A kind of low-density δ-ferrite-regulated high-permeability low-carbon steel and its preparation method

Abstract

The present invention provides a low-density δ-ferrite-regulated high-permeability low-carbon steel and a preparation method thereof, belonging to the technical field of high-permeability low-carbon steel soft magnetic materials; the method comprises the following steps: S1, molten steel is cast into a slab through a mold; S2, the slab is heated in a heating furnace at a heating rate of 1-2 °C / S, a heating temperature of 800-900 °C, and a heat preservation time of 30-60 min; S3, then hot-rolled to obtain a hot-rolled sheet, and then the hot-rolled sheet is cooled at a cooling rate of 10-15 °C / s to 700-750 °C, heat-preserved for 20-40 min, and then water-cooled; S4, finally annealed: during annealing, a rapid heating method is adopted in the heating section, the heating rate is 20-30 °C / S, heated to the target annealing temperature of 550-650 °C, heat-preserved for 2-3 h, and then air-cooled to room temperature. The low-carbon steel prepared by the method of the present invention has low density, high permeability and an appropriate δ-ferrite content.

Description

Technical Field

[0001] The present invention relates to the technical field of high-permeability low-carbon steel soft magnetic materials, and particularly to a high-permeability low-carbon steel with low-density δ-ferrite regulation and a preparation method thereof. Background Art

[0002] Magnetic encoders involved in some special numerical control machine tools and the like require soft magnetic materials with both high processing performance and magnetic properties. Therefore, there is an urgent need for high-permeability low-carbon steel with high magnetic permeability, excellent processing performance, and low density and light weight.

[0003] CN113897558B discloses a high-saturation magnetic induction high-permeability iron-based soft magnetic material and a preparation method thereof. The high-saturation magnetic induction high-permeability iron-based soft magnetic material contains the following components: 0-5.0 wt% Co, 2.0-6.0 wt% Si, 0-4.0 wt% Cr, 0-2.0 wt% Mo, 0-2.0 wt% Al, 0-0.06 wt% C, and the balance is Fe; the preparation method includes the following steps: S1, weighing the above raw materials; S2, completely melting the weighed raw materials and casting them into alloy ingots; S3, forging the alloy ingots at 900-1200 °C to obtain hot-worked alloy profiles; the forging ratio is not less than 3:1; S4, hot-rolling the hot-worked alloy profiles at 900-1100 °C to obtain cold-rolled billets; S5, cold-working the cold-rolled billets to cold-rolled semi-finished products and performing continuous annealing treatment;

[0004] After continuous annealing, continue cold-working to obtain a high-saturation magnetic induction high-permeability iron-based soft magnetic material. Although it has the advantages of high saturation magnetic induction, high magnetic permeability, low coercivity, high resistivity, low density, etc., it has the following deficiencies: it is a low-carbon content material with poor processing performance and cannot be processed into special-shaped parts. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a high-permeability low-carbon steel with low-density δ-ferrite regulation and a preparation method thereof, which has low density, high magnetic permeability with high carbon content and an appropriate δ-ferrite content, and can be processed into special-shaped parts.

[0006] To solve the above technical problems, the present invention provides the following technical solutions:

[0007] A preparation method of a high-permeability low-carbon steel with low-density δ-ferrite regulation includes the following steps:

[0008] S1. The molten steel is cast into slabs through continuous casting. The slabs include the following chemical components by mass percentage: C 0.2% - 0.25%, 0.10% ≤ Si ≤ 1.00%, 0.10% ≤ Mn ≤ 3.0%, P ≤ 0.0050%, 1.8% ≤ Alt ≤ 2.4%, preferably ≤ 2.0%, S ≤ 0.0030%, and the rest is Fe and inevitable impurities, and Alt / Si = 1.9 - 2.5;

[0009] S2. The slabs are heated in a heating furnace at a heating rate of 1 - 2 °C / s, a heating temperature of 800 - 900 °C, and a holding time of 30 - 60 min;

[0010] S3. Then hot-rolled to obtain hot-rolled sheets, and then the hot-rolled sheets are cooled at a cooling rate of 10 - 15 °C / s to 700 - 750 °C, held for 20 - 40 min, and then water-cooled;

[0011] S4. Finally, annealing: In the heating section during annealing, a rapid heating method is adopted, with a heating rate of 20 - 35 °C / s, heated to the target annealing temperature of 550 - 650 °C, held for 2 - 3 h, and then air-cooled to room temperature.

