Titanium alloy forge piece and preparation process thereof

Abstract

The invention discloses a titanium alloy forge piece which is composed of, by mass, 4.0%-5.5% of Al, 0.3%-0.6% of Fe, 2.5%-3.4% of V, 7.5%-8.5% of Cr and the balance Ti. Sponge titanium, iron-chromium intermediate alloy, iron blocks, aluminum shots and titanium dioxide are mixed and then pressed to obtain electrode blocks, the pressed electrode blocks are installed and welded, three times of vacuum self-consuming electric arc smelting is adopted, and the titanium alloy forge piece is obtained. Two-heating-number cogging forging is conducted, a primary forging blank is heated to the process temperature for multi-heating-number modified forging, multi-heating-number modified forging is conducted on an intermediate forging blank when the temperature is lower than the phase transformation point, and after-forging solution treatment and aging treatment are conducted on the obtained forge piece; the titanium alloy forge piece is reasonable in design, the alloy performance is optimized and improved by reasonably controlling the content of all alloy elements, and the titanium alloy forge piece has the advantages of being high in strength, high in heat resistance, good in oxidation resistance and corrosion resistance and the like and is suitable for manufacturing parts with high performance requirements.

Description

Technical Field

[0001] The present invention relates to the technical field of titanium alloys, and more specifically, to a titanium alloy forging and a preparation process thereof. Background Art

[0002] Titanium alloy refers to a variety of alloy metals made of titanium and other metals. Titanium is an important structural metal developed in the 1950s. Titanium alloy has high strength, good corrosion resistance and high heat resistance. In the 1950s and 1960s, the main focus was on the development of high-temperature titanium alloys for aircraft engines and structural titanium alloys for fuselages. The density of titanium alloys is generally around 4.51g / cm3, which is only 60% of that of steel. Some high-strength titanium alloys exceed the strength of many alloy structural steels. Therefore, the specific strength of titanium alloys is much greater than that of other metal structural materials, and parts with high unit strength, good rigidity and light weight can be produced. Titanium alloys are used in aircraft engine components, frames, skins, fasteners and landing gear.

[0003] The main limitation of titanium alloy is its poor chemical reactivity with other materials at high temperature. This property forces titanium alloy to be different from the general traditional refining, melting and casting technology, and even often causes damage to the mold; as a result, the price of titanium alloy becomes very expensive, which is the biggest fatal flaw that prevents titanium alloy from being developed. Titanium alloy forgings use multiple forgings during the forging process, which easily leads to surface cracks and affects the quality of titanium alloy preparation. To this end, we proposed a preparation process for titanium alloy forgings. Summary of the invention

[0004] The purpose of the present invention is to provide a titanium alloy forging and a preparation process thereof, so as to overcome the technical problems existing in the prior art.

[0005] In order to achieve the above technical objectives and the above technical effects, the present invention provides the following technical solutions:

[0006] A titanium alloy forging consists of the following components in percentage by mass: 4.0-5.5% Al, 0.3-0.6% Fe, 2.5-3.4% V, 7.5-8.5% Cr, and the remainder is Ti.

[0007] A preparation process of a titanium alloy forging comprises the following steps:

[0008] Step 1: Mix titanium sponge, iron-chromium master alloy, iron block, aluminum bean and titanium dioxide, and then press them to obtain an electrode block;

[0009] Step 2: Weld the pressed electrode blocks to obtain long strip electrodes;

[0010] Step 3: Using three vacuum consumable arc melting to obtain an ingot with uniform composition and no metallurgical defects;

[0011] Step 4: The titanium alloy ingot is subjected to two-fire forging at an initial forging temperature of 1150-1000° C., and the primary forging blank is cut and cut;

[0012] Step 5, heating the primary forging blank to the process temperature and performing multiple forging to obtain an intermediate forging blank;

[0013] Step 6: The intermediate forging blank is subjected to multiple fire reforging when the temperature is lower than the phase transformation point. The reforging method is upsetting and drawing. Each fire is 2 upsetting and 2 drawing. The blank is chamfered after each drawing. After 1 upsetting and drawing, the blank is reversed in axial and radial directions to finally obtain a refined forging.

