Classifications

• • 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
  • 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
  • C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
  • C21D1/06—Surface hardening
• • 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
  • C21D8/04—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing
  • C21D8/0421—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing characterised by the working steps
  • C21D8/0426—Hot rolling
• • 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
  • C21D8/04—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing
  • C21D8/0447—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing characterised by the heat treatment
  • C21D8/0457—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing characterised by the heat treatment with diffusion of elements, e.g. decarburising, nitriding
• • 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
  • C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
  • C21D9/48—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals deep-drawing sheets
• • 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
  • C22C38/004—Very low carbon steels, i.e. having a carbon content of less than 0,01%
• • 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
  • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
• • 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
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
  • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
  • C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
• • 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
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
  • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
  • C22C38/48—Ferrous alloys, e.g. steel alloys containing chromium with nickel with niobium or tantalum
• • 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
  • C22C38/60—Ferrous alloys, e.g. steel alloys containing lead, selenium, tellurium, or antimony, or more than 0.04% by weight of sulfur
• • 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
  • B21B1/40—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 foils which present special problems, e.g. because of thinness
• • 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
  • C21D2201/00—Treatment for obtaining particular effects
  • C21D2201/05—Grain orientation
• • 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
  • C21D2211/00—Microstructure comprising significant phases
  • C21D2211/004—Dispersions; Precipitations
• • 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
  • C21D2211/00—Microstructure comprising significant phases
  • C21D2211/005—Ferrite
• • 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
  • C21D8/04—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing
  • C21D8/0421—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing characterised by the working steps
  • C21D8/0436—Cold rolling
• • 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
  • C21D8/04—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing
  • C21D8/0421—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing characterised by the working steps
  • C21D8/0442—Flattening; Dressing; Flexing

Definitions

• the present invention relates to a thin steel plate having a thickness of 0.400 mm or less, including a surface-treated steel plate used for electrical equipment, electronic parts, building materials and metal containers, and a method for producing the same.
• Thin steel plates with a thickness of 0.400mm or less are used in various applications such as electrical equipment, electronic parts, building materials and metal containers. Sheer ⁇ is progressing. As the material becomes thinner, the strength of the material that uses it will also decrease, so it is generally required to make the material thinner and harder.
• One of the problems that manifests itself with such ultra-thin hard materials is deterioration of workability. Compared to thick materials used for automobiles, thin materials in particular tend to break immediately when constriction occurs, so uniform deformation is extremely important. This means that in the tensile test that is generally applied as an evaluation of the steel sheet properties, it is hardened without reducing the uniform elongation.
• Patent Documents 1 to 3 have been disclosed in order to ensure workability particularly in steel plates for containers in which severe processing such as drawing, ironing, and tensile elongation is performed.
• Patent Document 1 JP-A-2-118026
• Patent Document 2 JP-A-3-257123
• Patent Document 3 Japanese Patent Laid-Open No. 10-72640
• An object of the present invention is to prevent breakage and constriction due to lack of uniform deformability, which are problems when using a hard ultrathin material.
• uniform elongation is ensured by giving priority to the degradation of local elongation in the degradation of elongation due to the hardening of the material, and even when the total elongation is the same, the occurrence of local deformation (necking) is suppressed to a higher strain range. It is an issue.
• An object of the present invention is to clarify the material conditions for this purpose, and to provide a steel sheet to which the material conditions are applied and a method for manufacturing the steel sheet.
• the present inventors conducted research to disperse various second phases in the steel sheet.
• the parent phase is an Fe ferrite phase, and the orientation of the second phase is arranged in a specific direction relative to the parent phase.
• the second phase having an average major axis Z average minor axis ⁇ 2.0 of 0.05 / zm or more is contained in a volume fraction of 0.05% or more.
• the hard ultrathin steel sheet according to (1) wherein the average major axis is 0.5 m or more, the average minor axis is not less than 0.0, and the average major axis Z average minor axis ⁇ 2.0.
• the two phases are simple substances or composite compounds of oxides, sulfides, carbides, nitrides, and intermetallic compounds.
