Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C1/00—Making non-ferrous alloys
  • C22C1/04—Making non-ferrous alloys by powder metallurgy
  • C22C1/0433—Nickel- or cobalt-based alloys
• • 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
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
  • C21C1/00—Refining of pig-iron; Cast iron
  • C21C1/10—Making spheroidal graphite cast-iron
  • C21C1/105—Nodularising additive agents
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C1/00—Making non-ferrous alloys
  • C22C1/04—Making non-ferrous alloys by powder metallurgy

Definitions

• the present invention is directed to a novel nickelmagnesium briquetted agent produced by powder metallurgical methods and to the method for producing the said briquetted agent.
• Patents have been prepared ,by melting and casting the alloys into slabs and crushing the slabs to provide lumps of material which vary considerably. in size and shape and grading the crushed product to provide the lump size ranges desired in the iron foundry.
• the crushing operation employed to produce the alloys in graded particulate form within the desired sizerange, e.g., Vs inch or inch or larger lumps, has always resulted in the production of a substantial quantity of fine material.
• These fines have been found to be of little use for the foundry production of ductile iron since the ,fines oxidize rap-idly in contact with the molten iron with the result that they are ineffective for the purpose of introducing magnesium in the molten cast iron.
• the method provided in accordance with the invention comprises blending fine nickel powder having a particle size not exceeding about 10 microns with magnesium powder having a particle size of at least about 40 microns but not greater than about 1000 microns, cold pressing the blended powder mixture into a coherent form,
• the resulting sintered material contains at least about 4% up to about 20% magnesium, e.g., about 10% to about 17% mag nesium, has a porosity of about 20% to about 50% and a crushing strength of at least about 12,000 pounds per square inch (p.s.i.).
• the sintered material containing about 4% to about 20% magnesium in briquetted form has substantial sterngth, withstands normal commercial handling and-is particularly useful for the introduction of magnesium into molten cast iron.
• the sintered briquettes have a surface area to volume ratio of at least about 8 to 1 when used to introduce magnesium into molten cast iron.
• a nickel powder having a particle size not exceeding about 10 microns e.g., about 3 to about 7 microns
• Carbonyl nickel powder having a particle size not exceeding about 7 microns is a satisfactory starting material particularly in view of the high purity of this powder including the almost complete absence of sulfur and oxygen therefrom.
• the oxygen content of the nickel powder should not exceed about 0.75% as it is found that greater amounts of oxygen interfere with the sintering operation and with magnesium recovery when the sintered material is added to molten cast iron.
• the initial powder mixture may contain up to about 25% of iron powder having a particle size not exceeding about microns. More advantageously, from the standpoint of reactivity, etc., the iron content does not exceed about 15%.
• the iron powder may be carbonyl iron, reduced iron oxide, etc. It is preferred that the magnesium powder employed in the initial powder blend have a particle size of at least about 200 microns since it is found that the use of finer magnesium powders results in final sintered agents having a finer average pore size and less desirable addition characteristics.
• the powder blend presses readily at ambient temperatures to form dense briquettes and other forms which may readily be handled.
• the resulting briquettes are then sintered in a protective atmosphere, e.g., hydrogen, argon or other essentially nitrogen-free atmosphere which will prevent oxidation of the magnesium-bearing briquettes.
• a protective atmosphere e.g., hydrogen, argon or other essentially nitrogen-free atmosphere which will prevent oxidation of the magnesium-bearing briquettes.
• magnesium will form nitrides when heated in a nitrogen-containing atmosphere. These nitrides will react with water vapor to form magnesium oxide and ammonia.
• the sintering temperature should exceed approximately 950 F.
• the melting temperature of the lowest melting eutectic formed in the nickel-magnesium binary system is the melting temperature of the lowest melting eutectic formed in the nickel-magnesium binary system.
• a sintering temperature of about 1000 F. is satisfactory.
• the time of sintering should be sufficient to cause substantially complete liquid-phase sintering throughout the entire cross section of the briquette. Sintering times of about one to about three hours, e.g., about one hour per inch of cross section, are satisfactory.
• the sintering operation results in the formation of a liquid phase and the formation of a porous sintered structure. It is found that the sintered material should be cooled from the sintering temperature at a rate of at least about 2 F. per minute, e.g., 5 F.
• the sintered briquettes are characterized by high crushing strength, e.g., the briquettes will withstand a compressive load of at least about 12,000 p.s.i. before crushing. This high strength permits shipment of the briquettes produced in accordance with the invention by usual commercial means without encountering undesirable size degradation leading to the uneconomic production of fines, and accompanying loss of material.
• the sintering operation is essential in accordance with the concepts of the present invention in order to provide agents, e.g., briquetted agents, having the special controlled porosity and quiet introduction characteristics when the briquettes are employed for the purpose of introducing magnesium into cast iron.
• agents e.g., briquetted agents
• green (unsintered) briquettes i.e., briquettes which have been formed by isotati-c pressing at ambient temperatures
• they have insufficient strength, generate excessive fines during handling, are considerably more reactive in contact with molten cast iron, and give a lower magnesium recovery in cast iron than do briquettes sintered as taught herein.
• Illustrative data are set forth in Table III hereinafter.
• the briquetted and sintered agents are employed for the purpose of introducing magnesium into molten cast iron by the commonly-employed practice wherein the magnesium-containing agent is placed at the bottom of a ladle and molten cast iron to be treated (at a temperature of about 2500 F. to about 2750 F., or even 2850 F. e.g., 2650 F.) is poured thereover, it is particularly advantageous for purposes of minimizing reactivity to provide the agents in a form which will not fioat to the surface of the molten cast iron.
