TWI799028B - Manufacturing method and manufacturing equipment of cold-rolled steel sheet - Google Patents

Abstract

The manufacturing method of the cold-rolled steel plate of the present invention uses: a horizontal full-width heating device to heat the steel plate across the entire width direction of the steel plate; On the downstream side of the cold-rolled steel sheet, the method for manufacturing the cold-rolled steel sheet includes the steps of: using a transverse full-width The heating device heats the steel plate.

Description

Manufacturing method and manufacturing equipment of cold-rolled steel sheet

The invention relates to a method and equipment for manufacturing cold-rolled steel plates.

Conventionally, in cold rolling, single-stand reversing rolling mills such as Sendzimir mills or continuous rolling mills including multiple stands have been used, but in most cases, the first-pass rolling mill feed The temperature of the steel plate on the side is room temperature. Therefore, in cold rolling of a silicon steel sheet (electrical steel sheet) having a high Si content, brittle fracture of the steel sheet tends to occur when the temperature of the steel sheet is low. As the form of fracture at this time, there are cases where the steel sheet is fractured from the widthwise end portions or from the widthwise central portion, etc. As a fracture countermeasure, it is effective to increase the steel sheet temperature during cold rolling. Based on this background, a method of suppressing fracture of the silicon steel sheet by heating the silicon steel sheet before cold rolling is proposed. For example, Patent Document 1 describes a method of heating the widthwise end portion of a steel plate so as to reach a target temperature specified on the feed side of a rolling mill. Also, Patent Document 2 describes a method of uniformly heating the entire steel sheet and rolling it.

[Prior art literature]

[Patent Document]

Patent Document 1: Japanese Patent Laid-Open No. 2012-148310

Patent Document 2: Japanese Patent Laid-Open No. 2011-79025

As described above, there has been proposed a technique for suppressing the occurrence of brittle fracture during cold rolling of a silicon steel sheet with a high Si content. However, in the technique of heating only the end portions in the width direction of the steel sheet, since the temperature of the steel sheet near the center portion in the width direction is low, brittle fractures in the center portion in the width direction may occur. In addition, in the technology of uniformly heating across the entire width direction of the steel plate, there is a possibility that more than necessary energy is input to heat the entire steel plate, and it is considered that there is room for improvement from the viewpoint of sustainable development goals (Sustainable Development Goals, SDGs). room.

The present invention was made in view of the above problems, and an object of the present invention is to provide a manufacturing method and manufacturing facility for a cold-rolled steel sheet capable of rolling a silicon steel sheet stably with low environmental load.

The inventors of the present invention conducted intensive studies to achieve the above object, and found that the fracture suppression temperature (steel plate temperature having a high fracture suppression effect) is higher at the widthwise end portions than at the widthwise central portion. Therefore, the inventors thought that appropriately controlling the output of a transverse full-width heating device that heats across the entire width direction of a steel plate is very effective in terms of fracture suppression and the environment, and conceived the following invention.

The manufacturing method of the cold-rolled steel plate of the present invention uses: a horizontal full-width heating device for heating the steel plate across the entire width direction of the steel plate; Arranged on the downstream side of the rolling direction, the manufacturing method of the cold-rolled steel plate includes the following steps: The steel plate is heated using the above-mentioned transverse full-width heating device so that the temperature at the widthwise end portions of the steel plate at the sides is higher than the temperature at the widthwise central portion.

It may be possible that the temperatures of the widthwise central portion and the widthwise end portions of the steel sheet at the feed side of the cold rolling mill vary depending on the Si content of the steel sheet.

The temperatures of the widthwise central portion and the widthwise end portions of the steel sheet at the feed side of the cold rolling mill can be determined by the following equations (1) and (2) that vary according to the Si content α. calculated temperature.

200℃ T _C : Steel plate temperature at the center of the steel plate width direction at the feed side of the rolling mill [°C] T _C

200℃

200℃ T _E : Steel plate temperature at the edge of the steel plate in the width direction at the feed side of the rolling mill [°C] T _E

200℃

4.5 α: Si content [%] 0<α

4.5

The manufacturing equipment of the cold-rolled steel plate of the present invention includes: a transverse full-width heating device for heating the steel plate across the entire width direction of the steel plate; Arranged on the downstream side in the rolling direction, the transverse full-width heating device heats the steel sheet so that the temperature at the end portions in the width direction of the steel sheet is higher than the temperature at the central portion in the width direction on the feed side of the cold rolling mill. .

The horizontal full-width heating device can be made according to the Si content of the steel plate The temperature change of the width direction central part and the width direction edge part of the steel plate at the feed side of a cold rolling mill is mentioned above.

The temperature of the width direction central part and the width direction end part of the steel plate at the feed side of the cold rolling mill can be heated by the said transverse full-width heating device by the following formula which changes according to the Si content α (1), the temperature calculated by formula (2).

