Forging method of Ti1100 alloy with high strength, high creep resistance and high structure stability

Abstract

The invention relates to a forging method of a high-strength, high-creep-resistance and high-structure-stability Ti1100 alloy bar, belongs to the technical field of titanium alloys, and aims to solve the problems that in the forging process of an existing method, macrosegregation is prone to occurring; at least one of the problems that the process is difficult to control due to narrowing of a machining window, forging is difficult due to great increase of deformation resistance, cracking is caused due to plasticity reduction, and the Ti1100 alloy bar is poor in structure stability and short in service time are solved. According to the forging method of the Ti1100 alloy bar, through one-heating-number blooming forging, one-heating-number grain refinement and homogenization forging and 2-4-heating-number cross-phase region forging, the problem of macrosegregation caused by high alloy element content in the forging process is solved; and the problems that the process is difficult to control due to narrowing of a machining window, forging is difficult due to great increase of deformation resistance, and cracking is caused due to plasticity reduction are solved.

Description

Technical Field

[0001] This invention relates to the field of titanium alloy technology, and in particular to a forging method for Ti1100 alloy bars with high strength, high creep resistance and high microstructure stability. Background Technology

[0002] Ti1100 alloy, through the synergistic effect of solid solution strengthening (Al, Sn, Zr), precipitation strengthening (Si), phase stabilization (Al, Mo), and oxidation resistance (Al, Zr), possesses key indicators such as high-temperature strength, long creep life, and strong oxidation resistance. Ultimately, this makes it a high-temperature structural material for aero-engines that can operate at 600-700℃ for extended periods, meeting the aerospace industry's demand for "lightweight, high-temperature resistant, and long-life" titanium alloy components.

[0003] The ASM Ti-104 standard has clearly defined the proportions of various alloying elements in the alloy. Within the range of compositional control, the higher the content of alloying elements, the more significant their strengthening effect on the alloy's service strength and creep resistance. Therefore, in industrial applications, a high proportion of alloying elements is generally desirable. However, a high proportion of alloying elements will bring a series of problems to subsequent forging, specifically: (1) Macro segregation during forging is difficult to eliminate. If the element content is too high during the melting process of Ti1100 alloy (such as vacuum arc furnace VAR), it will exceed the uniform mixing capacity of the melt, resulting in compositional segregation (such as Al enrichment zone and Si agglomeration zone) inside the ingot. Although forging can improve macro segregation, it cannot completely eliminate micro segregation.

[0004] (2) The narrowing of the processing window makes the process difficult to control. The forging of Ti1100 requires finding a stable hot working window between the "plastic range" and the "phase transformation range". However, excessive alloying elements will directly compress this window. For example, α-stabilizing elements such as Al and Sn will increase the β phase transformation point, while β-stabilizing elements such as Mo will decrease the β phase transformation point. If the element content exceeds the range, the calculation accuracy of the β phase transformation point will decrease (for example, for every 0.5% increase in Al content, the β phase transformation point may increase by 20-30℃). This will cause the originally set forging temperature to be close to or exceed the phase transformation point. If it is too low below the phase transformation point, the plasticity will be insufficient, and if it is close to the phase transformation point, defects such as local coarse grains or microstructure delamination are likely to occur. On the other hand, during the forging process, the refinement of alloy grains mainly depends on "dynamic recrystallization". Excessive alloying elements (especially Si and Mo) will be adsorbed at grain boundaries or dislocations, hindering dislocation migration and grain boundary movement, inhibiting the occurrence of dynamic recrystallization, and ultimately the forging is prone to "uneven grain size", which leads to a wider range of fluctuations in mechanical properties (such as tensile strength and fatigue life) and cannot meet the "performance consistency requirements" of key components such as aero-engine blades.

[0005] (3) The significant increase in deformation resistance makes forging difficult. The atomic radii of alloying elements differ from those of Ti atoms (e.g., Al atomic radius is 13% smaller than Ti, and Zr is 8% larger than Ti). Excessive addition will lead to increased lattice distortion: after foreign atoms are incorporated into the Ti matrix, they will destroy the regularity of the lattice and form a lattice stress field. During forging, dislocation movement must overcome the resistance of this stress field, resulting in a significant increase in the hot deformation resistance of the alloy.

