JPH0332420A - Manufacture of resistance welded tube - Google Patents

Abstract

PURPOSE:To obtain a resistance welded tube easy of bead cutting and excellent in inside shape by form ing both edge surfaces of a steel strip so that a part near a steel plate surface making the inside of a tube protrudes to both sides in the width direction before the steel strip is formed in a tubular shape. CONSTITUTION:An edge shaver is provide before an edge forming roll stand and the shaving angle of the edge part 1a of the steel strip, or the inclination from a perpendicular to the steel plate surface of the steel strip preferably is 5-10 degrees so that the width of the lower surface side or the plate surface making the outer surface of the tube is smaller than the width of the steel plate surface making the upper surface side or the steel plate surface making the inner surface of the tube. Then, by an edge forming roll stand, a part 1c near the upper surface of the edge surface 1b makes a sharp angle to the upper surface 1e of the steel strip 1 and a part 1d near the lower surface of the edge surface 1b forms nearly right angles to the lower surface 1f of the steel strip 1. The steel strip having a formed edge part 1a is introduced into a breakdown roll stand and formed in a tubular shape so that the upper surface 1e of the steel strip makes the inner surface of the tube, then, the edge surface 1b is formed flatly by a prescribed roll.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to the production of electric resistance welded pipes, in which a steel band is formed into a cylindrical shape by a group of forming rolls, and the joints are electrically welded to continuously produce pipes. Regarding the method.

[Prior art]

FIG. 7 is a plan view showing the configuration of a conventional electric resistance welded tube manufacturing apparatus, and FIG. 8 is a front view of the main parts of a fin pass roll. Band steel 21
are the breakdown rolls 22a to 2 at the initial and middle stages of molding.
2e and side cluster rolls 23a and 23b, the tube is rolled down in the circumferential direction by fin pass rolls 24'a to 24d as finishing forming rolls, and an edge surface 21c is formed. The edges 21b on both sides are welded by the squeeze roll 26 via the seam guide roll 25, and the raw pipe 21 is
a is formed.

The fin pass rolls 24a to 24d of each stage have substantially truncated conical upper rolls 27 and 28 on the same axis, and the outer peripheral surfaces of these upper rolls 27 and 28 form an arc as a whole. Between the upper rolls 27 and 28 are provided fins 29 whose thickness decreases toward the rear stage! has been done. Each fin 29 of the fin pass rolls 24a to 24d
is a tubular band whose portion presses against both edge surfaces 21c of the steel band 21! 1121 has a linear tapered surface 29a that tapers toward the center.

By the way, the edge part 21b of the band 1m21 immediately before being introduced into the fin pass roll 24a is formed by edge sagging and band [
21 into a tubular shape by the breakdown rolls 22a to 22e, the thickness becomes thinner toward the edge surface 21c. However, as described above, since the tapered surface 29a of the fin 29 is linear, in the fin bath rolls 24a to 24d, the strip steel 21
It is not possible to increase the thickness of the thin edge portion 21b. As a result, both edge surfaces 21b of the steel strip 21 are welded by the squeeze roll 26 while the edge surface 21b remains thin, so the cross section of the edge portion 21b after welding is shown in FIG. It looks like this.

That is, the edge surface 21c of the thinnest part swells as beads 30.31 on the outer circumferential surface 210 and inner circumferential surface 21f of the raw pipe 21a, respectively, due to the reduction by welding, but the bead 30°31
Since the edge portions 21b on both sides remain thinner toward the edge surface 21c, grooves 32 and 33 extending in the axial direction of the blank pipe 21a are formed on both sides of the bead 31 on the inner surface, respectively.

Such a bead 30.31 will be cut and removed by the cutting tool 34 in the subsequent process, but if the cutting tool 34 is sent to position X and the amount of cutting is increased to eliminate the grooves 32.33, the maximum The difference with the wall thickness a exceeds the specified value, resulting in a height defect. On the other hand, if the cutting tool 34 is fed to position iY and the amount of cutting is reduced in order to prevent bead height defects, there is a problem that the grooves 32 and 33 remain even after cutting.

Furthermore, if the cutting amount is increased to widen the cutting width of the beads 30, 31, there is also the problem that the cutting tool 34 scrapes the inner surface of the raw tube 21a on both sides of the beads 30, 31, causing scratches.

Therefore, in order to solve these problems, a method is proposed in JP-A-59-12528 in which the shape of the fin 29 is changed to be thicker so that the edge portion is thickened toward the inner peripheral surface of the tube.
It is disclosed in Publication No. 0.

