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Investigation of Microstructure and Mechanical Properties after Performing Cold Rolling and Annealing on Severely Deformed Low Carbon Steel

Jafari, Zahra | 2023

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 56752 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Kazeminezhad, Mohsen
  7. Abstract:
  8. According to the conducted research, severe deformation of low-carbon steel sheets using the constrained groove pressing method causes a decrease in grain size and increases the strength and hardness of the sample after one pass. However, continuing this process in subsequent passes does not significantly increase strength and hardness, and sometimes it remains constant. Therefore, in this project, cold rolling has been used to improve the strength of the steel sheet and improve the surface smoothness of the final piece. After severe deformation and rolling due to the high applied strain, the strength of the sample increased and the percentage of its elongation decreased. Therefore, annealing was used to improve the ductility of the rolled sample without a significant decrease in strength. In this study, samples were grooved pressed to reduce the cross-sectional area by 30, 50, and 70 percent, and then annealed at three temperatures of 400, 500, and 600 degrees Celsius for 20 minutes. To investigate the effect of severe deformation, the primary sheet was rolled and annealed without grooved pressing. After each operation, hardness testing, tensile testing, and optical microscopy were used to study the mechanical properties and microstructure of the samples. The optimal sample was the sample with 50 percent deformation rolled and annealed at 400 degrees Celsius, where the strength of the sheet increased from 323 megapascals to 605 megapascals, and the percentage of its elongation decreased from 47 percent to 9.5 percent. This is while recrystallization occurs at higher temperatures, and the strength of the sample decreases significantly. Furthermore, this research has shown that the effect of severe deformation on the properties and microstructure of samples that are heavily strained by cold rolling is minimal
  9. Keywords:
  10. Low Carbon Steel ; Cold Rolling ; Annealing ; Microstructure ; Mechanical Properties ; Severe Plastic Deformation ; Constrained Groove Pressing (CGP)

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