Background
Titanium and titanium alloy have the advantages of high specific strength, corrosion resistance, good biocompatibility and the like, and become important materials in the fields of aerospace, chemical engineering, biomedical treatment and the like. Generally, the production of titanium alloy products includes the steps of casting an alloy ingot, forging and rolling, and part fabrication. However, titanium alloys have poor machinability and high machining costs, which makes titanium alloy products expensive. As a near net shape forming technique, powder metallurgy can reduce or even eliminate machining, with obvious advantages. In addition, the titanium and the titanium alloy prepared by the powder metallurgy method can obtain fine and uniform crystal grains, and can reduce component segregation and improve component uniformity. However, titanium has a relatively high oxygen solubility and a relatively large specific surface area of the titanium powder, which results in a titanium powder metallurgy product having a relatively high oxygen concentration due to the oxygen concentration in the titanium powder. Oxygen in titanium has a great adverse effect on the physical, mechanical and electrical properties of titanium products. For example, high oxygen concentrations in the electronics industry can reduce the conductive properties of titanium sputtered films. Therefore, reducing the oxygen content in the titanium powder is of great importance for improving the performance of the titanium powder metallurgical product.
Calcium is often used as a deoxidizer for titanium powder due to its extremely strong oxygen affinity and high vapor pressure. Fisher et al use liquid sodium as a carrier to perform oxygen reduction (DOSS) on titanium and titanium alloy powder by using liquid calcium at high temperature, and the added sodium carrier can make calcium deoxidizer uniformly contact with metal powder (U.S. Pat. No. 4,983), but the titanium powder reduced in oxygen by the method usually agglomerates and even sinters into blocks. J.M.Oh and the like directly mix titanium powder and calcium according to the mass ratio of 2:1, and carry out oxygen reduction below the melting point of calcium, so that the problem of oxygen reduction and agglomeration of coarse titanium powder is successfully solved, the oxygen concentration of the titanium powder with the particle size of 115 mu m can be reduced to 1080ppm at 830 ℃, but the oxygen reduction temperature is low, the titanium powder with the oxygen concentration lower than 1000ppm is difficult to obtain, and the agglomeration problem of fine titanium powder still exists (Mater. Trans. 2012, 53: 1075-doped 1077). J.M. Oh et al also propose a calcium non-contact oxygen reduction method, i.e. under high vacuum environment, the mass ratio is 1: 1 and reducing agent calcium, and reducing oxygen above the melting point of calcium, wherein the oxygen concentration of the titanium Powder with the diameter of 115 mu m can be reduced to 820ppm by the method, but the method consumes more reducing agent calcium and is not beneficial to large-scale production (Powder technology. 2012, 55: 402-) -404). In addition, when the non-contact oxygen reduction is carried out on the fine titanium powder, particularly the titanium powder with the particle size less than 45 mu m, obvious agglomeration and even agglomeration can occur between the titanium powder, so that the leaching and the removal of the by-products are difficult.
Disclosure of Invention
In order to solve the problems that fine titanium powder is easy to agglomerate and even sinter into blocks in the calcium oxygen reduction process, the using amount of reducing agent calcium is high and the like, the invention provides a method for reducing the oxygen content of the fine titanium powder.
The invention is realized by adopting the following technical scheme:
a method for reducing the oxygen content of fine titanium powder comprises the following steps:
(1) uniformly mixing fine titanium powder and calcium oxide powder (the mass ratio of the fine titanium powder to the calcium oxide powder is 2-6: 1);
(2) uniformly mixing the mixed powder obtained in the step (1) with calcium particles (the mass ratio of the mixed powder to the calcium particles is 6-10: 1), and then reacting at high temperature (raising the temperature to 850-1200 ℃ in vacuum or protective atmosphere) for 0.5-4 h;
(3) and (3) after cooling, washing the product obtained in the step (2) with dilute acid, then washing with pure water, and drying to obtain the low-oxygen fine titanium powder.
According to the method for reducing the oxygen content of the fine titanium powder, the calcium oxide powder in the step (1) has the purity of 99-99.99% and the particle size of 0.1-30 mu m; the mixing is carried out in a mixer for 1-20 h, and the mixing process is carried out in an argon atmosphere.
According to the method for reducing the oxygen content of the fine titanium powder, the purity of the calcium particles in the step (2) is 99-99.99%, and the particle size is 1-10 mm; the protective atmosphere is hydrogen or argon or a mixed gas of hydrogen and argon.
According to the method for reducing the oxygen content of the fine titanium powder, the dilute acid in the step (3) is hydrochloric acid, nitric acid or sulfuric acid.
