Production of forging ingots without axial shrinkage defects. Part I^*

method is proposed for calculating the geometric and technological parameters for the casting of forging ingots – including large ingots – without axial shrinkage defects. It is shown that axial porosity can be eliminated by observing two conditions: 1) the conicity of the ingot mold should be sufficient to ensure directional solidification of the ingot and should have values of 1.5–2.0 % for H/D ≤ 1.0 and 14.5–16.0 % for larger values of H/D; 2) the parameters of the hot top, its thermal insulation, and the temperature-rate regimes used for casting should ensure that a sufficient quantity of molten metal is continuously supplied to the solidifying ingot during the entire time that it is being formed. It is recommended that outdated norms for the design of large forging ingots (in the standard OST 108.962.02-85) be revised. Ingots cast in accordance with these norms do not satisfy modern quality requirements.