PROCESS AND EQUIPMENT TO DETERMINE DISTURBANCE VARIABLES WHEN POURING MOLTEN METAL FROM A CONTAINER

Abstract: In the process to determine disturbance variables when pouring molten metal from a container (10) having an outlet channel (13), vibrations generated by the melt flowing on the container (10), respectively on its connecting parts (15, 16, 18) on the lip, are measured and the deviations from a desired vibrational characteristic are determined. From these vibrations disturbance variables such as blockages in the outlet channel, vortexes and, above all, also the outflow of slag can be detected. With this process the reliability of the pouring process can be significantly increased.

Description: Process and Ξcuipiaeπt To Determine Disturbance Variables wnun FΌUΠΠG Molten Metal From A Container The invention relates to a process to determine disturbance variables wnen pouring molten metal from a container having an outlet channel ana related equipment. When pouring molten me al, disturbance vaπaoies occur primarily in the form of vortex, discharge of slag, blockages in the outlet channel and/or due to defective, refractory material -forming the outlet channel. In known processes of publication (W0-A1 86/02583), in particular to detect slag in steel melts, voltages that are evaluated rεquency-selectively are induced by means of the transmitting and receiving coil enclosing the stream of metal melt without makinq contact. The distribution of conductivity over the cross-section of flow and from that the proportion of slag in the passing metal melt is determined from the frequency analysis of said voltages. In addition to thi 5, measurements of the changing temperature of the melt and the measuring sensors are performed that are coupled to measured values of the induced voltage spectrum. Since said transmitting and receiving coils are subject to intensive heat, on the one hand, they wear relatively rapidly, and, on the other hand, incidences that disturb normal operation cannot, therefore, be ruled out. In addition to this, this method of measurement is time-consuming and, therefore, also not reliable. The object of the present invention is to design a process and equipment of the a orementioned kind in such a manner that with said process disturbance variables can be determined reliably and quite simply. The invention solves the problem in that vibrations αenerated by means of the melt flowing on the container, respectively on its connecting parts on the iip, are measured and disturbance variables are detected from any deviations from a desired vibrational characteristic. In this manner disturbances during pouring can be determined early, and thus the efficiency during pouring can also be increased. ήt the snd of the pour when the container is almost enotv, trie vibrational characteristic shOHs an aDrupt variation witn rsEDεct r . o the cesireo characteristic from which the dιsch3rαe oτ soiten metal :s immediately stepped or after a pre-set period of tins. Thus a pouring c-f 3I30 can be avoided with certaintv and at the same time the r3sιoual melt remaining in the container can be reduced to a minimum. In a similar manner other disturbance variables such as blockaαes in trie outlet channel or the like can be determined. The equipment of the invention to carry out the process has a vibration measuring device on the container and/or on a connecting part on the container lip. Said measuring device permits disturbance variables to be detected at a distance from the melt radiating αuite intensive heat. Other advantages and an embodiment of the invention are exDlained in detail with reference to the drawing. Figure 1 is a schematic presentation of equipment of the invention on a container containing aetal melt. Figure 2 is a diagram of the vibrational characteristics as a function of time, illustrated at the eno of the pour. Fig. 1 shows a container 10 containing metal melt; said container can be, for example, a ladle containing steel melt or a tundish for continuous casting. At its suspension points 11 weighing cells to measure the weight of the container are provided that send a signal to a process control computer 30. At the lip of the container 10 15 a closing member 15, which serves to pour the Quantity of melt in 3 controlleo raanner and which is designed as a slide gate nozzle in the illustrated case. A pouring pipe 18 that is held in position oy a holding device 16 and from which the metal melt flows, for example, into a mould when the gate IS is open, is adjoined to this gate 15 so as to seal. The container 10 and the a orementioned connecting parts 15. 18 at the lio are made of refractory material in the region that makes contact with the liquid melt. The mechanical vibrations caused by the stream of the metal nelt flowing on the container 10 and on its connecting parts 15, ii, 18 are measured by a vibration measuring device 22 in wnich a conventi onai . so-called piezo-electπc accelerometer can be used. The measurinα device 22 as mounted on the pouring pipe holding device 16 in a vertical or horizontal direction so aε to be detachable. Of course, it could also be mounted directly on the pouring pipe 18, st the gate 15 anα/or 3lso on the container, aε indicated with the measuring devices 22'. A mounting on the pouring pipe changing device 16 has the advantage that when changing the container 10, thiε device 22 and its connecting lead to the measurement processor 20, 24 can be left and consequently when changing the ladle there is no need for additional assembly or disassembly work. The electrical signals of the vibrational amplitude y, measured by the measuring device 22, are fed to a process control computer 30 from an amplifier 20 via a filter 24, which has a high pass 24' and a low pass • filter 24"'. This process control computer 30 records the measured signals. It compares the vibrational character stic with a desired vibrational characteristic, from which disturbance variables are detected and, when possible disturbances occur, an alarm signal 33 and/or closing member or other means are activated. By means of the weight measurement 11 of the container 10 a signal is fed to the computer 30; from which signal said computer knows how much melt the container still contains. At the end of the pour the weight determination is used as a support to detect the outflow of slag. The actual detection of a vortex <eddy formation in the bath) and outflow of slag is performed by measuring the vibrational characteristi , as shown in Fig. 2. The actual characteristic 40 of the vibrational amplitudes y experiences an abrupt variation and thus a deviation from the desired characteristic 45, a condition that can be traced to vortex formation and to related outflow of slag. Having determined these disturbance variables, the process control computer 30 indicates an alarm 33 and the pouring stops by means of closing the gate 15, said stoppage can be delayed if, as experience has shown, the slag does not exit immediately after the abrupt variation but rather after a determinable amount of time, a state that can be determined bv means of microstructural analysis of the steel poured at the end of the pour. When the outflow is stopped, the vibration 48 drops to zero. The vibrational amplitude 40 is approximately linear as a function of the degree of opening 44 of the closing member 15, The more the gate is opened the greater the vibrational amplitude and vies versa. Another disturbance variable can occur if the outlet channel 13 is clogged, a state resulting from alumina deposits in the channel wails. The greater the accumulation of deposits, the more the amplitude of vibration is dampened. If the process control computer 30 detects such 3 dampening, an alarm is triggered and counterme^sures are initiated, for example, by blowing gas into the outlet cnanπel 13 inot illustrated) cr changing the opening position of the gate 15 for a short period of time. With this method of measurement a defect of one or more of the refractory parts 10, 15, IB enclosing the melt can be determined; said defect in turn manifests itself in a deviation of the vibrational amplitude from the desired amplitude. Thus early intervention can also occur here. The invention can be applied not merely to the arrangement illustrated in Figure 1. Detection is just as applicable to other container systems such as a free running nozzle or other closing memoer (plug).

