Patent Application
20240033795
The present invention relates to a cold rolling method for cold-rolling a material to be rolled, cold rolling equipment, and a cold-rolled steel sheet manufacturing method.
In a cold-rolled steel sheet manufacturing line, sheet breakage may occur due to various factors during cold rolling of a material to be rolled. One of the reasons for the sheet breakage is occurrence of an edge crack based on a crack which occurred due to a tension applied to an edge portion increased due to a defective sheet thickness distribution (for example, edge drop) in a sheet width direction of the material to be rolled, and this may lead to the sheet breakage. In order to reduce such sheet breakage, it is important to suppress the generation of cracks and an increase of the generated cracks in their size. The edge drop refers to a phenomenon of rapid sheet thickness reduction particularly at both end portions in a sheet width direction in a sheet thickness deviation in the sheet width direction that occurs on a sheet material during the rolling.
In the related art, a method for controlling a sheet thickness of a sheet material in a width direction disclosed in PTL 1 has been proposed as, for example, a method for reducing the amount of the edge drop and improving the sheet thickness distribution in the sheet width direction.
In the method for controlling the sheet thickness in the width direction of a sheet material disclosed in PTL 1, the sheet thickness of the sheet material in the width direction is controlled by a rolling mill including a mechanism of shifting and a mechanism of crossing a work roll having a tapered roll end portion in a plurality of stands.
According to the method for controlling the sheet thickness of the sheet material in the width direction disclosed in PTL 1, it is possible to accurately perform the control in a divided manner using the plurality of stands. Accordingly, it is possible to obtain an excellent sheet thickness distribution over the entire sheet width from a sheet thickness deviation that is gently generated from a sheet width center toward a sheet end side to a sheet thickness deviation sharply generated on a sheet width end portion (edge drop).
PTL 1: JP H10-29010 A
However, the method for controlling the sheet thickness of the sheet material in the width direction disclosed in PTL 1 has the following problems.
That is, in the method for controlling the sheet thickness of the sheet material in the width direction disclosed in PTL 1, the excellent sheet thickness distribution is obtained over the entire sheet width, but according to a test of the inventors, it was found that the occurrence of edge cracks of a material to be rolled during cold rolling cannot be sufficiently suppressed and sheet breakage during the cold rolling cannot be sufficiently suppressed.
Therefore, the present invention has been made to solve the problems of the related art, and an object thereof is to provide a cold rolling method capable of preventing sheet breakage by sufficiently suppressing occurrence of an edge crack of a material to be rolled during cold rolling, cold rolling equipment, and a cold-rolled steel sheet manufacturing method.
In order to achieve the aforementioned object, there is provided a cold rolling method according to an aspect of the present invention for cold-rolling a material to be rolled by a rolling mill including a plurality of stands, in which an N-th stand (N is a natural number equal to or greater than 2) arranged in an N-th position from an upstream side of the material to be rolled in a transfer direction among the plurality of stands, includes a tapered work roll having a taper formed on an end portion of a roll having a uniform diameter, and the N-th stand rolls the material to be rolled with a linear load of 0.8 t/mm or more.
In addition, there is provided a cold rolling method according to another aspect of the present invention for cold-rolling a material to be rolled by a rolling mill including a plurality of stands, in which an N-th stand (N is a natural number equal to or greater than 2) arranged in an N-th position from an upstream side of the material to be rolled in a transfer direction and an (N+1)-th stand arranged in an (N+1)-th position on a downstream side of the N-th stand among the plurality of stands, include a tapered work roll having a taper formed on an end portion of a roll having a uniform diameter, and each of the N-th stand and the (N+1)-th stand rolls the material to be rolled with a linear load of 1.7 t/mm or more and a tapered rolling portion width WRδ which is a length, which faces the material to be rolled, of the taper formed on the tapered work roll of each of the N-th stand and the (N+1)-th stand is set as −50 mm to −5 mm.
In addition, there is provided a cold rolling equipment according to still another aspect of the present invention having a rolling mill including a plurality of stands for rolling a material to be rolled, in which an N-th stand (N is a natural number equal to or greater than 2) arranged in an N-th position from an upstream side of the material to be rolled in a transfer direction among the plurality of stands, includes a tapered work roll having a taper formed on an end portion of a roll having a uniform diameter, and a linear load of the N-th stand is set as 0.8 t/mm or more.
In addition, there is provided a cold rolling equipment according to still another aspect of the present invention including a rolling mill having a plurality of stands for rolling a material to be rolled, in which each of an N-th stand (N is a natural number equal to or greater than 2) arranged in an N-th position from an upstream side of the material to be rolled in a transfer direction and an (N+1)-th stand arranged in an (N+1)-th position on a downstream side of the N-th stand among the plurality of stands, includes a tapered work roll having a taper formed on an end portion of a roll having a uniform diameter, and a linear load of each of the N-th stand and the (N+1)-th stand is set as 1.7 t/mm or more, and a tapered rolling portion width WRδ, which is a length, which faces the material to be rolled, of the taper formed on the tapered work roll of each of the N-th stand and the (N+1)-th stand is set as −50 mm to −5 mm.
