JP2003164908A - Device for manufacturing seam welded steel pipe - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device for manufacturing a seam welded steel pipe capable of reducing the hydrogen induced cracking of the seam welded steel pipe. <P>SOLUTION: The device for manufacturing a seam welded steel pipe is sequentially provided with forming rolls to form a steel strip into a cylindrical shape, squeeze rolls to weld the abutting parts of both ends in the width direction of the cylinder-shaped steel strip, a bead cutting means to remove weld beads from the inside face and the outside face of the welded parts, a seam annealer to anneal the welded parts and a water spraying nozzle to cool the welded parts, and a reducing mill to adjust the dimensions of the pipe after cooling. A heating unit to heat the running pipe at 550-850°C is installed between the seam annealer and the water spraying nozzle. In this case, the heating unit is preferably composed of induction coils. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric resistance welded steel pipe manufacturing apparatus, and more particularly to a technique for preventing hydrogen-induced cracking that occurs in an electric resistance welded steel pipe.

[0002]

2. Description of the Related Art Generally, an electric resistance welded steel pipe is continuously formed into a cylindrical shape by a group of forming rolls while a raw material steel strip is running, and then the widthwise ends of the abutted steel strips are welded. Manufactured. There are various methods for manufacturing the device and there are various devices, and an example is shown in FIG.

First, a steel strip 1, which is a raw material, has been fed from a steel strip feeder (not shown) to a group of forming rolls 2 with the steel strip surface horizontal and fed at a constant speed. Examples of the forming roll 2 include an edge bend roll 3 in which both ends in the width direction of the steel strip are sequentially bent upward from the entrance side, a center bend roll 4 in which a central portion is bent, and a cage for forming an end portion. The roll 5 and the fin pass roll 6 for finish forming are arranged in series. The steel strip 1 formed into a cylindrical shape by these forming rolls 2 is subsequently heated at its abutted width direction end portions (hereinafter simply referred to as abutting portions or edge portions) with an induction coil 7 or the like, and the squeeze roll 8
It is pressed, pressed, and welded to form a temporary tube body 9. The bead cutting means 10 cuts and removes the bead (not shown in the figure) which is generated on the inner and outer surfaces of the tubular body 9 by the above-mentioned welding, but is a screw-shaped material. Furthermore, ultrasonic flaw detector 1
1. Defect inspection in 1; annealing of welded part (also called seam) in annealing device called seam aniler 12 and water injection nozzle 1
The cooling in 3 is performed sequentially. After that, the dimensions are adjusted by a squeeze rolling machine 14 such as a stretch reducer or sizer, and then cut to a desired length by a cutter 15 on a payout conveying line to obtain a product electric resistance welded steel pipe.

By the way, when the electric resistance welded steel pipe obtained in such a manufacturing process is used as a material for a so-called "line pipe" which is a facility for transporting gas, oil, etc., cracks frequently occur in the electric resistance welded steel pipe. Sometimes. When the cause of this crack was investigated, the material steel corroded and melted under the use environment to generate hydrogen, and the so-called "hydrogen-induced cracking" (hereinafter referred to as HIC) was caused by the hydrogen being stored inside the steel. Say)
It was considered.

Generally, in the steel material, some defects such as non-metallic inclusions and center segregation of the components are generated in the stage of casting from molten steel, but hydrogen is accumulated in these defect parts and HIC
It is said to cause Therefore, as a countermeasure for HIC, refining or casting of molten steel may be performed so as to eliminate defects such as center segregation of these nonmetallic inclusions and components.

However, the HIC generated in the above-mentioned electric resistance welded steel pipe was different from that caused by non-metallic inclusions or center segregation of components.

[0007]

SUMMARY OF THE INVENTION In view of the above circumstances, an object of the present invention is to provide an apparatus for manufacturing an electric resistance welded steel pipe which can reduce hydrogen-induced cracking occurring in the electric resistance welded steel pipe as compared with the prior art.

