JP6733152B2 - Breakout detection method and continuous casting method - Google Patents

Description

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

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

Detecting constrained breakouts is typically based on the mold temperature measured using a thermocouple. The detection of high-speed breakout using a thermocouple is to judge that molten steel comes into contact with the mold due to poor lubrication by increasing the mold temperature. However, since the mold temperature fluctuates from normal times, it is difficult to accurately determine the increase in mold temperature due to molten steel contact, and many false detections or overdetections have occurred.

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

JP-A-57-44456 JP-A-61-52973

However, Patent Document 1 does not show a concrete breakout detection standard. Further, in Patent Document 2 described above, the breakout is merely predicted from the average behavior of the lubricating resistance between the solidified shell and the mold, and it is difficult to detect the breakout with high accuracy.

Therefore, 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 to provide a continuous casting method.

In order to solve the above problems, according to an aspect of the present invention, before continuous casting to continuously cast the slab by solidifying the molten steel in the mold while oscillating the mold, vibrating the mold in the absence of slab A mold resistance value acquisition step of acquiring time series data of the first mold resistance value when the molding is performed, and acquiring time series data of the second mold resistance value generated between the mold and the slab during continuous casting, Mold lubrication resistance value acquisition step of obtaining time series data of mold lubrication resistance value by differentiating time series data of first mold resistance value and time series data of second mold resistance value, and mold lubrication resistance value And a determination step of determining a possibility of breakout occurrence based on a waveform change at least in a rising section where the mold lubrication resistance value is rising among the waveforms of the time series data. To be done.

In the mold lubrication resistance value acquisition step, the unit time-series data divided corresponding to one cycle of the vibration of the mold is specified for the time-series data of the first mold resistance value and the time-series data of the second mold resistance value. Alternatively, 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 determination step, at least in the rising section by fitting the following formula to the waveform of the time-series data of the mold lubrication resistance value, the powder solid phase elastic coefficient is calculated, and when the powder solid phase elastic coefficient changes by a predetermined value or more. It may be determined that there is a possibility of breakout.

In the above formula, F _M is mold lubricant resistance, t is time, M is a constant of the liquid friction between the solid phase of the cast piece and the mold powder, K is a powder solid modulus, d is the vibration of the mold Amplitude, ω is the vibration frequency of the mold, φ is the phase shift of the waveform of the mold lubrication resistance value with respect to the vibration waveform of the mold, Vc is the casting speed, Mo is the solid friction force 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 , and the value of α is 1 .

The powder solid phase elastic coefficient may be calculated by fitting a formula based on the data for one cycle of the vibration of the mold in the waveform of the time series data of the mold lubrication resistance value.

Further, in the determination step, the displacement of the mold in the vertical direction of the mold displacement waveform is the bottom end position, and the waveform of the time-series data of the mold lubrication resistance value is the bottom end of the lubrication resistance phase difference representing the difference. The possibility of breakout occurrence may be determined based on the change.

Further, in the determining step, it may be determined that a breakout may occur when the slope of the waveform in the rising section of the waveform of the time series data of the mold lubrication resistance value changes by a predetermined value or more.

In the mold resistance value acquisition step, the mold resistance value may be acquired based on the output value of the driving 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 problems, according to another aspect of the present invention, when it is determined that there is a possibility of breakout occurrence by the above 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, it is possible to detect the occurrence of breakout with high accuracy.

It is explanatory drawing which shows the state of the slab in the casting mold 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 continuous casting of FIG. It is explanatory drawing which shows the continuous casting lubrication state when 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 when the solid phase of mold powder has cut|disconnected. As Example 1, a detection result (Example A) in the case of performing breakout detection based on the slope of the waveform of the mold lubrication resistance value and the lubrication resistance phase difference is shown. As Example 1, a detection result (Example B) in the case of performing breakout detection based on the slope 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) in the case of performing breakout detection based on the slope of the waveform of the mold lubrication resistance value and the lubrication resistance phase difference is shown. As Example 2, a detection result when breakout detection is performed based on the powder solid phase elastic modulus obtained by fitting the mold lubrication resistance value to the waveform is shown.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In this specification and the drawings, constituent elements having substantially the same functional configuration are designated by the same reference numerals, and a duplicate description will be omitted.

