Ti al alloy valve blank and method of making

Abstract

The application discloses a TiAl alloy valve blank and a preparation method thereof, and belongs to the technical field of alloy material processing. The TiAl alloy valve blank preparation method comprises the following steps: preparing a TiAl alloy extrusion blank; heating the TiAl alloy extrusion blank and placing the TiAl alloy extrusion blank in a preheated extrusion die for extrusion to obtain an extruded part; and supplementing the temperature of the extruded part and die forging the extruded part to obtain a TiAl alloy valve blank. The application realizes the processing of the TiAl alloy under the condition of no cover, and the valve blank is prepared, and the problem that the TiAl alloy is difficult to form is effectively overcome.

Description

Technical Field

[0001] This application relates to the field of alloy material processing technology, and in particular to a TiAl alloy valve blank and its preparation method. Background Technology

[0002] Valve is a key hot-end component of an internal combustion engine, used to control the flow of gas in and out, directly affecting engine performance and lifespan. Its service environment is complex, requiring it to withstand high temperatures, corrosion, and alternating loads. Intake valve temperatures are approximately 300–450℃, while exhaust valve temperatures reach as high as 700–850℃. Therefore, valve materials must possess characteristics such as high hardness, heat resistance, impact resistance, corrosion resistance, resistance to deformation, and lightweight. γ-TiAl alloy, with its low density (approximately 4.0 g / cm³), [is suitable for this purpose]. 3 With its advantages such as high specific strength and high creep resistance, it is considered an ideal lightweight structural material for high-temperature environments of 600-900℃, and has broad application prospects, especially in the fields of aerospace, high-end racing cars, motorcycles and other internal combustion engine hot-end components.

[0003] However, TiAl alloys, as intermetallic compounds, are extremely difficult to form at high temperatures, especially when preparing valves with small rod diameters. Conventional hot rolling processes are difficult to achieve this, which severely limits their application in the valve field. Summary of the Invention

[0004] The main objective of this application is to provide a TiAl alloy valve blank and its preparation method, aiming to solve the problem of the high difficulty in forming TiAl alloys.

[0005] To achieve the above objectives, this application provides a method for preparing a TiAl alloy valve blank, comprising the following steps:

[0006] Preparation of TiAl alloy extruded billets;

[0007] The TiAl alloy extrusion billet is heated and placed in a preheated extrusion die for extrusion to obtain an extruded part;

[0008] The extruded part is subjected to heat treatment and die forging to obtain a TiAl alloy valve blank.

[0009] In one embodiment, the TiAl alloy extrusion billet comprises, by atomic percentage: 40.0-46.0% Al, 1.0-5.0% Mn, 0-3.5% Nb, 0-1.0% W, 0-1.5% Mo, 0-0.3% B, 0-0.3% C, 0-0.3% Si, 0-0.1% Y, with the balance being Ti.

[0010] In one embodiment, the step of preparing the TiAl alloy extrusion billet includes:

[0011] The TiAl alloy extruded billet is prepared by vacuum induction melting; or...

[0012] The TiAl alloy extruded billet is prepared by vacuum induction melting and hot rolling; or...

[0013] The TiAl alloy extruded billet was prepared by a combination of vacuum induction melting and vacuum consumable melting, followed by hot rolling.

[0014] In one embodiment, the preheating temperature of the extrusion die is 300–600°C;

[0015] And / or, the heating temperature for heating the TiAl alloy extruded billet is 1240–1300°C;

[0016] And / or, the reheating temperature of the extruded part is 1240-1300℃.

[0017] In one embodiment, the step of heating the TiAl alloy extrusion billet and placing it in a preheated extrusion die for extrusion includes:

[0018] The TiAl alloy extrusion billet is heated and coated with glass powder before being placed in a preheated extrusion die for extrusion.

[0019] In one embodiment, the diameter of the extruded part and / or the TiAl alloy valve blank is 4 to 6 mm.

[0020] In one embodiment, the pressing force of the extrusion is 60-100t, and the feed speed is 1500-2000rpm.

[0021] In one embodiment, the forging step includes:

[0022] The head cylinder of the extrusion is forged into a valve disc.

[0023] In one embodiment, the forging pressure of the die forging is 40-80t, and the feed speed is 1500-2000rpm.

[0024] This application also provides a TiAl alloy valve blank, which is prepared by the TiAl alloy valve blank preparation method described above.

