JPS63180328A - Manufacture of resistance welded steel pipe - Google Patents

Abstract

PURPOSE:To equalize a variance of wall thickness of a resistance welded steel pipe, and to obtain steel pipes of different wall thickness from one kind of steel band, by performing the rolling in the wall thickness direction to an intermediate part of the steel band, and making the side end part thicker than the intermediate part. CONSTITUTION:In a breakdown stand group of a resistance welded pipe forming machine, a forming roller of first inlet side stand is reformed to rolling rollers 23, 24 having notch parts 23b, 24b in corner parts of the roller side ends and changed to a rolling stand, and rolling in the wall thickness direction is performed to the intermediate part of a slit material 1 before it is formed to a tubular body. An end part 1c of the slit material 1 which has been cut is formed to a crossing shape being thicker than the intermediate part. The slit material 1 which has been formed in such a way is formed to a tubular shape successively by a breakdown roller 2, a side roller 3, and also, a fin pass roller 4, brought to induction heating by a work coil 5, and both edges of an open pipe are pressed and joined by a squeeze roller 6.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention is applicable to manufacturing electric resistance welded steel pipes using steel strips, in which steel pipes with different wall thicknesses are manufactured from one type of steel strip, and in which the wall thickness of the steel pipes is The present invention relates to a method of manufacturing an electric resistance welded steel pipe with uniform thickness.

[Prior Art] Electric resistance welded steel pipes are made by continuously forming a steel strip into a tubular body using a group of forming rolls such as breakdown rolls, and then forming the joint part with an electric resistance fI! Connect and connect.

will be outfitted. However, if there is variation in the thickness of the steel strip that is the material, this variation in f directly affects the quality of the steel pipe. For example, a steel strip inevitably has uneven thickness in the width direction of the steel strip called a crown, and when the steel strip is used by slitting it into multiple strips as shown in FIG. The difference in thickness remains as non-uniform thickness of the tube. Cold rolling using a skin pass line is usually used to make the thickness of the steel strip uniform, but since it is a separate process, the number of work steps increases and there is a problem of reduced production efficiency. Since the target is wide steel strips, capital investment is large.

Furthermore, as shown in FIG. 12, the slit material 1 has sag 1a at its side ends, and the wall becomes thinner than the center, which leads to uneven thickness of the tube.

Therefore, the inventors first decided to use t! ! j Gansho 61-22811
A method for manufacturing an electric resistance welded steel pipe as disclosed in No. 3 was provided.

That is, when manufacturing an electric resistance welded steel pipe using a slit material obtained by longitudinally splitting a steel strip into a plurality of strips, the slit material is rolled in the thickness direction before being formed into a tubular shape.

[Problems to be solved by the invention] Prevention of unevenness in pipe wall thickness due to variations in thickness due to crowns, etc. that are destined to exist in the steel strip used as the material, or thinning of the side end portions due to sagging of the slit material. , even 1
The above-mentioned Japanese Patent Application No. 61-228113, in which a plurality of steel walls of different thicknesses can be manufactured from a steel strip of 81 m, has been highly effective in achieving the same quality and increasing the variety of products in small quantities.

However, the slit material with uniform wall thickness is 1A when formed into a tubular shape using a breakdown roll.

Although there are some differences, the side edges are subjected to the effect of becoming thinner.

FIG. 13 shows the case of echnobend forming, in which the slit material 1 is formed at the side end 1 by the upper roll 2a and the lower roll 2b.
When B is bent and formed, the corners are strongly pressed by the lower roll 2b and the thickness is reduced (points indicated by arrows in the figure). Although the extent of this thinning varies, A concave groove is created next to the bead after joining.In other words, the cross-sectional shape of the pipe of the electric resistance welded torsion wave is such that peels rllh and llb are formed on the inner and outer surfaces under pressure when the t-trough melts and collapses, as shown in Figure 14. Although each rises, the thin wall portion forms a concave groove portion 11c on the side of the bead.

The beads xxa and 1xbf'l are removed by a cutting tool placed at the welding position, but they are cut according to the standards! When the bead is removed by jk (broken MA in FIG. 14), a concave groove portion 11a remains. It is possible to increase the number of cutting lids by deepening the cutting depth of the cutting tool rather than leaving this groove portion lie (broken line B in FIG. 14).

