WO2022044194A1 - Surface-treated steel sheet and method for processing surface-treated steel sheet - Google Patents

Surface-treated steel sheet and method for processing surface-treated steel sheet Download PDF

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Publication number
WO2022044194A1
WO2022044194A1 PCT/JP2020/032349 JP2020032349W WO2022044194A1 WO 2022044194 A1 WO2022044194 A1 WO 2022044194A1 JP 2020032349 W JP2020032349 W JP 2020032349W WO 2022044194 A1 WO2022044194 A1 WO 2022044194A1
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Prior art keywords
steel sheet
treated steel
mass
less
treated
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PCT/JP2020/032349
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French (fr)
Japanese (ja)
Inventor
智永 岩津
雅典 松野
秀時 森
晋 上野
真 清水
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日本製鉄株式会社
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Priority to PCT/JP2020/032349 priority Critical patent/WO2022044194A1/en
Priority to CN202080104311.6A priority patent/CN116133768A/en
Publication of WO2022044194A1 publication Critical patent/WO2022044194A1/en

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D22/00—Shaping without cutting, by stamping, spinning, or deep-drawing
    • B21D22/20—Deep-drawing
    • 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
    • C21D1/18—Hardening; Quenching with or without subsequent tempering
    • 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
    • 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
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C22/05—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions
    • C23C22/06—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6
    • C23C22/48—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6 not containing phosphates, hexavalent chromium compounds, fluorides or complex fluorides, molybdates, tungstates, vanadates or oxalates
    • C23C22/50—Treatment of iron or alloys based thereon

