JPS60250825A - Forming method of electric welded pipe - Google Patents

Abstract

PURPOSE:To stabilize the formation of a strip by detecting the camber quantity of the strip and controlling the formation in accordance with the camber quantity. CONSTITUTION:The camber of the strip 10 is detected by a strip camber detector 15. The rolling reduction of fin pass rolls is determined from the detected camber quantity in the stage when the camber part is formed by fin pass rolling if the detected camber quantity of the strip 10 exceeds the reference set camber quantity permissible in fin pass rolling. The draft is then changed and controlled in accordance with rolling reduction of the fin pass rolls. A central processing unit 13 operates the delay time for the execution of the screw-down control of the fin pass rolls from the distance from a mill speed and camber detector 15 to the positions of the fin pass rolls 22, 24, 26 to be controlled. The unit outputs the command so as to execute adequate control in the stage when the strip part having the camber quantity passes through the respectively controlled fin pass roll positions.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for forming a strip in the manufacturing process of electric resistance welded steel pipes, and more particularly to a method for controlling the forming of a strip having camber.

[Conventional technology]

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

In general, for ERW steel pipes, a coiled strip 10 is unwound by an uncoiler, flattened by a leveler 12, and then both sides of the strip are trimmed to a predetermined width by a trimming device 14, and the strip joints are 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, and circumferential reduction is performed using fin pass rolls 22, 24, and 26. The joint edge part 34a is finished and formed into a blank pipe 34 of a predetermined shape and size while stably forming the joint edge part by rolling the joint edge part 34a.Then, the joint edge part 34a is high-frequency heated and upset welded with a squeeze roll 30. A bead cutting device 37 (32a) installed on the downstream side of the squeeze roll cuts the molten steel bead produced by upset welding.

32b) by cutting and removing.

In manufacturing the above-mentioned electric resistance welded steel pipes, the shape of the strip,
In particular, the influence of the camber of the strip lo on the formability and weldability of the raw tube is extremely large.

Here, the camber of the strip plate 10 means that 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, as shown in a partial plane of the strip plate 10 in FIG. Refers to the condition.

The band plate having camber can be slightly cut as shown in Fig. 3(a) by adjusting the trimming allowance of the left and right edges in the side trimming process using the rotary shear one-way method or milling method, which is a pre-processing step in manufacturing the ERW steel pipe. can be processed to reduce the amount of camber, but for large cambers, sufficient adjustment processing is required in order to reduce the yield due to the set band width Ws and the trim loss ΔW indicated by diagonal lines in the figure. 3rd
As shown in Figure (b), the band plate still has camber after the trimming process.

If the camber correction were to be completely corrected by trimming, as shown in Figure 3 (C), the band width would be insufficient (Ws), making it impossible to manufacture a steel pipe with the specified outer diameter. It may not be possible.

As a method for correcting the camber of a rolled product coil, for example, there is a method of correcting the coil camber using a camber correction device on the molding entry side as shown in JP-A-53-1c) 0157. There was a problem.

(1) Rolling and stretching the coil requires a large-scale orthodontic device, which increases equipment costs.

(2) Roll the edge on one side to correct the camber,
In the case of distraction, the plate thickness of the left and right edges is different due to the decrease in the plate thickness of one edge, leading to edge lap and bead cutting defects in welding upsets.

(3) The edge portion of the coil that has been elongated by straightening rolling tends to be wavy in the longitudinal direction.

On the other hand, if a strip plate with camber is rolled into a semi-cylindrical shape using rough forming rolls such as breakdown rolls or cage rolls in the forming process, and then finished forming into a blank pipe using a fin pass roll, which is a finishing forming roll, the above-mentioned results will be obtained. In the strip plate portion having such camber, several forming defects as described below occur, leading to defective welding or defective bead cutting, etc., resulting in a decrease in yield.