The invention has the following positive and beneficial effects:
the invention is suitable for oxygen reduction, the fine titanium powder with the granularity less than 50 mu m is used, the surface fine powder is not required to be treated in advance, the calcium oxide powder is added to prevent the fine titanium powder from directly contacting with each other so as to avoid agglomeration and even sintering of the fine titanium powder in the high-temperature oxygen reduction process, the direct contact oxygen reduction of the reducing agent calcium and the titanium powder is realized, the consumption of the reducing agent is less, the production cost is low, and the invention is suitable for large-scale production.
Detailed Description
The technical solution of the present invention is further described in detail with reference to the following examples, but the scope of the present invention is not limited thereto.
Example 1
A method for reducing the oxygen content of fine titanium powder specifically comprises the following steps:
(1) uniformly mixing titanium powder with oxygen content of 5500ppm and particle size of 10 mu m and calcium oxide powder with purity of 99.99% and particle size of 1 mu m in a mixer according to the mass ratio of 4:1, wherein the mixing time is 16h, and the mixing process is carried out in argon atmosphere;
(2) uniformly mixing the mixed powder obtained in the step (1) with calcium particles with the purity of 99.9% and the particle size of 5mm according to the mass ratio of 7:1, then placing the mixture into a stainless steel crucible, then placing the stainless steel crucible into a high-temperature furnace, heating to 1000 ℃ at the speed of 10 ℃/min under the protection of argon, reacting for 2 hours, and cooling to room temperature along with the furnace;
(3) and (3) taking out the powder obtained in the step (2), washing the powder with 10% hydrochloric acid, washing the powder with pure water, then placing the powder in a vacuum drying oven for drying to obtain low-oxygen fine titanium powder, carrying out SEM observation, as shown in figure 1, and carrying out oxygen content measurement by using an NCS-3000 oxygen-nitrogen-hydrogen tester, as shown in figure 2.
Example 2
A method for reducing the oxygen content of fine titanium powder specifically comprises the following steps:
(1) uniformly mixing 4500ppm of titanium powder with the granularity of 15 mu m and calcium oxide powder with the purity of 99.9% and the granularity of 5 mu m in a mixer according to the mass ratio of 3:1, wherein the mixing time is 8 hours, and the mixing process is carried out in an argon atmosphere;
(2) uniformly mixing the mixed powder obtained in the step (1) with calcium particles with the purity of 99.9% and the particle size of 5mm according to the mass ratio of 9:1, then placing the mixture into a stainless steel crucible, then placing the stainless steel crucible into a high-temperature furnace, heating to 1000 ℃ at the speed of 5 ℃/min under the protection of argon, reacting for 3 hours, and then cooling to room temperature along with the furnace;
(3) and (3) taking out the powder obtained in the step (2), washing the powder with 10% hydrochloric acid, washing the powder with pure water, and then drying the powder in a vacuum drying oven to obtain the low-oxygen fine titanium powder.
Example 3
A method for reducing the oxygen content of fine titanium powder specifically comprises the following steps:
(1) uniformly mixing titanium powder with the oxygen content of 4000ppm and the granularity of 20 mu m and calcium oxide powder with the purity of 99.99 percent and the granularity of 8 mu m in a mixer according to the mass ratio of 5:1 for 10 hours, wherein the mixing process is carried out in an argon atmosphere;
(2) uniformly mixing the mixed powder obtained in the step (1) with calcium particles with the purity of 99.9% and the particle size of 3mm according to the mass ratio of 6:1, then placing the mixture into a stainless steel crucible, then placing the stainless steel crucible into a high-temperature furnace, heating to 1050 ℃ at the speed of 5 ℃/min under the protection of argon, reacting for 1h, and cooling to room temperature along with the furnace;
(3) and (3) taking out the powder obtained in the step (2), washing the powder with 10% hydrochloric acid, washing the powder with pure water, and then drying the powder in a vacuum drying oven to obtain the low-oxygen fine titanium powder.
Example 4
A method for reducing the oxygen content of fine titanium powder specifically comprises the following steps:
(1) uniformly mixing 4800ppm of titanium powder with the granularity of 10 mu m and calcium oxide powder with the purity of 99.9% and the granularity of 5 mu m in a mixer according to the mass ratio of 4:1 for 10 hours, wherein the mixing process is carried out in an argon atmosphere;
(2) uniformly mixing the mixed powder obtained in the step (1) with calcium particles with the purity of 99.9% and the particle size of 6mm according to the mass ratio of 7:1, then placing the mixture into a stainless steel crucible, then placing the stainless steel crucible into a high-temperature furnace, heating to 960 ℃ at the speed of 6 ℃/min under the protection of argon, reacting for 4 hours, and cooling to room temperature along with the furnace;
(3) and (3) taking out the powder obtained in the step (2), washing the powder with 10% hydrochloric acid, washing the powder with pure water, and then drying the powder in a vacuum drying oven to obtain the low-oxygen fine titanium powder.
