A method for preparing a titanium-nickel pipe joint alloy

Abstract

The application discloses a preparation method of a titanium-nickel pipe joint alloy, and comprises the following steps: step one, pressing raw materials into electrodes; step two, vacuum medium-frequency induction smelting and vacuum consumable arc smelting; step three, homogenization treatment; step four, cutting off risers; step five, forging treatment; step six, checking and grinding the forged blanks; step seven, solid solution, rolling and straightening treatment. The preparation method of the application reduces the probability of defects, such as overheat, unevenness, cavities and cracks, of the titanium-nickel pipe joint alloy in the forging process by adopting twice smelting combined with homogenization treatment and temperature monitoring in the whole forging process of the alloy ingot, controls the uniformity of the structure and performance of the titanium-nickel pipe joint alloy, effectively improves the mechanical properties of the titanium-nickel pipe joint alloy, and can be applied to hydraulic pipelines with high connection strength requirements in high-pressure environments.

Description

Technical Field

[0001] This invention belongs to the field of shape memory alloy preparation technology, and in particular relates to a method for preparing a titanium-nickel pipe joint alloy. Background Technology

[0002] Currently, shape memory alloy (MME) pipe fittings are widely used in hydraulic and pneumatic systems of aerospace, aviation, and oil pipelines. Compared to traditional welding, bonding, and mechanical threaded connections, MME pipe fittings are widely used due to their stable and easily controllable martensitic phase transformation point, excellent mechanical properties, good corrosion resistance, and large shape memory effect. Currently, most MME pipe fittings are manufactured using TiNiFe alloys. However, existing technologies for manufacturing TiNiFe alloys are prone to undesirable microstructures and metallurgical defects. Forging processes can easily result in overheating, uneven microstructure, voids, and cracks, severely affecting the mechanical properties of the finished MME pipe fittings and making them unsuitable for use in hydraulic pipelines requiring high connection strength and operating under high pressure, such as aircraft fuel lines. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for preparing titanium-nickel pipe fitting alloys. This method, through secondary melting combined with homogenization treatment and temperature monitoring throughout the alloy ingot forging process, reduces the probability of defects such as overheating, inhomogeneity, voids, and cracks in the titanium-nickel pipe fitting alloy during forging. This controls the uniformity of the microstructure and properties of the titanium-nickel pipe fitting alloy, effectively improving its mechanical properties. It solves the problems of microstructure and metallurgical defects in TiNiFe alloys prepared by existing technologies, resulting in poor mechanical properties of shape memory alloy pipe fittings that cannot be used in hydraulic pipelines with high connection strength requirements and high-pressure environments.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is: a method for preparing a titanium-nickel pipe joint alloy, characterized in that the method includes the following steps:

[0005] Step 1: Using grade 0 small-particle sponge titanium, grade 1 electrolytic nickel, intermediate alloy TiFe and iron as raw materials, weigh them according to the ratio and put them into a mold. Use a press to press the raw materials in the mold into tightly bonded strips, and then weld the electrode rod to obtain the electrode.

[0006] Step 2: The electrodes obtained in Step 1 are subjected to vacuum medium-frequency induction melting and vacuum consumable arc melting in sequence to obtain alloy ingots.

[0007] Step 3: Place the alloy ingot obtained in Step 2 into a furnace for homogenization treatment;

[0008] Step 4: Remove the risers at both ends of the alloy ingot after the homogenization treatment in Step 3;

[0009] Step 5: After heating and holding the alloy ingot with the riser removed in Step 4, forge it. Monitor the temperature of the alloy ingot throughout the forging process. Whenever the temperature of the alloy ingot drops, reheat and hold the alloy ingot again and continue forging until the forging is completed and a forging billet is obtained.

[0010] Step 6: Inspect and grind the forged billet completed in Step 5 to obtain a forged billet without forging defects;

[0011] Step 7: The forging billet without forging defects from Step 6 is subjected to solution treatment, heating and holding followed by rolling, and heating and holding followed by straightening to obtain the titanium-nickel pipe joint alloy.

[0012] This invention reduces the probability of structural defects in titanium-nickel pipe joint alloys by removing risers from both ends of the alloy ingot, which are lower in the middle and higher around the edges. By inspecting the forged billet for forging defects such as folds and cracks, and grinding the detected defects, the invention ensures that the forged billet is free of forging defects visible to the naked eye.

