Transcript Welding 101 - Two Rivers Public School District

Welding 101
Objectives
• Upon successful completion of this unit of study, you
will be able to …
– Identify definitions and terminology associated with
welding
– Demonstrate safe working habits in the welding
environment
– Name the parts and types of welds and weld joints
– Interpret basic welding symbol information
– Identify opportunities available to welders
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What is it?
• Definition
A joining process that uses heat, pressure, and/or
chemicals to fuse two materials together
permanently.
Why Learn to Weld?
– Welding can help build a successful career so you can get
the things you want in life
– Skilled welders are in demand – people use things that are
welded everyday!
– Welding can be fun and safe
– It is challenging and high-tech
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STEM Connection
• Many of the same concepts you learn in other classes are
practiced in welding. In what other classes might you
study the following terms?
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75/25 – gas mixture
Volts
Amps
Degree/hr – cooling rate
In/min
Angles/degrees
Metallurgy
Fillet size
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Current
Tension
Compression
Tensile strength
Yield
Blueprints
Depth/width ratio
Preheat temperature
Cubic feet per hour
Careers in Welding
Job opportunities in welding are changing …
Welding can be valuable as a job skill or as a full-time job
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Engineering
Racing
Industrial Sales
Farm Repair and Fabrication
Production Welding
Military
Teaching
Maintenance
• Robotics
• Ironworker/ Skilled
Trades
• Auto Technician
• Artist
• Metal Sculpting
• Owning Your Own
Business
How Much Money Can You Make?
• Recent statistics show
that some welding jobs
pay $25.00 per hour
• Local employers pay
around $13-$22
• 83% of people with
welding jobs were
offered medical benefits
- Higher than any other
work sector except
government
Job Openings
• http://www.indeed.com/q-Welding-lManitowoc-County,-WI-jobs.html
Welder vs. Weld Operator
• Welder
– One who performs a manual or semiautomatic
welding operation
• Weld Operator
– One who operates adaptive control, automatic
mechanized or robotic welding equipment.
Methods of Application
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MA: Manual Welding
SA: Semiautomatic
ME: Mechanized Welding
AU: Automatic Welding
MA: Manual Welding
• Welding with the torch, gun, or electrode holder held
and manipulated by hand.
• Oxy-fuel welding
• Gas Tungsten Arc Welding (GTAW)
• Shielded Metal Arc Welding (SMAW)
• Shielded Metal Arc Welding (SMAW)
SA: Semiautomatic Welding
• Manual welding with equipment that
automatically controls one or more of the
welding conditions
• Gas Metal Arc Welding (GMAW)
ME: Mechanized Welding
• Welding equipment that requires manual
adjustment of the equipment controls in
response to a visual observation.
AU: Automatic Welding
• Welding with equipment that requires only
occasional or no observation and no manual
adjustment of controls.
• Robots
Electrical Terms in Welding
Voltage
pressure, force, or push Volts
Current
flow of electron
Amps
Resistance hinders current flow
Ohms
DCEP
Direct Current Electrode DC+
Positive
Straight polarity
(-) to (+)
DCEN
DCDirect Current Electrode
Reverse Polarity
Negative
(+) to (-)
AC
Changes polarity
Alternating current
120/second
Constant Voltage – CV Welders
• Welding Circuit Consists of Power Source,
Wire Feeder, and Work and Electrode
Cables/Leads
• Voltage is Proportional to Arc Length
• Current Changes Dramatically
to Maintain Constant
Arc Length
Constant Current – CC Welders
• Welding Circuit Consists of Power Source,
Voltage Sensing Wire Feeder, Work and
Electrode Cables/Leads
• Voltage is Proportional to Arc Length
• Current Remains Constant
Even for Changes in Voltage
Due to Changes in
Arc Length
Math Terms in Welding
IPM Travel Speed = Inches per
Minute Travel Speed
The speed the electrode moves
along the base material
IPM Wire Feed Speed= Inches per
Minute Wire Feed Speed
The speed at which the wire is fed
during wire welding
Lbs/hr = Pounds per Hour
Electrode deposition rate
CFH= Cubic Feet per Hour
Shielding gas flow rate (wire
welding)
PSI= Pounds per Square Inch
Tensile strength of a material and
the pressure in gas cylinders
L = Leg
Fillet size measurement
% = percent
Shielding gas mixture composition
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PPE includes:
• Hat or Beanie
• #12-14 Mask
• Safety Glasses
• Ear Plugs
• Jacket
• Gloves
• Jeans
• Boots
Welding Safety
• List PPE head to toe
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Common Welding Tools
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Clamps
Magnets
Side Cutter
Wire Brush
Slag Hammer
Metal Preparation
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A real welder takes the time!
