JP7295419B2 - Rolling equipment and rolling method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a rolling facility and a rolling method for omitting the hot coil annealing step by self-annealing a coil wound after hot rolling in the cooling process, and performing cold tandem rolling on the self-annealed coil. It is.

The steel type of the self-annealed coil is high-alloy steel, and specific examples thereof include high-strength steel plate (high-tensile steel plate), stainless steel plate, and electromagnetic steel plate. In addition, as a process for manufacturing a hot-rolled steel strip (hot-rolled steel strip), a steel slab is hot-rolled by a rough rolling mill and a finishing rolling mill, wound into a coil, and the coil is cooled in the atmosphere. There are manufacturing processes such as a manufacturing process in which rough rolling is omitted, hot rolling corresponding to finish rolling is performed, coiling is performed, and the coil is cooled in the air. In addition, for thin cast slabs (thin slabs) produced by twin roll continuous casting or belt continuous casting known as thin plate continuous casting and rolling, they are equivalent to finishing rolling mills immediately without rough rolling. A manufacturing process in which the steel is rolled down in an inline mill, wound into a coil, and then cooled in the air. Furthermore, continuous casting, hot rough rolling, and hot finish rolling are performed continuously without interruption. There is also a process.

Hereafter, as an example, a steel slab is hot-rolled by a rough rolling mill and a finishing rolling mill, wound into a coil, and the coil is further cooled in the atmosphere to cold-roll the strip coil. A case of manufacturing a non-directional electromagnetic wave will be described as an example.

For example, in Patent Document 1, C ≤ 0.008, 2 ≤ Si + Al ≤ 3, 0.02 ≤ Mn ≤ 1.0, S ≤ 0.003, N ≤ 0.002, Ti ≤ 0.003 in mass% , 0.001 ≤ REM ≤ 0.02, and 0.3 ≤ Al/(Si + Al) ≤ 0.5. Hot finish rolling is performed in a temperature range such that the interfinishing rolling temperature is 1050 ° C. or higher, the subsequent no water injection time is 1 second or more and 7 seconds or less, and the winding is performed at 700 ° C. or less by water injection cooling. A manufacturing method is disclosed in which a cooling process after hot finish rolling replaces the hot-rolled plate annealing process.

JP 2010-242186 A JP-A-60-46804 JP-A-2002-239617 Japanese Patent Application Laid-Open No. 2003-340510 JP-A-3-60810 JP 2014-8520 A JP 2015-167992 A

"Illustrated Electromagnetic Steel Sheet" (Shin Nippon Steel Co., Ltd., 1994), p.67

However, as shown in Patent Document 1, for example, self-annealing coils for non-oriented electrical steel sheets, which are wound into coils by omitting the hot coil annealing process due to self-annealing in the cooling process after continuous hot rolling, It has been recognized that there are the following problems when pickling and continuously cold-rolling with a cold tandem rolling mill.

1) A hot-rolled steel strip after hot rolling is usually coiled at, for example, 700° C. or less, and then cooled in the atmosphere while still in the coiled state. In such a cooling process, the cooling rate varies depending on the position of the material within the coil. Specifically, the cooling rate of the outer peripheral part of the coil is higher than the cooling rate of the inner peripheral part, and the cooling rate of the end (edge part) in the strip width direction is lower than that of the central part in the strip width direction. speed increases.
Due to such variations in the cooling rate in the coil, non-uniformity of the material in the longitudinal direction and the width direction of the plate, particularly non-uniformity in strength, and thus non-uniformity in cold deformation resistance occur. . Such coils are referred to herein as self-annealed coils.

The material (steel type) of the self-annealing coil is not limited to the non-oriented electromagnetic plate described above. It means a steel type that causes non-uniform deformation resistance in the cold.

Further, the self-annealed coil is not limited to the coil obtained by hot-rolling the steel slab with the roughing mill and the finishing mill as described above, winding the coil into a coil, and further cooling the coil in the atmosphere. It also includes coils obtained by omitting rolling, performing hot rolling corresponding to finish rolling, winding into coils, and cooling the coils in the atmosphere. For example, a thin slab produced by a twin-roll continuous casting method known as a thin-plate continuous casting-rolling method or a belt-type continuous casting method is directly equivalent to a finishing rolling mill without performing rough rolling. It is intended to include such coils, which may be reduced in an in-line mill and wound into coils, which are then cooled in air.
Furthermore, a process is known in which continuous casting, hot rough rolling, and hot finish rolling are performed continuously without interruption. Coils cooled in air are also included.

2) As described above, in the self-annealed coil, non-uniformity of the material in the longitudinal direction and the sheet width direction in the coil is caused near the outer periphery and near the edge of the self-annealed coil (the width direction end of the hot rolled steel strip being wound). The unevenness occurs in the area 150 mm to 250 mm inward from the end (edge part) in the sheet width direction in 2 to 3 turns on the outer peripheral side of the self-annealing coil. In the region of (2), the strength of the widthwise ends of the strip may be about 10% to 20% higher than the strength of the central portion in the widthwise direction.

