JP5573895B2 - Method for determining whether or not there is a risk of occurrence of surface roughness scale flaws, a hot finishing rolling mill train using the determination method, a method for determining the degree of surface roughness of a work roll, and a hot finishing rolling mill train using the determination method - Google Patents

Description

  The present invention relates to a method for determining whether or not there is a risk of occurrence of surface roughness scale flaws, a hot finishing rolling mill using the determination method, a method for determining the degree of surface roughness of a work roll, and hot finishing using the determination method. It relates to rolling mill rows.

  Metal strips, especially thin steel plates typified by strips, are cast, cast into slabs, then manufactured through hot rolling, cold rolling, or further plated. Some will do.

  FIG. 34 shows an example of a hot rolling line (hot rolling mill row) 100 that has been conventionally used. A metal material 8 having a thickness of 150 to 300 mm (hereinafter referred to as a material to be rolled) heated to several hundred to several hundreds of degrees Celsius by the heating furnace 10 has a thickness of 1 to 25 mm by a rough rolling mill row 12 and a hot finish rolling mill row 18. Rolled to a thin thickness.

  In the case of the hot rolling line (hot rolling mill) 100 shown in FIG. 34, each of the rough rolling mills (stands) constituting the rough rolling mill row 12 has three units R1, R2, and R3. Is not limited to this. In many cases, the number is four, and a part (often one) is reciprocally rolled, and the remaining rolling mill is called a 3/4 continuous type in which unidirectional rolling is performed. However, three of the four aircraft are not limited to the one-way type, and for example, one of the three aircraft includes a one-way type and is called 3/4 continuous.

  In the case of the hot rolling line (hot rolling mill) 100 shown in FIG. 34, the rolling mills (stands) constituting the hot finish rolling mill row 18 are 7 groups F1 to F7, but 6 groups. In some cases.

  As described above, the hot rolled material 8 heated to several hundred to several hundreds of degrees Celsius has a fish scale-like film (hereinafter referred to as scale) of iron oxide on the front and back surfaces when extracted from the heating furnace 10. Is generated. In addition, since the rolled material 8 is exposed to the atmosphere at a high temperature even in the process of being rolled and thinned and lowered in temperature by heat radiation, new scales are generated on the front and back surfaces of the rolled material 8. For this reason, on the entry side of each of the rough rolling mills in the row 12 of rough rolling mills, the scale is removed by spraying high and low pressure water of 10 to 30 MPa on the front and back surfaces of the material to be rolled 8 as the supply pressure from the pump. A descaling device 16 is installed to remove the scale.

  In FIG. 34, 14 is a crop shear for cutting and shaping the front and rear end crop of the material 8 to be rolled (finished and rear end of the material to be rolled 8) before finish rolling, A cooling zone for cooling the rolled material 8 after finish rolling with water or air, 24 is a coiler for winding the rolled material 8 after cooling, and 28 is an online work roll 19 (hereinafter simply referred to as a roll). ) Is an online roll grinder, 90 is a control device, 92 is a process computer, and 94 is a business computer.

  According to Patent Document 1, the online roll grinder 28 is preferably installed in the last three stands (F5 to F7 in FIG. 34) in the hot finish rolling mill row 18.

This is because, as shown in FIG. 35 (a), only the portion of the roll 19 corresponding to the rolled material passing plate portion is worn, and there is a wear step between the rolled material non-passing plate portion (unworn portion). Therefore, if the material to be rolled is rolled in a state where this wear step is as large as about several tens of μm, the deviation from the target of the plate thickness becomes large, or the material to be rolled next is the widest after the material to be narrowed. When rolling the material, there is a problem that the shape of the material to be rolled during rolling becomes defective. As shown in FIG. If the roll 19 is flattened in the width direction of the material to be rolled, the problems can be solved, and the effect is that the ratio (influence coefficient) at which the roll wear is transferred to the material to be rolled is hot. The rear stand in the finishing mill row becomes larger, and is further rolled by the rear stand. If the ratio remaining until after rolling by the final stand (influence coefficient), also larger because as the rear of the stand, the final 3-effective to install online role grinder 28 to stand, based on a consideration of the.

  In Patent Document 1, furthermore, the elimination of the wear level difference by the online roll grinder 28 is performed as shown in FIG. 36 (a), with the configuration of the material width in the rolling order from one roll change to the next roll change. After the maximum width of the material to be rolled, the conventional rolling restriction that only the transition from wide to narrow is eliminated, and wide transition (width reversal) as shown in FIG. 36 (b) is enabled. Thus, it is said that it becomes a foothold that enables so-called schedule-free rolling in which the order of steel output = the order of rolling.

  As shown in FIG. 37, Patent Document 3 describes that the entire grinding of the roll 19 is used in addition to eliminating the wear level difference by grinding.

  FIG. 38 shows the structure of the online roll grinder 28. As shown in the side view of FIG. 38A and the perspective view of FIG. 38B, two grinding units 30 are provided for each of the upper and lower rolls 19 in the roll body length direction. The grinding unit 30 is coupled by a separator 32 and is moved in the roll body length direction (corresponding to the width direction of the material to be rolled) by the oscillating device 34 integrally with the grinding unit 30 and the separator 32. The two grinding units 30 each grind one side at the center of the roll drum length and grind the entire range of the roll drum length.

  FIG. 38C shows the structure of the grinding unit 30. The grinding unit 30 includes a grindstone 36, a pressing device 38, and a rotating device 40. The roll 19 is ground by pressing the grindstone 36 against the roll 19 by the rod 38 </ b> R of the pressing device 38 while rotating the grindstone 36 by the rotating device 40.

  The connecting shaft 42 that connects the rotating device 40 and the grindstone 36 has a grooved shape called a spline 44, as can be seen in the AA cross section shown on the right side of FIG. The shaft 46 on the apparatus 40 side and the shaft 48 on the grindstone 36 side are engaged with each other by the spline 44, so that the distance between the rotating apparatus 40 and the grindstone 36 changes, and even if the positions are shifted from each other in the axial direction, 36.

  The pressing device 38 uses a hydraulic cylinder, and moves the grindstone holder 50 back and forth with the hydraulic cylinder.

  A bearing 52 is installed between the grindstone holder 50 and the grindstone 36 and can be pressed while rotating the grindstone 36. Further, a rubber U-packing is often used for the seal 54 of the hydraulic cylinder.

  The pressing device 38 is not necessarily a hydraulic cylinder, but may be any actuator as long as it is an actuator capable of pressing the grindstone 36 against the roll 19 and positioning in the pressing direction, such as a servo motor or a stepping motor. The cylinder is most preferable because it has a simple structure and requires a small installation space. Further, the packing is not limited to rubber, but may be made of resin or metal.

  In addition, in patent document 1, the scale resulting from the rough surface of a roll in the front stage stand (No.1-No.3 stand F1-F3 or No.4 stand F4) of the finishing mill normally comprised from 6 to 7 stands. Since there is concern about the occurrence, it has been conventionally proposed to perform rough surface removal grinding of the threaded plate portion by the online roll grinder 28 (Japanese Patent Laid-Open No. 61-49713: Patent Document 4). Patent Document 4 does not clearly indicate in which stand the online roll grinder should be installed.

  Here, the definition of the rear stage stand, which is a synonym, is divided into three ways in domestic steel companies, and may refer to 4 stands from F4 to F7, or 3 stands from F5 to F7. In some cases, there are places where there are only six stands constituting the finish rolling mill 18, and in such a case, from the opposite interpretation that three stands from F4 to F6 may be pointed out, at least F1 This corresponds to the 3 stands from F3 to F3.

  Conventionally, an online roll grinder has never been installed in the front stand. And an online roll grinder has never been installed in the roughing mill.

  Although it is a different story here, in Patent Document 5 cited later in the description of the embodiment, the relationship between the rolling load and the depth of the rolling roll fatigue layer formed according to the rolling load is obtained in advance, It is described that every time the rolling load of the roll reaches a predetermined amount, the entire roll roll fatigue layer is ground and removed by an online roll grinder.

  Similarly, in Patent Document 6 cited later in the description of the embodiment, after cutting the rear end portion of the preceding material (preceding rolled material) and the leading end portion of the succeeding material (following rolled material), the preceding material, In a method of manufacturing a hot-rolled high-tensile steel sheet by a hot-rolling continuous process in which subsequent materials are joined and continuously rolled, lubrication is applied to the finish rolling after joining, and at least the stage after the finish rolling is ORG (online It is described that rolling with a high-speed roll while utilizing a roll grinder).

  Moreover, in patent document 7 quoted by description of embodiment later, a sheet bar joining apparatus is arrange | positioned at the line entrance side of a finishing mill, and the full width of a sheet bar is provided between this sheet bar joining apparatus and a finishing mill. It describes a continuous hot rolling facility in which a sheet bar heating device (sheet bar heater) for heating and an edge heating device for heating the edge portion of the sheet bar are arranged.

JP 09-155418 A Japanese Patent Laid-Open No. 06-190410 Japanese Patent Laid-Open No. 05-042310 JP 61-049713 A JP-A-10-328716 JP-A-10-146602 Japanese Patent No. 3368573

  By the way, hot rolling operations are roughly divided into the following three.

(1) Improvement of product quality (2) Improvement of operating rate and production efficiency (3) Reduction of energy intensity (there is a contribution reduced by (2))

  The items contributing to the above three items will be described in further detail below.

(1) Improvement of product quality One of the improvements in product quality is the suppression of surface roughness scale wrinkles.

  The quality of the front and back surfaces of products that are hot-rolled at a high temperature of several hundred to several hundreds of degrees Celsius (hereinafter simply referred to as “surface” for simplicity) is that the surface is covered with scale in the process of rolling, The surface condition of the roll deteriorates due to the heat load, and it is generally inferior to the surface quality of the cold-rolled product because it is transferred to the material to be rolled. Since the scale is removed by pickling after hot rolling and before cold rolling, the surface quality of the cold rolled product is better.

  It is not cold-rolled after hot rolling, it is either hot-rolled, or only scale is removed after hot-rolling (in either case, part of the width edge may be cut off, etc.) ) In the case of products to be shipped, when hot rolling is performed with a roll whose surface condition has deteriorated, surface quality defects called surface roughness scales occur locally or sporadically with respect to the entire length of the product metal strip. If this is the case, this part must be discarded before shipping. For this reason, the yield of a product falls. In the case of products that are cold-rolled and shipped after hot rolling, the same is true as long as the rough surface scale wrinkles are caught in the material to be rolled.

  FIG. 39 shows a state of poor surface quality of the surface roughness scale ridge 8A generated on the surface of the material 8 to be rolled when rolled by such a hot rolling line (hot rolling mill row) 100. A black streak pattern is present in a part of the surface of the material to be rolled 8 in the width direction, and is scattered in the length direction of the material to be rolled 8. This black stripe pattern is a trace of the scale biting into the material 8 to be rolled.

  Due to the reduction in overall product thickness in recent years, the higher temperature of the material to be rolled with the increase in material strength, and the increase in rolling load, the above-described surface roughness scale wrinkles are more frequently generated than before. ing.

  In addition, in order to suppress the occurrence of surface roughness scale wrinkles, the types of surface roughness scale wrinkles that are likely to occur, the number of continuous rolls of the material to be rolled, the number of rolls that should be rolled within the roll immediately after polishing, Inconvenience that must be dealt with by such a roll chance regulation, and there is a case where it is necessary to frequently replace the roll, which has become a major obstacle in operation.

  That is, an object of the present invention is to suppress the occurrence of surface quality defects of surface roughness scale wrinkles in a product manufactured by hot rolling, and to improve the quality of the product.

(2) -1 Increase of operation rate and production efficiency by suppressing the occurrence of slip between the roll and the tip of the material to be rolled As one of the measures to improve the operation rate and production efficiency, For example, the occurrence of slip between the tip and the tip can be suppressed.

  As described in Patent Document 1, conventional online roll grinding is performed in order to eliminate a level difference caused by wear of the roll surface layer and maintain a flat roll surface at all times.

However, during the hot rolling operation, while rolling some of the material to be rolled 8, each of the rough rolling mill row 12 and the hot finish rolling mill row 18 that are in direct contact with the hot rolled material 8 is used. Part of the scale generated in the surface layer of the material to be rolled 8 is gradually attached to the surface of the roll 19 (or the surface layer of the roll 19 is oxidized by heat input received by contact with the material to be rolled 8 at a high temperature. It is said that the contribution is about 10%, but the surface of each roll 19 is magnetite (Fe ₃₎ called black skin.
It is covered with a film of O ₄ ). When the surface layer of the roll 19 is in this state, the material to be rolled 8
And the coefficient of friction between the roll 19 and the surface of the roll 19 become small.

  When the friction coefficient becomes small, slip may occur between the material to be rolled 8 and the surface of the roll 19 when the tip of the material to be rolled 8 bites into the roll 19.

  Incidentally, the lower limit of the coefficient of friction μ between the material to be rolled 8 and the surface of the roll 19 is determined as follows.

  That is, as shown in FIG. 40A, the tip of the material 8 to be rolled is illustrated as a roll 19 (in FIG. 40, the roll 19 of the finish rolling mill 18 is illustrated, but the roll 13 of the rough rolling mill 12 is also illustrated. The force received from the roll 19 when biting is set to P, and the biting angle is α, the rolled material 8 is placed between the upper and lower rolls 19 as shown in FIG. 40 (b). A force fh that attempts to be pulled in the gap, that is, the conveyance direction indicated by an arrow in the figure, acts on the tip of the material 8 to be rolled from the roll 19. If the force fh is not less than the force Ph that prevents the rolled material 8 from entering the gap between the upper and lower rolls 19 and pushes it back in the direction opposite to the conveying direction, the tip of the rolled material 8 is Since it enters the gap between the rolls 19, rolling can be started. Otherwise, slip occurs between the material to be rolled 8 and the surface of the roll 19. In the limit state of whether or not this slip occurs, the following equation is established. Therefore, the lower limit of the friction coefficient μ that does not slip is tanα.

