JP2010179333A - Method of manufacturing cold-rolled steel sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of stably manufacturing a cold-rolled steel sheet with good quality by preventing a push-in flaw due to properties of an edge part of a product and trimming after cold rolling. <P>SOLUTION: A pair of upper and lower circular rotary blades are pressed to a predetermined depth from the above and the below with respect to an edge part of a hot rolled steel sheet before pickling. Shearing is applied to the edge part in an unseparated state. The edge parts are separated through pinching by narrow width rolls installed at the respective edge parts and capable of pinching only the edge parts, and then pickling and cold rolling with a reduction rate of ≥30% are applied. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for producing a cold-rolled steel sheet, and more particularly to a method for stably producing a cold-rolled steel sheet having good quality by preventing the properties and surface flaws of a product edge after cold rolling.

  Cold-rolled steel sheets manufactured by pickling and cold-rolling hot-rolled steel sheets manufactured by hot rolling are used for a wide range of applications such as automobiles, electrical products, and building materials. The steel sheet after cold rolling becomes a final product through processes such as plating treatment, annealing heat treatment, leveler correction, and press working according to the application. The characteristics of cold-rolled steel sheets are that they are thinner than hot-rolled steel sheets, but also have excellent dimensional accuracy, clean and smooth flat surfaces, excellent flatness (steel plate shape), and a wide range of workability. It has adaptability. The hot-rolled steel sheet has the thinnest thickness of about 1.2 mm, whereas the cold-rolled steel sheet has a minimum thickness of 1/10 or less. Here, a rolling reduction defined by the following equation is introduced as a parameter representing a plate thickness change in cold rolling. Reduction ratio = (1−plate thickness after rolling / plate thickness before rolling) (× 100%). In order to reduce the sheet thickness after cold rolling, it is necessary to increase the reduction ratio. In addition, the rolling reduction is an important parameter in order to make the r value, which is one of the indexes of formability, a good value. However, when trying to increase the rolling reduction in the cold rolling, there is a problem that the edge properties are deteriorated during the cold rolling and the plate is easily broken. As a reason for this, the defect of the edge portion in the hot-rolled steel sheet before cold rolling is considered first. Therefore, trimming of the edge of the steel sheet before cold rolling or pickling is carried out, but the edge properties after trimming often have a burr, and in subsequent pickling or cold rolling the roll Troubles such as putting on firewood had occurred.

  On the other hand, even in steel sheets that have been cold-rolled after pickling hot-rolled steel sheets after trimming, notched properties (also referred to as ear cracks, rough ears, edge cracks, etc.) tend to remain at the edges, It was easy to cause operational troubles such as plate breakage when passing through the plating line after rolling, annealing line, leveler correction. Further, it is needless to say that in applications where the edge portion is used as it is as the final product of the plate material, good edge properties without edge cracks are required. Therefore, trimming the edge portion of the steel sheet after cold rolling has been performed, but trimming over the entire length of the steel sheet increased in length by cold rolling, not only the work load is enormous, Yield decline was also invited. Further, when trimming a cold-rolled steel sheet, the edge property after trimming often has a burr, which has been a cause of wrinkles in press working. For this reason, various techniques have been developed for improving the properties of the product edge portion of a cold-rolled steel sheet while preventing operational troubles.

  In patent document 1, in the process line which processes a strip steel plate, the apparatus which can remove the burr of the strip steel plate edge part which arises by trimming by rotating and pressing a cylindrical grindstone or a brush etc. is disclosed. is doing.

  In Patent Document 2, after trimming the end of the strip-shaped metal plate, the masher roll is pressed against the burr portion of the end of the strip-shaped metal plate to remove the burr so that an appropriate rolling force distribution of the masher roll can be obtained. Discloses a method of inclining and pressing the masher roll.

  In Non-Patent Document 1, as a trimming method that does not generate burr, a trimming method is disclosed in which trimming is performed so that the edge portion is not separated by adjusting the trimmer blade, and then the unseparated edge portion is separated by pressing with a roll from above and below. is doing. This method is also referred to as a roll cut trimming method.

  Patent Document 3 discloses a roll-cut trimming method in which a steel plate is sandwiched from above and below by combining masher rolls.

