Preparation method of gradient flow guide pipe suitable for long-time atomization

Abstract

According to the preparation method of the gradient flow guide pipe suitable for long-time atomization, on the basis of an existing zirconium oxide flow guide pipe, raw materials with different granularities are selected, and a gradient sintering technology is adopted, so that a compact structure with the ceramic end and a loose structure with the granular middle-upper portion are prepared, and the gradient flow guide pipe is prepared; and scouring and erosion of the metal melt to the end are reduced, the content of inclusions in the powder is reduced, the purpose of long-time atomization is achieved, and the yield of the powder is further increased. According to the method, the gradient flow guide pipe with the volume density gradually reduced from the end part to the middle upper part is formed by adjusting parameters such as the granularity of raw materials and the sintering process, erosion and stripping of the end face of the flow guide pipe can be avoided, the inclusion content is reduced, long-time atomization is achieved, and the powder yield is increased. According to the method, the end face of the flow guide pipe is prevented from falling off, and the inclusion content in the prepared high-temperature alloy powder can be further reduced on the basis that the yield is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of metal powder atomization preparation, in particular to a method for preparing a gradient flow guide tube for long-term atomization operation, which is suitable for preparing high-temperature alloy powder in the fields of powder metallurgy and additive manufacturing. Background Art

[0002] In the process of metal powder atomization, the flow guide is a key component that guides the molten metal into the atomization chamber. Its performance directly affects the atomization quality, inclusion content and yield. Due to the single material structure, the end of the traditional zirconia flow guide is easily eroded and chemically corroded by the high-temperature metal melt during the long-term atomization process, resulting in the end falling off and damage, affecting the atomization stability and powder quality.

[0003] In the prior art, the service life of the flow guide tube can be extended by increasing the thickness of the flow guide tube or using corrosion-resistant materials, but this is often accompanied by an increase in cost and cannot completely solve the problem of corrosion at the end of the flow guide tube. Therefore, there is an urgent need for a gradient structure flow guide tube that can extend the atomization time and improve the powder yield while ensuring the stability of the flow guide tube. Summary of the invention

[0004] The purpose of the present invention is to provide a method for preparing a gradient flow guide tube suitable for long-term atomization, and to prepare a gradient flow guide tube with a gradually decreasing volume density from the end to the middle and upper part by selecting raw materials and optimizing the sintering process. The end of the flow guide tube is a ceramic-type dense structure with good anti-scouring and anti-erosion performance; the middle and upper part is a granular loose structure with good flow-guiding performance and thermal stability, which can effectively reduce the probability of damage to the flow guide tube during the atomization process and reduce the inclusion content in the powder, thereby achieving long-term stable atomization and further improving the powder yield.

[0005] The technical solution of the present invention is:

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

[0007] Step 1, selecting ceramic zirconium oxide powder with a particle size range of 1 μm to 5 μm, and fully mixing the ceramic zirconium oxide powder with a magnesium oxide stabilizer to obtain a ceramic mixture;

[0008] Selecting granular zirconium oxide powder as a loose material, the particle size range is 5 μm to 2 mm, and fully mixing the granular zirconium oxide powder with a magnesium oxide stabilizer to obtain a granular mixed material;

[0009] Step 2, melting the ceramic type mixture and the particle type mixture separately by electric heating;

[0010] Step 3, preparing a ceramic granulated material from the melted ceramic mixture by a granulation process, and preparing a granulated granulated material from the melted granular mixture by a granulation process; and the particle size of the granular granulated material is larger than the particle size of the ceramic granulated material;

[0011] Step 4, filling the ceramic granulation material and the particle-type granulation material into the mold, the mold is a guide tube mold, the inner tube of the guide tube gradually narrows from the upper end to the lower end to form an inverted cone; and the guide tube is divided into an upper part, a middle part and a lower part from top to bottom; the ceramic granulation material is filled in the mold cavity corresponding to the lower part of the mold, the particle-type granulation material is filled in the mold cavity corresponding to the upper part of the mold, and the ceramic granulation material and the particle-type granulation material are filled in the mold cavity corresponding to the middle part of the mold, and the ceramic granulation material in the mold cavity corresponding to the middle part is gradually reduced from bottom to top, and the particle-type granulation material is gradually reduced from top to bottom;

[0012] Step 5, pressing the ceramic granulated material and the particle granulated material into a guide tube blank through a mold;

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

[0014] Step 7: In the pre-sintering stage: continue to raise the temperature to 800℃ to 1000℃, keep it warm for 3 to 5 hours, and perform pre-sintering to initially shape the guide tube blank and enhance its mechanical strength.

