Preparation method of ultra-low-oxygen low-impurity high-purity water-atomized pure iron powder

Abstract

The invention relates to a preparation method of ultra-low-oxygen low-impurity high-purity water-atomized pure iron powder. The preparation method comprises the steps of raw material pretreatment, primary smelting (pre-deoxidation), refining (deep deoxidation), molten steel purification, atomization treatment to obtain iron powder slurry, iron powder slurry dehydration, drying and magnetic separation to obtain the ultra-low-oxygen low-impurity pure iron powder. According to the method, through full-process control of raw material optimization, composite refining and multi-stage purification, the oxygen content of the iron powder is smaller than or equal to 0.15%, the total impurity content is smaller than or equal to 0.05%, the ASTM F1580 medical metal powder standard is met, the production cost is reduced, meanwhile, technological obstacles are overcome, and the technological optimization meets the high-added-value application requirements of MIM feeding, high-frequency soft magnetism, ASTM F1580 medical metal powder and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of metal powder preparation, in particular to a preparation method of high-purity water-atomized pure iron powder with ultra-low oxygen and low impurities. BACKGROUND

[0002] Metal powder has a wide demand in the fields of MIM feed, high-frequency soft magnet, medical metal powder, etc., and its own purity directly affects the quality of products. How to develop iron powder with ultra-low impurity content is an important way to solve the above problems.

[0003] At present, the main preparation method of pure iron powder is water atomization, mainly using scrap steel, pure iron, etc. as raw materials, melting the steel in a medium-frequency furnace or an electric arc furnace, and then atomizing the iron powder through a water atomization device. It is widely used because of its short process flow, high efficiency and low emission. However, the traditional water atomization iron powder production process has the following defects: first, the oxygen content control is insufficient, the deoxidation in the steel refining stage is not complete, and the atomization process is easy to be re-oxidized; second, the impurity residual rate is high, and non-metallic inclusions and magnetic impurities are difficult to remove efficiently. SUMMARY

[0004] The present application provides a preparation method of high-purity water-atomized pure iron powder with ultra-low oxygen and low impurities to overcome the shortcomings of the prior art.

[0005] The present application is realized by the following technical scheme, a preparation method of high-purity water-atomized pure iron powder with ultra-low oxygen and low impurities, comprising the following steps: S1, raw material pretreatment: Q235 steel plate and low alloy pig iron are selected and mixed according to a ratio of 7:3; S2, initial smelting: the mixed material is heated to 1650-1680℃ in an electric arc furnace, silicon-iron alloy is added for pre-deoxidation, and the terminal oxygen activity is controlled to be less than or equal to 100ppm; S3, refining: the mixed material after initial smelting is added into an LF furnace, a slagging agent is added, the slag amount of the slagging agent is 2.5-3.5kg / t, the basicity of the refining slag is controlled to be between 3.5-4.2, the melting point is less than or equal to 1400℃, the refining time is greater than or equal to 40min, industrial aluminum particles and silicon-calcium alloy are added into the LF furnace for deep deoxidation; S4, molten steel purification: after tapping, the molten steel is transferred into a ladle and left for 10-20min, carbonized rice husk heat preservation agent is covered on the surface of the molten steel, and the thickness of the carbonized rice husk heat preservation agent is greater than or equal to 50mm; S5, atomization treatment to obtain iron powder slurry; S6, dehydration, drying and magnetic separation of the iron powder slurry to obtain iron powder.

[0006] As an optimization, in step S1, the C content in the Q235 steel plate is less than or equal to 0.22%, the S and P content is less than or equal to 0.035%, the Si content in the low alloy pig iron is less than or equal to 0.5%, and the Mn content is less than or equal to 0.3%.

[0007] As optimization, in step S2, the silicon content in the ferrosilicon alloy is 73-75%.

[0008] As optimization, in step S3, the slag forming agent is composed of high-purity lime, fluorite and carbide in a mass ratio of 6:2:1.

[0009] As optimization, the CaO content in the high-purity lime is ≥92%, the CaF2 content in the fluorite is ≥90%, and the CaC2 content in the carbide is ≥75%.

[0010] As optimization, in step S3, the aluminum content in the industrial aluminum particles is ≥98.5%, the particle size of the industrial aluminum particles is 1-3 mm, the silicon content in the ferrosilicon-calcium alloy is 60%, and the calcium content is 30%.

[0011] As optimization, in step S3, argon is blown into the molten steel after refining for 40 min to stir, and the argon blowing time is ≥15 min.

