Evolution of inclusions in the production process of Ca-treated improved H11 steel
In order to study the evolution law of inclusions during the production process of improved H11 steel,the type,morphology and size of inclusions were statistically analysed by scanning electron microscope(SEM)and en-ergy spectrum analyser(EDS).The results showed that the Al2O3 and MgO-Al2O3 were modified toxxCaO-yAl2O3-zMgO by adding silica-calcium powder during LF refining,and low-melting-point xCaO-yAl2O3(-MgO)domi-nated after VD.While the low melting point calcium aluminates were uplifted during casting,undenatured MgO-Al2 O3 remained in the steel,and the type of inclusions remained unchanged in the finished product after forging.The oxygen and aluminium content gradually decreased during the refining process,while the size of inclusions was also gradually reduced,and the average size of inclusions after forging was 3.2 um.According to the experimental results and the thermodynamic equilibrium curve of calcium-aluminate generation,the composition of calcium-alu-minate at the end of the LF refining was between 12CaO-7Al2O3 and 3CaO-Al2O3,and the composition of low-melting-point calcium-aluminate formed at the end of the VD was close to 3CaO-Al2O3,and VD vacuum degassing can significantly increase the CaO mass fraction in calcium aluminates.Thermodynamic calculations show that con-trolling the[Ca]mass fraction at 0.00095％versus 0.004％is sufficient to denature Al2O3-like inclusions into low melting point calcium aluminates.
Ca treatmentevolutionary patterninclusionscalcium aluminatesthermodynamic modelling
万方数据
维普