[0006] (4) Reduced plasticity leads to cracking. Ti1100 is a near-α type titanium alloy, and its plasticity mainly depends on the slip system of the α phase and the grain boundary bonding strength. When the content of key alloying elements is too high, it will directly destroy the plasticity basis: Al and Sn content is too high: Both are α-stabilizing elements. Excessive addition will lead to excessive refinement of α phase grains or the formation of supersaturated α solid solutions, which will cause disordered atomic arrangement and reduced bonding strength at the grain boundaries. During forging, the grain boundaries are prone to become stress concentration points, resulting in "intergranular cracking"; at the same time, the slip resistance of the supersaturated solid solution increases, and the alloy is prone to "brittle deformation", especially during low-temperature forging, the risk of cracking will increase exponentially. Si content is too high: Si is prone to form Ti5Si3 intermetallic compounds (hard and brittle phase) in titanium alloys, and this phase is mostly distributed along the grain boundaries. During the forging process, Ti5Si3 cannot undergo plastic deformation along with the matrix. Instead, it acts like a "microcrack source" and expands rapidly under stress, leading to "split-type cracks" on the surface or inside the forging. These cracks are more likely to occur during large deformation processes such as upsetting and drawing.

[0007] Therefore, for the forging process of Ti1100 titanium alloy with high alloying element content, it is urgent to find a forging method to avoid the above problems in order to prepare Ti1100 alloy with high strength, high creep resistance and high microstructure stability. Summary of the Invention

[0008] Based on the above analysis, the present invention aims to provide a forging method for Ti1100 alloy bars with high strength, high creep resistance and high microstructure stability, in order to solve at least one of the following problems in the existing methods: macroscopic segregation during the forging process, narrowing of the processing window leading to difficulty in process control, significant increase in deformation resistance leading to difficulty in forging, reduced plasticity leading to cracking, poor microstructure stability of Ti1100 alloy bars, and short service life.

[0009] To achieve the above objectives, the present invention adopts the following technical solution: A forging method for high-strength, high-creep-resistance, and high-structural-stability Ti1100 alloy bars includes the following steps: S1: First-pass forging: The Ti1100 ingot is held at a temperature above the β phase transformation point and then subjected to multiple drawing and upsetting processes. S2: 1-stage grain refinement and homogenization forging: after holding below the β phase transformation point, multiple upsetting and drawing are performed; after holding above the β phase transformation point, multiple upsetting and drawing are performed. S3: 2~4 heat-stretching across phases: holding above the β phase transformation point and performing multiple upsetting and drawing processes; S4: First-stage radial forging: holding the temperature above the β phase transformation point, then radial forging; S5: Heat treatment and machining to obtain the Ti1100 alloy bar.

[0010] Furthermore, in S1, the temperature is maintained at 50-150°C above the β phase transition point for 120-200 minutes.

[0011] Furthermore, in S1, the deformation amount per pass of the multiple elongation is ≤5%, and the multiple elongation results in a height-to-diameter ratio of 1.7 to 2.0.

[0012] Furthermore, in S1, the deformation of the upsetting is 40-50%.

[0013] Furthermore, in S2, the temperature is maintained at 20-30°C below the β phase transition point for 120-200 min, and at 20-70°C above the β phase transition point for 60-120 min.

[0014] Furthermore, in S2, the deformation amount controlled by the multiple upsetting and drawing processes is 30-45%.

[0015] Furthermore, in S2, multiple upsetting and drawing processes are performed at 20~70℃ above the β phase transformation point, with intermediate reheating in the furnace to control the final forging temperature above the β phase transformation point. The forging is then reversed to a parallel height of 180~200mm, air-cooled, and fully ground.

[0016] Furthermore, in S3, the temperature is maintained at 20-50°C above the β phase transition point for 80-200 minutes.

[0017] Furthermore, in S3, the deformation amount of the multiple upsetting and drawing processes is 35-45%.

[0018] Furthermore, in S4, the temperature is maintained at 10-30°C above the β phase transition point for 50-90 minutes.

[0019] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects: (1) The forging method of Ti1100 alloy bars of the present invention eliminates the problems of macroscopic segregation caused by high alloy element content during forging, as well as the problems of narrowing processing window leading to difficult process control, significantly increased deformation resistance leading to difficult forging, and reduced plasticity leading to cracking, through the matching settings of multi-fire forging process. The Ti1100 alloy bars prepared by the present invention have deformed Widmanstätten structure, high strength and creep resistance, and high structural stability, and can be used for a long time.

[0020] (2) The forging method of the present invention controls the temperature, deformation amount, time and other parameters in each step to prepare Ti1100 alloy bars with deformed Widmanstätten structure, which has high strength and creep resistance as well as high structural stability and can be used for a long time.

