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Arc Welding

Arc Welding

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Arc Welding

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  1. Arc Welding Basic Safety

  2. Warnings • Welding can be safe when proper measures are taken to protect yourself and others from potential hazards. • Understand and follow all warning labels found on equipment and with all consumables.

  3. Potential Hazards • Protect yourself and others from potential hazards including: • Fumes and Gases • Electric Shock • Arc Rays • Fire and Explosion Hazards • Noise • Hot objects • Welding Sparks

  4. Fumes and Gases Welding fumes can be harmful to the welder causing implications such as: Irritation of the respiratory tract Metal fume fever Slightly increase the risk of lung cancer Use enough ventilation, exhaust at the arc, or both, to keep fumes and gases from your breathing zone and the general area Use a respirator if needed or required by the process. The ventilation system must be on while welding at all times.

  5. Electrical Shock Electric shock can kill Do not touch live electrical parts Primary Voltage –208 - 240, 416 - 480 volt input power Secondary Voltage – 6 to 100 volts for welding Insulate yourself from work and ground Follow all warnings on welding equipment Wear insulated clothing Always shut off machinery when done and roll the cords up neatly Do not make repairs yourself, alert your instructor immediately!

  6. U.V. Rays Welding will produce ultraviolet rays that are harmful to the human eye and skin. Proper protection is needed to avoid bodily harm. Arc rays are ten times brighter than the sun and can injure eyes and burn skin Precaution must be taken to protect your eyes and skin from UV radiation. The welding arc is brighter than the sun Wear correct eye and body protection 10 shade helmet Safety Glasses under the helmet Gloves Arm and Body Protection Jacket Shoulder Covers Coveralls

  7. Fire Hazards and Material Safety • Welding sparks can cause fires and explosions • Sparks and spatter from the welding arc can spray up to 35 feet from your work • Flammable materials should be removed from the welding area or shielded from sparks and spatter • Always clean painted materials • All welding booths should be cleaned thoroughly • Have a fire extinguisher ready • Inspect area for fires 30 minutes after welding • Watch for sharp metal edges • Cool all welded metal in the water tank.

  8. Ear Protection • Loud noises can damage your hearing • Keep loud noises at a safe level by using proper hearing protection such as: • Ear plugs • Ear muffs

  9. ProtectiveClothing Welders must wear protective clothing for Protection from sparks, spatter and UV radiation Insulation from electric shock Protective clothing includes … Fire-proof clothing without rolled sleeves, cuffs or frays Work boots Welding gloves, shirts jackets, bibs, and fire-proof pants Welding cap, helmet and safety glasses Ear protection – ear plugs and muffs Most importantly safety glasses are to be worn at all times in the shop

  10. Improper Protective Clothing • List and describe what is wrong in this picture

  11. Basic Electricity and Welding Arc Welding Basic Safety

  12. Arc Welding Circuit and Concept • The electricity flows from the power source, through the electrode and across the arc, through the base material to the work lead and back to the power source. Identify all the above parts for the arc welder, describe the function of each part, and determine each of the parts safety aspects.

  13. Electrical Concepts DC - DC + Voltage – The electrical potential or pressure that causes current to flow Measured in Volts Current – The movement of charged particles in a specific direction Measured in Amps Polarity DC- (Direct Current Electrode Negative) DC+ (Direct Current Electrode Positive) AC (Alternating Current) ALWAYS REMEMBER THAT VOLTAGE WILL HURT BUT AMPERAGE CAN BE FATAL AC

  14. Electrical Lead Condition Before starting an operation, always check the condition of all electrical leads. Cracked and worn leads can lead to fatal shock. All electrode holders or “stingers” should be in tack and not cracked or missing pieces. All plugs and outlets should be in tack. Never set-up a welder with a broken plug or into a broken outlet. Never operate a welder with splices showing in the leads.

