A method of producing an ultra-thin high-magnetic-induction oriented silicon steel by double rolling and a product thereof

Abstract

The application relates to a method for preparing ultra-thin high-magnetic-susceptibility oriented silicon steel by secondary rolling and the product, belonging to the field of oriented silicon steel manufacturing, and characterized in that the chemical composition of the prepared product is as follows: C: 0.035%-0.055%, Si: 2.9%-3.3%, Mn: 0.09%-0.15%, Cu: 0.1%-0.2%, S: <=0.005%, Al: 0.02%-0.04%, N: 0.009%-0.013%, Sn: 0.1%-0.2%, P: <=0.003%, and the rest is Fe and other impurities; the thickness of the ultra-thin high-magnetic-susceptibility oriented silicon steel is 0.08-0.1 mm; in the technical scheme, inhibitors are reasonably selected, asynchronous rolling technology is cited, secondary rolling is implemented, and laser marking is adopted to refine magnetic domains, so that the prepared ultra-thin high-magnetic-susceptibility oriented silicon steel strip has a magnetic induction B8 of >=1.96T and an iron loss P 1.7 / 50 <=1.10W / Kg.

Description

Technical Field

[0001] This invention relates to the field of grain-oriented silicon steel used in saturated reactor cores, and particularly to a method and product for producing ultra-thin high-magnetic-induction grain-oriented silicon steel by secondary rolling. Background Technology

[0002] Grain-oriented silicon steel is a soft magnetic alloy with excellent magnetic properties, widely used in the power industry as a transformer core material. During transformer operation, grain-oriented silicon steel inevitably generates hysteresis loss, current loss, and anomalous loss, dissipating electrical energy as heat—this is known as iron loss. Improving the performance of grain-oriented silicon steel through technological advancements to reduce energy loss during transmission is therefore urgent. As a core material determining transformer losses, the magnitude of iron loss in grain-oriented silicon steel directly affects the overall transformer loss. Since Goss first prepared grain-oriented silicon steel in 1934, its production technology has developed for over 80 years. Based on the fundamental principles of losses generated by grain-oriented silicon steel, domestic research institutions have conducted extensive research on hysteresis loss, eddy current loss, and anomalous loss, significantly optimizing the iron loss performance of grain-oriented silicon steel. Studies have shown that increasing the orientation of Gaussian grains and reducing the thickness of silicon steel sheets can significantly reduce hysteresis loss and eddy current loss. With the continuous improvement of production technology, the orientation degree of Gaussian grains has been improved to a state that is very close to the ideal. At the same time, the thickness of silicon steel sheets has been reduced to 0.18mm and 0.15mm. Further reduction will make the production technology more difficult.

[0003] In ultra-high voltage (UHV) transmission lines, converter valves are the core system of the transmission project. These valves contain thyristors and saturated reactors. The saturated reactors mitigate surge currents caused by line faults by suppressing the rate of current rise (di / dt) when the valve's internal components are turned on, thus protecting the thyristors. Ultra-thin grain-oriented silicon steel is a key material for manufacturing the core of saturated reactors. However, the preparation of ultra-thin silicon steel strips is challenging due to the difficulty in controlling the composition of high-quality, base-material silicon steel without a substrate. Furthermore, the impact mechanisms of process parameters such as cold rolling, recrystallization annealing, and coating on the performance of ultra-thin silicon steel are relatively unclear. This results in domestically produced ultra-thin silicon steel failing to meet the application requirements of UHVDC projects in terms of medium-frequency magnetic properties, coating performance, and plate quality. Summary of the Invention

[0004] To address the problems in the preparation of medium-frequency ultrathin oriented silicon steel strip, this invention studies the selection of raw materials, control of rolling and annealing decarburization processes, addition of inhibitors affecting the nucleation and growth of Goss-oriented grains, and laser marking, and has invented a method and product for preparing ultrathin high magnetic induction oriented silicon steel with a thickness of no more than 0.1 mm through a secondary rolling process.

[0005] The technical solution of this invention lies in rationally selecting grain growth inhibitors, using asynchronous rolling technology, implementing secondary rolling, and refining magnetic domains with laser marking to prepare ultrathin high magnetic induction oriented silicon steel strip.

