Rolling data collecting method and system

The rolling data collecting system according to this invention collects rolling data of a rolled strip to be serially rolled through a tandem rolling mill, using the first rolling data measuring means installed at each roll stand and the second rolling data measuring means installed in the rolling line. The measuring point decision means decides a measuring point on a rolled strip which is used for measuring data by the first and second rolling data measuring means. The tracking means detects that the decided measuring point has reached each roll stand locating from the entry side of the tandem rolling mill and to the delivery side thereof, and the location of the second rolling data measuring means. Every time when the measuring point reaches each roll stand and the second rolling data measuring means, the rolling data collecting means collects the rolling data of the rolled strip or rolled strip measured by the first and second rolling data measuring means.

BACKGROUND OF THE INVENTION
 1. Field of the Invention
 This invention relates to a rolling data collecting method and system to be
 used for a tandem hot rolling mill.
 2. Related Background Art
 So far, collecting of rolling data in a tandem hot rolling mill has been
 made as follows: The rolling data measuring devices installed for all of
 the roll stands in the tandem hot rolling mill collected rolling data
 simultaneously at a timing when a point on the rolled strip a few or
 several meters away from the leading (or trailing) edge of the rolled
 strip just enters the stands.
 According to the prior art, all rolling data generated at all of the stands
 are collected at the same timing, so that the obtained rolling data can be
 said to represent no recognition or consideration for the past rolling
 history of the rolled strip, thereby resulting in a possible inaccuracy
 when making the analysis of rolling mechanism or the learning of
 established calculation method using these rolling data.
 SUMMARY OF THE INVENTION
 In view of the aforementioned problems, this invention intends to provide a
 rolling data collecting method and system which can enhance the analysis
 of rolling mechanism or the learning of established calculation method.
 Further, the invention intends to provide a rolling data collecting method
 and system which can produce a high accuracy of analysis of rolling
 mechanism, using the rolling data obtained.
 Furthermore, the invention intends to provide a rolling data collecting
 method and system which can enhance the accuracy of the setting and
 learning for the subsequent sheet and on forward by way of already
 collected rolling data.
 To achieve these above-described purposes, the rolling data collecting
 method according to the invention which collects rolling data of a rolled
 strip to be serially rolled by a tandem rolling mill, using a first
 rolling data measuring means provided at every roll stand and a second
 rolling data measuring means provided in the rolling line, the method
 comprising the steps of;
 deciding a data-measuring point of a rolled strip by way of the first and
 second rolling data measuring means;
 detecting that the above-decided data-measuring point has reached each
 stand and the installation position of the second rolling data measuring
 means; and
 collecting the rolling data measured by the first and second rolling data
 measuring means, every time when the measuring point reached each stand
 and the second rolling data measuring means.
 In other words, using this rolling data collecting method according to the
 invention, the data-measuring point of a rolled strip is decided by way of
 the first and second rolling data measuring means, whether the
 above-decided data-measuring point has reached the every stand and the
 installation point of the second rolling data measuring means is detected
 and then the rolling data measured by the first and second rolling data
 measuring means are collected, every time when the measuring point reached
 the every stand and the second rolling data measuring means.
 Further, the rolling data collecting system according to the invention
 comprises:
 first rolling data measuring means provided at each stand installed from
 the entry side to the delivery side for obtaining rolling data of a rolled
 strip to be serially rolled;
 second rolling data measuring means provided in the rolling line for
 obtaining rolling data of the rolled strip;
 measuring point decision means for deciding a measuring point on the rolled
 strip for obtaining rolling data using the first and second rolling data
 measuring means;
 tracking means for detecting that the measuring point has reached each roll
 stand and the installation position of the second rolling data measuring
 means; and
 rolling data collecting means for obtaining the rolling data measured by
 the first and second rolling data measuring means every time when the
 measuring point has reached each stand and the installation position of
 the second rolling data measuring means.
 The second rolling data measuring means may be installed at the delivery
 side of the tandem rolling mill, so that the measuring point decision
 means can select (as the suitable measuring point on the rolled strip) the
 rolling point of the rolled strip at the leading stand, which takes place
 just at the timing when the leading edge of the rolled strip reached the
 second rolling data measuring means.