For example, in the case of forming a band plate portion having a camber as shown in FIG. 4(a), the forming condition of the band plate portion that breaks the camber and occurrence of molding defects in each forming process will be explained. As shown in Fig. 4(a), the band plate portion having a convex camber to the left when facing the plane of the paper is formed by breaktown roll or cage roll forming in the rough forming area, and as shown in Fig. 4(b), the band plate portion has a convex camber to the left. On the other hand, the center of the strip rotates clockwise, resulting in a so-called rolling phenomenon of the strip. When the semi-cylindrical blank tube in such a rolling state is finished formed by the fin pass rolls at the subsequent stage, the amount of forming work at the left and right edge portions differs greatly, as shown in FIG. 4(C).

In other words, when the rolling state as shown in Fig. 4(b) is exhibited, the amount of forming processing on the left edge portion in fin pass roll forming is extremely large compared to the processing amount on the right edge portion, as shown in Fig. 4(C). In this case, the degree of compression bending of the right edge portion becomes smaller and falls below the appropriate amount of compression in fin pass roll forming, resulting in processing defects. For this reason, as shown in FIG. 4(d), an edge wave is generated at the right edge portion, resulting in an open pipe that cannot be welded.

[Problem that the invention seeks to solve]

The present invention aims to eliminate molding defects when molding a strip plate having a camber as described above without correcting the camber.
The present invention provides a method for forming an electric resistance welded steel pipe, the purpose of which is to stabilize the forming of a strip by controlling the forming of the can/height portions according to the amount of camber.

[Means for solving problems]

The present inventor conducted a series of camber investigation molding experiments in order to resolve the causal relationship between the molding behavior and the occurrence of molding defects in each molding process of a strip plate portion having camber, and by analyzing the data, the results shown in Fig. 4 are shown. The series of forming behaviors shown were investigated and understood.

The present invention was completed based on this knowledge, and includes detecting the amount of camber of the strip and controlling the forming based on the detected amount of camber when forming a strip having camber into an ERW steel pipe. It is characterized by

In addition, as an embodiment of the forming control based on the amount of camber, when the camber portion of the strip is formed with the fin pass roll, a forming force method is used in which the amount of reduction of the fin pass roll is controlled based on the detected camber amount. It is.

An example of molding defects that occur during the molding process of a strip plate portion having camber is the generation of edge waves in fin pass molding. Accordingly, by performing stratification control by controlling the amount of fin pass reduction, occurrence of molding defects due to camber is prevented.

As for the reduction control, the fin pass reduction is controlled in the direction of increasing the force by 1 to solve the insufficient compression bending of the concave edge of the gapper and provide a degree of processing within the appropriate reduction range. As a reduction control method, for example, a method of controlling the glue reduction of the first fin pass roll according to the detected amount of camber, or a method of controlling the reduction distribution of the fin passes as the same,
There are methods of controlling the entire fin path glide reduction, and any of them may be used.

The fin path reduction control amount is calculated and determined as a function of the camber amount Ci, the strip strength σy, the plate thickness t, and the tube outer diameter.

Hereinafter, an embodiment of the forming control method for a strip plate having camber according to the present invention will be described based on an example of control output.

FIG. 1 is a block diagram of an embodiment of the present invention, and FIG. 5 shows an example of control output.

FIG. 5 is an explanatory diagram of can/to detection and fin path reduction amount, and in the longitudinal direction of the strip,
1 shows an embodiment of the control according to the invention when there is a camber of a strip having a maximum camber icmax;

In FIG. 1, the camber of the strip is detected by a strip camber detector 15 installed on the exit side of the strip machining/trimming device 14.

If the detected amount of camber C1 of the strip plate exceeds the camber amount Cf set in the fin pass forming allowable standard, as shown in Fig. 4(d), the edge on the concave side of the camber or the fin pass forming may be insufficiently processed, resulting in what is called a wavy edge. An edge wave will occur.

Therefore, if the camber detection amount Ci exceeds the camber/height amount Cf set by the fin pass forming allowable standard, the reduction amount of the fin pass roll is detected when the camber part of the steel strip is formed by fin pass roll forming. It is determined from the camber amount C1, and the reduction is changed and controlled based on the amount of reduction of the fin pass roll.

