JP6086694B2 - Method for estimating tension between stands in strip rolling and rolling mill for strip rolling - Google Patents

Description

The present invention relates to an estimation method for accurately estimating the tension between stands in the strip rolling for rolling the strip, and a rolling mill for the strip rolling that can employ this estimation method.

Conventionally, in steel bar rolling, which manufactures steel bars (steel bars) such as wire rods, bar bars, and steel bars, rolling is performed while measuring the tension between rolling stands that roll the rolled material that is the source of the bar bars (referred to as inter-stand tension). The material is rolled. In such bar rolling, there are techniques shown in Patent Documents 1 to 5 as techniques for obtaining tension between stands.
In Patent Document 1, the passage of the last end of the strip material (rolled material) in each stand is detected, and while the last end exists in the i-th stand through which the last end has passed and the next i + 1th stand, the strip material is present. The width dimension fluctuation value is obtained, and the tension is obtained from the width dimension fluctuation value and the influence coefficient of the width of the strip. That is, in Patent Document 1, the tension between the stands is estimated from the change in the width dimension of the rolled material when the rolled material falls out.

In Patent Literature 2, the tension between the stands at each time of the tip of the rolled material, the center of the rolled material, and the tail end of the rolled material is estimated from the amount of change in the load and torque of the rolling stand. In Patent Document 3, the tension between the stands is estimated from the load of the rolling stand when the rolled material falls out, the torque of the rolling stand, and the width of the rolled material.
Moreover, in patent document 4, the change of the electromagnetic characteristic by tension | tensile_strength is detected and the tension | tensile_strength between stands is estimated.

Moreover, in patent document 5, while calculating | requiring the change of rolling torque from the rolling load of a rolling stand, the voltage of a drive motor, and an electric current, tension | tensile_strength between stands is based on the change of rolling torque when a rolling material bites into a rolling stand. Estimated.
In other words, Patent Documents 1 to 5 include a method (Patent Document 1) for estimating the tension between the stands from the width dimension of the rolled material when the rolled material slips through, and a rolling model based on the rolling load and rolling torque. A method (Patent Documents 2, 3, and 5) for estimating the tension between the stands by using the method and a method (Patent Document 4) for estimating the tension between the stands by a change in electrical property due to the tension are disclosed.

Japanese Patent Publication No. 5-41334 Japanese Patent No. 2510090 Japanese Patent Publication No. 8-4813 JP-A-6-94547 Japanese Patent Publication No. 4-8124

  In rolling a steel sheet, when a certain amount of rolled material is rolled, the rolling roll is replaced for reasons such as roll wear and rough skin. On the other hand, in a rolling line for producing strip rolling, different from a rolling line that rolls steel sheets, etc., not only rolling rolls but also rolling stands are frequently exchanged depending on the size and shape of the rolled material. . For this reason, it is necessary to repeatedly remove, reattach, and adjust (calibrate) the load cell for measuring the rolling load with replacement of the rolling stand. In order to make the measurement with the load cell accurate, it is necessary to make adjustments and calibrations after the load cell has been attached. For this reason, it is difficult to measure the rolling load using a load cell and obtain the inter-stand tension from the obtained rolling load in the strip rolling line. In addition, for the same reason, it is difficult to accurately calculate the rolling torque from the measured value by the load cell and obtain the inter-stand tension from the obtained rolling torque.

In other words, Patent Documents 2, 3, and 5 disclose that the tension between stands is obtained using a rolling load and a rolling torque. However, obtaining the tension between stands using these techniques is an actual site. In many cases, it is extremely difficult.
On the other hand, Patent Document 1 discloses a technique of a residual tension estimation method for estimating a tension based on a width dimension of a rolled material when the rolled material slips through. However, in the upstream rolling stand in the actual steel bar rolling, the change in tension at the bottom does not significantly affect the change in the width dimension of the rolled material, and the width dimension of the rolled material as in the technique of Patent Document 1. It is difficult to obtain the tension between the upstream stands based on the above.

  Further, Patent Document 4 discloses that the tension between the stands is obtained by a change in electromagnetic characteristics, but the rolled material has a temperature unevenness (for example, a portion in contact with the skid is at a lower temperature than other portions). ), And the electromagnetic characteristics change due to the influence of this temperature unevenness. Therefore, even if the technique of Patent Document 4 is used, the tension between the stands cannot be obtained stably.

