JP5742525B2 - Width reduction method for hot stainless steel slabs - Google Patents

Description

  The present invention relates to a method for reducing the width of a hot stainless steel slab, and more specifically, in hot rolling of stainless steel, a yield reduction due to a seam ridge generated in the entire length in the longitudinal direction near the width direction plate end of the hot rolled steel plate, In particular, the present invention relates to a method for reducing the width of a hot stainless steel slab, which can reduce the yield deterioration due to the large rounding of seam seams at the leading end of the coil.

  As a means for changing the width of the hot slab, the temperature of the slab manufactured by the continuous casting process is not lowered, or after the temperature is lowered, the slab is heated to a predetermined temperature after being put into a heating furnace, and then the hot slab is heated. 2. Description of the Related Art A width press apparatus that uses a pair of dies installed so as to face each other in the plate width direction of the slab to intermittently reduce the hot slab in the plate width direction is used. One and the other of the pair of molds are mirror images of each other, and are disposed at positions symmetrical with respect to the center plane in the rolling line width direction. In such a width press apparatus, a maximum width of about 300 to 350 mm is usually applied to a hot slab having a width of about 900 to 2000 mm, which is different from a slab cast to the same width by continuous casting. It is possible to manufacture steel sheets with a wide width. This greatly reduces the number of width changes due to mold changes in the continuous casting process, expands schedule-free rolling with variable width in the hot rolling process, and increases the coil weight, greatly improving the productivity and streamlining of the steel sheet manufacturing process. The merit is increased as the width reduction capability of the width press device increases.

  However, when the width reduction amount by the width press increases, a linear surface defect may occur depending on the deformation characteristics in the vicinity of the sheet width edge depending on the steel type. For example, in ultra-low carbon steel, the temperature at which transformation from the austenite phase to the ferrite phase is high, and the deformability of both phases is different (the ferrite phase is soft). Since it softens with it, the linear wrinkles which overlap | superposed locally by the width reduction by a width press or horizontal rolling may generate | occur | produce. Since this linear wrinkle occurs in the entire length of the coil, it can cause a significant decrease in product yield. Therefore, it is necessary to reduce the temperature near the corner of the hot slab. On the other hand, it has been proposed to form a concave groove called a caliber and form the slab corner part into an obtuse angle under a width pressure to suppress a temperature drop of the slab corner part (for example, Patent Document 1).

  Further, in the hot rolling of stainless steel, wrinkle-like micro unevenness is formed on the side surface of the slab, which is the free surface, during horizontal rolling of the slab at the initial stage of rough rolling. Since the deformation leads to the vicinity of the plate width end on the front and back surfaces of the plate, in the state of the hot-rolled steel plate, an aggregate of linear defects called seam flaws is formed over a range of several tens mm from the plate width. For this reason, since a hot-rolled steel sheet is manufactured by setting a surplus width in consideration of the width of the seam ridge in advance, the seam ridge portion must be trimmed and removed, resulting in a significant decrease in yield. It was. As a technique for reducing such a stainless steel seam wrinkle, a die having a trapezoidal convex portion at the center in the height direction of the squeezing surface of the width reduction die is used, and the subsequent rough rolling is performed. In the initial three passes, it has been proposed not to perform width reduction by an edger roll (for example, Patent Document 2). This is because the stainless steel seam trough expands as the slab side surface wraps around due to bulge deformation, so the slab side surface is formed into a concave shape in advance by a width press to reduce the amount of width bulge due to bulge deformation and rough rolling. By not carrying out the width reduction by the heel roll at the initial stage, the concave shape of the side surface of the slab formed by the width press is maintained, and the effect of preventing the side material from entering the front and back surfaces is exhibited. In addition, stainless steel seams have a feature that the amount of wrapping from the side of the slab increases at the leading end in the longitudinal direction of the coil, so a technology to change the width reduction amount by the width press in the longitudinal direction of the slab is proposed. (For example, Patent Documents 3 and 4). A width reduction method using a plurality of inclined portions and parallel portions formed on the pressing surface of the width reduction mold has also been proposed (for example, Patent Documents 5 and 6).

