JP2017087254A - Breakout detection method and continuous casting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a breakout detection method by which occurrence of breakout can be detected with a high accuracy.SOLUTION: A breakout detection method including: a casting mold resistance value acquisition step at which before a molten steel in a casting mold is solidified while oscillating the casting mold and cast pieces are continuously cast, time sequence data of a first casting mold resistance value is acquired when the casting mold is oscillated in a cast piece-free state, and when continuous casting, time sequence data of a second casting mold resistance value, which is generated the casting mold and the cast piece, is acquired; a casting mold lubrication resistance value acquisition step at which time sequence data of the first casting mold resistance vale and time sequence data of the second casting mold resistance value are subtracted to thereby acquire time sequence data of a casting mold lubrication resistance value; and a determination step at which possibility of occurrence of breakout is determined based on a waveform change in an elevation zone, in which at least casting mold lubrication resistance value is elevated, among waveforms of time sequence data of the casting mold lubrication resistance value.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a breakout detection method and continuous casting method in continuous casting.

  In order to improve productivity in continuous casting, it is important to reduce operational abnormalities. In particular, since the breakout in which the solidified shell is broken and the molten steel leaks greatly hinders production, it is desired that the occurrence can be predicted at an early stage. The most typical constraining breakout among breakouts is caused by poor lubrication of the slab due to the molten steel sticking to the inner surface of the mold. Thus, it is common practice to diagnose the lubrication state of the mold and detect a constraining breakout.

  The detection of the constraining breakout is generally performed based on the mold temperature measured using a thermocouple. The detection of high-speed breakout using a thermocouple is to determine that the molten steel has come into contact with the mold due to poor lubrication by increasing the mold temperature. However, since the mold temperature fluctuates from normal, it is difficult to accurately determine an increase in the mold temperature due to molten steel contact, and many false detections or overdetections occur.

  Therefore, a method for detecting a constraining breakout based on information other than the mold temperature has been proposed. For example, Patent Document 1 compares the vibration transmission characteristics of the mold vibration system at no load with the vibration transmission characteristics at the time of continuous casting, and the lubrication state between the slab and the mold is determined based on the difference between these transmission characteristics. A method for detecting a change or abnormality is disclosed. Further, in Patent Document 2, based on the change in the hydraulic pressure difference between the push side and the push back side of the hydraulic cylinder that vibrates the mold of the continuous casting machine, there is a gap between the solidified shell of molten steel injected into the mold and the mold. A method for grasping the state of lubrication and predicting the occurrence of breakout of an unsolidified cast slab pulled out from a mold is disclosed.

JP-A-57-44456 Japanese Patent Laid-Open No. 61-52973

  However, the above-mentioned Patent Document 1 does not show specific breakout detection criteria. Moreover, in the said patent document 2, only the breakout is predicted from the average behavior of the lubrication resistance between the solidified shell and the mold, and it is difficult to detect the breakout with high accuracy.

  Accordingly, the present invention has been made in view of the above problems, and an object of the present invention is to provide a new and improved breakout detection method capable of detecting the occurrence of breakout with high accuracy. And providing a continuous casting method.

  In order to solve the above problems, according to one aspect of the present invention, the mold is vibrated in the absence of a slab before continuous casting in which the molten steel in the mold is solidified while continuously casting the slab while vibrating the mold. A mold resistance value acquisition step of acquiring time series data of the first mold resistance value at the time of performing, and acquiring time series data of a second mold resistance value generated between the mold and the slab at the time of continuous casting; A mold lubrication resistance value acquisition step for obtaining time series data of a mold lubrication resistance value by subtracting the time series data of the first mold resistance value and the time series data of the second mold resistance value, and a mold lubrication resistance value A breakout detection method comprising: a determination step for determining the possibility of occurrence of a breakout based on at least a waveform change in the rising section in which the mold lubrication resistance value is rising among the waveforms of the time series data of Is done.

  In the mold lubrication resistance value acquisition step, unit time series data segmented corresponding to one cycle of mold vibration is specified for the time series data of the first mold resistance value and the time series data of the second mold resistance value. The average value of the same number of unit time series data may be calculated, and the difference between the average values of the unit time series data may be used as the time series data of the mold lubrication resistance value.

  In the judgment step, the following equation is fitted to the waveform of the time series data of the mold lubrication resistance value at least in the rising section to calculate the powder solid phase elastic modulus, and when the powder solid phase elastic modulus changes by more than a predetermined value It may be determined that a breakout may occur.

  In the above formula, M is the constant of liquid friction between the slab and the solid phase of the mold powder, K is the powder solid phase elastic modulus, d is the vibration amplitude of the mold, ω is the vibration frequency of the mold, and φ is the mold. Deviation of phase of mold lubrication resistance value relative to vibration waveform of Vc, Vc is casting speed, Mo is a coefficient of solid friction between the slab and the solid phase of the mold powder, and α is a viscosity distribution of the liquid phase of the mold powder Coefficient.

  The powder solid phase elastic modulus may be calculated by fitting an equation based on data for one period of the mold vibration in the waveform of the time series data of the mold lubrication resistance value.

  Further, in the determination step, the lubrication resistance phase difference representing the difference between the position where the displacement in the vertical direction of the mold is the lowest end in the mold displacement waveform and the position where the waveform of the time series data of the mold lubrication resistance value is the lowest end Based on the change, the possibility of occurrence of a breakout may be determined.

  Further, in the determination step, it may be determined that there is a possibility of breakout when the slope of the waveform changes at least a predetermined value or more in the rising section of the waveform of the time series data of the mold lubrication resistance value.