<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 the mold and the slab of a continuous casting machine, and at least the resistance value is at least the time series data of the acquired mold lubrication resistance value. This is a method of determining the possibility of breakout occurrence by utilizing the waveform change in the rising section.

The time-series data of the mold lubrication resistance value is acquired by measuring the output value of the drive 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 lubricating behavior between the mold and the slab in the continuous casting machine, the resistance value generated based on the accuracy of the driving device or mechanism that vibrates the mold is removed. A process of generating time series data of the mold lubrication resistance value is performed. In addition, in the time series data of the mold lubrication resistance value, a change is likely to occur when the possibility of breakout occurrence increases in the increase section of the resistance value. Therefore, in the breakout detection method according to the present embodiment, the possibility of breakout occurrence 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 over-detection or erroneous detection. Hereinafter, the breakout detection method according to this embodiment will be described in detail.

<2. Breakout detection method>
[2-1. Mold lubrication resistance and continuous casting lubrication model]
First, based on FIGS. 1 and 2, a description will be given of a continuous casting lubrication model that represents a mold lubrication resistance value used in implementing the breakout detection method according to the present embodiment and a lubrication state of the mold 10 and the solidification shell 5a. To do. FIG. 1 is an explanatory view showing a state of a slab in a mold in continuous casting according to this embodiment. FIG. 2 is an explanatory diagram showing a continuous casting lubrication model that models the state during continuous casting in FIG. Note that FIG. 1 shows a partial cross section of the mold 10, and the molten steel in contact with the inner surface of the mold 10 is assumed to be in the state described below with reference to FIG. 1.

(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 cast piece to be manufactured. The molten steel 5 poured into the mold 10 solidifies from the portion in contact with the mold 10 while being drawn downward, and becomes a cast piece. Mold powder 7 is added to the inner surface of the mold 10 as a lubricant for the mold 10 and the solidified shell 5 a that is the 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, the mold powder 7 is present between the mold 10 and the molten steel. During continuous casting, the mold 10 is vibrated in the casting direction at a predetermined cycle. As a result, the mold powder 7 flows between the mold 10 and the solidified shell 5a and functions as a lubricant. The mold powder 7 exists as a solid phase 7b in the portion in contact with the mold 10 as in the state at the time of addition, but is melted by the heat of the molten steel 5 in contact between the mold 10 and the solidified shell 5a and the molten steel surface portion. However, the liquid phase is 7a. The molten steel 5 is cooled by the water-cooled mold 10 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, the solid phase 7b of the mold powder 7 of the mold 10 is fixed to the mold 10 (or solid friction occurs) on the upstream side in the casting direction as shown in FIG. 1, but is solid on the downstream side in the casting direction. A space Vo is generated between the mold 10 and the solid phase 7b when the mold 10 is separated from the mold 10. As a result, due to 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 that occurs when the cast piece is pulled out, the solid phase of the mold powder 7 in the area A. 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 solidification shell 5a with which the solid phase 7b is in contact.

On the other hand, if the lubrication between the mold 10 and the solidified shell 5a becomes poor, the solidified shell 5a may be broken and a breakout may occur in which the molten steel 5 leaks out. Therefore, it is considered that the occurrence of breakout due to poor lubrication can be detected by detecting the 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 of the mold 10 and the solidification shell 5a is estimated from the resistance value of the mold 10 vibrating in a predetermined cycle, and the breakout can be generated from the change in the resistance value. Detect sex.

