A structure resulting from transformation of austenite at temperature considerably below the usual range, achieved by rapid cooling. It is made up of ultra-hard, needlelike crystals that are a supersaturated solid solution of carbon in iron.

A welding process where the torch or electrode holder is manipulated by hand. MIG. See Gas Metal Arc Welding (GMAW).

Welding with a coated electrode where the operator?s hand controls travel speed and the rate the electrode is fed into the arc.

A multiple header for interconnection of gas or fluid sources with distribution points.

A metal bar serving as a core around which other metals are cast, forged, or extruded, forming a true, center hole.