D N SHARMA – TRAINING OFFICER
Training Programme for CoE Instructors
FOREMEN TRAINING INSTITUTE, DGE & T , Ministry of Labour, Govt. of India,
Bangalore
HAND BOOK ON “ WELDING
HISTRORY ”
FOREMEN TRAINING INSTITUTE
BANGALORE
D N SHARMA – TRAINING OFFICER
Training Programme for CoE Instructors
FOREMEN TRAINING INSTITUTE, DGE & T , Ministry of Labour, Govt. of India,
Bangalore
Great Versatility of welding: A proud occupation
Welding is the most economical and efficient way to join metals permanently. It is the only way of
joining two or more pieces of metal to make them act as a single piece. Since its job is integration,
Welding is vital to any country’s economy. For an example, it is often said that over 50% of the
gross national product of the U.S.A. is related to welding in one way or another. Welding ranks high
among industrial processes and involves more sciences and variables than those involved in any
other industrial process. Hence it speaks volumes about the importance and significance of welding
to the development of any nation.
The versatility of welding process can be without any effort can be visualized by its vast
applications. There are many ways to make a weld and many different kinds of welds. Some
processes cause sparks and others do not even require extra heat. Welding can be done anywhere…
outdoors
or
indoors,
underwater
and
FOREMEN TRAINING INSTITUTE
BANGALORE
in
outer
space.
D N SHARMA – TRAINING OFFICER
Training Programme for CoE Instructors
FOREMEN TRAINING INSTITUTE, DGE & T , Ministry of Labour, Govt. of India,
Bangalore
Nearly everything we use in our daily life is welded or made by equipment that is welded. Welders
help build metal products from coffeepots to skyscrapers. They help build space vehicles and
millions of other products ranging from oil drilling rigs to automobiles. In construction, welders are
virtually rebuilding the world, extending subways, building bridges, and helping to improve the
environment by building pollution control devices. The use of welding is practically unlimited.
There is no lack of variety of the type of work that is done. Some consider welding as an art and
some
as
science.
Probably the smallest group of welders, but perhaps those with the biggest impact on the public is
the artist and sculptors. The St. Louis Arch is possibly one of the best known. But there are many
other fountains and sculptures in cities and neighborhoods around the world.
Welders are employed in many industry groups. Machinery manufacturers are responsible for
agricultural, construction, and mining machinery. They are also involved in bulldozers, cranes,
material handling equipment, food-processing machinery, papermaking and printing equipment,
textiles, and office machinery.
The fabricated metals product compiles another group including manufacturers of pressure vessels,
heat exchangers, tanks, sheet metal, prefabricated metal buildings and architectural and ornamental
work. Transportation is divided into two major groups: manufacturers of transportation equipment
except motor vehicles; and motor vehicles and equipment. The first includes shipbuilding, aircraft,
spacecraft, and railroads. The second includes automobiles, trucks, buses, trailers, and associated
equipment.
A small group of welders belongs to the group of repair services. This includes maintenance and
repair on automobiles or refers to the welding performed on industrial and electrical machinery to
repair worn parts.
FOREMEN TRAINING INSTITUTE
BANGALORE
D N SHARMA – TRAINING OFFICER
Training Programme for CoE Instructors
FOREMEN TRAINING INSTITUTE, DGE & T , Ministry of Labour, Govt. of India,
Bangalore
The mining, oil extraction, and gas extraction industries form yet another group. A large portion of
the work involves drilling and extracting oil and gas or mining of ores, stone, sand and gravel.
Welders are also employed in the primary metals industries to include steel mills, iron and steel
foundries, smelting and refining plants. Much of this work is maintenance and repair of facilities and
equipment. Another group is the electrical and electronic equipment companies. Welding done by
this group runs from work on electric generators, battery chargers, to household appliances.
Public administration employs welders to perform maintenance welding that is done on utilities,
bridges, government armories and bases, etc. Yet another group involves wholesale and retail
establishments. These would include auto and agricultural equipment dealerships, metal service
centers, and scrap yards.
