JP3200220B2 - Method of joining billets in continuous hot rolling - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art Conventionally, in a hot rolling line for steel slabs, steel slabs to be rolled have been heated, rough-rolled and finish-rolled one by one to finish a hot-rolled sheet having a desired thickness. Such a rolling method, in the finish rolling, inevitably stops the line due to poor biting of the rolled material, and also has a significant disadvantage that the yield reduction due to the defective shape of the leading and trailing ends of the rolled material is remarkable. .

For this reason, a rolling method has recently been adopted in which the rear end and the front end of a steel slab to be rolled are joined prior to finish rolling, and this is continuously supplied to a hot rolling line for rolling. It has become. JP-A-60-40601 is referred to as prior art in this regard.

[0004] The technique disclosed in Japanese Patent Application Laid-Open No. 61-40601 discloses a steel slab conveyed in advance (hereinafter referred to as a precedent slab) and a steel slab conveyed subsequently. (Less than,
(Referred to as a succeeding billet), each of which is cut, and immediately thereafter, both cut surfaces are pressed to be joined to each other and then rolled. However, this technique has the following problems since it cuts a steel slab vertically.

That is, in order to press the cut surfaces of the slab, the preceding slab and the following slab are each clamped in the thickness direction (to prevent positional fluctuation), and then a force is applied in the longitudinal direction of the slab. Buckling at the joints and local temperature drop due to clamping, resulting in poor quality around the joints after finish rolling. In the process, a sufficient pressing force cannot be applied, so that the bonding strength may not be sufficient. In such a case, there is a possibility that a serious accident in which the bonded portion breaks and separates during the finish rolling may occur. Furthermore, such a joining method requires a certain amount of time between cutting of the slab and completion of joining, so scale is generated on the cut surface. (When the cut surface is exposed to air for 0.1 seconds, the surface has a thickness of 1 μm or more. However, this has an adverse effect on the bonding strength and is not a reliable bonding technique.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to propose a method for joining a preceding and succeeding steel slab over the entire width simply and quickly without causing a local temperature drop during the welding. Where you do it.

[0007]

SUMMARY OF THE INVENTION According to the present invention, a rear end of a preceding steel slab and a front end of a succeeding steel slab are joined to each other and then fed to a finishing rolling mill group to continuously heat the same. In the inter-rolling, the rear end area of the preceding slab and the front end area of the succeeding slab are placed one above the other with an interval between them, and the shear blade sandwiching the slab vertically and the intermediate shear between the slabs The joint work of the blade cuts each billet end area diagonally, and the preceding billet and the movement of at least one of the preceding billets accompanying this cutting are made to match and press the cut surface of each billet. In the present invention, it is preferable to blow an inert gas or a reducing gas between the steel slabs. Further, it is preferable that the cutting angle of the billet is about 20 ° to 80 °.

FIG. 1 shows a configuration of equipment suitable for carrying out the present invention. In the figure, reference numeral 1 denotes a preceding steel slab that has passed through a rough rolling mill R, and reference numeral 2 denotes a succeeding steel slab following the preceding steel slab 1. Also, 3
Removes scale from the surface of the slab (especially the end area of the slab)
4 is a leading billet 1 and a trailing billet 2
Is a device for vertically stacking the end areas of each of them at intervals from one another, and this device 4 moves at least one of the rollers 4a and 4b provided thereon to the steel slab to move the steel slab above or below the transport line. Let it.

Reference numeral 5 denotes a shear blade 5a, 5b for vertically sandwiching the billets 1, 2 and an intermediate shear blade 5 located between the billets.
c, 5d shearing and joining equipment (a looper with a small stroke can be installed at the entrance of this equipment to avoid local cooling of the succeeding billet), especially in the middle of this equipment 5 The shear blades 5c and 5d have a structure capable of moving forward and backward in the width direction of the slab, or have a structure having a rotation axis in a direction orthogonal to the longitudinal direction of the slab (the intermediate shear blade is connected after the slab is joined). (Function for returning to the initial position)
Apply Reference numeral 6 denotes a looper for stopping the joining area of the slab in the line (if the descaling device 3, the slab stacking device 4 and the shear joining device 5 can be moved synchronously with the slab, it can be omitted). Is a scale breaker for removing scale formed on the surface of the billet prior to finish rolling, 8 is a group of finishing mills, 9 is a table roller, and the table roller 9 avoids local cooling of the billet. For this purpose, a mechanism capable of moving in the longitudinal direction of the billet or the thickness direction of the billet can be provided. And
Reference numeral 10 denotes an entry-side pinch roll which preferably has a mechanism similar to that of the table roller 9.