[0006] According to the technical solution provided by this invention, an ultra-thin high-magnetic-induction oriented silicon steel product is provided. The chemical composition of this ultra-thin high-magnetic-induction oriented silicon steel by mass percentage is: C: 0.035%~0.055%, Si: 2.9%~3.3%, Mn: 0.09%~0.15%, Cu: 0.1%~0.2%, S≤0.005%, Als: 0.02%~0.04%, N: 0.009%~0.013%, Sn: 0.1%~0.2%, P≤0.003%, with the balance being Fe and other impurity elements.

[0007] The ultra-thin high magnetic induction oriented silicon steel uses AlN as the main inhibitor and Cu2S and Sn as auxiliary inhibitors. Sn is used as an auxiliary inhibitor by utilizing its segregation ability at grain boundaries.

[0008] The thickness of the ultra-thin high-magnetic-induction oriented silicon steel is 0.08–0.1 mm;

[0009] The ultra-thin high-magnetic-induction oriented silicon steel has the following magnetic properties: when the Sn addition amount is 0.1-0.2%, the magnetic induction B8 is ≥1.96T, and the iron loss P... 1.7 / 50 ≤1.10W / Kg.

[0010] Furthermore, the preparation method of the ultra-thin high magnetic induction oriented silicon steel is carried out according to the following two-stage rolling production steps: primary rolling → alkaline cleaning → primary decarburization annealing → nitriding treatment → secondary rolling → magnesium oxide coating drying → secondary high-temperature annealing → hot stretching and leveling and coating with insulating layer → laser marking → flattening and coiling, wherein:

[0011] 1) Single rolling: The 0.8mm thick hot-rolled coil is repeatedly cold-rolled in one pass using a Senkimir 20-roll mill to achieve the target thickness of 0.2-0.3mm; the rolling temperature is 40-50℃.

[0012] 2) Alkaline cleaning: The surface of the cold-rolled strip obtained after one cold rolling is cleaned with alkaline solution to remove oil and other contaminants such as rolling coolant, and then dried.

[0013] 3) Primary decarburization annealing: The cold-rolled strip is decarburized and annealed in an annealing furnace; the decarburization annealing temperature is 800-860℃ and the time is 3-6 minutes to achieve primary recrystallization;

[0014] 4) Nitriding treatment: NH4+ is introduced into the annealing furnace. 3，The cold-rolled strip that has undergone decarburization annealing is subjected to nitriding treatment at a temperature of 760-860℃. The amount of NH3 introduced is adjusted according to the nitriding value test results. The target nitriding value is 160-250ppm. The nitriding time is ≥30 seconds. Then it is cooled to room temperature.

[0015] 5) Secondary rolling: The secondary rolling adopts an asynchronous rolling mill, in which the circumferential speed ratio of the upper and lower work rolls of the asynchronous mill is 1:1.01 to 1:1.30. The cold-rolled strip is rolled in three passes, with an average reduction rate of 20% to 25% per pass; each single pass reduces the strip by 10% to 40%, and the final thickness of the secondary cold-rolled strip reaches 0.08 to 0.1 mm.

[0016] 6) Drying of magnesium oxide coating: The surface of the secondary cold-rolled strip that has undergone decarburization annealing and nitriding treatment is coated with MgO. The temperature of the MgO solution during coating is 4-10℃. After coating with MgO, it is dried. The moisture content of the dried MgO is <3%.

[0017] 7) Secondary high-temperature annealing: The high-temperature annealing heating section uses an atmosphere of 60-75% H2 + 25-40% N2, and the temperature is raised to 1200℃ at a heating rate of 20-25℃ / hour; then it is held at 1200℃ for 8-10 hours in a holding atmosphere of 100% H2, with all gases in volume ratio, to achieve secondary recrystallization of Goss grains;

[0018] 8) Hot stretching and leveling and coating with insulation layer: Hot stretching and leveling eliminates the wavy edges of the secondary cold-rolled strip and coating with insulation layer;

[0019] 9) Laser scribing: Laser scribing is used to refine the magnetic domains.

[0020] 10) Flatten and roll up to obtain ultra-thin high magnetic induction oriented silicon steel.

