High-temperature-annealing-free special-grade electromagnetic pure iron and preparation method thereof

Abstract

The invention belongs to the technical field of production of electromagnetic pure iron cold-rolled strips, and particularly relates to high-temperature-annealing-free special-grade electromagnetic pure iron and a preparation method thereof. S1, smelting and continuous casting; s2, hot rolling is conducted, specifically, the continuous casting slab is heated and rolled, the slab heating staying time in a furnace is longer than or equal to 3 h, and the slab temperature is 1000-1250 DEG C; the finish rolling temperature is 850 DEG C to 950 DEG C, and the coiling temperature is 650 DEG C to 750 DEG C; s3, acid pickling; s4, primary cold rolling is conducted, specifically, cold rolling is conducted in 2-4 passes, and the reduction rate of primary cold rolling is controlled to range from 40% to 80%; s5, intermediate annealing is conducted, specifically, a steel coil is obtained through intermediate annealing; s6, secondary cold rolling is conducted, specifically, secondary cold rolling is conducted in 2-3 passes, and the reduction rate of secondary cold rolling is controlled to range from 20% to 60%; and S7, recrystallization annealing is conducted, specifically, a continuous annealing mode is adopted, the protective atmosphere is nitrogen and hydrogen mixed gas, the temperature of a soaking zone is controlled to be 850-1000 DEG C, the annealing speed is controlled to be 30-80 m / min, and the temperature of a pure iron strip at the outlet position of an annealing furnace is not higher than 300 DEG C. The special-grade electromagnetic pure iron obtained through the preparation method can obtain the magnetic performance without high-temperature magnetic annealing, and the use cost of a user is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of production of electromagnetic pure iron cold-rolled strips, and in particular relates to a special-grade electromagnetic pure iron free of high-temperature annealing and a preparation method thereof. Background Art

[0002] Electromagnetic pure iron is a low-carbon, low-sulfur, low-phosphorus steel with an iron content of more than 99.5% and a carbon content of less than 0.010%. It is a special functional material with excellent soft magnetic properties. It has the advantages of high magnetic induction intensity B, high magnetic permeability μ, low coercivity Hc, good cold and hot processing performance, and low price. It is widely used in the manufacture of DC electromagnetic relays, solenoid valves, clutches and other components and DC motors, magnetic shielding and other equipment. GB / 6983 divides electromagnetic pure iron into four grades according to the coercive force: general grade DT4, advanced DT4A, special grade DT4E and super DT4C.

[0003] In recent years, the electrical, telecommunications, and instrument manufacturing industries have developed rapidly. Along with the high performance of components and the complexity of the shapes of electromagnetic parts, higher requirements have been put forward for the stamping efficiency, formability, processing dimensional accuracy, and magnetic properties of electromagnetic pure iron cold-rolled strips. Due to the high hardness and poor ductility of rolled electromagnetic pure iron, the internal stress generated during the rolling process causes the material to crack or break easily during the downstream stamping process, resulting in low production efficiency; in addition, after the electromagnetic pure iron cold-rolled strip is formed by punching in the downstream, it needs to be further subjected to high-temperature magnetic annealing treatment to obtain the required magnetic properties, including coercive force, magnetic induction intensity, and magnetic permeability. The magnetic properties are greatly affected by raw materials and production processes, especially heat treatment processes, and are prone to performance fluctuations, which may cause product instability in application and affect the normal operation of components. Summary of the invention

[0004] The purpose of the present invention is to provide a special grade electromagnetic pure iron that does not require high temperature annealing and a preparation method thereof, so as to solve the problems that traditional electromagnetic pure iron is prone to cracks or breakages during the rolling process, has low production efficiency and requires high temperature annealing after processing to obtain the required magnetic properties.

