Welded Joints
Joining -
Welding, brazing, soldering and adhesive bonding.
-
Permenent joints
Assembly -
Mechanical methods (like screws, nut and bolts, pivots)
Some methods allows easy disassembly while others do not.
-
Welding - Joining process of two or more parts, combine at there surfaces by applying
heat and preassure.
(mostly use heat, some times preassure only, also some times use filler materials.)
&
Welding is a process of fusing multiple pieces of metal together by heating the filler metal to
a liquid state.
Structural welding is used to create metal frameworks for buildings, bridges, vehicles,
and a variety of other complex structures. Structural welding is also used to cut and repair
beams, columns, and girders.
↑
If rivets are used rather than welding we can't 100% efficiency. (rivets only can achive around 60-80% efficiency).
-
Properly welded joint is stronger than the base metal.
Importance of welding
&
Provides permenent hoints (single body)
&
In mterial usage and fabrication cost, most ecenomical way of joining. (don't need additional parts like screws, nuts)
-
Can accompolish even in the field. (not only in factory environment)
Limitations and Drawbacks
Mostly done by manually. (labor cost)
!Most processes utilize high energy.
Can't conveniently disassembly.
-
Can have quality defects which are difficult to detect.
Types of welding process
-
American Welding Society (AWS) catalogued 50 different types of welding processes.
-
These processes can divided into,
Fusion Welding
Solid State Welding
, Fusion Welding (Joining processes that melt the base metals)
In many fusion welding operations, a filler metal is added to the molten pool to facilitate the
process and provide bulk and added strength to the welded joint
A fusion welding operation in which no filler metal is added is called an autogenous weld.
(A fusion welding process using heat without the addition of filler metal to join two pieces of the same metal)
Examples : Arc welding (electric arc)
Resistance Welding (melts by heat from resistance to electrical current between faying
surfaces held together under pressure)
Oxyfuel Gas Welding (acetylene used)
Solid State Welding (coalescence results from application of pressure alone or a combination of heat
and pressure)
If heat is used, temperature is below melting point of metals being welded
No filler metal is added in solid state welding
Examples : Diffusion Welding (solid state fusion between two surfaces held under pressure at
elevated temperature.)
Friction Welding (coalescence by heat of friction between two surfaces.)
Ultrasonic Welding (ultrasonic oscillating motion in direction parallel to contacting
surface of two parts held together under preassure.)
Welding Applications
Constructions - buildings, bridges
piping, pressure vessel, boilers
shipbuilding
Automotive
Railroad
Three distinct zones of welded joints
Weld Metal (Fusion Zone)
HAZ
I
Base metal -
·
Heat affected zone
-
Weld metal Parent Metal
Joining -
Welding, brazing, soldering and adhesive bonding.
-
Permenent joints
Assembly -
Mechanical methods (like screws, nut and bolts, pivots)
Some methods allows easy disassembly while others do not.
-
Welding - Joining process of two or more parts, combine at there surfaces by applying
heat and preassure.
(mostly use heat, some times preassure only, also some times use filler materials.)
&
Welding is a process of fusing multiple pieces of metal together by heating the filler metal to
a liquid state.
Structural welding is used to create metal frameworks for buildings, bridges, vehicles,
and a variety of other complex structures. Structural welding is also used to cut and repair
beams, columns, and girders.
↑
If rivets are used rather than welding we can't 100% efficiency. (rivets only can achive around 60-80% efficiency).
-
Properly welded joint is stronger than the base metal.
Importance of welding
&
Provides permenent hoints (single body)
&
In mterial usage and fabrication cost, most ecenomical way of joining. (don't need additional parts like screws, nuts)
-
Can accompolish even in the field. (not only in factory environment)
Limitations and Drawbacks
Mostly done by manually. (labor cost)
!Most processes utilize high energy.
Can't conveniently disassembly.
-
Can have quality defects which are difficult to detect.
Types of welding process
-
American Welding Society (AWS) catalogued 50 different types of welding processes.
-
These processes can divided into,
Fusion Welding
Solid State Welding
, Fusion Welding (Joining processes that melt the base metals)
In many fusion welding operations, a filler metal is added to the molten pool to facilitate the
process and provide bulk and added strength to the welded joint
A fusion welding operation in which no filler metal is added is called an autogenous weld.
(A fusion welding process using heat without the addition of filler metal to join two pieces of the same metal)
Examples : Arc welding (electric arc)
Resistance Welding (melts by heat from resistance to electrical current between faying
surfaces held together under pressure)
Oxyfuel Gas Welding (acetylene used)
Solid State Welding (coalescence results from application of pressure alone or a combination of heat
and pressure)
If heat is used, temperature is below melting point of metals being welded
No filler metal is added in solid state welding
Examples : Diffusion Welding (solid state fusion between two surfaces held under pressure at
elevated temperature.)
Friction Welding (coalescence by heat of friction between two surfaces.)
Ultrasonic Welding (ultrasonic oscillating motion in direction parallel to contacting
surface of two parts held together under preassure.)
Welding Applications
Constructions - buildings, bridges
piping, pressure vessel, boilers
shipbuilding
Automotive
Railroad
Three distinct zones of welded joints
Weld Metal (Fusion Zone)
HAZ
I
Base metal -
·
Heat affected zone
-
Weld metal Parent Metal
