Hasung is a Professional Precious Metals Casting And Melting Machines Manufacturer since 2019.
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Hasung is a Professional Precious Metals Casting And Melting Machines Manufacturer since 2019.
Gold, as a precious and widely applicable metal, its smelting process is crucial. In gold smelting, gold flux plays an indispensable role. It can significantly affect various factors such as smelting efficiency, quality, and the purity of the final gold. A deep understanding of the role of gold flux in the gold smelting process is of great significance for optimizing the gold production process and improving the quality of gold.
1.Basic concept of gold flux
（1） Definition
Gold flux is a type of chemical substance added during the gold smelting process, whose main function is to lower the melting point of gold and its impurities, and promote the smooth progress of the smelting process. Flux is usually composed of a mixture of various compounds with specific chemical properties that can react chemically with impurities in gold or alter the physical properties of the gold melt.
（2） Common types
Common gold fluxes include borax, sodium carbonate, quartz sand, etc. Borax is a commonly used fluxing agent, mainly composed of sodium tetraborate. At high temperatures, borax can react with metal oxide impurities in gold to form low melting point borate compounds. Sodium carbonate can react with acidic oxide impurities during the smelting process, playing a role in removing impurities. Quartz sand is mainly used to adjust the properties of slag and help separate impurities from gold.
2.Reduce melting temperature
（1） Principle
The melting point of pure gold is about 1064 ℃, but in the actual melting process, adding fluxing agents can lower the melting point of gold. This is because certain components in the flux can form a low eutectic mixture with gold. Low melting point mixture refers to a mixture formed by mixing two or more substances, which has a melting point lower than that of each constituent substance. For example, when borax is mixed with gold, a low eutectic mixture can be formed at a certain ratio, thereby reducing the overall melting point and allowing gold to melt at relatively low temperatures.
（2） Advantages
Lowering the melting temperature has multiple advantages. Firstly, it can reduce energy consumption. A lower melting temperature means a reduction in the energy required for heating, which can significantly lower production costs for large-scale gold smelting enterprises. Secondly, lower temperatures can reduce the volatilization loss of gold at high temperatures. Gold will undergo a certain degree of volatilization at high temperatures. If the melting temperature can be lowered, this volatilization loss can be effectively reduced and the recovery rate of gold can be improved.
3.Remove impurities
（1） Reacting with impurities
Gold ore or recycled gold raw materials usually contain various impurities, such as metal impurities such as copper, lead, zinc, as well as some non-metallic impurities. Fluxes can undergo chemical reactions with these impurities. Taking borax as an example, at high temperatures, borax can react with metal oxide impurities to form borates. For example, borax reacts with copper oxide to produce copper borate, which has a lower melting point and a density different from gold. During the smelting process, it can be separated from gold to achieve the goal of removing impurities.
（2） Change the physical properties of impurities
Flux can not only undergo chemical reactions with impurities, but also change the physical properties of impurities. For example, some fluxes can make the particles of impurities finer, increasing the difficulty of separating them from the gold melt, thereby promoting the separation of impurities from gold. At the same time, flux can also reduce the viscosity of slag, making it easier for slag to flow and facilitate its discharge from the gold melt, further improving the purity of gold.
4.Promote metal fusion
（1） Improve melt flowability
Good melt flowability is crucial in the gold smelting process, especially when it is necessary to alloy gold of different purities or add other metals. Flux can improve the fluidity of gold melt. It can reduce the surface tension of the melt, making it easier for the melt to flow in the furnace and promoting uniform mixing between different metals. For example, when making gold alloys, adding an appropriate amount of flux can ensure that various metals can fully fuse and form alloys with uniform composition.
（2） Reduce metal segregation
Metal segregation refers to the uneven distribution of metals with different compositions in castings during the solidification process of alloys. The use of fluxing agents helps to reduce the occurrence of metal segregation. By improving the fluidity of the melt and promoting metal fusion, fluxing agents enable various metals to be more evenly distributed in the melt, resulting in a more uniform composition of the alloy after solidification, thereby improving the quality and properties of the alloy.
5.Protect gold from oxidation
（1） Form a protective film
During the high-temperature melting process, gold easily reacts with oxygen in the air to form oxides. Flux can form a protective film on the surface of gold melt at high temperatures, preventing oxygen from coming into contact with gold and reducing its oxidation. For example, certain fluxes decompose at high temperatures to produce gases, which form a gas film on the surface of the gold melt, serving to isolate oxygen.
（2） Reduce the solubility of oxygen
Flux can also reduce the solubility of oxygen in gold melt. When the solubility of oxygen decreases, the possibility of gold reacting with oxygen also decreases. This helps to maintain the purity of gold and avoid quality degradation caused by oxidation.
Conclusion
Gold flux plays multiple important roles in the process of gold melting, including reducing melting temperature, removing impurities, promoting metal fusion, and protecting gold from oxidation. By selecting and using fluxes reasonably, the efficiency of gold smelting can be improved, production costs can be reduced, and the purity and quality of gold can be enhanced. With the continuous development of the gold industry, research and application of gold fluxes are also deepening. In the future, more efficient and environmentally friendly fluxes are expected to be developed, further promoting the progress of gold smelting technology.
Shenzhen Hasung Precious Metals Equipment Technology Co., Ltd. is a mechanical engineering company located in the south of China, in the beautiful and the most fastest economic growing city, Shenzhen. The company is a technological leader in the area of heating and casting equipment for the precious metals and new materials industry.
Our strong knowledge in vacuum casting technology further enables us to serve industrial customers to cast high-alloyed steel, high vacuum required platinum-rhodium alloy, gold and silver, etc.
