Preparation method of super-long W-Ni-Fe alloy bar

Abstract

The invention relates to the technical field of powder metallurgy and welding, in particular to a preparation method of an ultra-long W-Ni-Fe alloy bar. The method comprises the following steps: converting an ultra-long W-Ni-Fe bar billet into a plurality of small W-Ni-Fe alloy sintered bar billets with the same diameter and the same components, machining and cleaning the end surfaces of the sintered bar billets, spraying Ni-Fe coatings on the end surfaces of the sintered bar billets, and then performing high-temperature hydrogen reduction deoxidation, rotary friction welding and final vacuum heat treatment, thereby obtaining the W-Ni-Fe alloy bar billets. And the preparation of the W-Ni-Fe alloy bar with the ultra-long specification is realized. According to the super-long-specification W-Ni-Fe alloy bar prepared through the method, the tensile strength of the weld joint part and the edge part can reach 91% or above of that of a parent material, and the tensile strength of the core part can reach 85% or above of that of the parent material. The method can also be used for welding tungsten-nickel-iron alloy bar billets of different brands.

Description

Technical Field

[0001] This invention relates to the fields of powder metallurgy and welding technology, specifically to a method for preparing ultra-long W-Ni-Fe alloy rods. Background Technology

[0002] W-Ni-Fe high-density tungsten alloys possess numerous superior characteristics, such as high density, high strength, high toughness, low coefficient of thermal expansion, and strong radiation absorption, making them widely used in military, aerospace, and machinery industries. With the development of industry and the military, the specifications of required W-Ni-Fe rods have also changed significantly. Due to the increasing weight of modern military missile core materials, the required length of W-Ni-Fe alloy rods has gradually increased. Therefore, the demand for ultra-long W-Ni-Fe alloy rods with a length ≥600mm is becoming increasingly apparent.

[0003] Existing methods for preparing ultra-long tungsten-nickel-iron rods mainly involve: using a large-size sintering furnace with a long constant-temperature zone to prepare long W-Ni-Fe sintered billets via powder metallurgy; or directly sintering large-diameter W-Ni-Fe billets and then using multi-pass deformation forging to obtain ultra-long tungsten alloy rods. Both of these methods require large-scale equipment to prepare long or large-diameter W-Ni-Fe alloy billets. However, since W-Ni-Fe sintering is a typical liquid-phase sintering process, large billets are prone to collapse and deformation under their own gravity during sintering, increasing the risk of subsequent ultra-long W-Ni-Fe rod preparation. Summary of the Invention

[0004] To address the challenges of high equipment requirements and complex control of the liquid-phase sintering process in the traditional powder metallurgy sintering method for directly preparing ultra-long W-Ni-Fe rods, this invention provides a method for preparing ultra-long W-Ni-Fe alloy rods via rotary friction welding. This invention transforms ultra-long W-Ni-Fe rods into several smaller W-Ni-Fe alloy billets of the same diameter and composition. The end faces of the billets are then machined, cleaned, and coated with a Ni-Fe coating. Following high-temperature hydrogen reduction deoxidation, rotary friction welding, and final vacuum heat treatment, the ultra-long W-Ni-Fe alloy rods are successfully prepared.

[0005] The present invention is specifically implemented through the following technical solutions.

[0006] This invention provides a method for preparing ultra-long W-Ni-Fe alloy rods, comprising the following steps: According to the length requirements of the target ultra-long W-Ni-Fe alloy rod (length ≥ 600 mm), several small W-Ni-Fe alloy rod blanks with a length of 300 mm to 500 mm were prepared.

[0007] After machining the small-sized W-Ni-Fe alloy billet to a flattened end and cleaning it, a Ni-Fe coating is sprayed onto the end face of the billet to be welded.

