Review Reports

Round 1

Reviewer 1 Report

In this study, it was considered that the wire structure is a key factor in determining the welding arc stability, especially when using the metal core method with iron powder as the main component. It is argued that the mechanism underlying the effect of flux ratio on metal core wire is still not well known, and this paper examines the effect of flux ratio on the metal transfer behavior of metal core wire.

Question 1) Under welding conditions of a wire with a diameter of 1.2mm, 220A is hard to see as low current. Since the author examines all metal transfer is a spray mode condition, globular mode condition must be examined and compared.

 

Question 2) It is necessary to mention the wire feed conditions, and in general, as the current increases, the wire feed speed also increases, which affects the metal transfer phenomenon. It is necessary to analyze whether the wire feed conditions are the same or have an effect on the metal transfer phenomenon.

 

Question 3) It was said that the effect on the flux ratio was large at low current. At low current, the droplet transfer frequency is large, but the flux is not completely melted, which is expected to cause internal defects. Have you analyzed this problem?

 

 

Question 4) It is well known fact that in metal cored wire, the current density is naturally increased, so that the metal transfer is good even at a relatively low current and the deposition amount is large. There seems to be a lack of in-depth consideration on this, and it is necessary to add a simple analysis to explain the effect of Lorentz’s force. Also, in Figure 5c and d, repetitive figures with same tag make the quality of paper poor. Figure 6 is the same. 

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

I thank the authors for this interesting article with this outstanding experimental study.

Summarizing, the conclusions and also the argumentation line are comprehensible. But from the shadowgraph images it is very difficult for the reader to comprehend the tapering effect. 
And regrettably, the undoubtedly existing chemical effects onto the viscosity and surface tension are are not discussed.  

P1
L15 Insert a space between xy and % according to int. standards there is a generally a space between the numerical value and unit symbol,
see e.g.: Guide for the Use of the International ystem of Units (SI) from NIST. Please check all the document. 
L25 GMAW is missing in the abstract
L 47 ... 50 is underwater welding focussed here in this paper? Please delete if not.
P2
L68 ... 86 What is meant with wire electrode structure in this paragraph?
L71 in reference to hollow-sheathed vs. folded sheath as investigated in [21]? ... 
L84 ... does "These studies show that wire structure is a key factor ..." refer to the whole paragraph with all references here? 
P3
L100 0%: missing space
L101ff why this spefic flux was selected and not others?
L106 what is the sheath metal composition, what the flux? And what is the sheath thiscknesses?
L111 These voltages appear to be unusually high for practical use. 
L112 missing space
P4
L141 does the arc have the ability to push the droplet upwards or is this caused by other effects, secondary ones? How about the metal evapouration and the plasma flow
P5
Figure 1 (a) how did you realise this short-circuiting-free droplet transfer? 
Generally, it was a good decision to choose the current parameters in this way. Typically, in case of 1.2 mm non flux wires at currents from ~ 230 A ... 250 A a spray appears. In the transition region a globular droplet transfer cannot be realised without short-circuiting.
P9
Figure 5 The out diameter is 1.2 mm, ok. But the thicknesses of the sheath seam to vary with the flux thicknesses. Thus, the amount of sheath is reversed proportional to that of flux. Is tihs correct? Please amend in this figure the thickenesses 
Figure 6 with reference to figure 3 Although the schematic representation in figure 6 is understandable, it is very difficult for the reader to comprehend it. 

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

The effect of flux ratio on droplet transfer behavior is studied in this manuscript. It is very interesting and important in metal-cored arc welding fields. It is suggested to be accepted.

However, there are still some points to be discussed or demonstrated.

(1)     In Fig.2 and Fig.3, it can be found that the number of spatters in metal-cored arc welding is more than that in solid wire. If both advantages and disadvantages are shown in this manuscript, it may be better.

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

All answers have been adequately answered.