High-carbon niobium-tungsten alloy bar for fastener and preparation method of high-carbon niobium-tungsten alloy bar

Abstract

The invention discloses a high-carbon niobium-tungsten alloy bar for a fastener and a preparation method of the high-carbon niobium-tungsten alloy bar. The method comprises the following steps: 1, selecting an extruded-state high-carbon niobium-tungsten alloy bar blank which is not damaged by grinding, and carrying out radial forging to obtain a forged bar blank; secondly, the forged bar blank is subjected to scaling and polishing treatment; thirdly, the polished forged bar blank is subjected to room-temperature rotary forging and heat treatment, and a rotary forging blank is obtained; fourthly, the room-temperature rotary swaging and heat treatment processes in the third step are repeated on the rotary swaging blank till the target product size is achieved, and a rotary swaging bar is obtained; and fifthly, the rotary swaging bar is subjected to machining and heat treatment, and the high-carbon niobium-tungsten alloy bar is obtained. According to the method, the extrusion-state high-carbon niobium-tungsten alloy bar blank is machined through the radial forging technology and the rotary forging technology, the technological parameters such as the heating temperature, the deformation amount and the cooling mode are controlled, the yield and the production efficiency are effectively improved, and the high-carbon niobium-tungsten alloy bar good in surface quality, uniform in structure and small in grain size is obtained; the material is suitable for high-temperature fields of fasteners for aerospace and the like.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of niobium-tungsten alloy preparation, and particularly relates to a high-carbon niobium-tungsten alloy rod for fasteners and a preparation method thereof. BACKGROUND

[0002] Niobium-tungsten alloy is a material with excellent high-temperature performance and corrosion resistance, which is widely used in the fields of aerospace, nuclear reactors, high-temperature equipment, etc. The characteristics of niobium-tungsten alloy include a high melting point (about 2630℃), good high-temperature strength (tensile strength ≥ 100 MPa at 1600℃), good processing performance and welding performance, and the ability to maintain good mechanical properties at high temperatures. The application of niobium-tungsten alloy fasteners is mainly reflected in the field of aerospace, especially in the manufacturing of aerospace fasteners. Nb521 niobium-tungsten alloy is a new type of niobium-tungsten alloy with excellent process performance and high-temperature performance, which can meet the use requirements of aerospace fasteners on material performance.

[0003] With the continuous development of the aerospace industry, higher requirements have been put forward for fasteners used in aerospace and space engines. Introducing carbon (C) element into Nb521 niobium-tungsten alloy to form a high-hardness carbide dispersion phase is considered to be an effective way to further improve its comprehensive performance. Carbon can form high-melting-point, high-hardness carbide particles (such as NbC, WC, etc.) with niobium and other active elements in the matrix, which can effectively pin dislocations and grain boundaries as a second strengthening phase, thereby making it have more excellent performance in high-temperature and high-stress environments. However, the existing high-carbon niobium-tungsten alloy rod processing has many problems, such as high billet cracking sensitivity, easy cracking during hot working, uneven and coarse rod structure, unstable performance, low yield, etc., which cannot meet the large-scale production demand. Therefore, how to optimize the processing technology to improve the yield and improve the uniformity of the structure is an important technical problem currently faced. SUMMARY

[0004] The technical problem to be solved by the present application is to provide a preparation method of a high-carbon niobium-tungsten alloy rod for fasteners to solve the problems of the prior art. The method adopts radial forging and rotary forging process to process the extruded high-carbon niobium-tungsten alloy rod blank, and controls the heating temperature, deformation amount, cooling method and other process parameters, to obtain a high-carbon niobium-tungsten alloy rod with uniform structure and fine grains, solving the problems of easy cracking during high-carbon niobium-tungsten alloy processing, large grinding loss, low yield, and unstable structure and performance indicators.

[0005] To solve the above technical problems, the technical scheme adopted by the present application is as follows: a preparation method of a high-carbon niobium-tungsten alloy rod for fasteners, characterized in that the method comprises the following steps: Step one, select the extruded high-carbon niobium-tungsten alloy rod blank without damage for radial forging to obtain a forged rod blank; Step two, the forging bar obtained in step one is peeled and polished; Step three, the forging bar after polishing in step two is room temperature rotary swaged and heat treated to obtain a rotary swaged blank; Step four, the rotary swaged blank obtained in step three is repeatedly subjected to the room temperature rotary swaging and heat treatment process in step three until the size of the target product high-carbon niobium-tungsten alloy rod is reached to obtain a rotary swaged rod; Step five, the rotary swaged rod obtained in step four is machined and heat treated to obtain a high-carbon niobium-tungsten alloy rod.

