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ASTM B243-2019 pdf free download

ASTM B243-2019 pdf free download.Standard Terminology of Powder Metallurgy
3. Terminology
3.1 Definitions: acicular powder, n—needle-shaped particles. activated sintering, n—a sintering process during which the rate of sintering is increased, for example, by addition of a substance to the powder or by changing sintering conditions. agglomerate, n—several particles adhering together. air classification, n—the separation of powder into particle size fractions by means of an air stream of controlled velocity. angle ofrepose, n—the basal angle ofa pile formed by powder when freely poured under specified conditions onto a hori- zontal surface. apparent density, n—the mass of a unit volume of powder, usually expressed as grams per cubic centimetre, determined by a specified method. apparent hardness, n—the hardness of a PM material (includ- ing the effects of porosity), measured using macroindenta- tion hardness equipment. D ISCUSSION —See general description of production, properties, and uses of sintered metal powder bearings and structural parts, paragraph on density and mechanical properties, information on hardness measurement, Volume 02.05. 2 apparent porosity, n—specific to cemented carbides, micro- structural features that appear to be pores in a properly prepared, unetched surface; these features may result from uncombined carbon or nonmetallic inclusions as well as actual porosity. atomization, n—the dispersion ofa molten metal into particles by a rapidly moving gas or liquid stream or by mechanical means.atomized metal powder, n—metal powder produced by the dispersion of a molten metal by a rapidly moving gas, or liquid stream, or by mechanical dispersion binder, n—a cementing medium; either a material added to the powder to increase the green strength of the compact, and which is expelled during sintering; or a material (usually of relatively lower melting point) added to a powder mixture for the specific purpose of cementing together powder particles which alone would not sinter into a strong body. binder (MIM), n—a mixture ofpolymers or other materials, or both, that when combined with metal powders enables the mixture to flow during the injection molding process. The binder imparts green strength to the MIM part and allows it to retain its molded shape. binder removal, n—the chemical or thermal extraction of binder from a compact. Synonymous with debinding. blank, n—a pressed, presintered, or fully sintered compact, usually in the unfinished condition, requiring cutting, machining, or some other operation to give it its final shape.blending, n—the thorough intermingling of powders of the same nominal composition (not to be confused with mixing). blister crack, n—typically small defects (star burst) over or around a bump or blister. D ISCUSSION —These may occur during sintering as a result of rapid outgassing of the lubricant. The rapid outgassing may be caused by the specified amount of lubricant being subjected to an excessive heating rate. The defects may also be caused by “concentrated balls” of lubricant, or moisture. During the sintering of the copper base PM parts, hydrogen gas from the furnace atmosphere can diffuse into the compact and react with residual oxygen, producing steam that can form blisters and cracks. In that industry, this is also called embrittlement, and is not to be confused with the hydrogen embrittlement of high strength steel. blistered compact, n—a sintered object characterized by having blisters or eruptions on the surface. D ISCUSSION —In ferrous materials, this effect is often caused by in situ gas decomposition and soot formation that forces particles apart and causes the compact to blister. bridging, n—the formation of arched cavities in a powder mass. briquet, n—see compact. brown part, n—an MIM part that has had a majority of the binder (first stage) removed. Synonymous with debound part. bulk density, n—the mass per unit volume of a powder under nonstandard conditions, for example, in a shipping container (not to be confused with apparent density).

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