JP-A 63-192503 JP-A-9-256050 JP 2010-64123 A JP 2010-75977 A JP 2007-222894 A JP 2009-190049 A

However, the conventional seam wrinkle reduction techniques for stainless steel sheets described above have the following problems.
In the technique disclosed in Patent Document 2, a large seam wrinkle reduction effect is recognized by optimizing the size of the trapezoidal convex portion formed on the die pressing surface. However, although this effect is large in the stationary part except for the vicinity of the leading end of the coil in the longitudinal direction, there is still a problem that the amount of seam wrap around the leading end of the coil is large. In Patent Document 2, a concave shape is formed on the side surface of the slab with a mold having a convex portion, and in order to maintain this effect, the width reduction by the edger roll is not performed in the initial three passes of rough rolling. It is inevitable that the flare at the end (bowl-shaped width spread) becomes large (for example, see “Theory and Practice of Plate Rolling” p. 83).

  In the subsequent rough rolling, if the width reduction by the edger roll is performed in order to compensate for the breadth in horizontal rolling, the width reduction amount in the flare part having a wider width than that in the steady part becomes large, and accordingly The amount of wrapping around the seam trough at the tip end will also increase. After all, in order to obtain the same width over the entire length of the steel sheet after hot rolling, the trim amount at the edge of the sheet width is limited by the trim amount at the leading end of the coil where the amount of wrap around the seam seam is the largest. There is a problem that the trim portion over the entire length of the steel plate occurs frequently and the yield is not improved so much.

  Patent Documents 3 and 4 propose a technique for changing the amount of width reduction by the width press in the longitudinal direction of the slab as a measure for reducing the amount of seam wrap around the tail end of the coil. Then, the difference in the amount of width reduction (hereinafter referred to as the step amount) and the length of the step (hereinafter referred to as the step length) between the slab steady part and the leading end of the width press, and the analysis of the operation data The relational expression using the coefficient obtained from However, according to the study by the present inventors, the appropriate step amount and step length largely depend on the relationship between the mold shape and the contact start position of the slab (hereinafter referred to as the pre-molding length), In Patent Documents 3 and 4, no mention is made regarding the preforming length.

  The present invention has been intensively studied to overcome the above-mentioned problems of the prior art, and the yield reduction due to the seam wrinkles generated in the entire length in the longitudinal direction in the vicinity of the plate end of the stainless hot-rolled steel sheet, particularly the coil tip. The present invention provides a method for reducing the width of a hot stainless steel slab that makes it possible to prevent a decrease in yield due to a large amount of seam trough at the tail end.

In order to solve the above-mentioned problems, the present inventors have conducted intensive studies and found a method for reducing the width of a hot stainless steel slab that prevents the yield from being lowered due to the seam of the stainless steel plate. That is, the present invention is as follows.
(1) An upstream inclined portion that narrows the distance between the opposing surfaces of the rolling reduction molds facing each other on both sides of the rolling line from the upstream side to the downstream side of the rolling line, and the rolling line direction. Width reduction using the pair of molds in which the parallel part parallel to the downstream side and the downstream inclined part that increases the distance between the faces toward the downstream side are connected in this order, and then during the multiple passes of rough rolling A method of reducing the width of a hot stainless steel slab that is reduced in width by using an edger roll, wherein the mold is used, and the most advanced portion of the slab is at the upstream inclined portion, and the most distal end of the slab. In the downstream inclined portion, the remaining portion of the slab is reduced in width by the parallel portion, and the slab thickness of the slab is 200 to 300 mm and the slab width is 800. and ~2000mm, the most Actual width reduction amount of the end portion and the outermost tail part, as well as to 30~50mm larger than the actual width reduction amount of the constant region, to the 50~350mm the actual width reduction ratio of the constant region A method for reducing the width of a hot stainless steel slab.
(2) The method for reducing the width of a hot stainless steel slab according to (1) above, wherein the upstream inclined portion and the downstream inclined portion have an inclination angle of 12 ° or more with respect to the rolling line.
(3) The method for reducing the width of a hot stainless steel slab according to (1) or (2) above, wherein the pressed surface has a trapezoidal convex portion at the center in the height direction.
(4) The width reduction by the edger roll is performed after the total reduction ratio from the slab thickness on the rough rolling entry side to the plate thickness of the rough intermediate pass becomes 50% or more, (1 ) A method for reducing the width of a hot stainless steel slab according to any one of (3) to (3).

