Views:0 Author:Site Editor Publish Time: 2021-09-15 Origin:Site
Challenge coins are another language of military coins. Challenge coins can not only give the army a sense of collective honor but also represent respect. So how are the materials selected for military coins and how are the alloys made? The following is a detailed introduction.
Blank cake processing
Different metal materials can be used to make coins. The more common and relatively inexpensive metals are used to cast low-denomination coins, while rare metals such as gold, silver, and platinum are used to cast commemorative coins with investment and collection value.
A good coin material requires certain physical properties, such as a soft metal texture that can be easily processed and formed, and at the same time, a considerable hardness so that it can withstand wear and tear during circulation. Since there are very few metals with the above characteristics, the material of the coin is usually an alloy of two or more metals fused into one body. In the United States and many other countries, the commonly used metals are copper, zinc, nickel, iron, aluminum, etc., among which copper itself or its constituent alloys is a very ideal coin material. Gold and silver are usually alloyed with other metals to increase hardness, and copper is the material of choice. The usual "pure" general-purpose gold and silver coins actually contain traces of other metal components. Of course, their value is mainly estimated based on the content of precious metals in the coin. The specific process of making alloys is:
(1) The selected metal is melted into a liquid alloy in a furnace, poured into an ingot (tank) to cool, or pressed into a strip (thicker).
(2) In the hydraulic workshop, the ingot or thicker strips are rolled several times to make them into strips whose thickness meets the requirements of the billet.
(3) Punching the strips into semi-finished blanks and waiting for further processing.
Coins are embossed from blank cake. The quality of the blank cake directly affects the quality of the finished product. Therefore, the processing of blank cakes is a very critical link. The blank cake stamped from the alloy strip is very rough, the surface is not smooth and there are burrs around it, and further finishing is required. The specific steps are:
(l) Put the blank cake into a cylindrical annealing furnace similar in shape to a special mixer, and the annealing furnace rotates. The high temperature softens the blank cake.
(2) The annealed and softened blank cake is placed in a diluted acid or soap solution for cleaning.
(3) Use special machinery and equipment to grind and polish the blank cake. After the above treatment, the blank cake can be directly used to imprint coins.
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