[0014] Step 7: The obtained forging is subjected to solution treatment and aging treatment after forging;

[0015] Step 8: The processed titanium alloy forgings are finished on a lathe and put into storage after passing the appearance inspection.

[0016] Preferably, in a process for preparing a titanium alloy forging, in step three, the smelting current is 5-12KA, and the smelting voltage is controlled at 30-45V.

[0017] Preferably, in a process for preparing a titanium alloy forging, the initial forging temperature of the first fire forging in step 4 is greater than the initial forging temperature of the second fire forging.

[0018] Preferably, in a process for preparing a titanium alloy forging, the forging method in step five is upsetting and drawing, each time of forging includes 2 upsetting and 2 drawing, and the blank is chamfered after each drawing.

[0019] Preferably, in a process for preparing a titanium alloy forging, water cooling is used for cooling after forging in step six, and air cooling is used for cooling the last forging.

[0020] Preferably, in a preparation process of a titanium alloy forging, in step seven, the forging is heated to 800-850°C by solution treatment, kept warm for 4 hours, and then quickly cooled in water, and the forging after solution treatment is heated to 600-650°C by aging treatment, kept warm for 8 hours, and then air-cooled.

[0021] Preferably, in a process for preparing a titanium alloy forging, the surface roughness during the appearance inspection in step eight is not greater than 6.3.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1. The present invention is reasonably designed and optimizes and improves the alloy performance by reasonably controlling the content of each alloy element. This titanium alloy forging has the characteristics of high strength, high heat resistance, good oxidation resistance and corrosion resistance, and is suitable for manufacturing parts with high performance requirements;

[0024] 2. The present invention adopts three vacuum consumable arc melting to further remove impurities, refine grains, improve component uniformity, and reduce metallurgical defects such as pores and inclusions, which is beneficial to ensure the quality of titanium alloy preparation;

[0025] 3. The present invention heats the primary forging blank to the process temperature for multiple-fire forging, and performs multiple-fire forging on the intermediate forging blank when the temperature is lower than the phase transition point, which can further refine the structure, improve the performance, and gradually adjust the shape and size of the forging blank to the requirements close to the final product. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solution of the present invention, the drawings required for use in the description of the specific implementation methods will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0027] Figure 1 It is a schematic diagram of the process of the present invention. DETAILED DESCRIPTION

[0028] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] A titanium alloy forging is composed of the following components in mass percentage: 4.0-5.5% Al, 0.3-0.6% Fe, 2.5-3.4% V, 7.5-8.5% Cr, and the balance is Ti. Adding an appropriate amount of aluminum to the titanium alloy can significantly improve the strength and heat resistance of the alloy. Aluminum can form a strengthening phase with titanium, thereby enhancing the performance of the alloy. Iron is one of the common impurity elements in titanium alloys, and its content needs to be controlled within a certain range to ensure the stability of the alloy's performance. Vanadium is one of the important alloying elements in titanium alloys, which can significantly improve the high temperature strength and creep strength of titanium alloys, while improving the plasticity and toughness of the alloy. Chromium is also one of the important alloying elements in titanium alloys, which can improve the oxidation resistance and corrosion resistance of the alloy while maintaining the strength and plasticity of the alloy. In the titanium alloy forging, the chromium content is relatively high, which helps to improve the comprehensive performance of the alloy. As the matrix element of the alloy, the titanium content occupies the vast majority of the alloy. Titanium has excellent properties such as low density, high strength and good corrosion resistance. It is an ideal material for manufacturing important parts in the fields of aerospace, chemical industry, etc. This titanium alloy forging optimizes and improves the alloy performance by reasonably controlling the content of each alloy element. This titanium alloy forging has the characteristics of high strength, high heat resistance, good oxidation resistance and corrosion resistance, and is suitable for manufacturing parts with high performance requirements.

[0030] A preparation process of a titanium alloy forging comprises the following steps:

[0031] Step 1: Mix sponge titanium, iron-chromium master alloy, iron block, aluminum bean and titanium dioxide, and then press them to obtain electrode blocks. Put the mixed raw materials into a mold and press them. The purpose of pressing is to make the raw materials tightly combined to form an electrode block with a certain shape and density. The pressure and pressing time need to be controlled during the pressing process to ensure the quality of the electrode block.

