JP2019111571A - Cold rolling method of ferrite stainless steel strip - Google Patents

Abstract

To provide a cold rolling method of a ferritic stainless steel strip capable of determining properly a treatment to be applied to the ferritic stainless steel strip in which edge cracking is generated during cold rolling.SOLUTION: In a cold rolling method of a ferritic stainless steel strip, a treatment to be applied to the ferritic stainless steel strip is determined by using as an index, a depth and an angle of edge cracking generated in the ferritic stainless steel strip which is a rolling object during cold rolling, and the determined treatment is applied to the ferritic stainless steel strip.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method of cold rolling a ferritic stainless steel strip.

  When cold-rolled to a ferritic stainless steel strip after hot rolling to produce a cold-rolled steel sheet, edge cracks (edge portions) in the width direction of the steel strip in the middle of cold rolling A minute crack called may occur (Fig. 1 (A)).

  When cold rolling is performed on the steel strip in which the edge crack has occurred, the edge crack extends in the depth direction (the width direction of the steel strip), and in the worst case, the steel strip breaks. If the steel strip breaks during cold rolling, it is necessary to remove the broken steel strip from the cold rolling mill or to replace a member such as a work roll damaged by the broken steel strip. It takes a long time to restart, and the yield is also reduced, and the productivity of the cold-rolled steel plate is significantly reduced.

  Therefore, conventionally, processing (trimming processing) for removing the edge cracks generated at the edge portion of the steel strip by a trimming device is performed (for example, Patent Document 1). By applying such a trimming process, it is possible to suppress the breakage of the steel strip that is caused by the extension of the ear cracks due to rolling. However, if the steel strip is subjected to the trimming process by stopping the rolling whenever the occurrence of the edge cracking is found, the production efficiency is low and the productivity of the cold rolled steel sheet is reduced.

JP, 2017-52018, A

  An object of the present invention is to provide a cold rolling method of a ferritic stainless steel strip which can appropriately determine a process to be applied to a ferritic stainless steel strip in which an edge crack has occurred during cold rolling.

  As a result of detailed studies by the present inventors, the following findings were obtained.

1) When cold rolling is applied to a steel strip in which an edge crack has occurred, the crack may or may not extend in the depth direction of the edge crack (in the width direction of the steel strip).
2) The extension of the crack in the ear cracks is affected by the depth and angle of the ear cracks.

  Then, the inventors of the present invention further study and use ferritic stainless steel in which the ear cracking occurs during cold rolling by using the depth and angle of the ear cracking generated in the ferritic stainless steel strip to be rolled as an index. It has been found that the treatment to be applied to the steel strip can be properly determined, and the present invention has been completed.

That is, the present invention comprises the following configuration.
[1] Using the depth and angle of edge cracks generated in a ferritic stainless steel strip to be rolled during cold rolling as an index, determine the treatment to be applied to the ferritic stainless steel strip,
The cold-rolling method of a ferritic stainless steel strip which subjects the said judged process to the said ferritic stainless steel strip.
[2] The method of cold rolling of a ferritic stainless steel strip according to the above [1], wherein an ear crack having a depth of 3 mm or more and an angle of 90 ° or less is used as an index.
[3] As an index of judgment of processing to apply edge cracks of depth 3 mm or more and angle 90 ° or less to a ferritic stainless steel strip to be rolled,
Whether the ferritic stainless steel strip is subjected to cold rolling by reducing the speed from the intended cold rolling speed when the above-mentioned edge cracking occurs in the ferritic stainless steel strip to be rolled during cold rolling Or judge to stop cold rolling,
It is judged that it is possible to cold-roll the ferritic stainless steel strip at a planned cold-rolling speed when the edge crack is not generated in the ferritic stainless steel strip,
The cold-rolling method of a ferritic stainless steel strip which subjects the said judged process to the said ferritic stainless steel strip.

