Effect Of Nb And V Alloying On The Structure And Properties Of Cast Iron Rolls

Low-cost,highly adaptable centrifugal cast high-chromium cast iron and high-nickel-chromium infinite chilled cast iron rolls have always been the first choice rolls for the front and back work rolls in the finishing zone of the hot strip continuous rolling mill.With the fierce competition in the steel industry,higher requirements have been put forward on the performance of work rolls in the finishing rolling zone.Coarse eutectic carbides in the solidified structure of cast iron are the most important factor affecting the service performance of rolls.Therefore,it is of great significance to refine the solidification structure of high chromium cast iron and high nickel chromium infinitely chilled cast iron rolls,improve the performance of work rolls in finishing rolling area,and extend the on Mill time of rolls,so as to improve the rolling efficiency and reduce the production cost of iron and steel metallurgy industry.This article uses induction melting furnace,metallography,X-ray diffractometer,scanning electron microscope and energy spectrometer,hardness tester,and thermo-calc software,etc,based on the composition of high-chromium cast iron and high-nickel-chromium infinite chilled cast iron rolls,which are the most widely used in hot continuous rolling finishing rolling stands,have studied the effects of microalloying elements Nb and V on the solidification structure of high chromium cast iron rolls and Nb on the solidification structure of high nickel chromium infinite chilled cast iron rolls,and microalloying elements on high chromium cast iron and high nickel the influence of chromium infinite chilled cast iron on the structure and properties after heat treatment provides experimental data for the study of further improving the properties of cast iron rolls.The as-cast structure of high chromium cast iron is based on martensite and retained austenite,and a large number of coarse M₇C₃ eutectic carbides are distributed around it.The microalloying elements Nb and V are added to high chromium cast iron,MC type carbides are precipitated in the solidification structure,and the eutectic structure and eutectic carbides are refined.The eutectic M₇C₃ carbides transform from long strips to islands;with the increase of Nb and V addition,the number of MC type carbides increases,and the number of eutectic structure and eutectic carbides decreases.The hardness of high chromium cast iron first increases and then decreases with the increase of Nb and V additions.The hardness of microalloyed high chromium cast iron increases with the increase of quenching temperature,and the maximum hardness can be obtained when tempered at 470℃.From the hardness results,the best addition amount of Nb in high chromium cast iron is 0.5%,and the best addition amount of V is 1.5%.The as-cast structure of high nickel-chromium infinite chilled cast iron is based on martensite and retained austenite,and a large number of coarse M₃C carbides are distributed around it.The microalloying element Nb is added to the high nickel-chromium infinite chilled cast iron,and Nb C is precipitated in the solidification structure,which refines the eutectic structure and eutectic carbide;the hardness of the high nickel-chromium infinite chilled cast iron increases with the increase of Nb addition,and the maximum hardness can be obtained when tempered at 500°C.From the hardness results,the best addition amount of Nb in high nickel-chromium infinite chilled cast iron is 0.5%.