EP2235226B1 - Verfahren zur wahl der zusammensetzung von stahl und verwendung davon - Google Patents

Verfahren zur wahl der zusammensetzung von stahl und verwendung davon Download PDF

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EP2235226B1
EP2235226B1 EP08856442.2A EP08856442A EP2235226B1 EP 2235226 B1 EP2235226 B1 EP 2235226B1 EP 08856442 A EP08856442 A EP 08856442A EP 2235226 B1 EP2235226 B1 EP 2235226B1
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Prior art keywords
steel
concentration
composition
mpa
strength
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EP2235226A1 (de
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Jyri Outinen
Jukka KÖMI
David Porter
Kimmo KELTAMÄKI
Heikki Kinnunen
Tero Rasmus
Tero Intonen
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Rautaruukki Oyj
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Rautaruukki Oyj
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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
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • 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
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • 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
    • C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium

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  • the invention relates to a method for selecting the composition of low-alloy steel, and for manufacturing a steel product, for applications exposed to high temperatures.
  • the invention also relates to a low-alloy hot rolled or normalized steel for use in applications, where endurance to high temperatures and heat resistance is required, the steel having a carbon concentration of above 0.01 percent by weight.
  • This steel may be called fireproof steel and it is preferably hot-rolled.
  • the invention further relates to the use of the steel of the invention.
  • a special feature of fireproof structural steel is that its strength at high temperatures caused by fire is higher than conventional structural steels. In conventional structural steels, the strength decreases essentially as temperature rises, because the movement of steel dislocations becomes easier due to increasing thermal activation. The strength of fireproof steel is less sensitive to temperature increases than that of conventional structural steel.
  • M-C clusters cause interactive solid solution hardening that is an effective hardening mechanism in heat-resistant steels.
  • M x C y precipitations may already be in the steel in supply condition or they may be formed during the heating caused by fire.
  • Patent JP2004339549 discloses a fireproof steel with a tensile strength grade of 490 MPa and yield strength grade of 325 MPa.
  • the publication teaches that boron and molybdenum are necessary alloying elements (Mo: 0.1- ⁇ 0.5%, B: 0.0005-0.003%).
  • manganese is limited to small concentrations (Mn 0.1- ⁇ 0.9%), and during manufacturing the cooling rate after rolling is limited to values larger than 0.3 °C/s.
  • the microstructure of steel should contain 20-90% bainite with the rest being ferrite. Fire properties remain good up to 750°C.
  • the publication does not teach how to select fireproof steel with a yield strength of above 355, 420, 460, 500, or 690 MPa and fire properties that remain good up to 800°C.
  • Published patent JP2002173733 discloses a fireproof steel that maintains good strength up to 800°C.
  • the invention is based on alloying elements that increase austenite formation temperature (A c1 ) up to 800 to 900°C.
  • the publication mentions for instance the following alloying elements and their concentrations: Si 0.2-1.2%, Mn ⁇ 0.5%, 0.05% ⁇ Al ⁇ 1%, Mo 0.4-1.5%, V 0.05-0.2%.
  • the tensile strength grades of the steels are 400 and 490 MPa.
  • the corresponding yield strength grades are 235 and 325 MPa.
  • This publication also does not teach how to manufacture fireproof steel with a yield strength of above 355, 420, 460, 500, or 690 MPa.
  • JP2006241552 discloses a high-strength fireproof steel with a yield strength grade of 440 MPa and tensile strength grade of 590 MPa.
  • the fire-resistance properties are mainly based on high molybdenum concentrations and rather high carbon concentrations: 0.3% ⁇ Mo ⁇ 0.7%, C 0.04-0.14%. Only a small amount of niobium is used, Nb 0.01-0.05%. According to the teachings of the publication, it is not possible to manufacture fireproof steel with a molybdenum concentration below 0.3%, carbon concentration below 0.04%, or niobium concentration above 0.05%.
  • US patent application 2006/0063335 A1 discloses a high-strength fire-resistant low-alloy steel. Its fire-resistant properties are based on a relatively high molybdenum concentration and on the use of boron.
  • the molybdenum concentration is preferably 0.2-1.1 wt % and boron 0.0005-0.003 wt %.
  • the impact strength of the steel is not especially good, because the alloying of boron weakens it.
