WELCOME

ABSTRACTThe present work aims to evaluate the effect of GAS

TUNGSTUN ARC WELDING process parameters on the quality of the weld bead.

Process parameters : Wire Diameter, Welding Current, Wire Feed Speed, Ratio of wire feed rate to travel speed & Plate Thickness.

The quality of the weld bead can be assessed by the bead characteristics such as Penetration, Reinforcement and Bead width. Experiments were conducted to study the effects of the WELDING process parameters using automatic GTAW machine and the results are tabulated and plotted. Also mathematical models are developed.

INTRODUCTON The GTAW (Gas Tungsten Arc welding) process

is easily found in any industry whose products

requires metal joining in a large scale.

The quality of the welded material can be

evaluated by many characteristics, such as bead

geometric parameters (penetration, width and

height) and deposition efficiency (ratio of weight

of metal deposited to the weight of electrode

consumed).

GTAW System setup

Advantage of the GTAW Process

• Weld more kinds of metals and metal alloy.

– Stainless steel, nickel alloys, titanium, aluminum,

copper, brass

• Also can weld dissimilar metals to each other.

– Copper to brass

– Stainless steel to mild steel.

Other Advantages

• Concentrated Arc– Pin point control of heat input to the work piece.– Narrow heat affected zone– This is where the base metal has undergone a

change due to the superheating of the arc and fast cooling rate.

• No Slag• No Sparks, Spatter or Noise• No Smoke or Fumes

GTAW Disadvantages

• Low filler metal deposition rate.

• Arc Rays are brighter than normal welding.

• Need additional care to protect skin with

proper clothes and welding lens.

STATISTICAL DESIGN OF EXPERIMENTS AND TAGUCHI

METHOD

INTRODUCTION

Statistical designed experiments with 5 process

parameters (each at 3 levels) are conducted to study the effect

of these parameters on bead geometry. It is found from the

analysis of variance (ANOVA).

The phases in design of experiments

Importance of Taguchi Method

• Taguchi’s approach complements these two important areas.

1. Clearly defines a set of general design for factorial experiments that cover many applications.

2. Devised a standard method for analysis of the results.

EXPERIMENTAL PROCEDURE

• The aim of this project is to find the optimum

welding process parameters like welding

current, wire feed speed, welding speed, wire

diameter and plate thickness in a GTA welding

process.

Automatic GTAW Machine

Control Parameters & Its Levels

PARAMETERS UNITS NOTATIONFACTOR LEVELS

1 2 3

Current (X1) A I 140 160 180

Wire diameter (X2) mm D 1.2 1.4 1.6

Wire feed rate (X3) mm/min WFR 1500 2000 2500

Ratio of wire feed rate to

travel speed (X4)- WFR/TS 6 8 10

Pipe thickness (X5) mm PT 8 12 16

Experimental Number

Current (A)

Wire Diameter (mm)

Wire Feed Rate (mm/min)

Ratio of wire feed rate to travel speed

Plate Thickness (mm)

E01 1 1 1 1 1

E02 1 2 2 2 2

E03 1 3 3 3 3

E04 2 1 1 2 2

E05 2 2 2 3 3

E06 2 3 3 1 1

E07 3 1 2 1 3

E08 3 2 3 2 1

E09 3 3 1 3 2

E10 1 1 3 3 2

E11 1 2 2 2 3

E12 1 3 1 1 1

E13 2 1 2 3 1

E14 2 2 3 1 2

E15 2 3 1 2 3

E16 3 1 3 2 3

E17 3 2 2 3 1

E18 3 3 1 1 2

Bead Geometry

To Calculate Bead parametersFiller metal being deposited using GTAW

machine and bead geometry was found by using microscopic examination.

1.Grinding & polishing2.Etching- Reagent (Picric acid)

NEOPHOT 2 Microscope is used for

Microscopic examination.

NEOPHOT 2 Microscope

Heat Input

J =

Where J is heat input in kj/mm V is welding voltage in volts I is Welding current in amps GTS is Gun travel speed in mm/min η is Arc Efficiency for GTAW (0.6)

Wire Deposition Efficiency %

=

Where V1 =

V2 =

RESULTS & DISCUSSIONS

S. No.

D (mm)

I (Amp)

GTS (mm/min)

WFR (mm/min)

PT (mm)

