KR20230160928A - Manufacturing method and manufacturing equipment for cold rolled steel sheets - Google Patents

Abstract

The method of manufacturing a cold-rolled steel sheet according to the present invention includes a transverse-type full-width heating device that heats the steel sheet over the entire width direction of the steel sheet, and a steel sheet disposed downstream in the rolling direction with respect to the transverse-type full-width heating device. A method of manufacturing a cold rolled steel sheet using a cold rolling mill for rolling, comprising heating the steel sheet using a transverse full width heating device so that the temperature of the width direction end portion is higher than the temperature of the width direction center portion of the steel sheet at the entrance of the cold rolling mill. Includes steps.

Description

Manufacturing method and manufacturing equipment for cold rolled steel sheets

The present invention relates to a manufacturing method and manufacturing equipment for cold rolled steel sheets.

Conventionally, in cold rolling, single-stand reverse mills such as Senzimere mills or tandem mills with multiple stands are used, but in either case, the temperature of the steel sheet at the entrance to the rolling mill in the first pass is room temperature. There are many cases. However, in cold rolling of a silicon steel sheet (electronic steel sheet) with a high Si content, when the steel sheet temperature is low, brittle fracture of the steel sheet is likely to occur. The fracture type at this time includes fracture from the end of the steel sheet in the width direction or fracture from the center portion of the steel sheet in the width direction. However, as a countermeasure against fracture, it is effective to increase the temperature of the steel sheet during cold rolling. Against this background, a method of suppressing fracture of a silicon steel sheet by heating the silicon steel sheet before cold rolling has been proposed. For example, Patent Document 1 describes a method of heating the width direction end portion of a steel plate to reach a target temperature specified at the entrance to the rolling mill. Additionally, Patent Document 2 describes a method of uniformly heating and rolling the entire steel plate.

Japanese Patent Publication No. 2012-148310 Japanese Patent Publication No. 2011-79025

As described above, a technology has been proposed to suppress the occurrence of brittle fracture when cold rolling a silicon steel sheet with a high Si content. However, in the technique of heating only the width direction end portion of the steel sheet, there is a possibility that brittle fracture may occur in the width direction center portion because the temperature of the steel sheet near the width direction center portion is low. In addition, in the technology of uniformly heating the entire width direction of the steel sheet, there is a possibility that more energy than necessary is used to heat the entire steel sheet, and it is thought that there is room for reexamination from the perspective of SDGs (Sustainable Development Goals).

The present invention was made in view of the above problems, and its purpose is to provide a manufacturing method and manufacturing equipment for cold-rolled steel sheets that can roll silicon steel sheets stably with low environmental load.

In order to achieve the above object, the inventors of the present invention conducted extensive research and discovered that the fracture suppression temperature (steel sheet temperature with a high fracture suppression effect) is higher at the ends in the width direction compared to the center portion in the width direction. Therefore, the inventors believed that appropriately controlling the output of a transverse-type full-width heating device that heats the entire width direction of the steel sheet would be very effective in terms of fracture suppression and the environment, and as follows: The invention came to fruition.

The method of manufacturing a cold-rolled steel sheet according to the present invention includes a transverse full-width heating device that heats a steel sheet over the entire width direction of the steel sheet, and a transverse full-width heating device disposed downstream in the rolling direction with respect to the transverse full-width heating device. A method of manufacturing a cold rolled steel sheet using a cold rolling mill for rolling a steel sheet, using the transverse full width heating device so that the temperature of the width direction end portion of the steel sheet is higher than the temperature of the width direction central portion of the steel sheet at the entrance of the cold rolling mill. It includes a step of heating the steel plate.

The temperature of the central portion in the width direction and the ends in the width direction of the steel sheet at the entrance to the cold rolling mill may vary depending on the Si content of the steel sheet.

The temperature of the width direction central portion and the width direction end portion of the steel sheet at the entrance side of the cold rolling mill may be the temperature calculated by the following equations (1) and (2) that vary depending on the Si content α.

The cold-rolled steel sheet manufacturing equipment according to the present invention includes a transverse full-width heating device that heats a steel sheet over the entire width direction of the steel sheet, and a transverse full-width heating device disposed downstream in the rolling direction with respect to the transverse full-width heating device. A cold rolling mill for rolling a steel sheet is provided, and the transverse full-width heating device heats the steel sheet so that the temperature of the width direction end portion is higher than the temperature of the width direction center portion of the steel sheet at the entrance of the cold rolling mill.

The transverse full-width heating device may change the temperature of the central portion in the width direction and the ends in the width direction of the steel plate at the entrance to the cold rolling mill in accordance with the Si content of the steel plate.

The transverse-type full-width heating device calculates the temperature of the width-direction central portion and the width-direction end portion of the steel sheet at the entrance of the cold rolling mill using the following equations (1) and (2) that vary depending on the Si content α. It is best to heat it to the desired temperature.

