Medium-density high-strength high-plasticity nickel-tungsten alloy rod and preparation method thereof

Abstract

The application belongs to the technical field of nickel tungsten alloy preparation, and particularly discloses a medium-density high-strength high-plasticity and high-toughness nickel tungsten alloy rod and a preparation method thereof, which comprises the steps of ingot preparation, high-temperature homogenization, blooming forging, intermediate forging, finished product forging and heat treatment; the ingot is prepared through vacuum induction melting and vacuum consumable arc melting, after high-temperature homogenization, the blooming forging adopts hard sleeve combined with soft sleeve and upset and draw deformation, the intermediate forging reduces the temperature and adopts upset + edge surface alternation + eight-side deformation, the finished product forging is subjected to solid solution treatment and then cold deformation at room temperature, and finally, the aging heat treatment is performed to promote the precipitation of Ni4W phase. The nickel tungsten alloy rod prepared by the application has a density of 10.9 g / cm 3 ~ 11.6 g / cm 3 , a tensile tensile strength of 1600 MPa, and the characteristics of uniform structure, small grain size, medium density, high strength, high plasticity and high toughness, and is suitable for industrial manufacturing, mechanical engineering and other fields.

Description

Technical Field

[0001] This invention belongs to the field of nickel-tungsten alloy preparation technology, specifically relating to a medium-density, high-strength, high-ductility and high-toughness nickel-tungsten alloy rod and its preparation method. Background Technology

[0002] In many fields such as industrial manufacturing and mechanical engineering, the performance of metallic materials directly affects the operating efficiency and service life of equipment, thus imposing diverse and stringent requirements. Currently, the high-strength / high-density metallic materials widely used in defense applications mainly fall into two categories: ultra-high-strength steel (such as DT300, G50, AerMet100, etc.) and high-density tungsten alloys (such as 93WNiFe, GW-1, GW-2S, etc.). Among them, ultra-high-strength steel is mostly body-centered cubic with fewer slip systems, which limits its plasticity and toughness. Simultaneously, its density is relatively low, approximately 7.7–7.9 g / cm³, making it difficult to meet the requirements of some applications with specific material density requirements. More importantly, under heavy loads, ultra-high-strength steel is prone to adiabatic shear fracture, severely affecting the normal operation of equipment and significantly shortening its service life. While high-density tungsten alloys have high density and can adapt to some applications with weight requirements, their preparation using powder metallurgy sintering processes has certain limitations. In addition, the weak interfacial bonding between tungsten particles and the binder phase results in poor strength and plasticity of high-density tungsten alloys, making them prone to fracture failure under external forces, which greatly limits their application in a wider range of fields.

[0003] Against this backdrop, to address the challenges of low density and limited slip systems in ultra-high strength steel, as well as the relatively low strength and toughness of high-density tungsten alloys due to powder metallurgy sintering and weak interfacial bonding, the traditional design concept for high-density tungsten alloys was completely abandoned. Instead, a fully solid solution structure was adopted, based on the face-centered cubic (FCC) structure and the principle of age-induced precipitation dispersion strengthening phases. A high-density tungsten element (ρ=19.35 g / cm³) was selected. 3As a solid solution strengthening phase, tungsten can improve the density and strength of the alloy and achieve high penetration capability. Nickel, with its face-centered cubic (FCC) structure, was selected as the solid solution matrix for two reasons: firstly, tungsten has a high solid solubility in nickel (reaching 32% at 800℃); secondly, the addition of tungsten to the nickel matrix not only improves the interatomic bonding force and increases its diffusion activation energy Q, but the difference in atomic radii between tungsten and nickel also enhances solid solution strengthening; and thirdly, nickel's FCC structure increases the internal density and strength of the alloy. The increased number of slip systems during deformation can generate more slip bands and twins, thus avoiding the stress concentration and adiabatic shear band problems common in ultra-high strength steel. Cobalt is an austenite-forming element; adding cobalt can reduce the stacking fault energy of the matrix, which not only strengthens the alloy through solid solution but also promotes the formation of precipitates, improving the alloy's hot working properties, toughness, and impact resistance. Molybdenum and tantalum, as trace additives, can strengthen the alloy through solid solution, increase lattice dislocations, and promote the precipitation of precipitates within the alloy, thereby improving the alloy's strength and plasticity.

[0004] However, in the existing technology, the conventional preparation of nickel-tungsten alloy rods mainly adopts hot deformation, with a deformation temperature of 1180℃~1200℃ and a simple square-to-square upsetting and drawing method. This method has the following technical disadvantages: (1) The deformation temperature is relatively high, and the alloy grains are prone to grow, resulting in an insignificant grain refinement effect; (2) The simple square-to-square upsetting and drawing method is prone to deformation dead zones, making it difficult to control the uniformity of the alloy structure; (3) The upper limit of alloy deformation strengthening is limited by hot deformation alone, and the strength cannot reach more than 1600MPa. These problems seriously affect the further improvement of the performance of nickel-tungsten alloy rods and their widespread application.

[0005] In view of this, this invention is hereby proposed. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a medium-density, high-strength, high-ductility, and high-toughness nickel-tungsten alloy rod and its preparation method. It is mainly used to solve the problems of insufficient ductility and toughness of existing ultra-high strength steel, low density and easy thermal shear fracture, poor strength and ductility of high-density tungsten alloy due to preparation process and interface bonding problems, and insufficient strength due to high deformation temperature, poor microstructure uniformity and only hot deformation in the preparation of conventional nickel-tungsten alloy rods.

