comparision of essc with sasc

1. COMPARISION BETWEEN
ELECTROSLAG STRIP CLADDING &
SUBMERGED ARC STRIP CLADDING
NAME : PAREKH JAYESH M
Branch : M.E-I (WELDING)
SUBJECT : WELDING PROCESS & POWER
CONTROLS
ROLL NO. : 388

2. Introduction
All hydro processing reactors need to be internally protected
from high-temperature corrosion effects or hydrogen attack.
The overlay welding in heavy-wall pressure vessels is
commonly carried out using strip electrodes and the two most
productive systems for surfacing large components are
submerged arc strip cladding (SASC) and electro slag strip
cladding (ESSC).
Both SASC and ESSC are characterized by a high deposition
rate and low dilution, as well as a high deposit quality.
As a rule of thumb, electro slag strip surfacing decreases
dilution by up to 50% in contrast with submerged arc strip
surfacing for the same heat input with a significantly higher
deposition rate.

3. Fig. Diagram For Submerge Arc Strip
Cladding

4. Cladding
Cladding is the bonding together of dissimilar metals. In many
cases, corrosion resistance is required only on the surface of
the material and carbon or alloy steel can be clad with a more
corrosion resistant alloy.
Compared to carbon and alloy steels, all corrosion resistant
alloys are expensive. Cladding can save up to 80% of the
cost of using solid alloy.
Cladding of carbon or low alloy steel can be accomplished in
several ways including roll bonding, explosive bonding, weld
overlaying and wallpapering.
Clad materials are widely used in the chemical process,
offshore oil production, oil refining and electric power
generation industries. The use of clad steel is not new.
Corrosion resistant alloy clad steel has been available for
over 40 years

5. Weld overlaying technique of cladding is commonly used to
clad the surfaces of fabricated steel structures. The actual
weld overlay process used depends on many factors
including access, welding position, the alloy applied, and
economics.
Applications of Strip Cladding:
1) The process is usually confined to relatively large and thick
components which need to be manipulated to enable
welding to be carried out in the flat position.
2) The technique finds its widest application in the oil, gas and
fertilizer related industries and in the nuclear power
generation field.
3) Generally used for surfacing the internal surfaces of
pressure vessels and large diameter pipe and in the
reclamation of steel mill rolls.

6. Submerged arc Strip Cladding (SASC)
 This well-known SAW method has been widely used with
strip electrodes since the mid-1960s.
 There is no fundamental difference between submerged arc
welding and cladding.
 The welding wire is merely replaced with the cladding strip.
The equipment is the same, except the head must be
adapted to guide the strip. The principle is the same.
 The energy to melt the strip and the base metal is supplied
by the electric arc struck between them. On melting, the
agglomerated flux protect the liquid metal and where
applicable enriches it with alloying elements.
 In the SAW process the strip is feed down through the
contact jaws at the same time as the flux is feed down on
both sides of the strip.

7.  The strip generates an arc between itself and the base
material, the arc is not uniform and static, it wanders along
the width of the strip but is all time sub merged under the
molten slag.
 It uses a strip, normally with a thickness of 0.5 mm and the
width normally varies from 30 to 120 mm, but other widths
are
available for special applications.

8. Electro Slag Strip Cladding (ESSC)
 The electro slag welding process was patented in USA in
February 1940 and is a process that can weld material
thicknesses from 25 up to 300 mm. It works in the vertical or
very close to vertical position.
 It is in use for hull welding of ships; it is used for welding
heavy wall thickness vessels of different kinds and many
more applications.
 In the early 70’s the electro slag concept was adjusted to fit
the cladding process with a metal strip.
 Technological developments have driven temperatures and
pressures used in the petroleum, chemical, pulp, and paper,
and environmental protection industries, and increased the
likelihood of serve corrosion and wear in the process
pressure vessels.

9.  The electro slag welding (ESSC) process is suitable for
applying weld deposits over large surface areas using strip
electrodes .
Fig. Schematic diagram of the ESSC
process

10. COMPARISION BETWEEN ESSC & SASC
1) The penetration achieved with ESSC is less than that with
for SASC because the molten slag pool is used to melt the
strip and some of the parent material.
2) ESSC uses higher welding currents than SASC so the
welding heads used are more heavy duty.
3) In ESSC Increased deposition rate of 60% to 80% than
SASC.
4) Only half of the dilution (10%–15%) from the base material
due to less penetration in ESSC.
5) Lower arc voltage (24–26 V) in ESSC.
6) Higher amperage and current density (About 1000–1250 A
with strips of 60mm width, corresponding to 33–42 A/mm²).
Specially developed fluxes for high productivity purposes
can be welded with amperage in excess of 2000A which
corresponds to a current density about 70 A/mm2.

11. 7) Increased welding speed (50%–200%), resulting in a
higher
area coverage
8) Lower flux consumption (about 0.5 kg/kg strip).
9) The solidification rate of the ESSC weld metal is lower,
aids
de-gassing and increases resistance to porosity. Oxides
can
rise easier out of the molten pool to the surface; resulting
in a metallurgical cleaner weld metal which is less
sensitive to hot cracking and corrosion.

12. SR.
NO.
PARAMETER SASC ESSC
1 Strip (mm) 60x0.5 60x0.5
2 Welding current (A) 750 1250
3 Voltage (V) 26 24
4 Travel speed (cm/min) 10 18
5 Current density (A/mm²) 25 42
6 Arc yes no
7 Heat input (kJ/mm) 11.7 11.25
8 Bead height (mm) 4.5 4.5
9 Bead width (mm) 65 68
10 Dilution (%) 18 9
11 Deposition rate (kg/hr) 14 22
12 Flux composition (kg/kg
strip)
0.8 0.6
13 Number of layers 2 1
Typical comparison between ESSC & SASC

13. References
1)Y. K. Oh, J. H. Devletian and S. J. Chen, Welding
Journal, 69 (1990)
2)Technical handbook, ESAB
3)Consumable handbook, Vostelpine Bohler
4)B. E. Paton 1997. Electro slag Welding,2nd edition
5)YU. M. KUSOV 2001. A New Approach to Electro
slag Welding-Welding journal

14. Thank You….