  On the other hand, in patent document 4, in order to prevent the deterioration of the edge property in cold rolling, after the edge part of the hot-rolled steel strip before cold rolling is trimmed, the work hardening by trimming is carried out by machining with a grinder or a bite. A method for removing portions is disclosed.

JP-A-10-315108 JP-A-11-267713 JP-A-62-282811 JP 54-124857 A

"No slitting slitting" (The 63rd Symposium on Plasticity Processing, 1978, P36-45)

  As described above, it is extremely important in terms of the manufacturing process and product quality of the cold-rolled steel sheet that the edge portion has good properties in the steel sheet before and after the cold rolling.

  When the method disclosed in Patent Document 1 is applied, the end of the steel plate is burred by pressing a cylindrical grindstone or brush or the like on the edge of the steel plate with a rotatable structure over the entire length of the steel plate after trimming. To be removed. Therefore, there is a problem that the work efficiency is remarkably deteriorated due to the addition of the process and the manufacturing cost is increased. A grindstone, a brush, or the like wears and deteriorates depending on the amount of use, so that the steel plate production efficiency decreases due to the replacement, and the maintenance cost also increases the production cost. Moreover, when it tries to apply with respect to a steel plate with thin plate | board thickness, there exists a problem of being easy to cause the plate breakage resulting from the contact of a grindstone or a brush.

  When the method disclosed in Patent Document 2 is applied, the burr is removed by pressing a masher roll against the burr portion generated at the end of the steel plate after trimming. This is a portion protruding from the burr steel plate. Is simply pressed with a roll, so there is a problem that the degree of burr is lightened or only the action of changing the direction of protrusion to the horizontal direction is not achieved, and it does not improve the notched shape of the edge part. is there.

  When the conventional roll-cut type trimming method disclosed in Non-Patent Document 1 is applied, it is possible to eliminate the burr at the edge of the steel sheet by improving the trimming method itself in the steel sheet before or after cold rolling. It becomes possible. However, the roll used for separating the edge portion that has been unseparated by pressing with a roll from above and below is a roll having a body length wider than the maximum plate width of the steel plate as shown in FIG. When this wide roll is used up and down, the surface of the roll may be wrinkled when the edge is cut off, but when the same roll is used for steel plates with different plate widths, the edge of the narrow material is cut off. There is a problem in that the roll wrinkles generated in the above process are transferred to the surface of the wide material and cause quality defects. Also, if some of the burrs near the center of the sheet thickness are scattered and adhere to the steel sheet surface or roll surface of the edge separating roll, it bites between the upper and lower wide roll rolls and the steel sheet that are under great pressure. There is a problem that tends to become surface flaws.

  In connection with the trimming disclosed in Patent Document 3, a masher roll is a device that is usually applied to remove burr after trimming. It is a device with a small rolling force due to its structure, and by pressing only on the edge of the steel sheet, the local stress of the pressed part increases, and the burr localized at the edge of the plate is pressed and removed. it can. However, when the smasher rolls as in Patent Document 3 are combined up and down to sandwich the steel sheet surface from above and below and try to separate the unseparated edge portion, a small rolling force is dispersed on the wide steel sheet surface, Therefore, sufficient stress cannot be applied to the edge portion. According to the study by the present inventors, it has been found that an unseparated portion cannot be separated and a reduction device having a structure with higher strength is required.

  When the method disclosed in Patent Document 4 is applied, after the edge portion of the hot-rolled steel strip before cold rolling is trimmed, a process of removing the work-hardened portion by trimming by grinding with a grinder or a bit is necessary. Therefore, there is a problem that the work efficiency is remarkably lowered. In general, the sheeting speed in such a machining process is significantly slower than the sheeting speed in trimming, pickling and cold rolling, so the above machining cannot be performed online, This process is required. In addition, when a part of the edge is removed by machining such as grinder or bite, the removed part is generated as chips and scattered on the steel sheet, causing surface flaws. Is also likely to occur.

  As a result of investigating conventional knowledge, along with the notched properties of the edge of the steel sheet, the steel sheet is cold-rolled while preventing surface flaws during trimming to stabilize a good quality cold-rolled steel sheet. I couldn't find any manufacturing technology.