  In the mold resistance value acquisition step, the mold resistance value may be acquired based on the output value of the drive device that vibrates the mold. The drive device may be, for example, a hydraulic device or a motor.

  Further, in order to solve the above problem, according to another aspect of the present invention, when it is determined that there is a possibility of occurrence of breakout by the above-described breakout detection method, the casting speed of continuous casting is reduced. A continuous casting method is provided.

  As described above, according to the present invention, occurrence of breakout can be detected with high accuracy.

It is explanatory drawing which shows the state of the slab in the casting_mold | template in the continuous casting which concerns on one Embodiment of this invention. It is explanatory drawing which shows the continuous casting lubrication model which modeled the state at the time of the continuous casting of FIG. It is explanatory drawing which shows the continuous casting lubrication state in case the solid phase of mold powder shows the state which repeats elastic deformation and plastic deformation periodically. It is explanatory drawing which shows the continuous casting lubrication state in case the solid phase of mold powder has cut | disconnected. As Example 1, the detection result (Example A) when breakout detection is performed based on the inclination of the waveform of the mold lubrication resistance value and the lubrication resistance phase difference is shown. As Example 1, the detection result (Example B) when breakout detection is performed based on the inclination of the waveform of the mold lubrication resistance value and the lubrication resistance phase difference is shown. As Example 1, a detection result (Example C) when breakout detection is performed based on the inclination of the waveform of the mold lubrication resistance value and the lubrication resistance phase difference is shown. As Example 2, the detection result in the case of performing breakout detection based on the powder solid phase elastic modulus obtained by fitting the mold lubrication resistance value to the waveform is shown.

  Exemplary embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In addition, in this specification and drawing, about the component which has the substantially same function structure, duplication description is abbreviate | omitted by attaching | subjecting the same code | symbol.

<1. Overview>
First, an outline of a breakout detection method in continuous casting according to an embodiment of the present invention will be described. The breakout detection method according to the present embodiment acquires a mold lubrication resistance value generated between a mold and a slab of a continuous casting machine, and at least the resistance value is included in time series data of the acquired mold lubrication resistance value. This is a method of determining the possibility of occurrence of a breakout by using the waveform change in the rising section that is rising.

  The time-series data of the mold lubrication resistance value is obtained by measuring the output value of the driving device that vibrates the mold of the continuous casting machine. In the breakout detection method according to the present embodiment, in order to more accurately grasp the lubrication behavior between the mold and the slab in the continuous casting machine, the resistance value generated based on the accuracy of the drive device and mechanism that vibrates the mold is removed. A process of generating time series data of the mold lubrication resistance value is performed. Further, in the time series data of the mold lubrication resistance value, a change is likely to appear when the possibility of occurrence of a breakout is increased in the increasing range of the resistance value. Therefore, in the breakout detection method according to the present embodiment, the possibility of occurrence of a breakout is determined based on at least the waveform of the resistance value increase section of the time series data. As a result, it is possible to provide an accurate breakout detection method earlier and with less overdetection or erroneous detection. Hereinafter, the breakout detection method according to the present embodiment will be described in detail.

<2. Breakout detection method>
[2-1. Mold lubrication resistance value and continuous casting lubrication model]
First, based on FIG.1 and FIG.2, the continuous casting lubrication model showing the lubrication state of the mold | die lubrication resistance value used when implementing the breakout detection method which concerns on this embodiment, and the casting_mold | template 10 and the solidification shell 5a is demonstrated. To do. FIG. 1 is an explanatory diagram showing a state of a slab in a mold in continuous casting according to the present embodiment. FIG. 2 is an explanatory view showing a continuous casting lubrication model in which the state at the time of continuous casting in FIG. 1 is modeled. In addition, in FIG. 1, the partial cross section of the casting_mold | template 10 is shown, and the molten steel which touches the inner surface of the casting_mold | template 10 shall be in the state demonstrated below based on FIG.

(1) Mold lubrication resistance value In the continuous casting machine, the mold 10 is a member that accommodates the molten steel 5 poured from a tundish (not shown) and defines the shape of a slab to be manufactured. The molten steel 5 poured into the mold 10 is solidified from a portion in contact with the mold 10 while being drawn downward, and is formed into a cast piece. Mold powder 7 is added to the inner surface of the mold 10 as a lubricant between the mold 10 and the solidified shell 5a which is a solidified portion of the molten steel 5. The mold powder 7 also has functions such as keeping the molten steel surface warm and preventing oxidation.

  The contact portion between the mold 10 and the molten steel 5 will be described in detail. As shown in FIG. 1, a mold powder 7 is interposed between the mold 10 and the molten steel. During continuous casting, the mold 10 is vibrated at a predetermined cycle in the casting direction. Thereby, mold powder 7 flows in between mold 10 and solidification shell 5a, and functions as a lubricant. The mold powder 7 exists as a solid phase 7b at the portion in contact with the mold 10 as in the addition state, but is melted by the heat of the molten steel 5 in contact between the mold 10 and the solidified shell 5a or at the surface of the molten steel. And it is the liquid phase 7a. The molten steel 5 is cooled by the mold 10 which is cooled with water and solidifies from the mold 10 side to form a solidified shell 5a. The thickness of the solidified shell 5a gradually increases toward the downstream side in the casting direction.

  Here, as shown in FIG. 1, the solid phase 7b of the mold powder 7 of the mold 10 is fixed to the mold 10 on the upstream side in the casting direction (or solid friction occurs), but on the downstream side in the casting direction. A gap Vo is generated between the template 10 and the solid phase 7b, away from the template 10. Thus, the solid phase of the mold powder 7 in the region A is caused by the periodic vibration of the mold 10 and the friction between the solid phase 7b of the mold powder 7 and the solidified shell 5a generated when the slab is pulled out. 7b repeats elastic deformation and plastic deformation. That is, the solid phase 7b of the mold powder 7 is deformed by the movement of the mold 10 and the solidified shell 5a that are in contact with the solid phase 7b.