[0007] The objective of this invention is achieved through the following technical solution:

[0008] In a first aspect, the present invention provides a method for preparing a medium-density, high-strength, high-ductility, and high-toughness nickel-tungsten alloy rod, the method comprising the following steps:

[0009] Step 1: Preparation of ingots: According to the proportion of each element in the nickel-tungsten alloy, a nickel-tungsten alloy ingot with uniform composition is prepared by vacuum induction melting and vacuum consumable arc melting technology.

[0010] Step 2, High-temperature homogenization: The nickel-tungsten alloy ingot prepared in step 1 is subjected to high-temperature homogenization treatment at 1170℃~1200℃ for 50h~60h.

[0011] Step 3, billet forging: First, the nickel-tungsten alloy ingot treated by high temperature in step 2 is clad, and then held at 1170℃~1200℃ for 2h~6h, and then forged in 2~4 fires to obtain the intermediate billet.

[0012] Step 4, intermediate forging: First, the intermediate billet obtained in step 3 is encased, and then held at 1050℃~1150℃ for 2h~5h, and then subjected to 3~5 fires of intermediate forging to obtain intermediate bar billet;

[0013] Step 5, Finished product forging: The intermediate bar billet obtained in Step 4 is first subjected to solution treatment, and then cold-deformed at room temperature to obtain the intermediate bar stock;

[0014] Step 6, Heat treatment: The intermediate bar obtained in step 5 is subjected to aging heat treatment to obtain the target nickel-tungsten alloy bar.

[0015] Further, in step 1, the composition and mass percentage of the nickel-tungsten alloy are as follows: W: 35%–42%, Co: 5%–10%, Mo: 1%–5%, Ta: 1%–3%, with the balance being Ni and unavoidable trace elements and impurity elements;

[0016] The refining temperature during vacuum induction melting is 1550℃~1570℃, and the casting temperature is 1620℃~1640℃.

[0017] The melting rate during vacuum self-consuming arc melting is 2.5 kg / min to 3.8 kg / min.

[0018] Furthermore, in step 3, when the nickel-tungsten alloy ingot is sheathed, a combination of soft sheathing (such as asbestos) and hard sheathing (such as carbon steel, stainless steel, etc.) is used to reduce the risk of cracking caused by rapid temperature drop, and to successfully complete the billet forging. If the sheath falls off during the billet forging process, the forging must be stopped, the ingot must be re-sheathed and heated, and then the billet forging process can continue.

[0019] Furthermore, in step 3, the upsetting and drawing deformation method is adopted during the billet forging. The forging ratio is controlled between 1.3 and 1.7 during upsetting, and the deformation amount is controlled between 25% and 40% during drawing to ensure that the as-cast structure is sufficiently refined and the uniformity of different positions.

[0020] The final forging temperature during the initial forging process is greater than or equal to 1050℃. If the temperature is less than 1050℃, the forging is carried out in the furnace to be heated to 1170℃~1200℃ before forging. After forging, the forging is air-cooled.

[0021] Furthermore, in step 4, when the intermediate billet is sheathed, a soft sheath (such as asbestos) is used. If the sheath falls off during the intermediate forging process, the forging must be stopped, the intermediate billet is re-sheathed and heated, and then the forging process can continue.

[0022] Furthermore, in step 4, the intermediate forging adopts the method of upsetting and drawing + alternating faceting + octagonal deformation, the upsetting ratio is controlled between 1.5 and 2.0, and the drawing deformation is controlled between 30% and 50% to ensure the forgeability of the alloy and the uniformity of the transverse and longitudinal structure.

[0023] During intermediate forging, the final forging temperature is greater than or equal to 900℃. If the temperature is less than 900℃, the temperature is returned to the furnace to be heated to 1050℃~1150℃ before forging, and then air-cooled after forging.

[0024] Furthermore, in step 5, the specific process of forging the finished product is as follows: first, the intermediate billet is heated to 1050℃~1200℃, held for 2h~4h, and then removed from the furnace and water-cooled to complete the solution treatment; then, after the intermediate billet cools to room temperature (20℃~30℃), it is cold-deformed by drawing, with the drawing deformation controlled at 10%~25%, and the final forging temperature less than or equal to 400℃, thereby increasing the dislocation density of the alloy and enhancing the deformation strengthening effect.

[0025] Furthermore, in step 6, the aging heat treatment temperature is 600℃~800℃ and the time is 4h~10h. The purpose of aging strengthening is to promote the precipitation of Ni4W phase, thereby solving the limitation of the upper limit of the strength of nickel-tungsten alloy.

[0026] Secondly, the present invention also provides a medium-density, high-strength, high-ductility, and high-toughness nickel-tungsten alloy rod, which is prepared based on the above-described preparation method. The properties of the nickel-tungsten alloy rod are as follows: density ρ is 10.9 g / cm³. 3 ~11.6g / cm 3 Tensile strength R m >1600MPa, yield strength R p0.2 >1350MPa, elongation A>15%, reduction of area Z>30%, impact toughness aku>70J / cm 2 .