Then, in view of the said problem, this invention aims at providing the estimation method of the tension between stands in the strip rolling which can obtain | require the tension between stands stably, and the rolling mill of a strip rolling.

In order to achieve the above object, the present invention takes the following technical means.
That is, the technical means for solving the problem in the present invention is that when performing strip rolling while measuring the tension between the rolling stands by a rolling mill having a plurality of rolling stands driven by a motor, The motor of the i-th rolling stand before the rolling material bites into the i + 1-th rolling stand when determining the tension between the rolling stands between the i + 1-th rolling stand and the i + 1-th rolling stand located downstream of the i-th rolling stand. The difference between the current and the motor current of the i-th rolling stand after the rolling material is caught in the i + 1-th rolling stand is obtained, and the tension between the rolling stands is determined using the difference current and the rolling model. JP a and requests, and the difference current, the determination of the tension between the rolling stands with a rolling model shown in Equation 1] To.

Preferably, after biting into the i-th rolling stand, the motor current detected before biting into the i + 1-th rolling stand goes back several seconds from the time when the rolling material bites into the i + 1-th rolling stand. The difference current may be obtained on the basis of the motor current of the i-th rolling stand that is stable in the last section and the motor current of the i-th rolling stand that is stable in the section that is advanced for several seconds from the time when the rolled material is caught. .

Preferably, the cycle of obtaining the difference currents have good when below 0.5 seconds.
The technical means for solving the problems in the present invention is a rolling mill having a plurality of rolling stands driven by a motor and performing strip rolling while measuring the tension between the rolling stands, the motor of the rolling stand Based on the current detection means for detecting the current and the motor current detected by the current detection means, a difference current that is a change amount of the motor current of the rolling stand is calculated, and the calculated difference current and the rolling model are used. Tension calculating means for obtaining a tension between the rolling stands, and as the plurality of rolling stands, an i-th rolling stand, and an i + 1-th rolling stand located downstream of the i-th rolling stand, The current detection means includes a motor current of the i-th rolling stand before the rolled material bites into the i + 1-th rolling stand, and the i + 1-th rolling stand. And a motor current of the i-th rolling stand after the rolling material is caught in the extension stand, and the tension calculating means obtains a difference current from the detected motor current and obtains the difference current And the rolling model are used to determine the tension between the i-th rolling stand and the i + 1-th rolling stand, and the difference current and the rolling model shown in [Equation 1] are used. It is comprised so that the tension | tensile_strength between the said rolling stands may be calculated | required .

According to the present invention, when performing strip rolling by a rolling mill having a plurality of rolling stands, the tension between the stands can be obtained stably at a very low cost without incurring a maintenance cost by the motor current of the motor that drives the rolling stand. .

It is a schematic diagram of the rolling line of a strip steel wire. It is a figure which shows the relationship between the biting condition of a rolling material, and a motor current. It is the figure which showed the time transition of the motor current. It is the figure which showed the detection result of the difference electric current between rolling stands, and the calculation result of tension | tensile_strength.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows an outline of a rolling mill (rolling line) for rolling bar steel (steel bar material) such as bar steel, wire rod, and shape steel.
The rolling mill 1 rolls a rolled material (raw material) 3 transferred from a heating furnace 2 into a strip, and comprises a rough rolling mill 4, an intermediate rolling mill 5, a finish rolling mill (block mill) 6, a pinch roll 7 A winding machine (laying head) 8 or a cutting device (cold shear) and a cooling bed are provided. A rough rolling mill 4 is disposed on the downstream side of the heating furnace 2, and an intermediate rolling mill 5, a finish rolling mill 6, a pinch roll 7, and a winder 8 are sequentially disposed from the rough rolling mill 4 toward the downstream side. ing.

  Each rolling mill 4, 5, 6 includes a plurality of rolling stands 9. Each rolling stand 9 includes a rolling roll 10, and the rolling roll 10 is provided with a motor (not shown) that rotationally drives the rolling roll 10. The current (referred to as motor current) of the motor that rotationally drives each rolling roll 10 can be detected by current detection means 12 configured by an ammeter or the like, and the detected motor current is controlled by a control device 11 configured by a process controller. To be input.

