Electric heating – Metal heating – Nonatmospheric environment at hot spot
Reexamination Certificate
1999-06-30
2001-08-14
Shaw, Clifford C. (Department: 1725)
Electric heating
Metal heating
Nonatmospheric environment at hot spot
C219S13700R
Reexamination Certificate
active
06274838
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATION
Not applicable
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not applicable
BACKGROUND OF THE INVENTION
This invention relates to gas metal arc welding, flux cored arc welding, and composite cored arc welding, and in particular to a shielding gas composition for use in these processes.
It is well known in the welding art that in shielded metal arc welding, gas metal arc welding, flux cored arc welding, and composite cored arc welding, the shielding gas can affect the process and the quality of the resulting weld.
In these processes it has been common practice to employ a shielding gas which has as its main ingredient argon, an inert gas. Blended into the argon are various mixtures of other gases selected from the group consisting of oxygen, carbon dioxide, and helium. A detailed explanation of shielding gases can be found in publication ANSI/AWS C5.10-94 published by the American Welding Society under the title “Recommended Practices For Shielding Gases For Welding And Plasma Arc Cutting”.
The underlying welding processes, in particular gas metal arc welding (GMAW) and flux cored arc welding (FCAW) are explained in detail in volume 2 of the eighth edition of the welding hand book, chapters 4 and 5 respectively, published by the American Welding Society.
According to the Welding Handbook various shielding gas mixtures having been employed in the welding processes that basically combine transfer of metal from a consumable electrode, be it a stick electrode or continuous wire, to a weld pool to create a joint between prepared base metals to be joined.
The gas metal arc welding (GMAW) process is an arc welding process that uses an arc struck between a continuous filler metal electrode and the weld pool. The process is used with shielding supplied by a gas mixture without the application of pressure. The shielding gas mixtures are basically argon with one or more addatives such as oxygen, carbon dioxide, helium or hydrogen.
The flux cored arc welding (FCAW) process involves an arc between a continuous filler metal electrode and the weld pool. The process is used with shielding from a flux contained within the tubular electrode, with or without additional shielding from an externally supplied gas, and without the application of pressure. In the case of flux cored arc welding using external shielding gases, the shielding gases are basically argon with one or more components selected from the group consisting of helium, oxygen and carbon dioxide.
Composite cored arc welding(CCAW) is used to describe an arc welding process where a tublar wire having a center filled with metal powder is used as the electrode material. This process also relies on the use of shielding gases to protect the arc and weld pool.
The various industrial gas suppliers and welding supply manufacturers offer numerous shielding gas mixtures.
In particular Air Products and Chemicals, Inc. has marketed a gas mixture called Astec HP for high deposition of metal and high arc travel speed in the gas metal arc welding process in the flat or horizontal position. The composition offered by this company contains 65% argon 25% helium and 10% carbon dioxide. This particular shielding gas mixture makes it difficult to control the molten metal while welding in positions other than the flat or horizontal position. Furthermore, fine short circuit arc transfer is not easily effected with this mixture.
BRIEF SUMMARY OF THE INVENTION
It has been discovered that a gas mixture containing, by volume, 62-74% argon, 17-23% helium and 9-16% carbon dioxide can satisfy the long felt need to have a single shielding gas mixture that can be used with gas metal arc welding, flux cored arc welding, and composite cored arc welding in any mode of metal transfer and in any welding position. In a preferred embodiment the shielding gas contains 68% argon, 20% helium and 12% carbon dioxide by volume.
Therefore, in one aspect the present invention is a shielding gas mixture for arc welding consisting essentially of 62-74% by volume argon, 17-23% by volume helium and 9-16% by volume carbon dioxide.
In another aspect, the present invention is a gas metal arc welding process wherein an arc is maintained between a continuous filler metal electrode and a weld pool with shielding of the arc generated between the filler metal and the weld pool with a gas mixture of 68% by volume argon, 20% by volume helium, and 12% by volume carbon dioxide.
In yet another aspect, the present invention is a flux cored arc welding process wherein an arc is maintained between a continuous filler metal electrode consisting essentially of a metal enclosing fluxing materials and a weld pool with shielding of the arc with a gas mixture consisting essentially of 68% by volume argon, 20% by volume helium and 12% by volume carbon dioxide.
In still another aspect, the present invention is a composite cored arc welding process wherein an arc is maintained between a filler metal electrode and a weld pool with shielding of the arc with a gas mixture consisting essentially of 68% by volume argon, 20% by volume helium and 12% by volume carbon dioxide.
The present invention also pertains to a gas metal arc welding process wherein metal is transferred from an electrode by one of short circuiting transfer, globular transfer, spray transfer, pulsed spray transfer, high current density spray transfer, high current density rotational spray transfer or high current density non-rotational spray transfer and wherein a shielding gas consisting essentially of, by volume, 68% argon, 20% helium and 12% carbon dioxide is used to shield the arc generated during the process.
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Dilthey, U., “Schutzgase Zum Magm-Hochleistungsschweissen”, Schweissen Und Schneiden, vol. 47, No. 2, Feb. 1, 1995, pp. 118-123, XP000493509.
International Search Report (PCT/US97/22337), mailed Aug. 28, 1998, 5 pp.
Demers Claude Raymond
LeHouillier Guy
Air Products and Chemicals Inc.
Ratner & Prestia
Shaw Clifford C.
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