The resistance value of the mold 10 can be acquired, for example, based on the 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, the resistance value of the mold 10 may be measured and used, for example, a motor output value of a load cell or a cam. That is, for example, when vibrating the mold 10 using a hydraulic device as a drive device, the hydraulic pressure is converted into a resistance value. Further, for example, when the mold 10 is vibrated by 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 drive device is considered to be a resistance value generated mainly by mechanical precision of the drive device or a mechanism for driving the mold 10. Hereinafter, the resistance value measured when there is no cast piece in the mold 10 is also referred to as "first mold resistance value". On the other hand, when there is a slab in the mold 10, that is, during continuous casting, the output value of the drive device includes the lubricating resistance between the mold 10 and the solidification shell 5a in addition to the first mold resistance value. Be done. Hereinafter, the resistance value measured when there is a cast piece in the mold 10 is also referred to as “second mold resistance value”.

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

First, the first mold resistance value when there is no cast piece in the mold 10 is acquired. The first mold resistance value is acquired in advance before the start of continuous casting, and for example, the output value of the hydraulic device when the mold 10 is vibrated at a predetermined cycle and amplitude by the hydraulic device. The first template resistance value is acquired at a predetermined timing and obtained as time series data.

Next, the second mold resistance value when there is a cast piece in the mold 10 is acquired. The second mold resistance value is acquired in advance during continuous casting, and similarly to the first mold resistance value, a value used as the mold resistance value such as the output value of the hydraulic device is acquired. At this time, the mold 10 is vibrated with the same period and the same amplitude as when the first mold resistance value was acquired. The second template resistance value is also acquired at a predetermined timing and 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. In practice, since it is difficult to measure at the same timing, 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 the breakout detection is obtained. The second mold resistance value obtained during the continuous casting includes not only the lubricating resistance generated between the mold 10 and the slab but also the mechanical resistance of the driving device of the continuous casting machine and the like. In the present embodiment, in order to improve the accuracy of breakout detection, the possibility of breakout occurrence is determined from the change in the lubricating resistance that is highly associated with the occurrence of breakout. Therefore, the period of the time series data of the first mold resistance value and the time series data of the second mold resistance value (that is, the vibration period of the mold 10 when these are acquired) are made to correspond to each other, and the first mold 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 the time series data of the mold lubrication resistance value.

The time-series data of the mold lubrication resistance value may be the difference between the time-series data of the first mold resistance value and the second time-series data for each cycle of vibration of the mold 10. Alternatively, when the waveform of each time-series data is observed for each cycle of vibration of the mold 10, the acquired mold resistance value may vary, and the waveform may not fit in a certain shape. In this case, the time series data of the mold resistance value for one cycle of vibration of the plurality of molds 10 (hereinafter, referred to as " Also referred to as “unit time-series data”) to obtain time-series data of the template resistance value having a stable waveform. The number of unit time-series data used for averaging is set so that the variation in 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, the standard deviation. In this case, for example, an average is calculated with a preset number of unit time-series data, and a standard deviation is obtained. If this standard deviation is larger than a predetermined value, the number of unit time-series data is increased and the average is re-averaged. Try to take. Then, when the standard deviation becomes equal to or less 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. As described above, the accuracy of breakout detection can be improved by reducing the variation in the time series data of the mold lubrication resistance value used to evaluate the possibility of breakout occurrence.

In addition, when a plurality of unit time series data is averaged for one of the time series data of the first mold resistance value and 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 averages of the unit time-series data are subtracted from each other 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. Therefore, when the unit time-series data of the first template resistance value is averaged, the same number of unit time-series data of the second template resistance value as the number of unit time-series data used in the first template resistance value are used. Make an average using the data.

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

(2) Continuous casting lubrication model As a mathematical model showing the lubrication behavior of 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 cycle. The slab model 5M is set as an object that moves downstream (X-axis negative direction side) in the casting direction 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 It is set as an object. Further, the object B7M _B is set as an object that moves according to the movement of the slab model 5M while causing solid friction or liquid friction with the slab model 5M.

