JPH0985317A - Control of sheet thickness in stainless steel sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain the displacement of a sheet thickness and to improve the quality of products by obtaining the deviation of a roll reduction position using the function due to the rolling velocity, the sheet width, a plasticity constant and a mill constant and controlling the roll reduction position based on the deviation value, at the time of acceleration or deceleration. SOLUTION: A first and secondary speed meters 7a and 7b are installed to each of a first and secondary deflector rolls 6a and 6b provided at the inlet and outlet sides of the mill 2 to measure the rolling velocity υ. A reduction position detector 8 is installed to a hydraulic screwdown device 4 to detect the roll reduction position S. And the steel sheet 1 recoiled from a first coiler 9a is rolled with the mill 2, coiled with a secondary coiler 9b, recoiled from the secondary coiler 9b again to roll with the mill 2 and coiled with the first coiler 9a. At the time of this rolling, the sheet thickness (h) at respective outlet sides is controlled by controlling the deviation ΔS of reduction position with an arithmetic and control unit 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plate thickness control method for a stainless steel plate, and more particularly to a control method suitable for preventing a plate thickness variation that occurs when a rolling mill accelerates or decelerates.

[0002]

2. Description of the Related Art Generally, when a stainless steel plate is rolled by using a rolling mill, when the steel plate is accelerated or decelerated, the delivery side plate thickness of the rolling mill fluctuates. Since this plate thickness fluctuation occurs just below the rolling roll, the conventional automatic plate thickness that measures the plate thickness and rolling speed on the inlet side or the outlet side of the rolling mill and controls the roll reduction position and tension based on the measured values. Control (hereinafter abbreviated as AGC) cannot sufficiently cope with the situation.

Therefore, with respect to such plate thickness variation,
Usually, a method of estimating a rolling force change by a function of a rolling speed and a coefficient of friction between a rolling roll and a steel sheet (for example, see JP-A-51-95964), or continuous rolling speed and rolling load. The sheet thickness variation is controlled by a method of performing a positive measurement to predictively correct the reduction position correction amount (see, for example, JP-A-47-25045).

[0004]

However, when it is attempted to control a cold reversible multiple rolling mill such as a cluster mill by using the above conventional method, the plate thickness changes due to the number of passes. However, there is a problem in that it is not possible to appropriately correct the roll reduction position because the friction coefficient also changes.

In order to solve such a problem, the applicant of the present invention has already proposed a plate thickness control method for stainless steel plates in Japanese Patent Application No. 6-140419. The contents are as follows: When rolling a stainless steel sheet, the roll rolling position deviation ΔS is calculated using the function expressed by the following formula (1) depending on the rolling speed P and the delivery side plate thickness h, and the obtained roll rolling position is It is intended to control the roll reduction position by performing acceleration / deceleration compensation based on the value of the deviation ΔS.

ΔS / Δv = c ₁ · (P / Δh) + c ₂ (1) where Δv: rolling speed deviation, Δh: delivery side thickness deviation, c
₁ , c ₂ ; coefficients. However, even with this plate thickness control method, the relationship between the load fluctuation ΔP and the rolling speed deviation Δv is ΔP.
Assuming that / Δv = constant and approximating P / Δh = Q, the calculation accuracy of ΔS is poor, and there is a drawback that the roll rolling position cannot be sufficiently corrected.

It is an object of the present invention to provide a plate thickness control method for a stainless steel plate which can solve the above problems and can suppress the plate thickness variation during acceleration / deceleration during rolling of the stainless steel plate.

[0008]

The present invention is a method for controlling the plate thickness when rolling a stainless steel plate using a rolling mill having an AGC function, and when accelerating or decelerating,
The roll rolling position deviation ΔS is obtained using a function based on the rolling speed v, the strip width b, the plastic constant Q, and the mill constant M, and the roll rolling position is controlled based on the value of the obtained roll rolling position deviation ΔS. Is a method for controlling the thickness of a stainless steel plate.

The roll-rolling position deviation is preferably given by the following formula ΔS = (Q / M ² + 1 / M) · b · (αv ² + βv). Here, α and β are constants. Further, it is preferably applied when the type of stainless steel sheet to be rolled is austenitic.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The principle of the present invention will be described below. The inventors of the present invention conducted various experiments and studies on the mechanism of occurrence of strip thickness variation using a rolling mill equipped with an AGC function, and as the rolling speed v increased, the roll bite inlet represented by the following formula (2) It was found that the oil film thickness t _{o1 of P.}

T _o1 = {3η · R ′ / (p ₁ · L)} · (v _P + v _R ) ... (2) Where, η; friction coefficient, R ′; Hitchcock flat roll Radius, p ₁ ; pressure applied to the oil film at the roll bite inlet,
L: contact arc length of roll bite, v _P : plate speed, v _R ;
Roll speed. As the oil film thickness t _o1 increases, the friction coefficient η represented by the following equation (3) decreases, the shear stress τ in the oil film decreases, and therefore the rolling load P decreases.

