Metal treatment – Compositions – Fluxing
Patent
1987-03-24
1988-12-13
Rosenberg, Peter D.
Metal treatment
Compositions
Fluxing
148 26, B23K 3534
Patent
active
047908874
DESCRIPTION:
BRIEF SUMMARY
This invention relates to the additive according to the preamble of the claim 1 being adaptable for use especially in underwater arc welding.
Enterprises making welding works and manufacturing welding devices and equipment have strived to produce an arc welding method and equipment, by which the welding process and the end result would not be affected by outer conditions. It is well-known in the art that arc weldilng--particularly in good conditions very easy-to-use protective arc welding--cannot succesfully be performed in windy, draughty, rainy and/or wet surroundings let alone underwater conditions.
Underwater welding has in recent years been an object of ever-increasing interest and development work. Repairs and servicing of drilling platforms, particularly their underwater supporting structures and gas and/or oil pipes, ships and dock structures and equipment are the objects, in which underwater welding has primarily been used. The structures to be welded are generally such, that their lifting to the water surface is impossible or becomes very costly. The objective in underwater welding, as well as in welding generally, is and always will be the achievement of the highest quality welds.
The known methods for underwater welding are divided on grounds of the welding conditions into two main groups: wet methods and dry methods. In the known wet methods in the rod welding mainly usual welding rods are used coated by water-tight vinyl paint or paraffin to prevent wetting, and in gas arc welding besides the conventional equipment also a welding device, in which a from the outer perimeter of the nozzle directed conical water jet keeps the arc area separated from the water. Water jet has been used with relatively good results in the carbon dioxide wet method. In wet methods water may come, as even the name implies, unhindered to the arc area. In the dry methods the access of water to the arc area is prevented by covering the arc area with an essentially closed (weldable seam is naturally free) or at the lower end open opaque or transparent welding shield. The welding device is brought to the welding shields open at their lower end usually from below or to the entirely closed welding shields through the wall. If the welding shield is sufficiently large, the welder may work inside the shield. The welding shields are provided with either a protective gas or air atmosphere.
In underwater welding the welds of almost the same quality are achieved as in welding performed in favourable conditions above the ground level. The drawbacks in dry methods are, however, the time-consuming mountings and transfers of welding shields and also the inconvenience and inflexibility of the welding work due to the use of shields. There are also many places, where the use of welding shield is impossible. Wet welding, to which the present invention is particularly connected, is a rather flexible and economic system for underwater welding works. It can, if the welding is performed manually, be carried out except the diving equipment by the same devices as welding above the groun level. The weld quality in wet methods has not been even nearly as good as in the dry welding methods. Mainly because of this fact various classification institutions have not accepted the use of wet methods in the objects under their inspection. Three problems appear in the wet welding and all of them are caused by the surrounding water. They comprise a high cooling rate, high hydrogen content and the ambient pressure influencing to the reactions in the arc and also to the transfer of material as well as to the reactions between the melt and the slag especially in deeper depths.
The worst problem in wet methods is the appearance of hydrogen cracks. It is expressly caused by the large amount of hydrogen in the welding seam. High cooling rate makes further diffusion of water more difficult from the welding seam, and pre- or afterheatings cannot be used in practice to remove the hydrogen, to reduce strains or to avoid fragile microstructure. As a result of the hig
REFERENCES:
patent: 2841513 (1958-07-01), Morrison
patent: 2978369 (1961-04-01), Battle
patent: 3436278 (1969-04-01), Poliak
patent: 4180616 (1979-12-01), Lovering
patent: 4220486 (1980-09-01), Anderson
GSS General Sea Safety Ltd.
Rosenberg Peter D.
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