Mechanical testing research on railway steels : evaluation of hardness distribution and microstructure of thermite weld and railway steels

• Main Author: Yong, Ivan Zhen Shun
• Other Authors: Pang Hock Lye, John
• Format: Final Year Project
• Language: English
• Published: 2019
• Subjects: Engineering::Mechanical engineering
• Online Access: http://hdl.handle.net/10356/78767
• Institution: Nanyang Technological University

This paper provides a robust insight of the correlation of mechanical properties (hardness and strength) to the microstructure of rail thermite weld. Several mechanical tests including the tensile tests and hardness measurements have been conducted to understand the service characteristics and performance of thermite weld and heat affected zone. The tensile properties for the rail steel with material grade of R260 and thermite weld have been investigated. Furthermore, Rockwell hardness mapping has been completed for transverse section extracted from different region along the weld (plain rail, heat-affected-zone, welding centre) and the results have been summarized as contour to study the hardness distribution. Based on the testing results, the correlation between the mechanical properties and microstructure has been investigated and discussed for rail steel of R260 and thermite weld as followed: 1) The linear regression correlation between the hardness and yield strength; 2) The Hall-Petch relation between the yield strength and the interlamellar spacing of pearlite microstructure. It concluded that: 1) For the correlation between the hardness and yield strength, it shows that the current transfer functions following ISO15653 appear to provide a better agreement with experimental data for plain rail of R260 but not suitable for thermite weld due to the high hardness which is not within the applicable range; 2) For the correlation between the microstructure and yield strength, it shows that the modified Hall-Petch relation is applicable for both plain rail of R260 and thermite weld. Upon arriving at a holistic approach, Nanyang Technological University partnered with SMRT Corp Laboratory to carry out various tests on the plain rail of R260 and thermite weld to determine the above.