JP3504425B2 - Method for producing stainless steel sheet capable of reducing edge seam flaws - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a stainless steel sheet, and more particularly to a long defect (edge seam flaw) in the rolling direction which occurs near the edge portion in the width direction of a material to be rolled during hot rolling of a slab. The present invention relates to a method for manufacturing a stainless steel plate that can reduce

[0002]

2. Description of the Related Art As one of means for adjusting the width of a hot slab over a wide range, a width reduction technique by a horizontal counter- press has been developed. This method has good rolling efficiency due to the large contact length during width reduction, and is widely adopted at domestic and overseas hot rolling plants because it can set the molding conditions at the slab front and rear ends to minimize cropping. .

Using an anvil used in this horizontal counter- press, for the purpose of preventing edge seam flaws, which is one of the surface defects occurring at the edge portion (width end portion) of the plate,
Japanese Patent Laid-Open Publication No. Hei 9 (1999) -31980 discloses a technique in which a slab heating temperature is set to 1000 to 1300 ° C., and an anvil (convex anvil) in which a convex portion is formed in a central portion (meaning a central portion in a thickness direction on a press working surface of an anvil. The same applies hereinafter) Japanese Patent Laid-Open No. 5-277510 discloses a method for preventing buckling of a slab and reducing edge seam flaws.

These techniques reduce the wraparound of edge seam flaws by making the side face of the slab concave by a width press using a convex anvil and compensating for the bulging that occurs at the end of the slab width in the horizontal rough rolling stage after the width press. To do. On the other hand, as a surface defect mitigation technique not limited to the width press, for example, Japanese Patent Laid-Open No. 3-124304 discloses no specific disclosure relating the slab heating temperature and the edge seam flaw, but a martensitic stainless steel slab. It has been proposed that the heating temperature is 1200 ° C. or higher and the heating time is 4 hours or less.

[0005]

However, the prior art for the purpose of preventing edge seam flaws occurring in the widthwise edge portion after hot finish rolling has the following problems. In the technique disclosed in JP-A-5-123713, even when the width reduction amount is small, the convex shape imparted to the anvil is largely transferred to the slab side surface because the top length of the convex portion is short. For this reason, the depth of the recesses becomes deep, and even after the edge rolling, the edge seam flaws on the plate surface can be reduced, but the recesses sometimes remain as defects inside the plate. Further, when the width reduction amount is large, the dent amount on the side surface of the slab becomes larger and the internal defects after finish rolling become larger.

Further, when the width reduction amount is large, the compressive strain in the width direction becomes large even in the surface layer of the slab.
Due to this compressive deformation, the crystal grains on the surface of the slab became uneven, and the crystal grains on the convex portion collapsed to form an edge seam flaw. In Japanese Patent Laid-Open No. 5-123713, the heating temperature is 10
It is described that the temperature is 00 to 1300 ° C, but there is no description regarding the heating time. Further, there is no description about the relationship between the heating temperature in this temperature range and the edge seam flaw.

On the other hand, in Japanese Patent Laid-Open No. 5-277510, a large width reduction amount is obtained by a width press using an anvil having a convex portion at the center of the W-shaped groove. However, even if a large amount of width reduction is obtained, the crystal grains in the surface layer become uneven due to the compressive deformation of the slab in the width direction due to the W-shaped groove, and the unevenness of the crystal grains collapses and remains on the plate surface until after finish rolling, resulting in an edge seam. It was a flaw. When the edge seam flaw is large as described above, it remains on the upper and lower surfaces of the plate until after the cold rolling, which makes it difficult to reduce the edge cutting margin (trim amount), and the yield is reduced.

Further, as proposed in Japanese Patent Laid-Open No. 3-124304, if the heating temperature is set to 1200 ° C. or higher and heating is performed for 4 hours or less, rough skin can be prevented, but crystals of the decarburized layer of the slab surface layer can be prevented. Due to the occurrence of edge seam flaws due to the unevenness of the grains, the amount of edge seam flaws wrapping around even after cold rolling was large, and the edge cutting margin had to be reduced. An object of the present invention is to solve these problems of the prior art all at once, and to prevent the occurrence of edge seam flaws and rough skin of a stainless steel sheet manufactured through a series of hot rolling including width reduction by a width press and / or a vertical roll. An object of the present invention is to provide a method for manufacturing a stainless steel plate that can be effectively reduced.

