Cooperative control method for particle size and sintering change rate in pulverization-sintering integrated process

Abstract

The invention discloses a cooperative control method for particle size and sintering change rate in a pulverization-sintering integrated process, and belongs to the technical field of powder metallurgy. The method comprises the following steps: 1) mixing: stirring and mixing 100-mesh iron powder and oil, adding bronze powder, carbon powder with the particle size of 45-53 microns and lubricating oil, continuously mixing and stirring, and standing to obtain mixed powder; (2) forming, wherein the mixed powder is put into a mold of a forming machine to be pressed and formed, and a formed green body is obtained; and 3) sintering: sintering the green body in a sintering furnace to obtain a sintered product. According to the invention, the fine carbon powder is selected to replace scaly carbon powder, so that the sintering change rate can be obviously reduced by 0.25-0.3%, and the dimensional precision of the product is greatly improved. And the fine carbon powder is dispersed more uniformly in the sintering process, so that local expansion or shrinkage difference caused by non-uniform particle distribution can be reduced, and the risk of size fluctuation is reduced.

Description

Technical Field

[0001] This invention belongs to the field of powder metallurgy technology, specifically relating to a method for synergistic control of particle size and sintering change rate in an integrated powder preparation-sintering process. Background Technology

[0002] Powder metallurgy is a technology that manufactures desired parts through powder mixing, powder pressing, sintering, and post-sintering treatment. It offers high-quality manufacturing, meeting the demands for parts with high dimensional accuracy, complex shapes, and good overall performance. It also features material conservation, energy efficiency, and high overall performance, making it widely used in the automotive, machinery, electronics, and aerospace industries. Powder metallurgy mechanical parts, primarily made of iron-based materials (accounting for about 70%), can produce precision components such as gears, bearings, and tools. The industry is upgrading towards high performance and intelligent manufacturing, becoming an indispensable key link in modern manufacturing.

[0003] Fe-Cu-Sn-C alloy is a widely used material in iron-copper based powder metallurgy parts, often used in the production of bearing parts. In order to improve the compressive strength and sintering dimensional change rate of the product, better control the product performance and dimensional accuracy, and achieve relative controllability of the sintering process, we studied the relationship between the content of each component, raw material process and sintering change rate by studying the mixed powder raw materials with different formulations. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method for synergistic control of particle size and sintering change rate in an integrated powder-sintering process. This method can reduce the sintering change rate while maintaining good compressive strength of the product. By controlling the raw material ratio and stirring process, the formula can be flexibly adjusted to meet different performance requirements while ensuring dimensional stability.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0006] A method for synergistic control of particle size and sintering change rate in an integrated powder preparation-sintering process includes the following steps:

[0007] 1) Mixing: Mix 100-mesh iron powder with oil, then add bronze powder, carbon powder with a particle size of 45-53μm and lubricating oil and continue mixing and stirring. Let stand to obtain mixed powder.

[0008] 2) Molding: The mixed powder obtained in step 1) is placed into the mold of the molding machine and pressed to form a molded green body;

[0009] 3) Sintering: The green blank obtained in step 2) is placed in a sintering furnace for sintering to obtain the sintered product.

[0010] Furthermore, in step 1), the powder material composition is 2% bronze powder, 2% carbon powder, and 96% iron powder.

[0011] Furthermore, in step 1), the lubricant is vinyl bis-stearamide.

[0012] Furthermore, in step 1), the toner is added in three parts, with 1 / 3 added each time, and every 5 minutes.

[0013] Furthermore, in step 2), the molding density is 5.8 g / cm³. 3 Each formulation sample was made in quantities of 500 pieces.

[0014] Furthermore, in step 2), the forming weight is controlled to be 1.978-2.012g.

[0015] Furthermore, in step 3), the size of the sintered mesh is 450 mm.

[0016] Furthermore, in step 3), the sintering temperature is 1070–1110°C, and the holding time is 25 min.

