Partition Coefficients of Alloying Elements to Primary Austenite and Eutectic Phases of Chromium Irons for Rolls

抄録

The partition coefficients of chromium and carbon to primary austenite were measured on Fe-Cr-C ternary alloys containing 1.1 to 3.6 mass% C and 1.5 to 26 mass% Cr. Each alloy specimen was held for 1 h at a temperature just below the liquidus and then quenched in water cooled copper mold. Partition coefficients were in the range of 0.53 to 0.80 for chromium and 0.25 to 0.38 for carbon. Partition coefficients of third elements to primary austenite were also evaluated on 5 and 15 mass% Cr quaternary alloys. The coefficients of silicon, nickel and copper were larger than unity and increased with an increase in carbon content, while those of molybdenum, manganese and vanadium were smaller than unity and decreased with increasing carbon content of alloy. The partition coefficient of chromium was little influenced by the third elements.
The partitions of alloying elements between liquid and eutectic phases were evaluated on eutectic alloy specimens with 2, 5, 15 and 30 mass% Cr that were quenched during freezing unidirectionally at 10 mm/h. The irons containing 2 and 5 mass% Cr froze in austenite+(Fe, Cr)₃C eutectic, and the 15 and 30 mass% Cr irions crystallized into austenite+(Cr, Fe)₇C₃ eutectic. In each alloy system chromium, molybdenum, manganese and vanadium were distributed preferentially to eutectic carbide, white silicon and nickel dissolved selectively into eutectic austenite. The partition coefficient of each alloying element to eutectic, defined as the ratio of the average eutectic composition at cell tip to alloy content of liquid near freezing front, were also determined in this study.