US3615916A - Manufacture of permanent magnets - Google Patents

Manufacture of permanent magnets Download PDF

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Publication number
US3615916A
US3615916A US794158*A US3615916DA US3615916A US 3615916 A US3615916 A US 3615916A US 3615916D A US3615916D A US 3615916DA US 3615916 A US3615916 A US 3615916A
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United States
Prior art keywords
titanium
melt
process according
aluminum
percent
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Expired - Lifetime
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US794158*A
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English (en)
Inventor
Stuart Walter Ker Shaw
Derek Jim Palmer
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Huntington Alloys Corp
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International Nickel Co Inc
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Publication date
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
    • H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
    • H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
    • H01F1/032—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials
    • H01F1/04—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials metals or alloys
    • 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
    • C22C1/02—Making non-ferrous alloys by melting
    • C22C1/023—Alloys based on nickel
    • 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
    • C22C19/07—Alloys based on nickel or cobalt based on cobalt
    • 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

  • Pinel ABSTRACT An improved process of forming ingots of ironaluminum-nickel-cobalt-titanium alloys, with or without copper and columbium, with a columnar crystal structure, useful for making magnets, comprising introducing sulfur, aluminum and titanium into a carbon-containing deoxidized melt of the other alloy constituents.
  • An object of the invention is to provide an improved method of making ingots of iron-aluminum-nickel-cobalttitanium alloys with a columnar crystal structure.
  • Another object is to provide permanent magnets of ironaluminum-nickel-cobalt-titanium alloys having a columnar crystal structure.
  • the invention is based on the discovery that if appropriate steps are taken in the production of ingots of the alloys it is possible by a simple and industrially practical process to obtain columnar structures in ingots of alloys in which Kamata and Anbo obtained only equiaxed structures, and greater columnar lengths than in ingots produced by the methods described by either Harrison and Wright or Kamata and Anbo.
  • the accompanying drawing shows a chart depicting the aluminum content times titanium content against the sum of sulfur content plus carbon content for iron-nickel-aluminumtitanium magnet alloys.
  • the alloys in which such columnar structures can be produced are those containing from 5 to ll percent aluminum, from 7 to 25 percent nickel, from 20 to 55 percent cobalt, from l to ll percent titanium, from 0 to 10 percent copper and from 0 to 4 percent columbium, the balance except for impurities being iron.
  • commercial sources of columbium generally contain some tantalum, and all references in this specification to columbium are to the total quantity of columbium and tantalum.
  • the essential steps comprise forming a carbon-containing deoxidized melt of the iron, nickel, cobalt and any copper and columbium in the alloy from a base charge part of which may be scrap from a previous melt, but without titanium or aluminum except any introduced as scrap, and adding the titanium and aluminum (or the remaining titanium and aluminum) and sulfur to the melt.
  • the melt may be formed entirely from virgin materials or in part from scrap produced in a previous process according to the invention. in the latter case, it will of course contain both titanium and aluminum. The necessary steps in the process depend to some extent upon the presence or absence of scrap, and the amount of any scrap that is present.
  • the preferred procedure is as follows.
  • a base charge of the iron, nickel, cobalt and any copper and columbium is melted, the melt is deoxidized, advantageously by small amounts of aluminum or silicon, and the aluminum and titanium are added, the carbonbeing added to the base charge or to the melt before the addition of the titanium, and the sulfur being added to the deoxidized melt with or after the titanium.
  • the reason why the melt is deoxidized before the main addition of aluminum, instead of allowing the aluminum to effect the deoxidation, is that the amount of aluminum required for the deoxidation is variable and it is desirable to introduce as accurate an amount as possible into the final alloy.
  • the invention enables the columnar length in any given ingot to be longer than it would have been if the ingot had been produced by the methods of the prior art.
  • our object is to produce the greatest possible columnar length.
  • the numerous ingots we have produced a number of which are described in detail below, were made by pouring the treated alloy at a temperature of l,650 C. into a cylindrical refractory mold 6.5 inches high and 6 inches in external diameter with a conical opening leading to an internal cylindrical cavity 4.5inches high and 1.875 inches in diameter and open at the bottom, the mold with this open cavity being placed on a water-cooled copper base.
  • carbon When carbon is added otherwise than by way of the scrap, it may be incorporated in the main melt before deoxidation either as a Constituent of the base charge, e.g., as graphite or as an iron-carbon alloy, or as a separate addition to the melt, for example by immersing a carbon rod in the melt until the boil" caused by the reaction with oxygen in the melt has subsided.
  • the latter process generally results in the incorporation of 0.03 to 0.1 percent of carbon in the melt, but it is difficult to control accurately, and preferably the carbon is added to the melt after deoxidation, e.g., as an iron-carbon alloy.
  • an addition of 0.05 percent carbon after deoxidation is satisfactory.
  • the carbon is added as part of the base charge, the amount used is preferably increased, e.g. to at least 0.1 percent, to compensate for the greater loss by oxidatron.
  • the minimum amount of sulfur introduced into the melt whether as part of the scrap or as the added sulfur is 0.2 percent, but this amount is effective only if the combined contents of titanium, aluminum and columbium are not too high, and in particular if the titanium content does not exceed 6 percent.
  • the amount of sulfur required is mainly affected by the present in the base charge the melt is subjected to vacuum to remove the carbon monoxide formed, and the sulfur is added to the melt with or after the titanium.
  • the use of vacuum melting generally has the advantage that less sulfur is required to produce a satisfactory columnar length at any given titanium content.
