Preparation method of electrical steel and electrical steel

Abstract

The invention discloses a preparation method of electrical steel and the electrical steel. The method comprises the following steps: a preheating step: at least one electrical steel plate blank and a plurality of other steel plate blanks are stacked and preheated, and the electrical steel plate blank comprises the following chemical components in percentage by mass: less than or equal to 0.0050% of C, more than or equal to 1.20% and less than or equal to 1.50% of Si, more than or equal to 0.20% and less than or equal to 0.40% of Mn, less than or equal to 0.04% of P, less than or equal to 0.005% of S, more than or equal to 0.20% and less than or equal to 0.40% of Als and the balance of iron and inevitable trace elements; the temperature of the electrical steel plate blank is less than or equal to 200 DEG C; the temperature of the plate blanks of other steel types is higher than the temperature of the electrical steel plate blank; the target temperature of preheating is greater than or equal to 300 DEG C; the preheating time is 16 to 24 hours; a charging and heating step: charging and heating the preheated plate blank; and a rolling step: rolling the plate blank which is charged and heated. According to the preparation method, the surface quality of the electrical steel is normal, direct waste judgment of the electrical steel plate blank is avoided, and the yield of the electrical steel is increased.

Description

Technical Field

[0001] The present application belongs to the technical field of electrical steel preparation, and specifically relates to a method for preparing electrical steel and electrical steel. Background Art

[0002] Medium and high grade electrical steel has high Si content and low thermal conductivity, which places strict requirements on the preparation process of electrical steel. After continuous casting, the temperature of the electrical steel slab will drop during the placement process. Because the production line is not equipped with a dedicated slab insulation pit or it fails, the temperature of the electrical steel slab drops significantly.

[0003] When a small amount of medium and high grade electrical steel is not loaded into the furnace in time due to rolling line failure, the temperature of the slab entering the furnace is too low. The thermal stress generated by the too fast heating rate during the heating process causes cracks in the slab, and large holes appear during the rolling process. The slabs that are not loaded into the furnace in time can only be scrapped, resulting in great economic losses and seriously affecting the yield rate. Therefore, a process is urgently needed to improve the cracks and large holes in electrical steel. Summary of the invention

[0004] In view of this, the present application provides a method for preparing electrical steel and electrical steel, aiming to provide a preparation method that can significantly improve the surface quality of electrical steel, increase the yield rate of electrical steel, and avoid the problem of low quality yield rate of electrical steel caused by the production line not being equipped with a dedicated slab insulation pit or its failure.

[0005] In a first aspect, an embodiment of the present application provides a method for preparing electrical steel, comprising:

[0006] A preheating step, stacking and preheating at least one electrical steel slab with a plurality of other steel slabs, wherein the electrical steel slab comprises the following chemical composition by mass fraction: C≤0.0050%, 1.20%≤Si≤1.50%, 0.20%≤Mn≤0.40%, P≤0.04%, S≤0.005%, 0.20%≤Als≤0.40%, and the remainder is iron and unavoidable trace elements; the temperature of the electrical steel slab is ≤200°C; the temperature of the other steel slabs is greater than the temperature of the electrical steel slab; the target temperature of preheating is ≥300°C; and the preheating time is 16-24h;

[0007] A furnace charging and heating step, charging the preheated slab into a furnace for heating;

[0008] In the rolling step, the slab heated in the furnace is rolled.

[0009] According to an embodiment of one aspect of the present application, the target temperature of preheating is ≥500°C.

[0010] According to an embodiment of one aspect of the present application, the temperature of the slab of other steel grades is 500 to 820°C.

[0011] According to an embodiment of one aspect of the present application, the preheating step includes: stacking and preheating the electrical steel slabs and other steel type slabs in a hot field surrounded by the other steel type slabs.

[0012] According to an embodiment of one aspect of the present application, the difference in width between any other steel grade slab and any electrical steel slab is ≥50 mm.

[0013] According to an embodiment of one aspect of the present application, the preheating step includes: stacking the electrical steel slabs and other steel slabs in the vertical direction in the following order:

[0014] A1-(BC) n -A2-A3,

[0015] Wherein, n is 1 to 10, A1, B, A2, A3, respectively independently represent other steel slabs, and C represents electrical steel slabs.

