Brazing is a joining procedure in which a filler metal is melted and dispersed between the faying surfaces of the metal pieces to be bonded through capillary action.
Brazing does not cause the base metals to melt; only the filler melts.
The liquidus temperature of the filler material (spelter – 427°C) used for brazing is more than 450°C but lower than the solidus temperature of the base metal.
Capillary motion (the entry of fluid into tightly fitted surfaces) draws the filler metal into the joint.
The joint strength is greater than soldering due to the higher melting point of the filler material.
Almost all metals can be brazed together, with the exception of aluminium and magnesium, which are difficult to braze.
Brazing can be used to combine dissimilar metals such as stainless steel and cast iron.
Brazed joints are less prone to deformation because to the lower temperatures employed.
Without much talent, the joint can be completed rapidly. Because of the ease of the technique, it is frequently a cost-effective joining method with enough joint strength.
The brazed joints are somewhat stronger, depending on the filler metal strength.
However, due to the low melting temperature of the filler metal, the brazed joint is not suitable for high-temperature applications.
The colour of the filler metal in the brazed joint may differ from the colour of the base metal as well.
Because the filler metal is delivered to the joint via capillary action, it is critical that the joint be appropriately built.
The clearance between the two sections that will be linked must be closely monitored.
Another key consideration is the temperature of the filler metal as it enters the joint.
The base metal of the two components to be connected is not melted during brazing.
The filler metal must moisten the base metal surfaces on which it is applied, which is a critical condition.
The base metal of the two components to be connected is not melted during brazing.
The filler metal must moisten the base metal surfaces on which it is applied, which is a critical condition.
The filler metal diffuses or alloys with the base metal even if the base metal does not reach its solidus temperature.
Before brazing, the surfaces to be bonded must be chemically clean. Fluxes, on the other hand, are used to remove oxides from the surfaces.
During the brazing process, borax is the most commonly utilised flux. It dissolves the oxides of the majority of common metals.
Methods of Brazing:
Torch Brazing
It’s the most used brazing process. In most cases, heat is produced by burning a mixture of oxy-acetylene gas, as in gas welding. A carbonising flame is ideal for this since it generates the high temperatures required for brazing.
Furnace
It’s ideal for brazing a large number of small or medium-sized components. Typically, brazing filler metal is applied to the joint in the form of granule, powder, or strips, and then the assembly is heated in the furnace. In a furnace, a large number of small pieces can be brazed at the same time.
Braze
By way of phase transitions and oxide production, welding techniques where the base metal joint is melted and a joint with higher joint strength is formed are likely to cause metallurgical damage. The base metal is not melted in this technique; instead, a filler metal is used to create the junction.
When compared to welding, brazing has various advantages: (1) any metals, including dissimilar metals, can be joined; (2) certain brazing methods can be performed quickly and consistently, allowing for high cycle rates and automated production; (3) some methods can braze multiple joints at once; (4) brazing can be used to join thin-walled parts that cannot be welded; (5) Less heat and power are required in general than in fusion welding; (6) issues with the heat-affected zone in the base metal at the joint are decreased; and (7) joint locations that are inaccessible by many people are decreased.
Because capillary action draws the molten filler metal into the junction, welding procedures can be brazed.
- Joint strength is generally less than that of a welded joint; (2) while the strength of a good brazed joint is greater than that of the filler metal, it is likely to be less than that of the base metals; (3) high service temperatures may weaken a brazed joint; and (4) the colour of the metal in the brazed joint may not match the colour of the base metals.
- Brazing is widely utilised in many industries, including automotive (for example, joining tubes and pipes), electrical equipment (for example, joining wires and cables), cutting tools (for example, brazing cemented carbide inserts to shanks), and jewellery creation. In addition, brazing is used to join metal pipes and tubes in the chemical processing business, as well as plumbing and heating contractors. In practically all industries, the method is widely utilised for repair and maintenance work.
