Category: Welding

Induction Brazing | 7 Common Things Nobody Told You About Furnace Brazing Today | Copper Brazing Torch Ultimate Guide | Why You Must Experience Infrared Brazing Process At Least Once In Your Lifetime

Induction Brazing

There are numerous brazing methods are available. Some of them are Induction Brazing,  Furnace Brazing, copper brazing torch, infrared brazing, laser brazing, dip brazing, resistance brazing etc.

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Induction brazing is a method of joining two metals using a filler substance that melts, flows, and wets the metal surfaces at a temperature lower than the two metals melting temperatures. Induction brazing machines are capable of brazing copper, steel, brass, aluminium, and a variety of other metal combinations.

Induction brazing heats just the areas of your item that require it, resulting in a very uniform and reproducible process that produces a precise, consistent quality braze every time. The tiny size of induction brazing allows it to be easily incorporated into lean production processes, freeing up valuable floor space.

Induction Brazing process steps:

Step 1: Both joints are cleaned (not polished) and fluxed

Step 2: A heat (about 450° C) is applied to the base metal, were the filler metal is melted. Excess heat burn the fluxes. So we have to repeat the process again.

Step 3: Filler metal is applied to the joint

Step 4: Filler metal adheres to both the surfaces forming a bead

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The Advantages of the Induction Brazing Process

Induction brazing is a great way to connect steel pieces when welding isn’t an option. Many advantages of a well-designed induction brazed steel joint include part geometry integrity and lowered part stress. Carbon and stainless steel have a high resistance, which allows them to easily pair with induction energy and heat. Induction brazing of steel pieces, on the other hand, should not be hurried due to their poor heat conductivity. For appropriate flow and wetting out of the braze material with steel, it is critical that the heat be allowed to soak through to the joint surface.

Various classifications of Induction Brazing’s are:

Hand Torch brazing:

In torch brazing, flux is applied to the part surfaces and a torch is used to direct a flame against the work in the surrounding area of the joint. A reducing flame is typically used to inhibit oxidation. After the work piece joint areas have been heated to a suitable temperature, filler wire is added to the joint, usually in wire or rod form. Fuels used in torch brazing include acetylene, propane and other gases with air or oxygen.

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In our manufacturing environment, brazing is one of three joining methods that employs heat and a molten filler metal to build complicated structures. The three joining processes namely welding, soldering and brazing.

Requirements for Torch-Brazing

Torch brazing, or flame brazing as many seem to name it, is the process of joining metals with a non-oxidizing flame. If feasible, the flame should wrap around the whole joint to uniformly heat the base metal across the joint region, allowing the heat in the base metal to melt a Brazing Filler Metal that is touched to its surface rather than the torch flame melting the Brazing Filler Metal.

01-hand gas torch brazing

In addition to the numerous ferrous alloys on which it is widely employed, this torch brazing method has shown to be helpful in connecting a wide range of base metals, including aluminium, copper, copper alloys, and many other nonferrous metals.

Is it possible to braze using only propane?

Certainly possible, but you’ll need to keep the environment under control such that heat loss to the ambient and components is less than the heat injected into the braze joint. It’s a typical braze alloy typically melts between 1250 and 1305 degrees Fahrenheit.

Is it possible to melt steel using a butane torch?

No, a butane torch doesn’t provide much heat or energy to melt metals like steel. The heat generated by a butane flame is significantly lower than that produced by other welding torches, and it cannot melt metals. The temperature of a blue focused flame would be very near to 2500 degrees Fahrenheit, but the difficulty is that the heat would be drawn away from the metal, as previously stated.

Furnace brazing:

Furnace brazing uses a furnace to supply heat for brazing and is best suited to medium and high production. In medium production (usually in batches), the components and brazing metal are loaded into furnace, heated to brazing temperature and then cooled and removed.

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Furnace brazing is a semi-automated method of joining metal components using a lower filler metal that is dissimilar. Simple or sophisticated designs of one joint or multiple joint assemblies can be joined using furnace brazing.

Vacuum brazing is one of the most frequent types of furnace brazing that takes place in a vacuum furnace. Cleaning the parts to be connected, applying brazing filler metal to the surfaces to be joined, and then placing them in the furnace. After the furnace has been evacuated from the air, the entire assembly is brought to brazing temperature in order to eliminate any oxidation or contamination caused by the melting of the brazes and flowing into the joints.

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Brazing furnace types

A number of methods are used for furnace brazing. They contain several furnace designs, including batch and continuous furnaces.

  • Vacuum type
  • Atmosphere controlled type
  • Continuous belt/mesh
  • Atmosphere reduction type

What are the benefits of furnace brazing?

Other metal-joining methods, such as induction or torch brazing and welding, have numerous disadvantages. Furnace brazing does not melt the joint’s base metal. The technique provides clean components and brazed joints without the need for additional polishing, allowing for tighter tolerances.

Why is it that bike frames are brazed rather than welded? The decision is both aesthetic and financial. Because brazed frames require more finishing work than TIG welded frames, they are more costly.

Induction brazing:

Induction brazing utilized heat from electrical resistance to a high frequency current induced in the work. The parts are pre-loaded with filler metal and placed in a high frequency AC field. The parts do not directly contact the induction coils. Frequency ranges from 5 kHz to 5 Mhz.

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Resistance brazing:

Heat to melt the filler metal in resistance brazing is obtained by resistance to the flow of electrical current through the parts. As distinguished from induction brazing, the parts are directly connected to the electrical circuit in resistance brazing. The equipment is similar to that used in induction welding, except that a lower power level is required for brazing.

