Experimental Research for the Establishment of the Optimal Forging and Heat Treatment Technical Parameters for Special Purpose Forged Semi-Finishes

Round 1

Reviewer 1 Report (Previous Reviewer 2)

Dear Authors:

You state that: "The purpose of this comparative study is to establish the best forging and heat treatment parameters to obtain the best ratio between the mechanical characteristics obtained and the cycle parameters to produce forged semi-finished products."

I expect that the "study to establish th ebest forging and HT parameters " involve a parameter window that put in correlation with results can lead you to the "best production cycle" selection.

Reading more I found: "The novelty of the work is the performance of experimental research on samples of three different brands of steel,  10CrMo9-10, 25CrMo4 and 42CrMo4, subjected to forging and heat treatments under the same experimental conditions."

This is a no-sense: How can You optimise the forging condition if you apply  the same parameters to the three different steels? In fact only one of these 3 steels performs better than the other two...but this is surprising You? It is obvious.

Probably I cannot understand your approach, but this is my concern.

 

Author Response

For Review 1

1. Dear Authors:

You state that: "The purpose of this comparative study is to establish the best forging and heat treatment parameters to obtain the best ratio between the mechanical characteristics obtained and the cycle parameters to produce forged semi-finished products."

I expect that the "study to establish th ebest forging and HT parameters " involve a parameter window that put in correlation with results can lead you to the "best production cycle" selection.

Reading more I found: "The novelty of the work is the performance of experimental research on samples of three different brands of steel, 10CrMo9-10, 25CrMo4 and 42CrMo4, subjected to forging and heat treatments under the same experimental conditions."

This is a no-sense: How can You optimise the forging condition if you apply the same parameters to the three different steels? In fact, only one of these 3 steels performs better than the other two...but this is surprising You? It is obvious.

Probably I cannot understand your approach, but this is my concern.

The purpose of this study was to test under the same identical experimental conditions of forging and heat treatment of three samples made of three different grades of steels 10CrMo9-10, 25CrMo4 and 42CrMo4.

Analyzing the experimental results obtained, it can be seen for which of the three brands of tested steels the best forging and heat treatment parameters are obtained.

The experimental research and results presented in this article represent a small part of an extensive experimental research carried out on several samples of each of the steel grades 10CrMo9-10, 25CrMo4 and 42CrMo4, under various experimental conditions, in order to optimize the processes of forging and heat treatment, for each brand analyzed.

These researches are not the subject of this article, which is why we accept without reservation your observation that what we have presented is a comparative study to identify the brand of steel for which the best results are obtained and not the optimization of the forging and heat treatment processes.

The details of the research for the optimization of these processes are to be done in subsequent works.

I have made the correction in the text of the article according to your observation.

 

Reviewer 2 Report (Previous Reviewer 3)

Accept in present form

Author Response

Thank you for your acceptance.

Reviewer 3 Report (Previous Reviewer 4)

The authors have addressed well most of the explanations. Overall, this is a good study. I supposed it can be considered for publication in Materials.

Author Response

Thank you for your acceptance.

 

Reviewer 4 Report (New Reviewer)

Authors are requested to take the following into account:

Lines: 53-54 ‘’ The mechanical properties of structural constituents are different and therefore, during plastic deformation processes, do not deform evenly.’’

In this claim there is no support coming from other literature works, I suggest to consider the following options: 

1.  Morales-Cruz, E. U., Vargas-Ramírez, M., Lobo-Guerrero, A., Cruz-Ramírez, A., Colin-García, E., Sánchez-Alvarado, R. G., , V.H. Gutiérrez-Pérez, Martínez-Vázquez, J. M. Effect of low aluminum additions in the microstructure and mechanical properties of hot forged high-manganese steels. Journal of Mining and Metallurgy, Section B: Metallurgy, 2023, 00, 7-7.