[Problem to be solved by the invention]

By the way, in the method of increasing the thickness of the edge part by changing the shape of the fins, even when manufacturing tubes with the same outer diameter, if the wall thicknesses differ, fin plates with shapes adapted to the different wall thicknesses are used. There is a problem in that it requires a great deal of cost to own these, it takes time to replace them, and too much load is placed on the fin pass rolls.

The present invention was made in view of the above circumstances, and includes an edge shaver and an edge forming roll provided in front of a forming stand equipped with a breakdown roll, and thickening of the edge portion by interaction between these and a normal fin pass roll. The purpose of the present invention is to provide a method of manufacturing an electric resistance welded pipe that makes it possible to

[Means to solve the problem]

The method for manufacturing an ERW pipe according to the present invention includes sequentially introducing a steel band into a forming roll and a fin pass roll in the longitudinal direction to form a cylindrical shape, and welding the edge surfaces together. , before introducing the steel strip into the forming rolls, cut both edge surfaces of the steel strip so that the width of the first surface of the steel strip, which is the outer surface of the tube, is narrower than the width of the second surface of the steel strip, which is the inner surface. so that the portion of the edge surface closer to the first surface and the first surface form a substantially right angle, and the portion of the edge surface closer to the second surface and the second surface form an acute angle. It is characterized in that both the edge surfaces are formed so as to form the same shape.

[Effect]

Before the steel strip is introduced into the forming rolls, both edge surfaces are first cut so that the width of the first surface of the steel strip, which is the outer surface of the tube, is narrower than the width of the second surface of the steel strip, which is the inner surface. , then, so that the portion of the edge surface closer to the first surface of the trumpet and the first surface form a substantially right angle, and the portion of the edge surface closer to the second surface and the second surface form an acute angle. molded. As a result, both edge surfaces near the second surface, which is the inner surface of the tube, protrude to both sides in the width direction, and when these are pressed together by the fin pass roll, the wall thickness of the edge portion on the inner surface of the tube is increased. .

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below based on drawings showing embodiments thereof. FIG. 1 is a front view showing the configuration of an edge forming roll stand showing an embodiment of the present invention. The edge forming roll stand is provided in front of the breakdown roll stand shown in FIG. 7, and an edge shaver (not shown) is further provided in front of the edge forming roll stand.

The edge forming roll stand is provided with a pinch roll 3°3 that contacts the drawing board surface of the steel strip 1 and rotates as the steel strip 1 is conveyed, regulating the vertical movement of the steel strip 1. On both sides of these, that is, on both edge portion sides of the steel strip I, are provided edge forming rolls 2, 2 whose axial length directions are orthogonal to the surface direction of the steel strip I.

Each edge forming roll 2 has a cylindrical roll surface 2b and a roll surface 2a formed into a conical shape with the upper part thereof at a certain angle. It is configured so that it can be moved to.

Now, as shown in Fig. 2, the steel strip 1 drawn out from the uncoiler has a shape in which the edge part 1a has slit sag, so the width on the lower surface side is wider and it protrudes to both sides in the width direction (in the figure). Only one side is shown>.If the steel strip l is introduced into the edge forming roll stand as it is and is to be formed according to the shape of the edge forming roll 2 described above, it is necessary to apply extremely large pressure to the edge forming roll 2. As a result, various problems arise, which is not preferable.

Therefore, in the method of the present invention, an edge shaver is provided in front of the edge forming roll stand, and the edge forming roll 2
The edges are removed in advance to create a shape that reduces the load on the surface.

FIG. 3 is a cross-sectional view showing the edge portion of the steel strip l after shaving, and the shaving angle of the edge portion 1a is such that the width of the steel plate surface that is the lower surface side, that is, the outer surface of the tube, is on the upper surface side, that is, the inner surface of the tube. It is desirable that the inclination of the steel strip l from the perpendicular to the steel plate surface be 5 to 10 degrees so that the width is narrower than the width of the steel plate surface.

After this, the steel strip 1 is placed in the fourth stage by an edge forming roll stand.
The edge portion 1a is formed into a shape as shown in the cross-sectional view of the figure. In other words, the edge portion 1a is rolled down by the edge forming roll 2, and the upper surface of the edge surface 1b is pressed against the roll surface 2a of the edge forming roll 2, and the lower surface is pressed against the roll surface 2b, so that the upper surface of the edge surface 1b The closer portion 1c is formed at an acute angle with the upper surface 1e of the steel strip 1, and the lower surface portion 1d of the edge surface 1b is formed at an approximately right angle with the lower surface U of the steel strip 1.

