JP2002066604A - Hot rolling apparatus and hot rolling method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for reducing the time for connecting crude bars preventing a drop of a temperature of the bar. SOLUTION: A roughing mill 1, a solenoid-type induction heater 3, a connector 4 and a finishing mill 5 are disposed in such an order as this sequence. Temperatures of a top edge and a bottom edge of the crude bar are raised to around the required temperature by the solenoid-type induction heater 3 on the way being carried to the finishing mill 5 from the roughing mill 1. Thus, a heating time at a connecting unit 4 is reduced as well as a heat loss of the crude bar is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hot rolling facility for performing continuous hot rolling by joining front and rear ends of two or more coarse bars, and a hot rolling method using the hot rolling facility. It is about.

[0002]

2. Description of the Related Art In hot rolling in which a slab is rolled into a hot-rolled steel strip, conventionally, batch rolling in which slabs are rolled one by one has been performed. However, in this batch rolling, there is a problem that a line stop occurs due to a poor biting when a material to be rolled bites into a rolling mill. In addition, there is also a problem that the shape and material are defective due to the unrestricted front and rear ends of the material to be rolled, thereby lowering the yield.

Accordingly, in recent years, a continuous hot rolling method has been developed in which the front and rear ends of a plurality of coarse bars are sequentially joined to form a continuous coarse bar and finish rolling is continuously performed. Various proposals have been made on a method of joining a rough bar, which is an essential and key technology for such a continuous hot rolling method. As a representative example thereof, JP-A-4-8910
No. 9 discloses that the leading end and the trailing end of each coarse bar are brought into contact,
There is disclosed a technique in which an alternating magnetic field that penetrates a coarse bar in a thickness direction is applied to heat the coarse bar, and the coarse bar is joined by pressing the coarse bar.

FIG. 5 shows this technique. In FIG. 5, 6
Is a transverse flux type induction heating device, 7 is a clamp, 8a is a preceding coarse bar, and 8b is a following coarse bar. Transverse flux type induction heating device 6
Heats the rear end of the preceding coarse bar 8a and the front end of the following coarse bar 8b. The heated portions are pressed and joined. During heating and pressing, the coarse bars 8a and 8b are clamped.
Supported by

As a technique similar to the present invention, Japanese Patent Application Laid-Open No. Hei 10-244301 discloses a hot rolling facility in which a rough rolling mill, a joining device, an induction heating device, and a finish rolling mill are installed in this order, and The rolling method used is disclosed.

[0006]

However, the technique disclosed in Japanese Patent Laid-Open No. 4-89109 has the following problems. That is, since the joining of the rough bar is performed by heating and pressure welding, the rough bar stops during that time, and the temperature of the rough bar drops. For this reason, problems such as an increase in the finish rolling load and difficulty in securing the rolling finish temperature occur. Therefore, there is a need for a technique for reducing the joining time.

[0007] In the technique disclosed in Japanese Patent Application Laid-Open No. 10-244301, an induction heating device is provided behind a joining device, and is not at all useful for shortening the joining time.
This prior art aims at temperature compensation of the cold parts before and after the joint. The low-temperature portion is caused by the clamp at the time of joining and the fact that the temperature at the front and rear ends of the rough bar is lower than the other portions.

These low-temperature portions exist immediately before and immediately after the joint, and it is extremely difficult to heat only the low-temperature portion so as not to affect the joint. Once the joint is heated, it is more likely that it will break during finish rolling. Conversely, if the low-temperature portion is not heated before finish rolling, the material will deteriorate there.

The present invention has been made in view of such circumstances, and it is an object of the present invention to provide a method for shortening a time required for joining a rough bar and preventing a temperature of the rough bar from lowering.

[0010]

A first means for solving the above problems is a rough rolling mill for rolling a slab into a rough bar, and a finish rolling for rolling a rough bar into a hot rolled steel strip. In the hot rolling equipment having a mill, between the rough rolling mill and the finish rolling mill, an induction heating device that heats the rough bar over the entire width direction, and the rear end of the preceding coarse bar and the leading end of the subsequent coarse bar. A hot-rolling facility (Claim 1) characterized in that joining devices for pressing the two after heating are arranged in this order.

