Review on interlamellar spacing and spheroidization rate for hypoeutectoid steel and hypereutectoid steel

• Main Author: Arjun Dev Pandey.
• Other Authors: Oh Joo Tien
• Format: Final Year Project
• Language: English
• Published: 2009
• Subjects: DRNTU::Engineering::Materials::Metallic materials
• Online Access: http://hdl.handle.net/10356/15451
• Institution: Nanyang Technological University

This Final Year Project shows how the rate of spheroidization is dependent on the thickness of the pearlite layers or lamellar. When pearlite microstructure is subjected to an appropriate temperature for a prolong period of time, spheroidization occurs. The pearlite structure breaks down into cementite globules or coalesces into spheroids in a ferrite matrix. This project was carried out on hypoeutectoid steel and hypereutectoid steel over varying duration of heat treatment time. After each heat treatment, specimens were subjected to uniform metallography procedures. Specimens’ surfaces were polished and etched to reveal the microstructure characteristics of the specimens. The distribution of thickness or inter-lamellar spacing of pearlite is measured. The relationship between increasing heat treatment time at a constant temperature below the eutectoid temperature and interlamellar spacing distance is studied. It is observed that spacing distance increases, initially, for hypereutectoid specimen but decreases for hypoeutectoid specimens. Analysis on the relationship between interlamellar spacing and rate of spheroidization was carried out. It is observed in this experiment that decreasing interlamellar spacing distance for hypoeutectoid steel increases the rate of spheroidization. The spheroidization process begins much earlier for hypoeutectoid steel. For hypereutectoid steel, it is observed that coarse pearlite appears with longer heat treatment time, hence, reducing spheroidization rate.