[0025] One or more technical solutions proposed in this application have at least the following technical effects: A method for preparing TiAl alloy valve blanks is provided. First, TiAl alloy extrusion blanks are prepared. During the preparation of the TiAl alloy extrusion blanks, methods such as vacuum induction melting, vacuum induction melting and hot rolling, dual melting of vacuum induction melting and vacuum arc remelting, and hot rolling can be used. Melting the TiAl alloy in a vacuum environment can effectively reduce impurities and gas content in the alloy, improve the purity and uniformity of the material, thereby improving its mechanical properties and high-temperature performance. It also reduces surface defects in the cast rod, such as cracks and porosity, thus avoiding extrusion defects caused by surface quality problems. It can also ensure performance without the need for a casing. The extrusion process proceeds smoothly. Secondly, preheating the extrusion die reduces the flow stress of the alloy during extrusion, decreases the frictional resistance of the die on the alloy, making the alloy easier to flow and deform, and improving extrusion efficiency and quality. The heated TiAl alloy extrusion billet is in a more suitable deformation temperature range during extrusion, improving its plasticity and enabling it to better adapt to complex deformation requirements, thus obtaining extruded parts with higher dimensional accuracy and more uniform microstructure. Finally, reheating the extruded parts allows them to maintain good plasticity and deformation capacity during die forging. Forging in a specific die further improves its microstructure, increases density and performance uniformity, ultimately yielding high-quality TiAl alloy valve blanks. Attached Figure Description

[0026] Figure 1 This is a schematic flowchart of the method for preparing TiAl alloy valve blanks involved in the embodiments of this application;

[0027] Figure 2 This is a process flow diagram related to Embodiment 1 of this application;

[0028] Figure 3 This is a process flow diagram related to Embodiment 2 of this application;

[0029] Figure 4 These are appearance drawings of the extruded parts involved in Embodiments 1 and 2 of this application;

[0030] Figure 5 These are appearance drawings of the valve blanks involved in Embodiments 1 and 2 of this application.

[0031] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0033] The embodiments of the TiAl alloy valve blank and its preparation method of this application are disclosed in detail below with appropriate reference to the accompanying drawings. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of actually identical structures may be omitted. This is to avoid making the following description unnecessarily lengthy and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0034] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60–120 and 80–110 are listed for a specific parameter, it is understood that ranges of 60–110 and 80–120 are also expected. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1–3, 1–4, 1–5, 2–3, 2–4, and 2–5. In this application, unless otherwise stated, the numerical range "a–b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0~5" indicates that all real numbers between "0~5" have been listed in this article; "0~5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0035] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0036] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0037] Unless otherwise specified, all steps of this application may be performed sequentially or randomly, preferably sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, if the method may also include step (c), it means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0038] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0039] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0040] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the technical solution of this application is further described below in conjunction with the accompanying drawings and embodiments. However, this application is not limited to the listed embodiments, but should also include any other well-known modifications within the scope of the claims made in this application.

[0041] The term "an embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of this application. The phrase "in one embodiment" appearing in different places throughout this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0042] To better understand the technical solution of this application, a detailed description will be provided below in conjunction with the accompanying drawings and specific implementation methods.

[0043] In conventional technologies, TiAl alloys, as intermetallic compounds, are extremely difficult to form at high temperatures, especially when preparing valves with small rod diameters. Conventional hot rolling processes are difficult to obtain, which severely limits their application in the valve field.

[0044] In this embodiment, firstly, a TiAl alloy extrusion billet is prepared. During the preparation of the TiAl alloy extrusion billet, methods such as vacuum induction melting, vacuum induction melting and hot rolling, dual melting of vacuum induction melting and vacuum arc remelting, and hot rolling can be used. Melting the TiAl alloy in a vacuum environment can effectively reduce impurities and gas content in the alloy, improve the purity and uniformity of the material, thereby improving its mechanical and high-temperature properties, reducing surface defects in the cast rod such as cracks and porosity, and thus avoiding extrusion defects caused by surface quality issues. Extrusion can proceed smoothly without the need for a sheath. Then, the extrusion die is preheated. This reduces the flow stress of the alloy during extrusion, decreases the frictional resistance of the die on the alloy, making the alloy easier to flow and deform, and improving extrusion efficiency and quality. The heated TiAl alloy extrusion billet is in a more suitable deformation temperature range during the extrusion process, and its plasticity is improved, which can better adapt to complex deformation requirements, thereby obtaining extruded parts with higher dimensional accuracy and more uniform structure. Furthermore, the extruded parts can be heated to maintain good plasticity and deformation capacity during die forging. The forming in a specific die during die forging can further improve its microstructure, increase density and performance uniformity, and finally obtain high-quality TiAl alloy valve blanks.

