JP5935707B2 - Rolling method and rolling equipment for unequal side angle steel - Google Patents

Description

  The present invention relates to a rolling method and rolling equipment for unequal angle irons for producing unequal angle irons having two different sides by rolling.

  The unequal angle iron is an angle steel with two sides with different lengths (widths). The unequal sides with the same thickness on the two sides and the unequal sides with different sides. There are two main types. These unequal angle irons are used, for example, as a hull stiffener to reinforce the inside of the outer plate that constitutes the hull, and by welding a number of unequal angle irons in the length direction of the hull, Used in applications that increase strength.

  In general, unequal angle irons are manufactured by hot rolling, and after heating a raw steel piece with a rectangular cross section, etc., it is rolled using a number of perforations to obtain the target product cross-section shape steel. Many manufacturing methods are used.

  However, in this type of unequal beveled steel manufacturing method using perforated rolling, rolling with an asymmetrical cross-sectional shape is performed in a U-shaped posture, so that the rolled material is easily bent left and right, and the rolling is very There was a problem of being unstable. In addition, since the radius of the perforated roll that contacts the unequal angle iron varies depending on the position in the width direction, there is a problem that a large difference between the rolling material and the roll peripheral speed occurs, and the surface quality is likely to deteriorate. There was also.

  Therefore, in order to solve these problems, Patent Document 1 proposes a rolling method and rolling equipment using a universal rolling mill that is applied to hot rolling of H-section steel. This technique is a method of preventing the rolling of the rolled material from side to side by rolling one end of the long side with one vertical roll simultaneously with the reduction of the flange and the web using one universal rolling mill. Further, an edger rolling mill is provided in the vicinity of the universal rolling mill to reduce the end of the short side flange and to make the long side thickness constant.

  Patent Document 2 discloses a method for manufacturing unequal side unequal thick angle steel using two types of universal rolling mills. As shown in FIG. 12, this technology uses unequal sides using rolling equipment provided with two types of universal rolling mills UR and UF and an edger rolling mill E after the walking beam furnace RH and the roughing mill BD. Produces unequal thick angle steel.

  Of these two types of universal rolling mills, one universal rolling mill UR has a short side 100a and a long side 100b of a rolled material 100 in a rolling posture in which the short side 100a is oriented in a substantially vertical direction, as shown in FIG. Both have horizontal roll pairs 102a and 102b and heel roll pairs 104a and 104b that are rolled down in the thickness direction. Further, as shown in FIG. 14, the other universal rolling mill UF includes horizontal roll pairs 106 a and 106 b and saddle roll pairs that squeeze both the short side 100 a and the long side 100 b of the rolled material 100 in the rolling posture in the width direction. 108a and 108b.

JP-A-6-254601 JP 2003-205301 A

  In patent documents 1 and 2, it is supposed that the problem of rolling bending that has occurred in the hole rolling can be solved by using the above rolling equipment. Moreover, in universal rolling, since the difference in speed between the roll peripheral speed and the material to be rolled can be reduced, it is considered that the surface quality is also improved. Furthermore, Patent Document 2 also describes that the rolling efficiency is improved by using two universal rolling mills.

  However, according to studies by the present inventors, it has been clarified that the following problems are likely to occur in the rolling methods shown in Patent Documents 1 and 2.

  First, the problem of Patent Document 2 will be described. As shown in FIG. 13, in one universal rolling mill UR, there is a gap between the lower horizontal roll 102b and the heel roll 104b at the end of the long side 100b located at the lower part of the short side 100a of the rolled material 100. The biting portion 100c is generated at this portion. With respect to this biting portion 100c, in Patent Document 2, when using the other universal rolling mill UF arranged close to the universal rolling mill UR, when rolling the unequal angle iron in the state shown in FIG. The pair 106a, 106b squeezes the short side 100a in the width direction, so that the biting portion 100c can be eliminated.

  However, as shown in FIG. 14, the lower horizontal roll 106 b of the other universal rolling mill UF is provided with a recess 110 at a portion that compresses the end of the long side 100 b on the short side 100 a side. 100c cannot be completely flattened, and a bulge 100d remains at the end of the long side 100b. In other words, since the cross-sectional shape of the unequal angle iron must be uniform (see FIG. 1), a step of further removing or flattening such a bulge 100d is required. In this regard, Patent Document 2 describes a method of performing finish rolling using a perforated roll. However, as a result of investigations by the present inventors, the perforation 100d is reduced by performing perforated rolling. Then, as shown in FIG. 15, in the rolled material 100 (unequal edge angle steel) after the completion of the process, a dent 100e may occur on the outer surface of the long side 100b adjacent to the originally swelled portion. It became clear.

  Furthermore, the present inventors have a problem that the thickness of the long side 100b after rolling becomes uneven due to the recess 100e if the recess 110 is eliminated and the flat horizontal outer surface 106b of the universal rolling mill UF is removed. Therefore, an experiment was conducted to roll the unequal angle iron using a universal rolling mill UF equipped with a flat lower horizontal roll (not shown). However, as a result of this experiment, even when the lower horizontal roll of the universal rolling mill UF is configured to be flat, a dent 100e with a small plate thickness may occur on the outer surface of the long side 100b as shown in FIG. all right.

  That is, in rolling in the state shown in FIG. 14, both ends of the short side 100a are squeezed by the upper horizontal roll 106a. Therefore, although it is easy to adjust the width dimension of the short side 100a, the short side 100a cannot be squeezed in the thickness direction. Further, in order to balance the stretching of the unequal side angle steel to be rolled, the thickness of the long side 100b can hardly be reduced, that is, the universal rolling mill UF is used only for forming the end portion. And since the plate thickness is not substantially reduced by the universal rolling mill UF, when only the biting portion 100c is reduced, a gap is likely to be formed in the lower surface portion of the adjacent long side 100b, and a recess 100e is generated in this gap. This is because it is thought that

  Since the thickness of the unequal angle iron is required to be manufactured within the dimensional tolerances defined by a predetermined standard (for example, JIS), if the depth of the dent 100e is large, the dimension becomes defective and the product is sold as a product. There is a concern that a large number of defective products cannot be produced and the yield is lowered.

  Moreover, in the universal rolling mill UF that reduces the width of the short side 100a and the long side 100b as described above, since the thickness can hardly be reduced, one that can substantially reduce the thickness is one of the universal rolling mill UR. It is only a stand, and it is difficult to desire a great improvement in rolling efficiency.