[0017] Furthermore, in step 3), the sintering atmosphere is the exothermic reaction of ammonia decomposition.

[0018] Compared with the prior art, the present invention has the following advantages:

[0019] (1) By using fine carbon powder instead of flake carbon powder, the present invention can significantly reduce the sintering change rate by 0.25-0.3%, thereby greatly improving the dimensional accuracy of the product. Fine carbon powder is more uniformly dispersed during sintering, which can reduce the local expansion or contraction differences caused by uneven particle distribution and reduce the risk of dimensional fluctuations.

[0020] (2) While reducing the sintering change rate, the product can still maintain good compressive strength. By controlling the raw material ratio and stirring process, the formula can be flexibly adjusted to meet different performance requirements while ensuring dimensional stability. Attached Figure Description

[0021] Figure 1 This is a graph showing the sintering change rate of sintered products 1-7# in this application;

[0022] Figure 2 The diagram shows the compressive strength results of sintered products 1-7# in this application. Detailed Implementation

[0023] The present invention will be further illustrated below with reference to specific embodiments. These embodiments are implemented based on the technical solutions of the present invention, and it should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention.

[0024] In the following examples, bronze powder A, bronze powder B, and bronze powder C were purchased from different manufacturers in China; fine carbon powder D with a particle size of 45 μm was purchased from a Japanese manufacturer; flake carbon powder E with a particle size of 53 μm was purchased from a Chinese manufacturer; and iron powder F and iron powder G with a particle size of 100 mesh were purchased from different manufacturers in China.

[0025] Example 1

[0026] A method for synergistic control of particle size and sintering change rate in an integrated powder preparation-sintering process includes the following steps:

[0027] (1) Mixing: Stir iron powder and oil for 10 minutes, then add bronze powder, carbon powder and lubricant and stir for another 30 minutes (the carbon powder is added in three parts, 1 / 3 each time, every 5 minutes). Let stand for 24 hours to obtain mixed powder. The specific amount of each raw material is shown in Table 1.

[0028] (2) Molding: The mold was installed on a 3T molding machine. After installation, the machine was confirmed to be operating normally. The mixed powder obtained in step (1) was pressed into shape in the mold. The molding weight was controlled between 1.978-2.012g. 500 pieces of each formulation were molded, resulting in a molding density of 5.8g / cm³. 3 raw blanks;

[0029] (3) Sintering: The green blanks obtained above are sintered in a 450mm mesh belt sintering furnace under the exothermic reaction of ammonia decomposition. The sintering temperature is 1090±20℃ and the holding time is 25min to obtain the sintered product.

[0030] The specific product formula is shown in Table 1.

[0031] Table 1 Specific Product Formulas

[0032]

[0033] The outer diameter of products 1-7# was measured using a micrometer, the inner diameter using a cylinder gauge, and the maximum crushing load using a strength testing machine. The data were processed to calculate the sintering change rate and the compressive strength of the samples. The results are shown in Table 2. Figure 1-2 As shown.

[0034] The sintering shrinkage rate refers to the ratio of the shrinkage of the formed green body after sintering to the size of the forming die. The calculation formula is as follows:

[0035]

[0036]

[0037] Where Z1 is the outer diameter sintering change rate, Dα is the outer diameter of the sintered sample, and D is the outer diameter of the forming mold; Z2 is the inner diameter sintering change rate, dα is the inner diameter of the sintered sample, and d is the inner diameter of the forming mold.

[0038] Specimen compressive strength: After measuring the specimen dimensions, a destructive test is performed. The sintered cylindrical specimen is placed on a worktable, and the radial load is slowly and continuously increased until fracture occurs. The crushing load (i.e., the maximum crushing load) is measured. The radial crushing strength is calculated using the relationship between the crushing load and the dimensions of the cylindrical specimen. The calculation formula is as follows:

[0039]

[0040] Where K is the radial crushing strength, and the unit is megapascals (MPa);

[0041] F represents the breakdown load, measured in Newtons (N).

[0042] L is the total length of the sample, in millimeters (mm).

