A method for preparing a gradient guide tube suitable for long-term atomization

Abstract

This invention discloses a method for preparing a gradient guide tube suitable for long-term atomization. Based on existing zirconia guide tubes, this method employs raw materials with different particle sizes and a gradient sintering process to create a dense ceramic structure at the ends and a loose granular structure in the middle and upper parts. This gradient guide tube reduces the erosion and corrosion of the ends by the molten metal, lowers the inclusion content in the powder, achieves long-term atomization, and further improves powder yield. By adjusting parameters such as raw material particle size and sintering process, this method forms a gradient guide tube with gradually decreasing bulk density from the ends to the middle and upper parts. This avoids erosion and spalling of the guide tube end face, reduces inclusion content, achieves long-term atomization, and improves powder yield. This method avoids the spalling of the guide tube end face, and while ensuring improved yield, it can further reduce the inclusion content in the prepared high-temperature alloy powder.

Description

Technical Field

[0001] This invention relates to the field of metal powder atomization preparation technology, and in particular to a method for preparing a gradient guide tube for long-term atomization operation, applicable to the preparation of high-temperature alloy powders in the fields of powder metallurgy and additive manufacturing. Background Technology

[0002] In the metal powder atomization process, the guide tube is a key component that guides molten metal into the atomization chamber, and its performance directly affects the atomization quality, inclusion content, and yield. Traditional zirconia guide tubes, due to their single material structure, are susceptible to erosion and chemical corrosion of the ends by the high-temperature molten metal during long-term atomization, leading to end detachment and damage, which affects atomization stability and powder quality.

[0003] In existing technologies, increasing the thickness of the guide tube or using corrosion-resistant materials can extend its service life, but this often comes at the cost of increased costs and cannot completely solve the problem of erosion at the end of the guide tube. Therefore, there is an urgent need for a gradient structure guide tube that can extend atomization time and improve powder yield while ensuring the stability of the guide tube. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing a gradient guide tube suitable for long-term atomization. By selecting raw materials and optimizing the sintering process, a gradient guide tube with a gradually decreasing bulk density from the end to the upper middle section is prepared. The end of the guide tube has a dense ceramic structure with good erosion and corrosion resistance; the upper middle section has a loose granular structure with good flow conductivity and thermal stability. This effectively reduces the probability of damage to the guide tube during atomization, reduces the inclusion content in the powder, thereby achieving stable atomization over a long period and further improving the powder yield.

[0005] The technical solution of this invention is:

[0006] A method for preparing a gradient guide tube suitable for long-term atomization is provided, comprising the following steps:

[0007] Step 1: Select ceramic-type zirconia powder with a particle size range of 1μm to 5μm, and mix the ceramic-type zirconia powder with magnesium oxide stabilizer to obtain a ceramic-type mixture;

[0008] Granular zirconium oxide powder with a particle size range of 5μm to 2mm was selected as the loose material. The granular zirconium oxide powder was thoroughly mixed with magnesium oxide stabilizer to obtain a granular mixture.

[0009] Step 2: Melt the ceramic-type mixture and the granular mixture separately using electric heating;

[0010] Step 3: Prepare ceramic granules from the molten ceramic mixture using an agent granulation process, and prepare granules from the molten granular mixture using an agent granulation process; wherein the particle size of the granules is larger than that of the ceramic granules.

[0011] Step 4: Fill the mold with ceramic granules and granules. The mold is a guide tube mold. The inner tube of the guide tube gradually narrows from the top to the bottom, forming an inverted cone shape. The guide tube is divided into an upper part, a middle part, and a lower part from top to bottom. Fill the lower part of the mold with ceramic granules, fill the upper part of the mold with granules, and fill the middle part of the mold with both ceramic granules and granules. In the middle part of the mold, the amount of ceramic granules gradually decreases from bottom to top, and the amount of granules gradually decreases from top to bottom.

