EP0497642A1 - Verfahren zum Herstellen von massiven Stahlwerkstücken und so hergestellte Werkstücke - Google Patents

Verfahren zum Herstellen von massiven Stahlwerkstücken und so hergestellte Werkstücke Download PDF

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Publication number
EP0497642A1
EP0497642A1 EP92400092A EP92400092A EP0497642A1 EP 0497642 A1 EP0497642 A1 EP 0497642A1 EP 92400092 A EP92400092 A EP 92400092A EP 92400092 A EP92400092 A EP 92400092A EP 0497642 A1 EP0497642 A1 EP 0497642A1
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EP
European Patent Office
Prior art keywords
quenching
steel
block
core
less
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
EP92400092A
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English (en)
French (fr)
Inventor
Régis BLONDEAU
Philippe Bourges
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.)
Creusot Loire SA
Creusot Loire Industrie SA
Original Assignee
Creusot Loire SA
Creusot Loire Industrie SA
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 Creusot Loire SA, Creusot Loire Industrie SA filed Critical Creusot Loire SA
Publication of EP0497642A1 publication Critical patent/EP0497642A1/de
Withdrawn legal-status Critical Current

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    • 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
    • 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
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/001—Heat treatment of ferrous alloys containing Ni

Definitions

  • the present invention relates to a method for manufacturing blocks or solid pieces of steel having at all points high mechanical tensile characteristics, good toughness and good weldability.
  • the invention also relates to the definition of a family of steels allowing the implementation of the process and the blocks or parts obtained by the process.
  • one of the best known steels, intended to make thick parts and having an elastic limit R e0,2 greater than or equal to 900 MPa has guaranteed properties in elastic limit only for thicknesses less than or equal to 4 "or 101.6 mm, its resilience is only guaranteed for temperatures greater than or equal to - 18 ° C and it is difficult to weld.
  • cryogenic steels for example 9% nickel steel.
  • Such a steel allows good resilience to be obtained up to -196 ° C., but its yield strength is limited to around 600 MPa and on thicknesses less than or equal to 50 mm; on the other hand it is very weldable.
  • the object of the present invention is therefore to propose a method for manufacturing solid steel parts and for determining a family of steels which, going beyond the limits of the current technique, makes it possible to produce blocks or parts having a compromise elastic limit, toughness at low temperature, weldability significantly improved compared to what we know how to do today and this for very massive blocks or parts.
  • the object of the present invention is a method of manufacturing a block or a solid piece of steel having at all points high tensile mechanical characteristics and good toughness and which is weldable.
  • the invention also relates to a solid piece or block of steel having a fully martensitic structure after quenching and tempering, although the quenching is carried out under conditions of implementation such that the cooling rate at the core of the piece is lower than the critical rate of martensitic transformation of steel.
  • the quenching is a quenching with water.
  • the steel used to implement the invention has a determined chemical composition by solving the mathematical programming problem in which it is sought to minimize the equivalent carbon:
  • VS eq C + Mn 6 + Cr + Mo + V 5 + Cu + Ni 15 while satisfying at least the following three constraints:
  • H Vo and T o are values that the skilled person chooses to define the mechanical characteristics he is looking for on the part.
  • Such a steel used by the process which is the subject of the invention makes it possible to obtain a martensitic structure at heart on blocks or parts whose massivity m is such that the cooling speed at heart V RC (m) during quenching is less than the critical martensitic speed V1.
  • this steel contains less than 0.01% of P and less than 0.01% of S.
  • the invention finally, relates to any block or any part manufactured by applying the method according to the invention, using a steel defined in the context of the implementation of this method.
  • Figure 1 is a diagram showing the distribution of cooling rates within two plates cooled by quenching.
  • Figure 2 is an example of a TRC (Continuous Cooling) diagram of a steel.
  • FIG. 3 represents the variation in hardness of a steel as a function of the cooling rate during a quenching.
  • FIG. 4 represents the variation of hardness inside of hardened plates.
  • FIG. 5 is an explanatory diagram of the principle of the invention.
  • the massiveness of a block is a dimension which characterizes the heat transfers inside this block.
  • this dimension is the thickness; for a cylinder, it is the diameter; for a block of any shape, it is a dimension that a person skilled in the art knows how to determine from the drawing of the block.
  • a point of the steel block a1 whose cooling rate V R is greater than V1 (domain 1) will have a martensitic structure at the end of quenching; if this speed is between V1 and V3, the structure will be mainly bainitic; if the speed is lower than V3 the structure will be ferrite-perlite.
  • FIGS. 2 and 3 the diagrams corresponding to two steels are shown: a1 having a critical quenching speed V1 and a2, more quenching than a1, having a critical quenching speed V1 * ⁇ V1.
  • the critical quenching speed offset caused by hydrostatic constraints is not sufficient.
  • the stress system generated by the cooling and the martensitic transformation is not hydrostatic but has a strong shear component, particularly in the zone being transformed.
  • the TRC diagram of the steel taken as an example has a particularity: the point M S is approximately 380 ° and the bainitic domain of the TRC diagram comprises a plateau for the point B S of the start of bainitic transformation located at approximately 450 ° C. . There is only 70 ° C between point M S and point B S.
  • This phenomenon has the advantage of making it possible to obtain high mechanical characteristics on solid blocks with steels having very good weldability.
  • the invention consists in using the phenomenon which has just been described. It will be noted that, in all that follows, the TRC diagrams, the critical quenching rates, the temperatures at the start of transformation are the diagrams and the quantities measured under the usual conditions, that is to say in the absence of constraints.
  • the quenching conditions are determined according to the type of steel used, the targeted mechanical characteristics, the technical quenching possibilities and the geometry of the part.
  • the adjustment of the mechanical tensile and resilience characteristics is done using an income heat treatment, the conditions of which are determined on a case-by-case basis by applying the rules of the art.
  • V RC the cooling rate at the core
  • V RP the cooling speed in skin of this block or this piece
  • the steel belonging to the family concerned by the invention must therefore satisfy, for a block or a piece of massiveness m, the following system of equation: B S - M S ⁇ ⁇ log V1 ⁇ log V RP (m) log V3 ⁇ log V RC (m) and C eq minimum.
  • the mathematical programming problem that we solve will include five constraints: B S - M S ⁇ ⁇ log V1 ⁇ log V RP (m) log V3 ⁇ log V RC (m) H Vm ⁇ H V aim T vs ⁇ T o and we minimize the equivalent carbon, C eq minimum.
  • toughness can be affected by co-aggregation at the joints of the phosphorus grains accompanied by manganese, chromium, nickel. But phosphorus can be trapped inside the grains by molybdenum to as long as it does not react with carbon, these reactions taking place during tempering.
  • Such a steel has a critical martensitic speed V1 of: 71 ° C / s which corresponds to the cooling rate at the heart of a 25 mm thick plate soaked in water.
  • this steel makes it possible to obtain a martensitic structure at the heart of plates with a thickness of at least 40 mm, which, for those skilled in the art, would have required a critical quenching speed V1 of less than 28 ° C / s.
  • the invention also relates to all the blocks or parts produced using the process which is the subject of the invention using a steel according to the invention.