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A variant of the resistance welding technique is resistance brazing. The heat is provided by Joules Law H= I2RT, much like in spot welding. A squeeze weld and hold cycle is used to process the resistance brazing operation. Electrodes are present and they are holded to applying the brazing operation. A small piece of braze alloy is placed between the pieces being connected to distinguish the procedure.

The objective is to melt the braze material and bind it to both mating surfaces by heating it. The current is then switched off, and allowing the braze material to solidify. As a consequence, the pieces are joined together via a brazed joint. Adjustable holders with a low force are commonly utilised. This method is used to bind materials that are difficult to spot weld, such as copper, brass, and precious metals.

Dip brazing:

In dip brazing, either a molten salt bath or a molten bath accomplishes heating. In both methods, assembled parts are immersed in the baths contained in a heating pot. Solidification occurs when the parts are removed from the bath.

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Using an extremely high temperature filler metal, dip induction brazing connects distinct components without melting the base metals of each piece (liquidus temperature of over 840 degrees Fahrenheit). The joint’s tight fit is achieved by capillary action, which distributes the filler metal along the bond.

Dip induction brazing is particularly well suited to brazing aluminium since air is removed from the operation, avoiding oxide development. Brazing is used in almost every aspect of the manufacturing industry. The filler metal in aluminium dip brazing is essentially 88 percent aluminium and 12 percent silicon.

After being chemically treated, the brazed components are joined with the filler metal positioned as close to the joints as feasible. The assembly is next warmed to 1,025°F in an air furnace to ensure that all of the different masses in the assembly are at the same temperature. After that, the component is submerged in a molten salt bath. 

Aluminum brazing flux is what these salts are. In a salt bath furnace, the bath is kept at 1,095°F5°F. The molten flux comes into touch with all internal and exterior surfaces simultaneously when the assembly is submerged or dipped. The length of time spent immersed is governed by the mass to be heated, although it is seldom more than two minutes.

Infrared brazing:

Infrared brazing uses heat from a high intensity infrared lamp. Some IR lamps are capable of generating up to 5000 W of radiant heat energy, which can be directed at the work-piece for brazing.

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With a high heating rate of up to 50 degrees Celsius per second, infrared heating is a great option. It is a highly powerful instrument used in the brazing process. Because of the high demand from the chemical and aerospace industries, the relevance of brazing Ti alloys has grown over the last two decades.

Focused light energy (usually from high-intensity quartz lamps) is utilised to heat components to brazing temperature in infrared brazing. Furthermore, because energy transmission is not dependent on the production of electrical currents inside the assembly, concentrated light energy has the capacity to heat non-metallic components.

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Brazing Technology | How To Brazing | Brazing Joints | Brazing Filler and Flux

What is Brazing

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Brazing Technology is a joining process in which a filler metal is melted and dispersed by capillary action between the faying surfaces of the metal parts being joined. No melting of the base metals occurs in brazing; only the filler metals are melted. In brazing, the filler metal (also called as brazing metal), has a melting point is above 840° F (450° C) but below the melting point of the base metal to be joined. Tensile strength of the joint is about 40000 psi.

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Advantages of Brazing:

Brazing has numerous advantages compared to welding:

  1. Any metals can be joined including dissimilar metals
  2. Certain brazing methods can be performed quickly and consistently, thus permitting high cycle rates and automated production
  3. Some methods allow multiple joints to be brazed simultaneously
  4. Brazing can be applied to join thin walled parts (But welding doesn’t)
  5. Less heat and power are required than in fusion welding
  6. Brazed joint’s never penetrate the base metal (were the welded joint penetrate the base metal)

Limitations of Brazing:

Brazing also has some disadvantages:

  1. Brazing’s joint strength is normally less than that of a welded joint
  2. Even though the strength of a good brazed joint is better than that of the filler metal, it is likely to be less than that of the base metals
  3. High operational temperatures may weaken the brazed joint
  4. The color of the metal in the brazed joint may not match the color of the base metal parts. It is an aesthetic disadvantage.

Brazing Joints:

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Brazing Filler metal:

  • Copper brazing filler metal
  • Silver brazing filler metal
  • Coated brass brazing filler metal
  • Nickel brazing
  • Aluminum brazing
  • Mild steel brazing
  • Aluminium – silicon brazing
  • Copper – phosphorus brazing
  • Magnesium brazing

To qualify as a brazing metal, the following characteristics are needed:

  1. Melting temperature must be compatible with base metal
  2. Low surface tension in liquid phase for good weldability
  3. High fluidity for penetration into the interface
  4. Capability of being brazed into a joint of adequate strength for the application
  5. Avoidance of chemical and physical interactions with base metal

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Filler metals practiced to the brazing operation in a variety of ways. The brazed metal comes as wire, rod, sheets, strips, powders, pastes and preformed parts made of braze metal. They designed to fit a particular joining configuration and cladding on one surface to be brazed.

Brazing Flux:

Brazing fluxes (aluminum brazing flux, silver brazing flux) serve as a similar purpose as in welding. They dissolve or combine or slow down the formation of oxides and other unwanted by products in the brazing process. Use of a flux doesn’t substitute for the cleaning steps described previously.

Brazing Fluxes are available in three phases. They are:

  1. Paste
  2. Powder
  3. Liquid

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Characteristics of a good flux include:
  1. Flux has low melting temperature
  2. It has low viscosity so that it can be displaced by the filler metal
  3. Fluxes facilitates wetting
  4. It protects the joint until solidification of the filler metal starts. The flux should also be easy to remove after brazing operations.
  5. Chemically cleans the metal surfaces
  6. It shields the process from oxidation and atmospheric contamination

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