GH2909 alloy is an important engineering material for advanced aeroengines to achieve gap control technology. It is mainly used to manufacture gap control parts such as turbine middle casings, load-bearing rings and honeycomb support rings of fourth-generation engines to reduce air leakage losses, improve efficiency, Reduce fuel consumption. GH2909 is developed based on the GH2907 alloy by increasing the Si content and adjusting the heat treatment process. GH2909 is a new type of Fe-Ni-Co based age-hardening low-expansion high-temperature alloy. It has high strength and plasticity below 650°C, low thermal expansion coefficient, almost constant elastic modulus, and good resistance to oxidation and thermal fatigue and other comprehensive mechanics. It can reduce the gap between rotating parts and stationary parts, achieve gap control, save energy, reduce consumption, and increase engine thrust. It is an ideal high-temperature alloy material for aviation and aerospace engines, so it has been widely used in aircraft engines.
Over the years, due to the limitations of forging equipment conditions: there are only 2,000-ton fast forging presses, the production of large-size high-temperature alloy forged rods has been a shortcoming in the development of high-temperature alloys for a certain company. The main problems of large-size GH2909 alloy rods are: (1) The structure is coarse and uneven, which leads to high ultrasonic flaw detection clutter and even severe bottom wave attenuation; (2) Performance testing data fluctuates greatly. With the improvement of forging equipment conditions: the 4500-ton fast forging press and the 1800-ton precision forging machine were put into operation, and in order to improve and enhance the quality of GH2909 alloy large-size forgings, the forging process was carried out to study the structure and properties of GH2909 alloy large-size bars. Affect the study.
The GH2909 alloy smelting process route is vacuum induction + vacuum arc remelting. The Φ440mm electrode vacuum arc is remelted into a Φ508mm steel ingot. After the steel ingot is homogenized and heat treated, it is forged to produce large-sized high-temperature alloy forged materials.
The blank forging adopts the stepwise cooling large deformation forging process, and the deformation amount in each fire is more than 30%; the final fire forging heating temperature: 1000℃; most of the deformation temperature: ≤955℃, the final forging temperature: ≥870℃; and Three forging methods are used:
(1) A 2000-ton fast forging press directly pulls the entire steel ingot into length + mid-cut segmentation + separate forging into materials;
(2) The entire steel ingot is made into steel using a 4,500-ton fast forging press with two upsetting and two-drawing operations + mid-cut segmentation + a separate 1,800-ton precision forging machine;
(3) A 4500-ton fast forging press is used to draw out the whole bar + make clamps at both ends + cut into sections + use a leaking plate to make two upsetting and two-drawing parts respectively + a 1800-ton one-fire precision forging machine to make the bar; then, cut the bars separately For the center, 1/2R and edge tissue and transverse performance samples, an optical microscope is used to observe the microstructure and detect mechanical properties, and the finished product is inspected by ultrasonic flaw detection after polishing.
The results showed that:
(1) The tonnage of the 2000-ton fast forging press equipment is obviously limited.
(2) After method 2, there is a small amount of mixed crystal structure in the center and 1/2R of the bar cross section after forging, and the edge grains reach level 8, and the structure is uniform and fine.
(3) After method 3, the cross-section of the bar after forging is uniform in the center, 1/2R, and edges. The grains in each part are relatively consistent, and the grain size is around level 6. Compared with method 1, the room temperature tensile yield strength and tensile strength of method 3 are both increased by more than 70MPa, and the room temperature tensile plasticity is also significantly increased, reaching more than 3%; the high temperature tensile yield strength and tensile strength are both increased by more than 20MPa, and the high temperature tensile plasticity is Reduced; the durable life is reduced, and the durable plasticity is equivalent. The performance test results of Method 3 and Method 2 are equivalent.
Therefore, method 3, that is, using a 4500-ton press to draw the entire length + clamping at both ends + cutting into segments + using a leaking plate for two upsetting and two-drawing + an 1800-ton one-fire precision forging machine, can make GH2909 alloy large The specifications of the rods are uniform and fine in structure, achieving good comprehensive performance that meets the requirements of standard indicators.
