KR102402938B1 - Method for manufacturing iron-based powders - Google Patents

Abstract

The iron-based powder manufacturing method according to an embodiment of the present invention comprises one of Mn, Si, Al, Mg, Ti, Zr, Ca, Cr, Mo, Ni and V, or two or more of these non-reducing elements. preparing iron-based molten steel; discharging molten steel; preparing an iron-based powder by spraying a jetting liquid on the discharged molten steel; Separating the iron-based powder and moisture; and removing the satellite powder by applying ultrasonic waves to the iron-based powder.

Description

Method for manufacturing iron-based powder {METHOD FOR MANUFACTURING IRON-BASED POWDERS}

It relates to a method for producing iron-based powder.

Part manufacturing technology using powder has the advantages of increasing the dimensional accuracy of the final part, facilitating mass production, and reducing machining and material loss.

In addition, it has the advantage of being able to maximize product performance through easy component control, so its importance as a core technology in the precision parts and material manufacturing industry is greatly increasing.

In particular, by applying the powder metallurgy process to the manufacturing of automobiles and electronic mechanical parts, it is possible to produce at a cost that is 40% or more lower than that of the existing machining process.

Recently, as the demand for sintered parts increases along with the development of automobile and home appliance industries, the amount of powder used is rapidly increasing. In order to manufacture sintered parts for automobiles, the powder itself must have excellent quality so that high-density sintered compacts such as appropriate particle size, fluidity, apparent density, molding density, and high cleanliness can be manufactured.

The existing iron-based powder manufacturing process uses a converter or electric furnace to drop the molten metal vertically through a tundish and molten metal nozzle while spraying high-pressure water onto the molten metal stem to powder the molten metal. It consists of a dehydration and drying process for separating water to remove moisture, a reduction process for removing the oxide layer on the surface of the powder generated during the water spraying process, and a grinding and mixing process.

Meanwhile, beyond the simple manufacturing process, the infinite potential of 3D printing technology, which is becoming a convergence technology with sports, culture, life, and nano science, is in the spotlight all over the world. In particular, 3D printing technology based on metal powder material is being applied to smart mold, aviation, space, and medical fields. there is In order for metal powder-based 3D printing technology to be spread throughout the industry, it is essential to develop a metal powder manufacturing technology that can be mass-produced economically.

Existing powder manufacturing process for 3D printing is manufactured with expensive production processes such as gas injection method and plasma powder manufacturing method. It is sold as an expensive powder of In order to respond to this, it is urgently required to secure technology and price competitiveness in domestic related industries through localization of powder manufacturing for 3D printing.
[Prior art literature]
Prior art 1: Japanese Patent Laid-Open No. Hei 07-113107
Prior art 2: Laid-open Patent Publication No. 10-2012-0125232
Prior art 3: Laid-open Patent Publication No. 10-2014-0090709
Prior art 4: Japanese Patent Laid-Open No. Hei 07-138619
Prior art 5: Japanese Patent Laid-Open No. Hei 09-302401

One embodiment of the present invention is to provide a method of manufacturing an iron-based powder capable of improving price competitiveness by simplifying the process by presenting a manufacturing process of iron-based powder that can omit the reduction process by minimizing the oxidation layer of the powder.

In addition, one embodiment of the present invention is to provide a method for producing iron-based powder having excellent quality, such as high cleanliness, high fluidity, low geometric deviation.

One embodiment of the present invention is to provide a method of manufacturing an iron-based powder that can be used for 3D printing by precisely controlling the particle size of the powder.

The iron-based powder manufacturing method according to an embodiment of the present invention comprises one of Mn, Si, Al, Mg, Ti, Zr, Ca, Cr, Mo, Ni and V, or two or more of these non-reducing elements. preparing iron-based molten steel; discharging molten steel; preparing an iron-based powder by spraying a jetting liquid on the discharged molten steel; Separating the iron-based powder and moisture; and removing the satellite powder by applying ultrasonic waves to the iron-based powder.

In the step of preparing molten iron-based steel; in the molten steel may include 1 to 80% by weight of a non-reducing element and iron as the balance.