The control device 11 includes tension calculation means 13 for obtaining the tension between the stands from the motor current, the motor voltage, the motor rotation number, and the like, and drives each rolling roll 10 with the tension between the stands obtained by the tension calculation means 13. The gap of the motor and the rolling roll 10 can be controlled.
In order to roll the rolled material 3 into a strip using such a rolling mill 1, first, the rolled material 3 such as a billet is heated in the heating furnace 2, and then the heated rolled material 3 is subjected to a roughing mill. 4. Introduced in the order of the intermediate rolling mill 5 and the finishing rolling mill 6, the cross section of the rolled material 3 is deformed in the order of square, oval, and round by a caliber provided on the rolling roll 10, and the rolled material 3 is formed in a desired shape. Use a cross-sectional shape. The rolled material that has become the long bar by the finish rolling mill 6 is wound around the winder 8. In this strip rolling, when the rolled material 3 is caught in the rolling stand 9, the inter-stand tension between the rolling stand 9 and the immediately preceding (one upstream side) of the rolling stand 9 is obtained. Control of bar rolling based on the inter tension.

Hereinafter, the tension estimation method performed by the tension calculation means 13 provided in the control device 11 will be described in detail.
FIG. 2 shows the relationship between the biting of the rolled material 3 and the motor current.
As shown in FIG. 2 (a), before the rolled material 3 bites into the i-th rolling stand 9, the motor current of the i-th rolling stand 9 is very close to zero. As shown in FIG. 2 (b), when the rolled material 3 bites into the i-th rolling stand 9, the motor current of the i-th rolling stand 9 increases rapidly. Then, as shown in FIG. 2 (c), the rolled material 3 is caught in the i + 1-th rolling stand 9 which is the next rolling stand 9, and between the i-th rolling stand 9 and the i + 1-th rolling stand 9. When the tension between the stands is generated, for example, the motor current of the i-th rolling stand 9 is further increased.

Thus, since the tension between the stands and the motor current are related, in the present invention, when the tension calculating means 13 obtains the tension between the stands, each motor current for driving each rolling stand is used. Yes.
In order to obtain the tension between the rolling stands, first, as shown in FIGS. 2B and 2C, after the rolled material 3 is bitten into the i-th rolling stand 9, before it is bitten into the i + 1-th rolling stand 9. The motor current in the i-th rolling stand 9 until is detected by the current detection means 12, and this motor current is sequentially stored. For convenience of explanation, the motor current detected after the rolled material 3 “after biting into the i-th rolling stand 9 and before biting into the i + 1-th rolling stand 9” is referred to as “pre-motor current”.

  Next, as shown in FIG. 2 (c), after the rolled material 3 has bitten into the (i + 1) -th rolling stand 9, the motor current of the i-th rolling stand 9 is similarly detected by the current detection means 12. The motor current is stored sequentially. For convenience of explanation, the motor current detected after the rolling material 3 “after biting into the i-th rolling stand 9 and after biting into the (i + 1) -th rolling stand 9” is referred to as “post-motor current”. That's it.

Then, the tension calculation means 13 provided in the control device 11 obtains a difference current that is a difference between the front motor current and the rear motor current. Then, the obtained difference current is applied to the rolling model, and the inter-stand tension between the i-th rolling stand 9 and the i + 1-th rolling stand 9 is obtained.
Hereinafter, the calculation of the tension between the stands will be described in detail using three rolling stands as an example with reference to FIG.

  FIG. 3 (a) shows the change in motor current of the first rolling stand 9, and FIG. 3 (b) shows the change in motor current of the second rolling stand 9. FIG. 3C shows a change in motor current of the third rolling stand 9. For convenience of explanation, the first rolling stand 9 is called a first rolling stand, the second rolling stand 9 is called a second rolling stand, and the third rolling stand 9 is called a third rolling stand.

  When the rolling of the rolled material 3 starts, the motor currents in the first to third rolling stands 9 are measured by the current detection means 12, and each motor current is input to the control device 11. When each motor current exceeds a predetermined threshold, rolling is started. For example, as shown in FIG. 3A, in the first rolling stand 9, since the motor current suddenly increases at the point A and exceeds the threshold value, the control device 11 has the first rolling stand 9 at the point A. It is detected that rolling has started. Similarly, the start of rolling of the second rolling stand 9 is detected at point B, and the start of rolling of the third rolling stand 9 is detected at point C.