  Therefore, the present invention aims to provide a method for stably producing a cold-rolled steel sheet having good quality by preventing the properties of the product edge portion after cold rolling and the indentation due to trimming. .

  In order to achieve the above object, the present invention has the following features.

  [1] A pair of upper and lower circular rotary blades are pressed from the upper and lower sides to a predetermined depth against the edge portion of the hot rolled steel sheet before pickling to shear the edge portion to an unseparated state, and then each edge portion A cold-rolled steel sheet characterized by being subjected to pickling and cold rolling with a total rolling reduction of 30% or more after the edge portion is cut by clamping with a narrow roll capable of clamping only the edge portion. Production method.

  According to the present invention, it becomes possible to stably produce a cold-rolled steel sheet having good quality by preventing notch-like properties and surface flaws at the product edge after cold rolling.

The schematic diagram which shows the installation for manufacturing the cold-rolled steel plate in this invention. The schematic diagram which shows the installation for manufacturing the cold-rolled steel plate in a comparative example. The schematic diagram which shows the state in which the edge part became a notch-like property (it is also called an ear crack, ear roughness, an edge crack, etc.) in a cold-rolled steel plate. Schematic diagram showing a conventional trimming method. The enlarged view of the schematic diagram which shows the rotary blade of one side. The schematic diagram which shows the trimming process in the roll cut type trimming method. The figure which shows the pinching roll in the conventional roll cut type trimming method. The figure which shows the pinching roll in the roll cut type trimming method by this invention. The figure which shows the pinching roll in the roll cut type trimming method by this invention. The schematic diagram which shows the cut surface at the time of applying the conventional trimming method. The schematic diagram which shows the cut surface at the time of applying a roll cut type trimming method. The schematic diagram which shows the edge part vicinity at the time of performing the pickling after the trimming by the roll cut type trimming method. The figure which shows the edge crack depth in each trimming method. The figure which shows the steel plate surface defect generation number in each trimming method. The figure which shows the relationship between the edge crack depth in each trimming method, and a cold total rolling reduction. The figure which shows the relationship between the magnitude | size of a burr | flash in each trimming method, and a cold total reduction rate.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 3 schematically shows a state in which the edge portion of the cold-rolled steel sheet has a notch-like property (also referred to as an ear crack, a rough ear, or an edge crack). When such edge properties occur in cold rolling, sheet breakage tends to occur and it becomes difficult to stably roll. Moreover, if it remains after cold rolling, it is a problem that wrinkles are likely to occur in the press of the next process. As a cause of the edge failure, defects at the edge of the hot-rolled steel sheet are listed first. Therefore, in order to remove the defect, trimming is usually performed before cold rolling. However, even if the hot-rolled steel sheet is trimmed, the actual situation is that notch-like properties occur at the edge of the cold-rolled steel sheet. Although this may occur depending on the material and cold rolling operating conditions, it has been found by examination of the present inventors that it is often caused by burr generated by trimming of the edge portion of the hot-rolled steel sheet. It was.

  In order to stably produce a cold-rolled steel sheet that does not cause surface defects such as wrinkles on the surface of the steel sheet, the present inventors have achieved a good cold-rolled steel sheet. The inventors of the present invention have intensively studied focusing on the trimming method of the edge portion with respect to the mother board before pickling, not after rolling but before cold rolling, and reached the present invention.

  In the conventional trimming method, as shown in FIG. 4, a pair of upper and lower circular rotary blades are pressed against the edge portion of the hot-rolled steel sheet from the upper and lower sides to a predetermined depth and cut. Here, 1 is a steel plate, 10A and 10B are upper rotary blades at both ends, and 11A and 11B are lower rotary blades, respectively. In order to explain the setting method of the rotary blade in detail, FIG. 5 shows an enlarged view of the rotary blade on one side. Reference numeral 1 denotes a steel plate, and 1A denotes a portion that is cut off by trimming. In FIG. 5, C is a horizontal gap (also referred to as a clearance) between the upper and lower rotary blades, and the direction in which the gap between the two opens is positive (+). L is the vertical overlap amount (also referred to as a wrap) of the upper and lower rotary blades, and the one with the larger overlap amount is defined as positive (+). In the conventional trimming method, the clearance C is set to a value substantially proportional to the thickness of the steel plate. FIG. 10 schematically shows a cross section of the edge portion after trimming by a conventional trimming method, wherein 31 is a sheared surface, 32 is a fractured surface, and 33 is a burr. Thus, it can be seen that burr that becomes the starting point of the edge crack occurs in the cross section of the steel sheet. Further, the corner 36 of the shear surface on the plate surface is sharp. The schematic diagram of the cross section of the edge part in FIG. 10 shows the cross section on the right side of the steel plate in the arrangement of the upper and lower cutting blades shown in FIG.