Definitions

  • the present invention relates to a surface-treated steel sheet and a method for processing a surface-treated steel sheet.
  • Hot stamping is known as one of the processing methods for steel sheets. Hot stamping is a processing method in which a steel sheet is heated to an austenite region of around 900 ° C., and molding and quenching are performed simultaneously in a mold.
  • ultra-high-strength steel plates used in automobile cabins, etc.
  • springback This occurs, and there is a problem that the dimensional accuracy tends to decrease.
  • hot stamping steel that has been softened by heating to around 900 ° C. is placed in a die and pressed, and at the same time, the steel is cooled by contact with the die and quenched. Hot stamping has the features of excellent moldability and less springback.
  • oxides formed by oxidizing Fe and the like in the steel may be generated on the surface of the processed steel sheet. From the viewpoint of increasing the productivity of the processed steel sheet, there is a demand for a method for processing the steel sheet so that this oxide is difficult to form.
  • Patent Document 1 describes a stainless steel material in which the structure of a passivation film on the surface of stainless steel is Cr or a structure rich in Cr and Si, and an alkali silicate is adhered to the surface thereof. .. According to Patent Document 1, the stainless steel material is prevented from invading oxygen in the atmosphere and diffusing metal elements from the stainless steel substrate even when exposed to a high temperature such that the surface temperature reaches 650 ° C. or higher. Therefore, it is said that the generation of temper color due to the oxide produced by the reaction of these can be suppressed.
  • Patent Document 2 describes a heat treatment steel sheet in which the amounts of C, Si, Mn, Cr and Ni are adjusted.
  • the heat treatment steel sheet can be a medium to high carbon steel sheet having a C content of 0.3 to 1.2% by weight by setting the amount of Cr to 0.1 to 2% by weight.
  • the peeling of the oxide scale during heat treatment can be prevented.
  • Patent Document 1 even if stainless steel is exposed to a high temperature such that the surface temperature reaches 650 ° C. or higher, temper color due to Cr—Fe—O oxide can be suppressed.
  • oxides are more likely to be generated than the test conditions of Patent Document 1 in which the steel sheet is heated only to around 700 ° C.
  • hot stamping tends to produce thicker, grayer scales on the surface of the steel sheet. Therefore, processing of a steel sheet by hot stamping requires processing such as shot blasting to remove the scale, which may reduce productivity. Therefore, the steel sheet for hot stamping is required to further suppress the generation of oxides.
  • Patent Document 2 in order to prevent the scale from peeling off in a process such as a press temper and causing an indentation defect, it is attempted to prevent the scale from peeling off. However, if the occurrence of scale is suppressed in the first place, the occurrence of indentation flaws can also be suppressed.
  • the present invention has been made in view of this point, and an object of the present invention is to provide a surface-treated steel sheet in which scale is less likely to occur when a steel sheet is processed by hot stamping, and a method for processing the surface-treated steel sheet. And.
  • the surface-treated steel sheet according to the embodiment of the present invention for solving the above problems is arranged in contact with a steel sheet having a Cr content of 0.2% by mass or more and 2.0% by mass or less and the surface of the steel sheet. It also has an alkaline silicate film.
  • the method for processing the surface-treated steel sheet according to the embodiment of the present invention for solving the above-mentioned problems includes a step of heating the surface-treated steel sheet to a temperature range of Ac 3 points or more and 1100 ° C. or less of the steel sheet. It has a step of arranging a heated surface-treated steel sheet inside a die, hot-pressing it, and cooling the surface-treated steel sheet by the die.
  • a surface-treated steel sheet in which scale is less likely to occur when the steel sheet is processed by hot stamping a method for processing the surface-treated steel sheet, and a processed surface treatment obtained by processing the surface-treated steel sheet.
  • Steel sheets are provided.
  • the present invention relates to a surface-treated steel sheet for hot stamping.
  • the steel sheet may be any steel sheet having a Cr content of 0.2% by mass or more and 2.0% by mass or less.
  • Examples of the steel sheet include nickel chrome steel sheet, chrome molybdenum steel sheet, nickel chrome molybdenum steel sheet (JIS G 4053: alloy steel for machine structure) and the like.
  • the steel sheet may be a galvanized steel sheet, a Zn—Al alloy plated steel sheet, a Zn—Al—Mg alloy plated steel sheet, an aluminum plated steel sheet, or the like. Further, the steel sheet may be a cold-rolled steel sheet or a hot-rolled steel sheet.
  • M is an alkali metal or an alkaline earth metal.
  • X is M. When it is an alkali metal, it is 2, and when M is an alkaline earth metal, it is 1.
  • n is, for example, an arbitrary number of 1 or more and 8 or less) and Si—Cr—M. -Forms an O-based reaction layer.
  • the reaction layer is highly stable at high temperatures. Therefore, the reaction layer preferably suppresses the diffusion of atoms (particularly Fe) contained in the steel sheet from the steel sheet to the alkaline silicate film during hot stamping. As a result, the reaction layer suppresses the formation of oxides such as FeO, Fe 3 O 4 and Fe 2 O 3 due to the reaction of Fe diffused from the steel plate with oxygen (O 2 ) in the air during hot stamping. However, it is possible to suppress the generation of scale due to the deposition of these oxides.
  • the Cr content in the steel sheet is 0.2% by mass or more, the reaction layer having a sufficient thickness is formed on the surface of the steel sheet, and the diffusion of Fe from the steel sheet can be sufficiently suppressed. Occurrence is also sufficiently suppressed.
  • the Cr content in the steel sheet exceeds 2.0% by mass, the effect is saturated.
  • the Cr content in the steel sheet is preferably 0.4% by mass or more and 1.7% by mass or less, and more preferably 0.6% by mass or more and 1.6% by mass or less.
  • the steel sheet may contain elements other than Fe and Cr, such as C, Si, Mn, P, S, Mo, V, Ti, Bi and W.
  • the content of these elements can be arbitrarily determined according to the characteristics required for the steel sheet and the like.
  • the content of C can be 0.1% by mass or more and 1.2% by mass or less, preferably 0.2% by mass or more and 1.2% by mass or less, and 0.4% by mass or more. It is more preferably 1.0% by mass or less.
  • the Si content can be 0.1% by mass or more and 2.5% by mass or less, and preferably 0.1% by mass or more and 1.5% by mass or less.
  • the Mn content can be 0.4% by mass or more and 3.0% by mass or less, and preferably 0.4% by mass or more and 2.0% by mass or less.
  • the thickness of the steel sheet may be such that it can be processed by hot stamping, for example, it may be about 0.5 mm or more and 4.0 mm or less.
  • Alkaline silicate film is a film containing an alkali silicate that covers the surface of the steel plate.
  • the alkali silicate film is formed in contact with the surface of the steel sheet.
  • the alkali silicate film may be formed on only one surface of the steel sheet, or may be formed on both surfaces of the steel sheet.
  • the alkali silicate film reacts with Cr contained in the steel sheet during hot stamping to form the Si—Cr—MO-based reaction layer described above.
  • the alkaline silicate film suppresses the diffusion of Fe from the steel plate to the alkaline silicate film during hot stamping, and the diffused Fe reacts with oxygen (O 2 ) in the air. It is possible to suppress the formation of oxides and suppress the generation of scale due to the deposition of these oxides.
