JP7498413B2 - Method for producing hot stamped plated steel sheet and hot stamped product, and hot stamped product - Google Patents
Method for producing hot stamped plated steel sheet and hot stamped product, and hot stamped product Download PDFInfo
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- 229910000831 Steel Inorganic materials 0.000 title claims description 55
- 239000010959 steel Substances 0.000 title claims description 55
- 238000004519 manufacturing process Methods 0.000 title claims description 32
- 239000010410 layer Substances 0.000 claims description 97
- 238000007747 plating Methods 0.000 claims description 83
- 239000011701 zinc Substances 0.000 claims description 70
- 238000000227 grinding Methods 0.000 claims description 47
- 229910052725 zinc Inorganic materials 0.000 claims description 46
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 claims description 44
- 238000000034 method Methods 0.000 claims description 37
- 238000010438 heat treatment Methods 0.000 claims description 31
- 239000000463 material Substances 0.000 claims description 27
- 238000005246 galvanizing Methods 0.000 claims description 22
- 239000000758 substrate Substances 0.000 claims description 21
- 239000011248 coating agent Substances 0.000 claims description 18
- 238000000576 coating method Methods 0.000 claims description 18
- 238000001816 cooling Methods 0.000 claims description 13
- 239000000203 mixture Substances 0.000 claims description 12
- 239000000126 substance Substances 0.000 claims description 12
- 230000015572 biosynthetic process Effects 0.000 claims description 9
- 239000002344 surface layer Substances 0.000 claims description 2
- 241000239290 Araneae Species 0.000 description 19
- 230000007547 defect Effects 0.000 description 15
- 238000005259 measurement Methods 0.000 description 12
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 9
- 238000004090 dissolution Methods 0.000 description 7
- 230000002787 reinforcement Effects 0.000 description 7
- 229910052782 aluminium Inorganic materials 0.000 description 5
- 239000010960 cold rolled steel Substances 0.000 description 5
- 230000007797 corrosion Effects 0.000 description 5
- 238000005260 corrosion Methods 0.000 description 5
- 238000009792 diffusion process Methods 0.000 description 5
- 238000004070 electrodeposition Methods 0.000 description 5
- 229910001335 Galvanized steel Inorganic materials 0.000 description 4
- 239000008397 galvanized steel Substances 0.000 description 4
- 239000007789 gas Substances 0.000 description 4
- 229910000765 intermetallic Inorganic materials 0.000 description 4
- 239000003973 paint Substances 0.000 description 4
- 238000012360 testing method Methods 0.000 description 4
- 238000005275 alloying Methods 0.000 description 3
- 238000004458 analytical method Methods 0.000 description 3
- 229910052742 iron Inorganic materials 0.000 description 3
- 229910052748 manganese Inorganic materials 0.000 description 3
- 229910052710 silicon Inorganic materials 0.000 description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 3
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N Iron oxide Chemical compound [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 description 2
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 2
- 239000006061 abrasive grain Substances 0.000 description 2
- 238000005266 casting Methods 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 229910052804 chromium Inorganic materials 0.000 description 2
- 239000012141 concentrate Substances 0.000 description 2
- 239000000112 cooling gas Substances 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000010828 elution Methods 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 238000011156 evaluation Methods 0.000 description 2
- 239000012535 impurity Substances 0.000 description 2
- 239000007791 liquid phase Substances 0.000 description 2
- 230000003287 optical effect Effects 0.000 description 2
- 230000003647 oxidation Effects 0.000 description 2
- 238000007254 oxidation reaction Methods 0.000 description 2
- 238000005554 pickling Methods 0.000 description 2
- 230000005855 radiation Effects 0.000 description 2
- 238000005507 spraying Methods 0.000 description 2
- 238000003466 welding Methods 0.000 description 2
- 238000004876 x-ray fluorescence Methods 0.000 description 2
