JPH0623559A - Method for joining metallic strips - Google Patents

Abstract

PURPOSE:To prevent separation of a joined part by a spot-welding without adding a special device. CONSTITUTION:In a continuous treating line of a metallic strip 1, the tail end of a preceeding strip and the tip end of a succeeding strip are superposed, spot-welded 11 in a transverse direction to joint both strips and at least three points including the center and both ends are spot-welded 12 behind the spot- welded string of the superposed part and in the transverse direction in parallel with the spot-welded string.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a connection method for connecting a tail end of a leading strip and a tip of a trailing strip by spot welding in a continuous processing line for metal strips.

[0002]

2. Description of the Related Art Conventionally, in a continuous processing line for metal strips, welding methods such as butt resistance welding and lap resistance welding have been adopted when connecting the tail end of a leading strip and the tip of a trailing strip. Sometimes, spot welding is adopted in order to shorten the welding time and the equipment cost.

An example of a continuous processing line for metal strips is shown in FIG. 1 is a metal strip, 2 is a payout reel,
3 is a spot welder, 4 is an entrance bridle, 5 is a skin pass mill, 6 is an exit bridle, 7 is a shear, and 8 is a take-up reel. The coil-shaped metal strip 1 loaded in the delivery reel 2 is rewound and its tip reaches the spot welder 3 and is connected to the tail end of the preceding strip waiting here. It becomes a continuous strip and advances along the line in the direction of the arrow, and with a predetermined tension applied between the entrance side bridle 4 and the exit side bridle 6, the skin pass mill 5 undergoes the desired shape correction processing and the like, 7
Are appropriately divided and are wound again by the take-up reel 8 into a coil shape.

FIG. 6 shows a conventional spot welding method for metal strips. (A) is a plan view and (b) is a side view. Spot welding is performed in one row in the width direction of the connection portion at substantially equal intervals. By the way, this welded part undergoes a deformation called "opening" as shown in Fig. 7 under high tension, and when this part is wrapped around the bridle roll, the end of the strip that opened the opening as shown in Fig. 8 is formed. Not only does the rubber bridle roll bite into and damage the surface of the bridle roll, but the mouth opening is also bent in the opposite direction for each bridle roll, which causes repeated bending, often leading to weld fracture. .

As a method of preventing such a mouth opening phenomenon, for example, according to Japanese Patent Publication No. 61-24109, as shown in FIG. 9, both ends 1 and 1 of a strip to be connected are butted to each other to assist both front and back sides. There is a method in which the steel plate 13 is sandwiched and fixed by spot welding 11, 11 or the like, so that the welded portion has a strength that is not subjected to bending deformation even when passing through a curved surface of a line. This method is considered to be effective as a connection method that does not cause opening, but since a large welding machine is required to insert and fix the auxiliary steel plates on the front and back sides, and the connection work also takes a long time, It has the drawback of diminishing the benefits of using spot welding. Further, according to Japanese Patent Laid-Open No. 54-161556, as shown in FIG. 10, both ends 1, 1 of the strips to be connected are superposed, and slits 14 are formed at arbitrary intervals beside the superposed parts. There is also a method of locally weakening the portion so that the slit portion is bent and deformed before the spot welded portion 11 opens. This also seems to be effective for preventing mouth opening, but in addition to the spot welding machine, a punching device for forming slits must be provided, and it takes extra time for the work, which is not realistic.

[0006]

DISCLOSURE OF THE INVENTION The present invention provides a strip connecting method which does not require such special equipment, can be processed in a working time which is not much different from the conventional one, and can prevent the opening of the mouth. To aim.

[0007]

According to the present invention, a tail end of a leading strip and a tip of a trailing strip are superposed on each other in a continuous processing line for metal strips, and spot welding is performed in the width direction to connect both strips. A method for connecting metal strips is characterized in that at least three spot welding points including the center and both ends are performed in the width direction in parallel with the spot welding row at the rear of the overlapping portion in the overlapping portion.

[0008]

[Operation] According to the present invention, the conventional spot welding having the welding strength corresponding to the original line tension is performed, and the spot welding for preventing the opening of the material is performed backward when viewed from the line advancing direction. At least three points including the center and both ends are applied in the width direction, and the welding points are arranged in two rows in the traveling direction. Therefore, as shown in FIG. 2, even if line tension acts, the strip end can open the mouth. Therefore, as shown in FIG. 3, even if it contacts a curved surface of a bridle roll or the like, the surface thereof is not damaged.