  Also in the rolling method of Patent Document 1, the universal rolling roll has a gap at the short side end portion on the long side, so that swelling occurs at this portion. Although both ends of the short side are squeezed by the edger rolling mill arranged in close proximity, the thickness of the short side cannot be squeezed, so that a dent is generated on the long side surface in the vicinity of the short side as in Patent Document 2. there were.

  The present invention has been made in consideration of the above-mentioned conventional problems, and provides a rolling method and rolling equipment for unequal angle irons capable of ensuring good dimensional accuracy and surface quality and improving production efficiency. The purpose is to do.

The rolling method of the unequal angle iron according to the present invention is a rolling method of an unequal angle iron that rolls the unequal angle iron by reducing the short side and the long side of the rolled material roughly formed into an L-shaped cross section. , relative to the rolled material, by using the first universal mill, as well as reduction of the thickness of the long side except for both end portions in the width across the thickness and width direction of the short side, short in the width direction of the long side The step of rolling down the tip opposite to the boundary side with the side in the width direction, and using the second universal rolling mill, the thickness of the short side and the width of the long side excluding the vicinity of the boundary with the long side in the width direction A rolling step of reducing the overall thickness and a step of reducing the short side in the width direction using an edger rolling mill at least once each to form the rolled material in a desired cross-sectional shape, By performing finish rolling on the rolled material formed into a desired cross-sectional shape by the rolling process, And having a finishing rolling step to obtain a scalene angle steel products cross-sectional shape that.

Moreover, the rolling equipment of the unequal angle iron according to the present invention is a rolling equipment of the unequal angle iron that rolls the unequal side angle steel by rolling down the short side and the long side of the rolled material roughly formed into an L-shaped cross section. A pair of upper and lower horizontal rolls that reduce the thickness of the long side excluding both ends in the width direction, one hard roll that reduces the thickness of the entire outer surface of the short side, and the short side in the width direction of the long side. A first universal rolling mill having the other hard roll that squeezes the tip opposite to the boundary side in the width direction, a pair of upper and lower horizontal rolls that squeeze the entire thickness of the long side, and long in the width direction Rolling provided with at least one second universal rolling mill having a hard roll that reduces the thickness of the short side excluding the vicinity of the boundary with the side and one or more edger rolling mills having a roll that reduces the short side in the width direction. It has a group of machines.

  According to such a method and apparatus, in order to reduce the thickness of the short side and the long side with a plurality of universal rolling mills, the bulge and the dent generated on the long side are prevented, and a good cross-sectional shape with a uniform thickness is obtained. It is possible to produce the unequal angle iron having. In addition, since the thickness of the long side and the short side can be reduced by a plurality of universal rolling mills, the number of passes for reciprocal rolling in the intermediate rolling process can be reduced, and the rolling efficiency can be greatly improved.

  In the rolling method, in the rolling step, each step is performed using a step using the first universal rolling mill, a step using the second universal rolling mill, and a step using the edger rolling mill. One pass may be performed once in a predetermined order, and rolling for one or more passes may be performed. Thereby, a rolling material can be smoothly shape | molded to the desired cross-sectional shape suitable for rolling in the next finish rolling process.

  In the rolling method, the boundary between the long side and the short side of the rolled material at least on the entry side of one or both of the first universal rolling mill and the second universal rolling mill. If the vicinity is constrained not to move in the direction of the outer surface of the long side, it is possible to suppress the occurrence of bulging at the end of the short side of the outer surface of the long side. Can be manufactured.

  In the rolling method, a finishing universal rolling mill can be used in the finishing rolling step. In this case, at least on the entry side of the finishing universal rolling mill, in the vicinity of the boundary between the long side and the short side of the rolled material If it is constrained so that it does not move in the direction of the outer surface of the long side, it is possible to prevent the occurrence of bulging at the end of the short side of the outer surface of the long side, and to manufacture an unequal angle iron with good dimensional accuracy Can do.

  In the rolling equipment, the width W2U of the horizontal roll that reduces the inner side of the long side of the rolled material in the first universal rolling mill with respect to the width LH on the inner side of the unequal angle iron with the target product cross-sectional shape. It is preferable that the width W4U of the horizontal roll that rolls down the inner side of the rolled material in the second universal rolling mill has a relationship of W2U ≦ LH <W4U. That is, by ensuring the relationship of W2U ≦ LH, the first universal rolling mill can surely reduce the tip of the long side while reducing the long side in the thickness direction, and further, LH <W4U By ensuring the relationship with, in the second universal rolling mill, the thickness can be reduced over the entire width up to the tip of the long side.

  In the rolling facility, a boundary between the long side and the short side of the rolled material is provided at least on the entry side of one or both of the first universal rolling mill and the second universal rolling mill. Providing a guide device that constrains the vicinity so that it does not move in the direction of the outer side of the long side can suppress the occurrence of bulging at the end of the short side of the outer side of the long side in universal rolling. Can be produced.

  Further, the rolling equipment may have a finishing universal rolling mill that performs finish rolling on a rolled material formed into a desired cross-sectional shape by rolling by the rolling mill group. In this case, the finishing universal When a guide device is provided at least on the entry side of the rolling mill so that the vicinity of the boundary between the long side and the short side of the rolled material does not move in the direction of the outer side of the long side, the short side of the long side outer surface in finish universal rolling is provided. It is possible to suppress the occurrence of bulge at the side end and to manufacture an unequal angle iron with good dimensional accuracy.

  According to the present invention, by reducing the thickness of the short side and the long side with a plurality of universal rolling mills, the dent generated on the long side is prevented, the dimensional system is high, and the surface quality and the cross-sectional shape are good. It is possible to produce unequal sides angle steel. Moreover, since the thickness of the long side and the short side is reduced by a plurality of universal rolling mills, the number of passes for reciprocating rolling in the intermediate rolling process can be reduced, and the rolling efficiency can be greatly improved.

