JPH0724868B2 - Method and apparatus for manufacturing ERW steel pipe - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to increasing the width of the end face of the steel strip and the angle between the surface and the end face when manufacturing an electric resistance welded steel pipe using the steel strip. The present invention relates to a method and an apparatus for manufacturing an electric resistance welded steel pipe including a step of making the outside of the steel pipe an acute angle.

[Conventional technology]

A conventional method for manufacturing an electric resistance welded steel pipe will be described. As shown in FIG. 6, first, a wide hot-rolled steel strip is put on a slitter, and a slit knife 61 is used to slit a multi-row narrow steel strip 1.
Next, the process of manufacturing this narrow steel strip 1 into an electric resistance welded steel pipe
Shown in the figure. The slit narrow steel strip 1 is bent by the breakdown roll 2 and then the side roll 3
Butt the ends together. Furthermore, the fin pass roll 4 rubs the end face to be welded in a later step to make the face smooth. Then, when passing through the work coil 5, an electric current is generated in the circumferential direction of the narrow steel strip 1 formed on the pipe body by the work coil 5, whereby the butt surfaces are induction-heated and brought into a molten state. A pressing force by the squeeze roll 6 is applied to the abutting surface in the molten state, and the abutting surface is pressed to form an electric resistance welded steel pipe.

[Problems to be solved by the invention]

The above-mentioned conventional method for manufacturing an electric resistance welded steel pipe has the following problems.

(1) When a wide hot-rolled steel strip is slitted into slits in a multi-strand narrow steel strip 1, a side wall thinning portion 71 as shown in FIG. Edge thinning 11 occurs in the molding, and as shown in FIG. 9, the vicinity of the inner surface welded portion is molded with the metal thinning, resulting in a shape lacking a perfect circle.

(2) When forming a steel strip into a tubular body, the butt shape at the time of electric resistance butt welding becomes an extreme V shape due to an excessive difference in circumferential length between the inner and outer surfaces of the pipe, and thus a sound welded portion. Quality cannot be obtained.

Therefore, when it becomes an electric resistance welded steel pipe product, it may not be able to be used as a structural steel pipe beyond the limits in terms of dimensional accuracy and strength, and as a transportation pipe, cleaning of the pipe inner surface and protruding bead cutting may occur. May be necessary.

The present invention has been made to solve such problems, and even when an electric resistance welded steel pipe is manufactured by using a narrow steel strip as a material, the welding protrusion is maintained while keeping the inner and outer surfaces of the electric resistance welded steel pipe in a perfect circle. An object of the present invention is to obtain a method and an apparatus for manufacturing an electric resistance welded steel pipe capable of smoothly adhering mating surfaces.

[Means for solving problems]

This invention, in the process of manufacturing an electric resistance welded steel pipe, first rolls the side end of the corrugated steel strip in the width direction by an upset roll before continuously forming the steel strip into a tubular body, and There is a step of increasing the thickness of the side end portion and making the angle between the side end surface and the pipe outer side surface an acute angle, and then cutting and smoothing the side end surface of the steel strip by a milling cutting device.

Further, as an apparatus directly used for this method, the side end of the steel strip is rolled in the width direction in the preceding stage of the apparatus for continuously forming the steel strip into a tubular body, and the thickness of the side end of the steel strip is increased in the thickness direction. In addition to increasing the number, it has an upset roll that makes the angle between the side end face and the pipe outer side surface an acute angle, and following this upset roll, a milling cutting device that smoothly cuts the side end face of the steel strip was installed consecutively. It features an ERW steel pipe manufacturing device.

[Action]

In the method and apparatus of the present invention, an electric resistance welded steel pipe manufacturing apparatus is provided with an upset roll and a milling cutting device subsequently to the side edge part of the steel strip is compressed in the plate width direction by an upset roll with a caliber to obtain a steel strip meat. With increasing thickness,
The angle between the outer surface of the steel pipe outer surface and the side end surface is made acute, and then the side end surface is made smooth by a milling cutting device, and the angle between the outer surface of the steel pipe outer surface and the side end surface is made acute. .