  On the other hand, in the conventional roll cut trimming method, as shown in FIG. 6, the trimming wrap L is set to negative (−), the edge cut-off portion is set in an unseparated state, and then, as shown in FIG. This is a trimming method in which a steel plate is sandwiched between an upper roll 12 and a lower roll 13 to separate an unseparated portion of the edge. The edge cut-off portions 1A and 1B that have not been separated are separated from the steel plate main body by the roll clamping pressure. Here, the roll for pinching applied by the prior art shown in FIG. 7 had a body length wider than the maximum plate width of the steel plate to be passed. Hereinafter, the pinching roll in the conventional roll cut type trimming method is also referred to as a wide roll. FIG. 11 schematically shows a cross section of an edge portion after trimming by a conventional roll cut trimming method, wherein 31 is a shear surface, 32 is a fractured surface, 34 is a sag, and 35 is a burr. Since the fracture surface exists only in the vicinity of the center of the plate thickness and not on the surface of the steel plate, the burr that becomes the starting point of the edge crack does not occur. Instead, a burr 35 is generated near the center of the fracture surface. In addition, while the plate surface on the shearing surface side that is formed when trimming with the upper and lower blades has a sharp corner portion 36, a sag 34 is generated on the shearing surface side that is formed when the roll is clamped, so the corner portion is You can see that it is rounded.

  Since the corner of the shearing surface located on the steel sheet surface generated by the above trimming is sharp, if the corner hits a threading roll or the like, wrinkles or missing corners may occur. It has been found that the surface properties of are adversely affected. Further, this corner portion becomes smooth as shown in 37 of FIG. 12 by pickling, and it is found that trimming should be performed before pickling because wrinkles are not generated on the sheet passing roll. .

  The present invention uses narrow rolls 14A and 14B installed at respective edge portions as rolls used for roll clamping pressure as shown in FIG. 8 in the roll cut trimming method. If the roll body length is made as short as possible, the probability of biting scattered burrs and the like is reduced, and surface flaws can be suppressed, which is advantageous. In addition, even when the same roll is used for steel plates having different plate widths, even if the wrinkle of the roll 13 generated by cutting off the edge portion of the narrow material enters, the rolling force that sandwiches the steel plate at the central portion of the plate width with the wide material is Because it is not, it is difficult to be a surface flaw.

  When burrs or the like bite into the pinching roll, if there are rolls above and below, the rolling force between them is large, and the roll is easily bitten between the roll and the steel plate and easily becomes surface defects. On the other hand, if there is only a roll on either the top or bottom, there is no rolling force to sandwich the steel plate in the center of the plate width, so burrs caught between the roll and the steel plate are hard to be crushed and become surface flaws. It is difficult.

  Therefore, it is not necessary to narrow the pinching roll in the unseparated portion both in the upper and lower directions, and only one of the rolls may be narrow, and the other roll may be wide. As shown in FIG. 8, the upper roll need not be narrow and the lower roll need not be wide. For example, as shown in FIG. 9, the upper roll may be wide and only the lower roll may be narrow.

  The body length of the narrow roll necessary for separating the unseparated edge cut-off portion may be approximately 10 times or more the plate thickness of the steel plate. Accordingly, the body length of the narrow roll may be 10 times or more the maximum specification plate thickness of the edge trimming apparatus. In addition, the position of the narrow roll is appropriately changed according to the plate width of the steel plate and the edge cut-off amount. In addition, what is necessary is just to implement on the conditions similar to the roll cut type trimming method using the conventional wide roll except applying a narrow roll to at least one of upper and lower sides and performing roll clamping.

