JoEAM (2014) 1-8 © STM Journals 2014. All Rights Reserved Page 1 Journal of Experimental & Applied Mechanics ISSN: 2230-9845 (online), ISSN: 2321-516X (print) Volume 5, Issue 3 www.stmjournals.com Analysis of Mechanical Properties of EN 24 Steel after Austempering and Martempering Tridib Kumar Mahata* Manipal Institute of technology, Manipal, Karnataka-576104 Abstract The mechanical properties of steel decide its applicability for a particular condition. Heat treatment processes are commonly used to enhance the required properties of steel. The present work aims at experimentally investigating the effects of normalizing, austempering and timed quenching on AISI 4340 steel. The material was machined to ASTM standards and then different tests like microstructure analysis, hardness test, impact test, and were carried out after the heat treatment processes. All the tests were carried out in the mechanical workshops and laboratories under the supervision of their respective faculty, at the MIT campus, Manipal. It was found that normalized steel was least hard and while timed quenched steel was hardest. The ASTM grain size affirmed these results by displaying a similar trend. An increase in brittleness was observed with the increase in hardness, with the timed quenched specimen displaying the least impact strength. Heat treatment is necessary to obtain the required mechanical and physical properties for a material to make it suitable for fabrication. For this reason, the knowledge of heat treatment is necessary to suitably condition the material for the subsequent stages of manufacture, or in the case of semi-finished component to impart the desired mechanical and physical properties such as increased strength, toughness and wear resistance. Heat treatment is also resorted to relieve internal stresses and to soften hard metals in order to improve machinability. The outstanding advantage of steel as an engineering material is due to its versatility. Its properties can be controlled and changed at will by the heat treatment. Thus, if steel is to be formed into some intricate shape, it can be made very soft and ductile by the heat treatment, if, on the other hand, it is to resist water, it can be heat treated to a very hard, wear-resisting condition. Keywords: Austempering, martempering, tensile, steel *Author for Correspondence E-mail: INTRODUCTION Heat treatment is a combination of heating and cooling operations carried out on a metal or alloy in the solid state so as to produce a particular microstructure and hence the desired properties. The objective of heat treatment is to improve the mechanical properties like tensile strength, impact strength, to improve machinability, to improve Hardness, to modify magnetic and electrical properties, to refine the grains, to produce hard surfaces and soft interiors, to relieve internal stresses and residual stress, to overcome the effects of strain hardening and restore ductile properties. Applications on EN24 Steel: is used in components subject to high stress and with a large cross section. AISI 4340 alloy steel is mainly used in power transmission gears and shafts, aircraft landing gear and other structural parts. It is also used in heavy-duty axles, spindles, pins, studs, collets, bolts, couplings, sprockets, torsion bars, connecting rods, crow bars, conveyor parts etc. EN24 steel is a high tensile alloy steel renowned for its wear resistance properties and also where high strength properties are required. EN 24 Equivalents BS970: 1955 EN24 BS970/PD970: 1970 onwards 817M40 European 34CrNiMo6 Werkstoff No. 1.6582 US SAE (AISI) 4340