[0008] Under a reducing atmosphere, the billet coated with Ni-Fe is subjected to reduction deoxidation; then, under an inert atmosphere, the billet to be welded is subjected to rotational friction welding. During the welding process, the particles on the end face to be welded undergo solid solution and rearrangement under the action of the Ni-Fe coating. Afterward, the welded W-Ni-Fe alloy rod is subjected to vacuum heat treatment, which can significantly improve the mechanical properties of the weld, thus producing ultra-long W-Ni-Fe alloy rods.

[0009] Preferably, based on the grade and specifications of the target ultra-long W-Ni-Fe alloy rod, maintaining consistent composition and diameter, it is divided into several smaller rod blanks with lengths ranging from 300mm to 500mm along the length direction. According to the composition of the target W-Ni-Fe alloy rod, corresponding W, Ni, and Fe powders are weighed and subjected to mixing, pressing, pre-sintering, and sintering processes using conventional powder metallurgy sintering methods to prepare several smaller W-Ni-Fe alloy rod blanks. The sum of the lengths of all smaller W-Ni-Fe alloy rod blanks is greater than the length of the target ultra-long W-Ni-Fe alloy rod; the excess length is used to compensate for length losses during machining and welding. The diameter of the smaller W-Ni-Fe alloy rod blanks is the same as the diameter of the target ultra-long W-Ni-Fe alloy rod, and the composition of each smaller W-Ni-Fe alloy rod blank is the same as that of the target ultra-long W-Ni-Fe alloy rod. In practice, the target ultra-long W-Ni-Fe alloy rod can be split into 2, 3, or more smaller W-Ni-Fe alloy billets, depending on its length. The process involves using W, Ni, and Fe powders as initial raw materials, and following the required W-Ni-Fe alloy grade for batching, mixing, cold isostatic pressing, pre-sintering, and sintering. The sintering process produces smaller W-Ni-Fe alloy billets with the same diameter as the final target rod. After obtaining several smaller sintered W-Ni-Fe alloy billets, their ends are machined to ensure a smooth and flat surface. The machined ends are then immersed in acetone or alcohol for 10-15 minutes, cleaned, and dried at a low temperature. Finally, a Ni-Fe coating is applied to the machined ends of the smaller W-Ni-Fe billets.

[0010] Preferably, in the Ni-Fe coating, the Ni to Fe ratio is the same as that in the target ultra-long W-Ni-Fe bar, and the coating thickness is 3μm~10μm. It should be noted that the Ni and Fe elements are uniformly distributed in the Ni-Fe coating.

[0011] Preferably, during reduction deoxygenation, the reducing atmosphere is hydrogen, the reduction temperature is 700℃~900℃, and the reduction time is 2h~4h.

[0012] Preferably, during the first welding operation of rotary friction welding, the specific steps include: A small-diameter W-Ni-Fe alloy billet is used as the clamping and fixing end, and another W-Ni-Fe billet is used as the working feed rotating end. Under the protection of an inert atmosphere, they slowly approach each other and briefly come into contact with each other, causing the end face of the workpiece to gradually heat up. Then they are quickly separated to a position 3mm apart. The spindle drives the rotating working feed end to rotate at high speed, with a speed of 1200r / min~2300r / min. At the same time, it comes into contact with the welding surface of the tungsten nickel iron billet at the clamping and fixing end. The friction pressure is 25MPa~38MPa, the upsetting pressure is 170MPa~210MPa, the upsetting time is 5s~10s, the friction feed speed is 2.5mm / s~4.0mm / s, and the upsetting speed is 23mm / s~30mm / s.

[0013] When a single weld cannot achieve the target length of the W-Ni-Fe alloy billet, the W-Ni-Fe alloy billet after the first weld is used as the clamping and fixing end, and another W-Ni-Fe alloy billet is used as the feed and rotating end, and then welded again in the same way. That is, according to the length requirements of the final product, multiple welds can be performed to achieve the preparation of ultra-long W-Ni-Fe alloy rods.

[0014] Preferably, during vacuum heat treatment, the temperature is 700℃~1000℃ and the holding time is 2h~4h.

