A method for calcium treatment of non-oriented electrical steel using ferrosilicon-calcium alloy

Abstract

This application relates to the technical field of metallurgical continuous casting, and particularly to a method for calcium treatment of non-oriented electrical steel using calcium-silicon alloy. The method includes: performing converter smelting on molten steel to make the molten steel meet the set composition requirements, and then refining; decarburizing the refined molten steel to make the decarburized molten steel reach the deoxidized oxygen activity and the target carbon content; alloying the decarburized molten steel through a metal alloy; performing calcium treatment on the alloyed molten steel by controlling the chemical composition of calcium-silicon-barium alloy and the addition amount of calcium-silicon-barium alloy, so that the calcium-treated molten steel reaches the target calcium content. The content of this application solves the technical problem of low calcium absorption rate in the existing calcium treatment process for non-oriented electrical steel. In the embodiments of this application, the Ca absorption rate is 44% - 50%.

Description

Technical Field

[0001] This application relates to the technical field of metallurgical continuous casting, and particularly to a method for calcium treatment of non-oriented electrical steel using calcium-silicon alloy. Background Art

[0002] Calcium has been added as an additive to steel for more than a hundred years. In 1906, Watts added CaSi to the molten steel and found that it could improve the cleanliness of the steel. Calcium is often used as a deoxidizer and desulfurizer to control the oxygen and sulfur contents in the steel below a certain level, so that it can fully carry out the modification of inclusions.

[0003] At present, the calcium treatment process has been widely used, but the most difficult thing to achieve is precise control. Currently, most steel mills commonly use the method of feeding pure calcium wire or calcium alloy wire, but the calcium recovery rate is often very low and unstable. Summary of the Invention

[0004] This application provides a method for calcium treatment of non-oriented electrical steel using calcium-silicon alloy to solve the technical problem of low calcium absorption rate in the existing calcium treatment process for non-oriented electrical steel.

[0005] In a first aspect, this application provides a method for calcium treatment of non-oriented electrical steel using calcium-silicon alloy, and the method includes:

[0006] Carry out converter smelting on the molten steel to make the molten steel meet the set composition requirements, and then refine it;

[0007] Carry out decarburization on the refined molten steel to make the decarburized molten steel reach the deoxidized oxygen activity and the target carbon content;

[0008] Alloy the decarburized molten steel through a metal alloy;

[0009] Carry out calcium treatment on the alloyed molten steel by controlling the chemical composition of the calcium-silicon-barium alloy and the addition amount of the calcium-silicon-barium alloy, so that the calcium-treated molten steel reaches the target calcium content.

[0010] Optionally, the chemical composition of the calcium-silicon-barium alloy includes:

[0011] The content of Si is ≥50 wt%, the content of P is ≤0.02 wt%, the content of S is ≤0.05 wt%, the content of Ba is ≤15 wt%, the content of Ca is ≥15 wt%, the content of Al is ≤5 wt%, the content of Ti is ≤0.01 wt%, and the content of N is ≤0.02 wt%.

[0012] Optionally, the addition amount of the calcium-silicon-barium alloy is 50 kg - 200 kg, and the target calcium content is 15 ppm - 72 ppm.

[0013] Optionally, the set composition requirements include: the tapping oxygen activity of the molten steel ≤ 900 ppm, the content of TFe in the steel slag

[0014] ≤ 20 wt% and the basicity of the steel slag ≤ 3.5.

[0015] Optionally, the deoxidation oxygen activity ≤ 500 ppm.

[0016] Optionally, the target carbon content is ≤ 20 ppm.

[0017] Optionally, after the converter smelting of the molten steel to make the molten steel meet the set composition requirements, it further includes:

[0018] Adding a slag deoxidizer to the molten steel with a set composition to reduce the oxidability of the steel slag;

[0019] The weight of the slag deoxidizer is 500 kg - 1000 kg.

[0020] Optionally, the ferroalloys include: ferrosilicon, ferrotitanium and ferromanganese alloy.

[0021] Optionally, after alloying the decarburized molten steel with ferroalloys, it further includes:

[0022] Circulating the alloyed molten steel under the condition of the first set time;

[0023] The first set time is 3 min - 5 min.

