STUDY ON THE EQUI-AXIAL CRYSTALLIZATION OF AUSTENITE IN NI-HARD CAST IRON FOR OUTER SHELL OF NHW ROLL.

Research Project

Project/Area Number	59470053
Research Category	Grant-in-Aid for General Scientific Research (B)
Allocation Type	Single-year Grants
Research Field	金属加工(含鋳造)
Research Institution	WSEDA UNIVERSITY
Principal Investigator	TSUTSUMI NOBUHISA METAL ENGINEERING DIVISION, SCIENCE & ENGINEERING SCHOOL, 理工学部, 教授 (80063171)
Project Period (FY)	1984 – 1986
Project Status	Completed (Fiscal Year 1986)
Budget Amount *help	¥4,000,000 (Direct Cost: ¥4,000,000) Fiscal Year 1986: ¥1,200,000 (Direct Cost: ¥1,200,000) Fiscal Year 1985: ¥1,200,000 (Direct Cost: ¥1,200,000) Fiscal Year 1984: ¥1,600,000 (Direct Cost: ¥1,600,000)
Keywords	Ni-Hard cast iron / Titanium / Niobium / Directional solidification Equi-axial crystal / デンドライト・アームスペーシング
Research Abstract	Ni-Hard cast iron for outer shell castings of FHW roll has the good properties of high hardness and abrasion resistance. At present,however,it is necessary to have relatively superior resistance for dispersion of cracks originated in the roll. With a view of investigating the equi-axial crystallization of austenite in Ni-Hard cast iron, titanium and niobium are added in the level of 0.005 to 0.70% into normal chemical composition of Ni-Hard cast iron and observed the dendritic structure and eutectic cell. In the first experiment, the molten metal including titanium and niobium in the designed level of quantity are poure respectively into sand mold having copper chill plate in the bottom and heat insulating sleeve in the side wall and also exothermic powder on the top. Nextthe molten metal having simultaneouly titanium and niobium are poured into the same sand mold. In all specimen series, Ni-Hard cast iron having 0 to 1.2%Nb, 0 to 1.50% Ti, and 0 to 0.5% Ti with 1.5% Nb, both decrease of primary and secondary arm-spacing and increase of cell number are recognized with the increase ofaddition of these alloying element. In the second experiment, Uni-directional solidification apparatus wre applied for the solidification of Ni-Hard iron having arroun the same level of titanium and niobium content. Under the condition of G=10.1゜C/mm, R=200 mm/h and G=12.3゜C/mm, R=70 mm/h, molten iron in tammann tube made by alumina is solidified as arroun the same cooling rate in practical NHW roll of centrifugal castings. As the result of this experiment, the decrease of both primary and secondary arm-spacing and increase of cell are obtained by titanium addition. However, no distinct variation are recognized by niobium addition. It is seems that the non-metallic inclusion as Ti(C,N)or Nb(C,N) suppress the growth of austenitic dendrites.