There are many different reasons why laser welding is superior to soldering. To better understand the differences, we must first look closely at the two processes.
Soldering, or more appropriately brazing, is a capillary fill system where solder is heated with a gas-oxygen torch or open flame. When the solder reaches its melting point, the solder then flows across and bridges the noble metals together. Solder is an alloy that is designed to melt at a lower temperature than the noble metal one is soldering; therefore, it is a different alloy than the noble metal. The heat used for this process is very high, and thus often results in a visible seam, discoloration or fire stain in the solder area.
Laser welding is a process in which light energy is used to weld the noble metals to themselves; this process fuses the noble metal on a molecular level resulting in a finished product that is all one alloy. When it is necessary to add metal or "filler wire" with the laser welder, we will almost always add the same noble alloy. The heat used in the welding process is so localized that it results in a seamless, undetectable work zone that is not discolored in any way.
When soldering with a torch, the heat is applied to a relatively large area resulting in heat transfer. If the user is not careful, he can burn or destroy heat sensitive stones and other heat sensitive materials that are in close proximity to the flame. The jeweler is forced to either remove these stones or protect these areas with a heat absorbing substance.
The laser has a finely focused beam resulting in a minimal heat-affected zone or "bombardment Zone." During the welding process, the metal adjacent to the bombardment zone does not become molten. This precision heat source allows the user to weld metal in close proximity of heat sensitive stones and materials such as epoxy, enamel, pearls, and stringing thread to name a few, without affecting the stone or material. Because of this pinpoint heat source, the laser will not anneal springs or clips eliminating the need to replace damaged findings. Also, due to the high concentration of heat, existing patinas and antiquing will usually not be affected, thus making the laser the tool of choice for delicate and antique restoration.
There are many different applications the laser can be used to perform. The following are just a few of the most common involving silverware.
1. The laser is an excellent tool for filling in engraving on flatware, tea services, and anything else in which engraving needs to be removed. Shallow engraving can be removed by simply re-flowing the surface of the metal; deep engraving may need to be filled in with the parent alloy. The laser is also used to repair disposal marring of flatware.
2. Repair of stress points, hinges, cracks, handles, feet, finials.
3. Repair of handles on flatware.
For more information on laser welding, contact:
Crafford - LaserStar Technologies