  On the other hand, if the lubrication between the mold 10 and the solidified shell 5a is poor, there is a possibility that a breakout occurs in which the solidified shell 5a is broken and the molten steel 5 leaks. Therefore, it is considered that occurrence of breakout due to poor lubrication can be detected by detecting a change in the lubrication state between the mold 10 and the solidified shell 5a. In the breakout detection method according to the present embodiment, the lubrication state between the mold 10 and the solidified shell 5a is estimated from the resistance value of the mold 10 that vibrates at a predetermined cycle, and breakout can occur from the change in the resistance value. Detect gender.

  The resistance value of the mold 10 can be acquired based on, for example, an output value of a drive device (for example, a hydraulic device such as a hydraulic cylinder) that vibrates the mold 10. In addition to the output value of the hydraulic device, for example, the resistance value of the mold 10 can also be measured and used as a load cell or a motor output value of a cam. That is, for example, when the mold 10 is vibrated using a hydraulic device as a driving device, the hydraulic pressure is converted into a resistance value. For example, when the mold 10 is vibrated using a cam rotated by a motor as a driving device, the motor output value is converted into a resistance value.

  Here, the information contained in the output value of the drive device differs depending on the presence or absence of a slab in the mold 10. When there is no slab in the mold 10, the output value of the driving device is considered to be a resistance value generated mainly by mechanical accuracy of the driving device or a mechanism for driving the mold 10. The resistance value measured when there is no slab in the mold 10 is hereinafter also referred to as “first mold resistance value”. On the other hand, when there is a slab in the mold 10, that is, at the time of continuous casting, the output value of the drive device includes the lubrication resistance between the mold 10 and the solidified shell 5a in addition to the first mold resistance value. It is. Hereinafter, the resistance value measured when there is a slab in the mold 10 is also referred to as a “second mold resistance value”.

  In the breakout detection method according to the present embodiment, in order to grasp the lubrication state between the mold 10 and the solidified shell 5a more accurately, only the lubrication resistance between the mold 10 and the solidified shell 5a included in the second resistance value is obtained. Used to detect the possibility of breakout. That is, the possibility of occurrence of breakout is detected using a value obtained by subtracting the first mold resistance value from the second mold resistance value as the mold lubrication resistance value. More specifically, the mold lubrication resistance value is acquired as follows.

  First, a first mold resistance value is obtained when there is no slab in the mold 10. The first mold resistance value is acquired in advance before the start of continuous casting. For example, the output value of the hydraulic apparatus when the mold 10 is vibrated with a predetermined period and amplitude by the hydraulic apparatus is acquired. The first mold resistance value is acquired at a predetermined timing and is obtained as time series data.

  Next, a second mold resistance value in the case where there is a slab in the mold 10 is acquired. The second mold resistance value is acquired in advance during continuous casting, and a value used as a mold resistance value such as an output value of the hydraulic device is acquired in the same manner as the first mold resistance value. At this time, the mold 10 is vibrated at the same period and the same amplitude as when the first mold resistance value is acquired. The second mold resistance value is also acquired at a predetermined timing and is obtained as time series data. The predetermined timing of the first mold resistance value and the predetermined timing of the second mold resistance value are preferably the same, but may be different. Actually, since measurement at the same timing is difficult, the first mold resistance value and the second mold resistance value are acquired at different timings.

  Then, based on the time series data of the first mold resistance value and the second time series data, the time series data of the mold lubrication resistance value used for breakout detection is obtained. The second mold resistance value acquired during the continuous casting includes not only the lubrication resistance generated between the mold 10 and the cast slab, but also the mechanical resistance of the driving device of the continuous casting machine. In the present embodiment, in order to improve the accuracy of breakout detection, the possibility of occurrence of breakout is determined from the change in lubrication resistance that is highly related to occurrence of breakout. Therefore, the first mold resistance value time-series data and the second mold resistance value time-series data are associated with the period (that is, the vibration period of the mold 10 when these are acquired) to correspond to the first mold resistance value time-series data. A value obtained by subtracting the time series data of the second mold resistance value from the time series data of the resistance value is acquired as time series data of the mold lubrication resistance value.

  The time series data of the mold lubrication resistance value may take a difference between the time series data of the first mold resistance value and the second time series data for each period of vibration of the mold 10. Alternatively, when the waveform of each time series data is seen for each period of vibration of the mold 10, the acquired mold resistance value varies, and the waveform may not fit in a certain shape. In this case, the time series data of the mold resistance values for one period of the vibrations of the plurality of molds 10 (hereinafter, “ It is also possible to obtain the time series data of the template resistance value having a stable waveform by taking an average of “unit time series data”. The number of unit time series data used for averaging is set so that the variation of the unit time series data is equal to or less than a predetermined value.

  The variation of the unit time series data may be evaluated using, for example, standard deviation. In this case, for example, an average is taken with a preset number of unit time series data to obtain a standard deviation. If this standard deviation is larger than a predetermined value, the number of unit time series data is increased and averaged again. To take. Then, when the standard deviation is equal to or smaller than a predetermined value, the time series data of the mold lubrication resistance value is acquired using the average of the unit time series data at that time. Thus, the accuracy of breakout detection can be improved by reducing the variation in the time-series data of the mold lubrication resistance value used for evaluating the possibility of occurrence of breakout.