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] The preparation method provided by this invention firstly involves wrapping the nickel-tungsten alloy ingot with both hard and soft sheaths during the initial forging process, and wrapping the intermediate billet with a soft sheath during the intermediate forging process. This effectively prevents cracking of the material due to temperature reduction, ensuring the smooth progress of the forging process and laying a stable foundation for subsequent processes. Secondly, the initial forging process employs upsetting and drawing deformation, avoiding uneven deformation and dead zones, ensuring sufficient refinement of the as-cast microstructure and guaranteeing uniformity at different locations. During the intermediate forging process, the forging temperature is lowered to prevent excessive grain growth. Simultaneously, the composite deformation method of upsetting, alternating facets, and octagonal deformation further reduces deformation dead zones and ensures the alloy's forgeability and the uniformity of its transverse and longitudinal microstructure, resulting in consistent properties across all parts of the material. Finally, solution treatment followed by room temperature cold deformation effectively increased the dislocation density of the alloy and enhanced the strain hardening effect. Subsequent aging treatment effectively promoted the precipitation of the Ni4W phase. Through this synergistic effect, the limitation of increasing the upper limit of the strength of nickel-tungsten alloys was successfully overcome. The resulting medium-density ultra-high strength nickel-tungsten alloy rods exhibited a uniform microstructure and fine grains, with a density of 10.9 g / cm³. 3 ~11.6g / cm 3 With a tensile strength greater than 1600MPa and taking into account other mechanical properties, it can effectively make up for the shortcomings of ultra-high strength steel and high-density tungsten alloys in terms of performance, and broaden the application prospects of nickel-tungsten alloys in industrial manufacturing, mechanical engineering and other fields. Attached Figure Description

[0029] The accompanying drawings are incorporated in and form part of this specification, and together with the description serve to explain the principles of the invention.

[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 This is a flowchart of the preparation method of the medium-density, high-strength, high-ductility, and high-toughness nickel-tungsten alloy rod of the present invention;

[0032] Figure 2 High-magnification micrograph of a Φ220mm intermediate bar billet prepared in the forging state according to Example 1 of the present invention;

[0033] Figure 3 TEM image of dislocations after cold deformation of a Φ210mm intermediate bar prepared in Example 1 of this invention;

[0034] Figure 4This is a TEM image showing the Ni4W phase diffraction spots after aging of a Φ200mm nickel-tungsten alloy rod prepared in Example 1 of this invention.

[0035] Figure 5 TEM image of the Ni4W phase after aging of a Φ200mm nickel-tungsten alloy rod prepared in Example 1 of this invention;

[0036] Figure 6 This is a high-magnification micrograph of a Φ175mm intermediate bar billet in the forging state prepared in Example 2 of the present invention;

[0037] Figure 7 TEM image of the Ni4W phase after aging of a Φ150mm nickel-tungsten alloy rod prepared in Example 2 of this invention;

[0038] Figure 8 This is a high-magnification micrograph of a Φ130mm intermediate bar billet prepared in the forging state according to Example 3 of the present invention;

[0039] Figure 9 TEM image of the Ni4W phase after aging of the Φ100mm nickel-tungsten alloy rod prepared in Example 3 of this invention. Detailed Implementation

[0040] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Rather, they are merely examples consistent with some aspects of the invention as detailed in the appended claims.

[0041] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0042] Please see Figure 1 The present invention provides a method for preparing a medium-density, high-strength, high-ductility, and high-toughness nickel-tungsten alloy rod, which specifically includes the following steps:

[0043] Step 1: Prepare the ingot

[0044] Based on the proportions of each element in the nickel-tungsten alloy, a two-stage technology combining vacuum induction melting and vacuum consumable arc melting was used to prepare a nickel-tungsten alloy ingot with uniform composition.

[0045] The composition and mass percentage of the nickel-tungsten alloy are as follows: W: 35%–42%, Co: 5%–10%, Mo: 1%–5%, Ta: 1%–3%, with the balance being Ni and unavoidable trace elements and impurities; the refining temperature during vacuum induction melting is 1550℃–1570℃, and the casting temperature is 1620℃–1640℃; the melting rate during vacuum consumable arc melting is 2.5 kg / min–3.8 kg / min.

[0046] Step 2, High-temperature homogenization

[0047] The nickel-tungsten alloy ingot prepared in step 1 is subjected to high-temperature homogenization treatment at 1170℃~1200℃ for 50h~60h to eliminate ingot microstructure segregation and achieve chemical composition homogenization, thus preparing for billet forging.

[0048] Step 3: Forging the billet

[0049] First, the nickel-tungsten alloy ingots that have undergone high-temperature homogenization treatment in step 2 are treated with soft cladding (asbestos) and hard cladding (carbon steel, stainless steel); then, they are held at 1170℃~1200℃ for 2h~6h, and then subjected to 2~4 fires of forging to obtain intermediate billets.