Here, the height of the edge forming roll 2 is set so that the boundary position between each surface 1c and ld on the edge surface 1b, that is, the bending position, is on the upper surface side than the thickness A of the steel strip 1. desirable.

Further, it is desirable to form the roll surface 2a of the edge forming roll 2 so that the angle between the upper surface side portion 1c of the edge surface 1b and the perpendicular to the steel plate surface of the strip steel l is 10 to 30 degrees.

Now, the steel strip 1 with the edge portion 1a formed as described above is
Introduced into a breakdown roll stand (not shown),
Breakdown roll and next side cluster roll (
After the steel strip 1 is successively formed into a tubular shape using the steps (both not shown) so that the upper surface 1e becomes the inner surface of the tube, the upper roll is used to install the fins 5 in the middle as shown in the cross-sectional view of FIG. 4
a and the lower roll 4b, the edge surface 1b is formed to be smooth.

In other words, as the edge forming roll stand passes, the upper surface portion 1c of the edge surface 1b is formed to protrude to both sides in the width direction, so that the upper roll 4a
When the tube is pressed against the fins 5, the inner surface of the tube is thickened.

FIG. 6 is a cross-sectional view showing a welded portion that has been welded via a seam guide roll and a squeeze roll (not shown) after the above steps. Peades 6 and 7 are formed on the outer and inner surfaces of the edge portion 1a, respectively.

As is clear from the figure, the bead 7 on the inner side is formed on the thickened part, so the cutting position of the cutting tool 11 should be determined so that the bead 7 is cut and removed including this thickened part. This allows the bead height of the welded portion to be made appropriate.

As a single example, when manufacturing a tube with an outer diameter of 2 mm using a steel strip with a thickness of 11n+, the shaving angle with respect to the perpendicular line using an edge shaver is set to 7 m.The bending position of the edge surface using an edge forming roll is set to sl/3
When the forming angle for protruding to both sides in the width direction was set to 20° with respect to the perpendicular line, a good welded part with increased thickness on the inner surface side was obtained.

〔effect〕

As described above, in the method for manufacturing an electric resistance welded pipe according to the present invention,
Before forming the steel strip into a tube shape, by forming both edge surfaces of the steel strip so that the portions closer to the steel plate surface, which will become the inner surface of the tube, protrude to both sides in the width direction, the welded part is enlarged on the inner surface of the tube. Meat can be rolled using a regular fin-pass roll without placing a large load on the fin-pass roll. As a result, it is possible to manufacture ERW pipes that are easy to bead cut and have an excellent inner shape without increasing costs or replacing the fin pass rolls, resulting in a significant improvement in quality. The present invention has excellent effects.

[Brief explanation of drawings]

Fig. 1 is a front view of an edge forming roll stand showing the implementation state of the method for producing an ERW pipe according to the present invention, Fig. 2 is a cross-sectional view showing the edge portion of the steel strip led out from the uncoiler, and Fig. 3 is a A cross-sectional view showing the edge portion of the steel strip removed by the edge shaver, Fig. 4 is a cross-sectional view showing the edge portion formed by the edge forming roll, and Fig. 5 is a cross-sectional view showing the edge portion introduced into the fin pass roll. , FIG. 6 is a sectional view showing a welded part by the method of the present invention, FIG. 7 is a plan view showing the configuration of a conventional ERW pipe manufacturing apparatus, and FIG. 8 is a front view of the main parts of the same conventional fin pass roll. , FIG. 9 is a sectional view showing a conventional welded part. 1... Band II 2... Edge forming roll 3...
・Pinch roll 4... Fin pass roll 5...
Fin 6゜7...bead

Claims (1)

[Claims] 1. A method for manufacturing an electric resistance welded pipe, in which a steel strip is sequentially introduced into a forming roll and a fin pass roll in the longitudinal direction to form a cylindrical shape, and the edge surfaces are welded together, comprising: Before introducing the steel strip into the pipe, both edge surfaces of the steel strip are removed such that the width of the first surface of the steel strip, which becomes the outer surface of the tube, is narrower than the width of the second surface of the steel strip, which becomes the inner surface, A portion of the edge surface closer to the first surface and the first
The electric resistance welded tube is characterized in that both edge surfaces are formed so that the two surfaces form a substantially right angle with each other, and so that a portion of the edge surface closer to the second surface forms an acute angle with the second surface. Production method.