With such a continuous casting lubrication model, the state of the powder 7 that is deformed by the movement of the mold 10 and the cast piece 5 can be represented, and the lubrication state of the mold 10 and the cast piece 5 can be represented. As will be described later, the continuous casting lubrication model adapts time series data of the mold lubrication resistance value obtained from the continuous casting machine to the model, and calculates the solid phase elastic modulus of the mold powder 7 and the solid phase 7b of the mold powder 7. It is used to obtain the frictional force between the slab and the mold 10.

[2-2. Continuous casting lubrication condition]
Next, the lubrication state of the mold, the vibration displacement of the mold, and the resistance value of the mold will be described as the continuous casting lubrication state based on FIGS. 3 is an explanatory diagram showing a continuous casting lubrication state in the case where 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 diagram showing a continuous casting lubrication state when the solid phase 7b of the mold powder 7 is cut.

(1) When the solid phase of the mold powder 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 in response to the periodic vibration of the mold 10. May indicate a state of repeating. 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 vibration in which the mold 10 moves up and down.

First, in the section a in which the mold 10 rises, the solid phase 7b moves between the part in contact with the mold 10 and the part in contact with the solidification shell 5a in the solid phase 7b as the mold 10 rises. (A region A in FIG. 1) elastically deforms and extends. At this time, the mold resistance value continues to rise. Then, when the mold resistance value reaches a predetermined value _Ffri , the solid phase 7b becomes plastically deformed (section b). After that, when the mold 10 starts to descend, the solid phase 7b moves downward as the mold 10 descends, so that a portion in contact with the mold 10 moves downward, and a portion between the portion in contact with the mold 10 and the portion in contact with the solidified shell 5a ( Area A) in FIG. 1 elastically deforms and contracts (section c).

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

(2) When the solid phase of the mold powder 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 portion of the solid phase 7b that is in contact with the mold 10 and the solidification shell 5a are cut at the portion B, each portion is subjected to either vibration of the mold 10 or movement of the solidification shell 5a. Move with great influence. Therefore, 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 falls during one cycle of the vibration of the mold 10. ..

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

[2-3. Judgment method]
Hereinafter, a method of determining the possibility of breakout occurrence 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 rising, It is used to determine the possibility of breakout occurrence. Specifically, the time series data of the mold lubrication resistance value is used to obtain an evaluation index for evaluating the possibility of breakout occurrence, and the possibility of breakout occurrence is determined.

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

If multiple evaluation indicators are used, the breakout occurrence may be notified when it is determined that there is a possibility of a breakout occurrence based on at least one of the evaluation indicators. The breakout occurrence may be notified when it is determined that the breakout may occur. Hereinafter, a method of determining the possibility of breakout occurrence based on each evaluation index will be described.

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

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

In the above formula (1), F _M is mold lubricant resistance, t is time, M is a constant of the liquid friction between the solid phase of the cast piece and the mold powder, K is a powder solid modulus, d is The vibration amplitude of the mold and ω represent the vibration frequency of the mold. Further, φ represents the phase shift of the waveform of the mold lubrication resistance value with respect to the vibration waveform of the mold, and is the phase from the lowest end position of the vibration waveform of the mold to the lowest resistance position of the mold lubrication resistance value. When the vibration waveform of the mold is preceded by the waveform of the lubricating resistance of the mold, it is defined as positive. Vc is the casting speed, and Mo is the solid frictional force between the slab and the solid phase of the mold powder. α is a coefficient that reflects the viscosity distribution of the liquid phase of the mold powder, and is set to 1 in this embodiment assuming that the viscosity distribution is uniform.

