WO2019038923A1 - Tôle d'acier résistante à l'usure présentant une excellente ténacité - Google Patents

Tôle d'acier résistante à l'usure présentant une excellente ténacité Download PDF

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WO2019038923A1
WO2019038923A1 PCT/JP2017/030614 JP2017030614W WO2019038923A1 WO 2019038923 A1 WO2019038923 A1 WO 2019038923A1 JP 2017030614 W JP2017030614 W JP 2017030614W WO 2019038923 A1 WO2019038923 A1 WO 2019038923A1
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rolling
cold rolling
annealing
carbide
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PCT/JP2017/030614
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Japanese (ja)
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大 宮脇
勝 藤原
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日新製鋼株式会社
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Priority to CN201780094374.6A priority Critical patent/CN111373064A/zh
Priority to US16/634,671 priority patent/US20200199702A1/en
Priority to PCT/JP2017/030614 priority patent/WO2019038923A1/fr
Priority to KR1020207008415A priority patent/KR20200044879A/ko
Priority to EP17922610.5A priority patent/EP3674432A4/fr
Publication of WO2019038923A1 publication Critical patent/WO2019038923A1/fr

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    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0226—Hot rolling
    • 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
    • C21D1/26—Methods of annealing
    • C21D1/30—Stress-relieving
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0236—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
    • C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
    • C21D8/0263—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment following 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
    • C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
    • C21D8/0268—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment between cold rolling steps
    • 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
    • C21D8/0421—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
    • C21D8/0447—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
    • C21D8/0473—Final recrystallisation annealing
    • 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
    • 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
    • C22C38/12—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
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
    • 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
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/50—Ferrous alloys, e.g. steel alloys containing chromium with nickel with titanium or zirconium
    • 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
    • C21D2211/006—Graphite
    • 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

