CN110756808B - Powder increment sintering forming method for complex closed hollow thin-wall part - Google Patents
Powder increment sintering forming method for complex closed hollow thin-wall part Download PDFInfo
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- 238000000280 densification Methods 0.000 claims description 6
- 238000007731 hot pressing Methods 0.000 claims description 6
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
- B22F3/12—Both compacting and sintering
- B22F3/14—Both compacting and sintering simultaneously
- B22F3/15—Hot isostatic pressing
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
- B22F3/10—Sintering only
- B22F3/105—Sintering only by using electric current other than for infrared radiant energy, laser radiation or plasma ; by ultrasonic bonding
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
- B22F3/12—Both compacting and sintering
- B22F3/14—Both compacting and sintering simultaneously
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F5/00—Manufacture of workpieces or articles from metallic powder characterised by the special shape of the product
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B33—ADDITIVE MANUFACTURING TECHNOLOGY
- B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
- B33Y10/00—Processes of additive manufacturing
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- Powder Metallurgy (AREA)
Abstract
The invention discloses a powder increment sintering forming method of a complex closed hollow thin-wall part. It mainly comprises the following steps: (1) sintering the powder raw material for the 1 st time under a certain condition to obtain a prefabricated blank with a certain shape and density; (2) according to the shape, size and structural characteristics of an actual component, sintering the powder raw materials from 2 to nth times (n is more than or equal to 2) in a step-by-step and partition mode, and integrally and compactly connecting the powder raw materials with a prefabricated blank obtained by sintering from the (n-1) th time; (3) the final complex closed hollow thin-wall part is obtained through increment accumulation and sintering compact connection of the powder raw materials, has no welding line and high safety and reliability. The method has the advantages of improving the compactness and microstructure uniformity of the member and the overall mechanical property, and breaks through the technical bottlenecks of difficult forming and structural property control of the complex closed hollow thin-wall integral member made of the material.
Description
Technical Field
The invention relates to the technical field of powder metallurgy forming, in particular to a powder increment sintering forming method of a complex closed hollow thin-walled part.
Background
In the industrial fields of national defense equipment and the like, the application of the complex-shaped integral thin-wall component is very wide, for example: closed section hollow thin wall type components (high speed aircraft inlet duct, spray pipe, cladding tube, etc.), etc. Due to the requirements of service conditions, such components often need to be made of high temperature resistant materials which are difficult to deform.
The complex closed hollow thin-wall part made of the material difficult to deform is formed by the conventional process, and the process has the disadvantages of complex steps, high cost, long period and poor component performance. For example: TiAl alloy and other materials have complex components and are difficult to smelt and fill; NiAl alloy and other materials have large solidification latent heat, and the liquid-solid phase change preparation forming is adopted, so that thermal cracks are easy to generate; the liquid forming member of a material such as high-speed tool steel has a coarse structure, and is likely to suffer from porosity and composition segregation, resulting in poor performance. In addition, the plastic forming temperature of materials such as high-temperature alloy, hard alloy, ceramic and the like is ultrahigh, and the requirements on forming equipment and conditions are severe or plastic forming cannot be performed. Particularly, the forming and processing difficulty of complex closed hollow thin-wall parts with high precision and high performance requirements is particularly prominent, and the complex closed hollow thin-wall parts become one of bottleneck problems restricting the development of manufacturing technology of important equipment high-performance components in the fields of national defense and the like in China.
In recent years, forming a member of a material difficult to deform by a powder metallurgy process route has been a hot point of research. The process advantages of powder metallurgy mainly include: the method has the advantages of relatively simple process steps, high efficiency and material utilization rate, low cost, fine microstructure of the formed member, uniform components and relatively high performance. However, during powder sintering forming, the friction force between the powder raw material and the die material can cause uneven distribution of microscopic sintering stress field, which in turn causes uneven densification degree and microstructure of the sintered material, and influences the service performance of the material. Taking thin-walled hollow pipe members as an example, the density and microstructure of the formed blank are different due to the stress distribution gradient in the loading direction. The problems of uneven density, uneven microstructure and mechanical property of the member are particularly prominent for the integral thin-walled member with a complex shape.
