JP2003277833A - Method and device for manufacturing metal plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and a device for manufacturing a metal plate including a steel strip without any defective shape caused by the out-of-plane deformation during cooling. <P>SOLUTION: In the metal plate manufacturing method for cooling the traveling metal plate by a cooling apparatus, the out-of-plane deformation is suppressed by restricting the metal plate from both sides in an area in which a compressive stress is exerted in the plate width direction by cooling the metal plate or an area in the vicinity thereof. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for manufacturing a metal plate for preventing a defective shape due to out-of-plane deformation of the metal plate which occurs during cooling of the metal plate.

[0002]

2. Description of the Related Art In the production of metal sheets such as steel strip, the metal sheet is cooled after hot working or after heating,
The material is made by causing a phase transformation. At that time, there is a problem in that the metal plate may have a defective shape due to out-of-plane deformation such as warpage or corrugation.

Quenching and cooling in a continuous annealing line is an example where this problem becomes particularly noticeable.

For example, in Japanese Unexamined Patent Publication (Kokai) No. 11-193418, when quenching and cooling a high temperature steel strip after annealing in a continuous annealing process after cold rolling, an arcuate warp occurs in the width direction of the steel sheet. It has been shown that the deterioration of the flatness of the steel strip shape becomes remarkable. If the shape defect of the steel strip occurs, the stripability in the continuous annealing furnace deteriorates, leading to a decrease in the transport speed and stripping trouble, and it also causes trouble in the next step such as press working.

As a measure against the defective shape of the steel strip that occurs during quenching and cooling of the continuous annealing line, Japanese Patent Laid-Open No. 4-289120 discloses a method for improving the shape of the steel strip by controlling the microstructure. Kaihei 11-193418 discloses a method of pressurizing with a pressure of 500 N / m ² or more over at least the entire width direction of the front and back surfaces of the steel strip during quenching.

[0006]

However, the above-mentioned conventional techniques have the following problems, respectively.

The method of Japanese Patent Laid-Open No. 4-289120 is a technique for stabilizing the shape of the steel strip by precipitating 3 to 20% of ferrite and then cooling it so that the deformation due to martensitic transformation is absorbed by the ferrite. ,As a matter of course,
Not applicable to martensitic single phase steel.

According to the method disclosed in JP-A-11-193418,
In principle, it can be applied to steel with any structure, but there are the following problems. That is, JP-A-11-193418
According to FIG. 1 of the publication, even when the present invention is carried out, the floating height (warpage amount) may be about 10 mm, and in FIG. 2 showing the influence of tension, the tension of 15 N / m
The amount of warpage is reduced to about several mm at m ² , but such high tension may cause drawing of the steel strip. Recent demands from customers are strict, and the amount of warpage may be limited to 5 mm or less, and such a strict demand cannot be met by the method disclosed in JP-A-11-193418.

The present invention solves the problems of the prior art as described above, and when manufacturing a metal plate such as a steel strip,
An object of the present invention is to provide a metal plate manufacturing method and a metal plate manufacturing apparatus capable of manufacturing a metal plate without causing a defective shape due to out-of-plane deformation during cooling.

[0010]

As a particularly prominent example of a shape defect due to out-of-plane deformation of a metal plate, there is a shape defect in the width direction of a steel strip caused by quenching and cooling in a continuous annealing line of a steel strip. As a result of the inventors' earnest studies on the cause of occurrence of the above, it has been found that a defective shape occurs due to the following mechanism.

First, in the first generation mechanism, as schematically shown in FIG. 7, at the quenching start point (cooling start point), thermal stress in the compression direction is generated in the width direction of the steel strip, and the steel strip is stretched in the width direction. Is to buckle. In other words, when a part of the steel strip starts quenching, the quenching part undergoes heat contraction in the width direction, but the high temperature part in contact with the quenching part where quenching has not started is pulled by the heat shrinkage of the quenching part and is compressed. Subject to thermal stress. Then, the high temperature portion of the steel strip which is subjected to the compressive thermal stress as described above easily buckles in the width direction and a defective shape occurs.

