Cast iron, magnetic properties

Tellurium also improves the properties of electrical steels by aiding in the magnetic anisotropy, malleable cast iron (77), and spheroidal (graphitic) cast irons (see also Metal surface TiiEATiffiNTs). 

In addition to nickel alloys, nickel also forms an important alloying element in stainless steels and in cast irons, in both of which it confers additional corrosion resistance and improved mechanical and engineering properties, and in Fe-Ni alloys for obtaining controlled physical and magnetic properties (see Chapter 3). With non-ferrous metals nickel also forms important types of alloys, especially with copper, i.e. cupro-nickels and nickel silvers these are dealt with in Section 4.2. 

Experiment 188. — (a) Examine cast iron, wrought iron, and steel, and state their most obvious physical properties. Try the action of a magnet on each. Drop a pinch of iron powder into the Bunsen flame. Hold a piece of fine iron wire in the Bunsen flame. Describe the results and draw conclusions. 

Iron-chromium alloys, free from carbon, may be prepared from chromite by the alumino-thermic method. From a study of the cooling-and freezing-point curves it has been suggested that a compound, Cr Fe, exists, but this is questioned by Janecke, who studied the iron-chromium system by means of fusion curves and by the microscopic study of polished sections of various alloys between the limits 10 Fe 90 Cr and 90 Fe 10 Cr, and came to the conclusion that the system consists of a single eutectic which can form mixed crystals with either component. The eutectic contains 75 per cent, of chromium and melts at 1320° C. The addition of chromium to iron increases the readiness of attack by hydrochloric and sulphuric acids, but towards concentrated nitric acid the alloys are rendered passive. They remain bright in air and in water. The presence of carbon increases the resistance to acids and renders them very hard if carbon-free, they are softer than cast iron. All the alloys up to 80 per cent, chromium are magnetic. Molybdenum, titanium, vanadium, and tungsten improve the mechanical properties and increase the resistance to acids. 

Properties Steel-gray, shining, hard, ductile, somewhat malleable metal ferromagnetic, with permeability two-thirds that of iron has exceptional magnetic properties in alloys. D 8.9, mp 1493C, bp 3100C. Attacked by dilute hydrochloric and sulfuric acids, soluble in nitric acid. Corrodes readily in air. Hardness cast 124 Brinell, electrodeposited 300 Brinell. An important trace element in soils and necessary for animal nutrition. Cobalt has unusual coordinating properties, especially the trivalent ion. Noncombustible except as powder. 

Ferrous A word used to describe all metals in which the main constituent is iron. The word ferrous comes from the Latin word ferrum, meaning iron. Ferrous metals have magnetic properties. Cast iron, wrought iron and steel are all ferrous metals. 

Study of membrane extraction processes is a matter of primary importance for intensive development of separation and concentration methods of different nature substrates, especially such valuable ones as rare and scattered metals. The imique properties of rare earth metals (REM) allow using them in different realms of modem science and technology when making selective catalysts, magnets (samarium and neodymium), optical systems, luminophors, and ceramic capacitors. REMs are used in metallurgy for production of special cast iron grades, steel, and nonferrous metals alloys. REM additives increase quality of metallurgical products improve their properties, particularly shock resistance, viscosity, and corrosion resistance. Such materials are used primarily in aerospace industry. Extraction of REM from minerals is a complex process. 

---