Numerical simulation of central shrinkage crack formation in a 234-t steel ingot

Abstract

Abstract:Central shrinkage crack is a common defect encountered in steel ingot casting. It is necessary to limit the degree of crack in case of further propagation in forging. A 234-t steel ingot was dissected to check the internal quality, and a central shrinkage crack band of 1,400 mm in height and 120 mm in width, was found at a distance of 450 mm under the riser bottom line. Then, thermo-mechanical simulation using an elasto-viscoplastic finite-element model was conducted to analyze the stress-strain evolution during ingot solidification. A new criterion considering mush mechanical property in the brittle temperature range as well as shrinkage porosity was used to identify the shrinkage crack potential, where the degree of shrinkage porosity is regarded as a probability factor using a modified sigmoid function. Different casting processes, such as pouring speed, mould preheating and riser insulation, were optimized with the simulation model. The results show that fast pouring, proper mould preheating and good riser insulation can alleviate shrinkage crack potential in the ingot center.

Shrinkage Porosity Model for Steel Ingots with Reduction Deformation during Solidification

“…Its presence in downstream steel products diminishes material density, reduces effective load‐bearing areas, induces stress concentrations, and markedly degrades the product's mechanical properties. [ 5–7 ] Analogous detrimental impacts of shrinkage porosity are also observed in continuous casting billets.…”

Internal shrinkage crack in a 10 t water-cooled steel ingot with a large height-to-diameter ratio

“…Recently, a 234 t ingot was dissected and a shrinkage crack potential criterion considering shrinkage porosity as well as mushy zone mechanical property was proposed [20] . However, grain size, which is influenced by the cooling intensity, was rarely considered in the hot cracking potential (HCP) criterion.…”