In the present embodiment, the powder solid phase elastic coefficient K is obtained by making the above equation (1) correspond to the waveform of time series data of the mold lubrication resistance value. At this time, the above formula (1) may be fitted to at least a portion (section a in FIG. 3) in which the solid phase of the mold powder elastically deforms when the mold rises in the waveform of the time series data of the mold lubrication resistance value. This is because, in the waveform of the mold lubrication resistance value, the solid-phase elastic deformation section when the mold rises easily changes when the possibility of breakout occurrence increases. The present invention is not limited to such an example, and in the waveform of the time-series data of the mold lubrication resistance value, not only the solid-phase elastic deformation section when the mold is raised, but also the other elastic deformation sections are expressed by the above formula (1). The powder solid phase elastic coefficient K may be determined so that

When the powder solid phase elastic coefficient 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 coefficient 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 coefficient K obtained by the fitting of the above equation (1) has suddenly increased. As a result, a rapid increase in the powder solid phase elastic coefficient K is detected, and it is detected that the possibility of breakout is increased. For example, when the powder solid phase elastic modulus K obtained by fitting exceeds a value three times the standard deviation (3σ) of the average value of the powder solid phase elastic modulus K, there is a possibility of breakout occurrence. It may be determined that there is.

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

(B) Phase difference between mold vibration displacement waveform and mold lubrication resistance value waveform Next, as an evaluation index, the phase difference between the mold vibration displacement waveform and the mold lubrication resistance value waveform (hereinafter referred to as "lubrication resistance phase difference"). (Also referred to as “.”) 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 mold resistance value waveform shown in FIG. The 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 waveform of the mold lubrication resistance value. Also in this case, in the waveform of the mold lubrication resistance value, the position where the mold lubrication resistance value is the minimum can be regarded as a part of the section in which the solid phase of the mold powder elastically deforms when the mold is raised. Consider it as information that represents changes in the waveform of a section.

The mold 10 vibrates when a cam is driven by a driving 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 arranging the calculated displacements of the mold 10 in time series, the 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 represented by the following equation (2). In the following formula (2), M is a liquid friction coefficient between the cast piece and the solid phase of the mold powder, K is a powder solid phase elastic coefficient, and ω is a vibration frequency of the mold.

The lubrication resistance phase difference φ is a value that increases as the powder solid phase elastic coefficient K increases. Therefore, the larger the lubrication resistance phase difference φ, the higher the possibility of being constrained. Therefore, the possibility of breakout occurrence 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 breakout may occur. When it is determined by the breakout detection method that a breakout may occur, it is possible to prevent the breakout from actually occurring by taking measures such as reducing the casting speed of continuous casting. it can.

(C) Slope of Waveform of Mold Lubrication Resistance Value Further, a breakout detection method in the case of using the slope of the waveform of 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 waveform of the mold lubrication resistance value is such that the mold lubrication resistance value has a minimum position (the lowest point) and the mold lubrication resistance value has the maximum value from the lowest point in the waveform of the mold lubrication resistance value. It means the slope of a straight line passing through the point (intermediate point) on the waveform of the mold lubrication resistance value at the 1/2 position of the time interval to the position (uppermost point). It is the inclination of the straight line L shown in FIGS.

The value of the slope of this straight line increases as the probability of breakout occurring increases. As described above, for example, in the continuous casting lubrication state of FIG. 3, when the constraint occurs, the powder solid phase elastic modulus apparently increases, and at the same time, the friction between the solid phase 7b and the slab increases and the solidified shell 5a It is more likely to break and cause a breakout. At this time, in the waveform of the mold lubrication resistance value, the elastic deformation section of the solid phase when the mold is raised becomes shorter, and the mold lubrication resistance value becomes a predetermined value F _fr than in the normal state in which the possibility of breakout occurrence is low. It will arrive sooner. Therefore, when the possibility of breakout increases, the slope of the waveform of the mold lubrication resistance value becomes larger than in the normal state. Therefore, the possibility of breakout occurrence is determined by using the slope of the waveform of the mold lubrication resistance value as an evaluation index and observing the change in that value. 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 breakout may occur.

In this way, when it is determined by the breakout detection method that there is a possibility of breakout occurrence, for example, by taking measures such as reducing the casting speed of continuous casting, it is possible to prevent the breakout from actually occurring. Can be prevented.