Definitions

  • Wear resistance is required for automotive parts, chain parts for industrial machines, power transmission members such as gears, and blade members such as circular saws and band saws used for cutting and mowing wood.
  • the wear resistance of steel materials is improved by increasing the hardness. Therefore, steel members made hard by heat treatment such as quenching and steel materials having a high content of alloy elements such as carbon are often used for members that place importance on wear resistance. That is, the hardness and wear resistance of steel materials are in a close relationship, and conventionally, as a method for imparting wear resistance to steel materials, it is general to adopt a method of increasing hardness.
  • Patent Literatures 1 and 2 describe that the wear resistance of the steel is improved by hardening and reducing the area ratio of the ferrite phase that promotes wear in the steel for hot forging.
  • the steel targeted in these documents has a ferrite-pearlite structure, which is inferior to the ferrite-spheroidized cementite structure in toughness.
  • Patent Document 3 discloses a technique for obtaining a machine structural component that can be used without a tempering heat treatment by directly cutting a hot rolled steel material to which high strength and high toughness are imparted by refining crystal grains. ing. However, in applications requiring wear resistance, induction hardening-tempering treatment is required.
  • Patent Document 4 discloses a steel plate for a circular saw which combines wear resistance and toughness by cladding a high carbon steel coating material and a low carbon steel core material. However, a cladding process is required.
  • Patent Documents 5 and 6 disclose techniques for improving the wear resistance by using the dispersion of hard Nb-Ti carbides. These techniques are directed to a tempering material which is hardened by quenching and tempering treatment. Although high wear resistance can be obtained, further improvement is desired in terms of toughness.
  • JP 10-137888 A Japanese Patent Application Laid-Open No. 2003-201536 JP, 2011-195858, A Japanese Patent Application Laid-Open No. 60-82647 JP, 2010-138453, A JP 2013-136820 A
  • An object of the present invention is to make "abrasion resistance” and “toughness” compatible at a high level in a non-tempered material.
  • the above object is, by mass%, C: 0.60 to 1.25%, Si: 0.50% or less, Mn: 0.30 to 1.20%, P: 0.030% or less, S: 0. 030% or less, Cr: 0.30 to 1.50%, Nb: 0.10 to 0.50%, Ti: 0 to 0.50%, Mo: 0 to 0.50%, V: 0 to 0..
  • Carbide having a chemical composition consisting of 50%, Ni: 0 to 2.00%, the balance Fe and unavoidable impurities, and containing cementite particles and one or more of Nb and Ti in the metal base of the ferrite phase
  • Nb ⁇ Ti system having a metal structure in which particles of “Nb ⁇ Ti carbide” are dispersed and having a circle equivalent diameter of 0.5 ⁇ m or more in a cross section (L section) parallel to the rolling direction and the thickness direction the number density of carbide particles 3,000 to 9,000 / mm 2, the number density of the equivalent circle diameter 1.0 ⁇ m or more voids 1250 / m Is achieved by the steel plate is 2 or less.
  • Ti, Mo, V, and Ni are optional addition elements.
  • the thickness of this steel plate is, for example, 0.2 to 4.0 mm.
  • Nb-Ti-based carbide is a hard carbide containing one or two of Nb and Ti as metal elements constituting the carbide.
  • the types of Nb / Ti carbides include those based on NbC, those based on TiC, and those based on (Nb, Ti) C.
  • the present invention is directed to a steel containing a predetermined amount of Nb, and therefore, when Ti is not contained in the steel component, hard carbide of a type mainly composed of NbC is formed.
  • Such Ti-free Nb-containing hard carbides are also referred to herein as "Nb-Ti-based carbides”.
  • the steel component contains Ti
  • a type mainly composed of (Nb, Ti) C is generated, and it is considered that a type mainly composed of TiC or a type mainly composed of NbC may be mixed according to the Ti content.
  • Be Spheroidized cementite (Fe 3 C) particles also exist in the steel base. Whether or not a certain carbide is a Nb-Ti carbide can be confirmed by an analysis method such as EDX (energy dispersive fluorescent X-ray analysis).
  • Voids are existing voids between the surface of the Nb / Ti carbide particles and the steel matrix.
  • the number density of voids having an equivalent circle diameter of 1.0 ⁇ m or more can be determined as follows.
  • the observation surface obtained by polishing a cross section (L cross section) parallel to the rolling direction and the plate thickness direction is observed with a confocal laser microscope, and equivalent to a circle among voids existing adjacent to Nb ⁇ Ti carbides on the observation image Count the number of voids having a diameter of 1.0 ⁇ m or more, and divide the total number of counts by the total observation area (mm 2 ) to obtain the number density (number / mm 2 ) of voids having an equivalent diameter of 1.0 ⁇ m or more.
  • the observation area is 90 ⁇ m ⁇ 60 ⁇ m ⁇ 20 fields of view.
