JPS6057403B2 - Tension control method for continuous rolling mill - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a rolling mill tension control method in a continuous rolling mill.

Generally, when rolling strip materials, especially steel bars, wire rods, etc., using a continuous rolling mill, the tension applied to the rolled material is kept constant at zero or a small value over the entire length, thereby making the shape of the rolled material uniform over the entire length. In many cases, so-called tension control is performed to increase the tension.

Currently, the most advanced tension control method for continuous rolling mills is the direct tension detection method, which excludes the effects of skid marks, thermal rundowns, shape changes, etc. on the torque of the rolled material, and is based on the influence of tension 2. There is a rolling car torque method that detects only torque changes.

The conventional rolling car torque control system, which assumes that the load torque arm does not change due to tension, calculates tension based on the following equation (1) and performs tension control.

FIG. 1 is an explanatory diagram thereof. PN-AN-GN+FN-
, RbNFN=・・・・・・(1) However, GN: Rolling torque after applying tension (TON-M), PN:
Rolling load after tension (TON), AN: Load torque arm x 2 (M), F, N-, ,: Rear tension (TON), FN: Front tension (TON), RbN: Rear tension torque arm (M) ), and RfN:
Front tension torque arm (M).

The subscript N is the rolling mill number, N-1 indicates the rolling mill number one upstream of the rolling mill, and N+1 indicates the rolling mill number one downstream of the rolling mill (the same applies hereinafter). PN can be determined by actual measurement, and GN can be determined by actual measurement or from the following general formula (2).

VN-IN-IN゜・RN GN=KN×・・・・・・(2) Where, KN: Constant, VN: Terminal voltage of drive motor (V), IN: Current of drive motor (A), RN: The armature resistance (Ω) of the drive motor, and nN: the rotation speed (RPM) of the drive motor.

AN is determined by the following equation (3) from PN and GN before the rolling equipment engages the (N+1) stand. Rb? ．． and R
Many systems use the roll operating radius as fN, but in the present invention, which will be described later, RbN is the roll radius at the center position between the neutral point X2 and the product entrance X1, as shown in Figures 1a and 1b, and RfN is Let it be the roll radius at the center position between the neutral point X2 and the product exit X3. The reason is that when tension is generated in the rolling mill, the rolling distribution within the roll bite is
It is a generally well-known fact that changes occur as shown in the figure.
This is because the rolling direction stress p changes together with the width direction stress σ due to a change in the rolling direction stress σ due to the tension. In other words, it can be said that tension is acting on the part where the stress p in the rolling direction changes within the roll bite. These R
bN and RfN can be determined by theoretical or experimental formulas. As mentioned above, FN in equation (1) is F(N-1)
It turns out that if you are given, you can find it.

As for the #1 rolling mill, the rear tension F, N-1) is zero, so F1 can be found from equation (1). Since the rear tension of the #2 rolling mill is the same as the front tension F1 of the #1 rolling mill, F2 can be obtained from equation (1). The rolling force-torque method uses equation (1) to determine the front tension of the downstream rolling mills one after another from the detection of the front tension of #1 rolling mill, and calculates the rotational speed imbalance of each rolling mill using equation (4). The purpose is to control ΔNN. However, ΔNN: rotation speed unbalance (RPM), FN: forward tension (TON), FN: target tension (TON), NN: roll rotation speed (RPM) of the rolling mill, and.

However, when this conventional rolling force-torque method was applied to actual machines, good control could not be obtained and roll errors often occurred. That is, in the detection of the forward tension using equation (1), the rear tension F(N-1) in the equation uses the forward tension FN obtained from equation (1) at one upstream stand, so it was obtained using equation (1). It was thought that if there was an error in the forward tension, the error would accumulate as the downstream stand was calculated, leading to unstable control. Changes in the load torque arm, rolling load, finished product width, and advanced width due to tension are shown in FIGS. 3 to 6.

FIG. 3 shows changes in the load torque arm AN due to tension, and the changes are relatively small. σFN and σB in Figure 3
N are the front tension stress and back tension stress for the N stand, respectively. ΔPN Figure 4 shows the relationship between tension and rolling load change, but since the change due to the tension of the load torque arm AN is small (1)
The decrease in PN-AN in the equation is approximately equal to the decrease in GN, and it is thought that the influence of error in determining FN is small.

In FIG. 3, σ and N are the front tension stress and rear tension stress for the N stand, k is the deformation resistance of the rolled material, and the front and rear tensions on the x-axis are made dimensionless. From the above, it has been thought that the error in the front tension force FN in equation (1) depends on the accuracy of the rear tension torque arm RbN and the front tension torque arm RfN.