2.  A. Di Schino, M. Gaggiotti, C. Testani. Heat treatment effect on microstructure evolution in a 7% Cr steel for forging, Metals, 10(6), 808, 2020. DOI: 10.3390/met10060808

3. S. Mengaroni, F. Cianetti, M. Calderini, E. Evangelista, A. Di Schino, H. McQueen. Tool steels: forging simulation and microstructure evolution of large scale ingot. Acta Physica Polonica A, 128(4), 629-632, 2015. DOI: 10.12693/APhysPolA.128.629  

- line 223: SEM is electron scanning microscopy and not scavenging;

- line 380: the following sentence should be reconsidered in English to make it clear and unambiguous. "Considering all these aspects we can relate relatively the superiority of the sample characteristics of 42CrMo4, 380 but it cannot be neglected in use at high semi-finished temperatures of 10CrMo9-10 and the cost of elaboration 381 (forging + thermal treatments) lower than the other samples analyzed.";

- line 357, 366 etc: consider a table to compare the three different steels instead of drowning the test results in the text;

- line 446: velocity (vectorial quantity) should be used insted of speed.

 

Author Response

1. Authors are requested to take the following into account:

Lines: 53-54 ‘’ The mechanical properties of structural constituents are different and therefore, during plastic deformation processes, do not deform evenly.’’

In this claim there is no support coming from other literature works, I suggest considering the following options:

1. Morales-Cruz, E. U., Vargas-Ramírez, M., Lobo-Guerrero, A., Cruz-Ramírez, A., Colin-García, E., Sánchez-Alvarado, R. G., V.H. Gutiérrez-Pérez, Martínez-Vázquez, J. M. Effect of low aluminum additions in the microstructure and mechanical properties of hot forged high-manganese steels. Journal of Mining and Metallurgy, Section B: Metallurgy, 2023, 00, 7-7.
2. A. Di Schino, M. Gaggiotti, C. Testani. Heat treatment effect on microstructure evolution in a 7% Cr steel for forging, Metals, 10(6), 808, 2020. DOI: 10.3390/met10060808
3. S. Mengaroni, F. Cianetti, M. Calderini, E. Evangelista, A. Di Schino, H. McQueen. Tool steels: forging simulation and microstructure evolution of large-scale ingot. Acta Physica Polonica A, 128(4), 629-632, 2015. DOI: 10.12693/APhysPolA.128.629 .

 

Your comments have been taken into account, the three indicated works have been read and cited in the text of the article.

 

2. line 223: SEM is electron scanning microscopy and not scavenging.

 

The text of the article has been corrected according to your suggestion.

 

3. line 380: the following sentence should be reconsidered in English to make it clear and unambiguous. "Considering all these aspects we can relate relatively the superiority of the sample characteristics of 42CrMo4, 380 but it cannot be neglected in use at high semi-finished temperatures of 10CrMo9-10 and the cost of elaboration 381 (forging + thermal treatments) lower than the other samples analyzed.”

 

The respective phrases have been reformulated according to your observation.

 

4. line 357, 366 etc: consider a table to compare the three different steels instead of drowning the test results in the text.

 

Your suggestion has been taken into account and the results have been tabulated in table 13 for two steel brands where possible.

5. line 446: velocity (vectorial quantity) should be used insted of speed.

 

The text of the article has been corrected according to your suggestion.

 

The authors thank the referees for all their comments and suggestions.

All this was done in order to improve and accept the publication of the work.

 

Round 2

Reviewer 1 Report (Previous Reviewer 2)

 

Dear Authors,

thank you for having explained the targets of the paper in so clear way and improved the text.

 As you state in the Conclusions, confirming my opinion, ... it is obvious that one steel is the best performant for some property and some other for another property...this is my concern since the initial review.

In any case the paper is clear, I do not like your approach that is usefull only for some forging shops, but the paper is really well written and I will recommand it for publication.

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.

Round 1

Reviewer 1 Report

1. The results obtained in the manuscript are not discussed fully.

2. The austenitic grain size is 6~7 mm in Table 5, which is much larger than that shown in Fig.4. 

3. The austenitic grain boundary is not clear as shown in Fig.7.  How to determine the austenitic grain size?

4. In the Abstract: This statement is supported by the following aspects: high forgeability; reducing energy consumption; machining by chipping is superior...... There are not sufficient experimental results to support this conclusions.

 

Author Response

1. The results obtained in the manuscript are not discussed fully.

The discussion of the results was completed, according to the reviewers' requirements.

2. The austenitic grain size is 6~7 mm in Table 5, which is much larger than that shown in Fig.4.

The error was corrected, in tables 5, 8 and 1, where the size of the austenite grains, the measurement unit (mm) was wrongly entered.

Figures 3, 7 and 11 were added for Microscopic appearance of austenitic grains for the forged semi-finished product for the three types of steels.