[0050] During the initial forging process, if the cladding falls off, forging must be stopped, the nickel-tungsten alloy ingot re-clad and heated, and then the forging process can continue. The initial forging employs an upsetting and drawing deformation method. During upsetting, the forging ratio is controlled between 1.3 and 1.7, and during drawing, the deformation is controlled between 25% and 40%. The final forging temperature is never lower than 1050℃ (if the temperature is lower than 1050℃, it is returned to the furnace to be heated to 1170℃–1200℃ before forging). After forging, air cooling is performed to ensure sufficient refinement of the as-cast microstructure and uniformity in different locations. The initial forging uses a multi-heat upsetting and drawing deformation method to avoid uneven deformation and dead zones. Simultaneously, the continuous furnace reheating method prevents grain growth after refinement due to excessive heating time, fully ensuring the degree of microstructure refinement and effectively guaranteeing the uniformity of microstructure and properties.

[0051] Step 4, Intermediate Forging

[0052] First, the intermediate billet obtained in step 3 is treated with a soft sheath (asbestos); then, it is held at 1050℃~1150℃ for 2h~5h and subjected to 3~5 heat intermediate forging to obtain an intermediate bar billet.

[0053] During intermediate forging, if the sheath falls off, forging must be stopped, the intermediate billet must be re-sheathed and heated, and then the forging process can continue. Intermediate forging adopts upsetting, drawing, alternating faceting, and octagonal deformation. The upsetting ratio is controlled between 1.5 and 2.0, the drawing deformation is controlled between 30% and 50%, and the final forging temperature is not lower than 900℃ (if the temperature is lower than 900℃, it is returned to the furnace to be heated to 1050℃ to 1150℃ before forging, and then air-cooled after forging) to ensure the forgeability of the alloy and the uniformity of the transverse and longitudinal structure.

[0054] Step 5: Finished Product Forging

[0055] First, heat the intermediate billet obtained in step 4 to 1050℃~1200℃, hold it for 2h~4h, remove it from the furnace and water cool it. Through solution treatment, the plasticity of the alloy is improved. Then, the intermediate billet is drawn and cold deformed at room temperature to improve the dislocation density and strain hardening of the alloy. The deformation amount is controlled at 10%~25%, and the final forging temperature is not higher than 400℃.

[0056] Step 6, Heat Treatment

[0057] The intermediate bar obtained in step 5 is subjected to aging heat treatment with the following process parameters: temperature range of 600℃~800℃ and heat treatment time of 4h~10h.

[0058] To further verify the effectiveness of the present invention, the inventors conducted the following specific experiments:

[0059] Example 1

[0060] This embodiment aims to prepare a medium-density, high-strength, high-ductility, and high-toughness nickel-tungsten alloy rod with a diameter of 200 mm. Its composition and the mass percentage of each component are as follows: W: 35%, Co: 5%, Mo: 1%, Ta: 3%, with the balance being Ni and unavoidable trace elements and impurities. The detailed preparation process is as follows:

[0061] 1) Ingot preparation

[0062] According to the proportions of each element in the nickel-tungsten alloy, vacuum induction melting was first used, with a refining temperature of 1550℃ and a casting temperature of 1620℃, to cast the alloy liquid into electrodes; then, vacuum consumable arc melting was used at a melting rate of 2.5 kg / min to prepare qualified (uniform composition) nickel-tungsten alloy ingots.

[0063] 2) High-temperature homogenization

[0064] The nickel-tungsten alloy ingot prepared in step 1) was subjected to high-temperature homogenization treatment at 1200℃ for 50 hours and then air-cooled.

[0065] 3) Forging of billets

[0066] First, the nickel-tungsten alloy ingots treated with high-temperature homogenization in step 2) are subjected to soft cladding (asbestos) and hard cladding (carbon steel); then, they are heated and held at that temperature for 4-fire forging, the specific process of which is as follows:

[0067] First, the nickel-tungsten alloy ingot is heated to 1200℃ and held for 6 hours. The forging process uses upsetting and drawing deformation, with the upsetting-to-forging ratio controlled at 1.3, the drawing deformation controlled at 25%, and the final forging temperature controlled above 1050℃ for the first forging. Then, asbestos-coated hot material is returned to the furnace to 1200℃ and held for 2 hours for the second forging. The forging process again uses upsetting and drawing deformation, with the upsetting-to-forging ratio controlled at 1.5, the drawing deformation controlled at 30%, and the final forging temperature controlled above 1050℃. After forging, the material is air-cooled. After air-cooling, the material is ground and cleaned, then soft-sheathed. The material is treated with asbestos and a hard sheath (carbon steel); then heated to 1170℃ and held for 5 hours for a third forging, with the upsetting ratio controlled at 1.5, the elongation deformation controlled at 30%, and the final forging temperature controlled above 1050℃; then the hot asbestos material is returned to the furnace to 1170℃ and held for 2 hours for a fourth forging, with the forging process using upsetting and drawing deformation, the upsetting ratio controlled at 1.7, the elongation deformation controlled at 40%, and the final forging temperature controlled above 1050℃. After forging, it is air-cooled to obtain an intermediate billet with an octagonal cross-section of 440mm.

