The test provides numerical results to quantify the hardness of a material, which is expressed by the Brinell hardness number – HB. For softer materials, a smaller force is used for harder materials, a tungsten carbide ball is substituted for the steel ball. The load is maintained constant for a specified time (between 10 and 30 s). The typical test uses a 10 mm (0.39 in) diameter hardened steel ball as an indenter with a 3,000 kgf (29.42 kN 6,614 lbf) force. In Brinell tests, a hard, spherical indenter is forced under a specific load into the surface of the metal to be tested. Hardness is important from an engineering standpoint because resistance to wear by either friction or erosion by steam, oil, and water generally increases with hardness.īrinell hardness test is one of indentation hardness tests, that has been developed for hardness testing. Hardness is probably the most poorly defined material property because it may indicate resistance to scratching, resistance to abrasion, resistance to indentation or even resistance to shaping or localized plastic deformation. In materials science, hardness is the ability to withstand surface indentation ( localized plastic deformation) and scratching. By adding chromium to steel, its resistance to corrosion can be enhanced, creating stainless steel, while adding silicon will alter its electrical characteristics, producing silicon steel. The principal disadvantage of many ferrous alloys is their susceptibility to corrosion. Ferrous alloys are extremely versatile, in that they may be tailored to have a wide range of mechanical and physical properties.Metallic iron and steel alloys may be produced using relatively economical extraction, refining, alloying, and fabrication techniques.Iron containing compounds exist in abundant quantities within the Earth’s crust.Their widespread use is accounted for by following factors: Due to its very-high strength, but still substantial toughness, and its ability to be greatly altered by heat treatment, steel is one of the most useful and common ferrous alloy in modern use. Adding a small amount of non-metallic carbon to iron trades its great ductility for the greater strength. Steels consist of iron (Fe) alloyed with carbon (C) (about 0.1% to 1%, depending on type). According ot AISI classification, carbon steel is broken down into four classes based on carbon content. The mechanical properties are sensitive to the content of carbon, which is normally less than 1.0 wt%. There are thousands of alloys that have different compositions and/or heat treatments. Steels are iron–carbon alloys that may contain appreciable concentrations of other alloying elements. Source: Läpple, Volker – Wärmebehandlung des Stahls Grundlagen. The percentage of carbon determines the type of the ferrous alloy: iron, steel or cast iron. The percentage of carbon present and the temperature define the phase of the iron carbon alloy and therefore its physical characteristics and mechanical properties. In the figure, there is the iron–iron carbide (Fe–Fe3C) phase diagram.
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