[0015] The ultra-long W-Ni-Fe alloy rods prepared by this invention have a length ranging from 600 mm to 2000 mm.

[0016] Compared with the prior art, the present invention has the following beneficial effects: This invention transforms ultra-long W-Ni-Fe alloy rods into several smaller W-Ni-Fe alloy billets of the same diameter and composition. Specifically, using W-Ni-Fe alloy billets of conventional length (300mm-500mm) as raw materials, the end faces of the sintered billets undergo simple machining, cleaning, and Ni-Fe coating spraying. Then, high-temperature hydrogen reduction deoxidation, rotary friction welding, and final vacuum heat treatment are performed to achieve the preparation of ultra-long W-Ni-Fe alloy rods. This invention overcomes the limitations of conventional rotary friction welding, which directly welds the W-Ni-Fe billets without special treatment, resulting in welded rods with significantly lower mechanical properties at the weld seam compared to the base material, greatly restricting their application. In this invention, after machining, a Ni-Fe coating of a certain thickness is sprayed. During high-speed rotary friction welding, the tungsten particles in both sections undergo solid solution treatment and rearrangement, equivalent to a short-term secondary sintering at the weld seam. Combined with appropriate heat treatment processes, the mechanical properties at the weld seam can be significantly improved. Furthermore, the linear velocity and energy are greater closer to the edge during rotation, while the core has relatively lower energy. Therefore, at the weld joint, the tensile strength of the edge can reach over 91% of the base material, and the tensile strength of the core can reach over 85% of the base material. This invention can also be used for welding tungsten-nickel-iron alloy billets of different grades.

[0017] Compared with traditional powder metallurgy sintering methods, this invention does not require large equipment and avoids the problem of large billets collapsing and deforming due to their own gravity during liquid phase sintering. The method of this invention is simple and has successfully prepared ultra-long W-Ni-Fe alloy rods. The prepared rods have excellent mechanical properties and can meet application requirements. Therefore, the method of this invention is suitable for the mass production of ultra-long W-Ni-Fe alloy rods. Attached Figure Description

[0018] Figure 1 The image shows the microstructure of the weld seam of the ultra-long W-Ni-Fe alloy bar prepared in Example 2 at a scale of 100 μm.

[0019] Figure 2 Microscopic morphology of the weld seam of the ultra-long W-Ni-Fe alloy bar prepared for Comparative Example 1 at the 100 μm scale. Detailed Implementation

[0020] To enable those skilled in the art to better understand and implement the technical solutions of the present invention, the present invention will be further described below with reference to specific embodiments and accompanying drawings. However, the embodiments described are not intended to limit the present invention. Unless otherwise specified, the experimental methods and detection methods described in the following embodiments are conventional methods; unless otherwise specified, the reagents and materials described are commercially available.

[0021] A method for preparing ultra-long W-Ni-Fe alloy rods includes the following steps: Step 1, prepare small-sized sintered rod blanks: Based on the dimensions and composition of the target ultra-long W-Ni-Fe alloy rod, the required raw material W, Ni, and Fe powders are mixed, cold isostatically pressed into rod blanks, pre-sintered, and sintered to produce several small-sized W-Ni-Fe alloy sintered rod blanks with the same diameter as the target alloy and a length of 300mm to 500mm. Considering the subsequent machining and welding processes, the sum of the lengths of all small-sized W-Ni-Fe alloy rod blanks should be greater than the length of the target alloy rod.

[0022] It should be noted that, according to the composition of the target W-Ni-Fe alloy rod to be prepared, this invention selects the appropriate grade of W-Ni-Fe alloy rod and weighs the W powder, Ni powder, Fe powder, and other doping materials accordingly. For example, the W-Ni-Fe system high-density tungsten alloy rods targeted by this invention include, but are not limited to, grades 90W-7Ni-3Fe, 93W-4.9Ni-2.1Fe, and 95W-3.5Ni-1.5Fe. It should also be noted that the method for preparing small-sized W-Ni-Fe alloy rod blanks in this invention is a conventional powder metallurgy sintering method. When preparing ultra-long W-Ni-Fe alloy rods, the small-sized W-Ni-Fe alloy rod blanks can directly use existing rod blanks or can be prepared again from raw material powders. It is only necessary to ensure that the composition and diameter of the sintered small-sized W-Ni-Fe alloy rod blank are consistent with the target ultra-long W-Ni-Fe alloy rod, and the length is 300mm~500mm.

