JPH0724507A - Method for joining slab in continuous hot rolling - Google Patents

Abstract

PURPOSE:To drastically improve the followup ability of a screw down device which is used for thickness control and to execute stable continuous rolling by restraining rapid fluctuation of interstand tension. CONSTITUTION:At the time of joining by butting the rear end part of a preceding slab 1 and the tip part of the succeeding slab 2 on the inlet side of hot finish rolling equipment, before heating/pressing process for mutually joining each slab, about one of the preceding slab or the succeeding slab, the planar shape in the end part is formed into a symmetrical projecting shape or recessed shape by bordering the center in the width direction and the planar shape in the end part of the other slab is formed into the recessed shape or the projecting shape that is fitted to the projecting or recessed part.

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 pieces such as sheet bars, slabs, billets or blooms, which is convenient for continuously rolling several or dozens of steel pieces. is there.

[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 to finish a hot-rolled sheet having a desired thickness. In such a rolling method, in the finish rolling, line stop due to defective biting of rolling material or defective slip-out is unavoidable, and yield loss due to defective shape of the front and rear ends of the rolling material is also caused. There was a significant disadvantage.

For this reason, recently, a rolling type is adopted in which the rear end and the front end of the steel pieces to be rolled are joined prior to the finish rolling, and this is continuously fed to the hot rolling equipment for rolling. It started to come.

In this regard, the rear end portion of the preceding steel piece and the leading end portion of the following steel piece are cut in parallel with the plate width direction using a shear or the like (cut in a direction orthogonal to the longitudinal direction of the steel piece). ,
A method of joining both steel pieces by plastically deforming them while heating and pressing them has been considered.

By the way, in the above-mentioned method, the temperature of the joint portion of the steel slab becomes higher than that of the peripheral region thereof, so that there are the following problems and the solution thereof has been desired.

1) For example, when performing plate thickness control using a hydraulic pressure reduction device in a rolling process, such a temperature difference causes disturbance and makes it difficult for the device to follow the plate thickness control. 2) It is difficult to carry out stable endless rolling because the leading steel strip and trailing steel strip break apart during rolling due to large fluctuations in the tension between stands.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to propose a joining method capable of carrying out stable continuous hot rolling without the above-mentioned problems caused by the temperature difference between the joined portion of a steel slab and the region excluding it. Is the purpose of.

[0008]

SUMMARY OF THE INVENTION The present invention relates to joining the rear end portion of the preceding steel piece and the leading end portion of the following steel piece by abutting them on the entry side of the hot finish rolling facility. Prior to the heating / pressing treatment for joining the two to each other, the planar shape of the end of one of the preceding steel piece and the following steel piece is formed into a symmetrical convex or concave shape with the center in the plate width direction as a boundary, It is a method for joining steel slabs in continuous hot rolling, characterized in that the planar shape of the other end is formed into a concave shape or a convex shape that matches the convex shape or the concave shape portion.

[0009]

FIG. 1 is a plan view of a V-shaped flat plate in which the rear end of the preceding steel slab 1 is cut off obliquely from the end in the plate width direction toward the center according to the present invention. It shows an example in which the tip of the row steel piece 2 has a planar shape that conforms to the V-shape.

When the end portions of the preceding steel piece 1 and the following steel piece 2 are formed into such a shape (the contact length at the joint portion is increased) and then heated and pressed to join, the temperature of the area is Although it is slightly higher than the temperature of the region, when focusing on the longitudinal direction of the steel slab, the absolute amount of temperature deviation from the peripheral part of the average temperature in the width direction at the joint is the width of the end of the steel slab. Since it can be made smaller than in the case of cutting and heating and pressing in parallel to the direction as shown in FIG. 2, the disturbance due to the temperature difference is reduced, and the follow-up characteristic of the rolling down device can be greatly improved. FIG. 3 shows the average temperature deviation in the plate width direction in the longitudinal direction of a steel slab (sheet bar) joined according to the present invention, and the steel in the state shown in FIG. 2 above in FIG. The average temperature deviation in the plate width direction in the longitudinal direction of the steel pieces when the pieces are joined is shown.

Further, according to the present invention, the planar shape of the joining portion of the steel pieces is symmetrical with respect to the center in the plate width direction, and both steel pieces 1 and 2 are obliquely contacted in a butted state. Therefore, even when joining steel pieces having different deformation resistances, the average deformation resistance in the strip width direction can be gradually changed along the longitudinal direction, which is convenient for rolling (for example, disturbance in strip thickness control). Reduction)
Not only that, the flattening of the temperature distribution in the longitudinal direction of the steel slabs can suppress abrupt changes in the tension between the stands, and the joined steel slabs will not break and separate during rolling.

Here, the above-mentioned average deformation resistance is given when the deformation resistance of the preceding billet is k ₁ , the deformation resistance of the trailing billet is k ₂ , and the average deformation resistance is k _m , w ₀ = w ₁ + w _2. k _m = k ₁ ·
It is represented by w ₁ + k ₂ · w ₂ ) / w ₀ (see FIG. 9).

In the present invention, the case where the end of one steel piece is cut into a V shape and the end of the other steel piece is shaped to conform to the V shape and the steel pieces are joined together has been described. For example, as shown in FIG. 5 (a), the end of one steel piece may be cut into a W shape, and the end of the other steel piece may be shaped into a shape that conforms to this W shape before joining. Well, it may be cut into a U shape as shown in Fig. 5 (b), and one of the ends of one of the steel pieces should be cut so that the temperature in the longitudinal direction of the steel piece does not change abruptly. The shape is particularly limited if the planar shape is bilaterally symmetrical convex or concave with the center in the plate width direction as the boundary and the planar shape of the other end is concave or convex conforming to the convex or concave shape. It is not something that will be done. In the present invention, the angle θ formed by the end face with the width end of the steel slab as a reference is 30 to 70.
It is preferable that the angle is ° (see Fig. 1).

