Brazing Process & Types of Brazing Rods

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Brazing Process & Types of Brazing Rods

Table of Contents

  • Principle of Brazing Process
  • Brazing
  • Four Requirements of Non-fusion welding
  • Important Properties in Brazing Rods
  • Key steps to successful Brazing Application
  • Advantages of Non-fusion – Brazing Process
  • Disadvantages of Non-fusion – Brazing Process\
  • Types of Brazing Rods

 

Brazing is based on the principle of solid phase welding process. Let us understand the process in further detail.

Principle of Brazing Process:

  • Solid phase welding is carried out
    • Below the melting point of base metal
    • Without using any filler additions
    • Often with the use of pressure
    • Union is often formed by plastic flow

Welding comes under Fusion process, whereas Brazing comes under Solid phase welding process.

Brazing:

In Brazing process, the joining happens with diffusion welding methodology, The joining takes place by atomic diffusion of the two surfaces in contact. Surfaces are usually heated to high temperatures but kept below the melting point of the base metal & pressure may be employed to ensure joining.

  • Brazing: This is a process that happens between 450 degrees and 750 degrees temperature. In this process, alloys with silver or copper base are used for Brazing.

Four Requirements of Non-fusion welding:

1. Clean Surface: In a non-fusion process, the metals bond with each other through adhesion, which occurs because of the molecular attraction between the bodies in contact.

    • Molecular bonding requires a clean surface.

2. Filler Rods: Filler rods are available for many non-fusion processes.

    • Brazing: Brazing rods are available as bare rods or flux coated rods.
    • Soldering: Solder can be solid or flux core/paste which can be tin, silver or zinc alloy.

3. Flux: Flux must be used with all non-fusion welding processes.
The purpose of flux is to:

    1. Chemically clean the metal
    2. Shield the process oxidation and atmospheric contamination
    3. Filler rods are available for many non-fusion processes.
    4. Brazing: Brazing rod is available as bare rods or flux coated.

4. Heat Source: The temperature of the base metal needs to be raised sufficiently above the melting point of the filler rod. Several heat sources can be used, as detailed below:

    • Oxyacetylene
    • Air acetylene
    • Air propane (LPG)
    • Oxy-propane
    • Electric soldering iron
    • Electric soldering gun

Important Properties in Brazing Rods:

  • Capillary Action: The capillary effect is a function or the ability of the liquid molten brazing material to wet a particular base material. Capillary action takes place when the metal surfaces, clean surfaces and flux are in close proximity to each other.

Key steps to successful Brazing Application:

  • Tinning: In the brazing process, before assembling the joint/seam, there is a step that requires both the surfaces to be coated with a thin layer of filler using the brazing rod. Popularly known as tinning, this step is followed by brazing to assemble sheet metal joints/seams.
  • Controlling Heat: Metals are excellent conductors of heat
    • When heat gets applied to a joint, it will move away to heat up the surrounding metal.
    • The greater the mass of metal that must be heated–the greater the heat requirement.

By applying excessive heat, we can make the flux burn. It could contaminate the joint requiring us to clean the joint again before brazing. There is a need for better manipulation of the heat source, if we are to heat both pieces evenly.

Advantages of Non-fusion – Brazing Process:

  • Lower temperature process
  • Easy assembly of parts
  • Weld dissimilar metals
  • Allow disassembly/realignment
  • Join metals of different thicknesses
  • Join diverse types of metal

Disadvantages of Non-fusion – Brazing Process:

  • Results in lower tensile strength
  • Not an efficient method for thick metal
  • Not an efficient method for large parts.

Types of Brazing Rods:

Brazing Rods are available in both ferrous and non-ferrous process for joining/welding different base materials.

  1. Aluminium
  2. Copper & its alloys
  3. Silver Brazing Alloys
  4. Steel

Hence is widely used in industries for joining various components. ADFL serves the industry by manufacturing and supplying the entire range of Brazing products, suitable for use in all three processes.

Difference between Welding, Brazing and Soldering

Table of Contents

  • Principle of Welding Processes
  • Principle of Brazing and Soldering Process
  • Welding / Shielded Metal Arc process (SMAW)
  • Basic Requirements for Welding / SMAW process
  • Welding Process Advantages
  • Limitations of Welding Process
  • Soldering & Brazing
  • Four Requirements of Non-Fusion Welding
  • Advantages of Non-Fusion –Brazing and Soldering Process
  • Dis-advantages of Non-Fusion – Brazing and Soldering Process

To understand the basic difference between the three processes namely welding, brazing & soldering, we need to know about types of welding processes by principle.

