JPH10211559A - Method for continuously casting different kinds of steels and continuous caster suitable to continuous casting of different kinds of steels - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a continuous casting method of different kinds of steels which can shorten a joining waste and improve the yield by accurately controlling remained molten steel quantity in a tundish, in the case of executing the continuous casting of different kinds of steels in the condition of remaining the molten steel in the tundish at the end stage of casting the previous kind of steel by successively supplying the molten steel of the following kind of steel to cast the molten steel of the following kind of steel. SOLUTION: Before supplying the molten steel of the following kind of steel 1b into the tundish 5 at the end stage of casting the previous kind of steel 1a, the wt. of the tundish 5 is continuously measured. The remained molten steel quantity of the previous kinds of steel 1a in the tundish 5 and the joining range of the different kinds of steels to be remained, are calculated from the remained quantity of the steel and slag according to the above measured value and the pre-inputted using history (times of uses) of the tundish. Then, the molten steel of the following kind of steel 1b is supplied into the tundish 5 remaining a little quantity of molten steel of the previous kind of steel 1a so as to shift the casting of the following kind of steel 1b.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method for producing a molten steel of the first charge of the next steel type in a tundish while leaving a small amount (predetermined amount) of molten steel in the final stage of casting of the final charge of the previous steel type. And the transition to casting of the next steel type.

[0002]

2. Description of the Related Art Generally, in a continuous casting machine used for continuous casting of steel, conceptually, as shown in FIG.
The molten steel 1 is supplied to the tundish 5 from the injection nozzle 4 of the ladle 3 having the sliding nozzle 2, and the stopper 6 and the immersion nozzle 7 are supplied from the injection hole 5 n of the tundish.
And into the water-cooled mold 8.

The solidified shell 1s is formed by cooling with this mold, and the obtained cast slab 1c is supported by a large number of support rolls 9 arranged below a water-cooled mold 8, sent out while being cooled by a cooling device 10, and cut by a cutting machine. At 11, it has a structure of measuring to a predetermined length and carrying it out to the next step by the transport roll 12.

[0004] In recent years, in the field of continuous casting, orders of small lots of many steel types have been increasing, and in order to maintain high continuity of operation and high productivity, for example, several tens of charges per cast. During continuous casting in which casting is performed, continuous casting of different steel types in which dozens of steel types are continuously cast is performed.

[0005] In the case of continuous casting of different types of steel, when molten steel of the next type of steel is supplied to the tundish, the molten steel of the previous type of steel must be left in the tundish 5 at the end of casting of the previous type of steel. Since the amount of the slag 13s mixed into 1c increases and the yield decreases, the continuity of operation is impaired, and the productivity is reduced. 2 to 4 tons) leave 13 bullion
The molten steel of the next steel type is supplied in a state where i and the slag 13s are left, and the casting of the next steel type is performed.

Therefore, there is a mixture of molten steel of the preceding steel type and molten steel of the next steel type in the tundish 5, and the cast slab obtained by continuous casting has the following before and after the supply start position of the next steel type as shown in FIG. Then, a mixed portion of the previous steel type A and the next steel type B, that is, a "different steel type joint" AB is generated. This "dissimilar steel joint" AB
Does not belong to any of the steel types A and B and does not become a product, so that it is cut and removed in the cutting step. Therefore, in consideration of the product yield, it is important to minimize the length between the seam start position and the seam end position of the "different steel type seam portion" AB, that is, the seam range (seam scrap).

Conventionally, the residual molten metal amount of the preceding steel type and the joint range between different steel types are uniformly set in advance, the weight of the tundish 5 is measured by the load cell 14, and the measured value is a value corresponding to the set residual molten metal amount. , The molten steel of the next steel type is supplied to the tundish from another ladle to start casting of the next steel type, and the seam range (seam scrap) between the different steel types of the obtained slab 1c is cut by a cutting machine. 11 for cutting and removing.

However, the amount of residual hot water in the tundish 5 varies depending on the structure, capacity, and number of times of use of the tundish, and it is very difficult to properly grasp the amount of residual hot water due to the influence of the deposited metal 13i and the slag 13s. When cutting and removing at the joint length AB of dissimilar steel from AB, there is a concern that there may be cases where the joint AB of dissimilar steel cannot be cut off without fail, so the safe side remaining hot water amount and joint range are always set, As a result, cutting and removing more than necessary is performed, and the yield is reduced, which causes an increase in cost.

[0009]

DISCLOSURE OF THE INVENTION The present invention relates to a dissimilar steel type for cutting and removing the amount of residual hot metal of a preceding steel type in a tundish in a continuous casting of a dissimilar steel type in consideration of the influence of ingots and slag. Suitable for continuous casting of different steel types and continuous casting of different steel types to optimize the seam range, prevent excessive cutting and removal of different steel type joints, improve product yield and reduce factory costs To provide a continuous casting machine.

