FABRICATION AND WELDING TC II NOTES BASIC

Note for Technical Colleges

1. FABRICATION AND WELDING TC2
What is Welding?
Welding is a fabrication process that lets you join materials like metals by using heat at high
temperatures. Welding uses high temperature to join the materials, whereas soldering and
brazing do not allow the base metal to melt. After cooling, the base metal and the filler metal get
attached.
The welding process came to light when there was a search for the technique for developing iron
into useful shapes. Welded blades were the first result of welding in the early years—the
carburization of iron produced hard steel that was very brittle for usage. Later interlaying the
rigid and soft iron with high-carbon material and hammer forging resulted in a tough and durable
blade.
The process of welding uses filler material. The filler material is the pool of molten material that
aids in the formation of a strong link between the base metal. The shielding process after welding
the metals protects both the base and filler components from being oxidised.
From gas flame to ultrasound, many energies are used in welding like electron beams, electric
arc, LASER, and friction. Now let us understand various types of welding.
Types of Welding
There are many types of welding used for various purposes under different situations. They are:
Manual welding includes:
 Forge welding
 Arc welding
 Oxy-fuel welding
 Shielded metal arc welding
 Gas metal arc welding
 submerged arc welding
 flux-cored arc welding
 electroslag welding
 Laser beam welding
 electron beam welding

2.  magnetic pulse welding
 friction stir welding
Forge Welding
Forge welding is the early version of welding where it was used to join the small iron pieces to
make larger valuable pieces. It is the simplest welding method where two metals are heated and
joined, and later hammered for the finishing purpose.
Arc Welding
Arc welding is the most common type of welding seen today. Arc welding is a type of welding in
which an electric arc is created to heat and join metals. Tiny globules of molten metal are
transferred from the metal electrode to the weld joint.
Oxy-Fuel Welding
Oxy-fuel welding is oxy welding, gas welding, or oxy acetylene welding. This process uses the
combustion of fuel gases like acetylene and oxygen to weld or cuts the metals. Edmond Fouché
and Charles Picard, French engineers in 1903, developed Oxy-fuel welding.
When acetylene and oxygen are mixed in proper measures inside the hand-held torch or
blowpipe, the hot flame is produced in the hand-held torch measuring 3,200 degrees Celsius. The
flame’s intensity can be manipulated by altering the proportion of the volume of oxygen to
acetylene. Welding can be done using this flame.
Shielded Metal Arc Welding
Various names like flux shielded arc welding, manual metal arc welding, or stick welding are
known as shielded metal arc welding. It is a manual welding process that uses an electrode
covered with flux to perform welding.
AC or DC power supply forms an electric arc between the electrode and the metals to be joined.
Gas Metal Arc Welding
Gas metal arc welding in which an electric arc is formed between a consumable metal inert gas
wire electrode and the work piece metal. The generated heat melts the work piece metal and is
then joined. It is a semi-automatic or automatic process which uses AC or DC from the power
supply.

3. Submerged Arc Welding
Submerged arc welding is a type of arc welding process that involves forming an arc between the
electrode and the work piece. A blanket of granular fusible material shields the arc on the work.
Flux-Cored Arc Welding
Flux-cored arc welding is a semi-automatic or automatic arc welding process. Flux-cored arc
welding is similar to the metal active gas welding process. It uses a continuous wire fed electrode
and a constant-voltage welding power supply.
Electroslag Welding
Electroslag welding is the most effective welding used to weld materials more significant than 25
mm up to about 300 mm. In electro slag welding, heat is generated by passing electricity
between the filler metal and the workpiece through a molten slag covering the weld surface.
Laser Beam Welding
Laser beam welding is the process in which the metal or thermoplastic materials are joined
together with the aid of LASER (Light Amplification by Stimulated Emission of Radiation). It is
an efficient technique that can perform deep welds. Laser beam welding is a non-contact process
requiring access to the weld zone from one side of the welded parts. Since the LASER beam is
monochromatic and single phased, without any divergence, high energy light produced is
channelised to perform welding.
Electron Beam Welding
Electron beam welding is a technique in which high-velocity electrons are applied to the
materials to be welded. Electron beam welding is undertaken under vacuum conditions to
prevent dissipation of the electron beam. The kinetic energy from the electrons is transformed
into heat, and the materials are welded. The electron gun is used to generate electrons, and the
electron gun helps control the flow of the electrons. Electron beam welding is performed in a
vacuum condition to avoid the scattering of electrons.
Magnetic Pulse Welding
Magnetic pulse welding is a technique that uses magnetic force to weld two materials together. It
is the solid-state welding developed in 1970 and is used extensively in automotive industries. It