Τ = (v _P −v _R ) · η / t _o1 (3) Subsequently, when the rolling mill elastically restores, the gap amount between the upper and lower work rolls decreases, so the delivery side plate thickness h Becomes thin due to the relationship shown in Eq. (4). Δh = (1 / M) · ΔP (4) where M is a mill constant.

More specifically, as shown in FIG. 2, the plate thickness h ₁ after rolling is obtained as an intersection point m between the mill rigidity curve B ₁ and the plastic characteristic curve A ₁ during rolling of the material. However, the roll rolling position at this time is S ₁ , and the rolling load is P ₁ . Now, assuming that the deformation resistance of the material apparently changes due to the increase (acceleration) of the rolling speed v increasing the oil film thickness t _o1 at the roll bite inlet and the decrease of the friction coefficient η, the plastic characteristic curve changes from A ₁ to It will be changed to a _2, instead the thickness of the material only Δh from h ₁ to h _2, the rolling load varies only ΔP from P ₁ to P _2. Therefore, in order to obtain the target delivery side plate thickness h ₁ , the mill rigidity curve is changed from B ₁ to B ₂ so that the rolling load is changed from P ₂ to P ₃ by ΔP ′, and the roll rolling position is changed to S. _The control is performed so that ΔS is changed from ₁ to S ₂ .

Therefore, ΔP / Δh = M, ΔP '/ Δh =
Since Q and (ΔP + ΔP ′) / ΔS = M, ΔS
When is sorted by M, Q, and ΔP, it is expressed by the following equation (5). ΔS = (Q / M ² + 1 / M) · ΔP (5) By the way, in the conventional acceleration / deceleration compensation (Japanese Patent Application No. 6-140419) shown in the equation (1), acceleration is performed. The speed deviation of Δv
Then, when ΔP / Δv = constant, P / Δh = Q, and when used in actual operation, by adding an offset term, it is expressed by the following formula (6), and the rolling position is controlled based on this formula. Then, it is intended to control the output side plate thickness during acceleration / deceleration.

ΔS = {c ₁ · (P / Δh) + c ₂ } · Δv (6) Here, c ₁ and c ₂ are constants that vary depending on the steel type and the previous process. However, in the present invention, the acceleration / deceleration compensation is attempted by accurately obtaining the rolling load fluctuation amount ΔP from the relationship between the rolling load fluctuation and the rolling speed fluctuation and using the set calculation value for the plasticity coefficient Q. is there.

In the first place, the rolling load is a load applied to the entire rolling roll, and is also called a roll separating force because it tries to push and open the roll. When obtaining the relationship between the rolling load and the rolling speed, it is possible to simply use the value of the rolling load P when rolling under the same rolling conditions, but when the roll diameter, tension, etc. change, It is necessary to use the indicated average rolling pressure ps.

Ps = P / {b · √ (R ′ · Δh)} (7) where, b: average strip width of rolled material, R ′: roll radius changed by elastic deformation of roll Is. By the way, rolling load, that is, average rolling pressure ps (hereinafter simply referred to as ps)
The influencing factors for are listed below. (1) Friction: ps increases as μ increases. (2) Material: ps increases due to an increase in deformation resistance (yield stress). (3) Reduction: ps increases as the reduction increases. (4) Temperature: Deformation resistance decreases and ps decreases as the temperature rises. (5) Speed: At higher speeds, deformation resistance increases and ps increases. (6) Plate thickness: As the thickness decreases, ps increases due to the effect of friction. (7) Roll diameter: ps due to increase in contact length as roll diameter increases
Will increase. (8) Tension: ps decreases with increasing tension. Especially, the influence of the rear tension is large.

Among these influencing factors, the present inventors
The reduction factors (the reduction factor for each pass and the total reduction factor up to that pass), the rolling speed, the inlet plate thickness, and the work roll diameter were considered as influencing factors. Therefore, in order to investigate other influential factors based on the rolling speed, the austenitic representative steel grade SUS 304 and the ferritic representative steel grade SUS 430 were respectively processed in the process shown in FIG. A rolling experiment using a 12-step cluster mill was conducted using the manufactured three process materials of HAP material, TCM material, and CAP material. For simplicity, the unit plate width load pw (=
It was decided to compare using P / b). Among the above-mentioned process materials, the HAP material was rolled in a hot rolling mill and then sent directly from the annealing / pickling equipment for hot rolled stainless steel sheets to the cold reversible multiple rolling mill. Is immediately after being rolled in a cold-rolled tandem mill, and the CAP material is annealed through a cold-rolled stainless steel sheet annealing / pickling facility.

