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Questions and Answers
What is the primary factor that determines the range of welding current and voltage in the GMA welding process?
What is the typical shielding gas used for welding mild steel in the GMA welding process?
What is the advantage of using a mixture of argon and oxygen for welding low-alloyed and stainless steels in the GMA welding process?
What is the primary limitation of the GMA welding process?
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What is the significance of Table 9.1 in the context of the GMA welding process?
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What is the characteristic of the GMA welding process that makes it suitable for welding a wide range of thicknesses and positions?
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What are the components of hydro and steam power generation systems that are fabricated by welding?
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Which of the following industries uses welding to a limited extent?
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What is the term used to describe the process of welding without filler material?
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Which of the following classification criteria is most widely used for welding processes?
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What type of welding is used for joining of thin wire to wire, foil to foil, and foil to wire?
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Which of the following applications of welding involves the joining of pipes during laying of crude oil and gas pipelines?
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What was the major development in welding that took place in 1903?
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What was the first major application of welding in the early 20th century?
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What was the main reason for the introduction of welding in bridge construction in Australia?
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What was the event that gave a big jolt to the application of welding in 1942?
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What is one of the benefits of welding in the construction of steel buildings?
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What is the main advantage of welding in the construction of space vehicles?
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What is the primary purpose of using welding symbols in welding engineering?
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What is the characteristics of the power source required in GMAW process?
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What is the type of weld joint where the plates are approximately perpendicular to each other at one side of the plates being welded?
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What is the purpose of the pressure adjusting screw in the electrode wire feeding system?
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What is the term used for the process of gas metal arc welding when the shielding gas is an active gas such as CO2 or a mixture of inert and active gases?
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What is the primary factor that classifies the type of weld joint?
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What is the primary purpose of welding?
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What is the term used when no filler metal is used during welding?
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In which year was the first application of welding with a carbon electrode developed?
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What was the significant development in 1902 that made oxy-acetylene welding feasible?
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What was developed in 1907 that made manual metal arc welding viable for production on a large scale?
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What was the primary method of joining parts during the 'Bronze Age'?
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What is the purpose of using flux in forge welding?
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What is the typical temperature range for heating the work plates in forge welding?
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What is the primary requirement for the interface surface in forge welding?
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What is the final stage of the forge welding process?
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What is the common application of forge welding in cookware?
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What is the principle of forge welding?
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What is the function of the hammer in forge welding?
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What is the common application of forge welding in ancient times?
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What is the typical welding process used to join boiler plates?
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What is the solid state welding process that forge welding is based on?
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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
Learn the basics of welding, including the process of joining metallic components and the history of welding techniques from the Bronze Age to modern applications.