[0021] Specifically, the laser marking steps of 9) are as follows: by controlling the laser power, scanning rate, and marking line spacing, several parallel linear or dotted grooves are marked on the secondary cold-rolled strip perpendicular to the rolling direction. The line spacing between adjacent linear or dotted grooves is 3-4 mm, and the groove depth of each linear or dotted groove is 4-10 μm and the groove width is 20-30 μm.

[0022] The beneficial effects of this invention are mainly reflected in:

[0023] 1. Using 0.8mm thick hot-rolled coil as the base material, and through two rolling processes, the technical problem of not being able to manufacture ≤0.1mm ultra-thin high magnetic orientation silicon steel strip has been basically overcome.

[0024] 2. The production process adopts a two-stage rolling process, especially the asynchronous rolling technology. The rolling effect of the asynchronous rolling mill is more obvious, which can achieve large reduction deformation, thereby breaking the columnar crystals and forming random grain orientation, which is conducive to secondary recrystallization to form Gaussian texture.

[0025] 3. AlN is used as the main inhibitor, with Cu2S and Sn as auxiliary inhibitors. Refining the grain structure of the hot-rolled strip provides sufficient sites for inhibitor precipitation, enhancing the inhibitor's suppressive ability. It can form a large number of subsurface shear deformation structures, providing sites for Goss grain nucleation and sufficient Goss nuclei for secondary recrystallization. Ultimately, this increases the Goss grain orientation, improves magnetic induction, and significantly reduces the hysteresis loss and eddy current loss of the silicon steel sheet. Its magnetic induction B8: ≥1.96T, iron loss P... 1.7 / 50 ≤1.10W / Kg. Detailed Implementation

[0026] The invention will be further described below with reference to the embodiments.

[0027] Example 1

[0028] Ultra-thin high-magnetic-induction oriented silicon steel is manufactured using 0.8mm thick hot-rolled coils as the basic raw material and through the following two-stage rolling process:

[0029] 1) Single rolling: Using a Senkimir 20-roll mill, hot-rolled coils with a thickness of 0.8mm are repeatedly cold-rolled in one pass to a cold-rolled strip with a target thickness of 0.2mm; the rolling temperature is 45℃±2℃;

[0030] 2) Alkaline cleaning: The surface of the cold-rolled strip obtained after one cold rolling is cleaned with alkaline solution to remove oil and other contaminants such as rolling coolant, and then dried.

[0031] 3) Primary decarburization annealing: The cold-rolled strip is subjected to decarburization annealing treatment; the decarburization annealing temperature is 840℃ and the time is 5 minutes to achieve the initial recrystallization;

[0032] 4) Nitriding treatment: NH4+ is introduced into the annealing furnace. 3， The cold-rolled strip that has undergone one decarburization annealing is subjected to nitriding treatment at a temperature of 790℃, a nitriding value of 210ppm, and a nitriding time of 50 seconds, and then cooled to room temperature.

[0033] 5) Secondary rolling: The secondary rolling adopts an asynchronous rolling mill, in which the circumferential speed ratio of the upper and lower work rolls of the asynchronous mill is 1:1.25. The cold-rolled strip with a thickness of 0.2mm is rolled in three passes. The average reduction of the three passes is 20%. The first pass has a reduction of 30%, reaching 0.14. The second pass has a reduction of about 20%, reaching 0.112. The third pass has a reduction of about 15%. The final rolled thickness is 0.087mm.

[0034] 6) Drying of magnesium oxide coating: The surface of the cold-rolled strip that has undergone decarburization annealing and nitriding treatment is coated with MgO. The temperature of the MgO solution during coating is 6℃. After coating with MgO, it is dried. The moisture content of the dried MgO is 2.2%.

[0035] 7) Secondary high-temperature annealing: The high-temperature annealing heating section uses an atmosphere of 75% H2 + 25% N2, and the temperature is raised to 1200℃ at a heating rate of 20℃ / hour; then it is held at 1200℃ for 10 hours in an atmosphere of 100% H2, with all gases in volume ratio, to achieve secondary recrystallization of Goss grains.

[0036] 8) Hot stretching and leveling and coating with insulation layer: Hot stretching and leveling eliminates the wavy edges of the secondary cold-rolled strip and coating with insulation layer;

[0037] 9) Laser marking: A parallel linear groove is marked on the secondary cold-rolled strip at 4mm intervals perpendicular to the rolling direction. The groove depth of each linear or dotted groove is 4μm and the groove width is 25μm.