The transverse type full-width heating device may be installed within 10 m from the entrance of the cold rolling mill.

According to the cold-rolled steel sheet manufacturing method and manufacturing equipment according to the present invention, silicon steel sheet can be rolled stably with low environmental load.

1 is a schematic diagram showing the configuration of a cold-rolled steel sheet manufacturing facility according to an embodiment of the present invention.
Figure 2 is a diagram showing the results of evaluating the temperature dependence of bending crack resistance of a silicon steel sheet.
Figure 3 is a diagram showing the estimation results of the steel sheet temperature required to suppress brittle fracture depending on the Si content of the steel sheet.
Figure 4 is a diagram showing the results of evaluating the temperature dependence of the edge crack resistance of a silicon steel sheet.
Figure 5 is a diagram showing the estimation results of the steel sheet temperature required to suppress edge cracks depending on the Si content of the steel sheet.

(Form for carrying out the invention)

Hereinafter, with reference to the drawings, a manufacturing method and manufacturing equipment for a cold rolled steel sheet according to an embodiment of the present invention will be described. In addition, the constituent elements in the embodiment shown below include elements that can be easily replaced by those skilled in the art, or elements that are substantially the same.

〔composition〕

First, with reference to FIG. 1, the configuration of a cold-rolled steel sheet manufacturing facility according to an embodiment of the present invention will be described.

1 is a schematic diagram showing the configuration of a cold-rolled steel sheet manufacturing facility according to an embodiment of the present invention. As shown in FIG. 1, a cold-rolled steel sheet manufacturing facility (hereinafter abbreviated as “manufacturing facility”), which is an embodiment of the present invention, is a continuous tandem rolling line with a plurality of stands, and a pay-off reel. )(1), joining device (2), looper (3), full width heating device (4), thermometer (plate temperature measuring device) (5), cold tandem rolling mill (6), cutter (cutting device) ( 7) and a tension reel (8).

The payoff reel 1 is a device that discharges the steel plate S. The manufacturing facility may be equipped with a plurality of pay-off reels 1. In this case, the plurality of payoff reels each send out different steel plates (S).

The joining device 2 connects the tail end of the steel sheet (preceding material) exported earlier from the pay-off reel 1 and the steel sheet (following material) exported later from the pay-off reel 1. It is a device that forms a bonded steel plate by joining the ends. As the joining device 2, a laser welder is suitably used.

The looper 3 is a steel sheet (S) so that cold rolling by the cold tandem rolling mill 6 can be continued until the steel sheets are joined to each other by the joining device 2 (until joining is completed). ) is a device that stores.

The full-width heating device 4 is a device that heats the steel sheet S over the entire width direction and rolling direction (longitudinal direction) of the steel sheet S. The full-width heating device 4 creates a temperature gradient in the width direction of the steel sheet S, making the temperature of the edge portion (width direction end portion) of the steel plate S higher than the temperature of the width direction center portion of the steel plate S. It is composed of a transverse induction heating device that can operate. In addition, the full-width heating device 4 is such that the temperature of the central portion and edge portion in the width direction of the steel sheet S at the entrance side of the cold tandem rolling mill 6 is calculated by equations (1) and (2) shown below, respectively. The steel sheet (S) may be heated to a temperature T _C and temperature T _E depending on the Si content of the steel sheet (S). Accordingly, brittle fracture and edge cracking of the steel plate S can be effectively suppressed.

The thermometer 5 is a device that measures the surface temperature of the steel plate S. The thermometer 5 may be installed closest to the entrance of the cold tandem rolling mill 6. However, in reality, the steel sheet temperature measured by the thermometer 5 is not used as is, but a value that compensates for the steel sheet temperature that drops between the thermometer 5 and the entrance to the cold tandem rolling mill 6 is used. Provided for practical use.

The cold tandem rolling mill 6 is a device that cold rolls the steel sheet S heated by the full-width heating device 4 in order to set the sheet thickness of the steel sheet S to a target thickness. In this embodiment, the cold tandem rolling mill 6 is equipped with five stands, but the number of stands is not particularly limited. In addition, in this embodiment, the cold tandem rolling mill 6 takes a type called 4Hi, which has four rolls on one stand, but it is not limited to this, and other types such as 6Hi, for example, can also be applied. .

The cutter 7 is a device that cuts the steel sheet S after cold rolling.

The tension reel 8 is a device that winds the steel plate S cut by the cutter 7. The type of the tension reel 8 is not limited, and for example, a carousel tension reel may be used. Additionally, the manufacturing equipment may be equipped with a plurality of tension reels 8. In this case, the plurality of tension reels 8 continuously wind the plurality of steel plates S.

