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Unformatted text preview: d 11:16 PM Page 1 21/08/2009 EFFECT of THE INDIVIDUAL ALLOYING ELEMENT ON THE MATERIAL PROPERTIES By : Farid Moch. Zamil 2. Special Alloying elements : (a). Aluminium ( Al ) 0 2.0 % (2 %) (Trace element). Strong de oxidising and de nitriding element (NMI Al2O3), diminishes sisceptibility to ageing by bonding with N ; grain refinement in fine grain construction steels. Improvement of resistance to scaling in heat resistant steel. Nitirde forms in nitrising steels ; long term magnetic materials (Fe ; Al ; Ni ; Co Alloys). (b). Boron ( B ) 0.01 % (4 %) (Trace element). As an additional element for Austenitic creep resisting steels and high temperature tensile strength and creep rupture properties ; improved through hardening capabilities. Steel with 1 4% B used as a safety requirement for nuclear reactors have a lesser corrosion resistance in 18/8 Cr Ni Steels. (c). Chromium ( Cr ) 0 - 30 % (Important Alloying element). Increases the tensile properties, limits the critical cooling rate dramatically and thus increases the depth of harderning (Oil and Air Cooling). Diminishes impact strength ; Forms Carbide and therefore used in high speed steels, increases edge holding properties, wear resistance, heat resistance and resistance to scaling. More than 12% Cr has an inertia effect, i.e limits Corrosion. < 1.0 % Cr in unalloyed tool steels. < 6.0 % Cr in Highly Contruction tensile steels (i.e. heat treatable steels). > 13 % Cr in Corrosion resistant and ledeburite tool steels (magnetic). > 18 % Cr with > 8 % Ni in corrosion resistant steels (non magnetic). (d). Calsium( Ca ) (trace element). Good de oxidation medium, generally in conjunction with Si, form easily polishable NMI. (e). Cobalt( Co ) 0 25 %(Alloying element). Mostly used in conjunction with other alloying elements ; increase the critical cooling rate inhibits grain growth. Co in conjuntion with Cr, Mo, T and V, increases high temperature resistance properties in high-speed steels and high temperature resistant alloys. Co is used...
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