Patent Application
20190118249
The present invention relates to an apparatus for the automatic startup of a continuous casting line, particularly for the production of aluminum or zinc strips.
More particularly, the invention relates to a system installed in a caster for controlling the flow of metal with which the tip of the caster is fed.
Conventionally, the startup of a continuous casting machine is a completely manual operation effected by the operator, the person in charge of the caster line, until the standard production conditions are reached, which include:
1) metal level;
2) strip thickness;
3) line speed;
4) roller lubrication;
5) temperature of casting roller cooling water.
The startup of the continuous casting (caster), as well as control of the metal level, is a critical step in the operation of the system.
The startup is in fact a very delicate operation that determines the final quality of the product.
The entire operation is entrusted to the management of the line on the part of the operator, who, depending on his experience, might perform the operation more or less appropriately.
The duration of a startup is around 15-20 minutes and the operations to be performed are numerous and must be performed in a timely and sequential manner, considering the duration of the event, which is limited.
The startup of a continuous casting for aluminum or zinc consists in making liquid metal flow by means of casting channels, passing through a vessel known as a head box, which has a barrier at the end in order to prevent the access of the liquid metal to the inside of the tip while waiting for the required metal temperature to be reached (for aluminum approximately 735° C. and 470° C. for zinc), the metal is conveyed into the collection vessels (ladles).
Once the required temperature has been reached, the operator throttles the flow of metal by means of the level control (actuator), using the manual closing/opening controls that are present on the control post.
At this point the operator visually checks that the metal level that is present in the head box reaches the required level.
Once the level height has been reached, the operator prepares for removal of the manual barrier (monolith plate) arranged in the end of the head box, making the liquid metal converge toward the inlet of the tip; in this operation, which lasts approximately 20-30 seconds, the operator must pay maximum attention to correctly dosing the quantity of metal, then he must adjust the flow constantly and precisely, assisted by the commands of the operators who wait for the solid strip at the output of the caster (on the front part of is the cylinders), until the tip is completely filled.
Once the colleagues upstream of the line, who are waiting for the solidification of the strip, have given clearance, the operator who is performing the starting operation must adjust the level by means of a flow regulator (actuator) by means of the manual controls (open/close button).
During the adjustment step, the operator controls the level detected by the laser that is present above the head box.
Once the level has stabilized, the operator engages the automatic metal level adjustment control by pressing the “automatic level” button.
This function provides for the flow regulator (actuator) to enter a symbiosis with the laser, giving rise to an automatic adjustment, using the latter as feedback for the closure of the PID adjustment loop.
During casting it is necessary to complete the rest of the operations, which are:
power-on of the spraying system (graphite);
power-on of the cylinder cooling water pump.
These two operations are manually controlled by the operator.
The spraying system is fundamental in order to avoid the adhesion of the aluminum strip on the casting cylinders; graphite performs the role of release agent and also is fundamental in the first minutes of casting; an excessive or insufficient quantity would compromise the continuation of casting.
The power-on of the water pump avoids an overheating of the jacket of the steel roller, usually the water must be activated after reaching the surface temperature of the jacket, not before 200° C. in order to avoid thermal shocks to the steel, thus the operator must perform manual control, after ascertaining the temperature of the jacket he can proceed with flushing of the cooling water.
The aim of the present invention is to improve the prior art.
Within the scope of this aim, an object of the invention is to provide an apparatus which, in a continuous casting line, or caster, allows to perform the appropriate automatic adjustments in relation to the working conditions required to start the line automatically.
Another object of the present invention is to provide a reliable and safe apparatus.
This aim and these objects and others which will become better apparent hereinafter are achieved by an apparatus for the automatic starting of a continuous casting line.
Further characteristics and advantages will become better apparent from the description of preferred but not exclusive embodiments of the invention, illustrated by way of nonlimiting example in the accompanying drawings, wherein:
With reference to the cited figures, the automatic starting apparatus according to the invention, globally designated by the reference numeral 1, is inserted in a continuous casting line for the production of aluminum or zinc strips, known as caster, which is shown schematically in
The apparatus 1 according to the present invention is installed in the caster to control the flow of metal with which the nozzle, or tip, 2 is fed.
The tip 2 distributes the molten metal in a casting housing which is constituted by two casting rollers 3 and 4, which are water-cooled by means of a spraying system 5, where the molten metal is cooled and solidified to form a strip 6.
The water is provided by means of a water feeding system which includes:
an upper roller water intake, having a temperature control thermocouple 20, a flow control valve 23, and a pressure control valve 25,
a lower roller water intake having a temperature control thermocouple 21, a flow control valve 24, and a pressure control valve 26,
an upper roller water outlet having a pressure control valve 27, and a temperature control thermocouple 29,
a lower roller water outlet having a pressure control valve 28 and a temperature control thermocouple 30.
