Niobium-tungsten alloy bar and medium-temperature radial forging method thereof

Abstract

The medium-temperature radial forging method comprises the steps that pretreatment is conducted, specifically, a niobium-tungsten alloy extrusion bar blank is heated for 60-180 minutes at the temperature of 750-950 DEG C, rapid forging and straightening are conducted, and a medium-temperature radial forging bar blank is obtained and annealed for 60-120 minutes at the temperature of 1250-1450 DEG C; medium-temperature radial forging is conducted, specifically, a two-step method is adopted, in the first step, a bar blank is preheated to 80-100 DEG C and coated with Ta1350 high-temperature glass powder, heat preservation is conducted for 90-180 minutes at the temperature of 1050-1150 DEG C, and the bar blank is forged into a bar with the diameter of 70 + / -1 mm in the mode that the diameter is reduced by 7-10 mm every time; and in the second step, the heating and coating processes are repeated, the diameter is reduced by 5-7 mm every time, and the bar with the required specification is manufactured. By optimizing the medium-temperature forging and annealing process, the fine grain structure is controlled, the high-temperature mechanical property, creep resistance and oxidation resistance of the material are improved, and the material is suitable for aerospace engines and other high-temperature and high-pressure scenes. Compared with a traditional method, the technology improves the yield, shortens the production period, reduces the labor intensity, is suitable for large-scale production, reduces surface air suction, oxidation and burning loss, and improves the production efficiency and the finished product quality.

Description

Technical Field

[0001] The invention relates to the field of preparation of niobium-tungsten alloy, and in particular to a niobium-tungsten alloy (NbW5-1) bar and a medium-temperature radial forging method thereof. Background Art

[0002] The attitude and orbit control engine (ATC engine) is one of the core components of spacecraft such as rockets and satellites. Its main components include tanks, injectors, nozzles, etc. The nozzle is a key component for generating thrust. The pressure inside it can reach 200 atmospheres and the temperature can reach 3000-4000℃. The nozzle wall needs to be cooled. The existing technology usually uses liquid film cooling to reduce the temperature of the nozzle.

[0003] Niobium tungsten alloy for aerospace, especially NbW5-1 alloy, as a solid solution strengthened and secondary precipitation dispersion strengthened niobium alloy, has excellent high temperature high specific strength, high temperature creep performance, plasticity and welding performance. The nominal composition of NbW5-1 is Nb5W2Mo1Zr0.08C, which is a niobium tungsten alloy grade registered by the national military standard. It realizes solid solution strengthening through W (tungsten) and Mo (molybdenum) elements, and dispersion strengthening through ZrC particles formed by the combination of Zr (zirconium) and C (carbon). These alloying measures significantly improve the high temperature performance, creep resistance and oxidation resistance of the alloy.

[0004] In order to meet the requirements of the new attitude and orbit control engine, the niobium tungsten (NbW5-1) alloy not only needs to have a small density, but also requires high room temperature and high temperature strength, as well as good plasticity and welding properties. However, the existing niobium tungsten (NbW5-1) alloy bar processing technology has many problems, such as coarse structure, unevenness, cracking during forging, long forging cycle, low yield rate, etc., which cannot meet the needs of large-scale production. Therefore, how to ensure the stability and performance of niobium tungsten alloy during the forging process by controlling the forging heating temperature, heating method and forging process parameters is an important technical problem currently faced. Summary of the invention

[0005] The present invention provides a medium-temperature radial forging method for niobium tungsten (NbW5-1) alloy, aiming to solve the problems of easy cracking, uneven structure and low yield of niobium tungsten alloy in the forging process in the prior art. Through the present invention, the internal structure of niobium tungsten alloy can be significantly improved, its room temperature and high temperature performance can be improved, and the production efficiency can be improved at the same time.

