钢轨钢材低温力学性能的试验研究

Experimental Study on the Mechanical Properties of Rail Steel at low Temperature

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： At a low temperature, the mechanical properties of rail steel get worse and brittle failures can happen more easily. This threatens the railway transportation seriously. It is necessary to find out the mechanical properties of rail steel at low temperature because there are more and more railway constructions at low temperature, such as Qinghai - Tibet railway. The study of this paper will provide a basis of the railway constructions in cold areas. Research methods： This paper carries out a tension experiment with the U71Mn and U75V 60 kg/m at ＋20℃, 0℃, -20℃, -40℃, -60℃ and gets the strength and plasticity index steels. The datum of the experiment are analyzed from the recent research results about steel. rail steels which are of the tow type of rail steels. The datum of the experiment are analyzed from the recent research results about steel. Research results： The experiment of this paper gets the tensile strength, proof strength （ non - proportional extension）, percentage elongation after fracture and percentage reduction of area of U71 Mn and U75V he echanical properties of rail steels at a series of low temperatures. Temperature sensitivity coefficients of the two type of rail steels are calculated and then the tensile strengths at low temperature ean be foreeasted. Whieh type of rail steel should be ehosen at low temperature is proposed through the eomparison of U71Mn and U75V. Research conclusions：When the temperature drops, the strength of rail steels rises and the plasticity descends. The U71Mn steel has a good plasticity at -60℃ while the U75V steel get brittle seriously, so U71Mn rail steel should be chosen when the temperature of the environment is low.