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Oxyfuel Cutting and Welding. 8609-A Instructional Materials Service Texas A&M University. Introduction. Oxyfuel : the process of combining pure oxygen with a combustible fuel gas to produce a flame Can be used for welding, brazing, cutting, and heating metals

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Oxyfuel cutting and welding

Oxyfuel Cutting and Welding

8609-A

Instructional Materials Service

Texas A&M University



  • Oxyfuel: the process of combining pure oxygen with a combustible fuel gas to produce a flame

  • Can be used for welding, brazing, cutting, and heating metals

  • Oxygen & 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 assemblies

    • Burn as they are discharged through special tips


  • Fuel gases:

    • Propane, natural gas, propylene & acetylene

    • Vary in their chemical composition

    • React with the metal in different ways

  • Factors to consider in selecting a gas:

    • Availability & cost

    • Welding process or operation to be performed

    • Thickness of metal & type of welded joint to be produced

    • Physical properties of metals

    • Chemical properties of metals



  • Supplied 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 areas

  • Due to cost, propane cutting is heavily used in the metal recycling industry.


Propylene c 3 h 6
Propylene (C varies with temperature3H6)


  • Has been used for approximately 30 years varies with temperature

  • Stable in both liquid and gas states

  • Economical

  • Produces little slag

  • Has a high heat value

  • Does not have the withdrawal pressure limitations that are necessary with acetylene

  • Approximately 5% propylene, 87% propane & traces of other gases


Acetylene c 2 h 2
Acetylene (C varies with temperature2H2)





Facts about oxygen o 2
Facts About Oxygen (O applications2)


  • Odorless applications, colorless, tasteless & heavier than air

  • Makes up about 20% of the atmosphere

  • Will not burn by itself

  • Produced commercially by causing air to liquefy

  • Compressed into steel cylinders at 1,800 to 2,400 pounds per in2 (psi)

  • Supports combustion and is explosive if handled improperly

  • Cylinder sizes = 80 to 244 ft3


Facts about acetylene c 2 h 2
Facts About Acetylene (C applications2H2)


  • Colorless, but has a very distinct odor applications

  • Highly combustible

  • Cylinder sizes = 60 to 300 ft3

  • Cylinder contains a porous substance saturated with liquid acetone

  • Acetylene is pumped into the cylinder, displacing some of the acetone

  • Not under extremely high pressure

    • Full cylinder is pressurized to approximately 250 psi

  • May not be withdrawn at a rate higher than 15 psi



  • Oxyfuel 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 rod

    • Brazing: the joining of metals by adding bronze filler

    • Soft 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.


Assembly of the oxyfuel rig
Assembly of the Oxyfuel Rig rekindling temperature (1,400


  • Secure 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.


  • Check 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.

  • DoNot use a wrench to attach the welding tip or cutting attachment to the torch.


Oxyfuel equipment
Oxyfuel Equipment mild soapy water and a clean brush.


  • Designed with several built-in safety precautions: mild soapy water and a clean brush.

    • 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.


  • Cylinders mild soapy water and a clean brush.:

    • Two

  • Regulators:

    • Two sets

    • Two stage regulators are the safest to use.

  • Hoses:

    • Color-coded & specifically designed based on use

    • Type R: designed specifically for acetylene use

    • Type T: approved for all fuel gases


  • Safety Check Valves mild soapy water and a clean brush.:

    • Two sets recommended

    • Attach 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 fires

  • Torch Handle:

    • Regulated by two valves

    • Often equipped with internal reverse flow check valves

  • Cutting Attachment:

    • Regulated by preheat oxygen control valve

    • Operated by depressing the cutting oxygen lever


Torch Butt mild soapy water and a clean brush.


Cutting Attachment mild soapy water and a clean brush.