 Otherwise, the second rolling data measuring means may be installed at the
 delivery side of the tandem rolling mill, so that the measuring point
 decision means can select (as the measuring point on the rolled strip) the
 rolling point of the rolled strip at the leading stand, which takes place
 a preset time after the timing when the leading edge of the rolled strip
 reached the second rolling data measuring means.
 The measuring point decision means may select the rolling point of the
 rolled strip at the leading stand, which takes place a preset time after
 the time when the leading edge of the rolled strip reached the leading
 stand, as the measuring point on the rolled strip.
 The measuring point decision means may select a point (on a rolled strip) a
 preset distance away from the leading edge of a rolled strip as the
 measuring point on the rolled strip.
 The measuring point decision means may select a point on a rolled strip as
 the first measuring point, and then select the rolling point of the rolled
 strip at the leading stand, which takes place when the first measuring
 point reached the second rolling data measuring means, as the second
 measuring point. This procedure is repeated until the rolling operation
 finishes.
 The measuring point decision means may select a point on a rolled strip as
 the first measuring point, and then select the rolling point of the rolled
 strip at the leading stand, which takes place a preset time after the
 timing when the first measuring point reached the second rolling data
 measuring means, as the second measuring point. This procedure is repeated
 until the rolling operation finishes.
 The tracking means may follow the track of a measuring point on a rolled
 strip, using a pulse value of a pulse generator at least connected to the
 motor driving the rolling mill, the roll diameter and forward slip.
 The tracking means may follow the track of a measuring point on a rolled
 strip, using a pulse value of a pulse generator connected to the motor
 driving the trailing stand, the roll diameter and forward slip, as well as
 the thickness of the strip at the delivery side of the trailing stand, and
 the delivery-side thickness of the rolled strip at the measuring point
 under tracking.
 The tracking means may decide how far the measuring point on a rolled strip
 advanced from the leading stand, using the sheet thickness at the entry
 and delivery sides of a roll stand, when the tracking means judged that
 the measuring point on the rolled strip reached the roll stand.
 The tracking means may correct the tracking position for the measuring
 point on a rolled strip, using the distance how far the sheet advanced
 from the leading stand.
 The tracking means may decide reaching times to the rolling mill and the
 second rolling data measuring means, using the peripheral speed and
 forward slip of the roll, stand spacing, and the distance between the
 rolling mill and the second rolling data measuring means. A setting of the
 calculated reaching times to a timer can follow the track of the measuring
 point of the rolled strip.
 The second rolling data measuring means may be installed at the entry side
 of a tandem rolling mill. The measuring point decision means selects a
 point on a rolled strip locating at the second rolling data measuring
 means as long as the measurements of the rolled strip by the second
 rolling data measuring means fall into a preset range during a preset
 period.
 When measurements of the second rolling data measuring means keep the
 preset range after the decision of the measuring point, the measuring
 point decision means selects the point on a rolled strip locating at the
 second rolling data measuring means as the measuring point, with a preset
 cycle period.
 The second rolling data measuring means may be installed between stands.
 The measuring point decision means selects a rolling point on a rolled
 strip locating at the leading stand as the measuring point, as long as the
 measurements of the rolled strip by the second rolling data measuring
 means fall into a preset range during a preset period.
 In a case after the decision of the measuring point has been made and when
 the measurements of a rolled strip given by the second rolling data
 measuring means fall into a preset range, the measuring point decision
 means selects the rolling point on the sheet at the leading stand as the
 measuring point, with a preset cycle period.
 The second rolling data measuring means may be installed at the delivery
 side of the tandem rolling mill, so that the measuring point decision
 means selects the rolling point on the sheet at the leading stand as the
 measuring point, when the measurements of the strip given by the second
 rolling data measuring means fall in a preset range for a preset period.
 In a case after the decision of the measuring point has been made and when
 the measurements of the strip given by the second rolling data measuring
 means continue to fall into a preset range, the measuring point decision
 means selects the rolling point on the sheet at the leading stand as the
 measuring point, with a preset cycle period.
