TITLE:
WELDING WIRE AND FLUX FOR SUBMERGED ARC WELDING OF 600MPa GRADE
STEEL
FIELD OF INVENTION:
This invention relates to the method of submerged arc welding of 600 MPa grade steel
with a combination of welding wire and flux. Defect free weld deposited achieves matching
base metal strength, acceptable weld bend ductility and weld toughness of 47 Joules at
temperature of-20°C.
BACKGROUND OF THE INVENTION:
This invention related to the submerged arc welding of silicon - manganese carbon steel
of having high-strength and good ductility and is more particularly directed to a welding
electrode and a welding flux which combine during melting to produce a weld deposit
capable of obtaining matching strength and toughness of the base metal.
Drum component of power boiler has been fabricated from steel SA299 Grade A having a
ultimate tensile strength of 515-655 Mpa along with appropriate percentage elongation of
minimum 16 percent. Traditionally, the plates of above mentioned grade are welded by
submerged arc welding using the wire and neutral flux combination which achieves the
strength of 550-570 MPa. Industries were constantly seeking solutions to reduce the

thickness of plate by using higher strength grade plates in order to achieve the advantage
of weight consumption. In this situation, SA299 grade B having ultimate tensile strength of
550-690 Mpa was selected as suitable candidate to replace the grade A. And attempts to
weld the higher strength grade steel with traditional electrodes and fluxes have proven
unsuccessful due to the inadequate strength in weld deposit.
OBJECTS OF THE INVENTION:
An object of the present invention is to propose a method of submerged arc welding of
high strength silicon manganese carbon steel.
Another object of the present invention is to propose a method of submerged arc welding
which produces a weld deposit capable of obtaining matching strength and toughness of
the base metal.
A further object of the present invention is to provide a welding flux, as aforesaid, which
contains a specific amount of silicon and manganese in order to deoxidize weld metal.
A still further object of the present invention is to propose a wire having low silicon in the
order of 0.05 percent while the flux is arranged to have free silicon to provide weld deposit
containing about 0.48 percent silicon.

BRIEF DESCRIPTION OF THE INVENTION:
This invention relates to a method of submerged arc welding of high strength silicon
manganese carbon steel comprising:
subjecting the said steel to the step of welding with a combination of welding wire and flux
characterized in that the said welding wire has the following chemical composition:
0.08 percent carbon, 1.54 percent manganese, 0.05 percent silicon, 0.026 percent nickel,
0.026 percent chromium, 0.51 percent molybdenum, 0.002 percent vanadium, 0.042
percent copper, 0.02 percent aluminum, 0.006 percent phosphorus and 0.005 percent
sulfur
and the said flux is of basic aluminate type having 1.75 percent manganese and about
0.49 percent of silicon, obtaining a weld deposit having 0.05 percent carbon, 1.75 percent
manganese, 0.49 percent silicon, 0.028 percent nickel, 0.029 percent chromium, 0.49
percent molybdenum, 0.009 percent vanadium, 0.07 percent copper, 0.014 percent
aluminium, 0.017 percent phosphorus, 0.010 percent sulfur and the balance of iron.
DETAILED DESCRIPTION OF THE INVENTION:
This invention to provides an improved combination of welding electrode and flux for the
submerged arc welding of this higher strength grade steel and weld deposit on subjecting
to post weld heat treatment for stress relieving purpose to provide a room temperature
ultimate tensile strength matching with base metal strength of 590-602Mpa, ductility as
measured by a reduction in area of at least 25 percent, acceptable weld bend ductility
evaluated through side bend test with mandrel diameter of 4T (4 times thickness) and
Charpy V-notch impact resistance of at least 27 J at room temperature.

The welding wire electrode has the following elements in percentage by weight: 0.08
percent carbon, 1.54 percent manganese. 0.05 percent silicon, 0.026 percent nickel, 0.026
percent chromium, 0.51 percent molybdenum, 0.002 percent vanadium, 0.042 percent
copper, 0.02 percent aluminum, 0.006 percent phosphorus and 0.005 percent sulfur. The
welding flux shall be of basic aluminate type with composition tailored to have about 1.75
percent manganese and about 0.49 percent of silicon in the final weld deposit. During the
melting of the welding electrode wire, a portion of the carbon lost through oxidation to have
final content of about 0.05 percent in deposit.
Here, the major portion of the silicon and minor portion of Mn in deposit were obtained
from flux and also this Mn and Si in the flux serves to deoxidize the molten weld deposit so
that the residual silicon and Manganese enters weld deposit. This optimum level of Mn and
Silicon content of the weld deposit provides desirable mechanical properties. This
particular electrode flux combination is utilized in accordance with standard welding
practice, the composition of the resulting weld deposit will fall within the following range as
a percentage by weight: 0.05 percent carbon, 1.75 percent manganese, 0.49 percent
silicon, 0.028 percent nickel, 0.029 percent chromium, 0.49 percent molybdenum, 0.009
percent vanadium, 0.07 percent copper, 0.014 percent aluminium, 0.017 percent
phosphorus, 0.010 percent sulfur and the balance of iron. When properly heat treated,
such alloy provides an optimum combination of Ultimate tensile strength (UTS) in weld
transverse direction of 609 MPa, weld toughness of 47 Joules, heat affected zone
toughness of 94 Joules at temperature of -20oC and weld hardness of 191 Hv were
achieved along with acceptable weld bend ductility.