[0012] As optimization, in step S5, the atomization treatment is high-pressure water atomization, the atomization pressure is 12-13 MPa, the water flow is 440-480 m³ / h, and the superheat degree of the molten steel is 120-140℃.

[0013] As optimization, in step S6, the drying temperature is 550-600℃, the drying time is 40 min, and the water content of the iron powder is ≤0.05%.

[0014] As optimization, in step S6, the iron powder is subjected to magnetic separation through three gradient magnetic fields.

[0015] The beneficial effects of the present application are: high adsorption slag system design: through lime-fluorite-carbide composite slagging, combined with alkalinity control, refining alkalinity 3.5-4.2, realizing sulfur content ≤0.005%, phosphorus ≤0.01%, reducing iron powder impurities; through arc furnace preliminary refining, through LF furnace refining, reducing residual value residue; Dynamic deoxidation technology: through pre-deoxidation in the preliminary refining process and deep deoxidation in the refining process, dynamic deoxidation operation is realized, deoxidation rate is improved, and oxygen content of the iron powder is reduced. Soft argon blowing at the end of refining promotes the collision and growth of inclusions to float up, further removing impurities; Atomization water synergistic deoxidation: through carbonized rice husk heat preservation agent, the molten steel is prevented from cooling too fast and coagulating, air is blocked to prevent secondary oxidation, 0.01-0.03% ascorbic acid is added in the atomization water as an oxygen capturing agent to inhibit the generation of iron powder surface oxidation film; Through the whole process control of raw material selection, composite refining and multi-stage purification, the oxygen content of the iron powder is less than or equal to 0.15%, and the total impurity content is less than or equal to 0.05%, which meets the ASTM F1580 medical metal powder standard. The production cost is reduced, the process obstacles are overcome, and the process optimization meets the high value-added application requirements of MIM feedstock, high-frequency soft magnetic material and medical metal powder. DETAILED DESCRIPTION

[0016] In order to clearly illustrate the technical features of the present application, the present application will be described below through specific embodiments.

[0017] A preparation method of ultra-low-oxygen and low-impurity high-purity water-atomized pure iron powder, comprising the following steps: S1, raw material pretreatment: Q235 steel plate and low alloy pig iron are selected according to a ratio of 7:3; the C content in the Q235 steel plate is less than or equal to 0.22%, and the S and P contents are less than or equal to 0.035%; the Si content in the low alloy pig iron is less than or equal to 0.5%, and the Mn content is less than or equal to 0.3%.

[0018] S2, initial refining: the ingredients are heated to 1650-1680℃ in an electric arc furnace, silicon-iron alloy is added for pre-deoxidation, and the terminal oxygen activity is controlled to be less than or equal to 100ppm; the silicon content in the silicon-iron alloy is 73-75%.

[0019] S3, refining: the ingredients after initial refining are added into an LF furnace, a slagging agent is added, the slag amount of the slagging agent is 2.5-3.5kg / t, the slagging agent is composed of high-purity lime, fluorite and carbide in a mass ratio of 6:2:1, the CaO content in the high-purity lime is greater than or equal to 92%, the CaF2 content in the fluorite is greater than or equal to 90%, and the CaC2 content in the carbide is greater than or equal to 75%; the basicity of the refining slag is controlled to be between 3.5 and 4.2, the melting point is less than or equal to 1400℃, and the refining time is greater than or equal to 40min; it should be noted that the basicity of the refining slag refers to the percentage content ratio of CaO to SiO2 in the refining slag, by accurately controlling the contents of CaO and SiO2 and other non-metallic inclusions, the impurity generation amount is reduced, and the impurity removal in the later stage is facilitated; industrial aluminum particles and silicon-calcium alloy are also added into the LF furnace for deep deoxidation, the aluminum content in the industrial aluminum particles is greater than or equal to 98.5%, the particle size of the industrial aluminum particles is 1-3mm, the silicon content in the silicon-calcium alloy is 60%, and the calcium content is 30%; After refining for 40min, argon is blown into the molten steel for stirring, the argon blowing time is greater than or equal to 15min, and by soft blowing of argon at the end of the refining, the collision and growth of inclusions are promoted, and the impurities are removed.

[0020] S4, molten steel purification: after tapping, transfer into ladle and stand for 10-20 min to eliminate slag entrapment caused by molten steel flowing into the ladle, promote the floating of micro-inclusions, and reduce the impurity content; cover the molten steel surface with carbonized rice husk insulating agent with a thickness of ≥50 mm to prevent the molten steel from solidifying due to rapid cooling and to prevent secondary oxidation.