  • Molybdenum also weakens the impact strength, and is also an expensive alloying element.
  • WO 2006/093282 discloses a low alloy hot-rolled fire resistant steel and a method for manufacturing the same.
  • a drawback of the above patent publications is that they do not teach how to select a composition of fireproof steel and to manufacture a steel product to correspond to a desired yield strength grade in the strength range of 355 to 690 MPa and a desired fire-resistant property (by utilizing the strengthening potential of the steel that depends on the composition of the steel).
  • An object of the invention is to provide a method with which the composition of steel may be selected to correspond to a desired fire-resistance and strength at high temperatures and a method for manufacturing a steel product having said composition.
  • LP 95 is the strengthening potential of the steel that provides an estimate on how much the yield strength of the steel (MPa) increases at room temperature, if steel is heated to a temperature of 600°C for one hour.
  • C is the carbon concentration of the steel (wt %), when the steel is in the hot-rolled condition, and C is the carbon concentration in solution in austenite, C sol , at the normalizing temperature of the steel, when the steel is normalized steel, and Nb is the niobium concentration of steel (wt %), when the steel is in the hot-rolled condition, and Nb is the niobium concentration in solution in austenite, Nb sol , at the normalizing temperature of the steel, when the steel is normalized steel.
  • the correctness of the strengthening potential has been tested to be approximately 95%, i.e., the room-temperature yield point of the steel heated to a temperature of 600 °C for one hour deducted by the yield point of the steel in delivery state will at a probability of 95% increase at least by the value LP 95 .
  • the value of the strengthening potential LP 95 is preferably selected to be above 50, whereby a steel has been selected having a good fire-resistance at high temperatures and a high strength reduction coefficient (the strength does not decrease much at high temperatures).
  • niobium greatly increases fire-resistance which is why the niobium concentration of steel is preferably at least 0.04 wt %. Most preferably, the niobium concentration is 0.08-0.12 wt %.
  • niobium precipitates into niobium carbides, which results in a smaller grain size of steel, improved ductility and strength.
  • Part of the niobium also precipitates into niobium carbides during the cooling after hot-rolling.
  • part of the niobium remains in the solution when the carbon concentration of steel is very low, such as in the steel of the invention; the higher concentration of niobium, the more of it remains in solution.
  • the niobium in solution joins the carbon of the steel and forms strengthening precipitations and clusters. As a result of this, the steel remains strong at temperatures caused by fire.
  • the carbon concentration is at least above 0.01 wt % and preferably above 0.03 wt %.
  • the maximum value of the steel strengthening potential is reached at a carbon concentration of below 0.05 wt %, which is why the upper limit for carbon concentration is preferably selected to be 0.05 wt %.
  • Another reason for preferably selecting 0.05% as the upper limit for carbon concentration is that the impact strength and weldability of the steel then remain good.
  • the molybdenum concentration of steel does not much increase the strengthening potential of steel, and molybdenum is also an expensive alloying element, the molybdenum concentration is preferably selected to be below 0.4 wt %.
  • the greatest advantages of the method of the invention are that, at a general level, it facilitates the selection of the composition of steel and manufacturing of a steel product, for the purpose of obtaining steel with good fire-resistance properties, whereby the method also makes it possible to minimize alloying element costs.
  • the method also facilitates the selection of the composition for the purpose of obtaining steel classified in various strength grades S355, S420, S460, S500, and S690 (the minimum values of yield strengths 355, 420, 460, 500, and 690 MPa).
  • the steel is preferably a hot-rolled plate or strip, even though other delivery forms may also apply.
  • Another object of the invention is to provide for use a fire-resistant low-alloy steel with good fire-resistance without needing to use high concentrations of expensive alloying elements in it.
  • the steel is also easy to manufacture and weld.
  • the steel is mainly characterised in that its composition in percentage by weight is as follows: C: above 0.01 and at most 0.05 Si: at most 0.7 Mn: 1.0-2.3 Ni: at most 1.5 Cr: at most 1.5 Mo: ⁇ 0.4 Cu: at most 0.3 Nb: 0.04-0.15 B: at most 0.004 N: at most 0.01 Al: at most 0.1 V: at most 0.02 Ti: at most 0.05 Ca: at most 0.006, whereby
  • the lower limit of the carbon concentration of the steel is 0.03 wt %, because carbon increases the strengthening potential significantly.
