Silver coins generally use pure silver with a purity of 999, and the fineness of 925 and 900 is the most widely used internationally. Gold coins are generally made of gold and silver or gold copper alloys such as 999999 and 22K. Both gold and silver are refined and prepared by the mint through electrolytic refining, and analyzed into dots by modern instruments. The analysis results represent the authoritative standards and technological advancement of a country.
2. Melt rolled strip plate
From the electric furnace, the molten metal is cast into various specifications of billets through a continuous casting machine, and then the surface is mechanically milled to remove impurities, and then cold rolled under extremely strict environmental requirements. On the special finishing mill, the mirror bright strip with extremely small thickness tolerance is rolled, and the error is not more than 0.005 mm.
3.Cake washing and cleaning
When the strip is put into the blank cake punched by the punch, the minimum burr and the best edge must be ensured. The surface of the green cake is dried with a special cleaner. Each green cake is weighed. The accuracy of the electronic scale is required to be 0.0001g. All green cakes that do not meet the tolerance shall be scrapped. Put the required perfect green cakes into a clean container with a lid according to the specified quantity for imprinting.
Mold design is a unique and important link in the coinage process. After strict examination and approval of the theme and pattern, through the complex and exquisite carving of the mint, combined with the use of modern precision equipment, the design intention was put on the mold.
Imprinting is carried out in a clean room with air filtration. Any tiny dust is the root cause of coin scrapping. Internationally, the scrapping rate of imprinting is usually 10%, while the scrapping rate of coins with large diameter and large mirror area is as high as 50%.
6. Protection and packaging
In order to maintain the original color of gold and silver commemorative coins for a certain period of time, the surface of each coin must be protected. At the same time, it is placed in a plastic box, sealed with a plastic film, and then put into a specially designed packaging box. All finished products must undergo strict inspection
Post time: Sep-01-2022