[0021] S5, obtain iron powder slurry by atomization treatment, the atomization treatment is high-pressure water atomization, the atomization pressure is 12-13 MPa, the water flow is 440-480 m³ / h, and the superheat of the molten steel is 120-140 °C; meanwhile, add 0.01-0.03% ascorbic acid as an oxygen capturing agent in the atomization water to inhibit the generation of the oxide film on the surface of the iron powder.

[0022] S6, obtain iron powder by dehydrating, drying, and magnetic separation of the iron powder slurry, the drying temperature is 550-600 °C, the drying time is 40 min, the water content of the obtained iron powder is ≤0.05%, and the iron powder is subjected to magnetic separation in three gradient magnetic fields of Gx, Gy, and Gz after drying to further screen out impurities and improve the purity.

[0023] Example 1: S1, cut a 4 mm Q235 steel plate into blocks and mix with low alloy pig iron at a ratio of 7:3, the C content in the Q235 steel plate in this example is 0.22%, the S and P contents are 0.035%, the Si content in the low alloy pig iron is 0.5%, and the Mn content is 0.3%.

[0024] S2, melt and heat the ingredients in the electric arc furnace to 1650 °C, and add ferrosilicon alloy for pre-deoxidation, the Si content in the ferrosilicon alloy in this example is 73%, and the terminal oxygen activity is controlled at 100 ppm.

[0025] S3, add the molten steel after initial refining to the LF furnace, and add a slag former, the slag former is composed of high-purity lime, fluorite, and carbide at a mass ratio of 6:2:1, and the slag amount of the slag former is 2.5 kg / t; the basicity of the refining slag in this example is controlled at 3.5, the melting point is 1400 °C, and the refining time is 40 min; The CaO content in the high-purity lime in this example is 92%, the CaF2 content in the fluorite is 90%, and the CaC2 content in the carbide is 75%; Meanwhile, add industrial aluminum particles and silicon-calcium alloy to the LF furnace for deep deoxidation, the aluminum content in the industrial aluminum particles in this example is 98.5%, the particle size of the industrial aluminum particles is 1 mm, the Si content in the silicon-calcium alloy is 60%, and the Ca content is 30%; After refining for 40 min, blow argon into the molten steel for stirring, and the argon blowing time is 15 min.

[0026] S4, after the molten steel refining, the molten steel is transferred into a ladle and is left for 10 minutes; carbonized rice husk insulating agent is covered on the surface of the molten steel, and the thickness of the carbonized rice husk insulating agent in the embodiment is 50 mm.

[0027] S5, the molten steel is atomized into powder, the atomization treatment is high-pressure water atomization, the atomization pressure in the embodiment is 12 MPa, the water flow is 440 m³ / h, and the superheat degree of the molten steel is 120 ℃, so that the iron powder slurry is obtained; meanwhile, 0.01% ascorbic acid is added into the atomized water as an oxygen capturing agent to inhibit the generation of the oxide film on the surface of the iron powder.

[0028] S6, the iron powder slurry is dehydrated, dried, and magnetically selected to obtain the iron powder, the drying temperature in the embodiment is 550 ℃, the drying time is 40 minutes, and the iron powder is magnetically selected through the magnetic fields with three gradients of Gx, Gy, and Gz to obtain the iron powder. The water content of the iron powder in the embodiment is 0.05%, the oxygen content of the iron powder is 0.15%, and the total impurity content of the iron powder is 0.05%, which reaches the standard of the ultra-low oxygen and low impurity pure iron powder of ASTM F1580 medical metal powder.

[0029] Example 2: S1, a 4 mm Q235 steel plate is selected and cut into blocks, and low alloy pig iron is proportioned according to 7:3, the C content in the Q235 steel plate in the embodiment is 0.19%, the S and P contents are 0.030%, the Si content in the low alloy pig iron is 0.4%, and the Mn content is 0.2%.

[0030] S2, the ingredients in the embodiment are melted and cleaned in an electric arc furnace to be heated to 1670 ℃, and ferrosilicon alloy is added for pre-deoxidization, the Si content in the ferrosilicon alloy in the embodiment is 74%, and the terminal oxygen activity is controlled to be 100 ppm.