• the hard ultrathin steel sheet according to (7) above having an average major axis of 0.5 ⁇ m or more and an average minor axis of 0 or more, and further, an average major axis Z an average minor axis ⁇ 2.
• the second phase which is 0 is an oxide containing one or two of Fe, Mn, Si, Al, Cr, REM, Ti and Nb.
• the second phase is a sulfide containing one or two of Ti, Mn, Cu, Ca, and REM.
• the second phase having a minor axis of 0.1 ⁇ m or more and an average major axis Z average minor axis ⁇ 2.0 is a carbide containing one or two of Fe, Ti, Nb, Si, and Cr.
• the hard ultrathin steel sheet according to (7) above having an average major axis of 0.5 m or more and an average minor axis of 0.1 ⁇ m or more, and an average major axis Z average minor axis ⁇ 2.
• the second phase which is 0 is a nitride containing one or two of Fe, Ti, Nb, Al, B and Cr.
• the hard ultra-thin steel sheet described in (7) above having an average major axis of 0.5 ⁇ m or more and an average minor axis of 0.1 ⁇ m or more, and an average major axis Z average minor axis ⁇ 2.
• the second phase that is 0 is an intermetallic compound containing one or two of Fe, Ti, Nb, Al, Si, and Mn.
• (21) A method for producing a hard ultrathin steel sheet according to (11) above, wherein after cold rolling, simultaneously with or after recrystallization annealing, in a temperature range of 600 to 700 ° C, ⁇ (nitriding time (Second)) * (nitridation temperature (° C)) ⁇ Z ⁇ (nitriding gas concentration (%))) * (cooling rate during nitriding (° CZ seconds)) ⁇ ⁇ 20 And increase the amount of N by more than 0.0002%.
• the present invention relates to a thin steel plate having a thickness of 0.400 mm or less and a method for producing the thin steel plate.
• a method for producing a part of the enameled steel plate a heat treatment is used to control the form of oxide.
• the oxide stretching in the present invention is completely different from the oxide stretch as a limitation of hot rolling conditions in the enameled steel sheet. Furthermore, as an extension technique for limiting the hot rolling conditions in enameled steel sheets, it has been extremely difficult to obtain the idea of using drawn oxides in the thin steel sheets targeted by the steel of the present invention. These are described in detail below.
• the content of acid oxide is suppressed as being extremely undesirable. This is because the base material itself is becoming thinner, and the deformation concentration around the oxide is very sensitive to the fracture of the base material.
• a prominent example is the flange formability in the can making process, and the steel used in this application is manufactured at a very low level, with the amount of oxide strictly controlled.
• the negative effect of the acid on thin materials is not limited to the acid itself, but if the drawn oxide like the enamel steel plate is crushed in the cold rolling process and voids are formed around it. In addition, the void exhibits an effect like a notch, and the deformability of the base material further deteriorates.
• the thin material targeted by the steel of the present invention has the idea of improving its properties by utilizing oxides and, moreover, stretched oxides that are crushed by cold rolling to form voids around them. That itself was impossible in the past.
• oxides are temporarily stretched during the hot rolling stage, but in the subsequent cold rolling process, the oxides are crushed and a large amount of empty space around the crushed acidic products. This is to create gaps, and in the final product, each acid product is isotropically crushed.
• the acid oxide is stretched at the final stage, and as one proposal, a hot rolling process is used.
• the oxide stretched by hot rolling remains stretched without being crushed after cold rolling and annealing, and it is necessary to maintain an anisotropic shape until the final product.
• This difference is basically caused by the difference in the composition of the oxide if the hot rolling conditions are the same.
• enameled steel plates are preferably combined with a relatively soft Mn-containing oxide and hard Nb and B-containing oxides to promote crushing.
• the oxide is uniform rather than a composite of oxides having different compositions, so that deformation during cold rolling is uniform and fracture is avoided.
