The Influence Of Strong Magnetic Field And An Alloying Element On The Continuous Slow Cooling Transformation And Microstructure Of High Carbon Steel

Adjusting the alloy composition and improving the heat treatment scheme are important approaches to improve the steel material performance.The application of strong magnetic field to the material heat treatment is an emerging way of heat treatment,which have brought a significant influence to the steel material field.The aim is to study the effects of strong magnetic field and alloying element on solid-state phase transformation of high carbon steel in our present work.In this paper,two groups of high carbon steel(Free-Al&1.37A1)were designed.The heat treatment was conducted with the superconducting high magnetic field equipment JMTD-12T100 and Gleeble 1500 simulator.After heat treatment,the tested samples were analyzed by OM(optical microscopy),SEM(scanning electron microscopy),TEM(transmission electron microscopy)and XRD(X-ray diffraction),Fe-C phase diagram calculation et al.We investigated the influence of strong magnetic field and Al element on the continuous slow cooling transformation and microstructures of high carbon steels.The main results are as follows:1.Under the strong magnetic field,the driving force for transformation of ??B was enhanced,and Bs temperation was increased,as a result,the bainite transformation was promoted.For Free-Al,bainite transformation didn't happen without magnetic field,however,under 12 T strong magnetic field,lots of bainite appeared.2.Under the strong magnetic field,the eutectoid point was shifted to high carbon and high temperature side,which raised the start temperature of the transformation of A?P,the driving force for transformation was enhanced,as a result,the pearlite transformation was promoted by strong magnetic field.For 1.37A1,the amount of pearlite was just 6±3 vol%,however,under 12 T strong magnetic field,full pearlite was obtained.3.Under the strong magnetic field,the incubation period of pearlite transformation was shortened.Both the critical cooling rate of pearlite transformation and the amount of final pearlite were increased.For 1.37A1,the pearlite transformation temperature increased by strong magnetic field.During the furnace cooling,at higher temperature range,the cooling speed is faster.The incubation period was shortened by strong magnetic field,which ensure the transformation more completely.As a result,austenitie was transformed to full pearlite.4.Under the strong magnetic field,the start temperature from austenite to pearlite was raised.Pearlite was formed at higher temperature,which enhanced carbon atoms diffused more fully and thus the interlamellar spacing was increased.For 1.37A1,the interlamellar spacing increased from 100±7 nm to 112±18 nm by strong magnetic field.5.After the addition of Al elements,the eutectoid point was shifted to high temperature side(53?),which increased the driving force and thus the pearlite transformation was promoted.6.After the addition of Al elements,the critical cooling rate of pearlite transformation was increased.At the tested cooling rate(0.05?0.1?1.0 ?/s),Pearlite transformation hasn't been observed in Free-Al alloy,but for 1.37A1 alloy,austenitie was transformed to full pearlite when cooling rate lower than 0.1?/s.7.After the addition of Al,the pearlite transformation time was shortened,that is to say the transformation rate was accelerated.8.The interlamellar spacing of isothermal pearlite decreased after the addition of Al.After transformation proceeding for same time at the same temperature,the tested interlamellar spacing of pearlite in 1.37A1 alloy much smaller than which in Free-Al alloy,and the reduction was 20-30%.