[2-4. Summary]
The breakout detection method during continuous casting according to this 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 among the acquired time series data of the mold lubrication resistance value. The possibility of breakout occurrence is determined by utilizing 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 by removing the resistance value generated based on the accuracy of the driving device and the mechanism for vibrating the mold, and the mold and the slab in the continuous casting machine. It is possible to more accurately grasp the lubrication behavior of. Further, the possibility of breakout occurrence is determined based on the waveform of the rising section of the resistance value of the time series data of the mold lubrication resistance value, which is likely to change when the possibility of breakout occurrence increases. As a result, it is possible to provide an accurate breakout detection method earlier and with less over-detection or erroneous detection.

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

[Example A]
In Example A, the possibility of breakout occurring when continuously casting low carbon steel having a casting thickness width of 500 mm and a casting 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 for vibrating the mold was obtained in a state where there was no slab in the mold and a state where there was slab in the mold, and the time series data of the first mold resistance value and the second value, respectively. It was used as time series data of the template resistance value of. 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 were used as they were without performing an averaging process on the time series data. FIG. 5 shows time series data of the mold lubrication resistance value in the normal state, 25 seconds after restraint, and 70 seconds after restraint at which breakout occurred.

The upper part of FIG. 5 shows time-series data of the mold lubrication resistance value in a normal state in which a breakout is unlikely to occur. In the upper waveform of FIG. 5, the slope of the waveform of the mold lubrication resistance value is the lowest point P _L1 and the mold lubrication resistance at the 1/2 position of the time interval from the lowest point P _L1 to the highest point P _H1. It is the slope of the straight line L ₁ that passes through the point (intermediate point P _M1 ) on the waveform of the value. The straight line L ₁ is also shown in the center and the lower side of FIG. 5 for comparison with the slope of the straight line at each time.

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. Since the slope of the straight line L ₂ was more than twice the slope of the straight line L _{1 in} the normal state, it was determined at this point that a breakout might occur. The phase difference of the lubricating resistance corresponds to the deviation of the lowest point from the normal state. The lowest point P _{L2 at} this time was deviated 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.

After that, at the time of 70 seconds after restraint when the breakout occurred, the slope of the straight line L ₃ is larger than the slope of the straight line L ₁ in the normal state as shown in the lower side of FIG. 5, but at the time of 25 seconds after restraint. It was smaller than the slope of the straight line L ₂ at. Also, regarding the lubricating resistance phase difference, the lowest point P _L3 was at substantially the same position as the lowest point P _{L1 in the} normal state.

The results of Example A showed that it was possible to detect the possibility of breakout occurring 45 seconds before the breakout occurred.

[Example B]
In Example B, the possibility of breakout occurring when continuously casting low carbon steel having a casting thickness of 500 mm and a casting thickness of 100 mm was determined. 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, similarly to Example A, the output value of the hydraulic device for vibrating the mold was obtained in a state where there was no slab in the mold and a state where there was slab in the mold, and the first mold resistance value It was used as time series data and time series data of the second template resistance value. 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, the time series data averaged 10 times was used. FIG. 6 shows time series data of the mold lubrication resistance value in the normal state, 10 seconds after restraint, and 35 seconds after restraint. In this Example B, a breakout occurred 40 seconds after the restraint.

The upper part of FIG. 6 shows time-series data of the mold lubrication resistance value in a normal state in which the possibility of breakout occurrence is low. The slope of the waveform of the mold lubrication resistance value is the lowermost point P _L1 in the upper waveform of FIG. 6 and the mold lubrication resistance at the 1/2 position of the time interval from the lowest point P _L1 to the highest point P _H1. It is the slope of the straight line L ₁ that passes through the point (intermediate point P _M1 ) on the waveform of the value. The straight line L ₁ is also shown in the center and the lower side of FIG. 6 for comparison with the slope of the straight line at each time.