Principle of Welding Processes:

  • Fusion welding
    • Welding done in liquid state without using pressure
    • Union is by molten metal bridging of mating surfaces

Principle of Brazing and soldering Process:

  • Solid phase welding
    • Welding done below the melting point without any filler additions
    • Pressure is often used in this type of welding
    • Union often occurs when material is in plastic flow

The Welding process is a Fusion process where as brazing and soldering are both solid phase welding processes.

Let us understand more about these three processes, which are widely used by many industries.

Welding / Shielded Metal Arc process (SMAW):

Shielded Metal Arc process is also known as manual metal arc welding process. In this process, an arc gets established between parent metal and a flux coated welding electrode using electrical energy. This arc melts the deposit weld metal and nn this process, actual melting of base metal and welding electrode bridges the gap and forms the welding This process is one of the most used welding processes in the world.

Basic Requirements for Welding / SMAW process:

Heat source – Welding Equipment Current Range 30-400 A –depending on size of electrode in general, even though welding machines  that use up to 600 Amps AC as well as DC welding machines are equally useful in a SMAW Operation.

Welding Consumable: Flux coated welding electrodes (1.6- 8 mm diameter) are needed for the process along with a welder who is trained to manage the welding.

SMAW or MMAW is a commonly used welding process in the world.

Welding Process advantages:

  • Simplest of all welding processes
  • The equipment used is portable
  • Cost of equipment is economic
  • It has a variety of applications
  • There’s wide availability of electrodes
  • Can weld a wide range of metals & their alloys
  • Welding can be done from any position
  • Welding can be done indoors & outdoors
  • Welding cable extension goes very far

Limitations of welding process:

  • Low productivity as in a 10-minute cycle, welding happens only for 6 minutes
  • Process also involves frequent change of welding electrode
  • Moisture from flux coatings can create weld-related problems
  • Safety issues with arc strike, shocks from stray current/electric power
  • Process is completely manual as the name ‘Manual metal arc welding’ suggests

Soldering & Brazing:

In both the above processes joining  happens by diffusion welding methodology, The joining happens through atomic diffusion of two surfaces in contact. Surfaces are usually heated to high temperature (below their melting point) & pressure may also be employed.

  • Soldering: Soldering as a process happens below 450 degrees Celsius Normally lead or tin based alloys are used for soldering
  • Brazing: This process happens between 450 degrees and 750 Degrees Celsius Silver & copper-based alloys are used for brazing.

Four Requirements of Non-Fusion Welding

  1. Clean Surface: Non-fusion processes bond metal by adhesion, where adhesion happens to be the molecular attraction between bodies in contact.
  • Molecular bonding requires a clean surface.
  1. Filler Rod:
  • Filler rods are used in many non-fusion processes.
  • Brazing:
    1. Brazing rods can be bare rods or flux coated.

    Soldering:

    1. Solder can be solid or flux core/paste
    2. Can be tin, silver or zinc alloy
    3. Promotes wetting
  1. Flux :

Flux has applications in all non-fusion welding processes.

Purpose of flux:

  1. Chemically cleans the metal
  2. Shields weld from oxidation and atmospheric contamination
  1. Heat Source

The heat must be sufficient (BTU”s) to raise the base metal temperature above the melting point of the filler rod.

To achieve this, several heat sources can be used.

  1. Oxyacetylene
  2. Air acetylene
  3. Air propane (LPG)
  4. Oxypropane
  5. Electric soldering iron
  6. Electric soldering gun

Advantages of Non-Fusion –Brazing and Soldering Process:

  • Lower temperature process
  • Easy assembly of parts
  • Welding dissimilar metals
  • Allows disassembly/realignment
  • Joins metals of different thicknesses
  • Joint different types of metal

Dis-advantages of Non-Fusion – Brazing and Soldering Process:

  • Lower tensile strength
  • Not an efficient method for thick metal
  • Not an efficient method for large parts.

So, the essential difference between Welding, Soldering & Brazing is as below.

  1. Welding is a fusion process, where there is a homogenous bonding of joining surfaces.
  2. While brazing and soldering are basically non-fusion processes which use diffusion to join materials.

