Solid lost-core material and application method thereof in preparation of hollow product with inner track type structure

Abstract

The invention relates to the technical field of metal product injection molding, in particular to a solid lost-core material and an application method thereof in preparation of a hollow product of an inner rail type structure. The solid lost-core material is prepared from the following components in percentage by mass: 33.3%-66.7% of POM (Polyoxymethylene) and 33.3%-66.7% of Al2O3 powder, and is used for a preparation process of a hollow product with an inner rail type structure. The method sequentially comprises the steps of pelletizing of the hollow product with the inner rail type structure, pelletizing of a core, injection molding, catalytic degreasing, presintering of an injection blank of the hollow product with the inner rail type structure, sintering, solution treatment, aging treatment and the like, and finally the hollow product with the inner rail type structure with low surface roughness is obtained. The solid lost core material is simple in preparation process and low in preparation raw material cost, the shrinkage rate is small after a core injection blank is formed, carbon residues in POM can be removed, and preparation of various complex hollow products of inner rail type structures can be met.

Description

Technical Field

[0001] The present application relates to the technical field of injection molding of metal products, and in particular to a solid lost-core material and an application method thereof in the preparation of hollow products with inner track structures. Background Art

[0002] Metal Powder Injection Molding (MIM) technology is a method of mixing metal powder with a binder for injection molding. It first mixes the required metal powder with a binder to obtain a mixed feed, then granulates the mixed feed and injects it into the required shape, and then removes the binder through processes such as catalytic degreasing and sintering to obtain a metal product. MIM technology is widely used in technical fields such as electronic products, automobile manufacturing, and medical equipment.

[0003] In recent years, with the rapid development of MIM technology in the automotive industry, traditional one-step injection molding is difficult to meet the production of hollow products with curved inner channels such as the return device of the ball screw, so lost core injection is required to achieve the required shape requirements. The lost core injection process has been used in foreign countries to mass produce large and complex structural parts, but most of them are through low-melting point alloy core method or water-soluble inorganic salt lost core material. Such processes or steps are cumbersome or costly, and the size shrinkage is difficult to control.

[0004] In the related technology, the solid lost core material in MIM technology uses pure polyoxymethylene (POM), but in the lost core process, residual carbon that cannot be removed will be left, resulting in high roughness of the inner surface of the metal product. Summary of the invention

[0005] The purpose of this application is to solve the technical problems of complex process and high core loss cost in the prior art, as well as poor overall dimensional shrinkage stability of hollow products, especially hollow products with inner track structure, and carbon residue in POM. A solid core loss material and its application method in the preparation of hollow products with inner track structure are provided. The process requires first using solid core loss material to inject the core of the inner channel model, using the core to realize one-step product molding, and then performing the core loss step on the molded product to finally realize the preparation of hollow products with inner track structure.

[0006] The technical solution of this application In a first aspect, the present application provides a solid lost core material, which adopts the following technical solution: The solid lost core material is composed of POM and alumina (Al2O3) powder. The raw material composition and content used in its preparation are as follows, calculated by mass percentage: POM 66.7%-33.3% Al2O3 powder 33.3%-66.7%.

[0007] Preferably, the raw material composition and content of the solid lost core material used for its preparation are calculated by mass percentage as follows: POM 50%-60% Al2O3 powder 40%-50%.

[0008] Preferably, the raw material composition and content of the solid lost core material used for its preparation are calculated by mass percentage as follows: POM 50% Al2O3 powder 50%.

[0009] By adopting the above technical solution, POM and Al2O3 powder are used as solid lost core materials. Since the melting point of Al2O3 powder in the solid lost core material exceeds 2000°C, the use temperature of the solid lost core material is 170-210°C, which can meet the injection molding of various types of thermoplastic plastics at present, and is far superior to traditional low-melting point alloy lost core materials (most of which have a melting point between 150-230°C); and, compared with water-soluble inorganic salt lost core materials, the solid lost core material of the present application has a lower cost.