  • Cutting Tips mild soapy water and a clean brush.:

    • 3 to 8 preheat orifices and 1 oxygen-cutting orifice

    • Drill size determines tip size

    • Propane tip is a 2-piece tip with at least 6 preheat orifices

  • Welding Tip:

    • 1 orifice for gas mixture

    • Size is determined by drill size of orifice


Safety precautions
Safety Precautions mild soapy water and a clean brush.


  • Keep 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.


  • Open 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.

  • DONOT convert an acetylene regulator to an oxygen regulator or vice versa.


  • Slowly open the oxygen cylinder valve to prevent a sudden surge of pressure.

  • Release or loosen the regulator adjusting screw before opening a cylinder valve.

  • DONOT walk with a lighted torch or lay down a lighted torch.

  • Purge hoses before attaching the torch

  • Repair hoses with proper hose splices, not friction tape. NEVER use a leaking hose.

  • Test for leaks with soap and water, not matches.


  • If 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.

  • DONOT 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.


  • NEVER supplier; undue force would be dangerous. 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.


Set up procedure for oxyfuel torch nozzle
Set-Up Procedure for supplier; undue force would be dangerous.Oxyfuel Torch Nozzle


  • Check torch body for closed valves. supplier; undue force would be dangerous.

  • 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.


  • Crack 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 cone

    • When 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.


Types of oxyfuel flames
Types of Oxyfuel Flames acetylene torch valve until soot disappears.


Shutdown procedure for torch nozzle
Shutdown Procedure acetylene torch valve until soot disappears.for Torch Nozzle


  • Turn off acetylene valve on torch butt. acetylene torch valve until soot disappears.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.


  • Bleed 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.



  • Metal to be cut should be clean, marked with a punch or soapstone, and placed in a suitable position for cutting.

  • DONOT 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 used

    • More oxygen pressure is needed


Steps to follow in making a cut
Steps to Follow in Making a Cut soapstone, and placed in a suitable position for cutting.

  • Hold blowpipe perpendicular to surface of metal unless bevels are to be cut

    • Hold 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 tip

    • Hold tip so that two preheat holes are in line with the cut

  • Hold torch at edge of metal until metal begins to melt

    • Top of torch may be slanted toward the cut & changed to a vertical position as cut progresses



  • Move 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 level

    • Losing 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.


Correct Cut pass completely through thick metal

Notice that the top edge is square and that the drag lines show a slight curve.

Oxygen Pressure Too Low

Produces a cut with rough surface, makes it difficult to hold cut and results in slow speed with too much lag.


Speed Too Fast pass completely through thick metal

Produces a rough cut with pronounced drag line very similar to too low oxygen pressure.

Oxygen Pressure Too High

Produces a rough surface, melts down top edge and wastes oxygen.


Too Much Acetylene in Preheats pass completely through thick metal

Reduces cutting speed approximately 25%. Forms carbon deposits on cut surface and wastes acetylene.

Correct Cut

Here the factors of tip size, pressures and speed are correct…results in square top edge and uniform narrow kerf.


Preheats Too Heavy pass completely through thick metal

Top edge is melted down, kerf irregular and excess gas is consumed by the preheat flame.

Preheats Too Small

Wastes time as maximum speed cannot be obtained. Low cutting speed results in gouges at bottom edge of cut.


Oversize Tip pass completely through thick metal

Produces a kerf which is too wide, causing not only a waste of plate but also a waste of both gases.

Undersize Tip

Inefficient cut because piece will not drop when end is reached as slag has not cleared the kerf and cutting time will be excessive.


Steps to follow when piercing holes
Steps to Follow When Piercing Holes pass completely through thick metal

  • Hold blowpipe tip perpendicular to the surface until a spot on the surface begins to melt

  • Raise torch until tip is about 1/2” from the surface and slowly press the lever as torch is raised

  • Move tip to one side of the heated area so that the slag can be blown out



Care of oxyfuel tips
Care of Oxyfuel Tips make the cut on the inside edge of the hole


  • Tips 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.


Preparing metal for welding
Preparing Metal for Welding materials that may cause inferior work.



