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INTRODUCTION TO ARC WELDING (SMAW)

INTRODUCTION TO ARC WELDING (SMAW). Terms & Definitions. Welding - Joining of two or more pieces of metal together by the fusion process NOTE: In arc welding, heat is produced by the electric arc created. SMAW - Shielded Metal Arc Welding

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INTRODUCTION TO ARC WELDING (SMAW)

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  1. INTRODUCTION TO ARC WELDING(SMAW)

  2. Terms & Definitions • Welding - Joining of two or more pieces of metal together by the fusion process • NOTE: In arc welding, heat is produced by the electric arc created. • SMAW - Shielded Metal Arc Welding • Electrode - Metal rod which conducts a current from the electrode holder to the base metal • Base Metal - Metal to be welded

  3. Continued • Bead Weld - Made by one pass of the electrode • Bevel – Type of edge preparation containing an angle • Butt Joint - Weld located between the two edges of metal. • Crater - Depression at the end of a weld

  4. Safety precautions in SMAW welding • Never look at the arc with the naked eye. • Use a welding hood that is in good condition and has a #12 shade. • Wear suitable clothing to protect all parts of the body. (PPE) personal protective equipment • Long sleeved shirt • Leather gloves • Collar buttoned

  5. Continued • Cuffs turned down • High topped shoes or boots • Do not strike an arc or weld until you are sure those in the vicinity have protective equipment or will look in the other direction. (Note) Yell “cover” before striking an arc.

  6. Continued • Do not weld around combustible or flammable materials. • Do not pick up hot metal with the hands. (NOTE) Use a pair of pliers • Do not weld in confined places without ventilation

  7. Continued • Always turn off main switch or disconnect plug when checking over a welder. • Do not leave electrode holder on the welding table or in contact with grounded metal. • Do not use worn or frayed cables.

  8. Continued • Stand on dry footing when welding. • Keep area around welder clean. • Keep tools and metals in proper location.

  9. Types of Arc Welders • A.C. – (Alternating current) Welder current alternates direction 120 times per second. • D.C. – (Direct current) Welder current flows in the same direction. • TIG – (Tungsten Inert Gas) Welder may use either A.C. or D.C. with a non-consumable tungsten electrode and an inert shielding gas.

  10. Continued • MIG – (Metal Inert Gas) May use A.C. or D.C. with a base wire filler material that is fed automatically into weld; also has an inert shielding gas.

  11. Common SMAW Tools • Welder • Electrode Holder • Ground clamp • Shield or helmet • Gloves • Chipping hammer • Safety goggles or glasses • Wire brush • Electrodes

  12. Types of Electrodes • Mild Steel • High Carbon Steel • Hard Surfacing • Alloys – special purpose

  13. Electrode Characteristics

  14. Electrode Characteristics continued

  15. Common Sizes of Electrodes • 1/8” • 5/32” • Sizes of electrodes range from 1/16” to 3/8”. • Electrode size is determined by the diameter of the wire core.

  16. AWS Classification E70XX-H4R • Electrode • Tensile in Ksi • Welding Position: • 1 = All Position, 2 = Flat & Horizontal • Type of Current and Coating • *Hydrogen: • H4 = Less than 4ml/100g weld metal, H8 = Less than 8ml/100g Weld Metal • or H16 = Less than 16ml/100g weld metal • *Meets Requirements of Absorbed Moisture Test • *Optional Designators

  17. Electrode Coating Functions • To Provide Deoxidizers & Scavengers • To Produce Shielding Gases • To Produce a Slag Covering • To Provide Mechanical and Physical Properties • To Increase Deposit Rates

  18. Effects of Raising & Lowering Current • Raising current • Produces more heat • Lowering current • Produces less heat (Note: On thicker metals more heat is necessary in order to get penetration of the weld.)

  19. Methods of Establishing an Arc • Scratching • Similar to striking a match • Tapping • Straight down and up

  20. Characteristics of Proper Arc Length • End of electrode is the same distance from the base metal as the diameter of electrode. • 1/8” electrode = arc length 1/8” • Correct arc length makes a steady hum of the welder. • Correct arc length makes a “frying” sound at the arc • Like bacon frying in a pan

  21. Parts of the welding process • Electrode • Wire core • Coating (flux) • Arc • Gaseous shield • Weld • Slag

  22. Parts Continued • Heat lines • Base metal • Penetration • Crater • 15 – 30 degree angle • Direction of travel

  23. Principles of the SMAW Process

  24. Kinds of Welds • Fillet • Groove • Bead

  25. Fillet Weld

  26. Groove Welds

  27. Continued

  28. Types of Weld Joints • Butt Joint • Lap Joint • Tee Joint • Corner Joint • Edge Joint

  29. Square Butt Joint

  30. A- plain tee B- single beveled C- double beveled D- single J E- double J Tee Joints

  31. A- single lap joint, one weld. B- single lap joint, two welds. C- offset lap joint. Lap Joints

  32. Corner Joints

  33. Edge Joints

  34. Welding Positions • Flat • 1F & 1G • Horizontal • 2F & 2G • Vertical • 3F & 3G • Overhead • 4F & 4G

  35. Weld Positions

  36. Reason for Poor Welds • Machine adjustment too hot or too cold • Electrode size too large or too small • Improper movement of electrode • Improper angle of holding electrode • Improper base metal preparation • Arc length too long or too short

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