200℃ T _C : Steel plate temperature at the center of the steel plate width direction at the feed side of the rolling mill [°C] T _C

200℃

200℃ T _E : Steel plate temperature at the edge of the steel plate in the width direction at the feed side of the rolling mill [°C] T _E

200℃

4.5 α: Si content [%] 0<α

4.5

The horizontal full-width heating device may be installed within 10 m from the feed side of the cold rolling mill.

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

1: Uncoiler

2: Engagement device

3: Ring

4:Full width heating device

5: Thermometer

6: Cold tandem rolling mill

7: Cutting machine

8: Tension reel

S: steel plate

FIG. 1 is a schematic diagram showing the configuration of a manufacturing facility for cold-rolled steel sheets as an embodiment of the present invention.

Fig. 2 is a graph showing the results obtained by evaluating the temperature dependence of the fracture resistance of silicon steel sheets.

Fig. 3 is a graph showing the estimated results of the steel sheet temperature required for suppressing brittle fracture according to the Si content of the steel sheet.

FIG. 4 is a graph showing the results of evaluating the temperature dependence of edge cracking resistance of silicon steel sheets.

Fig. 5 is a graph showing the estimated results of the steel sheet temperature required for suppressing edge cracks according to the Si content of the steel sheet.

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

〔structure〕

First, with reference to FIG. 1, the structure of the manufacturing facility of the cold-rolled steel plate which is one Embodiment of this invention is demonstrated.

FIG. 1 is a schematic diagram showing the configuration of a manufacturing facility for cold-rolled steel sheets as an embodiment of the present invention. As shown in FIG. 1, the manufacturing facility of cold-rolled steel sheet (hereinafter simply referred to as "manufacturing facility") as an embodiment of the present invention is a continuous rolling line including a plurality of stands, including an uncoiler 1 and a joining device 2. , ring 3, full-width heating device 4, thermometer (plate temperature measuring device) 5, cold tandem rolling mill 6, cutting machine (cutting device) 7, and tension reel 8.

The uncoiler 1 is a device for distributing the steel sheet S. Manufacturing equipment can include multiple open Roller 1. In this case, a plurality of uncoilers distribute different steel plates S, respectively.

The joining device 2 is a device that joins the tail end of the steel plate (preceding material) delivered first from the uncoiler 1 to the front end of the steel plate (subsequent material) delivered after the uncoiler 1 to form a joined steel plate. A laser welding machine can be suitably used as the joining device 2 .

The ring 3 is a device for storing the steel sheets S so that the cold rolling by the cold tandem rolling mill 6 can be continued until the steel sheets are joined by the joining device 2 (period before the joining is completed).

The entire width heating device 4 is a device for heating the steel sheet S over the entire width direction and the rolling direction (longitudinal direction) of the steel sheet S. The full-width heating device 4 can form a temperature gradient along the width direction of the steel sheet S, and includes a transverse induction heating device capable of making the temperature of the edges (ends in the width direction) of the steel sheet S higher than the temperature of the central part of the steel sheet S in the width direction . Furthermore, the full-width heating device 4 can heat the steel sheet S in such a manner that the temperatures of the central portion and the edge portion in the width direction of the steel sheet S at the feed side of the cold tandem rolling mill 6 are expressed by the following formulas: The temperature T _C and the temperature T _E corresponding to the Si content of the steel sheet S calculated by (1) and the formula (2). Thereby, brittle fracture and edge cracking of the steel sheet S can be effectively suppressed.

200℃ T _C : Steel plate temperature at the center of the steel plate width direction at the feed side of the rolling mill [°C] T _C

200℃

200℃ T _E : Steel plate temperature at the edge of the steel plate in the width direction at the feed side of the rolling mill [°C] T _E

200℃

4.5 α: Si content [%] 0<α

4.5

The thermometer 5 is a device for measuring the surface temperature of the steel sheet S. As shown in FIG. The thermometer 5 can be arranged at the nearest feed side of the cold tandem rolling mill 6 . However, in practice, the temperature of the steel sheet measured by the thermometer 5 is not directly used, and a value obtained by compensating for the temperature of the steel sheet dropped between the thermometer 5 and the feed side of the cold tandem rolling mill 6 is used in practice.

The cold tandem rolling mill 6 is a device for cold-rolling the steel sheet S so that the thickness of the steel sheet S heated by the full-width heating device 4 becomes a target thickness. In this embodiment, the cold tandem rolling mill 6 includes five stands, but the number of stands is not particularly limited. In addition, in this embodiment, the cold tandem rolling mill 6 adopts a form called 4Hi in which one stand includes four rolls, but it is not limited to this, and other forms such as 6Hi can also be applied.