  • the alkaline silicate film suppresses the invasion of oxygen (O 2 ) contained in the air into the steel sheet during hot stamping.
  • oxygen O 2
  • the alkali silicate film suppresses the formation of oxides such as FeO, Fe 3 O 4 and Fe 2 O 3 due to the reaction of oxygen that has entered the steel plate with Fe in the steel plate. It is also possible to suppress the generation of scale due to the deposition of these oxides.
  • the alkaline silicate may be any compound represented by the general formula MXO ⁇ nSiO 2 .
  • M is an alkali metal or an alkaline earth metal, and Li, Na, K or the like can be used as the alkali metal, and Mg, Ca or the like can be used as the alkaline earth metal.
  • M is Li because it is possible to form an alkaline silicate film by firing even at a lower temperature, and since the melting temperature is higher, scale can be efficiently suppressed even during hot stamping at a higher temperature. Is more preferable.
  • the alkali silicate may be a compound containing two different atoms of an alkali metal or an alkaline earth metal as M.
  • X is 2 when M is an alkali metal and 1 when M is an alkaline earth metal.
  • n is, for example, an arbitrary number of 3.5 or more and 7.5 or less.
  • n is 3.5 or more, a sufficient amount of Si is present in the alkali silicate film, so that the above reaction layer having a sufficient thickness is formed on the surface of the steel sheet, and the scale due to the diffusion of Fe from the steel sheet is formed. Can be further suppressed. Further, when n is 3.5 or more, the amount of the alkaline component in the alkaline silicate film is not too large, so that the alkaline component remaining on the surface of the steel sheet after hot stamping is water in the air, carbon dioxide gas, or the like. It is also possible to further suppress the whitening phenomenon caused by the reaction product produced by the reaction of the above.
  • n 7.5 or less
  • a sufficient amount of alkaline component is present in the alkaline silicate film, so that the above reaction layer having a sufficient thickness is formed on the surface of the steel sheet, and Fe from the steel sheet is formed. It is possible to further suppress the generation of scale due to the diffusion of. Further, when n is 7.5 or less, a sufficient amount of alkaline component is present in the alkaline silicate film, so that the strength of the alkaline silicate can be further increased.
  • the amount of the alkali silicate film adhered is preferably 0.05 g / m 2 or more and 1 g / m 2 or less in terms of Si.
  • the amount of adhesion is 0.05 g / m 2 or more, the generation of scale can be sufficiently suppressed.
  • the adhesion amount is 1 g / m 2 or more, the adhesion of the alkali silicate film to the steel sheet can be sufficiently enhanced.
  • the alkaline silicate film can be formed by applying an aqueous solution containing the alkaline silicate on the surface of a steel sheet and firing it.
  • the alkaline silicate film thus formed is a film mainly composed of a compound represented by the general formula MX O ⁇ nSiO 2 ⁇ yH 2 O.
  • the amount of water retained in the alkaline silicate film is smaller (in the above general formula). Is smaller than y).
  • the amount of the alkali silicate film adhering to the surface of the steel sheet can be adjusted.
  • the surface of the steel sheet may be subjected to known pretreatment such as degreasing and pickling.
  • Another embodiment of the present invention relates to a method for processing a surface-treated steel sheet, which heat-treats the above-mentioned surface-treated steel sheet.
  • the heat treatment may be a high heat treatment of the surface-treated steel sheet, and may be any known heat treatment such as hot stamping, quenching, annealing (canning), and normalizing. This embodiment can be carried out in the same manner as the known heat treatment except that the surface-treated steel sheet is used as the steel sheet.
  • the surface-treated steel sheet is heated to a temperature range in which the ferrite in the steel sheet transforms into austenite.
  • the surface-treated steel sheet is heated to a temperature range of 800 ° C. or higher and 1100 ° C. or lower, preferably Ac 3 points or higher and 1100 ° C. or lower of the steel sheet.
  • the temperature rising rate at this time may be adjusted in the range of 2 ° C./s or more.
  • the heated surface-treated steel sheet is placed inside the mold and hot pressed. Then, at the same time as hot pressing, the surface-treated steel sheet is cooled by the die. Specifically, the surface-treated steel sheet may be cooled to the Mf point (martensite transformation end point) or less of the steel sheet. Further, the cooling rate at this time may be adjusted in the range of 5 ° C./s or more and 40 ° C./s or less.
  • the surface-treated steel sheet processed in this way has a Si—Cr—MO reaction layer between the steel sheet and the alkali silicate film.
  • the steel sheet preferably has an area ratio of martensite of 90% or more in its cross section.
  • Each steel sheet was immersed in an alkaline aqueous solution at 40 ° C. having a pH of 14 with sodium orthosilicate for 30 seconds for alkaline degreasing.
  • lithium silicate Li 2O ⁇ nSiO 2 : n is 3 to 8 manufactured by Nippon Kagaku Kogyo Co., Ltd. or water glass No. 3 manufactured by Kishida Chemical Co., Ltd.
  • An aqueous solution obtained by diluting Na 2 O ⁇ nSiO 2 : n from 3 to 8) to a concentration of 5% was applied with bar coat # 3. After coating, it is heated to 180 ° C. in the air and fired to form an alkaline silicate film having an adhesion amount of 0.2 to 0.5 g / m 2 in terms of Si, and the surface-treated steel sheets 1 to surface are formed, respectively.
  • a treated steel sheet 14 was obtained.
  • a 50 mm ⁇ 50 mm test piece was cut out from each surface-treated steel sheet, and an atmospheric heating test was carried out in a heating furnace with an atmospheric temperature of 850 ° C or 900 ° C. The soaking time at this time was 10 minutes. After heating, the test piece was taken out from the furnace and allowed to cool at room temperature.
  • a cross section of a sufficiently cooled test piece is observed by SEM and GDS (Glow Discharge Emission Spectroscopy), the thickness of the oxide film formed by the atmospheric heating test is measured, and each surface treatment is performed according to the following criteria.
  • the steel plate was evaluated.
  • ⁇ The thickness of the oxide film is 0.3 ⁇ m or less ⁇
  • the thickness of the oxide film is larger than 0.3 ⁇ m and 1.0 ⁇ m or less ⁇
  • the thickness of the oxide film is larger than 1.0 ⁇ m ⁇ ⁇
  • the oxide film peels off Status
  • Tables 2 and 3 show the surface-treated steel sheets used for the test, the types of alkaline silicates, the heating conditions in the atmospheric heating test, and the evaluation results.
  • a surface-treated steel sheet 1, a surface-treated steel sheet 2, a surface-treated steel sheet 6, a surface-treated steel sheet 7, obtained by surface-treating a steel sheet having a Cr content of 0.4% by mass or more and 1.7% by mass or less. Even when the surface-treated steel sheet 12 and the surface-treated steel sheet 13 were subjected to atmospheric heating tests at 850 ° C. and 900 ° C., only an oxide film having a thickness of 0.3 ⁇ m or less was formed.
  • the surface-treated steel sheet 5, the surface-treated steel sheet 9, and the surface-treated steel sheet 14 obtained by surface-treating a steel sheet having a Cr content of less than 0.2% by mass are heated to the atmosphere at 850 ° C or 900 ° C.
  • an oxide film thicker than 1.0 ⁇ m was formed.
  • the surface-treated steel sheet of the present invention is less likely to cause scale when processed by hot stamping. Therefore, it is possible to shorten or eliminate the process such as scale removal and to process the steel sheet by hot stamping more easily and inexpensively. Therefore, the surface-treated steel sheet of the present invention is expected to contribute to the further spread of processing of steel sheets by hot stamping.

