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Welder’s Handbook
Matrix – The principal, physically continuous metallic constituent in which crystals or free atoms of other constituents are embedded. It serves as a binder, holding the entire mass together. Mechanized Welding – Pertaining to the control of a process with equipment that requires manual adjustment of the equipment controls in response to visual observation of the operation, with the torch, gun, wire guide assembly, or electrode holder held by a mechanical device.
Nondestructive Examination (NDE) – The act of determining the suitability of some material or component for its intended purpose using techniques that do not affect it serviceability
Non-Ferrous – Containing no iron. Example: Aluminium, copper, copper alloys.
Non-transferred Arc – An arc established between the electrode and the constricting nozzle of the plasma arc torch. The workpiece is not in the electrical circuit.
Melt Through – Visible root reinforcement produced in a joint welded from one side.
Nozzle – A “consumable” torch part containing a hole or orifice through which the arc passes.
Metal Active Gas (MAG) Welding – Similar to Metal Inert Gas (MIG) Welding.
Nozzle Diameter – The diameter of the nozzle through which the plasma arc passes. (Also referred to as orifice diameter).
Metallurgically Similar Steels – Multiple steel compositions that have essentially the same crystal structure, such as austenite or ferrite. Metallurgy – The science and technology of extracting metals from their ores, refining them, and preparing them for use. Microstructure – Structure that is visible only at a high magnification, with the aid of a microscope after preparation, such as polishing or etching. Metal Inert Gas (MIG) Welding – An arc welding process wherein coalescence is produced by heating with an arc between a continuous filler metal (consumable) electrode and the work. Shielding is obtained entirely from an externally supplied gas, or gas mixture. MIG welding requires the use of an inert shield gas.
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Off-Centre – Refers to the coating being eccentric and thicker on one side of the electrode than the opposite side. Also referred to as “Fingernailing”, which isn’t always due to coating eccentricity. Could be a result of formulation as well.
Ohm – Unit of electrical resistance to current flow.
Open Circuit Voltage – The voltage present at the electrode in the brief interval before the torch ignites and whenever the arc is extinguished with the power source still active.
Orifice Diameter – The diameter of the nozzle through which the plasma arc passes. (Also referred to as nozzle diameter).
Orifice Gas – A gas directed into the torch to surround the electrode, which becomes ionized by the arc to form a plasma and issues from the torch nozzle as a plasma jet. (Also referred to as plasma gas or cutting gas).
Mild Steel – An alloy of mostly iron with low content of alloying elements such as carbon and manganese.
Out-of-Position Welds – Welds made in positions other than flat or horizontal fillets.
Mill Scale – The iron oxide (FeO) coating normally found on the surface of hot rolled steels.
Overlap – The protrusion of weld metal beyond the weld toe or weld root.
MMA (Manual Metal Arc) Welding – An arc-welding process wherein coalescence is produced by heating with an arc between a covered metal (stick) electrode and the work. Shielding is obtained from decomposition of the electrode covering. Pressure is not used and filler metal is obtained from the electrode.
Oxy/Fuel Ratio – The relationship of cu. ft. of oxygen to cu. ft. of fuel gas mixture necessary to achieve maximum flame temperature. This ratio varies with fuel characteristics. Oxygen Bore – The orifice in the cutting nozzle through which oxygen is directed at the plate for cutting. It controls the amount of oxygen consumed during cutting. Oxygen Factor – The fuel efficiency times the oxy/fuel ratio for a given fuel to determine the multiples of oxygen needed to duplicate the performance of acetylene. The acetylene oxygen factor is 1.5.
Mottled Iron – Cast iron with a structure consisting of a mixture of free cementite, free graphite, and pearlite.
N Neutral Flame – An oxy/fuel gas flame that has characteristics neither oxidizing nor reducing.
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