CN110935878B

CN110935878B - Injection molding method of titanium alloy part

Info

Publication number: CN110935878B
Application number: CN201911390052.3A
Authority: CN
Inventors: 余勇; 李益民; 何浩; 胡幼华; 王霄
Original assignee: Hunan Injection High Technology Co ltd
Current assignee: Hunan Injection High Technology Co ltd
Priority date: 2019-12-30
Filing date: 2019-12-30
Publication date: 2022-04-05
Anticipated expiration: 2039-12-30
Also published as: CN110935878A

Abstract

The invention discloses an injection molding method of a titanium alloy part, which comprises the steps of mixing base material titanium alloy powder with a binder, granulating to obtain a feed, and injecting the feed into a mold cavity by using an injection molding machine to obtain a product green compact; and removing the binder in the green body by pure water degreasing and thermal degreasing processes, and finally sintering and densifying by Hot Isostatic Pressing (HIP) to obtain the titanium alloy part. Compared with the prior art, the invention adopts an environment-friendly and efficient water-soluble binder system and a HIP sintering method to prepare the titanium alloy part with excellent performance on the basis of the powder injection molding technology, has the advantages of high production efficiency, low production cost, easy realization of mass production and the like, and the tensile strength of the obtained titanium alloy product is more than or equal to 935MPa, the yield strength is more than or equal to 890MPa, the elongation is more than or equal to 10 percent, the relative density is more than or equal to 99 percent, and the like, and can well meet the requirements of customers.

Description

Injection molding method of titanium alloy part

Technical Field

The invention relates to a preparation method of a titanium alloy part, in particular to an injection molding method of the titanium alloy part.

Background

Titanium and titanium alloy have the advantages of small density, high specific strength, no magnetism, corrosion resistance, good biocompatibility and the like, are high-quality metal structural materials and functional materials, are widely applied in the fields of aerospace, automobiles, power generation, biological medicine and the like, and are known as 'third metal' and 'strategic metal' in development after steel and aluminum materials. However, titanium and titanium alloys have high melting points and hardness and poor machining, molding and cutting properties, so that equipment adopting the traditional machining method is expensive, low in efficiency, high in cost and large in material waste, and the application range of the titanium and titanium alloys is greatly limited. Metal Injection Molding (MIM) is a near-net-shape forming process formed by combining powder metallurgy technology and plastic injection molding technology, has the advantages of high raw material utilization rate, flexible component adjustment, low batch production cost and the like, can prepare high-dimensional and high-precision parts, and is an ideal method for preparing titanium and titanium alloy. The most common Ti-6A1-4V alloy of titanium alloys is an alpha + beta two-phase martensitic type alloy. It contains 6% of alpha stabilizing element aluminum, and the strength of alpha phase is improved by solid solution strengthening. Vanadium, as a beta stabilizer, lowers the transition temperature of alpha + beta and beta. Ti-6A1-4V alloy was first developed in 1954 in the United states, is widely used in the aerospace industry, and is the main support for the U.S. titanium alloy. Later, the Ti-6A1-4V alloy is gradually developed into an international titanium alloy, and in the production and application of titanium alloys in China, the Ti-6A1-4V alloy also dominates and is named as TC 4.

The MIM process of the TC4 titanium alloy mainly comprises powder preparation, mixing, injection molding, degreasing, sintering, necessary post-treatment and the like. Studies have shown that the performance of TC4 titanium alloy injection molded parts is affected primarily by relative density, carbon, oxygen content, and microstructure. Sintering is used as the last process in the metal injection molding process and is of great importance to the final performance of the product. Sintering process parameters (such as temperature, time, atmosphere, temperature increase and decrease rate, etc.) directly affect the performance and dimensional accuracy of the product. At present, the TC4 titanium alloy is usually sintered under normal pressure, the relative density is about 95%, and a certain proportion of air holes are inevitably left in a microstructure. These pores act as crack sources at the time of specimen fracture, and reduce the mechanical properties of the material, such as tensile strength, plasticity, and fatigue strength. In addition, the inventor finds that the sintering equipment adopts a resistance heating mechanism, mainly adopts radiation and conduction, has low heating efficiency, and generally needs heat preservation for 2-4 hours at the high temperature of 1250-1350 ℃, which is not beneficial to improving the production efficiency, causing the waste of resources and energy, and also causing the coarsening of crystal grains, the increase of oxygen content and the deterioration of material performance. Therefore, how to optimize the sintering process and obtain a fully-dense product on the premise of strictly controlling the contents of carbon and oxygen is a key preparation technology for realizing a high-performance titanium alloy MIM part.