According to the present invention, it is possible to appropriately determine the treatment to be applied to a ferritic stainless steel strip in which edge cracking has occurred during cold rolling.
According to the present invention, by using the depth and angle of the edge crack generated in the ferritic stainless steel strip to be rolled during cold rolling as an index, the ferrite stainless steel strip in which the edge crack is generated, It is possible to properly determine when cold rolling can not be performed at a planned cold rolling speed and when it is possible to perform cold rolling at a planned cold rolling speed. And the fracture | rupture of a steel strip can be suppressed and the productivity of a cold-rolled steel plate can be improved by giving the said judged process to the said ferritic stainless steel strip.

FIG. 1 (A) is a schematic view explaining an ear crack generated in a steel strip, and FIG. 1 (B) is an enlarged view thereof.

  Hereinafter, one embodiment of a method of cold rolling a ferritic stainless steel strip of the present invention will be described. However, the present invention is not limited to the embodiments described below.

  In the present invention, the method for producing a ferritic stainless steel strip to be rolled is not particularly limited. For example, steel is melted in a melting furnace such as a converter or an electric furnace, and further secondary refining such as ladle refining or vacuum refining is performed to make a steel having a predetermined composition, continuous casting method or ingot-lumping Use a steel sheet (slab) by a rolling method, and then make the slab a hot rolled sheet by hot rolling, and use this hot rolled sheet as a hot rolled annealed pickled sheet by annealing and pickling. Can.

  The present invention is applied to a case where a ferritic stainless steel strip is to be rolled, and is preferably applied particularly to a case where a ferritic stainless steel strip having a component composition containing 16 mass% or more of Cr is to be rolled. Ferritic stainless steel strips, particularly ferritic stainless steel strips having a component composition containing 16% by mass or more of Cr, have low elongation at low temperatures, and by applying cold rolling, edge cracks can easily extend in the depth direction There is a tendency. In addition, since the toughness is low, it tends to break easily. According to the present invention, when an edge crack occurs in such a ferritic stainless steel strip, breakage can be suppressed and appropriate treatment can be performed.

  The component composition of the ferritic stainless steel strip to which the present invention is applied is, for example, C: 0.12% or less, Si: 1.00% or less, Mn: 1.00% or less, P: 0 in mass% Component composition containing 040% or less, S: 0.030% or less, Cr: 10.5 to 24.0%, Ni: 1.00% or less, the balance being Fe and unavoidable impurities (component composition A Can be mentioned.

  In addition, the component composition A further contains one or two or more selected from among Ti: 0.50% or less, Nb: 0.80% or less, and Zr: 0.50% or less by mass%. The component composition (component composition B) may be used.

  In addition, the component composition A or B may further have a component composition containing, in mass%, one or two selected from among Cu: 1.00% or less and Mo: 2.50% or less.

  Here, in each of the above component compositions (hereinafter, “%” of the component composition means “% by mass”), the C content is preferably 0.001% or more. Also, the C content is preferably 0.06% or less. The Si content is preferably 0.01% or more. The Si content is preferably 0.60% or less. The Mn content is preferably 0.01% or more. Also, the Mn content is preferably 0.90% or less. The P content is preferably 0.035% or less. The Cr content is preferably 16.0% or more. Also, the Cr content is preferably 22.0% or less. The Ni content is preferably 0.01% or more. Further, the Ni content is preferably 0.60% or less.

  When Ti is contained, the content of Ti is preferably 0.01% or more. Further, the content of Ti is preferably 0.40% or less. When Nb is contained, the content of Nb is preferably 0.01% or more. Further, the content of Nb is preferably 0.65% or less. When Zr is contained, the content of Zr is preferably 0.01% or more. Further, the content of Zr is preferably 0.10% or less.

  As the above-mentioned ferritic stainless steel strip, SUS430 (16 mass% Cr), SUS 436 (18 mass% Cr-1 mass% Mo-0.3 mass% Ti), SUS 430 LX (specified in Japanese Industrial Standard JIS G 4305) 17 mass% Cr-0.3 mass% Ti), SUS 443 J 1 (21 mass% Cr-0.5 mass% Cu-0.3 mass% Ti), SUS 444 (19 mass% Cr-2 mass% Mo-0.3) Steel strips, such as mass% Nb), SUS445J2 (22 mass% Cr-1 mass% Mo-0.3 mass% Nb), etc. are mentioned.

