JPS62197209A - Camber controlling method for hot rolling of metal plate - Google Patents

Abstract

PURPOSE:To eliminate troubles after a finishing rolling and succeeding processes and to improve the yield of finished plate stocks by making a heated slab a symmetrical rough bar without cambers or wedges using a rough rolling mill and eliminating a difference between a right edge and a left edge temp. on the inlet side of a finishing rolling mill. CONSTITUTION:Temps. in the width direction of a heated slab are measured 5 on the inlet side of a reversible rough rolling mill 1 and the slab is roughly rolled 1 after making a right edge and a left edge temp. equal by adjusting an edge heater 4 by a controller 6. A camber meter 7 on the outlet side and a right and a left plate thickness meter 8a and 8b detect a slab shape and the rough bar 3 is formed into a symmetrical good shape without cambers or wedges by repetitive rolling. Again, the temp. in the width direction of the rough bar 3 is measured 5 and the bar 3 is carried to a tandem finishing rolling mill 2 after eliminating a difference between both edge temps. by controlling the edge heater 4 by the controller 6. Thus, occurrence of cambers being sensitive to temp. differences is prevented so as to remarkably reduce rolling troubles in the finishing and succeeding processes and to improve the yield of finished plate stocks.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention provides a method for controlling camber in hot rolling of plate materials;
In particular, the present invention relates to a method for preventing the occurrence of camber during double-finish rolling.

(Prior Art) In general, in hot rolling of plate materials, various asymmetries between the working side and the driving side (hereinafter, both sides are collectively referred to as left and right) of the rolling mill and the rolled material are often caused. Camber may occur in the rolled material. This is caused by a combination of factors such as the difference in the rolling position between the left and right sides, the difference in plate thickness between the left and right entrance sides, the temperature difference between the left and right plates, the difference in mill rigidity between the left and right sides, and the deviation between the center of the plate and the center of the mill, resulting in a difference in the rolling reduction rate between the left and right sides, which causes the difference in the rolling material. This causes camber.

If such camber occurs during rough rolling, it will cause rolling troubles such as poor sheet threading due to tip end face rounding during finish rolling, and rolling troubles such as narrowing due to meandering during tail end removal, and work efficiency will deteriorate significantly. , yield also decreases.

Various methods have been proposed for camber control in plate rolling, but correcting only the camber in a certain rolling process cannot sufficiently prevent the occurrence of camber in the next rolling process. In other words, among the factors that cause camber in plate rolling, the main factors related to the rolled material are the camber, wedge, and temperature difference between the left and right sides of the plate material, and even if there is no camber, camber will occur if there is a wedge or a temperature difference between the left and right sides. . FIG. 13 shows the relationship between the left and right temperature difference and the amount of camber, and it can be seen that a small temperature difference can cause a large camber.

As a method for preventing the occurrence of camber due to temperature differences between the left and right sides, for example, as seen in Japanese Patent Application Laid-Open No. 58-163512, the finishing mill The left and right rolling positions are being corrected.

(Problems to be Solved by the Invention) However, in the conventional method, since the relationship between the left and right temperature difference and the correction of the left and right rolling positions changes depending on the rolling conditions, it is difficult to quantify, and it is not always possible to sufficiently prevent the occurrence of camber. It doesn't necessarily mean it can be prevented. Therefore, especially when the temperature difference between the left and right sides is large, there are problems such as the occurrence of camber due to over-control or insufficient control, which may cause the above-mentioned rolling troubles.

The present invention was made in view of such problems, and it is possible to reduce the temperature difference between the left and right sides of the rolled material after rough rolling to zero.
It is an object of the present invention to provide a method for controlling camber in hot rolling of a plate material, which eliminates troubles such as recurrence of camber in the next finish rolling process and achieves a high yield.

(Means for Solving the Problems) In order to solve the above problems, the present invention corrects the camber and wedge of the material to be rolled in advance in rough rolling to form a rough bar with a symmetrical shape, and then rough rolling. A widthwise thermometer and edge heaters are provided on the left and right sides of the downstream side between the finishing rolling machine and the finishing mill, and the temperature of at least the widthwise both ends of the rough bar is measured by the widthwise thermometer, and Based on this, the left and right outputs of the edge heaters are adjusted so that the temperature difference between both ends of the rough bar becomes zero.

