| In order to achieve high safety,low cost and low energy consumption,this is also the main trend in the development of the third generation of advanced automotive steel.For this purpose,different rolling and heat treatment processes were designed for the experimental steels with different Mn contents of Fe-2Mn-4Al-0.4C and Fe-10Mn-4Al-0.4C.The hot rolling test was carried out on the experimental steel,and the rolled samples were annealed at different temperatures,and the microscopy was performed by Thermo-Calc,OM,XRD,EBSD,etc.The microstructure was observed and analyzed to study the effect of Mn content and different rolling annealing processes on the microstructure and properties of the experimental steel.The experimental conclusions were as follows:The as-cast phase composition showed that 2% Mn steel was mainly ferrite and carbide,and 10% Mn steel was coarse austenite grain distributed in the ferrite matrix.With the increase of Mn content,austenite content increased and the size and morphology of the two phases changed.The mechanical properties measured in the as-cast tensile specimens did not meet the requirements of the steel itself.After hot rolling treatment,the main phase composition of the two steels did not change significantly,the grains were distributed along the rolling direction,the grain size was finer than that in the as-cast state,and the yield of the hot-rolled steel was yielded.Both the strength and the tensile strength were improved compared with the as-cast condition.The elongation was still low,mainly due to the residual stress remaining after hot rolling,which affected the relevant mechanical properties of the steel.After annealing,the optimum annealing temperature of No.1 experimental steel was 900°C,and the strong plastic product reaches the highest at 42.8GPa·%.The optimum annealing temperature of experimental steel No.2 at 700°C was the highest in the strong plastic product,is 33.8GPa·%.Figure 39;Table 7;Reference 58. |
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