• the steel of the present invention is held with the oxide stretched in a specific form, its work hardening behavior changes dramatically, and local deformation is strongly suppressed, so that even a thin steel plate has practical ductility. It was newly discovered and invented that it acts preferably.
• FIG. 1 is a diagram for explaining a portion of a hard ultrathin steel plate according to the present invention in the thickness direction of the steel plate.
• the C amount is set to C: 0.800% or less in order to avoid deterioration of workability. Preferably it is 0.100% or less, more preferably 0.060% or less.
• the content is preferably 0.0050 to 0.040%, more preferably 0.0008 to 0.030%.
• the C content required from the viewpoint of securing the strength may be low.
• the N content is set to C: 0.800% or less in order to avoid deterioration of workability. Preferably it is 0.100% or less, more preferably 0.060% or less.
• the content is preferably 0.0050 to 0.040%, more preferably 0.0008 to 0.030%.
• the N content required from the viewpoint of securing the strength may be low.
• N Necessary strength can be ensured even if it is 0.0050% or less, 0.0030% or less may be sufficient, and 0.0015% or less is also possible. In order to improve the r value and maintain high drawability, the N amount is The lower one is preferable.
• Si may need to be 1.5% or less, and further 1.0% or less.
• Si content is low. 0.5% or less, further 0.1% or less, and further 0.07% or less improves the moldability.
• the preferable range of Mn is 0.05-: L 0%. More preferably, it is 0.15 to 0.8%, and more preferably 0.25 to 0.7%.
• the content is set to 0.10% or less to inhibit the carburizing and nitriding properties of the steel sheet. In order to keep the moldability high, a lower P content is preferable. 0.05% or less, and even 0.01% or less improves moldability.
• S degrades hot ductility and becomes a hindering factor for hot rolling, so it is made 0.10% or less.
• Mn, Cu, Ti, REM, etc. when a large amount of Mn, Cu, Ti, REM, etc. is added and these sulfides are used as the second phase required in the present invention, a useful element with little deterioration in hot ductility is used. But there is. Therefore, the preferable range of S is set to 0.015 to 0.080%. More preferably, it is 0.025 to 0.070%, and more preferably 0.035 to 0.060%.
• A1 is high, forging is difficult and surface wrinkles increase.
• A1 is a strong deoxidizing element, when using an oxide as the second phase in the steel of the present invention, it is difficult for oxygen to remain in the steel.
• it may be necessary to make the value 0.005% or less, 0.002% or less, and 0.001% or less.
• Force depending on the type and amount of metal elements that form a compound with A1 In this case, it is preferably 1.0% or more, more preferably 1.5% or more, and even more preferably 2.0% or more.
• O does not use an oxide as the second phase characteristic of the present invention.
• it is preferably deoxidized with Al, Si, Ti, or the like to 0.010% or less. . This is because if the oxide in the steel has no effect on the effect of the present invention and becomes isotropic (spherical), it is easy to start a crack. Even when an oxide is used as a useful second phase, an excess of the oxide tends to cause cracking, so the content is made 0.20% or less.
• it is 0.010-0.100%, More preferably, it is 0.020-0.080%, More preferably, it is 0.030-0.050%.
• Ti raises the recrystallization temperature of the steel sheet, and significantly deteriorates the annealability of the ultrathin steel sheet which is the subject of the present invention. For this reason, it will be 4.00% or less.
• a Ti compound is not used as the second phase, which is a feature of the present invention, it is not necessary to add Ti, and the content is made 0.04% or less, more preferably 0.01% or less.
• Ti oxides, sulfides, carbides, nitrides, and intermetallic compounds can be used as the second phase characteristic of the present invention, and depending on the type and amount of elements forming the compound, 0.06 If it is more than%, the effect is fully exhibited. More preferably, it is 0.100% or more.
• Nb has the same effect as Ti, raises the recrystallization temperature, and remarkably deteriorates the annealability of the ultrathin steel sheet targeted by the present invention. For this reason, it shall be 4.00% or less.
• Nb compound is not used as the second phase, which is a feature of the present invention, it is not necessary to add Nb, and the content is made 0.04% or less, more preferably 0.01% or less.
