Finished Bachelor Thesis

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Material Science and Engineering Faculty

German University in Cairo

Automatic welding table

(Bachelor Thesis)

Author: Sherif Mohamed Rozza

Supervisor: Dr. Yasser Fouad

Submission Date: 15 January

2012

This is to certify that:


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(i) The thesis comprises only my

original work towards the

bachelor degree.(ii) Due acknowledgment has been

made in the text to all other

material used.

Sherif mohamed

Abdel Hamed Rozza15

January 2012

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Acknowledgments:

I would like to show my gratitude

and grateful to my supervisor , Prof

Dr eng. Yasser Fouad for his great

help, support , advice and that this

thesis and all these results wouldnt

have been achieved without his hard

work with me.

Thank you Dr Yasser.

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Abstract

Automatic Welding is considered one of the most

important ways of welding. Welding is a fabrication orsculpturalprocess that joins materials, usually metals or

thermoplastics, by causing coalescence. Welding has

many processes as manual process, automatic process,

Machine process and robotic process. Welding may be

performed in many different environments, including

open air, under water and in outer space. It used to build

projects such as tanks, satellites, weapons, railroads,shopping malls etc. Welding is a potentially hazardous

undertaking and precautions are required to avoid burns,

electric shock, vision damage, inhalation of poisonous

gases and fumes, and exposure to intense ultraviolet

radiation. Therefore this project is carried out to produce

the automatic welding table which improves the

mechanical properties of the sheet. It improves the

hardness of the sheet. Automatic welding table allow

greater weld control, Improved and faster. Then the

tensile test is done to analyze the strength after the

welding process.

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http://en.wikipedia.org/wiki/Fabrication_(metal)http://en.wikipedia.org/wiki/Welded_sculpturehttp://en.wikipedia.org/wiki/Process_(science)http://en.wikipedia.org/wiki/Metalhttp://en.wikipedia.org/wiki/Thermoplastichttp://en.wiktionary.org/wiki/coalescehttp://en.wikipedia.org/wiki/Underwater_weldinghttp://en.wikipedia.org/wiki/Outer_spacehttp://en.wikipedia.org/wiki/Burnhttp://en.wikipedia.org/wiki/Electric_shockhttp://en.wikipedia.org/wiki/Welded_sculpturehttp://en.wikipedia.org/wiki/Process_(science)http://en.wikipedia.org/wiki/Metalhttp://en.wikipedia.org/wiki/Thermoplastichttp://en.wiktionary.org/wiki/coalescehttp://en.wikipedia.org/wiki/Underwater_weldinghttp://en.wikipedia.org/wiki/Outer_spacehttp://en.wikipedia.org/wiki/Burnhttp://en.wikipedia.org/wiki/Electric_shockhttp://en.wikipedia.org/wiki/Fabrication_(metal)


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ContentsChapter 1 Introduction.........

...................11.1 Motivation ...........41.2 Aim of the project .......4Chapter 2 Literature Review2.1 types of joining processes................5

2.1.1 Manual joining processes....5

2.1.2 Semi automatic joining processes...

6.2.1.3 Automatic joining processes .....7

2.1.4 Automated joining processes..7

2.1.5 Machine joining process.....8

2.1.6 Industrial robots welding ...92.2 ARC WELDING...........112.2.1Arc welding processes...

..112.2.1.1 Shielded metal arc welding ...

.112.2.1.2Tungsten Inert Gas Welding ...

122.2.1.3 Submerged arc welding ...

...142.2.1.4 Flux cored arc welding .....

..15

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2.2.1.5 Plasma welding...172.3 Electric resistance welding.........192.3.1 Resistance welding processes.........19

2.3.1.1 Spot welding ......192.3.1.2 Seam welding...

...202.3.1.3 Flash Welding.....

........202.3.1.4 Projection welding.

.....212.3.1.5 Resistance butt

welding......212.4 BRAZING..22

2.4.1 Brazing process.......222.4.1.1 Torch brazing .........222.5 SOLDERING.........232.6 Thermit welding.242.6.1Thermit welding processes...........24

2.6.1.1 Laser beam .........24

2.6.1.2 Electron beam welding ...

.......262.7 Gas welding....272.7.1 Gas welding process....27

2.7.1.1 Oxyacetylene welding.....27

2.7.1.2 Pressure gas welding...292.8 Solid state welding.............292.8.1 Solid state weldingprocess.29

2.8.1.1 Forge welding ....31

2.8.1.2 Ultrasonic welding .31

2.8.1.3 Cold workingwelding32

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2.8.1.4 Friction welding......32

2.8.1.5 Electroslag welding ....342.9 Metals ........35

2.10 Filler Metals........362.11Protecting metal from atmospheric contamination.......372.12 Control of weld metallurgy......372.13 Expansion and contraction of metals...382.14 Butt welds....39

Chapter 3 Experimentalsetup403.1The body and frame....41

3.1.1 Thetable.41

3.1.2 Upper part of the table...41

3.1.3 Wheels of thetable.43

3.1.4 Holder of the table.....44

3.1.5 Parts of the table section....46

3.1.6 The motor with gearbox seating....48

3.1.7 The shaft49

3.1.8 Gears......49

3.1.9 Rack...50

3.1.10 Pulley...51

3.1.11 Safety electronicbox523.2 Motor..533.3 Gear box ....553.4 Inverter...56

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3.5 Wire remote control...573.6 Assembly and Finishing.....583.7 Testing ...62

3.8 Experiment Results ...64

3.8.1 The tensile test.1....64

3.8.2 The tensile test.2....66Chapter 4 Conclusion......68

Contents of figures

Figure (2.1) manual joining

processes...5

Figure (2.2) Semi automatic joining processes .........6

Figure (2.3) Automated or automatic joining processes ...

...7

Figure (2.4) Machine joining process.........

...8

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Figure (2.5) Industrial robots welding ......

................9

Figure (2.6) Shielded metal arc welding......

............12

Figure ( 2.7) Tungsten Inert Gas Welding......

.........13

Figure (2.8) Submerged arc welding.........

...15

Figure (2.9) Flux cored arc welding

17

Figure (2.10) Plasma welding .........

18

Figure (2.11) Spot welding .........

20

Figure (2.12) Seam welding.........

20

Figure (2.13) Resistance butt welding ......

......21

Figure (2.14) Torch brazing .........

...23

Figure (2.15) Laser beam welding .........

.25

Figure (2.16) Electron beam welding .........

26

Figure (2.17) oxyacetylene welding .........

. 28

Figure (2.18) Forge welding.........

.. 30

Figure (2.19) Ultrasonic welding ......

......31

Figure (2.20) Friction welding .........

...33

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Figure (2.21) Electroslag welding .........

34

Figure (2.22) EXPANSION AND CONTRACTION of metals ...

......38

Figure (2.23) direction of welding ......

....39

Figure (3.1) the manufacturing table......

......41

Figure (3.2) Upper part of the table .........

...42

Figure (3.3) Machine that is used to do these holes on the upper part

....42

Figure (3.4) Wheels of the table .......

...43

Figure (3.5) this shape for connecting the wheels to it ...

....43

Figure (3.6) part of the

holder......44

Figure (3.7) part of the holder .........

...44

Figure (3.8) part of the holder ...........