Therefore, a new forming process of a complex closed hollow thin-wall part made of a difficult-to-deform material is urgently needed to be developed so as to meet the urgent requirements of the development of new-generation high-reliability equipment in China on an integral thin-wall component with high performance, high precision and a complex shape.
Disclosure of Invention
The invention aims to provide a powder increment sintering forming method of a complex closed hollow thin-walled part, which aims to solve the problems in the prior art and can obtain a difficult-to-deform material thin-walled component with uniform high density, no welding seam, uniform microstructure and excellent mechanical property.
In order to achieve the purpose, the invention provides the following scheme: the invention provides a powder increment sintering forming method of a complex closed hollow thin-walled part, which is characterized in that increment accumulation forming is realized by integrating step-by-step partition sintering-densification-connection of powder raw materials, and finally an integral thin-walled component with a complex shape is obtained, and the method specifically comprises the following steps:
1) placing the powder raw material into a die, applying sintering pressure on a pressure head, and performing the 1 st sintering to obtain a prefabricated blank;
2) adding powder raw materials to corresponding parts of the prefabricated blank in a step-by-step and partition mode according to the shape, size and structural characteristics of an actual component, applying sintering pressure on a pressure head, and performing sintering for the 2 nd time to obtain the prefabricated blank;
3) according to the shape, size and structural characteristics of the actual component, the operation in the step 2) is further circulated on the prefabricated blank obtained by the (n-1) th sintering, and the nth sintering is carried out, wherein n is more than or equal to 2;
4) and (4) taking the finally obtained integral thin-walled part out of the mold.
Preferably, the relative density of the preform or member obtained in the (n-1) th sintering is 90.0-99.9%.
Preferably, the powder raw materials used in the 2 nd to nth sintering may be different from those used in the n-1 st sintering.
Preferably, the thin member is a circular hollow thin member with a uniform cross section, a rectangular hollow thin member with a uniform cross section, or a hollow thin member with a special-shaped uniform cross section.
Preferably, the sintering method is hot-pressing sintering, electric current sintering, hot isostatic pressing sintering or liquid phase sintering.
Preferably, the sintering environment for sintering and shaping is vacuum, air or inert atmosphere.
Preferably, the inactive atmosphere is selected from at least one of a nitrogen atmosphere, a helium atmosphere, a neon atmosphere, an argon atmosphere, a krypton atmosphere, and a xenon atmosphere.
Compared with the prior art, the invention has the following technical effects:
the powder increment sintering forming method of the complex closed hollow thin-wall part breaks through the technical bottleneck that the complex-shaped integral thin-wall component of the material is difficult to deform and process. Compared with the traditional powder sintering forming method (figure 2), the method can greatly weaken the influence of the friction force on the tissue performance in the forming process of the integral thin-wall member, enables the microstructure to be more uniform, and improves the density and the performance of the member. In addition, the formed thin-wall component has no welding seam and high safety and reliability under service conditions.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.
FIG. 1 shows a powder incremental sintering forming route (taking a thin-wall hollow pipe member as an example) proposed by the present invention.
FIG. 2 is a schematic diagram of a conventional powder sintering process and densification (taking a thin-walled hollow tube member as an example).
FIG. 3 shows the simulation result of two-step unidirectional loading incremental sintering of a hollow cylindrical component with an outer diameter of 60mm, an inner diameter of 40mm and a height of 60mm according to the present invention: (a) and (b) the 1 st sintering (cylinder height 30 mm); (c) and (d) 2 nd sintering (cylinder height 30mm), wherein the cylinder blank obtained by the 1 st sintering is set as a compact material in 2 nd sintering simulation. Wherein (a), (c) are equivalent stress distributions; (b) and (d) is a pore volume fraction distribution.
FIG. 4 shows the simulation result of one-step unidirectional loading sintering of a hollow cylindrical member with an external diameter of 60mm, an internal diameter of 40mm and a height of 60mm for comparison: (a) is the equivalent stress distribution, and (b) is the pore volume fraction distribution.
