WO2011004554A1 - Process for production of cold-rolled steel sheet having excellent press moldability, and cold-rolled steel sheet - Google Patents

Process for production of cold-rolled steel sheet having excellent press moldability, and cold-rolled steel sheet Download PDF

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Publication number
WO2011004554A1
WO2011004554A1 PCT/JP2010/004062 JP2010004062W WO2011004554A1 WO 2011004554 A1 WO2011004554 A1 WO 2011004554A1 JP 2010004062 W JP2010004062 W JP 2010004062W WO 2011004554 A1 WO2011004554 A1 WO 2011004554A1
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Prior art keywords
steel sheet
rolled steel
cold
rolling
tensile strength
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PCT/JP2010/004062
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French (fr)
Japanese (ja)
Inventor
大井聡史
西山茂嘉
吉田冬樹
楠本雄二
秋末治
Original Assignee
東洋鋼鈑株式会社
株式会社中山製鋼所
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Application filed by 東洋鋼鈑株式会社, 株式会社中山製鋼所 filed Critical 東洋鋼鈑株式会社
Priority to US13/383,193 priority Critical patent/US20120234438A1/en
Priority to JP2011521800A priority patent/JP5717631B2/en
Priority to EP10796868.7A priority patent/EP2455499B1/en
Priority to CN201080028024.8A priority patent/CN102471821B/en
Publication of WO2011004554A1 publication Critical patent/WO2011004554A1/en

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • 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
    • 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
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/0006—Details, accessories not peculiar to any of the following furnaces
    • 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
    • C21D9/0037—Rotary furnaces with vertical axis; Furnaces with rotating floor
    • 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
    • C22C38/001—Ferrous alloys, e.g. steel alloys containing N
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/50—Ferrous alloys, e.g. steel alloys containing chromium with nickel with 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
    • C22C38/58—Ferrous alloys, e.g. steel alloys containing chromium with nickel with more than 1.5% by weight of manganese

Definitions

  • the present invention relates to a method for producing a cold-rolled steel sheet excellent in press formability and a cold-rolled steel sheet produced by the production method.
  • Liquid crystal frame parts used in mobile phones, notebook computers, etc. and gasket parts for automobile engines are often formed by cold pressing, so the thin cold-rolled steel sheets used require press formability. ing.
  • parts such as notebook PCs, mobile phones, digital cameras such as digital cameras, and automobile engine gaskets.
  • it is necessary to make the steel plate thinner, and furthermore, it is necessary to provide a high strength steel plate having a thin gauge and high strength because the strength as a pressed part cannot be secured with the same strength.
  • Patent Document 1 proposes a cold-rolled steel sheet for gasket material that has excellent spring properties, in which the steel sheet is heated to a recrystallization temperature or higher in continuous annealing, and is subjected to annealing after soaking and secondary cold rolling. .
  • an object of the present invention is to provide a high-strength cold-rolled steel sheet having a small load during cold rolling and excellent in press formability, and a method for producing the same.
  • the manufacturing method of the cold-rolled steel sheet of the present invention is mass%, C: 0.10 to 0.30, Mn: 0.2 or more, Ni: 0.01 or more, Mn + Ni: 0.5 to 2.5, Cr: 1.2 to 9.0,
  • the balance consists of iron and inevitable impurities
  • the method for producing a cold-rolled steel sheet according to the present invention is characterized in that, in (1), the hot-rolled steel sheet has a thickness of 1.2 to 3.0 mm.
  • the cold-rolled steel sheet of the present invention is mass%, C: 0.10 to 0.30, Mn: 0.2 or more, Ni: 0.01 or more, Mn + Ni: 0.5 to 2.5, Cr: 1.2 to 9.0,
  • the balance consists of iron and inevitable impurities,
  • the cold-rolled steel sheet of the present invention is characterized in that, in (3), the hot-rolled steel sheet has a thickness of 1.2 to 3.0 mm.
  • the cold rolling steel sheet excellent in the press forming which reduced the load at the time of cold rolling, and ensured high intensity
  • a cold-rolled steel sheet having 0.6 mm, tensile strength: 1280 MPa or more, and breaking elongation: 3% or more and having both strength and workability can be provided.
  • C 0.10 to 0.30
  • Mn 0.2 or more
  • Ni 0.01 or more
  • Mn + Ni 0.5 to 2.5
  • Cr 1.2 to 9.0
  • balance Fe and inevitable It is an element.
  • C is an important element for generating a low temperature transformation structure such as martensite in the steel sheet and obtaining high tensile strength. If it is less, the necessary tensile strength cannot be obtained, so the lower limit is set to 0.10.
  • the upper limit is set to 0.30.
  • a more preferable C range is 0.15 to 0.25.
  • both Mn and Ni are elements that enhance the hardenability and generate a low-temperature transformation structure during continuous annealing, and impart high tensile strength to the cold-rolled steel sheet after continuous annealing. If the total amount of both components is too small, strength cannot be obtained after continuous annealing, so the lower limit is set to 0.5. On the other hand, if the amount is too large, the effect is saturated, and the workability deteriorates due to segregation or the like, so the upper limit is set to 2.5. In addition, about each range of Mn and Ni, it is necessary to contain Mn 0.20 or more in order to prevent red heat due to impurity S, and Ni is 0.01 or more in order to ensure toughness after heat treatment. Addition is necessary. Since Ni is expensive, adjusting with Mn is advantageous in terms of cost.
  • Cr is also an element that enhances hardenability, and generates a low-temperature transformation structure during continuous annealing, resulting in high tensile strength. If it is less, tensile strength cannot be obtained after continuous annealing, so the lower limit is set to 1.2. If the amount is too large, the effect is saturated, and unnecessary costs are increased, so the upper limit is set to 9.0. More preferably, it is 2.0 to 5.5.
  • Si is an element effective for increasing the strength of a cold-rolled steel sheet, and the better it is to achieve its purpose, but if it exceeds 2.0%, the cold rolling load increases and the shape deteriorates. Therefore, the upper limit is set to 2.0%.
  • P is preferably added at a certain ratio because it increases the strength of the grain refinement component and the cold-rolled steel sheet. On the other hand, P segregates at the grain boundaries and causes embrittlement. To do.
  • S is an impurity component that causes red heat embrittlement during hot rolling, and it is desirable that S be as small as possible. However, S cannot be completely prevented from being mixed with raw materials, and desulfurization in the process is limited to some extent. Residue is unavoidable. Since red heat brittleness due to a small amount of residual S can be reduced by Mn, the upper limit value of the S component is set to 0.06%.
  • Cu can be added in a certain amount to improve the strength by solid solution strengthening or precipitation strengthening, but on the other hand, it may cause embrittlement during hot rolling. Therefore, the upper limit is 0.5%.
  • Al is added to the steel bath as a deoxidizer during steel making, reacts with solute N, precipitates as AlN, and contributes to refinement of crystal grains.
  • addition exceeding 0.10% makes the fixation of N remarkably and reduces the solid solution strengthening of N, so it is made 0.10% or less.
  • Ti has effects such as refinement of crystal grains, suppression of grain growth, and improvement of corrosion resistance, but the effect is saturated even if added excessively, so 0.30% or less.
