Transcript Document

SMAW
SMAW
 SHIELDED METAL ARC WELDING
AWS Classification
 ARC WELDING
 STICK WELDING
FACTS ABOUT SMAW
Originated at start of WWI for shipbuilding
SMAW is the least expensive arc welding processes
Is the most widely used welding process in the world
Can be used to weld most common metals and alloys
SMAW COMPONENTS
1- The Electrode
• Consumable…
• 2 Part Composition
Core Rod (Metal Filler)
Carries welding current &
Becomes part of the weld
Flux Coating
Produces a shielding gas &
helps form slag
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2- The Arc
Can you identify the weld joint
and position being used?
• Turn on the light…An arc
occurs when the electrode
comes in contact with the
work-piece and completes
the circuit
• The electric arc is
established in the space
between the end of the
electrode and the work
causing resistance
• The arc reaches
temperatures of 10,000°F
which melts the electrode
and base material
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3- 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
1/8” E6013 at
125 Amps AC
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4- Shielding Gas
• A shielding gas is formed when the flux melts.
• This protects the weld puddle from the atmosphere
preventing contamination during the molten state
The shielding gas protects the
molten puddle from the
atmosphere while stabilizing
the arc
Shielding Gas
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3
2
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5- Solidified Weld Metal
• 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
• Bead width = 2.5 to 3 times electrode diameter
3/8”
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6- Slag
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Combination of melted flux & base metal impurities
Quickly solidifies to form a shell
Slows the cooling rate of weld
Chip and clean with hammer & brush
If proper technique is used it should come off easy
Never weld over slag!!
ALWAYS SIDE CHIP SLAG, DON’T
HIT IT LIKE A HAMMER
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Slag You Drag!
• Slag Welding Processes
– ALWAYS PULL THE PUDDLE
– Shielded Metal Arc Welding (SMAW)
– Flux Core Arc Welding (FCAW)
• No-Slag Welding Processes
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ALWAYS PUSH THE PUDDLE
Gas Metal Arc Welding (GMAW)
Gas Tungsten Arc Welding (GTAW)
Oxy-Fuel Welding
SMAW Process
Electrode
1
Travel direction
4
6
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Shielding Gas
Slag
Slag
Weld Puddle 3
3 Weld Puddle
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5
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Solidified Weld Metal
Solidified Weld Metal
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2
Arc
Arc
Activity
Let’s review the SMAW process … • 1 = __________
1
• 2 = __________
• 3 = __________
4
• 4 = __________
6
• 5 = __________
3
2
• 6 = __________
5
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AWS Electrode Classification
Electrode Selection
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What type of welder do I have, AC or DC?
What am I welding, steel, cast, stainless, etc?
What is the metal condition, dirty or clean?
Is it a root or cover pass?
How strong does it have to be?
What electrodes do I have to chose from?
Electrode Selection
Amperage Chart
• Amperage is dependent on electrode
diameter, electrode type, and metal thickness
• Reference charts whenever possible.
Amperage Electrode
• Shorthand method will get you in the
ballpark for fast freeze electrodes.
Not 100% accurate for all electrodes!
AWS: 1/8” diameter E6013
1/8”= .125”
125 Amps
Electrode Care
• Electrodes must be kept dry
– Dampness will introduce hydrogen into the
weld causing cracking or brittleness
– Damp electrodes may cause the flux to “blow
away” & cause porosity
– Bake questionable electrodes for several
hours.
– 6010 & 6011 (fast freeze) are exempt
• Our electrodes are stored in a dry oven
Electrodes Care cont.
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Burn electrodes down to numbers!
Place stubs in stub box
Put unused electrodes back in oven
Only grab several electrodes at a time
Electrodes are not cheap
Striking an Arc and Making a Weld
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Striking an Arc
• To begin the SMAW Process, you must first
strike an arc.
– Scratch start – scratch the electrode on the base
metal like a match
– Tap Start – tap the rod against the base metal
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Work Angle
• The work angle is the
angle between the
electrode and the work
as depicted on the left
90°
• Work angles can vary
depending on the
position the weld is being
made in
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Travel Angle
• Also commonly called
Lead Angle
20-30°
• The travel (lead) angle
is the angle between
the electrode and the
plane perpendicular to
the weld axis
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Arc Length
• After striking the arc, maintain a 1/8”
distance between the electrode and the
workpiece
– Too short: electrode will fuse itself to metal
– Too long: spatter, undercut, and porosity
Arc Length = 1/8”
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Travel Speed
• Speed at which the electrode moves along the
base material while welding
– Too fast: ropey or convex weld
– Too slow: wide weld, excessive deposit
The travel speed impacts
the shape of the bead.
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Filling the Crater
• At the end of the weld, the operator breaks the
arc which creates a ‘crater’
• Use a short pause or slight back step at the end
of the weld to fill the crater
• Large craters can cause weld cracking
Back stepping is a short
move in the opposite
direction of weld travel
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Restarting a Bead
• Remove electrode from stinger
• Scratch electrode until metal can be seen
• Scratch in weld line: spatter
1. Strike Arc Here
2. Move Electrode to
Crown of Crater
3. Resume Travel
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Troubleshooting Activity
On a piece of scratch paper, describe welds A-G.
Good, bad, arc length, speed, lead angle, etc.
A
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B
C
D
E
F
G
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A – Good Weld: Proper Current, Speed and Arc Length
B – Current low: Ropey, convex bead appearance
C – Current too High: Excess spatter & burn-through
D – Arc Length too short: Poor wet-in at toes
E – Arc Length too Long: Spatter, undercut and porosity
F – Travel Speed too slow: Wide weld with excess deposit
G – Travel Speed too high: Ropey and convex bead
Lincoln V350 SMAW Setup
1.
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Plug ground cable into the (-) terminal
Plug the whip cable into the (+) terminal
Turn on the welder
Select SMAW (CC-Stick Soft) mode
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CC-Stick Crisp is for pipe welding
5. Select correct amps
6. Set Hot start to 2-3
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(This will make starting the arc easier)
7. Set Arc Control to +4-5
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(high arc control = crisp weld but more spatter)
(low arc control = soft weld with little spatter)