Dedan Kimathi University of Technology
Course; Manufacturing Processes I
BRAZING PROCESSES
This document provides an in-depth technical analysis of brazing, defined as a liquid phase process using capillary
attraction. It
details the critical role of fluxes in chemically removing oxides and reducing surface tension, alongside the selection of
filler metals like
aluminum-silicon and copper-phosphorus. The notes offer a comparative study of six industrial brazing methods,
complete with
operational diagrams, component functions, and specific troubleshooting protocols for joint failures.
Key Topics Covered:
• Fundamentals: Capillary action, melting points (>450°C), and surface preparation requirements.
• Flux Functions: Oxide removal, oxidation prevention, and cooling time reduction.
• 6 Core Methods:
o Furnace Brazing: Automated heating cycles and alignment.
o Resistance Brazing: Utilizing electrode pressure and electric current.
o Torch Brazing: Manual gas torch applications for versatile joint shapes.
o Dip Brazing: Molten salt bath immersion for uniform heating and fluxing.
o Induction Brazing: High-frequency magnetic fields for localized heating.
o Infrared Brazing: Radiant energy heating and reflectivity limitations.
• Troubleshooting: Solutions for non-wetting surfaces and filler metal flow issues.
Target Audience: Mechanical Engineering Students, Workshop Technicians, and Manufacturing Engineers.
, BRAZING
Brazing is a liquid phase process whereby molten filler metal is drawn into the gap between closely adjacent
surfaces by capillary attraction. The melting point of the parent material is usually higher than that for the filler
metal. In most cases, the melting point for the filler is above 450 degrees Celsius.
The filler material can be in form of wire, foil, filings, slugs, powder, paste, tape etc. The brazing filler metals
can be aluminium-silicon, copper, copper-zinc, copper-phosphorus, nickel-gold, magnesium and silver.
The material for the filler and parent metals should have similar chemical and physical properties and the
design of the joint should have a gap into which the filler metal will be drawn into.
Extremely clean surfaces for the joint produce quality joints. Preparations such as grinding, sandblasting, wire
brushing, filing and machining can be employed to remove dust, oil etc.
Functions of fluxes;
• Removes oxides from the surface chemically
• Avoid oxidation during preheat
• Helps to decrease the surface tension of the molten filler metal so that it can flow and spread over the
surface easily
• Reduce the co0ling time
Types of brazing
1. Furnace brazing
The cleaned parts are assembled in a furnace. The parts should are designed to hold themselves in the correct
alignment during the heating and cooling cycles without the need for external fixtures or clamps. The filler
metal is preplaced near or in the joint.
1|Page
Course; Manufacturing Processes I
BRAZING PROCESSES
This document provides an in-depth technical analysis of brazing, defined as a liquid phase process using capillary
attraction. It
details the critical role of fluxes in chemically removing oxides and reducing surface tension, alongside the selection of
filler metals like
aluminum-silicon and copper-phosphorus. The notes offer a comparative study of six industrial brazing methods,
complete with
operational diagrams, component functions, and specific troubleshooting protocols for joint failures.
Key Topics Covered:
• Fundamentals: Capillary action, melting points (>450°C), and surface preparation requirements.
• Flux Functions: Oxide removal, oxidation prevention, and cooling time reduction.
• 6 Core Methods:
o Furnace Brazing: Automated heating cycles and alignment.
o Resistance Brazing: Utilizing electrode pressure and electric current.
o Torch Brazing: Manual gas torch applications for versatile joint shapes.
o Dip Brazing: Molten salt bath immersion for uniform heating and fluxing.
o Induction Brazing: High-frequency magnetic fields for localized heating.
o Infrared Brazing: Radiant energy heating and reflectivity limitations.
• Troubleshooting: Solutions for non-wetting surfaces and filler metal flow issues.
Target Audience: Mechanical Engineering Students, Workshop Technicians, and Manufacturing Engineers.
, BRAZING
Brazing is a liquid phase process whereby molten filler metal is drawn into the gap between closely adjacent
surfaces by capillary attraction. The melting point of the parent material is usually higher than that for the filler
metal. In most cases, the melting point for the filler is above 450 degrees Celsius.
The filler material can be in form of wire, foil, filings, slugs, powder, paste, tape etc. The brazing filler metals
can be aluminium-silicon, copper, copper-zinc, copper-phosphorus, nickel-gold, magnesium and silver.
The material for the filler and parent metals should have similar chemical and physical properties and the
design of the joint should have a gap into which the filler metal will be drawn into.
Extremely clean surfaces for the joint produce quality joints. Preparations such as grinding, sandblasting, wire
brushing, filing and machining can be employed to remove dust, oil etc.
Functions of fluxes;
• Removes oxides from the surface chemically
• Avoid oxidation during preheat
• Helps to decrease the surface tension of the molten filler metal so that it can flow and spread over the
surface easily
• Reduce the co0ling time
Types of brazing
1. Furnace brazing
The cleaned parts are assembled in a furnace. The parts should are designed to hold themselves in the correct
alignment during the heating and cooling cycles without the need for external fixtures or clamps. The filler
metal is preplaced near or in the joint.
1|Page