In this means, as means for joining the coarse bar, after heating the rear end of the preceding coarse bar and the front end of the following coarse bar as disclosed in Japanese Patent Application Laid-Open No. 4-89109, A joining device for pressing the both is provided. And in order to shorten the joining time in this joining device, before this joining device, an induction heating device for heating the rough bar over the entire width direction is provided.
The portion to be joined of the coarse bar is pre-heated. Thereby, the heating time in the joining device is shortened, so that the time required for the joining is also shortened, and a decrease in the temperature of the rough bar can be prevented.

A second means for solving the above-mentioned problem is as follows.
The first means, wherein the induction heating device for heating the rough bar over the entire width direction is a solenoid-type induction heating device (Claim 2).

As the induction heating method for heating a plate-like object such as a coarse bar, there are known two types, a solenoid type and a transverse flux type. Among them, the plate thickness of the coarse bar is 30 to 50 mm. The heating efficiency is higher for the solenoid type. Also, due to the simplicity of the inductor, the solenoid-type induction heating device 3 is generally less expensive.
From the above, in this means, a solenoid-type induction heating device is used as the induction heating device.

A third means for solving the above-mentioned problem is as follows.
The first means or the second means, wherein a plurality of the induction heating devices are arranged one by one between each of the transport rollers (Claim 3).

The longer the length of the induction heating device is, the higher the heating capacity is. However, if the length is too long, the leading end of the coarse bar hangs down, and the induction heating device may be damaged. In this means, since the induction heating device is divided into a plurality of units and one unit is arranged between each of the transport rollers, the above-described problem occurs even if the induction heating device is made longer as a whole. Can be prevented.

A fourth means for solving the above-mentioned problem is as follows.
Any one of the first to third means, wherein the induction heating device is located closest to the joining device;
The leading and trailing ends of the coarse bar to be joined are 10
Characterized by being able to pass in less than a second (Claim 4)
It is.

As described above, if the time required for the joint to reach the joining device after the joint is heated by the induction heating device is long, the temperature of the joint heated by the induction heating device decreases, and The effect is lost. According to the results of the experiments by the inventors, the portion passed through the induction heating device was 10%.
It was found that if the temperature could reach the joining device within seconds, the degree of temperature decrease was small, and it was particularly effective in shortening the joining time in the joining device.

A fifth means for solving the above problem is as follows.
A hot rolling method using the hot rolling equipment according to any one of the first to fourth means, wherein a rear end of a preceding coarse bar and a front end of a subsequent coarse bar are guided by the induction heating device. A hot rolling method is characterized in that after heating, the rear end of the preceding coarse bar and the front end of the following coarse bar are joined by the joining device (claim 5).

As described above, according to this means, since the portion to be joined is heated in advance by the induction heating device, the joining time in the joining device can be shortened, and as a result,
A decrease in the temperature of the rough bar caused by the joining can be reduced.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows Embodiment 1 of the present invention.
It is a figure which shows the outline | summary of arrangement | positioning of the hot rolling equipment which is an example. In FIG. 1, 1 is a rough rolling machine, 2 is a conveying roller, 3 is a solenoid type induction heating device, 4 is a joining machine, and 5 is a finishing mill. In the present embodiment, as shown in FIG.
Rough rolling mill 1, solenoid type induction heating device 3, joining machine 4,
The finishing mills 5 are arranged in this order.

The joining device 4 employs a method including heating of a rough bar, such as heating and pressure welding. For example, as described in Japanese Patent Application Laid-Open No. 4-89109 shown in FIG. 5, the rear end of the preceding coarse bar 8a and the front end of the subsequent coarse bar 8b are connected to the transverse flux type induction heating device 6. A method in which the rough bars 8a and 8b are gripped by the clamp 7 and pressed against each other while heating is used can be used.

