Transcript The Science Of Welding - K

An integrated lesson
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Introduction
 What is Arc Welding?
 Why is Welding Important?
 Why Learn to Weld?
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Basic Electricity and the Science of Welding
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Electricity
Energy Transfers
Changes of State
Chemical Reactions
Welding Safety
Careers in Welding
www.istockphoto.com
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Arc welding is a process used to join two pieces
of metal together.
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How does it work?
 A welder creates an electric arc that melts the metal
and filler rod to create a pool of molten metal that
hardens to fuse the two pieces of metal together.
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Why is welding important?
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Many of the things you use need to be welded.
 Your parent’s car
 Power line towers
 Your school desk
 Your bicycle
dcist.com
www.cunninghamcycles.com
www.topspeed.com
assembly.state.ny.us
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Why Learn to Weld?
Welding can help build a successful career to earn
money to buy the things you want.
 Skilled Welders are in high demand.
 Welding is challenging and high tech.
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www.universalwelding.com
www.weldingschools.com
www.globalizedsourcing.com
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Voltage – The electrical potential or pressure
that causes current to flow
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Current – The movement of charged particles
in a specific direction
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Measured in Volts
Measured in Amps
Polarity
DC- (Direct Current
Electrode Negative)
 DC+ (Direct Current
Electrode Positive)
 AC (Alternating Current)
DC+
DC -
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AC
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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
Circuit – click on the link
to learn more.
Circuit Info.
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Use the following links to learn how electricity
works in a circuit
Conductors, Insulators, and electron flow
 Current and Voltage in a Circuit
 Resistance
 Ohms Law
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The electron flow you just learned about is
what creates the arc in arc welding.
This is a form of electrical energy
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How do we use that electrical energy to fuse metals
together?
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The energy transfers that take place in welding
Electrical
Thermal
The arc created by the
electric current is
converted into heat
because of the
resistance of electron
flow. The heat melts
the metal to fuse it
together.
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Here are some places to look to learn more
about energy and energy transfers.
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Forms of Energy
Energy Transformations
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Changes of State and Chemical Reactions
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During the welding process the metal changes states
or forms.
 What are the states of matter?
 Solid
 Liquid
 Gas
 Plasma
Click here to learn more about the changes of state
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Changes of State and Chemical Reactions
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So what changes of state occur during welding?
 Initially the metal is a solid
 When the arc starts the solid is converted into a liquid
 Some of the liquid is converted into a gas vapor
 When the arc stops the liquid cools to form a solid
again – this is the newly formed weld joint
Solid
Liquid
(gas vapor)
Solid
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Changes of State and Chemical Reactions
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Chemical Reactions
 During the welding process certain chemical reactions
take place.
 Hydrogen, Oxygen, and Nitrogen can react in the weld
puddle and cause changes in the structure of the weld
weakening the weld.
pt.chemicalstore.com
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Because of the chemical reactions, energy transfers, and
electricity involved in welding proper safety must be
addressed
Welding can be safe when sufficient measures are
taken to protect yourself and others from potential
hazards
Students should read and understand the following
before welding:
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Warning Labels
Material Safety Data Sheets (MSDS)
Students should also be familiar with the following
information
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‘Safety in Welding, Cutting, and Allied Processes’ (ANSI Z49.1)
Lincoln Electric’s ‘Arc Welding Safety’ (E205)
http://www.lincolnelectric.com/knowledge/training/weldcurriculum.asp
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Understand and follow all warning labels
found:
On welding equipment
 With all consumable packaging
 Within instruction manuals
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www.jpbrandit.com
http://www.lincolnelectric.com/knowledge/training/weldcurriculum.asp
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Material Safety Data
Sheets (MSDS) are:
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Required by law and
OSHA
Created by the
manufacturer of a
product per OSHA
guidelines
Designed to inform
users
Shipped with every box
of consumable product
Available free online at:

www.lincolnelectric.com/produc
ts/msds/
http://www.lincolnelectric.com/knowledge/training/weldcurriculum.asp
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MSDS outlines a
product’s:
 Identity and
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composition
Potential hazards
Safe use
Handling
information
Manufacturer
contact information
http://www.lincolnelectric.com/knowledge/training/weldcurriculum.asp
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Protect yourself and
others from
potential hazards
including:
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Fumes and Gases
Electric Shock
Arc Rays
Fire and Explosion
Hazards
Noise
Hot objects
http://www.lincolnelectric.com/knowledge/tra
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Fumes and gases can be
hazardous to your health
Keep your head out of the
fumes
Use enough ventilation,
exhaust at the arc, or both,
to keep fumes and gases
from your breathing zone
and the general area
See product labeling and
MSDS for ventilation and
respirator requirements
http://www.lincolnelectric.com/knowledge/training/weldcurriculum.asp
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Electric shock can kill
Do not touch live
electrical parts
Primary Voltage –230,
460 volt input power
 Secondary Voltage – 6
to 100 volts for welding
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Insulate yourself from
work and ground
Follow all warnings
on welding
equipment
http://www.lincolnelectric.com/knowledge/training/weldcurriculum.asp
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Welding sparks can cause
fires and explosions
Sparks and spatter from
the welding arc can spray
up to 35 feet from your
work
Flammable materials
should be removed from
the welding area or
shielded from sparks and
spatter
Have a fire extinguisher
ready
Inspect area for fires 30
minutes after welding
http://www.lincolnelectric.com/knowledge/training/weldcurriculum.asp
Welders must wear
protective clothing for
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Protection from sparks, spatter
and UV radiation
Insulation from electric shock
Protective clothing
includes …
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Fire-proof clothing without
rolled sleeves, cuffs or frays
Work boots
Welding gloves, jackets, bibs,
and fire-proof pants
Welding cap, helmet and
safety glasses
Ear protection – ear plugs and
muffs
http://www.lincolnelectric.com/knowledge/training/weldcurriculum.asp
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Education
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Penn College of
Technology
Penn College
Welding Video
Welding Schools
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Careers
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American Welding
Society
Career Guide
Welding Jobs
pro.corbis.com
www.sun-tech.org
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Here are some possible areas you can start a career
in welding
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Racing
Engineering
Farm
Auto Technician
Sculpting
Maintenance
Iron worker
Robotics
Production welder
Fabricator
And many more…
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Do you want to learn more about welding and
how to weld? If so, go to the link below for
more information on how to weld.
This is to be used if your school has access
http://www.lincolnelectric.com/knowledge/t
raining/weldcubrriculum.asp
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http://www.lincolnelectric.com/knowledge/t
raining/weldcurriculum.asp
http://www.weldinginfocenter.org/sci_tech/i
ndex.html
http://www.pct.edu/degreesthatwork/weldi
ng.htm
http://www.allaboutcircuits.com/vol_1/inde
x.html
All photographs are cited next to photograph