[0010] In the second aspect, the present application provides an application method of a solid lost core material in the preparation of a hollow product with an inner track structure, using the following technical solution: A method for applying a solid lost core material in the preparation of a hollow product with an inner track structure specifically comprises the following steps: S1. Granulation of hollow products with inner track structure: The metal powder raw material and the plastic-based binder used for preparing the inner track type structure hollow product are kneaded, mixed and granulated in sequence, and the temperature is controlled at 185-195° C. for mixing for 0.5-1.5 hours to obtain the inner track type structure hollow product particles; The amount of the above-mentioned metal powder raw material and plastic-based binder is calculated by mass ratio, and the metal powder raw material: plastic-based binder is 1-2.5:1; The metal powder raw material is 17-4PH stainless steel MIM powder, 316L stainless steel powder or high-strength lightweight steel Fe-Mn-Al-C powder, and the particle size of the metal powder raw material is 0.5-20 μm; The raw material components and contents of the 17-4PH stainless steel MIM powder are as follows: Chromium 15.5-17.5% Copper 3-5% Nickel 3-5% Niobium + Tantalum 0.15-0.45% Manganese ≤1.0% Silicon ≤1.0% Carbon ≤ 0.07% The balance is iron; The purity of the 17-4PH stainless steel powder is ≥99.5%; The raw material components and contents of the 316L stainless steel powder used in its preparation are as follows, calculated by mass percentage: Chromium 16.0-18.0% Nickel 10.0-14.0% Molybdenum 2.0-3.0% Manganese ≤2.0% Silicon ≤ 1.0% Carbon ≤ 0.03% The balance is iron; The purity of the 316L stainless steel powder is ≥99.5%; The raw material components and contents of the high-strength light-weight steel Fe-Mn-Al-C powder are as follows, calculated by mass percentage: Manganese 30.0-33.0% Aluminum 8.0-13.0% Carbon 0.8-1.0% The balance is iron; The purity of the high-strength lightweight steel Fe-Mn-Al-C powder is ≥99.5%; The above-mentioned plastic-based adhesive is a POM adhesive; S2. Granulation of core (solid lost core material): The POM and Al2O3 powders used to prepare the core are kneaded, mixed and granulated in sequence, and the temperature is controlled at 185-195°C for mixing for 0.5-1.5h to obtain core particles; The particle size of the Al2O3 powder is 0.5-20 μm; S3, Injection molding: (1) Inject the core particles obtained in S2 into the core mold. After pressure maintenance, cooling and solidification, open the core mold and take out the core injection blank. During the injection of the core particles, the injection temperature is controlled at 170-210°C and the injection speed is controlled at 35-85 cm 3 / s and injection pressure 60-120MPa; The above-mentioned pressure holding is 60-120MPa and the time is 2-10s; The temperature of the cooling and curing is 90-120°C and the time is 1-15s; (2) placing the core injection blank into the corresponding mold of the hollow product with inner track structure to obtain a mold closing; (3) Injecting the inner track type structure hollow product particles obtained in S1 into the mold cavity of the mold, and after pressure maintenance, cooling and solidification, opening the mold of the inner track type structure hollow product, and taking out the inner track type structure hollow product injection blank with the core injection blank; During the injection process of the above-mentioned inner track structure hollow product particles, the injection temperature is controlled at 170-210°C and the injection speed is controlled at 35-85cm 3 / s and injection pressure 60-120MPa; The above-mentioned pressure holding is 60-120MPa and the time is 2-10s; The temperature of the cooling and curing is 90-120°C and the time is 1-15s; S4, catalytic degreasing: The inner track structure hollow product injection blank with the core injection blank is subjected to acid stripping, and POM is catalytically removed by using 98% by mass gaseous nitric acid or oxalic acid, and then Al2O3 powder is blown away by air with a pressure of 0.1-0.6MPa to obtain the inner track structure hollow product injection blank; The catalytic temperature is 100-130°C and the time is 2-8h; S5. Pre-sinter and sinter the above-obtained inner track structure hollow product injection blank in accordance with the mechanical performance requirements of the inner track structure hollow product to be prepared, or pre-sinter, sinter, solution treatment and aging treatment in sequence to obtain the inner track structure hollow product.

[0011] Preferably, in the pre-sintering process, the temperature is controlled at 500-900° C. for 1-4 hours to obtain a pre-sintered blank; In the sintering process, the pre-sintered blank is sintered for 1-3 hours under vacuum conditions and the protection of hydrogen or inert gas (the inert gas is argon or nitrogen) to obtain a sintered blank; When the metal powder raw material used for preparing the inner track structure hollow product is 17-4PH stainless steel MIM powder, the sintering temperature is controlled to be 1250-1350°C; In the specific implementation of the present application, only 17-4PH stainless steel MIM powder with the following metal raw material composition and content is used as an example for description: 17-4PH stainless steel MIM powder, calculated by mass percentage, the raw material components and contents used in its preparation are as follows: Chromium 17% Copper 4% Nickel 4% Niobium + Tantalum 0.30% Manganese 1.0% Silicon 1.0% Carbon 0.07% The balance is iron; The purity of the 17-4PH stainless steel powder is ≥99.5%; When the metal powder raw material used in the preparation of the inner track structure hollow product is 316L stainless steel powder, the sintering temperature is controlled to be 1320-1420°C; In the specific implementation of the present application, only 316L stainless steel powder with the following metal raw material composition and content is used as an example for description: 316L stainless steel powder, calculated by mass percentage, the raw material components and contents used in its preparation are as follows: Chromium 17.0% Nickel 12.0% Molybdenum 2.5% Manganese 2.0% Silicon 1.0% Carbon 0.03% The balance is iron; The purity of the 316L stainless steel powder is ≥99.5%; When the metal powder raw material used in the preparation of the inner track structure hollow product is high-strength lightweight steel Fe-Mn-Al-C powder, the sintering temperature is controlled to be 1200-1270°C; In the specific implementation of the present application, only the high-strength lightweight steel Fe-Mn-Al-C powder with the following metal raw material composition and content is used as an example for description: The raw material components and contents of the high-strength light-weight steel Fe-Mn-Al-C powder are as follows: Manganese 32.0% Aluminum 10.0% Carbon 0.8% The balance is iron; The purity of the high-strength lightweight steel Fe-Mn-Al-C powder is ≥99.5%.

[0012] Preferably, the solution treatment is as follows: When the metal powder raw material used in the preparation of the inner track structure hollow product is 17-4PH stainless steel MIM powder, the solution treatment temperature is controlled to be 1030-1060°C and the time is 0.5-1.5h after sintering; When the metal powder raw material used for preparing the inner track structure hollow product is 316L stainless steel powder, the solution treatment temperature is controlled to be 950-1100°C and the time is 0.5-1.5h after sintering; When the metal powder raw material used in the preparation of the inner track structure hollow product is high-strength lightweight steel Fe-Mn-Al-C powder, the solution treatment temperature is controlled to be 950-1150°C and the time is 0.5-1.5h after sintering; The aging treatment is as follows: After the above solution treatment, the temperature is controlled at 400-550°C for aging treatment for 0.5-6h.

[0013] By adopting the above technical solution, the application of the core (solid lost core material) in the preparation of the inner track type structure hollow product has a relatively simple process and a wide range of applications. In addition, in the preparation of the inner track type structure hollow product, since the inner track type structure hollow product particles are injected, they contact the core injection blank after cooling and solidification, so that the surface of the inner track type structure hollow product is rapidly cooled, and the core injection blank is neither melted nor warped, so the integrity of the inner track type structure hollow product blank can be guaranteed, so that the final inner track type structure hollow product is quickly formed, and the inner surface roughness is low, so it can meet the requirements of the harsh injection process, and the solid lost core material of the present application can be used to form various complex inner track type structure hollow products.

