JPS5931423B2 - Slab length measurement method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention eliminates measurement errors that occur when measuring slab length using length measuring rolls, etc. at a predetermined point in time in a continuous casting machine, and accurately grasps the length of the residual pig iron slab at that point. It's about how to do it.

Compared to the agglomeration and blooming method, the continuous casting method reduces the amount of waste caused by cavities, etc., in the unit production volume, and can directly produce semi-finished products such as slabs and blooms without going through the agglomeration process. Continuous casting has the advantage of producing high yields, so the proportion of continuous casting in steel works is increasing year by year.

In addition, in order to further improve the yield which is an advantage of continuous casting, an operating method called continuous casting (or multiple continuous casting) is usually adopted in which continuous casting is performed one after another. In this continuous casting, the length of the slabs being drawn is measured and cutting is performed to minimize product loss.

In other words, the cutting length of the slab is determined by taking into account the length of the slab required by the finished product rolling process and the number of casters. The generated slabs at the melting point, the top slab at the start of casting, or the final slab at the end of casting are often scrapped or of low quality due to an increase in inclusions and other deterioration of the surface and internal quality of the slabs. It is necessary to take measures such as appropriation, and it is necessary to take this into consideration when determining the cutting position.

In addition, especially in the so-called continuous casting operation of different types of steel, in which molten steel of different types is continuously cast, in addition to the defects at the molten metal boundary described above, the slabs at the molten metal boundary are caused by molten steel of different compositions being mixed in the tundish. Since the composition will deviate from the target value, sufficient consideration must be taken in determining the cutting position.

As mentioned above, the position of the melting point can be recognized by measuring the length of the slab being pulled out, but the cutting machine that is placed downstream of the continuous casting machine generally cuts the length of the slab. This is done by integrating the pulses emitted by a rotary encoder that is installed upstream from each other and is interlocked with a length-measuring roll that rolls into contact with the slab that is being pulled out and moves.

However, errors occur in the measured values due to slippage between the length measuring roll and the slab, wear of the length measuring roll, etc., and at the end of continuous casting, the errors accumulate and, for example, the length of the pulled slab is When the distance reaches 600 to 700 m, the cumulative error becomes as much as 2 m, making it impossible to accurately recognize the hot water area.

Therefore, for the length of the slab to be disposed of or cut into a low-grade light contact section as described above, it is necessary to take into account the error in length measurement and add an amount equivalent to this, especially in the case of continuous casting of different steel types. In order to ensure safety, a large quantity had to be produced, leading to increased product loss and deterioration of yield.

The present invention has been made in view of the above circumstances, and its purpose is to replace the ladle or tundish during the ladle replacement period or tundish replacement period (the ladle replacement period or tundish replacement period means to Accurately determine the length of the remaining pig iron piece at an appropriate time when the actual molten metal level can be specified, such as during the period or at the end of replacement) or after the completion of casting, and eliminate the cumulative measurement error that has occurred up to that time. By doing so, it is possible to accurately recognize the hot melt boundary or the end of the final cast slab, and to prevent the amount of parts to be discarded or cut into low-grade light contact parts to be unnecessarily excessive, thereby improving the yield. To provide a method for measuring the length of one piece.

The slab length measuring method according to the present invention includes a separation distance 1 between a cutting machine disposed on the outlet side of a continuous casting machine and a tip of the slab located downstream of the cutting machine, and a distance between the cutting machine and the casting mold. The method is characterized in that the separation distance from the actual molten metal level is measured at a time when the actual molten metal level can be specified, and L+1 is taken as the length of the residual pig iron piece at that time.

In other words, the measured value obtained by the length measuring roll and rotary encoder up to that point is replaced with L+1.

For example, if such a data device is used at the end of tundish replacement, the slab length will be measured in the next continuous casting process using the tundish, starting from the time of replacement, and the accumulated measurement error up to that point will not be eliminated. That is.

Hereinafter, the method of the present invention will be explained in detail based on the drawings showing its implementation state.

