Production of Sinter

The sinter strand process, which transforms finely divided iron oxide into sintered agglomerates, suitable for charging into the blast furnace, is described in section 11.1.2. 

Some steel works add small amounts of quicklime (e.g. 1 kg/t of sinter) to bind smaller particles of ore (0.5 to 2 mm) into larger agglomerates and produce stronger green pellets. This helps to increase the porosity of the bed on the sinter strand and increases the potential output per unit area [27.4]. Larger amounts of quicklime (10 to 20 kg/t), are used by some producers to increase the output of the 

The quicklime used in the sinter process should preferably be low in sulfur, high in reactivity, and milled - e.g., S less than 0.( %, reactivity greater than 

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The production process is comparatively simple, even though — of course — the respective know-how is also decisive. The equipment for the production of sintered PVC separators is suitable in size and production capacity to be operated on its own by individual, medium-sized, starter battery plants, in contrast to the far larger units required for the production of polyethylene pocket material. 

A method by which a particulate mass is pressed in a stationary die between one moving and one fixed punch. Agglomerated product of sintering. 

Extruders are also used in the production of sintered industrial parts. Of special importance is their application for the manufacture of catalyst carriers (Section 6.3.2, Figs. 6.3-20 and 6.3-21). The use of wear-resistant alloys for all parts that come in contact with the material to be extruded make the extruders suitable for the processing of highly abrasive catalysts, other chemicals, and minerals, such as molecular sieves, high-purity aluminas, and kaolin carriers. Interchangeable die plates allow the extrusion of an almost unlimited variety of sizes and shapes on the same basic machine that is then equipped with a variable-speed screw-drive to adjust retention time, pressure, and production rate. 

The quality or state of being similar. A comparable aspect. Correspondence in kind or quality. See also SIMILARITY. A method by ivhich a PARTICULATE mass is pressed in a stationary DIE betv een one moving and one fixed PUNCH. AGGLOMERATED product of SINTERING. 

Compositions for the production of sintered molded parts are composed of a metallic, ceramic, and polymer material and a compaction aid. The latter is a mixture of a poly(glycol), and a montan wax (3). 

R. Lindenau, K. Dollmeier, and V. Arnhold, Composition for the production of sintered molded parts, US Patent 7 524 352, assigned to GKNM Sinter Metals GmbH (Radevormwald, DE), April 28,2009. 

Commercial polytetrafluoroethylene (PTFE) is usually the product of sintering and has its crystallinity reduced by the introduction of branched chains. PTFE (degree of crystallinity, 93-98%) has a melting point of 620 K and exhibits a helical structure which undergoes unit cell transitions at 292 and 303 Below 292 K the conformation can be described by a helix containing I3CF2... 

Binary grades WC-Co, basically used for applications considered here, represent about a third of the total production of sintered hard metals. 

Silicon Nitride. SiUcon nitride is manufactured either as a powder as a precursor for the production of hot-pressed parts or as self-bonded, reaction-sintered, siUcon nitride parts. a-SiUcon nitride, used in the manufacture of Si N intended for hot pressing, can be obtained by nitriding Si powder in an atmosphere of H2, N2, and NH. Reaction conditions, eg, temperature, time, and atmosphere, have to be controlled closely. Special additions, such as Fe202 to the precursor material, act as catalysts for the formation of predorninately a-Si N. SiUcon nitride is ball-milled to a very fine powder and is purified by acid leaching. SiUcon nitride can be hot pressed to full density by adding 1—5% MgO. 

Annual production of powdered BN is ca 180—200 metric tons per year and its cost is 50—250/kg, depending on purity and density. The price of cubic boron nitride is similar to that of synthetic diamond bort. Hot-pressed, dense BN parts are 3—10 times more expensive than reaction-sintered parts. 

Annual production of sihcon nitride is ca 100—200 t. Utility-grade sihcon nitride costs 4—5/kg in 100- to 500-kg quantities. The reaction-sintered parts are sold for 120 to 300/kg, depending on complexity of shape. Hot-pressed, fully dense Si N parts are priced 5—10 times higher than reaction-sintered parts. 

Gumylphenol. -Cumylphenol (PGP) or 4-(1-methyl-l-phenylethyl)phenol is produced by the alkylation of phenol with a-methylstyrene under acid catalysis. a-Methylstyrene is a by-product from the production of phenol via the cumene oxidation process. The principal by-products from the production of 4-cumylphenol result from the dimerization and intramolecular alkylation of a-methylstyrene to yield substituted indanes. 4-Cumylphenol [599-64-4] is purified by either fractional distillation or crystallization from a suitable solvent. Purification by crystallization results in the easy separation of the substituted indanes from the product and yields a soHd material which is packaged in plastic or paper bags (20 kg net weight). Purification of 4-cumylphenol by fractional distillation yields a product which is almost totally free of any dicumylphenol. The molten product resulting from purification by distillation can be flaked to yield a soHd form however, the soHd form of 4-cumylphenol sinters severely over time. PGP is best stored and transported as a molten material. 

Commercial production of bayerite is relatively small and employs CO2 neutralization of caustic aluminate Hquor obtained from either Bayer or sinter processes. The product obtained is about 90% crystalline bayerite having small amounts of gibbsite, pseudoboehmite, and amorphous aluminum hydroxides. 

Other Uses. The production of finished shapes from iron powder by compacting and sintering utilizes about 100,000 t of iron powder aimuaHy copper powder (2—10 wt %) is normally added as a sintering aid. Addition of 2% tin powder or equal amounts of tin and copper powder considerably lowers the sintering temperature and time of sintering at a cost saving. The tin addition also improves dimensional control. Iron powder plus 10 wt % powdered lead—tin metal is pressed and siatered to make pistons for use ia automotive hydrauHc brake cylinders. 

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