 The second rolling data measuring means may include at least one of a strip
 crown meter, temperature gage, strip width meter and flatness meter.

DESCRIPTION OF THE PREFERRED EMBODIMENT
 Referring to the preferred embodiments shown in the attached drawings,
 detail description will be made for the present invention:
 FIG. 1 is the schematic block diagram showing the first embodiment of the
 rolling data collecting system which carries out the rolling data
 collecting method according to the invention, inclusive of an applicable
 tandem rolling mill. In the drawing, the tandem rolling mill consists of
 six roll stands (stand 1.about.6) serially arranged. The stand locating at
 the entry side is called the first or leading stand, and the stand
 locating at the delivery side is called the sixth or trailing stand. A
 rolled strip 7 is rolled into a strip in the direction of an arrow 8. Each
 stand is provided with the first rolling data measuring means or device
 (not shown) to measure rolling load, bending force, pair cross angle, roll
 coolant flow rate and other rolling data.
 The second rolling data measuring means or device is installed at the entry
 or delivery side of the tandem rolling mill, or in between the roll stands
 to measure the temperature, thickness, width, sheet crown, flatness and
 length of a rolled strip, coolant flow rate and other rolling data.
 Here, for simplification of the drawing and description, only a sheet crown
 meter 9 to be used for measuring the sheet crown is shown instead of the
 variety of above-described measuring devices. Now,description will be made
 for the operation of the measuring point decision means or device 10
 according to the first embodiment to decide the measuring point on a
 rolled strip, referring to the measurements of the sheet crown meter 9 as
 an example:
 First, a rolled strip enters the tandem rolling mill, and advances from the
 first stand 1 to the sixth stand 6 while serially rolled. When the sheet 7
 reached the sheet crown meter 9, the measuring point decision means 10
 selects a point on the rolled strip being rolled in the first stand 1 as
 the first measuring point. Depending on a case, however, the sheet crown
 control may be executed at the timing when the sheet 7 reached the sheet
 crown meter 9. In such a case, the operation made by the rolling data
 collecting means or device 12 may result in collection of transient
 rolling data. To prevent such improper decision, the measuring point
 decision means 10 may select a point on the rolled strip just locating at
 the first stand 1 as the first measuring point, a fraction of second
 (e.g., 0.5 sec) after the strip 7 reached the sheet crown meter 9.
 The tracking means 11 keeps the track of the measuring point decided by the
 measuring point decision means 10 from the first stand 1 to the sixth
 stand 6. There are such two types of tracking methods as follows:
 The first tracking method:
 In general, the motors for driving roll stands 1, 2, . . . , 6 are
 connected directly or wired to a pulse generator. Now, the number of
 pulses generated by the pulse generator is abbreviated as the pulse value
 of motor.
 Before a rolled strip 7 enters the tandem rolling mill, the tracking means
 11 calculates a pulse value of each motor which is necessary for the
 rolled strip 7 to advance in between roll stands and between a roll stand
 and the rolling data measurement device. For example, the pulse value
 p.sub.1 +L of the motor for the first stand 1 which is necessary for the
 rolled strip 7 to advance from the first roll stand 1 to the second roll
 stand 2 is decided so as to satisfy the following expression:
 ##EQU1##
 where
 p.sub.1 : pulse value when the first stand motor makes one rotation
 f.sub.1 : forward slip of the first stand
 d.sub.1 : diameter of work roll of the first stand
 g.sub.1 : gear ratio of the first stand
 l.sub.12 : distance between the first and second stands.
 In this connection, the forward slip f.sub.1 is calculated using pass
 schedule and other factors by a calculation processing unit (not shown).
 Work roll diameter, gear ratio and distance between the first and second
 stands are known.
 When the rolled strip 7 entered the tandem rolling mill, and the measuring
 point on the sheet 7 reaches the first stand 1 the tracking means 11 sets
 the pulse value p.sub.1 +L of the first stand motor calculated by the
 expression (1) to the relevant pulse generator. When the first stand motor
 rotates just one pulse value p.sub.1 +L , the rotation is noticed to the
 tracking means 11 from the pulse generator. Receiving the notice, the
 tracking means 11 judges that the measuring point on the sheet 7 reached
 the second stand 2.