[0023] Step 2, end face machining and cleaning: It should be noted that, in order to ensure that the W-Ni-Fe alloy rods prepared after rotary friction welding have good straightness and weld strength, the end faces of the sintered small-sized W-Ni-Fe alloy rod blanks are flattened and exposed to light to make each end face flat and smooth. Then, acetone and alcohol are used to clean the machined end faces to effectively remove impurities introduced during the machining process.

[0024] Step 3, Spray Ni-Fe coating: It should be noted that, in order to effectively improve the mechanical properties of the weld, the present invention performs Ni-Fe element spraying on the end face to be welded, and the Ni / Fe ratio is consistent with the Ni / Fe ratio in the target W-Ni-Fe rod, and the spraying thickness only needs to be 3μm~10μm.

[0025] Step 4, High-temperature hydrogen reduction: It should be noted that, in order to further improve the purity and performance of the welding interface, the present invention performs high-temperature reduction deoxidation on small-sized W-Ni-Fe rod blanks coated with Ni-Fe coating under a hydrogen atmosphere, effectively removing oxygen elements and other impurity elements introduced during the spraying process. The reduction temperature of this high-temperature reduction process is 700℃~900℃, and the reduction time is 2h~4h. Step 5, Rotary Friction Welding: A small W-Ni-Fe alloy billet is used as the clamping and fixing end, and another W-Ni-Fe alloy billet is used as the working feed rotating end. After slowly approaching each other and briefly contacting and rubbing, the end face of the workpiece gradually heats up. Then, they are quickly separated to a position 3mm apart. The spindle drives the rotating working feed end to rotate at high speed, with a speed of 1200~2300 r / min. At the same time, it contacts the welding surface of the tungsten nickel iron rod at the clamping and fixing end. The friction pressure is 25~38MPa, the upsetting pressure is 170~210MPa, the upsetting time is 5~10s, the friction feed speed is 2.5~4.0mm / s, and the upsetting speed is 23~30mm / s. It should be noted that by maintaining an inert atmosphere at the welding interface during the welding process, the welding end face is in an inert atmosphere throughout the entire welding process, effectively isolating air and reducing the performance degradation of the interface due to oxygen content.

[0026] If the first weld fails to achieve the required length of the target extra-long W-Ni-Fe alloy bar, the W-Ni-Fe alloy bar blank after the first weld is used as the clamping and fixing end, and another small-sized W-Ni-Fe alloy bar blank is used as the working and rotating end. Welding is repeated in the same way. After multiple consecutive welds, the required length of the target extra-long W-Ni-Fe alloy bar is achieved.

[0027] Step 6, Vacuum heat treatment: The welded ultra-long W-Ni-Fe rod blanks were subjected to vacuum heat treatment at a temperature of 700℃~1000℃ for 2h~4h.

[0028] It should be noted that the present invention eliminates the stress generated during the welding process and removes residual impurities by performing vacuum heat treatment on the welded W-Ni-Fe alloy billet, thereby obtaining W-Ni-Fe alloy rods with good mechanical properties at the weld interface.

[0029] The invention will now be described in detail through the following embodiments.

[0030] Example 1 This embodiment provides a method for preparing ultra-long W-Ni-Fe alloy bars using rotary friction welding, including the following steps: Step 1, prepare small-sized sintered rod blanks: In this embodiment, a W-Ni-Fe alloy with grade 90W-7Ni-3Fe, a diameter of φ60mm, and a length of 1350mm was used as the final target rod. The corresponding W powder, Ni powder, and Fe powder were weighed according to the composition of grade 90W-7Ni-3Fe. The raw material powders were subjected to a traditional powder metallurgy process of mixing, cold isostatic pressing, pre-sintering, and sintering to prepare three W-Ni-Fe alloy rods with a diameter of φ60mm and a length of 500mm, for later use.