  The plate thickness (base thickness) of the ferritic stainless steel strip before cold rolling is not particularly limited, but an example is a plate thickness of 2.0 to 7.0 mm, preferably 3.0 to 5. It is 0 mm. Further, the final plate thickness (finished plate thickness) after cold rolling is also not particularly limited, but an example is a plate thickness of 0.3 to 4.0 mm, preferably 0.5 to 1.5 mm. It is.

  The cold rolling method of a ferritic stainless steel strip according to the present invention indicates the depth (d) and the angle (θ) of the edge cracks generated in the ferritic stainless steel strip to be rolled as described above during cold rolling. As (refer FIG. 1 (B)), the process given to the said ferritic stainless steel strip is judged.

  According to the detailed studies of the present inventors, when cold rolling is applied to a ferritic stainless steel strip in which an ear crack has occurred, whether or not the ear crack extends or does not extend in the depth direction is the ear crack Affected by the depth and angle of the

  When the edge crack generated in the ferritic stainless steel strip to be rolled is a predetermined depth (3 mm) or more and a predetermined angle (90 °) or less, cold rolling is performed at a scheduled cold rolling speed As a result, the edge cracks extend in the depth direction (the width direction of the steel strip) and there is a risk that the steel strip may break. In this case, in order to prevent breakage of the steel strip, it is effective to lower the cold rolling speed from the intended cold rolling speed and apply cold rolling or to stop cold rolling.

  On the other hand, if the edge crack generated in the ferritic stainless steel strip to be rolled is less than the predetermined depth, there is a risk that the steel strip will break even if cold rolling is performed at a cold rolling speed scheduled There is no sex. In addition, when the cold rolling is performed at a predetermined cold rolling speed when the edge cracking exceeds the predetermined angle even if the edge cracking is more than the predetermined depth, the edge cracking is in the depth direction It tends to spread more in the longitudinal direction of the steel strip and again there is no risk of the steel strip breaking. In such a case, it is effective to continue cold rolling without stopping cold rolling in terms of productivity. Furthermore, it is effective to perform cold rolling at a planned cold rolling speed or without reducing the speed from the planned cold rolling speed as much as possible.

The present invention has been made based on the above findings.
That is, the present invention uses the depth and angle of the edge crack generated in the ferritic stainless steel strip as an index, and when there is a risk of steel strip breakage, judges the processing for suppressing the steel strip breakage. If there is no risk of fracture of the steel strip, the steel strip is subjected to excessive treatment (treatment to stop cold rolling when the steel plate does not break even if cold rolling is applied, or cold rolling is scheduled If the steel sheet does not break even if it is applied at the cold rolling speed, the processing to avoid applying the cold rolling) is determined by extremely reducing the cold rolling speed. It is applied to a ferritic stainless steel strip to be rolled. This makes it possible to suppress the breakage of the steel strip and improve the productivity of the cold rolled steel sheet.

  Specifically, an ear crack having a depth of 3 mm or more and an angle of 90 ° or less is used as an index (hereinafter, an ear crack having a depth of 3 mm or more and an angle of 90 ° or less is also referred to as “specific ear crack”). Then, if specific ear cracks occur in the ferritic stainless steel strip to be rolled during cold rolling, cold rolling is performed by reducing the speed from the planned cold rolling speed, or To stop cold rolling, and apply cold rolling at a scheduled cold rolling speed if no specific edge cracking occurs in the ferritic stainless steel strip to be rolled during cold rolling Judging that it is possible, the above-mentioned processing is applied to the ferritic stainless steel strip.

  As described above, according to the present invention, it is possible that cold rolling can not be performed at a cold rolling speed planned for a ferritic stainless steel strip in which edge cracking has occurred during cold rolling. It is possible to appropriately determine when cold rolling can be performed at the cold rolling speed. Then, the ferritic stainless steel strip is subjected to the above-described determined processing to suppress the fracture of the steel strip, and to avoid applying the above-described excessive treatment to the steel strip, thereby enhancing the productivity of the cold rolled steel sheet. It becomes possible.