[0032] Step 2: Weld the pressed electrode blocks together to obtain long strip electrodes. Before welding, clean the welding parts of the electrode blocks to remove impurities such as oil, oxides, etc. This helps to improve the welding quality and prevent welding defects. During the welding process, it is necessary to control parameters such as welding temperature, welding speed and welding pressure to ensure welding quality. At the same time, it is also necessary to pay attention to the alignment and gap control of the welding joint to avoid welding defects such as lack of fusion and pores. After welding, the welding joint needs to be post-processed, including removing welding spatter and grinding the welding joint to eliminate unevenness and burrs. In addition, heat treatment and other process treatments can also be performed to eliminate welding stress and improve the performance of the welding joint.

[0033] Step 3: Use three vacuum consumable arc melting to obtain an ingot with uniform composition and no metallurgical defects. The melting current is 5-12KA, and the melting voltage is controlled at 30-45V. In a high vacuum environment, the high temperature of the arc is used to melt the consumable electrode and re-solidify it into an ingot, thereby effectively removing impurities, improving the uniformity of composition and reducing metallurgical defects. The ingot obtained from the first melting is reprocessed into a consumable electrode and placed in a melting furnace for the second and third melting, and the above melting, stirring and solidification steps are repeated. Each melting will further remove impurities, refine grains, improve the uniformity of composition, and reduce metallurgical defects such as pores and inclusions.

[0034] Step 4: The titanium alloy ingot is subjected to two-times of blank forging at an initial forging temperature of 1150-1000°C, and the primary forging blank is obtained by cutting and blanking. The initial forging temperature of the first-time blank forging is greater than the initial forging temperature of the second-time blank forging. The initial forging temperature of the titanium alloy is usually set between 1150 and 1000°C, which is determined based on the phase change temperature, thermoplasticity and work hardening characteristics of the titanium alloy. Within this temperature range, the titanium alloy has good thermoplasticity and low deformation resistance, which is conducive to the uniform flow of the metal and the refinement of the internal structure during the forging process. The first-time forging initially breaks the as-cast structure, eliminates casting defects, and improves the internal stress state of the material. The second-time forging further refines the grains, improves the density and mechanical properties of the material, and provides suitable blanks for subsequent cutting and blanking. In this process, more attention should be paid to controlling the forging temperature and deformation to avoid defects such as overheating, overburning or cracks. After two-time blank forging, the titanium alloy blank has good internal structure and mechanical properties. At this point, the blank can be cut into primary forging blanks of different sizes and shapes according to the needs of subsequent processing. During the cutting process, it is necessary to ensure that the cut is smooth and burr-free, and avoid excessive mechanical damage to the blank.

[0035] Step 5. Heat the primary forging blank to the process temperature and perform multiple reforging to obtain the intermediate forging blank. The reforging method is upsetting and drawing. Each reforging is 2 upsetting and 2 drawing. The blank is chamfered after each drawing. Perform multiple reforging according to actual needs. Each reforging will further refine the structure and improve the performance on the basis of the previous reforging, and gradually adjust the shape and size of the forging blank to the requirements of the final product. In subsequent reforgings, in addition to controlling the forging deformation, it is also necessary to pay attention to the adjustment of process parameters such as heating temperature, forging speed, and cooling method to ensure the stability of the forging process and the consistency of the forging quality.

[0036] Step 6: The intermediate forging billet is subjected to multiple fires of forging when the temperature is lower than the phase transformation point. The forging method is upsetting and drawing. Each fire is 2 upsettings and 2 drawing. The billet is chamfered after each drawing. After 1 upsetting and drawing, the billet is reversed in axial and radial directions to finally obtain a refined forging. Upsetting and drawing is a forging process that combines the two deformation modes of upsetting and drawing. Upsetting is to increase the cross-sectional area of ​​the billet by compressing it locally, while drawing is to reduce the length of the billet and increase its length dimension by stretching. In this process, 2 upsettings and 2 drawing are performed in each fire, which can alternately change the shape and size of the billet and promote the homogenization and refinement of the internal structure. It is an important step to chamfer the billet after each drawing. Chamfering can remove sharp edges and burrs caused by drawing, reduce stress concentration, and improve the surface quality and subsequent processing performance of forgings. At the same time, chamfering can also help improve the streamline distribution of forgings and further improve their mechanical properties. By reversing the direction, the force direction and deformation mode of the billet during the forging process can be changed, thereby avoiding obvious directional differences and stress concentration in the internal structure. At the same time, reversing the direction can also help eliminate internal defects and residual stress caused by the previous forging.