  • N is a component necessary for imparting high strength to the cold-rolled steel sheet and for strengthening the proof stress. However, if it is less than 0.002%, it causes difficulty in steelmaking. Addition exceeding 015% significantly reduces the yield of ferronitride added during steelmaking, lacks stability, and significantly deteriorates anisotropy during press molding. Furthermore, since cracks are generated on the surface of the continuous cast piece, resulting in casting defects, it is desirable in the present invention that the N component range be 0.015% or less.
  • ⁇ Manufacturing process> the manufacturing method of the cold-rolled steel sheet of this invention is described.
  • ⁇ Steel making> It is melted in a converter or an electric furnace and adjusted to the above component range to obtain a slab piece.
  • ⁇ Hot rolling> The component-adjusted slab piece is hot rolled to a thickness of 1.2 to 3.0 mm. If the plate thickness is small, the load is increased during hot rolling, so the lower limit is set to 1.2. Further, if the plate thickness is large, the load is increased during the subsequent cold rolling, so the upper limit is set to 3.0.
  • the slab piece having the above component range is heated at a temperature of 1100 ° C. or higher and a winding temperature is 600 ° C.
  • the heating temperature of the slab piece is less than 1100 ° C., it is not preferable because the active decomposition and dissolution of N is insufficient and the hot rolling load becomes high.
  • the winding temperature is 600 ° C. to 800 ° C. If the coiling temperature is low, the hot-rolled steel sheet is increased in strength, which is not preferable during cold rolling. Therefore, the lower limit of the coiling temperature is set to 600 ° C. On the other hand, if the coiling temperature exceeds 800 ° C., scale formation is promoted during hot rolling and an increase in load is caused during descaling by pickling, so the upper limit is set to 800 ° C.
  • the hot-rolled steel sheet manufactured under the above conditions can have a tensile strength of 1000 MPa or less. This is because a tensile strength exceeding 1000 MPa is not preferable because of an increase in rolling load during cold rolling.
  • ⁇ Pickling> After removing the scale of the surface produced at the time of hot rolling in an acid bath according to a conventional method, it is cold-rolled and continuously annealed.
  • Cold rolling is performed in one or several times at a total rolling rate of 60% or more to a predetermined product thickness of 0.05 to 0.6 mm. If this thickness is less than 0.05 mm, the rigidity will be reduced, and the shape will be deformed when used in products such as automobile gasoline engine gaskets, laptop computers, mobile phones, and digital camera LCD frames and frame parts. This is because it may become easy to manufacture the product.
  • this thickness is greater than 0.6 mm, it will be heavier than the design value when used in products such as gasoline engine gaskets for automobiles, laptop computers, mobile phones, and liquid crystal frames and frame parts for digital cameras. This is because there is a case where it is impossible to achieve downsizing.
  • the upper limit of the total rolling rate in cold rolling is not particularly specified, but is 98%. Further, after cold rolling, by performing continuous annealing at 500 ° C. or higher or batch annealing at 500 ° C. or higher, it is possible to soften the work-hardened rolled plate and perform cold rolling again.
  • the method of cold rolling and the number of cold rolling are not particularly specified, but can be appropriately selected according to the target plate thickness.
  • Continuous annealing removes distortion of the plate during cold rolling, but this continuous annealing can be performed each time when performing cold rolling a plurality of times.
  • the soaking is maintained at a soaking temperature of 750 ° C. or more and 1 s or more and 100 s or less.
  • the soaking temperature is less than 750 ° C., the Ae3 transformation temperature is not exceeded, so that sufficient tensile strength cannot be obtained.
  • the upper limit is set to 1000 ° C.
  • a part or the whole is austenitized by heating, and these are transformed into martensite or the like by subsequent cooling.
  • a predetermined strength can be obtained by the amount of martensite and the amount of alloy elements.
  • cooling is performed at a cooling rate of 3 ° C./s to 100 ° C./s.
  • the austenite structure of the plate is changed to a structure such as martensite, tempered martensite, and bainite. If the cooling rate is less than 3 ° C./s, the formation of a low temperature transformation structure such as martensite is insufficient, and the required strength cannot be obtained. On the other hand, if the cooling rate exceeds 100 ° C./s, the required strength can be obtained, but the shape of the steel sheet is deteriorated.
  • the cooling rate after continuous annealing is cooled at a much slower cooling rate compared to quenching using general water or the like in order to ensure the shape, thereby generating a low-temperature transformation structure to obtain a high-strength steel sheet.
  • Mn and Ni which are effective austenite stabilizing elements as general quenching elements, need to be added in a considerable amount in order to obtain the required strength at the above cooling rate. It brings high strength, increases the load during cold rolling, and hinders productivity, thus causing an increase in production cost.
  • the amount of Mn and Ni added is relatively small, and Cr, which is a ferrite stable element, is added in combination, so that it is relatively soft after hot rolling and has high strength in continuous annealing after cold rolling. It is possible to manufacture a steel plate, and the manufacturing load can be significantly reduced.
  • the tempering process is performed at the time of cooling. Equivalent effects can be obtained, and the tempering process can be omitted. Since the tempering process can be omitted, the manufacturing load can be greatly reduced.
  • the tensile strength of the cold-rolled steel sheet obtained by the production method of the present invention can be set to 1280 MPa or more.
  • the plate thickness is reduced to reduce weight, ensuring rigidity as a part even when used in mobile applications. be able to.
  • the elongation at break of the cold-rolled steel sheet can be 3% or more by the production method of the present invention.
  • the value of elongation at break indicating ductility is important in the case of press molding for applications such as automobile engine gaskets and electronic parts. If the elongation at break is less than 3%, cracks are likely to occur in the processed part such as mild overhanging or 90 ° bending.
  • the steel sheet manufactured by the above manufacturing method has a structure such as martensite, tempered martensite, and bainite structure of 60% or more in volume ratio, and has a high tensile strength of 1280 MPa or more even in a thin steel sheet and is ductile. Can be manufactured.
  • the steel sheet thus obtained can be subjected to temper rolling for adjusting the surface roughness and electroplating and chemical conversion treatment of Zn, Ni, etc. for rust prevention as required.
  • slab pieces having the components shown in Tables 1 to 18 shown in Table 1 were prepared. Samples 1 to 11, 17, and 18 are slab pieces that fall within the component range of the present invention, while Samples 12 to 16 are slab pieces outside the component range of the present invention.
  • slab pieces adjusted to the components shown in Samples 1 to 18 were heated to 1230 ° C. to produce hot rolled steel sheets having a thickness of 2.0 mm at the winding temperatures shown in Table 2.
  • Table 2 shows the characteristics of this hot-rolled steel sheet.
  • the soaking temperature is maintained at 900 ° C. for 20 s and then cooled at a cooling rate of 20 ° C./s.
  • Cold-rolled steel sheet The properties of this cold rolled steel sheet are shown in Table 2. As can be seen from Table 2, in Examples 1 to 15, the tensile strength of the hot-rolled steel sheet is 1000 MPa or less, and it can be thinned to the target 0.5 mm in the subsequent cold rolling. The tensile strength was 1280 MPa or more, and the elongation at break was 3% or more.
  • Example 3 the cooling rates after soaking were changed to 3 ° C./s and 100 ° C./s, respectively, but the tensile strengths of 1320 MPa and 1405 MPa, the elongation at break 6.2%, 6 A cold-rolled steel sheet having 0.0% could be obtained.