This should take longer than the weld
Clean, clean, clean!
Joint fit-up.
Debur sharp edges
Bevel material ¼” or thicker
Preheat material ½” or thicker
Gauge
• SHEET: measured by gauge (.0068″) to (.2391″)
• PLATE: measured by inch rule (1/4” and up)
For example, steel gauge and measurement in inches:
16 gauge = .062″
14 gauge = .078″
12 gauge = .105″
10 gauge = .135″
PLEASE NOTE: As the gauge number gets smaller … the material thickness gets larger.
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Welding Safety
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HOT PARTS can burn.
FUMES AND GASES can be hazardous.
ARC RAYS can burn eyes and skin.
WELDING can cause fire or explosion
FLYING METAL or DIRT can injure eyes.
BUILDUP OF GAS can injure or kill.
ELECTRIC AND MAGNETIC FIELDS (EMF)
can affect Implanted Medical Devices.
• NOISE can damage hearing.
• CYLINDERS can explode if damaged.
Welding Safety
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FIRE OR EXPLOSION hazard.
FALLING EQUIPMENT can injure.
OVERUSE can cause OVERHERATING
FLYING SPARKS can injure.
MOVING PARTS can injure.
WELDING WIRE can injure.
BATTERY EXPLOSION can injure.
AWS/ANSI Lens Shade Numbers
LENS SHADES SELECTION FOR GAS METAL ARC WELDING
Operation
Electrode Size
in. (mm)
GMAW
Arc
Current (A)
Minimum
Protective
Shade
Suggested *
Shade No.
(Comfort)
Less than 60
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60-160
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160-250
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250-550
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Not Specified
Per
AWS / ANSI
* As a rule of thumb, start with a shade that is too dark to see the weld zone. Then go to a lighter
shade, which gives sufficient view of the weld zone without going below the minimum.
The Arc Welding Circuit
• 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
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Duty Cycle
• “Length of time a welder can be used
continuously at its rated output in any 10
minute interval”
• Every welder has a duty cycle (60-80% common)
• TRHS Lincoln V350-PRO are 60% duty cycle
– May weld 6 minutes out of a 10 minute interval
– Fan kicks on and robes amperage
5 Basic Welding Joints
Welding Joints
• Can you identify theses joints?
AWS: Welding Positions
1: Flat
2:Horizontal
3: Vertical
4: Overhead
5&6: Pipe
G: Groove Weld
F: Fillet Weld
Electrode Travel
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Push, Pull
Up, Down
Lead Angle
Work Angle
Travel Speed
Arc Length
IMPORTANT: Weld bead profile is affected by
electrode angle, arc length, travel speed, and
thickness of base metal.
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Push Vs. Pull
– Push weld puddle
– Deep Penetration
– Less weld buildup
• Pull
– Pull weld puddle
– Less Penetration
– More weld buildup
Up vs. Down
• Vertical down is uncommon
• Heat rises making the puddle easier to control
• Arc hard to see
Travel Angle
20-30°
• Also commonly called
Lead Angle
• The travel (lead) angle
is the angle between
the electrode and the
plane perpendicular to
the weld axis
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Work Angle
90°
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• The work angle is the
angle between the
electrode and the work
as depicted on the left
• Work angles can vary
depending on the
position the weld is
being made in
Work vs. Travel
Arc Length
• The distance the arc stretches from the
electrode to the work-piece.
• Distance varies between processes
Bead Manipulation
• Stringer
• Weave
• Whip (6010, 6011, 6013 only)
Travel Speed
• The travel speed is the
speed at which the
electrode moves along the
base material while
welding
– Too fast of a travel speed
results in a ropey or convex
weld
– Too slow of a travel speed
results in a wide weld with
an excessive metal deposit
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End of Weld
The travel speed impacts the
shape of the bead.
Test Your Knowledge
• Identify good, fast, slow
C.L.A.M.S
Acronym used to recall proper welding technique
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C…Current (DCEP, DCEN, AC)
L….Length of arc (Drag, 1/16, 1/8, ½”, etc.)
