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
  • 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
  • C21D8/0205—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys
• • 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
  • C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
• • 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
  • C22C38/008—Ferrous alloys, e.g. steel alloys containing tin
• • 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
  • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
• • 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
  • C22C38/08—Ferrous alloys, e.g. steel alloys containing nickel
• • 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
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
• • 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
  • C22C38/16—Ferrous alloys, e.g. steel alloys containing copper

Definitions

• the present invention relates to a refractory steel used for a structural member of a building and a method for manufacturing the same.
• the present applicant has previously proposed a low-yield ratio steel for construction with excellent fire resistance and a steel material, as well as a method for producing the same, in Japanese Patent Laid-Open No. 2-775 2 3. .
• the gist of the prior invention is that Mo and Nb are added to improve the high-temperature strength so that the yield point at 600 ° C. is 70% or more at normal temperature.
• the design high-temperature strength of steel was set to 600 ° C based on the knowledge that it is the most economical because of the balance between the increase in steel costs due to alloying elements and the resulting cost of fireproof coating.
• This developed H-section steel has a low carbon-bearing structure by low carbonization and addition of trace amounts of Nb, B, and Cu, and the proof strength at 600 ° C is 2/3 of the 440MPa resistance at room temperature of 590MPa class standard High temperature over 293MPa It is characterized by making. (The resistance refers to the yield point when the yield point is clear, and to 0.2% resistance when the yield point is not clear.)
• JP-A-9-1 3 7 2 1 8 discloses Mo, Cu , H-section steel for building structures is disclosed in which quality variation is reduced by adding Ni.
• Japanese Patent Application Laid-Open No. 10-0 7 2 6 2 0 discloses a method for producing H-section steel with less material variation and excellent weldability. Disclosure of the invention
• the present inventors tried to apply the steel material produced by the above-mentioned prior application technique to various shaped steels, in particular, H-shaped steel materials having severe rolling restrictions from complex shapes.
• the structure due to differences in rolling finish temperature, reduction ratio, and cooling rate at each part of the web, flange, and fillet, the structure, particularly the bait ratio, varies greatly depending on the steel part.
• ductility and toughness varied, and there were parts that did not meet the criteria such as rolled steel for welded structures (JISG 3 106).
• the steel materials manufactured according to Patent Document 2 and Patent Document 3 described above had surface flaws due to high-temperature cracking due to Cu or poor fire resistance.
• the present invention has been made in view of such circumstances, and its purpose is to have excellent fire resistance capable of exhibiting a resistance of 60% or more at room temperature even at 600 ° C with less variation in materials. It is to provide steel and its manufacturing method.
• the present inventors conducted research, and in particular, the addition of Cu is effective in improving Cu resistance at 600 ° C because Cu, which had been dissolved at room temperature, precipitates in the steel structure at high temperature.
• suppression of hot cracking caused by Cu addition As a result, it was found that if too much Ni was added as a control, Cu was difficult to precipitate at high temperatures, and the resistance to copper due to Cu precipitation could not be sufficiently achieved.
• Cu was added by adding Ni so that the mass ratio of Ni / Cu was 0.6 or more and 0.9 or less, while Cu was contained by 0.7% to 2.0% by mass. We have obtained knowledge that we can enjoy a good balance between the suppression of hot cracking and the improvement of resistance to Cu deposition.
• the present invention is, in mass%, C: 0.01 to 0.03%, Mn: 0.1 to 1.7%, Si: 0.5% or less, Cu: 0.7 to 2%, o: 0.8% or less, Nb: 0.01 to 0.3%, Ti: 0.005-0.03%, N: 0.006% or less, B: 0.0003-0.003%, V: 0.2% or less, Cr: 1% or less, A1: 0.1% or less, P: 0.03% or less, S: 0.02%
• Ni is contained, and NiZCu is 0.6 or more and 0.9 or less by mass ratio, the balance is made of Fe and inevitable impurities, and the yield strength at 600 ° C is 6 of the yield strength at 21 ° C.
• a refractory steel characterized by being 0% or more. Note that the resistance refers to the yield point when the yield point is clear, and 0.2% resistance when the yield point is not clear.
• This refractory steel material contains, in mass%, one or more of Ca: 0.0005 to 0.005%, Mg: 0.0005 to 0.01%, REM: 0.0005 to 0.01%, and the balance May be composed of Fe and inevitable impurities.
• this refractory steel is, for example, a shape steel.
