CN107245646B - A kind of preparation method of plate face circumferential direction high-magnetic induction, low-iron loss non-orientation silicon steel - Google Patents

Abstract

The invention belongs to the technical field of metallurgy, and in particular relates to a method for preparing non-oriented silicon steel with high magnetic induction and low iron loss in the circumferential direction of the plate. Carry out according to the following steps: (1) Smelt molten steel according to the set composition, and its composition is by weight percentage: C 0.002～0.005%, Si 1.2～3.0%, Mn 0.2～0.3%, Al≤0.005%, P 0.008～0.03% , S 0.002～0.005%, N≤0.002%, O≤0.002%, Nb≤0.002%, V≤0.002%, Ti≤0.002%, the balance is Fe and unavoidable impurities; (2) after the strip continuous casting process Forming cast strip; (3) hot rolling under inert atmosphere condition; (4) pickling the hot coil strip and coating it with Al ₂ O ₃ release agent and then coiling again; (5) hot coiling into bell furnace for long Time heat treatment; (6) multi-pass cold rolling after cleaning the release agent; (7) recrystallization annealing of cold rolled coils; (8) coating insulating layer to obtain high-performance non-oriented silicon steel products. The strength of {100} texture in the initial structure is enhanced by heat treatment of the cast strip, the cold rolling reduction is matched according to the thickness of the cast strip, and the strong {100} finished texture is obtained by using the genetic effect of texture.

Description

A method for preparing non-oriented silicon steel with high magnetic induction and low iron loss in the circumferential direction of the plate

technical field

The invention belongs to the technical field of metallurgy, and in particular relates to a method for preparing non-oriented silicon steel with high magnetic induction and low iron loss in the circumferential direction of the plate.

Background technique

Non-oriented silicon steel is an important soft magnetic material, which is widely used in various motors due to its low core loss and high magnetic induction. In recent years, with the continuous improvement of society's awareness of energy conservation, emission reduction and resource environmental protection, the performance and output of high-grade non-oriented silicon steel cannot fully meet the needs of the electromechanical industry, which has also become a constraint to the miniaturization, high precision and high efficiency of electromechanical products. The main reason is that the technical potential of high-grade non-oriented silicon steel in the conventional process has been exhausted, and the magnetic induction cannot be improved while the iron loss is reduced, especially the circumferential magnetic induction and magnetic uniformity cannot be improved. This causes a decrease in the rotational torque of the motor and an increase in abnormal losses. Therefore, silicon steel with high circumferential magnetic induction and low iron loss meets the requirements of the next generation of high-efficiency motors for core materials.

At present, the production of non-oriented silicon steel mainly adopts the processes of casting, hot continuous rolling, cold rolling and annealing. Due to the large reduction, there is a strong {111} texture in the final finished plate, and the magnetic properties of the product are poor. In order to improve the magnetic properties of the product and prepare high-grade non-oriented silicon steel, a Chinese patent (publication number CN 102634729 A) discloses a method for preparing a high-grade non-oriented silicon steel with low iron loss and high magnetic induction. Two-stage cold rolling is carried out, and then the 0.35mm cold-rolled plate is annealed to obtain a high-grade non-oriented silicon steel with excellent performance. This process is relatively complicated and the production cost is increased. In order to reduce the production cost of non-oriented silicon steel and improve the magnetic properties of the final product, a new technical approach to prepare non-oriented silicon steel with high magnetic induction and low iron loss is urgently needed. In recent years, relevant technical reports have proposed the use of advanced short-flow strip continuous casting technology to prepare non-oriented silicon steel. The Chinese patent (Notice No. CN 102041367B) discloses a method for preparing non-oriented silicon steel by continuous casting of thin strips. The patent increases the proportion of equiaxed grains in the cast strip by controlling the degree of superheating. The magnetic induction value of the final product is 1.70-1.79T, and The problem of magnetic anisotropy of the product is not explained. U.S. Patent US5482107 discloses a method for producing silicon steel by continuous casting of thin strips. This patent proposes to use the genetic effect of the {100} favorable texture in the as-cast structure by reducing the degree of deformation, so as to obtain a finished product with a strong {100} texture. Steel, but the thickness of the cast strip and the thickness of the finished product are limited by this method.