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. Since the slope of the straight line L ₂ was more than twice the slope of the straight line L _{1 in} the normal state, it was determined at this point that a breakout might occur. The phase difference of the lubricating resistance corresponds to the deviation of the lowest point from the normal state. The lowest point P _{L2 at} this time was deviated 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.

Thereafter, 5 seconds before the breakout occurs and 35 seconds after the restraint, the slope of the straight line L ₃ is larger than the slope of the straight line L ₁ in the normal state as shown in the lower side of FIG. It was smaller than the slope of the straight line L ₂ at 10 seconds after. Regarding the lubricating resistance phase difference, the lowest point P _L3 was at substantially the same position as the lowest point P _L2 at 10 seconds after the restraint, and deviated from the normal state by π/6 or more.

The results of Example B showed that it was possible to detect the possibility of breakout occurrence 30 seconds before the breakout occurred.

[Example C]
In Example C, the possibility of breakout occurring during continuous casting of a low carbon steel having a casting thickness of 500 mm and a casting 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 was obtained in a state where there was no slab in the mold and a state where there was slab in the mold, and the time series data of the first mold resistance value and the second mold resistance were respectively obtained. The values were used as time series data. 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, the time series data averaged 17 times was used. FIG. 7 shows time-series data of the mold lubrication resistance value in the normal state, 15 seconds after restraint, and 35 seconds after restraint. In this Example C, a breakout occurred 40 seconds after the restraint.

The upper part of FIG. 7 shows time-series data of the mold lubrication resistance value in the normal state where the possibility of breakout occurrence is low. The slope of the waveform of the mold lubrication resistance value is shown in the upper waveform of FIG. 7 at the lowest point P _L1 and the mold lubrication resistance at the 1/2 position of the time interval from the lowest point P _L1 to the highest point P _H1. It is the slope of the straight line L ₁ that passes through the point (intermediate point P _M1 ) on the waveform of the value. The straight line L ₁ is also shown in the center and the lower side of FIG. 7 for comparison with the slope of the straight line at each time.

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. Since the slope of the straight line L ₂ was more than twice the slope of the straight line L _{1 in} the normal state, it was determined at this point that a breakout might occur. The phase difference of the lubricating resistance corresponds to the deviation of the lowest point from the normal state. The lowest point P _{L2 at} this time was deviated 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.

After that, 5 seconds before the breakout occurs and 35 seconds after the restraint, the slope of the straight line L ₃ is larger than the slope of the straight line L ₁ in the normal state as shown in the lower side of FIG. It was larger than the slope of the straight line L ₂ at 10 seconds. Also, regarding the lubricating resistance phase difference, the lowest point P _L3 was almost at the same position as the lowest point P _L2 at 10 seconds after the restraint, and deviated from the normal state by π/6 or more. Therefore, it was found that there is a possibility of breakout occurring at the time of 35 seconds after the restraint as at the time of 15 seconds after the restraint.

The results of Example C showed that it was possible to detect the possibility of breakout occurring 25 seconds before the breakout occurred.

As Example 2, FIG. 8 shows the detection results when breakout detection was 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 breakout occurring when continuously casting low carbon steel having a casting thickness of 500 mm and a casting 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 the second embodiment, the output value of the hydraulic device for vibrating the mold is acquired in a state where there is no cast piece in the mold and a state where there is a cast piece in the mold, and the time series data of the first mold resistance value and the second mold resistance value, respectively. It was used as time series data of the template resistance value of. 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 were used as they were without performing an averaging process on the time series data. The equation of the above equation (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 change over time of the solid phase elastic modulus of the powder. The time change of FIG. 8 is represented by the oscillation of the template. In addition, the time variation of the powder solid-phase elastic modulus at the time of an abnormality in which the possibility of breakout has increased is shown enlarged. In this enlarged view, the vehicle was restrained at the time of cycle 0, and a breakout occurred 63 seconds after the restraint.

