JPS60250886A - Manufacture of electric welded steel pipe - Google Patents

Abstract

PURPOSE:To manufacture an electric welded steel pipe having no defect by calculating the torsion quantity of a welding joint part from a detected camber quantity, and cutting exactly a seam part by controlling a bead cutting position, in a process of executing the seam welding by forming a continuous feed strip to a shape of a round pipe. CONSTITUTION:A camber quantity thetas of a band plate 10 whose both ends have been trimmed 14, of a continuous feed strip is detected 15, and an angle of torsion alphas after seaming is calculated by a prescribed expression by a central processor 13. When its camber part passes through cylindrical shape forming parts 16-28 and is brought to high frequency heating welding, and the inside and the outside of a bead are cut 32, the cutting is executed by shifting cutting devices 32a, 32b by the angle of torsion alphas. The seam part is always cut exactly, and an electric welded pipe becomes a product having no defect.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing an electric resistance welded steel pipe, and more particularly to a manufacturing method for controlling the cutting position of a weld bead in a steel pipe manufactured from a strip having a camber.

[Conventional technology]

An outline of the manufacturing process of electric resistance welded steel pipes will be explained with reference to FIG.

In general, an electric resistance welded steel pipe is manufactured by unwinding a coiled strip 10 using an uncoiler, flattening it using a reshaping device 12, and then trimming both sides of the strip to a predetermined width using a trimming device 14. A so-called pre-processing process is performed to finish the edge end face, and the strip is sequentially formed into a cylindrical shape using breakdown rolls 16 or cage rolls 20, etc., and circumferential reduction is performed using fin bath rolls 22, 24, and 26. The joint edge portion 34a is then finished formed into a blank pipe 34 of a predetermined shape and size while stably forming the joint edge portion by rolling the joint edge portion.Then, the joint edge portion 34a is subjected to high frequency heating and upset welded using a squeeze roll 30. A bead cutting device 132 (32a) is installed on the downstream side of a squeeze roll to remove a molten steel bead generated by upset welding.

32b) by a series of two steps.

In the production of electric resistance welded steel pipes as described in Section 2, the camber of the strip plate 10 has a very large influence on the molten steel bead cutting after welding.

Here, as shown in FIG. 3 showing a partial plane of the strip plate 10, the center line of the strip plate 10 is not a straight line but has an arc shape or a meandering shape along the longitudinal direction of the strip plate 10. It refers to the state of being

The band plate with camber is slightly trimmed as shown in Fig. 4(a) by adjusting the trimming allowance of the left and right edges in the side trimming process using rotary shear one-way or milling method, which is a pre-processing step in manufacturing the ERW steel pipe. Although processing can be performed to reduce the amount of camber, sufficient adjustment processing is required for large cambers due to the reduction in yield due to the set band width WS and the trim loss ΔW shown by the body line in the figure. However, as shown in FIG. 4(b), the strip plate still has camber even after the trimming process. If the correction is completely carried out by trimming, as shown in Fig. 4 (C), the band width will be insufficient as shown in Fig. 4 (C), and a steel pipe with the specified outer diameter will not be manufactured. That was impossible.

A strip plate having such camber is rolled into a semi-cylindrical shape using rough forming rolls such as breaktown rolls or cage rolls in the forming process, and is finished formed into a raw pipe using a fin pass roll, which is a finishing roll. When the edges of the parts are subjected to high-frequency heating and upset welding, the raw pipe parts with the above-mentioned camber will undergo so-called seam twisting, in which the weld seam rotates in the circumferential direction, after squeeze welding, that is, as it progresses from fin pass forming to the downstream process. This causes bead cutting defects due to misalignment of the bead cutting position in the inner and outer bead cutting equipment installed after squeeze roll welding. For this reason, at present, the operator visually observes the deviation of the bead position and changes the bead cutting position, or the tracking is insufficient, resulting in defective bead cutting and defective weld shape quality. is inviting.

FIG. 5 schematically shows the forming state of the raw pipe in the forming process and the bead cutting process when there are cans/heaves in the band plate.

For example, as shown in Fig. 5(a), a band plate portion having a convex camber to the left when viewed from the paper is formed by rough breakdown roll or cage roll forming, and is formed at the pass center as shown in Fig. 5(b). This results in a misaligned state in which the center of the strip rotates clockwise, a state that causes a so-called rolling phenomenon of the strip.