[0006] The preparation method of the high-carbon niobium-tungsten alloy rod for fasteners, characterized in that the diameter of the extruded high-carbon niobium-tungsten alloy rod blank in step one is Φ110mm~Φ120mm, and the extruded high-carbon niobium-tungsten alloy rod blank is composed of the following components in mass percentage: W 3%~4%, Zr 2.8%~3.8%, Mo 1%~3%, C 0.05%~0.1%, and the balance of Nb and unavoidable impurities.

[0007] The preparation method of the high-carbon niobium-tungsten alloy rod for fasteners, characterized in that the radial forging process in step one is as follows: Ta1350 glass powder, water and epoxy resin glue are mixed according to a mass ratio of 2:1:1 to prepare high-temperature paint, which is uniformly coated on the surface of the extruded high-carbon niobium-tungsten alloy rod blank with no damage after grinding, then after heat preservation at 1100℃~1150℃ for 40min~60min, the furnace is discharged for 2 fire times of radial forging, the deformation amount of each fire time is 55%~60%, and after cooling and root grinding, the surface oxide layer, cracks and other defects are removed.

[0008] The preparation method of the high-carbon niobium-tungsten alloy rod for fasteners, characterized in that the peeling amount of the forging bar in step two is less than 2mm, the polishing amount is less than 0.1mm, and the surface and end of the forging bar after polishing treatment have no visible defects.

[0009] The preparation method of the high-carbon niobium-tungsten alloy rod for fasteners, characterized in that the total deformation amount of the room temperature rotary swaging in step three is 40%~60%, the single pass radial compression amount is 0.5mm~1mm, the feeding speed is 2m / min~4m / min, and the visible defects are removed after each pass rotary swaging; the heat treatment system is as follows: 1350℃ for 90min, vacuum degree less than 5×10 -3 Pa, furnace cooling to below 50℃ and air cooling after discharging.

[0010] The preparation method of the high-carbon niobium-tungsten alloy rod for fasteners has the characteristics that the amount of machining of the swaged rod in step five is less than 0.1 mm; the heat treatment system is as follows: 1350 DEG C for 90 min, vacuum degree less than 5*10 - 3 Pa, furnace cooling to below 50 DEG C, and air cooling after discharge; and the diameter of the high-carbon niobium-tungsten alloy rod is Φ8 mm to Φ25 mm.

[0011] Meanwhile, the application also discloses the high-carbon niobium-tungsten alloy rod for fasteners prepared by the method.

[0012] Compared with the prior art, the application has the following advantages: 1. In view of the problems of high-temperature strength of niobium-tungsten alloy, higher crack sensitivity of high-carbon niobium-tungsten alloy, uneven deformation of the blank in the traditional forging process, easy crack and crack propagation, and low material yield, the radial forging process is adopted, the deformation amount of each pass is small and the deformation is uniform, the plasticity of the high-carbon niobium-tungsten alloy is improved, the risk of cracking of the rod blank is reduced, the material yield is improved, the production efficiency is high, and the surface quality is good; meanwhile, water cooling is adopted after radial forging, the high-temperature oxidation of the forged rod blank is reduced, and the material yield and production efficiency are further improved.

[0013] 2. In view of the problems of high-temperature strength of niobium-tungsten alloy, higher crack sensitivity of high-carbon niobium-tungsten alloy, uneven deformation of the blank in the traditional forging process, easy crack and crack propagation, and low material yield, the radial forging process is adopted, the deformation amount of each pass is small and the deformation is uniform, the plasticity of the high-carbon niobium-tungsten alloy is improved, the risk of cracking of the rod blank is reduced, the material yield is improved, the production efficiency is high, and the surface quality is good; meanwhile, water cooling is adopted after radial forging, the high-temperature oxidation of the forged rod blank is reduced, and the material yield and production efficiency are further improved.

[0014] 3. The application controls the deformation amount and single-pass radial compression amount of radial forging and cold swaging, reduces the crack sensitivity of high-carbon niobium-tungsten alloy, effectively avoids cracking of the rod during the machining process, deforms the high-carbon niobium-tungsten alloy composition, and has good uniformity, and the total material yield can reach more than 65%, which is suitable for fasteners.

[0015] The technical solutions of the application are further described below with reference to the drawings and examples. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 The high-power microstructure diagram of the high-carbon niobium-tungsten alloy rod for fasteners prepared in the embodiment 1 of the application.

