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Welding

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Welding

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  1. Welding LEMMONS

  2. Arc Welding – fusing two or more pieces of metal together using heat from an electric arc Advantages of Arc Welding • Quick repairs • Cheap to operate • Arc welder has other uses(cutting, gouging, beveling)

  3. I. ARC WELDER A. AC Welder SMAW(Shielded Metal Arc Welding) Plugs into any 240 volt outlet Uses AC current Runs up to 225 amps Types of Welding Machines

  4. Advantages Low cost Easy to maintain Flow 50% heat at electrode 50 % heat at work

  5. B. DC Reverse Current (DC+) • Deeper penetration • Higher possible amps

  6. 2/3rd heat at work 1/3rd heat at electrode C. DC Straight Current (DC-) Shallow penetration Lower amps Flatter bead 2/3rd heat at electrode 1/3rd heat at work

  7. AC/DC Welders • Combines all three processes into one machine Gasoline Driven Machines

  8. AC/DC welding machine powered by a gas or diesel engine • Portable • AC generator power to run other tools II. MIG(Metallic Inert Gas)

  9. Other names • hardwire, short arc, GMAW(Gas Metal Arc Welding), wire machine * Advantages • Can be used as an automatic welder • Can use flux core wire to eliminate gas • No slag • Continuous weld

  10. III. TIG(Tungsten Inert Gas)

  11. Other Names • GTAW(Gas Tungsten Arc Welding) Heliarc * Advantages • Welds are free of slag • Produces the strongest weld • No splatter • Almost all metals can be welded with the TIG process • Produce non corrosive welds

  12. Selecting a Welder * Factors to consider: • Cost • Use • Select a reliable manufacturer (Lincoln, Miller, ESAB) • Guarantee or warranty (90 Days, 1 yr, etc.) • Service

  13. * Other equipment needed • Welding hood • Assure proper electrical hookup • Pliers • Leather gloves • Chipping hammer • Wire brush • Grinder • Metal Table

  14. Electrodes A. Definition wire, either bare or with flux, used in the welding process B. Types of Electrodes 1. Coated – electrode metal should match base metal. Covered with powder flux.

  15. 2. Bare- requires excessive heat and is voltage sensitive. It is smoke free. 3. Carbon – special purpose rod for high carbon steel C. Electrode Classification 1. Universal color code and number system

  16. Example: E7018 E - electrode 70 - tensile strength in thousands pounds • } welding position 1 = all position 2 = flat and horizontal 3 = flat only

  17. Example: E7018 8 }current, penetration, flux, etc. numbers range 0 - 8 D. Electrode Size Size is determined by the diameter of the bare end of the electrode

  18. Examples: 3/32” electrode • 36 rods per pound • Run at 30-80 amps 1/8” electrode • 17 rods per pound • run at 70-120 amps 5/32” electrode • 11 rods per pound • Run at 120-170 amps

  19. E. Common Electrodes 6010 – mild steel , DC+ deep penetration 6011 – same as 6010, AC/DC 6013 – AC/DC, quiet, general purpose 7018 – AC/DC+, high carbon steel, iron powder flux

  20. Selecting an Electrode • ID of base metal • Available current • Metal thickness • Joint design • Welding position • Environmental conditions • Storage • Building Code

  21. 8 Essentials to a Proper Weld • Proper electrode • Metal preparation • Proper amperage • Proper electrode angle • Proper arc length • Correct travel speed • Proper curing of finished weld • Good connected ground

  22. I. Preparing Metal for Welding a. Metal should be cleaned b. Dirty metal is harder to weld and requires more heat c. Clean metal by brushing, filing, sanding, grinding, scraping, sandblasting, chemically

  23. d. Metal more than ¼” thick metal should be beveled at 30 degrees and spaced 1/16” apart e. Bevels – one-sided, two-sided, lap, corner

  24. II. Amperage a. Too high • Flat bead • Splatter on bead edge • Undercut edges • Extremely loud b. Too low • high, narrow bead • Weak penetration • Hard to keep arc going c. Correct • Even, steady sound • Adequate penetration • Uniform in shape

  25. III. Electrode Angle • Flat welds – electrode angle should be 15 degrees to the direction of travel and 90 degrees to each side • Vertical welds – electrode angle should be on the centerline and angled 30 degrees down

  26. IV. Arc Length • The distance between the electrode and work • Arc length should equal the diameter of the bare end of the electrode

  27. V. Travel Speed • How fast or slow the electrode moves across the work • The bead should remain the same width and height at all times • Watch the molten puddle to gauge travel speed

  28. Methods of Starting an Arc • Scratching - simply drag the electrode across the work, lifting it when arc starts • Tapping – tap the electrode to the work, picking it up quickly while maintaining the arc

  29. Causes of difficulty starting an arc • Flux chipped off end of electrode • Flux covering end of electrode • Improper amperage(too low) • Inadequate ground

  30. Electrode movement or patterns • Slight arch • Straight • Circular • Zig Zag • Horseshoe