On the whole, due to the technical characteristics of the process to prepare high magnetic induction non-oriented silicon steel by conventional process, the performance of the final product cannot meet the requirements. However, it is still insufficient to prepare high-grade non-oriented silicon steel by low-cost thin strip continuous casting.

Contents of the invention

In view of the above-mentioned problems existing in the preparation method of the existing high magnetic induction low iron loss non-oriented silicon steel, the present invention provides a preparation method of the plate surface circumferential high magnetic induction low iron loss non-oriented silicon steel, which is based on twin-roll thin strip continuous casting Understanding of the microstructure-texture system in the sub-rapid solidification process of silicon steel, making full use of the advantages of the {100} plane texture in the as-cast microstructure, and obtaining the initial microstructure of strong {100} texture with coarse grain size through heat treatment of the cast strip . After cold rolling and annealing, non-oriented silicon steel with high magnetic induction and low iron loss is obtained.

Technical scheme of the present invention is:

A method for preparing non-oriented silicon steel with high magnetic induction and low iron loss in the circumferential direction of the plate, which is carried out according to the following steps:

(1) Molten steel is smelted according to the set composition, and its composition by weight percentage is: C 0.002～0.005%, Si 1.2～3.0%, Mn0.2～0.3%, Al≤0.005%, P 0.008～0.03%, S 0.002～ 0.005%, N≤0.002%, O≤0.002%, Nb≤0.002%, V≤0.002%, Ti≤0.002%, the balance is Fe and unavoidable impurities;

(2) Strip continuous casting process: the molten steel enters the tundish through the gate, the preheating temperature of the tundish is 1200-1250°C, the superheating degree is controlled at 30-60°C, and the molten steel enters the strip continuous casting machine through the tundish to form a casting Belt, control the casting speed to 40-60m/min, control the height of molten pool liquid level to 100-180mm, and control the thickness of casting belt to 1.5-2.5mm;

(3) After the cast strip is taken out of the roll, it is naturally cooled to a hot rolling mill under inert atmosphere conditions. The hot rolling temperature is 950-1000°C, the final rolling temperature is 900-950°C, the reduction is 2-5%, and it is coiled after hot rolling;

(4) After pickling the hot coil, apply Al ₂ O ₃ release agent and then recoil, the particle size of Al ₂ O ₃ release agent is 10-20 μm;

(5) Hot rolling into bell furnace for heat treatment, under the condition of pure H ₂ circulation with dew point less than -30°C, first raise the temperature to 900-1050°C at a rate of 50-150°C/h, and hold for 2-30h for annealing;

(6) After removing the release agent from the hot coil, perform single-stage multi-pass cold rolling with a total reduction of 60-80% to obtain a cold-rolled coil;

(7) Perform recrystallization annealing on the cold-rolled strip at 850-950°C for 120-180s. During recrystallization annealing, the cold-rolled strip is carried out under protective atmosphere conditions, and the dew point of the atmosphere is controlled below -30°C, and then coated with Cover with an insulating layer and dry to obtain a high-performance non-oriented silicon steel product.

The final thickness of the non-oriented silicon steel is one of three specifications: 0.35mm, 0.50mm and 0.65mm.

The non-oriented silicon steel cast strip has a diameter of 3-15 mm obtained after heat treatment, and the ratio of {100}<0vw> orientation area fraction in grains is higher than 60%.

The {100}<0vw> orientation texture area fraction of the non-oriented silicon steel cold-rolled and annealed sheet in the step (7) exceeds 40%.

The magnetic properties of the non-oriented silicon steel finished product are: P _15/50 is 1.2-3.5W/kg, and the circumferential magnetic induction B ₅₀ of the plate surface is 1.74-1.86T.

In the step (6), the reduction in each pass of single-stage multi-pass cold rolling is 5%-20%.