[0016] According to an embodiment of one aspect of the present application, the preheating step includes: transferring a plurality of slabs of other steel grades from a production line for producing slabs to the preheating step within 2 hours or less.

[0017] According to an embodiment of one aspect of the present application, between the preheating step and the furnace charging and heating step, the method further includes: transferring the preheated electrical steel slab to the heating furnace within ≤20 min.

[0018] According to an embodiment of one aspect of the present application, the thickness of other steel grade slabs and electrical steel slabs are independently 230-240 mm.

[0019] In a second aspect, an embodiment of the present application provides an electrical steel product, which is prepared by the preparation method of the first aspect.

[0020] This application has at least the following beneficial effects:

[0021] The preparation method provided in the present application is to stack and preheat the electrical steel slabs with multiple other steel grade slabs, and without adding a slab insulation pit, use the hot slabs of other steel grades to preheat the low-temperature, medium and high-grade electrical steel slabs to above 300°C, load the furnace and heat and roll them normally, so that the surface quality of the produced electrical steel is normal, which avoids the direct scrapping of the electrical steel slabs and improves the yield rate of electrical steel. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solution of the implementation regulations of this application, the following is a brief introduction to the drawings required for use in the embodiments of this application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0023] Figure 1A schematic diagram of stacking and preheating the electrical steel slab of Example 1 of the present application and a plurality of slabs of other steel grades is shown.

[0024] Figure 2 A schematic diagram of stacking and preheating the electrical steel slab of Example 1 of the present application and a plurality of slabs of other steel grades is shown.

[0025] Figure 3 A schematic diagram of stacking and preheating the electrical steel slab of Example 1 of the present application and a plurality of slabs of other steel grades is shown.

[0026] Figure 4 The surface quality appearance of the electrical steel of the comparative example of the present application is shown. DETAILED DESCRIPTION

[0027] In order to make the application purpose, technical solution and beneficial technical effect of this application clearer, the application is further described in detail below in conjunction with the embodiments. It should be understood that the implementation regulations described in this specification are only for explaining this application, not for limiting this application.

[0028] For simplicity, the present application only explicitly discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form an unclearly recorded range; and any lower limit can be combined with other lower limits to form an unclearly recorded range, and any upper limit can be combined with any other upper limit to form an unclearly recorded range. In addition, although not clearly recorded, each point or single value between the range endpoints is included in the range. Thus, each point or single value can be combined with any other point or single value as its own lower limit or upper limit or with other lower limits or upper limits to form an unclearly recorded range.

[0029] In the description of the present application, it should be noted that, unless otherwise specified, “above” and “below” are inclusive of the number, and the “multiple” in “one or more” means two or more than two.

[0030] The above application content of the present application is not intended to describe each disclosed embodiment or each implementation in the present application. The following description more specifically illustrates exemplary embodiments. In many places throughout the application, guidance is provided through a series of embodiments, and these implementation regulations can be used in various combinations. In each example, enumeration is only used as a representative group and should not be interpreted as exhaustive.

[0031] Method for preparing electrical steel

[0032] In a first aspect, an embodiment of the present application provides a method for preparing electrical steel, comprising: a preheating step, a furnace charging and heating step, and a rolling step.

[0033] In some optional embodiments, the preheating step includes: transferring a plurality of slabs of other steel grades from a casting production line to the preheating step within 2 hours or less.

[0034] According to the embodiment of the present application, multiple other steel slabs are transferred from the production line of the casting to the preheating step within 2 hours or less, and the temperature drop of the multiple other steel slabs is controlled within a small range. The temperature of the multiple other steel slabs on the production line is about 800°C. Limited by the high temperature of the multiple other steel slabs and the limitations of the equipment and site for transfer, the transfer time is less than or equal to 2 hours, which can control the temperature of the multiple other steel slabs in the preheating step to reach above 300°C.

[0035] In some optional embodiments, the temperature of the slab of other steel grades is 500 to 820°C.

