JPH06339704A - Joining method of steel slab in continuous hot rolling - Google Patents

Abstract

(57) [Summary] [Structure] The joining area between the steel strips is gradually increased by abutting the rear end of the preceding steel strip and the leading end of the subsequent steel strip that follows and pressing while heating. After carrying out the joining process, the joining surface pressure required for joining the steel slabs in feeding to the finishing rolling mill group for continuous hot rolling is calculated in advance and calculated from this joining surface pressure. The steel piece is pressed based on the applied load pattern. [Effect] It is possible to obtain a good joint by avoiding a joint failure caused by a spark, a material burn-through, or the like that occurs when the ends of the steel pieces are butted against each other.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a joining method suitable for joining steel pieces such as sheet bars, slabs, billets or blooms when continuously rolling several or dozens of steel pieces. It is about the method.

[0002]

2. Description of the Related Art Conventionally, in a hot rolling line for billets, the billets to be rolled are individually heated, rough-rolled and finish-rolled into hot-rolled sheets having a desired thickness. In such a rolling method, stoppage of the line due to defective biting of the rolled material is unavoidable in finish rolling, and there is a significant disadvantage that the yield is reduced due to defective shape of the leading end and the trailing end of the rolled material.

For this reason, recently, a rolling system has been adopted in which the rear end portion and the front end portion of the steel pieces to be rolled are joined prior to the finish rolling, and this is continuously supplied to the hot rolling line for rolling. It's starting to happen. Reference is made to JP-A-61-144203 as prior art regarding this point.

The technique disclosed in the above-mentioned Japanese Patent Laid-Open No. 61-144203 is such that a steel piece that is conveyed first (hereinafter referred to as a preceding steel piece) and a steel piece that is conveyed subsequently. (Less than,
The leading end of a trailing steel piece) is butted over the entire surface and both ends in the width direction thereof are pre-bonded and rolling is performed while maintaining this state. However, this technique requires a long joining time in order to give a sufficient joining strength to the pre-joint portion, which is disadvantageous in that the line is extended.

The inventors of the present invention have attempted to solve such a problem by alternating the rear end portion of the preceding steel piece and the front end portion of the following steel piece so that the steel piece penetrates in that region in the thickness direction of the steel piece. We have developed a joining method consisting of a combination of heating and pressing, in which a magnetic field is applied and the joint surface is heated and pressed by the induced current induced by this alternating magnetic field.
No. 109 and No. 4-89110. With the development of this joining method, the joining work has become quicker and easier than ever before.

[0006]

By the way, the above-mentioned joining method still has the following problems to be solved. That is, at the beginning of the joining process involving heating and pressing of the steel billet, the contact width of the preceding steel billet and the trailing steel billet is 10 to 20.
Since it is very narrow, it has the disadvantages that if there is a deviation in the longitudinal direction of the steel slab, poor contact may occur and the contact width at both ends of the steel slab may differ. Here, poor contact of the steel pieces causes sparks, and the material at the planned joining portion scatters or melts down, which makes joining very difficult. Also, if there is a difference in the contact width at both ends of the width direction of the steel slab, the heating rate will be different at each part, so partial burn through will occur before joining is completed, which will lead to sparking. . When the steel pieces have been joined to some extent, sparks do not occur immediately even if there is material burn-through, but there is a gap in the burn-through area, so no induction current flows especially when joining steel pieces that employ the induction heating method. Since the portion also appears, the desired contact width cannot be obtained, and the induced current continues to flow in the same portion, so that the material starts to burn through from the already joined portion.

It is an object of the present invention to propose a new joining method capable of solving the above-mentioned problems that occur when joining steel pieces to each other.

[0008]

SUMMARY OF THE INVENTION According to the present invention, at least the width direction of a steel strip is abutted on each of the rear end portion of the preceding steel strip and the leading end portion of the succeeding steel strip that follows the steel strip. After performing a cutting process in which both ends contact each other, the steel pieces are butted at their ends and pressed while heating to gradually increase the joint area between the steel pieces. When the steel pieces are fed to the machine group and continuously hot-rolled, the joining surface pressure required for joining the steel pieces is obtained in advance, and the steel pieces are pressed based on the load pattern calculated from this joining surface pressure. A method of joining steel slabs in continuous hot rolling, characterized by
In particular, when pressing the steel slab, the joining surface pressure obtained from the actual load is measured, and this joining surface pressure is successively compared with the preset joining surface pressure obtained in advance so that It is desirable to control the pressing load.

