Heißrissigen

Heißrissigen is a term used in metallurgy to describe materials, structures, or conditions that are prone to hot cracking (hot tearing). It refers to the tendency of a metal or alloy to develop cracks while still at elevated temperatures, typically during solidification or under high-temperature restraint.

The phenomenon arises from a combination of factors. A restrained contraction of the casting or weldment creates tensile stresses as liquid metal solidifies and shrinks. If feeding of liquid metal is insufficient through the mushy or semi-solid region, interdendritic liquid cannot relieve the stresses, allowing cracks to form along weak, partially solidified zones. A wide or complex solidification range and low ductility at high temperatures further increase susceptibility.

Hot cracking can occur in various metallurgical processes, including metal casting, welding, and additive manufacturing, particularly in alloys with restricted feeding, significant thermal gradients, or strong restraint. Alloys with long solidification ranges or brittle semi-solid microstructures are especially prone, though occurrence depends on geometry, mold design, and cooling conditions.

Prevention and mitigation focus on improving feeding and reducing restraint, as well as adjusting material properties. Design measures include proper gating and risers, feeders, and mold design to promote directional solidification. Material approaches involve selecting alloys with narrower solidification ranges or higher high-temperature ductility, using preheating or controlled cooling to minimize thermal gradients, and applying process controls to reduce residual stresses.

Assessment of heißrissigen behavior relies on casting trials, welding simulations, and other modeling approaches to evaluate hot-tearing susceptibility and guide design choices.