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
  • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
  • C21D1/18—Hardening; Quenching with or without subsequent tempering
  • C21D1/19—Hardening; Quenching with or without subsequent tempering by interrupted quenching
  • C21D1/20—Isothermal quenching, e.g. bainitic hardening
• • 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
  • C21D9/04—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for rails
• • 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

Definitions

• the invention relates to a rail or rail track, consisting of a rail head, a rail and a web connecting these areas, made of an iron-based alloy containing carbon, silicon, manganese, optionally chromium, special carbide forming and the conversion behavior of the material influencing elements and / or microalloying additives, remainder Iron and production-related as well as usual impurities, with over the cross-section at least partially formed by accelerated cooling of the austenite of the alloy formed microstructure.
• the invention comprises a method for producing such rail or rail tracks of an iron-based alloy containing carbon, silicon, manganese, optionally chromium, special carbide forming and the conversion behavior of the material influencing elements and / or Mikroegleiterszu algorithms, remainder iron and production-related and conventional impurities, with the cross section at least partially by accelerated cooling from the austenite region of the alloy formed microstructure, wherein at least parts of the surface of the provided Austenit with coolant or introduced into this.
• the property profile of the component is adapted to the requirements of these or if corresponding to the pronounced individual loads on the part of these specifically high material characteristics.
• the rails should on the one hand have a high wear resistance in the head area or on the surface carrying the wheels and, on the other hand, due to the bending stress in the track, high toughness, strength and resistance to breakage in the remaining cross-sectional area.
• EP-186373-B1 Another method for forming a stable perlite structure in rails has become known from EP-186373-B1, which method essentially uses a nozzle arrangement for a coolant for accelerated cooling of the rail and the distance between the nozzle assembly and rail head depending on the Rail head to be achieved hardness value and the carbon equivalent of the steel is adjusted.
• a method and a device for carrying out the method for heat treatment of profiled rolling, in particular rails, EP-693562-A can be seen, in particular in the rail head, a fine-pearlitic structure with increased hardness and abrasion resistance is formed.
• Another method for creating a fine-pearlitic microstructure in the head region of the rail is disclosed in EP-293002. The rail head is cooled by hot water blasting to 420 ° C and then treated by means of a stream of air.
• a rail with high wear resistance at the head and high resistance to fracture in the foot is achieved according to EP-136613-A or DE-3336006-A by a method in which the rail after rolling and cooling in air at 810 ° C to 890 ° C. austenitized and then cooled accelerated. The cooling takes place in such a way that a fine-pearlitic microstructure is created in the area of the head and a martensitic structure in the area of the foot, which is then tempered.
• a rolling stock with advantageous mechanical properties preferably a driving or railway track with high abrasion resistance, in particular of the head, and high toughness of the other areas, according to the prior art in the material to set a fine-pearlitic microstructure and an inter-stage structure or bainite , possibly with martensite, to avoid.
• the resulting carbides are designed to be significantly larger, arranged between the ferrite, significantly deteriorate the material toughness and promote material fatigue and increase the risk of breakage of the part, especially at impact loads. For this reason, rails should have no Bainitanteile in the structure.
• a carbide-free bainitic steel with high abrasion resistance and improved contact fatigue resistance has become known from WO-96/22396.
• high silicon and / or aluminum contents of 1.0 to 3.0% by weight in a low-alloyed 0.05 to 0.5% by weight of carbon and 0.5 to 2.5% by weight of manganese and 0 Steel containing from 25 to 0.5% by weight of chromium in the rolling stock is to be adjusted by continuous cooling from the rolling temperature to a substantially carbide-free "upper bainite" microstructure, which is a mixed structure of bainitic ferrite, retained austenite and high-carbon-containing martensite. At low temperatures and / or under mechanical stress, however, at least parts of the retained austenite in the microstructure can fold down to form martensite and / or a so-called deformation martensite, which increases the risk of crack initiation at the phase boundaries.
• a method and a device in which a rail can also be heat-treated with a structural design of the lower bainite step is disclosed in DE-AS-1533982.
• rails from the rolling heat are immersed in a fluidized bed and cooled to fluidized bed temperature and then taken out of the fluidized bed for further cooling.
• rails with a pearlitic or bainitic structure and with the material properties determined by the microstructure can be created over the entire cross section.
• the previously known rolling stock of low alloyed iron-based materials and the method, in particular heat treatment process for producing the same with improved performance characteristics is generally based on the disadvantage that the prior art according to a further increase in abrasion resistance and toughness of the material can be achieved only by expensive alloying measures ,
• the invention seeks to remedy the situation and sets itself the goal of specifying a driving or rail track with an optimal combination of high abrasion resistance and high wear resistance of the head with increased toughness and material hardness and resistance to contact fatigue.
