874 Modern Welding Liquid: A physical state in which a substance has a fi xed volume but no fi xed shape. Liquid metal: Metal in liquid form, which is transferred to the weld through the arc stream. Liquid penetrant inspection: Inspection method that uses colored liquid dyes and fl uorescent liquid penetrant to check for surface fl aws in metals. Liquidus: Lowest temperature at which a metal or alloy is completely liquid. Liquidus line: The line on an iron-carbon diagram that denotes the temperature at which the material mixture is entirely liquid. Lock-out: Procedure that locks a circuit breaker in the “off” position. Longitudinal face and root bends: Bend tests that are done with the weld going along the length of the test sample. Low-hydrogen electrodes: Electrodes that deposit a minimum of hydrogen in the weld. Low-pressure gauge: The gauge of a pressure regulator that shows the working pressure, or the pressure of the gas being delivered to the torch. Lugs: Uninsulated terminals that provide a fi rm means of attaching the electrode lead and the workpiece lead to the machine or worktable. M Macro-etch: Eating away of the metal surface to make gross structural details stand out so that they can be observed with the naked eye or with magnifi cation of up to 10 times. Macrograph: Photographic or graphic reproduction of the surface of a prepared specimen that has been magnifi ed up to 10 times normal size. Macroscopic: Pictures are magnifi ed 10 to 40 times (10× to 40×). Macrostructure: The physical makeup or structure of metals revealed under magnifi cation of not more than 10 times. Magnetic amplifi er control: Transformer output control that uses the welding current coils and diodes in series with the control coils. Magnetic lens: The electromagnets in an electron beam welding machine that focus and concentrate the streams of electrons. Magnetic particle inspection (MT): Inspection method used on materials that can be magnetized to check a weld for surface or near-surface fl aws. Magnetic test: An elementary test used to separate iron and steel metals from nonferrous metals. Malleability: The ability of a metal to be deformed without breaking. Malleable castings: Cast forms of metal that have been heat treated to reduce their brittleness. Malleable cast iron: Cast iron made by annealing white cast iron while the metal undergoes decarburization, graphitization, or both. The process eliminates all or most of the cementite. Mandrel: A metal rod with a tapered head that forms the inner diameter of tubing during the drawing process. Manifold: A pipe or cylinder with several inlet and outlet fi ttings. It is designed so that several gas or oxygen cylin- ders can be connected together and the material piped to a number of locations or stations. Manual mode: Mode of operation in which the operator is in direct control of a robot’s movements. Maraging steels: Steels that are characterized by high strength and toughness, and good weldability. They contain less than 0.03% carbon, less than 0.10% manganese and silicon, and less than 0.010% phosphorus and sulfur. They contain about 18% nickel, about 10% cobalt, up to 5% molybdenum, and small amounts of titanium and aluminum. Martensite: A very hard and brittle form of steel. It is formed by rapid cooling from the austenite phase. Martensitic steels: Steels that are very hard and not very ductile. They contain about 11.5% to 18% chromium (Cr) and carbon contents of from 0.15% to 1.20%. Master regulator: A device that controls the fl ow of gases from the manifold to the welding station line. Mechanical cleaning: Cleaning done with a grinding wheel, media blasting, emery cloth, and/or a wire brush. Mechanical drawing: Drawing that accurately commu- nicates a designer’s ideas and includes all information required by the people who will manufacture a part or assembly. Mechanical properties: Descriptions of a material’s behavior when force is applied for purpose of deter- mining the material’s suitability for mechanical use. Properties described include modulus of elasticity, elon- gation, fatigue limit, hardness, and tensile strength. Mechanized GTAW: A welding technique in which a carriage or manipulator is used to move the torch at a set height above the base metal. Mechanized welding: Welding that requires manual adjust- ment of controls and variables and visual observation while the torch or gun is held in a mechanical device. Megapascal (Mpa): One million pascals a unit of measure- ment for pressure in SI Metric. See Pascal. Melting temperature: The temperature at which an alloy begins to melt. Melt-through symbol: Symbol that is used when 100% penetration is required on one-side welds. Metal composition: The individual components in the metal and the ratio at which they are combined. Metal powder cutting (OC-P): An oxygen cutting process that uses a powder, such as iron or aluminum, to improve the cutting of metal. Metal transfer: The transfer of molten fi ller metal from the electrode to the weld pool. Metallic: Term indicating that a material contains metal. Metallography: The scientifi c study of the constitution and structure of metals and alloys, as observed by the naked eye or with the aid of magnifi cation and x-ray. Metallurgy: The science and technology of metal. Metric drill sets: Drill sets that include sizes from 0.100mm (0.0039″) to 25.50mm (1.004″).