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Abstract <p>The solidification of the surface layer of fixed-length iron cast hollow billets have been studied. The billets are produced by continuous-cyclic freeze casting without a core due to one-sided heat removal and the elimination of a liquid phase deficiency over the hollow casting formation time. This process results in a dense, defect-free structure across the wall thickness, and subsequent heat treatment ensures the required phase composition. The growing number of the manufacturers of synthetic cast iron and the abundant supply of steel scrap have generated significant interest in studying the structure formation of lamellar graphite iron melted from a charge containing at least 80% steel scrap. Computer modeling is used to construct a characteristic pseudobinary phase diagram for the melt composition of gray synthetic cast iron determined during a pouring campaign (chemical composition was determined in castings 5, 9, 12, 22). We have determined the temperature of precipitation of 0.65 primary austenite dendritic crystals and the corresponding degree of supercooling for the composition under study using the concept of cessation of dendritic growth after the formation of the maximum possible volume fraction of dendritic arms in a melt (which was developed by A.V.&#xa0;Il’inskii and L.V. Kostyleva for the alloys forming limited solid solutions) and geometric constructions. The microstructure of the surface zone, which consists of two regions formed by a flat substrate dendrite and dendritic crystals with developed secondary arms, is investigated. The absence of graphite and cementite inclusions in the surface zone is substantiated. The revealed features of melt solidification in the contact zone with the casting machine mold is shown to prevent a direct application of the Lapshin theory of wall solidification, in which the filling of the mold is considered as a periodic layer-by-layer flow of the melt meniscus to the mold wall during filling. According to the wall solidification theory, the mold is filled only for the first casting at the moment the entire gating system and the casting machine mold are filled. Therefore, further development of measures to improve the surface quality of hollow cylindrical castings produced by continuous-cyclic freeze casting requires additions based on an extensive series of investigations.</p>

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On the Possibility of Applying the Theory of Contact Zone Solidification to Hollow Cylindrical Cast Iron Castings Produced by Continuous-Cyclic Freeze Casting

  • 期刊论文

  • 发表日期：

    2025年8月1日

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  • M. S. Solov’eva,
  • L. V. Palatkina,
  • V. P. Grusha

摘要

Abstract

The solidification of the surface layer of fixed-length iron cast hollow billets have been studied. The billets are produced by continuous-cyclic freeze casting without a core due to one-sided heat removal and the elimination of a liquid phase deficiency over the hollow casting formation time. This process results in a dense, defect-free structure across the wall thickness, and subsequent heat treatment ensures the required phase composition. The growing number of the manufacturers of synthetic cast iron and the abundant supply of steel scrap have generated significant interest in studying the structure formation of lamellar graphite iron melted from a charge containing at least 80% steel scrap. Computer modeling is used to construct a characteristic pseudobinary phase diagram for the melt composition of gray synthetic cast iron determined during a pouring campaign (chemical composition was determined in castings 5, 9, 12, 22). We have determined the temperature of precipitation of 0.65 primary austenite dendritic crystals and the corresponding degree of supercooling for the composition under study using the concept of cessation of dendritic growth after the formation of the maximum possible volume fraction of dendritic arms in a melt (which was developed by A.V. Il’inskii and L.V. Kostyleva for the alloys forming limited solid solutions) and geometric constructions. The microstructure of the surface zone, which consists of two regions formed by a flat substrate dendrite and dendritic crystals with developed secondary arms, is investigated. The absence of graphite and cementite inclusions in the surface zone is substantiated. The revealed features of melt solidification in the contact zone with the casting machine mold is shown to prevent a direct application of the Lapshin theory of wall solidification, in which the filling of the mold is considered as a periodic layer-by-layer flow of the melt meniscus to the mold wall during filling. According to the wall solidification theory, the mold is filled only for the first casting at the moment the entire gating system and the casting machine mold are filled. Therefore, further development of measures to improve the surface quality of hollow cylindrical castings produced by continuous-cyclic freeze casting requires additions based on an extensive series of investigations.