Sizing-rolling method for continuous length sections, rolling mill driving mechanism, roll depressing mechanism and roll fixing mechanism

Abstract: The invention is directed to provide a rolling method which enables an enlarged range of reduction ratio in sizing-rolling in the common drive system. The invention provides that when tension applied to rolled material between the upstream and downstream-placed mills is made higher than a value that tension/average resistance to deformation of rolled material is 0.2, the upstream-placed mill is caused to perform force rolling, and when compressive force of the rolled material is made higher than a value that compresssive force/average resistance to deformation of rolled material is 0.1, the downstream-placed mill together with the upstream-placed mill are caused to perform tensile rolling in the common drive system. The rolling methods provides a stable rolling in a larger sizing range without decrease of diameter or buckling of rolled material.

Description: FIELD OF THE INVENTION The invention relates to a rolling mill driving mechanism according to the precharacterising part of the claim. BACKGROUND OF THE INVENTION There generally are such two systems for applying driving force to a plurality of rolling mills arranged along rolling line for rolling continuous length sections such as bar, wire rod or the like that the rolling mills may be provided with respective motors to be driven separately, or that a plurality of rolling mills are interlocked through a driving mechanism to be given a driving force by a single motor (this is herein called the "common drive system"). In the former system providing the respective motors for each rolling mill, rotating speed of the motors are set separately in consideration of variance of tension applied to the rolled material between the rolling mills corresponding to variance of area reduction ratio of the material being delivered from each of the stands in question. By contrast, the prior art common drive system lacks versatility in that, once a specific gear ratio is set in a gear transmission assembly, the relative roll speed of the two stands cannot be varied unless the gear ratio is changed. Finish rolling of continuous length sections in heated rolling line may be conducted in such a manner that roll calibers are exchanged corresponding to variance of specific sizes of rolled products, or that a single roll caliber is used to depress the rolls into desired positions for providing rolled products with separate sizes (the technique is herein called "sizing-rolling"). The trouble is that, every time the parting of the mill rolls is adjusted at one or more of roll stands in a rolling mill having a plurality of serially connected roll stands driven by a common drive, the material undergoes a sharp increase or decrease in the tension between the stands. Consequently, product quality is adversely affected by an undesirable decrease in the diameters of products and breakage of rolled material by tensile, increment of products diameters by compressive force and buckling of rolled material. Hence, an extent of sizing with adjustment of depressed positions of rolls is limited. The above problem may be prevented, in sizing-rolling in the aforesaid common-drive system by use, for example, of 3-roll rolling technique, by that in a range where a total area reduction ratio of rolled material summed up at all of interlocked rolling mills is less than a few percent, the drive systems for the respective rolling mills are connected to apply a rotational force to the rolling mills before rolled material is caught by the rolling mills, and an one-way clutch is operated just when the rolled material is caught by the rolling mills to cause only one rolling mill to be driven by a motor with the remaining rolling mills being not driven, thereby enabling force rolling by the driven mill (as disclosed in a catalogue issued by KOCK Inc., Germany). The rolling technique does not provide a stable rolling in sizing-rolling operation at a higher area reduction ratio, for example, of 20% by use of two 3-roll rolling mills as disclosed in Japanese Unexamined Patent Publication No. 43702/1988 since tension applied to rolled material between rolling mills varies largely corresponding to the specific amounts sizing and the rolled material is subjected to a higher compressive force due to force rolling. For carrying out a stable sizing-rolling, it is required to reduce a sizing range, lessen intervals between the rolling mills for eliminating influences on rolled material with