Recrystallization Behavior of Warm Rolling and Cold Rolling Cr-Ti-B Steel during Annealing

Round 1

Reviewer 1 Report

This paper presents the recrystallization texture evolution of Cr-Ti-B steel during annealing and contains some interesting results, but the following points should be reconsidered.

1) There are some misunderstandings in this paper. For instance, the authors described “recrystallized γ grains (Page 2, Line 48)” and “recrystallized α grains (Page 2, Line 54)”. It is likely that recrystallized γ grain means “recrystallized austenite grain” and recrystallized α grain also means “recrystallized ferrite grain”. Therefore, the authors should describe “γ-fiber” and “α-fiber”.

2) In the section 1 (Introduction), the reason for the addition of B in this study is unclear. The authors should explain the role of B on recrystallization texture evolution.

3) In the section 2 (Materials and Methods), is the annealing temperatures in the ferrite single-phase region? The authors should describe the Ac₁ and Ac₃ temperatures.

4) The authors should explain the method for judging the nucleation site. For instance, the authors described that Goss grains nucleated at shear band and were hardly observed at grain boundaries.

5) The authors insisted that recrystallization nucleation at grain boundary is the main mechanism because of the weakening of Goss texture. However, it appears that the authors cannot insist for sure. For instance, the number of recrystallized grains at each site is unknown, and this is important information for discussing the recrystallization mechanism. The authors should explain the recrystallization mechanism in more detail.

6) The conclusions are too sketchy. In particular, third sentence should be mentioned in more detail. For instance, the role of shear bands on recrystallization texture evolution is not clearly mentioned.

Author Response

Title: Recrystallization behavior of warm rolling + cold rolling Cr-Ti-B low-carbon steel during annealing

Manuscript ID: metals-1800357

Thank you very much for taking time to review this manuscript.

We truly appreciate all your comments and suggestions and have thoroughly revised the submission. The modified parts of the paper have been marked with yellow. Detailed information regarding the revisions is provided as follows:

1) There are some misunderstandings in this paper. For instance, the authors described “recrystallized γ grains (Page 2, Line 48)” and “recrystallized α grains (Page 2, Line 54)”. It is likely that recrystallized γ grain means “recrystallized austenite grain” and recrystallized α grain also means “recrystallized ferrite grain”. Therefore, the authors should describe “γ-fiber” and “α-fiber”.

Reply: Thank you for pointing it out. We have been corrected it.

2) In the section 1 (Introduction), the reason for the addition of B in this study is unclear. The authors should explain the role of B on recrystallization texture evolution.

Reply: Thank you for pointing it out. The addition of B is beneficial to promote shear bands. Timokhina^[1] found that Cr-Ti-B steel would generate more shear bands during warm rolling. Therefore, Cr, Ti and B elements are added to obtain many shear bands in warm rolling.

[1] Timokhina, I.B.; Nosenkov, A.I.; Humphreys, A.O. Effect of Alloying Elements on the Microstructure and Texture of Warm Rolled Steels, ISIJ. INT. 2004, 44, 717-724.

3) In the section 2 (Materials and Methods), is the annealing temperatures in the ferrite single-phase region? The authors should describe the Ac1 and Ac3 temperatures.

Reply: Thank you for pointing it out. The annealing temperature in the experiment is in the single-phase region. The temperatures in Ac1 and Ac3 are 771.9℃ and 923.4℃ respectively, which have been added in the article.

4) The authors should explain the method for judging the nucleation site. For instance, the authors described that Goss grains nucleated at shear band and were hardly observed at grain boundaries.

Reply: Thank you for your advice. The shear band is located in the grain and is generally 45 ° from the rolling direction, so the recrystallization of nucleation in the shear band also has the same characteristics. Grain boundary nucleation can be clearly observed that recrystallization nucleates along grain boundaries. We have added in the article.

5) The authors insisted that recrystallization nucleation at grain boundary is the main mechanism because of the weakening of Goss texture. However, it appears that the authors cannot insist for sure. For instance, the number of recrystallized grains at each site is unknown, and this is important information for discussing the recrystallization mechanism. The authors should explain the recrystallization mechanism in more detail.

Reply: Thank you for good suggestion! We cannot say that recrystallization nucleation is the main mechanism. Both shear band nucleation and grain boundary nucleation play an important role in the recrystallization mechanism. At the initial stage of recrystallization, the shear band and grain boundary nucleated simultaneously, and Goss and {111} textures were appeared. With the increase of annealing temperature, the shear band first completely recrystallized, and then Goss grains began to grow. There is a high grain boundary mobility between Goss texture and {111} texture, so Goss grains grew by swallowing the surrounding {111} deformed matrix. This caused the enhancement of Goss texture and the weakening of {111} texture with the increase of annealing temperature. When the grain boundary was completely recrystallized, {111} grains increased and competed with Goss grains, which weakened Goss texture.

6) The conclusions are too sketchy. In particular, third sentence should be mentioned in more detail. For instance, the role of shear bands on recrystallization texture evolution is not clearly mentioned.