[0045] The first aspect of this application provides a method for preparing a TiAl alloy valve blank, referring to... Figure 1 This includes the following steps:

[0046] Step S10: Prepare TiAl alloy extruded billet;

[0047] In one feasible embodiment, the TiAl alloy extruded billet required for extrusion is prepared, wherein the TiAl alloy extruded billet required for extrusion can be prepared by, for example, vacuum induction melting, vacuum induction melting and hot rolling, dual melting of vacuum induction melting and vacuum arc remelting, and hot rolling.

[0048] Optionally, high-purity titanium, aluminum and other alloying elements are selected, mixed in a certain proportion, and placed in a vacuum induction furnace. Under high temperature and vacuum or low pressure conditions, the raw materials are melted using the principle of electromagnetic induction. The molten alloy liquid is then poured into a preheated mold, cooled and solidified to form a cast rod, which is then used as an extrusion billet.

[0049] In one feasible embodiment, step S10, the step of preparing the TiAl alloy extrusion billet, includes any one of the following:

[0050] Step S11: Prepare the TiAl alloy extrusion billet by vacuum induction melting;

[0051] In one feasible embodiment, vacuum induction melting is a melting method carried out in a vacuum environment, which can effectively reduce the impurities and gas content in the alloy, improve the purity and uniformity of the material, thereby improving its mechanical properties and high-temperature performance. At the same time, vacuum induction melting can avoid the mixing of impurities and gases, reduce surface defects of the cast rod, such as cracks and pores, and thus avoid extrusion defects caused by surface quality problems. Extrusion can be carried out smoothly without the need for a sheath.

[0052] Step S12: Prepare TiAl alloy extruded billets by vacuum induction melting and hot rolling;

[0053] In one feasible embodiment, high-purity titanium, aluminum and other alloying elements are selected and mixed in a certain proportion. The raw materials are placed in a vacuum induction furnace and melted using the principle of electromagnetic induction under high temperature and vacuum or low pressure conditions. The molten alloy liquid is then poured into a preheated mold, cooled and solidified to form a cast rod. The heated cast rod is then rolled by a rolling mill to deform it into a rod of the required size and shape, which is then used as an extrusion billet.

[0054] In this embodiment, heating the casting rod improves its plasticity during rolling, enabling it to better adapt to deformation requirements. The repeated plastic deformation of the material during rolling helps to refine the grains, improve the strength and toughness of the material, make the material structure more uniform, and reduce segregation and defects.

[0055] Step S13: TiAl alloy extrusion billets are prepared by a combination of vacuum induction melting and vacuum consumable melting, followed by hot rolling.

[0056] In one feasible embodiment, high-purity titanium, aluminum and other alloying elements are selected, mixed in a certain proportion, and the raw materials are placed in a vacuum induction furnace to be melted into electrodes. The electrodes obtained by melting are then melted in a vacuum arc furnace. Through contact melting between the electrodes and the molten pool, a pure ingot is obtained. The ingot is then heated and forged using forging equipment to initially deform it. The forged billet is then hot-rolled to finally form the required bar and used as an extrusion billet.

[0057] In this embodiment, processing in a vacuum environment through vacuum induction and vacuum self-consumption can effectively remove impurities and gases from the material, further improving the purity of the material. The self-consumption melting of the electrode can reduce internal defects and improve the density of the material. The dual melting process can make the composition and structure of the material more uniform, improve the stability of performance, and combine forging and hot rolling to refine the grains, thereby improving the strength and toughness of the material.

[0058] In one feasible embodiment, the TiAl alloy comprises, by atomic percentage: 40.0-46.0% Al, 1.0-5.0% Mn, 0-3.5% Nb, 0-1.0% W, 0-1.5% Mo, 0-0.3% B, 0-0.3% C, 0-0.3% Si, 0-0.1% Y, with the balance being Ti.

