Mechanical Behavior and Damage of Zinc Coating for Hot Dip Galvanized Steel Sheet DP600

Reviewer 1 Report

1. Lines 39-40: “…easily left in the basket” – what does this mean?

We are very sorry for making you confuse. left in the basket” is proverb expression of " neglected". It means that the thickness of the coating is the micron level, which is often neglected in the macro level compared with the thickness of the steel substrate. We have modified the expression in the revised manuscript , which can be more intuitive and accurate.

2. Line 62: “train” should be strain

We were really sorry for careless mistakes. We have corrected this mistake.

3. Line 63: “machines” should be mechanisms

Thank you very much for your careful review. We have corrected this mistake.

4. Line 63: “trans granular” should be all one word

Thank you very much. We have corrected “trans to a word “trans granular”.

5. Line 64: “uncorrected” – Not sure what is meant using this word

Thank you for your suggestion. The word “uncorrected” a is redundant and has been deleted.

6. Line 78: “abscission of coatings” – should it be abrasion?

Thanks for your nice suggestions. Abscission refers to the coating layer falling off the substrate, while abscission refers to the coating wear When the steel specimen is under uniaxial tension, the coating falls off under the action of internal stress and strain, and there is no sliding friction with other tools which makes the coating wear So the word “abscission” is used here.

7. Line 134: Introduce the composition of steel DP600

We are very grateful for the reviewer's suggestion. We have added composition of D600 to the revised manuscript please refer to line 132-134 for details.

8. Line 155: Figure 2 does not supply much useful information and may be considered for deletion

Thank you again for your comments on our manuscript. We carefully considered the author's suggestion. Figure 2 shows that the surface material of the coating layer is much looser than that of the substrate. This is one of the main reasons that the coating is easily powdered and damaged when it is deformed and then affects the mechanical properties of the steel. It also indirectly shows that the mechanical properties of the zinc coating and the steel substrate will be very different. Therefore, the author hopes to keep Figure 2.

9. For Table 1, is there any statistical significance for YS and TS between samples tested?

Thank you for your kind suggestions Table 2 shows the uniaxial tensile test results of galvanized steel samples before and after removing the coating layer which further explains the influence of zinc coating layer on the mechanical properties of steel plate It is not only the influence of YS and TS but also has an obvious influence on other mechanical property parameters. Therefore, the author hopes to keep the statistical data of each parameter in this table.

10. Line 173-208: I do not see the point in presenting the Oliver/Pharr derivation, as it has been previously published and referenced many times.

Thanks for the reviewer s kind advice. We have removed the derivation of power function la w proposed by Oliver and Pharr.

11. Equation 16: Missing “]” in first line

Thank you very much for your careful review. We h ave corrected this mistake.

12. Figure 13: “(d)” should be “(c)”

Thank you very much. We have corrected this mistake.

13. Line 395: Mpa should be MPa

Thank you very much for your careful review. We have corrected this mistake.

14. Line 443: The conclusion that the five layer model has the highest accuracy should be quantified.

Thank you for your suggestion. We analyzed the simulation accuracy of the maximum forming force simulated by different element models The added table 5 gives a comparative analysis of the quantitative results. The maximum forming force deviation of five layers model is 0.645%, and its accuracy is the highest, compared with 2.979% of single layer element and 1.173% of 3 layer element. At the same time, the five layer s model can simulate the damage evolution of the zinc coating, which cannot be realized by the other two finite element models.
Please refer to table 5 and relevant descriptions in the revised manuscript for details.

15. Lines 523 – 538 should be completed.

Thank you very much for y our suggestions. We have reorganized and re written the contents of Author Contributions, Funding and Acknowledgments, and supplemented them completely.

Reviewer 2 Report

1. In some cases, the abbreviations need to be explained for better and smooth readability. I recommend explaining the abbreviations not just in the text, but better in small legend beside the equations.

Thanks for your nice suggestions. We have added the details that the abbreviation represents after each abbreviation. Moreover, the meaning of each symbolic variable is explained in a separate paragraph after each equation. We hope that these changes can help you read and understand the paper more easily.

2. Give the origin and reference for your equations, please! Are there any books you can refer to or are they your own bring out?

Thank you very much for your comments. We are very sorry for not citing the relevant equations according to the specification. We have marked the relevant references after the cited equations.

3. Hot dipping of steel in zinc results in a multilayer coating with some intermetallic phases. The intermetallic phases ensure very good adherence and a minor increase in hardness, which is important for the wear resistance. Did the Ni interlayer prevent this effects?

Thanks for your very nice suggestions.
In order to improve the coating quality, a nickel layer was pre-electroplated on the steel substrate before galvanizing and it’s found that there is an improvement in the coating the coating quality. The experimental results show that the compact Ni. The experimental results show that the compact Ni₃₃Zn₂₂ intermetallic layer formed at the zinc/nickel interface during the galvanizing process, prohibiting the nucleation and the growth of the z-Zn phase layer and resulting in the improvement of the zinc coating adhesion. Therefore, the nickel intermediate layer improves the adhesion of the coating and the hardness, which is conducive to enhancing the wear resistance of the coated steel sheet.

Please refer to the following references for details:
Zhong N, Zhang K, Li J, Hu WB (2011) Improvement of the galvanized coating quality of high strength dual phase steels by pre‐electroplating nickel layer. Steel Res Int 82(3):180–186; doi: 10.1002/srin.201000124.

4. Your drawings are very informative (i.e. fig. 3).

Thank you very much for y our suggestions. We simplify some unnecessary information in Figure 3, so that the figure can accurately and concisely express the principle of Nano indentation experiment. Please refer to the revised manuscript for details.

5. In some cases, you have written the S.I. unit Mpa. Please write MPa.

Thank you very much for your careful review. We have corrected this mistake.

6. I don't understand the dimension in table 2.

We are very sorry for making you confuse. A quantity, if its value depends on the scale adopted, that is, on the measurement unit system, is called a quantitative dimension. If some of these quantities are taken as basic quantities and the units of measurement are specified for them, it will express the units of measurement use d for all the remaining quantities in a definite form by the units of measurement of the basic quantities. If the length unit, mass unit and time unit are selected as the basic measurement units, and they are respectively expressed in accordance with L, m and T, then the dimension of area is L² , the dimension of velocity is L/T, and the dimension of force is ML/T² . We often use the symbol introduced by Maxwell, namely [a], to mark the dimension of any quantity a, for example, it records the dimension of force F as [F] = ML/T². In the dimension symbols of the quantities listed in column 2 of Table 2, we have omitted symbol ”[]”, and we have corrected all of them in the revised manuscript.

7. What is the unit for the "strain" in figure 5a?

Thanks for your nice suggestions. There is no unit for strain. Under the action of external force, the object will produce certain deformation, and the degree of deformation is called strain. The strain is the relative change of length and the ratio of deformation to original length. It is expressed by the mathematical symbol ε. That is, ε = ΔL/L, dimensionless, usually expressed as a percentage.