SU817081A1 - Method of thermal treatment of cold-rolled electroengineering steel - Google Patents

Description

interglacial non-oxidizing or decarburizing annealing, second cold rolling to final thickness with reduction. 515% and final annealing in a muffle at 650-750 ° С or in a continuous furnace at 780880е.

Such a treatment contributes to the formation of a more grain-grained structure and makes it possible to reduce the specific loss of steel compared with similar temperatures of the final annealing.

The closest to the present invention is a method of heat treatment of cold-rolled electrical steel, according to which, in order to produce steel with very low watt loss, a metal containing 2.5-4.0% of silicon is subjected to hot rolling, annealing, and cold rolling on the final sheet. ., non-carbonizing annealing and final annealing to complete the second recrystallization 4.

Such processing contributes to a significant improvement in the specific watt loss and magnetic induction due to the formation of a preferential crystallographic texture of the type (110) 001 (edge texture). However, this texture provides high magnetic properties in only one direction - along the rolling. In other areas, properties are much worse, i.e. steel has a high anisotropy, reaching DV 2500 - 0.35-0.55 T.

This steel is used for the manufacture of transformers, however it is unsuitable for the magnetic cores of rotating machines, where ABjsod is 0.16 T (in accordance with GOST 21427, 2-75).

The purpose of the invention is the improvement of the isotropic: magnetic properties of electrical steel.

The goal is achieved by conducting the final annealing depending on the temperature of the secondary recrystallization in two steps: the first - at a temperature of 50-80 ° C below the temperature of the secondary recrist) allysadium with a peak of 2-18 h, the second at a temperature of 1000-1200 ° C with an exposure time of 0.5-2.5 hours, with the heating rate being regulated within the range of 10-50 ° C / h in the first heating stage and 4-16 ° C / min in the second stage.

Steel production with a content of 2.5-3.5% silicon f is conducted in an electric arc furnace or an oxygen converter. After hot rolling to a thickness of 1.5-4.0 mm and acid etching, cold rolling is performed once or twice to the final thickness. When cold rolled once, the metal is decarburized in the final

thickness before final annealing. In cold rolling twice, the anti-carbonizing annealing is carried out in an intermediate thickness before the second cold rolling. The pressing during the second cold rolling is 16-19%. Before the final annealing, the temperature of the secondary recrystallization is determined by gradient annealing of the samples of the finished steel. In accordance with the received

With the results, the final annealing is carried out in two steps: the first — at 50–80 ° C below the temperature of the secondary recrystallization; with an exposure of 2–18 h, the second — at 1QOO –1300 ° C with 0.5–2.5 h. The rate of heating is adjusted so that at the first stage it is 10-50 ° C / h, and at the second stage it is 4-16 ° C / min.

In the first stage of annealing, the initial metal structure is formed. To ensure high and isotropic; The magnetic properties of the metal should have a homogeneous medium-grain initial structure with a grain size of 0.2-0.5 mm. The number of grains with the orientation (100) 001 in this structure should not exceed 25%. Such conditions are provided by the proposed annealing mode at the first stage. A decrease in the annealing temperature at the first stage by more than 80 ° C from the temperature of the secondary recrystallization contributes to the formation of a fine-grained structure, with a grain size of 0.050, 1 mm, which worsens the specific watt loss. A similar effect is exerted by a decrease in the charge of less than 2 h at the annealing temperature and an increase in the heating rate of more than 50 ° C / h. An increase in the annealing temperature in the first stage due to a decrease in the difference between the secondary recrystallization temperature and the annealing temperature in the first stage by less than 50 ° C leads to the development

0 orientation (PO) 001, as a result of which its quantity increases to 50%, which increases the anisotropy of magnetic properties. The same effect has an increase in exposure. ki at annealing temperatures of more than 18 h, and

5 reduction in the speed of yagreva less than 10 ° C / h.