Example of Invention

 Specific examples of the present invention will be described below with reference to the drawings.

FIG. 1 is a plan view showing an embodiment of the electric resistance welded steel pipe manufacturing apparatus of the present invention. One set of rolls on the right side is an upset which is incorporated in an upset roll stand having a vertical rotation axis and a caliber cut. It is roll 7. Subsequently, a roller having a horizontal rotation axis, that is, a guide roll 8 is provided to keep the pass line of the steel strip constant. Following this, a milling cutting device 9 whose axis of rotation is vertical is provided.

Further to this, a pair of guide rolls 10 each having a horizontal rotation axis are provided to keep the pass line of the steel strip constant.

After that, four sets of breakdown rolls 2, three sets of side rolls 3, and further fin pass rolls 4 are sequentially arranged, and squeeze rolls pressurize and join both edges of the open pipe induction-heated by the work coil 5. 6 is provided.

The upset roll 7, which is a feature of the present invention, is incorporated in an upset roll stand as shown in FIG. Here, the upset roll 7 is held by two shafts 21 provided on the left and right, and this is driven by a reduction gear motor 22. Further, the guide roll 8 is held by two upper and lower shafts 23. Since the milling cutting device and the stand of the guide roll 10 have the same structure as shown in FIG. 2, their illustration is omitted.

As shown in FIG. 5, the breakdown roll 2 shown in FIG. 1 is held by two upper and lower shafts 51.

Next, a case where an electric resistance welded steel pipe is manufactured using the apparatus of the present invention as shown in FIGS. 1 and 2 will be described in detail.

The narrow width steel strip 1 slit into a plurality of lines by a slitter is compressed by an upset roll in the width direction as shown in FIG. 3 so that the side end portion has an increased thickness and the outer surface and the side end surface of the steel pipe have an acute angle. Become.

Next, as shown in FIG. 4, the side end surface of the narrow steel strip 1 is smoothly cut by the milling cutting device 9, and at the same time, the angle formed between the outer surface of the steel pipe and the side end surface is sharpened. The narrow steel strip 1 thus formed is formed into a tubular shape through a breakdown roll 2, a side roll 3 and a fin pass roll 4 in order, and squeeze rolls are applied to both edges of an open pipe induction-heated by a work coil 5. It is pressure-bonded at 6.

Rolling with the upset roll according to the method of the present invention increases the thickness of the material width side end portion, so that there is no thinned portion at the material width side end portion during the breakdown roll forming. Therefore, the ninth
There is no thinned portion near the weld as shown in the figure. Further, since the end portion on the material width side is adjusted in shape so as to have an appropriate angle, the material yield loss in the groove processing by milling in the subsequent process is small.

Then, cut the edge end face with a milling cutting device,
The butt shape at the time when the edge face is angled to form a tube forms a groove suitable for welding. At the same time, since the milling cutting device intermittently generates chips, it is possible to perform unmanned operation without the trouble of cutting chips. With this method, it is possible to scarf the sheared surface at the time of slitting, and it is possible to excise the thinned region at the time of slitting.

When the electric resistance welded steel pipe is manufactured by the above method, the side wall of the slit narrow steel strip 1 used as a material is thinned, and the outer peripheral portion of the steel pipe after butt forming is formed due to the difference in peripheral length between the inner and outer surfaces of the steel pipe. Since it can be avoided that the butt gap becomes too large, unevenness of the pipe wall will not occur near the welded part after welding the steel pipe, and similarly, no excessive bead will be generated in the welded part. At that time, a flaw (called a sputter flaw) does not occur.