In the figure: 1, molding; 2 pressure head.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention aims to provide a powder increment sintering forming method of a complex closed hollow thin-walled part, which aims to solve the problems in the prior art and can obtain a difficult-to-deform material thin-walled component with uniform high density, no welding seam, uniform microstructure and excellent mechanical property.
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in further detail below.
As shown in fig. 1-4, the invention provides a powder incremental sintering forming method for a complex closed hollow thin-walled part made of a difficult-to-deform material, which comprises the following steps:
(1) taking a thin-walled hollow tube member as an example, a powder raw material a having a predetermined composition is placed in a die 1 under a predetermined condition (temperature, pressure, time, etc.), and a sintering pressure P is applied to a ram 2 to perform the first sintering, thereby obtaining a thin-walled hollow tube blank B having a predetermined density (see fig. 1(a) to (B)).
(2) Taking thin-wall hollow pipe members as an example, according to the shape, size and structural characteristics of a pipe fitting, adding a powder raw material A to the upper end and the lower end of a thin-wall hollow pipe blank B with certain compactness step by step and in a partition mode, applying sintering pressure P on a pressure head 2, sintering for the 2 nd to the nth time (n is more than or equal to 2), and integrally and compactly connecting the powder raw material A with the pipe blank obtained by the n-1 st sintering. The schematic diagrams 1(c) - (d) show that powder raw materials A are respectively added to the upper end and the lower end of the 1 st sintered pipe blank B, and the dense connection of three parts of pipe blanks is realized while powder is densified.
(3) Taking thin-wall hollow pipe type components as an example, the final long-size integral thin-wall pipe compact component C is obtained through incremental accumulation and sintering compact connection of powder raw materials. The influence of the friction force on the tissue performance of the thin-wall hollow pipe type component in the height direction is greatly weakened, the density of the component is improved, and the tissue performance is more uniform.
The component materials in the steps (1) to (3) are special steel, metal matrix composite materials, intermetallic compounds, titanium alloy, high-temperature alloy, hard alloy and ceramic materials; the thin-wall component comprises a round uniform-section hollow thin-wall component, a rectangular uniform-section hollow thin-wall component and a special-shaped uniform-section hollow thin-wall component, and the section of the closed section is round, rectangular or special-shaped.
The preparation method of the powder raw material comprises an atomization solidification method, a mechanical alloying method, a reduction method, an electrolysis method, a dehydrogenation method and a reaction method; the sintering forming method comprises hot-pressing sintering, current sintering, hot isostatic pressing and liquid phase sintering, wherein the sintering environment for sintering forming is vacuum, air or an inert atmosphere, and the inert atmosphere is preferably at least one selected from nitrogen atmosphere, helium atmosphere, neon atmosphere, argon atmosphere, krypton atmosphere and xenon atmosphere.
The relative density of the preformed blank or the component with certain shape and density obtained by the n-1 th sintering (n is more than or equal to 2) in the steps (1) to (3) is 90.0 to 99.9 percent.
The conventional powder sintering forming method shown in fig. 2 is as follows: (1) in the case of a thin-walled hollow tube member, a powder material a having a predetermined composition is placed in a die 1 under predetermined conditions (temperature, pressure, time, etc.), and a sintering pressure P is applied to a ram 2 to perform sintering (see fig. 2 (a)). (2) As the sintering proceeds, the powder near the position of the upper and lower indenters 2 first becomes a dense region C, while the powder relatively far from the position of the upper and lower indenters 2 gradually becomes a denser region B, but the powder at the middle position in the height direction (where the stroke of the upper and lower indenters is maximum) remains in an original powder state a (as shown in fig. 2 (B)). (3) At the end of sintering, the powder near the upper and lower pressing heads 2 has become a dense region C, but at the maximum stroke of the upper and lower pressing heads, the powder state is still a relatively dense state B due to the influence of friction, and complete densification cannot be achieved.