[0013] The above-mentioned method for preparing a titanium-nickel pipe joint alloy is characterized in that, in step one, the particle size of the grade 0 small-particle sponge titanium is not greater than 12.5 mm, the mass percentage content of titanium in the grade 0 small-particle sponge titanium is not less than 99.7%, the mass percentage content of nickel in the grade 1 electrolytic nickel is not less than 99.7%, and the mass percentage content of iron in the iron is not less than 99.9%.

[0014] The above-mentioned method for preparing a titanium-nickel pipe fitting alloy is characterized in that the press in step one is a 500-ton powder product hydraulic press.

[0015] This invention uses a 500-ton powder product hydraulic press to compress granular metal and powder metal into a dense state, ensuring that each metal component is not lost and guaranteeing that the alloy element composition is up to standard.

[0016] The above-mentioned method for preparing a titanium-nickel pipe joint alloy is characterized in that the vacuum induction melting in step two is carried out in a medium-frequency vacuum induction furnace, and the medium-frequency vacuum induction furnace uses a graphite crucible melting electrode.

[0017] This invention utilizes a graphite crucible in a medium-frequency vacuum induction furnace, enabling induction stirring, which ensures thorough electrode melting and uniform composition, effectively improving the mechanical properties of titanium-nickel pipe joint alloys.

[0018] The preparation method of the above-mentioned titanium-nickel pipe joint alloy is characterized in that the homogenization treatment in step three is carried out by heating to 800℃~930℃ in a box-type resistance furnace and holding for 5h~6h.

[0019] The above-mentioned method for preparing a titanium-nickel pipe joint alloy is characterized in that the forging in step five is carried out using a 1600-ton forging press, the heating temperature is 750℃~900℃, the holding time is 40min~90min, and the temperature drop is not greater than 10℃.

[0020] This invention employs a 1600-ton forging press for forging, enabling the forging deformation to reach the core of the alloy ingot. By using appropriate forging force and deformation rate, voids and cracks can be avoided, resulting in a uniform microstructure and good grain consistency in the forging. The temperature is strictly controlled during the heat treatment before forging to prevent overheating of the microstructure.

[0021] The preparation method of the above-mentioned titanium-nickel pipe joint alloy is characterized in that the solution treatment in step six is ​​as follows: heating to 850℃~1050℃ and holding for 2h~3h; the rolling treatment is carried out using a transverse universal pass bar mill, with a heating temperature of 750℃~900℃ and a holding time of 40min~90min; the straightening treatment is carried out using a two-roll straightener, with a heating temperature of 600℃~700℃ and a holding time of 20min~60min.

[0022] The preparation method of the above-mentioned titanium-nickel pipe fitting alloy is characterized in that the titanium-nickel pipe fitting alloy is composed of the following components in mass percentage: Ni 46.35%~47.35%, Fe 2.65%~3.65%, C not more than 0.06%, O not more than 0.07%, H not more than 0.01%, N not more than 0.05%, Si not more than 0.05%, C+O not more than 0.12%, and the balance is Ti.

[0023] Compared with the prior art, the present invention has the following advantages:

[0024] 1. This invention reduces the probability of defects such as overheating, unevenness, voids and cracks in the titanium-nickel pipe joint alloy during the forging process by adopting secondary melting combined with homogenization treatment and temperature monitoring throughout the alloy ingot forging process. This controls the uniformity of the microstructure and properties of the titanium-nickel pipe joint alloy and effectively improves its mechanical properties.

[0025] 2. This invention achieves precise temperature control throughout the entire preparation process of titanium-nickel pipe joint alloys, combined with forging using a large-tonnage forging press. Simultaneously, it strictly controls the heat treatment temperature of each process during preparation to prevent overheating, resulting in a titanium-nickel pipe joint alloy with uniform microstructure and good grain consistency, effectively improving the quality stability of the titanium-nickel pipe joint alloy.

[0026] 3. The titanium-nickel pipe joint alloy prepared by this invention, through machining, produces a shape memory alloy pipe joint, which significantly improves the connection strength between the joint and the connecting pipeline.

[0027] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0028] Figure 1 This is a magnified micrograph of the as-cast alloy ingot after homogenization treatment in Example 1 of the present invention, magnified 50 times.

[0029] Figure 2 This is a magnified 100x micrograph of the as-cast state of the alloy ingot after homogenization treatment in Example 1 of the present invention.