  • the voids partially protruding from the observation field of view are counted as long as the equivalent circle diameter of the portion appearing in the observation field of view is 1.0 ⁇ m or more.
  • the equivalent circle diameter of a certain void is the diameter of a circle equal to the area of the void on the observation image.
  • the area of the void can be measured by processing the observation image with image processing software.
  • the number density of Nb ⁇ Ti carbide particles having a circle equivalent diameter of 0.5 ⁇ m or more is more preferably 3,000 to 9,000 / mm 2 .
  • the number density of the Nb-containing carbide particles can be determined as follows.
  • a cross section (L cross section) parallel to the rolling direction and thickness direction is polished and then the etched observation surface is observed with a confocal laser microscope, and an Nb ⁇ Ti system having an equivalent circle diameter of 0.5 ⁇ m or more on the observation image
  • the number of carbide particles is counted, and the total number of counts is divided by the observed total area (mm 2 ) to obtain the number density (pieces / mm 2 ) of Nb ⁇ Ti carbide particles having a circle equivalent diameter of 0.5 ⁇ m or more.
  • the observation area is 90 ⁇ m ⁇ 60 ⁇ m ⁇ 20 fields of view.
  • the Nb / Ti-based carbide particles partially protruding from the observation field of view are counted as long as the equivalent circle diameter of the portion appearing in the observation field of view is 0.5 ⁇ m or more.
  • the equivalent circle diameter of a certain Nb-Ti carbide particle is the diameter of a circle which is equal to the area of the Nb-Ti carbide particle on the observation image.
  • the area of the Nb / Ti carbide particles can be measured by processing the observation image with image processing software.
  • the steel plate can be manufactured, for example, by the following method.
  • Process of manufacturing a slab by controlling the cooling rate to 5 to 20 ° C./min while the molten steel is cooled from the liquidus temperature to the solidus temperature (casting process) Heating and holding the slab at 1200 to 1350 ° C. for 0.5 to 4 hours (slab heating step); Hot rolling process (hot rolling process), A step of applying annealing to the hot rolled steel sheet obtained in the hot rolling step for 10 to 50 hours after holding at a temperature of 500 ° C. or more and less than one point for 10 to 50 hours (hot rolled sheet annealing step) Performing one or more steps of performing cold rolling with a rolling reduction of 35% or less, and then holding the temperature at 500 ° C.
  • the rolling ratio is determined by the following equation (1).
  • Rolling ratio (%) (h 0 -h 1 ) / h 0 ⁇ 100 (1)
  • h 0 is the sheet thickness before rolling (mm)
  • h 1 is the thickness after rolling (mm).
  • the toughness can be improved in the non-heat-refined material of Nb-containing steel.
  • This steel has excellent wear resistance and toughness.
  • a cutlery component to which a non-tempered material has conventionally been applied such as a circular saw for cutting fruits, grains, cotton and the like
  • a life extending effect can be obtained by the improvement of the wear resistance.
  • the deterioration of the toughness, which has conventionally been traded with the improvement of the wear resistance is suppressed.
  • C is an element necessary to secure the strength of the steel plate.
  • steels with a C content of 0.60% or more are targeted.
  • the C content is limited to 1.25% or less.
  • Si may be added as a deoxidizer, but if it is contained in a large amount, toughness deteriorates.
  • the Si content is limited to 0.50% or less. Generally, the content may be adjusted in the range of 0.01 to 0.50%.
  • Mn is effective for improving the strength of the steel plate and secures a content of 0.30% or more.
  • a large amount of Mn content causes hardening of the heat-rolled steel sheet and causes a reduction in productivity.
  • the Mn content is limited to 1.20% or less and may be controlled to less than 1.00%.
  • P is limited to 0.030% or less, and S is limited to 0.030% or less.
  • P may be adjusted in the range of 0.001% or more and S in the range of 0.0005% or more.
  • Cr is effective for improving the strength of the steel plate, and secures a content of 0.30% or more.
  • a large amount of Cr content causes a decrease in toughness.
  • the Cr content is limited to 1.50% or less.
  • Nb forms very hard Nb / Ti carbide particles in the steel in the cooling process after casting, and contributes to the improvement of the wear resistance, particularly the abrasive wear resistance.
  • action 0.10% or more of Nb content is ensured.
  • the Nb content is 0.50% or less. You may manage to less than 0.45%.
  • Ti forms very hard Nb / Ti-based carbide particles in steel in the cooling process after casting, and contributes to the improvement of the wear resistance. Therefore, Ti can be added as needed. In that case, it is more effective to make it Ti content of 0.01% or more. However, addition of a large amount of Ti causes a loss of toughness. As a result of various examinations, when adding Ti, it is necessary to carry out in 0.50% or less of content range. You may manage to Ti content of 0.30% or less.