HISTORY OF WELDING: A Grand look back
The great events, only documented ones, are compiled here to appreciate one of the grand human
manifestations towards his journey to eternity. The means and methods are changing their faces to
meet the needs and desires of the humanity as a whole. The welding process is no exception. In all
cosmetic events, bonding, de-bonding
Middle Ages
Welding process can trace its historic development back to ancient times. The earliest examples
come from the Bronze Age. Small gold circular boxes were made by pressure welding lap joints
together. It is estimated that these boxes were made more than 2000 years ago. During the Iron Age
the Egyptians and people in the eastern Mediterranean area learned to weld pieces of iron together.
Many tools were found which were made approximately 1000 B.C.
FOREMEN TRAINING INSTITUTE
BANGALORE
D N SHARMA – TRAINING OFFICER
Training Programme for CoE Instructors
FOREMEN TRAINING INSTITUTE, DGE & T , Ministry of Labour, Govt. of India,
Bangalore
During the middle Ages, the art of blacksmithing was developed and many items of iron were
produced which were welded by hammering. It was not until the 19th century that welding, as we
know it today was invented.
1800
Edmund Davy of England is credited with the discovery of acetylene in 1836. The production of an
arc between two carbon electrodes using a battery is credited to Sir Humphry Davy in 1800. In the
mid-nineteenth century, the electric generator was invented and arc lighting became popular. During
the late 1800s, gas welding and cutting was developed. Arc welding with the carbon arc and metal
arc was developed and resistance welding became a practical joining process.
1880
Auguste De Meritens, working in the Cabot Laboratory in France, used the heat of an arc for joining
lead plates for storage batteries in the year 1881. It was his pupil, a Russian, Nikolai N. Benardos,
working in the French laboratory, who was granted a patent for welding. He, with a fellow Russian,
Stanislaus Olszewski, secured a British patent in 1885 and an American patent in 1887. The patents
show an early electrode holder. This was the beginning of carbon arc welding. Bernardos' efforts
were restricted to carbon arc welding, although he was able to weld iron as well as lead. Carbon arc
welding became popular during the late 1890s and early 1900s.
1890
In 1890, C.L. Coffin of Detroit was awarded the first U.S. patent for an arc welding process using a
metal electrode. This was the first record of the metal melted from the electrode carried across the
arc to deposit filler metal in the joint to make a weld. About the same time, N.G. Slavianoff, a
Russian, presented the same idea of transferring metal across an arc, but to cast metal in a mold.
1900
Approximately 1900, Strohmenger introduced a coated metal electrode in Great Britain. There was a
thin coating of clay or lime, but it provided a more stable arc. Oscar Kjellberg of Sweden invented a
FOREMEN TRAINING INSTITUTE
BANGALORE
D N SHARMA – TRAINING OFFICER
Training Programme for CoE Instructors
FOREMEN TRAINING INSTITUTE, DGE & T , Ministry of Labour, Govt. of India,
Bangalore
covered or coated electrode during the period of 1907 to 1914. Stick electrodes were produced by
dipping short lengths of bare iron wire in thick mixtures of carbonates and silicates, and allowing the
coating
to
dry.
Meanwhile, resistance welding processes were developed, including spot welding, seam welding,
projection welding and flash butt welding. Elihu Thompson originated resistance welding. His
patents were dated 1885-1900. In 1903, a German named Goldschmidt invented thermite welding
that
was
first
used
to
weld
railroad
rails.
Gas welding and cutting were perfected during this period as well. The production of oxygen and
later the liquefying of air, along with the introduction of a blow pipe or torch in 1887, helped the
development of both welding and cutting. Before 1900, hydrogen and coal gas were used with
oxygen. However, in about 1900 a torch suitable for use with low-pressure acetylene was developed.
World War I brought a tremendous demand for armament production and welding was pressed into
service. Many companies sprang up in America and in Europe to manufacture welding machines and
electrodes to meet the requirements.
1919
Immediately after the war in 1919, twenty members of the Wartime Welding Committee of the
Emergency Fleet Corporation under the leadership of Comfort Avery Adams, founded the American
Welding Society as a nonprofit organization dedicated to the advancement of welding and allied
processes. Alternating current was invented in 1919 by C.J. Holslag; however it did not become
popular until the 1930s when the heavy-coated electrode found widespread use.
1920
In 1920, automatic welding was introduced. It utilized bare electrode wire operated on direct current
and utilized arc voltage as the basis of regulating the feed rate. Automatic welding was invented by
P.O. Nobel of the General Electric Company. It was used to build up worn motor shafts and worn
crane wheels. It was also used by the automobile industry to produce rear axle housings.
