JP2000282152A - Production of ferritic stainless steel sheet excellent in workability - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the workability of a steel sheet and to reduce the creeping amt. of edge seam flaws by coating the side face of a ferritic stainless steel slab with an antioxidant contg. a reducing agent, executing heating and specifying the draft in the horizontal rolling in rough rolling and the draft in width rolling. SOLUTION: A slab of ferritic stainless steel having a prescribed componential compsn. is heated by a heating furnace 10, is thereafter subjected to rough rolling by a rough rolling mill line R in which rigid rolls E1 to E4 and horizontal rolls R1 to R4 are combined, this rough rolling stock is joined to a preceding rough rolling stock by a sheet bar joining device 30, is subjected to finish rolling by a finish rolling mill line F provided with horizontal rolls F1 to F7 and is coiled around a coiler 20. At this time, the side face of the slab is coated with an antioxidant contg. a reducing agent, which is heated to suppress decarburization and to prevent the coarsening of crystal grains. Moreover, the draft in the horizontal rolling pass in the rough rolling is controlled to 40 to 75%, and the width draft in the width rolling pass is controlled to the range of 0.8 to 1.5 times to the sheet width difference in the thickness direction of the stock to be rolled after the horizontal rolling pass.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a ferritic stainless steel sheet having excellent workability, and more particularly, to a surface defect which is long in the rolling direction and is generated near an edge in the width direction of the steel sheet during hot rolling. (Hereinafter referred to as edge seam flaws).

[0002]

2. Description of the Related Art Ferritic stainless steel sheets are usually
A slab of ferritic stainless steel obtained by continuous casting is heated in a heating furnace, and hot rolling is performed in which a rough rolling in which a width rolling pass and a horizontal rolling pass are combined a plurality of times and a finish rolling having a plurality of horizontal rolling passes are performed. Rolling process (including hot strip annealing)
And the steps of pickling, cold rolling, and finish annealing.

[0003] The ferritic stainless steel sheet manufactured in this manner is generally superior in stress corrosion cracking resistance and inexpensive as compared with the austenitic stainless steel sheet. It is used. Among them, a ferritic stainless steel sheet having excellent workability with good ridging resistance and deep drawability (r value) is provided by setting the thickness reduction rate of at least one pass in the rough rolling to be in the range of 40% to 75%. It is known that it can be manufactured.

For example, Japanese Patent Application Laid-Open No. 7-310122 discloses an object of producing a ferritic stainless steel sheet having excellent r-value and ridging resistance, low in-plane anisotropy, and particularly excellent in stretch forming property. In at least one pass of the rough rolling step, the thickness reduction rate is in the range of 40% to 75%, the rolling temperature is 1000 to 1150 ° C., the friction coefficient is 0.3 or less, and the strain rate is 7 to 100 s ⁻¹ . There is disclosed a method for producing a ferritic stainless steel sheet having excellent stretch formability, which is performed.

However, a ferritic stainless steel sheet excellent in workability has a thickness reduction ratio of at least one pass in the rough rolling within a range of 40% to 75%, so that edge seam flaws extend to the inside of the sheet width. As a result, the margin for trimming increased and the product yield was poor. As a method of reducing the edge seam flaw wraparound amount (the maximum value of the distance from the side end of the material to be rolled to the edge seam flaw), for example, Japanese Patent Publication No. Hei 6-241 discloses a horizontal rolling method performed between width rolling passes. Stainless steel with a total rolling reduction of 50% or less in the pass and a width reduction in one width rolling pass within the range of 0.40 to 1.5 with respect to the thickness width difference of the material to be rolled after the horizontal rolling pass Hot rolling methods for steel have been proposed.

Japanese Patent Application Laid-Open No. Hei 10-52701 discloses that an antioxidant is applied to a side surface of a slab before charging in a heating furnace in a range of 1/4 or more of a slab thickness from an upper end and a lower end, respectively. The width is reduced by 50% or more by horizontal rolls only in the first three passes of rough rolling after the width press with the anvil, and then the width reduction by the vertical rolls is reduced by 30 per pass.
A method for producing a stainless steel sheet that reduces the amount of edge seam flaw wraparound by limiting the diameter to mm or less has been proposed.

