JP2870432B2 - Manufacturing method of welded steel pipe - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a steel strip which is continuously conveyed and formed into a cylindrical shape such that both ends of the steel strip face each other.
The present invention relates to a method for manufacturing a welded steel pipe in which ends of steel strips on both sides are butted, ends of steel strips on both sides are preheated, and the butted portions are irradiated with a high-density energy beam for welding.

[0002]

2. Description of the Related Art A method of manufacturing a steel pipe in which a steel strip is continuously conveyed and formed into a cylindrical shape so that both ends of the steel strip face each other, and a butt portion of the steel strip end is welded. Among them, the most efficient pipe production method is the electric resistance welding method. This welding method
The joint is heated and melted by induction heating of a high-frequency current or by passing a high-frequency current to the joint through a contact, and then the melt is pressurized with a squeeze roll to remove impurities and oxidation present in the melt. This is a method of performing welding while removing objects. However, when the opposite end of the steel strip is heated and melted, high-melting-point oxides composed of alloy components such as Mn, Si, and Cr in the material are not discharged by the oxygen in the atmosphere and remain in the welded portion. However, a welding defect called a penetrator may occur.

[0003] The welding method developed under such circumstances is a pipe welding method using a high-density energy beam such as a laser beam. This method is a method in which the butted end of a steel strip (hereinafter referred to as a V-shape junction) is melted and welded by irradiation with a high-density energy beam. Since the molten metal does not come into contact with the atmosphere, it includes oxide inclusions and the like. It is known that welding defects are less likely to occur and a high quality welded steel pipe can be obtained.

For example, in the laser welding method, the laser beam converges to about 0.5 mm and is irradiated to the above-mentioned V-shape meeting point for welding. Is liable to occur. In order to solve such a problem, various seam tracking methods for accurately irradiating a laser beam to a V-shape meeting point have been proposed. For example, it is disclosed in JP-A-6-668 and JP-B-3-5615.

The former Japanese Patent Application Laid-Open No. 6-668 discloses that when a copying roller is inserted into a butt portion on the upstream side of a V-shape junction and the butt portion is displaced laterally, the deflecting direction is changed. In this method, the scanning roller moves, the laser welding head is moved in the moving direction, and the laser irradiation position accurately follows the abutting surface. The mechanical copying method using the copying roller has an advantage that it is mechanically simple and has little failure and malfunction due to spatter, fume and other disturbances at the time of welding. In addition, since this method controls the copying by inserting a roller upstream of the V-shape meeting point, the copying roller is required to have high strength and high toughness in terms of material, and usually a metal roller is used. I have. However, if a metal roller is used in the pipe welding method in which laser welding is performed after preheating with a high-frequency power supply, a short circuit occurs between the metal roller and the steel strip edge, and current flows through the metal roller, and the V-shape joint point There was a problem that preheating was poor. On the other hand, when a ceramic roller, which is an electrical insulator, is used, there is a problem in that the roller is broken due to poor mechanical strength.

The latter Japanese Patent Publication No. Hei 3-5615 is an electrical copying method using a seam sensor such as a CCD. However, this method is affected by dust, oil, water, high frequency, etc. around the welded portion, and furthermore, spatter generated from the welded portion,
Failure or malfunction may be caused by fumes or the like.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the problems of the above-described mechanical copying method using the copying roller. It is an object of the present invention to provide a method for producing a welded steel pipe by seam tracking that induces a laser irradiation position with respect to a V-shape junction point with high precision using a roller that is electrically insulated, and that causes less failure and malfunction.

[0008]

SUMMARY OF THE INVENTION A method of manufacturing a welded steel pipe according to the present invention is characterized in that a steel strip is continuously conveyed and formed into a cylindrical shape such that ends of the steel strips on both sides face each other. Inserting a copying roller into the gap on the upstream side of the V shape point formed by the end, and heating the steel strip ends on both sides by high-frequency current,
In the method for manufacturing a welded steel pipe for welding by irradiating a high-density energy beam to a butt portion of a steel strip end portion, using a composite roller in which a central portion is ceramics and both sides are integrated with metal as the copying roller, The beam irradiation position is made to follow the butting portion and welding is performed.

[0009]

In the present invention, as the copying roller inserted into the gap on the upstream side of the V-shape point, a composite roller in which the central portion is made of ceramics and both sides are made of metal is used, so that the electrical insulating function and It becomes a copying roller with steel strength and high toughness functions, and can produce high quality welded steel pipes.

[0010]

1 is a schematic view of an apparatus for manufacturing a welded steel pipe used in the method of the present invention. In this embodiment, the steel strip 1 is formed into a cylindrical shape while being continuously conveyed, and a copying roller 2 configured as described later is inserted between the steel strip ends 1a and 1b on opposite sides thereof. The ends 1a and 1b of the steel strips on both sides are preheated by a high-frequency power source 3 as a first heating source, and a laser beam 4 as a second heating source is converged by a reflecting mirror 5 and a converging mirror 6 so that V The butt portion 12 is welded by irradiating it to a position downstream of the shape junction point 7 (however, a position near the intersection 11 between the line 9 connecting the centers of the squeeze rolls 8a and 8b and the butt line 10). Also, the squeeze roll 8 is welded at the
a, 8b are pressurized to join the welds.