  Furthermore, when cold-rolling using a steel plate trimmed according to the present invention, edge cracks are remarkably reduced and sheet breakage is less likely to occur. Since burrs and the like are not easily scattered inside, the number of jumping flaws is reduced and cold rolling can be performed efficiently and with high quality.

  In FIG. 13, the edge crack depth in each trimming method to the edge part of a hot-rolled steel plate is shown. An SPCC steel 1.2 mm thick hot-rolled steel sheet was prepared as a target material, and an edge material by each trimming method was trimmed and pickled to prepare an experimental material. Except for the comparative example, pickling was performed after trimming, and in the comparative example, trimming was performed after pickling. In the conventional trimming method, the edge portion was cut off with a clearance C of 0.10 mm and a lap L of +0.4 mm, and then the burr protruding from the steel sheet surface was pushed and bent laterally by a masher roll. In the roll-cut trimming method, the trimming was performed so that the edge portion was not separated with a clearance C of 0.05 mm and a lap L of −0.5 mm, and then the unseparated edge portion was separated by pressing with a roll from above and below. For cold rolling, a reverse four-stage rolling mill having a work roll diameter of 500 mm was used, and three passes were rolled at a reduction rate of about 20% per pass. The thickness of the steel sheet after the 3-pass rolling was about 0.6 mm, and the total cold rolling reduction was about 50%.

  In FIG. 14, the result of investigating the surface defect of the steel plate surface after cold rolling in each trimming method to the edge part of a hot-rolled steel plate is shown. Here, for the cold rolled steel sheet 10 coil having a width of 860 mm to 1200 mm obtained by cold rolling the 1.2 mm thick base plate of the SPCC steel to about 0.6 mm, an optical surface inspection device is provided on the steel sheet surface. Thus, defects having a size of 2 mm or more and a depth of 0.1 mm or more were detected and evaluated by the number per 100 m length.

  With respect to the edge crack depth in each trimming method shown in FIG. 13, the edge crack depth is large in the conventional trimming method, whereas the conventional wide roll cut trimming method, the narrow roll cut method before cold rolling. In the trimming method and the present invention, the edge crack depth was small, and the edge properties were good.

  In the conventional trimming method, sheet breakage occurred during cold rolling, but none occurred in the conventional wide roll cut trimming method and the present invention.

  In the number of wrinkles on the surface of the steel sheet shown in FIG. 14, there were many surface wrinkles in the conventional wide roll cut trimming method. This is presumed to be caused by the fact that there were many streak defects in the vicinity of the edge, and the roll wrinkles generated when the relatively narrow plate width was roll-cut were transferred to the surface of the wide steel plate. In addition, a part of the burr is scattered during trimming, and wrinkles caught between the wide roll and the steel plate are also affected.

  Even with the conventional trimming method, the number of ridges is large, and some edge cracks caused by burr are missing during cold rolling and jump between the work roll and the steel sheet, and the roll crease is transferred to the steel sheet surface. It is estimated to be.

In the comparative example to which the narrow roll cut trimming method before cold rolling was applied, many streak defects were found near the edge portion of the upper surface of the steel sheet. As shown in FIG. 11, it is presumed that wrinkles occurred on the work roll due to the sharp corners of the edges generated during trimming, and the roll wrinkles were transferred to the steel sheet surface.
On the other hand, in the method of the present invention, as shown in FIG. 12, since the steel plate edge portion was rounded by pickling, wrinkles were hardly generated on the work roll, and there were few wrinkles on the surface of the steel plate and the surface quality was good.

  Next, FIG. 15 shows the relationship between the conventional trimming method, the condition under which burr is removed using a masher roll or machining method after the conventional trimming method, and the cold rolling reduction ratio and the edge crack depth in the method of the present invention. . A high carbon steel 2.0 mm thick hot rolled steel sheet was used as the target material. The cold rolling was performed using a reverse two-stage rolling mill having a work roll diameter of 400 mm. In the conventional trimming method and the conventional trimming method + masher roll, it can be seen that the edge crack depth suddenly increases when the cold rolling reduction is 30% or more. In the conventional trimming method + machining method, the size of the edge crack does not increase even when the cold rolling reduction increases. However, some of the conventional trimming method + machining method had large edge cracks, but this was because the burr was not sufficiently removed by machining with a grinder. all right. In the method of the present invention, the size of the edge crack did not increase even when the cold rolling reduction was increased. That is, in the conventional trimming method and the conventional trimming method + masher roll, when the cold rolling total rolling reduction exceeds 30%, the edge properties after cold rolling deteriorate, whereas in the method of the present invention, cold rolling is performed. It is possible to reliably prevent the deterioration of the later edge properties.