• oxides, sulfides, carbides, nitrides, and intermetallic compounds of Nb can be used as the second phase that is characteristic of the present invention, and depending on the type and amount of elements forming the compound, 0 The effect is fully demonstrated when it is over 06%. More preferably, it is 0.100% or more.
• REM is a powerful element that has the same effect as Ti and Nb. To do.
• the REM compound is not used as the second phase, which is a feature of the present invention, it is not necessary to add REM, and the content is made 0.04% or less, more preferably 0.01% or less.
• REM oxides, sulfides, carbides, nitrides, and intermetallic compounds can be used as the second phase that is characteristic of the present invention, and depending on the type and amount of elements forming the compound, 0 If the value is 06% or more, the effect will be fully exerted. More preferably, it is 0.100% or more.
• [0030] B also has the same effect as Ti and Nb.
• the strength depending on the amount of addition When Ti and Nb are added at the same time as these elements for the purpose of forming carbides and nitrides as the second phase, the ability to form carbonitrides is small compared to Ti and Nb.
• the recrystallization temperature of the steel sheet is increased, and the annealing passability of the ultrathin steel sheet targeted by the present invention is significantly deteriorated. Therefore, it is useful when the content of Ti and Nb is low.
• the upper limit is set to 0.0300%.
• the B compound When the B compound is not used as the second phase, which is a feature of the present invention, it is not necessary to add B, and it is 0.0010% or less, more preferably 0.0010% or less.
• the oxides, carbides, nitrides, and intermetallic compounds of B can be used as the second phase that is characteristic of the present invention, and the force depending on the type and amount of the elements forming the compound is 0.0040% or more. The effect is fully demonstrated. More preferably, it is 0.0100% or more.
• the recrystallization temperature will rise remarkably and the surface properties will be deteriorated by force, and workability and plating properties will deteriorate.
• a metallic Cu phase or an intermetallic compound phase can be used as the second phase.
• the preferable range is set to 0.10 to 4.00%. More preferably, it is 0.20 to 3.00%, and more preferably 0.30 to 2.50%.
• Ca is a useful element because it is easy to obtain a stretched sulfide when a sulfide is used as the second phase.
• a preferable range is 0.01 to 0.50%. More preferably, it is 0.05 to 30%.
• Ni is an expensive element and should be 8.00% or less.
• intermetalization such as Ni A1
• a compound forming element As a compound forming element, it has a favorable effect on the dispersion of the second phase required in the present invention. 1.0% or more, depending on the type and amount of metal elements that form a compound with Ni Is preferably 1.5% or more, more preferably 2.0% or more.
• Cr is also an expensive element and should be 20.00% or less.
• a Cr compound is not used as the second phase, which is a feature of the present invention, it is not necessary to add Cr, and it is 0.06% or less, more preferably 0.02% or less.
• Cr oxides, sulfides, carbides, nitrides, and intermetallic compounds can be used as the second phase that is characteristic of the present invention, and depending on the type and amount of elements forming the compound, 0 The effect is fully demonstrated when it is 10% or more. More preferably, it is 0.50% or more, more preferably 1.50% or more, and further preferably 2.50% or more.
• the content of the elements other than the above is not particularly limited, but Sn, Sb, Mo, Ta, V, and W are added to each element in an amount of 0.1% to 10% in order to impart characteristics not specified in the present invention.
• the total content of 0.50% or less does not impair the effects of the present invention.
• the content of each element is preferably 0.010% or less and the total is preferably 0.050% or less. More preferably, it is TO. 0020% or less for each element, the total is 0.0050% or less, more preferably 0.0010% or less for each element, and the total is 0.0003% or less.
• the second phase observation method limited in the present invention is not particularly limited.
• the form can be directly observed with a physical measuring instrument capable of observing the micro area such as an electron microscope. Observation with a high-magnification optical microscope is possible if it is relatively large.
• a physical measuring instrument capable of observing the micro area
• Observation with a high-magnification optical microscope is possible if it is relatively large.
