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.
