Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D1/00—Treatment of fused masses in the ladle or the supply runners before casting

Definitions

• the nuclei are introduced into a melt of the metal or alloy in a metal carrier that dissolves in the melt, being present in the carrier as particles formed by internal oxidation of metal of the carrier and not greater than 2 microns, and preferably not greater than 1 micron, in size.
• the carrier is introduced into the melt and the metal of the carrier dissolves, the oxide particles are left as a fine dispersion in the melt. Because of the small size of the particles and the good wetting of the surfaces of the particles by the molten metal, the grain refining is excellent.
• the reduction in the grain size depends upon the composition of the alloy, the size of the ingot or casting produced from the melt and otherfactors, but it has proved possible by means of the invention to cause an alloy which, without any addition of nuclei, would have had an average grain size of over 2 cm. to solidify with an average grain size of less than 1 mm.
• the carrier is preferably of small section, and it is most advantageously strip or foil from 0.05 to 0.4 mm. thick.
• Another reason for using such foil is that the depth of penetration of the internal oxidation is a function of time and temperature, and a metal carrier of greater thickness requires a longer time at the oxidizing temperature if it is to be uniformly internally oxidized. While it is not essential that the carrier should be internally oxidized throughout, it is often better that it should be, so as to avoid the introduction of more of the metal of the carrier than is necessary.
• the choice of the alloy that is internally oxidized to form the metal carrier depends on a number of factors. It must contain at least one element which is preferentially oxidized so that a dispersion of oxide particles in metal can be produced. These particles must be effective as nuclei in the melt, and so must have melting points distinctly higher than the temperature of the melt.
• the metal which remains unoxidized must readily dissolve in the melt, though it is not essential that it 1 should have a melting point less than the temperature of the melt. In the amount added the unoxidized metal should not be a harmful constituent of the ingot or casting produced on the solidification of the melt.
• the alloy is preferably single-phase, since in a two-phase alloy the second phase may enter the melt as undissolved particles which, while not necessarily harmful, serve no useful purpose and may interfere with the nucleating process.
• Such alloys include those which have a base composed of from 20 to 80 percent nickel, 5 to 35 ercent chromium, 0 to 40 percent cobalt and 0 to 50 percent iron, and which may also contain one or more other elements such as aluminum or titanium up to percent each, and niobium tantalum, tungsten, zirconium, boron and hafnium in the amounts commonly present in high-temperature alloys.
• metal carriers consisting of internally oxidized copper-nickel, copper-cobalt and coppernickel-cobalt alloys containing by weight 90 percent or more copper are suitable. Examples of composition are 95 percent copper and 5 percent nickel; 96 percent copper and 4 percent cobalt; and 92.5 percent copper, 5 percent nickel and 2.5 percent cobalt.
• melts which are refined and cast at lower temperatures for example melts of copper-aluminum alloys, alloys containing iron as a preferentially oxidized element are suitable, examples being alloys of copper and iron or copper, iron and nickel, again containing at least percent copper.
• alloys containing iron as a preferentially oxidized element are suitable, examples being alloys of copper and iron or copper, iron and nickel, again containing at least percent copper.
• composition are percent copper and 5 percent iron and 92 percent copper, 4 percent iron and 4 percent nickel.
• the metal carrier may be externally as well as internally oxidized; for example the surfaces of a carrier consisting predominantly of copper are converted to copper oxide, with loss of weight of the carrier. It is desirable to remove any surface oxide by brushing before the carrier is added to the melt.
• the carrier may advantageously be degreased before the addition.
• EXAMPLE 1 Strip 0.2 mm. thick and 4 cm. wide of an alloy consisting of 95 percent copper and 5 percent nickel was heated in air at 850 C. for 4 hours. At the end of this time the strip was reduced in thickness to 0.1 mm. as a result of oxidation of the surface, and substantially all the nickel in it was present as particles of nickel oxide, less than 1 micron in size, uniformly dispersed throughout.