[0024] Optionally, after subjecting the alloyed molten steel to calcium treatment by controlling the chemical composition and the addition amount of calcium silicobarium alloy to make the molten steel after calcium treatment reach the target calcium content, it further includes:

[0025] Pure circulating the molten steel after calcium treatment under the condition of the second set time;

[0026] Sedating the molten steel after pure circulation under the condition of the third set time to make inclusions float.

[0027] The second set time is ≥ 5 min; the third set time is 13 min - 20 min.

[0028] The above technical solutions provided by the embodiments of the present application have the following advantages compared with the prior art:

[0029] The method for calcium treatment of non-oriented electrical steel using ferrosilicon calcium provided by the embodiments of the present application controls the composition of the molten steel at the end point through converter smelting and controls the oxygen activity of the molten steel after decarburization; after alloying, the chemical composition of the calcium silicate barium alloy is designed and its addition amount is controlled to control the calcium content in the molten steel, better removing the inclusions in the steel and thus improving the calcium absorption rate. Description of the Drawings

[0030] The drawings herein are incorporated into the specification and form a part of this specification, showing embodiments consistent with the present application and used together with the specification to explain the principles of the present application.

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, for those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0032] Figure 1 It is a schematic flow chart of a method for calcium treatment of non-oriented electrical steel using ferrosilicon calcium provided by the embodiments of the present application;

[0033] Figure 2 It is the curve of improving the magnetic induction of electrical steel obtained with different addition amounts in the embodiments of the present application;

[0034] Figure 3 It is the curve of improving the iron loss of electrical steel obtained with different addition amounts in the embodiments of the present application. Detailed Embodiments

[0035] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present application with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some, but not all, of the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present application.

[0036] The various embodiments of the present application may exist in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity, and should not be construed as a rigid limitation on the scope of the present application; therefore, it should be considered that the described range description has specifically disclosed all possible sub-ranges and individual values within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and individual numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Additionally, whenever a numerical range is indicated herein, it means including any cited number (fraction or integer) within the indicated range.

[0037] In the present application, unless otherwise stated, the orientation terms such as "upper" and "lower" specifically refer to the drawing direction in the drawings. Additionally, in the description of the specification of the present application, the terms "include", "comprise", etc. mean "include but not limited to". In this document, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. In this document, "and / or" describes the association relationship of associated objects and indicates that three relationships can exist. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. Where A and B can be singular or plural. In this document, "at least one" means one or more, and "multiple" means two or more. "At least one kind", "at least one of the following items (pieces)" or similar expressions refer to any combination of these items, including any combination of single item (piece) or plural items (pieces). For example, "at least one of a, b, or c", or, "at least one of a, b, and c" can both represent: a, b, c, a - b (i.e., a and b), a - c, b - c, or a - b - c, where a, b, and c can be single or multiple respectively.

[0038] Unless otherwise specifically stated, various raw materials, reagents, instruments, equipment, etc. used in the present application can be obtained through market purchase or can be prepared by existing methods.

[0039] In a first aspect, the present application provides a method for calcium treatment of non-oriented electrical steel using ferrosilicon calcium alloy. Please refer to Figure 1 , the method includes:

[0040] S1. Conduct converter smelting on the molten steel to make the molten steel meet the set composition requirements, and then refine it;

[0041] S2. Decarburize the refined molten steel so that the decarburized molten steel reaches the deoxidized oxygen activity and the target carbon content;

[0042] S3. Alloy the decarburized molten steel with a metal alloy;

[0043] S4. Through controlling the chemical composition of the calcium-silicon-barium alloy and the addition amount of the calcium-silicon-barium alloy, perform calcium treatment on the alloyed molten steel so that the calcium-treated molten steel reaches the target calcium content.

[0044] In the embodiment of the present application, the oxygen activity of the molten steel is mainly controlled by converter smelting and secondary refining to lay a foundation for the subsequent calcium treatment of the molten steel. In the calcium treatment process of the molten steel, a calcium-silicon-barium alloy is used and its chemical composition is controlled, so as to obtain the target calcium content, achieve the effect of removing inclusions in the molten steel, and obtain pure molten steel.

