Nodule Count, End of Solidification Cooling Rate, and Shrinkage Porosity Correlations in High Silicon Spheroidal Graphite Iron

Round 1

Reviewer 1 Report

The article presents a vital topic, nowadays SSDI is used in highly responsible places, such as offshore wind turbines so the improvement of its properties is desirable. The submission is written coherently, the literature overview is extensive and sufficient, it shows the issue from different sides.

I really liked reading this article, it was interesting, in my opinion it is ready for publishing. Nevertheless, I have a question and a suggestion.

Why didn’t you show the characteristic crystallisation temperatures (Tl, TE_start, TE_low, TE_high, TS) obtained with each inoculant? Was there no correlation between used inoculant and those temperatures or you just decided not to add them?

I suggest adding regression formulas as well as R² to all curves in Figure 7.

Best regards!

Author Response

First of all, thank you very much for your time and for your work to improve the paper. Regarding to your comments:

The main objective of the paper is to relate the quantifying the size of microporisity in SG iron with the chemical composition of inoculant used, more than with the characteristic crystallization temperatures (although I am sure that it would be interesting). In any case, the paper was complemented with other work published in AFS 2021 with industrial results, where the influence of parameters such as recalescence, pouring temperature and maximum cooling rate have been considered.

Regression formulas (R²) were included in Fig. 7

Reviewer 2 Report

The authors will find a small number of suggested corrections below and in the annotated attached file.

1. Line 31, from.
2. Label the line of solidus temperature and TE-low in figure 3.
3. For easier understanding I suggest to ad in text green and red line as labeled in attached file.
4. Improve the sentence in line 75 regarding production of SG. Also ad (LG).
5. Line 88, references for „recent work“ are missing at the and of the sentence.
6. Line 91, who supports Campbell? There are references at the end but I suggest to rewrite the sentence for easier understanding.
7. Line 128, please explain why did you chose these examples.
8. Line 145, 1.8Ce.
9. Figure 5. N/mm² has to be changed to for example Nod./mm². N/mm² is a SI unit for strength.
10. Line 164, Figure 6. What if there is more or les porosity 5 mm above or below? Why did you cut in the middle? Please give additional explanation in Experimental procedure part.
11. Line 175, increase is maybe better then acceleration.

Comments for author File: Comments.pdf

Author Response

First of all, thank you very much for your time and for your work to improve the paper. Regarding to your comments:

1.Done (changed form by from)

2.The figure is quoted from ref.[3]. As a quote it can not be modified. The relevant temperatures are shown on Fig.2

3.Done (green line and red line was added in the text in lines 66, 67 and 70) 

4. LG is added in line 73. "Normal production" is changed by "the ordinary manufacturing of "in line 77.

5.Reference has been added.

6.The references in the text all support Campbell's theory.

7. It is not neccesary to include the cooling curves of all samples, so we have chosen those where the cooling curves and their first derivatives are easily identified.

8. Ce is added. Done

9. Done

10. We have not mentioned any related to the length of porosity, only %porosity which should be as low as possible. The samples were cut because we need a flat surface, sanded and polished in order to apply the 2D analysis with image J to measure the porosity, and the middle of the sample is the place where probably the shrinkage is higher. The sentence " The TA cups were sectioned by the middle with the objective to detect higher shrinkage" was added in the text in Experimental Procedure (line 118)

11. Change done

Reviewer 3 Report

1. Could the author better elaborate on how to determine the end of the solidification point? Was Ts used as the point as end of solidification?
2. Fig 4b, y axis title unit, change C/s to oC/s
3. It should be made clear about the CRmax was determined not using the min of the entire 1st derivative curve. It was the value from the 2nd valley from the curve.  
4. The graphite nucleation may happen in multiple waves (Dr. Lekakh did some study on this). There may be early nucleation and later nucleation events, which leads to graphite nodule size distribution to have multiple peaks. The higher nodule count sample same to have improved later graphite nucleation. Did you see these (smaller later formed graphite nodules) are contributing better to the mitigation of shrinkage?
5. Continue on my question 4, may be the fading effect of different type of addition should be considered in the result of higher fraction of later graphite nucleation (smaller nodules). Like Ce?

Author Response

First of all, thank you very much for your time and for your work to improve the paper. Regarding to your comments:

1.Yes. The end of solidification is determined by the solidus temperature

2.Done

3.It is already included in teh text on line 171 as "the maximum cooling rate at the end of solidification (CR_max)"

4. We could not find nucleation waves as suggested by Lekakh. According to our results, the nucleation of spheroidal graphite follows a monotonic trend with only one maximum on the size distribution curve, so none of inoculants produced a second nucleation wave. With the exception of sample no inoculated, all the samples present the maximum higher frequency of nodule distribution for nodule diameters of 5-10μm which seems to be related with low porosity (see Fig. 7b), so it is factible to assume that the smaller later formed graphite nodules contribute better to the mitigation of shrinkage.

5.Yes, this is an interesting thought. Unfortunately, in this research we were unable to evaluate the effect of time over the nodule count (fading)