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
  • C22C38/08—Ferrous alloys, e.g. steel alloys containing nickel

Definitions

• the present invention relates to alloys and, more particularly, to nickel-containing ferrous alloys adapted to be brought to high strength and hardness levels by means of appropriate heat treatment.
• chromium-containing and nickel-chrornium-containing steels of the austenitic type which have good corrosion-resistance characteristics are not normally capable of being hardened to such high hardness levels as represented by a value in the order of about 513 V.H.N. '01 higher.
• Chromium-containing stainless steels of the'martensitic type are also not usually capable of being hardened to such high hardness levels.
• martensitic chromium-containing steels having a high carbon content While these steels can be produced in a highly hardened condition, it is to be noted that under. these circumstances these steels exhibit almostno ductility and are incapable of being readily welded.
• alloys can be provided which upon suitable heat treatment will exhibit a high combination of useful char: acteristics including hardness, corrosion resistance, yield strength, ultimate tensile strength, ductility, impact resistance, weldability, etc.
• the invention also contemplates providing a novel process for the production of an alloy having a high level of useful characteristics.
• a further object of the invention is to provide a novel process for heat treating alloys.
• the present invention contemplates alloys containing about 24% to about 30% nickel, about 1.5% to about 9% titanium and/ or aluminum, up to about 0.1% carbon, up to about 2% niobium, up to about 0.5% silicon, up to about 1.0% manganese, up to about 10% cobalt, up to about 0.10% calcium, up to about 0.1% boron, up to about 0.1% zirconium, up to about 0.25% vanadium with the balance being essentially iron including small amounts of other elements which do not adversely affect the novel characteristics of the alloy.
• titanium is present in the alloy in amounts of about 1% to 3%.
• Carbon is advantageously maintained below about 0.05% and more advantageously below about 0.03% and even below about 0.01%.
• niobium is advantageously present in the alloy in amounts at least about ten times the carbon content and up to 100 times the carbon content or higher.
• the aluminum plus titanium content is low, e.g., about 3% or lower, it is normally advantageous to maintain the nickel content below about 28%
• maximum hardness e.g., about 830 V.H.N. (65 R0) or higher is desired, it is most advantageous to have about 5% to about 9% of aluminum plus titanium in the alloy.
• Impurities such as sulfur, phosphorus, nitrogen, etc., should be maintained at the lowest levels which are practical.
• the total amount of these impurities should be not in excess of about 0.05% and should, if possible, be even lower.
• chromium and/or molybdenum should not be present in the alloys and, in any event, chromiumand/or molybdenum should not be present in amounts greater than about 2% total when it is desired to obtain the best combination of maximum hardness and ductility.- If desired, the cobalt content of the alloys can be as high as 20%.
• the alloys can be hot worked at temperatures in excess of about 1400 F. and, more particularly, within the range. of about 1400 F. to about 2150 F. or even higher. These alloys can also be readily cold worked provided the metal is cooled rapidly from a solution treating temperature of about 1400 F. to about 1800" F. It is to be noted that the alloys can be hardened by cold working and this hardening can be supplemented by heat treatment as disclosed hereinafter. If it is not necessary for the alloy to be amenable to softening to 'facilitate cold Working operations, the nickel content can be decreased. For-example, the nickel content can be as low as 20% or even 18% in alloys which do not require substantial amounts of cold working. I
• the afore mentioned alloys which contain about 18% to about 30% nickel can be heat treated from the solution treated condition produced by heating the alloy at temperatures in the range of about 1400 F. to about 2150 F. for 025 hour or longer, e.g., one hour, by subjecting them to a first aging treatment for a period of from 1 to 24 hours at a temperature above the mar-tensitic transformation range and within the range of from about 1100 F. to about 1400 F.; cooling the alloys to a temperature at least below F. to effect a transformation and conducting a second aging treatment at a temperature below about 1200 F., for example, within the range of about 500 F. to about 1200 F., for a period of about A to about 24 hours.
• about 1000 F. can be employed as the maximum temperature in the second aging step.
• the heat treatment it is usually advantageous to employ longer aging times in association with lower temperatures and vice versa during each step.
• alloys having nickel contents near the lower end of the range for example, about 18% to about 23% nickel, it is sometimes advantageous to omit the first aging step after solution treatment.
• the cooling step can be varied with respect to both time and temperature.
• the alloys can be refrigerated for several hours or can be permitted to remain at room temperature for a period of time ranging from a few minutes to several days.
• one alloy can have uniform hardness characteristics in sections of up to 24 inches thick and even thicker with the hardness ranging in different specimens from 42 Re up to 5 8 Re, i.e., from about 412 to about 655 V.H.N.
• Other alloys have been made which have hardnesses up to at least about 67 Re (900 V.H.N.).
• alloys in accordance with the present invention containing greater than about 24% nickel are quenched from the solution treated condition, hardnesses of between about 4 and about 15 Rc are commonly exhibited.
• alloys which in the solution treated condition exhibit hardnesses of the order of about 150 V.H.N. Rc), can be hardened to levels in excess of about 513 V.H.N. (50 Rc) and even up to 830 V.H.N. (65 Rc) and higher. Other physical characteristics are equally controllable.
• These alloys exhibit very low yield strengths in the solution treated condition and thus can be readily worked.
• the alloys exhibit yield strengths in the range of about 150,000 pounds per square inch (p.s.i.) up to about 290,000 p.s.i.
