SU1747512A1 - Method of heat treatment of electric and technical isothropic steel - Google Patents

Abstract

SUMMARY OF THE INVENTION: The decarburized-recrystallization annealing is carried out at a temperature depending on the content of silicon and aluminum, according to the ratio t 780 + 22 (Su + A1) & WITH.

Description

The invention relates to ferrous metallurgy, in particular, to the technology of heat treatment and cold-rolled strips of finite thickness of electrical isotropic steel in continuous annealing units with humidified nitrogen-hydrogen atmospheres.

The technological scheme for the production of electrical isotropic steel includes the normalization of hot rolled steel strips with a silicon content of 1.2–3.5%, aluminum 0.3–0.7%, carbon 0.03–0.07%, at temperatures up to 1050 ° C and etching in hydrochloric acid at 80-100 ° C; cold rolling to a final thickness of 0.5 mm; decarburization and recrystallization in continuous annealing units (ANO); coating and drying.

Heating of the cold-rolled strips in ANO is carried out in humidified nitric atmospheres to a temperature of 800 ° C, held for 4.5-6 min (for decarburization), heated again to 1050 ° C and kept recrystallized) is cooled to 60 ° C, coated and dried.

The purpose of the invention is to reduce the specific magnetic losses due to obtaining

low and extremely low final concentrations of carbon in steel and a decrease in its oxidation.

The goal is achieved by increasing the decarburization temperature within strictly regulated limits in order to compensate for the harmful effects of silicon and aluminum and the deterioration of carbon diffusion in steel. The more silicon and aluminum in steel, the higher should be the decarburization temperature, but within the limits defined by the ratio:

t 780 + 22 (SI + A) ° C, where SI + A is their content in steel,%.

The use of the proposed heat treatment method with temperature adjustment depending on the content of silicon and aluminum in annealed steel provided deeper deactivation and less oxidation of the alloying elements, which was accompanied by a decrease in specific magnetic losses and, as a result, an increase in the output of higher grades of these steels.

It is known that silicon and aluminum in electrical steels have become somewhat worse

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Carbon diffusion during decarburization. To compensate for this deterioration, it is necessary to raise the temperature depending on the content of silicon and aluminum. Therefore, the proposed formula:

t - 780 + 22 (SI + AI). ° C. where 780 is the temperature at the boundary of the transformation of Fe + С + 3% SI; 22 - compensation coefficient (selected on the basis of large static processing of laboratory and industrial experiments).

Example. Melting 4814368 divided into three parts. One part was decarburized at 855 ° С (compensation coefficient 22), the second part at 878 С (coefficient of comp. 28). third at 830 ° C (coeff. comp. 15). The content of alloying elements and carbon in smelting is the same:

SI3.1%, AIO, 4% .CO, 04%.

Formula: t - 780 + 22 Г3.1 + 0.4) - 855 ° С; t - 780 + 28 (3.1 + 0.4) - 878 ° С: t 780 +15 (3.1 + 0.4) 831 ° С. Magnetic loss PI w / kg 5/50; 2.96, - 3.02, - 3.22.

It can be seen from the above example that the smallest losses were achieved with a compensation factor of 22. There are a large number of such examples. This method was tested under LPC-5 NLMK conditions.

Claims (1)

The method of heat treatment of electrical isotropic steel containing not more than 0.08 wt.% of carbon, 1.2–3.5 wt.% of silicon, 0.3–0.7 wt.% of aluminum, including decarburization-recrystallization annealing in the temperature range 800–1050 ° C in a humid nitrogen-nitrogen atmosphere. characterized in that, in order to improve the magnetic properties by obtaining particularly low carbon contents and reducing the oxidation of alloying elements, decarburization-recrystallization annealing is carried out at temperatures determined depending on the silicon and aluminum content in steel from the expression t ° 780 + 22 (SI + AI). ° C.