4. is the fastest way of welding, which consumes only microseconds without the need for welding
consumables or shielding gases.
Friction Stir Welding
Friction stir welding is also a solid-state welding process that uses frictional heat generated by a
rotating tool to join materials.
The tool, equipped with a profiled probe and shoulder, is rotated and plunged into the interface
between two workpieces. The tool, when moved along the joint line, causes the material to heat
and soften. The shoulder also acts to contain this plasticized material, which is mechanically
mixed to create a solid phase weld.
Advantages and Disadvantages of Welding
Advantages
 Welding establishes strong, durable, and permanent joint links.
 It is a simple process that results in a great finish.
 The technique, when used with filler material, produces a stronger weld than the base
material.
 It can be performed at any place
 It is an economical and affordable process
 It is used in various sectors like construction, automobile, and many more industries.
Disadvantages
 It is hazardous when performed under the safety and security guidelines.
 It is a difficult task to dismantle the joined material through welding.
 Requires skilled labor and electric supply.
The Different Types of Fasteners and Their Uses
Fasteners are used to mechanically join two or more objects together, either permanently or non-
permanently. There are many different types of fastener, each with their own purpose.
Fasteners can broadly be categorised as either Permanent or Non-Permanent. Permanent
Fasteners, such as rivets and nails, are single-use fasteners that are designed to permanently join
two materials or parts. Removing the fastener destroys it.

5. Non-Permanent fasteners, on the other hand are designed to allow for easy removal and re-use.
Fasteners such as bolts and screws are commonly used in a number of industries and products as
they allow for parts to be dissassmbled and re-assembled if required. Non-Permanent fasteners
can be threaded (bolts, screws, etc.) or non-threaded (pins, retaining rings, etc.).
Threaded Fasteners
Threaded fasteners are among the most commonly used for assembling components due to the
ease in which they can be installed and uninstalled as needed. There are three main types of
threaded fastener; Bolts, Screws and Studs.
Bolts have a head on one end (this is usually a hex head) and are threaded on the other. They are
generally used in conjunction with a nut (and sometimes a washer) to hold them in place.
Screws are similar to bolts in that they have a head on one end and a thread on the other. They
key difference is thet screws are usually used to screw into an internally threaded hole. There are
many different types of screws, such as Cap Screws, Machine Screws, and Woodscrews.
Studs are threaded on both ends, and therefore have no head. They are used to join two
components with internally threaded holes together.
Fastener threads are standardised to two major standards: ISO (Metric) and ANSI (Unified).
Threads can also be right-handed or left-handed, depending on the application. However, the
majority of common fasteners are right-hand threaded.
Types of Threaded Fastener
Bolts and Setscrews - Bolts and Setscrews usually feature a hexagonal head with a thread, and
can be used either in conjunction with a nut or in a threaded hole. Bolts generally have a shank
beneath the head, while Setscrews are threaded all the way up to the head.
Carriage Bolts - Also known as Cup Square Hex Bolts, these have a smooth rounded head with
a square beneath. They are used for securing metal to wood.
Eye Bolts - These bolts have a circular ring instead of a traditional head and are used to fix rope
or chain to a surface.
U-Bolts - These bolts are used for attaching round objects such as pipes and tubes to a wall or
other surface.
Wood Screws - Featuring a smooth shank and tapered point, these screws are used in wood and
come in different head shapes such as Philips, Slotted or Pozidriv.

