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METAL JOINING TECHNIQUES
1. WELDING
2. BRAZING
3. SOLDERING

BRAZING
IT IS A GROUP OF WELDING PROCESSES IN WHICH COALESCENCE IS PRODUCED BY HEATING TO SUITABLE TEMPERATURE ABOVE 8000F BUT BELOW THAT OF BARE METALS
TYPES OF BRAZING
1. TORCH BRAZING
2. FURNACE BRAZING
3. INDUCTION BRAZING
4. RESISTANCE BRAZING
EXOTHERMIC BRAZING
PROCESS IN WHICH HEAT REQUIRED TO MELT AND FLOW A COMMERCIAL FILLER METAL ALLOY IS GENERATED BY A SOLID STATE EXOTHERMIC CHEMICAL REACTION.
EXOTHERMIC PARAMETERS
IGNITION TEMPERATURE
REACTION DURATION
NET AVAILABLE ENERGY
IGNITION TEMPERATURE
SIGNIFIES THE TEMPERATURE AT WHICH SYSTEM INITIATES SPONTANEOUS PROPOGATIVE REACTION.
ESSENTIAL REQUIREMENT IS THAT HEAT GAINED FROM THE REACTION PLUS ANY HEAT SUPPLIED EXTERNALLY MUST BE GREATER THAN THE HEAT ENERGY ABSORBED WHEN ACTIVATING ADDITIONAL ADJACENT REACTING MOLECULES.
REACTION DURATION
RATE AT WHICH REACTANTS ARE CONSUMED AND THE PRODUCTS ARE FORMED.
CAN BE VARIED BY,
* ADDITION OF INERT MATERIALS THAT ABSORB HEAT
* ADDING A THIRD SUBSTANCE THAT REACTS AT A DIFFERENT RATE
* USING NON STOCHIOMETRIC PROPORTIONS
* VARYING POWDER PARTICLE SIZES
NET AVAILABLE ENERGY
DEFINES THE USEFUL HEAT OF ANY PARTICULAR REACTION.
EXPERIMENTALLY IT CAN BE DETERMINED BY MEASURING THE AREA BENEATH THE TIME TEMPERATURE GRAPH FOR ANY PARTICULAR REACTION.
EQUIPMENT AND PROCEDURE
SIMPLE TOOLING AND EQUIPMENT
SELECTION OF HEAT SOURCE AND BRAZE ALLOY
PARTS ARE CHEMICALLY AND MECHANICALLY CLEANED
EXTERNAL REACTION PRODUCTS ARE WASHED AWAY WITH HOT WATER
ADVANTAGES
NO EXTERNAL HEATING DEVICES ARE NEEDED
SOMETIMES NO SEPARATE FILLER METAL IS NEEDED
NO HUGE POWER REQUIREMENTS
SHORT HEATING TIMES
MINIMAL THERMAL EFFECTS DUE TO LOCALIZED HEAT
EASE OF HANDLING
REDUCED COST
INDUSTRIAL APPLICATIONS
TO BRAZE HONEYCOMB SANDWITCH PANELS
TO BRAZE INSERTS INTO PANELS LOCALLY
TO ATTACH SMALL PARTS TO LARGER STRUCTURES
IN BRAZING HYDRAULIC AND FUEL LINES IN A FUEL TANK
TO MAKE TUBING JOINTS