【発明の詳細な説明】[Detailed description of the invention]
本発明は高周波誘導溶接または高周波抵抗溶接
法により多層鋼管を製造する際、溶接欠陥の著し
く少い高品質の多層鋼管を製造する方法に関する
ものである。
多層鋼管は金属製外管と内管および断熱性中間
材で構成され、断熱性が対騒音性を有する鋼管等
として実用に供せられる。これらの管は、外管用
帯鋼と中間材および内管用帯鋼帯を重ねロール成
形して高周波溶接法により内外管を同時溶接して
製造される。この場合の溶接点での鋼帯側面温度
は高周波誘導によるときは公知技術として下記式
が知られている。
Tp＝ｆ（Ｗ・Ｖ・ｌ・θ・ｔ・dp／Dw）
Tp 溶接点温度
Ｗ 溶接電力
Ｖ 溶接速度
ｌ 溶接点とワークコイルの距離
θ Vee角度
dp パイプ径
Dw ワークコイル径
ｔ パイプ厚
多層鋼管を電縫管方式で連続製造する場合、上
記式において溶接速度Ｖ、溶接点とワークコイル
の距離ｌ、ワークコイル径DWは内外管共同じで
あるが、パイプ外径dpは内外管では必ず異なる
し、内外管の厚さも異なる。又溶接電力Ｗは内管
と外管を分離してコントロールすることは出来な
いため、溶接点温度Tpは内管と外管では温度差
が生じ、内外管の加熱温度を均一にすることは出
来ない。このため、温度差は溶接時の加熱不足又
は加熱過多となり、内外管の溶接強度がアンバラ
ンスになる。すなわち、多層管の実用試験におい
て内管又は外管のみ溶接強度不足と言う、多層鋼
管特有の欠陥が発生する。本発明は多層管の高周
波溶接における加熱温度差を補正し、ほぼ均一な
加熱温度とし、溶接することにより、溶接部強さ
の安定かつ高品質の多層鋼管を連続製造する装置
を提供するものである。
本発明は多層管の製造において多層鋼帯を管状
に成形し高周波電流により帯鋼側面部を加熱しス
クイズロールにて圧接する直前のＶスロート部に
酸素ガスを吹付けることを特徴とするものであ
る。高周波電流によつて加熱された内外管帯鋼側
面すなわち溶接衝動面が酸素ガスとの酸化熱で昇
温するとともに内外管側面の温度差も修正され
る。これによりほぼ均一な側面温度となり安定し
た加熱条件の連続溶接が可能となる。酸素吹付に
より発生すると考えられた酸化物については、溶
接衝合部のミクロ組織調査で残留が認められず溶
接部は極めて健全である。これは酸素吹付による
酸化物発生が極めて微量であるとともに溶接時に
圧縮排出するため衝合部に残留しないためであ
る。
本発明による多層鋼管の品質と従来方式による
ものと比較した試験例を表−１で示す。この検定
結果から本発明による鋼管の品質が明らかに向上
することが確認された。
The present invention relates to a method for manufacturing high-quality multilayer steel pipes with significantly fewer weld defects when manufacturing multilayer steel pipes by high frequency induction welding or high frequency resistance welding. A multilayer steel pipe is composed of a metal outer pipe, an inner pipe, and a heat-insulating intermediate material, and is used practically as a steel pipe that has heat-insulating properties and noise-resistance properties. These tubes are manufactured by stacking and roll-forming a steel strip for an outer tube, an intermediate material, and a steel strip for an inner tube, and simultaneously welding the inner and outer tubes using a high-frequency welding method. In this case, when the temperature of the side surface of the steel strip at the welding point is determined by high-frequency induction, the following formula is known as a known technique. T p = f (W・V・l・θ・t・d p /D w ) T p Welding point temperature W Welding power V Welding speed l Distance between welding point and work coil θ V ee angle d p Pipe diameter D w Work coil diameter t Pipe thickness When manufacturing multilayer steel pipes continuously using the electric resistance welding pipe method, in the above formula, welding speed V, distance l between the welding point and work coil, and work coil diameter D W are the same for both the inner and outer pipes. The outer diameter dp is always different between the inner and outer tubes, and the thickness of the inner and outer tubes is also different. Also, since the welding power W cannot be controlled separately for the inner and outer tubes, there will be a difference in the welding point temperature T p between the inner and outer tubes, making it impossible to equalize the heating temperature of the inner and outer tubes. Can not. Therefore, the temperature difference results in insufficient or excessive heating during welding, resulting in an imbalance in the welding strength between the inner and outer tubes. That is, in practical tests of multilayer pipes, a defect unique to multilayer steel pipes occurs, where only the inner pipe or the outer pipe has insufficient welding strength. The present invention provides an apparatus for continuously manufacturing multilayer steel pipes with stable weld strength and high quality by correcting heating temperature differences in high-frequency welding of multilayer pipes, making the heating temperature almost uniform, and welding. be. The present invention is characterized in that, in the production of multilayer pipes, a multilayer steel strip is formed into a tubular shape, the side surfaces of the steel strip are heated by high-frequency current, and oxygen gas is sprayed onto the V-throat section immediately before being pressed together with a squeeze roll. be. The temperature of the side surfaces of the inner and outer tube strip steel, that is, the welding impulse surfaces heated by the high-frequency current increases due to the heat of oxidation with oxygen gas, and the temperature difference between the inner and outer tube side surfaces is also corrected. This makes it possible to achieve a substantially uniform side surface temperature and to perform continuous welding under stable heating conditions. Regarding the oxides thought to be generated by oxygen spraying, no residual oxides were found in the microstructure investigation of the welded joint, and the welded joint is extremely sound. This is because the amount of oxides generated by oxygen spraying is extremely small, and because they are compressed and discharged during welding, they do not remain in the abutment area. Table 1 shows test examples comparing the quality of the multilayer steel pipe according to the present invention with that of the conventional method. From this test result, it was confirmed that the quality of the steel pipe according to the present invention was clearly improved.