  • the niobium concentration of the steel is preferably 0.08-0.12 wt %.
  • the boron concentration of the steel is above 0.0005 wt %, it is advantageous for the impact strength of the steel that at the same time the manganese concentration is above 1.6 wt % and the molybdenum concentration is below 0.1 wt %.
  • the molybdenum concentration of the steel is preferably below 0.4 wt %, even though the boron concentration of the steel ⁇ 0.0005 wt %.
  • the reduction coefficient of the low-alloy steel of the invention at 700°C is significantly higher than the reduction coefficient presented in SFS standard EN 1993-1-2.
  • the reduction coefficient achievable for the steel is above 0.3 and more preferably above 0.4 at 700°C as measured using a transient test.
  • the steel according to the invention has fire resistance is good and the fire resistance is achieved with a small amount of expensive alloying elements.
  • the steel can be easily and economically manufactured for yield strength grades 355, 420, 460, 500, and 690 MPa, and its composition is suitable for both thick and thin forms.
  • the steel is preferably a hot-rolled plate or strip, even though other products or forms may also apply.
  • the steel according to the invention is used in applications requiring high strength at temperatures above 400°C, even 600 to 800°C. Such applications include those in which the steel must be fire resistant.
  • These typically include steel structures of buildings wherein the steel is preferably used in building beams and lattice structures.
  • the building beams may for instance be welded double-web Q beams or single-web I beams, in which steel is used in the entire beam or only in parts significant for fire protection, such as the top or bottom flange.
  • the steel of the invention works especially well for instance in situations where the intermediate floor slab system of a building is supported by a Q beam and the bottom or top flange of the beam is not protected by the slab system or concreting, whereby the flange requires especially good fire resistance. Other fire protection means are not needed when the required part of the beam is made of the steel of the invention.
  • molybdenum and boron are not necessary, even though they may be utilised (Mo: 0-0.7 wt %, preferably ⁇ 0.4 wt %, B: 0-0.0040 wt %).
  • Manganese is an essential alloying element to provide strength and impact strength, which is why manganese is alloyed in 1-2.3 wt % depending on the boron concentration of the steel. It has been noted that in hot-rolled steel both molybdenum and boron reduce the impact strength of the steel, whereas by increasing the manganese concentration, the impact strength of the steels according to the invention improves.
  • the transition temperature of impact strength may increase as much as 50°C when boron is alloyed in steel.
  • the manganese concentration is selected to be above 1.6 wt % and/or (preferably and than or) the molybdenum concentration at most 0.1 wt%.
  • the proportions of bainite and ferrite in the microstructure are not restricted.
  • the invention makes it possible to design steel structures with desired fire-resistance properties at manufacturing costs that are as economical as possible.
  • the correctness of the formula has been tested to be approximately 95%, i.e., the room-temperature yield point of the steel heated to a temperature of 600 °C for one hour deducted by the yield point of the steel in delivery state will at a probability of 95% increase at least by the value LP 95 .
  • LP 95 > 50 and in applications requiring very high fire resistance, LP 95 > 100 is selected.
  • the effect of carbon on the strengthening potential is great, and this may also be observed from the attached figure that shows steel that contains not only carbon, but also 0.04 wt % of Nb, 0.14 wt % of Cr, 0.17 wt % of Mo, and 0.76 wt % of Ni.
  • the carbon concentration of the steel is at least 0.01 wt %.
  • the carbon concentration of the steel is above 0.03 wt % and at most 0.05 wt %, and its niobium concentration is 0.04-0.15 wt % and more preferably 0.08-0.12 wt %.
  • the aim is to keep the molybdenum concentration relatively low due to the high price of molybdenum.
  • the molybdenum concentration is preferably below 0.4 wt %, and if the steel contains above 0.0005 wt % of boron, the molybdenum concentration is below 0.1 wt %.
  • a r3 + °C 910 - 310 ⁇ C - 80 ⁇ Mn - 20 ⁇ Cu - 15 ⁇ Cr - 55 ⁇ Ni - 80 ⁇ Mo .
  • Cooling after plate-rolling may take place freely in air or as accelerated cooling with water, for instance, as long as the cooling time from 750°C to 400°C is shorter than 5000 s which corresponds to the average cooling rate that is higher than 0.07°C/s at 750 to 400°C.