  When the average of a plurality of unit time series data is taken for either one of the time series data of the first mold resistance value or the time series data of the second mold resistance value, the same number of units is used for the other. An average is taken from the time series data, and the average of the unit time series data is subtracted to obtain the time series data of the mold lubrication resistance value. Usually, it is determined whether or not to take the average of the unit time series data according to the variation of the time series data of the first template resistance value acquired in advance. Accordingly, when the unit time series data is averaged for the first mold resistance value, the same number of unit time series of second template resistance values as the number of unit time series data used in the first mold resistance value is obtained. Try to average using the data.

  Through the above process, time series data of the mold lubrication resistance value is acquired.

(2) Continuous casting lubrication model As a mathematical model representing the lubrication behavior between the mold 10 and the solidified shell 5a shown in FIG. 1, for example, the continuous casting lubrication model shown in FIG. 2 is set. The continuous casting lubrication model includes a mold model 10M representing the mold 10, a slab model 5M representing a slab, and a powder model 7M connecting the mold model 10M and the slab model 5M. Powder model 7M, shooting A7M _A in contact with the template model 10M, object B7M _B in contact with the slab model 5M, and made of an elastic model 7M _K for coupling the object A7M _A and the object B7M _B.

The mold model 10M is set as an object that vibrates in the casting direction (X-axis direction) at a predetermined period. The slab model 5M is set as an object that moves to the downstream side in the casting direction (X-axis negative direction side) at a predetermined speed. The powder model 7M, the object A7M _A, by fixing the template model 10M, which the object moves together or, in accordance with the movement of the mold model 10M, move while generating the solid friction between the mold model 10M Set as an object. Further, the object B7M _B, depending on the movement of the slab model 5M, is set as a moving object while generating a solid friction or liquid friction between the slab model 5M.

  By such a continuous casting lubrication model, the state of the powder 7 that is deformed by the movement of the mold 10 and the slab 5 can be represented, and the lubrication state of the mold 10 and the slab 5 can be represented. As will be described later, the continuous casting lubrication model adapts the time series data of the mold lubrication resistance value obtained from the continuous casting machine to the model, and the solid phase elastic modulus of the mold powder 7 and the solid phase 7b of the mold powder 7 And is used for obtaining a frictional force with the slab or the mold 10.

[2-2. Continuous casting lubrication state]
Next, based on FIG. 3 and FIG. 4, the mold lubrication state, the mold vibration displacement, and the mold resistance value will be described as the continuous casting lubrication state. FIG. 3 is an explanatory diagram showing a continuous casting lubrication state when the solid phase 7b of the mold powder 7 shows a state in which elastic deformation and plastic deformation are periodically repeated. FIG. 4 is an explanatory view showing a continuous casting lubrication state when the solid phase 7b of the mold powder 7 is cut.

(1) When the mold powder solid phase undergoes elastic deformation and plastic deformation As an example of the continuous casting lubrication state, the solid phase 7b of the mold powder 7 periodically undergoes elastic deformation and plastic deformation according to the periodic vibration of the mold 10. May indicate a repeated state. As shown in the graph of FIG. 3, the solid phase 7b of the mold powder 7 takes three deformed states during one cycle of the vibration in which the mold 10 rises and falls.

First, in the section a in which the mold 10 rises, the solid phase 7b moves upward between the part in contact with the mold 10 and the part in contact with the solidified shell 5a. (Area A in FIG. 1) is elastically deformed and stretched. At this time, the mold resistance value continues to rise. When the mold resistance value becomes a predetermined value F _fri , the solid phase 7b is plastically deformed (section b). Thereafter, when the mold 10 starts to descend, the solid phase 7b moves downward between the part in contact with the mold 10 and the part in contact with the solidified shell 5a as the mold 10 descends. The area A) in FIG. 1 is elastically deformed and contracts (section c).

  During one period of such vibration of the mold 10, the solid phase 7 b of the mold powder 7 repeats the state of elastic deformation and plastic deformation.

(2) When the mold powder solid phase is cut As another example of the continuous casting lubrication state, the solid phase 7b of the mold powder 7 may be cut. In this case, as shown in FIG. The solid phase 7b behaves differently from FIG. As shown in FIG. 4, when the solid phase 7b is cut at a portion B where the portion in contact with the mold 10 and the solidified shell 5a are cut at the portion B, each portion is subjected to either vibration of the mold 10 or movement of the solidified shell 5a. Move with great influence. For this reason, the solid phase 7b elastically deforms and expands and contracts as the mold 10 moves up and down. Therefore, as shown in the graph of FIG. 4, the time series data of the mold resistance value has a waveform that rises as the mold 10 rises and falls as the mold 10 descends during one vibration period of the mold 10. .

  In the breakout detection method according to the present embodiment, the possibility of occurrence of breakout is detected not only in the continuous casting lubrication state shown in FIGS. 3 and 4 but also in other continuous casting lubrication states. Is possible.

[2-3. Judgment method]
Hereinafter, a method for determining the possibility of occurrence of a breakout according to the present embodiment will be described. In the breakout detection method according to the present embodiment, among the time series data of the mold lubrication resistance value generated between the mold and the slab of the continuous casting machine, at least the waveform change in the rising section in which the resistance value is increasing. Use this to determine the possibility of breakout. Specifically, an evaluation index for evaluating the possibility of occurrence of breakout is obtained using time series data of mold lubrication resistance values, and the possibility of occurrence of breakout is determined.

In the present embodiment, at least one of the following three is used as the evaluation index.
(A) Elastic modulus of solid phase of mold powder (B) Phase difference between mold vibration displacement waveform and mold lubrication resistance value waveform (C) Slope of mold lubrication resistance value waveform

  In the case where a plurality of evaluation indicators are used, the occurrence of a breakout may be notified when it is determined that there is a possibility of occurrence of a breakout based on at least one of the evaluation indicators. A breakout occurrence may be notified when it is determined that there is a possibility of a breakout occurrence. Hereinafter, a method for determining the possibility of occurrence of a breakout based on each evaluation index will be described.

