JP5803865B2 - Manufacturing method of stainless steel cold-rolled steel strip - Google Patents

Description

  The present invention relates to a method for producing a stainless steel cold rolled steel strip. Specifically, for example, a heat treatment such as continuous annealing is performed on a stainless steel strip that has been cold-rolled by a cluster type rolling mill such as a 20-stage Sendier mill. When the stainless cold-rolled steel strip is transported with bending deformation in the transport direction after being performed, the stainless cold-rolled steel strip is manufactured while suppressing the occurrence of shape defects such as warping in the width direction and cooling breakage, for example. Regarding the method.

  In cold rolling of stainless steel cold-rolled steel strip, in order to efficiently roll a hard and thin material to be rolled, a cluster-type rolling mill, for example, a work having an extremely small diameter is provided by including a 20-stage roll arranged in a cluster shape. A 20-stage Sendemia rolling mill that includes a roll and is capable of rolling a hard and thin material to be rolled under high pressure is frequently used. This cluster type rolling mill uses a work roll having a smaller diameter than a normal four- and six-stage rolling mill, and various types of elongation, particularly shape defects including quarter elongation, are caused by stainless steel cooling after cold rolling. It tends to occur in steel strips.

  As a shape defect after cold rolling of a stainless steel cold-rolled steel strip, elongation in the rolling direction (longitudinal direction of the steel strip) occurs at both ends in the plate width direction and the center of the plate width direction is flat, The center in the plate width direction extends in the rolling direction and both ends are flat, and the quarter elongation (Q elongation) in which two places between both ends and the center in the plate width direction extend in the rolling direction. There are various elongations that occur due to overlapping.

  The stainless cold-rolled steel strip after the cold rolling is subsequently transferred to a heat treatment line such as a bright annealing line (hereinafter referred to as “BA line”), continuous annealing and pickling line (hereinafter referred to as “AP line”), and subjected to heat treatment. After that, it is conveyed to a slitter line and cut to a predetermined size.

  FIG. 1 is an explanatory diagram schematically showing the BA line 1, and FIG. 2 is an explanatory diagram schematically showing the slitter line 19.

  As shown in FIG. 1, a stainless cold-rolled steel strip 2 that has been cold-rolled by a cluster rolling mill is unwound from an unwinding reel 3, passes through a welding machine 4, and is sent to an alkali cleaning device 5. After being washed with alkali, it is sent to the bright annealing furnace 9 through the bridle roll 6, the entrance-side accumulator 7, and the bridle roll 8. The stainless cold-rolled steel strip 2 brightly annealed by the heating zone 9 a and the cooling zone 9 b of the bright annealing furnace 9 is taken up by a take-up reel 13 through a bridle roll 10, a delivery side accumulator 11, and a bridle roll 12. In addition, the code | symbol 9c in FIG. 1 shows a sealing device, and the code | symbol 9d shows a top roll.

  Further, as shown in FIG. 2, the stainless cold-rolled steel strip 2 that has been brightly annealed by the BA line 1 is unwound from the unwinding reel 14 and sent to the arbor 16 via the entry-side loop 15 to be predetermined. And is taken up by the take-up reel 18 through the outlet loop 17.

  When the stainless cold-rolled steel strip 2 having a shape defect including the above-described quarter elongation is passed through the BA line 1 or AP line, warpage in the plate width direction is caused in the process of being cooled from the heating in the bright annealing furnace 9. May occur. At this time, as shown in FIG. 1, the stainless cold-rolled steel strip 2 is continuously passed through the BA line 1 having many front and rear devices such as the alkali cleaning device 5 and the accumulators 7 and 11. Due to the warpage in the plate width direction, contact flaws due to contact with the structure downstream from the bright annealing furnace 9 occur, and the plateability is hindered due to the inability to loop when the slitter line 19 is passed through. There is. In particular, in the turn roll after exiting the bright annealing furnace 9, if the peak portion (convex portion) existing in the quarter extension portion is subjected to bending deformation in the opposite direction, this convex portion becomes the stainless cold-rolled steel strip. Cooling folds that fold in the longitudinal direction of 2 may occur. The cooling fold is handled as a defect on the appearance of the stainless cold-rolled steel strip 2, so that the yield reduction is promoted.

