Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
  • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
  • C22C38/46—Ferrous alloys, e.g. steel alloys containing chromium with nickel with vanadium
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
  • C22C38/30—Ferrous alloys, e.g. steel alloys containing chromium with cobalt
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
  • C22C38/34—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of silicon
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
  • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
  • C22C38/52—Ferrous alloys, e.g. steel alloys containing chromium with nickel with cobalt
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F28—HEAT EXCHANGE IN GENERAL
  • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
  • F28F21/00—Constructions of heat-exchange apparatus characterised by the selection of particular materials
  • F28F21/08—Constructions of heat-exchange apparatus characterised by the selection of particular materials of metal
  • F28F21/081—Heat exchange elements made from metals or metal alloys
  • F28F21/082—Heat exchange elements made from metals or metal alloys from steel or ferrous alloys
  • F28F21/083—Heat exchange elements made from metals or metal alloys from steel or ferrous alloys from stainless steel

Definitions

• ABSTRACT A non-austenitic (i.e., ferritic) corrosion resistant alloy useful in sea water environment has the following broad composition range: Chromium 16%28%; Cobalt 4.5%7.25%; Nickel 0%6.5%; Silicon 1%-2.0%; Vanadium 0%-2.25%; Molybdenum O%4.25%; Carbon 0%0.03%; Manganese 0%-0.1%; lron the balance; all parts by weight percent.
• a narrower composition range of these alloys is as follows: Chromium l6.5%27%; Cobalt 4.75%-7.07z; Silicon 1.0%2.0%; Molybdenum O%4.0%; Carbon 0%0.01%; Manganese 0%-0.05%; Vanadium 0%2.0%; Nickel 0%6.0%; the balance iron; all parts by weight percent.
• This invention relates to a new and improved alloy composition and more specifically to an alloy having corrosion-resistant properties, particularly in a sea water environment.
• Copper-nickel alloys currently employed for heat exchanger pipes in desalination plants are typically 90-10 copper-nickel and 70-30 copper-nickel. However, the corrosion rate for these two alloys are 50 and 8 mils per year respectively (at 300F), and their ultimate tensile strengths are 44 X 10 and 55 X 10 psi respectively.
• Iron based alloys particularly stainless steels, are less expensive than copper-nickel alloys and can be tailored to provide some of the desired properties such as corrosion resistance, thermal conductivity, tensile and burst strengths. However, all of these properties cannot be realized in any of the known conventional stainless steels. V
• stainless steels require carbon to obtain good tensile and burst strengths, but the presence of carbon in significant quantities results in high corrosion rates when the steel is used in elevated temperature sea water.
• the use of carbon in very low amounts, or its entire omission, from a stainless steel will generally improve its corrosion resistance in sea water; however, the tensile and burst strengths may be lowered to unacceptable levels. Consequently,
• stainless steels only provide a part of the essential char- It would be desirable to obtain an alloy having a corrosion rate in elevated temperature sea water of less than about 13 mils per year, a yield strength about three times that of the copper'nickel alloy and containing a large concentration of iron to reduce the cost of the materials employed in the alloy.
• the alloy composition retain its ferritic phase, body-centered, cubic structure at room temperature after undergoing temperature cycling and not the face-centered lattice structure of austenite steel.
• the broad limit of the non-austenitic (i.e., ferrite) corrosion resistant alloy composition is as follows: Chromium l6%-28%; Cobalt 4.5%-7.25%; Nickel 0%6.5%; Silicon 1%2.0%; Vanadium 0%-2.25%; Molybdenum 0%-4.25%; Carbon 0%-0.03%; Manganese 0%-0.1%; Iron the balance; all parts by weight percent.
• a narrower composition range of these alloys is as follows: Chromium 16.5%-27%; Cobalt 4.75%-7.0%; Silicon 1.0%2.0%; Molybdenum 0%4.0%; Carbon 0%0.01%; Manganese 0%0.05%; Vanadium 0%-2.0%; Nickel 0%-6.0%; the balance iron; all parts by weight percent.
• the carbon content is about 0.005%, while the manganese content is less than about 0.1%.
• tungsten can be substituted in part for molybdenum, while columbium and/or tantalum may be substituted in whole or in part for vanadium.
• the alloys of the invention are ferritic phase, having a body-centered cubic lattice structure at room temperature.
