JPH0550112A - Continuous hot rolling method for steel billet - Google Patents

Abstract

(57) [Summary] [Structure] Upset processing is applied to a region excluding at least both ends in the width direction of the trailing end portion of the preceding steel piece subjected to the cutting work and / or the leading end portion of the following steel piece, and After the contact areas in the end-to-end butted state are at least both ends in the width direction, the contact areas are heated and pressed to join the steel pieces together, and then subjected to finish rolling. [Effect] Continuous hot rolling with high productivity can be carried out without fear of fracture separation of the joint during rolling.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuous hot rolling method suitable for continuously rolling several to several tens of steel pieces such as sheet bars, slabs, billets or blooms.

[0002]

2. Description of the Related Art Conventionally, in a hot rolling line, steel strips to be rolled are rough-rolled one by one and then finish-rolled to a predetermined thickness.
In the finish rolling, the line stop easily occurred due to the biting failure of the rolled material, and the yield reduction due to the defective shape of the leading end portion and the trailing end portion of the rolled material was remarkable. Therefore, recently, in order to avoid the above problems, a rolling method is adopted in which the leading end and the trailing end of these steel sheets are joined and continuously supplied to a hot rolling line prior to finish rolling. It has become like this (for example, JP-A-61-1
144203, etc.).

The technique disclosed in the above-mentioned Japanese Patent Laid-Open Publication No. 61-144203 is such that the front end of a steel piece (hereinafter referred to as the preceding steel piece) conveyed in advance at the entrance side of the finish rolling mill. After making abutting the leading edge of the billet to be conveyed afterward (hereinafter referred to as the trailing billet) over the entire surface, pre-join both widthwise ends of the billet, and try to hold this state before rolling. To do. However, according to the above method, a long joining time is required in order to give the pre-joint a sufficient joining strength, so that there is a problem that the line must be extended.

[0004] In order to solve the above problems, the present inventors first made contact between the trailing end portion of the preceding steel piece and the leading end portion of the following steel piece at least at both widthwise end portions of each steel piece. On the other hand, a gap is provided between them, and a joining method comprising locally heating and pressing the contact portion was developed, and disclosed in Japanese Patent Application Nos. 2-203991 and 2-203992. did. With the development of the above-mentioned joining method, the joining work has become quicker and easier than ever before.

[0005]

However, in the above method, the gap provided between the steel pieces may not be completely eliminated during the rolling process. In such a case, the fracture separation at the joint portion of the steel pieces may occur. It is hard to say that this will never occur, and there was room for improvement in this respect. The present invention advantageously solves the above problems, on the entrance side of the finish rolling mill, while simply and quickly joining the steel pieces together,
It is an object of the present invention to propose a new hot rolling method capable of strengthening the joining between steel pieces with the progress of finish rolling.

[0006]

[Means for Solving the Problems] That is, the present invention joins a preceding steel piece that has undergone the rough rolling process and a succeeding steel piece that is subsequently conveyed to this steel piece at the entrance side of a finish rolling facility. After that, it is fed to a finishing rolling facility and continuously hot-rolled, and at least both widthwise end portions of the trailing end portion of the preceding steel piece and / or the leading end portion of the trailing steel piece subjected to the cutting work are carried out. By applying upset processing to the area except, after the contact area in the abutted state of each end at least both ends in the width direction, heating the contact area, to join both steel pieces by performing a pressing process, This is a continuous hot rolling method for billets, which is then subjected to finish rolling.

The present invention will be described in detail below. Figure 1
Fig. 1 schematically shows a hot rolling facility suitable for use in carrying out the present invention. In the figure, reference numeral 1 is a preceding steel slab that has passed through a rough rolling mill a, and 2 is a trailing steel that is subsequently conveyed to the preceding steel slab 1. 1 and 3 are hot finish rolling mills in a tandem arrangement of rolling mill stands F1, F2, ----, 4 is a cutting device for cutting the tip and the rear end of the steel billet, and 5 is the cutting leading A processing device that performs upset processing on the rear end of the steel slab 1 and / or the tip of the trailing steel slab 2 in a region except at least the vicinity of both ends in the width direction, and 6 heats and bonds the steel slab. And 7 is a scale breaker for removing scale formed on the surfaces of the steel pieces 1 and 2 prior to finish rolling.