The cutter 7 is a device for cutting the steel sheet S after cold rolling.

The tension reel 8 is a device for winding the steel plate S cut by the cutting machine 7 . The form of the tension reel 8 is not limited, for example, it may also be a Carrousel tension reel. Also, the manufacturing facility may include a plurality of tension reels 8 . In this case, the some tension reel 8 winds up several steel plates S continuously.

The devices included in the manufacturing facility are not limited to the above devices. The manufacturing equipment only needs to arrange (preferably adjacently arranged) the full-width heating device 4 and the feeding side of the cold tandem rolling mill 6 sequentially within 10m. Therefore, the rolling mill can also be a reversing rolling mill instead of a tandem rolling mill. In this case, the full-width heating device 4 and the rolling mill are sequentially arranged in the first pass. In addition, the cold rolling step and the pickling step as its preparatory step can also be continuous, and a pickling device for pickling the steel sheet S can be arranged between the ring 3 and the cold tandem rolling mill 6. place.

〔Heating step〕

Next, the characteristic feature of the manufacturing method of the cold-rolled steel sheet according to one embodiment of the present invention, that is, the heating step of the steel sheet S by the full-width heating device 4 will be described. Furthermore, the full-width heating device 4 heats at least one of the upper surface and the lower surface of the steel sheet S, but it is more preferable to heat both the upper surface and the lower surface.

In the heating step of the steel sheet S in the present embodiment, the full-width heating device 4 is based on the temperature of the steel sheet S measured by the thermometer 5, the target temperature of the steel sheet S at the discharge side of the full-width heating device 4, and the temperature of the steel sheet S passing through the entire width. The time of the wide heating device 4 (that is, the heating time) and the thickness of the steel sheet S determine the target temperature of the full-width heating device 4 . Furthermore, the target temperature of the steel sheet S heated by the full-width heating device 4 needs to be set to a temperature in consideration of 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 . For example, when the distance from the full-width heating device 4 to the cold tandem rolling mill 6 is very short, even if the target temperature of the steel plate S at the discharge side of the full-width heating device 4 is set to be heated by the full-width heating device 4 The target temperature of the steel sheet S is also not a big problem. On the other hand, when even any one of the full-width heating device 4, the thermometer 5, and the cold tandem rolling mill 6 is far away, it is necessary to consider the temperature drop before the steel plate S reaches the feed side of the cold tandem rolling mill 6. And the target temperature of the steel plate S heated by the full-width heating apparatus 4 is set. However, from the viewpoint of environmental load, the energy used for heating the steel plate should be small, and the full-width heating device 4 and the thermometer 5 should be 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 silicon steel plate in row rolling mill. The results show that the silicon steel sheet with high Si content has a higher fracture rate than the silicon steel sheet with low Si content. Also, as a result of investigating the cause of the breakage, it was found that the breakage at the upstream side of #1std (hereinafter, the N-th stand from the upstream side of the conveying direction of the steel plate is expressed as "#Nstd") or #2std is closely related to #4std or #5std, etc. The cause of the breakage at the downstream side is different. That is, regarding the fracture at the upstream side, especially the fracture directly below #1std or at the discharge side, it is presumed that the cause is local shrinkage of the steel plate shape such as a mid wave or a lug, or passing through a roll or in a shape detector. Bending deformation. Generally, the reduction rate of #1std is the highest among all frames, and it is considered that the rapid change of the shape of the steel plate is likely to cause fracture. In addition, as a result of further investigation on fractures on the upstream side, the fracture rate (crack occurrence rate) varies depending on the season. For example, the fracture rate in winter is higher than in summer, and the outside air temperature (temperature in the rolling factory) is estimated. will affect the fracture rate. On the other hand, with regard to the fracture at the downstream side, an example in which an edge crack developed at the frame on the upstream side developed to cause fracture was confirmed. Therefore, the location and the cause of fractures are different, but it is considered that any fracture can be suppressed by increasing the temperature of the steel sheet at the feed side of #1std.

In order to verify the above speculation, first, the fracture resistance in the case of imparting bending deformation to the steel plate on a laboratory scale was evaluated. The reason for this is that the fracture resistance in this experiment is considered to be related to the brittle fracture caused by the bending deformation of the passing roller or the shape detector at the frame on the upstream side. As the material to be tested, a silicon steel sheet with a thickness of 2 mm and a Si content of 1.8 mass%, 2.8 mass%, 3.3 mass%, and 3.7 mass% (hereinafter, a silicon steel sheet with a Si content of M mass% is referred to as "M%Si steel") ) of the four silicon steel sheets were annealed at 800°C (equivalent to hot-rolled sheet annealing). Then, the annealed silicon The steel plate is pickled and cut into 24mm wide and 250mm long material to be tested using a shearing machine. Thereafter, processing deformation generated during shearing was removed by grinding each of the two end surfaces by 2 mm. Thereby, occurrence of cracking at the edge portion is suppressed. Furthermore, in an actual continuous cold rolling production line, 1.8% Si steel and 2.8% Si steel are steel types that are not prone to brittle fracture. 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 about several percent especially in the frame on the upstream side. Usually, in cold rolling, the temperature of the steel plate on the feed side of the rolling mill is about the same as the temperature in the factory, and it is about 15° C. in winter.

