International Journal of Innovative Technology and Exploring Engineering (IJITEE) ISSN: 2278-3075, Volume-3, Issue-5, October 2013 36 Thermo Mechanical Processing Of Hypereutectoid Steel Wire Rod in Lead Patenting S. S. Bargujer, N. M. Suri, R. M. Belokar Abstract - Lead patenting process is the most efficient way to transform hot rolled steel wire rod of different chemical composition into fine pearlitic steel. However, the optimization of various parameters of lead patenting process is critical to achieve high efficiency of transformation process in mass production of hypereutectoid steel wires. The experiment was conducted to find out the optimum range of austenitic temperature, lead bath temperature and phase transformation time. The effect of carbon percentage, size of steel wire rod and drawn strain prior-to- patenting on mechanical properties are also observed through various experiments and evaluated. KEY WORDS: Tensile strength; Torsion strength; Hypereutectoid steel; Lead patenting process. I. INTRODUCTION Lead patenting process is the most efficient process used to transform phase of hypereutectoid steel. The critical parameters of this process are austenitic temperature, Lead Bath temperature and transformation time which affect the efficiency of process. The other parameters which affect output of the lead patenting process are the quality of material and the size of material. Hypereutectoid steel wires are used where high strength, wear resistance, ductility, toughness and low cost are important. Hypereutectoid steel wires are among the strongest available bulk material with tensile strength currently above 5 GPa Wires used for bridges have strength of 1250 – 1800 MPa Wires used for cord wire of tires have strength of 2750 – 4500 MPa The springs steel wires used for major applications have strength of 1500 – 3500 MPa. The strength of steel increases with increase in carbon content and it is governed by Hall-Petch relationship. σ = σ o + K λ -1/2 , (1) Where, σ is stress σ o is frictional stress K is Hall-Petch constant λ is interlamellar spacing in pearlitic steel. The Nippon Steel Corporation, Japan [1-4] studied the effects of austenitic temperature, lead bath temperature and transformation time of hypereutectoid steel having 0.82 % carbon(C), 0.84 % Manganese (Mn) and 0.92 % C, 0.91 % Mn. The interlamellar spacing decreases with increase in carbon content. Manuscript received October, 2013. S. S. Bargujer, Ordnance Cable Factory, Chandigarh-160002, India. N. M. Suri, PEC University of Technology, Chandigarh-160012,India. R. M. Belokar, PEC University of Technology, Chandigarh-160012,India. The same has been experimentally found correct. The effect of carbon content on Hall-Petch parameter studied by W. J. Nam et al [5] and Choi & Park [6] , The effect of chromium on strength investigated by T. Tarui et al [7] , M. Munirajulu et al [8] , D.B. Park et al [9] and H. R. Song et al [10] and found that chromium reduces the interlamellar spacing of pearlite. Similarly, the effect of silicon (Si) and vanadium (V) has been investigated by K. Han et al. [11] and found that vanadium reduces the grain size of pearlite. Si & V both suppresses the formation of a network of continuous grain boundary cementite. Xu Jin-qiao et al [12] developed the model for interlamellar spacing in pearlite colony of 0.82 % C, 0.84 % Mn. Caballero [13] developed the model for interlamellar spacing in pearlite colony of 0.76 % C, 0.91 % Mn. Elawazri et al [14] carried out experiment at static condition in laboratory to provide sufficient time for austenitization and also sufficient time for full transformation of austenite into pearlite. However, in mass production of wires, practically, it is not economical and feasible to provide such long time for austenitization and transformation. The cent-percent efficiency of transformation in mass production is not feasible. So, optimization of lead patenting process is studied in this paper. It mainly deals with the optimization of following parameters in lead patenting process to obtain best mechanical properties. Effect of austenitic temp. on mechanical properties Effect of transformation temperature on mechanical properties. Effect of transformation time on mechanical properties Effect of cross sectional area on mechanical properties. Effect of composition of wire rod on mechanical properties Effect of drawn strain prior-to-patenting on mechanical properties. II. EXPERIMENTAL PROCEDURE 2.1 Material Condition and Processing Steel used in this study is hot rolled wire rods of different dia. with chemical composition mentioned in table-1. Table 1