In order to develop cold rolled Ti-microalloyed steel strips, the effects of annealing temperature on recrys-tallization behavior of experimental steel were researched by optical microscopy （OM）, transmission electr...In order to develop cold rolled Ti-microalloyed steel strips, the effects of annealing temperature on recrys-tallization behavior of experimental steel were researched by optical microscopy （OM）, transmission electron micros-copy （TEM） and Vickers hardness test. The annealing treatment could be divided into three distinct stages： recovery, recrystallization and grain growth. Reerystallization took place from 933 to 1033 K, during which a large number of recrystallized grains appear and hardness drops sharply. The morphology and size of TiN particles nearly remained unchanged at different stages of processing. With increasing annealing temperature, nanometer precipitates coarsened and the dislocation density was significantly reduced. In comparison with annealing time, annealing temperature was more crucial for recrystallization of cold rolled Ti microalloyed steel. It could be concluded that the pinning force of nanometer particles on dislocations increased the recrystallization temperature. At higher annealing temperature, re crystallization took place because of precipitates coarsening caused by Ostwald ripening.展开更多
In this paper, the response of TiN particles to welding thermal cycle and the kinetic behavior of the grain growth in weld heat-affected zone of the Ti-microalloyed steel have been studied by using the simulation tech...In this paper, the response of TiN particles to welding thermal cycle and the kinetic behavior of the grain growth in weld heat-affected zone of the Ti-microalloyed steel have been studied by using the simulation technology. Based on the theory of the TiN particle dissolution and coarsening kinetic models in weld thermal cycle and some metallographic data from thermal simulated samples, the grain growth diagram of Ti-microalloyed steel is presented. The experimental data from thermal simulated weld samples agreed well with the value of the diagram predicted.展开更多
The influence of cooling rate on microstructural evolution and precipitation behavior in Ti,Ti–Nb and Ti-Mo low-carbon steels during the continuous cooling process was studied by dilatometer method,optical microscopy...The influence of cooling rate on microstructural evolution and precipitation behavior in Ti,Ti–Nb and Ti-Mo low-carbon steels during the continuous cooling process was studied by dilatometer method,optical microscopy,and transmission electron microscopy.The results indicated that austenite transformation temperature decreased with the increasing cooling rate in three steels.The addition of Nb and Mo promoted bainite and martensite transformation and improved the hardenability of steels.In addition,precipitates formed in deformed austenite and ferrite can be observed simultaneously.Deformation in the austenite non-recrystallization zone can introduce a large number of deformation bands,and then,the precipitates preferentially nucleated in these deformation bands.In the following process,randomly distributed precipitates and interphase precipitates will be formed in ferrite.The precipitates formed in deformed austenite obey Kurdjumov-Sachs orientation relationship with the matrix,while the precipitates formed in ferrite obey Baker-Nutting orientation relationship with the matrix.The addition of Nb and Mo in Ti-bearing steels decreased the precipitates size and increased the number density of precipitates and then improved the precipitation hardening.And the effect of Mo addition is more obvious than that of Nb addition.展开更多
文摘In order to develop cold rolled Ti-microalloyed steel strips, the effects of annealing temperature on recrys-tallization behavior of experimental steel were researched by optical microscopy （OM）, transmission electron micros-copy （TEM） and Vickers hardness test. The annealing treatment could be divided into three distinct stages： recovery, recrystallization and grain growth. Reerystallization took place from 933 to 1033 K, during which a large number of recrystallized grains appear and hardness drops sharply. The morphology and size of TiN particles nearly remained unchanged at different stages of processing. With increasing annealing temperature, nanometer precipitates coarsened and the dislocation density was significantly reduced. In comparison with annealing time, annealing temperature was more crucial for recrystallization of cold rolled Ti microalloyed steel. It could be concluded that the pinning force of nanometer particles on dislocations increased the recrystallization temperature. At higher annealing temperature, re crystallization took place because of precipitates coarsening caused by Ostwald ripening.
文摘In this paper, the response of TiN particles to welding thermal cycle and the kinetic behavior of the grain growth in weld heat-affected zone of the Ti-microalloyed steel have been studied by using the simulation technology. Based on the theory of the TiN particle dissolution and coarsening kinetic models in weld thermal cycle and some metallographic data from thermal simulated samples, the grain growth diagram of Ti-microalloyed steel is presented. The experimental data from thermal simulated weld samples agreed well with the value of the diagram predicted.
基金supported by the National Natural Science Foundation of China(Grant No.52004224)the Fundamental Research Funds for the Central Universities(No.D5000200031)China Postdoctoral Science Foundation(2020M683559).
文摘The influence of cooling rate on microstructural evolution and precipitation behavior in Ti,Ti–Nb and Ti-Mo low-carbon steels during the continuous cooling process was studied by dilatometer method,optical microscopy,and transmission electron microscopy.The results indicated that austenite transformation temperature decreased with the increasing cooling rate in three steels.The addition of Nb and Mo promoted bainite and martensite transformation and improved the hardenability of steels.In addition,precipitates formed in deformed austenite and ferrite can be observed simultaneously.Deformation in the austenite non-recrystallization zone can introduce a large number of deformation bands,and then,the precipitates preferentially nucleated in these deformation bands.In the following process,randomly distributed precipitates and interphase precipitates will be formed in ferrite.The precipitates formed in deformed austenite obey Kurdjumov-Sachs orientation relationship with the matrix,while the precipitates formed in ferrite obey Baker-Nutting orientation relationship with the matrix.The addition of Nb and Mo in Ti-bearing steels decreased the precipitates size and increased the number density of precipitates and then improved the precipitation hardening.And the effect of Mo addition is more obvious than that of Nb addition.