The second annealing stage serves to provide deep refining of the metal from harmful impurities and foriroma and the final structure. To ensure high magnetic properties, the amount of non-metallic inclusions in steel should not exceed 0.010% of the volume, and the structure should (be uniform with grain sizes of 0.4-0.8 mm; the number of grains with orientation (PO) 001 should not exceed 5% of 40%. These conditions are provided by the annealing mode at the second stage: a temperature of 1000-1200 C with a charge of 0.5-2.5 h and a heating rate to this temperature of 416 ° C / min. A decrease in the annealing temperature below 10.00 ° C as well as lowering the shutter speed less than 0 , 5 hours or an increase in the heating rate of more than, 16 ° C / min contributes from grain size to 3 mm. In addition, the conditions for annealing do not provide deep refining of steel from harmful impurities: the number of nonmetallic inclusions is 0,018-0,025% by volume. All this significantly increases the specific loss and reduces magnetic induction. Increasing annealing temperature above 1200 ° C, an increase in the exposure time of more than 2.5 h or a decrease in the heating rate of less than 4 ° C / min contributes to the development of (110) 001 orientation, which increases to 50-80%, as a result of which the isotropy of magnetic oystv. The final annealing is carried out in cap furnaces. As a protective environment, any non-carbonized and non-carbonic atmosphere is used: hydrogen (preferably), nitrogen gas, vacuum, etc. When adjusting the temperature and holding, it is recommended to take into account the thermal nature of the annealing (lower temperatures correspond to elevated temperatures and vice versa). For example, the annealing temperature at the second stage of 1000 ° C corresponds to 2.5 hours, the temperature to 1200 ° C is 0.5 hours. Example. After hot rolling, 2.5 mm steel containing 0.038% C is on a toliosu; 3.0% Si; 0.07% MP; 0.07% Nt; 0.14% C; . 0.004% S; 0.010% A1; 0007% P; 0.04% Cr; the rest of Fe is etched and cold rolled once to a thickness of 0.50 mm. The decarburization of steel is carried out in a horizontal passage furnace in a moist nitrogen gas environment with 5% Hj at a gas humidity at a dew point of + 18 ° C. During decarburization, samples of this steel are taken for the implementation of gradient annealing, which is carried out in a laboratory furnace at 850-1100 ° C along the length of the pattern. Macrostructural analysis of the samples recorded selective grain growth U) and 940 ° C, i.e. The second recrystallization temperature for this steel is 940 ° C. The first stage of the final annealing is carried out at 890 ° С (50% lower than the secondary recrystallization) with a holding time of 2 h at this temperature. Heating to the target temperature is conducted at a rate of 10 ° C / h. Then, this steel is further heated to 1000 ° C at a rate of 4 ° C / min and a shutter speed of 2.5 hours; The cooling of the steel is carried out with an arbitrary circumference. Dry hydrogen is used as a protective medium during heating and cooling at a dew point humidity of -50 ° C. As a result of this treatment, the following level of magnetic properties is obtained: Pt; o / so 1.17 W / kg; 2.93 W / kg; Bjsoo 1.56 T; ABzsoo 0.12 T. These properties are 6% better than the guaranteed GOST 21427, 2-75 for the highest grade of this class 2412, (Pi / 50 1.3 W / kg; Pi, 5 / 5o -M W / kg; BZSOO 1 , 50; T; ABisoo 0.16 T). EXAMPLE 2 The chemical composition and the pretreatment of steel are similar to Example 1. The rate of secondary recrystallization, as in Example 1, is 940 ° C. ° After decarburization, the final annealing is carried out in two steps. First, the metal is heated to 875 ° C (65 ° C below the secondary recrystallization) at a rate of 30 ° C / h. The holding at this temperature is 10 hours. Then, further heating of this steel to 1100 ° C at a rate of 10 ° C / min and a delay of 1.5 hours is carried out. The magnetic properties of this steel are as follows: 1.14 W / kg ; PV / SO 2.86 W / kg; BZSOO 1.55 T; ABj5oo DHS T; which is 8% better than the guaranteed GOST 21427, 2-75 for the highest grade 2412. EXAMPLE 3. Steel in composition and processing, similar to Example 1, is subjected to final annealing in two steps: at 860 ° C (80 ° Lower secondary recrystallization) with an output of 18 h at 1200 ° C with a holding time of 0.5 h. At the first stage, the heating rate is 50 ° C / h, at the second - 16 ° C / min. The magnetic properties obtained after such processing are 5% better than the guaranteed GOST 21427, 2-75 for the highest grade 2412 :. PI / SO 1.20 W / kg; Pi, s / so 2.95 W / kg; Vgoo 1.54 T; ABjsoo 0.13 T. PRI me R 4 (control). The pretreatment and chemical composition of steel are similar to example 1. The final annealing of the metal is carried out under conditions different from the formula of the proposed method. The first stage of annealing is carried out at 900 ° C (40 ° C below the secondary recrystallization) with a charge of 20 h. The heating rate is 5 ° C / h. Further heating to 1250 ° C is carried out at a rate of 3 ° C / min and holding for 3 hours. After this treatment, the following level of magnetic properties is obtained: Pwso 1.05 W / kg; PI, S / SO 2.61 W / kg; Bjjoo 1.61 T; AB2SOO 0.31 T (according to GOST 21427, 2-75 DVg500 0.16T). Example 5. (control). For the study, we used steel made in Example 1. Final annealing was carried out under conditions different from the formulas of the proposed method. First, the steel is heated with a corrosion rate of 60 ° C / h to 850 ° C (90 ° C below the secondary recrystallization) with a holding time of 1 hour at this temperature. Further heating to 950 ° C is carried out at a rate of 18 ° C / min. The discharge at this temperature was 0.3 h.

