EP0345206A1 - Procédé de fabrication de tôles fortes - Google Patents

Procédé de fabrication de tôles fortes Download PDF

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Publication number
EP0345206A1
EP0345206A1 EP89730129A EP89730129A EP0345206A1 EP 0345206 A1 EP0345206 A1 EP 0345206A1 EP 89730129 A EP89730129 A EP 89730129A EP 89730129 A EP89730129 A EP 89730129A EP 0345206 A1 EP0345206 A1 EP 0345206A1
Authority
EP
European Patent Office
Prior art keywords
max
rolling
slabs
cooled
thickness
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.)
Withdrawn
Application number
EP89730129A
Other languages
German (de)
English (en)
Inventor
Ingo Dr.-Ing. Von Hagen
Hans-Georg Dr.-Ing. Hillenbrand
Christoph Dr.-Ing. Prasser
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.)
Vodafone GmbH
Original Assignee
Mannesmann AG
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 Mannesmann AG filed Critical Mannesmann AG
Publication of EP0345206A1 publication Critical patent/EP0345206A1/fr
Withdrawn legal-status Critical Current

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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
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/0081—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for slabs; for billets
    • 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
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/021—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips involving a particular fabrication or treatment of ingot or slab
    • 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
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0226—Hot rolling

Definitions

  • the invention relates to a method for producing heavy plates according to the preamble of patent claim 1.
  • thermomechanical rolling of continuous cast rams made of microalloyed steel These slabs generally have a thickness of at least 200 mm and are heated to approx. 1,100 to 1,200 o C for roughing.
  • the rough rolling is completed at temperatures above 1000 o C.
  • the austenitic structure can therefore be refined by recrystallization.
  • the second rolling phase usually takes place at temperatures of 850 to 780 o C, ie in the temperature range of the no longer recrystallizing austenite.
  • the grains are stretched; the grain boundary surfaces are enlarged and offer more space for nucleation if the temperature drops further.
  • thermo-mechanical rolling is still a Endwalzphase closes in the temperature range between about 740 and 680 o C on.
  • Heavy plates produced in this way usually have a yield strength R t0.5 between 300 and 600 N / mm2 and a tensile strength R m between 400 and 800 N / mm2.
  • a generic method can be found in DE-PS 34 37 637. It provides for the production of heavy plates from a micro-alloyed steel that is 0.05 to 0.20% C, max. 0.60% Si, 0.5 to 2.0% Mn, max. 0.025% P, Max. 0.015% S, 0.02 to 0.08% Al, 0.001 to 0.015% N as well as individually or in groups of 0.01 to 0.60% Cu, 0.01 to 0.80% Ni, 0.01 to 0.80% Mo, 0, 01 to 0.05% Nb, 0.01 to 0.10% V, 0.005 to 0.025% Ti, balance iron and usual impurities. Steel slabs, which were produced by continuous casting and are heated to 950 to 1,200 o C for pre-rolling, are assumed.
  • the roughing is carried out with a total degree of deformation of at least 40% at a temperature above 900 o C.
  • finish rolling is carried out as thermomechanical rolling at temperatures below 900 o C to above Ar3 + 20 o C with a total degree of deformation of at least 60% and more than 5% deformation in the last pass.
  • the sheets are cooled at a rate of 5 to 25 K / s to a temperature above the martensite temperature and then in air to room temperature at the latest 30 seconds after the last rolling pass.
  • the sheets produced in this way are characterized by good weldability and a high yield strength.
  • the object of the invention is therefore to propose a method of the generic type with which heavy plates of high strength (at least corresponding to X 52) can be produced with very good toughness and DWTT properties and in which the required energy expenditure should be as low as possible.
  • the starting material is so-called thin slabs, ie slabs as wide as possible with a thickness of about 40 to max. 100 mm, which were produced in a continuous casting process (e.g. thin slab continuous casting or casting rolls).
  • the production of thin slabs already in the casting process has the great technological advantage that the solidification of the thin slabs can take place very quickly because of the large specific surface, so that a comparatively fine casting structure results.
