JPH09295011A - Joining method of steel plate end faces - Google Patents

Abstract

(57) Abstract: The present invention provides a method for preventing molten metal from flowing out from an edge portion when joining end faces of steel sheets to each other. SOLUTION: At the time of joining a position inside a predetermined distance from an edge portion of an end surface portion of a moving steel sheet and an edge portion of a trailing material portion by a laser welding machine, a cooling gas is applied to a welding edge portion of the steel sheet. A method of joining steel plate end faces, which comprises spraying a body or holding a cooling side plate in contact with it. [Effect] The molten metal is prevented from being burnt down at the edges of the steel sheets, the steel sheets can be reliably joined, and complete continuous rolling can be performed without breaking the joined portions.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steel sheet, for example, in the field of hot rolling, in which a plurality of steel sheets after hot rough rolling (hereinafter referred to as rough bars) are connected to each other to perform hot continuous rolling for finishing. The present invention relates to a method for joining a hot rough bar for continuous operation without breakage, and particularly to a method for welding a rough bar joining edge portion.

[0002]

2. Description of the Related Art In a conventional hot rolling line, slabs are heated, rough rolled, and finish rolled one by one. In this method, temperature control during hot rolling of the front and rear end portions of the material to be rolled is performed. Since it is difficult to control cooling and cooling, defects in materials and defects are likely to occur, resulting in a decrease in yield. So in recent years,
In order to solve this problem, a method has been adopted in which a rough bar is joined before finishing continuous rolling and several to several tens are collectively rolled for finish rolling.

Various proposals have been made for joining the coarse bars for this purpose. For example, Japanese Laid-Open Patent Application No. 4-2889.
JP-A-06-104107 and JP-A-5-104107 propose a method in which both end portions are brought into contact with each other and a bar end face shape in which the width center portion is thicker than the width end portions is rolled. Tokuhei 5-
Japanese Patent No. 62035 proposes a method in which the rear end portion of the preceding rolled material and the leading end portion of the trailing rolled material are superposed and cut in the longitudinal direction, so that the entire surface is contacted in the thickness direction. Further, in Japanese Examined Patent Publication No. 4644/1980, an attempt is made to reduce the joint thickness by thinning the end face by pressing. Also,
There is a laser welding joining method as such joining means,
Currently used as a joining method for coarse bars.

[0004]

An important point in the joining of rough bars is that the joining portion does not break between the finish rolling and the winding. Since the tension is set between the stands and between the coils, it is necessary to secure a joint strength equal to or higher than the tension while repeatedly rolling the joint. For this reason, since it is necessary to join the entire length of the end surface of the rough bar, in the laser welding of the rough bar, the welding was started from the edge portion and the laser was irradiated for a predetermined time to secure the welding thickness. For this reason, the metal melted at the edge of the coarse bar inevitably flows downward and damages the equipment below the coarse bar.

In order to prevent such a molten metal flow from flowing down, a laser irradiation power is initially reduced at the rough bar edge portion at the start of welding, and a slow-in system is adopted in which the irradiation power is gradually increased. At the end of the rough bar edge at the end, a slowdown method was adopted to reduce the irradiation power as it went to the edge, and measures were taken. As a result, it was possible to prevent the molten metal from flowing down from the edge portion, but the weld thickness at the edge portion (predetermined value for preventing fracture) could not be secured, and due to insufficient weld thickness, welding was performed during finish rolling. Occasionally, a failure may occur that the part breaks.
There has been a strong demand for a solution. It is an object of the present invention to solve the above problems and to provide a method for preventing the outflow of molten metal from the edge portion of the rough bar by welding and joining the edge portion.

[0006]

The present invention has been made in order to solve the above-mentioned problems. The means are as follows: (1) Edge portions of the end surface of the preceding material and the end surface of the trailing material of the moving rough bar. From the above, the method for joining rough bar end faces is characterized in that, at the time of joining the position inside the predetermined distance with a laser welding machine, a cooling gas body is blown to the welding edge portion of the rough bar. (2) When joining a position, which is inside a predetermined distance from the edge portion of the leading material and the edge portion of the trailing material of the moving rough bar, with a laser welding machine, cooling to the welding edge portion of the rough bar A method for joining rough bar end faces, characterized in that side plates are held in contact with each other.

(3) The edge of the coarse bar is irradiated with a laser at a position 3 mm to 20 mm inside from the edge portion of the rough bar end face according to (1) or (2). Joining method. (4) The method for joining rough bar end faces according to (1), wherein the pressure of the cooling gas body blown onto the welding edge portion of the rough bar is set to 0.5 to ² kg / cm ² . (5) The method of joining rough bar end faces according to (2), characterized in that the side plate that is held in contact with the weld edge portion of the rough bar from the outside is made of ceramics. (6) The method for joining rough bar end faces according to (5), characterized in that the thickness of the side plate that is kept in contact with and held from the outside by the weld edge portion of the rough bar is 10 to 30 mm.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The inventors of the present invention have conducted extensive experiments and conducted various experiments on a laser welding method which does not have the above-mentioned problems. We came to see the development of the most suitable welding method.