Therefore, the temperature dependence of the fracture resistance of the silicon steel sheet was investigated when the steel sheet temperature was in the range of 15°C to 45°C. In this experiment, first, a steel plate with a thickness of 2 mm was rolled at a rolling reduction of 50% to produce a steel plate with a thickness of 1 mm. This is a simulation of #1std. Second, the bending deformation of the steel plate through the roll leveler is simulated in rolls or shape detectors. Then, bending deformation was imparted to the steel plate, and the fracture resistance was evaluated. The roller leveler consists of 11 working rollers with a diameter of 50mm, and the interval between the rollers is 60mm. The bending stress applied to the surface of the steel plate can be given an arbitrary value by changing the locking amount of the upper work roll. In this experiment, various changes were made by changing the temperature of the steel plate at intervals of 10°C and the amount of roll locking at intervals of 0.5 mm, and the fracture limit of the steel plate was checked. It is considered that the larger the locking amount at the time of breaking, the less likely it is to break in the cold rolling line. Figure 2 shows the results obtained in this experiment. Furthermore, in view of the breakability in the actual continuous rolling mill, it is considered that as long as it can pass through without breaking before the locking amount of 4.0 mm under the conditions of this experiment, it will not break in the actual continuous rolling mill, and the locking amount No breakage at 4.0 mm was set as the target value of this experiment.

As shown in Figure 2, if compared according to the Si content, the 1.8%Si steel Regardless of the temperature of the steel plate (15°C to 45°C), no breakage occurred until the locking amount was 4.0mm. Also, the 2.8% Si steel cracked at the locking amount of 3.5mm when the steel plate temperature was 15°C, but did not break until the locking amount of 4.0mm at 25°C or higher. Also, the 3.3% Si steel fractured at a locking amount of 1.5 mm when the steel plate temperature was 15°C, and fractured at a locking amount of 3.0 mm at a temperature of 25°C. However, when the temperature of the steel plate was 35°C or higher, no fracture occurred until the locking amount was 4.0mm. In addition, the 3.7% Si steel fractured at a locking amount of 1.0mm when the steel plate temperature was 15°C, fractured at 1.5mm at 25°C, and fractured at 2.5mm at 35°C. When the temperature of the steel plate was set at 45° C., no fracture occurred until the locking amount was 4.0 mm. As a result of the above experiments, it was confirmed that the Si content has a large influence on the fracture resistance of the steel sheet, and that the higher the Si content, the easier the steel sheet is to fracture. This situation is also consistent with the actual situation of fracture in the actual continuous cold rolling mill. Especially for 3.3%Si steel and 3.7%Si steel, as a result of experiments performed while changing the temperature of the steel sheet, the higher the temperature, the more suppressed the brittle fracture.

FIG. 3 shows the results obtained by estimating the temperature of the steel sheet required for the suppression of brittle fracture in accordance with the Si content of the steel sheet based on the results of this experiment. The approximate curve in the figure is represented by the following formula (3). In this experiment, the 1.8% Si steel did not undergo brittle fracture up to the locking distance of 4.0 mm even at a steel plate temperature of 15° C., so it is considered unnecessary to heat the steel plate with the full-width heating device 4 . However, for 2.8% Si steel, when the temperature of the steel plate is 15° C., fracture occurs at a locking amount of 3.5 mm. Therefore, it is considered that the steel plate needs to be heated by the full-width heating device 4 when the temperature of the steel plate is lowered. Therefore, it can be considered that the value of the Si content α[%] in the formula (3) is about α>2 in practice. In addition, the steel sheet temperature T _Cmin calculated from the formula (3) is the minimum necessary temperature, and from the viewpoint of fracture suppression, it may be equal to or higher than this temperature. However, if the temperature of the steel plate is too high, the shape and lubricity of the steel plate will be affected, so the temperature of the steel plate is set to 200° C. or lower. In addition, the upper limit of Si content α of 4.5% is set based on the range in which the temperature of the edge portion of the steel sheet becomes 200° C. or lower, which will be described later.