  Here, the conventional trimming method, the conditions under which burr is removed using a masher roll or machining method after the conventional trimming method, and the results of investigating the relationship between the cold reduction rate and the burr size in the method of the present invention are shown in FIG. 16 shows. Note that the survey site is different from FIG. The size of the burr was evaluated by the length in the thickness direction of the burr protruding from the steel plate surface by cutting out the edge part in the cross section across the width direction. In the conventional trimming method, there is a large burr, the burr becomes smaller as the cold total reduction ratio becomes larger, and the burr is remarkably reduced when the cold total reduction ratio reaches about 30%. The reason why the burr becomes smaller as the total cold rolling reduction increases is presumed that the part of the burr that protrudes from the steel plate surface is crushed or bent sideways by rolling. As shown in FIG. 10, there are minute cracks that become the starting point of edge cracks on the burr, and the cracks progress when deformed by cold rolling. When the total cold rolling reduction is 30% or more, it is presumed that the edge crack starting from this microcrack rapidly expands and increases with the rolling reduction.

  In the conventional trimming method + masher roll, there is no burr before cold rolling, but there are micro cracks that are the starting point of edge cracks, so that the total cold reduction ratio is 30% or more as in the conventional trimming method. Edge cracks are expanding rapidly.

  In the conventional trimming method + machining method and the method of the present invention, since there are no burr and micro crack before cold rolling, no edge crack is generated. However, since the machining method has a low processing speed, the productivity is low, and a problem remains in stability.

  As described above, in the production of a cold-rolled steel sheet having a cold reduction ratio of 30% or more, the cold-rolled steel sheet having good quality and surface quality at the product edge after cold rolling is stable and efficient. As a result, the present invention has been intensively studied with regard to a practical manufacturing method.

  In the present invention, a pair of upper and lower circular rotary blades are pressed from the upper and lower sides to a predetermined depth against the edge portion of the hot rolled steel sheet before pickling, and the edge portion is sheared to an unseparated state, and then each edge Cold-rolled steel sheet, characterized in that it is installed in a section and is subjected to cold rolling with a pickling and a total rolling reduction of 30% or more after the edge section is cut by clamping with a narrow roll capable of clamping only the edge section It was set as the manufacturing method of this.

  The upper limit of the total cold rolling reduction is not limited from the viewpoint of edge properties, but the total rolling reduction in industrial cold rolling is about 95%, so the application of the present invention. The upper limit is about 95%.

  The lower limit of the body length of the narrow roll used for roll cutting is sufficient if it is wide enough to stably roll the steel sheet. In this case, it is sufficient if it is 20 mm or more. In addition, since the upper limit is set on both sides, it is natural that the upper limit is half or less of the plate width. However, 200 mm or less is desirable in order to prevent burrs and the like from scattering and biting and generating surface flaws on the steel plate.

  Since either of the upper and lower rolls has a narrow width, the force acting when shearing the unseparated steel sheet is extremely large in the width direction where the rolls exist both in the upper and lower directions, and only one of the upper and lower rolls This is because the portion having no roll is extremely small, so that the roll wrinkle and the biting wrinkle hardly occur in the portion having only one of the upper and lower rolls.

  Further, the structure for supporting these rolls has sufficient support strength to shear the unseparated plate.

  About the present invention, after trimming the edge part of a hot-rolled steel sheet and pickling in the pickling section, using the example of manufacturing a cold-rolled steel sheet in a cold tandem rolling mill composed of 5 stands, the details Explained.

