JPH0241362B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control method when changing the pass schedule during hot rolling to change the thickness of the finished product. When it changes,
The present invention provides a method for controlling the width of the finished product to a desired accuracy in response to this change.

The technology of changing the pass schedule during rolling to change the thickness of the finished product (hereinafter referred to as "change of running thickness") has already been introduced in cold rolling, and involves welding the tail end of the preceding coil and the tip of the succeeding coil. Combined with continuous rolling technology, this has resulted in significant improvements in productivity. On the other hand, the use of continuously cast slabs is increasing in hot rolling, but it is not easy to change the slab size in continuous casting, and a technology that can roll products of various sizes from the same slab size is desired. , rolling multiple coils from a single slab is also advantageous in terms of productivity;
Development of this technology is desired.

However, it has been discovered that when changing the running strip thickness in a hot strip mill, consideration must be given to changing the strip width, which is significantly different from cold rolling. In other words, it is no exaggeration to say that there is no variation in the strip width between the entrance and exit sides of the stand due to cold rolling, and there is no need to take strip width control into account, but in hot rolling, rolling with rolls , plastic flow occurs in the width direction of the plate, causing width expansion.

The width expansion rate η due to rolling can be expressed as η=Wout−Win/Win=(H, h, Win, R, T) (1). However, in equation (1), W _IN : Stand entry side plate width R: Roll radius Wout: Stand exit side plate width H: Inlet side plate thickness T: Plate temperature h: Outlet side plate thickness, (H, h, Win, R, T ) means a function.

Figure 1 shows the relationship between the rolling reduction rate γ (γ = (H-h)/H) and the width expansion rate η.As can be seen from this figure, the entrance side plate thickness and exit side plate thickness change, When the width changes, the width expansion rate also changes, and the width of the stand exit side plate also changes. Therefore, when the plate thickness is changed from the first target thickness h ₁₀ to the second target thickness h ₂₀ by changing the running plate thickness as shown in Fig. 2a, as shown in Fig. 2b When a change in width occurs and the second target thickness _h20 is smaller than the first target thickness _h10 , the roll gap is changed to increase the reduction amount of each stand, so the width after the thickness change is It was found that the width was larger than the target width, making it impossible to obtain the desired width accuracy.

The present invention was made in view of such technical needs.

A detailed description will be given below with reference to FIG. 3 for explaining a conventional hot rolling strip thickness changing method and FIG. 4 showing an apparatus to which an embodiment of the present invention is applied.

In Fig. 3, the roll gap change amount ΔSi of each stand when changing from the target plate thickness h ₁₀ before the plate thickness change to the target plate thickness h ₂₀ after the plate thickness change, and the stands before and after the stand by changing the stand and roll gap. The speed correction amount ΔVi of that stand and the stand one upstream from that stand in order to correct the collapse of the mass flow balance with
ΔV _i-1 is calculated and determined in advance by the calculation device 4. When the plate thickness change point reaches stand 1a,
At the same time, in order to balance the mass flow between stand 1a and stand 1b, the rolling speed of stand _1a is changed by the rolling rate speed control device 3a by the speed correction amount ΔV. Change only ₁ a and ₁ b. Next, when the plate thickness change point reaches stand 1b, the roll gap control device 2b changes the roll gap by the amount of change ΔS ₁ b in exactly the same way, and at the same time, the stand 1 upstream of the stand
The rolling speeds of stand a and stand 1b are simultaneously corrected by speed correction amounts ΔV ₁ a, ₁ b and ΔV ₁ b, ₁ c, respectively.

In this way, each time the plate thickness change point sequentially reaches each downstream stand, the calculation unit 4 calculates the amount of roll gap correction and speed correction required in advance to maintain the mass flow balance at that stand and upstream from the stand. By modifying the roll gap and rolling speed of each side stand, the desired thickness can be changed while maintaining the mass flow between the stands. However, Fig. 2 a, b
As shown in , the pass schedule of the rough rolling stand, rough edger, and finishing stand is given in advance so that the target width W ₀ is achieved for the tip side from the plate thickness change point, but for the tail side from the plate thickness change point. However, no measures have been taken to deal with changes in board width due to changes in board thickness, resulting in board width errors.

The present invention has been made in order to prevent the occurrence of this width error. That is, as shown in FIG. 4, an edger 5 that performs rolling in the width direction is arranged upstream of the finishing stand group, and the reduction roll gap change amount ΔSi of each stand calculated by the calculation device 4 and (1)
Using the relationship in the formula, when changing the roll gap of each stand, calculate the plate width change ΔWi at the outlet side of each stand and the plate width error ΔW at the final stand outlet side, and calculate the width difference ΔW to eliminate this plate width error ΔW. The edger roll gap change amount ΔE of the edger 5 and the edger speed change amount ΔVE for maintaining the mass flow balance are determined in advance by the calculation devices 6 and 4.
At the timing when the plate thickness change point reaches the edge 5, the edge roll gap control device 2f changes the edge roll gap by a predetermined edge roll gap change amount ΔE, and at the same time maintains the mass flow balance. Therefore, the edger speed is changed by the edger speed change amount ΔVE determined in advance by the edger speed control device 3f.

In order to change the edger roll gap and speed in Fig. 4, the change in the width of the plate that will occur due to the change in plate thickness at each stand is predicted in advance, and in order to absorb the variation in the width of the plate, the edger roll gap and speed are changed. This is done to control the width of the board after the thickness change point, and it can be changed when the board thickness change portion passes through the edger roll.

