JPS6323847B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for controlling the setup of a rolling mill, particularly a rough rolling mill and a finishing mill in a hot strip mill. For example, in a finishing mill, so-called set-up control is performed to set the roll speed, roll opening degree, etc. of each stand before threading the strip material, and after that, the thickness is left to AGC, etc. If the setup is not appropriate, the off-gauge that occurs at the tip of the strip will become long and the yield will decrease, and in extreme cases, problems such as breakage of the strip material and the formation of loops will occur. Setup control has become one of the important management items. Calculation of the roll speed and roll opening degree for this set-up is as well known. After determining the draft schedule using the power curve, the roll speed (or rotational speed) is determined using the rolling theory formula and the mass flow balance formula. Furthermore, the thermal rundown of the strip material temperature is predicted, the deformation resistance of the strip material for each stand is calculated, the rolling load for each stand is determined based on this, and the roll opening degree is determined using a gauge meter method. By the way, the temperature of the strip material used in this setup calculation has conventionally been measured as shown in FIG. FIG. 3 is a schematic side view showing a part of the rough rolling mill and the finishing mill of the tandem mill, and in the figure R
is a rough rolling mill (only the final stand is shown),
F is a finishing rolling mill, T is a thermometer placed on the exit side of the rough rolling mill, and K is a flying crop shear (hereinafter simply referred to as flying shear) placed on the entry side of the finishing rolling mill F. The strip material B, which is the material to be rolled, is passed through a rough rolling mill R from the direction of the white arrow, and then passed through a finishing mill F. The strip material B leaving the rough rolling mill R passes under a thermometer T to measure its temperature for use in setup calculations in the finishing mill F, and then passes through a flying shear K to measure the temperature of the strip material B. Parts of the raw material B that are significantly deformed in shape at the leading and trailing ends are cut and removed, and in this state, the raw material B is passed through the finishing mill F. The temperature of the strip material B used for setup calculations is actually measured from its top part, but as mentioned above, the portion of the tip that is significantly deformed is cut off by the flying shear K, so the tip is measured by the thermometer T. The temperature of the top part is sampled at a certain timing from when the part to be cut by the flying shear K has passed after a certain period of time has passed, and the average or maximum value is taken as the strip material temperature. Perform set-up calculations as follows, determine the position where the desired plate thickness should be achieved through set-up control, that is, the target position of set-up control, and use this position for plate thickness control (hereinafter referred to as AGC).
Setup is performed by determining the switching position to . However, the shape of the tip usually differs depending on the strip material B, and therefore the length of the part cut off by the flying shear K also differs, so it is important to make sure that the temperature sampling position is not included in the cut part. , change the temperature measurement position to strip material B within a range that does not interfere with the setup control timing.
Temperature sampling is typically performed at a location well away from the end of the device. In fact, if there is no particularly large variation in the temperature of the strip material, the temperature sampling described above will not cause any particular trouble. However, as energy-saving measures have been promoted in recent years, the method of heating the strip material in the heating furnace has been replaced by the traditional indirect heating method that uses the atmosphere inside the heating furnace, and now the flame of the burner is used to heat the strip material. Increasingly, direct heating methods are being adopted, but due to the location of the burners in the heating furnace, the temperature distribution in the longitudinal direction of the strip material, especially As shown in FIG. 4, there is a tendency for the temperature gradient at the leading and trailing ends to be significantly larger than at other parts. The graph in Figure 4 shows the temperature at the exit side of the rough rolling mill on the vertical axis, and each position in the longitudinal direction of the strip material on the horizontal axis. In addition to the thermal rundown that appears from the tip to the rear end, and the temperature variation between the skid mark and non-skid mark parts that appear in the middle of the strip material, there is a significant temperature difference between the front and rear ends of the strip material. It is recognized that the price has increased. When rolling a strip material with such a temperature distribution, if setup control is performed using the conventional method, the temperature measurement position in the strip material does not match the target position of setup control. If setup control is carried out in an area with a steep gradient, and the target position of the setup control is a position with a gentle temperature gradient, the actual thickness of the rolled material at the target position will deviate from the target thickness. Normally, the AGC control start position is made to match the target position of setup control, but if the plate thickness at the AGC control start position is significantly different from the target plate thickness.
