JP7484855B2 - Slab width reduction control device and method - Google Patents

Description

The present invention relates to a slab width reduction control device and a control method using the device in a width press facility equipped with pinch rolls that conveys a steel piece (slab) to be used for hot rolling or the like in the slab's longitudinal direction while pressing it intermittently from both sides in the width direction with a pair of dies to perform width reduction rolling (hereinafter also simply referred to as "width reduction").

When a slab is width-reduced using a width press machine called a sizing press, buckling and twisting can easily occur in the width direction of the slab (Non-Patent Document 1). Buckling is a plastically unstable state caused by width reduction, in which the slab bends upward (convex) or downward (concave) during width reduction. Twisting is a phenomenon in which the front or rear end of a hot slab that is being width-reduced in an unsteady state, being supported by multiple conveying pinch rolls installed in the conveying direction and becoming a free end, becomes tilted from the horizontal plane.

As a technology to suppress the above-mentioned buckling phenomenon, a technology has been disclosed in which a width reduction device having a die for width reduction of the material and a pair of upper and lower (buckling prevention) pressure rolls that press both sides of the central part of the material in the width direction at a position equivalent to the center of the die longitudinal direction, a feed roller and a measuring roll that can press the entire width of the material (slab) are provided as a pair at at least two places on the inlet and outlet sides of the die to grip the material during width reduction and prevent buckling and twisting of the material (Patent Document 1). In addition, a method has been disclosed in which a buckling restraint roll is installed to prevent buckling at the leading edge of the slab, and the upper and lower height positions of the buckling restraint rolls are appropriately adjusted in consideration of the deformation of the slab due to width reduction according to the predicted value of the thickness increase at the leading edge and steady part of the hot slab due to width reduction, taking into account the deformation of the slab due to width reduction (Patent Document 2).

On the other hand, with regard to the twisting phenomenon, a technology has been disclosed that prevents the twisting phenomenon, which is likely to occur at the leading and/or trailing ends of a slab when the slab is being reduced in width, by arranging a pair of upper and lower vertical movement restraining rolls at multiple positions in the width direction of the slab to restrain the vertical movement of the slab during width reduction (Patent Document 3).

Nikaido et al. "Highly Reliable Hitachi Sizing Press": Hitachi Review vol. 72, No. 5, p397-402 (May 1990)

Japanese Patent Application Laid-Open No. 6-154810 JP 2009-248186 A JP 2018-144083 A

However, slab twisting during width reduction is not limited to the leading or trailing ends of the slab, and excessive slab twisting (for example, one side of the slab lifts up by 50 mm or more for a slab width of 1,300 mm) may occur from the steady part to the tail end of the slab. If width reduction of a slab twisted in the steady part continues intermittently, the slab striking positions of the left and right dies shift in the height direction, generating a rotational moment that rotates the slab struck by the dies around the center of the slab's width cross section, and the horizontal impact load that the slab receives from the dies is converted into a vertical impact load that causes the slab to push up on the dies. If the impact load that pushes up the dies vertically exceeds the load capacity of the width press equipment, it will cause equipment damage, which is a problem.

However, the technologies disclosed in Patent Documents 1 and 2 are intended to prevent the buckling phenomenon in which the central part of the slab in the width direction bends upward or downward, and the technology disclosed in Patent Document 3 is intended to prevent slab twisting in the non-steady parts of the leading and/or trailing ends, but neither technology prevents excessive slab twisting from the steady part of the slab to the trailing end.

Therefore, in the past, it was difficult to avoid damage to the width press equipment due to such excessive slab twist, which would cause the vertical press load during width reduction to exceed the load capacity of the width press equipment.

In view of the problems with the conventional technology described above, the present invention aims to provide a width reduction control device and method that prevents the vertical press load caused by slab twist from becoming an overload state that exceeds the vertical load capacity of the width press equipment.

[How the present invention was made]
In order to solve the above-mentioned problems, the inventors have conducted extensive research into a method for preventing damage to the width press equipment by interrupting width reduction midway when excessive slab twist occurs from the steady portion to the tail end of the slab.

In order to investigate the cause of the excessive twisting that occurs from the steady part of the slab to the tail end and that can cause equipment damage, the researchers observed the twisted slab and noted that the amount of twisting was small at the longitudinal tip of the slab, but gradually increased towards the longitudinal tail end.

In the width press equipment, the torsion is assumed to gradually increase as the slab is conveyed and compressed in width by intermittent impact loads. As such, we investigated the relationship between the balance of forces in the width cross section of slab S and the torsional moment around the center of the width cross section of slab S, as shown in Figure 2.

When the inclination direction line 22, which passes through the center of the width cross section of the slab S and indicates the twist, is inclined at a slab twist angle φ with respect to the horizontal direction (horizontal direction line 20), the relationship between the force that causes one side of the slab in the width direction to rise vertically upward, which generates a twisting moment around the center of the slab width cross section (hereinafter referred to as the "uplifting force F"), and the press load P is F = P × tan φ (4)
It becomes.

If there is a slight twist (initial slab twist angle φ is φ0) at the slab stage before width reduction by the width press equipment, when the width is reduced with the press load P, a lifting force F of magnitude P x tanφ0 is generated according to formula (4), and the torsional moment causes the slab twist angle φ after width reduction to be larger than the initial slab twist angle φ0. It was thought that in the process of intermittently reducing the width of the slab while transporting it, the slab twist angle φ increases, developing into an excessive twist that could cause equipment damage.

Therefore, an FEM analysis was performed on a process in which a slab S having a slight initial slab twist angle φ0 is intermittently reduced in width while being conveyed, at a stage before the width reduction.
As shown in Fig. 3(a) which shows the cross section of the slab S before and after width reduction, the slab twist increases before and after width reduction. That is, the twist amount δ increases from δ0 to δ1, and the slab twist angle φ increases from φ0 to φ1. As shown in Fig. 3(b) which shows the change in the longitudinal twist amount after width reduction (= slab width after width reduction × longitudinal tanφ), the twist increases toward the tail end (TE). Note that the slab twist angle φ is positive in the clockwise direction around the slab width center from the horizontal line 20, and negative in the counterclockwise direction.