[0068] 4) Intermediate forging

[0069] First, the intermediate billet obtained in step 3) is treated with a soft sheath (asbestos); then it is heated and held at that temperature for a three-fire intermediate forging process, as follows:

[0070] First, the intermediate billet is heated to 1150℃ and held for 5 hours. The upsetting-to-forging ratio is controlled at 1.5, the elongation deformation is controlled at 30%, and the final forging temperature is controlled above 1000℃ for the first forging. Then, asbestos-coated hot material is wrapped and the billet is reheated to 1150℃ and held for 2 hours for the second forging. The upsetting-to-forging ratio is controlled at 1.7, the elongation deformation is controlled at 40%, and the final forging temperature is controlled above 1000℃. Next, asbestos-coated hot material is wrapped and the billet is reheated to 1100℃ and held for 2 hours for the third forging. The upsetting-to-forging ratio is controlled at 1.7, the elongation deformation is controlled at 40%, and the final forging temperature is controlled above 900℃. After forging, the billet is air-cooled, resulting in an intermediate billet with a diameter of 220mm. The forging process employs a stepped cooling + upsetting-drawing + alternating faceting + octagonal deformation method to ensure the alloy's forgeability and the uniformity of its transverse and longitudinal microstructure.

[0071] 5) Finished product forging

[0072] First, heat the intermediate bar billet obtained in step 4) to 1200℃, hold it for 4 hours, and then perform solution treatment by water cooling after taking it out of the furnace; then perform cold deformation at room temperature, with a drawing deformation rate of 5-10 mm / s, a deformation amount of 10%, and a final forging temperature not higher than 400℃. After air cooling, an intermediate bar with a diameter of 210 mm is obtained.

[0073] 6) Heat treatment

[0074] The intermediate bar obtained in step 5) is subjected to air-cooling aging heat treatment at 600℃ for 4 hours to promote the precipitation of Ni4W phase. Finally, it is machined to Φ200mm to obtain the target nickel-tungsten alloy bar.

[0075] Performance testing

[0076] The internal microstructure of the intermediate material in Example 1 and the internal microstructure and mechanical properties of the final Φ200mm nickel-tungsten alloy rod were tested. Figure 2 (High-magnification micrograph of the Φ220mm intermediate bar billet in the forging state prepared in Example 1 (after processing in step 4)). Figure 3 (TEM image of dislocations after cold transformation of Φ210mm intermediate bar prepared in Example 1 (after processing in step 5)). Figure 4 (TEM image of Ni4W phase diffraction spots after aging of Φ200mm nickel-tungsten alloy rod prepared in Example 1 (after processing in step 6)). Figure 5 TEM images of the Ni4W phase distribution after aging of the Φ200mm nickel-tungsten alloy rod prepared in Example 1. Table 1 below shows the test results of the mechanical properties of the Φ200mm nickel-tungsten alloy rod prepared in Example 1.

[0077] Table 1. Test results of mechanical properties of Φ200mm nickel-tungsten alloy bars prepared in Example 1

[0078]

[0079] Results Analysis

[0080] Figure 2 The high-magnification microstructure of the Φ220mm intermediate bar billet prepared in step 4) of Example 1 of the present invention shows that the grain size is about 35μm, which is relatively fine and uniform, and can achieve the effect of fine grain strengthening. Figure 3 The dislocation TEM structure of the Φ210mm intermediate bar after room temperature cold deformation in step 5) shows that after cold deformation, the dislocations in the alloy become entangled with each other, forming dislocation pile-up and dislocation network, which are cellular structures. The pinning effect is enhanced, the deformation strengthening is obvious, and it also provides more nucleation sites for the precipitation of Ni4W phase during the aging process. Figure 4 , Figure 5The TEM microstructure of the Φ200mm nickel-tungsten alloy rod after aging in step 6) shows that the precipitated phase is Ni4W, with a tetragonal crystal system, space group I4 / m, and cell parameters a=b=0.5730 and c=0.3553. Furthermore, aging reveals the precipitation of a large amount of nano-sized Ni4W phase, achieving age-strengthening and thus overcoming the limitation of the upper strength limit of nickel-tungsten alloys. Table 1 shows the mechanical property test results, indicating that the density of the nickel-tungsten alloy rod prepared in this embodiment is 10.9 g / cm³. 3 It has a tensile strength greater than 1600MPa, a tensile yield strength greater than 1350MPa, and good plasticity and toughness, exhibiting excellent overall performance.

[0081] Example 2

[0082] This embodiment aims to prepare a medium-density, high-strength, high-ductility, and high-toughness nickel-tungsten alloy rod with a diameter of 150 mm. Its composition and the mass percentage of each component are as follows: W: 38%, Co: 7%, Mo: 3%, Ta: 2%, with the balance being Ni and unavoidable trace elements and impurities. The detailed preparation process is as follows:

[0083] 1) Ingot preparation

[0084] According to the proportions of each element in the nickel-tungsten alloy, vacuum induction melting was first used, with a refining temperature of 1560℃ and a casting temperature of 1630℃, to cast the alloy liquid into electrodes; then, vacuum consumable arc melting was used at a melting rate of 3.0 kg / min to prepare qualified (uniform composition) nickel-tungsten alloy ingots.

[0085] 2) High-temperature homogenization

[0086] The nickel-tungsten alloy ingot prepared in step 1) was subjected to high-temperature homogenization treatment at 1170℃ for 60 hours and then air-cooled.

