JPH06106203A - Continuous hot rolling method for billet - Google Patents

Abstract

PURPOSE:To stably execute hot finish rolling under perfect joining over the whole area in the width direction by cooling the preliminary joining part of billets on the inlet side of finish rolling equipment after executing joining treatment in the rear end part of a preceding billet and the tip part of the successively following billet. CONSTITUTION:Cutting work is respectively executed in the rear end and tip parts of the billets 2, 3 with a cutting device 4, the respective billets 2, 3 are brought into contact with each other, also pressurized while heating, the joining area of the billets is gradually expanded and at least both end parts in the width direction are preliminarily joined by a heating/pressurizing means 5. Next, after the preliminary joining part of the billets is cooled by a cooling device 6, secondary scale on the surface of the billet is removed with a scale breaker 7 and the billets are transported to the finish rolling equipment 8. At the 1st stand of the finish rolling equipment 8, the gap in the joined part of the billets is closed by promotion of metal flow or material and joining or high pressure-welding strength is attained.

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 for steel slabs, and more particularly, to further strengthen the bonding condition between the steel slabs.

[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. Such a rolling method has the following problems.

A) Bad biting of the tip of the steel piece. b) Narrowing the rear end of the billet. c) Trouble running on the runout table at the tip of the billet. d) Dimensional defects at the front and rear ends of the steel piece.

Therefore, recently, in order to solve such a problem, the rear end portion and the tip end portion of the steel pieces obtained before the finish rolling are joined and continuously supplied to the hot rolling line. So-called endless rolling has been proposed, and along with this, various methods have been developed as a method for joining steel pieces.

For example, Japanese Unexamined Patent Publication No. 60-244401 discloses an induction heating pressure welding technique using a solenoid type coil, and Japanese Unexamined Patent Publication No. 61-159285 discloses an electric heating pressure welding technique. , Respectively disclosed. further,
In Japanese Patent Laid-Open No. 61-144203, the rear end portion of the preceding steel piece and the front end portion of the following steel piece are butted to each other, and at least both end regions in the width direction of the butted portion are pre-joined, and then a reduction of 20% or more is performed. A joining method is disclosed which comprises rolling at a rate.

However, in the techniques disclosed in Japanese Patent Laid-Open No. 60-244401 and Japanese Patent Laid-Open No. 61-159285, the rear end surface of the preceding steel piece and the entire front end surface of the following steel piece are used as joint surfaces, 1) A large amount of electric power is required for heating, because the entire heating area is heated. 2) The heating time required to reach the desired bonding temperature is long. 3) A long rope is required when heating is performed without stopping the heating means during the transportation of the billet, while a long distance is required when heating is performed between runs, and the equipment length is long. Be long. Further, the method disclosed in JP-A-61-144203 requires a long time to obtain a pre-bonded portion with sufficient bonding strength, and the problem 3) above still remains, and 4) bonding There was a disadvantage that the work became complicated.

In order to solve the above-mentioned problems, the inventors of the present invention heated the area by contacting the trailing end of the preceding billet and the leading end of the trailing billet at the entrance side of the hot rolling equipment. At least both ends in the plate width direction are connected by pressing, and the unoccluded part remaining in the center part in the plate width direction in the subsequent rolling process.
A method of press-contacting (hereinafter simply referred to as a gap) with a metal flow of a material has been developed, and is disclosed in JP-A-4-89109 and JP-A-4-89109.
-89110 and the like. By these methods, the joining work can be performed more quickly and easily than ever before.

[0008]

By the way, in the above method, it is desired that the gap is closed and erased in the subsequent rolling to join the entire area in the sheet width direction (particularly,
When performing tension control rolling for the purpose of strip width control in finish rolling, it is preferable to use the first pass as much as possible.
However, depending on the size of the gap and the amount of tension, the joining may not be completed in the previous pass, and it may be difficult to obtain sufficient joint strength. There was a risk that it would significantly hinder work.

