Welding, soldering, and brazing are methods of joining metal pieces. Welding joins metals using only heat or heat and pressure. It is classified into pressure welding and non-pressure welding. Soldering joins similar or dissimilar metals using a filler metal with a melting point below 450°C. It is classified into soft and hard soldering. Brazing also joins similar or dissimilar metals, but uses a special fusible alloy and flux above the alloy's melting point to form a bond.

1. 1. Welding
2. Soldering
3. Brazing

2. It is a metallurgical joining of two metal
pieces together to produce a single piece of
metal with or without filler material using (i)
only heat, or (ii) heat and pressure at plastic
state.
Types or classification of Welding
It is classified in to two types based on
the basic principles
(i) Pressure welding
(ii) Non-pressure or Fusion welding

7. Depending on the gas ratio(0.95 to 1.5) ,
 Neutral flame- 1:1
 Carburising flame- 0.95 to 1
 Oxidizing flame-1.15 to 1.5

8. Soldering is a method of joining similar or dissimilar metals by the application
of heat and using a filler metal or alloy called solder, whose liquidus
temperature is below 450 C.
Soldering is classified into soft soldering and hard soldering
Soft soldering is used extensively in sheet metal work, plumbing work and
electrical junctions for joining parts that are not exposed to the action of high
temperatures and are not subjected to excessive loads and forces or vibrations.
Hard soldering is used to produce a joint which can withstand higher load
and temperature also.
Basic steps of soldering process
i. Cleaning of the joining surfaces
ii. Flux applications
iii. Tinning of surfaces
iv. Heating
v. Final clean up

9. Brazing is the method of joining two similar or dissimilar metals
using a special fusible alloy.
Method of brazing
1. Cleaning the surface of the parts.
2. Application of flux at the place of joint.
3. Common borax and mixture of borax and boric
acid is used as flux.
4. The joint and the filler material are heated by gas
welding torch above the melting
temperature of the filler material.
5. It flows into the joint space and a solid joint is
formed after cooling.