3) When the self-annealed coil having non-uniformity in material as described above is welded into a continuous strip, pickled and cold-tandem rolled, the above-mentioned coil is placed in the first stand of the cold tandem rolling mill. Since the difference in deformation resistance at the non-uniform material portion, that is, the deformation resistance at both ends in the width direction of the plate is greater than the deformation resistance at the central portion in the width direction, the shape of the rolled plate becomes medium elongation, which is the so-called Squeezing may occur and plate breakage may occur.

4) If sheet breakage occurs due to drawing due to medium elongation, damage to the work rolls in the rolling stand in the cold tandem rolling mill often occurs. In that case, rolling must be stopped and work rolls must be replaced, resulting in a significant drop in productivity.

5) Furthermore, when sheet breakage due to drawing is severe (in the case of sheet breakage due to severe middle elongation), it is necessary to replace not only the work rolls but also the intermediate rolls or backup rolls in contact with the work rolls. Become.

6) Especially during high-speed rolling, sheet breakage due to drawing is severe, and it may take a long time of about 10 hours to recover, resulting in a significant decrease in productivity.

As described above, in the subsequent cold tandem rolling of the self-annealed coil, sheet breakage due to drawing is likely to occur, and the actual situation is that there is a strong possibility that productivity will be hindered.
Therefore, there has been a demand for the development of a rolling facility and a rolling method for obtaining a self-annealed coil that has little variation in deformation resistance in the sheet width direction and is capable of preventing sheet breakage in cold tandem rolling.

In general, it is known to control the plate shape during cold rolling in order to prevent reduction in cold rolling. That is, a shape detector is installed on the delivery side of the cold rolling mill stand to measure the shape of the rolled strip, and the cold rolling mill stand is adjusted so as to fit in the desired strip shape, for example, so as not to become a middle-stretched shape. It is known to control the shape control edge (e.g. work roll bender force) of (e.g. U.S. Pat. Such shape control is typically performed at the final stand of the cold rolling mill.

Further, Patent Document 3 proposes a method of controlling the shape by installing a shape detector on the delivery side of the rolling mill in the first stand of the cold tandem rolling mill to measure the shape of the rolled strip. Furthermore, Patent Document 4 proposes a method for controlling the shape by installing a shape detector on the delivery side of the rolling mill in the first stand and the second stand of the cold tandem rolling mill to measure the shape of the rolled strip. ing. Further, Patent Document 5 proposes a method of installing a shape detector on the delivery side of the rolling mill in all the stands of the cold tandem rolling mill, measuring the shape of the rolled strip, and controlling the shape.

On the other hand, Patent Literature 6 discloses a shape control method when there is uneven deformation resistance distribution in the plate width direction. That is, in Patent Document 6, the yield stress in the width direction of the hot-rolled steel strip is measured in advance at the positions of the tip, center, and tail in the longitudinal direction of the hot-rolled steel strip, and the deformation resistance distribution pattern is investigated. A method of presetting the shape of the rolling mill based on the results (performing different shape presets at the front end, center, and tail end positions of the hot-rolled steel strip in the longitudinal direction) is disclosed.

The shape control methods disclosed in Patent Documents 2 to 5 above measure the plate shape by a shape detector installed on the delivery side of one or more rolling mill stands, and the measured plate shape is the target. It is a method of feedback-controlling the shape control end of the rolling mill stand so that it conforms. Although this method is effective for hot-rolled steel strips in which drawing does not easily occur even if the plate shape changes, and for relatively gradual changes such as thermal crown, self-annealing is the main object of the present invention. It is recognized that coils are not always effective.

The reason for this is that the self-annealed coil, in which the hot coil annealing process is omitted, has a large non-uniform deformation resistance distribution and abrupt change in the longitudinal direction. However, in the shape control methods by feedback control as shown in Patent Documents 2 to 5, there is dead time between the hot-rolled steel strip from a certain rolling mill stand to the shape detector on the delivery side of the rolling mill stand. There is Therefore, when the shape change is large and sudden, the feedback control is not in time.

When the inventors of the present invention investigated the data of the plate breakage of the first stand due to drawing of the self-annealed coil, it was found that at a rolling speed of 200 m / min at the first stand, the edge elongation with a steepness of 1% was obtained in about 2 seconds. It has been confirmed that the elongation changes from 1 to 2%, and as a result, the drawing occurs and the plate breaks. In this case, since the shape detector is installed 3m away from the exit of the roll bite of the 1st stand (it is impossible to make it less than 3m due to space considerations), it takes about 1 second to detect the shape. Even if the shape control is started after that, it takes about 1 second. Therefore, it takes about 2 seconds of wasted time until the shape control is actually performed after leaving the roll bite. Therefore, it is difficult to prevent plate breakage in time for the sudden change in shape. At this time, if the rolling speed at the first stand is reduced to 100 m/min, the relative rolling length at which shape control starts will be shortened by half, but the dead time until the shape is detected will be doubled. Therefore, it is difficult to prevent sheet breakage even if the rolling speed is lowered.