[0036] According to the embodiment of the present application, the temperature of the slab of other steel types can be any value or a range composed of 500°C, 510°C, 520°C, 530°C, 540°C, 550°C, 560°C, 570°C, 580°C, 590°C, 600°C, 610°C, 620°C, 630°C, 640°C, 650°C, 660°C, 670°C, 680°C, 690°C, 700°C, 710°C, 720°C, 730°C, 740°C, 750°C, 760°C, 770°C, 780°C, 790°C, 800°C, 810°C, and 820°C. By controlling the temperature of the slab of other steel types within the above range, the electrical steel slab can be further uniformly heated to above 300°C.

[0037] In some optional embodiments, in the preheating step, at least one electrical steel slab is stacked and preheated with multiple other steel grade slabs, wherein the electrical steel slabs include the following chemical compositions by mass fraction: C≤0.0050%, 1.20%≤Si≤1.50%, 0.20%≤Mn≤0.40%, P≤0.04%, S≤0.005%, 0.20%≤Als≤0.40%, and the rest are iron and unavoidable trace elements; the temperature of the electrical steel slab is ≤200°C; the temperature of the other steel grade slabs is greater than the temperature of the electrical steel slab; the preheating target temperature is ≥300°C; and the preheating time is 16-24h.

[0038] According to the embodiment of the present application, electrical steel (also known as silicon steel or transformer steel) is mainly used to manufacture the core of transformers, generators and motors, and its performance mainly includes magnetic properties and mechanical properties, which are directly affected by surface quality. When the electrical steel slab does not have a slab insulation pit or a fault, the electrical steel slab is directly subjected to the furnace heating step and the rolling step when the temperature is lowered, resulting in poor surface quality of the electrical steel.

[0039] According to the embodiment of the present application, the electrical steel slab is stacked and preheated with multiple other steel grade slabs. The electrical steel slabs with a temperature of ≤200°C are preheated for 16-24h by stacking. The uniformity of the preheating of the electrical steel slab can be improved, and the target temperature of the preheating of the electrical steel slab can be made ≥300°C. This can improve the surface quality of the electrical steel in the subsequent furnace heating step and rolling step, and also improve the yield rate of the electrical steel.

[0040] In some optional embodiments, the preheating step includes: stacking the electrical steel slabs with other steel slabs in a heat field surrounded by the other steel slabs for preheating. Stacking the electrical steel slabs with other steel slabs in a heat field surrounded by the other steel slabs for preheating can further improve the uniformity of preheating the electrical steel slabs, and further improve the surface quality and yield rate of the electrical steel.

[0041] In some optional embodiments, the width difference between any other steel slab and any electrical steel slab is ≥50 mm. Optionally, the width difference between any other steel slab and any electrical steel slab can be any value between 50 mm, 55 mm, 60 mm, 65 mm, 70 mm, 75 mm, 80 mm, 85 mm, 90 mm, 95 mm, 100 mm or a range thereof.

[0042] In some optional embodiments, in order to further improve the heating uniformity, heating degree or heating temperature of the electrical steel slab, the preheating step includes: stacking the electrical steel slab and other steel slabs in the vertical direction in the following order:

[0043] A1-(BC) n -A2-A3,

[0044] Wherein, n is 1 to 10, A1, B, A2, A3, respectively independently represent other steel slabs, and C represents electrical steel slabs.

[0045] For example, the stacking positions of electrical steel slabs and other steel slabs in the vertical direction can be as follows: Figures 1 to 3 shown.

[0046] In some optional embodiments, in order to further improve the uniformity of heating and ensure the temperature of the electrical steel slab before heating, the thickness of the slabs of other steel types and the electrical steel slab are independently 230-240 mm.

[0047] In some optional embodiments, in order to take into account both heat conservation and the surface quality and yield rate of the electrical steel slab, the target temperature of preheating is ≥500°C.

[0048] In some optional embodiments, between the preheating step and the furnace charging and heating step, the method further comprises: transferring the preheated electrical steel slab to the heating furnace within ≤ 20 min. Optionally, the preheated electrical steel slab is transferred to the heating furnace within 0 min, 2 min, 4 min, 6 min, 8 min, 10 min, 12 min, 14 min, 16 min, 18 min, 20 min.