[0014] Furthermore, the core (solid lost core material) is used in the preparation of the inner track type structure hollow product. During the process, when the core and the inner track type structure hollow product are subjected to one-step catalytic degreasing, the Al2O3 powder in the core can absorb the residual carbon of POM, and the Al2O3 powder after catalysis can be easily removed with an air gun, thus solving the technical defect of irremovable carbon residue after catalysis, thereby further ensuring the integrity of the injection blank of the inner track type structure hollow product during the catalytic process, and the shrinkage rate of the core injection blank after molding is small, thereby ensuring that the size and position deviation of the inner track type structure hollow product is small and can be controlled within ±0.5%.

[0015] Preferably, a plasticizer is added to the plastic-based binder for granulating the hollow product with the inner track structure in S1 at a ratio of 1-3% of the total mass of the plastic-based binder, and the plasticizer is vegetable oil.

[0016] Preferably, the vegetable oil is castor oil, but the present application is not limited to castor oil, and vegetable oils such as rapeseed oil, peanut oil and soybean oil are also suitable for the present application.

[0017] By adopting the above technical scheme, the plasticizer can increase the bonding strength between the metal powder raw material and the plastic-based adhesive in the injection blank of the inner track type structure hollow product, ensure the integrity of the injection blank of the inner track type structure hollow product, and reduce the problems of cracking in the injection blank of the inner track type structure hollow product.

[0018] Beneficial technical effects of this application A solid lost core material of the present application is obtained by simple injection molding using a certain proportion of POM and Al2O3 powder as raw materials, so it has the characteristics of low raw material cost and simple preparation process, and the obtained solid lost core material has high comprehensive performance and can withstand the impact force generated by high-pressure injection.

[0019] The solid lost core material of the present application has an operating temperature of 170-210° C., which can meet the injection process requirements of various thermoplastics at present, and is much higher than low melting point alloys.

[0020] When a solid lost core material of the present application is used in the preparation of an inner track type hollow product, the inner surface roughness of the inner track type hollow product finally obtained can be low, so it can meet the preparation of various complex inner track type hollow products. The pioneering research of the solid lost core material in the MIM industry can develop a huge new market for lost core injection molding in the MIM industry.

[0021] Furthermore, when a solid lost core material of the present application is used in the preparation of a hollow product with an inner track structure, since POM and Al2O3 powder are used to form the core together, when the core and the hollow product with an inner track structure are degreased by a one-step catalytic method, the Al2O3 powder in the lost core material can absorb the residual carbon of the POM, and the Al2O3 powder can be easily removed with an air gun after catalysis, thereby solving the technical defect of having irremovable carbon residue after catalysis, thereby further ensuring the integrity of the injection blank of the hollow product with an inner track structure during the catalytic process, the sintered blank is not prone to cracking in the subsequent sintering process, the inner surface of the hollow product with an inner track structure in contact with the core injection blank is not prone to peeling, and the shrinkage rate of the core injection blank after molding is small, thereby ensuring that the size and position deviation of the hollow product with an inner track structure is small and can be controlled within ±0.5%.

[0022] Furthermore, when a solid lost core material of the present application is used in the preparation of an inner track type hollow product, since the solid lost core material uses POM with low cost, and the solid lost core material can be used to form various complex inner track type hollow products, compared with traditional forming methods, it effectively reduces the product development cost and improves the qualification rate and production efficiency of the inner track type hollow products. DETAILED DESCRIPTION

[0023] The present application is further described in detail below in conjunction with various embodiments.

[0024] Except for the special raw materials listed below, all the raw materials used in the embodiments of the present application are commercially available: 17-4PH stainless steel MIM powder, calculated by mass percentage, the raw material components and contents used in its preparation are as follows: Chromium 17% Copper 4% Nickel 4% Niobium + Tantalum 0.30% Manganese 1.0% Silicon 1.0% Carbon 0.07% The balance is iron; The purity of the 17-4PH stainless steel powder is ≥99.5%; 316L stainless steel powder, calculated by mass percentage, the raw material components and contents used in its preparation are as follows: Chromium 17.0% Nickel 12.0% Molybdenum 2.5% Manganese 2.0% Silicon 1.0% Carbon 0.03% The balance is iron; The purity of the 316L stainless steel powder is ≥99.5%; The raw material components and contents of the high-strength light-weight steel Fe-Mn-Al-C powder are as follows: Manganese 32.0% Aluminum 10.0% Carbon 0.8% The balance is iron; The purity of the high-strength lightweight steel Fe-Mn-Al-C powder is ≥99.5%.

[0025] In each embodiment of the present application, the names, models and manufacturers of various equipment used are as follows: Kneading and granulating machine, model LGJ-400, manufactured by Nanjing Zhongbing Enso Technology Co., Ltd.; Horizontal injection molding machine, model NEX110IIIT-12E, manufactured by Nissei Plastic Industrial Co., Ltd. Vacuum debinding sintering furnace, model VM48 / 48 / 200, manufactured by Ningbo Hengpu Vacuum Technology Co., Ltd.

[0026] In each embodiment of the present application, the test method of each performance parameter and the name, model and manufacturer information of the equipment used for the test are as follows: 1. Dimensional accuracy test Test method: Use a three-coordinate measuring machine to test the core injection blank, compare the measured data with the designed standard data, and calculate the dimensional accuracy of the core injection blank. The specific calculation formula is as follows: Dimensional accuracy = absolute value of [(measured data - standard data) / standard data] × 100%; Test results: When the dimensional accuracy is ≤0.20%, it meets the requirements of dimensional accuracy of the core injection blank; 2. Density test Test method: The density of hollow products with inner track structure is tested using the method in GB / T 3850-2015 "Determination of density of dense sintered metal materials and cemented carbide"; Test results: When the metal powder raw material is 17-4PH stainless steel powder, the density range of the inner track structure hollow product is ≥7.6g / cm 3 ; When the metal powder raw material is 316L stainless steel powder, the density range of the hollow product with inner track structure is ≥7.8g / cm 3 ; When the metal powder raw material is high-strength lightweight steel Fe-Mn-Al-C powder, the density range of the inner track structure hollow product is ≥6.0g / cm 3 ; 3. Surface roughness test Test method: Use the stylus method to test the surface roughness of the inner surface of the hollow product with inner track structure; Test results: When the arithmetic average roughness (Ra) is between 0.05-3.50μm, it meets the surface roughness requirements of the inner surface of the hollow product with an inner track structure.

