JPH0694061B2 - Cutting method of continuous casting slab - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention is directed to a defective portion of a slab produced when a casting speed is reduced in order to prevent breakout occurring during casting in a continuous casting method. Regarding how to disconnect.

[Conventional technology]

In continuous casting, when the undeveloped shell of the solidified shell during casting breaks or the solidified shell is restrained by the mold, the molten steel flows out from the shell, causing a so-called breakout. When a breakout occurs, the operation must be stopped immediately and the recovery process must be performed, which hinders the operation.

Therefore, in order to prevent the occurrence of breakout, breakout prediction is performed on the basis of the detection result by a sensor such as a thermocouple in the mold and a mold level gauge. When a breakout is predicted by the sensor and an alarm for notifying the breakout is output, the casting speed is reduced to a predetermined value or less for a predetermined time to develop a solidified shell to prevent the breakout.

[Problems to be Solved by the Invention]

However, if the casting speed is reduced to a predetermined value or less, that portion becomes a defective slab, and there is a problem that it cannot be used as a product slab.

For this reason, the operating operator judges the defective portion of the cast piece caused by the decrease in the casting speed and cuts the portion. However, according to this method, it is necessary to give a margin to the length of the defective slab to be cut, so that there is a problem that the good slab is also cut and the yield is low.

The present invention has been made to solve such a problem, and accurately cuts a defective slab generated by reducing the casting speed to prevent breakout in continuous casting, and improves the product yield. With the goal.

[Means for Solving the Problems]

The method for cutting a continuously cast slab according to the present invention is a method for cutting a continuously cast slab for cutting a defective portion of the slab that occurs when the casting speed is reduced to prevent breakout. Detecting, based on this casting speed, the position information until the position of each part in the longitudinal direction of the slab reaches the cutting position is calculated in time series, and the casting speed decreases below a predetermined value. However, when it continues for a predetermined time or more, the portion cast during that time is regarded as a defective portion, and the defective portion may reach the cutting position based on the time-series position information of each longitudinal portion of the defective portion. It is also characterized by cutting and removing this defective portion.

[Action]

By chronologically obtaining the position information of each part in the longitudinal direction of the slab based on the casting speed during continuous casting, it is possible to accurately recognize that the defective part has reached the cutting position and cut it. Can be removed.

〔Example〕

Hereinafter, the method of the present invention will be specifically described with reference to the drawings showing an embodiment thereof.

FIG. 1 is a schematic diagram for explaining an implementation state of a method for cutting a continuously cast slab of the present invention. The molten steel 1 accommodated in the ladle 2 is temporarily stored in the tundish 3 below the ladle 2, passed through a tundish nozzle 33, and charged into a mold 4 which is vertically vibrating at a constant cycle. Molten steel 1 charged in mold 4
Are guided by guide rolls 5, 5 ... Provided below the mold 4 to form a solidified shell that is cooled and forms a solidified shell, and becomes a slab, and the pinch provided below the guide rolls 5, 5 ... The rolls 6, 6 ... Transform the 90.degree. Direction horizontally and pull it out downward. The cast slab that has been pulled out is cut into a suitable length by the fusing torch 7, and is sequentially made into individual cast slabs 8, 8.

Further, the mold 4 is provided with a temperature measuring means (not shown) such as a thermocouple, by which the mold temperature is measured and input to the breakout prediction device 17. The breakout prediction device 17 is preliminarily input with the information of the mold temperature change pattern when the breakout occurs, and the temperature abnormality is judged based on this information, and the breakout is predicted.

When the breakout prediction device 17 predicts the breakout and outputs an alarm, the operator reduces the pouring speed for a certain period of time in order to prevent the breakout, and accelerates the solidification of the molten steel.

For detecting the change in the casting speed for preventing the breakout as described above, the casting speed detection device 10 is used for the casting speed pinch roll.
Detected by the number of rotations of the drive motor 9 for driving 6, 6, ... And inputted to the breakout pouring speed decrease detecting device 13.

FIG. 2 is a graph showing changes in the pouring speed inputted to the apparatus 13, in which the vertical axis represents the pouring speed (mm / min) and the horizontal axis represents the time. Breakout Pouring speed decrease detector
In Fig. 13, the casting speed indicated by A in the figure decreases to 200 mm / min or less, and the part where it continues for 10 seconds or more is defined as the part where the defective slab has occurred, and the detection time is the breakout casting speed decrease It is input to the arithmetic and control unit 15 as a signal.