[0021] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained from what is particularly pointed out in the description and drawings. Attached Figure Description

[0022] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts. Figure 1 This is a metallographic image of the edge of the bar prepared in Example 1 of the present invention; Figure 2 This is a metallographic diagram of the center of the bar prepared in Example 1 of the present invention. Detailed Implementation

[0023] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which constitute a part of the present invention and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0024] Forging Ti1100 titanium alloy bars is more difficult than forging plates, with the core challenges lying in forming stability, microstructure uniformity, and defect control. Bar forging aims for "longitudinal elongation + regular cross-section," using mostly round ingots as raw material. It requires multiple upsetting and elongation processes, necessitating precise matching of the reduction, feed rate, and forging temperature; otherwise, it easily results in narrow waists, spiral patterns, or bending and eccentricity. Round ingots are inherently prone to segregation and porosity at the center, requiring sufficient deformation during forging to eliminate these defects, yet this presents a contradiction: increased length-to-diameter ratio leads to decreased stability. In contrast, plate forging primarily involves lateral widening, resulting in a simpler deformation path and easier control over plate shape and thickness. Bar forging also requires ensuring cross-sectional accuracy throughout its length and longitudinal microstructure continuity, resulting in a low tolerance for process errors and more stringent requirements for equipment precision and operational control.

[0025] Therefore, the forging of Ti1100 titanium alloy bars differs significantly from plate forming in terms of deformation mechanism, defect control, geometric accuracy, microstructure uniformity, and process stability. Plate forming focuses on lateral widening, with a simple deformation path, and does not involve key technical requirements such as longitudinal elongation, cross-sectional regularity, aspect ratio control, and central defect closure. Bar forming, however, requires multiple upsetting-elongation composite deformation passes to achieve microstructure densification and shape accuracy. Its process tolerance is extremely low, imposing stringent requirements on reduction, feed rate, temperature field, die alignment, and equipment rigidity. Therefore, plate forging processes are not applicable to bar production; the two differ fundamentally in process logic and implementation. The challenges of bar forming cannot be solved by simply adjusting plate forming processes; a dedicated bar forging process system must be developed.

[0026] A specific embodiment of the present invention discloses a forging method for Ti1100 alloy bars with high strength, high creep resistance and high microstructure stability, comprising the following steps: S1: First-pass forging: The Ti1100 ingot is held at a temperature above the β phase transformation point and then subjected to multiple drawing and upsetting processes. S2: 1-stage grain refinement and homogenization forging: after holding below the β phase transformation point, multiple upsetting and drawing are performed; after holding above the β phase transformation point, multiple upsetting and drawing are performed. S3: 2~4 heat-stretching across phases: holding above the β phase transformation point and performing multiple upsetting and drawing processes; S4: First-stage radial forging: holding the temperature above the β phase transformation point, then radial forging; S5: Heat treatment and machining to obtain the Ti1100 alloy bar.

[0027] Compared with existing technologies, the forging method of Ti1100 alloy bars of this invention eliminates the problems of macroscopic segregation caused by high alloy element content during forging, as well as the problems of narrowing processing window leading to difficulty in process control, significantly increased deformation resistance leading to difficulty in forging, and reduced plasticity leading to cracking, through the matching settings of multi-fire forging process. The Ti1100 alloy bars prepared by this invention have a deformed Widmanstätten structure, exhibiting high strength, creep resistance, and high structural stability, enabling long-term service.

[0028] Specifically, in S1, the chemical elements of the Ti1100 ingot are as follows by mass percentage: Al: 5.60~6.40%; Sn: 2.40~3.00%; Zr: 3.50~4.50%; Mo: 0.35~0.50%; Si: 0.35~0.50%, with the balance being Ti, and the ingot diameter is 200mm.

[0029] Specifically, in S1, the temperature is maintained at 50~150℃ above the β phase transition point for 120~200min (e.g., 50℃, 60℃, 70℃, 80℃, 90℃, 100℃, 110℃, 120℃, 130℃, 140℃, 150℃) for 120~200min (e.g., 120min, 130min, 140min, 150min, 160min, 170min, 180min, 190min, 200min).

[0030] It should be noted that the temperature 50-150℃ above the β phase transformation point is the billet opening temperature. During the initial billet opening, the alloy exhibits a large-sized, as-cast microstructure with extremely poor plasticity, requiring high temperatures to enhance its plasticity. This temperature is chosen to ensure forging plasticity and reduce deformation resistance. The lower limit of 50℃ is chosen precisely to cross the phase transformation point, ensuring the material enters the higher-temperature phase region with better plasticity, avoiding poor plasticity and cracking due to insufficient temperature. The upper limit of 150℃ is chosen to prevent excessively high temperatures from causing abnormal grain growth, while also avoiding alloy element burn-out or accelerated oxidation, ensuring the uniformity of the billet's microstructure after opening.