• SEM scanning electron microscope
• TEM transmission electron microscope
• TEM transmission electron microscope
• a residue obtained by dissolving the parent phase by electrolytic extraction may be observed.
• the identification of the observed second phase is a force that can be performed by EDX or electron diffraction patterns, etc. You can use it.
• the point is that the shape, size and number density of the second phase, and if necessary, the type can be determined by a method that is recognized as appropriate. Depending on the type, it is a composite of various phases, and it may be difficult to distinguish completely.
• the effect of the present invention can be obtained by dispersing the second phase in a specific form regardless of the type, and therefore, the type of which cannot be determined is also included in the present invention. Volume fractions and number densities will increase if finer nitrides are taken into account using more sophisticated analytical instruments, but more than 0.02 m using normal level physical instruments The effect of the present invention can be discriminated if the target is of a size of.
• the average major axis is 0.10 m or more
• the average minor axis is 0.05 m or more
• the average major axis Z the average minor axis ⁇ 2.0.
• the phase is contained in a volume fraction of 0.05% or more.
• the size is preferably about 0.20 m or more with respect to the average major axis, more preferably 0.50 m or more, more preferably 1.00 m or more, more preferably 2.00 / zm or more, more preferably 5. 00 / zm or more.
• an excessively large second phase is present, it becomes the starting point of fracture at the initial stage of processing, and the ductility may be significantly deteriorated.
• the average major axis The average minor axis Z is preferably 3.0 or more, more preferably 5.0 or more, and still more preferably 8.0 or more. Further, the volume fraction is preferably 0.1% or more, more preferably 0.3% or more, further preferably 1.0% or more, and further preferably 2.0% or more. However, if the amount of the second phase is too large, it becomes a starting point of fracture at the initial stage of processing, and the ductility may be remarkably deteriorated. More preferably, it is 10% or less.
• the second phase in the present invention is harder than the Fe phase, which is the parent phase, when the steel sheet is deformed, the deformation of the parent phase occurs preferentially. Furthermore, since the deformation of the parent phase is constrained by the second phase, the work hardening of the parent phase becomes significant. For this reason, it is considered that the strain propagation is improved, the deformation continues while taking on the deformation in a wider area, and the uniform elongation becomes higher. When the anisotropic second phase is dispersed, the parent phase constraint is considered to be greater than the general isotropic second phase.
• the second phase with strong anisotropy is weakly bonded to the parent phase, and its interface slips along with the deformation, and further deforms by generating many voids. It is thought that it is. For this reason, the deformation of the base metal itself is suppressed to a higher strain region, and it is considered that the uniform deformation continues.
• the steel of the present invention has a large work hardening amount and at the same time the local deformability is often lowered, but the mechanism that can fully explain the phenomenon is not clear.
• this main phase is Fe.
• this main phase is assumed to be a ferrite phase of Fe, and its volume fraction is preferably 80% or more.
• pearlite, bainite, martensite phase, etc. are known as the phase mainly composed of Fe.
• the increase in strength is achieved by the dispersion of the second phase. This is because a soft and uniform phase is preferred from the viewpoint of workability.
• the volume ratio is preferably 85% or more, more preferably 90% or more in order to avoid ductile deterioration due to the generation of an excessive second phase.
• the orientation relationship between the second phase and the main phase is also an important requirement.
• the force mentioned in the above mechanism The effect of the present invention is related to the fact that it is considered to be due to the combined state of the Fe phase and the second phase, and the direction of the average major axis of the second phase is the Fe in contact with the second phase. It is preferred that the phase is 100> orientation or 110> orientation. This orientation relationship can be detected by ordinary electron beam diffraction. [0039] Next, the type of the second phase itself will be described. In the present invention, a remarkable effect can be obtained when the second phase is a simple substance or a composite compound of an oxide, a sulfide, a carbide, a nitride, or an intermetallic compound.
