研究目的:目前我国主要的几条重载铁路铺设使用了当今世界上断面最大的75 kg/m钢轨，国外重载铁 路发达的国家则大量使用美国铁路保养协会钢轨技术条件(AREMA-2004)中规定的136RE(68 kg/m)断面 的钢轨，且较为成熟。因此开展68 kg/m钢轨的试验研究，可为我国重载铁路钢轨的铺用提供更多的选择，对 发展我国重载铁路运输具有重要的意义。
研究结论:热轧钢轨室温抗拉强度为1 080 MPa,轨顶面硬度达到 300 HB;成品钢轨中的氢含量为0. 5 x10-4%，氧含量为12. 3 x 10 -4%;轨头踏面及轨角处的显微组织为片状珠光体及少量铁素体;轨底最大残余拉应 力为200.2 MPa; -20℃断裂韧性K1C为32. 5MPa?m1/2， 裂纹尖端强度因子?K=10 MPa?m1/2及13.5 MPa?m1/2时 疲劳裂纹扩展速率da/dN分别为9.55 m/Gc和31.98 m/Gc。由以上试验研究结果可知，我国68 kg/m热轧 钢轨的各项性能指标均达到了《68 kg/m钢轨暂行技术条件》的要求，可以上道试铺。
Research purposes： Now 75 kg/m rails are applied on heavy haul railway lines in domestic，but AREMA 136RE (68 kg/m) rails are applied widely and maturely on heavy haul railway lines in countries which have developed heavy haul railway network. It is necessary to investigate properties of 68 kg/m(136RE) rails in order to provide more type of rails for heavy haul railway in domestic.
Research conclusions: The ultimate tensile strength at room temperature of hot-rolled rails is 1 080 MPa, and hardness of tread is up to 300 HB. The H and O contents of finished rails are 0. 5 x 10-4% and 12. 3 x 10-4% respectively. The microstructure of tread and gauge comer is consist of pearlite and a little ferrite. The largest residual tensile stress in rails bottom is 200. 2MPa. The fracture toughness ( K1C) at -20℃is 32. 5 MPa?m1/2. When the stress intensity factor (?K) is 10 MPa?m1/2}and 13. 5 MPa?m1/2，the fatigue crack growth rate(da/dN ) is respectively 9. 55 m/Gc and 31.98 m/Gc. All results show that the 68kg/m hot-rolled rails satisfy requirements of”tentative technical specifications of 68kg/m rails"，and could be laid on heavy haul railway line.
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