Casting Technology of Nickel Alloy

Casting is the process of filling the liquid metal into the mold cavity under the action of external force or gravity. When the liquid metal is cooled, it can obtain the required shape blank. Therefore, it is suitable for the production of complex boxes, pump bodies, cylinder blocks, and other products. However, the cast finished products also have disadvantages, such as loose structure, shrinkage, and pores in the casting, These phenomena will lead to poor mechanical properties of castings. Therefore, it is very important to select materials with good thermochemical properties, deformation resistance, air permeability, and thermal stability to make castings.

Nickel base superalloys (hereinafter referred to as nickel-base alloys) began to develop in the late 1930s. In 1941, the first British company produced nickel base alloy Nimonic 75 (ni-20cr-0.4ti) 13; In order to improve the creep strength and add aluminum, Nimonic 80 (ni-20cr-2.5ti-1.3al) 14 was developed. Later, American special metals successively developed various nickel alloy brands such as Inconel 718, Inconel 600, Inconel 800, and Monel R405. A large number of alloy elements can be dissolved in nickel-based alloys to form a coherent and orderly structure, which has higher high-temperature strength than other alloys. It has good oxidation resistance, heat and corrosion resistance, and ultra-high-strength. It has good application prospects in aerospace, marine engineering, automobile, and other fields. Nickel alloy has good high-temperature creep strength and fatigue resistance. It can be used to manufacture castings with high-temperature resistance and high strength.

The technological process of nickel alloy capacity casting is as follows:

Casting drawing → 3D modeling → EPS model processing (on CNC) → → drying → → roasting (forming mold shell) → plate assembly → furnace loading and pouring → sand cleaning → finishing → warehousing. The following briefly describes the precautions for each process:

1. The calcination temperature has a great impact on the shell quality. Through the test of shell strength with calcination temperatures of 950 ℃, 1000 ℃, and 1050 ℃, it is finally concluded that the calcination temperature is 1000 ℃, and the quality is the highest

2. Clean up the impurities in the mold shell by water washing. The washed shell is baked in the preheating furnace to remove water. The temperature in the furnace is 200 ℃± 10 ℃, and the baking time is more than 3 hours. When the shell is put into the preheating furnace, ensure that the tray is clean, pay attention to the placement direction of the shell, avoid dust in the furnace from falling into the shell, and then block the opening.

3. Plate assembly and pouring. During packing, ensure that the sand is tight enough. Then push the sandbox into the vacuum arc condensing shell furnace for pouring.

4. Before charging, check whether the shell has cracks or damaged parts (if reinforced with iron wire or refractory mud), and ensure that all exhaust holes are tightly blocked. The roasted degassed graphite sprue is used for furnace loading. During furnace loading, the sprue is aligned with the center of the tray or centrifugal disk. Ensure that the mold shell is firmly assembled and there is no gap at the graphite mouth ring to avoid liquid leakage.

5. In order to remove the reaction layer between molten liquid and refractory materials, the castings need to be pickled. The castings are pickled with mixed acid of nitric acid, ferric sulfate, and hydrofluoric acid. After pickling to the required size, wash them with clean water. After repeated pickling, many times, a relatively smooth casting is finally obtained.

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