Parametric Optimization of the GMAW Welding Process in Thin Thickness of Austenitic Stainless Steel by Taguchi Method

Round 1

Reviewer 1 Report

The paper aims to evaluate the optimal welding parameters of austhenitic stinless steels using Taguchi method and ANOVA. The investigated parameters, welding voltage, inclination of the electrode and welding current, are studied referring to a case study consisting in welding together two 1.5 mm thick tubes, whose diameters are 63.1 mm and 68.1 mm respectively.

The argument is quite interesting, but the description of the experiments lack of clarity and the conclusions disregards some relevant features of the experiments, so that the paper cannot be accepted in the present form. In the reviewer opinion, to improve the paper, the Authors should adequately consider the following aspects:

1. Two experiments are declared, but it seems that they are simply two different sets of nine specimens each, characterized by the same triplets of parameters, but in Figure 1, it appears that specimens are nine for tube 1 and nine for tube 2, which is in contrast with Figure2. In any case some explanation is needed.
2. In figure 2 c the result of welding the two tube is not regular as the cut of the tube b is not planar, why?
3. From each specimen, three samples of welding are extracted, according to Figure 3, so that 54 samples are obtained, but 9 have been discarded due to imperfections:

• What are the main features of the samples extracted from the same welding? Are they regular and homogenous? (see also remark n. 5)
• What are the reasons for discarding some samples?
• What is the effect of disregarding these samples on the outcomes?
• The relevance of this aspect is confirmed by the sentence in line 238: “In relation to test 7, due to failures in the welding process caused by the absence of material at the points where the cuts were made, it was not possible to obtain the values.”

4. In lines 185-186 the Authors write “Since the measured parameters in Table 3 do not follow a Gaussian distribution, as they are defined positive, the mean and standard deviation are reported only for informative purposes.” The argument seems debatable. Can the Gaussian distribution still be excluded if deviations from nominal values are considered, instead of considering the parameters, ?
5. In Figure 5, they are represented three samples: what is the origin of each of them? Are they coming from the same specimen or not? In the reviewer opinion, the samples differ a lot: for example, the upper right sample is characterized by a significant overthickness, that could significantly affects fatigue resistance. Since defects like incomplete penetration, underthickness, and overthickness can heavily reduce the welding performance, also information about extremes values of measured parameters should be given considering individual samples. Actually, only penetration and width of the weld bead are given, in figures 6 and 7, respectively, but it is not said how they have been determined. (figure 7 is repeated)

In the reviewer opinion a critical discussion of the outcomes is necessary, also assessing, by means of a suitable sensitivity analysis, the influence of the “outliers” which have been disregarded. Consequently, the aim of the study and the conclusions should be duly amended.

Author Response

The authors would like to acknowledge the careful revision done by the Referee, as well as their precious suggestions and comments. Also, we would like to thank the Editor for the opportunity that was given to us regarding the improvement of the original version of the manuscript (MS) and the further resubmission of the improved MS. Hence, we hope that this new version of the MS is worth publishing in the Journal of Applied Sciences.

We answer all the referee questions in the attached document.

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Resultados de tradução

Author Response File: Author Response.doc

Reviewer 2 Report

Thank you very much for inviting me to review the manuscript " Parametric optimization of the GMAW welding process in thin 2 thickness of austenitic stainless steel by Taguchi method”. The manuscript is interesting, but from my humble point of view, this requires some changes and explanations should be made previously that the manuscript will be published in Applied Sciences

 Major Corrections

The abstract must be expanded and improved. It is also recommended that the authors show some of the results obtained in the work.

What is the reason for selecting these 3 parameters for the manufacture of the specimens and not taking into account the speed, but considering the movement angle? Usually, this parameter is less influential than speed since it represents the energy input and the heating power to the weld bead. Please justify.

Are the authors sure that the analysis carried out with the Taguchi method in this work using only 9 specimens is correct? Please justify.

It is convenient that the authors of the manuscript specify the way in which the specimens were manufactured, how they were subjected to the robot and under what conditions they were manufactured. Please justify.

Has there been edge preparation on the parts to be welded to make the specimens? Please justify.

Has there been any treatment on the faces of the cuts prior to the macrographs? Please justify.

What is the reason for choosing that study range for these parameters? Have the authors carried out any previous study to fix this range? Please justify.

What is the reason for choosing a Taguchi L9 orthogonal matrix design in this case? In this case, with 9 specimens, can the authors guarantee that the results obtained are good? Please justify.

In the ANOVA, it would be more convenient for the authors to determine the P-value instead of the F-value and to justify from which value the authors have considered the level of significance. This section must be rigorously better explained.

How do you justify that some of the correlation coefficients of the Correlation matrix are so low? Please justify.

It is not clear whether the ideal welding parameters have been experimentally validated or not. Normally, in an optimization process, whatever the procedure, they are usually validated experimentally so that later their error can be determined, which finally represents the goodness of the regression model proposed to predict. Please justify.