[0010]

Means for Solving the Problems The first invention of the present invention is:
With the molten steel at the end of casting of the previous steel type remaining in the tundish in a small amount, the molten steel of the next steel type is continuously supplied to shift to the casting of the next steel type. In the continuous casting method of dissimilar steel type, which is cut and removed in the process, before the molten steel of the next steel type is supplied into the tundish, the weight of the tundish is continuously measured, and the measured value and the tundish previously input are used. Calculate the amount of residual hot metal in the tundish of the previous steel type and the seam range of the different steel types to be cut and removed from the remaining amount of ingot and slag according to the usage history (number of uses) of A continuous casting method of a different steel type, characterized in that molten steel of the next steel type is supplied into the tundish to shift to casting of the next steel type.

[0011] The second invention is positioned as an example of a continuous casting machine for carrying out the first invention, wherein a small amount of molten steel in the last stage of casting of the preceding steel type is left in a tundish, A continuous casting machine suitable for continuous casting of dissimilar steel types that continuously supplies molten steel of the next steel type and shifts to casting, wherein a load cell for continuously measuring the weight of a tundish and a tundish in the tundish based on a signal from the load cell are provided. And an information input device containing tundish information such as the type of steel, the type of tundish used, the number of uses, the amount of remaining hot water by the number of uses, the seam range coefficient, and the like. A tandem calculation device having a correction screen display function for calculating the seam range by correcting the remaining hot metal amount taking into account the remaining amount of the metal and the noro based on the information of the molten steel amount and the information input device. It is characterized in that it comprises a computing device in the remaining hot water correction and different grades seam range Mesh.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, the influence of a metal or a slag based on the use history (the number of uses) for each tundish is obtained by actual results, and this is input to a process computer in advance, for example. By replacing the input information with the weight of the tundish and reflecting it in the calculation of the joint range of different steel types, the amount of remaining hot water can be accurately controlled, the length of the joint range (seam scrap) of different steel types can be shortened, and the product part of the slab Can be prevented from being excessively cut and removed, the product yield can be improved, and the factory cost can be reduced.

Conventionally, when the injection of molten steel from the inside of the tundish into the mold is completed and the tundish is emptied, the number of times the tundish is used increases, and the adhesion of metal and slag increases. It is conceptually known that when the (tare) becomes gradually heavy and a certain amount of remaining hot water is secured in the tundish, this amount needs to be taken into account. However, since the demand for small lots of multiple steel grades has not been so high, continuous casting of different steel grades is rarely performed, and the fact is that the system has not yet been systematized to a practical level.

In order to judge the possibility of systematization to a practical level, the present inventors, for each tundish used, determine the residual amount of metal and slag (including adhesion) according to the number of times the tundish is used. The number of times the tundish was used and the amount of residual hot water in the tundish (tons) were analyzed for the presence or absence of a correlation.

As a result, in the case of a tundish, for example, it has been found that there is a correlation between the amount of remaining hot water and the number of times the tundish is used, as shown in FIG. . Y = aX + b Here, Y is the amount of remaining hot water (tons) in the tundish, X is the number of uses, and a and b are coefficients for each tundish obtained by actual results. In other words, FIG. 1 shows that the residual amount (including the adhesion) of the metal and the slag increases as the number of uses increases, and in order to secure the residual hot water amount, the increased amount is added. This indicates that it is necessary to set the remaining hot water amount according to the number of times.

Therefore, in the present invention, a correction formula of the tundish weight and the seam range based on the above-mentioned correlation equation between the remaining hot water amount and the number of times of use for each tundish, which is obtained in advance based on the results, is used for each tundish. Separately, according to the operation schedule, by incorporating the remaining hot water amount based on the weight (amount of molten steel) information of the tundish containing the remaining hot water and the arithmetic formula of the seam range, the predetermined remaining hot water amount and cutting and removal are removed on the correction screen. It is intended to accurately control the range of the different steel types to be joined. Therefore, while maintaining the continuity of operation sufficiently, it is possible to secure a predetermined amount of remaining hot water with high precision and reduce the amount of remaining hot water, shorten the seam range (seam scrap length) of the previous steel type and the next steel type, and reduce the length of cutting and removing. And the product yield can be improved.

Hereinafter, an example of a continuous casting method of a different type of steel and an example of a continuous casting machine of a different type of steel according to the present invention will be described with reference to FIGS. The continuous casting machine in this embodiment is of a fixed mold type, and shows a state in which continuous casting of the preceding steel type is being performed.

