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研究目的:钢轨钢材在低温下力学性能变差,容易发生脆性破坏,这直接威胁着铁路运输的安全。随着青藏铁路等低温地区的铁路建设大规模的展开,了解钢轨钢材力学性能指标受温度的影响规律成为越来越迫切的课题,本文试验测得我国常用钢轨钢材在低温下的各项力学指标将给寒冷地区的铁路建设提供试验依据。研究方法:本文通过制造人工低温环境,在+20℃、0℃、-20℃、-40℃、-60℃五个温度点下对我国目前铁路工程中常用的60 kg/m的U71Mn和U75V两种钢轨钢材进行拉伸试验,得到这两种钢轨钢材低温下的强度和塑性指标,并根据已有研究成果对试验数据进行分析和拟和。研究结果:本文试验得到了U71Mn和U75V两种钢轨钢材抗拉强度、规定非比例延伸强度、断后伸长率和断面收缩率随温度的变化规律,计算了2种钢轨钢材的温度敏感系数,得到预测钢轨钢材低温下抗拉强度的公式。由2种钢轨钢材低温力学性能的比较,本文对低温地区铁路建设选用钢轨提出了建议。研究结论:随着温度的降低,钢轨钢材的抗拉强度和非比例延伸强度略有升高,但断后伸长率和断面收缩率下降,塑性变差。U71Mn钢材在-60℃时仍具有良好的塑性,而U75V钢材在低温下塑性明显变差,呈现出脆性破坏,所以在寒冷地区的铁路建设中宜优先选用U71Mn钢轨钢材。
Research purposes: The mechanical properties of rail steel deteriorate under low temperature and are prone to brittle failure, which directly threatens the safety of railway transportation. With the large-scale railway construction in areas with a low temperature such as the Qinghai-Tibet Railway, it is an increasingly urgent issue to understand the laws of the mechanical properties of rail steel under the influence of temperature. In this paper, the mechanical properties of the commonly used rail steel at low temperatures It will provide experimental basis for railway construction in cold area. Research methods: In this paper, by artificial low temperature environment, the temperature of +20 ℃, 0 ℃, -20 ℃, -40 ℃, -60 ℃ five points of China’s current railway engineering commonly used 60kg / m U71Mn and U75V Tensile tests of the two kinds of rail steel were carried out, the strength and plasticity index of the two kinds of rail steel at low temperature were obtained, and the experimental data were analyzed and simulated according to the existing research results. Research results: In this paper, the tensile strength of U71Mn and U75V steel rails were obtained, and the law of non-proportional extension strength, elongation at break and reduction of area with temperature were obtained. The temperature sensitivity coefficients of the two kinds of rail steel were obtained. The formula for predicting the tensile strength of rail steel at low temperature. Based on the comparison of the mechanical properties of the two kinds of rail steel at low temperature, this paper puts forward suggestions on the selection of rails for the railway construction in the low temperature area. Research conclusions: As the temperature decreases, the tensile strength and non-proportional tensile strength of rail steel slightly increase, but the elongation at break and the reduction of area decrease, the plasticity deteriorates. U71Mn steel still has good plasticity at -60 ℃. However, U75V steel obviously deteriorates at low temperature and shows brittle failure, so it is preferable to use U71Mn rail steel in the railway construction in cold regions.