Electric heating – Metal heating – By arc
Patent
1994-09-28
1996-09-17
Paschall, Mark H.
Electric heating
Metal heating
By arc
21912147, 21912151, 219 7616, B23K 1000
Patent
active
055565603
DESCRIPTION:
BRIEF SUMMARY
The present invention is related to a powderized filler material feed assembly according to the preamble of claim 1 particularly suited to plasma and laser welding.
Use of powderized filler material in mechanized welding is well known in the art. Powderized filler material is conventionally added during the welding of wide-gap downhand welds in horizontal position as well as in plasma spray coating. In the welding of joints the added powderized filler is similar to the parent materials to be joined, while in plasma spray coating the powderized filler materials can be varied widely according to the coating desired. A powderized filler material is particularly advantageously employed in plasma and laser welding.
In prior-art embodiments the dosing of the powderized filler material is typically arranged so that a stripe of the powderized filler material is applied via a nozzle orifice at the bottom of powderized material container onto a moving support such as a roller or band. The dosed powderized material is transferred from the support surface by gravity or compressed gas into a transport system that conveys the powderized filler material to the weld pool. The transport system conventionally is a mere pipe opening in the vicinity of the plasma arc so that the powderized filler material fed via the pipe is directed into the plasma. Occasionally the powderized material tends to clog the feed line, whereby a pulsating feed of the powderized material stream results. A constant feed rate of the powderized material stream has been attempted by means of a small-diameter feed line combined with high flow speed.
In a plasma torch the main arc used for welding is excited between the center electrode of the torch and the work piece. The nozzle part of the torch comprises two coaxially situated chambers. The inner chamber houses a centered tungsten electrode and the chamber is provided with an orifice aligned at the electrode tip. The orifice gas to be ionized into a plasma is fed into this chamber. The inner chamber is coaxially enclosed by a second chamber having an annular exit slot surrounding the nozzle of the inner chamber. This outer chamber is fed with a shielding gas whose exit flow protects the main arc. Obviously, the feed of the powderized filler material into the arc of the plasma torch is difficult. The plasma arc in itself causes a relatively strong blast which repels the powderized material, and moreover, the arc is surrounded by a shielding gas envelope through which the powderized material must be projected into the main arc. If large amounts of powderized material can be used, the mass of the powderized material flow is substantial, whereby its penetration capability into the plasma arc is also improved. Typically, however, the feed nozzle orifice of the powderized material dosing device in high-capacity torches is located relatively far from the arc, whereby a portion of the filler material cannot reach the correct target point, but instead, is lost outside the molten pool. Moreover, the long distance between the nozzle orifice and the intended target allows the jet of powderized material to spread resulting in a fanned shape of the jet. The spreading angle,is further widened by the distributed velocity profile of the jet particles. For large mass rates of filler material, the proportion of stray stream relative to the total mass rate is not decisive, whereby small changes in the stray stream cause no greater error in the actual filler material quantity reaching the main arc. At low mass rates, in the order of a few grams per hour, variations in the proportion of the stray stream of filler material can easily cause high deviations in the actual mass rate of applied filler material, thus necessitating accurate aiming of the filler material into the plasma arc.
Conventional methods of filler material feed in the form of a wire or stick, whether in mechanized or manual welding, cannot fully replace the use of powderized filler material. When a very low rate of filler material feed is desired, wire fee
REFERENCES:
patent: 3071678 (1993-01-01), Neely et al.
patent: 3591759 (1971-07-01), Stand
patent: 4389559 (1983-06-01), Rotolico et al.
patent: 4627990 (1986-12-01), Saga et al.
patent: 4672171 (1987-06-01), Cusimano et al.
patent: 5043548 (1991-08-01), Whitney et al.
Ahola Kari
Ahola Tom
Paschall Mark H.
Plasma Modules Oy
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