[0006] The technical solution adopted by the present invention is as follows:

[0007] A medium-temperature radial forging method for niobium-tungsten alloy comprises the following steps:

[0008] 1) Pretreatment of niobium-tungsten alloy extruded rods: heat the niobium-tungsten alloy extruded rods at 750-950°C for 60-180 minutes, perform rapid forging and straightening to obtain medium-temperature radial forging rods, and anneal at 1250-1450°C for 60-120 minutes;

[0009] 2) Medium temperature radial forging: a two-step method is adopted. In the first step, the medium temperature radial forging bar blank is preheated to 80-100°C, Ta1350 high temperature glass powder is coated on its surface, and then it is kept at 1050-1150°C for 90-180min, and the medium temperature radial forging bar blank is forged into a bar with a diameter of 70±1mm by a radial forging process in a manner that the diameter is reduced by 7-10mm each time; in the second step, the obtained bar is preheated to 80-100°C again, Ta1350 high temperature glass powder is coated on its surface, and then it is kept at 1050-1150°C for 90-180min, and the medium temperature radial forging bar blank is forged into a bar with a required specification by a radial forging process in a manner that the diameter is reduced by 5-7mm each time.

[0010] The niobium-tungsten alloy rod prepared by the medium-temperature radial forging method has uniform and fine internal structure and high high-temperature strength. The weight of a single section of the rod is 125-135Kg. The rod is suitable for the manufacture of aerospace engine thrust chambers and high-temperature structural parts.

[0011] The principle of the present invention is based on medium temperature radial forging technology, which improves the microstructure and mechanical properties of niobium tungsten alloy (NbW5-1) by forging it within a specific temperature range. The specific principle is as follows:

[0012] 1. Principles of solid solution strengthening and dispersion strengthening

[0013] Tungsten (W), molybdenum (Mo) and other elements in niobium tungsten alloy improve the high temperature strength of the material through solid solution strengthening. At the same time, the added zirconium (Zr) combines with carbon (C) to form dispersed ZrC particles, which play a precipitation strengthening role on the material. Through this alloying method, the high temperature creep performance and oxidation resistance of niobium tungsten alloy are improved.

[0014] 2. Medium temperature radial forging principle

[0015] During the forging process, the material is gradually reduced and stretched without exceeding its plastic deformation limit through medium temperature (1050-1150℃) heating and radial forging. This medium temperature forging can avoid the problems of oxidation, air absorption and material burning caused by high temperature forging, and effectively refine the grain structure of the material, improve the uniformity of its internal structure, and enhance the tensile strength and ductility of the material.

[0016] 3. Principle of organizational optimization by multiple forging and annealing

[0017] Through multiple medium-temperature radial forging combined with vacuum annealing, the forging process can gradually break up the coarse grains in the material, and eliminate the stress concentration of the material through annealing, further homogenizing the structure. Annealing also improves the plasticity and toughness of the material, allowing the material to maintain excellent mechanical properties under high temperature and high pressure environments.

[0018] 4. Low oxidation and low aspiration principle

[0019] The medium temperature heating process of the present invention reduces the oxygen absorption and oxidation of the material in a high temperature environment by coating the surface with high temperature glass powder, which not only improves the surface quality of the material, but also avoids the brittle cracking problem caused by oxidation.

[0020] The present invention realizes the fine grain structure control of niobium tungsten alloy rods by optimizing the medium temperature forging and annealing process, significantly improves the high temperature mechanical properties, creep resistance and oxidation resistance of the material, and is suitable for high temperature and high pressure application scenarios such as aerospace engines. Its advantages are mainly reflected in the following aspects: First, the internal structure of the material is uniform and the particles are fine, which helps to improve the overall performance; secondly, through the one-time heating forging process, the entire processing process is completed efficiently, oxygen absorption is reduced, and material cracking during the forging process is effectively avoided. In addition, the weight of a single section forging can reach 125-135 kg, and the production efficiency is significantly improved. Compared with traditional methods, the forging rate of the present invention is higher, the production cycle is shortened, and the labor intensity is reduced, which is very suitable for large-scale batch production. The medium temperature radial forging technology not only reduces the problems of surface air absorption, oxidation and burning, but also reduces the number of heating times by optimizing the heating process, further improving the overall production efficiency and finished product quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is the microstructure diagram of the rod of Example 1 after radial forging.

[0022] Figure 2 It is a single value control chart of the tensile strength (Rm) of the niobium tungsten alloy rod of Example 2 at 1800°C according to different forging methods.