Devices equipped with manufacturing equipment are not limited to the devices described above. In the manufacturing facility, the entrance sides of the full-width heating device 4 and the cold tandem rolling mill 6 may be arranged in this order within 10 m (more preferably adjacent to each other). Therefore, the rolling mill may not be a tandem rolling mill but may be a reverse rolling mill. In this case, the full-width heating device 4 and the rolling mill are arranged in this order in the first pass. In addition, it is possible to serialize the cold rolling process and the acid cleaning process, which is the previous process, and an acid cleaning device for acid cleaning the steel sheet S may be disposed between the looper 3 and the cold tandem rolling mill 6.

[Heating process]

Next, the heating process of the steel sheet S by the full-width heating device 4, which is a feature of the method for manufacturing a cold-rolled steel sheet according to an embodiment of the present invention, will be described. In addition, the full width heating device 4 heats at least one of the upper and lower surfaces of the steel plate S, but it is more preferable to heat both the upper and lower surfaces.

In the heating process of the steel sheet S of this embodiment, the full width heating device 4 determines the temperature of the steel sheet S measured by the thermometer 5 and the temperature of the steel sheet S on the exit side of the full width heating device 4. Based on the target temperature of (S), the time for the steel sheet (S) to pass through the full-width heating device (4) (i.e. heating time), and the sheet thickness of the steel sheet (S), the target of the full-width heating device (4) Determine the temperature. In addition, the target temperature of the steel sheet S heated by the full-width heating device 4 is the distance between the thermometer 5 and the full-width heating device 4, and the distance between the thermometer 5 and the cold tandem rolling mill 6. ) It is necessary to set the temperature considering the distance between them. For example, when the distance from the full-width heating device 4 to the cold tandem rolling mill 6 is very short, the target temperature of the steel sheet S on the exit side of the full-width heating device 4 is set to the full-width heating device ( Even if it is set to the target temperature of the steel sheet S heated by 4), there is no problem. On the other hand, if any of the full width heating device 4, the thermometer 5, and the cold tandem rolling mill 6 are separated by a distance, when the steel sheet S reaches the entrance side of the cold tandem rolling mill 6 It is necessary to set the target temperature of the steel sheet S heated by the full-width heating device 4 in consideration of the temperature drop to . However, from the viewpoint of environmental load, the amount of energy used to heat the steel sheet should be small, and the full-width heating device 4 and thermometer 5 should be placed as close to the cold tandem rolling mill 6 as possible.

Here, the inventors of the present invention investigated the fracture rate when cold rolling a silicon steel sheet using a tandem rolling mill having five stands. As a result, it was found that the fracture rate of a silicon steel sheet with a high Si content was higher compared to a silicon steel sheet with a low Si content. In addition, as a result of investigating the cause of the fracture, it was found that there was fracture on the upstream side of #1std (hereinafter, the N stand from the upstream side of the steel sheet transport direction is denoted as “#Nstd”) and #2std, and fracture of #4std and #5std, etc. It was found that the cause of the fracture on the downstream side was different. In other words, fracture on the upstream side, especially fracture just below or on the exit side of #1std, is caused by local squeezing of the steel sheet shape such as body elongation or edge elongation, or bending deformation by the sheet roll or shape detector. It was assumed that this was the cause. The reduction ratio of #1std is generally the highest among all stands, and it is thought that sudden changes in the shape of the steel plate are likely to cause fracture. In addition, as a result of additional investigation into fracture on the upstream side, the fracture rate (rupture incidence rate) is different depending on the season. For example, the fracture rate is higher in winter than in summer, and the outside temperature (temperature inside the rolling mill) increases the fracture rate. It was estimated that it was having an impact. On the other hand, regarding fracture on the downstream side, a case was confirmed in which the edge crack created in the stand on the upstream side progressed and led to fracture. For this reason, although the location and cause of fracture are different, it was thought that any fracture could be suppressed by increasing the temperature of the steel sheet at the entrance to #1std.

In order to verify the above speculation, first, bending crack resistance was evaluated when bending strain was applied to a steel plate on a laboratory scale. This is because it is believed that the bending crack resistance in this experiment is related to the brittle fracture caused by bending deformation in the plate roll or shape detector on the upstream stand described above. As a sample material, the sheet thickness is 2 mm, and the Si content is 1.8 mass%, 2.8 mass%, 3.3 mass%, and 3.7 mass% (hereinafter, silicon steel sheets with a Si content of Mmass% are referred to as “M% Si”) Four types of silicon steel sheets (indicated as “steel”) were annealed at 800°C (equivalent to hot-rolled sheet annealing). Then, the annealed silicon steel sheet was acid-cleaned, and a specimen with a width of 24 mm and a length of 250 mm was cut out using a shear. After that, both cross-sections were ground 2 mm each to remove processing distortion that occurred during shearing. Accordingly, the occurrence of edge fracture was suppressed. In addition, in an actual continuous cold rolling line, 1.8% Si steel and 2.8% Si steel are steel types in which brittle fracture is unlikely to occur. On the other hand, 3.3% Si steel and 3.7% Si steel are steel types in which brittle fracture occurs at a frequency of several percent, especially in the upstream stand. Normally, in cold rolling, the temperature of the steel sheet at the entrance to the rolling mill is about the same as the temperature inside the factory, and the temperature in the same temperature range is around 15°C.

