鋼中MnO-SiO<SUB>2</SUB>-Al<SUB>2</SUB>O<SUB>3</SUB>系介在物の熱間圧延過程における挙動と鋼の引張り強さなどにおよぼす影響

Abstract

The oxide inclusions in commercial steels consist mainly of the simple orthe complex oxides formed from the system MnO-SiO2-Al2O3.In the present investigations, the behavior of those oxide inclusions in steels during hot-rolling was observed by the same procedures as used for our previous work: that is, the steel specimens containing uniformly a certain amount of those oxide inclusions were prepared by powder metallurgy technique. These steel specimens were hot-rolled under the following conditions: the rolling temperatures were 1250-1000°C and 1000-800°C, the rolling ratio was 1/5. Then, changes of inclusions in shape, composition and crystallographic structure during hot-rolling were examined. The tensile tests of rolled steel specimens in the rolling direction were carried out to examine the influence of those inclusions on tensile strength of the steels.The main results were as follows:(I) The complex inclusions having nearly the same melting or softening points as the rolling temperature, were deformed plastically and turned into the stringer type. When both the rolling temperature and ratio are maintained to constant, the lower the melting point of inclusion and the better the homogeneity in composition of inclusion are, the larger the degree of deformation of inclusion becomes.(2) The complex inclusions formed from the system MnO-SiO2, having low melting points were softened at 1000°C.(3) When the steel specimens coexisting MnO and SiO2 of simple oxide inclusions were rolled between 1250°C and 1000°C, both inclusions were consolidated, tusned into manganese silicates whose melting points were lower, and deformed plastically. Those manganese silicates were partly crystallized into tephroite (2MnO.SiO2).(4) Those oxide inclusions in steels affected scarecely tensile strength of steels.