CN115896502A - Preparation method of high-purity nickel-titanium alloy material - Google Patents
Preparation method of high-purity nickel-titanium alloy material Download PDFInfo
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- CN115896502A CN115896502A CN202310237560.8A CN202310237560A CN115896502A CN 115896502 A CN115896502 A CN 115896502A CN 202310237560 A CN202310237560 A CN 202310237560A CN 115896502 A CN115896502 A CN 115896502A
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Abstract
The invention discloses a preparation method of a high-purity nickel-titanium alloy material, and relates to the technical field of nickel-titanium alloy material preparation. The method comprises the following steps: 1. selecting high-purity raw materials; 2. preparing a nickel-titanium ingot by adopting a vacuum induction melting process; 3. after dead heads and the surface of the cast ingot are removed and polished, forging the cast ingot into a bar, and polishing the surface of the bar; 4. and smelting the bar into an ingot by adopting an electron beam remelting process to obtain the high-purity nickel-titanium alloy material. The preparation method is simple, the prepared nickel-titanium alloy has high purity, the maximum size of nonmetallic inclusions is less than 10 mu m, the content of the nonmetallic inclusions is less than 0.5 percent, the component uniformity and the phase change temperature consistency are good, the phase change temperature deviation of different parts of the same ingot is less than 3 ℃, and the requirement of a high fatigue application scene of the nickel-titanium alloy material can be met.
Description
Technical Field
The invention relates to the technical field of nickel-titanium alloy material preparation, in particular to a preparation method of a high-purity nickel-titanium alloy material.
Background
Nickel titanium alloy is a functional material with a variety of technical application values. It has peculiar shape memory effect, super elasticity and damping property, excellent wear resistance and corrosion resistance, excellent mechanical property and wide application range, and relates to the fields of medical treatment, aerospace, machinery, electronics, chemical industry, energy, building and the like.
Improving the purity of alloy materials is an important research direction in the field of nickel-titanium alloy at present. This pair of enhanced nickel-titanium alloy elementsThe fatigue life of the device is of great significance. The purity of the nickel-titanium alloy material refers to nonmetallic inclusions (TiC and Ti) in the material 4 Ni 2 O x ) And the size, content and distribution of the pores. These technical parameters depend on the raw materials, the smelting process and the thermomechanical processes of the subsequent material processing.
The melting method of the nickel-titanium alloy material in China generally adopts vacuum induction melting, and the crucible material adopts a graphite crucible or a calcium oxide crucible. The nickel-titanium alloy material prepared by the process can meet most application occasions, but the purity of the nickel-titanium alloy material can only reach the following level: the maximum size of the non-metallic inclusion is less than 39 μm, and the content is less than 2.8% (including porosity). The nickel-titanium alloy material of the common level can not meet the application requirements of high fatigue requirements, such as a nickel-titanium stent for a heart valve, an ultrafine wire for electric actuation and the like.
Electron beam melting is a special metallurgical technology which is developed in the 50 th of the 20 th century, and has the outstanding advantages that: the working vacuum degree is high, which is very favorable for removing gas, nonmetallic inclusion and metallic impurities. Electron beam melting has been widely used in the melting of refractory metals, superalloys, precision alloys, semiconductor materials and some steel grades having special uses.
However, since nitinol is very sensitive to composition, small fluctuations in nickel content can cause large variations in the transformation temperature. Generally, the phase transition temperature changes by about 10 ℃ per 0.1wt% change in nickel content. Due to the characteristics of high vacuum and high temperature, the electron beam melting has large element volatilization, so that the consistency of components is difficult to maintain.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a preparation method of a high-purity nickel-titanium alloy material, which is simple and can obtain the high-purity nickel-titanium alloy and keep the consistency of components and phase transition temperature.
In order to realize the purpose, the invention is realized by the following technical scheme: a preparation method of a high-purity nickel-titanium alloy material comprises the following steps:
1. selecting high-purity raw materials;
2. preparing a nickel-titanium ingot by adopting a vacuum induction melting process;
3. after dead heads and the surface of the cast ingot are removed and polished, forging the cast ingot into a bar, and polishing the surface of the bar;
4. and smelting the bar into an ingot by adopting an electron beam remelting process to obtain the high-purity nickel-titanium alloy material.
Preferably, the high-purity raw material in the step 1 has an oxygen content of less than 300ppm, a carbon content of less than 100ppm, and a Brinell hardness of less than 87HB; the nickel material is Ni9999.
Preferably, the vacuum induction melting process in the step 2 adopts a calcium oxide crucible as a melting crucible, and the carbon content of the melted nickel-titanium ingot is less than 100ppm.
Preferably, the forging in step 3 is to forge the ingot into a bar by an axial upsetting and radial drawing method.
