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Basic Electricity and Welding

Basic Electricity and Welding

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The Arc Welding Circuit 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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Basic ElectricityBasic Electricity

• Voltage – The electrical potential or pressure that causes current to flow– Measured in Volts

• Current – The movement of charged particles in a specific direction– Measured in Amps

• Polarity– DC- (Direct Current

Electrode Negative)– DC+ (Direct Current

Electrode Positive)– AC (Alternating Current)

DC+

DC -

AC

Arc Welding BasicsArc Welding Basics

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Unit Topics Unit Topics

• Topics included in this overview are:– Introduction

What is Arc Welding? Why is Welding Important? Why Learn to Weld?

– Careers in Welding– The American Welding

Society (AWS)– Welding Safety– Basic Electricity– Welding Fundamentals– Welding Certification

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ObjectivesObjectives

• 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

Introduction Introduction

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What is Arc Welding?What is Arc Welding?

• Arc welding is most commonly used to join two pieces of metal – The welder creates an electric arc that melts the

base metals and filler metal (consumable) together so that they all fuse into one solid piece of metal

Steel Pipe – Tack Welded

Root Pass or “Stringer Bead”

Final weld after several beads are made

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Why is Welding Important?Why is Welding Important?

• Many things around us are welded …– Pipelines that bring fresh water – Towers that carry electricity to houses– Cars and buses that take people where they need to go

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Why Learn to Weld?Why Learn to Weld?

• Welding is so HOT …. it’s COOL!– 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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Basic Steps of Arc WeldingBasic Steps of Arc Welding

• Prepare the base materials: remove paint and rust• Choose the right welding process• Choose the right filler material• Assess and comply with safety requirements• Use proper welding techniques and be sure to protect

the molten puddle from contaminants in the air• Inspect the weld

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English, Math, and Science Connection

English, Math, and Science Connection

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English, Math, and Science Connection

English, Math, and Science 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?

75/25 – gas mixture Volts Amps Degree/hr – cooling rate In/min Angles/degrees Metallurgy Fillet size

Current Tension Compression Tensile strength Yield Blueprints Depth/width ratio Preheat temperature Cubic feet per hour

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Math Terms and Welding

Math Terms and Welding

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Math Terms in Welding Math Terms in Welding

• Believe it or not, a lot of math is used 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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Welding SymbolsWelding Symbols

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What are Welding Symbols?What are Welding Symbols?

• Welding symbols give the welder specific instructions about the weld including:– Placement– Size– Length– Process– Any other special notes

• Welding symbols are– Universally used– Governed by the AWS– Found on engineering drawings

“How to Read Shop Drawings” available at www.jflf.org

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Welding SymbolsWelding Symbols

• Welding symbols contain information about the weld to be made – S – leg dimension of the weld– Triangle – the weld is to be made on the arrow side of this joint– Tail – any additional information required (i.e. position the weld

is to be made)– Arrow - the joint the welding symbol applies to

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Parts of a WeldParts of a Weld

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Parts of a WeldParts of a Weld

Joint and WeldHeat Affected Zone

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Fillet and Groove WeldsFillet and Groove Welds

• Groove and fillet welds can be made on many types of joints

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Fillet Weld InspectionFillet 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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Welding PositionsWelding Positions

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What are Welding Positions?What are Welding Positions?

• There are various positions that a weld can be made in: