VDM® Alloy 400

Brine heater and recompression evaporator in saltworks, sulfuric and hydrofluoric acid alkylation, heat exchangers in the chemical industry, plating components for mineral oil distillation plants, splash zone lining on offshore platforms, impellers and pump shafts in marine technology, refining plants for the production of nuclear fuel, pumps and valves in production lines for tetrachlorethylene (perchlorethylene) and chlorinated plastics, heating tubes for monoethanolamine (MEA), sour-gas resistant components for oil and gas production. Alloy 400 is approved for pressure vessels from -10 to 425 °C pursuant to VdTÜV Material Sheet 263 and up to 480 °C in accordance with ASME Boiler and Pressure Vessel Code.

VDM® Alloy 400 is easily cold-shaped. However, it has a slightly higher work-hardening than does carbon steel. This must be taken into account during design and selection of forming tools and equipment and during the planning of forming processes. Intermediate annealing is necessary during cold working. The strength of VDM® Alloy 400 can be increased by hardening, though. Stress relief annealing is recommended in such cases, though, especially when used in media that can cause stress corrosion cracking in nickel-copper alloys, such as mercury and its compounds or fluorosilicic acid.

VDM® Alloy 400 has excellent resistance to neutral and alkaline salts and has long been the standard material for salt production systems. VDM® Alloy 400 is one of the few materials which can be used in contact with fluorine, hydrofluoric acid and hydrogen fluoride or their compounds. The material has a very high resistance to alkaline media. Its behavior in seawater is also excellent compared to copper-based alloys with an increased resistance to cavitation. VDM® Alloy 400 can be used in contact with highly diluted mineral acids, such as sulfuric and hydrochloric acid, provided that they are not ventilated. Since the alloy does not contain chromium, the corrosion rates can increase significantly under oxidizing conditions. While VDM® Alloy 400 is resistant to stress corrosion cracking, it can display stress cracks in the presence of mercury or in moist, aerated HF vapors. Stress relief annealing is necessary in these conditions.

VDM® Alloy 400 can be easily machined in the soft-annealed condition. Strain-hardened, stress relieved material is a more favorable processing behavior in most machining processes. Since the alloy has a tendency to hardening, a low cutting speed should be selected and the cutting tool should stay engaged at all times. An adequate depth of cut is important in order to cut below the previously formed work-hardened zone. Optimum heat dissipation through the use of large quantities of suitable, preferably aqueous, lubricants has considerable influence on a stable machining process.

The soft annealing should be performed at temperatures of 700 to 900°C (1,292 to 1,652°F), preferably at about 825°C (1,517°F). The retention time commences with material temperature equalization of the workpiece. Cooling down should be accelerated with air to achieve optimum corrosion-protection properties. To form a fine grain structure, the observance of heat treatment temperature and time is very important. The values are to be set precisely. Under certain circumstances, an increase in strength by cold forming is advantageous. Stress-relief annealing at about 550 to 650°C (1,022 to 1,202°F) should then occur, in order to prevent stress corrosion cracking

VDM® Alloy 400 can be hot formed in the temperature range of 800 to 1,200°C (1,472 to 2,192°F), but only slight deformations should occur at 925°C (1,697°F). Hot bending is performed from 1,200 to 1,025°C (2,192 to 1,877°F). For preheating, the workpieces may be placed in the furnace which has already been preheated to the maximum hot forming temperature. The workpieces should remain in the furnace for around 60 minutes per 100 mm (3.94 in) of thickness once the furnace has reached its temperature again. After this, the workpiece should be removed from the furnace immediately and formed within the temperature interval stated above. Heat treatment after hot forming is recommended for the achievement of optimal mechanical properties and corrosion resistance.

VDM® Alloy 400 is a binary nickel-copper alloy with a face-centered cubic microstructure.

The material VDM® Alloy 400 is welded with the common welding processes, such as GTAW (TIG), GTAW (TIG) hot wire, plasma, GMAW (MIG/MAG) and submerged arc welding. The material should be in its annealed condition for welding and should be free of scale, grease and markings. During welding, everything has to be scrupulously clean.