Ph = fh (1)
Psinα = fcosα (2)
Psinα = μPcosα (3)
μ = tan α (4)

  However, the actual coefficient of friction between the material to be rolled 8 and the surface of the roll 19 depends on the state of formation of the black skin as described above and the degree of the production, and the rolling of the previous material to be rolled is not limited. The rolling oil supplied at the time of combustion is exhausted and left behind (usually, the rolling oil supplied to the roll stops and adheres to the roll for the roll circumferential length corresponding to at least one roll circumference at the tail end of the material to be rolled. It is estimated that the rolling oil is hard to find, and may vary depending on factors that vary.

  As described above, the actual friction coefficient tends to be lower in the state where the black skin is generated than in the state where the roll 19 is freshly polished, and slipping is likely to occur. As the biting angle α increases, the lower limit of the friction coefficient μ that does not slip increases. Therefore, slipping easily occurs in this case.

  On the other hand, hard materials typified by high carbon steel, austenitic stainless steel, martensitic stainless steel having a carbon content of 0.1% by mass or more are difficult to bite into the roll 19 as a material characteristic, and slip. It tends to be easy. This is because high carbon steel and the like are originally hard on the material, and the tip of the material to be rolled 8 is heat-extracted on three sides by water sprayed from the descaling device 16, as shown in FIG. Compared with the parts other than the tip, it is synergistic that it is easily cooled locally, so the tip of the material to be rolled 8 becomes harder and less likely to be deformed, and smoothly enters the gap between the upper and lower rolls 19. Because it disappears.

  The scale produced on the front and back surfaces of stainless steel is difficult to peel, whereas the scale produced on the front and back surfaces of high-carbon steel is particularly easy to peel off.

  Furthermore, due to the influence of trace additive elements and the like due to the recent increase in quality requirements of consumers, for example, there are harder ones among high carbon steels, but such hard materials are scattered in the rolling cycle. If this is the case, when the material to be rolled is rolled one after another, such a hard material is suddenly encountered, and this problem becomes even more pronounced.

  As described above, if slip occurs between the roll and the tip of the material 8 to be rolled, there is a risk of hindering smooth continuation of the hot rolling operation.

(2) -2 Improvement of operation rate and production efficiency due to reduction of roll replacement frequency By the way, for hot rolling operations, the operation stop time accompanying the replacement of the rolls in the hot finishing mill row 18 is the operating rate. As a factor to reduce, it occupies a considerable weight. FIG. 42 shows a breakdown of the outage rate and the operation rate in the operation of the hot rolling line (hot rolling mill row) for one month, and it can be said that “roll replacement” is the largest factor in the outage rate. Therefore, reducing the downtime associated with the roll replacement contributes to an increase in operating rate and production efficiency.

According to the first aspect of the present invention, when the surface roughness index φ obtained by the following equation (A) is equal to or greater than a certain value before rolling the material to be rolled by a rolling mill, determines that there is a risk of the surface roughness scale defects occur due to the destruction and aggregation of scale on the surface, the surface the surface roughness index φ is you determined that there is no risk of the surface roughness scale defects occur when the below a certain value A method for determining whether or not there is a risk of rough scale wrinkling ,
Surface roughness index φ = φ0 · K2 / D · Σ (K1 · L · P / W) (A)
here,
φ0: Proportional constant (m / kN)
K1: Constant determined by product type K2: Constant determined by rolling mill L: Rolling length of a material to be rolled in the rolling mill (m)
P: Rolling load (kN) of the material to be rolled in the rolling mill
W: Width of the material to be rolled in the rolling mill (m)
D: Diameter of roll in the rolling mill (m)
Σ: Sum for each rolled material
The value of K1 when the material to be rolled is stainless steel is 0.1 times the value of K1 when the material to be rolled is carbon steel. This is a method for determining whether or not there is any.

  According to a second aspect of the present invention, there is provided a hot finish rolling mill using the method for determining whether or not there is a risk of occurrence of the rough surface scale flaw.

According to a third aspect of the present invention, the degree of surface roughness of the work roll of the rolling mill is based on the value of the surface roughness index φ obtained by the following equation (B) before rolling the material to be rolled by the rolling mill. a method of determining the degree of surface roughness of the determination to Ruwa over crawl,
Surface roughness index φ = φ0 · K2 / D · Σ (K1 · L · P / W) (B)
here,
φ0: Proportional constant (m / kN)
K1: Constant determined by product type K2: Constant determined by rolling mill L: Rolling length of a material to be rolled in the rolling mill (m)
P: Rolling load (kN) of the material to be rolled in the rolling mill
W: Width of the material to be rolled in the rolling mill (m)
D: Diameter of roll in the rolling mill (m)
Σ: Sum for each rolled material
When the material to be rolled is stainless steel, the value of K1 is 0.1 times the value of K1 when the material to be rolled is carbon steel. This is a determination method.

  A fourth aspect of the present invention is a hot finish rolling mill train using a method for determining the degree of surface roughness of the work roll.

  ADVANTAGE OF THE INVENTION According to this invention, it can suppress that the surface quality defect of the surface roughness scale wrinkle generate | occur | produces in the product manufactured by hot rolling. Furthermore, the reduction in the frequency of roll replacement improves the operating rate and production efficiency of the hot rolling operation.

The figure which shows the state of the surface of the work roll extracted immediately after the surface quality defect of the surface roughness scale ridge generated on the surface of the material to be rolled The figure which shows the experimental result which measured the change of the thickness of the scale of F2 roll, and the surface roughness by the number of rolling. Diagram showing roughening scale wrinkle generation mechanism Figure showing changes in scale thickness and surface roughness index of finishing mill rolls depending on the number of rolls. The figure which shows the change by the number of rolling of the thickness of the scale of the F2 roll at the time of rolling the to-be-rolled material of each kind The figure which shows 1 reference example of the equipment row | line of the hot rolling line (hot rolling mill row | line) which has an online roll grinder Front view and side view showing an example of an online roll grinder The figure which shows the change with the number of rolling of the F2 roll grinding result with the online roll grinder Enlarged view showing roll section The figure which shows an example of the hot rolling line (hot rolling mill row) of this invention The figure which shows the example of a structure of the order of the number of rolling of a rolling material of F1 interval for demonstrating the conditions leading to this invention In order to explain the conditions leading to the present invention, the thickness of the rolled material after finishing rolling, the width of the rolled material, the length of the rolled material, the tensile strength (command value) in the order of the number of rolled materials Illustration showing an example Figure showing comparison between the set grinding amount and the actual grinding amount using a conventional online roll grinder Diagram showing examples of defects due to uneven product thickness in the width direction Plan view for explaining the cause of the error of the lap amount at the center of the width of two grinding units Sectional view showing the structure of the grinding unit of the online roll grinder after applying the measure Sectional view 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 Pipeline diagram schematically showing a hydraulic piping system including a hydraulic cylinder as a pressing device A figure comparing and comparing the level difference at the center of the product thickness after each measure is applied The figure which shows the example of the defect of the product thickness of the width center wrap part Diagram showing the variation in time from the wheel advance command to the roll contact before and after applying this measure The figure which shows the change experiment result of lap amount Diagram showing the progress of fatigue layer due to rolling length A diagram showing the grinding ability of a roll with an online roll grinder as a function of pressing line pressure Diagram showing the relationship between grinding wheel and roll of online roll grinder Diagram showing distribution of cumulative rolling load in roll length direction Diagram explaining the transitional control method when shifting from grinding in the region corresponding to a certain plate path to grinding in the region corresponding to the next plate path when grinding to the fatigue layer Figure showing a reference example of a hot rolling line (hot rolling mill line) A chart showing the breakdown of the outage rate and the operating rate for each level of the present invention The figure which shows an example of the hot rolling line (hot rolling mill line) which can apply this invention The figure which shows the example of the conventional hot rolling line (hot rolling mill row) The figure which shows the other example of the conventional hot rolling line (hot rolling mill row) The figure which shows the further another example of the conventional hot rolling line (hot rolling mill row) Cross-sectional view showing grinding of wear steps with conventional technology The figure which shows the structure of the to-be-rolled width | variety of the rolling order from one roll change to the next roll change by a prior art Diagram showing an example of grinding range according to the prior art The figure which shows an example of a structure of the online roll grinder of a prior art The figure which shows an example of the surface roughness scale wrinkles which generate | occur | produced on the surface of the material to be rolled by the prior art Illustration for explaining the wear coefficient between the material to be rolled and the roll surface Illustration for explaining the problems of the prior art Diagram showing breakdown and utilization rate of outage rate when applying conventional technology

  FIG. 34 described above shows an example of an equipment row of a hot rolling line (hot rolling mill row) 100 that has been conventionally many. The hot rolling line (hot rolling mill train) to which the present invention is to be applied is not necessarily limited thereto, but for the sake of convenience, the process leading to the present invention will be described below as an example.

(Condition (1): Product quality improvement by suppressing the occurrence of surface roughness scale wrinkles)
FIG. 39 shows a state of surface quality failure of the surface roughness scale ridge 8A generated on the surface of the material to be rolled 8 when rolled by such a hot rolling line (hot rolling mill row) 100. FIG. 1A shows the state of the roll 19 extracted from a certain rolling mill in the hot finish rolling mill row 18 immediately after the surface roughness scale flaw is generated. FIG. 1B shows the same thing as FIG. The scale 19S is densely attached to the surface of the roll 19 in a range corresponding to the width of the material to be rolled immediately before. It can be seen that the scale is peeled off at the portion 19A on the surface 19.

  The surface roughness scale 疵 has a high rolling load due to the fact that the target material to be rolled is a thin product with a thickness of less than 2 mm, called a thin material, or a medium carbon steel or high-tensile steel, etc. Often occurs when the temperature of the material to be rolled is higher than a certain level, and the peeling of the scale from the surface layer of the roll 19 that is the cause of the material in the hot finish rolling mill row 18 Although it has been empirically known that it frequently occurs in the rolling mills in front (especially F2 and F3), the condition that the scale peels from the surface layer of the roll 19 and the surface roughness scale wrinkle. The mechanism was not always clear.

  In order to clarify the generation mechanism of the surface roughness scale flaw, the inventors investigated the scale thickness and surface roughness of the surface layer of the roll 19 every time several rolls of the material to be rolled were rolled. The target materials were low carbon steel having a product thickness of 2 to 5 mm and a product width of 800 to 1500 mm for the first to fifteenth items, and low carbon steel having a product thickness of 1.2 mm and a product width of 1200 mm for the sixteenth and subsequent items. The rolling conditions are shown in Table 1, and the investigation results are shown in Table 2 and FIG.

Incidentally, FIG. 2 shows the number of rolled F2 rolls, the thickness of the scale (magnetite (Fe ₃ O ₄ ) called black skin), the surface, and the second rolling mill from the front of the hot finish rolling mill row 18. It is the result of investigating the roughness. The data is based on JISB0601-2001 and JISB0651-2001, a stylus type surface roughness tester is applied to the roll surface, moved in the axial direction of the roll, and the reference length lr (λc) for the roughness curve is obtained. It is a value measured with 0.8 mm, the reference length lw (λf) for the waviness curve being 8 mm, and the reference length lp for the sectional curve, that is, the evaluation length ln being 40 mm. Incidentally, it was measured at the center of the roll in the barrel length direction. As shown in FIG. 2, it was found that the scale thickness increases as the number of rollings increases. It was also found that the surface roughness once increased and then increased. In this investigation, peeling of the scale similar to that shown in FIG. 1A was observed on the surface of the roll 19 at the 50th roll.

  The inventors described the same investigation as described later as rolls 13 and 19 (hereinafter, representatively 19) of each rolling mill (stand) in the rough rolling mill row 12 and the hot finish rolling mill row 18 as described later. ) And other types of rolled materials such as stainless steel. As a result, the conditions for the peeling of the scale from the roll 19 and the mechanism for the rough surface scale wrinkle were elucidated. The outline is shown in FIG.

  As shown in FIG. 3A, a roll 19 as shown in FIG. 3B is formed on the surface of the material 8 from which the scale 8S has been once removed by the descaling device 16 on the rolling mill entrance side. The scale grows until it is actually rolled. As shown in FIG. 3C, the scale 19 </ b> S adheres and grows on the surface of the roll 19 by rolling the material to be rolled 8. As described above, as shown in FIG. 3 (d), the thickness of the scale 19S on the surface layer of the roll 19 and the surface roughness are increased as many materials to be rolled are rolled. Since a shearing force is acting between the roll 19 being rolled and the material 8 to be rolled, as shown in FIG. 3E, it is considered that the scale 19S on the surface layer of the roll 19 is peeled off. Here, if rolling of the material 8 to be rolled is continued at the recessed portion 19A of the roll from which the scale has been peeled off, the surface of the material to be rolled is reduced each time the roll 19 rotates and the material 8 is rolled at the portion 19A. The scale 8S generated in this manner is broken only at the location of the material 8 to be rolled at the recessed portion 19A of the roll 19 and is periodically aggregated in the length direction on the surface of the material 8 to be rolled. It adheres and is pushed into the material to be rolled 8 by rolling in the next rolling mill and becomes a surface roughness scale ridge 8A.