(Example) Next, one embodiment of the present invention will be described with reference to the drawings.

(1) Configuration of hot rolling line FIG. 1 shows a schematic configuration of a hot rolling line to which the present invention is applied. That is, in this hot rolling line, a rough rolling mill 1 is arranged on the upstream side, and a tandem-type finishing mill 2 is arranged on the downstream side.

An edge heater 4 that heats both sides of the material to be rolled 3 is installed on the entry side of the rough rolling mill I, and a controller 6 is activated based on the temperature difference between the left and right sides detected by a width direction thermometer 5 installed on the upstream side of the edge heater 4. Through this, the temperature of the edge heater 4 can be adjusted.

Further, on the exit side of the rough rolling mill 1, a camber gauge 7 for actually measuring the amount of camber of the rolled material 3, and left and right plate thickness gauges 8a and 8b for detecting the left and right thicknesses of the rolled material 3 are provided. Based on the signals from the camber gauge 7 and the left and right plate thickness gauges 8a and 8b, the left and right rolling positions of the roughing mill I are set via the controller 9.

On the other hand, on the entry side of the second rolling mill 2, an edge heater 41, a width direction thermometer 5, and a controller 6 are provided, similar to the rough rolling mill 1 described above.

The edge heater 4 is originally intended to make the mechanical properties of the plate uniform in the width direction, and as shown in FIG. In order to eliminate this, control is performed to adjust the output of the edge heater 4. However, in the method according to the present invention, since the edge heater 4 is intended to suppress the generation of camber by eliminating the temperature difference between the left and right sides, as shown in FIG. It is sufficient to have a control function to make them the same. As described above, although the present invention uses a known edge heater, its purpose and method of use are completely different.

(2) Specific example of camber control method in rough rolling stage In a hot rolling line configured as above, first, a method for correcting camber and wedge in the rough rolling stage to obtain a symmetrically shaped rough bar will be explained. .

First, in any i-th pass of rough rolling in the rough rolling mill 1 excluding the final two passes, the camber amount and wedge amount are actually measured using the camber total 7 and left and right plate thickness totals 8a and 8b, and the camber curvature and Calculate the wedge rate.

Alternatively, a method may be used in which the camber curvature and wedge ratio are estimated based on the amount of change in the left and right rolling load difference in the first pass. This estimation method will be explained below based on steps I to 4 of the flowchart shown in FIG.

First, in any i-th pass of rolling, as Step 7, the left and right rolling load difference Pdfi is measured at any point 2 or more during rolling, and the time interval between the measurement points and the amount of change δPdfi in the left and right rolling load difference during that time are calculated. demand. Note that the subscript df represents the difference between the left and right sides, and the direction of meandering toward the drive side is defined as positive.

Next, in step 2, from this time interval and the change amount δPdfi in the left and right rolling load difference, the deviation amount Δ5dfi of the left and right rolling position difference from the appropriate value 5dfi* in the relevant pass is estimated by an experimental formula or a theoretical formula.

FIG. 5 shows the relationship between the deviation amount ΔSdf of the left-right rolling position difference and the change amount δPdf of the left-right rolling load difference at a certain time interval, which was determined by an experiment using an aluminum plate, and the two are approximately proportional. Therefore, if the relationship between the front levers is determined through experiments, it is possible to measure δPdfi and estimate Δ5dfi.

Further, Δ5dfi can also be calculated theoretically from δPdfi. The change in the difference in the rolling load between the left and right sides is mainly caused by the meandering of the rolled material, and the difference in the rolling load between the left and right sides between a certain time A and B changes from PdfA to parB, and the amount of meandering shown in Fig. 6 changes from yA to VB. Then, the relationship between the two is expressed by the following equation from the balance of force and moment.

Here, P is the sum of the left and right rolling loads, and L is the distance between the supporting points of the backup rolls. The change in meandering amount as rolling progresses is expressed by the following equation.

=8- Here, yo is the off-center amount at the time of biting, X is the rolling length, and γ is a constant determined from the specifications of the rolling mill and the rolling conditions. f (z) is an influence term of various left-right asymmetry factors, and for example, considering the left-right Mill constant difference Mar as one of the left-right asymmetry factors, it is expressed by the following equation.