[0023] Figure 3 This is a single value control chart of the elongation of the niobium tungsten alloy rod of Example 2 measured at 1800°C according to different forging methods. DETAILED DESCRIPTION

[0024] In order to better understand the technical solution of the present invention, the medium temperature radial forging method and its products of the present invention are described in detail in combination with specific embodiments. These embodiments are only for illustration and are not intended to limit the scope of the present invention.

[0025] The marking process of the present invention is as follows:

[0026] The forging and processing of niobium tungsten alloy (NbW5-1) bars are carried out according to the standard process. The specific steps are as follows:

[0027] Forging billet: Select extruded rod billet with specification of φ119-128mm as raw material.

[0028] Tail shrinkage sawing: saw the tail shrinkage part of the extruded rod, and the length is controlled at 80-120mm.

[0029] Hot straightening: Heat the bar blank to 750-950℃ in a box-type resistance furnace, keep it warm for 60-180 minutes, and perform quick forging straightening to improve the straightness of the bar. The straightness is controlled at 5-8mm / bar.

[0030] Grinding: Use a bench grinder to grind the bar through the root to remove surface defects such as oxide layer and thermal cracks.

[0031] Pickling: Use hydrofluoric acid: hydrochloric acid: nitric acid in a volume ratio of 1:2:3 to pickle and remove surface stains, where:

[0032] Nitric acid: concentration 65%-68%, reference 68%, analytical grade;

[0033] Hydrochloric acid: concentration ≥35%, 36%-38%, analytical grade;

[0034] Hydrofluoric acid: concentration ≥40%, reference 42%, analytical grade.

[0035] Annealing: Annealing in a vacuum annealing furnace at a temperature of 1250-1450°C for 60-120 minutes to improve the plasticity and mechanical properties of the material.

[0036] Medium temperature radial forging heating:

[0037] After preheating to 80-100°C, Ta1350 high temperature glass powder is coated on the surface of the rod;

[0038] Heat to 1050-1150℃, keep warm for 90-180 minutes, then take out of the furnace for forging.

[0039] Radial forging 1: Forge the bars into φ120±1mm, φ115±1mm, φ108±1mm, φ101±1mm, φ94±1mm, φ86±1mm, φ78±1mm, and φ70±1mm in sequence.

[0040] Sawing and dividing: Saw the bars into 800-1000mm sections.

[0041] Medium temperature radial forging heating:

[0042] After preheating to 80-100°C, Ta1350 high temperature glass powder is coated on the surface of the rod again;

[0043] Heat to 1050-1150℃, keep warm for 90-180 minutes, then take out of the furnace for the second forging.

[0044] Radial forging 2: Forge the bars into φ65±1mm, φ60±1mm, φ55±1mm, φ50±1mm, φ45±1mm and φ40±1mm in sequence.

[0045] Finished product processing: Sawing and machining are carried out according to the specific finished product specifications, with a machining allowance of 5-6mm.

[0046] According to the above process, 4 embodiments are designed as follows:

[0047] Example 1: Large-size billet forging process (850°C, 120 minutes of heat preservation)

[0048] In this embodiment, for a large-sized blank with a specification of φ128 mm, the specific steps are as follows:

[0049] Forging billet: Select extruded bar billet with a specification of φ128mm.

[0050] Tail-shrinking sawing: Saw the extruded rod billet to a length of 120 mm.

[0051] Hot straightening: Heat the bar to 850℃, keep it warm for 120 minutes, and perform quick forging straightening. The straightness is controlled at 6mm / bar.

[0052] Grinding: The surface of the bar is grinded by a bench grinder to remove the oxide layer and thermal cracks.

[0053] Pickling: Use hydrofluoric acid: hydrochloric acid: nitric acid in a volume ratio of 1:2:3 for pickling to remove surface stains.

[0054] Annealing: Annealing was carried out in a vacuum annealing furnace at 1250°C for 60 minutes.

[0055] First medium temperature radial forging heating:

[0056] Preheat to 80°C and coat the surface of the rod with high-temperature glass powder;

[0057] After heating to 1050℃ and keeping warm for 90 minutes, the first radial forging is performed to forge the bar from φ128mm to φ70±1mm.

[0058] Sawing and dividing: The forged bars are sawn into 800mm long sections.