  • Comparative Example 1 was manufactured from Sample 1 which is the same component as Example 1, but since the coiling temperature was lowered to 480 ° C., the tensile strength of the hot rolled steel sheet was as high as 1108 MPa, and since it was hard, Cold rolling was stopped because it was not possible to reduce the thickness to 0.5 mm, which was the target in cold rolling, and cracking occurred when the rolling load and rolling frequency were increased.
  • the hot-rolled steel sheet of Comparative Example 2 was manufactured from Sample 2 having the same components as in Examples 2 to 4. However, since the coiling temperature was lowered to 500 ° C., the tensile strength of the hot-rolled steel sheet was as high as 1216 MPa.
  • Comparative Examples 3 and 4 C is 0.10 or less, Comparative Example 5 is Cr is 1.2% or less, and Comparative Example 7 is low in Mn and Ni and Mn + Ni is 0.5% or less. For this reason, the tensile strength of each cold-rolled steel sheet was 1280 MPa or less, and the strength was insufficient when used as a gasket or frame part, which was not applicable.
  • the cold rolling steel sheet excellent in the press forming which reduced the load at the time of cold rolling, and ensured high intensity
  • strength and ductility can be provided.
  • Cold-rolled steel sheet can be provided, and industrial applicability is extremely high.

Abstract

Disclosed are: a cold-rolled steel sheet which undergoes less load during cold rolling and has excellent press moldability and high strength; and a process for producing the cold-rolled steel sheet. A hot-rolled steel sheet comprising 0.10 to 0.30 mass% of C, 0.2 mass% or more of Mn, 0.01 mass% or more of Ni (wherein the sum total of Mn and Ni is 0.5 to 2.5 mass%), and 1.2 to 9.0 mass% of Cr, with the remainder being iron and unavoidable impurities, and having a tensile strength of 1000 MPa or less is washed with an acid, and is subjected to cold rolling at a total rolling ratio of 60% or more, thereby producing a cold-rolled steel sheet. The cold-rolled steel sheet is subjected to the final continuous annealing treatment at a homogenizing temperature of 750˚C or higher and a cooling rate of 3 to 100˚C/s. In this manner, a cold-rolled steel sheet having a tensile strength of 1280 MPa or more, a breaking elongation of 3% or more, and a thickness of 0.05 to 0.60 mm.

Description

プレス成形性に優れた冷延鋼板の製造方法及び冷延鋼板Cold-rolled steel sheet manufacturing method and cold-rolled steel sheet excellent in press formability
　本発明は、プレス成形性に優れた冷延鋼板の製造方法及びその製造方法により製造された冷延鋼板に関する。 The present invention relates to a method for producing a cold-rolled steel sheet excellent in press formability and a cold-rolled steel sheet produced by the production method.
　携帯電話やノートパソコン等に用いられる液晶のフレーム部品や、自動車エンジン用ガスケット部品等は、冷間プレスで成形されることが多いため、使用される薄板の冷延鋼板はプレス成形性が求められている。
　また、ノートパソコンや携帯電話、デジタルカメラに代表される電子部品や自動車エンジン用ガスケットなどの部品においては、軽量化や小型化の要求もあり、これらの部品を軽量化、小型化するためには、鋼板を薄くする必要があり、さらに、同じ強度ではプレス部品としての強度を確保できないため、薄ゲージかつ高強度を有する高強度鋼板を提供する必要がある。
　このような技術的背景から、自動車のバンパーやドアの補強部材としての用途向けに、マルテンサイト又はベイナイト組織を有する、引張強度１１８０ＭＰａ以上の超高強度鋼板が提案されている（特許文献１参照）。
　また、特許文献２には、連続焼鈍において鋼板を再結晶温度以上に加熱し、均熱後焼鈍、２次冷延を施した、ばね性に優れたガスケット材用冷延鋼板が提案されている。 Liquid crystal frame parts used in mobile phones, notebook computers, etc. and gasket parts for automobile engines are often formed by cold pressing, so the thin cold-rolled steel sheets used require press formability. ing.
In addition, there are demands for weight reduction and miniaturization of parts such as notebook PCs, mobile phones, digital cameras such as digital cameras, and automobile engine gaskets. To make these parts lighter and smaller Further, it is necessary to make the steel plate thinner, and furthermore, it is necessary to provide a high strength steel plate having a thin gauge and high strength because the strength as a pressed part cannot be secured with the same strength.
From such a technical background, an ultra-high strength steel sheet having a martensite or bainite structure and having a tensile strength of 1180 MPa or more has been proposed for use as a reinforcing member for automobile bumpers or doors (see Patent Document 1). .
Patent Document 2 proposes a cold-rolled steel sheet for gasket material that has excellent spring properties, in which the steel sheet is heated to a recrystallization temperature or higher in continuous annealing, and is subjected to annealing after soaking and secondary cold rolling. .
特許第３２５４１０６号公報Japanese Patent No. 3254106 特開平９－１９４９３５号公報JP-A-9-194935
　しかし、特許文献１や特許文献２に記載のような高強度鋼板は、高強度化を図ったために延性が低下し、プレス成形時に割れが発生し、プレス成形性に劣っているという問題点がある。
　また、高強度熱延鋼板の冷延時において、薄ゲージ化するためには、冷間圧延時の負荷が増大し、作業性の低下と歩留りロスの増加のため生産性が阻害されるという問題点もある。
　本発明は、上記課題を解決するため、冷間圧延時の負荷が少なく、しかもプレス成形性に優れた高強度の冷延鋼板及びその製造方法を提供することを目的とする。 However, high strength steel sheets such as those described in Patent Document 1 and Patent Document 2 have problems in that ductility is reduced due to increased strength, cracking occurs during press molding, and press formability is poor. is there.
In addition, in order to reduce the thickness of a high-strength hot-rolled steel sheet, the load during cold rolling increases, and the productivity is hindered due to a decrease in workability and an increase in yield loss. There is also.
In order to solve the above-described problems, an object of the present invention is to provide a high-strength cold-rolled steel sheet having a small load during cold rolling and excellent in press formability, and a method for producing the same.