[0059] Optionally, the main system of the TiAl alloy is Ti-Al-Mn-X, where X is at least one of Mo, W, and Nb. The addition of Mo, W, and / or Nb effectively improves the hot deformability of the TiAl alloy at high temperatures, broadens its hot working window, and ensures good oxidation resistance. Therefore, it reduces the requirements for forging conditions, allowing for a simpler forging method without a clasp, thus lowering forging costs.

[0060] Optionally, the TiAl alloy composition, by atomic percentage, includes 41.0–44.0% Al, 4.0–5.0% Mn, and the balance Ti. The Al content, within the range of 41.0–44.0%, maintains the basic properties of TiAl alloys, while the addition of appropriate amounts of Mn enhances the alloy's strength and toughness, and improves its oxidation resistance and creep resistance at high temperatures.

[0061] Optionally, the TiAl alloy composition, by atomic percentage, includes 41.0–46.0% Al, 1.0–5.0% Mn, 2.0–3.5% Nb, 0.1–0.3% B, 0.1–0.3% C, 0–0.3% Si, 0–0.1% Y, with the balance being Ti. By adding elements such as Nb, B, and C, the high-temperature performance of the alloy is significantly improved. Nb can enhance the alloy's high-temperature strength and creep resistance; B and C can refine the grains, improving the alloy's high-temperature stability and oxidation resistance; and the addition of Y can further enhance the alloy's oxidation resistance, enabling it to better resist oxidation corrosion at high temperatures and extend its service life.

[0062] Optionally, the TiAl alloy composition, by atomic percentage, includes 40.0–44.0% Al, 1.0–4.0% Mn, 0.2–1.0% Mo, 0.1–0.3% B, 0.1–0.3% C, 0–0.3% Si, 0–0.1% Y, with the balance being Ti. The addition of Mo can improve the alloy's high-temperature strength and creep resistance, enabling it to withstand larger loads at high temperatures. The addition of B and C elements helps refine the grains, improving the alloy's creep resistance and allowing it to maintain good performance under prolonged high-temperature loads.

[0063] Optionally, the TiAl alloy composition, by atomic percentage, includes 41.0–46.0% Al, 1.0–4.0% Mn, 0.1–1.0% W, 0.1–0.3% B, 0.1–0.3% C, 0–0.3% Si, 0–0.1% Y, with the balance being Ti. The addition of W can significantly improve the alloy's high-temperature strength and creep resistance, giving it better stability and load-bearing capacity at high temperatures. The addition of B and C can improve the alloy's oxidation resistance, enabling it to better resist oxidation corrosion at high temperatures.

[0064] Optionally, the TiAl alloy composition, by atomic percentage, includes 41.0–46.0% Al, 1.0–4.0% Mn, 0.3–1.5% Mo, 0.1–1.0% W, 0.1–0.3% B, 0.1–0.3% C, 0–0.3% Si, 0–0.1% Y, with the balance being Ti. The addition of Mo and W further enhances the high-temperature performance of the alloy. Both Mo and W improve the alloy's high-temperature strength and creep resistance, resulting in better stability and load-bearing capacity at high temperatures. The addition of B and C improves the alloy's oxidation resistance, enabling it to better resist oxidation corrosion at high temperatures.

[0065] In this embodiment, the alloy used in this application has a certain effective hot working window, which provides material support for the extrusion forming of TiAl alloy valves with small rod diameters.

[0066] Step S20: The TiAl alloy extrusion billet is heated and placed in a preheated extrusion die for extrusion to obtain an extruded part;

[0067] In one feasible embodiment, the extrusion die is preheated, the TiAl alloy extrusion billet is heated, and then placed in the preheated extrusion die for extrusion to obtain an extruded part.

[0068] Optionally, the extrusion die is made of tungsten steel or H13 die steel.

[0069] Optionally, the preheating temperature of the extrusion die is 300–600℃, for example, 300℃, 320℃, 340℃, 360℃, 380℃, 400℃, 420℃, 440℃, 460℃, 480℃, 500℃, 520℃, 540℃, 560℃, 580℃, 600℃, etc. Preheating the extrusion die effectively avoids the problem of the valve stem not being able to be extruded smoothly due to the extruded billet cooling too quickly upon contact with the die. It also reduces the flow stress of the alloy during extrusion, reduces the frictional resistance between the die and the alloy, making the alloy easier to flow and deform, thus improving extrusion efficiency and quality. However, if the preheating temperature is too high, it will cause changes in the metallographic structure of the die material, leading to a decrease in the hardness and strength of the die, thereby reducing the die's service life. Furthermore, excessively high temperatures may also cause oxide scale to form on the die surface, further weakening the die's performance, consuming more energy, and increasing production costs. Therefore, in this embodiment of the application, the preheating temperature of the extrusion die is determined to be 300-600°C.

