lack of fusion (LOF)
A condition in a welded joint in which fusion is less than complete.
lack of penetration (LOP)
A condition in a welded joint in which joint penetration is less than that specified.
Metal receptacle frequently lined with refractories used for transporting and pouring molten metal.
Degassing processes for steel carried out in a ladle.
Occurs in the base metal adjacent to weldments due to high through-thickness strains introduced by weld metal shrinkage in highly restrained joints. Tearing occurs by decohesion and linking along the working direction of the base metal; cracks usually run roughly parallel to the fusion line and are steplike in appearance.
(1) A composite metal, usually in the form of flat sheets, composed of two or more metal layers so bonded that the composite metal forms a structural member. (2) To form a metallic product of two or more bonded layers.
(1) A type of discontinuity with separation or weakness generally aligned parallel to the worked surface of a metal. May be the result of pipe, blisters, seams, inclusions, or segregation elongated and made directional by working. Laminations may also occur in powder metallurgy compacts. (2) In electrical products such as motors, a blanked piece of electrical sheet that is stacked up with several other identical pieces to make a stator or rotor.
(1) A press operation in which a single-line cut is made in strip stock without producing a detached slug. Chiefly used to free metal for forming, or to cut partial contours for blanked parts, particularly in progressive dies. (2) A piercing (cutting) process carried out by metal powder cutting or oxyfuel gas cutting.
(1) For profile-sharpened milling cutters, the relieved portion immediately behind the cutting edge. (2) For reamers, drills, and taps, the solid section between the flutes. (3) On punches, the portion adjacent to the nose that is parallel to the axis and of maximum diameter.
A surface imperfection, with the appearance of a seam, caused by hot metal, fins, or sharp corners being folded over and then being rolled or forged into the surface but without being welded.
A finishing operation using fine abrasive grits loaded into a lapping material such as cast iron. Lapping provides major refinements in the workpiece including extreme accuracy of dimension, correction of minor imperfections of shape, refinement of surface finish, and close fit between mating surfaces.
A device that produces a concentrated coherent light beam by stimulating electronic or molecular transitions to lower energy levels. Laser is an acronym for light amplification by stimulated emission of radiation.
See laser surface processing.
laser beam cutting
A thermal cutting process that severs materials by melting or vaporizing them with the heat obtained from a laser beam, with or without the application of gas jets to augment the removal of material.
laser beam machining
Use of a highly focused monofrequency collimated beam of light to melt or sublime material at the point of impingement on a workpiece.
laser beam welding (LBW)
A welding process that produces coalescence of materials with the heat obtained from the application of a concentrated coherent light beam impinging upon the joint.
A surface-hardening process that uses a laser to quickly heat a surface. Heat conduction into the interior of the part will quickly cool the surface, leaving a shallow martensitic layer.
laser surface processing
The use of lasers with continuous outputs of 0.5 to 10 kW to modify the metallurgical structure of a surface and to tailor the surface properties without adversely affecting the bulk properties. The surface modification can take the following three forms. The first is transformation hardening in which a surface is heated so that thermal diffusion and solid-state transformations can take place. The second is surface melting, which results in a refinement of the structure due to the rapid quenching from the melt. The third is surface (laser) alloying, in which alloying elements are added to the melt pool to change the composition of the surface. The novel structures produced by laser surface melting and alloying can exhibit improved electrochemical and tribological behavior.
Thermal energy absorbed or released when a substance undergoes a phase change.
An operation in which the product is extruded sideways through an orifice in the container wall.
Martensite formed partly in steels containing less than approximately 1.0% C and solely in steels containing less than approximately 0.5% C as parallel arrays of packets of lath-shape units 0.1 to 0.3 m thick.
See lattice parameter.
The length of any side of a unit cell of a given crystal structure. The term is also used for the fractional coordinates x, y, and z of lattice points when these are variable.
(1) A channel for transporting molten metal. (2) A box conduit conveying particles suspended in water.
Direction of predominant surface pattern remaining after cutting, grinding, lapping, or other processing.
(1) The axial advance of a helix in one complete turn. (2) The slight bevel at the outer end of a face cutting edge of a face mill.
In cutting tools, the helix angle of the flutes.
A misnomer for welding of lead.
A nondestructive test for determining the escape or entry of liquids or gases from pressurized or into evacuated components or systems intended to hold these liquids. Leak testing systems, which employ a variety of gas detectors, are used for locating (detecting and pinpointing) leaks, determining the rate of leakage from one leak or from a system, or monitoring for leakage.