[0017] Figure 2 The high-power microstructure diagram of the high-carbon niobium-tungsten alloy rod for fasteners prepared in the embodiment 2 of the application.

[0018] Figure 3 High magnification microstructure of high carbon Nb-W alloy rod for fastener prepared in Example 3. DETAILED DESCRIPTION

[0019] Example 1 The present example comprises the following steps: Step one, select the straight diameter of Φ120mm±1mm extrusion state high carbon Nb-W alloy rod blank for radial forging, first Ta1350 glass powder, water and epoxy resin glue according to the mass ratio of 2:1:1 to prepare high temperature paint, the high temperature paint is evenly coated on the surface of the straight extrusion state high carbon Nb-W alloy rod blank, then after 60min of heat preservation at 1100℃, the first fire radial forging is carried out, the total variable is about 55.5%, the diameter Φ80mm±1mm is obtained, the water cooling and the root grinding are carried out, the surface oxide layer, crack and other defects are removed to the diameter Φ78mm±1mm, then the surface is coated with high temperature paint, after 40min of heat preservation at 1100℃, the second fire radial forging is carried out, the total variable is about 58.9%, the diameter Φ50mm±1mm of two fire forging blank is obtained, after the end of water cooling and root grinding, the surface oxide layer, crack and other defects are removed, and the forged rod blank is obtained; the extrusion state high carbon Nb-W alloy rod blank is composed of the following mass percentage of components: W 3.5%, Zr 3.0%, Mo 1.2%, C0.07%, the balance is Nb and inevitable impurities; Step two, the forged rod blank obtained in step one is peeled and polished to a diameter of Φ46mm, the peeling amount is about 1.6mm, the polishing amount is about 0.07mm, and the surface and end of the polished forged rod blank has no visible defects; Step three, the polished forged rod blank in step two is subjected to room temperature rotary forging, the feeding speed is 2m / min, the single pass radial compression amount is 1mm, the visible defects are removed after each pass rotary forging, the total deformation amount of room temperature rotary forging is 43.3%, and then vacuum annealing heat treatment is carried out, the heat treatment system is: 1350℃ for 90min, the vacuum degree is less than 5×10 - 3 Pa, the furnace is cooled to below 50℃, and the rotary forging blank is obtained by air cooling after furnace cooling; Step four, the rotary forging blank obtained in step three is repeatedly subjected to the room temperature rotary forging and heat treatment process in step three until the diameter Φ25mm±0.1mm is reached, and the rotary forging rod is obtained; Step five, the rotary forging rod obtained in step four is polished, the polishing amount is 0.08mm, and then heat treatment is carried out, the heat treatment system is: 1350℃ for 90min, the vacuum degree is less than 5×10 -3Pa, cooled in the furnace to below 50°C, then air-cooled to obtain a high-carbon niobium-tungsten alloy rod for fasteners with a diameter of Φ25mm.

[0020] Figure 1 This is a high-magnification micrograph of the high-carbon niobium-tungsten alloy rod for fasteners prepared in this embodiment. Figure 1 It can be seen that the high-carbon niobium-tungsten alloy rod has a uniform high-magnification grain structure, fine grains, and a grain size of grade 7.

