JPS6056460A - Detection of abnormality in continuous casting mold - Google Patents

Abstract

PURPOSE:To detect effectively the abnormality in a casting mold and to enable prediction of generation of breakout by attaching at least two thermocouple arrays into which plural thermocouples are incorporated to the lower part of the casting mold and detecting the difference in the electromotive force between the thermocouple arrays. CONSTITUTION:Seven thermocouples 1-1-1-7 are linearly disposed at a specified pitch and are connected in series. The thermocouples are coated and molded by an insulating material 3 except the tips 2-1-2-7 at the temp. sensing parts and output leads 4 to obtain a thermocouple array 15. The thermocouple arrays 15, 15' constituted in the above-mentioned way are disposed in the lower part of a casting mold 10 consisting of water cooling boxes 10-1 and copper plates 10-2 in parallel with a billet 12 drawn from the mold by means of foot rolls 13, etc. apart at about 2-5mm. from the surface of the billet 12 so that the surface temp. of the billet 12 right under the mold 10 is made measurable. The difference in the electromotive force between said arrays 15 and 15' is detected with an amplifier 5 and the abnormality such as generation of the residual shell 11 in the mold generated owing to the defective inflow of powder is detected.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention utilizes means for measuring the powder flow state during casting or the cooling state of a slab in a continuous casting line mold to achieve uniform powder flow operation or uniform cooling percentage of the slab surface. The present invention also relates to a method for detecting an abnormality in a mold for use in preventing breakouts due to mold bleeding or seizure.

As is well known, a continuous casting line is a facility that continuously draws molten steel while continuously cooling and solidifying it in a mold. During operation, the mold is hooked during oscillation to prevent seizure between the inner wall of the mold and the slab. It is reciprocated 50 to 200 times per minute in the single drawing direction at a stator rate of about ±3 to 5 degrees, and at the same time, a powder called powder is thrown into the self-melting steel surface of the mold. The powder is melted by the heat of the molten steel and flows between the inner wall of the mold and the slab to prevent seizure, and at the same time has the function of filling the air gap caused by contraction of the slab shell and allowing uniform heat removal from the slab.

However, the inflow of the powder may become uneven,
When the powder temporarily does not flow into most of the width of the mold, the heat transfer between the water-cooled mold inner wall and the slab becomes insufficient, and the development of the solidified slab shell is delayed, causing local damage. The shell layer becomes thinner than other parts, making it easier to break.When it breaks, molten steel spews out from the bottom end of the mold, which is called a breakout, and when it does not break, vertical cracks occur on the surface of the slab. Even if the powder does not flow in a part of the width direction, the slab and the mold inner wall may seize in that area, and the solidified shell near the seized area may break, resulting in a breakout. Even if an air gap occurs locally due to contraction, if powder does not flow into that area, heat removal from that area will be inhibited, but if powder flows in, the air gap will be filled with powder. It is filled and heat can be removed well.

@ In Nashi, the above-mentioned abnormalities occur, but all of these abnormalities can be detected as temperature information, and conventionally,
In order to obtain this temperature information, many thermocouples were embedded in the molded copper plate. The copper mold plate generally has a thickness of 40 to 70 w, and after being used for a certain period of time, it is reused after being cut by about 2 to 3 #s to remove scratches and roughness on the inner wall surface of the copper mold plate.

By the way, in order to improve the responsiveness of the thermocouple when embedding it, it is necessary to bury it as deeply as possible (close to the inner wall surface of the mold). However, if you bury it deeply, 1-2
A hole was left in the 7iJ cut rl13-4c copper plate. Therefore, taking into consideration the responsiveness of the thermocouple and the number of times the mold is used, conventionally the thermocouple was embedded at a position about 10 degrees Iff from the inner wall surface of the copper plate, but even then, the lifespan was about 5 cuttings, and the number of times the mold was used.

This method has the disadvantage that the responsiveness changes because the thermocouple embedding depth changes.

The present invention aims to provide a method for detecting abnormalities within a mold that solves these drawbacks, and the method of the present invention also has the advantage of being cheaper to implement than conventional methods.