However, the hot rolling method for stainless steel described in Japanese Patent Publication No. Hei 6-241 discloses a method in which the thickness reduction of at least one pass in the rough rolling is set in a range of 40% to 75%. In addition, there is a problem that the edge seam flaw wraparound amount increases. Further, when the antioxidant disclosed in JP-A-10-52701 is simply applied to a slab of a ferritic stainless steel sheet, the thickness reduction rate of at least one pass in the rough rolling is set in a range of 40% to 75%. Has a problem that the amount of edge seam flaws cannot be reduced.

[0008]

Therefore, an object of the present invention is to reduce the thickness reduction rate of at least one pass in rough rolling by 40%.
An object of the present invention is to provide a method for producing a ferritic stainless steel sheet excellent in workability with a small amount of edge seam flaw wraparound even within the range of% to 75%.

[0009]

Means for Solving the Problems Even if an antioxidant is applied to the entire side surface of a slab of a ferritic stainless steel sheet before being charged into a heating furnace, the present invention still requires that That the decarburization caused by the oxidized scale on the side of the slab is occurring during the heating, and studied a coating agent that suppresses this decarburization and a width rolling pass to reduce the amount of edge seam flaw wraparound. It was completed by examining the width reduction amount.

That is, in the first invention, a slab of ferritic stainless steel obtained by continuous casting is heated in a heating furnace, and rough rolling in which a width rolling pass and a horizontal rolling pass are combined a plurality of times; In the method for producing a ferritic stainless steel sheet having excellent workability of performing a finish rolling having a rolling pass, an antioxidant containing a reducing agent is applied to the entire surface of the side surface of the slab before being charged into the heating furnace. In addition, the rolling reduction of at least one horizontal rolling pass excluding the last horizontal rolling pass in the rough rolling is 40% to 75%.
%, And the width reduction in the width rolling pass in the rough rolling after the horizontal rolling pass is in the range of 0.80 to 1.5 times the sheet width difference in the thickness direction of the material to be rolled after the horizontal rolling pass. This is a method for producing a ferritic stainless steel sheet having excellent workability.

[0011] The second invention provides a rough rolling in which a slab of ferritic stainless steel obtained by continuous casting is heated in a heating furnace to combine a width rolling pass and a horizontal rolling pass a plurality of times; In the method for producing a ferritic stainless steel sheet having excellent workability of performing a previous one width rolling pass and a finish rolling having a plurality of horizontal rolling passes, the entire surface of the slab side before being charged into the heating furnace. And applying an antioxidant containing a reducing agent, and setting the rolling reduction of the last horizontal rolling pass in the rough rolling to within a range of 40% to 75%, and the width rolling pass in the finish rolling after the horizontal rolling pass. Production of a ferritic stainless steel sheet excellent in workability, characterized in that the width reduction in the width is in the range of 0.80 to 1.5 times the sheet width difference in the thickness direction of the material to be rolled after the horizontal rolling pass. By the way .

Further, it is preferable to perform the finish rolling after joining the preceding material to be subjected to the rough rolling and the material to be subjected to the rough rolling, and then perform the finish rolling. It is a manufacturing method. Here, the first
The invention relates to the case where the finish rolling having a plurality of horizontal rolling passes is performed, and the second invention relates to the workability in the case where the finish rolling having one width rolling pass and a plurality of horizontal rolling passes before the horizontal rolling pass is performed. This is a method for producing an excellent ferritic stainless steel sheet.

Further, the difference in the thickness direction of the material to be rolled after the horizontal rolling pass of the first invention or the second invention is defined as a reduction of 40%.
% To 75% after the horizontal rolling pass and before the width rolling pass, the thickness difference in the thickness direction on the operation side in the material to be rolled.
(B _OP shown in FIG. 5) and the total width difference in the thickness direction on the driving side, and is hereinafter referred to as a specific bulging amount.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a layout of a hot rolling equipment line used in the present invention. 10 is a heating furnace, R is a row of rough rolling mills, F
Is a finishing rolling mill row, 20 is a coiler, and 30 is a sheet bar joining device. It is preferable to provide the sheet bar joining device 30.
The rough rolling mill row R includes vertical rolls (E1, E2, E3, E4) and horizontal rolls (R1, R2, R3, R4). Finishing mill row F
Has horizontal rolls F1 to F7. It is preferable that the finishing roll F be provided with a vertical roll FE1 on the upstream side of the horizontal roll F1. On the upstream side of the vertical rolls (E1, E2, E3, E4 and FE1), the edge drop meters (D1, D2, D3, D4 and FD)
It is preferable to provide 1) respectively.