The binder is the core of MIM, acting as a mobile carrier, and is eventually removed by degreasing techniques. The design of the binder determines the quality of the whole process, directly influences the working procedures of mixing, injection molding, degreasing and the like, and has great influence on the quality of an injection molding blank, degreasing efficiency, sintering behavior, product dimensional accuracy, performance and the like. The binder system influences the selection of the degreasing process, in terms of process and cost, the degreasing time is as short as possible, the degreasing temperature is as low as possible, if the degreasing process is improperly controlled or the binder is incompletely removed, the defects of degreasing dirtying, deformation, bubbling and the like are easily caused, and meanwhile, because the titanium activity is high, the mechanical property of the titanium is very sensitive to the content of the impurity element C, H, O, and researches show that the oxygen content is increased most severely during the thermal degreasing period. Currently, the common binder systems used for MIM-TC4 titanium alloys are wax-based systems, aromatic-based systems, and polyoxymethylene systems. However, these systems are all deficient to varying degrees. The wax-based system binder plays an important role in the MIM process, but the solvent degreasing efficiency is low, and the carbon content of the obtained product is high, so the development is limited. The aromatic compound-based binder has higher solvent degreasing efficiency than the wax-based binder, but the aromatic compound contained therein has adverse effects on the environment and human health, and is not suitable for large-scale application. For a polyformaldehyde system, in the injection process, because polyformaldehyde may be decomposed to generate formaldehyde with high toxicity, strong acid used in the catalytic degreasing process has a large corrosion effect on equipment, and the time for subsequent thermal degreasing is increased, the oxygen content may be increased suddenly, so that the large-scale production of the polyformaldehyde system is limited. Therefore, the development of new and efficient binder systems is the main research direction in TC4 titanium alloy powder injection molding.

In view of the above, it is an urgent need to provide a powder injection molding method for titanium alloy parts with high performance and suitable for mass production.

Disclosure of Invention

The invention aims to solve the defects in the prior art, provides an injection molding method of a titanium alloy part, introduces a novel water-soluble binder on the basis of powder injection molding, combines Hot Isostatic Pressing (HIP) sintering and other methods to prepare the titanium alloy part with high performance, is suitable for large-scale production, and overcomes the defects of the process.

The invention relates to an injection molding method of a titanium alloy part, which comprises the following steps: mixing titanium alloy powder with a binder, and granulating to obtain a feed; feeding and injecting the raw materials into a die cavity to obtain a green body, sequentially carrying out pure water degreasing and thermal degreasing on the green body to obtain a degreased green body, and carrying out isostatic pressing (HIP) sintering on the green body to obtain a titanium alloy part; the adhesive comprises the following components in percentage by mass: 60-85% of polyethylene glycol (PEG); 15-35% of polyethylene wax (PE wax); 1-10% of Stearic Acid (SA).

The invention provides a water-soluble binder with simple components for injection molding of titanium alloy, excellent fluidity and the capability of maintaining the shape of a part can be achieved through the synergistic effect of polyethylene glycol, polyethylene wax and stearic acid, meanwhile, pure water degreasing is firstly carried out, and the combined formula of the water-soluble binder can ensure that the polyethylene glycol with the main content is completely removed in the pure water degreasing link, thereby greatly reducing the time of thermal degreasing and reducing the carbon content. Therefore, the part prepared by the invention has more excellent plasticity, and the elongation of the titanium alloy is improved by more than 30% compared with the titanium alloy formed by injection molding in the prior art.

Preferably, the invention relates to an injection molding method of a titanium alloy part, wherein the binder comprises the following components in percentage by mass: 60-70% of polyethylene glycol (PEG); 25-30% of polyethylene wax (PE wax); 5-10% of Stearic Acid (SA).