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Abstract

A purpose of the present invention is to provide a surface-treated steel sheet wherein scale is not readily produced when the steel sheet is processed by hot stamping. The present invention, which solves this problem, relates to a surface-treated steel sheet. This surface-treated steel sheet has: a steel sheet with a Cr content of 0.2 mass% to 2.0 mass%; and an alkali silicate film that is positioned in contact with a surface of the steel sheet.

Description

表面処理鋼板および表面処理鋼板の加工方法Processing method of surface-treated steel sheet and surface-treated steel sheet
　本発明は、表面処理鋼板および表面処理鋼板の加工方法に関する。 The present invention relates to a surface-treated steel sheet and a method for processing a surface-treated steel sheet.
　鋼板の加工方法の一つとして、ホットスタンピングが知られている。ホットスタンピングは、鋼板を９００℃前後のオーステナイト域まで加熱し、成形と焼き入れとを金型内で同時に行う加工方法である。 Hot stamping is known as one of the processing methods for steel sheets. Hot stamping is a processing method in which a steel sheet is heated to an austenite region of around 900 ° C., and molding and quenching are performed simultaneously in a mold.
　たとえば自動車のキャビンなどに用いられる超高張力鋼板（超ハイテン）などは、冷間でのプレス加工を行おうとすると、金型から外される際の応力の開放によって弾性変形する、いわゆるスプリングバックが生じてしまい、寸法精度が低下しやすいという問題を有する。これに対し、ホットスタンピングでは、９００℃前後に加熱して軟質化させた鋼を金型に入れてプレス加工し、同時に金型との接触によって鋼を冷却させて焼き入れを行う。ホットスタンピングは、成形性に優れ、かつ、スプリングバックも少ないという特長を有する。 For example, ultra-high-strength steel plates (ultra-high-tensile steel) used in automobile cabins, etc., are elastically deformed by releasing stress when they are removed from the mold when cold-pressed, so-called springback. This occurs, and there is a problem that the dimensional accuracy tends to decrease. On the other hand, in hot stamping, steel that has been softened by heating to around 900 ° C. is placed in a die and pressed, and at the same time, the steel is cooled by contact with the die and quenched. Hot stamping has the features of excellent moldability and less springback.
　なお、鋼を加熱すると、鋼中のＦｅなどが酸化してなる酸化物が、加工後の鋼板の表面に生成することがある。加工鋼板の生産性を高める観点からは、この酸化物が生成しにくいような、鋼板の加工方法が求められている。 When steel is heated, oxides formed by oxidizing Fe and the like in the steel may be generated on the surface of the processed steel sheet. From the viewpoint of increasing the productivity of the processed steel sheet, there is a demand for a method for processing the steel sheet so that this oxide is difficult to form.
　たとえば、特許文献１には、ステンレス鋼の表面の不動態皮膜の構造を、Ｃｒ、またはＣｒとＳｉがリッチな構造とし、その表面にアルカリケイ酸塩を付着した、ステンレス鋼材が記載されている。特許文献１によれば、上記ステンレス鋼材は、表面の到達温度が６５０℃以上となるような高温に曝されても、大気中の酸素の侵入およびステンレス鋼素地からの金属元素の拡散が防止されるため、これらが反応して生成する酸化物によるテンパーカラーの発生を抑止できるとされている。 For example, Patent Document 1 describes a stainless steel material in which the structure of a passivation film on the surface of stainless steel is Cr or a structure rich in Cr and Si, and an alkali silicate is adhered to the surface thereof. .. According to Patent Document 1, the stainless steel material is prevented from invading oxygen in the atmosphere and diffusing metal elements from the stainless steel substrate even when exposed to a high temperature such that the surface temperature reaches 650 ° C. or higher. Therefore, it is said that the generation of temper color due to the oxide produced by the reaction of these can be suppressed.
　また、特許文献２には、Ｃ、Ｓｉ、Ｍｎ、ＣｒおよびＮｉの量を調整した熱処理用鋼板が記載されている。特許文献２によれば、上記熱処理用鋼板は、Ｃｒの量を０．１～２重量％とすることで、Ｃの量が０．３～１．２重量％である中～高炭素鋼板に対して、熱処理時の酸化スケールの剥離を防止できるとされている。 Further, Patent Document 2 describes a heat treatment steel sheet in which the amounts of C, Si, Mn, Cr and Ni are adjusted. According to Patent Document 2, the heat treatment steel sheet can be a medium to high carbon steel sheet having a C content of 0.3 to 1.2% by weight by setting the amount of Cr to 0.1 to 2% by weight. On the other hand, it is said that the peeling of the oxide scale during heat treatment can be prevented.
特開２００８－２３１５５１号公報Japanese Unexamined Patent Publication No. 2008-231551 特開平９－２５６１０７号公報Japanese Unexamined Patent Publication No. 9-256107
　特許文献１によれば、表面の到達温度が６５０℃以上となるような高温にステンレス鋼を曝しても、Ｃｒ－Ｆｅ－Ｏ系の酸化物によるテンパーカラーを抑制できるとされている。 According to Patent Document 1, even if stainless steel is exposed to a high temperature such that the surface temperature reaches 650 ° C. or higher, temper color due to Cr—Fe—O oxide can be suppressed.
　これに対し、９００℃前後というさらに高温の領域にまで鋼板を加熱するホットスタンピングでは、７００℃前後までしか加熱していない特許文献１の試験条件よりも酸化物がさらに生じやすい。たとえば、ホットスタンピングでは、より厚く堆積して灰色となったスケールが鋼板表面に生じやすい。そのため、ホットスタンピングによる鋼板の加工には、上記スケールを除去するためのショットブラストなどの処理が必要であり、これによって生産性が低下しかねない。そのため、ホットスタンピング用の鋼板には、酸化物の発生をさらに抑制することが求められる。 On the other hand, in hot stamping that heats the steel sheet to a higher temperature region of around 900 ° C, oxides are more likely to be generated than the test conditions of Patent Document 1 in which the steel sheet is heated only to around 700 ° C. For example, hot stamping tends to produce thicker, grayer scales on the surface of the steel sheet. Therefore, processing of a steel sheet by hot stamping requires processing such as shot blasting to remove the scale, which may reduce productivity. Therefore, the steel sheet for hot stamping is required to further suppress the generation of oxides.
　また、特許文献２では、プレステンパーなどの工程においてスケールが剥離して、押込み疵を発生させることを抑制するために、スケールの剥離を防止しようとしている。しかし、そもそもスケールの発生を抑制すれば、押込み疵の発生も抑制できる。 Further, in Patent Document 2, in order to prevent the scale from peeling off in a process such as a press temper and causing an indentation defect, it is attempted to prevent the scale from peeling off. However, if the occurrence of scale is suppressed in the first place, the occurrence of indentation flaws can also be suppressed.
　本発明は、かかる点に鑑みてなされたものであり、ホットスタンピングによる鋼板の加工を行ったときにスケールが発生しにくい表面処理鋼板、および当該表面処理鋼板の加工方法を提供することをその目的とする。 The present invention has been made in view of this point, and an object of the present invention is to provide a surface-treated steel sheet in which scale is less likely to occur when a steel sheet is processed by hot stamping, and a method for processing the surface-treated steel sheet. And.
　上記課題を解決するための本発明の一実施形態に関する表面処理鋼板は、Ｃｒの含有量が０．２質量％以上２．０質量％以下である鋼板と、前記鋼板の表面に接して配置された、アルカリケイ酸塩皮膜と、を有する。 The surface-treated steel sheet according to the embodiment of the present invention for solving the above problems is arranged in contact with a steel sheet having a Cr content of 0.2% by mass or more and 2.0% by mass or less and the surface of the steel sheet. It also has an alkaline silicate film.
