<p>A strain-rate-dependent total inelastic strain damage framework was developed to predict bulging-induced intermediate cracks in a 410 × 530 mm<sup>2</sup> 42CrMo continuous casting bloom. A three-dimensional thermo-mechanical finite element (FE) model was established by coupling transient heat transfer and solidification, ferrostatic pressure, roll–bloom contact, thermal shrinkage, high-temperature creep, and plastic deformation. The normalized Cockcroft–Latham (NC&L) criterion was reformulated using the equivalent total inelastic strain increment to describe plastic–creep-coupled damage accumulation during high-temperature inter-roll bulging. High-temperature tensile tests and fracture characterization identified 1390 °C as the representative crack-sensitive temperature. FE-assisted tensile calibration showed that the critical damage value decreased from 0.102 to 0.011 as the strain rate decreased from <InlineEquation ID="IEq1"> <EquationSource Format="TEX">$1\times {10}^{-3}$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mn>1</mn> <mo>×</mo> <msup> <mrow> <mn>10</mn> </mrow> <mrow> <mo>-</mo> <mn>3</mn> </mrow> </msup> </mrow> </math></EquationSource> </InlineEquation> to <InlineEquation ID="IEq2"> <EquationSource Format="TEX">$1\times {10}^{-5} {\text{s}}^{-1}$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mn>1</mn> <mo>×</mo> <msup> <mrow> <mn>10</mn> </mrow> <mrow> <mo>-</mo> <mn>5</mn> </mrow> </msup> <msup> <mrow> <mtext>s</mtext> </mrow> <mrow> <mo>-</mo> <mn>1</mn> </mrow> </msup> </mrow> </math></EquationSource> </InlineEquation>, demonstrating a pronounced reduction in damage tolerance with decreasing strain rate. Under the baseline condition, the maximum bulging displacement occurred near the inter-roll center, whereas tensile strain localization and crack risk were concentrated near the roll-contact region close to the solidification front. Parametric results showed that roll pitch had the most pronounced influence: increasing it from 300 to 380 mm enlarged the wide- and narrow-face bulging by 2.20 and 0.55 mm, respectively, and expanded the predicted crack-risk region toward the triangular zone. Casting speed also enhanced crack risk by reducing shell stiffness, whereas superheat showed a moderate thermal effect and roll diameter mainly produced a secondary local-contact effect.</p>

Strain-Rate-Dependent Total Inelastic Strain Damage Framework for Predicting Bulging-Induced Intermediate Cracks in Continuous Casting Blooms

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发表日期：

2026年8月3日

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Junlong Ju,
Kaixiang Li,
Dexiang Liu,
Hai Chang,
Cheng Ji,
Miaoyong Zhu

摘要

A strain-rate-dependent total inelastic strain damage framework was developed to predict bulging-induced intermediate cracks in a 410 × 530 mm² 42CrMo continuous casting bloom. A three-dimensional thermo-mechanical finite element (FE) model was established by coupling transient heat transfer and solidification, ferrostatic pressure, roll–bloom contact, thermal shrinkage, high-temperature creep, and plastic deformation. The normalized Cockcroft–Latham (NC&L) criterion was reformulated using the equivalent total inelastic strain increment to describe plastic–creep-coupled damage accumulation during high-temperature inter-roll bulging. High-temperature tensile tests and fracture characterization identified 1390 °C as the representative crack-sensitive temperature. FE-assisted tensile calibration showed that the critical damage value decreased from 0.102 to 0.011 as the strain rate decreased from $1\times {10}^{-3}$ $1 \times 10^{- 3}$ to $1\times {10}^{-5} {\text{s}}^{-1}$ $1 \times 10^{- 5} s^{- 1}$ , demonstrating a pronounced reduction in damage tolerance with decreasing strain rate. Under the baseline condition, the maximum bulging displacement occurred near the inter-roll center, whereas tensile strain localization and crack risk were concentrated near the roll-contact region close to the solidification front. Parametric results showed that roll pitch had the most pronounced influence: increasing it from 300 to 380 mm enlarged the wide- and narrow-face bulging by 2.20 and 0.55 mm, respectively, and expanded the predicted crack-risk region toward the triangular zone. Casting speed also enhanced crack risk by reducing shell stiffness, whereas superheat showed a moderate thermal effect and roll diameter mainly produced a secondary local-contact effect.