(A) Elastic Modulus of Solid Phase of Mold Powder First, a breakout detection method in the case where the elastic modulus of the solid phase of the mold powder (hereinafter also referred to as “powder solid phase elastic modulus”) is used as an evaluation index will be described. Restraint breakout is caused by poor lubrication of the slab due to molten steel sticking to the mold inner surface. Inside the mold 10, a mold powder 7 is added as a lubricant between the mold 10 and the solidified shell 5 a. When the powder solid phase elastic modulus of the mold powder 7 is restrained, the resistance increases and the elastic modulus apparently increases. For example, in the continuous casting lubrication state of FIG. 3, when the mold 10 is raised, the solid phase 7b apparently does not substantially elastically deform. Therefore, the possibility of the occurrence of breakout is determined by using the powder solid phase elastic modulus at the time of continuous casting as an evaluation index and looking at the change in the value.

  In the present embodiment, the powder solid phase elastic modulus is obtained by fitting a mold lubrication resistance value expression represented by the following expression (1) to the waveform of the time series data of the mold lubrication resistance value.

  In the above equation (1), M is the constant of liquid friction between the slab and the solid phase of the mold powder, K is the powder solid phase elastic modulus, d is the vibration amplitude of the mold, and ω is the vibration frequency of the mold. Represent. Φ represents the phase shift of the mold lubrication resistance value waveform relative to the mold vibration waveform, and is the phase from the lowest end position of the mold vibration waveform to the lowest resistance position of the mold lubrication resistance value. The time when the mold lubrication resistance waveform precedes the mold vibration waveform is positive. Vc is the casting speed, and Mo is the solid friction coefficient between the slab and the solid phase of the mold powder. α is a coefficient reflecting the viscosity distribution of the liquid phase of the mold powder. In this embodiment, α is set to 1 because the viscosity distribution is uniform.

  In the present embodiment, the powder solid phase elastic modulus K is obtained by correlating the above equation (1) with the waveform of the time series data of the mold lubrication resistance value. At this time, the above equation (1) may be fitted to at least a portion of the waveform of the time series data of the mold lubrication resistance value where the solid phase of the mold powder is elastically deformed when the mold is raised (section a in FIG. 3). This is because, in the mold lubrication resistance value waveform, the change in the solid phase elastic deformation section when the mold rises is likely to occur when the possibility of occurrence of breakout increases. The present invention is not limited to such an example. Of the waveform of the time series data of the mold lubrication resistance value, the above formula (1) applies not only to the solid phase elastic deformation section when the mold is raised, but also to other elastic deformation sections. May be obtained so that the powder solid phase elastic modulus K is obtained.

  When the powder solid phase elastic modulus K is calculated by fitting the following formula (1) to the waveform of the time series data of the mold lubrication resistance value, the value is the average of the powder solid phase elastic modulus K calculated so far. It is determined whether or not the value exceeds a predetermined range. That is, it is determined whether or not the powder solid phase elastic modulus K obtained by the fitting of the above formula (1) has suddenly increased. Thereby, a rapid rise in the powder solid phase elastic modulus K is detected, and it is detected that the possibility of occurrence of breakout has increased. For example, when the powder solid phase elastic modulus K obtained by fitting becomes a value exceeding three times the standard deviation (3σ) with respect to the average value of the powder solid phase elastic modulus K, the possibility of occurrence of breakout It may be determined that there is.

  When it is determined by the breakout detection method that a breakout may occur, for example, by taking measures such as reducing the casting speed of continuous casting, it is possible to prevent the breakout from actually occurring. it can.

(B) Phase difference between mold vibration displacement waveform and mold lubrication resistance value waveform Next, as an evaluation index, phase difference between mold vibration displacement waveform and mold lubrication resistance value waveform (hereinafter referred to as “lubrication resistance phase difference”). A breakout detection method in the case of using also.) Will be described. The lubrication resistance phase difference corresponds to the phase difference φ between the vibration displacement waveform of the mold 10 and the waveform of the mold resistance value shown in FIG. This lubrication resistance phase difference φ is a phase from a position where the mold displacement is at the lowest end in the vibration displacement waveform of the mold 10 to a position where the mold lubrication resistance value is minimum in the mold lubrication resistance value waveform. Also in this case, the position where the mold lubrication resistance value becomes the smallest in the mold lubrication resistance value waveform can be regarded as a part of the section in which the solid phase of the mold powder undergoes elastic deformation when the mold is raised, It is considered as information representing the waveform change in the section.

  The mold 10 vibrates by driving a cam by a drive device such as a hydraulic cylinder or a motor. Therefore, the displacement of the mold 10 can be calculated by measuring the position of the hydraulic cylinder, the cam angle, and the like. By aligning the calculated displacement of the mold 10 in time series, a mold displacement waveform due to the vibration of the mold 10 is acquired, and from this, the position where the vertical displacement of the mold 10 in the mold displacement waveform is the lowest point is specified. be able to.

  The lubrication resistance phase difference φ is expressed by the following formula (2). In the following formula (2), M represents a liquid friction coefficient between the slab and the solid phase of the mold powder, K represents a powder solid phase elastic coefficient, and ω represents a vibration frequency of the mold.