[0027] Example 1 A solid lost core material, the raw material composition and content used in its preparation are calculated by mass percentage as shown in the following table: content(%) Example 1 POM 50% <![CDATA[Al2O3 powder]]> 50% The method for applying the above-mentioned solid lost core material in the preparation of hollow products with inner track structure comprises the following specific steps: S1. Granulation of hollow products with inner track structure: The metal powder raw materials and plastic-based adhesive used for preparing the inner track type structure hollow product are sequentially poured into the kneading and granulating integrated machine for kneading, mixing and granulating, and the temperature is controlled at 190° C. for mixing for 1 hour to obtain the inner track type structure hollow product particles; The above-mentioned metal powder raw material and plastic-based binder are used in a mass ratio of 1:1. The above-mentioned metal powder raw material is 17-4PH stainless steel MIM powder; The above-mentioned plastic-based adhesive is a POM adhesive; S2. Granulation of core (solid lost core material): The POM and Al2O3 powders used to prepare the core are sequentially poured into a kneading and granulating machine for kneading, mixing and granulation, and the temperature is controlled at 190°C for mixing for 1 hour to obtain core particles; S3, Injection molding: (1) Inject the core particles obtained in S2 into a core mold through a horizontal injection machine. After pressure maintenance, cooling and solidification, open the core mold and take out the core injection blank; During the injection of the core particles, the injection temperature was controlled at 190°C and the injection speed was 60 cm 3 / s and injection pressure 90MPa; The above-mentioned holding pressure is 90MPa and the time is 6s; The above cooling and curing temperature is 100°C and the time is 10s; (2) placing the core injection blank into the corresponding mold of the hollow product with inner track structure to obtain a mold closing; (3) Injecting the inner track type structure hollow product particles obtained in S1 into the mold cavity of the mold, and after pressure maintenance, cooling and solidification, opening the mold of the inner track type structure hollow product, and taking out the inner track type structure hollow product injection blank with the core injection blank; During the injection process of the hollow product particles with the inner track structure, the injection temperature was controlled at 190°C and the injection speed was 60 cm 3 / s and injection pressure 90MPa; The above-mentioned holding pressure is 90MPa and the time is 6s; The above cooling and curing temperature is 100°C and the time is 10s; S4, catalytic degreasing: The inner track type structure hollow product injection blank with the core injection blank is placed in 98% by mass gaseous nitric acid for catalysis at a catalytic temperature of 135°C for 8 hours, and then the Al2O3 powder is blown away with air at a pressure of 0.3MPa to obtain the inner track type structure hollow product injection blank; S5, subjecting the obtained inner track type structure hollow product injection blank to pre-sintering, sintering, solution treatment and aging treatment in sequence to obtain an inner track type structure hollow product; The pre-sintering process is controlled at a temperature of 700° C. for 2 h to obtain a pre-sintered blank. In the sintering process, the obtained pre-sintered blank is sintered for 2 hours in a vacuum degreasing sintering furnace under the protection of nitrogen at a pressure of 0.05 MPa and a temperature of 1300° C. to obtain a sintered blank; The solution treatment process is to control the temperature at 1050° C. in a vacuum degreasing sintering furnace for 1.0 h. In the aging treatment process, the temperature is controlled at 500° C. in a vacuum degreasing sintering furnace for aging treatment for 3 hours.

[0028] Embodiment 2-4 A solid lost core material, which is different from Example 1 in that the composition and content of the raw materials used in its preparation are calculated by mass percentage as shown in the following table: content(%) Example 2 Example 3 Example 4 POM 33.3% 60% 66.7% <![CDATA[Al2O3 powder]]> 66.7% 40% 33.3% The specific steps of the method for applying the above-mentioned solid lost core material in the preparation of hollow products with inner track structure are the same as those in Example 1.

[0029] Comparative Example 1 A solid lost core material, which is different from Example 1 in that the composition and content of the raw materials used in its preparation are calculated by mass percentage as shown in the following table: content(%) Comparative Example 1 POM 100% <![CDATA[Al2O3 powder]]> 0 The specific steps of the method for applying the above-mentioned solid lost core material in the preparation of hollow products with inner track structure are the same as those in Example 1.

[0030] The dimensional accuracy of the core injection blanks obtained in the above Examples 1-4 and Comparative Example 1, the density and surface roughness of the hollow products with inner track structures were tested, and the test results are shown in the following table: Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Dimensional accuracy 0.08% 0.09% 0.14% 0.18% 0.22% density <![CDATA[7.7g / cm 3 ]]> <![CDATA[7.7g / cm 3 ]]> <![CDATA[7.7g / cm 3 ]]> <![CDATA[7.7g / cm 3 ]]> <![CDATA[7.6g / cm 3 ]]> Surface roughness (Ra) 0.62μm 0.75μm 0.68μm 0.89μm 3.58μm From the data analysis of the dimensional accuracy of the core injection blanks obtained in Examples 1-4 in the above table, the density and surface roughness of the hollow products with inner track structures, it can be seen that the core injection blanks obtained by mixing the solid lost core material with POM and Al2O3 powder have good dimensional accuracy, so the shrinkage rate of the hollow products with inner track structures obtained in the end is small; Furthermore, the inner surface roughness of the obtained hollow product with inner track structure is only 0.62 μm-0.89 μm, which is 75.1%-82.7% higher than the surface roughness of the hollow product with inner track structure obtained by using 100% POM in the solid lost core material of Comparative Example 1. This shows that when the solid lost core material of the present application is used for the preparation of hollow products with inner track structure, the shrinkage rate of the core after injection molding is small, and the inner surface roughness of the hollow product with inner track structure finally obtained is low, which can meet the preparation of various complex hollow products with inner track structure.