Preferably, the diameter ratio of the nickel titanium forging rod used in the electron beam remelting of the step 4 to the ingot casting crucible is less than 1:2.
Preferably, in the electron beam remelting process in the step 4, the smelting vacuum is controlled to be less than 1 x 10 -2 Pa; controlling the smelting speed to be less than 10kg/h.
Preferably, the rod used for the electron beam remelting of step 4 is prepared from a single induction melting ingot.
The invention has the following beneficial effects:
1. the method prepares the high-purity nickel-titanium alloy through the process route of vacuum induction melting, forging and electron beam remelting, uses common equipment in the field, and has high process feasibility.
2. The invention selects high-purity raw materials, and can reduce the impurity content in the final finished product to the maximum extent.
3. After the nickel-titanium cast ingot is prepared by adopting the vacuum induction melting process, the nickel and titanium elements are fully alloyed, the components are basically consistent, and the phase change temperature basically meets the design requirement. Furthermore, a calcium oxide crucible is used as a smelting crucible, and the oxygen and carbon content in the smelted nickel-titanium ingot is obviously less than that of a graphite crucible, especially less than 100ppm, so that the method is very beneficial to controlling oxygen and carbon impurity elements in the subsequent electron beam remelting process.
4. The measures for removing the dead head and polishing the surface can eliminate the risk of increasing 6 impurities in the subsequent process. The measure of forging the bar can refine grains, reduce looseness and make the structure more uniform, which is very good for stably realizing the subsequent electron beam remelting process and can well keep the component consistency of the alloy. Furthermore, forging the cast ingot into a bar material by an axial upsetting and radial drawing method; the forging method can eliminate component deviation of the upper part and the lower part of the ingot due to gravity factors, and improve consistency of components and phase transition temperature to the maximum extent.
5. The invention adopts the electron beam process to remelt the nickel-titanium forged rod, and can obtain the nickel-titanium cast ingot with higher purity. Furthermore, the diameter ratio of the nickel titanium forging rod used for the electron beam remelting and the ingot casting crucible is less than 1:2. The shielding effect of the forging rod on electron beams can be reduced by reducing the diameter ratio of the forging rod to the crucible, so that most of the electron beam energy is used for maintaining the temperature of a crucible molten pool and keeping the stirring effect on the molten pool except for a small part of the electron beam energy used for remelting the forging rod. This has an effect of improving the purification effect and the uniformity of the components. Furthermore, during the electron beam remelting process, the melting vacuum is controlled to be less than 1 x 10 -2 Pa. For nitinol alloys, when the melting vacuum value is large, e.g. greater than 1 x 10 -2 When Pa is higher, the titanium element in the alloy is easy to combine with oxygen, so that the oxygen content in the alloy is increased; when the melting vacuum value is small, especially less than 1 to 10 -2 When Pa is needed, the oxide in the alloy begins to decompose, so that the content of the oxide can be effectively reduced, and the purification effect is achieved. Furthermore, in the electron beam remelting process, the smelting speed is controlled to be less than 10kg/h. The smelting speed is low, impurities in the melt can be fully diffused, decomposed and separated out, and alloy purification is facilitated. Further, the rod used for the electron beam remelting is prepared from a single induction melting ingot. The use of more than two ingots is difficult to eliminateThe forged rod prepared by the same induction melting cast ingot is subjected to electron beam remelting, and the obtained cast ingot also has obvious macroscopic difference. This difference can be avoided by using a single ingot rod for electron beam remelting.
6. The invention provides a new way for preparing the high-purity nickel-titanium alloy material, the prepared nickel-titanium alloy material not only has high purity, wherein the maximum size of non-metallic inclusions is less than 10 mu m, the content is less than 0.5 percent, but also has good component uniformity and phase change temperature consistency, the phase change temperature deviation of different parts of the same ingot is less than 3 ℃, and the nickel-titanium alloy material can be used for products such as nickel-titanium stents for heart valves, ultrafine wires for electric drive and the like with high fatigue life application, has good application prospect and has certain economic benefit and social benefit.
Detailed Description
In order to make the technical means, the creation characteristics, the achievement purposes and the effects of the invention easy to understand, the invention is further described with the specific embodiments.
The specific implementation mode adopts the following technical scheme: a preparation method of a high-purity nickel-titanium alloy material comprises the following steps:
1. selecting high-purity raw materials;
2. preparing a nickel-titanium ingot by adopting a vacuum induction melting process;
3. after dead heads and the surface of the cast ingot are removed and polished, forging the cast ingot into a bar, and polishing the surface of the bar;
4. and smelting the bar into an ingot by adopting an electron beam remelting process to obtain the high-purity nickel-titanium alloy material.