（１）本発明の冷延鋼板の製造方法は、質量％で、
Ｃ：０．１０～０．３０、
Ｍｎ；０．２以上、
Ｎｉ；０．０１以上、
Ｍｎ＋Ｎｉ：０．５～２．５、
Ｃｒ：１．２～９．０、
残部が鉄及び不可避的不純物からなり、
引張強度が１０００ＭＰａ以下である熱間圧延鋼板を、酸洗後、合計で６０％以上の圧延率の冷間圧延を行って冷延鋼板とし、
最終の連続焼鈍処理を、均熱温度を７５０℃以上とし、冷却速度を３℃／ｓ～１００℃／ｓとし、
引張強度が１２８０ＭＰａ以上、破断伸びが３％以上、厚み０．０５～０．６０ｍｍであることを特徴とする。
（２）本発明の冷延鋼板の製造方法は、前記（１）において、前記熱間圧延鋼板の厚みが１．２～３．０ｍｍであることを特徴とする。
（３）本発明の冷延鋼板は、質量％で、
Ｃ：０．１０～０．３０、
Ｍｎ；０．２以上、
Ｎｉ；０．０１以上、
Ｍｎ＋Ｎｉ：０．５～２．５、
Ｃｒ：１．２～９．０、
残部が鉄及び不可避的不純物からなり、
引張強度が１０００ＭＰａ以下である熱間圧延鋼板を、
酸洗後、合計で６０％以上の圧延率の冷間圧延を行って冷延鋼板とし、
最終の連続焼鈍処理を、均熱温度を７５０℃以上とし、冷却速度を３℃／ｓ～１００℃／ｓとし、
引張強度が１２８０ＭＰａ以上、破断伸びが３％以上、厚み０．０５～０．６０ｍｍであることを特徴とする。
（４）本発明の冷延鋼板は、前記（３）において、前記熱間圧延鋼板の厚みが１．２～３．０ｍｍであることを特徴とする。 (1) The manufacturing method of the cold-rolled steel sheet of the present invention is mass%,
C: 0.10 to 0.30,
Mn: 0.2 or more,
Ni: 0.01 or more,
Mn + Ni: 0.5 to 2.5,
Cr: 1.2 to 9.0,
The balance consists of iron and inevitable impurities,
A hot-rolled steel sheet having a tensile strength of 1000 MPa or less, after pickling, is cold-rolled steel sheet by performing cold rolling at a rolling rate of 60% or more in total,
In the final continuous annealing treatment, the soaking temperature is set to 750 ° C. or more, the cooling rate is set to 3 ° C./s to 100 ° C./s,
The tensile strength is 1280 MPa or more, the elongation at break is 3% or more, and the thickness is 0.05 to 0.60 mm.
(2) The method for producing a cold-rolled steel sheet according to the present invention is characterized in that, in (1), the hot-rolled steel sheet has a thickness of 1.2 to 3.0 mm.
(3) The cold-rolled steel sheet of the present invention is mass%,
C: 0.10 to 0.30,
Mn: 0.2 or more,
Ni: 0.01 or more,
Mn + Ni: 0.5 to 2.5,
Cr: 1.2 to 9.0,
The balance consists of iron and inevitable impurities,
A hot rolled steel sheet having a tensile strength of 1000 MPa or less,
After pickling, cold rolling at a rolling rate of 60% or more in total is made into a cold rolled steel sheet,
In the final continuous annealing treatment, the soaking temperature is set to 750 ° C. or more, the cooling rate is set to 3 ° C./s to 100 ° C./s,
The tensile strength is 1280 MPa or more, the elongation at break is 3% or more, and the thickness is 0.05 to 0.60 mm.
(4) The cold-rolled steel sheet of the present invention is characterized in that, in (3), the hot-rolled steel sheet has a thickness of 1.2 to 3.0 mm.
　本発明によれば、冷間圧延時の負荷を軽減し、高強度かつ延性を確保したプレス成形に優れた冷延鋼板を提供することができる。
　また、本発明の冷延鋼板の製造方法によれば、自動車のガソリンエンジンのガスケット、ノートパソコン、携帯電話、デジタルカメラの液晶フレームやフレーム部品等に用いる素材として求められる厚さ：０．０５ｍｍ～０．６ｍｍ、引張強度：１２８０ＭＰａ以上、破断伸び：３％以上を有する、強度と加工性を同時に備えた冷延鋼板を提供できる。 ADVANTAGE OF THE INVENTION According to this invention, the cold rolling steel sheet excellent in the press forming which reduced the load at the time of cold rolling, and ensured high intensity | strength and ductility can be provided.
In addition, according to the method for producing a cold-rolled steel sheet of the present invention, a thickness required as a material used for a gasoline engine gasket of an automobile, a notebook computer, a mobile phone, a liquid crystal frame or a frame part of a digital camera, etc .: 0.05 mm A cold-rolled steel sheet having 0.6 mm, tensile strength: 1280 MPa or more, and breaking elongation: 3% or more and having both strength and workability can be provided.
＜熱間圧延鋼板の成分＞
熱間圧延鋼板の成分は、質量％で、下記の範囲とする。
Ｃ；０．１０～０．３０、Ｍｎ；０．２以上、Ｎｉ；０．０１以上、Ｍｎ＋Ｎｉ；０．５～２．５、Ｃｒ；１．２～９．０、残部；Ｆｅ及び不可避的元素である。
Ｃは、鋼板中にマルテンサイト等低温変態組織を生成させ、高い引張強度を得るに重要な元素である。
少ないと、必要な引張強度が得られないため下限を０．１０とする。一方で多すぎると、熱延及び冷延時の圧延負荷を増大させ、形状劣化等、生産性を阻害するため、上限を０．３０とする。より好ましいＣ範囲は、０．１５～０．２５である。 <Components of hot-rolled steel sheet>
The components of the hot-rolled steel sheet are in mass% and are in the following range.
C: 0.10 to 0.30, Mn: 0.2 or more, Ni: 0.01 or more, Mn + Ni: 0.5 to 2.5, Cr: 1.2 to 9.0, balance: Fe and inevitable It is an element.
C is an important element for generating a low temperature transformation structure such as martensite in the steel sheet and obtaining high tensile strength.
If it is less, the necessary tensile strength cannot be obtained, so the lower limit is set to 0.10. On the other hand, if the amount is too large, the rolling load during hot rolling and cold rolling is increased, and the productivity such as shape deterioration is hindered, so the upper limit is set to 0.30. A more preferable C range is 0.15 to 0.25.
　本発明において、Ｍｎ及びＮｉは、共に焼き入れ性を高め、連続焼鈍時に低温変態組織を生成させる元素であり、連続焼鈍後の冷延鋼板に高い引張強度を付与する。両成分の合計量が少なすぎると連続焼鈍後に強度が得られないので、下限を０．５とする。一方多すぎると効果が飽和し、また偏析等によって加工性が低下するので、上限を２．５とする。
なお、ＭｎとＮｉのそれぞれの範囲については、Ｍｎは不純物であるＳによる赤熱防止するため０．２０以上含有させることが必要であり、Ｎｉは熱処理後の靭性を確保するため０．０１以上の添加が必要である。Ｎｉは高価であるため、Ｍｎで調整するほうがコスト的には有利である。 In the present invention, both Mn and Ni are elements that enhance the hardenability and generate a low-temperature transformation structure during continuous annealing, and impart high tensile strength to the cold-rolled steel sheet after continuous annealing. If the total amount of both components is too small, strength cannot be obtained after continuous annealing, so the lower limit is set to 0.5. On the other hand, if the amount is too large, the effect is saturated, and the workability deteriorates due to segregation or the like, so the upper limit is set to 2.5.
In addition, about each range of Mn and Ni, it is necessary to contain Mn 0.20 or more in order to prevent red heat due to impurity S, and Ni is 0.01 or more in order to ensure toughness after heat treatment. Addition is necessary. Since Ni is expensive, adjusting with Mn is advantageous in terms of cost.