Next, the second generation mechanism is due to a phase transformation at a temperature lower than the cooling start temperature, particularly a martensite transformation, as also schematically shown in FIG. When austenite transforms into martensite, it causes volume expansion. Therefore, the portion of the steel strip where the martensitic transformation is occurring tends to widen in the width direction. However, since the portion that does not cause martensite transformation in contact with that portion restrains the width expansion of the portion where martensite has occurred,
The portion where the martensitic transformation has occurred first buckles due to the compressive stress generated in the width direction, resulting in a defective shape.

Comparing the two, the first mechanism, which occurs at a higher temperature, is the main cause of the defective shape.

Further, based on the elucidation of the above-mentioned generation mechanism, the inventors restrain the out-of-plane deformation by restraining from both sides of the steel strip in the region where the compressive stress acts in the widthwise direction of the steel strip or in the vicinity thereof. It was found that the buckling of the steel strip in the width direction, that is, the defective shape of the steel strip can be prevented by doing so, and the present invention has been completed. This is because the widthwise buckling load of the steel strip can be increased by restraining the steel strip from both sides.

The present invention has been made on the basis of such findings, and its features are as follows.

(1) In a method of manufacturing a metal plate in which a running metal plate is cooled by a cooling device, both surfaces of the metal plate are formed in a region where compressive stress is generated in the plate width direction due to cooling of the metal plate or a region in the vicinity thereof. A method for manufacturing a metal plate, characterized by restraining out-of-plane deformation by restraining the metal plate from the side.

(2) The distance between the position where the compressive stress generated in the width direction of the metal plate is maximum and the position where the metal plate is constrained from both sides of the metal plate in the longitudinal direction of the metal plate is within 0.2 m. The method for producing a metal plate according to (1) above, which is characterized.

(3) To restrain out-of-plane deformation by constraining the metal plate from both sides thereof at a position where the differential coefficient obtained by differentiating the temperature of the metal plate twice at the position in the conveying direction is 1000 ° C./m ² or more. The method for producing a metal plate according to the above (1) or (2), characterized in that

(4) A metal plate restraining device for restraining the out-of-plane deformation by restraining the metal plate from both sides thereof at a position within 0.2 m of the cooling start position by the cooling device on the metal plate passing line. An apparatus for manufacturing a metal plate, which is provided with.

(5) The apparatus for manufacturing a metal plate as described in (4) above, wherein the device for restraining the metal plate is a pinch roll.

[0021]

1 is a side view showing an embodiment of a metal plate manufacturing apparatus of the present invention.

In the embodiment shown in FIG. 1, the present invention is applied to a cooling device provided on the exit side of an annealing zone of a continuous annealing furnace.
This cooling device includes a water tank 8 and a cooling unit 2 for cooling the steel strip 4 annealed in the annealing zone of the continuous annealing furnace to a predetermined temperature by spraying cooling water, and for raising the steel strip upward. And a sync roll 3. Then, 0.2 m from the cooling unit inlet surface, which is the strong cooling start position, in the longitudinal direction of the steel strip.
Within, pinch roll 1 to restrain the steel strip from both sides
Is provided.

The steel strip 4 annealed in the annealing zone of the continuous annealing furnace enters the water surface 5 from the upper side, is sprayed with cooling water in the cooling unit 2 to be strongly cooled, and is cooled to a predetermined temperature. Pulled up via 3.

At this time, a compressive thermal stress is generated in the width direction of the steel strip 4 at the inlet surface of the cooling unit where strong cooling is started, and the steel strip 4 buckles in the width direction and a shape defect occurs due to out-of-plane deformation. Cause. On the other hand, in the present invention, the pinch roll 1 is provided in the vicinity of the strong cooling start position, and the steel strip 4 is restrained from both sides thereof to suppress the out-of-plane deformation. The interval S in the steel strip longitudinal direction between the cooling unit inlet surface, which is the strong cooling start position, and the steel strip restraining position by the pinch roll 1 should be within 0.2 m, as is clear from the experimental results in the examples described later. Is desirable. In the case of FIG. 1, pinch roll 1
The restraint position of the steel strip due to may be either above the water surface or below the water surface.

The present invention is applicable in principle to any manufacturing apparatus for cooling a metal plate while it is being conveyed. But,
The effect of the present invention is clearly manifested in that a compressive stress is generated in the width direction (direction perpendicular to the transport direction) of the metal plate, which causes buckling of the metal plate in the width direction, resulting in an out-of-plane deformation. This is the case. Such a manufacturing apparatus generally has the following prerequisites.