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 238000000137 annealing Methods 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 239000000919 ceramic Substances 0.000 description 1
- 239000002826 coolant Substances 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 230000002542 deteriorative effect Effects 0.000 description 1
- 238000005485 electric heating Methods 0.000 description 1
- 238000007654 immersion Methods 0.000 description 1
- 230000006698 induction Effects 0.000 description 1
- 230000002401 inhibitory effect Effects 0.000 description 1
- 238000011835 investigation Methods 0.000 description 1
- 239000011572 manganese Substances 0.000 description 1
- 239000003595 mist Substances 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 238000010422 painting Methods 0.000 description 1
- 238000007591 painting process Methods 0.000 description 1
- 239000011295 pitch Substances 0.000 description 1
- 238000003825 pressing Methods 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 230000001737 promoting effect Effects 0.000 description 1
- 230000000171 quenching effect Effects 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 239000011780 sodium chloride Substances 0.000 description 1
- 238000004544 sputter deposition Methods 0.000 description 1
- 229910052717 sulfur Inorganic materials 0.000 description 1
- LRXTYHSAJDENHV-UHFFFAOYSA-H zinc phosphate Chemical compound [Zn+2].[Zn+2].[Zn+2].[O-]P([O-])([O-])=O.[O-]P([O-])([O-])=O LRXTYHSAJDENHV-UHFFFAOYSA-H 0.000 description 1
- 229910000165 zinc phosphate Inorganic materials 0.000 description 1
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
- 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
- C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
- C23C2/02—Pretreatment of the material to be coated, e.g. for coating on selected surface areas
-
- 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
- C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
- C23C2/04—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor characterised by the coating material
- C23C2/06—Zinc or cadmium or alloys based thereon
-
- 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
- C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
- C23C2/26—After-treatment
-
- 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
- C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
- C23C2/34—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor characterised by the shape of the material to be treated
- C23C2/36—Elongated material
- C23C2/40—Plates; Strips
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Coating With Molten Metal (AREA)
Description
本発明は、ホットスタンプ用めっき鋼板およびホットスタンプ成形体の製造方法、ならびにホットスタンプ成形体に関する。 The present invention relates to a method for producing a plated steel sheet for hot stamping and a hot stamped body, as well as a hot stamped body.
自動車の車体を構成する各種の自動車部品には、当該部品の用途に応じて多様な性能が要求されている。例えば、Aピラーレインフォース、Bピラーレインフォース、バンパーレインフォース、トンネルレインフォース、サイドシルレインフォース、ルーフレインフォースまたはフロアークロスメンバー等の自動車部品には、それぞれの自動車部品における特定部位だけが、この特定部位を除く一般部位よりも高い強度を有することが要求される。そこで、自動車部品における補強が必要な特定部位に相当する部分だけにホットスタンプ成形して、ホットスタンプ部材とする工法が一部採用されている。Various automobile parts that make up an automobile body are required to have various performance characteristics depending on the use of the part. For example, in automobile parts such as A-pillar reinforcement, B-pillar reinforcement, bumper reinforcement, tunnel reinforcement, side sill reinforcement, roof reinforcement, and floor cross member, only specific parts of each automobile part are required to have higher strength than general parts excluding these specific parts. Therefore, a method is adopted in which only the parts corresponding to the specific parts that require reinforcement in the automobile part are hot stamped to form them into hot stamped members.
この際、表面処理を施していない冷延鋼板を用いると、加熱中に鋼板表面に鉄の酸化スケールが発生する。この酸化スケールは、成形中に剥離して金型を損耗するだけでなく、鋼板表面に疵が生じる原因となる。また、成形後の鋼板表面に酸化スケールが残れば、後の溶接工程における溶接不良、または塗装工程における塗装の密着性不良の原因になることがある。If untreated cold-rolled steel sheet is used in this process, iron oxide scale will form on the surface of the steel sheet during heating. This oxide scale will peel off during forming, not only causing wear on the mold, but also causing scratches on the steel sheet surface. Furthermore, if oxide scale remains on the steel sheet surface after forming, it can cause poor welding in the subsequent welding process or poor paint adhesion in the painting process.
