JPH0919773A - Thinning method for crushing thin steel strip lap welds - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent metallic swelling and breaking and to obtain a smooth steel strip by rolling a crushing and reducing roller back and forth in plural number of times on a weld joint formed by electric resistance welding and also varying the rolling down force for each rolling. SOLUTION: A lap joint part is formed by superposing in a welding equipment the rear end of a steel sheet of a preceding coil and the front end of a succeeding coil, and then electric resistance welding is performed. Then, a succeeding crushing and reducing roll 9 is passed on the welded zone with a reduction set about 10-20kg/cm<2> . Successively, the roll is passed in the second reciprocating rolling with a reduction set about 35kg/cm<2> . As a result, no metallic swelling or breaking is generated around the weld zone, enabling smooth skinpass rolling to be performed. In this method, it is desirable to successively increase the rolling-down force each time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for crushing and reducing the thickness of thin steel strip lap welds, and more particularly to a technique effective for temper rolling of a tin plate.

[0002]

2. Description of the Related Art When manufacturing a coiled product of a steel strip, a trailing end portion of a preceding steel strip and a leading end portion of a following steel strip on a rolling line are sometimes joined by electric resistance welding. For example, when a thin steel strip is temper-rolled and wound into a coil, the temper-rolling work and the refining work of the thin steel strip are conventionally performed in different lines, and the temper-rolling is performed for each coil. After that, the defective portion was sheared off from the thin steel strip in another line, and the preceding and following steel strips were superposed and welded to obtain a product coil. However, since such a method is inefficient, it may be integrated into a single line, and as shown in FIGS. 2 and 3, the leading and trailing steel strips 2 and 3 on the inlet side of the temper rolling mill 1 may be integrated. A method has been proposed in which the ends are overlapped with each other and electrowelded.

However, according to this method, the rolled materials 2, 3
If the plate thickness is thin, welding of the steel strip surface is likely to occur, so that the rolling force of the electrode wheel 6 of the welding machine 4 cannot be increased and the resistance heat input part is cooled quickly. The joint portion (hereinafter, simply referred to as a welded portion) 8 becomes thicker than other portions. Further, the welded portion 8 is also a portion where the plate ends are overlapped with each other, but the plate ends tend to be excessively thickened due to the blade turning at the time of shearing and the protrusion of the ridge. Therefore, conventionally, when the welded portion 8 passes through, the space between the upper and lower rolls 7 of the temper rolling mill 1 is opened to reduce the rolling so that the roll 7 of the temper rolling mill 1 is not damaged by a sudden change in plate thickness. I was trying not to do it. As a result, there is a quality problem that a coiled product having defective portions before and after the welded portion 8 is manufactured.

To solve this problem, Japanese Patent Laid-Open No. 59-5 has been proposed.
Japanese Patent No. 6902 discloses a method of arranging a crushing thickness reducing roll in the welding machine 4 and adjusting a defect of the welded portion 8. That is, as shown in FIG. 1, the welding machine 4 is moving toward the width direction (welding portion 8) of the steel strips 2 and 3 traveling in the direction perpendicular to the paper surface. As shown in FIG. 6, another roll (hereinafter, referred to as a crushing thickness reducing roll 9) that rolls down the welded portion 8 is arranged, and the welded portion 8 welded by the electrode wheel 6 is trailed to reduce the thickness. To send the steel strip to the temper rolling mill 1.

However, in this method, since the periphery of the welded portion 8 is pressed down with a considerably large force, a bulge due to metal buckling is generated at that portion, and if the rolling down force is further increased to press the bulge, the welding is There was a problem that the part 8 was also torn off. As a method of preventing the metal bumps, Japanese Patent Laid-Open No. 60-54285 discloses, as shown in FIG. 4, a pair of upper and lower portions having an arc-shaped outer peripheral pressure surface along the lap welding portion 8 of the steel strip. A method of arranging another pair of upper and lower pressing rolls 10 each having a flat outer peripheral pressing surface behind the crushing and reducing roll 9 and crushing the metal ridge generated by the crushing and depressurizing roll 9 in the preceding stage with the flat roll is described. Disclosed. In addition, as a method for preventing the lap welding portion 8 from being torn off, it is generally known to reduce the rolling force of the crushing and reducing roll 9.

[0006]

However, in the method described in Japanese Patent Laid-Open No. 60-54285, which is a measure for preventing the metal bumps described above, the metal rolls are further increased by the rolling roll 10 having a flat outer peripheral surface arranged rearward. There is a possibility that the welding machine 4 may be made larger and the welding machine 4 itself may be enlarged.
In addition, the method of reducing the pressing force of the crushing reduced-thickness roll 9 as a measure against pressing and tearing of the welded part has a problem that the plate thickness of the welded part 8 is not reduced to the desired thickness.

