JPH07256305A - Continuous hot rolling method - Google Patents

Abstract

PURPOSE:To confine a shaping cutting only to a part required for laser cutting, to reduce time for laser cutting and to shorten time in the continuous rolling stage of hot rolled stock by confining the shape of shear cutting in order to efficiently execute the shaping cutting with a laser beam. CONSTITUTION:In this continuous rolling method by which the rear end part of a preceding rolled stock is butt-joined with the tip part of the succeeding rolled stock on the finishing inlet side in a rolling mill of a hot rolling device then the joined rolled stocks are continuously rolled, the end parts of the preceding stock and succeeding stock are cut into a curved shape with a curved blade shear having the radii R of curvature so that the max. gap between both materials is <=1/5 of bar thickness when the preceding stock 1a is butted on the succeeding stock 1b after cutting the rear end part of the preceding stock and the tip part of the succeeding stock. After that, both end parts in the direction of width are respectively formed by cutting the parts into the length of 4-10% of the entire width of bar with the laser beam, the preceding stock 1a is butted on the succeeding stock 1b and, the parts where are formed by cutting is joined by welding with the laser beam, then the hot rolled stock is pressure- welded and continuously rolled.

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 capable of producing hot strip by complete continuous rolling.

[0002]

2. Description of the Related Art In a conventional hot rolling line, slabs are extracted from a heating furnace one by one and rolled into a sheet bar having a required thickness by a group of rough rolling machines. After being rolled into a strip, it is wound into a coil by a coiler. This conventional hot rolling line has the following problems because the rolled material is subjected to rough rolling and finish rolling one by one.

That is, since it is necessary to smoothly engage each rolled material with the upper and lower rolling rolls of the rough rolling mill group and the finishing rolling mill group, the shape of the tip and the plate thickness can be adjusted for each rolled material. It is necessary, and uniform quality cannot be obtained from the front end to the rear end. In addition, the difference in temperature between the front and rear ends of the rolled material causes uneven product quality. Especially in thin strip rolling, the strip speed cannot be increased until the tip of the strip reaches the coiler, resulting in poor productivity. Since there is a space that is not involved in the work at all, there is a problem that the utilization efficiency of the equipment is low and the production efficiency is poor.

In order to solve these problems of the conventional hot rolling line, in recent years, in order to continuously hot roll the sheet bar, the trailing end portion of the traveling preceding rolled material and the leading end portion of the trailing rolled material during rolling. A method has been proposed in which and are butt-joined with each other while the cut surfaces of shear cutting are being performed, and the joined sheet bars are continuously rolled. However, since the cut surfaces remain as they are, the abutting state is poor, and a large gap exists, so that it is impossible to perform joining using a laser that requires narrowing of a narrow beam (usually 1 mm or less). For this reason, as a method other than laser, for example, in Japanese Patent Laid-Open No. 4-89109, both ends are made to abut each other, and high frequency heating is applied to the both ends, and pressure welding is performed to shorten the heating time or save the input power. This is what I aimed for. Further, Japanese Patent Laid-Open No. 4-376384 discloses a method of cutting a hot-rolled steel plate or the like with two laser processing heads, and then laser bonding, and Japanese Patent Laid-Open No. 56-163088 shapes only one of the steel plates by laser cutting. After that, laser bonding is disclosed.

[0005]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
Since the 89109 publication is premised on high frequency heating,
It merely defines the cutting shape effective for high-frequency heating joining. The initial gap is not particularly limited because it is premised that the initial gap between the preceding material and the following material is reduced because the end portions heated by high frequency are pressed and joined. Further, Japanese Patent Laid-Open No. 4-366384 and Japanese Patent Laid-Open No. 56-163088 are improvements in that the hot-rolled material is continuously joined in the conventional manner while the cut surface of shear cutting is used, but the preceding material is used. Since both ends of the trailing material are cut across the entire width, the laser cutting time is long and the process time until the hot-rolled material is continuous is long, resulting in an excessive facility cost.

[0006]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems and limits the shear cutting shape for efficiently performing shaping cutting by a laser. By experimentally calculating the gap between possible hot rolled materials and limiting the shear cutting shape,
It is intended to provide a continuous hot rolling method in which a portion required for laser cutting is reduced, a laser cutting time is shortened, and a time in a hot rolled material continuous process is shortened. The gist of the invention is that, on the finishing entry side of the rolling mill of the hot rolling apparatus, the trailing end portion of the preceding rolled material and the leading edge of the trailing rolled material are butt-joined, and the joined rolled material is In the continuous rolling method of continuously rolling, when the trailing edge of the preceding material and the leading edge of the following material are cut and the preceding material and the following material are abutted, the maximum gap between both materials is 1 / bar thickness. A curved blade shear having a radius of curvature R of 5 or less cuts the edges of the preceding material and the following material into a curved shape, and then the laser beam is applied to the both end portions of the plate to a length of 4 to 10% of the entire bar width. Continuous hot rolling, characterized in that the hot-rolled material is continuously rolled after being cut and formed into a piece, the preceding material and the following material are butted, the cut-formed parts are welded and joined by a laser beam, and then the hot-rolled material is pressed. On the way.