5df=Sdf*+ASdr Here, M is the sum of the left and right Mill constants. (2) As is clear from the equation, if the material to be rolled is not off center at the time of biting (yo=o), meandering will not occur when f(z)-〇. Therefore, the appropriate value S df* of the difference in left and right lowering positions to prevent meandering can be found using the formula 0 as f(z)−〇.

When the left and right pressure position difference deviates from the proper value S df*, f (z) is expressed by the deviation amount ΔSdf from the proper value as follows.

Since f (z) is also expressed as a linear combination of each term for other left-right asymmetry factors as in equation 0, the appropriate value of the left-right depression position difference S df for any asymmetry factor
* exists and meandering occurs when there is a deviation amount ΔSdf from the appropriate value. Substituting yA and YB found from formula ■ into equation 0, -e-7XA) ・・Substituting equation 0 into equation 00 and setting yo=0, ・ΔSdf
...■, and δPdf and ΔSdf
It can be seen that there is a proportional relationship. Therefore, if δPdf is actually measured, ΔSdf can be calculated using equation (2).

Figure 7 shows the amount of change in the left and right rolling load difference calculated from the actual ΔSdf (δP df)c and the measured value (δP df).
This study investigated the relationship between M. Although the two are almost proportional, the actual measured value is slightly smaller than the calculated value.

To compensate for this, a correction coefficient is introduced, and (δPdf)M-α・(δPdf)c ・・
It can be expressed as ■. Here, α is a correction coefficient determined by experiment. From equation (2) and equation (0), the amount of deviation ΔSd4 in the left and right rolling position difference of the pass can be determined from the amount of change (δPdf)m in the actual rolling load difference using the following equation.

・(δPdf)M ・As the 0th step shadow, the wedge rate φ after the relevant pass is estimated from the shift amount ΔSdf of the left and right lowering position difference. If the wedge is generated following the inclination of the work roll, the relationship between the wedge fihdf and ΔSdl' is expressed by the following equation from a geometrical relationship.

Here, B is the plate width. The wedge rate φ is defined by the following equation.

Here, h is the average outlet side plate thickness. From the [phase] equation and the 0 equation, the relationship between ΔSdf and φ is expressed by the following equation.

The wedge ratio φ can be estimated from the deviation amount ΔSdf of the left and right lowering position difference using the equation 0. Note that from the [phase] equation, the relationship between the amount of change in ΔSdf and the amount of change in hdf between the i-th pass and the (i-1)th pass can be determined by the following equation.

Figure 8 shows the results of an experiment conducted to confirm Equation 0.
hdf, −hdf, −+ and ΔSdf, −Δ5d4i−
, are in a proportional relationship, and it can be seen that equation 0 is correct. However, in this case, the wedge is defined as the plate thickness at the 10 mm position from the plate width edge, so the theoretical formula in the figure is B in the [phase] formula.
is designated as B-20.

Next, in step 4, the camber curvature ρ is estimated from the wedge ratio φ. The relationship between the wedge ratio and camber curvature of the i-th pass and the (i-1)th pass is expressed by the following equation, assuming a plane distortion state.

Here, λi is the elongation rate of the i-th pass (λ, =h, -1/
h, ), and it can be seen that even if the wedge ratio does not change, the camber curvature decreases by the amount of elongation. However, since three-dimensional deformation actually occurs, the camber curvature does not change even though the wedge ratio changes. FIG. 9 shows the relationship between the wedge ratio change and the camber curvature change, which was determined through experiments.

Although the two have a substantially constant proportional relationship regardless of the plate thickness, the actual change in camber curvature is smaller than when plane distortion is assumed (a straight line with an inclination of 45°). Here, the slope of the straight line representing the actual proportional relationship between the two is defined as the camber change coefficient ξ. FIG. 1O shows the relationship between the rolling reduction r and the camber change coefficient ξ, which was obtained through experiments. The larger the reduction rate r is, the smaller the camber change coefficient ξ is. Therefore, the relationship between the actual wedge ratio change and the camber curvature change is expressed by the following equation.

