Inconel 718 alloy is a high-temperature alloy with a chemical composition similar to that of the former Soviet Union’s ЭИ868. It contains a large amount of Cr and W for solid solution strengthening, which narrows the alloy’s hot processing temperature range and makes it difficult to produce seamless pipes. However, in order to meet the overhaul needs of advanced aircraft engine fuel main pipes and other pipe parts, ANTON METAL Company started in 2006 and successfully trial-produced eight specifications of qualified pipes through about 10 months of research and development work. These pipes have passed the long-term test run assessment and have been used in the overhaul of the engine.
The chemical composition (%) of Inconel 718 alloy is: C, ≤0.1; Al, ≤0.5; Cr, 23.5-26.5; Fe, ≤4.0; W, 13.0-16.0; Mo, ≤1.5; Mn, ≤0.5; Ti, 0.3 -0.7; Ca, ≤0.05; S, ≤0.013; P, ≤0.013; Si, ≤0.8; Ni, remainder. It can be seen that the alloy contains a large amount of Cr and W for solid solution strengthening, and its content is 36.5%-42.5%, which produces a strong solid solution strengthening effect and significantly deteriorated thermoplasticity.
In order to produce these pipes in a timely manner, when it is impossible to produce raw pipes using the hot piercing process like GH2984 alloy in the short term, a new process is used to machine the inner holes of hot-rolled rods or hot-extruded rods and then perform cold rolling. This process requires the following steps:
1. Alloy smelting:
Inconel 718 alloy ingots are produced using double smelting of non-vacuum induction furnace + vacuum consumable furnace. The vacuum consumable furnace ingot type adopts Φ250mm, and the electrode size is Φ200mm×1700mm. A 200kg vacuum induction furnace is used to melt the Inconel 718 alloy and cast into electrode rods. Then the vacuum self-consumable remelting duplex process is used to produce alloy ingots.
2. Alloy forging and rolling:
Inconel 718 alloy vacuum consumable ingot is turned and peeled off about 5mm on one side, and if there are local defects, it is ground again. The steel ingots are heated in a continuous furnace. Heating temperature 1160℃±10℃, heat preservation ≥2h. Reheating time: blank ≥200mm, keep warm for 50 minutes. Blank <200mm, keep warm for 40 minutes. Stop forging temperature ≥950℃, pile up and cool after forging. Rolling is carried out in the 550 rolling mill. The Institute of Metals uses extrusion technology to prepare rods for tube blanks.
3. Tube blank machining inner hole and cold rolling:
Cut the Ф55mm hot-rolled bars into a length of about 450mm each. Solid solution treatment is performed to improve its cold working properties. Then the boring method is used to machine it into a tube blank of Ф52mm×Ф38mm. After the tube blank is made, it is cold rolled using SG-50, SG-30, LD-30, LB-20, LB-8 and other cold rolling mills. During the cold rolling process, appropriate rolling process parameters, such as rolling temperature, rolling pressure, rolling speed, etc., need to be adopted to ensure the dimensional accuracy and surface quality of the pipe.
4. Pipe annealing:
In order to further improve the performance of the pipe, annealing is required. The annealing temperature is 1150℃±10℃, and the holding time is 2h. Then use water cooling or air cooling for annealing.
5. Pipe surface treatment:
During the production process, the pipe needs to be surface treated, such as pickling, polishing, etc., to ensure the smoothness and purity of the pipe surface.
Generally speaking, the production process of Inconel 718 seamless pipes includes steps such as alloy smelting, forging and rolling, pipe blank machining and cold rolling, pipe annealing and pipe surface treatment. These steps require the use of appropriate process parameters and technical means to ensure the quality and performance of the pipe.
Tianjin Anton Metal Manufacture Co., Ltd. is a company specializing in the production of various nickel-based alloys, Hastelloy alloys and high-temperature alloy materials. The company was established in 1989 with a registered capital of 10.0 million, specializing in the production and sales of alloy materials. Anton Metal’s products are widely used in aerospace, chemical industry, electric power, automobile, nuclear energy and other fields, and can also provide customized alloy material solutions according to customer needs. If you need to know the price consultation of alloy materials or provide customized alloy material solutions, please feel free to contact the sales staff.
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Post time: Dec-22-2023