In addition, there is provided a cold-rolled steel sheet manufacturing method according to still another aspect of the present invention including cold-rolling a steel sheet to manufacture a cold-rolled steel sheet by the cold rolling method described above.
According to the cold rolling method, the cold rolling equipment, and the cold-rolled steel sheet manufacturing method according to the present invention, it is possible to prevent sheet breakage by sufficiently suppressing occurrence of an edge crack of a material to be rolled during cold rolling.
Hereinafter, embodiments of the present invention will be described with reference to the drawings. The embodiments illustrated below are examples of a device or a method for implementing technical idea of the present invention and the technical idea of the present invention does not intend to specify materials, shapes, structures, arrangement, and the like of the constituent components to the following embodiments. Also, the drawings are schematically illustrated. Therefore, it should be noted that a relationship, a ratio, and the like between a thickness and a planar dimension are different from the actual ones, and the drawings include portions where the relationship or ratio thereof are different from each other.
Cold rolling equipment 1 illustrated in
Each of the first stand 31 to the fourth stand 34 includes a pair of upper and lower work rolls 4a for rolling the steel sheet S as a material to be rolled, a pair of upper and lower back-up rolls 4b for supporting the work rolls 4a, and a pair of upper and lower intermediate rolls 4c arranged between each work roll 4a and each back-up roll 4b.
In addition, each work roll 4a of the second stand 32 is configured as a tapered work roll 4a1 (hatched in
The reason why each work roll 4a of the second stand 32 is configured with the tapered work roll 4a1 as described above will be described below.
As illustrated in
As a result of investigating a starting point of a crack by rolling the electromagnetic steel sheet with the rolling mill 2, it was confirmed that the edge crack occurred on an outer side of the third stand 33. In order to identify the factor, an edge drop ratio of each of the first stand 31 to the fourth stand 34 was measured.
Here, the edge drop refers to a phenomenon of rapid sheet thickness reduction particularly at both end portions in a sheet width direction in a sheet thickness deviation in the sheet width direction that occurs on the steel sheet S during the rolling. The edge drop ratio is represented by the following equation, in a case where a sheet thickness at 5 mm from both end surfaces of the steel sheet S in the sheet width direction is defined as E5 and a sheet thickness at 20 mm from the both end surfaces is defined as E20, as illustrated in
Edge drop ratio Ed=(E5−E20)/E20
An edge-up known as a sheet thickness deviation in contrast to the edge drop refers to a phenomenon of a rapid sheet thickness increase particularly at both end portions in the sheet width direction in the sheet thickness deviation in the sheet width direction that occurs on the steel sheet S during the rolling. An edge-up amount is represented by the following equation, in a case where a sheet thickness at 5 mm from both end surfaces of the steel sheet S in the sheet width direction is defined as E5 and a sheet thickness at 20 mm from the both end surfaces is defined as E20, as illustrated in
Edge-up amount Eu=E5−E20
In
As a result of measuring the edge drop ratio of each of the first stand 31 to the fourth stand 34, it was found that the edge drop ratio was greatly increased and exceeded a suitable range on the third stand 33, and then the edge drop ratio was decreased on the fourth stand 34. Here, an increase in the edge drop ratio means that a numerical value of the edge drop ratio increases on a negative side, and a decrease in the edge drop ratio means that a numerical value of the edge drop ratio decreases on a negative side.
In other words, it was found that, in a case where a difference between the edge drop ratio on the fourth stand 34 and the edge drop ratio on the third stand 33 is large (the difference is 0.02 or more on a+side), the sheet breakage easily occurs.
It was assumed that this was because an excessive tension was applied to both edge portions of an electromagnetic steel sheet in a sheet width direction in the third stand 33 and the edge crack occurred on the outer side of the third stand 33 due to a crack or the like on an edge portion occurred in the second stand 32 on the upstream side as a starting point.
For this reason, the present inventors make a uniform sheet thickness distribution of the steel sheet by setting the work roll 4a of the second stand 32 on the upstream side as the tapered work roll 4a1, and set the work roll 4a of the third stand 33 on the downstream side as the flat work roll 4a2. Accordingly, the present inventors acquired findings in that the edge drop ratio on the first stand 31, the second stand 32, the third stand 33, and the fourth stand 34 can be set in the suitable range, the difference between the edge drop ratio on the fourth stand 34 and the edge drop ratio on the third stand 33 is decreased, and the tension applied to the edge portion of the third stand 33 on the downstream side is decreased, thereby preventing the edge crack of the steel sheet.