[0059] Second medium temperature radial forging heating:

[0060] Preheat to 80°C and apply high temperature glass powder;

[0061] Heat to 1050℃, keep warm for 90 minutes and then perform the second radial forging to forge the bar into φ65±1mm.

[0062] Finishing: Machined to final specifications with an allowance of 5-6mm.

[0063] Example 2: Large-size billet forging process (900°C, 180 minutes of heat preservation)

[0064] In this embodiment, for a large-sized blank with a specification of φ128 mm, the specific steps are as follows:

[0065] Forging billet: Select extruded bar billet with a specification of φ128mm.

[0066] Tail-cutting: The length after cutting is 80mm.

[0067] Hot straightening: Heat the bar to 900℃, keep it warm for 180 minutes, and perform quick forging straightening. The straightness is controlled within 6mm / bar.

[0068] Grinding: Grinding is used to remove surface oxide layers and cracks.

[0069] Pickling: Use hydrofluoric acid, hydrochloric acid and nitric acid for pickling to remove surface stains.

[0070] Annealing: Annealing was carried out in a vacuum annealing furnace at 1450°C for 120 minutes.

[0071] First medium temperature radial forging heating:

[0072] Preheat to 100°C and apply high-temperature glass powder on the surface;

[0073] After heating to 1150°C and keeping warm for 180 minutes, the first radial forging is performed to forge the bar into φ70±1mm.

[0074] Sawing and dividing: Saw the bars into 1000mm sections.

[0075] Second medium temperature radial forging heating:

[0076] Preheat to 100°C and apply high temperature glass powder;

[0077] Heat to 1150℃, keep warm for 180 minutes and then perform the second radial forging to forge the bar into φ60±1mm.

[0078] Finished product processing: Processing is carried out according to the finished product specifications, with a margin of 5-6mm.

[0079] Example 3: Small-size billet forging process (750°C, 90 minutes of heat preservation)

[0080] In this embodiment, for a small-sized blank with a specification of φ119 mm, the specific steps are as follows:

[0081] Forging billet: Select extruded bar billet with a specification of φ119mm.

[0082] Tail-shrinking sawing: Saw the extruded rod into 100mm sections.

[0083] Hot straightening: Heat the bar to 750℃, keep it warm for 90 minutes, and perform quick forging straightening. The straightness is controlled within 5mm / bar.

[0084] Grinding: Grind the surface of the bar to remove the oxide layer and cracks.

[0085] Pickling: Use hydrofluoric acid, hydrochloric acid and nitric acid in a volume ratio of 1:2:3 for pickling.

[0086] Annealing: Annealing in a vacuum annealing furnace at 1250°C for 60 minutes.

[0087] First medium temperature radial forging heating:

[0088] Preheat to 80°C and coat the surface with high-temperature glass powder;

[0089] Heat to 1050℃, keep warm for 90 minutes and then carry out the first radial forging to forge the bar into φ40±1mm.

[0090] Sawing and dividing: the forged bars are sawn into 900mm sections.

[0091] Second medium temperature radial forging heating:

[0092] Preheat to 80°C and apply high temperature glass powder again;

[0093] After heating to 1050℃ and keeping warm for 90 minutes, the second radial forging is performed to further forge the bar into φ50±1mm.

[0094] Finishing: Machined to final specifications with an allowance of 5-6mm.

[0095] Example 4: Forging process of small-sized billet (800°C, 150 minutes of heat preservation)

[0096] In this embodiment, for a small-sized blank with a specification of φ119 mm, the specific steps are as follows:

[0097] Forging billet: Select extruded bar billet with a specification of φ119mm.

[0098] Tail-shrinking sawing: Saw the extruded rod into 100mm sections.

[0099] Hot straightening: Heat the bar to 800℃, keep it warm for 150 minutes, and perform quick forging straightening. The straightness is controlled within 5mm / bar.

[0100] Sanding: Use a bench sander to remove surface imperfections.

[0101] Pickling: Use hydrofluoric acid: hydrochloric acid: nitric acid in a volume ratio of 1:2:3 to remove surface stains.

[0102] Annealing: vacuum annealing at 1450°C for 120 minutes.

