884 Modern Welding Weld pool: Portion of the weld that is molten due to the heat of welding. Weld reinforcement: The amount of buildup above the surface of the base metal. Weld root: The point where the weld intersects the base metal surface near the bottom of the joint. Weld sequence: The squeeze time, weld time, and hold time required to make a spot weld. Weld size: The depth of penetration in a groove weld. Also, the nominal length of a leg in a fi llet weld. Weld symbol: A symbol that shows what type of weld is to be placed in a joint. The weld symbol is part of the overall welding symbol, which contains all the informa- tion about a welded joint. Weld time: In resistance spot welding, the time that the current fl ows and heats the metal. Weld toe: The point where the weld bead contacts the base metal surface. Wet welding: Underwater welding in which the weld joint and welder are completely submerged in water. Whipping motion: A quick movement of the electrode tip from the weld pool and back again. Whiskers: Lengths of welding wire that stick through the root side of a groove weld. White cast iron: Very hard and brittle cast iron made by cooling the casting quickly. Carbon is present throughout the microstructure. White cast iron is not weldable. White heat: Heat level just short of the rapid oxidizing or burning point. Work angle: The angle between a line perpendicular (90°) to the major workpiece and a plane determined by the centerline of the torch tip and the weld axis. Work envelope: The working volume of a robot. Working drawings: Drawings that are used to produce a part or product. They may be detail or assembly drawings. Working pressure: The gas pressure set on the low-pres- sure regulator. Also called torch pressure. Working volume: The volume of space that can be covered by a robot at the full extent of its reach in all directions. Workpiece: The part that is to be welded, brazed, cut, or surfaced. Workpiece lead: Electrical conductor that carries the current between the welding machine and the workpiece. WPQR: See Welding procedure qualifi cation record. WPQT: See Welder performance qualifi cation test. WPS: See Welding procedure specifi cation. Wrought aluminum: All forms of aluminum other than cast aluminum, such as plates, sheets, rolled forms, extruded forms, and aluminum pipe. Wrought iron: Commercial iron made up of slag (also known as iron silicate) fi bers entrained in a ferrite matrix. Contains a maximum of .2% carbon. X X-ray inspection: Checking a weld for discontinuities by using X-ray equipment to produce a radiograph. Y Yield point: The lowest stress to which a material or body can be subjected. The point at which strain increases without an appreciable or proportionate increase in stress. Yield strength: Stress value in psi or kPa at which a spec- imen assumes a specifi ed limiting permanent set. Z Zero point: See Set-up point. Zirconium: A rare metal that oxidizes easily and is used as an alloying element in alloy steels.