On the other hand, disclosed in Patent Document 6, the yield stress in the width direction of the material at the tip, center, and tail in the longitudinal direction of the original plate coil was measured in advance to investigate the deformation resistance distribution pattern, and the investigation results ( The method of performing shape presetting (feedforward control) in the rolling mill stand based on the prediction result) is effective for reproducible materials for each coil of hot-rolled steel strip. However, the self-annealed coil, which is the object of the present invention, is affected by changes in the sheet shape during cold rolling, depending on the sheet shape and scale after hot rolling and the coil cooling conditions after winding (coil arrangement position, seasonal factors, etc.). The situation is very different. For this reason, there is a large variation in prediction results, and it cannot be said that there is practical reproducibility. That is, it is difficult to pattern the deformation resistance distribution over the entire length of the coil based on predictive research. By the way, if an inappropriate pattern is input, there is a risk that it will promote medium elongation and induce strip breakage.

In addition, without predicting the deformation resistance distribution pattern as described above, it is conceivable to preset the rolling mill stand in an end-elongation shape so that the rolling mill stand does not become middle elongation even if the deformation resistance distribution changes. In this method, the deformation resistance distribution of the hot-rolled steel strip is not so large, the deformation resistance does not change much in the length direction of the hot-rolled steel strip, and there is no variation in each coil of the hot-rolled steel strip. is effective to some extent. However, in the self-annealed coil, which is the main object of the present invention, the distribution of deformation resistance in the width direction of the hot-rolled steel strip varies greatly in the length direction. Therefore, in order to prevent middle elongation, if you preset so that edge elongation occurs even in places where deformation resistance distribution is uneven (plate edges are hard), edge elongation can be achieved in places where deformation resistance distribution is uniform (plate edges are hard). becomes too large, conversely, constriction occurs due to excessive edge elongation, which may induce plate breakage.

As described above, conventionally, when cold tandem rolling is performed on a coil such as a self-annealed coil that has large non-uniform deformation resistance distribution in the longitudinal direction and width direction of the hot-rolled steel strip, the occurrence of strip breakage is reliably prevented. The fact is that the method to do so has not yet been established.

It is known that the non-uniformity of the material in the sheet width direction of the self-annealed coil as described above is caused by non-uniform cooling of the wound coil after hot rolling. In order to cool the coil as uniformly as possible, for example, Patent Document 7 proposes a method in which a coil wound after hot rolling is enclosed in a box and slowly cooled. However, this method requires large-scale equipment and a large space, and although it is effective for steel grades with low production volumes, it has cost and space problems for steel grades with high production volumes. Development of a rolling facility and a rolling method with excellent performance (including workability) is desired.

The present invention has been made in view of the above problems, and prevents the material variation in the sheet width direction even in a coil that is self-annealed after hot rolling (self-annealed coil), so that it can be used in the subsequent cold tandem rolling mill. To provide a rolling facility and a rolling method that prevent breakage of a sheet due to drawing during rolling, and are excellent in space saving and high efficiency (including workability) at low cost. be.

Specific aspects of the rolling equipment and rolling method of the present invention are shown below.

The rolling facility of the basic aspect (first aspect) of the present invention includes:
In a rolling facility that cools the hot-rolled and wound coil in the atmosphere and then cold-rolls it with a cold tandem rolling mill,
A hollow cylindrical sleeve for inserting the coil when cooling the wound coil after hot rolling in the atmosphere,
The sleeve is characterized in that both ends in the axial direction thereof are open, and at least a part in the thickness direction is made of a heat insulating material.

Further, the rolling facility of the second aspect of the present invention is
In the rolling facility of the first aspect,
The sleeve is characterized in that its axial length L satisfies the following formula (1).
L≧W+2·(D _S −3·D _CO /4−D _CI /4) tan30 (1)
Here, in formula (1),
W: coil plate width,
D _CO : coil outer diameter,
D _CI : coil inner diameter,
D _S : inner diameter of sleeve, angle of tan (30) is in degrees, and all other dimensions are in mm.

Furthermore, the rolling facility of the third aspect of the present invention is
In the rolling facility of the first aspect,
The sleeve is characterized in that a reflective layer is formed on an upper portion of the inner peripheral surface of the sleeve when the sleeve is arranged so that the central axis thereof is horizontal.

Further, the rolling method of the fourth aspect of the present invention is
In hot rolling and winding into a coil by the rolling equipment of any one of the first to third aspects, cooling the coil in the atmosphere, and then cold rolling by a cold tandem rolling mill,
It is characterized in that the coil wound after hot rolling is inserted into the sleeve and cooled in the atmosphere.

In the rolling equipment and rolling method of the present invention, even in a coil that has been self-annealed after hot rolling (self-annealed coil), it is possible to prevent material variations in the sheet width direction, It is possible to prevent breakage, and it is low-cost, space-saving, and highly efficient (including workability).