FOREMEN TRAINING INSTITUTE
BANGALORE
D N SHARMA – TRAINING OFFICER
Training Programme for CoE Instructors
FOREMEN TRAINING INSTITUTE, DGE & T , Ministry of Labour, Govt. of India,
Bangalore
During the 1920s, various types of welding electrodes were developed. There was considerable
controversy during the 1920s about the advantage of the heavy-coated rods versus light-coated rods.
The heavy-coated electrodes, which were made by extruding, were developed by Langstroth and
Wunder of the A.O. Smith Company and were used by that company in 1927. In 1929, Lincoln
Electric Company produced extruded electrode rods that were sold to the public. By 1930, covered
electrodes were widely used. Welding codes appeared which required higher-quality weld metal,
which increased the use of covered electrodes.
During the 1920s there was considerable research in shielding the arc and weld area by externally
applied gases. The atmosphere of oxygen and nitrogen in contact with the molten weld metal caused
brittle and sometime porous welds. Research work was done utilizing gas shielding techniques.
Alexander and Langmuir did work in chambers using hydrogen as a welding atmosphere. They
utilized two electrodes starting with carbon electrodes but later changing to tungsten electrodes. The
hydrogen was changed to atomic hydrogen in the arc. It was then blown out of the arc forming an
intensely hot flame of atomic hydrogen during to the molecular form and liberating heat. This arc
produced half again as much heat as an oxyacetylene flame. This became the atomic hydrogen
welding process. Atomic hydrogen never became popular but was used during the 1930s and 1940s
for
special
applications
of
welding
and
later
on
for
welding
of
tool
steels.
H.M. Hobart and P.K. Devers were doing similar work but using atmospheres of argon and helium.
In their patents applied for in 1926, arc welding utilizing gas supplied around the arc was a
forerunner of the gas tungsten arc welding process. They also showed welding with a concentric
nozzle and with the electrode being fed as a wire through the nozzle. This was the forerunner of the
gas metal arc welding process. These processes were developed much later.
1930
FOREMEN TRAINING INSTITUTE
BANGALORE
D N SHARMA – TRAINING OFFICER
Training Programme for CoE Instructors
FOREMEN TRAINING INSTITUTE, DGE & T , Ministry of Labour, Govt. of India,
Bangalore
Stud welding was developed in 1930 at the New York Navy Yard, specifically for attaching wood
decking over a metal surface. Stud welding became popular in the shipbuilding and construction
industries.
The automatic process that became popular was the submerged arc welding process. This "under
powder" or smothered arc welding process was developed by the National Tube Company for a pipe
mill at McKeesport, Pennsylvania. It was designed to make the longitudinal seams in the pipe. The
process was patented by Robinoff in 1930 and was later sold to Linde Air Products Company, where
it was renamed Unionmelt® welding. Submerged arc welding was used during the defense buildup
in 1938 in shipyards and in ordnance factories. It is one of the most productive welding processes
and remains popular today.
1940
Gas tungsten arc welding (GTAW) had its beginnings from an idea by C.L. Coffin to weld in a
nonoxidizing gas atmosphere, which he patented in 1890. The concept was further refined in the late
1920s by H.M.Hobart, who used helium for shielding, and P.K. Devers, who used argon. This
process was ideal for welding magnesium and also for welding stainless and aluminum. It was
perfected in 1941, patented by Meredith, and named Heliarc® welding. It was later licensed to Linde
Air Products, where the water-cooled torch was developed. The gas tungsten arc welding process has
become one of the most important.
The gas shielded metal arc welding (GMAW) process was successfully developed at Battelle
Memorial Institute in 1948 under the sponsorship of the Air Reduction Company. This development
utilized the gas shielded arc similar to the gas tungsten arc, but replaced the tungsten electrode with a
continuously fed electrode wire. One of the basic changes that made the process more usable was the
small-diameter electrode wires and the constant-voltage poser source. This principle had been
patented earlier by H.E. Kennedy. The initial introduction of GMAW was for welding nonferrous
metals. The high deposition rate led users to try the process on steel. The cost of inert gas was
relatively high and the cost savings were not immediately available.