【表】
第１図ａは試験方法を示す図で、多層鋼管１０
の管端をコーン１２に当て、矢印方向に力を加え
て管径Ｄの1.2倍まで拡径する。溶接不良などが
あるとこの試験で管に割れが発生する。第１図ｂ
は内管割れ、同図ｃは外管割れを示す。
前述のように本発明は、複合２重管などの多層
管の電縫管方式による製造に係る。複合２重管な
どの多層管は主として自動車の排気管として使用
され、従来の単管より優れた低騒音性を持つもの
として注目される。ところでかゝる多層管を製造
するには電縫管方式、絞り加工方式及びその他の
方式の採用が考えられるが、本発明は電縫管方式
での連続製造に係るものである。
単管製造に広く用いられる電縫鋼管方式に多層
管製造方式を加えた装置は第２図に示す如くな
る。この図で１，２は内外管構成用鋼ストリツ
プ、３は中間材、４は成形ロール群、５は加熱コ
イル、６は高周波電源、７はスクイズロールであ
る。ストリツプ１，２及び中間材３は３枚重ねら
れて成形ロール列４に入り、ここで管状に成形さ
れ、ストリツプ両縁の対向部が加熱コイル５で高
周波誘導加熱され、スクイズロール７で圧着され
電縫多層管８となる。
第３図ａ，ｂ，ｃは、成形中の多層管の断面を
示す。ａは管に曲げ始めた状態、ｂはほゞ管に曲
げた状態、ｃは溶接して管にした状態の各断面を
示す。１，２，３は外管鋼ストリツプ、内管鋼ス
トリツプ、中間材であり、４は溶接部、５は溶接
衝合部を示す。図のａ，ｂに示す形状時における
内外管材１，２のズレ防止は困難をともなうもの
である。特に溶接直前形状ｂにおける溶接衝合部
５における形状の微調整は極めてむずかしいもの
である。
第４図は、従来法による電縫鋼管溶接部を示
す。３層に重ねられた外管用鋼ストリツプ１、中
間材３、内管用鋼ストリツプ２は管状に曲げられ
て誘導溶接ワークコイル５を通り、電流を誘導さ
れて該電流で突合せ部を加熱され溶接される。溶
接後スクイズロール７を通つて圧着、成形され、
完成多層管８となる。６は高周波電源である。第
５図は本発明の酸素吹付装置を付加したものであ
る。すなわち、成形した多層管１，２，３を誘導
コイル５で鋼ストリツプ側縁部を加熱しスクイズ
ロール７で圧着するときの該鋼ストリツプ側縁部
に生じるＶスロート部分に酸素ガスを吹付けるも
のである。１１はその酸素ノズルである。第５図
のａは側面斜視図、ｂは平面図で、１２は酸素吹
付け部分をまた１３は溶接シームを示す。第６図
はガス吹付装置の詳細図である。ノズル１１の先
端は5φ程度の銅管でＬ字型に曲つており、その
先端から酸素を鋼管８、スクイズロール７が囲む
先細り空間へ放出する。吹付条件は表−２に示
す。[Table] Figure 1a shows the test method.