Preferably, in the injection molding method of a titanium alloy part according to the present invention, the titanium alloy powder is an atomized powder.

Preferably, in the injection molding method of the titanium alloy part, the particle size of the titanium alloy powder is less than or equal to 150um, and preferably 10-60 um.

In a further preferred scheme, the particle size of the titanium alloy powder is 20-45 um.

Preferably, the titanium alloy powder is Ti-6Al-4V pre-alloy powder.

In the injection molding method of the titanium alloy part, the volume ratio of the binder in the feed material is as follows: the ratio of titanium alloy powder is 30-50: 50-70; preferably 35-43: 57-65; more preferably 35-40: 60-65.

Preferably, the injection molding method of the titanium alloy part comprises the steps of mixing at the temperature of 140-170 ℃ for 1-4 h and at the rotating speed of 80-120 r/min.

Preferably, in the injection molding method of the titanium alloy part, the injection temperature is 140-170 ℃, the injection pressure is 70-130 MPa, the injection speed is 30-90 g/s, and the mold temperature is 40-60 ℃.

Preferably, in the injection molding method of the titanium alloy part, the time for degreasing the titanium alloy part by pure water is 4-6 h, and the degreasing temperature is 30-50 ℃.

Under the formula of the binder, organic solvent is not required to be added, and polyethylene glycol with the largest content can be completely removed only by combining the technological parameters of pure water degreasing.

Certainly, the pure water degreasing process also needs to be effectively controlled, if the degreasing time is too short, polyethylene glycol residue is caused, and the carbon content is greatly increased after sintering, so that the product performance is reduced; if the degreasing temperature is too high, the dissolution rate of the polyethylene glycol is too high, the shape of the embryo body is damaged, and a large number of cracks appear.

Preferably, the injection molding method of the titanium alloy part comprises the following steps: under the protection of argon atmosphere, heating to 400-500 ℃ at a heating rate of 1-3 ℃/min, preserving heat for 1-4 h, heating to 700-800 ℃ at a heating rate of 3-8 ℃/min, preserving heat for 1-4 h, and cooling to room temperature along with a furnace. After pure water degreasing, the thermal degreasing efficiency of the invention is improved, and the required thermal degreasing time is reduced.

Preferably, the hot isostatic pressing sintering process of the injection molding method of the titanium alloy part comprises the following steps: heating to 900-1000 ℃ at a heating rate of 100-500 ℃/min, preserving heat for 5-30 min, and then cooling to room temperature along with the furnace, wherein the sintering pressure is 100-200 MPa.

In the invention, in the HIP sintering process, firstly vacuum pumping is carried out, then temperature rising is carried out, argon is filled, and before argon is filled, the vacuum degree is controlled to be less than or equal to 5 x 10^-3Pa。

In the invention, after degreasing, parameters of hot isostatic pressing sintering densification and hot isostatic pressing net pressure need to be effectively controlled at a lower temperature, if the parameters are unreasonably set, the material preparation fails, and if the sintering temperature is too low, the density of the product is poor, and the performance is reduced; if the sintering temperature is too high, the product is over-burnt.

The cost of the product obtained by the invention is greatly lower than that of the existing similar products. The production efficiency is 1-2 times of that of the prior production technology, and the degreasing efficiency is about 3 times of that of the prior art because the invention adopts pure water for degreasing. Meanwhile, under the synergistic effect of other process conditions, the yield of the product is more than or equal to 92 percent and is far higher than that of the prior process.

The tensile strength of the product obtained by the invention is more than or equal to 935MPa, the yield strength is more than or equal to 890MPa, the elongation is more than or equal to 10 percent, the relative density is more than or equal to 99 percent, the product is superior to the similar product by 20 percent, especially the elongation is greatly improved, and the product can be comparable to the performance of cast titanium alloy.

Principles and advantages

Based on a powder injection molding technology, firstly, mixing base material titanium alloy powder with a binder, granulating to obtain a feed, and then injecting the feed into a mold cavity by using an injection molding machine to obtain a product green compact; and removing the binder in the green body by pure water degreasing and thermal degreasing processes, and finally sintering and densifying by adopting HIP to obtain the titanium alloy part.