[0031] S3, the molten steel after primary refining is added into an LF furnace, and a slagging agent is added, the slagging agent is composed of high-purity lime, fluorite, and carbide in a mass ratio of 6:2:1, and the slag amount of the slagging agent is 3 kg / t; the basicity of the refining slag in the embodiment is controlled to be 3.8, the melting point is 1350 ℃, and the refining time is 50 minutes. The CaO content in the high-purity lime in the embodiment is 94%, the CaF2 content in the fluorite is 94%, and the CaC2 content in the carbide is 80%; Meanwhile, industrial aluminum particles and silicon-calcium alloy are added into the LF furnace for deep deoxidization, the aluminum content in the industrial aluminum particles in the embodiment is 98.7%, the particle size of the industrial aluminum particles is 2 mm, the Si content in the silicon-calcium alloy is 60%, and the Ca content is 30%; After refining for 40 minutes, argon is blown into the molten steel for stirring, and the argon blowing time is 20 minutes.

[0032] S4, after the molten steel refining, the molten steel is transferred into a ladle and is left for 15 minutes; carbonized rice husk insulating agent is covered on the surface of the molten steel, and the thickness of the carbonized rice husk insulating agent in the embodiment is 55 mm.

[0033] S5, the molten steel is atomized into powder, the atomization treatment is high-pressure water atomization, the atomization pressure in the embodiment is 12 MPa, the water flow is 460 m³ / h, and the superheat degree of the molten steel is 130 ℃, so that the iron powder slurry is obtained; meanwhile, 0.02% ascorbic acid is added into the atomized water as an oxygen capturing agent to inhibit the generation of the oxide film on the surface of the iron powder.

[0034] S6, the iron powder slurry is dehydrated, dried and magnetically selected to obtain the iron powder, the drying temperature in the embodiment is 570 ℃, the drying time is 40 minutes, and the iron powder is magnetically selected through the magnetic fields with three gradients of Gx, Gy and Gz to obtain the iron powder. The water content of the iron powder in the embodiment is 0.035%, the oxygen content of the iron powder is 0.13%, and the total impurity content of the iron powder is 0.042%, which reaches the standard of the ultra-low oxygen and low impurity pure iron powder of ASTM F1580 medical metal powder.

[0035] Example 3: S1, a 4 mm Q235 steel plate is selected and cut into blocks, and low alloy pig iron is proportioned according to 7:3, the C content in the Q235 steel plate in the embodiment is 0.15%, the S and P contents are 0.025%, the Si content in the low alloy pig iron is 0.35%, and the Mn content is 0.15%.

[0036] S2, the proportioning in the embodiment is melted and cleaned in an electric arc furnace and is heated to 1680 ℃, and ferrosilicon alloy is added for pre-deoxidization, the Si content in the ferrosilicon alloy in the embodiment is 75%, and the terminal oxygen activity is controlled to be 95 ppm.

[0037] S3, the molten steel after primary refining is added into an LF furnace, and a slagging agent is added, the slagging agent is composed of high-purity lime, fluorite and carbide in a mass ratio of 6:2:1, and the slag amount of the slagging agent is 3.5 kg / t; the basicity of the refining slag in the embodiment is controlled to be 4.2, the melting point is 1350 ℃, and the refining time is 50 minutes. The CaO content in the high-purity lime in the embodiment is 94%, the CaF2 content in the fluorite is 94%, and the CaC2 content in the carbide is 80%; industrial aluminum particles and silicon-calcium alloy are also added into the LF furnace for deep deoxidization, the aluminum content in the industrial aluminum particles in the embodiment is 98.7%, the particle size of the industrial aluminum particles is 3 mm, the Si content in the silicon-calcium alloy is 60%, and the Ca content is 30%; After refining for 40 minutes, argon is blown into the molten steel for stirring, and the argon blowing time is 20 minutes.

[0038] S4, after the molten steel refining, the molten steel is transferred into a ladle and is placed for 20 min; a carbonized rice husk heat preservation agent is covered on the surface of the molten steel, and the thickness of the carbonized rice husk heat preservation agent in the embodiment is 55 mm.

[0039] S5, the molten steel is atomized into powder, the atomization treatment is high-pressure water atomization, the atomization pressure in the embodiment is 13 MPa, the water flow is 480 m³ / h, the superheat degree of the molten steel is 140 ℃, and the iron powder slurry is obtained; meanwhile, 0.03% ascorbic acid is added into the atomization water as an oxygen capturing agent to inhibit the generation of the oxide film on the surface of the iron powder.