[0030] Figure 3 This is a magnified metallographic image of the titanium-nickel pipe joint alloy prepared in Example 1 of the present invention, magnified 20 times. Detailed Implementation

[0031] Example 1

[0032] This embodiment includes the following steps:

[0033] Step 1: Using grade 0 small-particle sponge titanium with a particle size of 12.5mm and a titanium content of 99.7% by mass, grade 1 electrolytic nickel with a nickel content of 99.7% by mass, TiFe intermediate alloy, and iron with a iron content of 99.9% by mass as raw materials, weigh them according to the ratio and put them into a mold. Use a 500-ton powder product hydraulic press to press the raw materials in the mold into strips, and then weld electrode rods to obtain electrodes.

[0034] Step 2: Place the electrode obtained in Step 1 into a medium-frequency vacuum induction furnace with a graphite crucible for vacuum medium-frequency induction melting, and then perform vacuum consumable arc melting to obtain an alloy ingot.

[0035] Step 3: Place the alloy ingot obtained in Step 2 into a box-type resistance furnace and heat it to 850℃ and hold it for 6 hours to complete the homogenization process.

[0036] Step 4: Remove the risers at both ends of the alloy ingot after the homogenization treatment in Step 3;

[0037] Step 5: After heating the alloy ingot with the riser removed in Step 4 to 900℃ and holding it for 90 minutes, forge it using a 1600-ton forging press. Monitor the temperature of the alloy ingot throughout the forging process. Whenever the temperature of the alloy ingot drops to 890℃, reheat the alloy ingot to 900℃, hold it for 90 minutes, and continue forging until the forging is completed and a forging billet is obtained.

[0038] Step 6: Inspect and grind the forging billet obtained in Step 5 to obtain a forging billet without forging defects;

[0039] Step 7: Heat the forging billet without forging defects from Step 6 to 1050℃ and hold for 3 hours, then cool it to 820℃ and hold for 90 minutes. Roll it using a transverse universal pass bar mill, then heat it to 700℃ and hold for 60 minutes. Straighten it using a two-roll straightener to obtain the titanium-nickel pipe joint alloy. The titanium-nickel pipe joint alloy is composed of the following components by mass percentage: Ni 46.35%, Fe 3.65%, C 0.06%, O 0.06%, H 0.01%, N 0.05%, Si 0.05%, C+O 0.12%, with the balance being Ti.

[0040] The titanium-nickel pipe joint alloy prepared in this embodiment was subjected to tensile stress-strain testing using an MTS2880 universal testing machine. A standard tensile specimen with a length of 70 mm was used, and the tensile strength R at room temperature was measured at a displacement rate of 0.15 mm / min. m The yield strength is 865 MPa, and the yield strength R is... p0.2 It has a strength of 560 MPa and an elongation at break (A) of 31%.

[0041] The titanium-nickel pipe fitting alloy prepared in this embodiment was used to make an alloy fitting, which was then connected to a TA18 titanium alloy connecting pipe. The connection strength was measured to be 10452N.

[0042] Figure 1 This is a magnified 50x as-cast micrograph of the alloy ingot after homogenization treatment in this embodiment. Figure 2 This is a magnified 100x as-cast micrograph of the alloy ingot after homogenization treatment in this embodiment, as shown below. Figure 1 and Figure 2 As shown, after vacuum medium-frequency induction melting, vacuum consumable arc melting and homogenization treatment, the as-cast microstructure of the alloy ingot was improved and the uniformity of the structure was effectively enhanced.

[0043] Figure 3 Here is a magnified metallographic image of the titanium-nickel pipe joint alloy prepared in this embodiment, magnified 20 times. Figure 3 As shown, the titanium-nickel pipe joint alloy, after forging, rolling and straightening, effectively refines the internal grains and has good grain uniformity.

[0044] In summary, the titanium-nickel pipe joint alloy prepared in this embodiment has refined internal grains after each processing step, resulting in excellent mechanical and working properties.

[0045] Example 2

[0046] This embodiment includes the following steps:

[0047] Step 1: Using grade 0 small-particle sponge titanium with a particle size of 12.0 mm and a titanium content of 99.7% by mass, grade 1 electrolytic nickel with a nickel content of 99.7% by mass, TiFe intermediate alloy, and iron with a iron content of 99.9% by mass as raw materials, weigh them according to the ratio and put them into a mold. Use a 500-ton powder product hydraulic press to press the raw materials in the mold into strips, and then weld electrode rods to obtain the electrode.

