JP4715095B2 - Online roll grinder and grinding method of work rolls using the same - Google Patents

Description

  The present invention relates to an on-line roll grinder and a rolling mill work roll grinding method using the same.

  Metal plates (including metal strips, the same shall apply hereinafter), in particular, thin steel plates typified by strips, are cast and made into slabs after melting, and then manufactured through hot rolling and cold rolling, Alternatively, a plating process is further performed.

  FIG. 1 shows an example of an equipment row of a hot rolling line 4 that has been conventionally used. A 150 to 300 mm thick metal material (hereinafter referred to as the material to be rolled 6) heated to 1000 to 1300 ° C. by the heating furnace 5 is, for example, three stands of R1 to R3 rough rolling mill group 7, for example, seven stands of F1 to F7. Are rolled to a thickness of 1 to 25 mm by the finish rolling mill group 10 and thinly extended.

  The upper and lower work rolls 14 and 15 (hereinafter referred to as rolls) of a rolling mill in hot rolling that rolls a high-temperature rolled material 6 of several hundred to several hundreds of degrees Celsius are heat loads when contacting the high-temperature rolled material 6. Due to the frictional force, the roll surface is worn at the contact portion with the material 6 to be rolled. This wear is due to the various widths of the material to be rolled 6, and while rolling many materials to be rolled 6, the roll length direction of the rolls 14 and 15 having high contact frequency with the material to be rolled 6 The development is such that there is a step at the boundary between the center region and the both ends in the body length direction where the contact frequency is low, but the step generated on the surface layer of the rolls 14 and 15 is not transferred to the material 6 to be rolled. As described in Patent Document 1, Patent Document 2, Patent Document 3, etc., for the purpose of eliminating the level difference from the central region in the body length direction by grinding the body length direction end regions of the rolls 14, 15 The on-line roll grinder 11 grinds the roll in the rolling mill while continuing the hot rolling operation, and the rear stand of the finishing mill 10 in the hot rolling line (refers to the rear 3 stands among the 6 to 7 stands). On the other hand, it has been put into practical use.

  In addition to grinding both ends in the body length direction of the roll, in order to flatten the level difference due to variation in wear amount in the center area in the body length direction of the rolls 14 and 15 having high contact frequency with the material 6 to be rolled. In addition, a technique for grinding the center region in the body length direction of the rolls 14 and 15 has been put into practical use.

  In the figure, 1 is a business computer, 2 is a process computer, 3 is a control device, 8 is a descaling device, 9 is a crop shear, 12 is a cooling zone, and 13 is a coiler.

Japanese Patent Laid-Open No. 08-039115 Japanese Patent Laid-Open No. 07-314018 Japanese Patent Laid-Open No. 06-335716

  However, even if the conventional online roll grinder described above is used, the problem of defects caused by the thickness of the product metal strip after hot rolling called build-up, low spot, and high spot is not flat in the width direction is It has not been resolved. Further, it has been found that the use of an on-line roll grinder may frequently cause such defects, which has been a problem. In such a case, the on-line roll grinder must be not used, and it is necessary to change the roll frequently so that the step due to wear on the roll surface is not transferred to the material to be rolled, or the same roll is used. When the number of rolls exceeds a certain number, the width connection of the material to be rolled must be limited only to a transition from a wide width to a narrow width, which is a significant operational limitation.

  An object of the present invention is to suppress the occurrence of defects in which the thickness of a rolled product metal band caused by grinding with an on-line roll grinder is not flat in the width direction, eliminates the need to frequently replace the roll, and reduces the width of the material to be rolled. By relaxing or eliminating the connection restrictions, it is possible to relieve operational restrictions, and to significantly improve productivity and reduce roll running costs.

The present invention includes a grindstone, a grindstone rotating device, a grinding unit including a pressing device that presses the grindstone against a work roll of a rolling mill, and an oscillating device that moves the grinding unit in the body length direction of the work roll. In the online roll grinder, the pressing device is a hydraulic cylinder, an oil sump is installed on the head side of the hydraulic piping of the hydraulic cylinder, an accumulator is installed on the rod side, and the mechanical resistance in the pressing direction of the pressing device is expressed by the following formula: The above-mentioned problem is solved by setting the value within the range.

