JPH07144203A - Method of joining steel slabs - Google Patents

Abstract

(57) [Abstract] [Purpose] When joining steel slabs by induction heating, it enables the joining of wide steel slabs and the efficient welding of narrow steel slabs. [Structure] A plurality of induction heating coils are prepared so that the length of the magnetic pole surface in the direction parallel to the width direction of the billet is the maximum width for actual operation. The arrangement of the induction heating coils in the joining area is adjusted according to the width of the steel pieces to be joined. For example, when the width of the steel pieces 2a and 2b to be joined is less than the maximum width of the magnetic pole surface, one induction heating coil 1a is arranged on the steel piece and the other induction heating coils 1b are arranged.
And the width of the steel piece to be joined exceeds the maximum width of this magnetic pole surface, two or more induction heating coils 1a and 1b are arranged symmetrically close to the steel piece along the width direction of the steel piece. To do.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for joining steel slabs, and more particularly to a method for joining steel slabs utilizing induction heating, and enables the joining of wide steel slabs and the efficient welding of narrow steel slabs. It is intended to propose a method to do.

[0002]

2. Description of the Related Art In recent years, research has been conducted on a technique for joining steel pieces by induction heating. For example, on the entry side of the hot rolling line, the trailing end of the billet to be conveyed (hereinafter referred to as the preceding billet) and the billet to be conveyed following this billet (hereinafter referred to as the trailing billet) It is attempted to join several tips to several tens of rolling materials to the rolling line continuously by induction heating, and thus to solve problems such as line stop and improve yield. There is. Regarding such a joining method, for example, JP-A-62-23
There is a proposal in Japanese Patent No. 4679 and Japanese Patent Laid-Open No. 62-238083. In these methods, the rear end of the preceding steel piece and the tip of the following steel piece are opposed to each other in a non-contact state, and induction heating is arranged so as to sandwich the rear end of the preceding steel piece and the tip of the following steel piece. A medium or high frequency power is supplied to the coil to apply an alternating magnetic field penetrating in the thickness direction of the steel slab, and the steel slab is pressed by induction heating to join the steel slab.

[0003]

When joining steel slabs by induction heating as described above, in order to improve the production efficiency, when aiming at joining in a shorter time, the induction heating coil is inevitable. Although it is necessary to increase the electric power to be applied to the core, the electric power to be applied is limited by the allowable magnetic flux density of the iron core, and even if a grain-oriented silicon steel sheet with excellent magnetization characteristics is used for the iron core, the allowable magnetic flux density is at the saturation point. However, there was a problem that it was difficult to obtain a satisfactory result because the electric power could not be supplied more than that.

Further, when the steel pieces to be joined have a wide width, it is necessary to use an induction heating coil having a large magnetic pole width in order to achieve uniform heating in the width direction of the steel pieces. However, applying a large amount of power proportional to the increased magnetic pole area causes an excessive current to flow in the induction heating coil, and the current causes the induction heating coil to generate Joule heat. In this case, cooling was insufficient, the induction heating coil was overheated, and it was difficult to melt the coil and the like. In addition, due to the limitation of the installation space, when the iron core of the C-shaped frame in which a pair of magnetic poles are connected by the iron core as shown in FIG. As the magnetic flux density becomes locally high at the bent neck part, etc., and melting occurs, it is necessary to take measures such as partially enlarging the cross-sectional area through which the magnetic flux passes, as shown in FIG. However, there was a problem that the iron core became large and it could not be established as equipment due to the balance with the installation space. However, when using a small magnetic pole width, not only uniform heating in the width direction of the billet becomes difficult, but as in the case where it is aimed to join in a short time as described above, There is a problem that the allowable magnetic flux density of the iron core reaches the saturation point.

The above-mentioned problems can be solved, especially in a hot rolling line, by joining the trailing edge of the preceding rolled material and the leading edge of the following rolled material by induction heating at the entrance side of the rolling mill, and then rolling. In order to avoid the increase in construction cost due to the extension of the line and to prevent the temperature drop of the rolled material by joining in a short time, the entire line length and the preceding rolled material are strongly desired. , It is possible to shorten the line length required for joining both steel pieces such as trailing rolled material as much as possible, and from narrow rolled material of about 600 mm to wide rolled material of more than 2000 mm. Up to now, it has been demanded to support the joining of steel strips of all widths.

SUMMARY OF THE INVENTION It is an object of the present invention to propose a method for joining steel pieces which enables wide-width steel pieces and narrow-width steel pieces to be joined with high efficiency in order to advantageously meet the above requirements.