The purpose of the present invention is to more accurately control the tension between rolling mills, and for this reason, in the present invention, changes in the advance rate and finished product width due to the tension between rolling mills can be controlled between rolling mills one upstream and one downstream. In view of the discovery of the fact that tension is generated between rolling mills, the tension between the rolling mills one upstream and one downstream, calculated in advance from the tension between rolling mills determined using the conventional method, is calculated as follows: The true inter-mill tension is determined by subtracting the tension, and tension control is performed based on that value.

Fig. 5 shows the experimental data of [Change in product width due to tension]J, and it can be seen that the product width decreases with both front tension and rear tension, and this tendency is greater with rear tension.

In FIG. 5, σFN and σBN are the front tension stress and rear tension stress for the N stand, k is the deformation resistance of the rolled material, and the front and rear tensions on the x-axis are made dimensionless.
Also, Figure 6 shows the change in advance rate due to tension. It can be seen that the forward tension increases with forward tension and decreases with backward tension. The forward and backward tensions on the X axis in FIG. 6 are also dimensionless. Figure 7 shows #3 rolling mill~
The rotation speed of #2 rolling mill and #5 rolling mill is changed while the rotation speed between #4 rolling mill is originally set to have no tension, and the rotation speed between #2 rolling mill and #3 rolling mill and #4 rolling mill are changed. ~#5 This shows a state in which tensions F2 and F4 are generated between the rolling mills.

When considering the tension ΔF3 generated between the #3 rolling mill and the #4 rolling mill at this time, the #3 rolling mill rear tension F2
Therefore, the advance rate of #3 rolling mill decreases by ΔF3 from F3,
#3 The product width on the exit side of the rolling mill is reduced by Δ8 from the formula. what if,
When Xx (reduction rate of width) = reduction rate of product cross-sectional area, (x is width-to-cross-sectional area conversion coefficient), -(nowε+X3・乍n)
It is presumed that this causes a decrease in mass flow, and tension is generated between the #3 rolling mill and #4 rolling mill in accordance with the amount of decrease in mass flow. Further, due to the front tension F4 of the #4 rolling mill, the advance rate of the #4 rolling mill increases by ΔF4 from F4, and the product width at the exit side of the #4 rolling mill decreases from B4 by ΔB4. However, as is clear from FIGS. 5 and 6, the difference υ〉ΔB4ΔF4. B
4l'', it is presumed that the mass flow of (-T7--X4) increases, and a slight tension is generated in the #3 rolling mill to #4 rolling mill in accordance with the increase in mass flow.

ΔFN and ΔBN are absolute values. FIG. 8 shows the relationship between the rotational speed imbalance and the tension generated between the rolling mills. The change in mass flow due to the tension between upstream stands and the tension between downstream stands was determined from FIGS. 5 and 6, and the change in mass flow from FIG. 8 was replaced with tension in FIG. 9.
As can be seen from FIG. 9, it is presumed that the tension generated between the downstream rolling mills is extremely large. FIG. 10 shows a summary of calculated values and actual measured values of the tension generated between one downstream stand by the inter-stand tension.

This is between #1 rolling mill and #2 rolling mill and between #2 rolling mill and #2 rolling mill.
After adjusting the roll rotation speed of each rolling mill so that there is no tension between the three rolling mills, the roll rotation speed of #1 rolling mill is decreased.
The calculated values are based on experimental data obtained by rolling several times, and the calculated values are in good agreement with the measured values. From the above facts, it is obvious that control using equations (1) and (4), which are rolling force-torque systems, cannot provide good control.

Therefore, the present invention calculates the front tension of each rolling mill using equation (1),
Also, from equations (5) and (6) below, the tension generated between the rolling mills one upstream of the tension ΔFf (N-0) and the tension generated between the rolling mills one downstream ΔFb (N+
1) is calculated for all the rolling mills that are biting the rolled material,
The tension between the rolling mills is targeted by calculating only the tension W due to the unbalance of the rotation speed between the rolling mills from the equation (7) described below, and controlling the rotation speed of ΔNN obtained from the equation (8) below. This is a method in which the value is controlled mainly by M.

In formulas (5) and (6), A? A(L Sho: Change in advance rate due to tension, FN5f(N
+1) A? A? ±stop: Change in product width due to tension, BFJ3B (
N+1) XN, X(N+1): Width-cross-sectional area conversion coefficient, y(N-1
), y(N+1): Mass flow imbalance-to-stand tension conversion coefficient ('ION/M2) and D(N-1)
9D(N+1): Stand exit side finished product cross-sectional area (M2), and all values are absolute values.

(8) In the formula, ΔNN: rotational speed unbalance (RPM), NN: roll rotational speed (RPM) of the rolling machine, and GN: control gain (
I/TON).

Next, means for carrying out the tension control method of the present invention will be explained.

First, the forward tension FN of all the stands in which the pressing material is being bitten is detected at the same time.