6. Machine Screws - Machine Screws are used with a nut or tapped hole. Thread Cutting Machine
Screws are also available, which feature a thread cutting point.
Self-Tapping Screws - Often referred to as Self-Tappers, these screws are used for in sheet
metals. Self-tapping screws tap their own thread.
Socket Screws - These screws feature a smooth shank and an Allen head, and are fastened using
an Allen key. Socket screws come with different head shapes, such as Button, Socket Cap and
Countersunk.
Grub Screws - Grub screws are a special type fo screw which usually do not have a head. They
are used to prevent movement or rotation between two parts.
Nuts
Nuts are used in conjunction with a bolt to clamo two or more parts together. The most common
type of nut is a Hexagonal Nut, but there are several different types of nuts for use in different
applications.
Hex Nuts - A plain, hexagonal nut with an internal thread. These are by far the most common
type of nut, and are used in numerous industries and applications.
Lock Nuts - These nuts are used when the nut needs to be locked in place without clamping on
to another object.
Nylon Insert Nuts - Commonly referred to as a Nyloc nut, these hexagonal shaped nuts have a
nylon insert which prevents the nut from coming loose due to vibration.
Shear Nuts - These cone shaped nuts feature a hexagonal gripping point which snaps off when
the maximum torque has been reached, leaving just the cone-shaped nut which is difficult to
remove.
Wing Nuts - Commonly used in applications where the nut needs to be removed often, Wing
Nuts feature two external "wings" which allow for manual turning.
Washers
Washers are commonly used between the head of a bolt, screw or nut and the material they are
clamping. Their primary function is to increase the bearing area of the head whilst also
protecting the material underneath from damage. There are several different types of Washer,
each with their own uses.
Flat Washers - These are the most common type of washer and are used to evenly distribute the
load of the bolt, screw or nut as the fastener is tightened.

7. Spring Washers - These locking washers are designed to stop the bolt, screw or nut from
vibrating loose.
Cup Washers - Cup Washers form a cup for the head of the fastener to fit in, creating a flush
finish with the fastener head. They are used in conjunction with a wood screw.
Repair Washers - Also commonly referred to as Penny Washers or Fender Washers, they
feature a small inside diameter hole and are design to create a greater bearing surface and prevent
pull-through.
Rivets
Rivets are a permanent fastener, in that once removed, they cannot be re-used. Rivets are used in
a number of industries and applications but are most commonly used to join metal sheets and
plates.
Pop Rivets - Consisting of a hat and mandrel, Pop Rivets are used to join two materials together.
During installation, the mandrel is forced into the rivet body, forcing the body to expand and grip
onto the material(s). Once gripped, the remaining mandrel snaps off.
Large Flange Pop Rivets - Large Flange Pop Rivets are similar to Pop Rivets in their
application but feature a much large flange.
Multi-Grip Rivets - These rivets are used when joining materials with differing thicknesses,
which would normally require multiple rivet sizes. They are very versatile and cost-effective.
What is Forging?
Forging, a metal shaping technique using compressive, localized forces, has been a staple metal
fabrication technique since the time of the ancient Mesopotamians. Since its origins in the fertile
crescent, forging has experienced significant changes, resulting in a more efficient, faster, and
more durable process. This is because today, forging is most commonly performed with the use
of forging presses or hammering tools that are powered by electricity, hydraulics or compressed
air. Some of the common materials used for forging are carbon steel, alloy steel, microalloy
steel, stainless steel, aluminum, and titanium.
What is the purpose of forging?
The purpose of forging is to create metal parts. Compared to other manufacturing methods, metal
forging produces some of the sturdiest manufactured parts available. As metal is heated and
pressed, minor cracks are sealed, and any empty spaces in the metal close.
The hot forging process also breaks up impurities in the metal and redistributes such material
across the metalwork. This vastly reduces inclusions in the forged part. Inclusions are compound

