effect of heat input and speed of welding

International Journal of Industrial Engineering Research and Development (IJIERD), ISSN 0976 –

6979(Print), ISSN 0976 – 6987(Online) Volume 3, Issue 2, July-December (2012), © IAEME

42

EFFECT OF HEAT INPUT AND SPEED OF WELDING ON

DISTORTION IN MIG WELDING

1Mr. Harshal K. Chavan

2Mr. Gunwant D. Shelake

3Dr. M. S. Kadam

M.E. (Manufacturing) M.E. (Manufacturing) HOD (Mechanical Department)

JNEC Aurangabad (M.S.) JNEC Aurangabad (M.S.) JNEC Aurangabad (M.S.)

[email protected] [email protected] [email protected]

ABSTRACT

The objective of this research is to simulate the complex arc welding process by using the

finite element method(ANSYS)[�]. After the model is built and verified, the main objective of

the research is to study the effects of varying the welding process parameters on the thermo-

mechanical responses. In addition to that, the aim of this research is also to find a relationship

between welding parameters and thermo-elasto-plastic responses.

In this research paper, the responses of single pass corner-joint of arc welding are evaluated

through the finite element software (ANSYS). The study of this research paper covers only

the effects of varying heat input, welding speed on the thermo mechanical responses of the

weldment after cooling down to room temperature.

Keywords: - Heat, Weld speed, Distortion, strain, FEA

INTRODUCTION

The problem of welding distortion during large steel fabrications causes to the dimensional

inaccuracies and misalignments of structural members, which can result in corrective tasks or

rework when tolerance limits are exceeded. This in turn, increases the production cost and

leads to delays. In fabrication and design industries, expenses for rework such as

straightening could cost lacks of Rupees. Therefore, the problems of distortion and residual

stresses are always of great concern in welding industry. In order to deal with this problem, it

is necessary to define prediction of the amount of distortion resulting from the welding

operations. One way to predict the distortion and shrinkage of steel welding is through

numerical analysis such as finite element analysis (FEA). Once the techniques of prediction

of the distortion and shrinkage are identified, then the problems can be controlled

accordingly.

INTERNATIONAL JOURNAL OF INDUSTRIAL ENGINEERING

RESEARCH AND DEVELOPMENT (IJIERD)

ISSN 0976 – 6979 (Print) ISSN 0976 – 6987 (Online)

Volume 3, Issue 2, July-December (2012), pp. 42-50

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Within the welding procedures, there are many factors such as welding process type,

welding process parameters, welding sequence, preheat patterns, level of constraint and joint

details that contribute to the distortion of the welded structure. Knowing which parameters

have a major effect on the quality of the weld and which parameters give the most

significant effects on the weld quality are the main issues in welding industry. The research

activity in welding simulation started decades ago. Rosenthal (1941,1946)[37,39,41]

was among

the first researchers to develop an analytical solution of heat flow during welding based on

conduction heat transfer for predicting the shape of the weld pool for two and three-

dimensional welds. Understanding of the theory of heat flow is essential in order to study the

welding process analytically, numerically or experimentally since the pioneering work of

Rosenthal (1946), considerable interest in the thermal aspects of welding was expressed by

many researchers such as. Chen et al. (2003)[10]

Andrea Capriccioli, (2009)[12] ,

and Heinze

et al. (2012)[13].

PROCEDURE FOR FINITE ELEMENT MODEL

Present work requires that finite element model be created to study the effect of process

parameter on , deformation, residual stress & strain. We must setup a transient thermal

analysis to determine thermal state in the weld and surrounding components. Following this

we are required to import the thermal loading to setup structural analysis which results in

deformation, residual stress & strain. The weldment material properties employed in this

paper were mild steel, which were taken from Andrea Capriccioli et al. (2009)[12].

