JPH0356831B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is made of a metal strip having a thickness of 0.5 mm or less, and has an outer diameter plate thickness ratio (outer diameter/plate thickness) of 20 to 150.
The present invention relates to a method of manufacturing a thin-walled round tube-shaped electric resistance welded tube within the scope of the present invention, and particularly relates to a method of bending and forming a metal strip into a round tube shape using a series of rolls.

A conventional method of manufacturing a thin-walled electric resistance welded tube is shown in FIGS. 1 to 5. First, as shown in Figure 1,
The metal strip 8 wound around the uncoiler 1 is formed into a round shape by the roll group 2, the abutting end surfaces of the metal strip 8 are heated and melted by the heating coil 3 connected to the high frequency oscillator 7, and the molten metal is heated by the squeeze roll 4. Extrude and pressure bond. Thereafter, the outer bead is cut by a cutting tool 5 and shaped or corrected into a predetermined shape by a group of shaping rolls 6 to continuously manufacture the electric resistance welded tube 9. The pipe forming speed at that time is 60 to 200 m/min. In the forming roll group 2 produced by this manufacturing method, as shown in the forming cross-sectional view in FIG. Close. The roll forming state at that time is shown in FIG. The formed cross section 11 shown in FIG. 2 is obtained by the center forming roll 23 shown in FIG. 3a,
The formed section 12 is formed by a fin pass roll 24 shown in FIG. 3b. However, the forming rolls 23 and 24 have a slight runout of about 10 μm with respect to the axis. This runout cannot be eliminated, but there is a limit to how much it can be reduced due to roll manufacturing. For this reason, in forming using the oval center forming roll 23 shown in FIG. 3a, the clearance between the upper and lower rolls 23 changes due to the deflection of the forming roll 23, and the stress in the thickness direction changes. For this reason, the molded material 14 shown in FIG. 4 twisted by center forming causes a difference in elongation (longitudinal direction) from side to side, causing a variation in the amount x. The x amount shows positive and negative values in synchronization with roll runout (0.01 to 0.03 mm). At this time, the molded material 14 is twisted as shown in FIG. 5a. This twisted formed material 14 is subjected to a geometrical restraining force to become straight between the fiber rolls 24, one of which has a compression roll 24a.
As shown in Figure b, end face strain 15 occurs on the end face side of the strip where the elongation is large. The end face distortion 15 becomes a joint defective portion 16 shown in FIG. 5c during the next welding process, which greatly deteriorates the quality of the electric resistance welded pipe. FIG. 5d shows a cross section of the poorly bonded portion 16.

In addition, Japanese Patent Application Laid-open No. 58-196181 discloses that in roller forming of thin-walled electric resistance welded tubes, thin-walled electric resistance welding is performed to form a part of a certain length from the end of the plate into a shape close to an ellipse (or oval) without bending it. A method of forming a tube is disclosed.
The purpose of this forming method is to prevent the occurrence of edge backling due to edge bending, prevent deterioration of the butt shape due to spring back, etc., and obtain an ideal end face shape. However, the above-mentioned problem that the clearance between the upper and lower rolls fluctuates due to the runout of the center forming rolls, resulting in fluctuations in stress in the plate thickness direction, resulting in end face distortion and defective joints, remains unsolved. .

The present invention has been made in view of the above-mentioned points, and an object of the present invention is to provide a method for manufacturing a thin-walled electric resistance welded pipe that eliminates end face distortion that occurs on the end face of a metal strip.

The configuration of the present invention will be described below with reference to FIGS. 6 to 13.

First, the flat metal strip 8 that is continuously supplied from the uncoiler 1 is rounded by turning only the end surface of the strip as shown in FIG. 6a.
The formed cross section 10 is formed by an edge forming roll 22 that performs a bending (curved surface bending) process. Next, as shown in FIG. 6b, only the central part of the strip forming the formed cross section 10 is bent,
Set it to 7. The tip of the V-shaped bend forms a radius of 1 to 3 mm. The optimal V-shaped bending angle is 80° to 120°. The seventh figure shows a perspective view of the configuration of V-shaped bending.
Also shown in the figure. After the V-shaped bending, a series of round forming steps were carried out to form a round strip having a forming cross section 12 using a fin pass roll 24 having a compression roll 24a on one side, as shown in FIG. 6c. A sectional view of the molded material in this series of steps is shown in FIG. In this process of the method of the present invention, the end face is first processed into an R (curved surface) like a strip by the formed cross section 10, so the rigidity of the end face of the material is increased and the end face strain 15 is less likely to occur. In addition, the upper mold 1 of the V-show shown in FIG.
In the forming method according to No. 8, since a long forming area in the longitudinal direction can be obtained without applying stress in the thickness direction of the material, the forming amount is similar to that of the center forming roll 23 shown in FIG. Moreover, since the forming process does not apply stress to the plate thickness, even if the horizontal guide rolls 19 run out, there will be no difference in elongation in the left and right longitudinal directions of the V-shaped strip 17. That is, unlike the conventional case, the twisted state 14 shown in FIG. 5A does not occur, so that the end face strain 15 does not occur. Furthermore, by forming the plate while applying compressive stress in the width direction when processing it from a V-shape to a round shape using the fin-pass roll 24 having the compression roll 24a shown in FIG. 6c, the fin-pass roll 24 No edge distortion occurs after molding.