Claims: Patent Claimε 1. Process to determine the disturbance variables when pouring molten metal from a container, having an outlet channel, in which process disturbance variables such as the outflow of slag, vortex and/or blockages in the outlet channel are detected, wherein vibrations generated by means of the melt flowing on the container (10), respectively on its connecting parts (15, 16, 18) on the lip, are measured and disturbance variables are detected from the deviations of a desired vibrational characteristic (45). 2. Process, as claimed in claim 1, wherein towards the end of the pour with almost empty container the measured vibration characteristic (40) changes abruptly due to the vortex that arises and the outflow of slag and as a result the discharge of melt is stopped immediately or after a pre-determined period of time. 3. Process, as claimed in claim 1, wherein the blockages of the outlet channel (13) cause an attenuation of the vibrational characteristic with respect to the desired characteristic; the determined and corresponding activations such as introduction of gas into the outlet channel, at the gate are a result of the short-term variation in the degree of opening or other means to alleviate the blockage. 4. Process, as claimed in claim 1, wherein the pouring process iε checked when during pouring the vibrational characteristic deviates from the desired characteristic. 5. Equipment to carry..out the process of claim 1, wherein a vibration measuring device (22) is mounted on the container (10) and/or on a connecting part (15, 16, 18) on the container lip. 6. Equipment, as claimed in claim 5, wherein the electric signal measured by the vibration measuring device (22) iε guided by means of a measurement processing device (20, 24) to a pour process control computer (30) to evaluate the measuring signal. 7. Device, 3S claimed in claim ό, wherein the measurement processing device has a signal amplifier (20) and at least one filter ( 24) to suppress the disturbance signals. 3. Equipment, as claimed in one of the claims 5 to 7, wherein the vibration measuπnq device (22) comprises at least one commercially-available pιe20-electric accelerometer. -.. Equipment, as claimed in one of the claims 5 to 8, wherein the vibration measuring device ( 22, 22') is mounted to the holding device (16) holding the pour pipe (18).

Inventors: ARDELL RICKARD, KURSFELD ARMIN, ARDELL, RICKARD, KURSFELD, ARMIN
Applicants: STOPINC AG, STOPINC AKTIENGESELLSCHAFT
Application year: 1990
Main classification: B22D37
IPC codes: B22D37