Classifications

• • 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
  • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
  • C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
• • 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
  • C21D7/00—Modifying the physical properties of iron or steel by deformation
  • C21D7/13—Modifying the physical properties of iron or steel by deformation by hot working
• • 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
  • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
• • 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
  • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
• • 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
  • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
  • C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
• • 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
  • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
  • C22C38/46—Ferrous alloys, e.g. steel alloys containing chromium with nickel with vanadium
• • 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
  • C21D1/02—Hardening articles or materials formed by forging or rolling, with no further heating beyond that required for the formation
• • 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
  • C21D1/34—Methods of heating
  • C21D1/42—Induction heating
• • 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
  • C21D1/84—Controlled slow cooling
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P10/00—Technologies related to metal processing
  • Y02P10/25—Process efficiency

Definitions

• the present invention relates to a new steel composition, die-formed parts produced therefrom, a method for producing the die-formed parts and their use as chassis parts for passenger cars and commercial vehicles.
• Forged chassis components for motor vehicles are safety-relevant parts for which, apart from a high degree of strength, a high degree of toughness (characterized, e.g., by the characteristic values of elongation at fracture, contraction at fracture, notch impact strength) is required. Therefore, up into the 1980s, these components were subjected, nearly without exception, to an expensive and/or laborious final heat treatment (quenching and tempering) after hot forming.
• a high degree of toughness characterized, e.g., by the characteristic values of elongation at fracture, contraction at fracture, notch impact strength
• a further variant focussed on titanium alloy additives for grain refining and thereby for improving toughness.
• the problem herein was that grain refining was achieved by titanium nitrides.
• the nitrogen required for an increase in toughness was thereby in bound form and thus not available.
• the consequence was a far inferior toughness in comparison to quenched and tempered steels.
• the underlying problem of the invention is therefore to provide a steel composition for precipitation hardening ferritic-perlitic steels for the production of die-formed parts, which, without additional heat treatment, display a high degree of strength and simultaneously a high degree of toughness in these construction parts, so that they can be used as chassis parts also for commercial vehicles.
• a central point of the invention is that the necessary improvement in toughness is achieved by a reduction in the carbon content of the steel in comparison to the concentrations usual today at a given level of strength.
• the loss in strength that is to be expected due to this measure according to the prior art is, according to the invention, not only completely eliminated but even overcompensated for by the particular combination of the remaining components.
• the above-mentioned steel composition is excellently suited to the production of die-formed parts that can be used as chassis parts such as axle legs for passenger cars or commercial vehicles.
• the die-formed parts according to the invention are produced by a method comprising the following steps:
• an ingoing material produced from the steel composition according to the invention in a commercially available geometry, e.g. long steel, is heated to 1,000 to 1,300° C.
• the material is kept in this temperature range at least until a homogenous austenitic structure has formed.
• the duration is 5 to 10 minutes.
• the ingoing material have a mass of more than 15 kg.
• an ingoing material of a mass between 5 and 14 kg is usually utilized.
• step (b) the ingoing material, in a usual forming process, is formed by forging into the desired shape in one or more forming steps.
• the forming process in step (b) takes place immediately after the heating of the ingoing material in step (a), so that the ingoing material has a temperature in the range of 950 and 1,250° C. during its forming.
• step (c) the die-formed part obtained in step (b) is cooled to room temperature.
• the cooling rate is at least 0.2° C./s until a temperature of 580° C.
• the mechanical properties of the die-formed part can be adjusted in a defined manner according to requirements.
• the cooling rate during cooling of the die-formed parts made of the steel according to the invention to 580° C. is preferably chosen in the range from 0.2 to 6° C./s. More preferable is a cooling rate in the range of 0.2 to 0.6° C./s. This corresponds to the cooling of heavy commercial vehicle parts in resting air. This has the advantage that the die-formed parts for a commercial vehicle of step (b) can be cooled merely by standing in air.
• a rate of cooling to 580° C. of 0.7° C./s to 6° C./s is especially preferred.
• the setting of a cooling rate in this range for commercial vehicle parts with a mass of more than 15 kg is achieved, e.g., by means of a water cooling stretch that is flexible with regard to the number of active water nozzles and their orientation as well as with regard to pressure and flow rate.
• cooling rate For the lighter passenger car parts made of the steel according to the present invention, the same connections between cooling rate and properties apply. Due to the lower mass of passenger car parts, accelerated cooling is, in contrast to the commercial vehicle parts, only required for setting the cooling rate when the cooling rate is to lie in the upper half of the given range. Cooling rates of about 0.7 to about 2.0° C./s occur automatically with mere cooling in resting air.
• the cooling rate below 580° C. can be chosen arbitrarily and has no influence with regard to strength and toughness of the obtained die-formed part.
• the die-formed part produced according to the present invention displays the following mechanical properties after cooling from the forming heat:
• a die-formed part produced according to the particularly preferred method can, depending upon the chosen cooling rate, display the following mechanical characteristic values:
• die-formed parts with the following properties can be produced:
• the die-formed parts according to the present invention display a high degree of strength and simultaneously a high degree of toughness after cooling from the forming heat, in comparison to the prior art. Therefore, the die-formed parts according to the present invention can be used as safety-relevant chassis components such as axle legs for passenger cars and even for commercial vehicles.
• Cooling of the axle leg from 1,100° C. to 580° C. on a cooling stretch at a cooling rate of 3.9° C./s.
• axle leg displays the following mechanical properties which are determined according to DIN EN 10002 at room temperature and DIN EN 50115:
• Cooling of the axle leg from 1,150° C. to 580° C. in resting air at a cooling rate of 0.5° C./s.
• the axle leg displays the following mechanical properties, which are determined at room temperature according to DIN EN 10002:
• Cooling of the axle leg from 1,150° C. to 580° C. on a cooling stretch at a cooling rate of 1.8° C./s.
• the axle leg displays the following mechanical properties, which are determined at room temperature according to DIN EN 10002:

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Crystallography & Structural Chemistry (AREA)
• Heat Treatment Of Steel (AREA)
• Forging (AREA)
• Body Structure For Vehicles (AREA)
• Heat Treatment Of Articles (AREA)
• Powder Metallurgy (AREA)
• Treatment Of Steel In Its Molten State (AREA)

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• 2002
  • 2002-09-27 EP EP02021820A patent/EP1408131A1/de not_active Withdrawn
• 2003
  • 2003-09-05 EP EP03747975A patent/EP1546426B1/de not_active Expired - Lifetime
  • 2003-09-05 BR BRPI0314708-8B1A patent/BR0314708B1/pt active IP Right Grant
  • 2003-09-05 ES ES03747975T patent/ES2302935T3/es not_active Expired - Lifetime
  • 2003-09-05 CN CNB038230992A patent/CN100374602C/zh not_active Expired - Lifetime
  • 2003-09-05 AU AU2003267053A patent/AU2003267053A1/en not_active Abandoned
  • 2003-09-05 AT AT03747975T patent/ATE391795T1/de not_active IP Right Cessation
  • 2003-09-05 DE DE50309590T patent/DE50309590D1/de not_active Expired - Lifetime
  • 2003-09-05 US US10/529,268 patent/US20060102257A1/en not_active Abandoned
  • 2003-09-05 JP JP2004540590A patent/JP2006500474A/ja active Pending
  • 2003-09-05 WO PCT/EP2003/009893 patent/WO2004031428A1/de active IP Right Grant
  • 2003-09-05 SI SI200331258T patent/SI1546426T1/sl unknown
  • 2003-09-05 DK DK03747975T patent/DK1546426T3/da active
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