In the step (7), the protective atmosphere is pure hydrogen or a mixed atmosphere of hydrogen and nitrogen, wherein the volume ratio of hydrogen is not lower than 30%.

The present invention further increases the fraction of {100} plane texture in the heat treatment process of the casting strip by utilizing the advantageous effect of the {100} texture in the thin strip continuous casting non-oriented silicon steel casting strip, and obtains a strong {100} texture with a coarse structure The initial structure, texture inheritance is realized in the subsequent cold rolling-annealing process, and the low-cost preparation of non-oriented silicon steel with high magnetic induction and low iron loss is realized. The technical principles are as follows:

Molten steel flows into the crystallization roll through the tundish. During the sub-rapid solidification process of thin strip continuous casting, the fastest crystallization direction is parallel to the maximum temperature gradient direction, and the solidification structure of the obtained cast strip is {100} texture with high strength. The cast strip is heat-treated for a long time after heat-leveling. Under the condition of pure H ₂ circulation with a dew point less than -30°C, under the combined effect of surface energy and grain size advantages, {100}<0vw>-oriented grains grow abnormally, The {100} texture is further enhanced. According to the initial thickness of the cast strip to match the corresponding cold rolling reduction, in the subsequent cold rolling-annealing process, the inheritance of the strong {100} texture of the abnormally long cast strip is used to obtain the {100}<0vw> texture area The finished board with a score of more than 40% has three specifications of finished thickness: 0.35mm, 0.50mm and 0.65mm. {100}<0vw> is an ideal non-oriented silicon steel texture type, because it is isotropic and has no hard magnetization direction[111], so the performance of the finished board is significantly improved, and the B ₅₀ in any direction on the board surface It is 1.74~1.86T, and P _15/50 is 1.2~3.5W/kg.

Compared with prior art, advantage and beneficial effect of the present invention are:

1. The present invention combines the texture characteristics of sub-rapid solidification of thin strip continuous casting, heat-treats the cast strip under the condition of pure _H2 for a long time, and obtains a grain state with a diameter of 3-15mm and a well-developed {100}<0vw> orientation initial organization. Under the condition that the on-site technology can meet, the strength of {100} texture is further enhanced to provide the basis for its texture inheritance.

2. The present invention is based on the strong {100} texture type of the initial organization, and utilizes its genetic effect in the cold rolling-annealing process to obtain a finished sheet with a {100}<0vw> texture area fraction exceeding 40%, and a finished annealed sheet Significantly improved isotropy, B ₅₀ is 1.74-1.86T in any direction on the plate surface, and P _15/50 is 1.2-3.5W/kg, meeting the performance requirements of high-grade, high magnetic induction, low iron loss non-oriented silicon steel.

3. The present invention can realize the preparation of high-grade non-oriented silicon steel with final thicknesses of 0.35mm, 0.50mm and 0.65mm in combination with the cold rolling reduction corresponding to the thickness matching of the cast strip, breaking through the use of texture inheritance for The limitation of finished product thickness realizes the preparation of thin-gauge and high-grade non-oriented silicon steel.

4. The invention is based on the thin strip continuous casting process, with short process flow, simple manufacturing method, obvious energy saving and consumption reduction, and excellent magnetic properties of the finished product.

Description of drawings

Fig. 1 is the schematic flow chart of the preparation method of high magnetic induction low iron loss non-oriented silicon steel of the present invention;

Fig. 2 is the low-magnification structure of the cast strip coil after heat treatment in Example 2 of the present invention.

Detailed ways

In the specific implementation process, the thin strip continuous casting machine adopted is the thin strip continuous casting machine disclosed in the patent (publication number CN103551532A). As shown in Figure 1, the production process of non-oriented silicon steel with high magnetic induction and low iron loss in the circumferential direction of the plate is as follows: molten steel is smelted according to the set composition, and then enters the strip continuous casting machine to complete the strip continuous casting process, and the cast strip after exiting the casting machine Carry out one hot rolling, the hot-rolled strip is pickled and then coated with a release agent for heat treatment, and then the release agent is cleaned and cold-rolled to obtain a thin strip of target thickness, then recrystallization annealed, the surface of the annealed plate is coated with an insulating coating and dried to obtain Finished non-oriented silicon steel.