  • the cooling must be accelerated with water to a temperature of 450°C or below.
  • composition limits of the steel according to the invention are shown in Table 1.
  • Table 2 shows compositions of steel plates according to the invention within the alloying element concentrations given in Table 1. Yield point and tensile strength values were measured for these steel plates, see Table 3.
  • Table 2 Chemical compositions of plates (wt %) Plate Thickness mm Type C % Si % Mn % Cu % Cr % Ni % Mo % Nb % B % BL ST 1142-1 / -2 12 miniature 0.024 0.17 1.99 0.22 0.03 0.82 0.26 0.054 0.0003 0 4.7 1143-1 / -2 12 miniature 0.043 0.18 1.99 0.23 0.03 0.81 0.26 0.054 0.0003 0 5.3 1144-1 / -2 12 miniature 0.011 0.19 1.98 0.22 0.03 0.82 0.26 0.052 0.0003 0 4.3 1145-1 / -2 12 miniature 0.040 0.18 2.08 0.21 0.03 0.13 0.11 0.103 0.0013 1 5.6 1146-1 / -2 12 miniature 0.022 0.17 2.09 0.22 0.03 1.01 0.11
  • C, Si, Mn, Cr, Mo, and Cu refer to the alloying element concentrations in percent by weight.
  • C is the carbon concentration of the steel (wt %), when the steel is hot-rolled steel, and C is the carbon concentration in solution in austenite, C sol , at the normalization temperature of the steel, when the steel is normalized steel.
  • CR refers to the average cooling rate at 750 to 400°C.
  • the above formula predicting the yield strength is used when it is necessary to select steel that corresponds to a desired yield strength grade.
  • Table 3 also proves that by selecting the composition and manufacturing parameters of the steel by using the limits and formulas of the invention, it is possible to manufacture plates for yield strength grades 420, 460, 500, or 690 MPa, for instance.
  • the impact strength of the steel is also adjusted to the desired level by controlling the impurities contents (S, P, O, N), calcium processing, and rolling and cooling conditions.
  • Tables 2 and 3 show that the cooling rate does not much affect the strength properties of the plates at least when the cooling rates are low, so it is easy to use the presented strengthening potential formula to design compositions for fireproof steels in such a manner that it is possible to use the same composition to manufacture both thick and thin plates and strip plates.
  • the examples of Table 3 show that a given strength grade may be manufactured of the same composition regardless of the cooling rate.
  • Table 4 shows calculated strengthening potentials LP 50 and LP 95 and measured strength increases. It can be noted that in only two cases of thirty three the measured strengthening potential is lower than the LP 95 prediction. The highest predicted LP 95 value is 161 MPa that is achieved with the relatively high-alloy plate 1148.
  • Table 5 shows the chemical composition of three comparison steels.
  • Table 5 The chemical composition of three comparison materials (wt %) Plate Thickness mm CR °C/s C % Si % Mn % Al % Nb % V % Ti % Cr % Cu % Ni % Mo % N % B % 41278-024 30 0.3 0.12 0.35 1.56 0.040 0.037 0.004 0.005 0.02 0.01 0.04 0.00 0.0068 0.0002 50902-013 20 0.4 0.14 0.36 1.50 0.042 0.040 0.039 0.017 0.02 0.01 0.48 0.00 0.0099 0.0003 14630-034 20 16 0.08 0.16 1.51 0.035 0.037 0.005 0.017 0.02 0.28 0.76 0.00 0.0060 0.0003
  • Plates 41278-024 and 50902-013 were cooled freely in air. Plate 14630-034 was cooled accelerated at 750-550°C.
  • Table 6 shows the mechanical properties of comparison steels rolled and after heat treatment.
  • the table shows that the measured strengthening potentials, R eH (AR) - R eH (1h600°C) that correspond to the LP 50 value, are typically negative.
  • the comparison steels have clearly higher carbon concentrations than the steels of the invention, and on the basis of the LP 95 formula, it is expected that EP decreases when the carbon concentration increases above approximately 0.040%.