When a semi-cylindrical blank tube with such rolling is finished formed by the fin pass rolls in the subsequent stage, the apparent low link is corrected by the restraining force from the fin rolls, but such camber is If the raw pipe section that has the material passes through the fin pass roll, the binding force of the raw pipe edge will weaken,
At the position of the heat cutting device after welding, seam twist occurs in which the beat position rotates in the circumferential direction, as shown in FIG. 5(c). For this reason, when camber exists in the band plate, the seam twisting causes bead cutting failure and bead cutting failure, which necessitates re-cutting the bead in a subsequent process, leading to an increase in the number of maintenance steps.

[Problem that the invention seeks to solve]

In order to solve the problems such as defective bead cutting caused by seam twisting of a strip plate having camber as described above, the present invention has the following features:
By detecting the amount of camber of the band plate portion having a can/height, calculating the seam twist at the bead cutting position based on the detected amount, and controlling the position of the bead cutting device based on the calculation result, the camber can be adjusted. The present invention provides a method of manufacturing an electric resistance welded steel pipe with the aim of stabilizing bead cutting of a band plate portion.

[Means for solving problems]

In order to eliminate the causal relationship between the forming behavior and the occurrence of forming defects in each forming process of a band plate section having camber, the inventor conducted a series of camber/contact forming experiments, and analyzed the data. We have clearly understood the relationship between board camber and seam twist.

The present invention was completed based on this knowledge, and involves forming a continuously fed strip into a cylindrical blank pipe, welding the joint edges, and cutting off the molten steel bead that occurs at the weld. When manufacturing electric resistance welded steel pipes to be welded pipes, the camber of the strip is detected by a camber detector, and from the detected amount of camber, the amount of seam twist at the weld joint caused by the camber of the strip is calculated, and the seam twist is calculated. The present invention is characterized in that the cutting position of the bead cutting device is controlled based on the amount.

The present invention will be specifically explained below.

FIG. 1 is a block diagram showing the overall process of the present invention, and FIG. 2 is a cross-sectional view of an electric resistance welded steel pipe showing the cutting position of the inner and outer bead cutting device according to the present invention.

The present invention calculates the amount of seam twist at the heat cutting position due to the camber of the strip lO based on the detected camber information obtained from the camber detector 15 installed on the entry side of the ERW tube forming machine. When the camber portion is bead cut by the bead cutting devices 32a and 32b shown in FIG. control the rotation to
This is intended to prevent bead cutting defects.

According to research conducted by the present inventor, it has been found that there is a close correspondence between the camber of the strip and the seam twist as shown in FIG. Figure 6 is an example of actual measurement results of the strip camber amount Ci and seam twist θS when there is meandering camber.The tube size is 20 inches outside diameter and the plate thickness! It is 15mm.

The amount of seam twist O8 is shown as a function of the camber amount C1 of the strip, the distance Z from the final fin pass of the heat cutting device, the strip strength σy, the strip thickness t, the outer diameter D, and the fin pass reduction r.

θS=±(Ci, Z, cry, t, D, r)・
...(1) Here, once the pipe size is determined, σy, t.

D and r are determined, and Z is usually fixed constant by a pipe making machine. Therefore, once the pipe size is determined, the amount of seam twist O8 is uniquely determined by the amount of camber C1. Figure 7 shows the amount of seam twist θ after determining the pipe size.
This shows the relationship between S and the camber amount C1, and there is an almost linear relationship between the two, and the camber amount C1 of the strip plate
Once i is determined, the amount of seam twist θS can be estimated.

Furthermore, once the convex side of the camber is determined, the direction of seam twist is also determined.

As mentioned above, once the pipe size is determined, σy.

t, D, and r+Z are determined, and the rotation of the beat after welding, that is, the seam twist amount O8 and its twist direction can be calculated from the detected can/height amount Ci. and,
Reseam twist angle αS from calculated seam twist amount O8
is calculated by the following formula.

θs
External bead cutting device 32a, internal bead cutting device 32b
Controls the rotation of the cutting position.

[Effect]

Hereinafter, the implementation procedure of the method for controlling the bead cutting position after welding of a strip having a camber according to the present invention will be explained based on an example of the control output.

