Welding Fundamentals

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Questions and Answers

In which century were the present day welding processes developed?

Within a period of about 50 years

19th century

20th century

Last century (correct)

What type of welding process is used when no filler metal is used?

Manual Metal Arc Welding Process

Forge Welding Process

Autogenous Welding Process (correct)

Oxy-Acetylene Welding Process

In which year was the first application of welding with carbon electrode developed?

1902

1905

1890

1885 (correct)

What led to the feasibility of oxy-acetylene welding in Europe in 1903?

Production of cheap oxygen Signup and view all the answers

When was resistance butt welding invented in the USA?

1886 Signup and view all the answers

What was the significance of developments in 1885 and 1890?

They were the base for present day welding processes Signup and view all the answers

What is the year when the first all-welded bridge was erected in the UK?

1934 Signup and view all the answers

What is the primary reason why welding replaced riveting in ship building?

Welding allowed for the use of semiskilled/unskilled labor and pre-fabrication Signup and view all the answers

What is the year when welding started to be used in the fabrication of pressure vessels?

Early 20th century Signup and view all the answers

What is the primary reason why welding was initially used in bridge construction in Australia?

Due to the remote location of the construction sites Signup and view all the answers

What is the year when the problem of fracture in welded structures was highlighted?

1942 Signup and view all the answers

What is the year when the process of submerged arc welding was developed?

1935 Signup and view all the answers

What is the primary reason why the classification of welding processes based on the source of energy is not justified?

Because all other forms of energy are generated from electrical energy for welding Signup and view all the answers

What is the main limitation of the classification of welding processes based on the presence or absence of filler material?

Many welding processes fall into both categories Signup and view all the answers

What is the primary application of micro-joining in the industry?

Producing junctions of thermocouples and strain gauges to wire leads Signup and view all the answers

What is the main difference between fusion welding and pressure welding?

In fusion welding, molten metal solidifies freely, while in pressure welding, molten metal solidifies under pressure Signup and view all the answers

What is the primary application of welding in the nuclear industry?

Fabrication of spheres for nuclear reactors Signup and view all the answers

What is the limitation of the classification of welding processes based on arc and non-arc welding?

It is difficult to assign electroslag welding and flash butt welding to either category Signup and view all the answers

What is the primary purpose of welding symbols in welding engineering?

To represent the welding procedure and other conditions Signup and view all the answers

Which type of weld joint is formed when two plates are approximately perpendicular to each other at one side of the plates being welded?

Corner joint Signup and view all the answers

What is the term used to describe the process of gas metal arc welding when an active gas such as CO2 or a mixture of inert and active gases is used as the shielding gas?

MAG welding Signup and view all the answers

What is the requirement of the power source for GMAW process?

Direct current flat characteristic power source Signup and view all the answers

What is the purpose of the copper coating on the electrode wire in GMAW process?

To increase the current carrying capacity and to avoid atmospheric corrosion Signup and view all the answers

What is the term used to describe the type of weld that is made by melting the edges of two plates to be welded?

Edge weld Signup and view all the answers

What is the main factor that determines the range of welding current and voltage in GMA welding?

Electrode size and mode of metal transfer Signup and view all the answers

What is the typical shielding gas used for welding mild steel in GMA welding?

Carbon dioxide Signup and view all the answers

What is the primary reason why GMA welding is preferred over manual metal arc welding for welding nonferrous metals like aluminum and copper based alloys?

Higher deposition rate Signup and view all the answers

What is the primary purpose of using flux in forge welding?

To prevent the welding surface from oxidation Signup and view all the answers

What is the main advantage of GMA welding over other arc welding processes?

High quality welds without slag removal Signup and view all the answers

What is the effect of air draught on the GMA welding process?

Disturbs the arc and produces poor quality welds Signup and view all the answers

What is the approximate temperature range for heating the workpieces in forge welding?

50 to 90% of its melting temperature Signup and view all the answers

What is the primary reason why GMA welding is used in industries such as shipbuilding and chemical plants?

High deposition rate and versatility in welding positions Signup and view all the answers

What type of welding process is forge welding?

Solid state welding process Signup and view all the answers

What is the result of repeated hammering or high pressure load on the workpieces in forge welding?

Formation of a strong weld joint Signup and view all the answers

What is the main requirement for the interface surface of the plates in forge welding?

Clean surface free from oxide or contaminants Signup and view all the answers

What is the primary tool used for manual hammering in forge welding?

Blacksmith hammer Signup and view all the answers

What is the primary use of mechanical hammering in forge welding?

