Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C29/00—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides
  • C22C29/02—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides based on carbides or carbonitrides
  • C22C29/06—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides based on carbides or carbonitrides based on carbides, but not containing other metal compounds
  • C22C29/067—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides based on carbides or carbonitrides based on carbides, but not containing other metal compounds comprising a particular metallic binder
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C29/00—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F7/00—Manufacture of composite layers, workpieces, or articles, comprising metallic powder, by sintering the powder, with or without compacting wherein at least one part is obtained by sintering or compression
  • B22F7/06—Manufacture of composite layers, workpieces, or articles, comprising metallic powder, by sintering the powder, with or without compacting wherein at least one part is obtained by sintering or compression of composite workpieces or articles from parts, e.g. to form tipped tools

Definitions

• This invention concerns cemented carbide rolls for hot-forming steel rod in multi-stand rolling mills, especially in a finished rod diameter range-of 5.5 mm to 12.7 mm.
• Carbide rolls operating at rod temperatures typically in the 927°C to 1204°C range, have gained wide use in multi-stand steel-rod rolling mills and, to a large extent, have replaced chilled cast iron rolls, especially in finishing roll mill stands.
• Rolls used for slower rolling speeds and larger rolling diameters are subject to even greater thermal stress because thermal cycling is accelerated by longer time intervals of roll-to-work contact and cooling exposure and, also, higher rolling torque and stresses due to the slower speed.
• One of the causes of mill roll failure is due to the tensile stress imposed on the inside diameter of the mill roll when mounted in working position.
• the rolls are usually mounted on mandrels with means for exerting radially outward contact with the inside diameter of the roll.
• the contact with the mandrel must be sufficient so as to effect torque transmission between the mandrel and the roll.
• cemented carbides are usually relatively weak in tensile strength, the tensile force imposed by the mandrel can cause failure of the roll. Bending stresses due to high torque transmission can also attribute to roll failures.
• tantalum carbide TiC
• the said reference discloses a dual compact roll having an outer layer comprising, by volume, 45 to 72% tungsten carbide, 5 to 13% tantalum carbide, and 23 to 42% cobalt, and an inner layer comprising, by volume, 57 to 76% tungsten carbide and 24 to 43% cobalt, respectively. Both zones form a solid, integrated roll body with a sinter-bonded interface.
• Ni nickel
• Co cobalt
• a hot forming rod mill roll embodying the present invention comprises:
• a cemented carbide roll can have the thermal fatigue and toughness properties increased by the addition of nickel to the roll composition.
• the composition of the roll near its inner surface will comprise, by volume: tungsten carbide-70 percent; nickel-10 percent; and cobalt-20 percent; however, the composition may be in the range, by volume, of: tungsten carbide-45 to 72 percent; nickel-5 to 30 percent; and cobalt-0 to 42 percent.
• nickel is also more economical in a dual compact roll with an outer layer preferably comprised of, by volume, 70 percent tungsten carbide and 30 percent cobalt.
• the outer layer may be in the range of, by volume, 24 to 43 percent cobalt, and the balance tungsten carbide and singly or in combination tantalum carbide, tantalum, nickel and chrome.
• the invention concerns a dual-composition carbide roll comprising a longer-wearing peripheral or outer cemented carbide zone in which the rolling grooves, or working surfaces, are formed and possessing exceptional thermal fatique and wear resistance compositions, and a mechanically tough inner support core of tungsten carbide-cobalt-nickel or tungsten carbide-nickel alloy preferably possessing a binder volume and carbide grain structure identical with or similar to that which exists in the peripheral or outer zone.
• Both zones form a solid, integrated roll body with a sinter-bonded interface.
• Carbide-cobalt-nickel powder blends suitable for each zone are first pressed together in a powder compacting press, then sintered together as a single pressing.