The magnetic properties of the steel after this treatment are at the level of: PI / SO 1.68W / kg; PI, S / SO 3.74 W / kg; Bjsoo 1.59 T; 0.09 T. According to GOST 21427, 2-75 for the lowest grade steel of this class is 2411 3.6 W / kg.

The results of steel processing by the proposed method are presented in the table.

In order to test the proposed method, steel smelting with a minimum (2.5%), medium (3.0%) and maximum (3.5%) silicon oxide content was achieved in an electric arc furnace. After rolling finishes for 2.5 mm thick and etching in sulfuric acid baths, the steel is cold rolled once for thickness mm and decarburization annealing in horizontal continuous furnaces. For the determination of the secondary recrystallization temperature, fadiene samples were annealed in a laboratory furnace. Depending on the . secondary recrystallization temperatures; final annealing of the plant is carried out in two steps: the first at an aturus rate of 50-80 ° C below the temperature of the secondary recrystallization with an exposure time of 2-18 h,

A reduction of 0.5-2.5 hours. The heating rate at the first stage is 10-50 ° C / h, at the second 4-16 ° C / min. Annealing is carried out in a cap furnace in dry hydrogen with a recrystallization temperature (-40 ° C). When cooled to 150-200 ° C, the speed is not controlled.

Reducing the heating rate, increasing the annealing temperature, increasing the holding time of the first or second stage of the final burning promote the development of (110) 001 orientation and worsening the isotropy of the ABjsoo- magnetic properties. lead to the formation of fine-grained structure and an increase in specific watt losses.

The method can be implemented in metallurgical plants equipped with high-temperature furnace caps with protective atmosphere.

The expected economic effect in the national economy from the foreign policy of the proposed invention due to the reflection of the magnetic properties will be 958 m. in year.

00

15 81708116

Formulation of finding information sources,

Thermal processing is cold-taken into account during examination.

tanoy i electrical steel containing

, 5% Kremishm, including the final Dubrov NF and Lapkin N.I. Electrojig, which replicates the fact that technical steel has become .s. Moscow, Metallurgizdat, 1963, with the aim of improving the isotropy of industrial sites. 217-223.

properties, annealing is carried out in two stages: per-2. U.S. Patent No. 3,948,691, Cl. 148-112,

VA step is 50-80 ° C below the temperature1976.

secondary recrystallization with aging 3. For France of France No. 1472238, class B21B,

2-18 h at a heating rate of 10-AIA / h, WTO-JQ 67.

Step level - at 1000-1200 ° С with a shutter speed4. For France of France No. 2214754, cl. C 21 O 7/00,

0.5-2.5 hours at a rate of 4–16 s / min. 1974.

Claims (1)

The method of heat treatment of cold-rolled · electrical steel containing 23-3.5% silicon, including final annealing, characterized in that, with the aim of improving the isotropy of magnetic properties, annealing is carried out in two stages: the first stage is 50-80 ° C below the secondary recrystallization temperature with a holding time of 2-18 hours at a heating rate of 10–50 ° C / h, the second stage is at 1000–1200 ° C with an exposure of 0.5–2.5 hours at a heating rate of 4–1 ° C / min.