In such a bonding method, the rear end of the rough bar 8a and the front end of the rough bar 8b must be kept in the bonding device 4 during the heating and pressing, and the heat during the bonding time is not secured. Loss is a problem. Therefore, in the hot rolling equipment of the present embodiment, the solenoid-type induction heating device 3 is provided before the joining device 4.
Is installed. The leading and trailing ends of the coarse bar are heated to near the required temperature by the solenoid type induction heating device 3 while being transported from the rough rolling mill 1 to the finishing rolling mill 5. Thus, the heat loss in the rough bars 8a and 8b can be reduced by shortening the heating time in the joining device 4.

In the hot rolling method of the present invention, the rough bars 8a,
Since the heating device 8b is heated during conveyance, it is preferable that the heating device installed on the entry side of the joining device 4 has a high temperature rising rate and high heating efficiency. An induction heating device is used as a heating method with the highest temperature rising rate. As an induction heating method for heating a plate-like object such as a rough bar, two types, a solenoid type and a transverse flux type, are known. Among them, the solenoid type has higher heating efficiency when compared with the performance of heating a coarse bar having a thickness of 30 to 50 mm. Also, due to the simplicity of the inductor, the solenoid-type induction heating device 3 is generally less expensive. From the above, the solenoid-type induction heating device 3 is employed in the hot rolling equipment of the present embodiment.

Before entering the joining apparatus 4, in order to secure a required amount of temperature increase, the inductor of the solenoid type induction heating apparatus 3 must be made sufficiently long to increase the heating time. However, the length of the heating device cannot be unnecessarily lengthened. If the heating device is lengthened unnecessarily,
This is because the leading end or the trailing end of the rough bar 8 may bend between the transport rollers 2 and come into contact with the solenoid-type induction heating device 3 to damage the inductor, as shown in FIG. Therefore, in the hot rolling equipment of the present invention, the solenoid-type induction heating device 3 is divided into a plurality, and the transport roller 2 is always sandwiched between them.

Care must be taken when using a solenoid type induction heating device for heating the coarse bar. In the solenoid type induction heating device, the surface effect of the rough bar is intensively heated by the skin effect. Since the heat is quickly dissipated from the hot surface, the rough bar should be joined immediately after the induction heating is completed. It is desirable that the time from the end of heating the coarse bar by the solenoid type induction heating device to the start of the joining be 10 seconds or less. By doing so, Joule heat, which is peculiar to the solenoid type induction heating device and is intensively applied to the surface of the rough bar, can be used for shortening the bonding time.

In the hot rolling equipment of the present invention, the order of the solenoid type induction heating device and the joining device is described in Japanese Patent Application Laid-Open No. H10-2443.
It is the reverse of the equipment described in JP 01. If a portion that becomes a low-temperature portion after joining is heated before joining with the solenoid-type induction heating device, the temperature of the low-temperature portion can be compensated without further heating the joining portion with the solenoid-type induction heating device. Therefore, the present invention is superior.

In the hot rolling method of the present invention, a hot-rolled steel strip is manufactured using the hot rolling equipment described above. The slab is rolled by the rough rolling mill 1 to form a coarse bar, and while being transported to the joining device 4, the rear end of the preceding coarse bar 8a and the front end of the subsequent coarse bar 8b are moved by the solenoid type induction heating device 3 After that, the bonding is performed by the bonding apparatus 4. Since the coarse bar is previously heated by the solenoid-type induction heating device 3, the heating time of the coarse bar by the joining device 6 can be shortened, and the joining time itself is also shortened. The rough bar after joining is rolled by a finish rolling mill 5 into a hot-rolled steel strip in the same manner as ordinary continuous hot rolling.

[0028]

EXAMPLES The effects of the present invention will be described with reference to examples. (Example 1) In the hot rolling equipment of the present example, the capacity
Eight solenoid-type induction heating devices 3 each having a length of 6000 kW and a length of 500 mm in the transport direction are provided, one each being provided between the transport rollers 2. The joining device 4 has a capacity as shown in FIG.
3000kW transverse flux induction heater 6
It has.