The shape of the strip usually shows either a belly extension in which the center in the width direction extends or an edge extension in which the ends extend, and the spot welding in the width direction is performed at least at the center and both ends as described above. With three points, it is possible to cope with strips having any of these tendencies. Regarding the welding strength, in the case of the conventional single-row welding, as shown in FIG. 7 above, the overlapping portion of the strip is inclined by the angle α with respect to the tension P, and the shearing force Pt and the tensile force Pn act. . Here the angle α is, tanα = t / - located in (L ² t ^{2) 1/2} relationship, t is the plate thickness, L is the diameter of the welding points (nugget).

However, in the case of the double-row spot welding according to the present invention, it is understood that L is the distance between the welding rows and the inclination angle α is greatly reduced. That is, in the conventional single-row spot welding, while a small circle is used for tension,
In the two-row spot welding of the present invention, the two rows are opposed to each other at intervals, so that the present invention is extremely advantageous in terms of welding strength.

[0011]

1 is a plan view and FIG. 1 (b) is a side view of the connection portion of a strip according to an embodiment of the present invention. Original spot welding 11 in the first row is 13 at 70mm pitch
The spot welds 12 for preventing mouth opening in the second row are six points at the 420 mm pitch and three points at the center and both ends.

FIG. 2 is an enlarged view of the side surface of the connecting portion, showing the positional relationship of spot welding with respect to the plate thickness t ₁ of the leading strip and the plate thickness t ₂ of the trailing strip. The distances L ₁ and L ₂ are 10 to 15 times t ₁ and t ₂ , and the interval L ₃ between the two rows of spot welding is preferably 7.5 times or more the sum of t ₁ and t ₂ . FIG. 3 shows a state in which the connection portion of the strip of the present invention is wound around the surface of the bridle roll, and it is shown that damage to the roll is prevented as a result of suppressing opening of the mouth.

FIG. 4 is a graph showing the relationship between the line tension and the opening amount when spot welding a plain steel strip having a plate thickness of 4.5 mm at a welding pitch of 70 mm. The vertical axis represents the opening amount and the horizontal axis represents the tension. In each case, the opening amount and the tension value at the time of fracture of the welded portion are set to 1 and shown by the ratio value. The solid line is the case of conventional spot welding of only one row, and the opening phenomenon appears at a tension of 50 to 60% against breakage. Therefore, if you operate with low tension, there is no problem, but the recent demand for quality requires even higher tension,
Reducing tension is not the solution.

On the other hand, the joint performance of the double-row spot welding according to the present invention is shown by the broken line in FIG. Even in this case, the mouth opening occurs from about 80% of the breaking tension, but the mouth opening amount remains at about 1/5 of the conventional value even at the time of breaking.

[0015]

The present invention does not require any other equipment,
It can be performed by operating the conventional spot welder only twice. Further, according to the present invention, the opening amount of the strip connection portion is reduced, damage to the bridle roll is eliminated, welding breakage is prevented, and the operating rate of the line is improved.

[Brief description of drawings]

1 shows a connection of a strip according to the invention (a).
Is a plan view and (b) is a side view.

FIG. 2 is an enlarged view of FIG. 1 (b).

FIG. 3 is a partial side view showing a state in which the connecting portion of the present invention is wound around a bridle roll.

FIG. 4 is a graph showing the relationship between the line tension and the mouth opening according to the present invention.

FIG. 5 is a layout view showing an example of a continuous strip processing line according to the present invention.

FIG. 6A is a plan view and FIG. 6B is a side view showing a connection portion of a conventionally known strip.

FIG. 7 is an enlarged view of FIG. 6 (b).

FIG. 8 is a partial side view showing a state in which a connection portion of a conventionally known strip is wound around a bridle roll.

FIG. 9 is a side view showing a connection portion according to a conventional technique.

FIG. 10 is a perspective view showing a connection portion according to another conventional technique.

[Explanation of symbols]

 1 Strip 11 Spot weld 12 Open spot prevention weld

Claims (1)

[Claims] 1. In a continuous processing line for metal strips, a tail end of a preceding strip and a tip of a trailing strip are overlapped and spot welding is performed in the width direction to connect both strips, and the spot welding of the overlapped portion is performed. A method for connecting metal strips, characterized in that spot welding is performed at the rear of the row in parallel with the widthwise direction at least at three points including the center and both ends.