[0049] In some optional embodiments, in the furnace heating step, the preheated slab is heated in the furnace.

[0050] In some optional embodiments, the charging and heating step includes: the charging temperature of the slab is ≥300°C. The charging and heating step includes: controlling the heating temperature of the casting to 1150±20°C, the maximum heating rate is 5°C / min, the total time of the slab in the furnace is controlled to be 130-350min, and the temperature out of the furnace is controlled to be 1120±20°C.

[0051] In some optional embodiments, in the rolling step, the slab heated in the furnace is rolled.

[0052] In some optional embodiments, the rolling step includes rough rolling and finish rolling. In some optional embodiments, the rough rolling includes: 5 rolling passes. In some optional embodiments, the finish rolling includes: the final rolling temperature is controlled at 860±20°C.

[0053] In some optional embodiments, the rolling step may be hot continuous rolling, the main purpose of which is to roll the slab to a target thickness and ensure good temperature, plate shape, and surface quality.

[0054] Electrical Steel Products

[0055] In a second aspect, an embodiment of the present application provides an electrical steel product, which is prepared by the preparation method of the first aspect.

[0056] According to the embodiments of the present application, the yield rate of electrical steel is greater than or equal to 98%, and the surface quality is good.

[0057] Example

[0058] The following examples describe the disclosure of the present application in more detail, and these examples are intended for illustrative purposes only, as it will be apparent to those skilled in the art that various modifications and variations may be made within the scope of the disclosure of the present application. Unless otherwise stated, all parts, percentages, and ratios reported in the following examples are by weight, and all reagents used in the examples are commercially available or synthesized according to conventional methods and can be used directly without further processing, and the instruments used in the examples are commercially available.

[0059] Example 1 to Example 3

[0060] The present application provides a method for preparing electrical steel, comprising:

[0061] Process route: molten iron pre-desulfurization → converter molten steel smelting → RH vacuum treatment → continuous casting → slab warehouse → preheating → heating → rough rolling → finishing rolling → warehousing.

[0062] Hot metal pre-desulfurization: KR mechanical stirring desulfurization technology is used, the outlet [S] is controlled at ≤0.0030%, and the outlet temperature is controlled at ≥1250℃.

[0063] Converter steelmaking: the tapping end point [C] is controlled at 0.020%-0.060%, the tapping end point [O] is controlled at 0.04-0.085%, and the converter end point temperature is controlled at 1630-1680℃.

[0064] RH vacuum treatment: The primary molten steel from the converter is vacuum degassed in the RH furnace, and the temperature and composition are adjusted. After all the alloys are added, it is circulated for 6-12 minutes under the ultimate vacuum degree before being discharged from the station.

[0065] Continuous casting: The superheat of the continuous casting ladle is controlled at 15-35°C, and the casting speed is controlled in the range of ≥1.2m / min.

[0066] A preheating step, stacking and preheating at least one electrical steel slab with a plurality of other steel slabs, and stacking and preheating the electrical steel slab and the other steel slabs in a hot field surrounded by the other steel slabs; wherein the electrical steel slabs include the following chemical components by mass fraction: C≤0.0050%, 1.20%≤Si≤1.50%, 0.20%≤Mn≤0.40%, P≤0.04%, S≤0.005%, 0.20%≤Als≤0.40% , the rest are iron and unavoidable trace elements; the temperature of the electrical steel slab is 90°C; the temperature of the other steel slabs is greater than the temperature of the electrical steel slab; the preheating target temperature is ≥300°C; the preheating time is 16-24h; multiple other steel slabs are transferred from the casting production line to the preheating step within 2h or less; the preheated electrical steel slabs are transferred to the heating furnace within ≤20min; the thickness of the electrical steel slabs and other steel slabs is 2.5mm.

[0067] The step of charging and heating the preheated slab into a furnace is to charge and heat the preheated slab into a furnace. In some optional embodiments, the difference in width between any of the other steel grade slabs and any of the electrical steel slabs is 50 mm.

