39378800 Arc Welding Introduction and Fundamentals

Arc Welding

By Ryan Saucier

History of Arc Welding• Arc welding dates back to the late 1800’s• First developed following the invention of

AC electricity• Pioneered when a man was welding with a

bare metal rod on iron, the sparks from the welding caught a stack of newspapers on fire near him and while welding, he noticed that his welds started looking a lot better. The reason for this was the smoke took the oxygen out of his welding environment and decreased porosity.

What is Arc Welding?

• The fusing of two or more pieces of metal together by using the heat produced from an electric arc welding machine.

Basics of Arc Welding

• The arc is struck between the electrode and the metal. It then heats the metal to a melting point. The electrode is then removed, breaking the arc between the electrode and the metal. This allows the molten metal to “freeze” or solidify.

How an arc is formed?

• The arc is like a flame of intense heat that is generated as the electrical current passes through a highly resistant air gap.

Welding Processes

• SMAW (Shielded Metal Arc Welding)

• GMAW (Gas Metal Arc Welding)

• GTAW (Gas Tungsten Arc Welding)

• Oxygen/ Fuel Welding

SMAW• Also referred to as “Stick Welding”• Used for everything from pipeline

welding, farm repair and complex fabrication.

• Uses a “stick” shaped electrode. • Can weld: steel, cast iron, stainless steel,

etc.• Can also hardface with correct electrode.

Examples of SMAW Welds

GMAW

• Also referred to as “MIG” welding• Uses a shield gas and a continuous

wire electrode• Used for all types of fabrication• Great for thin metals up to ¼”• Excellent speed of deposition• Used for metals such as: steel,

aluminum and stainless steel.

GMAW Welds

MIG Welding Benefits

• All position capability •  Higher deposition rates than

SMAW •  Less operator skill required •  Long welds can be made without

starts and stops •  Minimal post weld cleaning is

required

GTAW•Also referred to as “TIG” Welding

•Uses a shield gas, a non-consumable tungsten electrode and a hand fed filler rod

•Excellent for welding thin metals, pipeline welding and exotic metals

•Highly skilled labor needed for this process

GTAW Welding Benefits

•  Superior quality welds •  Welds can be made with or

without filler metal •  Precise control of welding

variables (heat) •  Free of spatter •  Low distortion

Oxygen/ Fuel Welding• Utilizes oxygen and a fuel gas to heat

metal until it is in a molten state and fuse multiple pieces of metal together. Can be used with or without a filler rod.

• Great for brazing dissimilar metals together.

• Older technology that can be replaced by GTAW

Types of SMAW Machines

AC Welding Machine

Most common type found in homes, farms, etc.

Good for farm repairs, light jobs.

Low cost

DC Welding Machines

• Often generator type machines

• Diesel or gasoline engine driven

• Portable

• Expensive

AC/DC Welders

• Can weld in AC or DC polarity

• Less expensive than DC machine

• Quieter than DC machine

Arc Welding

PPE