Oxy-Arc Cutting: Principles and Techniques for Underwater Welding
Oxy-Arc Cutting: Principles and Techniques
Introduction
The oxy-arc method is an oxygen cutting process where metal is cut by a chemical reaction with oxygen at high temperatures. This temperature is maintained by an electric arc between the electrode and the metal, as well as chemical reactions within the electrode itself. While exothermic cutting has become more prevalent, oxy-arc cutting remains a valuable technique with a long history and proven effectiveness.
This process is particularly well-suited for cutting steel, but can also be used to cut other metals successfully. The effectiveness of oxy-arc cutting relies on the rapid oxidation of metals during the cutting process.
How Oxy-Arc Cutting Works
During operation, a specific point on the metal is heated to incandescence by the electric arc between the metal and the tip of the hollow tubular electrode. This method provides a significant amount of heat, resulting in instantaneous heating. Once the point is preheated to a red glow, a high-speed stream of oxygen is directly projected onto it.
The oxygen jet serves two crucial functions:
- Produces heat through the oxidation of the metal.
- Drags away the molten metal and oxides.
The electrode tip is also exposed to heat and oxidation, leading to its rapid consumption. In the oxy-arc method, the arc functions similarly to the flame preheating in a gas cutting torch. DC power is recommended for optimal results, while AC power is slightly more dangerous.
Grounding the Work
. The first step when performing a cutting and underwater welding arc, is to connect the ground cable to work. This will select the point at which to place, taking into account that the clamp must be in the line of sight of the diver, cutting as close as practical and so that the diver is not in the middle of the circuit. As you progress the court may be necessary to change the position of the mass to prevent the diver is in the middle of the circuit. Once selected the item will be cleaned with a scraper or brush, until the metal look shiny. If the embedding is very large may be necessary to clean both the point mass and the cut line. For safety of the diver the clamp must be of type “C”. Secure it firmly to work and leave the cable with sufficient breast. It may be necessary to secure a spot weld if you are not properly asserted.
Court of heavy plate steel tubular electrodes. When cutting sheet thicker than 1 / 4 “(6.36 mm.), Use the technique of” dredging “(fig.5.7): 1. Maintain the electrode perpendicular to the cutting surface, open the valve oxygen and ask “CLOSE MACHETE.” approximate the electrode and tap against the work, to start the arc. 2. As soon as you start cutting the entire thickness of the plate, dragging the electrode along the line cut perpendicular to keep working as cutting progresses. It has to push in two directions: into the cut, to give the retreat and in the forward direction. Do not keep the bow as it remains on the surface. To apply pressure the forward direction, hold the electrode with a free hand about four inches from the end. When the electrode is consumed, making it more manageable, you can release the hand of the electrode. 3. It may cause incomplete cutting by low oxygen pressure , cutting speed too fast or mishandling of the electrode. An incomplete cut will produce a flashback. In these cases stop the advance and go back to complete the cut. 4. When the electrode has been used up about 7 cm.’s electrode break the bow, cut off oxygen to the surface and say “OPEN MACHETE.” Touching a couple of times with the electrode on the job to ensure that power has been cut. 5. preamplifier and continue the operation.
Cutting veneer with tubular steel electrodes. The technique of cutting sheet metal less than 1 / 4 “(6.35 mm.) Thick differs from thick sheet metal cutting pressure on the job. In this case hardly puts pressure on the cutting edge while moving in the desired direction. In case of poor visibility can be used an alternative technique (see Figure 5.7 .. Acting as if it were a thicker sheet. This electrode is tilted about 45 degrees. The effective thickness of the veneer older, you can apply normal pressure to the electrode.
Court smelting and nonferrous metals. While the metal arc process and ultratérmico are considered the best methods of casting and nonferrous metals, oxy-arc process will only be used for these cases in an emergency. When materials that oxidize quickly becomes a casting process instead of oxidation. Does not derive any benefit from using oxygen except the mechanical drag of the molten metal out of court. We recommend replacing the air oxygen. Hoses never be used for oxygen air after use. 1. It is recommended that you use all the power available to a maximum of 500 Amps and the cutting action of heat is directly provided by the arc. 2. The operator must manipulate the electrode tip into and out of court and that fusion occurs only in the immediate vicinity of the arc. 3. Veneer tubs do not need the manipulation of the electrode and the operation is the same as when cutting thin steel plate. 4. The dredging technique used in cutting steel can not be used successfully when cutting non-ferrous metal smelting.