3Can be used for welding, brazing, cutting, and heating metals Oxyfuel: the process of combining pure oxygen with a combustible fuel gas to produce a flameCan be used for welding, brazing, cutting, and heating metalsOxygen & fuel gases are stored under pressure in cylinders and are released as individual gases through valves, regulators, and hoses.Mixed as they flow through torch assembliesBurn as they are discharged through special tips
4Factors to consider in selecting a gas: Fuel gases:Propane, natural gas, propylene & acetyleneVary in their chemical compositionReact with the metal in different waysFactors to consider in selecting a gas:Availability & costWelding process or operation to be performedThickness of metal & type of welded joint to be producedPhysical properties of metalsChemical properties of metals
6Supplied in a liquid form under positive pressure, which varies with temperature Most oxyfuel cutting torches can use LP gas, but special hoses and cutting tips are required.Readily available in most areasDue to cost, propane cutting is heavily used in the metal recycling industry.
8Has been used for approximately 30 years Stable in both liquid and gas statesEconomicalProduces little slagHas a high heat valueDoes not have the withdrawal pressure limitations that are necessary with acetyleneApproximately 5% propylene, 87% propane & traces of other gases
10Most widely used fuel gas for welding and cutting applications Produces a clean weld and a controllable flameLess stable and more expensive than other fuel gasesPerforms most functions well and is widely available
14Odorless, colorless, tasteless & heavier than air Makes up about 20% of the atmosphereWill not burn by itselfProduced commercially by causing air to liquefyCompressed into steel cylinders at 1,800 to 2,400 pounds per in2 (psi)Supports combustion and is explosive if handled improperlyCylinder sizes = 80 to 244 ft3
16Colorless, but has a very distinct odor Highly combustible Cylinder sizes = 60 to 300 ft3Cylinder contains a porous substance saturated with liquid acetoneAcetylene is pumped into the cylinder, displacing some of the acetoneNot under extremely high pressureFull cylinder is pressurized to approximately 250 psiMay not be withdrawn at a rate higher than 15 psi
18Oxyfuel cutting of mild carbon steel heats the metal to rekindling temperature (1,400oF to 1,800oF), then oxidizes and blows the slag from the cut with a stream of pure oxygen.Oxyfuel welding fuses two pieces of metal by heating them to the melting point with a combustible mixture of oxygen and fuel gas.Can be done with or without the use of a welding rodBrazing: the joining of metals by adding bronze fillerSoft and hard solders (lead & silver alloys) are the filler materials used in soldering.The oxyfuel flame is also used to bend, shape, preheat, stress relieve, post-heat & temper metal.
20Secure the oxygen and fuel gas cylinders to a wall, a special cylinder cart, or a special rack if transported to job sites in a truck.Remove the valve protection caps and wipe off any dirt accumulation with a clean, dry cloth (free from oil or grease).Slightly open (crack) both cylinders to make sure they do not stick and to blow out any dirt or dust lodged in the valve. Close the valves.
21Check all valves, connections, and soft plugs for leaks with mild soapy water and a clean brush. Attach the regulators to the cylinders pointing toward the sky to prevent someone from getting in front of the regulator.The regulators, safety check valves, and hoses should be tightened securely with a wrench.Do Not use a wrench to attach the welding tip or cutting attachment to the torch.
25Designed with several built-in safety precautions: Oxygen hoses are usually green.Fuel gas hoses are red.All oxygen connections and cylinders have right-hand threads.All fuel gas connections and cylinders have left-hand threads.Fuel gas fittings have a “V” notch cut around the the outside of the connectors.Oxygen fittings and connectors are smooth.
26Cylinders: Regulators: Hoses: Two Two sets Two stage regulators are the safest to use.Hoses:Color-coded & specifically designed based on useType R: designed specifically for acetylene useType T: approved for all fuel gases
28Safety Check Valves: Torch Handle: Cutting Attachment: Two sets recommendedAttach between regulators and hoses and between hoses and torch to prevent reverse flow of the gases and flame that could cause hose fires, regulator ruptures, and cylinder firesTorch Handle:Regulated by two valvesOften equipped with internal reverse flow check valvesCutting Attachment:Regulated by preheat oxygen control valveOperated by depressing the cutting oxygen lever
33Cutting Tips: Welding Tip: 3 to 8 preheat orifices and 1 oxygen-cutting orificeDrill size determines tip sizePropane tip is a 2-piece tip with at least 6 preheat orificesWelding Tip:1 orifice for gas mixtureSize is determined by drill size of orifice
38Keep oil and grease away from all parts of the oxyfuel apparatus. Secure the cylinders in an upright position so they cannot be overturned.Face the regulator gauges toward the sky making it impossible to stand in front of them.Store and use oxyfuel units in well ventilated areas adequately separated from other activities.Acetylene pressure in the lines should NEVER exceed 15 psi.