FOREMEN TRAINING INSTITUTE
BANGALORE
D N SHARMA – TRAINING OFFICER
Training Programme for CoE Instructors
FOREMEN TRAINING INSTITUTE, DGE & T , Ministry of Labour, Govt. of India,
Bangalore
1950
In 1953, Lyubavskii and Novoshilov announced the use of welding with consumable electrodes in
an atmosphere of CO2 gas. The CO2 welding process immediately gained favor since it utilized
equipment developed for inert gas metal arc welding, but could now be used for economically
welding steels. The CO2 arc is a hot arc and the larger electrode wires required fairly high currents.
The process became widely used with the introduction of smaller-diameter electrode wires and
refined power supplies. This development was the short-circuit arc variation which was known as
Micro-wire®, short-arc, and dip transfer welding, all of which appeared late in 1958 and early in
1959. This variation allowed all-position welding on thin materials and soon became the most
popular of the gas metal arc welding process variations.
1960
Another variation was the use of inert gas with small amounts of oxygen that provided the spraytype arc transfer. It became popular in the early 1960s. A recent variation is the use of pulsed
current. The current is switched from a high to a low value at a rate of once or twice the line
frequency.
Soon after the introduction of CO2 welding, a variation utilizing a special electrode wire was
developed. This wire, described as an inside-outside electrode, was tubular in cross section with the
fluxing agents on the inside. The process was called Dualshield®, which indicated that external
shielding gas was utilized, as well as the gas produced by the flux in the core of the wire, for arc
shielding. This process, invented by Bernard, was announced in 1954, but was patented in 1957,
when the National Cylinder Gas Company reintroduced it.
The electroslag welding process was announced by the Soviets at the Brussels World Fair in
Belgium in 1958. It had been used in the Soviet Union since 1951, but was based on work done in
the United States by R.K. Hopkins, who was granted patents in 1940. The Hopkins process was
never used to a very great degree for joining. The process was perfected and equipment was
FOREMEN TRAINING INSTITUTE
BANGALORE
D N SHARMA – TRAINING OFFICER
Training Programme for CoE Instructors
FOREMEN TRAINING INSTITUTE, DGE & T , Ministry of Labour, Govt. of India,
Bangalore
developed at the Paton Institute Laboratory in Kiev, Ukraine, and also at the Welding Research
Laboratory in Bratislava, Czechoslovakia. The first production use in the U.S. was at the
Electromotive Division of General Motors Corporation in Chicago, where it was called the Electromolding process. It was announced in December 1959 for the fabrication of welded diesel engine
blocks. The process and its variation, using a consumable guide tube, are used for welding thicker
materials.
The Arcos Corporation introduced another vertical welding method, called Electrogas, in 1961. It
utilized equipment developed for electroslag welding, but employed a flux-cored electrode wire and
an externally supplied gas shield. It is an open arc process since a slag bath is not involved. A newer
development uses self-shielding electrode wires and a variation uses solid wire but with gas
shielding. These methods allow the welding of thinner materials than can be welded with the
electroslag process.
Electro slag welding is a very efficient, single pass process carried out in the vertical or near vertical
position and used for joining steel plates/sections in thicknesses of 25mm and above. It was
developed by the Paton Institute in the Ukraine in the early 1950s and superseded the very high
current submerged arc process for making longitudinal welds in thick-walled pressure vessels.
Unlike other high current fusion processes, electro slag welding is not an arc process. Heat required
for melting both the welding wire and the plate edges is generated through a molten slag's resistance
to the passage of an electric current.
In its original form, plates are held vertically approximately 30mm apart with the edges of the plate
cut normal to the surface. A bridging run-on piece of the same thickness is attached to the bottom of
the plates. Water cooled copper shoes are then placed each side of the joint, forming a rectangular
cavity open at the top. Filler wire, which is also the current carrier, is then fed into this cavity,
initially striking an arc through a small amount of flux. Additional flux is added which melts
forming a flux bath which rises and extinguishes the arc. The added wire then melts into this bath
sinking to the bottom before solidifying to form the weld. For thick sections, additional wires may be
added and an even distribution of weld metal is achieved by oscillating the wires across the joint. As
FOREMEN TRAINING INSTITUTE
BANGALORE
D N SHARMA – TRAINING OFFICER
Training Programme for CoE Instructors
FOREMEN TRAINING INSTITUTE, DGE & T , Ministry of Labour, Govt. of India,
Bangalore
welding progresses, both the wire feed mechanism and the copper shoes are moved progressively
upwards until the top of the weld is reached.