As shown in Figure 4, the correlation diagram between the uplift force F and the press load P x tan (initial slab torsion angle φ0) also shows the relationship in formula (4).

Furthermore, the inventors investigated the initial slab twist angle φ0 from actual data for a certain period of time on the inclination of the pinch rolls on the inlet side of the width press equipment, and found that it was 0.1° on average (tan φ0 = 0.002) and 1.5° at maximum (tan φ0 = 0.027). For example, in the case of a slab with a width of 1,300 mm, the lift of one side in the width direction from the horizontal direction (amount of slab twist) was 3 mm and 35 mm, respectively.

Figure 5 shows a schematic diagram of the relationship between the press load P and the uplift force F when the initial slab twist angle φ0 is different.

In Figure 5, (a) is the case where φ0 is an average of 0.1° (tan φ0 = 0.002), (b) is the case where φ0 is a maximum of 1.5° (tan φ0 = 0.027), and (c) is the case where φ0 is a maximum of 3.1° (tan φ0 = 0.054), twice the maximum of 1.5° in (b). Pcr is the load capacity (horizontal load capacity) against a horizontal impact load applied to the die of the width press equipment, and Fcr is the load capacity (vertical load capacity) against a vertical impact load applied to the die.

When φ0 is 0.1° in (a), the lifting force F is significantly lower than the vertical load capacity Fcr. However, when φ0 is 1.5° in (b), the lifting force F increases significantly with an increase in press load P, and when the press load P reaches the horizontal load capacity Pcr, the lifting force F reaches the vertical load capacity Fcr.

Furthermore, when φ0 becomes 3.1° in (c), the lifting force F reaches the vertical load capacity Fcr when the press load P is at Pmax before it reaches the horizontal load capacity Pcr, and if a press load P exceeding Pmax is applied, the impact load pushing up the die in the vertical direction will cause equipment damage. Here, Pmax is the estimated upper limit press load determined by the relationship between the slab twist angle φ and the vertical load capacity Fcr, and is calculated using formula (5).

Pmax = Fcr / tan φ Equation (5)
Therefore, by predicting the press load P before width reduction and, if it exceeds the estimated upper limit press load Pmax, stopping the slab transport and interrupting the width reduction, damage to the width press equipment can be prevented.

The width press equipment is also equipped with a load cell that measures the press load P. After width reduction has begun, the press load during width reduction is actually measured using the load cell (actual press load Pa). If the press load exceeds the estimated upper limit press load Pmax, the slab transport is stopped and width reduction is interrupted, thereby preventing damage to the width press equipment.

Next, the inventors of the present invention have studied a method for predicting the press load before the slab enters the width press equipment. The press load P can be predicted by applying the width reduction (strain), deformation rate (strain rate), slab feed rate (die contact projection length), thickness of the material to be rolled (slab), etc., which are press conditions, and the slab temperature, material properties of the slab, etc., which are material conditions, to the following formula (6), for example.
Pp = Qp x Km x H x Lp ... formula (6)
Here, Pp = predicted press load, Km = deformation resistance (according to Misaka's formula), H = slab thickness, Qp = rolling force function, and Lp = die contact projection length.

The inventors believe that the press load is dominated by the slab temperature when the press conditions and the material properties of the slab are the same, and therefore measured or predicted the slab temperature before entering the width press equipment and investigated the relationship with the press load.

Here, as a method for estimating the slab temperature before entering the width press equipment, we considered a method in which the slab temperature at the time of extraction from the heating furnace is used as a basis, and the cross-sectional temperature distribution of the slab is estimated by numerical calculations such as the finite difference method based on the descaling after extraction and the time history.
The target temperature of the slab when removed from the heating furnace is set within a range of, for example, 1000 to 1200°C, but since there is an oxide scale layer on the surface of the slab during transport in the furnace, the slab temperature is not directly measured using a radiation thermometer or the like, but is generally estimated by calculating the amount of heat input from the slab surface based on the atmospheric temperature in the heating furnace and the time the slab has been in the furnace at the atmospheric temperature using an overall heat transfer coefficient φcg that represents the form of heat transfer to the slab, and using a differential calculation model or the like. However, when the slab is retained in the heating furnace for a long time due to an operational trouble and the input amount of heated combustion gas into the heating furnace is large, the scale layer formed on the surface of the slab becomes thicker due to the long stay in the furnace, and the heat input to the slab becomes lower than expected, etc., and there is a problem that the calculation accuracy cannot be sufficiently obtained.

The inventors therefore investigated a method of directly measuring the slab surface temperature before it enters the width press equipment (called the press entry temperature) using a radiation thermometer. As mentioned above, a scale layer formed in the heating furnace is present on the surface of the slab when it is extracted from the heating furnace, and the emissivity varies depending on the thickness and color of the scale layer and the unevenness (roughness) of the surface, making accurate temperature measurement difficult.

As shown in Figure 6(a) showing an outline of the equipment layout and (b) showing the temperature history, the slab S extracted from the heating furnace was descaled (descaled) by the high-pressure water descaling device 3 to remove the scale layer from the slab surface, and then the press entry temperature was measured with a radiation thermometer as the temperature measuring means in the temperature measuring section 5 at the inlet side of the width press equipment, where the slab surface temperature can be measured about 20 seconds after descaling, when the slab surface temperature of the slab surface layer that had dropped due to descaling recovers and stabilizes. Note that after descaling, the environment is one in which water vapor is generated, and it is preferable to use a two-wavelength radiation thermometer that converts the temperature into a value by calculating the ratio of the radiance of two different measurement wavelengths.