[0012] Step 5: Press the ceramic granules and granules into a guide tube blank using a mold;

[0013] Step 6: Place the guide tube blank into the sintering furnace, slowly raise the temperature to 300℃ to 500℃, and hold for 1 to 2 hours; (This step is a drying step to remove moisture from the inside of the blank and prevent cracks from forming during sintering)

[0014] Step 7: In the pre-sintering stage: continue heating to 800℃ to 1000℃ and hold for 3 to 5 hours to perform pre-sintering, so that the guide tube blank is initially shaped and its mechanical strength is enhanced.

[0015] Step 8, Gradient Firing Stage: Heat the furnace to 1750℃ to 1780℃ and hold for 6 to 8 hours; then use a heat insulation cover to insulate and protect the middle and upper parts of the heated blank, and introduce and exhaust inert gas into the heat insulation cover. By controlling the gas flow rate, the temperature inside the heat insulation cover is lowered, so that the heating temperature of the lower part of the heated blank is higher than that of the middle and upper parts; so that the lower part of the blank of the guide tube forms a dense ceramic structure, and the middle and upper parts form a loose granular structure.

[0016] Furthermore, the particle size of the granulated material is controlled by the amount of binder added during the granulation process. Adding a binder binds the material into larger particles, thereby improving its flowability, compaction, and sintering properties.

[0017] Furthermore, in step 4, the two types of granulated materials are layered and filled. Even further, during the spreading process, the amount of ceramic-type granulated material is gradually reduced from bottom to top, while the amount of granular-type granulated material is gradually reduced from top to bottom; the ceramic-type granulated material is spread multiple times, and the granular-type granulated material is also spread multiple times, with the spreading of ceramic-type and granular-type granulated materials alternating. The lower part is filled with ceramic-type zirconia granulated material to form a dense structure, while the middle and upper parts are filled with granular-type zirconia granulated material to form a loose structure.

[0018] Furthermore, the content of the magnesium oxide stabilizer is 2.0% to 3.5%.

[0019] Furthermore, stability is controlled in step 2 by adding a magnesium oxide stabilizer, which can form partially or completely stable zirconium oxide.

[0020] Furthermore, the heat insulation cover is connected to an air inlet pipe and an air outlet pipe for introducing and discharging gas.

[0021] Furthermore, a high-temperature sealing mud is wrapped around the lower part of the billet. This is used for heat preservation and to ensure that the temperature of the lower part is higher than that of the middle and upper parts. Even further, a thermocouple is provided inside the heating furnace, corresponding to the lower part, to provide heating to the lower part, ensuring that the temperature of the lower part is higher than that of the middle and upper parts.

[0022] Furthermore, the pressure of the inert gas is 0.5 MPa to 0.8 MPa.

[0023] The advantages of this invention are:

[0024] 1. Extended atomization time: The dense ceramic structure at the end and the loose granular structure in the middle and upper part effectively reduce the scouring and erosion of the guide tube end by the molten metal, significantly extending the service life of the guide tube and ensuring the stability of the atomization process.

[0025] 2. Improve powder yield: Stable long-term atomization operation helps to improve the yield of metal powder and reduce production costs.

[0026] 3. Reduce inclusion content: By avoiding peeling off the end of the guide tube, non-metallic inclusions in the powder are reduced, improving the purity of high-temperature alloy powder and meeting the high-quality requirements of powder metallurgy and additive manufacturing.

[0027] 4. High adaptability: The gradient structure of the guide tube can be adjusted according to the specifications of different atomizing equipment, and has a wide range of application adaptability. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the cross-section of the gradient guide tube;

[0029] Figure 2 Schematic diagram of gradient guide tube packing;

[0030] Figure 3 This is a schematic diagram of gradient sintering of a gradient guide tube.

[0031] Figure 4 Flowchart for the fabrication of gradient guide tubes; Detailed Implementation

[0032] The disclosed examples will be described more fully with reference to the accompanying drawings, in which some (but not all) of the disclosed examples are shown. In fact, many different examples may be described, and these examples should not be construed as limited to those set forth herein. Rather, these examples are described so that this disclosure will be thorough and complete, and will fully convey the scope of this disclosure to those skilled in the art.