First, the first invention will be described. The first invention is suitable when the vertical roll FE1 is not provided in the finishing mill row F shown in FIG. The ferrite stainless steel slab excellent in workability used in the first invention is obtained by continuously casting molten steel adjusted to a predetermined component.

One of the features of the manufacturing method of the first invention is that FIG.
Slab 1 before charging into slab heating furnace 10 as shown in
By applying an antioxidant containing a reducing agent to the entire surface of the side surface of the slab (reference numeral 2 in FIG. 2), decarburization due to the oxidized scale on the slab side surface generated before charging into the heating furnace 10 can be prevented. It is preventing. After the antioxidant containing the reducing agent is dried, the antioxidant is heated to a predetermined temperature in the heating furnace 10, and the rough rolling in which the width rolling pass and the horizontal rolling pass in the rough rolling mill row R are combined a plurality of times is performed. A finish rolling having a plurality of horizontal rolling passes in a rolling mill row F is performed, and a hot rolled coil of a ferritic stainless steel sheet having excellent workability, which is wound by the coiler 20, is manufactured.

Here, another feature of the production method of the first invention is that the rolling reduction of at least one horizontal rolling pass, excluding the last horizontal rolling pass in rough rolling, is in the range of 40% to 75%. The width reduction in the width rolling pass in the rough rolling after the horizontal rolling pass is 0.80 to 1.
By setting it within the range of 5 times, the structure of the hot-rolled coil of the ferritic stainless steel sheet having excellent workability is obtained, and wrinkles on the side surfaces formed by the horizontal rolling pass are smoothed.

The reason for limiting the application of the antioxidant containing the reducing agent to the entire surface of the slab side before charging into the slab heating furnace of the first invention will be described. The oxide scale is already present on the slab surface of the ferritic stainless steel before charging into the heating furnace 10 before charging into the continuously cast heating furnace used in the first invention.

In the conventional method, an antioxidant containing no reducing agent is applied to the side surface of the slab via an oxide scale. Therefore, at the time of heating, the antioxidant is accompanied by oxidation with oxygen in the atmosphere in the heating furnace. Decarburization of slab side end (Decarburization reaction of ground iron)
However, the decarburization of the slab side end proceeded due to oxidation with oxygen in the oxide scale, and decarburization at the slab side end occurred to some extent. For this reason, the crystal grains at the side ends of the slab were coarsened.

On the other hand, in the first invention, since the antioxidant containing the reducing agent is applied to the side surface of the slab through the oxide scale, the slab side end is removed during the heating due to the oxidation with the oxide scale. Before the coal progresses, the reducing agent
The reaction to reduce the oxide scale proceeds. Therefore, decarburization of the slab side end caused by oxidation with oxygen in the oxidation scale does not occur, and decarburization of the slab side end caused by oxidation with oxygen in the atmosphere in the heating furnace is an antioxidant. Therefore, decarburization at the slab side end is almost completely suppressed. For this reason, coarsening of crystal grains due to decarburization at the side end of the slab can be almost completely suppressed.

The relationship between the coarsening of the crystal grains in the surface layer on the slab side end and the formation of edge seam flaws is explained as follows. In the process of repeatedly applying the width reduction by the vertical roll and the thickness reduction by the horizontal roll, irregularities are formed on the side of the slab, which is a free surface in the unit of coarsened crystal grains in the initial stage of the thickness reduction, and the irregularities are reduced in width. The rolling and the thickness rolling are repeated to form long wrinkles in the rolling direction. The wrinkles wrap around the slab surface near the edge in the width direction of the slab due to bulge deformation (swelling of the side surface) of the slab, resulting in edge seam flaws on the surface of the stainless steel plate.