Penetration (P) mm

Reinforcement ( R ) mm

Width (W) mm

Heat input (J) kJ/mm

Weld Bead Volume

(V1)mm3

Wire deposition

Volume (V2) mm3

Wire Deposition Efficiency

%

1 1 1 1 1 1 0.78 1.84 0.75 1.95 5.25 27.78 0.84

2 1 2 2 2 2 0.97 1.89 0.91 2.26 7.45 28.13 0.50

3 1 3 3 3 3 0.87 1.94 1.96 4.95 4.83 28.57 0.36

4 2 1 1 2 2 0.92 2.02 0.82 1.96 3.22 28.57 0.58

5 2 2 2 3 3 1.06 2.30 1.31 3.21 3.78 28.89 0.41

6 2 3 3 1 1 0.98 2.42 2.25 5.14 10.45 30.67 0.96

7 3 1 2 1 3 1.19 2.54 1.76 2.75 6.34 39.13 1.08

8 3 2 3 2 1 1.25 2.65 1.91 3.12 7.22 38.78 0.65

9 3 3 1 3 2 1.42 3.00 1.18 2.1 3.28 37.50 0.46

10 1 1 3 3 2 0.75 1.80 0.75 1.95 7.13 27.78 0.36

11 1 2 2 2 3 1.03 2.23 0.91 2.28 6.34 28.13 0.84

12 1 3 1 1 1 0.58 1.50 0.98 2.58 8.28 27.93 0.50

13 2 1 2 3 1 1.73 3.42 0.76 2.34 4.12 25.81 0.41

14 2 2 3 1 2 1.09 2.34 2.41 4.05 9.24 37.50 0.96

15 2 3 1 2 3 0.81 1.88 2.18 2.98 3.04 39.22 0.58

16 3 1 3 2 3 0.94 2.85 1.78 2.53 5.98 40.00 0.65

17 3 2 2 3 1 1.34 2.03 1.14 1.65 3.02 34.48 0.46

18 3 3 1 1 2 1.22 2.60 2.1 2.93 9.6 39.62 1.08

effect of factor levels on depth of penetration in GTAW

A3 B3 C3 D1 E3

180160140

1.8

1.6

1.4

1.2

1.01.61.41.2 300020001000

1086

1.8

1.6

1.4

1.2

1.016128

A

Mean o

f M

eans

B C

D E

Main Effects Plot for MeansData Means

effect of factor levels on reinforcement height in GTAW

A2 B3 C3 D1 E3

180160140

3.6

3.2

2.8

2.4

2.01.61.41.2 300020001000

1086

3.6

3.2

2.8

2.4

2.016128

A

Mean o

f M

eans

B C

D E

Main Effects Plot for MeansData Means

effect of factor levels on bead width in GTAW

A1 B3 C3 D1 E2

180160140

8

7

6

5

4

1.61.41.2 300020001000

1086

8

7

6

5

4

16128

A

Mean o

f M

eans

B C

D E

Main Effects Plot for MeansData Means

Mathematical Models• The multiple regression analysis resulted the following equations

Y = 10aX1bX2

cX3dX4

eX5f

• Penetration P = -- (5.1)

• Reinforcement R = -- (5.2)

• Width W = -- (5.3)

Predicted value Vs Experimental value of penetration in GTAW

Predicted depth of penetration at different wire feed rates in GTAW

(on 8 mm thick plate)

Predicted depth of penetration at different wire feed rates in GTAW (on 12 mm thick plate)

Predicted depth of penetration at different wire feed rates in GTAW (on 16 mm thick plate)

Predicted value Vs Experimental value of reinforcement height in GTAW

Predicted reinforcement at different wire feed rates in GTAW (on 8 mm thick plate)

Predicted reinforcement at different wire feed rates in GTAW (on 12 mm thick plate)

Predicted reinforcement at different wire feed rates in GTAW (on 16 mm thick plate)

Predicted value Vs Experimental value of bead width in GTAW

Predicted width at different wire feed rates in GTAW (on 8 mm thick plate)

Predicted width at different wire feed rates in GTAW (on 12 mm thick plate)

Predicted width at different wire feed rates in GTAW (on 16 mm thick plate)

CONCLUSION • It is observed that penetration is increasing from 0.75mm to 2.25mm,

when the wire feed rate is increased from 1000mm/min to 3000mm/min. It is also observed that penetration is decreasing with decrease in the ratio of wire feed rate to travel speed.

• Reinforcement and bead width are following almost the same trend. Increase in 2.12mm in the case of reinforcement was obtained by increasing wire freed rate from 1000mm/min to 3000mm/min.

• With increase in plate thickness penetration and bead width were found to be decreasing. That may be due to requirement of high heat input.

• The effect of wire diameter was found to be insignificant compare to other input parameters considered.

• At high values of heat input micro cracks and discontinues bead formation was also observed.

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