  • Table 6 The mechanical properties of comparison materials rolled and after heat treatment Plate Thick CR Rolled Heat treated 600°C ReH(600°C)-ReH(AR) mm °C/s ReH MPa Rm MPa A5 % Temp °C Time min ReH MPa Rm MPa A5 % MPa 41278-024 30 0.3 455 557 30 600 60 445 553 32 -10 50902-013 20 0.4 503 642 24 600 40 501 623 24 -2 14630-034 20 16 577 685 14 600 40 572 657 21 -5
  • the fire-resistance of the plates of the invention was tested in transient tests. Their mechanical properties in delivery state are shown in Table 7.
  • Table 7 The mechanical properties of plates tested in transient tests Plate No. Thickness Cooling rate As rolled Heat-treated 1h600°C Charpy V as rolled crosswise, -60 °C R p0.2 R m A R p0.2 Rm A mm °C/s MPa MPa % MPa MPa % J 74705-031 20 12 569 660 22 613 670 23 310 15874-016 12 25 569 656 21 591 652 22 207 15874-033 20 11 571 644 21 589 648 23 271
  • Table 8 shows the strength properties measured by transient tests at high temperatures for the steel plates of the invention and conventional structural steels.
  • transient tests the strength of the material (steel) is measured in hot tensile tests, wherein a piece of steel is loaded in a test furnace at different tensile loads by increasing the temperature from 20°C to 900°C at the same time. Yield strength values at different temperatures are measured for the material (steel) on the basis of the load tests. Yield strength is the level of stress at a selected elongation value.
  • the fire resistance of the plates made according to the invention has been tested in transient tests according to the standard EN 10002-5. A transient test is suitable when there is a need to define the strength properties of the material in fire conditions.
  • Table 8 shows the reduction coefficients (k y,e ) of yield points of steels at high temperatures.
  • k y , ⁇ f y , ⁇ at increased temperature ⁇ / f y at room temperature , wherein f y is an effective yield point at a total elongation of 2%.
  • Table 8 shows that the fire properties of the steel plates of the invention are clearly better than those of conventional structural steels: at 700°C, the reduction coefficient of the effective yield point is 82 to 90% higher in the steel of the invention than in conventional steel.
  • the reduction coefficient of the steels of the invention is above 0.3 and preferably above 0.4 at 700°C, which values can be seen to be true, see Table 8.
  • Table 8 Strength properties measured by transient tests at high temperatures Plate of the invention Temperature Measured reduction coefficient Reduction coefficient SFS EN 1993-1-2 Ratio °C k y, ⁇ (measured) k y, ⁇ (EN 1993-1-2) k y, ⁇ (measured) / k y, ⁇ (EN 1993-1-2) 74705-031 20 1.000 1.000 1.00 400 1.000 1.000 1.00 500 0.872 0.780 1.12 600 0.655 0.470 1.39 700 0.419 0.230 1.82 800 0.140 0.110 1.27 900 0.061 0.060 1.02 15874-016 20 1.000 1.000 1.00 400 1.000 1.000 1.00 500 0.932 0.780 1.20 600 0.670 0.470 1.42 700 0.438 0.230 1.90 800 0.152 0.110 1.38 900 0.064 0.060 1.07
  • Table 9 shows composition information of normalized plates and the niobium dissolution temperature NBDT
  • Table 10 shows mechanical properties and strengthening potentials LP 50 and LP 95 of normalized plates.
  • Plates 15874-016 and 15874-033 were normalized at 950°C that is very close to the dissolution temperature of niobium (NBDT) calculated according to the Dong formula 957°C. In practice, this leads to C sol and Nb sol being very close to the total carbon and niobium concentrations of the plates.
