Курс повышения квалификации
Курс повышения квалификации
Курс профессиональной переподготовки
Classification of welding processes
Plasma arc welding
Arc welding is a type of welding that uses a welding power supply to create an electric arc between an electrode and the base material to melt the metals at the welding point. They can use either direct or alternating current, and consumable or non-consumable electrodes. The welding region is usually protected by some type of shielding gas, vapor, or slag. Arc welding processes may be manual, semi-automatic, or fully automated vehicles.
Diagram of arc and weld area,
in shielded metal arc welding
1. Coating Flow
3. Shield Gas
5. Base metal
6. Weld metal
7. Solidified Slag Diagram of arc and
weld area, in shielded metal arc welding
Laser Welding (LW) is a welding process, in which heat is generated by a high energy laser beam targeted on the work piece. The laser beam heats and melts the work pieces edges, forming a joint.
Thermite Welding is a welding process utilizing heat generated by exothermic chemical reaction between the components of the thermite (a mixture of a metal oxide and aluminum powder). The molten metal, produced by the reaction, acts as a filler material joining the work pieces after Solidification.
Electroslag Welding is a welding process, in which the heat is generated by an electric current passing between the consumable electrode and the work piece through a molten slag covering the weld surface.
Prior to welding the gap between the two work pieces is filled with a welding flux. Electro-slag Welding is initiated by an arc between the electrode and the work piece (or starting plate). Heat, generated by the arc, melts the fluxing powder and forms molten slag. The slag, having low electric conductivity, is maintained in liquid state due to heat produced by the electric current.
Plasma Arc Welding is the welding process utilizing heat generated by a constricted arc struck between a tungsten non-consumable electrode and either the work piece (transferred arc process) or water cooled constricting nozzle (non-transferred arc process).
Electron Beam Welding is a welding process utilizing a heat generated by a beam of high energy electrons. The electrons strike the work piece and their kinetic energy converts into thermal energy heating the metal so that the edges of work piece are fused and joined together forming a weld after Solidification.
Resistance Welding is a welding process, in which work pieces are welded due to a combination of a pressure applied to them and a localized heat generated by a high electric current flowing through the contact area of the weld.
Diffusion Welding is a Solid State Welding process, in which pressure applied to two work pieces with carefully cleaned surfaces and at an elevated temperature below the melting point of the metals. Bonding of the materials is a result of mutual diffusion of their interface atoms.
Advantages of Diffusion Welding: Dissimilar materials may be welded; Welds of high quality are obtained; No limitation in the work pieces thickness.
Disadvantages of Diffusion Welding: Time consuming process with low productivity; Very thorough surface preparation is required prior to welding process; The mating surfaces must be precisely fitted to each other;
Forge Welding is a Solid State Welding process, in which low carbon steel parts are heated to about 1800°F (1000°C) and then forged (hammered).
Prior to Forge Welding, the parts are scarfed in order to prevent entrapment of oxides in the joint.
Forge Welding is used in general blacksmith shops and for manufacturing metal art pieces and welded tubes.
Friction Welding is a Solid State Welding process, in which two cylindrical parts are brought in contact by a friction pressure when one of them rotates. Friction between the parts results in heating their ends. Forge pressure is then applied to the pieces providing formation of the joint.
Ultrasonic Welding is a Solid State Welding process, in which two work pieces are bonded as a result of a pressure exerted to the welded parts combined with application of high frequency acoustic vibration.
Advantages of Ultrasonic Welding:
Dissimilar metals may be joined;
Very low deformation of the work pieces surfaces;
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.
Explosive Welding is a Solid State Welding process, in which welded parts (plates) are metallurgically bonded as a result of oblique impact pressure exerted on them by a controlled detonation of an explosive charge.
Advantages of Explosive Welding
Large surfaces may be welded;
Low cost and simple process;
Surface preparation is not required.
Disadvantages of Explosive Welding:
Brittle materials cannot be processed;
Only simple shape parts may be bonded: plates, cylinders;
Thickness of flyer plate is limited - less than 2.5” (63 mm);
Safety and security aspects of storage and using explosives.
Cold Welding is a Solid State Welding process, in which two work pieces are joined together at room temperature and under a pressure, causing a substantial deformation of the welded parts and providing an intimate contact between the welded surfaces.
As a result of the deformation, the oxide film covering the welded parts breaks up, and clean metal surfaces reveal. Intimate contact between these pure surfaces provide a strong and defectless bonding.
Aluminum alloys, Copper alloys, low carbon steels, Nickel alloys, and other ductile metals may be welded by Cold Welding.
Cold Welding is widely used for manufacturing bi-metal steel - aluminum alloy strips, for cladding of aluminum alloy strips by other aluminum alloys or pure aluminum. Bi-metal strips are produced by Rolling technology. Presses are also used for Cold Welding.
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