RU2211249C1 - Method for production of cold-rolled isotropic electrical-sheet steel - Google Patents

Abstract

FIELD: ferrous metallurgy. SUBSTANCE: the method for production of cold-rolled isotropic electrical-sheet steel consists in melting, hot rolling, pickling, cold rolling and thermal treatment, the temperature of process annealing in the process of thermal treatment of cold-rolled steel with content, percent by mass: carbon not more than 0.04; phosphorus within 0.20 to 0.40; silicon not more than 0.20; manganese not more than 0.40; aluminum not more than 0.20; sulfur not more than 0.0115; the rest iron and inevitable impurities are determined depending on the content of phosphorus and the thickness of cold-rolled metal in accordance with relation: tp=K₁(K₂+P,[%])= +-20C, where temperature of process annealing, C; K₁, K₂ - experimentally determined coefficients; K₁= 730, [C/%] , K₂ - 1.0[%] - at H< 0.60 mm, K₂= 1.03[%] - at H> 0.60 mm, P-content of phosphorus in steel, percent by mass; H-thickness of cold-rolled strips, mm. EFFECT: enhanced degree of isotropism in the specific magnetic loss and the level of electromagnetic induction of cold-rolled isotropic electrical sheet steel. 2 tbl, 2 ex

Description

 The invention relates to ferrous metallurgy and can be used in the production of cold-rolled isotropic electrical steel.

 A known method of manufacturing cold-rolled isotropic electrical steel, described in the German patent, application 19918484 from 04/23/1999, in which to improve the electromagnetic properties of silicon steel is additionally alloyed with phosphorus.

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 ^o C, etching and cold rolling to a thickness of 0.20-1.0 mm with a total degree of deformation of not more than 85% , the final recrystallization annealing of cold rolled steel at a temperature of 580-780 ^o C and the training of metal with compression of 15%. The disadvantage of this method is, firstly, a large number of technological operations, which increases the cost of metal products, and secondly, the training of annealed steel at the final stage of the process leads to a decrease in the electromagnetic induction of the finished isotropic electrical steel.

 Closest to the described invention in technical essence is a method for producing isotropic electrical steel, described in Russian patent RU 2155234 C1 dated 06/28/1999 g, which also uses alloying of silicon steel with phosphorus.

при изменении содержания кремния 1,4-2,6% и фосфора 0,05-0,15%.The technological process includes smelting, hot and cold rolling, decarburization-recrystallization annealing, while the temperature of the final recrystallization annealing after cold rolling is determined taking into account the content of silicon and phosphorus from the ratio:

with a change in the silicon content of 1.4-2.6% and phosphorus 0.05-0.15%.

The disadvantage of this method is that the polygonized structure of the hot-rolled metal causes an increased heterogeneity of the finished steel microstructure, which leads to an increase in the anisotropy of the specific magnetic losses ΔP _{1.5 / 50} (%), and the relatively high silicon content in the metal determines the production of rolled products with a low level of electromagnetic induction B ₂₅₀₀ (t).

 The technical problem to which the invention is directed is to improve the electromagnetic properties of cold-rolled isotropic electrical steel, namely, increasing the degree of isotropy while reducing the anisotropy of specific magnetic losses and increasing the level of electromagnetic induction.

The problem is achieved in that the temperature of recrystallization annealing during the heat treatment of cold rolled steel containing, by weight. %: carbon not more than 0.04; phosphorus 0.20-0.40; silicon not more than 0.20; manganese not more than 0.40; aluminum no more than 0.20; sulfur not more than 0.015; the rest of the iron and the inevitable impurities and past smelting, hot rolling, pickling and cold rolling, are determined depending on the phosphorus content and thickness of the cold-rolled metal in accordance with the ratio:
tp = K ₁ • (K ₂ + P, [%]) ± 20 ^o С
where: tp is the temperature of recrystallization annealing, ^o С;
To ₁ , To ₂ - experimentally determined coefficients;
K ₁ = 730, [ ^o C /%];
K ₂ = 1.0 [%] - at H <0.60 mm;
K ₂ = 1.03 [%] - at H≥0.60 mm;
P is the phosphorus content in steel, wt.%;
N is the thickness of the cold rolled strips, mm

 The necessary condition for reducing the specific magnetic loss anisotropy and obtaining a high level of electromagnetic induction of the finished isotropic electrical steel is the formation of the optimal micrograin size and an increase in the pole density of the metal {200} in the metal with a pole density of {200}.