  The lubrication resistance phase difference φ is a value that increases as the powder solid phase elastic modulus K increases. Therefore, the possibility of being restrained increases as the lubrication resistance phase difference φ increases. Therefore, the possibility of occurrence of breakout can be determined by using the lubrication resistance phase difference φ as an evaluation index and observing the change in the value. For example, when the lubrication resistance phase difference φ changes by π / 6 or more, it may be determined that a breakout may occur. When it is determined by the breakout detection method that a breakout may occur, for example, by taking measures such as reducing the casting speed of continuous casting, it is possible to prevent the breakout from actually occurring. it can.

(C) Slope of Waveform of Mold Lubrication Resistance Value A breakout detection method in the case of using the slope of the waveform of the mold lubrication resistance value (hereinafter also simply referred to as “slope”) as an evaluation index will be described. In the present embodiment, the slope of the mold lubrication resistance value waveform is such that the mold lubrication resistance value is at the minimum (the lowest point) in the mold lubrication resistance value waveform, and the mold lubrication resistance value is maximum from the lowest point. The slope of a straight line passing through a point (intermediate point) on the waveform of the mold lubrication resistance value at a half position of the time interval up to the position (uppermost point). It is the inclination of the straight line L shown in FIGS.

The slope of this straight line increases as the possibility of breakout increases. As described above, for example, in the continuous casting lubrication state of FIG. 3, when restraint occurs, the powder solid phase elastic modulus apparently increases, and at the same time, the friction between the solid phase 7 b and the slab increases, and the solidified shell 5 a The possibility of breakout and breakout increases. At this time, the mold lubrication resistance value has a waveform in which the section where the solid phase is elastically deformed when the mold is raised becomes shorter, and the mold lubrication resistance value becomes a predetermined value F _fri than the normal state where the possibility of breakout occurrence is low. To reach early. Therefore, when the possibility of occurrence of breakout increases, the slope of the mold lubrication resistance value waveform becomes larger than that in the normal state. Therefore, by using the inclination of the waveform of the mold lubrication resistance value as an evaluation index and looking at the change in the value, the possibility of occurrence of breakout is determined. For example, when the slope of the waveform of the mold lubrication resistance value exceeds twice the average value of the slopes calculated so far, it may be determined that a breakout may occur.

  Thus, when it is determined by the breakout detection method that there is a possibility of occurrence of a breakout, for example, by taking measures such as reducing the casting speed of continuous casting, the breakout actually occurs. Can be prevented.

[2-4. Summary]
The breakout detection method during continuous casting according to the present embodiment has been described above. According to such a breakout detection method, the mold lubrication resistance value generated between the mold and the slab of the continuous casting machine is acquired, and at least the resistance value increases in the time series data of the acquired mold lubrication resistance value. The possibility of a breakout occurrence is determined using the waveform change in the rising section. At this time, the time series data of the mold lubrication resistance value is set to the mold lubrication resistance value from which the resistance value generated based on the accuracy of the drive device and the mechanism that vibrates the mold is removed. It is possible to more accurately grasp the lubrication behavior. Further, the possibility of the occurrence of breakout is determined based on the waveform of the resistance increase section in the time series data of the mold lubrication resistance value, which is likely to change when the possibility of occurrence of breakout increases. As a result, it is possible to provide an accurate breakout detection method earlier and with less overdetection or erroneous detection.

  As Example 1, FIGS. 5 to 7 show detection results when breakout detection is performed based on the slope of the mold lubrication resistance value waveform and the lubrication resistance phase difference. In the following examples, the restrained time was derived by specifying the restrained position by examining the slab surface after the breakout occurred.

[Example A]
In Example A, the possibility of occurrence of a breakout when continuously casting a low carbon steel having a cast width of 500 mm and a cast thickness of 300 mm was determined. The casting speed was 0.8 m / min, the oscillation cycle was 60 cpm, and the oscillation stroke was 8 mm (pp). In Example A, the output value of the hydraulic device that vibrates the mold is acquired in a state where there is no slab in the mold and in a state where there is a slab in the mold, and the time series data of the first mold resistance value and the second It was used as time series data of the mold resistance value. The time series data of the mold lubrication resistance value acquired based on the time series data of the first mold resistance value and the time series data of the second mold resistance value was used as they were without performing an averaging process on the time series data. FIG. 5 shows time series data of mold lubrication resistance values at normal time, 25 seconds after restraint, and 70 seconds after restraint when breakout occurs.

The upper side of FIG. 5 shows time-series data of mold lubrication resistance values in a normal state where the possibility of breakout occurrence is low. The slope of the waveform of the mold lubrication resistance value is represented by the mold lubrication resistance at the lowest point P _L1 and a half position of the time interval from the lowest point P _L1 to the highest point P _H1 in the upper waveform of FIG. This is the slope of the straight line L ₁ passing through a point on the waveform of the value (intermediate point P _M1 ). Incidentally, also the center and the lower side of FIG. 5, for comparison with the slope of the straight line at each time described the straight line L _1.

Looking at the time series data of the mold lubricant resistance value when the result 25 seconds have elapsed the constrained state from the normal state, the straight line L ₂ at this time slope, as shown in FIG. 5 middle, in the normal state of the straight line L ₁ It is larger than the slope. The slope of the straight line L ₂ is, because it was equal to or greater than twice the slope of the straight line L ₁ in a normal state, it is determined that there is the possibility of breakout occurrence at this point. Further, the lubrication resistance phase difference corresponds to the shift of the lowest point from the normal state. The lowest point P _{L2 at} this time was shifted from the lowest point P _{L1 in the} normal state by π / 6 or more. Therefore, it was found from the lubrication resistance phase difference that breakout may occur at this point.

Then, at the time of 70 seconds after restraint breakout occurs, the slope of the straight line L _3, as shown in FIG. 5 lower, but greater than the slope of the straight line L ₁ in the normal state, the time of 25 seconds after constraining smaller than the slope of the straight line L ₂ in. In addition, regarding the lubrication resistance phase difference, the lowest point P _L3 was almost at the same position as the lowest point P _{L1 in the} normal state.