8. materials implanted inside steel throughout manufacturing that cause stress points in the final
forged parts.
While impurities should be managed during the initial casting process, forging further refines the
metal.
Another way that forging strengthens metal is by alternating its grain structure, which is the
metal material's grain flow as it deforms. Through forging, a favorable grain structure can be
created, making the forged metal sturdier.
The forging process is highly multipurpose and can be used on small parts just a few inches in
size to large components that weigh up to 700,000 lbs. It is used to produce critical aircraft parts
and transportation equipment. Forging is also used to fortify hand tools such as chisels, rivets,
screws, and bolts.
What are the different types of forging?
The pounding action of forging deforms and shapes the metal, which results in unbroken grain
flow. This causes the metal to retain its strength. Ancillary effects of this unique grain flow
include the elimination of defects, inclusions, and porosity in the product. Another advantage of
forging is the relatively low costs associated with moderate and long production runs. Once the
forging tools have been created, products can be manufactured at relatively high speeds with
minimal downtime.There are two main types of forging: hot and cold.
Hot Forging
Hot forging requires the metal to be heated above its recrystallization temperature. This can
mean heating metals up to 2,300 degrees Fahrenheit. The main benefit of hot forging is the
decrease in energy required to form the metal properly. This is because excessive heat decreases
yield strength and improves ductility. Hot forged products also benefit from the elimination of
chemical inconsistencies.
Need a hot forging company? Thomas' Supplier Discovery has a vetted list of Hot Forging
Companies in the U.S. and Canada.
Cold Forging
Cold forging typically refers to forging a metal at room temperature, though any temperature
below recrystallization is possible. Many metals, such as steel high in carbon, are simply too
strong for cold forging. Despite this hindrance, cold forging does edge out its warmer equivalent
when it comes to standards of dimensional control, product uniformity, surface finish, and
contamination. Cold forging encompasses numerous forging techniques, including bending,
extruding, cold drawing, coining, and cold heading. However, this increased versatility comes at
a cost, because cold forging requires more powerful equipment and may call for the use of
intermediate anneals.

9. What are the different forging processes?
Beyond basic hot and cold forging, many specific processes exist. This broad range of processes
can be grouped into three primary umbrella groups:
Draw forming decreases the width of
the product and increases length. Upset forging increases the width of the products and decreases
length. Compression forming provides forging flow in multiple or customized directions.
These three categories entail many different specific types of metal forging methods.
Drop Forging Process
Drop forging gets its name from the process of dropping a hammer onto the metal to mold it into
the shape of the die. The die is the surface that comes into contact with the metal. There are two
types of drop forging: open-die and closed-die forging. Dies are typically flat in shape with some
having distinctively shaped surfaces for specialized operations.
Open Die Forging Process
When flat dies that have no precut profiles engage in forging, the forge process is called open die
forging (or smith forging). The open design allows the metal to flow everywhere except where it
touches the die. To achieve maximum results, correct movement of the workpiece, which should
be over 200,000 lbs. in weight and 80 feet long, is essential. It is useful for short-run art smithing
or for shaping ingots prior to secondary shaping measures. Open die forging creates pieces with
better fatigue resistance and strength and reduces the chance of error or holes. It can also be used
for a finer grain size than other processes.
Closed Die Forging Process
Closed die forging, sometimes called impression die forging, employs the use of molds. These
molds are attached to an anvil while a hammer forces molten metal to flow into the cavities of
the die. Multiple strikes and/or die cavities are often used when forging complex geometries.
High initial tooling costs make closed die forging expensive for short-run operations, but the
forging process becomes cost-effective as parts produced increases. Closed die forging also
provides exceptional strength over alternative methods. Common applications of closed die
forging include the production of automobile components and hardware tools.
Press Forging Process
In press forging, the main forming factor is compression. The metal sits on a stationary die while
a compression die applies continuous pressure, achieving the desired shape. The metal's contact
time with the dies is considerably longer than other types of forging, but the forging process
benefits from being able to simultaneously deform the entire product, as opposed to a localized
section. Another benefit of press forging is the ability of the manufacturer to monitor and control

