With the application of many new technologies in the coin industry, the casting technology of the metal challenge coin has improved day by day, and the level of craftsmanship has been continuously improved. The casting process mainly includes the following steps:
Material selection and identification
Silver coins are generally made of pure silver with a purity of 999, up to a silver-copper alloy containing 500 silver. The fineness of 925 and 900 is the most widely used internationally. Gold coins are generally made of gold, silver or gold-copper alloys such as 9999, 999, and 22K.
Melt-rolled strip version
The molten metal from the electric furnace is passed through a continuous casting machine to cast various specifications of billets, and then the surface is milled by machinery to remove impurities, and then cold rolled under extremely strict environmental requirements. On a dedicated finishing mill, a mirror-bright strip with a very small thickness tolerance is rolled, with an error of no more than 0.005 mm.
Cake washing, cleaning
Put the strips into the blanks that are punched out by the punching machine, and it is necessary to ensure that the smallest burrs and the best edges are obtained. The surface of the green cake is dried with a special cleaning agent, and each green cake must be weighed. The accuracy of the electronic scale is 0.0001 grams.
Mould
Mold design is a unique and important link in the coinage process. Strictly approved themes and patterns, through the Mint’s complex and superb carvings, combined with the use of modern precision equipment, the design intent is on the mold.
Imprint
Imprinting is carried out in a clean room with air filtration. Any tiny dust is the source of the scrapping of challenge coins. The scrap rate of imprinting is usually 10% in the world, and the large diameter and large mirror area The scrap rate of coins is as high as 50%.