All three processes have a wide variety of applications in industries depending on the uses and requirements. ADFL serves the industry with manufacture and supply of products in all three processes.

Repair – Do not replace

welding brazing and soldering

Non-Fusion Welding with Brazing & Soldering

Table of Contents

  • Advantages & Disadvantages with Non-fusion welding
    • Advantages
    • Disadvantages
  • Four Requirements of Brazing and Soldering Process
    • Clean Metal
    • Filler Rod
    • Flux
    • Heat Source
  • Importance of Controlling Heat in Soldering & brazing
  • Soldering
  • Brazing

Brazing and soldering

Soldering and Brazing form a part of non-fusion welding processes, where only the filler rod is melted in the process.

The three common processes used in non-fusion welding are :

  • Soldering
  • Brazing 
  • Braze welding

Advantages & Disadvantages with Non-fusion welding

Let’s take a look at the advantages and disadvantages of this type of welding.

Advantages

  • Lower temperature
  • Easy assembly
  • Welds dissimilar metals
  • Allows disassembly/realignment
  • Joins metals of different thicknesses
  • Joins different types of metal

Disadvantages

  • Results in lower tensile strength
  • Not an efficient method for thick metal 
  • Not an efficient method for large parts 

Depending on the specific application, this welding is also an accepted method.

Four Requirements of Brazing and Soldering Process

  • Clean metal
  • Appropriate filler rod
  • Correct flux
  • Heat

Clean Metal:

This process needs the metal being welded to be clean, for the following reasons.

  • For Soldering and brazing processes bond metal by adhesion, which is the molecular attraction exerted between bodies in contact.
  • Molecular bonding requires a clean surface – not a polished surface.

Filler Rod 

Suitable filler rods are an essential part of the process. Such filler rods are available for many soldering and brazing processes.  

  • Brazing: A brazing rod is available as a bare rod or a flux-coated rod.
  • Soldering: 
    • Solder can be a solid or flux core/paste
    • Can be made of tin, silver, or zinc alloy.

 Flux:

Flux must be used with all soldering and brazing processes.

  • Three purposes of flux.
    • Chemically clean the metal
    • Shield from oxidation and atmospheric contamination
    • Promote wetting
  • Flux must be appropriate for the metal and filler material.
  • Flux is available in three (3) forms.
    • Paste
    • Powder
    • Liquid

Heat Source:

  • Heat is measured in British Thermal Units and must be sufficient in measure to raise the base metal temperature above the melting point of the filler rod to make soldering or brazing joint
  • Several heat sources can be used.
    • Oxyacetylene
    • Air acetylene
    • Air propane (LPG)
    • Oxy propane
    • Electric soldering iron
    • Electric soldering gun

Importance of Controlling Heat in Soldering & brazing:

  • Metals are excellent conductors of heat
    • Heat applied to the joint moves away from the joint.
    • The greater the mass of metal that must be heated–the greater the heat requirement.
  • Excessive heat will cause the flux to burn.
    • Contaminates the joint.
    • Joint must be re-cleaned
  • Manipulation of the heat source may be necessary to heat both pieces evenly.

Let’s understand Brazing and Soldering:

Soldering:

Soldering is a process that uses a metal alloy that melts below 450oC and may or may not use capillary action. Capillary action (wicking) occurs when a substance is able to draw another substance into it, like a wick draws oil in.

Solders are divided into two categories:

    • Soft
    • Hard
  • Soft soldering
    • Lead or lead replacement solder
    • Lower tensile strength
    • Copper pipe and sheet metal
    • Stained glass
  • Hard soldering
    • Silver-based solders
    • Jewelry

Brazing:

The brazing process uses a metal alloy that melts above 450oC but has a lower melting point in comparison to the base metal. The melted filler metal gets drawn into the joint or kept in the joint through capillary action, and the brazing process relies on this. The capillary effect requires very minute gaps between metal surfaces, clean surfaces, and flux, and is a function of the ability of a liquid to wet a particular material. This is why the basic difference between soldering and brazing is the temperature of the process.

ADFL is one of the few companies in India manufacturing Brazing Alloys and Soldering alloys with the required flux. This product range of Ador Fontech limited signifies our concept of Life Enhancement of Industrial components to the complete satisfaction of customers.  

Reclaim. Do not Replace.

 

Also read:- Corrosion and Cracks in Kiln Shells