Proper welding tip positions
Proper Welding Tip Positions other foreign material. Heat the metal with the torch, and then clean with a wire brush.


  • The 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.


Oxyfuel welding procedures
Oxyfuel Welding Procedures a pencil when sitting.


  • 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 formed

    • Welding speed should be adapted to maintain a uniform puddle width.

    • Inner cone held 1/16” to 1/8” above surface

    • Slow speed: flame burns a hole through the metal

    • Fast speed: bead will be irregular and narrow


  • Most common movement pattern for fusion welding is the circular motion

  • Zigzag motion is best when using a filler rod

  • Torch should be held at about 45o to the surface

  • Welding rod should be held at 45o, but slanted away from the torch tip

  • Rod diameter should be equal to the thickness of the metal

  • Torch may be held so tip is pointed in direction of weld (forehand welding) or tip pointed toward weld (backhand welding)


Types of welded joints
Types of Welded Joints circular motion



Welding cast iron
Welding Cast Iron circular motion



  • Practice procedure for welding cast iron: metal must be matched

    • 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.


  • Practice Procedure for Braze Welding: metal must be matched

    • Does not require extremely high welding temperature

    • Clean surface to be welded

    • Bevel and align edges of the metal

    • Use neutral flame and heat the end of the rod and dip into the flux

    • Heat the area to be welded to a dull red and tack ends

    • Apply 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.


Hardsurfacing
Hardsurfacing metal must be matched


  • Application 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.


  • Touch 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.


American welding society certification
American Welding 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.Society Certification



  • Certification process for Entry Level Weldor consists of: organization responsible for setting standards for the certification of weldors.

    • A Practical Knowledge Test:

      • Welding/cutting theory

      • Welding/cutting inspection & testing

      • Skill-related vocabulary

      • Metal identification

      • Welding variables

      • Electrical fundamentals

      • Welding symbol interpretation

      • Fabrication principles & practices

      • Safety

      • Requires a minimum passing grade of 75%, with a minimum score of 90% on safety-related questions


  • A Performance Test: organization responsible for setting standards for the certification of weldors.

    • Reading welding symbols

    • Following written procedures

    • Cutting parts to proper specifications

    • Fitting parts correctly

    • Performing specific welding techniques

    • Prepare test coupon by oxyfuel (OFC) and plasma-arc cutting (PAC)

      • Includes both cutting straight lines and piercing holes


Checking for cylinder leaks
Checking for Cylinder Leaks organization responsible for setting standards for the certification of weldors.


  • Standard acetylene cylinder contains from 90 to 154 ft organization responsible for setting standards for the certification of weldors.3, stored in a porous filler saturated with acetone

  • Cylinders 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.


  • To guard against fire damage, a good practice is to check acetylene cylinders for leaks when delivered.

  • Materials:

    • Small paintbrush

    • One-quart container

    • One pint liquid soap, or a soap and water solution

  • Procedure:

    • Lay acetylene cylinder on its side and “paint” the soft plugs with the soap solution. A leak here will cause bubbles to form.


  • Stand the cylinder upright and paint the soft plugs on the shoulders of the bottle. DONOT 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.


  • Oxygen cylinders can be checked in the same manner EXCEPT:

    • A commercial leak detector liquid such as “SnoopTM” should be used (BEST IDEA).

      OR

    • A non-petroleum based liquid detergent must be used (such as IvoryTM liquid).

    • Remember, oxygen cylinders are pressurized to about 2,200 lbs. psi.


  • Acknowledgements
    Acknowledgements valve; paint the regulator ring nut and repaint the cylinder valve stem.

    Kirk 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.


    All rights reserved
    All Rights Reserved valve; paint the regulator ring nut and repaint the cylinder valve stem.

    Reproduction or redistribution of all, or part,

    of this presentation without written permission is prohibited.

    Instructional Materials Service

    Texas A&M University

    2588 TAMUS

    College Station, Texas 77843-2588

    http://www-ims.tamu.edu

    2007


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