The eutectic of the iron-carbon system, the constituents of which are austenite and cementite. The austenite decomposes into ferrite and cementite on cooling below Ar1, the temperature at which transformation of austenite to ferrite or ferrite plus cementite is completed during cooling.
left-hand cutting tool
A cutter all of whose flutes twist away in a counterclockwise direction when viewed from either end.
Slow cooling rates associated with a hot vapor blanket that surrounds a part being quenched in a liquid medium such as water. The gaseous vapor envelope acts as an insulator, thus slowing the cooling rate.
Lines on sheet or strip running transverse to the direction of roller leveling. These lines may be seen upon stoning or light sanding after leveling (but before drawing) and can usually be removed by moderate stretching.
Flattening of rolled sheet, strip, or plate by reducing or eliminating distortions. See also stretcher leveling and roller leveling.
(1) Separation of fine powder from coarser material by forming a suspension of the fine material in a liquid. (2) A means of classifying a material as to particle size by the rate of settling from a suspension.
An induction melting process in which the metal being melted is suspended by the electromagnetic field and is not in contact with a container.
An imprecise term, applied to drawn products such as wire and tubing, that indicates a lesser amount of cold reduction than for hard drawn products.
lightly coated electrode
A filler-metal electrode used in arc welding, consisting of a metal wire with a light coating, usually of metal oxides and silicates, applied subsequent to the drawing operation primarily for stabilizing the arc. Contrast with covered electrode.
One of the low-density metals, such as aluminum, magnesium, titanium, beryllium, or their alloys.
limiting current density
The maximum current density that can be used to obtain a desired electrode reaction without undue interference such as from polarization.
limiting dome height (LDH) test
A mechanical test, usually performed unlubricated on sheet metal, that simulates the fracture conditions in a practical press-forming operation.
(1) Deviations from perfect alignment of parallel arms of a columnar dendrite as a result of interdendritic shrinkage during solidification from a liquid. This type of deviation may vary in orientation from a few minutes to as much as two degrees of arc. (2) A type of substructure consisting of elongated subgrains.
linear elastic fracture mechanics
A method of fracture analysis that can determine the stress (or load) required to induce fracture instability in a structure containing a cracklike flaw of known size and shape. See also fracture mechanics and stress-intensity factor.
linear (tensile or compressive) strain
The change per unit length due to force in an original linear dimension. An increase in length is considered positive.
(1) The slab of coating metal that is placed on the core alloy and is subsequently rolled down to clad sheet as a composite. (2) In extrusion, a removable alloy steel cylindrical chamber, having an outside longitudinal taper firmly positioned in the container or main body of the press, into which the billet is placed for extrusion.
Simultaneous reaming of coaxial holes in various sections of a workpiece with a reamer having cutting faces or piloted surfaces with the desired alignment.
Ladle in which the molten metal is poured over a lip, much as water is poured out of a bucket.
(1) The separation of a low-melting constituent of an alloy from the remaining constituents, usually apparent in alloys having a wide melting range. (2) Partial melting of an alloy, usually as a result of coring or other compositional heterogeneities.
The lowest temperature at which partial melting can occur in an alloy that exhibits the greatest possible degree of segregation.
Surface hardening of steel by immersion into a molten bath consisting of cyanides and other salts.
Producing a finely polished finish by directing an air-ejected chemical emulsion containing fine abrasives against the surface to be finished.
liquid metal embrittlement (LME)
Catastrophic brittle failure of a normally ductile metal when in contact with a liquid metal and subsequently stressed in tension. See also solid metal embrittlement.
A method of surface hardening in which molten nitrogen-bearing, fused-salt baths containing both cyanides and cyanates are exposed to parts at subcritical temperatures.
A nitrocarburizing process (where both carbon and nitrogen are absorbed into the surface) utilizing molten liquid salt baths below the lower critical temperature.
liquid penetrant inspection
A type of nondestructive inspection that locates discontinuities that are open to the surface of a metal by first allowing a penetrating dye or fluorescent liquid to infiltrate the discontinuity, removing the excess penetrant, and then applying a developing agent that causes the penetrant to seep back out of the discontinuity and register as an indication. Liquid penetrant inspection is suitable for both ferrous and nonferrous materials, but is limited to the detection of open surface discontinuities in nonporous solids.
liquid phase sintering
Sintering of a compact or loose powder aggregate under conditions where a liquid phase is present during part of the sintering cycle.