Place the end of the tube on the cone 12 and apply force in the direction of the arrow to expand the tube diameter to 1.2 times the tube diameter D. If there is a defect in welding, cracks will occur in the pipe during this test. Figure 1b
Figure c shows a crack in the inner tube, and Figure c shows a crack in the outer tube. As mentioned above, the present invention relates to the production of multilayer pipes such as composite double pipes using the electric resistance welding pipe method. Multilayer pipes such as composite double pipes are mainly used as exhaust pipes for automobiles, and are attracting attention as having superior low-noise properties to conventional single pipes. By the way, in order to manufacture such a multi-layered pipe, it is possible to adopt an electric resistance welded pipe method, a drawing method, and other methods, but the present invention relates to continuous manufacturing using the electric resistance welded pipe method. An apparatus that combines the electric resistance welded steel pipe method widely used for manufacturing single pipes with the multilayer pipe manufacturing method is shown in FIG. 2. In this figure, 1 and 2 are steel strips for forming the inner and outer tubes, 3 is an intermediate material, 4 is a forming roll group, 5 is a heating coil, 6 is a high frequency power source, and 7 is a squeeze roll. The strips 1 and 2 and the intermediate material 3 are stacked in three layers and enter the forming roll row 4, where they are formed into a tube shape. This becomes an electric resistance welded multilayer pipe 8. Figures 3a, b, c show cross-sections of the multilayer tube during forming. A shows the cross-section of the product when it has begun to be bent into a tube, b shows the state when it is almost bent into a tube, and c shows the cross-section when it is welded into a tube. Reference numerals 1, 2, and 3 indicate an outer tube steel strip, an inner tube steel strip, and an intermediate member, 4 a welded portion, and 5 a welded abutment portion. It is difficult to prevent the inner and outer tube members 1 and 2 from shifting in the shapes shown in a and b in the figures. In particular, fine adjustment of the shape of the welding abutment portion 5 in the shape b immediately before welding is extremely difficult. FIG. 4 shows an electric resistance welded steel pipe welded by a conventional method. The steel strip 1 for the outer tube, the intermediate material 3, and the steel strip 2 for the inner tube, stacked in three layers, are bent into a tubular shape and pass through an induction welding work coil 5, where a current is induced and the abutting portions are heated and welded by the current. Ru. After welding, it is crimped and formed through a squeeze roll 7,
A completed multilayer pipe 8 is obtained. 6 is a high frequency power source. FIG. 5 shows the oxygen blowing device of the present invention added. That is, when the formed multilayer tubes 1, 2, and 3 are heated at the side edges of the steel strips with an induction coil 5 and crimped with a squeeze roll 7, oxygen gas is sprayed onto the V-throat portions formed at the side edges of the steel strips. It is. 11 is its oxygen nozzle. In FIG. 5, a is a side perspective view and b is a plan view, 12 indicates an oxygen sprayed portion, and 13 indicates a welding seam. FIG. 6 is a detailed view of the gas blowing device. The tip of the nozzle 11 is a copper tube of about 5φ bent in an L shape, and oxygen is released from the tip into the tapered space surrounded by the steel tube 8 and the squeeze roll 7. The spraying conditions are shown in Table-2.
【表】
本発明の酸素吹付による電縫鋼管溶接方式は単
純もしくは複合２重管などの多層管を連続的に製
造するときに甚だ有効であり、これにより良好な
溶接状態を保つことが出来る。[Table] The electric resistance welding steel pipe welding method using oxygen spraying of the present invention is extremely effective when continuously manufacturing multilayer pipes such as simple or composite double pipes, and as a result, good welding conditions can be maintained.
【図面の簡単な説明】[Brief explanation of drawings]
第１図は鋼管の実用試験押しひろげおよび欠陥
の説明図、第２図は多層管製造装置の説明図、第
３図は多層管成形工程の各段階における断面図、
第４図は従来方式による電縫管溶接装置の要部説
明図、第５図は本発明による酸素欠如装置を付加
した電縫管溶接装置の要部説明図、第６図はガス
吹付装置の詳細を示す側面図である。
図面で、１０は多層鋼管、１は外管用鋼ストリ
ツプ、２は内管用鋼ストリツプ、１１は酸素ノズ
ルである。
Fig. 1 is an explanatory diagram of practical test push expansion and defects of steel pipes, Fig. 2 is an explanatory diagram of a multilayer pipe manufacturing equipment, and Fig. 3 is a cross-sectional view at each stage of the multilayer pipe forming process.
Fig. 4 is an explanatory diagram of the main parts of a conventional ERW pipe welding device, Fig. 5 is an explanatory diagram of the main parts of an ERW pipe welding device to which an oxygen depletion device according to the present invention is added, and Fig. 6 is an explanatory diagram of the main parts of an ERW pipe welding device according to the present invention. It is a side view showing details. In the drawing, 10 is a multilayer steel pipe, 1 is a steel strip for the outer pipe, 2 is a steel strip for the inner pipe, and 11 is an oxygen nozzle.