Abstract
Freezing conditions for preventing cast cracks in aluminum alloy castings were investigated in terms of the tensile strength of the alloy in the solid-liquid temperature range and contraction stress which was estimated by the calculation on a simple freezing model. Whether the material is susceptible to cast cracks or not is determined by comparing ‘cast cracking parameter’ with ‘critical cast cracking parameter’. The former is expressed as a ratio of temperature decrease at the region of final stage of freezing to that at the region of initial stage of freezing. This parameter is empirically determined by the casting conditions. The latter is mainly determined by the physical and mechanical properties of the alloy such as semi-solidus temperature range, strength increase and elongation in this zone, coefficient of linear shrinkage and Young’s modulus.