• the briquetted and sintered agents are produced in a physical form such that the ratio of surface area to volume is at least 8 to 1.
• a series of sintered 85% nickel-15% magne- :siurn agents having surface area to volume ratios from 9.5 to 1 to 4.26 to 1 was prepared by mixing fine carbonyl nickel powder with magnesium powder having a particle size in the range minus 20 mesh, plus 70 mesh (Tyler), 'isostatically pressing the mixture to the various briquette :sizes and sintering the resulting briquettes at 1000 F. in hydrogen.
• the resulting briquettes were then employed to treat 150 pound batches of molten cast iron having the same composition in each instance by ladling the molten cast iron at a temperature of about 2750 F. upon about 1.2 pounds of the sintered briquettes. Data pertaining to these tests are set forth in the following Table I.
• An advantageous means for producing briquettes in accordance with the invention comprehends the use of rubber molds wherein the initial powder mix is molded under isostatic pressure to the desired final size having regard for the shrinkage which takes place during pressing and sintering.
• a plurality of shaped cavities canbe punched in a rubber disc having the desired thickness.
• One end of the cavities can be sealed off by vulcanizing a rubber sheet on one side of the rubber disc to provide a plurality of cup-like cavities in the disc.
• the disc or a plurality of discs can be filled with powder and stacked in a rubber casing so as to permit isostatic pressing of a number of briquettes simultaneously at a commercial production rate.
• billets can be pressed from the initial powder mixture and-the sintered billet can be crushed to lump form, although this technique provides an undesired loss of material in the form of fines.
• Example I A series of powder blends containing fine carbonyl nickel powder of about 5 micron particle size and magnesium powder of minus 20, plus 70 mesh particle size with hydrogen-reduced iron powder of minus 325 mesh size as an optional addition was prepared and briquettes were pressed isostatically therefrom at about 30,000 psi. pressure using rubber briquette molds. The resulting green briquettes were sintered at about 1000 F. in hydrogen. The resulting briquettes were porous and quite strong in each instance. The compositions of the resulting briquettes are set forth in Table II.
• the briquettes made .of'Alloys 1 through 5 were 1 inch in diameter by about /8 inch thick and had a'surface area to volume ratio of about 6.3 to 1 while the briquettes made of Alloys 6 through 10 were about 0.65 inch in diameter by about 1 inch thick and had a surface area to volume ratio of about 8.14 to 1.
• the briquettes had a surface area to volume ratio of about 8.14 to 1.
• the sintered briquettes were employed on a commercial foundry scale for the production of ductile iron.
• the molten cast iron was prepared in an induction furnace and contained about 3.58% carbon, about 2.36% silicon, about 0.1% manganese, about 0.011% sulfur, about 0.005% phosphorus and the balance essentially iron.
• About 300 pounds of molten iron at a temperature between 2800 F. and 2850 F. were poured over about 3 /2 pounds of the briquettes held in the bottom of a ladle.
• the briquettes did not float.
• the iron was inoculated with about 0.15% silicon as a graphitizing inoculant and was poured to provide ductile iron castings.
• the last iron poured from the ladle contained about 0.058% magnesium.
• the briquettes provided in accordance with the present invention are useful not only for the purpose of introducing magnesium into cast iron but also for the purpose of introducing magnesium into melts of other metals, e.g., nickel, copper, ferrous-base metals, etc., for deoxidation, desulfurization, alloying and other purposes.
• other metals e.g., nickel, copper, ferrous-base metals, etc.
• the briquettes provided in accordance with the invention When the briquettes provided in accordance with the invention are employed for the purpose of treating molten cast iron, they contain nickel, magnesium and optionally iron as described hereinbefore. Carbon in amounts of up to about 2% may be introducedinto the briquettes without harmfully affecting. reactivity thereof with respect to molten cast iron. Copper in amounts up to about 15% or about 20% does not adversely afliect the addition characteristics of the briquettes with respect to cast iron. Although copper is an undesirable constituent in ductile iron, copper-containing briquettes may be employed in treating other types of molten metals. The addition of silicon powder in elemental form to an initial powder mixture results in foaming of the resulting briquettes during sintering. Silicon as a pre-alloyed powder with nickel and magnesium can be introduced into the briquette in amounts up to about 15 or 20% but such an expedient is uneconomic.
• a sintered briquette having high crushing strength containing about 4% to about 20% magnesium, up to about 25% iron, with the balance essentially nickel, having a porosity of about 20% to about 50% and an average pore size of about 50 to about 500 microns.
• a briquette according to claim 1 having a crushing strength of at least about 12,000 p.s.i.
• a briquette according to claim 1 containing not more than about 15% iron and having a surface area to volume ratio of at least about 8 to 1.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Mechanical Engineering (AREA)
• Manufacture And Refinement Of Metals (AREA)
• Liquid Carbonaceous Fuels (AREA)

Priority Applications (9)

Applications Claiming Priority (1)

Publications (1)

Family

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Family Applications (1)

Country Status (8)

Cited By (2)

Citations (8)

• 1966
  • 1966-03-29 US US538197A patent/US3298801A/en not_active Expired - Lifetime
• 1967
  • 1967-03-20 GB GB12994/67A patent/GB1111800A/en not_active Expired
  • 1967-03-23 AT AT279667A patent/AT288455B/de not_active IP Right Cessation
  • 1967-03-25 DE DE19671558511 patent/DE1558511A1/de active Pending
  • 1967-03-28 NO NO167462A patent/NO117769B/no unknown
  • 1967-03-28 ES ES338556A patent/ES338556A1/es not_active Expired
  • 1967-03-29 SE SE4248/67A patent/SE309787B/xx unknown
  • 1967-03-29 BE BE696241D patent/BE696241A/xx unknown

Patent Citations (8)

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