45

Figure (3.9) c-clamp.........

...45

Figure (3.10) this part let the bearing hub wheel to move on it ...

...46

Figure (3.11) this part to prevent the bearing hub to move away ....

...46

Figure (3.12) bearing hub wheel while moving ......

47

Figure (3.13) eight bearing hub wheel ......

......47

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Figure (3.14) the motor with gearbox seating from the top view ...

....48

Figure (3.15) the motor with gearbox seating from the side view...

....48

Figure (3.16) the motor shaft .......

...49

Figure (3.17) Gears ..........

...49

Figure (3.18) Gears when it is connected to the shaft ......

...49

Figure (3.19) Rack............

...50

Figure (3.20) Rack with the gear .........

...50

Figure (3.21) Pulley with open key hole ......

...51

Figure (3.22) Pulley with small hole ........

...51

Figure (3.23) Safety inverter box with an open and close door .....

...52

Figure (3.24) Motor ..........

...54

Figure (3.25) Gear box side view .........

...55

Figure (3.26) Gear box upper view..

55

Figure (3.27) Inverter ...........

...56

Figure (3.28) Wire remote control .......

...57

Figure (3.29) first the design of the table ......

......58

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Figure (3.30) Grinding some parts and the edges of the table for finishing

...58

Figure (3.31) screws to attach some parts with others......

...59

Figure (3.32) Welding the small parts on the table to install the upper parts of table

that will move.........59

Figure (3.33) the seating of the motor with the gearbox is done and ready to

work...60

Figure (3.34) Assembling and installing all the system different parts altogether

(motor, gearbox, control unit, gears, pulleys, wheels) ......

......... 60

Figure (3.35) Holding the torch of the welding and can do the

operation...61

Figure (3.36) Universal testing machine......

....63

Figure (3.37) Normal sample before testing......

....64

Figure (3.38) Normal sample after testing ......

....65

Figure (3.39) the two samples which are welded before testing...

...66

Figure (3.40) the two samples which are welded after testing...

......66

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CHAPTER 1

Welding is widely used by metalworkers in the fabrication, maintenance, and

repair of parts and structures. While there are many methods for joining

metals, welding is one of the most convenient and rapid methods available.

The term welding refers to the process of joining metals by heating them to

their melting temperature and causing the molten metal to flow together.

These range from simple steel brackets to nuclear reactors.

Welding is a fabrication or sculpturalprocess that joins materials, usually

metals or thermoplastics, by causing coalescence. This is often done by

melting the work pieces and adding a filler material to form a pool of molten

material that cools to become a strong joint, with pressure sometimes usedin conjunction with heat, or by itself, to produce the weld.

Welding may be performed in many different environments, including open

air, under water and in outer space. Welding is a potentially hazardous

undertaking and precautions are required to avoid burns, electric shock,

vision damage, inhalation of poisonous gases and fumes, and exposure to

intense ultraviolet radiation.

Welding, like any skilled trade, is broad in scope and you cannot become a

welder simply by reading a book. You need practice and experience as wellas patience; however, much can be gained through study. For instance, by

learning the correct method or procedure for accomplishing a job from a

book, you may eliminate many mistakes that otherwise would occur through

trial and error.

This chapter is designed to equip you with a background of basic information

applicable to welding in general. If you take time to study this material

carefully, it will provide you with the foundation needed to become a skilled

welder.

Until the end of the 19th century, the only welding process was forge welding which

blacksmiths had used for centuries to join iron and steel by heating and hammering.

Arc welding and oxyfuel welding were among the first processes to develop late in

the century, and electric resistance welding followed soon after. Welding technology

advanced quickly during the early 20th century as World War I and World War II

drove the demand for reliable and inexpensive joining methods. Following the wars,

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several modern welding techniques were developed, including manual methods like

shielded metal arc welding, now one of the most popular welding methods,

as well as semi-automatic and automatic processes such as gas metal arcwelding, submerged arc welding, flux-cored arc welding and electro slag

welding. Developments continued with the invention oflaser beam welding,

electron beam welding, electromagnetic pulse welding and friction stir

welding in the latter half of the century. Today, the science continues to

advance. Robot welding is commonplace in industrial settings, and

researchers continue to develop new welding methods and gain greater

understanding of weld quality and properties.

Welding is one of the principle activities in modern fabrication, ship building

and offshore industry. The performance of these industries regarding product

quality, delivery schedule and productivity depends upon structural design,

production planning, welding technology adopted and distortion control

measures implemented during fabrication.

The quality of welding depends on the following parameters:

Skill of welder

Welding parameters

Shielding medium

Work layout

Plate edge preparation

Fit-up and alignment

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Correct process and procedures

Suitable distortion control.

Welding is basically a joining process. Ideally a weld should achieve a

complete continuity between the parts being joined such that the joint is

indistinguishable from the metal in which the joint is made. Such an ideal

situation is unachievable but welds giving satisfactory service can be made

in several ways. The choice of a particular welding process will depend on

the following factors:

Types of metal and its metallurgical characteristics;

Types of joint, its location and welding position;

End use of the joint;

Cost of production;

Structural size;

Desired performance;

Experience and abilities of manpower;

Joint accessibility ;

Joint design;

Welding equipment available;

Work sequence;

Welder skill.

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1.1 Motivation

Observing any welding process can make any materials to be welded

This project is done because it allow greater weld control, Improved and faster.

The motivation behind this study was raised first from the need for such an automatic welding

table in the workshop here at the GUC. The workshop has a manual welding but the automatic

welding table lacks is enormously required in the presence of many students in welding classes.

Thus, it was decided to design and manufacture this automatic welding table to form thematerials that will be weld faster than the manual also to have an accurate final work.

1.2 Aim of the project

The objectives of this bachelor work are:

1) Surveying the automatic welding table system that can adapt to theworkshop environment.2) Designing of an automatic welding table with all its related components.3) Manufacturing of all parts individually and assembling the whole device.4) Installing the part at the workshop.5) Testing the part for consistent performance.

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CHAPTER 2

Literature Review

Today, there are many welding processes available, provides a list of

processes used in modern metal fabrication and repair.

The classes are classified into subclasses which is the most popular weldingprocesses

2.1 Types of joining processes

2.1.1 Manual joining processes

A manual joining process is one that is completely performed by hand. The

welder controls all of the manipulation, rate of travel, joint tracking and in

some cases, the rate at which filler metal is added to the weld. The

manipulation of the electrode or torch in a straight line or oscillating patternaffects the size and the shape of the weld.

The manipulation pattern may also be used to control the size of the weld

pool during out of position welding. The rate of travel or speed AT WHICH

THE WELD progresses along the joint affects the width, reinforcement of the

weld.

The placement or location of the weld bead within the weld joint affects the

strength, appearance and possible acceptance of the joint. The rate at which

filler metal is added to the weld affects the reinforcement, width of the weld.

The most commonly used manual arc welding process is shielded metal arc

welding (SMAW) .the flexibility the welder has in performing the weld makes

this process one of the most versatile. By changing the manipulation, rate of

the travel or joint tracking, the welder can make an acceptable weld on a

variety of material thicknesses

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The most commonly used manual arc welding, gas welding and brazing

process.