An object of the present invention is to obviate and eliminate the gaps between pre-joined portions by promoting the metal flow of the material in order to solve the above-mentioned conventional problems, and in the finish rolling, the entire area in the plate width direction. We are proposing a continuous hot rolling method for steel slabs that enables complete joining over the entire length.

[0010]

According to the present invention, a cutting treatment is applied to each of the trailing end portion of a preceding steel piece and the leading end portion of a trailing steel piece following this, and then the respective steel pieces are brought into contact with each other and heated.・ When pressing and joining at least both ends in the strip width direction to feed it to the finishing rolling equipment and continuously hot rolling it, at the entrance of the finishing rolling equipment, It is a continuous hot rolling method for steel slabs, characterized in that the joint is cooled.

[0011]

[Operation] In the case of adopting a joining form in which the trailing end portion of the preceding steel piece and the leading end portion of the trailing steel piece are pre-joined at least at both ends in the strip width direction on the entrance side of the finishing rolling facility, the joining treatment At the end of the rolling, there will be a gap of approximately 5 to 50 mm in the center of the sheet width direction. If it is possible to promote the metal flow in the central area, the unbonded surface of each steel piece is pressure welded over its entire width direction,
It can be said that it is a very effective means in that it can be joined and the time required for the joining process can be shortened.

However, when the tension control rolling is performed for the purpose of controlling the strip width during the finish rolling, or depending on the size of the gap, sufficient joining cannot be expected.

According to the present invention, after the joining process of each steel slab is completed, the pre-joining part is cooled with cooling water or the like to lower its temperature (increase the deformation resistance), and it is particularly sandwiched between the pre-joining parts. In the initial stage of finish rolling, especially in the 1st stand, the metal flow in the closed region is preferentially promoted to completely close and press the gap. The joining strength between the steel pieces is extremely high, so that the plates do not separate and break during rolling.

FIG. 1 shows the configuration of equipment suitable for carrying out the present invention.

In the figure, 1 is a rough rolling mill, 2 is a preceding steel slab that has undergone the rough rolling 1, 3 is a trailing steel slab that is conveyed subsequently to the preceding steel slab 2,
Reference numeral 4 denotes a device (such as a drum shear having a curved blade) for cutting the rear end portion of the preceding steel piece 2 and the front end portion of the trailing steel piece 3 into a plane shape as shown in FIG. 2, for example. , 3
A heating / pressing means for performing a joining process of gradually increasing the joining area of the steel pieces as shown in FIG. 3 by bringing the pieces into contact with each other at the cut surface and pressing while heating. Although not shown in detail, reference numeral 5 is composed of, for example, an alternating magnetic field generator capable of heating in a predetermined temperature range in a short time and a pinch roll which sandwiches a steel piece between the upper and lower sides.

Further, 6 is a cooling device arranged on the outlet side of the heating / pressing means 5, and the cooling device 6 cools the pre-joint portions of the steel pieces 2 and 3. Reference numeral 7 is a scale breaker for removing the scale generated on the surface of the joined steel slab prior to finish rolling, and 8 is a hot finish rolling facility having a tandem arrangement of rolling mills F ₁ , F _2, ...

Continuous hot rolling of the billet according to the present invention is performed as follows.

First, the cutting processing device 4 is used to cut the rear ends and the front ends of the steel pieces 2 and 3 as shown in FIG.

Then, the heating / pressing means 5 brings the steel pieces 2 and 3 into contact with each other and presses them while heating them to gradually increase the joining area of the steel pieces as shown in FIG. Pre-join at least both ends in the width direction.

Then, after cooling the pre-bonded portion of the steel slab by the cooling device 6, the secondary scale produced on the surface of the steel slab is removed by the scale breaker 7 and the prescaled steel is conveyed to the finish rolling facility 8.

