Graphite crucibles are primarily made from natural flake graphite, processed with plastic refractory clay or carbonaceous materials as binders. They possess characteristics such as high temperature resistance, strong thermal conductivity, good corrosion resistance, and a long service life. During high-temperature use, they exhibit a low coefficient of thermal expansion and have a certain resistance to stress from rapid heating and cooling. They are highly resistant to acidic and alkaline solutions, possessing excellent chemical stability, and do not participate in any chemical reactions during the melting process. The inner wall of the graphite crucible is smooth, preventing molten metal from leaking or adhering to the crucible wall, thus ensuring good fluidity and castability of the molten metal, making it suitable for casting into various molds. Due to these excellent characteristics, graphite crucibles are widely used in the smelting of alloy tool steel and non-ferrous metals and their alloys.
The main use of graphite crucibles is for melting non-ferrous metals such as copper, aluminum, gold, silver, lead, zinc, and their alloys, as well as for laboratory experiments. Because metals have high melting and boiling points, other materials and ordinary ceramic crucibles would melt, failing to meet the requirements. Graphite, with a melting point of 3652°C, is ideal, and it is also corrosion-resistant and strong. Therefore, graphite crucibles are the best vessels for melting non-ferrous metals, capable of withstanding the melting temperatures of most non-ferrous metals without failing due to insufficient temperature resistance or inability to withstand the melting temperature of the metal.
During the metal smelting process, the crucible needs to be heated or cooled rapidly according to the process requirements. This raises the question of whether the graphite crucible can withstand rapid heating and cooling.
For example, when smelting copper alloys, the melting point of copper is 1083.4 degrees Celsius. When the crucible reaches this temperature, the copper metal melts. However, according to process requirements, rapid cooling to a certain temperature is necessary, which places demands on the crucible. Graphite crucibles belong to the ceramic product category, and their properties are similar to those of ceramics and glass. They cannot withstand rapid heating and cooling, which can cause the crucible to crack, and in severe cases, to shatter.