For welding large workpieces Signup and view all the answers

What is the primary material joined using forge welding?

Steel or iron Signup and view all the answers

What is the primary use of dies in forge welding?

To provide a finished surface Signup and view all the answers

What is the primary historical use of forge welding?

To make swords and other weapons Signup and view all the answers

Study Notes

Welding

Welding is the process of joining two metallic components with the application of heat, with or without the application of pressure, and with or without the use of filler metal.
Heat can be obtained by chemical reaction, electric arc, electrical resistance, frictional heat, sound, and light energy.

History of Welding

During the Bronze Age, parts were joined by forge welding to produce tools, weapons, and ornaments.
The first application of welding with a carbon electrode was developed in 1885.
Metal arc welding with a bare electrode was patented in 1890.
Resistance butt welding was invented in the USA in 1886.
Other resistance welding processes such as spot and flash welding were developed around 1905.
The production of cheap oxygen in 1902 led to the development of oxy-acetylene welding in Europe in 1903.
The development of coated electrodes in 1907 made manual metal arc welding viable for production and fabrication.

Types of Welding

Thermit welding (1903)
Cellulosic electrodes (1918)
Arc stud welding (1918)
Seam welding of tubes (1922)
Mechanical flash welder for joining rails (1924)
Extruded coating for MMAW electrodes (1926)
Submerged arc welding (1935)
Air arc gouging (1939)
Inert gas tungsten arc (TIG) welding (1941)
Iron powder electrodes with high recovery (1944)
Inert gas metal arc (MIG) welding (1948)
Electro slag welding (1951)
Flux cored wire with CO2 shielding (1954)
Electron beam welding (1954)
Constricted arc (plasma) for cutting (1955)
Friction welding (1956)
Plasma arc welding (1957)
Electro gas welding (1957)
Short circuit transfer for low current, low voltage welding with CO2 shielding (1957)
Vacuum diffusion welding (1959)
Explosive welding (1960)
Laser beam welding (1961)
High-power CO2 laser beam welding (1964)

Applications of Welding

Fabrication of pressure vessels, bridges, building structures, aircraft, and space crafts
Shipbuilding, automobile, electrical, electronic, and defense industries
Laying of pipelines and railway tracks
Nuclear installations
Construction of transport tankers, welded tubes, and pipes
Steel furniture, gates, doors, and other items
Micro-joining (junctions of thermocouples, strain gauges to wire leads, etc.)

Classification of Welding Processes

Welding with or without filler material
Source of energy of welding
Arc and non-arc welding
Fusion and pressure welding
Fusion welding (molten metal solidifies freely)
Pressure welding (molten metal, if any, is retained in a confined space under pressure)

Welding Symbols

Symbols used to show the type of weld to be made
Symbols used to show not only the type of weld but also relevant aspects related to welding (size, location, welding process, edge preparation, bead geometry, etc.)

Types of Weld Joints

Butt joint (plates in the same horizontal plane, aligned with a maximum deviation of 50)
Lap joint (plates overlapping each other, with the overlap on one or both sides)
Corner joint (joint made by melting the corners of two plates, approximately perpendicular to each other)
Edge joint (joint made by melting the edges of two plates, almost parallel)
T joint (one plate approximately perpendicular to another plate)

Types of Welds

Groove weld
Fillet weld
Plug weld
Bead on plate weld

Gas Metal Arc Welding (GMAW)

Process in which an arc is struck between a bare wire electrode and the workpiece
Arc is shielded by a shielding gas (inert or active)
Electrode wire is fed continuously through a contact tube
Power source is a direct current (DC) flat characteristic
Electrode wire is connected to the positive terminal of the power source
Shielding gases used: argon, helium, CO2, and mixtures
Wire feeding system: pressure adjusting screw, wire feeding rolls, and grooves

Arc Welding Process

Applies heat generated by an electric arc to melt the faying surfaces of the base metal
Common arc welding processes: manual metal or shielded metal arc welding (MMA or SMA), metal inert gas arc (MIG), tungsten inert gas (TIG), submerged arc (SA), plasma arc (PA), and carbon arc (CA)

Forge Welding

A solid-state welding process in which both plates are heated below their melting temperature
Plastic deformation occurs, and inter-molecular diffusion takes place at the interface surface
Requires a clean interface surface, free from oxide or other contaminant particles
Flux is used to prevent oxidation and to flow out the oxide layer during heating and hammering

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Description

Introduction to welding, a process of joining two metallic components using heat, with or without pressure and filler metal, and its various methods.