As shown in FIG. 2, the copying roller 2 is composed of a metal part 21 disposed on both sides and a ceramic part 22 disposed in the center for electrically insulating the metal parts 21 on both sides mechanically or by a roller. It is a composite roller integrated by attaching. The copying roller 2 composed of such a composite roller is inserted into the gap between the ends of the steel strip on the upstream side of the V-shape junction 7 where the ends 1a and 1b of the steel strips on both sides first come into contact with each other, and the displacement of the butted portion 12 is shifted. Is detected, and the deviation amount is fed back to the laser welding head to accurately irradiate the butting portion 12 with a laser beam. Since the copying roller 2 is electrically insulated by the ceramic portion 22 at the center, the current from the high-frequency power supply 3 does not short-circuit through the copying roller 2, so that the preheating temperature of the V-shape junction 7 is not lowered. . Further, the portions in contact with the steel strip ends 1a, 1b on both sides are the metal portions 21, so that the mechanical strength and the toughness are high.

Next, the results of manufacturing carbon steel welded steel pipes having an outer diameter of 304 to 508 mm and a plate thickness of 5.0 to 12.7 mm using the manufacturing apparatus having the above configuration will be described.

[0013] The chemical composition of the material is expressed in terms of% by weight, C: 0.
05, Si: 0.15, Mn: 1.20, P: 0.010, S: 0.001
, Nb: 0.05, V: 0.03. As the laser, a carbon dioxide laser having a maximum output of 20 kW was used, and welding was performed at a welding speed (tube forming speed) of 4 m / min. Zr is used for the copying roller.
A composite roller manufactured by sandwiching a ceramic plate such as O ₂ , SiAlON and Al ₂ O _{3 with} a metal such as cemented carbide, Kovar or stainless steel by mechanical or brazing method was used. The brazing of the ceramic and the metal was performed by a brazing method using Ag-Cu-Ti or the like. As a comparative example, ZrO ₂ , SiAlO
A single ceramic roller made of N and Al ₂ O ₃ and a single metal roller made of cemented carbide, Kovar, and stainless steel were also subjected to the tube making test. Table 1 shows the manufacturing conditions and the evaluation results of the quality of the welded parts of the present invention example and the comparative example.

[0014]

[Table 1]

Inventive Example No. 1 to 5 are metal parts made of cemented carbide, Kovar and stainless steel and ZrO ₂ , Si
In the case of using a composite roller with a ceramic part composed of AlON and Al ₂ O _3, the butted surface at the end of the steel strip and the laser irradiation point were accurately matched, and a sound weld was obtained. . On the other hand, in Comparative Example No. Nos. 6 and 7 are cases in which a single metal roller is used. When heated by a high-frequency power supply, the end of the steel strip and the roller are short-circuited, and the heating at the V-shape junction is insufficient. Did not penetrate the thickness. Also, in Comparative Example No. 8 to 10 are cases in which a single ceramic roller was used. The roller was damaged during pipe forming welding, the end of the steel strip did not match the laser irradiation point, and a defect of poor fusion occurred in the weld. . As a result, when the metal roller was used in the comparative example, the end of the steel strip and the roller were short-circuited, and the heating at the V-shape junction was insufficient, resulting in non-penetration welding. Further, when a ceramic roller was used, the roller was damaged and a defective fusion defect occurred at the welded portion. Therefore, only when the composite roller of the metal and ceramic of the present invention which does not cause such a problem is used, the V-shape junction point can be uniformly heated, can accurately follow, and a sound weld can be obtained. Was done.

[0016]

As described above, according to the present invention, a steel strip to be continuously conveyed is formed into a cylindrical shape, and a copying roller is formed in a gap upstream of a V-shape point formed by both ends of the steel strip. While heating the ends of the steel strips on both sides with high-frequency current,
In a method of manufacturing a welded steel pipe in which a high-density energy beam is applied to a butt portion of a steel strip by welding, a beam is radiated using a copying roller including a composite roller in which a central portion is made of ceramics and both sides are made of metal. Since welding is performed while the position follows the butt, poor preheating,
A high-quality welded steel pipe can be manufactured without any damage to the rollers and therefore no welding defects such as poor fusion.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a manufacturing apparatus used in the method of the present invention.

FIG. 2 is a sectional view of a copying roller.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Steel strip 1a, 1b Steel strip end part 2 Copying roller 3 High frequency power supply 4 Laser beam 7 V shape meeting point 8a, 8b Squeeze roll 12 Butt part 21 Metal part 22 Ceramic part

────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Masaki Omura 1-1-2 Marunouchi, Chiyoda-ku, Tokyo Nippon Kokan Co., Ltd. (72) Inventor Toshihiro Takamura 1-1-2 Marunouchi, Chiyoda-ku, Tokyo Japan Inside Kokan Co., Ltd. (72) Inventor Hiroshi Nagahama 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Japan Kokan Co., Ltd. (56) References JP-A-59-76690 (JP, A) JP-A-60-46890 ( JP, A) JP-A-1-118392 (JP, A) JP-A-5-88780 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) B23K 26/00-26/18

Claims (1)

(57) [Claims] 1. A steel strip is continuously conveyed and formed into a cylindrical shape such that both ends of the steel strip face each other, and the steel strip is formed in a gap upstream of a V-shape meeting point formed by the ends of the steel strips. A method for manufacturing a welded steel pipe in which a copying roller is inserted and a high-density energy beam is applied to a butt portion of the steel strip and welded while heating the ends of the steel strips on both sides by high-frequency current, A method for manufacturing a welded steel pipe, wherein a welding is performed by using a composite roller in which a central portion is made of ceramics and both sides are made of metal, and a beam irradiation position follows the butted portion.