• the present invention is, by mass%, C: 0.01 to 0.03%, Mn: 0.2 to 1.7%, Si: 0.5% or less, Cu: 0.7 to 2%, Mo: 0.8% or less, Nb: 0.01 to 0.3%, Ti: 0.005-0.03%, ⁇ : -'0.006% or less,.: 0.0003-0.003%, V: 0.2% or less, Cr: 1% or less, A1: 0.1% or less, P: 0.03% or less , S: 0.02% or less, and NiZCu is contained in a mass ratio of 0.6 or more and 0.9 or less, and the balance is made of Fe and inevitable impurities.
• Rolling is started after heating to the temperature range, and after the end of rolling, the temperature range from 800 ° C to 500 ° C is cooled at an average cooling rate of 0.1 ° CZs or more.
• a method for producing a refractory steel material is provided.
• This production method contains, by mass%, Ca: 0.0005 to 0.005%, Mg: 0.0005 to 0.01%, REM: 0.0005 to 0.01%, and the balance Rolling was started after heating a piece of Fe and inevitable impurities to a temperature range of 1200-1350, and after the end of rolling, the temperature range of 800 ° C-500 ° C averaged 0.1 l ° CZ s or more. It may be cooled at a cooling rate. Moreover, this manufacturing method may manufacture a shape steel, for example by rolling.
• FIG. 1 is an explanatory view of a rolling apparatus used in an embodiment of the present invention.
• Fig. 2 is a cross-sectional view of the H-section steel showing the sampling position of the mechanical specimen.
• Fig. 3 shows the Ni / Cu ratio and the resistance to heat (high temperature PS) at 600 ° C.
• the high-temperature strength of steel is almost the same as the strengthening mechanism at room temperature below 700 ° C, which is approximately 1/2 the melting point of iron.
• Ferrite, crystal grain size refinement 2. Depending on alloying elements It is governed by solid solution strengthening, 3. dispersion strengthening by hardened phase, and 4. precipitation strengthening by fine precipitates.
• the increase in high-temperature strength is achieved by increasing the softening resistance at high temperatures by strengthening precipitation and suppressing the disappearance of dislocations by adding Mo and Cr. Only However, low carbon bainitic steels with a carbon content of over 0.03% produced island martensite and the low temperature toughness significantly decreased, resulting in non-standard sites.
• C is added to strengthen the steel. If it is less than 0.01%, the strength required for structural steel cannot be obtained. Moreover, excessive addition exceeding 0.03% generates island-shaped martensite between the Baynai trusses and significantly lowers the base metal toughness, so the lower limit was set to 0.01% and the upper limit was set to 0.03%.
• Mn Mn requires 0.2% or more of addition to ensure the strength and toughness of the base metal, but the upper limit is set to 1.7% within the allowable range of toughness and cracking of the weld.
• Si is necessary for securing the strength of the base metal and preliminary deoxidation of the molten steel, but when it exceeds 0.5%, it forms high carbon island martensite with a hardened structure in the structure of the heat affected zone, and welding In order to reduce joint toughness, the upper limit of Si content was limited to 0.5% or less. Si is not necessarily contained. It's okay.
• Mo is an element effective for securing the base metal strength and high-temperature strength. However, if it exceeds 0.8%, the hardenability increases too much, and the toughness of the base metal and the weld heat affected zone deteriorates. Restricted to. Note that Mo is not necessarily contained.
• Cu lowers the transformation point and increases the room temperature strength. Furthermore, Cu that was not precipitated in the Paynite transformation and became supersaturated was dissolved in the structure at room temperature, and the Cu phase was precipitated on the dislocations introduced by the Paynite transformation when heated to 600 ° C as the refractory steel. The precipitation hardening of the base metal is increased by the precipitation hardening. However, if the Cu phase precipitation in ⁇ is less than 0.7%, it is within the solid solubility limit of Cu in a, and no precipitation occurs, so the above-mentioned strengthening cannot be obtained. If it exceeds 2%, the precipitation strengthening is saturated and the toughness is lowered. Therefore, Cu is limited to 0.7-2%.
• Nb is formed by forming Nb carbonitride (, fixing N and suppressing the formation of boron carbonitride and boron compounds that promote nucleation of ferrite, and keep B in a solid solution state.
• solid solution Nb delays the grain growth of ferai cocoon due to the drag effect, it keeps the untransformed a to the bainitic transformation point even at a relatively slow cooling rate, and stably produces bait.
• the solid solution Nb becomes a hindrance to dislocation migration at high temperature due to the drag effect, and contributes to securing high temperature strength, so to improve high temperature strength, 0..05
• the effect is saturated when it exceeds 0.3%, it is limited to 0.3% or less from the viewpoint of economy.
• N produced B nitride and promoted the formation of ferrite, so the N content was limited to 0.006% or less.