  Further, when the sheet is conveyed while being subjected to bending deformation in the conveying direction to the stainless cold-rolled steel strip 2 in the entrance side loop 15 and the exit side loop 17 in the slitter line 19 shown in FIG. The yield and production efficiency are likely to decrease.

  So far, a method for suppressing shape defects including quarter elongation in a stainless cold-rolled steel strip that has been cold-rolled by a cluster rolling mill has been proposed. For example, Patent Document 1 discloses an invention in which cold rolling is performed using a roll in which an axis and a sleeve are fitted and fixed, and Patent Document 2 has a reduced diameter portion that is recessed in a gentle concave shape. An invention for performing cold rolling using a roll is disclosed.

JP 61-226105 A JP-A-1-284410

  Although these conventional technologies are all related to the suppression of quarter elongation caused by cold rolling, this is performed after heat treatment such as continuous annealing is performed on a stainless steel strip that has been cold rolled by a cluster rolling mill. It is neither disclosed nor suggested to suppress a shape defect such as a warp in the width direction or a cooling fold when the stainless cold-rolled steel strip is conveyed while circling around the conveyance roll.

  In addition, since these conventional techniques use a roll having a concave shape in addition to the generally used tapered shape of an intermediate roll, an increase in manufacturing cost cannot be denied.

  The object of the present invention is to, for example, carry out heat treatment such as continuous annealing on a stainless steel strip that has been cold-rolled by a cluster type rolling mill such as a 20-stage Sendier mill, and then transfer the stainless cold-rolled steel strip in the conveying direction. When transporting with bending deformation, the use of rolls with special structures such as those disclosed in Patent Documents 1 and 2, generation of contact defects, occurrence of shape defects such as warping in the width direction, cooling folds, etc. Is to produce a stainless steel cold-rolled steel strip.

  As a result of intensive studies to solve the above problems, the present inventor, for example, in performing cold rolling of a stainless cold-rolled steel strip in a cluster type rolling mill such as a 20-stage Sendier mill, The shape of the cold-rolled steel strip is a simple ear-stretched shape in which elongation occurs at both ends in the plate width direction and the quarter elongation or middle elongation is 50 I-unit or less. By making the shape excellent in flatness, it is possible to improve the yield because it can suppress the occurrence of contact flaws and cooling breakage at the time of conveyance, and it can eliminate the inability to loop on the slitter line following the BA line The inventors have found that a stainless cold-rolled steel strip can be produced while increasing the efficiency, and have completed the present invention.

  In ordinary cold rolling of a stainless steel cold rolled steel strip using a cluster rolling mill, quarter elongation and medium elongation are inevitably generated to some extent. According to the knowledge of the present inventor, the document “Plasticity and processing vol. .20 no. 217 (1979-2) ”on page 89-90, even if it has a quarter-elongation shape and a middle-elongation shape with a flatness I-Unit of 50 I-unit or less, Inability to loop will not occur.

The present invention is as described below.
(1) A stainless cold-rolled steel strip that has been cold-rolled using a cluster rolling mill is subjected to a heat treatment in a heat treatment line, and then the stainless cold-rolled steel strip that has been subjected to the heat treatment is moved in the conveying direction. When producing a stainless steel cold-rolled steel strip by carrying it while applying bending deformation,
The shape of the stainless cold-rolled steel strip at the end of the cold rolling is a simple ear stretch shape in which elongation occurs at both ends in the sheet width direction and the quarter elongation or middle elongation is 50 I-unit or less, and By controlling the conditions of cold rolling by the cluster type rolling mill so that the ear extension depth is 330 mm or less, the occurrence of shape defects when the bending deformation is given is suppressed. A method for producing a stainless cold-rolled steel strip.

  (2) The manufacturing method of the stainless cold-rolled steel strip described in the item (1), wherein the heat treatment line is a continuous annealing line.