  • Table 9 Composition information of normalized plates and dissolution temperature of niobium NBDT Plate Thickness mm Normalizing temperature Ti N N* NBDT C sol Nb sol °C ppm ppm ppm °C % % 15874-016 12 950 160 55 8 957 0.016 0.042 15874-033 20 950 160 55 8 957 0.016 0.042

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Claims (13)

  1. Verfahren zur Herstellung eines Stahlprodukts, welches Verfahren das Auswählen eines niedriglegierten warmgewalzten oder normalisierten Stahls für Anwendungen, die hohen Temperaturen ausgesetzt sind, umfasst, gekennzeichnet durch
    Auswählen des C-, Si-, Mn-, Cr-, Mo-, Ni-, Cu- und B-Gehalts und der Abkühlgeschwindigkeit (CR) des Stahls nach dem Warmwalzen,
    Berechnen der Streckgrenze des Stahls, der die ausgewählte Zusammensetzung hat, unter Verwendung der Formel R p ⁢ 0 , 2 Mpa = 261 + 2198 ⁢ C + 96 ⁢ Si + 52 ⁢ Mn + 59 ⁢ Cr + 137 ⁢ Mo + 48 ⁢ Ni + 35 ⁢ Cu + 41 ⁢ BL + - 131 + 86 ⁢ Mn + 58 ⁢ BL ⁢ log 10 CR ,
    Figure imgb0023
    C die Kohlenstoffkonzentration des Stahls (Gew.-%) ist,
    Si die Siliciumkonzentration des Stahls (Gew.-%) ist,
    Mn die Mangankonzentration des Stahls (Gew.-%) ist,
    Cr die Chromkonzentration des Stahls (Gew.-%) ist,
    Mo die Molybdänkonzentration des Stahls (Gew.-%) ist,
    Ni die Nickelkonzentration des Stahls (Gew.-%) ist,
    Cu die Kupferkonzentration des Stahls (Gew.-%) ist, und
    BL sich auf den Borgehalt des Stahls bezieht, und
    BL = 0, wenn B ≤ 0,0005 und BL = 1, wenn B > 0,0008, wobei B die Borkonzentration des Stahls (Gew.-%) ist, und
    CR sich auf die Abkühlgeschwindigkeit nach dem Warmwalzen (°C/s) bezieht, Vergleichen der berechneten Streckgrenze mit einem gewünschten Streckgrenzengrad, der für die Anwendung spezifiziert ist,
    wenn die berechnete Streckgrenze den gewünschten Streckgrenzengrad erfüllt, Berechnen eines Verfestigungspotenzials LP95 für den Stahl, der die Zusammensetzung hat, unter Verwendung der Formel - 177 + 9000 ⁢ C - 115.000 ⁢ C 2 + 750 ⁢ Nb + 71 ⁢ Mo + 33 ⁢ Ni - 36 ⁢ Cr ,
    Figure imgb0024
     wobei
    Nb die Niobkonzentration des Stahls (Gew.-%) ist, und,
    wenn das berechnete Verfestigungspotenzial LP95 > 0, der die Zusammensetzung aufweisende Stahl für die Verwendung in dieser Anwendung geeignet ist; und
    wobei das Verfahren ferner die Herstellung des Stahlprodukts unter Verwendung der ausgewählten Zusammensetzung und der ausgewählten Abkühlgeschwindigkeit umfasst.
  2. Verfahren nach Anspruch 1, dadurch gekennzeichnet, dass die Zusammensetzung des Stahls so ausgewählt wird, dass seine Zusammensetzung in Gewichtsprozent beträgt: C: 0,01-0,05 Si: höchstens 0,7 Mn: 1,0-2,3 Ni: höchstens 1,5 Cr: höchstens 1,5 Mo: höchstens 0,7 Cu: höchstens 0,3 Nb: 0,04-0,15 B: höchstens 0,004 N: höchstens 0,01 Al: höchstens 0,1 V: höchstens 0,02 Ti: höchstens 0,05 Ca: höchstens 0,006, wobei
    die Konzentrationen von Mangan und Molybdän so gewählt sind, dass Mn > 1,6 oder Mo < 0,1, wenn B > 0,0005, und
    das Legierungsniveau des Stahls ST = 33,8C + 0,98Si + 1,15Mn + 0,47Cr + 2,32Mo + 0,85Ni + 0,47Cu + 1,16BL, so dass sein Wert 3,0-8,0 beträgt, wobei BL = 0, wenn B ≤ 0,0005 und BL = 1, wenn B > 0,0008.