[0009]

A first aspect of the present invention is a stainless steel sheet including a series of hot rolling processes in which a continuously cast slab of stainless steel is heated in a heating furnace and rough rolling is performed after width reduction and finish rolling is performed. In the manufacturing method, the heating temperature of the slab is 900 to 1100 ° C., the heating time is 6 hours or less, and the width end temperature of the rolled material after rough rolling and before finish rolling is 800 ° C. or more. A method for manufacturing a stainless steel plate capable of reducing edge seam flaws .

A second aspect of the present invention is a series of continuous casting, in which a continuously cast stainless steel slab is heated in a heating furnace, width-pressed by a horizontal counter-press anvil, and then rough-rolled including width reduction by a vertical roll. In the method of manufacturing a stainless steel sheet including hot rolling, the heating temperature of the slab is set to 900 to 1100.
C., the heating time is 6 hours or less, the horizontal counterpress anvil is a convex anvil having a trapezoidal convex portion in the center, and the height of the convex portion related to the cross section of the convex anvil is 1/15 to 1 / the slab thickness. 4. Set the convex top length to 1/3 to 3/4 of the slab thickness, and the convex bottom length to the slab thickness + (10 to 30) mm, and make it vertical in the first 3 passes of the rough rolling after the width press. An edge seam characterized by reducing the width by 50% or more without width reduction by rolls, and by further increasing the width edge temperature of the rolled material after rough rolling to finish rolling to 800 ° C or higher.
This is a method for manufacturing a stainless steel plate capable of reducing flaws .

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 2 is a layout of hot rolling equipment rows suitable for carrying out the present invention. 10 is a heating furnace, 11 is a width press machine, 12 is a rough rolling machine row, and 13 is an edge heater. , 14 is a finish rolling mill row, 15 is a coiler for winding the steel plate rolled by the finishing rolling mill row 14, and 16 is a vertical roll rolling installed at each rough rolling mill entry side and the finishing rolling mill row 14 entry side. Machine (also known as edger).

According to the examination results of the present inventors, the causes of the occurrence of edge seam flaws are as follows. In order to control the width of the material to be rolled, in the normal rolling mill row, the edger 16 is arranged only on the inlet side of the horizontal rolling mill, or on both the inlet side and the outlet side, the rough rolling mill row 12 and the finishing rolling mill row. It has a structure in which the roll axis positions of the 14 horizontal rolls and the edger 16 vertical roll are shifted by several meters in the rolling direction.

Therefore, since the vertical rolls do not act on the width ends of the horizontally rolled cross section, the free surface of the width ends undergoes bulge deformation, and wrinkles occur in that region. The wrinkles gradually become larger by a plurality of passes made by the edger 16 on the downstream side, and finally reach the surface of the material to be rolled and become an edge seam flaw. The main cause of this wrinkle is the deformation and collapse of the coarse crystal grains on the surface. That is, in the continuously cast stainless steel slab, the surface layer is decarburized when heated in a heating furnace, the crystal grains of the surface layer of the slab become coarse, and the crystal grains become convex due to the compression deformation in the width direction during the width reduction. (The crystal grains project from the surface layer), and the projecting crystal grains fall down during rough rolling and finish rolling, resulting in edge seam flaws.

Particularly, ferritic stainless steel having a ferrite crystal structure has a larger decarburization amount than other stainless steels, and the decarburized layer has a thickness of 1 mm to several millimeters.
In addition, since the range of unevenness in the width press is wide, the amount of wraparound of edge seam defects is large. The first aspect of the present invention prevents grain coarsening due to decarburization of the surface layer of the slab by lowering the heating temperature of the slab and regulating the heating time, and further regulates the width end temperature of the sheet bar before finish rolling. By doing so, rough skin is prevented.

By lowering the heating temperature, the thickness of the decarburized layer becomes thin, the unevenness of the crystal grains in the compressive deformation in the width direction at the time of width reduction becomes small, and the depth becomes shallow enough not to collapse and cool. Edge seam defects disappear after hot rolling. The reason for this is that if you lower the heating temperature to a certain level,
1mm that tends to develop into edge seam flaws on the surface of the slab.
This is because the above-mentioned coarse crystal grains disappear.