Therefore, the bending crack resistance of silicon steel sheets was investigated for temperature dependence when the steel sheet temperature was in the range of 15°C to 45°C. In this experiment, first, a 2 mm thick steel plate was rolled at a reduction ratio of 50% to produce a 1 mm thick steel plate. This is mocking #1std. Next, the bending deformation of the steel sheet was simulated using the sheeting roll or shape detector, and the sheet was sheeted on a roller leveler. Then, bending strain was applied to the steel sheet to evaluate bending crack resistance. The roller leveler has 11 work rolls with a diameter of 50 mm from the top and bottom, and the roll spacing is 60 mm. The bending stress on the surface of the steel sheet can be given an arbitrary value by changing the tightening amount of the upper work roll. In this experiment, the steel sheet temperature was varied at 10°C intervals and the roll tightening amount was varied at 0.5 mm intervals to summarize the fracture limits of the steel sheet. It is believed that the greater the amount of tightening when breaking, the more difficult it is to break even on a cold rolling line. Figure 2 shows the results obtained in this experiment. In addition, taking into account the breakability in an actual continuous rolling mill, it was assumed that if a sheet could be rolled without breaking up to a tightening amount of 4.0 mm under the conditions of this experiment, it would not break in an actual continuous rolling mill, and the Non-occurrence of fracture was set as the target value of this experiment.

As shown in Figure 2, when compared for each Si content, in 1.8% Si steel, no fracture occurred up to a tightening amount of 4.0 mm, regardless of the temperature (15 to 45°C) of the steel sheet. Additionally, in 2.8% Si steel, when the steel sheet temperature was 15°C, fracture occurred at a tightening amount of 3.5 mm, but at 25°C or higher, fracture did not occur up to a tightening amount of 4.0 mm. Additionally, in 3.3% Si steel, fracture occurred at a tightening amount of 1.5 mm when the steel sheet temperature was 15°C, and at a tightening amount of 3.0 mm when the steel sheet temperature was 25°C. However, when the steel sheet temperature was 35°C or higher, fracture did not occur up to a tightening amount of 4.0 mm. Additionally, in 3.7% Si steel, fracture occurred at a tightening amount of 1.0 mm when the steel sheet temperature was 15°C, at 1.5 mm when the steel plate temperature was 25°C, and at 2.5 mm when the temperature was 35°C. When the steel plate temperature was set to 45°C, no fracture occurred up to a tightening amount of 4.0 mm. As a result of the above experiment, it was confirmed that the Si content has a great influence on the fracture resistance of the steel sheet, and that the higher the Si content, the easier it is for the steel sheet to fracture. This is also consistent with the actual state of fracture in an actual continuous cold rolling mill. In particular, for 3.3% Si steel and 3.7% Si steel, experiments were conducted while changing the temperature of the steel sheet, and as a result, brittle fracture could be suppressed as the temperature increased.

Figure 3 shows the results of estimating the steel sheet temperature required to suppress brittle fracture according to the Si content of the steel sheet based on the results of this experiment. The approximate curve in the figure is expressed by equation (3) shown below. In this experiment, for 1.8% Si steel, brittle fracture did not occur even at a steel sheet temperature of 15°C up to a tightening amount of 4.0 mm, so heating the steel sheet by the full-width heating device 4 is considered unnecessary. However, for 2.8% Si steel, fracture occurred at a tightening amount of 3.5 mm when the steel sheet temperature was 15°C, so it is considered necessary to heat the steel sheet with the full-width heating device 4 when the steel sheet temperature decreases. . Therefore, the value of Si content α[%] in equation (3) can be considered to be approximately α>2 in practical terms. In addition, the steel sheet temperature T _Cmin calculated from equation (3) is the minimum required temperature, and from the viewpoint of fracture suppression, it can be above this temperature. However, if the steel sheet temperature becomes too high, the shape and lubricity of the steel sheet will be affected, so the steel sheet temperature is set to 200°C or lower. In addition, the upper limit of Si content α of 4.5% was set from the range where the temperature of the edge portion of the steel sheet, which will be described later, is 200°C or less.