  3. Niedriglegierter warmgewalzter oder normalisierten Stahl zur Verwendung bei Anwendungen, die Hochtemperaturfestigkeit und Wärmebeständigkeit erfordern, wobei der Kohlenstoffgehalt des Stahls > 0,01 Gew.-% beträgt, dadurch gekennzeichnet, dass die Zusammensetzung des Stahls in Gewichtsprozent wie folgt ist: C: über 0,01 und höchstens 0,05 Si: höchstens 0,7 Mn: 1,0-2,3 Ni: höchstens 1,5 Cr: höchstens 1,5 Mo: < 0,4 Cu: höchstens 0,3 Nb: 0,04-0,15 B: höchstens 0,004 N: höchstens 0,01 Al: höchstens 0,1 V: höchstens 0,02 Ti: höchstens 0,05 Ca: höchstens 0,006, wobei
    Mn > 1,6 oder Mo < 0,1, wenn B > 0,0005, und
    das Legierungsniveau des Stahls ST = 33,8C + 0,98Si + 1,15Mn + 0,47Cr + 2,32Mo + 0,85Ni + 0,47Cu + 1,16BL, = 3,0-8,0 beträgt, wobei BL = 0, wenn B ≤ 0,0005 und BL = 1, wenn B > 0,0008, und die Zusammensetzung des Stahls das Kriterium - 177 + 9000 ⁢ C - 115.000 ⁢ C 2 + 750 ⁢ Nb + 71 ⁢ Mo + 33 ⁢ Ni - 36 ⁢ Cr > 0
    Figure imgb0025
     erfüllt.
  4. Stahl nach Anspruch 3, dadurch gekennzeichnet, dass -177 + 9000C - 115.000C2 + 750Nb + 71Mo + 33Ni - 36Cr > 50.
  5. Stahl nach Anspruch 3, dadurch gekennzeichnet, dass -177 + 9000C - 115.000C2 + 750Nb + 71Mo + 33Ni - 36Cr > 100.
  6. Stahl nach einem der vorhergehenden Ansprüche 3-5, dadurch gekennzeichnet, dass die Kohlenstoffkonzentration des Stahls 0,03 Gew.-% beträgt.
  7. Stahl nach einem der vorhergehenden Ansprüche 3-6, dadurch gekennzeichnet, dass die Niobkonzentration des Stahls mindestens 0,08-0,12 Gew.-% beträgt.
  8. Stahl nach einem der vorhergehenden Ansprüche 3-7, dadurch gekennzeichnet, dass B ≤ 0,0005, N < 0,008 und 2 < Ti/N < 3.
  9. Stahl nach einem der vorhergehenden Ansprüche 3-7, dadurch gekennzeichnet, dass der Stahl frei von Bor ist.
  10. Stahl nach einem der vorhergehenden Ansprüche 3-7, dadurch gekennzeichnet, dass Ti/N > 3,4 oder Al/N > 8 wenn B > 0,0005.
  11. Stahl nach einem der vorhergehenden Ansprüche 3-10, dadurch gekennzeichnet, dass der Reduzierungskoeffizient seiner Festigkeit bei 700 °C, gemessen in einer transienten Prüfung, > 0,3 ist.
  12. Verwendung eines Stahls nach einem der vorhergehenden Ansprüche 3-11 in Anwendungen, die eine hohe Festigkeit bei Temperaturen über 400 °C erfordern.
  13. Verwendung des Stahls nach Anspruch 12 in Bauwerksträgern.
EP08856442.2A 2007-12-07 2008-12-05 Verfahren zur wahl der zusammensetzung von stahl und verwendung davon Not-in-force EP2235226B1 (de)

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FI20075886A FI20075886L (fi) 2007-12-07 2007-12-07 Menetelmä teräksen koostumuksen valitsemiseksi, teräs ja sen käyttö
PCT/FI2008/050715 WO2009071752A1 (en) 2007-12-07 2008-12-05 Method for selecting composition of steel and its use

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JPH10204573A (ja) * 1997-01-24 1998-08-04 Nippon Steel Corp ７００℃耐火圧延形鋼およびその製造方法
JP4860071B2 (ja) 2000-09-28 2012-01-25 新日本製鐵株式会社 ８００℃高温耐火建築構造用鋼およびその製造方法
US6841825B2 (en) 2002-06-05 2005-01-11 Shindengen Electric Manufacturing Co., Ltd. Semiconductor device
JP4031730B2 (ja) 2003-05-14 2008-01-09 新日本製鐵株式会社 溶接性、ガス切断性に優れた構造用４９０ＭＰａ級高張力耐火鋼ならびにその製造方法
JP4718866B2 (ja) 2005-03-04 2011-07-06 新日本製鐵株式会社 溶接性およびガス切断性に優れた高張力耐火鋼およびその製造方法

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PL2235226T3 (pl) 2014-09-30
FI20075886A0 (fi) 2007-12-07

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