The reduction in volume of liquid metal as it cools to the liquidus.
(1) The lowest temperature at which a metal or an alloy is completely liquid.(2) In a phase diagram, the locus of points representing the temperatures at which the various compositions in the system begin to freeze on cooling or finish melting on heating. See also solidus.
(1) In cutting, building up of a cutting tool back of the cutting edge by undesired adherence of material removed from the work. (2) In grinding, filling the pores of a grinding wheel with material from the work, usually resulting in a decrease in production and quality of finish. (3) In powder metallurgy, filling of the die cavity with powder.
A molding material consisting of sand, silt, and clay, used over brickwork or other structural backup material for making massive castings, usually of iron or steel.
Corrosion due to the action of "local cells," that is, galvanic cells resulting from inhomogeneities between adjacent areas on a metal surface exposed to an electrolyte.
A galvanic cell resulting from inhomogeneities between areas on a metal surface in an electrolyte. The inhomogeneities may be of physical or chemical nature in either the metal or its environment.
local current density
Current density at a point or on a small area.
Corrosion at discrete sites, for example, crevice corrosion, pitting, and stress-corrosion cracking.
Precipitation from a supersaturated solid solution similar to continuous precipitation , except that the precipitate particles form at preferred locations, such as along slip planes, grain boundaries, or incoherent twin boundaries.
In forging, a condition in which the flash line is not entirely in one plane. Where two or more plane changes occur, it is called compound lock. Where a lock is placed in the die to compensate for die shift caused by a steep lock, it is called a counterlock.
That direction parallel to the direction of maximum elongation in a worked material. See also normal direction and transverse direction.
A magnetic field that extends within a magnetized part from one or more poles to one or more other poles and that is completed through a path external to the part.
longitudinal resistance seam welding
The making of a resistance seam weld in a direction essentially parallel to the throat depth of a resistance welding machine.
See transverse direction.
An arrangement of hot rolling stands such that a hot bar, while being discharged from one stand, is fed into a second stand in the opposite direction.
Refers to an area in a formed panel that is not stiff enough to hold its shape, may be confused with oil canning.
lost foam casting
An expendable pattern process in which an expandable polystyrene pattern surrounded by the unbonded sand, is vaporized during pouring of the molten metal.
lost wax process
An investment casting process in which a wax pattern is used.
(1) A specific amount of material produced at one time using one process and constant conditions of manufacture, and offered for sale as a unit quantity. (2) A quantity of material that is thought to be uniform in one or more stated properties such as isotopic, chemical, or physical characteristics. (3) A quantity of bulk material of similar composition whose properties are under study. Compare with batch.
A category of ferrous materials that exhibit mechanical properties superior to plain carbon steels as the result of additions of such alloying elements as nickel, chromium, and molybdenum. Total alloy content can range from 2.07% up to levels just below that of stainless steels, which contain a minimum of 10% Cr.
Fatigue that occurs at relatively small numbers of cycles (<104 cycles). Low-cycle fatigue may be accompanied by some plastic, or permanent, deformation. Compare with high-cycle fatigue.
The part of a pneumatic or hydraulic press that is moving in a lower cylinder and transmits pressure to the lower punch.
A covered arc welding electrode that provides an atmosphere around the arc and molten weld metal that is low in hydrogen.
Deoxidized copper with residual phosphorus present in amounts (usually 0.004 to 0.012%) generally too small to decrease appreciably the electrical conductivity of the copper.
(1) Any substance interposed between two surfaces in relative motion for the purpose of reducing the friction or wear between them. (2) A material applied to dies, molds, plungers, or workpieces that promotes the flow of metal, reduces friction and wear, and aids in the release of the finished part.
(1) The reduction of frictional resistance and wear, or other forms of surface deterioration, between two load-bearing surfaces by the application of a lubricant. (2) Mixing or incorporating a lubricant with a powder to facilitate compacting and ejecting of the compact from the die cavity; also, applying a lubricant to die walls and/or punch surfaces.
Elongated surface markings or depressions in sheet metal, often visible with the unaided eye, caused by discontinuous (inhomogeneous) yielding. Also known as Lüders bands, Hartmann lines, Piobert lines, or stretcher strains.
A bright, as-rolled finish, produced on ground metal rolls; it is suitable for decorative painting or plating, but usually must undergo additional surface preparation after forming.