  FIG. 1 is a diagram schematically showing a part of a process for producing a cold-rolled steel sheet using a cold tandem rolling mill according to the present invention. In FIG. 1, 1 is a steel plate, 20 is a trimming device, 21 is a roll for clamping the steel plate from above and below to separate the unseparated portion of the edge from above and below, and 22 is to remove iron oxide (scale) on the surface of the steel plate. Pickling section, 23 is a bridle roll for controlling the tension applied to the steel plate being threaded, 24 is a cold tandem rolling mill consisting of 5 stands of a four-high rolling mill, and 25 is after rolling It is a coil obtained by winding a cold rolled steel sheet. In FIG. 1, all of the cold rolling mills 24 are represented as a four-stage stand, but the present invention is not limited to a four-stage stand, and is a two-stage or six-stage roll stand. Alternatively, a configuration in which two-stage, four-stage and six-stage rolling stands are mixed may be used. Moreover, in FIG. 1, although the cold rolling mill 24 is described as 5 stands, it is not limited to the case of 5 stands, and may be 4 stands or 6 stands. In FIG. 1, the steel plate is passed in the direction of the arrow, and on the upstream side not shown in the figure, a payoff reel for delivering the hot-rolled steel plate coil, the tail end of the preceding material and the tip of the following material are connected. A welding device for matching, a looper portion for adjusting a plate passing speed during welding, and the like are arranged. The looper part may be arranged in the pickling section.

  The trimming device 20 has circular rotary blades arranged on both edges of the steel plate, and can adjust the blade clearance C and lap L as shown in FIG.

  In the present invention example, an example in which a cold-rolled steel sheet having a thickness of 0.5 mm and a width of 1000 mm is manufactured from a hot-rolled steel sheet having a thickness of 2.0 mm and a width of 1020 mm will be described. The steel type is SPCC steel.

  The hot-rolled steel sheet paid out from the payoff reel is welded to the preceding material, and then the edge portions on both sides are trimmed by 10 mm each. Here, in the trimming according to the present invention, in the trimming apparatus 20, the clearance C was set to 0.10 mm and the lap L was set to -0.5 mm. As the values of the clearance C and the lap L, appropriate values calculated in advance according to the plate thickness were set. Under this condition, the edge cut-off portion is in an unseparated state. Then, the steel plate is clamped from above and below with 21 rolls, and the unseparated portion of the edge is separated from above and below.

  Here, the roll of 21 is a narrow roll on at least one of the upper and lower sides as shown in FIG. 8 or FIG. In roll No. 21, in order to cut off the uncut-off edge cut-off portion, the roll gap may be set to the same value as the thickness of the steel plate. According to this trimming method, the edge portion is not burred.

After removing the surface scale from the pickled section 22 on a hot rolled steel sheet having a thickness of 1000 mm by trimming both edges, the steel sheet is rolled to 0.5 mm by a 5-stand cold tandem rolling mill. The reduction rate of each stand was set to be uniform, and the tension applied to the steel plate between the stands was set to 10 kgf / mm ² . This is a common cold rolling operation mode.

  About the steel plate as it is cold-rolled, 10 points were selected arbitrarily in the longitudinal direction, and the properties of the edge portions were investigated, but the edge cracks were extremely small at less than 0.1 mm in all locations, and the edge properties were good. there were.

  In the manufacturing apparatus in which the trimming process, the subsequent pickling section, and the cold rolling process are directly connected as shown in FIG. Is significantly limited, and production efficiency is reduced. Further, since the chips generated by the machining are cold-rolled while being wound on the steel sheet, the risk of deterioration of the surface quality becomes extremely high, so that the application is impossible.

  In the example of the present invention, the best mode for carrying out the invention in the facility in which the trimming process, the pickling section, and the cold rolling mill are directly connected has been described, but the trimming process, the pickling section, and the cold rolling mill are respectively Even in the case of another facility, the same effect can be obtained by performing pickling after trimming and then performing cold rolling.

  As described above, according to the present invention, it is possible to provide a stable method for producing a cold-rolled steel sheet having good properties at the product edge after cold rolling and preventing wrinkles on the steel sheet surface.

  The present invention will be described based on an example of manufacturing a cold rolled steel sheet in a cold tandem rolling mill having 5 stands. Implementation conditions are shown in Tables 1 and 2.

