Robotic Oxyacetylene Welding
Oxyacetylene welding usually referred to as gas welding or oxyfuel gas welding is a process which depends on combustion of oxygen and acetylene. When assimilated in correct proportions within a hand-held torch or blowpipe, a fairly hot flame is fashioned within a temperature of about 5,792 degrees Fahrenheit. The chemical combination of the oxyacetylene flame can be adjusted by converting the ratio of the volume of oxygen to acetylene.
Three distinctive flame settings are used: neutral, oxidizing and carburizing.
Welding is generally carried out using the neutral flame setting which has equal amounts of oxygen and acetylene. The oxidizing flame is acquired by increasing just the oxygen flow rate while the carburizing flame is obtained by increasing acetylene flow in correlation to oxygen flow. Steel melts at temperatures above 2,732 degrees Fahrenheit, so the combination of oxygen and acetylene is used because it is the only gas blend with enough heat to weld steel. However, other gases such as propane, hydrogen and coal gas can be used for joining lower melting point, non-ferrous metals, as well as for brazing and silver soldering.
Equipment
Oxyacetylene equipment is convenient and easy to use. It encompasses oxygen and acetylene gases stored under pressure in steel cylinders. The cylinders are fixed with regulators and flexible hoses leading to the blowpipe. Specifically designed safety devices such as flame traps are flanked by the hoses and the cylinder regulators. The flame trap averts flames generated by a 'flashback' from reaching the cylinders; primary causes of flashbacks are the failure to sluice the hoses and overheating of the blowpipe nozzle.
Operating Characteristics
The action of the oxyacetylene flame on the surface of the material to be welded can be attuned to produce a soft, harsh or violent effect by changing the gas flows. There are practical limits as to the sort of flame which can be used for welding. A harsh, forceful flame will cause the molten weld pool to be blown away, but too soft a flame will not be steady near the point of application. The blowpipe is consequently designed to contain different sizes of a swan neck copper nozzle which permits the correct amount of flame to be used. The connection between material thickness, blowpipe nozzle size and welding speed, is imperative. The addition of filler metal in the form of a rod can be made when required when carrying out fusion welding. The primary methods employed in oxyacetylene welding are leftward, rightward and all-positional rightward.
The former is used almost exclusively and is idyllically suited for welding butt, fillet and lap joints in sheet thicknesses up to approximately 5mm. The rightward technique locates function on plate thicknesses above 5mm for welding in the flat and horizontal-vertical position. The all-positional rightward method is a amendment of the rightward technique and is ideally suited for welding steel plate and in particular pipework where positional welding, (vertical and overhead) has to be implemented. The rightward and all- positional rightward techniques facilitate the welder to acquire a uniform penetration bead with added control over the molten weldpool and weld metal. Furthermore, the welder has a clear view of the weldpool and can work in absolute freedom of movement. These techniques are highly skilled and are used less often than the regular leftward technique.
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