EP1281777B1 - Herstellungsverfahren für gewalzte h-profilstahl mit gleichmässiger mikrostruktur und mechanischeneigenschaften - Google Patents

Herstellungsverfahren für gewalzte h-profilstahl mit gleichmässiger mikrostruktur und mechanischeneigenschaften Download PDF

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EP1281777B1
EP1281777B1 EP01919779A EP01919779A EP1281777B1 EP 1281777 B1 EP1281777 B1 EP 1281777B1 EP 01919779 A EP01919779 A EP 01919779A EP 01919779 A EP01919779 A EP 01919779A EP 1281777 B1 EP1281777 B1 EP 1281777B1
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Prior art keywords
flange
web
rolling
fillet
section
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French (fr)
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EP1281777A4 (de
EP1281777A1 (de
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Suguru NIPPON STEEL CORPORATION YOSHIDA
Hironori C/O NIPPON STEEL CORPORATION SATOH
Takeshi NIPPON STEEL CORP. SAKAI WORKS YAMAMOTO
Eiji NIPPON STEEL CORP. KIMITSU WORKS SAIKI
Masao NIPPON STEEL CORP. SAKAI WORKS KUROKAWA
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Nippon Steel Corp
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    • 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
    • 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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B1/00—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations
    • B21B1/08—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling structural sections, i.e. work of special cross-section, e.g. angle steel
    • B21B1/0815—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling structural sections, i.e. work of special cross-section, e.g. angle steel from flat-rolled products, e.g. by longitudinal shearing
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B1/00—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations
    • B21B1/08—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling structural sections, i.e. work of special cross-section, e.g. angle steel
    • B21B1/088—H- or I-sections
    • 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
    • C21D9/0068—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for particular articles not mentioned below

Definitions

  • the present invention relates to a method of producing an H-section used as a member for building structures and, in particular, to a rolled H-section having uniform microstructures and uniform mechanical properties.
  • section steels for example H-sections
  • the cross-sectional dimensions of section steels, for example H-sections, produced by hot rolling greatly vary depending on the sizes of products, and there may be cases where the amounts of rolling reduction at the time of rolling and temperature histories during and after the rolling greatly vary depending on positions in a cross section.
  • a 1/2 flange portion (hereinafter referred to as a fillet portion) within a flange portion, at which the flange and a web are joined together, is characterized in that the amount of strain caused by rolling is small as compared with the other portions of the flange and, in addition to that, this portion is forcedly worked in a high temperature range.
  • microstructural disparities are generated among different positions in a cross section of a flange portion thereof.
  • These microstructural disparities have an influence on mechanical properties such as strength and toughness and, more specifically, constitute a main factor in decreasing the strength and toughness of a fillet portion.
  • Such disparities in material quality within a cross section tend to stand out in the case of a large size and a thick wall size, and tend to stand out in the case of a heavy building structure using such H-sections.
  • the prescribed values of mechanical properties such as strength and toughness have so far been assured by making up for decreases in the strength and toughness of a fillet portion, that is the weakest portion, by a method of increasing the addition amount of alloy or the like.
  • the mechanical properties of portions other than a fillet portion are superior to those of the fillet portion and are distributed at a level sufficient to satisfy the prescribed values; however, there is a case where a member having disparities in material quality within a cross section of a flange portion is inappropriate for use in a stricter steel structure design. That is to say, a problem arising in a case where an accidental large load is imposed on such a member is that cracks originate in a fillet portion.
  • envisaged is a method of controlling microstructures by making use of the introduction of working strain caused by a large-reduction rolling in a rolling stage and subsequent recuperation and recrystallization phenomena.
  • rolling H-sections it has so far been impossible to uniformalize the microstructures because of the restrictions on their production as it is shown hereafter.
  • the production processes of an H-section consists of a breakdown process for rolling a heated cast steel into an H-shaped rough form (hereinafter referred to as a rough formed cast steel) and intermediate and finish rolling processes for forming it into a product having prescribed sizes in thickness, width and height.
  • a cast steel is formed so that the proportion of the flange thickness of a rough formed cast steel finished in a breakdown process to the web thickness thereof comes close to the proportion of the flange thickness of a product to the web thickness thereof.