However, by increasing the number of bead-cut lids, even if the appearance is favorable, the problem of insufficient wall thickness remains.

The present invention has been devised to solve the above-mentioned problems of the prior art, and is designed to equalize the variation in wall thickness of electric resistance welded steel pipes caused by non-uniform steel strip thickness. The present invention provides a new method for manufacturing an electric resistance welded steel pipe that can produce a thick steel pipe.

[Means for Solving the Problems] The present invention involves continuously forming a steel strip into a tubular body to produce an electric resistance welded steel pipe. The purpose is to roll the removed middle part in the thickness direction.

[Function] The middle part of the steel strip is rolled in the thickness direction to make the side ends thicker than the middle part. This offsets the thinning of the part and the sagging of the slit material. This eliminates the formation of concave grooves on the side of the bead after spot welding, and prevents the pipe from forming due to variations in thickness due to crowns, etc. that are destined to exist in the steel strip, or from thinning of the side end due to sagging of the slit material. It has the effect of eliminating the non-uniformity of wall thickness, and furthermore, making it possible to manufacture a plurality of different wall thicknesses W1 from one type of steel strip.

Exemplary Pretexts Specific examples of the present invention will be described below. Figure 1 is a plan view showing a group of ERW tube forming machines.The four sets of rolls on the right side of the drawing are breakdown rolls 2.

Also, the 3 sets of vertical rolls next to it are side roll 3, father,
The four sets of rolls in @S are the fin bath rolls 4, and in addition, the set of rolls on the left side of the drawing is the squeeze roll 6 that presses and joins the artist's horns of the open pipes that are induction heated by the work coil 5 in the front. It shows. Among them, the stand that supports and drives the breakdown roll 2 is shown in FIG.

Forming rolls 21. are attached to the upper and lower two shafts 21* and 22*.
22 (referring to the above plate roll 2) is held, and is generally called a breakdown stand. In this embodiment, the forming rolls 21 and 22 of the stand closest to the person in the breakdown stand group of the T-gutter forming machine having the roll arrangement shown in FIG. 1 are shown in FIG.

The rolling rolls 23 and 2a having notches 23b and 24b at the corners of the roll side ends are replaced with a rolling stand, and a wall thickness direction is inserted into the middle part of the slit material 1 before it is formed into a tubular body. As shown in the figure, the cross-sectional shape is thicker than the middle part due to rolling.

The slit material 1 formed in this way is passed from the plate roll 2 to the side roll 3 and further to the fin pass roll 4.
Both edges of the open pipe, which has been successively formed into a tubular shape and heated by fat conduction in the work coil 5, are squeezed with a squeeze roll 6.
Pressurize and join. The shape of the cross section of the welded portion of the steel pipes thus joined is shown in Figure 't-i7. As is clear from Fig. 7, the concave groove 11a that occurred on the side of the female dome 11m was hardly recognized, and by removing the bead by the amount of cutting (fracture 11!A) according to the standard, a good shape without a concave groove was obtained. An electric resistance weld is obtained. It is sufficient that the width of the unrolled side end (6 in FIG. 4) is 1.5 times the rolled wall thickness.

Figure 8 shows the actual wall thickness of the center and end portions of a hot rolled steel strip with a nominal wall thickness of 13.7 m, and the actual wall thickness of the slit material side end obtained from the end of this hot rolled steel strip. This is the result of measuring the actual wall thickness of the side end of the slit material after the slit material was plated and 9-roll formed.

In a hot-rolled steel strip, the central portion thereof is thicker than the end portions, and this is due to the presence of cracks in the hot-rolled steel strip. The side edges of the 9-slit material obtained by longitudinally cutting a hot-rolled steel strip are thinner due to sagging (cross-marked lines in Figure 8).
. When such slit material is formed into a tubular shape using a group of electric resistance welding tube forming machines, the side edges of the slit material, which have thinned due to edging, will further increase in thickness due to breakdown roll forming (Fig. 8). ). However, because the middle part of the hot-rolled steel strip is thick due to the presence of the crown (No. 8
(marked in the figure), offsets the thinning caused by the sagging or breakdown rolls that occur at the side edges of the slit material. Therefore, even if the actual thickness of the side end portion of the slit material obtained from the middle portion of the hot rolled steel strip is greater or less than the nominal thickness, the difference will be small.