 When the measuring point on the sheet 7 reached the second stand 2,
 similarly in the case of the first stand 1 the tracking means 11 sets the
 pulse value p.sub.2 +L of the second stand motor to the relevant pulse
 generator. When the second stand motor rotates just one pulse value
 p.sub.2 +L , the rotation is noticed to the tracking means 11 from the
 pulse generator. Receiving the notice, the tracking means 11 judges that
 the measuring point on the sheet 7 reached the third stand 3.
 Similar operation is repeated until the measuring point on the sheet or
 strip reaches the strip crown meter 9 installed at the delivery side of
 the tandem rolling mill. These sequential operations can keep the track of
 the measuring point on the sheet 7 from the first stand 1 up to the strip
 crown meter 9.
 The above described the case where the measuring point on the rolled strip
 7 is kept tracked from the first stand 1. There may be a case where
 tracking of the measuring point on the rolled strip 7 starts before
 entering the first stand 1. In this case, backward slip which is
 calculated using the expression (1) may be used in place of forward slip,
 where the expression (1) must be rewritten by backward slip. In a case
 where a pinch roll or a measuring roll is installed in front of the tandem
 rolling mill, the pulse value of the pulse generator for this pinch roll
 or measuring roll also can be used for tracking, thus considerably
 enhancing the tracking accuracy.
 The second tracking method:
 Before the rolled strip 7 enters the tandem rolling mill, the tracking
 means 11 calculates the pulse value of the sixth stand motor which is
 necessary for the sheet 7 to advance in between roll stands and between a
 roll stand and the rolling data measurement device. For example, the pulse
 value p.sub.61 +L of the sixth stand motor which is necessary for the
 rolled strip 7 to advance from the first roll stand 1 to the second roll
 stand 2 is decided so as to satisfy the following expression:
 ##EQU2##
 where
 p.sub.6 : pulse value when the sixth stand motor makes one rotation
 f.sub.6 : forward slip of the sixth stand
 d.sub.6 : diameter of work roll of the sixth stand
 g.sub.6 : gear ratio of the sixth stand
 h.sub.6 : the thickness of the strip at the delivery side of the sixth
 stand
 h.sub.1 : the thickness of the rolled strip at the delivery side of the
 first stand
 l.sub.12 : distance between the first and second stands.
 In this connection, the forward slip is calculated using pass schedule and
 other factors by a calculation processing unit (not shown). Work roll
 diameter, gear ratio and distance between the stands are known. The sheet
 thickness of the rolled strip or strip 7 can be estimated using e.g.,
 gauge meter and the like.
 When the sheet 7 entered the tandem rolling mill, and then the measuring
 point on the sheet 7 just reached the first stand 1 the tracking means 11
 sets the pulse value p.sub.61 +L of the sixth stand motor calculated by
 the expression (2) to the pulse generator for the sixth stand motor. When
 the sixth stand motor rotated the pulse value p.sub.61, receiving the
 notice from the pulse generator, the tracking means 11 judges that the
 measuring point on the sheet 7 reached the second stand 2.
 When the measuring point on the sheet 7 just reached the second stand 2,
 similarly to the case in the first stand 1 the tracking means 11 sets the
 pulse value p.sub.62 +L of the sixth stand motor to the pulse generator
 for the sixth stand motor. When the second stand motor just rotated the
 pulse value p.sub.62 +L , receiving the notice from the pulse generator,
 the tracking means 11 judges that the measuring point on the sheet 7
 reached the third stand 3.
 Similar operation is repeated until the measuring point on the sheet or
 strip reaches the strip crown meter 9 installed at the delivery side of
 the tandem rolling mill. These sequential operations can keep the track of
 the measuring point on the sheet 7 from the first stand 1 up to the strip
 crown meter 9.
 However, both the above-described methods must issue an notice from the
 pulse generator every time when the motor rotates just the pulse value,
 thereby increasing the system cost, thus resulting in a possibility of
 losing their application. Therefore, description will be made for a more
 cost-effective system where motor pulse value is just counted.
