RU2459876C1 - Method of producing cold-rolled isotropic electric steel - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: proposed method comprises casting, hot rolling, hot-rolled strip thermal processing, etching, cold rolling and cold-rolled strip thermal processing. Steel casing is conducted subject to the following ratio 0.41%<Al+Sb<1.76%, at the following ratio of components, wt %: carbon - not over 0.010, silicon - 2.15-3.20, aluminium - 0.40-1.60, stibium - 0.01-0.16, manganese - not over 0.40, phosphorus - not over 0.10, sulfur - not over 0.010, nitrogen - not over 0.006, iron and unavoidable impurities making the rest. Strip resulted from hot rolling is subjected to thermal processing consisting in normalisation of its temperature at the following conditions: T_S>A_C3 at (Si+Al)<3.30, wt % and T_S<A_C3 at (Si+Al)>3.30, wt % where: T_S is thermal processing temperature, °C; A_C3 is temperature of phase conversion of ferrite in austenite, 911°C; Si is silicon content in steel, wt %; Al is aluminium content in steel, wt %. Sb is stibium content in steel, wt %.

EFFECT: better magnetic properties.

1 ex, 1 tbl

Description

The invention relates to ferrous metallurgy, specifically to the production of cold-rolled electrical isotropic steel used for the manufacture of magnetic circuits of electrical machines (electric motors, generators, chokes, etc.).

One of the main quality requirements of such steel is a low level of specific magnetic losses with their minimal anisotropy and a high level of magnetic induction. In many respects, these characteristics are determined by the chemical composition and technology of steel processing.

The basic element that determines the magnetic properties of cold-rolled strips of electrical isotropic steel is silicon. It reduces the specific magnetic loss in steel by increasing the electrical resistivity of the material. The harmful effect of silicon is manifested in a decrease in the saturation magnetic induction, which causes difficulties in the production of cold-rolled strips of electrotechnical isotropic steel with low magnetic losses and high magnetic induction.

Along with silicon in electrical isotropic steel, the main element is also aluminum. It almost to the same extent increases electrical resistance. The beneficial effect of aluminum is due to its effect on the texture of the metal.

When silicon steel is alloyed with aluminum during the heat treatment of hot-rolled and cold-rolled strips, the formation of cubic texture orientations (200) and (310) is facilitated, which improves the magnetic properties of the metal.

The improvement of magnetic properties is achieved due to the good development of the favorable components of the texture (200), (310), while the texture (111), which worsens the magnetic properties, should be poorly developed or suppressed.

One of the methods for suppressing (111) texture, which is harmful in terms of magnetic properties, is the addition of special elements, such as antimony, which allows you to control the texture. Antimony, segregating to the strip surface, reduces the surface energy of grains of cubic orientations of texture (200), (310) and promotes their growth due to grains with orientation (111).

When introducing antimony into steel, it is necessary to take into account the level of metal alloying with aluminum, since their ratio affects the texture formation of steel and the manufacturability of rolled products.

A known method for the production of cold-rolled electrical isotropic steel is given in Russian patent No. 2219253, C21D 8/12, 01/28/2002.

,The method involves obtaining steel with a chemical composition (in wt.%): Silicon 0.9-2.8; carbon not more than 0.04; sulfur not more than 0.010; aluminum 0.1-1.5; phosphorus not more than 0.16; manganese 0.10-1.00; nitrogen not more than 0.009. Antimony is also introduced into the chemical composition with a content, wt.%, 0.003-0.20. The technological process includes hot rolling, normalization of a strip with heating not lower than A _C3 , etching, cold rolling, heat treatment of a cold-rolled strip. At the same time, the holding temperature for a time of 90-270 seconds during the normalization of the hot-rolled strip is selected depending on the silicon and carbon content in accordance with the ratio:

,

The main disadvantage of this method is that the optimal ratio of aluminum to antimony is not achieved in all declared ranges of their content, and when choosing the normalization temperature of steel, the sum of the silicon and aluminum content in the metal is not taken into account, which leads to a deterioration in the magnetic properties of the finished steel.