[0045] In some embodiments, the chemical composition of the calcium-silicon-barium alloy includes:

[0046] The content of Si is ≥50% by weight, the content of P is ≤0.02% by weight, the content of S is ≤0.05% by weight, the content of Ba is ≤15% by weight, the content of Ca is ≥15% by weight, the content of Al is ≤5% by weight, the content of Ti is ≤0.01% by weight, and the content of N is ≤0.02% by weight.

[0047] The positive effect of controlling the content of Si to be ≥50% by weight: Ensure the purity of the molten steel. If the Si content is too low, to a certain extent, it will increase the content of other impurities. Specifically, the content of Si can be 50% by weight, 52% by weight, 54% by weight, 56% by weight, 58% by weight, etc.

[0048] The positive effect of controlling the content of P to be ≤0.02% by weight: If the P content is too high, to a certain extent, it will increase the P content in the steel and cause cold brittleness. Specifically, the content of P can be 0.02% by weight, 0.015% by weight, 0.01% by weight, etc.

[0049] The positive effect of controlling the content of S to be ≤0.05% by weight: If the S content is too high, to a certain extent, it will increase the S content in the steel and affect the magnetic properties. Specifically, the content of S can be 0.05% by weight, 0.04% by weight, 0.03% by weight, 0.02% by weight, 0.01% by weight, etc.

[0050] The positive effect of controlling the content of Ba to be ≤15% by weight: If the Ba content is too high, to a certain extent, it will affect the cooling cleanliness. Specifically, the content of Ba can be 15% by weight, 14% by weight, 13% by weight, 12% by weight, etc.

[0051] Positive effects of controlling the Ca content to be ≥ 15% by weight: If the Ca content is too low, to a certain extent, it will affect the effect of calcium treatment. Specifically, the Ca content can be 15% by weight, 16% by weight, 17% by weight, 18% by weight, etc.

[0052] Positive effects of controlling the Al content to be ≤ 5% by weight: If the Al content is too high, to a certain extent, it will increase the possibility of calcium-aluminum composite inclusions. Specifically, the Al content can be 5% by weight, 4% by weight, 3% by weight, etc.

[0053] Positive effects of controlling the Ti content to be ≤ 0.01% by weight: If the Ti content is too high, to a certain extent, it will increase the Ti content in the steel and affect the magnetic properties. Specifically, the Ti content can be 0.01% by weight, 0.009% by weight, 0.008% by weight, etc.

[0054] Positive effects of controlling the N content to be ≤ 0.02% by weight: If the N content is too high, to a certain extent, it will increase the N content in the steel and affect the magnetic properties. Specifically, the N content can be 0.02% by weight, 0.01% by weight, 0.005% by weight, etc.

[0055] In some embodiments, the addition amount of the calcium-silicon-barium alloy is 50 kg - 200 kg, and the target calcium content is 15 ppm - 72 ppm.

[0056] Positive effects of controlling the addition amount of the calcium-silicon-barium alloy to be 50 kg - 200 kg: It can ensure the magnetic properties of the finished product and fully carry out calcium treatment. If the addition amount of the calcium-silicon-barium alloy is too high, to a certain extent, it will form too many calcium-aluminum composite inclusions and affect the magnetic properties; if the addition amount of the calcium-silicon-barium alloy is too low, to a certain extent, it will not achieve the purpose of effective calcium treatment. Specifically, the addition amount of the calcium-silicon-barium alloy can be 75 kg, 100 kg, 150 kg, 200 kg, etc.

[0057] Positive effects of controlling the target calcium content to be 15 ppm - 72 ppm: It can fully remove inclusions. If the target calcium content is too high, new string-like Ca compound inclusions will be introduced; if the target calcium content is too low, the effect of removing inclusions such as MnS will not be achieved. Specifically, the target calcium content can be 15 ppm, 20 ppm, 25 ppm, 30 ppm, 35 ppm, etc.

[0058] In some embodiments, the set composition requirements include: the tapping oxygen activity of the molten steel ≤ 900 ppm, the content of TFe in the steel slag ≤ 20% by weight, and the basicity of the steel slag ≤ 3.5.

