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1. OHMS LAW!

   • V = VOLTS
   • I = AMPS
   • R = RESISTANCE
   • VOLTS = AMPS x RESISTANCE
     • AMPS = VOLTS / RESISTANCE
       • RESISTANCE = VOLTS / AMPS
   • WATT = VOLTAGE x AMPS
   • TYPES OF CURRENT...
     • AC = ALTERNATING CURRENT, THE DIRECTION OF FLOW OF ELECTRONS IN AN AC CIRCUIT IS AUTOMATICALLY RESERVED AT REQUIRED INTERVALS.
       • DC = DIRECT CURRENT, THE FLOW OF ELECTRONS IN A DC CIRCUIT ARE IN ONE DIRECTION ONLY.
         • COMMON SYMBOL OF A DIODE.
   • POLARITY!
     • 66% OF THE HEAT GENERATED IN A DC CIRCUIT IS AT THE POSITIVE POLE
       • ELECTRON FLOW IS FROM NEGATIVE TO POSITIVE POLES
         • 33% ELECTRODE 66% BASE PLATE = NEGATIVE
           • 66% ELECTRODE 33% BASE PLATE = POSITIVE
             • 50% ELECTRODE 50% BASE PLATE = AC CURRENT

2. PURGING A WELD

   • BACK PURGE IS REQUIRED WHEN WELDING STAINLESS STELLS AND OTHER ALLOYS
     • ITS A SUPPLY OF A SHIELDING GAS WITH A FLOW RATE OF USUALLY 4LPM TO THE INSIDE OF THE ROOT TO PROTECT IT FROM ATMOSPHERE WHEN WELDING
   • WHY BACK PURGE?
     • KEEPS INSIDE OF THE PIPE CLEAN
       • STOPS OXIDISATION
         • WHEN OXIDISATION OCCURS IT REDUCES THE CORROSION RESISTANCE OF THE ROOT
           • STOPS BAD DEFECTS IN THE WELD

3. PPE

   • OVERALLS
   • WELDING SCREEN
   • TIG WELDING GAUNTLETS
   • SAFETY BOOTS

4. TUNGSTEN ARC GAS SHIELD WELDING

   • 5 ADVANTAGES!
     • CLEANER , I.E NO SPATTER OR SPARKS
       • USED ON VARIOUS STEELS ( ALUMINIUM, COPPER)
         • DEEPER PENETRATION
           • EASIER TO CONTROL
     • WELDER CAN DECIDE WHEN TO DEPOSIT ADDITIONAL FILLER WIRE

5. TYPES OF TUNGSTENS

   • PURE TUNGSTEN
     • MAY BE USE FOR ANY APPLICATION BUT OTHER TYPES LISTED GIVE BETTER REULTS
   • THORIATED TUNGSTEN
     • RECOMMENDED FOR DC WELDING
       • THE ADDITIONAL 1-2% OF THORIUM OXIDE MAINTAINS A SHARPPOINT ON THE ELECTRODE
         • INCREASES ITS CURRENT CARRYING CAPACITY
   • ZINCONIATED TUNGSTEN
     • RECOMMENDED FOR AC WELDING
       • THE ADDITION OF A SMALL AMOUNT OF ZINCONIUM OXIDE IMPROVES ARC STABILITY
         • REDUCES THE RISK OF TUNGSTEN INCLUSION IN THE WELD
   • CERIATED TUNGSTEN
     • SAFER TO USE
       • DO NOT CONTAIN RADIOACTIVE MATERIAL BUT STILL GIVE EXCELLENT RESUTLS
   • UP TO 3.2MM DIA... l = 3xDIA
     • ABOVE 3.2MM DIA... L=2xDIA
       • THE TIP OF THE ELECTRODE SHOULD BE 45 DEGREES

6. SHIELDING GASES

   • ARGON
     • HELIUM
       • ARGON + HELIUM MIXTURE
         • ARGON + HYDROGEN MIXTURE
           • ARGON + NITROGEN MIXTURE
         • DESIRABLE ON THICK MATERIAL WHERE DEEPER PENETRATION IS REQUIRED
           • HIGHER TRAVEL SPEEDS ARE NEED
       • TENDS TO RISE RAPIDLY FROM THE ARC AREA
         • FLOW RATE OF THIS GAS IS USUALLY 2-3 TIMES THAT OF ARGON
           • HIGH THERMAL CONDUCTIVITY
     • TENDS TO FORM A BLANKET OVER THE WELD
       • HAS A LOW THERMAL CONDUCTIVITY
         • MORE COMPACT HIGHER DENSITY ARC

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