  15. Shielded Metal Arc Welding SMAW

  16. SMAW Process

  17. SMAW Key Parts • Electrode Holder: Also known as the “stinger” Handle-like tool that holds the electrode while welding. • Never hold this part with your bare hand while welding. • Ground Connection: Also known as the “workpiece connection clamp” that connects to the work to complete the electrical circuit • Power Source: Where the welder plugs into • Amperage Scale: Determines the amount of “heat” or power the welder will operate at. • Polarity Switch: Setting that determines how the electrons will flow during the welding process. • On / Off Switch: Turns the welder on / off. Make sure the switch function properly at all times.

  18. SMAW Principles • The American Welding Society defines SMAW as Shielded Metal Arc Welding • SMAW: • Is commonly known as ‘Stick’ welding or manual arc welding • Is the most widely used arc welding process in the world • Can be used to weld most common metals and alloys

  19. SMAW Welding Circuit • Current flows through the electrode cable, to the electrode holder, through the electrode, and across the arc • On the work side of the arc, the current flows through the base material to the work clamp and back to the welding machine

  20. SMAW Process Identify all the above segments for the SMAW process, describe the function of each segment, and determine if any safety aspects exist.

  21. The ElectrodeWhat is it? • Is a consumable - it gets melted during the welding process • Is composed of two parts • Core Rod (Metal Filler) • Carries welding current • Becomes part of the weld • Flux Coating • Produces a shielding gas • Can provide additional filler • Forms a slag

  22. Electrode Classification Electrodes are classified by a numbering system E6013 E = Electrode 60 or first two numbers = Tensile strength (thousands of pounds 1 or third number = Welding position 3 or fourth number = Welding current type and depth of weld penetration. Pictured above are E-7018 electrodes. Identify what the tensile strength is for this electrode.

  23. Electrode ClassificationThird Digit Third Digit E_ _ 1 _ = Usable in all directions E_ _ 2 _ = Usable in flat and horizontal positions only E_ _ 4 _ = Usable for vertical down only Pictured above are E-6011 electrodes. Identify what each digit resembles up to the third digit.

  24. Electrode ClassificationFourth Digit Fourth Digit E_ _ _ 0 = DC reverse polarity only E_ _ _ 1 = AC and DC reverse polarity E_ _ _ 2 = AC and DC straight polarity E_ _ _ 3 = AC and DC E_ _ _ 4 = AC and DC E_ _ _ 5 = DC reverse polarity E_ _ _ 6 = AC and DC reverse polarity E_ _ _ 8 = AC and DC reverse polarity Pictured above are E-6013 electrodes. Identify what each digit resembles.

  25. The Arc • An arc occurs when the electrode comes in contact with the work-piece and completes the circuit … like turning on a light! • The electric arc is established in the space between the end of the electrode and the work • The arc reaches temperatures of 10,000°F which melts the electrode and base material • Don’t look at the arc without proper eye protection. • Wear proper body protection. The UV rays will cause bodily harm. Arc burning off the electrode

  26. Weld Puddle As the core rod, flux coating, and work pieces heat up and melt, they form a pool of molten material called a weld puddle The weld puddle is what a welder watches and manipulates while welding Don’t touch the hot puddle!!! The metal is hot!!!

  27. Shielding Gas 4 3 2 Shielding Gas A shielding gas is formed when the flux coating melts. This protects the weld puddle from the atmosphere preventing contamination during the molten state Don’t touch the metal!!! The metal is hot!!! Shielding gas can cause bodily harm. Be sure proper ventilation is being used. The shielding gas protects the molten puddle from the atmosphere while stabilizing the arc

  28. Solidified Weldment As the molten weld puddle solidifies, it forms a joint or connection between two pieces of base material When done properly on steel, it results in a weld stronger than the surrounding base metal Don’t touch the metal!!! The metal is hot!!!

  29. Slag Slag is a combination of the flux coating and impurities from the base metal that float to the surface of the weld. Slag quickly solidifies to form a solid coating which slows the cooling rate of the weld The slag can be chipped away and cleaned with a wire brush when hard Don’t touch the metal!!! The metal is hot!!! Slag can be dangerous when being removed. Wear the proper safety protection. This welder chips the slag off of a weld during the repair of railroad tracks

  30. Gas Metal Arc Welding GMAW “Mig”

  31. GMAW Defined • An arc welding process that uses an arc between a continuous filler metal electrode and the weld pool. • The process uses a shielding gas that protects the weld from contamination. • Without using a shielding gas the weld becomes pitted and contains no strength value.