FIG. 4 is a schematic diagram showing in stages how a wound coil after hot finish rolling is cooled using a rolling facility according to an embodiment of the present invention. 1 is a longitudinal side view showing a first example of a sleeve used in the rolling equipment of the present invention; FIG. FIG. 3 is a cross-sectional view taken along line III-III in FIG. 2; FIG. 4 is a longitudinal side view showing a second example of the sleeve used in the rolling equipment of the present invention; FIG. 5 is a cross-sectional view taken along line VV in FIG. 4; FIG. 11 is a longitudinal side view showing a third example of the sleeve used in the rolling equipment of the present invention; FIG. 7 is a cross-sectional view taken along line VII-VII in FIG. 6; FIG. 10 is a longitudinal side view showing a fourth example of the sleeve used in the rolling equipment of the present invention; FIG. 9 is a cross-sectional view taken along line IX-IX in FIG. 8; FIG. 11 is a longitudinal side view showing a fifth example of the sleeve used in the rolling equipment of the present invention; FIG. 9 is a cross-sectional view taken along line XI-XI in FIG. 8; FIG. 2 is a vertical cross-sectional side view of a sleeve for explaining preferred dimensional relationships of the sleeve used in the rolling equipment of the present invention; 4 is a graph showing the relationship between the angle θ and the intensity ratio according to experiments conducted by the inventors. FIG. 11 is a longitudinal side view showing a sixth example of the sleeve used in the rolling equipment of the present invention; FIG. 15 is a cross-sectional view taken along line XV-XV in FIG. 14; It is a schematic diagram showing an example of a hot rolling equipment portion in the rolling equipment of the present invention. It is a schematic diagram showing an example of a cold rolling equipment portion in the rolling equipment of the present invention.

The rolling equipment of the present invention comprises, as an example, the equipment shown in FIGS. 16 and 17, which will be described later.
FIG. 16 is a diagram showing the parts after the finishing mill of the hot rolling equipment. Although not shown, the steel slab is heated in a heating furnace, then width-adjusted by a sizing press, and then rolled to halfway thickness by a rough rolling mill. As shown in FIG. 16, the slab 2 that has been rolled out to an intermediate thickness by the roughing mill is rolled to a finished thickness by the finishing rolling mill 3, and then passed through the cooling zone 4 and coiled. It is wound into a coil by the machine 5 . The wound coil 15 becomes self-annealed coils C1 and C2 by cooling in the air. After that, the self-annealed coils C1 and C2 are cold-rolled by a cold tandem rolling mill 11 to be stretched thinner as shown in FIG. 17, for example.

Here, in the rolling equipment of the present invention, as shown in FIG. 16 as an example, a hollow cylindrical sleeve for inserting the coil 15 after hot finish rolling is cooled in the air. 20. The sleeve 20 is open at both ends in the axial direction, and at least a portion in the thickness direction is made of a heat insulating material.

FIG. 1 shows step by step an example of such a rolling facility in which a hot-rolled and wound coil is inserted into a sleeve and cooled in the atmosphere.

In FIG. 1, (a) shows a coil 15 immediately after winding after hot finish rolling. This coil 15 is still in a high temperature state of a little less than 700.degree.
The coil 15 is removed from the winding shaft (mandrel) of the winder (coiler), and an appropriate support shaft 16 extends horizontally along the hollow portion on the inner peripheral side thereof as shown in FIG. 1(b). and is transported by the support shaft 16 to the position of the sleeve 20 (near the winder). The support shaft 16 may be, for example, a fork of a forklift or a dedicated cantilever support rod. The sleeve 20 is on standby near a winder (not shown) so that its central axis Os is horizontal. Here, the sleeve 20 is made so that its axial length L is larger than the width W of the coil 15 (the width of the wound plate).

Then, the coil 15 is horizontally inserted into the inner hollow portion of the sleeve 20, as shown in FIG. 1(c). Here, the coil 15 is arranged such that the central position Mc in the width direction (the width direction of the wound plate) coincides with the central position Ms in the axial length of the sleeve 20 or is positioned close thereto. , is inserted into the sleeve 20 .

After that, the support shaft 16 is lowered, and as shown in FIG. 1 (d)). While maintaining this state, the coil 15 is allowed to cool in the atmosphere, and self-annealing proceeds. The self-annealed coil (self-annealed coil) is subjected to cold tandem rolling as described later with reference to FIG.

As described above, by allowing the coil 15 to cool (self-anneal) while being inserted into the sleeve 20, the self-annealed coil has a difference in strength in the sheet width direction (non-uniform deformation resistance distribution) in the portion on the outer peripheral side. ) becomes smaller.
The reason is as follows.

That is, the conventional self-annealed coil is air-cooled without a heat insulating member such as a cover after hot finish rolling and coiling. At this time, in the coil heated during hot rolling, the coil outer peripheral portion and coil end portion (width direction plate end portion) cools faster, so the temperature drop is faster than the plate center portion. As a result, the growth of crystal grains is suppressed, and the grains become finer and harder than in the central portion of the plate. As a result, the difference in strength in the sheet width direction (non-uniform deformation resistance distribution) increases, and as already described, sheet breakage due to drawing tends to occur in the subsequent cold tandem rolling.

