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Joining and Cutting Processes

Joining and Cutting Processes. Fusion Welding Processes. Fusion Welding involves heating two materials above their melting temperatures (electrically or chemically). Filler (rods) metals are added to the weld area during the welding of a joint (supply additional material to weld zone).

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Joining and Cutting Processes

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  1. Joining and Cutting Processes

  2. Fusion Welding Processes • Fusion Welding involves heating two materials above their melting temperatures (electrically or chemically). • Filler (rods) metals are added to the weld area during the welding of a joint (supply additional material to weld zone). Engr 241-R1

  3. Processes Oxyfuel Gas Arc Consumed Electrode Non-Consumed Electrode Resistance Solid State Other – “High Energy” Engr 241-R1

  4. Oxyfuel Gas Welding • Process that uses a fuel gas combined with oxygen to produce a flame • Typically used for structural sheet-metal fabrication, automotive bodies, and various repair tasks • Most common fuels used - acetylene (oxyacetylene). • Manual operation, portable & flexible.Low equipment cost. Engr 241-R1

  5. Torch • allows for controlling and mixing gases

  6. Oxygen and fuel gas cylinders

  7. Cylinder Safety • Caps on when moving • Secure to truck or wall • Keep upright (Acetylene) (1/7 Rule) • Hand over regulator when opening • Read labels – don’t rely on colors • Dangers of compressed oxygen Engr 241-R1

  8. Oxyfuel Gas Welding- Flame Types • Neutral Flame: 1:1 ratio (oxygen vs. fuel). • Oxidizing Flame: greater oxygen supply (not for steels). • Reducing (Carburizing) Flame: lower oxygen supply (lower temperature)- brazing. Engr 241-R1

  9. Neutral - the oxygen and fuel gases combine • oxygen burns up the carbon and the hydrogen in the fuel gas then releases only heat and harmless gases • flame temp is 5589 deg F.

  10. Oxyfuel Gas Welding- Flux • Retard oxidation of surfaces of the parts being welded • Dissolves/Removes oxides or other substances • Stronger joints Engr 241-R1

  11. Arc Welding Processes (Consumable Electrode) • Developed in the mid-1800s • Heat obtained through electrical energy Engr 241-R1

  12. Shielded Metal Arc Welding (SMAW) • Stick welding • 50% of all large-scale industrial welding operations- portable process. • Electric arc generated between tip of coated electrode and the workpiece. • Electrode coating produces a shielding gas to protect from oxygen. Engr 241-R1

  13. Engr 241-R1

  14. Electric arc between flux covered electrode and base metal

  15. Engr 241-R1

  16. SMAW (Cont.) • (DCEN) electrode negative • Workpiece positive, electrode negative. • Sheet metals - shallow penetration, gap joints. • (DCEP) electrode positive • Electrode positive, workpiece negative. • Deeper penetration. • (AC) Alternating current Engr 241-R1

  17. Engr 241-R1

  18. SMAW (Cont.) • Thick sections, large electrodes at max current. • Manual, portable, and flexible. AC-DC machines, low cost equipment Engr 241-R1

  19. Submerged Arc Welding • Weld arc is shielded by a granular flux. • Flux is fed to weld zone by gravity. • Flux covers molten metal which prevents spatter, sparks, UV radiation, or fumes. • Flux is recovered. • 4-10 times productivity of SMAW, automatic, horizontal, low skill, Engr 241-R1

  20. Submerged Arc

  21. Underwater SMAW • use well insulated electrode holder and special water proof covered electrodes • because of rapid cooling - use stringer beads not weaving • short arc length and DCEN • poor visibility - use #4 or #8 lens • communication system • normally have 80% of the tensile strength and 50 of the ductility of normal welds

  22. Gas Metal Arc Welding (GMAW) • Formerly MIG (Metal Inert Gas). • Argon, helium, carbon dioxide, or mix (Shield the arc to prevent oxidation). • Wire fed automatically through nozzle into arc. Engr 241-R1