FIG. 1 shows a block diagram of the present invention, and FIG. 8 is an explanatory diagram of camber measurement and cutting position control. This shows an example of the present invention in which there is a / to.

In FIG. 1, the camber of the strip is detected by a strip camber detector 15 installed on the exit side of the strip edge I/rimming device 14. The amount of strip camber is determined by the central processing unit 1.
In step 3, the magnitude of the detected camber amount is determined. As a method of camber detection control, for example, as shown in FIG. 8, the camber amount Ci is detected and stored every minute time ΔT from the point at which the camber detection amount exceeds the set camber detection level Cs. Then, the central processing unit 13 calculates and determines the rotation amount αS of the inner and outer bead cutting device from the detected camber amount Ci, and at the same time determines the rotation control direction.

Furthermore, the delay time for implementing bead cutting position control is calculated from the mill speed and the distance from the camber detector to the bead cutting device position, and appropriate controlled cutting is performed when the strip having a camber amount Ci passes through the inner and outer bead cutting devices. make it possible.

FIG. 9 is a flowchart showing the following steps.

〔Example〕

2. The effect of controlling the bead cutting position of a strip plate when it has a camber according to the present invention will be explained in comparison with conventional molding.

Implemented pipe size: 24 inches x 6.35, API 5L'
X, When the bead cutting position control method of the present invention is used (example) and when it is not used (comparative example)
shows.

When the control according to the present invention is carried out, the bead cutting of the inner and outer surfaces at the camber portion is good as shown in FIG. Manufacture has become possible.

In the comparative example, as shown in FIG. 10(b), bead remains 40 on some of the inner and outer surfaces and a step defect 42 due to scraping of the raw tube portion occurred, resulting in defective bead cutting at the welded portion.

[Effects of the Invention] When manufacturing an ERW steel pipe from a strip having camber, the present invention detects the amount of camber, calculates the seam twist, and controls the cutting position of the bead cutting device, which eliminates the need for time and effort. It is possible to cut beats accurately and stably without any defects, and to manufacture excellent ERW steel pipes without defects.

[Brief explanation of drawings]

Fig. 1 is a process diagram showing the manufacturing process of an ERW steel pipe to which the present invention is applied, Fig. 2 is a sectional view of the ERW pipe showing cutting position control of the inner and outer bead cutting device according to the invention, and Fig. 3 is a band plate. FIG. 4 is a plan view showing the state of edge I and rimming of a strip plate with camber, and FIG. 5 is an explanation showing the forming process of the strip plate with camber and the bead cutting process. Figure 6 is a graph showing an actual measurement example of the camber of the strip plate and the seam twist at the bead cutting position.
FIG. 7 is a graph showing the relationship between the amount of strip camber and the amount of seam twist, FIG. 8 is an explanatory diagram showing an example of control output in controlling the cutting position of the inner and outer bead according to the present invention, and FIG. 9 is the operation of the present invention. A flowchart showing the procedure, FIG. 10 is (a)
FIG. 3 is a partial cross-sectional view of an electric resistance welded pipe showing a bead cutting state in a practical comparison between an example of the present invention and a comparative example (b). IO...Strip plate 12...Leveler 13...Central processing unit 14...I-rimming device 15...Camber detector 16...Break town roll 18...Edge forming roll 20... ...Cage roll 22.24.26...Fin pass roll 27...Contact chip 28...Seam kite roll 30...Swivel roll 32a...Outer surface bead cutting device 32b...Inner bead cutting device 33 ...Seam 34...Made pipe 34a...Made pipe edge 36...Welded pipe 40...Bead cutting remaining 42...Step defect due to cutting of the material pipe portion Applicant Kawasaki Steel Co., Ltd. Agent Patent Attorney Yoshi Kosugi Male Patent Attorney 10 Fumoto Kazunori Fuji Figure 4 (Q) (C) Figure 5 (a) Figure 8 Figure 6

Claims (1)

[Claims] ■ Camber detection is used when manufacturing ERW steel pipes, in which continuously fed strips are formed into cylindrical blank pipes, the seam edges are welded, and the molten steel beads that form at the welds are cut to create welded pipes. Detecting the camber of the strip plate using a device, calculating the seam twist amount of the weld joint caused by the camber of the strip plate from the detected amount of camber, and controlling the cutting position of the bead cutting device based on the seam twist amount. A method for manufacturing an electric resistance welded steel pipe.