Here, the antioxidant used in the first invention is:
It is composed of an oxide, anhydrous water glass, an acrylic resin and water. The oxide may be one or more selected from Al ₂ O ₃ , Cr ₂ O ₃ , and ZrO ₂ , the side end of the ferritic stainless steel slab accompanying oxidation with oxygen in the furnace atmosphere. It is preferable because decarburization of the part can be suppressed. Further, the reducing agent used in the first invention is one or more selected from among Si, SiC, Al, B, and C, and is easily available and inexpensive. Before the decarburization of the slab side end caused by the oxide scale proceeds, the reducing agent is preferable because it reduces the oxide scale and can suppress decarburization to some extent.

Further, when the reducing agents are B and SiC or B and Al, the decarburization accompanying oxidation with the oxide scale at the end of the slab can be completely suppressed, and the amount of the edge seam flaw wraparound can be minimized. More preferred. The addition amount of the reducing agent used in the first invention may be appropriately determined according to the scale amount of the side surface of the slab, and the method of applying the antioxidant containing the reducing agent is preferably applied uniformly by spraying or brushing, The coating amount is preferably about 300 to 600 g / m ² .

By the way, the oxide scale on the side surface of the slab is removed by a grinder or the like before being charged into the heating furnace, and then an antioxidant containing no reducing agent is applied to the entire side surface of the slab. Although the amount of wraparound can be reduced, it is not preferable because the yield decreases and the number of steps for cleaning the grinder increases. Except for the last horizontal rolling pass in the rough rolling according to another feature of the first invention, the rolling reduction of at least one horizontal rolling pass is set in a range of 40% to 75%, and the width in the rough rolling after the horizontal rolling pass is set. Explain the reason why the width reduction amount of the rolling pass is limited to the range of 0.80 to 1.5 times the specific bulging amount.The reason for excluding the last horizontal rolling pass in rough rolling is that 40% to 75 reduction
%, The vertical roll FE is added to the finishing mill row F.
This is because, because no 1 is provided, the wrinkles on the side surfaces formed in the horizontal rolling pass cannot be smoothed, and the amount of edge seam flaws wraparound cannot be reduced.

The reason why the rolling reduction of at least one horizontal rolling pass is limited to the range of 40% to 75% is as follows. If the rolling reduction of the rough rolling is less than 40%, the workability is inferior due to insufficient formation of the recrystallized structure. On the other hand, when the rolling reduction of the rough rolling exceeds 75%, the rolling load becomes excessively large, and it becomes difficult to perform the rolling. Therefore, the rolling reduction of the horizontal rolling pass is 40
% To 75%.

At least one horizontal rolling pass is performed at any stage of the rough rolling so that the rolling reduction of the horizontal rolling pass is from 40% to 40%.
Although it may be within the range of 75%, it is better to perform in a later pass in terms of material properties and rolling mill capacity. Further, the width reduction amount of the width rolling pass after the horizontal rolling pass with the reduction ratio in the range of 40% to 75% is set to 0.80 to 1.5 with respect to the specific bulging amount.
The reason why the value is within the double range is as follows.

If the specific bulging amount is less than 0.80, the wrinkles on the side surfaces formed by the high pressure reduction cannot be smoothed, and the edge seam flaw wraparound amount cannot be reduced. On the other hand, for a specific bulging amount
If it exceeds 1.5 times, buckling of the material to be rolled in the width direction occurs, and the width cannot be reduced. For this reason, the width reduction amount of the width rolling pass after the horizontal rolling pass with the high reduction rate is set in the range of 0.80 to 1.5 times the specific bulging amount.

Next, the second invention will be described. In the second invention, as shown in FIG.
This is a preferred method in the case where is provided. In the second invention, a slab of ferritic stainless steel obtained by continuous casting is heated in a heating furnace, and rough rolling in which a width rolling pass and a horizontal rolling pass are combined a plurality of times and finish rolling are performed. It is similar to the first invention, but different from the manufacturing method of the first invention in the following two points.

That is, one is that instead of the finish rolling having a plurality of horizontal rolling passes, a finish rolling having one width rolling pass and a plurality of horizontal rolling passes before the horizontal rolling pass is performed. The second is to reduce the rolling reduction of at least one horizontal rolling pass, excluding the last horizontal rolling pass in rough rolling.
Instead of being in the range of 40% to 75%, the rolling reduction of the last horizontal rolling pass in the rough rolling is in the range of 40% to 75%.

