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
  • C22C38/52—Ferrous alloys, e.g. steel alloys containing chromium with nickel with cobalt
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C19/00—Alloys based on nickel or cobalt
  • C22C19/03—Alloys based on nickel or cobalt based on nickel
  • C22C19/05—Alloys based on nickel or cobalt based on nickel with chromium
  • C22C19/051—Alloys based on nickel or cobalt based on nickel with chromium and Mo or W
  • C22C19/055—Alloys based on nickel or cobalt based on nickel with chromium and Mo or W with the maximum Cr content being at least 20% but less than 30%

Definitions

• the invention relates to an alloy based on iron with a high elastic limit resistant to corrosion by calm or rough sea water, sea mud, salt spray and brackish water.
• submarine cables Certain parts associated with submarine cables are subjected during their laying at the bottom of the seas and oceans or during their ascent for verification or maintenance work to extremely important constraints which depend on the depth of immersion and the sea state at the time of laying or lifting the cable.
• the underwater repeaters linked to the remote transmission cables may require lifting several years after their installation, this operation being able to cause tensions in the repeater, of extremely high amplitude.
• seawater-resistant stainless steels commonly used although they resist corrosion well during long immersion, nevertheless have an insufficient elastic limit so that the parts can withstand the considerable stresses that can involve lifting operations after several years of immersion.
• alloys resistant to corrosion by seawater and marine sludge have not been known as well as stainless steels, such as steel marketed under the brand URANUS 50, by the applicant and having at the same time time a high elastic limit after quenching and aging treatment, for example an elastic limit greater than 600 Newtons / mm2.
• refractory alloys with structural hardening containing mainly chromium, nickel, iron and cobalt as basic elements as well as molybdenum, tungsten, aluminum, titanium and niobium as hardening elements. .
• Such alloys described in British Patent 1,070,103 exhibit very good mechanical resistance, in particular at high temperature, due to the hardening of the matrix of the alloy as well as to the nature and the distribution of the precipitates appearing in the. alloy after appropriate heat treatment.
• such alloys do not have a resistance to corrosion by seawater comparable to that of stainless steels such as URANUS 50, if the respective contents of the various basic elements are chosen in any way within the fields recommended in British patent 1,070,103.
• the object of the invention is therefore to propose an alloy having a high elastic limit after a quenching and aging treatment and resistant to corrosion by sea water during long-term immersions on sea beds of such so that the submerged alloy parts keep their high mechanical properties during these long-term immersions.
• the alloy according to the invention based on iron, contains in proportion by weight, less than 0.15% of carbon, less than 2% of manganese, less than 1.5% of silicon, less than 0, 03% sulfur and phosphorus, 34 to 40% nickel, 16 to 21% chromium, 6 to 18% cobalt, 2 to 3.5% molybdenum, less than 0.25% aluminum, from 2.5 to 3.5% titanium, less than 2% of tungsten, less than 0.015% of boron, the remainder with the exception of the inevitable impurities being constituted by iron.
• an embodiment of an alloy according to the invention will be described by way of non-limiting example, used for the manufacture of parts which must resist corrosion in the marine environment for immersion, at great depth. , long term.
• Part of the metal was used to fabricate mechanical test specimens and part to develop the anchors which were used for corrosion tests by seawater in the laboratory and in full size by immersion in large.
• the ingots produced in a vacuum oven undergo a heat treatment comprising hyper-quenching and an aging treatment in several stages.
• the alloys produced have an austenitic structure and comprise phase precipitates y 'of composition Ni 3 TiAI and carbides after the heat treatment described above.
• the alloys according to the invention are non-magnetic.
• the alloy retains sufficient ductility and good resilience after heat treatment.
• the URANUS 50 stainless steel samples were also very resistant overall, except in one case where corrosion was observed.
• the alloys according to the invention after an aging heat treatment not only have mechanical properties much superior to those of stainless steels resistant to corrosion by sea water but, on the other hand, corrosion resistance which is itself superior to that of stainless steels of the URANUS 50 type with 21% chromium and 7% nickel.
• the alloys according to the invention have a tungsten content of between 0.5 and 2%, this element contributing with molybdenum to the hardening of the alloy in solid solution.
• Cobalt additions of up to 18% have also been recommended, however a preferred range for these cobalt additions is between 6 and 11%.
• An additional advantage of a weak addition of cobalt is that the cost price of the alloy is thereby reduced.
• the alloy according to the invention can be used not only for the manufacture of parts intended for the connection of submarine cables which must have a very good resistance to corrosion by sea water during prolonged immersions and a high elastic limit. making it possible to withstand significant tensions during the lifting of the cable, but also for the manufacture of all parts intended for use in seawater and having to withstand significant stresses.
• the alloy can therefore be used in the field of underwater construction and more particularly for the manufacture of parts for periscope tubes. Its non-magnetism also makes it very suitable for this kind of application.
• the alloys according to the invention can also be used in all cases where very good resistance to corrosion in a chlorinated medium is required.

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Preventing Corrosion Or Incrustation Of Metals (AREA)
• Heat Treatment Of Articles (AREA)
• Prevention Of Electric Corrosion (AREA)
• Insulated Conductors (AREA)
• Laying Of Electric Cables Or Lines Outside (AREA)
• Heat Treatment Of Steel (AREA)

Applications Claiming Priority (2)

Publications (2)

Family

ID=9203633

Family Applications (1)

Country Status (5)

Families Citing this family (10)

Family Cites Families (8)

• 1978
  • 1978-01-19 FR FR7801452A patent/FR2415149A1/fr active Granted
  • 1978-12-27 EP EP78400264A patent/EP0003272B1/fr not_active Expired
  • 1978-12-27 DE DE7878400264T patent/DE2860268D1/de not_active Expired
• 1979
  • 1979-01-11 US US06/002,748 patent/US4255186A/en not_active Expired - Lifetime
  • 1979-01-19 JP JP650279A patent/JPS54112321A/ja active Pending

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