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
  • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
• • 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
  • C22C38/001—Ferrous alloys, e.g. steel alloys containing N
• • 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
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
  • C22C38/32—Ferrous alloys, e.g. steel alloys containing chromium with boron
• • 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
  • C21D2211/00—Microstructure comprising significant phases
  • C21D2211/002—Bainite
• • 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
  • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
  • C21D8/06—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires

Definitions

• the invention relates to a use of a steel and a method for the manufacture of a steel part shaped by cold plastic deformation.
• the steel used has a carbon content of between 0.2% and 0.42% (by weight). It is combined with either chromium, chromium - molybdenum, nickel - chromium or nickel - chromium - molybdenum or, finally, with manganese - chromium, so as to be sufficiently soaking to obtain after quenching a structure. martensitique, structure necessary to obtain after income the desired mechanical characteristics which are on the one hand a high tensile strength, on the other hand a good ductility.
• the steel In order to be able to be cold-formed, the steel must first be subjected to a heat treatment of globulization or "maximum softening" consisting of holding at a temperature above 650 ° C. for a long time that can reach several dozens of hours. This treatment gives the steel a pearlitic structure globulized, easy to deform cold.
• This technique has the disadvantage, in particular, of requiring three heat treatments, which complicates the manufacture and increases costs.
• the document JP-A-50 655 40 discloses a method of manufacturing a high strength bolt of composition by weight:
• the object of the present invention is to overcome this disadvantage by providing a means for manufacturing, by forming by cold plastic deformation, a high-grade steel mechanical part, without the need to do or treatment. maximum heat transfer or softening temperature or heat treatment of income.
• the subject of the invention is a use of a steel according to claim 1.
• the invention also relates to a method for the manufacture of a steel part shaped by cold plastic deformation which comprises for heat treatment only, quenching.
• quenching is used, here and throughout, in the broad sense, that is to say that it is a fast enough cooling to obtain a structure which is practically not ferrito-pearlite and which is not essentially martensitic either.
• the process consists in hot rolling a half-product made of steel to obtain a hot-rolled product, possibly cutting a slug in the hot-rolled product, and shaping the slug or slab by cold plastic deformation. rolled product.
• Quenching which is intended to give the part an essentially bainitic structure, can be carried out both before and after the cold forming.
• quenching can be carried out both directly in the hot rolling mill and after reheating austenitization over AC 3 .
• quenching is performed after austenitization by reheating above AC 3 .
• the invention relates to a cold-formed steel part according to claim 8.
• the chemical composition of steel must satisfy the relationship: Mn + 0.9 x Cr + 1.3 x Mo + 1.6 x V ⁇ 2.2% which ensures that the combination of the manganese, chromium, molybdenum and vanadium contents makes it possible to obtain the desired strength characteristics and an essentially bainitic structure.
• This steel has the advantage of having a very good ability to cold plastic deformation and to obtain, without the need for income, a bainitic type structure having excellent ductility and high characteristics mechanical.
• the ductility can be measured by the necking Z which is greater than 45%, and even greater than 50%.
• the tensile strength Rm is greater than 650 MPa and can exceed 1200 MPa.
• a semi-finished steel product having the above-mentioned composition is supplied and hot-rolled after reheating above 940 ° C to obtain a hot-rolled product such as a bar , a billet, or a wire rod.
• the hot rolling is finished at a temperature of between 900 ° C. and 1050 ° C. and the hot-rolled product is immersed directly in the hot rolling mill by cooling with the blown air, at oil, mist, water or water with polymers, according to its section.
• the product thus obtained is then cut into pieces and then shaped in the cold form, for example by cold forging or cold forging.
• the final mechanical characteristics, obtained directly after cold forming result, in particular, the work hardening generated by the cold forming operation.
• the rolled product is quenched after austenitization and then cut into pieces which are shaped by cold plastic deformation, or the slugs are cut before the quenching and then the setting in cold form.
• the austenitization consists of a heating between AC 3 and 970 ° C
• the quenching is carried out by cooling with the blown air, the oil, the fog, the water or the water added with polymers, depending on the product section.
• the final mechanical characteristics, obtained directly after cold forming result, in particular, the work hardening generated by the forming operation.
• the end-of-rolling conditions are not of particular importance.
• the cold forming operation is performed on a cut slug in the hot rolled product and quenching is carried out after cold forming.
• the quenching is carried out after heating between AC 3 and 970 ° C and by cooling with blown air, oil, mist, water or water containing polymers.
• the end-of-rolling conditions are also not of particular importance.
• the invention intended more particularly for the manufacture of mechanical parts is also applicable to the manufacture of cold drawn bars, wire drawn and machine son unwound, cold drawing, drawing and unwinding being modes. particular shaping by cold plastic deformation.
• Drawn bars and machine or drawn wire may be peeled, shaved or ground to a flawless surface condition.
• the term "cold-formed steel part” covers all these products, and the term “slug” covers, in particular, any section of bar or wire; in some cases, the bars or wires are not cut into pieces before being cold-formed.
• the invention may, finally, be used to manufacture pretreated bars or pretreated yarns, or more generally pretreated steel products, intended to be used in the state for the manufacture of parts by cold forming without additional heat treatment .
• These steel products are quenched after hot rolling either directly in the hot rolling or after austenitization, in order to have a substantially bainitic structure (bainite ⁇ 50%). They can be peeled or shaved to have a flawless surface condition.
• the cold tensile-torsion test consists of subjecting a specimen to 3 turns of cold twisting to simulate the shaping by plastic deformation, before performing a tensile test at ambient temperature.
• the increase in resistance corresponds to the relative increase in resistance between the hardened state (after 3 turns of torsion) and the normal state (before the 3 turns of torsion).
• the results obtained show that, even after a large cold deformation (three turns of torsion), the necking remains greater than 50%, and that the tensile strength can exceed 1200 MPa.
• the work hardening capacity, measured by the increase in resistance after deformation by cold twisting, is high in all cases.
• the rounds were subjected to cold forging shaping tests consisting of the measurement of the Limited Crush Rate (T.E.L.) by crushing rolled cylinders along a generator.
• the Crush Rate Limit expressed in%, is the crush rate above which appears the first crack by cold press forging in the notch made following the generatrix of the cylinder.
• This steel according to the prior art had previously been subjected to a globularization annealing of the perlite to make it suitable for cold deformation.
• the steel used according to the invention has a cold forging shaping capacity substantially greater than the steel according to the prior art, despite a higher hardness, and this whatever the level of resistance, even if it is high (treatment F).
• these steels were hot-rolled in the form of bars of diameter 28 mm. After rolling and before cold forming, the bars were subjected to a warm oil quenching treatment at 50 ° C after austenitization at 950 ° C. The bars were cut to obtain pieces from which the pieces were shaped by cold stamping at the deformation rate of 60%.
• cold forming ability is excellent since, despite high initial strength levels and high cold deformation (60%), cold-worked parts have been found to be free of internal defects. external.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Crystallography & Structural Chemistry (AREA)
• Heat Treatment Of Steel (AREA)
• Heat Treatment Of Sheet Steel (AREA)
• Metal Rolling (AREA)
• Thermotherapy And Cooling Therapy Devices (AREA)
• Control Of Metal Rolling (AREA)
• Inert Electrodes (AREA)