The discharging of the molten steel may include injecting the molten steel into the tundish and discharging the molten steel through a nozzle connected to the tundish.

In the step of discharging the molten steel; in an inert gas and hydrogen (H ₂ ) It can be controlled to an atmosphere containing gas.

The inert gas may be Ar, N ₂ , or a combination thereof.

The atmosphere may contain 1% to 90% by volume of hydrogen gas and the balance of inert gas. Specifically, the atmosphere may include 25% to 75% by volume of hydrogen gas and an inert gas as the balance. More specifically, the atmosphere may include 30% to 60% by volume of hydrogen gas and the balance of inert gas.

In the step of preparing an iron-based powder by spraying the spraying liquid to the discharged molten steel; in, the spraying pressure of the spraying liquid may be 100 bar to 2000 bar. More specifically, it may be 900 bar to 1800 bar.

In the step of preparing an iron-based powder by spraying the spraying liquid on the discharged molten steel; in, the spraying liquid may include a rust preventive agent.

The content of the rust preventive agent in the spray liquid may be 0.01 wt% to 20 wt%, based on 100 wt% of the total amount of the spray liquid.

The rust preventive agent may be a water-soluble or vaporizable rust preventive agent.

The rust inhibitor may include at least one of an amine-based compound, a phosphate-based compound, a nitrate-based compound, and a borate-based compound.

The rust inhibitor may include triethanolamine, calcium phosphate, calcium nitrite, and calcium borate.

Separating the iron-based powder and moisture; It may further include; drying the iron-based powder thereafter.

Drying the iron-based powder; may be performed at a temperature of 30 ℃ to 250 ℃ for 30 minutes to and 24 hours.

In the step of removing the satellite powder by applying ultrasonic waves to the iron-based powder; the ultrasonic wave may be applied for 5 to 120 minutes to remove the satellite powder.

In the step of removing the satellite powder by applying ultrasonic waves to the iron-based powder; the frequency of the ultrasonic waves may be 10 to 200 kHz. More specifically, it may be 70 to 100 kHz.

The particle diameter of the finally prepared iron-based powder may be 20 to 150 μm, the oxygen concentration of the iron-based powder may be 0.1 to 2.0% by weight, and the sphericity of the iron-based powder may be 80 to 97. More specifically, the sphericity of the iron-based powder may be 90 to 95.

According to the method for manufacturing iron-based powder according to an embodiment of the present invention, it is possible to have the effect of reducing the cost of powder manufacturing by omitting the reduction process, and thus it is possible to increase the production per unit time in the same facility.

In addition, according to the manufacturing method of the iron-based powder according to an embodiment of the present invention, it is possible to provide an iron-based powder having excellent qualities such as high cleanliness, high fluidity, and minimal geometric deviation.

1 is a flowchart of a method for manufacturing an iron-based powder according to an embodiment of the present invention.
2 is a scanning electron microscope (SEM) photograph of the iron-based powder prepared in Example 5.
3 is a scanning electron microscope (SEM) photograph of the iron-based powder just before sonication in Example 5.

Hereinafter, embodiments of the present invention will be described in detail. However, this is provided as an example, and the present invention is not limited thereto, and the present invention is only defined by the scope of the claims to be described later.

Throughout the specification, when a part "includes" a certain element, it means that other elements may be further included, rather than excluding other elements, unless otherwise stated.

In general, when iron-based powder is produced by water spraying, Fe + H ₂ O → FeO + H ₂ reaction occurs due to contact between molten steel droplets at a high temperature of about 1,300°C or more and sprayed water/cooling water. It has an unavoidable oxide layer. Therefore, it was possible to obtain a powder having excellent moldability only through an additional process for removing the oxide layer. The reduction process for controlling the oxygen concentration in the powder is an important process that influences the components and properties of the controlled powder, and it is also a process that requires a lot of cost among the entire process. Among the entire manufacturing process, the reduction process has the slowest processing speed per hour, which acts as a bottleneck process and cannot improve the final productivity.

