Optimization of Tempering Process Parameters of AISI 3140 Low Alloy Steel to Conserve Furnace Energy using Tukey’s Honestly Significant Difference Test

Abstract

Quenching and Tempering of AISI 3140 alloy steel is a necessary heat treatment process to attain desired hardness and toughness. However the tempering process consumes remarkable amount of energy in furnace. One of the usual tempering processes of AISI 3140 steel is performed by heating it to a temperature of 425°C in crucible furnace and holding at that same temperature for 2 hours. Furnace energy consumption may be reduced by increasing tempering temperature to 540°C and holding for a relatively lesser duration. Therefore, 20 specimens of AISI 3140 steel are oil quenched. Few specimens are tempered at lower temperature of 425°C for 2 hours. Remaining specimens are tempered in 4 batches at higher temperature of 540°C for various holding time of 50 minutes, 40 minutes, 30 minutes and 20 minutes respectively. The heat treated specimens are subjected to Izod’s Impact test and Rockwell Hardness test. Test results are statistically analyzed using Tukey’s Honestly Significant Difference Test and it is found that impact toughness and hardness attained by tempering at 425°C for 2 hours is significantly equal to that attained at 540°C for 30 minutes. It is observed that the furnace energy consumed is decreased significantly by increasing furnace temperature and reducing holding time during tempering process while other process parameters are kept identical. Thus energy and time are conserved without compromising the vital mechanical properties by optimizing tempering process parameters.