• heating more of the same strip in air at 600 C. results in oxidation predominantly or solely at the grain boundaries.
• Heating at 700 C. requires a much longer time to produce adequate internal oxidation.
• Heating at 900 C. leads to undesirable coarser particles and heating at l,000 C. leads to oxidized particles averaging 20 microns in size, which are ineffective in reducing the grain size of the metal into which they are introduced.
• EXAMPLE 2 Strip 0.2 mm. thick and 4 cm. wide of an alloy consisting of 92.5 percent copper, 5 percent nickel and 2.5 percent cobalt was heated in air at 850 C. for 4 hours. At the end of this time the strip was reduced in thickness to 0.1 mm., and substantially all the nickel and cobalt in it were present as particles of nickel oxide and cobalt oxide, less than 1 micron in size, unifonnly dispersed throughout.
• EXAMPLE 3 Strip'OA mm. thick and 6 cm. wide of an alloy consisting of 92 percent copper, 4 percent nickel and 4 percent iron was heated in air at 850 C. for 16 hours. At the end of this time the strip was reduced in thickness to 0.2 mm., and substantially all the nickel and iron in it were present as particles of nickel oxide and iron oxide, less than 1 micron in size, uniformly dispersed throughout.
• EXAMPLE 4 Strip 0.2 mm. thick and 4 cm. wide of a two-phase alloy consisting of 96 percent copper and 4 percent cobalt was heated in air at 850 C. for 4 hours. At the end of this time the strip was reduced in thickness to 0.08 mm. and the majority of the cobalt in it was present as particles of cobalt oxide, less than 1 micron in size, uniformly dispersed throughout, but
• EXAMPLE 5 Strip 0.4 mm. thick and 6 cm. wide of a two-phase alloy consisting of 95 percent copper and 5 percent iron was heated in air at 850 C. for 16 hours. At the end of this time the strip was reduced in thickness to 0.2 mm. and the majority of the iron in it was present as particles of iron oxide, less than 1 micron in size, uniformly dispersed throughout, but secondphase particles of iron in it oxidized to give some particles of iron oxide greater than 5 microns.
• EXAMPLE 6 A melt of 2,000 lb. of an alloy of nominal composition 92 percent copper and 8 percent aluminum was made, and while it was at a temperature of 1,150 O, strips produced as described in example 5 and containing iron oxide particles were successively dropped onto the surface of the melt and forced downwards by steel rods until a total of 1.5 lb. of strip had been introduced. The melt was then cast into a sand mould with a carbon bottom to form slabs 20 cm. deep by 60 cm. by 60 cm.
• the average grain size in the resultant slabs was less than 1 mm.
• the average grain size was 2 cm.
• EXAMPLE 7 A melt of 100 lb. of an alloy of nominal composition 92 percent copper and 8 percent aluminum was made, and while it was at a temperature of l,150 C. strips produced as described in example 3, wrapped round 80/20 nickel-chromium wires of 2-mm. diameter, were plunged below the surface of the melt until a total of 0.1 lb. of strip had been introduced. The melt was then cast into a metal mould 18 cm. in diameter. The average grain size in the resultant ingots was less than 1 mm. In contrast, when metal of the same nominal composition was cast into ingots in a similar manner, but without any nucleating addition the average grain size was 1 cm.
• EXAMPLE 8 A melt of lb. of an alloy of nominal composition 93 percent copper and 7 percent aluminum was made and cast into a refractory mould 7 cm. in diameter which had been preheated to l,000 C. When the temperature of the molten metal in the mould had fallen to l,l30 C. a piece of strip weighing 0.01 lb., produced as described in example 5 and wrapped around 80/20 nickelchromiurn wire of l-mm. diameter, was plunged below the surface. The average grain size in the resultant ingot was less than 1 mm. In contrast, when metal of the same nominal composition was cast into ingots in a similar manner but without any nucleating addition the average grain size was 0.6 cm. The plunging of a nickel-chromium wire alone had no effect on grain size.
• EXAMPLE 9 A melt of 10 lb. of an alloy of nominal composition 93 percent copper and 7 percent aluminum was made and cast into a refractory mould 7 cm. in diameter which had been preheated to 1,000 C. When the temperature of the molten metal in the mould had fallen to 1,130 C. a piece of strip weighing 0.007 1b., produced as described in example 3 and wrapped around 80/20 nickel-chromium wire of l-mm. diameter, was plunged below the surface. The average grain size in the resultant ingot was less than 1 mm. In contrast, when metal of the same nominal composition was cast into ingots in a similar manner but without any nucleating addition the average grain size was 0.6 cm.