As a specific example, conventionally, a process has been applied that can simultaneously obtain the effect of removing the oxide layer and softening the internal tissue by maintaining a hydrogen atmosphere in a continuous furnace heated to a temperature range of 800°C to 1,000°C, but the process time is 1 hour There were problems such as an increase in process cost due to the excessive consumption and the use of a large amount of expensive hydrogen.

In addition, in the case of iron-based powder production, there was a limit to the removal of the oxide layer in the powder despite the massive use of hydrogen in a separate reduction process.

In addition, when iron-based powder is manufactured through water injection, the particle size of the iron-based powder is not constant due to various variables such as changes in the injection amount generated during the water injection process, changes in injection pressure, etc. There is a problem in that the sphericity of the iron-based powder is lowered due to the contact of the powder.

An embodiment of the present invention seeks to solve this problem.

1 schematically shows a flowchart of a method for manufacturing iron-based powder according to an embodiment of the present invention. The flowchart of the manufacturing method of the iron-based powder of FIG. 1 is only for illustrating the present invention, and the present invention is not limited thereto. Therefore, the method of manufacturing the iron-based powder can be variously modified.

Hereinafter, a method of manufacturing an iron-based powder according to an embodiment of the present invention will be described with reference to FIG. 1 .

The method for producing an iron-based powder according to an embodiment of the present invention includes at least one of Mn, Si, Al, Mg, Ti, Zr, Ca, Cr, Mo, Ni and V, or two or more of these non-reducing elements. preparing an iron-based molten steel (S10); discharging the molten steel (S20); Preparing an iron-based powder by spraying a spraying liquid to the discharged molten steel (S30); Separating the iron-based powder and moisture (S40); and removing the satellite powder by applying ultrasonic waves to the iron-based powder (S50). In addition, if necessary, the method for producing the iron-based powder may further include other steps.

First, in step S10, an iron-based molten steel including one or more non-reducing elements among Mn, Si, Al, Mg, Ti, Zr, Ca, Cr, Mo, Ni and V, or two or more of these, is prepared. Specifically, the molten steel may include 1 to 80 wt% of a non-reducing element and iron as the balance. More specifically, 10 wt% to 80 wt% of a non-reducing element; 10% to 70% by weight; 10% to 60% by weight; 10% to 50% by weight; 10% to 40% by weight; 10% to 30% by weight; 10% to 20% by weight; 12% to 20% by weight; 14% to 20% by weight; Or 16 wt% to 20 wt% may be included. More specifically, it may include Cr among non-reducing elements. More specifically, 10 to 20% by weight of Cr, 10 to 15% by weight of Ni, 1 to 5% by weight of Mo, and iron may be included in the balance.

Next, step S20 discharges the molten steel.

Step S20 may include injecting molten steel into the tundish and discharging the molten steel through a nozzle connected to the tundish.

In order to suppress the formation of an oxide layer on the surface of the powder during water injection by lowering the oxygen concentration in the molten steel in step (S20), an atmosphere containing an inert gas and hydrogen (H ₂ ) gas may be controlled. In this case, the inert gas may be Ar, N ₂ , or a combination thereof. However, the present invention is not limited thereto, and other types of gases may be used as long as the inert gas is capable of forming an inert atmosphere.

Hydrogen gas (H ₂ ) may be further included along with the inert gas, and by further including hydrogen gas, a reducing atmosphere is created, thereby preventing the molten steel surface from being oxidized and the formation of an oxide layer when water is sprayed. At this time, the content of hydrogen gas may be 1% by volume to 90% by volume based on 100% by volume of the total volume. More specifically, it may be 25% by volume to 75% by volume. More specifically, it may be 30% by volume to 60% by volume.

If the hydrogen content is too small, the effect of inhibiting the oxide layer may be insignificant. If the hydrogen content is too large, the efficiency may be improved, but a problem may arise in that the cost cost increases. An inert gas may be included in the balance.

Next, in step S30, an iron-based powder is prepared by spraying the jetting liquid on the discharged molten steel.