Therefore, this method is suitable for producing thick-walled small-diameter welded steel pipes, and in the production of electric resistance welded steel pipes with an outer diameter of more than 10 mm and a diameter of 40 mmφ or less, according to the prior art, prevents the occurrence of concave grooves. It was almost impossible to do so, and many spatter defects occurred, and the yield of good products was extremely low, which was not economically feasible. For the first time, it was possible to economically produce thick, small-diameter ERW steel pipe with a diameter of 40 mmφ or less while ensuring a high yield.

〔The invention's effect〕

According to the method and apparatus of the present invention, since the ERW steel pipe manufacturing apparatus is provided with the upset roll and the milling cutting device subsequently to the roll, it is possible to increase the wall thickness at both end portions and to open the side end portion opening of the pipe outer diameter surface. It is possible to prevent the gap from being excessively large as compared with the gap between the side end portions of the inner diameter surface of the pipe. Therefore, it is possible to prevent a groove from being formed beside the inner bead of the electric resistance welded steel pipe of the product. Further, the welding butt surface can be an optimum I-shaped butt surface by cutting the edge end surface with a milling cutting device at an appropriate angle.

As a result, it is possible to prevent the generation of rejected products due to insufficient wall thickness. Further, as compared with the conventional cutting process, since the deformation process of the side end portion is performed by the upset roll, there is no cutting and the yield is remarkably improved, which is an extremely excellent invention in production.

[Brief description of drawings]

FIG. 1 is a plan view showing an embodiment of the electric resistance welded steel pipe manufacturing apparatus of the present invention, FIG. 2 is a front view showing a stand incorporating the upset roll shown in FIG. 1, and FIG. FIG. 4 is an explanatory view showing a state in which the side end portion of the narrow steel strip slit by a set roll is rolled, and FIG. 4 shows the side end surface of the narrow steel strip slit by the milling cutting device in FIG. FIG. 5 is a front view of a stand incorporating the breakdown roll in FIG. 1, FIG. 6 is an explanatory view showing a conventional steel strip slitted by a slitter, and FIG. The figure is an explanatory view showing the state of thinning of the side end of a slit narrow steel strip, FIG. 8 is a plan view of a conventional electric resistance welded steel pipe manufacturing apparatus, and FIG. It is explanatory drawing of the thin part which generate | occur | produces in the vicinity. 1 ... Slit narrow steel strip, 2 ... Breakdown roll, 3 ... Side roll, 4 ... Fin pass roll, 5 ... Work coil, 6 ... Squeeze roll, 7 ...
… Upset rolls, 8,10 …… Passline rolls, 9
…… Milling cutting device, 11 …… Edge thinning, 21 …… Upset roll drive motor, 61 …… Slitter knife, 71 …… Side edge thinning part of steel strip slit narrowly.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP 62-77121 (JP, A) JP 59-197317 (JP, A) JP 61-115685 (JP, A) JP 62- 74519 (JP, A) Japanese Patent Sho 51-26895 (JP, B2)

Claims (2)

[Claims] 1. In a process for producing an electric resistance welded steel pipe, before continuously forming a steel strip into a tubular body, first, a side end portion of the steel strip is rolled in a width direction by an upset roll to make the steel strip in a thickness direction. It is characterized by increasing the thickness of the side end of the steel sheet and making the angle between the side end surface and the pipe outer surface an acute angle, and then cutting the side end surface of the steel strip with a milling cutting device to form a smooth butting surface. ERW steel pipe manufacturing method. 2. An apparatus for producing an electric resistance welded steel pipe, wherein a side end portion of a steel strip is rolled in a width direction before a device for continuously forming a steel strip into a tubular body, and a side end portion of the steel strip is formed in a thickness direction. Milling cutting that increases the thickness and has an upset roll that makes the angle between the side end surface and the pipe outer surface an acute angle, and then follows the upset roll to cut the side end surface of the steel strip into a smooth butt surface. An electric resistance welded steel pipe manufacturing device, which is characterized in that the devices are connected in series.