Synopsis In order to clarify the eilect of melting procedure on the properties of cast steels, melting /Jrocedure in an electric arc furnace was statistically evaluated in terms of the relation between the ductility and the toughness, namely the elongatioll, the reduction of area, the impact value, and the tensile strength . E.Dixts of the type, the properties and the siz e of inclusion on the ductility and the toughness were investigated for the as-cast and the forged sp ecimens. The results

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... tained are summarized as follows: ( I) Factors increasing the ductility and the toughness at the same level of tensile strength are higher content of silicon, lower content of sulfur and smaller grain size, besides higher degree if demanganization during the oxidation /Jeriod and the proper amount if oxygen blowing. (2) As the distribution of inclusions was not uniform in the as-cast specimens, it is necessary to take a sufficient number of inspection jield: the ins/Jection jield ado/Jted in the current work was 90. (3 ) The cleanliness if the as-cast specimen was indepmdent on the elongation, the reduction if area and the im/Jact value. There is a trend that the elongation and the impact value decrease with increasing number Q{ jine inclusions having the size smaller than 5 I'\~' (4 ) Inc/usions elongated byjorging were com/Josed princi/Jally of (Fe, M n )S ty/Je inclusions, and the number of elongated inclusions was less than that if gmnular inclusions, however, the elongation, the reduction of area and the impact value of the as-cast s/Jecimens were lowered with increasing number of elollgated inclusions. (5) NOll-deformed grallular inclusiolls obtained by forging consisted mostly of S i0 2 type, and they had no influence upon the elongation, the reductioll of area and the impact value. (6) From these resuits, it was found that (Fe, Mn )S type inclusions ill the as-cast specimens qlfected p rimarily on the ductility and the toughness of cast steels. These results agreed with the e.!fects of sulfur in the results obtained by the statistical calculation. * FSi 2: FerrosiliconJIS G2302 S i% 75 -80, C% < O.2, P %< 0.05, S %< 0.02 ** FMnH2: FerromanganeseJIS G2301 Mn % 73-78, C %< 7.0, Si%< 3.0, p aa < 0.4, s aa< O.02 *** .lIS G5 101 : Tensile strength > 46 kg/mm 2 t J IS Z2202 o. 5: Charpy tes t piece U notc h 10 mm 0 X 55 tt JIS Z2201 No.4: T ens ion tes t piece D = 14 mm Technical Report