Figure (2.1) Manual joining

processes

2.1.2 Semi automatic joining processes

Semi automatic joining processes is one in which the filler metal is fed into

the weld automatically. All other functions are controlled manually by the

welder. The additions of the filler metal to the weld by an automatic wire-

feeder system enables the welder to increase the uniformity of the welds ,

productivity and the weld quality , the distance of the welding gun or torchfrom the work remains constant . This gives the welder better manipulative

control; as compared to , for example shielded metal arc welding , in which

the electrode holder starts at a distance of 14 in from the work . This

distance exaggerates the slightest accidental movement made during the

first part of the weld .in the SMAW process , The electrode holder must be

lowered steadily as the weld progresses to feed the electrode and maintain

the correct arc length .This constant changing of the distance above the

work causes the welder to shift body position frequently.

Because the filler metal is being fed from a large spool, the welder does nothave to stop welding to change filler electrodes or filler metal. SMA

electrodes cannot be used completely as they have a waste sub of

approximately 2 in. This waste stub represents approximately 15 % of the

filler metal that must be discarded.

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The frequent stopping for rod and electrode changes, followed by restarting,

wastes time and increase the number of the weld craters.

These craters are often a source of cracks and other discontinuous. In some

welding procedures each weld crater must be chipped and ground before the

weld can be restarted.

Examples: gas metal arc welding, flux cored arc welding, submerged arc

welding, gas tungsten arc welding, cold-hot wire feed.

Figure (2.2) Semi automatic joining processes

2.1.3 Automatic joining processes

An automatic joining process is a dedicated process that does not require

adjustments to be made by the operator during the actual welding cycle, all

operating guidelines are preset, and parts may or may not be loaded or

unloaded by the operator. Automatic equipment is often dedicated to one

type of product or part; a large investment is usually required in jigs and

fixtures used to hold the parts to be joined in the proper alignment. The

operational cycle can be controlled mechanically or numerically (computer).

The cycle may be as simple as starting and stopping points, or it may be

more complex. A more complex cycle may include such steps as prep urge

time, hot start, and initial current, pulse power, down slope, final current and

post purge time. Automatic welding or brazing is best suited to large volume

production runs because of the expense involved in specially jigs and

fixtures.

Some examples: typical GTAW automatic welding program.

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2.1.4 Automated joining processes

Are similar to automatic joining except it is more flexible and easily adjusted

or changed. Unlike automatic welding, there is no dedicated machine foreach product. The industrial robot is rapidly becoming the main component

in automated welding or joining stations. The welding are often controlled by

microprocessors or computers , the equipment is controlled by programs or

some commands expressed in codes that direct in welding also the programs

can be stored and changed.

Figure (2.3) Automated or automatic joiningprocesses

2.1.5 Machine joining process

A machine joining processes is one in which the joining is performed by theequipment requiring the welding operator to observe the progress of the

weld and make adjustments as required. The parts being joined may or not

be loaded or unloaded automatic. The operator may monitor the joining

progress by watching it directly, observing instruments only, or using a

combination of both methods. Adjustments in travel speed, joint-tracking,

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work to gun or work to torch distance may be needed to ensure that the joint

is made according to specifications

The work may move past a stationary welding or it may be held stationary

and the welding machine moves on a beam or track along the joint .on some

large machine welds, the operator may ride with the welding head along thepath of the weld to minimize adjustments during machine welds, a test weld

is often performed just before the actual weld is produced. This practice weld

helps increase the already high reliability of machine welds.

Figure (2.4) Machine joining process

2.1.6 Industrial robots welding

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An industrial robots is a reprogrammable design to move materials .industrial

robots are powered by electric stepping motors , hydraulics or pneumatics

and are controlled by a program , Robots can perform movements in x and y

and z directions .

Robots can be used with other components to increase production and theflexibility of the system. A computer or microprocessor can synchronize the

robots operation to postioners, conveyors, automatic fixtures and other

production machines parallel or multiple work stations increase the duty

cycle and reduce the cycle time parts can be loaded and unloaded by the

operator at one station while the robot welds at another station.

Figure (2.5) Industrial robots welding

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2.2 ARC WELDING

Arc welding is a process that uses an electric arc to join the metals being

welded. A distinct advantage of arc welding over gas welding is the

concentration of heat. In gas welding the flame spreads over a large area,

sometimes causing heat distortion. The concentration of heat, characteristic

of arc welding, is an advantage because less heat spread reduces buckling

and warping. This heat concentration also increases the depth of penetration

and speeds up the welding operation; therefore, you will find that arc

welding is often more practical and economical than gas welding. All arc-

welding processes have three things in common: a heat source, filler metal,

and shielding. The source of heat in arc welding is produced by the arcing of

an electrical current between two contacts.

2.2.1 Arc welding processes

2.2.1.1 Shielded metal arc welding

Shielded Metal Arc Welding (SMAW) also called Stick welding or manual

welding is a process, which melts and joins metals by heating them with an

arc between a coated metal electrode and the work piece. The electrode

outer coating, called flux, assists in creating the arc and provides the

shielding gas and slag covering to protect the weld from contamination and

coming in contact with air. The electrode core provides most of the weld fillermetal.

The SMAW welding power source provides constant current power slope (CC)

and may be alternating current (AC) or direct current (DC), depending many

factors such as the electrode being used, the material being welded.

The power in a welding circuit is measured in voltage and current. The

voltage (Volts) is governed by the arc length between the electrode and the

work piece and is influenced by electrode diameter.

Current is a more practical measure of the power in a weld circuit and is

measured in amperes (Amps). The amperage needed to weld depends onelectrode diameter, the size and thickness of the pieces to be welded, and

the position of the welding. Thin metals require less current than thick

metals, and a small electrode requires less amperage than a large one.

Advantages of Shielded Metal Arc Welding:

Simple, portable and inexpensive equipment.

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Wide variety of metals, welding positions and electrodes are

applicable.

Suitable for outdoor applications.

Disadvantages of Shielded Metal Arc Welding:

The process is discontinuous due to limited length of the electrodes;

Weld may contain slag inclusions;

Fumes make difficult the process control

Figure (2.6) Shielded metal arc welding

2.2.1.2 Tungsten Inert Gas Welding

Tungsten inert gas (TIG) welding process, also known as (GTAW) is an arc

welding process where a non-consumable tungsten electrode is employed to

initiate the arc increases the arc emissivity. The weld area is protected from

atmospheric contamination by a shielding gas, usually an inert gas such as

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argon or Helium or Mixtures of both, and a filler metal may or may not be

used depending on the thicknesses being welded. Constant current welding

power supply produces energy, which is conducted across the arc through a

column of highly ionized gas.

TIG is used to weld stainless steel, nickel alloys, titanium, aluminum, and

magnesium, copper, brass, bronze and even gold. TIG can also join dissimilar

metals to one another such as copper to brass and stainless to mild steel.

Some Applications as It is used extensively in the manufacture of space

vehicles, and is also frequently employed to weld small-diameter, thin-wall

tubing such as those used in the bicycle industry ,GTAW is often used to

make root or first pass welds for piping of various sizes. In maintenance and

repair work, the process is commonly used to repair tools and dies,

especially components made of aluminum and magnesium.