[0031] Step 2, end face machining and cleaning: The small-sized W-Ni-Fe alloy billet obtained in the above steps is machined to make the end face flat and the roughness ≤0.8μm; the machined end face is soaked and cleaned with acetone for 10 minutes, and then dried at low temperature.

[0032] Step 3, Spray Ni-Fe coating: The W-Ni-Fe rod blank obtained by the above steps is then coated with Ni-Fe, wherein the Ni / Fe ratio in the coating material is 7:3 and the coating thickness is 5μm.

[0033] Step 4, High-temperature hydrogen reduction: The W-Ni-Fe rod blank with Ni-Fe coating obtained in step 3 was subjected to high-temperature hydrogen reduction in a hydrogen furnace. The hydrogen flow rate was set to 5 L / min, the heating rate was 3℃ / min, the reduction temperature was 800℃, and the reduction time was 4 h.

[0034] Step 5, Rotary Friction Welding: Of the three W-Ni-Fe billets obtained in step 4, the first one serves as the clamping and fixing end, and the second one as the working feed rotating end. Under an argon atmosphere, they are slowly brought close together and briefly come into contact with each other, causing the workpiece end face to gradually heat up. Then, they are quickly separated to a position 3 mm apart. The spindle drives the rotating working feed end to rotate at a high speed of 1500 r / min, while simultaneously contacting the welding surface of the tungsten nickel iron rod at the clamping and fixing end. The friction pressure is 38 MPa, the upsetting pressure is 180 MPa, the upsetting time is 6 s, the friction feed speed is 3.2 mm / s, and the upsetting speed is 26 mm / s.

[0035] The W-Ni-Fe alloy billet after the first welding is used as the clamping and fixing end, and the third one is used as the working and rotating end. They are then welded again with relevant process parameters to obtain an ultra-long W-Ni-Fe alloy billet.

[0036] Step 6, Vacuum heat treatment: The above steps yielded W-Ni-Fe alloy billets, which were then heat-treated in a vacuum annealing furnace at a temperature of 700℃ for 2 hours.

[0037] By testing the room temperature mechanical properties of the weld and the base material, it can be found that the tensile strength of the base material is 934 MPa, the tensile strength of the edge of the weld is 869 MPa, and the tensile strength of the core is 803 MPa.

[0038] Example 2 This embodiment provides a method for preparing ultra-long W-Ni-Fe alloy bars using rotary friction welding, including the following steps: Step 1, prepare small-sized sintered rod blanks: In this embodiment, a W-Ni-Fe alloy with the grade 92.5W-4.9Ni-2.1Fe-0.5Co, a diameter of φ80mm, and a length of not less than 900mm is used as the final target bar material. The corresponding W powder, Ni powder, Fe powder, and Co powder are weighed according to the composition of the grade 92.5W-4.9Ni-2.1Fe-0.5Co. The raw material powders are mixed, cold isostatically pressed, pre-sintered, and sintered using a traditional powder metallurgy process to prepare two W-Ni-Fe bar blanks with a diameter of φ80mm and a length of 500mm, for later use.

[0039] Step 2, end face machining and cleaning: The small-sized W-Ni-Fe alloy billet obtained in the above steps is machined to make the end face flat and the roughness ≤0.8μm; the machined end face is soaked and cleaned with anhydrous ethanol for 15 minutes, and then dried at low temperature.

[0040] Step 3, Spray Ni-Fe coating: The W-Ni-Fe alloy billet obtained by the above steps is then coated with Ni-Fe, wherein the Ni / Fe ratio in the coating material is 7:3 and the coating thickness is 7μm.