compressive force applied thereto and enlarge diameters of rolled products. Let it be supposed that two roll stands are connected to a common drive through a gear transmission assembly, that a gear ratio set in the gear transmission assembly is such that the material undergoes no tension between the stands when they are operated with an area reduction of 20% to be finally attained at the roll stand disposed at the downstream side, and that the actual parting of the mill rolls is such that an area reduction which can be finally attained at the roll stand disposed at the downstream side is much smaller than 20%. When the two roll stands are operated under this condition, the material undergoes unusually high tension between the rolling mills, thereby decreasing the diameter of the rolled material and possibly breaking the same. DE-A 34 45 219 comprising the closest prior art discloses an upstream rolling mill and a downstream rolling mill driven by a common drive 16. A one-way clutch 17 is provided for disengaging said downstream rolling mill from said common drive 16. However, DE-A 34 45 219 makes no mention of how to cope with the case where the material 5 lying in space between two rolling mills undergoes unusually high tension such as mentioned above. SUMMARY OF THE INVENTION The present invention has been designed to overcome the above problem. An object of the present invention is to provide a rolling mill driving mechanism for conducting a sizing-rolling method in a wider sizing range with a stable rolling operation wholly therethrough. To achieve the object, the driving mechanism for the rolling mill of the present invention comprises the features stated in the claim. BRIEF DESCRIPTION OF THE DRAWINGS Fig 1 is an explanatory view for sizing-rolling method in common drive dystem showing an example of a rolling range when the gear ratio is set to have 15 to 20% of area reduction ratio and the state of no tension. Fig. 2 is an explanatory view for variance of tension generated in sizing-rolling in the common drive system. Fig. 3 is a schematic perspective view of the driving mechanism according to the present invention. Fig. 4 is a sectional view taken from the line A-A in Fig. 3. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be detailed with referring to Figs. 1 to 4. Fig. 3 shows a drive transmission route of the gear train provided by the two 3-roll rolling mills, i.e., the n+1 th one placed downstream in the rolling direction and the n th one placed upstream in the same direction. In Fig. 3 is shown the 3-roll rolling mills in which two rolls 3, 3' (not shown at the mill placed downstream) are arranged at an interval of 120 with respect to rolls 2, 2' fixed on drive shafts 1, 1'. To cause a drive gear 4 connected to the drive shaft 1' of the first (n th) mill placed upstream and an input gear 6 connected to a universal joint 5 to correspond in rotational direction to each other, the gears 4 and 6 are provided with an intermediate gear 7. In this case, a driving force from a motor 19 is transmitted to the rolls through the universal joint 5 - input gear 6 - intermediate gear 7 - drive gear 4 - drive shaft 1' - bevel gears 8 and 9. The second (n + 1 th) mill placed downstream is so disposed that it has arrangement of rolls symmetrized to that of the mill placed upstream with respect to an axis of the rolling line, and is positioned downstream in the running direction of rolled material 20 with respect to the upstream placed mill. The downstream-placed mill is provided with two systems of drive transmission routes. One of the drive transmission routes is a first transmission mechanism wherein a driving force is transmitted as upper input gear 10 - oneway clutch 11 - lower input gear 12 - lower intermediate gear 13 - drive gear 14 when a connecting clutch 16 disposed between the upper intermediate gear 15 and lower intermediate gear 13 is disconnected (in the state shown in Fig. 4 where the clutch rod 17 is in position indicated by solid line). In operation of the above transmission mechanism, a rotational speed of the rolls of the downstream-placed mill is lower than the running speed of rolled material 20' at the upstream-placed mill, so that when the rolled material is caught by the downstream-placed mill, the one-way clutch 11 is activated to stop transmission of driving force from the motor, thereby causing the upstream-placed mill to perform force rolling. The other transmission route is a second transmission mechanism wherein a clutch rod 17 of a connecting clutch 16 mounted between an upper intermediate gear 15 and lower