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Information × Registration Number 0215U000626, 0112U002773 , R & D reports Title Optimization of structural-phase state and fatigue crack growth resistance characteristics of wheel steels to reduce the damaging of the rolling surface of high-strength railway wheels popup.stage_title Head Ostash Orest, Registration Date 20-03-2015 Organization Karpenko Physico-Mechanical Institute of the National Academy of Science of Ukraine popup.description2 It is shown that high-strength steel wheels with dispersed lamellar pearlitic structure of grade T have high wear resistance, but low fatigue crack growth resistance, which leads to a high liability to pitting and shelling of wheels tread surface. Test data based on the construction strength diagram confirm that shelling of tread surface is determined primarily by the fatigue fracture toughness ?Kfc. It is established that the wheel steel with bainite structure has high fatigue crack resistance, however, low - wear resistance. It is revealed that the increased durability of the raiway wheels on the criteria of wear resistance and shelling of tread surface can provide a wheel steel (type 65G) with bainite-martensitic structure, for which the fatigue threshold Kth is twice and fatigue fracture toughness Kfc - 1.22 times higher compared to steel of grade T. It is established that the presence of free carbon inclusions in the structure of the graphitic steel (HS) leads to a high wear resistance, however they possess not high enough strength (300...550 MPa), hardness (200...250 HB) and fracture toughness ( Kfc = 20...50 MPa m1/2). To improve these characteristics a thermo-mechanical processing of the HS is proposed. It is revealed that application of the thermo-mechanical processing by pressing (the degree of deformation 29...49% at 900…1150 0C) with cooling in air leads to an increase of the hardness to 52...54 НRC of hypoeutectoid HS, 56...58 HRC - eutectoid HS; 47...57 HRC - hypereutectoid complex alloyed HS. But it fracture toughness Kfc decreases in 1.7...4.2 times. It is shown that the mechanical characteristics of thеrmo-deformated HS substantially depend on the tempering temperature. Unlike traditional steels, where with the increasing of tempering temperature (Тtemp.) the hardness monotonously decreases, for thеrmo-deformated hypereutectoid HS at Тtemp.=100 0С the hardness at first sharply decreases (38.40 НRC). For the increase of tempering temperature from 100 to 500 0С it increases to 54…57 HRC, and with further increasing of tempering temperature to 700 0С it decreases to 34…37 HRC. Thus, at Тtemp.= 400 0С fracture toughness Kfc does not change, but at Тtemp.= 600 0С the value Kfc increases to the initial level of no thеrmo-deformated material ( Kfc = 40 MПa m1/2) at high enough hardness 38...41 HRC. Product Description popup.authors Андрейко Ігор Михайлович Віра Володимир Володимирович Горак Ігор Степанович Грибовська Вікторія Іванівна Дзера Володимир Юрійович Кулик Володимир Володимирович popup.nrat_date 2020-04-02 Close