[0041] Step 4, High-temperature hydrogen reduction: The W-Ni-Fe alloy billet with Ni-Fe coating obtained in step 3 was subjected to high-temperature hydrogen reduction in a hydrogen furnace. The hydrogen flow rate was set to 5 L / min, the heating rate was 3 °C / min, the reduction temperature was 900 °C, and the reduction time was 3 h.

[0042] Step 5, Rotary Friction Welding: The two W-Ni-Fe alloy billets obtained in step 4 are used as follows: the first billet is used as the clamping and fixing end, and the second billet is used as the working feed rotating end. Under an argon atmosphere, the billets are slowly brought close together and briefly come into contact with each other, causing the workpiece end face to gradually heat up. Then, they are quickly separated to a position 3 mm apart. The spindle drives the rotating working feed end to rotate at high speed of 1850 r / min, while simultaneously contacting the welding surface of the tungsten nickel iron billet at the clamping and fixing end. The friction pressure is 34 MPa, the upsetting pressure is 205 MPa, the upsetting time is 9 s, the friction feed speed is 2.8 mm / s, and the upsetting speed is 25 mm / s.

[0043] Step 6, Vacuum heat treatment: The W-Ni-Fe alloy billet obtained in step 5 above was heat-treated in a vacuum annealing furnace at a temperature of 800℃ for 3 hours.

[0044] Figure 1 This is a microscopic image of the weld seam of the ultra-long W-Ni-Fe alloy bar prepared in Example 2 at a scale of 100 μm. The room temperature mechanical properties of the weld seam and the base material were tested, revealing that the tensile strength of the base material is 950 MPa, the edge tensile strength of the weld seam is 895 MPa, and the core tensile strength is 808 MPa.

[0045] Example 3 This embodiment provides a method for preparing ultra-long W-Ni-Fe alloy bars using rotary friction welding, including the following steps: Step 1, prepare small-sized sintered rod blanks: In this embodiment, a W-Ni-Fe alloy with grade 96.7W-2.1Ni-0.9Fe-0.3Co, a diameter of φ50mm, and a length of not less than 1000mm is used as the final target rod. The corresponding W powder, Ni powder, Fe powder, and Co powder are weighed according to the composition of grade 92.5W-4.9Ni-2.1Fe-0.5Co. The raw material powders are mixed, cold isostatically pressed, pre-sintered, and sintered using a traditional powder metallurgy process to prepare three W-Ni-Fe rod blanks with a diameter of φ80mm and a length of 400mm, for later use.

[0046] Step 2, end face machining and cleaning: The small-sized W-Ni-Fe alloy billet obtained in the above steps is machined to make the end face flat and the roughness ≤0.8μm; the machined end face is soaked and cleaned with acetone for 10 minutes, and then dried at low temperature.

[0047] Step 3, Spray Ni-Fe coating: The W-Ni-Fe alloy billet obtained by the above steps is then coated with Ni-Fe, wherein the Ni / Fe ratio in the coating material is 7:3 and the coating thickness is 10μm.

[0048] Step 4, High-temperature hydrogen reduction: The W-Ni-Fe alloy billet with Ni-Fe coating obtained in step 3 was subjected to high-temperature hydrogen reduction in a hydrogen furnace. The hydrogen flow rate was set to 6 L / min, the heating rate was 3℃ / min, the reduction temperature was 900℃, and the reduction time was 4 h.

[0049] Step 5, Rotary Friction Welding: Of the three W-Ni-Fe alloy billets obtained in step 4, the first one serves as the clamping and fixing end, and the second one as the working feed rotating end. Under an argon atmosphere, they are slowly brought close together and briefly come into contact with each other, causing the workpiece end face to gradually heat up. Then, they are quickly separated to a position 3 mm apart. The spindle drives the rotating working feed end to rotate at a high speed of 2200 r / min, while simultaneously contacting the welding surface of the tungsten nickel iron rod at the clamping and fixing end. The friction pressure is 30 MPa, the upsetting pressure is 190 MPa, the upsetting time is 6 s, the friction feed speed is 3.4 mm / s, and the upsetting speed is 23 mm / s.