39Open the acetylene cylinder valve ¼ to ½ turns; if it is the wheel type, open all the way. Use an approved spark lighter to light the torch; never use matches or cigarette lighters.NEVER use oxygen to operate pneumatic tools, blow out lines, inflate tires, or dust off clothing.NEVER hang clothing on cylinders, running the risk of saturating them with oxygen and acetylene.DO NOT convert an acetylene regulator to an oxygen regulator or vice versa.
41Slowly open the oxygen cylinder valve to prevent a sudden surge of pressure. Release or loosen the regulator adjusting screw before opening a cylinder valve.DO NOT walk with a lighted torch or lay down a lighted torch.Purge hoses before attaching the torchRepair hoses with proper hose splices, not friction tape. NEVER use a leaking hose.Test for leaks with soap and water, not matches.
43If valves on cylinders are faulty or too tight, notify the supplier; undue force would be dangerous. Keep a fire extinguisher handy at all times.Dress properly and wear eye protection.Prevent heat and sparks from getting to cylinders and hoses.DO NOT strike an arc on a cylinder or hit a cylinder with a metal object.NEVER use a cylinder as a ground in an electrical circuit.
45NEVER guess; get the correct information from a qualified person. Mark, isolate, or otherwise designate empty cylinders.Oxygen and fuel gas cylinders (either full or empty) MUST be stored separately in accordance with safety and fire codes.
47Check torch body for closed valves. Check regulator for loose regulator adjusting screw.Open acetylene cylinder valve ¼ to ½ turn (wheel-type valves one turn) maximum.Turn acetylene regulator adjusting screw to desired working pressure.Open oxygen cylinder valve completely.Turn oxygen regulator adjusting screw to desired working pressure.
48Crack acetylene torch valve and light the torch, open acetylene torch valve until soot disappears. Open oxygen torch valve to adjust to neutral flame; no acetylene feather and sharp inner coneWhen welding, the ratio of oxygen to acetylene is approximately 1:1.Oxygen and acetylene settings will vary depending on the attachment tip and thickness of metal to cut or weld.
52Turn off acetylene valve on torch butt. NEVER turn off oxygen first. Turn off oxygen valve on torch butt.Close acetylene cylinder valve.Bleed acetylene hose by opening acetylene torch valve; close valve.Back acetylene regulator adjusting screw until loose.Close oxygen cylinder valve.
53Bleed oxygen hose by opening oxygen torch valve; close valve. Back oxygen regulator adjusting screw until loose.Recheck valves for closure, roll up hoses.If rig is not to be used for some time, remove the regulators and put the safety caps back on the cylinders.NEVER leave equipment under pressure 24 hours a day.
55DO NOT cut over a concrete floor. Metal to be cut should be clean, marked with a punch or soapstone, and placed in a suitable position for cutting.DO NOT cut over a concrete floor.Use a container or special cutting table device to catch the molten metal.Oxyfuel cutting is limited to ferrous metals.Steels with a high tungsten or chromium content or stainless steel cannot be cut with oxyfuel.Cast iron is more difficult to cut than steel.An excess fuel flame is usedMore oxygen pressure is needed
56Steps to Follow in Making a Cut Hold blowpipe perpendicular to surface of metal unless bevels are to be cutHold the flame inner cone about 1/16 to 1/8 inch above the plate.Proper distance away from plate will prevent metal from sticking to the tipHold tip so that two preheat holes are in line with the cutHold torch at edge of metal until metal begins to meltTop of torch may be slanted toward the cut & changed to a vertical position as cut progresses
61Tilt torch tip toward direction of cut on thin metal Press down slowly on the cutting oxygen lever until cutting valve is completely openWhen the cut is through the metal, move torch along markTilt torch tip toward direction of cut on thin metalIt should be held in a vertical position on thick metal
63Move torch slowly along surface or oxygen stream will not pass completely through thick metal To restart the cut, release cutting lever and reheat metal again before pressing cutting levelLosing the cut may cause irregular edges.When beveling plate edges or cutting at an angle, lean the tip at the desired angle and hold the torch parallel to the work.