Now, FIG. 1 shows the structure of equipment suitable for carrying out the present invention. In FIG. 1, 1 is a cutting means such as a drum shear, and this cutting means 1 is as shown in FIG. Then, a cutting process is performed in which at least both ends in the width direction of the steel piece are brought into contact with the rear end portion of the preceding steel piece A and the front end portion of the following steel piece B in a state where the steel pieces are abutted against each other.

2 is obtained by bringing the steel pieces A and B into contact with each other at the cut surface and pressing them while heating.
The joining means for joining the steel pieces to each other by gradually enlarging the joining area of the steel pieces as shown in FIG. 2, the joining means 2 is not shown in detail in the drawing, but is heated to a predetermined temperature range in a short time, for example. A possible alternating magnetic field generator (of a mechanism in which an alternating magnetic field penetrating in the thickness direction of the steel slab is applied and heated by an induced current induced by this, see JP-A-4-89120) and the steel slabs A and B. Each of them is composed of a plurality of sets of pressing pinch rolls which are sandwiched vertically.

Reference numeral 3 is a scale breaker for descaling the joined steel pieces A and B over their entire length.
4 is a rolling mill group for performing hot finish rolling on the joined steel pieces from which scale has been removed.

The joining process of the preceding steel slab A and the following steel slab B and the subsequent hot finish rolling are carried out according to the following procedure.

On each of the steel strips A and B that have undergone rough rolling,
Using the cutting means 1, the steel pieces are cut into a flat shape such that at least both ends in the width direction are in contact with each other in the abutting state, and then the joining means 2 is used to cut the steel pieces A and B. As shown in FIG. 3, the joining area of the steel pieces is gradually expanded by bringing them into contact with each other and pressing them while heating them so that the entire area in the width direction or a predetermined joining length W is obtained. After joining and passing through the scale breaker 3 for removing the surface scale, it is fed to the rolling mill group 4 to perform hot finish rolling.

[0014]

[Operation] The method of joining the preceding steel piece and the following steel piece at least at both ends in the width direction is an extremely effective means in terms of shortening the joining time, but depending on the situation of the butting of the steel pieces, poor joining may occur. As described above, it is easy to generate.

In order to prevent sparks and material burn-through, which are problems in joining steel slabs, it is necessary to ensure that the materials are brought into contact with each other at the intended joining portion and that the intended joining portion is heated more than necessary. It is effective to increase the load related to the pressing of the steel slab. Therefore, in the present invention, the joint surface pressure required at the time of joining the steel slabs is obtained in advance and calculated from this joint surface pressure. The steel slab was pressed based on the load pattern. It has been clarified that the joining surface pressure required for joining the steel pieces is about 0.5 to 1.5 kgf / mm ² , and even when joining the steel pieces according to the present invention, the joining surface pressure should be within the above range. .

When the joining surface pressure required for joining the steel pieces is obtained in advance and the steel pieces are pressed based on the load pattern calculated from the joining surface pressure, the intended joining portion is targeted due to disturbance. When the temperature becomes higher than the temperature, the deformation resistance of such a portion becomes small, so that the contact area increases in an extremely short time.

The load pattern when joining steel pieces according to the present invention is as follows:
It may be given as a function of the pressing time or the pressing amount from the optimum bonding surface pressure at the time of bonding, which has been obtained as a past record, in consideration of the plate thickness, the plate width, the bonding length, the bonding area and the like.

If the steel slab is pressed based on the load pattern given in the above manner, the occurrence of sparks and the like will be greatly reduced. However, when the actual joint surface pressure is calculated based on the joint length and plate thickness of the steel slab or the actual load simultaneously with such an operation, the actual joint surface pressure may not always match the set surface pressure. Therefore, in the present invention, FIG.
The pressing load is controlled so that the actual joint surface pressure becomes the set joint surface pressure in accordance with the procedure shown in.

Table 1 shows the results of trial and error of the set joint surface pressures for various materials having a plate thickness of 28 mm and a plate width of 1000 mm.

[Table 1]

According to Table 1, the range of the optimum joining surface pressure for each steel type is slightly wide, but this is because the deformation resistance changes greatly with a slight temperature change near the melting point when joining the steel pieces. It is thought that this is the result.