Hereinafter, a method of calculating the edge roll gap change amount ΔE and edger speed change amount ΔVE will be specifically described. For example, the empirical formula for predicting the width spread after rolling by a group of finishing stands is as follows:
"Paper of the 1974 Spring Lecture on Plasticity Working",
(1979.5.17-19) P489-P492, "Modeling of width behavior of hot strip (steady part)". The following equation is based on the above paper and embodies equation (1).

ΔW _i =W _i {10 ^a (100γ _i )〓+(0.01T _i −11) (0.67Δh _i /H _i +0.33)} …(2) (However, when γ _i 0.1) ΔW _i =W _i {10 ^a (100γ _i )〓 + (0.01T _i −11)・γ _i } …(3) (However, when γ _i <0.1) Here, a=(0.0084R _i /H _i −0.25) W _INi /H _i +0.1512R _i /H _i −1.325 α=(−0.002R _i /H _i −0.064)W _INi /H _i −0.0118R _i /H _i +1.49 Δh _i =h _i −H _i Transforming equations (2) and (3), W _i+1 = W _i +ΔW _i = W _i +X _i・W _i = (1+X _i )・W _i = (1+X _i ) (1+X _i-1 )... (1+X ₂ )(1+X ₁ )・W ₁ …(4) ΔW=ΔW _o = {1−(1+X _o-1 )(1+X _o-2 ) …(1+X ₂ )(1+X ₁ )}・W ₁ …( 5) Here, X _i =10 ^a・(100γ _i )〓+(0.01T _i −11) (0.67Δh _i /H _i +0.033) (However, when γ _i 0.1) X _i =10 ^a・(100γ _i ) 〓 + (0.01T _i −11) γ _i (when γ _i <0.1) n is the final stand number.

From formula (5), the target plate thickness h ₁₀ is the target plate thickness after changing the plate thickness.
The board width error ΔW at the exit side of the final stand due to the change to h ₂₀ is determined, and in order to correct this ΔW, the edge roll gap change amount ΔE and the edge speed change amount ΔVE to maintain the mass flow balance are determined. Bye.

From the mass flow balance, h _{i Vi} W _i = h ₁₀・V ₁₀・W ₀ = h ₂₀・V ₂₀・W ₀ = h ₁・VE・W ₁ = h ₁ (VE+ΔVE) (W ₁ −ΔW)
…(6) Here, V ₁₀ , V ₂₀ Plate speed before and after the plate thickness change VE Edger speed before plate thickness change Therefore, from equation (6), ΔVE=h ₂₀・V ₂₀・W ₀ /h ₁ (W ₁ −ΔW)−VE…(7) The edger speed change amount ΔVE can be obtained.

On the other hand, the rolling process in an edger is generally as follows.

W ₁ = E + P _E /M _EHere , W ₁ : Width of the plate on the edge exit side E: Edge roll gap M _E : Edge mill steel P _E : Edge rolling load In other words, the width of the edge plate exiting from the edge roll gap is the edge width. It is considered a type of spring rather than a rigid body, and it expands under load, meaning that it becomes wider by the amount of expansion. Therefore, E and P _E become ΔE and ΔP _E
When W 1 changes by ΔW, W ₁ changes by ΔW. It can be expressed as the following formula.

W ₁ −ΔW=E+ΔE+P _E +ΔP _E /M _E …(8) Therefore, from equation (8), as ΔE=W ₁ −ΔW−E−P _E +ΔP _E /M _E , the edge roll gap change amount E is can get.

In this way, when changing plate thickness during running in a group of finishing stands, the roll gap is changed at the point where the plate thickness is changed, and the width spread due to rolling changes accordingly, so the width error before and after the plate thickness change can be predicted in advance. By calculating and controlling the edge roll gap at the point of change in plate thickness in order to absorb the plate width error, it is possible to change the running plate thickness in hot rolling without producing a plate width error.

Here, the features of the present invention have been explained using an embodiment in which an edger is newly arranged upstream of a group of finishing stands. It is also possible to change the plate width in advance from the planned plate thickness change point to the tail end side so as to absorb the plate width error that would occur due to the roll gap change of the finishing stand group. Furthermore, an edger may be placed between the stands of the finishing stand group to perform the same function.

As described in detail above, by using the present invention, it is possible to change the strip thickness during running while ensuring the desired strip width control accuracy in hot rolling.

[Brief explanation of drawings]

Figure 1 is a characteristic diagram showing the relationship between rolling reduction and width expansion ratio, Figure 2 a and b are characteristic diagrams showing the relationship between plate thickness change and plate width change, and Figure 3 is a characteristic diagram showing the relationship between plate thickness change and plate width change. FIG. 4 is a block diagram illustrating an example of an apparatus to which the method of changing the thickness of a hot rolling sheet according to the present invention is applied. In the figure, 1a, 1b, 1c...1e are stands, 2a, 2b, 2c...2e are roll cap control devices, 2f is an edge roll gap control device, 3a, 3b, 3c...3e are rolling speed control devices, 3f is an edger speed control device, 4 and 6 are arithmetic units, and 5 is an edger. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] 1. In a hot rolling strip thickness changing method in which the rolling speed is changed to maintain the roll gap and mass flow balance in order to change the strip thickness when the strip thickness change point of one rolled material reaches each stand, Predictively calculate the amount of change in plate width at the exit side of each stand due to the change in roll gap at each stand, and calculate the amount of change in the edger roll gap and the amount of speed change in the edger to eliminate the above-mentioned plate width change based on this predicted amount of plate width change. A method for changing the thickness of a hot rolled sheet during running, characterized in that variation in the width of the sheet during changing the thickness of the sheet during running is controlled by changing the speed of the edger roll gap and the edger.