The technical problem to which the invention is directed is to improve the magnetic properties of cold-rolled electrical isotropic steel, namely, a decrease in specific magnetic losses, an increase in the degree of isotropy with a decrease in anisotropy of specific magnetic losses, and an increase in the level of magnetic induction.

To solve the problem in the proposed method for the production of cold rolled electrotechnical isotropic steel, including smelting, hot rolling, heat treatment of a hot rolled strip, pickling, cold rolling and heat treatment of a cold rolled strip, the ratio 0.41% ≤Al + Sb≤1.76% is fulfilled in steel melting , at the following content of components, wt.%: carbon no more than 0,010; silicon 2.15-3.20; aluminum 0.40-1.60; antimony 0.01-0.16; manganese not more than 0.40; phosphorus not more than 0.10; sulfur not more than 0.010; nitrogen not more than 0.006; iron and inevitable impurities rest. Heat treatment of a hot-rolled strip of such steel is set in accordance with the condition:

T _p ≥A _C3 at (Si + Al) ≤3.30 (%)

T _{p <A C3} at (Si + Al)> 3.30 (%)

where: T _p - heat treatment temperature of the hot-rolled strip, ° C;

And _C3 = 911 - the temperature of the phase conversion of ferrite to austenite, ° C;

Si — silicon content in steel, wt.%;

Al — aluminum content in steel, wt.%;

Sb is the antimony content in steel, wt.%.

In order to obtain a high level of magnetic properties in cold rolled electrical isotropic isotropic steel, it is necessary to form an optimal micrograin size in the metal and increase the pole density of the cubic texture orientations (200) and (310).

The conducted studies suggest that in order to obtain the optimal micrograin size and increase the pole density of the cubic orientations (200) and (310) in the texture of the hot-rolled strips, it is necessary to use steel with a certain ratio of aluminum to antimony, and the heat treatment temperature of hot-rolled steel from such steel must be set based on from the sum of silicon and aluminum in steel.

Based on laboratory and industrial experiments, boundary conditions were established for the sum of the contents of aluminum and antimony and the sum of the contents of silicon and aluminum.

The heat treatment of hot rolled strips at a temperature of T _p ≥A _C3 and an increase in the amount of (Si + Al)> 3.30% under the phase transformation of ferrite to austenite leads to uncontrolled growth of micrograins, redistribution of aluminum along grain boundaries and an increase in the proportion of rib orientation (220) in the texture, which, firstly, reduces the ductility of the metal, and secondly, increases the anisotropy of specific magnetic losses and reduces magnetic induction in the finished steel. Heat treatment of hot-rolled strips at a temperature of T _p <A _C3 and a decrease in the amount of (Si + Al) ≤3.30% does not provide strips with an optimal microstructure, reduces the fraction of cubic components of the finished steel texture (200) and (310), which leads to increase specific magnetic losses.

The range of values of the degree of alloying with silicon steel on the basis of laboratory and industrial experiments was chosen equal to 2.15-3.2%. The lower limit is due to an increase in the specific magnetic losses of the finished steel due to a decrease in the electrical resistivity of the metal with a silicon content of less than 2.15%, and the upper limit is due to a decrease in the manufacturability of rolled products due to an increase in the hardness of the metal with a silicon content of more than 3.2%.

The range of alloying steel with aluminum is set equal to 0.4-1.6%. The lower limit is due to a decrease in the impact on the structural and texture state of finished steel with an aluminum content of less than 0.4%, the upper limit is due to an increase in the number of non-metallic inclusions with an aluminum content of more than 1.6%, which leads to a deterioration in the magnetic properties of the finished steel.

The range of antimony content in the metal, equal to 0.01-0.16%, is established based on the limits of the ratio of the content of aluminum and antimony of 0.41% ≤Al + Sb≤1.76%. The lower limit of the antimony content is due to a decrease in the effect of suppressing texture (111) in the strip surface with a decrease in the ratio of aluminum to antimony (Al + Sb) of less than 0.42, and the upper limit is due to a decrease in the ductility of the metal during cold rolling of hot rolled steel with the ratio of aluminum to antimony (Al + Sb) more than 1.76%.

