When choosing a graphite crucible for metal melting, the key factors to consider are its high-temperature resistance, corrosion resistance, thermal shock resistance, and service life. The core is to match the type of metal being melted, the temperature, and the scale of melting. Choosing an inappropriate crucible can lead to leakage, cracking, and metal contamination. First, select the appropriate crucible material based on the type of metal being melted. For melting copper, aluminum, and other non-ferrous metals, a clay graphite crucible can be used, as it has good thermal conductivity and moderate cost. For melting gold, silver, platinum, etc., a high-purity graphite crucible (with a purity of ≥ 99.95%) should be selected to avoid impurities mixing with the metal and affecting the purity of the precious metals. For melting high-temperature alloys and special metals, a special graphite crucible with high-temperature resistance and corrosion resistance is required, suitable for temperatures above 1600°C. Secondly, pay attention to the key performance indicators of the crucible: high-temperature resistance must meet the melting temperature requirements, leaving a temperature margin of 100-200°C to avoid high-temperature deformation; thermal shock resistance determines the service life of the crucible. In melting scenarios with frequent temperature changes, a crucible with excellent thermal shock resistance should be prioritized to reduce the risk of cracking; corrosion resistance needs to be adapted to the chemical properties of the metal liquid to avoid reactions between the metal liquid and the crucible, resulting in crucible wear and metal contamination. At the same time, select the crucible size based on the melting scale. Small-scale melting can use small crucibles, while large-scale production can use large crucibles, balancing melting efficiency and cost. Finally, during purchase, check the appearance quality of the crucible to ensure there are no cracks, pores, or sand holes, and verify the test reports on purity, high-temperature limit, etc. Before use, perform preheating treatment to avoid cracking due to direct high-temperature heating; during use, avoid sudden cooling and heating, and regularly check the crucible wear condition to replace it in time to ensure a safe and stable melting process.
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