3. The austenitic grain boundary is not clear as shown in Fig.7. How to determine the austenitic grain size?

The method used to highlight the austenitic grain is the method of controlled oxidation and is done as follows:

- A flat face of the sample must be sanded, and the rest must show no signs of oxidation. [9,10]

- The sample is placed in the oven with the surface sanded up and is kept for 1 hour at the austenite temperature provided for each quality of material; then open the oven door and leave the sample in its door for about 10-15 seconds for oxidation, then iron in water. - In the case of significant oxidation, the oxide adhering to the polished surface is easily removed by grinding with a fine sandpaper, after which the sample is attacked with Villella reagent (1 g picric acid, 5 ml hydrochloric acid, 100 ml ethyl alcohol).  

The size index of the austenitic grain is determined on the microscope using a 100x magnification. The determination of the size index of the austenitic grain will be done by the method of comparing with standard images.

4. In the Abstract: This statement is supported by the following aspects: high forgeability; reducing energy consumption; machining by chipping is superior...... There are not sufficient experimental results to support this conclusion.

The conclusions were completely rewritten, based on those presented in the paper.

Reviewer 2 Report

Dear Authors,

The paper structure is confused and misleading.

Please, re-write it paying attention to the introduction/description of the experimental activities and methods adopted/ then discussion that means an original interpretation of your results in comparison with the literature indication or already obtained published results.

Please, report in the “Conclusion chapter” only the Conclusions: you have mixed, experimental/introduction and even some consideration for Discussion…really reconsider the entire paper structure and improve the photo quality.

Only for this reason the paper cannot be accepted, but I recommend to reconsider it after an heavy revised version.

Below some suggestions: 

 

Line 25:  Please, indicate, what the Authors intended for “plasticity properties are superior”. Elongation to rupture? High temperature elongation? Flow Stress? Area ratio to fracture? Thermal cracking susceptibility (directly correlated with plastic elongation and thermal expansion coefficient)?

 Fig.2: Please translate in English all the caption or delete the figure: ..it is not interesting

 Line 90: queuing? What? Quenching?

 

 Move lines 242 -256 to the Experimental these are not a discussion

 Line 89-95: At this point of the paper several questions arises:  All the different steels have been treated with the same thermal cycle and forging history? Please sate this fact. Moreover , are you sure that the forging standard and thermal treatment procedure is the same for the three steels? Please give a reference for the three standards.

Please, give a rationale for this decision? Why the three steels have been treated with the same condition? Or the three steels have been treated with three different cycles and than compared?

 Then, in the conclusion many questions are solved, please reorganise your paper before resubmitting it.

 Line 257: The authors state that: “From an economic and energy consumption, the imposed characteristics were obtained with the lowest costs for 257 steel 10CrMo9-10. The mechanical characteristics obtained are relatively close to the highest.”  It is not sufficient state these: please add details about energy consumption, in terms of energy required (KW) for the three different cycles (indicate in  comparative table the data utilised for reaching such conclusion)

 Line 270-279: these lines are more suited (belongs) more to an introduction not to an analyses of experimental results

 Line 285  - 287 and followings: these are part of the experimental activities.

 Line 293-314: All these line must be moved part to the introduction, part to the experimental

Author Response

Line 25:  Please, indicate, what the Authors intended for “plasticity properties are superior”. Elongation to rupture? High temperature elongation? Flow Stress? Area ratio to fracture? Thermal cracking susceptibility (directly correlated with plastic elongation and thermal expansion coefficient)?

The plasticity characteristics of the analyzed materials were given by the results of elongation at break and elongation at high temperatures.

 Fig.2: Please translate in English all the caption or delete the figure:  .. it is not interesting.

 Figure 2 has been corrected.

 

 Line 90: queuing? What? Quenching?

Rows 91 and 93 have been corrected.

  Move lines 242 -256 to the Experimental these are not a discussion

These lines have been moved to the description of the experienced part.

 Line 89-95: At this point of the paper several questions arises:  All the different steels have been treated with the same thermal cycle and forging history? Please sate this fact. Moreover , are you sure that the forging standard and thermal treatment procedure is the same for the three steels? Please give a reference for the three standards.

Please, give a rationale for this decision? Why the three steels have been treated with the same condition? Or the three steels have been treated with three different cycles and then compared?