intermediate gear 13 is connected as shown by dotted line in Fig. 4 to transmit a driving force between the gears 15 and 13. In operation of the second transmission mechanism, a rotational speed ratio of the upper input gear 10 and upper intermediate gear 15 is larger than that of the lower input gear 12 and lower intermediate gear 13, so that the lower input gear 12 is rotated at higher speed than the upper input gear 10 to activate the oneway clutch 11, thereby stopping drive transmission between the upper input gear 10 and lower input gear 12. Hence, a driving force from the motor is transmitted from the universal joint 5' to upper input gear 10 - upper intermediate gear 15 - connecting clutch 16 - lower intermediate gear 13 - drive gear 14. Since the driving force form the motor is transmitted to the rolls in this transmission route, tensile rolling in the common drive system is enabled. Next, a specific mechanism for drive transmission at the rolling mills will be referred to with Fig. 4. Fig. 4 is a sectional view taken from the line A-A in Fig. 3 and shows a principal portion of the transmission mechanism, i.e., input gears 10, 12, intermediate gears 13 and 15 and drive gear. Difference in drive transmission system between force rolling and tensile rolling in the common drive will be detailed. When conducting force rolling, the connecting clutch rod 17 is pulled up to the position shown by the solid line by use of a hydraulic cylinder 18 and there is no transmission of driving force between the upper and lower intermediate gears 15 and 13. Driving force from the motor 19 is transmitted from the upper input gear 10, through the oneway clutch 11 to the lower input gear 12, lower intermediate gear 13 and drive gear 14. In this case, rotational speed ratio of the input gears 10, 12, intermediate gears 13, 15 and drive gear 14 is set to be lower than that in the upstream-placed mill, so that the rolls when not rolling the material are rotated by the drive force from the motor. When the material rolled at the upstream-placed mill is caught by the downstream-placed mill, the roll 2, drive shaft 1, drive gear 14, lower intermediate gear 13 and lower input gear 12 of the downstream-placed mill are rotated by the rolled material since the material's running speed is higher than the rotational speed of the roll. The oneway clutch 11 which is mounted in a direction to transmit driving force in the state of no rolling of material is activated through rotation of the lower input gear 12 at higher speed than upper input gear 10 due to force rolling by the upstream-placed mill, so that a driving force from the motor is not transmitted to the roll of the downstream-placed mill, thereby allowing force rolling from the upstream-placed mill to the downstream-place mill. For conducting tensile rolling in the common drive system, the connecting clutch rod 17 is moved down to the position shown by dotted line by use of the hydraulic cylinder 18. The sliding portions of the connecting clutch rod 17, upper and lower intermediate gears 15 and 13 are splined, so that the gears 15 and 13 are connected through the clutch rod 17 to allow driving force to be transmitted between the gears 15 and 13. Gear ratios of the upper input and intermediate gears 10, 15, lower intermediate gear 13 and drive gear 14 of the downstream-placed mill are so set that when the downstream-placed mill has a maximum area reduction ratio, there is no tension applied to rolled material between the upstream and downstream placed mills, thereby enabling rolling therebetween in the common drive system. Rotational speed ratio of the upper input and intermediate gears 10 and 15 is set higher than that of lower input and intermediate gears 12, 13 for enabling both of the common drive rolling and force rolling, so that the lower input gear 12 is rotated faster than the upper input gear 10 to activate the oneway clutch 11 and stop transmission of drive force by the lower and upper input gears 12 and 10, resulting in that a drive force from the motor is transmitted as upper input gear 10 - upper intermediate gear 15 - connecting clutch rod 17 - lower intermediate gear 13 - drive gear 14. Next, performance of sizing-rolling by driving two 3-roll rolling mills with a single motor will be detailed with referring to Fig. 3. In the range that the downstream-placed mill has a smaller sizing amount (at a smaller area reduction ratio), in turn, compressive force generated by force rolling through the oneway clutch and applied to material between the mills is not made higher than a value that compressive