Evaluation of Mechanical Properties and Microstructure of X70 Pipeline Steel with Strain-Based Design
, Yifan Dong 1, Rutao Li 1, Jinxing Jiang 4, Xiaoyuan Li 2,*, Zhenlong Wang 3,* and Xiurong Zuo 1,*Round 1
Reviewer 1 Report
Review on “Evaluation of mechanical properties and microstructure of X70 pipeline steel with strain-based design” by Liu et al.
Abstract
1. Please quantify where possible. Try to avoid general statements and expose those of your main mechanical findings using numbers.
Introduction
2. The reviewer feels that this subsection does not present the state of the art sufficiently. Please expose the main findings in the field, the knowledge gap and the motivation of your work. Highlight the novelty of your research properly.
Materials and methods
3. Please specify how the chemical composition was measured or add the reference to Table 1.
4. How many sections were used to measure the hardness distribution?
5. The engineering drawings of specimens for mechanical testing would be beneficial (although not mandatory).
6. How the low temperature of the testing specimens was ensured during CVN?
Results
7. The error bars should be provided in Figure 3b. Please add HV10 in the axis description.
8. Figure 3b: What does “far from weld” mean? 50 mm? 100 mm? Be precise. It should be also corrected in the Microstructure section.
9. Table 2: It would be beneficial to put an additional column with the minimal parameters that the pipe needs to meet in terms of strength and ductility requirements. They were not mentioned elsewhere.
10. Could results for CVN and SFA could be compared to the one reported in the literature?
11. Table 3: The CVN results for BM and HAZ have a quite wide range. It surely affects the average value thus it is recommended to perform more tests or add more data to improve the reliability of the tests performed. The conclusions based on just these three measurements per condition are questionable in a presented way.
12. Figure 5: the micrographs are a bit blurry. Please increase the brightness.
13. Lines 167: please avoid words like “smaller, higher, lower”. Quantify where possible. How much smaller these grains were? The same with the hardness in Line 169: decrease of hardness by 10HV/100HV?
14. Lines 178-181: The same comment as above. “From one boundary near FGHAZ to another boundary near SCHAZ in ICHAZ, the volume fraction of martensite/bainite and the size of the ferrite grain decreased gradually by …… and …… respectively with the decrease of the peak temperature of weld process to …….°C (Figure 6c,d), resulting in the further decrease of hardness from……HV to …… HV.” Be precise.
15. Line 187. Line 196. As above.
Discussion
16. Figure 8b: are they any experimental studies or microstructural observations that could confirm the dependence of volume fraction on temperature for the TiN and NbC? Would it be possible to validate these results by comparing such experimental data with model predictions?
17. Lines 241-245 – Since the mechanical properties of HAZ could change significantly, are there any requirements for welds that make them mechanically accepted? In other words, how big differences in the mechanical response could appear to accept the weld in terms of strength?
18. Relate your results to avaiable literature in the field.
Conclusions
19. Please quantify where possible. Try to avoid that something was “smaller/lower/higher” etc. Use numbers/percentages to demonstrate your findings.
The manuscript must be significantly improved before the next submission. The reviewer will reconsider it again after a major revision. Comment 11 should be particularly considered. Professional proofreading is recommended.
Author Response
Please see the attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The article is devoted to the description of quality control of pipes made of X70 steel.
I had questions and comments when reviewing the paper:
1. The introduction is very short and does not contain a description of the problems and features of the work performed earlier by other researchers. Now there are only 9 articles in the introduction of references. This is not enough. It is necessary to give more detailed information about previously performed studies and indicate what need for your studies.
2. Now the work is done as a current quality control of products in serial production in industrial conditions. What is scientific novelty? What technological modes (TMCP) did you change compared to the current ones?
3. In the paper it is necessary to give a description of the technology for manufacturing sheet metal from which the pipe is made.
https://doi.org/10.3390/ma15020501
https://doi.org/10.3390/ma13122839
https://doi.org/10.3390/met12081239
4. The JCOE process needs to be deciphered and a description of the technology for manufacturing a pipe from a sheet should be given. See works: https://doi.org/10.1007/s40436-016-0154-5 https://doi.org/10.4028/www.scientific.net/SSP.316.538
DOI: 10.1115/OMAE2017-61540
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
The paper was improved according reviewers sugestions thus it could be considered for publication.
Reviewer 2 Report
The authors of the article took into account my comments. The article has been corrected. I recommend publishing the article in the presented version.