[0048] Step 2: Place the electrode obtained in Step 1 into a medium-frequency vacuum induction furnace with a graphite crucible for vacuum medium-frequency induction melting, and then perform vacuum consumable arc melting to obtain an alloy ingot.

[0049] Step 3: Place the alloy ingot obtained in Step 2 into a box-type resistance furnace and heat it to 800℃ and hold it for 5.5 hours to complete the homogenization process.

[0050] Step 4: Remove the risers at both ends of the alloy ingot after the homogenization treatment in Step 3;

[0051] Step 5: After heating the alloy ingot with the riser removed in Step 4 to 850℃ and holding it for 60 minutes, forge it using a 1600-ton forging press. Monitor the temperature of the alloy ingot throughout the forging process. Whenever the temperature of the alloy ingot drops to 840℃, reheat the alloy ingot to 850℃, hold it for 60 minutes, and continue forging until the forging is completed and a forging billet is obtained.

[0052] Step 6: Inspect and grind the forging billet obtained in Step 5 to obtain a forging billet without forging defects;

[0053] Step 7: Heat the forging billet without forging defects from Step 6 to 850℃ and hold for 2 hours, then cool it to 750℃ and hold for 40 minutes. Roll it using a transverse universal pass bar mill, then heat it to 650℃ and hold for 40 minutes. Straighten it using a two-roll straightener to obtain the titanium-nickel pipe joint alloy. The titanium-nickel pipe joint alloy is composed of the following components by mass percentage: Ni 47.35%, Fe 2.65%, C 0.06%, O 0.06%, H 0.01%, N 0.05%, Si 0.05%, C+O 0.12%, with the balance being Ti.

[0054] The titanium-nickel pipe joint alloy prepared in this embodiment was subjected to tensile stress-strain testing using an MTS2880 universal testing machine. A standard tensile specimen with a length of 70 mm was used, and the tensile strength R at room temperature was measured at a displacement rate of 0.15 mm / min. m The yield strength is 712 MPa, and the yield strength R is... p0.2 It has a strength of 420 MPa and an elongation at break (A) of 25%.

[0055] The titanium-nickel pipe fitting alloy prepared in this embodiment was used to make an alloy fitting, which was then connected to a TA18 titanium alloy connecting pipe. The connection strength was measured to be 9124N.

[0056] Example 3

[0057] This embodiment includes the following steps:

[0058] Step 1: Using grade 0 small-particle sponge titanium with a particle size of 12.5mm and a titanium content of 99.7% by mass, grade 1 electrolytic nickel with a nickel content of 99.7% by mass, TiFe intermediate alloy, and iron with a iron content of 99.9% by mass as raw materials, weigh them according to the ratio and put them into a mold. Use a 500-ton powder product hydraulic press to press the raw materials in the mold into strips, and then weld electrode rods to obtain electrodes.

[0059] Step 2: Place the electrode obtained in Step 1 into a medium-frequency vacuum induction furnace with a graphite crucible for vacuum medium-frequency induction melting, and then perform vacuum consumable arc melting to obtain an alloy ingot.

[0060] Step 3: Place the alloy ingot obtained in Step 2 into a box-type resistance furnace and heat it to 930℃ and hold it for 5 hours to complete the homogenization process.

[0061] Step 4: Remove the risers at both ends of the alloy ingot after the homogenization treatment in Step 3;

[0062] Step 5: After heating the alloy ingot with the riser removed in Step 4 to 750℃ and holding it for 40 minutes, forge it using a 1600-ton forging press. Monitor the temperature of the alloy ingot throughout the forging process. Whenever the temperature of the alloy ingot drops to 740℃, reheat the alloy ingot to 750℃, hold it for 40 minutes, and continue forging until the forging is completed and a forging billet is obtained.

[0063] Step 6: Inspect and grind the forging billet obtained in Step 5 to obtain a forging billet without forging defects;

[0064] Step 7: Heat the forging billet without forging defects from Step 6 to 1000℃ and hold for 2.5 hours. Then, cool it to 900℃ and hold for 50 minutes. Roll it using a transverse universal pass bar mill. Heat it to 600℃ and hold for 20 minutes. Then, straighten it using a two-roll straightener to obtain the titanium-nickel pipe joint alloy. The titanium-nickel pipe joint alloy is composed of the following components by mass percentage: Ni 46.85%, Fe 3.15%, C 0.06%, O 0.06%, H 0.01%, N 0.05%, Si 0.05%, C+O 0.12%, with the balance being Ti.