On the other hand, in air cooling using a sleeve as described above, the inner peripheral surface of the sleeve functions as a heat barrier, and the heat radiated from the plate end portion of the coil hits the inner peripheral surface of the sleeve and is reflected by radiation. , coming back to the coil side. As a result, the cooling rate at the edge of the sheet at the outer periphery of the coil is slowed down, promoting the growth of crystal grains in that area, resulting in a difference in strength between the center of the sheet and the edge of the sheet (irregularity in deformation resistance distribution). uniformity) becomes smaller.

Further, here, by simply inserting the coil into a sleeve having a simple shape such as a hollow cylinder with both ends open, a self-annealing coil with small variations in deformation resistance distribution can be obtained as described above. It can be said that the rolling equipment and rolling method are low in cost and excellent in space saving and high efficiency (including workability) as compared with the case of using a box as shown.

Further, examples of specific configurations of the sleeve 20 will be described with reference to FIGS. 2 to 11. FIG.

The overall shape of the sleeve 20 is a hollow cylinder with both ends open. At least a portion of the outer peripheral portion (cylindrical portion) of the sleeve 20 in the thickness direction (the radial direction of the cylinder) is made of a heat insulating material. Specifically, as shown in FIGS. 2 and 3 as a first example, ceramic fibers (ceramic wool) are applied to the inner periphery of a hollow cylindrical high-rigidity outer cylinder 20a made of a high-rigidity material such as iron. ), rock wool fiber, silica wool, or other heat insulating material is fitted in or adhered to form a two-layer structure.

As shown in FIGS. 4 and 5 as a second example, the sleeve 20 is coated with an inner surface coating layer 20c made of the same heat insulating material on the inner peripheral surface of the same high-rigidity outer cylindrical portion 20a. A two-layer structure may also be used.

As shown in FIGS. 6 and 7 as a third example, the sleeve 20 includes a high-rigidity outer cylindrical portion 20a similar to that described above and a small-diameter hollow cylindrical high-rigidity outer cylinder portion 20a made of a high-rigidity material such as iron. A three-layer structure may be employed in which a heat insulating intermediate cylindrical portion 20e made of the same heat insulating material as described above is interposed between the inner cylindrical portion 20d and the inner cylindrical portion 20d.

In addition, although not shown, if sufficient rigidity can be ensured only by a heat insulating material (for example, when a hard ceramic sintered body is used), a one-layer structure in which the entire sleeve 20 is integrally formed by a heat insulating material is used. It is also possible to
In any case, the axial length of the heat insulating material portion of the sleeve 20 (the length in the direction corresponding to the plate width direction of the self-annealing coil) is preferably equal to the total length L of the sleeve 20 . In other words, the heat insulating material portion is preferably formed over the entire length L of the sleeve 20 .

In either case, the inner diameter of the sleeve 20 is set to be somewhat larger than the outer diameter of the coil 15 and the length L in the axial direction is set to be somewhat larger than the width (plate width) of the coil 15 . As a result, the coil 15 wound after hot finish rolling can be easily inserted into the sleeve 20, and the coil 15 is inserted into the sleeve 20 so that both ends of the coil 15 in the width direction do not protrude from both ends of the sleeve 20. A coil 15 can be accommodated.

Further, as shown in FIGS. 8 and 9, the inner peripheral surface of the sleeve 20 is provided with projections 21 for positioning the coil 15 (or for preventing the coil from sliding within the sleeve). good too. Also, as shown in FIGS. 10 and 11, a stopper 22 may be provided to prevent the sleeve 20 itself from rolling.

In the above description, the case where the coil 15 is removed from the winding shaft (mandrel) of the winding machine (coiler) and then inserted into the sleeve 20 has been described. A sleeve 20 may be attached to surround the coil 15 before it is removed from the winding shaft (mandrel) of the (coiler).

Preferred conditions for the dimensions of the sleeve 20 as described above, particularly the length L in the axial direction, will be described with reference to FIG.

The axial length L of the sleeve 20 preferably satisfies the following formula (1).
L≧W+2·(D _S −3·D _CO /4−D _CI /4) tan30 (1)
Here, in formula (1),
W: coil plate width,
D _CO : coil outer diameter,
D _CI : coil inner diameter,
D _S : inner diameter of sleeve, tan angle unit is degrees, and all other dimensions are mm. The sleeve inner diameter _DS means the inner diameter of the entire sleeve including the heat insulating material.

The meaning of the expression (1) is as follows.

As shown in FIG. 12, the coil 15 is placed in the sleeve 20 so that the center position Oc of the coil 15 in the longitudinal direction coincides with the center position _OS of the sleeve 20 in the sheet width direction (therefore, the lower surface of the coil 15 is 20).
Further, from the outer peripheral surface 15a of the coil 15 toward the inner peripheral surface 15b of the coil, the coil width direction end position at the position of 1/4 of the outer diameter / inner diameter difference D (= D _CO - D _CI ) of the coil 15 is Let P. Also, let Q be the position of the inner peripheral surface of the end of the sleeve 20 in the longitudinal direction. Let θ be the angle formed by the line segment M extending from the position P to the position Q with respect to the plane N perpendicular to the central axis of the coil 15 .

