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pISSN : 1598-706X / eISSN : 2288-8381


(논문)연구논문

한국주조공학회지 (27권5호 203-208)

High Temperature Properties of Vanadium and Molybdenum Added High Silicon Ductile Iron

바나듐과 몰리브덴이 첨가된 고규소 구상흑연주철의 고온특성

Heung-ll Park, Hae-Yong Jeong

Pukyong National University

Abstract

The high temperature properties of vanadium and molybdenum added high silicon ductile iron, so called V-Mo-Si ductile iron, were investigated. The (V,Mo) complex carbides and Mo carbides precipitated at the cellular boundaries of the as-cast specimens. The microhardness of the (V,Mo) carbides were in the range of 553-619, while that of the Mo carbides in the range of 341-390. The thermo-mechanical tests were carried out with a Gleeble system at 700 and 800℃ under vacuum condition. The tensile strengths of the specimen tested at 700℃ with the dynamic deformation rate of 50 mm/sec and those with the static deformation rate of 0.15 mm/sec were 235.7 and 115.3 MPa, while the reduction in area were 23.7 and 22.4%, respectively. At the high dynamic deformation rates, the tensile strength was steeply increased due to promoting the brittle fracture of pearlite in the matrix of the specimens. But the changes of the reduction in area with the deformation rates on the same specimens were negligible. The weight gain of the V-Mo-Si specimens oxidized in the air atmosphere for 6 hours at 800 and 900℃ were 1.1 and 4.1.%, respectively. The cross-sectional microstructure of oxidized specimens consisted of the porous external scale layer grown outside from the original surface, the dense internal scale layer grown into the original surface, the decarburized ferrite layer between the internal scale and the matrix of base metal. The (V,Mo) carbides and Mo carbides formed in the matrix of as-cast specimen did not decompose during oxidation at 900 for 24 hours in air atmosphere.

Keywords

V-Mo-Si ductile iron, Thermo-mechanical Gleeble test, Oxidation resistance