JPH0919749A - Method for controlling cut-off of cast slab in continuous casting - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cast slab cut-off method which executes the most quick cut-off speed while holding the cut-off surface to flat without failure of the cut-off by selecting the cut-off speed having the best successful possibility completed within the limited time based on the actual result of cast slab temp. and cooling in a continuous caster, etc., and setting the cut-off speed. SOLUTION: Molten steel is poured into a mold 1 from a ladle through a tundish. The cast slab 2 come out from the mold 1 is carried to a cast slab cut-off zone under condition of perfectly solidifying with spray for cooling in a cast slab cooling zone. In the cast slab cut-off zone, a cast slab surface temp. measuring instrument 4 and a cut-off machine 5 are arranged to execute the cut-off in the optimum condition at a cut-off position 6 within the travelling range of the cut-off machine 5. In this case, the relation between the cast slab surface temp. and the cut-off speed is introduced in each cast slab thickness. The suitable cut-off speed in each temp. is set by ranking in each successful possibility, and the cut-off speed having the most successful possibility, in which the cut-off completes within the limit time till completing the cut-off regulated from the length, width and casting speed of the cast slab, is selected based on the actual cast slab temp.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention eliminates cutting failure due to uncut residue and gas blow-up in cutting slabs in continuous casting of molten metal, keeps the cut surface smooth and maximizes the cutting speed. It is for disconnection control.

[0002]

2. Description of the Related Art In continuous casting, the selection of the slab cutting speed in a cutting machine is a very important factor in ensuring stable operation and quality. The fastest slab that eliminates unsuccessful cutting due to blow-up of the gas (usually acetylene gas is used) used when cutting the slab and cutting, and while ensuring / maintaining a smooth slab cutting surface Obtaining the cutting speed is the main focus in cutting a slab. The slab cutting speed varies depending on factors such as the slab thickness, the slab temperature, and the slab cutting site. For example, when the slab temperature is low and the slab thickness is large, the optimum cutting speed by the cutting machine becomes slow. On the other hand, when the slab temperature is high and the slab thickness is thin, the optimum cutting speed by the cutting machine is high. Conventionally, automation of slab cutting control has been developed that collectively controls various slab cutting conditions that are different from each other. For example, in Japanese Unexamined Patent Publication No. 2-155552, a method in which a slab cutting machine is synchronized and automatic calculation of a slab cutting length is combined, or in slab cutting as disclosed in Japanese Unexamined Patent Publication No. 60-177944. A method of correcting the length based on information obtained from cutting scraps generated during cutting of a cast in order to automatically calculate the length is disclosed.

[0003]

However, a technique for automatically selecting the cutting speed has not been established yet, and a dedicated operator is attached to the operation of the cutting machine. Further, since the selection of the optimum speed is left to the operator's judgment, the quality of the cut surface is likely to vary. The present invention, in order to most efficiently cut the slab, cut at the optimum cutting speed according to the operating conditions, by automatically controlling the cutting speed setting conventionally entrusted to the operator, the operation The purpose is stabilization and labor saving.

[0004]

DISCLOSURE OF THE INVENTION The present invention is directed to a cutting speed at which a slab surface temperature, a cooling strength in a continuous casting machine, a passage time in the continuous casting machine and a cutting failure due to uncut material do not occur and a cutting surface is smooth. The relationship with the slab thickness is derived, the appropriate speed under each condition is set by ranking according to the success accuracy, and within the time limit for cutting, which is defined by the length, width and casting speed of the slab to be cut. This is a slab cutting method that sets the cutting speed by selecting the cutting speed with the highest success probability of completing the cutting based on the continuously measured slab temperature results and cooling results in the continuous casting machine. . Also, the slab surface temperature and slab internal temperature distribution differ greatly from other parts, but even at the same slab surface temperature, the temperature of the slab center is low and the optimum cutting speed is slower than other parts. The gist of the present invention is to use a slab cutting method in which the cutting speed is corrected to be slow depending on the part of the slab, such as before and after the iron plate, immediately before the end of casting, and in the operation abnormality occurrence part.