FIG. 1 is an explanatory diagram illustrating an example of a cross-sectional shape of an unequal angle iron manufactured by a rolling method according to an embodiment of the present invention. FIG. 2 is a configuration diagram showing an example of a rolling facility for manufacturing the unequal side angle steel shown in FIG. FIG. 3 is a cross-sectional explanatory view showing a state in which the rolled material is rolled by the first rough universal rolling mill. FIG. 4 is a cross-sectional explanatory view showing a state in which the rolled material is rolled by the second rough universal rolling mill. FIG. 5 is a cross-sectional explanatory view showing a state in which the rolled material is rolled by an edger rolling mill. FIG. 6 is a cross-sectional explanatory view showing a state in which the rolled material is rolled by the finishing universal rolling mill. FIG. 7 is a cross-sectional explanatory view showing a state in which a rolled material is rolled by a first rough universal rolling mill provided with a horizontal roll having a corner portion according to a modification. FIG. 8 is a cross-sectional explanatory view showing a state in which a rolled material is rolled by a first rough universal rolling mill provided with a horizontal roll having a corner portion according to another modification. FIG. 9 is an explanatory diagram showing an example of a guide device that is installed in the universal rolling mill and restrains the vicinity of the boundary between the long side and the short side of the rolled material so as not to move in the outer surface side direction of the long side. FIG. 10 is an explanatory diagram illustrating an example of a guide device that is installed in the universal rolling mill and restrains the vicinity of the boundary between the long side and the short side of the rolled material so as not to move in the outer surface direction of the long side. FIG. 11 is a diagram illustrating an example of a movement state of the rolled material on the entry side of the universal rolling mill. FIG. 12 is a block diagram of a conventional rolling equipment. FIG. 13 is a cross-sectional explanatory view showing a state in which a rolled material is being rolled by a universal rolling mill provided in the rolling facility shown in FIG. FIG. 14 is an explanatory cross-sectional view showing a state in which the rolled material is being rolled by another universal rolling mill provided in the rolling facility shown in FIG. FIG. 15 is an explanatory view showing a cross-sectional shape of an unequal angle iron rolled by the rolling equipment shown in FIG.

  Hereinafter, the rolling method of unequal angle irons according to the present invention will be described in detail with reference to the accompanying drawings by giving preferred embodiments in relation to rolling equipment for performing this method.

  In order to solve the dent 100e of the long side 100b, which has been a problem in the above-described conventional technology (see FIGS. 12 to 15), the present inventors have conducted various studies. As a result, it has been found that the depression 100e can be prevented from occurring by reducing the biting portion 100c below the short side 100a while substantially reducing the thickness of the long side 100b and the short side 100a. In addition, it was found that it is important to appropriately control the vertical position (position in the rolling direction of the horizontal roll) of the boundary between the long side and the short side of the rolled material with respect to the universal rolling mill. Therefore, as a result of intensive studies on the shape, guide device, and rolling method of a rolling roll capable of performing such rolling, the inventors have devised a rolling method and rolling equipment described below.

  FIG. 1 is an explanatory view showing an example of a cross-sectional shape of an unequal angle iron 10 manufactured by a rolling method according to an embodiment of the present invention. As shown in FIG. 1, the unequal angle iron 10 is formed such that the thicknesses t <b> 2 and t <b> 1 of the short side 10 a and the long side 10 b are each uniformly within a dimensional tolerance defined by a predetermined standard (for example, JIS). It has become. In the following description, the upper surface 11a of the long side 10b is referred to as the inner surface and the lower surface 11b is referred to as the outer surface in the posture shown in FIG. 1, and the long side 26b (see FIG. 3) of the rolled material 26 that is in the process of manufacturing will be described later. The same shall apply.

  FIG. 2 is a configuration diagram illustrating an example of the rolling equipment 12 that manufactures the unequal angle iron 10 shown in FIG. 1. The rolling equipment 12 includes a rough shaping rolling mill 14, a first rough universal rolling mill 16, an edger rolling mill 18, and a second rough universal rolling in order from the upstream side to the downstream side in the manufacturing process of the unequal side angle steel 10. An intermediate rolling mill group 22 provided with the rolling mill 20 and a finishing universal rolling mill 24 are provided.

  In the rolling equipment 12, a raw steel slab having a rectangular cross-sectional shape extracted from a heating furnace (not shown) is converted into a rough slab (not shown) having an L-shaped cross-sectional shape by a rough shaping rolling mill 14. And then rolling the round shaped steel slab with the intermediate rolling mill group 22 using three rolling mills (16, 18, 20). In the intermediate rolling mill group 22, the thickness of the rolled material 26 is reduced by a plurality of rolling passes, and the length of the long side 26 b and the short side 26 a is set to a target dimension suitable for finishing rolling in the finishing universal rolling mill 24. Mold. Then, in the finishing universal rolling mill 24, the rolled material 26 that has passed through the intermediate rolling mill group 22 is manufactured as an unequal side angle steel 10 having a product cross-sectional shape.

  First, the rough shaping rolling mill 14 is an apparatus for performing a rough rolling step of rolling a material steel piece having a rectangular cross-sectional shape extracted from the heating furnace into a rough shape steel piece having an L-shaped cross-sectional shape. Yes, for example, a known rolling mill using a perforated roll may be used.

  Next, the intermediate rolling mill group (rolling mill group) 22 further rolls the rough shaped steel slab formed by the rough shaping rolling mill 14 and supplies it to the finished universal rolling mill 24 close to the target product cross-sectional shape. In this embodiment, the apparatus includes two rough universal rolling mills 16 and 20 and an edger rolling mill 18.

  FIG. 3 is a cross-sectional explanatory view showing a state in which the rolled material 26 is rolled by the first rough universal rolling mill 16.

  As shown in FIG. 3, the first rough universal rolling mill (first universal rolling mill) 16 includes a pair of upper and lower horizontal rolls 28a and 28b (hereinafter referred to as “upper horizontal roll 28a” and “lower horizontal roll 28b”). And a pair of left and right hard rolls 30a, 30b. The horizontal rolls 28a and 28b can rotate about the rotation axes A1 and A2, and the rigid rolls 30a and 30b can rotate about the rotation axes B1 and B2.

  In the first rough universal rolling mill 16, the long side 26b of the rolled material 26 is reduced in the thickness direction by the upper and lower horizontal rolls 28a, 28b, and the thickness is reduced. The thickness of the long side 26b is preferably reduced at a reduction rate of 5% or more, and the rolling efficiency is improved because the thickness of the long side 26b can be reduced with a smaller number of rolling passes as the further reduction is applied. In order to effectively reduce the long side 26b, it is desirable that the outer circumferences of the horizontal rolls 28a and 28b have a flat cylindrical shape.