• the improved mill roll possesses as its preferable feature a dual-composition cemented carbide structure, of which the outer or rolling zone will be a hard wear resistant material, preferably a tungsten carbide-cobalt cemented carbide composition and an inner zone of cemented tungsten carbide-cobalt nickel, preferably having identical or similar volume percent of binder metal.
• Cemented carbide rings were made having an outer zone composition in terms of percent by volume of tungsten carbide-70 percent; tantalum carbide-12 percent; and cobalt-30 percent, integrated by means of a sinter-bonded interface with an inner cemented carbide core zone having a composition in percent by volume of tungsten carbide-70 percent and cobalt-20 percent, and nickel-10 percent.
• Both zones were made to have a tungsten carbide grain size range of approximately 90 percent 3 to 12 micron.
• the design density of the outer and inner zone was approximately 13.55 grams per cubic centimeter.
• the outer zone was 6.35 mm thick, just sufficient in ratio to provide for outer zone material both to accommodate the form of the rolling groove and the subsequent grinding of the groove between roll passes in an actual rod mill roll.
• Carbide grain size ranges typically used in rolls in accord with the current art vary according to the precepts of manufacturers; it is recognized that at least some of the economic benefit of this invention will occur independently of grain size ranges employed in the peripheral and inner zones.
• volume percent of binder, as well as the binder composition may be altered in either or both zones without impairing some or any of the economic benefits of this invention, and that, further, the benefits of this invention can be realized in hot rolling metals other than steel.
• Test rings having approximate size of 88.9 mm outer diameterx48.3 mm inner diameterx12.7 mm thick were formed in a mechanical press. Initially, the outer ring of the designated composition and the inner ring of the designated composition were separated by a thin, metal sleeve. The sleeve was carefully removed and the powder was compacted in a single pressing and sintered as a single unit. Fifty percent of the specimens were further subjected to hot isostatic pressing process.
• Hot isostatic processing conditions for Items 2 and 4 were hot isostatically pressed at 1366°C to 1371°C for an eight hour time period and Item 6 was hot isostatically pressed at 1266°C to 1299°C for an eight hour time period.
• the ring specimens were ground outside diameter, inside diameter and sides. The testing was accomplished by the use of a tapered sleeve and a tapered ram fitted into the inside diameter of the rings. Strain gauges were mounted on the outside diameter of each ring. The rings were placed into a hydraulic press and pressure was applied to the tapered ram and the tapered sleeve which expanded the ring specimens until failure occurred, and strain measurements recorded. Duplicate procedures were used to test rings consisting of only tungsten carbide and cobalt. The results of the test provided data indicating that-the composite constructed rings possessed a tensile strength of approximately sixty percent higher than that of a single composition ring having the same percent binder and grain size.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Composite Materials (AREA)
• Manufacturing & Machinery (AREA)
• Reduction Rolling/Reduction Stand/Operation Of Reduction Machine (AREA)

Applications Claiming Priority (2)

Publications (3)

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• 1984
  • 1984-03-20 EP EP84103048A patent/EP0120441B1/en not_active Expired - Lifetime
  • 1984-03-20 DE DE8484103048T patent/DE3483214D1/de not_active Expired - Fee Related
  • 1984-03-20 DE DE198484103048T patent/DE120441T1/de active Pending
  • 1984-03-20 ZA ZA842059A patent/ZA842059B/xx unknown
  • 1984-03-23 JP JP59055926A patent/JPS59218205A/ja active Pending
  • 1984-03-23 AU AU26042/84A patent/AU2604284A/en not_active Abandoned
  • 1984-03-27 KR KR1019840001574A patent/KR880000639B1/ko not_active IP Right Cessation
  • 1984-03-27 CA CA000450613A patent/CA1229005A/en not_active Expired
  • 1984-03-27 MX MX200789A patent/MX162066A/es unknown
  • 1984-03-28 AR AR296133A patent/AR231806A1/es active
  • 1984-03-28 BR BR8401476A patent/BR8401476A/pt unknown

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