[0005] In order to achieve the above object, the present invention adopts the following technical scheme: A special-grade electromagnetic pure iron free of high-temperature annealing, the chemical composition content, measured by mass percentage, includes: C≤0.0030%, Si≤0.01%, Mn: 0.05-0.25%, P≤0.010%, S≤0.0030%, Al: 0-0.80%, Ti≤0.0010%, and the balance is Fe and other inevitable impurities.

[0006] Furthermore, the finished product thickness of the special-grade electromagnetic pure iron is 0.1-5.0 mm.

[0007] Furthermore, the Vickers hardness of the special-grade electromagnetic pure iron is 100±10HV5, and has good stamping performance.

[0008] Furthermore, after the stamping process, no magnetic annealing treatment is performed, and the coercivity of the special grade electromagnetic pure iron is H c≤48A / m.

[0009] Furthermore, after low temperature annealing, the coercive force Hc≤20A / m and the magnetic induction intensity B 10000 ≥1.85T, maximum magnetic permeability μ m ≥15.1mH / m.

[0010] The above-mentioned method for preparing the special grade electromagnetic pure iron without high temperature annealing comprises the following specific steps: S1: Smelting and continuous casting: The process flow is "hot metal pretreatment → top and bottom double blowing converter → RH refining → continuous casting"; the process parameters and composition control design are as follows: (1) At the end of hot metal pretreatment, hot metal S≤0.0015%, P≤0.060%; (2) During converter slag making, dephosphorization, decarburization and demanganese are performed. No deoxidizer is required for steelmaking, and the slag amount at steelmaking is ≤3.5kg / ton of steel; (3) During RH refining, decarburization is performed first. When the carbon content reaches the design requirement, aluminum is added for deoxidation and alloying. The total RH refining time is not less than 30 minutes, and the carbon content C at the end of refining is ≤0.0025%; (4) The molten steel is cast into continuous casting slabs, and argon protection is used throughout the casting process; S2: hot rolling: heating and rolling the continuous casting slab obtained in step S1, wherein the slab heating furnace time is ≥ 3h, the slab temperature is 1000℃~1250℃; the final rolling temperature is 850℃~950℃, the coiling temperature is 650℃~750℃, and the rolling thickness is 2.3mm~8.0mm; S3: Pickling: Use hydrochloric acid pickling, continuous pickling process, the belt threading speed is controlled in the range of 15-40m / min, and the speed is adjusted according to the pickling effect; the acid temperature is controlled in the range of 70-90℃; S4: One-pass cold rolling: The cold rolling is carried out in 2 to 4 passes, and the reduction rate of the first cold rolling is controlled to be 40% to 80%; S5: Intermediate annealing: After intermediate annealing, the steel coil is obtained; S6: Secondary cold rolling: The steel coil processed in step S5 is subjected to secondary cold rolling, the cold rolling is performed in 2-3 passes, and the secondary cold rolling reduction rate is controlled to be 20%-60%; S7: Recrystallization annealing: Continuous annealing is adopted, the protective atmosphere is nitrogen-hydrogen mixed gas, the temperature of the soaking section is controlled at 850℃~1000℃, the annealing speed is 30~80m / min, and the temperature of the pure iron strip at the outlet of the annealing furnace is not higher than 300℃.

[0011] Furthermore, there are two intermediate annealing methods in step S5, namely continuous annealing or hood annealing. When continuous annealing is adopted, nitrogen and hydrogen mixed atmosphere protection is adopted, and the soaking section temperature is controlled to be 700°C~1000°C and the annealing speed is 30~80m / min; when hood annealing is adopted, hydrogen protection is adopted throughout the process, the primary cold-rolled coil is first degreased, the cold coil is heated to the soaking temperature of 500°C~650°C, and kept warm for 6~15h. After the end of the insulation, hydrogen is continued to be passed, and the cooling hood is cooled until it is below 90°C before being taken out of the furnace.