[0031] Specifically, in S1, the deformation amount of each single pass of the multiple elongation is ≤5%, and the multiple elongation results in a height-to-diameter ratio of 1.7 to 2.0, for example, 1.7, 1.75, 1.8, 1.85, 1.9, 1.95, or 2.0.

[0032] It should be noted that the single-pass deformation amount is the forging parameter of the first hammer of the ingot. By using a small deformation amount (≤5%), the surface structure of the ingot is optimized and the surface grains are refined. The above-mentioned deformation amount has the following advantages: 1. It avoids cracking of the ingot surface caused by excessive deformation in subsequent forging; 2. The deformation area of ​​the alloy just covers the deformation dead zone of the subsequent large deformation area, promoting uniform alloy deformation.

[0033] Specifically, in S1, the process between drawing and upsetting also includes surface shaping followed by a return to the original furnace for 30-40 minutes, for example, 30 minutes, 31 minutes, 32 minutes, 33 minutes, 34 minutes, 35 minutes, 36 minutes, 37 minutes, 38 minutes, 39 minutes, and 40 minutes.

[0034] Specifically, in S1, the upsetting deformation is 40-50%, for example, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%.

[0035] It should be noted that in S1, a large deformation is used in the upsetting process to increase the alloy's forging penetration. If the deformation exceeds 50%, the internal stress of the titanium alloy will accumulate rapidly, which can easily lead to shear bands or local cracking. If it is less than 40%, the forging penetration will be poor, the core defects will not be completely eliminated, and the grains will not be sufficiently broken, thus failing to achieve the core purpose of this billet optimization process.

[0036] Preferably, the upsetting and drawing process involves one upsetting and one drawing with a deformation controlled at 40-50% (e.g., 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%), followed by one diagonal upsetting and one drawing with a deformation controlled at 40-50% (e.g., 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%).

[0037] More preferably, in S1, after upsetting and drawing, the material is further inverted to an octagonal height of 180~200mm, for example, 180mm, 182mm, 184mm, 186mm, 188mm, 190mm, 192mm, 194mm, 196mm, 198mm, 200mm, followed by air cooling and full grinding.

[0038] Specifically, in S2, the temperature is maintained at 20-30°C below the β phase transition point (e.g., 20°C, 21°C, 22°C, 23°C, 24°C, 25°C, 26°C, 27°C, 28°C, 29°C, 30°C) for 120-200 min (e.g., 120 min, 130 min, 140 min, 150 min, 160 min, 170 min, 180 min, 190 min, 200 min), and at 20-70°C above the β phase transition point (e.g., 20°C, 30°C, 40°C, 50°C, 60°C, 70°C) for 60-120 min (e.g., 60 min, 70 min, 80 min, 90 min, 100 min, 110 min, 120 min).

[0039] It should be noted that in S2, forging below the phase transformation point first refines the microstructure, and then forging above the phase transformation point promotes dynamic recrystallization of the alloy and homogenizes the microstructure. The temperature range below the phase transformation point (20~30℃ below the phase transformation point) is to obtain a strong and tough balanced α+β dual-phase microstructure, balancing microstructure refinement and forming stability. Above 20℃ below the phase transformation point, the forging process will approach or even enter the single-phase β region, and the final forged microstructure cannot achieve the purpose of refinement, and it is difficult to form an ideal strong and tough dual-phase microstructure. Below 30℃ below the phase transformation point, the proportion of α phase is too high and the hardness increases, the deformation resistance rises sharply, and defects such as microstructure tearing and surface cracks are prone to occur during forging.

[0040] Upsetting and forging should be performed at 20–70°C above the β-phase transformation point. Below 20°C above the transformation point, the temperature approaches the two-phase region, resulting in insufficient β-phase content, making full recrystallization difficult and leading to poor microstructure refinement. Above 70°C above the transformation point, excessive β-grain growth occurs, forming coarse transformed microstructure upon cooling, reducing the material's final strength and plasticity. The narrow range of 20–70°C achieves microstructure optimization while avoiding the adverse effects of high temperatures on microstructure stability, balancing microstructure refinement with process controllability.

[0041] Specifically, in S2, the deformation amount controlled by multiple upsetting and drawing is 30-45%, for example, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%.

[0042] It should be noted that the upsetting deformation in S2 is relatively smaller than that in S1. This is because it is difficult to achieve large deformation forging at this temperature. A deformation of less than 30% cannot achieve the effect of plastic deformation, and a deformation of more than 45% makes the alloy prone to cracking. Preferably, the deformation of multiple upsettings after holding at a temperature below the β phase transformation point is 30-45%, and the deformation of multiple upsettings after holding at a temperature above the β phase transformation point is also 30-45%.

