Process Diagnosis of Liquid Steel Flow in a Slab Mold Operated with a Slide Valve
, Carlos Rodrigo Muñiz-Valdés 1, Rodolfo Morales-Dávila 2,* and Alfonso Nàjera-Bastida 3
Round 1
Reviewer 1 Report
I would strongly suggest the article for publication. Its content, novelty, and industrial importance make it a good fit for the journal of Crystals. The article is well written and interesting from a practical point of view. The introduction provides useful background information for the readers to understand the study. The experimental research has been properly designed. It is quite easy for the reader to assess the paper structure as the figures and tables are properly linked to the corresponding text section. I would suggest the article to be accepted as is.
Author Response
REV. 1
TITLE:
Process Diagnosis of Liquid Steel Flow in a Slab Mold Operated with a Slide Valve
REV. 1
I would strongly suggest the article for publication. Its content, novelty, and industrial importance make it a good fit for the journal of Crystals. The article is well written and interesting from a practical point of view. The introduction provides useful background information for the readers to understand the study. The experimental research has been properly designed. It is quite easy for the reader to assess the paper structure as the figures and tables are properly linked to the corresponding text section. I would suggest the article to be accepted as is.
Answer. Thank you very much, Sir, Miss, we understand that you liked our paper, and we feel encouraged to pursue this research. We acknowledge your dedication and your valuable time employed in this task.
Author Response File: 
Author Response.docx
Reviewer 2 Report
This is an important work aimed at improving equipment for pouring liquid metal using modern mathematical and physical modeling tools. From the point of view of the relevance and adequacy of the means used, the work certainly deserves publication.
However, as it is presented in this text, the work leaves the impression of incompleteness. In fact, with the help of mathematical and physical modeling tools, the existing equipment was criticized. However, the proposals to change the state of affairs look vague. The authors write "This caster's operating conditions demand a nozzle with a different design that must guarantee unbiased flows and stabilize the meniscus."
Who will suggest this different nozzle design? Maybe the authors of the paper? Why didn't they do it in this paper if they know how to change the design of the nozzle and they have the means to validate their proposals using simulation?
In addition, the work is not free of minor design errors (eg Polit [ecnico on line 387).
Author Response
REV.2
This is an important work aimed at improving equipment for pouring liquid metal using modern mathematical and physical modeling tools. From the point of view of the relevance and adequacy of the means used, the work certainly deserves publication.
However, as it is presented in this text, the work leaves the impression of incompleteness. In fact, with the help of mathematical and physical modeling tools, the existing equipment was criticized. However, the proposals to change the state of affairs look vague. The authors write "This caster's operating conditions demand a nozzle with a different design that must guarantee unbiased flows and stabilize the meniscus."
Answer. Dear reviewer, we think that your perception is correct. Therefore, we added a new paragraph to make clear the scope of this work.
Who will suggest this different nozzle design? Maybe the authors of the paper? Why didn't they do it in this paper if they know how to change the design of the nozzle and they have the means to validate their proposals using simulation?
Answer. We are the ones to deal with this problem. We clarify this task in the corrected manuscript. We did not make the proposal of a new design for improving the flow because the material generated in this task will enlarge, unnecessarily, the present contribution. We will leave that new future material for incoming papers. This aspect is mentioned in the new paper.
In other words, according to the experience of the authors, a redesign involves many computers runs as the shape of these deflectors and their specific position in the nozzle change radically the dissipation rate of the kinetic energy. Besides, these computational activities must be complemented with the physical model. These great amounts of information will give origin to further publications as the company has commissioned the new design to the author's laboratory.
In addition, the work is not free of minor design errors (eg Polit [ecnico on line 387).
Thanks again, we corrected it in the corrected manuscript.
Reviewer 3 Report
Dear authors, I have some questions and suggestions:
113 – Which version of Ansys did you used?
Why did you choose k-e model instead of k-omega which is currently recommended model for fluid flow in Ansys 2020+?
At what time did you get a convergent solution?
How much time reduction the k-e model helped to achieve a convergent solution of the large eddy model?
How many iteration steps did you use for your simulation?
185 –What was the quality of the mesh based on Skewness and Orthogonal Quality criteria?
What cell shape did you use in your mesh?
How many boundary layers have you defined for flow near a wall?
Why don't you have atmospheric pressure defined as 101 325 but use 101 000? Is this difference negligible?
34 Simultaneously, the flow of liquid steel inside the nozzle fixes the flow patterns in the mold. – What does it mean „to fix the flow patterns in the mold “?
35-43 In my opinion, it is not necessary to describe the function of the sliding gate. Maybe some drawing might be better here.
55-67 The influence of the slide valve rotation on the flow pattern can be also explained using drawings.
83-97 The drawing, or the picture of water model is missing.
84 Explain the dimensions 1650X200X1700 mm (Width, height, depth)
112 Table 1: How did you calculate Water flow rate? Is your calculation exact? Which value of density of solidified steel you used?
233 Figure 5b: You should use more pictures form simulations using the water model. This picture is lack. In which time after adding of a tracer is taken this picture?