そこで、酸化スケールの生成を防止するために、特許文献1に記載されるように、亜鉛系等のめっき鋼板が用いられることがある。亜鉛系のめっき鋼板を用いることにより、鉄よりも先に亜鉛が少量酸化されることで、鉄の酸化を抑制し、溶接性および塗装性を大幅に改善することができる。Therefore, in order to prevent the formation of oxide scale, zinc-based or other plated steel sheets are sometimes used, as described in Patent Document 1. By using zinc-based plated steel sheets, a small amount of zinc is oxidized before the iron, suppressing the oxidation of the iron and greatly improving weldability and paintability.
さらに近年では、これらの部品にも耐食性が求められるようになり、例えば、特許文献2~5では、加熱前の鋼板のめっき付着量を厚目付にして、加熱後のめっき表面にZn含有量が約70%で残部がFeを主成分とするめっきを残存させ、耐食性を向上させる技術が開発されている。Furthermore, in recent years, corrosion resistance has also come to be required for these parts, and for example, in Patent Documents 2 to 5, a technology has been developed in which the amount of plating applied to the steel sheet before heating is made thicker, and a plating with a Zn content of approximately 70% and the remainder being mainly Fe remains on the plated surface after heating, thereby improving corrosion resistance.
ところで、連続ラインで溶融亜鉛めっき処理により亜鉛めっき層を形成する場合、めっき浴中のZnと基材中のFeとが反応して過度に合金化するのを抑制するため、めっき浴中には少量のAlを含有させる必要がある。However, when forming a zinc plating layer by hot-dip galvanizing processing on a continuous line, it is necessary to contain a small amount of Al in the plating bath to prevent the Zn in the plating bath from reacting with the Fe in the base material and causing excessive alloying.
特に、厚目付のAl含有Znめっきを用いた際に、加熱して成形後に蜘蛛の巣状の表面欠陥が発生することがある。この蜘蛛の巣状の表面欠陥は凸状欠陥であり、自動車用の塗装した後も表面に浮き出てくることがあるため、品質上好ましくない。In particular, when thick aluminum-containing zinc plating is used, spider web-like surface defects can occur after heating and forming. These spider web-like surface defects are convex defects that can appear on the surface even after automotive painting, which is undesirable from the perspective of quality.
したがって、この蜘蛛の巣状の欠陥を抑制する必要がある。しかし、その発生メカニズムも、それを抑制する手法についてもよく分かっていなかったのが実情である。Therefore, it is necessary to suppress these spider web defects. However, the mechanism by which they occur and the methods for suppressing them were not well understood.
本発明は、上記の問題点を解決し、Al含有Znめっきを用いた場合において、蜘蛛の巣状の表面欠陥を抑制することが可能なホットスタンプ用めっき鋼板およびホットスタンプ成形体の製造方法、ならびにホットスタンプ成形体を提供することを目的とする。The present invention aims to solve the above problems and provide a plated steel sheet for hot stamping, a method for producing a hot stamped body, and a hot stamped body that can suppress spider web-like surface defects when Al-containing Zn plating is used.
本発明は、上記課題を解決するためになされたものであり、下記のホットスタンプ用めっき鋼板およびホットスタンプ成形体の製造方法、ならびにホットスタンプ成形体を要旨とする。The present invention has been made to solve the above problems, and its gist is the following plated steel sheet for hot stamping, a method for manufacturing a hot stamped body, and a hot stamped body.
