JP2000000608A - Weight control method of steel slab in hot direct rolling - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily and surely conduct the weight control of a steel slab without measuring the weight by cutting the continuously cast steel slab in the cut length corresponding to the prescribed weight for every plural strands, rolling it and correcting the cut length of the steel slab in accordance with the elongation length of a product after rolling. SOLUTION: A steel slab to be cast by a continuous caster 1 is divided to plural strands 7, transferred and cut to the cut length corresponding to the prescribed weight by a cutting device 2. The cut steel slab is transferred, while keeping its temp., makes reheating complete in a prescribed time and is hot- direct-rolled by a rolling device 3. Further, in accordance with the elongation length of a product after rolling, the cut length of the steel slab is corrected at the cutting devices 2 of the respective strands. By this method, without conducting the weight measurement of the steel slab, the weight control of the steel slab at the plural strands is easily and precisely conducted, the labor and time of a worker are reduced and the productivity is improved. Further, a product yield is improved as well.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for managing the weight of a billet in direct rolling. More specifically, the present invention relates to a method for managing weight of a billet in a process in which a continuous casting process and a rolling process are connected by direct feeding.

[0002]

2. Description of the Related Art Conventionally, billets, such as billets, cast by a continuous casting machine have been used for the purpose of energy saving, high yield and high productivity by using a device in which a continuous casting device and a rolling device are directly connected by a transfer line. Direct rolling methods are known.

For example, as shown in FIG. 5, a continuous rolling device described in Japanese Patent Application Laid-Open No. 57-187102 includes a continuous casting machine 51, a cutting device 52, and a rolling device 54.
Are connected to each other by a transport line. Further, there is a method in which an induction heating device or a heating furnace 53 is provided in the middle of a transport line between the cutting device 52 and the rolling device 54, and only the surface of the material is heated to a temperature required for rolling.

[0004]

SUMMARY OF THE INVENTION In continuous casting,
In order to cut a continuously produced steel slab (cast piece) to a predetermined weight, it is cut to a predetermined cutting length. At this time, the cross-sectional area of the slab changes depending on the wear of the mold or the casting speed during use at that time, and even if this is corrected, a measuring roll for measuring the length of the slab is used. Since there are many factors that cause errors such as abrasion of rolling and unevenness of rolling adjustment in a rolling process, the elongation length of a product after rolling varies, and a yield loss is usually caused.

For example, a predetermined weight (for example, 480)
kg) of a steel slab and then rolling to produce a steel bar of a predetermined length (for example, 80 m), if the steel slab is cut in excess of a predetermined weight (for example, 2 kg more), the rolled steel bar is cut. The elongation length occurs as retention loss (for example, an extra 0.3 m). Conversely, if the steel slab is cut less than the predetermined weight, and the bar after rolling is cut at a predetermined order length, a bar less than the order length occurs at the end of the bar as a yield loss. .

[0006] In order to compensate for such variation in the weight of the billet, the weight of the cut billet is measured (weighed) before rolling.
Although the accuracy of steel bill weight management is improved by correcting the cutting length of the steel billet, etc., it is impossible to measure the weight of all steel bills due to productivity problems.

[0007] The variation in the elongation length of the product causes not only a yield loss but also a failure to obtain a predetermined order length and even a delay in delivery.

Further, in the step of rolling a billet manufactured by ordinary continuous casting, when a plurality of strands are provided,
In order to control the weight of billets, it is necessary to make each billet correspond to a product obtained after rolling. For that purpose, it is necessary to set up a complicated tracking system for tracking individual billets or to perform marking of billets using identification numbers or the like.

A typical continuous casting machine has 4 to 8 strands, and quality control may be performed by tracking in charge units. Especially in the process that passes through a cold slab heating furnace, the number of pieces is very complicated, so tracking for each slab is not performed, and it is difficult to handle between the slab and the product. It is difficult to correct the weight of a billet.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and can control the weight of a slab without measuring the weight of the slab. It is an object of the present invention to provide a method for managing weight of steel slab in direct rolling, which can easily and accurately control weight of slab.

[0011]

According to the present invention, there is provided a method for managing weight of a billet in direct-feed rolling, comprising the steps of: using a continuous casting machine for casting a billet and a rolling device for rolling the billet; (A) a casting step of continuously casting a billet by the continuous casting machine, and (b) a cutting device for cutting the billet. (C) a rolling step of rolling the cut steel slab by the rolling device, wherein the continuous casting machine cuts a plurality of strands. A step of directly feeding a slab from a plurality of strands of the continuous casting machine to a rolling device within a predetermined time, and correcting a cutting length of the slab according to an elongation length of a product after rolling. It is characterized by including.

[0012]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view showing a method for managing the weight of a slab in direct rolling according to the present invention. FIG. 1 is a flowchart showing an embodiment of a direct rolling method to which the weight management method of the present invention is applied, FIG. 2 is a control flowchart for automatically executing the weight management method of the present invention, and FIG. And FIG. 4 is a partially enlarged front view showing the steel slab immediately after the continuous casting machine in FIG. 3.

As shown in FIG. 1, the direct rolling method to which the method for controlling weight of a slab of the present invention is applied is a continuous casting machine 1 for casting a slab such as a billet or a slab, and This is a continuous rolling method for producing a long steel material such as a wire rod or a steel bar using a rolling device 3 for rolling. Specifically, (a) a casting step for continuously casting a billet by the continuous casting machine 1 and (b) the billet is cut by the cutting device 2 to a cutting length corresponding to a predetermined weight. And (c) a rolling step of rolling the cut steel slab by the rolling device 3.

As shown in FIG. 3, a general continuous slab caster 1 is provided with a plurality of strands 7 and a cutting device 2 for each of the strands 7 so that the material can be fed to a predetermined length. The sheet is cut into pieces and sent to a common rolling device 3.

