How to choose rail materials in a cold climate

The winter climate in the northern country is cold, and the minimum temperature in winter in some areas is close to -40 ℃. The railway rail in these areas has to work at low temperatures for a long time. In recent years, railway construction in cold areas has been carried out on a large scale, such as the Qinghai-Tibet Railway Project, where the railways in some sections are laid in the alpine and permafrost areas, and the steel rails are in low-temperature service for many years. The low temperature further increases the brittleness of the rail steel and its welds, and the tendency of brittle fracture increases directly affects the safety of railway transportation.

rail materials in cold climate

When laying railways in cold areas, it is necessary to understand the mechanical properties of rail steel at low temperatures, but there is still a lack of data in this area in China. Research on the mechanical properties of rail steel at low temperatures will provide experimental evidence for railway construction in cold regions. A series of low-temperature tensile tests were carried out on 60kg/m u71Mn and u75V rails commonly used in engineering construction. By creating an artificial low-temperature environment, two kinds of rail steel, 60kg/m u7lMn and u75v commonly used in railway engineering in my country, are drawn at five temperature points of +20 ℃, 0 ℃, -20 ℃, -40 ℃, and -60 ℃. The tensile test was carried out to obtain the strength and plasticity indexes of the two rail sheets of steel at low temperatures, and the test data were analyzed and fitted according to the existing research results. The mechanical properties of steel vary with temperature. From normal temperature ( 20 ℃ ), with the decrease in temperature, the tensile strength, yield strength, and elastic modulus of steel increase, while the plasticity of steel decreases, and the values of elongation and area shrinkage decrease. When the temperature is lowered to a certain level, the toughness of the steel decreases sharply, and within a small temperature range, the failure mode of the steel changes from ductile failure to brittle failure.

Research results: In this paper, the tensile strength of u71Mn and u75v two kinds of rail steel have been obtained. The non-proportional elongation strength after fracture elongation and area shrinkage rate change with temperature, the temperature sensitivity coefficients of the two kinds of rail steels are calculated, and the predicted rails are obtained. The formula for tensile strength of steel at low temperatures. Based on the comparison of low-temperature mechanical properties of two kinds of rail steel, this paper puts forward suggestions on the selection of rails for railway construction in low-temperature areas. Research conclusion: With the decrease in temperature, the tensile strength and non-proportional tensile strength of rail steel increased slightly, but the elongation after fracture and the cashmere rate decreased, and the plasticity deteriorated. U71Mn steel still has good plasticity at -60 ℃, while U75V steel has obvious poor plasticity at low temperatures, showing brittle failure, so U7 Mn rail steel should be preferred in railway construction in cold regions.