Next, in order to suppress fracture caused by edge cracking of the steel sheet, the steel sheet was rolled on a laboratory scale and the presence or absence of edge cracking was evaluated. This experiment was conducted on the fracture mode in which the edge crack that occurred on the upstream side of the rolling direction expanded and fractured as it progressed to the stand on the downstream side of the rolling direction, and the edge crack on the upstream stand was completely eliminated. It was thought that if this could be suppressed, fracture due to cracking of the steel plate edge could be suppressed. As test materials, four types of silicon steel sheets, each with a sheet thickness of 2 mm, 1.8% Si steel, 2.8% Si steel, 3.3% Si steel, and 3.7% Si steel, were cut into 20 mm width and 250 mm length, and heated at 800°C. Annealed (equivalent to hot-rolled sheet annealing). Then, the annealed silicon steel sheet was acid washed. The state of the steel sheet edge portion at this time can be considered close to the state at the entrance to the actual continuous cold rolling mill.

In addition, in an actual continuous cold rolling line, 1.8% Si steel is a steel type in which cracks at the edge of the steel sheet are unlikely to occur. On the other hand, 3.3% Si steel and 3.7% Si steel are steel types in which cracks occur at the edge of the steel sheet with a frequency of about several percent. Normally, in cold rolling, the temperature of the steel sheet at the entrance to the rolling mill is the same as the temperature inside the factory, and the temperature in the winter is around 15°C. Therefore, the temperature dependence of the edge cracking resistance of the silicon steel sheet when the steel sheet temperature was in the range of 15°C to 65°C was investigated. In this experiment, #1std was simulated and the inner edge area was measured by the number of cracks (cracks of 1 mm or more) occurring on both cross-sections (longitudinal direction) of the steel plate when a specimen of w20×L250 mm was rolled at a reduction ratio of 50%. Crack resistance was evaluated. In addition, the number of rollings at each Si amount and temperature is 5 times, and the number of edge cracks is the average of 5 times. In addition, the steel sheet temperature was set at intervals of 10°C. Figure 4 shows the results obtained in this experiment.

As shown in Figure 4, in the case of a steel sheet temperature of 15°C, when compared for each Si content, in the 1.8% Si steel, not a single edge crack occurred in both cross sections. In the 2.8% Si steel, 7 edge cracks occurred in total in both cross sections. In the 3.3% Si steel, 15 edge cracks occurred in total on both cross sections, and in the 3.7% Si steel, 30 edge cracks occurred. When the steel sheet temperature was 25°C, the total number of edge cracks in both cross sections became 0 for both 1.8% Si steel and 2.8% Si steel. On the other hand, there were 11 in 3.3% Si steel and 27 in 3.7% Si steel. When the steel sheet temperature was 35°C, the total number of edge cracks in both cross sections was 0 for 1.8% Si steel and 2.8% Si steel. On the other hand, in the 3.3% Si steel, 5 edge cracks occurred in both cross sections, and in the 3.7% Si steel, 20 edge cracks occurred. When the steel sheet temperature was 45°C, the total number of edge cracks in both cross sections became 0 in 3.3% Si steel in addition to 1.8% Si steel and 2.8% Si steel. On the other hand, 10 edge cracks occurred in the 3.7% Si steel. When the steel sheet temperature was 55°C, the total number of edge cracks in both cross sections became 0 for 3.3% Si steel in addition to 1.8% Si steel and 2.8% Si steel. On the other hand, three edge cracks occurred in the 3.7% Si steel. When the steel sheet temperature was 65°C, the total number of edge cracks in both cross sections became 0 in 1.8% Si steel, 2.8% Si steel, and 3.3% Si steel as well as 3.7% Si steel. From the results of the above experiment, it was confirmed that the Si content has a large influence on the crack resistance of the edge portion, and that the higher the Si content, the more likely it is that the edge portion of the steel sheet will crack. This is consistent with the actual situation of cracking at the edge of a steel sheet in an actual continuous cold rolling mill.

Figure 5 shows the results of estimating the temperature required to suppress cracking at the edge of the steel sheet according to the Si content of the steel sheet based on the results of this experiment. The approximate curve in the figure is expressed by equation (4) shown below. In this experiment, for 1.8% Si steel, no cracking occurred at the edge of the steel sheet even at a steel sheet temperature of 15°C, so heating the steel sheet by the full-width heating device 4 is considered unnecessary. However, for 2.8% Si steel, cracking occurred at the edge of the steel sheet when the steel sheet temperature was 15°C, so it is considered necessary to heat the steel sheet with the full-width heating device 4 when the steel sheet temperature decreases. Therefore, the Si content α[%] in equation (4) can be considered to be approximately α>2 in practical terms. In addition, the steel sheet temperature T _Emin calculated from equation (4) is the minimum required temperature, and from the viewpoint of suppressing fracture, it can be above this temperature. However, if the steel sheet temperature becomes too high, the shape and lubricity of the steel sheet will be affected, so the steel sheet temperature is set to 200°C or lower. In addition, the upper limit value of Si content α of 4.5% was set within the range where the temperature of the edge portion of the steel sheet calculated from equation (4) was 200°C or less. Additionally, the heating range of the steel sheet is set to be 30 mm or more from the edge portion of the steel sheet. This is because what affects cracking at the edge of the steel sheet is the influence range of the width expansion during cold rolling, and the range is generally said to be about 30 mm from the edge of the steel sheet.