Fig. Electro slag welding
The consumable guide variant of the process uses a much simpler set-up and equipment arrangement
which does not require the wire feed mechanism to climb. In this case, the wire is delivered to the
weld pool down a consumable, thick-walled tube which extends from the top of the joint to the
weldpool. Support for the molten bath is provided by two pairs of copper shoes which are moved
upwards, leapfrogging each other as welding progresses. The tubular guides can be further
supplemented by additional consumable plates attached to the tube. Generally, as the thickness of
plate increases, the number of wires/guides increases, approximately in the ratio of one wire per
50mm of thickness,
FOREMEN TRAINING INSTITUTE
BANGALORE
D N SHARMA – TRAINING OFFICER
Training Programme for CoE Instructors
FOREMEN TRAINING INSTITUTE, DGE & T , Ministry of Labour, Govt. of India,
Bangalore
Fig. Consumable guide welding
Current status
In the fabrication industry, the process continues to be used for thick walled pressure vessels which
are post-weld normalised and for structures such as blast furnace shells and steel ladles which are
used at above ambient temperatures. The process is also extensively used for the welding of railway
points.
Robert F. Gage invented plasma arc welding in 1957. This process uses a constricted arc or an arc
through an orifice, which creates an arc plasma that has a higher temperature than the tungsten arc. It
is also used for metal spraying and for cutting. The plasma welding details are elaborated below.
Plasma Arc Welding
In plasma arc welding, a shielded arc is struck between a non consumable electrode and the torch
body, and this arc transforms an inert gas into plasma. A plasma is a gas which is heated to an
extremely high temperature and ionized so that it becomes electrically conductive. Similar to GTAW
(TIG), the plasma arc welding process uses this plasma to transfer an electric arc to a work piece.
The metal to be welded is melted by the intense heat of the arc and fuses together. In the plasma
FOREMEN TRAINING INSTITUTE
BANGALORE
D N SHARMA – TRAINING OFFICER
Training Programme for CoE Instructors
FOREMEN TRAINING INSTITUTE, DGE & T , Ministry of Labour, Govt. of India,
Bangalore
welding torch a tungsten electrode is located within a copper nozzle having a small opening at the
tip. A pilot arc is initiated between the torch electrode and nozzle tip. This arc is then transferred to
the metal to be welded. Shielding gas is obtained from the hot ionized gas issuing from the orifice.
Auxiliary inert shielding gas or a mixture of inert gases is normally used.
By forcing the plasma gas and arc through a constricted orifice, the torch delivers a high
concentration of heat to a small area. With high performance welding equipment, the plasma process
produces exceptionally high quality welds. Like gas tungsten arc welding, the plasma arc welding
process can be used to weld most commercial metals, and it can be used for a wide variety of metal
thicknesses.
The electron beam welding process, which uses a focused beam of electrons as a heat source in a
vacuum chamber, was developed in France. J.A. Stohr of the French Atomic Energy Commission
made the first public disclosure of the process on November 23, 1957. In the United States, the
automotive and aircraft engine industries are the major users of electron beam welding.
As the electrons strike the workpiece, their energy is converted into heat, instantly vaporizing the
metal under temperatures near 25,000 °C. The heat penetrates deeply, making it possible to weld
much thicker workpieces than is possible with most other welding processes. However, because the
FOREMEN TRAINING INSTITUTE
BANGALORE
D N SHARMA – TRAINING OFFICER
Training Programme for CoE Instructors
FOREMEN TRAINING INSTITUTE, DGE & T , Ministry of Labour, Govt. of India,
Bangalore
electron beam is tightly focused, the total heat input is actually much lower than that of any arc
welding process. As a result, the effect of welding on the surrounding material is minimal, and the
heat-affected zone is small. Distortion is slight, and the workpiece cools rapidly, and while normally
an advantage, this can lead to cracking in high-carbon steel. Almost all metals can be welded by the
process, but the most commonly welded are stainless steels, superalloys, and reactive and refractory
metals. The process is also widely used to perform welds of a variety of dissimilar metals
combinations. However, attempting to weld plain carbon steel in a vacuum causes the metal to emit
gases as it melts, so deoxidizers must be used to prevent weld porosity. Electron Beam Welding is a
very similar process to Laser Beam Welding, except that electrons are focussed instead of photons in
the case of lasers. The advantage of using an electron beam is that the beam does not have a
tendency to diverge as laser beams do when they contact the workpiece. Some of the uses of EB
welding include making aerospace and automotive parts, as well as semiconductor parts and even
jewelry.
