Method for preparing industrial pure iron for neodymium iron boron permanent magnet material

Abstract

The invention discloses a method for preparing industrial pure iron for a neodymium-iron-boron permanent magnet material, which comprises the following steps of: 1) pre-demanganizing and desulfurizing molten iron, namely injecting the molten iron into a pre-demanganizing and desulfurizing device, and adding iron oxide scale and iron red for pre-demanganizing and desulfurizing, so that the weight percentage of manganese in the desulfurized and demanganized molten iron is lower than 0.04 percent, and the weight percentage of sulfur is lower than 0.0015 percent; 2) converter smelting: injecting the molten iron subjected to pre-demanganization and desulfurization treatment into a converter, adding iron oxide scale and iron oxide red, heating to 50-70 DEG C, carrying out secondary demanganization and desulfurization treatment, and pouring slag; then, carrying out dephosphorization and decarbonization treatment; according to the method, iron oxide scale and iron oxide red are mainly adopted as demanganizing and desulfurizing agents, under the synergistic effect of the iron oxide scale and the iron oxide red, the demanganizing rate is increased, the manganese element content in product pure iron is reduced, and therefore the performance requirement of high-end application such as neodymium iron boron permanent magnet materials for industrial pure iron is met.

Description

Technical Field

[0001] The invention relates to the technical field of iron and steel metallurgy, in particular to a method for preparing industrial pure iron for NdFeB permanent magnet material. Background Art

[0002] High purity industrial pure iron is a high-quality alloy material with a strictly controlled carbon content below 0.04% and an iron content of 99.9% or more. This material is widely used in the production of magnetic materials, electronic and electrical fields, new energy batteries, cables, motors, and solenoid valves for electric meters due to its low coercivity, excellent electromagnetic properties, high toughness, and good thermal conductivity. As a key basic raw material in the steel material system, the purity of industrial pure iron directly determines the performance of the final metal product.

[0003] Given the importance of pure iron purity, domestic and foreign academic and industrial circles are committed to developing more advanced technical means and production processes to further improve the purity of pure iron. Among them, for high-end industrial pure iron, the control of manganese content in molten steel is particularly strict. However, current technical means still face challenges.

[0004] Specifically, the existing patent case CN202210840074.0 proposes a technical solution called "Non-aluminum deoxidation raw material pure iron for amorphous soft magnetic thin strip and its preparation method", which aims to reduce the manganese content in pure iron through a series of complex pretreatment and smelting processes, including molten iron pretreatment desulfurization and demanganese, full molten iron loading in the converter, double slag method deep demanganese and dephosphorization, and maintenance of molten steel [O] content during refining. However, the solution uses iron oxide scale as the only demanganese agent, and its demanganese effect is not ideal. The manganese content in the obtained pure iron is still too high, which cannot meet the performance requirements of industrial pure iron for high-end applications such as NdFeB permanent magnet materials.

[0005] Therefore, how to effectively reduce the manganese content in pure iron and achieve stable control of ultra-low manganese content has become a key technical problem that needs to be solved in the current preparation of high-purity iron. Solving this problem is of great significance to promoting the development of industrial pure iron materials and enhancing their application value in high-end fields. Summary of the invention

[0006] The invention provides a method for preparing industrial pure iron for NdFeB permanent magnet material. The preparation method effectively reduces the manganese content in the pure iron, realizes stable control of ultra-low manganese content, and thus solves the problem of high manganese content in pure iron obtained by existing industrial pure iron smelting methods.

[0007] To achieve the above purpose, the technical solution adopted by the present invention is: It includes using iron oxide scale and red iron as demanganese agents.

[0008] In the above technical solution, a more specific technical solution may also be: the mass ratio of the iron oxide scale to the red iron oxide is 0.3 to 0.4.

[0009] Furthermore, the addition amount of iron oxide scale and iron red is 0.15% to 0.20% of the mass of the raw material molten iron.

