How do you stress relieve Monel 400?
Description
Alloy 400 is a nickel-copper solid solution strengthened alloy. The alloy is characterized by moderate strength, good weldability, general corrosion resistance, and good toughness. It can be used at temperatures up to 1000°F (538°C). Alloy 400 has excellent resistance to fast flowing salt water or seawater where resistance to cavitation and corrosion is required. It is particularly resistant to degassed hydrochloric and hydrofluoric acids. Alloy 400 is slightly magnetic at room temperature.
Applications
Some typical applications for 400 alloy include:
• Chlorinated solvents
• Crude distillation columns
• Ethyl chloride purification
• HF alkylation
• HF reboilers
• Marine components
• Marine splash zone jackets
• MEA reboilers
• Oil well recovery pumps
• Salt production
• Salt residue compounds
• Shafting
• Wire mesh for insulation
Corrosion resistance
400 alloy is virtually unaffected by chloride ion stress corrosion cracking in typical environments. Generally, its corrosion resistance is very good in reducing environments but poor under oxidizing conditions.
Alloy 400 is resistant to most alkalis, salts, water (including brine or brackish water), foods, organic materials, and atmospheric conditions at normal and elevated temperatures.
The alloy is not suitable for use with highly oxidizing acids such as nitric and nitrous acids. It is resistant to sulfuric acid solutions up to 80% and hydrochloric acid solutions up to 20%.
Oxidizing impurities such as ferric chloride, ferric sulfate, chromates, nitrates, peroxides, and copper salts may cause corrosion in relatively mild media for the alloy.
Machinability
Hot/Cold Working
Alloy 400 can be readily hot or cold worked. Hot working ranges from 1700°F to 2150°F. Optimum working temperature is about 2000°F. By properly controlling the amount of hot and/or cold working and selecting the appropriate heat treatment, finished products with a fairly wide range of mechanical properties can be produced.
Machinability
The alloy can be worked at satisfactory rates with machine tools commonly used in industry. Cold drawn or cold-stress relieved material is generally recommended for best machinability and smoothest surfaces.
Joining
The alloy can be welded, brazed, or soldered. Gas or electric welding methods may be employed. When gas welding, the flame must be closed to neutral (on the reducing side) and the work must be completed quickly without re-welding.
Heat Treatment
Both cold-worked and hot-worked 400 alloy may be annealed or stress relieved to obtain the desired combination of strength and ductility and to minimize distortion during subsequent processing.
Annealing
Heating should be done in a sulfur-free reducing atmosphere. Annealing ranges from 1300 to 1800°F, but 1600 to 1800°F is most typical. Lower annealing temperatures (e.g. 1300 to 1500°F) and longer dwell times at this temperature may be used to minimize grain coarsening.
Stress Relief
Stress relieving will reduce stresses without recrystallizing the grain structure. Heating to 1000/1050°F for 1 to 2 hours will relieve strains in hot-worked or cold-worked products.