AGC works effectively and it takes time for the actual thickness to reach the target thickness, resulting in large transient deviations.
There were drawbacks such as a long off-gauge that occurred at the tip. The present invention has been made in view of the above circumstances, and its purpose is to determine the optimum target position at the tip of the rolled material on the exit side of the rolling machine in order to reduce off-gauge as much as possible. , by going back and calculating the position of the rolled material on the entrance side of the rolling mill that corresponds to the target position, actually measuring the temperature from this position, performing setup calculations using this actual measurement value, and performing setup control. Therefore, it is an object of the present invention to provide a setup control method for a rolling mill, which improves the accuracy of the thickness of the tip of a material to be rolled and reduces the off-gauge length as much as possible. The set-up control method for a rolling mill according to the present invention sets a position at the tip of the rolled material when it passes through the rolling mill, which is a target position in the set-up control and a starting position of the sheet thickness control, at least during the set-up control. The position of the tip of the rolled material before rolling, which corresponds to this position, is determined based on the rolling conditions of the rolling mill, and the determined position of the tip of the rolled material is The temperature at the entrance of the rolling mill is actually measured, and based on this measured value, the roll speed and roll opening degree of the rolling mill are calculated according to a gauge meter formula and a constant mass flow formula, and the rolling mill is set up. do. The present invention will be specifically explained below based on the drawings.
Fig. 1 is a schematic side view of an apparatus for carrying out the setup control method for a rolling mill according to the present invention (hereinafter referred to as the method of the present invention), and Fig. 2 A to D show the process of determining the target position for setup control in the method of the present invention. is an explanatory diagram, in which R represents a rough rolling mill, F a finishing rolling mill, T a thermometer, K a flying shear, and SE a strip material. strip material
The SE is passed through a rough rolling mill R from the direction of the white arrow, passed through a thermometer T and a flying shear K, and then passed through a finishing mill F to be finished into a strip ST with predetermined standard dimensions. Strip material B
When the tip of the thermometer passes through the thermometer T, the control section
The temperature at a predetermined position is measured based on a command signal from the CN, and the temperature measurement position on the strip material B is determined as follows. Figure 2 A to D show the strip material B after it leaves the rough rolling mill R until it leaves the finishing mill F.
2A and 2B are schematic views showing the positional relationship between the tip of the strip ST and the tip of the strip material _B1 on the exit side of the rough rolling mill, and FIG. Figure 2 C shows the exit side of the first stand of finishing rolling mill F, and Figure 2 D shows finishing rolling mill F.
The strip materials B ₂ and B ₃ on the exit side of the fifth stand and the tip of the strip ST are shown. Then, the strip material B ₁ (second
In determining the temperature measurement position _A1 in Figure A) above, first locate the position on the strip ST on the exit side of the finishing rolling mill F where the target thickness of the set-up control is to be achieved, that is, the target position of the set-up control. , and also determines a position _A4 which should also be the starting position of AGC, etc. When determining this position _A4 , the strip ST should be adjusted so as to avoid excessive deformation and excessive pressure load fluctuation areas that tend to occur at the top of the strip ST, and to minimize the off-gauge area. plate thickness tolerance, or the controllable limit of AGC (AGC is ineffective when threading the strip material, removing the bottom end, etc., and there are limits to its application to the leading and trailing ends of the strip material), etc. and set the most desirable position theoretically and empirically. The position A ₄ determined in this way can be used, for example, as the time (Δt ₄ ) from when the tip of the strip ST leaves the final stand (6th stand) to when the position A ₄ comes out, and also as the time from the tip of the strip ST to the exit of the Specify as the distance (Δl ₄ ) to A ₄ . Once the position _A4 on the strip ST is determined, the strip material at the exit side of the first stand of the finishing rolling mill F is determined using the constant volume formula based on the rolling schedule of the finishing rolling mill.