Compared with the traditional powder sintering forming method (figure 2), the method can greatly weaken the influence of the friction force on the tissue performance in the forming process of the integral thin-wall member, enables the microstructure to be more uniform, and improves the density and the performance of the member. In addition, the formed thin-wall component has no welding seam and high safety and reliability under service conditions.
Example one
And (3) simulating two-step unidirectional loading incremental sintering of the hollow cylindrical member.
The incremental sintering method simulation of the present embodiment includes the following steps:
(1) the selected raw material is M42 high-speed steel, the density is 8.25g/cm3, the elastic modulus is set to be 188000MPa, the Young modulus is selected to be 0.315, and the material is selected to be isotropic. The cell type was chosen explicit, the blank cell size was chosen to be 3.5, the die was chosen to be 4.5, and the sintered part cell was chosen to be 4. And in the calculation step, kinetic display calculation is selected, the step length is 1s, and the powder does not deform any more after the powder densification process is finished. The friction type is defined as a penalty function type, the friction coefficient between the die and the billet is defined as 0.3, and the contact surfaces include all the contact surfaces of the billet and the die. The loading mode adopts pressure loading, and the contact surface of the upper die and the blank is selected as a loading surface (unidirectional loading).
(2) The simulated sintering method is hot-pressing sintering under the vacuum condition, the sintering temperature is 970 ℃, the sintering time is 10 minutes, and the sintering loading surface pressure is 50 MPa.
(3) The outer diameter of the 1 st sintering forming simulation cylinder blank is 60mm, the inner diameter is 40mm, and the height is 30 mm. Fig. 3(a) is the 1 st sintering equivalent stress distribution, and fig. 3(b) is the 1 st sintering pore volume fraction distribution. And during the 2 nd sintering simulation, setting the cylinder blank obtained by the 1 st sintering as a compact material, wherein the outer diameter of the simulated cylinder blank is 60mm, the inner diameter is 40mm, and the height is 30 mm. Fig. 3(c) is the 2 nd sintering equivalent stress distribution, and fig. 3(d) is the 2 nd sintering pore volume fraction distribution.
(4) As can be seen from FIG. 3, when two-step unidirectional loading incremental sintering is performed, the equivalent stress distribution of the two-part cylindrical blank along the loading direction is relatively uniform, and the influence of the friction force is relatively weak. In addition, the density distribution of the formed member along the loading direction is relatively uniform, and the difference of the pore volume fractions of the upper end and the lower end of the member is small.
For comparison with inventive example 1, a simulation was performed on a one-step unidirectional loading sintering method of a conventional hollow cylindrical member. The comparative simulation comprises the following steps: (1) the selected raw material is M42 high-speed steel, the density is 8.25g/cm3, the elastic modulus is set to be 188000MPa, the Young modulus is selected to be 0.315, and the material is selected to be isotropic. The cell type was chosen explicit, the blank cell size was chosen to be 3.5, the die was chosen to be 4.5, and the sintered part cell was chosen to be 4. And in the calculation step, kinetic display calculation is selected, the step length is 1s, and the powder does not deform any more after the powder densification process is finished. The friction type is defined as a penalty function type, the friction coefficient between the die and the billet is defined as 0.3, and the contact surfaces include all the contact surfaces of the billet and the die. The loading mode adopts pressure loading, and the contact surface of the upper die and the blank is selected as a loading surface (unidirectional loading). (2) The simulated sintering method is hot-pressing sintering under vacuum conditions, wherein the simulated sintering method is hot-pressing sintering, the sintering temperature is 970 ℃, the sintering time is 10 minutes, and the sintering loading surface pressure is 50 MPa. (3) The equivalent stress distribution and the pore volume fraction distribution of the final sintered hollow cylindrical member are shown in fig. 4(a) and 4(b), respectively. It can be seen that when one-step unidirectional loading sintering forming is carried out, under the influence of friction force, the phenomenon that the equivalent stress of the component is gradually reduced along the loading direction occurs; at the maximum loading displacement position (the lowest end of the member), the friction force influence is maximum, the equivalent stress is minimum, and the difference of the equivalent stress of the upper end and the lower end of the member is large. Meanwhile, the density of the member also has a variation trend similar to the equivalent stress, the density gradually decreases along the loading direction (the pore volume fraction gradually increases), and the pore volume fraction is the largest at the lowest end of the member; the density difference between the upper end and the lower end of the component is larger.
