阅读说明：本技术 一种金属粉末注射成型工艺制备镜面抛光产品的方法 (Method for preparing mirror-polished product by metal powder injection molding process ) 是由 严新华 杨虎 侯春伟 陈勇 于 2021-07-28 设计创作，主要内容包括：本发明公开了一种金属粉末注射成型工艺制备镜面抛光产品的方法,所述方法包括以下步骤：取金属粉末和塑基无石蜡粘结剂,均匀密炼后造粒,得到金属粉末喂料；取所述金属粉末喂料,用注射机注入模具,通过填充、保压、冷却,得到生坯；将所述生坯用浓硝酸脱脂；将脱脂后的所述生坯在氩气保护下分段烧结,然后冷却,得到高致密度烧结件；对所述高致密度烧结件进行表面锻压处理,抛光后得到镜面抛光的高致密度产品。本发明使用高振实密度的金属粉末及粒度配比,改进了烧结工艺,使得金属粉末注射成型得到的产品表面致密度可以达到98％-99％。然后再进行表面锻压处理,进一步提升表面致密度和细化晶体组织,使产品能够达到镜面抛光的效果。(The invention discloses a method for preparing a mirror-polished product by a metal powder injection molding process, which comprises the following steps: taking metal powder and a plastic-based paraffin-free binder, uniformly banburying and then granulating to obtain metal powder feed; feeding the metal powder, injecting the metal powder into a mold by using an injection machine, and filling, maintaining pressure and cooling to obtain a green body; degreasing the green body by using concentrated nitric acid; sintering the degreased green body in a segmented manner under the protection of argon, and then cooling to obtain a high-density sintered part; and carrying out surface forging treatment on the high-density sintered part, and polishing to obtain a mirror-polished high-density product. The invention uses the metal powder with high tap density and the granularity ratio, improves the sintering process, and ensures that the surface density of the product obtained by metal powder injection molding can reach 98-99%. Then, surface forging and pressing treatment is carried out, so that the surface density is further improved, the crystal structure is further refined, and the mirror polishing effect of the product can be achieved.)

1. A method of preparing a mirror-finished product by a metal powder injection molding process, the method comprising the steps of:

taking metal powder and a plastic-based paraffin-free binder, uniformly banburying and then granulating to obtain metal powder feed;

feeding the metal powder, injecting the metal powder into a mold by using an injection machine, and filling, maintaining pressure and cooling to obtain a green body;

degreasing the green body by using concentrated nitric acid;

sintering the degreased green body in a segmented manner under the protection of argon, and then cooling to obtain a high-density sintered part;

and carrying out surface forging treatment on the high-density sintered part, and polishing to obtain a mirror-polished high-density product.

2. The method of claim 1, wherein the metal powder is a smooth surfaced, spherical, ellipsoidal, subsphaeroidal, or subsphaeroidal powder having a tap density of 4.55g/cm or more³(ii) a The gradient ratio of the powder particles is 20-30% of powder with the granularity of 1-3 mu m in percentage by mass; 20-30% of powder with the granularity of 3-6 mu m and 40-60% of powder with the granularity of 6-12 mu m; the oxygen content is < 2000 ppm.

3. The method according to claim 1, wherein the plastic-based paraffin-free binder comprises, in mass percent: 5% of polyethylene PE, 85% of polyformaldehyde POM, 5% of stearic acid, 3% of EVA and 9002% of a heat stabilizer.

4. The method of claim 1, wherein the metal powder and the plastic-based paraffin-free binder are present in a volume ratio of (62-65): (35-38).

5. The method according to claim 1, wherein the specific parameters of filling, pressure holding and cooling are as follows: the mold temperature is 100-140 ℃, the material temperature is 185-200 ℃, the injection pressure is 60-200MPa, the pressure maintaining time is 2-5S, and the cooling time is 5-20S.