 In the present invention, the optimal structural and texture state of the finished isotropic electrical steel is achieved by changing the type of alloying of the metal, in which phosphorus (P) is used as the main alloying element of silicon (Si).

In its effect on the magnetic properties of isotropic electrical steel, phosphorus is similar to silicon. It, which forms a substitutional solid solution with iron, more intensively increases the electrical resistance of steel than silicon, which has a positive effect on the level of magnetic properties. The positive effect of phosphorus on magnetic properties is also associated with its refining effect. He has a great tool with oxygen (O ₂ ), which contributes to the purification of steel from this impurity, the effect of which is manifested in the formation of stable finely dispersed oxides (Al ₂ O ₃ , SiO ₂ , TiO ₂ ), which worsen magnetic properties.

 Being an active structural-forming element that sharply narrows the γ-region, which positively affects the growth of ferrite grains in iron, phosphorus provides an equiaxed, uniform recrystallized structure and increases the pole density of cubic orientation in the texture of finished isotropic electrical steel.

 The phosphorus content in the metal and the thickness of the annealed cold-rolled strips affects the grain size of the steel and the formation of the crystallographic texture, which ultimately affects the level of magnetic properties.

 Therefore, when setting the temperature of recrystallization annealing during the heat treatment of cold rolled steel, it is necessary to take into account the phosphorus content in the metal and the thickness of the cold rolled strips, which makes it possible to obtain the optimal structural and textural state of the finished isotropic electrical steel.

In combination with a low silicon content in the metal, this provides a decrease in the level of anisotropy of specific magnetic losses ΔP _{1.5 / 50} and an increase in the level of electromagnetic induction of finished steel B ₂₅₀₀ .

 The range of values of the degree of alloying of steel with phosphorus based on laboratory and industrial experiments was chosen equal to 0.20-0.40%. The lower limit is due to a decrease in the impact on the structural-texture state of finished phosphorus steel at a content of less than 0.20%, and the upper limit is due to a decrease in the processability of rolled metal processing due to an increase in metal hardness, with a phosphorus content of more than 0.40%.

The application of the invention allows to improve the electromagnetic properties of cold-rolled isotropic electrical steel, including reducing the anisotropy of specific magnetic losses ΔP _{1.5 / 50} by 5-9% and increasing the electromagnetic induction B ₂₅₀₀ by 0.03-0.10 t.

 A method of manufacturing a cold rolled isotropic electrical steel is as follows.

 Example 1

Smelted steel with a carbon content of 0.03%; phosphorus 0.21; silicon 0.10; Manganese 0.20%; aluminum 0.047%; sulfur of 0.012% was subjected to hot rolling to a thickness of 2.2 mm, etching, cold rolling to a thickness of 0.65 mm and heat treatment. The temperature of the recrystallization annealing during the heat treatment of cold rolled steel was set equal to 920 ^o C.

 Example 2

Steel was smelted with a carbon content of 0.04%; phosphorus 0.27%; silicon 0.06%; manganese 0.25%; aluminum 0.050%; sulfur of 0.006%, then it was subjected to hot rolling to a thickness of 2.2 mm, etching, cold rolling to a thickness of 0.50 mm and heat treatment. The temperature of recrystallization annealing during the heat treatment of cold rolled steel was set equal to 940 ^o C.

Claims (1)

1. A method of manufacturing cold rolled isotropic electrical steel, including smelting, hot rolling, pickling, cold rolling and recrystallization annealing of cold rolled steel, characterized in that the steel is smelted containing, by weight. %:
Carbon - Not more than 0.04
Phosphorus - 0.20-0.40
Silicon - Not more than 0.20
Manganese - Not more than 0.40
Aluminum - Not more than 0.20
Sulfur - Not more than 0.015
Iron and Inevitable Impurities - Else
the temperature of recrystallization annealing is determined depending on the phosphorus content and thickness of the cold rolled steel in accordance with the ratio:
Tr. about. = K ₁ (K ₂ + P, [%]) ± 20 ^o C,
where Tr. about. - temperature of recrystallization annealing, ^o С;
K ₁ , K ₂ - experimentally determined coefficients;
K ₁ = 730, [ ^o C /%];
K ₂ = 1.0 [%] at H <0.60 mm;
K ₂ = 1.03 [%] at H≥0.60 mm;
P is the phosphorus content in steel, wt. %;
N - thickness of cold rolled steel, mm

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