  Every time the rolled material 8 is rolled at the recessed portion 19A of the roll, the scale 8S that has been uniformly formed on the surface of the rolled material 8 is broken and periodically on the surface of the rolled material 8 in the length direction. Aggregation is presumed to be because, as shown in the enlarged view of FIG. 3 (e), the portion of the roll from which the scale peeled gave a stronger shearing force to the material to be rolled than the portion that did not. .

  Based on this mechanism, the inventors devised the surface roughness index shown below.

φ = φ0 · K2 / D · Σ (K1 · L · P / W) (5)
φ: Surface roughness index where
φ0: Proportional constant (m / kN)
K1: Constant determined by product type K2: Constant determined by rolling mill L: Rolling length of a material to be rolled in the rolling mill (m)
P: Rolling load (kN) of the material to be rolled in the rolling mill
W: Width of the material to be rolled in the rolling mill (m)
D: Diameter of roll in the rolling mill (m)
Σ: Represents the sum of each material to be rolled.

  That is, when a certain rolling mill is used, the longer the cumulative rolling length obtained by summing the rolling length L of the material 8 to be rolled in the rolling mill, the smaller the roll diameter D is. Since the number of times of contact between the roll and the material to be rolled increases and the scale of the roll becomes thick, surface roughness scale wrinkles are likely to occur with this partial peeling. P / W indicates the rolling load per unit width, and the larger this, the greater the shearing force applied to the scale, and the more likely the surface roughness scale wrinkles occur.

  K2 is a constant determined by the rolling mill. For each rolling mill in the rough rolling mill row 12 and each rolling mill in the hot finish rolling mill row 18 in the equipment row shown in FIG. Decided.

  In the rough rolling mill (R1, 2, 3), K2 = 0. In the rough rolling mill, the distance from the descaling device 16 to the place where the roll 19 and the material to be rolled 8 are in contact (roll bite). Is about 1 to 3 m, shorter than the inside and outside of 5 m in the case of the first stand F1 in the hot finishing rolling mill row 18, and the conveying speed is 100 mpm or more, in the case of the hot finishing rolling mill row. In addition to the fact that the scale thickness on the surface of the material to be rolled is relatively thin, the scale is once peeled off from the roll and rolled by the dent of the roll part where the scale is peeled off. Even if the scale on the surface of the material to be rolled is destroyed, the scale is removed again by another descaling device 16 on the entry side of the next rolling pass, so that it is not pushed in by the next rolling mill, It is considered because rough scale defects does not occur.

  The value of K2 in each rolling mill (F1 to F7) in the hot finish rolling mill row 18 was determined from the experimental results for the low-carbon steel thin objects shown in Table 1 and FIG. FIG. 4 shows the results of scale thickness of each rolling mill (F1 to F7) in the hot finish rolling mill row 18, and a straight line representing the surface roughness index calculated based on the rolling conditions of each material to be rolled. Are shown together. It can be seen that F1 has a smaller scale thickness of about 1/10 at the same number of rollings than F2. This is because the distance from the descaling device 16 is shorter than the inside and outside of 5 m and the inside and outside of 10 m of F2, and the scale thickness on the surface of the material to be rolled is relatively thin. Further, almost no scale adhered to the hot finish rolling mills F5, F6, and F7. This is because, as is conventionally known, since the peripheral speed of the roll is high, the roll is worn and the scale does not grow.

  For F3, the scale thickness was 80% of F2. F4 was 5% of F2. It is considered that there is an influence that the wear of the roll is larger than that of F2.

  K2 of each rolling mill is a coefficient representing the ease of surface roughness of each rolling mill when indices other than K2 in the surface roughness index formula are the same, and was determined as K2 = 1 in F2. For example, K2 in F1 was found to be 0.2 by multiplying the ratio of the scale thickness 1/10 to the rolling load ratio 26186/28635 and the ratio 243/131 of the length of the material to be rolled on the exit side of the rolling mill. K2 in F3 was determined to be 0.5 by multiplying the ratio of the scale thickness 0.8 to the rolling load ratio 26186/23972 and the ratio 243/441 of the length of the material to be rolled on the exit side of the rolling mill.

  K2 in F4 was found to be 0.02 by multiplying the ratio 1/20 of the scale thickness by the rolling load ratio 26186/18245 and the ratio 243/722 of the length of the material to be rolled on the rolling mill exit side. K2 in F5, F6, and F7 was set to 0 because almost no scale adhered to the roll.

  K1 is a constant determined by the type of material to be rolled. From the experimental results shown in FIG. 5, the slope of the regression line was 0.1 times in the case of stainless steel compared to the types other than stainless steel. , Determined as shown in Table 4.

Here, the distinction between low carbon steel, medium carbon steel and high carbon steel is based on C% (mass%), but the other components are JIS G 3131 in the case of low carbon steel and medium carbon steel. JIS for steel
According to G 3311. In the case of stainless steel, JIS G 4304 was followed.

  FIG. 5 is a material to be rolled having a product thickness of 3.0 mm under the same rolling conditions, in which different types of materials to be rolled are rolled and the thicknesses of the F2 roll scales are compared. Compared to low carbon steel, medium carbon steel, and high carbon steel, stainless steel had a scale thickness of 1/10. Stainless steel contains a large amount of Cr, and it is difficult for scales to be generated on the surface of the material to be rolled, and rough surface scale wrinkles are unlikely to occur.

  On the other hand, although it is φ0, this may be an appropriate proportionality constant.

However, for ease of understanding, this φ0 is preferably handled as a normalization constant such that φ = 1 at the reference condition. For example, although it is tentatively, 50 slabs having a thickness of 260 mm and a length of 8.12 m are continuously provided, the outgoing side plate in each rolling mill in the hot finish rolling mill row 18 as shown in Table 5 When rolling to thickness and delivery length (F7 delivery thickness 1.2mm, width is not shown but 1200mm), F2 (rolling load is not shown but 26186kN) is the standard condition. Φ0 = 3.0215E−09.
(3.0215E-09 × 1 / 0.8 × 50 × 1 × 242.7 × 26186 / 1.2 = 1)

  Then, when φ = 1 or more, it is determined that there is a risk of surface roughness scale soot. If φ <1, it is determined that there is no risk of surface roughness scale soot. Therefore, it is convenient to easily determine whether or not there is a risk of surface roughness scale flaws above and below the surface roughness index φ = 1. However, since the surface roughness index φ increases with each rolling of each material to be rolled, not only the presence or absence of the risk of surface roughness scale flaws, but also the surface of the work roll. The degree of roughness can be estimated for each rolled material.

  The method of determining whether or not there is a risk of surface roughness scale wrinkles in the present invention and the method of estimating the degree of surface roughness of the work roll are above and below the surface roughness index φ = 1 as described above. Anyway, whatever value is applied as the proportional constant φ0, the surface roughness index φ has a certain value as a boundary, and the risk of surface roughness scale wrinkles occurring above and below it. What is necessary is just to be able to judge the presence or absence and to estimate the degree of surface roughness of the work roll.

  FIG. 6 is a reference example of an equipment row of a hot rolling line (hot rolling mill row) that can be an object of the present invention. Here, the hot rolling line (hot rolling mill row) 200 is assumed. In addition to the conventional equipment row shown in FIG. 34, the on-line roll grinder 28 is also installed in the rolling mills F2 and F3 in the hot finish rolling mill row 18.

  FIG. 7 is a diagram showing an example of the structure of the online roll grinder 28. One grinding unit 30 is installed for each of the upper and lower rolls 19. Each grinding unit 30 includes a grindstone 36, a pressing device 38, a rotating device 40, an oscillating motor 56, wheels 58, a pinion 66, and the like. In a state where the grindstone 36 is rotated by the rotating device 40, the grindstone 36 is pressed against the roll 19 by the pressing device 38, and the roll 19 is ground. The grinding unit 30 rotates the pinion 66 with the oscillating motor 56 and meshes with the rack 68 installed on the tilting frame 60, so that the grinding unit 30 moves along the rail 70 in the width direction of the material 8 to be rolled. Further, the tilt frame 60 is configured to freely rotate around a tilt fulcrum pin 64 installed on the base frame 62. The base frame 62 is provided with a tilting jack 72 and a stabilizer cylinder 74, and determines a rotational position of the tilting frame 60 with respect to the base frame 62. Thereby, the center of the grindstone 36 can be directed to the center of the roll 19 in accordance with the change in the diameter of the roll 19. The roll 19 rotates in the conveying direction of the material 8 to be rolled, and the grindstone 36 rotates in the direction opposite to the roll on the contact surface with the roll 19.

  The entire range of the surface of the roll 19 is ground by tilting, rotating, pressing, and oscillating the online roll grinder 28 having such a structure in accordance with a command from the process computer 92.

  If the depth is 0.5 μm or more per radius of the roll, the occurrence of surface roughness scale wrinkles can be sufficiently suppressed.

  FIG. 8 shows the result of applying grinding of the roll 19 by the on-line roll grinder 28 to the rolling of 250 continuous materials to be rolled, including the thin low-carbon steel whose conditions are shown in Table 1. The horizontal axis represents the number of rolled sheets, and the vertical axis represents the scale thickness and surface roughness index of the F2 roll. Both F2 and F3 were ground once by 40 with the on-line roll grinder 28. As the number of rolls increases, both the thickness of the scale and the surface roughness index increase, but it can be seen that grinding with the online roll grinder 28 decreases both the thickness of the scale and the surface roughness index. By repeating this, a good result was obtained that 250 or more scales were not peeled off from the roll 19 and neither surface roughness scale wrinkles occurred.

  The roll of the hot finish rolling mill is pulled out of the rolling mill every time it is judged that the thickness of the fatigue layer (cracked layer) that has not been scale exfoliation has progressed beyond a certain level. Although the rolls were exchanged, the grinding by the on-line roll grinder 28 was performed at F2 and F3. As a result, even when 250 rolled materials were rolled, the rolls were not exchanged for polished ones.

  The number of rolls of 250 corresponds to about 5000 tons as the weight of the material to be rolled, which is sufficiently large compared to the conventional limit of about 100 and about 2000 tons where grinding by the on-line roll grinder 28 was not performed. Converted to the length at the F7 outlet side, the rolling length is 1730 m (243 m for F2) per one rolled material, and the type of the F7 outlet side with a thickness of less than 2 mm (refer to Table 2) The condition is 1.2 mm), and as many as 250 can be rolled, but the length on the F7 outlet side of one rolled material including other than the thin material is actually 1000 m on average. Below. The inventors have verified that 350 rolls do not have to be replaced with polished ones. There is also a possibility that the rolling can be continued without replacing the roll (250 × 1730 ÷ 1000 = 425) with a polished one.

  However, the effect exerted by the online roll grinder 28 is actually more than that, and if the fatigue layer grinding described later is performed, the roll does not need to be substantially replaced with a ground one. Details of this will be described later.

  For the rough rolling mills (R1, R2, R3) and hot finish rolling mills (F1, F4), the online roll grinder 28 is not installed, but the surface roughness index is less than 1, and the scale delamination occurs. There wasn't. For the hot finish rolling mills (F5, F6, F7), an online roll grinder 28 was installed and used for the purpose of eliminating and flattening the wear level difference on the roll surface.

  Here, the case of grinding once per 40 is shown, but for this grinding pattern, the surface roughness index may be less than 1, and the grinding timing (every other or constant grinding during rolling) Needless to say, the grinding amount (whether the roll surface scale is completely removed or left) can be appropriately adjusted depending on various conditions.

  In the online roll grinder 28 that is currently in practical use mainly in the rear three stands of the hot finish rolling mill row 18, not only the scale of the roll surface layer but also the uncut plates at both ends of the roll body length. About the part, it is necessary to grind the whole roll material, and it is necessary to make the specification that the grinding volume per unit time (grinding ability) of the roll can be exhibited at 10 to 20 cc / min. Per unit time with one grindstone 36 Since the grinding volume of 6 to 8 cc / min, it was necessary to use two or more grindstones 36 and therefore two or more grinding units 30 for each of the upper and lower rolls 19.

  On the other hand, according to the evaluation method of the present invention, the on-line roll grinder 28 installed in F2 and F3 does not have to be ground and removed together with the roll dough. The grinding volume per unit time may be about 1 to 3 cc / min, and the grindstone and grinding unit should be at least up and down from the viewpoint of suppressing the occurrence of surface roughness scale wrinkles. Each roll 19 can have one grindstone and a grinding unit.

  The on-line roll grinder is retracted from the roll in order to prevent the impact from being transmitted and broken when the tip of the material to be rolled 8 bites into the roll and when the tail end slips out. The roll is ground during the rolling time of the rolled material 8 in that roll (referred to as in-bar grinding) or the interval (after the tail end of the preceding rolled material has passed through the rolling mill, The roll is ground (called inter-bar grinding) during the non-rolling time period until the tip bites into the rolling mill. However, if there is only one grinding unit for grinding between the bars, it takes too much time and the production efficiency is lowered. Therefore, it is better to aim for in-bar grinding as much as possible. The time from when the roll bites the tip of the material to be rolled 8 until the tail end slips out, although there is a difference of up to several seconds at each stand in the hot finish rolling mill row 18, on average, It is inside and outside for 60 seconds per material to be rolled. However, if the product thickness is thick or the material to be rolled itself is short, it may be as short as 30 seconds inside or outside, and if the product thickness is thin or the material to be rolled itself is long, it may be as long as 120 seconds inside or outside. During this time, it is preferable that the entire roll surface can be ground. If the time given to grind the entire roll surface is 60 seconds, 3.14 × roll diameter 0.8 m × roll barrel length 2.2 m × grinding depth 0.5 μm = 2.76 cc. It can be understood from the calculation that it is in the range of ˜3 cc / min.