Example 5
A method for reducing the oxygen content of fine titanium powder specifically comprises the following steps:
(1) uniformly mixing 6500ppm of titanium powder with the granularity of 8 mu m and calcium oxide powder with the purity of 99.9 percent and the granularity of 2 mu m in a mixer according to the mass ratio of 3:1 for 12 hours, wherein the mixing process is carried out in an argon atmosphere;
(2) uniformly mixing the mixed powder obtained in the step (1) with calcium particles with the purity of 99.9% and the particle size of 5mm according to the mass ratio of 6:1, then placing the mixture into a stainless steel crucible, then placing the stainless steel crucible into a high-temperature furnace, heating to 950 ℃ at the speed of 5 ℃/min under the protection of argon, reacting for 3 hours, and then cooling to room temperature along with the furnace;
(3) and (3) taking out the powder obtained in the step (2), washing the powder with 10% hydrochloric acid, washing the powder with pure water, and then drying the powder in a vacuum drying oven to obtain the low-oxygen fine titanium powder.
Comparative example 1
A method for reducing the oxygen content of fine titanium powder specifically comprises the following steps:
(1) placing titanium powder with oxygen content of 5500ppm and particle size of 10 μm in a stainless steel crucible, then placing the stainless steel crucible in a high temperature furnace, heating to 1000 ℃ at a speed of 5 ℃/min under the protection of argon, preserving heat for 2h, and cooling to room temperature along with the furnace;
(2) taking out the powder obtained in the step (1).
Comparative example 2
A method for reducing the oxygen content of fine titanium powder specifically comprises the following steps:
(1) uniformly mixing titanium powder with oxygen content of 5500ppm and particle size of 10 mu m and calcium oxide powder with purity of 99.9% and particle size of 2 mu m in a mixer according to the mass ratio of 6:1 for 12 hours;
(2) placing the mixed powder obtained in the step (1) in a stainless steel crucible, then placing the stainless steel crucible in a high-temperature furnace, heating to 1000 ℃ at the speed of 5 ℃/min under the protection of argon, preserving heat for 2h, and then cooling to room temperature along with the furnace;
(3) and (3) taking out the powder obtained in the step (2).
Comparative example 3
A method for reducing the oxygen content of fine titanium powder specifically comprises the following steps:
(1) uniformly mixing titanium powder with oxygen content of 5500ppm and particle size of 10 mu m and calcium particles with purity of 99.9% and particle size of 5mm according to a mass ratio of 5:1, placing the mixture in a stainless steel crucible, then placing the stainless steel crucible in a high-temperature furnace, heating to 1000 ℃ at a speed of 5 ℃/min under the protection of argon, reacting for 2 hours, and cooling to room temperature along with the furnace;
(2) and (2) taking out the powder obtained in the step (1), washing the powder with 10% hydrochloric acid, washing the powder with pure water, and then drying the powder in a vacuum drying oven to obtain the low-oxygen fine titanium powder.
Comparative example 4
A method for reducing the oxygen content of fine titanium powder specifically comprises the following steps:
(1) uniformly mixing titanium powder with oxygen content of 2500ppm and granularity of 115 mu m and calcium particles with purity of 99.9% and granularity of 5mm according to the mass ratio of 6:1, placing the mixture in a stainless steel crucible, then placing the stainless steel crucible in a high-temperature furnace, heating to 1000 ℃ at the speed of 8 ℃/min under the protection of argon, reacting for 2h, and cooling to room temperature along with the furnace;
(2) and (2) taking out the powder obtained in the step (1), washing the powder with 10% hydrochloric acid, washing the powder with pure water, and then drying the powder in a vacuum drying oven to obtain the low-oxygen fine titanium powder.
TABLE 1 Effect of oxygen reduction treatment and caking behavior in the respective embodiments
Comparative example 5
A method for reducing the oxygen content of fine titanium powder specifically comprises the following steps:
(1) uniformly mixing titanium powder with the oxygen content of 4000ppm and the granularity of 10 mu m and calcium oxide powder with the purity of 99.9 percent and the granularity of 2 mu m in a mixer according to the mass ratio of 4:1 for 12 hours;
(2) uniformly mixing the mixed powder obtained in the step (1) with calcium particles with the purity of 99.9% and the particle size of 5mm according to the mass ratio of 4:1, then placing the mixture into a stainless steel crucible, then placing the stainless steel crucible into a high-temperature furnace, heating to 1000 ℃ at the speed of 6 ℃/min under the protection of argon, reacting for 1h, and cooling to room temperature along with the furnace;
(3) and (3) taking out the powder obtained in the step (2), washing the powder with 10% hydrochloric acid, washing the powder with pure water, and then drying the powder in a vacuum drying oven to obtain the low-oxygen fine titanium powder.