Introduction about welding processes

Welding :-

Welding is process of joining of two similar or dissimilar materials by the application of heat and with or without the application of pressure and with or without application of filler materials. On Cooling the molten edges fuse together to form a strong joint. A filler material is added to the molten parent metal.

Welding (GMAW)

In simple words-

Process of joining metals/alloys
The process performed by Heat with or without Pressure
Filler metal may or may not be used
The joint will be homogeneous

Classification of Welding:-

Pressure Welding- With Heat & Pressure
Fusion Welding- With Heat & mostly with Filler

Comments

Electroslag Welding (ESW)

ELECTROSLAG WELDING The Process :- Electroslag welding (ESW) is a process that melts and joins metals by heating them with a pool of molten slag held between the metals and continuously feeding a filler wire electrode into it, as shown in Figure. The weld pool is covered with molten slag and moves upward as welding progresses. A pair of water-cooled copper shoes, one in the front of the workpiece and one behind it, keeps the weld pool and the molten slag from breaking out. Similar to SAW , the molten slag in ESW protects the weld metal from air and refines it. Strictly speaking, however, ESW is not an arc welding process, because the arc exists only during the initiation period of the process, that is, when the arc heats up the flux and melts it. The arc is then extinguished, and the resistance heating generated by the electric current passing through the slag keeps it molten. In order to make heating more uniform, the electrode is often oscillated, especially when welding thicker

Gas–Tungsten arc welding (GTAW)

GTAW The Process Gas–tungsten arc welding (GTAW) is a process that melts and joins metals by heating them with an arc established between a non consumable tungsten electrode and the metals, as shown in Figure. The torch holding the tungsten electrode is connected to a shielding gas cylinder as well as one terminal of the power source, as shown in Figure a . The tungsten electrode is usually in contact with a water-cooled copper tube, called the contact tube, as shown in Figure b , which is connected to the welding cable (cable 1) from the terminal. This allows both the welding current from the power source to enter the electrode and the electrode to be cooled to prevent overheating.The workpiece is connected to the other terminal of the power source through a different cable (cable 2). The shielding gas goes through the torch body and is directed by a nozzle toward the weld pool to protect it from the air. Protection from the air is much better in GTAW than in SMAW because

Electron Beam Welding (EBW)

ELECTRON BEAM WELDING The Process:- Electron beam welding (EBW) is a process that melts and joins metals by heating them with an electron beam. As shown in Figure 1a, the cathode of the electron beam gun is a negatively charged filament.When heated up to its thermionic emission temperature, this filament emits electrons. These electrons are accelerated by the electric field between a negatively charged bias electrode (located slightly below the cathode) and the anode. They pass through the hole in the anode and are focused by an electromagnetic coil to a point at the workpiece surface. The beam currents and the accelerating voltages employed for typical EBW vary over the ranges of 50–1000mA and 30–175kV, respectively. An electron beam of very high intensity can vaporize the metal and form a vapour hole during welding, that is, a keyhole, as depicted in Figure 1b. 1 Electron beam welding: (a) process; (b) keyhole. Modified from Arata Figure 2 shows that the beam diameter dec

Welding

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