| Rail is the most important part of railway development.This experiment mainly analyzed the influence of deformation temperature,deformation amount and cooling speed on the microstructure evolution of the 75kg/m BGRE heavy load rail,the effect of different contents of Cr,Nb and RE on Cr-Nb Microalloyed Rail,the influence of different cooling rate on the quantity and morphology of inclusion in rail during heat treatment,and the influence of different pearlite lamellar spacing on the fatigue performance of rail.The experimental results can make the rail achieve low cost,high efficiency and better quality in the production process of the factory.In this paper,the 75kg/m BGRE heavy-duty rail produced by Baotou Iron and Steel Co.,and the Cr-Nb micro-alloy rail smelted on the basis of BGRE rail are taken as the research object.The rail is heat-treated in different ways by a thermal simulator,the differences of microstructure,lamellar spacing,hardness,inclusion distribution and fatigue properties of rail after different heat treatment were compared and analyzed.The heavy load rail of 75kg/m BGRE2 was heat treated by Gleeble-1500 D thermal simulation test machine,the deformation temperature was 850℃,900℃,930℃,950℃,and the deformation was 30%,50%,70%,to find out the optimum deformation temperature and deformation of BGRE2 rail and its influence on rail microstructure and performance.Then the heat treatment was carried out by means of subsection cooling with keeping the deformation temperature and deformation unchanged,and the effect of the second cooling rate on the microstructure and properties of the material was observed.The Cr-Nb microalloy rail with slightly different content of microalloy was heat-treated in the same way,and the results showed that Cr,Nb and RE contents of microalloy elements were different,which would lead to different degree of pearlite transformation and different grain size.The BGRE1 rolled rail and the Cr-Nb microalloyed rail(10382#,10385#)were treated by jet water spraying respectively,the cooling rate was controlled to3℃/s,5℃/s,8℃/s,respectively.The microstructure of the rolled unheat treated BGRE rail and the heat treated BGRE rail of Baotou Steel were compared,finding that with the increase of the cooling rate,the pearlite lamellar spacing of the rail will decrease gradually,and even reach the nanometer level,the hardness will also increase,the number of fatigue cycles will increase,and the fatigue performance will be more and more excellent.In addition,through the field emission scanning electron microscopy,it can be found that with the increase of cooling rate,the number of large size inclusions in the rail decreases and the shape tends to be smooth.Through the above experimental study,we can fully understand the microstructure evolution of BGRE heavy duty rail and Cr-Nb microalloyed rail under different heat treatment conditions,as well as the methods to reduce the number and size of inclusions and improve the properties of rail,such as hardness,fatigue,etc.It provides a scientific and reasonable theoretical basis for further improving the production of heavy rail quality and has guiding significance. |
PDF Full Text Request