64Correct CutNotice that the top edge is square and that the drag lines show a slight curve.Oxygen Pressure Too LowProduces a cut with rough surface, makes it difficult to hold cut and results in slow speed with too much lag.
65Speed Too FastProduces a rough cut with pronounced drag line very similar to too low oxygen pressure.Oxygen Pressure Too HighProduces a rough surface, melts down top edge and wastes oxygen.
66Too Much Acetylene in Preheats Reduces cutting speed approximately 25%. Forms carbon deposits on cut surface and wastes acetylene.Correct CutHere the factors of tip size, pressures and speed are correct…results in square top edge and uniform narrow kerf.
67Preheats Too HeavyTop edge is melted down, kerf irregular and excess gas is consumed by the preheat flame.Preheats Too SmallWastes time as maximum speed cannot be obtained. Low cutting speed results in gouges at bottom edge of cut.
68Oversize TipProduces a kerf which is too wide, causing not only a waste of plate but also a waste of both gases.Undersize TipInefficient cut because piece will not drop when end is reached as slag has not cleared the kerf and cutting time will be excessive.
69Steps to Follow When Piercing Holes Hold blowpipe tip perpendicular to the surface until a spot on the surface begins to meltRaise torch until tip is about 1/2” from the surface and slowly press the lever as torch is raisedMove tip to one side of the heated area so that the slag can be blown out
70Move inner cone within about 1/8” from the surface and make the cut on the inside edge of the hole To facilitate the cutting of a hole in thick metal, drill a hole 1/4” in diameter or larger and start the piercing in this hole.
73Tips frequently become spattered with metal or other materials that may cause inferior work. To clean tips:Rub emery cloth, steel wool, or the file on a tip cleaner to clean and square the tip point.Insert the correct size cleaner into each orifice. Push in and pull out; do not twist or bend the cleaner.Open oxygen slightly during this procedure to blow out foreign particles.Care should be taken not to damage the threads and seats of the tips.
75Free the metal from oil, paint, grease, dirt, rust, and other foreign material. Heat the metal with the torch, and then clean with a wire brush.Thick metal should be beveled with a grinder or torch.Align the plates to be welded and tack weld them to prevent warping.
77The blowpipe can be held like a hammer when standing or like a pencil when sitting. The tip and welding rod should be held at a 45o angle to the work surface.The inner cone flame should be 1/16” to 1/8” above the metal.Preheating the metal is very important in making a successful weld; therefore, the flame should be moved in the direction of the weld, and the cone should stay inside the puddle.
79Forming & running the bead: One of the most important steps in learning to weld with oxyfuel is to carry a molten puddle of metal along the line or seam of parts to be joined.Forming & running the bead:Flame held at starting point until a bright round pool (1/4” to 3/8” in diameter) is formedWelding speed should be adapted to maintain a uniform puddle width.Inner cone held 1/16” to 1/8” above surfaceSlow speed: flame burns a hole through the metalFast speed: bead will be irregular and narrow
81Most common movement pattern for fusion welding is the circular motion Zigzag motion is best when using a filler rodTorch should be held at about 45o to the surfaceWelding rod should be held at 45o, but slanted away from the torch tipRod diameter should be equal to the thickness of the metalTorch may be held so tip is pointed in direction of weld (forehand welding) or tip pointed toward weld (backhand welding)
85Most are either butt joints or fillet joints Butt welding: Two pieces of metal are butted together and welded, with or without bevelingFillet welding:Metal pieces are joined together forming an angle
87Usually done with a bronze rod, unless the color of the base metal must be matched Cast iron rods require higher preheating than bronze rods.
88Practice procedure for welding cast iron: Select the correct flux.Clean and bevel the edges of the stock.Use a 3/16” rod with a neutral flame and tack the ends together.Heat the rod tip to a red-colored heat and dip it in the flux, then dip the tip into the molten puddle of cast iron.Weld in the same manner as fusion welding on mild steel. Dip the hot tip of the rod in flux from time to time. If bubbles appear, add more flux.
