Skip to main content

Submerged Arc Welding (SAW)

SUBMERGED ARC WELDING

 The Process :-
Submerged arc welding (SAW) is a process that melts and joins metals by heating them with an arc established between a consumable wire electrode and the metals, with the arc being shielded by a molten slag and granular flux, as shown in Figure. This process differs from the arc welding processes discussed so far in that the arc is submerged and thus invisible.The flux is supplied from a hopper (Figure a), which travels with the torch. No shielding gas is needed because the molten metal is separated from the air by the molten
slag and granular flux (Figure b). Direct-current electrode positive is most often used. However, at very high welding currents (e.g., above 900A) AC is preferred in order to minimize arc blow. Arc blow is caused by the electromagnetic (Lorentz) force as a result of the interaction between the electric current itself and the magnetic field it induces.

 In short:-
•Automatic / Semi Automatic
•Arc Between Consumable Electrode And Work
•Arc Covered Under granular Flux
•Wire / Electrode Continuously Fed To Weld Pool
•Wire / Arc Under Flux Moves Along The Groove
•Wire, BM & Flux Close to Arc Melt Under Flux 
•On Cooling Weld Metal Solidifies
•Molten Flux Forms Thick Slag Coating On Weld




Function Of Flux In SAW:-
•Stabilizes Arc
•Prevents contamination of weld metal
•Cleans the weld from unwanted impurities
•Increases Fluidity of molten metal
•Generates inert gas shielding while metal transfers
•Forms slag after melting & covers weld
•Allows deposited metal to cool slowly
•Compensates alloying elements Within the weld
•Eliminates spatter generation
•Helps in even & uniform bead finish
Baking Requirements For Flux :-
•Spread the loose Flux in a Tray Of baking Oven
•Identify The Tray With The Quality/Grade Of Flux
•Bake Tray in an Oven Between 300° C to 350° C
• Baking Time 2Hrs to 3 Hrs
•Reduce the temperature to 100 ° C  to 150 ° C
•Hold the Flux at this temperature till use

Advantages and Disadvantages :-

 The protecting and refining action of the slag helps produce clean welds in SAW. Since the arc is submerged, spatter and heat losses to the surrounding air are eliminated even at high welding currents. Both alloying elements and metal powders can be added to the granular flux to control the weld metal composition and increase the deposition rate, respectively. Using two or more electrodes in tandem further increases the deposition rate. Because of its high deposition rate, workpieces much thicker than that in GTAW and GMAW can be welded by SAW. However, the relatively large volumes of molten slag and metal pool often limit SAW to flat-position welding and circumferential welding (of pipes). The relatively high heat input can reduce the weld quality and increase distortions.

  Read More about Fusion Welding  <<<<< Click Here >>>>>

Comments

Post a Comment

Popular posts from this blog

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
Post a Comment
Read more

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
Post a Comment
Read more

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
Post a Comment
Read more