Analysis of the patent literature shows the lack of coincidence of the distinctive features of the claimed 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 cold-rolled electrical isotropic steel, including reducing specific magnetic losses P _{1.5 / 50} by 0.10-0.20 W / kg and anisotropy of specific magnetic losses Δ P _{1.5 / 50} by 4- 7%, increase magnetic induction by 0.01-0.03 T.

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

Example.

Electrotechnical isotropic steel was smelted with a ratio of aluminum and antimony (Al + Sb) = 1.11% with a carbon content of 0.005%; silicon 3.0%; aluminum 1.05%; antimony 0.06%; manganese 0.2%; phosphorus 0.008%; sulfur 0.005%; nitrogen 0.004%; iron and inevitable impurities rest. Steel was poured into slabs and hot rolled to a thickness of 2.0 mm. The hot-rolled strip was subjected to heat treatment in a normalization unit at a temperature T _p = 863 ° C in accordance with the condition T _p <911 ° C with the sum of alloying elements (Si + Al) = (3.0 + 1.05) = 4.05> 3 ,thirty%. Next, the annealed hot rolled strip was subjected to etching and cold rolling to a thickness of 0.50 mm. The cold-rolled strip was subjected to final heat treatment in a continuous annealing unit.

Implementation options for the production of cold rolled electrical isotropic steel in a thickness of 0.50 mm with different contents of silicon, aluminum, antimony and their magnetic properties are shown in table 1.

Table 1 Technological processing parameters and magnetic properties of cold-rolled electrical isotropic steel No. p / p The content of elements,% The temperature of the heat treatment of the hot rolled strip, ° C Magnetic properties Al Sb Ad + Sb Si (Si + Al) P _{1,5 / 50} , W / kg Δ P _{1.5 / 50} ,% B ₂₅₀₀ , T one 0.40 0.01 0.41 2.15 2,55 954 2.93 6.0 1,60 2 0.80 0.04 0.84 2,35 3.15 935 2.81 7.0 1,58 3 0.75 0,03 0.78 2,53 3.28 928 2.72 8.0 1,57 four 0.60 0.10 0.70 2.70 3.30 911 2.68 7.0 1,56 5 0.45 0.13 0.58 2.87 3.32 890 2.64 7.0 1.55 6 1.05 0.06 1,11 3.00 4.05 863 2.42 8.0 1,54 7 1,60 0.16 1.76 3.20 4.80 815 2,36 9.0 1,53 8* 0.39 0.005 0.395 2.20 2.59 905 3.08 10.0 1,58 9* 0.76 0.05 0.81 2.40 3.16 902 2.98 11.0 1.55 10* 0.67 0.12 0.79 2.68 3.35 917 2.87 11.0 1,54 eleven* 1,03 0,07 1.10 3.05 4.08 921 2,53 15.0 1.51 12** 1,61 0.17 1.78 3.22 4.83 810 - - - Note: * - processing without taking into account the operational parameters of steel production;
** - brittle metal, has not been processed.

Claims (1)

Method for the production of cold rolled electrical isotropic steel, including smelting, hot rolling, heat treatment of a hot rolled strip, etching, cold rolling and heat treatment of a cold rolled strip, characterized in that the steel is smelted with a ratio of 0.41% ≤Al + Sb≤1.76% in the following content of components, wt.%: carbon not more than 0.010, silicon 2.15-3.20, aluminum 0.40-1.60, antimony 0.01-0.16, manganese not more than 0.40, phosphorus not more than 0 , 10, sulfur not more than 0.010, nitrogen not more than 0.006; iron and unavoidable impurities - the rest, and the strip obtained after hot rolling is subjected to heat treatment by normalization at a temperature in accordance with the condition:
≥A T _{n C3} when (Si + Al) ≤3,30, wt.% And T _n <A _C3 when (Si + Al)> 3,30 wt.%,
where T _p - the temperature of the heat treatment of the hot rolled strip, ° C;
And _C3 is the temperature of the phase conversion of ferrite to austenite, 911 ° C;
Si — silicon content in steel, wt.%;
Al is the aluminum content in steel, wt.%;
Sb is the antimony content in steel, wt.%.