It has been found that in order to prevent the molten metal from flowing down at the edge welded portion of the rough bar, the welding start point should be positioned within a few mm from the edge portion. However, the fracture of the bonded portion due to welding is mainly due to the fact that there are many unbonded portions of the edge portion. From the past results of the present inventors, the amount of adhesion due to welding of the edge portion is at least 40 of the total thickness. %, It is not possible to secure the adhesive force due to the tensile stress during rolling in the finish rolling mill, and it is not possible to maintain the joining of the front and rear rough bars, and that portion is the starting point. As a result, the coarse bar is broken.

Therefore, since the welding start point is made to enter the inside of the rough bar edge portion, the melting of the metal proceeds to the edge portion, and the first means is to secure the adhesive force due to the solidification of the molten metal. As shown in FIG. 1, a cooling gas is sprayed toward the edge portion from diagonally above the edge portion welding of the rough bar to prevent the molten metal from flowing out and falling. As shown, the side plate is brought into contact with the edge of the welded portion of the rough bar to form a weir to prevent the molten metal from flowing out and falling.

What is common to both of these means is that the heat of the molten metal at the edge is taken away, whether the cooling gas is sprayed or the weir is made by the side plate, and the trailing edge and trailing edge of the preceding material. It is to accelerate the solidification of the molten metal flowing out from the joint of the butted part at the tip of the material.By forming the solidified wall of the molten metal at the edge of this joint, the molten metal in the molten pool is prevented from falling. At the same time, the molten metal is solidified, so that the rough bars are securely welded and fixed to each other to complete the joining of the edge welded portions.

FIG. 1 shows a state in which a nozzle for blowing a cooling gas is installed in the vicinity of the laser torch part of the laser welding machine in the first means. Cooling gas spray nozzle 2
And a nozzle (not shown) for the final stage of welding is installed.

FIG. 2 shows a state in which the side plate 3 is held near the laser torch part of the laser welding machine by the second means, and the side plate 3 is a cylinder (not shown) from a part of the welding machine. It is supported by the arm 4 and the welding edge portion 5 is pressed from the outside to form a weir body.

Here, the selection of the position of the laser welded portion in the initial and final stages of welding is not possible to be uniformly limited depending on the laser irradiation ability and the plate thickness of the rough bar, but any ordinary material can be used in the present invention. From the results of their experiments,
It is suitable to start from a position inside the 3 to 20 mm edge portion. If it is outside 3 mm, it does not change much from the conventional starting from the edge portion, and even if cooling gas is sprayed, it is not possible to completely prevent the molten metal from burning through. Further, if it is inside 20 mm, the joint may break during rolling.

Further, the pressure of the cooling gas blown from the outside to the rough bar welding edge portion in the above means 1 also has an appropriate range, and the lower limit overcomes the static pressure of the molten metal and melts down. 0.5kg / cm ² to prevent
The above is required, and the upper limit may be ² kg / cm ² or less at which molten metal is not blown off. further,
The cooling gas used for spraying may be compressed air usually used in a factory, but an inert gas is more preferable in terms of preventing oxidation of the welded portion.

On the other hand, the side plate forming the weir by restraining the rough bar welding edge portion in the means 2 from the outside is preferably made of a material having a small affinity (not welding) with the molten metal. From this point of view, it is a different material from molten metal,
Ceramics that are resistant to heat are the best choice. Further, the thickness of the side plate may be thin as long as it prevents the molten metal from falling, but from the viewpoint of cooling the molten metal at the edge portion, 10 to 30 mm is appropriate from the viewpoint of heat capacity, and within this range. By the time of the next welding, thermal recovery has been achieved, and continuous use is no problem.

[0017]

According to the present invention, the melt-through of molten metal, which has been a problem at the time of joining the edge portion of the rough bar, is solved,
The rough bar can be reliably joined, complete continuous rolling can be performed without breakage of the joined portion, the advantage in the production of hot-rolled steel sheet can be ensured, and its economical effect is large and it is an industrially useful invention.

[Brief description of drawings]

FIG. 1 is a partially enlarged perspective view showing a state in which a cooling gas is sprayed on a rough bar edge weld portion.

FIG. 2 is a partially enlarged perspective view showing a state in which a weir is formed by a side plate at a rough bar edge weld portion.

[Explanation of symbols]

 1 Laser torch 2 Cooling gas spray nozzle 3 Side plate 4 Arm 5 Weld edge

Claims (6)

[Claims] 1. When joining a position inside a predetermined distance from an edge portion of an end surface portion of a moving steel sheet and an edge portion of a trailing material portion by a laser welding machine, cooling is performed to a welding edge portion of the steel sheet. A method for joining end faces of steel plates, which comprises spraying a gas body. 2. When joining a position that is inside a predetermined distance from the edge portion of the leading material and the edge portion of the trailing material of the moving steel sheet by a laser welding machine, the welding edge portion of the steel sheet is cooled. A method for joining steel plate end faces, characterized in that side plates are held in contact with each other. 3. The method of joining steel plate end faces according to claim 1, wherein the position of irradiating the laser on the edge of the steel plate is set to a position inside 3 to 20 mm from the edge portion. 4. The method for joining steel sheet end faces according to claim 1, wherein the pressure of the cooling gas body blown onto the weld edge portion of the steel sheet is set to 0.5 to ² kg / cm ² . 5. The method of joining steel sheet end faces according to claim 2, wherein the side plate that is held in contact with the weld edge portion of the steel plate from the outside is made of ceramics. 6. The method of joining steel sheet end faces according to claim 5, wherein the thickness of the side plate which is held in contact with the weld edge portion of the steel plate from the outside is 10 to 30 mm.