• Ultimate tensile strengths of the hardened alloys can be as high as 305,000 psi. and even higher.
• the alloys also exhibit advantageous oxidationand corrosion resistance when compared to carbon steels which can be hardened by a dilferent mechanism to hardness levels of similar magnitude.
• the alloys of the present invention can be hardened by heat treatment to produce high hardness values.
• Some specific hardening treatments in accordance with the present invention which are advantageously employed after the alloy has been subjected to a solution treatment by maintaining it at a temperature of about 1450 F. to about 1600 F. for a period of about 0.25 hour to about 4 hours, e.g., about 1 hour, are set iiorth in Table II:
• the alloy when it is indicated that the alloy is refrigerated, for example, held for 16 hours at -100 F., the alloy is first cooled from the aging temperature to room temperature in some convenient medium, for example, cooled in air, in water, in oil, in furnace atmosphere, etc.
• alloys of the present invention which are adapted to be produced in the soft condition, it is generally advantageous to cool the alloy after solution treatment to a temperature at least below about 1000" F. at a rate of the order of about 10 'F. per second when a high yield strength of the order of about 250,000 p.s.i. iOEl higher in the fully heat treated condition is desirable.
• examples of alloys of the present invention exhibited high 0.2% yield strengths of the order of about 250,000 p.s.i. to about 290,000 p.s.i. or higher in the aged condition.
• Another alloy of the present invention containing about 20% nickel and about 3% aluminum plus titanium exhibited in the aged condition a yield strength of about 292,000 p.s.i. and an ultimate tensile strength of about 305,000 p.s.i. with Jan elongation of 6% and a reduction in area of about 22%.
• An additional advantageous characteristic of the alloys of the present invention is that cooling rates scarcely affect the final hardness obtained.
• a difierent situation prevails, however, with respect to hardness after solution treatment.
• alloys 'of the present invention are particularly adapted to be formed into parts, structures, machines, etc., wherein a wide variety of metallurgical and physical characteristics are desired.
• alloys of the present invention can be employed as cutting tools, including knife edges, saws, lathe tools, files, high temperature bearings and bearing parts, forming tools, razor blades, forging dies, etc.
• the alloys of the present invention can also be employed in applications requiring high strength including pressure vessels, aircraft structural members, marine structural members, missile parts, skins and other members of supersonic aircraft, armor plate, armor piercing projectiles, etc.
• the alloys of the present invention also retain a good combination of physical characteristics at moderately elevated temperatures, the alloys can be advantageously employed in structures subjected in use to elevated temperatures of the order of about up to 1000 F. Because of the excellent formability of the alloys in accordance with the present invention, structural forms such as wire, rod, tube, bar, sheet, plate, etc., can be employed wherever required. Because of the good resistance to thermal shock and to stress cracking these structural forms can be readily assembled by welding to any desired configuration. In addition, if desired the alloys can be produced in cast forms, for example, precision castings.
• a process of hardening ferrous-base alloys containing at least about 1.5% of metal selected from the group consisting of titanium and aluminum, not more than about 0.1% carbon and about 18% to about 30% nickel comprising first aging said alloy at a temperature above the martensitic transformation range and within the range of about 1100 F. to about 1400 F. for about 1 hour to about 24 hours, cooling said alloy to a temperature at least below about 90 F. to effect a transformation therein and thereafter again aging said alloy at a temperature of about 500 F. to about 1200 F. for about hour to about 24 hours.
• a process of hardening ferrous-base alloys containing at least about 1.5% of metal selected from the group consisting of titanium and aluminum, not more than about 0.1% carbon and about 24% to about 30% nickel comprising first aging said alloy at a temperature above the martensitic transformation range and within the range of about 1100 F. to about 1400 F. for about 1 hour to about 24 hours, cooling said alloy to a temperature at least below about 90 F. to effect a transformation therein and thereafter again aging said alloy at a temperature of about 500 F. to about 1200 F. Ior about hour to about 24 hours.
• a martensitic iron-base alloy containing about 18% to about 24% nickel, 1.5% to about 3% of metal selected from the group consisting of titaniumv and aluminum and mixtures thereof, carbon in unavoidable amounts up to 0.05%, columbium in an amount of at least 10 times the carbon content and up to 2%, up to 1% manganese, less than about 0.5% silicon, up to about 10% cobalt, up to about 0.1% calcium, up to 0.1% boron, up to 0.1% zirconium, up to not more than 2% chromium, and the balance essentially iron, said martensitic alloy being characterized in the solution treated condition by good hot and cold workability and said martensitic alloy being further characterized when in the age hardened condition by high yield and tensile strengths and high hardness combined with good ductility and weldability.

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)

Priority Applications (6)

Applications Claiming Priority (1)

Publications (1)

Family

ID=25279349

Family Applications (1)

Country Status (4)

Cited By (11)

Families Citing this family (3)

Citations (7)

• 1959
  • 1959-09-11 US US839296A patent/US3093518A/en not_active Expired - Lifetime
• 1960
  • 1960-09-02 GB GB21719/63A patent/GB948355A/en not_active Expired
  • 1960-09-02 GB GB30385/60A patent/GB948354A/en not_active Expired
  • 1960-09-09 CH CH1022660A patent/CH404965A/fr unknown
  • 1960-09-09 BE BE594885A patent/BE594885A/fr unknown
  • 1960-09-09 CH CH701665A patent/CH431104A/fr unknown

Patent Citations (7)

Also Published As

Similar Documents