FIG. 1 is a schematic diagram of a slab length measuring mechanism shown together with a curved continuous casting machine.

In the case of a multi-strand continuous casting machine, molten steel in a ladle 1 placed on a stand such as a dollar car (not shown) is distributed and injected into a plurality of molds 3 (only one is shown in the figure).

Slab 7 in which a solidified shell has been formed by primary cooling in mold 3
With molten steel inside, it is pulled out to a secondary cooling zone consisting of a group of support guide rolls arranged on an approximately 1/4 arc and a spray nozzle (not shown), where it undergoes forced cooling by spray water and solidification progresses. Then, it reaches an air-cooling zone consisting of a support guide roll, a straightening roll, and a pinch roll located downstream of the secondary cooling zone, and solidification is completed in the secondary cooling zone or the air-cooling zone.

The slab that has been solidified in this way is placed in an air-cooled zone, and is passed through a slab length measuring device 5 that includes a length measuring roll and a rotary encoder connected thereto. The slab length is measured and the slab length is MIJ5? When the length of the tip of the slab 7 located downstream of the cutting machine 6 (usually a gas cutting machine synchronized with the drawing speed is used) disposed downstream of the vessel 5 reaches the required length. The cutting machine 6 operates to cut the slab 7, and the tip of the cut slab 7 becomes a semi-finished product 7.
’.

The slab length measuring device 5 measures the slab 7 moving toward the cutting machine 6.
This is a known method that outputs as length measurement data a number of pulses corresponding to the amount of movement from a rotary encoder interlockingly connected to a length measuring roll that makes contact with the casting length counter 8.1 counter 9. and is input to the S counter 14.

A casting length counter 8 indicates the distance between a standard molten metal level set at an appropriate position in the mold 3 and the cutting machine 6.

A constant value obtained by subtracting the separation distance S between the cutting machine 6 and the slab length measuring device 5 from

-8, that is, the separation distance between the standard melt level position and the slab length measuring device 5 is set as an initial value (equipment length), and the casting length counter 8 indicates that the tip of the slab is the first point after the start of drawing. Counting of the passage length of the slab starts from the moment it passes through the slab length measuring device 5, adds up the above-mentioned initial value and the passage length, and calculates the sum by the process control computer (hereinafter referred to as a pro-computer) 13.
Output to.

The processing controller 13 recognizes this total value as the casting length from the start of casting.

As is clear from the above, this casting length is based on the reference molten metal surface position.

■The counter 9 is for measuring the separation distance l between the cutting machine 6 and the tip of the remaining slab located downstream of the cutting machine 6,
Counting starts from the time when the tip of the slab passes through the slab length measuring device 5 for the first time after the start of drawing.

Then, when the count value reaches S by the S counter 14 only when the tip of the slab passes, it is once reset to zero.

However, the count value of this 1 counter 9 is input to the comparator 12, but the comparator 12 also receives the "cutting length 18" corresponding to the cutting schedule from the processor 13. A match signal is emitted when the human power values match.

This coincidence signal is input to the 1 counter 9 to reset the count value to zero or as a 7-seg I signal R8T, and to the cutting machine 6 as a cutting command signal CC8.

Since such a coincidence signal is issued every time the count value of the l counter 9 and 18 match, the count value of the l counter 9 always represents the separation distance l between the tip of the remaining slab and the cutting machine 6.

By the way, in this way, the casting length and l values that are expressed as the count values of each of the casting length counters 8 and 9 are smaller than the actual values due to slipping between the length measuring roll and the slab. This includes a measurement error in which the diameter of the length-measuring roll becomes smaller due to wear, resulting in a larger value than the actual value, regardless of the l value, which is reset to zero each time the slab is cut. As a result, the casting length accumulated from the start of drawing will include a large amount of error due to the accumulation of these errors and repeated continuous casting.

