IJRET: International Journal of Research in Engineering and Technology eISSN: 2319-1163 | pISSN: 2321-7308 __________________________________________________________________________________________ Volume: 03 Issue: 04 | Apr-2014, Available @ http://www.ijret.org 169 INFLUENCE OF DEEP-CRYOGENIC TREATMENT ON THE WEAR BEHAVIOR AND MECHANICAL PROPERTIES OF MILD STEEL Mandeep Singh 1 , Harpreet Singh 2 1 Assistant Professor, Mechanical Engineering, Lovely Professional University, Phagwara, India 2 Assistant Professor, Mechanical Engineering, C.T. Group of Institution, Jalandhar, Punjab Abstract Deep Cryogenic Treatment (DCT) is now extensively used as supplementary process for the achievement of specific goals in many engineering applications like manufacturing of high precision & accurate parts, press tools, welding tips, improving wear resistance etc. In the present study DCT was applied to inter critically heat treated low carbon steel to improve their mechanical properties and wear behaviour. The specimen was held for duration of 28 hours in cryogenic processor at a temperature of -193 0 C followed by tempering at a temperature of 150 0 C for 1 hour. A comparative study between intercritical heat treated and deep cryogenic treated specimen have been carried out to show the wear behaviour at different load and speed. Also hardness test and microstructure test have been performed. The experimental results have shown an increase in wear resistance for deep cryogenic treated samples as well as for intercritical heat treated samples. Keywords— wear, mild steel, deep cryogenic treatment, micro hardness, impact, other manufacturing processes. -----------------------------------------------------------------------***------------------------------------------------------------------- 1. INTRODUCTION Steel is widely used in the various engineering application such as automotive, agricultural, constructional purposes etc. Steel generally contains 0.02–2.1% carbon content and depending upon the need of industry steel is selected for different processes. After that there are different types of heat treatment processes which used for improving its various mechanical properties by altering the microstructure of steel. Properties of heat treated specifically depend on three different phases such as heating temperature, soaking period and cooling rate. Over the past few decades, extensive interest has been shown in the effect of low-temperature treatment on the performance of tool steels [1, 2, 3]. Low-temperature treatment is generally classified as either “cold treatment” at temperatures down to about −80 C (dry ice) or “Deep Cryogenic treatment” at liquid nitrogen temperature of −196 C [5].Cryogenic treatment is not a substitute for heat treatment, as often mistaken for, but it is a supplementary process to conventional heat treatment before tempering [2, 5].Cryogenic treatment is an optimal method for reducing percent of retained austenite. Cryogenic treatment consists of heating steel up to austenite temperature, cooling it in quench environment and then immediately putting it in sub- zero centigrade degree and then tempering heat treatment. Increasing resistance to wear, reduction of internal stresses, consistency of dimensions and deposition of micro carbides in the field can be regarded as the most important privileges of using cryogenic heat treatment. The less the temperature of cryogenic environment, improvement in properties is performed with more rapidity. [4] With deep-cryogenic treatment applied immediately after quenching, residual austenite is reduced, and spots for the nucleation of -carbides created during tempering are created in martensite. Cryogenic treatments can produce not only transformation of retained austenite to martensite, but also can produce metallurgical changes within the martensite. This offers many benefits where ductility and wear resistance are desirable in hardened steels [6] Previous research studies mainly focuses on the enhancement of the properties of high speed steel, tungsten carbide, aluminum, die steel and its micro structural changes. The objective of this work was to investigate the effects of deep cryogenic treatment in conjunction with the intercritical heat treatment on the wear behavior, hardness and microstructure changes in low carbon steel. 2. EXPERIMENTAL PROCEDURE The investigations were made by using the specimen made from the flat having dimensions 50mm wide & 12 mm thick. For the suitable heat treatment, knowledge of the upper and lower critical temperature is needed. The critical temperature can be found out with the help of Andrew’s Equation Ac 1 = 723 − 10.7Mn − 16.9Ni + 29.1Si + 16.9Cr+ 290 As + 6.38W. Ac 3 = 910 − 203√C − 15.2Ni + 44.7Si+ 104V + 31.5Mo + 13.1W. First of all the specimen were intercritical heat treated in a rotary furnace at a temperature of 815 o C for about 40 minutes followed by water quenching. After that the specimen were