Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C37/00—Cast-iron alloys
  • C22C37/04—Cast-iron alloys containing spheroidal graphite
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C33/00—Making ferrous alloys
  • C22C33/08—Making cast-iron alloys
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C37/00—Cast-iron alloys
  • C22C37/10—Cast-iron alloys containing aluminium or silicon

Definitions

• the present invention relates to a method for the manufacture of Cast iron castings with spheroidal graphite and cast iron as obtained by the implementation of the method.
• Patent FR 2,839,727 discloses a specific process for manufacture of spheroidal graphite cast iron parts, which combines successively combining the techniques of molding, forging and heat treatment.
• the process described in this patent makes it possible to obtain Spheroidal graphite cast iron parts with very high characteristics Mechanical (Rm> 1000 Mpa, Rp 0.2 / Rm> 0.68 and A% between 4 and 14%), with dimensional and geometric accuracy close to that of conventional forging, therefore greater than that obtained by classic foundry techniques.
• the weak point in fatigue stress is located at the level of the burrs that are located at the joint plane generally located at the middle part of the room.
• This embodiment of the method according to the invention makes it possible to obtain a spheroidal graphite cast iron with a structure essentially bainitic, which gives the pieces of very high characteristics mechanical, but with a fatigue limit greater than that obtained with the process according to patent FR 2 839 727.
• Essentially bainitic means here a structure constituted at least 50% of bainite.
• said molded part is cooled calibrated at room temperature freely, controlled or by quenching, to give the piece the mechanical characteristics desired; this in replacement of bainitic stepped quenching.
• This embodiment of the invention makes it possible to obtain a graphite cast iron spheroidal with a structure made up of variable proportions of ferrite and / or perlite; The structure then being essentially ferritic or essentially pearlitic, or ferrito-pearlitic.
• essentially ferritic or essentially pearlitic one means here, and in all that follows, a structure constituted 50% or more of ferrite, or 50% or more of perlite.
• This intermediate operation is intended to rid the draft molded of all its casting appendages, but also if necessary to perfect its geometry or its volume, in view of the calibration operation following.
• This operation may include, in addition, an operation of cleaning of said blank of the workpiece, for example by brushing or another process, in order to rid it of oxides or residues from of the molding operation, before the calibration operation.
• the rate of plastic deformation during the calibration operation is deliberately limited to avoid excessive crushing of nodules of graphite which are oriented in the direction of the flow of the metal.
• the shape given to the molded blank of the piece is determined from the final shape of the piece to allow for a rate of deformation in all parts of the blank during the operation of calibration, between 1 and 20% maximum, and to orient the flow of the metal during this operation in a direction favorable to mechanical characteristics, and in particular to fatigue stresses of the piece in use.
• this cooling is carried out in the open, at blown air, or in a confined atmosphere or environment as the case may be.
• Controlled cooling here refers to a cooling carried out with a speed imposed and controlled for allow to obtain a previously defined and desired structure on the room.
• a heat treatment of income after the cooling operation of the molded part calibrated intended to adjust the structure and / or the characteristics mechanical components of said calibrated molded part.
• the invention also relates to a spheroidal graphite cast iron developed and shaped according to the process of the invention, the structure of which is either essentially bainitic or essentially pearlitic or essentially ferritic, consisting of ferrite and pearlite in variable proportions.
• the cast has undergone a plastic deformation rate limited and contained during the calibration operation, thus limiting the crushing graphite nodules.
• the rate of deformation in all parts of the blank during the operation of calibration is between 1 and 20% maximum, thus allowing to guide the flow of the metal during the calibration operation in a favorable to the mechanical characteristics and in particular to the fatigue loads of the part in service, thus favoring the limitation of deformation of spheroidal graphite nodules.
• the invention also relates to a casting made of cast iron spheroidal graphite cast iron elaborated and shaped according to one any of the embodiments of the method according to the invention.