  According to the present invention, it is possible to prevent a decrease in yield due to a seam trough that occurs in the entire length in the longitudinal direction in the vicinity of the end of the plate during hot-rolling of a stainless steel plate, and in particular, a decrease in yield due to a large round of the seam trough at the end of the coil. be able to.

It is a graph which shows an example of the flare reduction effect by this invention. It is a graph which shows another example of the flare reduction effect by this invention. It is a top view which shows an example of the flare reduction effect by this invention. It is a top view which shows an example of the metal mold | die used for this invention. It is explanatory drawing which shows one example of the width press (width reduction using a metal mold | die) method of the slab front-end | tip part by this invention. It is explanatory drawing which shows one example of the width press (width reduction using a metal mold | die) method of the slab tail end part by this invention. It is a definition explanatory drawing of preforming length. It is a definition explanatory drawing of level difference width reduction. It is a three-dimensional view showing an example of a mold having a trapezoidal convex portion at the center of the pressure surface in the height direction. It is principal part sectional drawing of FIG.

Hereinafter, embodiments of the present invention will be described with reference to FIGS.
In the manufacture of stainless steel sheets, seam wrinkles are generated as described above, so that the width having a trapezoidal convex portion near the center in the height direction of the die pressing surface is reduced for the purpose of reducing the amount of rolling around the slab side surface due to rolling. A reduction mold 1 is used (see FIGS. 9 and 10). When a slab width press using such a mold is performed, a dent is formed on the side surface of the slab, so that a bulge deformation of the side surface of the slab by subsequent horizontal rolling is provided by providing a convex shape with an appropriate dimension. Can be almost offset. That is, by applying such a width press to a stainless steel slab, the region where the edge seam wrinkles of the stainless steel plate are generated can be greatly reduced.

  On the other hand, the dotted line in FIG. 3 schematically shows the material widening behavior in plate rolling, and the tip and tail ends of the material are unsteady deformation regions in rolling. It becomes a bowl spreading shape called. This is because, in plate rolling, the width of the roll bite in the steady part excluding the leading end part of the material (the unsteady deformation region, hereinafter also referred to as the leading end unsteady part) is Since it is constrained by the presence of the non-deformable material parts located at the front and back, the breadth is not very large, but the leading edge has no material to restrain the breadth and deformation at the front, and the tail end is the On the other hand, there is no material constraining the widening deformation, and therefore the widening becomes large. Usually, in the rough rolling process of hot slabs, width reduction is performed with an edger roll provided in each roughing mill for the purpose of changing the slab width and for the purpose of compensating for the breadth in horizontal rolling. Yes. And in order to reduce the width | variety fluctuation | variation in a leading-end unsteady part, the short stroke control which controls the width reduction amount by an edger scissors roll is performed in the slab front-end | tip and the tail end vicinity.

  In addition, in the manufacture of stainless steel sheets, as described above, the slab side surface is formed into a concave shape by using a mold for reducing the width of the slab with a convex shape to reduce seam wrinkles. In the first half pass of rough rolling, the width of the dent on the side surface of the slab is reduced when the width is reduced by the edger roll, so this is not usually performed. In the prior art (for example, Patent Document 2), it is proposed not to carry out the width reduction by the edger roll until the total reduction ratio from the slab thickness on the rough rolling entry side to the plate thickness of the rough intermediate pass exceeds 50%. The present inventors have confirmed that the present technology has a great effect from the viewpoint of reducing the amount of seam wrap around. Therefore, in the present invention, it is preferable to execute the width reduction by the edger roll after the total reduction ratio becomes 50% or more. However, if the total rolling reduction exceeds 95%, it is difficult to reduce the thickness even if the number of passes is increased beyond the rolling capacity limit of the rolling mill. More preferably, the total rolling reduction is 50 to 95%. Within the range, the width reduction by the edger roll is executed.