　また、上記課題を解決するための本発明の一実施形態に関する表面処理鋼板の加工方法は、上記表面処理鋼板を、前記鋼板のＡｃ３点以上１１００℃以下の温度範囲にまで加熱する工程と、前記加熱された表面処理鋼板を金型の内部に配置して熱間プレスし、かつ、前記金型によって前記表面処理鋼板を冷却する工程と、を有する。 Further, the method for processing the surface-treated steel sheet according to the embodiment of the present invention for solving the above-mentioned problems includes a step of heating the surface-treated steel sheet to a temperature range of Ac 3 points or more and 1100 ° C. or less of the steel sheet. It has a step of arranging a heated surface-treated steel sheet inside a die, hot-pressing it, and cooling the surface-treated steel sheet by the die.
　本発明によれば、ホットスタンピングによる鋼板の加工を行ったときにスケールが発生しにくい表面処理鋼板、当該表面処理鋼板の加工方法、および当該表面処理鋼板を加工して得られる加工された表面処理鋼板が提供される。 According to the present invention, a surface-treated steel sheet in which scale is less likely to occur when the steel sheet is processed by hot stamping, a method for processing the surface-treated steel sheet, and a processed surface treatment obtained by processing the surface-treated steel sheet. Steel sheets are provided.
　１．表面処理鋼板
　本発明の一実施形態は、Ｃｒの含有量が０．２質量％以上２．０質量％以下である鋼板と、上記鋼板の表面に接して形成されたアルカリケイ酸塩皮膜と、を有する、ホットスタンピング用の表面処理鋼板に関する。 1. 1. Surface-treated steel sheet In one embodiment of the present invention, a steel sheet having a Cr content of 0.2% by mass or more and 2.0% by mass or less, an alkali silicate film formed in contact with the surface of the steel sheet, and the like. The present invention relates to a surface-treated steel sheet for hot stamping.
　１－１．鋼板
　上記鋼板は、Ｃｒの含有量が０．２質量％以上２．０質量％以下である鋼板であればよい。上記鋼板の例には、ニッケルクロム鋼板、クロムモリブデン鋼板、およびニッケルクロムモリブデン鋼板（ＪＩＳ　Ｇ　４０５３：機械構造用合金鋼鋼材）などが含まれる。上記鋼板は、亜鉛めっき鋼板、Ｚｎ－Ａｌ合金めっき鋼板、Ｚｎ－Ａｌ－Ｍｇ合金めっき鋼板、およびアルミニウムめっき鋼板などのめっき鋼板であってもよい。また、上記鋼板は、冷延鋼板であってもよいし、熱延鋼板であってもよい。 1-1. Steel Sheet The steel sheet may be any steel sheet having a Cr content of 0.2% by mass or more and 2.0% by mass or less. Examples of the steel sheet include nickel chrome steel sheet, chrome molybdenum steel sheet, nickel chrome molybdenum steel sheet (JIS G 4053: alloy steel for machine structure) and the like. The steel sheet may be a galvanized steel sheet, a Zn—Al alloy plated steel sheet, a Zn—Al—Mg alloy plated steel sheet, an aluminum plated steel sheet, or the like. Further, the steel sheet may be a cold-rolled steel sheet or a hot-rolled steel sheet.
　上記鋼板に含まれるＣｒは、ホットスタンピング時に、アルカリケイ酸塩皮膜に含まれるアルカリケイ酸塩（ＭＸＯ・ｎＳｉＯ２：Ｍは、アルカリ金属またはアルカリ土類金属である。Ｘは、Ｍがアルカリ金属であるときは２であり、Ｍがアルカリ土類金属であるときは１である。ｎは、たとえば１以上８以下の任意の数である。）と反応して、Ｓｉ－Ｃｒ－Ｍ－Ｏ系の反応層を形成する。 Cr contained in the steel plate is an alkali silicate contained in an alkali silicate film at the time of hot stamping (MX O · nSiO 2 : M is an alkali metal or an alkaline earth metal. X is M. When it is an alkali metal, it is 2, and when M is an alkaline earth metal, it is 1. n is, for example, an arbitrary number of 1 or more and 8 or less) and Si—Cr—M. -Forms an O-based reaction layer.
　上記反応層は、高温時の安定性が高い。そのため、上記反応層は、ホットスタンピング時に、鋼板からアルカリケイ酸塩皮膜への、鋼板に含まれる原子（特にはＦｅ）の拡散を好適に抑制する。これにより、上記反応層は、ホットスタンピング時に鋼板から拡散したＦｅが空気中の酸素（Ｏ２）と反応することによる、ＦｅＯ、Ｆｅ３Ｏ４およびＦｅ２Ｏ３などの酸化物の生成を抑制し、これらの酸化物が堆積することによるスケールの発生を抑制することができる。 The reaction layer is highly stable at high temperatures. Therefore, the reaction layer preferably suppresses the diffusion of atoms (particularly Fe) contained in the steel sheet from the steel sheet to the alkaline silicate film during hot stamping. As a result, the reaction layer suppresses the formation of oxides such as FeO, Fe 3 O 4 and Fe 2 O 3 due to the reaction of Fe diffused from the steel plate with oxygen (O 2 ) in the air during hot stamping. However, it is possible to suppress the generation of scale due to the deposition of these oxides.
　本発明者らの新たな知見によると、このとき、鋼板中のＣｒの含有量が０．２質量％以上２．０質量％以下であると、ホットスタンピング時に上記スケールの発生を抑制する効果が顕著に高まる。この理由は定かではないが、本発明者らは、以下のように考えている。 According to the new findings of the present inventors, at this time, when the Cr content in the steel sheet is 0.2% by mass or more and 2.0% by mass or less, the effect of suppressing the generation of the scale during hot stamping is effective. Significantly increased. The reason for this is not clear, but the present inventors think as follows.
　つまり、鋼板中のＣｒの含有量が０．２質量％以上であると、鋼板の表面に十分な厚みの上記反応層が形成され、鋼板からのＦｅの拡散を十分に抑制できるため、スケールの発生も十分に抑制される。一方で、鋼板中のＣｒの含有量が２．０質量％を越えるとその効果は飽和する。上記観点からは、鋼板中のＣｒの含有量は０．４質量％以上１．７質量％以下であることが好ましく、０．６質量％以上１．６質量％以下であることがより好ましい。 That is, when the Cr content in the steel sheet is 0.2% by mass or more, the reaction layer having a sufficient thickness is formed on the surface of the steel sheet, and the diffusion of Fe from the steel sheet can be sufficiently suppressed. Occurrence is also sufficiently suppressed. On the other hand, when the Cr content in the steel sheet exceeds 2.0% by mass, the effect is saturated. From the above viewpoint, the Cr content in the steel sheet is preferably 0.4% by mass or more and 1.7% by mass or less, and more preferably 0.6% by mass or more and 1.6% by mass or less.
　上記鋼板は、Ｃ、Ｓｉ、Ｍｎ、Ｐ、Ｓ、Ｍｏ、Ｖ、Ｔｉ、ＢｉおよびＷなどの、ＦｅおよびＣｒ以外の元素を含んでもよい。これらの元素の含有量は、上記鋼板に要求される特性などに応じて任意に定めることができる。 The steel sheet may contain elements other than Fe and Cr, such as C, Si, Mn, P, S, Mo, V, Ti, Bi and W. The content of these elements can be arbitrarily determined according to the characteristics required for the steel sheet and the like.
　たとえば、Ｃの含有量は、０．１質量％以上１．２質量％以下とすることができ、０．２質量％以上１．２質量％以下であることが好ましく、０．４質量％以上１．０質量％以下であることがより好ましい。 For example, the content of C can be 0.1% by mass or more and 1.2% by mass or less, preferably 0.2% by mass or more and 1.2% by mass or less, and 0.4% by mass or more. It is more preferably 1.0% by mass or less.
　また、Ｓｉの含有量は、０．１質量％以上２．５質量％以下とすることができ、０．１質量％以上１．５質量％以下とすることが好ましい。 Further, the Si content can be 0.1% by mass or more and 2.5% by mass or less, and preferably 0.1% by mass or more and 1.5% by mass or less.
　また、Ｍｎの含有量は、０．４質量％以上３．０質量％以下とすることができ、０．４質量％以上２．０質量％以下とすることが好ましい。 Further, the Mn content can be 0.4% by mass or more and 3.0% by mass or less, and preferably 0.4% by mass or more and 2.0% by mass or less.