[0012] Preferably, Alt / Si = 2 - 2.2. This preferred scheme is more conducive to obtaining low-density, high-permeability low-carbon steel with an appropriate δ-ferrite content.

[0013] Preferably, in S2, the heating rate is 1 - 1.5 °C / s. This preferred scheme can more effectively ensure fine grains and better temperature uniformity, thus being more conducive to obtaining low-density, high-permeability low-carbon steel with an appropriate δ-ferrite content. If the heating rate is too large or too small, the temperature will be uneven and the grains will be coarser.

[0014] Preferably, in S2, the heating temperature is 850 - 900 °C. This preferred scheme can ensure fine grains, thus being more conducive to obtaining low-density, high-permeability low-carbon steel with an appropriate δ-ferrite content. If the heating temperature is too large or too small, the grains will be coarser or not fully austenitized.

[0015] Preferably, in S4, the heating rate is 20 - 30 °C / s. This preferred scheme can reduce dislocation recovery, thus being more conducive to obtaining low-density, high-permeability low-carbon steel with an appropriate δ-ferrite content. If the heating rate is too large or too small, the dislocation density will recover too quickly during heating.

[0016] The present invention also provides a low-density δ-ferrite-regulated high-permeability low-carbon steel prepared by the above preparation method.

[0017] Preferably, the proportion of δ-ferrite in the high-permeability low-carbon steel is above 20% by volume, the grain size is not higher than grade 6, and the density is not higher than 7.5 g / cm3 Its relative permeability is above 2000 H / m.

[0018] The beneficial effects of the above technical solutions of the present invention are as follows:

[0019] Through specific composition components, especially through the reasonable combination of Alt / Si in a specific proportion, the present invention can simultaneously increase the permeability and reduce the density of low-carbon steel. For example, its density can be reduced from the traditional 7.85 g / cm 3 to 7.5 g / cm 3 ; The coordination of Al / Si regulates the proportion of δ-ferrite in the steel; at the same time, through process coordination, especially by improving the heating temperature, heating rate and heating time, the tissue state and internal stress are improved to obtain excellent low-density and high-permeability low-carbon steel, making the morphology of δ-ferrite approximately equiaxed, better ensuring the permeability and processing performance, and increasing the permeability by 20% compared with ordinary 25# steel.

[0020] Specifically, (1) From the perspective of alloy design, the present invention innovatively introduces the reasonable combination of Al and Si. The addition of the two expands the δ-phase region of the steel grade, enabling the steel grade to still retain more than 20% of δ-ferrite at room temperature. At the same time, it expands the lattice lattice of δ-ferrite. When passing through a special heat treatment process, by adjusting the tissue morphology and size of ferrite, it is beneficial to improve the magnetic properties. (2) The reasonable combination of Al and Si in the present invention reduces the density of the steel grade by about 4%, making the density of the steel grade less than 7.5 g / m 3 , expanding the application scope and application scenarios of the steel grade. Specific Embodiments

[0021] To make the technical problems, technical solutions and advantages to be solved by the present invention clearer, the following will be described in detail with specific examples.

[0022] Example 1:

[0023] A kind of low-density high-permeability low-carbon steel with δ-ferrite regulation, the preparation method is as follows:

[0024] By mass percentage of chemical element composition: C 0.23%, Mn 2.5%, Si 0.92%, Alt 1.90%, P 0.0046%, S 0.0025%, with the balance being Fe. Alloying is carried out with industrial pure iron, metallic Mn, Al and ferrosilicon. The alloy is melted in a 50 kg vacuum induction furnace, and after adding vacuum stirring and smelting, it is ingoted. The ingot weighs 45 kg. The ingot is cut off the riser, peeled, and then forged into a slab of appropriate size. It is heated to 900 °C at a rate of 1.5 °C / s and held for 30 min, and then hot-rolled into a 6 mm thick steel plate. Then, accelerated cooling is carried out to 750 °C at a rate of 10 °C / s, held for 30 min, and then air-cooled. After that, the steel plate is heated to 700 °C at a rate of 20 °C / s, held for 2 h, and then air-cooled to room temperature.

