Experimental Investigation of the Effect of Input Control Variables and Thermal Treatments on the Impact Toughness of EN-31 Steel

To meet the engineering applications, mechanical and physical properties of materials especially steels and their alloys are improved through thermal treatments. This research aimed to augment the impact toughness of EN-31 steel by picking the combinations of different levels of Charpy impact test control variables and thermal treatments built in three-level (L9) Orthogonal Arrays (OAs). For this reason, the experimental runs were conducted to examine the influence of varying V-notch angles (30°, 45° and 60°), heights of the hammer (1370 mm, 1570 mm, and 1755 mm), temperatures (-196°C, -50°C, and 28°C), and heat treatments (hardening followed by cryogenic treatment and low-temperature tempering - HCTLTT, hardening followed by cryogenic treatment and medium-temperature tempering - HCTMTT, and hardening followed by cryogenic treatment and high-temperature tempering - HCTHTT) on the impact toughness of EN-31 Steel specimens. Several patterns of thermal treatment sequences were executed with an aim to modify the material properties. Cryogenic treatment (CT) was conducted through a cryocan at 77K. The hardness of specimens were measured by employing a Brinell hardness tester. The results reported that height of the hammer and thermal treatments enhanced the toughness and hardness of the specimens most significantly.