Graphite crucible has become an ideal tool for smelting precious metals due to its high temperature resistance, good thermal conductivity, and strong chemical stability. The following are the steps and precautions for correctly using graphite crucible to smelt precious metals:
1.Choose graphite crucible：
Determine the material and size of the graphite crucible according to the type and amount of metal to be smelted.
2.Clean the crucible：
Before use, remove all impurities and dust from the crucible, and check whether there are cracks and whether the crucible is completely dry,Clean with alcohol or deionized water if necessary and dry thoroughly.
3.Preheat crucible：
Before smelting, slowly heat the crucible to 200-300°C to remove residual moisture and prevent thermal shock.
4.Add the metal to be melted
Put the metal raw materials evenly into the crucible. The main thing is not to fill the metal completely, but to leave room for expansion after heating.Then put the graphite crucible into the smelting furnace and let the temperature slowly rise to the melting point of the metal. During this period, use a thermometer to monitor the temperature at all times to avoid the crucible rupturing due to excessive temperature rise or excessive temperature rise.After reaching the melting point, melt the metal completely. If necessary, stir with a stirring rod to ensure that the metal is completely melted.
5.Pour the molten metal into shape：
After melting, pour the molten metal into the preheated mold, avoiding direct contact with cold surfaces.Allow the metal to cool naturally in the mold to avoid rapid cooling or heating that may cause cracking or deformation of the metal or mold.
During smelting, we should pay attention to avoid exceeding the maximum heat-resistant temperature of the crucible, which is usually around 2500°C. When heating, slowly increase the temperature to prevent thermal shock, ensure the cleanliness of the crucible and metal, and prevent contamination. Professional tools should be used during the operation. Wear protective equipment such as gloves, masks and gowns.
Check the crucible regularly after smelting and replace it if cracks or damage are found. Clean after use and store dry to avoid humid conditions.
Summarize：
The correct use of graphite crucibles for smelting precious metals requires selecting the appropriate crucible, controlling temperature, preventing contamination and paying attention to safety. Through standardized operation and regular maintenance, the smelting process can be ensured to be safe and efficient, and the crucible life can be extended.