The results of these rolling experiments are shown in FIGS. 4 and 5, FIG. 6 and FIG. 7, FIG. 8 and FIG. 9 have the same pre-process, but different steel types are SUS 304 and SUS 430. Unit plate width load pw attached to each figure
From the result of approximating the rolling speed v by a linear expression, there is a correlation between the unit strip width load and the rolling speed for SUS 304, but a correlation is found for SUS 430 as compared with SUS 304 in the previous process. Even if it is considered that there is a correlation, the change in the unit strip width load with respect to the change in rolling speed is about 1/2 to 1/3.
It turns out that it is a degree. From this, it can be seen that the rolling load fluctuation with respect to the rolling speed for SUS 430 is smaller than that for SUS 304, so that there is no clear correlation between the rolling speed and the unit strip width load in Figs. .

Therefore, considering the plate thickness control at the time of accelerating and decelerating the rolling speed limited to SUS 304, the unit plate width load pw can be predicted by approximating it with a quadratic expression of the rolling speed v. The unit plate width load predicted value pw ^* is expressed as follows together with the factors that affect the plate thickness variation. pw ^* = αv ² + βv + γr + εT + ζ / φ + ηh + m (8) where r: rolling reduction (%) of each pass, T: total rolling reduction (%), φ: work roll diameter (mm), α, β , Γ, ε,
ζ, η, m: constants that change in the previous process.

The measured results of the unit plate width load predicted value pw ^* and the unit plate width load actual measured value pw are shown in FIGS. As is clear from these figures, the reduction ratio, work roll diameter,
It was found that the change of the unit strip width load due to the change of the rolling speed can be accurately predicted by the equation (8) even if the conditions such as the entry side strip thickness change. Therefore, the present invention is to construct a plate thickness control system based on the above formula (8). That is, first, the unit plate width load variation Δpw when the rolling speed changes in the same pass is expressed as follows.

Δpw = 2αΔv · v + αΔv ² + βΔv (9) Further, the reduction position S is expressed as follows. S = S ₀ + ΔS (10) Where, S ₀ is the rolling position at the start of rolling, ΔS: (Q / M ² + 1 / M) b (αv ² + βv) ………… (11 ).

The rolling position change amount ΔS when the rolling speed changes is ΔS = (Q / M ² + 1 / M) · b · Δpw (12), which satisfies the above equation (5). It will be. As described above, according to the present invention, it is possible to suppress the variation of the outlet plate thickness by controlling the rolling position by using the expression (11).

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A cold reversible multiple rolling mill for carrying out the method of the present invention is constructed as shown in the block diagram of FIG. That is, a cold reversible multiple rolling mill 2 for rolling the stainless steel plate 1 is equipped with a rolling load meter 3 to measure a rolling load P applied to the rolling mill 2, and the hydraulic rolling down device 4 rolls down a roll rolling position S. Is controlled. Further, first and second plate thickness gauges 5a and 5b are attached to the front and rear of the rolling mill 2 to detect the delivery side plate thickness h. First and second speedometers 7a and 7b are attached to the first and second deflector rolls 6a and 6b provided on the entrance and exit sides of the rolling mill 2, respectively, and the rolling speed v is measured. A reduction position detector 8 is attached to the hydraulic pressure reduction device 4, and the roll reduction position S is detected.

Then, the stainless steel plate 1 unwound from the first coiler 9a is rolled by the rolling mill 2 and wound up by the second coiler 9b, and then unwound again from the second coiler 9b. It is rolled by 2 and wound up by the first coiler 9a. By repeating such a reversible rolling pass a plurality of times, the stainless steel plate 1 having a predetermined plate thickness is manufactured. During this rolling, the roll reduction position deviation ΔS is controlled by the arithmetic and control unit 10. By this, each exit side plate thickness h is controlled.

In the arithmetic and control unit 10, the arithmetical control of the roll rolling position deviation ΔS is performed by using the equation (10) and the following equation (13) which is a modification of the equation (11). ΔS = (Q / M ² + 1 / M) · b · α ′ · v · (v−β ′) (13) An example of the values of the constants α ′ and β ′ in the equation (13) is shown in Table 1 It was shown to.

