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
  • C22C19/058—Alloys based on nickel or cobalt based on nickel with chromium without Mo and W

Definitions

• alloys which are (a) markedly corrosion resistant to various media, including stagnant seawater and other chlorides, (b) hardenable to tensile strengths as high as 200,000 psi, and (c) amenable to both hot and cold working.
• alloys in accordance herewith contain (by weight) about 22 to 40 percent chromium, about to 25 0.04 percent nickel, about 12 to 30 percent cobalt, up to 0.2 percent magnesium, aluminum, to to 2.5 percent silicon, up to'3 manganese, and the balance essentially iron, the iron constituting at least 15 percent of the total composition.
• the chromium content should be at least 24 percent, e.g., 26 percent or more. It can be as low as 21 percent or possibly percent but at the sacrifice in corrosion resistance. Advantageously, it does not exceed 32 or 33 percent since hot working difl'ficulties can ensue, the higher chromium percentages tending to introduce or contribute to the formation of embrittling phases, notably sigma. A chromium range of 24 to 32 percent is quite satisfactory. I
• Nickel contributes to achieving a desired microstructure. 1t greatly resists the tendency for hard martensite to form during processing, particularly during cold working. A range of 15 or 16 to 23 percent nickel is particularly beneficial.
• the alloys should be cold worked.
• the alloys are basically of an austenitic matrix, but by reason of cold working, relatively thin platelets, virtually parallel in arrangement, are formed and distributed throughout the austenitic matrix. These platelets appear to be much on the order of deformation twins.” At least a small but efiective amount of these thin platelets should be present to enhance tensile strength, e.g., at least 2 or 3 percent by volume.
• cobalt is deemed to greatly influence this platelet formation and is thus considered to play a significant role in the strenghtening process.
• a cobalt range of 17 to 23 or 25 percent is quite effective, although it can be as high as 30 percent as above indicated. As a practical matter, the improvements conferred at higher percentages do not appear to justify the added cost. Above 25 percent cobalt, say, 27 or 28 percent or more, it is con sidered that epsilon phase may be present.
• a range of from 0.001 to 0.03 or 0.04 percent is preferred, although it may less desirably be up to 0.1 or 0.15 percent.
• magnesium it is considered beneficial in respect of hot workability, especially in respect of edge cracking.
• Experimental data have not shown such other constituents as calcium, titanium and aluminum to be as effective in this regard.
• a retained magnesium levelof from about 0.002 or 0.005 percent and up to 0.1 percent or possibly 0.15 percent is deemed quite desirable.
• aluminum and titanium can be used for added strength or other purposes but excessive amounts should be avoided to minimize hot workability problems.
• a range of 0.02 to 1 or 2 percent of aluminum and from 0.01 to 0.4 percent titanium can be utilized.
• Up to 2.5 percent silicon can be incorporated for castings, but for wrought alloys it is of benefit that the silicon content not extend beyond about 1.5 or 2 percent, this to obviate promoting edge cracking or other working difficulties.
• Manganese need not exceed 1 or 1.5 percent and should be held to 0.8 percent or less.
• a range of 0.1 or 0.2 to 0.8 percent is preferred for both silicon and manganese.
• an alloy containing 31 percent chromium, 21.1 percent nickel, 19.8 percent cobalt, 0.024 percent magnesium, 0.026 percent carbon, 0.36 percent silicon, 0.48 percent manganese, balance iron and impurities was prepared using electrolytic nickel, cobalt, manganese and iron, lowcarbon ferrochromium, and spectrographic carbon.
• the iron, nickel, cobalt and carbon were first charged and heated to 2,850F. The carbon boil was allowed to run to completion at which point the ferrochromium, manganese and silicon were added. The melt was held for about 2 mins. and then deoxidized with magnesium (added in the form of nickel-magnesium).
• Air melting as well as vacuum processing can be used in production of the alloys.
• a cold rolled 0.375 inch specimen gave a Y.S. of approximately 170,000 psi, an U.T.S. of 198,000 psi, an elongation of 9 percent and a reduction in area of 38.5 percent.