[Number 4] T _Cmin =0.1α ^4.5 +15...(3)

T _Cmin : Required minimum temperature at the central portion of the steel sheet in the width direction at the feed side of the rolling mill [°C]

4.5 α: Si content [%] 0<α

4.5

Next, in order to suppress the fracture caused by edge cracking of the steel plate, the steel plate was rolled on a laboratory scale, and the presence or absence of edge cracking was evaluated. This experiment is devoted to solving the fracture pattern in which edge cracks generated on the upstream side of the rolling direction are amplified by entering the frame on the downstream side of the rolling direction. Suppresses breakage caused by cracking at the edge of the steel sheet. As the material to be tested, four kinds of silicon steel plates with a plate thickness of 2 mm and 1.8% Si steel, 2.8% Si steel, 3.3% Si steel, and 3.7% Si steel were cut into 20 mm wide and 250 mm long, and annealed at 800 ° C. (Equivalent to hot-rolled sheet annealing). Then, the annealed silicon steel plate is pickled. It is considered that the state of the edge portion of the steel sheet at this time is close to the actual state on the feed side of the continuous cold rolling mill.

Furthermore, in an actual continuous cold rolling line, 1.8% Si steel is a steel type that is less prone to cracking at the edge of the steel plate. On the other hand, 3.3%Si steel and 3.7%Si steel are based on A steel type in which cracking occurs at the edge of the steel plate at a frequency of several percent. Usually, in cold rolling, the temperature of the steel plate on the feed side of the rolling mill is about the same as the temperature in the factory, and it is about 15°C in winter. Therefore, regarding the edge cracking resistance of the silicon steel sheet, the temperature dependence when the steel sheet temperature is in the range of 15°C to 65°C was investigated. In this experiment, #1std was simulated, and edge resistance was evaluated based on the number of cracks (cracks of 1mm or more) that occurred on both ends of the steel plate (in the longitudinal direction) when the material to be tested was rolled at a reduction rate of 50% (w20mm×L250mm) Partiality. In addition, each amount of Si and the number of times of rolling at each temperature were five times, and the number of edge cracks was an average value of five times. In addition, the temperature of the steel sheet was set at intervals of 10°C. Figure 4 shows the results obtained in this experiment.

As shown in FIG. 4 , when the steel sheet temperature is 15°C, no edge cracking occurs on both end surfaces of the 1.8% Si steel when compared for each Si content. A total of 7 edge cracks occurred on both ends of the 2.8% Si steel. A total of 15 edge cracks occurred on both end surfaces of the 3.3% Si steel, and a total of 30 edge cracks occurred on the 3.7% Si steel. When the steel plate temperature was 25° C., the total number of edge cracks on both end surfaces of the 2.8% Si steel was 0 in addition to the 1.8% Si steel. On the other hand, 3.3% Si steel had 11, and 3.7% Si steel had 27. When the temperature of the steel plate was 35° C., the number of edge cracks in the sum of both end surfaces in the 1.8% Si steel and the 2.8% Si steel was zero. On the other hand, a total of 5 edge cracks occurred on both end surfaces of the 3.3% Si steel, and a total of 20 edge cracks occurred in the 3.7% Si steel. When the steel plate temperature was 45° C., the total number of edge cracks on both end surfaces of the 3.3% Si steel was zero except for the 1.8% Si steel and the 2.8% Si steel. On the other hand, 3.7% Si steel had 10 edge cracks. When the steel plate temperature is 55°C, except for 1.8%Si steel and 2.8%Si steel, the two parts of 3.3%Si steel The number of edge cracks in the total end faces was also zero. On the other hand, the 3.7% Si steel had three edge cracks. When the steel plate temperature was 65° C., the total number of edge cracks on both end surfaces of the 3.7% Si steel was zero except for the 1.8% Si steel, 2.8% Si steel, and 3.3% Si steel. From the results of the above experiment, it was confirmed that the Si content has a large influence on the edge cracking resistance, and that the higher the Si content, the easier the edge cracking of the steel sheet occurs. This also coincides with the fact that the edges of steel sheets are cracked in an actual continuous cold rolling mill.

FIG. 5 shows the results of estimating the temperature required for suppressing cracking at the edge of the steel sheet in accordance with the Si content of the steel sheet based on the results of this experiment. The approximate curve in the figure is represented by the following formula (4). In this experiment, for the 1.8% Si steel, even when the temperature of the steel plate was 15° C., no edge cracking occurred in the steel plate, so it is considered unnecessary to heat the steel plate with the full-width heating device 4 . However, in the case of 2.8% Si steel, cracks occur at the edge of the steel plate at a steel plate temperature of 15° C., so it is considered necessary to heat the steel plate with the full-width heating device 4 when the steel plate temperature is lowered. Therefore, it can be considered that the Si content α[%] in the formula (4) is practically α>2. In addition, the steel sheet temperature T _Emin calculated from the formula (4) is the necessary minimum temperature, and it is only necessary to be at or above this temperature from the viewpoint of fracture suppression. However, if the temperature of the steel plate is too high, the shape and lubricity of the steel plate will be affected, so the temperature of the steel plate is set to 200° C. or lower. In addition, the upper limit value of 4.5% of the Si content α is set so that the temperature of the edge portion of the steel sheet calculated by the formula (4) is in the range of 200° C. or lower. In addition, the heating range of the steel plate is set to a range of 30 mm or more from the edge portion of the steel plate. The reason for this is that it is the range affected by elongation during cold rolling that affects cracking at the edge of the steel sheet, and this range is considered to be approximately 30 mm from the edge of the steel sheet.

