Metals ferrous

This automatic velocity measurement method (AUTO-V) has also been suecessfijlly applied to other materials sueh as non-ferrous metals and even eeramics and plasties. The only requirement for this type of sequential velocity and thickness measurement is a certain isotropy of the material materials having anisotropie properties will lead to incorrect thickness readings due to the velocity difference in the two orthogonal directions. 

When processing municipal solid wastes, an eddy current separation unit is often used to separate aluminum and other nonferrous metals from the waste stream. This is done after removal of the ferrous metals (see Fig. 1). The eddy current separator produces an electromagnetic field through which the waste passes. The nonferrous metals produce currents having a magnetic moment that is phased to repel the moment of the appHed magnetic field. This repulsion causes the nonferrous metals to be thrown out of the process stream away from nonmetallic objects (13). 

Refractoriness (Melting Temperature). Instantaneous grinding temperatures may exceed 3500°C at the interface between an abrasive and the workpiece being ground (14). Hence melting temperature is an important property. Additionady, for alumina, sdicon carbide, B C, and many other materials, hardness decreases rapidly with increasing temperature (7). Fortunately, ferrous metals also soften with increasing temperatures and do so even more rapidly than abrasives (15). 

Typically, dry potassium nitrate is pulverized in a ball mill. Sulfur is milled into cellular charcoal to form a uniform mix in a separate ball mill. The nitrate and the sulfur—charcoal mix are screened and then loosely mixed by hand or in a tumbling machine. Magnetic separators may be used to ensure the absence of ferrous metals. The preliminary mix is transferred to an edge-mimer wheel mill with large, heavy cast iron wheels. A clearance between the pan and the wheels is required for safety purposes. The size of this gap also contributes to the density of the black powder granules obtained. Water is added to minimize dusting and improve incorporation of the nitrate into the charcoal. The milling operation requires ca 3 to 6 h. 

Because of the vast quantities of scrap steel available from automobiles and appHances, recycling of steel cans has been growing at a relatively modest rate. As of 1992 up to 30% of steel cans are returned and remelted (see Recycling, ferrous metals). 

A. E. Richards, Symposium on Ref ning Non-Ferrous Metals, Institute of Mining and Metallurgy, London, 1950, pp. 73—118. 

As can be seen in Figure 8, the proportion of world pig iron produced in the United States has decreased dramatically since 1950. Also notable is the widening gap between pig iron and steel production, indicating the increasing use of recycled iron or scrap (see Recycling, ferrous metals) and alternative iron sources such as DRI and HBI. The increased demand for scrap is reflected in scrap iron prices (Fig. 9), which in turn have spurred growth in direct reduction processes. 

Total merchant shipments of DRI and HBI in 1993 reached 5.1 x 10 t. The primary DRI exporting countries were Venezuela, Russia, Malaysia, Trinidad, and India. The price of merchant HBI in 1993 was in the range of 125 to 167/1 on a deUvered basis. Although there are expectations that the value of merchant DRI should some day stand on its own, the historic price has been tied to the price of ferrous scrap. A general mle of thumb has been that the value of merchant DRI is comparable to prime scrap (No. 1 Bundles or No. 1 Bushelings) in industrial countries, and comparable to imported shredded scrap in developing countries (see RECYCLING, FERROUS METALS). 

Air Quality Criteria forTead Supplement to the 1986 Addendum, U.S. EPA, Environmental Criteria and Assessment Office, Washington, D.C., 1990. Technical Support Document to Proposed Airborne Toxic Control Measure for Emissions of Toxic Metalsfrom Non-Ferrous Metal Melting, State of California Air Resources Board, Stationary Source Division, Sacramento, Calif., 1992. 

T. Z. REzynsH, International Conference on WeldingandFabrication of Non-Ferrous Metals,Eastbourne, Maj 2 andMaj 3, 1972, Cambridge, U.K, The Welding Institute, 1972. 

Coatings, Paints, and Pigments. Various slightly soluble molybdates, such as those of zinc, calcium, and strontium, provide long-term corrosion control as undercoatings on ferrous metals (90—92). The mechanism of action presumably involves the slow release of molybdate ion, which forms an insoluble ferric molybdate protective layer. This layer is insoluble in neutral or basic solution. A primary impetus for the use of molybdenum, generally in place of chromium, is the lower toxicity of the molybdenum compound. 

This aqueous alkaline remover is used for stripping the finish from wood or ferrous metals at a mix ratio of 30—600 g/L (0.25—5 lbs/gal). 

Fused State Baths. Sodium hydroxide and salt can be heated to a fused state in baths to allow the removal of finishes from ferrous metals. The most common use of this method is the removal of heavy concentrations of paint on conveyer parts and hangers used in production spray systems. 

The use of ammonium fluoroborate (NH BF as a catalyst for this reaction, is claimed to be advantageous, since the catalyst can be recycled and is noncorrosive to ferrous metals (16). 

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