OCTOBER 19-20, 2012 - YMCA University of Science & Technology

Proceedings of the National Conference on
Trends and Advances in Mechanical Engineering,
YMCA University of Science & Technology, Faridabad, Haryana, Oct 19-20, 2012
HAZ Width = [+ 1.604 - 0.075*WFR + 0.018*OCV - 0.118*WS + 2.316×10 -03 *WFR*OCV] 2
….….6
HAZ Area = - 26.381 + 0.061*WFR + 3.023*OCV - 6.442*WS
……..7
Final Equation in Terms of Actual Factors with electrode negative:
HAZ Width = [+ 0.649 - 0.037*WFR + 0.018*OCV - 0.118*WS + 2.316×10 -03 *WFR*OCV] 2
HAZ Area = - 66.763+ 1.694*WFR + 3.023*OCV - 6.442*WS
……..8
……..9
5. Results
Mathematical models represented by Eqs. 4-9 may be used to predict both responses i.e. HAZ width and HAZ
area. Predicted values can be found by substituting parameter values either in the coded form (Eqs. 4 & 5) or
actual parameter values can be used in Eqs. 6-9 for direct results.
Figure 5Figure 10 depict the variation of responses in the form of graphical representation. The advantage of
using cube plots is that, for a given response, main effects and interaction effects of three parameters can be studied
simultaneously in a single illustration.
6. Discussion
6.1. Direct effect of processes parameters on responses
Eqs. 4 & 5 shows that direct effect of process parameters is the same on both HAZ width and area. Wire feed rate
and open circuit voltage have positive effect and welding speed is seen oppositely related. In other words, both
increase with an increase in wire feed rate and open circuit voltage. A reduction is noted as there is an increase in
welding speed. This can be explained as following; Heat affected zone is influenced by amount of heat input per
unit length of the weld. Heat input is calculated as
Heat Input, J/m = η × (welding current, Amp × welding voltage, Volt) / welding speed, m/s
Where, η is arc efficiency
…..10
It is indicated from the Eq. 10 that increase in welding current and voltage and decrease in welding speed will
increase the amount of heat input per unit length and in turn HAZ size will increase. From ANOVA (tables 4 &
5, it is found that open circuit voltage and welding speed with 43 and 31% contribution respectively are the most
effective parameters for HAZ width, while contribution of same parameters for HAZ area was calculated as 40%
and 46%. Main effect of polarity is not so significant in both the cases, but the relationship is positive.
6.2. Interaction effect of process parameters on HAZ width
From Error! Reference source not found., it can be noted that at low open circuit voltage apparently there
is no change in HAZ width with increase in wire feed rates, but at higher open circuit voltage, an increase is seen
under electrode positive polarity. On the other hand, even at low open circuit voltage, HAZ width increases significantly
with the increase in wire feed rates but rate of increase is not influenced by high open circuit voltage
under electrode negative. Main effect of polarity is not so significant as compared to other variables. It has interactive
influence with wire feed rate as can be seen in
Figure 6 &Figure 7. Low wire feed rates under electrode positive produced wider HAZ as compared to electrode
negative, while at high wire feed rates wider HAZ is obtained with electrode negative. In other words, HAZ
width can be said more sensitive to wire feed rates under electrode negative conditions. No interactions of welding
speed are present with wire feed rates, open circuit voltage or polarity, but from the model equation 4 it is
eminent that a slight positive interaction effect between open circuit voltage and wire feed rate is present. As a
result of this interaction, higher heat affected zone width is produced when both the parameters are at their high
levels.
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