The molten metal flows in a channel 8, until it reaches a vessel 9, known as head box, which reaches the tip 2.
Ducts 15 connect the vessel 9 to molten metal collection trays 16, 17, 18.
The strip 6 then passes through a series of apparatuses which include shears 10 and a winding spool 11.
According to the present invention, the apparatus, includes a laser device 12 for controlling the level of the metal inside the vessel 9, a level control device 7, which adjusts the introduction of the liquid metal in the vessel 9 and a gate actuator 13 for the control of the gate for providing a barrier between the vessel and the mouth of the tip.
The apparatus also has a temperature transducer, constituted by a thermocouple 14, for controlling the temperature of the metal in the vessel 9, and a PLC management unit with a corresponding operator panel.
The operation of the automatic control apparatus according to the present invention is as follows.
Initially, the molten metal is made to flow into the vessel 9, the end of which is blocked by the refractory barrier, i.e., the gate, which is not visible in the figures, connected to the motorized system constituted by the gate actuator 13, until the required parameters are reached.
Once the start temperature, measured by means of the thermocouple 14, has been reached, the electronic control system sends a command to the level control device 7, which reaches a set closure position, waiting to reach the preset level, through the drain channel, which is calibrated depending on the thickness of the strip, on the widths and on the alloys.
The level of the metal, previously established by a set point, is further confirmed by means of a reading performed by the laser device 12, which actuates the gate actuator 13 so that the motorized refractory barrier opens gradually and progressively, according to a positioning profile stored previously on a work recipe.
The gate actuator is operated by a gear train having zero play connected to a brushless motor with feedback position control.
Once the filling of the tip 2 has been completed, the level of the metal in the vessel 9 is adjusted by means of an automatic system, in order to ensure a correct and continuous flow of metal toward the casting rollers 3 and 4.
During the entire starting step, the level control device 7, communicating with the laser device 12, maintains the previously entered set point, i.e. the optimum casting level.
Once the casting strip has formed, the automatic control system adjusts three other fundamental parameters: the speed of the rollers 3 and 4, the cooling water dispensed by the spraying system 5, and the release agent 5 on the cylinders.
Description of Software Management And Operation
Automatic. Startup Sequence
The procedure for automatic line startup can be performed from the operator panel and its various steps can be monitored from the same panel. After choosing a previously recorded file (work recipe) and loading it in the “Load/Save Rec Files” page, it is possible to:
start the sequence
monitor the state of advancement of the preliminary steps
monitor the advancement of the execution of the recorded file.
STEP1: The first step of the automatic startup sequence consists in fluxing the molten metal inside the channels 15 toward the collection trays 16, 17 and 18; this step is performed with the gate fully closed and the level adjustment actuator fully open; in this step, the temperature of the metal bath is monitored with the thermocouple 14.
Cast Temp: When this temperature is higher than the Tresh Temp, the procedure moves on to the next step.
Cast Temp: Display field in which the measured temperature of the metal bath is monitored.
Tresh Temp: Input field in which it is possible to set the threshold temperature for moving on to the next step of the sequence.
STEP2: The second step of the automatic startup sequence consists in waiting for the metal to continue to flux and keep its temperature constant for a specified time. If the temperature drops below the required value (Tresh Temp) during this wait time, the procedure returns to STEP 1.
Wait time: Display field in which the elapsing of the pause time is monitored.
Set time: Input field in which it is possible to set the pause time during which the metal must continue fluxing at the required temperature.
STEP3: The third step of the automatic startup sequence consists in closing the metal level, adjustment actuator 7 to a position that can be preset, so as to empty the bath to the point of interrupting the fluxing of the metal; when the actuator reaches the preset position, the procedure moves on to the next step.
Act Pos: Display field in which the position reached by the actuator is monitored so as to check the progress of the action;
Set Pos: Input field in which it is possible to set the position of the actuator for adjusting the level of metal to be reached.
STEP4: The fourth step of the automatic startup sequence consists in waiting for the level of the metal bath to drop below a preset level, which must be lower than the level of the bath fluxing drain channels; as soon as the level of the metal drops below the preset level, the procedure moves on to the next step;
Met. Lev.: Display field in which the level of the metal measured by the laser sensor is monitored.
Set Lev.: Input field in which it is possible to set the level to be reached in order to be able to move on to the next step.