[0015] Step 8, gradient sintering stage: the heating furnace is heated to 1750°C to 1780°C and kept warm for 6 to 8 hours; then, a heat insulation cover is used to insulate the middle and upper parts of the heated green body, and an inert gas is introduced into and discharged from the heat insulation cover. By controlling the gas flow rate, the temperature inside the heat insulation cover is reduced so that the heating temperature of the lower part of the heated green body is higher than that of the middle and upper parts; so that the lower part of the guide tube green body forms a dense ceramic structure, and the middle and upper parts form a loose granular structure.

[0016] Furthermore, the particle size of the granular material is controlled by adding a binder in the granulation process, and the binder is added to bond the granules into larger particles to improve their fluidity, compactness and sintering properties.

[0017] Furthermore, in step 4, the two granulation materials are layered and filled. Furthermore, when spreading the materials, the ceramic granulation material gradually reduces the amount of material spread from bottom to top, and the granular granulation material gradually reduces the amount of material spread from top to bottom; the ceramic granulation material is spread multiple times, the granular granulation material is spread multiple times, and the ceramic granulation material and the granular granulation material are spread alternately. The lower part is filled with ceramic zirconia granulation material to form a dense structure, and the middle and upper part is filled with granular zirconia granulation material to form a loose structure.

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

[0019] Furthermore, in step 2, the stability is regulated by adding a magnesium oxide stabilizer, so that partially or completely stabilized zirconium oxide can be formed.

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

[0021] Furthermore, the lower part corresponding to the blank is also wrapped with high-temperature sealing mud, which is used for heat preservation and making the temperature of the lower part higher than that of the middle and upper parts. Furthermore, a thermocouple is also provided in the heating furnace, which corresponds to the lower part and is used for heating the lower part, so 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 the present invention are:

[0024] 1. Extend the atomization time: The dense ceramic structure at the end and the loose particle structure in the middle and upper parts effectively reduce the scouring and erosion of the end of the guide tube by the metal melt, significantly extend the service life of the guide tube, and ensure the stability of the atomization process.

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

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

[0027] 4. Strong adaptability: The gradient structure of the guide tube can be adjusted according to the specifications of different atomization equipment, and has a wide range of application adaptability. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0029] Figure 2 This is a schematic diagram of the gradient flow guide tube packing;

[0030] Figure 3 This is a schematic diagram of gradient sintering in a gradient flow guide tube;

[0031] Figure 4 Prepare a flow chart for the gradient flow tube; DETAILED DESCRIPTION

[0032] The disclosed examples will be more fully described 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 the examples set forth herein. Instead, these examples are described so that this disclosure will be thorough and complete and will fully convey the scope of the disclosure to those skilled in the art.

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

[0034] Step 1, selecting ceramic zirconium oxide powder with a particle size range of 1 μm to 5 μm, and fully mixing the ceramic zirconium oxide powder with a magnesium oxide stabilizer to obtain a ceramic mixture;

[0035] Selecting granular zirconium oxide powder as a loose material, the particle size range is 5 μm to 2 mm, and fully mixing the granular zirconium oxide powder with a magnesium oxide stabilizer to obtain a granular mixed material;

[0036] Step 2, melting the ceramic type mixture and the particle type mixture separately by electric heating;

[0037] Step 3, preparing a ceramic granulated material from the melted ceramic mixture by a granulation process, and preparing a granulated granulated material from the melted granular mixture by a granulation process; and the particle size of the granular granulated material is larger than the particle size of the ceramic granulated material;

[0038] Step 4, filling the ceramic granulation material and the particle-type granulation material into the mold, the mold is a guide tube mold, the inner tube of the guide tube gradually narrows from the upper end to the lower end to form an inverted cone; and the guide tube is divided into an upper part, a middle part and a lower part from top to bottom; the ceramic granulation material is filled in the mold cavity corresponding to the lower part of the mold, the particle-type granulation material is filled in the mold cavity corresponding to the upper part of the mold, and the ceramic granulation material and the particle-type granulation material are filled in the mold cavity corresponding to the middle part of the mold, and the ceramic granulation material in the mold cavity corresponding to the middle part is gradually reduced from bottom to top, and the particle-type granulation material is gradually reduced from top to bottom;

[0039] Step 5, pressing the ceramic granulated material and the particle granulated material into a guide tube blank through a mold;

[0040] Step 6: Place the guide tube blank into a sintering furnace, slowly raise the temperature to 300° C. to 500° C., and keep it at this temperature for 1 to 2 hours;

[0041] Step 7: In the pre-sintering stage: continue to raise the temperature to 800℃ to 1000℃, keep it warm for 3 to 5 hours, and perform pre-sintering to initially shape the guide tube blank and enhance its mechanical strength.