Therefore, if ξ(r) is found experimentally in advance, then ρ1-1-0. By setting φ1-1=0, the camber curvature ρi after the i-th pass is determined from the wedge ratio φi after the i-th pass.

Next, as step 5, the wedge rate φ after the first pass is actually measured or estimated according to steps 1 to 4.
1, the camber curvature ρi, and the pass schedule after the (i+1)th pass, the wedge ratio φ after the (i+1)th pass
Target values of j+1 and camber curvature ρj+1 are determined.

This determination method will be explained below with reference to the control conceptual diagram shown in FIG.

Now, the wedge ratio φi and the camber curvature ρi after the i-th pass
is known by the above estimation. Here φi and ρ1
is represented by a point A on coordinates with the camber 1llI ratio on the vertical axis and the wedge ratio on the horizontal axis.

Next, in the (i+1)th pass, the wedge ratio and camber curvature change according to equation 0, but this process can be divided into a component in which the wedge ratio does not change due to uniform pressure on the left and right sides, and a component in which the wedge ratio changes due to uneven pressure on the left and right sides. Think separately. First, the camber curvature is from ρ1 to ρj/λ
The state where r+1 (tatashi, λ, +I-hI/h, +,) is reached is point A' on the coordinates, and the wedge ratio and camber curvature change from φi to φ1+1, ρ, /λ21+1, respectively due to the left and right uneven pressure. The state where ρi+1 is reached is point B. In other words, point B is point A.

It is a point on a straight line Q1 passing through the line and having a slope ξ(ri + 1).

Similarly, in the (i+2)th pass, the wedge ratio and camber curvature change from point B (φi+1.ρ1+1) to point B' (φi+
1°ρ, +1/λ1+2) to point C(φ, +2.ρ,
+2).

Here, point B' is a point where the value of the vertical axis of point B is month/λr+2, similar to the point to the point on the (i+1)th pass. Point B is on the straight line Q with slope ξ(ri+1), so it is point B.

is the intersection of the straight line 121 and the horizontal axis (pI+1−ρ1+1/λr
+2-0) and lies on the straight line ρ2 with a slope ξ(ri+1)/λ12+2.

On the other hand, since the goal is to make both the camber and wedge zero after the (i+2)th pass, the state (point C) after the (i+2)th pass must be at the origin. Therefore, point B°
is a straight line Q passing through the origin and having a slope ξ(ri+2).

It needs to be on top. Therefore, point B' for achieving the goal is determined as the intersection of straight line Q2 and straight line Q3, and the intersection of the line drawn parallel to the vertical axis from point B° and straight line O is the target point B, that is, the (i+1)th point. Wedge rate after pass φ1
+1 and camber curvature ρ1+1.

Next, in step 6, using the target value of wedge ratio φ, +1 after the (i+1)th pass determined in step 5, the (i+1th)
Find the amount of correction for the difference in left and right lowering positions in the pass.

Δ5df1+l−ΔSdf, =L(h,+lφi+1
-hiφi)... [phase] Next, in step 7, the initial setting left and right downward position is set to S.
As D1+1 and SWi+1, the corrected left and right lowering positions S, '', +1 and sWi+1 in the (t+1)th pass are determined by the following equations.

-h, φ1)) -h, φi)) . . . 0 Then, the rolling position is set according to the left and right rolling positions obtained from formula 0, and the (i+1)th pass of rolling is performed.

Next, as step 8, the (i+1)th pass is
i+2) Calculate the amount of correction of the left and right pressure position difference of the pass. Here, since the wedge after the (4+2)th pass is set to zero, the shift amount of the left and right bottom position difference of the (i+2)th pass from equation 0 is Δ5df1+2-0...
Becomes a [stock]. That is, in the (i+2)th pass, the wedge is set to zero, so the appropriate value of the left and right pressure position difference S df*
Rolling is done so as to eliminate the amount of deviation from the surface. Note that, as described above, the appropriate value S df* of the difference in the left and right pressing positions can be obtained from the formula 0, for example, when there is a difference in the mill constant between the left and right sides.

In the above specific example, the camber and wedge were detected in the arbitrary i-th pass and corrected in the following two passes, but based on the same principle, the camber and wedge are corrected in the subsequent three or more passes. It is also possible.