Advantages of Tungsten Inert Gas Arc Welding:

Weld composition is close to that of the parent metal;

High quality weld structure

Slag removal is not required (no slag);

Thermal distortions of work pieces are minimal due to concentration of

heat in small zone.

Disadvantages of Tungsten Inert Gas Arc Welding: Low welding rate;

Relatively expensive;

Requires high level of operators skill.

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Figure ( 2.7) Tungsten Inert Gas Welding

2.2.1.3 Submerged arc welding

Submerged arc welding (SAW) is a common arc welding process. It requires

a continuously fed consumable solid or tubular electrode. The molten weld

and the arc zone are protected from atmospheric contamination by beingsubmerged under a blanket of granular fusible flux consisting oflime,

silica, manganese oxide, calcium fluoride, and other compounds. When

molten, the flux becomes conductive and provides a current path between

the electrode and the work. This thick layer of flux completely covers the

molten metal thus preventing spatter and sparks.

SAW is normally operated in the automatic or mechanized mode, however,

semi-automatic (SAW) guns with pressurized or gravity flux feed delivery are

available. The process is normally limited to the flat or horizontal-fillet

welding positions.

Single or multiple (2 to 5) electrode wire variations of the process exist. SAW

strip-cladding utilizes a flat strip electrode (e.g. 60 mm wide x 0.5 mm thick).

DC or AC power can be used, and combinations of DC and AC are common

on multiple electrode systems.

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Constant voltage welding power supplies are most commonly used; however,

constant current systems in combination with a voltage sensing wire-feeder

are available.

Advantages of Submerged Arc Welding:

High deposition rates.

High operating factors in mechanized applications.

Deep weld penetration.

Sound welds are readily made (with good process design and control).

High speed welding of thin sheet steels up to 5 m/min (16 ft/min) is

possible.

Minimal welding fume or arc light is emitted.

Practically no edge preparation is necessary.

The process is suitable for both indoor and outdoor works.

Distortion is much less.

Welds produced are sound, uniform, ductile, and corrosion resistant and

have good impact value.

Single pass welds can be made in thick plates with normal equipment

Disadvantages of Submerged Arc Welding:

Weld may contain slag inclusions;

Limited applications of the process - mostly for welding horizontally

located plates.

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Figure (2.8) Submerged arc welding

2.2.1.4 Flux cored arc welding

Flux-cored arc welding is a semi-automatic or automatic arc welding process.

FCAW requires a continuously-fed consumable tubular electrode containing a

flux and a constant-voltage or, less commonly, a constant-currentweldingpower supply. An externally supplied shielding gas is sometimes used, but

often the flux itself is relied upon to generate the necessary protection from

the atmosphere.

The process is widely used in construction because of its high welding speed

and portability.

The advantage of FCAW over SMAW is that the use of the stick electrodes

used in SMAW is unnecessary. This helped FCAW to overcome many of the

restrictions associated with SMAW.

There is two types of flux cored arc welding. One type of FCAW requires no

shielding gas. This is made possible by the flux core in the tubular

consumable electrode.

However, this core contains more than just flux; it also contains various

ingredients that when exposed to the high temperatures of welding generate

a shielding gas for protecting the arc. This type of FCAW is attractive

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because it is portable and generally has good penetration into the base

metal. Some disadvantages are that this process can produce excessive,

noxious, under some conditions it can produce welds with inferior

mechanical properties; the slag is often difficult and time-consuming to

remove; and operator skill can be a major factor.

Another type of FCAW uses a shielding gas that must be supplied by an

external supply. This is known informally as "dual shield" welding. This type

of FCAW was developed primarily for welding structural steels. In fact, since

it uses both a flux-cored electrode and an external shielding gas, one might

say that it is a combination of gas metal (GMAW) and flux-cored arc welding

(FCAW). This particular style of FCAW is preferable for welding thicker and

out-of-position metals. The slag created by the flux is also easy to remove.

The main advantages of this process is that in a closed shop environment, it

generally produces welds of better and more consistent mechanical

properties, with fewer weld defects than either the SMAW or GMAW

processes. it also allows a higher production rate.

Advantages of Flux cored arc welding:

FCAW may be an "all-position" process with the right filler metals.

No shielding gas needed making it suitable for outdoor welding and/or

windy conditions

A high-deposition rate process.

Some "high-speed" (e.g., automotive applications)

Less precleaning of metal required

Metallurgical benefits from the flux such as the weld metal being

protected initially from external factors until the flux is chipped away

Disadvantages ofFlux cored arc welding:

Melted Contact Tip happens when the electrode actually contacts the

base metal.

Irregular wire feed typically a mechanical problem

Porosity More costly filler material/wire.

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Figure (2.9) Flux cored arc welding

2.2.1.5 Plasma welding

The plasma welding is one type ofarc welding process by which single body

is produced by heat is obtained from plasma between the work piece and

tungsten or tungsten alloy electrode.

There are two types of inert gas is employed for plasma welding process, one

formed the plasma and other is shielding the plasma.

Plasma is the ionized state of gas atoms. When an ionized gas passes

through the electric current, it becomes mixture of ions, electron and highly

excited atoms. Thus the energy of plasma and the temperature is dependent

on the amount of the electrical power employed. A tremendous amount of

temperature is obtained from plasma torch is about 500000F. There are two

types of plasma arc torch is used, 1.Transferred arc torch, 2. Non-transferred

torch.

In the non transfer arc process the arc is produced between the tungsten

electrode (-) and water cooled nozzle (+). Plasma is produced as a flame.

The arc is totally independent of the work piece and it does not help to

completion of electrical circuit.

In the transferred arc process is also an arc is produced between the work

piece (+) and electrode (-). In this process the produced arc is transferred

electrode to work piece. It has extraordinary power of plasma arc, which

posses high jet velocity and high plasma density. By this facility, it is used tocut and weld the metals. Which metals we cannot cut by means oxy-

acetylene process, there plasma arc can do very effectively due to its high

arc travel speed. A pilot arc is established in between the electrode and

nozzle for initial ignition. As the pilot arc touches the job, then immediately

the main current start to flow between the work and electrode. Thus the arc

is produced. Some Applications as Nuclear submarine pipe welding ,

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Cryogenic and aerospace component welding ,Nickel and high nickel alloy

welding ,Melting the high melting point temperature metals ,Titanium plate

welding up to 8 mm thickness ,Welding the stainless tubes up to 1/4

thickness.

Advantages of plasma welding: It has excellent type weld quality.

Arc is stabilized.

It needs very simple types fixture.

Root welding does not required.

Penetration is uniformed.

It produces radio-graphic quality welding.

Disadvantages of Plasma Welding:

Expensive equipment;

High distortions and wide welds as a result of high heat input.

Figure (2.10) Plasma welding

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2.3 Electric resistance welding

Electric resistance welding refers to a group of welding processes such as

spot and seam welding that produce coalescence of faying surfaces where

heat to form the weld is generated by the electrical resistance of material is

the time and the force used to hold the materials together during welding.

Some factors influencing heat or welding temperatures are the proportions of

the work pieces, the coating or the lack of coating, the electrode materials,

electrode geometry, electrode pressing force, weld current and weld time.

Small pools of molten metal are formed at the point of most electrical

resistance (the connecting surfaces) as a high current (100100,000 A) is

passed through the metal. In general, resistance welding methods areefficient and cause little pollution, but their applications are limited to

relatively thin materials and the equipment cost can be high.