Figure 7 shows the correlation between the press entry temperature and the measured press load Pa. It was found that the press entry temperature (measured value) correlates with the measured press load Pa. If the correlation between the press entry temperature and the measured press load Pa is determined in advance for each category stratified by basic press data including the slab steel type, dimensions (slab thickness, width), width reduction amount, and transport amount, it is possible to predict the press load P from the actually measured press entry temperature.

Moreover, the slab twist angle φ in the formula (5) can be determined as follows.
Fig. 8(a) is an overall schematic diagram of the width press equipment 2. The inlet pinch roll 30 and the outlet pinch roll 32 sandwich the slab S between the upper and lower rolls and transport the slab S. The inlet pinch roll 30 and the outlet pinch roll 32 sandwich the slab S with a constant pressing force, but cannot correct the slab twist, and as shown in Fig. 8(b), the inlet pinch roll 30 (similar to the outlet pinch roll 32) is inclined relative to the horizontal direction in accordance with the twisted slab shape. The slab twist angle φ can be measured from the difference in the left and right cylinder positions of the holding cylinders 40 arranged at both ends (left and right) of the pinch roll 30 in the width direction.

When the slab enters the width press equipment and the leading edge of the slab is clamped by the entry pinch roll 30, the inclination angle of the entry pinch roll 30 can be obtained as the slab twist angle φ before the press width reduction.

In addition, when the slab being rolled is clamped between the entry pinch roll 30 and/or the exit pinch roll 32 while being reduced in width by pressing with the die 10, the inclination angle of the entry pinch roll 30 or the exit pinch roll 32, or the average value of both, can be obtained as the slab twist angle φ during width reduction.
[Summary of the present invention]
The present invention has been made based on the above-mentioned studies, and the gist of the present invention is as follows.
[1] A width reduction control device that prevents vertical overloading of a width press facility equipped with pinch rolls and a load cell, comprising a temperature measurement unit, a predicted press load calculation unit, a slab twist angle acquisition unit, and a reduction feasibility determination unit,
The temperature measuring unit includes a means for measuring a press entry temperature, which is a surface temperature of the slab when it enters the width press equipment;
The predicted press load calculation unit includes a means for calculating a predicted press load Pp during width reduction of the slab using the press entry temperature,
The slab twist angle acquisition unit includes a means for measuring a slab twist angle φ from a pinch roll inclination angle of a pinch roll on an entry side and/or an exit side of the width press equipment,
The rolling possibility determination unit derives an estimated upper limit press load Pmax based on the slab twist angle φ measured by the slab twist angle acquisition unit and the vertical load capacity Fcr of the width press equipment, compares it with the predicted press load Pp, and includes a means for stopping slab transportation when Pp exceeds Pmax.
A width reduction control device characterized by the above.
[2] The width reduction control device described in [1], characterized in that the rolling possibility determination unit acquires the actual press load Pa during width reduction of the slab from the load cell, compares it with the estimated upper limit press load Pmax, and has a means for stopping slab transportation and width reduction if Pa exceeds Pmax.
[3] The width reduction control device according to [1] or [2], characterized in that the press entry temperature is a temperature 20 seconds after the surface scale of the slab extracted from the heating furnace is removed.
[4] The width reduction control device according to any one of claims 1 to 3, characterized in that the means for measuring the press entry temperature is a radiation thermometer.
[5] The width reduction control device according to any one of [1] to [4], characterized in that the means for calculating the predicted press load is configured with a linear equation having the press entry temperature as an explanatory variable and the predicted press load as a target variable.
[6] The width reduction control device according to any one of [1] to [5], characterized in that the rolling possibility determination unit includes means for calculating an estimated upper limit press load Pmax based on the slab twist angle φ and the vertical load capacity Fcr by the following equations (1) and (2), respectively.
Pmax1 = Fcr / tan φmax (1)
Pmax2 = Fcr / tan φ (2)
Here, Pmax1 is the estimated upper limit press load according to formula (1), Pmax2 is the estimated upper limit press load according to formula (2), Fcr is the vertical load capacity of the width press equipment, φ is the slab twist angle, and φmax is the allowable upper limit twist angle.
[7] A method for controlling width reduction using the width reduction control device according to any one of [1] to [6] to prevent vertical overload of a width press facility,
The maximum value of the measurement data of the slab twist angle φ, which was previously measured by the slab twist angle acquisition unit when the width press equipment was not damaged, is obtained in advance as the allowable upper limit twist angle φmax,
Before the slab is pinched by the pinch rolls at the inlet side of the width press equipment,
The temperature measuring unit measures a press entry temperature,
The predicted press load calculation unit calculates a predicted press load P1 during width reduction of the slab using the press entry temperature measured by the temperature measurement unit,
The width reduction control method is characterized in that the rolling down feasibility determination unit calculates an estimated upper limit press load Pmax1 using the allowable upper limit torsion angle φmax and the vertical load capacity Fcr of the width press equipment by the following formula (1), compares it with the predicted press load P1, and stops slab transportation if P1 exceeds Pmax1.
Pmax1 = Fcr / tan φmax (1)
Here, Pmax1 is the estimated upper limit press load according to formula (1), Fcr is the vertical load capacity of the width press equipment, and φmax is the allowable upper limit torsion angle.