[0007]

The present invention will be described in detail below with reference to the drawings. FIG. 1 is a view showing a shape in which a butt portion between a trailing end portion of a preceding material and a leading end portion of a following material according to the present invention is cut by a laser beam. FIG. 1 (A) is a diagram showing a state before cutting with a laser beam. When the preceding material trailing end coil 1a and the following material leading end coil 1b are abutted, the preceding material trailing end portion 2a and the following material leading end portion An uneven shape is formed in the width direction of 2b, and large gaps are generated at both ends.

FIG. 1 (B) shows the shape of the edge after cutting the tip with a laser beam. As shown in FIG. 1B, the trailing end coil 1a of the preceding material and the trailing end coil 1b of the following material are cut by a laser beam, so that the rolled material is cut parallel to the width direction to form a butt shape. FIG. 2 is a cross-sectional view of the butted state. Figure 2 (A)
1A is a cross-sectional view taken along the line AA ′ of FIG. 1A, and FIG.
It is a cross-sectional view and shows a state in which a cutting line is wavy as shown in FIG. Also, in the horizontal cross-sectional shape, AA
′ And BB ′ cross-sectional views show that there are completely different gap states, and there are few gaps (Gap-U) above the edges, but gaps (Gap-L) below the edges. ) Will be bigger. If it is left as it is, it is difficult to join it by laser welding in the next step. Therefore, it is necessary to form a cut surface by laser cutting so as to have a parallel butted portion as shown in FIG. 2 (C) over the entire rolling width.

That is, FIG. 2 (C) shows the shape of the edge after cutting the tip with a laser beam. By cutting the trailing edge of the preceding material and the leading edge of the following material with a laser beam, the rolled material is cut parallel to the width direction.
As can be seen from this figure, the state has parallel butted parts. As described above, when the shearing cutting shape is cut linearly perpendicular to the plate longitudinal direction, the cutting line is wavy as shown in FIG. There is a possibility that it is necessary to perform laser cutting for the entire width of the plate in order to realize a small gap butting that enables laser bonding.

At this time, when the shearing shape is cut linearly perpendicular to the longitudinal direction of the plate, the cutting line may be wavy as shown in FIG. 1 (A) or the gap condition may be different depending on the place. It is necessary to perform the laser cutting over the entire width of the plate in order to realize a butt joint with a small gap that enables laser bonding. However, in order to make the hot rolled material continuous, laser welding requires an area ratio of only 8% of the total cross-sectional area of the plate at a strength level that secures the strength that does not break with the roll pressure welding roll (and the joining sites are preferably at both ends). ). Therefore, in the conventional method, the process time is wasted because the portion which does not require laser welding is formed and cut. In addition, the increase in process time is closely related to the line length, and in a large-scale equipment such as a hot rolling line, the line length is lengthened, resulting in a large increase in equipment cost.

FIG. 3 is a view showing a cut surface obtained by cutting both ends of the rolled material in a convex shape from the central portion. FIG. 3 (A) shows a state where both ends of the hot-rolled material are cut in a convex shape with respect to the center part by using a curved blade on the shear, and the leading material and the trailing material are butted in a curved state as a whole. Shows. In this case, if both ends of the hot rolled material are cut off with a laser, as shown in FIG. 3 (B), the forming and cutting process for the length of the portion requiring laser welding is completed. Since both ends of the central blade are recessed, if both ends are molded and cut, it is possible to create a state in which a butt gap does not occur in the portion to be laser-bonded. That is, since there is no portion of the central portion that abuts on both ends, the abutting is limited to both ends.

According to the present invention, as a result of cutting the ends of the preceding material and the following material with the curved blade shear, when the preceding material and the following material are abutted after the cutting, the maximum gap between the two materials is equal to that of the rolled material. The so-called curved cutting is performed with a radius of curvature R that is ⅕ or less of the thickness. Maximum gap is 1
If it exceeds / 5, the preceding material and the following material are not well pressure-bonded in the pressure-bonding step after laser-bonding the both ends, and as a result, the bonding strength withstanding rolling cannot be obtained. Therefore, the maximum gap is set to 1/5 or less of the plate thickness. Further, the reason for welding and joining the parts where the both ends of the plate width are cut and formed to a length of 4 to 10% of the full width of the bar by the laser beam is to rupture in the roll pressure welding step if less than 4%, and to continue the hot rolled material. Rolling becomes impossible. Further, if it exceeds 10%, the welding process time is wasted because the welding is performed up to the portion where laser welding is not required. Therefore, 4 to 10% of the entire width of each bar is welded and joined.

