Commemorative Coins are legal tender issued by a country to commemorate major events, outstanding figures, places of historic interest, rare animals and plants, and sports events in the international or domestic political, historical and cultural fields, including ordinary commemorative Coins and precious metal .
With the application of many new technologies in the coinage industry, the foundry technology of metal commemorative COINS has been improved day by day and the technological level has been continuously improved.The casting process mainly includes the following steps:
1. Selection and identification of materials: silver COINS are generally made of pure silver with a purity of 999 until silver copper alloy containing 500 silver, and the most commonly used in the world are 925 and 900.Gold COINS are generally made of 9999, 999,22k gold and silver or gold-copper alloys.
2, melt rolling plate: from the electric furnace will melt the metal through the continuous casting machine, cast into various specifications of the slab, then with mechanical milling surface, remove impurities, and then in the environment under extremely strict requirements of cold rolling.In the special finishing mill rolled out the thickness tolerance is very small mirror bright strip, the error does not exceed 0.005 mm.
3. Cake processing and cleaning: put the strips into the blanks that have been rushed out by the punch, and ensure to get the minimum burr and the best edge.The surface of the preform cake is dried with special detergent. Each preform cake should be weighed and the precision of the electronic scale should be 0.0001 g.
4. Mold: mold design is a unique and important part of coinage process.After a strict examination of the theme, pattern, through the mint complex superb fine carvings, combined with the use of modern precision equipment, the design meaning chart mold.
5. Imprinting: the imprinting is carried out in a purification room with air filtration. Any tiny dust is the root cause of coin scrapping.
6. Protection and packaging: in order to maintain the original color and luster of the commemorative coin within a certain period of time, the surface of each coin shall be treated and sealed with plastic film.
In order to make the COINS better reflect the design theme, the mint's engineers also developed many new techniques in the process.Such as:
1. On the basis of the circular coin, the special-shaped coin is added, mainly including rectangle, polygon, fan and club shape.
2. On the basis of the original coin, the color coin series is developed, that is, the color pattern is printed on the side of the gold and silver coin by a special process to increase the new artistic effect of the gold and silver coin. The color is wear-resistant and corrosion-resistant, and can keep bright for a long time.
3. In casting, sand blasting, high relief and other processes are also widely used.Spray the part of the pattern into a very fine frosted surface, in the production of gold and silver COINS, the part of the pattern is a beautiful layer of silver;Or make design height is above money face, increase its stereo feeling and administrative levels feeling.
4. On the basis of single metal coin, we developed bimetal coin and partial gold-plated silver coin. One coin is made of two metals of different colors, with inner and outer ring die-cast, such as gold core and silver outer ring;The local gilding of a silver coin is a pattern in which the silver coin is partially inlaid with metal.
Jiabo Crafts, is a professional crafts manufacturer, specializing in the production of a wide range of badges, medals, coins, keychains, bottle openers, bookmarks, plates, trophies and other metal products.