• the iron-based alloy has a concentration of the elements in wt .-%: carbon 0.51 to 1.3 manganese 0.31 to 2.55 silicon Max 0.93 aluminum Max 0.06 Silicon plus aluminum below 0.99 possibly chrome 0.21 to 2.45 molybdenum to 0.88 tungsten to 1.69 vanadium to 0.39 Niobium and / or tantalum and / or zirconium and / or hafnium and / or titanium, individually or in total to 0.28 nickel to 2.4 boron to 0.006
• a rail head with a structural design corresponding to a transformation in the lower bainite region has substantially improved mechanical properties.
• the prerequisite for this are strictly limited silicon and / or aluminum contents of the material.
• Higher concentrations of silicon and / or aluminum in low-alloyed iron-base materials reduce the gamma region in the state of the material system, so that a largely complete transformation of the structure of austenite in the region of the lower intermediate stage only at contents of silicon in wt.% Of Max 0, 93 and aluminum of max 0.06 and silicon plus aluminum below 0.99.
• This advantageous carbide formation and carbide distribution in the structure of the lower intermediate stage obviously leads to a substantial improvement in the hardness and strength, toughness, resistance to breakage, abrasion resistance and wear resistance and to a high contact fatigue resistance of the rolling stock in the rail head.
• the iron-based alloy essentially contains the elements in% by weight: carbon to 0.98 manganese 0.91 to 1.95 silicon 0.21 to 0.69 aluminum below 0.03 iron as rest having.
• the mechanical property values of the material in the rail head can be further increased or improved if the iron-base alloy further contains the elements in% by weight: Chrome if necessary 0.38 to 1.95 molybdenum to 0.49 tungsten to 0.95 vanadium to 0.19 furthermore niobium and / or tantalum and / or zirconium and / or hafnium and / or titanium individually or in total to 0.19, such as nickel to 2.4, preferably to 0.95 boron to 0.006, preferably 0.004 having.
• the iron-based alloy has the elements silicon, aluminum and carbon in concentrations such that the value is formed from 2.75 times%. Silicon and / or aluminum minus% carbon is equal to or less than 2.2.
• the strongly ferrite-forming elements silicon and aluminum and the effective austenite-forming element carbon are advantageously assigned to each other in a conversion kinetically or coordinated with one another.
• a rail track consisting of a rail head, a rail foot and a web connecting these areas, in which the lower bainite formed in the head of the rail structure has a depth of at least 15 mm, from the surface, especially highly loaded surface areas outstanding stability provide.
• the rail in the head area with lower bainitic structure has a hardness of at least 400 HB, in particular from 420 HB to 600 HB.
• the further object of the invention is achieved in a method of the abovementioned type by selecting the composition of the alloy as specified in claim 7, determining its transformation behavior during cooling from the austenite region and producing the rolling stock from the selected alloy, followed in the longitudinal direction only the head of the rail by means of a cooling liquid from the austenite region to a temperature between the martensite of the alloy and a value exceeding this by at most 250 ° C, preferably by at most 190 ° C, in particular to a temperature in the range of 5 ° C to 110 ° C is cooled above the martensite point and the structure in the lower bainite is allowed to convert isothermally.
• the advantages achieved by the method according to the invention are essentially to see that an accurate manufacturing and quality planning for the rail can be created, the mechanical properties are significantly improved.
• a low-cost chemical alloy composition which ensures the required property profile of the product at best, can be selected
• the inventive transformation temperature control can be determined.
• Particularly advantageous material properties of the rail head are achieved when the transformation of the microstructure isothermal in a temperature fluctuation range of at most PLUS MINUS 60 ° C. This results in most of the steels that are used for heavy-duty railroad tracks, a transformation temperature of at most 450 ° C, preferably of at most 400 ° C, in particular from 300 ° C to 380 ° C to adjust an inventive structure of the lower bainite.
• the uniformity of the cooling over the cross section can be further improved, in the head rail profiles, when the rail in a first step in a cooling liquid fully immersed, after reaching a temperature of a surface area of at least 2 ° C, but especially 160 ° C above the martensite point of the alloy from which coolant is at least partially applied and in a second step only the region of the rail head with a high mass concentration is optionally temporarily left in the immersion bath or temporarily introduced into it.
• the heat treatment technology for the conventional alloyed rail steels can be determined in such a way that a microstructure transformation takes place in the lower bainite region of the mixing region over essentially the entire cross section.
• the rail immediately aligned after the deformation using the rolling heat achsavuchtend and creating a special material properties by converting the lower bainite of the material over the cross-section cooling process is supplied.
• the method according to the invention is particularly advantageously applicable when railroad tracks, in particular high-performance lines, having high abrasion resistance or high wear resistance, high toughness and low contact fatigue are produced under high specific load, after rolling and thermal setting of a structure of the lower bainite area in the rail head subsequent straightening process, in particular Bieachvon at room temperature or slightly elevated temperature, to maintain the material properties with stable alignment of the rails is performed.
• a rolling stock with a substantially H-shaped profile should be produced with a hardness between 550 HV and 600 HV and the highest possible toughness.
• continuous ZTU diagram continuous ZTU diagram

