A Study On Precipitation Behavior In Medium Manganese Steel With Different TMCP Processes

Mn content in medium manganese steel is slightly lower compared with high manganese steel. The content of austenite decreases at room temperature. This feature enables the surface easy to generate work hardening under the condition of medium strong impact. Martensite is induced under the strain.Thus shows excellent wear resistance..However,the stability of supercooled austenite variation due to the shrinking of Mn content. Study of the precipitation of manganese steel is mainly focused on the traditional heat treatment process, including quenching and tempering at different temperatures and so on.These processes are generally need to undertake secondary heating, spending a lot of energy.It is cost saving and energy saving for medium manganese wear-resistant steel to study rolling production online control technology,and it is of great significance for steel types development and industralized production.This article is mainly studied on the medium manganese steel hot rolled by Baoshan iron and steel plant.Doing different thermal simulation experiments with Gleeble-3800 thermal simulator.Determined by the various parameters of the static recrystallization to develop traditional TMCP including austenitic recrystallization zone, unrecrystallization zone and NG-TMCP including rolling on high austenitic recrystallization zone and fast-cooling.Observe micro-zone and analyse energy spectrum using Tecnai G220 field emission transmission electron microscope. Make the reasonable rolling process through the analysis of the precipitates’ size and distribution.The major experimental results are as follows:Isothermal static recrystallization curve is obtained through the stress-strain curve by the double-hit compression experiment. At the beginning of the softening rate curve appeared a significant platform at 950℃,980℃ and 1020℃.It is due to the precipitates pinning grain boundary and restrain the austenitic grain size growing up. At 1050℃ and 1100℃, no apparent platform appears, due to the precipitates less and bigger size compared to lower temperature.Tnr≈970℃ due to RTT curve. Qr= 314.58 kJmol-1, softening rate index n= 0.65475 through linear regression.The PTT curve is obstained under the condition of reduction of 20% and 50%, at 900℃,950℃,900℃,1050℃ and 1100℃, and its nose temperature is 1050℃.Insulation at 1050℃ for different time,with the extension of time, the precipitates from several nanometers to tens of nanometers.Crystal grains pinning effect is reduced, and the grain size is increased.Precipitates’size with 20% reduction in is bigger than the size of the 50% reduction.At 900℃, the size of the precipitates decreases, and precipitation amount increases.Pressing at 1200℃ and 1250℃ with reduction 20% and 50%, and insulating at 600℃,650℃ and 700℃.Insulating at 650℃ with reduction 20%, the precipitates size is minimum and the amount is most. Insulating at 650℃ with reduction 50% the precipitates size is maxmum and the amount is least. With the increase of strain rate from Is-1 up to 5s-1 the amount of precipitation decreases.