In hot rolling a steel slab according to the present invention, first, the cutting device 4 is used to remove the rear end of the preceding steel slab 1 and the front end of the trailing steel slab 2 respectively, as shown in FIG.
Cut into a shape as shown in. At this stage, there is almost no gap between the steel pieces in the butt contact state of the preceding steel piece 1 and the following steel piece 2. Then, at least one of the rear end portion of the preceding steel piece 1 and the leading end portion of the following steel piece 2 is subjected to upset processing in a region excluding at least the vicinity of both end portions in the width direction thereof. As a result, as shown in FIG. 2B (in this example, both the rear end portion of the preceding steel piece 1 and the front end portion of the following steel piece 2 are upset), the steel is upset. The plate thickness of the part excluding at least both ends in the width direction of the one piece increases, and when the preceding steel piece and the following steel piece are butted, a gap is formed in the upset portion. Then, as shown in FIG. 2C, both ends of the preceding steel piece 1 and the following steel piece 2 are combined by a combination of heating by the heating and joining device 6 and pressing operation by adjusting the transport speed of the steel pieces 1, 2. After the compressive stress is generated in the vicinity area to bring them into close contact with each other and join them, the finish rolling mill 3
To perform hot finish rolling.

As shown in FIG. 2 (c), the area to be joined on the inlet side of the hot finish rolling mill 3 is only the area near both widthwise end portions of each steel slab. In the state of having the above, it is joined in an extremely short time. This gap is a gap left by the upset process prior to the butt joining, and the plate thickness of the machined part is increased due to the nature of the upset process. When the finish rolling mill 3 performs rolling as shown in FIG. 2 (d) in this state, the plate thickness of the region where the gap exists at the leading end and the trailing end of the steel pieces 1 and 2 is large. , The metal flow that tries to fill the gap is promoted, and as a result, the end face of each billet is
As shown in FIG. 2 (e), the entire surface in the width direction is firmly joined, so that even in the case where tension is applied to the rolled material in order to adjust the dimensions in finish rolling, they are easily joined. It does not break apart.

[0010]

In the present invention, the cutting shape of the steel piece end is not only flat as shown in FIG.
Various shapes such as a combination of a convex shape and a concave shape as shown in FIGS. 3B and 3C can be applied, and as a cutting means for obtaining the above shape, a shear, a gas cutting or a laser is used. Suitable for fusing.

As a method for performing the upset process, in addition to the apparatus having the reduction roll as shown in FIG. 1 above, an anvil for forging process can be applied. The position in the width direction where the upset processing is performed here is to heat the vicinity of both end portions in the width direction that are easily broken during finish rolling.
It is a part excluding at least the vicinity of both ends in the width direction so that they can be joined.

Then, after the two steel pieces are butted, they are heated,
Perform pressing process. The heating and pressing treatments include: i) a method of stopping heating when the temperature of the planned joining portion reaches the target temperature and then pressing, ii) if the temperature of the planned joining portion reaches the joinable temperature,
Method of starting pressing while heating is continued (however, the melting temperature of steel pieces does not exceed), iii) Method of pressing steel pieces from the beginning and simultaneously heating the contact area, iv) Predetermined joining margin Any method may be used, such as a method of heating after pressing until the joining margin at both ends of the steel piece is preferably 1/10 or more of the width of the steel piece. By performing the heating and pressing treatments as described above, the deformation starts from both end regions which are high temperature parts, the joint region gradually expands from both end regions to the central region, and the joint force is effectively strengthened. .. Here, it is preferable that the joining margin W at both ends in the width direction is 0.1 times or more, and 0.2 times or more in total at least in both end regions, with respect to the width B of the billet. This is because if the total joining allowance is less than 0.2 times the width of the steel sheet, the front and rear steel pieces may be separated and fractured during the subsequent finish rolling.