[0012] Compared with the prior art, the present invention has the following beneficial effects: (1) Adding the intermediate annealing process can not only significantly reduce the cold rolling reduction rate of the finished product, but also avoid the deterioration of the plate plasticity caused by work hardening during the cold rolling process, and prevent problems such as uneven deformation, cracks, and fractures caused by rolling at a high reduction rate. While improving production efficiency, it can also further regulate the microstructure before secondary cold rolling and improve the processing performance and soft magnetic properties of the finished product; (2) Through the secondary cold rolling process, the secondary cold rolling reduction rate is controlled to obtain a more ideal finished product microstructure and texture, and the uniform organizational structure improves the toughness and ductility of the material; (3) Adding recrystallization annealing process to eliminate cold rolling strain, make the cold rolled sheet recrystallize and make the grain grow, balance the contradiction between stamping performance and soft magnetic properties, and obtain electromagnetic pure iron cold rolled sheet with good formability and high magnetic properties; (4) The special-grade electromagnetic pure iron obtained by this preparation method is a high-efficiency and high-quality special-grade electromagnetic pure iron material, which does not require further high-temperature magnetic annealing treatment to obtain magnetic properties, thereby reducing the user's use cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is a metallographic photograph of the super-grade electromagnetic pure iron obtained by the preparation method of Example 1; Figure 2 This is a φ2=45° cross-sectional view of the surface texture of the special-grade electromagnetic pure iron obtained by the preparation method of Example 1. DETAILED DESCRIPTION

[0014] The technical solution of the present invention is described clearly and completely below in conjunction with the accompanying drawings and embodiments. Example 1

[0015] A method for preparing special-grade electromagnetic pure iron without high-temperature annealing, the specific steps are as follows: S1: Smelting and continuous casting: The process flow is "hot metal pretreatment → top and bottom double blowing converter → RH refining → continuous casting"; the process parameters and composition control are as follows: (1) At the end of hot metal pretreatment, hot metal S: 0.0015%, P: 0.045%; (2) Dephosphorization, decarburization and demanganese removal in converter slag making, no deoxidizer is added during steelmaking, and the slag amount at steelmaking is 3.1 kg / ton of steel; (3) RH refining first forces decarburization, and when the carbon content reaches the design requirement, aluminum is added for deoxidation and alloying. The total RH refining time is 31 minutes, and the carbon content C at the end of refining is 0.0021%; (4) The molten steel is cast into continuous casting slabs, and argon protection is used throughout the casting process; S2: hot rolling: heating and rolling the continuous casting slab obtained in step S1, wherein the slab heating furnace time is 3.5h, the slab temperature is 1000°C; the final rolling temperature is 850°C, the coiling temperature is 650°C, and the rolling thickness is 6.0mm; S3: Pickling: Use hydrochloric acid pickling, continuous pickling process, belt threading speed is 15m / min, acid temperature is 70℃; S4: primary cold rolling: the cold rolling is carried out in 3 passes, the primary cold rolling reduction rate is controlled to be 41.67%, and the thickness of the cold rolled coil is 3.5 mm; S5: Intermediate annealing: Hood annealing is adopted, and hydrogen protection is adopted throughout the process. First, the cold rolled coil is degreased, and the cold rolled coil is heated to the equalizing temperature of 580℃ and kept warm for 12h. After the end of the heat preservation, hydrogen is continued to be passed, and the cooling hood is cooled until the temperature is below 90℃ before being taken out of the furnace; S6: secondary cold rolling: the steel coil processed in step S5 is subjected to secondary cold rolling, the cold rolling is performed in two passes, the secondary cold rolling reduction rate is controlled to be 42.9%, and the thickness of the cold rolled coil is 2.0 mm; S7: Recrystallization annealing: Continuous annealing is adopted, the protective atmosphere is nitrogen-hydrogen mixed gas, the temperature of the soaking section is controlled to be 930°C, the annealing speed is 30m / min, and the temperature of the pure iron strip at the outlet of the annealing furnace is not higher than 300°C.

