WO2019038923A1 - Wear-resistant steel sheet having excellent toughness - Google Patents

Wear-resistant steel sheet having excellent toughness Download PDF

Info

Publication number
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
Authority
WO
WIPO (PCT)
Prior art keywords
less
rolling
cold rolling
annealing
carbide
Prior art date
Application number
PCT/JP2017/030614
Other languages
French (fr)
Japanese (ja)
Inventor
大 宮脇
勝 藤原
Original Assignee
日新製鋼株式会社
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by 日新製鋼株式会社 filed Critical 日新製鋼株式会社
Priority to PCT/JP2017/030614 priority Critical patent/WO2019038923A1/en
Priority to EP17922610.5A priority patent/EP3674432A4/en
Priority to CN201780094374.6A priority patent/CN111373064A/en
Priority to US16/634,671 priority patent/US20200199702A1/en
Priority to KR1020207008415A priority patent/KR20200044879A/en
Publication of WO2019038923A1 publication Critical patent/WO2019038923A1/en

Links

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
    • C21D8/0221—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.

Abstract

The present invention enables a non-heat treated material to achieve a good balance between "wear resistance" and "toughness" at high levels. A steel sheet which has a chemical composition that contains, in mass%, 0.60-1.25% of C, 0.50% or less of Si, 0.30-1.20% of Mn, 0.030% or less of P, 0.030% or less of S, 0.30-1.50% of Cr, 0.10-0.50% of Nb, 0-0.50% of Ti, 0-0.50% of Mo, 0-0.50% of V and 0-2.00% of Ni, with the balance made up of Fe and unavoidable impurities. This steel sheet has a metal structure wherein cementite particles and particles of a carbide that contains Nb and/or Ti (hereinafter referred to as "Nb/Ti carbide") are dispersed in a ferrite phase metal matrix; and in a cross-section (L section) that is parallel to the rolling direction and the sheet thickness direction, the number density of the Nb/Ti carbide particles having a circle-equivalent diameter of 0.5 μm or more is 3,000-9,000 particles/mm2 and the number density of voids having a circle-equivalent diameter of 1.0 μm or more is 1,250 voids/mm2 or less.