The present invention also provides a grinding unit comprising a grindstone, a grindstone rotating device, and a pressing device that presses the grindstone against a work roll of a rolling mill, and an oscillating device that moves the grinding unit in the body length direction of the work roll. In the on-line roll grinder, the pressing device is a hydraulic cylinder, the connecting shaft that connects the rotating device and the grindstone is provided with a spline, the seal of the hydraulic cylinder is made of resin, and the spline is a ball spline. Further, the oil is accumulated on the head side of the hydraulic piping of the hydraulic cylinder, and the accumulator is installed on the rod side .

Also, it is obtained by installing the position sensor to the hydraulic cylinder.

  In the present invention, the lap amount in the roll body length direction grinding range of adjacent grinding units is set to 5 to 10 mm using an online roll grinder in which a plurality of the grinding units are installed in the body length direction of the work roll. A rolling mill work roll grinding method using an on-line roll grinder is provided.

  According to the present invention, it is possible to suppress the occurrence of defects in which the thickness of the product metal strip after rolling caused by grinding of the roll in the online roll grinder is not flat in the width direction, eliminating the need to frequently replace the roll, and the material to be rolled This can greatly improve productivity and reduce the running cost of rolls by relaxing or eliminating restrictions on the width connection.

  One example of the equipment row of the hot rolling line 4 that has been conventionally used in FIG. 1 is shown. The hot rolling line to which the present invention is to be applied is not necessarily limited to this, and the present invention can be applied not only to the hot rolling line but also to the cold rolling line. Taking the case of the line 4 as an example, the background to the present invention will be described below.

  On-line roll grinders 11 are installed at the four rear stands (F4 to F7 in the example of FIG. 1) of the finish rolling mill group 10.

  FIG. 2 shows the structure of the online roll grinder 11. For each of the upper and lower rolls 14 and 15, two grinding units 17 are provided in the roll body length direction. The grinding unit 17 is coupled by a separator 18, and is moved in the roll body length direction by the oscillating device 19 together with the grinding unit 17 and the separator 18. The two grinding units 17 each grind one side at the center of the roll drum length, and grind the entire range of the roll drum length.

  FIG. 3 is a view showing the structure of the grinding unit 17. The grinding unit 17 includes a grindstone 20, a pressing device 21, and a rotating device 22. The roll 14 or 15 is ground by pressing the grindstone 20 against the roll 14 or 15 with the rod 21 </ b> R of the pressing device 21 while rotating the grindstone 20 with the rotating device 22.

  The connecting shaft 23 that connects the rotating device 22 and the grindstone 20 has a grooved shape called a spline (26), as can be seen in the AA cross section shown on the right side of FIG. As the shaft 24 on the side and the shaft 25 on the side of the grindstone 20 are engaged with each other at the spline portion, even if the distance between the rotating device 22 and the grindstone 20 is changed, the positions are shifted from each other in the axial direction and the force in the rotational direction is applied to the grindstone 20. I can tell you.

  The pressing device 21 uses a hydraulic cylinder, and moves the grindstone holder 27 back and forth with the hydraulic cylinder.

  A bearing 28 is installed between the grindstone holder 27 and the grindstone 20 and can be pressed while rotating the grindstone 20. A rubber U-packing is used for the seal portion 29 of the hydraulic cylinder.

  The pressing device 21 is not necessarily a hydraulic cylinder, but may be any actuator that can press the grindstone 20 against the rolls 14 and 15 and position in the pressing direction, such as a servo motor or a stepping motor. The hydraulic cylinder is most preferable because the structure is simple and the installation space is small. Further, the packing is not limited to rubber, but may be made of resin or metal.

  The mechanical resistance referred to in the present invention means a sliding resistance between the rod 21R of the hydraulic cylinder and the packing of the seal portion 29 when the pressing device 21 is a hydraulic cylinder, and in the case of a hydraulic motor or a stepping motor. Means friction between vane and casing, friction of bearing between motor shaft and casing, etc. In any case, including sliding resistance of spline 24, etc., anyway mechanical resistance Used for cases that fall under.

