JP2001179335A - Hot-rolled coil and its treatment method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a hot-rolled coil which is made of 2-3.5 mm thick plate of a high-carbon steel, and is not more than 40 mm in difference between long and short diameters of an inside diameter after the down end conveyance. SOLUTION: The high-carbon steel is wound around the coiler, then held and cooled for 2-4 minutes while being wound around a mandrel. After cooling, it is detached from the mandrel and conveyed. Forced cooling may be substituted for holding and cooling.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a hot-rolled coil and a method for treating the coil. More specifically, the thickness is 2 to 3.5.
The present invention relates to a technology for preventing deformation of the inner diameter of a high carbon steel coil of 1 mm.

[0002]

2. Description of the Related Art After a hot-rolled coil is wound up by a mandrel of a coiler and then conveyed on a coil conveying conveyor in a down-end posture (coil axis is horizontal), there is a tendency that the inner diameter of the coil is deformed to be distorted. is there. In this case, when the steel plate is thick, there is no problem, but when the plate thickness is thin, the deformation is remarkable. In addition, high-carbon steel has a high probability of being re-transformed and deformed due to the effect of the reheating process even after winding is completed.

[0003] If the inner diameter of such a hot-rolled coil is deformed from a circular shape to an elliptical shape, the deformed inner diameter may interfere with the coil rewinding shaft in the next step and be inserted into the rewinding shaft. The problem of becoming difficult arises. In addition, scratches occur during rewinding, which lowers the yield.

In order to solve such a problem, there is a technique of providing a device for correcting the inner diameter of the coil, or providing a device for changing the transfer posture of the coil to an up-end posture (a posture in which the coil axis is vertical). However, it is not preferable to take such a special deformation prevention measure because the cost is increased. Various other improved techniques have also been proposed.

For example, Japanese Unexamined Utility Model Publication No. 1-143609 discloses a technique for preventing deformation of a hot-rolled coil.
A coil that may be deformed is extracted based on the coil deformation amount estimated from the coil plate thickness and the coil winding temperature, and the extracted coil is tilted at an angle of 55 ° to 75 ° of the inclined plate.
A technique has been disclosed in which the apparatus is mounted on a deformation correction table having a pair of inclined plates set within the range described above to prevent deformation. In this technique, it is necessary to extract a coil that may be deformed, prepare a deformation correction table for the coil, and transport the coil on the coil.

Japanese Unexamined Patent Publication (Kokai) No. 61-37647 discloses that a hot coil formed by winding a hot-rolled steel strip is taken out from or taken out of a winding shaft of a coiler, and the center of the hot coil is taken up from the center axis of the hole of the coil. A technology for rotating a coil to prevent deformation is disclosed. In this technique, a high-temperature coil pulled out of a mandrel is rotated around a center axis of a hole of the coil in a transfer device, and it is necessary to provide a special rotating device.

[0007] As a technique which does not use such a special additional device, there is a technique for reducing winding loosening by improving the winding tension. Due to the limitations, it is difficult to improve the winding tension. As another technique, a technique for suppressing retransformation by reducing the winding temperature is conceivable, but reducing the winding temperature leads to an increase in the hardness of the product, and such measures are limited by the needs of customers.

[0008]

SUMMARY OF THE INVENTION The present invention provides a hot-rolling apparatus which can easily and reliably prevent the deformation of the coil inner diameter without using the above-mentioned special deformation preventing device or changing the rolling conditions. It is an object to provide a coil and a processing method thereof. The deformation of the coil inner diameter is evaluated by the difference between the major axis and the minor axis of the inner diameter.

[0009]

According to the present invention, a sheet having a thickness of 2-3.
A hot-rolled coil made of high-carbon steel of 5 mm, cooled on a coiler, and having a difference in major and minor diameters of 40 mm or less after down-end conveyance. If the plate thickness is less than 2 mm, even if it is cooled on the coiler for a long time, deformation of 40 mm or more occurs, so it is excluded. When the plate thickness exceeds 3.5 mm, the effect of cooling on the coiler is not observed, so that the target is set to 3.5 mm or less. In addition, low carbon steel has no problem of deformation due to transformation, and has an advantage when applied to high carbon steel. Here, the high carbon steel is C: 1 to 5.5%.

