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Oxyfuel Gas Welding & Cutting

Oxyfuel Gas Welding & Cutting. Welding. process in which metals are joined by heating them to the melting point and allowg the molten portions to flow together to form one. Processes confused with oxyfuel gas welding are:.

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Oxyfuel Gas Welding & Cutting

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  1. Oxyfuel Gas Welding & Cutting

  2. Welding • process in which metals are joined by heating them to the melting point and allowg the molten portions to flow together to form one

  3. Processes confused with oxyfuel gas welding are: • soldering - two metals not melted are joined by a third metal with a melting point below 840 deg F. • brazing - temps above 840 deg F.

  4. Torch • allows for controlling and mixing gases

  5. Torch tip cleaner

  6. Fuel Gasses used with O2 • acetylene • hydrogen • natural gas - (high hydrogen concentration – brittle welds) • propane - • mapp – (methylacetylene-propadiene) (no special containers)

  7. Acetylene (most common) • most unstable • 1/7 rule of contents - 1/7 on contents per hour • asbestus and porous concrete or balsa core filled with acetone liquid

  8. Acetylene (Cont.) • unstable acetylene is suspended in core • keep upright or acetone leaks out of core into cylinder • open valve - get acetone • takes 7 hours for acetone to migrate back into core

  9. Oxyfuel Flames • Carburizing - too much fuel gas - adds carbon to the metal being welded

  10. Oxidizing - too much oxygen - burns the metal

  11. 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.

  12. Temps required to melt various metals

  13. Quantity of heat determined by: • type of gas • number of cubit feet per hour of gas burned • for more heat - larger orifice in torch tip along with more pressure to feed gas through

  14. Safety

  15. Clothing and Eye protection

  16. Acetylene more dangerous than oxygen? • Makes things burn faster • oxygen must be consumed even under water • no O2 in air tools • no blowing off clothes • 20 lb propane grill tanks in car trunks

  17. Oxygen cylinders

  18. Cylinder safety • read label - different colors for same gas • orange - O2 or helium • red - O2 or hydrogen • blue - O2 or nitrous oxide • green

  19. Handling cylinders • caps on when moving • secure to truck or wall • keep upright

  20. Preparing cylinders and hoses • cylinder valve should be opened slightly to blow out dirt • high pressure valves - open all the way • gas valves - open 1/4 to 1/2 turn

  21. Preparing (Cont.) • hose and cylinder valve threads • fuel gas - left hand • oxygen - right hand • after assembly - test for leaks with soap suds • flash arrestor - stops reverse flow of gases and fire • put at tank for torch?

  22. Torch position, angle, motion

  23. Joints

  24. Plug Weld

  25. Use additional filler rod where joint design and strength require

  26. Positioning • Tacking • Shrinkage • Wedge

  27. Turning on and shutting down the oxy acetylene welding outfit

  28. Cutting

  29. oxyfuel gas flame is used to heat the metal and an oxygen jet is used to perform the cutting

  30. steel is combustible if sufficiently heated

  31. burning metal helps to maintain the high temp

  32. Process • same flame as for welding • preheat flame about 1/16 to 1/8” from surface • heat a spot on steel to cherry red (1300 to 1400 deg F) • oxygen jet is turned on • torch moved • preheat flame kept operating during cutting action

  33. Cutting torch outfit differs from welding only in • torch - separate passage for oxygen jet - center orifice • possibly a higher pressure O2 regulator • oxygen cutting lever to control cutting operation

  34. indicator of a good cut • no slag at bottom of cut • no bell-mouthed kurf

  35. Alignment of torch tip orifices with the kerf • one orifice should proceed and one should follow the cut

  36. Usually no torch motion used - sometimes oscillating

  37. torch movement should be away from operator so kerf can be seen

  38. Speed

  39. safety • leggings • safety boots with high tops • no cuffs

  40. Cutting thin steel • under 1/2” • smallest cutting tip available • point tip in direction the torch is traveling (15-20 deg) from metal

  41. Metal over 1/2” thick • Tip perpendicular

  42. Starting a cut - thicker material • cuts normally started at the edge of the work

  43. Pipe • small diameter - hold tip almost tangent to pipe • large diameter (over 4”) tip perpendicular

  44. Beveled edge on plate

  45. Beveled end on pipe

  46. Turning on and shutting down the oxy acetylene welding outfit

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