First, the plate thickness of the metal plate must be 3 mm or less. When a high temperature metal plate is cooled in order to create a material, the temperature of the metal plate before cooling is 1000 ° C. or lower. In this temperature range, even if a metal plate having a plate thickness of 3 mm or more is cooled in a generally known cooling direction, it will not buckle.

In the cooling device targeted by the present invention, the temperature T at a certain point of the metal plate before and after the cooling device typically changes as shown in FIG. At this time, the differential coefficient ∂T / ∂X obtained by differentiating the temperature T at a certain point of the metal plate in the same area in the conveyance direction position X and the differential coefficient ∂ ² T obtained by differentiating the temperature T twice in the conveyance direction position X. / ∂X ² is also schematically shown in FIGS. 3 and 4. According to the study by the inventors,
It is known that the stress σ _Y acting in the width direction of the metal plate is proportional to ∂ ² T / ∂X ² . As can be seen from FIG. 4, ∂ ² T / ∂X ² is the largest at the cooling start position. That is, it is at the position where cooling starts that the compressive stress in the width direction of the metal plate becomes maximum and out-of-plane deformation is likely to occur. In order for the metal plate to be deformed out-of-plane by the compressive stress in the width direction, ∂ ² T / ∂X ² is 1 at the cooling start position of the metal plate, as is clear from the experimental results in Examples described later.
It is necessary to be 000 ° C / m ² or more. In other words, the differential coefficient ∂ ² T /
In the position ∂X ² becomes 1000 ° C. / m ² or more, it is effective and preferred to suppress to plane deformation restraining a metal sheet from the both sides.

Cooling methods used in the continuous annealing furnace include gas jet cooling, roll quenching, mist cooling and water quenching. Roll quenching is a method of cooling by winding a metal plate around a water-cooled roll, but since this method allows out-of-plane deformation, the metal plate in the present invention is restrained from both sides thereof. Is not applicable. This is because, as shown in FIG. 5, out-of-plane deformation may occur in the direction opposite to the water cooling roll 6. As shown in FIG. 6, it is possible to pinch the metal plate 4 by installing a restraining roll 7 on the opposite side of the water-cooling roll 6 for restraining the out-of-plane deformation by restraining the metal plate from both sides thereof. To implement.

In the above description, the out-of-plane deformation at the cooling start position has been a problem, but in reality, the shape defect due to the out-of-plane deformation may occur due to other factors such as martensitic transformation. Suppressing out-of-plane deformation by restraining from both sides of the metal plate in the region where the compressive stress acting in the plate width direction of the metal plate occurs or in the vicinity thereof has the effect of improving the shape of the metal plate.

[0030]

[Examples] In order to examine a widthwise shape defect of a steel strip due to quenching cooling (water quench) of a continuous annealing line, an experimental apparatus as shown in Fig. 8 was manufactured. After heating the coil J2 of the steel strip to a predetermined temperature in the electric heating furnace J1, the steel strip J9 is discharged and conveyed to the coiler J11. On the way, the cooling unit J6 sprays cooling water onto the steel strip J9 to cool it to a predetermined temperature. Steel strip J9 after cooling
Is wound by a coiler J11 via a sink roll J7. The cooling device inlet side thermometer J4 measures the quenching start temperature of the steel strip J9, and the cooling device outlet side thermometer J10 measures the quenching end temperature of the steel strip J9.

The steel strip J9 used in the experiment has a plate thickness of 1.0 m.
m, width 1000 mm, 0.1% carbon as a component,
It contains 1.5% manganese and inevitable impurities. Martensitic transformation start temperature of steel strip J9 is about 450
℃. The coil J2 was heated to 850 ° C. in the electric heating furnace J1, discharged, and conveyed at 1 m / s. Cooling water was sprayed on the cooling unit J6 to cool it, and the coiler J11 wound it up. Quenching start temperature is 750 ° C, quenching end temperature is 1
It was 50 ° C.

When the coil after the experiment was rewound, a wavy shape defect was observed in the plate width direction as shown in FIG. Examination of the cross section of the coil revealed that almost 100% was a martensitic single phase steel with a martensitic structure. Therefore,
The out-of-plane deformation was suppressed by approaching the position where the steel strip J9 was started to be cooled and restraining it from both sides of the steel strip by a pinch roll J5 that pinches the entire width of the steel strip.

