880 Modern Welding Sequence: The order in which operations take place. Servomotor: A motor that can move in small increments according to electrical signals. Used for steering mechan- ical devices, robots, and welding guns. Set-up point: A specifi c reference point in space from which all movements of a robot arm or electrode tip are measured. Shear: Force that causes two parts of the same body touching each other to slide parallel to their contacting surfaces. Shear fracture: A type of break in which crystalline material separates by sliding under action of shear stress. Shear strength: Stress required to fracture a part in a cross-sectional plane when two forces being applied are parallel and opposite, but are offset somewhat. Shield: An eye and face protector. It enables a person to look directly at the electric arc through a special lens without being harmed. Shielded metal arc cutting (SMAC): An arc cutting process in which metal is cut by melting it with the heat of an arc between a covered electrode and the base metal. Shielded metal arc welding (SMAW): Arc welding process that melts and fuses the metals using the heat of an arc between a covered electrode and the base metal. As it melts, the electrode also provides the fi ller metal. Shielding gas: A gas that protects the arc and weld from the atmosphere. Short arc: Gas metal arc process that uses a low arc voltage. The arc is continuously interrupted as the molten elec- trode metal bridges the arc gap. Shot peening: Working the surface of a metal by bombarding it with metal shot. Side bend: A bend test in which the sample is bent parallel to the weld axis. Silicon-controlled rectifi er (SCR): A semiconductor device with three terminals that can be switched from conducting to nonconducting through the use of signals controlled by logic gates. Silver brazing: Brazing using a silver-based fi ller alloy. Simple alloy: Two metals combined in any proportion. Sine wave: See Sinusoidal wave. Sinusoidal wave: In alternating current, a plot of time against amperage fl ow. An ac sine wave pattern. Slag: Nonmetallic byproduct of smelting and refi ning made up of fl ux and nonmetallic impurities. Also, material that forms on the underside of an oxyfuel gas or arc cut. Slag inclusions: Nonfused, nonmetallic substances in the weld metal. Slot weld: A weld made through and in a hole that is not round. The hole is cut into one piece of metal that is lapped over another piece. Soaking pit: A heated pit that allows a steel ingot to reach a uniform temperature throughout before additional processing occurs. Soapsuds: A soap and water solution. Solder: A binding, or joining, metal that melts at a tempera- ture below 840°F (450°C). Soldered connections: Connections made by soldering special fi ttings onto tubing. Soldering: A means of fastening metals together by adhering one metal to another by means of solder at a temperature below 840°F (450°C). Only the fi ller metal is melted. Solenoid: An electromagnetic device used to open or close switches or valves. Solid pellet oxyfuel gas welding: A portable welding system using fuel gas with pellets. Pellets produce oxygen and eliminate need for bulky oxygen cylinders. Solid-state controller: An electronic controller that uses transistors, diodes, and other semiconductor devices. Solid-state devices: The small, solid electronic compo- nents that have replaced vacuum tubes and switching circuits in modern electronic equipment. Solid-state welding (SSW): Welding processes that use the application of pressure to produce coalescence without melting any of the joint components. Solidus: The highest temperature at which a metal or alloy is completely solid. Solidus line: The line on an iron-carbon diagram that denotes the temperature at which the material mixture is entirely solid. Solvents: Chemicals that dissolve or break up surface contaminants on metal. Sonotrode: The part of an ultrasonic welding machine that transfers vibrations into the base metal. Spalling: An undesirable condition in which surfacing material breaks off from the base metal or a previous hardfacing layer. Spark lighter: A device used to ignite the welding fl ame. Spatter: Metal particles from a welding process that do not become part of the weld. Particles may adhere to the base metal. Spattering: Scattering of solidifi ed metal drops on the base metal surface. Specific gravity test: A test used to determine the density of a substance relative to the density of water. Spheroidizing: The process of heating and cooling steel to produce a spheroidal or globular form of carbide in the metal. Spool guns: Gas metal arc welding guns that have self- contained wire drive units. Spot weld: A small molten spot formed where metal pieces contact each other between the electrodes in the resis- tance spot welding process. Spot welding: Forming a small weld nugget to join lapped material. Spray arc: A gas metal arc process with an arc voltage high enough to continuously transfer the electrode metal across the arc in small globules. Square-wave: Type of power supply that can change the current from electrode-positive to electrode-negative very quickly. Squeeze time: In resistance spot welding, the time required for the electrodes to close on the workpiece and apply the proper force. Stack cutting: Cutting many layers of metal at the same time. Staggered intermittent welds: Welds that are offset so the welded segments do not line up on each side of the joint.
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