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Arc Welding: Introduction and Fundamentals

Arc Welding: Introduction and Fundamentals. IMS Curriculum 8609-B. Objectives. Students will know the following after the presentation: Students will be familiar with vocabulary Students will know pieces of ARC welders Students will know accessories of ARC welding. Arc Welding Electrode

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Arc Welding: Introduction and Fundamentals

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  1. Arc Welding:Introduction and Fundamentals IMS Curriculum 8609-B

  2. Objectives • Students will know the following after the presentation: • Students will be familiar with vocabulary • Students will know pieces of ARC welders • Students will know accessories of ARC welding

  3. Arc Welding Electrode Welders Rectifier Alternating Current Direct Current Duty Cycle Flux Polarity Slag Welder Base Metal Vocabulary

  4. History • Dates back to the 19th century • Arc Welding is the process of fusing two or more pieces of metal together through the use of an electric arc.

  5. The Process of Welding The process uses an arc struck between and electrode and metal. The arc heats the metal to a melting point. The electrode is removed to break the arc, allowing metal to freeze or solidify. This flame (arc) of intense heat is generated as the electric current passes through a highly resistant air gap.

  6. Challenge to Strengthen Welds • Molten metal would get O2 and N2 in it and it would destroy the strength of the weld. • Some form of cover was needed to “shield” the molten pool of the metal.

  7. Shielded Metal Arc Welding

  8. Shielded Metal Arc Welding Process

  9. SMAW Process Again

  10. SMAW

  11. SMAW • http://www.me.gatech.edu/jonathan.colton/me4210/arcwelding.mpeg

  12. Types of ARC Welding Machines • AC ( alternating current ) • DC ( direct current ) • AC/DC ( alternating and direct current ) • TIG ( tungsten inert gas ) • MIG ( metallic inert gas )

  13. AC/DC

  14. MIG

  15. MIG Again

  16. TIG

  17. TIG Again

  18. Duty Cycle • All machines have a duty cycle • Duty cycle is the percentage of a ten-minute period that a welding machine can be safely operated at a given output. • A 225-ampere AC welding machine typically will have a duty cycle of 20%. • As amperage increases, duty cycle decreases and vice versa.

  19. Electrodes • Three types: • 1. Coated • Most common used • 2. Bare • Smoke free • Weld is visible • 3. Carbon • Melts slowly

  20. Electrode • An Electrode is a core wire that can be left bare or covered with a flux. • Flux is the fusible material that covers the electrode that is meant to produce a shielding gas during the welding process.

  21. Flux • Prevents the formation of oxides, nitrides, and other undesirable inclusions during welding. • As a person welds the flux floats out he impurities in the air and then settles on top of the weld as slag.

  22. Slag • Is beneficial in most welding processes because it holds heat and keeps the weld from cooling too quickly,

  23. Selecting Electrodes • Depends on three factors: • Metal Type • Metal thickness • Welding Postion

  24. Electrode Classification • The American Welding Society (AWS) provides a standardized way for classifying rods. • First set-up in 1942. • Uses a number system with 4 digits that represents four factors.

  25. The Digits • 1st and 2nd digit represents the minimum tensile strength of the weld metal. • 3rd digit refers the welding position the rod should be used in. • 1 = All positions • 2 = Flat and Horizontal • 3 = Flat only • 4th digit indicates the weld current that is to be used and the type of flux covering.

  26. E6010 • E = electrode • 60 = 60,000 psi tensile strength • 1 = welds in all positions • 0 = indicates DC and electrode positive current

  27. Size of the Electrode • The diameter of the “bare” end of the rod determines the size of the electrode. • Ex. 1/16, 3/32, 1/8, 5/32, 3/16, 7/32, ¼, 5/16, 3/8 • As a general rule, the diameter of the electrode should never exceed the thickness of the metal being welded.

  28. Arc Welding Fundamentals • 1. Body position • 2. Correct electrode size • 3. Correct electrode type • 4. Correct amperage setting • 5. Correct arc length • 6. Correct travel speed • 7. Correct electrode angle

  29. Striking an Arc • People who have never welded struggle most with this.

  30. Arc length • Maintain a constant arc length and move in a circular pattern.

  31. Arc Angle

  32. Factors Shown

  33. The End • Now time for some hands on experience!

  34. Picture Sources • http://www.twi.co.uk/j32k/twiimages/spgvmar98f1.jpg • http://www.tollgas.com/products/images/arc_access.jpg • http://images.encarta.msn.com/xrefmedia/sharemed/targets/images/pho/t048/T048805A.jpg

  35. Picture Sources • http://images.google.com/imgres?imgurl=http://class.et.byu.edu/mfg130/processes/descriptions/thermaljoining/smawwelding1.jpg&imgrefurl=http://class.et.byu.edu/mfg130/processes/descriptions/thermaljoining/smawwelding.htm&h=278&w=459&sz=37&tbnid=RuzWWCIuL3oJ:&tbnh=75&tbnw=123&start=4&prev=/images%3Fq%3Dshielded%2Bmetal%2Barc%26hl%3Den%26lr%3D

  36. Pictures • http://www.murexwelding.co.uk/mrxcont/images/sixofbest.jpg

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