[0010] To join the leading billet 1 and the trailing billet 2, the billets are piled up at intervals in their end regions using the device 4 described above. In the shearing / joining apparatus 5, the shear blades 5a and 5b and the intermediate shear blades 5c and 5d are connected to each other as shown in FIG.
As shown in FIGS. 2B and 2C, the end areas 1a and 2a of each billet are respectively angled by the joint work of the shear blades 5a and 5b and the intermediate shear blades 5c and 5d.
And cut it off. In this cutting operation, at least one of the preceding billet 1 and the following billet moves by being pushed by the shearing blade (in this example, the trailing billet 2 moves downward by being pushed by the shearing blade 5a). 2) As shown in FIG. 2d, the cut surfaces of the steel slabs are made to match in accordance with this movement, and the steel slabs are pressed and joined in the plate thickness direction.

[0011]

The joining mechanism of the steel slab according to the present invention will be described below. In the state shown in FIG.
When a load is applied to a and 5d, the billets 1 and 2 are cut along the broken lines in the drawing. Since a clean new surface appears due to the shaving shear by the intermediate shear blades 5c and 5d on the cut surface serving as the joining interface between the billets ₁ and ₂ , immediately after that, the cut surfaces c ₁ and c ₂ match with each other as shown in FIG. When pressed, a high-strength joint is formed without being affected by the formation of scale.

When the cutting angle の of the slab is smaller, the joining area becomes larger, so that the strength of the joint becomes higher. However, when the cutting angle 小 さ く is smaller than 20 °, the shearing becomes difficult and exceeds 80 °. Therefore, since the bonding area is small, the bonding strength is greatly reduced. In the present invention, the cutting angle Θ
Make an angle between 20 ° and 80 °. In the present invention, it is most preferable to perform shearing at an angle of about 45 ° at which the maximum shear stress is obtained when pressed from above and below. Further, since the intermediate shear blades 5c and 5d are used for producing a new surface for joining the steel pieces to each other, it is necessary to prepare a particularly sharp blade.

In the joining of the slab according to the present invention, the temperature of the slab (particularly the temperature of the joining area) is short (about 2 to 6 seconds) from cutting the slab to matching the cut surface. Since the new surface comes into contact with the atmosphere at about 1000 ° C., it cannot be said that there is no influence of scale on that surface. In order to surely prevent the formation of scale in such a region, as shown in FIG. 5, a gas containing no oxygen is provided between the intermediate shear blades 5c and 5d to prevent the formation of scale.
(For example, an inert gas such as Ar gas or N gas or a reducing gas containing a small amount of H ₂ gas) may be blown to purge the gas, whereby a more reliable joint can be obtained. In FIG. 5 described above, a gas blowing nozzle N is provided in the intermediate shear blade 5c, and an inert gas or the like is blown through the nozzle N.

[0014]

EXAMPLE A descaling device 3 was used to perform continuous hot rolling of a sheet bar having a width of 1200 mm and a thickness of 30 mm in a facility as shown in FIG. The scale of the overlap area is removed, the sheet bar is overlapped by the apparatus 4, and the shear joining apparatus 5 is used.
The cutting and joining of the end portions of the sheet bar were sequentially performed, and the joining state of the obtained joining portions was examined. As a result, it was confirmed that the succeeding sheet bar was strongly metal-bonded.

[0015]

According to the present invention, the preceding and succeeding slabs can be easily and quickly spread over the entire area in the thickness direction without causing a local temperature drop or shape deterioration of the slabs. Bonding with sufficient strength enables continuous hot rolling with high productivity.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of equipment suitable for use in carrying out the present invention.

FIGS. 2A to 2D are explanatory views of a joining procedure of a steel slab.

FIG. 3 is an explanatory view of a shearing state of a billet.

FIG. 4 is an explanatory diagram of a joining state of a billet.

FIG. 5 is a diagram showing an example of a gas blowing structure.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Leading billet 2 Trailing billet 3 Descaling device 4 Billet stacking device 5 Shearing / joining device 5a Shearing blade 5b Shearing blade 5c Intermediate shearing blade 5d Intermediate shearing blade 6 Looper 7 Scale breaker 8 Finishing rolling mill group 9 Table Roller 10 Inlet pinch roll

Continuation of the front page (72) Inventor Yasuo Yarida 1st Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Kawasaki Steel Engineering Co., Ltd. Technology Research Division (56) References JP-A-4-157002 (JP, A) JP-A-51- 130665 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) B21B 15/00 B21B 1/26

Claims (3)

(57) [Claims] After joining a rear end portion of a preceding billet and a leading end portion of a succeeding billet following the preceding billet, when feeding to a finishing rolling mill group and performing continuous hot rolling, the preceding billet is used. The rear end area and the front end area of the succeeding slab are placed one above the other at an interval from each other, and each steel sheet is jointly worked by a shear blade sandwiching the slab vertically and an intermediate shear blade between the slabs. A continuous hot cutting method in which one end area is cut off diagonally, and the cut surfaces of the steel pieces are matched and pressed in accordance with the movement of at least one of the preceding steel piece and the following steel piece accompanying this cutting work. Method of joining billets in rolling. 2. The method according to claim 1, wherein an inert gas or a reducing gas is blown between the billets. 3. The method according to claim 1, wherein the cutting angle of the slab is 20 ° to 80 °.