  FIG. 4 shows a hydraulic piping diagram when the pressing device 21 is a hydraulic cylinder. The pressure on the head side of the hydraulic cylinder 30 supplied from the pressure line 34 is controlled by the proportional pressure reducing valve 31, and the pressure on the rod side of the hydraulic cylinder 30 also supplied from the pressure line 34 is controlled by the pressure reducing valve 32. Is done. In addition, both the head side and the rod side have a relief valve 33 so that an abnormally high pressure will not occur when compressed in a state where oil is contained in the pipe. When the pressure exceeds the set pressure, oil is released to the tank (not shown) through the relief valve 33 and the tank line 35 to reduce the pressure. The set pressure of the relief valve 33 is set to 10 to 15% higher than the set pressure of the proportional pressure reducing valve 31 and the pressure reducing valve 32 on both the head side and the rod side so that the relief valve 33 is not always operated. In the figure, PT is a hydraulic pressure sensor.

  FIG. 5 shows a roll grinding method using such an on-line roll grinder 11. By rolling, the roll surface 36 is worn at the contact portion with the material to be rolled. This wear is caused by the fact that the material to be rolled has various widths, and while rolling a number of the material to be rolled 6, the center region in the roll body length direction 37 having a high contact frequency with the material to be rolled 6 The development is such that there is a step at the boundary between the two ends of the roll in the body length direction with a low contact frequency. Also in the central region in the roll body length direction, steps due to non-uniform wear occur everywhere as indicated by arrows. In order to prevent such a step from being transferred to the material 6 to be rolled, the online roll grinder grinds the step grinding range 38 at both ends in the roll barrel length direction in accordance with a command from the process computer 2 shown in FIG. Two types of grinding, step grinding for the purpose of flattening by eliminating the level difference from the region, and whole surface grinding for grinding the entire surface grinding range 39 to flatten the level difference due to variation in wear amount By carrying out, unevenness on the roll surface 36 is removed.

  FIG. 6 shows an example of a defect due to non-uniformity in the width direction of the product thickness that occurs even when grinding by such an online roll grinder. In FIG. 6A, the thickness changes by 11 μm from the width central portion. In FIG.6 (b), the thickness reduction part is seen by the width end part. In FIG.6 (c), the thickness reduction part of 7 micrometers is seen by the width center part. Depending on the company, such a thickness step becomes a defect called a low spot or a high spot when the thickness is 5 μm or more, and the yield is greatly reduced by truncation. FIG. 6 only shows the sheet thickness distribution in the cross section in the width direction, but since the material to be rolled extends in the longitudinal direction in practice, the total length of these defective portions must be cut off. It is.

  FIG. 7 shows the state of the roll surface of the F7 stand that is the final rolling mill of the finish rolling mill group 10 when the defect of FIG. 6 occurs. It can be seen that a level difference is also generated at a position corresponding to the level difference of the product thickness. The inventors have found that the cause of such a level difference is the conventional online roll grinder.

  FIG. 8 shows the cause of the occurrence of steps on various roll surfaces as shown in FIG. 7 by a conventional online roll grinder divided into three types in association with the form. The inventors have found that such a step is caused by an error in the grinding amount by the on-line roll grinder and an error in the lap amount at the center of the width of the two grinding units, and has made the present invention.

  Incidentally, in FIG. 8, the grinding range indicated by reference numeral 40, which corresponds to the portion surrounded by the roll surface 36 (after grinding) and that before grinding, includes the step grinding range 38 shown in FIG. The added grinding range means that a step may occur on the roll surface 36 after grinding (after grinding). FIGS. 8A, 8B, and 8C show the steps. The cause of occurrence is shown in three types in association with its form. In the figure, 41 is a lap amount of two grinding units, and 42 is a step due to an error in the lap amount.

  FIG. 9 is a diagram showing a comparison between the grinding amount set by a conventional online roll grinder evaluated by measuring the roll diameter before and after grinding and the actual grinding amount. There may be a difference of about ± 30% between the setting and the actual result, and the difference varies. In the final F7 stand that affects the accuracy of the product thickness of the metal strip in the hot rolling line 4 that is the subject of the inventors, the grinding amount (grinding depth) for one roll is about 50 μm at maximum. Therefore, in that case, an error in the grinding amount of about 15 μm (50 μm × 0.3) can occur. As the difference in the grinding amount between the two grinding units, assuming that an error of actual results with respect to the setting occurs ± 30%, the maximum is 30 μm (15 μm × 2). It can be seen that the step profile can be easily generated.