Next, the tension calculating means 13 proceeds to a process for obtaining a difference current between the motor currents.
First, as shown in FIG. 3A, after the rolling of the first rolling stand 9 is started, the previous motor current in the first rolling stand 9 is sequentially changed every sampling time until the second rolling stand 9 starts rolling. Remember. Then, after the second rolling stand 9 starts rolling (point B at which the rolled material 3 is caught in the second rolling stand 9), the first rolling stand is kept until the rolled material 3 is caught in the third rolling stand 9. The post motor current at 9 is sequentially stored every sampling time.

That is, the motor current before and after the point B where the rolling material 3 is bitten into the second rolling stand 9, that is, the motor current before the first rolling stand 9 and the motor current after the first rolling stand 9 are expressed. Remember.
When the storage of the front motor current and the rear motor current of the first rolling stand 9 is completed, the tension calculating means 13 calls the data of the front motor current in the first rolling stand 9 and starts from the point B for a few seconds (for example, 2 The previous motor current which is stable in the data traced back in seconds) is set as the first current value Ib for calculating the difference current. Similarly, the tension calculating means 13 calls the post-motor current of the first rolling stand 9 and sets the post-motor current that is stable in the data advanced for several seconds (for example, 2 seconds) from the point B to the differential current. Is a second current Ia for calculating. In other words, a current value that is stable in a section retroactive for a few seconds from point B in the previous motor current is adopted as the first current value Ib, and a few seconds from point B in the rear motor current is advanced. A current value that is stable in the section is adopted as the second current value Ia.

Then, a difference current of the first rolling stand 9 is obtained by subtracting the first current value Ib from the second current value Ia (difference current = Ia−Ib).
When the rolled material 3 is caught in the rolling stand 9, a large current fluctuation (impact) occurs. As described above, when the difference current is obtained, the motor is several seconds before and after the point B (for example, 2 seconds). Since the current is used, the difference current in a portion excluding a large current fluctuation (impact) can be obtained.

  In addition, when calculating | requiring a difference electric current, when the rolling speed is slow, the 1st current value Ib and the 2nd current value Ia which are employ | adopted are good also as an average value of about 0.5 to 1 second in a motor current, and rolling speed If this is early, an average value of about 0.1 to 0.5 seconds in the motor current may be used. For this reason, in each rolling stand 9, the period for obtaining the difference current is preferably 0.5 seconds or less.

  As described above, in obtaining the inter-stand tension between the first rolling stand 9 and the second rolling stand 9, first, the first rolling stand 9 before and after the rolling material 3 bites into the second rolling stand 9. Difference current (= Ia−Ib). Similarly, in obtaining the inter-stand tension between the second rolling stand 9 and the third rolling stand 9, the difference current of the second rolling stand 9 before and after the rolling material 3 bites into the third rolling stand 9 is obtained. I am going to do that.

  Then, the inter-stand tension ΔσF is calculated by the equation (1) based on the obtained difference current ΔA.

The motor torque G used in equation (1) may be calculated by equation (2).
In the case of this embodiment, the deformation resistance kfm used in the calculation of the expression (2) is determined by a person skilled in the art from the actual values of the roll rotation speed N and the motor load (motor current A × motor voltage V) in a state where no tension is applied. This is estimated using a law deformation resistance model (for example, Equations (3) to (5)). That is, the deformation resistance kfm is estimated based on the motor current A, and the tension between the stands is obtained based on the estimated deformation resistance kfm.

Now, the derivation method of the above-described formula (1) is as follows.
First, the relationship among the torque G, voltage V, and current A acting on the motor is expressed as shown in Equation (6).

  When this equation (6) is modified, equations (7) and (8) are obtained.

By using the equations (7) and (8), the inter-stand tension can be obtained by obtaining the difference current (current change amount) when the inter-stand tension is applied. However, σF is the front tension and σB is the rear tension.
Here, even if a forward tension is generated in the rolling stand, the rear tension is kept constant (even if the rolled material 3 is caught, it does not affect the tension between the stands already caught, that is, ΔρB = 0. ), Assuming that the roll gap (roll gap) does not change even if the rolling load is changed due to the generation of tension between the stands, that is, assuming that Δh = 0, equations (7) and (8) for obtaining the tension between the stands Can be transformed into equation (1).

