AMRITA SCHOOL OF ENGINEERING,
SANDEEP NAIR (CB.EN.P2MFG15018)
M.TECH (MANUFACTURING )
ELECTROSLAG MELTING AND
This process was developed originally in the erstwhile
USSR in 1930.
Electro-slag melting is also known as Electro-flux melting is
a process of melting and refining steel and super alloys for
mission critical application.
It principle is based on the electro-slag welding process.
It dispenses completely with the rising and gating system
and also with the need for separate melting unit ,pouring
ladle and transportation arrangements.
Graphite and ceramic mould has been used in place of
Consumable steel electrodes are used.
WORKING OF ESM FURNACE
The electro-slag melting process is used to melt and refine
steels and various super-alloys, resulting in high quality
Electric current (generally AC) is passed between the
electrode and new ingots ,which is formed in the bottom
of a water-cooled copper mold.
The new ingot is covered in a engineering slag that is
superheated by the electric current.
These metal droplets travels through the slag to the
bottom of the water cooled mold and slowly freeze as the
ingot is directionally solidified upwards from the bottom
Solidification takes place without any contact with the
The slag pool floats above the refined alloys, continuously
floating upward as the alloy solidifies.
The molten metal is cleaned of impurities that chemically
react with slag or otherwise float to the top of the molten
pool as the molten droplets pass through the slag's.
Electro-slag melting uses highly reactive slags to reduce
the amount of sulfide present in bio-metal alloys.
ESM furnaces can be designed for melting of round,
square and rectangular (slab) ingots.
WORKING OF ESM FURNACE
SLAG USED AND ITS PROPERTIES
Slag for electro-slag melting are usually based on calcium
fluoride (caf2), lime (Cao) and alumina (al2o3). magnesia
(mgo), titania (tio2) and silica (sio2) may also be added,
depending on the alloy to be melted.
To perform its intended functions, the slag must have some
well-defined properties, such as:-
1). Its melting point must be lower than that of the metal to be
2). It must be electrically efficient.
3). Its composition should be selected to ensure the desired
4). It must have suitable viscosity at melting temperature.
ESM PROCESS INVOLVES FEWER STEPS THAN SAND CASTING
No removal of hydrogen and nitrogen.
Minimum sulphur content due to slag reaction.
Smooth surface due to slag skin on surface.
Less material defect due to melting of dendrite
Electrode can be used in cast condition due to
cleaning by slag.
Melt rate choose to slag skin equal to dendrite arm
No manganese losses in alloys.
Ingot weights from 100 kg to 165 metric tons.
Alternating current as re-melting energy with melting currents
from 3 ka to 92 ka.
Ingot diameters from 170 mm to 2,300 mm, depending on
material being melted.
Circular, square and rectangular ingot shapes are possible.
Surface electrode preparation normally not ground.
Melting effect on gas content - constant nitrogen and
No modification ; maximal homogeneity.
Casting yield is almost 100%.
NEW DEVELOPMENT IN ESM PROCESS
Electro-slag melting under Vacuum (VAC-ESM):
Melting is carried out under
vacuum as in VAR, however, using
a slag. Problems of oxidation of the
melt do not arise. In addition,
dissolved gases such as hydrogen
and nitrogen, can be removed .
The danger of white spots, as
encountered during VAR, is
reduced to a minimum. That is of
interest for super-alloys or titanium
Low gas content in final material
,then VAR process is chosen.
This is a great step forward in freeing the ESM
process from hydrogen pick-up problem and the
influence of seasonal atmospheric changes. In
addition it allows melting under oxygen-free inert
The following results have been obtained:-
Oxidation of electrode and slag is completely
Oxidizing loss of elements such as Ti, Zr, Al, Si,
etc. is almost completely avoided.
This is especially important when melting high Al
and Ti-containing alloys, like super- alloys with very
narrow analytical ranges:-
1). Better cleanliness in the ingot is achieved.
2). When using argon as the inert gas, pick-up of
nitrogen and hydrogen is avoided.
Due to the absence of oxygen in the furnace
atmosphere, desulfurization via the gas phase is no
1) Uniform mechanical properties in the longitudinal and
2) Very large ingots such as 3000mm diameter and more than
200ton weight can be produced.
3) Homogeneous, sound and directionally solidified structure.
4) High degree of cleanliness.
5) Free of internal flaws (e.g. hydrogen flakes).
6) Free of macro-segregation.
7) Smooth ingot surface resulting in a high ingot yield.
1) Slag treatment to achieve lowest hydrogen in
2) Closed melting to avoid hydrogen pick-up from
3) Melt rate adjusted according to slag system, alloy
composition and furnace size.
4) Gases (like nitrogen & hydrogen) need to be
adjusted to lowest level in the electrode.
5) Adjustment of slag chemistry and composition of
1. Plug lid
2. Cardboard lid
3. Primer lid
4. Axis of firing pin
6. Firing pin
7. Leather circlet
8. Screw thread
9. Body of plug
New Technology of Electro slag Casting of Solid Horn-
Shaped CoresE.N. Eremin,Omsk State Technical
University, Omsk, Russia.
Materials Research and Engineering Edited by B.
Ilschner and N.J. Grant.
Commercialization effort in support of electroslac-
casting technology ,V. K. Sikka.
Principle of foundary technology, P.L. Jain