A study of thickness effects on cooling rate and hardness of gray cast iron in metal and sand molds

Аннотация

This study investigates the influence of mold thickness on the cooling rate and hardness of gray cast CITATION iron in two distinct mold types: metal and sand molds. The experiment is conducted by casting gray cast iron in molds of varying thickness and measuring the cooling COPYRIGHT rate and hardness at different intervals during © 2025 Original content from this work may be used under the terms of the creative commons attributes 4.0 License. solidification. The results indicate that both mold type and thickness significantly affect the cooling rate and the hardness properties of the cast iron. Metal molds lead to faster cooling and higher hardness, while sand molds show slower cooling rates and lower hardness. This study provides insight into how mold design and thickness can optimize casting quality and material properties for industrial applications. Keywords: Gray Cast Iron, Cooling Rate, Hardness, Thickness Effects, Metal Molds, Sand Molds, Solidification, Casting Process, Molding Materials, Thermal Conductivity. Introduction: Gray cast iron is one of the most commonly used materials in manufacturing due to its excellent combination of properties, such as wear resistance, good machinability, and ease of casting. It is widely employed in the production of engine blocks, machine parts, pipes, and other structural components. One of the critical factors that influence the final mechanical properties, such as hardness, strength, and wear resistance, of gray cast iron is the cooling rate during the solidification process. The cooling rate impacts the microstructure of the cast, particularly the graphite structure, which in turn affects the material's overall properties. The cooling rate of a cast metal is primarily determined by the heat extraction process during solidification. The The American Journal of Engineering and Technology 01 https://www.theamericanjournals.com/index.php/tajet The American Journal of Engineering and Technology mold material, its thermal conductivity, and the mold will help to understand the role of mold material and thickness play a significant role in this process. Molds thickness in determining the final mechanical properties with high thermal conductivity, such as metal molds, of cast iron, which is crucial for optimizing the casting extract heat more efficiently, leading to faster cooling process. rates. On the other hand, molds with lower thermal METHODS conductivity, like sand molds, cool the metal more Materials slowly. This difference in cooling rates can lead to variations in the final properties of the cast metal. • Gray Cast Iron: A standard alloy consisting of 3.0-4.0% carbon, 1.8-2.8% silicon, and the balance iron, Mold thickness is another crucial parameter which is used in the experiment. influencing cooling rate. Thinner molds, regardless of material, generally allow for faster cooling compared • Molds: Two types of molds were used: to thicker molds. The heat transfer from the molten 1. Metal Mold: Made from a high thermal metal to the mold is more rapid in thin molds, as the conductivity material (steel). heat is dissipated over a smaller mass. Conversely, 2. Sand Mold: Made from silica sand mixed with a thicker molds can trap more heat, slowing down the binder. cooling process and resulting in different Experimental Setup microstructural characteristics and hardness. • Mold Thickness: Molds of varying thickness (5 Hardness, one of the most important mechanical mm, 10 mm, and 15 mm) were prepared for both metal properties of cast iron, is strongly influenced by the and sand molds. cooling rate. Rapid cooling generally results in a finer microstructure, which leads to higher hardness, • Pouring Temperature: Gray cast iron was whereas slower cooling allows for the formation of melted to a temperature of 1,250°C and poured into the coarser graphite structures, reducing the hardness of molds. the material. Since hardness is closely related to wear • Cooling Rate Measurement: The temperature resistance and overall durability, understanding the was monitored at various intervals during the cooling dynamics and their effects on the hardness of solidification process using thermocouples embedded gray cast iron is essential for improving casting quality. at different points within the castings. This study aims to investigate the combined effects of • Hardness Testing: After solidification, hardness mold material (metal vs. sand) and mold thickness was measured using the Brinell hardness test at three (ranging from 5 mm to 15 mm) on the cooling rate and different locations on each casting. hardness of gray cast iron. The focus will be on how Procedure these variables influence the cooling rate during solidification, and how these rates in turn affect the 1. The molds were prepared by casting gray cast hardness and mechanical properties of the final cast. iron of the specified thickness. By understanding the relationship between mold 2. The molten iron was poured into the