[0038] 10) Flatten and roll up to obtain ultra-thin high magnetic induction oriented silicon steel.

[0039] The chemical composition of the obtained ultrathin high magnetic induction oriented silicon steel is as follows by mass percentage: C: 0.040%, Si: 3.0%, Mn: 0.12%, Cu: 0.13%, S: 0.005%, Als: 0.03%, N: 0.010%, Sn: 0.18%, P: 0.002%, with the balance being Fe and other impurity elements.

[0040] The resulting ultrathin high magnetic induction oriented silicon steel uses AlN as the main inhibitor and Cu2S and Sn as auxiliary inhibitors.

[0041] The obtained ultrathin high-magnetic-induction oriented silicon steel has a magnetic induction B8 = 1.98T and an iron loss P. 1.7 / 50 = 1.10 W / kg.

[0042] Example 2

[0043] Ultra-thin high-magnetic-induction oriented silicon steel is manufactured using 0.8mm thick hot-rolled coils as the basic raw material and through the following production process:

[0044] 1) Single rolling: The 0.8mm thick hot-rolled coil is repeatedly cold-rolled to the target thickness of 0.25mm in one pass using a Senkimir 20-roll mill; the rolling temperature is 50℃.

[0045] 2) Alkaline cleaning: The surface of the cold-rolled strip obtained after one cold rolling is cleaned with alkaline solution to remove oil and other contaminants such as rolling coolant, and then dried.

[0046] 3) Primary decarburization annealing: The cold-rolled strip is decarburized and annealed in an annealing furnace; the decarburization annealing temperature is 800-860℃ and the time is 6 minutes to achieve primary recrystallization;

[0047] 4) Nitriding treatment: NH3 is introduced into the annealing furnace to nitrid the cold-rolled strip that has undergone one decarburization annealing. The treatment temperature is 810℃. The amount of NH3 introduced is adjusted according to the nitriding value test results. The target nitriding value is 200ppm. The nitriding time is 60 seconds. Then it is cooled to room temperature.

[0048] 5) Secondary rolling: The secondary rolling adopts an asynchronous rolling mill, in which the circumferential speed ratio of the upper and lower work rolls of the asynchronous mill is 1:1.5. The cold-rolled strip is rolled in three passes, with each pass reducing the thickness by 10% to 40%. The final thickness of the secondary cold-rolled strip is 0.09 mm.

[0049] 6) Drying of magnesium oxide coating: The surface of the secondary cold-rolled strip that has undergone decarburization annealing and nitriding treatment is coated with MgO. The temperature of the MgO solution during coating is 5℃. After coating with MgO, it is dried. The moisture content of the dried MgO is 2.5%.

[0050] 7) Secondary high-temperature annealing: The high-temperature annealing heating section uses an atmosphere of 75% H2 + 25% N2, and the temperature is raised to 1200℃ at a heating rate of 25℃ / hour; then it is held at 1200℃ for 9 hours in an atmosphere of 100% H2, with all gases in volume ratio, to achieve secondary recrystallization of Goss grains.

[0051] 8) Hot stretching and leveling and coating with insulation layer: Hot stretching and leveling eliminates the wavy edges of the secondary cold-rolled strip and coating with insulation layer;

[0052] 9) Laser marking: Laser marking is used to refine magnetic domains. A parallel dot-line groove is marked on the secondary cold-rolled strip at 4mm intervals perpendicular to the rolling direction. The groove depth of each dot-line groove is 3μm and the groove width is 20μm.

[0053] 10) Flatten and roll up to obtain ultra-thin high magnetic induction oriented silicon steel.

[0054] The chemical composition of the obtained ultrathin high magnetic induction oriented silicon steel is as follows (by mass percentage): C: 0.045%, Si: 3.2%, Mn: 0.14%, Cu: 0.18%, S: 0.004%, Als: 0.03%, N: 0.011%, Sn: 0.2%, P: 0.002%, with the balance being Fe and other impurity elements.