Therefore, it is necessary to accurately grasp the actual molten metal level position during the ladle replacement period, the actual molten metal level position in the event of an abnormal situation such as tundish nozzle blockage, the molten metal boundary during the tundish replacement period, or the final slab at the end of casting. Determining it from the final casting length will contain many errors.

Therefore, in the present invention, the length of the residual pig iron piece at an appropriate point in time during these periods during which the actual molten metal level can be specified is accurately determined, and the length of the residual pig iron piece is made to be recognized by the program controller 13.

This is realized by the adder 10 etc. shown in FIG.

That is, the adder 10 has the output of the counter 9 as the distance l between the tip of the slab and the cutting machine 6, and the distance d( The case where the actual hot water level position a is higher than the reference hot water level position a is positive) is input over time as the output of a hot water level position sensor 4 such as an eddy current sensor attached to the mold 3, and The distance between the hot water level and the cutting machine 6.

(a constant value) is input as the value to be added, and the adder 1
0 calculates and outputs the sum of these three human forces, 1+d+Lo.

L. Since +d is equivalent to the above-mentioned L, in short, the output of the adder 10, which is changed in accordance with the changes in d and ■, is L+1.

This output L+1 is input to the processor 13 via a gate circuit 11 whose opening and closing are controlled by a gate control signal GC8.

The gate control signal GC8 is a signal that controls the gate circuit 11 to open only at the time when the length of the residual pig iron piece should be corrected and recognized.
3, but it may also be provided by a limit switch or the like that is activated by replacing the ladle 1 or tundish 2.

Therefore, the program controller 13 determines the length of the residual pig iron piece at the time when the gate control signal GC8 is issued, without being influenced by the cumulative error up to this point, and approximately accurately within the error included in the count value of the counter 9. You will recognize it.

Therefore, if the cutting schedule by the processor 13 is to be changed based on the length L+1 of the residual pig iron chip input in this way, the slab will be cut for scrapping or allocation to a low-grade material near the hot melting point or at the final end of the slab. The cutting position of the slab to be cut can be determined with significantly higher precision than in the past, and yields are greatly improved.

Furthermore, if subsequent casting length counting is performed using this correction time as a reference point, it becomes possible to perform measurements that do not include accumulated errors up to that point.

Figure 2 shows a case in which the accumulation of measurement errors is prevented by implementing the method of the present invention each time the tundish is replaced (solid line).
The cumulative measurement error between the case where the measurement error is accumulated by the conventional method (broken line) and the number of times the tundish is replaced is shown.

As is clear from this figure, in the past, errors accumulated and reached 2 m at the end of continuous casting, but by adopting the method of the present invention, the measurement error was kept to less than 0.1 m until the end of continuous casting. As a result, the method of the present invention was proven to be extremely effective.

As described above, in the method of the present invention, the cumulative error that increases due to repeated continuous casting is eliminated, and as a result, the measurement error becomes extremely small, product loss is reduced, and it has an excellent effect on improving yield. be.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIG. 1 is a schematic diagram of a slab length measuring mechanism shown together with a curved continuous casting machine, and FIG. 2 is a graph showing the effects of the method of the present invention. 1...Ladle, 2...Tanditshu,
3...mold, 4...molten metal level position sensor,
5... Slab length measuring device, 6... Cutting machine,
7... Slab, 8... Casting length counter,
9...1 counter, 10...adder,
11...Gate circuit, 12...Comparator, 13...Process control computer.

Claims (1)

[Claims] 1. A method for measuring the length of a slab produced by continuous casting operation of a continuous casting machine, comprising: a cutting machine disposed on the outlet side of the continuous casting machine; and a cutting machine located downstream of the cutting machine. The actual molten metal surface is measured at the time when it is possible to specify the separation distance from the tip of the cast slab, and the separation distance between the cutting machine and the actual molten metal surface, and the phase of both separation distances is taken as the length of the remaining pig iron piece at that point. A slab length measurement method characterized by the following. 2. The slab length measuring method according to claim 1, wherein the time point is a ladle replacement period, a tundish replacement period, or an appropriate time after the end of casting.