  FIG. 10 shows the cause of the error in the lap amount at the center in the roll body length direction during grinding by the two grinding units shown in FIG. Although it has been described that two grinding units shown in FIG. 3 grind one side at the center of the roll body length direction, the unground part remains in the center part of the roll body length direction as shown in FIG. In this way, the grinding range of the two grinding units is lapped by a lapping amount 41 (about 20 mm) which is about half of the grinding wheel and roll contact width. The thin line in the figure shows a simplified profile of the roll surface 36 before grinding. Returning to FIG. 10, before grinding, the on-line roll grinder 11 is at the end of the roll body length direction, and the pressing unit is retracted so that the grinding unit 17 is separated from the roll by a predetermined distance. One side 44 is pressed by a grindstone advance command from the process computer 2 slightly before the grinding so that grinding can be started from the position in the roll cylinder length direction where grinding should be started while moving in the roll cylinder length direction by the oscillating device 19. To start moving forward to the roll side. Grinding is started when the control device 3 recognizes that the roll has been touched. However, when the rising of the load due to the contact is used as a trigger, the value of the load sensor varies, and thus the timer value from the start of forward movement must be used. When the track record of the time from the start of advancement to contact deviates from the timer value, the grinding position in the roll body length direction deviates, and when a certain position is taken, the grinding depth deviates from a desired value. When the oscillation progresses and it is about to grind the second half close to the center part in the roll body length direction, the other grinding unit 43 starts to advance toward the roll side. In many cases, the time difference from the start of advancement to contact is different from that of the other grinding unit 44. Then, the level | step difference in a lap | wrap part as shown to Fig.8 (a) generate | occur | produces.

  The level difference of the lapping portion as shown in FIG. 8A occurs when the grinding unit in the standby state 43 requires a shorter time from the start of advancement to the contact than the grinding unit in the grinding state 44. .

  On the other hand, the profile as shown in FIG. 8 (b) shows that, for some reason, the grinding unit in the grinding state 44 and the grinding unit in the standby state 43 have a time from the start of advancement to the roll side until contact is less than the desired value. If the profile is too short and overgrinding, the profile as shown in FIG. 8 (c) is not changed between the start of advancement to the roll side and the contact of the grinding unit in the grinding state 44 and the grinding unit in the standby state 43 for some reason. It shows a case where the time is longer than the desired value and grinding is insufficient. In such a case, an error from a desired value is likely to occur in the lap amount of the two grinding units in the center portion in the roll drum length direction, and as a result, a convex shape is formed in the center portion in the roll drum length direction. The step 42 is likely to occur.

  FIG. 11 shows the result of investigating the variation in the time from the command to start the grindstone advance until it comes into contact with the roll. It was found that the conventional online roll grinder varies as much as σ = 0.14 seconds. The displacement of the grinding position in the roll body length direction is 17 mm (120 mm / second x 0.14 seconds) because the moving speed in the roll body length direction by the oscillating device is about 120 mm / second, and lapping is performed at the center in the roll body length direction. Since the error in the amount is the sum of the errors in the two grinding units, it can be seen that about 34 mm is easily generated, and an unground portion is easily left with a lapping amount of about 20 mm. Moreover, since the lapping part is inherently over-grinding from the other range in the roll body length direction to be ground by one grinding unit on the principle of grinding by two grinding units, of course, when the lap amount becomes large, Even if the set value is about 20 mm, there is a possibility that a step is generated.

  As described above, the conventional online roll grinder is not sufficient in that the thickness of the product metal strip after rolling may cause a defect that is not flat in the width direction.

(Explanation of the first, second and third inventions)
FIG. 12 shows the structure of the grinding unit of the on-line roll grinder of the present invention that can solve such problems and suppress the occurrence of defects in which the thickness of the product metal strip after rolling is not flat in the width direction. The sealing portion of the pressing device 21 that has been conventionally made of rubber is a resin seal 51. Further, the connecting shaft 23 that connects the rotating device 22 and the grindstone 20 has a spline shape, but between the grindstone 20 and the rotating device 22 between the shaft on the rotating device 22 side and the spline groove of the shaft on the grindstone 20 side. A ball spline 52 in which steel balls that roll when the distance changes is arranged. A position sensor 60 is installed in the cylinder portion of the pressing device 21.

  FIG. 13: has shown the piping system diagram of the hydraulic_pressure | hydraulic around the hydraulic cylinder 30 of the pressing apparatus 21 of the online roll grinder of this invention. Compared to the conventional system diagram, an oil sump 53 with a capacity of 10 L is installed on the head side of the hydraulic cylinder 30 and an accumulator 54 with a capacity of 5 L is installed on the rod side.