[0103] First medium temperature radial forging heating:

[0104] Preheat to 100°C and apply high temperature glass powder;

[0105] After heating to 1150°C and keeping warm for 150 minutes, the first radial forging is performed to forge the bar into φ70±1mm.

[0106] Sawing and dividing: the forged bars are sawn into 1000mm long sections.

[0107] Second medium temperature radial forging heating:

[0108] Preheat to 100°C and apply high temperature glass powder again;

[0109] After heating to 1150°C and keeping warm for 150 minutes, the second radial forging is performed to further forge the bar into φ40±1mm.

[0110] Finished product processing: Machining is carried out according to the final finished product specifications, with a margin of 5-6mm.

[0111] Figure 1 This is the microstructure diagram of the niobium tungsten alloy rod of Example 1 after radial forging. The material structure after radial forging is uniform and fine, indicating that the process can effectively improve the microstructure of the material and improve the comprehensive mechanical properties of the material, such as strength, toughness and durability.

[0112] Figure 2 It is a single value control chart of the tensile strength (Rm) of the niobium tungsten alloy rod of Example 2 at 1800°C according to different forging methods.

[0113] according to Figure 2 The results show that the present invention has innovativeness and technical advantages:

[0114] 1. The influence of forging method on the tensile strength of materials

[0115] Figure 2 The effect of different forging methods on the tensile strength (Rm) of niobium-tungsten alloy rods at 1800℃ is shown.

[0116] Radial forging method: The tensile strength (Rm) gradually increases with the observed value, and the fluctuation is small, indicating that this forging method can effectively control the performance consistency and stability of the material. The radial forging method can evenly refine the grain structure of the material after multiple forgings, thereby improving the overall tensile strength of the material.

[0117] Free forging method: The tensile strength of free forging is significantly improved under certain observation values ​​(such as the 9th point reaching 69MPa), but the overall fluctuation is large. This shows that although free forging may have higher tensile strength in local areas, its consistency and stability are not as good as radial forging, and there are large fluctuations in material properties.

[0118] 2. Uniformity and stability advantages

[0119] pass Figure 2 It can be seen that the tensile strength of the material forged by radial forging is more uniform and less volatile. This is precisely the advantage of the medium-temperature radial forging method of the present invention. During the radial forging process, the material gradually reduces in diameter in the radial direction and is evenly stressed, avoiding the stress concentration problem that may occur during the free forging process, thereby ensuring the uniform refinement of the material structure and improving the stability of the tensile strength.

[0120] 3. Optimization of tensile strength and forging process

[0121] Figure 2 The upper control limit (UCL) is 69.57MPa, the lower control limit (LCL) is 45.10MPa, and the average The tensile strength of radial forging is close to the average value at most points, indicating that the process performs well in improving tensile strength while reducing instability. In contrast, although free forging achieves higher tensile strength at some points, it is not conducive to high-demand aerospace and aviation applications due to its large fluctuations.

[0122] 4. Technical effect support of the present invention

[0123] The present invention effectively controls the heating temperature, forging reduction and process steps through a medium-temperature radial forging method, reduces the structural heterogeneity and material property fluctuations during the forging process, and achieves the purpose of significantly improving the tensile strength. Figure 2 The comparison results further prove the advantages of the present invention in improving the tensile strength of materials, especially in thrust chambers and structural parts of aerospace engines that require high temperature and high pressure, the use of radial forging methods can better ensure product quality and consistency.

[0124] In summary, Figure 2The data and trends fully support the technical solution of the present invention, that is, through the optimized medium-temperature radial forging process, the tensile strength of niobium-tungsten alloy bars can be significantly improved, and their stability and consistency can be enhanced, making them more suitable for large-scale industrial applications.

[0125] Figure 3 This is a single value control chart of the elongation of the niobium tungsten alloy rod of Example 2 measured at 1800°C according to different forging methods. The yield strength (Rp0.2) control conditions under radial forging and free forging are compared, and it can be seen that:

[0126] 1. Effect of forging method on yield strength

[0127] Radial forging method: From observation values ​​1 to 6, it can be seen that the yield strength under the radial forging method shows a relatively stable trend, and the observed values ​​gradually increase with small fluctuations, indicating that this forging method can effectively control the consistency of the yield strength of the material. This is consistent with the effect of achieving grain refinement and uniform organization by optimizing the radial forging process in the present invention.