[0037] Step 7: The obtained forgings are subjected to solution treatment and aging treatment. For solution treatment, the forgings are heated to 800-850°C, kept warm for 4 hours, and then quickly cooled in water. For aging treatment, the forgings after solution treatment are heated to 600-650°C, kept warm for 8 hours, and then air-cooled. The combination of these two treatment processes can significantly improve the internal structure and mechanical properties of the material, making it more in line with the use requirements.

[0038] Step 8. The treated titanium alloy forgings are finished on a lathe and put into storage after passing the appearance inspection. The surface roughness is not more than 6.3. After the titanium alloy bars are annealed, in order to further improve their dimensional accuracy and surface quality, they are usually finished on a lathe. Finishing is an important process in metal processing, which aims to remove tiny unevenness and excess on the surface of the material to achieve the required dimensional accuracy and surface roughness requirements, providing reliable quality assurance for subsequent use.

[0039] The embodiments described in the present invention are merely descriptions of the preferred implementation modes of the present invention, and are not intended to limit the concept and scope of the present invention. Without departing from the design concept of the present invention, various modifications and improvements made to the technical solutions of the present invention by engineers and technicians in this field should fall within the protection scope of the present invention. The technical contents for which protection is sought in the present invention have all been recorded in the claims.

Claims

1. A titanium alloy forging, characterized in that: It is composed of the following components in mass percentage: 4.0-5.5% Al, 0.3-0.6% Fe, 2.5-3.4% V, 7.5-8.5% Cr, and the balance is Ti.

2. A process for preparing a titanium alloy forging, characterized in that: The following steps are involved: Step 1: Mix titanium sponge, iron-chromium master alloy, iron block, aluminum bean and titanium dioxide, and then press them to obtain an electrode block; Step 2: Weld the pressed electrode blocks to obtain long strip electrodes; Step 3: Using three vacuum consumable arc melting to obtain an ingot with uniform composition and no metallurgical defects; Step 4: The titanium alloy ingot is subjected to two-fire forging at an initial forging temperature of 1150-1000° C., and the primary forging blank is cut and cut; Step 5, heating the primary forging blank to the process temperature and performing multiple forging to obtain an intermediate forging blank; Step 6: The intermediate forging blank is subjected to multiple fire reforging when the temperature is lower than the phase transformation point. The reforging method is upsetting and drawing. Each fire is 2 upsetting and 2 drawing. The blank is chamfered after each drawing. After 1 upsetting and drawing, the blank is reversed in axial and radial directions to finally obtain a refined forging. Step 7: The obtained forging is subjected to solution treatment and aging treatment after forging; Step 8: The processed titanium alloy forgings are finished on a lathe and put into storage after passing the appearance inspection.

3. The process for preparing a titanium alloy forging according to claim 2, characterized in that: In step 3, the smelting current is 5-12KA, and the smelting voltage is controlled at 30-45V.

4. The process for preparing a titanium alloy forging according to claim 2, characterized in that: In step 4, the initial forging temperature of the first fire forging is greater than the initial forging temperature of the second fire forging.

5. The process for preparing a titanium alloy forging according to claim 2, characterized in that: In step five, the forging method is changed to upsetting and drawing, and each time is 2 times of upsetting and 2 times of drawing. After each time of drawing, the blank is chamfered.

6. The process for preparing a titanium alloy forging according to claim 2, characterized in that: After forging in step six, water cooling is used for cooling, and the cooling method for the last fire is air cooling.

7. The process for preparing a titanium alloy forging according to claim 2, characterized in that: In step seven, the forging is heated to 800-850°C for solution treatment, kept at this temperature for 4 hours, and then quickly cooled in water. In the aging treatment, the forging after solution treatment is heated to 600-650°C, kept at this temperature for 8 hours, and then air-cooled.

8. The process for preparing a titanium alloy forging according to claim 2, characterized in that: During the appearance inspection in step 8, the surface roughness shall not exceed 6.3.

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