The most common way currently used in the art for producing nitinol materials is vacuum induction melting. The smelting crucible adopts a graphite crucible or a calcium oxide crucible. Nickel titanium materials smelted by a graphite crucible generally have an oxygen content of about 200-400ppm and a carbon content of 300-500ppm; nickel titanium material smelted using a calcium oxide crucible typically has an oxygen content of about 250-400ppm and a carbon content of less than 100ppm. The nickel titanium material smelted by the two methods has low purity, the size of the maximum non-metallic inclusion is less than 39 mu m, and the content is less than 2.8 percent (including pores).
In the specific embodiment, high-purity raw materials are adopted, a nickel-titanium ingot is prepared by using a vacuum induction melting process, a dead head and the surface of the ingot are removed, a bar is forged and the surface of the bar is polished, and then the bar is melted into the ingot by using an electron beam remelting process, so that the high-purity nickel-titanium alloy material is obtained. The high-purity nickel-titanium alloy material prepared by the method has the maximum size of non-metallic inclusions smaller than 10 mu m, the content of the non-metallic inclusions smaller than 0.5 percent, good component uniformity and phase change temperature consistency, and the phase change temperature deviation of different parts of the same ingot less than 3 ℃, and can be used for nickel-titanium stents for heart valves, ultrafine wires for electric drive and other products with high fatigue life application.
Example 1: a preparation method of a high-purity nickel-titanium alloy material comprises the following steps:
s1, selecting a high-purity raw material;
s2, preparing a nickel-titanium ingot by adopting a vacuum induction melting process;
s3, removing risers and polishing the surface of the cast ingot, forging the cast ingot into a bar, and polishing the surface of the bar;
and S4, smelting the bar into an ingot by adopting an electron beam remelting process to obtain the high-purity nickel-titanium alloy material.
In this embodiment, in the step S2, the graphite crucible is used as the melting crucible in the vacuum induction melting process. And in the step S3, forging the ingot into a bar by an axial drawing method, wherein the diameter of the bar is 80mm. In the step S4, the diameter of the crucible used for the electron beam remelting is 100mm, and the diameter ratio of the nickel-titanium forging rod to the ingot casting crucible is 1.25. In the step S4, in the electron beam remelting process, the smelting vacuum is controlled to be 1 x 10 -1 Pa. In the step S4, the smelting speed is controlled to be 20kg/h in the electron beam remelting process. In the step S4, the bar material used for the electron beam remelting is two bar materials, and the two bar materials are respectively from two different induction melting cast ingots.
Example 2: this example differs from example 1 in that:
in step S2 of this embodiment, the vacuum induction melting process uses a calcium oxide crucible as a melting crucible.
Example 3: the present example differs from example 2 in that:
and in the step S3, forging the ingot into a bar by using an axial upsetting and radial drawing method, wherein the diameter of the bar is 80mm.
Example 4: the present embodiment differs from embodiment 3 in that:
and in the step S3, forging the ingot into a bar by an axial drawing method, wherein the diameter of the bar is 50mm.
In the step S4, the diameter of the crucible used for the electron beam remelting is 100mm, and the diameter ratio of the nickel titanium forging rod to the ingot casting crucible is 1:2.
Example 5: this example differs from example 4 in that:
in the step S4, in the electron beam remelting process, the smelting vacuum is controlled to be 6 x 10 -3 Pa。
Example 6: this example differs from example 5 in that:
in the step S4, the smelting speed is controlled to be 10kg/h in the electron beam remelting process.
Example 7:
this example differs from example 6 in that:
in the step S4, the rod material used for the electron beam remelting is a single rod material.
The following are inventive examples 1-7:
nickel titanium alloy materials were prepared according to examples 1-7, respectively, and were processed into wire rods of Φ 10 by a forging and rolling process, and the prepared products were the products according to examples 1-7, respectively.
The nickel-titanium alloy material prepared by the vacuum induction melting method (using a calcium oxide crucible) is processed into a wire rod with phi 10 by adopting a forging and rolling process, and the prepared product is used as the product of the comparative example 1.
The products of examples 1 to 7, and comparative example 1 were each subjected to quality inspection.
The oxygen content, the carbon content, the maximum phase transition temperature deviation (for short, phase transition temperature deviation), the maximum size of non-metallic inclusions (for short, maximum inclusion size) and the content of non-metallic inclusions (for short, inclusion content) are respectively detected, and specific results are shown in table 1.
Table 1 table of quality test results
It can be seen from the data in table 1 that the maximum inclusion size and inclusion content of the products of examples 1-7 of the present application are all significantly better than the product of comparative example 1 after remelting by electron beam. Therefore, the electron beam remelting has obvious effect on improving the purity of the alloy.