To simplify

the heat transfer analysis, Dean Denga,(2007)[2] ,

Bonifaz (2000)[40]

, assumptions were

made. The heat input from weld electrode is modeled by using heat flux as input from

electrode to weld surface and is depends on the efficiency of arc and welder setting. The heat

flux distribution on the surface of weldment is given by Goldak et al. (1986) [30]

RESULT

Effect of Heat Input

Heat input is one of the most important process parameters in controlling weld response. It

can be referred to as an electrical energy supplied by the welding arc to the weldment. In

practice, however, heat input can approximately (i.e., if the arc efficiency is not taken into

consideration) be characterized as the ratio of the arc power supplied to the electrode to the

arc travel speed, as shown in the following equation.

Q=V××××I××××60/υ……………….

Where, I is welding current; V is welding arc voltage; v is the arc welding speed, and Q is the

heat input. In this work, the effect of heat input on welding responses was evaluated using

three values (heat input in Watt), characterized as low, medium, and high. Table 1 illustrates

the values used for the analyses. This evaluation was carried out by considering the rest of



44

parameters; welding speed was kept constant at low value and restraint was kept constant at

high value.

Table 1 Range of heat input used for FEA [27]

LOW MEDIUM HIGH

1278W 1448W 1704W

HEAT FLUX CALCULATION FOR FEA

Voltage and current values for High, medium & low heat flux

1) For High Heat Flux

Welding Voltage 14.2 V

Welding Current 20 A

2) For Medium Heat Flux



3) For Low Heat Flux



Electrode Diameter = 25.4/8 = 3.175 mm

Area of electrode = 3.1416×3.175×3.175/4 = 7.9173mm2 = 0.0000079173 m

2

Q= I×V×60/ν

1) HIGH

Q=20×14.2×60/10= 1704W

q=Q/a= 1704/0.0000079173= 2.15e8W/m2

2) MEDIUM

Q=17×14.2×60/10=1448W

q=Q/a= 1448/0.0000079173= 1.82e8W/m2

3) LOW

Q=15×14.2×60/10 = 1278W

q=Q/a = 1278/0.0000079173= 1.61e8 W/m2

(Where q is heat input per unit area, a is area and Q is Heat input)

International Journal of Industrial Engineering Research and Development (IJIERD), ISSN 0976

6979(Print), ISSN 0976 – 6987(Online) Volume 3, Issue 2,

ANALYSIS OF RESULTS

Fig 1 shows that x elastic strain and y elastic strains are sensitive to heat input. As heat input

changes strain changes respectively.

Fig 2 shows that stress value decreases as heat input increases. This is due to fact that we

cannot consider cooling time in the solution. As we can see from the graph that X

the vertical plate is more sensitive to the heat input. Also we can see that Y

horizontal plate is more sensitive to heat input as compare to other directional stresses.

As heat input increases stresses decreases, this is due to the fact material properties such as

young’s modulus decreases as temperature in the material increases. As the

increases temperature generates in the plate increases and thus the stress generated decreases.

ANALYSIS OF RESULTS

The effects of varying heat input on the thermo mechanical responses is

Figure 1 Obviously, the results showed t

the welding responses. When the heat input increases, the responses such as displacements,

strain increase. An increase of 12 % of heat input results in a significant increase in the Y

displacement (65 %), Z-displacement (10%), and X

As shown in figure 1 X-

as compared to other directional displacement i.e. y and z displacement, from figure it is

observed that maximum displacement occurs at 20mm cross section which is in the heat

affected zone.