[0010] Furthermore, the preparation method comprises the following steps in sequence: 1) Pre-demanganese and desulfurization treatment of molten iron: The molten iron is injected into a pre-demanganese and desulfurization device, and iron oxide scale and iron red are added to perform pre-demanganese and desulfurization treatment, so that the manganese weight percentage of the molten iron after desulfurization and demanganese is less than 0.04%, and the sulfur weight percentage is less than 0.0015%; 2) Converter smelting: The molten iron which has been pre-demanganized and desulfurized is injected into the converter, iron oxide scale and iron oxide red are added, and the temperature is increased by 50°C to 70°C based on the reaction temperature in step 1) to perform secondary demanganization and desulfurization treatment, and the slag is poured; then, dephosphorization and decarburization treatment are performed; 3) LF refining deep deoxidation and desulfurization treatment; 4) RH refining deep decarburization, dealumination and degassing treatment; 5) Continuous casting.

[0011] Furthermore, in the above step 2) of converter smelting, the method of dephosphorization is: using iron oxide, lime and fluorite as slag-making raw materials, and performing dephosphorization according to the slag-making method; wherein the mass ratios of iron oxide, lime and fluorite are 40%, 20% and 40%.

[0012] Furthermore, the method of the above step 3) LF refining deep deoxidation and desulfurization treatment is: first adding aluminum powder for deoxidation treatment, and then adding calcium oxide for desulfurization treatment.

[0013] Furthermore, in the above step 5) continuous casting, the superheat is 30° C. and the casting speed is 1.0 m / min.

[0014] Due to the adoption of the above technical solution, the present invention has the following beneficial effects compared with the prior art: 1. The present invention mainly adopts iron oxide scale and iron red as demanganese and desulfurization agents. Under the synergistic effect of the two, the demanganese rate is improved and the manganese content in the product pure iron is reduced (the Mn content can be as low as 0.018%), thereby meeting the performance requirements of industrial pure iron for high-end applications such as NdFeB permanent magnet materials.

[0015] 2. Furthermore, in the present invention, under the condition of using iron oxide scale and iron red as demanganese desulfurization agents, two demanganese desulfurization treatments are carried out by adopting a two-step method (i.e., in the first step, iron oxide scale and iron red are first added for pre-demanganese desulfurization treatment; then, iron oxide scale and iron red are added again, and the temperature is increased by 50 to 70° C. on the basis of the reaction temperature in the first step for secondary demanganese and desulfurization treatment), so that the comprehensive manganese removal rate of the two demanganese desulfurization treatments reaches an average of 40 to 50%, thereby further reducing the manganese content in the product pure iron. DETAILED DESCRIPTION

[0016] The present invention is further described in detail below with reference to examples; The method for preparing industrial pure iron for NdFeB permanent magnet material comprises the following steps in sequence: 1) Pre-demanganese and desulfurization treatment of molten iron: The molten iron is injected into a pre-demanganese and desulfurization device, and iron oxide scale and iron red are added to perform pre-demanganese and desulfurization treatment, so that the manganese weight percentage of the molten iron after desulfurization and demanganese is less than 0.04%, and the sulfur weight percentage is less than 0.0015%; 2) Converter smelting: The molten iron which has undergone the pre-demanganese and desulfurization treatment is injected into the converter, iron oxide scale and iron red are added, and the temperature is increased by 50°C to 70°C based on the reaction temperature of step 1) for secondary demanganese and desulfurization treatment, and the slag is poured; then, dephosphorization and decarbonization treatment are carried out; wherein the dephosphorization treatment method is: using iron oxide, lime and fluorite as slag-making raw materials, and dephosphorization treatment is carried out according to the slag-making method; wherein the mass ratios of iron oxide, lime and fluorite are 40%, 20% and 40%; 3) LF refining deep deoxidation and desulfurization treatment: first add aluminum powder for deoxidation treatment and blow, stir with argon; then heat up and add calcium oxide for desulfurization; 4) RH refining deep decarburization, dealumination and degassing treatment: enter the RH station, evacuate, then blow in argon to start the steel liquid circulation, and blow oxygen and argon at the same time; 5) Continuous casting: superheat is 30°C and pulling speed is 1.0m / min.

[0017] Examples 1-4 and the comparative example all adopt the above process steps to prepare industrial pure iron for NdFeB permanent magnet materials, and their specific raw materials and process parameters are shown in Tables 1-5.

[0018] Table 1 shows the process parameters of Examples 1-4 and Comparative Example Step 1) Pre-demanganese and desulfurization treatment of molten iron .