Let Lp be the horizontal length of the end of the sleeve 20 protruding from the end of the coil 15 (protrusion length on one side).
Lp=( _DS -3- _DCO /4- _DCI /4) tan θ (2)
can be expressed as
The total length L of the sleeve is
L=W+2·Lp (3)
Therefore, the following equation (4) is derived from equations (2) and (3).
L=W+2·(D _S −3·D _CO /4−D _CI /4) tan θ (4)

If the angle .theta. in the equation (4) is set to 30 degrees or more, the above equation (1) is obtained. That is, as will be described later, as a result of various experiments conducted by the present inventors, when the angle θ is 30 degrees or more, the cooling rate at the outer circumference of the coil and at the edge of the width of the strip is slowed down. It was found that the growth of the crystal grains is promoted, and the difference in strength between the plate center and the plate edge (non-uniform deformation resistance distribution) is reduced.

Here, in order to exhibit the heat-retaining effect of the sleeve, especially the heat-retaining effect of the outer peripheral portion of the coil and both end portions in the sheet width direction, the radiant heat from that portion of the coil must be dissipated from both ends of the gap between the sleeve and the coil. It is preferable not to escape to the outside as much as possible. Conditions for this, particularly conditions for enhancing the heat retaining effect of the portion by reflecting the radiant heat from the outer peripheral portion of the coil and both ends in the plate width direction on the inner peripheral surface of the sleeve and returning to the coil as radiant heat, are as follows: It was found through experiments that it is preferable that the angle .theta.

FIG. 13 shows some results of experiments by the inventors.
FIG. 13 shows the value (strength ratio) obtained by dividing the strength of the plate end (yield strength 5 mm inside from the plate end) by the strength of the plate center (yield strength of the plate center) in the coil after self-annealing. It shows the result of examining the influence of A coil having a width of 1220 mm, a unit weight of 15 tons, a coil inner diameter of 51 mm and a coil outer diameter of 1500 mm was mainly used.
The sleeve has a two-layer structure as shown in FIGS. 2 and 3, and the iron high-rigidity outer cylindrical portion 20a has a thickness of 50 mm and an inner diameter of 1760 mm, 1860 mm, and 1960 mm. In addition, the heat-insulating inner cylindrical portion 20b on the inner surface (whole area, entire circumference) side of the sleeve was formed of ceramic fiber with a thickness of 30 mm. Therefore, the inner diameter of the entire sleeve (including the heat insulating material) is three levels of 1700 mm, 1800 mm and 1900 mm.

Self-annealing is performed by setting sleeves with various angles .theta. (thus varying the sleeve length L) from one without a sleeve (angle .theta. is 0 degree) to .theta.=60 degrees. The intensity ratio was investigated. The self-annealing conditions were as follows: hot finish rolling end temperature 1080°C, coiling temperature 680°C. Air cooled.

From the results shown in FIG. 13, the intensity ratio decreases as the angle θ increases from zero to about 30 degrees, and the effect saturates when the angle θ increases beyond about 30 degrees. I found They also found that the intensity ratio is less than 5% when the angle θ is about 30 degrees or more. Here, when the strength ratio is less than 5%, although a slight change in shape may occur in the subsequent cold tandem rolling, there is no severe medium elongation that causes reduction, in other words, medium elongation It was confirmed that plate breakage due to

Furthermore, when the same investigation was conducted by variously changing the plate width, coil unit weight, coil inner diameter and coil outer diameter, the results shown in Tables 1A and 1B were obtained. In Tables 1A and 1B, ○ in the non-uniformity evaluation column indicates an intensity ratio of less than 5%, and x indicates an intensity ratio of 5% or more.

It is clear from Tables 1A and 1B that the strength ratio can be suppressed to less than 5% by setting the sleeve length L so that the angle θ is 30 degrees or more.

As shown in FIGS. 14 and 15, the sleeve 20 has a reflective layer 23 on the upper part of the inner peripheral surface of the sleeve 20 when the sleeve is arranged so that the central axis of the sleeve 20 is horizontal. may be formed. By forming such a reflective layer 23, it is possible to effectively reflect radiant heat from the edge of the outer periphery of the coil in the plate width direction. As a result, the length of the sleeve can be shortened by about 5 to 20% compared to when the reflective layer is not provided. The reflective layer 23 may be composed of, for example, a metal plate having metallic luster or may be formed by coating. It is preferable to set the angular range α with respect to the center axis position O to be 100 degrees or more, more preferably 110 degrees or more.

<Embodiment of rolling equipment>

Furthermore, a preferred example of the overall configuration of a rolling facility in which the rolling method of the present invention is applied to a production line for electrical steel sheets will be described with reference to FIGS. 16 and 17. FIG.

