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
  • C22C38/10—Ferrous alloys, e.g. steel alloys containing cobalt
  • C22C38/105—Ferrous alloys, e.g. steel alloys containing cobalt containing Co and Ni

Definitions

• the alloy essentially contains less than 0.005% each of carbon and sulfur, 15- 20% nickel, 5-l0% cobalt, 38% molybdenum, up to 1.5% titanium, up to 0.5% aluminum, and the balance iron with normal incidental impurities. Hn another embodiment, toughness can be increased appreciably with an insignificant sacrifice in strength by subsituting tungsten for molybdenum.
• maraging steels low-carbon, high-nickel martensitic wrought alloy steels known as maraging steels. Unlike iron-carbon martensite, these iron-nickel martensitic alloys are relatively soft and ductile in the quenched condition, and became strong, hard and tough when tempered or aged. These alloys are therefore readily formable and weldable, and yet can be aged to exhibit yield strengths up to 300,000 p.s.i. and at the same time provide a relatively high degree of ductility and toughness. In addition to these physical properties, the maraging steel alloys have an exceptional resistance to stress-corrosion cracking, and can be easily welded in the high-strength aged condition.
• the first maraging steel used commercially contained about 0.01% carbon, 20 or 25% nickel, and 1.5 to 2.5% titanium and 0.3% aluminum.
• the latter is disclosed in US. Pat. 3,093,519, R. F. Decker et al., June 11, 1963.
• the alloy of this invention can be aged to produce a greater degree of toughness, impact toughness and ductility with little sacrifice in strength and other desired properties.
• the alloy of this invention is therefore comparable in all respects to the prior art 18% nickel maraging steel except that it provides a substantially greater degree of toughness.
• this improved maraging steel is substantially like the prior art 18% nickel maraging steel chemically except that carbon and sulfur must be critically controlled to levels below 0.005% each.
• toughness can be increased appreciably without a significant sacrifice in strength by partially or completely substituting tungsten for the molybdenum in amounts of from 3 to 8%.
• the maraging steel of this invention has a composition, in weight percentages, as follows:
• the above composition differs essentially from the prior art 18% nickel maraging steel in critically limiting the carbon and sulfur contents to less than 0.005
• improvement in the steels toughness is realized within the above composition range, it can be further optimized by completely substituting tungsten for the molybdenum.
• the alloy additives are preferably restricted to about 8.0% tungsten or molybdenum, about 18% nickel and about 10% cobalt as a compromise between optimum physical properties and economy.
• the alloy of this invention contains only 3 to 8 weight percent tungsten, an amount equal to almost half the atomic weight percent molybdenum in the 250-grade maraging steel.
• the higher concentrations of tungsten are preferred, i.e., about 7 to 8%.
• auxiliary hardeners e.g. titanium, aluminum, columbium and vanadium
• titanium, aluminum, columbium and vanadium may be added to the alloy to cooperate with the tungsten or molybdenum in providing strength. If present in excessive amounts, hoW- ever, these elements may over-harden the alloy, thereby appreciably reducing ductility. Nevertheless, inclusion of these additives, particularly about 0.6 to 1.5% titanium and about 0.5% aluminum is preferable because optimum physical properties can be achieved at lower tungsten contents of about To more graphically illustrate the advantages of this invention, a few of our tests, and the results thereof, are exemplified below.
• Table II shows the physical properties of a 250-grade maraging steel having carbon and-sulfur contents below 0.005% in accordance with the first embodiment of this invention-
• the samples in Table II all had substantially the same composition approximately as follows: 0.004% carbon, 0.02% manganese, 0.001% phosphorus, 0.0015% sulfur, 0.02% silicon, 17.5% nickel, 8% cobalt, 0.4% titanium, 0.08% aluminum and 4.8% molybdenum.
• the samples shown in Table III' were'identical to those shown in Table II except that they contained 5.1% tungsten instead of 4.8% molybdenum in accordance with the second embodiment 'of thisinvention. Except for variable annealing times as noted in the tables, all samples were processed identically.
• a maraging steel alloy consistingfessentially of 3 to 8% molybdenum, 15 to 20% nickelfS to 10% cobalt, less than 0.005% carbon, less than 0.005% sulfur and the balance essentially iron plus incidental impurities in conventional residual amounts, said steel alloy, in the aged martensitic condition, characterized by a yield strength within the range 200 to 300 k.s.i. and a Oharpy V-Notch Energy at 80 F. above 30 ft. lbs.
• the maraging steel alloy of claim 1 containing about 8% molybdenum, about 18% nickel and about cobalt.
• the maraging steel alloy of claim 1 further containing up to 1.5% titanium and up to 0.5% aluminum.
• a maraging steel alloy consisting essentially of 3 to 8% tungsten, to nickel, 5 to 10% cobalt, less than 0.005% carbon, less than 0.005% sulfur and the balance essentially iron plus incidental impurities in conventional residual amounts, said steel alloy, in the aged martensitic condition, characterized by a yield strength within the range 200 to 300 k.s.i. and a Charpy V-Notch Energy at 80 F. above ft. lbs.
• the maraging steel alloy of claim 4 containing about 8% tungsten, about 18% nickel and about 10% cobalt.
• the maraging steel alloy of claim 4 further containing up to 1.5% titanium and up to 0.5% aluminum.

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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)
• Heat Treatment Of Sheet Steel (AREA)

Applications Claiming Priority (1)

Publications (1)

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ID=21949947

Family Applications (1)

Country Status (6)

Cited By (7)

Families Citing this family (2)

• 1970
  • 1970-06-18 US US00047611A patent/US3723196A/en not_active Expired - Lifetime
• 1971
  • 1971-05-19 CA CA113,421A patent/CA948000A/en not_active Expired
  • 1971-05-25 GB GB1702371A patent/GB1352744A/en not_active Expired
  • 1971-05-31 IT IT68857/71A patent/IT942424B/it active
  • 1971-06-02 DE DE19712127389 patent/DE2127389A1/de active Pending
  • 1971-06-14 FR FR7121525A patent/FR2096302A5/fr not_active Expired

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