Other examples will be described.

1. Although the present invention has been described in terms of high-frequency induction welding in the manufacture of ERW tubes, it can be applied to any joining method such as high-frequency resistance welding, etc. 2. The explanation was made by making a pipe, but as shown in Figure 12a, the welded part 1
3 is the elliptical tube located at the minimum curvature part, the first
Fig. 2b shows an elliptical tube in which the welded part 13 is located at the maximum curvature, Fig. 13a shows the welded part 13
Flat tube where is located in the curvature part, Fig. 13b
The present invention can also be applied to flat tubes in which the welded portion 13 is located on a flat portion, and other irregularly shaped tubes.

3. The method of bending into a V-shape in the series and forming process of the present invention is as shown in FIGS. I installed it, but the 8th
As shown in the figure, the upper side is a V-shoe upper die 18, and the lower side is a V-shoe lower die 20 instead of the guide roll. Even if the V-Show lower mold 20 is installed in the 10th
As shown in the figure, V-shaped bending is also possible by installing a vertical V-shaped roll 21 on the upper side and a vertical V-shaped roll 21 on the lower side.

As described above, in the manufacturing method of the present invention, first, only the end face of the flat metal strip is subjected to R bending, so that the rigidity of the end face can be increased and the occurrence of end face strain can be prevented. Next, only the central part of the metal strip is bent into a V-shape, and since no stress is applied in the thickness direction of the metal strip during the V-bending process, the left and right sides of the V-shaped metal strip are There is no difference in elongation in the longitudinal direction, and at the same time an appropriate amount of molding is obtained, the metal strip is less likely to become twisted, which prevents end face strain from occurring, and then the entire circumference of the metal strip is restrained. Since we use the fin pass forming method that applies compressive stress in the width direction of the plate, no edge distortion occurs at all. Therefore, there is an excellent effect that there will be no defective joints when welding processed metal strips.

[Brief explanation of drawings]

Fig. 1 is a front view showing the conventional manufacturing process, Fig. 2 is a sectional view showing the forming state of the metal strip, Fig. 3 is a sectional view showing the roll forming state at that time, and Fig. 4 is the torsion of the formed material. Cross-sectional view showing the state, Figure 5 a, b,
c is a perspective view showing a state where poor bonding appears;
Figure d is a cross-sectional view of the defective joint. 6 to 13 are drawings for explaining the method of the present invention, and FIG.
Figures a, b, and c are cross-sectional views showing the molding state; Figure 7 is a perspective view showing the molding state shown in Figure 6b; Figures 8 to 10 are perspective views showing other embodiments; The figure is a cross-sectional view showing a molded state by the method of the present invention, and FIGS. 12 and 13 are cross-sectional views showing other shapes of the electric resistance welded tube manufactured by the method of the present invention. 9... ERW pipe, 10... Formed cross section by edge forming, 12... Formed cross section by fin pass roll, 13... Welded part, 17... V-shaped strip formed into V-shape, 18... Upper mold of V show,
19... V show horizontal guide roll, 20... V
Lower die of shoe, 21... Vertical V-shaped roll of V shoe, 22... Edge forming roll for forming the end of the strip, 24... Fin pass roll.

Claims (1)

[Claims] 1. Only the end face of a flat metal strip is bent into a curved surface, then only the center part is bent into a V shape without applying stress in the thickness direction of this metal strip, and then the metal strip is bent into a V-shape. A method for manufacturing a thin-walled electric resistance welded pipe, which is characterized by constraining the entire circumference and bending the pipe into a predetermined cross-sectional shape while applying compressive stress in the width direction of the pipe.