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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 Articles (AREA)
  • Heat Treatment Of Steel (AREA)
EP92400092A 1991-01-31 1992-01-14 Verfahren zum Herstellen von massiven Stahlwerkstücken und so hergestellte Werkstücke Withdrawn EP0497642A1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR9101112 1991-01-31
FR9101112A FR2673197B1 (fr) 1991-01-31 1991-01-31 Procede de fabrication de blocs ou pieces massives en acier et pieces obtenues.

Publications (1)

Publication Number Publication Date
EP0497642A1 true EP0497642A1 (de) 1992-08-05

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Family Applications (1)

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EP92400092A Withdrawn EP0497642A1 (de) 1991-01-31 1992-01-14 Verfahren zum Herstellen von massiven Stahlwerkstücken und so hergestellte Werkstücke

Country Status (4)

Country Link
EP (1) EP0497642A1 (de)
JP (1) JPH0693330A (de)
CA (1) CA2060410A1 (de)
FR (1) FR2673197B1 (de)

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2773071B1 (fr) 1997-12-30 2001-01-05 Oreal Agent reducteur a plusieurs composants et procede de deformation permanente des cheveux le mettant en oeuvre
FR2773072B1 (fr) 1997-12-30 2001-03-23 Oreal Agent oxydant a plusieurs composants et procede de deformation permanente des cheveux le mettant en oeuvre

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3444011A (en) * 1963-11-18 1969-05-13 Yawata Seitetsu Kk Low-temperature tough steel
FR2307879A1 (fr) * 1975-04-18 1976-11-12 Siderurgie Fse Inst Rech Toles en acier au nickel pour utilisation a basse temperature

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS6240313A (ja) * 1985-08-15 1987-02-21 Kawasaki Steel Corp 極厚調質鋼材の製造方法
JPS6425951A (en) * 1987-07-20 1989-01-27 Kobe Steel Ltd Alloy steel for thick steel forgings of cryogenic use

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3444011A (en) * 1963-11-18 1969-05-13 Yawata Seitetsu Kk Low-temperature tough steel
FR2307879A1 (fr) * 1975-04-18 1976-11-12 Siderurgie Fse Inst Rech Toles en acier au nickel pour utilisation a basse temperature

Non-Patent Citations (6)

* Cited by examiner, † Cited by third party
Title
MEMOIRES SCIENTIFIQUES DE LA REVUE DE METALLURGIE. vol. 84, no. 4, Avril 1987, PARIS FR pages 195 - 204; P.PAHUTA: 'Aciers à structure martensitique pour utilisations cryogéniques' *
METAL SCIENCE AND HEAT TREATMENT. vol. 23, no. 3-4, Avril 1981, NEW YORK US pages 229 - 234; P.V.SKLYUEV: 'Methods of calculating critical hardening rates and the hardness of intermediate productions of constructional steels' *
PATENT ABSTRACTS OF JAPAN vol. 11, no. 229 (C-436)(2676) 25 Juillet 1987 & JP-A-62 040 313 ( KAWASAKI STEEL ) 21 Février 1987 *
PATENT ABSTRACTS OF JAPAN vol. 13, no. 208 (C-596)(3556) 16 Mai 1989 & JP-A-1 025 951 ( KOBE STEEL ) 27 Janvier 1989 *
STAHL UND EISEN. vol. 96, no. 23, 18 Novembre 1976, DUSSELDORF DE pages 1168 - 1176; E.SCHMIDTMANN ET AL: 'Influence de contraintes de compression sur le comportement à la transformtion lors de la trempe de grosses pièces de forge en acier 21CrMoV 5 11' *
VDI ZEITSCHRIFT. vol. 120, no. 17, Septembre 1978, DUSSELDORF DE pages 775 - 789; K.ACHTELIK ET AL: 'Verg}tungsstahlguss f}r Gussst}cke mit Wanddicken }ber 100mm' *

Also Published As

Publication number Publication date
CA2060410A1 (fr) 1992-08-01
JPH0693330A (ja) 1994-04-05
FR2673197B1 (fr) 1994-02-04
FR2673197A1 (fr) 1992-08-28

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