[0059] Positive effects of controlling the tapping oxygen activity of molten steel ≤ 900 ppm: It enables the molten steel to have a certain oxygen activity without affecting the next operation. If the deoxidation oxygen activity is too high, it will cause the molten steel to be over-oxidized to a certain extent. Specifically, the tapping oxygen activity can be 900 ppm, 850 ppm, 800 ppm, 750 ppm, etc.

[0060] Positive effects of controlling the content of TFe in steel slag ≤ 20%: It ensures the low oxidizability of molten steel. If the content of TFe in steel slag is too high, it will affect the oxidizability of molten steel to a certain extent. Specifically, the content of TFe in steel slag can be 20%, 19%, 18%, 17%, etc.

[0061] Positive effects of controlling the basicity of steel slag ≤ 3.5: It is conducive to fully removing inclusions. If the basicity of steel slag is too high, it will affect the floating of inclusions to a certain extent. Specifically, the basicity of steel slag can be 3.5, 3, 2.5, etc.

[0062] In some embodiments, the deoxidation oxygen activity ≤ 500 ppm.

[0063] Positive effects of controlling the deoxidation oxygen activity ≤ 500 ppm: If the deoxidation oxygen activity is too high, it will increase the formation probability of oxide inclusions. Specifically, the deoxidation oxygen activity can be 500 ppm, 450 ppm, 400 ppm, 350 ppm, etc.

[0064] In some embodiments, the target carbon content is ≤ 20 ppm.

[0065] Positive effects of controlling the target carbon content ≤ 20 ppm: It ensures the aging resistance of the finished steel. If the target carbon content is too high, it will cause the aging resistance of the finished product to deteriorate due to high C in the steel to a certain extent. Specifically, the target carbon content can be 20 ppm, 18 ppm, 16 ppm, 14 ppm, etc.

[0066] In some embodiments, after the molten steel is subjected to converter smelting to meet the set composition requirements, it further includes:

[0067] Adding a slag deoxidizer to the molten steel with the set composition to reduce the oxidizability of the steel slag;

[0068] The weight of the slag deoxidizer is 500 kg - 1000 kg.

[0069] Positive effects of controlling the weight of the slag deoxidizer to be 500 kg - 1000 kg: It fully reduces the oxidizability of the steel slag. If the weight of the slag deoxidizer is too high, it will increase the cost to a certain extent; if the weight of the slag deoxidizer is too low, it will affect the slag deoxidation effect to a certain extent. Specifically, the weight of the slag deoxidizer is 500 kg, 600 kg, 700 kg, 800 kg, 900 kg, 1000 kg, etc.

[0070] In some embodiments, the metal alloy includes: ferrosilicon, ferroaluminum, and ferromanganese alloys.

[0071] Positive effects of ferrosilicon, ferroaluminum, and ferromanganese alloys: alloying treatment of main elements such as Si, Mn, Al, etc.

[0072] In some embodiments, after alloying the decarburized molten steel with the metal alloy, the following steps are further included:

[0073] Circulating the alloyed molten steel under the condition of the first set time;

[0074] The first set time is 3 min - 5 min.

[0075] "The first set time" represents the circulation time. Positive effects of setting the circulation time to 3 min - 5 min: promoting the full floating and removal of formed CaS inclusions and CaO·Al₂O₃ inclusions. If the circulation time is too high, it will affect the treatment cycle; if the circulation time is too low, it will increase the CaO·Al₂O₃ inclusions. Specifically, the circulation time can be 3 min, 4 min, 5 min, etc.

[0076] In some embodiments, after performing calcium treatment on the alloyed molten steel by controlling the chemical composition and addition amount of the calcium silicon barium alloy to make the molten steel after calcium treatment reach the target calcium content, the following steps are further included:

[0077] Performing pure circulation on the molten steel after calcium treatment under the condition of the second set time;

[0078] Performing calming on the molten steel after pure circulation under the condition of the third set time to make the inclusions float.

[0079] The second set time is ≥5 min; the third set time is 13 min - 20 min.

[0080] "The second set time" represents the pure circulation time, and "the third set time" represents the calming time;

[0081] Positive effects of setting the pure circulation time to ≥5 min: making the formed CaS inclusions and CaO·Al₂O₃ inclusions fully float and remove. If the circulation time is too low, it will affect the floating and removal effect of the inclusions. Specifically, the pure circulation time can be 5 min, 6 min, 7 min, 8 min, etc.