  • the above-mentioned rolling method tends to cause the temperature of a web to drop remarkably during rolling and to increase the temperature variations within an H-shaped cross section.
  • the distribution of temperatures shows the maximum value at a fillet and the minimum value at the middle of a web, and the temperature difference between them becomes as large as 150 to 200C in some cases.
  • EP-A-0 609 559 discloses a method for producing low Ceq rolled steel shapes by controlled rolling for providing steel sections of various contours and dimensions from minimized varieties of steel compositions, where the production process comprising the steps of; intermediate hot rolling comprises water-cooling the flange portion of the rough-rolled steel section between rolling passes in the intermediate rolling to cool the surface layer of the flange to a temperature not higher than 750C, and rolling the flange portion during recuperation of the surface layer of the flange at least one time between the rolling passes with a total draft not less than 20% and at an average rolling temperature not higher than 950C, and cooling the outer surface of the flange after finishing hot rolling with a cooling rate range of 0.5-10C/sec depending on the thickness of the flange.
  • JP-A-9-137218 discloses a manufacture of wide flange shape for building construction excellent in refractoriness and weldability, where the steel contains C: 0.001-0.030%, Si: 0.60% or less, Mn: 0.20-3.00%, Al: 0.100% or less, Ti: 0.005-0.20%, B: 0.0003-0.0050%, N: 0.0100% or less, and further contains one or more of Mo: 0.05-0.6%, Cu: 0.7-2.0% and Ni: 0.7-2.0% and the balance being Fe and unavoidable impurities, and that the steel is produced by the steps of; reheating the steel to 1200-1350C, finishing hot rolling with a temperature difference between a web part and flange part when it becomes less than 100C and both parts of web and flange reach a temperature of more than 700C, and cooling it in air for reducing a quality fracture in the cross-sectional area of the rolled H-shape steel.
  • the present invention solves the above-mentioned various problems and provides a method of producing rolled H-sections of various sizes produced by hot rolling and, in particular, rolled H-sections each having uniform mechanical properties within a cross section thereof by reducing microstructural variations in respective portions of each of the H-sections of large sizes and thick-walled sizes.
  • Fig. 1 is a schematic view showing the portions of an H-section and the positions where test pieces are cut out and
  • Fig. 2 is a graph showing the transition of the average grain size of austenite after recrystallization depending on the rolling temperature history.
  • a 1/2 flange portion (fillet portion) at which the flange and a web are joined together has a small amount of strain caused by rolling as compared with the other portions of the flange, and in addition to that, this portion is forcedly worked in a high temperature range. Therefore, within the very same member, microstructural disparities are generated among different positions in a cross section of the flange portion and the microstructural disparities cause the strength and toughness of the fillet portion to decrease.
  • the microstructure of the web portion tends to become finer than that of the flange portion because the web portion undergoes the production conditions of comparatively low temperature and large reduction. Further, along with this, the web portion tends to have lower hardenability and a lower pearlite rate than the flange portion.
  • microstructural disparities have a significant influence on strength and toughness, and more specifically, cause the yield ratio of a web portion to increase. Further, the microstructural disparities and material quality disparities tend to be conspicuous when the proportion of the thickness of a flange to that of a web is large and the thickness of the web portion is thin.
  • a method of shortening the time required up to the production by rolling more specifically, a method of limiting the extension length of a steel material, namely reducing the weight of a cast steel, and accelerating the rolling and conveying speed, has so far been tried.
  • an H-section produced by conventional production processes has material quality disparities existing between a web and a flange, and there may be a case where such an H-section is inappropriate for a member used in a strict steel structure design, depending on the conditions.
  • a conventional H-section is used as a member of a structure designed to be earthquake-proof, there is a danger that, when a large earthquake happens, a collapse pattern unpredictable in a designing stage may occur due to the disparities in material quality generated within a cross section of the member.
  • the present inventors made various studies to eliminate the above-mentioned microstructural disparities and, as a result, discovered that to control the average grain sizes of ferrite or the average rates of pearlite in microstructures on the basis of a 1/4 flange portion in a cross section of an H-section and/or to control mechanical properties such as yield strength and tensile strength at a 1/2 flange portion, a web portion and a fillet portion are important factors. This will be now explained in detail.
