Preparation method of fine-grain Ti2AlNb-based alloy ring piece

Abstract

The invention discloses a preparation method of a fine-grain Ti2AlNb-based alloy ring piece, which is characterized by comprising the following steps: taking a Ti2AlNb-based alloy cast ingot, carrying out densification treatment, then carrying out cogging forging, carrying out upsetting and punching to obtain an intermediate ring blank, putting the intermediate ring blank on a ring rolling machine, and carrying out rolling forming at a relatively low rolling speed to obtain the fine-grain Ti2AlNb-based alloy ring piece. And the Ti2AlNb-based alloy ring piece which is compact in structure and fine in crystal grain is obtained, and the problem that the crystal grain of an annular forge piece is coarse due to the fact that the Ti2AlNb-based alloy prepared in the prior art is coarse in as-cast structure is solved. The forging method is suitable for forging the Ti2AlNb-based alloy ring piece in the aerospace field.

Description

Technical Field

[0001] The present invention relates to a grain refinement method, and particularly to a preparation method for a fine-grained Ti2AlNb-based alloy ring. Background Art

[0002] As a new type of lightweight high-temperature resistant structural material with high Nb content, Ti2AlNb-based alloy has the advantages of high specific strength, high fracture toughness, good oxidation resistance, excellent heat resistance, non-magnetic and flame retardant properties, etc. It can be used for a long time in the range of 700 - 800 °C, and the short-term use temperature can be higher than 1100 °C, thus becoming a research hotspot in the aerospace field. Different from nickel-based superalloys such as GH4169 whose fracture toughness gradually decreases with the increase of temperature, the fracture toughness of Ti2AlNb-based alloy continuously increases with the increase of working temperature, thereby reducing the risk of high-temperature application of key structural components. Currently, this alloy is mainly used to replace or partially replace high-density structural materials such as nickel-based superalloys (weight reduction of nearly 40%) to reduce the weight of engines and their own weight of various vehicles, and improve the thrust-to-weight ratio and efficiency of the engine. It is the main selected material for important components such as compressor casings, combustion chamber casings, compressor disks and blades of high-performance engines. The United States has used a high-strength and high-toughness Ti2AlNb-based alloy and cast TiAl alloy blades to make a novel bimetallic centrifugal impeller, whose cost and weight are lower than the traditional design.

[0003] At present, the as-cast microstructure of Ti2AlNb-based alloys produced at home and abroad is generally coarse equiaxed grains, resulting in low room-temperature workability of this material, which seriously affects its practical application process. Although domestic and foreign researchers have refined its microstructure by improving hot working processes to obtain duplex or triplex structures, cyclic heat treatment and other methods to achieve the purpose of improving plasticity, the coarse original microstructure of the alloy will seriously affect the implementation effect of these methods and it is difficult to achieve the purpose of improving plasticity. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a preparation method for a fine-grained Ti2AlNb-based alloy ring to obtain a Ti2AlNb-based alloy ring with a dense structure and fine grains.

[0005] To solve the above problems, the preparation method for the fine-grained Ti2AlNb-based alloy ring of the present invention comprises the following steps:

[0006] 1) Take a Ti2AlNb-based alloy ingot, and its chemical composition is: Ti is 35.5% - 57.9%, Al is 10% - 16%, Nb is 30% - 38%, V is 1% - 5%, Mo is 1% - 5%, and Si is 0.1% - 0.5%;

[0007] 2) First, the surface of the Ti2AlNb ingot is treated to make it smooth, and then it is encapsulated. The encapsulated Ti2AlNb ingot is placed in a heating furnace and heated to 1000°C - 1100°C at a rate of 8°C / s - 12°C / s. It is held at this temperature for 4h - 8h for densification treatment, and then the Ti2AlNb ingot is cooled in the furnace to room temperature and taken out;

[0008] 3) The densified Ti2AlNb ingot is placed in a heating furnace and heated to 1060°C - 1200°C. After holding for a period of time, it is taken out and subjected to cogging forging at a temperature of 1000°C - 1060°C, and then annealed in the furnace. The annealing temperature is 1060°C - 1200°C, and the annealing time is 20min - 60min. The annealed forged billet is heated to 1000°C and forged at a temperature of 960°C - 1000°C. The forging direction is perpendicular to the cogging forging direction. After forging, the encapsulation is removed by machining methods, and then after upsetting and punching, an intermediate ring blank is obtained;

[0009] 4) The intermediate ring blank is placed in a heating furnace and heated to 900°C - 960°C, held for 30min - 60min, and then rolled into shape on a ring rolling mill to obtain a Ti2AlNb-based ring forging with fine grains. The rolling speed is strictly controlled during the rolling process. The main roller speed is 1.5rad / s, and the core roller feed speed is 1.0mm / s - 1.5mm / s. The total deformation amount during the rolling process is 45% - 60%;

[0010] 5) The Ti2AlNb-based ring forging is placed in a heating furnace and heated to 800°C - 850°C and held for 20min - 60min for annealing treatment.

