effect of alternate shielding gas on gmaw.ppt

EFFECT OF ALTERNATE SUPPLY OF SHIELDING GAS ON MECHANICAL AND

METALLURGICAL CHARCTERISTICS OF CARBON STEEL GAS METAL ARC WELDING

Presented by

Sreejith T.S.212110019Welding EngineeringMME Department

OVERVIEW

• Work plan

• Introduction

• 0bjective

• Mechanical properties of weld metal

1. Tensile test

2. impact test

• Result and discussion • Reference

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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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• 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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• 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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• 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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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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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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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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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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MECHANICAL TESTINGS

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

1. TENSILE TEST

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UTS (MPa)

YS (MPa)

% elongation

100% CO2 569 482 29

80% Ar&20%CO2 591 493 31

Alternate supply of shielding gas

597 495 31

2. IMPACT TEST

Test Standard: AWS B4

Testing Temperature : 270C

Specimen Size: 10*10*55mm

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toughness value joule at 280 C

100% CO2 132, 136, 134

80% Ar&20%CO2 140,142,148

Alternate supply of shielding gas

156,160,158

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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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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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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THANK YOU

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