[0031] In particular, calculated by mass percentage, when POM is 50%-60% and Al2O3 powder is 40%-50%, the surface roughness of the inner track structure hollow product obtained by using 100% POM as the solid lost core material in Comparative Example 1 is increased by 81.0%-82.7%.

[0032] More particularly, in Example 1, when POM is 50% and Al2O3 powder is 50%, the surface roughness of the inner track structure hollow product obtained by using 100% POM as the solid lost core material in Comparative Example 1 is increased by 82.7%.

[0033] When the core injection blanks prepared in the above-mentioned Examples 1-4 and Comparative Example 1 were subjected to catalytic debinding and core loss, the core injection blanks in Examples 1 and 3 were more able to maintain their original shapes and required a little force to be pressed into powder; The core injection blank of Example 2 has a strong bonding force with the inner track structure hollow product injection blank, and needs to be pressed hard to be pressed into powder; The core injection blank of Example 4 forms a loosely structured Al2O3 powder, which can be collapsed into powder with a slight press; The solid lost core material of Comparative Example 1 uses a 100% POM core injection blank which disintegrates by itself during the catalytic degreasing process, leaving residual carbon that cannot be removed; The above results show that when the POM content in the solid lost core material is 50%-60% and the Al2O3 powder content is 40%-50%, especially when the POM content in the solid lost core material is 50% and the Al2O3 powder content is 50%, the integrity of the inner orbital structure hollow product blank during the catalytic process can be guaranteed, thereby solving the problems of cracks in the inner orbital structure hollow product injection blank caused by stress release during the lost core injection process, cracking of the inner orbital structure hollow product injection blank, and peeling of the inner surface of the inner orbital structure hollow product in contact with the core injection blank.

[0034] Example 5 A solid lost core material, wherein the raw material composition and content used in its preparation are the same as the raw material composition and content used in the preparation of the solid lost core material in Example 1, calculated by mass percentage.

[0035] The above-mentioned method for applying a solid lost core material in the preparation of a hollow product with an inner track structure is different from the method for applying a solid lost core material in the preparation of a hollow product with an inner track structure in Example 1 in that: In the granulation of the track-type structure hollow product in step S1, the amount of the metal powder raw material and the plastic-based binder is calculated by mass ratio, and the metal powder raw material: plastic-based binder is 2.5:1.

[0036] Example 6 A solid lost core material, wherein the raw material composition and content used in its preparation are the same as the raw material composition and content used in the preparation of the solid lost core material in Example 1, calculated by mass percentage.

[0037] The above-mentioned method for applying a solid lost core material in the preparation of a hollow product with an inner track structure is different from the method for applying a solid lost core material in the preparation of a hollow product with an inner track structure in Example 1 in that: In the granulation of the track-type structure hollow product in step S1, the amount of the metal powder raw material and the plastic-based binder is calculated by mass ratio, and the metal powder raw material: plastic-based binder is 1.5:1.

[0038] The density and surface roughness of the hollow products with inner track structures obtained in the above Examples 5-6 were tested and compared with the test results of Example 1. The test results are shown in the following table: Example 1 Example 5 Example 6 density <![CDATA[7.7g / cm 3 ]]> <![CDATA[7.9g / cm 3 ]]> <![CDATA[7.8g / cm 3 ]]> Surface roughness (Ra) 0.62μm 0.65μm 0.69μm From the analysis of the data in the above table, it can be seen that in the granulation process of the inner track type structure hollow product, the amount of metal powder raw material and plastic-based binder, calculated by mass ratio, when the metal powder raw material: plastic-based binder is 1-2.5:1, the density and surface roughness of the inner track type structure hollow product meet the design requirements.

[0039] Example 7 A solid lost core material, wherein the raw material composition and content used in its preparation are the same as the raw material composition and content used in the solid lost core material of Example 1, calculated by mass percentage.

[0040] The above-mentioned method for applying a solid lost core material in the preparation of a hollow product with an inner track structure is different from that in Example 1 in that: In the granulation step of the track-type structure hollow product in step S1, a plasticizer is added to the plastic-based binder in a proportion of 2% of the total mass of the plastic-based binder, and the plasticizer is castor oil.

[0041] Example 8 A solid lost core material, wherein the raw material composition and content used in its preparation are the same as the raw material composition and content used in the solid lost core material of Example 1, calculated by mass percentage.

[0042] The above-mentioned method for applying a solid lost core material in the preparation of a hollow product with an inner track structure is different from that in Example 1 in that: In the granulation step of the track-type structure hollow product in step S1, a plasticizer is added to the plastic-based binder in a proportion of 1% of the total mass of the plastic-based binder, and the plasticizer is castor oil.

[0043] Example 9 A solid lost core material, wherein the raw material composition and content used in its preparation are the same as the raw material composition and content used in the solid lost core material of Example 1, calculated by mass percentage.

[0044] The above-mentioned method for applying a solid lost core material in the preparation of a hollow product with an inner track structure is different from that in Example 1 in that: In the granulation step of the track-type structure hollow product in step S1, a plasticizer is added to the plastic-based binder in a proportion of 3% of the total mass of the plastic-based binder, and the plasticizer is castor oil.

[0045] The density and surface roughness of the hollow products with inner track structures obtained in the above Examples 7-9 were tested and compared with the test results of Example 1. The test results are shown in the following table: Example 1 Example 7 Example 8 Example 9 density <![CDATA[7.7g / cm 3 ]]> <![CDATA[7.8g / cm 3 ]]> <![CDATA[7.8g / cm 3 ]]> <![CDATA[7.7g / cm 3 ]]> Surface roughness (Ra) 0.62μm 0.59μm 0.60μm 0.58μm Through the analysis of the data in the above table, it can be seen that in the granulation process of the inner orbital structure hollow product, a plasticizer is added to the plastic-based binder at a ratio of 1-3% of the total mass of the plastic-based binder. The density and surface roughness of the inner orbital structure hollow product meet the design requirements. In the actual preparation process, the plasticizer increases the bonding force between the metal powder raw material and the plastic-based adhesive in the injection blank of the inner orbital structure hollow product. Therefore, in the subsequent catalytic process, the integrity of the injection blank of the inner orbital structure hollow product is guaranteed, thereby reducing the cracking of the injection blank of the inner orbital structure hollow product.