At this time, the injection pressure of the injection liquid can be adjusted to 100 bar to 2000 bar. Specifically, it can be adjusted to 900 bar to 1800 bar. More specifically, it can be adjusted to 1000 bar to 1500 bar. When the injection pressure is too low, a problem occurs in that the particle size of the iron-based powder to be produced becomes too large. When the injection pressure is too high, the particle size of the iron-based powder to be manufactured becomes too small, and there may be a problem in that the particle size deviation increases.

As such, by precisely controlling the injection pressure and the injection amount of the injection liquid, the particle diameter of the iron-based powder to be manufactured can be controlled to 20 to 150 μm, and variations in particle diameter can be reduced. As a result, the iron-based powder prepared in one embodiment of the present invention can be usefully used as a material for 3D printing.

At this time, in order to suppress the formation of an oxide layer on the surface of the powder, the spray liquid may include a rust inhibitor.

The rust inhibitor may be a water-soluble or vaporizable rust inhibitor. More specifically, the rust inhibitor may include at least one of an amine-based compound, a phosphate-based compound, a nitrate-based compound, and a borate-based compound.

Specifically, the amine-based compound may be a C1 to C10 primary amine, a C1 to C10 secondary amine, or a C1 to C10 tertiary amine. Also, in the amine compounds, a substituent such as a hydroxyl group (-OH) or a carboxyl group (-COOH) may be substituted on a C1 to C10 carbon chain. More specifically, it may be triethanolamine.

Specifically, the phosphate-based compound may be a salt containing phosphate (PO ₄ ^{3 -} ), and more specifically, may be calcium phosphate.

Specifically, the nitrate-based compound may be a salt containing nitrate (NO ² -), and more specifically, may be calcium nitrite.

Specifically, the borate-based compound may be a salt including borate (BO ₃ ^3- ), and more specifically, may be calcium borate.

These rust inhibitors have properties that can control the interfacial tension in the powder and the degree of activation with moisture, and when used by adding to the spray solution when spraying with water, it is possible to suppress the occurrence of an oxide layer on the surface of the iron-based powder to be manufactured. .

More specifically, the rust inhibitor may include triethanolamine, calcium phosphate, calcium nitrite, and calcium borate.

In addition, the content of the rust preventive agent in the spray liquid in step (S30), with respect to 100% by weight of the total amount of the spray liquid, may be 0.01% by weight to 20% by weight. More specifically, 0.5 wt% to 5 wt%; 0.5% to 4% by weight; 0.5% to 3% by weight; or 0.5 wt% to 2 wt%.

If the content of the rust inhibitor in the spray liquid is too small, the rust prevention effect may be insignificant. Even if the content of the rust inhibitor in the spray liquid increases, there is no significant difference in the efficiency of inhibiting the generation of the oxide layer. there may be

As such, by including the rust preventive agent in the spray liquid in step (S30), the oxygen concentration of the iron-based powder produced can be adjusted to 0.01 to 2.0 wt% without adding a separate reduction process.

Next, step S40 separates the iron-based powder and moisture. Specifically, the iron-based powder and water may be separated by centrifugal dehydration. When centrifugal dehydration is used, iron-based powder and water may be separated by dehydration for 1 to 60 minutes. However, this may be appropriately adjusted according to the content of the powder to be produced, the amount of the spray liquid used for water injection, and the like. If the dehydration time is too short or the centrifugation speed is too slow, the moisture in the powder is not sufficiently removed and the drying step may be delayed. can be

After the step (S40), if necessary, it may further include a step of drying the iron-based powder. Drying may be performed at a temperature of 30° C. to 250° C. for 30 minutes to 24 hours. If the drying temperature is too low or the drying time is too short, there may be a problem in that the moisture in the powder is not sufficiently removed. If the drying temperature is too high or the drying time is too long, there may be a problem that the powder may be reoxidized.

Next, in step S50, the satellite powder is removed by applying ultrasonic waves to the iron-based powder.