Below, the present invention is described in further detail through examples.

Example 1

In this embodiment, molten steel is smelted according to the set composition, and its composition by weight percentage is: C 0.0035%, Si1.2%, Mn 0.2%, Al 0.003%, P 0.008%, S 0.002%, N 0.0015%, O 0.0012 %, Nb0.0010%, V 0.0010%, Ti 0.0010%, the balance is Fe;

Strip continuous casting process: molten steel enters the tundish through the gate, the tundish preheating temperature is 1230°C, and the superheating degree is controlled at 60°C. The molten steel enters the thin strip continuous casting machine through the tundish to form a casting strip, and the casting speed is controlled at 45m/ min, control the height of molten pool liquid level to 180mm, and control the thickness of casting belt to 2.5mm;

After the cast strip comes out of the roll, it is naturally cooled to a hot rolling mill under inert atmosphere conditions. The hot rolling temperature is 960°C, the final rolling temperature is 910°C, the reduction is 3%, and it is coiled after hot rolling;

The hot coil is pickled, coated with Al ₂ O ₃ release agent, and then recoiled. The particle size of Al ₂ O ₃ release agent is 15 μm;

Hot rolled into bell furnace for heat treatment, under the condition of pure H ₂ circulation with dew point less than -30°C, first raise the temperature to 950°C at a rate of 70°C/h, keep it warm for 20h for annealing; non-oriented silicon steel cast strips are obtained after heat treatment It has a diameter of 3-15mm, and the proportion of {100}<0vw> orientation area fraction in the grain is 80%.

After the release agent is removed from the hot coil, single-stage multi-pass cold rolling is carried out, the total reduction is 70%, and the reduction per pass is 15-20%, to obtain a cold-rolled coil with a thickness of 0.65mm;

The cold-rolled strip is recrystallized and annealed at 850°C for 180s. During the recrystallization annealing, the cold-rolled strip is carried out under the conditions of a nitrogen-hydrogen mixed atmosphere (hydrogen volume ratio: 40%), and the dew point of the mixed atmosphere is controlled below -30°C , and then coated with an insulating layer and dried to obtain a high-performance non-oriented silicon steel product. The area fraction of {100}<0vw> orientation texture of non-oriented silicon steel cold-rolled annealed sheet is 65%, and the magnetic properties of the finished product are 1.83T in the three directions B ₅₀ of the sheet surface, 1.83T in the transverse direction, and 1.80T in the 45° rolling direction. , the comprehensive iron loss P _15/50 is 3.5W/kg.

Example 2

In this embodiment, molten steel is smelted according to the set composition, and its composition by weight percentage is: C 0.003%, Si 1.6%, Mn 0.25%, Al 0.0028%, P 0.01%, S 0.004%, N0.0008%, O0.0007%, Nb0.0009%, V0.0006%, Ti0.0006%, the balance is Fe;

Strip continuous casting process: the molten steel enters the tundish through the gate, the tundish preheating temperature is 1250°C, and the superheating degree is controlled at 50°C. min, control the height of molten pool liquid level to 150mm, and control the thickness of casting belt to 2.0mm;

After the cast strip comes out of the roll, it is naturally cooled to a hot rolling mill under inert atmosphere conditions. The hot rolling temperature is 980°C, the final rolling temperature is 900°C, the reduction is 2%, and it is coiled after hot rolling;

The hot coil is pickled, coated with Al ₂ O ₃ release agent, and then recoiled. The particle size of the Al ₂ O ₃ release agent is 12 μm;

Hot roll into bell furnace for heat treatment, under the condition of dew point less than -30°C pure H ₂ circulation, first raise the temperature to 985°C at a rate of 100°C/h, keep it warm for 15h for annealing; non-oriented silicon steel cast strips are obtained after heat treatment It has a diameter of 3-10mm, and the proportion of {100}<0vw> orientation area fraction in the crystal grain is 70%.

