The electroslag welding (esw) process, the metal coalescence produced by molten slag. When the molten slag is melt the thick work piece and filler materials. Thus the molten metal pool is shielded by molten slag.
In this process consist of two cooled copper shoes and it’s clamped along with side of thick work piece. The electric arc is generated between the electrode and block at bottom of vertical joint position. The welding flux is added in between shoes.
Oxides of silicon, calcium, fluorspar, manganese are commonly used in welding flux. This is melted by the arc and to generate form of molten slag with some sufficient thickness. Now, the current is passed through molten metal from electrode to the work piece. In this molten slog can be pass high resistance electric current that high resistance made more heat, which heat is used to melt the work piece and electrode. The wire electrode is supplied to metal pool.
The molten metal temperature range is approximately 1850⁰c.The heat is fuse the edge of the electrode and thick work piece. The liquid form of molten metal (come from electrode) is covered to the solidification process start from bottom to upward, along the solidification process the shoes move for upward direction.
In this process the arc voltage under 25- 30 V. The constant potential power source with 750 to 1000 amps and open circuit voltage may be as 60 V. The electrode form of solid form or flux _cored, fed the electrode rate of 20 to 150 mm per second. Which process, the voltage is increased at same time increased the depth of fusion and width of weld. The welding current increase together also the deposition rate and depth of molten weld pool will increased, the high current result become in high deposits and which will be crack prone.
Advantages of electroslag welding:
- Thicker plate will be welded in this process.
- It is suitable temperature gradient in direction of weld flow.
- The molten slag shield in liquid form, so reduce the oxidation of metals.
- In this weld the clean weld is formed, so no cleaning required for after welding.
- Which process having continuous addition of slag not required
- Defects such as porosity, undercut, notches, and slag inclusions are not encountered.
- No edge preparation.
- High production.
The horizontal welding of very long plates up to 450 mm or more, require special equipment in large machinery and the nuclear reactor vessels.