  • the slabs after casting and before use in the drawing furnace of the rolling mill have to be cooled down to below Ar 1, if possible to at least 200 K below Ar 1.
  • the preheating temperature can be kept correspondingly lower compared to normal slabs. Not only is energy saved, but also a stronger austenite grain growth is avoided; the good structural properties of the thin slabs are retained.
  • a pre-rolling phase which can take place at lower temperatures anyway (eg 850 to 950 o C), can even be dispensed with entirely.
  • the number of passes required is in any case lower, so that the rolling power (t / d) of the rolling train used is increased considerably.
  • the reheating should, however, take place the thin slab to be rolled as possible to temperatures above Ac3, maximum up to 1,050 o C.
  • the breakpoint Ac1 must be exceeded in any case during heating.
  • the rolling itself can be carried out in three stages in a known manner or else in two stages without the preliminary rolling stage.
  • the starting thickness of the thin slab is advantageously selected as a function of the final sheet thickness so that the degree of deformation is at least about 3-4 so that the core zone of the slab is sufficiently compacted.
  • accelerated cooling can be connected after the finish rolling to increase the toughness properties.
  • the cooling rates are expediently in the range 5 to 35 K / s. When about 550 o C has been reached, the further cooling can readily take place in air.
  • the method according to the invention provides heavy plates with good strength values and at the same time significantly improved toughness properties at low temperatures compared to the prior art of Tecknik.
  • Sheets were examined which were rolled from a raw material of the following composition produced as a thin slab with a thickness of 66 mm: C. 0.088 % Si 0.25 % Mn 1.4 % Nb 0.027 % Al 0.027 % S 0.0015 % N 0.0085 %
  • the rolling was carried out in the form of a 3-stage TM rolling with a final degree of deformation of about 4.5 to a final sheet thickness of 15 mm. That draw temperatures were as shown in Figure 1 at the Rolling trials, the reheating temperature of the thin slabs used in the oven between 800 o C and 1200 o C varriert ie. At values around 580 N / mm2 for the tensile strength R m, the differences were less than 20 N / mm2. With regard to the yield point R t0.5 , there were values around 530 N / mm2 with a slightly decreasing tendency at a higher drawing temperature, although the differences are still within the normal range.
  • FIG. 3 shows the course of the transition temperature T cv100 in the comparison between 3-stage TM-rolled samples and 2-stage TM-rolled and additionally accelerated cooled samples. It can be seen that at drawing temperatures above 850 o C, the 2-stage rolled samples have a lower transition temperature overall. The curves have a cup shape and show particularly favorable values in the drawing temperature range of 800 - 1050 o C. Higher drawing temperatures lead to considerable deterioration.
  • transition temperatures 85% FATT determined on another sample form are shown in a corresponding manner as in FIG. 3.
  • the 2-stage samples rolled with subsequent accelerated final cooling with the exception of the drawing temperature range above 1150 o C, have more favorable values than for 3-stage rolled sheets (without accelerated final cooling).
  • Particularly good results can be expected for drawing temperatures of 850 - 950 o C.
  • the tensile strength R m for the sheet metal produced according to the invention is 580 N / mm 2, somewhat less than that for the sheet metal (615 or 590) produced from the normal slab (sample 1) or from the thin slab with excessive drawing temperature (sample 2) N / mm2).
  • the differences amount to 35 and 10 N / mm2 and are practically still in the order of magnitude of the normal range.
  • the differences in the yield strength R t0.5 are even smaller, for which sample 3 with 520 N / mm2 was higher than sample 2 (505 N / mm2) and the best value for sample 1 (530 N / mm2) was almost achieved.
  • there are clear differences in the criteria for toughness behavior are clear.
  • sample 3 produced according to the invention still provides a shear fracture fraction of 100% down to -80 ° C., while this is only the case for samples 1 and 2 down to -40 ° C. or -20 ° C.
  • the shear fracture fraction of sample 1 is still around 25%. This behavior, which is significantly better than that of sample 1 and sample 2, is also evident when evaluating the impact energy.
  • the corresponding value of sample 3 is 110 J and the value of samples 1 and 2 is only 20 J.

