Page 125 - CITS - Welder - Trade Theory

WELDER - CITS

Brazing filler road and fluxes, necessity of cleaning,

brazing parameter, Brazing techniques and cleaning

Objectives : At the end of this lesson you shall be able to
• describe the brazing filler and flux
• describe the brazing parameter
• explain the of brazing techniques and cleaning.

Brazing Filler Rod: Brazing is a process in which a non–ferrous filler alloy metal (copper + zinc) is used for
joining and having a melting point above 427°C.
Brazing filler wire melting point is the lower than base metal.
It is melted and made to flow between closely fitted surface by capillary attraction/capillary action.
No direct melting of Base metal (only preheating).
a (non – ferrous alloy metal)
b Brass filler wire - copper + zinc alloy.

c Aluminum + silicon alloy .
d Heat –resisting brazing alloys and
e Silver Brazing filler wire (silver + copper + zinc)
Brazing Flux
The following list of chemical compound includes the most common ingredients of fluxes.
1 Sodium
2 Potassium
3 Lithium
4 Borax, boric
5 Wetting agents

A flux is a chemical compound used in brazing.
Fluxed main work
1 Used to dissolve the oxide on the job and clean the surface.
2 During brazing flux to prevent atmosphere contents–air /Oxidation.
3 Brazing flux formed the slag and cover the bead and prevent the atmosphere contamination and cool the job
slowly, Control the temperature.
The common commercial fluxes
a Paste form
b Liquid form
c Powder form
Brazing Techniques: Clean the job and filler wire - free from oxides, oil, grease, dust, paint, moisture by using
wire brush. Filling, Grinding and acid cleaning/solvent cleaning/Alkaline cleaning.
1 Fluxing both the base metal and filler metal.
2 Alignment the base meat parts to be joined.
3 Heating the joint by gas flame (high pressure system/low pressure system),use oxidizing flame.
4 Heating the filler wire and deep the flux.
5 Applying brazing filler wire in to joint.
6 Cooling of the brazed joint Slowly.
7 Clean the joint.

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CITS : CG & M - Welder - Lesson 31 & 32