  • the mechanical properties of a steel material having microstructures mainly composed of a ferrite phase and a pearlite phase can be predicted from the grain size of ferrite and the rate of pearlite.
  • plastic deformation starts to appear in the ferrite phase which is softer than the pearlite phase, and thereby the steel material yields.
  • the mechanical properties depend on the crystal grain size of ferrite. That is to say, it has been shown theoretically and experimentally that yield strength has dependence on the grain size of ferrite, and specifically has a linear correlation with the square root of the ferrite grain size.
  • tensile strength depends not only on the strength of ferrite which is a soft phase but also on the strength of pearlite which is a hard phase. This is because a rupture limit in a tensile test, which represents tensile strength, results from the plastic deformation of both ferrite and pearlite. Since the tensile strength of a composite structure is generally considered to be the weighted average of the tensile strengths of phases constituting the structure, the total sum of each product of the strength and the rate of a constituent phase in the structure can be used as a predictive expression of the tensile strength.
  • tensile strength is a quantity which depends on the grain size of ferrite and the rate of pearlite because of the two reasons that the ferrite rate is equal to a value acquired by subtracting the pearlite rate from 1 because the number of main constituent phases is two and that the dependency of tensile strength on the grain size of pearlite is negligible because the plastic deformation of pearlite is very small compared with the plastic deformation of ferrite.
  • the tensile strength of a steel material is expressed by the following experimental formula (1) according to Pickering and the strength level of a rolled steel is substantially determined by the values of alloy-designed chemical constituents, the rate of pearlite, and the grain size of ferrite:
  • Tensilestrength MPa 15.4 ⁇ 19.1 + 1.8 Mn + 5.4 Si + 0.25 % pearlite + 0.5 ⁇ d - 1 / 2 where, d is a ferrite grain size (mm).
  • the crystal grain size of ferrite is determined by the number of ferrite transformation sites and the growth rate of the ferrite crystals during the transformation of austenite into ferrite, and depends chiefly on the following conditions: 1) the grain size of austenite just before it is transformed into ferrite, and 2) a temperature at working, the amount of strain, a cooling rate in a transformation range and the like, in a working and heat treatment represented by an accelerated cooling type controlled rolling (TMCP). Further, the rate of pearlite is mainly determined by the transformation temperature of the pearlite.
  • the present invention actualizes the uniformity of microstructures and that of mechanical properties in a cross section of an H-section by reducing microstructural disparities among a web, a flange and a fillet of the rolled H-section formed by rolling using the methods shown hereafter.
  • the following measures can be enumerated as methods of eliminating microstructural disparities among a 1/4 flange portion, a 1/2 flange portion and a fillet portion and uniformalizing their mechanical properties:
  • the deviations of the average grain sizes of ferrite in microstructures of a 1/2 flange portion and a fillet portion from that of a 1/4 flange portion are within 15% thereof or the deviations of the average rates of pearlite in the microstructures of a 1/2 flange portion and a fillet portion from that of a 1/4 flange portion are within 8% thereof.
  • This composition range corresponds to the chemical compositions of a rolled steel for general structure, a rolled steel for welded structure, a rolled steel for building structure and the like defined as SN400, SS400, SM400, SN490, SM490, etc. in the JIS standards.
  • This composition range represents the tensile strengths of 400 MPa to 610 MPa and allows achieving high toughness and high weldability. Further, when a carbon equivalent is within this range, the microstructure of a steel having such composition is mainly composed of a ferrite phase and a pearlite phase and, as mentioned above, a mechanism comes into existence wherein the microstructure has an influence on mechanical properties.
  • the carbon equivalent formula shown in the claims is described also in the JIS standards, and it is shown there that the lower the value is, the more excellent the weldability is. Further, with respect to toughness, it is empirically known that the lower the value of the carbon equivalent formula is, the better is the value of toughness obtained.