By calculating the forward tension ΔσF from the difference current ΔA using the formula (1) thus obtained, the inter-stand tension can be obtained.
FIG. 4 is a diagram showing a result of detecting a difference current between rolling stands and calculating a tension.
In FIG. 4, the i-th rolling stand is represented by “# 1 stand” and the i + 1-th rolling stand is represented by “# 1 + 1 stand”.

  As shown in FIG. 4, when the rolled material 3 bites into the i-th rolling stand 9, the motor current of the i-th rolling stand 9 rapidly increases. When the rolled material 3 bites into the (i + 1) -th rolling stand 9, the motor current of the i-th rolling stand 9 slightly increases. Then, when the difference current is detected and the inter-stand tension is obtained when the time exceeds 20 seconds, the inter-stand tension is 0.5 kg / mm 2. In addition, after the rolling material 3 slips through and the first rolling (one pass) is completed, in the second rolling (two passes), when the rolling material 3 bites into the i-th rolling stand 9 (the next material is # 1 stand biting), the tension between the stands (0.15 kg / mm 2) when the next material is rolled in the vicinity of 75 seconds can be obtained.

As described above, by determining the tension between the rolling stands using the difference in motor current between the adjacent rolling stands and the rolling model, the tension between the stands can be determined stably and accurately.
The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

1 Rolling mill (rolling line)
2 Heating furnace 3 Rolled material 4 Rough rolling mill 5 Intermediate rolling mill 6 Finishing rolling mill 7 Pinch roll 8 Winding machine 9 Rolling stand 10 Rolling roll 11 Current detection means 12 Controller 13 Tension calculation means

Claims (4)

When performing strip rolling while measuring the tension between the rolling stands by a rolling mill having a plurality of rolling stands driven by a motor,
When determining the tension between the rolling stands between the i-th rolling stand and the i + 1-th rolling stand located on the downstream side of the i-th rolling stand,
The difference current between the motor current of the i-th rolling stand before the rolling material bites into the i + 1th rolling stand and the motor current of the i-th rolling stand after the rolling material bites into the i + 1-th rolling stand. Seeking
Using the difference current and the rolling model, the tension between the rolling stands is obtained,
A method for estimating an inter-stand tension in strip rolling, wherein the tension between the rolling stands is obtained using the difference current and the following rolling model .
  After being bitten into the i-th rolling stand, the section of the motor current detected before biting into the i + 1-th rolling stand is a section that goes back several seconds from the time when the rolled material bites into the i + 1-th rolling stand. The difference current is obtained on the basis of the motor current of the stable i-th rolling stand and the motor current of the i-th rolling stand that is stable in a section advanced for several seconds from the time when the rolled material is caught. The estimation method of the tension | tensile_strength between stands in the strip rolling of Claim 1. The method for estimating the inter-stand tension in the strip rolling according to claim 1 or 2 , wherein a period for obtaining the difference current is 0.5 seconds or less. A rolling mill having a plurality of rolling stands driven by a motor and performing strip rolling while measuring the tension between the rolling stands,
Current detecting means for detecting a motor current of the rolling stand;
Based on the motor current detected by the current detection means, a difference current that is a change amount of the motor current of the rolling stand is calculated, and the tension between the rolling stands is calculated using the calculated difference current and a rolling model. The required tension calculation means;
With
As the plurality of rolling stands, an i-th rolling stand and an i + 1-th rolling stand located on the downstream side of the i-th rolling stand,
The current detection means includes a motor current of the i-th rolling stand before the rolling material is caught in the i + 1-th rolling stand, and a motor of the i-th rolling stand after the rolling material is caught in the i + 1-th rolling stand. Configured to detect current and
The tension calculating means obtains a difference current from the detected motor current and obtains a tension between the i-th rolling stand and the i + 1-th rolling stand using the obtained difference current and the rolling model. Configured ,
A strip rolling mill characterized by being configured to obtain the tension between the rolling stands using the difference current and the following rolling model .