  From the result of Example A, it was shown that it was possible to detect that a breakout could occur 45 seconds before the breakout occurred.

[Example B]
In Example B, the possibility of occurrence of breakout was determined when continuously casting a low carbon steel having a cast width of 500 mm and a cast thickness of 100 mm. The casting speed was 1.0 m / min, the oscillation cycle was 60 cpm, and the oscillation stroke was 5 mm (pp). In Example B, as in Example A, the output value of the hydraulic device that vibrates the mold is acquired in a state where there is no slab in the mold and in a state where there is a slab in the mold, and each of the first mold resistance values is obtained. Time series data and second series resistance value time series data were used. The time series data averaged 10 times was used for the time series data of the mold lubrication resistance value acquired based on the time series data of the first mold resistance value and the time series data of the second mold resistance value. FIG. 6 shows time-series data of mold lubrication resistance values at normal time, 10 seconds after restraint, and 35 seconds after restraint. In Example B, a breakout occurred at 40 seconds after restraint.

The upper part of FIG. 6 shows time-series data of mold lubrication resistance values in a normal state where the possibility of breakout occurrence is low. The slope of the waveform of the mold lubrication resistance value is the mold lubrication resistance at the lower half point P _L1 and a half position of the time interval from the lowest point P _L1 to the highest point P _H1 in the upper waveform of FIG. This is the slope of the straight line L ₁ passing through a point on the waveform of the value (intermediate point P _M1 ). Also in the center and the lower side of FIG. 6, for comparison with the slope of the straight line at each time it described the straight line L _1.

Looking at the time series data of the mold lubricant resistance value when the result 10 seconds have elapsed the constrained state from the normal state, the straight line L ₂ at this time slope, as shown in FIG. 6 the center, in the normal state of the straight line L ₁ It is larger than the slope. The slope of the straight line L ₂ is, because it was equal to or greater than twice the slope of the straight line L ₁ in a normal state, it is determined that there is the possibility of breakout occurrence at this point. Further, the lubrication resistance phase difference corresponds to the shift of the lowest point from the normal state. The lowest point P _{L2 at} this time was shifted from the lowest point P _{L1 in the} normal state by π / 6 or more. Therefore, it was found from the lubrication resistance phase difference that breakout may occur at this point.

Then, 5 seconds before the breakout occurs, at the time of 35 seconds after restraint, the slope of the straight line L _3, as shown in FIG. 6 lower, but greater than the slope of the straight line L ₁ in a normal state, restraining smaller than the slope of the straight line L ₂ at the time of 10 seconds after. In addition, regarding the lubrication resistance phase difference, the lowest point P _L3 was almost at the same position as the lowest point P _L2 at 10 seconds after restraint, and was shifted by π / 6 or more from the normal state.

  From the result of Example B, it was shown that the possibility of the occurrence of a breakout can be detected 30 seconds before the occurrence of the breakout.

[Example C]
In Example C, the possibility of occurrence of a breakout when continuously casting a low carbon steel having a cast width of 500 mm and a cast thickness of 100 mm was determined. The casting speed was 1.0 m / min, the oscillation cycle was 58 cpm, and the oscillation stroke was 5 mm (pp). In Example C, the motor torque for vibrating the mold is acquired in a state where there is no slab in the mold and in a state where there is a slab in the mold, and the time series data of the first mold resistance value and the second mold resistance are respectively obtained. Used as time-series data of values. The time series data averaged 17 times was used as the time series data of the mold lubrication resistance value acquired based on the time series data of the first mold resistance value and the time series data of the second mold resistance value. FIG. 7 shows time series data of mold lubrication resistance values at normal time, 15 seconds after restraint, and 35 seconds after restraint. In Example C, a breakout occurred at 40 seconds after restraint.

The upper part of FIG. 7 shows the time series data of the mold lubrication resistance value in a normal state where the possibility of breakout occurrence is low. The slope of the waveform of the mold lubrication resistance value corresponds to the mold lubrication resistance at the lowest point P _L1 and a half position of the time interval from the lowest point P _L1 to the highest point P _H1 in the upper waveform of FIG. This is the slope of the straight line L ₁ passing through a point on the waveform of the value (intermediate point P _M1 ). Even in the middle and the lower side of FIG. 7, for comparison with the slope of the straight line at each time described the straight line L _1.

Looking at the time series data of the mold lubricant resistance value when the result 15 seconds have elapsed the constrained state from the normal state, the straight line L ₂ at this time slope, as shown in FIG. 7 center, in the normal state of the straight line L ₁ It is larger than the slope. The slope of the straight line L ₂ is, because it was equal to or greater than twice the slope of the straight line L ₁ in a normal state, it is determined that there is the possibility of breakout occurrence at this point. Further, the lubrication resistance phase difference corresponds to the shift of the lowest point from the normal state. The lowest point P _{L2 at} this time was shifted from the lowest point P _{L1 in the} normal state by π / 6 or more. Therefore, it was found from the lubrication resistance phase difference that breakout may occur at this point.

Then, 5 seconds before the breakout occurs, at the time of 35 seconds after restraint, the slope of the straight line L _3, as shown in FIG. 7 the lower, greater than the slope of the straight line L ₁ in a normal state, after constraining It was greater than the slope of the straight line L ₂ at the time of 10 seconds. In addition, regarding the lubrication resistance phase difference, the lowest point P _L3 was almost at the same position as the lowest point P _L2 at 10 seconds after restraint, and was shifted by π / 6 or more from the normal state. Therefore, it was found that a breakout may occur at the time of 35 seconds after restraint as well as at the time of 15 seconds after restraint.