[0082] Positive effects of calming: Further promote the full floating and removal of CaS inclusions and CaO·Al₂O₃ inclusions. If the calming time is too long, it will affect the production rhythm to a certain extent; if the calming time is too short, it will affect the floating and removal of inclusions to a certain extent. Specifically, the calming time can be 13 min, 15 min, 17 min, 19 min, etc. At the same time, bottom blowing argon is used.

[0083] The following further elaborates on this application in combination with specific embodiments. It should be understood that these embodiments are only used to illustrate this application and not to limit the scope of this application. For the experimental methods without specific conditions in the following embodiments, they are usually determined according to national standards. If there is no corresponding national standard, they are carried out according to general international standards, conventional conditions, or the conditions recommended by the manufacturer.

[0084] Table 1 Chemical composition of calcium-silicon-barium alloy (wt%).

[0085]

[0086]

[0087] Table 2 End-point composition of converter-smelted molten steel.

[0088]

[0089] Table 3 Calcium treatment process of molten steel.

[0090]

[0091]

[0092] Through a method for calcium treatment of non-oriented electrical steel using calcium-silicon alloy in an embodiment of this application, when the addition amount of calcium-silicon-barium alloy is 50 kg to 200 kg, the Ca absorption rate reaches more than 44%; the finally prepared non-oriented electrical steel has excellent magnetic properties. Especially when the weight of calcium-silicon-barium alloy reaches more than 100 kg, the magnetic induction of non-oriented electrical steel increases and the iron loss decreases; there is an optimal addition amount between 100 kg and 200 kg, which makes the magnetic properties of non-oriented electrical steel the best. See Figure 2 and Figure 3 .

[0093] The above are only specific embodiments of the present application, enabling those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be obvious to those skilled in the art. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown herein, but rather will conform to the broadest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for calcium treatment of non-oriented electrical steel using ferrosilicon-calcium alloy, characterized in that, The method includes: Performing converter smelting on the molten steel to make the molten steel meet the set composition requirements, and then refining; Decarburizing the refined molten steel to make the decarburized molten steel reach the deoxidized oxygen activity and the target carbon content; Alloying the decarburized molten steel with a metal alloy, and circulating the alloyed molten steel under the condition of a first set time, the first set time being 3 min - 5 min; Performing calcium treatment on the alloyed molten steel by controlling the chemical composition and the addition amount of the calcium silicon barium alloy to make the calcium-treated molten steel reach the target calcium content; Performing pure circulation on the calcium-treated molten steel under the condition of a second set time; Performing calming on the pure-circulated molten steel under the condition of a third set time to make inclusions float; The second set time is ≥5 min; the third set time is 13 min - 20 min; The chemical composition of the calcium silicon barium alloy includes: The content of Si is ≥50 wt%, the content of P is ≤0.02 wt%, the content of S is ≤0.05 wt%, 12 wt% ≤ the content of Ba is ≤15 wt%, the content of Ca is ≥15 wt%, 3 wt% ≤ the content of Al is ≤5 wt%, 0.008 wt% ≤ the content of Ti is ≤0.01 wt%, 0.005 wt% ≤ the content of N is ≤0.02 wt%; The addition amount of the calcium silicon barium alloy is 100 kg - 200 kg, the target calcium content is 15 ppm - 72 ppm, and the absorption rate of Ca is more than 44%; The set composition requirements include: the tapping oxygen activity of the molten steel is ≤900 ppm, the content of TFe in the steel slag is ≤20 wt%, and the basicity of the steel slag is ≤3.

5.

2. The method according to claim 1, characterized in that, The deoxidized oxygen activity is ≤500 ppm.

3. The method according to claim 1, characterized in that, The target carbon content is ≤20 ppm.

4. The method according to claim 1, characterized in that, After performing converter smelting on the molten steel to make the molten steel meet the set composition requirements, it further includes: Adding a slag deoxidizer to the molten steel with the set composition to reduce the oxidability of the steel slag; The weight of the slag deoxidizer is 500 kg - 1000 kg.

5. The method according to claim 1, characterized in that, The metal alloy includes: ferrosilicon, ferroaluminum, and ferromanganese alloy.

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