The amount of heat input, and thus the penetration, depends on several variables, most notably the
number and speed of electrons impacting the workpiece, the diameter of the electron beam, and the
travel speed. Greater beam current causes an increase in heat input and penetration, while higher
travel speed decreases the amount of heat input and reduces penetration. The diameter of the beam
can be varied by moving the focal point with respect to the workpiece—focusing the beam below the
surface increases the penetration, while placing the focal point above the surface increases the width
of the weld.
Most Recent:
Friction welding, which uses rotational speed and upset pressure to provide friction heat, was
developed in the Soviet Union. It is a specialized process and has applications only where a
sufficient volume of similar parts is to be welded because of the initial expense for equipment and
tooling. This process is called inertia welding.
FOREMEN TRAINING INSTITUTE
BANGALORE
D N SHARMA – TRAINING OFFICER
Training Programme for CoE Instructors
FOREMEN TRAINING INSTITUTE, DGE & T , Ministry of Labour, Govt. of India,
Bangalore
Laser welding is one of the newest processes. The laser was originally developed at the Bell
Telephone Laboratories as a communications device. Because of the tremendous concentration of
energy in a small space, it proved to be a powerful heat source. It has been used for cutting metals
and nonmetals. Continuous pulse equipment is available. The laser is finding welding applications in
automotive metalworking operations. A device that produces a concentrated coherent light beam by
stimulating electronic or molecular transitions to lower energy levels. Laser is an acronym for light
amplication by stimulated emission of radiation.
Two sources of welding energy that are focused beams that operate according to the laws of optics
are

LASER BEAM

ELECTRON BEAM
Two types of lasers are used for welding;
SOLID STATE LASERS
 GAS LASERS
Solid state lasers are single crystals or glass doped with small contractions of transition elements.

RUBY

Nd GLASS/ Nd-YAG
FOREMEN TRAINING INSTITUTE
BANGALORE
D N SHARMA – TRAINING OFFICER
Training Programme for CoE Instructors
FOREMEN TRAINING INSTITUTE, DGE & T , Ministry of Labour, Govt. of India,
Bangalore
Industrial gas lasers are carbon dioxide lasers. They can operate continuously or pulsed at very high
rate like Nd-YAG lasers.
In 1991 The Welding Institute (TWI), UK invented new solid state joining process and is called as
“Friction Stir Welding “( FSW) process. This process really stirred the entire welding community.
This process stretched its wings from the rail car to nuclear waste disposable containers, cylinders to
space shuttles. The maximum number of patents is given to this process.
The welding process developed using friction is given below.
Friction stitch
Welding
Friction Taper
Plug Welding
Friction
Plunge
Friction Hydro Pillar
Processing-FHPP
Friction Seam
Welding
Orbital friction
welding
Friction
Forming
Third- body
Friction joining
Friction
Surfacing
Friction
Brazing
Friction
Welding
Friction Transformation
Processing
Friction Acoustic
Bonding
Friction
Extrusion
Friction Filler
Processing
Friction
Cutting
Linear friction
welding
Arcuate friction
welding
Friction Stir
Welding
Inertia friction
welding
Radial friction
welding
Related technology
Third-body
Wear
tribology
Continuous Drive
Friction welding
Friction stud
welding
FOREMEN TRAINING INSTITUTE
BANGALORE
Skew-stir
Combined
Motion Stir
D N SHARMA – TRAINING OFFICER
Training Programme for CoE Instructors
FOREMEN TRAINING INSTITUTE, DGE & T , Ministry of Labour, Govt. of India,
Bangalore
AWS master chart of welding and allied processes
Laser Hybrid welding :
It is a type of welding process that combines the principles of laser beam welding and arc welding.
Introduction
The combination of laser light and an electrical arc into an amalgamated welding process has been
known since the 1970's, but has only recently been used in industrial applications. There are three
main types of hybrid welding process, depending on the arc used; TIG, Plasma arc or MIG
augmented laser welding. While TIG augmented laser welding was the first to be researched, MIG is
the first to go into industry and is commonly known as hybrid laser welding.