　Ｃｒもまた焼き入れ性を高める元素であり，連続焼鈍時に低温変態組織を生成させ高い引張強度が得られる。少ないと連続焼鈍後に引張強度が得られないため、下限を１．２とする。多すぎると効果が飽和し，また無駄なコストアップを引き起こすので，上限を９．０とする。より好ましくは２．０～５．５である。 Cr is also an element that enhances hardenability, and generates a low-temperature transformation structure during continuous annealing, resulting in high tensile strength. If it is less, tensile strength cannot be obtained after continuous annealing, so the lower limit is set to 1.2. If the amount is too large, the effect is saturated, and unnecessary costs are increased, so the upper limit is set to 9.0. More preferably, it is 2.0 to 5.5.
　Ｓｉは、冷延鋼板を高強度化するのに有効な元素であり、その目的を達成するためには多い程良いが、２．０％を超えると冷間圧延の負荷の増大、形状の劣化を招くため上限値を２．０％とする。 Si is an element effective for increasing the strength of a cold-rolled steel sheet, and the better it is to achieve its purpose, but if it exceeds 2.0%, the cold rolling load increases and the shape deteriorates. Therefore, the upper limit is set to 2.0%.
　Ｐは、結晶粒微細化成分、冷延鋼板の強度を高めることから一定の割合で添加することが望ましいが、一方で結晶粒界に偏析し、脆化を引き起こすため、０．０６％以下とする。 P is preferably added at a certain ratio because it increases the strength of the grain refinement component and the cold-rolled steel sheet. On the other hand, P segregates at the grain boundaries and causes embrittlement. To do.
　Ｓは、熱延中において赤熱脆性を生じる不純物成分であり、極力少ないことが望ましいが、原料等からの混入を完全に防止することができず、工程中の脱硫も限界があることからある程度の残留もやむをえない。少量の残留Ｓによる赤熱脆性はＭｎにより軽減できるため、Ｓ成分の上限値は０．０６％とする。 S is an impurity component that causes red heat embrittlement during hot rolling, and it is desirable that S be as small as possible. However, S cannot be completely prevented from being mixed with raw materials, and desulfurization in the process is limited to some extent. Residue is unavoidable. Since red heat brittleness due to a small amount of residual S can be reduced by Mn, the upper limit value of the S component is set to 0.06%.
　Ｃｕは、固溶強化もしくは析出強化によって強度を向上させるため一定量を添加することができるが、一方で熱間圧延時の脆化を引き起こすおそれがある。よって、上限を０．５％とする。 Cu can be added in a certain amount to improve the strength by solid solution strengthening or precipitation strengthening, but on the other hand, it may cause embrittlement during hot rolling. Therefore, the upper limit is 0.5%.
　Ａｌは、製鋼に際し脱酸剤として鋼浴中に添加され、固溶Ｎと反応してＡｌＮとして析出し結晶粒の細粒化に寄与する。一方で、０．１０％を超える添加はＮの固定が著しくなり、Ｎの固溶強化が低減するので、０．１０％以下とする。 Al is added to the steel bath as a deoxidizer during steel making, reacts with solute N, precipitates as AlN, and contributes to refinement of crystal grains. On the other hand, addition exceeding 0.10% makes the fixation of N remarkably and reduces the solid solution strengthening of N, so it is made 0.10% or less.
　Ｔｉは、結晶粒の微細化、粒成長抑制、耐食性向上などの効果を有するが、過多に添加しても効果は飽和するので、０．３０％以下とする。 Ti has effects such as refinement of crystal grains, suppression of grain growth, and improvement of corrosion resistance, but the effect is saturated even if added excessively, so 0.30% or less.
　Ｎは、Ｃ，Ｍｎと同様に冷延鋼板に高い強度を与え耐力強化のために必要な成分であるが、０．００２％より少なくすることは製鋼上の困難を生じ、一方で、０．０１５％を超える添加は製鋼時に添加するフェロ窒化物の歩留の低下が著しく、安定性に欠けるとともに、プレス成形時の異方性を著しく劣化させる。
　さらに連続鋳造片の表面に割れが生じ、鋳造欠陥となるため、本発明ではＮ成分範囲を０．０１５％以下とすることが望ましい。 N, like C and Mn, is a component necessary for imparting high strength to the cold-rolled steel sheet and for strengthening the proof stress. However, if it is less than 0.002%, it causes difficulty in steelmaking. Addition exceeding 015% significantly reduces the yield of ferronitride added during steelmaking, lacks stability, and significantly deteriorates anisotropy during press molding.
Furthermore, since cracks are generated on the surface of the continuous cast piece, resulting in casting defects, it is desirable in the present invention that the N component range be 0.015% or less.
＜製造工程＞
　以下、本発明の冷延鋼板の製造方法について述べる。
＜製鋼＞
　転炉もしくは電気炉で溶解し、上記成分範囲に成分調整してスラブ片とする。
＜熱間圧延＞
　成分調整済みのスラブ片を、熱間圧延にて板厚１．２～３．０ｍｍとする。板厚が薄いと熱間圧延時の負荷増大を引き起こすため下限を１．２とする。また板厚が厚いとその後の冷間圧延時に負荷の増大を引き起こすため上限を３．０とする。
　熱間圧延工程においては、上記成分範囲のスラブ片を加熱温度を１１００℃以上とし、巻取り温度を６００℃以上で行う。スラブ片の加熱温度が１１００℃未満では、Ｎの積極的分解固溶が不足すること、熱延負荷が高くなることから好ましくない。
　また、巻取り温度は６００℃～８００℃とする。巻取り温度が低いと熱延鋼板が高強度化を引き起こすので，冷延時に好ましくないため，巻取り温度の下限を６００℃とする。
一方、巻取り温度が８００℃を超えると、熱延時にスケール生成が促進され酸洗での脱スケール時に負荷の増大を引き起こすため、上限を８００℃とする。
　上記のような条件で製造された熱延鋼板は、引張強度１０００ＭＰa以下とすることができる。引張強度が１０００ＭＰaを超えると、冷間圧延時の圧延負荷の増大のため好ましくないからである。 <Manufacturing process>
Hereinafter, the manufacturing method of the cold-rolled steel sheet of this invention is described.
<Steel making>
It is melted in a converter or an electric furnace and adjusted to the above component range to obtain a slab piece.
<Hot rolling>
The component-adjusted slab piece is hot rolled to a thickness of 1.2 to 3.0 mm. If the plate thickness is small, the load is increased during hot rolling, so the lower limit is set to 1.2. Further, if the plate thickness is large, the load is increased during the subsequent cold rolling, so the upper limit is set to 3.0.
In the hot rolling step, the slab piece having the above component range is heated at a temperature of 1100 ° C. or higher and a winding temperature is 600 ° C. or higher. If the heating temperature of the slab piece is less than 1100 ° C., it is not preferable because the active decomposition and dissolution of N is insufficient and the hot rolling load becomes high.
The winding temperature is 600 ° C. to 800 ° C. If the coiling temperature is low, the hot-rolled steel sheet is increased in strength, which is not preferable during cold rolling. Therefore, the lower limit of the coiling temperature is set to 600 ° C.
On the other hand, if the coiling temperature exceeds 800 ° C., scale formation is promoted during hot rolling and an increase in load is caused during descaling by pickling, so the upper limit is set to 800 ° C.
The hot-rolled steel sheet manufactured under the above conditions can have a tensile strength of 1000 MPa or less. This is because a tensile strength exceeding 1000 MPa is not preferable because of an increase in rolling load during cold rolling.