• A1 is added to deoxidize molten steel and fix N as A1N. If it exceeds 0.1%, alumina is produced and fatigue strength is reduced. To bring it down, it was set to 0.1 or less. A1 is not necessarily contained.
• Ti is added to reduce solid solution N by precipitation of TiN and to suppress precipitation of BN by fine grain refinement, increase the amount of solid solution B and enhance the hardenability of B. is there. This increases the normal temperature and high temperature strength. Therefore, if the amount is less than 0.005%, the amount of TiN deposited is insufficient, and these effects are not exhibited. Therefore, the lower limit of the amount of Ti is set to 0.005%. However, if it exceeds 0.03%, excessive Ti precipitates TiC, and its precipitation hardening deteriorates the toughness of the base metal and weld heat affected zone, so it was limited to 0.03% or less.
• B is added in a small amount to increase hardenability and contribute to strength increase. However, if it is less than 0.0003%, the effect is not sufficient, and if it exceeds 0.003%, iron boron compounds are produced and hardenability is reduced. Therefore, the B content was limited to 0.0003 to 0.03%.
• Ni needs to contain Ni with a Ni-ZCu ratio of 0.6 or more to prevent hot cracks during rolling due to the addition of Cu. On the other hand, Ni increases the solid solubility limit of Cu and decreases the amount of Cu precipitation. To ensure high-temperature strength, Ni has a Ni / Cu ratio of 0.9 or less.
• Cr Cr is effective in strengthening the base metal by improving hardenability. However, excessive addition exceeding 1% is harmful from the viewpoint of toughness and curability, so the upper limit was made 1%. Note that Cr is not necessarily contained.
• V can refine the rolling structure by adding a small amount, and strengthen it by precipitation of V carbonitride, so that it can be alloyed and weld characteristics can be improved.
• V the upper limit of the content was set to V: 0.2%.
• V does not necessarily have to be contained.
• Mg Mg is preferably added for the purpose of finely dispersing inclusions by refining oxides and forming sulfides. The reason for limiting the amount of Mg to 0.0005% to 0.01% is that Mg is a strong deoxidizing element, and the crystallized Mg oxide is easily levitated and separated in the molten steel.
• the Mg alloys used for adding Mg are, for example, S i -Mg and N i -Mg.
• the reason for using the Mg alloy is to reduce the Mg concentration by alloying, to suppress the reaction during the formation of Mg oxide, to ensure safety during addition and to increase the yield of Mg.
• Ca, REM Ca and REM are preferably added to control the shape of the sulfide and oxide.
• C a 0.005% to 0.005%
• REM 0.005% to 0.001% is limited to below the lower limit, because these elements do not produce enough sulfides and oxides. Above the upper limit, the oxide was coarsened, resulting in a reduction in toughness and ductility.
• the amount of P and S contained as inevitable impurities is not particularly limited, but they should be reduced as much as possible because they cause weld cracking and toughness reduction due to solidification segregation. Desirably, the amount of P is 0.03% or less, S The amount is less than 0.02%.
• a piece having the above composition is heated so that the surface temperature is in a temperature range of 1200 to 1350 ° C.
• the reason for limiting the heating temperature to this temperature range is that the production of shape steel by hot working requires heating at 1200 ° C or higher in order to facilitate plastic deformation, and elements such as V and Nb are sufficient.
• the lower limit of the heating temperature was set to 1200 ° C because it must be dissolved.
• the upper limit was set to 1350 due to the performance and economy of the furnace.
• the average cooling rate in the temperature range of 800 to 500 ° C was set to 0.1 l ° CZ s or more in order to ensure a sufficient bainitic structure during cooling and to increase the amount of dissolved Cu as much as possible. .
• the refractory steel material of the present invention produced in this way is supersaturated with almost no Cu precipitation in the Paynite transformation due to the alloy design by adding a small amount of Nb and B and adding high Cu.
• this is heated to 600 ° C, Cu that has been dissolved at room temperature precipitates in the steel structure, and the resistance to heat at 600 ° C can be improved.
• the refractory steel material of the present invention has excellent fire resistance capable of exhibiting a resistance of 60% or more at room temperature even at 600 ° C.
• the fire-resistant steel materials of the present invention are: H-shaped steel, I-shaped steel, angle-shaped steel, groove-shaped steel, unequal-sided unequal thick angle-shaped steel, etc. that are suitably used for structural members of buildings, It is embodied as a steel plate such as a thick plate.
• a steel plate such as a thick plate.
• the web, flange, and fillet of It shows almost uniform mechanical properties at each part, and it has sufficient strength and toughness even at a flange plate thickness of 1/2 part and a width of 1 Z 2 part, which are the most difficult to guarantee mechanical test characteristics of H-section steel.