FIG. 16 is a diagram showing an example of the portion after the finish rolling mill in the hot rolling equipment of the rolling equipment of the present invention.
In FIG. 16, a slab 2 is rolled by a finish rolling mill 5 to a thickness of, for example, about 2 to 5 mm. It is continuously wound by the winder 5 to form the coil 15 .

The wound coil 15 is removed from the winder 5 and inserted into a sleeve 20 located near the winder 5 . At this time, the coil 15 immediately after being wound may be temporarily moved by, for example, a crane and mounted on the sleeve 20 by using a forklift. Also, although not shown, a facility for automatically attaching the sleeve may be provided.
The coils (self-annealed coils C1 and C2) self-annealed by being air-cooled while being inserted into the sleeve as described above are sent to a cold tandem rolling facility as shown in FIG. 17 described later.

As an example of the present invention, C≦0.008%, 2%≦(Si+Al)≦3, 0%. 02%≤Mn≤1.0%, S≤0.003%, N≤0.002%, Ti≤0.003%, 0.001%≤REM≤0.02%, and 0.001%≤REM≤0.02%. Satisfying the relationship of 3% ≤ Al / (Si + Al) ≤ 0.5%, using a slab for non-oriented electrical steel sheet containing the balance Fe and inevitable impurities, hot finish rolling temperature is 1050 ° C. or higher Hot finish rolling is performed in a temperature range of 1 second or more and 7 seconds or less without water injection. to form the self-annealed coils C1 and C2.

The self-annealed coils C1 and C2 obtained by the hot rolling equipment shown in FIG. 16 are sent to the cold rolling equipment shown in FIG.
In FIG. 17, self-annealed coils C1 and C2 are supplied to the coil dispenser 7. In FIG. The strips discharged from the self-annealed coils C1 and C2 by the coil discharger 7 are welded by the welding machine 8 at the tail end of the plate from the preceding coil and the front end of the plate from the following coil to form a continuous strip. It becomes (self-annealed strip) S and is sent to the looper 9 . In the following. The self-annealed strip S discharged from the self-annealed coils C1 and C2 and made continuous is sometimes simply referred to as a strip or a self-annealed plate.
The looper 9 is controlled so that there is no stagnation of strip supply in the downstream process even when there is no payout during coil joining in the welding machine 8 (that is, when the running of the strip is stopped). The self-annealing coils C1 and C2 supplied to the coil dispensing machine 7 may be heated in advance to a temperature of 60° C. or higher using a hot bath or the like.

The self-annealed strip S that has passed through the looper 9 is supplied to the pickling facility 10 . In this pickling equipment 10, the surface scale of the self-annealed coil is removed (scraped). In order to increase the cutting efficiency before pickling, a rolling mill for cracking the surface of the self-annealed strip S, a leveler or tension leveler, shot blasting (dry or wet), or a grinder may be installed.

The self-annealed strip S, which has been pickled to remove surface scales, is sent to a cold tandem rolling mill 11 and rolled to a thinner thickness.

In this embodiment, the cold tandem rolling mill 11 is composed of five rolling mill stands 11a to 11e arranged in series. (4Hi mil).
Furthermore, in the cold tandem rolling mill 11, although not shown, rolling lubricating oil called coolant is mixed with water and made into an emulsion, and is supplied to the entrance and exit sides of each stand. . The supplied coolant is collected in a tank (not shown), and is again supplied to each stand for resuscitation lubrication.

In the cold tandem rolling mill 11, for example, a self-annealed strip for non-oriented electrical steel sheet having a thickness of 2.3 mm and a width of 1200 mm is rolled to a thickness of 0.3 mm. As the coolant, for example, rolling lubricating oil based on synthetic ester (hindered complex ester) is supplied to each stand at a concentration of 2% and a temperature of 60° C. at a rate of 1 to 3 m ³ /min (on the inlet side and the outlet side). total), providing rolling lubrication and work roll cooling.

The work roll diameter of each rolling mill stand 11a to 11e is, for example, 500 mm to 700 mm, the backup roll diameter is, for example, 1,300 mm to 1,600 mm, and the barrel length is, for example, 2,000 mm.

A cutting machine 12 for cutting the continuously rolled self-annealed strip is provided downstream of the cold tandem rolling mill 11, and downstream thereof is a car for winding the continuously rolled self-annealed strip. Roselle reel 13 is deployed. Although not shown, the coil wound by the carousel reel 13 and cut is discharged from the roll, placed on a conveyor, and transported to a factory or the like for the next process.

Examples (invention examples) and comparative examples (prior art) relating to the rolling method of the present invention will be described below.
Both Examples and Comparative Examples were carried out in rolling equipment having the configuration shown in FIGS. 16 and 17 .

The strips subjected to tandem cold rolling in the examples and comparative examples were self-annealed strips for non-oriented electrical steel sheets with a thickness of 2.3 mm and a width of 1200 mm, and C: 0.007% by mass, ( Si + Al): 2.5%, Mn: 0.5%, S: 0.001%, N: 0.001%, Ti: 0.001%, REM: 0.01%, and further Al / (Si + Al): Using a slab for non-oriented electrical steel sheet that satisfies the relationship of 0.4% and contains the balance Fe and unavoidable impurities, hot finish rolling is performed at a hot finish rolling temperature of 1090 ° C. and coiled at 680°C.