＜酸洗＞
　熱間圧延時に生成した表面のスケールを常法に従って酸浴中で除去した後、冷間圧延し、連続焼鈍する。
＜冷間圧延＞
　冷間圧延は、１回もしくは数回に分けて合計６０％以上の圧延率で，所定の製品厚み０．０５～０．６ｍｍまで圧延を行う。この厚みが０．０５ｍｍよりも薄くなると、剛性が小さくなり、自動車のガソリンエンジンのガスケット、ノートパソコン、携帯電話、デジタルカメラの液晶フレームやフレーム部品等の製品に用いたときに、形状が変形しやすくなり製品の製造ができなくなる場合があるからである。
　また、この厚みが０．６ｍｍよりも厚くなると、自動車のガソリンエンジンのガスケット、ノートパソコン、携帯電話、デジタルカメラの液晶フレームやフレーム部品等の製品に用いたときに、設計値よりも重量が大きくなったり、小型化が実現できない場合があるからである。 <Pickling>
After removing the scale of the surface produced at the time of hot rolling in an acid bath according to a conventional method, it is cold-rolled and continuously annealed.
<Cold rolling>
Cold rolling is performed in one or several times at a total rolling rate of 60% or more to a predetermined product thickness of 0.05 to 0.6 mm. If this thickness is less than 0.05 mm, the rigidity will be reduced, and the shape will be deformed when used in products such as automobile gasoline engine gaskets, laptop computers, mobile phones, and digital camera LCD frames and frame parts. This is because it may become easy to manufacture the product.
Also, if this thickness is greater than 0.6 mm, it will be heavier than the design value when used in products such as gasoline engine gaskets for automobiles, laptop computers, mobile phones, and liquid crystal frames and frame parts for digital cameras. This is because there is a case where it is impossible to achieve downsizing.
　冷間圧延における合計圧延率の上限は特に規定するものではないが、９８％とする。
また、冷間圧延後に、５００℃以上の連続焼鈍もしくは５００℃以上のバッチ焼鈍を行うことによって、加工硬化した圧延板を軟質化させ、再度冷間圧延を行うことが可能である。
　冷間圧延の方法や冷間圧延回数は、特に指定するものではないが、目的とする板厚に応じて適宜選択することができる。 The upper limit of the total rolling rate in cold rolling is not particularly specified, but is 98%.
Further, after cold rolling, by performing continuous annealing at 500 ° C. or higher or batch annealing at 500 ° C. or higher, it is possible to soften the work-hardened rolled plate and perform cold rolling again.
The method of cold rolling and the number of cold rolling are not particularly specified, but can be appropriately selected according to the target plate thickness.
＜連続焼鈍＞
　連続焼鈍は、冷間圧延時における板の歪みを除去するものであるが、この連続焼鈍は、複数回の冷間圧延を行う場合は、その都度行うことができる。
　なお、本発明において、最終の連続焼鈍は、均熱温度７５０℃以上で１ｓ以上１００ｓ以下の均熱保持をする。均熱温度が７５０℃未満では、Ａｅ３変態温度を超えないため十分な引張強度を得ることができない。
　また、均熱温度が１０００℃を超えても特に利点が無く、工業的にも無駄であるため，上限を１０００℃とする。
　この最終連続焼鈍は、加熱により一部又は全部をオーステナイト化させ、その後の冷却によって、これらをマルテンサイト等に変態させるものである。
　本発明においては、このマルテンサイトの量と合金元素の量とによって、所定の強度を得ることができる。 <Continuous annealing>
Continuous annealing removes distortion of the plate during cold rolling, but this continuous annealing can be performed each time when performing cold rolling a plurality of times.
In the present invention, in the final continuous annealing, the soaking is maintained at a soaking temperature of 750 ° C. or more and 1 s or more and 100 s or less. When the soaking temperature is less than 750 ° C., the Ae3 transformation temperature is not exceeded, so that sufficient tensile strength cannot be obtained.
Further, even if the soaking temperature exceeds 1000 ° C., there is no particular advantage and it is industrially useless, so the upper limit is set to 1000 ° C.
In this final continuous annealing, a part or the whole is austenitized by heating, and these are transformed into martensite or the like by subsequent cooling.
In the present invention, a predetermined strength can be obtained by the amount of martensite and the amount of alloy elements.
　上記均熱温度７５０℃以上で１ｓ以上１００ｓ以下の均熱保持後に，冷却速度３℃／ｓから１００℃／ｓで冷却を行う。この冷却によって、板のオーステナイト組織を、マルテンサイト、焼戻しマルテンサイト、ベイナイト等の組織とするのである。上記冷却速度が３℃／ｓ未満では、マルテンサイト等の低温変態組織の生成が不十分となり必要な強度が得られない。また、冷却速度が１００℃／ｓを超えると、必要な強度は得られるものの鋼板の形状が悪くなるため，プレス用途などに適さない。 After the soaking temperature is maintained at 750 ° C. or more and 1 s or more and 100 s or less, cooling is performed at a cooling rate of 3 ° C./s to 100 ° C./s. By this cooling, the austenite structure of the plate is changed to a structure such as martensite, tempered martensite, and bainite. If the cooling rate is less than 3 ° C./s, the formation of a low temperature transformation structure such as martensite is insufficient, and the required strength cannot be obtained. On the other hand, if the cooling rate exceeds 100 ° C./s, the required strength can be obtained, but the shape of the steel sheet is deteriorated.
　本発明において、連続焼鈍後の冷却速度は、形状確保のために、一般的な水等を用いた焼入れに比べると格段に遅い冷却速度で冷却して低温変態組織を生成させ高強度鋼板を得ることにある。
　一般的な焼入れ元素として効果的なオーステナイト安定化元素であるＭｎやＮｉは、上記の冷却速度で必要な強度を得る為には相当量添加する必要あるが、相当量の添加は熱間圧延後に高い強度をもたらし、冷間圧延時負荷を増大させ、生産性を阻害するため、生産コストの増加を引き起こす。
　よって、本発明では、Ｍｎ及びＮｉ添加量を比較的少なくし、フェライト安定元素であるＣｒを複合添加することによって、熱間圧延後には比較的軟質で、冷間圧延後の連続焼鈍において高強度鋼板を製造することを可能とし、製造負荷を格段に減らすことができる。 In the present invention, the cooling rate after continuous annealing is cooled at a much slower cooling rate compared to quenching using general water or the like in order to ensure the shape, thereby generating a low-temperature transformation structure to obtain a high-strength steel sheet. There is.
Mn and Ni, which are effective austenite stabilizing elements as general quenching elements, need to be added in a considerable amount in order to obtain the required strength at the above cooling rate. It brings high strength, increases the load during cold rolling, and hinders productivity, thus causing an increase in production cost.
Therefore, in the present invention, the amount of Mn and Ni added is relatively small, and Cr, which is a ferrite stable element, is added in combination, so that it is relatively soft after hot rolling and has high strength in continuous annealing after cold rolling. It is possible to manufacture a steel plate, and the manufacturing load can be significantly reduced.