[0046] Example 10 A solid lost core material, wherein the raw material composition and content used in its preparation are the same as the raw material composition and content used in the solid lost core material of Example 1, calculated by mass percentage.

[0047] The above-mentioned method for applying a solid lost core material in the preparation of a hollow product with an inner track structure is different from the method for applying a solid lost core material in the preparation of a hollow product with an inner track structure in Example 1 in that: In step S1, in the granulation of the hollow product with inner track structure, the raw material used for preparing the hollow product with inner track structure is 316L stainless steel powder; In step S5, the obtained inner track type structure hollow product injection blank is subjected to pre-sintering, sintering, solution treatment and aging treatment in sequence to obtain the inner track type structure hollow product; The pre-sintering process is controlled at a temperature of 700° C. for 2 h to obtain a pre-sintered blank. In the sintering process, the obtained pre-sintered blank is sintered for 2 hours in a vacuum degreasing sintering furnace under the protection of nitrogen at a pressure of 0.05 MPa and a temperature of 1400° C. to obtain a sintered blank; The solution treatment process is to control the temperature at 1000° C. in a vacuum degreasing sintering furnace for solution treatment for 1.0 h; In the aging treatment process, the temperature is controlled at 500° C. in a vacuum degreasing sintering furnace for aging treatment for 3 hours.

[0048] Embodiment 11 A solid lost core material, wherein the raw material composition and content used in its preparation are the same as the raw material composition and content used in the solid lost core material of Example 1, calculated by mass percentage.

[0049] The above-mentioned method for applying a solid lost core material in the preparation of a hollow product with an inner track structure is different from the method for applying a solid lost core material in the preparation of a hollow product with an inner track structure in Example 1 in that: In step S1, in the granulation of the inner track type structure hollow product, the raw material used for preparing the inner track type structure hollow product is high strength light steel Fe-Mn-Al-C powder; In step S5, the obtained inner track type structure hollow product injection blank is subjected to pre-sintering, sintering, solution treatment and aging treatment in sequence to obtain the inner track type structure hollow product; The pre-sintering process is controlled at a temperature of 700° C. for 2 h to obtain a pre-sintered blank. In the sintering process, the obtained pre-sintered blank is sintered for 2 hours in a vacuum degreasing sintering furnace at a controlled pressure of 0.05 MPa and a temperature of 1250° C. under the protection of nitrogen to obtain a sintered blank; The solution treatment process is to control the temperature at 1000° C. in a vacuum degreasing sintering furnace for solution treatment for 1.0 h; In the aging treatment process, the temperature is controlled at 500° C. in a vacuum degreasing sintering furnace for aging treatment for 3 hours.

[0050] The density and surface roughness of the hollow products with inner track structures obtained in the above Examples 9-10 were tested, and the test results are shown in the following table: Example 10 Embodiment 11 density <![CDATA[7.8g / cm 3 ]]> <![CDATA[6.2g / cm 3 ]]> Surface roughness (Ra) 0.63μm 0.61μm Through the analysis of the data in the above table, it can be seen that when the raw materials used for the preparation of the inner track type structure hollow product are 316L stainless steel powder or high-strength lightweight steel Fe-Mn-Al-C powder, the density and surface roughness of the obtained inner track type structure hollow product meet the design requirements.

[0051] Example 12 A solid lost core material, wherein the raw material composition and content used in its preparation are the same as the raw material composition and content used in the solid lost core material of Example 1, calculated by mass percentage.

[0052] The above-mentioned method for applying a solid lost core material in the preparation of a hollow product with an inner track structure is different from the method for applying a solid lost core material in the preparation of a hollow product with an inner track structure in Example 1 in that: In step S4, catalytic degreasing is performed using oxalic acid.

[0053] The density and surface roughness of the hollow product with inner track structure obtained in Example 12 above were tested, and the test results are shown in the following table: Example 12 density <![CDATA[7.7g / cm 3 ]]> Surface roughness (Ra) 0.63μm Through the analysis of the data in the above table, it can be seen that the density and surface roughness of the hollow product with inner track structure obtained by catalytic degreasing with oxalic acid also meet the design requirements.

[0054] Example 13 A solid lost core material, wherein the raw material composition and content used in its preparation are the same as the raw material composition and content used in the solid lost core material of Example 1, calculated by mass percentage.