Description

[規則26に基づく補充 22.09.2017]　靭性に優れる耐摩耗性鋼板および製造法[Repletion based on rule 26 22.09.2017] Abrasion resistant steel plate and manufacturing method excellent in toughness
　本発明は、硬質なＮｂ・Ｔｉ系炭化物を分散させた耐摩耗性鋼板において、特に靭性の改善を図った鋼板に関する。 The present invention relates to a wear resistant steel plate in which hard Nb-Ti carbides are dispersed, and in particular to a steel plate in which the toughness is improved.
　自動車部品、産業機械のチェーン部品、歯車などの動力伝達部材や、木材の切断・草刈等に使用する丸鋸、帯鋸などの刃物部材には、耐摩耗性が要求される。一般に鋼材の耐摩耗性は、硬さを高めることによって向上する。そのため、耐摩耗性を重視する部材には、焼入れ等の熱処理を利用して硬質化させた鋼材や、炭素等の合金元素含有量の高い鋼材が多用される。すなわち、鋼材の硬さと耐摩耗性は密接な関係にあり、従来、鋼材に耐摩耗性を付与する手法としては硬さを増大させる手法を採用することが一般的である。 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. In general, 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.
　一方、刃が高速回転する丸鋸などの刃物部材では、使用中に折損しないことが重要である。折損を防止するためには鋼材の靭性を確保する必要がある。耐摩耗性の向上に有利な硬質化は、靭性を低下させる要因となる。そのため、一般に「耐摩耗性」と「靭性」はトレードオフの関係にある。 On the other hand, it is important for blade members such as circular saws whose blades rotate at high speed not to break during use. In order to prevent breakage, it is necessary to secure the toughness of the steel material. Hardening that is advantageous for improving wear resistance is a factor that reduces toughness. Therefore, in general, "wear resistance" and "toughness" are in a trade-off relationship.
　果実、穀物、綿花等の農産物を刈り取る丸鋸など一部の刃物においては、摩耗が比較的穏やかであることから、硬さよりも、折損防止に有利な「靭性」が重視される。そのような刃物用途では、焼入れ等の調質熱処理を経て硬質化された「調質材」ではなく、フェライト相＋球状化セメンタイト組織の「非調質材」が適用されることも多い。しかしながら、製品の長寿命化に対する要求は根強く、摩耗が比較的穏やかな用途であっても、耐摩耗性の改善要望が高まりつつある。非調質材において「耐摩耗性」と「靭性」を高いレベルで両立させる技術の構築が望まれる。 In some cutting tools such as circular saws for harvesting agricultural products such as fruits, grains, cotton and the like, since the wear is relatively mild, "toughness" advantageous for breakage prevention is emphasized rather than hardness. In such blade applications, a "non-refined material" of a ferrite phase + a spheroidized cementite structure is often applied instead of the "refined material" hardened through temper heat treatment such as quenching. However, the demand for long life of the product is persistent, and there is a growing demand for improvement of the wear resistance even in applications where the wear is relatively mild. In non-tempered materials, it is desirable to construct a technology that achieves both "abrasion resistance" and "toughness" at a high level.
　特許文献１、２には、熱間鍛造用鋼において摩耗を促進させるフェライト相の硬質化および面積率低減によって鋼の耐摩耗性を向上させることが記載されている。しかし、これらの文献で対象としている鋼はフェライト－パーライト組織であり、フェライト－球状化セメンタイト組織に比べ靭性が劣る。 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. However, the steel targeted in these documents has a ferrite-pearlite structure, which is inferior to the ferrite-spheroidized cementite structure in toughness.
　特許文献３には、結晶粒を微細化させて高強度・高靭性を付与した熱延鋼材を直接切削加工することにより、調質熱処理せずに使用できる機械構造用部品を得る技術が開示されている。しかし、耐摩耗性を必要とする用途では高周波焼入れ－焼戻しの処理が必要となる。 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.
　特許文献４には、高炭素鋼の衣材と低炭素鋼の芯材をクラッド化することにより耐摩耗性と靭性を兼備させた丸鋸用鋼板が開示されている。しかし、クラッド化の工程が必要となる。 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.
　特許文献５、６には、硬質なＮｂ・Ｔｉ系炭化物の分散を利用して耐摩耗性を向上させる技術が開示されている。これらの技術は焼入れ焼戻し処理によって硬質化を図る調質材を対象とするものでる。高い耐摩耗性が得られるが、靭性面では更なる改善が望まれる。 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.
特開平１０－１３７８８８号公報JP 10-137888 A 特開２００３－２０１５３６号公報Japanese Patent Application Laid-Open No. 2003-201536 特開２０１１－１９５８５８号公報JP, 2011-195858, A 特開昭６０－８２６４７号公報Japanese Patent Application Laid-Open No. 60-82647 特開２０１０－１３８４５３号公報JP, 2010-138453, A 特開２０１３－１３６８２０号公報JP 2013-136820 A
　本発明は、非調質材において、「耐摩耗性」と「靭性」を高いレベルで両立させることを目的とする。 An object of the present invention is to make "abrasion resistance" and "toughness" compatible at a high level in a non-tempered material.
　発明者らの調査によれば、特許文献５、６に開示されるような硬質なＮｂ・Ｔｉ系炭化物を利用して耐摩耗性を付与する技術において、焼入れ等の調質熱処理を施す前の鋼板（非調質材）は比較的軟質であるにもかかわらず、その段階で、必ずしも良好な靭性を呈するとは限らないことがわかった。詳細な調査の結果、冷間圧延時に硬質な炭化物粒子の近傍にボイドが生じ、それが靭性を阻害する要因となっていることを突き止めた。そこで発明者らは、ボイドが生じにくい製造条件を見つけるべく研究を進めた。その結果、まず、冷間圧延率を低減するとボイドは生じにくくなる傾向が認められた。さらに研究を進めた結果、冷間圧延と焼鈍を繰り返す場合には、中間における冷間圧延率が３５％を超えると靭性が著しく劣化する場合があることがわかった。３５％以下の比較的軽い圧延率で中間冷間圧延を行い、中間焼鈍を施し、その後、最終的な仕上げ冷間圧延を施す工程によって、粗大なボイドの形成が少ない鋼板が得られ、安定して高い靭性が付与できることを見いだした。この場合、仕上げ冷間圧延率は６０％程度まで許容されることが確認された。本発明はこのような知見に基づくものである。 According to the investigations of the inventors, in the technology for imparting wear resistance using hard Nb / Ti carbides as disclosed in Patent Documents 5 and 6, the heat treatment such as quenching is performed before the heat treatment. Although it was relatively soft, the steel plate (non-tempered material) was found to not necessarily exhibit good toughness at that stage. As a result of detailed investigations, it was found that voids were formed in the vicinity of hard carbide particles at the time of cold rolling, which is a factor that inhibits toughness. Therefore, the inventors proceeded with research to find manufacturing conditions in which voids do not easily occur. As a result, it was first found that when the cold rolling reduction rate was reduced, voids were less likely to occur. As a result of further research, it was found that when cold rolling and annealing are repeated, if the cold rolling ratio in the middle exceeds 35%, the toughness may be significantly deteriorated. Intermediate cold rolling is performed at a relatively light rolling ratio of 35% or less, intermediate annealing is performed, and then final finishing cold rolling is performed to obtain a steel plate with less formation of coarse voids, which is stable. Found that high toughness can be imparted. In this case, it was confirmed that the finish cold rolling reduction rate is acceptable up to about 60%. The present invention is based on such findings.
　上記目的は、質量％で、Ｃ：０.６０～１.２５％、Ｓｉ：０.５０％以下、Ｍｎ：０.３０～１.２０％、Ｐ：０.０３０％以下、Ｓ：０.０３０％以下、Ｃｒ：０.３０～１.５０％、Ｎｂ：０.１０～０.５０％、Ｔｉ：０～０.５０％、Ｍｏ：０～０.５０％、Ｖ：０～０.５０％、Ｎｉ：０～２.００％、残部Ｆｅおよび不可避的不純物からなる化学組成を有し、フェライト相の金属素地中に、セメンタイト粒子と、Ｎｂ、Ｔｉの１種以上を含有する炭化物（以下「Ｎｂ・Ｔｉ系炭化物」という。）の粒子が分散した金属組織を有し、圧延方向および板厚方向に平行な断面（Ｌ断面）において、円相当径０.５μｍ以上のＮｂ・Ｔｉ系炭化物粒子の個数密度が３０００～９０００個／ｍｍ２、円相当径１.０μｍ以上のボイドの個数密度が１２５０個／ｍｍ２以下である鋼板によって達成される。ここで、Ｔｉ、Ｍｏ、Ｖ、Ｎｉは任意添加元素である。この鋼板の板厚は例えば０.２～４.０ｍｍである。 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 μm 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 1.0μm or more voids 1250 / m Is achieved by the steel plate is 2 or less. Here, Ti, Mo, V, and Ni are optional addition elements. The thickness of this steel plate is, for example, 0.2 to 4.0 mm.
　ここで言う「Ｎｂ・Ｔｉ系炭化物」は、炭化物を構成する金属元素としてＮｂおよびＴｉの１種または２種を含有する硬質炭化物である。Ｎｂ・Ｔｉ系炭化物の種類としては、ＮｂＣを主体とするタイプ、ＴｉＣを主体とするタイプ、および(Ｎｂ,Ｔｉ)Ｃを主体とするタイプが挙げられる。本発明では所定量のＮｂを含有する鋼を対象としているので、鋼成分にＴｉを含有しない場合はＮｂＣを主体とするタイプの硬質炭化物が生成する。このようなＴｉを含有しないタイプのＮｂ含有硬質炭化物も、本明細書では「Ｎｂ・Ｔｉ系炭化物」と呼んでいる。鋼成分にＴｉを含有する場合は(Ｎｂ,Ｔｉ)Ｃを主体とするタイプが生成する他、Ｔｉ含有量に応じてＴｉＣを主体とするタイプやＮｂＣを主体とするタイプも混在し得ると考えられる。鋼素地中には球状化したセメンタイト（Ｆｅ３Ｃ）の粒子も存在する。ある炭化物がＮｂ・Ｔｉ系炭化物であるかどうかは、ＥＤＸ（エネルギー分散型蛍光Ｘ線分析法）等の分析手法により確認できる。 The "Nb-Ti-based carbide" referred to herein 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". If 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).