[0042] Step 8, gradient sintering stage: the heating furnace is heated to 1750°C to 1780°C, and kept warm for 6 to 8 hours; then, a heat shield is used to insulate the middle and upper parts of the heated blank, and an inert gas is introduced into and discharged from the heat shield, and the heat shield is cooled by controlling the gas flow rate, so that the heating temperature of the lower part of the heated blank is higher than the temperature of the middle and upper parts; so that the lower part of the guide tube blank forms a dense ceramic structure, and the middle and upper parts form a loose particle structure. Therefore, the dense ceramic structure at the end of the present invention and the loose particle structure in the middle and upper parts effectively reduce the scouring and erosion of the end of the guide tube by the metal melt, significantly extend the service life of the guide tube, ensure the stability of the atomization process, and extend the atomization time. The stable and long-term atomization operation helps to improve the recovery rate 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 with an air inlet pipe and an air outlet pipe for introducing and discharging gas.

[0045] The lower part of the blank is also wrapped with high-temperature sealing mud for heat preservation and making the temperature of the lower part higher than that of the middle and upper parts. A thermocouple is also arranged in the heating furnace, corresponding to the lower part, for heating 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] The description of different advantageous arrangements has been presented for purposes of illustration and description, but the description is not intended to be exclusive or limited to examples of the disclosed form. Many modifications and variations will be apparent to those of ordinary skill in the art. Additionally, different advantageous examples may describe different advantages over other advantageous examples. The selected example or examples are chosen and described in order to best illustrate the principles of the examples, the practical application, and to enable those of ordinary skill in the art to understand the disclosure with various examples with various modifications suitable for the particular use contemplated.

Claims

1. A method for preparing a gradient flow guide tube suitable for long-term atomization, characterized in that: The steps include: Step 1, selecting ceramic zirconium oxide powder with a particle size range of 1 μm to 5 μm, and fully mixing the ceramic zirconium oxide powder with a magnesium oxide stabilizer to obtain a ceramic mixture; Selecting granular zirconium oxide powder as a loose material, the particle size range is 5 μm to 2 mm, and fully mixing the granular zirconium oxide powder with a magnesium oxide stabilizer to obtain a granular mixed material; Step 2, melting the ceramic type mixture and the particle type mixture separately by electric heating; Step 3, preparing a ceramic granulated material from the melted ceramic mixture by a granulation process, and preparing a granulated granulated material from the melted granular mixture by a granulation process; and the particle size of the granular granulated material is larger than the particle size of the ceramic granulated material; Step 4, filling the ceramic granulation material and the particle-type granulation material into the mold, the mold is a guide tube mold, the inner tube of the guide tube gradually narrows from the upper end to the lower end to form an inverted cone; and the guide tube is divided into an upper part, a middle part and a lower part from top to bottom; the ceramic granulation material is filled in the mold cavity corresponding to the lower part of the mold, the particle-type granulation material is filled in the mold cavity corresponding to the upper part of the mold, and the ceramic granulation material and the particle-type granulation material are filled in the mold cavity corresponding to the middle part of the mold, and the ceramic granulation material in the mold cavity corresponding to the middle part is gradually reduced from bottom to top, and the particle-type granulation material is gradually reduced from top to bottom; Step 5, pressing the ceramic granulated material and the particle granulated material into a guide tube blank through a mold; Step 6: Place the guide tube blank into a sintering furnace, slowly raise the temperature to 300° C. to 500° C., and keep it at this temperature for 1 to 2 hours; Step 7, in the pre-sintering stage: continue to raise the temperature to 800°C to 1000°C, keep the temperature for 3 to 5 hours, and perform pre-sintering to initially shape the guide tube blank and enhance its mechanical strength. Step 8, gradient sintering stage: the heating furnace is heated to 1750°C to 1780°C and kept warm for 6 to 8 hours; then, a heat insulation cover is used to insulate the middle and upper parts of the heated green body, and an inert gas is introduced into and discharged from the heat insulation cover. By controlling the gas flow rate, the temperature inside the heat insulation cover is reduced so that the heating temperature of the lower part of the heated green body is higher than that of the middle and upper parts; so that the lower part of the guide tube green body forms a dense ceramic structure, and the middle and upper parts form a loose granular structure.

2. A method for preparing a gradient flow guide tube suitable for long-term atomization according to claim 1, characterized in that: The particle size of the granular material is controlled by adding a binder in the granulation process.

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

4. A method for preparing a gradient flow guide tube suitable for long-term atomization according to claim 3, characterized in that: When spreading materials, the ceramic type granulation material gradually reduces the spreading amount from bottom to top, and the granular type granulation material gradually reduces the spreading amount from top to bottom; the ceramic type granulation material is spread multiple times, and the granular type granulation material is spread multiple times, and the spreading of the ceramic type granulation material and the granular type granulation material are carried out alternately.

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

6. A method for preparing a gradient flow guide tube suitable for long-term atomization according to claim 1, characterized in that: In step 2, the stability is regulated by adding a magnesium oxide stabilizer.

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

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

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

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

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