As shown in FIG. 8, the elastic modulus shows a substantially constant value in the normal time when the possibility of breakout occurrence is low. After that, in the restrained state, as shown in the enlarged view of FIG. 8, the value of the powder solid phase elastic modulus sharply increased to a value exceeding the predetermined range of 3σ. Specifically, the average value of the powder solid phase elastic modulus under normal conditions was 1.9E+06 and the standard deviation σ was 4.8E+05, but the powder solid phase elastic modulus under abnormal conditions was 734 times the standard deviation σ. It was In the present example, it was determined that there was a possibility of breakout occurring when the standard deviation σ exceeded three times, and it was found that the abnormality could be detected 30 seconds before the breakout occurred.

The preferred embodiments of the present invention have been described above in detail with reference to the accompanying drawings, but the present invention is not limited to these 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 (8)

Before continuous casting in which the molten steel in the mold is solidified while continuously vibrating the mold while vibrating the mold, the time series data of the first mold resistance value when the mold is vibrated in the absence of the slab is shown. A mold resistance value acquisition step of 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 acquisition step of acquiring time series data of the mold lubrication resistance value by differentiating the time series data of the first mold resistance value and the time series data of the second mold resistance value;
Of the waveform of the time-series data of the mold lubrication resistance value, at least the determination step of determining the possibility of breakout occurrence based on the waveform change in the rising section in which the mold lubrication resistance value is increasing,
Including
In the determination step,
Fit the following formula to the waveform of the time-series data of the mold lubricating resistance value in at least the rising section to calculate the powder solid phase elastic modulus,
A breakout detection method for determining that a breakout may occur when the powder solid phase elastic coefficient changes by a predetermined value or more.

In the above formula, F _M is mold lubricant resistance, t is time, M is the liquid friction coefficient between the solid phase of the cast piece and the mold powder, K is a powder solid modulus, d is the vibration amplitude of the mold , Ω is the vibration frequency of the mold, φ is the phase shift of the waveform of the mold lubrication resistance value with respect to the vibration waveform of the mold, Vc is the casting speed, Mo is the solid friction force 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 , and the value of α is 1 . The solid phase elastic modulus of powder is calculated by fitting the equation based on data of one cycle of vibration of the mold in a waveform of time series data of the mold lubrication resistance value. Breakout detection method. Before continuous casting in which the molten steel in the mold is solidified while continuously vibrating the mold while vibrating the mold, the time series data of the first mold resistance value when the mold is vibrated in the absence of the slab is shown. A mold resistance value acquisition step of 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 acquisition step of acquiring time series data of the mold lubrication resistance value by differentiating the time series data of the first mold resistance value and the time series data of the second mold resistance value;
Of the waveform of the time-series data of the mold lubrication resistance value, at least the determination step of determining the possibility of breakout occurrence based on the waveform change in the rising section in which the mold lubrication resistance value is increasing,
Including
In the determining step, the displacement in the vertical direction of the mold in the mold displacement waveform is the lowest end position, and the lubricating resistance phase difference indicating the difference between the position where the waveform of the time series data of the mold lubrication resistance value is the lowest end. A breakout detection method for determining the possibility of breakout occurrence based on changes in. The determination step, wherein it is determined that there is a possibility of breakout when at least the slope of the waveform in the rising section of the waveform of the time series data of the mold lubrication resistance value changes by a predetermined value or more. Breakout detection method. In the mold lubrication resistance value acquisition step,
With respect to the time series data of the first mold resistance value and the time series data of the second mold resistance value, the unit time series data divided corresponding to one cycle of the vibration of the mold is specified, and the same number of units are respectively specified. Calculate the average value of the time series data,
The breakout detection method according to any one of claims 1 to 4, wherein a difference between average values of the unit time-series data is used as time-series data of a mold lubrication resistance value. The breakout detection method according to claim 1, 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 6, wherein the drive 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 7 that breakout may occur.

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