  According to the present invention, for example, when cold rolling a stainless cold-rolled steel strip with a cluster rolling mill such as a 20-stage Sendier mill, the shape of the stainless cold-rolled steel strip at the end of the cold rolling is changed in the sheet width direction. Elongation occurs at both ends, and the quarter elongation or middle elongation is a simple ear extension shape of 50 I-unit or less, and the ear extension depth is 330 mm or less, so it has excellent flatness after heat treatment Thus, it is possible to suppress the occurrence of contact wrinkles and cooling folds when the stainless cold-rolled steel strip is conveyed while being subjected to bending deformation in the conveyance direction after the heat treatment. For this reason, according to the present invention, the yield of the stainless cold-rolled steel strip can be improved without using a roll having a special structure as disclosed in Patent Documents 1 and 2.

FIG. 1 is an explanatory diagram schematically showing a BA line. FIG. 2 is an explanatory diagram schematically showing a slitter line. FIG. 3 is a graph showing the result of simulating the effect of the shape after cold rolling of the stainless cold-rolled steel strip on the shape after bright annealing, and FIG. 3 (a) shows the flat shape after cold rolling. FIG. 3 (b) shows a case where the shape after cold rolling is a simple ear extension shape, and FIG. 3 (c) shows a case where the shape after cold rolling is a middle extension shape. FIG. 3 (d) shows a case where the shape after cold rolling is a quarter-elongation shape, and FIG. 3 (e) shows a case where the shape after cold-rolling is a shape in which the ear and the middle elongation are combined. Further, FIG. 3 (f) shows a case where the shape after the cold rolling is a combination of the ear and the quarter elongation. FIG. 4 is an explanatory view schematically showing a mechanism of occurrence of warpage in the width direction of the stainless cold-rolled steel strip 2. FIG. 5 is a graph showing a result of simulating the influence of the shape after cold rolling of the stainless cold-rolled steel strip on the shape after bright annealing, and FIG. 5 (a) is a stainless cold-rolled steel after cold rolling. FIG. 5 (b) shows a case where the ear extension height in the stainless cold-rolled steel strip after cold rolling is 50I-unit, and FIG. c) shows the case where the edge extension height in the stainless cold-rolled steel strip after cold rolling is 100 I-unit, and FIG. 5 (d) shows the ear extension depth in the stainless cold-rolled steel strip after cold rolling ( The distance from the sheet edge to the sheet width center direction) is 100 mm from the edge, and FIG. 5E shows the case where the ear extension depth in the stainless cold-rolled steel strip after cold rolling is 300 mm from the edge. In addition, FIG. Ear elongation depth in stainless cold-rolled steel strip after cold rolling is shown a case where 500mm from the edge. 6 (a) and 6 (b) show the shapes of the stainless cold-rolled steel strips after cold rolling in the inventive examples and comparative examples shown in Table 1, respectively. FIG. 6 (c) and FIG. 6 (d) ) Shows the shape of the stainless cold-rolled steel strip after bright annealing in each of the inventive examples and comparative examples shown in Table 1. FIGS. 7A and 7B are graphs collectively showing the results derived from the simulations of FIGS. 3 and 5, and FIG. 7C is a graph derived from the graph of FIG. 7B. It is. FIG. 8 is an explanatory view showing the taper shape of the first intermediate roll that is desirably used in the present invention.

  A mode for carrying out the present invention will be described. In the following description, a 20-stage Sendmir rolling mill is used that has a work roll with a very small diameter by providing 20-stage rolls arranged in a cluster, and is capable of high-pressure rolling of a hard and thin material to be rolled. A case where a stainless cold-rolled steel strip is manufactured through cold rolling, bright annealing treatment using a BA line shown in FIG. 1, and cutting using a slitter line shown in FIG. 2 is taken as an example.

  A stainless cold-rolled steel strip 2 is manufactured by performing cold rolling using a 20-stage Sendier mill.

  In this cold rolling, by controlling the conditions of the cold rolling by a 20-stage Sendier mill, the shape of the stainless cold-rolled steel strip 2 at the end of the cold rolling is extended at both ends in the sheet width direction. It is controlled to have a simple ear extension shape that is generated and has a quarter or medium extension of 50 I-unit or less and an ear extension depth of 330 mm or less.