　上記鋼板の厚さは、ホットスタンピングによる加工ができる程度であればよく、たとえば０．５ｍｍ以上４．０ｍｍ以下程度であればよい。 The thickness of the steel sheet may be such that it can be processed by hot stamping, for example, it may be about 0.5 mm or more and 4.0 mm or less.
　１－２．アルカリケイ酸塩皮膜
　上記アルカリケイ酸塩皮膜は、上記鋼板の表面を被覆する、アルカリケイ酸塩を含む皮膜である。上記アルカリケイ酸塩皮膜は、上記鋼板の表面に接して形成されている。上記アルカリケイ酸塩皮膜は、上記鋼板の一方の表面にのみ形成されていてもよいし、上記鋼板の両方の表面に形成されていてもよい。 1-2. Alkaline silicate film The alkali silicate film is a film containing an alkali silicate that covers the surface of the steel plate. The alkali silicate film is formed in contact with the surface of the steel sheet. The alkali silicate film may be formed on only one surface of the steel sheet, or may be formed on both surfaces of the steel sheet.
　上記アルカリケイ酸塩皮膜は、ホットスタンピング時に、上記鋼板に含まれるＣｒと反応して上述したＳｉ－Ｃｒ－Ｍ－Ｏ系の反応層を形成する。これにより、上記アルカリケイ酸塩皮膜は、ホットスタンピング時に、鋼板からアルカリケイ酸塩皮膜へのＦｅの拡散を抑制して、上記拡散したＦｅが空気中の酸素（Ｏ２）と反応することによる酸化物の生成を抑制し、これらの酸化物が堆積することによるスケールの発生を抑制することができる The alkali silicate film reacts with Cr contained in the steel sheet during hot stamping to form the Si—Cr—MO-based reaction layer described above. As a result, the alkaline silicate film suppresses the diffusion of Fe from the steel plate to the alkaline silicate film during hot stamping, and the diffused Fe reacts with oxygen (O 2 ) in the air. It is possible to suppress the formation of oxides and suppress the generation of scale due to the deposition of these oxides.
　また、上記アルカリケイ酸塩皮膜は、ホットスタンピング時に、空気中に含まれる酸素（Ｏ２）の鋼板中への侵入を抑制する。これにより、上記アルカリケイ酸塩皮膜は、上記鋼板中へ侵入した酸素が鋼板中のＦｅと反応することによる、ＦｅＯ、Ｆｅ３Ｏ４およびＦｅ２Ｏ３などの酸化物の生成を抑制し、これらの酸化物が堆積することによるスケールの発生を抑制することもできる。 Further, the alkaline silicate film suppresses the invasion of oxygen (O 2 ) contained in the air into the steel sheet during hot stamping. As a result, the alkali silicate film suppresses the formation of oxides such as FeO, Fe 3 O 4 and Fe 2 O 3 due to the reaction of oxygen that has entered the steel plate with Fe in the steel plate. It is also possible to suppress the generation of scale due to the deposition of these oxides.
　上記アルカリケイ酸塩は、一般式ＭＸＯ・ｎＳｉＯ２ で表される化合物であればよい。 The alkaline silicate may be any compound represented by the general formula MXO · nSiO 2 .
　上記一般式において、Ｍは、アルカリ金属またはアルカリ土類金属であり、アルカリ金属としてはＬｉ、Ｎａ、およびＫなどを、アルカリ土類金属としてはＭｇおよびＣａなどを、用いることができる。これらのうち、理由は明確ではないがＭがＬｉであると最も効果的であり好ましい。さらには焼成によるアルカリケイ酸塩皮膜の形成がより低温でも可能であり、かつ、溶融温度がより高いためより高温でのホットスタンピング時にもスケールを効率的に抑制できることから、ＭはＬｉであることがより好ましい。 In the above general formula, M is an alkali metal or an alkaline earth metal, and Li, Na, K or the like can be used as the alkali metal, and Mg, Ca or the like can be used as the alkaline earth metal. Of these, although the reason is not clear, it is most effective and preferable that M is Li. Furthermore, M is Li because it is possible to form an alkaline silicate film by firing even at a lower temperature, and since the melting temperature is higher, scale can be efficiently suppressed even during hot stamping at a higher temperature. Is more preferable.
　なお、上記アルカリケイ酸塩は、アルカリ金属またはアルカリ土類金属のうち異なる２種類の原子をＭとして含む化合物であってもよい。 The alkali silicate may be a compound containing two different atoms of an alkali metal or an alkaline earth metal as M.
　上記一般式において、Ｘは、Ｍがアルカリ金属であるときは２であり、Ｍがアルカリ土類金属であるときは１である。 In the above general formula, X is 2 when M is an alkali metal and 1 when M is an alkaline earth metal.
　上記一般式において、ｎは、たとえば３．５以上７．５以下の任意の数である。 In the above general formula, n is, for example, an arbitrary number of 3.5 or more and 7.5 or less.
　ｎが３．５以上であると、アルカリケイ酸塩皮膜中に十分な量のＳｉが存在するため、鋼板の表面に十分な厚みの上記反応層が形成され、鋼板からのＦｅの拡散によるスケールの発生をより抑制することができる。また、ｎが３．５以上であると、アルカリケイ酸塩皮膜中のアルカリ成分量が多すぎることがないため、ホットスタンピング後の鋼板表面に残留したアルカリ成分が空気中の水分および炭酸ガスなどを反応して生成される反応生成物による、白化現象をより抑制することもできる。 When n is 3.5 or more, a sufficient amount of Si is present in the alkali silicate film, so that the above reaction layer having a sufficient thickness is formed on the surface of the steel sheet, and the scale due to the diffusion of Fe from the steel sheet is formed. Can be further suppressed. Further, when n is 3.5 or more, the amount of the alkaline component in the alkaline silicate film is not too large, so that the alkaline component remaining on the surface of the steel sheet after hot stamping is water in the air, carbon dioxide gas, or the like. It is also possible to further suppress the whitening phenomenon caused by the reaction product produced by the reaction of the above.
　一方で、ｎが７．５以下であると、アルカリケイ酸塩皮膜中に十分な量のアルカリ成分が存在するため、鋼板の表面に十分な厚みの上記反応層が形成され、鋼板からのＦｅの拡散によるスケールの発生をより抑制することができる。また、ｎが７．５以下であると、アルカリケイ酸塩皮膜中に十分な量のアルカリ成分が存在するため、アルカリケイ酸塩の強度をより高めることができる。 On the other hand, when n is 7.5 or less, a sufficient amount of alkaline component is present in the alkaline silicate film, so that the above reaction layer having a sufficient thickness is formed on the surface of the steel sheet, and Fe from the steel sheet is formed. It is possible to further suppress the generation of scale due to the diffusion of. Further, when n is 7.5 or less, a sufficient amount of alkaline component is present in the alkaline silicate film, so that the strength of the alkaline silicate can be further increased.
　上記アルカリケイ酸塩皮膜の付着量は、Ｓｉ換算で０．０５ｇ／ｍ２以上１ｇ／ｍ２以下であることが好ましい。上記付着量が０．０５ｇ／ｍ２以上であると、スケールの発生を十分に抑制することができる。一方で、上記付着量が１ｇ／ｍ２以上であると、アルカリケイ酸塩皮膜の鋼板への密着性を十分に高めることができる。 The amount of the alkali silicate film adhered is preferably 0.05 g / m 2 or more and 1 g / m 2 or less in terms of Si. When the amount of adhesion is 0.05 g / m 2 or more, the generation of scale can be sufficiently suppressed. On the other hand, when the adhesion amount is 1 g / m 2 or more, the adhesion of the alkali silicate film to the steel sheet can be sufficiently enhanced.
　上記アルカリケイ酸塩皮膜は、上記アルカリケイ酸塩を含む水溶液を鋼板の表面上に塗布し、焼成して形成することができる。このようにして形成されたアルカリケイ酸塩皮膜は、一般式ＭＸＯ・ｎＳｉＯ２・ｙＨ２Ｏで表される化合物を主体とした皮膜である。 The alkaline silicate film can be formed by applying an aqueous solution containing the alkaline silicate on the surface of a steel sheet and firing it. The alkaline silicate film thus formed is a film mainly composed of a compound represented by the general formula MX O · nSiO 2 · yH 2 O.