Figure 9 shows a slit material obtained from the middle part of a hot-rolled steel strip (which has a thick wall due to the presence of a crown), which is slit by the method of the present invention so that the actual wall thickness of the middle part is 13.7 m+. The results of measuring the wall thickness in the circumferential direction when rolled into an electrical resistance welded steel pipe show that an extremely excellent electrical resistance welded steel pipe with a dimension of N was obtained without forming deep grooves on the side of the bead. Furthermore, Fig. 10 shows an example of obtaining T-seam tubes with different wall thicknesses by actively rolling the middle part of the slit material.
This is the measurement result of the wall thickness in the circumferential direction when it is 3.2m,
In this case as well, steel pipes with different wall thicknesses with extremely excellent dimensional accuracy were obtained.

In one actual example, both the upper roll and the lower roll that define rolling in the thickness direction at the middle part of the slit material were rolls having notches at the corners of the roll side ends. Either the upper roll or the lower roll is a flat roll with no notches at the corners of the roll side edges.
By rolling the middle part of the slit material, the end shape of the slit material is changed to a shape 1d, le as shown in FIG. 5 or 6.
The same effect can be obtained as well.

[Effects of the Invention] As explained above, according to the present invention, the uneven wall thickness of the slit material, which is inevitably derived from the uneven wall thickness caused by the crown etc. present in the hot rolled steel strip, can be made uniform. ,Also,
Due to the sagging of the slit material and the thinning of the side end portion caused by the breakdown roll forming, it is possible to prevent the formation of grooves on the side of the peed when sewing the sewn steel pipe. As a result, an extremely excellent effect can be obtained in that it is possible to prevent the occurrence of rejected products due to insufficient wall thickness.

Furthermore, since steel pipes with different wall thicknesses can be obtained from LFI type steel strips by actively rolling the slit material, there is no need to generate surplus material in the case of small-volume, high-mix orders.

In addition, there is no need to install new equipment for rolling the middle part of the slit material in the thickness direction, and only minor changes are required, making it extremely economical with little capital investment. Effects can be obtained.

[Brief explanation of the drawing]

Fig. 1 is a plan view showing a group of ERW pipe forming machines, Fig. 2 is a front view of a general breakdown stand, and Fig. 3 is a plan view showing a group of ERW pipe forming machines. At the corners on both sides of the rolls that are incorporated into the group! FIG. 4 is a front view of a breakdown stand with a crack, FIG. 4 is a state diagram of the side end of the slit material rolled by the break stand shown in FIG. 3, and FIGS. A diagram showing the state of the side end of the slit material when the middle part of the slit material is rolled according to another example, and FIG. 7 is a diagram showing the cross-sectional shape of the ERW welded part of the ERW welded steel pipe obtained by the present invention. Figure 8 is a diagram showing an example of dimensional changes after the hot-rolled steel strip, slit material, and slit material are broken down roll-formed, and Figure 9 is a diagram showing an example of dimensional changes after the hot-rolled steel strip, slit material, and slit material are broken down roll-formed. FIG. 10 is a diagram showing an example of the circumferential thickness measurement results of electric resistance welded steel pipes with different wall thicknesses obtained by the method of the present invention; is a perspective view showing that slit materials with different wall thicknesses can be obtained from a steel strip having a crown, FIG. 12 is a schematic diagram of esso sagging at the end of the slit material, and FIG. 13 is a diagram showing that the end of the slit material is a breakdown roll. Figure 1 showing the state of being strongly pressed by
FIG. 4 is a diagram showing the cross-sectional shape of the n7'c [line welded part] obtained by the prior art. 1...Slit material%2...Flake down roll,
3... Side roll, 4... Fuinno (Throll,
5... Work coil, 6... Squeeze roll, 23
．． 24...Rolling roll. Applicant's Representative Patent Attorney Takehiko Suzue Figure 1 Figure 2 Figure 11 Figure 12 Figure 13 Figure 14

Claims (1)

[Claims] When manufacturing an electric resistance welded steel pipe by continuously forming a steel strip into a tubular body, rolling is performed in the thickness direction on the intermediate portion of the steel strip excluding the side ends during the forming process of continuously forming the steel strip into a tubular body. Characteristic manufacturing method of ERW steel pipes.