  However, as described above, when the width reduction by the edger punch roll is not performed, the flare at the leading edge increases, so the amount of edge seam wrapping around the leading edge increases, and the trim margin increases in the subsequent process. It is inevitable that the yield is further reduced. For this reason, in the pass in the latter half of the rough rolling, it is necessary to reduce the flare by reducing the width by the edger roll and to make the plate width distribution uniform over the entire length in the longitudinal direction. However, in order to do so, the width reduction amount at the leading end flare portion where the width spread has already become large increases, and accordingly, the amount of seam wrap around the leading end increases. It becomes inevitable. After all, in the plate width trim in the post process after hot rolling, the trim is performed over the entire length in accordance with the steel plate leading end where the amount of seam wrap is large, resulting in a large yield loss. End up.

  The inventors of the present invention have proposed a width reduction mold having a trapezoidal convex portion at the center in the height direction of the pressing surface (see FIGS. 9 and 10). H = 15 to 65 mm, trapezoid upper side length = 85 to 200 mm, trapezoid lower side length = 200 to 300 mm), and methods for efficiently reducing the amount of seam wrap around the slab tip As a technology to minimize the amount of seam wrapping over the entire coil length by effectively reducing the flare by making the best use of the inclined part of the squeezing surface of the width reduction mold The present invention has been completed. On the way to completion, as described above, in the remaining steady portion excluding the leading end unsteady portion, using a mold having a convex-shaped pressing surface, the total reduction ratio from the slab thickness to the plate thickness is By executing the width reduction with the edger roll after reaching 50% or more, it is possible to obtain a large effect of reducing the amount of seam wrapping. Therefore, assuming these two technical matters, there are inclined parts on both sides of the parallel part. The pre-molding technology of the slab tip end using a mold with continuous pressed surfaces was studied repeatedly. As a result, it has been found that the amount of seam wrapping at the front and rear end portions can be greatly reduced by appropriately performing width pressing at the inclined portion of the mold at both the tip and tail ends of the slab.

FIG. 4 is a plan view showing an example of a width reduction mold (abbreviated as a mold) used in the present invention (however, the pressed surface has a trapezoidal convex portion as shown in FIGS. 9 and 10). In addition, the illustrated mold 1 is one of a pair of facing installations on both sides of the rolling line, and the other is the same shape as the mirror image of the illustrated mold 1, and the mold 1 with respect to the center line of the rolling line width. It is installed in a plane symmetrical position. The lower part of the figure of the mold 1 shown in FIG. 4 is a squeezing surface, and the squeezing surface has an upstream inclined portion 2 that narrows the facing distance from the upstream side to the downstream side of the rolling line, and the rolling line direction. The parallel portion 4 that is parallel to the downstream side and the downstream side inclined portion 3 that increases the distance between the faces toward the downstream side are connected in this order. The upstream inclined portion 2 and the downstream inclined portion 3 have inclination angles θ ₁ and θ ₂ with respect to the rolling line direction, respectively. Here, θ ₁ and θ ₂ are preferably set to 12 ° or more because they are less than 12 ° because the effect of reducing the amount of wrap around the edge seam is small. However, if these exceed 30 °, the slab becomes difficult to bite into the mold, so θ ₁ and θ ₂ are more preferably 12 ° to 30 °.

FIG. 5 is a view showing a width pressing method of a slab tip portion according to the present invention, and a width after width reduction at a stationary portion excluding a leading end with respect to a slab (hot stainless steel slab) 5 having a slab width W. Shows a condition in which the width is reduced by setting (width reduction amount ΔW = W−w) to be w, and the slab 5 is conveyed by a distance L downstream of the rolling line between the width reduction passes. In the present invention, the slab leading-edge corner is width-reduced by the upstream inclined portion 2 of the mold 1, and the width reduction amount is the slab full width with respect to the steady portion width reduction amount ΔW as shown in FIG. [Delta] W ₁ (in the slab side surface ΔW _1/2) is to the width reduction so as to increase only. As shown in FIG. 8, ΔW ₁ is an increase in the set width reduction amount of the mold, while an increase in the actual width reduction amount of the slab tip portion relative to the slab steady portion (referred to as an actual width reduction increase amount). distinguishes between the [Delta] W ₁ as [delta] _1. This is because the actual width reduction increase δ ₁ in the actual slab changes due to the positional relationship between the slab and the mold when the slab tip is reduced, even with the same set width reduction increase ΔW _1. The explanation is based on this.

