Selecting and Using Arc Welding Equipment

1
Selecting and Using Arc Welding Equipment

• Ag Mechanics

2
Arc Welding Introduction

• Heat for arc welding electricity
• OR electric motors or gas engines driving special
  generators

3
Arc Welding Introduction

• Arc welder machine that produces current for
  welding
• Arc discharge of electricity through an air
  space
• Welder person who welds

4
Process and Principles

• SMAW shielded metal arc welding
• Arc welding or stick welding
• Electrodes flux-coated metal welding rods
  called
• Shielded gaseous cloud formed around weld by
  burning flux
• Help electrode burn evenly as it mixes with base
  metal
• Flux removes impurities from base metal and
  prevents oxidation
• Slag flux and impurities that form a layer on
  top of weld

5
Advantages of Arc Welding

• Electricity is relatively inexpensive as a source
  of heat for welding
• Electric welders are relatively inexpensive
• Work on ordinary 230-volt or 120-volt household
  wiring
• Engine-driven portable welders

6
Advantages continued

• Fast and reliable
• Can master quickly
• Can be used for heating, brazing, and
  hardsurfacing as well as welding
• Hardsurfacing buildup of wear-resistant metals
  to a parts surface

7
Temperature

• Arc 9000oF
• Exact temperature varies with
• Length of arc
• Size of electrode
• Amperage setting
• Typically range from 20 to 225 amps

8
Duty Cycle

• Duty cycle percentage of time a welder can
  operate without overheating
• Number of minutes out of 60
• 20 duty cycle should weld only 12 minutes out
  of every hour
• Welders available with duty cycles from 20 to
  100
• Based on midrange setting
• Shorter if used at higher settings
• Longer if used at lower settings

9
Electricity continued

• Welders put out high amperage and relatively low
  voltage
• Low voltage allows safety while putting out so
  much energy
• Requires 60 volts to push current through human
  body
• Low to moderate settings put out less than 60
  volts
• STILL NEED TO BE CAUTIOUS

10
Alternating Current

• Transformers convert high voltage and low
  amperage to low voltage and high amperage
• Welders that are transformers receive current
  directly from utility power lines
• Called alternating current welders
• Alternating current (AC) current reverses
  direction 60 times per second
• 60-cycle current

11
Direct Current

• Direct current (DC) current flows in one
  direction only in accordance with how the welder
  is set
• Straight or reverse polarity

12
Polarity

• Polarity direction of flow of electricity in
  welding
• Certain electrodes and jobs work better with
  current flowing a certain way
• Straight polarity work positive pole and
  electrode negative pole
• Reverse polarity work negative pole and
  electrode positive pole

13
Welding Equipment

• Cables
• Electrode holders
• Ground clamps
• Welding table and booth
• Equipment for cleaning welds

14
Cables

• Cables welders need large electrical cables
• Carry current from welder to electrode, across
  arc, and back to welder
• CAREFUL Protect cables from forceful impact and
  contact with sharp objects
• Coverings insulate conductors and prevent
  dangerous shocks and electrical shorts

15
Electrode Holders

• Electrode holder spring loaded device with
  insulated handles used to grip a welding
  electrode
• Cable to holder has copper or aluminum core
• Insulated sleeve slides over connection to
  protect operator from electric shock
• All parts insulated except jaws

16
Ground Clamp

• Ground clamp Spring-loaded clamp attached to an
  electrical cable
• Not insulated
• Not a shock hazard
• Carries current between welding table or project
  to welder

17
Welding Table and Booth

• Operator can stand or sit comfortably
• Curtains protect other workers from blinding
  light flashes
• Exhaust equipment
• Fire-resistant and free of flammable materials

18
Equipment for Cleaning Welds

• Tongs or pliers useful for handling hot metal
• Hand wire brushes and chipping hammers used for
  removing slag