[0055] The method for applying the above-mentioned solid lost core material in the preparation of hollow products with inner track structure specifically comprises the following steps: S1. Granulation of hollow products with inner track structure: The metal powder raw materials and plastic-based adhesive used for preparing the inner track type structure hollow product are sequentially poured into the kneading and granulating integrated machine for kneading, mixing and granulating, and the temperature is controlled at 185° C. for mixing for 1.5 hours to obtain the inner track type structure hollow product particles; The above-mentioned metal powder raw material and plastic-based binder are used in a mass ratio of 1:1. The above-mentioned metal powder raw material is 17-4PH stainless steel MIM powder; The above-mentioned plastic-based adhesive is a POM adhesive; S2. Granulation of core (solid lost core material): The POM and Al2O3 powders used to prepare the core were sequentially poured into a kneading and granulating machine for kneading, mixing and granulation, and the temperature was controlled at 185°C for mixing for 1.5 hours to obtain core particles; The particle size of the Al2O3 powder is 0.5-20 μm; S3, Injection molding: (1) Inject the core particles obtained in S2 into a core mold through a horizontal injection machine. After pressure maintenance, cooling and solidification, open the core mold and take out the core injection blank; During the injection of the core particles, the injection temperature was controlled at 170°C and the injection speed was controlled at 35 cm 3 / s and injection pressure 60MPa; The above-mentioned holding pressure is 60MPa and the time is 10s; The above cooling and curing temperature is 120°C and the time is 15s; (2) placing the core injection blank into the corresponding mold of the hollow product with inner track structure to obtain a mold closing; (3) Injecting the inner track type structure hollow product particles obtained in S1 into the mold cavity of the mold, and after pressure maintenance, cooling and solidification, opening the mold of the inner track type structure hollow product, and taking out the inner track type structure hollow product injection blank with the core injection blank; During the injection process of the above-mentioned inner track structure hollow product particles, the injection temperature was controlled at 210°C and the injection speed was 85 cm 3 / s and injection pressure 120MPa; The above-mentioned holding pressure is 120MPa and the time is 2s; The above cooling and curing temperature is 90°C and the time is 1 second; S4, catalytic degreasing: The inner track type structure hollow product injection blank with the core injection blank is placed in 98% by mass gaseous nitric acid for catalysis at a catalytic temperature of 100°C for a catalytic time of 8 hours, and then the Al2O3 powder is blown away with air at a pressure of 0.1MPa to obtain the inner track type structure hollow product injection blank; S5, subjecting the obtained inner track type structure hollow product injection blank to pre-sintering, sintering, solution treatment and aging treatment in sequence to obtain an inner track type structure hollow product; The pre-sintering process is controlled at a temperature of 500° C. for 4 hours to obtain a pre-sintered blank. In the sintering process, the obtained pre-sintered blank is sintered for 1 hour in a vacuum degreasing sintering furnace under the protection of nitrogen at a pressure of 0.01 MPa and a temperature of 1270° C. to obtain a sintered blank; The solution treatment process is to control the temperature at 1050° C. in a vacuum degreasing sintering furnace for 0.5 h. In the aging treatment process, the temperature is controlled at 550° C. in a vacuum degreasing sintering furnace for 0.5 h.

[0056] Embodiment 14 A solid lost core material, wherein the raw material composition and content used in its preparation are the same as the raw material composition and content used in the solid lost core material of Example 1, calculated by mass percentage.

[0057] The method for applying the above-mentioned solid lost core material in the preparation of hollow products with inner track structure specifically comprises the following steps: S1. Granulation of hollow products with inner track structure: The metal powder raw materials and plastic-based adhesive used for preparing the inner track type structure hollow product are sequentially poured into the kneading and granulating integrated machine for kneading, mixing and granulating, and the temperature is controlled at 195° C. for mixing for 0.5 h to obtain the inner track type structure hollow product particles; The above-mentioned metal powder raw material and plastic-based binder are used in a mass ratio of 1:1. The above-mentioned metal powder raw material is 17-4PH stainless steel MIM powder; The above-mentioned plastic-based adhesive is a POM adhesive; S2. Granulation of core (solid lost core material): The POM and Al2O3 powders used to prepare the core were sequentially poured into a kneading and granulating machine for kneading, mixing and granulation, and the temperature was controlled at 195°C for mixing for 0.5h to obtain core particles; The particle size of the Al2O3 powder is 0.5-20 μm; S3, Injection molding: (1) Inject the core particles obtained in S2 into a core mold through a horizontal injection machine. After pressure maintenance, cooling and solidification, open the core mold and take out the core injection blank; During the injection of the core particles, the injection temperature was controlled at 210°C and the injection speed was 85 cm 3 / s and injection pressure 120MPa; The above-mentioned holding pressure is 120MPa and the time is 2s; The above cooling and curing temperature is 90°C and the time is 1 second; (2) placing the core injection blank into the corresponding mold of the hollow product with inner track structure to obtain a mold closing; (3) Injecting the inner track type structure hollow product particles obtained in S1 into the mold cavity of the mold, and after pressure maintenance, cooling and solidification, opening the mold of the inner track type structure hollow product, and taking out the inner track type structure hollow product injection blank with the core injection blank; During the injection process of the hollow product particles with the inner track structure, the injection temperature was controlled at 170°C and the injection speed was controlled at 35 cm 3 / s and injection pressure 60MPa; The above-mentioned holding pressure is 60MPa and the time is 10s; The above cooling and curing temperature is 120°C and the time is 15s; S4, catalytic degreasing: The inner track type structure hollow product injection blank with the core injection blank is placed in 98% by mass gaseous nitric acid for catalysis at a catalytic temperature of 130°C for a catalytic time of 8 hours, and then the Al2O3 powder is blown away with air at a pressure of 0.6MPa to obtain the inner track type structure hollow product injection blank; S5, subjecting the obtained inner track type structure hollow product injection blank to pre-sintering, sintering, solution treatment and aging treatment in sequence to obtain an inner track type structure hollow product; The pre-sintering process is controlled at a temperature of 900° C. for 1 hour to obtain a pre-sintered blank. In the sintering process, the obtained pre-sintered blank is sintered for 3 hours in a vacuum degreasing sintering furnace under the protection of argon gas at a controlled pressure of 0.08 MPa and a temperature of 1050° C. to obtain a sintered blank; The solution treatment process is to control the temperature at 950°C in a vacuum degreasing sintering furnace for 1.5 hours; In the aging treatment process, the temperature is controlled at 400° C. in a vacuum degreasing sintering furnace for aging treatment for 6.0 hours.

[0058] The dimensional accuracy of the core injection blanks obtained in the above Examples 13-14, the density and surface roughness of the hollow products with inner track structures were tested, and the test results are shown in the following table: Example 13 Embodiment 14 Dimensional accuracy 0.10% 0.09% density <![CDATA[7.7g / cm 3 ]]> <![CDATA[7.7g / cm 3 ]]> Surface roughness (Ra) 0.63μm 0.62μm By analyzing the data in the above table, it can be seen that the dimensional accuracy of the core injection blank of a solid lost core material, the density and surface roughness of the hollow product with an inner track structure described in Examples 13-14 all meet the design requirements.

