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<p>Heavy-section pearlitic ductile iron castings are attractive alternatives to forged components, but their long and position-dependent solidification/cooling histories can cause location-dependent variations in microstructure and graphite morphology, leading to scatter in hardness and strength and increasing the risk of shrinkage-related defects. This study presents a practical validation approach for a 6-ton steam-tube dryer roller casting (maximum section thickness 430 mm) produced as a pearlitic high-strength ductile iron. Because the rolling surface is subjected to repeated contact and load, controlling the hardness distribution on the machined surface is essential, while internal soundness must also satisfy forged-like nondestructive inspection criteria. First, a 600-mm cube block was cast to reproduce representative heavy-section thermal conditions and to evaluate hardness distribution, tensile properties, microstructure including graphite morphology, and defect tendency. Based on the block results, the alloying strategy and chill conditions were refined for the full-scale roller to prevent hardness overshooting while meeting the 700 MPa-class strength requirement (ISO 1083 JS/700-2 equivalent). The revised conditions achieved the targeted hardness window on the machined surface together with 700 MPa-class tensile strength. Shrinkage prediction was further compared with inspection and observed defect locations, highlighting that the selection of a defect-evaluation method can influence design decisions for heavy-section ductile iron castings.</p>

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Production of Heavy-Section 6-Ton High-strength Ductile Iron Castings for Steam-Tube Dryer Roller

  • 期刊论文

  • 发表日期：

    2026年3月23日

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  • Yutaka Miyamoto,
  • Shunsuke Shiraoka,
  • Yuuki Kuramoto,
  • Baochu Ri

摘要

Heavy-section pearlitic ductile iron castings are attractive alternatives to forged components, but their long and position-dependent solidification/cooling histories can cause location-dependent variations in microstructure and graphite morphology, leading to scatter in hardness and strength and increasing the risk of shrinkage-related defects. This study presents a practical validation approach for a 6-ton steam-tube dryer roller casting (maximum section thickness 430 mm) produced as a pearlitic high-strength ductile iron. Because the rolling surface is subjected to repeated contact and load, controlling the hardness distribution on the machined surface is essential, while internal soundness must also satisfy forged-like nondestructive inspection criteria. First, a 600-mm cube block was cast to reproduce representative heavy-section thermal conditions and to evaluate hardness distribution, tensile properties, microstructure including graphite morphology, and defect tendency. Based on the block results, the alloying strategy and chill conditions were refined for the full-scale roller to prevent hardness overshooting while meeting the 700 MPa-class strength requirement (ISO 1083 JS/700-2 equivalent). The revised conditions achieved the targeted hardness window on the machined surface together with 700 MPa-class tensile strength. Shrinkage prediction was further compared with inspection and observed defect locations, highlighting that the selection of a defect-evaluation method can influence design decisions for heavy-section ductile iron castings.