Effect of Oxygen Content in He-O₂ Shielding Gas on Weld Shape in Ultra Deep Penetration TIG

Fujii, Hidetoshi; Lu, Shanping; Sato, Toyoyuki; Nogi, Kiyoshi

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タイトル	Effect of Oxygen Content in He-O₂ Shielding Gas on Weld Shape in Ultra Deep Penetration TIG
著者	Fujii, Hidetoshi Fujii, Hidetoshi
	Lu, Shanping Lu, Shanping
	Sato, Toyoyuki Sato, Toyoyuki
	Nogi, Kiyoshi Nogi, Kiyoshi
キーワード等	Weld shape
	Oxygen
	Helium
	Marangoni convection
	Electromagnetic convection
	Double shielding gas
	Welding current
	Welding speed
	Tensile strength
	Charpy impact test
	Bending test
抄録	A new type of TIG welding has been developed, in which an ultra-deep penetration (10mm for one pass) is obtained. In order to control the Marangoni convection induced by the surface tension gradient on the molten pool, He gas containing a small amount of oxidizing gas was used. The effect of the concentration of O₂ and CO₂ in the shielding gas on the weld shape was studied for the bead-on-plate TIG welding of SUS304 stainless under He-O₂ and He-CO₂ mixed shielding gases. Because oxygen is a surface active element for stainless steel, the addition of oxygen to the molten pool can control the Marangoni convection from the outward to inward direction on the liquid pool surface. When the oxygen content in the liquid pool is over a critical value, around 70ppm, the weld shape suddenly changes from a wide shallow shape to a deep narrow shape due to the change in the direction of the Marangoni convection. Also, for He based shielding gas, a high welding current will strengthen both the inward Marangoni convection on the pool surface and the inward electromagnetic convection in the liquid pool. Accordingly, at a welding speed of 0.75mm/s, the welding current of 160A and the electrode gap of 1mm under the He-0.4%O₂ shielding, the depth/width ratio reaches 1.8, which is much larger than for Ar-O₂ shielding gas (0.7) and Ar shielding gas (0.2). The effects of the welding parameters, such as welding speed and welding current, were also systematically investigated. In addition, a double shielding gas method has been developed to prevent any consumption of the tungsten electrode. along the heating line, the inherent deformation of smaller plates, with the same thickness and formed under the same heating and cooling conditions, can be accurately and easily predicted.
公開者	大阪大学接合科学研究所
公開者の別表記	Joining and Welding Research Institute, Osaka University
公開者 (ヨミ)	オオサカダイガクセツゴウカガクケンキュウジョ
掲載誌名	Transactions of JWRI
巻	37
号	1
開始ページ	19
終了ページ	26
刊行年月	2008-07
ISSN	03874508
NCID	AA00867058
URL	http://hdl.handle.net/11094/6051
言語	英語
カテゴリ	紀要論文 Departmental Bulletin Paper
カテゴリ	Transactions of JWRI / Vol.37 No.1 (2008-07)

著者版フラグ	publisher
NII資源タイプ	紀要論文
ローカル資源タイプ	紀要論文
dcmi資源タイプ	text
DCTERMS.bibliographicCitation	Transactions of JWRI.37(1) P.19-P.26
DC.title	Effect of Oxygen Content in He-O₂ Shielding Gas on Weld Shape in Ultra Deep Penetration TIG
DC.creator	Fujii, Hidetoshi
	Lu, Shanping
	Sato, Toyoyuki
	Nogi, Kiyoshi
DC.publisher	大阪大学接合科学研究所
DC.language" scheme="DCTERMS.RFC1766	英語
DCTERMS.issued" scheme="DCTERMS.W3CDTF	2008-07
DC.identifier" scheme="DCTERMS.URI	http://hdl.handle.net/11094/6051
DC.subject	Weld shape
	Oxygen
	Helium
	Marangoni convection
	Electromagnetic convection
	Double shielding gas
	Welding current
	Welding speed
	Tensile strength
	Charpy impact test
	Bending test
DCTERMS.abstract	A new type of TIG welding has been developed, in which an ultra-deep penetration (10mm for one pass) is obtained. In order to control the Marangoni convection induced by the surface tension gradient on the molten pool, He gas containing a small amount of oxidizing gas was used. The effect of the concentration of O₂ and CO₂ in the shielding gas on the weld shape was studied for the bead-on-plate TIG welding of SUS304 stainless under He-O₂ and He-CO₂ mixed shielding gases. Because oxygen is a surface active element for stainless steel, the addition of oxygen to the molten pool can control the Marangoni convection from the outward to inward direction on the liquid pool surface. When the oxygen content in the liquid pool is over a critical value, around 70ppm, the weld shape suddenly changes from a wide shallow shape to a deep narrow shape due to the change in the direction of the Marangoni convection. Also, for He based shielding gas, a high welding current will strengthen both the inward Marangoni convection on the pool surface and the inward electromagnetic convection in the liquid pool. Accordingly, at a welding speed of 0.75mm/s, the welding current of 160A and the electrode gap of 1mm under the He-0.4%O₂ shielding, the depth/width ratio reaches 1.8, which is much larger than for Ar-O₂ shielding gas (0.7) and Ar shielding gas (0.2). The effects of the welding parameters, such as welding speed and welding current, were also systematically investigated. In addition, a double shielding gas method has been developed to prevent any consumption of the tungsten electrode. along the heating line, the inherent deformation of smaller plates, with the same thickness and formed under the same heating and cooling conditions, can be accurately and easily predicted.
citation_title	Effect of Oxygen Content in He-O₂ Shielding Gas on Weld Shape in Ultra Deep Penetration TIG
citation_author	Fujii, Hidetoshi
	Lu, Shanping
	Sato, Toyoyuki
	Nogi, Kiyoshi
citation_publisher	大阪大学接合科学研究所
citation_language	英語
citation_date	2008-07
citation_journal_title	Transactions of JWRI
citation_volume	37
citation_issue	1
citation_firstpage	19
citation_lastpage	26
citation_issn	03874508
citation_public_url	http://hdl.handle.net/11094/6051
citation_keywords	Weld shape
	Oxygen
	Helium
	Marangoni convection
	Electromagnetic convection
	Double shielding gas
	Welding current
	Welding speed
	Tensile strength
	Charpy impact test
	Bending test

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