  Further, in the first rough universal rolling mill 16, the short side 26a of the rolled material 26 is squeezed in the thickness direction between one side (right side in FIG. 3) and the side surface of the upper horizontal roll 28a. Reduce thickness. Since the entire width of the short side 26a is reduced in the thickness direction by the heel roll 30a, it is possible to reduce the effective thickness with a reduction rate of 5% or more as with the long side 26b. In order to effectively reduce the short side 26a, it is desirable to roll the short side 26a in a state where an inclination to the side (outside) opposite to the long side 26b is provided.

  At this time, the side surface of one of the horizontal rolls 28a and 28b (the short side 26a side of the rolled material 26) has an inclination angle θ of 2 ° or more with respect to the vertical direction in order to reduce friction with the short side 26a. At the same time, the inclination angle θ is preferably set to 15 ° or less in order to smooth the rolling in which the short side 26a is vertically formed by finish rolling described later. Similarly, the outer periphery of one of the rigid rolls 30a is preferably inclined in a direction away from the short side 26a with an inclination angle of 2 ° to 15 ° with respect to the vertical direction. In other words, as shown in FIG. 3, the thickness (width) of the horizontal rolls 28a and 28b in the axial direction gradually decreases from the rotation axes A1 and A2 toward the outer diameter direction on one side surface side. The hard roll 30a has a shape in which the radial dimension of the outer peripheral surface gradually decreases from the center line O of the long side 26b of the rolled material 26 in the width direction.

  Further, in the first rough universal rolling mill 16, the tip of the long side 26b is crushed in the width direction by the other (left side in FIG. 3) roll roll 30b, and the width dimension of the long side 26b is adjusted to the target dimension. The end (end face) is formed flat. As for the shape of the scissors roll 30b on the tip side of the long side 26b, it is desirable that the outer periphery is a flat cylindrical shape, and the outer periphery is disposed at a position in contact with the side surfaces of the upper and lower horizontal rolls 28a and 28b. On the other hand, it is desirable that the other side surface (the tip side of the long side 26b) of the horizontal rolls 28a and 28b in contact with the heel roll 30b has a vertical shape with no inclination.

  In this case, the corners 29a and 29b, which are the corners between the side surfaces and the outer peripheral surface of the upper and lower horizontal rolls 28a and 28b facing the outer peripheral surface of the rigid roll 30b, are squeezed down by the heel roll 30b. It is preferable to have a shape with some relief in the thickness direction of the long side 26b so that deformation with increasing thickness is possible. As the shape of such corner portions 29a and 29b, an arc having a larger radius than that of the corner portion on the short side 26a side (see FIG. 3), oblique chamfering (see FIG. 7), or a roll radius is small only at the end portion. A stepped shape (see FIG. 8) and the like can be exemplified, but any shape may be used as long as it has a relief that does not prevent an increase in the thickness of the tip of the long side 26b.

  As shown in FIG. 3, in the first rough universal rolling mill 16, the width W2U of the upper horizontal roll 28a that is the inner surface side of the long side 26b is the long side 10b of the unequal angle iron 10 that is the product shown in FIG. The dimension is set to be equal to or smaller than the inner width LH (W2U ≦ LH), and the tip of the long side 26b can be reduced. Further, the width W2D of the lower horizontal roll 28b on the outer surface side of the long side 26b may be equal to or larger than the width W2U of the upper horizontal roll 28a on the inner surface side of the long side 26b (W2D ≧ W2U), that is, the width W2D The width W2U may be the same width or a different width.

  In the first rough universal rolling mill 16, the short side 26a on the outer side (lower side) of the long side 26b is the free surface F1, but effective reduction is applied to both the long side 26b and the short side 26a. Since the rolled material 26 is stretched, the bulge of this portion is suppressed, so that the generated bulge is small, and there is no particular problem in the subsequent rolling.

  FIG. 4 is an explanatory cross-sectional view showing a state in which the rolled material 26 is being rolled by the second rough universal rolling mill 20.

  As shown in FIG. 4, the second rough universal rolling mill (second universal rolling mill) 20 includes a pair of upper and lower horizontal rolls 32a and 32b (hereinafter referred to as “upper horizontal roll 32a” and “lower horizontal roll 32b”). And a pair of left and right rigid rolls 34a, 34b. The horizontal rolls 32a and 32b can rotate around the rotation axes A3 and A4, and the rigid rolls 34a and 34b can rotate around the rotation axes B3 and B4.

  In the second rough universal rolling mill 20, the long side 26b of the rolled material 26 is pressed down in the thickness direction by the upper and lower horizontal rolls 32a and 32b. The width W4U of the horizontal roll 32a on the inner surface side of the long side 26b is made larger than the width LH inside the long side 10b of the unequal angle iron 10 which is the product shown in FIG. 1 (LH <W4U. That is, W2U ≦ LH <W4U, so that the thickness can be reduced over the entire width up to the tip of the long side 26b. The width W4D of the lower horizontal roll 32b that is the outer surface side of the long side 26b is further larger than the width W4U of the upper horizontal roll 32a that is the inner surface side of the long side 26b so that the outer side of the long side 26b is in contact with the entire width. Increase (W4D> W4U). At this time, it is desirable to apply an effective reduction with a reduction ratio of 5% or more for the reduction of the thickness of the long side 26b. In order to effectively reduce the long side 26b, it is desirable that the outer circumferences of the horizontal rolls 32a and 32b have a flat cylindrical shape.

  Further, in the second rough universal rolling mill 20, the short side 26a is reduced in the thickness direction between one of the hard rolls 34a (right side in FIG. 4) and the side surface of the upper horizontal roll 32a. Therefore, the side surface of one of the horizontal rolls 32a (the short side 26a side of the rolled material 26) has an inclination angle of 2 ° to 15 ° with respect to the vertical direction, like the horizontal roll 28a of the first rough universal rolling mill 16. It is preferable to be inclined outward with Similarly, a part (upper part) of the outer periphery of the rigid roll 34a is preferably inclined in a direction away from the short side 26a with an inclination angle of 2 ° to 15 ° with respect to the vertical direction.