[0007]

[Means for Solving the Problems] Instead of using only one induction heating coil to meet the above-mentioned technical requirements for short-time welding and wide steel billet welding, two or more induction heating coils are used. The present invention, which is addressed by effectively operating the steel sheet, has a rear end portion of a steel piece to be conveyed in advance and a front end portion of a steel piece to be conveyed following the steel piece, and is arranged to face each other with a gap, In a method of applying an alternating magnetic field penetrating the steel piece in the thickness direction by the magnetic pole pair of the induction heating coil arranged to sandwich the rear end portion and the front end portion in the vertical direction to induction-heat the rear end portion and the front end portion, As the above-mentioned induction heating coil, prepare a plurality of coils in which the length in the direction parallel to the width direction of the steel piece on the magnetic pole surface is the maximum width that can be actually operated, and correspond to the width of the steel piece to be joined. Adjust the array of induction heating coils in the joint area DOO is a method of joining the steel pieces characterized by (first invention).

In this case, it is preferable that the induction heating coil is an induction heating coil having a C-shaped iron core in which magnetic pole pairs are connected by an iron core (second invention).

A specific example of the adjustment of the induction heating coil array is as follows. When the width of the steel piece to be joined is less than the maximum width of the magnetic pole surface, one induction heating coil is arranged on the steel piece. If the width of the steel piece to be joined exceeds the maximum width of this magnetic pole surface, retract two or more induction heating coils and place two or more induction heating coils on the steel piece along the width direction of the steel piece. They are arranged symmetrically close to each other (third invention).

Another example of the specific adjustment of the induction heating coil array is that when the width of the steel piece to be joined is less than or equal to the maximum width of this magnetic pole surface, the rear end portion of the steel piece to be conveyed in advance. Further, one piece is arranged at each of the front end portions of the steel pieces that are conveyed following this steel piece (fourth invention).

Further, it is desirable that the joining of the steel pieces as described above is carried out at the entrance side of the hot rolling equipment and the joined steel pieces are subjected to hot rolling (fifth invention).

[0012]

The present invention will be described in more detail below with reference to the drawings. FIG. 1 shows a perspective view of a main part of an example of a joining device used in the joining method of the present invention. In the drawing, 1a and 1b are induction heating coils. A C-type iron core is wound with a coil conductor, and this coil conductor is connected to an AC power source to generate an alternating magnetic field in the gap between the magnetic pole pairs. Induction heating is carried out by carrying the joint portion (coil conductor and power source are not shown). The length (width) of the magnetic poles in the direction parallel to the width direction of the billet depends on the capacity of the power supply that can raise the temperature to the temperature at which the billet can be welded in a few seconds, the size of the power supply facility, and the magnetic flux density that penetrates the iron core. Considering the limit value, melting of coil and iron core, size of induction heating coil and installation space, etc.
The limit is 1000 mm. For this induction heating coil, the length in the direction parallel to the width direction of the billet on the magnetic pole surface is the maximum width that can be actually operated in view of the constraints of the coil installation space and the saturation magnetic flux density. When arranging two of them in opposition to each other and joining at the entrance side of the hot rolling equipment,
It is placed on the traveling carriage 3 that moves in synchronization with the rolling speed so as to follow the movement of the preceding steel piece 2a and the following steel piece 2b. The induction heating coil 1 can move back and forth on the traveling carriage 3 in the width direction of the billet.

When a steel piece (1000 mm or less) having a width narrower than the magnetic pole width is to be welded by using such a welding apparatus, as shown in FIG.
As shown in Fig. 1, one induction heating coil 1a is moved so that the entire width of the steel piece is within the magnetic pole width of the induction heating coil 1a, and an induction current is applied by applying an alternating current to the induction heating coil 1a. , The steel pieces are pressed against each other to join. The other induction heating coil 1b is retracted from the steel piece and no alternating current is applied.

Next, as shown in FIGS. 5 and 6, when joining steel pieces 2c and 2d wider than the magnetic pole width (over 1000 mm), they are symmetrical with respect to the widthwise center of the steel pieces. As described above, the induction heating coils 1a and 1b are arranged close to each other, and an alternating current is applied to both of the induction heating coils 1a and 1b in a state that the entire width of the steel piece is within the magnetic pole width of the induction heating coils 1a and 1b. Induction heating. At this time, the induction heating coil 1
The gap between a and 1b is preferably as small as possible. In this way, when the width of the billet is larger than the width of the magnetic pole, a plurality of induction heating coils are arranged in the width direction and used, so that it is difficult to join the wide billet by a single induction heating coil. Can be done efficiently.