6. The method according to claim 1, wherein the degreasing treatment is in particular: and (3) introducing nitrogen into the degreasing furnace, wherein the oxygen content in the degreasing furnace is less than or equal to 4.5%, the supply amount of concentrated nitric acid in the degreasing process is 280mL/H, the supply amount of nitrogen is 1100L/H, the degreasing temperature is 110-130 ℃, the degreasing time is 2-4 hours, and the degreasing rate is more than or equal to 7.6%.

7. The method according to claim 1, characterized in that the step sintering is in particular:

a first stage: putting the degreased metal powder green body into a sintering furnace, performing negative pressure air extraction on the sintering furnace, keeping the pressure in the sintering furnace at 0-5Kpa, introducing nitrogen into the sintering furnace at the flow rate of 40L/min, heating from room temperature to 600 ℃ at the heating rate of 5 ℃/min, preserving heat for 2 hours, and performing negative pressure degreasing;

two stages: controlling the pressure in the sintering furnace to be 0-10Kpa, introducing nitrogen into the sintering furnace at the flow rate of 40L/min, heating from 600 ℃ to 1200 ℃ at the heating rate of 4-6 ℃/min, preserving heat for 2 hours, and cleaning at high temperature;

three stages: controlling the vacuum degree in the sintering furnace to be 0-20pa, heating from 1200 ℃ to 1320 ℃ at the heating rate of 4-6 ℃/min, preserving the heat for 0.5-1 hour, and performing vacuum sintering;

the fourth stage: and (2) filling argon into the sintering furnace for protection, wherein the pressure is 20-60Kpa, and the flow of the argon is as follows: heating to reach temperature of from 1320 ℃ to 1380 ℃ at a heating rate of 4-6 ℃/min at 40L/min, preserving heat for 3-5 hours, and compacting at high temperature;

and a fifth stage: and (6) cooling.

8. The method according to claim 1, wherein the surface forging is performed by: the pressure is 10-100T, the pressure maintaining time is 1-10S, the forging frequency is 1-5 times, and the temperature is 20-600 ℃.

Technical Field

The invention relates to the technical field of powder injection molding, in particular to a method for preparing a mirror-polished product by a metal powder injection molding process.

Background

Compared with other metal processing techniques, the metal powder injection molding technique has the advantages of near net shape, high size precision, high material utilization rate, uniform structure and the like. However, the metal powder injection molding process product has only about 95% of surface compactness, and cannot meet the high-requirement polishing effect.

The Hot Isostatic Pressing (HIP) process is to place the product in a closed container, apply equal pressure to the product and high temperature, and under the action of high temperature and high pressure, the product is densified.

Although the metal powder injection moulding process product can be made to be 99% surface dense by hot isostatic pressing, the hot isostatic pressing requires extremely high pressures and temperatures, which makes the process expensive and some materials unsuitable for hot isostatic pressing.

Disclosure of Invention

In order to solve the problems in the prior art, embodiments of the present invention provide a method for preparing a mirror-finished product by using a metal powder injection molding process. The technical scheme is as follows:

in a first aspect, there is provided a method of preparing a mirror-finished product by a metal powder injection molding process, the method comprising the steps of:

taking metal powder and a plastic-based paraffin-free binder, uniformly banburying and then granulating to obtain metal powder feed;

feeding the metal powder, injecting the metal powder into a mold by using an injection machine, and filling, maintaining pressure and cooling to obtain a green body;

degreasing the green body by using concentrated nitric acid;

sintering the degreased green body in a segmented manner under the protection of argon, and then cooling to obtain a high-density sintered part;

and carrying out surface forging treatment on the high-density sintered part, and polishing to obtain a mirror-polished high-density product.

Further, the method can be used for preparing a novel materialThe metal powder is spherical, ellipsoidal, subsphaeroidal or subsphaeroidal powder with smooth surface, and the tap density of the powder is more than or equal to 4.55g/cm³(ii) a The gradient ratio of the powder particles is 20-30% of powder with the granularity of 1-3 mu m in percentage by mass; 20-30% of powder with the granularity of 3-6 mu m and 40-60% of powder with the granularity of 6-12 mu m; the oxygen content is < 2000 ppm.