　ボイドはＮｂ・Ｔｉ系炭化物粒子の表面と鋼素地（マトリックス）の間の存在する空隙である。円相当径１.０μｍ以上のボイドの個数密度は以下のようにして求めることができる。 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 μm or more can be determined as follows.
〔ボイドの個数密度の求め方〕
　圧延方向および板厚方向に平行な断面（Ｌ断面）を研磨した観察面を共焦点レーザー顕微鏡により観察し、観察画像上で、Ｎｂ・Ｔｉ系炭化物に隣接して存在するボイドのうち、円相当径が１.０μｍ以上であるボイドの個数をカウントし、そのカウント総数を観察総面積（ｍｍ２）で除した値を相当径１.０μｍ以上のボイドの個数密度（個／ｍｍ２）とする。ただし、観察面積は９０μｍ×６０μｍ×２０視野とする。観察視野から一部がはみ出しているボイドは、観察視野内に現れている部分の円相当径が１.０μｍ以上であればカウント対象とする。ここで、あるボイドの円相当径は、観察画像上における当該ボイドの面積と等しい円の直径である。ボイドの面積は観察画像を画像処理ソフトウェアで処理することにより測定することができる。 [How to determine the number density of voids]
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 μm 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 μm or more. . However, the observation area is 90 μm × 60 μm × 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 μm or more. Here, 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.
　上記鋼板において、円相当径０.５μｍ以上のＮｂ・Ｔｉ系炭化物粒子の個数密度が３０００～９０００個／ｍｍ２であることがより好ましい。Ｎｂ含有炭化物粒子の個数密度は以下のようにして求めることができる。 In the above steel plate, the number density of Nb · Ti carbide particles having a circle equivalent diameter of 0.5 μm 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.
〔Ｎｂ・Ｔｉ系炭化物粒子の個数密度の求め方〕
　圧延方向および板厚方向に平行な断面（Ｌ断面）を研磨したのちエッチングした観察面を共焦点レーザー顕微鏡により観察し、観察画像上で、円相当径が０.５μｍ以上であるＮｂ・Ｔｉ系炭化物粒子の個数をカウントし、そのカウント総数を観察総面積（ｍｍ２）で除した値を円相当径０.５μｍ以上のＮｂ・Ｔｉ系炭化物粒子の個数密度（個／ｍｍ２）とする。ただし、観察面積は９０μｍ×６０μｍ×２０視野とする。観察視野から一部がはみ出しているＮｂ・Ｔｉ系炭化物粒子は、観察視野内に現れている部分の円相当径が０.５μｍ以上であればカウント対象とする。ここで、あるＮｂ・Ｔｉ系炭化物粒子の円相当径は、観察画像上における当該Ｎｂ・Ｔｉ系炭化物粒子の面積と等しい円の直径である。Ｎｂ・Ｔｉ系炭化物粒子の面積は観察画像を画像処理ソフトウェアで処理することにより測定できる。 [How to determine the number density of Nb / Ti carbide particles]
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 μm 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 μm or more. However, the observation area is 90 μm × 60 μm × 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 μm or more. Here, 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.
　上記鋼板は例えば以下の方法により製造することができる。
　溶鋼が液相線温度から固相線温度まで冷却する間の冷却速度を５～２０℃／ｍｉｎに制御して鋳片を製造する工程（鋳造工程）、
　鋳片を１２００～１３５０℃に０.５～４時間加熱保持する工程（鋳片加熱工程）、
　熱間圧延を施す工程（熱延工程）、
　必要に応じて、熱延工程で得た熱延鋼板に５００℃以上Ａｃ１点未満の温度で１０～５０時間保持したのち冷却する焼鈍を施す工程（熱延板焼鈍工程）、
圧延率３５％以下の冷間圧延を施し、次いで５００℃以上Ａｃ１点未満の温度で１０～５０時間保持したのち冷却する手順を、１回以上行う工程（中間冷延焼鈍工程）、
　圧延率６０％以下の冷間圧延を施す工程（仕上げ冷延工程）、
　必要に応じて、３００～５００℃で１～５時間保持する焼鈍を施す工程（歪取り焼鈍工程）、
を上記の順に有する製造方法。 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. or more and less than Ac 1 point for 10 to 50 hours and cooling once (intermediate cold rolling annealing step);
Cold rolling with a rolling ratio of 60% or less (finishing cold rolling)
Optionally carrying out annealing at 300 to 500 ° C. for 1 to 5 hours (strain relief annealing step);
The manufacturing method which has the said order.
　圧延率は下記（１）式によって定まる。
　圧延率（％）＝（ｈ０－ｈ１）／ｈ０×１００　…（１）
　ここで、ｈ０は圧延前の板厚（ｍｍ）、ｈ１は圧延後の板厚（ｍｍ）である。 The rolling ratio is determined by the following equation (1).
Rolling ratio (%) = (h 0 -h 1 ) / h 0 × 100 (1)
Here, h 0 is the sheet thickness before rolling (mm), h 1 is the thickness after rolling (mm).
　本発明によれば、Ｎｂ含有鋼の非調質材において、靭性を改善することができた。この鋼材は優れた耐摩耗性と靭性を兼ね備えている。果実、穀物、綿花等を刈り取る丸鋸など、従来、非調質材を適用していた刃物部品においては、耐摩耗性向上による寿命延伸効果が得られる。また、従来、耐摩耗性の向上とトレードオフであった靭性の劣化が抑制される。 According to the present invention, the toughness can be improved in the non-heat-refined material of Nb-containing steel. This steel has excellent wear resistance and toughness. In the case of 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. In addition, the deterioration of the toughness, which has conventionally been traded with the improvement of the wear resistance, is suppressed.
〔化学組成〕
　本明細書において、鋼の成分元素に関する「％」は特に断らない限り「質量％」を意味する。 [Chemical composition]
In the present specification, “%” relating to the component elements of steel means “% by mass” unless otherwise specified.
　Ｃは、鋼板の強度を確保するために必要な元素である。ここではＣ含有量０.６０％以上の鋼を対象とする。Ｃ含有量が高くなると粗大な炭化物が多くなり靭性低下の要因となる。Ｃ含有量は１.２５％以下に制限される。 C is an element necessary to secure the strength of the steel plate. Here, steels with a C content of 0.60% or more are targeted. When the C content is high, coarse carbides increase and cause a decrease in toughness. The C content is limited to 1.25% or less.
　Ｓｉは、脱酸剤として添加されることがあるが、多量に含有すると靭性が劣化する。Ｓｉ含有量は０.５０％以下に制限される。通常、０.０１～０.５０％の含有量範囲で調整すればよい。 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は、鋼板の強度向上に有効であり、０.３０％以上の含有量を確保する。多量のＭｎ含有は熱延鋼板の硬質化を招き、製造性低下の要因となる。Ｍｎ含有量は１.２０％以下に制限され、１.００％未満に管理してもよい。 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およびＳは、靭性に悪影響を及ぼすので、含有量は少ないことが望ましい。Ｐは０.０３０％以下、Ｓは０.０３０％以下にそれぞれ制限される。通常、Ｐは０.００１％以上、Ｓは０.０００５％以上の範囲で調整すればよい。 Since P and S adversely affect the toughness, it is desirable that the content be small. P is limited to 0.030% or less, and S is limited to 0.030% or less. Generally, P may be adjusted in the range of 0.001% or more and S in the range of 0.0005% or more.
　Ｃｒは、鋼板の強度向上に有効であり、０.３０％以上の含有量を確保する。多量のＣｒ含有は靭性低下の要因となる。Ｃｒ含有量は１.５０％以下に制限される。 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は、鋳造後の冷却過程で鋼中に非常に硬質なＮｂ・Ｔｉ系炭化物粒子を形成し、耐摩耗性、特に耐アブレシブ摩耗性の向上に寄与する。上記作用を十分に発揮させるために０.１０％以上のＮｂ含有量を確保する。ただし、Ｎｂを多量に添加するとＮｂ・Ｔｉ系炭化物粒子の生成量が過大となり、靭性を損なう要因となる。種々検討の結果、Ｎｂ含有量は０.５０％以下に制限する必要がある。０.４５％以下に管理してもよい。 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. In order to fully exhibit the said effect | action, 0.10% or more of Nb content is ensured. However, when a large amount of Nb is added, the amount of Nb / Ti-based carbide particles formed becomes excessive, which causes a loss in toughness. As a result of various studies, it is necessary to limit the Nb content to 0.50% or less. You may manage to less than 0.45%.
　Ｔｉは、Ｎｂと同様、鋳造後の冷却過程で鋼中に非常に硬質なＮｂ・Ｔｉ系炭化物粒子を形成し、耐摩耗性の向上に寄与する。従って、必要に応じてＴｉを添加することができる。その場合０.０１％以上のＴｉ含有量とすることがより効果的である。ただし、Ｔｉを多量に添加すると靭性を損なう要因となる。種々検討の結果、Ｔｉを添加する場合は０.５０％以下の含有量範囲で行う必要がある。０.３０％以下のＴｉ含有量に管理してもよい。 Like Nb, 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およびＮｉは、いずれも靭性向上に有効な元素である。そのため必要に応じてこれらの１種以上を添加することができる。その場合、Ｍｏは０.１０％以上、Ｖは０.１０％以上、Ｎｉは０.１０％以上の含有量とすることがより効果的である。これらの元素を過剰に添加してもコストに見合った靭性向上効果は期待できない。Ｍｏは０.５０％以下、Ｖは０.５０％以下、Ｎｉは２.００％以下の含有量範囲に抑えることが望ましい。 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.
〔金属組織〕
　本発明では、焼入れ焼戻しやオーステンパーに代表される相変態を利用した組織調整（いわゆる調質熱処理）を施していない、非調質材における耐摩耗性と靭性の両立を意図している。従って、本発明に従う鋼板は、金属素地（マトリックス）がフェライト相である。その金属素地中に球状化セメンタイト粒子と、Ｎｂ・Ｔｉ系炭化物粒子が分散している。 [Metal structure]
In the present invention, coexistence of wear resistance and toughness in a non-refined material which is not subjected to structure adjustment (so-called temper heat treatment) utilizing phase transformation represented by quenching and tempering or austempering is intended. Therefore, in the steel plate according to the present invention, the metal base (matrix) is a ferrite phase. Spheroidized cementite particles and Nb / Ti carbide particles are dispersed in the metal base.