• the raw material was melted in the converter, the alloy was added, then Ti and B were added, and the steel was forged into 240-300 mm thick pieces by continuous forging.
• the cooling of the piece was controlled by selecting the amount of water in the secondary cooling zone below the mold and the drawing speed of the piece.
• Table 1 shows the chemical composition values of each steel type used in the examples. Steel types 1 to 17 are within the scope of the present invention, and steel types 18 to 38 are comparative steels outside the scope of the present invention.
• the steel pieces shown in Table 1 were heated to 1300 ° C, and in the universal rolling mill row shown in Fig. 1, the material to be rolled 5 (slab) from the heating furnace 1 was rough rolled 2, intermediate rolling Machine 3 and finish rolling mill 4 were passed in this order, and rolled into an H-section steel (H458x417x30x50) having an H-shaped cross section consisting of a web 6 and a pair of flanges 7 as shown in FIG. It is well known that the rolling heating temperature is set to 1300 ° C. In general, lowering the heating temperature reduces the grain size and improves the mechanical properties. This is because it was judged that this value can represent the characteristics at heating temperatures below that value.
• Table 2 shows the mechanical test characteristics of H-shaped steels manufactured from each steel grade. 0.2% resistance to 600 ° C (600 ° CPS (MPa)), resistance to resistance at room temperature (21 ° C) (yield point) Stress YP (MPa)) and tensile strength (TS (MPa)), 0.2% resistance at 600 ° C (600 ° CPS) and _ resistance at normal temperature (21 ° C) (yield point stress YP) Ratio of
• the tensile strength TS at room temperature (21 ° C) is 590MPa or higher
• the resistance (YP) is 440MPa or higher
• each H-section steel manufactured with steel types 1 to 17 within the scope of the present invention could clear the above acceptance criteria.
• steel grades 1 ⁇ 8 to 3 8 (comparative steel) outside the scope of the present invention partially satisfy the above acceptance criteria. I could't do it.
• the steel types 2 7 and 28 having a Ni / Cu ratio exceeding 0.9 had a yield strength at 600 ° C of less than 60% of the yield strength at 21 ° C.
• the steel types 25 and 26 with a Ni / Cu ratio of less than 0.6 experienced high-temperature cracking flaws during rolling.
• Fig. 3 shows the range of the present invention (optimal range) defined by the ratio (in this invention, .60% or more).
• Steel types 2 7 and 2 8 and steel types 2 5 and 2 6 that are outside the scope of the present invention are shown in FIG.
• Table 3 shows the mechanical test characteristics of steel type 2 in Table 1 when the average cooling rate in the temperature range from 800 to 500 ° C is changed after rolling. After the end of rolling, all of the test pieces 1 to 3 having an average cooling rate in the temperature range of 800 to 500 ° C of 0.1 ° C / s or more were able to clear the above acceptance criteria. On the other hand, for the test piece 4 of the comparative example in which the average cooling rate in the temperature range of 800 to 500 C after rolling is less than 0.1 l ⁇ / s, the cooling rate is too low. Prior to the vein transformation, a large amount of microstructure was generated, so the yield ratio was lowered and the acceptance criteria were not satisfied.
• Each H-section steel within the scope of the present invention has sufficient room temperature and high temperature even when the flange plate thickness is 1/2 and the width is 1/2, which is the most difficult to guarantee the mechanical test characteristics of the rolled shape steel. It was strong and had excellent fire resistance and toughness.
• the rolled steel materials targeted by the present invention are not limited to the H-section steels of the above-mentioned examples, but are not limited to I-section steel, angle steel, channel steel, unequal sides.
• the present invention can also be applied to various types of steel such as equal thickness angle steel, and steel plates such as thick plates. Industrial applicability
• the present invention can be used for, for example, a fire-resistant steel used for a structural member of a building.

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• Physics & Mathematics (AREA)
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• Crystallography & Structural Chemistry (AREA)
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• 2006
  • 2006-04-24 JP JP2006118826A patent/JP5098210B2/ja not_active Expired - Fee Related
  • 2006-04-28 KR KR1020077025349A patent/KR20070116686A/ko active Application Filing
  • 2006-04-28 KR KR1020107007869A patent/KR20100046068A/ko not_active Application Discontinuation
  • 2006-04-28 EP EP06746178.0A patent/EP1878810B1/de not_active Ceased
  • 2006-04-28 WO PCT/JP2006/309347 patent/WO2006118339A1/ja active Application Filing
  • 2006-04-28 US US11/919,781 patent/US20090087335A1/en not_active Abandoned
  • 2006-04-28 CN CN2006800151857A patent/CN101171354B/zh not_active Expired - Fee Related

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