  However, in order to reduce the entire width of the long side 26b with the lower horizontal roll 32b, as shown in FIG. 4, the roll diameter is set at the lower portion of the heel roll 34a in order to prevent interference with the lower horizontal roll 32b. A small diameter portion 36 is provided. For this reason, a free surface F2 that does not come into contact with the lower horizontal roll 32b or the heel roll 34a is formed on the short side 26a in the vicinity of the boundary with the long side 26b. However, both the long side 26b and the short side 26a are formed. If effective rolling is applied and the rolled material 26 is stretched in the length direction (perpendicular to the plane of the paper in FIG. 4), the bulge in this portion is suppressed and a large bulge does not occur. In order to obtain the effects of suppressing the swelling and improving the rolling efficiency, it is desirable to apply an effective reduction of 5% or more for the reduction ratio of the thickness of the short side 26a. In addition, the bulge outside the short side 26a is flattened by being squeezed by the roll 30a when rolled by the first rough universal rolling mill 16 in the next rolling pass. As shown in FIG. 4, the rigid roll 34 a becomes a relief portion in which the radial dimension of the upper part of the outer peripheral surface gradually decreases around the center line O of the long side 26 b of the rolled material 26 and the radial dimension is reduced at the lower part. The small diameter portion 36 is provided.

  By the way, in the rolling method of the said patent document 2, as shown in FIG. 14, since the width | variety of the short side 100a was adjusted with the universal rolling mill UF, the free surface F0 where the scissors roll 108b does not contact the both ends of the short side 100a is formed. Yes, the thickness of the short side 100a could not be reduced.

  On the other hand, in this embodiment, it is not necessary to provide such a restriction. That is, the second rough universal rolling mill 20 flattens the outside of the long side 26b while effectively reducing the thickness of the long side 26b and the short side 26a, thereby forming a dent 100e such as an unequal side angle iron shown in FIG. Does not occur, and the thickness of the long side 26b can be made uniform. According to the present embodiment, the first rough universal rolling mill 16 and the second rough universal rolling mill 20 can alternately squeeze the bulge generating portion of the long side 26b or the short side 26a flatly. Growth can be prevented and a product with a uniform thickness can be produced.

  FIG. 5 is a cross-sectional explanatory view showing a state in which the rolled material 26 is rolled by the edger rolling mill 18.

  As shown in FIG. 5, the edger rolling mill 18 includes a pair of upper and lower rolls 38a and 38b (hereinafter also referred to as “upper roll 38a” and “lower roll 38b”). The rolls 38a and 38b are rotatable around the rotation axes C1 and C2.

  In the edger rolling mill 18, the width of the short side 26a is reduced between the small diameter portion 39 of the upper roll 38a and the lower roll 38b, and the width dimension of the short side 26a is adjusted to the target dimension. That is, since the first and second rough universal rolling mills 16 and 20 do not have a function of reducing the width of the short side 26a in order to achieve effective thickness reduction, the edger rolling mill 18 Then, the width reduction of the short side 26a is essential. In the edger rolling mill 18, it is desirable that the thickness of the long side 26b is light pressure of several percent or less, or the upper roll 38a is not in contact with the long side 26b and the thickness of the long side 26b is not reduced. As shown in FIG. 5, the outer peripheries of the rolls 38a and 38b have a flat cylindrical shape, but a small diameter portion 39 having a reduced roll diameter is formed on the short side 26a side of the upper roll 38a. The outer periphery of the small-diameter portion 39 is slightly inclined so that the roll diameter gradually increases outward in the axial direction.

  In the intermediate rolling mill group 22 as described above, reciprocating rolling is performed on the rolling material 26 formed by the rough shaping rolling mill 14 using the above three rolling mills (16, 18, 20), and this reciprocating rolling is performed. A plurality of rolling passes are repeatedly performed, and an intermediate rolling process is performed in which the thickness and width of the long side 26b and the short side 26a are reduced to the same dimension (product dimension) as the unequal side angle steel 10 as a product.

  Next, the finishing universal rolling mill 24 further rolls the rolled material 26 rolled into a desired cross-sectional shape by the intermediate rolling mill group 22 so that the angles of the short side 26a and the long side 26b become a right angle, This is an apparatus for performing a finishing rolling process (finishing universal rolling process) to finish the unequal side angle steel 10 having a product cross-sectional shape to be performed, and is normally performed only in one pass.

  FIG. 6 is an explanatory cross-sectional view showing a state in which the rolled material 26 is being rolled by the finishing universal rolling mill 24.

  As shown in FIG. 6, the finishing universal rolling mill 24 includes a pair of upper and lower horizontal rolls 40a and 40b (hereinafter also referred to as “upper horizontal roll 40a” and “lower horizontal roll 40b”), and a pair of left and right rigid rolls 42a. 42b. The horizontal rolls 40a and 40b can rotate about the rotation axes A5 and A6, and the rigid rolls 42a and 42b can rotate about the rotation axes B5 and B6.

  In the finishing universal rolling mill 24, the width W5U of the upper horizontal roll 40a which is the inner surface side of the long side 26b of the rolled material 26 is larger than the width LH inside the long side 10b of the unequal angle iron 10 which is the product shown in FIG. The width W5D of the lower horizontal roll 40b is set to be equal to or greater than the width W5U of the upper horizontal roll 40a (W5D ≧ W5U).

  By setting it as such a roll width dimension, the thickness of the long side 26b is lightly reduced by all the widths by the upper and lower horizontal rolls 40a and 40b. Further, the side surfaces of the upper and lower horizontal rolls 40a and 40b are at an angle perpendicular to the rotation axes A5 and A6 that are roll axes, and the heel roll 42a on the short side 26a side is a cylindrical roll with a flat outer periphery. Thereby, while the thickness of the short side 26a is lightly reduced, the angle between the short side 26a and the long side 26b can be formed at a right angle. In addition, the outer periphery of the other rigid roll 42b may be a flat cylindrical shape, and may be applied to the other side surface of the horizontal rolls 40a and 40b. Here, light reduction means thickness reduction of several percent or less, and it is desirable to apply such light reduction in order to adjust the cross-sectional shape of the rolled material 26 to a target product cross-sectional shape.

  Note that such a finish rolling step may be performed by other than the universal rolling using other than the finishing universal rolling machine 24 shown in FIG. 6, for example, by the hole rolling as in the above-described conventional technique. Good.

  As a more preferable rolling facility of the present invention, a guide device is provided on at least the entrance side of the universal rolling mill to restrain the vicinity of the boundary between the long side and the short side of the rolled material from moving in the outer surface direction of the long side. Even if such a guide device is provided in any of the first universal rolling mill, the second universal rolling mill, and the finishing universal rolling mill, a bulge occurs at the short side end of the long side outer surface. However, installation in the first universal rolling mill is particularly effective.