For this reason, each work roll 4a of the second stand 32 was configured with the tapered work roll 4a1. Accordingly, it was found that, by performing the rolling with the tapered work roll 4a1 in the second stand 32, the occurrence of the excessive edge drop was suppressed, and even when the rolling is performed with the flat work roll in the subsequent third stand 33, the tension applied to the edge portion was decreased, thereby suppressing the occurrence of the crack. As a result of cold-rolling the electromagnetic steel sheet as the material to be rolled by the rolling mill 2 illustrated in
As illustrated in
In addition,
As illustrated in
When each breakage occurrence ratio is compared, the breakage occurrence ratio can be decreased by configuring the work roll 4a of the second stand 32 with the tapered work roll 4a1 as illustrated in
From the above, by configuring the work roll 4a of the second stand 32 with the tapered work roll 4a1, it is possible to reinforce the findings in that the occurrence of the excessive edge drop on the second stand 32 on the upstream side can be suppressed and the tension applied to the edge portion of the steel sheet S on the third stand 33 on the downstream side can be decreased to suppress the occurrence of the edge crack.
The above result is obtained in a case where the second stand 32 having the tapered work rolls 4a1 rolls the steel sheet S with a linear load (rolling load/sheet width) of 1.4 t/mm.
As a result of further tests, as illustrated in Tables 1,
Table 1 and
As illustrated in Table 1 and
In addition, Table 2 and
As illustrated in Table 2 and
A lower limit value of the linear load at which the edge crack of the steel sheet S occurs is 0.8 t/mm, unless the second stand 32 is shifted in the positive direction. In other words, in a case where the steel sheet S is rolled with a linear load of less than 0.8 t/mm, the edge crack of the steel sheet S does not occur regardless of the shift direction of the second stand 32.
In addition, as a result of further tests, as illustrated in Tables 3,
Table 3 and
As illustrated in Table 3 and
In addition, Table 4 and
As illustrated in Table 4 and
From the above, the work roll 4a of the second stand 32 is configured with the tapered work roll 4a1, and the second stand 32 having the tapered work roll 4a1 rolls the steel sheet S with a linear load of 0.8 t/mm or more. When the second stand 32 rolls the steel sheet S with a linear load of less than 1.4 t/mm, the steel sheet S is rolled by setting the tapered rolling portion width WRδ of the tapered work roll. 4a1 of the second stand 32 as ±0 mm to +50 mm. In addition, when the second stand 32 rolls the steel sheet S with a linear load of 1.4 t/mm or more, the steel sheet S is rolled by setting the tapered rolling portion width WRδ of the tapered work roll 4a1 of the second stand 32 as −50 mm to −5 mm. It was found that by this, both edge drop and edge-up can be appropriately controlled, and the occurrence of edge crack can be suppressed.
The reason for determining whether to shift the tapered work roll 4a1 of the second stand 32 in the positive direction or shift the tapered work roll 4a1 in the negative direction based on the linear load, 1.4 t/mm, of the second stand 32 having the tapered work roll 4a1 is as described below. That is, in a case where the linear load of the second stand 32 having the tapered work roll 4a1 is set as 1.4 t/mm or more, the material to be rolled is a high-load material, and the tapered work roll 4a1 easily bend. Accordingly, by shifting the tapered work roll 4a1 in the negative direction, the excessive edge drop is suppressed. On the other hand, in a case where the linear load of the second stand 32 having the tapered work roll 4a1 is set as less than 1.4 t/mm, the material to be rolled is a low-load material, and the tapered work roll 4a1 is less likely to bend and the edge-up easily occurs. Accordingly, by shifting the tapered work roll 4a1 in the positive direction, it is held on the edge drop side.
Next, the configuration of the tapered work roll 4a1 will be described with reference to
The tapered rolling portion width WRδ of the tapered work roll 4a1 is a length of the taper 4ab facing the steel sheet S, and is a length from a taper start end 4ac to a width direction end surface of the steel sheet S in
In addition, as described above, when the second stand 32 rolls the steel sheet S with a linear load of 1.4 t/mm or more, the steel sheet S is rolled by setting the tapered rolling portion width WRδ of the tapered work roll 4a1 of the second stand 32 as −50 mm to −5 mm. That is, it is preferable to roll the steel sheet S by shifting the tapered work roll 4a1 of the second stand 32 in the negative direction.
In a case where the width direction end surface of the steel sheet S protrudes from the taper start end 4ac, the tapered rolling portion width WRδ is a negative value, and in a case where the width direction end surface of the steel sheet S is recessed from the taper start end 4ac, the tapered rolling portion width WRδ is a positive value. A case where the tapered rolling portion width WRδ is a positive value is the same operation as a case where the flat work roll 4a2 is used.