Similarly, FIG. 6 is a view showing a method for reducing the width of the tail end of the slab according to the present invention, where the corner of the slab end is reduced by the downstream inclined portion 3 of the mold, and as shown in FIG. the width reduction amount is to width reduction so as to increase by ([Delta] W _2/2 in the slab side surface) [Delta] W ₂ in slab entire width with respect to the steady portion width reduction amount [Delta] W. Similar to the tip, the actual width reduction increase in the actual slab is distinguished as δ ₂ .

  As described above, conventionally, the flare shape has occurred at the leading end of the steel plate as indicated by the dotted line in FIG. 3 by horizontal rolling, whereas the width reduction method of the present invention shown in FIGS. By carrying out the steel plate as shown by the solid line in FIG. 3 even when the width reduction by the edger roll is not performed in the first half pass of rough rolling (pass where the total reduction ratio from slab thickness to sheet thickness is less than about 50%). The plate width can be made substantially uniform over the entire length.

Hereinafter, the effects of the present invention will be described more specifically with reference to FIGS. FIGS. 1 and 2 show a hot slab of ferritic stainless steel having a thickness of 218 mm and a width of 1120 mm, and a mold for width reduction shown in FIG. 4 (where the pressing surface is a trapezoidal convex portion as shown in FIGS. 9 and 10). The width of the sheet is reduced by using a convex mold having a thickness of 160 mm (width reduction amount at the stationary part is 160 mm), and then the sheet thickness is 107 mm (total reduction ratio = (1) in 3 passes without performing width reduction by the edger roll. -107/218) * 100 ≈ 51%) This is data obtained by examining the flare amount at the leading end in a state where the pressure is reduced to 51%. It should be noted that the upstream side inclination angle θ ₁ and the downstream side inclination angle θ ₂ of the mold 1 (specifically, the pressing surface of the mold 1) are both 12 °. FIG. 1 shows the pre-forming length L ₀ when rolling down the slab leading edge and the increment ΔW ₁ of the leading edge with respect to the set width reduction amount of the mold to the stationary part (hereinafter referred to as gold at the tip). FIG. 5 is a relationship diagram between a mold step width reduction amount and an average flare amount at the tip after three-pass rolling. As shown in FIG. 7, the pre-molding length is from the most advanced position of the slab 5 when the slab most advanced part is reduced in width to the intersection position between the upstream inclined part 2 and the parallel part 4 of the mold 1. The state in which the leading edge position of the slab 5 starts from the origin (L ₀ = 0) and the tip side width reduction starts at the upstream inclined portion 2 is L ₀ <0, parallel portion The state in which the tip width reduction starts at 4 is L ₀ > 0. Moreover, in the state after 3 pass rolling, the concave shape of the side surface of the slab formed by the convex mold overlaps with the bulge deformation by the subsequent rolling, and the width end of the plate becomes an uneven shape of several mm in the thickness direction. Therefore, the width profile in the longitudinal direction at the 1/4 thickness, 1/2 thickness, and 3/4 thickness positions in the plate thickness direction is measured, and the steady-state width at the three positions and the vicinity of the foremost portion are measured. The difference from the maximum width was averaged to obtain the average flare amount.

