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

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

11. Oxidizing - too much oxygen - burns the metal

12. 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.

13. Temps required to melt various metals

14. 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

15. Safety

16. Clothing and Eye protection

17. 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

18. Oxygen cylinders

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

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

21. 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

22. 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?

23. Torch position, angle, motion

24. Joints

25. Plug Weld

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

27. Positioning
Tacking
Shrinkage
Wedge

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

29. Cutting

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

31. steel is combustible if sufficiently heated

32. burning metal helps to maintain the high temp

33. 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

34. 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

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

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

37. Usually no torch motion used - sometimes oscillating

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

39. Speed

40. safety
leggings
safety boots with high tops
no cuffs

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

42. Metal over 1/2” thick
Tip perpendicular

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

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

45. Beveled edge on plate

46. Beveled end on pipe

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