  • Nb at 0.005 to 0.035 mass % is added to the chemical composition satisfying the above-mentioned limited range of the carbon equivalent formula in order to improve strength and toughness. It is known that the addition of Nb acts so as to suppress recrystallization of steel. For example, even in a case where Nb at 0.005 mass %, that is the minimum amount of Nb addition, is added, a non-recrystallization temperature range can be raised to a temperature range of, for example, the order of 950C, provided that the carbon equivalent is in the range according to the present invention.
  • the concentration of added Nb exceeds 0.035 mass %, coarse Nb-based carbides disperse, which may impair the toughness and weldability of a base metal. Therefore, the upper limit of Nb is set at 0.035 mass %.
  • the reason why the reheating temperature of a cast steel is limited to within the temperature range of 1,100 to 1,300C at the time of starting the rolling of an H-section is that heating up to 1,100C or higher is required in order to make plastic deformation easy when a section steel is produced by hot rolling, and that the upper limit is set at 1,300C from the viewpoints of the capability and economical efficiency of a reheating furnace.
  • a heated cast steel is then rolled and formed in the processes of rough rolling, intermediate rolling and finish rolling.
  • a large-reduction rolling with a reduction ratio of 20% or more per pass in the intermediate rolling process can be mentioned.
  • the reason why the temperature range is limited to 950 to 1,100C when a large-reduction rolling with a reduction ratio of 20% or more per pass is adopted is that the effect of recrystallization on fining the grain size in an austenite structure is maximized within this temperature range. The more the strain is imposed during rolling, the finer the grain size in the structure of austenite after recrystallization is.
  • the effect of recrystallization per pass on fining a grain size tends to decrease as the frequency of rolling increases.
  • a part of work-induced strain is accumulated in austenite grains, acts as ferrite transformation nuclei in the austenite grains, and has the function of fining the grain size of a microstructure finally.
  • the number of rolling passes is reduced, the time required to roll a reheated cast steel into an H-section of a prescribed size is shortened, and temperature differences among portions in a cross section of the H-section are reduced. That is to say, temperature differences among the portions during a rolling pass are reduced and thus variations in the temperature histories of the portions are reduced.
  • the temperature of a fillet gradually comes closer to the temperature of a web or that of a flange, and microstructural disparities within a cross section are further reduced.
  • a method of cooling the flange so that the surface temperature of the flange portion is cooled down to 750C or lower just after the water cooling and rolling the steel material while the surface of the steel material is recuperated is effective for fining the grain size of a microstructure, and, by applying the method at least once or by repeating it a plurality of times, the effect of fining a grain size is further exhibited.
  • this water cooling gives a temperature gradient extending from the surface layer portion of the flange to the interior, increases the permeation of working by rolling into the interior as compared with a case where water cooling is not applied, and also gives the effect of assisting the fining of the size of grains in the inner part of the wall thickness.
  • the number of repetition of the water cooling and the recuperation rolling depends on the thickness of a rolled material, the thickness of a flange for example, and two or more repetitions are employed when the thickness is large.
  • a reason to limit the temperature of the surface layer portion of a cooled flange to 750C or lower is that the cooling is performed not only to lower the temperature of a rolled material but also to obtain the effect of revealing the function of suppressing the quench hardening of a surface layer portion.
  • a rolled material is once cooled down to the austenite-ferrite transformation temperature (Ar 3 temperature) or lower by water cooling to transform austenite into ferrite, and undergoes a process of rolling the material in the austenite-ferrite two-phase domain and a process of transforming the ferrite, which is transformed once by recuperating heat and raising the temperature before the subsequent rolling pass, into austenite again as a reverse transformation, and by these processes, the grain size of the microstructure in the surface layer portion is fined, the hardenability can be remarkably lowered, and the quench-hardening of the surface layer portion can be prevented even when an accelerated cooling is applied after the completion of rolling.
  • the austenite-ferrite transformation temperature Ar 3 temperature
  • the purpose of finish cooling the flange portion at a cooling rate of 0.5 to 10C/sec. after the completion of rolling is to suppress the grain growth of ferrite by an accelerated cooling and thus to uniformalize the microstructures of the respective portions in the cross section with their grains being kept fine, and also to increase the rate of pearlite in a structure and thus to obtain targeted strength with the small amounts of alloys.
  • Experimentally produced steels were melted and refined in a basic oxygen furnace and cast into cast steels 240 to 300 mm in thickness by a continuous casting method, and the cast steels were heated and then rolled into H-sections.