  In addition, the level | step difference like Fig.7 (a) can be suppressed at least by installing the position sensor 60 in the cylinder part of the pressing apparatus 21. FIG. According to the timer value, it is inevitable that a time variation occurs in the contact from the advance command to the roll. However, in this respect, the output of the position sensor 60 is from the grinding surface of the grindstone 20 at the retreat limit of the pressing device to the roll surface. If the mechanical distance up to (geometrically determined by measuring the roll diameter) is reached, it is difficult to make a difference in the grinding depth between the two grinding units by stopping the advancement of the grinding wheel. Because it becomes. The mechanical distance from the grinding surface of the grindstone 20 to the roll surface is determined by detecting the load from the advance command of one of the plurality of grinding units (the output of the hydraulic pressure sensor PT indicates that a certain load threshold has been exceeded). Is stored in the control device 3 with the amount of movement viewed from the change in the output of the position sensor 60 until the other grinding unit has advanced by that amount of movement after receiving the advance command. It is also possible to operate in such a manner that it is in contact with 20.

  However, even if the position sensor is used for control, if the absolute forward speed of the pressing device is faster or slower than a desired value, the steps as shown in FIGS. 7B and 7C are suppressed. The problem still occurs without any problems. The inventors have conceived how to suppress this and have arrived at the present invention.

  Here, as the main point of the present invention is discussed, the inventors reduced the mechanical resistance in the pressing direction of the rotating device 22 and the pressing device 21 from the conventional online roll grinder so as to satisfy the following formula, thereby grinding. It was found that the error was remarkably reduced.

  FIG. 14 shows a mechanism for improving grinding accuracy by reducing mechanical resistance. As described above, the pressing of the grindstone 20 to the rolls 14 and 15 is performed by the hydraulic cylinder which is the pressing device 21, but the pressing force 55 to the roll is generated from the output 57 of the hydraulic cylinder from the rotation device and the pressing device. The value is obtained by subtracting the mechanical resistance 56 in the pressing direction. When the mechanical resistance fluctuates, the pressing force to the rolls 14 and 15 also fluctuates.

  Also, the direction of mechanical resistance differs depending on whether the hydraulic cylinder is (a) forward or backward (b), and the pressing force of the grindstone 20 against the rolls 14 and 15 varies. This means that if you try to push something through a resistance object, you can only push it with the force minus the mechanical resistance, and conversely, when you loosen the pushing force As can be easily understood from the fact that the resistance is added so that it is pushed back, the value obtained by subtracting the mechanical resistance when pressing the hydraulic cylinder in the forward direction becomes the pressing force 55 to the roll, and the reverse direction When the pressure is pressed (returned back), the value obtained by adding the mechanical resistance becomes the pressing force 55 to the roll. The above formula should be used to reduce the mechanical resistance in the pressing direction of the pressing device to less than the allowable value in order to keep the thickness error of the material to be rolled on the exit side of the F7 stand as the final rolling mill as the final rolling mill. The higher the set value of the pressing force of the target rolling mill and the allowable thickness error of the material to be rolled on the finish rolling mill exit side, the larger the target. The larger the ratio of the rolling mill's maximum grinding depth of the work roll and the level difference of the work roll surface layer transferred to the sheet thickness of the material to be rolled on the exit side of the F7 stand, which is the final rolling mill of the finishing mill, is smaller.

  This transfer ratio η takes a value for each finishing mill. The transfer ratio in rolling mills other than the F7 stand, which is the final rolling mill, is determined by how much the step transferred to the rolled material by the rolling machine ahead of the F7 stand is affected by the rolled material on the exit side of the F7 stand. Since it is an index indicating whether or not it remains in the plate thickness, it can be said to be an inheritance rate. It is obtained by experiments.

  α is a value determined by regressing the relationship between the pressing force and the grinding depth obtained by experiments or the like, and is a value between 0 and 1. In this example, the mechanical resistance in the pressing direction of the pressing device (hereinafter simply referred to as mechanical resistance) and other values are common to each of the finishing mills F4 to F7 provided with an online roll grinder, Fn = 900N, ΔHcrit = 0. 0.0005 m, Tmax = 0.00005 m, α = 0.6, and η = 0.63. As a result, Fμ = 298N.

