Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
  • B22D11/06—Continuous casting of metals, i.e. casting in indefinite lengths into moulds with travelling walls, e.g. with rolls, plates, belts, caterpillars
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
  • B22D11/005—Continuous casting of metals, i.e. casting in indefinite lengths of wire

Definitions

• the chill body may be a rotating wheel or cylinder, and the molten metal may be impinged onto the flat peripheral surface of the wheel or onto the inner surface of the cylinder.
• the chill body may also be a traveling belt, usually an endless belt. The metal may be impinged onto the surface of the chill body by methods such as jetting the molten metal onto the surface.
• High heat conductivity metals previously proposed to serve as chill body surface such as copper, aluminum, beryllium copper or silver, do not have the desired wear characteristics.
• the present invention further provides an improvement in the apparatus for making metal strip directly from the melt by impinging molten metal onto the flat surface of a rapidly moving chill body, which apparatus includes a chill body having a flat surface adapted to receive molten metal to be impinged thereon for rapid quenching together with means functionally connected with said chill body for impinging molten metal onto its surface, wherein the improvement comprises providing a chill body having a surface of molybdenum.
• the molybdenum chill surface is readily wetted by the molten metal - especially by iron, nickel or cobalt-based alloys which upon rapid quenching from the melt form amorphous structures.
• the molybdenum surface further provides for good adhesion of the solidified metal strip, which is essential to effect thorough quenching of the metal if a ductile, amorphous metal strip is desired, yet it also affords clean release of the solidified strip from the surface.
• the molybdenum surface has excellent wear-resistant properties as compared to chill surfaces previously, used in the melt-spin process wherein molten metal is impinged onto the chill surface.
• the molybdenum has adequate heat conductivity to permit sufficiently rapid quenching, at rates in excess of 10 4 or 10 5 degrees centigrade per second, of thin layers of molten metal (in the order of a few thousands inch thickness), as is required for formation of amorphous metal strip.
• chill bodies having a molybdenum surface in the process of making flat metal strip directly from the melt by impinging the molten metal onto the rapidly moving flat surface of a chill body are obtained regardless of the configuration of the chill body.
• the chill body may be a rapidly rotating drum having a flat exterior surface which serves as the chill surface; it may be a rapidly rotating cylinder whereof the flat inner surface furnishes the chill surface, a moving belt or an other suitable structure which provides a flat surface.
• a flat strip is a slender body whose transverse dimensions are less than its length, and whose thickness is much less than its width, typically having a width at least about ten times its thickness, and having smooth and even top and bottom surfaces which are generally parallel to each other.
• a flat chill body surface is an endless surface provided by an endless belt, or the exterior or interior surface of a drum or cylinder, and which is smooth and even and which is straight in transverse direction, upon which a flat strip, as above-defined, may be cast.
• Fig. 1 is a cross-sectional view of an annular chill roll, the exterior surface of which is provided with a layer of molybdenum metal, to provide a casting surface of molybdenum.
• Fig. 2 is a cross-sectional view of an annular chill roll having, a ring of molybdenum inserted in its surface.
• Fig. 3 is a cross-sectional view of a cylindrical chill body having an inner molybdenum-clad chill surface inclined with respect to the axis of rotation.
• Fig. 4 is a side view in partial cross section showing means for jetting molten metal onto a rotating chill roll and a rotating chill roll provided with a chill surface of molybdenum metal.
• Fig. 5 is a somewhat simplified perspective view of apparatus including means for depositing molten metal onto a chill surface in the form of a moving endless belt having a surface of molybdenum.
• Chill casting processes for making flat metal strip - polycrystalline as well as amorphous (glassy) metal strip - by impinging molten metal onto the flat surface of a rapidly moving chill surface of a heat extracting member (chill body) are well known. It has now been found that for use in such chill casting processes molybdenum has a desirable combination of properties required of a good chill surface, namely high melting point (2650oC); relatively low coefficient of thermal expansion (lower than that of copper); moderately high thermal conductivity (about 35% of that of copper); and moderately high hardness.
• molybdenum has the required wetting properties for the molten metal and release properties for the solidified strip which, in combination with the aforementioned properties, make it eminently suitable for use as chill surface in quench casting of amorphous metal strips, especially ductile amorphous metal strips.