  • an H-section production method comprising a breakdown process basically by the use of groove rolling, an intermediate rolling process by the use of a group of intermediate universal mills comprising an edger mill and a universal mill, and a finish rolling process by the use of a universal mill.
  • this method may include an additional skew-roll rolling process for controlling the height of the web of an H-section.
  • a cast steel is shaped so as to have a proper flange width and web height by being rolled in the width direction of the cast steel by the use of rolling rolls each having a plurality of grooves disposed therein, each of which grooves has a projection in the center of the groove bottom which width is different from those of other grooves.
  • the flange width is shaped by the edger mill, and the web thickness and the flange thickness are shaped by the universal mill.
  • the steel is shaped by the finishing mill into the prescribed size of an H-section.
  • a cast steel undergoes the above-mentioned rolling in a breakdown process and thereafter a single web rolling process by the use of grooves, called flat pass rolling.
  • the reduction of the thickness of the web in the early stage in consequence of the single web rolling causes the temperature drops of the web in the succeeding processes to be conspicuous, and the web has to be rolled in a low temperature range as compared with the other portions.
  • a reduction ratio per pass in the universal mill is relatively small in the intermediate rolling process, the time needed for the production by rolling is prolonged, temperature differences among the portions are expanded accordingly, and that causes the disparities of rolling temperature histories.
  • microstructures shown in Table 1 were obtained when the above-mentioned process was used to produce H-sections each having a web thickness of 9 mm, a flange thickness of 12 mm, a web height of 500 mm and a flange width of 200 mm, and H-sections of large size each having a web thickness of 40 mm, a flange thickness of 60 mm, a web height of 500 mm and a flange width of 500 mm.
  • an H-section according to the present invention which uniformalizes strength within a cross section, can be obtained not only in the cases of the above-described sizes but also similarly in the cases of, for example, an H-section of heavy wall thickness having a web thickness of 40 mm, a flange thickness of 60 mm, a web height of 500 mm and a flange width of 500 mm, and an H-section of large size having a web thickness of 19 mm, a flange thickness of 37 mm, a web height of 300 mm and a flange width of 900 mm.
  • the mechanical properties of the H-sections thus produced were obtained by taking test pieces from positions at 1/4 and 1/2 (1/4B and 1/2B) of the total width (B) of a flange 2 along the center line located in the center (1/2t 2 ) of the wall thickness t 2 of the flange 2, and from a position at 1/2 (1/2H) of the height of the web along the center line located in the center of the wall thickness of a web 3, as shown in Fig. 1 .
  • 1/4B corresponds to a 1/4 flange portion, 1/2B to a fillet portion or 1/2 flange portion, and 1/2H to a 1/2 web portion.
  • Table 1 shows the results of measuring the average grain sizes of ferrite and the average rates of pearlite in the microstructures of a 1/4 flange portion, a fillet portion and a 1/2 web portion, and proportions between those values of two portions, namely a 1/4 flange portion and a fillet portion, and between those values of two portions, namely a 1/4 flange portion and a 1/2 web portion, with respect to each of the experimentally produced steels.
  • the average grain sizes of ferrite and the average rates of pearlite of the steels according to the present invention distribute in the ranges specified by the present invention, those of conventional steels (comparative steels) do not satisfy the ranges specified by the present invention and therefore desired strength or toughness has not been achieved.
  • a method of measuring the average grain sizes of ferrite and the average rates of pearlite based on microstructural observation is not specifically restricted. At least an optical microscope can be used for the observation, and when an average value is to be obtained, it is desirable to measure each value in a visual field about 0.4 mm x about 0.4 mm or larger in size within a domain in which local variations in an observed portion are judged to be sufficiently small.