In FIG. 2, reference numeral 1a denotes molten steel of the preceding steel type, which is refined in a converter (not shown) and accommodated in a ladle 3a having an injection nozzle 4 whose opening is adjusted by a sliding nozzle 2. This ladle is arranged on a tundish 5 of a continuous casting machine by a crane (not shown), and is placed on one receiving stand 16a of a turret 15 which can be moved up and down and rotatable. The molten steel 1a from the injection nozzle 4 of the ladle 3a is supplied into the tundish 5 and supplied to the water-cooled mold 8 through the stopper 6 and the immersion nozzle 7 from the injection holes arranged at the bottom of the tundish. ing.

Reference numeral 9 denotes a plurality of support rolls disposed below the water-cooled mold 8 for vertically-bending-horizontally supporting the slab 1c from the water-cooled mold 8. In addition, 11 is a cutting machine for cutting the slab 1c to a predetermined length or cutting and removing seam dust, and 12 is a transport roll.

In the method for continuously casting different types of steel according to the present invention,
With the continuous casting machine as described above, casting of the preceding steel type is first performed, and at the end of the casting, a predetermined amount of molten steel 1a of the preceding steel type is left in the tundish 5 and the tundish 5 is removed from another ladle 3b. Then, the supply of molten steel 1b of the next steel type is started, and the casting of the next steel type is performed following the casting of the previous steel type.

Therefore, it is inevitable that the molten steel 1a of the preceding steel type and the molten steel 1b of the next steel type are mixed in the tundish 5, and the slab 1c obtained by continuous casting is integrated, At the boundary between the steel type and the next steel type, a joint AB having a different component composition from the previous steel type and the next steel type is formed as shown in FIG. Since this seam portion AB does not become a product, the cutting machine 1
1, it is necessary to cut and remove, and the yield decreases as the length L of the joint portion increases.

In order to shorten the joint and prevent the yield from lowering, it is necessary to minimize the amount of residual hot water within a range that does not impair the continuity of operation. Remaining molten metal amount of molten steel 1a of previous steel type and molten steel 1b of next steel type
It is necessary to precisely manage the seam range of the.

Therefore, here, a load cell 14 for measuring the weight of the tundish 5 is provided, and the weight of the tundish 5 before supplying the molten steel 1b of the next steel type is continuously measured. The remaining hot water amount can also be obtained by subtracting the weight of the tundish 5 from the measured weight value.
Since there is a residual (including adhesion) of 3i and slag 13s, and there is a considerable difference from the actual amount of residual hot water due to this effect, the weight measurement signal from the load cell 14 is converted into a molten steel amount by a computing unit (microcomputer) 17. Input to the arithmetic unit (PROCON) 18
In order to obtain a predetermined amount of remaining hot water input to the arithmetic unit, the bullion 13i according to the number of times each tundish 5 is used is used.
And the ladle 3b when the tundish weight (the amount of molten steel) in consideration of the residual amount (including the attached amount) of the slag 13s
Then, the supply of molten steel 1b of the next steel type into the tundish 5 is started to perform casting of the next steel type.

Reference numeral 19 denotes a tundish information input device (vidicon) connected to the arithmetic unit 18, and the remaining amount of metal and slag (including adhesion) by type of steel, by type of tundish used, and by number of uses. Tundish information such as tundish weight (amount of molten steel) taking into account the amount of steel) and the coefficient of seam range (seam scrap) for calculating the seam range (seam scrap) length based on the component difference between different steel types are stored. Is input to the arithmetic unit 19 as appropriate, and the seam start position and the seam end position can be calculated based on the obtained remaining hot water amount.

FIG. 3 shows the weight (WTD) in which the residual amount (including the attached amount) of the base metal 13i and the slag 13s according to the number of times the tundish is used, which corresponds to the predetermined remaining hot water amount, and the component between different steel types. Calculation of the length (Lp) from the seam start position to the supply start position which is the seam range (seam scrap length L) based on the seam range coefficient a to d based on the difference + the seam end position (Lm) from the supply start position Here is an example of the formula.

The above-described seam range coefficients a to d are obtained in advance based on actual results. The present invention is not limited to the above example, but includes, for example, structural conditions of a ladle, a turret, a tundish, a cutting machine, etc., a tundish weight measuring means, etc., calculation of remaining hot water amount and seam range. The circuit and the like are changed according to the type of steel to be cast, the structural conditions of the continuous casting machine, the operating conditions, and the like, within a range that satisfies the components described in the claims.

[0027]

EXAMPLE Using a continuous casting machine employing the present invention as shown in FIG. 2, the present invention was applied to carry out a continuous casting operation of 1 cast and 30 charges. Table 1 shows the pouring schedule in the continuous casting operation. Here, four tundishes having different conditions (shape, type of brick, wear, number of repairs, etc. are all different) are used, For 10 steel types, 19 types of steel type switching were performed, and each time this switching was performed, the remaining hot water amount of the preceding steel type in the tundish and the range of different steel type joints were determined for each tundish,
Continuous casting of different types of steel was performed.