Using such a facility, a plate thickness of 40 mm and a width of 12 mm
Two 50 mm coarse bars were joined. Before carrying out the method of the present invention, that is, when the solenoid type induction heating device 3 was not used, the bonding time was about 20 seconds, during which time the temperature of the coarse bar had dropped by about 30 ° C. When the method of the present invention is performed and the rear end of the preceding coarse bar 8a and the front end of the subsequent coarse bar 8b are heated while being conveyed by the solenoid-type induction heating device 3, the joining time is reduced to about 7 seconds. During this time, the temperature drop of the coarse bar was about 10 ° C., and the heat loss was reduced to about one third.

(Example 2) Using the same hot rolling equipment as in Example 1, the relationship between the elapsed time after the completion of heating the coarse bar by the solenoid type induction heating device and the surface temperature of the coarse bar was examined. . The coarse bar used for the test was 30 mm thick and 1000 mm wide.
And a plate with a thickness of 40 mm and a width of 1000 mm. After heating the tip of the coarse bar with a solenoid-type induction heating device, the tip was taken out of the solenoid-type induction heating device and left as it was to measure the surface temperature. FIG. 3 shows the time change of the surface temperature.
Regardless of the thickness, the surface temperature is high immediately after heating,
The surface temperature drops rapidly. Thereafter, the temperature distribution in the plate thickness direction becomes a steady state, and the cooling rate becomes constant.

FIG. 4 schematically shows the temperature distribution in the thickness direction of the rough bar immediately after the induction heating and in the steady state. The switching time from the unsteady state where the surface temperature after the induction heating is high to the steady state is about 10 seconds after the end of the heating. In order to use the amount of heat that is concentrated on the surface layer of the coarse bar, which is unique to the solenoid-type induction heating device, the coarse bar must be heated within 10 seconds after the heating of the coarse bar by the solenoid-type induction heating device. It is desirable to join.

[0032]

As described above, according to the present invention,
The time required for joining the coarse bar is reduced, and the effects of improving productivity and reducing heat loss are obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing an outline of an arrangement of a hot rolling facility which is an example of an embodiment of the present invention.

FIG. 2 is a diagram showing a problem when the length of a solenoid-type induction heating device is long.

FIG. 3 is a diagram showing changes in elapsed time and temperature of a coarse bar after heating by a solenoid-type induction heating device.

FIG. 4 is a diagram schematically showing a temperature distribution in a thickness direction of a rough bar in a state immediately after induction heating and in a steady state.

FIG. 5 is a schematic view showing a conventional bonding apparatus.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Rough rolling machine, 2 ... Conveyance roller, 3 ... Solenoid type induction heating device, 4 ... Joining device, 5 ... Finishing rolling machine, 6 ... Transverse flux type induction heating device, 7 ... Clamp, 8 ... Coarse bar, 8a: preceding coarse bar, 8b: following coarse bar

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Yoichi Honashiki 1-2-1 Marunouchi, Chiyoda-ku, Tokyo F-term in Nihon Kokan Co., Ltd. (Reference) 4E002 AD02 AD04 BD05 CB08

Claims (5)

[Claims] In a hot rolling facility having a rough rolling mill for rolling a slab into a rough bar and a finishing rolling mill for rolling a rough bar into a hot-rolled steel strip, the rough rolling mill and the finish rolling mill In the meantime, an induction heating device that heats the coarse bar over the entire width direction, and a joining device that heats the rear end of the preceding coarse bar and the front end of the following coarse bar and presses them together are arranged in this order. Hot rolling equipment. 2. The hot rolling equipment according to claim 1, wherein the induction heating device that heats the coarse bar over the entire width direction is a solenoid-type induction heating device. 3. The hot rolling equipment according to claim 1, wherein a plurality of the induction heating devices are disposed one by one between the transport rollers. 4. The method according to claim 1, wherein the front and rear ends of the coarse bar to be joined can pass between the induction heating device closest to the joining device and the joining device in less than 10 seconds. The hot rolling equipment according to claim 3. 5. The method according to claim 1, wherein
A hot rolling method using the hot rolling equipment according to the item, after heating the rear end of the preceding coarse bar and the leading end of the subsequent coarse bar in the induction heating device, after the preceding coarse bar A hot rolling method, wherein the end and the leading end of a subsequent rough bar are joined by the joining device.