[0050] The W-Ni-Fe billet after the first welding is used as the clamping and fixing end, and the third one is used as the working and rotating end. They are then welded again with relevant process parameters to obtain an ultra-long W-Ni-Fe billet.

[0051] Step 6, Vacuum heat treatment: The above steps yielded W-Ni-Fe billets, which were then heat-treated in a vacuum annealing furnace at a temperature of 900℃ for 4 hours.

[0052] By testing the room temperature mechanical properties of the weld and the base material, it can be found that the tensile strength of the base material is 975 MPa, the tensile strength of the edge of the weld is 889 MPa, and the tensile strength of the core is 831 MPa.

[0053] Comparative Example 1 Step 1, prepare small-sized sintered rod blanks: This comparative example will primarily utilize the traditional rotary friction welding method. To ensure accurate comparison of final performance, the preparation of the raw material billets, rotary friction welding parameters, and heat treatment processes will be identical to those in Example 1. Using a W-Ni-Fe alloy with grade 90W-7Ni-3Fe, a diameter of φ60mm, and a length of 1350mm as the final target rod, the corresponding W powder, Ni powder, and Fe powder were weighed according to the composition of grade 90W-7Ni-3Fe. The raw material powders underwent a traditional powder metallurgy process involving mixing, cold isostatic pressing, pre-sintering, and sintering to prepare three W-Ni-Fe billets with a diameter of φ60mm and a length of 500mm, for later use.

[0054] Step 2, end face machining and cleaning: The small-sized W-Ni-Fe alloy billet obtained in the above steps is machined to make the end face flat and the roughness ≤0.8μm. The machined end face is then soaked and cleaned with acetone for 10 minutes and then dried at low temperature.

[0055] Step 3, Rotary Friction Welding: Of the three W-Ni-Fe billets obtained in the above steps, the first one serves as the clamping and fixing end, and the second one serves as the working feed rotating end. After slowly approaching each other and briefly contacting and rubbing, the end face of the workpiece gradually heats up. Then, they are quickly separated to a position 3 mm apart. The spindle drives the rotating working feed end to rotate at high speed of 1500 r / min, while simultaneously contacting the welding surface of the tungsten nickel iron rod at the clamping and fixing end. The friction pressure is 38 MPa, the upsetting pressure is 180 MPa, the upsetting time is 6 s, the friction feed speed is 3.2 mm / s, and the upsetting speed is 26 mm / s.

[0056] The W-Ni-Fe alloy billet after the first welding is used as the clamping and fixing end, and the third one is used as the working and rotating end. They are then welded again with relevant process parameters to obtain an ultra-long W-Ni-Fe billet.

[0057] Step 4, Vacuum heat treatment: The W-Ni-Fe billet obtained in the above steps was heat-treated in a vacuum annealing furnace at a temperature of 700℃ for 2 hours.

[0058] Figure 2The image shows the microstructure of the weld seam of the ultra-long W-Ni-Fe alloy rod prepared for Comparative Example 1 at a scale of 100 μm. Room temperature mechanical properties of the weld seam and the base material were tested, revealing a tensile strength of 930 MPa for the base material, 471 MPa for the edge of the weld seam, and 227 MPa for the core. It is evident that directly performing rotary friction welding on the W-Ni-Fe rod blank results in significantly lower mechanical properties at the weld seam compared to the base material, severely limiting its application. However, in Examples 1-3 of this invention, after machining, a Ni-Fe coating of a certain thickness is sprayed, and impurities are removed by high-temperature hydrogen reduction. During high-speed rotary friction welding, the tungsten particles in both sections undergo solid solution treatment and rearrangement, effectively performing a short-term secondary sintering at the weld seam. Combined with appropriate heat treatment processes to eliminate stress generated during welding and remove residual impurities, the mechanical properties of the weld seam are significantly improved. Compared with traditional powder metallurgy sintering methods, this invention does not require large equipment and avoids the problem of large billets collapsing and deforming under their own gravity during liquid phase sintering. The method of this invention is simple and has successfully prepared ultra-long W-Ni-Fe alloy rods. The prepared rods have excellent mechanical properties and can meet application requirements.

