Skip to main content

Shielded metal arc welding (SMAW)

SMAW

The Process:-

Shielded metal arc welding (SMAW) is a process that melts and joins metals by heating them with an arc established between a sticklike covered electrode and the metals, as shown in Figure below. It is often called stick welding. The electrode holder is connected through a welding cable to one terminal of the power source and the workpiece is connected through a second cable to the other terminal of the power source (Figure a). The core of the covered electrode, the core wire, conducts the electric current to the arc and provides filler metal for the joint. For electrical contact, the top 1.5 cm of the core wire is bare and held by the electrode holder. The electrode holder is essentially a metal clamp with an electrically insulated outside shell for the welder to hold safely. The heat of the arc causes both the core wire and the flux covering at the electrode tip to melt off as droplets (Figure b). The molten metal collects in the weld pool and solidifies into the weld metal. The lighter molten flux, on the other hand, floats on the pool surface and solidifies into a slag layer at the top of the weld metal.
 
FUSION WELDING
SMAW
In short:- 
  •       An electric Arc struck between electrode and base metal joint
  •       Base metal melts under arc
  •       Electrode tip melts in drops and transfers to molten pool of base metal
  •       Electrode with Arc moves along the joint keeping constant arc length
  •       On cooling pool solidifies

Advantages and Disadvantages of SMAW:-

       The welding equipment is relatively simple, portable, and inexpensive as compared to other arc welding processes. For this reason, SMAW is often used for maintenance, repair, and field construction. However, the gas shield in SMAW is not clean enough for reactive metals such as aluminium and titanium. The deposition rate is limited by the fact that the electrode covering tends to overheat and fall off when excessively high welding currents are used. The limited length of the electrode (about 35 cm) requires electrode changing, and this further reduces the overall production rate.

Advantages:-
  •          Versatile
  •          Welding in all positions
  •          Areas of restricted access
  •          Wide variety of materials can be welded
  •          Material thickness above 3 mm
  •          Equipment: simple and light

Limitations:-
  •          Low productivity
  •          Automation not possible
  •          Dependent on welder skill
  •          Non-availability of Consumables for exotic material
  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