Classifications

• • 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 present invention relates to alloys having good resistance to corrosion in chloride media and in acid media combined with good hot and cold workability and also weldability.
• parts of chemical process plant may be exposed on one side to highly corrosive acid solutions, and on the other to chloride-containing brackish or seawater used for cooling or heating.
• effective resistance is required to stress-corrosion cracking, intergranular corrosion, pitting and crevice corrosion.
• Resistance to pitting, crevice corrosion and stress-corrosion is also required for articles immersed in seawater, for example, woven wire rope for mooring cables and the like, which additionally require high tensile and yield strength, and cable armouring.
• crevice corrosion is a particularly strong form of attack which can occur in metal or alloy parts possessing recesses or pockets where stagnant liquid can collect. Such recesses may result, for example, where two parts are joined together or where the part meets a gasket or washer, etc. and the liquid which collects may be that in which the part is immersed or a liquid which is being passed through or round the part. Crevice corrosion is particularly likely to occur in chloride containing environments.
• An object of the present invention is to provide an economic, corrosion-resistant alloy suitable for these and a wide. range of other uses.
• the present invention contemplates a corrosion-resistant alloy containing 33% to 45% nickel and 1.4% to 3.5% copper with the sum of the nickel and copper contents being at least 35%, 14.5% to 20.5 chromium and from 8.5% to 9.5% molybdenum with the value of the relationship:
• alloy constituents be carefully correlated in order to achieve the desired combination of properties. Departure from the defined range with respect to any one of the constituents can detrimentally affect one or more of the properties.
• Nickel in an amount of at least 33% is necessary for adequate resistance to crevice corrosion resistance but amounts in excess of 45 unduly increase the cost of the alloys.
• the nickel content preferably does not exceed 41.5% and more preferably does not exceed 38%.
• Copper imparts resistance to corrosion in acid media and an amount of at least 1.4% must be present for this purpose. However an amount in excess of 3.5% impairs the hot workability of the alloys and preferably the copper contents does not exceed 2%.
• the nickel plus copper content must be at least 35% for adequate resistance to crevice corrosion.
• the nickel plus copper content preferably does not exceed 43% and more preferably is from 35.4% to 39.4%.
• Chromium imparts corrosion resistance in general to the alloys and at least 14.5 is necessary for this purpose, especially with regard to crevice corrosion resistance. Amounts in excess of 20.5% however detrimentally affect crevice corrosion resistance and additionally have an adverse effect on the workability of the alloys.
• the chromium content is from 17% to 18%.
• Molybdenum must be present in an amount of from 8.5% to 9.5% for imparting resistance to crevice corrosion and amounts below or above this closely defined range are found to adversely affect this property. Amounts in excess of 9.5 molybdenum additionally lead to bad workability. Preferably the molybdenum content does not exceed 9.3%.
• Niobium can be optionally present in the alloys in an amount not exceeding 0.9% to stabilize carbides and minimize intergranular corrosion in the welded condition and preferably at least 0.3% niobium is present for this purpose. Carbon can also be present in an amount which, in order to avoid weld decay, must not exceed 0.05%, and preferably should not exceed 0.03%. When the carbon content does not exceed 0.03%, the niobium content is preferably less than 0.7%.
• titanium and aluminum may tend to form oxide inclusions which may impair the surface quality of sheet rolled from the alloys
• the residual titanium content is preferably from 0.2% to 0.7% and the residual aluminum content is preferably from 0.05% to 0.15%. Titanium may also act in the alloys as a carbide stabilizer.
• Preferred alloys of the invention nominally contain about 35% nickel, 17.5% chromium, 9% molybdenum and 1.7% copper, up to 0.5% niobium, up to 0.5 titanium and up to 0.03% carbon.
• the alloys can be made by air melting, desirably in a basic lined high-frequency induction furnace, though vacuum-melting may be used if desired. When air-melting is employed it is beneficial to dcoxidize the alloys with calcium a suitable addition being 0.05% as calcium silicide, nickel-calcium or calcium-aluminum. The retained calcium content should not exceed 0.05% and is advantageously from 0.004% to 0.01%. Silicon can also be employed as a primary deoxidant in its own right. Yet, the residual silicon content of the alloy should not exceed 0.5%
• Each specimen containing 33.5% nickel, 17.1% chromium, 8.8% molyb- 20 was of uniform size and consisted of two parts, the first denum, 1.95% copper, 0.48% niobium, 0.035 carbon, of which was a cylindrical sleeve and the second had 0.27% manganese, 0.27% silicon, 0.38% titanium, 0.47% a narrowed piston-shaped portion which was dimenaluminum, 0.005% calcium, with the balance, apart from sioned to fit closely within the first part.
• the second part impurities, being iron (Alloy No. 1).
• the alloy was additionally possessed a shoulder on which the first part prepared by vacuum induction melting, including a final could rest, the shoulder being so shaped that a crevice step of deoxidation with calcium.
• the ingot was forged was formed between the shoulder and the first part. at 1150 C. to 20 mm. thick plate and then hot-rolled to When the two parts were fitted together, the specimen 3 mm. plate.
• After surface grinding to remove oxidation was essentially cylindrical externally, its diameter being scale, the plate was annealed for one hour at 1150 C., 12.7 mm. and its length being 45 mm.
• Each specimen descaled in potassium permanganate sodium hydroxide was immersed in 10% ferric chloride solution at 60 solution, and cold-rolled to 1 mm. thick sheet. After C. for 18 hours.
• Each specimen was weighed before and cold-rolling the sheet material was again annealed for after immersion and the loss in weight is shown in the one hour at 1150 C. Samples cut from the annealed Table.
• EXAMPLE [II emphasizes the careful control of the molybdenum con- A 3 kg. extrusion ingot cast from the same alloy as in tent necessary to achieve the desired properties.
• Example I was extruded from 50 mm. diameter to 16 The alloys can be readily hot and cold-worked. Thus mm. diameter, centerless ground to 8.6 mm. diameter and they can be extruded, rolled or forged, for example, cold drawn to wire 0.25 mm. in diameter with anneals at 1150 C., cold-rolled to sheet or strip, cold-drawn to at 1150 C. at various stages during the cold reduction. wire and cold-headed.
• Articles and parts which may advantageously be made 47% i bi 1 carbon, 0,23% manganese, from the alloys include plate heat exchangers, tubular 0.25% silicon, 0.25% titanium, 0.004% calcium, the balheat exchangers.
• marine wire rope, cable armouring, ance, apart from impurities being iron (Alloy No. 2) was fasteners, evapofators, for Phosphoric acid ch10- prepared by vacuum induction melting, cast to ingots and Tide solutions, P p and P p bleaching P and processed to 1 mm. thick sheet by procedures similar to gical implants
• the alloys are also useful for forming those described in Example I.
• Crevice corrosion tests Overlays 0h i which y be subject to Crevice were performed by placing samples 50 mm. x 25 corrosion, e.g., on tube plates, valve seats and variable cut from the annealed sheet material, horizontally be- Pitch p p tween two watch glasses so that the convex surfaces of
• the Present invention has been described in the watch glasses were in contact with the flat surfaces of Conjunction with Preferred embodiments, it is t0 he the sample, thus forming crevices near the points of conunderstood that modifications and variations may be tact.
• the specimen assemblies were immersed in 1% resorted to without departing from the spirit and scope of the invention, as those skilled in the art will readily understand. Such modification and variations are considered to be within the purview and scope of the invention and appended claims.
• An alloy according to claim 2 containing from 17% to 18% chromium.
• An alloy according to claim 1 containing 17% to 18% chromium, not more than 9.3% molybdenum and not more than 38% nickel and wherein the sum of the nickel and copper contents is 35.4% to 39.4%.
• An alloy according to claim 1 containing nickel, 17.5% chromium, 9% molybdenum and 1.7% copper.
• An alloy according to claim 9 containing 0.5% niobium, 0.5% titanium and not more than 003% carbon.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Heat Treatment Of Steel (AREA)
• Materials For Medical Uses (AREA)
• Extrusion Of Metal (AREA)

