Classifications

• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
  • C21D9/40—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for rings; for bearing races
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
  • C21D1/74—Methods of treatment in inert gas, controlled atmosphere, vacuum or pulverulent material
  • C21D1/76—Adjusting the composition of the atmosphere
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D6/00—Heat treatment of ferrous alloys
  • C21D6/001—Heat treatment of ferrous alloys containing Ni
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D6/00—Heat treatment of ferrous alloys
  • C21D6/007—Heat treatment of ferrous alloys containing Co
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D6/00—Heat treatment of ferrous alloys
  • C21D6/02—Hardening by precipitation
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
  • C21D9/0068—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for particular articles not mentioned below
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
  • C21D9/32—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for gear wheels, worm wheels, or the like
• • 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
  • C22C38/08—Ferrous alloys, e.g. steel alloys containing nickel
• • 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
• • 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
• • 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
  • C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
  • C23C8/02—Pretreatment of the material to be coated
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
  • C23C8/06—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases
  • C23C8/08—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases only one element being applied
  • C23C8/24—Nitriding
  • C23C8/26—Nitriding of ferrous surfaces
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16G—BELTS, CABLES, OR ROPES, PREDOMINANTLY USED FOR DRIVING PURPOSES; CHAINS; FITTINGS PREDOMINANTLY USED THEREFOR
  • F16G5/00—V-belts, i.e. belts of tapered cross-section
  • F16G5/16—V-belts, i.e. belts of tapered cross-section consisting of several parts