From the two experiments described above, it can be seen that the heating temperatures of the steel sheet required to suppress fracture from the center portion in the width direction of the steel sheet and fracture from the edge portion are different. For example, in the case of 3.7% Si steel, the temperature required to suppress fracture from the center portion in the width direction is 45°C or higher, and the temperature required to suppress cracking at the edge portion is 65°C or higher. As described above, in order to suppress the fracture of a silicon steel sheet, in addition to adjusting the heating amount according to the Si content, it is necessary to provide a temperature gradient in the width direction of the steel sheet that raises the temperature at the edge portion compared to the center portion in the width direction even for the same steel type. It was found that there was a , and the present invention was conceived. In addition, when a plurality of steel sheets with different Si contents are transported in the same equipment, the heating device 6 acquires information indicating the Si content of the preceding and succeeding materials, and changes and determines the target temperature based on the information. good night. In addition, in this embodiment, the material to be rolled is described as a silicon steel plate, but the type of steel plate is not limited. Examples of steel sheets to which the technology of the present invention can be suitably applied other than silicon steel sheets include high-strength steel sheets and high-alloy steel sheets.

As described above, according to the manufacturing equipment and manufacturing method of cold rolled steel strip, which is an embodiment of the present invention, the full width heating device 4 capable of providing a temperature gradient in the width direction of the steel sheet S is used to heat the steel sheet S in the width direction. Fracture of the steel sheet is suppressed by appropriately controlling the temperature necessary to suppress fracture in the center and edge cracks. Therefore, according to the cold-rolled steel strip manufacturing equipment and the cold-rolled steel strip manufacturing method of one embodiment of the present invention, when cold rolling a silicon steel sheet, fracture of the steel sheet can be suppressed with the minimum necessary energy, so the environmental load is minimal. This allows stable cold rolling of silicon steel sheets.

(Example)

An example showing the effect of the present invention will be described. In this embodiment, the full-width heating device 4 is installed at the entrance to the cold rolling mill, and the temperature of the steel sheet at the entrance to the rolling mill can be set to an arbitrary temperature. Then, the plate was finished to the predetermined thickness using a 5-stand cold tandem rolling mill. All steel types used in this example were silicon steel plates, and were divided into three groups based on Si content. Specifically, there are three groups: a group with a Si content of 1.0 mass% to 2.0 mass%, a group with a Si content of 2.0 mass% to 3.0 mass%, and a group with a Si content of 3.0 mass% to 3.5 mass%. In any group, the plate thickness before rolling is 1.8 mm to 2.4 mm, and the plate thickness after rolling is 0.3 mm to 0.5 mm. In order to investigate the fracture rate due to differences in Si content, care was taken to ensure that there was no bias in plate thickness depending on the group. The breakage rate of 200 coils in each group was investigated. Additionally, the outside temperature (temperature inside the factory) was about 15°C. The coils and conditions investigated are shown in Table 1. The steel sheet temperature was measured using a thermometer installed at the entrance to the rolling mill.

[Reference example]

An example is shown where the steel sheet is not heated by the full width heating device, that is, when the temperature of the steel sheet at the entrance to the rolling mill is about 15°C. The breakage rate of 200 coils with a Si content of 1.0 mass% to 2.0 mass% was 0%. On the other hand, the fracture rate of 200 coils with Si content of 2.0 mass% to 3.0 mass% was 1%, and the fracture rate of 200 coils with Si content of 3.0 mass% to 3.5 mass% was 3%.

[Invention Example 1]

An example is shown where the temperature of the steel sheet at the entrance to the cold tandem rolling mill is calculated according to the Si content of the silicon steel sheet from the above equations (1) and (2), and the steel sheet is heated by the full-width heating device based on this. The distance between the cold tandem rolling mill and the full width heating device is 10 m. In the example of the present invention, the temperature of the edge portion is higher than the temperature of the central portion in the width direction. The fracture rate of 200 coils (width center 17°C, edge portion 18°C) with a Si content of 1.0 mass% to 2.0 mass% was 0%. In addition, the fracture rate of 200 coils with a Si content of 2.0 mass% to 3.0 mass% (width center 30°C, edge portion 35°C) is 0%, and 200 coils with 3.0 mass% to 3.5 mass% Si content (width center 45°C, edge portion) is 0%. The breakage rate (60°C) was also 0%. Based on the present invention, it was confirmed that the fracture of the steel sheet can be significantly reduced by heating the silicon steel sheet.