In addition, an inclination of the taper 4ab is represented as L/H, in a case where a length from the taper start end 4ac to a taper final end surface (axial direction end surface of the tapered work roll 4a1) is defined as L and a difference in height between an outer peripheral surface of the roll 4aa and an outer periphery of the taper final end surface is defined as H. The inclination L/H of the taper 4ab is preferably 1/800 to 1/400. In a case where the inclination L/H of the taper 4ab is smaller than 1/800, there is a problem that the edge drop cannot be suppressed. On the other hand, in a case where the inclination L/H of the taper 4ab is larger than 1/400, there is a problem that the edge-up excessively occurs.
In addition, in the description of the configuration of the flat work roll 4a2, the flat work roll 4a2 is configured with a roll having a uniform diameter in the body length direction. The work roll 4a, which is the flat work roll 4a2, is configured to be shifted in an axial direction (a roll body length direction, a sheet width direction of the steel sheet S).
As described above, in the cold rolling equipment 1 according to the first embodiment, among the four stands of the first stands 31 to the fourth stands 34, the second stand 32 arranged in the second position from the upstream side of the steel sheet S, as the material to be rolled, in the transfer direction includes the tapered work roll 4a1 having the taper 4ab formed on the end portion of the roll 4aa having a uniform diameter. A linear load of the second stand 32 is set as 0.8 t/mm or more. When the linear load of the second stand 32 is set as less than 1.4 t/mm, the tapered rolling portion width WRδ of the tapered work roll 4a1 of the second stand 32 is ±0 mm and +50 mm. In addition, when the linear load of the second stand 32 is set as 1.4 t/mm or more, the tapered rolling portion width WRδ of the tapered work roll 4a1 of the second stand 32 is set as −50 mm to −5 mm.
Therefore, the edge drop ratio on the first stand 31 to the fourth stand 34 is kept within the appropriate range, and the occurrence of edge crack on the steel sheet S as the material to be rolled during the cold rolling is sufficiently suppressed, thereby suppressing the sheet breakage.
In addition, in the cold rolling equipment 1 according to the first embodiment, among the four stands of first stands 31 to the fourth stand 34, the third stand 33 arranged in the third position on the downstream side of the second stand 32 includes the flat work roll 4a2 having a uniform diameter of a roll.
Accordingly, the effect of promoting the edge drop is exhibited.
In addition, in the cold rolling equipment 1 according to the first embodiment, among the four stands of first stands 31 to the fourth stands 34, the first stand 31 arranged on the uppermost stream side includes the flat work roll 4a2, but may include the tapered work roll 4a1.
Accordingly, the effect of suppressing the edge drop is exhibited.
In addition, in a cold rolling method according to the first embodiment, the steel sheet S as the material to be rolled is cold-rolled by the rolling mill 2 in the cold rolling equipment 1 illustrated in
When the second stand 32 rolls the steel sheet S with a linear load of less than 1.4 t/mm, the steel sheet S is rolled by setting the tapered rolling portion width WRδ which is a length of the taper 4ab, facing the steel sheet S, which is formed on the tapered work roll 4a1 of the second stand 32 as ±0 mm to +50 mm.
Meanwhile, when the second stand 32 rolls the steel sheet S with a linear load of 1.4 t/mm or more, the steel sheet S is rolled by setting the tapered rolling portion width WRδ which is a length of the taper 4ab, facing the steel sheet S, which is formed on the tapered work roll 4a1 of the second stand 32 as −50 mm to −5 mm.
Therefore, the edge drop ratio on the first stand 31 to the fourth stand 34 is kept within the appropriate range, and the occurrence of edge crack on the steel sheet S as the material to be rolled during the cold rolling is sufficiently suppressed, thereby suppressing the sheet breakage.
In the cold-rolled steel sheet manufacturing method according to the first embodiment, the steel sheet S is cold-rolled by the cold rolling method according to the first embodiment to manufacture the cold-rolled steel sheet.
Next, cold rolling equipment according to a second embodiment of the present invention will be described with reference to
Unlike the cold rolling equipment 1 illustrated in
The reason why each work roll 4a of the second stand 32 and each work roll 4a of the third stand 33 is configured with the tapered work roll 4a1 as described above will be described below.
As illustrated in
On the other hand, as illustrated in
Accordingly, a tension applied to an edge portion on the third stand 33 is further reduced, and edge crack of the steel sheet can be more appropriately suppressed.
Therefore, in the cold rolling equipment 1 illustrated in
However, in a case where the linear load of the second stand 32 and the third stand 33 having the tapered work rolls 4a1 is set as 1.7 t/mm or more, the tapered rolling portion width WRδ of the tapered work rolls 4a1 of the second stand 32 and the third stand 32 is set as −50 mm to −5 mm, due to the same reason as described above in the first embodiment.