[0068] The stacking positions of electrical steel slabs and other steel slabs in the vertical direction are as follows:

[0069] A1-(BC) n -A2-A3,

[0070] Wherein, n is 4, A1, B, A2, A3, respectively independently represent the other steel slabs, and C represents the electrical steel slab. The stacking position of the electrical steel slab and the other steel slabs in the vertical direction is as follows: Figure 1 shown.

[0071] In the rolling step, the slab heated in the furnace is rolled.

[0072] The electrical steel slab includes the following chemical components by mass fraction as shown in Table 1.

[0073] Table 1

[0074]

[0075]

[0076] The following insulation control is performed using the ingot numbers starting with 7505906 and 1604121 in Example 1, the ingot number starting with 7505907 in Example 2, and the ingot number starting with 8500483 in Example 3.

[0077] Table 2

[0078]

[0079] Test Section

[0080] The hot rolled plates made from different ingot numbers were tested.

[0081] The evaluation criteria for the surface quality of hot-rolled coils are as follows (only the quality level corresponding to the hole defect is described):

[0082] Quality Grade defect Detection tools First-class products No holes Meter Tester Waste With holes Meter Tester

[0083] The calculation formula for the yield rate is: steel coil weight / slab weight.

[0084] The quality of hot rolled slabs is shown in the following table.

[0085] Table 3

[0086]

[0087] Table 4 Surface quality and yield rate test results of the embodiment.

[0088]

[0089]

[0090] The above measured performance parameters are average values.

[0091] The surface appearance of electrical steel with billet number 1604121011030 is as follows Figure 4 As shown, its surface quality does not meet the standards and is waste.

[0092] The above are only specific implementations of the present application, but the protection scope of the present application is not limited thereto, and any familiarity with the present technology or replacement should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A method for preparing electrical steel, characterized in that: include: A preheating step, stacking and preheating at least one electrical steel slab with a plurality of other steel slabs, wherein the electrical steel slab comprises the following chemical composition by mass fraction: C≤0.0050%, 1.20%≤Si≤1.50%, 0.20%≤Mn≤0.40%, P≤0.04%, S≤0.005%, 0.20%≤Als≤0.40%, and the remainder is iron and inevitable trace elements; the temperature of the electrical steel slab is ≤200°C; the temperature of the other steel slabs is greater than the temperature of the electrical steel slab; the target temperature of the preheating is ≥300°C; and the preheating time is 16-24h; A furnace charging and heating step, charging the preheated slab into a furnace for heating; In the rolling step, the slab heated in the furnace is rolled.

2. The preparation method according to claim 1, characterized in that: The target temperature of the preheating is ≥500°C.

3. The preparation method according to claim 1, characterized in that: The temperature of the slab of other steel grades is 500 to 820°C.

4. The preparation method according to claim 1, characterized in that: The preheating step includes: stacking and preheating the electrical steel slabs and other steel type slabs in a hot field surrounded by the other steel type slabs.

5. The preparation method according to claim 1, characterized in that: The difference in width between any of the other steel grade slabs and any of the electrical steel slabs is ≥50 mm.

6. The preparation method according to claim 1, characterized in that: The preheating step includes: stacking the electrical steel slabs and other steel slabs in the following positions in the vertical direction: <h2 style=";text-align:left;direction:ltr">A1-(BC)<h2 style=";text-align:left;direction:ltr"> n <h2 style=";text-align:left;direction:ltr"> -A2-A3, Wherein, n is 1 to 10, A1, B, A2, A3, respectively independently represent the other steel slabs, and C represents an electrical steel slab.

7. The preparation method according to claim 1, characterized in that: The preheating step includes: transferring a plurality of slabs of other steel grades from a production line for producing slabs to the preheating step within 2 hours or less.

8. The preparation method according to claim 1, characterized in that: Between the preheating step and the furnace charging and heating step, the method further comprises: transferring the preheated electrical steel slab to the heating furnace within ≤20 min.

9. The preparation method according to claim 1, characterized in that: The thickness of the other steel slabs and the electrical steel slabs are independently 230-240 mm.

10. An electrical steel product, characterized in that: The method is described in any one of claims 1 to 9.

Images