• Most significant is the ability of molybdenum chill surfaces to resist erosion and wear by the impinging stream of molten metal, whether the casting takes place under vacuum or in a gaseous atmosphere, which may be air or a protective atmosphere such as nitrogen, helium and the like. This is in contrast to the presently employed copper chill surfaces.
• refractory metals e.g., molybdenum, tungsten, chromium, hafnium, iridium, niobium, osmium, platinum, rhenium, rhodium, ruthenium, tantalum, thorium, vanadium, and zirconium.
• refractory metals e.g., molybdenum, tungsten, chromium, hafnium, iridium, niobium, osmium, platinum, rhenium, rhodium, ruthenium, tantalum, thorium, vanadium, and zirconium.
• use of a chill surface of molybdenum is particularly advantageous when casting under vacuum (say under absolutepressure of less than about 1 in. Hg.), or when casting glass-forming alloys containing one or more refractory metals, and especially when casting such alloys under vacuum.
• the form of the chill body and the mode of the casting operation are not critical for purposes of the present invention, so long as a flat casting surface is provided.
• casting may take place against the peripheral surface of a rapidly rotating drum by jetting molten metal against that surface, as disclosed in the above-mentioned patents to Bedell et al. and Kavesh.
• the molten metal may be deposited under pressure from a slotted nozzle onto the flat chill surface, as described in U.S.P. 4,142,571 to Narasimhan.
• the chill surface may be furnished by the interior surface of a rotating cylinder, as described in U.S.P. 3,881,540 to Kavesh and U.S.P.
• the chill surface of molybdenum may, in accordance with the present invention, be provided by fabricating the chill body of molybdenum, or by merely providing a surface layer of molybdenum on a chill body constructed of other material, suitably material having high thermal conductivity, such as copper or silver.
• Chill bodies made of molybdenum may be fabricated employing methods usually employed for fabrication of molybdenum, including machining from solid stock, such as cast pieces, or fabrication by known powder metallurgical methods.
• a particularly desirable embodiment of the present invention is a composite chill body, especially a chill roll, made of copper provided with a hoop of molybdenum, as illustrated in Figs. 1 and 2. With reference to Fig.
• chill roll 1 made of copper is mounted for rotation on shaft 2.
• the flat exterior surface of chill roll 1 is provided with a hoop of molybdenum 3.
• the hoop of molybdenum covers the total peripheral surface of the chill roll.
• a narrower hoop of molybdenum 3 is provided covering only part of the peripheral surface of the chill roll.
• the molybdenum hoop may be affixed to the copper chill roll, e.g. by shrink fitting.
• a molybdenum surface may be provided by any other conventional surface coating method, as for example oxyacetylene spraying, a method which involves feeding a molybdenum wire into the cone of an oxygen/acetylene flame to melt the metal, and then propelling the molten metal in droplet form against the surface to be coated.
• oxyacetylene spraying a method which involves feeding a molybdenum wire into the cone of an oxygen/acetylene flame to melt the metal, and then propelling the molten metal in droplet form against the surface to be coated.
• suitable methods include plasma arc spraying and conventional cladding procedures.
• Example 1 The following example further illustrates the present invention and sets forth the best mode presently contemplated for its practice.
• Example 1
• Fig. 4 employing a chill roll of construction as shown in
• the chill roll had an outer diameter of 8 inches, and its quench surface was 0.5 inches wide. It was rotated at a speed of about 2000 rpm.
• the apparatus was enclosed in a vacuum chamber. All tests were conducted under vacuum of about 100 mm. Concurrent experiments employing a chill roll made of copper having an outer diameter of 8 inches and a width of 1 inch rotated at 2000 rpm, were conducted, also under vacuum of about 100 mm.
• a number of different glass forming alloys alloys which upon rapid quenching from the melt, at a rate in excess of about 10 4 to 10 5 °C/sec. form an amorphous solid structure (see, e.g. U.S.P.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Continuous Casting (AREA)

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Cited By (3)

Citations (6)

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• 1979
  • 1979-05-04 WO PCT/US1979/000303 patent/WO1979001054A1/en not_active Ceased
  • 1979-05-04 DE DE7979900571T patent/DE2965347D1/de not_active Expired
  • 1979-05-04 JP JP54500849A patent/JPH029900B2/ja not_active Expired
  • 1979-05-04 EP EP79900571A patent/EP0016006B1/en not_active Expired
  • 1979-05-10 CA CA000327353A patent/CA1151389A/en not_active Expired

Patent Citations (6)

Non-Patent Citations (1)

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