[0070] In one feasible embodiment, the heating temperature for heating the TiAl alloy extrusion billet is 1240–1300°C, for example, the heating temperature of the TiAl alloy extrusion billet is 1240°C, 1245°C, 1250°C, 1255°C, 1260°C, 1265°C, 1270°C, 1275°C, 1280°C, 1285°C, 1290°C, 1295°C, 1300°C, etc. If the heating temperature of the TiAl alloy is too high, it may cause abnormal growth of TiAl alloy grains, forming a coarse grain structure. This will reduce the strength and toughness of the material, making it prone to cracking and fracture during subsequent processing and use. Furthermore, at high temperatures, TiAl alloy is prone to react with oxygen, nitrogen, etc. in the air, leading to surface oxidation and gas absorption, forming defects such as oxide scale and pores, affecting the surface quality and internal density of the extruded part. If the heating temperature of the TiAl alloy is too low, its plasticity will decrease, making it prone to defects such as cracking and fracture during extrusion, thus reducing the yield and quality of the extruded parts. Therefore, in this application, the heating temperature for heating the TiAl alloy extrusion billet is determined to be 1240–1300°C.

[0071] In one feasible embodiment, step S20, which involves heating the TiAl alloy extrusion billet and placing it in a preheated extrusion die for extrusion, includes:

[0072] Step S21: The TiAl alloy extrusion billet is heated and then coated with glass powder before being placed in a preheated extrusion die for extrusion.

[0073] In one feasible embodiment, the TiAl alloy extrusion billet is heated to 1240-1300°C and quickly coated with a layer of glass powder, and then extruded rapidly under the set hot extrusion parameters to produce an extruded part with a cylindrical head and a rod diameter of 4-6 mm.

[0074] In this embodiment, by coating the extruded billet with a layer of glass powder that has heat insulation, lubrication and force transmission functions after heating, the tendency to crack caused by direct contact between the high-temperature TiAl alloy extruded billet and the extrusion die and punch is reduced.

[0075] Optionally, the extrusion pressing force is 60-100t, for example, 60t, 62t, 64t, 66t, 68t, 70t, 72t, 74t, 76t, 78t, 80t, 82t, 84t, 86t, 88t, 90t, 92t, 94t, 96t, 98t, 100t, etc. If the extrusion pressing force is too high, it will accelerate the wear and damage of the mold, shorten the mold's service life, and increase production costs. Furthermore, in extreme cases, excessive pressure may cause internal defects in the material, such as cracks. If the pressing force is insufficient, the material may have difficulty flowing in the mold, failing to completely fill the mold, thus affecting the shape and dimensional accuracy of the extruded part, and resulting in an uneven surface with scratches, pits, and other defects. Therefore, the embodiments of this application determine the extrusion pressing force to be 60-100t.

[0076] Optionally, the extrusion feed speed is 1500–2000 rpm, for example, 1500 rpm, 1550 rpm, 1600 rpm, 1650 rpm, 1700 rpm, 1750 rpm, 1800 rpm, 1850 rpm, 1900 rpm, 1950 rpm, 2000 rpm, etc. If the feed speed is too high, it may increase frictional heat during the extrusion process, raising the temperature of the die and material, potentially affecting material performance and die life, and possibly causing defects such as ripples and vibration marks on the surface of the extruded part, reducing surface quality. Conversely, if the feed speed is too low, it may reduce the extrusion speed, thereby reducing production efficiency, increasing production costs, and causing the material to remain in the die for too long, resulting in excessively rapid cooling, affecting material flowability and deformation, and leading to a decrease in the dimensional accuracy and surface quality of the extruded part. Therefore, in this embodiment, the extrusion feed speed is determined to be 1500–2000 rpm.

[0077] Step S30: The extruded part is heated and then die-forged to obtain a TiAl alloy valve blank.

[0078] In one feasible embodiment, the extruded part is subjected to heat treatment, and the cylindrical portion of the extruded part is die-forged into a valve disc to obtain a TiAl alloy valve blank. Since titanium-aluminum alloy has better plasticity at high temperatures and can better adapt to complex deformation requirements, heat treatment can ensure that the extruded part is within a suitable temperature range during die forging, thereby improving its plasticity and reducing the occurrence of defects such as cracking and fracture.