[0010] In the processing method for obtaining the hot-rolled coil of the present invention, a high carbon steel sheet having a thickness of 2 to 3.5 mm is wound into a coiler, cooled and held while being wound on a mandrel, removed from the mandrel after cooling, and transported This is a method for processing a hot-rolled coil. In this case, the holding and cooling time is preferably set to 2 to 4 minutes, and the forced cooling may be performed instead of the holding and cooling. As the forced cooling, means such as air cooling by a fan or the like, fog cooling, or the like may be used.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventor conducted an operation experiment to obtain a hot-rolled coil having an inner diameter difference of 40 mm or less after down-end conveyance, and obtained the results shown in FIG. As a countermeasure against deformation, after winding the coiler, the coil was cooled without removing the coil from the mandrel. FIG. 1 shows the amount of deformation when holding and cooling in the coiler and when not holding and cooling.

FIG. 1 shows the thickness of a steel strip obtained by winding a steel strip of C: 1.0 to 5.5% at a winding temperature of 480 to 640 ° C. on the abscissa, and the amount of deformation on the ordinate. It is shown for. Here, the deformation amount is the difference between the major and minor diameters of the coil inner diameter (m
m). When the plate thickness is 1.6 mm, the one held in the coiler for 5 minutes is 130 mm in diameter and the deformation is 75 even after 8 minutes.
mm. A plate having a thickness of 2 mm and held for 3 minutes in the coiler had a diameter change amount of 40 mm. Also, with a sheet thickness of 2.6 mm, the deformation amount was 170 mm although it was not held in the coiler,
Although they were 150 mm and 50 mm, the deformation amount was 20 mm and 5 mm in the case where the inside of the coiler was held for 3 minutes. When the plate thickness is 3.2 mm, the deformation amount is 10 mm, 10 mm, and 0 mm.
mm, no change was observed in the amount of deformation even after storage in the lower part of the two-layer stack of coils. Further, the plate thickness is 3.
At 6 mm, the deformation amount was about 5 mm without holding the coiler, and was about 10 mm after being stored in the lower part of the two-tiered stack. When the plate thickness was 5 to 8.5 mm, the deformation amount was 0 to 10 mm.

As described above, in the case of the 2.6 mm-thick material, the deformation of 50 to 170 mm occurs without the holding and cooling according to the present invention, but it is apparent that the holding can be suppressed to 20 mm or less by holding for 3 minutes. Was. Note that the deformation is caused by the weight of the coil, and occurs during transportation from the coiler.
No difference in the amount of deformation was seen at the lower stage. In addition, plate thickness 2mm
If less, it is difficult to prevent deformation by the present invention.

FIG. 2 shows the experimental results of the deformation amount and the cutoff length. When the deformation amount is 20 mm, no scratch is generated. Even if flaws are generated, they are only slightly generated at the end. If the deformation exceeds 50 mm, scratches will occur,
The truncation length increases. Further, a coil rewinding step for deformation correction is required. By suppressing the deformation amount to about 20 mm, truncation due to scratches is shortened by 10 to 30 m. Also, rewinding due to deformation is not required.

[0015]

According to the present invention, after the coil is cooled on the mandrel and extracted and conveyed without using a special device, the high-carbon steel coil having a thickness of 2 to 3.5 mm is conveyed after the down-end convey. It was possible to make the difference between the major and minor diameters of the inner diameter of the sample within 40 mm or less.

[Brief description of the drawings]

FIG. 1 is a graph showing a relationship between a plate thickness and a deformation amount.

FIG. 2 is a graph showing a relationship between a deformation amount and a truncation length.

Claims (4)

[Claims] 1. A hot-rolled coil comprising a high-carbon steel sheet having a thickness of 2 to 3.5 mm, cooled on a coiler, and having a difference in major and minor diameters of the inner diameter after down-end conveyance of 40 mm or less. 2. A hot-rolled coil processing wherein a high-carbon steel sheet having a thickness of 2 to 3.5 mm is wound around a coiler, cooled while holding it around a mandrel, and after cooling, removed from the mandrel and transported. Method. 3. A method for treating a hot-rolled coil, wherein the holding and cooling time is 2 to 4 minutes. 4. The hot-rolled coil processing method according to claim 2, wherein forcible cooling is performed instead of the holding cooling.