This document provides an introduction to welding and related processes. It discusses weldability, the different types of welding including plastic, fusion and cold welding. It classifies welding processes and discusses the metallurgy and structural changes involved in welding. Specifically, it describes gas welding and oxy-acetylene welding in detail, including the flame types, welding technique and required equipment. The document serves as an overview and introduction to various welding concepts and processes.

1. Basic of Welding 1
Welding and Related Processes
Session-I
By Rahul S.

2. Basic of Welding 2
Content:
• Introduction
• Weldability
• Types of welding
• Classification of welding processes
• Metallurgy of weld
• Gas welding
– Oxy-Acetylene Welding
• Welding Equipment

3. Basic of Welding 3
Introduction
• Welding is process of joining similar metals by application of
heat
• Fabrication industry depends on the welding
• Deriving new material depends on its weldability

4. Basic of Welding 4
Weldability
• Capacity of being welded having specific properties as weld strength,
proper structure
• Weld quality and the ease it can be done
• Weldabilty depends on
– melting point
– thermal conductivity
– thermal expansion
– surface condition
– change in microstructure
• Metallurgical, chemical, physical and thermal characteristics can be
controlled by,
– proper shielding atmosphere
– proper fluxing material
– proper filler material
– proper welding procedure
– proper heat treatment of the metal before and after deposition

5. Basic of Welding 5
Types of Welding
• Plastic welding
– Pressure welding
– Metal heated upto plastic state and then forced together by external pressure
– e.g. forge welding, resistance welidng.
• Fusion welding
– nonpressure welding
– metal is heated to molten state and the allowed to solidify
– e.g. gas welding, thermit welding.
• Cold-welding
– Without application of heat
– parts are joined by application of pressure, by bonding of inter surface
molecular structure
– used for nonferous materials like aluminium and its alloys.

6. Basic of Welding 6
Classification of welding processes

7. Basic of Welding 7
Metallurgy of weld
• Fusion welding
– Number of runs made to deposite the weld material
– In single run long columnar crystal will meet at the centre.
– In multirun welding second run normalises the first layer, results inthe proper
grain structure.
– In multirun there is possibility of slag and gas inclusions.
• Pressure welding
– Metal is heated to the plastic condition and compressed while hot
– hot working result in some grain refinement
• Heat affected zones

8. Basic of Welding 8
Structural changes in Welding

9. Basic of Welding 9
Gas Welding
• Burning a combustible gas with air or oxygen in a concentrated
flame of high temperature
• Flame is used to heat and melt the parent metal and the filler rod
• Oxy-Acetylene Welding
– Oxygen and Acetylene are used for the producing the flame
– The flame melts the edges or surface to be joined, so molten metal flows
and solidify to produce a joint on cooling
– Used from 2mm to 50mm thickness plates
– For thickness more than 15mm filler rod to be used
– Filler rod material mostly as same as the parent material
– Flux to be used to avoid impurities and the oxidation

10. Basic of Welding 10
Oxy-Acetylene Welding
• Flame temperature of different gases

11. Basic of Welding 11
Oxy-Acetylene Welding
• Neutral Flame
– Oxygen and acetylene are in same proportion
– Sharp brilliant cone of short distance from tip of the torch
– Outer cone faintly luminous and bluish in colour
– First developes heat and secong protect molten metal from oxidation
• Carburising Flame
– Excess of acetylene
– Sharply defined inner cone
– intermediate cone of whitish colour
– Bluish outer cone
– It gives higher carbon content results in hard and brittle weld
• Oxidising Flame
– Excess of oxygen
– Small inner cone which has purplish tinge
– Outer cone or envolope
– Used for welding brass

12. Basic of Welding 12
Gas welding technique

13. Basic of Welding 13
Welding Equipment
• Welding torch
• Welding tip
• Pressure regulator
• Hose and hose
fittings
• Goggles, gloves and
spark-lighter
• Gas cylinder

14. Basic of Welding 14
• Thank you...
– Next session will be on other welding processes as arc welding,
resistance welding, thermit welding etc