[0027]

[Table 1]

[0028] Steel type is SUS 304 and the thickness of the previous process is TCM material
When a 2.0 mm stainless steel plate was rolled with a cold reversible multiple rolling mill to a final target plate thickness of 0.92 mm in 7 passes, the acceleration / deceleration compensation of the method of the present invention was applied to the 6th pass of the finishing schedule. The outlet plate thickness was controlled. The results are shown in Fig. 13.
For comparison, FIG. 14 shows the result of the output side plate thickness accuracy controlled using the acceleration / deceleration compensation of the conventional method. This is the same steel grade as SUS 304, and the previous process is TCM material, and the schedule for finishing 9 passes from the plate thickness of 1.4 mm to the final target plate thickness of 0.495 mm
It shows the result of controlling the exit side plate thickness of the pass.

As is clear from these figures, in the example of the present invention, the plastic constant and the mill constant are introduced as a function of the rolling position correction amount. It can be seen that good results are obtained.

[0030]

As described above, according to the present invention,
When rolling a stainless steel plate, it is possible to suppress the plate thickness variation and contribute to the improvement of product quality. According to the present invention, the rolling load predicted from the rolling speed is used as a function to correct the rolling position during acceleration / deceleration, so that it is possible to accurately suppress the plate thickness variation during acceleration / deceleration.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an exemplary embodiment of the present invention.

FIG. 2 is a characteristic diagram showing the relationship between plate thickness, roll reduction position and rolling load.

FIG. 3 is a process drawing showing a manufacturing stage of a stainless steel plate.

FIG. 4 is a characteristic diagram showing the relationship between the rolling speed of SUS 304 HAP material and the unit plate width load.

FIG. 5 is a characteristic diagram showing the relationship between the rolling speed of SUS 430 HAP material and the unit plate width load.

FIG. 6 is a characteristic diagram showing a relationship between a rolling speed and a unit strip width load of a SUS 304 TCM material.

FIG. 7 is a characteristic diagram showing the relationship between the rolling speed and the unit plate width load of a TCM material of SUS 430.

FIG. 8 is a characteristic diagram showing a relationship between a rolling speed and a unit plate width load of a SUS 304 CAP material.

FIG. 9 is a characteristic diagram showing the relationship between the rolling speed and the unit plate width load of a SUS 430 CAP material.

FIG. 10 is a characteristic diagram showing a relationship between a predicted value and a measured value of a unit plate width load of a SUS 304 HAP material.

FIG. 11 is a characteristic diagram showing a relationship between a predicted value and an actually measured value of a unit plate width load of a TCM material of SUS 304.

FIG. 12 is a characteristic diagram showing a relationship between a predicted value and a measured value of a unit plate width load of a SUS 304 CAP material.

FIG. 13 is a characteristic diagram showing an application example of the method of the present invention.

FIG. 14 is a characteristic diagram showing an application example of a conventional method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Stainless steel plate 2 Rolling mill (cold reversible multiple rolling mill) 3 Rolling load meter 4 Hydraulic pressure reduction device 5a 1st thickness gauge 5b 2nd thickness gauge 6a 1st deflector roll 6b 2nd deflector roll 7a 1st speedometer 7b 2nd speedometer 8 Rolling down position detector 9 Coirer 10 Computational control device ΔS Roll rolling down position deviation Q Plastic constant M Mill constant b Strip width v Rolling speed α, β constant

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Yoshihiro Satake, 1st Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Inside the Chiba Works, Kawasaki Steel (72) Setsuo Kakihara 1st Kawasaki-cho, Chuo-ku, Chiba, Kawasaki (72) Inventor Akira Matsuda 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Kawasaki Steel Co., Ltd., Chiba Works

Claims (3)

[Claims] 1. A method for controlling a plate thickness when a stainless steel plate is rolled using a rolling mill having an AGC function, wherein a rolling speed v, a plate width b, a plastic constant Q, a mill when accelerating or decelerating. A plate thickness control method for a stainless steel sheet, comprising: determining a roll reduction position deviation ΔS using a function of a constant M; and controlling the roll reduction position based on the value of the obtained roll reduction position deviation ΔS. 2. The plate thickness control method for a stainless steel plate according to claim 1, wherein the roll reduction position deviation ΔS is given by the following equation. ΔS = (Q / M ² + 1 / M) · b · (αv ² + βv) where α and β are constants. 3. The method for controlling the thickness of a stainless steel sheet according to claim 1, wherein the method is applied when the type of rolled stainless steel sheet is an austenitic type.