[0016] The chemical composition content of the special-grade electromagnetic pure iron obtained by the preparation method is C: 0.0025%, Si: 0.0199%, Mn: 0.1932%, P: 0.0081%, S: 0.0024%, Al: 0.7406%, Co: 0.10%, Ni: 0.15%, Ti: 0.0004%, and the balance is Fe and other inevitable impurities. Calculated by mass percentage, the finished product thickness is 2.0 mm, the Vickers hardness is 105HV5, the coercive force Hc is 20.31A / m, and the magnetic induction intensity B 10000 is 1.863T, the maximum magnetic permeability μ m It is 15.2mH / m.

[0017] like Figure 1The metallographic photographs of the special grade electromagnetic pure iron prepared in Example 1 are shown, all of which are equiaxed ferrite crystals with uniform and large grain sizes, which effectively reduce the coercive force of the material; Figure 2 The figure shows a φ2=45° cross-sectional view of the surface texture of the super-grade electromagnetic pure iron prepared in Example 1. The strong Gaussian texture makes the material have a higher magnetic induction intensity and magnetic permeability, which ensures that the super-grade electromagnetic pure iron obtains excellent comprehensive magnetic properties from the aspects of grain size and grain orientation. Example 2

[0018] A method for preparing special-grade electromagnetic pure iron without high-temperature annealing, the specific steps are as follows: S1: Smelting and continuous casting: The process flow is "hot metal pretreatment → top and bottom double blowing converter → RH refining → continuous casting"; the process parameters and composition control are as follows: (1) At the end of hot metal pretreatment, hot metal S: 0.0013%, P: 0.053%; (2) Dephosphorization, decarburization and demanganese removal in converter slag making, no deoxidizer is added during steelmaking, and the slag amount at steelmaking is 3.4 kg / ton of steel; (3) RH refining first forces decarburization, and when the carbon content reaches the design requirement, aluminum is added for deoxidation and alloying. The total RH refining time is 35 minutes, and the carbon content C at the end of refining is 0.0022%; (4) The molten steel is cast into continuous casting slabs, and argon protection is used throughout the casting process; S2: hot rolling: heating and rolling the continuous casting slab obtained in step S1, wherein the slab heating furnace time is 3.1h, the slab temperature is 1105°C; the final rolling temperature is 880°C, the coiling temperature is 680°C, and the rolling thickness is 6.0mm; S3: Pickling: Use hydrochloric acid pickling, continuous pickling process, belt threading speed is 25m / min, acid temperature is 80℃; S4: primary cold rolling: the cold rolling is carried out in 4 passes, the primary cold rolling reduction rate is controlled to be 61.67%, and the thickness of the primary cold rolled coil is 2.3 mm; S5: Intermediate annealing: Hood annealing is adopted, and hydrogen protection is adopted throughout the process. First, the cold rolled coil is degreased, and the cold rolled coil is heated to the equalizing temperature of 550℃ and kept warm for 10h. After the end of the heat preservation, hydrogen is continued to be passed, and the cooling hood is cooled until the temperature is below 90℃ before being taken out of the furnace; S6: secondary cold rolling: the steel coil processed in step S5 is subjected to secondary cold rolling, the cold rolling is performed in two passes, the secondary cold rolling reduction rate is controlled to be 34.8%, and the thickness of the finished product is 1.5 mm; S7: Recrystallization annealing: Continuous annealing is adopted, the protective atmosphere is nitrogen-hydrogen mixed gas, the temperature of the soaking section is controlled to be 930°C, the annealing speed is 42m / min, and the temperature of the pure iron strip at the outlet of the annealing furnace is not higher than 300°C.

