Abstract
The mechanical properties obtainable in a high Mn ductile iron containing 3·52%C, 2·64%Si, 0·67%Mn, 0·007%P, 0·013%S, 0·25%Mo, 0·25%Cu, and 0·04%Mg are defined. Measurements of ultimate tensile strength, 0·2% proof strength, impact energy, and elongation are presented as afunction of austempering time in the range 1–4320 minfor austempering temperatures of 285 and 375°C and austenitising temperatures of 870, 900, and 920°C. The austempering processing window is shown to be openfor the three austenitising temperatures at an austempering temperature of 285°C, and the mechanical properties satisfy the austempered ductile iron (AD I) standard AST MA897 M:1990. Decreasing the austenitising temperature is shown to increase the closure temperature of the processing window, but for the lowest austenitising temperature the window is still closed for an austempering temperature of 375°C. The improvement in ductility obtained by using an austenitising temperature of 870°C is insufficient to satisfy the AD I standard.
MST/3118
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