For example, in the above casting schedule, N
o. 2-No. No. 15 used in charge No. 15 2
The relationship between the remaining hot water amount and the number of times of use in the case of the tundish is as shown in FIG. 4, and the remaining hot water amount of the preceding steel type at the time of steel type switching was obtained from this. Further, the range of the different steel joints was determined by using a calculation formula as shown in FIG. 3 based on the residual hot water amount determined by FIG. In FIG. 4, the plot of x indicates the relationship between the remaining hot water amount obtained by the conventional method and the number of times of use, and the remaining hot water amount by the conventional method is the same as the remaining hot water amount in the present invention obtained as described above. In comparison, it is increased by about 1 t.

As described above, the present invention was applied to carry out continuous casting of different types of steel, and as a result, the amount of scrap per operation was reduced by about 0.2% as compared with the case of using the remaining amount of hot metal according to the conventional method. And the composition ratio of the following steels was not different from the conventional one.

[0030]

[Table 1]

[0031]

[Table 2]

[0032]

According to the present invention, in the case of continuous casting of different types of steel, the influence of metal and slag based on the use history of each tundish is determined by actual results, and this management information is used to measure the weight of the tundish. By reflecting the values in the values, the amount of remaining hot water and the range of seams of different steel types can be controlled accurately, and the product part of the slab can be prevented from being excessively cut and removed. Can be saved.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating the correlation between the number of times a tundish is used and the amount of residual hot water in the tundish.

FIG. 2 is a partial cross-sectional side schematic explanatory view showing an example of a different steel type continuous casting machine for implementing the present invention.

FIG. 3 is an explanatory diagram of an example of a formula for calculating a seam range (seam scrap length) based on a tundish weight and a seam range coefficient corresponding to a predetermined remaining hot water amount in the present invention.

FIG. 4 is a diagram showing a sample No. used in the embodiment of the present invention. FIG. 2 is an explanatory diagram showing the correlation between the number of uses of the tundish and the amount of residual hot water in the tundish.

FIG. 5 is a schematic side sectional explanatory view showing a structural example of a conventional continuous casting machine.

FIG. 6 is an explanatory diagram of a joint portion of a different steel type generated in a slab obtained by continuous casting of a different steel type.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Molten steel 1a Molten steel (previous steel type) 1b Molten steel (next steel type) 2 Sliding nozzle 3 Ladle 3a Ladle (for previous steel type) 3b Ladle (for next steel type) 4 Injection nozzle 5 Tundish 5n Injection hole 6 Stopper 7 Immersion nozzle Reference Signs List 8 water-cooled mold 9 support roll 10 cooling device 11 cutting machine 12 transport roll 13s noro 13i adhesion metal 14 load cell 15 turret 16a, 16b cradle 17 arithmetic unit (microcomputer) 18 arithmetic unit (procon) 19 information input unit (visicon)

Claims (2)

[Claims] In a state where a small amount of molten steel at the end of casting of a previous steel type is left in a tundish, molten steel of the next steel type is continuously supplied to shift to casting of the next steel type, and the obtained slab is mixed with a different steel type. In a dissimilar steel type continuous casting method that cuts and removes a seam portion in a subsequent process, before supplying molten steel of the next steel type into the tundish, the tundish weight is continuously measured, and this measured value is input in advance with the measured value. From the remaining amount of metal and noro according to the usage history (number of times of use) of the tundish, the amount of residual hot water in the tundish of the previous steel type and the seam range of the different steel type to be cut and removed are calculated. A continuous casting method of a different steel type, characterized in that molten steel of the next steel type is supplied into a tundish in which a small amount of residual steel has been left to shift to casting of the next steel type. 2. A continuous caster suitable for continuous casting of a different steel type, in which a small amount of molten steel at the end of casting of a previous steel type is left in a tundish while continuing to supply molten steel of the next steel type and shift to casting. A load cell that continuously measures the weight of the tundish, an arithmetic unit that calculates the amount of molten steel in the tundish based on the signal of the load cell, and a balance by steel type, used tundish, number of uses, and number of uses Based on the information input device containing the tundish information such as the amount of hot water and the seam range coefficient, and the amount of molten steel calculated by the calculator and the information from the information input device, it is corrected to the remaining hot water amount taking into account the remaining amount of the ingot and the noro. A continuous type of different steels, comprising a calculation device having a correction screen display function for calculating a joint range and calculating a remaining hot water amount in a tundish and a range of a different type of seam. Continuous casting machine suitable for casting.