  • the effect of varying the carbon content is shown by a series of tests.
  • the object was to make an alloy (Alloy X) having the nominal composition 5 percent titanium, 8 percent aluminum, 30 percent cobalt, 15 percent nickel and 3 percent copper, the balance being iron.
  • a base charge of the iron, nickel, cobalt and copper was melted in air and deoxidized with silicon, carbon was added as an iron-carbon alloy containing 3.6 percent carbon, the titanium, aluminum and 0.2 percent of sulfur as ferrous sulfide were immediately added, and the melts were held for 10 minutes at l,650 C. and then cast. A similar casting was made with no addition of carbon for purposes of comparison.
  • the titanium content of titanium and columbium is 7.5 percent; at least 0.4 percent sulfur must be added if the titanium content is 9.5 percent; and at least 0.6 percent sulfur if the titanium content is 10 percent or more.
  • the amount of sulfur added should be as small as is consistent with obtaining the desired columnar crystallization, since sulfur adversely affects the magnetic properties of the alloy by combining with titanium to form titanium sulfide. Although as much as 1 percent or even l.2 percent sulfur may be added, it is generally unnecessary to add more than 0.8 percent sulfur.
  • the sulfur may be added in the form of any convenient sulfur-containing compound, e.g., is ferrous sulfide.
  • melt is also preferably held for at least 2 minutes after the carbon addition and before any aluminum or titanium is added.
  • the casting temperature Another factor affecting the columnar length is the casting temperature. It is well known that the extent of columnar growth increases with this temperature, and although this may be as low as 1,550 C. it is preferably 1,650" C. Since as the casting temperature increases, so do the wear of the refractory linings and the loss of the more highly reactive elements, and in particular titanium and aluminum, we prefer not to exceed 1,700 C.
  • the loss of heat through the sides of the ingot mold should be reduced to a minimum, and accordingly the use of exothermic molds is advantageous.
  • the ingots can be produced by vacuum melting.
  • the carbon and sulfur analyses were carried out on specimens taken from the top of the cylindrical part of each ingot, and becat-ise of segregation in the ingots the contents given are likely to be higher than in the columnar zone.
  • Table V shows that it is generally desirable to hold the treated melt for some time after adding the sulfur and before casting. It also shows that better results may be obtained by holding after the carbon addition and before adding the aluminum, titanium and sulfur; as well as increasing the extent of columnar crystallization, this also improves the sharpness of the texture of the columnar crystals obtained, i.e., the closeness with which their direction corresponds with that of the longitudinal axis of the casting.
  • the process When the process is carried on in a vacuum furnace, it is preferred to effect melting under an inert gas, then subject the melt to vacuum, add the aluminum, titanium and sulfur under 5 an inert gas, and again subject the melt to vacuum.
  • an inert gas When the use of virgin raw materials the process may advantageously be carried out in detail in the following way.
  • the amount of carbon so introduced should be at least 0.05 percent and is preferably about 0.1 percent.
  • the casting is effected in the furnace. It is desirable to avoid lateral heat loss from the cast metal, and therefore, unless the furnace is so constructed that a preheated mold can be introduced without the admission of air, the melt is advantageously cast into an exothermic mold with a bottom chill. Argon is admitted to the furnace at a pressure of 700 mm. of mercury before the casting, since otherwise the violent evolution of gas from the exothermic mould in vacuum might destroy the mold. When the metal has been cast, it is desirable to open the furnace as soon as possible and put an exothermic compound on top of the molten metal, which is then left undisturbed until solidification is complete.
  • Metal from the columnar portions of ingots produced in accordance with the invention may be magnetized by any conventional method to form magnets, and the invention specifically includes these.
  • a columnar crystal structure which comprises forming a carbon-containing deoxidized melt of the iron, nickel, cobalt and any copper and columbium from a base charge part of which may be scrap form a previous melt, but without titanium or aluminum except any introduced as scrap, and adding the titanium and aluminum (or the remaining titanium and aluminum) and sulfur to the melt.
  • melt is formed wholly of virgin raw materials, a base charge of the iron, nickel, cobalt and any copper and columbium is melted, the melt is deoxidized, and the aluminum and titanium are added, the carbon being added to the base charge or to the melt before the addition of the titanium and the sulfur being added to the deoxidized melt with or after the titanium.
  • melt is formed wholly of virgin raw materials.
  • a process according to claim 8 in which the melting is effected under an inert gas, the melt is then subjected to the vacuum, the aluminum and titanium and sulfur are added under an inert gas, and the melt is again subjected to vacuum.
  • melt is formed from a base charge composed partly of scrap produced in a previous process according to claim 1 and partly of virgin raw materials, except for virgin titanium and aluminunijfid the remaining tita niu m and aluminum andadditional sulfur are added to the melt thus formed.
  • a process for making an iron-aluminum-nickel-cobalt alloy containing 5 percent to l 1 percent aluminum, 7 percent to 25 percent nickel, 20 percent to 55 percent cobalt, l percent to l 1 percent titanium, up to 10 percent copper and up to 4 percent columbium with the balance except for carbon, sulfur and impurities being iron comprising:
  • a process comprising melting a base charge composed partly of metal produced by the process set forth in claim 25 and partly of virgin raw material to provide a composition as set forth in claim 25 and then adding aluminum and thereafter titanium for said composition, adding sulfur to the melt with or after the titanium, provided that when less than 40 percent of the base charge is metal produced according to the process of claim 25 carbon is added before adding the titanium, holding the melt at least 5 minutes after the sulfur addition and then casting metal from the melt into a mold with a bottom chill and solidifying the cast metal to produce an ingot having a columnar crystal structure.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Power Engineering (AREA)
  • Manufacture And Refinement Of Metals (AREA)
US794158*A 1968-01-30 1969-01-27 Manufacture of permanent magnets Expired - Lifetime US3615916A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB4799/68A GB1204586A (en) 1968-01-30 1968-01-30 Manufacture of permanent magnets