As described above, in the cold rolling equipment 1 according to the second embodiment, among the four stands of the first stands 31 to the fourth stands 34, the second stand 32 arranged in the second position from the upstream side of the steel sheet S, as the material to be rolled, in the transfer direction and the third stand 33 arranged in the third position on the downstream side of the second stand 32 include the tapered work roll 4a1 having the taper 4ab formed on the end portion of the roll 4aa having a uniform diameter. The linear load of the second stand 32 and the third stand 33 is set as 1.7 t/mm or more, and the tapered rolling portion width WRδ which is a length of the taper 4ab, facing the steel sheet S, which is formed on the tapered work roll 4a1 of each of the second stand 32 and the third stand 33 is set as −50 mm to −5 mm.
Therefore, the edge drop ratio on the first stand 31 to the fourth stand 34 is kept within the appropriate range, and the occurrence of edge crack on the steel sheet S as the material to be rolled during the cold rolling is more sufficiently suppressed, thereby suppressing the sheet breakage.
In addition, in the cold rolling equipment 1 according to the second embodiment, among the four stands of first stands 31 to the fourth stand 34, the fourth stand 34 arranged in the fourth position on the downstream side of the third stand 33 includes the flat work roll 4a2 having a uniform diameter.
Accordingly, the effect of promoting the edge drop is exhibited.
In addition, in the cold rolling equipment 1 according to the second embodiment, among the four stands of first stands 31 to the fourth stands 34, the first stand 31 arranged on the uppermost stream side includes the flat work roll 4a2, but may include the tapered work roll 4a1.
Accordingly, the effect of suppressing the edge drop is exhibited.
In addition, in a cold rolling method according to the second embodiment, the steel sheet S as the material to be rolled is cold-rolled by the rolling mill 2 in the cold rolling equipment 1 illustrated in
Therefore, the edge drop ratio on the first stand 31 to the fourth stand 34 is kept within the appropriate range, and the occurrence of edge crack on the steel sheet S as the material to be rolled during the cold rolling is more sufficiently suppressed, thereby suppressing the sheet breakage.
Here, the configuration of the tapered work roll 4a1 is the same as that illustrated in
When a case where the width direction end surface of the steel sheet S protrudes from the taper start end 4ac is set as negative, and when a case where the width direction end surface of the steel sheet S is recessed than the taper start end 4ac is set as positive, as described above, the steel sheet S is rolled by setting the tapered rolling portion width WRδ which is a length of the taper 4ab facing the steel sheet S as −50 mm to −5 mm. In addition, the inclination L/H of the taper 4ab is preferably 1/800 to 1/400 as described above.
By the way, even when the tapered work roll 4a1 is used, if the tapered rolling portion width WRδ is greater than 0 mm on the positive side, the flat work roll 4a2 can be used.
Therefore, in both the cold rolling equipment 1 of the first embodiment and the second embodiment, each work roll 4a of the second stand 32 and each work roll 4a of the third stand 33 are set as the tapered work roll 4a1, and the steel sheet can also be rolled in a preferred aspect by shifting each work roll 4a in the axial direction according to the linear load.
That is, when the linear load is 0.8 t/mm or more and less than 1.4 t/mm, the tapered work roll 4a1 may be used as the flat work roll 4a2 by shifting each work roll 4a in the axial direction so that the tapered rolling portion width WRδ in the second stand 32 is set as ±0 mm to +50 mm and the tapered rolling portion width WRδ in the third stand 32 is greater than 0 mm.
In addition, when the linear load is 1.4 t/mm or more and less than 1.7 t/mm, the work roll may be used as the flat work roll 4a2 by shifting each work roll 4a in the axial direction so that the tapered rolling portion width WRδ in the second stand 32 is set as −50 mm to −5 mm and the tapered rolling portion width WRδ in the third stand 33 is greater than 0 mm.
Furthermore, when the linear load is 1.7 t/mm or more, the work roll may be used as the tapered work roll 4a1 by shifting each work roll 4a in the axial direction so that the tapered rolling portion width WRδ of each of the second stand 32 and the third stand 33 is set as −50 mm to −5 mm.
In the cold-rolled steel sheet manufacturing method according to the second embodiment, the steel sheet S is cold-rolled by the cold rolling method according to the second embodiment to manufacture the cold-rolled steel sheet.
Although the embodiments of the present invention have been described above, the present invention is not limited thereto and can be modified and improved in various ways.
In the first embodiment and the second embodiment, the rolling mill (tandem rolling mill) 2 including the four stands of the first stands 31 to the fourth stands 34 was described as an example, but the number of stands is not limited thereto, and the rolling mill 2 including five or more stands may be used. When five or more stands are provided, in a case where the number of stands including the work roll 4a as the tapered work roll 4a1 is one as in the first embodiment, one stand may be selected from stands in a preceding stage, except a stand on the uppermost stream side. In addition, when the number of stands including the work roll 4a as the tapered work roll 4a1 is two continuously provided as in the second embodiment, at least one stand among these may be one stand selected from the stands in a preceding stage may be used, except for a stand on the uppermost stream side.
