Classification and Grades of Silver Brazing Filler Metals
Silver Brazing is an excellent joining method for a wide range of materials, such as steels, stainless steels, nickel-base, titanium and aluminum alloys. Silver brazing filler metals or alloys are bonding materials used to join surfaces of base metal, largely due to its high strength and improved resistance to corrosion and oxidation.
Silver brazing is not new and has been widely used for supplying metal joint-making in industries for decades. The silver brazing alloys have undergone a transformation from a manual material to sophisticated and consistent material, compliant with the quality standards of todays industry. Silver-based brazing filler metals are commercially available in various grades, classes, and composition ranges to meet different applications.
Classification
Silver brazing filler metals are classified mainly by their fluxing or non-fluxing properties and can be used in both gas and electric welding.
Non-Fluxed Filler Metals: Non-fluxed filler metals are the solid form of silver-based alloys and are often used for brazing joints that do not require a flux. These alloys have no addition of phosphorus, making them strong and resistant to corrosion and oxidation. Non-fluxed silver alloys are generally used for joining refractory metals such as titanium, nickel, and stainless steel.
Fluxed Filler Metals: Fluxed filler metals are impregnated with a flux coating on the powder form of silver-based alloys. The brazing flux helps the surface to remain clean and protects the surface from oxidation and contamination while the joining process is in progress. These alloys generally require preheating and controlled cooling. Fluxed silver alloys are mainly used for joining malleable cast iron, low-alloy steels, and carbon steels.
Grades
Silver Brazing Filler Metals are available in various grades or types, such as low-fuming silver brazing alloys, high-melting silver brazing alloys, silver brazing alloys with other metals, and unconstrained silver brazing alloys.
Low-Fuming Silver Brazing Alloys: These alloys are low in fuming, allowing them to be used in the open air. These fluxing brazing alloys are superior in strength and durability. Low-fuming silver alloys are suitable for joining stainless steel, nickel alloys, aluminum, and other types of metals.
High-Melting Silver Brazing Alloys: These alloys have a high melting point and are used for a variety of applications that require higher temperature brazing. These alloys can be used for combining parts to one another that have high surface tension or similar metals which require strong brazing. High-melting silver alloys are suitable for joining copper, copper alloys, and aluminum alloys.
Silver Brazing Alloys with Other Metals: These alloys are available in various compositions with other metals such as aluminum, copper, tin, or zinc. These alloys are usually used for joining and repairing cast iron items or to fill gaps or joints between larger or thicker items.
Unconstrained Silver Brazing Alloys: Unconstrained silver brazing alloys are ideal for joining components of dissimilar materials that have a large gap between them. These alloys are used for quick and efficient filling of larger gaps, cracks, and seams.
Grades of GB 10064-88
GB 10064-88 is the Chinese National Standard for silver brazing filler metals, classified on the basis of the type of flux used in the alloy and its chemical compositions. The standard comprises three classes, out of which two are non-fluxed and one is fluxed.
Class A Non-Fluxed Silver Brazing Filler Metals: This class of non-fluxed alloys is made of mainly silver and containing not more than 10% of other metals such as copper, zinc, and tin. This class of alloys are mainly used for joining non-metallic materials and various types of ordinary steels.
Class B Non-Fluxed Silver Brazing Filler Metals: This class of alloys is largely composed of silver and containing not more than 10% of other metals. It is mainly used for joining ordinary steels and stainless steels.
Class C Fluxed Silver Brazing Filler Metals: This class of fluxed alloys is mainly composed of silver and containing not more than 10% of other metals. These alloys are mainly used for joining everyday steels and ordinary cast irons.
In conclusion, there are various grades, classes, and compositions of silver brazing filler metals compliant with the quality standards of todays industry. Silver brazing is an excellent joining method for a wide range of materials due to its high strength and improved resistance to corrosion and oxidation. GB 10064-88 is the Chinese National Standard for silver brazing filler metals, divided mainly into three classes. It is important to select the appropriate silver brazing filler metals for a specific application in order to achieve a good quality joint.