(1)基材の表面に亜鉛めっき層を形成してめっき鋼板とする溶融亜鉛めっき処理工程と、
前記めっき鋼板に対して表面研削を施す表面研削工程と、を備え、
前記溶融亜鉛めっき処理工程では、
前記亜鉛めっき層を形成してから、前記亜鉛めっき層の表面の温度が400℃まで冷却する間の平均冷却速度を10℃/s以上とし、
前記亜鉛めっき層のめっき付着量を、Zn含有量において、65~150g/m2とし、かつ、前記亜鉛めっき層中のAl含有量を、質量%で、0.15~0.70%とし、
前記表面研削工程では、前記亜鉛めっき層のZn含有量換算でのめっき付着量をM、前記亜鉛めっき層中のAl含有量をAとした時に、研削量G(g/m2)が、下記(i)式で定義されるLとの関係において、下記(ii)式を満足する条件で表面研削を施す、
ホットスタンプ用めっき鋼板の製造方法。
L=0.0048×A×M+0.138 ・・・(i)
L≦G≦10L ・・・(ii)
(1) a hot-dip galvanizing process for forming a zinc-plated layer on a surface of a substrate to obtain a plated steel sheet;
A surface grinding step of grinding the surface of the plated steel sheet,
In the hot dip galvanizing treatment step,
The average cooling rate during the period from the formation of the zinc-plated layer to the temperature of the surface of the zinc-plated layer being cooled to 400° C. is set to 10° C./s or more;
The coating weight of the zinc-plated layer is 65 to 150 g/ m2 in terms of Zn content, and the Al content in the zinc-plated layer is 0.15 to 0.70% in terms of mass%,
In the surface grinding step, when the coating weight of the zinc-plated layer in terms of Zn content is M and the Al content in the zinc-plated layer is A, the surface grinding is performed under conditions such that the grinding amount G (g/m 2 ) satisfies the following formula (ii) in relation to L defined by the following formula (i):
A manufacturing method of plated steel sheet for hot stamping.
L = 0.0048 × A × M + 0.138 ... (i)
L≦G≦10L (ii)
(2)前記基材中のMn含有量が、質量%で、1.3%超である、
上記(1)に記載のホットスタンプ用めっき鋼板の製造方法。
(2) The Mn content in the base material is, in mass%, more than 1.3%;
The method for producing the plated steel sheet for hot stamping according to (1) above.
(3)基材の表面に亜鉛めっき層を形成してめっき鋼板とする溶融亜鉛めっき処理工程と、
前記めっき鋼板に対して表面研削を施す表面研削工程と、
前記表面研削を施した後の前記めっき鋼板を加熱し、その後に、成形および焼入れを同時に行うホットスタンプ工程と、を備え、
前記溶融亜鉛めっき処理工程では、
前記亜鉛めっき層を形成してから、前記亜鉛めっき層の表面の温度が400℃まで冷却する間の平均冷却速度を10℃/s以上とし、
前記亜鉛めっき層のめっき付着量を、Zn含有量において、65~150g/m2とし、かつ、前記亜鉛めっき層中のAl含有量を、質量%で、0.15~0.70%とし、
前記表面研削工程では、前記亜鉛めっき層のZn含有量換算でのめっき付着量をM、前記亜鉛めっき層中のAl含有量をAとした時に、研削量G(g/m2)が、下記(i)式で定義されるLとの関係において、下記(ii)式を満足する条件で表面研削を施す、
ホットスタンプ成形体の製造方法。
L=0.0048×A×M+0.138 ・・・(i)
L≦G≦10L ・・・(ii)
(3) a hot-dip galvanizing process for forming a zinc-plated layer on the surface of the substrate to obtain a plated steel sheet;
a surface grinding step of grinding the surface of the plated steel sheet;
a hot stamping process in which the plated steel sheet after the surface grinding is heated and then formed and quenched at the same time,
In the hot dip galvanizing treatment step,
The average cooling rate during the period from the formation of the zinc-plated layer to the temperature of the surface of the zinc-plated layer being cooled to 400° C. is set to 10° C./s or more;
The coating weight of the zinc-plated layer is 65 to 150 g/ m2 in terms of Zn content, and the Al content in the zinc-plated layer is 0.15 to 0.70% in terms of mass%,
In the surface grinding step, when the coating weight of the zinc-plated layer in terms of Zn content is M and the Al content in the zinc-plated layer is A, the surface grinding is performed under conditions such that the grinding amount G (g/m 2 ) satisfies the following formula (ii) in relation to L defined by the following formula (i):
A method for producing a hot stamped product.