[0087] 3) Forging of billets

[0088] First, the nickel-tungsten alloy ingots subjected to the high-temperature homogenization treatment in step 2) are treated with a soft sheath (asbestos) and a hard sheath (stainless steel); then, they are heated and held at that temperature for three-stage forging. The specific process is as follows:

[0089] First, the nickel-tungsten alloy ingot is heated to 1200℃ and held for 5 hours. The forging process adopts upsetting and drawing deformation, with the upsetting-to-roughing ratio controlled at 1.4, the drawing deformation controlled at 30%, and the final forging temperature controlled above 1050℃ for the first forging. Then, asbestos hot material is wrapped and the furnace is heated to 1170℃ and held for 2 hours for the second forging. The forging process adopts upsetting and drawing deformation, with the upsetting-to-roughing ratio controlled at 1.7, the drawing deformation controlled at 40%, and the final forging temperature controlled above 1050℃. After forging, asbestos hot material is wrapped and the furnace is heated to 1170℃ and held for 2 hours for the third forging. The forging process adopts upsetting and drawing deformation, with the upsetting-to-roughing ratio controlled at 1.7, the drawing deformation controlled at 40%, and the final forging temperature controlled above 1050℃. After forging, it is air-cooled to obtain an intermediate billet with an octagonal cross-section of 400mm.

[0090] 4) Intermediate forging

[0091] First, the intermediate billet obtained in step 3) is treated with a soft sheath (asbestos); then it is heated and held at that temperature for 4-fire intermediate forging, the specific process of which is as follows:

[0092] First, the intermediate billet is heated to 1150℃ and held for 5 hours. The upsetting ratio is controlled at 1.5, the elongation deformation is controlled at 30%, and the final forging temperature is controlled above 1000℃ for the first forging. Then, asbestos hot material is wrapped around the billet and the billet is reheated to 1100℃ and held for 2 hours for the second forging. The upsetting ratio is controlled at 1.7, the elongation deformation is controlled at 40%, and the final forging temperature is controlled above 900℃. After forging, the billet is air-cooled. After grinding and cleaning, the billet is heated to 1050℃ and held for 4 hours for the third forging. The upsetting ratio is controlled at 2.0, the elongation deformation is controlled at 40%, and then asbestos hot material is wrapped around the billet and the billet is reheated to 1050℃ and held for 2 hours for the fourth forging. The elongation deformation is controlled at 50%, and the final forging temperature is controlled above 900℃. After forging, the billet is air-cooled to obtain an intermediate billet with a diameter of 175mm. The forging process employs a stepped cooling + upsetting + alternating faceting + octagonal deformation method to ensure the alloy's forgeability and the uniformity of its transverse and longitudinal microstructure.

[0093] 5) Finished product forging

[0094] First, heat the intermediate bar billet obtained in step 4) to 1100℃, hold it for 3 hours, and then perform solution treatment by water cooling after taking it out of the furnace; then perform cold deformation at room temperature, with a drawing deformation rate of 5-10 mm / s, a deformation amount of 15%, and a final forging temperature not higher than 400℃. After air cooling, an intermediate bar with a diameter of 160 mm is obtained.

[0095] 6) Heat treatment

[0096] The intermediate bar obtained in step 5) is subjected to air-cooling aging heat treatment at 700℃ for 6 hours to promote the precipitation of Ni4W phase. Finally, it is machined to Φ150mm to obtain the target nickel-tungsten alloy bar.

[0097] Performance testing

[0098] The internal microstructure of the intermediate material in Example 2 and the internal microstructure and mechanical properties of the final Φ150mm nickel-tungsten alloy rod were tested. Figure 6 (High-magnification micrograph of the Φ175mm intermediate bar billet in the forging state prepared in Example 2 (after processing in step 4)). Figure 7 The image below shows the TEM image of the Ni4W phase after aging of the Φ150mm nickel-tungsten alloy rod prepared in Example 2 (after processing in step 6). Table 2 below shows the test results of the mechanical properties of the Φ150mm nickel-tungsten alloy rod prepared in Example 2.

[0099] Table 2. Test results of mechanical properties of Φ150mm nickel-tungsten alloy bars prepared in Example 2

[0100]

[0101] Results Analysis

[0102] Figure 6 The high-magnification microstructure of the Φ175mm intermediate bar billet prepared in step 4) of Example 2 of the present invention shows that the grain size is about 30μm, which is relatively fine and uniform, and achieves the effect of fine grain strengthening. Figure 7 The image shows the Ni4W phase TEM image of a Φ150mm nickel-tungsten alloy rod after aging in step 6) of Example 2, demonstrating the achievement of age-hardening. Table 2 shows that the density of the prepared nickel-tungsten alloy rod is 11.0 g / cm³. 3 It has a tensile strength greater than 1650 MPa, a tensile yield strength greater than 1430 MPa, and good plasticity and toughness, exhibiting excellent overall performance.

[0103] Example 3

[0104] This embodiment aims to prepare a medium-density, high-strength, high-ductility, and high-toughness nickel-tungsten alloy rod with a diameter of 100 mm. Its composition and the mass percentage of each component are as follows: W: 42%, Co: 10%, Mo: 5%, Ta: 1%, with the balance being Ni and unavoidable trace elements and impurities. The detailed preparation process is as follows:

[0105] 1) Ingot preparation

[0106] According to the proportions of each element in the nickel-tungsten alloy, vacuum induction melting was first used, with a refining temperature of 1570℃ and a casting temperature of 1640℃, to cast the alloy liquid into electrodes; then, vacuum consumable arc melting was used at a melting rate of 3.8 kg / min to prepare qualified (uniformly composed) nickel-tungsten alloy ingots.

