Arc Welding Shielded Metal Arc Welding (SMAW). Electricity

1
Arc Welding

• Shielded Metal Arc Welding (SMAW). Electricity,
  as it jumps a gaseous gap between two conductors.
  Produces an arc as intense as 9000?.

2
Types of Welders

• Motor Generator
• Gasoline engine drives a generator.
• Electric motor drives a generator.
• Rectifier
• D.C. (Direct Current) Electricity is converted
  from A.C (Alternating Current) through
  transformers and rectifiers.
• A.C./D.C dual purpose.
• A.C. Alternating current is transformed from
  high voltage/ low amps to low voltage/high amps.

3
Electrodes

• Lengths usually 14
• Diameters 3/32, 1/8, and 5/32 are most
  common
• Classification Brand names differ but the A.W.S
  number system is the standard.

4
Electrode classification breakdown

• E Electrode
• 70 Tensile strength of deposited weld metal
  times 1000 p.s.i.
• 1 Rod position (1all, 2horizontal or flat,
  3flat only)
• 8 Dealer characteristics
• (Dealer characteristics are things like polarity,
  application, flux composition.)

5
Five functions of flux or slag

• Cleans the metal of oxides
• Stabilizes the arc
• Keeps oxygen away
• Forms the weld
• Lets the weld cool slowly

6
Polarities
7
Direct current Electrode Negative- (D.C.E.N)

• D.C. electricity flows in one direction only
  (neg. to pos.). 1/3 of the heat is at the rod and
  2/3 of the heat is at the base.
• It has shallow penetration-good for thin metals
• Prone to arc blow.

8
Direct current Electrode Positive (D.C.E.P)

• DCRP flows in one direction also, (-to) but the
  leads are reversed
• 1/3 of the heat at the base metal and 2/3 at the
  electrode.
• Deep penetration good for thick metals
• Prone to arc blow.

9
Alternating Current (A.C.)

• The current reverses itself so frequently that
  there is no polarity.
• 50 of the heat at the base and 50 at the
  electrode.
• It has moderate to deep penetration with no arc
  blow.
• It is more economical to buy and it uses most all
  rods.

10
Striking the arc.

• Like striking a match, touch the electrode to the
  metal and strike. When the arc appears, hold for
  a second and then drop the electrode down to the
  metal.
• Motion For the welds you are doing, there is no
  motion. Simply drag the rod in a straight line.

11
Weld Joints
12
But joint.

• Prepare the joint. The metal must be clean.
  Always tack and V thick pieces for penetration.
• In both oxy-acet and arc welding, gap the pieces
  for penetration.

13
Flange (edge joint)

• This is one of the easiest welds.
• This weld is done with no filler rod in oxy-acet
  welding.

14
Lap Joint

• Very common weld. The plug, rosette, and slot
  weld are all variations of the lap weld.
• In oxy-acet and arc, concentrate the majority of
  heat at the bottom plate and wait to fill in to
  the top.

15
Inside corner (T joint)

• This weld is very similar to a lap weld.
• Concentrate the majority of heat on the bottom
  plate.

16
Outside Joint

• This weld is done without filler rod in oxy-acet.
• In arc welding try to allow for a natural V.

17
Welding Positions

• FLAT
• HORIZONTAL
• VERTICAL
• OVERHEAD

18
Flat

• This is the easiest welding position.
• Basically as it sounds, the pieces are flat on
  the table and the weld is done with the normal
  motion.
• The rod is held perpendicular to the base metal
  then inclines 20? toward the direction of travel.
• Drag the weld, backhand.

19
Horizontal

• In this weld, the plates are standing vertically
  and the weld is made horizontally across.
• In both oxy and arc the torch and electrode must
  point upward to counteract the sagging effect of
  gravity.
• Angle the rod toward yourself 30 to 45? and
  incline 20? toward the direction of travel. Drag
  the weld.

20
Vertical

• This weld is made with two vertical pieces either
  welded upward or down. Quite difficult.
• The torch or electrode must be pointed up to
  counteract the sagging effect of gravity.
• Some motion may be needed to keep the weld up.
• Down is easier but has less penetration.
• Up is harder with more penetration.

21
Overhead

• Very difficult and must only be done when
  trained.
• You must have full leather protection from head
  to toe.
• You will not be doing this weld without express
  permission from me and I will give instruction at
  that time.

22
Problems
23
Arc Blow

• A magnetic force that deflects the weld into
  splitting.
• This is only a problem on DC polarities.
• To cure, reestablish the ground or shorten the
  arc length.

24
Undercut

• A trough or erosion cut on either side of the
  weld.
• To cure this, turn down the amps, shorten arc
  length or hesitate at the edges to allow for fill
  in.

25
Rod sticks

• Break the circuit or current flow by releasing
  the electrode from the electrode holder.
• Break the rod free from the metal with a gloved
  hand and start again.
• This can be avoided by turning the amps up, not
  touching down to the metal or by using the
  correct electrode.

26
Arc wont start

• Check the following
• Machine set up and switches.
• Check the ground.
• Check the rod, is it in the stinger correctly and
  is the end of the rod glassed over.

27
Welds

• The weld may split. Go slower to let the metal
  fill in.
• Excessive spatter. Check the electrode, polarity
  and arc length.
• If the weld breaks, there is not enough
  penetration. Penetration is the depth that the
  weld penetrates the base metal. Poor weld prep
  and set up, too low amperage, or cooling the weld
  in water will lead to shallow penetration.
• Scrambled eggs- welding over unresolved slag or
  too long of an arc length.

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Safety
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Protective equipment

• All of the following equipment protects you from
  heat, splatter and harmful rays (ultra violet and
  infrared).
• Gloves leather. Do not handle hot metal or get
  them wet. Leather will burn, shrink and harden.
• Jacket leather. Not to be used as a shop coat.
  For welding only.
• Helmet a full head and face shield. Headgear
  can be adjusted. The lenses are 10-12 filter
  plate.

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Always

• Wear protective gear and protect your eyes. Say,
  cover before striking an arc.
• Report any faulty equipment.
• Use pliers to handle hot material.
• Make sure nothing is wet.

31
Never

• Expose skin or eyes to flash or arc.
• Change the amperage setting while the machine is
  under a load.
• Chip slag without eye and face protection.
• Get your gloves wet.
• Exceed the work limits. The duty cycle of the
  machine is a ten-minute span. It is the amount
  of time out of ten minutes that you can weld
  continuously. Ex. 70 7 out of 10 minutes.