Further, in the first embodiment, the tapered work roll 4a1 is applied to the second stand 32, and this is because that, in the rolling mill 2 of the first embodiment, since the breakage occurs on the third stand 33, the stand on the upstream side thereof is selected. In the second embodiment, the tapered work roll 4a1 is applied to the second stand 32 and the third stand 33, and this is also because the breakage occurs on the third stand 33. In the first and second embodiments, the tapered work roll 4a1 may be applied to other stands according to the configuration of the rolling mill (tandem rolling mill) 2 or the like.
Based on the above, in the cold rolling method, the cold rolling equipment, and the cold-rolled steel sheet manufacturing method according to the present invention, among the plurality of stands 31 to 34, the N-th stand 3N arranged in the N-th position (N is a natural number equal to or greater than 2) from the upstream side of the steel sheet S, as the material to be rolled, in the transfer direction includes the tapered work roll 4a1 having the taper 4ab formed on the end portion of the roll 4aa having a uniform diameter. Then, on the N-th stand 3N, the steel sheet S as the material to be rolled is rolled with a linear load of 0.8 t/mm or more.
In addition, when the N-th stand 3N rolls the steel sheet S with a linear load of less than 1.4 t/mm, it is preferable that the steel sheet S is rolled by setting the tapered rolling portion width WRδ which is a length of the taper 4ab, facing the steel sheet S, which is formed on the tapered work roll 4a1 of the N-th stand 3N as ±50 mm to +50 mm.
Meanwhile, when the N-th stand 3N rolls the steel sheet S with a linear load of 1.4 t/mm or more, it is preferable that the steel sheet S is rolled by setting the tapered rolling portion width WRδ which is a length of the taper 4ab, facing the steel sheet S, which is formed on the tapered work roll 4a1 of the N-th stand 3N as −50 mm to −5 mm.
In the cold rolling method, the cold rolling equipment, and the cold-rolled steel sheet manufacturing method according to the present invention, it is preferable that, among the plurality of stands 31 to 34, the (N+1)-th stand 3N+1 arranged in the (N+1)-th position on the downstream side of the N-th stand 3N includes the flat work roll 4a2 having a uniform diameter of the roll to roll the steel sheet S as the material to be rolled.
In addition, in the cold rolling method, the cold rolling equipment, and the cold-rolled steel sheet manufacturing method according to the present invention, among the plurality of stands 31 to 34, the N-th stand 3N arranged in the N-th position (N is a natural number equal to or greater than 2) from the upstream side of the steel sheet S, as the material to be rolled, in the transfer direction and the (N+1)-th stand 3N+1 arranged in the (N+1)-th position on the downstream side of the N-th stand 3N include the tapered work roll 4a1 having the taper 4ab formed on the end portion of the roll 4aa having a uniform diameter. The N-th stand 3N and the (N+1)-th stand 3N+1 rolls the steel sheet S with a linear load of 1.7 t/mm or more, and by setting the tapered rolling portion width WRδ which is a length of the taper 4ab, facing the steel sheet S, which is formed on the tapered work roll 4a1 of each of the N-th stand 3N and the (N+1)-th stand 3N+1 as −50 mm to −5 mm.
In the cold rolling method, the cold rolling equipment, and the cold-rolled steel sheet manufacturing method according to the present invention, it is preferable that, among the plurality of stands 31 to 34, the (N+2)-th stand 3N+2 arranged in the (N+2)-th position on the downstream side of the (N+1)-th stand 3N+1 includes the flat work roll 4a2 having a uniform diameter of the roll to roll the steel sheet S as the material to be rolled.
In addition, in the first and second embodiments, the electromagnetic steel sheet was used as the material to be rolled in the test, but the steel type of the steel sheet S is not limited to the electromagnetic steel sheet. A stainless steel sheet, a high-carbon steel sheet, an electromagnetic steel sheet, and the like are known as steel types in which edge cracks are generally likely to occur on the edge portion, and a significant effect is exhibited by using the cold rolling method, the cold rolling equipment, and the cold-rolled steel sheet manufacturing method of the present invention.
In order to verify the effect of the present invention, the cold rolling was performed using the cold rolling equipment 1 under conditions illustrated in Tables 5 and 6. In Tables 5 and 6, a rolling reduction is calculated based on a sheet thickness of the material to be rolled on an inner side of the first stand 31 and a sheet thickness of the material to be rolled on the outer side of the fourth stand 34.