  Various grinding unit structures were experimented to reduce the mechanical resistance. The results are shown in FIG. The conventional rubber seal and spline structure has a mechanical resistance of 600 N. This is a value actually measured by pulling the rod with a spring balance. What applied the lubricant to the spline part improved somewhat, but it was 500 N, and the effect was insufficient. Eventually, by using a resin seal and a spline as a ball spline, the mechanical resistance was 250 N, which is 298 N or less of the present invention.

(Explanation of the third invention)
There was also a problem with the hydraulic system. Even if the pressure on the head side is set to a predetermined pressure, when the grindstone 20 is pushed back from the roll, the oil in the pipe is compressed and the internal pressure rises. As shown in FIG. 4 described above, the relief valve 33 is provided so that the internal pressure in the pipe does not increase, but the set pressure of the relief valve 33 is made 10 to 15% larger than the set pressure of the proportional pressure reducing valve 31. Therefore, if the pressure is between the set pressure of the proportional pressure reducing valve 31 and the set pressure of the relief valve 33, the pressure will increase. On the rod side, in order to prevent vibration of the grindstone 20 during grinding, the value at the time of pressing is used, but the rod side is also used with a pressure of about 2.4 MPa, and the hydraulic cylinder 30 moves forward. In the same manner as in the head side, the oil in the pipe is compressed on the rod side, and the pressure fluctuates within the range of the set pressure of the relief valve 33.

  When the head side diameter of the hydraulic cylinder 30 is 0.032 m, the rod side diameter is 0.025 m, the set pressure of the pressure reducing valve 32 on the rod side is 2.4 MPa, and the set value of the pressing force is 90 N, the proportionality on the head side The set pressure of the pressure reducing valve 31 is 2.1 MPa (2.4 × 10 ^ 6 × π / 4 × (0.032 ^ 2-0.025 ^ 2) +900) / (π / 4 × 0.032 ^ 2) ), The set pressure of the relief valve 33 is 2.4 MPa (2.1 × 1.15) on the head side and 2.8 MPa on the rod side, 0.3 to 0.4 MPa for each of the proportional pressure reducing valve 31 and the pressure reducing valve 32. Greater than each set pressure. When the pressure fluctuation of 0.3 to 0.4 MPa is converted into the pressing force of the grindstone 20 against the roll 14 or 15, the maximum is 322N (0.4 × 10 ^ 6 × π / 4 × 0.032 ^ 2). Since it becomes equal to the target value 298N of the mechanical resistance, it can be seen that it cannot be ignored. Conventionally, the variation in the performance of a general relief valve with respect to the set pressure target is about ± 1 MPa at the minimum, and it has been difficult to keep the pressure fluctuation within the range of 0.3 to 0.4 MPa.

  Therefore, the inventors have caused such a pressure increase by pushing back the grindstone with a roll if it is on the head side, and if it is on the rod side, it is caused by a hindrance due to mechanical resistance against the advance of the hydraulic cylinder. Focusing on the fact, as shown in FIG. 13, the inventors came up with the idea of installing an oil pool 53 and an accumulator 54 that absorb the pressure increase caused by the compression of oil in the pipe due to such a phenomenon. On the head side, the amount of pushing back of the grindstone 20 by the roll 14 or 15 is as small as about 1 mm, so that it is not an accumulator containing a balloon-shaped object filled with compressible gas, but a simple oil pool. The volume of the oil puddle is set so that the target pressure fluctuation amount is 0.05 MPa that does not affect the grinding ability at all, the volume elastic modulus of the oil is 650 MPa, the pipe volume is 0.7 m 3, and the volume pushed back is 8 × 10 ^ −7 Assuming m3 (0.001 × π / 4 × 0.032 ^ 2), 10 L ((650 × 10 ^ 6 × 8 × 10 ^ −7 / (0.05 × 10 ^ 6) −0.7) × 1000). On the rod side, the amount pushed back is about 200 mm of the stroke of the hydraulic cylinder, so that a mere oil pool becomes very large. For this reason, a 5 L accumulator was installed so that the pressure fluctuation amount was 0.05 MPa or less by the same calculation.

(Explanation of the fourth invention)
In addition, installing the position sensor 60 in the cylinder part of the pressing device 21 has no problem. According to the timer value, it is inevitable that there will be time variations in the contact from the advance command to the roll, but in this respect, the output of the position sensor is from the grinding surface of the grindstone to the roll surface at the retreat limit of the pressing device. When the mechanical distance is reached, if the advancement of the grindstone is stopped, it becomes difficult to make a difference in the grinding depth between the two grinding units. Also in the first to third inventions described above, This is because there is no change.