  An example in which a guide device is installed on the entry side of the first rough universal rolling mill 16 is shown in FIG. In FIG. 9, since the short side 26a is located on the upper side, in order to restrain the movement of the rolled material 26 to the outer side of the long side 26b, it is only necessary to restrain the downward movement of the rolled material 26. For the purpose, a guide device 50 is installed below the rolled material 26. By this guide device 50, it can restrain that the boundary vicinity 26c of the long side 26b of the rolling material 26 and the short side 26a moves to the outer surface side direction of the long side 26b. FIG. 10 shows another example of the guide device. In FIG. 10, the guide device 51 is installed at a position facing the free surface F1 (see FIG. 3) generated below the short side 26a of the rolled material 26, that is, the outer surface side of the end of the long side 26b on the short side 26a. The boundary vicinity 26c between the long side 26b and the short side 26a of the rolled material 26 is restrained from moving in the direction of the outer surface of the long side 26b. In this way, if only the vicinity of the free surface F1 where the bulge is generated in the rolled material 26 is constrained, it is possible to suppress the occurrence of the bulge at the end portion on the short side 26a side of the outer surface of the long side 26b. The rolling direction position of the guide device is desirably as close as possible to the rolling roll. As in the guide device 51 shown in FIG. 10, the rolling material 26 is more effectively provided by having a shape that penetrates from the entry side to the exit side of the universal rolling mill in the gap between the lower horizontal roll 28 b and the saddle roll 30 a. Can be restrained from moving downward.

  By providing the guide device 50 or the guide device 51 described above and restraining the vicinity 26c of the boundary between the long side 26b and the short side 26a from moving in the direction of the outer surface of the long side 26b, the short side 26a of the outer surface of the long side 26b can be restrained. The reason why it is effective in preventing the bulge generated at the side end is as follows. That is, as a result of observing in detail the situation where the rolled material bites into the universal rolling mill, the short side 26a side of the rolled material 26 moves to the outer side of the long side 26b immediately before the rolled material bites as shown in FIG. It became clear that Thus, when the short side 26a bites into the rolling mill with the short side 26a side of the rolled material 26 moved to the outer surface side of the long side 26b, the portion of the long side 26b to be rolled is between the horizontal rolls 28a and 28b. The bulge of the outer surface is increased by being pushed up. Therefore, the movement of the long side 26b of the rolled material 26 to the outer surface side is constrained, or the movement of the rolling part 26 near the boundary 26c between the short side 26a and the long side 26b to the outer side of the long side 26b is constrained. When the guide devices 51 and 52 were applied, the height of the bulge generated on the short side 26a side of the outer surface of the long side 26b after rolling was significantly reduced.

  In addition, the guide apparatus of this invention is not limited to the shape shown in FIG.9 and FIG.10, Other shapes may be sufficient if the movement of the rolling material shown in FIG. 11 can be suppressed. Moreover, you may install not only in the entrance side of a universal rolling mill but in an exit side, and the penetration type | mold guide apparatus with which the entrance side and the exit side were connected like said guide apparatus 51 may be sufficient. The universal rolling mill in which the guide device is installed may be the second rough universal rolling mill 20 or the finishing universal rolling mill 24. Even in the second rough universal rolling mill 20 and the finishing universal rolling mill 24, when the rolled material 26 is bitten, there is no movement of the boundary portion 26c toward the outer surface side of the long side 26b. By doing, it can suppress that a bulge generate | occur | produces in the short side 26a side of the long side 26b outer surface after rolling. A guide device may be provided in all of the universal rolling mills, or a guide device may be provided in any one or two of the universal rolling mills.

  The rolling method of the unequal side angle steel 10 according to the present embodiment is performed by the following procedure, for example, using the rolling equipment 12 as described above.

  First, for the rolled material (rough shaped steel slab) 26 roughly formed into an L-shaped cross section by the rough shaping rolling mill 14, the first rough universal rolling mill 16 is used to determine the thickness of the entire width of the short side 26a and The thickness of the long side excluding both ends is reduced, and the tip of the long side 26b is reduced. Subsequently, after reducing the width of the short side 26a using the edger rolling mill 18, the thickness and the long side of the short side 26a excluding the vicinity of the boundary with the long side 26b are used using the second rough universal rolling mill 20. The entire thickness of 26b is reduced. Here, the rolling process by each rolling mill (16, 18, 20) of the intermediate rolling mill group 22 is performed by reciprocating rolling, and each process by each rolling mill (16, 18, 20) is performed once. A rolling process (intermediate rolling process) in which the rolled material 26 has a desired cross-sectional shape is performed by repeatedly performing a plurality of rolling passes (for example, 3 passes).

  Next, by using the finishing universal rolling mill 24, the rolling material 26 formed into a desired cross-sectional shape by the above-described intermediate rolling process is subjected to finish rolling to obtain a target product cross-sectional shape, thereby forming an unequal side mountain shape. A finish rolling step for obtaining steel 10 is performed. Thereby, the unequal side angle steel 10 which has favorable dimensional accuracy and surface quality can be manufactured with high manufacturing efficiency.

  In the above rolling method, if the vicinity 26c of the boundary between the long side 26b and the short side 26a of the rolled material 26 is constrained not to move in the outer surface direction of the long side 26b at the entrance side of the universal rolling mill, further dimensional accuracy can be obtained. A good unequal angle iron 10 can be produced.

  Note that the rolling equipment for carrying out the rolling method according to the present embodiment is not limited to the equipment layout, the number of rolling mills, and the like of the rolling equipment 12 shown in FIG. Two or more second rough universal rolling mills 16 and 20 and edger rolling mill 18 may be provided. When the number of rolling mills is increased, the number of reciprocating rolling passes can be further reduced, so that productivity is further improved. In addition, if a sufficiently large number of rolling mills are installed, the intermediate rolling process can be made one pass and continuous with finish rolling, and productivity can be dramatically increased. In addition, in the intermediate rolling mill group 22, if one or more of the first and second rough universal rolling mills 16 and 20 and the edger rolling mill 18 are installed, the installation order of the rolling mills may be changed. Further, as shown in FIGS. 3 to 6, the rolling posture of the rolled material 26 may be other than the posture in which the short side 26 a faces upward. For example, the short side 26 a may be in a downward posture. .