Crystal grains are arranged in a single layer on the surface of the slab, and the crystal grains are most strongly decarburized during heating. In order to find an effective means for reducing the thickness of this decarburized layer to 1 mm or less, a 200 mm thick slab is heated, the heating temperature, heating time and oxygen partial pressure are variously changed, The thickness of the decarburized layer on the slab surface was investigated. Fig. 3 shows the resulting decarburized layer thickness of the slab surface layer, heating temperature, heating time,
It is a graph which illustrates the relationship with oxygen partial pressure.

As illustrated in FIG. 3 (a), the decarburized layer thickness has a large correlation with the heating temperature, and becomes thicker with the heating temperature, and is thin at about 0.3 mm up to 1100 ° C, but rapidly increases above 1200 ° C. It reaches more than 4mm at 1300 ℃. The thickness of the decarburized layer increases with the partial pressure of oxygen as illustrated in FIG. 3B, but the rate of increase is small. In terms of easiness of rolling, we would like to suppress the thickness of the decarburized layer by raising the heating temperature and lowering the oxygen partial pressure, but in actual operation there is a limit to the sealing during slab insertion and extraction, and the oxygen partial pressure is 1 %, It is difficult to reduce the thickness to below 0%, and in order to reduce the thickness of the decarburized layer, it is industrially effective means to lower the heating temperature to the extent that rolling is not hindered.

Based on the results of the investigation, it was found that it is preferable to set the heating temperature to 1100 ° C. or lower in order to stably obtain the slab decarburized layer thickness of 1 mm or less in consideration of the variation in the actual operation. However, if the heating temperature is lower than 900 ° C, rolling becomes difficult, so the heating temperature must be 900 ° C or higher. Regarding the heating time, as shown in FIG. 3C, for example, the longer the heating time, the thicker the decarburized layer tends to be, but the increase rate is not so large. However, when the heating temperature is the upper limit (1100 ° C.) of the above-mentioned suitable range, the decarburized layer thickness becomes 1 mm or more when the heating time exceeds 6 hours, so the heating time should be 6 hours or less. desirable.

In consideration of uniform heating up to the center of the slab, for example, when the heating temperature is 900 ° C. which is the lower limit of the preferable range, it is preferable to hold the heating temperature for 3 hours or more. On the other hand, if the heating temperature is regulated to 900 to 1100 ° C and the heating time is regulated to 6 hours or less as described above, the temperature of the width end portion of the rolled material is likely to drop to less than 800 ° C in finish rolling. If this happens, the rolling load will increase and the black skin on the surface of the roll will peel off, causing considerable irregularities on the roll and causing roughening of the plate.
14 At the inlet side, for example, the edge heater 13 etc.
It is necessary to maintain the temperature above 0 ° C.

When the temperature is 900 ° C. or higher, the generation and growth of the black skin on the roll surface exceeds the peeling and the roll surface is uniformly covered with the black skin, so that the width end temperature is 900 from the viewpoint of preventing rough skin. It is even more preferable to maintain the temperature above ℃. The first aspect of the present invention is particularly effective when applied to a ferritic stainless steel sheet having a relatively large amount of decarburization and the crystal grains of the surface layer of which are likely to coarsen. It is effective even if applied.

Next, the second invention will be described. Figure 1
Relates to the shape and arrangement of the convex anvil according to the present invention,
(A) is an external perspective view, (b) is a sectional view of a convex portion, (c) is a plan layout view, respectively, 1 is a convex metal floor, 2 is an inlet side inclined surface for introducing a hot slab, 3 Is an intermediate parallel surface that is connected to this inlet side inclined surface 2 and is parallel to the hot slab transfer line, 4
Is an outlet side inclined surface connected to the intermediate parallel surface 3 and useful for forming the rear end portion of the slab, and a press work surface is formed by a combination of the inlet side inclined surface 2, the intermediate parallel surface 3 and the outlet side inclined surface 4. It Reference numeral 5 indicates the top of the convex portion, 6 indicates the inclined portion of the convex portion, 7 indicates the bottom portion of the convex portion, and KH, KA, and KB are the convex portion height and the convex portion top side length in the cross section of the convex anvil 1, respectively. It represents the length of the bottom of the convex portion, and M is a slab (hot slab).