  • Table 2 Major division No. Name of portion Position in Fig. 1 Frequency of large-reduction passes (time) *1 Fre-quency of passes with water cooling (time) *2 Finish rolling temperature Maximum difference in finishing temperature Total reduction ratio in the temperature range of 950 or lower Cooling rate after rolling Carbon equivalent, Nb concentration Average ferrite grain size *5 Maximum deviation Pearlite rate *5 Maximum deviation (C/s)*3 (%) *4 1 1/4 flange, 1/4F Flange: 0 0 879 37 (Less than 60%) (Natural cooling) 0.36 0.000% 10.5 12.4% 18.8% 1.6% fillet, 1/2F 900 (Less than 60%) 11.8 -2.9% 17.6% -6.4% 1/2 web 1/2W web: 0 863 (Less than 60%) 10.2 19.1% 2 1/4 flange, 1/4F Flange: 3 0 910 31 (Less than 60%) (Natural cooling) 0.30 0.000% 11.8 4.
  • Table 3 shows the results of measuring the yield strength and tensile strength of a 1/4 flange portion, a fillet portion and a 1/2 web portion, and the proportions between those values of two portions, namely a 1/4 flange portion and a fillet portion, and between those values of two portions, namely a 1/4 flange portion and a 1/2 web portion, with respect to each of the experimentally produced steels.
  • Table 3 shows the results of measuring the yield strength and tensile strength of a 1/4 flange portion, a fillet portion and a 1/2 web portion, and the proportions between those values of two portions, namely a 1/4 flange portion and a fillet portion, and between those values of two portions, namely a 1/4 flange portion and a 1/2 web portion, with respect to each of the experimentally produced steels.
  • test pieces for measuring tensile strength and yield strength is not specifically restricted, it is desirable to use at least JIS standards and a method compliant with JIS standards.
  • Table 3 Mechanical properties of respective portions in a cross section of each H-section of invented steels and conventional steels (comparative steels) Steel No. Carbon equivalent Name of portion Position in Fig.
  • the present invention makes it possible to provide an H-section having few microstructural disparities among respective portions of the H-section and having uniform mechanical properties within a cross section of the H-section.

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Claims (4)

  1. Verfahren zur Herstellung eines gewalzten H-Profils mit gleichmigen Mikrostrukturen und gleichmigen mechanischen Eigenschaften, wobei das H-Profil aus einem Gustahl mit einer chemischen Zusammensetzung, die Ceq, definiert durch die Kohlenstffquivalentformel Ceq = C + Si/24 + Mn/6 + Ni/40 + Cr/5 + Mo/4 + V/14, mit 0,15 bis 0,40 Masse-% enthlt, durch ein- oder mehrmaliges Walzen des Gustahls mit einem Walzgrad von mindestens 20 % je Stich jeweils an einem Flansch und einem Steg hergestellt wird, whrend die mittlere Temperatur entlang der Wanddicke eines Flansch- und eines Stegabschnitts im Bereich zwischen 950 und 1100 C liegt; und die Mikrostrukturen mindestens eine der folgenden Bedingungen auf der Grundlage eines 1/4-Flanschabschnitts in einem Querschnitt des H-Profils durch Anwenden von Fertigwalzen erfllen, wobei die Fertigwalztemperaturen, jeweils ausgedrckt in einer Oberflchentemperatur beim Fertigwalzen, der drei Abschnitte, d. h. eines 1/4-Flanschabschnitts, eines Kehlungsabschnitts und eines 1/2-Stegabschnitts, in einem Querschnitt des H-Profils innerhalb von 50 C variieren:
    1) die Abweichungen der mittleren Korngren von Ferrit in den Mikrostrukturen eines 1/2-Flanschabschnitts und eines Kehlungsabschnitts von der des 1/4-Flanschabschnitts liegen innerhalb von 15 %,
    2) die Abweichung der mittleren Korngre von Ferrit in der Mikrostruktur eines 1/2-Stegabschnitts von der des 1/4-Flanschabschnitts liegt innerhalb von 15 %,
    3) die Abweichungen der mittleren Raten von Perlit in den Mikrostrukturen eines 1/2-Flanschabschnitts und eines Kehlungsabschnitts von der des 1/4-Flanschabschnitts liegen innerhalb von 8 % und
    4) die Abweichung der mittleren Rate von Perlit in der Mikrostruktur eines 1/2-Stegabschnitts von der des 1/4-Flanschabschnitts liegt innerhalb von 8 %.