　このとき、皮膜中の分子同士の結合力を高めて、アルカリケイ酸塩皮膜の密着性をより高める観点からは、アルカリケイ酸塩皮膜中が保持する水の量はより少ない（上記一般式中のｙがより小さい）ことが好ましい。上記水の量をより低減させたアルカリケイ酸塩皮膜を形成するためには、鋼板の表面上に塗布された上記水溶液を、３５０℃以上の温度で焼成させることが好ましい。 At this time, from the viewpoint of increasing the binding force between the molecules in the film and further enhancing the adhesion of the alkaline silicate film, the amount of water retained in the alkaline silicate film is smaller (in the above general formula). Is smaller than y). In order to form an alkaline silicate film in which the amount of water is further reduced, it is preferable to bake the aqueous solution applied on the surface of the steel sheet at a temperature of 350 ° C. or higher.
　なお、このとき塗布する水溶液中のアルカリケイ酸塩の含有量や、水溶液の塗布量などを調整することで、鋼板表面への上記アルカリケイ酸塩皮膜の付着量を調整することができる。 By adjusting the content of the alkali silicate in the aqueous solution to be applied at this time, the amount of the aqueous solution applied, and the like, the amount of the alkali silicate film adhering to the surface of the steel sheet can be adjusted.
　また、上記水溶液を塗布する前に、鋼板の表面に対して、脱脂、酸洗などの公知の前処理を施してもよい。 Further, before applying the above aqueous solution, the surface of the steel sheet may be subjected to known pretreatment such as degreasing and pickling.
　２．表面処理鋼板の加工方法
　本発明の他の実施形態は、上述した表面処理鋼板を熱処理する、表面処理鋼板の加工方法に関する。上記熱処理は、表面処理鋼板を高熱処理すればよく、ホットスタンピングや、焼入れ、焼なまし（焼鈍）、焼きならしなどの公知の熱処理であればよい。本実施形態は、鋼板として上記表面処理鋼板を用いるほかは、公知の熱処理と同様に実施することができる。 2. 2. Method for processing surface-treated steel sheet Another embodiment of the present invention relates to a method for processing a surface-treated steel sheet, which heat-treats the above-mentioned surface-treated steel sheet. The heat treatment may be a high heat treatment of the surface-treated steel sheet, and may be any known heat treatment such as hot stamping, quenching, annealing (canning), and normalizing. This embodiment can be carried out in the same manner as the known heat treatment except that the surface-treated steel sheet is used as the steel sheet.
　具体的には、まず、上記表面処理鋼板を、鋼板中のフェライトがオーステナイトに変態する温度領域まで加熱する。具体的には、上記表面処理鋼板を、８００℃以上１１００℃以下、好ましくは上記鋼板のＡｃ３点以上１１００℃以下の温度範囲にまで加熱する。このときの昇温速度は、２℃／ｓ以上の範囲で調整すればよい。 Specifically, first, the surface-treated steel sheet is heated to a temperature range in which the ferrite in the steel sheet transforms into austenite. Specifically, the surface-treated steel sheet is heated to a temperature range of 800 ° C. or higher and 1100 ° C. or lower, preferably Ac 3 points or higher and 1100 ° C. or lower of the steel sheet. The temperature rising rate at this time may be adjusted in the range of 2 ° C./s or more.
　次に、上記加熱した表面処理鋼板を金型の内部に配置して、熱間プレスする。そして、熱間プレスと同時に、上記金型によって上記表面処理鋼板を冷却する。具体的には、上記表面処理鋼板を、上記鋼板のＭｆ点（マルテンサイト変態終了点）以下にまで冷却すればよい。また、このときの冷却速度は、５℃／ｓ以上４０℃／ｓ以下の範囲で調整すればよい。 Next, the heated surface-treated steel sheet is placed inside the mold and hot pressed. Then, at the same time as hot pressing, the surface-treated steel sheet is cooled by the die. Specifically, the surface-treated steel sheet may be cooled to the Mf point (martensite transformation end point) or less of the steel sheet. Further, the cooling rate at this time may be adjusted in the range of 5 ° C./s or more and 40 ° C./s or less.
　このようにして加工された表面処理鋼板は、鋼板とアルカリケイ酸塩皮膜との間に、Ｓｉ－Ｃｒ－Ｍ－Ｏ系の反応層を有する。上記鋼板は、その断面におけるマルテンサイトの面積率が９０％以上であることが好ましい。 The surface-treated steel sheet processed in this way has a Si—Cr—MO reaction layer between the steel sheet and the alkali silicate film. The steel sheet preferably has an area ratio of martensite of 90% or more in its cross section.
　以下、本発明について実施例を参照して詳細に説明するが、本発明はこれらの実施例により限定されない。 Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited to these Examples.
　１．鋼板の作製
　表１に記載の組成を有する、いずれも板厚が１．２ｍｍの鋼板１～鋼板１４を用意した。 1. 1. Preparation of Steel Sheets Steel plates 1 to 14 having the compositions shown in Table 1 and having a thickness of 1.2 mm were prepared.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
　それぞれの鋼板を、オルソ珪酸ソーダによってｐＨを１４とした４０℃のアルカリ水溶液に３０秒間浸漬して、アルカリ脱脂した。その後、アルカリ脱脂した鋼板の表面に、アルカリケイ酸塩として日本化学工業株式会社製のリチウムシリケート（Ｌｉ２Ｏ・ｎＳｉＯ２：ｎは３～８）またはキシダ化学株式会社製の水ガラス３号（Ｎａ２Ｏ・ｎＳｉＯ２：ｎは３～８）を濃度５％に希釈した水溶液を、バーコート＃３で塗布した。塗布後、大気中で１８０℃に加熱して焼成し、付着量がＳｉ換算で０．２～０．５ｇ／ｍ２であるアルカリケイ酸塩皮膜を形成して、それぞれ表面処理鋼板１～表面処理鋼板１４を得た。 Each steel sheet was immersed in an alkaline aqueous solution at 40 ° C. having a pH of 14 with sodium orthosilicate for 30 seconds for alkaline degreasing. After that, on the surface of the alkaline degreased steel plate, lithium silicate (Li 2O · nSiO 2 : n is 3 to 8) manufactured by Nippon Kagaku Kogyo Co., Ltd. or water glass No. 3 manufactured by Kishida Chemical Co., Ltd. An aqueous solution obtained by diluting Na 2 O · nSiO 2 : n from 3 to 8) to a concentration of 5% was applied with bar coat # 3. After coating, it is heated to 180 ° C. in the air and fired to form an alkaline silicate film having an adhesion amount of 0.2 to 0.5 g / m 2 in terms of Si, and the surface-treated steel sheets 1 to surface are formed, respectively. A treated steel sheet 14 was obtained.
　その後、それぞれの表面処理鋼板から５０ｍｍ×５０ｍｍの試験片を切り出し、雰囲気温度を８５０℃または９００℃として加熱炉にて大気加熱試験を実施した。このときの均熱時間は、１０分とした。加熱後、試験片を炉から取出して常温にて放冷した。 After that, a 50 mm × 50 mm test piece was cut out from each surface-treated steel sheet, and an atmospheric heating test was carried out in a heating furnace with an atmospheric temperature of 850 ° C or 900 ° C. The soaking time at this time was 10 minutes. After heating, the test piece was taken out from the furnace and allowed to cool at room temperature.
　十分に冷却された試験片の断面を、ＳＥＭおよびＧＤＳ（グロー放電発光分光分析）により観察し、大気加熱試験により形成された酸化皮膜の厚さを測定して、以下の基準でそれぞれの表面処理鋼板を評価した。
　◎　酸化皮膜の厚さは０．３μｍ以下である
　○　酸化皮膜の厚さは０．３μｍより大きく１．０μｍ以下である
　×　酸化皮膜の厚さは１．０μｍより大きい××　酸化皮膜が剥がれ落ちる状態 A cross section of a sufficiently cooled test piece is observed by SEM and GDS (Glow Discharge Emission Spectroscopy), the thickness of the oxide film formed by the atmospheric heating test is measured, and each surface treatment is performed according to the following criteria. The steel plate was evaluated.
◎ The thickness of the oxide film is 0.3 μm or less ○ The thickness of the oxide film is larger than 0.3 μm and 1.0 μm or less × The thickness of the oxide film is larger than 1.0 μm × × The oxide film peels off Status
　試験に供した表面処理鋼板、アルカリケイ酸塩の種類、大気加熱試験における加熱条件、および評価結果を、表２および表３に示す。 Tables 2 and 3 show the surface-treated steel sheets used for the test, the types of alkaline silicates, the heating conditions in the atmospheric heating test, and the evaluation results.
Figure JPOXMLDOC01-appb-T000002
  