[0019] The chemical composition content of the special-grade electromagnetic pure iron obtained by the preparation method is C: 0.0023%, Si: 0.0051%, Mn: 0.1822%, P: 0.0091%, S: 0.0028%, Al: 0.4226%, Co: 0.19%, Ni: 0.35%, Ti: 0.0003%, and the remainder is Fe and other inevitable impurities. Calculated by mass percentage, the finished product thickness is 1.5mm, the Vickers hardness is 103HV5, the coercive force Hc is 17.75A / m, and the magnetic induction intensity B 10000 is 1.868T, the maximum magnetic permeability μ m It is 15.5mH / m. Example 3

[0020] A method for preparing special-grade electromagnetic pure iron without high-temperature annealing, the specific steps are as follows: S1: Smelting and continuous casting: The process flow is "molten iron pretreatment → top and bottom double blowing converter → RH refining → continuous casting"; the process parameters and composition control are as follows: (1) At the end of molten iron pretreatment, molten iron S: 0.0014%, P: 0.060%; (2) Dephosphorization, decarburization and demanganese removal in converter slag making, no deoxidizer is added during steelmaking, and the slag amount at steelmaking is 3.5 kg / ton of steel; (3) RH refining first forces decarburization, and when the carbon content reaches the design requirement, aluminum is added for deoxidation and alloying. The total RH refining time is 36 minutes, and the carbon content C at the end of refining is 0.0023%; (4) The molten steel is cast into continuous casting slabs, and argon protection is used throughout the casting process; S2: hot rolling: heating and rolling the continuous casting slab obtained in step S1, wherein the slab heating furnace time is 3.4h, the slab temperature is 1200°C; the final rolling temperature is 930°C, the coiling temperature is 750°C, and the rolling thickness is 6.0mm; S3: Pickling: Use hydrochloric acid pickling, continuous pickling process, belt threading speed is 30m / min, acid temperature is 75℃; S4: primary cold rolling: the cold rolling is carried out in 4 passes, the primary cold rolling reduction rate is controlled to be 75%, and the thickness of the primary cold rolled coil is 1.5 mm; S5: Intermediate annealing: Continuous annealing is adopted, with nitrogen and hydrogen mixed atmosphere protection, the soaking section temperature is controlled at 980°C and the annealing speed is 42m / min; S6: Secondary cold rolling: The steel coil processed in step S5 is subjected to secondary cold rolling, the cold rolling is performed in 3 passes, the secondary cold rolling reduction rate is controlled to be 46.7%, and the finished product thickness is 0.8 mm; S7: Recrystallization annealing: Continuous annealing is adopted, the protective atmosphere is nitrogen-hydrogen mixed gas, the temperature of the soaking section is controlled to be 900°C, the annealing speed is 55m / min, and the temperature of the pure iron strip at the outlet of the annealing furnace is not higher than 300°C.

[0021] The chemical composition content of the special-grade electromagnetic pure iron obtained by the preparation method is C: 0.0017%, Si: 0.0032%, Mn: 0.1783%, P: 0.0075%, S: 0.0022%, Al: 0.0508%, Co: 0.30%, Ni: 0.30%, Ti: 0.0002%, and the balance is Fe and other inevitable impurities. Calculated by mass percentage, the finished product thickness is 0.8mm, the Vickers hardness is 108HV5, the coercive force Hc is 16.07A / m, and the magnetic induction intensity B 10000 is 1.8593T, the maximum magnetic permeability μ m It is 19.2mH / m. Example 4

