Temporal Evolution of Inclusions in Pipeline Steel: An Industrial Study via Robotic Sampling During Vacuum Degassing

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The manuscript deals with the evolution, kinetics, and transformation mechanisms of non-metallic inclusions in pipeline steel during the VD process based on an industrial study using robotic sampling. The topic is highly relevant due to the increasing demand for pipeline steels and the limited number of studies focusing specifically on inclusion evolution during VD. The authors attempt to reveal the dynamic evolution of inclusion composition, size distribution, and morphology during the VD process, which is a valuable contribution. The industrial-scale dataset and the application of robotic sampling are notable strengths compared with other studies on this topic. The results are meaningful for process optimization and inclusion control in practical steelmaking. Most conclusions are supported by the results, but several interpretations require additional evidence. Some corrections and clarifications are required. Major revision is needed.

 

General Comments:

– On the positive side, the continuous sampling during VD provides valuable insight into inclusion evolution. The observed trends in inclusion coarsening and Ca-modification are generally consistent with steelmaking practice.

– Some mechanistic explanations in five-stage inclusion evolution model are not proved, especially those related to inclusion liquefaction, fragmentation, Ostwald ripening, and over-modification stages. These interpretations should be strengthened by clearer comparison between experimental observations and hypotheses, as well as supported by appropriate references.

– Clearly articulate in the Introduction: What is fundamentally new in the study? How robotic sampling changes the current understanding of inclusion evolution during VD?

– The discussion of slag basicity fluctuations is reasonable, but the link between slag composition and inclusion modification remains largely qualitative. Expand this section with thermodynamic or kinetic justification highlighting the link.

 

I also highlighted some comments and questions according to the manuscript.

Line 23. ECD. The first-mentioned abbreviation should be deciphered.

Line 26. The abbreviations shouldn’t be used as keywords. Correct it.

Line 36-38. Please briefly introduce the RH process in one or two sentences for non-specialist readers.

Line 46-48. Please briefly introduce the VD process in one or two sentences for non-specialist readers.

Line 96, 99, 106. Indicate the devices for chemical analysis, SEM and XRF analysis according to MDPI requirements (instrument model, manufacturer, location).

Line 106. Indicate the sample preparation method for XRF analysis.

Line 108-112. Please, give characteristics of the correction in more detail. How sensitive were the experimental results to this correction?

Line 129. Fig. 3. Error bars are missing, add them.

Line 132-135. It is more suitable for Materials and Methods Section. Method of temperature measurement and model of the device should be added.

Line 143-145. Confirm by a relevant reference that the lighter color hue can be due to FeO/MnO reduction with their minor content.

Line 148-167. Two paragraphs are largely repetitive. Remove one of them.

Line 168. Table 2. Please clarify whether slag samples adhered to the probe are fully representative of bulk top slag. Possible sampling effects should be discussed.

Line 268, 278, 291. Fig. 9-11. The figures have similar titles. Correct the captions.

Line 279. Provide formula for ECD. Explain the choice of this parameter rather than another.

Comments on the Quality of English Language

The manuscript requires minor English language editing.

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

This article deals with steel production and processing. It describes in detail the issue of steel degassing in secondary metallurgy. The article is interesting from a technical point of view, but I have a few questions about the graphics.

Table 1 – Alt, what is it?

 

The reference to Figure 3 is on line 88, but the image itself is on line 128, which is not graphically well organized.

 

Very nicely labeled types of non-metallic inclusions

 

2.3. Chemical and Microstructural Analysis – please add images of the microstructural analysis of the samples. The composition of the inclusions was examined, but no microscope images are provided for comparison.

 

3. Results and Discussion

3.1. Variation in Molten Steel Composition

Put the resulting hydrogen, oxygen, nitrogen, and sulfur contents in a clear table. The contents are unclear in the text. Gas contents are usually marked in ppm.

 

3.3. Variation in Top Slag Figure 5 should be supplemented with EDS analysis of slag samples.

 

3.4.1. Scanned Area of Specimens – again, no SEM-EDS analyses are provided. Please add them.

 

 

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

The study investigates the dynamic evolution of non-metallic inclusions in low-carbon alloy pipeline steel during the Vacuum Degassing (VD) process. Using an automated sampling robot to extract samples during vacuum treatment, the authors tracked changes in molten steel chemistry, temperature, and inclusion morphology and composition.

Strengths

• Novel, interesting methodology This allows for faster sampling during the degassing phase than conventional, closed systems.
• Comprehensive Characterization: The study employs multiple analytical techniques,
• Practical Industrial Relevance.

 

Weaknesses

• Assumptions in Thermodynamic Correction: While other authors use the same approximation it still is a simplification
• Source of Calcium Enrichment: The authors attribute the inclusion modification to calcium "likely originating from slag entrapment... or interactions with the ladle lining". While plausible it is better if this source is clearly demonstrated (mass balance or tracer study might be usable...

• Figure Labeling Consistency: Figures 9, 10, and 11 all share the exact same caption: "Average composition change of inclusions during refining". It appears to be a copy-paste l error in the manuscript.

Author Response

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Author Response File: Author Response.pdf

Reviewer 4 Report

Comments and Suggestions for Authors

is a technical article on the temporal evolution of inclusions during vacuum degassing in steel pipelines. However, there are some aspects that warrant further review.

a) The authors should analyze the reproducibility of the results, improving the discussion.

b) Table 2 should indicate that the composition is by weight.

c) Table 3 is unnecessary. Add a comment in the text indicating that the scanned area is between 30 and 32.

d) Average values ​​in several figures. I recommend adding a bar with the statistical deviation of the results. How many experiments were conducted? 

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The authors have addressed all the comments and made the necessary revisions to the manuscript. I have no further comments on the revised version. The manuscript can be recommended for publication.

Reviewer 2 Report

Comments and Suggestions for Authors

The author has edited and added the requested information. The article is acceptable for publication.

Reviewer 4 Report

Comments and Suggestions for Authors

The authors modified the manuscript taking into account the comments of the reviewer.
The authors add new references.

The quality and soundness of the manuscript has been improved.
Thus, I recommend the publication