FOREMEN TRAINING INSTITUTE
BANGALORE
D N SHARMA – TRAINING OFFICER
Training Programme for CoE Instructors
FOREMEN TRAINING INSTITUTE, DGE & T , Ministry of Labour, Govt. of India,
Bangalore
Whereas in the early days laser sources still had to prove their suitability for industrial use, today
they are standard equipment in many manufacturing enterprises. The combination of laser welding
with another weld process is called a "hybrid welding process". This means that a laser beam and an
electrical arc act simultaneously in one welding zone, influencing and supporting each other.
Laser
Laser welding not only requires high laser power but also a high quality beam to obtain the desired
"deep-weld effect". The resulting higher quality of beam can be exploited either to obtain a smaller
focus diameter or a larger focal distance. A variety of laser types are used for this process, in
particular Nd:YAG where the laser light can be transmitted via a water cooled glass fiber. The beam
is projected onto the workpiece by collimating and focusing optics. Carbon dioxide laser can also be
used where the beam is transmitted via lens or mirrors.
Laser Hybrid process
For welding metallic objects, the laser beam is focused to obtain intensities of more than 1 MW/cm2.
When the laser beam hits the surface of the material, this spot is heated up to vaporization
temperature, and a vapor cavity is formed in the weld metal due to the escaping metal vapor. This is
known as a keyhole. The extraordinary feature of the weld seam is its high depth-to-width ratio. The
energy-flow density of the freely burning arc is slightly more than 100 kW/cm2. Unlike a dual
process where two separate weld processes act in succession, hybrid welding may be viewed as a
combination of both weld processes acting simultaneously in one and the same process zone.
Depending on the kind of arc or laser process used, and depending on the process parameters, the
two systems will influence each other in different ways.
The combination of the laser process and the arc process results in an increase in both weld
penetration depth and welding speed (as compared to each process alone). The metal vapor escaping
from the vapor cavity acts upon the arc plasma. Absorption of the laser radiation in the processing
FOREMEN TRAINING INSTITUTE
BANGALORE
D N SHARMA – TRAINING OFFICER
Training Programme for CoE Instructors
FOREMEN TRAINING INSTITUTE, DGE & T , Ministry of Labour, Govt. of India,
Bangalore
plasma remains negligible. Depending on the ratio of the two power inputs, the character of the
overall process may be mainly determined either by the laser or by the arc.
Absorption of the laser radiation is substantially influenced by the temperature of the workpiece
surface. Before the laser welding process can start, the initial reflectance must be overcome,
especially on aluminum surfaces. This can be achieved by preheating the material. In the hybrid
process, the arc heats the metal, helping the laser beam to couple in. After the vaporisation
temperature has been reached, the vapor cavity is formed, and nearly all radiation energy can be put
into the workpiece. The energy required for this is thus determined by the temperature dependent
absorption and by the amount of energy lost by conduction into the rest of the workpiece. In Laser
Hybrid welding, using MIG, vaporisation takes place not only from the surface of the workpiece but
also from the filler wire, so that more metal vapor is available to facilitate the absorption of the laser
radiation.
LASER-FSW HYBRID WELDING:
U.S. scientists say they've developed a hybrid process involving the use of a laser in friction-stir
welding to extend the application to more materials.
FSW, which has been in development for about 10 years, is a technique for joining small metal
alloys using a rotating tool to fasten metal components without melting.
The process is best suited for alloys with low melting points, such as aluminum, and materials that
are difficult to weld with conventional methods. However, extending FSW to high-temperature
metals and alloys such as steel and titanium has been problematic because of tool wear and material
requirements.
Scientists at the Oak Ridge National Laboratory say adding a laser to the FSW process to preheat
and soften the metal parts reduces wear on the tool.
FOREMEN TRAINING INSTITUTE
BANGALORE
D N SHARMA – TRAINING OFFICER
Training Programme for CoE Instructors
FOREMEN TRAINING INSTITUTE, DGE & T , Ministry of Labour, Govt. of India,
Bangalore
The researchers say the hybrid laser-assisted FSW technology will enable the industrial application
of FSW to joining high-temperature metals and alloys.
The U.S. Department of Energy's Office of Basic Energy Sciences, Energy Efficiency and
Renewable Energy and Fusion Materials fund the work.
FOREMEN TRAINING INSTITUTE
BANGALORE