With the application of many high-tech in the coinage industry, metal coin casting technology is progressing, the level of technology continues to increase. The casting process mainly includes the following steps:
1, the choice of materials and identification: silver generally used sterling silver sterling silver, until the silver-plated silver copper alloy to manufacture, the international use of the most is 925 and 900 fineness. Gold coins generally used 9999,999,22 K gold and silver or gold and copper alloy to cast.
2, the melting of the plate: from the furnace will be molten metal through continuous casting machine, cast into a variety of sheet blanks, and then mechanical milling surface, remove impurities, and then in the environment requires very strict conditions of cold rolling. In a special finishing mill rolling thickness tolerance of very small mirror of the strip, the error does not exceed 0.005 mm.
3, washed cake, cleaning: the strip into the punch out of the biscuit, must ensure that the minimum burr and the best edge. Billet surface with a special cleaning agent dry, each blanks have to be weighed, the accuracy of the electronic scale requirements of 0.0001 grams.
4, mold: mold design is a unique part of the coinage process. After rigorous validation of the subject matter, patterns, through the Mint complex sophisticated carved, combined with the use of modern precision equipment, the design intent performance in the mold.
5, imprint: imprint is in a clean room with air filtration, any tiny dust is the source of coins caused by scrap, the international is usually imprinting rate of 10%, while the diameter of large, Mirror area of large coins, the scrap rate of up to 50%.
6, protection and packaging: for a certain period of time, to maintain the original color of commemorative coins, the surface of each coin must be a certain treatment, and then sealed with plastic film.
In order to make the commemorative coins cast better and more perfectly reflect the design theme, the mint engineers are still in the process of coin development of many new processes. such as:
1, in the round coins on the basis of the increase in the amount of coins, mainly: rectangular, polygonal, fan-shaped, plum-shaped.
2, in the color of the currency based on the development of the color coins series, that is, in the side of the gold and silver coins with a special process printed on the color patterns, gold and silver coins to increase the new artistic effect, its color wear, corrosion resistance, long-term to keep bright.
3, in the casting, sandblasting, high relief and other processes are also widely used. The pattern part of the spray into a very delicate matte side, in the production of gold and silver coins, the pattern part of the emergence of a layer of beautiful silver; or make the pattern height higher than the face, to increase its three-dimensional and layered.
4, in a single metal base on the basis of the development of double metal coins and local gold-plated silver coins, a currency with two different colors of metal, divided into the inner and outer ring die-casting, such as gold core silver outer ring; silver gold is part of the silver Mosaic of metal on the pattern.