[0128] Free forging method: The yield strength of the free forging method (observation values ​​7 to 12) fluctuates greatly, especially reaching a peak at the 9th observation point. This shows that although free forging can obtain a higher yield strength locally, its consistency is poor and there is a large fluctuation.

[0129] 2. Uniformity and stability advantages

[0130] Figure 3 The yield strength of radial forging is more stable and is consistent with the average value. The results are relatively close, indicating that the process has better controllability. In contrast, although the yield strength of the free forging method is higher at some points, the fluctuation range is larger, which is not conducive to application scenarios with high performance requirements.

[0131] This stability is an important advantage of the medium temperature radial forging technology of the present invention. Through the precise control of the heating temperature, forging reduction and pass number, the material is subjected to more uniform force during the radial forging process, thereby reducing the fluctuation of material properties and improving the stability of yield strength.

[0132] 3. Optimization of yield strength and forging process

[0133] The figure shows that the upper control limit (UCL) is 65.27MPa, the lower control limit (LCL) is 45.06MPa, and the average yield strength is 55.17MPa. Most of the yield strength data points of radial forging are concentrated between 55-60MPa, and although free forging reaches higher values ​​at some points, its fluctuation is large and the instability is obvious.

[0134] This result verifies that the present invention can improve the yield strength of the material through the medium-temperature radial forging method, with a lower number of heating times and an optimized forging process, while ensuring the uniformity and consistency of the yield strength during the forging process.

[0135] 4. Technical effect support

[0136] Figure 3 It is clearly shown that under the condition of 1800°C, the medium-temperature radial forging method of the present invention can significantly improve the yield strength of niobium tungsten alloy bars. In particular, compared with free forging, the yield strength of the material under radial forging is more stable and less volatile, which is suitable for aerospace, aviation and other applications under high temperature and high pressure conditions.

[0137] pass Figure 3 The yield strength comparison results further prove that the technical solution of the present invention has significant advantages in the forging process. Medium-temperature radial forging can not only significantly improve the yield strength of niobium tungsten alloy, but also reduce the volatility of yield strength, making the material performance more stable and consistent, thereby improving its application reliability in high-temperature environments.

[0138] The above embodiment describes in detail all the steps and process parameters involved in the forging process, including heating temperature, forging reduction, forging speed control, etc. Through precise control of different temperature ranges, the present invention can effectively prevent the material from cracking during the forging process, while ensuring that the product has excellent room temperature and high temperature mechanical properties. In addition, the medium temperature radial forging process of the present invention can also significantly reduce surface oxidation and improve the durability and yield rate of the material.

Claims

1. A medium temperature radial forging method for niobium tungsten alloy, characterized in that: The following steps are involved: 1) Pretreatment of niobium-tungsten alloy extruded rods: heat the niobium-tungsten alloy extruded rods at 750-950°C for 60-180 minutes, perform rapid forging and straightening to obtain medium-temperature radial forging rods, and anneal at 1250-1450°C for 60-120 minutes; 2) Medium temperature radial forging: a two-step method is adopted. In the first step, the medium temperature radial forging bar blank is preheated to 80-100°C, Ta1350 high temperature glass powder is coated on its surface, and then it is kept at 1050-1150°C for 90-180min, and the medium temperature radial forging bar blank is forged into a bar with a diameter of 70±1mm by a radial forging process in a manner that the diameter is reduced by 7-10mm each time; in the second step, the obtained bar is preheated to 80-100°C again, Ta1350 high temperature glass powder is coated on its surface, and then it is kept at 1050-1150°C for 90-180min, and the medium temperature radial forging bar blank is forged into a bar with a required specification by a radial forging process in a manner that the diameter is reduced by 5-7mm each time.

2. The niobium-tungsten alloy rod prepared by the forging method according to claim 1, characterized in that: The rod has uniform and fine internal structure and has high high temperature strength.

3. The niobium-tungsten alloy rod according to claim 2, characterized in that: The weight of a single section of the rod is 125-135 kg.

4. The niobium-tungsten alloy rod according to claim 2, characterized in that: The rod is used for manufacturing aerospace engine thrust chambers and high-temperature structural parts.

Images