Further, the plastic-based paraffin-free binder comprises the following components in percentage by mass: 5% of polyethylene PE, 85% of polyformaldehyde POM, 5% of stearic acid, 3% of EVA and 9002% of a heat stabilizer.

Further, the volume ratio of the metal powder to the plastic-based paraffin-free binder is (62-65): (35-38).

Further, the specific parameters of filling, pressure maintaining and cooling are as follows: the mold temperature is 100-140 ℃, the material temperature is 185-200 ℃, the injection pressure is 60-200MPa, the pressure maintaining time is 2-5S, and the cooling time is 5-20S.

Further, the degreasing treatment specifically comprises: and (3) introducing nitrogen into the degreasing furnace, wherein the oxygen content in the degreasing furnace is less than or equal to 4.5 percent (volume fraction), the supply amount of concentrated nitric acid in the degreasing process is 280mL/H, the supply amount of nitrogen is 1100L/H, the degreasing temperature is 110-130 ℃, the degreasing time is 2-4 hours, and the degreasing rate is more than or equal to 7.6 percent to finish the degreasing.

Further, the step sintering specifically comprises:

a first stage: putting the degreased metal powder green body into a sintering furnace, performing negative pressure air extraction on the sintering furnace, keeping the pressure in the sintering furnace at 0-5Kpa, introducing nitrogen into the sintering furnace at the flow rate of 40L/min, heating from room temperature to 600 ℃ at the heating rate of 5 ℃/min, preserving heat for 2 hours, and performing negative pressure degreasing;

two stages: controlling the pressure in the sintering furnace to be 0-10Kpa, introducing nitrogen into the sintering furnace at the flow rate of 40L/min, heating from 600 ℃ to 1200 ℃ at the heating rate of 4-6 ℃/min, preserving heat for 2 hours, and cleaning at high temperature;

three stages: controlling the vacuum degree in the sintering furnace to be 0-20pa, heating from 1200 ℃ to 1320 ℃ at the heating rate of 4-6 ℃/min, preserving the heat for 0.5-1 hour, and performing vacuum sintering;

the fourth stage: and (2) filling argon into the sintering furnace for protection, wherein the pressure is 20-60Kpa, and the flow of the argon is as follows: heating to reach temperature of from 1320 ℃ to 1380 ℃ at a heating rate of 4-6 ℃/min at 40L/min, preserving heat for 3-5 hours, and compacting at high temperature;

and a fifth stage: and (6) cooling.

Further, the surface forging treatment specifically comprises: the pressure is 10-100T, the pressure maintaining time is 1-10S, the forging frequency is 1-5 times, and the temperature is 20-600 ℃.

The technical scheme provided by the embodiment of the invention has the following beneficial effects: in the embodiment of the invention, metal powder and plastic-based paraffin-free binder are taken, uniformly mixed and granulated to obtain metal powder feed; feeding the metal powder, injecting the metal powder into a mold by using an injection machine, and filling, maintaining pressure and cooling to obtain a green body; degreasing the green body by using concentrated nitric acid; sintering the degreased green body in a segmented manner under the protection of argon, and then cooling to obtain a high-density sintered part; and carrying out surface forging treatment on the high-density sintered part, and polishing to obtain a mirror-polished high-density product. The invention uses the metal powder with high tap density and the granularity ratio, improves the sintering process, and ensures that the surface density of the product obtained by metal powder injection molding can reach 98-99%. Then, surface forging and pressing treatment is carried out, so that the surface density is further improved, the crystal structure is further refined, and the mirror polishing effect of the product can be achieved.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, embodiments of the present invention will be described in further detail below.

Example 1

(1) The required element powder or alloy powder was taken and metal powder was prepared in the mass ratio shown in table 1.