• oxide it must be an oxide containing one or two of Fe, Mn, Si, Al, Cr, REM, Ti, Nb, and in the case of oxide, Ti, Mn, Cu It is a sulfide containing one or two of Ca, REM, and in the case of carbide, it is a carbide containing one or two of Fe, Ti, Nb, Si, Cr, and nitride. In the case of a nitride containing one or two of Fe, Ti, Nb, Al, B, Cr, and in the case of an intermetallic compound, one or two of Fe, Ti, Nb, Al, Si, Mn It is an intermetallic compound containing seeds.
• the pearlite structure observed in general steels that is, the layered structure of ferrite phase and cementite formed by transformation from the austenite phase at high temperature is excluded because the effect of the present invention cannot be obtained at all.
• the transformation intermetallic compounds include NiAl, Ni Al, Ni (Al, Ti), Ni TiAl, Ni Ti, Ni Mo, Ni Mo, Ni Nb, Co W, F
• Intermetallic compounds are compounds that are generally observed in steel materials and need not be special, but it is also possible to form special compounds in a form within the scope of the invention.
• the types are not limited to the above, but only representative elements are listed.
• the present invention includes a case where two or more types of second phases existing in steel are not limited to one type. These may be present independently or may form a composite compound. Furthermore, a phase that is not included in the present invention may be present at the same time.
• the morphological characteristics of the second phase are important. However, it is true that there is a slight difference in the magnitude of the effect depending on the second phase formed. This difference depends on the type and amount of the second phase that can be generated in the steel sheet, the difference in form that can be controlled by the manufacturing conditions described later, and the second phase itself that is also related to the bonding state with the parent phase. The kind of influence is also conceivable.
• the types of preferred second phases and the elements forming the second phase can be classified as follows.
• the types are: intermetallic compounds> carbides ⁇ nitrides>oxides> sulfates. However, this is the same form and quantity This order is only an estimate, because it may be difficult to secure the quantity and control the form depending on the type of production method and the second phase. Yes.
• the following can be said as the effect of each element.
• oxides those containing Fe, Mn, and REM are preferred.
• Si, Al, Cr, Ti, and Nb are less effective.
• Mn, Ca, and REM are preferred.
• Ti and Cu are less effective.
• Thinitride distribution on the front and back sides the present invention also covers such steel sheets with different front and back layers. This is also a force that can obtain the effect of improving the uniform deformability aimed by the present invention on only one side.
• the second phase characteristic of the present invention may be unevenly distributed in the plate thickness direction, which need not be uniformly distributed as a whole when considering the distribution in the plate thickness direction of the steel plate. . Rather, it is more convenient for the effect of the present invention if a multi-layer structure can be formed alternately in layers in the thickness direction, with layers having a large number of second phases and layers having a small number of second phases. Although this mechanism is not clear, it is thought that the amount of work hardening increases and the local deformation is suppressed when the layer with a large amount of the second phase and the layer with a small amount of each other restrain the deformation of the other.
• volume fraction of the second phase (volume fraction at the plate thickness surface layer 1Z8) Z (volume fraction at the plate thickness center layer 1Z4) ⁇ 10, or
• the number density is preferably (number density in the plate thickness surface layer 1Z8) Z (number density in the plate thickness center layer 1Z4) ⁇ 10.
• the present invention is limited to being applied to a steel plate having a thickness of 0.4 OO mm or less.
• a technique limited to only uniform elongation as in the technique of the present invention does not make sense. Because it disappears.
• the present technology demonstrates its usefulness with an ultra-thin steel sheet having a thickness of preferably 0.250 mm or less, more preferably 0.200 mm or less, and even more preferably 0.150 mm or less.
• the maximum strength is ⁇ 400 MPa and the Rockwell hardness is HR30T ⁇ 57, more preferably the maximum strength is ⁇ 450 MPa and the Rockwell hardness is HR30T ⁇ 61.
• the steel of the present invention is characterized by uniform elongation Z local elongation ⁇ 1.0 in the tensile test using the JIS No. 5 test piece. This ratio is preferably 1.5 or more, more preferably 2.0 or more, further preferably 3.5 or more, and further preferably 5.0 or more. Further, as described above, the steel of the present invention is also characterized by a large amount of work hardening.