　この鋼板は、冷間圧延工程でＮｂ・Ｔｉ系炭化物粒子の近傍に生成するボイドの存在量が少ない。具体的には、圧延方向および板厚方向に平行な断面（Ｌ断面）において円相当径１.０μｍ以上のボイドの個数密度が１２５０個／ｍｍ２以下、より好ましくは１０００個／ｍｍ２以下に抑えられている。この種のボイドのうち円相当径１.０μｍ以上のボイドは、非調質材である鋼板の靭性を低下させる大きな要因となることがわかった。Ｎｂ含有量およびＴｉ含有量が上述の適正範囲に抑えられていれば、円相当径１.０μｍ以上のボイド個数密度を１２５０個／ｍｍ２以下に制限することによって、靭性の顕著な改善効果が得られる。円相当径１.０μｍ以上のボイド個数密度は１０００個／ｍｍ２以下であることがより好ましい。ボイドの生成が少ないほど靭性改善には有利となるが、過剰にボイドを制限することは適切な板厚の冷間圧延製品を得る上で、工程上の制約を招く要因となる。通常、円相当径１.０μｍ以上のボイド個数密度は３００個／ｍｍ２以上の範囲とすればよい。このボイド個数密度の低減は、例えば、比較的軽圧延率での中間冷間圧延工程を挿入した製造方法（後述）によって実現できる。 This steel plate has a small amount of voids generated near the Nb / Ti carbide particles in the cold rolling process. Specifically, in a cross section (L cross section) parallel to the rolling direction and the plate thickness direction, the number density of voids having a circle equivalent diameter of 1.0 μm 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 μm or more become a major factor to lower the toughness of the steel sheet which is a non-refined material. If the Nb content and the Ti content are suppressed within the above-mentioned appropriate range, a remarkable improvement effect of toughness can be obtained by limiting the number density of voids with a circle equivalent diameter of 1.0 μm or more to 1250 pieces / mm 2 or less. can get. It is more preferable that the number density of voids having a circle equivalent diameter of 1.0 μm or more is 1000 pieces / mm 2 or less. Although less void formation is advantageous for toughness improvement, excessive void limitation is a factor causing process limitations in obtaining a cold-rolled product having an appropriate plate thickness. Generally, the number density of voids with a circle equivalent diameter of 1.0 μm 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.
　Ｎｂ・Ｔｉ系炭化物粒子は、耐摩耗性を向上させる機能を発揮する。特に、Ｌ断面において、円相当径０.５μｍ以上のＮｂ・Ｔｉ系炭化物粒子の個数密度が３０００～９０００個／ｍｍ２に調整されていることがより効果的である。Ｎｂ・Ｔｉ系炭化物粒子の個数密度は、鋳造時の冷却速度や熱間圧延前の鋳片加熱温度を適正化する公知の手法（例えば特許文献５に開示の技術）によってコントロール可能である。 The Nb / Ti carbide particles exhibit a function of improving the wear resistance. In particular, it is more effective that the number density of Nb--Ti-based carbide particles having a circle equivalent diameter of 0.5 μm or more is adjusted to 3000 to 9000 / mm 2 in the L cross section. 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.
〔製造方法〕
　本発明に従う耐摩耗性鋼板は、例えば以下の工程によって製造することができる。
　鋳造→鋳片加熱→熱間圧延→（熱延板焼鈍）→中間冷間圧延→中間焼鈍→仕上げ冷間圧延→（歪取り焼鈍）
　この場合、「中間冷間圧延→中間焼鈍」の部分の工程は１回または複数回行うことができる。本明細書では、１回または複数回行う「中間冷間圧延→中間焼鈍」の工程を「中間冷延焼鈍工程」と呼んでいる。なお、必要に応じて酸洗等のスケール除去工程が挿入される。以下、上記各工程について説明する。 〔Production method〕
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.
〔鋳造・鋳片加熱〕
　鋳造工程では冷却過程においてＮｂ・Ｔｉ系炭化物を生成させる。Ｎｂ・Ｔｉ系炭化物の形成サイズは鋳片の冷却速度および鋳片加熱温度によってコントロールすることができる。例えば、溶鋼が液相線温度から固相線温度まで冷却する間の冷却速度を５～２０℃／ｍｉｎに制御し、１５００℃から９００℃までの温度域の滞在時間を３０分以上確保し、得られた鋳片を１２００～１３５０℃に０.５～４.０時間加熱保持する手法が有効である。この鋳片の加熱処理は、熱間圧延前の鋳片加熱を利用して行うとよい。 [Casting and slab heating]
In the casting process, 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. For example, 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.
〔熱間圧延・（熱延板焼鈍）〕
　熱間圧延条件は例えば仕上圧延温度８００～９００℃、巻取温度７５０℃以下とすることができる。必要に応じて熱延板焼鈍を行うことができる。熱延板焼鈍を行う場合は、５００℃以上Ａｃ１点未満の温度域に例えば１０～５０時間加熱保持する条件が採用できる。上記の鋳造・鋳片加熱条件、および熱間圧延条件により、鋼板Ｌ断面における円相当径０.５μｍ以上のＮｂ・Ｔｉ系炭化物粒子の個数密度を３０００～９０００個／ｍｍ２とすることができる。この段階でのＮｂ・Ｔｉ系炭化物粒子の個数密度は、仕上げ冷間圧延後の鋼板にほぼ反映される。 [Hot rolling, (hot-rolled sheet annealing)]
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. When hot-rolled sheet annealing is performed, 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 μm 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.
〔中間冷間圧延〕
　上記の中間製品板材に圧延率３５％以下の比較的軽度の冷間圧延を施す。この冷間圧延は、最終的な仕上げ冷間圧延よりも前に行うことから、本明細書では「中間冷間圧延」と呼んでいる。中間冷間圧延率が３５％以下の場合には、仕上げ冷間圧延時にボイドの成長が生じ難くなることがわかった。そのメカニズムについてはまだ十分に解明されていないが、以下のようなことが考えられる。すなわち、Ｎｂ・Ｔｉ系炭化物粒子は非常に硬質で塑性変形しないため、冷間圧延時にＮｂ・Ｔｉ系炭化物粒子の周囲にボイドが発生するが、焼鈍において微細なボイドは消滅するため、発生したボイドが十分小さい場合には靭性は劣化しない。しかし、中間冷間圧延率が３５％を超えると焼鈍で消滅しない粗大なボイドが発生し、仕上げ冷間圧延にてこのボイドが成長することで円相当径１.０μｍ以上のボイドの個数密度が増加して靭性が劣化する場合があった。また、中間冷間圧延率が大きくなるにつれてこの影響は大きくなり、特に中間冷間圧延率が４５％を超えると靭性の劣化が著しかった。また、中間冷間圧延率が３５％超え４５％以下の範囲であっても、中間冷間圧延と中間焼鈍を複数回繰り返す場合には、中間焼鈍にて消滅しなかったボイドの残留と冷間圧延時のボイドの成長が繰り返されることで靭性が著しく劣化する場合が認められた。よって、中間冷間圧延はＮｂ・Ｔｉ系炭化物粒子の周囲に発生したボイドが焼鈍にて十分消滅するよう、圧延率３５％以下の範囲で行う。ただし、中間冷間圧延では例えば１０％以上の圧延率を確保することが効率的であり、１５％以上の圧延率に管理してもよいが、あまり低いとこの工程を設ける効果が十分に享受できない。 [Intermediate cold rolling]
The above-mentioned intermediate product sheet is subjected to relatively mild cold rolling with a rolling reduction of 35% or less. This cold rolling is referred to herein as "intermediate cold rolling" because it is performed prior to final finish cold rolling. It was found that when the intermediate cold rolling ratio is 35% or less, the growth of voids is less likely to occur during finish cold rolling. Although the mechanism has not been fully elucidated yet, the following may be considered. That is, since 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. However, if 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 μm or more In some cases, the toughness is deteriorated due to the increase. In addition, 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. In addition, even if 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. However, in intermediate cold rolling, for example, it is efficient to secure a rolling reduction of 10% or more, and it may be controlled to a rolling reduction of 15% or more, but if it is too low, the effect of providing this process is fully enjoyed Can not.
〔中間焼鈍〕
　上記中間冷間圧延を終えた鋼板に対して焼鈍を施す。この焼鈍は仕上げ冷間圧延より前に行うことから、本明細書では「中間焼鈍」と呼んでいる。中間焼鈍の加熱保持温度は５００℃以上Ａｃ１点未満とする。この温度で保持することにより、中間冷間圧延で発生したボイドの消滅が十分に進行する。また、セメンタイトの球状化も進行する。５００℃未満ではボイドの消滅が不十分となる。また、セメンタイトの球状化が不十分となる場合もある。一方、Ａｃ１点以上に昇温するとオーステナイト相が生成し、金属素地がフェライト相である組織状態が得られない。中間焼鈍の加熱保持時間（材料温度が５００℃以上Ａｃ１点未満の範囲にある時間）は１０～５０時間とすることが好ましい。 [Intermediate annealing]
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. On the other hand, when the temperature is raised to Ac 1 point or more, an austenite phase is formed, and a texture state in which the metal base is a ferrite phase can not be obtained. 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.
　なお、「中間冷間圧延→中間焼鈍」の工程は、必要に応じて複数回行ってもよい。その場合も各中間冷間圧延での圧延率は３５％以下とし、各中間焼鈍での加熱保持温度および加熱保持時間も上述の通りとする。 In addition, the process of "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.
〔仕上げ冷間圧延〕
　中間焼鈍後の鋼板に冷間圧延を施す。この冷間圧延は最終的な目標板厚に減じる工程であることから、本明細書では「仕上げ冷間圧延」と呼んでいる。仕上げ冷間圧延率は６０％以下とする必要がある。これより圧延率が大きくなると、上述の中間冷間圧延および中間焼鈍を適正条件で行ったものであっても、ボイドが過度に生成しやすい。すなわち、鋼板の靭性を安定して改善することが難しくなる。一方、この仕上げ冷間圧延は鋼板の最終的な形状（平坦性）を改善するためにも有効である。そのためには例えば１０％以上の圧延率を確保することが好ましい。最終板厚は例えば０.２～４.０ｍｍの範囲で設定することができる。 [Finish cold rolling]
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. On the other hand, 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.
〔歪取り焼鈍〕
　仕上げ冷間圧延後には必要に応じて歪取り焼鈍を行うことができる。化学組成および仕上げ冷間圧延率に応じて加熱温度、保持時間をコントロールすることにより、強度レベルを調整することができる。歪取り焼鈍の加熱温度は３００～５００℃の範囲で設定する。中間焼鈍の加熱保持時間（材料温度が３００℃以上５００以下の範囲にある時間）は１～５時間とすることが好ましい。 [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.
　表１に示す化学組成の鋼を溶製し、鋳造→鋳片加熱→熱間圧延→中間冷間圧延→中間焼鈍→仕上げ冷間圧延→歪取り焼鈍の工程で供試材の鋼板を得た。