After the release agent is removed from the hot coil, single-stage multi-pass cold rolling is carried out, the total reduction is 75%, and the reduction per pass is 15%, to obtain a 0.5mm thick cold-rolled coil;

The cold-rolled strip is recrystallized and annealed at 950°C for 150s. During the recrystallization annealing, the cold-rolled strip is carried out under the condition of a nitrogen-hydrogen mixed atmosphere (hydrogen volume ratio: 45%), and the dew point of the mixed atmosphere is controlled below -30°C , and then coated with an insulating layer and dried to obtain a high-performance non-oriented silicon steel product. The area fraction of {100}<0vw> orientation texture of non-oriented silicon steel cold-rolled annealed sheet is 60%, and the magnetic properties of the finished product are 1.83T in the three directions B ₅₀ of the sheet surface, 1.84T in the transverse direction, and 1.81T in the 45° rolling direction. , the comprehensive iron loss P _15/50 is 3.0W/kg.

As shown in Figure 2, it can be seen from the low-magnification structure of the cast strip after heat treatment that the cast strip has formed a larger grain size structure after heat treatment, with a diameter ranging from 3 to 10mm.

Example 3

In this embodiment, the molten steel is smelted according to the set composition, and its composition is by weight percentage: C 0.005%, Si3.0%, Mn 0.3%, Al0.0036%, P 0.03%, S 0.005%, N0.0010%, O0.0015%, Nb0.0011%, V0.0014%, Ti0.0018%, the balance is Fe;

Strip continuous casting process: molten steel enters the tundish through the gate, the tundish preheating temperature is 1210°C, and the superheating degree is controlled at 30°C, the molten steel enters the thin strip continuous casting machine through the tundish to form a casting strip, and the casting speed is controlled at 60m/ min, control the height of molten pool liquid level to 100mm, and control the thickness of casting belt to 1.5mm;

After the cast strip comes out of the roll, it is naturally cooled to a hot rolling mill under inert atmosphere conditions. The hot rolling temperature is 1000°C, the final rolling temperature is 950°C, the reduction is 5%, and it is coiled after hot rolling;

The hot coil is pickled, coated with Al ₂ O ₃ release agent, and then recoiled. The particle size of Al ₂ O ₃ release agent is 18 μm;

Hot roll into bell furnace for heat treatment, under the condition of pure H ₂ circulation with dew point less than -30°C, first raise the temperature to 1050°C at a rate of 150°C/h, keep it warm for 5h for annealing; non-oriented silicon steel cast strips are obtained after heat treatment It has a diameter of 3-15mm, and the proportion of {100}<0vw> orientation area fraction in the grain is 65%.

After the release agent is removed from the hot coil, single-stage multi-pass cold rolling is carried out, the total reduction is 75%, and the reduction per pass is 10-15%, to obtain a cold-rolled coil with a thickness of 0.35mm;

The cold-rolled strip is recrystallized and annealed at 950°C for 120s. During the recrystallization annealing, the cold-rolled strip is carried out under the condition of a nitrogen-hydrogen mixed atmosphere (hydrogen volume ratio is 35%), and the dew point of the mixed atmosphere is controlled below -30°C , and then coated with an insulating layer and dried to obtain a high-performance non-oriented silicon steel product. The area fraction of {100}<0vw> orientation texture of non-oriented silicon steel cold-rolled annealed sheet is 50%, and the magnetic properties of the finished product are 1.76T in the three directions B ₅₀ of the sheet surface, 1.76T in the transverse direction, and 1.74T in the 45° rolling direction. , the comprehensive iron loss P _15/50 is 1.2W/kg.

The results of the examples show that the present invention enhances the strength of the {100} texture in the initial structure through the heat treatment of the cast strip, matches the cold rolling reduction according to the thickness of the cast strip, and uses the genetic effect of the texture to obtain a strong {100} finished texture. The B ₅₀ in any direction of the high-grade non-oriented silicon steel plate surface is 1.74~1.86T, and the P _15/50 is 1.2~3.5W/kg.

