Analytical Study on Metallography Done By Hogerf Struer |
Metals can be heattreated to alter the properties of strength, ductility, toughness, hardnessor resistance to corrosion. Common heat treatment processes include annealing, precipitation strengthening, quenching,and tempering,. The annealing process softens the metal by heating it and thenallowing it to cool very slowly, which gets rid of stresses in the metal andmakes the grain structure large and soft-edged so that when the metal is hit orstressed it dents or perhaps bends, rather than breaking; it is also easier tosand, grind, or cut annealed metal. Quenchingis the process of cooling a high-carbon steel very quickly after you haveheated it, thus "freezing" the steel's molecules in the very hardmartensite form, which makes the metal harder. There is a balance betweenhardness and toughness in any steel, where the harder it is, the less tough orimpact-resistant it is, and the more impact-resistant it is, the less hard itis. Tempering relieves stressesin the metal that were caused by the hardening process; tempering makes themetal less hard while making it better able to sustain impacts withoutbreaking. Often, mechanical andthermal treatments are combined in what is known as thermo-mechanicaltreatments for better properties and more efficient processing of materials.