The amount of warpage δ is defined to represent the degree of shape defect. The steady portion of the steel strip J9 is cut out and placed on a plane, and the distance at the place where the plane and the steel strip J9 are most distant is the warpage amount δ. FIG. 9 shows the definition of the warpage amount δ. The warpage amount δ was about 20 mm when the pinch roll J5 was not used.

The following experiment was conducted in order to examine the optimum installation location of the pinch roll J5. Pinch roll J5
Interval S between the position for restraining the steel strip J9 with the cooling start position
Was defined as shown in FIG. 8, the interval S was changed, and the coil after the experiment was finished was rewound and the shape was observed. S is the distance between the pinch roll J5 and the cooling unit inlet surface, which is the strong cooling start position by the cooling unit. When S ≧ 0,
The pinch roll J5 is above the cooling start position. S <
When it is 0, it means that the pinch roll J5 is below the cooling start position. When performing the experiment of S <0, the cooling unit J6 was divided into upper and lower parts, and the pinch roll J5 was installed between the upper and lower cooling units J6.

FIG. 10 shows the experimental results of the relationship between the interval S between the strong cooling start position and the position where the pinch roll restrains the steel strip and the amount of warp of the steel strip. The horizontal axis represents the distance S between the position where the pinch roll J5 is installed and the strong cooling start position, and the vertical axis represents the warpage amount δ defined in FIG. The warp amount δ increases as the pinch roll moves away from the strong cooling start position. In the range of −0.2 ≦ S ≦ 0.2, the warpage amount δ is 5
It is less than or equal to mm. This sufficiently satisfies the most severe conditions currently demanded by customers.

According to the theoretical examination conducted by the inventors,
The compressive stress σ _Y generated in the metal plate during the cooling process is ∂ ² T /
It is proportional to ∂X ² and becomes maximum at the cooling start position. σ _Y
As described above, the metal plate buckles and a shape defect in the width direction occurs due to the above. So next, ∂ ² T
An experiment was conducted to investigate the causal relationship between / ∂X ² and the defective shape.

FIG. 11 shows an experimental apparatus for examining ∂ ² T / ∂X ² . After heating the sample K1 equipped with a thermocouple to a predetermined temperature by the heating device K2, the sample transport device K4
Cooling unit K that spouts cooling water on sample K1
Send to 3 and cool. FIG. 11A shows a state before the sample K1 is sent to the cooling unit K3 jetting the cooling water by the sample transfer device K4, and FIG.
Shows the state in which the sample transport device K4 has sent the sample K1 to the cooling unit K3 which jets cooling water.

Cooling unit K3 and cooling unit J of FIG.
6 is the same. Based on the temperature history measured by the thermocouple and the transport speed of the sample K1 from the heating device K2 to the cooling unit K3, ∂ ² T / ∂X ² at the cooling start point was calculated. The amount of cooling water jetted from the cooling unit K3 and the transport speed of the sample K1 were variously changed, and ∂ ² T / ∂X ² at the cooling start point was obtained for each condition.

Cooling unit K in the experimental apparatus shown in FIG.
8 and the steel strip J9 in the experimental apparatus shown in FIG. 8 under the same conditions as the combination of the jetting amount of cooling water and the transport speed of the sample K1.
The experiment was conducted by setting the combination of the conveyance speeds of 1 and the warp amount δ of the steel strip was measured. That is, ∂ ² T / ∂X ² at the cooling start point of sample K1 was calculated from the experimental apparatus shown in FIG. 11, and the amount of warpage of steel strip J9 having the same composition and the same plate thickness as sample K1 was calculated from the experimental apparatus shown in FIG. δ was measured. The steel strip J9 and sample K1 used in the experiment have a plate thickness of 0.8 to
It is 1.2 mm. Pinch roll J5 is not used.

FIG. 12 shows a plot of ∂ ² T / ∂X ² measured using the experimental apparatus of FIG. 11 on the horizontal axis and the amount of warpage δ measured using the experimental apparatus of FIG. 8 on the vertical axis. .

It can be seen that δ rapidly rises when ∂ ² T / ∂X ² exceeds 1000. From this result, in the present invention, ∂ ² T / ∂X ^{2 at} the cooling start point is
It turns out that it should be applied to more than 1000 chillers.