• the present invention is particularly suitable, without this restrictive, to the manufacture of mechanical parts of automobile engines, as the connecting rod for example, or other moving parts of the engine.
• the invention is particularly well adapted without this being restrictive, to parts that must have a high fatigue limit, with a weight saving compared to steel.
• Another important advantage of the invention is to enable the production of spheroidal graphite cast iron parts with shapes impossible to obtain on steel parts by conventional stamping, as for example hollow forms on the piece located perpendicularly to the joint plane so undercut from to the direction of typing or pressing. Easily obtained by casting in a mold, these shapes already present on the molded blank of the piece only require low plastic deformation rates to be put into the final forms of the piece; these low rates of plastic deformation being compatible with a calibration operation at hot in containers or closed dies with inserts or tools placed in the matrices, as is the case in the various embodiments of the invention.
• the connecting rod of motor where the soul, which is the central part of the connecting rod that connects the head and the foot, has a profile in the form of "H" whose hollows are placed in the direction of the joint plane that is to say in the direction suitable for stamping.
• this profile should be placed perpendicular to the current profile on the part but can not be realized as well as with standard steel stamping techniques.
• the method according to the invention makes it possible to produce the engine connecting rod with the profile of the soul perpendicular to the existing profile, that is to say with the hollow forms of the section of the soul placed perpendicularly by compared to the joint plane, allowing the piece a better hold when mechanical stresses in service.
• the shape to give to the molded rod blank to ensure a deformation rate of said molded rod blank during the calibration operation, between 1 and 20% maximum in all parts of it, and this with a volume of the rod blank substantially identical to that of the connecting rod Calibrated molded mold desired to obtain the molded connecting rod calibrated without lateral burr.
• a roughing volume equal to the volume of the calibrated molded part + 2%.
• Calibration tooling included two closed dies as well that a sliding element in one of the dies for the realization of the bore of the big end; an excess metal housing had been provided at different locations on the perimeter of this bore, where a subsequent machining operation, as well as in a cavity of the foot of connecting rod where there is also a subsequent machining operation.
• the final composition cast 3.7% of VS ; 2.62% Si; 0.19% Mn; 0.3% Ni; 0.4% Cu; 0.15% of Mo, with a residual magnesium content that remained within the range 0.028% - 0.042%, was developed in the electric oven at induction, treated with ferro-silico-magnesium, and then poured between 1380 ° C and 1450 ° C in a metal mold controlled at 270 ° C and coated a protective poteyage.
• the metal mold has four rod draft impressions, so that four rod-shaped rods made of spheroidal graphite cast iron are molded at each cycle of the mold.
• the molded rod blanks have been extracted from the mold at a temperature that has always remained during testing, between 980 ° C and 950 ° C.
• each casting group consisting of four rod blanks was placed in a tool of cutting mounted on a press for separation of the weights and the casting system.
• Each rod draft was then placed immediately into an oven under a controlled nitrogen atmosphere at a temperature of 950 ° C, to ensure temperature homogeneity throughout the entire section of the rod blank before calibration.
• the holding time of each blank in the oven is always remained between 15 and 35 minutes.
• the parts compared here obtained by the process according to the invention and those made simply by molding in a metal mold, have the same metallographic structure, ie predominantly pearlitic or ferritic dominant, since they have undergone the same speed controlled cooling.

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Heat Treatment Of Articles (AREA)
• Refinement Of Pig-Iron, Manufacture Of Cast Iron, And Steel Manufacture Other Than In Revolving Furnaces (AREA)
• Forging (AREA)

Applications Claiming Priority (2)

Publications (2)

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Family Applications (1)

Country Status (3)

Cited By (2)

Families Citing this family (3)

Family Cites Families (11)

• 2004
  • 2004-02-12 FR FR0401397A patent/FR2866351B1/fr not_active Expired - Fee Related
• 2005
  • 2005-02-03 EP EP05290234A patent/EP1566459A3/de not_active Withdrawn
  • 2005-02-16 CN CN 200510007764 patent/CN1670233A/zh active Pending

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