In addition, the specific example has a camber total of 7 and a left and right plate thickness total of 8 a.
, 8b showed a method of calculating the wedge ratio and camber curvature by actually measuring the wedge amount and camber amount of the rolled material 3, and a method of calculating the wedge ratio and camber curve from the amount of change in the left and right rolling load difference. It is also possible to actually measure either the wedge amount or the camber amount, and estimate the other amount using the above-mentioned formula 0.

Next, a specific example will be described in which the camber control method in the second rough rolling stage is actually applied to a hot rolling rough mill having the following specifications.

Backup roll dimensions 2 1430'mmmm x 213
4Q work roll dimensions: 1070'mmX
2186Qmm Backup roll distance between fulcrums/315
0mm mil constant: 380 TON/
mm In the second stand of the coarse mill with the above specifications, the thickness is 1
A bar having a diameter of 20 mm and a width of 1214 mm was rolled to a thickness of 30 mm in 3 passes by applying the method according to the present invention.

The reduction schedule is 120 mm → 75 mm-+ 4
．． 5 mm-+30 mm. FIG. 9 shows the wedge ratio and camber curvature of each pass, and the following explanation will be given based on this figure.

The camber curvature and wedge ratio at the exit side of the first stand of the rough mill were almost zero, but when the first pass of rolling was performed, camber occurred, and the amount of change in the left and right rolling load difference at this time was the same as that at the start of rolling. The amount was approximately 120 tons from start to finish.

If the camber curvature ρ1 and the wedge ratio φ1 are estimated from the amount of change in the left and right rolling load difference, as shown in the figure, ρ, -
1.0 x I O-” (]/mm), φ+=2.
Ox I was 0-6 (1/mm). Further, if calculation is performed according to the method according to the present invention, the target camber curvature ρ2 and target wedge ratio φ after the second pass will be ρ, −1. OX I 0-0 (1/mm),
φ2-1. Ox 10-80-8 (17, the amount of correction of the left and right pressure position difference to achieve the target is -0°6
It became 1+nm. The left and right rolling positions were set according to the difference in the left and right rolling positions, and a second pass of rolling was performed to generate reverse camber. Subsequently, a third pass of rolling was performed by setting the rolling position so that the deviation amount between the left and right rolling positions was zero, and a rough bar with substantially zero camber and wedge was obtained.

The camber control method in the above rough rolling stage is as follows:
Although this is the optimal method for obtaining a rough bar without camber and wedge, other methods may be used as long as they can correct camber and wedge at the same time.

(2) Camber control method in finish rolling stage A camber control method in the finish rolling stage, which is an embodiment of the present invention, will be described.

The temperature of at least the left and right plate ends of the material to be rolled 3 is detected by the width direction thermometer 5 provided on the entry side of the finishing rolling mill 2, and the temperature is controlled via the controller 6 so that the left and right temperatures are the same. to adjust the left and right outputs of the edge heater 4.

Since the material to be rolled 3 has already become a symmetrical rough bar without camber and wedge in the rough rolling stage, when the temperature difference between the left and right sides is removed by the edge heater 4 on the entry side of the finishing rolling mill 2, This means that the causes of camber generation have been almost completely eliminated. However, even in finish rolling, there are factors that cause camber, such as off-center during threading due to asymmetry of the rolling mill and improper setting of side guides, but the amount of camber that occurs due to these is small, and known control techniques It is fully controllable. Therefore, by applying the present invention in the finishing rolling stage on the premise that camber and wedges are removed in the rough rolling stage, it is possible to completely suppress the occurrence of camber in the finishing rolling.

In addition, in the finish rolling stage, considering that camber occurs mostly during sheet passing and sometimes during bottom removal, even if the present invention is applied only to the leading and trailing ends of the rough bar after rough rolling, You can achieve your goals. In particular, conventionally,
Since a camber control method for preventing the occurrence of camber at the tip end in finish rolling has not been established, it is effective to apply the present invention only to the tip end of finish rolling.

In this case, less energy is required for the edge heater 4 per roll of rolled material 3.

