Arc Welding

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ARC WELDING
ME 353 Presentation 11-3-2000 Presented by Damon Ogden

OUTLINE
• • • • • • What is Arc Welding The four most common types Non destructive testing Design considerations Strength Safety Feel free to ask questions at any questions at any time.

Arc Welding
• Welcome to the world of WELDING

What is Arc Welding?
An electric arc between the and electrode and the work piece generates heat. Sufficient heat is generated to melt the work pieces together. ELECTRODE ARC WORK PIECES

Electricity
The range of welding current used can be from 5 to 500 amps. The voltage ranges from 20 to 30 volts, AC or DC. Both are determined by the material thickness. A 60 watt light bulb draws .5 amps.

Four Common Types of Welding
•Stick SMAW (shielded metal arc welding) •Mig GMAW (Gas Metal Arc Welding) •Flux-Core FCAW (Flux-core Arc Welding) •Tig GTAW (Gas Tungsten Arc Welding)

Characteristics
Each welding process has unique traits that make it more suited for particular processes

Some Terms
Electrode This is where the current passes from the welder to the work piece. There are two types: 1) Contact/consumable 2) Non Contact

More Terms
Atmospheric protection There are 2 types: 1) Shielding Gas 2) Flux

Stick Weld Schematic

Current

Stick Welding
• Uses a consumable electrode (rod), with a flux coating. • Stick welding requires a moderate to high skill level. • Advantages: Portable Can be used in all environments Not as dependent on surface preparation

Electrode

Arc

Stick welder joins sections of oil pipe in Alaska.

MIG WELDING SCHEMATIC

Current

Mig Welding
• The electrode is a wire, fed from a spool to the end of the “gun”. • A shielding gas is used to give atmospheric protection. • This process requires a low to moderate skill level. Advantages: 1) Very fast process 2) Easy to learn Disadvantages: 1) Weld area must be protected from air movements

Flux Core Schematic

Flux Core
• This process is a hybrid between Mig and Stick welding. • It is the same process as Mig welding, except instead of a shielding gas, there is flux in welding wire. Advantages: 1) Can be done in all environments Disadvantages: 1) Requires additional clean up to remove flux

TIG WELDING SCHEMATIC

Filler rod

Tig Welding
• There is a Tungsten electrode through which the current is passed. (Melting pt. = 3700 degrees K) • Argon is used as a shielding gas. • Requires the highest skill level. Advantages: 1) Nearly all metals can be welded using this process. 2) Very precise Disadvantages: 1) Slow process

Filler Rod

Arc

TIG welding a Nascar chassis together.

PROBLEM 1 A semi-truck is parked along side I-80 with a broken air brake mount on it’s trailer. The mount is made out of standard steel. The truck can not be moved until the repair is made. Which welding process, (MIG, TIG, Stick, Flux Core) could be used to make the repair? Discuss what factors were involved in your selection process. Answer on page 4 of handout

ANSWER TO PROBLEM 1 There are two process that could be used to make the needed repair. Those two processes are flux core, and stick welding. Because the repair had to take place in the field, a process must be used that did not require an external shielding gas. Both of the processes are equally suited to make the repair. Stick welding requires a higher skill level than flux core, so the operator skill level is a factor.

Automatic/ Robotic Welding
• Can be done using the MIG or TIG processes • Used when there are long, reproducible weld joints • It can be used where the environment is hazardous to humans • Saves time and money

Weld Head This robotic TIG welder is sealing nuclear waste storage containers.

WELD HEAD

An automatic Multi-Head Mig welder joins sections of pipe together.

Radiography
• A non-destructive process to test welds using X-Rays

Welds with internal flaws can lead to failures

Flaw (porosity)

Radiograph...
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