[8] When the P1 is equal to or less than Pmax1,
Furthermore, during the transport of the slab, the temperature measuring unit measures the press entry temperature T2 in the longitudinal direction of the slab,
While the slab is being pinched by the pinch rolls on the inlet and/or outlet sides of the width press equipment,
the slab twist angle acquisition unit measures a slab twist angle φ in the longitudinal direction of the slab from the inlet and/or outlet pinch roll inclination angles,
The predicted press load calculation unit calculates a predicted press load P2 in the longitudinal direction using the press entry temperature T2 in the longitudinal direction,
The width reduction control method according to [7], characterized in that the rolling possibility determination unit calculates an estimated upper limit press load Pmax2 in the longitudinal direction using the longitudinal slab twist angle φ and the vertical load capacity Fcr of the width press equipment according to the following formula (2), compares it with the predicted press load P2 in the longitudinal direction, and stops slab transportation and width reduction if P2 exceeds Pmax2.
Pmax2 = Fcr / tan φ (2)
Here, Pmax2 is the estimated upper limit press load according to formula (2), Fcr is the vertical load capacity of the width press equipment, and φ is the slab twist angle from the inclination angle of the pinch rolls on the inlet and/or outlet sides.
[9] The width reduction control method according to [8], characterized in that the reduction feasibility determination unit acquires an actual measured press load Pa in the longitudinal direction during width reduction of the slab from the load cell, compares it with an estimated upper limit press load Pmax2 in the longitudinal direction, and stops slab transportation and width reduction if Pa exceeds Pmax2.

According to the present invention, before the slab enters the width press equipment (before the slab is clamped by the pinch rolls on the inlet side of the width press equipment), the press entry temperature is measured to calculate the predicted press load Pp, which is then compared with the estimated upper limit press load Pmax based on the slab's allowable upper limit twist angle φmax. If Pp exceeds Pmax, entry into the width press equipment can be prohibited in advance, thereby preventing equipment damage caused by an overload state that exceeds the vertical load capacity of the width press equipment.

In addition, after the slab enters the width press equipment (while the slab is clamped between the pinch rolls on the inlet and/or outlet side of the width press equipment), the press entry temperature in the longitudinal direction is measured to calculate the predicted press load Pp during width reduction, which is then compared with the estimated upper limit press load Pmax in the longitudinal direction based on the longitudinal slab twist angle φ measured from the pinch roll inclination angle. If Pp exceeds Pmax, the slab transport and width reduction can be stopped before the longitudinal position of the slab in question is actually width reduced with the die, thereby preventing equipment damage caused by an overload state that exceeds the vertical load capacity of the width press equipment.

Furthermore, the actual measured longitudinal press load Pa during width reduction of the slab is compared with the estimated upper limit longitudinal press load Pmax based on the longitudinal slab twist angle φ, and if Pa exceeds Pmax, slab transport and width reduction can be stopped immediately after the vertical press load caused by slab twist exceeds the vertical load capacity of the width press equipment, resulting in an overload state, thereby minimizing equipment damage.

FIG. 1 is a schematic diagram showing an example of an apparatus according to the present invention. FIG. 13 is a diagram for explaining the balance of forces in a slab width cross section and the torsional moment around the center of the slab width cross section. FIG. 13 is a diagram showing the results of an FEM analysis of width reduction by a die to confirm the phenomenon of slab twist. FIG. 1 is a diagram for explaining the relationship between the lift-up force F, the press load P, and the initial torsion angle φ0. FIG. 13 is a diagram for explaining the relationship between a press load P and a lift-up force F. FIG. 2 is a diagram for explaining the installation position of a radiation thermometer for measuring the slab surface temperature (press entry temperature) before entering the width press equipment. FIG. 1 is a diagram showing the relationship between the press entry temperature (actual measured value) and the actually measured press load Pa. FIG. 4 is a diagram for explaining a method for measuring a slab twist angle φ. FIG. 2 is a diagram showing the installation position of a dual-wavelength radiation thermometer in Examples 1 and 2. FIG. 13 is a diagram showing the results of measurement of the press entry temperature in the longitudinal direction of a slab using a dual-wavelength radiation thermometer in Example 2. FIG. 2 is a diagram for explaining the positional relationship between a slab and width press equipment in an embodiment of the method of the present invention.

Hereinafter, an embodiment of the present invention will be described.
[Width reduction control device]
FIG. 1 shows an example of a width reduction control device according to the present invention (hereinafter, also referred to as the device of the present invention).
The device of the present invention prevents the width press equipment 2 from being overloaded in the vertical direction. The slab S is extracted from a heating furnace (see FIG. 6(a)) not shown in FIG. 1, transported by a plurality of transport rollers 1, and arrives at the width press equipment 2 after the scale layer on the surface of the slab is removed by a high-pressure water descaling device 3. The width press equipment 2 is equipped with pinch rolls 30 and 32 on the inlet side and the outlet side, a die 10 for performing width reduction rolling by pressing, and upper and lower buckling prevention rolls 15, and further equipped with a load cell for measuring the press load during width reduction. The slab S that has arrived is clamped and transported by the pinch rolls 30 on the inlet side, while being width reduced by the die 10, and further clamped and transported by the pinch rolls 32 on the outlet side, while the width reduction is continued. During the progress of the width reduction, the slab is pressed down by the upper and lower buckling prevention rolls 15 to prevent buckling. At this time, the slab S may be twisted, causing an overload in the vertical direction of the width press equipment 2, which may induce equipment damage.

The device of the present invention determines whether or not a vertical overload has occurred within the width press equipment 2 before the slab S enters the width press equipment 2 and during width reduction after entry, and if it determines that an overload has occurred, it immediately interrupts the width reduction (stops the slab transport) in order to prevent damage to the equipment.To this end, the device has a temperature measurement unit 5, a predicted press load calculation unit 6, a slab twist angle acquisition unit 7, and a reduction feasibility determination unit 8, which will be described below.
Also, the data section 4 for storing slab specifications and setting conditions for the width press equipment (referred to as basic data for the press) will be described.

[Data section]
The data section 4 includes a means for storing basic data for the press (data storage means). The data storage means is preferably, for example, a memory means of a process computer. The basic data preferably includes the steel type of the slab S, slab specifications such as dimensions (slab thickness, slab width), and setting conditions of the width press equipment 2 such as width reduction amount and conveyance amount (average feed speed). These data are linked to the slab S, and are input to the calculation section 6 of the predicted press load Pp and used to calculate the predicted press load Pp. Examples of the value range of the basic data include the following:
Steel type: Steel types within the range stipulated by various standards such as JIS and ASTM. Dimensions: Thickness 140-300 mm, width 600-1910 mm, length 4500-10000 mm
Width reduction: 0 to 400 mm
Conveying amount (average feed speed): 5 to 20 mpm

[Temperature measurement section]
The temperature measurement unit 5 is equipped with a means (temperature measuring means) for measuring the press entry temperature, which is the surface temperature of the slab S extracted from the heating furnace when it enters the width press equipment 2. The measured press entry temperature is input to the predicted press load calculation unit 6 and is used to calculate the predicted press load Pp.
As a temperature measuring means, a radiation thermometer, which is considered to be suitable for measuring the temperature of high-temperature materials, is preferable, and in particular, a two-wavelength radiation thermometer (also known as a two-color thermometer), which is less susceptible to disturbances such as water vapor generated by descaling using the high-pressure water descaling device 3, is more preferable.

The press entry temperature is preferably the temperature after the slab S has completed its recovery (slab surface temperature rise) from the rapid heat removal (slab surface temperature drop) caused by the water cooling of descaling and the slab surface temperature has stabilized. This recovery is completed and the slab surface temperature stabilizes, for example, 20 seconds after descaling, as shown in FIG. 6(b). Therefore, it is preferable that the press entry temperature is the temperature after 20 seconds has passed since the scale layer on the surface of the slab extracted from the heating furnace has been removed.

The press entry temperature is preferably the temperature in the longitudinal direction of the slab (the temperature at multiple locations in the longitudinal direction of the slab). The reason for this is that if the press entry temperature is the temperature at only one location in the longitudinal direction of the slab, even if the temperature at that one location is a temperature that is determined to not cause equipment damage (safe temperature), the temperature at other locations may be lower and may be determined to cause equipment damage (dangerous temperature), which may be overlooked, increasing the risk of equipment damage.

The width press equipment 2 is part of a hot rolling line that includes a row of equipment from the heating furnace to the rough rolling mill, finishing rolling mill, and winder (none of which are shown) downstream of the width press equipment 2, and this hot rolling line is equipped with a tracking function that tracks the position on the line of the slab S (and the rolled material that uses this as the starting material). This tracking function allows the press entry temperature in the longitudinal direction of the slab to be associated with multiple positions in the longitudinal direction of the slab.

[Calculation of predicted press load]
The predicted press load calculation unit 6 includes a means (predicted load calculation means) for calculating a predicted press load Pp during width reduction of the slab S using the basic data and the press entry temperature. The calculated predicted press load Pp is input to the reduction feasibility determination unit 8.
In the predicted press load calculation unit 6, it is preferable that the predicted load calculation means acquires a press load prediction model for calculating a predicted press load Pp from a press entry temperature (Ts) based on a relationship between the press entry temperature (actual value) and the actual press load Pa (see, for example, FIG. 7) for each category stratified by basic data items including the slab specifications such as the steel type and dimensions (slab thickness and width) of the slab, and the width reduction and conveyance amount which are the setting conditions of the width press equipment, among the basic data. As the press load prediction model, for example, a linear equation with the press entry temperature Ts as an explanatory variable and the predicted press load Pp as a response variable as shown in the following formula (7) can be mentioned.
Pp = a × Ts + b (7)
where Pp is the predicted press load [ton], Ts is the press entry temperature [°C], and a [ton/°C] and b [ton] are regression coefficients. The regression coefficients a and b are obtained by performing regression analysis of the correlations as shown in Figure 7 for each category stratified in advance by basic data items including the slab steel type, dimensions (slab thickness, slab width), width reduction amount, and conveying amount, and are stored for each category in a storage means (not shown) in calculation unit 6 of the predicted press load.

[Slab torsion angle acquisition unit]
The slab twist angle acquisition unit 7 is equipped with a means (twist angle measurement means) for measuring the slab twist angle φ in the longitudinal direction of the slab from the pinch roll inclination angles of the pinch rolls 30 and 32 on the entry side and/or exit side of the width press equipment 2. As shown in FIG. 8B for the entry side pinch roll 30, for example, this twist angle measurement means detects the difference (e.g., 152 mm) in the holding height positions of the holding cylinders 40, 40 at both ends (left and right) of the pinch roll 30 in the width direction while the slab S is being clamped, and calculates the pinch roll inclination angle by the formula arctan (difference in holding height positions/horizontal spacing), and this calculation result is taken as the slab twist angle φ. The measured slab twist angle φ is input to the rolling down feasibility determination unit 8.

[Pressing down possibility determination unit]
The rolling down feasibility determination unit 8 derives an estimated upper limit press load Pmax based on the slab twist angle φ measured by the slab twist angle acquisition unit 7 and the vertical load capacity Fcr of the width press equipment 2, compares it with the predicted press load Pp, and is equipped with a means for stopping the slab transport if Pp exceeds Pmax.
The reduction feasibility determination unit 8 also includes a means for acquiring the actual press load Pa during width reduction of the slab from the load cell during width reduction of the slab, comparing it with the estimated upper limit press load Pmax, and stopping the slab transportation and width reduction if Pa exceeds Pmax.

In order to derive the estimated upper limit press load Pmax, it is possible to provide a calculation means for the following equations (1) and (2).
Pmax1 = Fcr / tan φmax (1)
Pmax2 = Fcr / tan φ (2)
Here, Pmax1 is the estimated upper limit press load according to formula (1), Pmax2 is the estimated upper limit press load according to formula (2), Fcr is the vertical load capacity of the width press equipment, φ is the slab twist angle, and φmax is the allowable upper limit twist angle.

Equation (1) is used to determine whether or not the slab S can enter the width press equipment 2 before the slab S enters the width press equipment 2, and equation (2) is used to determine whether or not the width reduction can continue while the slab width reduction is in progress within the width press equipment 2 after the slab S has entered the width press equipment 2.