[0008]

In order to achieve the above-mentioned object, the inventor examined in more detail the cause of hydrogen-induced cracking in an electric resistance welded steel pipe. As a result, in the process of manufacturing the electric resistance welded steel pipe, when the steel strip is formed (mainly with the fin pass roll 6), a reduction is applied in the circumferential direction as shown in FIG. It was determined that the later quality was good. That is, it was considered that the strain generated in the electric resistance welded steel pipe remained due to the stress generated when the steel strip 1 was formed into a circle and / or the stress generated during the butt welding, and the strain deteriorated the HIC resistance. Then, they continued to diligently study measures for preventing the deterioration, and completed the present invention.

That is, according to the present invention, a forming roll for making a steel strip into a cylindrical shape, a squeeze roll for welding the abutting portions of both ends of the cylindrical steel strip in the width direction, and beads from the inner and outer surfaces of the welding portion. A bead cutting means for removing, a seam-aniler for annealing the welded portion, a water jet nozzle for cooling, and an electric resistance welded steel pipe manufacturing apparatus sequentially provided with a drawing rolling machine for adjusting the dimensions of the pipe body after cooling, Seam
Between the aniler and the water injection nozzle, a running tube is installed.
This is a device for manufacturing an electric resistance welded steel pipe, wherein a heating device for heating to 50 to 850 ° C. is additionally provided. In this case, it is preferable that the heating device is an induction coil.

According to the present invention, the strain remaining in the steel pipe is removed by the heating by the newly installed device, and the generation of HIC due to the strain can be prevented. as a result,
It becomes possible to manufacture an electric resistance welded steel pipe with less occurrence of HIC than before, and it becomes possible to stably supply the material for line pipes.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below, including the background of the invention.

Generally, the residual strain of the processed steel material can be removed by heating and cooling the steel material to an appropriate temperature. Therefore, the inventor conducted an experiment in which a steel strip used for an electric resistance welded steel pipe of a steel type in which cracks are relatively frequently generated is subjected to bending and compression as shown in FIG. 4 and then heated. Then, sample pieces were taken from the steel strips subjected to these treatments, and after cross-section polishing, the cross-sections were visually observed and investigated.

As a result, as shown in FIG.
Among them, those that were not heat-treated and the heating temperature was 55
Clear cracks 17, which are considered to be caused by HIC, were recognized in the samples having a heating temperature of less than 0 ° C. and a short heating time.
On the other hand, no crack appeared at all at the heating temperature of 600 ° C. for 1 minute. Therefore, the inventor conducted such an experiment on various types of steel strips, and if all steel types were heated at a temperature of 550 ° C. or higher for several tens of seconds,
It has been found that the generation of cracks 17 can be prevented. Based on this finding, the inventors made an earnest effort to select a heating means and completed the present invention.

That is, according to the present invention, a forming roll 2 for making a steel strip 1 into a cylindrical shape, a squeeze roll 8 for welding abutting portions of both ends of the cylindrical steel strip in the width direction, and inner and outer surfaces of the welding portion. Bead cutting means 10 for removing beads from the
And a seam-aniler 12 for annealing the welded portion, a water jet nozzle 13 for cooling, and an existing electric resistance welded steel pipe manufacturing apparatus sequentially provided with a drawing and rolling mill for adjusting the dimensions of the pipe body after cooling, A heating device for heating the traveling pipe body to 550 to 850 ° C. is provided between the seam-aniler 12 and the water injection nozzle 13. In this case, the heating device is installed on the upstream side of the water injection nozzle 13 because it is economical because it is not necessary to install a cooling means separately. In addition,
The upper limit of 850 ° C. is set for the heating temperature because the effect is saturated even if the heating temperature is higher than that and power is wasted.

In the present invention, the heating means is not particularly limited, and a heating furnace using gas or liquid fuel may be used. However, in those furnaces, it takes a considerable amount of time to adjust the heating temperature to a desired value, and there are some practical problems. Further, since the furnace body becomes large, there is another problem that it is difficult to realize with existing equipment from the viewpoint of installation space. Therefore, in the present invention, as shown in FIG. 1, if the power supply device (inverter 18) is installed at a remote place, the space may be relatively small, and the heating temperature can be easily adjusted to a predetermined value. Installation of the induction coil 19 is preferred. In this case, it is possible to further save the installation space by increasing the capacity of the inverter 18.

Further, in the present invention, it is preferable to use, as the forming roll 2, rolling that starts with the edge bend roll 3 and ends with the fin pass roll 6. This is because, as compared with the other forming rolls 2, it is possible to form the shape quickly and stably.

