Influence of Nb, V and Ta on the Microstructure of Ni-hard type Cast Iron for Hot Steel Strip Mills

Volume 2, Issue 2, April 2017     |     PP. 1-11      |     PDF (898 K)    |     Pub. Date: July 12, 2017
DOI:    332 Downloads     3428 Views  

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. Volume 2, Issue 2, April 2017 | PP. 1-11.

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