The allowable upper limit torsion angle φmax is the maximum value of the measurement data of the slab torsion angle φ measured in the past by the slab torsion angle acquisition unit 7 when the width press equipment 2 was not damaged, and is obtained in advance and stored in the rolling possibility determination unit 8.

The vertical load capacity Fcr of the width press equipment 2 is determined, for example, based on the load capacity of the guides that restrain the components of the width press equipment 2 (outer block, inner block, etc.) from moving vertically when the lift-up force F exceeds their own weight. This Fcr is also determined in advance and stored in the pressing feasibility determination unit 8.

Then, before the slab S enters the width press equipment 2, the estimated upper limit press load Pmax1 derived from formula (1) is compared with the predicted press load Pp, and if Pp exceeds Pmax1, the slab transport is stopped. The means for stopping the slab transport includes a logical operation circuit that generates a signal to the width press equipment 2 to prohibit the slab from entering based on the comparison result between Pp and Pmax1, and stops the rotation of the transport roller 1.

In addition, after the slab S has entered the width press equipment 2, the estimated upper limit press load Pmax2 derived from equation (2) based on the slab twist angle φ is compared with the predicted press load Pp, and if Pp exceeds Pmax2, the slab transport and width reduction are stopped. An example of a means for stopping the slab transport is a logical operation circuit that stops the rotation of the transport roller 1 for the width press equipment 2 based on the comparison result between Pp and Pmax2. An example of a means for stopping the width reduction is a logical operation circuit that generates a signal for the width press equipment 2 to urgently open the die 10 based on the comparison result between Pp and Pmax2, and to prompt the interruption of the width reduction.

[Width reduction control method]
Next, an embodiment of a width reduction control method according to the present invention (hereinafter, also referred to as the present invention method) will be described.
The method of the present invention is a method for preventing vertical overload of the width press equipment 2 by using the above-mentioned device of the present invention.
Figure 11 shows the positional relationship between the slab S and the width press equipment 2 before the slab enters the width press equipment 2 (Figure 11 (a)) and after the slab enters the width press equipment 2 (Figures 11 (b) to (d)).

[Before the slab enters the width press equipment (FIG. 11(a)]
First, the maximum value of the measurement data of the slab twist angle φ, which was previously measured by the slab twist angle acquisition unit 7 when the width press equipment 2 was not damaged, is obtained in advance as the allowable upper limit twist angle φmax.

Before the slab S is clamped by the pinch rolls 30 on the inlet side of the width press equipment 2, the temperature measurement unit 5 measures the press entry temperature T1 before the slab enters the width press equipment 2. As described above, this press entry temperature T1 is preferably the temperature 20 seconds or more after the scale layer on the surface of the slab extracted from the heating furnace is removed. Also, as described above, the press entry temperature is preferably the temperature in the longitudinal direction of the slab (the temperature at multiple points in the longitudinal direction of the slab).

Then, the predicted press load calculation unit 6 uses the basic data for the press stored in the data unit 4 and the press entry temperature T1 measured by the temperature measurement unit 5 to calculate the predicted press load P1 during width reduction of the slab S according to the press load prediction model (e.g., formula (7)). In terms of the reliability of the final judgment result on whether or not the slab can be reduced, it is preferable to use the minimum temperature within the temperature measurement range in the longitudinal direction of the slab as the press entry temperature at this time.

Next, the pressing feasibility determination unit 8 calculates the estimated upper limit press load Pmax1 using the allowable upper limit torsion angle φmax and the vertical load capacity Fcr of the width press equipment 2 with the above formula (1), compares it with the predicted press load P1, and stops the slab transport (prohibits the slab from entering the width press equipment 2) if P1 exceeds Pmax1.

This makes it possible to predict the occurrence of a vertical overload before the slab enters the width press equipment 2, and to prohibit the slab from entering the equipment, thereby preventing damage to the equipment due to an overload that exceeds the vertical load capacity of the width press equipment.
[During width reduction in width press equipment (FIGS. 11(b) to (e))]
In the method of the present invention, when P1 is equal to or less than Pmax1, the slab S is allowed to enter the width press equipment 2, and further, even while the slab S is being transported within the width press equipment 2 or while the width reduction is in progress, the temperature measurement unit 5 continues to measure the press entry temperature T2 of the slab S in the longitudinal direction while the slab S is present directly below the temperature measurement unit 5 (Figures 11(b) and 11(c)).

Then, while the slab S is clamped between the pinch rolls 30 on the entry side and/or exit side of the width press equipment 2, the slab twist angle acquisition unit 7 measures the slab twist angle φ in the longitudinal direction of the slab from the inclination angle of the entry pinch roll.

Here, the slab twist angle φ is calculated based on the slab twist angle φe measured from the inclination angle of the pinch roll on the entry side, and the slab twist angle φo measured from the inclination angle of the pinch roll on the exit side. When the slab is held only by the pinch roll on the entry side (Figure 11 (b) and Figure 11 (c)), φe is used as the slab twist angle φ. When the slab is held by the pinch rolls on the entry side and the exit side (Figure 11 (d)), φe or φo, or the average value of φe and φo, is used as the slab twist angle φ. When the slab is held only by the pinch roll on the exit side (Figure 11 (e)), φo is used as the slab twist angle φ.

The predicted press load calculation unit 8 also calculates the predicted press load P2 in the longitudinal direction using the longitudinal press entry temperature T2.

The pressing feasibility determination unit 8 uses the longitudinal slab twist angle φ and the vertical load capacity Fcr of the width press equipment 2 to calculate the estimated upper limit press load Pmax2 in the longitudinal direction using the above formula (2), compares it with the predicted longitudinal press load P2, and stops slab transport and width pressing if P2 or Pa exceeds Pmax2.