[Number 5]T _Emin =0.1α ^4.8 +15...(4)

T _E : Necessary minimum temperature at the end of the steel plate in the width direction at the feed side of the rolling mill [°C]

4.5 α: Si content [%] 0<α

4.5

From the above two experiments, it was found that the heating temperature of the steel sheet required to suppress fracture from the central portion in the width direction and fracture from the edge portion of the steel sheet is different. For example, in the case of 3.7% Si steel, the temperature required to suppress cracking from the central 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 mentioned above, it was found that in order to suppress the cracking of the silicon steel sheet, in addition to setting the heating amount corresponding to the Si content, it is also necessary to form the temperature along the width direction of the steel sheet so that the temperature of the edge part is higher than that of the center part in the width direction in the same steel type. temperature gradient, thus conceived of the present invention. Furthermore, when a plurality of steel sheets with different Si contents are transported by the same facility, the heating device 6 may acquire information indicating the Si contents of the preceding material and the subsequent material, and change and determine the target temperature based on the information. In addition, in this embodiment, the material to be rolled is described as a silicon steel sheet, but the type of steel sheet is not limited. Examples of steel sheets to which the technique 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 a cold-rolled steel sheet as an embodiment of the present invention, the temperature from the central portion in the width direction is appropriately controlled using the full-width heating device 4 capable of forming a temperature gradient along the width direction of the steel sheet S. The temperature required for the suppression of cracking and edge cracking can be controlled, and the cracking of the steel plate can be suppressed. Therefore, the root According to the manufacturing equipment of cold-rolled steel sheet and the method of manufacturing cold-rolled steel sheet which are one embodiment of the present invention, when cold-rolling silicon steel sheet, it is possible to suppress the fracture of the steel sheet with the necessary minimum energy, so it is possible to use the minimum environmental load. Stable cold rolled silicon steel plate.

[Example]

Examples showing the effects of the present invention will be described. In this embodiment, the full-width heating device 4 is installed on the feed side of the cold rolling mill, and the temperature of the steel plate on the feed side of the rolling mill can be set to an arbitrary temperature. In addition, it is finished to a specific plate thickness by a cold tandem rolling mill with 5 stands. The steel types used in this embodiment are all silicon steel plates, which are divided into 3 groups according to the Si content. Specifically, there are three groups of Si content of 1.0 mass% to 2.0 mass%, the group of 2.0 mass% to 3.0 mass%, and the group of 3.0 mass% to 3.5 mass%. In either 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 under different Si contents, care was taken to avoid variation in plate thickness due to the group. The fracture rate of 200 steel coils was investigated in each group. In addition, the outside air temperature (temperature in the factory) is about 15°C. Table 1 shows the investigated steel coils and conditions. The temperature of the steel plate was measured using a thermometer installed on the feed side of the rolling mill.

〔Reference example〕

An example is shown of the case where the steel plate is not heated by the full-width heating device, that is, the temperature of the steel plate on the feed side of the rolling mill is about 15°C. The fracture rate of 200 steel coils with Si content ranging from 1.0 mass% to 2.0 mass% was 0%. On the other hand, the Si content is 2.0 mass% The fracture rate of 200 steel coils to 3.0 mass% is 1%, and the fracture rate of 200 steel coils from 3.0 mass% to 3.5 mass% is 3%.

[Invention Example 1]

It shows the situation where the temperature of the steel plate on the feed side of the cold tandem mill is calculated according to the Si content of the silicon steel plate according to the above formula (1) and formula (2), and the steel plate is heated by the full-width heating device based on this example. The distance between the cold tandem mill and the full width heating unit is 10m. 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 steel coils (width center 17°C, edge portion 18°C) with a Si content of 1.0 mass% to 2.0 mass% was 0%. Also, 200 steel coils with a Si content of 2.0 mass% to 3.0 mass% (30°C at the center of the width and 35°C at the edge) also had a fracture rate of 0%, and 200 steel coils with a Si content of 3.0 mass% to 3.5% (45°C at the center of the width) were also 0%. ℃, edge 60 ℃) fracture rate is also 0%. It was confirmed that the fracture of the steel sheet can be significantly reduced by heating the silicon steel sheet based on the present invention.