As shown in FIG. 1 (c), the convex anvil 1 is arranged so as to sandwich the hot slab M conveyed in the direction of the left arrow from both sides. By repeating the reciprocating motion of each other (the driving means is not shown), the slab M which is being conveyed is width-reduced over its entire length. As described at the beginning, such a width reduction is referred to as " horizontal counter- press".

In order to make it easier to bite into the side surface of the slab, the convex portions of the convex anvil 1 are "trapezoidal", that is, the intervals between the inclined portions 6 facing each other substantially symmetrically become narrower toward the top portion 5. A second aspect of the present invention is intended to suppress the occurrence of edge seam flaws when the width reduction of the stainless steel slab is performed by a width press using a horizontal opposing press anvil under the regulation of the first aspect of the present invention, By adopting a convex anvil with a specific cross-sectional dimension and forming the slab side into an appropriate concave shape, it compensates for the bulging of the slab side during horizontal rolling and prevents the wrinkles generated on the slab side from wrapping around the front and back surfaces. In addition, the compression force applied to the surface layer is relaxed, the unevenness of the crystal grains generated on the surface is reduced, the collapse of the crystal grains is prevented, and the occurrence of edge seam flaws can be limited to only the extreme edge portion of the width. it can.

The present inventors herein, through experimentation, to decrease over 50% more than the thickness in the first three passes of rough rolling, the width end portion cross-sectional shape of the third pass of the rough rolling after the end of the material to be rolled It was found that the closer to a rectangle, the smaller the amount of wraparound on the side surface in the downstream rough rolling and finish rolling, and based on this finding, the recesses carved on the side surface of the slab by the width press with the convex anvil have three initial passes. The preferable range of the cross-sectional dimension of the convex anvil was determined so that the width end cross section close to the rectangle can be obtained by being compensated by the bulging by the rough horizontal rolling.

Therefore, in the second aspect of the present invention, when the width reduction by the vertical roll intervenes during the first to third passes of the rough rolling, the width end of the rolled material on the entry side of the fourth pass becomes rectangular. In addition, the amount of side wraparound in the downstream rough rolling and finish rolling becomes large. Therefore, the width was limited to 50% or more without performing the width rolling with the vertical rolls in the first three passes of the rough rolling after the width pressing.

The reasons for limiting the cross-sectional dimensions of the relief anvil will be described below. [Height of convex part (KH)] A slab of ferritic stainless steel with a slab thickness of 200 to 260 mm is heated to 1000 ° C., and flat press with a flat press surface is used to perform width pressing with various width pressing amounts. Subsequently, a rough horizontal rolling without width reduction by vertical rolls was performed for 3 passes to perform a width press experiment with a total reduction ratio of 50%, and the amount of bulging after rough rolling was investigated.

In the present invention, the "width press amount" means a difference in slab thickness before and after the width press, and the "bulging amount" means that the slab side end corner portion before the width press is subjected to the rough horizontal rolling. It means the distance from the position moved to the plate surface after passing to the edge of the slab width after width pressing. An explanatory diagram of the bulging amount is shown in FIG. FIG. 4 shows a cross section of the width end portion of the slab after the width press, where P _SC is the slab side end corner portion before the width press and V is the bulging amount.

FIG. 5 is a graph obtained by arranging the results of the width press-rough rolling experiment, and is a graph showing the relationship between the width press amount by flat anvil and the bulging amount to the slab thickness ratio (V / H). is there. As shown in Fig. 5, V / H is the width press amount of 50 mm
From 1 to 15 to 1/4 with the increase from around to 200 mm
To increase. Therefore, by preliminarily providing a dent on the side surface of the slab with a depth suitable for this, the rough horizontal rolling 3
The bulging amount after the pass is compensated and the width end of the cross section of the rolled material becomes close to a rectangle. Therefore, it is preferable that the height KH of the convex portion of the convex anvil for providing such a depression is 1/15 to 1/4 of the slab thickness. [Convex portion top edge length (KA)] In the above width press experiment, the convex portion height KH is set to the above preferred range in place of the flatbed and the convex portion top side length KA and the convex portion bottom side length KB are variously changed. The amount of bulging after 3 passes of rough horizontal rolling (without width reduction by vertical rolls) was examined.

