A large, smoky, orange flame will result. Also, you must have your tinted welding facemask over safety glasses (or your welding goggles with a number 5 lens shade) on prior to lighting the flame.
•Increase the flame size by slowly opening the acetylene valve until most of the smoke disappears.
•Open the oxygen preheat valve on middle of the torch and adjust for a neutral flame.
•Actuate the cutting oxygen lever and examine the preheat flame. Further adjustment of the preheat oxygen valve may be needed to keep the preheat flame large enough when the cutting oxygen is used. This is because cutting oxygen use may cause the hose pressure to drop so much the oxygen to the preheat flame must be increased to keep a proper preheat flame.
•You are ready to begin cutting.
What is the best way to flame cut inch (6 mm) through inch (12.7mm) thick metal?
See Figure 2–8.
•The cutting torch tip is held perpendicular to the metal.
•Start the cut at the edge of the stock by preheating the edge of the stock. In thicker material, the torch may be angled away from the direction of travel so the preheat flame strikes down the edge of the material. When the stock becomes a dull cherry red, begin cutting by squeezing the oxygen cutting lever. Remember to hold the torch tip perpendicular to the surface of the stock when cutting action has begun.
•Move the torch along the cut line in a steady motion. For right-handed welders, cutting from right to left allows the welder to see the marks of the cutting line more easily. Left-handers will usually prefer cutting left to right.
Figure 2–8Position of cutting torch tip on 1/4 inch and thicker plate, starting (left) and cutting (right)
What is the best way to cut thin metal (10 guage- inch or thinner)?
•Utilize the smallest cutting tip available with two preheat flames.
•Hold the torch at a 20 degree to 40 degree angle to the metal surface to increase the kerf thickness.
•Adjust the flame to the smallest preheat flame that will permit cutting.
•Set oxygen pressure at 15psi (1 bar). See Figure 2–9.
Figure 2–9Torch position for cutting thin sheet metal, starting (left) and cutting (right)
When cutting thin-gauge sheet metal, what step can be taken if slag accumulates on the underside of the good part?
Tipping the torch away from the side you will use allows the slag to form on the scrap side of the kerf will keep slag off the good part.
What are the proper steps to shut down an oxyacetylene torch and its cylinders?
•Turn off the oxygen and then the acetylene with the torch handle valves.
•Turn off the oxygen and acetylene cylinders valves on the cylinders.
•One at a time, open and reclose the oxygen and acetylene valves on the torch handle to bleed the remaining gas in the lines and regulator to atmosphere. Verify that both the high-pressure and low-pressure gauges on both gases indicate zero pressure. Bleed off the oxygen first to eliminate the possibility of providing oxygen to the remaining acetylene.
•Unscrew the regulator pressure adjustment screws on both regulators in preparation for the next use of the equipment.
Applications
What metals can readily be cut using the OFC process?
•Cutting of new steel plate, beams, and pipes to size both in mills, in fabrication plants, and on construction sites.
•Cutting risers, gates, and defects from cast iron and steel castings in steel mills.
•Cutting up old steel and cast iron equipment for removal and salvage.
•Removing rivets from old equipment without damaging the surrounding steel.
•Removing damaged parts prior to welding new ones in place.
•Gouging the surface of steel plate edges in preparation for welding.
•Manufacturing steel parts by cutting them out of flat stock instead of machining them.
•Removing backing bars from a weld.
What is stack cutting?
In order to make multiple parts in a single cutting pass, multiple sheets or plates are stacked and clamped or welded together. Then the cutting proceeds manually, or more likely by machine. When the cutting is complete, the stack comes apart, leaving multiples of flame cut parts. Stack cutting is also useful in cutting stock so thin it could not be cut in a single layer. It can be used in place of shearing or die stamping when the production run does not justify making dies. There may also be substantial savings of fuel and oxygen in stack cutting as gas consumption is not directly proportional to total cut thickness. Generally the maximum thickness of plates in stack cutting must not exceed 0.5 inch (12.7 mm). Note that high-quality stack-cut parts require clean, flat plates (or sheets) securely clamped in position with no air gaps between the plate layers. If there is air between the plates, the cutting action will be extinguished and the parts will be ruined.
What metal would OFC definitely not a good choice?
Here are some examples:
•Aluminum
•Brass
•Copper
•Lead
•Magnesium
•Stainless steel
•Zinc
The OAC process can readily cut what metals?
•Mild steel (steel with a carbon content of less than 0.3% carbon)
•Low-alloy steels
•Cast iron (though not readily)
•Titanium
What materials can be cut by the OAC process if additional steps are taken?
•Stainless steel
•High-alloy steel (must be preheated)
Why do high-alloys of steel resist OFC?
As the number