[0011] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0012] The preparation method of the fine-grained Ti2AlNb-based alloy ring is designed in combination with the hot working characteristics and microstructural characteristics of the Ti2AlNb-based alloy. By densifying the Ti2AlNb-based alloy before forging, a well-densified structure is obtained, and the preparation of the fine-grained Ti2AlNb-based alloy ring is realized by using traditional equipment such as presses and ring rolling mills, obtaining a Ti2AlNb-based alloy ring with a dense structure and fine grains. Specific Embodiments

[0013] To implement the preparation method of the fine-grained Ti2AlNb-based alloy ring of the present invention, equipment such as a forging heating furnace, a press, a manipulator, and a ring rolling mill are required. The specific embodiments are as follows:

[0014] Take a Ti2AlNb-based alloy ingot with the following chemical composition: Ti is 35.5% - 57.9%, Al is 10% - 16%, Nb is 30% - 38%, V is 1% - 5%, Mo is 1% - 5%, and Si is 0.1% - 0.5%.

[0015] First, treat the surface of the Ti2AlNb ingot to make it smooth, then perform encapsulation. Place the encapsulated Ti2AlNb ingot in a heating furnace and heat it at a rate of 8°C / s - 12°C / s to 1000°C - 1100°C. Hold at this temperature for 4h - 8h for densification treatment, and then cool the Ti2AlNb ingot in the furnace to room temperature and take it out.

[0016] Place the densified Ti2AlNb ingot in a heating furnace and heat it to 1060°C - 1200°C. After holding for a period of time, take it out and perform cogging forging at a temperature of 1000°C - 1060°C. Then return it to the furnace for annealing. The annealing temperature is 1060°C - 1200°C, and the annealing time is 20min - 60min. Heat the annealed forged billet to 1000°C and perform forging at a temperature of 960°C - 1000°C. The forging direction is perpendicular to the cogging forging direction. After forging, use mechanical processing methods to remove the encapsulation, and then obtain an intermediate ring blank after upsetting and punching.

[0017] Place the intermediate ring blank in a heating furnace and heat it to 900°C - 960°C. Hold for 30min - 60min, and then perform ring rolling on a ring rolling machine to obtain a Ti2AlNb-based ring forging with fine grains. Strictly control the rolling speed during the rolling process. The main roller speed is 1.5rad / s, the core roller feed speed is 1.0mm / s - 1.5mm / s, and the total deformation amount during the rolling process is 45% - 60%.

[0018] Place the Ti2AlNb-based ring forging in a heating furnace and heat it to 800°C - 850°C and hold for 20min - 60min for annealing treatment.

Claims

1. A preparation method of a fine-grained Ti2AlNb-based alloy ring, characterized in that, It includes the following steps: 1) Take a Ti2AlNb-based alloy ingot, the chemical composition of which is: Ti is 35.5% - 57.9%, Al is 10% - 16%, Nb is 30% - 38%, V is 1% - 5%, Mo is 1% - 5%, and Si is 0.1% - 0.5%; 2) First, treat the surface of the Ti2AlNb ingot to make it smooth, then perform encapsulation. Put the encapsulated Ti2AlNb ingot into a heating furnace and heat it to 1000°C - 1100°C at a rate of 8°C / s - 12°C / s, hold at this temperature for 4h - 8h for densification treatment, and then cool the Ti2AlNb ingot in the furnace to room temperature and take it out; 3) Put the densified Ti2AlNb ingot into a heating furnace and heat it to 1060°C - 1200°C, take it out after holding for a period of time, perform cogging forging at a temperature of 1000°C - 1060°C, then return to the furnace for annealing, the annealing temperature is 1060°C - 1200°C, and the annealing time is 20min - 60min. Heat the annealed forged blank to 1000°C and perform forging at a temperature of 960°C - 1000°C, the forging direction is perpendicular to the cogging forging direction. After forging, use a machining method to remove the encapsulation, and then obtain an intermediate ring blank after upsetting and punching; 4) Put the intermediate ring blank into a heating furnace and heat it to 900°C - 960°C, hold for 30min - 60min, and then perform ring rolling on a ring rolling mill to obtain a Ti2AlNb-based ring forgings with fine grains. Strictly control the rolling speed during the rolling process, the main roller speed is 1.5rad / s, the core roll feed speed is 1.0mm / s - 1.5mm / s, and the total deformation amount during the rolling process is 45% - 60%; 5) Put the Ti2AlNb-based ring forgings into a heating furnace, heat it to 800°C - 850°C, hold for 20min - 60min for annealing treatment.