FIG. 6 is a graph showing the relationship between the resulting ridge slab length-to-slab thickness ratio (KA / H), the cross-sectional shape of the material to be rolled and the bulging amount (V). As shown in FIG. 6, when KA / H is less than 1/3, the cross-sectional shape becomes double bulging, and V increases as KA / H decreases. Further, when KA / H exceeds 3/4, the sectional shape becomes single bulging, and V increases as KA / H increases. In the range where KA / H is 1/3 to 3/4, the cross section has a shape close to a rectangle between the double bulging and the single bulging, and V has the lowest value in this range.

FIG. 6 illustrates the case where the slab thickness is 200 mm, the height of the convex portion of the convex anvil is KH18 mm, the length of the bottom of the convex portion is KB220 mm, and the width pressing amount is 100 mm. The tendency shown in FIG. Is similarly recognized over the preferable range of KH and KB according to the second aspect of the present invention and the range of the slab thickness and width pressing amount shown in FIG. Therefore, it is preferable that the apex length KA of the convex portion is 1/3 to 3/4 of the slab thickness. [Convex Base Length (KB)] FIG. 7 shows the transfer rate and the excess (KB) of the transfer ratio and the convex bottom length investigated for the slab after the width press and before the rough rolling in the above width press experiment.
It is a graph which shows the relationship with -H). Here, the "transfer rate" is the percentage (%) of the maximum dent depth of the slab side surface with respect to the convex portion height KH, and the state in which the convex portion height KH is completely transferred to the slab side surface is 100%. is there.

As shown in FIG. 7, when KB-H is less than 10 mm and the transfer rate is more than 90%, the slab side end corner portion is not the sloped portion of the convex portion of the anvil but the bottom side during width pressing. Since it is pushed by the flat portion, the compressive deformation in the width direction becomes large, and the unevenness of the crystal grains in the surface layer of the slab also becomes large due to it, and it tends to remain as an edge seam flaw. Further, if KB-H exceeds 30 mm, the transfer rate will be less than 80%, and the dent depth of the side surface of the slab will be insufficient, so that the cross section of the material to be rolled after 3 passes of rough rolling cannot be made close to a rectangle.

FIG. 7 shows an example in which KH is H / 10, width press amount is 200 to 220 mm, and KA / H is 1/3 and 3/4, but the tendency shown in FIG. The same was found over the preferable range of the KH according to the second present invention and the range of the slab thickness and the width pressing amount shown in FIG.
Therefore, the length KB of the bottom of the protrusion is the slab thickness H + (10 to 30) mm.
Is preferred.

[0033]

EXAMPLES In Examples A and B disclosed below, the slab is C: 0.05 wt%, Si: 0.3 wt%, Mn:
Continuous casting thickness of 200mm, containing 0.1wt%, Cr: 17wt%,
A ferritic stainless steel slab with a width of 1300 mm and a length of 6 m was hot-rolled using the hot-rolling equipment row shown in FIG. The work roll diameter of the rough rolling machine is 1300 mm,
The barrel length is 2200 mm, and the work roll diameter of the finishing mill is 7
00mm, the barrel length is 2000mm, the exit speed of the finishing rolling mill train 14 is 1000m / min. <Example A: In the case of no width press> After heating the above slab under the conditions of heating temperature and time shown in Table 1, width press was not performed and only vertical rolls on the side of the row of four rows of rough rolling mills were used. Rolling down the plate horizontally while rolling down the width, plate thickness 25 mm, width 13 at the exit side.
A 00 mm sheet bar was used, and the sheet bar was finish-rolled to a plate thickness of 4 mm by a 7-stand finishing rolling machine train and wound. At this time, for A1 to A3, heat the edge of the seat bar width with the edge heater on the line side of the finishing rolling mill, and
Maintained above.

Both the slab heating conditions (temperature ° C × time hr) and the sheet bar width end temperature satisfy the requirements of the present invention A1, A
2, A3 as an invention example, slab heating temperature, slab heating time,
The sheet bar width end temperature deviates from the regulations of the present invention, respectively A4, A
5, A6 was used as a comparative example. The "seam amount" column of Table 1 shows the results of investigation of the amount of edge seam flaws wrapping around the longitudinal middle portion of the hot rolled coil thus obtained. here,
The "seam amount" is an evaluation value of the edge seam flaw used in the present invention, and means the distance from the width end to the flaw closest to the center of the width (including both the edge seam flaw and the rough skin), and generally the trim amount. Corresponding to. The seam amount is O in the width direction.
The P (operator) side, the DR (drive) side, and the top and bottom surfaces (indicated as “OP top”, “DR bottom”, etc. in the table) were investigated (the same applies hereinafter).