[0025] Example 2:

[0026] It is carried out with reference to Example 1, except that by mass percentage of chemical element composition: C 0.21%, Si 0.95%, Mn 0.8%, Alt 1.95%, P 0.0043%, S 0.0022%, with the balance being Fe.

[0027] Example 3:

[0028] It is carried out with reference to Example 1, except that the amount of Alt is adjusted so that Alt / Si = 2.53. Specifically, by mass percentage of chemical element composition: C 0.22%, Mn 2.5%, Si 0.93%, Alt 2.35%, P 0.0010%, S 0.0018%, with the balance being Fe.

[0029] Example 4:

[0030] It is carried out with reference to Example 1, except that the amount of Alt is adjusted so that Alt / Si = 2.05. Specifically, by mass percentage of chemical element composition: C 0.22%, Mn 0.8%, Si 0.95%, Alt 1.95%, P 0.0043%, S 0.0022%, with the balance being Fe.

[0031] Example 5:

[0032] It is carried out with reference to Example 1, except that the heating temperature before hot rolling is 800 °C.

[0033] Comparative Example 1

[0034] It is carried out with reference to Example 1, except that by material composition: C 0.25%, Mn 0.5%, Si 0.2%, P 0.012%, S 0.015%, with the balance being Fe.

[0035] Comparative Example 2

[0036] It was carried out with reference to Example 1, except that the amount of Alt was adjusted so that Alt / Si = 1, and the balance was Fe.

[0037] Comparative Example 3

[0038] It was carried out with reference to Example 1, except that the amount of Alt was adjusted so that Alt / Si = 3, and the balance was Fe.

[0039] Comparative Example 4

[0040] It was carried out with reference to Example 1, except that after forging, it was heated to 1200 °C at 0.5 °C / S and then hot-rolled into a 6-mm-thick steel plate.

[0041] Test Example

[0042] The low-carbon steels obtained in the above examples and comparative examples were subjected to performance tests in accordance with GB / T228-2021, and the test data are shown in Table 1.

[0043] Table 1 Performance comparison between comparative examples and examples

[0044]

[0045] The above is the preferred embodiment of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle described in the present invention, several improvements and refinements can still be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A preparation method of a high magnetic permeability low-carbon steel with regulated low-density δ ferrite, characterized in that, It consists of the following steps: S1. The molten steel is cast into slabs by die casting; the slabs include chemical components with the following mass percentages: C 0.2%-0.25%, 0.10%≤Si≤1.00%, 0.10%≤Mn≤3.0%, P≤0.0050%, 1.8%≤Alt≤2.4%, S≤0.0030%, and the rest is Fe and inevitable impurities, and Alt / Si = 1.9-2.5; S2. The slabs are heated in a heating furnace at a heating rate of 1-2°C / S, a heating temperature of 800-900°C, and a holding time of 30-60 min; S3. Then hot-rolled to obtain hot-rolled sheets, and then the hot-rolled sheets are cooled at a cooling rate of 10-15°C / s to 700-750°C, held for 20-40 min, and then water-cooled; S4. Finally, annealing: During annealing, a rapid heating method is used in the heating section, the heating rate is 20-35°C / S, heated to the target annealing temperature of 550-650°C, held for 2-3 h, and then air-cooled to room temperature; The proportion of δ-ferrite in the high permeability low carbon steel is more than 20% by volume, the grain size is not higher than grade 6, and the density is not higher than 7.5 g / cm 3 , and its relative permeability is above 2000 H / m.

2. The preparation method according to claim 1, characterized in that, Alt / Si = 2-2.

2.

3. The preparation method according to claim 1, characterized in that, The heating rate in S2 is 1-1.5°C / s.

4. The preparation method according to claim 1, characterized in that, The heating temperature in S2 is 850-900°C.

5. The preparation method according to claim 1, wherein The heating rate in S4 is 20-30°C / s.

6. A low-density δ-ferrite-regulated high-permeability low-carbon steel prepared by the preparation method according to any one of claims 1-5.

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