Plasma MIG welding with plasma torch and MIG torch

Details Plasma MIG welding with plasma torch and MIG torch Plasma MIG welding with plasma torch and MIG torch

2002-04-01

2004-02-17

Paschall, Mark (Department: 3742)

Electric heating

Metal heating

By arc

C219S121460, C219S121480, C219S13700R, C219S075000

Reexamination Certificate

active

06693252

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates generally to the art of welding and welding power supplies. More specifically, it relates to welding with a plasma process or a TIG process and a MIG process.
BACKGROUND OF THE INVENTION
There are a wide number of known welding processes used for a variety of welding applications. Various processes have strengths and weaknesses with respect to characteristics such as speed, precision, workpiece composition, cost, flexibility, etc.
For example, MIG welding (metal inert gas welding) is relatively fast, but somewhat imprecise. The process is fast because, in part, a consumable wire electrode is used as a filler metal. However, for some applications, such as welding galvanized steel, MIG does not perform well, at least in part because the MIG process, which is typically DC, does not, effectively prepare for welding (or remove) the zinc on the steel. If not properly prepared the zinc can vaporize during the welding process and cause bubbles in the weld. Also, for some applications an even faster MIG process is desired.
Another process, TIG welding, is precise and can work with galvanized steel, but TIG is a relatively slow process. Thus, it is often used for high-quality, low speed applications.
Plasma arc welding (PAW) is a welding process that also does not lend itself readily to high speed welding. For example, PAW is best performed at under 100 amps, and it is particularly useful for welding under 20 amps and as low as 0.1 amp. If higher current is needed, PAW is performed in a keyhole process, where the plasma gas creates a hole in the workpiece, and molten metal flowing behind the moving hole creates the weld bead.
TIG welding has been combined with plasma welding in plasma TIG welding. Plasma TIG welding has been performed using a TIG torch, followed by a plasma torch, followed by a TIG torch. Plasma TIG welding is not well suited for galvanized steel, and TIG can be slow.
A weld process that can be fast and precise is laser MIG welding. This entails the simultaneous application of a laser beam and a MIG arc on the weld. While the process may be fast, precise, and useful on galvanized steel, it is expensive and may be difficult to use.
Accordingly, a welding process that provides for relative high speed, acceptable precision, without excess cost is desirable. Preferably the process will weld galvanized steel.
SUMMARY OF THE PRESENT INVENTION
According to a first aspect of the invention a method of plasma MIG welding includes creating a plasma arc and a MIG arc between torches and a workpiece. There is relative movement between the torches and a weld path.
A constant distance is maintained between the plasma torch and the MIG torch in one embodiment.
According to a second aspect of the invention a system of plasma MIG welding includes a plasma torch and a MIG torch. The MIG torch and the plasma torch are mounted such that they are a fixed distance from one another.
The angle of the plasma arc is between +10 degrees and −10° degrees, or between +5 degrees and perpendicular, and the angle of the MIG torch is preferably between +10 degrees and −45°, or between 0 degrees and −30 degrees, in various embodiments.
The distance between the plasma torch and the MIG torch is greater for faster movement along weld path in another embodiment.
According to a third aspect of the invention a system for plasma MIG welding includes at least one power source having a plasma power output and a MIG power output. The power source also has a control input and a controller is operatively connected to the control input.
The power source includes a plasma power source and a MIG power source, and the controller includes a plasma controller and a MIG controller in various embodiments.
According to a fourth aspect of the invention a product is formed by the process of plasma MIG welding a plurality of workpieces. At least one of the workpieces is comprised of galvanized steel, such as G-60 or G-90.
According to a fifth aspect of the invention a method of TIG MIG welding includes creating a TIG arc and a MIG arc between torches and a workpiece. There is relevant movement between the torches and a weld path.
A constant distance is maintained between the TIG torch and the MIG torch in one embodiment.
According to another aspect of the invention a system of TIG MIG welding includes a TIG torch and a MIG torch. The MIG torch and the TIG torch are mounted such that they are a fixed distance from one another.
The angle of the TIG arc is between +10 degrees and −10° degrees, or between +5 degrees and perpendicular, and the angle of the MIG torch is between +10 degrees and 45°, or between 0 degrees and −30 degrees, in various embodiments.
The distance between the TIG torch and the MIG torch is greater for faster movement along weld path in another embodiment.
According to yet another aspect of the invention a system for TIG MIG welding includes at least one power source having a TIG power output and a MIG power output. The power source also has a control input and a controller is operatively connected to the control input.
The power source includes a TIG power source and a MIG power source, and the controller includes a TIG controller and a MIG controller in other embodiments.
According to an eighth aspect of the invention a product is formed by the process of TIG MIG welding a plurality of work pieces. At least one of the workpieces is comprised of galvanized steel, such as G-60 or G-90.
The MIG and/or TIG process is performed EP or EN in various embodiments.
Other principal features and advantages of the invention will become apparent to those skilled in the art upon review of the following drawings, the detailed description and the appended claims.


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