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This is the most common state for finished articles such as tools and machine parts. In contrast, the same steel composition in annealed state is softer, as required for forming and machining. Depending on the temperature and composition of the steel, it can be hardened or softened. To make steel harder, it must be heated to very high temperatures.
The work-hardened steel bar has a large enough number of dislocations that the strain field interaction prevents all plastic deformation. Subsequent deformation requires a stress that varies linearly with the strain observed, the slope of the graph of stress vs. strain is the modulus of elasticity, as usual.
Steel which has a carbon content greater than ~0.25% can be direct-hardened by heating to around 600°C, and then quickly cooling, often by immersing in water or oil, known as quenching. Hardening is desirable for metal components because it gives increased strength and wear resistance, the tradeoff being that hardened steel is generally more ...
The quenched-steel is first sanded or polished, to remove any residual oxidation, revealing the bare metal underneath. The steel is then heated in a localized area, such as the hammering-end of a chisel or the handle-end of an axe. The smith then carefully gauges the temperature by watching the tempering colors of the steel. As the steel is ...
The use of diamonds in this manner allows the file to be used effectively against extremely hard materials, such as stone, glass or very hard metals such as hardened steel or carbide against which a standard steel file is ineffective. Diamond files are also the only type that may be used with a back-and-forth motion without damaging the file.
Vickers test scheme An indentation left in case-hardened steel after a Vickers hardness test. The hardness of a material is directly related to its incompressibility, elasticity and resistance to change in shape. A superhard material has high shear modulus, high bulk modulus, and does not deform plastically. Ideally superhard materials should ...
Induction heating is a non contact heating process which uses the principle of electromagnetic induction to produce heat inside the surface layer of a work-piece. By placing a conductive material into a strong alternating magnetic field, electric current can be made to flow in the material thereby creating heat due to the I 2 R losses in the material.
Very hard steel (e.g. chisels, quality knife blades): HRC 55–66 (Hardened High Speed Carbon and Tool Steels such as M2, W2, O1, CPM-M4, and D2, as well as many of the newer powder metallurgy Stainless Steels such as CPM-S30V, CPM-154, ZDP-189. There are alloys that hold a HRC upwards 68-70, such as the Hitachi developed HAP72.