Key Takeaways & Executive Findings
- •• The primary strength loss occurs between 600-800 °C due to intense resin decomposition. • Above 900 °C, structural reorganization of the carbon skeleton partially recovers strength. • Resin content, base sand type, and particle size significantly influence high-temperature compressive strength. • Findings provide critical data for optimizing sand casting processes to reduce defects like hot tearing and veining.
Abstract
During the casting process, no-bake resin-bonded sand molds and cores rapidly heat up upon contact with high-temperature molten metal, causing dramatic changes in the resin binder system and a significant deterioration in mechanical properties, which subsequently leads to casting defects. To reveal the mechanism behind the evolution of high-temperature performance, the effects of resin content, base sand type, and particle size on the compressive strength of alkaline phenolic no-bake resin-bonded sand at temperatures ranging from 600 °C to 1,000 °C were investigated. The results show that the temperature range of 600-800 °C represents the primary stage of strength loss, corresponding to intense resin decomposition. Meanwhile, structural reorganization of the carbon skeleton above 900 °C can lead to a partial recovery of strength. This study provides key data and theoretical support for understanding the high-temperature mechanical behavior of resin-bonded sand and its relationship with casting defects.
1. Introduction
Sand casting is one of the key forming processes for producing large-scale metal components with complex geometries, reliable quality, and cost-effectiveness [1-6]. Among various sand casting processes, no-bake resin-bonded sand technology has held a dominant position in molding and core making over the past decades [7, 8] due to its advantages such as high molding efficiency and good dimensional stability [9-11]. The fundamental principle of this process involves the uniform mixing of base sand, resin, and a curing agent. In this mixture, the resin undergoes a curing agent-catalyzed cross-linking reaction, coating the sand particles and forming robust resin bridges. This network of bonded sand particles constructs molds or cores with sufficient mechanical strength for foundry applications.
During pouring, the resin-bonded molds (and cores) come into direct contact with high-temperature molten metal. The resin binder system undergoes a series of complex physicochemical changes under high temperatures (typically exceeding 1,200 °C [12, 13]) and in an oxygen-deficient environment [14-16], leading to significant alterations in mechanical properties. When molten metal first contacts the sand mold, an ideal thermal contact exists between them. At this moment, the sensible heat of the liquid metal is rapidly released into the surface layer of the sand mold. During this stage, the interfacial heat transfer coefficient reaches its historical peak. Studies indicate that for preheated sand molds or those with specific coatings, the initial heat transfer coefficient can reach several thousand W·m-2·K-1, owing to the maximized direct contact area at solid-solid or liquid-solid interfaces. Such instantaneous high-intensity heat flux causes the temperature of the sand mold’s surface layer to rise to approximately 1,000 °C within a fraction of a second [17, 18]. This may subsequently induce casting defects such as hot tearing and veining, which are closely related to the high-temperature strength of the molds [19]. Therefore, a systematic evaluation of the mechanical behavior of no-bake resin-bonded sand under high-temperature conditions is of considerable engineering significance. It not only facilitates an in-depth understanding of its service performance but also provides a scientific basis for the rational selection of base sand type, particle size distribution, and resin content in actual production.
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Xin Peng, Yu-yang Qi, Peng Yu, Peng Wan, Zhen-wei Liu, Wen Li, Xu Shen, Xiao-yuan Ji, Ya-jun Yin, Yuan-cai Li, Jian-xin Zhou (2026). Factors influencing high-temperature compressive strength of alkaline phenolic resin-bonded sand. China Foundry. https://doi.org/10.1007/s41230-026-5243-x
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Frequently Asked Questions
What is the primary temperature range for strength loss in alkaline phenolic resin-bonded sand?
The primary stage of strength loss occurs between 600 °C and 800 °C, corresponding to intense resin decomposition.
How does temperature above 900 °C affect the strength of resin-bonded sand?
Above 900 °C, structural reorganization of the carbon skeleton can lead to a partial recovery of strength.
What factors were investigated in this study?
The study investigated the effects of resin content, base sand type, and particle size on the compressive strength of alkaline phenolic no-bake resin-bonded sand at temperatures from 600 °C to 1,000 °C.
Why is high-temperature strength testing important for sand casting?
High-temperature strength testing is crucial because it reflects the actual mechanical behavior of resin-bonded sand during pouring, helping to prevent casting defects such as hot tearing and veining.
What is the significance of this research for foundry practice?
The research provides key data and theoretical support for understanding high-temperature mechanical behavior, aiding in the rational selection of base sand type, particle size distribution, and resin content in production.
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