Abstract:The effects of Nb content on precipitation, microstructure, texture and magnetic properties of primary recrystallized grain-oriented silicon steel were investigated by various methods. The results show that the precipitates in primary recrystallized sheets are mainly MnS, Nb(C,N), composite precipitates of MnS and AlN, and composite precipitates of Nb(C,N) and AlN. Adding niobium could refine the primary recrystallized microstructure. The steel with 0.009 wt% Nb possesses the finest and the most dispersed prec… Show more
“…For an ideal microstructure, the abnormal growth is unlikely to occur in the absence of impurities under a fixed GB energy as discussed in 3.1. The second-phase particles, also known as inhibitors, such as AlN and MnS, have been introduced into silicon steels to trigger the abnormal growth in the industry [ 43 , 44 , 45 ]. Particles diffusely distribute in the microstructure and contribute to the pinning effects on GB movement during grain growth.…”
A phase-field model was revised to study the abnormal growth of Goss grains during the annealing process in Fe-3%Si steels, in which the interaction between the second-phase particles and Goss grain boundaries (GBs) was considered. The results indicate that the abnormal growth of Goss grains occurs due to the different dissolvability of the particles at Goss GBs compared with the other GBs. Moreover, the degree of abnormal growth increases first and then decreases with an increasing particle content. Meanwhile, the size advantage of Goss grain can further promote the degree of abnormal growth. Two types of island grains were found according to the simulated results, which is consistent with the experimental observations. A proper GB dissolvability of particles is the key factor for the formation of isolated island grains, and a higher local particle density at GBs is the main reason for the appearance of serial island grains. These findings can provide guidance for the desired texture control in silicon steels.
“…For an ideal microstructure, the abnormal growth is unlikely to occur in the absence of impurities under a fixed GB energy as discussed in 3.1. The second-phase particles, also known as inhibitors, such as AlN and MnS, have been introduced into silicon steels to trigger the abnormal growth in the industry [ 43 , 44 , 45 ]. Particles diffusely distribute in the microstructure and contribute to the pinning effects on GB movement during grain growth.…”
A phase-field model was revised to study the abnormal growth of Goss grains during the annealing process in Fe-3%Si steels, in which the interaction between the second-phase particles and Goss grain boundaries (GBs) was considered. The results indicate that the abnormal growth of Goss grains occurs due to the different dissolvability of the particles at Goss GBs compared with the other GBs. Moreover, the degree of abnormal growth increases first and then decreases with an increasing particle content. Meanwhile, the size advantage of Goss grain can further promote the degree of abnormal growth. Two types of island grains were found according to the simulated results, which is consistent with the experimental observations. A proper GB dissolvability of particles is the key factor for the formation of isolated island grains, and a higher local particle density at GBs is the main reason for the appearance of serial island grains. These findings can provide guidance for the desired texture control in silicon steels.
“…The macrostructure of finished products is presented in Figure 8 [36]. It can be seen that secondary recrystallization took place in both steels.…”
Section: Resultsmentioning
confidence: 99%
“…In present study, the reheating temperature is only 1180°C, which is much lower than the conventional reheating temperature (1250°C or even 1350°C). This result further indicates that niobium can be used as effective inhibitor formation element and produce high quality Nb-bearing grain oriented silicon steel manufactured by low-temperature slab reheating process. Figure 8. Macrostructure of secondary annealed sheet (a) CGO steel, (b) Nb-bearing GO steel [36]. …”
A comparative study of precipitates, microstructure, texture and magnetic properties between conventional and Nb-bearing grain oriented silicon steel was carried out. The results show that fine and dispersed Nb-bearing particles are formed in Nb-bearing steel and show stronger pinning force during the whole heat treatment process, which makes a significant effect on the microstructure and texture evolution during the preparation process. Compared to conventional grain oriented silicon steel, Nb-bearing steel exhibits finer microstructure and possesses more Goss grains in hot-rolled band and normalized band. In primary recrystallized band, fine and uniform microstructure is presented in Nb-bearing steel, meanwhile, it is also characterized by strong γfiber and {114}<481> texture. After final annealing, Nb-bearing steel shows better magnetic properties, B 800 =1.87 T and P 1.7/50 =1.25 W kg -1 . In summary, niobium can be used as an effective inhibitor formation element to produce high quality Nb-bearing grain oriented silicon steel manufactured by low-temperature slab reheating process.
“…The development of secondary recrystallization has a great impact on the magnetic properties of grain-oriented silicon steel. Many studies [1][2][3][4][5][6][7] have been conducted on the related factors affecting secondary recrystallization, including key element content, precipitate, primary recrystallization structure, high-temperature annealing process, etc.…”
The grain-oriented silicon steels were subjected to gradient heat conduction during high-temperature annealing by using thermal insulation cotton. The macrostructures of samples subjected to circumferential gradient heat conduction showed a “petal-like” morphology with peripheral columnar grains and central equiaxed grains, while samples subjected to transverse gradient heat conduction showed a morphology with approximately 50% columnar grains and 50% equiaxed grains. The grain orientations, magnetic domains as well as magnetic properties in different regions were detected. Results showed that the magnetic induction intensity of cylindrical grains was better than that of equiaxed grains while the iron loss was worse, which indicated that a fast heating rate during high-temperature annealing was conducive to the accuracy of Goss grains. The magnetic domains in columnar grains were wider than the equiaxed grains, which resulted in poorer iron loss. A theory of the competitive growth among secondary Goss grains was proposed. Under the condition of gradient heat conduction, once the Goss grains with the fastest heat conduction grew up abnormally, they would compete with other Goss grains which were supposed to survive in traditional processes and swallow up them until adjacent to the secondary equiaxed grains which were later developed.
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