FIELD OF INVENTION
The invention relates to a process development for making hardfacing of
different combination of filler wires using twin submerged arc welding
applications. More particularly, the invention relates to an improved method of
hardfacing of martenstic stainless steel adapting submerged welding technique.
BACKGROUND OF THE INVENTION
Hard facing is widely used for deposition of weld metal for corrosion resistance
and wear control applications in steel mills, chemical, nuclear and thermal power
plant equipment. This is normally carried out using single wire conventional
submerged arc welding process. In present practice, the submerged arc welding
wire (E430) 15-18 Cr of diameter 2.4 mm is used for depositing a buffer layer
after machining the final layer, the final layer being made with submerged arc
welding wire of (E410) 11-13.5 Cr of diameter 2.4 mm along with agglomerated
flux having hard faced in to the valve seat ring and valve wedges. This current
practice is a time consuming process being compressed of the steps of making
buffer layer, machining and forming the final layer to attain the required
chemistry and hardness.
US patent 4,572,936 discloses a submerged arc multiple wire welding system, in
which only one or two of the welding wires used are over or microalloyed wires.
The other wires are commercially available unalloyed or low-alloyed solid wires.
The process produces a weld metal which has unexpectedly high toughness
values, and can be performed more economically. This multiple wire welding
system is used in single or multiple-pass welding operations.

This process comprises a multiple wire system. That means they are feeding the
wires separately using different power sources and different wire feeders as
mentioned in the examples 1 to 4 of US patent. 'The first wire was connected to
810A at 30 V. the second wire was connected at 790 A at 33 V. The third wire
was connected to 680 A at 34 V. However, this process is also time consuming
and call for costly equipment.
OBJECTS OF THE INVENTION
It is therefore, an object of the present invention to propose an improved
method of hardfacing of martenstic stainless steel in valve wedges and seat rings
using a twin wire submerged arc welding.
Another object of the present invention is to propose an improved method of
hardfacing of martenstic stainless steel in which fillers of dissimilar compositions
can be used by adapting a twin wire submerged arc welding process, resulting in
reduced consumption of consumables.
Another object of the invention is to propose an improved method of hardfacing
of martenstic stainless steel in which dissimilar fillers are used by adapting a twin
wire technique which create a common weld pool to attain required composition
according to the code of highest quality welds, thereby achieving economy.
SUMMARY OF THE INVENTION
Thus the invention is directed to a further development that the dissimilar wire
combination is fed using a single wire feeder with a single nozzle drawing power
from a single power source with parameters of 425 A, 28 V and 0.5 m/min as
welding speed. A single weld pool is created in which the required weld

chemistry are achieved by the use of two wires of different composition. This
results in savings in consumables, cost and time.
Accordingly to the present invention, the submerged arc welding wires ER430 of
diameter 2.4 mm is used to deposit as buffer layer over the deposit finally
hardfacing is carried out using the wire ER410 of diameter 2.4 mm with
agglomerated flux in valve seat ring and valve wedges. Hardfacing is carried out
using two stainless steel electrodes such as ER430 & ER410 simultaneously fed
in twin wire torch in twin wire technique of submerged arc welding process. This
leads to less cycle time, lower consumables consumption while achieving the
required mechanical and chemical requirement of the deposit.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Fig. 1 is a prospective view of a twin-wire feeding device adaptable to Twin wire
submerged arc welding technique for hardfacing which achieves the method for
hardfacing martenstic stainless steel according to an invention.
DETAILED DESCRIPTION OF A PREFFERED EMBODIMENT OF THE
INVENTION
A twin wire feeding device can be fitted to conventional submerged arc welding
machine. By this technique same/different composition (1) of filler materials weld
metal combination can be done effectively. The construction of the twin wire
feeding device (2) is shown in fig. 1. The dissimilar wire combination is fed using
a single wire feeder with single nozzle drawings power from a single power
source (6) with parameters of 425 A, 28 V and 0.5 m/min as

welding speed. Thus, a single weld pool is created in which the required weld
chemistry are obtained by the use of two wires of different composition. In this
technique, to attain the required hardness properties as well as the required
microstructure of the weld metal, an improved technique of twin wire submerged
arc welding is adapted in which a common arc pool (4) is created. In the arc
cavity, the hardfacing fillers with different chemical composition of different alloy
wires are fed simultaneously in a single torch as shown in Fig. 1 i.e., one after
another which creates the common weld pool to give the desired weld
properties.
This new method enables welding/surfacing to be carried out in grooves having a
width of different sizes. The new twin wire technique can be used
surfacing/hardfacing of valves wedges and seat rings (3) of different sizes. This
technique can be used for both manual as well as mechanized mode. This results
in savings in consumables cost and time.

WE CLAIM
1. An improved method of hardfacing of martenstic stainless steel in valve wedges and
seat rings (3) carried out by a twin wire submerged arc welding technique, the said
method comprising;
creating a common arc pool (4);
feeding simultaneously the hardening fillers with different chemical composition (1)
of different alloy wires in a single torch one after another of a twin wire feeding
device (2) to create the common weld pool to give desired weld properties, wherein
the power is drawn from a single power source (6).
2. An improved method as claimed in claim 1, wherein the dissimilar wire combination
is fed through a single wire feeder with single nozzle.

ABSTRACT

AN IMPROVED METHOD FOR HARDFACING MARTENSTIC STAINLESS STEEL
CARRIED OUT BY SUBMERGED ARC WELDING (SAW) TECHNIQUE

An improved method of hardfacing of martenstic stainless steel in valve wedges and seat
rings (3) carried out by a twin wire submerged arc welding technique consists of creating
a common arc pool (4), feeding simultaneously the hardening fillers with different
chemical composition (1) of different alloy wires in a single torch one after another of a
twin wire feeding device (2) to create the common weld post to give desired weld
properties, wherein the power is drawn from a single power source (6).