Method of producing a cast multilayered alloy tube and the product thereof

A method for producing by centrifugal casting an alloy tubular article of manufacture in the form of a composite-tubular product comprised of an outer alloy layer of one composition of melting point of at least about 1300.degree. C. and at least one inner alloy layer of another composition of melting point at least about 1300.degree. C. while substantially inhibiting the formation of a metallurgical bond between layers in the as-cast condition which comprises:

• providing a rotatable centrifugal casting mold having a cylindrical inner surface and having a first open end and a second open end adapted to receive a molten metal alloy,
• pouring into the first open end of said rotatable mold a first alloy composition of melting point of at least about 1400.degree. C. and centrifugally casting said alloy to form a tubular outer layer during rotation of said mold,
• allowing said tubular outer to solidify so that its inner face has a temperature not exceeding about 92% of the absolute melting point in degrees Kelvin of said alloy,
• pouring into said solidified outer layer at least one second layer of an alloy of melting point of at least about 1300.degree. C. and thereby forming a casting of said composite tubular metal product thereof,
• said alloy of each of said first layer and at least one second layer being selected from the group consisting of structural steels comprising carbon steels, carbon-manganese steels, low alloy steels and high strength low alloy steels;
• stainless steels including austenitic stainless steels, super-austenitic stainless steels, duplex stainless steels, ferritic and martensitic stainless;
• chromium-containing iron/nickel-base alloys, Chromium-containing nickel-base alloys, nickel/cobalt-base alloys, and heat and corrosion resistant chromium-containing nickel-base and cobalt base alloys, the composition of each layer of the composite tabular product being different from the composition of an alloy layer adjacent to said each layer,
• and cooling said centrifugally cast composite tubular metal product to ambient temperature,
• said composite tubular product in the as-cast condition being characterized by an interface between said layers in which the formation of a metallurgical bond across said interface has been substantially inhibited.

A method for producing by centrifugal casting an alloy tubular article of manufacture in the form of a composite tubular product comprised of an outer alloy layer of one composition and at least one inner alloy layer of another composition while substantially inhibiting the formation of a metallurgical bond between layers in the as-cast condition which comprises:

• providing a rotatable centrifugal casting mold having a cylindrical inner surface adapted to receive a molten metal alloy,
• pouring into said rotatable mold a first alloy composition of melting point of at least about 1300.degree. C. and centrifugally casting said alloy to form a tubular outer layer during rotation of said mold,
• allowing said tubular outer layer to solidify so that its inner face has a temperature not exceeding about 92% of its absolute melting point in degrees Kelvin,
• pouring into said tubular outer layer at least one second layer of an alloy of melting point of at least about 1300.degree. C. at a pouring temperature sufficient to form said second layer within said tubular outer layer during rotation of said mold,
• said pouring temperature of each of the layers ranging from about 50.degree. C. to 125.degree. C. above the melting point of each of said alloys,
• the pouring temperature of the outer layer being at the upper end of the range and the pouring temperature of the inner layer being at the lower end of the range,
• and cooling said centrifugally cast composite tubular metal product to ambient temperature,
• said composite tubular product in the as-cast condition being characterized by an interface between said layers in which the formation of a metallurgical bond across said interface in the as-cast condition has been substantially inhibited, and
• subjecting said cast composite tubular product to reduction by hot mechanical working and thereby produce a composite tubular product of predetermined inner and outer diameters.

A method for producing by centrifugal casting and hot extrusion an alloy tubular article of manufacture in the form of a composite tubular product comprised of an outer alloy layer and at least one inner alloy layer while substantially inhibiting the formation of a metallurgical bond between layers in the as-cast which comprises:

• providing a rotatable centrifugal casting mold having a cylindrical inner surface adapted to receive a molten metal alloy,
• pouring into said rotatable mold a first alloy composition of melting point of at least about 1400.degree. C. and centrifugally casting said alloy as a tubular outer layer during rotation of said mold,
• allowing said outer layer to solidify so that the temperature of its inner face does not exceed about 92% of its absolute melting point in degrees Kelvin of said alloy,
• pouring into said tubular outer layer a second layer and after solidification and cooling of the second layer to a temperature at its inner face not exceeding about 92% of its absolute melting point followed by pouring a third inner layer alloy having a melting point of at least about 1300.degree. C. and at a pouring temperature ranging from about 50.degree. C. to 75.degree. C. above the melting point of said third inner layer alloy and thereby form a casting of said composite tubular metal product thereof comprised of a first outer layer and a second and third inner layer,
• and cooling said centrifugally cast composite tubular metal product to ambient temperature,
• said composite tubular product in the as-cast condition being characterized by interfaces between said layers in which the formation of a metallurgical bond across each of said interfaces has been substantially inhibited and subjecting said cast composite tubular product to reduction by hot extrusion at an elevated temperature sufficient to produce a product of predetermined inner and outer diameter characterized by a metallurgical bond across the interfaces thereof produced by solid state diffusion during hot extrusion.