The slab twist angle φ is measured at multiple locations in the slab's longitudinal direction. The press entry temperature T2 is also measured at multiple locations in the slab's longitudinal direction. The tracking function allows the slab twist angle φ at each slab longitudinal position where the press entry temperature T2 (or T1) is measured. Therefore, the P2 and Pmax2 are calculated using the press entry temperature T2 (or T1) and the slab twist angle φ at the same position in the slab's longitudinal direction, and the two are compared. Then, before the slab longitudinal position where P2 exceeds Pmax2 arrives at the pressing operation position of the mold 10, the slab transport is stopped (the rotation of the transport roller 1 is stopped) and the width reduction is performed (the mold 10 is opened in an emergency and the width reduction is interrupted).

This allows the slab transport and width reduction to be stopped before the slab's longitudinal position where P2 exceeds Pmax2 is actually width reduced, thereby preventing equipment damage caused by an overload condition that exceeds the vertical load capacity of the width press equipment.

Furthermore, the reduction feasibility determination unit 8 acquires the measured press load Pa in the longitudinal direction during the width reduction of the slab from the load cell, compares it with the estimated upper limit press load Pmax2 in the longitudinal direction, and stops the slab transport and width reduction if Pa exceeds Pmax2. At this time, the tracking function compares the measured press load Pa at the same position in the slab longitudinal direction with the estimated upper limit press load Pmax2.

As a result, if the measured press load Pa exceeds the estimated upper limit press load Pmax2, the slab transport and width reduction can be stopped immediately, minimizing equipment damage caused by the vertical press load resulting from slab twisting reaching an overload state that exceeds the vertical load capacity of the width press equipment.

[Example 1]
(Example before the width press equipment is installed)
A high-tensile steel slab having a slab thickness of 263 mm, a slab width of 1020 mm, and a width reduction of 356 mm was used as the starting material for the rolled material. A dual-wavelength radiation thermometer was installed as the temperature measuring means of the temperature measuring section 5 at the position shown in Figure 9, and the press entry temperature was measured in the temperature measuring section 5 20 seconds after the scale layer on the surface of the slab after removal from the heating furnace was removed by high-pressure water descaling, and was found to be 880°C.

In the predicted press load calculation section 6, in the classification of the slab used, which was previously stratified according to the slab width reduction amount, conveyance amount, slab thickness, and steel type, the coefficients a and b of the formula (7) used as the press load prediction model were a = -9.726 [ton/°C] and b = 11,308 [ton], respectively. From this, the predicted press load Pp was calculated to be 2,750 tons.

In the pressing feasibility determination unit 8, the vertical upward load capacity Fcr of the width press equipment 2 was 80 tons according to the equipment specifications. In addition, based on the inclination angle of the inlet pinch roll 30 or the outlet pinch roll 32 that holds the slab, the allowable upper limit torsion angle φmax previously obtained was 1.7° (tanφmax = 0.030), and the estimated upper limit press load Pmax1 was 2700 tons according to formula (1). Therefore, the predicted press load Pp = 2750 tons calculated and predicted in the predicted press load calculation unit 6 exceeds the estimated upper limit press load Pmax1 = 2700 tons, so the transport of the slab into the width press equipment 2 was stopped (entry prohibited).

[Example 2]
(Example of width reduction in progress in width press equipment)
A high carbon steel slab having a slab thickness of 250 mm, a slab width of 990 mm, and a press width reduction of 246 mm was used as the starting material for the rolled material. As in Example 1, the press entry temperature was measured using a dual wavelength radiation thermometer 20 seconds after the scale layer on the surface of the slab after removal from the heating furnace by high pressure water descaling, and was found to be 1020°C.

In the predicted press load calculation section 6, in the classification of the slab used, which was previously stratified according to the width reduction amount of the slab, the conveying amount, the slab thickness, and the steel type, the coefficients a and b of the formula (7) used as the press load prediction model in Example 2 were a = -9.175 [ton/°C] and b = 10668 [ton], respectively. From this, the predicted press load Pp was calculated to be 1310 tons. Since this Pp (= 1310 tons) is below the estimated upper limit press load (same as in Example 1) Pmax1 (= 2700 tons), the conveying of the slab into the width press equipment 2 was continued without stopping.

Furthermore, after the slab S was clamped by the inlet pinch rolls 30, the press entry temperature T2 of the slab S in the longitudinal direction was continuously measured using the dual-wavelength radiation thermometer. As shown in Figure 10, the actual measurement results of the press entry temperature T2 of the slab S in the longitudinal direction were 890°C, and the minimum temperature was 890°C. From the press load prediction model of Example 2, the predicted press load P2 at this minimum temperature of 890°C was calculated to be 2502 tons.

Meanwhile, while the slab was being transported in the width press equipment 2, the slab twist angle φe obtained in the slab twist angle acquisition section 5 from the inlet pinch roll inclination angle when the position in the longitudinal direction of the slab where the press entry temperature T2 was the lowest temperature of 890°C reached the inlet pinch roll 30 was 1.91°C (tan φe = 0.033).

In the reduction feasibility determination unit 8, the vertical load capacity Fcr of the sizing press is 80 tons according to the equipment specifications, and the slab torsion angle φe at the position where the press entry temperature was the minimum temperature of 890°C, acquired in the slab torsion angle acquisition unit 5, is 1.91°C (tanφ = 0.033), so the estimated upper limit press load Pmax2 is calculated to be 2400 tons from formula (2). Therefore, the predicted press load P2 = 2502 tons calculated in the predicted press load calculation unit 6 exceeds the estimated upper limit press load Pmax2 = 2400 tons, so the die 10 is opened in an emergency before the die 10 is used to reduce the width at the position where the longitudinal press entry temperature T2 is the minimum temperature of 890°C, and the press width reduction is interrupted.