It can also be seen from the data in table 1 that the maximum inclusion size and inclusion content are significantly reduced in example 2 of the present application relative to example 1. This shows that when the nickel-titanium alloy is vacuum induction smelted by using the calcium oxide crucible, although the oxygen content is slightly increased, the carbon content is obviously reduced, and the effect of improving the purity of the alloy is obvious.
It can be seen from the data in table 1 that the quality data of the products of examples 3 to 7 of the present application are further significantly improved, wherein the quality data of the product of example 7 are the most excellent. Therefore, the method has the advantages that various process parameters designed by the method can effectively reduce the oxygen-carbon content in the alloy, improve the uniformity of alloy components and the consistency of phase change temperature, and improve the purity of the alloy.
The foregoing shows and describes the general principles and broad features of the present invention and advantages thereof. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are described in the specification and illustrated only to illustrate the principle of the present invention, but that various changes and modifications may be made therein without departing from the spirit and scope of the present invention, which fall within the scope of the invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.
Claims (7)
1. A preparation method of a high-purity nickel-titanium alloy material is characterized by comprising the following steps:
(1) Selecting high-purity raw materials;
(2) Preparing nickel-titanium cast ingots by adopting a vacuum induction melting process;
(3) After dead heads of the cast ingots are removed and the surfaces of the cast ingots are polished, forging the cast ingots into bars, and polishing the surfaces of the bars;
(4) And smelting the bar into a cast ingot by adopting an electron beam remelting process to obtain the high-purity nickel-titanium alloy material.
2. The method of claim 1, wherein the high purity raw material of step (1) has an oxygen content of less than 300ppm, a carbon content of less than 100ppm, and a Brinell hardness of less than 87HB; the nickel material is Ni9999.
3. The method for preparing a high-purity nickel titanium alloy material according to claim 1, wherein the vacuum induction melting process in step (2) adopts a calcium oxide crucible as a melting crucible, and the carbon content of the melted nickel titanium ingot is less than 100ppm.
4. A method for preparing high purity nitinol material according to claim 1, wherein the forging in step (3) is performed by forging the ingot into a rod according to an axial upsetting and radial elongation method.
5. The method for preparing high purity nickel titanium alloy material according to claim 1, wherein the ratio of the diameter of the nickel titanium forging rod used in the electron beam remelting of the step (4) to the diameter of the ingot casting crucible is less than 1:2.
6. The method for preparing high purity nickel titanium alloy material according to claim 1, wherein the melting vacuum is controlled to be less than 1 x 10 during the electron beam remelting process in the step (4) -2 Pa, controlling the smelting speed to be less than 10kg/h.
7. The method of claim 1, wherein the rod material used in the step (4) of electron beam remelting is prepared from a single induction melting ingot.
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Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20120039740A1 (en) * | 2010-08-12 | 2012-02-16 | Ati Properties, Inc. | Processing of nickel-titanium alloys |
| US20140261912A1 (en) * | 2013-03-15 | 2014-09-18 | Ati Properties, Inc. | Thermo-mechanical processing of nickel-titanium alloys |
| CN111254318A (en) * | 2020-03-12 | 2020-06-09 | 西安华创新材料有限公司 | Fine smelting and purifying method for large-size nickel-titanium shape memory alloy cast ingot |
| CN111961897A (en) * | 2020-09-14 | 2020-11-20 | 大连理工大学 | Method for preparing high-purity nickel-based high-temperature alloy by vacuum induction melting-casting-electron beam refining process |
| CN114934205A (en) * | 2022-05-24 | 2022-08-23 | 西北工业大学 | Smelting method for high-purity nickel-based high-temperature alloy |
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- 2023-03-14 CN CN202310237560.8A patent/CN115896502A/en active Pending
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20120039740A1 (en) * | 2010-08-12 | 2012-02-16 | Ati Properties, Inc. | Processing of nickel-titanium alloys |
| US20140261912A1 (en) * | 2013-03-15 | 2014-09-18 | Ati Properties, Inc. | Thermo-mechanical processing of nickel-titanium alloys |
| CN111254318A (en) * | 2020-03-12 | 2020-06-09 | 西安华创新材料有限公司 | Fine smelting and purifying method for large-size nickel-titanium shape memory alloy cast ingot |
| CN111961897A (en) * | 2020-09-14 | 2020-11-20 | 大连理工大学 | Method for preparing high-purity nickel-based high-temperature alloy by vacuum induction melting-casting-electron beam refining process |
| CN114934205A (en) * | 2022-05-24 | 2022-08-23 | 西北工业大学 | Smelting method for high-purity nickel-based high-temperature alloy |
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