Study on Surface Longitudinal Crack Formation of Typical Hypoeutectoid Steel Produced on a Caster with Billet and Slab

Round 1

Reviewer 1 Report

The overall topic is interesting and compatible with journal scope. The methods used in article correspond to the topic (a numerical model in ProCAST combined with experiments in Gleeble).

 

However, the language of the article is low quality (too many lexical and grammatical errors). The English should be improved, proofreading by a native speaker is highly recommended. Authors confuse singular and plural form, in some sentences same words are repeated, etc.

 

I have also problem with the structure of paper. State of the art as well as experimental part should be extended. For instance, the part where the numerical model is described should be placed in section methodology instead of section result and discussion.

 

The work with literature is at an average level. In line 61, 86, 119, 126 , and 129 is Error in references.

 

Graphical style is on low level. The labels in axes are at different fonts and sizes. The caption in figures (in line 82, 107,115, 156, 177, 206, 208) is bold font on half with no reason. The axes caption in figure 2 C and F should be in English. Figure 2-ab should be referred as Figure 3 etc.

 

For me the week point is part optimization of local secondary cooling. There is no optimization algorithm use. The results “Optimized water flow rate” are very doubtful for me. Authors should look and inspired from the articles where optimization of the secondary cooling zone is described. In addition, boundary conditions beneath the nozzles are very simplified. Where is validation of numerical with the real casting process? Final crack-free surface results are maybe obtained due to coincidence rather than complicated optimization-numerical studies.

 

The article has a chance to be part of the journal, but it needs a major graphic and grammatical modifications. I would also recommends to authors to seek what the concept of optimization means and how it works.

Author Response

Responses to Comments

 

Dear Editor and Referees,

 

On behalf of my co-authors, we thank you very much for giving us an opportunity to revise our manuscript, we appreciate you and reviewers very much for your positive and constructive comments and suggestions on our manuscript entitled “Study on surface longitudinal cracks formation of typical hypoeutectoid steel produced on caster with billet and slab”. (Manuscript ID: metals-656497). We have studied reviewer’s comments carefully and have made revision which are highlighted in red in the revised manuscript. Meanwhile, we responded point by point to all the comments as listed below. Attached please find the revised version, which we would like to submit for your kind consideration.

 

Reply to the reviewer’s comments:

 

To referee 1:

 

The overall topic is interesting and compatible with journal scope. The methods used in article correspond to the topic (a numerical model in ProCAST combined with experiments in Gleeble).

 

Comment: However, the language of the article is low quality (too many lexical and grammatical errors). The English should be improved, proofreading by a native speaker is highly recommended. Authors confuse singular and plural form, in some sentences same words are repeated, etc.

 

Reply: Thanks for your nice comments. This revised manuscript has been proofread by native English speaker.

 

Comment: I have also problem with the structure of paper. State of the art as well as experimental part should be extended. For instance, the part where the numerical model is described should be placed in section methodology instead of section result and discussion.

 

Reply: Thanks for your valuable comments. State of the art and experimental part have been extended. And the part of numerical model has been placed in section methodology. (Please see Page 2, red-labeled part).

 

Comment: The work with literature is at an average level. In line 61, 86, 119, 126, and 129 is Error in references.

 

Reply: Thanks for your nice comments. We have corrected the error of reference source in the revised manuscript.

 

Comment: Graphical style is on low level. The labels in axes are at different fonts and sizes. The caption in figures (in line 82, 107,115, 156, 177, 206, 208) is bold font on half with no reason. The axes caption in figure 2 C and F should be in English. Figure 2-ab should be referred as Figure 3 etc.

 

Reply: Thanks for your nice comments. We have modified all the mistakes about the graphical style.

 

Comment: For me the week point is part optimization of local secondary cooling. There is no optimization algorithm use. The results “Optimized water flow rate” are very doubtful for me. Authors should look and inspired from the articles where optimization of the secondary cooling zone is described. In addition, boundary conditions beneath the nozzles are very simplified. Where is validation of numerical with the real casting process? Final crack-free surface results are maybe obtained due to coincidence rather than complicated optimization-numerical studies.

 

Reply: Thanks for your valuable comments. This paper does not use the optimization algorithm, because we have determined the direction of water optimization through experiments. However, when the water flow rate increases to a certain extent, it will have an adverse effect on the billet. In this paper, there are many kinds of optimized flow rate water to reduce the occurrence of cracks, and only one of them is selected here for explanation. The statement that the optimized water flow in this paper is not accurate, so it has been changed to the suggested water flow.