In the examples, the wound coil was inserted into the sleeve and air-cooled to room temperature as it was for self-annealing. The wound coil (hot-rolled finished coil) has a plate thickness of 2.3 mm, a plate width of 1220 mm, a coil inner diameter of 508 mm, a coil outer diameter of 1500 mm, and a coil unit weight of 15 tons. The sleeve used had an inner diameter (including ceramic material) of 1,600 mm and a sleeve length of 1,622 mm (angle θ = 30 degrees), with a heat insulating material (ceramic fiber) having a thickness of 30 mm provided on the inner surface (entire area, entire circumference). .

On the other hand, in the comparative example, the coil after hot finish rolling (each dimension and weight are the same as those of the example) was air-cooled to room temperature without doing anything (without being inserted into the sleeve) and self-annealed. bottom.

Furthermore, in both Examples and Comparative Examples, the strip discharged from the self-annealed coil was made continuous by welding and rolled as a self-annealed strip to a plate thickness of 0.3 mm by the cold tandem rolling mill. As for the rolling speed, the rolling speed of the final stand at the time of coil change was 250 m/min, and the maximum rolling speed of the final stand was 1100 m/min. Further, as shown in Table 2 below, the tension between each stand was set to 50 to 250 MPa.
100 coils of self-annealed strips were rolled for each of the examples and comparative examples, and the aforementioned strength ratio and occurrence of strip breakage were examined.

100 coils of self-annealed strips were rolled for each of the examples and comparative examples, and the aforementioned strength ratio and occurrence of strip breakage in the cold rolling mill were investigated.
The results are as follows.

In the comparative example (prior art), the strength ratio was 1.1 to 1.2, and the plate breakage probability was 89%.
On the other hand, in the examples (inventive examples), the strength ratio was 1.0 to 1.04, and no plate breakage was observed.

Although the preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, the present invention is not limited to such examples. It is obvious that a person having ordinary knowledge in the technical field to which the present invention belongs can conceive of various modifications or modifications within the scope of the technical idea described in the claims. It is understood that these also naturally belong to the technical scope of the present invention.

For example, in the above embodiments, the self-annealed material of the non-oriented electrical steel sheet is targeted, but the present invention is not limited to such an example. For example, grain-oriented electrical steel sheets, other high-strength steels, stainless steel sheets, etc., may be used as objects, and not only self-annealed hot-rolled strips, but also large non-uniform deformation resistance in the length direction and width direction of the strip. It can be applied in some cases to prevent plate breakage during cold tandem rolling.

In addition, the configuration of the upstream portion of the hot finishing mill in the rolling equipment of the present invention is not particularly limited. Generally, a hot rough rolling mill is installed upstream of the hot finish rolling mill, but it is manufactured by a twin roll continuous casting method or a belt continuous casting method known as a thin strip continuous casting and rolling method. When hot-rolling a thin cast piece (thin-walled slab), it is common to immediately roll it by an in-line mill corresponding to a finish rolling mill without performing rough rolling, and such a case is also included in the present invention.

Preferred embodiments and experimental examples of the present invention have been described above, but these embodiments and experimental examples are merely examples within the scope of the present invention, and are within the scope of the present invention. , additions, omissions, substitutions, and other changes are possible. That is, the present invention is not limited by the foregoing description, but is limited only by the scope of the appended claims, and can of course be modified within the scope thereof.

C1, C2 self-annealed coil S self-annealed strip 2 steel slab 3 finish rolling mill 5 winding machine 7 cold tandem rolling mill 15 coil 20 sleeve

Claims (3)

In a rolling facility that cools the coil that has been hot-rolled and wound into a coil in the atmosphere, and then cold-rolls it with a cold tandem rolling mill,
A hollow cylindrical sleeve for inserting the coil when cooling the wound coil after hot rolling in the atmosphere,
The sleeve is open at both ends in the axial direction, and at least a portion in the thickness direction is made of a heat insulating material,
A rolling facility , wherein the axial length L of the sleeve satisfies the following formula (1) .
L≧W+2·(D _S −3·D _CO /4−D _CI /4) tan30 (1)
Here, in formula (1),
W: coil plate width,
D _CO : coil outer diameter,
D _CI : coil inner diameter,
D _S : Sleeve inner diameter
, the angle unit of tan is degrees, and all other dimensions are mm. In the rolling equipment according to claim 1,
A rolling facility, wherein the sleeve has a reflective layer formed on an upper portion of an inner peripheral surface of the sleeve when the sleeve is arranged so that the central axis of the sleeve is horizontal. In hot rolling by the rolling equipment according to claim 1 or 2 and winding into a coil, further cooling the coil in the atmosphere, and then cold rolling by a cold tandem rolling mill,
A rolling method, characterized in that a coil wound after hot rolling is inserted into the sleeve and cooled in the atmosphere.

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