[0022] A method for preparing special-grade electromagnetic pure iron without high-temperature annealing, the specific steps are as follows: S1: Smelting and continuous casting: The process flow is "hot metal pretreatment → top and bottom double blowing converter → RH refining → continuous casting"; the process parameters and composition control are as follows: (1) At the end of hot metal pretreatment, hot metal S: 0.0015%, P: 0.055%; (2) Dephosphorization, decarburization and demanganese removal in converter slag making, no deoxidizer is added during steelmaking, and the slag amount at steelmaking is 3.0 kg / ton of steel; (3) RH refining first forces decarburization, and when the carbon content reaches the design requirement, aluminum is added for deoxidation and alloying. The total RH refining time is 30 minutes, and the carbon content C at the end of refining is 0.0025%; (4) The molten steel is cast into continuous casting slabs, and argon protection is used throughout the casting process; S2: hot rolling: heating and rolling the continuous casting slab obtained in step S1, wherein the slab heating furnace time is 4 hours, the slab temperature is 1230°C; the final rolling temperature is 950°C, the coiling temperature is 730°C, and the rolling thickness is 2.3mm; S3: Pickling: Use hydrochloric acid pickling, continuous pickling process, belt threading speed is 40m / min, acid temperature is 90℃; S4: primary cold rolling: the cold rolling is carried out in 4 passes, the primary cold rolling reduction rate is controlled to be 75%, and the thickness of the primary cold rolled coil is 0.75 mm; S5: Intermediate annealing: Continuous annealing is adopted, with nitrogen and hydrogen mixed atmosphere protection, the soaking section temperature is controlled at 850°C and the annealing speed is 66m / min; S6: Secondary cold rolling: The steel coil processed in step S5 is subjected to secondary cold rolling, the cold rolling is performed in 3 passes, the secondary cold rolling reduction rate is controlled to be 33.3%, and the finished product thickness is 0.5 mm; S7: Recrystallization annealing: Continuous annealing is adopted, the protective atmosphere is nitrogen-hydrogen mixed gas, the temperature of the soaking section is controlled to be 900°C, the annealing speed is 60m / min, and the temperature of the pure iron strip at the outlet of the annealing furnace is not higher than 300°C.

[0023] The chemical composition content of the special-grade electromagnetic pure iron obtained by the preparation method is C: 0.0015%, Si: 0.0065%, Mn: 0.1875%, P: 0.0076%, S: 0.0027%, Al: 0.0544%, Co: 0.25%, Ni: 0.25%, Ti: 0.0002%, and the balance is Fe and other inevitable impurities. Calculated by mass percentage, the finished product thickness is 0.5mm, the Vickers hardness is 97HV5, the coercive force Hc is 14.72A / m, and the magnetic induction intensity B 10000 is 1.8937T, the maximum magnetic permeability μ m It is 21.8mH / m.

[0024] Comparative Example 1 Traditional thin-gauge electromagnetic pure iron cold-rolled products are formed by cold rolling in one step without intermediate annealing. The specific steps are as follows: S1: Smelting and continuous casting: The process flow is "molten iron pretreatment → top and bottom double blowing converter → RH refining → continuous casting"; the process parameters and composition control are as follows: (1) At the end of molten iron pretreatment, molten iron S: 0.0014%, P: 0.060%; (2) Dephosphorization, decarburization and demanganese removal in converter slag making, no deoxidizer is added during steelmaking, and the slag amount at steelmaking is 3.8 kg / ton of steel; (3) RH refining first forces decarburization, and when the carbon content reaches the design requirement, aluminum is added for deoxidation and alloying. The total RH refining time is 36 minutes, and the carbon content C at the end of refining is 0.0021%; (4) The molten steel is cast into continuous casting slabs, and argon protection is used throughout the casting process; S2: hot rolling: heating and rolling the continuous casting slab obtained in step S1, wherein the slab heating furnace time is 3.8h, the slab temperature is 1220°C; the final rolling temperature is 930°C, the coiling temperature is 750°C, and the rolling thickness is 3.5mm; S3: Pickling: Use hydrochloric acid pickling, continuous pickling process, belt threading speed is 35m / min, acid temperature is 75℃; S4: Cold rolling: The cold rolling is carried out in 4 passes, and the reduction rate of the first cold rolling is controlled to be 77.14%, and the thickness of the finished product is 0.8 mm; S5: Recrystallization annealing: Continuous annealing is adopted, the protective atmosphere is nitrogen-hydrogen mixed gas, the temperature of the soaking section is controlled to be 900°C, the annealing speed is 55m / min, and the temperature of the pure iron strip at the outlet of the annealing furnace is not higher than 300°C.