[0015] Continuous casting is a method for continuously producing steel slabs of a predetermined size while cooling a molten steel material sequentially from the surface. In order to obtain, the center of the material may be solidified just before cutting.

More specifically, as shown in FIG. 4, in the continuous casting machine 1, molten steel in the ladle
Then, the molten steel is poured into the mold 15 for each strand through the nozzle 13, and while the surface is solidified, the steel piece 16 is pulled out by the roller 17 while being gradually cooled by the water cooling unit 15 for secondary cooling. Continuous casting. Then, the billet 16 is cut by the cutting device 2 at a predetermined cutting length, and then conveyed to a rolling device.

The cutting length may be, for example, such that seven or more products such as steel bars can be collected from one billet 16 by rolling.

In the case of rolling without cutting after cutting, for example, at least the upper surface and the side surface of the steel slab are kept for at least 30 seconds or more by the heat retaining cover during the transportation to recover the heat. Since the slab immediately before the temperature of 3 is equal to or higher than the temperature (900 ° C.) at which the rolling can be sufficiently uniformly performed, the rolling device 3 can perform rolling without heating.

The method for managing the weight of a slab in direct-feed rolling according to the present invention is as follows. The slab is directly fed from a plurality of strands of a continuous casting machine 1 to a rolling device 3 within a predetermined time, and the elongation length of the product after rolling is determined. The cutting length of the billet is corrected accordingly.

In the present specification, the term "direct feeding" refers to transporting to a rolling mill without substantially stopping for a long time. For example, not only non-stop transport but also short-term temperature rise ( This means transfer including a step of raising the temperature to about 10 to 100 ° C. in 1 to 15 minutes.

As described above, in the process in which the steel slab made from the continuous caster is directly connected to the rolling process without passing through the heating furnace (for example, the induction heating device or the heating furnace 53 in FIG. 5), It is possible to track the billet in units of strands, to distinguish which strand is the billet, and to immediately determine the elongation length of the product for each strand.
That is, the continuous casting step and the rolling step are substantially one step. In such a process, weight control of the billet by the conventional method is unnecessary, and it has been found that it is very effective to control the elongation length of the product and the cutting length of the billet by automatic control. .

That is, the result of the elongation length of the product is reflected on the cut length of the billet, and is automatically controlled to increase or decrease.

For example, the cutting length of the steel slab is automatically adjusted based on a control flowchart as shown in FIG. 2 (specifically, a block diagram of a control unit in which the flow of the control signal is understood). That is, first, the elongation length of the product after rolling is measured by the rolling elongation length measuring device 4 (the measuring time may be before or after cutting for each product). Then
The maximum yield calculator 5 calculates a correction value of the cutting length of the steel slab which maximizes the yield based on the elongation length of the product. Finally, the cutting length of the billet is corrected by adjusting the cutting timing of the cutting device by the continuous casting cutting length transmitter 6 based on the correction value.

By the above-described method of managing the weight of the billet, the yield loss can be almost eliminated, so that the yield of the product with respect to the billet (cast slab) is improved, and the number of cuts of the unordered length is reduced. There is an economic effect.

Further, by omitting weight management such as measuring the weight of steel slabs in continuous casting, productivity can be improved, and labor for operators can be saved.

Example An example in which a deformed bar (SD22) is manufactured by directly rolling a 480 kg slab from a continuous caster having four strands will be described. At this time, the product yield was 99.4% in the conventional weight management method using only continuous casting, but in the weight management method by measuring the product length after rolling in the present invention, the product yield was 99%. 0.6%. Therefore, according to the weight management method of the present invention, the conventional method for controlling the weight is 0.1%.
There was a 2% improvement in product yield.

[0027]

According to the present invention, the weight of a slab can be controlled without measuring the weight of the slab, and even when a plurality of strands are provided, the weight of the slab in each strand can be controlled. It can be done easily and accurately.

[Brief description of the drawings]

FIG. 1 is a flowchart showing one embodiment of a direct-feed rolling method to which a weight management method of the present invention is applied.

FIG. 2 is a control flowchart for automatically implementing the weight management method of the present invention.

FIG. 3 is a plan view of a direct-feed rolling device having a plurality of strands.

FIG. 4 is a partially enlarged front view showing a steel slab immediately after the continuous casting machine in FIG. 3;

FIG. 5 is a flowchart of a conventional continuous rolling method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Continuous casting machine 2 Cutting device 3 Rolling device 16 Steel slab

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B22D 11/16 B22D 11/16 D 104Q 104 B21B 37/00 BBF (72) Inventor Kenji Soeda Kitakyushu, Fukuoka 1F, Yasuse, Wakamatsu-ku Tokai Steel Industry Co., Ltd. F-term (reference) 4E002 AA04 BD02 BD06 CB07 CB08 CB10 4E004 MC08 MC09 MC26 MD05 PA10 4E024 AA20 FF10 GG10

Claims (1)

[Claims] 1. A method for managing weight of a billet in a direct-feed rolling for producing a long steel material, using a continuous casting machine for casting a billet and a rolling device for rolling the billet. (A) a casting step of continuously casting a steel slab by the continuous casting machine; (b) a cutting step of cutting the steel slab to a cutting length corresponding to a predetermined weight by a cutting device; c) a rolling step of rolling the cut slab by the rolling device, wherein the continuous casting machine includes a plurality of strands, and the plurality of strands of the continuous casting machine is used to feed the slab to the rolling device. A weight of the slab in direct-feed rolling, comprising a step of directly feeding the slab within a predetermined time and correcting the cutting length of the slab according to the elongation length of the product after rolling.