(Explanation of the fifth invention)
FIG. 16 shows the maximum value of 1000 products of the level difference (similar to that shown in FIG. 6A) at the center of the width of the product thickness after mechanical resistance reduction and hydraulic system improvement of the present invention. Is shown. According to the present invention, the step amount at the center of the width of the product thickness is 4 μm at the maximum, and a good result is obtained that the defect judgment value is 5 μm or less. Moreover, the level | step difference resulting from the grinding residue in the width | variety edge part as shown in FIG.6 (b) was also eradicated simultaneously.

  However, the inventors have come up with a method that can more reliably eliminate the defect of the lap portion at the center of the width shown in FIG. This will be described later.

  FIG. 17 shows the product thickness distribution in the width direction after implementing the first to fourth inventions. It can be seen that the range of 20 mm corresponding to the lap portion at the center of the width is thickened as the over-thickness portion 59.

  FIG. 18 shows the measurement of the time variation from the grindstone advance command shown in FIG. 11 to the roll contact after the mechanical resistance reduction and hydraulic system improvement of the present invention. In addition to reducing the variation in the advancing speed of the grindstone by reducing the mechanical resistance and improving the hydraulic system, a position sensor is installed in the hydraulic cylinder of the pressing device so that the distance between the roll and the grindstone can be measured accurately. In addition to the fact that the distance between the roll and the grinding wheel before grinding is conventionally about 50 mm so that the grinding stone does not come into contact with the roll, the distance from the grinding wheel advance command to roll contact The variation in time until σ = 0.02 seconds was greatly reduced, and the error of the lap amount 41 shown in FIG. 8 was 4.9 mm, which was sufficiently small with respect to the lap amount of 20 mm, but the variation was reduced. As a result, the phenomenon of ungrinding disappeared, but the two grinding units reliably grind the lapping part, so that the roll was cut too deeply and the product width center became thicker. It is considered that the waiting.

  FIG. 19 shows the result of an experiment for changing the lap amount performed to solve this problem. In the conventional online roll grinder, it was found that the thickness step defect at the center portion of the product width can be eradicated by setting 5 to 10 mm, which was difficult to set due to variations in time to roll contact, from the grinding wheel advance command. If it was smaller than 5 mm, grinding was insufficient.

  In the above description, the case where there are two grinding units has been described as an example, but even when there are three or more grinding units, the occurrence of overgrinding and insufficient grinding can be suppressed by setting each lapping amount to 5 to 10 mm. Needless to say.

Process diagram showing the outline of a conventional general hot rolling line Perspective view schematically showing the overall structure of the online roll grinder Sectional view showing the structure of the grinding unit A diagram schematically showing a hydraulic piping system including a hydraulic cylinder that is a pressing device of a conventional online roll grinder. Schematic illustration of roll grinding using an online roll grinder Examples of defects due to uneven product thickness in the width direction The figure which showed typically the mode of the roll surface of F7 stand which is a finishing rolling mill final rolling mill at the time of the defect of FIG. The figure for demonstrating the cause of the level | step difference of the roll surface of FIG. 7 by the conventional online roll grinder Figure showing comparison between the set grinding amount and the actual grinding amount using a conventional online roll grinder The figure for demonstrating the cause of the error of the lap amount in the center of the width of two grinding units The figure which shows the dispersion of time from whetstone advance command to roll contact Sectional drawing which shows the structure of the grinding unit of the on-line roll grinder of this invention The figure which shows typically the hydraulic piping system containing the hydraulic cylinder which is a pressing device similarly Diagram for explaining the mechanism of grinding accuracy improvement by reducing mechanical resistance The figure which shows the experimental result of the relationship between various structures and mechanical resistance The figure which shows the amount of level | step differences in the width center part of the product thickness before and after this invention application The figure which shows the example of the defect of the product thickness of the width center wrap part The figure which shows the dispersion | variation in the time from a grindstone advance command after this invention application to a roll contact The figure which shows the change experiment result of lap amount