In the second invention, by setting the rolling reduction of the last horizontal rolling pass in the rough rolling in the range of 40% to 75%, the structure of a hot-rolled coil of a ferritic stainless steel sheet having the most excellent workability can be obtained. In addition, using the vertical roll FE1 shown in FIG. 1, the formed wrinkles on the side surface can be smoothed by finish rolling having one width rolling pass before the horizontal rolling pass.

The features of the second invention other than those described above are the same as those of the first invention, and will not be described in detail. The reason why it is preferable to apply the finish rolling after joining the preceding material to be subjected to the rough rolling of the first invention or the second invention and the material to be subjected to the rough rolling, and then applying the finish rolling to the end of the hot rolled coil This is because a defective shape portion, a defective thickness portion, and a defective width portion at the end are reduced, and the yield is improved.

[0032]

[Example] (Example 1) Continuously cast ferritic stainless steel having a thickness of 200 mm and a width of 1300 mm (C: 0.07 wt%, Si:
(0.3wt%, Mn: 0.1wt%, Cr: 17wt%) 2 places (500mm × 2
(1000 mm), two kinds of coating agents (antioxidant and antioxidant containing reducing agent) having the composition shown in Table 1 were each spray-coated at 400 g / m ^{2 and} dried for 1 hour. It was charged into the heating furnace 10 shown and was soaked at 1200 ° C. for 2 hours.

Then, the slab is extracted from the heating furnace onto a line of a row of hot rolling equipment. After cooling, a sample is taken from the side of the slab side at the center of the thickness, observed by a microscope after etching, and decarburized layer thickness is measured. (Μm). The results are shown in Table 1.

[0034]

[Table 1]

From these results, it can be seen that the antioxidant containing a reducing agent used in the present invention can suppress the amount of decarburization as compared with the conventional antioxidant containing no reducing agent. Next, an antioxidant containing a reducing agent shown in Table 1 (coating agent symbol: A) is applied to the entire side surface of the continuously cast ferritic stainless steel slab having the same thickness, plate width and composition as described above.
Was spray-coated at 400 g / m ² each, dried for 1 hour, and then charged into a heating furnace 10 shown in FIG. 1 and heated at 1200 ° C. for 2 hours.

The heated slab was subjected to rough rolling in which a width rolling pass and a horizontal rolling pass shown in Table 2 were combined a plurality of times.
The sheet bar thickness was mm. As shown in Table 2, the rolling reduction in the horizontal rolling pass and the horizontal rolling pass in the rough rolling is 6 in the horizontal rolling pass and 1, 2, 3 in the horizontal roll R1.
Pass (reverse rolling) and 4, 5, 6 passes (unidirectional rolling) with horizontal rolls R2, R3, R4.

Also, as shown in Table 2, the width rolling pass and the width reduction amount in the rough rolling are as follows. 1, 3, 4, 5 and 6 passes of horizontal rolling were performed. In the example of the present invention, as shown in Table 2, except for the last horizontal rolling pass in the rough rolling, the rolling reduction of at least one horizontal rolling pass is set in the range of 40% to 75%, and the rough rolling after the horizontal rolling pass is performed. The width reduction of the width rolling pass was set in the range of 0.80 to 1.5 times the specific bulging amount.

The sheet bar was subjected to finish rolling having seven horizontal rolling passes to a sheet thickness of 4 mm, and was wound around a coiler 20 to obtain a hot-rolled coil. The hot rolled coil was subjected to hot rolled sheet annealing (box annealing at 840 ° C.) and the amount of edge seam flaw wraparound after pickling was measured by the following method according to an ordinary method. here,
The bulging amount is measured by each of the edge drop meters D1, D2, D3, D4, and FD1, for example, as shown in FIG. 5, but may be modeled in advance and predicted by rolling conditions. As shown in FIG. 4, the width reduction amount is calculated by the width reduction amount calculating device D10 using the measured bulging amount as shown in FIG.
1 by controlling the opening of the vertical rolls E1, E2, E3, E4 and FE1. The width reduction is the difference between the widths of the vertical rolls E1, E2, E3, E4 and FE1 before and after the width rolling. The diameter of the horizontal rolls R1 to R4 (work rolls) of the row R is 1300 mm, the barrel length is 2200 mm, and the diameter of the horizontal rolls F1 to F7 (work rolls) of the row F is 700 m.
m, the barrel length was 2000 mm, and the rolling speed on the exit side of the finishing mill row F was 1000 m / min.