  What is the material to be rolled in which the time from when the roll bites the tip of the material to be rolled 8 to the tail end is only 30 seconds or less, the product thickness is thick, or the material to be rolled itself is short? If the book continues, there is a possibility that it will be impossible to grind the worst in the bar, but in such a case it is rare, even if such a case is encountered, by extending the interval and performing inter-bar grinding, the production efficiency will be There are ways to continue operation, albeit a little. As a method that does not reduce the production efficiency, there is a method that uses continuous hot rolling described at the end of the winding.

  In the above example, the example in which the grinding unit installs one on-line roll grinder 28 on each of the upper and lower rolls in the hot finishing rolling mills F2 and F3 is shown, but for the purpose of suppressing the occurrence of surface roughness scale wrinkles. The on-line roll grinder 28 may be installed in another rolling mill in the rough rolling mill row 12 or the hot finish rolling mill row 18, and how many grinding units are installed in each of the upper and lower rolls is a rolling condition. Needless to say, it may be determined as appropriate according to the required grinding ability (from the shortest rolling time on the product mix, the longest time allowable as an interval, the depth to be ground, etc.). In particular, when it is desired to shorten the time required for grinding as much as possible, increasing the number of grinding units does not hinder this.

  However, even when two or more grindstones and grinding units are used, the number of installed on-line roll grinders 28 can be minimized by using the evaluation method as in the present invention, and the equipment cost can be suppressed. Besides, unnecessary wear of the grindstone 36 can be suppressed and the running cost can be minimized by the evaluation method as in the present invention.

  From the above, the following can be said.

From the viewpoint of improving the quality of the product by suppressing the occurrence of the first condition, that is, the occurrence of surface roughness scale wrinkles, as can be seen from the results in Table 3, in the hot finish rolling mill row 18,
F2>F3>F1> F4
Since the rough surface scale flaws are likely to occur in this order, the installation priority order of the online roll grinder 28 is also the same order.

Therefore, in addition to the last 3 stands of the hot finish rolling mill that has been equipped with the online roll grinder 28,
(1) It can be said that it is preferable to equip one or more stands with an online roll grinder, and
(2) Preferably, the second stand F2 and the third stand F3 are provided with an online roll grinder,
(3) Considering that surface roughness scale wrinkles may occur even in the fourth stand F4, the fourth stand F4 is also included (in the case of a hot finishing rolling mill consisting of 6 stands, it is included in the final 3 stands. Therefore, it is also preferable to provide an online roll grinder in all the stands after the second stand F2.
(4) On the other hand, in the present invention, in consideration of the fact that surface roughness scale wrinkles may occur even in the first stand F1, as shown in FIG. 10, all including the first stand F1. The stand is equipped with an online roll grinder. And the following can be said.
(5) Depending on whether it is only necessary to grind the scale of the roll surface layer, or whether it is necessary to grind the entire roll material, only one grinding unit or two or more grinding units are required. In view of whether or not there is, it is preferable that the number of grinding units of the on-line roll grinder is different depending on the stand. This is the same in both cases (1) to (4).

(Condition (2) -1: Increase in operating rate and production efficiency by suppressing the occurrence of slip between the roll and the tip of the material to be rolled)
The occurrence of slip between the roll and the tip of the material to be rolled can occur in any of the stands in the case of the hot finish rolling mill row 18. However, since it is not a property that frequently occurs, the effect on the operation rate is not so large, and it accounts for only 0.04% of 2.24% shown as misroll in FIG. . When it is corrected for each stand of F1, F2, F3, and F4, it becomes 0.01%, and in the rough rolling mill, the slip between the roll and the tip of the material to be rolled hardly occurs.

  Nevertheless, once a slip occurs between the roll and the tip of the material to be rolled, the operation of the hot rolling line (hot rolling mill row) is stopped for a long time of about 1 hr or more. It is meaningful to suppress the occurrence.

  In order to improve this situation, one of the F1, F2, F3, and F4 stands, or two or more stands, is provided with an online roll grinder 28, the surface of the roll 19 is ground, It is preferable to prevent slip from occurring between the rolling material and the tip. The example of the reference form is demonstrated below.

(First reference form)
Considering a hot rolling line (hot rolling mill row) 100 as shown in FIG. 34, a roll 19 of at least one of the front stands F1, F2, F3 of the finish rolling mill 18 during the rolling cycle. When a magnetite (Fe ₃ O ₄ ) called black skin is formed on the surface layer of the material, and the thickness becomes more than a certain level, the coefficient of friction between the tip of the material 8 to be rolled and the surface of the roll 19 decreases. The tip of the material 8 to be rolled and the surface of the roll 19 are likely to slip. It is difficult to actually measure the coefficient of friction. For this reason, when it is determined that the friction coefficient is indirectly reduced from other conditions, the tip of the material to be rolled 8 is easy to bite into the roll 19, so that the material to be rolled 8 is immediately before rolling. The roll 19 is ground by the online roll grinder 28. Thereby, the friction coefficient between the front-end | tip of the to-be-rolled material 8 and the roll 19 is raised, and it suppresses that the front-end | tip of the to-be-rolled material 8 slips and it is not bitten by the roll 19.

  The friction coefficient between the tip of the material to be rolled 8 and the roll 19 is presumed to depend on the state of formation of the black skin and the degree of generation, but the coefficient of friction between the tip of the material to be rolled 8 and the roll 19 is In order to increase the thickness, it is first considered to completely remove the black skin on the surface of the roll 19 as shown in FIG. 9, and in this case, 0.5 to 10 μm is ground per radius of the roll 19 (lower limit). 0.5 μm is determined from the condition (1), and the upper limit of 10 μm is determined from FIG.

  However, in practice, in order to achieve the purpose of suppressing the occurrence of slip between the tip of the material to be rolled 8 and the roll 19, the rolling oil supplied at the time of rolling the previous material to be rolled. In order to suppress that the tip of the material to be rolled 8 slips and does not get caught in the roll 19 due to the remaining exhaustion of the combustion, the image is like scraping the remaining rolling oil that has been exhausted by combustion, so that it is boiled slightly. Since only grinding is effective, it is preferable to grind 0.5 to 1.5 μm per radius of the roll 19.

  Here, the rolling cycle described above is usually 60 to 60 after the roll replacement in which the freshly ground roll 19 is incorporated in all the stands of the hot finish rolling mill 18 before the development and practical use of the online roll grinder 28. This was related to the fact that after rolling about 120 rolls 8, the rolls were changed and operated so that the next freshly-rolled roll 19 was incorporated in all the stands of the hot finish rolling mill row 18. As shown in FIG. 36, which is a concept, a freshly ground roll 19 is incorporated into all the stands of the hot finishing mill row 18 and then another freshly ground roll 19 is heated. A structure in which a group of rolled material 8 of about 60 to 120 is rolled in order of rolling until it is incorporated into all the stands of the intermediate finishing mill row 18, in other words, from one roll exchange to the next roll exchange. Is that of the unit.

  It is difficult to actually measure the coefficient of friction. However, according to the study by the inventors, when the material 8 to be rolled intermittently exceeds 15 pieces, in the front stage stand of the hot finishing rolling mill row 18, It has been confirmed that there is a possibility of slipping because the friction coefficient between the tips of the material to be rolled 8 becomes low.

  This number of 15 is found as a result of verification in the rolling cycle of high carbon steel, so when rolling a softer material to be rolled, it is considered that it will be a larger number, In this case, the present invention can also be applied to a case where other types of materials to be rolled are rolled by finding out the critical numbers for slipping as described above in experiments. In the above-described case, the roll 19 of the preceding stage is placed on the on-line roll grinder 28 immediately after rolling of the 16th workpiece 8 after the freshly ground roll 19 is incorporated into all the stands of the hot finish rolling mill row 18. Grind with.

  That is, in the present embodiment, the roll end of the next material to be rolled and the surface of the roll 19 are obtained by rolling a predetermined number of 15 material from the start of use of the roll or from the previous grinding. It is determined that the coefficient of friction between and has decreased to a value that may cause slipping.

  Here, the grinding for suppressing the slip of the surface of the roll 19 is performed on the entire surface of the roll 19 including only the passing plate portion of the material to be rolled 8 or the non-passing portion of the material to be rolled 8 among the surface of the roll 19. Any of them may be ground. Alternatively, a method of grinding such as grinding a region straddling the passing plate portion or the non-passing plate portion of the material to be rolled 8 is conceivable, but anyway, it is surely between the surface of the roll 19 and the tip of the material to be rolled 8. Any grinding method may be used as long as slip can be suppressed.

  Once grinding is carried out immediately before the rolling of the 16th rolled material 8, the grinding is performed after rolling the 15 rolled material 8, that is, immediately before rolling of the 31st rolled material 8. After that, grinding is performed just before the 46th, just before the 61st, and so on.

  When rolling another type of material to be rolled, assuming that the critical number to slip obtained by experimentation is N, the rolling of the (N + 1) th material to be rolled is assumed. Grinding may be performed immediately before, immediately before the (2N + 1) th, immediately before the (3N + 1) th, and so on.

  In the above example, the case where the grinding is performed every time the 15 workpieces 8 are rolled is described with respect to the front stage of the hot finish rolling mill row 18, that is, from F1 to F3. The invention is not limited to this. For example, when the on-line roll grinder 28 is installed only in F1 according to the actual situation of each company, it is only necessary to grind F15 every 15 pieces, and it is not a hot finish rolling mill row 18 but a rough rolling mill. In some cases, an online roll grinder 28 is installed in the row 12, or an online roll grinder 28 is installed in a part of or all of the stand of the preceding stage of the hot finish rolling mill row 18 and the rough rolling mill row 12. The grinding may be performed each time a predetermined number of the rolled materials 8 are rolled.

  In addition, since the temperature of the material to be rolled is different for each stand in each of the rough rolling mill row and the hot finish rolling mill row or both, the degree of black skin generation is also different. Different values may be used for the machine train and the hot finish rolling mill train or for each stand.

  Further, since the length of one material to be rolled varies from company to company, grinding is not limited to 15 and may be performed each time an appropriate number of rolls are rolled in accordance with the actual situation of each company. In other words, the predetermined number varies depending on the conditions of the material to be rolled, the conditions of the rolling equipment, and the like.

  Next, the second reference embodiment will be described.

(Second reference form)
When it is determined that the material of the material to be rolled 8 to be rolled next is particularly hard among high carbon steels for a specific rolling mill when the configuration is the same as the first reference embodiment. The roll 19 is ground by the online roll grinder 28 immediately before rolling the material 8 to be rolled by the roll 19 (in the case of a roll of a rough rolling mill, the roll 13; hereinafter, representatively referred to as roll 19). The black skin on the surface of 19 is partially ground to increase the coefficient of friction between the tip of the material 8 to be rolled and the surface of the roll 19. As a result, the tip of the material 8 to be rolled is prevented from slipping and being caught in the roll 19.

  That is, instead of performing grinding each time the 15 rolled materials 8 are rolled, or in combination, the roll 19 is rolled to the online roll grinder 28 immediately before rolling the rolled material 8 having a hard material. It is the same as that of the 1st reference form except the point made to grind with.

  For the material to be rolled 8 having a hard material, some index indicating that the material is hard is, for example, data associated with each material to be rolled 8 at the rolling instruction group stage, for example, a business computer in a reference example described later. It is given in a computer such as 94. As an example, it is easy to set some index indicating the hardness as a command value of the tensile strength at room temperature, but it is not limited to this. For example, Brinell, Rockwell, Vickers, Shore various hardness indicators, or others may of course be used. The hardness at high temperature and the tensile strength at room temperature are different in value, but since there is a correlation between hardness and softness, this is sufficient for practical use.

(Reference examples through first and second reference forms)
Hereinafter, the case where the present invention is applied to the hot rolling line (hot rolling mill row) 300 shown in FIG. 10 will be described as an example.

  A rolling cycle is created by an operator operation using the business computer 94. This is transmitted to the process computer 92 through the information transmission route. The process computer 92 stores and recognizes various kinds of data including the material of the material 8 to be rolled, the thickness of the material to be rolled on the exit side of each stand of the roughing mill 12 and the finishing mill 18 and the width of the material to be rolled. ing.

  On the basis of these data, from the process computer 92 to the control device 50, for which online roll grinder 28 of which stand (rolling mill), immediately before rolling which material 8 to be rolled, which region of the roll 19 is ground. Information on whether to perform is transmitted through the information transmission route.

  And in this reference example, when 15 rolled materials were rolled, the friction coefficient between the front-end | tip of the next-rolled material to roll and the said roll surface fell below predetermined, ie, the front-end | tip of a rolled material When the tensile strength (command value) of the material to be rolled is 550 MPa or more, the index (tensile strength) correlated with the hardness of the material to be rolled is not less than a predetermined value. If the program is incorporated into the process computer 92 so that one of the above determinations is satisfied, the roll 19 of the target rolling mill is ground by the online roll grinder 28 before rolling the next material to be rolled. Control to do.

  FIG. 10 shows an example in which an online roll grinder 28 is installed and ground on all the stands F1 to F7 of the hot finish rolling mill row 18.

  Here, since grinding requires a longer time than the inside and outside of the normal F1 interval of 40 seconds, the F1 interval is set to be extended to about 70 seconds as shown in FIG. is there.

  As described above, as a result of grinding by the online roll grinder 28, no slip occurred between the tip of the material 8 to be rolled and the surface of the roll 19. In FIG. 11 and FIG. 12 to be described next, illustration of the 50th and subsequent lines is omitted.