As shown in Table 1, there is no noticeable difference in the seam amount after hot rolling between the invention example and the comparative example. However, after pickling these hot-rolled coils, they were rolled by a 4-stand cold rolling mill.
The amount of seams investigated on the upper and lower surfaces of the longitudinal middle portion of the cold rolled coil obtained by cold rolling at 70% is the same as that of Invention Examples A1 to A3 and Comparative Example A.
There was a clear difference between No. 4 and A5, and the invention example obtained significantly better results. This is because in the invention example, the wraparound amount due to bulging in the hot rolling stage is not much different from the comparative example,
It is a proof that the wrinkles themselves can be suppressed to a dent that is smoothed by cold rolling.

Comparative Example A6 has the same slab heating conditions as those of Invention Example A3, but the edge bar temperature is less than 800 ° C. without heating by the edge heater, so that rough skin occurs and the seam amount is increased. Has grown. <Example B: With Width Press> As Invention Examples B1 to B6, the slab was heated to 1000 ° C. in a heating furnace.
After heating under the condition of 4 hours, 3 within the prescribed range of the cross-sectional dimension of the present invention
Width press amount of 50 mm and 200 mm
Horizontal counter- pressing was performed, and then, using a row of four-stand rough rolling mills, the first three passes were not reduced in width by vertical rolls and the thickness was reduced to 100 mm (thickness reduction rate 50%). Rough rolling is performed for a total of 6 passes, and the plate thickness is 25
mm, width 1300 mm sheet bar, and further, the width of the sheet bar is controlled by an edge heater on the entry side of the finishing rolling mill.
While maintaining the temperature at 800 ° C or higher, it was finish-rolled to a thickness of 4 mm by a 7-stand finishing rolling mill train and wound up.

Further, as Comparative Examples B7 to B10, after heating the slab in a heating furnace under the condition of 1200 ° C. × 4 hr, the method described in JP-A-5-1237 was used.
Japanese Patent Laid-Open No. 5-27
Using one type of anvil each having a convex portion at the center of the W-shaped groove described in Japanese Patent No. 7510, width pressing with a width pressing amount of 50 mm and 200 mm was performed, and thereafter, since the slab heating temperature was high, the finishing rolling mill entrance side In the same process as in the invention example except that the heating by the edge heater was not carried out, the product was finished rolled to a thickness of 4 mm and wound up.

Table 2 shows the cross-sectional dimensions (height KH of the convex portion, top length KA of the convex portion, bottom length KB of the convex portion) of the convex portions of the convex anvil of the invention example and the comparative example and the W-shaped groove anvil. As shown, the groove depth of the W-shaped grooved anvil was 300 mm. In addition, Comparative Examples B9 and B10 in Table 2 use W-shaped grooved anvils.
Table 2 shows the results of evaluation of the amount of seams after hot rolling of the thus obtained hot rolled coil in the same manner as in Example A. The amount of seams after cold rolling evaluated in the same manner for the coils obtained by cold-rolling these hot-rolled coils under the same conditions as in Example A was substantially the same as the amount of seams after hot-rolling.

Inventive Examples A1 to B6 of Example A1 to A6 of Example A shown in Table 1 were used for the seam amount after hot rolling regardless of the width pressing amount.
It's much smaller than that of the A3. That is,
In addition to the slab low temperature heating and the sheet bar width end temperature lower limit control according to the first aspect of the present invention, width reduction is performed by horizontal counter-pressing using the convex anvil according to the second aspect of the present invention, and the rough rolling initial three passes. By reducing the width to 50% or more without performing width reduction with a vertical roll, in addition to the effect of suppressing coarsening of the surface layer crystal grains and roughening of the skin, side wraparound control and surface layer compression relaxation by bulging (suppression of surface layer crystal grain irregularities and collapse) It can be said that such a good result was obtained because the effects were superposed.