During the water injection process, the satellite powder comes into contact with the iron-based powder, which adversely affects the sphericity of the iron-based powder. In this case, the satellite powder means a powder having a particle diameter in the range of 1 to 10 μm. In addition, sphericity refers to the degree to which a particle is close to a spherical shape, and is a value obtained by dividing the maximum diameter of the particle by the minimum diameter, and the closer to 1, the closer to a spherical shape.

By applying ultrasonic waves in step S50 to separate and remove the satellite powder in contact with the iron-based powder, the sphericity of the iron-based powder to be manufactured can be further increased, and it can be usefully used as a material for 3D printing.

Ultrasound can be applied for 5 to 120 minutes, and if the time is too short, the removal of the satellite powder is not sufficient, and even if the ultrasonic wave is applied for a longer time, there is a limit to improving the sphericity.

The sphericity of the iron-based powder produced by step S50 may be adjusted to 80 to 97. More specifically, the sphericity can be adjusted to 90 to 95.

Hereinafter, preferred examples and comparative examples of the present invention will be described. However, the following examples are only preferred examples of the present invention, and the present invention is not limited thereto.

Example : iron manufacture of powder

First, iron-based molten steel having the composition shown in Table 1 was prepared.

Thereafter, after injecting the iron-based molten steel into the tundish, water spraying was performed using an ultra-high pressure water spraying device of 1000 bar while dropping the molten steel through a nozzle.

In order to prevent oxidation of the molten steel discharged through the tundish and nozzle, the atmosphere at the time of water injection was controlled to 50% by volume of argon gas and 50% by volume of hydrogen gas. did

Vappro 849 (seller: Polartec) containing an amine-based compound, a phosphate-based compound, a nitrate-based compound, and a borate-based compound additive was used as the rust inhibitor, and a vaporizable white powder rust preventive agent with a pH of about 7 was used.

After the water spraying was completed, the powder was dehydrated for 10 minutes in a chamber in which the powder and water were leached to remove moisture.

Thereafter, the obtained powder was dried at 150° C. for 24 hours. The iron-based powder obtained after drying was analyzed with an optical microscope, and is shown in FIG. 3 . As shown in FIG. 3 , it was confirmed that a large amount of the satellite powder was in contact with the iron-based particles. The average sphericity was measured to be 75.

Thereafter, the obtained iron-based powder was subjected to ultrasonic treatment under the frequency conditions shown in Table 2 below using an ultrasonic generator to separate and remove the satellite powder. The sonicated iron-based powder was analyzed with an optical microscope and shown in FIG. 2 (Example 5). As shown in FIG. 2 , it was confirmed that most of the satellite powder was removed. The powder weight and yield before and after sphericity sonication are summarized in Table 2 below.

division Cr Ni Mo Fe content (wt%) 16.7 10.1 2.1 balance

Frequency (kHz) Amount of powder before sonication (g) Amount of powder after sonication (g) Loss (g) transference number(%) Sphericity (%) Example 1 10 200 177.8 22.2 88.9 81.1 Example 2 30 200 166.6 33.4 83.3 85.7 Example 3 50 200 169.2 30.8 84.6 85.4 Example 4 70 200 160 40 80.0 91.8 Example 5 100 200 152.2 47.8 76.1 94.2 Example 6 150 200 154.4 45.6 77.2 93.1 Example 7 200 200 146.2 53.8 73.1 96.4

As shown in Table 2, it was confirmed that the satellite powder was removed and the sphericity was improved through the ultrasonic treatment. However, it was confirmed that if the frequency during ultrasonic treatment is too high, the loss amount is significantly higher than the effect of improving the sphericity, which may become inefficient.

Experimental example

As a result of analyzing the oxygen concentration of the powder prepared in Example 5 using an N/O analyzer (manufacturer: LECO, model name TC-600), it was confirmed that the oxygen concentration was 0.6% by weight. It was found that the oxygen concentration in the prepared iron-based powder was significantly reduced.

Therefore, according to one embodiment of the present invention, it was found that by omitting the reduction process, it was possible to manufacture iron-based powder with high purity at a low cost compared to the conventionally commercialized iron-based powder manufacturing method.

