Braze welding process
Braze welding process is a method of joining materials together where a non-ferrous filler metal with a melting point, below that of the base metal but above (427 0C )is used. By this process, a groove fillet plug or slot weld can be welded easily.
Brazing and Braze welding process
There is a slight difference between the brazing and the Braze welding process. Brazing associated with melting of a relatively low melting point filler material, being distributed by capillary attraction whereas braze welding is normally employed for welding grove, plug slot and fillet welds. and filler metal is deposited directly at the point where it is desired.
In Braze welding process, the joining surfaces are only heated to a temperature that corresponds to the melting point of the filler rod used. Filler rods, when molten, adhere to surfaces based on (deposited) surface tension or it touches the surfaces and forms a sound joint when freezing.
Thus we can say that braze welding is an intermediate process between the brazing process and the welding process.
Braze welding resembles brazing in the following respects:
Only Non-ferrous filler metals are used, Bonding is achieved without melting the base metal,It can be used to fill grooves and to make fillets. however, braze welding process is used because of the low hazard.
Metals to be welded
Typically, braze welding is used on steel and cast iron, but copper, nickel, and nickel alloys are also welded by this method.
Fluxes
The use of flux is an essential thing in braze welding. The main purpose of using flux in braze welding is to remove oxides from the metal edges and provide a chemically clean surface.
Operation steps
Joint preparation
Joint preparation is similar to that employed in gas welding, square grooves may ve used for a thickness of 2 mm and less.
Since the bond strength of a braze welded joint is dependent upon the bond area, the latter is increased for strength purpose by beveling the edges of the joint. such as, over 2mm thickness of metal, single or double V-grooves are prepared with 900 to 120 0 included angle to achieved large bond areas between the base metal and the filler metal.
Cleaning process
The surface of the joint should be thoroughly cleaned for achieving maximum bond strength. All types of foreign materials, dirt, oil, grease etc, should be removed from the surface to be braze welded.
Tools for cleaning
Chemical(cleaning solutions), steel wool, grinder, stiff wire brush, file, emery cloth, etc, are commonly used for cleaning purpose.
Alignment and preheating
The alignment of the part to be brazed is must to get the desired joint. Preheating of the part to be brazed are usually 425 0 C to 480 0 C.
Advantages of braze welding
In braze welding, less heat is required resulting in less distortion than in conventional welding. The weld deposit is relatively soft and ductile, providing machinability and low residual stresses. Fuel consumption is low but the welding speed is high. Brittle metals, such as cast iron, can be welded without preheating too much. Braze welding equipment is simple and well suited for on-site repair applications.
Disadvantages of braze welding
The joints are not satisfactory for service at over around 2600C, or for dynamic loads of around 1000 kg/cm2 or above. he colour of the joint may alter from the colour of the base metal.