In the first stand of the finishing rolling facility 8, the gap g (see FIG. 3) at the joint portion of the steel slabs is closed due to the promotion of the metal flow of the material, and pressure welding and high-strength welding are performed. There is no fracture separation from that part during rolling.

In cooling the pre-bonded portion of the steel slab, it is preferable to lower the temperature by about 30 to 100 ° C. from the temperature in the central region in the plate width direction. This is because if the temperature drop at that portion is less than 30 ° C., it is not possible to eliminate the gap g during finish rolling and to generate a sufficient metal flow sufficient to complete the joining in the entire width direction of the sheet. This is because if the temperature exceeds 100 ° C, the deformation resistance of the pre-bonded portion becomes too large and the rolling roll may be damaged or trouble such as seizure may be caused. The cooling area (see the shaded area in Fig. 3) is about 0.1 W (W: strip width) on one side in the width direction of the steel slab, and in the longitudinal direction of the steel slab the center of the joint of the steel slabs. It is preferably about 3 times the contact arc length L of the roll bite.

As the cooling device 6, any structure such as a spray type can be applied, and it is particularly preferable that the cooling device 6 is provided with a shift mechanism or a rotation mechanism so as to cope with various plate widths and pre-bonding shapes.

[0024]

[Example] A sheet bar having a thickness of 30 mm and a width of 1000 mm subjected to rough rolling was cut by a cutting device, and then heated (heating using an alternating magnetic field was applied, input power: 2000 Kw, heating time: 3
Seconds, frequency: 500 Hz,) and pressing (pressing force: 2 kgf / mm ² , pressing time: 3 seconds). Then, at a point 2m before the scale breaker, the pre-joint was cooled by a spray nozzle cooling device equipped with a shift mechanism that can move in the plate width direction (conditions, 200 l / min per nozzle, 0.5 second injection), and passed through the scale breaker. To 50% reduction of the 1st pass
Hot-finishing rolling (7-stand tandem rolling mill) was performed under the following conditions, and the presence or absence of breakage of the plate during the finishing rolling process was investigated. As a result, the strip hot-rolled according to the present invention showed no breakage and separation of the plate, and could be stably subjected to finish rolling. On the other hand, in hot rolling under the same conditions except that the cooling at the pre-joint of the steel slab was omitted, rolling was performed with the gap at the joint remaining, and in some cases the plate was broken and separated in the rolling mill. An accident occurred.

[0025]

According to the present invention, it is possible to close the gap between the steel pieces generated during the pre-joining of the steel pieces in the initial stage of the finish rolling, so that the complete joining over the entire width direction of the sheet is performed. The hot finish rolling can be stably performed.

[Brief description of drawings]

FIG. 1 is a schematic view of a hot finish rolling line.

FIG. 2 is an explanatory view of a procedure for joining steel pieces according to the present invention.

FIG. 3 is an explanatory view of a procedure for joining steel pieces according to the present invention.

[Explanation of symbols] 1 rough rolling mill 2 preceding steel billet 3 trailing steel billet 4 cutting processing device 5 heating / pressing means 6 cooling device 7 scale breaker 8 hot finishing rolling facility

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Takeshi Hirabayashi 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Kawasaki Steel Co., Ltd. Chiba Steel Works (72) Inventor Katsuhiro Takebayashi 1 Kawasaki-cho, Chuo-ku, Chiba Chiba (72) Inventor Yusaku Fujii, 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Kawasaki Steel Co., Ltd.

Claims (1)

[Claims] 1. A cutting treatment is applied to each of a rear end portion of a preceding steel piece and a leading end portion of a succeeding steel piece subsequent to the preceding steel piece, and then the respective steel pieces are brought into contact with each other and heated and pressed to move in the plate width direction. At least the joining process of connecting both ends is performed, and then it is fed to the finishing rolling facility and continuously hot-rolled, the pre-bonded part of the steel slab is cooled at the entrance side of the finishing rolling facility. Method for continuous hot rolling of steel billets.