  • Mo, V and Ni are all elements effective for improving toughness. Therefore, one or more of these can be added as needed. In that case, it is more effective to make Mo into 0.10% or more, V into 0.10% or more, and Ni into 0.10% or more. Even if these elements are added in excess, the effect of improving the toughness corresponding to the cost can not be expected. It is desirable that the content of Mo be 0.50% or less, V be 0.50% or less, and Ni be 2.00% or less.
  • the metal base is a ferrite phase. Spheroidized cementite particles and Nb / Ti carbide particles are dispersed in the metal base.
  • This steel plate has a small amount of voids generated near the Nb / Ti carbide particles in the cold rolling process.
  • the number density of voids having a circle equivalent diameter of 1.0 ⁇ m or more is 1250 / mm 2 or less, more preferably 1000 / mm 2 or less It is suppressed. It has been found that among the voids of this type, voids having an equivalent circle diameter of 1.0 ⁇ m or more become a major factor to lower the toughness of the steel sheet which is a non-refined material.
  • the number density of voids with a circle equivalent diameter of 1.0 ⁇ m or more is 1000 pieces / mm 2 or less.
  • the number density of voids with a circle equivalent diameter of 1.0 ⁇ m or more may be in the range of 300 pieces / mm 2 or more.
  • the reduction of the void number density can be realized, for example, by a manufacturing method (described later) in which an intermediate cold rolling process at a relatively light rolling rate is inserted.
  • the Nb / Ti carbide particles exhibit a function of improving the wear resistance.
  • the number density of the Nb / Ti-based carbide particles can be controlled by a known method (for example, the technique disclosed in Patent Document 5) for optimizing the cooling rate during casting and the slab heating temperature before hot rolling.
  • the wear-resistant steel plate according to the present invention can be produced, for example, by the following steps. Casting ⁇ slab heating ⁇ hot rolling ⁇ (hot-rolled sheet annealing) ⁇ intermediate cold rolling ⁇ intermediate annealing ⁇ finish cold rolling ⁇ (strain relief annealing) In this case, the process of the part of "intermediate cold rolling-> intermediate annealing" can be performed once or plural times. In the present specification, the process of “intermediate cold rolling ⁇ intermediate annealing” performed once or a plurality of times is referred to as “intermediate cold rolling annealing process”. In addition, scale removal processes, such as pickling, are inserted as needed. Hereinafter, each said process is demonstrated.
  • Nb ⁇ Ti carbides are formed in the cooling process.
  • the formation size of the Nb.Ti based carbide can be controlled by the cooling rate of the slab and the slab heating temperature.
  • the cooling rate is controlled to 5 to 20 ° C./min while the molten steel is cooled from the liquidus temperature to the solidus temperature, and the residence time in the temperature range from 1500 ° C. to 900 ° C. is ensured for 30 minutes or more,
  • the method of heating and holding the obtained slab at 1200 to 1350 ° C. for 0.5 to 4.0 hours is effective.
  • the heat treatment of the cast slab may be performed using cast slab heating before hot rolling.
  • the hot rolling conditions can be, for example, a finish rolling temperature of 800 to 900 ° C. and a winding temperature of 750 ° C. or less.
  • Hot-rolled sheet annealing can be performed as needed.
  • conditions may be employed in which heating and holding is performed, for example, for 10 to 50 hours in a temperature range of 500 ° C. or more and less than 1 point Ac.
  • the number density of Nb / Ti carbide particles with an equivalent circle diameter of 0.5 ⁇ m or more in the cross section of the steel sheet L can be made 3000 to 9000 / mm 2 according to the above-described casting and slab heating conditions and hot rolling conditions. .
  • the number density of the Nb / Ti-based carbide particles at this stage is substantially reflected in the steel plate after finish cold rolling.
  • Nb / Ti carbide particles are very hard and do not undergo plastic deformation, voids are generated around Nb / Ti carbide particles during cold rolling, but fine voids are eliminated during annealing, so the generated voids
  • the toughness does not deteriorate when the value of D is sufficiently small.
  • the intermediate cold rolling ratio exceeds 35%, coarse voids that do not disappear due to annealing are generated, and this void grows by finishing cold rolling, so that the number density of voids with an equivalent circle diameter of 1.0 ⁇ m or more In some cases, the toughness is deteriorated due to the increase.
  • this effect increases as the intermediate cold rolling rate increases, and particularly when the intermediate cold rolling rate exceeds 45%, the toughness is significantly degraded.