By comparison, the influence of friction force is obviously weakened in the forming process of the hollow cylindrical member; the density distribution of the component in the height direction is more uniform, and the difference of the volume fractions of the pores at the upper end and the lower end is obviously reduced. In addition, the overall compactness of the component is generally improved: when the unidirectional loading sintering forming is carried out in the comparison step, the lowest density of the component layout area is 77%; when the two-step unidirectional loading incremental sintering forming is carried out, the lowest density of the component layout area is increased to 81%.
The principle and the implementation mode of the invention are explained by applying a specific example, and the description of the embodiment is only used for helping to understand the method and the core idea of the invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, the specific embodiments and the application range may be changed. In view of the above, the present disclosure should not be construed as limiting the invention.
Claims (6)
1. A powder increment sintering forming method of a complex closed hollow thin-wall part is characterized in that increment accumulation forming is realized by integrating step-by-step partition sintering, densification and connection of powder raw materials, and the complex closed hollow thin-wall part is finally obtained, and the method specifically comprises the following steps:
1) placing the powder raw material into a die, applying sintering pressure on a pressure head, and performing the 1 st sintering to obtain a prefabricated blank;
2) adding powder raw materials to corresponding parts of the prefabricated blank in a step-by-step and partition mode according to the shape, size and structural characteristics of an actual component, applying sintering pressure on a pressure head, and performing sintering for the 2 nd time to obtain the prefabricated blank;
3) according to the shape, size and structural characteristics of an actual component, the operation in the step 2) is further circulated on the prefabricated blank obtained by the (n-1) th sintering to carry out the (n) th sintering, wherein n is more than or equal to 2, and the powder raw materials adopted in the (2) th to n) th sintering can be different from that in the (n-1) th sintering and can also be the same as that in the (n-1) th sintering;
4) and (4) taking the finally obtained complex closed hollow thin-wall part out of the mold.
2. The powder incremental sintering forming method of the complex closed hollow thin-walled part according to claim 1, characterized by comprising the following steps: the relative density of the prefabricated blank or the component obtained by the n-1 sintering is 90.0-99.9%.
3. The powder incremental sintering forming method of the complex closed hollow thin-walled part according to claim 1, characterized by comprising the following steps: the thin-walled component is a circular hollow thin-walled component with uniform section, a rectangular hollow thin-walled component with uniform section or a special-shaped hollow thin-walled component with uniform section.
4. The powder incremental sintering forming method of the complex closed hollow thin-walled part according to claim 1, characterized by comprising the following steps: the sintering method is hot pressing sintering, current sintering, hot isostatic pressing sintering or liquid phase sintering.
5. The powder incremental sintering forming method of the complex closed hollow thin-walled part according to claim 1, characterized by comprising the following steps: the sintering environment for sintering and forming is vacuum, air or inert atmosphere.
6. The method for powder incremental sintering forming of a complex closed hollow thin-walled part according to claim 5, characterized in that: the inert gas atmosphere is at least one selected from the group consisting of a nitrogen gas atmosphere, a helium gas atmosphere, a neon gas atmosphere, an argon gas atmosphere, a krypton gas atmosphere, and a xenon gas atmosphere.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201911289175.8A CN110756808B (en) | 2019-12-13 | 2019-12-13 | Powder increment sintering forming method for complex closed hollow thin-wall part |
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| CN201911289175.8A CN110756808B (en) | 2019-12-13 | 2019-12-13 | Powder increment sintering forming method for complex closed hollow thin-wall part |
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| CN110756808A CN110756808A (en) | 2020-02-07 |
| CN110756808B true CN110756808B (en) | 2021-09-28 |
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