In view of such circumstances, it is an object of the present invention to provide a method for crushing and reducing the thickness of thin steel strip lap welds that does not cause quality defects in thin steel coil products.

[0008]

In order to achieve the above-mentioned object, the inventor has made earnest studies and found that the reduction force of the crushing and reducing roll is changed every time the crushing and reducing roll is run. That is, according to the present invention, the trailing end of the preceding thin steel strip and the leading end of the following thin steel strip are overlapped with each other, and the crushing and reducing roll is run on the welded joint formed by electric resistance welding. When reducing and reducing the thickness of the welded joint portion, the above-mentioned roll for crushing and reducing thickness is reciprocated a plurality of times, and each time has a different reduction force. Is. Further, the present invention is also a method for reducing the collapse thickness of a thin steel strip lap welding portion, which is characterized in that the rolling force for each time is increased successively.

[0009]

In the present invention, the trailing end of the preceding thin steel strip and the leading end of the trailing thin steel strip are overlapped with each other, and the crushing thickness reducing roll is run on the welded joint formed by electric resistance welding. When the welded joint portion is rolled down and reduced in thickness, the roll for crushing and reducing thickness is made to reciprocate a plurality of times, and each time the rolling force is made different. By changing between the eye and the first reciprocation, it is possible to prevent metal bumps generated around the welded portion of lap welding and to prevent the welded portion from being torn off. Further, in the present invention, since the above-mentioned rolling force for each time is sequentially increased, the above-mentioned effect can be reliably achieved. Hereinafter, the content of the present invention will be specifically described in Examples.

[0010]

Example A coil-shaped product was manufactured in the same rolling line as in FIG. 2, using a low carbon steel sheet for tin plate as a material to be temper-rolled. At that time, the rear end portion of the steel strip from the preceding coil 11 and the front end portion of the following coil formed a lap joint in the welding machine 4 and were welded. At that time, the traveling speed of the electrode wheel 6 of the welding machine was 15 m / min.

Next, the crushing thickness reducing roll 9 following the electrode wheel shown in FIG. 1 reduces the amount of reduction by 10 to 20 kg / c.
As m ^2, passed over the completion of the welding unit, subsequently 2
The rolling force at the time of reciprocation was set to 35 kg / cm ² and passed.
As a result, metal bumps and push-offs did not occur at all around the welded portion 8, and smooth temper rolling could be performed. The outer peripheral pressure surface of the crushing thickness reducing roll 9 used at this time is smooth.

For comparison, a steel strip for a tin plate running under the same conditions as above was used, and the rolling reduction was 35 kg / cm as before.
Passing the depressurizing roll only once at ² or 10 kg / cm ² for the first reduction and 10 kg / c for the second
The operation with m ² was also performed. However, as shown in Table 1 collectively, the results show that quality defects of the coil product due to metal bumps and push-offs were recognized, confirming that the method of the present invention is excellent.

[0013]

[Table 1]

Although the present embodiment shows the case of temper rolling of a thin steel strip, the present invention is not limited to this case and is applied to all cases in which lap welded joints of thin steel strips are formed on a production line. it can.

[0015]

As described above, according to the present invention, it is possible to prevent metal bumps and push-offs that have occurred around the lap welding portions of steel strips, and it is possible to smoothly manufacture thin steel strip coiled products. It became possible.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a welding machine used for carrying out a method for reducing the collapse thickness of a thin steel strip lap welding portion according to the present invention.

FIG. 2 is a view showing a temper rolling line for a thin steel strip.

FIG. 3 is a view showing a lap welding portion of thin steel strips.

FIG. 4 is a view showing a crushing thickness reducing roll described in JP-A-60-54285.

[Explanation of symbols]

 1 Temper rolling mill 2 Leading steel strip 3 Trailing steel strip 4 Welding machine 5 Steel plate retainer 6 Electrode wheel of welding machine 7 Roll of temper rolling mill 8 Weld zone 9 Crushing reduction roll 10 Different rolling rolls

Claims (2)

[Claims] 1. A welding method in which a trailing end of a preceding thin steel strip and a leading end of a trailing thin steel strip are overlapped with each other, and a crushing and reducing roll is run on a welded joint formed by electric resistance welding. A method for reducing the thickness of a thin steel strip lap welding part, wherein the above-mentioned roll for crushing and reducing thickness is reciprocated a plurality of times to reduce and reduce the thickness of the joint portion, and each time has a different reduction force. 2. The method for crushing and reducing thickness of a thin steel strip lap welding portion according to claim 1, wherein the rolling force at each time is increased successively.