TABLE 1 ratio of metal powders (316L)

C(％)

Cr(％)

Ni(％)

Mo(％)

Mn(％)

Si(％)

Fe(％)

≤0.03

16-18

10-14

2-3

≤2

≤1

Remainder of

(2) The metal powder is spherical, ellipsoidal, subsphaeroidal or subsphaeroidal powder with smooth surface, which can promote the formation and growth of sintering necks in the sintering process and is beneficial to the sintering shrinkage migration of the powder, thereby being beneficial to the sintering densification. The powder granularity is subjected to gradient proportioning to improve the powder tap density: the gradient ratio of the powder particles is 20-30% of powder with the granularity of 1-3 mu m in percentage by mass; 20-30% of powder with the granularity of 3-6 mu m and 40-60% of powder with the granularity of 6-12 mu m, and the tap density of the obtained metal powder is more than or equal to 4.55g/cm³. Since oxygen tends to form oxides at high temperatures, hindering densification and affecting gloss after polishing, it is desirable to control the amount of oxygen in the metal powder to be < 2000 ppm.

(3) Preparing polyethylene PE 5%, polyformaldehyde POM 85%, stearic acid 5%, EVA 3% and heat stabilizer B9002% according to mass ratioThe density of the plastic base adhesive is about 1.35g/cm without paraffin³. The adhesive does not contain paraffin, so that the green body is better in shape keeping, and the product is not easy to deform; the binder residue is less in the degreasing process, the impurities of the sintered part are lower, and the mechanical property and the polishing effect of the material are improved; the paraffin is prevented from gasifying and polluting the sintering furnace body to influence the sintering atmosphere.

(4) And adding the plastic-based paraffin-free binder into the prepared metal powder, wherein the volume ratio of the metal powder to the binder is 63:37, uniformly mixing by using mixing equipment, and granulating to obtain the metal powder feed with good formability and the shrinkage rate of 1.165.

(5) And feeding the metal powder, injecting the metal powder into a mold cavity by using an injection machine, and smoothly designing a mold runner and a gate so as to ensure smooth injection molding glue feeding and avoid the separation of the metal powder and the binder caused by shearing force. Under the conditions of mold temperature of 100 ℃, material temperature of 185 ℃, injection pressure of 200MPa, pressure maintaining time of 2S and cooling time of 5S, filling, pressure maintaining, cooling and solidifying to obtain a green body.

(6) And (3) putting the green body into a degreasing furnace, and degreasing the green body by using concentrated nitric acid with the concentration of more than 95%, wherein the degreasing temperature is 110 ℃. And in the degreasing process, introducing nitrogen into the degreasing furnace as a scavenging gas, and controlling the oxygen content in the degreasing furnace to be not more than 4.5 percent (volume fraction). In the degreasing process, the supply amount of concentrated nitric acid is 280mL/H, the supply amount of nitrogen is 1100L/H, the degreasing time is 4 hours, and the degreasing is finished when the degreasing rate is more than or equal to 7.6 percent. The degreasing by using the 95 percent concentrated nitric acid can ensure higher degreasing rate, avoid incomplete nitric acid catalytic degreasing, and prevent the residual binder from forming gas and carbon in the sintering process to hinder sintering densification.

(7) And (3) putting the degreased green body into a vacuum sintering furnace, filling argon gas into the vacuum sintering furnace as protective gas, and sintering in vacuum in a segmented manner to obtain a high-density sintered part.

