Nowadays, rail failure in low temperature environments is a serious problem in many countries across the world. Generally, rails are often damaged due to the large amount of fluctuating stress and impact forces during operation. Rails tend to be damaged in winter when it is cold and the difference between low and high temperatures is great. In addition, the abnormal climate caused by global warming causes a rapid decline in winter temperature and the railroads in extreme regions cannot avoid rail failure at low temperatures, which is a serious problem. According to the research, 60-80% of the rails were damaged in winter from November to March, and 83-121 rails were damged between November and February with relatively low temperature conditions.
In general, different methods of heat treatment and alloying of various elements are widely used to enhance the microstructure and properties of steel. In the past, Ni and V were traditionally used to improve the low temperature properties of steel. Recently, the use of Ti and RE has also been being investigated. Therefore, research has been carried out to apply such alloying or heat treatment methods to rail steels. However, Ni, Ti, RE, etc. are resource-poor and cost-inefficient.
Jon Song Won, a researcher at the Faculty of Material Science and Technology, fabricated rails by adding barium to enhance the low temperature properties of rails and investigated the effect of barium on their microstructure and properties.
He carried out tensile, hardness and impact tests at low temperature to measure and analyze the mechanical properties of the rail steel with Ba addition. The test results showed that the tensile strength of rail steel with 0.03% Ba increased to 1 020MPa, the elongation to 8.0%, and the hardness to HB275 and impact value to 6.8J/cm2 at low temperature.
He investigated the low-temperature toughness mechanisms on the metallic structure of the samples by metal microscopy and scanning electron microscopy. At 0.025wt.% Ba, the average size of pearlite grains in the rail steel was 15μm, and grain refinement was observed in the microstructure. Changes in the size, distribution and shape of inclusions were also observed.