[0043] More preferably, the multiple upsetting and drawing processes are two upsetting and two drawing processes.

[0044] Preferably, in S2, the forging process involves multiple upsetting and drawing processes with intermediate reheating at 20~70℃ above the β phase transformation point, controlling the final forging temperature above the β phase transformation point, turning the forging into an octagonal shape to a parallel height of 180~200mm, air cooling, and full grinding.

[0045] It should be noted that upsetting and forging at 20–70°C above the β phase transformation point aims to promote dynamic recrystallization and grain refinement of the alloy. Below 20°C above the phase transformation point, the temperature approaches the two-phase region, where the β phase proportion is insufficient, making it difficult to achieve sufficient recrystallization and resulting in poor microstructure refinement. Above 70°C above the phase transformation point, excessive β grain growth occurs, forming coarse transformation structures upon cooling, reducing the material's final strength and plasticity. The narrow range of 20–70°C achieves microstructure optimization while avoiding the adverse effects of high temperatures on microstructure stability, balancing refinement effect with process controllability.

[0046] Specifically, in S3, the temperature is maintained at 20-50°C (e.g., 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C) above the β phase transition point for 80-200 min (e.g., 80 min, 90 min, 100 min, 110 min, 120 min, 130 min, 140 min, 150 min, 160 min, 170 min, 180 min, 190 min, 200 min).

[0047] It should be noted that industrial forging of titanium alloys is all done under natural conditions. The forging process is actually cooling forging. The temperature at the beginning of forging is above the phase transformation point, and the temperature at the end of forging is below the phase transformation point, which easily forms a fine lath structure. This structure has excellent high-temperature load-bearing capacity and creep resistance. The temperature range of 20-50℃ is set to ensure that the forging start temperature is above the phase transformation point.

[0048] Specifically, in S3, the deformation amount of the multiple upsetting and drawing processes is 35% to 45%, for example, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, and 45%. If the deformation amount is less than 30%, the effect of plastic deformation cannot be achieved, and if the deformation amount is greater than 45%, the alloy is very prone to cracking.

[0049] Preferably, in S3, the deformation amount is controlled at 35~45% for one upsetting and one drawing, the deformation amount is controlled at 35~45% for one diagonal upsetting and one drawing, and then the furnace is reheated for 30~40 minutes, the deformation amount is controlled at 35~45% for one upsetting and one drawing, and the deformation amount is controlled at 35~45% for one diagonal upsetting and one drawing.

[0050] More preferably, in S3, after multiple upsetting and drawing, the octagonal shape is further adjusted to a parallel height of 180~200mm, for example, 180mm, 182mm, 184mm, 186mm, 188mm, 190mm, 192mm, 194mm, 196mm, 198mm, 200mm, followed by air cooling and full grinding.

[0051] It should be noted that in S3 of the present invention, 2 to 4 forging cycles across phase zones refers to repeated forging cycles of 2 to 4 times, with a minimum of 2 forging cycles.

[0052] Specifically, in S4, the temperature is maintained at 10~30℃ above the β phase transformation point (e.g., 10℃, 12℃, 14℃, 16℃, 18℃, 20℃, 22℃, 24℃, 26℃, 28℃, 30℃) for 50~90min (e.g., 50min, 60min, 70min, 80min, 90min). S4 is the radial forging step for the finished product. Compared with the preceding forging process, the radial forging temperature is slightly lower to ensure the final shape while precisely controlling the microstructure fineness, avoiding grain growth, and improving the final product performance.

[0053] Specifically, in S5, the heat treatment temperature is 700~850℃, for example, 700℃, 710℃, 720℃, 730℃, 740℃, 750℃, 760℃, 770℃, 780℃, 790℃, 800℃, 810℃, 820℃, 830℃, 840℃, 850℃, and held for 60~80 minutes, for example, 60 minutes, 62 minutes, 64 minutes, 66 minutes, 68 minutes, 70 minutes, 72 minutes, 74 minutes, 76 minutes, 78 minutes, 80 minutes. The temperature range of 700-850℃ is a homogenization heat treatment range, which can promote the homogenization of alloy microstructure. If it is too low, small grains will have difficulty growing, resulting in a bimodal distribution with large grains. If it is too high, the grains will merge and grow, resulting in an overly coarse microstructure.

[0054] Specifically, in S5, the diameter is forged to φ40~60×L mm. Where L is the length of the forging. Specifically, the diameter of the Ti1100 alloy rod is 40~60mm, for example, 40mm, 42mm, 44mm, 46mm, 48mm, 50mm, 52mm, 54mm, 56mm, 58mm, 60mm.

