RU2266340C1 - Method of production of isotropic electrical-sheet steel at increased magnetic induction - Google Patents

Abstract

FIELD: ferrous metallurgy; methods of production of isotropic electrical-sheet steel.

SUBSTANCE: proposed method of production of isotropic electrical-sheet steel includes melting, hot rolling, normalization of hot-rolled strips, pickling, cold rolling and heat treatment of cold-rolled strips; ratio of phosphorus to aluminum satisfies the following relationship: [P,(%)/Al, (%)]≥ 1.0 at the following content of components, mass-%: phosphorus, 0.08-0.30; aluminum, 0.03-0.30; carbon, no more than 0.04; silicon, no more than 2.65; manganese, no more than 1.5; sulfur, no more than 0.012; the remainder being iron and unavoidable admixtures. Strip obtained after hot rolling is subjected to normalization at temperature of 850-1000°C; P is content of phosphorus in steel and Al is content of aluminum in steel, mass-%.

EFFECT: increased level of magnetic induction and relative peak magnetic permeability of cold-rolled isotropic electrical-sheet steel.

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Description

The invention relates to ferrous metallurgy, specifically to the production of isotropic electrical steel used for the manufacture of magnetic circuits of electrical equipment.

One of the main quality requirements of such steel is a high level of magnetic induction and relative peak magnetic permeability. In many ways, these characteristics are determined by the chemical composition, steel processing technology. One of the ways to improve the magnetic properties of silicon isotropic electrical steel is to alloy it with phosphorus and aluminum and to normalize the hot-rolled strip.

A known method of producing cold-rolled isotropic electrical steel (A.S. USSR 1786134, C 21 D 8/12, 1993), containing 0.02-0.05% C; 0.1-0.4% Mn; 1.5-3.3% Si; 0.3-0.6% Al; 0.02-0.1% P, including smelting, hot rolling, normalization, etching, single rolling to a final thickness and decarburization-recrystallization annealing. When phosphorus and aluminum are introduced into this steel, normalization is carried out at a temperature of 810-830 ° C.

The disadvantage of this method is the relatively low degree of alloying of steel with phosphorus at a high aluminum content and low temperature normalization processing of the hot rolled strip, which leads, on the one hand, to an increase in the content of finely dispersed oxides in the metal, the main share of which is Al ₂ O ₃ , on the other hand , decrease in the pole density of the cubic orientations {200} and {310}. The magnetic properties of the finished isotropic electrical steel are deteriorating.

Closest to the described invention in technical essence is the method of manufacturing isotropic electrical steel, described in German patent application No. 19918484 from 04.23.1999, in which phosphorus and aluminum are also used to improve the magnetic properties of silicon isotropic electrical steel.

The method includes hot rolling a steel slab containing, wt.%: Carbon 0.06; silicon 0.02-2.5; aluminum no more than 0.40; manganese 0.05-1.0; phosphorus 0.08-0.25 to a thickness of not more than 3.5 mm, annealing of the hot-rolled strip at a temperature of 650-850 ° C, etching and cold rolling to a thickness of 0.2-1.0 mm with a total degree of deformation of not more than 85% recrystallization annealing of cold rolled steel at a temperature of 580-780 ° C and metal training with a compression of 15%.

However, this method does not take into account the influence of the chemical composition, the ratio of phosphorus to aluminum in the metal is chosen arbitrarily, which leads to an increase in the content of finely dispersed Al ₂ O ₃ oxide in the steel, the hot-rolled strip is annealed at low temperatures, and at the final stage of the technological process, training is performed. This reduces the level of magnetic induction and relative peak magnetic permeability.

The technical task of the invention is to improve the magnetic properties, namely increasing the level of magnetic induction and the magnitude of the relative peak magnetic permeability.

A necessary condition for increasing magnetic induction and relative peak magnetic permeability is a high degree of metal purity by the content of Al ₂ O ₃ oxide, the formation of an optimal micrograin size and an increase in the pole density of {200} and {310} cubic orientations in the metal.

In the present invention, the reduction in the proportion of finely dispersed Al ₂ O ₃ oxide in steel is achieved by metal smelting with a ratio of phosphorus to aluminum in accordance with the condition

with the following content of components, wt.%:

phosphorus 0.08-0.30; aluminum 0.03-0.30; carbon not more than 0.04; silicon not more than 2.65; manganese not more than 1.5; sulfur not more than 0.012; iron and inevitable impurities rest,

where P is the phosphorus content in steel, wt.%;

Al is the aluminum content in steel, wt.%.

The introduction of phosphorus into steel ensures the refinement of the metal, since it, having a high affinity for oxygen (O ₂ ), takes it away and helps to clean the steel from this harmful impurity, the effect of which is manifested in the formation of fine oxide Al ₂ O ₃ .

