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Effect of Decarburization Annealing Process on Microstructure and Texture of Niobium-containing Hi-B Steel

  • Time of issue:2018-10-22 18:40

(Summary description)With the help of infrared carbon-sulfur analysis and EBSD technology, the carbon content and texture changes of Niobium-containing Hi-B steel after different decarburization annealing processes were studied.   Cold-rolled oriented silicon steel is a ferrosilicon soft magnetic material with {110}<001> texture (Goss texture). Its production equipment is complex and the production process is strict. It is known as the "artwork" of steel materials.

Effect of Decarburization Annealing Process on Microstructure and Texture of Niobium-containing Hi-B Steel

(Summary description)With the help of infrared carbon-sulfur analysis and EBSD technology, the carbon content and texture changes of Niobium-containing Hi-B steel after different decarburization annealing processes were studied.   Cold-rolled oriented silicon steel is a ferrosilicon soft magnetic material with {110}<001> texture (Goss texture). Its production equipment is complex and the production process is strict. It is known as the "artwork" of steel materials.

  • Categories:Industry News
  • Author:Wang Junyang, Jia Juan et al
  • Origin:&#034;Journal of Wuhan University of Science and Technology&#034;
  • Time of issue:2018-10-22 18:40
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  With the help of infrared carbon-sulfur analysis and EBSD technology, the carbon content and texture changes of Niobium-containing Hi-B steel after different decarburization annealing processes were studied.

  Cold-rolled oriented silicon steel is a ferrosilicon soft magnetic material with {110}<001> texture (Goss texture). Its production equipment is complex and the production process is strict. It is known as the "artwork" of steel materials. In recent years, domestic and foreign researchers have devoted themselves to exploring new low-temperature solid solution inhibitors. Studies have shown that the nano-scale Nb (C, N) precipitates formed in the Nb-containing oriented silicon steel not only have a lower solid solution temperature and stability, but also when used as an inhibitor, it can effectively inhibit the re-regeneration of austenite. The growth of crystallization and primary recrystallization grains is in line with the production trend of oriented silicon steel towards low-temperature slab heating and thin gauges.

  "On the other hand, the carbon content in oriented silicon steel is closely related to its magnetic properties. In order to ensure proper microstructure evolution during hot rolling, cold rolling, and annealing, and obtain the best texture and magnetic properties of oriented silicon steel, the carbon content of the steel needs to be maintained at 0.04% to 0.07% before decarburization and annealing. At the same time, in order to ensure that the structure of the finished oriented silicon steel sheet is a single ferrite phase to eliminate the phenomenon of magnetic aging, the carbon content of the steel sheet after decarburization annealing process is generally not more than 50×10-6 to 60×10-6. After decarburization annealing, cold-rolled steel strip (thickness is usually within 0.3mm) will recrystallize once. In oriented silicon steel, {111}<112> and {111}<110> oriented grains can promote the abnormal growth of Goss nuclei and improve its magnetic properties. Rotating copper type {112}<110> and {001} oriented grains It is not conducive to the occurrence of secondary recrystallization. Therefore, the number and distribution of these oriented grains after primary recrystallization will have a greater impact on the secondary recrystallization of oriented silicon steel. However, at present, there is still a lack of systematic and in-depth research on the decarburization process parameters and texture evolution after initial recrystallization in niobium-containing Hi-B steel.

  Based on this, this paper takes Hi-B steel with a Nb content of 0.028% as the research object, investigates the influence of decarburization annealing conditions on the carbon content, primary recrystallization texture and grain size in the steel, and analyzes {111} <112> and {111}<110> and other crystal grains and Goss crystal grain orientation relationship.

  (1) When the protective atmosphere is 33%H2+67%N2 (volume fraction), the dew point of the atmosphere is 45℃, and the annealing temperature is 850℃ for 180s, the decarburization effect of niobium-containing Hi-B steel is the best. The carbon content is about 0.0037%.

  (2) After decarburization and annealing, all samples of Niobium-containing Hi-B steel have been completely recrystallized, and the texture is composed of strong {411}<148>, {111}<112> and {111}<110> textures Composition, a small amount of Goss grains are scattered among the {111}<112> or {411}<148> grains.

  (3) When the annealing time is 180s, as the decarburization temperature increases from 830°C to 850°C, the number of Σ9 and Σ13b grain boundaries in the niobium-containing Hi-B steel sample that are conducive to the abnormal growth of Goss grains increases first When the decarburization temperature is 850℃, the number of Σ9 and Σ13b grain boundaries increases with the extension of the holding time.

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