As shown in FIG. 1, the average flare amount decreases with an increase in the step width reduction amount ΔW ₁ of the die at the tip, and the effect is remarkable when the pre-molding length L ₀ is ₀ mm. When the step width reduction amount ΔW _{1 of the} mold is about 50 mm, the average flare amount is almost 0 mm. FIG. 5 shows the situation under the condition of the pre-forming length L ₀ = ₀ mm, but under this condition, the actual width reduction increase amount δ ₁ at the slab tip is equal to the step width reduction amount ΔW _{1 of the} mold. It is possible to form the tip corner in an inclined state most efficiently. For example, in order to set δ ₁ = 40 mm under the condition of the upstream angle of inclination θ ₁ = 12 ° of the mold and the preforming length L ₀ = ₀ mm, ΔW ₁ may be set to 40 mm. If length L ₀ = −50 mm, 50 mm × tan (12 °) = 10.6 mm in terms of one-side reduction amount, that is, the step width reduction amount ΔW ₁ on both sides is 40 mm + 2 × 10. It is necessary to set 6 mm = 61.6 mm. In addition, under the condition where the pre-forming length L ₀ is positive, the leading edge of the slab 5 is width-reduced by the parallel part 3 of the mold 1. The flare reduction effect is smaller than the condition of the length L ₀ = ₀ mm.

Similarly, FIG. 2 shows the step width reduction amount ΔW _{1 of the} mold at the slab tip under the condition of the pre-molding length L ₀ = ₀ mm, FIG. 6 is a relationship diagram between an increase ΔW ₂ (hereinafter referred to as a step width reduction amount of a die at the tail end) and an average flare amount at the tip and tail ends after three-pass rolling. As described above, the width spreading behavior in the plate rolling is greatly influenced by the restraint of the material on the roll bite entry / exit side with respect to the width spreading deformation in the roll bite, and generally the tail end rather than the tip part of the material (rolled material). The amount of flare at the part increases. For this reason, in FIG. 2, when the width press is performed so that the width of the step width is 0 mm, that is, the step width is not reduced at the leading end of the slab and the entire width of the slab is uniform. Compared with, the average flare amount at the tail end is larger. On the other hand, by performing step width reduction at the tail end of the slab according to the present invention, the average flare amount is almost 0 mm at the tail end portion under the condition that the step width reduction amount of the mold is about 50 mm. Thus, as shown in FIG. 3, the flare amount in the first half of the rough rolling can be reduced, and the width trim amount due to the seam of the stainless steel plate after hot rolling can be greatly reduced. In this case as well, the actual width reduction amount δ ₂ of the actual slab tail end portion is equal to the step width reduction amount ΔW ₂ under the present conditions, so that the slab tail end corner portion is inclined most efficiently. It is possible to mold it.

  In addition, although the above-mentioned effect is confirmed using the metal mold | die of the shape of FIG. 4 (however, the pressing surface is a convex metal mold | die with a trapezoidal convex part like FIG. 9, FIG. 10), Even if a mold having a parallel part and a plurality of inclined parts (for example, Patent Documents 5 and 6) is used, the same effect can be obtained. Similar effects can be obtained even when using a die whose pressing surface does not have a trapezoidal convex portion and is flat across the entire height direction (in other words, trapezoidal height = 0 mm).

In addition, the present inventors further performed numerical analysis such as experiments and FEM, and obtained the appropriate range of the actual width reduction amount δ ₁ , δ ₂ of the mold at the slab leading end, and as a result, the slab leading end Although the appropriate range of the actual width reduction amount δ ₁ and δ ₂ of the mold is affected by the slab width and the steady portion width reduction amount, the slab thickness is 300 mm or less (however, 200 mm or more), and the slab width is 2000 mm or less (however, It was found that the range of 30 mm to 50 mm was appropriate for both δ ₁ and δ ₂ under the conditions of 800 mm or more) and the steady-state width reduction amount of 350 mm or less (however, 50 mm or more). If the actual width reduction increase is set to be less than 30mm, in addition to the increase in the amount of wrapping around the seam, flare is formed at the leading end after hot rolling, and this must be removed. On the other hand, if the increase amount of the actual width reduction is set to be larger than 50 mm, the amount of seam wrap is increased and, after hot rolling, the tip of the width of the steady portion is increased. The width in the vicinity of the tail end becomes narrower than the target, and this portion has to be removed, resulting in a decrease in yield.