In addition, in this embodiment, an edge heater 4 similar to that of the finishing rolling mill 2 is installed on the inlet side of the rough rolling mill 1. The reason why the left and right thermometers 5 and the controller 6 are provided is when the rolled material 3 is in the rough rolling stage.
This is to improve the accuracy of camber control that simultaneously corrects camber and wedge by removing the temperature difference between the left and right sides.

(Effects of the Invention) As is clear from the above explanation, according to the present invention, a rough bar without gambar and wedge is obtained in the rough rolling stage,
The purpose is to eliminate the temperature difference between the left and right sides of the rough bar before rolling.

Therefore, the main cause of camber generation in the finish rolling stage is completely eliminated, and rolling troubles in the finish rolling and the next process can be significantly reduced, and the yield can be improved. It has an effect.

[Brief explanation of drawings]

Fig. 1 is an equipment configuration diagram of a hot rolling line to which the present invention is applied, Fig. 2 is an explanatory diagram of the original function of the edge heater, Fig. 3 is an explanatory diagram of the function of the edge heater used in the present invention, and Fig. 4 is an explanatory diagram of the function of the edge heater used in the present invention. A flowchart of the camber control method in the rough rolling stage, Fig. 5 is a diagram showing the relationship between the left and right rolling position difference and the amount of change in the left and right rolling load difference, Fig. 6 is an explanatory diagram of the meandering amount, and Fig. 7 is a change in the left and right rolling load difference. Figure 8 is a diagram showing the relationship between the calculated value and actual measured value, Figure 8 is a diagram showing the relationship between the modified type of left and right reduction position difference and the amount of change in the wedge, Figure 9 is a diagram showing the relationship between wedge ratio change and camber curvature change, and Figure 1O is the relationship diagram between the wedge ratio change and camber curvature change. Figure 11 is a diagram showing the relationship between rolling reduction and camber change coefficient, and Figure 11 is a conceptual diagram of the camber control method in the rough rolling stage.
Figure 2 is an example of the camber control method in a hot rolling rough mill, the first
FIG. 3 is a diagram showing the relationship between the temperature difference in the width direction and the amount of camber generated. I... Rough rolling mill, 2... Finishing rolling mill, 3... Rolled material (
Rough bar), 4... Edge heater, 5... Width direction thermometer, 6... Controller. Patent applicant Kobe Steel Co., Ltd. agent Patent attorney Two idiots ("'L'+1-10")
1JρLl−IOLJρ4(uoll)J+llJ
uJpd (11l1luu/ll h-+,, 1 Fig. 1 Fig. 12 i xlo-6 ->'2'' 2L - 冑控 Renichi 〇Establishment I direct'zen- Fig. 13 @ Nishiki Haruka Watari T” C.I.

Claims (3)

[Claims] (1) After correcting the camber and wedge of the rolled material in advance during rough rolling to make a rough bar with a symmetrical shape,
A width direction thermometer is provided between a rough rolling mill and a finishing rolling mill, and edge heaters are provided on the left and right sides of the downstream side thereof, and the temperature of at least the width direction both ends of the rough bar is measured by the width direction thermometer, A method for controlling camber in hot rolling of a sheet material, comprising adjusting the left and right outputs of the edge heaters based on the measurement results so that the temperature difference between both ends of the rough bar becomes zero. (2) The camber amount of the rolled material after passing through the i-th pass, which is determined by estimation or actual measurement in any i-th pass excluding at least two final plate rolling passes, of the symmetrically shaped rough bar in the rough rolling. Based on the wedge amount and the subsequent pass schedule, the i+th
Estimate the target camber amount and target wedge amount after passing one pass, calculate the correction amount of the rolling position difference between the working side and the drive side of the rolling mill after the i+1th pass from the target wedge amount, and correct this rolling position difference. Hot rolling of the plate material according to claim 1, characterized in that it is obtained by setting rolling positions on both sides according to the rolling amount and performing subsequent rolling from the i+1th pass onward. camber control method. (3) At least one of the camber amount and wedge amount is reduced on both sides based on the amount of change over time in the rolling load difference on both sides measured at two or more arbitrary points in the arbitrary i-th pass. The camber control method in hot rolling of a plate material according to claim 2, wherein after estimating the positional difference, the estimation is performed based on the rolling position difference.