The selection of the powder feedstock is an important step in the titanium alloy powder injection molding process. The particle size distribution and morphology of the powder directly affect the flowability and formability of the shot, the shape retention of the green body during degreasing, and the shrinkage during sintering. The currently common methods for preparing titanium and titanium alloy powders include mechanical methods and atomization methods. Atomization is a process in which a liquid metal or alloy stream is broken up into tiny droplets by some means and then condensed into metal powder. The whole preparation process can be carried out in a completely inert atmosphere, so that the high purity of the raw material powder is kept, and the prepared powder is spherical in shape, quite wide in particle size distribution and good in stacking performance. As the particle size is reduced and the specific surface area is increased, the content of impurity elements is increased. However, when the particle size of the powder is too large, the powder is easily separated from the binder during the injection process, and defects are formed. The selection of the powder particle size is therefore particularly critical. The prealloying powder has the advantages that each powder particle contains various metal elements for forming the alloy, and the elements are uniformly distributed compared with the elements of the mechanically mixed powder, so that the composition segregation is fundamentally avoided, and the composition uniformity of the prealloying powder is quite good. Secondly, the pre-alloying greatly reduces the activation energy required by the diffusion of metal atoms in the sintering process, the sintering performance is good, and a good foundation is laid for obtaining high-performance products. The atomized prealloying powder with the titanium alloy powder granularity of 20-45 um is preferably selected, so that the increase of impurity content can be avoided, the atomized prealloying powder can be fully and uniformly mixed with the binder, and finally, the compact titanium alloy part is obtained.

In the process, the process parameters of each link influence the final performance of the product. In order to achieve high performance of the titanium alloy part, technological parameters of all links need to be optimized. In the material mixing process, atomized titanium alloy powder and a water-soluble binder are fully mixed to obtain uniform feed, and the segregation of feed components is prevented by adjusting parameters such as powder loading capacity, mixing temperature, mixing time and the like, so that a blank with complete filling and stable workpiece size is obtained, uniform shrinkage after sintering is ensured, and the defects of deformation, cracking and the like are avoided. In the injection molding process, the invention obtains a good injection blank by adjusting important injection parameters such as injection temperature, injection pressure, injection speed, mold temperature and the like, and prevents the defects such as foaming, cracks, pores and the like on the surface of a product.

Of course, for injection molding, the composition of the binder is the key to material molding, and the invention provides a water-soluble binder with simple components, which can achieve excellent fluidity and the capability of maintaining the shape of parts through the synergistic action of polyethylene glycol, polyethylene wax and stearic acid.

In the degreasing process, the main component in the binder is polyethylene glycol, and the polyethylene glycol is an ethylene oxide polymer with the molecular weight of 200-20000, and has excellent water solubility and thermoplasticity. In addition, it is also a very safe chemical and is widely used in the food industry. The method comprises the following steps of firstly, dissolving polyethylene glycol components in a binder by using water in a degreasing mode of combining pure water degreasing and thermal degreasing, putting a sample into water preheated to 30-50 ℃, and completely dissolving polyethylene glycol in the water after 4-6 hours; and then removing the residual water-insoluble binder by a thermal degreasing process, effectively controlling the corresponding temperature rise rate and the heat preservation time, controlling the increment of oxygen within a minimum range, simultaneously ensuring that the organic binder is completely removed, and avoiding the increase of carbon content caused by the formation of carbide in the residual organic binder in the sintering process. Compared with the traditional degreasing process, the pure water degreasing has the following advantages. 1) Is green and environment-friendly. Pure water is used to replace the adhesive of aromatic compounds which have adverse effects on the environment and human health, and the degreased product is nontoxic, harmless and biodegradable; 2) high efficiency and energy saving. Compared with solvent degreasing, the production efficiency is about 3 times of that of the prior art, and the production cost is greatly saved; 3) the performance is excellent. The pore channel can be formed by removing the water-soluble binder, the hot degreasing is facilitated, the formation of cracks and defects is reduced, the carbon content can be controlled within 800ppm, the performance of the sintered product is greatly improved, particularly, the plasticity is obviously improved, and the elongation is improved by more than 30 percent compared with the material obtained by injection molding in the prior art.