On the other hand, in Comparative Examples B7 and B8, the slab width side corners directly contact the bottom of the convex portion of the anvil and the slab surface layer is strongly compressed in the width direction, so that the surface crystal grains become uneven, The amount of hot-rolled seams increased. The larger the width press amount, the larger the seam amount. In Comparative Examples B9 and B10, the slab surface layer was more strongly compressed in the width direction by the restraining force of the W-shaped groove, and as a result, the surface crystal grains were also increased in the degree of unevenness. It became the largest amount of hot rolled seams.

[0041]

[Table 1]

[0042]

[Table 2]

[0043]

EFFECTS OF THE INVENTION According to the present invention, edge seam flaws of a stainless steel sheet manufactured by a series of hot rolling including width reduction by a width press and / or a vertical roll can be further reduced as compared with the prior art, and rough skin can be suppressed. So, the conventional 30mm /
The trim effect of the stainless steel plate on one side can be reduced to 10 mmm / side or less, which is a remarkable effect.

[Brief description of drawings]

FIG. 1 relates to the shape and arrangement of a convex anvil according to the present invention,
(A) is an external perspective view, (b) is a sectional view of a convex portion, and (c) is a plan layout view, respectively.

FIG. 2 is a layout drawing of a row of hot rolling equipment suitable for implementing the present invention.

FIG. 3 is a graph illustrating a relationship between a decarburized layer thickness of a slab surface layer, a heating temperature, a heating time, and an oxygen partial pressure.

FIG. 4 is an explanatory diagram of a bulging amount.

FIG. 5 is a graph showing the relationship between the width press amount and the bulging amount relative to the slab thickness ratio (V / H) by flat anvil.

FIG. 6 is a graph showing a relationship between a slab thickness ratio (KA / H) of a convex top length, a cross-sectional shape of a material to be rolled, and a bulging amount (V).

FIG. 7 is a graph showing a relationship between a transfer rate and an excess amount (KB-H) of a bottom length of a convex portion with respect to a slab thickness.

[Explanation of symbols]

1 Convex anvil 2 Inlet side inclined surface 3 Intermediate parallel surface 4 Outlet side inclined surface 5 Top of convex portion 6 Inclined portion of convex portion 7 Bottom of convex portion 10 Heating furnace 11 Width press device 12 Rough rolling mill row 13 Edge heater 14 Finish Rolling mill row 15 Coila 16 Vertical roll rolling mill (edger) H Slab thickness KH Convex part height KA Convex part top side length KB Convex part bottom side length M Slab (hot slab) P _SC width Slab side end before pressing Corner V Vulging amount

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kunio Isobe               1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Kawasaki               Steel Engineering Co., Ltd. (72) Inventor Masao Akita               1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Kawasaki               Steel Engineering Co., Ltd.                (56) References JP-A-61-111703 (JP, A)                 JP-A-4-138803 (JP, A)                 JP-A-8-73995 (JP, A)                 JP-A-4-123802 (JP, A)                 JP-A-5-123713 (JP, A)

Claims (2)

(57) [Claims] 1. A method for manufacturing a stainless steel sheet, which comprises a series of hot rolling processes in which a continuously cast stainless steel slab is heated in a heating furnace, and rough rolling is followed by finish rolling including width reduction. C. to 1100 ° C., the heating time is 6 hours or less, characterized by further width end temperature of the rough rolling after finish rolling prior to the material to be rolled and 800 ° C. or higher edge
A method for manufacturing a stainless steel sheet capable of reducing seam flaws . 2. A series of hot rolling processes in which a continuously cast stainless steel slab is heated in a heating furnace, width-pressed in a horizontal counterpress anvil and then rough-rolled and finish-rolled including width reduction by a vertical roll. In the method of manufacturing a stainless steel plate, the heating temperature of the slab is 900 to 1100 ° C and the heating time is 6
The time is less than or equal to the time, and the horizontal counterpress anvil is a convex anvil having a trapezoidal convex portion in the central part, and the height of the convex portion related to the cross section of the convex anvil is 1/15 to 1/4 of the slab thickness, the convex top side The length is 1/3 to 3/4 of the slab thickness, and the length of the convex bottom is the slab thickness + (10 to
30mm, the width is reduced by 50% or more in the first three passes of rough rolling after width pressing without vertical reduction by vertical rolls, and the temperature at the width end of the rolled material after rough rolling and before finish rolling is 800 A method for producing a stainless steel sheet capable of reducing edge seam flaws, which is characterized in that the temperature is at least ℃.