[0025] The chemical composition content of the special-grade electromagnetic pure iron obtained by the preparation method is C: 0.0018%, Si: 0.0292%, Mn: 0.2076%, P: 0.01%, S: 0.0037%, Al: 0.7089%, Co: 0.19%, Ni: 0.35%, Ti: 0.0006%, and the remainder is Fe and other inevitable impurities. Calculated by mass percentage, the finished product thickness is 0.8mm, the Vickers hardness is 117HV5, the coercive force Hc is 98.7A / m, and the magnetic induction intensity B 10000 is 1.8249T, the maximum magnetic permeability μ m It is 14.5mH / m.

[0026] Comparative Example 2 Traditional thick-gauge electromagnetic pure iron cold-rolled products are formed by cold rolling in one step without intermediate annealing. The specific steps are as follows: S1: Smelting and continuous casting: The process flow is "hot metal pretreatment → top and bottom double blowing converter → RH refining → continuous casting"; the process parameters and composition control are as follows: (1) At the end of hot metal pretreatment, hot metal S: 0.0013%, P: 0.055%; (2) Dephosphorization, decarburization and demanganese removal in converter slag making, no deoxidizer is added during steelmaking, and the slag amount at steelmaking is 3.5 kg / ton of steel; (3) RH refining first forces decarburization, and when the carbon content reaches the design requirement, aluminum is added for deoxidation and alloying. The total RH refining time is 35 minutes, and the carbon content C at the end of refining is 0.0021%; (4) The molten steel is cast into continuous casting slabs, and argon protection is used throughout the casting process; S2: hot rolling: heating and rolling the continuous casting slab obtained in step S1, wherein the slab heating furnace time is 3.3h, the slab temperature is 1150°C; the final rolling temperature is 880°C, the coiling temperature is 680°C, and the rolling thickness is 6.0mm; S3: Pickling: Use hydrochloric acid pickling, continuous pickling process, belt threading speed is 32m / min, acid temperature is 80℃; S4: primary cold rolling: the cold rolling is carried out in 3 passes, the primary cold rolling reduction rate is controlled to be 50%, and the finished product thickness is 3mm; S5: Recrystallization annealing: Hood annealing is adopted, and hydrogen protection is used throughout the process. The cold rolled coil is first degreased, and the cold coil is heated to an even temperature of 580°C in the furnace and kept warm for 12 hours. After the end of the insulation, hydrogen is continued to be passed, and the cooling hood is cooled until it is below 90°C before being taken out of the furnace.

[0027] The chemical composition content of the special-grade electromagnetic pure iron obtained by the preparation method is C: 0.0023%, Si: 0.0098%, Mn: 0.1872%, P: 0.0087%, S: 0.0002%, Al: 0.4943%, Co: 0.17%, Ni: 0.34%, Ti: 0.0003%, and the remainder is Fe and other inevitable impurities. Calculated by mass percentage, the finished product thickness is 3.0 mm, the Vickers hardness is 101HV5, the coercive force Hc is 111.66A / m, and the magnetic induction intensity B 10000 is 1.8161T, the maximum magnetic permeability μ m It is 14.2mH / m.

[0028] Compared with Comparative Example 1-2, the Vickers hardness of the special grade electromagnetic pure iron obtained in each embodiment is 97~108HV5, and the coercive force Hc is 14.72~43.31 A / m. The coercive force of the finished product obtained in Comparative Example 1-2 is too high and cannot meet the requirement of direct use without high temperature annealing.

Claims

1. A special grade electromagnetic pure iron free of high temperature annealing, characterized in that: The chemical composition content is calculated by mass percentage, including: C≤0.0030%, Si≤0.01%, Mn: 0.05~0.25%, P≤0.010%, S≤0.0030%, Al: 0~0.80%, Ti≤0.0010%, and the balance is Fe and other inevitable impurities.