 In the above case, the tracking means 11 measures motor pulse value at a
 certain sampling interval of period, to accumulate the differences between
 the preceding pulse value and the current pulse value. For example, when
 the measuring point on the sheet 7 reached the first stand 1 according to
 the first method, the tracking means 11 clears the accumulated pulse value
 at the first stand 1 to zero, and then, from the next measuring timing,
 independently calculates a difference between the preceding pulse value
 and the current pulse value, to accumulate the differences. In other
 words, when the measuring point on the sheet 7 reached the first stand 1
 the calculation of the following expression (3) is started.
EQU p.sub.1t =.SIGMA.(p.sub.1p -p.sub.1pre) (3)
 where
 p.sub.1t : accumulated value of the differences of the pulse values of the
 first stand motor
 p.sub.1p : current pulse value of the first stand motor
 p.sub.1pre : preceding pulse value of the first stand motor.
 In the case of the second method also, similarly the tracking means 11
 clears the accumulated pulse value at the sixth stand 6 to zero, and then,
 when the measuring point on the sheet 7 reached the first stand 1 the
 calculation of the following expression (4) is started.
EQU p.sub.6t1 =.SIGMA.(p.sub.6p1 -p.sub.6pre1) (4)
 where
 p.sub.6t1 : accumulated value of the differences of the pulse values of the
 sixth stand motor
 p.sub.6p1 : current pulse value of the sixth stand motor
 p.sub.6pre1 : preceding pulse value of the sixth stand motor.
 In this connection, in the case where the above expression (4) is
 calculated, the pulse values of the motor return to zero every time when
 the motor makes one rotation. According to the first method, at this
 moment, the calculation of the expression (3) is carried out using
 "p.sub.1p " of the following expression (5) in place of the current pulse
 value p.sub.1p of the first stand motor.
EQU p.sub.1p +L =p.sub.1p +p.sub.1 (5)
 On the other hand, according to the second method, at this moment, the
 calculation of the expression (4) is carried out using "p.sub.6p1 " of the
 following expression (6) in place of the current pulse value p.sub.6p1 of
 the sixth stand motor.
EQU p.sub.6p1 +L =p.sub.6p1 +p.sub.6 (6)
 where
 p.sub.1 : pulse value taken when the first stand motor make one rotation
 p.sub.6 : pulse value taken when the sixth stand motor make one rotation.
 The tracking means 11 judges whether the measuring point on the rolled
 strip 7 has reached the second stand, using the motor pulse accumulated
 value p.sub.1t or p.sub.6t calculated using the expression (3) or (4) as
 follows:
 According to the first method, when the expression (7) changes into the
 expression (8), where.
 ##EQU3##
 According to the second method, when the expression (9) changes into the
 expression (10), where
 ##EQU4##
 the tracking means 11 judges that the measuring point on the sheet 7
 reached the second stand 2.
 In the above expressions,
 p.sub.1 : pulse value taken when the first stand motor makes one rotation
 f.sub.1 : forward slip of the first stand
 d.sub.1 : work roll diameter of the first stand
 g.sub.1 : gear ratio of the first stand
 l.sub.12 : distance between the first and second stands
 p.sub.6 : pulse value taken when the sixth stand motor makes one rotation
 f.sub.6 : forward slip of the sixth stand
 d.sub.6 : work roll diameter of the sixth stand
 g.sub.6 : gear ratio of the sixth stand
 h.sub.6 : thickness of rolled strip at the delivery side of the sixth stand
 h.sub.1 : thickness of rolled strip at the delivery side of the first
 stand.
 In this connection, when the tracking means 11 judged that the measuring
 point on the rolled strip 7 reached the second stand 2 using (7) and (8)
 expressions or (9) and (10) expressions, in most instances the measuring
 point would have passed through the second stand 2. Tracking up to the
 strip crown meter 9 as it is may produce a significant error, so that the
 obtained track of the measuring point shall be corrected so as to prevent
 such a significant error from taking place.