• EXAMPLE 10 A melt of 10 lb. of an alloy of nominal composition 88 percent copper and 12 percent aluminum was made and cast into a refractory mould 7 cm. in diameter which had been preheated to 1,000 C. When the temperature of the molten metal in the mould had fallen to 1,160 C. a piece of strip weighing 0.01 lb., produced as described in example 4 and wrapped around /20 nickel-chromium wire of l-mm. diameter, was plunged below the surface. The average grain size in the resultant ingot was less than 1 mm. In contrast, when metal of the same nominal composition was cast into ingots in a similar manner but without any nucleating addition the average grain size was 1.2 cm.
• EXAMPLE 1 l EXAMPLE l2 Strips of total weight 0.01 lb. produced as described in example l, wrapped round 80/20 nickel-chromium wire of 1- mm. diameter were plunged below the surface of a melt 10 lb. in weight. The alloy was then cast into a cast-iron mould 6 cm. in diameter. The average grain size in the resultant ingot was less than 1 mm.
• Example 12 was repeated except that the total weight of the strip was only 0.003 lb. Again, the average grain size in the resultant ingot was less than 1 mm.
• EXAMPLE 14 A melt of 20 1b. was made and strips of total weight 0.02 lb., produced as described in example 1 and wrapped around nickel-chromium rod of S-mm. diameter were plunged below the surface of the melt to introduce nuclei of nickel oxide. The alloy was then cast into a refractory mould 7.5 cm. in diameter which had been preheated to 850 C. The average grain size in the resultant ingot was less than 2 mm.
• EXAMPLE 15 The same result was obtained when example 14 was repeated with the substitution of strips produced as described in example 4 and so containing particles of cobalt oxide.
• EXAMPLE 16 The same result was obtained when example 14 'was repeated with the substitution of strips produced as described in example 2 and so containing particles of nickel oxide and cobalt oxide.
• the improvement which comprises introducing said nuclei into said melt in a metal carrier that dissolves in said melt, said nuclei being present in said carrier as oxide particles formed by internal oxidation of metal of said carrier, said particles being not greater than 2 microns in size.
• melt is an alloy comprising nickel and copper with from to 50 percent iron
• metal carrier is formed by internal oxidation of an alloy containing at least 90 percent copper, the remainder being metal selected from the group consisting of nickel and cobalt.
• melt is an alloy comprising from 20 to 80 percent nickel, 5 to 35 percent chromium, 0 to 40 percent cobalt and 0 to 50 percent iron
• metal carrier is formed by internal oxidation of an alloy containing at least percent copper, the remainder being metal selected from the group consisting of nickel and cobalt.
• melt comprises copper and aluminum which solidifies to form a singlephase alloy
• metal of said carrier is formed by internal oxidation of an alloy containing at least 90 percent copper, the remainder being metal selected from the group consisting of iron, nickel and cobalt.
• melt comprises copper and aluminum which solidifies to form an alloy containing the beta-phase
• metal of said carrier is formed by internal oxidation of an alloy containing at least 90 percent copper, the remainder being metal selected from the group consisting of iron, nickel and cobalt.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Manufacture Of Alloys Or Alloy Compounds (AREA)
• Manufacture And Refinement Of Metals (AREA)
• Continuous Casting (AREA)

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Publications (1)

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Cited By (6)

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Citations (8)

• 1968
  • 1968-11-21 GB GB5532868A patent/GB1239066A/en not_active Expired
• 1969
  • 1969-11-13 US US876587A patent/US3635701A/en not_active Expired - Lifetime
  • 1969-11-19 JP JP44092216A patent/JPS502842B1/ja active Pending
  • 1969-11-19 AT AT1083669A patent/AT293038B/de not_active IP Right Cessation
  • 1969-11-19 DE DE19691958207 patent/DE1958207B2/de active Granted
  • 1969-11-20 FR FR6939987A patent/FR2023803A1/fr not_active Withdrawn
  • 1969-11-20 SE SE15955/69A patent/SE349060B/xx unknown

Patent Citations (8)

Non-Patent Citations (1)

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