A…Angles (Travel angle, work angle)
M…Manipulation (Straight, weave, whip, etc.)
S…Speed of Travel (How fast you move)
Types of Welds
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Tack Weld
Intermittent (Stitch) Weld
Groove Weld
Fillet Welds
Plug or Slot Weld
Multipass Welds
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Root Pass
Hot Pass
Fill Pass
Cover Pass
Tack Welds
• Temporary but very important!
– Small enough to be welded over
– Strong enough to hold metal in position
– Position every 3-4 inches
– Tack all sides if possible
Tack Welds
• Tack welds prevent distortion and warping
• Tack weldment to table if practical
Intermittent (Stitch) Welding
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Welder doesn’t weld entire joint
Allows joint variation / flexibility
Lowers production cost
Reduces distortion
Grove Welds
• Welding pass that deposits filler material into
base material.
– Butt Joint
– Face Weld
Fillet Welds
• A fillet is a closed weld, which means the base
metal is not cut through to accommodate
weld metal.
• The process of joining two pieces of
metal together whether they be perpendicular
or at an angle.
Fillet Weld Inspection
• Fillet welds should:
– Have a flat to slightly convex face
– Be uniform in appearance
– Have equal leg size
– Have good wash-in into base materials
• This is an example of a good fillet weld:
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Plug /Slot Welds
• A circular fusion weld made in the hole of a
slotted lap or tee joint
Multi-Pass Welding
1. Root Pass
2. Hot Pass (within 5 min.)
3. Fill Pass
4. Cover Pass
5. Cover pass
6. Cover Pass
Bead Overlap should cover ~ 75% of previous pass.
Multi-Pass Welding
• Identify each pass (hot, fill, root, cover)
Weld Bead Terminology
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Concave vs. Convex
Leg
Toe
Face
Throat
Root
Fusion Zone
Concavity
Convexity
Parts of a Weld
Heat Affected Zone
Joint and Weld
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Joint Profiles
• Cross sectional view of the weld
Welding Symbols
Information that you needs to complete weld!
Weld Symbols
Heat-affected Zone (HAZ)
• Area of base metal which is not melted and
has had its microstructure and properties
altered by welding or heat.
• The heat from the welding process and
subsequent re-cooling causes molecular
change in the base metal.
Distortion
• Distortion: Metal expands with heat
• Warping: Contracts even more as it cools
• Impossible to get rid of it but able to manage it!
Controlling Distortion
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Quality tack welding
Intermittent welding
Weld little material as possible
Clamp or secure weldment to table
Alternate weld locations (front, back, front, etc)
Cool in sand or heated oven
Backstep welding
Back-step Welding
• Welding in short lengths reduces longitudinal
bowing but increases welding costs (time)
Cooling Welds
• Always handle hot metal with a pliers
• Assume metal is hot at all times
Sand - slow
Air - medium
Purge/Quench - Fast
* Swirl figure 8 pattern
Discontinuities & Defects
• Defect
– A flaw or flaws that by nature or accumulated effect
render a part or product unable to meet minimum
applicable acceptance standards or specifications.
– The term designates rejectability.
• Discontinuity
– An interruption of the typical structure of a material,
such as a lack of homogeneity in its mechanical,
metallurgical, or physical characteristics.
– A discontinuity is not necessarily a defect!
Types Discontinuities
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Misalignment
Undercut
Underfill
Concavity or Convexity
Excessive reinforcement
Improper reinforcement
Overlap
Burn-through
Poor Penetration
Incomplete Fusion
Surface irregularity
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Arc Strikes
Inclusions
Spatter
Arc Craters
Cracks
Base Metal Discontinuities
Porosity
Heat-affected zone
microstructure alteration
• Base Plate laminations
• Size or dimensions
Visual Inspection
Knowing what discontinuities are, is
the key to quality welds.
It is important for a welder to produce
and confirm a proper weld!
Good Weld Characteristics
Poor Weld Characteristics
Porosity
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Single Pore
Uniformly Scattered
Cluster
Linear
Piping
Overlap / Cold Lap
• Toes do not tie in metal
• Causes: Improper
technique, low heat
• No amount of overlap is
typically allowed.
Undercut
• Definition: Under fill
along the toes of the
weld.
• Cause: High amperage,
electrode angle, long arc
length, rust
Spatter
Burn Through
• Front
• Back