As the heating means, in addition to heating by a burner or high frequency heating by a solenoid type coil, an alternating magnetic field generating coil is used to heat by applying an alternating magnetic field that penetrates the steel piece in the thickness direction. The so-called transverse heating (see Japanese Patent Application No. 2-203991) can be applied.

[0014]

[Examples] Using the hot rolling equipment shown in FIG. 1 above, continuous hot rolling was carried out in the following manner. As the billet, a sheet bar having a width of 1000 mm and a thickness of 30 mm was used for both the leading and trailing billets. Now, after cutting the rear end portion of the preceding sheet bar and the front end portion of the following sheet bar into flat shapes as shown in FIG. 3 (a), as shown in FIG. In order to create a gap of 10 mm, the center area of each sheet bar excluding 100 mm on both ends is upset, and then heated and pressed to apply the heat treatment.
After being shaped as shown in Fig. 3, finish rolling was performed to finish a hot rolled sheet having a thickness of 3 mm. As a result, it was confirmed that the joint portion of the sheet bar did not break and separate during rolling, and stable rolling was possible. Further, after the finish rolling, the gap at the joint was completely filled, and a strong joint strength was obtained.

On the other hand, as shown in FIG. 6, the same planar shape as that shown in FIG. 4 is cut out by a cutting machine (therefore, the central region is not thick) and bonded under the same other conditions. After that, when finish rolling was performed, a gap remained at the joint portion of the sheet bar even after finish rolling, and in some cases, a serious accident occurred such as breakage and separation in the strip of the finish rolling machine.

[0016]

As described above, according to the present invention, the preceding steel piece and the following steel piece are first partially joined at the entrance side of the finish rolling facility, and the end portions of the steel pieces are contact-joined over the entire width direction in the finish rolling step to join Can be made even stronger, and therefore continuous hot rolling with high productivity can be realized without fear of fracture separation of the joint during rolling.

[Brief description of drawings]

FIG. 1 is a schematic diagram of hot rolling equipment suitable for use in implementing the present invention.

FIG. 2 is a view showing a procedure for joining steel pieces.

FIG. 3 is a view showing a cut shape of a steel slab.

FIG. 4 is a view showing a shape of a joint portion of a steel slab.

FIG. 5 is a diagram showing a joining state of a preceding steel piece and a following steel piece after heating and pressing.

FIG. 6 is a diagram showing a joining state of steel slabs by a conventional method.

[Explanation of Codes] 1 Leading steel slab 2 Trailing steel slab 3 Hot finishing rolling mill 4 Cutting device 5 Upset device 6 Heat bonding device 7 Scale breaker

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Norio Takashima, No. 1 Kawasaki-cho, Chiba-shi, Chiba Prefecture, Kawasaki Steel Co., Ltd. (72) Inventor Tosada Takechi, No. 1, Kawasaki-cho, Chiba, Chiba Kawasaki Steel Co., Ltd. Chiba Inside the Steel Works (72) Inventor Fujio Aoki 1 Kawasaki-cho, Chiba City, Chiba Prefecture Kawasaki Steel Co., Ltd. Inside the Chiba Works

Claims (1)

[Claims] 1. A preceding billet that has undergone a rough rolling step and a trailing billet that is subsequently conveyed to this billet are joined at the entrance side of the finishing rolling facility and then fed to the finishing rolling facility. Then
When performing hot rolling continuously, upset processing is applied to the region excluding at least both ends in the width direction of the trailing end portion of the preceding steel piece and / or the leading end portion of the trailing steel piece subjected to the cutting work. The contact areas in the abutting state of the respective end portions are defined as at least both end portions in the width direction, and the contact areas are heated and pressed to join the steel pieces together, and then subjected to finish rolling. Continuous hot rolling method for billet.