  By the way, FIG. 12 shows a configuration in the order of the number of rolled materials for the rolled material thickness, the rolled material width, the rolled material length, and the tensile strength (command value) of the rolled material 8 at this time.

  In FIG. 11, the interval is lengthened immediately before the 49th piece, because grinding is also performed here. This is because the tensile strength (command value) of the 49th workpiece is 550 MPa. This is because it was higher than other rolled materials. In this reference example, when a rolled material having a tensile strength (command value) of 550 MPa or more is subsequently rolled, as described above, the index (tensile strength) correlated with the hardness of the rolled material is a predetermined value or more. The F1, F2, and F3 online roll grinders are programmed to carry out grinding immediately before it is determined that the material is to be rolled.

  Table 6 shows information about the material to be rolled and the like in this reference example.

  Here, in the above-mentioned reference form, it is determined whether or not the friction coefficient has decreased to such an extent that slip occurs due to the number of rolls, but the present invention is not limited to this. For example, when paying attention to a specific rolling mill, the interval for the rolling mill (the time from the tail end of the preceding rolled material 8 slipping out until the leading edge of the next rolled material 8 is bitten) However, even when the scheduled time is exceeded, the friction coefficient between the tip of the material to be rolled 8 and the surface of the roll 19 is reduced, and slip is likely to occur between the tip of the material to be rolled 8 and the roll 19. Is empirically known. Therefore, when the interval for the rolling mill exceeds the scheduled time, it is determined that the friction coefficient has decreased to such an extent that slip occurs, and the online roll grinder 28 is immediately before rolling the next material to be rolled. Thus, the surface of the roll 19 may be ground.

  In the above description, the grinding is performed automatically. However, the present invention is not limited to this. Since the interval is predicted to exceed the predetermined time, when it is determined that the roll grinding time by the online roll grinder 28 can be ensured, the operator determines that the material to be rolled 8 is extracted from the heating furnace 10 by human judgment. A structure that allows a scheduled input of grinding instructions to the on-line roll grinder 28 by pressing a button, etc., and after the material 8 to be rolled is extracted from the heating furnace 10, the conveyance of the material 8 is temporarily stopped by pressing an operator button, etc. In addition, it is possible to use a mechanism that allows a grind instruction to be input to the online roll grinder 28, or these mechanisms may be provided together with a mechanism that automatically performs grinding. The predetermined time may be 90 seconds or 120 seconds, or may be recognized as a constant by an automatic system or a human system.

  Furthermore, in the above description, an example was shown in which the roll 19 of the hot finish rolling mill 18 at the start of the hot rolling operation was a freshly polished roll, but the hot finish rolling at the start of the hot rolling operation was performed. Even if the roll 19 of the machine row 18 is a reuse roll used at another rolling opportunity, the grinding timing may be adjusted by a command from the business computer 94 or the process computer 92 or by the operator's judgment. Moreover, in order to ensure the roll grinding time by the online roll grinder 28, it may be adjusted so as to extend the interval according to the judgment of the operator.

  Further, in the above description, the case where the online roll grinder 28 is provided in all the stands of the front stage stands (F1, F2, F3) in the hot finish rolling mill row 18 has been described as an example. Not only that, but the provision of the on-line roll grinder 28 in any one of the preceding stands (F1, F2, F3) of the hot finish rolling mill row 18 has the effect of suppressing the occurrence of slip. There is no doubt that the rolling mills other than the preceding stage stand, for example, one or more stands of the roughing mill row 12 and the on-line stand provided in the rear stage stand of the hot finishing rolling mill row 18 are provided. It goes without saying that the same effect can be obtained even with the roll grinder 28.

  In the above description, whether or not grinding is performed is determined by determining whether or not the index correlated with the hardness of the material to be rolled is greater than or equal to a predetermined value based on the command value of tensile strength. It is not limited to this.

  Based on the surface state of the actual roll 19 observed with a CCD camera or the like, it is determined whether or not the friction coefficient is less than a predetermined value, and whether or not grinding is performed is determined. By determining whether or not the index correlated with the hardness of the material to be rolled is equal to or greater than a predetermined value at the measured temperature at the tip of the rolled material 8, it is difficult to bite the material to be rolled 19 into the roll 19. It is considered that automatic determination and determination of whether or not grinding is performed is a means that can avoid a biting failure (slip) at the tip of the material 8 to be rolled with higher accuracy. Of course it is good.

  From the above, the following can be said.

From the viewpoint of improving the operation rate and the production efficiency by suppressing the occurrence of slip between the second condition, that is, the roll and the tip of the material to be rolled, In addition to the final 3 stands of the finishing mill,
(1) It can be said that it is preferable to equip one or more stands with an online roll grinder, and
(2) The second stand F2 and the third stand F3 may include an online roll grinder.
(3) Including the fourth stand F4 (in the case of a finishing mill consisting of six stands, since it is included in the final three stands, it will be provided as a result), in all the stands after the second stand F2, It is also preferred to provide an online roll grinder.
(4) In contrast, in the present invention, all the stands including the first stand F1 are provided with an online roll grinder.
And the following can be said. In order to suppress the occurrence of slip, the same idea as to whether it is necessary to grind even the scale of the roll surface layer, or whether it is necessary to grind the roll dough, how much depth should be ground? If it is verified whether it is good or not, it should be understood that whether it is necessary to have only one grinding unit or two or more grinding units.
(5) It is also preferable that the number of grinding units of the on-line roll grinder varies depending on the stand. This is the same in both cases (1) to (4).

(Condition of (2) -2: Improvement of operation rate and production efficiency by reducing roll replacement frequency)
In order to eliminate the need for roll replacement as much as possible in order to increase the operation rate, it is required that the deviation of the actual grinding depth with respect to the target grinding depth is small, that is, the grinding accuracy is high. For this purpose, it is effective to take measures as described below.

第３に、押付装置が油圧シリンダの場合、油圧シリンダのシールを樹脂製とすると共に回転装置と砥石をつなぐ連結軸のスプラインをボールスプラインとすること、
第４に、第３の施策における油圧シリンダの油圧配管のヘッド側に油だまり、ロッド側にアキュムレータを設置すること、
第５に、第１及至第４の施策のうちのいずれか１つ以上の形態を用いて、ロールの胴長方向に複数設置されたオンラインロールグラインダを用いて、隣り合う研削ユニットのロール胴長方向研削範囲のラップ量を５〜１０ｍｍとすること、である。 The measure is to first install a position sensor that measures the amount of movement of the pressing device,
Secondly, the mechanical resistance in the pressing direction of the pressing device is within the range of the following formula,

Third, when the pressing device is a hydraulic cylinder, the seal of the hydraulic cylinder is made of resin, and the spline of the connecting shaft that connects the rotating device and the grindstone is a ball spline.
Fourth, oil accumulation on the head side of the hydraulic piping of the hydraulic cylinder in the third measure, and installation of an accumulator on the rod side,
Fifth, using any one or more of the first to fourth measures, using a plurality of on-line roll grinders installed in the roll length direction, the roll length of adjacent grinding units The amount of lap in the directional grinding range is 5 to 10 mm.

  In the case of the fifth measure, it is premised that there are a plurality of grinding units. However, the cases of the third and fourth measures are particularly preferably adapted when there are a plurality of grinding units.

  Here, the mechanical resistance means a sliding resistance between the rod 38R of the hydraulic cylinder and the seal 54 in the case where the pressing device 38 is a hydraulic cylinder, and a vane in the case of a hydraulic motor or a stepping motor. It means the friction between the casing and the friction of the bearing between the motor shaft and the casing. In any case, it includes the sliding resistance of the spline 44, etc. Use for cases.

  These measures can suppress the occurrence of defects in which the thickness of the product metal strip after rolling is not flat in the width direction, so the frequency of roll replacement can be significantly reduced, and the hot rolling line (hot rolling mill line) operates. The rate goes up. The reason will be described below.

(First measure)
FIG. 13 is a diagram showing a comparison between a grinding amount set by a conventional online roll grinder and an actual grinding amount evaluated by measuring a roll diameter before and after grinding. There may be a difference of about ± 30% between the setting and the actual results, 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 (hot rolling mill) 300 or the like targeted by the inventors, the grinding amount (grinding depth) for one roll ) Is about 50 μm at the maximum, and in this case, an error in the grinding amount of about 15 μm (50 μm × 0.3) may occur. 14A and 14B, the difference in grinding amount between the two grinding units is 30 μm (15 μm × 2) at the maximum, assuming that the actual error with respect to the setting is ± 30%. It can be seen that the step profile can be easily generated.

  FIG. 15 shows the cause of the error in the lap amount at the center in the roll cylinder length direction during grinding by the two grinding units shown in FIG. It has been described that two grinding units grind one side at the center of the roll drum length direction, but the bottom (d) of FIG. As shown in FIG. 2, the grinding range of the two grinding units 30 is lapped by a lapping amount L (about 20 mm) which is about half of the grinding wheel and roll contact width.

  Before grinding, as shown in the uppermost figure (a) of FIG. 15, the on-line roll grinder 28 is at the end of the roll cylinder length direction (left end in the figure), and the pressing device (not shown) is in a retracted state. is there.

  The situation at the start of grinding will be described. As shown in the second drawing (b) from the top of FIG. 15, one of the grinding units 30 that is separated from the roll 19 by a certain distance G is driven by an oscillating motor 56 (see FIG. 7) (not shown). In order to start grinding from the position in the body length direction of the roll 19 to start grinding while moving in the body length direction of the roll 19, the pressing device moves the roll 19 to the roll 19 side by a grindstone advance command from the process computer 92. Start moving forward.

  As shown in the uppermost figure (a) of FIG. 15, one of the grinding units 30 is advanced to the roll 19 side by the pressing device with the online roll grinder 28 approaching the end of the roll cylinder length direction. In some cases, grinding may be started from the end of the roll body length direction.

  Grinding is started when the control device 90 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 30 advances to the roll side as shown in the third figure (c) from the top of FIG. To start. In many cases, the time difference from the start of advancement to contact is different from that of the other grinding unit 30. As a result, a step S at the lap portion as shown in FIG.

  The step S of the lapping portion as shown in FIG. 14A is when the grinding unit 30 in the standby state requires a shorter time from the start of advancement to the contact than the grinding unit 30 in the grinding state. Occur.

  On the other hand, the profile as shown in FIG. 14B has a desired value for the time from the start of advancement to the roll side until the contact between the grinding unit 30 in the grinding state and the grinding unit 30 in the standby state for some reason. 14C, the profile as shown in FIG. 14C shows that the grinding unit 30 in the grinding state and the grinding unit 30 in the standby state start to advance toward the roll 19 for some reason. It shows the case where the time from contact to contact is longer than the desired value and grinding is insufficient. In such a case, an error from the desired value is likely to occur in the center of the roll body length direction in the two grinding units, so that an error from a desired value is likely to occur. A convex step S is likely to occur at the center.

  In FIG. 14A, the thickness is changed by 11 μm from the width central portion. In FIG.14 (b), the thickness reduction part is seen by the width end part. In FIG.14 (c), the thickness reduction part of 7 micrometers is seen in 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. 14 only shows the plate 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 entire length of these defective portions must be cut off. It is.

  Thus, in the past, steps as shown in FIGS. 14 (a), 14 (b), and 14 (c) may occur, but a position sensor that measures the amount of movement of the pressing device is installed (the pressing device is In the case of the hydraulic cylinder 38, the step as shown in FIG. 14A can be suppressed at least by the position sensor 76 shown in FIG.

  According to the timer value, it is inevitable that a time variation occurs in the contact from the forward command to the roll 19. However, in this respect, the output of the position sensor 76 indicates that the grindstone 36 is in a state where the pressing device is in the backward limit. If a mechanical distance from the grinding surface to the surface of the roll 19 (geometrically known from the dimensional relationship with the peripheral equipment when incorporated in the rolling mill by measuring the diameter of the roll 19), This is because if the advancement of the grindstone 36 is stopped, it is difficult to make a difference between the two grinding units 30 in the grinding depth. The mechanical distance from the grinding surface of the grindstone 36 to the surface of the roll 19 is determined by detecting the load from the advance command of one of the plural grinding units (the output of the hydraulic pressure sensor PT indicates that a certain load threshold has been exceeded). The amount of movement viewed from the change in the output of the position sensor 76 until it is detected) is stored in the control device 90, and only the amount of movement after the other grinding unit 30 receives the forward command. It can also be operated such that the grindstone 36 comes into contact with the roll 19 when it moves forward.

  In addition, if the position sensor 76 is installed, the initial crown of the target roll 19 (when assuming that the roll is cut with a virtual cross section passing through the central axis, a concave or convex shape of 100 μm to 300 μm per radius is assumed. The displacement in the pressing direction of the pressing device 38 is controlled so that the curve follows a roll body length of 1500 to 2600 mm and a profile is formed so as to draw a curved shape such as a sine curve or an arc curve. Therefore, the on-line roll grinder 28 can be ground to form an initial crown on the roll 19.

  However, even if the position sensor 76 is used for control, the step as shown in FIGS. 14B and 14C is suppressed if the absolute pushing speed of the pressing device is faster or slower than a desired value. Problems that still occur without a problem remain. The inventors considered how to suppress this. This is described below.

(Second and third measures)
FIG. 16 shows the structure of the grinding unit of the on-line roll grinder of the present invention that can 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 38 that has been conventionally made of rubber is a resin-made seal 54P. Further, the connecting shaft 42 that connects the rotating device 40 and the grindstone 36 has a spline shape, but between the shaft on the rotating device 40 side and the spline groove of the shaft on the grindstone 36 side, A ball spline 44B is provided in which steel balls that roll when the distance between them changes.

