What is Silver Brazing?
Silver brazing is a process for joining metals by heating and melting a non-ferrous filler metal and distributing it between metal parts by capillary action. Silver brazing is characterized by use of filler metals and alloys of silver, copper, zinc, cadmium, etc.
At the liquidus temperature, the molten filler metal interfaces with a thin layer of the base metal, and upon cooling, an exceptionally strong, sealed joint is formed by means of interaction of grain structure. A joint braze remains a sandwich of different layers, however, still is metallurgically bonded with the other.
Heating sources are many, and the method for silver brazing can be torch, flame, acetylene, gas/air, induction, resistance, infrared, oven, furnace, etc.
Flux is a requirement for brazing to remove, and prevent reformation of surface oxides on the base metals.
Silver brazing produces strong, sealed, leak-proof joints. Silver brazing uses filler metals in solid pieces, like rings, wire, slugs, washers, powder, and paste. Good brazements start with good design of the joint.
Silver brazing produces joints that meet specifications that meet mechanical properties, electrical conductivity, pressure tightness, resistance corrosion, and service temperature. Silver brazing is a method often used in high production volume, metal joining operations.
Cadmium-free silver brazing alloys are commercially available and sold in paste form. Silver brazing is a method of choice for bonding or joining ferrous and non-ferrous base metals to much like steel to stainless steel to copper to brass.
Silver brazing can also be accomplished on automatic machines providing cost-efficient metal joining by producing metal joints at high production rates.
Read more About: What is Brazing?
Process of Silver Brazing
Silver brazing employs the same methods as all other brazing processes in regards to proper fit to provide capillary action, clean base metals, flux, heat the metals, and clean the assembly after brazing.
When heating the assembly, use uniform heat, but with extraneous heat on the thicker metal. If one metal has lower thermal conductivity, apply more heat to the metal with higher thermal conductivity.
Keep in mind that filler metals will flow to the source of the higher heat.
Warning
Fumes of cadmium oxide being produced by cadmium coated brazing alloys that are heated and melted are extremely hazardous. In order to prevent exposure to personnel, personal protective equipment must be utilized and(o) sufficient ventilation is provided.
The surfaces must be free from oxides, scale, grease, dirt, or any other foreign matter. Non-cadmium plated surfaces can be cleaned mechanically by wire brushing or an abrasive cloth and chemically by acid pickling or other methods.
Extreme care must be taken to grind all the cadmium surfaces to the base metals since cadmium oxide fumes from cadmium coated silver brazing alloys that are heated or melted are highly poisonous.
Silver Brazing Rod
Sometimes called “hard soldering” or “silver soldering,” silver brazing is a brazing process that is classified as low-temperature brazing, and it utilizes rods with melting temperatures ranging from 1145 °F to 1650 °F (618 °C to 899 °C) which are significantly lower than copper alloy brazing filler metals melting point.
Uses Of Silver Brazing
Silver brazing is an incredibly flexible process, it is a good process to know for any welder. It can be used to joint many dissimilar metals, stainless steel to copper to bronze to brass to carbon steel.
Silver brazing is typically used to joint carbide tooling inserts for machining operations, primarily for the reason that when silver brazing the metal does not usually approach a critical transition temperature that could lead to brittleness.
I once used silver braze to make a brass buckle with stainless steel hardware on the back. It is an powerful process sometimes more useful than welding.
FAQs
What is brazing silver?
Silver brazing is a joining process whereby a non-ferrous filler metal, alloy is heated to melting temperature (above 800°F) and distributed between two or more close-fitting parts by capillary attraction.
Which is stronger, silver solder or brazing?
Soldering, in addition to having a lower processing temperature, typically results in a lower-strength joint than a brazed joint. For many applications, this is suitable and even desirable. The shear strength of brazed joints typically exceeds that of soldered joints by a factor of five.
What gas do you use for silver brazing?
Silver Solder & Braze are both products used with either an Oxy Acetylene Torch or Oxy Propane Torch.
What is silver brazing flux used for?
A “flux” in metallurgy (derived from the Latin word fluxus – meaning “flow”) is the agent used for cleaning, flowing, or purifying. Their function can vary but are an essential component in brazing. Essentially, fluxes remove oxides and other contaminants in order to create solid, high quality brazed joints.
Can you silver braze without flux?
Like Silver Solder, the Braze material bonds with the surface of the metal being joined. Braze is used with a Flux, which chemically cleans the metal and keeps it clean during the Brazing process.
How much silver is in a silver brazing rod?
The most common rods used for typical HVAC brazing are 0%, 5%, and 15%, with several other levels mixed in there. The percentage is the percentage of silver content in the rod.