　また、最終の連続焼鈍後の冷却後に、必要に応じて６００℃以下の焼戻し処理をすることも可能であるが，本発明は比較的低い冷却速度で焼き入れ組織とするため，冷却時には焼戻し処理と同等な効果も得られ，焼戻し工程の省略が可能である。焼戻し工程を省略できることによって大幅に製造負荷削減に貢献できる。 Further, after cooling after the last continuous annealing, it is possible to perform a tempering process at 600 ° C. or lower as necessary. However, since the present invention forms a quenched structure at a relatively low cooling rate, the tempering process is performed at the time of cooling. Equivalent effects can be obtained, and the tempering process can be omitted. Since the tempering process can be omitted, the manufacturing load can be greatly reduced.
　上記の連続焼鈍によって、本発明の製造方法によって得られる冷延鋼板の引張強度を１２８０ＭＰａ以上とすることができる。このような強度を有することにより、冷延鋼板を自動車のガソリンエンジンのガスケットとして使用する場合、ガス漏れを起こすことがない。
　また、軽量化のため板厚を薄くして、ノートパソコン、携帯電話、デジタルカメラの液晶フレームやフレーム部品に適用した場合において、特にモバイル用途で使用した場合においても、部品としての剛性を確保することができる。 By the above-described continuous annealing, the tensile strength of the cold-rolled steel sheet obtained by the production method of the present invention can be set to 1280 MPa or more. By having such strength, when a cold-rolled steel sheet is used as a gasket for an automobile gasoline engine, gas leakage does not occur.
In addition, when it is applied to liquid crystal frames and frame parts of notebook computers, mobile phones, and digital cameras, the plate thickness is reduced to reduce weight, ensuring rigidity as a part even when used in mobile applications. be able to.
　また、本発明における製造方法によって、冷延鋼板の破断伸びを３％以上とすることができる。延性を示す破断伸びの値は、自動車エンジン用ガスケットや電子部品などの用途としてプレス成形する場合において重要である。破断伸びが３％未満であると、軽度の張り出し加工や、９０°折り曲げ等の加工部に割れが発生しやすくなる。 Moreover, the elongation at break of the cold-rolled steel sheet can be 3% or more by the production method of the present invention. The value of elongation at break indicating ductility is important in the case of press molding for applications such as automobile engine gaskets and electronic parts. If the elongation at break is less than 3%, cracks are likely to occur in the processed part such as mild overhanging or 90 ° bending.
　上記の製造方法によって製造された鋼板は、体積率で６０％以上の、マルテンサイト，焼戻しマルテンサイト，ベイナイト組織等の組織を有し，薄鋼板においても１２８０ＭＰａ以上の高い引張強度を有しかつ延性を確保した鋼板を製造することができる。 The steel sheet manufactured by the above manufacturing method has a structure such as martensite, tempered martensite, and bainite structure of 60% or more in volume ratio, and has a high tensile strength of 1280 MPa or more even in a thin steel sheet and is ductile. Can be manufactured.
＜調質圧延等＞
　このようにして得られた鋼板は必要に応じて，表面粗度調節のための調質圧延や、防錆のためのＺｎ，Ｎｉ等の電気めっき及び化成処理を行うことができる。 <Tempered rolling, etc.>
The steel sheet thus obtained can be subjected to temper rolling for adjusting the surface roughness and electroplating and chemical conversion treatment of Zn, Ni, etc. for rust prevention as required.
＜プレス成形＞
　本発明の製造方法によって得られた鋼板は、プレス成形用の素材として適用できるが、一般の冷延鋼板とは大幅に強度域が違うため，スプリングバック等に配慮する必要がある。 <Press molding>
Although the steel plate obtained by the manufacturing method of the present invention can be applied as a material for press forming, the strength range is significantly different from that of a general cold-rolled steel plate, so it is necessary to consider springback and the like.
　本発明の冷延鋼板を、実施例及び比較例にてさらに詳細に説明するため、表１に示す試料１～１８に示す成分のスラブ片を用意した。試料１～１１，１７，１８は本発明の成分範囲に入るスラブ片であるが、試料１２～１６は本発明の成分範囲外のスラブ片である。
　熱間圧延工程において、試料１～１８に示す成分に調整されたスラブ片を１２３０℃に加熱して、表２に示す巻取り温度で板厚２．０ｍｍの熱延鋼板を製造した。この熱延鋼板の特性を表２に示す。
　次に、この熱延鋼板を酸洗した後、０．５ｍｍまで冷間圧延し、その後、連続焼鈍工程において、均熱温度９００℃として２０ｓ均熱保持後、冷却速度２０℃／ｓで冷却して冷延鋼板とした。この冷延鋼板の特性を表２に示す。
　表２から分かるように、実施例１～１５は、熱延鋼板の引張強度は１０００ＭＰａ以下であり、その後の冷間圧延において目標とする０．５ｍｍまで薄くすることができるとともに、冷延鋼板の引張強度を１２８０ＭＰａ以上、破断伸びを３％以上とすることができた。
　なお、実施例３、４については均熱後の冷却速度を、それぞれ３℃／ｓ、１００℃／ｓとして変化させたが、それぞれ、１３２０ＭＰａ、１４０５ＭＰａの引張強度、破断伸び６．２％、６．０％を有する冷延鋼板を得ることができた。 In order to explain the cold-rolled steel sheet of the present invention in more detail in Examples and Comparative Examples, slab pieces having the components shown in Tables 1 to 18 shown in Table 1 were prepared. Samples 1 to 11, 17, and 18 are slab pieces that fall within the component range of the present invention, while Samples 12 to 16 are slab pieces outside the component range of the present invention.
In the hot rolling process, slab pieces adjusted to the components shown in Samples 1 to 18 were heated to 1230 ° C. to produce hot rolled steel sheets having a thickness of 2.0 mm at the winding temperatures shown in Table 2. Table 2 shows the characteristics of this hot-rolled steel sheet.
Next, after pickling the hot-rolled steel sheet, it is cold-rolled to 0.5 mm. After that, in the continuous annealing process, the soaking temperature is maintained at 900 ° C. for 20 s and then cooled at a cooling rate of 20 ° C./s. Cold-rolled steel sheet. The properties of this cold rolled steel sheet are shown in Table 2.
As can be seen from Table 2, in Examples 1 to 15, the tensile strength of the hot-rolled steel sheet is 1000 MPa or less, and it can be thinned to the target 0.5 mm in the subsequent cold rolling. The tensile strength was 1280 MPa or more, and the elongation at break was 3% or more.
In Examples 3 and 4, the cooling rates after soaking were changed to 3 ° C./s and 100 ° C./s, respectively, but the tensile strengths of 1320 MPa and 1405 MPa, the elongation at break 6.2%, 6 A cold-rolled steel sheet having 0.0% could be obtained.