[0019] From Table 1 above, we can see that: ① After the pre-demanganese and desulfurization treatment in step 1), the Mn content of molten iron is significantly reduced, and the demanganese rate can reach up to 80%; ② Compared with the comparative example using only iron oxide scale as the demanganizing agent, Examples 1-4 use iron oxide scale and iron red as the demanganizing agent, and the Mn content of the molten iron is significantly lower, and the demanganizing rate is also higher. It can be seen that the demanganizing effect of iron oxide scale and iron red as the demanganizing agent is significantly superior to the demanganizing effect of using only iron oxide scale as the demanganizing agent.

[0020] Table 2 shows the process parameters of converter smelting in Examples 1-4 and Comparative Example Step 2 .

[0021] From Table 2 above, we can see that: ① After the secondary demanganese and desulfurization treatment in step 2) converter smelting, the Mn content of molten iron is further reduced, and the demanganese rate is 40-50% on average; ② Similarly, compared with the comparative example using only iron oxide scale as the demanganizing agent, Examples 1-4 use iron oxide scale and iron red as the demanganizing agent, and the Mn content of the molten iron is significantly lower, and the demanganizing rate is also higher. It can be seen that the demanganizing effect of iron oxide scale and iron red as the demanganizing agent is significantly superior to the demanganizing effect of using only iron oxide scale as the demanganizing agent.

[0022] Table 3 shows the process parameters of LF refining deep deoxidation and desulfurization treatment in Examples 1-4 and Comparative Example Step 3) .

[0023] Table 4 shows the process parameters of deep decarburization, dealumination and degassing in Examples 1-4 and Comparative Example Step 4) RH refining .

[0024] Table 5 shows the process parameters of continuous casting in Examples 1-4 and Comparative Example Step 5) .

[0025] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing industrial pure iron for NdFeB permanent magnet material, characterized in that: Iron oxide scale and red iron are used as demanganese agents.

2. The method for preparing industrial pure iron for NdFeB permanent magnet material according to claim 1, characterized in that: The mass ratio of the iron oxide scale to the iron red is 0.3 to 0.

4.

3. The method for preparing industrial pure iron for NdFeB permanent magnet material according to claim 2, characterized in that: The amount of iron oxide scale and iron red added is 0.15% to 0.20% of the mass of the raw molten iron.

4. The method for preparing industrial pure iron for NdFeB permanent magnet material according to claim 1, 2 or 3, characterized in that The preparation method comprises the following sequential steps: 1) Pre-demanganese and desulfurization treatment of molten iron: The molten iron is injected into a pre-demanganese and desulfurization device, and iron oxide scale and iron red are added to perform pre-demanganese and desulfurization treatment, so that the manganese weight percentage of the molten iron after desulfurization and demanganese is less than 0.04%, and the sulfur weight percentage is less than 0.0015%; 2) Converter smelting: The molten iron which has been pre-demanganized and desulfurized is injected into the converter, iron oxide scale and iron oxide red are added, and the temperature is increased by 50°C to 70°C based on the reaction temperature in step 1) to perform secondary demanganization and desulfurization treatment, and the slag is poured; then, dephosphorization and decarburization treatment are performed; 3) LF refining deep deoxidation and desulfurization treatment; 4) RH refining deep decarburization, dealumination and degassing treatment; 5) Continuous casting.

5. The method for preparing industrial pure iron for NdFeB permanent magnet material according to claim 4, characterized in that: In the above step 2) of converter smelting, the method of dephosphorization is: using iron oxide, lime and fluorite as slag-making raw materials, and performing dephosphorization according to the slag-making method; wherein the mass ratios of iron oxide, lime and fluorite are 40%, 20% and 40%.

6. The method for preparing industrial pure iron for NdFeB permanent magnet material according to claim 5, characterized in that: The method of deep deoxidation and desulfurization treatment of LF refining in step 3) is: firstly add aluminum powder for deoxidation treatment, and then add calcium oxide for desulfurization treatment.

7. The method for preparing industrial pure iron for NdFeB permanent magnet material according to claim 6, characterized in that: In the above step 5) continuous casting, the superheat is 30°C and the pulling speed is 1.0 m / min.