89Practice Procedure for Braze Welding: Does not require extremely high welding temperatureClean surface to be weldedBevel and align edges of the metalUse neutral flame and heat the end of the rod and dip into the fluxHeat the area to be welded to a dull red and tack endsApply flux from rod on heated area, then pass rod into flame and deposit a small amount of bronze at the intervals until the weld is complete.Add flux from time to time.
91Application of an all alloy material to another metal for the purpose of reducing wear Procedure:Thoroughly clean the metal before applying alloy.Place the material to be hardsurfaced in a flat position.Heat a small section of the area with an excess acetylene flame until the metal begins to sweat.
92Touch the tip of the alloy rod to the surface and melt enough of the rod to form an alloy cover 1/16” thick and a desirable width without heating the base metal to a melting point.Maintain the hardsurfacing temperature in front of the path on the hard metal. Add just enough rod to the metal to maintain a uniform thickness and width.Hardsurfaced metal should be allowed to cool slowly. Dry lime serves as a good cover for cooling metal.Be sure to follow recommendations of the manufacturer of the hardsurfacing rods.
94The American Welding Society (AWS) is the professional organization responsible for setting standards for the certification of weldors.1st step in becoming a highly skilled craftsman is to certify as an Entry Level Weldor
95Certification process for Entry Level Weldor consists of: A Practical Knowledge Test:Welding/cutting theoryWelding/cutting inspection & testingSkill-related vocabularyMetal identificationWelding variablesElectrical fundamentalsWelding symbol interpretationFabrication principles & practicesSafetyRequires a minimum passing grade of 75%, with a minimum score of 90% on safety-related questions
96A Performance Test: Reading welding symbols Following written proceduresCutting parts to proper specificationsFitting parts correctlyPerforming specific welding techniquesPrepare test coupon by oxyfuel (OFC) and plasma-arc cutting (PAC)Includes both cutting straight lines and piercing holes
98Standard acetylene cylinder contains from 90 to 154 ft3, stored in a porous filler saturated with acetoneCylinders are filled under pressure and may develop leaks around the valve stem or in the “soft plugs”An acetylene cylinder leaking for an entire weekend into a closed facility can become a tragedy of significant proportions.Sparks from electrical switches or pilot lights on forced-air heaters can provide the necessary ignition source.
99To guard against fire damage, a good practice is to check acetylene cylinders for leaks when delivered.Materials:Small paintbrushOne-quart containerOne pint liquid soap, or a soap and water solutionProcedure:Lay acetylene cylinder on its side and “paint” the soft plugs with the soap solution. A leak here will cause bubbles to form.
100Stand the cylinder upright and paint the soft plugs on the shoulders of the bottle. DO NOT try to stop leaks in or around soft plugs—call the dealer and have the cylinder replaced!!Paint the regulator receptacle or main opening before attaching the regulator. If the bottle shows a leak now, this means that the main valve seat is damaged and leaking, regardless of how tightly the cylinder valve is closed.Paint the main valve stem around the ring nut at the top of the valve. If a leak is present here, stop the leak by tightening the ring nut with an adjustable wrench.
101Oxygen cylinders can be checked in the same manner EXCEPT: Attach the regulator to the cylinder and open the cylinder valve; paint the regulator ring nut and repaint the cylinder valve stem.Ask the distributor that any leaking bottles be replaced at their cost.Oxygen cylinders can be checked in the same manner EXCEPT:A commercial leak detector liquid such as “SnoopTM” should be used (BEST IDEA).ORA non-petroleum based liquid detergent must be used (such as IvoryTM liquid).Remember, oxygen cylinders are pressurized to about 2,200 lbs. psi.
102AcknowledgementsKirk Edney, Curriculum Specialist, Instructional Materials Service, edited and reviewed this PowerPoint presentation.Kristie Weller, Undergraduate Technician, Instructional Materials Service, organized and developed the information used in this PowerPoint presentation.
103All Rights Reserved Reproduction or redistribution of all, or part, of this presentation without written permission is prohibited.Instructional Materials ServiceTexas A&M University2588 TAMUSCollege Station, Texas2007