The damage mode of U75V rail steel in application is determined by its rolling wear behavior. In this paper, the pearlite microstructure of U75V steel is characterized to investigate the relationship between wear and fatigue behavior. The results show that, with decreasing of pearlite lamellar spacing, the wear resistance of the steel increases and the contact fatigue resistance decreases. The spacing decreasing causes the change of the wear mechanism from abrasive wear to adhesive wear, as well as the damage mode from wear damage to fatigue damage. The smaller the pearlite lamellar spacing is, the stronger the deformation of the cementite lamellar is. The thin cementite lamellar is hardly broken in the rolling friction to pile up a large number of dislocations in the ferrite matrix and the work hardening degree was improved. So, the plastic deformation layer is difficult to remove, and fatigue cracks are easy to initiate and extend to the interior of the material.
The lightweight of the steel structure can be achieved by the high strength and high toughness of steel. In this paper, the composition design and optimal manufacturing process of the experimental steel were investigated. The fine and uniform microstructure of tempered sorbite can be obtained under the conditions of TMCP (Thermo Mechanical Control Process), 920 °C quenching, and 650 °C tempering for the steel by micro-alloying with Nb, V, and Ti. The steel has properties as follows: yield strength of 1015 MPa, tensile strength of 1076 MPa, elongation of 14.5%, and -40 °C AKV 81 J. The parameters of quenching and tempering heat treatment have a decisive influence on the size and distribution of ferrite grains and precipitates of tempered sorbite.
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