  The ferritic stainless steel slab is used for the width reduction die shown in FIG. 9 (however, the trapezoidal height of the trapezoidal convex portion = 20 mm, the trapezoid upper side length = 110 mm, and the trapezoid lower side length = 210 mm). 1. The tail end part is subjected to width reduction (width press) under the indicated width reduction condition together with the width reduction amount of the stationary part excluding the leading end part in Table 2, and then the plate thickness from the slab in the first half of rough rolling. After the total rolling reduction to 50% or more, horizontal rolling is performed while performing width reduction with an edger roll, and then in the latter half of the rough rolling, width reduction is performed with an edger roll to control the overall width. The bar was formed into a sheet bar having a thickness of 33 mm, and a hot-rolled stainless steel sheet having a finishing plate thickness of 3 mm was manufactured by 7-pass finishing rolling immediately thereafter.

Seam determination and width determination were performed on the manufactured steel sheet. The results are shown in Tables 1 and 2. The evaluation value of the seam judgment in Table 1 is the case where there is an increase in the amount of wrap around 5 mm (one side) or more in the vicinity of the tip relative to the amount of wrap around the seam in the steady portion. ○. Moreover, the evaluation value of width determination is set to x when the width of the plateau of the stationary part is 5 mm or more narrowed or widened over the entire width. Conventional Example No. In Nos. 1 and 2, since the actual width reduction increase amount δ ₁ at the tip is small, the amount of wraparound of the seam rod is large. In _No. 4, the actual width reduction increase amount δ ₁ is too large, so that the width control effect by the edger roll in the latter half of the rough rolling is insufficient, and as a result, the tip width is narrowed. Conventional example No. _No. 5 is a case where the upstream side inclination angle θ ₁ is 10 °, and the flare reduction effect is small, and the seam determination is also x. On the other hand, in the examples of the present invention, both the seam determination and the width determination were ◯, and it was possible to manufacture hot-rolled steel sheets with good quality. Similarly, Table 2 shows the results when the same width reduction condition as that applied to the tip portion of Table 1 is applied to the tail end portion. In No. 11, the flare amount generated in the first half of the rough rolling was large, so the effect of the width control by the rolls in the second half of the rough rolling was insufficient, and the width judgment was also x. Both the examples and the examples of the present invention had the same results as those at the tip of Table 1, and it was possible to produce hot-rolled steel sheets with good quality by the width reduction method according to the present invention.

1 Mold (width reduction mold)
2 Upstream inclined part (inclination angle θ ₁ )
3 Downstream inclined part (inclination angle θ ₂ )
4 Parallel part 5 Slab (hot stainless steel slab)

Claims (4)

Each squeezing surface of the width reduction molds facing each other on both sides of the rolling line is parallel to the rolling line direction, and an upstream inclined part that narrows the distance between the facings from the upstream side to the downstream side of the rolling line. Using the pair of molds in which the parallel portion and the downstream inclined portion that increases the distance between the facing surfaces as they go downstream, the width is reduced using the pair of dies, and then the edger roll is rolled during a plurality of passes of rough rolling. A method of reducing the width of a hot stainless steel slab to reduce the width using
Using the mold, the most advanced portion of the slab is the upstream inclined portion, the rearmost end portion of the slab is the downstream inclined portion, and the stationary portion that is the remaining portion of the slab is the parallel portion. In this case, the slab thickness is 200 to 300 mm, the slab width is 800 to 2000 mm, and the actual width reduction amount of the most advanced part and the rearmost part is the steady state. A method for reducing the width of a hot stainless steel slab, characterized in that the actual width reduction amount is 30 to 50 mm larger than the actual width reduction amount of the portion, and the actual width reduction amount of the stationary portion is 50 to 350 mm.   2. The method for reducing the width of a hot stainless steel slab according to claim 1, wherein the upstream inclined portion and the downstream inclined portion have an inclination angle of 12 ° or more with respect to a rolling line.   3. The method for reducing the width of a hot stainless steel slab according to claim 1, wherein the pressing surface has a trapezoidal convex portion at a central portion in the height direction.   The width reduction by the edger punch roll is performed after the total reduction ratio from the slab thickness on the rough rolling entry side to the plate thickness of the rough halfway pass is 50% or more, The width reduction method of the hot stainless steel slab as described in any one of the above.

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