  The inventors have found that the grinding error is remarkably reduced by reducing the mechanical resistance in the pressing direction of the rotating device 40 and the pressing device 38 from the conventional online roll grinder so as to satisfy the following formula.

  A mechanism for improving the grinding accuracy by reducing the mechanical resistance will be described below with reference to FIG. As described above, the pressing of the grindstone 36 to the roll 19 is performed by the hydraulic cylinder 38 which is a pressing device. However, the pressing force Fr to the roll 19 is determined by the rotation of the rotating device and the pressing device from the output F of the hydraulic cylinder. The value is obtained by subtracting the mechanical resistance Fμ in the direction, and when the mechanical resistance varies, the pressing force Fr to the roll 19 also varies.

  Further, the direction of the mechanical resistance varies depending on whether the hydraulic cylinder is moved forward (a) or moved backward (b), and the pressing force of the grindstone 36 against the roll 19 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 Can easily be understood from the fact that the resistance is added so that it is pushed back. When the hydraulic cylinder 38 is pressed in the forward direction, the value obtained by subtracting the mechanical resistance Fμ is the pressing force Fr to the roll 19, When pressing in the backward direction (returned), the value obtained by adding the mechanical resistance Fμ is the pressing force Fr to the roll 19.

  The above formula suppresses the mechanical resistance in the pressing direction of the pressing device to a certain level in order to keep the thickness error of the material to be rolled on the exit side of the F7 stand, which is the final rolling mill of the hot finish rolling mill, below the allowable value. 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 at the hot finish rolling mill exit side, the larger the The smaller the ratio of the maximum grinding depth of the roll and the roll surface layer level transferred to the thickness of the rolled material on the exit side of the F7 stand that is the final rolling mill of the finishing mill, the smaller the rolling mill in question. .

  This transfer ratio η takes a value for each rolling mill of the hot finish rolling 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.

  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 hot finish rolling mills F4 to F7 in which an online roll grinder is installed in this example, Fn = 900N, ΔHcrit = 0.000005 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 was improved somewhat, but it was 500 N, and the effect was insufficient. Eventually, the seal was a resin seal and the spline was a ball spline, so that the mechanical resistance was 250 N, which was equal to or less than the 298 N determined above, and the above formula was satisfied.

(Fourth measure)
FIG. 19 shows a hydraulic piping diagram around the hydraulic cylinder 38 of the online roll grinder of the present invention. The pressure on the head side of the hydraulic cylinder 38 supplied from the pressure line 80 is controlled by the proportional pressure reducing valve 81, and the pressure on the rod side of the hydraulic cylinder 38 also supplied from the pressure line 80 is controlled by the pressure reducing valve 82. Is done. In addition, both the head side and the rod side have a relief valve 83 so that an abnormally high pressure will not occur when compressed in a state where oil is contained in the piping. When the pressure exceeds the set pressure, oil is released to a tank (not shown) through the relief valve 83 and the tank line 84 to reduce the pressure. The set pressure of the relief valve 83 is set to be 10 to 15% higher than the set pressure of the proportional pressure reducing valve 81 and the pressure reducing valve 82 on both the head side and the rod side so that the relief valve 83 is not always operated. In FIG. 19, 85 is a hydraulic pressure sensor (PT).

  A difference is that the oil reservoir 86 having a capacity of 10 L is installed on the head side of the hydraulic cylinder 38 and the accumulator 87 having a capacity of 5 L is installed on the rod side.

  In the hydraulic cylinder, even if the pressure on the head side is set to the target pressure, when the grindstone 36 is pushed back from the roll 19, the oil in the pipe is compressed and the internal pressure rises. As shown in FIG. 19, a relief valve 83 is provided to prevent the internal pressure in the pipe from increasing, but the set pressure of the relief valve 83 is 10 to 15% larger than the set pressure of the proportional pressure reducing valve 81. If the pressure is between the set pressure of the proportional pressure reducing valve 81 and the set pressure of the relief valve 83, the pressure will increase. On the rod side, the value at the time of pressing is used to suppress vibration of the grindstone 36 during grinding, but the rod side is also used with a pressure of about 2.4 MPa, and the hydraulic cylinder 38 moves forward. At the same time, the oil in the pipe is compressed on the rod side as well as the head side, and the pressure fluctuates within the range of the set pressure of the relief valve 83.

When the head side diameter of the hydraulic cylinder 38 is 0.032 m, the rod side diameter is 0.025 m, the set pressure of the pressure reducing valve 82 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 pressure setting of the pressure reducing valve 81 is 2.1 MPa (2.4 × 10 ⁶ × π / 4 × (0.032 ² −0.025 ² ) +900) / (π / 4 × 0.032 ² )), relief valve The set pressure of 83 is 2.4 MPa (2.1 × 1.15) on the head side and 2.8 MPa on the rod side, and each set pressure of the proportional pressure reducing valve 81 and the pressure reducing valve 82 is 0.3 to 0.4 MPa. large. When the pressure fluctuation of 0.3 to 0.4 MPa is converted into the pressing force Fr of the roll 19 of the grindstone 36, the maximum is 322 N (0.4 × 10 ⁶ × π / 4 × 0.032 ² ), which is the mechanical resistance described above. Since it is equivalent to the target value 298N, 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 36 by the roll 19 if it is on the head side, and if it is on the rod side, the cause is a hindrance by the mechanical resistance Fμ against the advance of the hydraulic cylinder 38. As shown in FIG. 19, the inventors have conceived of installing an oil reservoir 86 and an accumulator 87 that absorb the pressure increase caused by the compression of the oil in the pipe due to such a phenomenon. On the head side, the amount of pushing back of the grindstone 36 by the roll 19 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 performance at all, the volume elastic modulus of the oil is 650 MPa, the pipe volume is 0.7 m ³ , and the volume to be pushed back is 8 × 10 ^−7. m ³ (0.001 × π / 4 × 0.032 ² ) and 10 L ((650 × 10 ⁶ × 8 × 10 ⁻⁷ /(0.05×10 ⁶ ) −0.7) × 1000) Become. 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.

(5th measure)
FIG. 20 shows the maximum of 1000 products with a step amount S (similar to that shown in FIG. 14A) at the center of the product thickness after mechanical resistance reduction and hydraulic system improvement of the present invention. The value 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.14 (b) was also eradicated simultaneously.

  Here, 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. 21 shows the width direction distribution of the product thickness after the first to fourth measures are taken. It can be seen that a range of 20 mm corresponding to the lap portion at the center of the width becomes a step S and is thick.

  FIG. 22 is a graph showing variations in time from a grindstone advance command to roll contact measured (a) before mechanical resistance reduction and hydraulic system improvement of the present invention, and (b) mechanical resistance reduction and hydraulic system improvement of the present invention. It is the figure shown by comparing each other.

  (A) Before the mechanical resistance reduction and hydraulic system improvement of the present invention, the displacement of the grinding position in the roll body length direction is 17 mm (120 mm / second) because the moving speed in the roll body length direction by the oscillating device is about 120 mm / second. × 0.14 seconds), the error of the lap amount at the center in the roll drum length direction is the sum of the errors of the two grinding units. Therefore, about 34 mm is easily generated, and it is easy with the lap amount of about 20 mm. Left unground parts. 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.

  However, (b) after the mechanical resistance reduction and the hydraulic system improvement of the present invention, the mechanical resistance reduction and the hydraulic system improvement reduced the variation in the forward speed of the grindstone, and the position sensor 76 in the hydraulic cylinder portion of the pressing device. In addition to being able to accurately measure the distance between the roll and the grindstone, the distance between the roll and the grindstone before grinding has been conventionally separated by about 50 mm so that the grindstone does not contact the roll. It can be seen that the variation in time from the grindstone advance command to the roll contact is greatly reduced to [sigma] = 0.02 seconds by making the object close to about 10 mm.

  The error of the lapping amount L shown in FIG. 15 (the width in the roll barrel length direction in the region where the contact width between the grindstone 36 and the roll 19 between one grinding unit 30 and the other grinding unit 30 wraps) is also 4. .9mm, which is a sufficiently small value for the lapping amount of 20mm, but due to the reduced variation, the phenomenon of ungrinding disappeared, but two grinding units reliably grind the lapping part Therefore, it is considered that the roll was shaved too deeply and the center part of the product width became thick.

  FIG. 23 shows the result of an experiment for changing the lap amount performed to solve this problem. In the conventional online roll grinder, the thickness step failure at the center of the product width is eradicated by setting 5 to 10 mm, which was difficult to set due to variations in time from the forward command to the grindstone 36 until it contacts the roll 19. I understood that I could do it. If it was smaller than 5 mm, grinding was insufficient.

  In the above description, the case where there are two grinding units 30 has been described as an example, but even in the case where there are three or more grinding units 30, the occurrence of overgrinding and insufficient grinding can be suppressed by setting each lapping amount to 5 to 10 mm. Needless to say, you can.

  As described above, in order to increase the operating rate, the measures for improving the operating rate and the production efficiency by reducing the replacement frequency of the roll have been described, but it is particularly suitable for the case where there are two or more grinding units, Of the hot finish rolling mills 18, if the actual grinding depth shifts with respect to the target grinding depth, it is likely to be transferred to the material 8 and adversely affect the product thickness quality. It is particularly suitable for the online roll grinder 28 provided in the rear stand.

(About grinding of fatigue layer)
Now, the following will describe the fatigue layer grinding that is suitable for the online roll grinder 28 provided in the rear stand of the hot finish rolling mill 18 or the online roll grinder 28 provided in the front stand. It is a specific method of removing.

  On the surface layer of the roll 19, a fatigue layer due to so-called rolling fatigue is formed due to the influence of the rolling load and the repeated unloading accompanying rotation while receiving the rolling reaction force from the material 8 to be rolled. . In addition to this, the effect of heat input due to contact with the material to be rolled 8 is added, and a heat crack that appears to crack like a tortoise shell is generated on the surface layer of the roll 19, and then the rolling of the material to be rolled continues further. Does not disappear naturally. The turtle-shaped cracks on the surface of the roll 19 are roughly large enough to fit within a circle with a diameter of 3 to 5 mm. Although the outermost layer has a so-called black skin called magnetite layer, when one rolled material is rolled, first, a primary heat crack 19C extending in the depth direction of the roll 19 in FIG. If the rolling of the material to be rolled 8 is further continued, a secondary heat crack 19D is formed in a direction substantially parallel to the surface of the roll 19 in a form of branching from a shallower depth than the tip of the primary heat crack 19C.

  When the rolling of the material 8 to be rolled is further continued, the secondary heat crack 19D develops, the surface layer portion of the roll 19 closer to the surface of the roll 19 than the secondary heat crack 19D peels off, and the profile of the roll 19 Can make ups and downs. Then, when it is transferred to the material to be rolled 8 and the degree thereof becomes severe, it remains even after rolling by the roll 19 of the rear stage stand in the hot finishing rolling mill row 18, and the surface quality of the metal plate product is adversely affected. It may come out.

  Grinding and removing the entire fatigue layer can be said to be a direct measure that eliminates the need for roll replacement as much as possible, leading to improvements in operating rate and production efficiency.

  If the entire fatigue layer is ground and removed, the number of rolls that need to be replaced when the on-line roll grinder 28 is not provided, for example, 80 to 120 rolls are rolled, and then the interval (preceding roll) is finished. Compared to 10-60 seconds during operation compared to 10-60 seconds during operation after the tail end of the material passes through the rolling mill until the tip of the next material to be rolled bites into the rolling mill) It is preferable to extend the inside and outside for 70 to 300 seconds, and to grind and remove the roll together with the fatigue layer at that interval.

  If the fatigue layer is frequently ground and removed, such as every 1 or 5 or so, each time the grinding layer is removed, a new fatigue layer is generated and developed. This is because the basic unit deteriorates, and every time the entire fatigue layer is ground and removed, an interval of 70 to 300 seconds is required, and the production efficiency is lowered.

  FIG. 24 shows the progress of the fatigue layer due to the rolling length. It is estimated that the fatigue layer rapidly develops until the F7 outlet-side conversion rolling length is about 50 km. However, the subsequent progress is 0.32 μm / km and can be sufficiently ground by grinding between bars.

  If the fatigue layer depth is 80 μm per radius of the roll (F7 outlet side equivalent rolling length is about 80 km), the fatigue layer will not be ground and removed, but the fatigue layer will become saturated and the growth rate will be slower. Therefore, it is preferable. Until then, even if the fatigue layer is not ground and removed, the problem that the fatigue layer is chipped off and the roll surface becomes uneven, and the surface quality of the material to be rolled to which it is transferred can be avoided.

  However, the above-mentioned number of 80 μm is considered to depend on the compensation of the ratio of the material of the roll and the hard or soft material in the product mix of the material to be rolled, so it may be appropriately adjusted accordingly. Until a certain fatigue layer depth (because it is difficult to measure the fatigue layer depth during rolling, in practice it depends on the number of rolls per roll or the length of the roll after the roll is replaced with a polished one. Is to grind a part of the black skin for the purpose of suppressing the occurrence of surface roughness scale wrinkles or suppressing the slip when the tip of the material to be rolled bites into the roll. After reaching the layer depth, it is preferable to adjust the grinding depth so as to adjust the fatigue layer depth below the certain fatigue layer depth. The fatigue layer depth is defined as the depth at which the deepest secondary heat crack exists, as shown in FIG.

  Hereinafter, a specific method for grinding and removing the fatigue layer will be described in more detail.

(Grinding ability determination formula)
Assuming now that one roll is taken, an example is shown in the following formula (8) as a model formula representing the grinding ability in consideration of the cumulative rolling load for the roll.