  Here, with the cold rolling speed planned, the steel type of the ferritic stainless steel strip to be rolled, the plate thickness (original thickness), the final plate thickness after cold rolling (finished plate thickness), the cold rolling mill Set appropriately within the range where it is confirmed that the steel strip is not broken, plate thickness fluctuation, tension fluctuation, plate shape defect or surface defect due to the rolling performance and past performance values When cold rolling is performed, it is incorporated as a pass schedule in advance.

  As an example, the cold rolling speed scheduled as described above is appropriately set within the range of 100 to 1000 mpm.

  Moreover, as an example, the rolling reduction of each pass of cold rolling is suitably set within the range of 10 to 30%.

  The cold rolling mill to which the cold rolling is performed is not particularly limited, and a reverse rolling mill such as Zenzimia or a tandem rolling mill can be used.

  Next, an example of a specific procedure of the method of cold rolling a ferritic stainless steel strip of the present invention will be described.

  First, it is confirmed whether or not edge cracking has occurred in the edge portion of the ferritic stainless steel strip to be rolled.

  The inspection work may be performed by an inspector visually or by using a surface inspection apparatus or the like. In addition, the checking operation may be carried out by stopping the traveling of the steel strip, or may be performed while traveling the steel strip at a speed at which it is possible to confirm cracked ears.

  Moreover, the said confirmation operation can be implemented at an appropriate timing. For example, it may be carried out before cold rolling of each pass, or may be carried out after cold rolling of each pass. Furthermore, it may be carried out in the middle of the pass (after rolling in one direction in the case of reverse rolling and then, for example, between the third and fourth stages of rolling in the case of tandem rolling). Further, the confirmation operation may be performed for each pass, or may be performed for each of a plurality of passes.

  Preferably, confirmation is performed each time before cold rolling of each pass. Then, when it is confirmed that the edge cracks occur in the steel strip, the position is recorded, and the work of confirming the shape change of the edge cracks while performing cold rolling of each pass is performed. . By doing this, the occurrence of specific ear cracking can be confirmed earlier and more reliably.

  Then, when it is confirmed in the above-mentioned confirmation work that the ear cracking has occurred, the depth and angle of the ear cracking are examined.

  The survey may be conducted by an inspector visually or by using a measuring means such as a vernier caliper or a protractor. For example, a steel plate having a specific ear crack is prepared as a limit sample. It may be implemented by comparing with this limit sample. Moreover, you may implement using a surface inspection apparatus etc.

  Then, after investigating the depth and angle of the ear cracks, the processing to be applied to the ferritic stainless steel in which the ear cracks have occurred is determined using the depth and angle of the ear cracks as an index.

  As described above, more specifically, a specific ear crack having a depth of 3 mm or more and an angle of 90 ° or less is used as an index. And, when specific ear cracks occur in the ferritic stainless steel strip to be rolled during cold rolling, a process of reducing the speed from the planned cold rolling speed and performing cold rolling (deceleration processing) Judging the process (stop process) to stop cold rolling, if the specified edge crack does not occur, apply cold rolling to the ferritic stainless steel strip at the cold rolling speed scheduled It is judged that it is possible, and the above-mentioned judgment processing is performed to the above-mentioned ferritic stainless steel.

  When the reduction treatment is performed, cold rolling is preferably performed at a speed of 75% or less of the planned cold rolling speed, and more preferably 50% or less. That is, if the cold rolling speed planned is 400 mpm, it is preferable to perform cold rolling at a speed of 300 mpm or less, and more preferable to perform cold rolling at 200 mpm or less. As described above, by performing cold rolling by reducing the cold rolling speed, it is possible to suppress the fluctuation of the tension applied to the steel strip and to prevent the breakage of the steel strip. Moreover, it becomes easy to follow the shape change of the longitudinal direction of a steel strip, and it becomes easy to obtain the stable steel strip shape.

  Although the lower limit of the speed in the case of performing the decelerating treatment is not particularly limited, it is preferable to perform cold rolling at 25% or more of the planned cold rolling speed in consideration of productivity. That is, if the planned rolling speed is 400 mpm, it is preferable to perform cold rolling at a speed of 100 mpm or more.

  In addition, the decelerating treatment may be performed only when rolling the area of the steel strip in which the specific edge crack exists, or may be performed over the entire length of the steel strip.

