Seminar & Colloquium
세미나가 취소 되었습니다.
[세미나: 12월 15일(목), 오후 4시] Prof. Zhenghua Tang, Sichuan University
Title
Optimising the transformation and mechanical properties of V-Nb-Ti micro-alloyed low carbon line pipe steels through alloy and microstructural control
Speaker
Prof. Zhenghua Tang, School of Materials Science & Engineering, Sichuan University
Education
- 1979-1983 Chengdu University of Science & Technology*, under-graduate student
- 1985-1988 Chengdu University of Science & Technology, post-graduate student
- 2002-2006 University of Pretoria (South Africa), PhD student
* Chengdu University of Science & Technology was renamed Sichuan University
Professional Experience
- 1983-1985 Chongqing Instrument Materials Research Institute, technician
- 1988-2002 Sichuan University
- 2006 to date Sichuan University
| Date | Thursday, December 15th, 2022
| Time | 16:00 ~
| Venue | 33동 223호 (동부 세미나실)
[Abstract]
A low ratio yield strength to ultimate tensile strength (YS/UTS) is necessary for the safety of pipelines and this means a higher resistance to strain hardening during deformation is required. Thinner walled (about 6 mm thickness) line pipe steels for smaller diameter pipelines tend to have a relatively high ratio of YS/UTS of 0.93 or higher. This study focused on the effect of the microstructures, prior deformation in the austenite, cooling rate, coiling simulation and the additions of some micro-alloying elements V-Nb-Ti on the precipitates and YS/UTS ratio of line pipe steels. These researches included the experimental alloys smelt, simulation of the controlled hot rolling process, the determination of the strain-free as well as the strain affected continuous cooling transformation (CCT) diagrams, phase and precipitates identification and quantitative assessment of the microstructures by optical microscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM).
The transformed microstructures of the alloys were a mixture of acicular ferrite, pearlite plus polygonal ferrite and the volume fraction of acicular ferrite varied from 46.3% to 55.4%. The interface between acicular ferrite and polygonal ferrite was clearly revealed. The non-recrystallisation temperature (Tnr) was also determined through compression testing in order to design the controlled hot rolling process for the experimental alloys. Acicular ferrite in the present study, was typically of two types. The more typical acicular ferrite structure consisted of parallel laths, while the alternative type consisted of interwoven laths. A high density of dislocations was observed inside the laths, with no cementite inside or between these laths. It was determined that the YS/UTS ratio was a function of the microstructure, prior deformation in austenite, but not sensitive to cooling rate. The precipitate was affected by coiling temperature, finishing rolling temperature.
| Host | 한흥남 교수 (02-880-9240)
Title
Optimising the transformation and mechanical properties of V-Nb-Ti micro-alloyed low carbon line pipe steels through alloy and microstructural control
Speaker
Prof. Zhenghua Tang, School of Materials Science & Engineering, Sichuan University
Education
- 1979-1983 Chengdu University of Science & Technology*, under-graduate student
- 1985-1988 Chengdu University of Science & Technology, post-graduate student
- 2002-2006 University of Pretoria (South Africa), PhD student
* Chengdu University of Science & Technology was renamed Sichuan University
Professional Experience
- 1983-1985 Chongqing Instrument Materials Research Institute, technician
- 1988-2002 Sichuan University
- 2006 to date Sichuan University
| Date | Thursday, December 15th, 2022
| Time | 16:00 ~
| Venue | 33동 223호 (동부 세미나실)
[Abstract]
A low ratio yield strength to ultimate tensile strength (YS/UTS) is necessary for the safety of pipelines and this means a higher resistance to strain hardening during deformation is required. Thinner walled (about 6 mm thickness) line pipe steels for smaller diameter pipelines tend to have a relatively high ratio of YS/UTS of 0.93 or higher. This study focused on the effect of the microstructures, prior deformation in the austenite, cooling rate, coiling simulation and the additions of some micro-alloying elements V-Nb-Ti on the precipitates and YS/UTS ratio of line pipe steels. These researches included the experimental alloys smelt, simulation of the controlled hot rolling process, the determination of the strain-free as well as the strain affected continuous cooling transformation (CCT) diagrams, phase and precipitates identification and quantitative assessment of the microstructures by optical microscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM).
The transformed microstructures of the alloys were a mixture of acicular ferrite, pearlite plus polygonal ferrite and the volume fraction of acicular ferrite varied from 46.3% to 55.4%. The interface between acicular ferrite and polygonal ferrite was clearly revealed. The non-recrystallisation temperature (Tnr) was also determined through compression testing in order to design the controlled hot rolling process for the experimental alloys. Acicular ferrite in the present study, was typically of two types. The more typical acicular ferrite structure consisted of parallel laths, while the alternative type consisted of interwoven laths. A high density of dislocations was observed inside the laths, with no cementite inside or between these laths. It was determined that the YS/UTS ratio was a function of the microstructure, prior deformation in austenite, but not sensitive to cooling rate. The precipitate was affected by coiling temperature, finishing rolling temperature.
| Host | 한흥남 교수 (02-880-9240)