In the sintering process, the invention adopts a Hot Isostatic Pressing (HIP) sintering mode, which is a technology for sintering a titanium alloy product in a closed container by applying equal pressure to the titanium alloy product under the combined action of 900-1000 ℃ and 100-200 MPa by using inert gas such as argon and the like as a pressure transmission medium. The sintering of titanium alloy is generally solid phase sintering, and the main mass transfer modes are evaporation-condensation mass transfer and diffusion mass transfer, and compared with liquid phase sintering, the densification of the titanium alloy is difficult. The relative density of the article is often increased by increasing the sintering temperature to accelerate atomic diffusion, but it is difficult to prevent grain growth. In the hot isostatic pressing sintering, high temperature and high pressure are simultaneously applied to the titanium alloy powder, so that powder particles are deformed, the actual contact area of the powder is greatly increased, the atom migration distance is shortened, and the densification is rapidly completed. Meanwhile, the hot isostatic pressing temperature is lower than the common sintering temperature of the powder, so that the crystal grains are not gathered and grown, and a product with a fine crystal structure can be obtained. Therefore, by applying the hot isostatic pressing sintering process, the titanium alloy product can reach 100% compactness, has fine crystal grains, uniform tissue, no segregation of components and other good microstructures, solves the problem of low relative density in the prior art, and realizes the improvement of material performance. And then the defects of deformation, cracking and the like of the green body in the sintering process are avoided by controlling the heating and cooling rate and the heat preservation time. The invention adopts a whole set of optimized process parameters, can ensure that the product has excellent performance which is comparable to that of cast titanium alloy, and meets the requirements of customers on MIM titanium alloy parts.

Compared with the prior art, the invention adopts a novel water-soluble binder system and a Hot Isostatic Pressing (HIP) sintering process to prepare the high-performance titanium alloy part on the basis of the powder injection molding technology, and has the characteristics that:

1) the novel degreasing technology with environmental protection and high efficiency greatly improves the production efficiency;

2) the compactness is high, and the product performance is excellent and is 20% better than the similar products;

3) the mass production is easy to realize, the yield is more than or equal to 92 percent, and the method is higher than the prior production process.

In conclusion, the invention adopts the powder injection molding technology and combines the environment-friendly and efficient water-soluble binder system and the Hot Isostatic Pressing (HIP) sintering method to prepare the product with excellent performance, has the advantages of high production efficiency, easy realization of batch production, low production cost and the like, solves the problems of poor performance, low production efficiency, high cost and the like in the prior art, can well meet the customer requirements, and is very suitable for preparing MIM titanium alloy parts.

Drawings

FIG. 1 is SEM morphology of titanium alloy powder

FIG. 2 is a pictorial representation of a titanium alloy article

Detailed Description

The process of the present invention is further illustrated below with reference to five examples.

Example 1:

an injection molding method of a titanium alloy part comprises the following steps:

A. preparing raw materials: the substrate material uses atomized prealloyed titanium alloy powder with the average particle size of 30um, the components of the titanium alloy powder are shown in table 1, and fig. 1 is an SEM (scanning electron microscope) morphology graph of the titanium alloy powder;

TABLE 1 compositions of titanium alloy powders

B. Preparing a binder: according to the mass percentage, 60 percent of polyethylene glycol (PEG), 30 percent of polyethylene wax (PE wax) and 10 percent of Stearic Acid (SA) are mixed in a mixer for 4 hours at the temperature of 140 ℃ to prepare the binder;

C. preparing and feeding: mixing the binder and the matrix material according to a volume ratio of 35% to 65% to prepare a feed, wherein the mixing temperature is 140 ℃, the rotation speed of a mixer is 90r/min, and the mixing time is 4 h;

D. injection molding: injecting the feed into the die cavity by using an injection molding machine to obtain a product green body; the injection temperature is 140 ℃, the injection pressure is 110MPa, the injection speed is 60g/s, and the mold temperature is 60 ℃;