Advantages of Resistance Welding:

High welding rates;

Low fumes;

Cost effectiveness;

Easy automation;

No filler materials are required;

Low distortions.

Disadvantages of Resistance Welding:

High equipment cost;

Low strength of discontinuous welds;

Thickness of welded sheets is limited - up to 1/4 (6 mm);

2.3.1 Electric Resistance welding processes:

2.3.1.1 Spot welding

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Spot welding is a resistance welding method used to join two to three

overlapping metal sheets, studs, projections, electrical wiring hangers, some

heat exchanger fins, and some tubing. Usually power sources and welding

equipment are sized to the specific thickness and material being welded

together.

Figure (2.11) Spot welding

2.3.1.2 Seam welding

Seam welding is a Resistance seam welding is a process that produces a

weld at the faying surfaces of two similar metals. The seam may be a butt

joint or an overlap joint and is usually an automated process.

Figure (2.12) Seam welding

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2.3.1.3 Flash Welding

Flash Welding is a Resistance Welding (RW) process, in which ends of rods

(tubes, sheets) are heated and fused by an arc struck between them and

then forged (brought into a contact under a pressure) producing a weld. The

welded parts are held in electrode clamps, one of which is stationary and the

second is movable.

2.3.1.4 Projection welding

Projection welding is in group of resistance welding. In this welding process

where weld joint is produced by heating is obtained from electrical resistance

flow through the work, which held under electrode pressure. The localizedwelding joint is made by this welding method. The two surfaces of weld

metal are held together in under pressure by the electrodes. When an

electrical current flown through the weld electrode, it causes the projecting

metals are melts and fuse the both material which is contacted. Thus the

weld joint is made. In single operation a number of joint is made. The joint

strength is depending on nature of projection. Some Applications area very

common use of projection welding is the use of special nuts that have projections on the portion

of the part to be welded to the assembly. Also, used for welding parts of refrigerator, condensers,

refrigerator racks, grills etc

2.3.1.5 Resistance butt welding

Butt welding is another type of electric resistant welding. The two weld

metals are placed in a machine in face to face matching and both are

clamped separately. These clamps are act as a electrode. These clamps are

carry the current. The weld metals are matched correctly same axes and

same line touching each other. Both weld metals are holding under pressure.

The source current is given through the electrode to the weld metal and

supply is continuing until its reaching melting temperature. Previously load is

applied to the metal and sufficient melting temperature, both are play

master role for completed the butt weld. Some Applications as Pipes,

tubing, bars, rods, light and medium weight structural shapes may be welded

by butt weld ,Little thickness of ferrous and non-ferrous can be weld ,It has

large application in wire drawing industries.

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Figure (2.13) Resistance butt welding

2.6 BRAZING

Advantages of brazing:

Low thermal distortions and residual stresses in the joint parts;

Microstructure is not affected by heat;

Easily automated process;

Dissimilar materials may be joined;

High variety of materials may be joined;

Thin wall parts may be joined;

Moderate skill of the operator is required.

Disadvantages of brazing:

Careful removal of the flux residuals is required in order to prevent

corrosion;

No gas shielding may cause porosity of the joint;

Large sections cannot be joined;

Fluxes and filler materials may contain toxic components;

Relatively expensive filler materials.

2.4 Brazing process

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2.4.1.1 Torch brazing

Torch brazing is by far the most common method of mechanized brazing in

use. It is best used in small production volumes or in specialized operations,

and in some countries, it accounts for a majority of the brazing taking place.

There are three main categories of torch brazing in use manual, machine,and automatic torch brazing.

Manual torch brazing is a procedure where the heat is applied using a gas

flame placed on or near the joint being brazed. The torch can either be hand

held or held in a fixed position depending on if the operation is completely

manual or has some level of automation. Manual brazing is most commonly

used on small production volumes or in applications where the part size or

configuration makes other brazing methods impossible. The main drawback

is the high labor cost associated with the method as well as the operator skill

required to obtain quality brazed joints. The use of flux or self-fluxing

material is required to prevent oxidation.

Machine torch brazing is commonly used where a repetitive braze operation

is being carried out. This method is a mix of both automated and manual

operations with an operator often placing brazes material, flux and jigging

parts while the machine mechanism carries out the actual braze. The

advantage of this method is that it reduces the high labor and skill

requirement of manual brazing. The use of flux is also required for this

method as there is no protective atmosphere, and it is best suited to small to

medium production volumes.

Automatic torch brazing is a method that almost eliminates the need for

manual labor in the brazing operation, except for loading and unloading of

the machine. The main advantages of this method are: a high production

rate, uniform brazes quality, and reduced operating cost. The equipment

used is essentially the same as that used for Machine torch brazing, with the

main difference being that the machinery replaces the operator in the part

preparation.

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Figure (2.14) Torch brazing

2.5 Soldering

Advantages of soldering:

Low power is required;

Low process temperature;

No thermal distortions and residual stresses in the joint parts;

Microstructure is not affected by heat;


Dissimilar materials may be joined;

High variety of materials may be joined;

Thin wall parts may be joined;

Moderate skill of the operator is required.

Disadvantages of soldering:

Careful removal of the flux residuals is required in order to prevent

corrosion;

Large sections cannot be joined; Fluxes may contain toxic components;

Soldering joints cannot be used in high temperature applications;

Low strength of joints.

2.6 Thermit welding

Thermit Welding is a welding process utilizing heat generated by exothermic

chemical reaction between the components of the Thermit (a mixture of a

metal oxide and aluminum powder).

Advantages of Thermit Welding:

No external power source is required (heat of chemical reaction is

utilized);

Very large heavy section parts may be joined.

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Disadvantages of Resistance Welding: Only ferrous (steel, chromium, nickel) parts may be welded;

Slow welding rate;

High temperature process may cause distortions and changes in Grain

structure in the weld region.

Weld may contain gas (Hydrogen) and slag contaminations.

2.6.1Thermit welding processes

2.6.1.1 Laser beam welding

Laser beam welding is a welding technique used to join multiple pieces ofmetal through the use of a laser. The beam provides a concentrated heat

source, allowing for narrow, deep welds and high welding rates. The process

is frequently used in high volume applications, such as in the automotive

industry.

Laser beam welding has high power density (on the order of 1 MW/cm2)

resulting in small heat-affected zones and high heating and cooling rates.

The spot size of the laser can vary between 0.2 mm and 13 mm, though only

smaller sizes are used for welding. The depth of penetration is proportional

to the amount of power supplied.A continuous or pulsed laser beam may be used depending upon the

application. Milliseconds long pulses are used to weld thin materials such as

razor blades while continuous laser systems are employed for deep welds.

The LBW weld quality is high, similar to that of electron beam welding. The

speed of welding is proportional to the amount of power supplied but also

depends on the type and thickness of the work pieces. The high power

capability ofgas lasers make them especially suitable for high volume

applications. LBW is particularly dominant in the automotive industry.

Advantages of Laser Welding:


Controllable process parameters;

Very narrow weld may be obtained;

High quality of the weld structure;

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Very small heat affected zone;

Dissimilar materials may be welded.

