KR20110072963A - Apparatus for equalizing temperature of hot rolling strip and method thereof - Google Patents

Abstract

PURPOSE: A device and a method for equalizing the temperature of hot rolled steel sheets are provided to rapidly deal with the various temperature conditions of a hot rolled steel sheet using an electric heating device. CONSTITUTION: A device for equalizing the temperature of hot rolled steel sheets comprises a coil box(30), a mandrel(20), and a surface heating unit. The coil box is installed between a roughing mill and a finishing mill and is used as a furnace for maintaining the temperature of a hot rolled steel sheet. The mandrel is installed inside the coil box and winds and unwinds the hot rolled steel sheet. The surface heating unit is installed inside the mandrel in a width direction.

Description

Apparatus for equalizing temperature of hot rolling strip and method

The present invention relates to an apparatus and a method for uniformizing the temperature of a hot rolled steel sheet, and more particularly, to an apparatus and a method for uniformizing the longitudinal temperature of a steel sheet in a hot rolling apparatus having a coil box using a mandrel.

Consistent steel mills produce various types of steel from iron ore as raw materials through a series of processes such as steelmaking-> steelmaking-> continuous casting-> hot rolling. Briefly describing each process, steelmaking is a process of obtaining molten iron by charging hot air from the bottom after charging the ingot-shaped iron ore and coke through the upper part of the blast furnace. It is a process of obtaining molten steel by removing impurities through various stages of component adjustment such as refining.

Continuous casting is a process of continuously cooling and solidifying molten steel in a liquid state through a continuous casting machine in a curved form to obtain an intermediate material such as a slab having a thickness of 250 mm, and hot rolling reheats the intermediate material to a high temperature of 1100 to 1300 ° C. After the rough rolling and finishing rolling, the final rolling process to the thickness and width desired by the customer. When more excellent quality is required, such as automotive steel sheets, a cold rolled and plated process may be performed with a hot rolled steel sheet. However, a basic steelmaking process includes the steelmaking, steelmaking, continuous casting, and hot rolling.

Minimill process was developed to improve efficiency by improving the traditional steelmaking process described above. The mini mill uses molten steel produced by dissolving scrap metal in an electric furnace, so it has excellent resource recycling ability. The product is continuously hot rolled to a thin slab of 50 to 100 mm produced through a continuous casting machine. Production facilities are not only compact but also highly productive. Difficult to control the composition of the steel sheet is difficult to produce a variety of disadvantages, but is gradually improved by the development of the operation technology.

In a conventional steelmaking process or mini mill process, a mandrel type coil box may be provided in the middle in order to maintain a constant temperature of a steel sheet, especially a longitudinal temperature of a hot rolled steel sheet during hot rolling. The mandrel type coil box is a device that is usually located between rough rolling and finish rolling to allow the hot rolled steel sheet to be wound or unrolled. The use of the mandrel type coil box is determined by the thickness of the hot rolled steel sheet, but in general, when the thickness of the steel sheet is 20mm or less, it is known that the mandrel can be wound in a circular shape.

In the case of using the mandrel, the coil box is also configured to serve as a furnace in order to maintain the temperature of the mandrel and prevent the temperature drop of the inner coil portion. However, even if a heating furnace is installed in order to keep the mandrel at a high temperature, some equipment such as some shafts and support bearings are located outside the heating furnace for rotation of the mandrel, which inevitably causes a temperature drop. As a result, a few turns of the inner circumference of the coil in contact with the mandrel caused a decrease in temperature, resulting in a thickness error or material deviation after finishing rolling.

In addition, the exit temperature of the coil box, that is, the entrance temperature of the finish rolling varies in accordance with the temperature conditions of the finish rolling, there was a problem that the coil box employing only the gas burner can not quickly respond to such various temperature changes.

The present invention was developed to prevent the deterioration of the product quality due to the temperature drop of the mandrel, to improve the structural problems of the coil box to prevent the temperature drop of the mandrel surface and to quickly respond to various temperature conditions of the hot rolled steel sheet Its main purpose is to provide an apparatus and method which can be used.