L = 0.0048 × A × M + 0.138 ... (i)
L≦G≦10L (ii)
(4)前記基材中のMn含有量が、質量%で、1.3%超である、
上記(3)に記載のホットスタンプ成形体の製造方法。
(4) The Mn content in the base material is, in mass%, more than 1.3%;
The method for producing a hot stamped product according to (3) above.
(5)前記ホットスタンプ工程では、20℃/s未満の平均加熱速度でAc3点~950℃の温度範囲まで加熱する、
上記(3)または(4)に記載のホットスタンプ成形体の製造方法。
(5) In the hot stamping process, heating is performed to a temperature range of Ac 3 point to 950 ° C. at an average heating rate of less than 20 ° C./s;
The method for producing a hot stamped product according to (3) or (4) above.
(6)基材の表面に厚さ1μm以上の亜鉛めっき層を有し、
前記亜鉛めっき層中のAl含有量が、質量%で、0.15~0.70%であり、
前記亜鉛めっき層の表面から深さ1μmまでの表層領域における化学組成が、下記(iii)式を満足する、
ホットスタンプ成形体。
Mn/Al≧5.0 ・・・(iii)
但し、上記式中の元素記号は、前記表層領域中における各元素の含有量(質量%)を表す。
(6) A zinc plating layer having a thickness of 1 μm or more is provided on the surface of the base material;
The Al content in the zinc plating layer is, in mass%, 0.15 to 0.70%;
The chemical composition of a surface region of the zinc plating layer from the surface to a depth of 1 μm satisfies the following formula (iii):
Hot stamped compact.
Mn/Al≧5.0 (iii)
In the above formula, the element symbols represent the content (mass %) of each element in the surface layer region.
(7)前記基材中のMn含有量が、質量%で、1.3%超である、
上記(6)に記載のホットスタンプ成形体。
(7) The Mn content in the base material is, in mass%, more than 1.3%;
The hot stamped compact according to (6) above.
本発明に係る製造方法よれば、Al含有Znめっきを用いた場合において、ホットスタンプ成形体を製造する際に、蜘蛛の巣状の表面欠陥を抑制することが可能となる。 According to the manufacturing method of the present invention, when Al-containing Zn plating is used, it is possible to suppress spider web-like surface defects when manufacturing hot stamped bodies.
本発明者らは、蜘蛛の巣状の表面欠陥が発生する原因について調査した結果、以下の知見を得た。The inventors investigated the cause of the spider web-like surface defects and obtained the following findings:
(a)上述のように、めっき浴中にAlを含有させる場合、亜鉛めっき層の表面には、薄いAlを含む酸化物層が形成する。特に厚目付の場合、ホットスタンプ時の加熱により、亜鉛めっき層が液相となって流動し、酸化物層に局所的なひび割れが生じる。(a) As mentioned above, when Al is contained in the plating bath, a thin oxide layer containing Al is formed on the surface of the zinc plating layer. In particular, when the zinc plating layer is thick, the heating during hot stamping causes the zinc plating layer to turn into a liquid phase and flow, causing localized cracks in the oxide layer.
(b)酸化物層のひび割れによって生じる隙間にめっき中のMn等が流入し、これらの酸化物が充填することで、蜘蛛の巣状の色むらが発生し、表面性状が悪化する。(b) Mn and other elements in the plating flow into gaps created by cracks in the oxide layer, and these oxides fill the gaps, causing spider web-like color unevenness and deteriorating surface properties.
本発明者らは、酸化物層のひび割れに起因する表面欠陥を抑制する方法について鋭意検討を行い、以下の着想を得るに至った。The inventors have conducted extensive research into methods for suppressing surface defects caused by cracks in the oxide layer and have come up with the following idea.