[0107] 2) High-temperature homogenization

[0108] The nickel-tungsten alloy ingot prepared in step 1) was subjected to high-temperature homogenization treatment at 1180℃ for 55 hours and then air-cooled.

[0109] 3) Forging of billets

[0110] First, the nickel-tungsten alloy ingots treated with high-temperature homogenization in step 2) are subjected to soft cladding (asbestos) and hard cladding (carbon steel, stainless steel); then, they are heated and held at that temperature for two-stage forging. The specific process is as follows:

[0111] First, the nickel-tungsten alloy ingot is heated to 1180℃ and held for 5 hours. The forging process adopts upsetting and drawing deformation, with the upsetting-to-roughing ratio controlled at 1.4, the drawing deformation controlled at 30%, and the final forging temperature controlled above 1050℃ for the first forging. Then, asbestos hot material is wrapped and returned to the furnace to 1180℃ and held for 2 hours for the second forging. The forging process adopts upsetting and drawing deformation, with the upsetting-to-roughing ratio controlled at 1.7, the drawing deformation controlled at 40%, and the final forging temperature controlled above 1050℃. After forging, it is air-cooled to obtain an intermediate billet with an octagonal cross-section of 420mm.

[0112] 4) Intermediate forging

[0113] First, the intermediate billet obtained in step 3) is treated with a soft sheath (asbestos); then it is heated and held at that temperature for 5 heats of intermediate forging. The specific process is as follows:

[0114] First, heat the intermediate billet to 1150℃ and hold for 5 hours. Control the upsetting ratio at 1.5, the elongation deformation at 30%, and the final forging temperature above 1000℃ for the first forging. Then, wrap the hot asbestos charge and reheat to 1150℃, holding for 2 hours for the second forging. Control the upsetting ratio at 1.7, the elongation deformation at 40%, and the final forging temperature above 900℃. Air cool after forging. After grinding and cleaning, wrap the billet with asbestos and heat to 1100℃, holding for 4 hours, and then proceed with... The third forging process involves upsetting to a ratio of 1.7, with the elongation deformation controlled at 40%. Then, asbestos-coated hot material is reheated to 1100℃ and held for 2 hours for the fourth forging process, again with elongation deformation controlled at 40% and a final forging temperature above 900℃. This is followed by reheating to 1050℃ with asbestos-coated hot material and holding for 2 hours for the fifth forging process, with elongation deformation controlled at 50% and a final forging temperature above 900℃. After forging, the material is air-cooled, resulting in a 130mm diameter intermediate billet. The forging process employs a stepped cooling + upsetting + alternating faceting + octagonal deformation method to ensure the alloy's forgeability and the uniformity of its transverse and longitudinal microstructure.

[0115] 5) Finished product forging

[0116] First, heat the intermediate bar billet obtained in step 4) to 1050℃, hold it for 2 hours, and then perform a solution treatment by water cooling after taking it out of the furnace; then perform cold deformation at room temperature, with a drawing deformation rate of 5-10 mm / s, a deformation amount of 25%, and a final forging temperature not higher than 400℃. After air cooling, an intermediate bar with a diameter of 110 mm is obtained.

[0117] 6) Heat treatment

[0118] The intermediate bar obtained in step 5) is subjected to air-cooling aging heat treatment at 800℃ for 10 hours to promote the precipitation of Ni4W phase. Finally, it is machined to Φ100mm to obtain the target nickel-tungsten alloy bar.

[0119] Performance testing

[0120] The internal microstructure of the intermediate material in Example 3 and the internal microstructure and mechanical properties of the final Φ100mm nickel-tungsten alloy rod were tested. Figure 8 (High-magnification micrograph of the Φ130mm intermediate bar billet in the forging state prepared in Example 3 (after processing in step 4)). Figure 9 The image below shows the TEM image of the Ni4W phase after aging of the Φ100mm nickel-tungsten alloy rod prepared in Example 3 (after processing in step 6). Table 3 below shows the test results of the mechanical properties of the Φ100mm nickel-tungsten alloy rod prepared in Example 3.

[0121] Table 3. Test results of mechanical properties of Φ100mm nickel-tungsten alloy rods prepared in Example 3

[0122]

[0123] Results Analysis

[0124] Figure 8 The high-magnification microstructure of the Φ130mm intermediate bar billet prepared in step 4) of Example 3 of the present invention shows that the grain size is about 15μm, which is relatively fine and uniform, and achieves the effect of fine grain strengthening. Figure 9 The image shows the Ni4W phase TEM image of the Φ100mm nickel-tungsten alloy rod after aging in step 6) of Example 3, demonstrating the achievement of age-hardening effect. Table 3 shows that the density of the prepared nickel-tungsten alloy rod is 11.6 g / cm³. 3 It has a tensile strength greater than 1700 MPa, a tensile yield strength greater than 1500 MPa, and good plasticity and toughness, exhibiting excellent overall performance.

[0125] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention.

[0126] It should be understood that the present invention is not limited to the content already described above, and various modifications and changes can be made without departing from its scope. The scope of the present invention is limited only by the appended claims.