 Then, in the conclusion many questions are solved, please reorganise your paper before resubmitting it.

Comparative experimental research was carried out, using samples from three different brands of steel.

The experimental conditions, the forging process, the primary heat treatment and the secondary heat treatment were the same for all types of steels, in order to obtain comparative results.

The work was reorganized according to the requirements and indications of the referees.

 Line 257: The authors state that: “From an economic and energy consumption, the imposed characteristics were obtained with the lowest costs for 257 steel 10CrMo9-10. The mechanical characteristics obtained are relatively close to the highest.”  It is not sufficient state these: please add details about energy consumption, in terms of energy required (KW) for the three different cycles (indicate in  comparative table the data utilised for reaching such conclusion).

The phrase related to energy consumption was excluded, because no values of this energy consumption were recorded.

 Line 270-279: these lines are more suited (belongs) more to an introduction not to an analysis of experimental results.

 Line 285  - 287 and followings: these are part of the experimental activities.

 Line 293-314: All these line must be moved part to the introduction, part to the experimental

The conclusions’ part was completely rewritten according to the reviewers' instructions.

Reviewer 3 Report

1. Please explain the novelty of the current work.

2. Introduction section to be refined with many references and should bring the problem definition.

3. The authors can refer and cite https://doi.org/10.1016/j.jallcom.2021.163451, and https://doi.org/10.1007/s12666-019-01591-6 and strengthen their introduction and discussion.

4. Conclusions are too wordy. Please make it crisp and take the other portions to results and discussion section.

5. Results and discussion to be made more stronger with relevant points.

6. Please check the format of references and include a few more references.

 

Author Response

1. Please explain the novelty of the current work.

The novelty of the work is the performance of experimental research on samples of three different brands of steel, 10CrMo9-10, 25CrMo4 and 42CrMo4, subjected to forging and heat treatments under the same experimental conditions.

The purpose of the research is to find the best relationship between the resulting mechanical characteristics, heat treatment parameters and the requirements of standards and international certification bodies.

Another novelty element is the exact establishment of a technology for the execution of a semi-finished product from 10CrMo9-10 with the best ratio of mechanical characteristics capable of meeting the conditions of international certification DNVGL-RP-0034-SFC2 and NACE MR0175 (maximum 22-23 HRC).

2. Introduction section to be refined with many references and should bring the problem definition.

The introduction has been corrected.

3. The authors can refer and cite https://doi.org/10.1016/j.jallcom.2021.163451, and https://doi.org/10.1007/s12666-019-01591-6 and strengthen their introduction and discussion.

The articles related to the subject of this work were read and cited.

4. Conclusions are too wordy. Please make it crisp and take the other portions to results and discussion section.

The conclusions’ part was completely rewritten according to the reviewers' instructions.

5. Results and discussion to be made more stronger with relevant points.

The results and discussions were corrected and completed.

6. Please check the format of references and include a few more references.

The format has been corrected and more bibliographic references have been added.

Reviewer 4 Report

General review:

 

Overall, the authors tried to present in this paper the experimental results and conclusions obtained after conducting a comparative study on 3 samples of forged semi-finished products from the steel brands 10CrMo9-10, 25CrMo4 and 42CrMo4. These are common heat-resistant alloy steels used in various industries nationally and internationally. The purpose of this comparative study is to establish the best forging and heat treatment parameters to obtain the best ratio between the mechanical characteristics obtained and the cycle parameters to produce forged semi-finished products. Following experimental research, the best material was determined by analyzing the results obtained for the mechanical characteristics (tests according to DNVGL-RP0034-SFC2 and NACE MR0175 hardness 207-235 HBW), austenitic grain size, structure, and production costs for the 3 types of steels. The authors determined that among the three analyzed materials, 10CrMo9-10 behaves best. This statement is supported by the following aspects: high forgeability; reducing energy consumption; machining by chipping is superior because the stresses in the piece are partially eliminated; plasticity properties are superior. However, before it can be published, I have some questions about this article and some suggestions:

 

Minor review:

 

1.     For Introduction, the first and second paragraphs are too general. I strongly recommend to mention more details about the materials.

 

2.     In Experimental, the authors should mention the forging conditions for these materials in details. In addition, why did you use these specific heat treatment conditions?