E. degreasing: removing polyethylene glycol components from a product green blank by water, degreasing for 6h at 35 ℃, then thermally degreasing in a vacuum degreasing furnace, heating to 450 ℃ at a heating rate of 2 ℃/min and keeping the temperature for 2h in the protection of argon atmosphere, heating to 800 ℃ at a heating rate of 5 ℃/min and keeping the temperature for 2h, and then cooling to room temperature along with the furnace;

F. and (3) sintering: sintering the degreased product blank in a hot isostatic pressing furnace; and (3) filling argon into the furnace before the vacuum degree is 5 x 10-3Pa, heating and filling argon, wherein the sintering pressure is 200MPa (provided by the argon), heating to 950 ℃ at the heating rate of 300 ℃/min, keeping the temperature for 20min, and cooling to room temperature along with the furnace to obtain a finished product. The tensile strength, the yield strength, the elongation and the relative density of the alloy can reach 940MPa, 899MPa, 12 percent and 99.6 percent respectively by testing the performance.

G. 200 samples were prepared according to the above process steps and parameters, with a yield of 93%.

Example 2:

B. preparing a binder: according to the mass percentage, 65 percent of polyethylene glycol (PEG), 30 percent of polyethylene wax (PE wax) and 5 percent of Stearic Acid (SA) are mixed in a mixer at the temperature of 150 ℃ for 3 hours to prepare the binder;

C. preparing and feeding: mixing the binder and the matrix material according to a volume ratio of 38% to 62% and granulating to prepare a feed, wherein the mixing temperature is 150 ℃, the rotating speed of a mixing mill is 90r/min, and the mixing time is 3 h;

D. injection molding: injecting the feed into the die cavity by using an injection molding machine to obtain a product green body; the injection temperature is 150 ℃, the injection pressure is 100MPa, the injection speed is 60g/s, and the mold temperature is 60 ℃;

E. degreasing: removing polyethylene glycol components from a product green blank by water, degreasing for 5h at 40 ℃, then thermally degreasing in a vacuum degreasing furnace, heating to 450 ℃ at a heating rate of 2 ℃/min under the protection of argon atmosphere, preserving heat for 2h, heating to 750 ℃ at a heating rate of 5 ℃/min, preserving heat for 3h, and cooling to room temperature along with the furnace;

F. and (3) sintering: sintering the degreased product blank in a hot isostatic pressing furnace; and (3) filling argon into the furnace before the vacuum degree is 5 x 10-3Pa, heating and filling argon, wherein the sintering pressure is 200MPa (provided by the argon), heating to 1000 ℃ at the heating rate of 300 ℃/min, keeping the temperature for 15min, and cooling to room temperature along with the furnace to obtain the finished product. The tensile strength, yield strength, elongation and relative density of the alloy can reach 940MPa, 900MPa, 12 percent and 99.8 percent respectively by testing performance.

Example 3:

B. preparing a binder: according to the mass percentage, 70 percent of polyethylene glycol (PEG), 25 percent of polyethylene wax (PE wax) and 5 percent of Stearic Acid (SA) are mixed in a mixer for 2 hours at the temperature of 160 ℃ to prepare the binder;

C. preparing and feeding: mixing the binder and the matrix material according to a volume ratio of 40% to 60% and granulating to prepare a feed, wherein the mixing temperature is 160 ℃, the rotating speed of a mixing mill is 100r/min, and the mixing time is 2 h;

D. injection molding: injecting the feed into the die cavity by using an injection molding machine to obtain a product green body; the injection temperature is 160 ℃, the injection pressure is 90MPa, the injection speed is 60g/s, and the mold temperature is 50 ℃;

E. degreasing: removing polyethylene glycol components from a product green blank by water, degreasing for 5h at 40 ℃, then thermally degreasing in a vacuum degreasing furnace, heating to 450 ℃ at a heating rate of 2 ℃/min and keeping the temperature for 2h in the protection of argon atmosphere, heating to 800 ℃ at a heating rate of 5 ℃/min and keeping the temperature for 2h, and then cooling to room temperature along with the furnace;

F. and (3) sintering: sintering the degreased product blank in a hot isostatic pressing furnace; and (3) filling argon into the furnace before the vacuum degree is 5 x 10-3Pa, heating and filling argon, wherein the sintering pressure is 200MPa (provided by the argon), heating to 1000 ℃ at the heating rate of 400 ℃/min, keeping the temperature for 15min, and cooling to room temperature along with the furnace to obtain the finished product. The tensile strength, the yield strength, the elongation and the relative density can reach 956MPa, 904MPa, 14 percent and 99.8 percent respectively by detecting the performance.