[0055] The forging method of the present invention, by controlling parameters such as temperature, deformation amount, and time in each step, produces Ti1100 alloy bars with deformed Widmanstätten structure, which have high strength, creep resistance, and high structural stability, and can be used for a long time.

[0056] The technical solution of the present invention will be further explained below with reference to specific embodiments.

[0057] Example 1 In this embodiment, a φ43mm Ti1100 bar was prepared. The ingot composition was as follows: raw materials were mixed according to the upper limit of the following element mass fractions: Al: 6.3%; Sn: 2.88%; Zr: 4.35%; Mo: 0.49%; Si: 0.447%, with the balance being Ti. A φ200mm Ti1100 ingot was then subjected to three VAR melting processes to obtain a Ti1100 ingot with uniform composition and no obvious segregation. The height-to-diameter ratio was required to be 1.3~1.5, and the measured β phase transformation point was 1025℃.

[0058] A forging method for high-strength, high-creep-resistance, and high-structural-stability Ti1100 alloy bars includes the following steps: S1: 1-pass forging: Heat the empty furnace to 1150℃ and hold for 150min → Control the single-pass deformation of the alloy to ≤5%, and draw the ingot multiple times to a height-to-diameter ratio of 1.9 → After surface shaping, return to the original furnace for 30min → Control the deformation to 45% and perform conventional upsetting and drawing → Control the deformation to 45% and perform diagonal upsetting and drawing → Turn the ingot into an octagon to a parallel height of 180mm, water cool → Grind completely. S2: First-pass forging for grain refinement and homogenization: air-cooled heating to 995℃, holding for 150min → controlling deformation amount to 38% for conventional two upsetting and two drawing → reheating in the furnace for 60min, reheating in the furnace at 1050℃ → controlling deformation amount to 38% for conventional two upsetting and two drawing, reheating in the furnace in between, controlling the final forging temperature at the β phase transformation point → turning octagonal to a parallel height of 180mm, air-cooled → full grinding; S3: Two-stage cross-phase forging: First firing: Heat the empty furnace to 1045℃ and hold for 150 minutes → Control the deformation amount to 40% and perform a conventional upsetting and pulling → Return to the furnace for 30 minutes → Control the deformation amount to 40% and perform a conventional upsetting and pulling → Control the deformation amount to 40% and perform a diagonal upsetting and pulling → Turn the octagon to a parallel height of 180mm → Air cool → Final firing and full grinding. Second firing: Heat the empty furnace to 1045℃ and hold for 150 minutes → Control the deformation amount to 40% and perform a conventional upsetting and pulling → Return to the furnace for 30 minutes → Control the deformation amount to 40% and perform a conventional upsetting and pulling → Control the deformation amount to 40% and perform a diagonal upsetting and pulling → Turn the octagon to a parallel height of 180mm → Air cool → Final firing and full grinding. S4: 1st forging: Heat the furnace to 1035℃ in an empty furnace and hold for 60 min → forge to φ47×L mm, then air cool; S5: Heat the empty furnace to 800℃, hold for 60 minutes for heat treatment, air cool, straighten at residual temperature, and machine to a finished φ43mm bar to obtain the Ti1100 alloy bar.

[0059] The metallographic structure of the edge of the bar prepared in Example 1 is as follows: Figure 1 As shown, the metallographic structure at the center is as follows Figure 2 As shown, the tissue samples taken from different locations are uniform and similar, exhibiting good homogeneity.