[0079] Optionally, the extrusion temperature is 1240–1300℃, for example, the extrusion temperature is 1240℃, 1245℃, 1250℃, 1255℃, 1260℃, 1265℃, 1270℃, 1275℃, 1280℃, 1285℃, 1290℃, 1295℃, 1300℃, etc.

[0080] Optionally, the forging pressure for die forging is 40–80t, for example, 40t, 42t, 44t, 46t, 48t, 50t, 52t, 54t, 56t, 58t, 60t, 62t, 64t, 66t, 68t, 70t, 72t, 74t, 76t, 78t, 80t, etc. If the forging pressure is too high, it will accelerate the wear and damage of the die, shorten the die's service life, and increase production costs. Furthermore, in extreme cases, excessive pressure may cause internal defects in the material, such as cracks. Insufficient pressure may cause difficulty in material flow within the die, preventing complete filling and affecting the product's shape and dimensional accuracy, resulting in an uneven surface with scratches, pits, and other defects. Therefore, in this embodiment, the forging pressure is determined to be 60–100t.

[0081] Optionally, the feed speed for die forging is 1500–2000 rpm, for example, feed speeds of 1500 rpm, 1550 rpm, 1600 rpm, 1650 rpm, 1700 rpm, 1750 rpm, 1800 rpm, 1850 rpm, 1900 rpm, 1950 rpm, 2000 rpm, etc. If the feed speed is too high, it may increase frictional heat during the die forging process, causing the temperature of the die and material to rise, potentially affecting the material's performance and the die's lifespan, and possibly leading to defects such as ripples and vibration marks on the product surface, reducing surface quality. Conversely, if the feed speed is too low, it may reduce the forging speed, thereby reducing production efficiency, increasing production costs, and causing the material to remain in the die for too long, resulting in excessively rapid cooling, affecting the material's fluidity and deformation degree, leading to a decrease in the product's dimensional accuracy and surface quality. Therefore, the embodiments of this application determine the feed speed for die forging to be 1500–2000 rpm.

[0082] In this embodiment, firstly, a TiAl alloy extrusion billet is prepared. During the preparation of the TiAl alloy extrusion billet, methods such as vacuum induction melting, vacuum induction melting and hot rolling, dual melting of vacuum induction melting and vacuum arc remelting, and hot rolling can be used. Melting the TiAl alloy in a vacuum environment can effectively reduce the impurities and gas content in the alloy, improve the purity and uniformity of the material, thereby improving its mechanical and high-temperature properties, reducing surface defects in the cast rod such as cracks and porosity, and thus avoiding extrusion defects caused by surface quality problems. Extrusion can proceed smoothly without the need for a sheath. Then, the extrusion die is preheated. This can reduce the flow stress of the alloy during the extrusion process, reduce the frictional resistance of the die on the alloy, make the alloy easier to flow and deform, and improve extrusion efficiency and quality. The heated TiAl alloy extrusion billet is in a more suitable deformation temperature range during the extrusion process, and its plasticity is improved, which can better adapt to complex deformation requirements, thereby obtaining extruded parts with higher dimensional accuracy and more uniform structure. Furthermore, the extruded parts can be heated to maintain good plasticity and deformation capacity during die forging. The forming in a specific die during die forging can further improve its microstructure, increase density and performance uniformity, and finally obtain high-quality TiAl alloy valve blanks.

[0083] In order to enable those skilled in the art to clearly understand the details and operations of the above embodiments of this application, and to demonstrate the significant improvement in performance of the embodiments of this application, the above technical solutions are illustrated below through multiple embodiments.

[0084] Example 1:

[0085] Reference Figure 2 The process shown is used to process TiAl alloy valve blanks.

[0086] (1) A series of diameters were produced by melting and casting in a vacuum induction melting furnace. A cylindrical extruded billet with a height of 50 mm, wherein the alloy composition is Ti-44Al-3Mn-0.8Mo-0.1B-0.1C (at.%);

[0087] (2) Heat the extrusion blank (1300℃), quickly coat the surface of the extrusion blank with a layer of glass powder after it reaches the temperature, and place it in a preheated (500℃) extrusion die for extrusion to obtain an extrusion part with a cylindrical head and a rod diameter of 6mm. The pressing force is 60t and the feed speed is 2000rpm.