Horizontal Plate


6987(Online) Volume 3, Issue 2, July-December (2012), © IAEME

45


changes strain changes respectively.

value decreases as heat input increases. This is due to fact that we

cannot consider cooling time in the solution. As we can see from the graph that X

the vertical plate is more sensitive to the heat input. Also we can see that Y

ntal plate is more sensitive to heat input as compare to other directional stresses.


young’s modulus decreases as temperature in the material increases. As the


The effects of varying heat input on the thermo mechanical responses is

Obviously, the results showed that the welding heat input has significant effect on


strain increase. An increase of 12 % of heat input results in a significant increase in the Y

displacement (10%), and X-Elastic strain (15 %).

displacements in vertical plate is more sensitive to heat input


displacement occurs at 20mm cross section which is in the heat

Vertical Plate


December (2012), © IAEME


value decreases as heat input increases. This is due to fact that we

cannot consider cooling time in the solution. As we can see from the graph that X-stress in

the vertical plate is more sensitive to the heat input. Also we can see that Y-stress in

ntal plate is more sensitive to heat input as compare to other directional stresses.


young’s modulus decreases as temperature in the material increases. As the heat input


The effects of varying heat input on the thermo mechanical responses is illustrated in

hat the welding heat input has significant effect on


strain increase. An increase of 12 % of heat input results in a significant increase in the Y-

displacements in vertical plate is more sensitive to heat input


displacement occurs at 20mm cross section which is in the heat



Figure 1 Graphs Illustrate the Effects of Varying Heat input on Displacement

EFFECT OF VARIABLE SPEEDWelding speed represents the distance of the torch traveled

unit of time. The heat input is inversely proportional to the welding speed. Therefore,

when the heat input is larger, the welding speed is slower for a constant heat input

rate.

In this research, low, medium, and high welding speeds were investigated

while considering the rest of parameters such as heat input is kept at low value and

restraints at high value.

Table 2 Range of Welding Speed for FEA

LOW

2mmps

ANALYSIS OF RESULTS Figure 2 shows the effect of varying welding speed. From figure it observed that as the

welding speed increases displacement, strain decreases. When welding speed increases

by 33%, X-displacement of horizontal plate

horizontal plate decreases by 11%.



46

Graphs Illustrate the Effects of Varying Heat input on Displacement

EFFECT OF VARIABLE SPEED Welding speed represents the distance of the torch traveled along the weld line per

time. The heat input is inversely proportional to the welding speed. Therefore,




Table 2 Range of Welding Speed for FEA

MEDIUM HIGH

3mmps 4mmps

Figure 2 shows the effect of varying welding speed. From figure it observed that as the


displacement of horizontal plate increases by 14% and Z-displacement of

horizontal plate decreases by 11%.



Graphs Illustrate the Effects of Varying Heat input on Displacement

along the weld line per

time. The heat input is inversely proportional to the welding speed. Therefore,




Figure 2 shows the effect of varying welding speed. From figure it observed that as the


displacement of



Horizontal plate Vertical Plate

Figure 2 Graph illustrate effect of varying welding speed on DisplacementAs the speed of welding increases the stresses induced in the plate decreases because

as welding speed increase time for welding decreases and thus It is noted that the

faster the welding speed is made, the less heat is absorbed by the base metal and thus



47

Horizontal plate Vertical Plate

Graph illustrate effect of varying welding speed on DisplacementAs the speed of welding increases the stresses induced in the plate decreases because





Graph illustrate effect of varying welding speed on Displacement As the speed of welding increases the stresses induced in the plate decreases because





48

stresses induced decreases. The graph also shows the same trend.

CONCLUSION After completion of this work, several conclusions are made from the results shown

above. Based on the simulation results i.e. results shown above in figures we can

predict the distortion, shrinkages of weldment numerically. This is cost saving process

because experimental processes are costly. From the simulation results we also

conclude that heat input, welding speed has significant impacts on the weld response

which are as follows

� When the heat input increases by, the responses such as displacements, strain

increase. An increase of 12 % of heat input results in a significant increase in

the Y-displacement (65 %), Z-displacement (10%), and X-Elastic strain (15

%).

� On the other hand, the opposite response behavior is observed when the

welding speed increases. When the welding speed increases by, the responses

such as displacement, strain decreases. An increase of 33% of welding speed

results in a significant decrease in Y-displacement (11%),Z-

displacement(12%),and X-elastic strain(35%).

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effect of heat input and speed of welding

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