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Method for producing high-grade non-oriented silicon steel by thin slab continuous casting and rolling process

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  How to use the thin slab continuous casting and rolling process to produce high-grade non-oriented silicon steel, so as to give full play to the advantages of thin slab continuous casting and rolling process, is a technical problem that needs to be solved in the prior art.

 

Application Number
CN201810310721.0
Application date
2018.04.09
Public (announcement) number
CN108374130A
Public (announcement) day
2018.08.07
 
  The non-oriented silicon steel of the present invention has a chemical composition mass percentage of:
  Si: 2.5 to 3.5%, Al: 0.10 to 1.5%, Mn: 0.10 to 1.5%, [S+O+C+N+Ti] ≤ 80 ppm, rare earth elements (La and/or Ce and/or Nd): 0.001 ~0.01%, the balance is Fe and other impurity elements.
  The method for producing non-oriented silicon steel in the thin slab continuous casting and rolling process of the present invention comprises the following steps: step A: smelting; step B: continuous casting; step C: heating; step D: hot continuous rolling; step E: pickling; Step F: cold rolling; step G: recrystallization annealing.
  As a further improvement of the present invention, in the step A smelting process, the converter smelting is first performed, and then the RH refining treatment is performed, and the mass percentage of the chemical composition of the molten steel end point after the treatment is:
  Si: 2.5 to 3.5%, Al: 0.10 to 1.5%, Mn: 0.10 to 1.5%, [S+O+C+N+Ti] ≤ 80 ppm, rare earth elements (La and/or Ce and/or Nd): 0.001 ~0.01%, the balance is Fe and other impurity elements;
  The rare earth element is added within 1 to 2 minutes after the completion of the RH refining alloying, and the rare earth element is added and stirred, and the stirring time is ≥3 minutes.
  As a further improvement of the present invention, in the continuous casting process of step B, the controlled drawing speed is 2.8 to 4.6 m/min, and the casting blank having a thickness of 30 to 70 mm is obtained by continuous casting.
  As a further improvement of the present invention, in the heating process of step C, the slab is sent to a tunnel furnace for heating, the slab is brought into a furnace temperature of >800 ° C, the heating temperature is 950 to 1150 ° C, and the soaking time is <30 minutes.
  As a further improvement of the present invention, in the step D hot rolling process, 7-stand hot rolling is performed, the rolling temperature is controlled at 950 to 1100 ° C, the final rolling temperature is controlled at 900 to 920 ° C, and the coiling temperature is controlled at 600 to 700 ° C. The target thickness of the hot rolled sheet is controlled to be 0.8 to 1.0 mm.
  As a further improvement of the present invention, in the step F cold rolling, cold rolling is performed to a thickness of 0.5 mm.
  As a further improvement of the present invention, in the step G recrystallization annealing process, the annealing temperature is controlled to 1000 to 1200 ° C, and the holding time is controlled for 1 to 3 minutes.
  As a further improvement of the present invention, in the continuous casting process of step B, the superheat of the tundish is controlled to be ≤ 0 ° C, and the equiaxed crystal ratio is ensured to be ≥ 80%; and the final reduction ratio of the hot rolling process in step D is greater than 50%; Step F cold rolling process control reduction rate ≤ 50%.
  As a further improvement of the present invention, the step F cold rolling process uses a single-stand reversing cold rolling mill or a cold tandem rolling mill; the step G recrystallization annealing process uses a pure hydrogen atmosphere.
  Beneficial effect
  Compared with the prior art, the technical solution provided by the invention has the following remarkable effects:
  (1) The existing thin slab continuous casting and rolling production process of low-grade non-oriented silicon steel is basically mature, but for high-grade non-oriented silicon steel, especially when the silicon content is more than 2.5%, there are obvious product defects, aiming at the above problems. The method for producing non-oriented silicon steel by the thin slab continuous casting and rolling process of the present invention, the process parameters of steps A to G are matched with each other, and the qualified high-grade non-oriented silicon steel is produced by the thin slab continuous casting and rolling process, thereby Give full play to the advantages of thin slab continuous casting and rolling process.
  (2) The method for producing non-oriented silicon steel in the thin slab continuous casting and rolling process of the present invention, which is produced by a reasonable setting of components and processes in the thin slab continuous casting and rolling process, without electromagnetic stirring and non-normalization process High-grade non-oriented silicon steel with silicon content >2.5%, the final product has high magnetic induction and low iron loss, which solves the corrugated defects that are easy to occur in the production of high-grade non-oriented silicon steel in the existing thin slab continuous casting and rolling process. The characteristics are: in the molten steel [S + O + C + N + Ti] ≤ 80ppm, ultra-pure molten steel; adding rare earth elements, one is to deepen the purification of molten steel, reduce inclusions, improve magnetic properties, and second, the use of rare earth sulfide As a nucleation particle, the columnar crystal of the slab is refined to eliminate the corrugated; the casting process adopts a negative superheat degree, so that the equiaxed crystal ratio is greater than 80%, and the corrugation is eliminated; the last reduction ratio of the hot rolling process is controlled to be greater than 50%, and the low temperature is low. Under large pressure, reduce the band structure of hot rolled sheet core, improve hot rolled structure, eliminate corrugated; optimize the thickness of hot rolled sheet, control the rolling reduction rate of cold rolling process ≤ 50%, medium reduction rate, reduce (111) texture ,increase 100) texture, improve the magnetic properties.