[0017]

EXAMPLE In the manufacturing process of the existing electric resistance welded steel pipe shown in FIG. 2, a total of 20 induction coils 19 are arranged between the seam-aniler 12 and the water injection nozzle 13, and one of the four induction coils 19 is provided. Inverter 18 with a power supply capacity of 5000 kW
Connected with. Of course, the installation location of the inverter 18 is far from the manufacturing process. And steel type API5LX65, width 1900mm, thickness 1
An electric resistance welded steel pipe was manufactured using a 2.7 mm steel strip.

The manufactured electric resistance welded steel pipe is NACE STA.
HIC resistance was investigated according to NDARD TM0284-96. The results are shown in FIG. 6 at the same time. From FIG. 6, it is clear that the present invention reduces HIC as compared with the conventional case.

[0019]

As described above, according to the present invention, the strain remaining in the steel pipe is removed by heating with the newly installed device, and the occurrence of HIC due to the strain can be prevented. As a result, it becomes possible to manufacture an electric resistance welded steel pipe with less generation of HIC than in the past, and it becomes possible to stably supply the material for line pipes.

[Brief description of drawings]

FIG. 1 is a diagram showing an arrangement of an induction coil and an inverter additionally installed in an existing electric resistance welded steel pipe manufacturing process.

FIG. 2 is a schematic view showing an existing electric resistance welded steel pipe manufacturing process.

FIG. 3 is a diagram for explaining the cause of residual strain in an electric resistance welded steel pipe, in which (a) is a shape of a steel strip in a fin-pass roll,
(B) has shown the state of the welding part in a reduction rolling mill.

FIG. 4 is a diagram showing a method of processing a sample piece used in an experiment, in which (a) is bending and (b) is compression processing.

FIG. 5 is a view showing a cut surface of a test piece obtained in an experiment.

FIG. 6 is a diagram showing experimental results.

[Explanation of symbols]

1 steel strip 2 forming rolls 3 Edge Bend Roll 4 Center Bend Roll 5 cage rolls 6 Fin Pass Roll 7 induction coil, etc. 8 Squeeze Roll 9 tube 10 Bead cutting means 11 ultrasonic flaw detector 12 Seam Aniler 13 Water injection nozzle 14 Drawing and rolling mill 15 cutter 16 test pieces 17 cracks 18 inverters 19 induction coil

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Eisuke Yamanaka             1-1 Kawasaki-cho, Handa-shi, Aichi Made in Kawasaki             Chita Works of Iron Co., Ltd. (72) Inventor Tomio Komatsu             1-1 Kawasaki-cho, Handa-shi, Aichi Made in Kawasaki             Chita Works of Iron Co., Ltd. (72) Inventor Nobuyuki Matsuo             1-1 Kawasaki-cho, Handa-shi, Aichi Made in Kawasaki             Chita Works of Iron Co., Ltd. (72) Inventor Hideyuki Yuzawa             1-1 Kawasaki-cho, Handa-shi, Aichi Made in Kawasaki             Chita Works of Iron Co., Ltd. (72) Inventor Yoshio Yamazaki             1-1 Kawasaki-cho, Handa-shi, Aichi Made in Kawasaki             Chita Works of Iron Co., Ltd. F-term (reference) 4K042 AA06 BA08 DA03 DC02 DE02

Claims (2)

[Claims] 1. A forming roll for making a steel strip into a cylindrical shape, a squeeze roll for welding abutting portions at both ends in the width direction of the cylindrical steel strip, and a bead cutting for removing beads from inner and outer surfaces of the welding portion. A means, a seam-aniler for annealing the welded portion, a water-jet nozzle for cooling, and an electric-resistance welded steel pipe manufacturing apparatus sequentially provided with a drawing-rolling machine for adjusting the dimensions of the cooled pipe body, wherein the seam-aniler An electric resistance welded steel pipe manufacturing apparatus, wherein a heating device for heating the traveling pipe body to 550 to 850 ° C. is additionally provided between the water injection nozzles. 2. The apparatus for manufacturing an electric resistance welded steel pipe according to claim 1, wherein the heating device is an induction coil.