[0021] Example 2 This embodiment includes the following steps: Step 1: Select a polished, undamaged extruded high-carbon niobium-tungsten alloy billet with a diameter of Φ115mm±1mm for radial forging. First, prepare a high-temperature coating by mixing Ta1350 glass powder, water, and epoxy resin adhesive in a mass ratio of 2:1:1. Apply the high-temperature coating evenly to the surface of the polished, undamaged extruded high-carbon niobium-tungsten alloy billet. Then, after holding at 1100℃ for 60 minutes, remove the billet from the furnace for the first radial forging. The total change is approximately 57.5%, resulting in a first-flush radial forging with a diameter of Φ75mm±1mm. The forged billet is water-cooled and ground through the core to remove surface defects such as oxide layer and cracks to a diameter of Φ72mm±1mm. Then, a high-temperature coating is applied to the surface, and after holding at 1100℃ for 40 minutes, it is taken out of the furnace for a second radial forging. The total change is about 59.8%, resulting in a second-fire forged billet with a diameter of Φ45mm±1mm. After the second fire, it is water-cooled and ground through the core to remove surface defects such as oxide layer and cracks, resulting in a forged bar billet. The extruded high-carbon niobium-tungsten alloy bar billet is composed of the following composition by mass percentage: W 3%, Zr 3.7%, Mo 2.8%, C 0.05%, with the balance being Nb and unavoidable impurities. Step 2: Peel and polish the forged billet obtained in Step 1 to a diameter of Φ41mm. The peeling amount is about 1.8mm and the polishing amount is about 0.07mm. After polishing, there are no visible defects on the surface and end of the forged billet. Step 3: The forged billet polished in Step 2 is subjected to room temperature rotary forging at a feed rate of 4 m / min and a single-pass radial compression of 0.5 mm. Visually visible defects are removed after each pass of rotary forging. The total deformation during room temperature rotary forging is 51.5%. Then, vacuum annealing heat treatment is performed at 1350℃ for 90 min under a vacuum degree of less than 5 × 10⁻⁶. - 3 Pa, cooled in the furnace to below 50°C, then air-cooled to obtain a rotary forged billet; Step 4: Repeat the room temperature rotary forging and heat treatment process in Step 3 on the rotary forging billet obtained in Step 3 until the diameter reaches Φ10mm±0.1mm to obtain rotary forging bar stock; Step 5: Polish the forged bar obtained in Step 4 by 0.05 mm, then perform heat treatment. The heat treatment process is as follows: hold at 1350℃ for 90 min, with a vacuum degree of less than 5 × 10⁻⁶. -3 Pa, cooled in the furnace to below 50°C and then air-cooled to obtain a high-carbon niobium-tungsten alloy rod for fasteners with a diameter of Φ10mm.

[0022] Figure 2 This is a high-magnification micrograph of the high-carbon niobium-tungsten alloy rod for fasteners prepared in this embodiment. Figure 2 It can be seen that the high-carbon niobium-tungsten alloy rod has a uniform high-magnification grain structure, fine grains, and a grain size of grade 8.

[0023] Example 3 This embodiment includes the following steps: Step 1: Select a polished, undamaged extruded high-carbon niobium-tungsten alloy billet with a diameter of Φ110mm±1mm for radial forging. First, prepare a high-temperature coating by mixing Ta1350 glass powder, water, and epoxy resin adhesive in a mass ratio of 2:1:1. Apply the high-temperature coating evenly to the surface of the polished, undamaged extruded high-carbon niobium-tungsten alloy billet. Then, after holding at 1150℃ for 40 minutes, remove the billet from the furnace for the first radial forging. The total change is approximately 59.5%, resulting in a first-flush radial forging with a diameter of Φ70mm±1mm. The forged billet is water-cooled and ground through the core to remove surface defects such as oxide layer and cracks to a diameter of Φ67mm±1mm. Then, a high-temperature coating is applied to the surface, and after holding at 1150℃ for 40 minutes, it is taken out of the furnace for a second radial forging. The total change is about 58.8%, resulting in a two-fire forged billet with a diameter of Φ43mm±1mm. After the second fire, it is water-cooled and ground through the core to remove surface defects such as oxide layer and cracks, resulting in a forged bar billet. The extruded high-carbon niobium-tungsten alloy bar billet is composed of the following composition by mass percentage: W 4%, Zr 2.8%, Mo 2.5%, C 0.09%, with the balance being Nb and unavoidable impurities. Step 2: Peel and polish the forged billet obtained in Step 1 to a diameter of Φ40mm. The peeling amount is about 1.5mm and the polishing amount is about 0.05mm. After polishing, there are no visible defects on the surface and end of the forged billet. Step 3: The forged billet polished in Step 2 is subjected to room temperature rotary forging at a feed rate of 3 m / min and a single-pass radial compression of 0.7 mm. Visually visible defects are removed after each pass of rotary forging. The total deformation during room temperature rotary forging is 57.4%. Then, vacuum annealing heat treatment is performed at 1350℃ for 90 min under a vacuum degree of less than 5 × 10⁻⁶. - 3 Pa, cooled in the furnace to below 50°C, then air-cooled to obtain a rotary forged billet; Step 4: Repeat the room temperature rotary forging and heat treatment process in Step 3 on the rotary forging billet obtained in Step 3 until the diameter reaches Φ8mm±0.1mm to obtain rotary forging bar stock; Step 5: Polish the forged bar obtained in Step 4 by 0.05 mm, then perform heat treatment. The heat treatment process is as follows: hold at 1350℃ for 90 min, with a vacuum degree of less than 5 × 10⁻⁶. -3 Pa, cooled in the furnace to below 50°C and then air-cooled to obtain a high-carbon niobium-tungsten alloy rod for fasteners with a diameter of Φ8mm.