　比較例１は、実施例１と同一成分である試料１から製造したものであるが、巻取り温度を４８０℃と低くしたため熱延鋼板の引張強度は１１０８ＭＰａと高くなり、硬いためにその後の冷間圧延において目標とする０．５ｍｍまで薄くすることができず、圧延の荷重と圧延回数を増大させると割れが生じたため冷間圧延を中止した。
　比較例２の熱延鋼板は、実施例２～４と同一成分である試料２から製造したものであるが、巻取り温度を５００℃と低くしたため熱延鋼板の引張強度は１２１６ＭＰａと高くなり、硬いためにその後の冷間圧延において目標とする０．５ｍｍまで薄くすることができず、圧延の荷重と圧延回数を増大させると割れが生じたため冷間圧延を中止した。
　比較例３、４は、Ｃが０．１０以下であり、比較例５は、Ｃｒが１．２％以下であり、比較例７は、Ｍｎ及びＮｉが少なくＭｎ+Ｎｉが０．５％以下のため、それぞれ、冷延鋼板の引張強度が１２８０ＭＰａ以下となり、ガスケットやフレーム部品として用いた場合に強度が足りず適用不可であった。
　比較例６は、Ｍｎ＋Ｎｉの合計含有量が３．４と多いため、熱延鋼板の引張強度が高くなり、その後の冷間圧延において目的とする厚さである０．５ｍｍにまで圧延することができなかった。具体的には、圧延しても硬いために薄くならないか、圧延の荷重と圧延回数を増大させると割れが生じて生産ができなかった。 Comparative Example 1 was manufactured from Sample 1 which is the same component as Example 1, but since the coiling temperature was lowered to 480 ° C., the tensile strength of the hot rolled steel sheet was as high as 1108 MPa, and since it was hard, Cold rolling was stopped because it was not possible to reduce the thickness to 0.5 mm, which was the target in cold rolling, and cracking occurred when the rolling load and rolling frequency were increased.
The hot-rolled steel sheet of Comparative Example 2 was manufactured from Sample 2 having the same components as in Examples 2 to 4. However, since the coiling temperature was lowered to 500 ° C., the tensile strength of the hot-rolled steel sheet was as high as 1216 MPa. Since it was hard, it could not be thinned to the target of 0.5 mm in the subsequent cold rolling, and when the rolling load and the number of rollings were increased, cracking occurred and cold rolling was stopped.
In Comparative Examples 3 and 4, C is 0.10 or less, Comparative Example 5 is Cr is 1.2% or less, and Comparative Example 7 is low in Mn and Ni and Mn + Ni is 0.5% or less. For this reason, the tensile strength of each cold-rolled steel sheet was 1280 MPa or less, and the strength was insufficient when used as a gasket or frame part, which was not applicable.
In Comparative Example 6, since the total content of Mn + Ni is as large as 3.4, the tensile strength of the hot-rolled steel sheet becomes high, and it can be rolled to 0.5 mm which is the target thickness in the subsequent cold rolling. could not. Specifically, since it is hard even if it is rolled, it does not become thin, or if the rolling load and the number of rolling are increased, cracks occur and production cannot be performed.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
　本発明によれば、冷間圧延時の負荷を軽減し、高強度かつ延性を確保したプレス成形に優れた冷延鋼板を提供することができ、自動車のガソリンエンジンのガスケット、ノートパソコン、携帯電話、デジタルカメラの液晶フレームやフレーム部品等に用いる素材として求められる厚さ：０．０５ｍｍ～０．６ｍｍ、引張強度：１２８０ＭＰａ以上、破断伸び：３％以上を有する、強度と加工性を同時に備えた冷延鋼板を提供でき、産業上の利用可能性が極めて高い。 ADVANTAGE OF THE INVENTION According to this invention, the cold rolling steel sheet excellent in the press forming which reduced the load at the time of cold rolling, and ensured high intensity | strength and ductility can be provided. The thickness required for materials used for liquid crystal frames and frame parts of digital cameras, etc .: 0.05 mm to 0.6 mm, tensile strength: 1280 MPa or more, elongation at break: 3% or more, provided with strength and workability at the same time Cold-rolled steel sheet can be provided, and industrial applicability is extremely high.

Claims (4)

  1. 質量％で、
    Ｃ：０．１０～０．３０、
    Ｍｎ；０．２以上、
    Ｎｉ；０．０１以上、
    Ｍｎ＋Ｎｉ：０．５～２．５、
    Ｃｒ：１．２～９．０、
    残部が鉄及び不可避的不純物からなり、
    引張強度が１０００ＭＰａ以下である熱間圧延鋼板を、
    酸洗後、
    合計で６０％以上の圧延率の冷間圧延を行って冷延鋼板とし、
    最終の連続焼鈍処理を、
    均熱温度を７５０℃以上とし、冷却速度を３℃／ｓ～１００℃／ｓとし、
    引張強度が１２８０ＭＰａ以上、破断伸びが３％以上、厚み０．０５～０．６０ｍｍとすることを特徴とする冷延鋼板の製造方法。     % By mass
    C: 0.10 to 0.30,
    Mn: 0.2 or more,
    Ni: 0.01 or more,
    Mn + Ni: 0.5 to 2.5,
    Cr: 1.2 to 9.0,
    The balance consists of iron and inevitable impurities,
    A hot rolled steel sheet having a tensile strength of 1000 MPa or less,
    After pickling
    Cold-rolled steel sheet by performing cold rolling with a rolling rate of 60% or more in total,
    Final continuous annealing treatment
    The soaking temperature is 750 ° C. or higher, the cooling rate is 3 ° C./s to 100 ° C./s,
    A method for producing a cold-rolled steel sheet, characterized by having a tensile strength of 1280 MPa or more, a breaking elongation of 3% or more, and a thickness of 0.05 to 0.60 mm.
  2. 前記熱間圧延鋼板の厚みが１．２～３．０ｍｍであることを特徴とする請求項１に記載の冷延鋼板の製造方法。 The method for producing a cold-rolled steel sheet according to claim 1, wherein the hot-rolled steel sheet has a thickness of 1.2 to 3.0 mm.
  3. 質量％で、
    Ｃ：０．１０～０．３０、
    Ｍｎ；０．２以上、
    Ｎｉ；０．０１以上、
    Ｍｎ＋Ｎｉ：０．５～２．５、
    Ｃｒ：１．２～９．０、
    残部が鉄及び不可避的不純物からなり、
    引張強度が１０００ＭＰａ以下である熱間圧延鋼板を、
    酸洗後、
    合計で６０％以上の圧延率の冷間圧延を行って冷延鋼板とし、
    最終の連続焼鈍処理を、
    均熱温度を７５０℃以上とし、冷却速度を３℃／ｓ～１００℃／ｓとし、
    引張強度が１２８０ＭＰａ以上、破断伸びが３％以上、厚み０．０５～０．６０ｍｍであることを特徴とする冷延鋼板。     % By mass
    C: 0.10 to 0.30,
    Mn: 0.2 or more,
    Ni: 0.01 or more,
    Mn + Ni: 0.5 to 2.5,
    Cr: 1.2 to 9.0,
    The balance consists of iron and inevitable impurities,
    A hot rolled steel sheet having a tensile strength of 1000 MPa or less,
    After pickling
    Cold-rolled steel sheet by performing cold rolling with a rolling rate of 60% or more in total,
    Final continuous annealing treatment
    The soaking temperature is 750 ° C. or higher, the cooling rate is 3 ° C./s to 100 ° C./s,
    A cold-rolled steel sheet having a tensile strength of 1280 MPa or more, a breaking elongation of 3% or more, and a thickness of 0.05 to 0.60 mm.
  4. 前記熱間圧延鋼板の厚みが１．２～３．０ｍｍであることを特徴とする請求項３に記載の冷延鋼板。 The cold-rolled steel sheet according to claim 3, wherein the hot-rolled steel sheet has a thickness of 1.2 to 3.0 mm.
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