(c)Mnは基材から溶出することでめっき中に含有され、そこからめっき表面へと拡散する。酸化物層に局所的なひび割れが生じると、局所的なMnの濃化が生じ、それが蜘蛛の巣状の色むらの原因となる。(c) Mn is dissolved from the base material and is contained in the plating, from which it diffuses to the plating surface. When localized cracks occur in the oxide layer, localized Mn concentration occurs, which causes spider web-like color unevenness.
(d)Mnの溶出・拡散を活用し、ホットスタンプ時にMnをめっき表面に均一に濃化させることができれば、色むらを抑制することが可能となる。 (d) If the dissolution and diffusion of Mn can be utilized to uniformly concentrate Mn on the plating surface during hot stamping, it will be possible to suppress color unevenness.
上記の着想に基づき、本発明者らは、特許文献6に記載される技術を採用し、ホットスタンプ前の鋼板に対して、表面研削を施し、事前に酸化物層の一部を除去し、残りの部分を細かく破砕しておくことで、表面欠陥の抑制を試みた。しかしながら、表面研削を行ったとしても、安定的に蜘蛛の巣状の色むらを抑制することができなかった。その原因についてさらに検討を行った結果、以下の知見を得た。Based on the above idea, the inventors adopted the technology described in Patent Document 6, and attempted to suppress surface defects by subjecting the steel sheet before hot stamping to surface grinding, removing part of the oxide layer in advance, and finely crushing the remaining part. However, even when surface grinding was performed, it was not possible to stably suppress the spider web-like color unevenness. Further investigation into the cause led to the following findings.
(e)めっき皮膜中のAl含有量が高いほど、そして、めっき皮膜のめっき付着量が大きいほど、より厚く酸化物層を除去し、かつ細かく粉砕する必要がある。すなわち、表面研削における研削量を、めっき皮膜中のAl含有量およびめっき皮膜のめっき付着量との関係で制御することが重要である。(e) The higher the Al content in the plating film and the greater the plating adhesion weight of the plating film, the thicker the oxide layer must be removed and the more finely pulverized it must be. In other words, it is important to control the amount of grinding in surface grinding in relation to the Al content in the plating film and the plating adhesion weight of the plating film.
(f)酸化物層を除去または細かく破砕したとしても、基材からのMnの溶出・拡散が不十分であると、Mnを表面に均一に濃化させることが困難となる。(f) Even if the oxide layer is removed or crushed into small pieces, if the dissolution and diffusion of Mn from the base material is insufficient, it will be difficult to uniformly concentrate Mn on the surface.
(g)めっき皮膜中における基材との界面付近において、Fe-Al金属間化合物層が厚く形成されていると、基材からのMnの溶出が著しく阻害される。(g) If a thick Fe-Al intermetallic compound layer is formed near the interface with the substrate in the plating film, the dissolution of Mn from the substrate is significantly hindered.
(h)めっき処理後にめっき皮膜が凝固するまでの間に速やかに冷却を行うことで、Fe-Al金属間化合物層の形成を抑制し、Mnの溶出を促進させることが可能となる。(h) By rapidly cooling the plated film after plating before it solidifies, it is possible to suppress the formation of an Fe-Al intermetallic compound layer and promote the dissolution of Mn.
(i)そして、めっき中に溶出したMnが細かく破砕された酸化物層の隙間に流入し、めっき表面に均一に濃化することで、蜘蛛の巣状の色むらの抑制が可能となる。 (i) Furthermore, the Mn dissolved during plating flows into the gaps in the finely crushed oxide layer and is uniformly concentrated on the plating surface, making it possible to suppress spider web-like color unevenness.
本発明は上記の知見に基づいてなされたものである。以下、本発明の各要件について詳しく説明する。The present invention has been made based on the above findings. Each of the requirements of the present invention will be explained in detail below.