Minor Corrections

The authors must be sure that the figures, tables and references must be in accordance with the format of the journal.

In order to facilitate the authors to improve their manuscript, the following papers show how their authors solved some of the key questions and points that should be improved in this manuscript (P-value, welding parameters in GMAW, range of parameters, prepararion of speciments, etc). I suggest that the authors review the attached papers as they can facilitate the improvement of their manuscript.

• Lostado Lorza, R., Escribano García, R., Martínez Calvo, M. Á., & Múgica Vidal, R. (2016). Improvement in the design of welded joints of EN 235JR low carbon steel by multiple response surface methodology. Metals, 6(9), 205.
• Olabi, A. G., Lorza, R. L., & Benyounis, K. Y. (2014). Quality control in welding process. In Comprehensive Materials Processing (Vol. 6, pp. 193-212).
• Olabi, A. G., Lostado, R., & Benyounis, K. Y. (2014). Review of microstructures, mechanical properties, and residual stresses of ferritic and martensitic stainless-steel welded joints.
• Lostado Lorza, R., Escribano García, R., Fernandez Martinez, R., & Martínez Calvo, M. Á. (2018). Using genetic algorithms with multi-objective optimization to adjust finite element models of welded joints. Metals, 8(4), 230.
• Lostado, R., Martinez, R. F., Mac Donald, B. J., & Villanueva, P. M. (2015). Combining soft computing techniques and the finite element method to design and optimize complex welded products. Integrated Computer-Aided Engineering, 22(2), 153-170.

Author Response

The authors would like to acknowledge the careful revision done by the Referee, as well as their precious suggestions and comments. Also, we would like to thank the Editor for the opportunity that was given to us regarding the improvement of the original version of the manuscript (MS) and the further resubmission of the improved MS. Hence, we hope that this new version of the MS is worth publishing in the Journal of Applied Sciences.

We answer all the referee questions in the attached document.

Author Response File: Author Response.doc

Reviewer 3 Report

This work studied the influence of welding parameters on the quality of the weld. Some points should be improved:

(1) Abstract: why is the welding speed as the very important welding parameter not investigated here?

(2) Introduction:

1) As you mentioned that the quality of the weld can be affected by many factors, however, you did not tell the authors why you focus on the investigation of welding parameters (voltage, etc.) here. 2) Furthermore, it is very important to stress that the welding quality here is reliable penetration and with of weld bead. This is because welding quality includes numerous aspects. 3) I do not understand this sentence really “Welded joints are the main sources of residual stress and distortion…”. 4) In the last paragraph, you did mention what kind of input parameters for welding is studied here. Again, why is the welding speed as the very important welding parameter not investigated here? 5) This introduction Section introduced many other works but not really related to the current work. Also, the most important aspects mentioned above are not illustrated clearly. It is recommended to reorganize and rewrite the Introduction.

(3) Materials and method:

1) What norm of the used two austenitic stainless steels? Same material but just with different diameters? 2) It is confused, why use “experiment 1 (or 2)” to represent the first/ second type tube. 3) It is hard to understand why the speed 150 cm/min is established directly here. The geometry of the weld bead is related to the heat input mainly determined by welding current, voltage, and speed. The reason you mentioned here should be discussed. 3) In table 1, what does the level mean here? Furthermore, it is better to schematically show the “travel angle”.

(4) Results and discussion:

1) Figure 77 and Figure 7 are duplicated.

2) It is necessary to mark what width of weld bead and penetration are in the tubes.

Author Response

The authors would like to acknowledge the careful revision done by the Referee, as well as their precious suggestions and comments. Also, we would like to thank the Editor for the opportunity that was given to us regarding the improvement of the original version of the manuscript (MS) and the further resubmission of the improved MS. Hence, we hope that this new version of the MS is worth publishing in the Journal of Applied Sciences.

We answer all the referee questions in the attached document.

Author Response File: Author Response.doc

Round 2

Reviewer 1 Report

Tha Authors satisfactorily addressed the reviewer remarks, so that the quality of the paper has been significantly improved, but some minor revision is still necessary.

In fact, in the reviewer opinion, conclusions (and abstract) should also mention that some samples have been disregarded, due to welding defects outside the permissible range, or caused by excessive melting of the base metals.  These additions are necessary to inform also the hasty reader about relevant issues, and the care that should be paid in choosing the most influencing parameters

Author Response

In fact, in the reviewer opinion, conclusions (and abstract) should also mention that some samples have been disregarded, due to welding defects outside the permissible range, or caused by excessive melting of the base metals. These additions are necessary to inform also the hasty reader about relevant issues, and the care that should be paid in choosing the most influencing parameters

 

(Answer). Thank you very much for your suggestion. We included this information in the abstract of the manuscript, as you can see in the new version (highlighted in yellow).