[0043] D is the outer diameter of the sample, in millimeters (mm).

[0044] e represents the sample wall thickness, in millimeters (mm).

[0045] Table 2 Sintering change rate and compressive strength results of sintered products 1-7#

[0046] 1# 2# 3# 4# 5# 6# 7# Outer diameter change rate % 0.421 0.163 0.355 0.343 0.354 0.423 0.485 Inner diameter change rate % 0.372 0.057 0.308 0.295 0.292 0.332 0.399 Pressure resistance MPa 371 336 347 355 381 370 365

[0047] From Table 1 and Figure 1-2 It can be seen that, under the same sintering conditions, comparing sintered products 1# and 2#, it can be seen that only the carbon powder changed, and the change rate decreased significantly (0.25-0.3), indicating that different particle sizes and shapes of carbon powder have a significant impact on the sintering change rate. Comparing sintered products 2#, 3#, and 4#, it can be seen that only the bronze powder changed, and the change rate of 2# decreased more significantly. After further verification and excluding other factors, the change rates of schemes 3# and 4# are relatively close.

[0048] Comparing sintered products #1 and #6, it can be seen that only the bronze powder changed, with a slight fluctuation in the change rate (within 0.05). Considering the different bronze powder production processes of different manufacturers, the impact of the change rate on the change rate is negligible. Comparing sintered products #1 and #5, it can be seen that only the iron powder changed, with a slight fluctuation in the change rate (within 0.1). Considering the different iron powders from different manufacturers using the same process, the impact of the change rate on the change rate is negligible. Comparing sintered products #6 and #7, it can be seen that only the carbon powder changed, with a slight increase in the change rate (around 0.06). Combining the comparison between schemes #1 and #2, it shows that different particle sizes and shapes of carbon powder have a certain impact on the sintering change rate.

[0049] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for synergistic control of particle size and sintering change rate in an integrated powder-sintering process, characterized in that: Includes the following steps: 1) Mixing: Mix 100-mesh iron powder with oil, then add bronze powder, carbon powder with a particle size of 45-53μm and lubricating oil and continue mixing and stirring. Let stand to obtain mixed powder. 2) Molding: The mixed powder obtained in step 1) is placed into the mold of the molding machine and pressed to form a molded green body; 3) Sintering: The green blank obtained in step 2) is placed in a sintering furnace for sintering to obtain the sintered product.

2. The method for synergistic control of particle size and sintering change rate in the integrated powder-sintering process according to claim 1, characterized in that: In step 1), the powder material composition is 2% bronze powder, 2% carbon powder and 96% iron powder.

3. The method for synergistic control of particle size and sintering change rate in the integrated powder-sintering process according to claim 1, characterized in that: In step 1), the lubricant is vinyl bis-stearamide.

4. The method for synergistic control of particle size and sintering change rate in the integrated powder-sintering process according to claim 1, characterized in that: In step 1), the toner is added in three parts, 1 / 3 each time, every 5 minutes.

5. The method for synergistic control of particle size and sintering change rate in the integrated powder-sintering process according to claim 1, characterized in that: In step 2), the forming density is 5.8 g / cm³. 3 Each formulation sample was made in quantities of 500 pieces.

6. The method for synergistic control of particle size and sintering change rate in the integrated powder-sintering process according to claim 1, characterized in that: In step 2), the forming weight is controlled to be 1.978-2.012g.

7. The method for synergistic control of particle size and sintering change rate in the integrated powder-sintering process according to claim 1, characterized in that: In step 3), the size of the sintered mesh is 450mm.

8. The method for synergistic control of particle size and sintering change rate in the integrated powder-sintering process according to claim 1, characterized in that: In step 3), the sintering temperature is 1070-1110℃ and the holding time is 25min.

9. The method for synergistic control of particle size and sintering change rate in the integrated powder-sintering process according to claim 1, characterized in that: In step 3), the sintering atmosphere is ammonia decomposition and exothermic.

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