The rolling was performed by setting the material to be rolled as an electromagnetic steel sheet A in Invention Examples 1 to 4, setting the material to be rolled as an electromagnetic steel sheet B in Invention Examples 5 to 8, setting the material to be rolled as an electromagnetic steel sheet C in Invention Examples 9 to 12, applying the tapered work roll 4a1 to the second stand 32, setting the linear load of the second stand 32 as 1.4 t/mm or more, and setting the tapered rolling portion width WRδ of the tapered work roll 4a1 of the second stand 32 as −50 mm to −5 mm which is in the range. In any of Invention Examples 1 to 12, the edge drop ratio of the stand (the second stand 32) and the next stand (the third stand 33) was within the suitable range, and there were no edge cracks in each of Invention Examples 1 to 12.
In addition, the rolling was performed by setting the material to be rolled as the electromagnetic steel sheet A in Comparative Example 1, setting the material to be rolled as the electromagnetic steel sheet B in Comparative Example 4, setting the material to be rolled as the electromagnetic steel sheet C in Comparative Example 7, applying the tapered work roll 4a1 to the second stand 32, setting the linear load of the second stand 32 as 1.4 t/mm or more, and setting the tapered rolling portion width WRδ of the tapered work roll 4a1 of the second stand 32 as −60 mm which is beyond the range in the negative direction. In any of Comparative Examples 1, 4, and 7, the stand (the second stand 32) was edged up, and edge cracks were found in each of Comparative Examples 1, 4, and 7.
The rolling was performed by setting the material to be rolled as the electromagnetic steel sheet A in Comparative Example 2, setting the material to be rolled as the electromagnetic steel sheet B in Comparative Example 5, setting the material to be rolled as the electromagnetic steel sheet C in Comparative Example 8, applying the tapered work roll 4a1 to the second stand 32, setting the linear load of the second stand 32 as 1.4 t/mm or more, and setting the tapered rolling portion width WRδ of the tapered work roll 4a1 of the second stand 32 as +5 mm which is beyond the range in the positive direction. In any of Comparative Examples 2, 5, and 8, the next stand (the third stand 33) of the stand (the second stand 32) was edged up, and edge cracks were found in each of Comparative Examples 2, 5, and 8.
In addition, the rolling was performed by setting the material to be rolled as the electromagnetic steel sheet A in Comparative Example 3, setting the material to be rolled as the electromagnetic steel sheet B in Comparative Example 6, setting the material to be rolled as the electromagnetic steel sheet C in Comparative Example 9, applying the flat work roll to all the first stand 31 to the fourth stand 34, and setting the linear load of the second stand 32 as 1.4 t/mm or more. In any of Comparative Examples 3, 6, and 9, the next stand (the third stand 33) of the stand (the second stand 32) including the flat work roll was edged up, and edge cracks were found in each of Comparative Examples 3, 6, and 9.
In addition, the rolling was performed by setting the material to be rolled as an electromagnetic steel sheet D in Reference Example 1, applying the tapered work roll 4a1 to the second stand 32, setting the linear load of the second stand 32 as 0.75 t/mm which is beyond the range, and setting the tapered rolling portion width WRδ of the tapered work roll 4a1 of the second stand 32 as −5 mm. In addition, the rolling was performed by setting the material to be rolled as the electromagnetic steel sheet D in Reference Example 2, applying the tapered work roll 4a1 to the second stand 32, setting the linear load of the second stand 32 as 0.75 t/mm which is beyond the range, and setting the tapered rolling portion width WRδ of the tapered work roll 4a1 of the second stand 32 as 0 mm. In addition, the rolling was performed by setting the material to be rolled as the electromagnetic steel sheet D in Reference Example 3, applying the tapered work roll 4a1 to the second stand 32, setting the linear load of the second stand 32 as 0.75 t/mm which is beyond the range, and setting the tapered rolling portion width WRδ of the tapered work roll 4a1 of the second stand 32 as +60 mm. Furthermore, the rolling was performed by setting the material to be rolled as the electromagnetic steel sheet D in Reference Example 4, applying the flat work roll to all the first stand 31 to the fourth stand 34, and setting the linear load of the second stand 32 as 0.75 t/mm or more which is beyond the range. In a case of Reference Example 1, due to the shifting of the second stand 32 in the negative direction under ultra-light pressure, the second stand 32 was edged up and the edge crack occurred. In a case of Reference Examples 2 to 4, the tapered rolling portion width WRδ of the tapered work roll 4a1 of the second stand 32 was changed to ±0 mm, +60 mm, and the work roll was changed to flat work roll. The edge drop ratio of the stand (the second stand 32) and the next stand (the third stand 33) was within the suitable range under ultra-light pressure, and in each of the Reference Examples 2 to 4, there were no edge cracks and the effect of setting the second stand 32 to the tapered work roll 4a1 was not exhibited.