  32. Pitted GMAW Weldment Weld is Pitted from improper flow of shielding gas

  33. GMAW Safety Points • Fumes and Gases can be dangerous • Keep your head out of the fumes • Use enough ventilation, exhaust at the arc, or both, to keep fumes and gases from your breathing zone and the general area • Local exhaust and mechanical ventilation can be used without reducing weld quality • Electric Shock can kill – to receive a shock your body must touch the electrode and work or ground at the same time • Do not touch the electrode or metal parts of the electrode holder with skin or wet clothing • Keep dry insulation between your body and the metal being welded or ground • The coil of wire is ‘electrically hot’ when the trigger is pulled

  34. GMAW Safety Points (Continued) • REMEMBER – Gas Cylinders require SPECIAL safety precautions • Cylinders must be secured in an upright position • Cylinders should be located in an area away from arc welding, cutting, heat, sparks, and flame • Shut off the gas cylinder when finished. • NCWHS uses a 75% carbon dioxide and a 25% argon mix for shielding gas. • Don’t bleed or purge the lines after an operation. This gas will not combust / burn.

  35. GMAW Process During the GMAW process, a solid metal wire is fed through a welding gun and becomes the filler material Instead of a flux, a shielding gas is used to protect the molten puddle from the atmosphere which results in a weld without slag

  36. GMAW Process (Continued) • Three things happen when the GMAW gun trigger is pulled: • The wire electrode begins to feed • The circuit becomes electrically ‘hot’ • Shielding gas flows through the gun and out the nozzle • Current flows from the power source through the gun cable, gun, contact tip to the wire and across the arc. • On the other side of the arc, current flows through the base metal to the work cable and back to the power source • Shielding gas flows through the gun and out the nozzle

  37. GMAW Parts

  38. GMAW Key Parts • Gun Housing: Holds or houses the welding wire liner, gas line, and trigger in one piece • Conductor Tube: The angled part of the gun that the wire and shielding gas flow through during the weld operation • Gas Diffuser: Disperses the shielding gas onto the weldment • Contact Tip: The part where the welding wire runs through. Different sized tips accommodate different sized wire. • Nozzle: The cover for the end of the gun that keeps spatter from sticking to the contact tip and gas diffuser and plugging the gun up.

  39. GMAW Process Welding Tip: Generally, drag on thin sheet metal and push on thicker materials Shielding Gas Solidified Weld Metal Arc Electrode Puddle

  40. GMAW Electrode • A GMAW electrode is: • A metal wire • Fed through the gun by the wire feeder • Measured by its diameter GMAW electrodes are commonly packaged on spools, reels and coils ranging from 1lb to 1000lbs

  41. GMAW Arc • An electric arc occurs in the gas filled space between the electrode wire and the work piece Electric arcs can generate temperatures up to 10,000°F

  42. GMAW Weld Puddle As the wire electrode and work piece heat up and melt, they form a pool of molten material called a weld puddle This is what the welder watches and manipulates while welding

  43. Shielding Gas GMAW welding requires a shielding gas to protect the weld puddle Shielding gas is usually CO2, argon, or a mixture of both

  44. Final Weld The welder “lays a bead” of molten metal that quickly solidifies into a weld The resulting weld is slag free

  45. Weld Examples • GOAL - Make Good Welds • Eliminate Porosity Eliminate Ropey Convex bead Eliminate Excessive Spatter


  47. Terms and Definitions • Backfire: A short pop of the torch flame followed by extinguishing of the flame or continued burning of the gases. • Flashback: when the torch flame moves into or beyond the mixing chamber. • Preheating: Heating prior to a welding or cutting operation

  48. Equipment Required • Oxygen cylinder • Acetylene cylinder • Pressure regulators • Two hoses encased together • Welding torch with tips • Welding goggles and safety glasses • Striker • Check valves to prevent flashback

  49. Acetylene Regulator