  As for the type of the cold rolling mill, 1-4 stands are 4 stages, 5 stands are 6 stages, and the work roll diameter of each stand is as shown in Table 2. Except for the cold tandem rolling mill, the other apparatuses are as shown in FIGS.

  The test material of an Example is a hot-rolled steel plate used as each base plate of SPCC steel which is a general cold-rolled steel plate, and SPFC340 which is a high-tensile steel plate. The base plate thickness is 1.6 to 2.6 mm, and the thickness after cold rolling is 0.2 to 1.4 mm.

  In Examples 1 to 6 of the present invention, a roll-cut trimming method using a narrow roll as an upper roll as the trimming apparatus 20 and the pinching roll 21 shown in FIG. The trimming conditions are as shown in Table 1.

  In Comparative Examples 1-1 and 2, a roll-cut trimming method using a narrow roll as an upper roll as the trimming apparatus 20 and the pinching roll 21 shown in FIG. The trimming conditions are as shown in Table 1. The total cold reduction was less than 30%.

  In Comparative Examples 2-1 and 2, the roll-cut type trimming method using a narrow roll as the upper roll as the trimming apparatus 20 and the pinching roll 21 shown in FIG. 2 is used before cold rolling (after the pickling section 22). I gave it. The trimming conditions are as shown in Table 1.

  In the conventional examples 1-1 to 4, the conventional trimming method for completely separating the edge cut-out portion with the rotary blade was performed before pickling using only the 20 trimming apparatuses shown in FIG. The trimming conditions are as shown in Table 1. After trimming, the burr protruding from the steel sheet surface was pushed and bent laterally using a masher roll, and then passed through the pickling section 22.

  In Conventional Examples 2-1 and 2, the roll-cut type trimming method using a wide roll as the trimming apparatus 20 and the pinching roll 21 shown in FIG. The trimming conditions are as shown in Table 1.

  As an evaluation of the edge properties, the properties of the edge portions were investigated by arbitrarily selecting 10 locations in the longitudinal direction of the steel sheet after cold rolling. In any part, the edge crack was good if it was less than 0.1 mm, and if there was a part of 0.1 mm or more even in one place, it was considered bad.

  As an evaluation of the surface quality, an optical surface inspection device detects defects with a size of 2 mm or more and a depth of 0.1 mm or more, and evaluates the number per 100 m length. If there was, it was considered good.

  As shown in Table 1, in Comparative Examples 1-1 and 1-2 and Conventional Examples 1-3 and 1-4, the total rolling reduction was less than 30%, and both edge properties and surface quality were good. However, under the condition that the total rolling reduction is 30% or more, either the edge property or the surface quality is poor in the comparative example and the conventional example, whereas both the edge property and the surface quality are good in the present invention example. Met. In Comparative Examples 2-1 and 2-2, a large edge crack was generated under the condition that the total rolling reduction was 30% or more, and part of the edge was scattered to cause wrinkles. The item was also bad.

  From the above results, according to the present invention, in the cold-rolled steel sheet that gives a cold reduction ratio of 30% or more, a cold-rolled steel sheet with good quality and surface quality of the product edge after cold rolling can be stably obtained. It can be manufactured.

DESCRIPTION OF SYMBOLS 1 Steel plate 1A, 1B The part to cut off by trimming 10A, 10B Upper rotary blade 11A, 11B Lower rotary blade 12 Upper wide pinching roll 13 Lower wide pinching roll 14A, 14B Upper narrow pinching roll 15A , 15B Lower narrow pinching roll 20 Trimming device 21 Pinching roll for cutting off unseparated plate edge 22 Pickling section 23 Bridle roll 24 Cold tandem mill 25 Winding coil 31 Shear surface 32 Broken surface 33 34 Sagging 35 Burr 36 Corner on the surface side of the sheared surface after trimming 37 Corner on the surface side pickled after trimming

Claims (1)

  A pair of upper and lower circular rotary blades are pressed against the edge of the hot-rolled steel sheet before pickling from the top and bottom to a predetermined depth, the edge is sheared to an unseparated state, and then installed on each edge. A method for producing a cold-rolled steel sheet, characterized in that the edge portion is cut by clamping with a narrow roll capable of clamping only the edge portion, and then pickling and cold rolling with a total rolling reduction of 30% or more.

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