After the measurement, cold rolling (rolling reduction 83%),
A cold-rolled steel sheet with a thickness of 0.7 mm was obtained by finish annealing (870 ° C). Using this cold-rolled steel sheet as a test material, the ridging height and r value were measured by the following methods. Edge seam flaw wraparound amount d _ES : As shown in FIG. 3, the distance from the end face of the innermost edge seam flaw to the longitudinal center of the hot-rolled coil that has been subjected to the pickling step is measured on both sides and the upper and lower surfaces of the sheet width. Each was measured at 10 points and the average value was obtained.

R value: After applying 15% tensile strain using a JIS No. 13 test piece, an average r value was determined by a three-point method. Ridging: 20% for JIS No. 5 test piece taken from rolling direction
After the tensile strain was given, the ridging height was measured with a surface roughness meter, and expressed as the maximum roughness Rmax (μm). Table 2 shows the results of the edge seam flaw wraparound amount d _ES , r value, and ridging height.

On the other hand, as a conventional example and a comparative example, an antioxidant (reducing agent) shown in Table 1 was applied to the entire side surface of a continuously cast ferritic stainless steel slab having the same thickness, width and composition as those of the invention example. Antioxidant containing no agent, coating agent symbol:
Each of B) was spray-coated at 400 g / m ² , dried for 1 hour, and then charged into a heating furnace 10 shown in FIG. 1 and soaked at 1200 ° C. for 2 hours. As shown in Table 2, the heated slab was subjected to rough rolling in which a width rolling pass and a horizontal rolling pass were combined a plurality of times to obtain a sheet bar thickness of 30 mm.

Here, in the conventional example, the rolling reduction of the horizontal rolling pass in the rough rolling is out of the range of the present invention, and in the comparative example, the width reduction in the width rolling pass is out of the range of the present invention. Things. Except for the above, hot-rolled sheet annealing of the hot-rolled coil obtained under the same conditions as the invention example (box annealing at 840 ° C.), the amount of edge seam flaw wraparound after pickling, and the cold-rolled steel sheet obtained under the same conditions as the invention example The measurement results of the ridging height and the r value are also shown in Table 2.

[0043]

[Table 2]

From these results, it is found that an antioxidant containing a reducing agent is applied to the entire side surface of the slab before the slab is charged into the heating furnace, and at least one horizontal rolling excluding the last horizontal rolling pass in the rough rolling. Pass reduction rate 40% to 75
%, And the width reduction of the width rolling pass in the rough rolling after the horizontal rolling pass is 0.80 to 1.5 with respect to the thickness width difference (specific bulging amount) of the material to be rolled after the horizontal rolling pass.
It can be seen that the invention example in which the range is doubled has better ridging height and r value than the conventional example, and the edge seam flaw wraparound amount is smaller than the comparative example. (Example 2) Using a slab of ferritic stainless steel obtained by continuous casting of the same thickness, sheet width and components as in Example 1, as shown in Table 3, the rolling reduction of the horizontal rolling pass and the width rolling pass Except that the width reduction was changed, the hot-rolled coil annealing (840)
Table 3 shows the results of measurement of the edge seam flaw wraparound amount after pickling and the edge seam flaws after pickling, and the ridging height and r value of the cold-rolled steel sheet obtained under the same conditions as those of the invention.

On the other hand, in the conventional example and the comparative example, the antioxidant shown in Table 1 was applied to the entire surface of the side surface of the slab of ferritic stainless steel obtained by continuous casting of the same thickness, sheet width and composition as the invention example. (Antioxidants that do not contain reducing agents, coating agent symbols:
B) was applied. In the conventional example, the width rolling pass in the finish rolling was an empty pass (no width reduction amount), and in the comparative example, the width reduction amount of the width rolling pass in the finish rolling was out of the range of the invention. Was the same as the invention example.

Table 3 shows the measurement results of the edge seam flaws of the obtained hot rolled coil and the ridging height and r value of the cold rolled steel sheet.

