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EP3617333A1 - Procédé de fabrication d'un produit d'acier hypereutectoïde par traitement thermomécanique - Google Patents

Procédé de fabrication d'un produit d'acier hypereutectoïde par traitement thermomécanique Download PDF

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Publication number
EP3617333A1
EP3617333A1 EP19193739.0A EP19193739A EP3617333A1 EP 3617333 A1 EP3617333 A1 EP 3617333A1 EP 19193739 A EP19193739 A EP 19193739A EP 3617333 A1 EP3617333 A1 EP 3617333A1
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EP
European Patent Office
Prior art keywords
blank
point
product
working
cycles
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Application number
EP19193739.0A
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German (de)
English (en)
Inventor
Heimo Roselli
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Roselli Oy
Original Assignee
Roselli Oy
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Filing date
Publication date
Application filed by Roselli Oy filed Critical Roselli Oy
Publication of EP3617333A1 publication Critical patent/EP3617333A1/fr
Withdrawn legal-status Critical Current

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Classifications

    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21DMODIFYING 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
    • C21D1/00General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/26Methods of annealing
    • C21D1/32Soft annealing, e.g. spheroidising
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21DMODIFYING 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
    • C21D1/00General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/18Hardening; Quenching with or without subsequent tempering
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21DMODIFYING 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
    • C21D1/00General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/18Hardening; Quenching with or without subsequent tempering
    • C21D1/25Hardening, combined with annealing between 300 degrees Celsius and 600 degrees Celsius, i.e. heat refining ("Vergüten")
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21DMODIFYING 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
    • C21D1/00General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/78Combined heat-treatments not provided for above
    • C21D1/785Thermocycling
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21DMODIFYING 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
    • C21D5/00Heat treatments of cast-iron
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21DMODIFYING 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
    • C21D6/00Heat treatment of ferrous alloys
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21DMODIFYING 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
    • C21D8/00Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/005Modifying the physical properties by deformation combined with, or followed by, heat treatment of ferrous alloys
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21DMODIFYING 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
    • C21D9/00Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor

Definitions

  • the object of the invention is a method for manufacturing a low-alloy hypereutectoid steel product by thermomechanical processing, in which
  • High-carbon steels are currently invariably used with a carbon content of up to approximately 2.0 %. With high carbon concentrations, a considerable hardness is imparted to the steel, but at the expense of brittleness.
  • Such steel is also very durable as a result of the action of the carbides therein, but nevertheless so brittle that its potential uses are quite limited. Typical uses are, inter alia, pulling tools, cutting blades, that are not subjected to impact stresses or high temperatures, and razor blades.
  • the cast steel products require "normalization” in order to remove the coarse cast structure. Normalization is further used to eliminate inhomogeneities in forged objects as well as phenomena ( inter alia grain growth) caused by an uneven heating of welded or flame-cut products. By means of normalization, the structure can again be rendered “fine-grained” and its mechanical properties simultaneously restored.
  • the steel is heated to an austenitic phase and is kept there until the "austenite” is homogenized and subsequently air-cooled.
  • a resilient and finely distributed "ferritic-perlitic" microstructure is achieved with the non-alloy structure steels.
  • the object of the invention is to provide a pure, in particular additive-free high-carbon steel product that has good strength properties.
  • the characterizing features of the invention are indicated in the claims.
  • the correct temperature of austenization annealing is important for normalization, as it is for other thermal processes. If austenization occurs at a temperature that is too high, grain growth is the consequence. For this reason, the austenization temperature with normal carbon steels can only be above an approximately 50 °C A 3 point.
  • a steel processing method similar to this invention is disclosed in the inventor certificate SU 456841 , but it only applies to a carbon content of over 2 %. The document also does not disclose any information beyond the processing of the blank.
  • thermomechanical processing the closest to the initial processing in accordance with the invention is an HTMT process in which a blank with a carbon content of 0.5% is subjected to high-temperature thermomechanical processing.
  • U.S. patent no. 3459599 discloses a method for thermomechanically quenching and tempering steel. In this process, the steel is worked vigorously slightly above the A 1 temperature and finally slightly below the latter. The steel contains chrome and manganese.
  • the patent US3178324 of the same applicant discloses a hypereutectoid, multi-cycle quenching and tempering always down to room temperature, but without working. In order to attain a fine-grained steel without alloy materials, the object is heated and cooled drastically above the A 1 point, so that the structure changes repeatedly between the martensitic and austenitic states while a heating to a temperature that accelerates grain growth is avoided. The cooling phase each time is rapid so that the change in state occurs in the ferritic direction.
  • Expensive alloy materials can be avoided - with inexpensive materials unique results are achieved. Alloy materials react in different ways to heat and some are poisonous. A product in accordance with the invention is natural and thus easy to recycle.
  • excess carbon is collected into evenly dispersed small carbide pockets. This is achieved by means of a rapid cooling and a small amount of sulphur and/or phosphorus, which form carbide nuclei in the absence of "better” additives.
  • the evenly dispersed small carbide pockets participate during the series of cycles in working as well as in the A 1 lattice transformation.
  • the method in accordance with the invention requires a remarkable level of expertise.
  • the hot working of the blank for attaining the product occurs within a narrow temperature range - heating momentarily and precisely to approximately 800 °C. Heating does not reach an austenitic phase (point A cm ), but the A 1 point is crossed. In the series of cycles, during working, the cooling is not particularly rapid so that the structure does not become heavily martensitic at any given time.
  • the weldability of the product obtained with the method according to the invention is outstanding and a welding rod can be made from the same.
  • the cutting ability of the product is outstanding (the cutting blade keeps its sharpness - shiny finish).
  • the thickness of the product to be quenched is advantageously 2 - 20 mm, most advantageously 5 - 12 mm.
  • the weight of the object can also vary significantly, typically 50 g - 30 kg, as the thinnest dimension is the most significant.
  • a continuous process is also possible, e.g. a process for a 400 - 1200 mm steel band requires several consecutive furnace-correction-roller assemblies, after which there is a quenching unit, from which the product is either wound onto a large drum or cut into sheets.
  • FIG. 2 shows a sectional view of a steel product in accordance with the invention. The grain boundaries are not visible to the naked eye.
  • This steel is, apart from its high carbon content, by composition a conventional fine-grained steel. Alloy materials are not at all necessary, as the processes in accordance with the invention impart a fine granularity, strength and hardness. The most important aspect for its properties is the combined multi-stage thermal and working processing or thermomechanical processing.
  • the fine-grained and evenly dispersed carbides break up the lattice cells during the series of cycles, from which the freed atoms move to the grain boundaries and plug them.
  • the success of the final result can be checked by checking whether or not the grain boundaries are visible to the naked eye.
  • the cooled object is in an austenitic + cementite phase and the nuclei of the hypereutectoid carbides are produced in this case either inside the crystals or at the grain boundaries under the influence of the working.
  • the formation of adverse carbide networks at the grain boundaries is substantially reduced for this reason while working is continued.
  • Carbides are formed more evenly both inside the crystals and at the grain boundaries.
  • the carbon content is 0.8-2.0 % depending on the desired properties.
  • the sulphur and phosphorus content must be kept low, but a small quantity of the same is required for the formation of the carbide nuclei.
  • thermomechanical processing means that there is nothing else in the blank besides iron and carbon.
  • concentrations of additives in the raw material are very low.
  • the sulphur content is nevertheless 0.007 - 0.038% and/or the phosphorus content is in the range of 0.005 - 0.026 %, so that the carbides with the most advantageous nuclei are formed. Aluminium and silicon are detrimental in this regard. Their concentrations must be extremely slight.
  • a raw material is chosen or produced that is free of vanadium, wolfram, molybdenum, chrome and nickel, the raw material, however, thus containing small quantities of sulphur and/or phosphorus for forming the carbide nuclei. It is possible to select a pure scrap metal while avoiding adverse additives that cannot be removed by means of refining processes.
  • composition of raw ore is known and does not contain any adverse compounds.
  • an ideal raw material is obtained. Any hydrogen in the raw ore must be removed. It causes hydrogen occlusions.
  • carbon in a concentration of 0.8 - 2.0 %, most advantageously 1.6 - 1.9 %, is added to the molten iron.
  • the blank is cast and cooled rapidly, a 5 kg object with salt water or at a corresponding speed, whereupon the mentioned carbide nuclei are formed so as to be small in size and evenly dispersed.
  • Casting is carried out at a rather low temperature, at 1500 °C. It is left to cool rapidly, as it is not possible to exploit the heat of the cast.
  • the speed of cooling can be fixed to be the same as that of a chill cast of a 5kg pellet with a cross section of 50 mm x 100 mm, ⁇ 30%. If the blank does not turn out, it must be heated again to over 1140 °C, generally in the range of 1000 - 1220 °C and the process started again from the beginning.
  • the blank is worked into its final shape.
  • the temperature is above the A 1 point, but is below the A 1 point right at the end in order to preserve its properties.
  • the blank is quenched into its final shape by heating it to approximately 780 °C, after which it is immediately rapidly quenched, blank having a cross section of 5 mm x 100 mm by salt water, ⁇ 30%, or by a method producing a corresponding cooling speed.
  • the quenched blank can be tempered in a known manner.
  • a thin object can also be quenched with oil. How the quenching is realized depends on the intended use and the composition of the object. If quenching is performed at the end, the final result is clearly martensitic. If less quenching is performed, the final result is bainitic or contains residual austenite. Quenching can optionally be performed as a surface quenching with quenching reaching a depth of 2 - 15 mm.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Mechanical Engineering (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Heat Treatment Of Steel (AREA)
  • Heat Treatment Of Sheet Steel (AREA)
EP19193739.0A 2018-08-27 2019-08-27 Procédé de fabrication d'un produit d'acier hypereutectoïde par traitement thermomécanique Withdrawn EP3617333A1 (fr)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
FI20185698A FI128299B (fi) 2018-08-27 2018-08-27 Menetelmä ylieutektoidisen terästuotteen valmistamiseksi termomekaanisella käsittelyllä