 

Reviewer 2 Report

Once the manuscript has been improved according to the suggestions proposed by the reviewers and from my point of view, the manuscript can be accepted for publication in the journal "Applied Science".

¡¡¡Congratulations¡¡¡

Author Response

Thank you very much.

Reviewer 3 Report

Some points still need to be improved.

 

(1) Abstract: why is the welding speed as the very important welding parameter not investigated here?

Thank you very much for your reminder. We are aware that the travel speed parameter is more important than the torch angle. However, most research works have studied the influence of travel speed more deeply and there are fewer researchers studying the influence of torch angle, so we chose to carry out this study to add more information about its influence on welding quality. However, we did some preliminary tests with the travel speed in welding to obtain the adequate speed to weld the tubes.

 

Further discussion:

(a) I agree with you that “there are fewer researchers studying the influence of torch angle”, however, “most research works have studied the influence of travel speed more deeply” is not the good reason that you did not study it here. Most research works have also studied the influence of current and voltage more deeply, while you studied them (without speed) here.

(b) “we did some preliminary tests with the travel speed in welding to obtain the adequate speed to weld the tubes”, I really wonder what the standard for “adequate speed” is here. Furthermore, I guess you did the preliminary tests with the constant welding current etc. right?

(c) In the Introduction, it is suggested to describe in detail why the current and voltage, travel angle were studied here (the reason could be as you said:

the most common and controllable in the industrial environment which are the current and voltage [I really do not understand where you got this sentence. why speed is not included here? is welding speed hard to be controlled in practise (by machine for example.)?],

the travel angle is less studied while the torch must be changing the position during the welding process of tubes).

 

For your future work, it is necessary to consider welding speed as one of the most welding parameters in your further research.

 

(2) “ Welded joints are the main sources of residual stresses [14,15] and structural distortions [16], “ this sentence should be rewritten as it is really easy to cause misunderstanding and even sounds wrong.

Comments for author File: Comments.docx

Author Response

(1) Abstract: why is the welding speed as the very important welding parameter not investigated here?

 

Thank you very much for your reminder. We are aware that the travel speed parameter is more important than the torch angle. However, most research works have studied the influence of travel speed more deeply and there are fewer researchers studying the influence of torch angle, so we chose to carry out this study to add more information about its influence on the welding quality. However, we did some preliminary tests with the travel speed in welding to obtain the adequate speed to weld the tubes.

 

 

 

Further discussion:

 

(a) I agree with you that “there are fewer researchers studying the influence of torch angle”, however, “most research works have studied the influence of travel speed more deeply” is not the good reason that you did not study it here. Most research works have also studied the influence of current and voltage more deeply, while you studied them (without speed) here.

 

(Answer (a)). I understand your point of view, and, in part, I agree with you. But, as I told you before, we tried to implement a different approach because we thought to try a study with a slightly different perspective than usual. Meanwhile, we have published recently other works in which we focus on the importance of the welding speed, not only, experimentally but also numerically (numerical simulations) as you see in doi: 10.3390/jmmp5020063, 10.6703/IJASE.202109_18(5).014, 10.3934/matersci.2021018.

 

 

(b) “we did some preliminary tests with the travel speed in welding to obtain the adequate speed to weld the tubes”, I really wonder what the standard for “adequate speed” is here. Furthermore, I guess you did the preliminary tests with the constant welding current etc. right?

 

(Answer (b)). Effectively, we did a lot of pre-testing before setting the levels set in this work. Thus, the maximum and minimum values are close to the limits where it would not be possible to obtain welds with an acceptable level of quality (for the material and thicknesses used). At the same time, that we determined the maximum and minimum limits (current, voltage, and torch angle) we adjust the welding speed.

 

 

(c) In the Introduction, it is suggested to describe in detail why the current and voltage, travel angle were studied here (the reason could be as you said:

 

the most common and controllable in the industrial environment are the current and voltage [I really do not understand where you got this sentence. why speed is not included here? is welding speed hard to be controlled in practice (by machine for example.)?],

 

the travel angle is less studied while the torch must be changing the position during the welding process of tubes).

 

For your future work, it is necessary to consider welding speed as one of the most welding parameters in your further research.

 

(Answer (c)). Thank you very much for your suggestion, we are agreeing with you and we already have done other works in which we give due importance to the welding speed.

 

(2) “ Welded joints are the main sources of residual stresses [14,15] and structural distortions [16], “ this sentence should be rewritten as it is really easy to cause misunderstanding and even sounds wrong.

 

(Answer 2). Thank you very much for your recommendation, indeed, the sentence is not very correct, is confused and, as you say, can cause misunderstanding. We change the sentence in the manuscript (highlighted in yellow).

Thank you for all your suggestions, they were very useful for us and significantly improved the quality of the manuscript. We are sorry if work has caused you any disappointment.