Study the effect of shallow cryogenic treatment on mechanical and microstructural properties of 30CrMnSiA steel heat treated in vacuum furnace and Box Type conventional air furnace.

Abstract

Heat treatment plays a major role in improving the material properties. With the addition of cryogenic treatment these properties can be further improved. In this paper heat treatment is carried out on low carbon low alloy structural steel in two different types of furnaces conventional box type air furnace and vacuum furnace along with shallow cryogenic treatment with the purpose to investigate the outcome of shallow cryogenic treatment on the material properties and to find out which type of furnace is more suitable with shallow cryogenic treatment. For this purpose, structural steel 30CrMnSiA was selected, and heat treatment was carried out in conventional box type air furnace (900°C × 40mins) and vacuum furnaces (900°C × 70mins), shallow cryogenic treatment (-75°C × 125mins) was carried out after the quenching and before tempering. For the physical properties of the material, hardness (HRC) was investigated using Brinell hardness tester HBD-62-5AP. Tensile samples were prepared as per ASTM E8/E8M and investigated using 100kN WAW-100B Electro-Hydraulic Servo Computer Control Universal Testing Machine. Impact toughness was measured by using electronic pendulum impact testing machine CBD-300 and specimens were prepared using ASTM standard E23-12c. Microstructural analysis for grain structure was carried out using Olympus DSX1000 optical microscope.