The gist of the present invention is to provide at least two thermocouple arrays in which double-broken thermocouple temperature-sensing parts are arranged at appropriate intervals and are connected in series so as to output the sum of the electromotive force of the thermocouples. Continuous casting characterized in that the thermocouple array is installed at the bottom of the mold with the temperature sensing part facing toward the surface of the slab and connected to obtain the difference in electromotive force between the thermocouple arrays, and abnormalities in the mold are detected from the magnitude VC of the difference. The problem lies in the method of detecting abnormalities within the mold.

The present invention will be explained in detail below using specific examples and drawings.

FIG. 1 is a plan view of a thermocouple array 15 (or thermocouple unit) of the present invention, and FIG. 2 is a perspective view of FIG. 1.

Thermocouples 1 (1-1 to 1-7) constituting the thermocouple play are made of copper and constancouple, for example, and the junction of the thermocouples, for example 2-1 in thermocouple 1-10, is the temperature sensing part. can be,
In the thermocouple play, the temperature sensing parts 2 (2-1 to 2-7) are arranged in a straight line at a constant pitch in the illustrated example, and each thermocouple is connected in series, so that the sum of the thermocouple outputs is It is output to the output lead wire 4. In the figure, seven thermocouples are used, but the number may be increased or decreased depending on the mold size, purpose of use, etc. The thermocouple unit 15 is coated with an insulating material 3 (
For example, parts other than the tips 2-1 to 2-7 of the temperature-sensing parts and the output lead wire 4 are coated with heat-resistant glass, ceramics, mica, glass wool, etc.).

Front views of three types of embodiments in which the thermocouple unit 15 having the above structure is disposed on the lower surface of the lower part of the continuous casting mold are shown in FIGS. 3, 4, and 5, and side views are shown in FIG. 6, respectively.

In the side view of Fig. 6, water cooling box 1O-1 and copper plate 10-2
A thermocouple unit 15 is disposed at the bottom of a mold 1θ consisting of a thermocouple unit 15 such that the tip of the temperature sensing part 2 is located parallel to the slab 12 at a distance of 2 to 5 degrees from the surface of the slab 12. This makes it possible to measure the surface temperature of the slab directly under the mold. The cooled and solidified slab 12 is transferred to the foot roll 1 directly under the mold.
3, and is continuously pulled downward by a subsequent group of guide rolls and a group of vinyl rolls (not shown).

Figure 3 shows an example in which two thermocouple units shown in Figure 2 are used, and a thermocouple unit 15°15' with the same number of temperature sensing parts is placed in the lower part of the long side of the continuous casting mold 1o. The thermocouple units 15 and 15' are arranged symmetrically with respect to the center, and are connected so that the difference in electromotive force between the thermocouple units 15 and 15' is output.

The shape of the hatched area 11 shown in the mold 10 is a typical shape of the shell remaining in the mold when breakout occurs. Third
The residual shell shown in the figure occurs when the inflow of powder is good in the left side of the center line in the casting pull direction in the mold vertical axis direction, and the powder inflow is poor in the right side of the mold. Seizing occurred between the mold and the shell.

It is thought that the shell was fractured near the burned part, and as a result, the remaining shell remained on the right side of the casting.

In the example of the present invention shown in FIG. 3, the difference in the outputs of the thermocouple units 15° and 15' arranged symmetrically at the bottom of the mold 10 is input to the amplifier 5, and when the output of the amplifier 5 is below a predetermined value, It was determined that the fleas flowed in almost uniformly between the outer surface of the shell and the inner wall of the mold in the width direction of the mold, and no breakout occurred. , Ii. Thermocouple unit 1-
When the differential output of 15.15' is above a predetermined value, it is possible to detect whether there is an abnormality in the powder flow defective area or the output value V of the amplifier.

This is because the surface temperature of the slab immediately below the mold depends on the state of flow of the nosauder between the inner wall of the mold and the slab shell. The above judgment can be made by any appropriate means such as reading the output of the amplifier or connecting it to the output signal.
This judgment is used for breakout prediction.