  The reason for limiting the shape of the stainless cold-rolled steel strip 2 at the end of cold rolling in this way will be described with reference to simulation results.

  In order to grasp how the shape of the stainless cold-rolled steel strip 2 changes due to the heat treatment, the inventor performed a simulation of the shape of the stainless cold-rolled steel strip after the bright annealing. The simulation was performed by FEM analysis simulating the thermal history of the stainless cold-rolled steel strip by moving the thermal boundary at a speed corresponding to the line speed.

  FIG. 3 is a graph showing the results of simulating the influence of the shape after cold rolling of the stainless cold-rolled steel strip 2 on the shape after bright annealing, and the broken lines in FIGS. 3 (a) to 3 (f) The shape after cold rolling is shown, and the solid line shows the shape after bright annealing.

  3A shows a case where the shape after cold rolling is a flat shape, FIG. 3B shows a case where the shape after cold rolling is a simple ear extension shape, and FIG. FIG. 3 (d) shows a case where the shape after cold rolling is a medium elongation shape, FIG. 3 (d) shows a case where the shape after cold rolling is a quarter elongation shape, and FIG. 3 (e) shows a shape after cold rolling. 3 shows a case where the shape of the earlobe and the middle elongation is combined, and FIG. 3F shows a case where the shape after the cold rolling is a shape where the earlobe and the quarter elongation are combined.

  Since it has been found that there is no problem in the plate-passability in the bright annealing furnace 9 when the amount of warpage of the stainless cold-rolled steel strip 2 is 75 mm or less, the amount of warpage (FIG. 3 (f), it was determined that the (out-of-plane displacement after annealing; mm) was 75 mm or less, and in this simulation, the definition of the warpage (out-of-plane displacement after annealing) is as shown in FIG. In the case of a simple warp (in the case of only one mountain) as shown by the solid lines in the graphs of a), FIG. 3B, FIG. 3C, and FIG. The maximum value of the mountain.

  On the other hand, in the case of quarter elongation having a plurality of peaks and valleys as shown by the solid lines in the graphs of FIGS. 3 (d) and 3 (f), when bending in the traveling direction, the bending strength is increased, The exact amount of warp cannot be expressed simply by measuring the height of the mountain. Therefore, in this simulation, the maximum value and the minimum value of peaks and valleys are integrated, and the integrated value is used as the warpage amount. By defining in this way, it is possible to accurately represent the phenomenon of inability to loop in the input side loop 15 and the output side loop 17.

  As shown in FIGS. 3 (a) to 3 (f), by this simulation, after the bright annealing when the shape after cold rolling is a shape including intermediate elongation as shown in the graph of FIG. 3 (c). When the shape after cold rolling is the largest, and the shape after cold rolling is a shape including quarter elongation as shown in the graphs of FIGS. 3 (d) and 3 (f), the amount of warpage is small. It has been found that the peak of warpage occurs in two places, resulting in a complicated shape.

  From this simulation result, the shape of the stainless cold-rolled steel strip 2 at the end of the cold rolling is changed to a simple ear extension shape in which elongation occurs at both ends in the plate width direction and the quarter elongation or middle elongation is 50 I-unit or less. It can be seen that control is necessary in order to suppress the occurrence of contact wrinkles and cooling breakage when the stainless cold-rolled steel strip is conveyed while being subjected to bending deformation in the conveyance direction after the heat treatment.

  That is, if the target shape at the time of cold rolling is the above-mentioned simple ear extension shape, the shape of the stainless cold-rolled steel strip with more ensured flatness after heat treatment can be obtained, thereby suppressing contact flaws and cooling breakage. It is possible to improve the yield by improving the productivity by improving the sheet feeding performance.

  FIG. 4 is an explanatory view schematically showing a mechanism of occurrence of warpage in the width direction of the stainless cold-rolled steel strip 2.

  As shown in FIG. 4, the warp in the width direction of the stainless cold-rolled steel strip 2 is caused by the tension generated in the edge portion due to the difference in thermal expansion at the boundary cooled from the soaking by the bright annealing furnace 9, and the warpage in the width direction is It is held by being cooled as it is. For this reason, if the shape of the stainless cold-rolled steel strip 2 after cold rolling is a simple ear elongation shape, the occurrence of warpage can be avoided by relaxing the tension by edge elongation.