STEP5: In the fifth step of the automatic startup sequence, the system starts reading the values of the main parameters that are significant for the line startup sequence, stored previously in a file, and uses them as set points of the line in the current startup step.
The parameters are sampled and recorded with a predefined interrupt time during recording, and likewise the samples are read and performed with the same interrupt time during execution, so as to faithfully repeat the entire startup process performed previously.
The main parameter that is reproduced is the position of the gate, which is opened in steps by reproducing exactly the maneuvers performed by the operator in the sampled sequence performed manually; at the same time, the system sets to automatic mode the metal level adjustment and therefore the actuator is actuated so that the level remains at the value set in the “Set Met Lev” field in the “Step 5” row. In this way, the system opens the gate gradually, causing the gradual lowering of the level of the metal, and this in turn causes the gradual opening of the metal level adjustment actuator in order to keep this level constant at the set value.
During sampling steps (work cycle recordings), the following line parameters are also monitored and recorded:
1) Roller speed 3 and 4
2) Casting roller cooling temperature
3) Upper and lower roller water flow-rate
4) Roller release agent translation speed and start 5
which are reproduced exactly in the startup step.
The management and correct holding of the water flow-rate and temperature at the casting rollers (present in the recipe) are ensured by the software management that the control unit (PLC) performs with the aid of the data that it receives from the thermocouples, flow control valves and pressure control valves, listed hereinafter:
Upper roller water intake temperature control thermocouple 20
1) Upper roller water outlet temperature control thermocouple 29;
2) Lower roller water intake temperature control thermocouple 21;
3) Lower roller water outlet temperature control thermocouple 30;
4) Upper roller water flow control valve 23;
5) Lower roller water flow control valve 24;
6) Upper roller water intake pressure control valve 25;
7) Upper roller water outlet pressure control valve 27;
8) Lower roller water intake pressure control valve 26;
9) Lower roller water outlet pressure control valve 28;
Sample in esecuz: Display field in which the sample number currently being executed in the startup sequence is displayed; the increment of this field allows to check the correct progress of the execution of the sequence.
Precond: This button allows to set the preconditions required to commence automatic startup; these preconditions are full closure of the gate (position=0) and level adjustment actuator open to at least 40%. If these conditions are met, the button becomes green and it is therefore possible to start the automatic startup sequence without pressing the button again.
START: This button allows to start the automatic startup sequence of the line;
STOP: This button allows to stop the automatic startup sequence of the line, returning the file execution index to the beginning.
RECORD STARTUP SEQUENCE: In the yellow box it is possible to store a sequence for the automatic startup of the line that has occurred with a positive outcome: it is necessary to execute the sequence manually, recording the main parameters in memory with an interrupt-based sampling, and once it has been verified that the startup has had a positive outcome it is necessary to decide to save the stored data in a file chosen at will or to delete the data.
During the manual sequence it is necessary to perform the entire fluxing step while the gate is fully closed and the actuator is fully open without starting the recording; at the end of the fluxing step the actuator is closed almost completely (it is usually left 3%-5% open in order to ensure a minimal passage of the metal) and the level of the metal decreases until the level of the drains is reached: this step, too, is not recorded; at this point it is necessary to click the “START REC” button, which will be stored without starting the recording; recording will actually start when the gate first leaves the fully closed position (height equal to 0 mm) and will last until the “STOP REC” button is clicked.
START REC: This button allows to start the startup data recording sequence; the button must be pressed after performing manually all the steps for fluxing, closure of the actuator with consequent level reduction, just before the opening of the gate; the pressing of the button will be recorded and the recording will begin only when the gate moves from the fully closed position.
STOP REC: This button allows to stop the data recording sequence.
Automatic Startup Parameters
The lower part of the screen displays all the main parameters that are important in the execution of startup; they are:
Metal level
Actuator position
Gate position
Roller speed
Casting roller cooling water temperature
Two values on two superimposed rows are presented for each one of these parameters:
SP—This is the value set by the system as adjustment set point, which is set manually when in the recording step or taken from the recording file or from the settings of steps 1-5 when in the step of execution of an automatic startup.
PV—This is the value measured by the system in real time, so that it is possible to appreciate any differences with respect to the set value.
Load/Save Recording File
When a startup sequence is recorded, its file remains in memory, ready to be saved in mass storage, until a new recording is made or the PLC is switched off; this means that a startup sequence performed manually with success and recorded can be saved to mass storage even several days after its recording and can also be saved multiple times in different paths or with different names until a new manual sequence is recorded.
Likewise, when a startup sequence is loaded from mass storage and is ready to be executed automatically, it remains in memory and can be executed again several times until a new file is loaded from mass storage or until the PLC is switched off.
