OxyFuel Gas Cutting and Welding Processes Unit 2 TSM 233

TSM 233 Metallurgy and Welding Process OxyFuel Processes Cutting Welding Soldering Brazing Heating

TSM 233 Metallurgy and Welding Process Applications of Gas Welding and Cutting Gas welding and cutting equipment is still widely used in industry. The same equipment can be used for a variety of applications, such as brazing, heating, shaping metal. The equipment is somewhat inexpensive and portable. Gas cutting is generally limited to ferrous type metals. Gas welding is considered a high level skill.

TSM 233 Metallurgy and Welding Process Equipment Tanks Regulators Check valves Hoses Torch body Torches (attachments) Cutting Welding Heating

TSM 233 Metallurgy and Welding Process Types of Fuel Gases Acetylene Hydrogen Methylacetylene propadiene (MAPP) Natural gas (Methane) Propane Propylene L-P gases

TSM 233 Metallurgy and Welding Process Acetylene Primary fuel gas for welding and cutting. C 2 H 2 Provides an excellent gaseous shield of carbon dioxide. Very unstable, explosive. Acetylene tanks are filled with a porous material and acetone to help stabilize the acetylene. The tanks also have fusible plugs that will release excess pressure. Always use the tanks in the upright position.

TSM 233 Metallurgy and Welding Process Comparison of Fuel Gases Acetylene- good for welding, brazing and cutting. MAPP, Propylene - good for cutting, soldering and heating. Propane, Methane, Natural Gas, LP-Gas - good for heating, brazing and soldering. Hydrogen - used in industrial applications for some welding, heating, soldering, brazing. Acetylene and Hydrogen are generally not as safe to work with as the other gases.

TSM 233 Metallurgy and Welding Process Flame Characteristics Acetylene burns with the oxygen provided to produce an inner cone. This produces water and CO. The CO combines with O 2 from the atmosphere to produce CO 2. The carbon dioxide produces a protective area that allows the metal to be heated without oxidation.

TSM 233 Metallurgy and Welding Process Types of Flames

TSM 233 Metallurgy and Welding Process Cutting Process Rapid oxidation of ferrous metals. Metal is preheated to “kindling” temperature. Pure oxygen stream is supplied. Force of the oxygen forces out the ferrous oxides and molten metal. (cutting video)

TSM 233 Metallurgy and Welding Process Cutting Process Conditions The melting point of the material must be above its kindling temperature in oxygen. The oxides of the metal should melt at a lower temperature than the metal itself. The heat produced by the combustion of the metal with oxygen must be sufficient to maintain the cut. The thermal conductivity must be low enough so that the materials can be brought to its kindling temperature The oxides formed in the cutting should be fluid when molten.

TSM 233 Metallurgy and Welding Process Key Factors for Cutting Determine if the metals can be oxy-fuel cut. Proper size tip. Correct pressures. Sufficient preheating. Ample supply of oxygen. Correct type of flame. Correct torch position and travel rate. Torch is in good shape, well maintained.

TSM 233 Metallurgy and Welding Process Welding Process Gases form a protective shield. Inner cone provides intense, concentrated heat to control a molten weld puddle. Metal solidifies as weld puddle moves forward. The size of the welding tip determines the amount of heat provided. Skill is needed to control travel speed, weld size, torch height, and maintain the gas shield.

TSM 233 Metallurgy and Welding Process Key Factors for Oxy-Fuel Welding Determine if the metals can be oxy-fuel welded. Proper size tip. Correct pressures. Sufficient heat provided. Correct type of flame. Correct torch position and travel rate. Torch is in good shape, well maintained.

TSM 233 Metallurgy and Welding Process OxyFuel Equipment Regulators Used to regulate the flow pressure of the gases. Differences between Fuel gas and oxygen? Type of threads Color coded Range of the gages. Single-stage vs. Two-stage? Master vs. Station? Maintenance: Keep clean Release pressure when not in use Do not use oil products

TSM 233 Metallurgy and Welding Process Torches Used to mix the fuel gas and oxygen Single vs. Multiple purpose? Equal pressure vs. Injection types? Parts: Body Valves Mixing Chamber Tips

TSM 233 Metallurgy and Welding Process Welding Tips Single orifice. One piece vs. two piece? Size is based upon the diameter of the orifice and the length of the tip. What determines the size tip to use? Type of materials Type of process Size of the materials

TSM 233 Metallurgy and Welding Process Check valves One-way gas flow valves. This one uses a stainless steel ball and spring. Are used to prevent the gases from burning back into the torch assembly (flashback) Generally, best to install at the regulator. Can also be installed at the torch body.

TSM 233 Metallurgy and Welding Process Goggles Used to protect the eyes and increase visibility. Lens shades: (the higher the # the darker the shade) #2 soldering #4 light welding #5 welding, light cutting #6 heavy cutting Maintenance: keep clean, use a protection clear plastic lens. replace broken/cracked lenses. often will break the glass lens if dropped.

TSM 233 Metallurgy and Welding Process References Chapters: 5, 6 and 7.

TSM 233 Metallurgy and Welding Process Summary What determines the oxyfuel process to use? What determines the type of fuel gas? What determines the size welding tip to use? What determines the pressures to use? Describe the welding process Describe the cutting process.