[0055] The obtained ultrathin high-magnetic-induction grain-oriented silicon steel has a magnetic induction B8 = 1.96T and an iron loss P.1.7 / 50 =1.07W / Kg。

Claims

1. A method for producing ultra-thin high-magnetic-induction grain-oriented silicon steel by secondary rolling, characterized in that... The preparation process is as follows: primary rolling → alkaline cleaning → primary decarburization annealing → nitriding treatment → secondary rolling → drying of magnesium oxide coating → secondary high-temperature annealing → hot stretching and leveling and coating with insulating layer → laser marking → flattening and winding, wherein: 1) Single rolling: The 0.8mm thick hot-rolled coil is repeatedly cold-rolled in one pass using a Senkimir 20-roll mill to achieve the target thickness of 0.2-0.3mm; the rolling temperature is 40-50℃. 2) Alkaline cleaning: The surface of the cold-rolled strip obtained after one cold rolling is cleaned with alkaline solution to remove oil and other contaminants such as rolling coolant, and then dried. 3) Primary decarburization annealing: The cold-rolled strip is decarburized and annealed in an annealing furnace; the decarburization annealing temperature is 800-860℃ and the time is 3-6 minutes to achieve primary recrystallization; 4) Nitriding treatment: NH4+ is introduced into the annealing furnace. 3， The cold-rolled strip that has undergone decarburization annealing is subjected to nitriding treatment at a temperature of 760-860℃. The amount of NH3 introduced is adjusted according to the nitriding value test results. The target nitriding value is 160-250ppm. The nitriding time is ≥30 seconds. Then it is cooled to room temperature. 5) Secondary rolling: The secondary rolling adopts an asynchronous rolling mill, in which the circumferential speed ratio of the upper and lower work rolls of the asynchronous mill is 1:1.01 to 1:1.

30. The cold-rolled strip is rolled in three passes, with an average reduction rate of 20% to 25% per pass; each single pass reduces the strip by 10% to 40%, and the final thickness of the secondary cold-rolled strip reaches 0.08 to 0.1 mm. 6) Drying of magnesium oxide coating: The surface of the secondary cold-rolled strip that has undergone decarburization annealing and nitriding treatment is coated with MgO. The temperature of the MgO solution during coating is 4-10℃. After coating with MgO, it is dried. The moisture content of the dried MgO is <3%. 7) Secondary high-temperature annealing: The high-temperature annealing heating section uses an atmosphere of 60-75% H2 + 25-40% N2, and the temperature is raised to 1200℃ at a heating rate of 20-25℃ / hour; then it is held at 1200℃ for 8-10 hours in a holding atmosphere of 100% H2, with all gases in volume ratio, to achieve secondary recrystallization of Goss grains; 8) Hot stretching and leveling and coating with insulation layer: Hot stretching and leveling eliminates the wavy edges of the secondary cold-rolled strip and coating with insulation layer; 9) Laser scribing: Laser scribing is used to refine the magnetic domains. 10) Flatten and roll up to obtain ultra-thin high magnetic induction oriented silicon steel.

2. The method for preparing an ultrathin high-magnetic-induction oriented silicon steel according to claim 1, characterized in that... Preparation step 9) Laser marking refers to marking several parallel linear or dotted grooves perpendicular to the rolling direction on the secondary cold-rolled strip. The spacing between adjacent linear or dotted grooves is 3-4 mm, and the groove depth of each linear or dotted groove is 4-10 μm and the groove width is 20-30 μm.

3. An ultra-thin high-magnetic-induction oriented silicon steel prepared according to claim 1, characterized in that... The chemical composition of this ultra-thin high magnetic induction oriented silicon steel, by mass percentage, is as follows: C: 0.035%–0.055%, Si: 2.9%–3.3%, Mn: 0.09%–0.15%, Cu: 0.1%–0.2%, S≤0.005%, Als: 0.02%–0.04%, N: 0.009%–0.013%, Sn: 0.1%–0.2%, P≤0.003%, with the balance being Fe and other impurity elements; The thickness of ultra-thin high magnetic induction oriented silicon steel is 0.08-0.1 mm.

4. The ultra-thin high magnetic induction oriented silicon steel according to claim 3, characterized in that... When the Sn addition amount is 0.1-0.2%, the magnetic induction B8 is ≥1.96T, and the iron loss P 1.7 / 50 ≤1.10W / Kg.