Moreover, one should bear in mind that the recorded sequences to be saved in mass storage and the ones loaded from mass storage to be executed occupy separate memory spaces and therefore, loading a new sequence from mass storage does not overwrite the manually recorded sequence and likewise the recording of a new sequence performed manually does not overwrite the last sequence loaded from mass storage.
For the same reason, a recorded manual startup sequence, in order to be executed automatically, must be first saved in mass storage, and therefore must be reloaded from mass storage.
SAVE FILE
Browse: This button allows to open a pop-up dialog box which allows to select the directory where the startup file with the stored data is to be saved; the default directory in which the file is stored is in the “Recipes” directory; in this directory it is possible to create further subdirectories or delete them or move files from one subdirectory to another, so as to create a customized file organization; however, one must bear in mind that it is necessary to choose a path before saving the file, otherwise the file will not be saved; the selected path must be confirmed with the “OK” button: pressing this button closes the directory selection pop-up dialog box and displays the selected path in the alphanumeric output field located directly to the right of the “Browse” button; to exit from the pop-up dialog box without making any selection, consequently confirming the previously saved path (if one has already been chosen), press the “CANCEL” button, which closes the selection pop-up dialog box without performing any action.
New File Name: This is an alphanumeric input/output field in which it is possible to enter the name to be given to the recording file; the name entered here must not have a suffix, since the system will automatically add the “.CSV” suffix to the file name; moreover, the system will concatenate the file name entered here with the path selected in the “BROWSE” field in order to obtain the complete path of the file to be recorded.
Save: This button allows to write all the data recorded during the last startup sequence to a file chosen at will on a mass storage medium connected to the controller; before starting the writing process it is necessary to select a valid directory and enter a valid file name. The stored file is a normal text file, with the “.CSV” extension, with the individual fields separated by “;” and the individual records separated by “NEW LINE” characters; therefore, the recorded files can be read and edited easily with any text editor (for example Notepad.exe) and can be imported into any spreadsheet (for example Microsoft Excel) that supports the “.CSV” format; in this manner it is possible to eliminate and/or edit any parts of the sequence that do not meet process requirements. It is also possible to provide a graphical representation of the variables.
Writing Recipe Record: This display field shows the number of the sample being written during the step for writing to file the stored data; in this manner it is possible to monitor the progress of the writing process and check, at the end of this process, how many samples form the file.
LOAD FILE
Browse: This button allows to open a pop-up dialog box, with which it is possible to select the directory from which the startup file to be executed with the stored data is to be loaded; the default directory from which the file is stored is in the mass storage of the PLC in the “Recipes” directory, where it is possible to create additional subdirectories or delete them or move files from one subdirectory to the other, so as to create a customized file organization; once the desired path has been selected, it is necessary to select the file that one intends to read and the selection must be confirmed by means of the. “OK” button: pressing this button closes the directory selection pop-up dialog box and displays the path, complete with the file name selected in the alphanumeric output field located directly to the right of the “Browse” button; to exit from the pop-up dialog box without performing any selection and accordingly confirming the previously saved file name and path (if already chosen), press the “CANCEL” button, which will close the selection pop-up dialog box without taking any action.
Load: This button allows to read all the recorded data from the selected file; before starting the reading process, it is necessary to select a valid directory and a valid file name from the ones proposed in the selection pop-up dialog box.
Reading Recipe Record: This is a display field which shows the number of the sample being read during the step for transferring the data of the file into system memory; in this manner it is possible to monitor the advancement of the reading process and, at its end, check how many samples form the file.
It has been found in practice that the invention has achieved the intended aim and objects, providing an apparatus for the automatic start of a continuous casting line that allows to obtain some important advantages with respect to traditional systems.
The present apparatus ensures an increase in startups performed successfully and a decrease in the waste of consumables (tip, end darn, fiber).
The apparatus according to the present invention furthermore offers an increase in productivity due to the higher percentage of startups completed successfully.
The apparatus according to the invention is susceptible of numerous modifications and variations, all of which are within the scope of the inventive concept; all the details may furthermore be replaced with technically equivalent elements.
The materials used, as well as the dimensions, may of course be any according to the requirements and the state of the art.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102016000037889 | Apr 2016 | IT | national |
| UA2016A002539 | Apr 2016 | IT | national |
This application is a continuation in part of application Ser. No. 15/483,363 filed Apr. 10, 2017 and claims the priority of Italian Patent Application No. UA2016A002539 (corresponding to No. 102016000037889), filed on 13 April 2016, the subject matter of which applications is incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 15483363 | Apr 2017 | US |
| Child | 16169725 | US |
