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MONEL400 alloy, also known as nickel alloy N04400, is accurately described as a nickel-copper alloy primarily composed of nickel and copper components. Let's delve into its heat treatment process following the footsteps of the ASTM Alloy!
In general, the annealing heat treatment of MONEL400 alloy should be conducted within the temperature range of 700 to 900°C (1300 to 1650°F), with a recommended temperature of around 825°C (1510°F). Rapid air cooling or water quenching is advised to achieve better corrosion resistance. For instance, a batch of hot-rolled flat plates in Japan is designed to undergo heat treatment at 850°C and water quenched for 6 minutes. Both temperature and holding time are crucial for subsequent grain size, thus careful consideration of these parameters is necessary when determining annealing parameters.
Hot Working:
MONEL400 alloy can undergo hot working in the temperature range of 1200 to 800°C (2200 to 1470°F), but only mild hot working should be carried out below 925°C (1700°F). Hot bending should be performed between 1200 and 1000°C (2200 and 1830°F). For heating, the workpiece can be loaded into the furnace at elevated operating temperatures. After the furnace has recovered to temperature, the workpiece, with a thickness of every 100mm (4 inches), should be held at temperature for 60 minutes. It should be promptly removed and worked within the aforementioned temperature range at the end of this period. If the metal temperature falls below the minimum working temperature, it must be reheated.
It is recommended to undergo annealing after hot working to achieve better performance and ensure excellent corrosion resistance.
Cold Working:
Cold working should be performed on annealed materials. The work hardening rate of MONEL400 alloy is slightly higher than that of carbon steel, so the forming equipment must be adjusted accordingly. Interstage annealing may be necessary for highly cold forming. Stress relief or annealing is required after cold working exceeds 5%.
In some cases, the increased strength resulting from cold working may be utilized. However, in such cases, stress in the alloy should be relieved by heating between 550 and 650°C (1020 and 1200°F). Cold rolling is sometimes used to improve mechanical properties. Subsequent stress relief is recommended in conditions where stress corrosion cracking may occur, such as in mercury or wet, sour HF vapors.
It is worth noting that regardless of the type of heat treatment, the material should be loaded into the heat treatment furnace for holding at elevated operating temperatures.