350 I don’t understand the title of this chapter „Casting Diagnosis“
Author Response
REV. 3
Dear authors, I have some questions and suggestions:
113 – Which version of Ansys did you used?
Answer: 17.2
Why did you choose k-e model instead of k-omega which is currently recommended model for fluid flow in Ansys 2020+?
- Answer: The k-omega model, developed in its modern version by Wilcox, D.C. Turbulence Modeling for CFD; DCW Industries: La Cañada, CA, USA, 2000; pp. 103-104, is the most recommendable turbulence model to deal with boundary layer problems. It is the preferred model of aeronautic engineers. We have employed it combined with the SST model in heat and momentum transfer through the boundary layers in liquid steel ladles (see O. Dávila, Rodolfo Morales, and L. García: Metall. and Mater. Trans, B, 17B, 2006, 71-87). However, in the present work, we are more interested in the flow patterns rather than in the details of the boundary layer. This model yields robustness and it is preferred for engineering problems. Besides, we have tested the k-epsilon model with other more sophisticated models without finding appreciable differences. Another plus of this model is its simplicity.
At what time did you get a convergent solution?
Answer: We did not record the time. The convergence criterion is when the sum of all residuals is less than 10-4 the iteration ends.
How much time reduction the k-e model helped to achieve a convergent solution of the large eddy model?
Answer: Again, we were not aware of a specific time saving. When you try to use the LES model directly the convergence is always a try an error process consuming long times. The length of this time is, evidently, variable and sometimes can be very long. Using first k-epsilon simplifies the convergence process.
How many iteration steps did you use for your simulation?
Answer: Five hundred with a time step of 0.01 s.
185 –What was the quality of the mesh based on Skewness and Orthogonal Quality criteria?
Answer: Orthogonality of 0.6
What cell shape did you use in your mesh?
Answer: Unstructured and tetrahedral
How many boundary layers have you defined for flow near a wall?
Answer: Wall function for the k-epsilon model and WALE for the LES.
Why don't you have atmospheric pressure defined as 101 325 but use 101 000? Is this difference negligible?
Answer: It is a misprinting. Anyhow, even if we would have used the second pressure, the effects will be negligible.
34 Simultaneously, the flow of liquid steel inside the nozzle fixes the flow patterns in the mold. – What does it mean „to fix the flow patterns in the mold “?
Answer: It means that it fixes the flow in the mold. The flow in the mold is a direct consequence of what is happening inside the nozzle. Literally, what happens in the mold has a previous history in the nozzle. Therefore, the phrase “it fixes” is literal!
35-43 In my opinion, it is not necessary to describe the function of the sliding gate. Maybe some drawing might be better here.
Answer: There are a clear written description and a drawing, see Figure 2a. Therefore, the figure and the text complement well to each other, so we decide to leave this description the way it is.
55-67 The influence of the slide valve rotation on the flow pattern can be also explained using drawings.
Answer: Yes, we agree, but it would not contribute with additional information. We leave it in its current form.
83-97 The drawing, or the picture of water model is missing.
Answer: We add a photo of the model.
84 Explain the dimensions 1650X200X1700 mm (Width, height, depth)
Answer: It must be interpreted as width, depth, and length. These dimensions are highlighted in the corrected manuscript.
112 Table 1: How did you calculate Water flow rate? Is your calculation exact? Which value of density of solidified steel you used?
Answer: Naturally, the solidification of steel is considered as the flow balance is made on a volume basis. We think it is unnecessary to mention this aspect as it is elemental, tough, we mention it in the corrected manuscript. The density of solid steel is 7840 kg/m3 and of liquid steel is 7100 kg/m3. We have an excel spreadsheet where the casting speed and the dimensions of the mold are the inputs and the output is the flow rate of water. Yes, our calculation is exact!
233 Figure 5b: You should use more pictures form simulations using the water model. This picture is lack. In which time after adding of a tracer is taken this picture?
Answer: The objective of Figure 5b is simple to demonstrate the existence of the biased flow, in the present case, toward the broad frontal face of the mold. Usually, we waited for 10 to 20 minutes to ensure a steady flow and once it was attained, the tracer was injected. Therefore, the exact time of the injection was not recorded. We use the mathematical model and the physical model as complementary tools. It was not our intention to test the prediction capacity ode the math model with the results of the physical model on viz to viz basis. The latter has plenty of information of the dynamics of the meniscus.
350 I don’t understand the title of this chapter „Casting Diagnosis“
Answer: Well, we think it is a diagnosis about how the nozzle is working and the consequences in the slab quality. If the word diagnosis is not suitable, we are open to your valuable suggestion. Probably Casting flow…..?
We appreciate very much your precious time reading with such detail our manuscript. Your main observations are included, in red, in the new manuscript.
Round 2
Reviewer 2 Report
This is an important work aimed at improving equipment for pouring liquid metal using modern mathematical and physical modeling tools. From the point of view of the relevance and adequacy of the means used, the work certainly deserves publication.
The authors took into account the comments of the reviewers.
Reviewer 3 Report
Dear authors,
I appreciate that you considered my comments and added more information and description into your manuscript, which now gives significantly more information about the physical and numerical model.