10. the specific compression rate. Applications of press forging are numerous, as there are relatively
no limits to the size of product that can be created. Press forging can be hot or cold forged.
Roll Forging Process
Roll forging is the process of increasing rods or wires in length. The manufacturer places heated
metal bars between two cylindrical rolls with grooves, which rotate and apply progressive
pressure to shape the metal. The precisely shaped geometry of these grooves forges the metal
part to the desired shape. The benefits of this forging method include the elimination of flashing
and a favorable grain structure. While roll forging uses rolls to produce parts and components, it
is still considered a metal forging process and not a rolling process. Roll forging is frequently
used to make parts for the automotive industry. It is also used to forge things like knives and
hand tools.
Upset Forging Process
Upset forging is a forging process that increases the diameter of the metal through compression.
Crank presses, a particular high-speed machine, are used in upset forging processes. Crank
presses are characteristically set on a horizontal plane to improve efficiency and the quick metal
exchange from one station to the next. Vertical crank presses or hydraulic presses are also used.
The advantages of this process are that it enables a high production rate of up to 4500 parts per
hour and full automation is possible. It also produces little to no waste.
Isothermal Forging Process
Isothermal forging is a forging process where the materials and the die are heated to the same
temperature. The name comes from “iso” which means "equal." This forging method is
commonly used for forging aluminium, which has a lower forging temperature than other metals
such as steel. Forging temperatures for aluminum are around 430 °C, while steels and super
alloys can be 930 to 1,260 °C. The benefits are the near net shapes lead to lower machining
requirements and, therefore, lower scrap rates, and the metal part is highly reproducible. Another
advantage is that smaller machines can be used to make the forging due to the lower heat loss. A
few disadvantages are the higher die material costs to handle temperatures and pressures and the
required uniform heating systems. It also has a low production rate.
What kind of equipment is used for forging?
The most popular type of forging equipment is the hammer and anvil. The idea behind the
hammer and anvil is still used today in drop hammer forging equipment. The hammer is raised
and then dropped or propelled into the workpiece, which rests on the anvil. The main variations
between drop hammers are how the hammer is powered, the most common being air and steam
hammers. Drop hammers typically operate in a vertical position. This is because the excess
energy that isn't released as heat or sound, meaning energy that isn't used to shape the workpiece,
needs to be conveyed to the foundation. A large machine base is also required to absorb the
impacts.

11. To overcome some shortcomings of the drop hammer, the counterblow machine or impactor is
used. Both the hammer and anvil move in a counterblow machine, with the workpiece held
between them. Here, excess energy becomes recoil, allowing the machine to work horizontally
and have a smaller base. This creates less noise, heat, and vibration. It also creates a distinctly
different flow pattern. These machines are used for open die or closed die forging.
A press is used for press forging. The two main types are mechanical and hydraulic presses.
Mechanical presses function using cams, cranks, and toggles to make preset and reproducible
hammer strikes. Because of the characteristics of this type of system, different forces are
available at different stroke positions. As a result, these presses are faster than their hydraulic
counterparts by 50 strokes per minute. Their capacities range from three to 160 MN. Hydraulic
presses use fluid pressure and a piston to produce force. The advantages of a hydraulic over a
mechanical are its flexibility and superior capacity. The disadvantages are that it is a slower,
larger, and costlier machine to operate.
The roll forging, automatic hot forging, and upsetting processes all use specialized machinery.