Alloy 400 is primarily a nickel copper with small additions of manganese, silicon and iron to enhance the grade’s overall strength and corrosion resistance. Structurally, this is a single phase, solid solution strengthened material which can be tempered or cold worked to improve its mechanical properties. Columbia Metals’ standard stock material is supplied in the cold worked stress relieved condition below 60mm diameter and in the hot worked stress relieved condition for larger sizes. This ensures the maximum mechanical strength, the optimum machinability and best surface condition for the ultimate application.
The high strength and toughness of Alloy 400 is maintained over a wide range of temperatures up to 400ºC. There is an increase in strength and hardness at sub-zero temperatures with only a slight decrease in elongation. Without a ductile to brittle transition temperature the Alloy 400 is also suited to many applications where ferrous metals cannot be used.
Alloy 400 exhibits exceptional corrosion resistance to hydrofluoric acid and many reducing media. It is one of only a few alloys that can be used in contact with fluorine and hydrogen fluoride. Alloy 400 is also highly resistant to many forms of sulphuric and hydrochloric acids under reducing conditions, as well as to alkalis. It offers excellent resistance in flowing seawater, making it widely utilised in chemical and marine engineering.
Alloy 400 offers good fabrication capabilities and can be hot or cold formed, readily machined and joined via welding, brazing, or soldering. The cold drawn stress relieved condition also offers the best machinability and surface finish.
Typical applications include marine propeller and pump shafts, water feed and steam generator tubing in power plants, splash zone sheathing, offshore valves, pumps, fittings and fasteners, chemical and hydrocar-bon processing equipment, industrial heat exchangers and cladding for oil distillation columns.
Monalloy 500 / NA18 / N05500
Alloy K500 is a precipitation hardening nickel copper alloy that retains the excellent corrosion resistance of Alloy 400 with the added advantage of increased strength and hardness that can be maintained up to 650ºC. The higher mechanical properties arise due to the small additions of aluminium and titanium to the composition which, upon aging, form Ni3 precipitates in the matrix. Alloy K500 also offers an exceptionally high-dimensional stability and, as with Alloy 400, its low temperature mechanical properties are very good with no transition temperature making the alloy suitable for many cryogenic applications.
The corrosion resistance of Alloy K500 is essentially the same as that of Alloy 400, except when in the age hardened condition. When heat treated Alloy K500 has a greater tendency toward stress-corrosion cracking in certain environments; however, it has been found to be resistant in sour-gas environments. The combination of its high strength and excellent marine corrosion resistance in high-velocity seawater make Alloy 500 particularly suitable for marine shafts and centrifugal pumps. In stagnant or slow-moving seawater fouling may occur followed by pitting, but this pitting does slow down after a fairly rapid initial attack.
Alloy K500 can be readily fabricated and can be hot and cold formed, although heavy deformation or machining is best achieved in the annealed condition. If heavy machining is to be carried out it is common practice to machine to near net shape and precipitation harden prior to finish machining. This enables a better surface finish to be achieved, as well as closer tolerances.