  The stop process is a process for stopping cold rolling without applying further rolling when specific ear cracks occur in the steel plate. The steel strip after the termination treatment may be trimmed to remove edge cracks, subjected to intermediate annealing if necessary, and then subjected to cold rolling again.

  In addition, when a specific edge crack has not generate | occur | produced in the steel strip, it can cold-roll on a steel strip at the cold-rolling speed planned. In this case, it is optional to perform cold rolling by lowering the speed lower than the intended cold rolling speed or to stop cold rolling.

Next, an example of a specific embodiment of the method of cold rolling a ferritic stainless steel strip of the present invention will be described.
Here, 7 pass reverse rolling is applied to a hot-rolled annealed pickling plate having a thickness of 2.0 to 7.0 mm using a Zenzimir rolling machine to obtain a SUS 430 having a finished thickness of 0.3 to 4.0 mm. It is assumed to manufacture a ferritic stainless cold rolled steel sheet.

  First, a pass schedule for manufacturing a SUS430 ferritic stainless steel cold rolled steel sheet having the above-mentioned finished plate thickness is set based on past performance values and the like. Here, it is assumed that the pass schedule is set by setting the cold rolling speed of the first pass to 200 mpm and the cold rolling speed from the second pass to the eighth pass to 400 mpm.

  Next, before performing cold rolling in the first pass, it is confirmed whether or not edge cracking has occurred in the edge portion of the hot-rolled annealed pickled plate discharged from the coil. When the edge cracking does not occur, the first pass cold rolling is applied at a rolling speed (200 mpm) scheduled. On the other hand, if ear cracking has occurred, the depth and angle of ear cracking are examined. And when the said ear crack is a specific ear crack, the process (deceleration process) which makes cold rolling lower than the rolling speed (200 mpm) which was scheduled for 1st pass cold rolling, or cold It is judged that it is possible to carry out cold rolling at a scheduled cold rolling speed if it is judged that the process (canceling process) for stopping rolling is not specific ear cracking, and the above-mentioned judged process is to be rolled Apply to ferritic stainless steel strip.

  In this case, as described above, it is preferable to perform cold rolling at a speed of 75% or less with respect to the planned cold rolling speed from the viewpoint of preventing breakage of the steel strip as described above. It is more preferable to use cold rolling at a speed of 50% or less. In addition, it is preferable to perform cold rolling at a speed of 25% or more of the planned cold rolling speed in terms of productivity.

  In addition, when the stopping process is performed, after the steel strip is subjected to a trimming process to remove edge cracks, intermediate annealing may be performed if necessary, and cold rolling may be performed again.

  Moreover, when it is not a specific ear crack, it can apply at the rolling speed (200 mpm) which was scheduled for 1st pass cold rolling.

  The above steps are repeated for the second and subsequent passes. That is, before cold rolling in the second pass, it is confirmed whether or not edge cracking has occurred in the edge portion of the steel strip after completion of the first pass rolling. When the edge cracking does not occur, the second pass cold rolling is applied at the rolling speed (400 mpm) scheduled. On the other hand, if ear cracking has occurred, the depth and angle of ear cracking are examined. Then, if the above-mentioned ear breakage is a specific ear breakage, it may be made lower (for example, 300 mpm) than the rolling speed for which cold rolling in the second pass is planned (for example, 300 mpm) (deceleration processing) Judging the process to stop rolling (stop process), if it is not a specific edge crack, it is judged that it is possible to apply at the rolling speed at which cold rolling in the second pass is scheduled, and the above determined process is rolled Apply to the target ferritic stainless steel strip.