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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)
  • Metal Rolling (AREA)
EP89730129A 1988-06-01 1989-05-25 Procédé de fabrication de tôles fortes Withdrawn EP0345206A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE19883818879 DE3818879C1 (fr) 1988-06-01 1988-06-01
DE3818879 1988-06-01

Publications (1)

Publication Number Publication Date
EP0345206A1 true EP0345206A1 (fr) 1989-12-06

Family

ID=6355763

Family Applications (1)

Application Number Title Priority Date Filing Date
EP89730129A Withdrawn EP0345206A1 (fr) 1988-06-01 1989-05-25 Procédé de fabrication de tôles fortes

Country Status (2)

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EP (1) EP0345206A1 (fr)
DE (1) DE3818879C1 (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0481575A2 (fr) * 1990-10-19 1992-04-22 Preussag Stahl Aktiengesellschaft Procédé de fabrication de tôles soudables à haute résistance mécanique et leur application
WO2001029273A1 (fr) * 1999-10-20 2001-04-26 Thyssenkrupp Stahl Ag Procede pour produire un feuillard a chaud

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3012139A1 (de) * 1979-03-30 1980-10-09 Nippon Steel Corp Verfahren zur herstellung eines im walzzustand hochfesten und hochzaehen stahles
EP0030309A2 (fr) * 1979-12-06 1981-06-17 Preussag Stahl Aktiengesellschaft Feuillard à chaud ou tôle forte en acier dénitruré et procédé pour sa fabrication
DE3437637C2 (fr) * 1984-10-13 1987-08-27 Thyssen Stahl Ag, 4100 Duisburg, De

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3012139A1 (de) * 1979-03-30 1980-10-09 Nippon Steel Corp Verfahren zur herstellung eines im walzzustand hochfesten und hochzaehen stahles
EP0030309A2 (fr) * 1979-12-06 1981-06-17 Preussag Stahl Aktiengesellschaft Feuillard à chaud ou tôle forte en acier dénitruré et procédé pour sa fabrication
DE3437637C2 (fr) * 1984-10-13 1987-08-27 Thyssen Stahl Ag, 4100 Duisburg, De

Non-Patent Citations (5)

* Cited by examiner, † Cited by third party
Title
PATENT ABSTRACTS OF JAPAN, Band 10, Nr. 172 (C-354)[2228], 18. Juni 1986; & JP-A-61 023 719 (SHIN NIPPON SEITETSU K.K.) 01-02-1986 *
PATENT ABSTRACTS OF JAPAN, Band 10, Nr. 28 (C-326)[2085], 4. Februar 1986; & JP-A-60 181 229 (SUMITOMO KINZOKU KOGYO K.K.) 14-09-1985 *
PATENT ABSTRACTS OF JAPAN, Band 9, Nr. 171 (C-291)[1894], 16. Juni 1985; & JP-A-60 43 431 (SHIN NIPPON SEITETSU K.K.) 08-03-1985 *
PATENT ABSTRACTS OF JAPAN, Band 9, Nr. 192 (C-296)[1915], 8. August 1985; & JP-A-60 59 018 (SHIN NIPPON SEITETSU K.K.) 05-04-1985 *
PATENT ABSTRACTS OF JAPAN, Band 9, Nr. 200 (C-298)[1923], 16. August 1985; & JP-A-60 67 619 (SHIN NIPPON SEITETSU K.K.) 18-04-1985 *

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0481575A2 (fr) * 1990-10-19 1992-04-22 Preussag Stahl Aktiengesellschaft Procédé de fabrication de tôles soudables à haute résistance mécanique et leur application
EP0481575A3 (en) * 1990-10-19 1992-08-26 Preussag Stahl Aktiengesellschaft Process for manufacturing weldable high-tensile steel sheets and use of these sheets
WO2001029273A1 (fr) * 1999-10-20 2001-04-26 Thyssenkrupp Stahl Ag Procede pour produire un feuillard a chaud
US6835253B1 (en) 1999-10-20 2004-12-28 Thyssenkrupp Stahl Ag Method for producing a hot strip

Also Published As

Publication number Publication date
DE3818879C1 (fr) 1989-11-16

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