[0088] (3) The extrusion is heated to 1270℃ and the head cylinder of the extrusion is die-forged into a valve disc to obtain a valve blank with a rod diameter of 6mm. The die-forging pressure is 50t and the feed speed is 2000rpm.

[0089] Example 2

[0090] Reference Figure 3 The process shown is used to process TiAl alloy valve blanks.

[0091] (1) A vacuum induction melting furnace was used to melt and cast out products with dimensions of [missing information]. The ingots, with an alloy composition of Ti-44Al-3Mn-0.4Mo-0.4W-0.1B-0.1C (at.%), were directly rolled into bars with a diameter of 16mm in a single pass using a Y-type rolling mill. The initial deformation temperature during rolling was 1380℃. The rolled bars were then cut into several pieces with a diameter of... Cylindrical extruded blank with a height of 50mm;

[0092] (2) Heat the extrusion blank (1280℃), quickly coat the surface of the extrusion blank with a layer of glass powder after it reaches the temperature, and place it in a preheated (450℃) extrusion die for extrusion to obtain an extrusion part with a cylindrical head and a rod diameter of 6mm. The pressing force is 60t and the feed speed is 2000rpm.

[0093] (3) The extrusion is heated (1260℃) and the head cylinder of the extrusion is die-forged into a valve disc to obtain a valve blank with a rod diameter of 6mm. The die-forging pressure is 40t and the feed speed is 2000rpm.

[0094] The surfaces of the extruded parts obtained in Examples 1 and 2 above are subjected to sandblasting treatment to obtain the following results: Figure 4 As shown in the extruded parts, the rod diameters of the extruded parts all meet the requirements. The valve blanks of Examples 1 and 2 were sandblasted to obtain the following results: Figure 5 The valve blank shown.

[0095] The above are merely preferred embodiments of this application and do not limit the patent scope of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the patent protection scope of this application.

Claims

1. A method for preparing TiAl alloy valve blanks, characterized in that, The preparation method includes the following steps: A TiAl alloy extrusion billet is prepared, wherein, by atomic percentage, the TiAl alloy comprises: 40.0~46.0% Al, 1.0~5.0% Mn, 0~3.5% Nb, 0~1.0% W, 0~1.5% Mo, 0~0.3% B, 0~0.3% C, 0~0.3% Si, 0~0.1% Y, with the balance being Ti; The TiAl alloy extrusion billet is heated and placed in a preheated extrusion die for unsheathed extrusion to obtain an extruded part. The preheating temperature of the extrusion die is 300~600 ℃, and the heating temperature of the TiAl alloy extrusion billet is 1240~1300 ℃. The extruded part is subjected to a reheating process and then die-forged to obtain a TiAl alloy valve blank. The reheating temperature of the extruded part is 1240~1300 ℃, and the rod diameter of the extruded part and / or the TiAl alloy valve blank is 4~6 mm.

2. The method for preparing TiAl alloy valve blanks as described in claim 1, characterized in that, The steps for preparing TiAl alloy extruded billets include: The TiAl alloy extruded billet is prepared by vacuum induction melting; or... The TiAl alloy extruded billet is prepared by vacuum induction melting and hot rolling; or... The TiAl alloy extruded billet was prepared by a combination of vacuum induction melting and vacuum consumable melting, followed by hot rolling.

3. The method for preparing TiAl alloy valve blanks as described in claim 1, characterized in that, The step of heating the TiAl alloy extrusion billet and placing it in a preheated extrusion die for extrusion includes: The TiAl alloy extrusion billet is heated and coated with glass powder before being placed in a preheated extrusion die for extrusion.

4. The method for preparing TiAl alloy valve blanks as described in claim 1 or 3, characterized in that, The extrusion pressing force is 60~100 t, and the feed speed is 1500~2000 rpm.

5. The method for preparing TiAl alloy valve blanks as described in claim 1, characterized in that, The forging process includes: The head cylinder of the extrusion is forged into a valve disc.

6. The method for preparing TiAl alloy valve blanks as described in claim 1 or 5, characterized in that, The forging pressure for the die forging process is 40~80 t, and the feed speed is 1500~2000 rpm.

7. A TiAl alloy valve blank, characterized in that, The TiAl alloy valve blank is prepared by the TiAl alloy valve blank preparation method as described in any one of claims 1 to 6.

Images