  A more preferable embodiment is an aspect of tracking and investigating ear cracks confirmed in the confirmation operation. For example, it is assumed that an ear crack (hereinafter referred to as “ear crack A”) having a depth of 2 mm and an angle of 60 ° has occurred in the steel strip before cold rolling in the first pass. In this case, since the ear cracks A do not satisfy the depth (3 mm or more) of the specific ear cracks, the first pass cold rolling can be applied at a planned cold rolling speed. Under the present circumstances, the position of the said ear crack A is recorded by visual inspection or surface inspection apparatus etc., The depth of the said ear crack A is after cold rolling of the 1st pass, or before 2nd cold rolling. Check the angle and angle again. And when the crack of the ear crack A extends in the depth direction and becomes 3 mm or more and becomes a specific ear crack, it is made lower than the cold rolling speed scheduled for cold rolling in the second pass (deceleration It is judged that the cold rolling of the second pass is to be canceled (canceled processing), and the above-mentioned judged processing is applied to the steel strip.

  According to such an aspect, the occurrence of specific ear cracks can be detected earlier and surely, the necessary treatment can be taken earlier and appropriately, and the fracture of the steel strip can be suppressed more reliably. it can.

  As described above, according to the present invention, by using the depth and angle of the edge cracks generated in the ferritic stainless steel strip during cold rolling as an indicator, the ferrite in which the edge cracks are generated during cold rolling It is appropriate to use a case where cold rolling can not be performed at a planned cold rolling speed and a case where cold rolling can be performed at a planned cold rolling speed on a stainless steel strip. It can be judged. Then, by subjecting the ferritic stainless steel strip to the above-described determined treatment, it is possible to suppress the breakage of the steel strip and to avoid applying an excessive treatment to the steel strip, thereby enhancing the productivity of the cold rolled steel sheet. .

  In the present embodiment, a ferritic stainless hot-rolled annealed pickled sheet having a plate thickness of 4.0 mm and a width of 1050 mm is subjected to 8-pass reverse rolling using a 20-stage Sendzimir rolling machine to obtain a finished plate thickness of 1.0 mm Ferritic stainless cold rolled steel sheet was manufactured. The planned rolling speed in this case is set to 200 mpm for the first pass and 400 mpm for the second to eighth passes from the past results.

Example 1
The cold rolling of the above-mentioned setting was performed to a SUS430 ferritic stainless steel hot-rolled annealing pickled plate having a thickness of 4.0 mm. At that time, before cold rolling of each pass, the edge of the steel strip is visually inspected to confirm the presence or absence of ear breakage, and if ear breakage has occurred, investigate the depth and angle of ear breakage did.
Before cold rolling of the 4th pass (plate thickness 2.4 mm), it was confirmed that an ear crack with a depth of 2 mm and an angle of 60 ° occurred in the steel strip, but it is not a specific ear crack, so 4 pass Apply cold rolling conditions (rolling speed 400 mpm) for which cold rolling is planned for the eyes, and then apply rolling conditions (rolling speed 400 mpm) for which cold rolling is also planned for the fifth to eighth passes, A cold-rolled steel plate with a finished plate thickness of 1.0 mm was manufactured. In addition, when the depth and angle of the said ear cracks were investigated after manufacture, it was 2 mm in depth and 120 degrees of ear cracks.

(Example 2)
The cold rolling of the above-mentioned setting was performed to a SUS430 ferritic stainless steel hot-rolled annealing pickled plate having a thickness of 4.0 mm. At that time, before cold rolling of each pass, the edge of the steel strip is visually inspected to confirm the presence or absence of ear breakage, and if ear breakage has occurred, investigate the depth and angle of ear breakage did.
Before applying the first pass cold rolling, it was confirmed that the steel strip had an edge crack with a depth of 3 mm and an angle of 120 °, but since there is no specific edge crack, the first pass cold rolling is scheduled The cold rolling conditions (rolling speed: 200 mpm) were applied, and then the cold rolling conditions (rolling speed: 400 mpm) where cold rolling from the second pass to the eighth pass was also planned, and the finished plate thickness 1. A 0 mm cold rolled steel plate was produced. In addition, when the depth and angle of the said ear crack were investigated after manufacture, it was 3 mm in depth, and an ear crack of angle 150 degrees.