G. 200 samples were prepared according to the above process steps and parameters, with a yield of 94%.

Example 4:

B. preparing a binder: according to the mass percentage, 75 percent of polyethylene glycol (PEG), 24 percent of polyethylene wax (PE wax) and 1 percent of Stearic Acid (SA) are mixed in a mixer for 1 hour at the temperature of 170 ℃ to prepare the binder;

C. preparing and feeding: mixing the binder and the matrix material according to a volume ratio of 40% to 60% and granulating to prepare a feed, wherein the mixing temperature is 170 ℃, the rotating speed of a mixing mill is 100r/min, and the mixing time is 1 h;

D. injection molding: injecting the feed into the die cavity by using an injection molding machine to obtain a product green body; the injection temperature is 170 ℃, the injection pressure is 85MPa, the injection speed is 70g/s, and the mold temperature is 50 ℃;

E. degreasing: removing polyethylene glycol components from a product green blank by water, degreasing for 4h at 50 ℃, then thermally degreasing in a vacuum degreasing furnace, heating to 450 ℃ at a heating rate of 2 ℃/min under the protection of argon atmosphere, preserving heat for 2h, heating to 750 ℃ at a heating rate of 5 ℃/min, preserving heat for 3h, and cooling to room temperature along with the furnace;

F. and (3) sintering: sintering the degreased product blank in a hot isostatic pressing furnace; and (3) filling argon into the furnace before the vacuum degree is 5 x 10-3Pa, heating and filling argon, wherein the sintering pressure is 150MPa (provided by the argon), heating to 900 ℃ at the heating rate of 400 ℃/min, keeping the temperature for 0.5h, and cooling to room temperature along with the furnace to obtain a finished product. The tensile strength, the yield strength, the elongation and the relative density of the material can reach 938MPa, 890MPa, 10 percent and 99.5 percent respectively by detecting the performance.

G. 200 samples were prepared according to the above process steps and parameters, with a yield of 92%.

Example 5:

B. preparing a binder: according to the mass percentage, 80 percent of polyethylene glycol (PEG), 19 percent of polyethylene wax (PE wax) and 1 percent of Stearic Acid (SA) are mixed in a mixer for 1 hour at the temperature of 170 ℃ to prepare the binder;

C. preparing and feeding: mixing the binder and the matrix material according to a volume ratio of 43% to 57%, granulating to prepare a feed, wherein the mixing temperature is 170 ℃, the rotating speed of a mixer is 85r/min, and the mixing time is 1 h;

D. injection molding: injecting the feed into the die cavity by using an injection molding machine to obtain a product green body; the injection temperature is 145 ℃, the injection pressure is 80MPa, the injection speed is 80g/s, and the mold temperature is 50 ℃;

F. and (3) sintering: sintering the degreased product blank in a hot isostatic pressing furnace; and (3) filling argon into the furnace before the vacuum degree is 5 x 10-3Pa, heating and filling argon, wherein the sintering pressure is 150MPa (provided by the argon), heating to 900 ℃ at the heating rate of 200 ℃/min, keeping the temperature for 0.5h, and cooling to room temperature along with the furnace to obtain a finished product. The tensile strength, yield strength, elongation and relative density of the material can reach 935MPa, 895MPa, 11 percent and 99.5 percent respectively by testing performance.

Comparative example 1:

comparative example 2:

in comparative examples 1 and 2, conditions other than those indicated above were the same as those in example 3.

Comparative example 3:

the comparative example uses a method substantially the same as that of example 3, except that a normal pressure sintering process is used, and the specific steps are as follows: sintering the degreased product blank in a vacuum sintering furnace; the vacuum degree in the furnace is 5 x 10-3Pa, the furnace is firstly heated to 600 ℃ at the speed of 5 ℃/min and is insulated for 4h, then the furnace is cooled to room temperature after being heated to 1250 ℃ at the speed of 5 ℃/min and is insulated for 4 h. The performance is detected, the tensile strength, the yield strength, the elongation and the relative density can respectively reach 845MPa, 798MPa, 9 percent and 95 percent, and compared with the performance of example 3, the performance is 15 percent lower.

