Induction brazing joins two identical or dissimilar metals by melting the filler metal below the base material. Induction heating is a fast, safe and energy-efficient brazing method. Most importantly, induction brazing guarantees consistent results. This is why it is increasingly used in industrial brazing.
Now, induction brazing is replacing flame brazing and it is increasingly used for joining metal joints. Before you choose to use induction brazing, you should understand the reasons for its popularity in numerous industries.
How does induction brazing work?
To understand how induction brazing works, you need to know the following:
Current density
Research led by Xiurong Fang for the prediction and optimization of large-diameter pipe induction brazing emphasizes that the correct current density during brazing is the most important parameter. One has to interplay between certain parameters, including air gap, current density, alloy viscosity, and capillary pressure.
If the chosen current density is accurate, then filler metal will flow between the gap and enable its distribution through capillary action in the joint area. The capillary action rate depends on the filler metal’s viscosity and the air gap. Joint strength depends on the bonding area; the greater the bonding area, the higher the strength of the joint.
Base metal must be cleaned prior to the induction brazing to remove oxides and prevent further oxidation. Wet the surface of the base metal with the flux. After brazing, flux is removed from the base metal under 400 ⁰C. Different methods are used to remove flux, but water quenching is the most famous one. Flux is not always essential, as phosphorous-bearing filler is used for brazing copper alloys.
Fixturing is also very important, as any fixture smaller than 50mm can be affected by electromagnetic current. It should be made with a non-magnetic material such as aluminum and austenitic stainless steel.
Filler metal
An article regarding brazing filler metals was published in the International Materials Reviewer by Way, M., Willingham, J., and Goodall, R. As per their research, a silver filler is normally used for brazing due to its low melting point. The eutectic temperature of the silver-copper braze is 593-898 ⁰C. Copper braze is the least expensive and has a melting temperature of 704-1176 ⁰C. Silver is the least common brazing filler with a melting temperature of 565-615 ⁰C.
Why induction brazing?
Induction brazing can produce strong, visually attractive, and shock-resistant joints compared to torch brazing. So, it overtakes conventional brazing due to the following potential benefits：
- Environment friendly
No open flame is involved in the induction brazing process. As in torch brazing, the flame is generated by fuel gases such as oxygen/acetylene or other gases. Explosion hazards are always associated with gas cylinders which must be handled carefully. No such hazard is involved in induction brazing.
- Quick and rapid heating
Induction heating supplies more energy per mm2 than an open flame. Induction heating can braze more parts per hour than any other brazing method. In furnace brazing, the entire assembly is brought into the furnace, whereas in the case of induction brazing, the localized part is heated, and filler flows into the joint through capillary action.
- High rate of repeatability
Variables such as time, positioning, fixtures, alloys, and temperature are controllable. Enter the required parameters, and the system will repeat the heating cycle. For temperature control, the induction brazing equipment installs pyrometers, thermocouples, or visual temperature sensors.
- No contact processes
No contact with the part is necessary during the process. It provides homogenous and minimal distortion.
- Small footprint
The device occupies a small space on the factory floor.
- No post machining
In flame brazing, oxidation, scaling, or carbon deposits can build up on the part. To clean the part, flux (which can weaken the joint) or expensive chemical baths are traditionally used. Vacuum bath furnaces can overcome these issues but possess limitations such as large size, lack of quality control, and poor efficiency. Induction brazing solves these problems as no post-milling or grinding is required since the joint is so clean and tidy.
What metals are joined by induction brazing?
As induction brazing is an excellent method for joining dissimilar metals such as steel copper, brass to copper, and steel to brass. Induction brazing is considered beneficial for joining steels where welding is not suitable. Well-designed induction brazed joint steel provides low stress/distortion by maintaining part integrity.
Through induction brazing, various materials can be brazed, including ferrous and even non-ferrous metals. Stainless steel, aluminum, cobalt, nickel, carbide, tungsten, chromium, diamond, noble metal, and stellites can be brazed by induction heating.
This joining technique can create multiple types of joints: a butt joint for flat plates and tubular parts, a lap joint for flat plates and tubular parts, and a butt lap joint for flat palates.
Industries that use induction brazing
Induction brazing is used in different industries worldwide, such as：
- Electricity Generator and Distributor: short circuit rings, switch gears, motors, transformer, turbo generators, strands, rings, wires and bars, and generators
- Aeronautic Industry: Hydraulic systems, fuel, fan blades, and blades for casings
- Automotive Parts: Brakes, fuel pipes, and AC
Its applications are also found in the appliances industry, agriculture, rails, tube, pipe, furniture, and aviation.
Choose your induction brazing equipment
Induction brazing consists of a generator rated by the generator’s frequency and power. It also has a heating coil equipped with a water cooling system. Various fixtures are available depending on the application to hold the part. Shroud the application to provide a vacuum or inert atmosphere to the component during induction brazing to prevent oxidation. Our company, FOCO, has automated equipment, which has increased the control over the brazing process parameters and, in turn, increased the product’s repeatability.
FOCO provides the ultimate solution to dimensional distortion and fume generation during brazing. Moreover, our induction brazing machine is well-equipped with a PLC control system and automatic feeding. Moreover, a wide range of induction brazing machines is available, whether it is an automated, handheld brazing machine or portable brazing machine.
If time is of the essence for you and you are looking for a rapid, cost-effective, efficient, and highly repeatable brazing process, then we offer you the solution for a wide range of materials and joint types.