Very small delicate work pieces may be welded;

Vacuum is not required;

Low distortion of work piece.

Disadvantages of laser Arc Welding:

High cost equipment;

Weld depth is limited.

Figure (2.15) Laser beam welding

2.6.1.2 Electron beam welding

Electron beam welding (EBW) is a fusion welding process in which a beam of

high-velocity electrons is applied to the materials being joined. The work

pieces melt as the kinetic energy of the electrons is transformed into heat

upon impact, and the filler metal, if used, also melts to form part of the weld.

The welding is often done in conditions of a vacuum to prevent dispersion of

the electron beam. When electrons of the beam impact the surface of a solid,

some of them may be reflected (as "backscattered" electrons), and others

penetrate under the surface, where they collide with the particles of the

solid. In non-elastic collisions they loose their kinetic energy.

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It has been proved, both theoretically and experimentally, that they can

"travel" only a very small distance under the surface before they transfer all

their kinetic energy into heat. This distance is proportional to their initial

energy and inversely proportional to the density of the solid. Under

conditions usual in welding practice the "travel distance" is of the order

hundreds of a millimeter. Just this fact enables, under certain conditions, the

fast penetration of the beam. Some Applications as, this process is used in

joining of reactor components, It has large use in spaceship building, It is used in

automobile engine component welding.

Advantages of Electron Beam Welding:

Tight continuous weld;

Low distortion;

Narrow weld and narrow heat affected zone;

Filler metal is not required.

Disadvantages of Electron Beam Welding:

Expensive equipment;

High production expenses;

X-ray irradiation.

Figure (2.16) Electron beam welding

2.7 Gas welding

One of the most popular welding methods uses a gas flame as a source of

heat. In the oxyfuel gas welding process heat is produced by burning a

combustible gas, such as MAPP (methylacetylene-propadiene) or acetylene,

mixed with oxygen. Gas welding is widely used in maintenance and repair

work because of the ease in transporting oxygen and fuel cylinders. Once

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you learn the basics of gas welding, you will find the oxyfuel process

adaptable to brazing, cutting, and heat treating all types of metals.

2.7.1 Gas welding process

2.7.1.1 Oxyacetylene welding

Oxyacetylene welding (commonly called oxyfuel welding, oxy welding, or gas

welding in the U.S.) and oxy-fuel cutting are processes that use fuel gases

and oxygen to weld and cut metals, respectively. Pure oxygen, instead ofair

(20% oxygen/80% nitrogen), is used to increase the flame temperature to

allow localized melting of the work piece material (e.g. steel) in a room

environment.

Oxy-fuel or oxyacetylene is one of the oldest welding processes. However, it

is still widely used for welding pipes and tubes, as well as repair work. It isalso frequently well-suited, and favored, for fabricating some types of metal-

based artwork.

In oxy-fuel or oxyacetylene welding, a welding torch is used to weld metals.

Welding metal results when two pieces are heated to a temperature that

produces a shared pool of molten metal. The molten pool is generally

supplied with additional metal called filler. Filler material depends upon the

metals to be welded.

Oxy-fuel processes may use a variety of fuel gases, the most common beingacetylene.

The acetylene is obtained by the action of oxygen and calcium carbide.

CaC2 + 2H2O = Ca (OH) 2 + C2H2

(Acetylene)

Acetylene is the primary fuel for oxy-fuel welding and is the fuel of choice for

repair work and general cutting and welding.

Acetylene gas is shipped in special cylinders designed to keep the gas

dissolved. The cylinders are packed with porous materials then filled toaround 50% capacity with acetone, as acetylene is acetone soluble.

Acetylene is unstable and has high cost

Advantages ofoxyacetylene welding:

In gas welding the heating and cooling rate is slow.

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The flame can be controlled easily where need low and high

temperature for welding or brazing or soldering.

Filler metal deposit rate can be controlled easily, because source of

heat and filler metals are separate.

Preheating facility is in welders hand. So where required it can beapplied.

it is low cost and low maintenance.

Figure (2.17) oxyacetylene welding

2.7.1.2 Pressure gas welding

The pressure gas welding is defined as, the coalescence body is produced by

the heating of weld metal and heat source is some gas of mixture. Then

apply the pressure on weld metal to complete the pressure gas welding. Any

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kind of filler metal is not used in this welding process. Its Application is

commonly used in sheet metal welding, pipe welding, railroad joining etc.

2.8 Solid state welding

Advantages of Solid State Welding: Weld (bonding) is free from microstructure defects (pores, non-metallic

inclusions, segregation ofalloying elements)

Mechanical properties of the weld are similar to those of the parent

metals

No consumable materials (filler material, fluxes, shielding gases) are

required

Dissimilar metals may be joined (steel - aluminum alloy steel - copperalloy).

Disadvantages of Solid State Welding: Thorough surface preparation is required (degreasing, oxides removal,

brushing/sanding)

Expensive equipment.

2.8.1 Solid state welding process

2.8.1.1 Forge welding

Forge welding is the oldest welding process. It has an application of the

blacksmiths method of metals joining. The metals which to be joint are

heated in furnace or some other source of heat to the plastic stage or just

below the molten stage of metals (looks like very bright). Then heated

metals are bring on anvil from heat source and superimposed the both

metals where to be joint. Apply the hammering or pressed together until a

joint has been created. The applying of heat must be uniformed. Otherwisethe joint is made weak or spongy rough appearance. So heat should not be

too high or too little. To avoidance of oxidation a little amount offlux may be

used in weld joint.

There are mainly three types of forge welding method is used:

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Hammer welding.

Roll welding.

Die welding.

Some Applications as

In sheet metal welding.

In ship building works.

In automobile workshop.

In refrigeration works.

Advantages of Forge Welding: Good quality weld may be obtained;

Parts of intricate shape may be welded;

No filler material is required.

Disadvantages of Forge Welding: Only low carbon steel may be welded;

High level of the operators skill is required;

Slow welding process;

Weld may be contaminated by the coke used in heating furnace.

Figure (2.18) Forge welding

2.8.1.2Ultrasonic welding

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Ultrasonic welding is an industrial technique whereby high-frequency

ultrasonicacousticvibrations are locally applied to work pieces being held

together under pressure to create a solid-state weld. It is commonly used for

plastics, and especially for joining dissimilar materials. In ultrasonic welding,

there are no connective bolts, nails, soldering materials, or adhesives

necessary to bind the materials together. The applications of ultrasonic

welding are extensive and are found in many industries including electrical

and computer, automotive and aerospace, medical, and packaging. Whether

two items can be ultrasonically welded is determined by their thickness. If

they are too thick this process will not join them. This is the main obstacle in

the welding of metals. However, wires, microcircuit connections, sheet

metal, foils, ribbons and meshes are often joined using ultrasonic welding.

Ultrasonic welding is a very popular technique for bonding thermoplastics. It

is fast and easily automated with weld times often below one second and

there is no ventilation system required to remove heat or exhaust. This typeof welding is often used to build assemblies that are too small, too complex,

or too delicate for more common welding techniques.

Advantages of Ultrasonic Welding:

Dissimilar metals may be joined;

Very low deformation of the work pieces surfaces;

High quality weld is obtained;

The process may be integrated into automated production lines;

Moderate operator skill level is enough.

