Comparison of the Flow Field in a Slab Continuous Casting Mold between the Thicknesses of 180 mm and 250 mm by High Temperature Quantitative Measurement and Numerical Simulation
Round 1
Reviewer 1 Report
This paper presents a simulation model flow field in slab continuous casting mold for the two different thicknesses, 180 mm and 250mm. The paper addresses a problem of actual interest, but there are fundamental concerns regarding the effectiveness of the proposed method. I have the following comments regarding this paper:
Line 275, please justify why two types of slab molds thickness (i.e., 180 and 250 mm) were selected for the analysis.
Line 280, the authors assume that the diameters and size distribution of argon gas bubbles with the argon gas flow rate is negligible. Please clarify this assumption.
Author Response
Dear Editor and Reviewers，
We sincerely appreciate you and the reviewers for your insightful, positive and constructive comments and suggestions on our manuscript entitled "Effect of mold thickness on the flow field in slab continuous casting mold by high temperature quantitative measurement and numerical simulation" (Manuscript ID: metals-1446274).
These comments are valuable and very helpful for revising and improving our article, which have the important guiding significance to our research. We have studied comments carefully and have made a major correction which we hope meet with approval. Point-by-point responses to the reviewers’ comments are listed below this letter.
We hope that the revised version of the manuscript is now suitable and acceptable for publication in Metals.
Responses to Reviewer 1’s comments
This paper presents a simulation model flow field in slab continuous casting mold for the two different thicknesses, 180 mm and 250mm. The paper addresses a problem of actual interest, but there are fundamental concerns regarding the effectiveness of the proposed method. I have the following comments regarding this paper:
- Line 275, please justify why two types of slab molds thickness (i.e., 180 and 250 mm) were selected for the analysis.
Response: Thank you and accept your suggestion.
In the industrial production, the automobile exposed panels are usually produced in the common commercial continuous caster with the mold thicknesses of 230 mm or 250 mm. However, they are sometimes manufactured with the continuous caster with the thickness of only 175 mm such as in Anshan Iron and Steel Group Co., LTD. in China. As far as we know, it is difficult to use the continuous caster with the thickness smaller than 175 mm to produce the automobile exposed panel to satisfy its strict surface quality requirement. This is the reason why two types of slab molds thickness (i.e., 180 and 250 mm) were selected for the analysis.
The above content has been added in the revised manuscript on line 163-171 in page 5.
- Line 280, the authors assume that the diameters and size distribution of argon gas bubbles with the argon gas flow rate is negligible. Please clarify this assumption.
Response: Thank you for your comment.
According to previous studies, under the certain continuous casting conditions, the bubble size indeed increases with the increase of argon gas flow rate1). As shown in Fig. 2 (a) in the reference, when the argon flow rate is only 2 L/min, the maximum bubble diameter in the flow field is only 2.2 mm. However, when the argon flow rate is increased to 8 L/min, the maximum bubble diameter is about 3.1 mm. However, it can be seen that the distribution of bubble diameters is almost the same when the argon gas flow is changed within a certain range. Therefore, the change of bubble diameter is simplified in the present study. The average diameter of 1.5 mm and the diameter range of 0.3-3 mm can cover those for the argon flow rates in the present study. In addition, according to the reference1), the spread parameter of the Rosin-Rammler distribution for the argon gas bubbles is fitted to 4.63. Actually, in many previous studies, the diameter and size distribution of argon gas bubbles with the argon gas flow rate are negligible. We would like to take the changes in the diameter and size distribution of argon gas bubbles with the argon gas flow rate into consideration in our future studies.
1) H.B. Lu, C.G. Cheng, Y. Li, M.L. Yang, Y. Jin, Distribution of argon bubble and fluctuation behavior of steel/slag interface in continuous casting mold, J. Iron & Steel. 53 (2018) 27-36+41.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
This work analyzes the hydrodynamics behavior inside the mold of a continuous casting machine using numerical simulations and plant measurements. Two mold thicknesses were studied under several operating conditions. The findings of this work are relevant; however, the following aspects must be addressed in a revised version of the manuscript :
i) Authors provide a brief description of the Rod Deflection Method (RDM) used to obtain plant measurements and directs to reference [15] for further details. This method allows measuring the horizontal component of the molten steel velocity near the top of the mold. So, the horizontal velocity component sign indicates the steel flow sense at the top of the mold, and therefore, the fluid flow pattern features inside the mold. This description must be included in the manuscript. Also, the relationship between the horizontal velocity component sign and the fluid flow pattern (DRF, SRF, and UF) must be explained.