The present invention will be described with reference to the drawings. FIG. 1 shows the continuous casting equipment mainly in the cutting area. Molten steel is poured into the mold 1 from a ladle through a tundish (not shown). The slab 2 that has left the mold is conveyed to the slab cutting area in the slab cooling zone in the completely solidified state by the cooling spray. In the slab cutting area, a slab surface temperature measuring device 4 and a traveling cutting machine 5 are provided, and cutting is performed under optimum conditions at a cutting position 6 within the traveling range of the cutting machine. FIG. 2 shows a cutting flow in the cutting portion of the cast slab. FIG. 3 shows a method of measuring the surface temperature of the slab immediately before the cutting machine shown in FIG. 1 in the slab cutting control, and calculating the cutting speed based on that value, and FIG. It shows a table method for controlling the cutting speed based on a table created in advance in the one-side cutting control. In the calculation method shown in FIG. 3, the cutting speed that has the highest success probability among the cutting speeds at which the cutting can be completed within the traveling range of the cutting machine is calculated based on the surface temperature of the slab and the operation information about the unsteady part. Is to be set. FIG.
In the table system shown in, by selecting the maximum cutting speed that can complete the cutting within the traveling range of the cutting machine from the table of the applicable conditions based on the slab thickness, the slab cooling strength and the arrival time to the cutting machine. To be achieved.

The slab surface temperature and possible cutting speed are shown in FIG.
As the example shows, the higher the surface temperature, the faster it becomes.
By quantitatively investigating these relationships and reflecting them in cutting control, it becomes possible to automatically control the slab cutting speed. Also, FIG.
As shown in FIG. 6, the possible cutting speed is different depending on the thickness of the cast piece, and as shown in FIG. 6, the cuttable speed is also different depending on the time to reach the cutting machine and the cooling pattern of the cast piece. Furthermore, Table 1
As shown in (Relationship between the slab surface temperature at the cutting position at the unsteady part and the optimum cutting speed), the bottom crop immediately after the start of casting, the top crop at the end of the casting, and the normal steel sheet immediately after the different steel type separation iron plate charging part Surface temperature is lower than that of the part.

[0007]

[Table 1]

By comprehensively processing these and calculating the maximum speed at which cutting is possible, operating troubles are prevented and automatic control is enabled.

[0009]

EXAMPLE An example of the present invention of a series of cutting control from the start to the end of casting under the condition that a 240 mm thick slab is cooled in the continuous casting machine at a water injection ratio of 1.0 l / kg will be described. First, as shown in Table 1, the scrap slab (bottom crop) immediately after the start of casting has a lower surface temperature, so a speed slower than usual is selected, and it is confirmed whether the cutting machine completes cutting within the stroke. 2
40mm thick slab, 325mm / mi at water injection ratio 1.0l / kg
When n is first selected and, for example, a slab with a width of 2000 mm and a cutting stroke of 7 m is to be cut at a casting speed of 1.8 m / min, if the time until cutting is simple, (20
00mm ÷ (325mm / min × 2) =) About 3.1 minutes, the time limit due to the stroke of the cutting machine is (7m ÷ 1.8m
/ Min =) Approximately 3.8 minutes, and it is judged that cutting is possible, and 325 mm / min is selected as it is. If the width is the same and cutting is performed at a casting speed of 2.5 m / min, the time until cutting is (2000 mm ÷ (325 mm / min × 2) =) about 3.1 minutes within the cutting stroke. Time is (7m ÷
2.5m / min =) Approximately 2.8 minutes, it is judged that cutting is not possible, 350mm / min with low accuracy is selected, and it is judged whether cutting is possible as before. The selected cutting speed is set in the electric sequencer controlling the cutting machine, and after the end face detection of the slab, the clamping, and the cutting operation at a low speed, the speed is increased to the target speed and the cutting is performed.

Since the bottom crop cutting is completed and the normal surface temperature is maintained in the cutting of the next cast slab, Table 2
Select the cutting speed shown in (Operation example of cutting speed table).

[0011]

[Table 2]

An appropriate cutting speed of 375 mm / min in strong cooling with a water injection ratio of 1.0 l / kg is automatically selected. In this case as well, similarly to the bottom cropping, the cutting possibility is determined and the cutting speed is set. The selected cutting speed is controlled by the electric sequencer as well as the bottom crop. During continuous casting, the surface temperature of the slabs before and after the different steel type iron plate charging part was approximately 780 ° C, and the optimum cutting speed was 350 mm /
min is selected and set in the electric sequencer.

Further, due to the occurrence of operational trouble, the casting speed is reduced and the time from the mold to the cutter reaches 6
When it reaches 0 minutes, the surface temperature becomes about 800 ° C., and the optimum cutting speed of 350 mm / min is selected and set in the electric sequencer. Finally, near the scrap (top crop) at the final casting site, the surface temperature is about 750 ° C,
The optimum cutting speed of 325 mm / min is selected and set in the electric sequencer for cutting.