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Thermal Sciences (AREA)
• Crystallography & Structural Chemistry (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Physics & Mathematics (AREA)
• Heat Treatment Of Articles (AREA)
• Metal Rolling (AREA)
• Heat Treatment Of Steel (AREA)
• Shaping Metal By Deep-Drawing, Or The Like (AREA)
• Formation And Processing Of Food Products (AREA)
• Bending Of Plates, Rods, And Pipes (AREA)
• Ceramic Capacitors (AREA)
• Golf Clubs (AREA)
• Forging (AREA)
• Powder Metallurgy (AREA)
• Laminated Bodies (AREA)
• Superconductors And Manufacturing Methods Therefor (AREA)
• Rolls And Other Rotary Bodies (AREA)
• Reduction Rolling/Reduction Stand/Operation Of Reduction Machine (AREA)

Priority Applications (1)

Applications Claiming Priority (3)

Publications (2)

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Country Status (19)

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• 1996
  • 1996-12-19 AT AT0222296A patent/AT407057B/de not_active IP Right Cessation
• 1997
  • 1997-12-09 RO RO97-02312A patent/RO119237B1/ro unknown
  • 1997-12-10 JP JP36969897A patent/JP4039474B2/ja not_active Expired - Fee Related
  • 1997-12-12 PL PL97323703A patent/PL184601B1/pl unknown
  • 1997-12-16 EP EP97890249A patent/EP0849368B1/de not_active Revoked
  • 1997-12-16 DK DK97890249T patent/DK0849368T3/da active
  • 1997-12-16 ES ES97890249T patent/ES2216123T3/es not_active Expired - Lifetime
  • 1997-12-16 PT PT97890249T patent/PT849368E/pt unknown
  • 1997-12-16 SI SI9730643T patent/SI0849368T1/xx unknown
  • 1997-12-16 AT AT97890249T patent/ATE265549T1/de not_active IP Right Cessation
  • 1997-12-16 DE DE59711569T patent/DE59711569D1/de not_active Revoked
  • 1997-12-18 UA UA97126153A patent/UA41454C2/uk unknown
  • 1997-12-18 CA CA2225240A patent/CA2225240C/en not_active Expired - Lifetime
  • 1997-12-18 RU RU97121919A patent/RU2136767C1/ru active
  • 1997-12-18 CN CN97108732A patent/CN1101856C/zh not_active Expired - Lifetime
  • 1997-12-18 AU AU48485/97A patent/AU728635B2/en not_active Expired
  • 1997-12-18 CZ CZ19974111A patent/CZ295574B6/cs not_active IP Right Cessation
  • 1997-12-18 HU HU9702498A patent/HU220124B/hu not_active IP Right Cessation
  • 1997-12-19 US US08/994,190 patent/US6086685A/en not_active Expired - Lifetime
  • 1997-12-19 BR BR9706423A patent/BR9706423A/pt not_active IP Right Cessation

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