In addition, the rolling was performed by setting the material to be rolled as an electromagnetic steel sheet E in Invention Examples 17 to 20, setting the material to be rolled as an electromagnetic steel sheet F in Invention Examples 21 to 24, setting the material to be rolled as an electromagnetic steel sheet G in Invention Examples 25 to 28, applying the tapered work roll 4a1 to the second stand 32, setting the linear load of the second stand 32 as 0.8 t/mm or more and less than 1.4 t/mm which is in the range, and setting the tapered rolling portion width WRδ of the tapered work roll 4a1 of the second stand 32 as ±0 mm to +50 mm which is in the range. In any of Invention Examples 17 to 25, the edge drop ratio of the stand (the second stand 32) and the next stand (the third stand 33) was within the suitable range, and there were no edge cracks in each of Invention Examples 1 to 12.
The rolling was performed by setting the material to be rolled as the electromagnetic steel sheet E in Comparative Example 10, setting the material to be rolled as the electromagnetic steel sheet F in Comparative Example 13, setting the material to be rolled as the electromagnetic steel sheet G in Comparative Example 16, applying the tapered work roll 4a1 to the second stand 32, setting the linear load of the second stand 32 as 0.8 t/mm or more and less than 1.4 t/mm, and setting the tapered rolling portion width WRδ of the tapered work roll 4a1 of the second stand 32 as +60 mm which is beyond the range in the positive direction. In any of Comparative Examples 10, 13, and 16, the next stand (the third stand 33) of the stand (the second stand 32) was edged up, and edge cracks were found in each of Comparative Examples 12, 15, and 18.
In addition, the rolling was performed by setting the material to be rolled as the electromagnetic steel sheet E in Comparative Example 11, setting the material to be rolled as the electromagnetic steel sheet F in Comparative Example 14, setting the material to be rolled as the electromagnetic steel sheet G in Comparative Example 17, applying the tapered work roll 4a1 to the second stand 32, setting the linear load of the second stand 32 as 0.8 t/mm or more and less than 1.4 t/mm, and setting the tapered rolling portion width WRδ of the tapered work roll 4a1 of the second stand 32 as −5 mm which is beyond the range in the negative direction. In any of Comparative Examples 11, 14, and 17, the stand (the second stand 32) was edged up, and edge cracks were found in each of Comparative Examples 11, 14, and 17.
In addition, the rolling was performed by setting the material to be rolled as the electromagnetic steel sheet E in Comparative Example 12, setting the material to be rolled as the electromagnetic steel sheet F in Comparative Example 15, setting the material to be rolled as the electromagnetic steel sheet G in Comparative Example 18, applying the flat work roll to all the first stand 31 to the fourth stand 34, and setting the linear load of the second stand 32 as 0.8 t/mm or more and less than 1.4 t/mm. In any of Comparative Examples 14, 17, and 20, the next stand (the third stand 33) of the stand (the second stand 32) including the flat work roll was edged up, and edge cracks were found in each of Comparative Examples 12, 15, and 18.
In addition, the rolling was performed by setting the material to be rolled as an electromagnetic steel sheet A in Invention Example 13, applying the tapered work roll 4a1 to the second stand 32, setting the linear load of the second stand 32 as 1.45 t/mm, and setting the tapered rolling portion width WRδ of the tapered work roll 4a1 of the second stand 32 as −30 mm which is in the range. The inclination L/H of the taper 4ab of the tapered work roll 4a1 was set to 1/400, which is in the preferred range. In Invention Example 13, the edge drop ratio of the stand (the second stand 32) and the next stand (the third stand 33) was in the suitable range and there were no edge cracks.
In addition, the rolling was performed by setting the material to be rolled as an electromagnetic steel sheet H in Invention Example 14, applying the tapered work roll 4a1 to the second stand 32 and the third stand 33, setting the linear load of the second stand 32 and the third stand 33 as 1.72 t/mm, and setting the tapered rolling portion width WRδ of the tapered work roll 4a1 of each of the second stand 32 and the third stand 33 as −30 mm which is in the range. In Invention Example 14, the edge drop ratio of the stand (the second stand 32) and the next stand (the third stand 33) was in the suitable range and there were no edge cracks.
In addition, the rolling was performed by setting the material to be rolled as a stainless steel sheet in Invention Example 15, setting the material to be rolled as a high-carbon steel sheet in Invention Example 16, applying the tapered work roll 4a1 to the second stand 32, setting the linear load of the second stand 32 as 1.4 t/mm or more, and setting the tapered rolling portion width WRδ of the tapered work roll 4a1 of the second stand 32 as −30 mm which is in the range. In any of Invention Examples 15 and 16, the edge drop ratio of the stand (the second stand 32) and the next stand (the third stand 33) was within the suitable range, and there were no edge cracks in each of Invention Examples 15 and 16.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2020-152348 | Sep 2020 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2021/032889 | 9/7/2021 | WO |