　鋳造に際しては溶鋼が液相線温度から固相線温度まで冷却する間の冷却速度を５～２０℃／ｍｉｎに制御して鋳片を得た。鋳片を１２５０～１３５０℃で１時間加熱保持したのち抽出して、熱間圧延を行った。熱間圧延条件は、仕上圧延温度（熱間圧延最終パスの圧延温度）８５０℃、巻取温度５９０℃とし、板厚７.０ｍｍの熱延鋼板を得た。後工程で仕上げ冷間圧延率を振った実験を行う際に得られる供試材の板厚を揃えるために、熱延鋼板を研削加工して、板厚３.１ｍｍ（４０％圧延用）、４.２ｍｍ（５５％圧延用）、または６.３ｍｍ（７０％圧延用）に調整した中間製品板材を用意した。 Steels of the chemical composition shown in Table 1 were melted, and steel sheets of specimens were obtained in the process of casting → billet heating → hot rolling → intermediate cold rolling → intermediate annealing → finishing cold rolling → strain relief annealing .
During casting, a slab was obtained by controlling the cooling rate to 5 to 20 ° C./min while the molten steel was cooled from the liquidus temperature to the solidus temperature. The slab was heated and held at 1250 to 1350 ° C. for 1 hour, then extracted and subjected to hot rolling. The hot rolling conditions were a finish rolling temperature (rolling temperature of the final pass of hot rolling) of 850 ° C. and a winding temperature of 590 ° C., to obtain a hot-rolled steel plate having a plate thickness of 7.0 mm. In order to make the plate thickness of the test material obtained when conducting experiments in which the finishing cold rolling ratio is shaken in the post process, 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.
　各中間製品板材に、圧延率２０％の中間冷間圧延を施したのち、５５０℃×１７時間の中間焼鈍を施した。中間焼鈍後の板材に表２中に記載した圧延率で仕上げ冷間圧延を施し、板厚１.５ｍｍの冷延鋼板を得た。その後、組成および仕上げ冷間圧延率に応じて、硬さが３２±２ＨＲＣとなるように３００～４５０℃の範囲に設定した温度で３時間保持する歪取り焼鈍を施し、供試材とした。 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. Thereafter, in accordance with the composition and finish cold rolling ratio, 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.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
　各供試材について、圧延方向および板厚方向に平行な断面（Ｌ断面）の金属組織観察を行った。その結果、いずれも金属素地がフェライト相であり、金属素地中に球状化セメンタイト粒子と、Ｎｂ・Ｔｉ系炭化物粒子が分散している金属組織を有していた。 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. As a result, in all cases, 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.
　また、各供試材のＬ断面を共焦点レーザー顕微鏡（ＯＬＹＭＰＵＳ社製；ＯＬＳ３０００）により観察し、円相当径０.５μｍ以上のＮｂ・Ｔｉ系炭化物粒子の個数密度、および円相当径１.０μｍ以上のボイドの個数密度を測定した。これらの測定は、それぞれ上掲の「Ｎｂ・Ｔｉ系炭化物粒子の個数密度の求め方」および「ボイドの個数密度の求め方」に従った。さらに、各供試材について、以下の方法で耐摩耗性試験および衝撃試験を行った。 In addition, the L cross section of 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 μm or more, and a circle equivalent diameter of 1.0 μm. 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”. Furthermore, the wear resistance test and the impact test were performed on each test material by the following method.
〔耐摩耗性試験〕
　供試材から摩擦面が直径１０ｍｍの円形となる試験片を切り出し、ピンオンディスク型摩耗試験機により試験を行った。摩耗材としてＪＩＳ　Ｒ６００１の規定による粒度が＃３０００であるＷＡ（アルミナ）砥粒を用意した。この砥粒を５０ｇあたり水３００ｍＬと混合して、研磨液を調製した。試験片を試料ホルダに固定して、鋼製の円板表面にバフ研磨布を貼付した回転体のフラットな表面上に、十分な量の研磨液を供給しながら、試験片表面を試験荷重Ｆ＝５Ｎで押し付け、摩擦速度０.４ｍ／ｓ、摩擦距離Ｌ＝７５０ｍの条件で摩耗試験を行った。試験前後の試料板厚差から摩耗により消失した材料の体積を算出し、これを摩耗減量Ｗ（ｍｍ３）とした。そして、下記（２）式により比摩耗量Ｃ（ｍｍ３／（Ｎｍ））を求めた。
　　比摩耗量Ｃ＝摩耗減量Ｗ／（試験荷重Ｆ×摩擦距離Ｌ）　…（２） [Abrasion resistance test]
From the test material, a test piece having a circular friction surface with a diameter of 10 mm was cut out and tested using a pin-on-disk type wear tester. As the wear material, WA (alumina) abrasive grains having a particle size of # 3000 according to JIS R6001 were prepared. The abrasive was mixed with 300 mL of water per 50 g to prepare a polishing solution. The test load F is fixed while supplying a sufficient amount of polishing liquid onto the flat surface of the rotating body with the buff polishing cloth attached to the surface of the steel disc with the test specimen fixed to the sample holder. The abrasion test was performed under the conditions of pressing at 5 N, friction speed 0.4 m / s, and friction distance L = 750 m. The volume of the material which disappeared by wear was calculated from the difference in sample plate thickness before and after the test, and this was taken as the wear loss W (mm 3 ). Then, the specific wear amount C (mm 3 / (Nm)) was determined by the following equation (2).
Specific wear amount C = wear loss W / (test load F × friction distance L) ... (2)
　上記砥粒の硬さは約１６００ＨＶである。この摩耗試験は微細な砂の混入によるアブレシブ摩耗を模擬している。硬さが３２±２ＨＲＣに調整された鋼材において、この試験による比摩耗量Ｃが５.０×１０－４ｍｍ３／Ｎｍ以下であれば優れた耐摩耗性を有していると判断できる。従って、比摩耗量Ｃが５.０×１０－４ｍｍ３／（Ｎｍ）以下であるものを合格（耐摩耗性；良好）と判定した。 The hardness of the abrasive grains is about 1600 HV. This wear test simulates abrasive wear due to the inclusion of fine sand. In a steel material adjusted to a hardness of 32 ± 2 HRC, if 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).
〔衝撃試験〕
　各供試材から、２ｍｍＵノッチ衝撃試験片（試験片長さ：５５ｍｍ、試験片高さ：１０ｍｍ、試験片幅：板厚＝１.５ｍｍ、衝撃方向：圧延方向）を作製し、ＪＩＳ　Ｚ２２４２：２００５に従う方法で常温（２３℃）のシャルピー衝撃値を測定した。ここでは試験数ｎ＝５とし、それらのうち最も低い値（成績の悪い値）を当該供試材の衝撃値として採用した。非調質材が適用可能な高速回転刃物（農産物刈り取り用丸鋸など）の素材として使用することを考慮した場合、この試験による衝撃値が５０Ｊ／ｃｍ２以上であることが望まれる。従って、この衝撃値が５０Ｊ／ｃｍ２以上であるものを合格（靭性；良好）と判定した。 [Impact test]
From each test material, a 2 mm U notch impact test specimen (test specimen length: 55 mm, specimen height: 10 mm, specimen width: plate thickness = 1.5 mm, impact direction: rolling direction) is prepared, JIS Z2242: 2005 The Charpy impact value at normal temperature (23 ° C.) was measured by the method according to Here, the number of tests was n = 5, and the lowest value among them (the value with poor performance) was adopted as the impact value of the test material. In consideration of using as a material of a high-speed rotary blade (such as a circular saw for crop cutting) to which the non-heat-treated material is applicable, it is desirable that the impact value by this test is 50 J / cm 2 or more. Therefore, a product having this impact value of 50 J / cm 2 or more was judged as pass (toughness: good).
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
　本発明例のものは、ボイドが少なく、靭性に優れる。耐摩耗性にも優れる。すなわち、非調質材において、優れた耐摩耗性と靭性を備える非調質材が実現された。 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.
　これに対し、比較例であるＮｏ.５、１０、１３は、仕上げ冷間圧延率が高いので円相当径１.０μｍ以上のボイドが多くなり、靭性が悪かった。比較例１４～１６はＮｂを含有しない鋼を用いたので硬質なＮｂ・Ｔｉ系炭化物の生成がなく、耐摩耗性が悪かった。比較例１７～１９はＣ含有量が少ない鋼を用いたので硬質なＮｂ・Ｔｉ系炭化物の生成が不足し、耐摩耗性の向上が不十分であった。Ｎｏ.２０、２１はＴｉ含有量が過剰である鋼、Ｎｏ.２２、２３はＮｂ含有量が過剰である鋼をそれぞれ用いたので、これらはＮｂ・Ｔｉ系炭化物の生成量が多く、それに伴って円相当径１.０μｍ以上のボイドが多くなった。その結果、靭性を改善することができなかった。 On the other hand, in the comparative examples No. 5, 10 and 13, since the finish cold rolling ratio was high, the number of voids with a circle equivalent diameter of 1.0 μm or more was large, and the toughness was bad. In Comparative Examples 14 to 16, since the steel containing no Nb was used, there was no formation of hard Nb · Ti carbides, and the wear resistance was poor. In Comparative Examples 17 to 19, since the steel having a small C content was used, the formation of hard Nb / Ti carbides was insufficient, and the improvement of the wear resistance was insufficient. Since No. 20 and 21 used steels with excessive Ti content, and Nos. 22 and 23 used steels with excessive Nb content, these produced a large amount of Nb · Ti carbides, As a result, voids having an equivalent circle diameter of 1.0 μm or more were increased. As a result, the toughness could not be improved.

