Chapter 18Welding Processes

Welding

The process of joining two or more pieces of like metal

Parts are heated enough to cause it to melt where they meet

When the metal cools it solidifies, joining the parts

Properly welded joints are as strong as or stronger than the original material

Considered a permanent fastening method

Welding Processes

All processes shown on page 673, fig 21.3 Most common types:

Oxygen Gas Welding Oxyacytlene welding (2 tanks) fig 21.4 Can be used with: natural gas, propane, propylene Typically used to fabricate thin materials Used mostly for repair work (portable) Can also be used to cut Low operating cost Slower than other processes

Also associated with brazing Brazing is considered bonding Base materials remain solid

while the filler material melts then cools to bond the pieces together

Shielded Metal Arc Welding (stick welding) Most traditionally used process Used on a variety of metals Used a flux covered metal

electrode to carry electric current that forms an arc to melt the metal

Electrode also melts and joins the melting base materials to form the weld

Gas Tungsten Arc Welding Tungsten inert gas welding (TIG) Can be used on a wider variety of

metals Produces clean high quality welds Usually limited to thin parts that

need high quality joint Slow process High cost for equipment and

materials Gas Metal Arc Welding (MIG)

Very fast and economical Used on thin or thick materials Used in mass production

Basic Welding Joints

Welding Drawings

Typically called weldments or welding assemblies

Shows parts together in multi-view Contains : Fabrication dimensions

Types of jointsWeld symbols

Parts are shown as separate pieces on the drawing (don’t unite solids)

All parts may not be dimensioned completely May have separate detail drawings

Weld Symbol

Directions for welded joints Gives information for type of weld,

size, process to be used, finishing processes, etc

Side Significance

Weld symbols can be on either side of the reference line, each side is meant for a specific side of the joint