force/average resistance to deformation of rolled material is 0.1, the two rolling mills are interconnected through their driving systems before rolled material is caught by the downstream-placed mill, so that the mills are driven by a single motor. After the rolled material is caught by the downstream-placed mill, the oneway clutch 11 is operated to stop transmission of driving force to the downstream-placed mill, thereby allowing the upstream-placed mill to conduct force rolling to the downstream-placed mill. As increasing the amount of sizing at the downstream-placed mill, compressive force exerted on the rolled material between the upstream and downstream-placed mills increases as shown by the line b in Fig. 2 and to a value that compressive force/average resistance to deformation of rolled material is 0.1. When compressive force increases to be higher than a value that compressive force/average resistance to deformation of rolled material is 0.1, driving of the two 3-roll mills are changed to the common drive system wherein both of the mills are driven at a predetermined gear ratio that is selected to be lower than a value that tension/average resistance to deformation of rolled material is 0.2 at a specific area reduction ratio for switching from the foregoing operation by the oneway clutch. Also, in the range of a larger sizing amount (at a larger area reduction ratio), both the mills are interlocked to be driven for performing rolling. As seen, the drive system for the plurality of rolling mills to be driven by a single motor is changed in the specific sizing ranges, thereby enabling a stable rolling operation wholy in a larger extent of sizing ranges. The present invention may be applicable to sizing-rolling in 2-roll rolling mills as well as in the aforesaid 3-roll rolling mills. Specific sizing-rolling will be explained hereunder. In heated rolling process of barstock by use of 3-roll rolling mills in the common drive system as shown in Fig. 3 provided rearwardly of the rough rolling mill group, sizing-rolling was applied for two sizes 48.4 ⊘ and 45.6 ⊘ in diameter for the rolled barstock of 50mm⊘ in diameter rolled by the rough rolling mill group. Rolling conditions are that gear ratio of the rolling mills are set to have no tension appplied to the material at area reduction ratio of 20%, and rolling systems at specific area reduction ratios for the above two sizes, i.e., force rolling or tensile rolling were selectively decided in view of Fig. 1 based on research of a stable rolling range at the same gear ratio. The material is those classified at S45C in JIS and adjusted of temperatue in pre-process to have 900° C between the rolling mills. The average resistance to deformation of the material at 900° C was confirmed to be 15.7·10³Pa in our preliminary inspection. Sizing-rolling for the abovesaid two sizes will be detailed hereunder. (1) Sizing-rolling for 48.4 mm ⊘ from 50mm⊘ diameter A general area reduction ratio was 6.3% but was changed to 4.4% at the upstream-placed mill and 1.9% at the downsteam-placed mill for the sizing operation. Since force rolling was carried out at the point that the area reductin ratio is 6.3% in Fig. 1, force rolling was adopted. Sizing-rolling was carried out through the first transmission mechanism at the downstream-placed mill wherein the connecting clutch 16 is disconnected (in the state where the clutch rod 17 is placed in position shown by solid line in Fig. 4), a driving force from the motor 19 is transmitted as input gear 10 - oneway clutch 11 - lower input gear 12 - lower intermediate gear 13 -drive gear 14, so that the roll 2 is driven through the drive shaft 1. In this case, rotation of the roll by the driving force from the motor is made before the material rolled at the upstream-placed mill is caught by the downstream-placed mill. Then, the oneway clutch 11 was operated since the running speed of rolled material 20' is higher than rotational speed of the roll, so that the roll was rotated through the force rolling by the upstream-placed mill, thereby providing a stable rolling without buckling of rolled material. Compressive force caused by force rolling and measured between the two rolling mills was 1.41 · 10³Pa so that: [(compressive force between the rolling mills)/(average resistance to deformation of rolled material) = (1.41 · 10³Pa)/(15.7 · 10³Pa)= 0.09 which value is in the range less than 0.1 of the present invention. (2) Sizing-rolling for 45.6 mm ⊘ from 50mm⊘ diameter A general area reduction ratio was 16.8% but was changed to 11.8% at the upstream-placed mill and 