  23. Engr 241-R1

  24. GMAW (Cont.) • Rapid, economical, twice SMAW productivity. • Most production done today • Can be automated (robots), low skill, DC, medium cost equipment. Engr 241-R1

  25. Engr 241-R1

  26. Engr 241-R1

  27. Flux Cored Arc Welding (FCAW) • Same as GMAW but electrode is tubular and filled with flux. • Automatic feeding of wire (like GMAW). • Uses no external gas source • Fast growing • Thin to thick sections. • Can be automated (robotics), DC, medium cost. Engr 241-R1

  28. Engr 241-R1

  29. Engr 241-R1

  30. Electrogas Welding • For welding butt joint edges vertically in one pass. • Metal deposited between two pieces joined – space enclosed by copper shoes sliding upward with weld • Also around pipe • 1/2” to 3” thickness. • Usually automated, High equipment cost. • For welding bridges, pipes, tanks, ships Engr 241-R1

  31. Electrogas - use shielding gas - flux cored wire fed in joint • arc maintained between electrode and weld

  32. Electro-slag Welding • Similar to EGW. • Weld begins at part bottom, molten slag extinguishes arc. • Heat then produced continuously by elect. Resist. of molten slag • Very thick sections - 2” to 36”. • High cost of equipment. Engr 241-R1

  33. Vertical joint - arc started between electrode & bottom

  34. Electrodes • Strength of deposited metal. • Type of coating. • Size (1/16 to 5/16 in diameter). Engr 241-R1

  35. Electrode Classifications • E6011-A1 • E - arc welding electrode • 60 – 60,000 psi min. tensile strength • 1 – next to last digit – position • 11 – last two digits together, type of covering and current to be used • A1 – alloying elements Engr 241-R1

  36. Electrode Coatings • Clay like material. • Silica binders and powdered materials (Oxides, carbonates, fluorides, metal alloys, cellulose) Engr 241-R1

  37. Electrode Coatings (Cont.) • Stabilize the arc. • Generate a gas shield. • Control rate at which the electrode melts. • Act as a flux to protect weld (from oxidation). • Add alloying elements to joint ie. Protect from becoming brittle). Engr 241-R1

  38. Arc Welding (Non-Consumable Electrode) • Gas Tungsten-Arc Welding (GTAW) • Plasma Arc Welding (PAW) Engr 241-R1

  39. Gas Tungsten-Arc Welding (GTAW) • Formerly TIG (Tungsten Inert Gas). • Shielding gas is supplied from an external source. Argon or helium (high cost). • Filler metal is supplied from filler wire. • Tungsten electrode is not consumed. Engr 241-R1

  40. GTAW-NCE (Cont.) • Good for thin parts, high quality welds. Used for welding aluminum, magnesium, titanium, and refractory metals. • all positions, AC-DC, medium distortion, portable equipment, medium cost of equipment. Engr 241-R1

  41. Plasma Arc Welding • Argon and helium. • Arc is hot ionized gas (60,000 degrees °F). • Transferred- workpiece is part of circuit. • Non-transferred- Arc between tungsten electrode and nozzle. • High energy, deep penetration, stable arc, less thermal distortion, high speed, > ¼” thick material, high skill, medium cost of equipment. Engr 241-R1

  42. Separate shielding gas protects the welding or cutting process

  43. Resistance Welding Processes • Spot • Seam • Projection • Stud • Flash Engr 241-R1

  44. 1.) Resistance Spot Welding • Uses pressure and resistivity of parts to form nugget. • Must be clean but not oxide free • Used for sheet metal parts Engr 241-R1

  45. Spot - most common

  46. Two pieces fused with small nugget

  47. 2.) Resistance Seam Welding • Like spot welding but with rollers. • Continuous or “roll spot welding”. Engr 241-R1

  48. two wheeled electrodes travel over metal - current passes through them

  49. can produce intermittent seam of overlapping spots for leak proofing

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