Definitions

• the present invention relates to a manufacturing method for a metal ring to be used in a drive belt, more in particular a heat treatment process part thereof as defined by the preamble of the following claim 1.
• the drive belt is typically used as the means for power transmission between two adjustable pulleys of the well-known continuously variable transmission that is mainly applied in motor vehicles.
• One well known type of drive belt is described in detail in EP-A-1403551 and is composed of a number of relatively thin transverse metal elements that are slideably incorporated on two laminated endless tensile means that are each composed of a set of mutually nested flat metal rings, alternatively denoted endless bands or hoops.
• Such rings are typically produced from a precipitation hardening steel, such as a maraging steel, that combines a/o the properties of great tensile strength and good resistance against tensile stress and bending fatigue with a relatively favourable possibility to process the steel from sheet material towards the desired shape and material characteristics of the end-product rings, which, preferably, should not vary along the circumference of the rings.
• the present invention in particular relates to the range of maraging steel alloys having a basic composition with 17 to 19 mass-% nickel, 4 to 6 mass-% molybdenum, 8 to 18 mass-% cobalt, less than 1 mass-% titanium, possibly containing small amounts (e.g. ⁇ 1 mass-%) of other alloying elements and/or impurities and with balance iron.
• the said desired material characteristics comprise a fair hardness of the ring core material for combining the properties of a great tensile strength together with sufficient elasticity to allow longitudinal bending of the ring and an extremely hard outer surface layer of the ring to provide wear resistance. Additionally, the outer surface layer is provided with a residual compressive stress to provide a high resistance against metal fatigue, which is a significant feature of the rings because of the numerous numbers of load and bending cycles the rings are subjected to during the service lifetime of the belt.
• the basics of the known manufacturing method for such rings have become well known in the art and are, for example, described in the European patent publication EP-A-1753889.
• the rings are formed out of a sheet base material, which is bent and welded into a cylindrical shape, or tube, which is heat treated, i.e. annealed, to restore the original material properties, i.e. to largely remove changes therein that were introduced by the bending and welding.
• the tube is then cut into a number of hoops, which are subsequently rolled and elongated to a required thickness, which is typically about 0.185 mm in the end product. After rolling the hoops are usually referred to as rings or bands.
• the rings are subjected to a further annealing step to remove the internal stresses introduced during rolling. Thereafter, the rings are calibrated, i.e. they are mounted around two rotating rollers and stretched to a predefined circumference length.
• the rings are subjected to a single, combined process step that includes both the heat treatments of precipitation hardening, i.e. ageing or core hardening, and of gas soft-nitriding, i.e. of case hardening by the insertion of Nitrogen atoms into the steel lattice of the rings.
• precipitation hardening i.e. ageing or core hardening
• gas soft-nitriding i.e. of case hardening by the insertion of Nitrogen atoms into the steel lattice of the rings.
• such combined process step of ageing and nitriding entails keeping the rings in an ammonia gas containing process atmosphere at 440 °C to 480 °C for 45 to 65 minutes.
• a heat treatment process including separate ageing and nitriding steps, wherein the ageing heat treatment entails keeping the rings in nitrogen gas at a temperature of 450 °C to 500 °C for more than 180 minutes and wherein the nitriding heat treatment entails keeping the rings in a process atmosphere containing a notional amount, but less than 12 volume-%, preferably less than 10 volume-% of ammonia gas at a temperature of 425 to 475 °C for 45 to 90 minutes.
• Figure 1 is a schematic illustration of the drive belt the present invention relates to and of the transmission in which such belt is applied.
• Figure 2 is a schematic illustration of the manner in which a laminated tensile means and a transverse element are mutually oriented within the drive belt.
• Figure 3 diagrammatically represents the known manufacturing method of a metal ring applied in the endless tensile means of the drive belt that includes the process step of combined ageing and nitriding.
• Figure 4 diagrammatically represents the ageing and nitriding heat treatment of the drive belt's tensile means ring component in accordance with the invention.
• FIG. 1 shows schematically a continuously variable transmission (CVT) with a drive belt 1 wrapped around two pulleys 4 and 5, which belt 1 is made up of a laminated, endless tensile means 2 in the form of two sets of mutually nested thin and flat metal rings 14 ( Figure 2), alternatively denoted bands 14 and a number of transverse members 3, alternatively denoted transverse elements, that are mounted in an essentially continuous row along the circumference of the tensile means 2 and that are free to slide along such circumference.
• CVT continuously variable transmission
• Figure 2 is a cross-section of the known belt 1 , providing a front view of a transverse member 3 and a cross-section of the tensile means 2.
• the transverse members 3, on either lateral side thereof, show side faces 6 by which it engages pulley sheaves of the two transmission pulleys 4, 5.
• the rings 14 of the tensile means 2 are produced of high quality maraging steel.
• a typical thickness of the rings 14 ranges from 0.15 to 0.25 mm, a typical width thereof ranges from 8 to 35 mm and a typical circumference length thereof ranges from 500 to 1000 mm.
• Figure 3 illustrates the presently relevant part of the known manufacturing method for the above described belt 1 , in particular for the rings 14 thereof, as is practised since the early years of metal push belt production.
• a sheet of base material 11 is bend into a cylindrical shape, whereby the sheet ends 12 that meet each other are. welded together in a second process step II to form a tube 13.
• the tube 13 is annealed at a temperature of more than 800 °C in an inert process atmosphere such as a vacuum or nitrogen gas N 2 .
• the tube 3 is cut into a number of hoops 14, which are subsequently -process step five V- rolled and elongated to a desired thickness.
• the hoops 14 are usually referred to as rings 14 or bands 14.
• the rings 14 are subjected to a further annealing process step VI to remove the internal stresses introduced during rolling.
• the rings 14 are calibrated, i.e. they are mounted around two rotating rollers and stretched to a predefined circumference length.
• an internal stress distribution is imposed on the rings 14, which defines the so-called curling radius of the respective ring 14.
• the rings 14 are subjected to the two heat treatments of precipitation hardening or ageing and of gas soft-nitriding, i.e.
• nitriding In nitriding the ring 14 is kept in an ammonia-gas containing process atmosphere. It has been a recent development to successfully apply an unprecedented low amount of less than 10 volume-% ammonia in nitriding. Although such low ammonia content in nitriding is favourable per se, it was found to come with the disadvantages of being less tolerant to variations in the process parameters (i.e. temperature, time and atmosphere) and to set more stringent requirements in relation to the ring material (i.e. maraging steel composition).
• the present invention provides a way to apply such low amount of less than 10 volume-% ammonia in nitriding for a broader range of ring material compositions, while losing the requirements in relation to the accuracy of the control of the process parameters.
• the heat treatments of ageing and of nitriding the ring 14 involve two separate, i.e. sequential, process steps Vlll-A, Vlll-B.
• the ring 14 is kept in a process atmosphere that is free from ammonia gas and that is solely, or at least mainly, composed of nitrogen gas, at a process temperature of 450 °C to 500 °C and for a process duration of more than 180 minutes.
• the ring 14 is kept in a process atmosphere that contains 2 to less than 12 volume-% ammonia gas, at a process temperature of 425 to 475 °C and for a process duration of 45 to 90 minutes.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Crystallography & Structural Chemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Engineering & Computer Science (AREA)
• Heat Treatment Of Articles (AREA)

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Publications (1)

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Citations (4)

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• 2011
  • 2011-11-30 JP JP2014544696A patent/JP6008976B2/ja not_active Expired - Fee Related
  • 2011-11-30 WO PCT/NL2011/000078 patent/WO2013081451A1/en not_active Ceased

Patent Citations (4)

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