Comparative example 4:

this comparative example used substantially the same procedure as in example 3, except that the binder was formulated in the following mass percentages of polyethylene glycol (PEG) 88%, polyethylene wax (PE wax) 7%, and Stearic Acid (SA) 5%. The tensile strength, the yield strength, the elongation and the relative density can reach 776MPa, 732MPa, 8 percent and 94 percent respectively by testing the performance, and compared with the performance of example 3, the performance is lower by more than 20 percent, especially the elongation is lower by 40 percent.

Comparative example 5:

this comparative example employed substantially the same procedure as in example 3, except that the binder was formulated in the following mass percentages, Paraffin Wax (PW) 60%, Polyethylene (PE) 35%, and Stearic Acid (SA) 5%. The tensile strength, the yield strength, the elongation and the relative density can reach 750MPa, 718MPa, 7 percent and 93 percent respectively by testing the performance, and compared with the performance of example 3, the performance is lower by more than 20 percent, especially the elongation is lower by 50 percent.

The comparison shows that the unreasonable binder formula and the normal pressure sintering process can cause defects of the product and further affect the performance due to the excessively high or low pure water degreasing temperature, pure water degreasing time, sintering temperature, sintering pressure and other process parameters.

The above-described embodiments are merely exemplary embodiments of the present invention, which should not be construed as limiting the scope of the invention, but rather as indicating any equivalent variations, modifications, substitutions and combinations of parts within the spirit and scope of the invention.

Claims

1. A method of injection molding a titanium alloy part, comprising the steps of: mixing titanium alloy powder with a binder, and granulating to obtain a feed; feeding and injecting the raw materials into a die cavity to obtain a green body, sequentially carrying out pure water degreasing and thermal degreasing on the green body to obtain a degreased green body, and carrying out isostatic pressing sintering on the green body to obtain a titanium alloy part;

the titanium alloy powder is gas atomized powder, the granularity of the titanium alloy powder is 20-45 mu m,

in the feeding, the volume ratio of the binder is as follows: the ratio of titanium alloy powder is 30-50: 50-70;

the adhesive comprises the following components in percentage by mass: 60-70% of polyethylene glycol; 25-30% of polyethylene wax; 5-10% of stearic acid;

the pure water degreasing time is 4-6 h, and the degreasing temperature is 30-50 ℃;

the thermal degreasing process comprises the following steps: under the protection of argon atmosphere, heating to 400-500 ℃ at a heating rate of 1-3 ℃/min, preserving heat for 1-4 h, heating to 700-800 ℃ at a heating rate of 3-8 ℃/min, preserving heat for 1-4 h, and cooling to room temperature along with a furnace;

the hot isostatic pressing sintering process comprises the steps of heating to 900-1000 ℃ at a heating rate of 100-500 ℃/min, preserving heat for 5-30 min, and then cooling to room temperature along with a furnace, wherein the sintering pressure is 100-200 MPa.

2. The injection molding method of a titanium alloy part according to claim 1, wherein in the feeding material, the ratio of the binder: the titanium alloy powder is 35-43: 57-65.

3. The method of claim 1, wherein the kneading is carried out at a kneading temperature of 140 to 170 ℃ for 1 to 4 hours and at a kneading machine rotation speed of 80 to 120 r/min.

4. The injection molding method of a titanium alloy part according to claim 1, wherein the injection temperature is 140 to 170 ℃, the injection pressure is 70 to 130MPa, the injection speed is 30 to 90g/s, and the mold temperature is 40 to 60 ℃ during the injection.

5. An injection molding method of a titanium alloy part according to any one of claims 1 to 4, characterized in that: the tensile strength of the obtained titanium alloy product is more than or equal to 935MPa, the yield strength is more than or equal to 890MPa, the elongation is more than or equal to 10 percent, and the relative density is more than or equal to 99 percent.