The present invention is not limited to the above embodiments, but can be manufactured in various different forms, and those of ordinary skill in the art to which the present invention pertains can take other specific forms without changing the technical spirit or essential features of the present invention. It will be understood that it can be implemented as Therefore, it should be understood that the embodiments described above are illustrative in all respects and not restrictive.

Claims (22)

Mn, Si, Al, Mg, Ti, Zr, Ca, Cr, Mo, Ni and V, comprising the steps of preparing an iron-based molten steel containing one, or two or more of these non-reducing elements;
discharging the molten steel;
preparing an iron-based powder by spraying a spraying liquid on the discharged molten steel;
separating the iron-based powder and moisture; and
removing the satellite powder by applying ultrasonic waves to the iron-based powder;
including,
removing the satellite powder by applying ultrasonic waves to the iron-based powder; in
The frequency of ultrasound is 70 to 100 kHz,
Remove the satellite powder by applying ultrasonic waves for 5 to 120 minutes,
A method for producing an iron-based powder having a sphericity of 90 to 95 of the finally prepared iron-based powder. According to claim 1,
In the step of preparing the iron-based molten steel;
The molten steel is a method for producing an iron-based powder comprising 1 to 80% by weight of the non-reducing element and iron as the balance. According to claim 1,
The step of discharging the molten steel is
A method for producing iron-based powder comprising the steps of injecting the molten steel into a tundish and discharging the molten steel through a nozzle connected to the tundish. According to claim 1,
discharging the molten steel; in,
Method for producing iron-based powder controlled in an atmosphere containing an inert gas and hydrogen (H ₂ ) gas. 5. The method of claim 4,
The inert gas is Ar, N ₂ , or a combination thereof. 5. The method of claim 4,
The atmosphere is a method for producing an iron-based powder comprising 1% to 90% by volume of the hydrogen gas and the inert gas as the balance. 7. The method of claim 6,
The atmosphere is a method of producing an iron-based powder comprising 25% to 75% by volume of the hydrogen gas and the inert gas as the balance. 8. The method of claim 7,
The atmosphere is a method for producing an iron-based powder comprising 30% to 60% by volume of the hydrogen gas and the inert gas as the balance. According to claim 1,
Preparing an iron-based powder by spraying the jetting liquid onto the discharged molten steel; in the method for producing an iron-based powder, the injection pressure of the jetting liquid is 100 bar to 2000 bar. According to claim 1,
Preparing an iron-based powder by spraying the jetted liquid onto the discharged molten steel; in, the injection pressure of the jetting solution is 900 bar to 1800 bar. According to claim 1,
Preparing an iron-based powder by spraying a spraying liquid to the discharged molten steel; In,
The injection liquid is a method of manufacturing an iron-based powder containing a rust inhibitor. 12. The method of claim 11,
The content of the rust preventive agent in the spray solution, based on the total amount of the spray solution 100% by weight, 0.01% to 20% by weight of the iron-based powder manufacturing method. 12. The method of claim 11,
The said rust preventive agent, the manufacturing method of the iron-type powder which is a water-soluble or vaporization rust preventive agent. 12. The method of claim 11,
The rust inhibitor is an amine-based compound, a phosphate-based compound, a nitrate-based compound, and a method for producing an iron-based powder comprising at least one of a borate-based compound. 12. The method of claim 11,
The rust inhibitor is triethanolamine (triethanol amine), calcium phosphate (Calcium phosphate), calcium nitrite (Calcium nitrite), and a method of producing an iron-based powder comprising calcium borate (Calcium borate). According to claim 1,
separating the iron-based powder and moisture; Since the
Drying the iron-based powder; Method for producing an iron-based powder further comprising. 17. The method of claim 16,
Drying the iron-based powder; is a method for producing an iron-based powder is carried out at a temperature of 30 ℃ to 250 ℃ for 30 minutes to and 24 hours. delete delete delete According to claim 1,
A method for producing an iron-based powder, wherein the final prepared iron-based powder has a particle diameter of 20 to 150㎛, and the oxygen concentration of the iron-based powder is 0.01 to 2.0% by weight. delete

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