Furthermore, the central processing unit 13 checks the delay time for implementing the fin pass roll reduction control based on the mill speed and can.
The controller calculates the distance from the camber to the fin pass roll position to be controlled, and outputs a command to perform appropriate control when the strip portion having the camber amount CI passes through each controlled fin pass roll position.

As a method of camber detection, for example, as shown in FIG. to be memorized.

The central processing unit M13 calculates and determines the control amount of the fin pass roll based on the detected offset amount Ci.

For example, the first fin pass reduction r (V) for changing the fin pass reduction control is calculated and output to the control device in accordance with the control output delay time.

Regarding the reduction control of the fin path, as shown in FIG. 5, it is sufficient to set the fin path forming permissible standard setting camber amount Cf, and perform control when this value exceeds the detected camber amount C1.

This is because there is a tolerance range in which the fin path has an appropriate reduction in which edge waves do not occur.
If the amount of reduction of the edge by the fin path is within this allowable reduction range, no edge wave will occur, and therefore there is no need to intentionally change the amount of reduction of the fin pass.

The above procedure of the present invention is shown in a flowchart in FIG.

〔Example〕

The effect of controlling the forming of a strip plate having camber according to the present invention will be explained in comparison with conventional forming. ERW steel pipes with the following specifications were manufactured.

Practical tube size: 24 inches x 6.35 API 5LX, Comparative example).

When the molding control according to the present invention is carried out, there is no occurrence of molding defects or bead cutting defects in the camber portion.
The ultrasonic flaw detection (UST) results of the weld are shown in Figure 7 (a) and (b).
), the results were good, and there were almost no micro-defects below the defect detection level.

In the conventional method, when the camber amount is 45 mm, edge waves occur at the camber part during fin pass forming, resulting in an unweldable open pipe, resulting in a yield drop of about 10% per coil. Welding was possible when the camber amount was 35 mm, but once the welding condition stabilized, a defect (penetrator) occurred in the weld, as shown in the ultrasonic flaw detection results shown in Figure 7 (C).
In addition, bead cutting failures occurred due to the generation of steps at the seam and seam twisting, resulting in frequent occurrence of micro defects, and eventually the camber portion became a defective product.

〔Effect of the invention〕

The present invention detects the amount of camber and controls the forming of the band when manufacturing an electric resistance welded steel pipe from a band having camber. This made it possible to stably form and weld the strips, which had previously been used in the past, to improve the material yield and produce ERW steel pipes with excellent welded shape quality.

[Brief explanation of drawings]

Fig. 1 is a process diagram showing the manufacturing process of an electric resistance welded steel pipe to which the present invention is applied, Fig. 2 is a plan view showing the camber of the strip, and Fig. 3 is a plan view showing the state of edge trimming of the strip with camber. Figure 4 is an explanatory diagram showing the molding condition and failure occurrence situation in the process of forming a strip plate with camber, and Figure 5
The figure is a graph showing an example of the output of forming control for a strip with camber, FIG. 6 is a flowchart showing the procedure of the present invention, and FIG. 7 is a chart showing the results of ultrasonic flaw detection of a welded part of a strip with camber. , (a) Example (Can AM35mm
), (b) Example (camber amount 45 mm), (C)
This is a comparative example (camber amount 35 mm). 10... Band plate 12... Leveler 13... Central processing unit 14... Edge trimming device 15... Yumper detector 16... Breakdown roll 18... Edge forming roll 20...・Cage roll 22, 24, 26...Fin pass roll 28...Seam kite roll 30...Squeeze roll 34...Main pipe 36...Welded pipe applicant Kawasaki Steel Co., Ltd. agent Patent attorney Kosugi Yoshio Patent Attorney Kazunori Saito Figure 2 1n Figure 3 (a) (c) Figure 6 Figure 7 (a) (c)

Claims (1)

[Scope of Claims] l A method for forming an ERW steel pipe, characterized in that when forming a band plate having camber into an ERW steel pipe, the amount of camber of the band plate is detected and the forming control is performed based on the amount of camber. Method. 2 Claims in which the forming control based on the amount of camber is controlling the amount of reduction of the fin pass roll based on the detected amount of camber when the camber portion of the strip plate is formed with the fin pass roll. The molding method according to item 1.