Welding Processes

Welding Processes

A Brief History of Welding

• Late 19th Century
• Scientists/engineers apply advances in electricity to heat and/or join metals (Le Chatelier, Joule, etc.)
• Early 20th Century
• Prior to WWI welding was not trusted as a method to join two metals due to crack issues
• 1930’s and 40’s
• Industrial welding gains acceptance and is used extensively in the war effort to build tanks, aircraft, ships, etc.
• Modern Welding•the nuclear/space age helps bring welding from an art to a science

        Fusion Welding Principles

•Base metal is melted

•Filler metal may be added

•Heat is supplied by various means

•Oxyacetylene gas

•Electric Arc

•Plasma Arc

•Laser

Weld Metal Protection

•During fusion welding, the molten metal in the weld “puddle” is susceptible to oxidation

•Must protect weld puddle (arc pool) from the atmosphere

•Methods

•Weld Fluxes

•Inert Gases

•Vacuum

Inert Gases

•Argon, helium, nitrogen, and carbon dioxide

•Form a protective envelope around the weld area

•Used in

•MIG

•TIG

•Shield Metal Arc

Vacuum

•Produce high-quality welds

•Used in electron beam welding

•Nuclear/special metal applications

•Zr, Hf, Ti

•Reduces impurities by a factor of 20 versus other methods

•Expensive and time-consuming

Types of Fusion Welding

•Oxyacetylene Cutting/Welding

•Shielded Metal Arc (“Stick”)

•Metal Inert Gas (MIG)

•Tungsten Inert Gas (TIG)