The control method shown above is a table-type control based on Table 2. Similarly, a method of calculating the cutting speed from the function of the slab surface temperature and the cutting speed will be described below. For example, if the slab thickness is 240 mm and the oxygen pressure of the gas cutter is 9.5 kg / cm ² , the surface temperature (T)
Then, the relationship of the formula (1) was obtained between the optimum cutting speed (V) with 100% accuracy in which the cut surface is smooth without causing uncut residue or gas blow-up.

V [mm / min] = 0.5 × T [° C.] − 50 (1) The scrap slab (bottom crop) immediately after the start of casting has a surface temperature of 750 ° C. as shown in Table 1. Therefore, the optimum cutting speed (V) is 325 mm / min, so select 325 mm / min for the electric sequencer first, and as described in the table method, perform the cutting possibility determination and then set the cutting automatically. To do.

When the bottom crop cutting is completed and the next cast piece is cut, the normal surface temperature becomes 840 ° C.
70mm / min is automatically set and cutting is performed. During continuous casting, the surface temperature of the slabs before and after the different steel type iron plate insertion portion becomes approximately 780 ° C, so 340 mm / min is automatically set and cutting is performed. In this way, the slab surface temperature immediately before the cutting machine is measured, the cutting speed is calculated based on the measured value, and the electric sequencer is automatically set to enable automatic cutting control.

[0017]

According to the present invention, it is possible to automatically set the optimum cutting speed at which the cutting surface is smooth without leaving uncut residue or gas blow-up, and it is possible to prevent operational troubles and automate the cutting work. By only monitoring the work content, it has become possible to save labor in continuous casting work.

[Brief description of the drawings]

FIG. 1 is a diagram showing an outline of a cutting machine of a continuous casting facility for carrying out the present invention.

FIG. 2 is an example of a cutting speed determination flow according to the present invention.

FIG. 3 is a diagram showing a determination logic when controlling the cutting speed as a function of a slab surface temperature.

FIG. 4 is an example of a cutting speed determination flow in a table method.

FIG. 5 is a diagram showing a relationship between a cutting speed and a surface temperature of a slab.

FIG. 6 is a diagram showing a relationship between a casting time and a slab surface temperature at a cutting machine position.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Mold 2 ... Cast piece 3 ... Cast piece cooling zone 4 ... Cast piece surface temperature measuring instrument 5 ... Cutting machine 6 ... Cutting position

Front page continuation (72) Inventor Yoichiro Orino 1 Kimitsu, Kimitsu-shi, Chiba Inside Nippon Steel Corporation Kimitsu Steel Co., Ltd. (72) Inventor Katsuhiko Hata 1 Kimitsu, Chiba Pref. Inside the steelworks

Claims (4)

[Claims] 1. A method of cutting a slab in continuous casting, wherein a relationship between a slab surface temperature and a cutting speed is derived for each slab thickness, and an appropriate cutting speed at each temperature is ranked and set according to success accuracy, The cutting speed with the highest degree of success in completing cutting within the time limit for cutting, which is defined by the length, width, and casting speed of the slab to be cut, is based on the slab temperature results that are continuously measured. A method for cutting a slab, characterized in that the cutting speed is set by selecting to. 2. In a method of cutting a slab in continuous casting, the relationship between the cooling strength in the continuous casting machine and the passage time in the continuous casting machine and the cutting speed is derived for each slab thickness, and the appropriate cutting speed at each temperature is successfully achieved. The continuous casting machine sets the cutting speed with the highest degree of success accuracy, which is set by ranking according to the accuracy and completes cutting within the time limit until the completion of cutting specified by the length, width and casting speed of the slab to be cut. The method for cutting a cast product, characterized in that the cutting speed is set by selecting based on the arrival time of the target cast product to the cutting machine, which is accumulated from the actual cooling water amount and the actual casting speed. 3. The slab surface temperature and the slab internal temperature distribution are significantly different from those of other parts, and even if the slab surface temperature is the same, the temperature of the slab center is low and the optimum cutting speed is slower than other parts. 3. The method for cutting a cast product according to claim 1 or 2, wherein the cast speed before and after the dissimilar steel plate for separating different steel types, immediately before the end of pouring, and the operation abnormality occurrence part are corrected to be slower according to the site. 4. A slab cutting control method comprising a combination of a plurality of control methods according to claim 1, 2, or 3.