Claims (4)

  1. 　質量％で、Ｃ：０.６０～１.２５％、Ｓｉ：０.５０％以下、Ｍｎ：０.３０～１.２０％、Ｐ：０.０３０％以下、Ｓ：０.０３０％以下、Ｃｒ：０.３０～１.５０％、Ｎｂ：０.１０～０.５０％、Ｔｉ：０～０.５０％、Ｍｏ：０～０.５０％、Ｖ：０～０.５０％、Ｎｉ：０～２.００％、残部Ｆｅおよび不可避的不純物からなる化学組成を有し、フェライト相の金属素地中に、セメンタイト粒子と、Ｎｂ、Ｔｉの１種以上を含有する炭化物（以下「Ｎｂ・Ｔｉ系炭化物」という。）の粒子が分散した金属組織を有し、圧延方向および板厚方向に平行な断面（Ｌ断面）において、円相当径０.５μｍ以上のＮｂ・Ｔｉ系炭化物粒子の個数密度が３０００～９０００個／ｍｍ２、円相当径１.０μｍ以上のボイドの個数密度が１２５０個／ｍｍ２以下である鋼板。 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 in mass% 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 0.50%, Ni Carbide: containing cementite particles and one or more of Nb and Ti in the metal base of the ferrite phase (hereinafter referred to as “Nb · The number of Nb · Ti carbide particles having a circle equivalent diameter of 0.5 μm or more in a cross section (L cross section) parallel to the rolling direction and the plate thickness direction with a metal structure in which particles of Ti carbide are dispersed. density 3,000 to 9,000 / mm 2, der number density of the circle equivalent diameter 1.0μm or more voids 1250 / mm 2 or less Steel plate.
  2. 　溶鋼が液相線温度から固相線温度まで冷却する間の冷却速度を５～２０℃／ｍｉｎに制御して鋳片を製造する工程（鋳造工程）、
    　鋳片を１２００～１３５０℃に０.５～４時間加熱保持する工程（鋳片加熱工程）、
    　熱間圧延を施す工程（熱延工程）、
    　圧延率３５％以下の冷間圧延を施し、次いで５００℃以上Ａｃ１点未満の温度で１０～５０時間保持したのち冷却する手順を、１回以上行う工程（中間冷延焼鈍工程）、
    　圧延率６０％以下の冷間圧延を施す工程（仕上げ冷延工程）、
    を上記の順に有する請求項１に記載の鋼板の製造方法。     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),
    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. or more and less than Ac 1 point for 10 to 50 hours and cooling once (intermediate cold rolling annealing step);
    Cold rolling with a rolling ratio of 60% or less (finishing cold rolling)
    The manufacturing method of the steel plate of Claim 1 which has these in order.
  3. 　上記熱延工程と中間冷延焼鈍工程の間に、
    　熱延工程で得た熱延鋼板に５００℃以上Ａｃ１点未満の温度で１０～５０時間保持したのち冷却する焼鈍を施す工程（熱延板焼鈍工程）、
    を有する請求項２に記載の鋼板の製造方法。     Between the hot rolling process and the intermediate cold rolling annealing process,
    A step of subjecting the heat-rolled steel sheet obtained in the hot-rolling step to annealing at a temperature of 500 ° C. or more and less than 1 point Ac for 10 to 50 hours and then cooling (hot-rolled sheet annealing step)
    The manufacturing method of the steel plate of Claim 2 which has.
  4. 　前記仕上げ冷延工程後に、
    　３００～５００℃で１～５時間保持する焼鈍を施す工程（歪取り焼鈍工程）、
    を有する請求項２または３に記載の鋼板の製造法。     After the finishing cold rolling process,
    Applying annealing at 300 to 500 ° C. for 1 to 5 hours (strain relief annealing step);
    The manufacturing method of the steel plate of Claim 2 or 3 which has.
PCT/JP2017/030614 2017-08-25 2017-08-25 Wear-resistant steel sheet having excellent toughness WO2019038923A1 (en)