  2. Verfahren zur Herstellung eines gewalzten H-Profils mit gleichmigen Mikrostrukturen und gleichmigen mechanischen Eigenschaften nach Anspruch 1, wobei ein Gustahl, der Nb mit 0,005 bis 0,035 Masse-% enthlt, das der chemischen Zusammensetzung nach Anspruch 1 ferner zugegeben ist, mit einem Gesamtwalzgrad von mindestens 60 % jeweils an einem Flanschabschnitt und einem Stegabschnitt fertiggewalzt wird, whrend die Temperatur der Oberflche des Stahlmaterials hchstens 950 C betrgt.
  3. Verfahren zur Herstellung eines gewalzten H-Profils mit gleichmigen Mikrostrukturen und gleichmigen mechanischen Eigenschaften nach Anspruch 1 oder 2, wobei das Walzen durch Anwenden, von Fertigwalzen durchgefhrt wird, whrend jede der Fertigwalztemperaturen der drei Abschnitte, d. h. eines 1/4-Flanschabschnitts, eines Kehlungsabschnitts und eines 1/2-Stegabschnitts, im Bereich von 650 C bis 860 C liegt.
  4. Verfahren zur Herstellung eines gewalzten H-Profils mit gleichmigen Mikrostrukturen und gleichmigen mechanischen Eigenschaften nach Anspruch 2 oder 3, wobei die Herstellung durch weiteres Anwenden eines der folgenden beiden Prozesse oder ihrer Kombination durchgefhrt wird:
    1) einer Prozegruppe, wobei der Abkhlungsproze eines Flanschs auf eine Oberflchenschichttemperatur von hchstens 750 C durch Wasserkhlung des Flanschs zwischen den Stichen von Reversierwalzen in einem Zwischenwalzproze und Walzen des Materials im Verlauf von Wrmerckgewinnung zwischen den Stichen des Reversierwalzens einmal oder mehrmals angewendet wird, und
    2) eines Prozesses der Anwendung einer beschleunigten Wasserkhlung mit einer mittleren Abkhlungsgeschwindigkeit von 0,5 bis 10 C/s in der Zeitspanne nach dem Walzabschlu im Fertigwalzproze, bis eine Temperatur 500 C erreicht (ist hierbei der Proze 2) nicht eingeschlossen, kommt natrliche Abkhlung auf 500 C nach dem Abschlu des Walzens zum Einsatz).
EP01919779A 2000-04-04 2001-04-04 Herstellungsverfahren für gewalzte h-profilstahl mit gleichmässiger mikrostruktur und mechanischeneigenschaften Expired - Lifetime EP1281777B1 (de)

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JP2005059032A (ja) * 2003-08-08 2005-03-10 Jfe Steel Kk 狭フランジ幅ｈ形鋼の圧延方法
JP4954507B2 (ja) * 2004-07-28 2012-06-20 新日本製鐵株式会社 耐火性に優れたｈ形鋼およびその製造方法
WO2008100292A2 (en) 2006-10-16 2008-08-21 Genelux Corporation Modified vaccinia virus strains for use in diagnostic and therapeutic methods
JP5565531B2 (ja) 2011-12-15 2014-08-06 新日鐵住金株式会社 高強度極厚ｈ形鋼
CN102644035B (zh) * 2012-04-17 2013-11-06 马钢(集团)控股有限公司 一种屈服强度460MPa级高耐候性热轧H型钢轧后冷却方法
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EP2975149B1 (de) 2013-03-14 2019-05-01 Nippon Steel & Sumitomo Metal Corporation H-förmiger stahl und verfahren zur herstellung davon
CN103834861A (zh) * 2014-03-20 2014-06-04 莱芜钢铁集团有限公司 一种320MPa级耐低温热轧H型钢及其制备方法
CN104004957B (zh) * 2014-06-12 2016-03-02 莱芜钢铁集团有限公司 利用氧化物冶金技术生产小压缩比低温用h型钢的方法
CA3054279A1 (en) 2017-03-15 2018-09-20 Nippon Steel Corporation H-section steel and method of producing the same
JP2022074057A (ja) * 2020-10-29 2022-05-17 Ｊｆｅスチール株式会社 突起付きｈ形鋼およびその製造方法

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JP4231226B2 (ja) 2009-02-25

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