The specific method of vacuum staged sintering is as follows:

a first stage: carrying out negative pressure air extraction on the vacuum sintering furnace, keeping the pressure in the sintering furnace at 0Kpa, introducing nitrogen into the sintering furnace at the flow rate of 40L/min, heating from room temperature to 600 ℃ at the heating rate of 5 ℃/min, preserving heat for 2 hours, and carrying out negative pressure degreasing;

two stages: controlling the pressure in the sintering furnace to be 0Kpa, introducing nitrogen into the sintering furnace at the flow rate of 40L/min, heating from 600 ℃ to 1200 ℃ at the heating rate of 4 ℃/min, preserving heat for 2 hours, and cleaning at high temperature;

three stages: controlling the vacuum degree in the sintering furnace to be 0pa, heating from 1200 ℃ to 1320 ℃ at the heating rate of 4 ℃/min, and preserving heat for 0.5 hour, wherein in the stage, vacuum sintering is kept before hole sealing is carried out on the surface of the sintered part, so that gas can be prevented from entering the interior of the sintered part to form pores, or gas in the interior of the sintered part is prevented from being discharged;

the fourth stage: filling argon into the sintering furnace for protection, wherein the pressure is 20Kpa, and the flow of the argon is as follows: the temperature is raised from 1320 ℃ to 1380 ℃ at the temperature raising rate of 4 ℃/min at 40L/min, the temperature is kept for 5 hours, the proportion of low-temperature elements in the alloy material in liquid phase sintering can be increased by adopting a high-temperature sintering mode, and the density is increased by filling pores of the material with the liquid phase;

and a fifth stage: and (6) cooling.

The high-density sintered piece obtained by the process has the density of more than 7.85g/cm through the adjustment of the high-tap-density powder feeding and molding sintering process³The surface density can reach 98-99%.

(8) And carrying out surface forging treatment on the high-density sintered part, wherein the pressure is 10T, the pressure maintaining time is 10S, the forging times are 5 times, and the temperature is 600 ℃. The thickness of the compact layer on the surface of the product can reach more than 0.5mm through surface forging, and the surface density reaches approximately 100%. Meanwhile, the surface forging and pressing can also play a role in refining surface crystals, so that the polishing and mechanical properties are improved, and the mirror polishing effect is achieved.

The forging and pressing can change the metal structure, improve the metal performance and improve the size precision of the sintered part. After forging and pressing, the sintered part is compacted or welded with the original looseness, pores, microcracks and the like; the original dendrites are broken to make the crystal grains thin; meanwhile, the segregation and uneven distribution of the original carbide are changed, so that the structure is uniform, and a product with compact, uniform and fine interior, good comprehensive performance and reliable use is obtained.

Example 2

(1) And (3) taking the required element powder or alloy powder, and preparing the metal powder according to a proper mass ratio.

(2) The metal powder is spherical, ellipsoidal, subsphaeroidal or subsphaeroidal powder with smooth surface. Carrying out gradient proportioning on the powder granularity: the gradient ratio of the powder particles is 20-30% of powder with the granularity of 1-3 mu m in percentage by mass; 20-30% of powder with the granularity of 3-6 mu m and 40-60% of powder with the granularity of 6-12 mu m, and the tap density of the obtained metal powder is more than or equal to 4.55g/cm³. The oxygen content in the metal powder was controlled to < 2000 ppm.

(3) Preparing 5 percent of polyethylene PE, 85 percent of polyformaldehyde POM, 5 percent of stearic acid, 3 percent of EVA and 9002 percent of heat stabilizer B according to the mass ratio to obtain the plastic-based paraffin-free binder with the density of 1.35g/cm³。

(4) And adding the plastic-based paraffin-free binder into the prepared metal powder, wherein the volume ratio of the metal powder to the binder is 65:35, uniformly mixing by using mixing equipment, and granulating to obtain the metal powder feed with good formability and the shrinkage rate of 1.167.

(5) And feeding the metal powder, injecting the metal powder into a mold cavity by using an injection machine, and smoothly designing a mold runner and a gate so as to ensure smooth injection molding glue feeding and avoid the separation of the metal powder and the binder caused by shearing force. And under the conditions of mold temperature of 120 ℃, material temperature of 190 ℃, injection pressure of 130MPa, dwell time of 3S and cooling time of 10S, filling, dwell, cooling and solidifying to obtain a green body.