• the specimen underwent a loss of 0.662 gram in the above-described Fe C1 test. After aging at 900F the corresponding tensile properties were as follows: 197,900 psi, 214.4 psi, 6 and 29 percent, respectively. In the aged condition, the corrosion loss was lower, being approximately 0.344 gram.
• l-lot rolled material is preferably annealed at 2,100F or above prior to cold working.
• the amount of cold working applied will, of course, depend on composition and the strength level desired. Generally speaking, sufficient cold work should be used to induce the formation of at least about percent, e.g., percent or more, by volume of the thin platelets above described. Not more than 25 to 40 percent of the platelets need be present. Aging, when used, should be carried out with the temperature span of 800 to l,000F.
• Alloys contemplated within the subject invention are useful as fasteners particularly in connection with oxidizing chloric solutions and marine environments.
• Other marinehardware would include parts for pumps,
• the alloys can also be used in chemical plant equipmerit and for such diverse utility as aerospace, desalinization and undersea mining applications. Also, they can be produced and used in conventional mill forms, including sheet, strip, bar and rod.
• the iron content of the alloys as constituting the balance or balance essentially, it is to be understood, as will be appreciated by those skilled in the art, that the presence of other elements is not excluded, such as those commonly present as incidental elements, e.g., deoxidizing and cleansing constituents, and impurities normally associated therewith in small amounts that do not adversely affect the basic characteristics of the alloys.
• Non essential elements that can be present include up to 2 percent each of copper and zirconium, up to 0.05 percent boron and up to 0.05 percent selenium.
• a corrosion resistant alloy characterized by a microstructure comprised of an austenitic matrix throughout which thin platelets are dispersed, the platelets being substantially parallel and present in an effective amount of at least about 5 percent by volume sufficient to' impart enhanced tensile strength to the matrix, said alloy consisting essentially of from 22 to 33 percent chromium, about 10 percent to 23 percent nickel, about 12 percent to 23 percent cobalt, up to about 0.04 percent carbon, up to about 0.2 percent magnesium, up to less than 0.5 percent titanium, up to about 3 percent aluminum, up to 2.5 percent silicon, up to 3 percent manganese, and the balance essentially iron, the iron constituting at least 15 percent of the alloy.
• a corrosion resistant alloy characterized by a microstructure comprised of an austenitic matrix throughout which thin platelets are dispersed, the platelets being present at least in a small but effective amount sufficient to impart enhanced tensile strength to the matrix, said alloy consisting essentially of about 26 to 33 percent chromium, about 17 to 23 percent nickel, about 17 to 23 percent cobalt, about 0.001 percent to about 0.03 percent carbon, up to 0.1 percent magnesium, up to 0.4 percent titanium, up to 1.5 percent aluminum, up to 0.8 percent silicon, up to'about 0.8 percent manganese and the balance being essentially iron, the iron constituting at least 15 percent of the alloy.
• a corrosion resistant alloy characterized by a microstructure comprised of an austenitic matrix throughout which thin platelets are dispersed, the platelets being present at least in a small but effective amount sufiicientto impart enhanced tensile strength to the matrix, said alloy consisting essentially of from 22 to 40 percent chromium, about '10 to 25 percent nickel, about 12 to 30 percent cobalt, up to about 0.04 percent carbon, about 0.002 percent to about 0.15 percent magnesium, up to less than 0.5 percent titanium, up to about 3 percent aluminum, up to 2.5 percent silicon, up to 3 percent manganese,'and the balance essentially iron, the iron constituting at least 15 percent of the alloy.

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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)

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Cited By (4)

Citations (3)

• 1972
  • 1972-08-25 US US00283810A patent/US3816106A/en not_active Expired - Lifetime
• 1973
  • 1973-05-03 CA CA170,292A patent/CA988750A/en not_active Expired
  • 1973-06-26 JP JP48071392A patent/JPS4959026A/ja active Pending

Patent Citations (3)

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