Publications (1)

Publication Number Publication Date
EP3617333A1 true EP3617333A1 (fr) 2020-03-04

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EP19193739.0A Withdrawn EP3617333A1 (fr) 2018-08-27 2019-08-27 Procédé de fabrication d'un produit d'acier hypereutectoïde par traitement thermomécanique

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EP (1) EP3617333A1 (fr)
FI (1) FI128299B (fr)

Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3178324A (en) 1963-06-03 1965-04-13 United States Steel Corp Method of producing ultrafine grained steel
US3459599A (en) 1966-10-17 1969-08-05 United States Steel Corp Method of thermomechanically annealing steel
SU456841A1 (ru) 1973-03-02 1975-01-15 Институт Металлургии Им.50-Летия Ссср Ан Грузинской Сср Способ обработки железо-углеродистых сплавов
US4030944A (en) * 1976-04-15 1977-06-21 Ceskoslovenska Akademie Ved Production of annular products from centrifugally cast steel structures
GB1495431A (en) * 1974-11-18 1977-12-21 Mitsubishi Heavy Ind Ltd Method of toughening metallic material
WO1983004267A1 (fr) * 1982-05-24 1983-12-08 The Board Of Trustees Of The Leland Stanford Junio Procede de transformation eutectoide divisee et production d'aciers a teneur en carbone ultra-elevee
RU2048540C1 (ru) * 1992-04-24 1995-11-20 Иосиф Ошерович Хазанов Способ обработки малолегированных заэвтектоидных сталей перлитного класса
EP0943693A1 (fr) * 1998-03-16 1999-09-22 Ovako Steel AB Procédé pour un recuit doux d'un acier riche en carbon

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3178324A (en) 1963-06-03 1965-04-13 United States Steel Corp Method of producing ultrafine grained steel
US3459599A (en) 1966-10-17 1969-08-05 United States Steel Corp Method of thermomechanically annealing steel
SU456841A1 (ru) 1973-03-02 1975-01-15 Институт Металлургии Им.50-Летия Ссср Ан Грузинской Сср Способ обработки железо-углеродистых сплавов
GB1495431A (en) * 1974-11-18 1977-12-21 Mitsubishi Heavy Ind Ltd Method of toughening metallic material
US4030944A (en) * 1976-04-15 1977-06-21 Ceskoslovenska Akademie Ved Production of annular products from centrifugally cast steel structures
WO1983004267A1 (fr) * 1982-05-24 1983-12-08 The Board Of Trustees Of The Leland Stanford Junio Procede de transformation eutectoide divisee et production d'aciers a teneur en carbone ultra-elevee
RU2048540C1 (ru) * 1992-04-24 1995-11-20 Иосиф Ошерович Хазанов Способ обработки малолегированных заэвтектоидных сталей перлитного класса
EP0943693A1 (fr) * 1998-03-16 1999-09-22 Ovako Steel AB Procédé pour un recuit doux d'un acier riche en carbon

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
MAEHARA Y ET AL: "Superplasticity of steels and ferrous alloys", MATERIALS SCIENCE AND ENGINEERING: A, ELSEVIER, AMSTERDAM, NL, vol. 128, no. 1, 15 August 1990 (1990-08-15), pages 1 - 13, XP026026284, ISSN: 0921-5093, [retrieved on 19900815], DOI: 10.1016/0921-5093(90)90090-P *

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FI20185698A1 (fi) 2020-02-28
FI128299B (fi) 2020-02-28

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