The aim of the present work is to study the influence of copper content on impact characteristics and mechanical properties of ductile cast irons. Five melts with different chemical compositions from 0 (i.e. FCD) to 2mass% of copper content were produced using a high frequency induction furnace. The melt was poured into a Y-block CO2 sand mould of 32mm in thickness.
The chemical compositions of the samples are similar to each other in terms of Carbon (3.66mass%) and Silicon (2.52mass%), and the graphite nodularity is about 86% in all samples.
In as-cast samples, the tensile strength (UTS), elongation, and Brinell hardness, of non-additive element samples (i.e. FCD) were 480MPa, 19.5%, and 157HBW, respectively. The Charpy impact value at room temperature (R.T.) of smooth samples was 95.2J/cm2.
The strength depends on the Cu contents, and showed the highest value of 958MPa for UTS, and the minimum value of 6.3% for elongation. However, the impact value of the sample containing 2mass% Cu was 25.8J/cm2 at R. T. The impact transition temperature also tends to increase toward R. T. with increasing Copper contents. In order to improve toughness of cast irons for samples containing 1% Cu (named Cu1.0) and 2% Cu (named Cu2.0), normalization heat treatment was carried out in which the treatment temperature is decided based on the thermal expansion measurement results.
As a result, the area fraction of pearlite in the Cu1.0 and Cu2.0 samples was found to decrease by heat treatment at 1073K. For Cu2.0 samples treated at 1173K, UTS was 951MPa and elongation was 9.5%. The fracture energy at R. T. of these samples was 70J/cm2.