[0060] Example 2 The same bar stock and ingot were prepared in this embodiment as in Example 1, and the specific forging method is as follows: S1: 1-pass forging: Heat the empty furnace to 1075℃ and hold for 120min → Control the single-pass deformation of the alloy to ≤5%, and draw the ingot multiple times to a height-to-diameter ratio of 1.7 → After surface shaping, return to the original furnace for 35min → Control the deformation to 40% and perform conventional upsetting and drawing → Control the deformation to 40% and perform diagonal upsetting and drawing → Turn the ingot into an octagon to a parallel height of 190mm, water cool → Grind completely. S2: First-pass forging for grain refinement and homogenization: air-cooled heating to 1000℃, holding for 120min → controlling deformation amount to 30% for conventional two upsetting and two drawing → reheating in the furnace for 120min, reheating in the furnace at 1095℃ → controlling deformation amount to 30% for conventional two upsetting and two drawing, reheating in the furnace in between, controlling the final forging temperature at the β phase transformation point → turning octagonal to a parallel height of 190mm, air-cooled → full grinding; S3: Three-stage cross-phase forging: First firing: Heat the empty furnace to 1060℃ and hold for 200min → Control the deformation amount to 35% and perform a conventional upsetting and pulling → Return to the furnace for 35min → Control the deformation amount to 35% and perform a conventional upsetting and pulling → Control the deformation amount to 35% and perform a diagonal upsetting and pulling → Turn the octagon to a parallel height of 190mm → Air cool → Final firing and full grinding. Second firing: Heat the empty furnace to 1060℃ and hold for 200min → Control the deformation amount to 35% and perform a conventional upsetting and pulling → Return to the furnace for 35min → Control the deformation amount to 35% and perform a conventional upsetting and pulling → Control the deformation amount to 35% and perform a diagonal upsetting and pulling → Turn the octagon to a parallel height of 190mm → Air cool → Final firing and full grinding. Third firing: Heat the empty furnace to 1060℃ and hold for 200min → Control the deformation amount to 35% and perform conventional upsetting and pulling → Return to the furnace for 35min → Control the deformation amount to 35% and perform conventional upsetting and pulling → Control the deformation amount to 35% and perform diagonal upsetting and pulling → Turn the octagon to a parallel height of 190mm → Air cool → Final firing and full grinding. S4: 1st heat radial forging: Heat the furnace to 1045℃ in an empty furnace and hold for 90 min → forge radially to φ40×L mm, then air cool; S5: Heat the empty furnace to 700℃, hold for 80 minutes for heat treatment, air cool, straighten at residual temperature, and machine to a finished φ43mm bar to obtain the Ti1100 alloy bar.

[0061] Example 3 The same bar stock and ingot were prepared in this embodiment as in Example 1, and the specific forging method is as follows: S1: 1-pass forging: Heat the empty furnace to 1175℃ and hold for 200min → Control the single-pass deformation of the alloy to ≤5%, and draw the ingot multiple times to a height-to-diameter ratio of 2.0 → After surface shaping, return to the original furnace for 40min → Control the deformation to 50% and perform conventional upsetting and drawing → Control the deformation to 50% and perform diagonal upsetting and drawing → Turn the octagon to a parallel height of 200mm, water cool → Grind completely; S2: First-pass forging for grain refinement and homogenization: air-cooled heating to 1005℃, holding for 200min → controlling deformation amount to 45% for conventional two upsetting and two drawing → reheating in the furnace for 90min, reheating in the furnace at 1070℃ → controlling deformation amount to 45% for conventional two upsetting and two drawing, reheating in the furnace in between, controlling the final forging temperature at the β phase transformation point → turning into an octagon to a parallel height of 200mm, air-cooled → full grinding; S3: Four-stage cross-phase forging: First firing: Heat the empty furnace to 1075℃ and hold for 80 minutes → Control the deformation amount to 45% and perform a conventional upsetting and pulling → Return to the furnace for 40 minutes → Control the deformation amount to 45% and perform a conventional upsetting and pulling → Control the deformation amount to 40% and perform a diagonal upsetting and pulling → Turn the octagon to a parallel height of 200mm → Air cool → Final firing and full grinding. Second firing: Heat the empty furnace to 1075℃ and hold for 80 minutes → Control the deformation amount to 45% and perform a conventional upsetting and pulling → Return to the furnace for 40 minutes → Control the deformation amount to 45% and perform a conventional upsetting and pulling → Control the deformation amount to 40% and perform a diagonal upsetting and pulling → Turn the octagon to a parallel height of 200mm → Air cool → Final firing and full grinding. Third firing: Heat the empty furnace to 1075℃ and hold for 80 minutes → Control the deformation amount to 45% and perform a conventional upsetting and pulling → Return to the furnace for 40 minutes → Control the deformation amount to 45% and perform a conventional upsetting and pulling → Control the deformation amount to 40% and perform a diagonal upsetting and pulling → Turn the octagon to a parallel height of 200mm → Air cool → Final firing and full grinding. Fourth firing: Heat the empty furnace to 1075℃ and hold for 80 minutes → Control the deformation amount to 45% and perform a conventional upsetting and pulling → Return to the furnace for 40 minutes → Control the deformation amount to 45% and perform a conventional upsetting and pulling → Control the deformation amount to 40% and perform a diagonal upsetting and pulling → Turn the octagon to a parallel height of 200mm → Air cool → Final firing and full grinding. S4: 1st forging: Heat the furnace to 1055℃ in an empty furnace and hold for 50 min → forge to φ60×L mm, then air cool; S5: Heat the empty furnace to 850℃, hold for 70 minutes for heat treatment, air cool, straighten at residual temperature, and machine to a finished φ43mm bar to obtain the Ti1100 alloy bar.