ii) The characteristics of the cases studied in this work must be reported in a table, indicating mold thickness, throughput, argon gas flow rate, and the observed fluid flow pattern. Apparently, the mold width is the same for all the cases. If not, include the corresponding value in the table.
iii) The boundary conditions associated with the mathematical models must be summarized in a table.
iv) Units in the vertical axis of the left panel in Figures 4 and 5 are incorrect.
v) Apparently, Figure 6 shows the results presented in Figure 3. Also, Figure 7 summarizes the results in Figures 4 and 5. If true, Figures 3, 4, and 5 must be eliminated.
vi) The captions style in Figures 8 to 12 can create confusion for the reader.
vii) Increasing the thickness of the mold can increase the importance of flow perpendicular to the mold wide-walls (Z direction). This fact can be seen in Figures 12b and 12f. Therefore, this aspect must be addressed in a revised version of the manuscript.
viii) Conclusion 4 states that "...it is benefit for the surface quality control by use of the mold with 250 thickness than the mold with 180 mm thickness in the production of the automobile exposed panel". However, this conclusion is apparently in contradiction with some observations raised previously in the manuscript:
Lines 363-366: "...For DRF, the direction of the velocities near the mold surface is from the narrow face to the nozzle, so that the slag particles trapped near the steel-slag interface are not easy to be captured by the solidified shell on the narrow face, which is conducive to improving the surface quality of the slab..."
Lines 374-375: "...This region is crucial for the formation and growth of solidified shell, so the SRF is not conducive to the formation of solidified shell..."
ix) Delete or provide the correct information in the following sections:
- Supplementary Materials.
- Data Availability Statement.
- Acknowledgments.
- Conflicts of Interest
x) Please ensure references follows the journal format. For instance, the authors' names in reference [4] are wrong.
xi) Please correct spelling, grammar, and typo errors in the manuscript.
Author Response
Dear Editor and Reviewers，
We sincerely appreciate you and the reviewers for your insightful, positive and constructive comments and suggestions on our manuscript entitled "Effect of mold thickness on the flow field in slab continuous casting mold by high temperature quantitative measurement and numerical simulation" (Manuscript ID: metals-1446274).
These comments are valuable and very helpful for revising and improving our article, which have the important guiding significance to our research. We have studied comments carefully and have made a major correction which we hope meet with approval. Point-by-point responses to the reviewers’ comments are listed below this letter.
We hope that the revised version of the manuscript is now suitable and acceptable for publication in Metals.
I look forward to hearing from you soon.
Best regards,
Sincerely yours,
Jian YANG
Doctor, Professor
Director of Department of Materials Engineering
Vice Director of State Key Laboratory of Advanced Special Steel
School of Materials Science and Engineering, Shanghai University
Address: Room 517, Rixin Building, School of Materials Science and Engineering,
Shanghai University, 333 Nanchen Road, Baoshan District
Shanghai, 200444, P.R. China
E-mail: [email protected]
Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 3 Report
The manuscript compares the flow field in slab continuous casting mold measurements with numerical simulations at high temperature.
In my opinion, authours should improve the introduction with more references, in particular more recent references. Moreover they should focus the attention about the novelty of the research.
What is the innovation respect to their previous articles (see ref. 15)?
Author Response
Dear Editor and Reviewers，
We sincerely appreciate you and the reviewers for your insightful, positive and constructive comments and suggestions on our manuscript entitled "Effect of mold thickness on the flow field in slab continuous casting mold by high temperature quantitative measurement and numerical simulation" (Manuscript ID: metals-1446274).
These comments are valuable and very helpful for revising and improving our article, which have the important guiding significance to our research. We have studied comments carefully and have made a major correction which we hope meet with approval. Point-by-point responses to the reviewers’ comments are listed below this letter.
We hope that the revised version of the manuscript is now suitable and acceptable for publication in Metals.
I look forward to hearing from you soon.
Best regards,
Sincerely yours,
Jian YANG
Doctor, Professor
Director of Department of Materials Engineering
Vice Director of State Key Laboratory of Advanced Special Steel
School of Materials Science and Engineering, Shanghai University
Address: Room 517, Rixin Building, School of Materials Science and Engineering,
Shanghai University, 333 Nanchen Road, Baoshan District
Shanghai, 200444, P.R. China
E-mail: [email protected]
Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 4 Report
Results of physical and mathematical modeling as applied to continuous casting mold are of course quite sensitive to mold and SEN geometry as well as to operating conditions such as liquid and gas flow rates. It is easy to reach specific conclusions and dangerous to generalize.
