EP0191873B1 - Verfahren und legierter Stahl zum Herstellen hochfester Schmiedestücke - Google Patents

Verfahren und legierter Stahl zum Herstellen hochfester Schmiedestücke Download PDF

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Publication number
EP0191873B1
EP0191873B1 EP85101721A EP85101721A EP0191873B1 EP 0191873 B1 EP0191873 B1 EP 0191873B1 EP 85101721 A EP85101721 A EP 85101721A EP 85101721 A EP85101721 A EP 85101721A EP 0191873 B1 EP0191873 B1 EP 0191873B1
Authority
EP
European Patent Office
Prior art keywords
forging
steel
forgings
tempering
producing high
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.)
Expired
Application number
EP85101721A
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English (en)
French (fr)
Other versions
EP0191873A1 (de
Inventor
Vesa Ollilainen
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.)
Ovako Bar Oy
Original Assignee
Ovako Oy AB
Ovako Steel Oy
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Ovako Oy AB, Ovako Steel Oy filed Critical Ovako Oy AB
Priority to DE8585101721T priority Critical patent/DE3571254D1/de
Priority to AT85101721T priority patent/ATE44290T1/de
Priority to EP85101721A priority patent/EP0191873B1/de
Publication of EP0191873A1 publication Critical patent/EP0191873A1/de
Application granted granted Critical
Publication of EP0191873B1 publication Critical patent/EP0191873B1/de
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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
    • C21D1/02—Hardening articles or materials formed by forging or rolling, with no further heating beyond that required for the formation
    • 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

Definitions

  • This invention concerns a method and a steel alloy for the production of high-strength hot forgings, the billets being cold sheared from cast or hot-rolled steel and the finished forging being immediately quenched from the forging temperature, machined and used without tempering.
  • the forgings can also be assembled by fusion welding a number of parts together.
  • the forgings can be immediately heat treated by quenching in water, machined and used without tempering.
  • the object of the method according to this invention is to present a method of producing hot forgings which does not exhibit the deficiencies inherent in existing methods.
  • a feature of the method covered by this invention is that, for manufacturing the forging, a steel is used of the following composition: with hardness, when air-cooled, of, at most, 225 HB.
  • the shearing of the billets from the cast bar or from the hot-rolled semi-products can be performed cold.
  • the method according to the invention is also characterized by the fact that the tensile strength of forgings obtained by this method is a least 900 N/mm 2 , when quenched from forging temperature and without tempering, 0.2-proof stress at least 700 N/mm 2 and the impact toughness at room temperature at least 25 J measured on a V-notched specimen.
  • Another feature of the method covered by this invention is that, on large diameter forgings, such as the front axle beams of lorries, in order to increase the hardenability, boron additives are used in the steel, so that the steel contains the following elements:
  • sulphur may also be added in the following proportion to improve machinability:
  • a further feature of the method according to the invention is that, because of the favourable composition of the steel, the forgings can be assembled by fusion welding from a number of parts.
  • the as-cast billets can be used directly as forging blanks.
  • the invention also concerns a steel alloy suitable for producing high-strength hot forgings by direct quenching.
  • a feature of this alloy is that the composition of the alloy is as follows: and in which without tempering the tensile strength is at least 900 N/mm 2 , 0.2-proof stress at least 700 N/mm 2 and the impact toughness at room temperature at least 25 J measured on a V-notched impact bar, and hardness, when air cooled, does not exceed 225 HB, when the forging produced from this alloy is intended to be immediately quenched (in water for instance) from the forging temperature.
  • the alloy according to the invention may also contain 0.02-0.15% sulphur to improve machinability.
  • the minimum carbon content is determined by the minimum tensile strength required, while the maximum is determined by the maximum hardness of the air-cooled steel and the need for weldability and machinability in the quenched condition.
  • Silicon is an element which greatly strengthens iron and its content should be kept as low as possible for segregation.
  • manganese During quenching, manganese also promotes the formation of brittle upper bainite in the microstructure together with martensite. After cooling in air, on the other hand, manganese greatly increases the amount of pearlite, thus strengthening the steel and making cold shearing difficult. For these reasons and also having regard to steel production techniques, the manganese content should not exceed about 1%.
  • Chromium is an advantageous alloying element for increasing hardenability. Chromium does not strengthen ferrite and its effect on strength is slight in the case of slow cooling.
  • Chromium promotes formation not only of martensite but also of a tough and ductile fine lamellar pearlite. Little chromium segregation occurs during solidification and chromium gives rise to no problems even in the manufacturing processes.
  • the minimum amount of chromium is determined by economic factors. If greater hardenability is required, it is economically advantageous to use boron additions which implies successful aluminium and/or titanium alloying. Alloying with boron does not in any way increase the strength of air-cooled steel and is therefore advantageous particularly when cold shearing is involved.
  • test results were obtained with hot forgings quenched in water from a finishing forging temperature of 950-1050 0 C without tempering.
  • the results show that with the method according to the invention it is possible to produce high-strength hot forgings by quenching the forgings immediately from forging temperature, with an impact strength equivalent to that of conventionally heat-treated steels.
  • Air-cooled steel according to the invention is-as far as hardness is concerned-suitable for cold shearing.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Heat Treatment Of Steel (AREA)

Claims (10)