However, the final stand is zero. FN can be a direct tension detection method that is directly detected by a load cell, or an indirect tension detection method such as a pressure force-torque method. For example, in the case of the pressure force-torque method, first check all the stands that are being bitten by the pressure material. At the same time, the terminal voltage VN of the drive motor, the current IN of the drive motor, the rotational speed NN1 of the drive conductor, and the rolling load PN are scanned, and the rolling torque of all stands is detected using equation (2). Next, calculate the forward tension FN from the upstream stand side using equation (1). In order to detect FN, the detection of F<N-1> must be completed, so the calculation of equation (1) needs to be performed from the upstream stand side. Front tension torque arm RfNl rear tension torque arm RbNl constant K in equations (1) and (2)
The armature resistance RN of the Nl drive motor may be provided separately.

Also, for AN with load torque arm x 2, the rolled material is already (
N+1) Detect by formula (3) before the stand is bitten. Next, from equation (5), we can calculate the tension ΔF<N-1> that the forward tension FN generates between the rolling mills one upstream, and the tension ΔF<N+1> that the forward tension FN generates between the rolling mills one downstream.
is calculated using equation (6) for all stands where FN has already been detected.

At this time, ΔFf<, - of the most upstream stand that detected FN
1> and ΔFb<N+ of the most downstream stand where FN was detected
The value of 1> is zero. Change in advance rate due to tension in equations (5) and (6) ΔFN/FN, Δf<N+1>/f<N
+1>, change in product width due to tension ΔBN/BN, ΔB<
N+1>/B<N+1> is σFN=σBN=FN/DN, respectively in Figures 6 and 6b.
Obtained from the relationships shown in Figures 5 and 5b, width to cross-sectional area conversion coefficient XN, X<N+1>, mass flow imbalance to stand tension conversion coefficient Y<N-1>, Y<N+1>, stand exit side The product cross-sectional areas D<N-1> and D<N+1> may be given separately.

Next, only the main tension w due to the rotational imbalance between the stands is calculated for all the stands for which the arms have already been detected using equation (7). Furthermore, the roll rotation unbalance control amount ΔN, for setting the front tension to the target value FN, is (8
) From the formula, for all stands that have already detected cabbage,
calculate. GN at this time is a control gain, and may be given separately together with FN.

Next, the roll rotation speeds of the stands are simultaneously controlled by ΔNN for all stands where FN has been detected. in this case,
Needless to say, the effect of the control amount of each stand is prevented from affecting other stands by succession jigging. Equation (8) is a method in which tension control is performed upstream, but it can also be performed downstream. For example, the series of processes described above is
By performing rolling until the rolled material passes through all the stands every r1S, it becomes possible to control the connection tension over the entire billet length.

As described above, the present invention proposes a new method that solves the tension control problems of conventional continuous rolling mills.
Nowadays, users have strict demands on the dimensional accuracy of finished products.
This is an effective way to deal with this.

[Brief explanation of the drawing]

Figure 1a is an explanatory diagram of the rolling force-torque method, Figure 1b is an enlarged view of section A in Figure 1a, Figures 2a and 2b are explanatory diagrams of the tension torque arm, and Figures 3a and 3b are based on tension. Figure 4 is a graph showing calculated values representing changes in load torque arm; Figure 4 is a graph showing experimental values representing changes in rolling load due to tension; Figures 5a and 5b are experimental values representing changes in product width due to tension. 6a and 6b are graphs showing experimental values representing changes in advance rate due to tension, and FIG. A conceptual diagram showing the influence on the tension between the side rolling mills, Fig. 8 is a graph showing experimental values showing the relationship between the rotational speed imbalance and the tension generated between the rolling mills, and Figs. 9a and 9b are the results of the present invention. Graph showing the predicted value of the influence of a certain rolling mill tension on the upstream rolling mill tension and the downstream rolling mill tension, obtained for the implementation of
FIG. 0 is a graph showing verification results by a model experiment showing an example of the present invention.

Claims (1)

[Claims] 1 In front of the N-th rolling mill that acts between the N-th rolling mill and the (N+1) rolling mill one downstream of this rolling mill among all the rolling mills in which the rolled material is biting in the continuous rolling mill. Determine the tension F_N, and calculate the front tension of the (N-1)th rolling mill and the (
N+1) The forward tension of the rolling mill generates tension components ΔFb_N and ΔFf_N between the N-th rolling mill and the (N+1)-th rolling mill one downstream of this rolling mill, respectively, depending on changes in advance rate and product width. F_N−ΔFb between each rolling mill is calculated in association with the change in mass flow caused by the change in mass flow.
A tension control method for a continuous rolling mill, characterized by controlling the value of _N-ΔFf_N to zero or a small value.