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US3615916A true US3615916A (en) 1971-10-26

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US (1) US3615916A (me)
BE (1) BE727676A (me)
CA (1) CA939935A (me)
CH (1) CH511287A (me)
DE (1) DE1903976A1 (me)
ES (1) ES363070A1 (me)
FR (1) FR2001000A1 (me)
GB (1) GB1204586A (me)
NL (1) NL6901344A (me)
SE (1) SE354488B (me)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113667861A (zh) * 2021-08-23 2021-11-19 中航上大高温合金材料股份有限公司 一种gh3625合金的冶炼方法

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN109371334A (zh) * 2018-11-14 2019-02-22 江苏万达新能源科技股份有限公司 一种用于锂电池分切机的高耐磨涂层材料

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113667861A (zh) * 2021-08-23 2021-11-19 中航上大高温合金材料股份有限公司 一种gh3625合金的冶炼方法

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Publication number Publication date
GB1204586A (en) 1970-09-09
CH511287A (fr) 1971-08-15
ES363070A1 (es) 1970-12-01
NL6901344A (me) 1969-08-01
BE727676A (me) 1969-07-30
FR2001000A1 (me) 1969-09-19
SE354488B (me) 1973-03-12
CA939935A (en) 1974-01-15
DE1903976A1 (de) 1969-09-11

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