| Microalloy treatment and modification in SS400 tested steel by Y-Mg alloy,detections of normal detecting methods of steel material, mechanism of the influence on tissue and performance in tested steel by Y-Mg alloy has been studied.The low temperature performance has been improved by microalloy treatment of Y-Mg alloy in tested steel,it only induced the pollution of harmful impurities in tested steel,but also changed the size,morphology and distribution characteristics of non-metallic inclusion in tested steel as we wish,so the performance of tested steel has been improved.The supplement alloying in tested steel by Y-Mg alloy contribute to precipitation with more dispersedly, uniformly and solwly,it has an important effect on plastic flow when tested steel was stretched.The result of Microalloy treatment in tested steel has been improved plasticity, low temperature impact toughness and other performances,tested steel within Y and Mg has higher mechanical properties.Being a surfactive substance, Y-Mg has decreased critical nucleation power,increased crystallization core,therefore the growth of coarse columnar grains has been enervated and cast structure of SS400 tested steel has been refined;The transverse growth of cementite has been inhibited,the orientation of pearlite interlaminar has been ameliorated,furthermore,anisotropy of SS400 steel has been improved by Y-Mg alloy. Y-Mg effectively inhibited the generation of banded structure after forging, banded structure has become reticular tissue by Y-Mg composite treatment,pearlite and ferrite grain has been unifromly distributed at last.In this experimental conditions,the cast structure,forged microstructure, structure after heat treatment and anisotropy have been improved obviously when addition amount of Y-Mg alloy is 0.012～0.024% ,mechanical properties of tested steel have been inhanced with different degree. |
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