The temperature homogenizer of the hot rolled steel sheet of the present invention for achieving the above object, continuously cooling the molten steel through a curved continuous casting machine to cast into a slab of a constant thickness, the final slab through the roughing mill and the finish rolling mill In a hot rolling apparatus manufactured from a hot rolled steel sheet having a thickness, a coil box installed between the rough rolling mill and the finish rolling mill to serve as a heating furnace for maintaining a longitudinal temperature of the hot rolled steel sheet, the coil box installed in the coil box and the hot rolled steel sheet The winding and unwinding mandrel and the inside of the mandrel is composed of surface heating means provided along the width direction.

On the other hand, in the method of uniformizing the temperature of the hot rolled steel sheet of the present invention, the molten steel is continuously cooled through a curved continuous casting machine and cast into a slab of a constant thickness, and the slab is converted into a hot rolled steel sheet of final thickness through a roughing mill and a finish rolling mill. In the hot rolling method for manufacturing, the inside of the mandrel 20 to maintain the longitudinal temperature of the hot-rolled steel sheet through a coil box provided between the roughing mill and the finish rolling mill, the coil box is installed in the coil box to wind and unwind the hot rolled steel sheet. It is configured to prevent a temperature drop of the inner coil portion through the surface heating means installed along the width direction.

According to the temperature uniforming device and method according to the present invention configured as described above, the coil inner winding portion is prevented from being supercooled by the mandrel while the hot rolled steel sheet is wound and unrolled in the coil box, so that the temperature of the inner winding portion and outer winding portion of the coil is prevented. Ensures that it is always uniform.

As such, when the temperature difference between the inner and outer windings of the coil is eliminated, the longitudinal temperature of the hot-rolled steel sheet is uniformly maintained, thereby ensuring a uniform material of the final product.

In addition, by installing a heat transfer device that can quickly change the surface temperature of the mandrel, it is possible to respond quickly to various temperature conditions of the hot rolled steel sheet compared to the gas burner-type heating furnace.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Basically, the hot rolling apparatus is configured to continuously cool molten steel through a curved continuous casting machine to cast slabs of a constant thickness, and to manufacture the slabs into hot-rolled steel sheets of final thickness through a rough rolling mill and a finish rolling mill. The hot rolled steel sheet temperature equalizing device according to the present invention can be applied to all types of hot rolling devices employing a mandrel type coil box.

1 and 2 show two representative types of hot rolling apparatuses to which the present invention is applicable.

First, Figure 1 shows a mini-mill apparatus of the ISP (In-line Strip Production) type. The molten steel supplied from the tundish 1 is cast into thin slabs of 50 to 100 mm through the continuous casting machine 2 of the curved type, and the thin slabs are first rolled through the roughing mill 3. The primary rolled hot rolled steel sheet is cut by the cutting unit 4 in the unit of weight corresponding to one coil length, and is uniformly reheated to a temperature of 1100 ° C. or more during the passage through the induction furnace 5.

The reheated hot rolled steel sheet is temporarily wound on the mandrel 20 installed in the coil box 6 to match the rolling speed of the finish rolling mill 7. In order to maintain a constant temperature while winding, the coil box 6 includes a furnace function. The hot rolled steel sheet unwound from the mandrel 20 is rolled to a thickness desired by the consumer in the finishing mill 7 and finally wound up to the down coiler 8.

2 shows a hot rolling apparatus employing a Steckel finish mill capable of reversibly finishing rolling. A slab of about 250 mm is continuously cast through a continuous casting machine, not shown, and the slab is reheated to 1100 ° C. or more in the heating furnace 10, and then the surface scale is removed in the scale breaker 11. The slab from which the surface scale has been removed is first rolled while passing through the roughing mill 12, cut by the cutter 13 in units of weight corresponding to one coil length, and then the mandrel 20 in the coil box 15. ) Is wound up.

As the finish rolling mill 14, since a stake finish rolling mill capable of rolling in both the forward and reverse directions is used, the coil box 15 is provided at both front and rear of the finish rolling mill 14. The hot rolled steel sheet is repeatedly wound and unrolled between the pair of coil boxes 15, rolled to the desired thickness by the finishing mill 14, and finally wound up to the down coiler 16.