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Cited By (7)

Families Citing this family (7)

• 0
  • BE BE795564D patent/BE795564A/xx unknown
• 1972
  • 1972-02-16 GB GB706472A patent/GB1412951A/en not_active Expired
• 1973
  • 1973-01-29 ZA ZA730610A patent/ZA73610B/xx unknown
  • 1973-02-05 NL NL7301592A patent/NL7301592A/xx unknown
  • 1973-02-06 IL IL41482A patent/IL41482A0/xx unknown
  • 1973-02-07 US US00330250A patent/US3813239A/en not_active Expired - Lifetime
  • 1973-02-09 CA CA163,408A patent/CA989208A/en not_active Expired
  • 1973-02-09 AU AU52027/73A patent/AU463540B2/en not_active Expired
  • 1973-02-13 JP JP48018222A patent/JPS4893524A/ja active Pending
  • 1973-02-14 IT IT7348232A patent/IT980414B/it active
  • 1973-02-14 LU LU67024A patent/LU67024A1/xx unknown
  • 1973-02-15 DE DE19732307363 patent/DE2307363A1/de active Pending
  • 1973-02-15 CH CH217873A patent/CH579637A5/xx not_active IP Right Cessation
  • 1973-02-15 ES ES411646A patent/ES411646A1/es not_active Expired
  • 1973-02-15 SE SE7302123A patent/SE383901B/xx unknown
  • 1973-02-15 FR FR7305426A patent/FR2172318B1/fr not_active Expired
  • 1973-02-15 AT AT137573A patent/AT328485B/de not_active IP Right Cessation

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