[0059] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, it is intended to include any modifications and variations that fall within the scope of the claims and their equivalents.

Claims

1. A method for preparing ultra-long W-Ni-Fe alloy rods, characterized in that, Includes the following steps: According to the length requirements of the target ultra-long W-Ni-Fe alloy rod, multiple W-Ni-Fe alloy rod blanks with a length of 300mm~500mm were prepared by powder metallurgy sintering method; the diameter and composition of each W-Ni-Fe alloy rod blank are the same as those of the target ultra-long W-Ni-Fe alloy rod. After machining and cleaning the end faces of the W-Ni-Fe alloy billet, a Ni-Fe coating is sprayed onto the end faces to be welded. The billet coated with the Ni-Fe coating is then deoxidized under a reducing atmosphere. Subsequently, multiple billets to be welded are sequentially subjected to rotary friction welding under an inert atmosphere. During the welding process, the particles on the end faces to be welded undergo solid solution and rearrangement under the action of the Ni-Fe coating. After vacuum heat treatment, ultra-long W-Ni-Fe alloy rods are obtained.

2. The method for preparing ultra-long W-Ni-Fe alloy rods according to claim 1, characterized in that, In the Ni-Fe coating, the ratio of Ni to Fe is the same as that in the target ultra-long W-Ni-Fe bar, and the coating thickness is 3μm~10μm.

3. The method for preparing ultra-long W-Ni-Fe alloy rods according to claim 1, characterized in that, The sum of the lengths of all W-Ni-Fe alloy billets is greater than the length of the target extra-long W-Ni-Fe alloy billet. The excess length is used to compensate for length loss during machining and welding.

4. The method for preparing ultra-long W-Ni-Fe alloy rods according to claim 1, characterized in that, The length of the extra-long W-Ni-Fe alloy bars ranges from 600mm to 2000mm.

5. The method for preparing ultra-long W-Ni-Fe alloy rods according to claim 1, characterized in that, During reduction deoxygenation, the reducing atmosphere is hydrogen, the reduction temperature is 700℃~900℃, and the reduction time is 2h~4h.

6. The method for preparing ultra-long W-Ni-Fe alloy rods according to claim 1, characterized in that, Rotary friction welding, for the first welding operation, specifically includes the following steps: One W-Ni-Fe alloy billet is used as the clamping and fixing end, and another W-Ni-Fe alloy billet is used as the working feed rotating end. Under the protection of an inert atmosphere, the working feed rotating end approaches the clamping and fixing end and the contact friction causes the end face of the workpiece to gradually heat up. Then, they separate, and the spindle drives the working feed rotating end to rotate at a speed of 1200 r / min to 2300 r / min. At the same time, it contacts the end face to be welded of the clamping and fixing end. The friction pressure is 25 MPa to 38 MPa, the upsetting pressure is 170 MPa to 210 MPa, the upsetting time is 5 s to 10 s, the friction feed speed is 2.5 mm / s to 4.0 mm / s, and the upsetting speed is 23 mm / s to 30 mm / s.

7. The method for preparing ultra-long W-Ni-Fe alloy rods according to claim 6, characterized in that, If the first weld fails to achieve the desired length of the extra-long W-Ni-Fe rod, use the W-Ni-Fe alloy billet from the first weld as the clamping and fixing end, and another W-Ni-Fe alloy billet as the working feed rotation end. Weld again using the same method, and continue welding multiple times until the desired length of the extra-long W-Ni-Fe alloy rod is achieved.

8. The method for preparing ultra-long W-Ni-Fe alloy rods according to claim 1, characterized in that, During vacuum heat treatment, the temperature is 700℃~1000℃ and the holding time is 2h~4h.

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