[Invention Example 2]

An example is shown where the temperature of the steel sheet at the entrance to the cold tandem rolling mill is calculated according to the Si content of the silicon steel sheet from the above equations (1) and (2), and the steel sheet is heated by the full-width heating device based on this. The distance between the cold tandem rolling mill and the full width heating device is 1 m. That is, compared to Invention Example 1, the distance between the cold tandem rolling mill and the full-width heating device is shortened. Other conditions are the same as Invention Example 1. In the present invention example, the breakage rate of 200 coils (width center 17°C, edge portion 18°C) with a Si content of 1.0 mass% to 2.0 mass% was 0%. In addition, the fracture rate of 200 coils with a Si content of 2.0 mass% to 3.0 mass% (width center 30°C, edge portion 35°C) is 0%, and 200 coils with 3.0 mass% to 3.5 mass% Si content (width center 45°C, edge portion) is 0%. The breakage rate (60°C) was also 0%. Focusing only on the fracture rate, fracture is suppressed until the Si content reaches 3.5 mass%, which is the same as Invention Example 1, but the energy usage is significantly reduced compared to Invention Example 1, demonstrating the superiority of Invention Example 2. I was able to confirm. Therefore, it was confirmed that from the viewpoint of energy consumption reduction (environmental resistance), the closer the distance between the cold tandem rolling mill and the full-width heating device, the better.

[Comparative Example 1]

An example is shown where the temperature of the steel sheet at the entrance of the rolling mill is calculated from the above equations (1) and (2) according to the Si content of the silicon steel sheet, and the steel sheet is heated by a full-width heating device based on this. The distance between the cold tandem rolling mill and the full width heating device is 20 m. That is, among the conditions of invention example 1, this is an example in which the distance between the cold tandem rolling mill and the full-width heating device is increased. Since the distance between the cold tandem rolling mill and the full-width heating device was long, the steel sheet temperature at the entrance to the rolling mill calculated from equations (1) and (2) could not be achieved even if the upper limit of the ability of the full-width heating device was used. The fracture rate of 200 coils (width center 15°C, 15°C) with Si content of 1.0 mass% to 2.0 mass% is 0%, and 200 coils with Si content of 2.0 mass% to 3.0 mass% (width center 25°C, The fracture rate of the edge portion (30°C) was also 0%. On the other hand, the breakage rate of 200 coils (width center 40°C, edge portion 50°C) with a Si content of 3.0 mass% to 3.5 mass% was 1%. The shorter the distance between the cold tandem rolling mill and the full-width heating device, the better. Even if the full-width heating device is used to the upper limit of its capacity, the steel sheet temperature calculated from the above equations (1) and (2) cannot be secured at a distance. When installed, it was confirmed that the higher the Si steel, the more prone to fracture.

[Comparative Example 2]

An example is shown in which a steel sheet is heated by a full-width heating device to a temperature that is approximately 30% lower than the temperature of the steel sheet at the entrance to the rolling mill according to the Si content of the silicon steel sheet calculated from the above equations (1) and (2). Other conditions are the same as Invention Example 1. The fracture rate of 200 coils (width center 15°C, 15°C) with Si content of 1.0 mass% to 2.0 mass% is 0%, and 200 coils with Si content of 2.0 mass% to 3.0 mass% (width center 20°C, The fracture rate of the edge portion (25°C) was also 0%. On the other hand, the breakage rate of 200 coils (width center 30°C, edge portion 40°C) with a Si content of 3.0 mass% to 3.5 mass% was 1.5%. It was confirmed that when the temperature is lower than the steel sheet temperature calculated from the above equations (1) and (2), fracture becomes more likely to occur in higher Si steel.

[Comparative Example 3]

An example of using a solenoid-type full-width heating device is shown. In a solenoid-type full-width heating device, a temperature gradient cannot be provided in the width direction of the steel sheet. The temperature of the steel sheet heated by the solenoid-type full-width heating device was calculated from equation (1). In other words, the temperature considered necessary to suppress cracking at the edge cannot be secured, and since the temperature of the steel sheet at the edge tends to decrease compared to the central portion in the width direction, the temperature of the edge portion is lower than that of the central portion in the width direction. This has been done. The fracture rate of 200 coils (width center 17°C, edge portion 16°C) with a Si content of 1.0 mass% to 2.0 mass% was 0%. On the other hand, the fracture rate of 200 coils with a Si content of 2.0 mass% to 3.0 mass% (width center 30°C, edge portion 25°C) is 0.5%, and 200 coils with 3.0 mass% to 3.5 mass% Si content (width center 45°C, The fracture rate of the edge portion (35°C) was 2%. As a result of examining the fracture form of the fractured coil, fracture from the center portion in the width direction was suppressed, but fracture due to cracking at the edge portion was not suppressed.