Disadvantages of Ultrasonic Welding:

Only small and thin parts may be welded;

Work pieces and equipment components may fatigue at the

reciprocating loads provided by ultrasonic vibration;

Work pieces may bond to the anvil.

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Figure (2.19) Ultrasonic

welding

2.8.1.3 Cold working welding

The cold welding process is performed in solid state, where metal joint isproduced in the room temperature and also under of mechanical pressure.

The joint is made without of filler rod.

The main characteristic of this welding process is total absence of heat and

flux.

A specially designed die is used for restricting or controlling the deformation

of weld parts. The pressure is applied by manually or with power driven.

The amount of pressure is applied on three factors:

1. Nature of surface area of die.2. Thickness of the metal.

3. Characteristic of material.

Some Applications as it is used in electronics industries for joining of small

transistors, also It has specific use in welding metals in explosive areas.

2.8.1.4 Friction welding

The friction welding is one of the solid state welding process, where weld

joint is made by heating is created from mechanically induced sliding motion

between rubbing surface in under pressure. The heat is generated by co-

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efficient of friction of the material. To get a quick heat from surface area,

when the rotational speed is high.

In this welding process the fusion is produced by rotating one of the weld

parts to be joined against the fixed surface of the other part. Until fusion

temperature is obtained in weld parts the rotation of rotating parts will be inhigh speed and under low pressure. Large amount of pressure will be applied

in until both weld parts are welded.

Different types of material can be welding by this process.

The materials are: Carbon steel, alloy steel, copper to carbon steel, copper to

aluminum, aluminum and its alloy, brass to bronze, tool steel, stainless steel,

stainless steel to aluminum, tungsten, etc. Some Applications as Drill, tap,

reamer etc. joining with shank, To joining of steering shaft and worm gear,

engine valves, power transmission shaft etc, To production of bimetallic shaft

joining ,To produce a bimetallic fastener which is used in nuclear plant.Advantages of Friction welding

It requires less time operation.

Operational hazardous is less.

The characteristic changing of granular structure is less.

The weld joint may have not heat treated again.

It has no need of flux, filler. So it is free of smoke, spatter and slag.

Simplicity of operation.

Power requirement is less.

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Figure (2.20) Friction welding

2. 8.1.5 Electroslag welding

Electroslag welding is a highly productive, single pass welding process for

thick in a vertical or close to vertical position. An electric arc is initially struckby wire that is fed into the desired weld location and then flux is added.

Additional flux is added until the molten slag, reaching the tip of the

electrode, extinguishes the arc. The wire is then continually fed through a

consumable guide tube into the surfaces of the metal work pieces and the

filler metal are then melted using the electrical resistance of the molten slag

to cause coalescence. The wire and tube then move up along the work piece

while a copper retaining shoe that was put into place before starting is used

to keep the weld between the plates that are being welded.

This process uses a direct current (DC) voltage usually ranging from about600A and 40-50V , higher currents are needed for thicker materials. Because

the arc is extinguished, this is not an arc process.

Some Applications as Electroslag welding is used mainly to join low carbon

steel plates and/or sections that are very thick, It can also be used on

structural steel if certain precautions are observed

Advantages

Benefits of the process include its high metal deposition ratesit can

lay metal at a rate between 15 and 20 kg per hour (35 and 45 lb/h) per

electrode

Its ability to weld thick materials.

The process is also very efficient, since joint preparation and materials

handling are minimized while filler metal utilization is high

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The process is also safe and clean, with no arc flash and low weld

splatter or distortion.

Electroslag welding easily lends itself to mechanization, thus reducing

the requirement for skilled manual welders.

Disadvantages of Electroslag welding:

Coarse grain structure of the weld;

Low toughness of the weld;

Figure (2.21) Electroslag welding

2.9 Metals

Properties of metals

Hardness

Brittleness

Ductility Toughness

Strength

Metals that can be used in welding

Carbon and alloy steels

These steels classified into low carbon, medium carbon, high carbon

depending on the percentage of the carbon in the materials

Common name Carbon content weldability

Low carbon 0.15% max excellent

Medium carbon 0.30%-0.50% fair

High carbon 0.50%-1.00% poor

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High manganese steel

High manganese steel are used for such items as a power shovels, rock

crushers, mine equipment, switch frogs.

Stainless steel

Stainless steel consists of alloys: austenitic, ferritic, martensitic, precipitation

hardening. They are used such as chemical equipment, cooking materials,

food processing equipment, and furnace parts.

Chromium molybdenum

Chromium molybdenum is used for high temperature service and aircrafts

parts

Copper and copper alloys

There are different types of copper alloys. Copper is often alloyed with other

metals such as zinc, nickel, iron, aluminum .Welding copper results in

economy, speed, strength, ductility.

Aluminum weldability

Their characteristic is that has a great affinity for oxygen.

Titanium

It is silvery grey metal most important properties of the titanium are high

strength to weight ration and excellent corrosion resistance.

Magnesium

It is an extremely light metal have a silver white color; it has considerable

resistance to corrosion.

Cast iron

Cast iron is important to guard against cracks due to expanding and

contractions during the welding process.

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2.10 Filler Metals

When welding two pieces of metal together, you often have to leave a space

between the joint. The material that you add to fill this space during the

welding process is known as the filler metal, or material. Two types of filler

metals commonly used in welding are welding rods and welding electrodes.

The term welding rodrefers to a form of filler metal that does not conduct an

electric current during the welding process. The only purpose of a welding

rod is to supply filler metal to the joint. This type of filler metal is often used

for gas welding. In electric-arc welding, the term electrode refers to the

component that conducts the current from the electrode holder to the metal

being welded. Electrodes are classified into two groups: consumable and nonconsumable.

Consumable electrodes not only provide a path for the current but they also

supply fuller metal to the joint. An example is the electrode used in shielded

metal-arc welding. No consumable electrodes are only used as a conductor

for the electrical current, such as in gas tungsten arc welding.

2.11Protecting metal from atmospheric contamination

Before performing any welding process, you must the base metal is clean.

No matter how much the base metal is physically cleaned, it still contains

impurities. These impurities, called oxides, result from oxygen combining

with the metal and other contaminants in the base metal. Unless these

oxides are removed by using a proper flux, a faulty weld may result. The

term fluxrefers to a material used to dissolve oxides and release trapped

gases and slag (impurities) from the base metal

Advantages of fluxes for welding

It remains stable and does not change to a vapor rapidly within the

temperature range of the welding procedure.

It dissolves all oxides and removes them from the joint surfaces.

It adheres to the metal surfaces while they are being heated and does

not ball up or blow away.

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It does not cause a glare that makes it difficult to see the progress of

welding or brazing.

It is easy to remove after the joint is welded.

It is available in an easily applied form.

2.12 Control of weld metallurgy

When the weld metal sodifies, the microstructures formed in the weld

and the heat affected zone region determines the mechanical

properties of the joint produced. Preheating and post welding heat-

treatment can be used to control the cooling rates in the weld and the

heat affected zone regions and thus control the microstructures and

properties of the welds produced. De oxidants and alloying elementsare added as in foundry to control the weld metal properties.

The foregoing discussion clearly shows that the status of welding has

now changed from skill to science. A scientific understanding of the

material and service requirements of the joints is necessary to produce

successful welds which will meet the challenge of hostile service

requirements.