[0033] A method for preparing a gradient guide tube suitable for long-term atomization is provided, comprising the following steps:

[0034] Step 1: Select ceramic-type zirconia powder with a particle size range of 1μm to 5μm, and mix the ceramic-type zirconia powder with magnesium oxide stabilizer to obtain a ceramic-type mixture;

[0035] Granular zirconium oxide powder with a particle size range of 5μm to 2mm was selected as the loose material. The granular zirconium oxide powder was thoroughly mixed with magnesium oxide stabilizer to obtain a granular mixture.

[0036] Step 2: Melt the ceramic-type mixture and the granular mixture separately using electric heating;

[0037] Step 3: Prepare ceramic granules from the molten ceramic mixture using an agent granulation process, and prepare granules from the molten granular mixture using an agent granulation process; wherein the particle size of the granules is larger than that of the ceramic granules.

[0038] Step 4: Fill the mold with ceramic granules and granules. The mold is a guide tube mold. The inner tube of the guide tube gradually narrows from the top to the bottom, forming an inverted cone shape. The guide tube is divided into an upper part, a middle part, and a lower part from top to bottom. Fill the lower part of the mold with ceramic granules, fill the upper part of the mold with granules, and fill the middle part of the mold with both ceramic granules and granules. In the middle part of the mold, the amount of ceramic granules gradually decreases from bottom to top, and the amount of granules gradually decreases from top to bottom.

[0039] Step 5: Press the ceramic granules and granules into a guide tube blank using a mold;

[0040] Step 6: Place the guide tube blank into the sintering furnace, slowly raise the temperature to 300℃ to 500℃, and hold it for 1 to 2 hours;

[0041] Step 7: In the pre-sintering stage: continue heating to 800℃ to 1000℃ and hold for 3 to 5 hours to perform pre-sintering, so that the guide tube blank is initially shaped and its mechanical strength is enhanced.

[0042] Step 8, Gradient Firing Stage: The furnace is heated to 1750℃ to 1780℃ and held for 6 to 8 hours. Then, a heat insulation cover is used to protect the middle and upper parts of the heated blank. Inert gas is introduced and discharged into the heat insulation cover, and the gas flow rate is controlled to cool the area inside the cover, ensuring that the heating temperature of the lower part of the heated blank is higher than that of the middle and upper parts. This results in a dense ceramic structure in the lower part of the blank and a loose granular structure in the middle and upper parts. Therefore, the dense ceramic structure at the end and the loose granular structure in the upper and middle parts effectively reduce the erosion and corrosion of the end of the guide tube by the molten metal, significantly extending the service life of the guide tube, ensuring the stability of the atomization process, and extending the atomization time. Stable, long-term atomization operation helps improve the yield of metal powder and reduce production costs.

[0043] The content of the magnesium oxide stabilizer is 2.0% to 3.5%.

[0044] The heat insulation cover is connected to an air inlet pipe and an air outlet pipe for introducing and discharging gas.

[0045] The lower part of the billet is also covered with high-temperature sealing mud. This is used for heat preservation and to ensure that the temperature of the lower part is higher than that of the middle and upper parts. A thermocouple is also provided in the heating furnace, corresponding to the lower part, to provide heating for the lower part, so that the temperature of the lower part is higher than that of the middle and upper parts.

[0046] The pressure of the inert gas is 0.5MPa~0.8MPa.

[0047] Descriptions of various advantageous arrangements have been shown for illustrative and descriptive purposes, but such descriptions are not intended to be exclusive or limited to the disclosed forms. Many modifications and variations will be apparent to those skilled in the art. Furthermore, different advantageous examples may describe different advantages compared to other advantageous examples. One or more examples have been selected and described in order to best illustrate the principles and practical application of the examples, and to enable those skilled in the art to understand that this disclosure contains various examples with various modifications suitable for the particular intended use.