  As described above, according to the rolling method of the unequal side angle steel according to the present embodiment, the thickness and the both ends of the entire width of the short side 26a are applied to the rolled material 26 using the first rough universal rolling mill 16. The thickness of the long side 26b excluding the portion is reduced and the tip of the long side 26b is reduced, and the second rough universal rolling mill 20 is used to reduce the length of the short side 26a except for the vicinity of the boundary with the long side 26b. The step of reducing the thickness and the entire thickness of the long side 26b and the step of reducing the width of the short side 26a using the edger rolling mill 18 are each performed one or more times to obtain the rolled material 26. A rolling process (intermediate rolling process) with a cross-sectional shape of the product, and by performing finish rolling on the rolled material 26 formed into a desired cross-sectional shape by this rolling process, an unequal crest shape of the target product cross-sectional shape A finish rolling process for obtaining steel 10 .

  In addition, the rolling equipment 12 according to this embodiment includes a pair of upper and lower horizontal rolls 28a and 28b for reducing the thickness of the long side 26b excluding both ends, and one of the rigid surfaces for reducing the entire outer surface of the short side 26a of the rolled material 26. A first rough universal rolling mill 16 having a roll 30a and the other hard roll 30b for reducing the tip of the long side 26b, and a pair of upper and lower horizontal rolls 32a and 32b for reducing the overall thickness of the long side 26b. An edger mill having a second rough universal rolling mill 20 having a hard roll 34a for reducing the thickness of the short side 26a excluding the vicinity of the boundary with the long side 26b, and an upper roll 38a for reducing the width of the short side 26a. 18 and an intermediate rolling mill group 22 having one or more each.

  Therefore, according to such a rolling method and the rolling equipment 12, since the thickness of the short side and the long side is reduced by the plurality of universal rolling mills (16, 20), the long side 100b, which is a problem in the above-described conventional technology, is reduced. It is possible to manufacture the unequal angle iron 10 having a uniform thickness and a good cross-sectional shape by preventing the occurrence of the bulge 100d and the recess 100e (see FIGS. 13 to 15). Moreover, since the thickness of the long side 26b and the short side 26a can be reduced by the plurality of rough universal rolling mills 16 and 20, the number of passes to be reciprocally rolled in the intermediate rolling process can be reduced, and the rolling efficiency can be greatly increased. Can be improved. In addition, the unequal side angle steel 10 manufactured in the present embodiment may be either an unequal side thickness steel or an unequal side thickness steel.

Moreover, in the rolling equipment 12, the inner side of the long side 26b of the rolling material 26 in the first rough universal rolling mill 16 is reduced with respect to the width LH inside the long side 10b of the unequal side angle steel 10 having the target product cross-sectional shape. The width W2U of the upper horizontal roll 28a and the width W4U of the upper horizontal roll 32a that squeezes the inner side of the long side 26b of the rolled material 26 in the second rough universal rolling mill 20 are in the relationship of the following expression (1).
W2U ≦ LH <W4U (1)

  That is, by ensuring the relationship of W2U ≦ LH, the first rough universal rolling mill 16 can surely reduce the tip of the long side 26b while reducing the long side 26b in the thickness direction. This is because the tip of the long side 26b can be flush with or protrude toward the rigid roll 30b side than the upper horizontal roll 28a. Furthermore, by ensuring the relationship LH <W4U, the second coarse universal rolling mill 20 can reduce the thickness over the entire width up to the tip of the long side 26b. This is because the tip of the long side 26b is shorter than the upper horizontal roll 32a.

  Next, the result of an experiment in which the rolling equipment 12 according to the present embodiment is used to roll the unequal side mountain shaped steel 10 by carrying out the rolling method of the unequal side angle shaped steel will be described. Needless to say, the present invention is not limited to the following examples.

Example 1
As an example, using the rolling equipment 12 shown in FIG. 2, the dimension LB of the long side 10b is 300 mm, the dimension LA of the short side 10a is 90 mm, the thickness t1 of the long side 10b is 10 mm, and the thickness t2 of the short side 10a. Produced an unequal side angle steel 10 having a thickness of 19 mm (see FIG. 1).

  As the rough shaping rolling mill 14, a double rolling mill having a pair of upper and lower horizontal rolls provided with a plurality of perforations was used. The intermediate rolling mill group 22 includes a first rough universal rolling mill 16 shown in FIG. 3, an edger rolling mill 18 shown in FIG. 5, and a second rough universal rolling mill 20 shown in FIG. 4 in this order from upstream to downstream. It was arranged and used. A finish universal rolling machine 24 shown in FIG. 6 was used for finish rolling.

  First, after heating a bloom (material steel piece) having a rectangular cross section with a thickness of 250 mm and a width of 310 mm, the rough shaping rolling mill 14 performs multi-pass perforation rolling similar to the prior art, and from the L-shaped cross section The resulting rolled material (coarse steel slab) was formed. The cross-sectional shape of the rolled material after rough shaping rolling had a long side dimension of about 350 mm, a short side dimension of about 105 mm, a long side thickness of about 22 mm, and a short side thickness of about 39 mm.

  The rolling material (coarse steel slab) having an L-shaped cross section was subjected to three-pass reciprocating rolling in the intermediate rolling mill group 22 to bring the thickness and width close to the product dimensions. That is, in the first and second rough universal rolling mills 16 and 20, an effective thickness reduction of 5% or more is applied to both the long side and the short side, and in the edger rolling mill 18, the short side is reduced in the width direction, The long side was rolled for light reduction of 1% or less. The cross-sectional dimensions of the rolled material after the three-pass reciprocating rolling were 299 mm for the long side, 89.5 mm for the short side, 10.2 mm for the long side, and 19.4 mm for the short side. A slight bulge was observed in the portion (free surface F2) that was not squeezed by the heel roll 34a (see FIG. 4) on the outer side of the short side, but its height was as small as 1 mm or less. There wasn't.

  Finally, the finish universal rolling mill 24 rolled one pass to slightly reduce the thickness of the long side and the short side, and formed the short side vertically to finish the product cross-sectional shape. When the cross-sectional dimension of the product was measured, a slight breadth occurred in the finish rolling, so that a product having a target cross-sectional dimension was obtained. In addition, there was almost no dent on the outside of the long side, and a product within dimensional tolerance could be manufactured.

  Moreover, when the guide apparatus 50 shown in FIG. 9 was installed in the entrance side and exit side of the 1st rough universal rolling mill 16 with the same rolling method, the unequal side unequal thickness angle steel of the same dimension was manufactured. A product with good dimensional accuracy in which no dent was found on the outer surface of the long side could be manufactured.