On the other hand, the number of revolutions of the major roll 11 provided along the slab pulled down by the pinch rolls 6 group is measured by the casting length counter 12, and the measured number of revolutions is input to the casting length management device 14. To do. The casting length management device 14 manages the length of the slab made of molten steel for two ladles,
The casting length is calculated from the rotation speed and input to the arithmetic and control unit 15. In the arithmetic and control unit 15, the position of each part in the longitudinal direction of the slab is calculated in time series based on the input casting speed and casting length data, and the calculated position information is sent to the cutting control unit 16. input. The cutting control device 16 tentatively determines the cutting dimension based on the input position information of each part in the longitudinal direction of the slab, and controls the torch 7 so that the slab is cut at the tentatively determined cutting dimension. On the other hand, when the break-out pouring speed decrease signal is detected by the cutting control device 16, the cutting control device 16 corrects the cutting dimension based on the time-series position information of each part in the longitudinal direction of the cast piece cast therebetween. Then, the fusing torch 7 is controlled so that the slab is cut with the corrected cutting dimension. As a result, the defective portion can be cut and removed.

Next, the signal processing procedure of the method of the present invention will be described. Third
The figure is a flow chart showing the flow of processing of the method of the present invention. First, the pouring speed is input from the pouring speed detecting device 10 to the breakout pouring speed lowering detecting device 13 for each fixed length of the slab, for example, every 10 cm. Further, the rotation speed of the major roll 11 measured by the casting length counter 12 is input to the casting length management device 14, which is converted into the casting length and input to the arithmetic and control unit 15 (S1). Based on the input data, the arithmetic and control unit 15 calculates the position of each part in the longitudinal direction of the slab in time series (S2),
It is input to the disconnection control device 16. The cutting control device 16 tentatively determines the cutting size based on the input information. on the other hand,
The breakout pouring speed detection device 13 transmits the breakout pouring speed lowering signal to the arithmetic control device 15 when the input pouring speed falls below a predetermined value and continues for a predetermined time or longer, and the arithmetic control device 15 further disconnects this device 16
Send to. When the cutting control device 16 detects this signal (S4), the cutting dimension is corrected so that the ingot cast during that time is cut and removed as a defective ingot (S5), and the corrected cutting dimension is used. The torch 7 is controlled so that the defective slab is cut (S6).

If the breakout casting speed decrease signal is not detected, the slab is cut to the tentatively determined size, and the individual slab 8,8
… Will be.

The cutting method of the continuous casting slab of the present invention described above 231 mm diameter
When the casting speed of the molten steel 1 was 1.9 to 2.6 m / min using the mold 4 of No. 4, the conventional defective slab was 2.1% mixed into the product, but it was reduced to 1.5%.

〔The invention's effect〕

As described in detail above, according to the method of the present invention, the defective portion can be automatically cut at the cutting position based on the time-series position information of each portion in the longitudinal direction of the defective portion of the cast piece, The cutting accuracy and the product yield are improved as compared with the conventional one.

[Brief description of drawings]

FIG. 1 is a schematic diagram for explaining an implementation state of a method for cutting a continuous cast product according to the present invention, FIG. 2 is a graph showing a change in casting speed, and FIG. 3 is a flowchart for the method according to the present invention. 4 ... Mold, 7 ... Cutting device, 10 ... Casting speed detector, 12 ... Casting length counter, 13 ... Breakout casting speed decrease detector, 14 ... Casting length management device, 15 ...... Arithmetic control device, 16 ...... Cutting control device

Claims (1)

[Claims] Claim: What is claimed is: 1. A continuous casting slab cutting method for cutting a defective part of a slab, which is produced when the casting speed is reduced to prevent breakout. The casting speed is detected and the casting speed is detected. Based on, while calculating the position information in time series until the position of each part in the longitudinal direction of the cast reaches the cutting position, the casting speed decreases below a predetermined value, and it continues for a predetermined time or more. In that case, the portion cast between them is regarded as a defective portion, and the defective portion is cut in accordance with the defective portion reaching the cutting position based on the time-series position information of each portion in the longitudinal direction of the defective portion, A method for cutting a continuously cast slab, which comprises removing the slab.