  Furthermore, the change in flatness of the stainless cold-rolled steel strip 2 after the heat treatment according to the occurrence state (height and depth) of the ear elongation in the cold-rolled stainless steel strip 2 after the cold rolling was examined using a simulation model.

  FIG. 5 is a graph showing the result of simulating the influence of the shape after cold rolling of the stainless cold-rolled steel strip 2 on the shape after bright annealing, and the broken lines in FIGS. 5 (a) to 5 (f) The shape after cold rolling is shown, and the solid line shows the shape after bright annealing.

  FIG. 5 (a) shows the case where the ear elongation height in the stainless cold-rolled steel strip 2 after cold rolling is 25I-unit, and FIG. 5 (b) shows the case in the stainless cold-rolled steel strip 2 after cold rolling. The case where the ear extension height is 50 I-unit is shown, and FIG. 5C shows the case where the ear extension height in the stainless cold-rolled steel strip 2 after cold rolling is 100 I-unit, and FIG. ) Shows the case where the ear elongation depth (distance from the plate edge to the center of the plate width) in the stainless cold-rolled steel strip 2 after cold rolling is 100 mm from the edge, and FIG. FIG. 5 (f) shows the case where the edge extension depth in the stainless cold-rolled steel strip 2 is 300 mm from the edge, and FIG. The case is shown.

  As described above, in FIGS. 5A to 5C, when the ear extension height of the stainless cold-rolled steel strip 2 after cold rolling is changed to 25, 50, 100 (I-unit). 5 (d) to FIG. 5 (f) show the extension depth of the cold-rolled stainless steel strip 2 after cold rolling to 100, 300, 500 (mm). The change in flatness after the heat treatment when changed is shown.

  Further, FIGS. 7A and 7B are graphs collectively showing the results derived from the simulations of FIGS. 3 and 5, and FIG. 7C is derived from the graph of FIG. 7B. It is a graph.

  As shown in the graph of FIG. 7 (c), in order to produce a stainless cold-rolled steel strip having a shape with excellent flatness after heat treatment, it is effective that the shape after cold rolling is a simple ear extension shape. It is.

  As shown in the graph in FIGS. 3A to 3F and FIGS. 5A to 5F, the shape of the stainless cold-rolled steel strip 2 after the cold rolling is changed in the sheet width direction. By adopting a simple ear stretch shape in which elongation occurs at both ends and quarter elongation or medium elongation is 50 I-unit or less, a stainless cold-rolled steel strip 2 having a shape excellent in flatness after heat treatment can be obtained. Thus, the stainless cold-rolled steel strip 2 can be manufactured while improving the yield by suppressing contact wrinkles and cooling breakage, and improving the productivity by improving the sheet passing property.

  In order to control the shape of the stainless cold-rolled steel strip 2 at the end of the cold rolling as described above, the shape of the first intermediate roll in the 20-stage Sendier mill used for cold rolling is a taper described below. The shape is exemplified. In addition, the 1st intermediate | middle roll in a 20-stage Sendemia mill means the intermediate roll which contacts a small diameter work roll directly.

  FIG. 8 is an explanatory view showing a taper shape of the first intermediate roll 20 that is preferably used in the present invention.

  As described above, in Patent Documents 1 and 2, as a method of suppressing quarter elongation, a method of using a roll having a dent in the opposite direction with respect to the tapered portion and the width center position of the first intermediate roll, A method of adding a new component to the conventional configuration, such as using a sleeve roll, is used.

  In the present invention, a rolling shape analysis model is constructed to evaluate the characteristics of the shape control actuator, and a new component is not added to the conventional configuration, but the taper portion has three different inclination angles shown in FIG. In the first intermediate roll 20 having a taper shape, if the ratio (h1 / L1) and the ratio (h3 / L3) are each a taper shape having a ratio of 1: 5 or more, rolling under the same rolling conditions as in the past, The desired simple ear stretch shape described above can be obtained after cold rolling.