(Comparative Example 1)
Although the rolling method of Patent Document 2 is slight, it reduces the thickness of the short side, so that it is considered that the effect of suppressing dents on the surface of the long side is higher than the rolling method of Patent Document 1. Thus, as a comparative example, using the rolling equipment shown in FIG. 12, using the universal rolling mill UR, the edger rolling mill E shown in FIG. 13, and the universal rolling mill UF shown in FIG. Unequal thick angle steel was rolled. The edger rolling mill E was provided with a perforated roll according to the product dimensions as described in Patent Document 2, and finally, only the edger rolling mill E was used to perform one-pass finish rolling.

  First, a rolled material (coarse steel slab) having an L-shaped cross section was formed by rough rolling in the same manner as in Example 1. Thereafter, reciprocal rolling is performed using the universal rolling mills UR and UF shown in FIGS. 13 and 14, and the long side dimension is 299 mm, the short side dimension is 89.5 mm, the long side thickness is 10.2 mm, and the short side thickness is When rolled to a cross section of 19.4 mm, the thickness reduction with the universal rolling mill UR of FIG. Further, as the finish rolling, only the edger rolling mill E was used and the hole-type rolling was performed. As a result, a recess having a depth of 1 mm remained at the position of the recess 100e in FIG.

  As described above, it was confirmed that by using the rolling method and the rolling equipment 12 according to the present embodiment, the unequal angle iron 10 which is a product with high productivity and good cross-sectional dimensions can be rolled.

  Note that the present invention is not limited to the above-described embodiments and examples, and it is needless to say that the present invention can be freely changed without departing from the gist of the present invention.

DESCRIPTION OF SYMBOLS 10 Unequal angle iron 10a, 26a, 100a Short side 10b, 26b, 100b Long side 12 Rolling equipment 14 Rough shaping rolling mill 16 1st rough universal rolling mill 18, E edger rolling mill 20 2nd rough universal rolling mill 22 Intermediate rolling mill group 24 Finish universal rolling mill 26, 100 Rolled material 28a, 28b, 32a, 32b, 40a, 40b Horizontal roll 30a, 30b, 34a, 34b, 42a, 42b Hard roll 38a, 38b Roll 50, 51 Guide device

Claims (10)

A rolling method of unequal side chevron that rolls the unequal side chevron by rolling down the short side and long side of the rolled material roughly formed into an L-shaped cross section,
With respect to the rolled material, by using the first universal mill, as well as reduction of the thickness of the long side except for both end portions in the width across the thickness and width direction of the short side, short side in the width direction of the long side A step of rolling the tip opposite to the boundary side with the width direction, and using the second universal rolling mill, the thickness of the short side and the entire width of the long side excluding the vicinity of the boundary with the long side in the width direction Rolling step to reduce the thickness and the step of rolling the short side in the width direction using an edger rolling mill at least once each to form the rolled material in a desired cross-sectional shape,
For the rolled material formed into a desired cross-sectional shape by the rolling step, by performing finish rolling, a finish rolling step to obtain a target product cross-sectional unequal angle iron,
A method for rolling an unequal angle iron, characterized by comprising: In the rolling method of unequal side angle steel according to claim 1,
In the rolling step, each of the steps using the first universal rolling mill, the step using the second universal rolling mill, and the step using the edger rolling mill is performed in a predetermined order. A rolling method for unequal angle irons, characterized in that rolling is performed one pass or more, and rolling is performed for one pass or more. In the rolling method of unequal side angle steel according to claim 1 or 2,
At least on the entry side of one or both of the first universal rolling mill and the second universal rolling mill, the vicinity of the boundary between the long side and the short side of the rolled material is a long side. A rolling method for unequal angle irons, characterized in that it is restrained from moving in the direction of the outer surface. In the rolling method of the unequal side angle steel of any one of Claims 1-3,
In the finish rolling process, a finish universal rolling mill is used. In the rolling method of unequal side angle steel according to claim 4,
A rolling method for unequal angle irons, characterized in that, at least on the entry side of the finishing universal rolling mill, the vicinity of the boundary between the long side and the short side of the rolled material is constrained not to move in the direction of the outer side of the long side. . Rolling equipment for unequal side angle irons for rolling unequal side angle irons by rolling down the short side and long side of the rolled material roughly formed into an L-shaped cross section,
A pair of upper and lower horizontal rolls that reduce the thickness of the long side excluding both ends in the width direction, one rigid roll that reduces the thickness of the entire outer surface of the short side, and a boundary side of the short side in the width direction of the long side; A first universal rolling mill having the other hard roll for reducing the opposite tip in the width direction ;
A second universal rolling mill having a pair of upper and lower horizontal rolls for reducing the thickness of the entire width of the long side, and a hard roll for reducing the thickness of the short side excluding the vicinity of the boundary with the long side in the width direction ;
An edger rolling mill having a roll that reduces the short side in the width direction ;
A rolling facility for unequal angle irons, comprising a group of rolling mills each having one or more of each. In the rolling equipment of unequal side angle steel according to claim 6,
The width W2U of the horizontal roll that squeezes the long side inside of the rolled material in the first universal rolling mill with respect to the width LH inside the long side of the unequal angle iron with the target product cross-sectional shape, and the second The rolling equipment for unequal angle irons, characterized in that the width W4U of the horizontal roll for rolling down the long side inside of the rolled material in the universal rolling mill is in the relationship of the following formula (1).
W2U ≦ LH <W4U (1) In the rolling equipment of unequal side angle steel according to claim 6 or 7,
At least on the entry side of one or both of the first universal rolling mill and the second universal rolling mill, the vicinity of the boundary between the long side and the short side of the rolled material is a long side. A rolling equipment for unequal angle irons, characterized in that a guide device is provided for restraining it from moving in the direction of the outer surface. In the rolling equipment of the unequal side angle-shaped steel of any one of Claims 6-8,
A rolling equipment for unequal angle irons, comprising a finishing universal rolling mill for performing finish rolling on a rolled material formed into a desired cross-sectional shape by rolling by the rolling mill group. In the rolling equipment of unequal side angle steel according to claim 9,
At least on the entry side of the finishing universal rolling mill, a guide device is provided for restraining the vicinity of the boundary between the long side and the short side of the rolled material so as not to move in the outer surface side direction of the long side. Yamagata rolling mill.

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