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
  • C22C38/02—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

Definitions

• the invention relates to a steel for the production of high-strength components with excellent low-temperature toughness.
• Steels of this type are used, for example, for the manufacture of stop or clamping means, such as are required for fastening and securing loads.
• These steels are, in particular, processed to form hot-rolled bar steel, rolled wire or bright steel, from which welded round steel chains are then made.
• the object of the invention was therefore to provide a high-strength steel that has excellent toughness even at low temperatures, so the risk of the component, which is produced in each case from the steel, breaking is reduced to a minimum even under unfavourable, hard operating conditions.
• Advantageous uses of this steel are also to be specified.
• steel according to the invention for the production of high-strength components with excellent low-temperature toughness has the following composition (in % by weight):
• the individual alloy components are selected such that a property profile that optimally satisfies the requirements set is achieved. This is achieved by the contents of Cr, Ni and N that are set according to the invention and the minimum sum of the contents of Nb and V. If the content ranges of these alloy elements that are set according to the invention are adhered to, a particularly high toughness, good hardenability, improved retention of hardness when tempering and a particularly fine grain structure are achieved.
• Steel according to the invention is also highly cold formable and has high strength in the finished processed state. It is also distinguished by high notch impact toughness and a low fracture appearance transition temperature such that brittle fracture occurs only at temperatures that are substantially lower than the brittle fracture temperature of steels known from the prior art.
• the C-contents located in the range from 0.08 to 0.25% by weight ensure the good low-temperature resistance of steels according to the invention. Particularly positive results are produced in this connection if the C content is from 0.16 to 0.23% by weight.
• the good hardenability and retention of hardness when tempering of the steel according to the invention are achieved by means of the limitation of the Cr contents to 0.40 to 0.80% by weight in combination with Mo contents from 0.30 to 0.50% by weight.
• the degree of certainty with which this combined effect is achieved may be increased in that the Cr contents are adjusted to 0.40 to 0.65% by weight and the Mo contents to 0.35 to 0.50% by weight.
• the contents of Al from 0.020 to 0.060% by weight, in particular 0.020 to 0.045% by weight, and of N from 0.007 to 0.018% by weight, in particular 0.007 to 0.015% by weight, lead in steels according to the invention to a particularly fine grain structure.
• steel according to the invention contains in total at least 0.02% by weight Nb and V, while the contents of V are limited to at most 0.15% by weight and of Nb to at most 0.07% by weight, ensures that the desired fine grain structure is still maintained even at elevated temperatures. It has surprisingly been found in this connection that this effect occurs particularly reliably if the steel according to the invention is free of vanadium.
• the fine grain remains stable even in the course of the temper-hardening treatment.
• Finished processed steel according to the invention therefore commonly has an austenite grain size that is finer than ASTM 10.
• the fineness of the structure of steel according to the invention is therefore substantially greater than that of known steels, for which an austenite grain size of ASTM 5 is required according to DIN 17 115.
• the invention therefore provides a steel that has excellent toughness even at low temperatures.
• the risk of a component produced from steel according to the invention breaking is reduced to a minimum even under unfavourable, hard operating conditions.
• Steel according to the invention is preferably processed to rolled steel.
• the aim of the processing is to preserve via each of the processing steps the finest possible grain structure of the steel according to the invention. This includes not only the process steps carried out during the heating and rolling, but also the annealing treatments that are carried out before and after the component formation.
• the heating and rolling conditions are thus selected such that despite the diffusion processes that occur during heating, high rolling temperatures may be avoided, in order to suppress the formation of coarse grain.
• the temperatures during the further deformation are also selected by means of a controlled withdrawal of energy during the heat deformation such that the desired construction with its fine grain structure is maintained.
• steel according to the invention is particularly suitable for the production of high-strength components by cold forming with subsequent temper-hardening.
• These components may, for example, be means for the carrying, pulling, lifting, conveying or securing of loads that are allocated to the highest strength class.
• Such articles which may be summarised under the general term “stop and clamping means”, include, for example, attachment points, hooks, clips, eyelets, chains, joints, catch elements, rockers, braces, spindle and ratchet clamps, attachment eyes and the like.
• Means for the connection of structural elements having excellent use properties may also be made from steel according to the invention.
• These structural elements are, for example, bolts or other connecting or force transmission elements, such as screws, clamps, rods or the like.
• Chains made of steel of the composition according to the invention reliably withstand heavy loads even at very cold temperatures, without any risk of fracture or comparable damage.
• Round steel chains, especially welded round steel chains, which are able to satisfy even the most stringent requirements, may thus be made of steel according to the invention.
• the components made of steel according to the invention commonly have a strength of at least 1,200 MPa, in particular more than 1,550 MPa, 1,600 MPa or 1,650 MPa. It should be emphasised in this connection that at a strength of at least 1,550 MPa, the fracture appearance transition temperature FATT of the components made of steel according to the invention is commonly at most ⁇ 60° C. This limit temperature is significantly lower than in known steels.
• the notch impact working value in the case of components produced from steel according to the invention, is commonly more than 45 J and the respective component has a technical crack initiation toughness J IC of more than 170 N/mm at ⁇ 60° C., in particular more than 185 N/mm.
• the crack initiation toughness J IC is a value defined in the ASTM 1820 that allows evaluation of the ductile fracture tendency of a steel material.
• the high degree of toughness of the steel according to the invention is also discernible in the fact that components produced from steel of this type commonly exhibit an elongation at break of more than 28%.
• a steel comprising (in % by weight)
• the rolled steel was shaped to form chain links, which were closed by welding once the chain had been assembled.
• the chains produced in this manner exhibited a fine grain structure of ASTM 11, a strength of 1,270 N/mm 2 and a fracture appearance transition temperature FATT determined at this strength of ⁇ 70° C.
• Their notch impact working value was 557 J at ⁇ 60° C. test temperature and the elongation at break was 28%.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Heat Treatment Of Steel (AREA)
• Heat Treatment Of Articles (AREA)

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• 2004
  • 2004-02-05 DE DE502004003457T patent/DE502004003457D1/de not_active Expired - Lifetime
  • 2004-02-05 AT AT04002612T patent/ATE359382T1/de active
  • 2004-02-05 EP EP04002612A patent/EP1561833B1/de not_active Expired - Lifetime
  • 2004-02-05 DK DK04002612T patent/DK1561833T3/da active
  • 2004-02-05 ES ES04002612T patent/ES2286518T3/es not_active Expired - Lifetime
• 2005
  • 2005-02-04 US US10/551,506 patent/US20070107808A1/en not_active Abandoned
  • 2005-02-04 JP JP2006551811A patent/JP2007520633A/ja active Pending
  • 2005-02-04 BR BRPI0503588-0B1A patent/BRPI0503588B1/pt active IP Right Grant
  • 2005-02-04 CN CN200580000079.7A patent/CN1764734B/zh active Active
  • 2005-02-04 WO PCT/EP2005/001163 patent/WO2005075693A1/de active Application Filing
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