  • the intermediate cold rolling ratio is in the range of more than 35% and 45% or less, when intermediate cold rolling and intermediate annealing are repeated multiple times, residual voids and cold which did not disappear in the intermediate annealing It was observed that toughness was significantly degraded by repeated void growth during rolling. Therefore, the intermediate cold rolling is performed at a rolling ratio of 35% or less so that the voids generated around the Nb / Ti carbide particles are sufficiently eliminated by annealing.
  • Intermediate annealing is performed on the steel plate which has finished the intermediate cold rolling. This annealing is referred to herein as "intermediate annealing" because it is performed prior to finish cold rolling.
  • the heating holding temperature of intermediate annealing is set to 500 ° C. or more and less than Ac 1 point. By maintaining at this temperature, the elimination of the void generated in the intermediate cold rolling sufficiently proceeds. In addition, spheroidization of cementite also proceeds. If the temperature is less than 500 ° C., the void disappears insufficiently. In addition, the spheroidization of cementite may be insufficient.
  • the heat holding time of the intermediate annealing (the time when the material temperature is in the range of 500 ° C. or more and less than 1 point of Ac) is preferably 10 to 50 hours.
  • intermediate cold rolling-> intermediate annealing may be performed multiple times as needed. Also in that case, the rolling reduction in each intermediate cold rolling is 35% or less, and the heating holding temperature and the heating holding time in each intermediate annealing are also as described above.
  • finish cold rolling is applied to the steel sheet after intermediate annealing. Since this cold rolling is a process of reducing the final target thickness, it is referred to as "finish cold rolling" in the present specification.
  • the finish cold rolling ratio needs to be 60% or less. If the rolling reduction is larger than this, voids are likely to be generated excessively even if the above-described intermediate cold rolling and intermediate annealing are performed under appropriate conditions. That is, it is difficult to stably improve the toughness of the steel plate.
  • this finish cold rolling is also effective for improving the final shape (flatness) of the steel sheet. For that purpose, for example, it is preferable to secure a rolling reduction of 10% or more.
  • the final thickness can be set, for example, in the range of 0.2 to 4.0 mm.
  • strain relief annealing After finish cold rolling, strain relief annealing can be performed as needed.
  • the strength level can be adjusted by controlling the heating temperature and the holding time in accordance with the chemical composition and the finish cold rolling rate.
  • the heating temperature for strain relief annealing is set in the range of 300 to 500.degree.
  • the heat holding time of the intermediate annealing (the time when the material temperature is in the range of 300 ° C. or more and 500 or less) is preferably set to 1 to 5 hours.
  • the hot rolled steel plate is ground to a plate thickness of 3.1 mm (for 40% rolling), The intermediate product plate material adjusted to 4.2 mm (for 55% rolling) or 6.3 mm (for 70% rolling) was prepared.
  • Each intermediate product plate was subjected to intermediate cold rolling at a rolling ratio of 20%, and then to intermediate annealing at 550 ° C. for 17 hours.
  • the plate material after intermediate annealing was subjected to finish cold rolling at a rolling ratio described in Table 2 to obtain a cold-rolled steel plate having a thickness of 1.5 mm.
  • strain relief annealing was performed for 3 hours at a temperature set in the range of 300 to 450 ° C. so as to obtain a hardness of 32 ⁇ 2 HRC, to obtain a test material.
  • the metal structure of a cross section (L cross section) parallel to the rolling direction and the thickness direction was observed for each test material.
  • the metal base was a ferrite phase, and the metal base had a metal structure in which spheroidized cementite particles and Nb / Ti-based carbide particles are dispersed.
  • each test material is observed with a confocal laser microscope (manufactured by OLYMPUS; OLS 3000), and the number density of Nb / Ti carbide particles having a circle equivalent diameter of 0.5 ⁇ m or more, and a circle equivalent diameter of 1.0 ⁇ m.
  • the number density of the above voids was measured. These measurements were in accordance with the above-mentioned “How to determine the number density of Nb / Ti-based carbide particles” and “how to determine the number density of voids”.
  • the wear resistance test and the impact test were performed on each test material by the following method.
  • the hardness of the abrasive grains is about 1600 HV.
  • This wear test simulates abrasive wear due to the inclusion of fine sand.
  • the specific wear amount C in this test is 5.0 ⁇ 10 ⁇ 4 mm 3 / Nm or less, it can be judged that the steel has excellent wear resistance. Therefore, a product having a specific wear amount C of 5.0 ⁇ 10 -4 mm 3 / (Nm) or less was judged as pass (abrasion resistance: good).
  • the example of the present invention has few voids and is excellent in toughness. Excellent wear resistance. That is, in the non-refined material, a non-refined material having excellent wear resistance and toughness was realized.