Next, a case of joining steel pieces (1000 mm or less) having a width narrower than the magnetic pole width in a shorter time will be described with reference to FIG. In this case, the induction heating coils 1c and 1d are arranged at the rear end of the preceding steel piece 2e and the front end of the following steel piece 2f, respectively, and an alternating current is applied to both of the induction heating coils 1c and 1d to perform induction heating. Is to do. Thus, Figure 1
Since the magnetic flux penetrating the steel slab is increased compared to the case where the narrow steel slab is induction-heated by one induction heating coil as shown in Fig. 5, it can be heated to a predetermined temperature in a shorter time. Like

When the number of induction heating coils prepared is two, a wide steel piece as shown in FIG.
In order to achieve both the joining and the induction heating / joining by arranging the induction heating coil at each of the ends of the narrow steel strip as shown in FIG. A means for moving in the direction is required. For example, by arranging a sub-carriage for each induction heating coil on the traveling carriage 3 and making the sub-carriage movable in the steel piece longitudinal direction, induction heating on the sub-carriage is possible. The coil may be moved in the longitudinal direction of the billet. As shown in the third induction heating coil 1e in FIG. 7, when the number of prepared induction heating coils is three or more, such a moving means in the longitudinal direction is unnecessary.

If the leading and trailing steel strips have different widths, the induction heating coil arrangement described above may be adjusted based on the width of the narrower steel strip. Good, but if the wider steel strip is wider than the induction heating coil and interferes with the C-shaped iron core, adjust the induction heating coil arrangement based on the width of the wide steel strip. I do.

The present invention is not limited to the matters described so far with reference to the drawings, but various modifications are possible. For example, the induction heating coil is not limited to the one having the C-shaped iron core, but may have the upper and lower individual iron cores as shown in FIG. When the width of the billet exceeds 2000 mm and the gap between the two induction heating coils shown in FIG. 5 becomes large, the induction heating coil shown in FIG. 8 is arranged in this gap. Good.

[0019]

【Example】

Example 1 Using the apparatus shown in FIG. 1, at the entrance side of hot rolling equipment,
Leading steel strip (width 1000 mm, thickness 30 mm) trailing edge and trailing steel strip (width 1000 mm, thickness 30 mm) with a gap of about 5 mm, while guiding at 60 mpm Heating was performed. Here, the magnetic pole size of the induction heating coil is the width
1000 mm, length 240 mm, input power 2 × 10 ⁶ W, frequency 640 Hz, move one induction heating coil so that the whole width of the steel piece is within the magnetic pole width of this induction heating coil. An alternating current was applied to the coil, and the other induction heating coil was retracted from the steel piece and no alternating current was applied. In this way, the temperature before induction heating of the leading and trailing steel slabs is set to 950 ℃ and heated to the target temperature of 1500 ℃, and then the rear end and the tip are pressed against each other with a pressing force of 2.0 kgf / mm ² . Joined by. The time from when the power was turned on to when the billet reached the target temperature was 5 seconds.

Next, joining was performed using wide steel pieces as the preceding steel piece and the following steel piece. Here, the width of the preceding billet is 1900m
The width of the trailing billet was 1900 mm. The thickness of the preceding billet and the thickness of the trailing billet and the size of the temperature induction heating coil before the start of induction heating are the same.

The induction heating coils are arranged so as to be symmetrical with respect to the center of the width direction of the steel piece so that the entire width of the steel piece is within the magnetic pole width of the induction heating coil. Induction heating was performed by applying a current. The power and frequency applied to the coil were the same as above, and the gap between the induction heating coils was 100 mm. The time from when the power was turned on to when the steel billet reached the target temperature was 5 seconds, and good welding was possible over the entire width of the steel billet.

Example 2 Next, when joining a narrow steel piece such as a preceding steel piece (width 1000 mm, thickness: 30 mm) and a trailing steel piece (width: 1000 mm, thickness: 30 mm), two pieces as shown in FIG. Induction heating coils (the size of which is the same as above) were placed at the rear end of the leading steel strip and the tip of the trailing steel strip, respectively, and induction heating was performed by applying an alternating current to the induction heating coil. The electric power applied to the coil, the frequency, the induction heating start temperature and the target heating temperature of the preceding steel piece and the following steel piece were the same as in Example 1. The time from when the power was turned on to when the slab reached the target temperature was 2.5 seconds, and good welding was possible over the entire width of the slab.

[0023]

According to the method for joining steel slabs of the present invention, a plurality of induction heating coils are prepared so that the length of the magnetic pole surface in the direction parallel to the width direction of the slab becomes the maximum width at which the steel sheet can actually be operated. Then, according to the width of the steel piece to be joined, by adjusting the arrangement of the induction heating coil in the joining area,
Steel strips of all widths can be heated and joined in a short time.

[Brief description of drawings]

FIG. 1 is a perspective view of a main part showing an example of a joining device used in a joining method of the present invention.