The drum is one of the important pressure vessel component used in boiler and this critical
product was fabricated from high thickness high strength steel plates. The material is of
typical Silicon - Manganese carbon steel and has 0.23% C, 1.4% Mn, 0.33% Si, 0.36% Ni,
0.11% Cr and 0.017% Nb. The typical yield strength (YS) and ultimate tensile strength
UTS of this plate is about 390 MPa and 600 Mpa against specified YS of 310 Mpa
(minimum) and UTS of 550-690 MPa respectively. These plates having thickness in the
range of 150-170 mm are hot formed to appropriate C shape and then are further welded
to the finished product. Submerged arc welding (SAW) was generally preferred for welding
the longitudinal and circumferential seam of weld joint due to the advantage of less cost
and time consumption. To find right combination of welding flux and wire to make defect
free weld deposit and to meet all requirement with respect to mechanical properties is a
big challege. Commercial low alloy welding electrode wire of high strength generally
contains at least 0.20 percent silicon in order to provide adequate deoxidation of the
resulting weld deposit. As a result, the percentage of silicon left by the wire as well as by
the flux is usually of sufficient magnitude to adversely effect the strength and ductility of the
weld deposit Hence in this invention, composition of the electrode wire is specifically
designed with very low Si content in the order of 0.05 percent. The additional quantity
required for the deoxidation of the mqiten wire is supplied by the silicon content of the flux.
The typical welding wire used for welding of high strength low alloy steels is of general
classification type as agreed between supplier and purchaser, chemical composition and
other requirements are not specified for this particular classification according to the
designation of the wire EG under the standard AWS A5.23 published by the American
Welding Society. Table 1 lists the nominal chemical composition of welding wire used. The

method of manufacture of this type of flux can be categorised as agglomerated flux.
Aggomerated basic fluxes have been widely accepted in this application to produce
smooth low defect welds without undercuts and other defects in the weld metal along the
weld joint. Flux used belongs to class 1 type, which are used for SAW welding of non-alloy
and fine grained steel and high strength steel, creep resisting steel and atmospheric
corrosion resisting steels. The chemical ingredients of flux is of aluminate basic AB type
and consists of Al203, CaO, MgO, Si02, CaF2 and other basic oxides. Total of weight
percentage of AI2O3, CaO & MgO are combinedly more than 40 wt.%. Weight percentage
of AI2O3 is above 20% and CaF2 is less than 22%. Due to high AI2O3 content, liquid slag is
fast freezing nature. Flux used is of the type active flux with respect to the chemical
reaction with welding wire, and contains considerable amount of deoxidisers such as
silicon (Si) and Manganese (Mn). Beacause of the presence of Si and Mn, there will be a
pick up of 0.1-0.3 fraction of Si and 0,3 - 0,5 fraction of Mn in the weld metal chemical
composition. Also welding parameters are to be tightly controlled to ensures the properly
balanced chemical composition. The welding current of 575 Amps, voltage of 30 V and
travel speed of 420 mm/min with calculated heat input of 2.5 kJ/mm were employed for
welding using electrode of 4 mm size. The particle size of flux comes under the size
category of 2-16 with grain size of 0.2 to 1.6mm. The basicity index of flux is 1.4. Basicity
index calculated according to the International Institute of Welding formula as given in
equation (1).


Table 2 contains the composition of the weld deposit produced with the electrode wire and
flux. It should be noted that the chemistry of weld metal are dependent upon the proper
selection of operating parameters such as current, voltage, travel speed and etc.
Accompanying Fig 1 shows the schematic of macro section of deposited butt joint made
using this particular wire and flux.


Table 2
Elements Chemical composition
ofWeld
~C 0.050
"Si 0.489
Ivln 1.748
"P 0.017
~S ~ 0.010
"Cr 0.029
~Mo 0.486
~Ni O028
~V 0.009
~A1 0.014
~CM 0.070
ll 0.002
"Nb " oTobl
"B o!ool

WE CLAIM:
1. A method of submerged arc welding of high strength silicon manganese carbon steel
comprising:
subjecting the said steel to the step of welding with a combination of welding wire and flux
characterized in that the said welding wire has the following chemical composition
0.08 percent carbon, 1.54 percent manganese, 0.05 percent silicon, 0.026 percent nickel,
0.026 percent chromium, 0.51 percent molybdenum, 0.002 percent vanadium, 0.042
percent copper, 0.02 percent aluminum, 0.006 percent phosphorus and 0.005 percent
sulfur
and the said flux is of basic aluminate type having 1.75 percent manganese and about
0.49 percent of silicon, obtaining a weld deposit having 0.05 percent carbon, 1.75 percent
manganese, 0.49 percent silicon, 0.028 percent nickel, 0.029 percent chromium, 0.49
percent molybdenum, 0.009 percent vanadium, 0.07 percent copper, 0.014 percent
aluminium, 0.017 percent phosphorus, 0.010 percent sulfur and the balance of iron.
2. The method as claimed in claim 1, wherein the said weld deposit has ultimate tensile
strength in (UTS) in weld transverse direction of 609 MPa, weld toughness of 47 Joules,
heat affected zone toughness of 94 Joules at temperature of -20°C and weld hardness of
191 Hv were achieved.