[0042]

According to the present invention, the defective shape of the metal plate due to cooling can be improved. As a result, the following effects can be expected. Yield improves. The transport speed can be increased and the productivity is improved. The handling property in the post-process such as press molding is improved. Temper etc.,
The shape correction step is omitted, and the manufacturing cost can be reduced.
When the metal plate is wound in a coil shape and shipped, the winding shape is improved, and a good impression can be given to consumers.

[Brief description of drawings]

FIG. 1 is a side view showing an embodiment of a metal plate manufacturing apparatus of the present invention.

FIG. 2 is an explanatory diagram showing a temperature change of a metal plate.

FIG. 3 is an explanatory diagram showing changes in a differential coefficient obtained by differentiating the temperature of a metal plate at a position in the transport direction.

FIG. 4 is an explanatory diagram showing changes in a differential coefficient obtained by differentiating the temperature of the metal plate twice at the position in the transport direction.

FIG. 5 is an explanatory diagram showing an example of roll quenching.

FIG. 6 is an explanatory view showing an embodiment when the present invention is applied to roll quench.

FIG. 7 is an explanatory diagram showing a mechanism of a defective shape of a metal plate.

FIG. 8 is an explanatory diagram showing an experimental device for verifying the effects of the present invention.

FIG. 9 is an explanatory diagram showing the definition of a defective shape of a steel strip and a warp amount.

FIG. 10 is a graph showing an example of a relationship between a pinch roll installation position and a warp amount of a steel strip.

FIG. 11 is an explanatory diagram showing an experimental apparatus for measuring ∂ ² T / ∂X ² of a sample.

FIG. 12 is a graph showing an example of the relationship between ∂ ² T / ∂X ² and the amount of warpage δ.

[Explanation of symbols]

1 pinch roll 2 cooling units 3 Syncroll 4 steel strip 5 water surface 6 water-cooled roll 7 Restraint roll 8 aquarium J1 heating furnace J2 coil J3 Looper J4 Cooling device inlet side thermometer J5 pinch roll J6 cooling unit J7 Syncroll J8 water tank J9 steel strip J10 Cooling device outlet thermometer J11 coiler K1 sample K2 heating device K3 cooling unit K4 sample transfer device

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hiroshi Sawada             1-2-1, Marunouchi, Chiyoda-ku, Tokyo             Main Steel Pipe Co., Ltd. (72) Inventor Masayuki Yamazaki             1-2-1, Marunouchi, Chiyoda-ku, Tokyo             Main Steel Pipe Co., Ltd. (72) Inventor Kenji Madate             1-2-1, Marunouchi, Chiyoda-ku, Tokyo             Main Steel Pipe Co., Ltd. (72) Inventor Hiroshi Yoshimura             1-2-1, Marunouchi, Chiyoda-ku, Tokyo             Main Steel Pipe Co., Ltd. F-term (reference) 4K032 BA01 CJ00 CM00                 4K037 FF00 FH01 FJ00 FK00 JA01

Claims (5)

[Claims] 1. A method of manufacturing a metal plate in which a running metal plate is cooled by a cooling device, wherein both sides of the metal plate are in a region where compressive stress is generated in the plate width direction due to cooling of the metal plate or a region in the vicinity thereof. A method for manufacturing a metal plate, which is characterized by suppressing out-of-plane deformation by restraining the metal plate. 2. The distance between the position where the compressive stress generated in the width direction of the metal plate is maximized and the position where the metal plate is constrained from both sides of the metal plate in the longitudinal direction of the metal plate is within 0.2 m. The method for manufacturing a metal plate according to claim 1. 3. A metal plate is restrained from out-of-plane deformation by restraining the metal plate from both sides thereof at a position where a differential coefficient obtained by differentiating the temperature of the metal plate twice at a position in the transport direction is 1000 ° C./m ² or more. The method for producing a metal plate according to claim 1, wherein the metal plate is produced. 4. A metal plate restraining device for restraining out-of-plane deformation by restraining a metal plate from both sides thereof at a position within 0.2 m of a cooling start position by a cooling device on a metal plate passing line. An apparatus for manufacturing a metal plate, which is provided. 5. The apparatus for manufacturing a metal plate according to claim 4, wherein the restraint device for the metal plate is a pinch roll.