Reply: Thank you for your advice. The conclusion has been corrected again in article.

Based on warm rolling and cold rolling Cr-Ti-B low carbon steel, three different re-crystallization nucleation sites were observed. The effects of different deformed micro-structures or nucleation positions on the final recrystallization texture were investigated.

(1) Compared with warm rolling process, warm rolling + cold rolling process can obtain stronger {111} deformation texture, which is conducive to the retention of {111} texture strength during annealing.

(2) Due to high dislocation density and the nucleation mechanism of merging of slender subgrains, recrystallization generally nucleated preferentially at the shear band. The recrystallization nucleated at the shear band was mainly Goss orientation, which was due to the existence of Goss subgrain. There is a high grain boundary mobility between Goss texture and {111} texture, so Goss grains grow by swallowing the surrounding {111} deformed matrix at the initial stage of recrystallization.

(3) The preferential recrystallization of grain boundaries was observed because of the high grain boundary energy. Although the recrystallization nucleation mechanism of the shear band and grain boundary was the subgrain combination, the recrystallization nucleation of the shear band was faster because of its slender subgrain. The texture component of recrystallization nucleation on grain boundaries was mostly {111}. Therefore, {111} texture was enhanced, and Goss texture was weakened after complete recrystallization.

(4) During the annealing process, recrystallization in deformation bands was observed at higher annealing temperatures. The recrystallization nucleation in deformation bands was much slower than that in shear bands and at grain boundaries. This is because recrystallization occurred easily at grain boundaries due to large distortion, and recrystallization occurred in shear bands prior to deformation bands due to the special nucleation mechanism.

Please see the attachment

Author Response File: Author Response.pdf

Reviewer 2 Report

The article is devoted to the study of the behavior of low-carbon steel during recrystallization after warm and cold deformation. The article is very well-written and has high-quality illustrations.

However, when reviewing the paper, I had several questions and comments to the authors:

1. What is the scientific novelty of research? The paper contains many References over 15 years old and only one article from 2021. What previously unknown results did you get in this study? This should be stated in more detail in the conclusions.

2. There is no description of equipment for rolling and annealing in the Materials and Methods. You need to add this information.

3. What justifies the recrystallization annealing time of 2 s? "The rolled plates were heated to 660, 680, 700, 720 and 740 ℃ at a heating rate of 10 ℃/s, held for 2 s, and then cooled with water to room temperature." It's not a mistake?

4. What is the rationale for choosing a warm rolling temperature of 450℃?

Author Response

Title: Recrystallization behavior of warm rolling + cold rolling Cr-Ti-B low-carbon steel during annealing

Manuscript ID: metals-1800357

Thank you very much for taking time to review this manuscript.

We truly appreciate all your comments and suggestions and have thoroughly revised the submission. The modified parts of the paper have been marked with yellow. Detailed information regarding the revisions is provided as follows:

1. What is the scientific novelty of research? The paper contains many References over 15 years old and only one article from 2021. What previously unknown results did you get in this study? This should be stated in more detail in the conclusions.

Reply: Thank you for for pointing it out! The traditional hot-rolled low carbon steel is annealed after warm rolling or cold rolling, but the annealed plate has a strong Goss texture, which is not conducive to deep drawing performance. There are many reports on the annealing process of cold rolling or warm rolling in the literature. In this article, we carried out technological innovation by adding cold rolling based on warm rolled low carbon steel and found that the annealed Goss texture was significantly weakened. At present, there is a lack of research on recrystallization of warm rolled + cold rolled low carbon steel. Some literatures describe the recrystallization of shear bands or grain boundaries during annealing, but there is no systematic summary of the recrystallization behavior at different locations throughout the annealing process.

2. There is no description of equipment for rolling and annealing in the Materials and Methods. You need to add this information.

Reply: Thank you for pointing out this deficiency. We have added it.

3. What justifies the recrystallization annealing time of 2 s? "The rolled plates were heated to 660, 680, 700, 720 and 740 ℃ at a heating rate of 10 ℃/s, held for 2 s, and then cooled with water to room temperature." It's not a mistake?

Reply: We anneal on the thermal simulator and set the holding time to homogenize the temperature. For example, in the thermal compression experiment of the thermal simulator, the sample will be hold for several seconds when heated to a certain temperature to ensure that the temperature is homogenized before compression.

4. What is the rationale for choosing a warm rolling temperature of 450℃?

Reply: According to our previous article, warm rolling at 450 ℃ is beneficial to obtain more shear bands.

[1] Huang A, Wang Z, Liu X, et al. Dynamic strain aging and serrated flow behavior of Cr-Ti-B low carbon steel during warm deformation[J]. Materials Characterization, 2021, 172: 110828.

Please see the attachment

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Corrections have been done.

Reviewer 2 Report

The authors of the article gave exhaustive answers to my questions. Made changes to the paper according to my comments. I recommend publishing the article in the presented version.