JPH07204815A - Method for adjusting request specification of cast slab - Google Patents

Abstract

PURPOSE:To provide a method for adjusting a request specification of a cast slab, by which after casting charge and a molten steel ladle to be used are tied up, the specification of the charge is adjusted to reduce non-adopted slab or the adopted slab out of the request. CONSTITUTION:In the method for deciding the specification of the cast slab in a continuous casting, at the time of tying up the charge and the molten steel ladle to be used, it is checked wether the initial requested good steel quantity for cast slab is in the range of the permissible good steel quantity of this molten steel ladle or not. In the case of out of the range, the specification of the cast slab is adjusted between the charges so as to come in the range of the permissible good steel quantity of the molten steel ladle of the same kind steel as this charge and the charge in the same casting in the range of no problem on the cast slab width and the quality level, etc.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for billing materials for continuous cast slabs, and in particular, by eliminating the mismatch between the billing and the allowable range of molten steel in a molten steel ladle, the occurrence of uncollected pieces and unclaimed pieces is reduced. The present invention relates to a billing material billing method for planned integrated production on order.

[0002]

2. Description of the Related Art Conventionally, when switching to a different steel type in continuous casting, a method of forming a barrier layer by immersing a cooling member in the molten steel in a mold in order to prevent mixing of the first molten steel and the second molten steel Is proposed. In addition, JP-A-62-162
As disclosed in Japanese Patent No. 410, a tracking device tracks the seam position of a slab generated when a tundish is exchanged in continuous casting, and a seam position signal from the tracking device is input to a cutting control device. In the continuous cast piece cutting control method in which the cutting position of the cutting device is calculated and a cutting signal is sent to the cutting device to cut and remove the seam, the seaming detector is provided upstream of the cutting device to detect the seam and the tracking device recognizes it. There is known a continuous cast slab cutting method that corrects the position of the seam.

[0003]

However, in the above continuous casting of molten steel of different steel grades, the cooling member is immersed in the molten steel in the mold to prevent the mixing of the first molten steel and the second molten steel to form the barrier layer. And the continuous casting slab cutting method of correcting the recognition of the joint position of the tracking device by detecting the joint portion of the slab from the temperature difference from the normal portion in JP-A-62-162410. The position of the seam is not accurately grasped considering the amount of molten steel and the actual amount of variation is large with respect to the planned amount of molten steel. As shown in Fig. 4 (a), the amount of molten steel is less than expected. In this case, uncast slabs are generated like the A and C charges in the figure. On the contrary, when there were many achievements, unbilled pieces were generated as shown by B charge in the figure.

[0004]

In order to solve the above-mentioned problems of the prior art, the object of the present invention is to eliminate the mismatch between the demand and the allowable molten steel amount range of the molten steel ladle in the method for billing the material of continuous cast slabs. In this way, the production of uncollected pieces and uninvoiced pieces is reduced, and planned integrated production of orders is performed. The gist of the invention is to grasp the actual amount of molten steel and the falling of the ladle for each molten steel ladle, and to determine the secondary refining process of the charge to be tapped after the next time and the amount of continuous cast slabs tied with the ladle. This is a method of accurately estimating the allowable range of molten steel in the molten steel ladle and adjusting the specifications so that it falls within the allowable range of molten steel.

[0005]

The present invention will be described in detail below with reference to the drawings. FIG. 1 is a schematic view of a continuous casting apparatus used in the present invention. As shown in FIG. 1, the molten steel 1 in the ladle 2 is cast into a mold 4 through a tundish (TD) 3, and the formed slab 6 is formed by a guide roll group 5, a straightening roll 7, and a pinch roll 8. After that, the cutting device 9 is reached. Further, a tracking device 10 of the process computer is provided, a signal for generating a seam in the mold 4 is input, the progress of the mold is known by an input from the major roll 11, the position of the seam is tracked, and the signal is cut by the cutting control device 12. Output to. The cutting control device 12 calculates the length of the slab 6 and sends a cutting command for the slab 6 to the cutting device 9 when the length reaches a predetermined length. Further, based on the signal from the tracking device 10, the joint has a middle piece (hereinafter referred to as M
So that it does not come into contact with the slab, the steel plate 13 of a predetermined length is adjusted so that a cutting command is sent to the cutting device 9, which cuts and removes the seam of the slab, and cuts the normal part to a predetermined length The method of cutting is used.

Next, a surface thermometer 15 which is a detecting portion of the seam detecting device 14 is installed below the cast piece 6 on the upstream side of the cutting device 9. The setting location of the surface thermometer 15 is the cutting device 9
It is desirable to be as close to the upstream side as possible. Further, for the detection, the surface temperature of the slab 6 is continuously measured by the surface thermometer 15 and a signal is sent to the seam detection device 14. In the continuous measurement, the temperature of the seam sharply drops, and the lower limit temperature is set in advance in the seam detection device 14. Therefore, when the surface temperature becomes lower than the lower limit temperature, the seam is judged and the cutting control device 12
Send a signal to. FIG. 2 shows a pot containing molten steel. Reference numeral 16 is a pot, 17 is molten steel, and 18 is slag.