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• 1996
  • 1996-12-31 FR FR9616254A patent/FR2757877B1/fr not_active Expired - Fee Related
• 1997
  • 1997-12-10 AT AT97402978T patent/ATE235579T1/de not_active IP Right Cessation
  • 1997-12-10 DE DE69720163T patent/DE69720163T3/de not_active Expired - Fee Related
  • 1997-12-10 EP EP97402978A patent/EP0851038B2/fr not_active Expired - Lifetime
  • 1997-12-10 PT PT97402978T patent/PT851038E/pt unknown
  • 1997-12-10 DK DK97402978T patent/DK0851038T4/da active
  • 1997-12-10 ES ES97402978T patent/ES2196279T5/es not_active Expired - Lifetime
  • 1997-12-17 CA CA002225782A patent/CA2225782A1/fr not_active Abandoned
  • 1997-12-19 HU HU9702515A patent/HUP9702515A3/hu unknown
  • 1997-12-19 CZ CZ974128A patent/CZ412897A3/cs unknown
  • 1997-12-23 SI SI9700323A patent/SI9700323A/sl unknown
  • 1997-12-26 RU RU97121986/02A patent/RU2201468C2/ru not_active IP Right Cessation
  • 1997-12-26 JP JP36835397A patent/JP3988095B2/ja not_active Expired - Fee Related
  • 1997-12-29 NO NO19976099A patent/NO321331B1/no not_active IP Right Cessation
  • 1997-12-29 AR ARP970106223A patent/AR011312A1/es unknown
  • 1997-12-30 CN CN97120811A patent/CN1195708A/zh active Pending
  • 1997-12-30 PL PL324075A patent/PL191871B1/pl not_active IP Right Cessation
  • 1997-12-30 BR BR9705637A patent/BR9705637A/pt not_active IP Right Cessation
  • 1997-12-31 KR KR1019970081219A patent/KR19980064836A/ko not_active Application Discontinuation
  • 1997-12-31 US US09/001,078 patent/US5919415A/en not_active Expired - Fee Related
• 2007
  • 2007-05-15 JP JP2007129436A patent/JP2007284796A/ja not_active Abandoned

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