• the yield stress Z maximum strength ⁇ 0.9, more preferably 0.8 or less, more preferably 0.7 or less, and even more preferably 0.6 or less.
• One of the preferred forms is a hot rolling process in which the acid oxide is stretched by rolling into a preferred form. It is something to change. For this purpose, a certain amount of processing is required, and it is preferable that the thickness of the steel slab after completion of forging be 50 mm or more. More preferably, it is 150 mm or more. In order to make the oxide have an appropriate size after stretching, the size of the oxide before being stretched is preferably 10 m to 25 m. Too fine ones that are difficult to stretch are not preferable for the effects of the present invention because the spatial dispersion after rolling becomes linear.
• the acidic product becomes stretched, partially crushed, and the moderately acicular shaped acidic product is placed in the steel plate at an appropriate interval. Will be dispersed. In order to appropriately stretch and disperse in this way, it is also important to control the strain rate in order to control the temperature control during hot rolling, the amount of strain in each temperature range, and the softening of the work-hardened steel.
• the second The preferred form of the phase is achieved, basically by anisotropically growing the carbides sufficiently at high temperature, for a long time and under slow cooling while suppressing the formation of carbide precipitation nuclei at low C concentrations.
• C that has entered the steel from the surface of the plate reaches the center of the plate thickness due to diffusion, and the above-mentioned double phase is developed.
• the force is 500 or less, more preferably 200 or less, etc.
• the conditions of the atmosphere including the type of carburizing gas are generally known.
• the carburizing method is not limited to the gas carburizing shown here, and it is possible to apply a generally known carburizing method. An amount of 0.00002% or more is a force that seems to be very small as the amount of increase. Considering the amount of increase in the surface layer of the steel sheet in an ultrathin material, it is a sufficient amount for manifesting the effect of the invention.
• the carburizing conditions are the conditions in the case of applying nitride by nitriding as the second phase, it is possible to obtain a preferable effect similar to that of carbide. That is, after cold rolling, simultaneously with recrystallization annealing, or after that, in the temperature range of 600 to 700 ° C, ⁇ (nitriding time (seconds)) * (nitriding temperature (° C)) ⁇ Z ⁇ (nitriding gas Concentration (%)) * (Cooling rate in nitriding treatment (° CZ sec)) ⁇ nitriding is performed under the condition of ⁇ 20, and the N content is increased by more than 0.0002%
• nitriding method is not limited to the gas nitriding shown here, and a generally known nitriding method can be applied, as in the case of carburizing.
• an intermetallic compound When an intermetallic compound is used as the second phase, formation may proceed mainly by growth of the intermetallic compound by slowly cooling from a state in which all or most of the intermetallic compound is dissolved.
• Preferred in the present invention is convenient for obtaining the second phase form.
• the cooling rate from 900 ° C to 500 ° C is cooled in 20 ° CZ seconds or less in the cooling process at a temperature of 900 ° C or higher, and the intermetallic compound is reduced in volume ratio. 2. Try to increase more than 0 times. If the temperature before the start of cooling is too low, intermetallic compounds Insufficient dissolution occurs and subsequent growth does not occur. On the other hand, if the cooling rate is too fast, the nucleation frequency of intermetallic compounds increases, and anisotropic growth does not occur, and isotropic intermetallic compounds are formed in high density.
• re-rolling may be performed after recrystallization annealing in order to adjust hardness or plate thickness.
• This rolling reduction has been put to practical use from a few percent close to the skin pass used for shape adjustment to 50% or more, which is the same as cold rolling.
• the effects of the present invention are not impaired at all.
• the rolling reduction is excessively high, the absolute value of the uniform force elongation that is natural is reduced.
• the amount of work hardening in the uniform elongation region is also reduced, and this is not an inherently preferred method in view of applying the effect of the present invention.
• it is 30% or less, more preferably 20% or less, preferably 10% or less, preferably 3% or less.
• the effect of the present invention does not depend on the heat history and the manufacturing history before the annealing after the component adjustment.
