PURPOSE: To obtain a roll of a low cost and high abrasion resistance for mills by specifying the composition of a high chromium type cast iron for the outside layer material of a double centrifugal cast roll.
CONSTITUTION: An outside layer material of high abrasion resistance of 3.0W6.0 C, 0.4W1.5 Si, 0.4W1.5 Mn, 20W25 Cr, 3.0W8.0 Nb, 3.0W6.0 Mo by weight %, and the balance Fe is cast. Thence, an inside layer material of cast iron of high machineability is cast, whereby the double centrifugal cast roll used in an as-cast state is obtained. The abrasion resistance of the high chromium type cast iron is affected by the amt. and hardness of precipitated carbide and the hardness of the base structure. Here, the amt. of carbide precipitation is increased by increasing the contents of Cr and C rather high, but an amt. of austenite of poor abrasion resistance increases in the grond structure. In order to decrease this and to recipitate NbC, Mo2C of hardness higher than that of (Fe, Cr)7C3, Nb and Mo are added. These are required to be above the lower limits, but if they exceed the upper limits, ductility and toughness degrade with Nb and ductility degrades considerably with Mo other than costs.
ONO SHIYUUJI
MATSUO SHINTAROU
UEDA MASATO