FIG. 2 is a front view showing an example of an induction heating coil.

FIG. 3 is a front view showing an example of an induction heating coil.

FIG. 4 is a front view of a main part of the joining device shown in FIG.

FIG. 5 is a perspective view of a main part showing another example of the joining device used in the joining method of the present invention.

6 is a front view of a main part of the joining device shown in FIG.

FIG. 7 is a perspective view of a main part showing another example of the joining device used in the joining method of the present invention.

FIG. 8 is a front view showing another example of the induction heating coil.

[Explanation of symbols]

 1a induction heating coil 1b induction heating coil 1c induction heating coil 1d induction heating coil 1e induction heating coil 1f induction heating coil 2a preceding billet 2b trailing billet 2c preceding billet 2d trailing billet 2e preceding billet 2f trailing steel Piece 2g Leading steel piece 2h Trailing steel piece

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Takeshi Hirabayashi 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Kawasaki Steel Co., Ltd. Chiba Works (72) Inventor Hideyuki Nikaido Kawasaki-cho, Chuo-ku, Chiba, Chiba Prefecture Kawasaki Steel Works Co., Ltd. Chiba Steel Works (72) Inventor Shigeru Isoyama 1 Kawasaki-cho, Chuo-ku, Chiba City, Chiba Prefecture Kawasaki Steel Works Co., Ltd. Chiba Steel Works (72) Toshiaki Amagasa, Kawasaki-cho, Chuo-ku, Chiba City Kawasaki Steel Works Co., Ltd. Chiba Steel Works (72) Inventor Kanji Hayashi 4-6-22 Kannon Shinmachi, Nishi-ku, Hiroshima City, Hiroshima Prefecture Mitsubishi Heavy Industries, Ltd. Hiroshima Works (72) Inventor Kazuo Morimoto 4-chome Kannon Shinmachi, Nishi-ku, Hiroshima City, Hiroshima Prefecture 6-22 No. 22 Hiroshima Research Laboratory, Mitsubishi Heavy Industries (72) Inventor Yoshinori Mito 4-6-2 Kannon Shinmachi, Nishi-ku, Hiroshima City, Hiroshima Prefecture No. 2 Mitsubishi Heavy Industries, Ltd. Hiroshima Works (72) Inventor Gakuo Hashimoto 8-1-1 Tsukaguchi Honcho, Amagasaki City, Hyogo Prefecture Sanryo Electric Co., Ltd. Itami Works (72) Hideo Sakamoto Tsukaguchi Honcho, Amagasaki City, Hyogo Prefecture 8-1, 1-1 Sanryo Electric Co., Ltd. Itami Works (72) Inventor Fumihiro Maeda 8-1-1, Tsukaguchihonmachi, Amagasaki City, Hyogo Prefecture Sanryo Electric Co., Ltd. Itami Works

Claims (5)

[Claims] 1. A rear end portion of a steel piece to be conveyed in advance and a front end portion of a steel piece to be conveyed following the steel piece are arranged to face each other with a gap, and the rear end portion and the front end portion are arranged. In the method of applying an alternating magnetic field penetrating a steel slab in the thickness direction by the magnetic pole pair of the induction heating coil which is sandwiched between the upper and lower sides to induction-heat the rear end portion and the front end portion and to join them, Prepare a plurality of strips whose length in the direction parallel to the width direction of the billet is the maximum width that can be actually operated. Induction heating coil in the joining area corresponding to the width of the billet to be joined. A method for joining steel slabs, the method comprising adjusting the arrangement of. 2. The method for joining steel pieces according to claim 1, wherein the induction heating coil is an induction heating coil having a C-shaped iron core formed by connecting magnetic pole pairs with an iron core. 3. The induction heating coil array is adjusted by arranging one induction heating coil on the steel piece when the width of the steel piece to be joined is equal to or less than the maximum width of the magnetic pole surface and then other induction heating coils are arranged. When the coil is retracted and the width of the steel piece to be joined exceeds the maximum width of this magnetic pole surface, two or more induction heating coils are arranged symmetrically close to the steel piece along the width direction of the steel piece. The method for joining steel pieces according to claim 1 or 2, wherein 4. The induction heating coil array is adjusted when the width of the steel piece to be joined is less than or equal to the maximum width of the magnetic pole face.
The method for joining steel pieces according to claim 1 or 2, wherein one piece is arranged at each of a rear end portion of the steel piece that is conveyed in advance and a tip end portion of the steel piece that is conveyed following this steel piece. . 5. A steel slab is joined at the entrance side of a hot rolling facility, and the joined steel slab is subjected to hot rolling.
The method for joining steel pieces according to 3 or 4.