Silver chain manufacture.

The production of silver chain is a high volume business. Traditionally Silver chain is produced using two methods of production. In the USA a solid wire with a solder core is used. In this process a large billet is cast and then drilled down its centre. A solder is then melted into the centre hole before the billet is reduced by rolling and drawing to the final size required for the chain. After the links of the chain have been formed it is passed through a furnace to melt the solder in the core, which then flows out and joins the links.
A method called “powder packing” is used in most other jewellery production centres in the world. In this method a solid wire is first drawn and then formed on a chain-making machine. To join the chain a zinc powder is packed between each link and the complete chain is then passed through a furnace.
Both of the standard production methods for silver chain are time consuming and expensive for different reasons. Gold chain by contrast is generally joined using lasers. The lasers are mounted directly on the chain-making machine and as each link is formed, the laser fires a single shot to the join link. Up to four hundred links a minute can be joined and when the chain leaves the chain-making machine, no further work is required. Standard sterling silver because of high conductivity and reflectivity has not proved to be suitable for laser joining. It does not produce welds with sufficient strength.
EP1699581 describes a method of making chain more efficiently with silver copper germanium alloys, using a laser to join the links. Silver is the most conductive of all metals and this is one reason it is difficult to weld. The addition of germanium to sterling silver increases the thermal and heat resistivity of the alloy. A resistive alloy traps the energy and welds more efficiently. Steel is a good example of a resistive metal that welds easily The infrared spectrum of the germanium also aids the laser light to couple with the silver. Sterling silver normally will reflect the majority of the laser power away from its surface.