In the planar shape as shown in FIG. 6, the left and right are asymmetrical with respect to the center in the plate width direction, so that the load fluctuation due to the high temperature of the joint portion is biased in the plate width direction. Therefore, it may be a cause of plate meandering, and there is a problem in operation, so it is considered difficult to apply, and therefore a bilaterally symmetrical shape is desirable.

As means for obtaining the above planar shape, shearing, gas cutting, laser fusing, or the like can be applied.

As a heating means for the steel slab, in addition to heating by a burner and high frequency heating by a solenoid type coil,
A so-called transverse heating method (see Japanese Patent Laid-Open No. 4-89109), which uses an alternating magnetic field generating coil to apply and heat an alternating magnetic field that penetrates the steel slab in the thickness direction, can be applied.

Further, when joining steel pieces, regardless of whether or not the portions to be joined are in contact, a method of stopping heating and then pressing when the temperature of the portions to be joined reaches the target temperature, or the joining is planned Regardless of whether the parts are in contact or not, if the temperature of the part to be joined reaches the joinable temperature, pressing is started while continuing heating. It is possible to apply a method of performing at the same time.

[0018]

[Embodiment] A leading material and a trailing material having a plate width of 1000 mm and a plate thickness of 30 mm obtained by rough rolling are processed so as to have a planar shape as shown in Fig. 1 (width end and joint surface). Angle θ =
After 45 °), the steel pieces were butt-joined to each other by heating and pressing according to the following conditions, and the temperature distribution in the longitudinal direction of the steel pieces at that time was investigated.

Joining conditions a. Heating method: Heating by the transverse method b. Pressing force: 1.8 kgf / mm ² , c. Heating time: 10 seconds, d. Heating temperature: 1400 ° C, e. Joining form: Joined part To stop heating and then press when the temperature reaches the target temperature

FIG. 3 above shows the results,
As is clear from the comparison with FIG. 4 above, according to the present invention, the temperature deviation (average temperature deviation in the plate width direction) is extremely small.

Further, regarding the steel pieces joined under the above conditions,
Plate on the 1st stand (rolling speed is 1.3m / sec) when using a finishing rolling mill group (hot finishing rolling facility) equipped with a hydraulic rolling device with a maximum rolling speed of 5mm / sec. The results of investigating the thickness deviation are shown in FIGS. Conventional method
According to (when joined in the shape shown in Fig. 2), the plate thickness variation was very large because the response of the device due to the disturbance caused by the temperature difference at the joint was poor (see Fig. 8).
However, according to the present invention, since the plate thickness is stable in the longitudinal direction as shown in FIG. 7, it can be confirmed that the responsiveness of the reduction device is good.

[0022]

EFFECT OF THE INVENTION According to the present invention, the temperature at the joint portion of the steel slab does not become significantly higher than other regions (the average temperature deviation in the plate width direction is small), so the plate thickness control is performed. It is possible to significantly improve the followability of the rolling down device used for. Further, even when joining steel pieces having different average deformation resistances, the average deformation resistance changes gently at the boundary and the temperature deviation in the longitudinal direction is small, so that abrupt fluctuation of tension between stands is suppressed. Stable continuous rolling can be performed.

[Brief description of drawings]

FIG. 1 is a diagram showing a joining state of a preceding steel piece and a following steel piece.

FIG. 2 is a diagram showing a joining state of a preceding steel piece and a following steel piece.

FIG. 3 is a view showing an average temperature deviation in a plate width direction in a longitudinal direction of a steel slab.

FIG. 4 is a diagram showing an average temperature deviation in a plate width direction in a longitudinal direction of a steel slab.

FIG. 5 is a view showing a planar shape of a steel slab according to the present invention.

FIG. 6 is a view showing a planar shape of a steel slab.

FIG. 7 is a diagram in which the deviation of the plate thickness on the delivery side of the first stand is examined when steel pieces are joined according to the present invention.

FIG. 8 is a diagram for examining the deviation of the plate thickness on the delivery side of the first stand when steel pieces are joined according to the conventional method.

FIG. 9 is a diagram showing a joining state of a preceding steel piece and a following steel piece.

[Explanation of symbols]

 1 Leading billet 2 Trailing billet

 ─────────────────────────────────────────────────── ─── Continued front page (72) Inventor Sadayuki Miyoshi 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Kawasaki Steel Co., Ltd. Chiba Steel Works (72) Yoshito Goto 1 Kawasaki-cho, Chuo-ku, Chiba, Chiba 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 Kazuya Tsurusaki 4 Kannon Shinmachi, Nishi-ku, Hiroshima City, Hiroshima Prefecture 6-22 No. 6 Hiroshima Research Laboratory, Mitsubishi Heavy Industries, Ltd.

Claims (1)

[Claims] Claim: What is claimed is: 1. On the entry side of a hot finish rolling facility, when the rear end portion of a preceding steel piece and the tip end portion of a trailing steel piece are butted and joined, heating and pressing for joining each steel piece to each other. Prior to the treatment, the planar shape of the end of one of the preceding steel piece and the following steel piece is formed into a symmetrical convex or concave shape with the center in the plate width direction as a boundary, and the planar shape of the other end is formed. A method for joining steel slabs in continuous hot rolling, characterized by forming into a concave shape or a convex shape conforming to the convex or concave portion.