Claims

1. A method for preparing a medium-density, high-strength, high-ductility, and high-toughness nickel-tungsten alloy rod, characterized in that, The preparation method includes the following steps: Step 1: Ingot preparation: According to the proportion of each element in the nickel-tungsten alloy, a two-stage technology of vacuum induction melting and vacuum consumable arc melting is used to prepare a nickel-tungsten alloy ingot with uniform composition. The composition and mass percentage of each component of the nickel-tungsten alloy are as follows: W: 35%~42%, Co: 5%~10%, Mo: 1%~5%, Ta: 1%~3%, with the balance being Ni and unavoidable trace elements and impurity elements. Step 2, High-temperature homogenization: The nickel-tungsten alloy ingot prepared in step 1 is subjected to high-temperature homogenization treatment at 1170℃~1200℃ for 50h~60h. Step 3, billet forging: First, the nickel-tungsten alloy ingot treated by high temperature in step 2 is clad, and then held at 1170℃~1200℃ for 2h~6h, and then forged in 2~4 fires to obtain the intermediate billet. Step 4, intermediate forging: First, the intermediate billet obtained in step 3 is encased, and then held at 1050℃~1150℃ for 2h~5h, and then subjected to 3~5 fires of intermediate forging to obtain intermediate bar billet; Step 5, Finished product forging: The intermediate bar billet obtained in Step 4 is first subjected to solution treatment, and then cold-deformed at room temperature to obtain the intermediate bar stock; Step 6, Heat treatment: The intermediate bar obtained in step 5 is subjected to aging heat treatment to obtain the target nickel-tungsten alloy bar.

2. The method for preparing the medium-density, high-strength, high-ductility, and high-toughness nickel-tungsten alloy rod according to claim 1, characterized in that, In step 1, the refining temperature during vacuum induction melting is 1550℃~1570℃, and the casting temperature is 1620℃~1640℃. The melting rate during vacuum self-consuming arc melting is 2.5 kg / min to 3.8 kg / min.

3. The method for preparing the medium-density, high-strength, high-ductility, and high-toughness nickel-tungsten alloy rod according to claim 1, characterized in that, In step 3, when the nickel-tungsten alloy ingot is clad, a combination of soft cladding and hard cladding is used. If the cladding falls off during the billet forging process, forging must be stopped, the nickel-tungsten alloy ingot is re-clad and heated, and then the billet forging process can continue.

4. The method for preparing the medium-density, high-strength, high-ductility, and high-toughness nickel-tungsten alloy rod according to claim 1, characterized in that, In step 3, the forging process involves upsetting and drawing deformation. During upsetting, the forging ratio is controlled at 1.3 to 1.7, and during drawing, the deformation is controlled at 25% to 40%. The final forging temperature during the initial forging process is greater than or equal to 1050℃. If the temperature is less than 1050℃, the forging is carried out in the furnace to be heated to 1170℃~1200℃ before forging. After forging, the forging is air-cooled.

5. The method for preparing the medium-density, high-strength, high-ductility, and high-toughness nickel-tungsten alloy rod according to claim 1, characterized in that, In step 4, when the intermediate billet is sheathed, a soft sheath is used. If the sheath falls off during the intermediate forging process, the forging must be stopped, the intermediate billet is re-sheathed and heated, and then the intermediate forging process can be continued.

6. The method for preparing the medium-density, high-strength, high-ductility, and high-toughness nickel-tungsten alloy rod according to claim 1, characterized in that, In step 4, the intermediate forging process employs an alternating upsetting and drawing process with faceting and octagonal deformation. The upsetting ratio is controlled between 1.5 and 2.0, and the drawing deformation is controlled between 30% and 50%. During intermediate forging, the final forging temperature is greater than or equal to 900℃. If the temperature is less than 900℃, the temperature is returned to the furnace to be heated to 1050℃~1150℃ before forging, and then air-cooled after forging.

7. The method for preparing the medium-density, high-strength, high-ductility, and high-toughness nickel-tungsten alloy rod according to claim 1, characterized in that, In step 5, the specific process of forging the finished product is as follows: first, the intermediate billet is heated to 1050℃~1200℃, held for 2h~4h, and then removed from the furnace and water-cooled to complete the solution treatment; then, after the intermediate billet cools to room temperature, it is cold-deformed by drawing, with the drawing deformation amount controlled at 10%~25%, and the final forging temperature less than or equal to 400℃.

8. The method for preparing the medium-density, high-strength, high-ductility, and high-toughness nickel-tungsten alloy rod according to claim 1, characterized in that, In step 6, the aging heat treatment temperature is 600℃~800℃, and the time is 4h~10h.

9. A medium-density, high-strength, high-ductility, and high-toughness nickel-tungsten alloy rod, characterized in that, The nickel-tungsten alloy rod is prepared according to any one of the preparation methods described in claims 1 to 8.

10. The medium-density, high-strength, high-ductility, and high-toughness nickel-tungsten alloy rod according to claim 9, characterized in that, The properties of the nickel-tungsten alloy rod are as follows: density ρ is 10.9 g / cm³. 3 ~11.6g / cm 3 Tensile strength R m >1600MPa, yield strength R p0.2 >1350MPa, elongation A>15%, reduction of area Z>30%, impact toughness aku>70J / cm 2 .

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