(6) And (3) putting the green body into a degreasing furnace, and degreasing the green body by using concentrated nitric acid with the concentration of more than 95%, wherein the degreasing temperature is 120 ℃. And in the degreasing process, introducing nitrogen into the degreasing furnace as a scavenging gas, and controlling the oxygen content in the degreasing furnace to be not more than 4.5 percent (volume fraction). In the degreasing process, the supply amount of concentrated nitric acid is 280mL/H, the supply amount of nitrogen is 1100L/H, the degreasing time is 3 hours, and the degreasing is finished when the degreasing rate is more than or equal to 7.6 percent.

(7) And (3) putting the degreased green body into a vacuum sintering furnace, filling argon gas into the vacuum sintering furnace as protective gas, and sintering in vacuum in a segmented manner to obtain a high-density sintered part.

The specific method of vacuum staged sintering is as follows:

a first stage: carrying out negative pressure air extraction on the vacuum sintering furnace, keeping the pressure in the sintering furnace at 3Kpa, introducing nitrogen into the sintering furnace at the flow rate of 40L/min, heating from room temperature to 600 ℃ at the heating rate of 5 ℃/min, preserving heat for 2 hours, and carrying out negative pressure degreasing;

two stages: controlling the pressure in the sintering furnace to be 8Kpa, introducing nitrogen into the sintering furnace at the flow rate of 40L/min, heating from 600 ℃ to 1200 ℃ at the heating rate of 5 ℃/min, preserving heat for 2 hours, and cleaning at high temperature;

three stages: controlling the vacuum degree in the sintering furnace to be 10pa, heating from 1200 ℃ to 1320 ℃ at the heating rate of 5 ℃/min, preserving the heat for 1 hour, and carrying out vacuum sintering;

the fourth stage: filling argon into the sintering furnace for protection, wherein the pressure is 40Kpa, and the flow rate of the argon is as follows: heating to reach temperature of from 1320 ℃ to 1380 ℃ at a heating rate of 5 ℃/min at 40L/min, preserving heat for 4 hours, and compacting at high temperature;

and a fifth stage: and (6) cooling.

Through the adjustment of the high-tap density powder feeding and molding sintering process, the surface density of the high-density sintered part obtained through the process can reach 98-99%.

(8) And carrying out surface forging treatment on the high-density sintered part, wherein the pressure is 50T, the pressure maintaining time is 5S, the forging times are 3 times, and the temperature is 300 ℃. The thickness of the compact layer on the surface of the product can reach more than 0.5mm through surface forging, and the surface density reaches approximately 100%.

Example 3

(1) And (3) taking the required element powder or alloy powder, and preparing the metal powder according to a proper mass ratio.

(2) The metal powder is spherical, ellipsoidal, subsphaeroidal or subsphaeroidal powder with smooth surface. Carrying out gradient proportioning on the powder granularity: the gradient ratio of the powder particles is 20-30% of powder with the granularity of 1-3 mu m in percentage by mass; 20-30% of powder with the granularity of 3-6 mu m and 40-60% of powder with the granularity of 6-12 mu m, and the tap density of the obtained metal powder is more than or equal to 4.55g/cm³. The oxygen content in the metal powder was controlled to < 2000 ppm.

(3) Taking 5 percent of polyethylene PE, 85 percent of polyformaldehyde POM and hard5 percent of fatty acid, 3 percent of EVA and 2 percent of heat stabilizer B9002 percent of plastic-based paraffin-free adhesive with the density of 1.35g/cm³。

(4) And adding the plastic-based paraffin-free binder into the prepared metal powder, wherein the volume ratio of the metal powder to the binder is 65:35, uniformly mixing by using mixing equipment, and granulating to obtain the metal powder feed with good formability and the shrinkage rate of 1.167.