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Business computer 2 ... Process computer 3 ... Control apparatus 4 ... Hot rolling line 5 ... Heating furnace 6 ... Rolled material 7 ... Rough rolling mill group 8 ... Descaling apparatus 9 ... Crop shear 10 ... Finishing mill group 11 ... Online roll grinder 12 ... Cooling zone 13 ... Coiler 14 ... Upper roll 15 ... Lower roll 17 ... Grinding unit 18 ... Separator 19 ... Oscillating device 20 ... Grinding wheel 21 ... Pushing device 22 ... Rotating device 23 ... Connecting shaft 24 ... On the rotating device side Shaft 25 ... Wheel side shaft 26 ... Spline 27 ... Wheel holder 28 ... Bearing 29 ... Seal part 30 ... Hydraulic cylinder 31 ... Proportional pressure reducing valve 32 ... Pressure reducing valve 33 ... Relief valve 34 ... Pressure line 35 ... Tank line 36 ... Roll surface 37 ... Roll body length direction 38 ... Step grinding range 39 ... Full grinding range 40 ... Two grinding wheels Unit grinding range 41 ... Lap amount 42 ... Step caused by lap amount error 43 ... Standby state 44 ... Grinding state 45 ... Oscillating direction 46 ... Predetermined distance 47 ... Wheel-roll contact width 48 ... Advance start state 49 ... Forward direction 50 ... Lap amount error 51 ... Resin seal 52 ... Ball spline 53 ... Oil puddle 54 ... Accumulator 55 ... Pressing force to roll 56 ... Mechanical resistance 57 ... Output of hydraulic cylinder 59 ... Overweight portion 60 ... Position Sensor PT ... Hydraulic pressure sensor

Claims (6)

An on-line roll grinder having a grindstone, a grindstone rotating device, a grinding unit having a pressing device for pressing the grindstone against a work roll of a rolling mill, and an oscillating device for moving the grinding unit in the body length direction of the work roll. In
The pressing device is a hydraulic cylinder, an oil pool is provided on the head side of the hydraulic piping of the hydraulic cylinder, an accumulator is installed on the rod side,
Furthermore, the on-line roll grinder characterized in that the mechanical resistance in the pressing direction of the pressing device falls within the range of the following formula.

An on-line roll grinder having a grindstone, a grindstone rotating device, a grinding unit having a pressing device for pressing the grindstone against a work roll of a rolling mill, and an oscillating device for moving the grinding unit in the body length direction of the work roll. In
The pressing device is a hydraulic cylinder, and further includes a spline on a connecting shaft that connects the rotating device and the grindstone, the seal of the hydraulic cylinder is made of resin, and the spline is a ball spline ,
An on-line roll grinder further comprising an oil reservoir on the head side of the hydraulic piping of the hydraulic cylinder and an accumulator installed on the rod side . The on- line roll grinder according to claim 1 or 2, wherein a position sensor is installed in the hydraulic cylinder. A plurality of grinding units are installed in the body length direction of the work roll, and the lap amount in the roll body length direction grinding range of adjacent grinding units is set to 5 to 5 using the online roll grinder according to any one of claims 1 to 3. A method of grinding a rolling mill work roll by an on-line roll grinder characterized by being 10 mm. An on-line roll grinder having a grindstone, a grindstone rotating device, a grinding unit having a pressing device for pressing the grindstone against a work roll of a rolling mill, and an oscillating device for moving the grinding unit in the body length direction of the work roll. In this case, a plurality of the grinding units are installed in the body length direction of the work roll, and further, using an online roll grinder in which the mechanical resistance in the pressing direction of the pressing device is within the range of the following formula,
A grinding method for a work roll of a rolling mill by an on-line roll grinder, wherein a lapping amount in a grinding range in the roll length direction of adjacent grinding units is 5 to 10 mm.

  An on-line roll grinder having a grindstone, a grindstone rotating device, a grinding unit having a pressing device for pressing the grindstone against a work roll of a rolling mill, and an oscillating device for moving the grinding unit in the body length direction of the work roll. The pressing device is a hydraulic cylinder, and further includes a spline on a connecting shaft that connects the rotating device and the grindstone, the seal of the hydraulic cylinder is made of resin, the spline is a ball spline, and Using an online roll grinder with multiple grinding units installed in the length direction of the work roll,
A grinding method for a work roll of a rolling mill by an on-line roll grinder, wherein a lapping amount in a grinding range in the roll length direction of adjacent grinding units is 5 to 10 mm.

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