1 Conveyor roller 2 Width press equipment 3 High-pressure water descaling device 4 Data unit 5 Temperature measurement unit (e.g., radiation thermometer)
6 Calculation unit for predicted press load 7 Slab twist acquisition unit 8 Rolling reduction feasibility determination unit 10 Die 15 Buckling prevention roll 20 Horizontal line passing through the center of the width cross section of the slab 22 Incline direction line that passes through the center of the width cross section of the slab and indicates twist 220 Initial inclination direction line 221 Incline direction line after width reduction 30 Entry pinch roll 32 Exit pinch roll 40 Holding cylinder F Lifting force Fcr Vertical load capacity P Press load Pcr Horizontal load capacity Pmax Estimated upper limit press load Pp, P1, P2 Predicted press load Pa Actual press load S Slab Ts, T1, T2 Press entry temperature φ Slab twist angle φ0 Initial slab twist angle φ1 Slab twist angle φmax after width reduction Allowable upper limit twist angle φe Slab twist angle φo measured from entry pinch roll inclination angle Slab twist angle δ measured from exit pinch roll inclination angle Amount of twist δ0 Initial twist amount δ1 Twist amount after width reduction

Claims (9)

A width reduction control device that prevents vertical overloading of a width press facility equipped with a pinch roll and a load cell, the device comprising: a temperature measurement unit; a predicted press load calculation unit; a slab torsion angle acquisition unit; and a reduction feasibility determination unit;
The temperature measuring unit includes a means for measuring a press entry temperature, which is a surface temperature of the slab when it enters the width press equipment;
The predicted press load calculation unit includes a means for calculating a predicted press load Pp during width reduction of the slab using the press entry temperature,
The slab twist angle acquisition unit includes a means for measuring a slab twist angle φ from a pinch roll inclination angle of a pinch roll on an entry side and/or an exit side of the width press equipment,
The rolling possibility determination unit derives an estimated upper limit press load Pmax based on the slab twist angle φ measured by the slab twist angle acquisition unit and the vertical load capacity Fcr of the width press equipment, compares it with the predicted press load Pp, and includes a means for stopping slab transportation when Pp exceeds Pmax.
A width reduction control device characterized by the above. The width reduction control device according to claim 1, characterized in that the reduction feasibility determination unit acquires the actual press load Pa during width reduction of the slab from the load cell, compares it with the estimated upper limit press load Pmax, and has a means for stopping slab transport and width reduction if Pa exceeds Pmax. The width reduction control device according to claim 1 or 2, characterized in that the press entry temperature is the temperature 20 seconds after the surface scale of the slab removed from the heating furnace. The width reduction control device according to any one of claims 1 to 3, characterized in that the means for measuring the press entry temperature is a radiation thermometer. The width reduction control device according to any one of claims 1 to 4, characterized in that the means for calculating the predicted press load is configured as a linear equation with the press entry temperature as an explanatory variable and the predicted press load as a target variable. The width reduction control device according to any one of claims 1 to 5, characterized in that the rolling down feasibility determination unit comprises means for calculating an estimated upper limit press load Pmax based on the slab twist angle φ and the vertical load capacity Fcr by the following formulas (1) and (2), respectively.
Pmax1 = Fcr / tan φmax (1)
Pmax2 = Fcr / tan φ (2)
Here, Pmax1 means the estimated upper limit press load Pmax obtained by formula (1) at the stage before the slab enters the width press equipment , and Pmax2 means the estimated upper limit press load Pmax obtained by formula (2) at the stage after the slab enters the width press equipment . In addition, Fcr is the vertical load capacity of the width press equipment, φ is the slab torsion angle, and φmax is the allowable upper limit torsion angle. A width reduction control method for preventing vertical overload of a width press facility using the width reduction control device according to any one of claims 1 to 6,
The maximum value of the measurement data of the slab twist angle φ, which was previously measured by the slab twist angle acquisition unit when the width press equipment was not damaged, is obtained in advance as the allowable upper limit twist angle φmax,
Before the slab is pinched by the pinch rolls at the inlet side of the width press equipment,
The temperature measuring unit measures a press entry temperature,
The predicted press load calculation unit calculates a predicted press load P1 during width reduction of the slab using the press entry temperature measured by the temperature measurement unit,
The width reduction control method is characterized in that the rolling down feasibility determination unit calculates an estimated upper limit press load Pmax1 using the allowable upper limit torsion angle φmax and the vertical load capacity Fcr of the width press equipment by the following formula (1), compares it with the predicted press load P1, and stops slab transportation if P1 exceeds Pmax1.
Pmax1 = Fcr / tan φmax (1)
Here, Pmax1 is the estimated upper limit press load according to formula (1), Fcr is the vertical load capacity of the width press equipment, and φmax is the allowable upper limit torsion angle. When the P1 is equal to or less than Pmax1,
Furthermore, during the transport of the slab, the temperature measuring unit measures the press entry temperature T2 in the longitudinal direction of the slab,
While the slab is being pinched by the pinch rolls on the inlet and/or outlet sides of the width press equipment,
the slab twist angle acquisition unit measures a slab twist angle φ in the longitudinal direction of the slab from the inlet and/or outlet pinch roll inclination angles,
The predicted press load calculation unit calculates a predicted press load P2 in the longitudinal direction using the press entry temperature T2 in the longitudinal direction,
The width reduction control method according to claim 7, characterized in that the rolling possibility determination unit calculates an estimated upper limit press load Pmax2 in the longitudinal direction using the longitudinal slab twist angle φ and the vertical load capacity Fcr of the width press equipment according to the following formula (2), compares it with the predicted press load P2 in the longitudinal direction, and stops slab transportation and width reduction if P2 exceeds Pmax2.
Pmax2 = Fcr / tan φ (2)
Here, Pmax2 is the estimated upper limit press load according to formula (2), Fcr is the vertical load capacity of the width press equipment, and φ is the slab twist angle from the inclination angle of the pinch rolls on the inlet and/or outlet sides. The method for controlling width reduction described in claim 8, characterized in that the unit for determining whether or not the width reduction is possible acquires the actual press load Pa in the longitudinal direction during the width reduction of the slab from the load cell, compares it with the estimated upper limit press load Pmax2 in the longitudinal direction, and stops the slab transport and width reduction if Pa exceeds Pmax2.

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