[Invention Example 2]

It shows the situation where the temperature of the steel plate on the feed side of the cold tandem mill is calculated according to the Si content of the silicon steel plate according to the above formula (1) and formula (2), and the steel plate is heated by the full-width heating device based on this example. The distance between the cold tandem mill and the full width heating unit is 1m. That is, compared with Inventive Example 1, the distance between the cold tandem rolling mill and the full-width heating device was shorter. Other conditions are the same as Invention Example 1. In the example of the present invention, the breakage rate of 200 steel 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 steel coils (30°C in the center of the width and 35°C at the edge) with a Si content of 2.0 mass% to 3.0 mass% is also 0%, 3.0 mass% The fracture rate of the 200 steel coil (width center 45°C, edge portion 60°C) to 3.5 mass% was also 0%. Focusing only on the fracture rate, fractures can be suppressed until the Si content reaches 3.5 mass%, which is the same as Invention Example 1, but the energy usage is significantly lower than Invention Example 1, and the superiority of Invention Example 2 can be confirmed. Therefore, it was confirmed that the shorter the distance between the cold tandem rolling mill and the full-width heating device, the better, from the viewpoint of reducing the amount of energy used (environmental resistance).

[Comparative Example 1]

An example is shown in which the steel sheet temperature on the feed side of the rolling mill is calculated according to the above-mentioned formula (1) and formula (2) according to the Si content of the silicon steel plate, and the steel plate is heated by the full-width heating device based on this. The distance between the cold tandem mill and the full width heating unit is 20m. That is, it is an example in which the distance between the cold tandem rolling mill and the full-width heating device is extended under the conditions of Invention Example 1. Since the distance between the cold tandem rolling mill and the full-width heating device is long, even if the upper limit of the capacity of the full-width heating device is used, it cannot be set as a rolling mill calculated from equations (1) and (2). Steel plate temperature on the feed side. 200 steel coils with a Si content of 1.0 mass% to 2.0 mass% (15°C in the center of the width and 15°C at the edge) have a fracture rate of 0%, and 200 steel coils with a Si content of 2.0 mass% to 3.0 mass% (25°C in the center of the width) ℃, edge 30 ℃) fracture rate is also 0%. On the other hand, the fracture rate of 200 steel coils (width center 40°C, edge portion 50°C) with a Si content of 3.0 mass% to 3.5 mass% was 1%. It can be confirmed that the short distance between the cold tandem rolling mill and the full-width heating device is better, and the upper limit of the capacity of the full-width heating device cannot be ensured according to the above formula (1) and formula (2) ) in the case of the calculated distance of the steel sheet temperature, the higher the Si steel is, the easier it is to fracture.

[Comparative Example 2]

It means that the temperature of the steel sheet on the feed side of the rolling mill is about 30% lower than the temperature of the steel sheet on the feed side of the rolling mill calculated from the above-mentioned formula (1) and formula (2) according to the Si content of the silicon steel plate. An example of a case where the device heats a steel plate. Other conditions are the same as Invention Example 1. 200 steel coils with a Si content of 1.0 mass% to 2.0 mass% (15°C in the center of the width, 15°C at the edge) have a fracture rate of 0%, and 200 steel coils with a Si content of 2.0 mass% to 3.0 mass% (20°C in the center of the width) ℃, edge 25 ℃) fracture rate is also 0%. On the other hand, the fracture rate of 200 steel coils (30°C in the center of the width and 40°C at the edges) 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 temperature of the steel sheet calculated from the above formula (1) and formula (2), the higher the Si steel is, the easier it is to fracture.

[Comparative Example 3]

An example of a case where a solenoid type full-width heating device is used is shown. In the solenoid type full-width heating device, a temperature gradient cannot be formed along the width direction of the steel plate. The temperature of the steel plate heated by the solenoid type full-width heating device was calculated from the formula (1). That is, the temperature considered necessary to suppress cracking at the edge cannot be ensured, and since the temperature of the steel sheet at the edge tends to drop compared to that at the center in the width direction, the temperature at the edge is lower than that at the center in the width direction. The fracture rate of 200 steel coils (17°C at the center of the width and 16°C at the edges) with a Si content of 1.0 mass% to 2.0 mass% was 0%. On the other hand, 200 steel coils with a Si content of 2.0 mass% to 3.0 mass% (30°C in the center of the width and 25°C at the edge) had a fracture rate of 0.5%, and 200 steel coils of 3.0 mass% to 3.5 mass% (the center of the width 45°C, edge 35°C) fracture rate was 2%. right As a result of investigating the fracture form of the fractured steel coil, it was found that although fractures from the center in the width direction could be suppressed, fractures due to edge cracks could not be suppressed.

