RU2000341C1 - Method for production of isotropic electric steel - Google Patents

Abstract

SUMMARY OF THE INVENTION: A method for producing isotropic electrical steel involves hot rolling, normalization, cold rolling to final thickness, decarburizing and final annealing. In this case, the temperature of the final annealing is set depending on the normalization temperature tH.o and the melting content of Mn, AI according to equation 1h.0 (° C) 1385 ° C - 0.31 tn (° C) - Ci Mn, weight% - C2 AI, weight% ± 7 ° C, where Ci 130 ° C /% is a dimensional coefficient; C2 72 ° C /% is a dimensional coefficient. 2 tab. about 8

Description

The invention relates to metallurgy, in particular to the production of isotropic electrical steel

A number of methods for the production of isotropic electrical steel are known. including hot rolling, normalization. cold rolling in one or two stages, decarburization in the final thickness and final annealing, but differing in the modes of final annealing. Thus, in the case of double cold rolling technology, a final annealing temperature of 3.0 is recommended in processes 1-3, from 850 to 1100 ° C. For single rolling technology, the recommended temperature range ta.o is even wider. Thus, the maximum temperature of 13 °, recommended in methods 4-6, is, respectively, 800.981.1000 ° C. In methods 7, 8 it was proposed to set t3.o 1050 ° C. which, according to the authors of application 8, provides a grain size of more than 100 microns in the central layers of the metal. In the heat treatment method 9, it is proposed to set the annealing temperature of cold rolled silicon steel depending on its silicon content. However, in method 9, the dependence of the optimum conditions on the content of other chemical elements is not determined. In method 10, it is recommended that annealing be carried out before decarburization at a temperature depending on the content of SI, AI, C in the steel. But further annealing makes subsequent decarburization difficult. Method 11 provides a method for producing isotropic steel which provides a grain size in the finished steel in the range of 100 + 3.5 (Si + AI) 2 D (µm) 170 + 5 (51 + AI) 2. However, in practice, it is necessary to have a technical solution that allows for any chemical composition of the steel to have a strictly defined grain size, which ensures a minimum of specific magnetization reversal losses,

The closest in technical essence and the achieved positive effect to the claimed solution is the production method, including hot rolling, normalization, single cold rolling, decarburization and final annealing. in which the temperature t3.o is set in the range of 900-1050 ° C 12. This temperature range in many cases includes the recommended temperatures in the claimed technical solution. On this basis, method 12 was chosen as a prototype. However, the disadvantage of method 12 is the lack of indications of the dependence of the optimum temperature t3 о on the chemical composition of steel and the normalization mode. This also leads to higher specific losses due to re-magnetization with the claimed solution

The aim of the invention is to reduce the specific magnetization reversal losses by providing an optimal grain size in the finished steel with a thickness of 0.5 mm.

The goal is achieved. that in a method including hot rolling, normalization, cold rolling to a final thickness, decarburization and final annealing, the final annealing temperature t3 о is set depending on the normalization temperature tH.o and the melting content Mn, A according to the equation:

0

151 ° (° С) 1385 ° С-0.31 thio (° С) -Ci Mn, weight. AI weight .

where Ci - 130 ° С /% - dimensional coefficient,

Sz 72 ° C /% - dimensional coefficient,

The level of specific magnetization reversal losses, ultimately, depends on the domain structure: domain sizes, their orientation and border mobility. Along with factors such as texture and the number of inclusions, the increase in D. affects the domain structure and grain size. On the one hand, this leads to a decrease in hysteresis losses and, on the other hand, to an increase in eddy current losses. In this regard, an optimal grain size must exist for each heat. Such a dependence, but /, experimentally studied on a metal of 90 melts of isotropic electrical steel in a thickness of 0.5 mm, is presented in the form of the equation

Opt (μm) 76 + 140. wt.% (1)

In order to predict the optimum temperature of the final annealing, which ensures a minimum of magnetic losses, it is necessary to know the dependence of D on the chemical composition, t3.o and the normalization temperature tH.o. Such a dependence in the form of equation (2) was obtained experimentally on a metal of 12 heats. Each heat was divided into 6-9 rolls, of which each was assigned to different temperatures of normalization and recrystallization

55D (μm) -86. 23.6 (b °

g - 1012

-) +

12 3 (

tn about.

g. - MR

Sr

„36 (-. 0.21.) + 0.06;

+ 4 I I AI. weight% -0.455. V0.085

t3.09 (.0) t

. „(,

Now the optimal temperature t3.0 can be obtained by substituting equation (1) 15 instead of the left side of equation (2). The result is the equation (3):

ta.o (° С) - 1385 - 0.31 IH.O (° С) - 130 х

, weight. 72 AI, wt.%. (3) Equation (3) has been tested under laboratory and semi-industrial conditions and is the basis of the claims. The influence of all other chemical elements with permissible changes in their content was limited to a change of t3.o in the amount of no more than ± 7 ° C.

PRI me R. In the experiment, a hot-rolled metal of alloying group IV was used (a total of 5 heats).

The chemical composition of the heats is given in table 1.

All metal was divided into two halves, which underwent normalization at Tn.o - 850 ° С and the so-called 0 - 950 ° С. Further, after rolling to a thickness of 0.5 mm, decarburization and final annealing were performed. In this case, the temperature of the final annealing was set in the range of 1000 - 1080 ° C, divided into 11 temperatures, in increments of 5 ° C. Table 2 shows only the results of Pi.s / so measurements in samples that were assigned at t3 about 1000 ° С, 1050 ° С „ta.o - 8 - 12 ° С. t3.o - 3 - 7 ° C, t3.o ± 2 ° C, t3.o + 3 - 7 ° C, ta.o f 8 - 12 ° C. At the same time, annealing at ts.o 1000, 1050 ° C is accepted as the prototype treatment. Final annealing at t3.o 1050 ° С was also carried out to compare the efficiency of the claimed technology

fifteen

twenty

25

thirty

40 45 50 solution compared to current technology. The value of t3 ° was calculated from equation (3) and is given in Table 2 to compare the calculated temperature and the optimum temperature found experimentally. From the presented results of Table 2, it follows that the final annealing at ta.o 1000 and 1050 ° C (accepted for processing according to the prototype) provides an average level of specific losses Pi, 5 / so of 3.12 W / kg. The same level is provided when processing according to the operating technology modes at NLMK. In the case of the final annealing at 1 s.Osc. ± 7 ° C, where T3. o.sc. was calculated according to equation (3). the specific loss level PI.S / SO averaged 3.03 W / kg, i.e. 0.09 W / kg better than the prototype.

Thus, the final annealing at a temperature of t3 о (° С) - 1385 ° С-0.31-tH.o (° C) -130 MP, weight. -72 AI, wt.% ± 7 ° C, reduces the Pi.s / so level by 0.09 W / kg for 0.5 mm thick steel; to increase the grade composition of the manufactured steel.

Claims (1)

SUMMARY OF THE INVENTION A method for producing isotropic electrical steel, including hot rolling, normalization, cold rolling to a final thickness, decarburization and final annealing, characterized in that, in order to reduce specific magnetization reversal losses by ensuring the optimal grain size in the finished steel and thickness 0.5 mm, the final annealing temperature t3.o is set depending on the normalization temperature tH о and the melting content of manganese Mn and aluminum AI according to the equation t-j.ofC) -1385 ° С-0.31-Tno (° С) -Ci Мп (wt.%) - С2 A1 (wt.%) ± 7 ° С. where Ci - 130 ° С /% and С2 72 ° С /% - dimensional coefficients. Table 1 table 2 Continuation of table 2