•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 and percentage of alloying elements increase, OFC becomes less effective. Oxides of the alloying elements have a higher melting point than the alloying elements themselves and are refractory in nature. (Remember that oxides of iron have melting points lower than the melting point of iron so they become fluid and they readily leave the kerf as molten slag.) Unlike iron oxides, an alloy’s oxides do not readily run out of the kerf to expose new iron to oxygen to keep the burning process going, and cutting becomes more difficult.
By what means can OFC be extended to metals and alloys not readily cut?
•Torch Oscillation
•Waster Plate
•Wire Feed
•Metal Powder Cutting
•Flux Cutting
How does torch oscillation work?
By torch manipulation the entire starting edge of the cut is brought to a bright red color before beginning the cut. This technique is usually used in conjunction with one of the other four cutting enhancement methods on low-alloy stainless steel up to 4 inches thick and on resistant cast iron.
How does a waster plate work?
A low-carbon steel waster plate is secured to the top of the stainless steel to be cut, and the cutting action begun on the waster plate. The heat released from the waster plate’s burning provides additional heat to the cutting action in the stainless below. Hot slag from the waster plate tends to flush the kerf of the stainless steel’s refractory oxides. Waster plate disadvantages are the extra cost of the waster plate, additional set-up time, slow cutting speeds, and rough cut.
How does wire feed cutting work?
A small diameter carbon steel wire is fed into the torch preheat flame just ahead of the cut and melts onto the surface of the alloy steel. The additional carbon steel works just like a waster plate to enhance cutting action. A motor feed and wire guides are needed as accessories.
How does metal powder cutting work?
Powder metal cutting (AWS abbreviation is POC) uses iron-rich powder