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Influence of Nb, V and Ta on the Microstructure of Ni-hard type Cast Iron for Hot Steel Strip Mills
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Author(s)
Sergio Villanueva B., Dept. of Materials Science and Engineering, Kyushu University, Fukuoka, 819-0395, JAPAN
Ishikawa S., Nippon Steel & Sumikin Rolls Corp, Kitakyushu, 804-0002
Yamamoto Kaoru, National Institute of Technology, Kurume College, Fukuoka, 830-8555, JAPAN
Miyahara Hirofumi, Dept. of Materials Science and Engineering, Kyushu University, Fukuoka, 819-0395, JAPAN
Ogi Keisaku, Emeritus Professor Dept. of Materials Science and Engineering, Kyushu University, JAPAN
Abstract
Typical Ni-hard type cast iron for hot strip milling rolls contains 3.37%C, 0.90% Si, 4.26%Ni, 1.87% Cr, and 0.55% Mo to crystallize a large amount of ledeburite and a small amount of graphite to achieve a good performance in hot milling of steel strip. Nb, Ta and V up to 2.0 mass % were added to the cast iron to distribute harder MC type carbides in the martensitic matrix. Although higher addition of MC formers results in a higher amount of MC carbides, the chemical composition should be adjusted to crystallize graphite and to suppress the formation of hyper-eutectic carbides which cause macro-segregation in a centrifugal casting. The crystallization of cast iron specimens with Nb-V and Ta-V proceeds in the order of primary γ, γ+MC, γ+M3C and γ+ graphite eutectic. The influence of alloying elements on the graphite formation is estimated by their effects on solubility limit of C to the molten iron. The element which decreases the solubility limit, promotes the graphite formation tendency. A simple mixing rule is applied to the evaluation of the total effect of alloy elements.
Keywords
MC type carbides , Niobium, Vanadium, Tantalum, graphite, Solubility Parameter
Cite this paper
Sergio Villanueva B.,
Ishikawa S.,
Yamamoto Kaoru,
Miyahara Hirofumi,
Ogi Keisaku,
Influence of Nb, V and Ta on the Microstructure of Ni-hard type Cast Iron for Hot Steel Strip Mills, SCIREA Journal of Metallurgical Engineering. Vol.
2
, No.
2
,
2017
, pp.
1
-
11
.
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