Vg = 9.8 (1 + d · L) · a · P b · Vr c ··· (8)
Vg: Grinding ability (cc / min)
P: Whetstone pressing linear pressure (kN / mm)
Vr: Relative sliding speed (mpm)
(Vr = VR + VG, VR: roll circumferential speed (mpm), VG: grinding wheel circumferential speed (mpm))
a, b, c, d: Grinding ability parameter L: Rolling length (km)
Predetermined value a = 0.0245 as a, b, c, d in this expression
b = 0.692
c = 0.503
d = 0.00750
FIG. 25 shows the relationship between the pressing line pressure and the grinding ability.

  However, the grinding parameters such as a, b, c, and d vary depending on the production type and configuration of dimensions (product mix) of the hot rolling line (hot rolling mill train), the material of the roll 19, and the like. Therefore, the values are not necessarily limited to the above values, but may be obtained by regression so as to match the measured data, and may be adjusted as appropriate.

  In addition, as the cumulative rolling load, it is not always necessary to use the rolling length as in the above example, and as a model expression representing the grinding ability, for example, the following expression (9) different from the above expression (8) A model formula or a completely different model formula may be used.

Vg = 9.8φΣ (L × Pr) ÷ (D × W) · a · P ^b · Vrc ^c (9)
Vg: Grinding ability (cc / min)
L: Rolling length (km)
Pr: Rolling load of material to be rolled (kN)
D: Roll diameter (mm)
W: Rolled material width (mm)
P: Whetstone pressing linear pressure (kN / mm)
Vr: Relative sliding speed (mpm)
(Vr = VR + VG, VR: roll circumferential speed (mpm), VG: grinding wheel circumferential speed (mpm))
φ, a, b, c, d: Grinding ability parameter Σ: Indicates that each material is to be rolled.

By the way, in the above formula (9),
φΣ (L × Pr) ÷ (D × W)
This part is obtained by multiplying the linear pressure obtained by dividing the load Pr received from the material to be rolled by the width W of the material to be rolled by the number of rolling times obtained by dividing the rolling length L of the material to be rolled by the roll diameter D. This is a parameter index indicating how much load is applied to the roll and the rolling load on the roll. Here, the circumference ratio π is included in φ. Cumulative rolling load is obtained by accumulating each material to be rolled with Σ.

  26 shows a plan view of the grindstone 36. The grindstone is composed of, for example, eight pieces and is arranged in a ring shape as a whole, the ring outer diameter is 200 mm, and the inner diameter is 120 mm. If the contact portion between the roll 19 and the grindstone 36 (not shown) is A, the width w of the roll drum length direction of A is determined, and the grindstone in the roll drum length direction per one rotation of the roll 19 is determined. When the amount of movement of the contact portion A between the roller 36 and the roll 19 is also constant at this width w, the phenomenon that the surface layer of the roller 19 is ground is the load generated by the contact pressure between the grindstone 36 and the roller 19 (pressing line pressure). And the number of times the roll 19 rotates and slides in a state where the grindstone 36 and the roll 19 are in contact with each other. Incidentally, a region indicated by A ′ surrounded by a dotted line in the figure indicates a contact portion between the grindstone 36 and the roll 19 after the roll 19 has just made one round.

(Control that changes the line pressure of the online roll grinder grindstone on the roll according to the distribution of the cumulative rolling load in the roll axis direction)
Now, there are materials with various widths in the material to be rolled, and the width direction of the material to be rolled is coincident with the roll body length direction, but there are materials with various widths in the material to be rolled. When viewed on a straight line in the roll body length direction, the vicinity of the center point in the roll body length direction is in contact with all the material to be rolled. Therefore, the inventors have found that the depth of the fatigue layer has a distribution in the roll cylinder length direction, which correlates with the distribution of the cumulative rolling load in the roll cylinder length direction.

  This is reflected in the control for changing the pressing line pressure of the grindstone to the roll according to the distribution of the cumulative rolling load in the roll body length direction. Here, as shown in FIG. 27, the distribution of the cumulative rolling load in the roll body length direction is, for example, when the end surface 19E of the roll 19 is the origin and the roll body length direction is the X axis. As a result of the rolling load being added or not depending on whether or not it is in contact with the material, the rolling load at that position is cumulatively added to a certain position in the X-axis direction to obtain a value. This is a distribution in which values of different points are connected in the X-axis direction. The pressing linear pressure is a value obtained by dividing the load at the time of pressing the grindstone 36 against the roll 19 by the width w in the roll barrel length direction of the contact portion A between the roll 19 and the grindstone 36.

(Control method)
The inventors have found that the depth of the fatigue layer has a stepwise distribution in the roll body length direction, which is proportional to the cumulative rolling load distribution in the roll body length direction.

  Because there are various widths of the material to be rolled, and considering that the width of the material to be rolled varies from one to another, when viewed on a certain roll body length direction straight line on the roll surface, The vicinity of the middle point in the body length direction is in contact with all of the material to be rolled, but as it goes to the end in the roll body length direction, only the material to be rolled in a wider width comes into contact.

(Transient control method when shifting from grinding of a region corresponding to a certain plate path to grinding of a region corresponding to the next plate path)
Then, the transitional control method when shifting from the grinding of the region corresponding to a certain plate path to the grinding of the region corresponding to the next plate path when the method described above is followed will be described below. The conclusion is reached that it is preferable to take the form. Incidentally, the plate path is a region on the roll that comes into contact with the material to be rolled.

  First, as shown in FIG. 28 (a), a plate path B of a material to be rolled which is present near the center point in the roll drum length direction, and the end in the roll drum length direction than the rolled material. Considering the case where the plate path C of another material to be rolled existing near the part is in the positional relationship between the contact portion A of the roll and the grindstone as shown in FIG. Starting from the point when the point p near the center point in the roll drum length direction of the contact portion A hits the plate path B of a material to be rolled that exists near the mid point in the roll drum length direction, the roll has made exactly 1/2 turn. Sometimes, the recognition in the drive control device (not shown) is switched from the cumulative rolling load in the region corresponding to the plate path C to the cumulative rolling load in the region corresponding to the plate path B, and the corresponding grinding ability is exhibited. Recognize that

  Here, the reason why the recognition is switched when the roll has just turned 1/2 is that the influence coefficient between the plate path B and the plate path C is assumed to be 0.5 each, but strictly 1 / Even if it does not make two rounds, there is no particular problem even if it is switched at any timing within the range of 0 to 1 round, and it can be adjusted as appropriate within this range.

  Compared with the region corresponding to the plate path C, the region corresponding to the plate path B exists closer to the center point in the roll body length direction, and therefore the cumulative rolling load is large, as shown in FIG. In view of the relationship, the grinding ability exhibited for the same pressing line pressure is increased, resulting in the result that the roll is ground deeper.

  Therefore, even when the cumulative rolling load in the region corresponding to the plate path C is shifted to the cumulative rolling load in the region corresponding to the plate path B, with the goal that the grinding ability is constant, Since the pressing linear pressure can be calculated back from the relationship shown in FIG. 25, the pressing linear pressure is controlled to be the value.

  Secondly, as shown in FIG. 28 (b), when the boundary of the plate path enters the contact portion A between the roll and the grindstone, there is a certain rolled material that is present near the middle point in the roll drum length direction. A sheet path B of the material, a sheet path E of another material to be rolled that is closer to the end of the roll body length than the material to be rolled, and still another position that is closer to the end of the roll body length direction than that Considering the case where the plate path F of the material to be rolled is in the positional relationship between the contact portion A between the roll and the grindstone as shown in FIG. 28B, the roll body length direction of the contact portion A between the roll and the grindstone. Starting from the time when the point p near the midpoint is on the plate path E of the material to be rolled, the roll E is determined from the cumulative rolling load in the region corresponding to the plate path C when the roll has just made 1/2 turn. The recognition in the control device 90 (not shown) is switched to the cumulative rolling load in the region corresponding to So as to recognize as one that should be exhibited. Then, when the point p near the center point in the roll drum length direction of the contact portion A between the roll and the grindstone is applied to the plate path B of the material to be rolled, The recognition in the control device 90 (not shown) is switched from the cumulative rolling load in the region corresponding to the road E to the cumulative rolling load in the region corresponding to the plate path B, and the grinding ability corresponding to that should be exhibited. To recognize. Even when the boundary of the plate path enters the contact portion A between the roll and the grindstone, the point p near the middle point in the roll drum length direction of the contact portion A between the roll and the grindstone gradually applied to the plate path of the material to be rolled. From the time, when the roll has just made 1/2 turn, the cumulative rolling load in the region corresponding to the previous plate path is changed from the cumulative rolling load in the region corresponding to the next plate path in the controller 90 (not shown). By switching the recognition in, recognize that the grinding ability corresponding to that should be demonstrated. However, even if it is not exactly 1/2 turn, it can be adjusted as appropriate within the range of 0 to 1 turn.

  In the case where the online roll grinder 28 is provided in the second rolling mill second stand F2 of the hot rolling line (hot rolling mill row) 400 as shown in FIG. 29, the roll surface layer is ground by the online roll grinder 28 as an example. A method will be described. Commanded by the control device 90, the online roll grinder 28 moves, and the grindstone 36 moves from the standby position toward the surface of the roll 19. When the grindstone 36 reaches a predetermined position before reaching the surface of the roll 19, the rotating device 40 that rotates the grindstone is driven and the grindstone 36 starts to rotate. Subsequently, the grindstone 36 is pressed against the surface of the roll 19 by the operation of the pressing device 38, and grinding of the surface layer of the roll 19 by the grindstone 36 starts. The grindstone 36 performs grinding while moving from one end side to the other end side in the body length direction of the roll 19, and after performing grinding of a predetermined amount of grinding ability in accordance with a cumulative rolling load, When is finished, the pressing device 38 operates in the backward direction, and the grindstone 36 moves backward. Thereafter, the grindstone 36 moves to the standby position to prepare for the next grinding.

((3) Improvement of operating rate and production efficiency by reducing roll replacement frequency)
As described above, in order to increase the operating rate, the facility measures and the fatigue layer grinding method for eliminating roll replacement as much as possible have been described. However, how much the operating rate is increased by the present invention will be described hereinafter. .

In the case of the conventional case where the online roll grinder 28 is installed in the last three stands in the hot finishing rolling mill row, out of the breakdown rate of 9.80% obtained by subtracting the operation rate of 90.20% from 100%, 3 Roll replacement (excluding backup roll replacement) accounted for .52%, and misroll accounted for 2.24%. Of 2.24%, 0.04% is due to the occurrence of slip between the roll and the tip of the material to be rolled. In contrast,
(I) When the online roll grinder 28 is installed in one or more stands in addition to the last three stands in the hot finish rolling mill row, the stopping rate decreases by 0.01% per stand, and the operating rate is 1 Increases by 0.01% per stand.
(II) When the on-line roll grinder 28 is installed on the stand including F2 and F3, in addition to the above-mentioned 0.01% for each stand, the contribution of increasing the rolling cycle by suppressing the occurrence of surface roughness scale wrinkles 0.5 As a result of adding%, the roll replacement frequency is reduced and the operating rate is increased (if F2 alone, 0.3% is increased).
(III) When the online roll grinder 28 is installed on all the stands in the hot finishing rolling mill row, the standstill rate is one stand by the number of stands added to other stands in addition to the last three stands. The operating rate is increased by 0.01% per unit, the operating rate is increased by 0.01% per stand, and roll replacement becomes unnecessary, so the 3.00% downtime decreases and the operating rate increases by 3.00%. If the hot finish rolling mill is 7 stands of F1 to F7, the number of additional stands is 4, so 0.04% for the occurrence of slip between the roll and the tip of the material to be rolled. In addition, since 3.00% is added for the part that does not require roll replacement, the suspension rate decreases by 3.04% in total, and the operating rate increases by 3.04%. Although the roll replacement is not necessary for all the stands in the hot finish rolling mill row, the suspension rate of 3.52% due to the roll replacement shown in FIG. 42 was not completely eliminated. This is because the work roll exchange of the rolling mill remains.
(IV) In the case where the online roll grinder 28 is installed in all the stands in the rough rolling mill row in addition to all the stands in the hot finishing rolling mill row, the final three in the hot finishing rolling mill row The standstill rate decreases by 0.01% per stand and the operation rate increases by 0.01% per stand by the number of additional stands added to the other stands in the hot finishing rolling mill in addition to the stand. At the same time, since the roll change requires neither a rough rolling mill row nor a hot finish rolling mill row, the 3.52% downtime decreases and the operating rate increases by 3.52%. If the hot finish rolling mill is 7 stands of F1 to F7, the number of additional stands is 4, so 0.04% for the occurrence of slip between the roll and the tip of the material to be rolled. In addition, since 3.52% is added for the part that does not require roll replacement, the suspension rate decreases by 3.56% in total, and the operating rate increases by 3.56%.
(V) When the online roll grinder 28 is installed in all the stands of the hot finishing rolling mill row and the rough rolling mill row and the online roll grinder 28 is also installed in the backup roll, No replacement is required. Although it is not limited to the case where it is installed in all the stands, if it is installed in all the stands, 24 hours of the planned suspension time zone 48 hours counted outside the operation rate is changed to a time zone in which operation is possible.

  FIG. 30 shows a decrease in the suspension rate and an increase in the operation rate due to the above (I) to (V).

  Every time the operating rate increases by 1%, 6.72 hr changes to a time when it can be operated. In that case, in the ultimate case (V), 6.72 hr × 3.52 + 24 = 47.65 hr will change to an operable time zone, so the production efficiency during operation is 600 ton / hr. For example, 28,600 tons can be increased every month.