Claims (7)

1. A method for preparing non-oriented silicon steel with high magnetic induction and low iron loss in the circumferential direction of the plate, is characterized in that, it is carried out according to the following steps: (1) Molten steel is smelted according to the set composition, and its composition by weight percentage is: C 0.002～0.005%, Si 1.2～3.0%, Mn 0.2～0.3%, Al≤0.005%, P 0.008～0.03%, S 0.002～0.005 %, N≤0.002%, O≤0.002%, Nb≤0.002%, V≤0.002%, Ti≤0.002%, the balance is Fe and unavoidable impurities; (2) Strip continuous casting process: the molten steel enters the tundish through the gate, the preheating temperature of the tundish is 1200-1250°C, the superheating degree is controlled at 30-60°C, and the molten steel enters the strip continuous casting machine through the tundish to form a casting Belt, control the casting speed to 40-60m/min, control the height of molten pool liquid level to 100-180mm, and control the thickness of casting belt to 1.5-2.5mm; (3) After the cast strip is taken out of the roll, it is naturally cooled to a hot rolling mill under inert atmosphere conditions. The hot rolling temperature is 950-1000°C, the final rolling temperature is 900-950°C, the reduction is 2-5%, and it is coiled after hot rolling; (4) After pickling the hot coil, apply Al ₂ O ₃ release agent and then recoil, the particle size of Al ₂ O ₃ release agent is 10-20 μm; (5) Hot rolling into bell furnace for heat treatment, under the condition of pure H ₂ circulation with dew point less than -30°C, first raise the temperature to 900-1050°C at a rate of 50-150°C/h, and hold for 2-30h for annealing; (6) After removing the release agent from the hot coil, perform single-stage multi-pass cold rolling with a total reduction of 60-80% to obtain a cold-rolled coil; (7) Perform recrystallization annealing on the cold-rolled strip at 850-950°C for 120-180s. During recrystallization annealing, the cold-rolled strip is carried out under protective atmosphere conditions, and the dew point of the atmosphere is controlled below -30°C, and then coated with Cover with an insulating layer and dry to obtain a high-performance non-oriented silicon steel product. 2. The method for preparing non-oriented silicon steel with high magnetic induction and low iron loss in the circumferential direction of the plate according to claim 1, characterized in that the final thickness of the non-oriented silicon steel is one of three specifications: 0.35mm, 0.50mm and 0.65mm . 3. the method for preparing non-oriented silicon steel with high magnetic induction and low iron loss in the circumferential direction of the plate surface according to claim 1, characterized in that, in the step (5), after the non-oriented silicon steel cast strip is heat-treated, { 100}<0vw> orientation area fraction ratio is higher than 60%. 4. The method for preparing non-oriented silicon steel with high magnetic induction and low iron loss in the circumferential direction of the plate according to claim 1, characterized in that the {100}<0vw> orientation of the non-oriented silicon steel cold-rolled annealed sheet in the step (7) The texture area fraction exceeds 40%. 5. The method for preparing non-oriented silicon steel with high magnetic induction and low iron loss in the circumferential direction of the plate according to claim 1, characterized in that the magnetic properties of the finished non-oriented silicon steel are: P _15/50 is 1.2-3.5W/ kg, and the circumferential magnetic induction B ₅₀ of the board surface is 1.74-1.86T. 6. The method for preparing non-oriented silicon steel with high magnetic induction and low iron loss in the circumferential direction of the plate according to claim 1, characterized in that, in the step (6), each pass of single-stage multi-pass cold rolling is reduced The amount is 5% to 20%. 7. The method for preparing non-oriented silicon steel with high magnetic induction and low iron loss in the circumferential direction of the plate according to claim 1, characterized in that, in the step (7), the protective atmosphere is pure hydrogen or a mixed atmosphere of hydrogen and nitrogen, wherein the hydrogen The volume ratio is not less than 30%.