[0062] Comparative Example 1 The Ti1100 bar stock and forging method in this comparative example are similar to those in Example 1, except that step S2 is not included.

[0063] Comparative Example 2 The Ti1100 bar stock and forging method in this comparative example are similar to those in Example 1, except that in S2, there is no intermediate reheating in the furnace.

[0064] Comparative Example 3 The Ti1100 bar stock and forging method in this comparative example are similar to those in Example 1, except that only the first cross-phase region forging is performed in S3.

[0065] Comparative Example 4 The Ti1100 bar stock and forging method in this comparative example are similar to those in Example 1, except that the deformation amount in S3 is 30%.

[0066] Comparative Example 5 The Ti1100 bar stock and forging method in this comparative example are similar to those in Example 1, except that the deformation amount in S3 is 60%.

[0067] Comparative Example 5 suffered severe cracking during forging, making further forging impossible.

[0068] Experimental Example 1 Forgings (forged state, R) after one pass of forging in S4 from both the example and comparative examples were taken as samples for testing of mechanical properties, creep properties, and microstructure. The creep test conditions were as follows: Mechanical property tests were conducted according to GB / T 228.1-2021 "Metallic materials - Tensile testing - Part 1: Test at room temperature", and the results are shown in Table 1.

[0069] Table 1

[0070] As shown in Table 1, the forgings obtained by this invention have a tensile strength ≥1190MPa, preferably 1190~1198MPa, a yield strength ≥1095MPa, preferably 1095-1103MPa, an elongation ≥12%, preferably 12~13%, and a reduction of area ≥19%, preferably 19-23%. Creep ≤0.0630ε%, preferably 0.0416-0.0630ε.

[0071] Experimental Example 2 To examine the stability of the microstructure, service simulation was performed on the alloy. The alloy in the forged state of Example 1 was used for service simulation. The sample was subjected to long-term heating for up to 512 hours to simulate a high-temperature service environment. The mechanical properties of the alloy at different service times are shown in Table 2. Each group was tested twice.

[0072] Table 2

[0073] As shown in Table 2, the mechanical properties of the alloy do not decrease significantly with increasing service time.

[0074] The same experiments were also conducted on other embodiments of the present invention, and the results were basically the same. Due to space limitations, they will not be listed one by one.

[0075] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A forging method for high-strength, high-creep-resistance, and high-structural-stability Ti1100 alloy bars, characterized in that, Includes the following steps: S1: First-pass forging: The Ti1100 ingot is held at a temperature above the β phase transformation point and then subjected to multiple drawing and upsetting processes. S2: 1-stage grain refinement and homogenization forging: after holding below the β phase transformation point, multiple upsetting and drawing are performed; after holding above the β phase transformation point, multiple upsetting and drawing are performed. S3: 2~4 heat-stretching across phases: holding above the β phase transformation point and performing multiple upsetting and drawing processes; S4: First-stage radial forging: holding the temperature above the β phase transformation point, then radial forging; S5: Heat treatment and machining to obtain the Ti1100 alloy bar.

2. The forging method according to claim 1, characterized in that, In S1, the temperature is maintained at 50~150℃ above the β phase transition point for 120~200 min.

3. The forging method according to claim 1, characterized in that, In S1, the deformation amount per pass of the multiple elongation is ≤5%, and the multiple elongation results in a height-to-diameter ratio of 1.7~2.

0.

4. The forging method according to any one of claims 1-3, characterized in that, In S1, the deformation of the upsetting and drawing process is 40-50%.

5. The forging method according to any one of claims 1-3, characterized in that, In S2, the temperature is maintained at 20-30℃ below the β phase transition point for 120-200 min, and at 20-70℃ above the β phase transition point for 60-120 min.

6. The forging method according to claim 5, characterized in that, In S2, the deformation amount controlled by the multiple upsetting and drawing processes is 30-45%.

7. The forging method according to claim 5, characterized in that, In S2, the forging process involves multiple upsetting and drawing operations at 20-70℃ above the β phase transformation point, followed by intermediate reheating in the furnace. The final forging temperature is controlled to be above the β phase transformation point. The forging is then reversed to a parallel height of 180-200mm, air-cooled, and fully ground.

8. The forging method according to claim 1, characterized in that, In S3, keep warm at 20~50℃ above the β phase transition point for 80~200 min.

9. The forging method according to claim 1, characterized in that, In S3, the deformation amount of the multiple upsetting and drawing processes is 35-45%.

10. The forging method according to claim 1, characterized in that, In S4, keep warm at 10~30℃ above the β phase transition point for 50~90 minutes.

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