The position A 3 corresponding to the position A ₄ on B _{3 is}
For example, it is determined as the time (Δt ₃ ) from when the tip of the strip material B ₃ leaves the first stand until the position A ₃ comes out, and as the distance from the tip of the strip material B ₃ (Δl ₃ ). Similarly, the position A ₂ corresponding to the above-mentioned position A ₃ on the strip material B ₂ after passing through the flying shear K is moved to the strip material B _{2 .}
After the tip exits the flying shear K, position A ₂
time (Δt ₂ ) or strip material
Find it as the distance (Δl ₂ ) from the tip of B ₂ . Further, a position _A1 corresponding to the above-mentioned position _A2 on the strip material _B1 on the outlet side of the rough rolling mill R is set to a position after the tip of the strip material _B1 leaves the rough rolling mill R.
It is determined as the time until A ₁ comes out (Δt ₁ ) or the distance from the tip of the strip material B ₁ (Δl ₁ ).
The strip material B ₁ after leaving the rough rolling mill R and the strip material B ₂ after leaving the flying shear K are different in length, and the top part of the latter strip material is cut by the flying shear K for a shorter length. Since there is no substantial change in length, by determining the cutting length by the flying shear K, the strip material B ₁ on the exit side of the rough rolling mill R can be obtained.
Position A ₁ on the top can be easily identified. Therefore, first, the cutting length α by the flying shear K is determined, and these are usually set empirically as follows. In other words, in the case of strip material B having the same dimensions, there is usually no particularly large variation in the length of the cut portion B', which is the portion of the top portion where the shape is significantly deformed. The length is determined empirically and this is defined as the cutting length. Of course, in addition to this, for example, if an image sensor is provided to recognize the shape of the tip of the strip material B, the cutting length may be determined for each strip material based on the measurement results. Then finishing rolling mill F
The relationship in time, that is, Δt 1 and Δt ₄ , between the position A ₄ on the strip ST on the exit side of the rough rolling mill R and the position A ₁ on the strip material B ₁ on the exit side of the rough rolling mill _R is as follows.
According to equation (1), the positional relationship, that is, Δl ₁ and Δl ₄ is given by equation (2) below. Δt ₁ = Δt ₄・N _f /N _R・D _f /D _R・(1+f _f )/(1−f _R
) ・h _f /H _R +α/π・N _R・D _R・(1+f _R ) …(1) However, N _f , N _R : Roll rotation speed D _{f ,} at the final stand of finishing rolling mill and rough rolling mill. D _R : Roll diameter at the final stand of the finishing rolling mill and roughing mill f _f , f _R : Roll advancement rate at the final stand of the finishing rolling mill and roughing rolling mill h _f : Finished plate thickness H _R : Output side of the rough rolling mill Plate thickness α: cutting length by flying shear Δl ₁ = h _f /H _R・Δl ₄ + α …(2) The above N _f , N _R , f _f , f _R , H _R are the rolling values of the rough rolling mill. The schedule and the preliminary finishing rolling schedule of the finishing rolling mill (referring to the rolling schedule using a predicted calculated value as the strip material temperature rather than the actual measured value) are used. Of course, it may be determined from a table created based on the rough rolling schedule and finish rolling instruction data.