 When the measuring point on the sheet 7 advanced "L" from the first stand 1
 and the tracking means 11 judged that the measuring point reached the
 second stand 2, L can be expressed by way of the first method in following
 expression (11):
 ##EQU5##
 while L can be expressed by way of the second method in following
 expression (12):
 ##EQU6##
 Here, taking a change of the thickness of the rolled strip 7 into
 consideration, the measuring point would have arrived at a point "L.sub.1
 " away from the second stand 2, where L.sub.1 can be calculated using the
 following expression (13):
 ##EQU7##
 where
 L: distance of measuring point from first stand
 l.sub.12 : spacing between first and second stands
 h.sub.1 : thickness of rolled strip at the delivery side of first stand
 h.sub.2 : thickness of rolled strip at the delivery side of second stand.
 In other words, the distance L.sub.1 calculated by (13) is an error to be
 produced when the tracking means 11 followed the track of the measuring
 point from the first stand 1 up to the second stand 2. Therefore, when the
 tracking means 11 follows the track of the measuring point from the second
 stand 2 up to the second stand 3, instead of similar expressions to (7)
 and (8) or (9) and (10), according to the first method, other expressions
 (14) and (15) are used taking the above-described correction caused by
 tracking into consideration, while according to the second method, other
 expressions (16) and (17) are used. Here, these expressions are as
 follows:
 ##EQU8##
 More particularly, according to the first method, when the condition of
 (14) changes into the condition of (14), the tracking means 11 judges that
 the measuring point has reached the third stand 3, while according to the
 second method, when the condition of (14) changes into the condition of
 (17), the tracking means 11 judges that the measuring point has reached
 the third stand 3.
 Here,
 p.sub.2t : accumulated value of the differences of pulse values of second
 stand motor
 p.sub.2 : pulse value when the second stand motor makes one rotation
 f.sub.2 : forward slip of second stand
 d.sub.2 : diameter of second stand work roll
 g.sub.2 : gear ratio of second stand
 l.sub.23 : distance between second and third stands
 p.sub.6t2 : accumulated value of the differences of pulse values of sixth
 stand motor
 p.sub.6 : pulse value when the sixth stand motor makes one rotation
 f.sub.6 : forward slip of sixth stand
 d.sub.6 : diameter of sixth stand work roll
 g.sub.6 : gear ratio of sixth stand
 h.sub.6 : strip thickness at the delivery side of sixth stand
 h.sub.2 : rolled strip thickness at the delivery side of second stand.
 When the measuring point further advances from the third stand 3 to the
 fourth stand 4, and so on, similar correction as shown above are repeated,
 so that the tracking of the measuring point can be adequately kept without
 any error up to the strip crown meter 9.
 On the other hand, when the rolling operation is made at a uniform speed
 without any acceleration or deceleration, time required for the rolled
 strip 7 to reach all of the roll stands or the rolling data measuring
 device is determined before the sheet 7 enters the tandem rolling mill,
 thereby allowing the timers to be used for following the track of the
 measuring point of the rolled strip 7. In the case where tracking is made
 from the first stand 1 up to the strip crown meter 9, time lengths which
 are required for the measuring point to reach them are determined using
 the following expressions (18), (19), (20), (21), (22) and (23):
 ##EQU9##
 where
 t.sub.i (i=2-6): time length required for measuring point to reach the ith
 stand
 to: time length required for measuring point to reach the strip crown meter
 l.sub.ii+1 (i=2-6): distance between the ith stand and the (i+1) th stand
 l.sup.6c : distance between the 6th stand and strip crown meter
 v.sub.i (i=2-6): peripheral speed of the work roll of the ith stand
 f.sub.i (i=2-6): forward slip of the ith stand.
 Here, the distances between stands are known. Peripheral speed of the work
 roll and forward slip are calculated in an operational processing device
 (not shown), using pass schedule and the like.
 When the measuring point reaches the first stand, the tracking means 11
 sets the time lengths determined using the expressions (18) to (23) to the
 timer. When the rolling process so advances that each time length has
 passed, the tracking means 11 judges that the measuring point has reached
 respective corresponding stands or the rolling data measuring device. In
 the case when such timer setting is made, the control time required is so
 sooner that tracking accuracy is enhanced. In this connection, the above
 process description is made for the case where the tracking means 11
 follows the track of the measuring point from the first stand up to the
 strip crown meter 9, but it may be quite evident that similar process can
 be applied for cases where the rolling data measuring device is located at
 the entry side of a tandem rolling mill, or between stands.