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  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
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  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
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  • Health & Medical Sciences (AREA)
  • Child & Adolescent Psychology (AREA)
  • Heat Treatment Of Sheet Steel (AREA)
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Abstract

La présente invention permet à un matériau non traité thermiquement d'obtenir un bon équilibre entre la « résistance à l'usure » et la « ténacité » à des niveaux élevés. L'invention concerne une tôle en acier présentant une composition chimique qui contient, en % en masse, de 0,60 à 1,25 % de C, 0,50 % de Si au maximum, de 0,30 à 1,20 % de Mn, 0,030 % de P au maximum, 0,030 % de S au maximum, de 0,30 à 1,50 % de Cr, de 0,10 à 0,50 % de Nb, de 0 à 0,50 % de Ti, de 0 à 0,50 % de Mo, de 0 à 0,50% de V et de 0 à 2,00 % de Ni, le reste étant constitué de Fe et d'impuretés inévitables. Cette tôle d'acier présente une structure métallique dans laquelle des particules de cémentite et des particules d'un carbure qui contient du Nb et/ou du Ti (ci-après appelé « carbure de Nb/Ti ») sont dispersées dans une matrice métallique en phase de ferrite ; et dans une section transversale (section L) qui est parallèle à la direction de laminage et à la direction d'épaisseur de la tôle, la densité de nombre des particules de carbure de Nb/Ti ayant un diamètre de cercle équivalent supérieur ou égal à 0,5 µm est de 3 000 à 9 000 particules/mm2 et la densité de nombre de vides ayant un diamètre de cercle équivalent supérieur ou égal à 1,0 µm est inférieure ou égale à 1 250 vides/mm2.
PCT/JP2017/030614 2017-08-25 2017-08-25 Tôle d'acier résistante à l'usure présentant une excellente ténacité WO2019038923A1 (fr)

Priority Applications (5)

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CN201780094374.6A CN111373064A (zh) 2017-08-25 2017-08-25 韧性优异的耐磨损性钢板
US16/634,671 US20200199702A1 (en) 2017-08-25 2017-08-25 Wear-resistant steel sheet having excellent toughness and production method
PCT/JP2017/030614 WO2019038923A1 (fr) 2017-08-25 2017-08-25 Tôle d'acier résistante à l'usure présentant une excellente ténacité
KR1020207008415A KR20200044879A (ko) 2017-08-25 2017-08-25 인성이 우수한 내마모성 강판 및 제조법
EP17922610.5A EP3674432A4 (fr) 2017-08-25 2017-08-25 Tôle d'acier résistante à l'usure présentant une excellente ténacité

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KR20200044879A (ko) 2020-04-29
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US20200199702A1 (en) 2020-06-25
CN111373064A (zh) 2020-07-03

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