 
Figure JPOXMLDOC01-appb-T000002
  
 
Figure JPOXMLDOC01-appb-T000003
Figure JPOXMLDOC01-appb-T000003
　Ｃｒの含有量が０．２質量％以上２．０質量％以下である鋼板を表面処理して得られた表面処理鋼板１～表面処理鋼板４、表面処理鋼板６～表面処理鋼板８、および表面処理鋼板１０～表面処理鋼板１３は、８５０℃および９００℃の大気加熱試験に供しても、１．０μｍ以下の厚さの酸化皮膜しか形成されなかった。 Surface-treated steel sheets 1 to 4 surface-treated steel sheets, surface-treated steel sheets 6 to surface-treated steel sheets 8, and surfaces obtained by surface-treating steel sheets with a Cr content of 0.2% by mass or more and 2.0% by mass or less. Even when the treated steel sheets 10 to 13 were subjected to atmospheric heating tests at 850 ° C. and 900 ° C., only an oxide film having a thickness of 1.0 μm or less was formed.
　特に、Ｃｒの含有量が０．４質量％以上１．７質量％以下である鋼板を表面処理して得られた表面処理鋼板１、表面処理鋼板２、表面処理鋼板６、表面処理鋼板７、表面処理鋼板１２、および表面処理鋼板１３は、８５０℃および９００℃の大気加熱試験に供しても、０．３μｍ以下の厚さの酸化皮膜しか形成されなかった。 In particular, a surface-treated steel sheet 1, a surface-treated steel sheet 2, a surface-treated steel sheet 6, a surface-treated steel sheet 7, obtained by surface-treating a steel sheet having a Cr content of 0.4% by mass or more and 1.7% by mass or less. Even when the surface-treated steel sheet 12 and the surface-treated steel sheet 13 were subjected to atmospheric heating tests at 850 ° C. and 900 ° C., only an oxide film having a thickness of 0.3 μm or less was formed.
　一方で、Ｃｒの含有量が０．２質量％未満である鋼板を表面処理して得られた表面処理鋼板５、表面処理鋼板９、および表面処理鋼板１４は、８５０℃または９００℃の大気加熱試験に供したときに、１．０μｍより厚い酸化皮膜が形成された。 On the other hand, the surface-treated steel sheet 5, the surface-treated steel sheet 9, and the surface-treated steel sheet 14 obtained by surface-treating a steel sheet having a Cr content of less than 0.2% by mass are heated to the atmosphere at 850 ° C or 900 ° C. When subjected to the test, an oxide film thicker than 1.0 μm was formed.
　本発明の表面処理鋼板は、ホットスタンピングによる加工を行ったときにスケールが発生しにくい。そのため、スケール除去などの工程を短縮化あるいは不要とし、ホットスタンピングによる鋼板の加工をより容易かつ安価に行うことを可能とする。そのため、本発明の表面処理鋼板は、ホットスタンピングによる鋼板の加工のさらなる普及に貢献すると期待される。 The surface-treated steel sheet of the present invention is less likely to cause scale when processed by hot stamping. Therefore, it is possible to shorten or eliminate the process such as scale removal and to process the steel sheet by hot stamping more easily and inexpensively. Therefore, the surface-treated steel sheet of the present invention is expected to contribute to the further spread of processing of steel sheets by hot stamping.

Claims (4)

  1. 　Ｃｒの含有量が０．２質量％以上２．０質量％以下である鋼板と、
    　前記鋼板の表面に接して配置された、アルカリケイ酸塩皮膜と、
    　を有する、表面処理鋼板。     Steel sheets with a Cr content of 0.2% by mass or more and 2.0% by mass or less,
    An alkali silicate film arranged in contact with the surface of the steel sheet and
    Has a surface-treated steel sheet.
  2. 　前記アルカリケイ酸塩皮膜の付着量は、Ｓｉ換算で０．０５ｇ／ｍ２以上１ｇ／ｍ２以下である、請求項１に記載の表面処理鋼板。 The surface-treated steel sheet according to claim 1, wherein the amount of the alkali silicate film adhered is 0.05 g / m 2 or more and 1 g / m 2 or less in terms of Si.
  3. 　ホットスタンピング用または８００℃以上の熱処理用である、請求項１または２に記載の表面処理鋼板。 The surface-treated steel sheet according to claim 1 or 2, which is used for hot stamping or heat treatment at 800 ° C. or higher.
  4. 　請求項１～３のいずれか１項に記載の表面処理鋼板を、前記鋼板のＡｃ３点以上１１００℃以下の温度範囲にまで加熱する工程と、
    　前記加熱された表面処理鋼板を金型の内部に配置して熱間プレスし、かつ、前記金型によって前記表面処理鋼板を冷却する工程と、
    　を有する、表面処理鋼板の加工方法。     A step of heating the surface-treated steel sheet according to any one of claims 1 to 3 to a temperature range of Ac 3 points or more and 1100 ° C. or less of the steel sheet.
    A step of arranging the heated surface-treated steel sheet inside a die, hot-pressing it, and cooling the surface-treated steel sheet by the die.
    A method for processing a surface-treated steel sheet.
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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS4958032A (en) * 1972-10-07 1974-06-05
JP2000017453A (en) * 1998-06-30 2000-01-18 Kobe Steel Ltd Rust stabilizing-treated steel
WO2003085171A1 (en) * 2002-04-08 2003-10-16 Nippon Steel Corporation Heat-resistant metal plate excellent in marring resistance and corrosion resistance
JP2020506981A (en) * 2017-01-09 2020-03-05 ヘンケル・アクチェンゲゼルシャフト・ウント・コムパニー・コマンディットゲゼルシャフト・アウフ・アクチェンＨｅｎｋｅｌ ＡＧ ＆ Ｃｏ． ＫＧａＡ Curable protective coating composition

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS4958032A (en) * 1972-10-07 1974-06-05
JP2000017453A (en) * 1998-06-30 2000-01-18 Kobe Steel Ltd Rust stabilizing-treated steel
WO2003085171A1 (en) * 2002-04-08 2003-10-16 Nippon Steel Corporation Heat-resistant metal plate excellent in marring resistance and corrosion resistance
JP2020506981A (en) * 2017-01-09 2020-03-05 ヘンケル・アクチェンゲゼルシャフト・ウント・コムパニー・コマンディットゲゼルシャフト・アウフ・アクチェンＨｅｎｋｅｌ ＡＧ ＆ Ｃｏ． ＫＧａＡ Curable protective coating composition

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