(5) And feeding the metal powder, injecting the metal powder into a mold cavity by using an injection machine, and smoothly designing a mold runner and a gate so as to ensure smooth injection molding glue feeding and avoid the separation of the metal powder and the binder caused by shearing force. And under the conditions of mold temperature of 140 ℃, material temperature of 200 ℃, injection pressure of 60MPa, dwell time of 5S and cooling time of 20S, filling, dwell, cooling and solidifying to obtain a green body.

(6) And (3) putting the green body into a degreasing furnace, and degreasing the green body by using concentrated nitric acid with the concentration of more than 95%, wherein the degreasing temperature is 130 ℃. And in the degreasing process, introducing nitrogen into the degreasing furnace as a scavenging gas, and controlling the oxygen content in the degreasing furnace to be not more than 4.5 percent (volume fraction). In the degreasing process, the supply amount of concentrated nitric acid is 280mL/H, the supply amount of nitrogen is 1100L/H, the degreasing time is 2 hours, and the degreasing is finished when the degreasing rate is more than or equal to 7.6 percent.

(7) And (3) putting the degreased green body into a vacuum sintering furnace, filling argon gas into the vacuum sintering furnace as protective gas, and sintering in vacuum in a segmented manner to obtain a high-density sintered part.

The specific method of vacuum staged sintering is as follows:

a first stage: carrying out negative pressure air extraction on the vacuum sintering furnace, keeping the pressure in the sintering furnace at 5Kpa, introducing nitrogen into the sintering furnace at the flow rate of 40L/min, heating from room temperature to 600 ℃ at the heating rate of 5 ℃/min, preserving heat for 2 hours, and carrying out negative pressure degreasing;

two stages: controlling the pressure in the sintering furnace to be 10Kpa, introducing nitrogen into the sintering furnace at the flow rate of 40L/min, heating from 600 ℃ to 1200 ℃ at the heating rate of 6 ℃/min, preserving heat for 2 hours, and cleaning at high temperature;

three stages: controlling the vacuum degree in the sintering furnace to be 20pa, heating from 1200 ℃ to 1320 ℃ at the heating rate of 6 ℃/min, preserving the heat for 1 hour, and carrying out vacuum sintering;

the fourth stage: filling argon into the sintering furnace for protection, wherein the pressure is 60Kpa, and the flow of the argon is as follows: heating to reach temperature of from 1320 ℃ to 1380 ℃ at a heating rate of 6 ℃/min at 40L/min, preserving heat for 3 hours, and compacting at high temperature;

and a fifth stage: and (6) cooling.

Through the adjustment of the high-tap density powder feeding and molding sintering process, the surface density of the high-density sintered part obtained through the process can reach 98-99%.

(8) And carrying out surface forging treatment on the high-density sintered part, wherein the pressure is 100T, the pressure maintaining time is 1S, the forging times are 1 time, and the temperature is 20 ℃. The thickness of the compact layer on the surface of the product can reach more than 0.5mm through surface forging, and the surface density reaches approximately 100%.

The technical scheme provided by the embodiment of the invention has the following beneficial effects: in the embodiment of the invention, metal powder and plastic-based paraffin-free binder are taken, uniformly mixed and granulated to obtain metal powder feed; feeding the metal powder, injecting the metal powder into a mold by using an injection machine, and filling, maintaining pressure and cooling to obtain a green body; degreasing the green body by using concentrated nitric acid; sintering the degreased green body in a segmented manner under the protection of argon, and then cooling to obtain a high-density sintered part; and carrying out surface forging treatment on the high-density sintered part, and polishing to obtain a mirror-polished high-density product. The invention uses the metal powder with high tap density and the granularity ratio, improves the sintering process, and ensures that the surface density of the product obtained by metal powder injection molding can reach 98-99%. Then, surface forging and pressing treatment is carried out, so that the surface density is further improved, the crystal structure is further refined, and the mirror polishing effect of the product can be achieved.

The present invention is not limited to the above preferred embodiments, and any modifications, equivalent replacements, improvements, etc. within the spirit and principle of the present invention should be included in the protection scope of the present invention.