(Example 3)
The cold rolling of the above-mentioned setting was performed to a SUS430 ferritic stainless steel hot-rolled annealing pickled plate having a thickness of 4.0 mm. At that time, before cold rolling of each pass, the edge of the steel strip is visually inspected to confirm the presence or absence of ear breakage, and if ear breakage has occurred, investigate the depth and angle of ear breakage did.
Since it was confirmed that a specific edge crack with a depth of 4 mm and an angle of 60 ° was generated in the steel strip before cold rolling in the first pass, rolling that was scheduled for cold rolling in the first pass Under the conditions (rolling speed 200 mpm), the rolling speed is reduced to 100 mpm, and then the rolling speed is reduced to 200 mpm from the rolling conditions (rolling speed 400 mpm) for which cold rolling from the second pass to the eighth pass is also planned. And a cold-rolled steel plate with a finished plate thickness of 1.0 mm was manufactured. In addition, when the depth and angle of the said ear crack were investigated after manufacture, it was 4 mm in depth, and an ear crack of angle 120 degrees.

(Example 4)
The cold rolling of the above-mentioned setting was performed to a SUS436 ferritic stainless steel hot-rolled annealing pickled plate with a plate thickness of 4.0 mm. At that time, before cold rolling of each pass, the edge of the steel strip is visually inspected to confirm the presence or absence of ear breakage, and if ear breakage has occurred, investigate the depth and angle of ear breakage did.
Since it was confirmed that a specific edge crack with a depth of 4 mm and an angle of 70 ° had occurred in the steel strip before cold rolling in the first pass, rolling that was scheduled for cold rolling in the first pass The rolling speed is reduced to 75 mpm from the conditions (rolling speed 200 mpm), and then the rolling speed is reduced to 200 mpm from the rolling conditions (rolling speed 400 mpm) for which cold rolling from the second pass to the eighth pass was also planned. And a cold-rolled steel plate with a finished plate thickness of 1.0 mm was manufactured. In addition, when the depth and angle of the said ear crack were investigated after manufacture, it was 4 mm in depth, and an ear crack of angle 140 degrees.

(Example 5)
The cold rolling of the above-mentioned setting was performed to SUS430LX ferritic stainless steel hot-rolled annealing pickled board with a plate thickness of 4.0 mm. At that time, before cold rolling of each pass, the edge of the steel strip is visually inspected to confirm the presence or absence of ear breakage, and if ear breakage has occurred, investigate the depth and angle of ear breakage did.
Before cold rolling of the 4th pass (plate thickness 2.4 mm), it was confirmed that an ear crack of 4 mm in depth and an angle of 120 ° occurred in the steel strip, but it is not a specific ear crack, so 4 passes Apply cold rolling conditions (rolling speed 400 mpm) for which cold rolling is planned for the eyes, and then apply rolling conditions (rolling speed 400 mpm) for which cold rolling is also planned for the fifth to eighth passes, A cold-rolled steel plate with a finished plate thickness of 1.0 mm was manufactured. In addition, when the depth and angle of the said ear crack were investigated after manufacture, it was 4 mm in depth, and an ear crack of angle 150 degrees.

(Example 6)
The cold rolling of the above-mentioned setting was performed to a SUS430 ferritic stainless steel hot-rolled annealing pickled plate having a thickness of 4.0 mm. At that time, before cold rolling of each pass, the edge of the steel strip is visually inspected to confirm the presence or absence of ear breakage, and if ear breakage has occurred, investigate the depth and angle of ear breakage did.
Before applying cold rolling in the first pass, it was confirmed that edge cracks of 2 mm in depth and an angle of 100 ° occurred in the steel strip, but since no specific edge cracking occurred, cold rolling in the first pass is scheduled Cold rolling conditions (rolling speed: 200 mpm) were applied, and cold rolling was also planned from the second pass to the third pass (rolling speed: 400 mpm).
Before cold rolling of the 4th pass (plate thickness 2.4 mm), it was confirmed that the above-mentioned cracked ears changed to a specified crack of 3 mm in depth and an angle of 80 °. The rolling speed is reduced to 200 mpm from the cold rolling conditions (rolling speed 400 mpm) scheduled for inter-rolling, and then the cold rolling conditions (5th to 8th passes) are also planned The rolling speed was reduced to 200 mpm from the rolling speed of 400 mpm) to manufacture a cold-rolled steel plate with a finished plate thickness of 1.0 mm. In addition, when the depth and angle of the said ear crack were investigated after manufacture, it was 3 mm in depth, and an ear crack of angle 120 degrees.