[0021]

[Embodiment] Based on the results shown in Table 1 so that the end shape of the steel piece is shaped as shown in FIG. 2 and the target welding length is 300 mm on one side, the steel piece is joined by load control in an actual machine. Conducted (set joint surface pressure was set to an intermediate value between the values of the respective steel types in Table 1) The joint situation at that time was investigated.

Heating conditions, induction heating method Heating temperature: No.1 (1480 ° C), No.2 (1430 ° C), No.3 (1400)
No.4 (1400 ° C), No.5 (1390 ° C), No.6 (1385 ° C) Heating time: No.1 (6 sec), No.2 (6 sec), No.3 (6
sec) No.4 (6 sec), No.5 (6 sec), No.6 (6 sec)

As a result, it was confirmed that, with regard to Nos. 1 to 5, the occurrence of sparks, material burn-through, etc. was quite satisfactory from the initial joining of steel slabs to the completion of joining. For No. 6 stainless steel,
Since the melting point is low and the thermal conductivity is low, the relationship between the joint length and the surface pressure is very likely to change, and the temperature rise tends to be delayed when pressed with the initial load pattern as shown by the broken line in FIG. If the joining is continued, the joining surface pressure largely deviates, and a good joining portion cannot be obtained. Therefore, as shown by the solid line in FIG. 6, the surface pressure was calculated from the measured joint length, the load at the joint length was calculated, and feedback control was performed to sequentially change the load pattern. As a result, the joining situation was advantageously improved.

[0024]

According to the present invention, a good joining portion can be obtained by avoiding a joining failure caused by a spark, a material burn-through, or the like, which occurs when joining ends of steel pieces by abutting. You can

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a steel piece joining facility suitable for carrying out continuous hot rolling.

FIG. 2 is a diagram showing a planar shape at the time of joining steel pieces.

FIG. 3 is an explanatory view of a procedure for joining steel pieces.

FIG. 4 is a diagram showing a procedure for calculating a load pattern.

FIG. 5 is a diagram showing a control procedure of a pressing load.

FIG. 6 is a graph showing the relationship between the bonding surface pressure and the measured bonding length.

[Explanation of symbols]

 1 Cutting Means 2 Joining Means 3 Scale Breaker 4 Finishing Rolling Machine Group A Leading Steel Billet B Trailing Steel Billet

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Norio Takashima, No. 1 Kawasaki-cho, Chuo-ku, Chiba, Chiba Prefecture, Kawasaki Steel Co., Ltd. Chiba Works (72) Takeshi Hirabayashi, No. 1, Kawasaki-cho, Chuo-ku, Chiba, Japan Kawasaki Steel Works Co., Ltd. Chiba Steel Works (72) Inventor Toshinada Takechi 1 Kawasaki-cho, Chuo-ku, Chiba City, Chiba Prefecture Kawasaki Steel Works Chiba Works (72) Inventor Shuji Amana 1 Kawasaki-cho, Chuo-ku, Chiba City Kawasaki Steel Co., Ltd. Chiba Works (72) Inventor Kanji Hayashi 4-22 Kannon Shinmachi, Nishi-ku, Hiroshima City, Hiroshima Prefecture Mitsubishi Heavy Industries, Ltd. Hiroshima Works (72) Inventor Kazuo Morimoto 4 Kannon Shinmachi, Nishi-ku, Hiroshima City, Hiroshima Prefecture 6-22 No. 6 Hiroshima Research Laboratory, Mitsubishi Heavy Industries, Ltd.

Claims (2)

[Claims] 1. A cutting process in which at least both ends in the width direction of the steel piece are brought into contact with each other at the rear end portion of the preceding steel piece and the front end portion of the succeeding steel piece that follows the steel piece in a butted state. Then, the steel pieces are butt-joined at their ends and pressed while heating to gradually increase the joint area between the steel pieces. In continuous hot rolling, the joining surface pressure required for joining the steel pieces is determined in advance, and the steel pieces are pressed based on the load pattern calculated from this joining surface pressure. Method of joining steel billets in hot rolling. 2. The pressure applied to the steel slab is adjusted so that the joint surface pressure obtained from the actual load is measured, and this joint surface pressure is sequentially compared with the preset joint surface pressure to obtain the set joint surface pressure. The bonding method according to claim 1, which is controlled.