The conducted studies suggest that the degree of alloying of steel with phosphorus should be no less than the degree of alloying with aluminum. In this case, a significant reduction in the proportion of Al ₂ O ₃ oxide in the steel is achieved. With a decrease in the phosphorus content in the steel relative to the aluminum content, the ratio

the amount of dissolved oxygen in the metal increases, which leads to an increase in the proportion of Al ₂ O ₃ oxide and a deterioration in magnetic properties.

Normalization processing of a hot-rolled strip of such steel must be carried out at a temperature of 850-1000 ° C. This ensures a homogeneous structure along the cross section of the strip and an increase in the pole density in the metal of cubic orientations, which are inherited during subsequent technological operations.

The normalization of the hot rolled strip at a temperature of less than 850 ° C causes incomplete recrystallization of the hot rolled metal. In the structure of the hot-rolled strip, there are polygonized zones, which determines the different grain size of the finished steel microstructure. The relative peak magnetic permeability of the finished steel is reduced.

And the normalization of the hot-rolled strip at a temperature of more than 1000 ° C in nitrogen-containing atmospheres leads to the diffusion of nitrogen (N ₂ ) into the metal with the formation of aluminum nitrides, which reduces the pole density of cubic orientations and the level of magnetic induction of the finished isotropic electrical steel.

обработка стали со степенью легирования металла по кремнию более 2,65% затруднена из-за повышения ее жесткости.The proposed method extends to isotropic electrical steel with a silicon content of up to 2.65%. The research results showed that under the condition

the processing of steel with a degree of alloying a metal with silicon of more than 2.65% is difficult due to the increase in its rigidity.

The analysis of the patent literature shows the lack of coincidence of the distinctive features of the proposed method with the signs of known technical solutions. Based on this, it is concluded that the claimed technical solution meets the criterion of "inventive step".

The application of the invention allows to improve the magnetic properties of isotropic electrical steel, including increasing the magnetic induction B ₂₅₀₀ by 0.02-0.03 T and the relative peak magnetic permeability μ _{1.5 / 50} by 300-500 units.

The following is an embodiment of the invention that does not exclude other variations within the scope of the claims.

A method for the production of isotropic electrical steel with increased magnetic induction is as follows.

Example.

Isotropic electrical steel was smelted with a phosphorus to aluminum ratio of

with a phosphorus content of 0.15%; aluminum 0.12%; carbon 0.03%; silicon 1.24%; manganese 0.35%; sulfur 0.005%; iron the rest.

Steel was poured into slabs and hot rolled to a thickness of 2.2 mm.

The hot-rolled strip was subjected to normalization at a temperature of 930 ° C, then etching, cold rolling to a thickness of 0.5 mm and heat treatment of the cold-rolled strip were performed.

Table 1 shows examples of the method with various technological parameters.

Table 1.
Magnetic properties of isotropic electrical steel. No. p / p The content of elements,%

Ratio

Normalization temperature of the hot-rolled strip, ° С Magnetic properties R A1 Si B ₂₅₀₀ , t μ _{l, 5/50} 1 0.30 0.05 0.09 6.00 850 1.70 2850 2 0.28 0.06 0.12 4.66 1000 1,69 2760 3 0.24 0.08 0.20 3.00 950 1.68 2705 4 0.20 0.20 0.50 1.00 880 1,67 2640 5 0.15 0.12 1.24 1.25 930 1,66 2300 6 0.14 0.10 2.07 1.40 990 1,64 2120 7 0.08 0.08 2.65 1.00 850 1,63 1950 8* 0.28 0.30 0.12 0.93 1010 1,66 2270 9* 0.20 0.27 0.50 0.74 880 1.65 2220 10* 0.08 0.09 2.64 0.89 840 1,61 1640 eleven** 0.08 0.08 2.80 1.00 - -

* - processing without taking into account the operational parameters of steel production;

** - brittle metal has not been processed.

Claims (1)

Method for the production of isotropic electrical steel with increased magnetic induction, including smelting, hot rolling, normalization of the hot rolled strip, etching, cold rolling and heat treatment of the cold rolled strip, characterized in that the steel is melted with a phosphorus to aluminum ratio in accordance with the condition

with the following content of components, wt.%: phosphorus 0.08-0.30; aluminum 0.03-0.30; carbon not more than 0.04; silicon not more than 2.65; manganese no more than 1.5; sulfur not more than 0.012; the rest and inevitable impurities, and the strip obtained after hot rolling is normalized at a temperature of 850-1000 ° С, where P is the phosphorus content in steel, wt.%; Al is the aluminum content in steel, wt.%.