Investigation Of Fine Grains Prepariation And Mechanical Properties Of Medium Carbone Steel During Warm Deformation

Medium carbon steel has been widely used in social production and living.But with the development of the society and the progress of science and technology,the requirements for higher strength and toughness were put forward.And the grain refinement can make the material possesses higher strength plastic combination;This requires that the steel materials have finer grain size;However,the traditional grain refinement method has been unable to meet the requirements of grain refinement.This research was carried out based on the medium carbon steel warm deformation,combined with the rolling steel process and surrounding deformation characteristic under phase transition point,ferrite grain size evolution and cementite layer dynamic spheroidizing behavior.Using SEM,TEM,EBSD,Thermal Simulation Machine,Rolling and testing analysis were carried out.The flow behavior,microstructure evolution and multi-pass deformation microstructure and properties evolution were studied.The experimental results are as follow:(1)It offers the method of deducing the friction fraction between the specimen and dies during compression.The flow stress curve was corrected by friction based on the method.Meanwhile,the effect of plastic work transforming heat on the flows tress was removed.The flow stress without effect of friction and temperature increasing caused by plastic deformation was obtained.(2)During the process of medium carbon steel warm deformation,the flow stress presents a softening feature in the process of low temperature and high-speed deformation,and presents the steady state characteristics with the high temperature and low speed deformation condition,it analysis the internal mechanism of the flow stress' different characteristics.(3)The area of unstability increase with the strain increasing and the property temperature range of 630-700??(4)The results of multi-pass plane compression show that: The fine ferrite grains could obtained by the constant temperature compression at 650 ?,the suitabletemperature rang is 720-650? for the fine and uniform microstructure during the variable temperature deformation.(5)The results of warm rolling and subsequent controlled cooling test show that:the fine ferrite grains were get and the furnace cooling could improve the comprehensive mechanical properties of the warm rolling specimens.