As described above, the hot rolling apparatus shown in FIGS. 1 and 2 has a different surface in that it uses a mini mill facility and a steak finish rolling mill, but a mandrel type coil box for winding a hot rolled steel sheet between the rough rolling mill and the finish rolling mill. Is common in that it is used. In addition to the two cases above, the hot rolled steel sheet temperature equalization device according to the present invention can be applied to various types of hot rolling devices employing a mandrel type coil box.

3 is a cross-sectional view showing a mandrel installed in a coil box. The mandrel 20 is rotatably mounted in the furnace body of the coil box 30. The inside of the coil box 30 is heated to maintain a constant temperature of the coil to be wound. As shown in FIG. 3, most of the configuration of the mandrel 20 is located inside the furnace body of the coil box 30, but in order for the mandrel 20 to be rotatably mounted, the rotating shaft 21 of the mandrel 20 is provided. ) Or the support bearing 22 is located outside the coil box 30.

As such, the surface temperature of the mandrel 20 is inevitably reduced due to some facilities located outside the coil box 30, and thus the temperature of the inner circle of the coil contacting the mandrel 20 is also increased. As it falls, a temperature deviation occurs in the longitudinal direction of the hot rolled steel sheet. As described above, such a temperature deviation affects the post-process finishing rolling to cause thickness and material errors of the final product.

4 shows the longitudinal temperature distribution (FET) of the hot rolled steel sheet at the exit side of the mandrel type coil box and the longitudinal temperature distribution (FDT) of the hot rolled steel sheet at the exit side of the finish mill. As shown in Figure 4, the temperature deviation occurs in the longitudinal direction of the hot rolled steel sheet constituting one coil, and the temperature drop of the mandrel installed in the coil box described above is pointed as one of the main causes.

The temperature uniforming device of the hot rolled steel sheet according to the present invention was developed to solve the above problems, and as shown in FIG. 5, continuously cooling the molten steel through a continuous casting machine of a curved type to cast into slabs having a constant thickness. In the hot rolling device for manufacturing the slab into a hot rolled steel sheet of the final thickness through the roughing mill and the finish rolling mill, a coil which is installed between the roughing mill and the finish rolling mill to serve as a heating furnace to maintain the longitudinal temperature of the hot rolled steel sheet The box 30, the coil box 30 is provided with a mandrel 20 for winding and unwinding the hot rolled steel sheet and the surface heating means installed in the width direction of the mandrel 20.

The surface heating means includes a heating part 43 extending along the width direction of the mandrel surface in the mandrel 20, and a power supply line extending from the heating part 43 to the outside of the mandrel 20. (42), a control unit for outputting a signal for controlling the amount of power supplied to the power supply unit 41 and the heating unit 43 for supplying power for heating to the heating unit 43 through the power supply line 42 It consists of 40.

The heating unit 43 is composed of a heat transfer device for converting electricity, such as chrome wire. The heat transfer device can rapidly change the temperature compared to the coil box using the gas burner method, and can quickly respond to various temperature conditions of the hot rolled steel sheet. In addition, the heating unit 43 is installed under the surface of the mandrel 20 in consideration of thermal efficiency, and is installed so as not to rotate together with the mandrel 20 to uniformly transfer heat to the entire cylindrical mandrel surface. It is preferable to be.

The power supply line 42 penetrates the inside of the rotating shaft 21 of the mandrel 20 and extends outside the furnace body of the coil box 30 to be connected to the power supply 41. At this time, the rotation shaft 21 of the mandrel 20 is always rotated in the process of winding and unwinding coil power supply line 42 should be installed so as not to interfere with the rotation of the shaft. To this end, a slip ring 44 is additionally installed at one side of the rotating shaft 21. The slip ring 44 is a metal ring for supplying or drawing current to the rotor windings of an electric motor and a generator, such as wrought iron, bronze, and brass.

The power supply unit 41 may be an external power supply, or a built-in power supply such as a battery may be used. The control unit 40 calculates the heating amount based on the temperature distribution of the coil to be wound, and accordingly outputs a control signal that can supply the required power. For accurate control, the surface heating means further includes a thermometer 45 measuring the surface temperature of the mandrel 20 in real time, and the controller 40 inputs the temperature value measured from the thermometer 45. And it may be configured to control the amount of power supplied to the heating unit 43 in accordance with this temperature value.