[0040] S6, the iron powder slurry is dehydrated, dried and magnetically selected to obtain the iron powder, the drying temperature in the embodiment is 600 ℃, the drying time is 40 min, the iron powder is dried and then is magnetically selected through the magnetic fields with three gradients of Gx, Gy and Gz to obtain the iron powder. The water content of the iron powder in the embodiment is 0.03%, the oxygen content of the iron powder is 0.12%, and the total impurity content of the iron powder is 0.04%, which reaches the standard of the ultra-low oxygen and low impurity pure iron powder of ASTM F1580 medical metal powder.

[0041] Of course, the above description is not limited to the above examples, and the technical features not described in the application can be realized by or using the prior art, which will not be described here; the above embodiments are only used to illustrate the technical solutions of the application and are not limited to the application, and the ordinary skilled in the art should understand that the changes, modifications, additions or replacements made by the ordinary skilled in the art within the essential scope of the application do not deviate from the purpose of the application, and should also belong to the protection scope of the claims of the application.

Claims

1. A method for preparing high-purity water-atomized pure iron powder with ultra-low oxygen and low impurities, characterized in that: The following steps are involved: S1. Raw material pretreatment: Q235 steel plate and low alloy pig iron are selected in a ratio of 7:3; S2. Primary refining: The ingredients are melted in an electric arc furnace and heated to 1650-1680℃, and ferrosilicon alloy is added for pre-deoxidation, and the end point oxygen activity is controlled to be ≤100ppm; S3, refining: add the ingredients after primary refining into the LF furnace, add slag-making agent, the slag amount of the slag-making agent is 2.5-3.5kg / t, control the basicity of the refined slag between 3.5-4.2, the melting point is ≤1400℃, and the refining time is ≥40min. At the same time, add industrial aluminum particles and silicon-calcium alloy into the LF furnace for deep deoxidation; S4. Molten steel purification: After tapping, transfer the steel into the ladle and let it stand for 10-20 minutes. Cover the surface of the molten steel with carbonized rice husk insulation. The thickness of the carbonized rice husk insulation should be ≥50mm. S5, atomizing to obtain iron powder slurry; S6. Dehydrating, drying and magnetically separating the iron powder slurry to obtain iron powder.

2. The method for preparing high-purity water-atomized pure iron powder with ultra-low oxygen and low impurities according to claim 1, characterized in that: In step S1, the C content in the Q235 steel plate is ≤0.22%, the S and P content are ≤0.035%, the Si content in the low alloy pig iron is ≤0.5%, and the Mn content is ≤0.3%.

3. The method for preparing high-purity water-atomized pure iron powder with ultra-low oxygen and low impurities according to claim 1, characterized in that: In step S2, the silicon content in the ferrosilicon alloy is 73-75%.

4. The method for preparing high-purity water-atomized pure iron powder with ultra-low oxygen and low impurities according to claim 1, characterized in that: In step S3, the slagging agent is made of high-purity lime, fluorite, and calcium carbide in a mass ratio of 6:2:

1.

5. The method for preparing high-purity water-atomized pure iron powder with ultra-low oxygen and low impurities according to claim 4, characterized in that: The CaO content in the high-purity lime is ≥92%, the CaF2 content in the fluorite is ≥90%, and the CaC2 content in the calcium carbide is ≥75%.

6. The method for preparing high-purity water-atomized pure iron powder with ultra-low oxygen and low impurities according to any one of claim 5, characterized in that: In step S3, the aluminum content in the industrial aluminum particles is ≥98.5%, the particle size of the industrial aluminum particles is 1-3 mm, the silicon content in the silicon-calcium alloy is 60%, and the calcium content is 30%.

7. The method for preparing high-purity water-atomized pure iron powder with ultra-low oxygen and low impurities according to any one of claims 1, 4, 5, and 6, characterized in that: In step S3, after refining for 40 minutes, argon gas is blown into the molten steel for stirring, and the blowing time is ≥15 minutes.

8. The method for preparing high-purity water-atomized pure iron powder with ultra-low oxygen and low impurities according to claim 1, characterized in that: In step S5, the atomization treatment is high-pressure water atomization, the atomization pressure is 12-13 MPa, the water flow rate is 440-480 m³ / h, and the superheat of the molten steel is 120-140°C.

9. The method for preparing high-purity water-atomized pure iron powder with ultra-low oxygen and low impurities according to claim 1, characterized in that: In step S6, the drying temperature is 550-600° C., the drying time is 40 min, and the moisture content of the obtained iron powder is ≤0.05%.

10. The method for preparing high-purity water-atomized pure iron powder with ultra-low oxygen and low impurities according to claim 1 or 9, characterized in that: In step S6, the iron powder is subjected to magnetic separation with three gradient magnetic fields.