FIG. 3C shows the cross-sectional shape of the abutting portion taken along the line D-D 'in FIG. 3B, and there is no problem as long as the distance and the shape allow roll pressure contact. FIG. 3D is a cross section taken along the line EE ′ of FIG. 3B, which is a butt shape capable of laser welding and has a small gap and an increased butt area. As a result, the laser cutting time is 1/5 to 1/10.
Since it can be shortened, the related time related to bar joining can be shortened by that amount, the line length can be shortened, the temperature drop of the bar as a material can be suppressed, and the facility cost can be greatly reduced.

[0014]

Example: A slab heated in a heating furnace is rolled by a rough rolling mill, followed by the same conditions as the trailing end of the preceding rolled material which is running at a plate thickness of 60 mm, a width of 1980 mm, a temperature of 1000 ° C. and 100 mpm. The tip of the rolled material is cut with a curved blade shear, and when the preceding material and the following material are abutted, the maximum gap between both materials is 1/6 of the thickness of the rolled material and is cut into a curved shape of 60 m. After that, both end portions of the plate width are cut and shaped by a laser beam into 100 mm each corresponding to 5% of the full width of the bar, and the ends are abutted to each other and laser output 25
kW and focus with a focusing mirror with a focal length of 500 mm,
Using a laser device under the conditions of a cutting speed of 60 mm / sec and a welding speed of 30 mm / sec, they were joined by a laser beam for 360 mm (the one-sided joint cross-sectional area ratio corresponds to 6% of the entire rolling cross-section). After that, rolling was performed with a finish rolling mill.

As a result, since the gap between the trailing end of the preceding material and the leading end of the following material is reduced, the joining cross section is small, and nevertheless, the non-joining end surface is pressed by the rolling mill. 80% of the total cross section when combined with the laser joint
The above is reached. Under this condition, continuous hot rolling is performed using the subsequent finishing mill to finish the product with a plate thickness of 6 mm.
Good rolling was performed without any breakage. Incidentally, the cutting shape by the shear of the present invention is not necessarily limited to the cutting by the curved blade having a constant curvature, and when the preceding material and the following material are butted after the laser cutting of both ends, the butt gap has a plate thickness of If it is ⅕ or less, it may be cut into a shape having a concave center as shown in FIG. That is, FIG. 4 is a shear cut shape diagram showing another embodiment.

[0016]

As described above, by improving the laser cutting shape according to the present invention, the portion that requires laser cutting is reduced, and the laser cutting time is ⅕ compared with the conventional case.
It can be shortened to ~ 1/10, the related time for bar joining can be shortened accordingly, the line length can be shortened, the temperature drop of the bar as a raw material can be suppressed, and a hot rolled material of good quality can be obtained. It has an excellent effect that productivity can be improved, rolling quality can be improved, and facility cost can be significantly reduced.

[Brief description of drawings]

FIG. 1 is a diagram showing a shape in which a butt portion of a trailing edge of a preceding material and a leading edge of a following material according to the present invention is cut by a laser beam;

FIG. 2 is a cross-sectional view of a butt state,

FIG. 3 is a diagram showing a butt state before forming and a state in which a cut surface is formed by laser cutting.

FIG. 4 is a shear cut shape diagram showing another embodiment.

[Explanation of symbols]

 1a Leading material trailing end coil 1b Trailing material leading end coil 2a Leading material trailing end portion 2b Trailing material leading end portion 3 Cutting portion

Claims (1)

[Claims] 1. The finishing entry side of the rolling mill of the hot rolling mill,
In a continuous rolling method of butt-joining a trailing end portion of a preceding rolled material and a leading end of a trailing rolled material, and then continuously rolling the joined rolled material, a trailing end portion of the preceding material and a leading end of the trailing material. After cutting the part, when the preceding material and the following material are butted against each other, the edge of the preceding material and the following material is formed by the curved blade shear having the radius of curvature R such that the maximum gap between the two materials becomes ⅕ or less of the bar thickness. The part is bent into a curved shape, and then both ends of the plate width are cut and shaped by a laser beam to a length of 4 to 10% of the full width of the bar, the preceding material and the following material are abutted, and the cut and shaped portion is laser beamed. The method for continuous hot rolling, comprising hot-rolling the hot-rolled material under pressure, and continuously rolling the hot-rolled material.