[Comparative Example 4]

An example of using a solenoid-type full-width heating device is shown. The temperature of the steel sheet heated by the solenoid-type full-width heating device was calculated from equation (2). That is, the steel sheet was heated across the entire width direction so that the temperature of the edge portion was reached at a temperature considered necessary to suppress edge cracking. The fracture rate of 200 coils with a Si content of 1.0 mass% to 2.0 mass% (width center 20°C, edge 18°C) is 0%, and 200 coils with Si content of 2.0 mass% to 3.0 mass% (width center 40°C, The fracture rate of the edge portion (35°C) was 0%, and the fracture rate of 200 coils (width center 70°C, edge portion 60°C) with a Si content of 3.0 mass% to 3.5 mass% was also 0%. However, the central portion of the steel sheet in the width direction is heated more than necessary from the viewpoint of suppressing fracture, so when considering environmental load, it is better to reduce the amount of input energy.

[Comparative Example 5]

An example is shown in which an edge heating device that heats only both ends in the width direction of the steel plate is used without using a full width heating device. The temperature of both ends in the width direction of the steel sheet heated by the edge heating device was calculated from equation (2). The fracture rate of 200 coils (width center 15°C, edge 35°C) with Si content of 1.0 mass% to 2.0 mass% was 0%. On the other hand, the fracture rate of 200 coils with a Si content of 2.0 mass% to 3.0 mass% (width center 15°C, edge 35°C) is 0.5%, and 200 coils with Si content of 3.0 mass% to 3.5 mass% (width center 15°C) are 0.5%. The fracture rate (°C, edge portion 60°C) was 2%. As a result of examining the fracture form of the fractured coil, fracture due to edge cracking was suppressed, but fracture from the central portion in the width direction was not suppressed.

As shown above, it was confirmed that fracture of the steel sheet can be suppressed by applying the present invention and heating the steel sheet at the entrance side of the cold tandem rolling mill. In particular, in the case of a silicon steel sheet with a Si content of 3 mass% or more, fracture of the steel sheet can be significantly reduced by heating the steel sheet to an appropriate temperature, thereby improving productivity and improving yield.

As mentioned above, the manufacturing equipment for cold rolled steel strips and the manufacturing method for cold rolled steel strips according to the present invention have been specifically described by way of embodiments and embodiments for carrying out the invention. However, the spirit of the present invention is not limited to these descriptions, and the patent It must be interpreted broadly based on the scope of the claims. In addition, it goes without saying that various changes and modifications made based on these descriptions are also included in the spirit of the present invention.

According to the present invention, it is possible to provide a manufacturing method and manufacturing equipment for a cold-rolled steel sheet capable of rolling a silicon steel sheet with low environmental load and stably.

1: Payoff reel
2: Bonding device
3: Looper
4: Full width heating device
5: thermometer
6: Cold tandem rolling mill
7: cutter
8: Tension reel
S: steel plate

Claims (7)

A transverse-type full-width heating device that heats the steel sheet over the entire width direction of the steel sheet, and a cold rolling mill that rolls the steel sheet, arranged downstream in the rolling direction with respect to the transverse-type full-width heating device. As a method of manufacturing a cold rolled steel sheet using,
A method of manufacturing a cold rolled steel sheet, comprising the step of heating the steel sheet using the transverse full width heating device so that the temperature of the width direction end portion is higher than the temperature of the width direction center portion of the steel sheet at the entrance side of the cold rolling mill. According to paragraph 1,
A method of manufacturing a cold rolled steel sheet, wherein the temperature of the width direction central portion and the width direction end portion of the steel plate at the entrance side of the cold rolling mill changes depending on the Si content of the steel plate. According to claim 1 or 2,
A method of manufacturing a cold rolled steel sheet, wherein the temperature of the width direction central portion and the width direction end portion of the steel plate at the entrance side of the cold rolling mill is a temperature calculated by the following formulas (1) and (2) that change depending on the Si content α.

A transverse-type full-width heating device that heats the steel sheet over the entire width direction of the steel sheet;
a cold rolling mill disposed downstream in a rolling direction with respect to the transverse full-width heating device and rolling the steel sheet;
The transverse type full width heating device is a cold rolled steel sheet manufacturing equipment that heats the steel sheet so that the temperature of the width direction end portion is higher than the temperature of the width direction center portion of the steel sheet at the entrance of the cold rolling mill. According to paragraph 4,
Cold-rolled steel sheet manufacturing equipment, wherein the transverse full-width heating device changes the temperature of the width-direction central portion and the width-direction end portions of the steel sheet at the entrance to the cold rolling mill in accordance with the Si content of the steel sheet. According to clause 4 or 5,
The transverse-type full-width heating device calculates the temperature of the width-direction central portion and the width-direction end portion of the steel sheet at the entrance of the cold rolling mill using the following equations (1) and (2) that vary depending on the Si content α. Manufacturing equipment for cold-rolled steel sheets that are heated to a certain temperature.

According to any one of claims 4 to 6,
The transverse-type full-width heating device is a cold-rolled steel sheet manufacturing facility installed at a position within 10 m from the entrance of the cold rolling mill.