2. The special grade electromagnetic pure iron free of high temperature annealing according to claim 1, characterized in that: The finished product thickness of the special-grade electromagnetic pure iron is 0.1-5.0 mm.

3. The special grade electromagnetic pure iron free of high temperature annealing according to claim 1, characterized in that: The Vickers hardness of the special-grade electromagnetic pure iron is 100±10HV5, and has good stamping performance.

4. The special grade electromagnetic pure iron free of high temperature annealing according to claim 1, characterized in that: After stamping and forming, without magnetic annealing, the coercivity of the special grade electromagnetic pure iron is H c≤48A / m.

5. The special grade electromagnetic pure iron free of high temperature annealing according to claim 4, characterized in that: After low temperature annealing, the coercive force Hc≤20A / m, the magnetic induction intensity B 10000 ≥1.85T, maximum magnetic permeability μ m ≥15.1mH / m.

6. The method for preparing the special grade electromagnetic pure iron without high temperature annealing as claimed in claim 1, characterized in that: The specific steps are as follows: S1: Smelting and continuous casting: The process flow is "hot metal pretreatment → top and bottom double blowing converter → RH refining → continuous casting"; the process parameters and composition control design are as follows: (1) At the end of hot metal pretreatment, hot metal S≤0.0015%, P≤0.060%; (2) During converter slag making, dephosphorization, decarburization and demanganese are performed. No deoxidizer is required for steelmaking, and the slag amount at steelmaking is ≤3.5kg / ton steel; (3) During RH refining, forced decarburization is performed first. When the carbon content reaches the design requirement, aluminum is added for deoxidation and alloying. The total RH refining time is not less than 30 minutes, and the carbon content C at the end of refining is ≤0.0025%; (4) The molten steel is cast into continuous casting slabs, and argon protection is used throughout the casting process; S2: hot rolling: heating and rolling the continuous casting slab obtained in step S1, wherein the slab heating furnace time is ≥ 3h, the slab temperature is 1000℃~1250℃; the final rolling temperature is 850℃~950℃, the coiling temperature is 650℃~750℃, and the rolling thickness is 2.3mm~8.0mm; S3: Pickling: Use hydrochloric acid pickling, continuous pickling process, the belt threading speed is controlled in the range of 15-40m / min, and the speed is adjusted according to the pickling effect; the acid temperature is controlled in the range of 70-90℃; S4: One-pass cold rolling: The cold rolling is carried out in 2 to 4 passes, and the reduction rate of the first cold rolling is controlled to be 40% to 80%; S5: Intermediate annealing: After intermediate annealing, the steel coil is obtained; S6: Secondary cold rolling: The steel coil processed in step S5 is subjected to secondary cold rolling, the cold rolling is performed in 2-3 passes, and the secondary cold rolling reduction rate is controlled to be 20%-60%; S7: Recrystallization annealing: Continuous annealing is adopted, the protective atmosphere is nitrogen-hydrogen mixed gas, the temperature of the soaking section is controlled at 850℃~1000℃, the annealing speed is 30~80m / min, and the temperature of the pure iron strip at the outlet of the annealing furnace is not higher than 300℃.

7. The method for preparing a high-grade electromagnetic pure iron free of high-temperature annealing according to claim 6, characterized in that: There are two intermediate annealing methods in step S5, namely continuous annealing or hood annealing. When continuous annealing is adopted, nitrogen and hydrogen mixed atmosphere is used for protection, the soaking section temperature is controlled to be 700°C~1000°C, and the annealing speed is 30~80m / min; when hood annealing is adopted, hydrogen protection is used throughout the whole process, the primary cold-rolled coil is firstly degreased, the cold coil is heated to the soaking temperature of 500°C~650°C, and kept warm for 6~15h. After the end of the insulation, hydrogen is continued to be passed, and the cooling hood is cooled until the temperature is below 90°C before being taken out of the furnace.

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