[Comparative Example 4]

An example of a case where a solenoid type full-width heating device is used is shown. The temperature of the steel plate heated by the solenoid type full-width heating device was calculated from the formula (2). That is, the steel sheet is heated across the entire width direction so that the temperature of the edge becomes a temperature considered necessary for suppressing edge cracking. 200 steel coils with a Si content of 1.0 mass% to 2.0 mass% (20°C in the center of the width, 18°C at the edge) have a fracture rate of 0%, and 200 steel coils with a Si content of 2.0 mass% to 3.0 mass% (40°C in the center of the width) ℃, edge portion 35°C) fracture rate is also 0%, and the fracture rate of 200 steel coils with Si content of 3.0 mass% to 3.5 mass% (width center 70°C, edge portion 60°C) is also 0%. However, from the viewpoint of fracture suppression, it is sufficient to heat the central portion in the width direction of the steel sheet more than necessary, and to reduce input energy in consideration of environmental load.

[Comparative Example 5]

An example is shown in which an edge heating device that heats only both ends in the width direction of a steel sheet is used without using a full-width heating device. The temperature at both ends in the width direction of the steel plate heated by the edge heating device was calculated from the formula (2). The fracture rate of 200 steel coils (15°C in the center of the width and 35°C at the edges) with a Si content of 1.0 mass% to 2.0 mass% was 0%. On the other hand, 200 steel coils with a Si content of 2.0 mass% to 3.0 mass% (15°C in the center of the width and 35°C at the edge) had a fracture rate of 0.5%, and 200 steel coils with a Si content of 3.0 mass% to 3.5 mass% (15°C at the center of the width, 60°C at the edge) had a fracture rate of 2%. The fracture morphology of the fractured steel coils was investigated and concluded that This is because although fractures due to cracks at the edge portions can be suppressed, fractures from the central portion in the width direction cannot be suppressed.

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

Above, the manufacturing equipment for cold-rolled steel sheets and the method for manufacturing cold-rolled steel sheets according to the present invention have been specifically described through the forms and examples for implementing the invention, but the gist of the present invention is not limited to these descriptions, and must be based on The scope of the patent application is broadly interpreted. Moreover, of course, what made various changes, changes, etc. based on these description is also included in the summary of this invention.

[industrial availability]

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

1: Uncoiler

2: Engagement device

3: Ring

4:Full width heating device

5: Thermometer

6: Cold tandem rolling mill

7: Cutting machine

8: Tension reel

S: steel plate

Claims (3)

A method for manufacturing a cold-rolled steel plate, which uses: a horizontal full-width heating device to heat the steel plate across the width direction of the steel plate and the rolling direction; and a cold rolling mill that rolls the steel plate. The full-width heating device is arranged on the downstream side of the rolling direction, and the manufacturing method of the cold-rolled steel sheet includes the following steps: The step of heating the steel sheet using the transverse full-width heating device in such a manner that the lowest temperature is higher than the lowest temperature at the widthwise central portion of the steel sheet excluding the widthwise end portions, that the feed side of the cold rolling mill The temperature of the width direction central part and the width direction end part of the steel plate at the position is the temperature calculated by the following formula (1) and formula (2) which change according to the Si content α,

T _C : Steel plate temperature at the center of the steel plate width direction at the feed side of the rolling mill [°C] T _C

200°C T _E : Steel plate temperature at the end of the steel plate in the width direction at the feed side of the rolling mill [°C] T _E

200℃ α: Si content [%]0<α

4.5. A manufacturing equipment for cold-rolled steel plates, comprising: a horizontal full-width heating device, which heats the steel plate across the width direction of the steel plate and the entire rolling direction; and a cold rolling mill, which rolls the steel plate. A wide heating device is arranged on the downstream side of the rolling direction, and the transverse full-width heating device has a minimum temperature of the width direction end of the steel plate in the range of 30 mm from the edge part at the feed side of the cold rolling mill higher than The steel plate is heated in such a manner that the lowest temperature of the width direction central portion of the steel plate other than the width direction end portion is reached, and the transverse full-width heating device heats the width direction central portion of the steel plate at the feed side of the cold rolling mill. And the temperature heating at the end portion in the width direction is the temperature calculated by the following formula (1) and formula (2) that change according to the Si content α,

T _C : Steel plate temperature at the central part in the width direction of the steel plate at the feed side of the rolling mill [°C] T _C

200°C T _E : Steel plate temperature at the end of the steel plate in the width direction at the feed side of the rolling mill [°C] T _E

200℃ α: Si content [%]0<α

4.5. The manufacturing equipment of cold-rolled steel plate according to claim 2, wherein the horizontal full-width heating device is arranged within 10 m from the feed side of the cold rolling mill.

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