FIG. 3 is a diagram showing the relationship between the number of times the pan is used and the weight according to the present invention. As shown in Fig. 3, the weight of the empty pot decreases as the number of times the pot is used increases due to the abrasion of the bricks. By repairing the pot brick, the weight of the empty pot increases again, but it decreases with each repeated use. However, this state is repeated every time. The maximum and minimum amounts of molten steel change accordingly. The shaded area in FIG. 2 shows the ton / charge (T / CH) allowable range, which is determined by the minimum molten steel amount and the maximum molten steel amount according to the change in the weight of the pan and the constraint of the crane. In this way, the amount of molten steel poured into the pot must be changed due to the wear of the pot brick.

Next, the pan down Max and the pan down Min
Will be described. Generally, a pan is equipped with a weighing machine, and the weight at the time of placing an empty pan before tapping from the converter and the weight at the time of molten steel and slag after tapping can be measured. The amount of molten steel can be found by measuring the thickness of the slag and correcting the weight of the slag. Without a weigher, slabs cast with a continuous casting machine and crops and tundish (T
The amount of molten steel may be obtained by summing D) and the metal attached to the pot. Next, measure the falling of the pot containing the molten steel described above. From the actual data of the amount of molten steel and the pan down, the pan down Min
If the amount of molten steel is adjusted to the amount of molten steel at the time of boiling and Max at the time of pan descent, this becomes the ton / charge (T / CH) allowable range. Note that it is difficult to accurately determine the allowable range for a pot that has just been repaired, so even if variations are taken into consideration, the target range is determined with a view to safety within the operable range.

The above is carried out for each pot. Here, the allowable pan down range is determined for each secondary refining process,
For example, in the case of RH that performs vacuum degassing, the limit that the overflow does not overflow outside the pan when the immersion pipe is immersed in the pan is taken into consideration by considering the slag and molten steel surface fluctuations, and the maximum allowable lifting stroke range of the equipment is lowered. Decide as Max. An example of a pan containing 300 ton of molten steel is Min down pan, 300 mm, Max pan down, 800 mm. Also, in the powder blowing method, the limit that the molten steel and slag that are agitated according to the amount of the blown powder and the carrier gas do not overflow to the outside of the pan is the pan down Min, and the maximum allowable range of the temperature measurement and sampling device is the pan down M
Decide as ax. Powder injection speed of 200 kg / min in a 300 t molten steel pan, carrier gas A
When the flow rate of r is 2 Nm ³ / min, the pan goes down Min, 4
00 mm, Max pan down from the stroke of the sampling device and 1200 mm As described above, the pan down Min to Max is determined from the secondary refining passage process and operating conditions.

The allowable range of good steel ton / charge determined as described above is obtained, and the present invention adjusts the billing details of the cast slab according to the following procedure. That is, check whether the claims accumulated from the product line match the allowable amount of good steel ton / charge seen from the pan. If there is an excess or deficiency, the type, quality level, and
Adjust the width and area to match the capacity of the pan.
Next, if it cannot be adjusted in the same type of steel cast, or if the demanded amount is higher than the upper limit of the pot allowable amount, those exceeding the allowable amount are reserved as preliminary specifications. Then, if the amount billed is less than the pan allowable lower limit, it is checked whether the above preliminary specifications cannot be applied.

FIG. 4 shows the casting plan and actual results of casting.
It is a schematic diagram which compared the conventional method (a) and this invention (b). Therefore, according to the above procedure, as shown in FIG.
It is possible to prevent the generation of unscraped steel pieces or unclaimed pieces. FIG. 5 is a schematic diagram comparing the conventional method (a) with the present invention (b) in a slab plan and actual results. That is, Fig. 5 (b) shows the occurrence rates of unclaimed and unclaimed pieces of thin plate material before and after the method of the present invention is actually applied, and the occurrence rate is about 1/3 of that of the conventional method. It can be seen that it is decreasing.

[0012]

As described above, according to the method for adjusting the specifications of the molten steel ladle and the slab tied together according to the present invention, the number of uncollected pieces is reduced, the number of reclaims of the slab is reduced, or the number of unclaimed pieces is reduced. Has reduced the amount of inventory.

[Brief description of drawings]

FIG. 1 is a schematic view of a continuous casting apparatus used in the present invention,

FIG. 2 is a diagram showing a pan containing molten steel,

FIG. 3 is a diagram showing the relationship between the number of times the pot is used and the weight according to the present invention,

FIG. 4 is a schematic diagram comparing a conventional method (a) with the present invention (b) in a slab plan and actual results.

FIG. 5 is a diagram comparing the conventional method (a) and the method of the present invention (b) in terms of the incidence of unclaimed pieces and uncollected pieces.

[Explanation of symbols]

 1 Molten Steel 2 Ladle 3 Tundish 4 Mold 5 Guide Roll Group 6 Cast Piece 7 Straightening Roll 8 Pinch Roll 9 Cutting Device 10 Tracking Device 11 Measure Roll 12 Cutting Control Device 13 Predetermined Length Steel Piece 14 Seam Detection Device 15 Surface Thermometer 16 Pan 17 Molten Steel 18 Slag

Claims (1)

[Claims] 1. In the method for determining the details of a slab in continuous casting, when the molten steel pot used for the charge is tied, whether or not the initially billed good steel amount is within the allowable good steel amount range of the molten steel pot. If it is out of the range, within the range of the allowable good steel amount of the molten steel ladle, within the range of the same steel type as the relevant charge, and the charge in the same cast, the slab width, quality level, etc. do not matter. A method for adjusting a bill specification of a slab, comprising adjusting the bill details between charges so as to come in.