• Slabs for hot rolling are not limited to manufacturing methods such as the ingot method and continuous forging method, and do not depend on the heat history until hot rolling, so the slab reheating method and the forged slab are reheated.
• the effect of the present invention can also be obtained by CC-DR method in which hot rolling is performed directly without making a thin slab without rough rolling.
• the effect of the present invention can be obtained by two-phase rolling in which the finishing temperature is ⁇ + ⁇ two-phase region or continuous hot rolling in which a rough bar is joined and rolled regardless of hot rolling conditions.
• the steel of the present invention when used as a material having a welded portion, it is particularly preferable because uniform deformation at the heat-affected zone can be improved and necking can be suppressed.
• the steel sheet of the present invention includes a case where it is used after being subjected to some surface treatment. If it is within the scope of the present invention, it is not damaged by the surface treatment by application.
• surface treatment For metal plating, tin, chromium (tin-free), Ni, zinc, aluminum, etc. are applied as usual.
• the effects of the present invention can be obtained with respect to an original sheet for a laminated steel sheet coated with an organic film that has been used in recent years.
• Average major axis The second phase satisfying the condition that the average major axis is 0.10 m or more, the average minor axis is 0.05 / zm or more, the average major axis Z the average minor axis ⁇ 2.0 The average value when measuring a sufficient number so that there is no.
• Average major axis Z Average minor axis Ratio of “average major axis” and “average minor axis”. It becomes an index indicating the degree of anisotropy of V, which is the root of the invention effect.
• “Contained element” an element detected from the second phase showing the characteristics of the present invention.
• Orientation The relationship between the direction of the average major axis of the second phase and the crystal orientation of the main phase in contact with the second phase. When the orientation is related, the crystal orientation of the main phase is indicated.
• “Flange formability” Prepare 10,000 barrels of 3-piece can body that is made by rounding a flat plate into a cylindrical shape and welding. For these, flange molding is performed using a mold. As a result, if all can flanges can be molded without breaking, it will be accepted. If even one can breaks, it will be rejected.
• Example 1 Table 2 shows the experimental results when the second phase is an oxide.
• the form of the oxide was controlled mainly by the oxide size according to the forging conditions and the stretching amount according to the hot rolling conditions.
• Acid The “number density” of the object was determined by cross-sectional observation with SEM. It can be confirmed that good uniform elongation can be obtained by controlling the state of the oxide within the range of the present invention.
• Table 3 shows the experimental results when the second phase is a sulfate.
• the form of the sulfide was controlled mainly by the sulfide size according to the forging conditions and the drawing amount by the hot rolling conditions.
• the “number density” of the sulfide was determined by TEM observation. It can be confirmed that good uniform elongation can be obtained by controlling the state of the sulfide within the range of the present invention.
• Example 3 shows the experimental results when the second phase is carbide or nitride.
• the carbide or nitride morphology was controlled primarily by carburizing or nitriding conditions.
• all the “base plates” are steel plates recrystallized and annealed at 700 ° C.
• the characteristics are also shown for a material that has been hardened to the same degree as a carburized or nitrided plate by re-rolling without carburizing and nitriding. Carbide or nitride was observed at the plate thickness 1Z8 position and the plate thickness center.
• the “number density” of carbide or nitride was determined by SEM observation of the residue when the plate thickness surface layer 1Z8 or plate thickness center layer 1Z4 was electrolyzed.
• the values related to “volume fraction”, “number density”, and main phase in the second phase in Table 4 are for the plate thickness surface layer 1Z8. It can be confirmed that good uniform elongation is obtained by controlling the state of the carbide or nitride within the range of the present invention.
• Table 5 shows the experimental results when the second phase was an intermetallic compound.
• the intermetallic compound is Ni A1, and its form is mainly the solution due to recrystallization annealing conditions, especially the annealing temperature.
• the present invention it is possible to obtain a hard ultrathin material having high uniform elongation even with the same strength and the same total elongation, and suppressing the occurrence of local deformation (necking) to a higher strain range.

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