 Now, description will be made for the operation performed by the measuring
 point decision means 10 when the measuring point reaches the strip crown
 meter 9:
 When the measuring point reaches the strip crown meter 9, the measuring
 point decision means 10 selects a point on the rolled strip 7 locating at
 the first stand as the second measuring point, when, in a similar way to
 the one taken when the first measuring point is decided, the second
 measuring point may be decided after timer setting.
 And then until the rolling operation is completely finished, same
 operations are repeated. In this connection, in the above description the
 measuring point on a rolled strip 7 is selected as its position just in
 contact with the rolls of the first stand 1 when the leading edge of the
 rolled strip 7 reached the strip crown meter 9, but a contact point on the
 rolled strip 7 which comes a fraction of second (e, g, 0.5 sec) later may
 be selected as the first measuring point, or otherwise a point three meter
 inside from the leading edge of the rolled strip 7 may be selected as the
 first measuring point.
 Now, description will be made for the rolling data collecting means 12:
 When the measuring point on a rolled strip 7 whose track the tracking means
 11 is always following has reached respective locating positions of roll
 stands and the rolling data measuring device, the rolling data collecting
 means 12 collects the rolling load, bending force, pair cross angle,
 temperature, thickness, width, crown, flatness and other rolling data of
 the rolled strip or rolled strip. Now, description will be made for the
 operation of the rolling data collecting means 12.
 As described previously, first, the measuring point decision means 10
 decides a point on a rolled strip locating under the rolls of the first
 stand 1 as the measuring point. Then, the tracking means 11 starts
 tracking of the measuring point. When the measuring point reached the
 first stand 1 the tracking means 11 noticed that to the rolling data
 collecting means 12. Receiving the notice signal, the rolling data
 collecting means 12 collects the rolling load, bending force, pair cross
 angle and other rolling data of the rolled strip at the first stand 1 and
 stores them in its memory.
 Then, the rolling operation advances further, and soon the measuring point
 reaches the second stand 2, when the tracking means 11 notices that to the
 rolling data collecting means 12. Receiving the notice signal, similarly
 to the case at the first stand 1 the rolling data collecting means 12
 collects the rolling load, bending force, pair cross angle and other
 rolling data of the rolled strip at the second stand 2, and stores the
 data in its memory.
 Similar operations to the above are repeated from the third stand 3 up to
 the sixth stand 6. Then, the rolling data collecting means 12 resulted in
 having collected all necessary rolling data at the measuring point on the
 rolled strip 7 from the first to sixth stands 1 to 6.
 Finally, the measuring point on the rolled strip or rolled strip 7 reaches
 the strip crown meter 9 installed at the delivery side of the sixth stand
 6. Here, similarly to the case at the first stand 1 the tracking means 11
 notices that to the rolling data collecting means 12. Receiving the notice
 signal, the rolling data collecting means 12 collects the measurements of
 the strip crown meter 9 as rolling data and stores the data in its memory.
 As an alternative way, every time when the measuring point on a rolled
 strip 7 reaches rolling data measuring devices (not shown), similarly to
 the above description, the tracking means 11 may give the rolling data
 collecting means 12 that reaching notices. Receiving the notice, the
 rolling data collecting means 12 collects the measurements of the rolling
 data measurement devices as rolling data and stores the data in its
 memory.
 FIG. 2 is the schematic block diagram showing the second embodiment of the
 rolling data collecting system which carries out the rolling data
 collecting method according to the invention, inclusive of an applicable
 tandem rolling mill. at Here, the tandem rolling mill is fundamentally the
 same as the one used in the first embodiment, and a single difference is
 that the rolling data measuring device the data of which the measuring
 point decision means 10 refers to is located at the entry side of the
 tandem rolling mill. The following description will be made, assuming that
 the rolling data measuring device is a temperature gauge.