[0065] The titanium-nickel pipe joint alloy prepared in this embodiment was subjected to tensile stress-strain testing using an MTS2880 universal testing machine. A standard tensile specimen with a length of 70 mm was used, and the tensile strength R at room temperature was measured at a displacement rate of 0.15 mm / min. m The yield strength is 743 MPa, and the yield strength R is... p0.2 The strength is 489 MPa, and the elongation after fracture (A) is 26%.

[0066] The titanium-nickel pipe joint alloy prepared in this embodiment was used to make an alloy joint, which was then connected to a TA18 titanium alloy connecting pipe. The connection strength was measured to be 9521N.

[0067] The above description is merely a preferred embodiment of the present invention and does not constitute any limitation on the present invention. Any simple modifications, alterations, or equivalent structural transformations made to the above embodiments based on the technical essence of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for preparing a titanium-nickel pipe fitting alloy, characterized in that, The method includes the following steps: Step 1: Using grade 0 small-particle sponge titanium, grade 1 electrolytic nickel, intermediate alloy TiFe, and iron as raw materials, weigh them according to the ratio and place them in a mold. Use a press to press the raw materials in the mold into tightly bonded strips, and then weld electrode rods to obtain the electrode. The titanium-nickel pipe joint alloy is composed of the following components by mass percentage: Ni 46.35%~47.35%, Fe 2.65%~3.65%, C not more than 0.06%, O not more than 0.07%, H not more than 0.01%, N not more than 0.05%, Si not more than 0.05%, C+O not more than 0.12%, with the balance being Ti. Step 2: The electrodes obtained in Step 1 are subjected to vacuum medium-frequency induction melting and vacuum consumable arc melting in sequence to obtain alloy ingots. Step 3: Place the alloy ingot obtained in Step 2 into a furnace for homogenization treatment; Step 4: Remove the risers at both ends of the alloy ingot after the homogenization treatment in Step 3; Step 5: After heating and holding the alloy ingot with the riser removed in Step 4, forge it. The temperature of the alloy ingot is monitored throughout the forging process. Whenever the temperature of the alloy ingot drops, the alloy ingot is reheated and held at the same temperature and forging is continued until the forging is completed and a forging billet is obtained. The forging is carried out using a 1600-ton forging press. The heating temperature is 750℃~900℃, the holding time is 40min~90min, and the temperature drop is no more than 10℃. Step 6: Inspect and grind the forged billet completed in Step 5 to obtain a forged billet without forging defects; Step 7: The forging billet without forging defects from Step 6 is subjected to solution treatment, heating and holding followed by rolling, and heating and holding followed by straightening to obtain the titanium-nickel pipe joint alloy. The solution treatment process is as follows: heating to 850℃~1050℃ and holding for 2h~3h; the rolling process is carried out using a transverse universal pass bar mill, with a heating temperature of 750℃~900℃ and a holding time of 40min~90min; the straightening process is carried out using a two-roll straightener, with a heating temperature of 600℃~700℃ and a holding time of 20min~60min.

2. The method for preparing a titanium-nickel pipe joint alloy according to claim 1, characterized in that, In step one, the particle size of the grade 0 small-particle sponge titanium is no greater than 12.5 mm, the mass percentage of titanium in the grade 0 small-particle sponge titanium is no less than 99.7%, the mass percentage of nickel in the grade 1 electrolytic nickel is no less than 99.7%, and the mass percentage of iron in the iron is no less than 99.9%.

3. The method for preparing a titanium-nickel pipe joint alloy according to claim 1, characterized in that, The press mentioned in step one is a 500-ton powder product hydraulic press.

4. The method for preparing a titanium-nickel pipe joint alloy according to claim 1, characterized in that, The vacuum induction melting described in step two is carried out in a medium-frequency vacuum induction furnace, which uses a graphite crucible melting electrode.

5. The method for preparing a titanium-nickel pipe joint alloy according to claim 1, characterized in that, The homogenization process described in step three involves heating the material in a box-type resistance furnace to 800℃~930℃ and holding it there for 5h~6h.

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