Figure 4 shows an example in which three thermocouple units (15, 15', 15") having the same number of thermocouples are arranged at the bottom of the mold 10 on the left, center, and right side in the width direction of the mold. 1 ot of mold.
If the remaining shell 11 at the time of a breakout is of a type in which the left and right sides are almost symmetrical as shown in the figure, in the arrangement shown in Figure 3 mentioned above, the difference in the output of the thermocouple unit) 15.15' is slight and normal. In some cases, the abnormality shown in FIG. 4 cannot be detected because it is difficult to distinguish between the abnormality and the abnormality. Abnormalities such as seizure and breakout caused by poor powder inflow approximately at the center of the mold can be detected with high accuracy by using three or more thermocouple units as shown in FIG.

The connections at the bottom of the mold in FIG. 4 are such that the thermocouple units 15 and 15', 15' and 15'' are connected to show the difference in output, and are input to A77''5.5' and output from the amplifier. When the value exceeds a predetermined value, it is determined that an abnormality has occurred.

Based on this judgment, appropriate operational actions are taken, such as changing the amount or type of flea feeder or reducing the extraction speed.

The number of thermocouple units at the bottom of the mold can be set to 10, but if the number increases, the wiring becomes complicated and multiple amplifiers are required, which impairs maintainability and increases installation costs, so it is better to reduce the number of thermocouple units. For practical purposes, dividing it into three parts is enough to achieve the purpose.

However, if the width of the mold is large, it is also effective to use 4 units as shown in Figure 5. In the case of 4 thermocouple units, thermocouple units 15 and 15', 15' and 15
", 15" and 15"' are connected to each other so as to indicate the difference in output. The difference in each output is determined by the amplifier 5.
5', 5", and when it is above the predetermined value, the example in Fig. 3,
The procedure is carried out in the same manner as in the example shown in FIG.

In the above explanation, only one side of the long side of the mold was explained (of course); in reality, the opposite long side (1!t1
A similar device is also installed at the site to monitor both sides of the slab.

Further, the temperature sensing portion of the thermocouple play is not limited to being arranged linearly, but may be arranged in a curved manner, such as on one circumference, if necessary. Furthermore, the temperature sensing parts may be arranged at appropriate intervals.

As explained above, according to the method of the present invention, at least two thermocouple arrays are arranged at the bottom of the mold. The lifespan of the copper plate is significantly increased because the thermocouple mounting hole does not penetrate through the cutting process and the lifespan of the molded copper plate is significantly increased. It is possible to predict the occurrence of a breakout.

As a result of implementing the present invention, the accuracy of detecting abnormalities in the mold, including the prediction of breakouts, has improved, and the occurrence of breakouts has been reduced by about 70% compared to the conventional method.

[Brief explanation of drawings]

FIG. 1 is a plan view of an example of a thermocouple play applied to the method of the present invention, and FIG. 2 is a perspective view of FIG. 1. Figure 3 S
4 and 5 are front views for explaining an embodiment of the method of the present invention in which a thermocouple unit is disposed at the lower end of a continuous casting mold, and FIG. 6 is a side view of the embodiment. 1 (1-1 to 1-7)...Thermocouple, 2 (2-
1-2-7)...Temperature sensing part, 3...Insulating material, 4...Lead wire extraction part, 5...Amplifier, 10... ... Mold, 10-1 ... Water cooling box, 10-2 ... Copper plate, 11 ... Residual shell in mold, 12 ... Slab , 13...
...Foot roll, 15.15', 15" 154N
・・・・・・Thermocouple unit agent Patent attorney Masaaki Akizawa 2 people Mitsugai 7t'1 Figure 4 Date of terrorist attack

Claims (1)

[Claims] (1) A plurality of thermocouple temperature-sensing parts are arranged at appropriate intervals, and at least two thermocouple arrays connected in series so as to output the sum of the electromotive force of the thermocouples are placed at the bottom of the mold in the direction of the slab surface. A method for detecting an abnormality in a continuous casting mold, characterized in that the thermocouple array is mounted with the temperature sensing part facing toward the direction of the thermocouple array, and the wiring is connected to obtain the difference in electromotive force between the thermocouple arrays, and an abnormality in the mold is detected based on the magnitude of the difference.