Comments are as follows:
- Line 277, the authors give the immersion depth “immersion depth of the nozzle is 110 mm,”. However it is not clear how this immersion is measured.
- Line 281, the authors give their bubble size distribution “The average diameter of argon gas bubbles is set to be 0.0015 m, and the minimum and maximum diameters are set to be 0.0003 m and 0.003 m, respectively. The diameters of bubbles obeying the Rosin-Rammler distribution”. However they give no clue in regard to how these values have been chosen. Of course bubble size distribution will affect the flow field.
- The simulation is an isothermal one. No treatment is given to gas thermal expansion and resulting buoyancy.
- The simulation is isothermal. Then one misses the effects of thermal buoyancy due to steel superheat combined with heat extraction from liquid pool to mold. This can affect the flow field.
- Line 288, the authors give scant information on the numerical procedure. What is the mesh size? The computer code is home made, a commercial one such as fluent or CFX or else? Do the authors mean a true transient simulation able to capture transition from DRF to UF to SRF and other?? Or do they mean a false transient simulation?
- Is the steel composition given in Table 1 relevant to steel properties given in table 2??
- The authors provide for a comparison of velocities measured by Deflection Rod Method and velocities given by mathematical simulation, line 299. Their conclusion is “It can be seen that all the calculated results are well consistent with the high temperature quantitative measurement results”. It could be true for this single point measurement. But it is hard to accept that this partial agreement would mean a close agreement on gas distribution inside the mold cavity and velocity distribution.
- The authors take their time to explain DRF, SRF “For DRF, the molten steel jet rushes out from the side hole of the nozzle, impinges on the narrow face, etc”. It seems unnecessary for a Metals reader. They go on in order to explain how gas flow rate, liquid flow rate and mold cross sectional area should affect the DRF transition to SRF, etc. This is all expected and documented in the literature; nothing really new.
- There is some specific information such as “the velocities of molten steel scouring down along the narrow face near the meniscus reach or even exceed 0.4 m/s.” But no discussion if these velocities exceed or get close to slag entrainment velocities. What are the consequences? The same comments in regards to level fluctuation, Figure 11!!
- Figure 8 makes apparent a no symmetrical flow condition. It is not made clear if this is due to numerical instabilities or to a truly transient simulation. Anyway it does not seem reasonable to perform a truly transient simulation without taking in consideration thermal effects, shell cavity taper and motion, etc.
There is not nothing really very wrong with this simulation. But is seems a limited one since thermal effects, thermal buoyancy, are not taken in consideration. The bubble size distribution is not discussed. SEN geometry neither. The resulting conclusions are sometimes debatable or quite generic. As an example:
“The results of numerical simulation are in good agreement with those of high temperature quantitative measurement, which verifies the accuracy and reliability of numerical simulation.” A single point measurement of velocity gives all that?
“For the DRF, as the argon bubbles can be flushed into the deeper region under the influence of strong jets on both sides, the argon bubbles distribute widely in the mold. For the SRF, as the argon bubbles float up quickly after leaving the side holes, the bubble distribution is more concentrated in the width direction.” Again these flow features are well known.
“Therefore, it is benefit for the surface quality control by use of the mold with 250 thickness than the mold with 180 mm thickness in the production of the automobile exposed panel.” Well, what about if the SEN geometry and depth of immersion are changed. Still true?
The same comments apply to the ABSTRACT.
Author Response
Dear Editor and Reviewers，
We sincerely appreciate you and the reviewers for your insightful, positive and constructive comments and suggestions on our manuscript entitled "Effect of mold thickness on the flow field in slab continuous casting mold by high temperature quantitative measurement and numerical simulation" (Manuscript ID: metals-1446274).
These comments are valuable and very helpful for revising and improving our article, which have the important guiding significance to our research. We have studied comments carefully and have made a major correction which we hope meet with approval. Point-by-point responses to the reviewers’ comments are listed below this letter.
We hope that the revised version of the manuscript is now suitable and acceptable for publication in Metals.
I look forward to hearing from you soon.
Best regards,
Sincerely yours,
Jian YANG
Doctor, Professor
Director of Department of Materials Engineering
Vice Director of State Key Laboratory of Advanced Special Steel
School of Materials Science and Engineering, Shanghai University
Address: Room 517, Rixin Building, School of Materials Science and Engineering,
Shanghai University, 333 Nanchen Road, Baoshan District
Shanghai, 200444, P.R. China
E-mail: [email protected]
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
The authors correctly addressed all the comments and suggestions raised to the manuscript. Also, the change of the paper's title is appropriate.
Reviewer 3 Report