• the effect in stainless steels of carbon and manganese is to increase tensile properties with increasing concentration of these two ingredients.
• the alloys of this invention by contrast have high tensile strengths comparable to the 300 stainless steel series when the carbon and manganese are present at very low levels, or are preferably omitted entirely.
• the overall effect is to provide an inexpensive iron based alloy having the high tensile and thermal conductivity properties of stainless steels, but which resists sea water corrosion to a very marked degree.
• Sample E which follows is another non-austenitic (i.e., ferritic phase) alloy composition of the invention having similar suitable properties for use as pipes, heat exchangers, etc., in a sea water environment and has the following approximate (11%) composition: Chromium 20.0%; Vanadium 2.0%; Silicon 1.2%; Nickel 6.0%; and the balance iron, all parts by weight percent. Cobalt is present only to the extent of itsbeing an impurity and usually present in nickel. Sample E also has a body-centered cubic lattice structure.
• the corrosion resistance of the alloys was determined by first preparing rolled strips of the alloy from are cast ingots. The rolling was carried out by heating the ingot to about l650-l 675C under Argon and then rolling in a standard cold rolling mill. The process was repeated until the rolled strip was of the desired thickness. Uncoated probes for electrical-resistance measurements were prepared from the strip and were tested in 300F (150 psi) natural sea water using a Magna Corrosometer. In the testing conditions used, the sea water was saturated with oxygen.
• samples A-E of the present invention had the following corrosion rates as shown in Table 2.
• 304 stainless steel has poor corrosion resistance to sea water due to its high carbon content (0.08%); this is in the order of at least l0 mils/year accompanied by severe pitting.
• the thermal conductivity of the alloys A-E varied .from about 8-1 1.3 BTU/hr/ft /ft/F 320% and is of the same magnitude as stainless steels.
• the alloy composition of the present invention represents a significant improvement over copper-nickel alloys employed in desalination plants not only from the standpoint of corrosion resistance, but also in tensile properties and in cost.
• the alloy of the present invention can be readily fabricated by conventional techniques without any deleterious results on end use. This permits it to be employed for a variety of uses such as in heat exchangers, boilers, pipes, etc. Since its tensile properties are significantly greater than those of coppernickel alloys, tubing thickness and hence weight can be significantly reduced. This in turn means that the structural requirements of a desalination plant employing the alloy of the present invention can be markedly reduced. Thus, a much less expensive plant design and capital investment is required.
• a ferritic phase alloy of body-centered cubic lattice structure consisting of Cobalt 6.9%; Chromium 20.5%; Silicon 1.7%; Mo-
• a ferritic phase alloy of body-centered cubic lattice structure consisting of Cobalt 4.8%; Chromium 16.7%; Silicon 2.0%; Mo-
• a ferritic phase alloy of body-centered cubic lattice structure consisting of Cobalt 5.9%; Chromium 26.7%; Silicon 1.0%; the
• balance iron all parts by weight percent.
• a ferritic phase alloy of body-centered cubic lattice structure consisting of Cobalt 6.0%; Chromium 18.5%; Silicon 1.0%; Mo-

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Heat Treatment Of Steel (AREA)
• Rigid Pipes And Flexible Pipes (AREA)

Priority Applications (12)

Applications Claiming Priority (6)

Publications (1)

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ID=27557668

Family Applications (1)

Country Status (10)

Cited By (1)

Families Citing this family (1)

Citations (10)

• 1971
  • 1971-12-06 US US205358A patent/US3859080A/en not_active Expired - Lifetime
  • 1971-12-15 GB GB5817471A patent/GB1324153A/en not_active Expired
  • 1971-12-23 BE BE777210A patent/BE777210A/xx unknown
  • 1971-12-30 SE SE7116882A patent/SE391197B/xx unknown
  • 1971-12-30 CH CH1920071A patent/CH583299A5/xx not_active IP Right Cessation
  • 1971-12-30 CA CA131,408A patent/CA949358A/en not_active Expired
  • 1971-12-31 NL NL717118187A patent/NL147788B/xx unknown
• 1972
  • 1972-01-03 FR FR7200071A patent/FR2121238A5/fr not_active Expired
  • 1972-01-03 IT IT1900572A patent/IT951875B/it active
  • 1972-01-03 IL IL38493A patent/IL38493A/xx unknown

Patent Citations (10)

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