  From the result of Example C, it was shown that the possibility of occurrence of breakout can be detected 25 seconds before occurrence of breakout.

  As Example 2, FIG. 8 shows the detection results when breakout detection is performed based on the powder solid phase elastic modulus obtained by fitting the mold lubrication resistance value to the waveform. In Example 2, the possibility of occurrence of breakout when continuously casting a low carbon steel having a cast width of 500 mm and a cast thickness of 300 mm was determined. The casting speed was 0.8 m / min, the oscillation cycle was 60 cpm, and the oscillation stroke was 8 mm (pp).

  In Example 2, the output value of the hydraulic device that vibrates the mold is acquired in a state where there is no slab in the mold and in a state where there is a slab in the mold, and the time-series data of the first mold resistance value and the second It was used as time series data of the mold resistance value. The time series data of the mold lubrication resistance value acquired based on the time series data of the first mold resistance value and the time series data of the second mold resistance value was used as they were without performing an averaging process on the time series data. The above formula (1) was fitted to the waveform of the time series data of the mold lubrication resistance value to obtain the powder solid phase elastic modulus. FIG. 8 shows the time change of the powder solid phase elastic modulus. The time change in FIG. 8 is represented by template oscillation. In addition, the time change of the powder solid phase elastic modulus at the time of abnormality when the possibility of occurrence of breakout increased was shown enlarged. In this enlarged view, restraint occurred at the time of cycle 0, and a breakout occurred at 63 seconds after restraint.

  As shown in FIG. 8, the elastic modulus shows a substantially constant value at the normal time when the possibility of breakout occurrence is low. Thereafter, when the restraint state was reached, as shown in the enlarged view of FIG. 8, the value of the powder solid phase elastic modulus suddenly increased and exceeded a predetermined range of 3σ. Specifically, the average value of the powder solid phase elastic modulus at normal time was 1.9E + 06 and the standard deviation σ was 4.8E + 05, but the powder solid phase elastic modulus at the time of abnormality was 734 times the standard deviation σ. It was. In this example, it was determined that there was a possibility of occurrence of breakout when the standard deviation σ exceeded 3 times, and it was found that anomaly could be detected 30 seconds before the breakout occurred.

  The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to such examples. It is obvious that a person having ordinary knowledge in the technical field to which the present invention pertains can come up with various changes or modifications within the scope of the technical idea described in the claims. Of course, it is understood that these also belong to the technical scope of the present invention.

5 Molten steel 5a Solidified shell 7 Mold powder 7a (Mold powder) Liquid phase 7b (Mold powder) Solid phase 10 Mold

Claims (9)

Time series data of the first mold resistance value when the mold is vibrated in the absence of a slab before continuous casting in which the molten steel in the mold is solidified while vibrating the mold to continuously cast the slab. A mold resistance value acquisition step for acquiring and acquiring time series data of a second mold resistance value generated between the mold and the slab during continuous casting;
A mold lubrication resistance value obtaining step for obtaining time series data of a mold lubrication resistance value by subtracting the time series data of the first mold resistance value and the time series data of the second mold resistance value;
A determination step of determining the possibility of occurrence of breakout based on at least a waveform change in the rising section in which the mold lubrication resistance value is rising among the waveforms of the time series data of the mold lubrication resistance value;
A breakout detection method including: In the mold lubrication resistance value acquisition step,
For the time series data of the first mold resistance value and the time series data of the second mold resistance value, unit time series data divided corresponding to one period of vibration of the mold is specified, and the same number of units are specified. Calculate the average value of time series data,
The breakout detection method according to claim 1, wherein a difference between average values of the unit time series data is used as time series data of mold lubrication resistance values. In the determination step,
Fitting the following formula to the waveform of the time series data of the mold lubrication resistance value in at least the rising section, to calculate the powder solid phase elastic modulus,
The breakout detection method according to claim 1, wherein when the powder solid phase elastic modulus changes by a predetermined value or more, it is determined that a breakout may occur.

In the above equation, M is the coefficient of liquid friction between the slab and the solid phase of the mold powder, K is the powder solid phase elastic modulus, d is the vibration amplitude of the mold, ω is the vibration frequency of the mold, and φ is the mold vibration frequency. Deviation of phase of mold lubrication resistance value waveform with respect to vibration waveform, Vc is casting speed, Mo is a coefficient of solid friction between slab and solid phase of mold powder, and α is a viscosity distribution of liquid phase of mold powder It is a coefficient.   The powder solid phase elastic modulus is calculated by fitting the equation based on data for one period of vibration of the mold in a waveform of time series data of the mold lubrication resistance value. Breakout detection method.   In the determining step, a lubrication resistance phase difference representing a difference between a position where the displacement in the vertical direction of the mold is the lowest end in the mold displacement waveform and a position where the waveform of the time series data of the mold lubrication resistance value is the lowest end. The breakout detection method according to claim 1, wherein the possibility of occurrence of a breakout is determined based on a change in the number of breakpoints.   3. In the determination step, it is determined that there is a possibility of a breakout when the slope of the waveform changes at least a predetermined value in the rising section of the waveform of the time series data of the mold lubrication resistance value. Breakout detection method described in 1.   The breakout detection method according to any one of claims 1 to 6, wherein, in the mold resistance value acquisition step, the mold resistance value is acquired based on an output value of a driving device that vibrates the mold.   The breakout detection method according to claim 7, wherein the driving device is a hydraulic device or a motor. A continuous casting method for reducing the casting speed of the continuous casting when it is determined by the breakout detection method according to any one of claims 1 to 8 that a breakout may occur.

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