1. Verfahren zur Herstellung von hochfesten Heißschmiedestücken, das aus den folgenden Verfahrensschritten besteht: (1) Heizen eines Barrens auf die Schmiedetemperatur von 800 bis 1300°C, (2) Schmeiden in ein Schmiedestück und (3) direktes Abschrecken des Schmiedestücks von der Schmiedehitze (z.B. in Wasser), bei welchem das Schmiedestück aus einem Stahl gefertigt ist, dessen chemische Zusammensetzung
Figure imgb0016
und in dem ohne Härtung die Zugfestigkeit des geschmiedeten Stückes wenigstens 900 N/mm2, die 0,2-Elastizitätsgrenze wenigstens 700 N/mm2 und die Schlagzähigkeit bei Raumtemperatur wenigstens 25 J ist, gemessen an einer V-eingekerbten Schlagstange, und die Härte, wenn luftgekühlt, 225 HB nicht überschreitet.
2. Verfahren nach Anspruch 1, in dem der Stahl
Figure imgb0017
enthält.
3. Verfahren nach Ansprüchen 1 und 2, in dem der Stahl die Elemente
Figure imgb0018
enthält.
4. Verfahren nach den Ansprüchen 1, 2 und 3, in dem der Stahl
Figure imgb0019
enthält.
5. Verfahren nach Ansprüchen 1 bis 4, in dem die Schmiedestücke durch Schmelzschweißung zusammengefügt sind.
6. Verfahren nach Ansprüchen 1 bis 4, in dem ein Strangguß-Produkt in einem wie gegossenen Zustand als Schmiedebarren verwendet wird.
7. Legierung für die Herstellung von hochfesten Heißschmiedestücken durch direkte Abschreckung, die
Figure imgb0020
und in welcher ohne Härtung die Zugfestigkeit des geschmiedeten Stückes wenigstens 900 N/mm2, die 0,2-Elastizitätsgrenze wenigstens 700 N/mm2 und die Schlagzähigkeit bei Raumtemperatur wenigstens 25 J ist, gemessen an einer V-eingekerbten Schlagstange, und die Härte, wenn luftgekühlt, 225 HB nicht überschreitet.
8. Legierung nach Anspruch 7, in der der C-Gehalt des Stahls
Figure imgb0021
ist.
9. Legierung nach Ansprüchen 7 und 8, worin der AI-, Ti- und B-Gehalt
Figure imgb0022
ist.'
10. Legierung nach Ansprüchen 7, 8 und 9, worin der Stahl
Figure imgb0023
enthält. ,
EP85101721A 1985-02-16 1985-02-16 Verfahren und legierter Stahl zum Herstellen hochfester Schmiedestücke Expired EP0191873B1 (de)

Priority Applications (3)

Application Number Priority Date Filing Date Title
DE8585101721T DE3571254D1 (en) 1985-02-16 1985-02-16 Method and steel alloy for producing high-strength hot forgings
AT85101721T ATE44290T1 (de) 1985-02-16 1985-02-16 Verfahren und legierter stahl zum herstellen hochfester schmiedestuecke.
EP85101721A EP0191873B1 (de) 1985-02-16 1985-02-16 Verfahren und legierter Stahl zum Herstellen hochfester Schmiedestücke

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
EP85101721A EP0191873B1 (de) 1985-02-16 1985-02-16 Verfahren und legierter Stahl zum Herstellen hochfester Schmiedestücke

Publications (2)

Publication Number Publication Date
EP0191873A1 EP0191873A1 (de) 1986-08-27
EP0191873B1 true EP0191873B1 (de) 1989-06-28

Family

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Country Status (3)

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EP (1) EP0191873B1 (de)
AT (1) ATE44290T1 (de)
DE (1) DE3571254D1 (de)

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0696742B2 (ja) * 1987-10-29 1994-11-30 日本鋼管株式会社 高強度・高靭性非調質鋼の製造方法
FR2741632B1 (fr) * 1995-11-27 1997-12-26 Ascometal Sa Acier pour la fabrication d'une piece forgee ayant une structure bainitique et procede de fabrication d'une piece
FR2756298B1 (fr) * 1996-11-26 1998-12-24 Ascometal Sa Acier et procede pour la fabrication d'une piece de mecanique ayant une structure bainitique
FR2757877B1 (fr) * 1996-12-31 1999-02-05 Ascometal Sa Acier et procede pour la fabrication d'une piece en acier mise en forme par deformation plastique a froid
DE102007023309A1 (de) * 2007-05-16 2008-11-20 Benteler Stahl/Rohr Gmbh Verwendung einer Stahllegierung für Achsrohre sowie Achsrohr aus einer Stahllegierung

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE749477C (de) * 1941-12-23 1953-03-23 Edelstahlwerke A G Krefeld Deu Stahl mit hohem Widerstand gegen schlagartige Beanspruchung
DE927213C (de) * 1942-08-12 1955-05-02 Oberhuetten Vereinigte Obersch Aus Baustaehlen bestehende Gegenstaende
DE1033692B (de) * 1952-11-29 1958-07-10 Boehler & Co Ag Geb Verwendung naturharter borhaltiger molybdaenfreier Baustaehle
DE3043439A1 (de) * 1980-11-18 1982-06-03 Volkswagenwerk Ag, 3180 Wolfsburg Verfahren zum herstellen eines hochbeanspruchbaren schmiedeteils aus stahl
JPS57137426A (en) * 1981-02-20 1982-08-25 Kawasaki Steel Corp Production of low yield ratio, high tensile hot rolled steel plate by mixed structure

Also Published As

Publication number Publication date
EP0191873A1 (de) 1986-08-27
DE3571254D1 (en) 1989-08-03
ATE44290T1 (de) 1989-07-15

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