 A rolled strip 7 reaches the temperature gauge 13 before it enters the
 tandem rolling mill. When the rolled strip 7 reached the temperature gauge
 13, it starts the measurement of the temperature of the rolled strip 7. If
 the temperature measurement T of the temperature gauge 13 falls in a
 predetermined temperature range at a preset time second, that is, the
 measurement satisfies the following expression (24), the measuring point
 decision means 10 decides a point on the rolled strip 7 locating at or
 passing the temperature gauge 13 as the measuring point.
EQU T.sub.min .ltoreq.T.ltoreq.T.sub.max (24)
 where
 T.sub.min : predetermined lower limit of temperature
 T: measurement of temperature
 T.sub.max : predetermined higher limit of temperature.
 For example, in the case where the preset time second is 0 second, when the
 measurement at 0 second satisfies the above expression (24), the point on
 the rolled strip 7 just passing the temperature gauge 13 is decided as the
 measuring point.
 Further, measuring point decision signals are issued at a preset period for
 confirmation. And as long as the measurements by the temperature gauge 13
 are continuously satisfying the expression (24), the rolling data are
 continuously collected for control purpose and stored in memory. There may
 be such four kinds of cyclic period to be conceived as follows in a), b),
 c) and d):
 a) Duration of time until the rolled strip 7 reaches the sixth stand 6 from
 the first stand 1.
 b) Duration of time until the rolled strip 7 reaches the rolling data
 measuring device (not shown) installed at the delivery side of the tandem
 rolling mill from the first stand 1.
 c) Duration of time until the rolled strip 7 reaches the sixth stand 6 from
 the rolling data measuring device (not shown) installed at the entry side
 of the tandem rolling mill or the temperature gauge 13.
 d) Duration of time until the rolled strip 7 reaches the rolling data
 measuring device (not shown) installed at the entry side of the tandem
 rolling mill, or until the rolled strip 7 reaches the rolling data
 measuring device (not shown) installed at the delivery side of the tandem
 rolling mill from the temperature gauge 13.
 After the measuring point is decided, the tracking means 11 and the rolling
 data collecting means 12 carry out the same operations as the first
 embodiment.
 FIG. 3 is the schematic block diagram showing the third embodiment of the
 rolling data collecting system which carries out the rolling data
 collecting method according to the invention, inclusive of an applicable
 tandem rolling mill. Here, the tandem rolling mill is fundamentally the
 same as the ones used in the first and second embodiments, and a single
 difference is that the temperature gauge 13 the data of which the
 measuring point decision means 10 refers to is located between roll
 stands. The operation of the third embodiment is similar to the one of the
 second embodiment (thus omitting the description), excepting that the
 rolling data measuring device 14 the data of which the measuring point
 decision means 10 refers to is located at a different position.
 FIG. 4 is the schematic block diagram showing the fourth embodiment of the
 rolling data collecting system which carries out the rolling data
 collecting method according to the invention, inclusive of an applicable
 tandem rolling mill. Here, the tandem rolling mill is fundamentally the
 same as the ones used in the first, second and third embodiments, and a
 single difference is that the temperature gauge 13 the data of which the
 measuring point decision means 10 refers to is located at the delivery
 side of the tandem rolling mill. The operation of the fourth embodiment is
 similar to the ones of the second and third embodiments (thus omitting the
 description), excepting that the rolling data measuring device 15 the data
 of which the measuring point decision means 10 refers to is located at a
 different position.
 In this connection, the above description of the embodiments are limited to
 the application for a tandem rolling mill, but this invention is not
 limited to such application. Further, in a case when the measuring point
 is decided based on the measurements of a rolling data measuring device
 located between roll stands or at the delivery side of the tandem rolling
 mill, a point on a rolled strip locating at the leading stand is selected
 as the measuring point, but a rolling data measuring device installed at
 the entry side of a tandem rolling mill can allow a point on the rolled
 strip just locating at the rolling data measuring device to be selected as
 the measuring point. In this connection, a rolling data measuring device
 to be installed between roll stands or at the delivery side of a tandem
 rolling mill, and a rolling data measuring device to be installed at the
 entry side of a tandem rolling mill must not necessary the same kind.