1. EFFECT OF ALTERNATE SUPPLY OF
SHIELDING GAS ON MECHANICAL AND
METALLURGICAL CHARCTERISTICS OF
CARBON STEEL GAS METAL ARC WELDING
Guided by
Presented by
Dr. V. Sivan
Sreejith T.S. Professor
212110019
Welding Engineering Dr. S. Natarajan
MME Department Professor
MME Department
NIT TRICHY
Dr. A. Raja
AGM
WRI, BHEL TRICHY

2. OVERVIEW
• Work plan
• Introduction
• 0bjective
• Mechanical properties of weld metal
1. Tensile test
2. impact test
• Result and discussion
• Reference
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4. Introduction
• Generally discrete alternate supply of shielding gas is a
new technology which alternately supplies the different
kinds of shielding gases in weld zone
• This technology is capable of achieving better quality and
high efficiency using the physical properties of welding
arc
• In GMAW, mixtures of two or more gases are often used
to shield the arc and the molten weld pool in order to
improve the fusion process and weld quality. These mixed
gases can be premixed at a filling plant and delivered in a
cylinder for use at a job site or two gases can be mixed at
the job site using a gas blender or mixer.
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5. • Shielding gas is very important in GMAW and therefore any
change in gas mix or flow parameters greatly affects the arc
transfer characteristics and resultant weld quality. The
shielding gas system thus greatly impacts productivity and
cost-effectiveness.
• The problem with the current shielding gas systems is mixed
cylinders are expensive and gas mixers are often inaccurate,
therefore more efficient, alternative shielding gas technologies
are of interest
schematic diagram of gas alternator
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6. • In the case of alternate supply of Argon and CO2 in
constant arc length, the welding current and the arc
voltage increases and decreases discretely.
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7. • Argon is supplied into welding arc, the welding current
decreases, and the arc voltage increases. Conversely CO2 is
supplied into welding arc, the welding current increases, and
the arc voltage decreases
• The periodic change of gas and arc pressure, increase the
fluidity of weld pool and reduce of surface tension of molten
metal to make grain of weld zone refine
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8. OBJECTIVE
• The purpose of this investigation is to study the effects of
alternate supply of shielding gas on mechanical and
metallurgical properties of carbon steel using gas metal arc
welding process.
• The investigation will determine if the pulsing of two pure
shielding gases create potential benefits relative to the use of
conventional gas mixtures.
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9. Work done so far
• Three arc weld metals were produced at nominal heat
input of 1.5 KJ / mm , using a SA 515 Grade 70 base
plate and 1.2 diameter wire, ER 70S-6
• For each welding, different kind of supply of shielding
gas is used, ie 100% CO2, mixture of Ar and CO2 ( 80%
Ar 20% CO2) and alternative shielding of argon and CO2
• Welding parameter used in the experiment were ; wire
feed rate of 10m/ min, welding voltage of 29 V, welding
speed of 240 mm / min and flow rate of gas 22L / min . In
case of alternative shielding gas, time period for supply
of each gas is 0.2 second.
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10. Work done so far
• For welding , a 150 mm x 250 mm plate of 20mm in
thickness as base metal and 45 degree in groove angle
and 12 mm in root gap as weld joint design is employed
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11. Work done so far
• Transverse sections were cut from each weldments and
their surfaces prepared for quantitative metallography
• Four rectangular charpy V notch specimen and one all
weld tensile specimen machined from weld metal.
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12. MECHANICAL TESTINGS
1. TENSILE TEST
Equipment used - UTE-60
Description of test item - carbon steel all weld tensile specimen
Size of specimen -180mm*Dia18mm and diameter of reduced section 12.5+/-0.25mm
ASTM A370 standard
UTS YS %
(MPa) (MPa) elongation
100% CO2 569 482 29
80% Ar&20%CO2 591 493 31
Alternate supply 597 495 31
of shielding gas
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13. 2. IMPACT TEST
Test Standard: AWS B4
Testing Temperature : 270C
Specimen Size: 10*10*55mm
toughness value
joule at 280 C
100% CO2 132, 136, 134
80% Ar&20%CO2 140,142,148
Alternate supply of 156,160,158
shielding gas
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14. Result and discussion
• The weld done with alternate shielding gas has more
toughness as compared to other two cases. This can be
explained on the basis of higher acicular ferrite percentage
in the weld metal.
• The presence of acicular ferrite will increase the
toughness of the material. Weld metal with high
proportion of acicular ferrite posses superior fracture
toughness because the randomly oriented short
interlocking ferrite plates along with it fine grain size
provide maximum resistance to crack propagation.
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15. Work to be done
• Chemical composition of weld metal APRIL 4-10
• Microscopic Analysis APRIL 10-15
• Quantitative analysis of the weld metal
microstructures APRIL 15-25
• Spectroscopy APRIL 25
• Microscopic study of inclusion and Volume
fraction of inclusion APRIL 25-30
• Thesis preparation MAY 1- 25
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16. Reference
• I.S. Kim, J.S. Son, H.J. Kim B.A. Chin( 2006) Development of a mathematical model to
study on variation of shielding gas in GTA welding. Journal of achievements in Materials
and manufacturing engineering
• S. Mukhopadhyay, T.K. Pal(2006), Effect of shielding gas mixture on gas metal arc
Welding of HSLA steel using solid and flux-cored wires, International Journal of
Advanced Manufacturing Technology, 29: 262–268
• Kang, B. Y,., Kang, M. J., Kim, H. J., & Kim, I. S. (2009) Characteristics of alternate
supply of shielding gases in aluminum GMA welding. Journal of Materials Processing
Technology, 209, pp. 4716-4721.
• S. Liu and D. L. Olson (1987) The Influence of Inclusion Chemical Composition on Weld
Metal Microstructure Journal . Mater. Eng. (1987) 9:237-251
• M. Ferrante, and R.A. Farrar, (1982) "The role of oxygen rich inclusions in
determining the microstructure of weld metal deposits," Journal of Materials Science, vol.
17,p. 3293.
• S. Liu and D.L. Olson. (1986) The Role of Inclusions in Controlling HSLA Steel Weld
Microstructures," Welding Journal, vol. 65(6); pp. 139-s-150-s.
• Sudarsanam Suresh Babu (2004) The mechanism of acicular ferrite in weld deposits
Current Opinion in Solid State and Materials Science 8 (2004) 267–278
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17. THANK YOU
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