier, the signal from this controlling the position of a blocking rod or stop means in the first mentioned pourer, whereby the level signal being arranged to convert the desired value for the weight of the casting box or the level in it so that the pouring speed from this box corresponds to the desired level in the casting mould. With such a means only a control circuit for tapping the melt is required and this provides considerably increased control stability compared with the double melt control according to the above.

The invention is further exemplified in the accompanying FIGS. where FIG. I shows schematically one embodiment of the invention, FIGS. 2 and 3 a casting mould-with accessories and FIG. 4 a second embodiment of the invention.

In FIG. 1 a transport ladle is shown at 11 containing steel or iron melt 12. The ladle, which is provided with a pourer 13 having controllable stop means such as a movable stop valve 14 according to the French Pat. No. l, 1 55,082 or the U.S. Pat. No. 31 1,902, may also be a ladle of another type, or a furnace provided with a similar pourer. The pourer may alternatively include a blocking rod which can be lifted or lowered (see FIG. 4).

The stop valve in FIG. I is controlled by a hydraulic servomotor 15 or by an electric motor depending on the level sensed in the casting mould and in the casting box (see below). The contents of the ladle 11 is poured into a casting box 16 which, together with its contents is weighed by a weight indicator 18, for example with known magnetostrictive emitter according to the U.S. Pat. No. 2,895,332 or other weight indicator, electronic or mechanical, and the signal from this indicator (electrical) will thus be proportional to the weight of the casting box and its contents. It is also possible to measure the melt level directly, for example with a thermoelement, photocell and light source or other known measuring means. The weight signal will then representthe level in the casting box. The use of such a signal to control a valve in a casting box is shown in Klepzig-Fachberichte 73 (I965) 3, FIG. 4.

Melt from the casting box is poured through the tapping opening 17, usually provided with a manually operated blocking rod or stop valve (not shown), to a casting mould 19 for continuous casting. A certain rough check may also be carried out by means of this stop.

FIG. 2 shows how melt 26 from the casting box 16 is poured into a liquid cooled copper mould 23, whereby a shell starts to solidify first. The solidified material is transported through a water cooler 24 for complete solidification with the help of transport rolls 25 (FIG. 3) underneath and further to a cutting means (not shown). (This technique is known per se.)

In the wall of the mould (FIG. I) are placed a ray source 20, for example for gamma rays and a receiver for these rays 22 with suitable optics 21 (all these means are known per se) and, depending on the melt level in the mould 19, more or less of these rays are absorbed so that the signal from the receiver 22 will be proportional to or in some other way dependent on the level in the casting mould (see Klepzig-Fachberichte 73, H965 FIG. 7, page 6). The level measurer according to FIG. I may be replaced by other known types of level indicators, for example according to FIG. 4 (see below).

The signals from the level indicator 20-22 and weight indicator' I8 are transmitted to a control means 27, such as a control amplifier, in which these signals are combined in a manner known per se. According to the invention the desired value for the weight, that is the level in the casting box. is modified by means of the signal for the level in the mould. Said signal may control a potentiometer the output voltage of which corresponds to said desired value. Alternatively, it is possible to subtract or add a difference voltage corresponding to the differences in mould level to a desired value voltage. Said desired value alteration may also be obtained by suitable analogy. by voltage division or by other means well known in this field. The desired level in the mould and/or level in the casting box can be manually adjusted in the control amplifier. The signal from this amplifier is transmitted to a control valve for the stop means 14. driven hydraulically, pneumatically or electrically.

If the pouring speed from the ladle II is designated v and the level in the casting box h, in principle r should be v *g* *h where g is the earth acceleration. Thus, when the level in the casting mould is too high. the level in the casting box is decreased and vice versa. The level indicator 20-22 for the mould sets the desired value for the level (11) in the casting box.

Control of the device according to FIG. 1 is carried out as follows:

Melt is tapped into the mould 19 up to a level according to FIG. I. Due to an insufficient supply of the melt the level in 19 decreases, which would incur risk of cracking if no action were taken. The level indicator 22 gives a signal indicating altered'level, the desired value on the weight indicator 18 is altered and the valve 28 receives a signal from the control amplifier 27 for increased supply of pressure medium to the servomeans' I5, and the tapping of melt from the ladle 11 increases. The level increases in the casting ladle to a new desired value and the tapping of melt to the casting mould 19 decreases so that the desired level in this is reinstated.

FIG. 4 shows an alternative embodiment. The level in the mould 19 is sensed by means of a thermoelement 29 or thermoelectric probes arid the signal is transmitted to the control amplifier 27, as well as the signal from the weight indicator 18. The different th'ermoelements 29 are in a conventional manner connected to the amplifier 27 and each element circuit has a different input voltage to said amplifier 27. The output signal from said amplifier 27 is transmitted to an electrically controlled valve 30 and pressure medium is supplied through said valve 31' in accordance withthe output ol'isai d i amplifier 27; Pressure medium is supplied to ahydraulic vomeans 32 for the blocking rod 31 and tapping from the ladle ll is controlled according to the above.

, The examples mentionedabove maybe varied in'n iany ways v within the scope of the following claims. i I T We claim:

ing device, a flow control element in said tapping device, the

output of said regulating device being dependent on the dif- ;fer ence bet-weenlth e actual weight signal and a signal for v; desiredweightin thecastingbox. said desired weight signal being depe'ndent on the signal representing theactual level in the mould and beingvariable therewith-.- said difference signal I being fed to the tapping device adjusting means'to adjust the weight of the casting box wi'th the melt therein tothe desired melt from the tapping device and a casting mould for receiving? V \the melt from thecasting box. said inould having a level in dicator, aweight indicator for the=casting box; a; regulating device, the output side of said. level indicator andr'the output side of .said weight indicator being connected to said regulat- 2. Means according to claim 'lfcharacterised in that the weight indicator comprises amagnejtostrictive emitter.

' 3. Means according to claim 1, characterized in that the weight indicator comprises an electronic weighing means.

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