[0047]

[Table 3]

From these results, it is found that an antioxidant containing a reducing agent is applied to the entire side surface of the slab before being charged into the heating furnace, and the rolling reduction of the last horizontal rolling pass in the rough rolling is 40% to 40%. Within the range of 75%, the width reduction in the width rolling pass in the finish rolling after the horizontal rolling pass is determined by the thickness width difference (specific bulging amount) in the thickness direction of the material to be rolled after the horizontal rolling pass.
It can be seen that the invention example in which the ratio is within the range of 0.80 to 1.5 times the edge seam flaw wraparound amount is smaller than the conventional example and the comparative example.

Further, by comparing the results shown in Table 2 with the results shown in Table 3, it was found that the reduction rate of the last horizontal rolling pass in the rough rolling was set in the range of 40% to 75%, and the ridging was better. It can be seen that the height and r value are good.

[0050]

According to the present invention, rolling lubrication oil is not supplied in rough rolling without being restricted by rolling chances.
The amount of wraparound of edge seam flaws can be reduced.

[Brief description of the drawings]

FIG. 1 is a layout view of a hot rolling mill equipment row used in the present invention.

FIG. 2 is a schematic view showing an application range of an application agent used in the present invention.

FIG. 3 is a schematic diagram showing a method of measuring the amount of edge seam flaw wraparound.

FIG. 4 is a schematic configuration diagram of a width reduction device used in the present invention.

FIG. 5 is a perspective view showing a method of measuring a bulging amount used in the present invention.

[Explanation of Signs] 1 Slab (rolled material) 2 Application range 3 Slab thickness 4 Coil plate width 10 Heating furnace 20 Coiler 30 Sheet bar joining device E1 to E4, FE1 Vertical roll R1 to R4, F1 to F7 Horizontal roll D1 to D4, FD1 Edge drop meter D10 Width reduction amount calculation device D11 Width reduction amount control device R Rough rolling mill row F Finish rolling mill row

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masanori Kitahama 1 Kawasaki-cho, Chuo-ku, Chiba City, Chiba Prefecture Inside the Technical Research Institute of Kawasaki Steel Co., Ltd. (72) Inventor Masao Yarida 1 Kawasaki-cho, Chuo-ku, Chiba City, Chiba Prefecture 4K032 BA01 CB01 CB02 4K037 EB14 FB06 FB10

Claims (3)

[Claims] 1. A slab of ferritic stainless steel obtained by continuous casting is heated in a heating furnace, and a rough rolling in which a width rolling pass and a horizontal rolling pass are combined a plurality of times, and a finish having a plurality of horizontal rolling passes. In a method for producing a ferritic stainless steel sheet having excellent workability by performing rolling, an antioxidant containing a reducing agent is applied to the entire surface of the side surface of the slab before being charged into the heating furnace, and the rough rolling is performed. Excluding the last horizontal rolling pass in, the rolling reduction of at least one horizontal rolling pass is in the range of 40% to 75%, the width reduction of the width rolling pass in the rough rolling after the horizontal rolling pass,
A method for producing a ferritic stainless steel sheet excellent in workability, characterized in that the difference in sheet thickness in the thickness direction of the material to be rolled after the horizontal rolling pass is within a range of 0.80 to 1.5 times. 2. A slab of ferritic stainless steel obtained by continuous casting is heated in a heating furnace, and is subjected to rough rolling in which a width rolling pass and a horizontal rolling pass are combined a plurality of times, and one time before a horizontal rolling pass. In the method for producing a ferritic stainless steel sheet having excellent workability of performing a width rolling pass and a finish rolling having a plurality of horizontal rolling passes, a reducing agent is contained on the entire side surface of the slab before being charged into the heating furnace. While applying an antioxidant, the rolling reduction of the last horizontal rolling pass in the rough rolling is set in the range of 40% to 75%, and the width reduction of the width rolling pass in the finish rolling after the horizontal rolling pass is reduced. A method for producing a ferritic stainless steel sheet having excellent workability, wherein the difference between the sheet width in the thickness direction of the material to be rolled after the horizontal rolling pass is within a range of 0.80 to 1.5 times. 3. The finish rolling is performed after joining the rough rolled preceding material to be rolled and the rough rolled material to be rolled.
3. A method for producing a ferritic stainless steel sheet having excellent workability according to item 1.