As far as I know, the boundary conditions beneath the nozzles are generally simplified to the following two ways:  or . Compared to the two simplified methods, the simplified method adopted in this paper is closer to the actual situation.

The validation of numerical with the real casting process have been added to the revised manuscript. Please see the following. “The surface temperature after optimization of the inner arc was tested by hand-held infrared thermometer, and the error between the test result and the calculation result was less than 3%, which confirmed the credibility of the model result.” (Please see Page 9, red-labeled part).

Figure 9. Simulation of the surface temperature profile of the billet.

The caster with billet and slab is three-machine three-flow, and the results of the other two-flow billet are the same as the billet in the manuscript, which confirms the reliability of optimization.

 

Comment: The article has a chance to be part of the journal, but it needs a major graphic and grammatical modifications. I would also recommend to authors to seek what the concept of optimization means and how it works.

Reply: Thanks for your nice comment. We have modified the graphic and grammatical in the revised manuscript and we already understand the meaning of the optimization concept and how it works.

 

Author Response File: Author Response.pdf

Reviewer 2 Report

The style and the paper's structure are well organised, although the conclusions are a little poor. This section could be improved with additional comments. It should be mentioned that this problem is of particular importance in the continuous casting process, avoiding the apparitions of cracks being a concern of all specialists in the field.

The aim and general purpose of the paper are well presented, documented and determined in all analysis performed (longitudinal crack distribution and features, analysis on the causes of longitudinal cracks, determining the peculiar conditions for formation of pro-eutectoid ferrite, and optimization of local secondary cooling in the continuous casting process).

The results are valid and reliable. The study offer good significance to the field of continuous casting process of hypoeutectoid steel. Therefore, it is a good contribution in the field. 

 

Author Response

Responses to Comments

 

Dear Editor and Referees,

 

On behalf of my co-authors, we thank you very much for giving us an opportunity to revise our manuscript, we appreciate you and reviewers very much for your positive and constructive comments and suggestions on our manuscript entitled “Study on surface longitudinal cracks formation of typical hypoeutectoid steel produced on caster with billet and slab”. (Manuscript ID: metals-656497). We have studied reviewer’s comments carefully and have made revision which are highlighted in red in the revised manuscript. Meanwhile, we responded point by point to all the comments as listed below. Attached please find the revised version, which we would like to submit for your kind consideration.

 

Reply to the reviewer’s comments:

 

To referee 2:

 

Comments: The style and the paper's structure are well organised, although the conclusions are a little poor. This section could be improved with additional comments. It should be mentioned that this problem is of particular importance in the continuous casting process, avoiding the apparitions of cracks being a concern of all specialists in the field.

The aim and general purpose of the paper are well presented, documented and determined in all analysis performed (longitudinal crack distribution and features, analysis on the causes of longitudinal cracks, determining the peculiar conditions for formation of pro-eutectoid ferrite, and optimization of local secondary cooling in the continuous casting process).

The results are valid and reliable. The study offers good significance to the field of continuous casting process of hypoeutectoid steel. Therefore, it is a good contribution in the field.

 

Reply: Thanks to the referee 2 for his/her positive comments, we will continue to work hard to explore this field. At the same time, we also improved the conclusion of this paper. Please see the following.

“In this paper, the causes of longitudinal crack in hypoeutectoid steel which is produced on caster with billet and slab are analyzed in detail. Also, the direction of crack control is provided. Conclusions are summarized from this research as follows:

(1) The formation of pro-eutectoid ferrite is the main cause of longitudinal crack for the hypoeutectoid steel. Due to the uneven cooling and insufficient cooling for the narrow face of the caster with billet and slab, the narrow surface is more likely to crack whilst the crack depth is deeper than the counterpart on the wide surface.

(2) The microhardness of pro-eutectoid ferrite is 37 HV lower than that of the matrix. Hence, the stress tends to accumulate on the ferrite film, and the crack occur when the stress reaches the ultimate stress of the steel.

(3) It can be found that the precipitation of pro-eutectoid ferrite can be effectively controlled when the cooling rate is as close to 50 °C/min as possible. At the same time, the reinforced cooling of the billet will not cause the crack due to excellent plasticity of the steel.

(4) After determining the surface temperature of the billet through the numerical simulation, it is decided to strengthen the cooling after zone 6. As a result, the surface temperature quickly passed through the phase transition zone of the pro-eutectoid ferrite, and the surface longitudinal crack no longer occurred.”. (Please see Page 10, red-labeled part).

 

 

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

I am satisfy with all corrections.