Effect of Y and Zr on MnS and microstructure and mechanical properties of non-quenched and tempered steel
The regulation of MnS has always been the focus and difficulty in the development of high-quality non-quenched and tempered steel.In order to improve the morphology and distribution of MnS in steel and enhance its mechanical properties,three furnaces of experimental steel were melted by vacuum induction furnace in the laborato-ry,and the ingot was forged to study the effects of Y and Zr on inclusions,microstructure and mechanical properties in steel.Inclusions in both as-cast(A1-A3)and as-forged(Bl-B3)samples were quantified and analyzed via scanning electron microscopy.Microstructural examination of the forged steel was conducted using metallographic micro-scope.The mechanical properties of the experimental steel were assessed using universal material testing machine and impact testing machine.Results indicate that the addition of Y and Zr lead to class Ⅲ and class Ⅰ MnS inclusions in A2 and A3 as-cast steels predominantly,with average diameters of 2.9 μm and 1.8 μm,respectively.The oxygen content is not the primary determinant of MnS morphology and distribution in the steel.YAlO3 and Y4Zr3O12 formed within the steel exhibit a slight lattice disregistries with MnS,facilitating heterogeneous nucleation and pre-cipitation with oxide as the core during solidification.MnS with oxide as the core demonstrates enhanced deforma-tion resistance during forging.Following Y and Zr alloying,the experimental steel experiences reduced grain size,heightened intragranular ferrite proportion,with average grain sizes decreasing from 36.5 μm(B1)to 22.8 μm(B2)and 11.4 μm(B3).Intragranular ferrite proportion increases from 2.4％(B1)to 6.2％(B2)and 11.1％(B3).Steel B3,exhibiting the smallest grain size,highest intragranular ferrite proportion,and smallest MnS size,demon-strates superior mechanical properties,with a yield strength of 840 MPa and room temperature impact energy of 52 J.The research results provide a theoretical reference for improving MnS and mechanical properties in non-quenched and tempered steel.
non-quenched and tempered steelMnSYZrmicrostructuremechanical property
NETL
NSTL
万方数据