(Example 7)
The cold rolling of the above-mentioned setting was performed to a SUS436 ferritic stainless steel hot-rolled annealing pickled plate with a plate thickness of 4.0 mm. At that time, before cold rolling of each pass, the edge of the steel strip is visually inspected to confirm the presence or absence of ear breakage, and if ear breakage has occurred, investigate the depth and angle of ear breakage did.
Before applying the first pass cold rolling, it was confirmed that the steel strip had an edge crack with a depth of 3 mm and an angle of 100 °, but since there is no specific edge crack, the first pass cold rolling is scheduled Cold rolling conditions (rolling speed: 200 mpm) were applied, and cold rolling was also planned from the second pass to the third pass (rolling speed: 400 mpm).
Before cold rolling of the fourth pass (plate thickness: 2.4 mm), it was confirmed that the above-mentioned ear breakage changed to a specific ear crack having a depth of 4 mm and an angle of 45 °. At this stage, cold rolling was stopped, and both ends of the steel strip were trimmed by 10 mm on each side with a trimming line (cut-off) to remove the specific ear cracks. Thereafter, cold rolling was resumed, and cold rolling was performed under the cold rolling conditions (rolling speed 400 mpm) where cold rolling was scheduled for the fourth to eighth passes, and a cold-rolled steel plate with a finished plate thickness of 1.0 mm was manufactured. .

(Comparative example 1)
The cold rolling of the above-mentioned setting was performed to a SUS430 ferritic stainless steel hot-rolled annealing pickled plate having a thickness of 4.0 mm. At that time, before cold rolling of each pass, the edge of the steel strip is visually inspected to confirm the presence or absence of ear breakage, and if ear breakage has occurred, investigate the depth and angle of ear breakage did.
Before cold rolling of the 4th pass (plate thickness 2.4 mm), it was confirmed that 3 mm deep and 60 ° angled ear cracking occurred. When the cold rolling in the fourth to sixth passes was applied under the rolling conditions (rolling speed: 400 mpm), the steel strip was broken in the sixth pass. When the broken steel strip was examined, it was found that the crack extended in the width direction of the steel strip starting from the edge crack and the steel strip was broken.

(Comparative example 2)
The cold rolling of the above-mentioned setting was performed to a SUS436 ferritic stainless steel hot-rolled annealing pickled plate with a plate thickness of 4.0 mm. At that time, before cold rolling of each pass, the edge of the steel strip is visually inspected to confirm the presence or absence of ear breakage, and if ear breakage has occurred, investigate the depth and angle of ear breakage did.
Before the cold rolling in the first pass, it was confirmed that an edge crack having a depth of 4 mm and an angle of 70 ° had occurred. When the first pass cold rolling was applied under rolling conditions (rolling speed: 200 mpm), the steel strip was broken. When the broken steel strip was examined, it was found that the crack extended in the width direction of the steel strip starting from the edge crack and the steel strip was broken.

Claims (3)

Determining the treatment to be applied to the ferritic stainless steel strip by using the depth and angle of the edge crack generated in the ferritic stainless steel strip to be rolled during cold rolling as an index;
The cold-rolling method of a ferritic stainless steel strip which subjects the said judged process to the said ferritic stainless steel strip. The cold rolling method for a ferritic stainless steel strip according to claim 1, wherein an edge crack having a depth of 3 mm or more and an angle of 90 ° or less is used as an index. As an index for judgment of processing to apply edge crack of depth 3 mm or more and angle 90 ° or less to ferritic stainless steel strip to be rolled,
Whether the ferritic stainless steel strip is subjected to cold rolling by reducing the speed from the intended cold rolling speed when the above-mentioned edge cracking occurs in the ferritic stainless steel strip to be rolled during cold rolling Or judge to stop cold rolling,
It is judged that it is possible to cold-roll the ferritic stainless steel strip at a planned cold-rolling speed when the edge crack is not generated in the ferritic stainless steel strip,
The cold-rolling method of a ferritic stainless steel strip which subjects the said judged process to the said ferritic stainless steel strip.

Images