 

3.     For Results and discussion, you should mention the relationships between the mechanical properties and microstructures of the three materials according to the heat treatment conditions. I strongly recommend to read and cite the manuscript, “Additive manufacturing of a shift block via laser powder bed fusion: the simultaneous utilisation of optimised topology and a lattice structure”.

 

4.     In the lines 107-108 in page 3, for a more detailed example about the application, you should read and cite this paper, “Additive manufacturing of a shift block via laser powder bed fusion: the simultaneous utilisation of optimised topology and a lattice structure”.

 

5.     Do not refer and replace the old references of more than 10 years.

Author Response

1. For Introduction, the first and second paragraphs are too general. I strongly recommend mentioning more details about the materials.

The first two paragraphs from the introduction were removed and replaced,  details about the materials used are presented in point 2. Materials and method, 2.1. Materials.

2. In Experimental, the authors should mention the forging conditions for these materials in details. In addition, why did you use these specific heat treatment conditions?

The forging method and the type of thermal treatments were presented in point 2.2. 2.2. Method.

The recommended heat treatment conditions were used   for these steel brands.

3. For Results and discussion, you should mention the relationships between the mechanical properties and microstructures of the three materials according to the heat treatment conditions. I strongly recommend to read and cite the manuscript, “Additive manufacturing of a shift block via laser powder bed fusion: the simultaneous utilisation of optimised topology and a lattice structure”.

It was mentioned in the conclusion point that:

The variation of austenitic grain size depends on the concentration of alloying elements and temperature, for the benchmark forged at 1150 oC from 42CrMo4 a coarse structure consisting of lamellar pearlite, bainite and ferrite in reduced proportions was found.

The final value of the mechanical characteristics depends on the type of operations in the technological flow: free forging, the type of primary heat treatment, the type of secondary heat treatment but also the chemical composition and alloying elements of the steels used.

4. In the lines 107-108 in page 3, for a more detailed example about the application, you should read and cite this paper, “Additive manufacturing of a shift block via laser powder bed fusion: the simultaneous utilisation of optimised topology and a lattice structure”.

The bibliographic work indicated by the reviewers was read and cited.

5. Do not refer and replace the old references of more than 10 years.

The references were corrected and completed, according to the instructions of the referents.

Round 2

Reviewer 1 Report

1. The results obtained in the manuscript revised are still not discussed fully.

2. There are not sufficient experimental results to support the conclusions in the Abstract. 

Reviewer 2 Report

Dear Authors,

the paper still remain very similar to a technical report. there are still grey zone that are not clear.

Just some of these are here reported, but other were negletted.

Line 34: delete this sentence:  For this brand of steel, the plasticity properties (elongation at break and 34 elongation at high temperature) are superior.

It is very surprising that the Authors still continue to use general words such as: plasticity properties  and indicate only the “elongation at break” (without any further detail: room or what temperature? Moreover, they continue to use the word “High temperature” without any indication of what they mean with ”high temperature”? Where are the results of the tensile tests at high temperature ?  Please, delete this sentence.

Traction Tests? probably "tensile tests".

Line 105: the recovery  range indicated is not acceptable: the range 540-680°C is to large. There are differences between recovery carried on at 540°C and 580°C…so the result scan be affected by this very large range adopted.

So without any other detail indicated in the paper: the results can be due to a not enough precise control of recovery temperature.

Moreover the impact tests have been carried at three different values: - 46, -29, -60 °C why?

Reviewer 3 Report

The following corrections were not incorporated.

1. Please explain the novelty of the current work. This should be added in introduction.

2. The authors can refer and cite https://doi.org/10.1016/j.jallcom.2021.163451, and https://doi.org/10.1007/s12666-019-01591-6 and strengthen their introduction and discussion.

This is not incorporated. 

3. Fig.11. Microscopic appearance of austenitic grains for the forged semi-finished product 42CrMo4 [1]

Is this the authors own image or taken from ref [1]. ?? If so, did the authors get copyright permissions for the same?

Where is the micron marker for the image inserted?

4. Fig.11 14. EDS spectrum and spot chemical analysis in selected area for 42CrMo4sample. Please name each figure separately to make it easy for the readers.

5. The authors have made lot of inappropriate self citations especially (Valentina Caloian et al). This is not right and has to be removed. 

I will recommend rejection if these changes are not done meticulously.