[0024] Figure 3 This is a high-magnification micrograph of the high-carbon niobium-tungsten alloy rod for fasteners prepared in this embodiment. Figure 3 It can be seen that the high-carbon niobium-tungsten alloy rod has a uniform high-magnification grain structure, fine grains, and a grain size of grade 8.

[0025] The tensile properties and grain size of the high-carbon niobium-tungsten alloy rods for fasteners prepared in Examples 1-3 of this invention were tested, and the results are shown in Table 1.

[0026] Table 1

[0027] As shown in Table 1, the high-carbon niobium-tungsten alloy rods prepared by this invention have a room temperature yield strength of over 350 MPa, a tensile strength of over 490 MPa, an elongation of over 34%, and a reduction of area of ​​over 68%. The rods have a uniform microstructure, fine grains, and good batch consistency, making them suitable for use in fasteners.

[0028] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any way. Any simple modifications, alterations, and equivalent changes made to the above embodiments based on the inventive essence shall still fall within the protection scope of the present invention.

Claims

1. A method for preparing high-carbon niobium-tungsten alloy rods for fasteners, characterized in that, The method includes the following steps: Step 1: Select a polished and undamaged extruded high-carbon niobium-tungsten alloy billet and perform radial forging to obtain a forged billet; Step 2: Peel and polish the forged billet obtained in Step 1; Step 3: Perform room temperature rotary forging and heat treatment on the polished forging billet from Step 2 to obtain a rotary forged billet; Step 4: Repeat the room temperature rotary forging and heat treatment process in Step 3 on the rotary forging billet obtained in Step 3 until the target product, high carbon niobium tungsten alloy bar, is obtained, thus obtaining the rotary forging bar. Step 5: The forged bar obtained in Step 4 is machined and heat-treated to obtain a high-carbon niobium-tungsten alloy bar.

2. The method for preparing a high-carbon niobium-tungsten alloy rod for fasteners according to claim 1, characterized in that, The extruded high-carbon niobium-tungsten alloy billet described in step one has a diameter of Φ110mm~Φ120mm and is composed of the following composition by mass percentage: W 3%~4%, Zr 2.8%~3.8%, Mo 1%~3%, C 0.05%~0.1%, with the balance being Nb and unavoidable impurities.

3. The method for preparing a high-carbon niobium-tungsten alloy rod for fasteners according to claim 1, characterized in that, The radial forging process described in step one is as follows: Ta1350 glass powder, water, and epoxy resin adhesive are mixed in a mass ratio of 2:1:1 to prepare a high-temperature coating, which is then uniformly coated on the surface of the extruded high-carbon niobium-tungsten alloy billet that has been ground without damage. After holding at 1100℃~1150℃ for 40min~60min, the billet is removed from the furnace and subjected to two radial forging cycles, with a deformation of 55%~60% per cycle. After the cycle, the billet is water-cooled and ground through the root to remove defects such as oxide layer and cracks from the surface.

4. The method for preparing a high-carbon niobium-tungsten alloy rod for fasteners according to claim 1, characterized in that, In step two, the amount of skin peeling of the forging billet is less than 2mm, the amount of polishing is less than 0.1mm, and there are no visible defects on the surface and end of the forging billet after polishing.

5. The method for preparing a high-carbon niobium-tungsten alloy rod for fasteners according to claim 1, characterized in that, In step three, the total deformation of the room temperature rotary forging is 40%~60%, the radial compression per pass is 0.5mm~1mm, the feed rate is 2m / min~4m / min, and visually visible defects are removed after each pass of rotary forging. The heat treatment process is as follows: holding at 1350℃ for 90min, with a vacuum degree of less than 5×10⁻⁶. -3 Pa, cooled in the furnace to below 50°C, then air-cooled.

6. The method for preparing a high-carbon niobium-tungsten alloy rod for fasteners according to claim 1, characterized in that, The machining allowance of the forged bar in step five is less than 0.1 mm; the heat treatment process is as follows: holding at 1350℃ for 90 min, with a vacuum degree of less than 5 × 10⁻⁶. -3 Pa, cooled in the furnace to below 50°C and then air-cooled; the diameter of the high-carbon niobium-tungsten alloy rod is Φ8mm~Φ25mm.

7. A high-carbon niobium-tungsten alloy rod for fasteners prepared by the method according to any one of claims 1 to 6.

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