09-11-2012, 04:23 PM
A REVIEW ON EFFECT OF ARC WELDING PARAMETERS ON MECHANICAL BEHAVIOUR OF FERROUS METALS/ALLOYS
A REVIEW ON EFFECT OF ARC.pdf (Size: 470.46 KB / Downloads: 74)
ABSTRACT:
In any fabrication industry Submerged Arc Welding (SAW) is used as a heavy metal deposition rate welding
process. The process is characterized by the use of granular flux blanket that covers the molten weld pool during
operation. Protection through atmospheric contamination of the weld bead and slower cooling rate, achieved by this
arrangement can enhance mechanical properties of the weldment. Selection of process parameters has great
influence on the quality of a welded connection. Welding input parameters play a very significant role in
determining the quality of a weld joint. The joint quality can be defined in terms of properties such as weld-bead
geometry, mechanical properties, and distortion. Generally, all welding processes are used with the aim of obtaining
a welded joint with the desired weld-bead parameters, excellent mechanical properties with minimum distortion.
This paper presents the exhaustive research review on effect of arc welding parameter on quality of welds.
INTRODUCTION:
The advantages of welding, as a joining process, include high joint efficiency, simple set up, flexibility and low
fabrication costs [16]. Because of its high reliability, deep penetration, smooth finish and high productivity,
submerged arc welding (SAW) has become a natural choice in industries for fabrication. As it is well known, the
residual stresses have a strong influence on weld deformation, fatigue strength, fracture toughness and buckling
strength [5, 15, 16]. Submerged arc welding (SAW) is widely recognized as a very productive welding process
which over the years has developed from the single wire approach to more productive variants such as twin wire,
tandem and metal powder addition[1,2]. Welding with cored wires continues the drive for increased productivity
with the SAW process [21].
FFECT OF PROCESS PARAMETERS ON MECHANICAL PROPERTIES
The independent controllable process parameters affecting mechanical properties are voltage, current, stick out, wire
feed rate, welding speed or travel, etc [30]. Fig 2(a-d) (Ref.30), shows direct effect of electrode stick out on
hardness, yield strength, Impact strength and UTS of the weldment. It is clear from the figures that, with increase in
electrode stick out, hardness of the weldment increases, yield strength and impact value decreases, ultimate tensile
strength of the joint initially decreases but thereafter increases provided welding current and voltage are kept at
constant levels.
REVIEW OF THE QUALITY OF WELD:
EFFECT OF BEAD GEOMETRY ON THE QUALITY OF WELD:
L.J. Yang, R.S. Chandel and M.J. Bibby [6] while investigating the effects of process variables on the bead width of
submerged-arc weld deposits concluded that bead width is affected by the electrode polarity, electrode diameter,
electrode extension, welding current, welding voltage and welding speed. A positive electrode polarity, a large
electrode diameter, a small electrode extension and a high welding voltage encourages a large bead width in most
cases. The bead width is not affected significantly by the power source, constant voltage or constant current, when
an acidic fused flux is used. However, when a basic fused flux is used, constant-current operation gives somewhat
larger bead widths.
N. Murugan, R.S. Parmar and S.K. Sud[12],while discussing the effect of submerged arc process variables on
dilution and bead geometry in single wire surfacing said that the control parameters are required to be fed to the
system according to some mathematical formulation to achieve the desired end results. The responses, namely,
penetration, reinforcement, width and dilution as affected by open-circuit voltage, wire feed-rate, welding speed and
nozzle-to-plate distance, have been investigated.
EFFECT OF PROCESS PARAMETERS ON THE QUALITY OF WELD:
P. Yongyutph ,K. Ghoshp, C. Guptaa, K. Patwardha and Satya Prakash [5] while studying the Influence of
Macro/Microstructure on the Toughness of'All Weld Multipass Submerged Arc Welded C-Mn steel deposits
concluded that Welding parameters have no effect on the chemical composition, the overall hardness and
microstructure in the as-welded condition. Impact toughness decreased with the increase in welding current.
N.D. Pandey, A. Bharti and S.R. Gupta [7], while studying the effect of submerged arc welding parameters and
fluxes on element transfer behavior and weld-metal chemistry concluded that welding current and voltage have an
appreciable influence on element transfer, as well as on weld composition. Weldments properties such as strength,
toughness and solidification cracking behaviour are affected by chemical composition.
Juha Lukkari, OY, Helsinki, Shaun Studholme, Waltham Cross[21] while discussing the Submerged arc welding
with cored wires summarized that deposition rates with cored wires at the same welding current are between 20 and
30% higher than with the equivalent diameter solid wire.
DISCUSSION:
It is understood that several process control parameters in SAW influence bead geometry, microstructure as well as
weld chemistry. Their combined effect is reflected on the mechanical properties of the weld in terms of weld quality
as well as joint performance. The study of the various works, review that, the selection of the suitable process
parameters are the primary means by which acceptable heat affected zone properties, optimized bead geometry and
minimum residual stresses are created. Some researchers realized that the mechanical properties of weld are
influenced by the composition of the base metal and to a large extent by the weld bead geometry and shape
relationship as well. Some of the researchers observed that with increase in electrode stick out, hardness of the
weldment increases, yield strength and impact value decreases, ultimate tensile strength of the joint initially
decreases but thereafter increases provided welding current and voltage are kept at constant levels. While discussing
the submerged arc welding with cored wires few researchers summarized that deposition rates with cored wires at
the same welding current are between 20 and 30% higher than with the equivalent diameter solid wire. Some
researchers studied the function of flux ingredients such as CaO, MgO, CaF2 and Al2O3 in submerged arc welding
and concluded that among the flux ingredients, MgO appears to be important on its own in influencing the
mechanical properties.