Electric heating – Metal heating – By arc
Patent
1983-12-22
1985-07-02
Envall, Jr., Roy N.
Electric heating
Metal heating
By arc
219 72, B23K 902
Patent
active
045270465
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method applicable to underwater arc welding.
The method is suitable only for the so-called Elin welding, wherein the electrode is not burned in the normal way as perpendicular to the object to be welded, but the electrode is placed lying on the parent material and is melted in this position like a fuse without participation of the welding operator in the process.
The invention also relates to an arrangement to be used for carrying out the method.
In prior art, a so-called "fire-cracker" method is known, in which one or several thick-coated electrodes placed in a groove are covered with a copper rail which accommodates one or several furrows for the electrodes. Into the space produced, gas is passed, usually air, whereby the water in the space is displaced. For igniting the light arc, either a thin wire fuse or a metal foil is used, upon whose destruction the arc of light starts burning between the electrodes and the parent material. The maximum length of the electrodes when welding on the ground is about 1 meter. It has, however, been noticed that in water it is possible to use electrodes twice as long. It is however, a drawback of this method that an external pressure-gas source is required in order to eliminate the water. This is inconvenient, especially when the welding is performed in deep waters. Moreover, it is difficult to make and to install the copper rail on several welding objects which are not straight or even, such as pipe joints.
From the U.S. Pat. No. 4,069,408, a method is known according to which the area to be welded is covered by means of a box-shaped structure that contains various pastes and powders and whose top portion is provided with a groove along which the vertically positioned welding electrode can be shifted. It is a drawback of this method that, as the welding area is out of sight, the welding must be performed "blindfold"
The object of the present invention is to eliminate the drawbacks present in the prior art technology and to provide a more practical method and arrangement of a novel type for underwater arc welding.
Another objective of use of the invention is to provide a dry space within the area of the arc and to prevent access of water onto the slag and weld melt about to be cooled.
The invention is based on the idea that by fitting both the electrode and the material covering the electrode tightly onto the object to be welded, which said material generates a gas while the arc is burning, the water can be displaced automatically.
In the method in accordance with the present invention, the object to be welded is first covered, over the entire distance to be welded, with a water-repellent semi-solid material, which is in the following called sealing material. It must be spread over an area as wide as possible and with a thickness of at least 1 cm. Hereupon the welding electrode is pressed into the sealing material so that it is parallel to the parent material to be welded and to the intended weld seam. After the welding electrode has been covered completely in the water-repellent sealing material, a resilient heat insulation board of solid material is pressed onto the material so tightly that it presses the electrode against the parent material. The heat insulation board is almost equally long as the electrode to be welded and wide enough so that the sealing material remains covered by the insulation board with the exception of any excessive sealing material extruded from the sides of the insulation material. The initial end of the electrode as well as its final end are allowed to remain visible for the purpose of ignition so that the electrode holder can be attached to the electrode. Hereupon the electrode can be ignited by instantaneously short-circuiting its initial end, e.g., by means of a carbon rod. When the arc is ignited, a tunnel is produced in the heat insulation when the electrode burns. Since the fire gases produced escape along this tunnel, water cannot follow the arc while the arc proceeds inside the heat insulation and th
REFERENCES:
patent: 3941974 (1976-03-01), Kano et al.
patent: 4069408 (1978-01-01), Masubuchi et al.
Envall Jr. Roy N.
Sigda C. M.
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