5.0% at the downsteam-placed mill for the sizing operation. Since tensile rolling in the common drive system was carried out at the point that the area reductin ratio is 16.8% in Fig. 1, tensile rolling was adopted. Tensile sizing-rolling in the common drive system was carried out through the second transmission mechanism at the downstream-placed mill with the upstream-placed mill wherein the connecting clutch rod 17 was placed in position shown by the dotted line in Fig. 4 by use of the hydralic cylinder18 to interlock the upper intermediate gear 15 with the lower intermediate gear 13, a driving force from the motor 19 is transmitted as upper input gear 10 - upper intermediate gear 15 - lower intermediate gear 13 - drive gear 14, so that the roll 2 is driven through the drive shaft 1. As a result, there caused no decrease of diameter of rolled material but obtained bar of a predetermined product size. Tension caused by the tensile rolling and measured between the two rolling mills was 0.78 · 10³Pa, so that: [(tension between the rolling mills)/(average resistance to deformation of rolled material) = (0.78 · 10³Pa)/(15.7 · 10³Pa) = 0.05 which value is satisfactorily in the range less than 0.2 of the present invention. As explained above, the conventional sizing-rolling for continuous length sections in the known common drive system provided sizing only in an extent of a few percent of the entire range of area reduction ratio. By contrary, the driving mechanism for performing the same of the present example can achieve the stable sizing-rolling in the entire range and provide the products of preferable sizes.

Claims: A driving mechanism in a hot rolling equipment for manufacturing bars, said hot rolling equipment including an upstream rolling mill and a downstream rolling mill driven by a common drive, said driving mechanism disengaging said downstream rolling mill from said common drive when material lying in a space between said upstream and downstream rolling mills comes to undergo tensile force having a magnitude in excess of a predetermined magnitude, and said driving mechanism engaging said downstream rolling mill with said common drive when said material lying in said space comes to undergo compressive force having a magnitude in excess of a predetermined magnitude, characterized in that said driving machanism comprises a first power transmission means for transmitting power from said common drive (19) to said downstream rolling mill through a common universal joint (5') when forced rolling is to be effected and a second power transmission means for transmitting power from said common drive (19) to said downstream rolling mill through said common universal joint (5') when tensile rolling is to be effected, that said first power transmission means comprises an upper input gear (10) located next to said universal joint (5'), a lower input gear (12) for engaging and disengaging said upper input gear (10) by means of a one-way clutch (11), and a lower intermediate gear (13) in mesh engagement with said lower input gear (12), that said one-way clutch (11) disengages said lower input gear (12) from said upper input gear (10) when said lower input gear (12) is revolved at a higher revolution speed than said upper input gear (10), that said second power transmission means comprises said upper input gear (10) and an upper intermediate gear (15) in mesh engagement with said upper input gear (10), and a connecting clutch (16) for engaging said upper intermediate gear (15) with said lower intermediate gear (13) when power transmission from said common drive (19) to said downstream rolling mill is to be effected through said second power transmission means, that the number of revolutions attained by said upper intermediate gear (15) during the time said upper input gear (10) makes one revolution is larger than the number of revolutions attained by said lower intermediate gear (13) during the time said lower input gear (12) makes one revolution, that a drive gear (14) mounted on a drive shaft (1) is in mesh engagement with said lower intermediate gear (13), and that a roll (2) secured to said drive shaft (1) is one of equidistantly spaced rolls which constitute said downstream rolling mill.

Inventors: ISHIBASHI TOSHIHIRO, NAKAMURA MITSURU, NOGUCHIO YUKIO, TODA YUKATA, ISHIBASHI,TOSHIHIRO, NAKAMURA, MITSURU, NOGUCHIO, YUKIO, TODA, YUKATA
Applicants: HITACHI SHIPBUILDING ENG CO, NIPPON STEEL CORP, HITACHI ZOSEN CORPORATION, NIPPON STEEL CORPORATION
Application year: 1991
Main classification: B21B1
IPC codes: B21B13, B21B1, B21B27, B21B35, B21B31