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Figure (2.22) EXPANSION AND CONTRACTION of metals

2.13 Expansion and contraction of metals

When a piece of metal is heated, the metal expands. Upon cooling, the metal

contracts and tries to resume its original shape. The effects of this expansionand contraction are shown in this figure. View a shows a bar that is not

restricted in any way. When the bar is heated, it is free to expand in all

directions. If the bar is allowed to cool without restraint, it contracts to its

original dimensions. When the bar is clamped in a vise (view B) and heated,

expansion is limited to the unrestricted sides of the bar. As the bar begins to

cool, it still contracts uniformly in all directions. As a result, the bar is now

deformed. It has become narrower and thicker, as shown in (view C).

These same expansion and contraction forces act on the weld metal and

base metal of a welded joint; however, when two pieces of metal are welded

together, Expansion and contraction may not be uniform throughout all parts

of the metal. This is due to the difference in the temperature from the actual

weld joint out to the edges of the joint. This difference in temperature leads

to internal stresses.

All metals, when exposed to heat buildup during welding, expand in the

direction of least resistance. Conversely, when the metal cools, it contracts

by the same amount; therefore, if you want to prevent or reduce the

distortion of the weldment, you have to use some method to overcome the

effects of heating and cooling.

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Figure (2.23) direction of welding

2.14 Butt welds

Butt welds are welds where two pieces of metal are joined at surfaces that

are at 90 degree angles to the surface of at least one of the other pieces.

The types of welds require only some preparation and are used with thin

sheet metals that can be welded with a single pass. Common issues that can

weaken a butt weld are the entrapment ofslag, excessive porosity, or

cracking. For strong welds, the goal is to use the least amount of welding

material possible. Butt welds are prevalent in automated welding processes,

such as submerged-arc welding, due to their relative ease of preparation.When metals are welded without human guidance; there is no operator to

make adjustments for non-ideal joint preparation. Because of this necessity,

butt welds can be utilized for their simplistic design to be fed through

automated welding machines efficiently.

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Chapter 3

Experimental Setup

In this chapter the steps of manufacturing and selecting each component of the automaticwelding table will be discussed and explained with the aid of pictures and figures.Every part was manufactured separately and later is being assembled to form the automaticwelding table.

Components of the automatic welding table are:

1- Body and frame.

2- Motor.

3- Gearbox.

4- Inverter.

5- Wire remote control.

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3.1The body and frame

3.1.1 The table

The table is a basic piece that is generally consists of a flat top that is

supported by either a set of legs. The table is made from metal; the table is a

mechanical table, and made from iron.

The table was designed by a length and width (100cm x 70cm) and thelength of the legs are 80cm.

Figure (3.1) the manufacturing table

3.1.2 Upper part of the table

This metal sheet with holes is the upper part of the table for holding the

samples on it by screws while welding, and it is moving freely

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Dimension: 100cmx70cm and thickness 2mm

Figure (3.2) Upper part of the table

Figure (3.3) Machine that is used to do these holes on the upper

part

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3.1.3 Wheels of the table

Common inexpensive casters may include a brake feature, which prevents

the wheel from turning. This is commonly achieved using a lever that presses

a brake cam against the wheel. These institutional casters are ideal for any

light duty application where the caster must be totally immobile when the

caster brake is applied. Caster has a unique brake which locks both thewheel and the swivel bearing at the same time. This "Total-Lock" brake

insures that the caster will not turn when the wheel is locked. This

combination wheel brake is essential for safety in some applications such as

on worktables, welding table, and medical equipment.

Figure (3.4) Wheels of the table

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Figure (3.5) this shape for connecting the wheels to it

3.1.4 Holder of the table

The holder is made from iron and installed in one side of the table and

contains three parts:

One part which can moving up and down depending on the length we

need for the welding while holding the torch and then Installing this

part by the screw

Dimension: length 75cm

Figure(3.6) part of the holder

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Second part which can moving right and left also depending on the

length we need for the welding while holding the torch and then

Installing the part by the screw ,


Figure(3.7) part of the holder

Third part is connected to C-Clamp

Dimensions: length 40cm

This type ofclamp device typically used to hold the torch of the welding.

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Figure(3.8) part of the holder Figure (3.9) c-clamp

3.1.5 Parts of the table section

(a) Two parts of a sheet with dimension 200cmx2.5cm with thickness 2.5cm

I used the two part of this sheet which welded on the table for the wheels

bearing hub to move on it.

Figure (3.10) this part let the bearing hub wheel to move on it

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Figure (3.11) this part to prevent the bearing hub to move away

(b)Wheel bearing hub

There are eight wheels bearing hub, which attached to the upper part of the

table to move on the table freely.

Dimension: diameter 3cm

Figure (3.12) bearing hub wheel while moving

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Figure (3.13) eight bearing hub wheel

3.1.6 The motor with gearbox seating

This shape were welded at the bottom of the table for motor with the

gearbox and it is installed by 4 screws

Dimensions of this Chassis: 35cmx20cmx80cm

Dimensions of the seating of the motor with gearbox: 20cmx20cm.

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Figure (3.14) the motor with gearbox seating from the top view

Figure (3.15) the motor with gearbox seating from the side view

3.1.7 The shaft

The Motor Shaft is primarily used as a mechanical component for torque

transmission. This shaft is connected directly to motor. I took the dimension

of the gears and pulley depends on it

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Figure (3.16) the motor shaft

3.1.8 Gears

Gears have many uses in our lives. They are used to:

- multiply or reduce speed and force, change the direction of motion,

transmit a force over a distance.

This type of gears is the pinion gears with Rack that are used to convert

rotation (From the pinion) into linear motion (of the rack)

Gears dimension: diameter 17cm

Figure (3.17) Gears Figure (3.18) Gears when it isconnected to the shaft

3.1.9 Rack

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it is attached down the upper part of the table and from the teeth side is

directly connected to the gear

Figure (3.19) Rack

Figure (3.20) Rack with the gear

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3.1.10 Pulley

There is one pulley with a hole look like shape of key slot is directly

connected to the shaft

Its Dimensions: diameter 6.5cm

Figure (3.21)Pulley with open key hole

And one pulley with a small hole connected to the shaft

Dimensions: diameter 5cm

Figure (3.22)Pulley with small hole

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3.1.11 Safety electronic box

Holding a box in the table for putting the inverter inside it for more safefrom the fumes of the welding and installed by 2 screws.

Figure (3.23) Safety inverter box with an open and close

door

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3.2 Motor

Power: 1HP

Ampere: 8A

Voltage: 380v

Speed: 60rpm

The motor was selected according to these specifications .The motor used in

the project is three-phaseinduction motor, but three-phase motors are

usually preferred for connecting it to the invertors. Various types of

synchronous motors offer advantages in some situations, Motors that are

designed for fixed-speed operation are often used. Certain enhancements to

the standard motor designs offer higher reliability and better VFD

performance.

The motor has a 4 wires connected from the inverter, the red wire, yellow

wire, and the green wire are connected to the motor and the black wire to

the ground.

Also the motor is connected to a gear box to reduce the speed.

Power= 1.732 x V x I x EFF

Finished Bachelor Thesis

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