  In this way, the stainless cold-rolled steel strip 2 that has been cold-rolled by the 20-stage Sendier mill is conveyed to the BA line 1 shown in FIG. 1 and subjected to heat treatment (bright annealing), and thereafter FIG. And is cut to a predetermined dimension.

  Thus, the stainless cold-rolled steel strip 2 that has been heat-treated by the bright annealing furnace 9 of the BA line 1 is, for example, when it circulates around the bridle roll 10, the outlet accumulator 11, and the bridle roll 12 shown in FIG. In addition, the entrance side loop 15 and the exit side loop 17 shown in FIG. 2 are transported while being bent in the transport direction. At the time of this conveyance, since the stainless cold-rolled steel strip 2 has the shape described above, it is possible to suppress the occurrence of shape defects (such as contact wrinkles and cooling folds) when being subjected to bending deformation during conveyance.

  In order to demonstrate the effect of the present invention, a stainless steel cold-rolled steel strip that was cold-rolled by a 20-stage Sendier mill was used to conduct a sheet passing test on the BA line shown in FIG. The rolling conditions are summarized in Table 1. Table 2 shows the main specifications of the 20-stage Sendier mill.

  In the example of the present invention, the amount of ear elongation was 70 to 100 I-unit, the depth from the edge of the ear elongation was 330 mm or less, and the quarter elongation or middle elongation was 50 I-unit or less. In the comparative example, the ear elongation amount was 50 to 70 I-unit, and the quarter elongation was 30 I-unit or less.

  6 (a) and 6 (b) show an example of the shape of the stainless cold-rolled steel strip after the cold rolling in each of the inventive examples and comparative examples shown in Table 1, and FIG. 6 (c) and FIG. (D) shows an example of the shape of the stainless cold-rolled steel strip after bright annealing in each of the inventive examples and comparative examples shown in Table 1.

  In the comparative example in which the target shape of the cold-rolled stainless steel strip after cold rolling is a shape in which ear elongation and quarter elongation are combined, the shape of the stainless cold-rolled steel strip after bright annealing has two bulges in the width direction. A warp in the width direction having occurred and a shape defect (contact flaw, cooling breakage, etc.) occurred when bending deformation was given during conveyance in the subsequent conveyance process.

  On the other hand, in the example of the present invention in which the target shape of the stainless cold-rolled steel strip after the cold rolling is a simple ear extension shape, the shape of the stainless cold-rolled steel strip after bright annealing is flat without causing warpage in the width direction. Because of the shape, there were no shape defects (contact flaws, cooling folds, etc.) when bending deformation during transportation was given in the subsequent transportation process.

DESCRIPTION OF SYMBOLS 1 BA line 2 Stainless steel cold-rolled steel strip 3 Unwinding reel 4 Welding machine 5 Alkali washing apparatus 6 Bridle roll 7 Inlet accumulator 8 Bridle roll 9 Bright annealing furnace 9a Heating zone 9b Cooling zone 9c Sealing device 9d Top roll 11 Outlet accumulator 12 Bridle roll 13 Take-up reel 14 Unwind reel 15 Incoming loop 16 Arbor 17 Outgoing loop 18 Take-up reel 19 Slitter line 20 First intermediate roll

Claims (2)

A stainless cold-rolled steel strip that has been cold-rolled using a cluster rolling mill is subjected to heat treatment in a heat treatment line, and then the stainless cold-rolled steel strip that has been subjected to the heat treatment is subjected to bending deformation in the conveying direction. When producing stainless steel cold-rolled steel strip by conveying while giving,
The shape of the stainless cold-rolled steel strip at the end of the cold rolling is a simple ear stretch shape in which elongation occurs at both ends in the sheet width direction and the quarter elongation or middle elongation is 50 I-unit or less, and Occurrence of shape defects occurring in the stainless cold-rolled steel strip during conveyance by the heat treatment by controlling the cold rolling conditions by the cluster type rolling mill so that the ear extension depth is 330 mm or less. The manufacturing method of the stainless cold-rolled steel strip characterized by suppressing.   The method for manufacturing a stainless cold-rolled steel strip according to claim 1, wherein the heat treatment line is a continuous annealing line.