Claims

1. A method for preparing a gradient guide tube suitable for long-term atomization, characterized in that, Includes the following steps: Step 1: Select ceramic-type zirconia powder with a particle size range of 1μm to 5μm, and mix the ceramic-type zirconia powder with magnesium oxide stabilizer to obtain a ceramic-type mixture; Granular zirconium oxide powder with a particle size range of 5μm to 2mm was selected as the loose material. The granular zirconium oxide powder was thoroughly mixed with magnesium oxide stabilizer to obtain a granular mixture. Step 2: Melt the ceramic-type mixture and the granular mixture separately using electric heating; Step 3: Prepare ceramic granules from the molten ceramic mixture using an agent granulation process, and prepare granules from the molten granular mixture using an agent granulation process; wherein the particle size of the granules is larger than that of the ceramic granules. Step 4: Fill the mold with ceramic granules and granules. The mold is a guide tube mold. The inner tube of the guide tube gradually narrows from the top to the bottom, forming an inverted cone shape. The guide tube is divided into an upper part, a middle part, and a lower part from top to bottom. Fill the lower part of the mold with ceramic granules, fill the upper part of the mold with granules, and fill the middle part of the mold with both ceramic granules and granules. In the middle part of the mold, the amount of ceramic granules gradually decreases from bottom to top, and the amount of granules gradually decreases from top to bottom. Step 5: Press the ceramic granules and granules into a guide tube blank using a mold; Step 6: Place the guide tube blank into the sintering furnace, slowly raise the temperature to 300℃ to 500℃, and hold it for 1 to 2 hours; Step 7: In the pre-sintering stage: continue to heat to 800℃ to 1000℃, hold for 3 to 5 hours, and carry out pre-sintering to pre-shape the flow tube blank and enhance its mechanical strength. Step 8, Gradient Firing Stage: Heat the furnace to 1750℃ to 1780℃ and hold for 6 to 8 hours; then use a heat insulation cover to insulate and protect the middle and upper parts of the heated blank, and introduce and exhaust inert gas into the heat insulation cover. By controlling the gas flow rate, the temperature inside the heat insulation cover is lowered, so that the heating temperature of the lower part of the heated blank is higher than that of the middle and upper parts; so that the lower part of the blank of the guide tube forms a dense ceramic structure, and the middle and upper parts form a loose granular structure.

2. The method for preparing a gradient guide tube suitable for long-term atomization as described in claim 1, characterized in that: The particle size of the granulated material is controlled by adding a binder during the granulation process.

3. The method for preparing a gradient guide tube suitable for long-term atomization as described in claim 1, characterized in that: In step 4, the two granulated materials are filled in layers.

4. The method for preparing a gradient guide tube suitable for long-term atomization as described in claim 3, characterized in that: When spreading the materials, the amount of ceramic granules is gradually reduced from bottom to top, while the amount of granular granules is gradually reduced from top to bottom. Ceramic granules are spread multiple times, and granular granules are spread multiple times. The spreading of ceramic granules and granular granules is carried out alternately.

5. The method for preparing a gradient guide tube suitable for long-term atomization as described in claim 1, characterized in that: The content of the magnesium oxide stabilizer is 2.0% to 3.5%.

6. The method for preparing a gradient guide tube suitable for long-term atomization as described in claim 1, characterized in that: In step 2, stability is controlled by adding magnesium oxide stabilizer.

7. The method for preparing a gradient guide tube suitable for long-term atomization as described in claim 1, characterized in that: The heat insulation cover is connected to an air inlet pipe and an air outlet pipe for introducing and discharging gas.

8. The method for preparing a gradient guide tube suitable for long-term atomization as described in claim 1, characterized in that: The lower part of the blank is also wrapped with high-temperature sealing mud for heat preservation and to make the temperature of the lower part higher than that of the middle and upper parts.

9. The method for preparing a gradient guide tube suitable for long-term atomization as described in claim 1, characterized in that: A thermocouple is also provided inside the heating furnace. The thermocouple corresponds to the lower part and is used to provide heating to the lower part, so that the temperature of the lower part is higher than that of the middle and upper parts.

10. The method for preparing a gradient guide tube suitable for long-term atomization as described in claim 1, characterized in that: The pressure of the inert gas is 0.5MPa~0.8MPa.

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