In the method of uniformizing the temperature of a hot rolled steel sheet according to the present invention, the molten steel is continuously cooled through a curved continuous casting machine to cast into slabs having a constant thickness, and the slabs are manufactured into hot rolled steel sheets having a final thickness through a rough rolling mill and a finish rolling mill. In the hot rolling method, the mandrel for maintaining the longitudinal temperature of the hot-rolled steel sheet through the coil box 30 provided between the roughing mill and the finish rolling mill, which is installed in the coil box 30 to wind and unwind the hot rolled steel sheet ( 20) is configured to prevent a temperature drop of the inner coil portion of the coil through surface heating means installed along the width direction thereof.

The surface heating means is composed of the heating unit 43, the power supply line 42, the power supply unit 41, the control unit 40 as described above with reference to FIG. The surface heating means compensates for the unavoidable temperature drop caused by some equipment of the mandrel 20 located outside the coil box, thereby reducing the temperature deviation of the inner and outer parts of the coil.

1 shows a first embodiment of a hot rolling apparatus according to the present invention;

Figure 2 shows a second embodiment of a hot rolling apparatus according to the present invention.

3 illustrates a typical mandrel device.

4 is a graph showing a hot rolling temperature distribution.

5 shows a mandrel device according to the invention.

[Description of Reference Numerals]

20: Mandrel 21: rotating shaft

22: support bearing 30: coil box

40: control unit 41: power supply unit

42: power supply line 43: heating

44: slip ring 45: thermometer

Claims (7)

In the hot rolling apparatus for continuously cooling the molten steel through a curved continuous casting machine to cast into a slab of a constant thickness, the slab is produced into a hot rolled steel sheet of the final thickness through a rough mill and a finish rolling mill, Coil box 30 installed between the roughing mill and the finish rolling mill to serve as a heating furnace for maintaining the longitudinal temperature of the hot rolled steel sheet, the mandrel 20 installed in the coil box 30 to wind and unwind the hot rolled steel sheet And a surface heating means installed in the mandrel 20 along the width direction thereof. The method according to claim 1, The thin slab manufactured by the curved continuous casting machine is continuously rolled through the roughing mill, the temperature of the hot rolled steel sheet, characterized in that the induction heating furnace for uniformly heating the hot-rolled steel sheet is installed between the roughing mill and the finish rolling mill Homogenizer. The method according to claim 1, The finish rolling mill is a Steckel finish mill (Steckel finish mill) that can be reversibly rolled, the coil box (30) is a temperature uniformizing device of the hot rolled steel sheet, characterized in that installed on both sides of the Stekel hot rolling mill. The method according to any one of claims 1 to 3, The surface heating means includes a heating part 43 extending along the width direction of the mandrel surface in the mandrel 20, and a power supply line extending from the heating part 43 to the outside of the mandrel 20. (42), a control unit for outputting a signal for controlling the amount of power supplied to the power supply unit 41 and the heating unit 43 for supplying power for heating to the heating unit 43 through the power supply line 42 Temperature homogenizer of the hot-rolled steel sheet, characterized in that consisting of (40). The method according to claim 4, The surface heating means further includes a slip ring 44 installed at one side of the shaft of the mandrel 20 to allow the power supply line 42 to be extended outward from the rotating mandrel 20. Temperature uniformity device of a hot rolled steel sheet, characterized in that. The method according to claim 4, The surface heating means further comprises a thermometer 45 for measuring the surface temperature of the mandrel 20 in real time, the control unit 40 receives the temperature value measured from the thermometer 44, this temperature The temperature uniformity device of the hot rolled steel sheet, characterized in that for controlling the amount of power supplied to the heating unit 43 according to the value. In the hot rolling method of continuously cooling the molten steel through a curved continuous casting machine to cast into a slab of a constant thickness, the slab is produced into a hot rolled steel sheet of the final thickness through a roughing mill and a finish rolling mill, Maintains the longitudinal temperature of the hot rolled steel sheet through the coil box 30 installed between the roughing mill and the finish rolling mill, and is installed in the coil box 30 and inside the mandrel 20 which winds and unwinds the hot rolled steel sheet. A method of uniformizing the temperature of a hot rolled steel sheet, characterized in that the temperature of the coil inner portion is prevented from dropping through the surface heating means installed along the width direction.

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