Priority Applications (5)

Application Number Priority Date Filing Date Title
PCT/JP2017/030614 WO2019038923A1 (en) 2017-08-25 2017-08-25 Wear-resistant steel sheet having excellent toughness
EP17922610.5A EP3674432A4 (en) 2017-08-25 2017-08-25 Wear-resistant steel sheet having excellent toughness
CN201780094374.6A CN111373064A (en) 2017-08-25 2017-08-25 Wear-resistant steel sheet having excellent toughness
US16/634,671 US20200199702A1 (en) 2017-08-25 2017-08-25 Wear-resistant steel sheet having excellent toughness and production method
KR1020207008415A KR20200044879A (en) 2017-08-25 2017-08-25 Abrasion-resistant steel sheet with excellent toughness and manufacturing method

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/JP2017/030614 WO2019038923A1 (en) 2017-08-25 2017-08-25 Wear-resistant steel sheet having excellent toughness

Publications (1)

Publication Number Publication Date
WO2019038923A1 true WO2019038923A1 (en) 2019-02-28

Family

ID=65438607

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/JP2017/030614 WO2019038923A1 (en) 2017-08-25 2017-08-25 Wear-resistant steel sheet having excellent toughness

Country Status (5)

Country Link
US (1) US20200199702A1 (en)
EP (1) EP3674432A4 (en)
KR (1) KR20200044879A (en)
CN (1) CN111373064A (en)
WO (1) WO2019038923A1 (en)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114737131B (en) * 2022-03-30 2023-05-16 鞍钢股份有限公司 Production method of extremely-thin, extremely-wide, high-strength and wear-resistant hot continuous rolled steel plate