Once the position A ₁ on the strip material B ₁ on the exit side of the rough rolling mill R is specified, when this position A ₁ passes the thermometer T, it will pass once or several times (at 0.2 second intervals). Measure the temperature (about 3 times) and calculate the roll speed and roll opening degree using that temperature as it is or using the average value or maximum value as the strip material temperature for setup calculations. Calculation of roll speed and roll opening degree is performed, for example, according to a known formula shown below. The roll opening degree S is determined from the following equation (3) using the gauge meter method. S=h-P/M (3) where P: load average value M: mill rigidity coefficient and roll speed V _R are determined from the following equation (4) using the constant mass flow equation. hφ _i V _Ri = constant...(4) However, i: Stand number hφ _i : Plate thickness at the neutral point of i stand (the point where the roll speed and material speed match) Note that the load average value P in equation (3) and hφ _i in equation (4) is determined by, for example, the Sims equation. That is, P=b・kpm・Q _p √′(−) …(5) However, b: Plate width H: Plate thickness at the entrance of the rolling machine h: Plate thickness at the exit side of the rolling machine R': Flat roll radius (radius on the roll projection plane under load) kpm: Average deformation resistance (determined using Misaka's formula, for example) During actual operation, N _f , α, etc. as described above are input into the control unit CN in advance, and when the tip of the strip material B ₁ exits the rough rolling mill R and passes through the thermometer T, the pulse generator Based on the movement speed data of strip material _B1 read from PG,
At the moment when position _A1 reaches thermometer T, or before and after that, read the temperature from thermometer T, perform setup calculations based on this actual measurement value, calculate roll speed and roll opening degree, and calculate this calculated value. Finishing rolling mill F is set up to match. The strip material B ₂ is passed through a finishing mill F, which has already been set up, after the portion of the tip end where the shape is significantly deformed is cut off by a flying shear K. Strip material B on the exit side of flying shear K ₂
Until the upper position A ₂ enters the finishing rolling mill F, that is, during strip passing, the finishing rolling mill F is held in the set-up state, and the moment the position A ₂ enters the finishing rolling mill F, the AGC is activated. is locked on, AGC is activated, and finishing mill F changes from the setup state.
This allows for smooth switching without causing any overrange or the like in AGC. In other words, the target position of the setup control for strip material B is
Since this position is accurately captured as A ₁ , this position can be made to match the measurement position of the strip material temperature used for setup calculations, and also coincides with the AGC start position, which can cause AGC overrange etc. The more this can be prevented, the more accurate the plate thickness can be. The above explanation is based on a thermometer T on the upstream side and a flying shear K on the downstream side between the rough rolling mill R and the finishing mill F.
We have explained the case where the Flying Shear K is placed on the upstream side and the thermometer T is placed on the downstream side. When measuring temperature, use equations (1) and (2) above to determine the position.
When specifying A ₁ , if α, which is the cutting length, is set to zero in the equation, it becomes possible to measure the temperature in the same manner as in the case described above. Table 1 shows the results of comparative tests between the method of the present invention and the conventional method.

[Table] Table 1 shows the plate thickness accuracy at the exit side of the hot finishing rolling machine.
It is expressed as the ratio of the number of rolled materials with a diameter within 100μ to the total number of rolled materials. The thickness of the rolled material is
A diameter of 2.30 to 6.00 mm was used. As is clear from Table 1, it can be seen that the method of the present invention significantly improves the plate thickness deviation regardless of the steel type, compared to the conventional method. As described above, in the method of the present invention, the temperature of the rolled material used in the setup calculation is determined by the position of the rolled material on the inlet side of the rolling mill, which corresponds to the position determined at the tip of the rolled material on the exit side of the rolling mill. Since the temperature measured from this position and its vicinity is used, it is possible to reduce overrange of thickness control and other variations in thickness during the transition from setup control to thickness control. The present invention has excellent effects such as a significant improvement in accuracy.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the implementation state of the method of the present invention,
Figure 2 is an explanatory diagram showing the process of determining the measurement position of the strip material temperature for setup calculation;
The figure is a schematic diagram showing the implementation state of the conventional method, and FIG. 4 is a graph showing the temperature distribution in the longitudinal direction of the strip material. R... Rough rolling mill, F... Finishing rolling mill, B, B ₁ ,
B ₂ , B ₃ ... Strip material, T ... Thermometer, K
...Flying shear, CN...control section, ST...
strip.

Claims (1)

[Claims] 1. At the tip of the rolled material when it is passed through the rolling mill, the target position in setup control and the starting position of plate thickness control should be set at a position that will at least interfere with the transition from setup control to plate thickness control. The temperature at the determined position of the tip of the rolled material was actually measured on the entrance side of the rolling mill. , a method for controlling the setup of a rolling mill, characterized in that the roll speed and roll opening degree of the rolling mill are calculated in accordance with a gauge meter formula and a constant mass flow formula based on the measured values, and the rolling mill is set up.