[0059] The specific embodiments of the present application are merely explanations of the present application and are not limitations of the present application. After reading this specification, those skilled in the art may make modifications to the embodiments without any creative contribution as needed. However, as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A solid lost core material, characterized in that: Calculated by mass percentage, the composition and content of the raw materials used in its preparation are as follows: POM 66.7%-33.3% Al2O3 powder 33.3%-66.7%.

2. A solid lost core material according to claim 1, characterized in that: The raw material composition and content of the solid lost core material are calculated by mass percentage as follows: POM 50%-60% Al2O3 powder 40%-50%.

3. A solid lost core material as claimed in claim 2, characterized in that: The raw material composition and content of the solid lost core material are calculated by mass percentage as follows: POM 50% Al2O3 powder 50%.

4. A method for using a solid lost core material as claimed in any one of claims 1 to 3 in the preparation of a hollow product with an inner track structure, characterized in that: The specific steps are as follows: S1. Granulation of hollow products with inner track structure: The metal powder raw material and the plastic-based binder used for preparing the inner track type structure hollow product are kneaded, mixed and granulated in sequence, and the temperature is controlled at 185-195° C. for mixing for 0.5-1.5 hours to obtain the inner track type structure hollow product particles; The amount of the above-mentioned metal powder raw material and plastic-based binder is calculated by mass ratio, and the metal powder raw material: plastic-based binder is 1-2.5:1; The metal powder raw material is 17-4PH stainless steel MIM powder, 316L stainless steel powder or high-strength lightweight steel Fe-Mn-Al-C powder, and the particle size of the metal powder raw material is 0.5-20 μm; The above-mentioned plastic-based adhesive is a POM adhesive; S2. Granulation of core: The solid lost core material used for preparing the core is kneaded, mixed and granulated, and the temperature is controlled to be 185-195° C. and mixed for 0.5-1.5 hours to obtain core particles; S3, Injection molding: (1) Inject the core particles obtained in S2 into the core mold. After pressure maintenance, cooling and solidification, open the core mold and take out the core injection blank. During the injection of the core particles, the injection temperature is controlled at 170-210°C and the injection speed is controlled at 35-85 cm 3 / s and injection pressure 60-120MPa; The above-mentioned pressure holding is 60-120MPa and the time is 2-10s; The temperature of the cooling and curing is 90-120°C and the time is 1-15s; (2) placing the core injection blank into the corresponding mold of the hollow product with inner track structure to obtain a mold closing; (3) Injecting the inner track type structure hollow product particles obtained in S1 into the mold cavity of the mold, and after pressure maintenance, cooling and solidification, opening the mold of the inner track type structure hollow product, and taking out the inner track type structure hollow product injection blank with the core injection blank; During the injection process of the above-mentioned inner track structure hollow product particles, the injection temperature is controlled at 170-210°C and the injection speed is controlled at 35-85cm 3 / s and injection pressure 60-120MPa; The above-mentioned pressure holding is 60-120MPa and the time is 2-10s; The above cooling and curing temperature is 90-120°C and the time is 1-15s; S4, catalytic degreasing: The inner track structure hollow product injection blank with the core injection blank is subjected to acid stripping, and POM is catalytically removed by using 98% by mass gaseous nitric acid or oxalic acid, and then Al2O3 powder is blown away by air with a pressure of 0.1-0.6MPa to obtain the inner track structure hollow product injection blank; S5. Pre-sintering and sintering the above-obtained hollow product injection blank, or pre-sintering, sintering, solution treatment and aging treatment in sequence, to obtain a hollow product with an inner track structure.

5. The method for applying a solid lost core material in the preparation of a hollow product with an inner track structure as claimed in claim 4, characterized in that: In S5, the pre-sintering process is performed by controlling the temperature to be 500-900° C. for 1-4 hours to obtain a pre-sintered blank.

6. The method for applying a solid lost core material in the preparation of a hollow product with an inner track structure as claimed in claim 4, characterized in that: In S5, the sintering process is to sinter the pre-sintered blank obtained by pre-sintering for 1-3 hours under vacuum conditions and under the protection of hydrogen or an inert gas to obtain a sintered blank, wherein the inert gas is argon or nitrogen; When the metal powder raw material used for preparing the inner track structure hollow product is 17-4PH stainless steel MIM powder, the sintering temperature is controlled to be 1250-1350°C; When the metal powder raw material used in the preparation of the inner track structure hollow product is 316L stainless steel powder, the sintering temperature is controlled to be 1320-1420°C; When the metal powder raw material used for preparing the inner track type structure hollow product is high-strength lightweight steel Fe-Mn-Al-C powder, the sintering temperature is controlled to be 1200-1270°C.

7. The method for applying a solid lost core material in the preparation of a hollow product with an inner track structure as claimed in claim 4, characterized in that: In S5, the solution treatment: When the metal powder raw material used in the preparation of the inner track structure hollow product is 17-4PH stainless steel MIM powder, the solution treatment temperature is controlled to be 1030-1060°C and the time is 0.5-1.5h after sintering; When the metal powder raw material used for preparing the inner track structure hollow product is 316L stainless steel powder, the solution treatment temperature is controlled to be 950-1100°C and the time is 0.5-1.5h after sintering; When the metal powder raw material used in the preparation of the inner track structure hollow product is high-strength lightweight steel Fe-Mn-Al-C powder, the solution treatment temperature is controlled to be 950-1150°C and the time is 0.5-1.5h after sintering; The aging treatment is as follows: the temperature is controlled at 400-550°C for 0.5-6h.

8. The method for using a solid lost core material in the preparation of a hollow product with an inner track structure as claimed in claim 4, characterized in that: In the plastic-based binder for granulating the hollow product of the track-type structure in S1, a plasticizer is added in a proportion of 1-3% of the total mass of the plastic-based binder, and the plasticizer is vegetable oil.

9. The method for using a solid lost core material in the preparation of a hollow product with an inner track structure as claimed in claim 8, characterized in that: The vegetable oil is rapeseed oil, peanut oil, castor oil or soybean oil.