Low-Temperature Toughness Requirements and Test Methods for Standard Rails
- Which countries' foreign - standard steel rails have clear requirements for low - temperature toughness?
Foreign - standard steel rails in cold - region countries such as Russia, Canada, and Nordic countries have strict requirements for low - temperature toughness. The Russian GOST standard stipulates that the impact toughness of rails at - 40℃ shall not be less than 25J; the Canadian CSA standard requires that the impact toughness at - 30℃ shall be ≥30J; the Swedish SSAB standard requires that the impact toughness of rails used near the Arctic Circle shall reach more than 20J at - 50℃ to cope with extreme low - temperature environments.
- What is the relationship between the low - temperature toughness of foreign - standard steel rails and material composition?
The contents of nickel and manganese in foreign - standard steel rails have a significant impact on low - temperature toughness. Appropriate addition of nickel (1% - 2%) can reduce the brittle transition temperature of steel and improve low - temperature impact toughness. Manganese can refine grains, and when combined with micro - alloying elements such as niobium and vanadium, it can improve low - temperature toughness while ensuring strength. Harmful elements such as sulfur and phosphorus must be strictly controlled. Excessive sulfur content will form low - melting point sulfides, leading to increased low - temperature brittleness. Foreign - standard steel rails usually require sulfur content ≤0.015% and phosphorus content ≤0.025%.
- What are the testing standards for low - temperature toughness of foreign - standard steel rails?
Common testing standards include ASTM E23 in the United States, which specifies the Charpy V - notch impact test method, applicable to toughness testing from - 60℃ to room temperature; EU EN 10045 - 1 standard, which specifies the sampling position and test steps of low - temperature impact test, with the minimum test temperature up to - 196℃; Japanese JIS Z2242 standard has detailed requirements for test equipment calibration and result judgment, and is widely used in the detection of foreign - standard steel rails in Asia.
- How do the impact toughness indexes of foreign - standard steel rails change at different test temperatures?
The impact toughness of foreign - standard steel rails decreases with the decrease of temperature. Taking Canadian CSA standard rails as an example, the impact toughness is about 80J at 20℃, drops to 50J at - 10℃, and needs to be maintained above 30J at - 30℃. Swedish SSAB rails have impact toughness ≥60J at 0℃, ≥40J at - 30℃, and can still maintain more than 20J at - 50℃, reflecting their excellent low - temperature performance. For every 10℃ decrease in temperature, the impact toughness generally decreases by 10% - 15%, and the specific range varies with materials.
- What risks will foreign - standard steel rails with insufficient low - temperature toughness have in use?
Foreign - standard steel rails with insufficient low - temperature toughness are prone to brittle fracture when subjected to train impact in cold regions, especially at rail joints and welding parts. When the temperature drops sharply in winter, the internal stress of the rail is concentrated, and insufficient toughness will lead to rapid crack propagation, causing rail breakage accidents. In addition, rails with poor low - temperature toughness have reduced fatigue resistance, and their service life will be shortened by 30% - 50% under repeated loads, increasing maintenance costs and potential safety hazards.