Further, as will be described below, it is possible to save the fuel that is wasted in the heating furnace 10 during the downtime, and the power that is causing the rolling mill to idle idle. that is,
(3) Reduction of energy intensity (there is a contribution reduced by (2))
The amount contributing to is as shown in the following example table.

  By the way, for F4, if only considering the suppression of surface roughness scale wrinkles, the number of grinding units may be one, but since the wear step is quite large, the number of grinding units is set to two for the purpose of grinding and removing this. ing.

  As described above, the present invention is not limited to 3/4 continuous hot rolling lines (hot rolling mill trains) 100, 200, 300, 400, but semi-continuous and fully continuous hot rolling lines ( Needless to say, the slab continuous casting equipment 26 and the hot rolling line (hot rolling mill line) 500 as shown in FIG. Needless to say, the present invention can also be applied to those directly connected via the heating furnace 10.

  Alternatively, as shown in FIG. 32 described in Patent Document 6, the preceding rolled material and the subsequent rolled material are joined by the joining device 15 and applied to a continuous hot rolling process in which rolling is performed continuously, or Further, as shown in FIG. 33 described in Patent Document 7, the preceding rolled material and the subsequent rolled material are joined, the entire width of the sheet bar is heated by the sheet bar heating device 17, and the sheet bar is heated by the edge heating device 171. The present invention does not prevent this from being applied to continuous hot rolling for heating the edge portion of the steel plate. Of course, in this hot rolling equipment line, the full width of the sheet bar is heated by the sheet bar heating device 17 without joining the preceding rolled material and the subsequent rolled material, and the edge portion of the sheet bar is heated by the edge heating device 171. You can also. In the figure, 11 is a coil box, 141 is a joining crop shear, 14 is a finishing crop shear, 23 is a cutting device, 25 is a high-speed plate device, and 102, 103 and 104 are thermometers.

  When applied to continuous hot rolling, the material to be rolled is joined and connected, so the impact is affected by the on-line roll grinder except when the tip of the first material to be rolled is bitten and when the tail end of the final roll ends is pulled out. It is possible to grind the roll without worrying about it. By doing so, even when the rolling material is rolled one by one, even if the rolling time is too short to be ground in the bar, the rolled material is joined and connected, so that the in-bar grinding is performed. This makes it possible to increase the production efficiency because there is no need to grind between the bars until the interval is extended.

  For this purpose, it is necessary to track the planned cutting portion with high accuracy. This is because the individual rolled materials to be rolled one after another are connected, and it becomes impossible to know how many rolled materials to be bonded are rolled by the roll in question. Hereinafter, the method of tracking the planned cutting portion will be described. When the material to be rolled is transported and rolled without interruption as in continuous hot rolling, the point on the method that is important for performing tracking is divided into the following three.

(1) Finish rolling of the first material to be rolled in continuous hot rolling to reach the coiler,
(2) Joined portion of the joined portion of the subsequent rolled material to finish rolling mill first stand F1,
(3) Finishing mill first stand F1 at the joining portion-generation of cutting scheduled portion-cutting,
Hereinafter, description will be given in this order.

(1) Finishing rolling of first rolled material in continuous hot rolling to reaching coiler At the leading end of the first joining, a thermometer 102 installed on the exit side of the joining device 15 and the entry side of the finishing mill 18 The tip of the thermometer 103 installed on the finishing roll 18 and the thermometer 104 installed on the exit side of the finishing mill 18 are sequentially and intermittently captured, and thereafter the connection to the shaft of the motor of the roll of the final stand of the finishing mill is illustrated. The mechanical distance to the coiler 24 is counted down with a value obtained by multiplying the pulse generated at each rolling from the drive device that does not perform a predetermined circumference (more precisely, the roll radius multiplied by the roll radius) and the advanced rate. To do. Instead of the arrival of the leading end of the first joining the thermometer 104 installed on the exit side of the finishing mill, it may be substituted by the arrival of the leading end of the first joining to the final stand of the finishing mill. . This can be done by raising the rolling load.

  Of course, these sensors may be replaced with other measuring sensors such as a sensor for measuring the thickness and width of the material 8 to be rolled, a torque meter of an electric motor, and the like.

(2) Joining portion of subsequent rolled material to finish rolling mill first stand F1 arrival For the joining portion, the traveling end position of the joining device 15 is set up to the post-joining finishing mill first stand F1. It is performed by the control device 90 receiving and counting pulses that are emitted from the measuring roll 9 that is rotated with the conveyance of the material to be rolled from the starting point for every predetermined circumferential length conveyance (the measuring roll 9 is prior to joining). It is pressed against the material 8 and begins to rotate).

(3) Finishing rolling mill first stand F1 arrival to generation and cutting of cutting scheduled portion of joining section Tracking from joining of finishing mill first stand F1 to finishing mill final stand is as follows. To do. Calculate the volume of material to be rolled in the finishing mill by calculating the product of the mechanical distance between each stand and the thickness of the material to be rolled at the exit of each stand for all the stands. Multiply the pulse generated for each rolling from a drive unit (not shown) connected to the shaft (more precisely, the roll radius multiplied by the roll rotation angle) by the advanced rate and the finishing mill exit side plate thickness. This is done by counting down in the control device 90 with the value converted into the transport volume distance.

  By doing so, it is possible to know the timing at which each joint passes through each finishing rolling mill, so that it is possible to know how many workpieces are currently rolled.

  Then, since the remaining time until the tail end of the final bond ends through the roll in question can be predicted from the remaining length of the material to be rolled and the peripheral speed of each roll, the time required for grinding the roll on the entire surface. If the value is less than, a new full-grinding pass is stopped, and if full-grinding is in progress, the grinding is controlled until the pass grinding is completed.

  The following is not related directly, but it is a tracking story related to cutting of the material to be rolled.

  The planned cutting portion is generated in the control device 90 in the vicinity of the joining portion (in this example, upstream in the conveying direction), for example, after the joining portion reaches the finishing stand of the finishing mill and after a predetermined distance rolling. On the other side, but may be downstream).

  From the arrival of the final stand of the finish rolling mill until the cut portion is cut by the cutting device 23, a predetermined roll circumference (more precisely, roll The value obtained by multiplying the roll radius by a predetermined rotation angle) is counted by the control device 90 receiving pulses counted for each rolling, and further multiplied by the advanced rate and converted into the rolling distance of the material to be rolled. This is done by counting down the mechanical distance from the last stand of the machine to the cutting device 23.

  In the above example, the tracking method of counting pulses emitted from the drive device connected to the motor shaft of the measuring roll 9 or the final stand of the finishing mill with the control device has been described as an example, but the present invention is not limited to this. Instead, other tracking methods such as using a laser speedometer may be used instead. In particular, (2) the joining portion of the subsequent rolled material to reach the finishing mill first stand F1, (3) the joining portion of the finishing mill first stand F1 to the scheduled cutting portion. For generation to cutting, it is preferable that tracking is performed with a laser speed meter installed on the entry side and the exit side of the finishing rolling mill, so that tracking can be performed with higher accuracy.

  Moreover, what is necessary is just to give the roll radius and the advanced rate which appeared in said (1)-(3) to the control apparatus 90 as follows.

Roll radius: Since the roll is periodically polished for operation, the operator measures the roll diameter immediately after polishing or automatically and inputs the measured value to the process computer 92 by hand or automatically. The calculation is performed in the process computer 92 to correct the roll radius, which is transmitted from the process computer 92 to the control device 90.
Advanced rate: Also stored in the process computer 92 as a predetermined value in a table corresponding to the grade, product dimensions, etc., and the attributes of the grade, product dimensions, etc. of the material to be rolled during finish rolling are key The predetermined value is retrieved from the table and transmitted to the control device 90.

  Alternatively, instead of such a table type, a model type corresponding to the product type, product size, etc. may be substituted.

  Alternatively, if heating by the sheet bar heating device 17 or the edge heating device 171 is also used in combination, it becomes possible to stably roll a harder rolled material or a thinner rolled material, and the quality is also the length of the rolled material. Both the width direction and the width direction become more uniform.

  Finally, Table 8 shows typical components (F2 and F6) of the roll (work roll) in the description of the embodiment of the present invention.

  F1 to F4 in the finishing mill line 18 often use high-speed rolls similar to F2 (not shown in Table 8 but may use high-chromium cast iron rolls). For the final three stands in the finishing rolling mill row 18, a high-speed roll similar to F2 may be used, or a nickel glen roll similar to F6 may be used. For the rough rolling mill row 12, a representative example is not shown in Table 8, but a high chromium cast steel roll is often used (a forged steel roll or an adamite roll may also be used). However, the components in Table 8 are merely representative and are not limited thereto.

  In the case of a high-speed roll, C: 1.5 to 3.5%, Si: 0.3 to 1.0%, Mn: 0.3 to 1.5%, Cr: 2 to 7% in mass%. In addition, Ni: 5% or less, Mo: 10% or less, V: 3-10%, W: 20% or less, Co: 10% or less The balance is substantially made of Fe.

  In the case of nickel glen roll, it is mass%, C: 3.2 to 3.4%, Si: 0.6 to 1.0%, Mn: 0.5 to 0.8%, Cr: 1.5 to It contains 1.9%, Ni: 4.2-4.6%, Mo: 0.3-0.6%, and the balance is substantially composed of Fe.

  In the case of a high chromium cast steel roll, the mass is C: 0.9 to 1.8%, Si: 0.8 to 1.5%, Mn: 0.5 to 1.2%, Cr: 7 to 14 %, Ni: 0.5 to 1.5%, Mo: 0.7 to 2.5%, with the balance being substantially Fe.

  As described above.

8 ... Material to be rolled 9 ... Measuring roll 10 ... Heating furnace 11 ... Coil box 12 ... Rough rolling mill row 13 ... Rough rolling mill work roll (roll)
DESCRIPTION OF SYMBOLS 14, 141 ... Crop shear 15 ... Joining device 16 ... Descaling device 18 ... Hot finishing rolling mill row 19 ... Finishing mill work roll (roll)
DESCRIPTION OF SYMBOLS 21 ... Bearing box 22 ... Cooling zone 23 ... Cutting device 24 ... Coiler 25 ... High speed threading device 26 ... Slab continuous casting equipment 28 ... Online roll grinder 30 ... Grinding unit 36 ... Grinding wheel 38 ... Pushing device 38R ... Rod 40 ... Rotating device 42 ... Connecting shaft 44, 44B ... Spline 46 ... Rotating device side shaft 48 ... Wheel side shaft 50 ... Grinding wheel holder 52 ... Bearing 54, 54P ... Seal 56 ... Oscillating motor 58 ... Wheel 60 ... Tilt frame 62 ... Base frame 64 ... Tilt fulcrum pin 66 ... Pinion 68 ... Rack 70 ... Rail 72 ... Tilt jack 74 ... Stabilizer cylinder 76 ... Position sensor 80 ... Pressure line 81 ... Proportional pressure reducing valve 82 ... Pressure reducing valve 83 ... Relief valve 84 ... Tank line 85 ... Hydraulic pressure Pressure sensor (PT)
86 ... Oil puddle 87 ... Accumulator OD ... Oscillating direction W ... Wheel and roll contact width FD ... Advancing direction L ... Lap amount S ... Step 90 ... Control device 92 ... Process computer 94 ... Business computer 102,103,104 ... thermometer 100, 200, 300, 400 ... hot rolling line (hot rolling mill line)
Fr: Pushing force on roll Fμ: Mechanical resistance F ... Output of hydraulic cylinder

Claims (4)

Before rolling the material to be rolled with a rolling mill,
When the surface roughness index φ determined by the following formula (A) is equal to or greater than a certain value, it is determined that there is a risk of surface roughness scale wrinkles due to scale destruction and aggregation of the surface of the material to be rolled, a method of determining the presence or absence of risk of judgment to that surface roughness scale defects occur when the surface roughness index φ there is no danger of the surface roughness scale defects occur when the below a certain value,
Surface roughness index φ = φ0 · K2 / D · Σ (K1 · L · P / W) (A)
here,
φ0: Proportional constant (m / kN)
K1: Constant determined by product type K2: Constant determined by rolling mill L: Rolling length of a material to be rolled in the rolling mill (m)
P: Rolling load (kN) of the material to be rolled in the rolling mill
W: Width of the material to be rolled in the rolling mill (m)
D: Diameter of roll in the rolling mill (m)
Σ: Sum for each rolled material
The value of K1 when the material to be rolled is stainless steel is 0.1 times the value of K1 when the material to be rolled is carbon steel. Judgment method of presence or absence. A hot finish rolling mill using the method for determining whether or not there is a risk of occurrence of surface roughness scale flaws according to claim 1. Before rolling the material to be rolled with a rolling mill,
Based on the value of the surface roughness index φ determined by the following formula (B), a method for determining the degree of surface roughness of the work roll for determining the degree of surface roughness of the work roll of the rolling mill,
Surface roughness index φ = φ0 · K2 / D · Σ (K1 · L · P / W) (B)
here,
φ0: Proportional constant (m / kN)
K1: Constant determined by product type
K2: Constant determined by rolling mill
L: Rolling length of a material to be rolled in the rolling mill (m)
P: Rolling load (kN) of the material to be rolled in the rolling mill
W: Width of the material to be rolled in the rolling mill (m)
D: Diameter of roll in the rolling mill (m)
Σ: Sum for each rolled material
When the material to be rolled is stainless steel, the value of K1 is 0.1 times the value of K1 when the material to be rolled is carbon steel. Judgment method. A hot finish rolling mill using the method for determining the degree of surface roughness of a work roll according to claim 3.

Images