Citations (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS6082647A (en) 1983-10-12 1985-05-10 Kawasaki Steel Corp Clad steel plate for disc saw
JPH10137888A (en) 1996-11-13 1998-05-26 Toa Steel Co Ltd Manufacture of hot forged parts excellent in wear resistance
JP2001059128A (en) * 1999-08-20 2001-03-06 Nisshin Steel Co Ltd Steel sheet for punched parts excellent in fatigue characteristics
JP2003201536A (en) 2002-01-07 2003-07-18 Kobe Steel Ltd Non-heat-treated steel for hot working having excellent wear resistance and hot worked product
JP2009215612A (en) * 2008-03-11 2009-09-24 Nisshin Steel Co Ltd Medium-high carbon steel sheet excellent in workability and production method therefor
JP2010138453A (en) 2008-12-11 2010-06-24 Nisshin Steel Co Ltd Steel for wear resistant quenched-tempered component, and method for producing the same
JP2011012316A (en) * 2009-07-02 2011-01-20 Nippon Steel Corp Soft high-carbon steel sheet superior in punchability and method for manufacturing the same
JP2011195858A (en) 2010-03-18 2011-10-06 Sumitomo Metal Ind Ltd Hot rolled steel for direct machining and method for producing the same
CN103173685A (en) * 2013-01-07 2013-06-26 宝钢集团新疆八一钢铁有限公司 Production method of high-strength saw bit steel coil
JP2013136820A (en) 2011-12-28 2013-07-11 Nisshin Steel Co Ltd Wear-resistant steel excellent in fatigue characteristic and production method thereof
JP2015190037A (en) * 2014-03-28 2015-11-02 日新製鋼株式会社 Raw material steel sheet for chain saw component and chain saw component
JP2016222990A (en) * 2015-06-02 2016-12-28 新日鐵住金株式会社 High carbon steel sheet and production method therefor
JP2017190494A (en) * 2016-04-13 2017-10-19 日新製鋼株式会社 Wear resistant steel sheet excellent in toughness

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2690189B1 (en) * 2011-03-25 2020-05-06 Nippon Steel Nisshin Co., Ltd. Steel plate with excellent durability for band-shaped die-cutting blade, and band-shaped die-cutting blade
EP2692890B1 (en) * 2011-03-29 2018-07-25 JFE Steel Corporation Abrasion-resistant steel plate or steel sheet and method for producing the same
JP6017341B2 (en) * 2013-02-19 2016-10-26 株式会社神戸製鋼所 High strength cold-rolled steel sheet with excellent bendability
JP6117140B2 (en) * 2014-03-28 2017-04-19 日新製鋼株式会社 Steel plate for textile machine parts and method for producing the same
CN107849650B (en) * 2015-07-16 2019-10-25 日铁日新制钢株式会社 Fiber mechanical part steel plate and its manufacturing method

Patent Citations (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS6082647A (en) 1983-10-12 1985-05-10 Kawasaki Steel Corp Clad steel plate for disc saw
JPH10137888A (en) 1996-11-13 1998-05-26 Toa Steel Co Ltd Manufacture of hot forged parts excellent in wear resistance
JP2001059128A (en) * 1999-08-20 2001-03-06 Nisshin Steel Co Ltd Steel sheet for punched parts excellent in fatigue characteristics
JP2003201536A (en) 2002-01-07 2003-07-18 Kobe Steel Ltd Non-heat-treated steel for hot working having excellent wear resistance and hot worked product
JP2009215612A (en) * 2008-03-11 2009-09-24 Nisshin Steel Co Ltd Medium-high carbon steel sheet excellent in workability and production method therefor
JP2010138453A (en) 2008-12-11 2010-06-24 Nisshin Steel Co Ltd Steel for wear resistant quenched-tempered component, and method for producing the same
JP2011012316A (en) * 2009-07-02 2011-01-20 Nippon Steel Corp Soft high-carbon steel sheet superior in punchability and method for manufacturing the same
JP2011195858A (en) 2010-03-18 2011-10-06 Sumitomo Metal Ind Ltd Hot rolled steel for direct machining and method for producing the same
JP2013136820A (en) 2011-12-28 2013-07-11 Nisshin Steel Co Ltd Wear-resistant steel excellent in fatigue characteristic and production method thereof
CN103173685A (en) * 2013-01-07 2013-06-26 宝钢集团新疆八一钢铁有限公司 Production method of high-strength saw bit steel coil
JP2015190037A (en) * 2014-03-28 2015-11-02 日新製鋼株式会社 Raw material steel sheet for chain saw component and chain saw component
JP2016222990A (en) * 2015-06-02 2016-12-28 新日鐵住金株式会社 High carbon steel sheet and production method therefor
JP2017190494A (en) * 2016-04-13 2017-10-19 日新製鋼株式会社 Wear resistant steel sheet excellent in toughness

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See also references of EP3674432A4 *

Also Published As

Publication number Publication date
EP3674432A1 (en) 2020-07-01
CN111373064A (en) 2020-07-03
EP3674432A4 (en) 2020-12-16
US20200199702A1 (en) 2020-06-25
KR20200044879A (en) 2020-04-29

Similar Documents

Publication Publication Date Title
JP6615039B2 (en) Wear-resistant steel plate with excellent toughness
JP5484103B2 (en) Steel plate for high-strength machine parts, method for producing the same, and method for producing high-strength machine parts
JP6880245B1 (en) High carbon cold rolled steel sheet and its manufacturing method and high carbon steel machine parts
WO2015125915A1 (en) Steel material for induction hardening
TW201708558A (en) Steel sheet and manufacturing method therefor
JP5280324B2 (en) High carbon steel sheet for precision punching
JPWO2020070810A1 (en) Manufacturing method of carburized steel sheet and carburized steel sheet
JP4465057B2 (en) High carbon steel sheet for precision punching
JP3485805B2 (en) Hot forged non-heat treated steel having high fatigue limit ratio and method for producing the same
EP3336206A1 (en) Method for manufacturing product member, and product member
JP5871085B2 (en) Case-hardened steel with excellent cold forgeability and ability to suppress grain coarsening
JP4266341B2 (en) Steel for omitting spheroidizing annealing with excellent cold forgeability and anti-roughening properties during case hardening, and method for producing the same
JP5207743B2 (en) Steel for blades with excellent wear resistance and toughness
JP6690792B1 (en) Steel sheet, method of manufacturing the same, and molded body
JP2002212679A (en) EDGE TOOL AND Fe-BASED ALLOY FOR EDGE TOOL USED THEREFOR
WO2019038923A1 (en) Wear-resistant steel sheet having excellent toughness
JP4159009B2 (en) Steel sheet for punched parts with excellent fatigue characteristics
JP3715802B2 (en) Steel wire rod capable of rapid spheroidization and excellent cold forgeability and method for producing the same
JP4161090B2 (en) High carbon steel plate with excellent punchability
JP7288177B2 (en) Steel plate and steel plate manufacturing method
WO2022264948A1 (en) Steel part and manufacturing method of steel part
JP2000265238A (en) Reclining seat gear made of steel
TW201912811A (en) Wear-resistant steel plate with excellent roughness and manufacturing method thereof
JP7336685B2 (en) Steel materials and parts for refining heat treatment
WO2022153790A1 (en) Martensite-based stainless steel material and method for producing same

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 17922610

Country of ref document: EP

Kind code of ref document: A1

NENP Non-entry into the national phase

Ref country code: DE

ENP Entry into the national phase

Ref document number: 20207008415

Country of ref document: KR

Kind code of ref document: A

ENP Entry into the national phase

Ref document number: 2017922610

Country of ref document: EP

Effective date: 20200325

NENP Non-entry into the national phase

Ref country code: JP