(A)ホットスタンプ用めっき鋼板の製造方法
本発明の一実施形態に係るホットスタンプ用めっき鋼板の製造方法は、溶融亜鉛めっき処理工程および表面研削工程を備える。また、基材製造工程をさらに備えてもよい。以下、各工程について、詳述する。
(A) Manufacturing method of plated steel sheet for hot stamping The manufacturing method of a plated steel sheet for hot stamping according to an embodiment of the present invention includes a hot-dip galvanizing treatment step and a surface grinding step. The manufacturing method may further include a base material manufacturing step. Each step will be described in detail below.
[基材製造工程]
基材製造工程では、ホットスタンプ用めっき鋼板の基材を製造する。例えば、所定の化学組成を有する溶鋼を製造し、この溶鋼を用いて、鋳造法によりスラブを製造するか、または、造塊法によりインゴットを製造する。次いで、スラブまたはインゴットを熱間圧延することにより、基材(熱延板)が得られる。
[Substrate manufacturing process]
In the substrate manufacturing process, a substrate for a plated steel sheet for hot stamping is manufactured. For example, molten steel having a predetermined chemical composition is manufactured, and this molten steel is used to manufacture a slab by a casting method or to manufacture an ingot by an ingot casting method. The slab or ingot is then hot rolled to obtain a substrate (hot-rolled sheet).
なお、上記熱延板に対して酸洗処理を行い、酸洗処理後の熱延板に対して表面研削を行って得られる冷延板を基材としてもよい。さらに、上記の熱延板または冷延板に焼鈍を施し、得られる熱延焼鈍板または冷延焼鈍板を基材としてもよい。The hot-rolled sheet may be subjected to pickling treatment, and the hot-rolled sheet after the pickling treatment may be subjected to surface grinding to obtain a cold-rolled sheet as the substrate. Furthermore, the hot-rolled sheet or cold-rolled sheet may be subjected to annealing, and the resulting hot-rolled annealed sheet or cold-rolled annealed sheet may be used as the substrate.
基材となる鋼の化学組成については特に制限はない。しかし、上述のように、本発明では、基材からのMnの溶出を活用する観点から、基材中のMn含有量が、質量%で、1.3%超であることが好ましく、1.5%以上であることがより好ましい。Mn含有量に上限を設ける必要はないが、3.0%以下であるのが好ましく、2.7%以下であるのがより好ましい。There are no particular limitations on the chemical composition of the steel that serves as the base material. However, as described above, in the present invention, from the viewpoint of utilizing the elution of Mn from the base material, the Mn content in the base material is preferably more than 1.3% by mass, and more preferably 1.5% or more. There is no need to set an upper limit on the Mn content, but it is preferably 3.0% or less, and more preferably 2.7% or less.
[溶融亜鉛めっき処理工程]
溶融亜鉛めっき処理工程では、上記の基材の表面に亜鉛めっき層を形成してめっき鋼板とする。亜鉛めっき層は、例えば、溶融めっき処理を行うことにより形成することができる。
[Hot-dip galvanizing treatment process]
In the hot-dip galvanizing process, a galvanized layer is formed on the surface of the above-mentioned base material to produce a plated steel sheet. The galvanized layer can be formed, for example, by hot-dip galvanizing.
例えば、溶融めっき処理による亜鉛めっき層の形成例は、以下のとおりである。すなわち、基材を、Zn、Alおよび不純物からなる溶融亜鉛めっき浴に浸漬し、基材表面に亜鉛めっき層を付着させる。溶融亜鉛めっき浴の化学組成は、Znが主体である。具体的には、Zn含有量が90質量%以上である。めっき浴の温度としては、440~470℃、さらには450~460℃が一般的である。For example, an example of forming a zinc plating layer by hot-dip galvanizing is as follows. That is, the substrate is immersed in a hot-dip galvanizing bath containing Zn, Al and impurities, and a zinc plating layer is adhered to the substrate surface. The chemical composition of the hot-dip galvanizing bath is mainly Zn. Specifically, the Zn content is 90 mass% or more. The temperature of the plating bath is generally 440 to 470°C, or even 450 to 460°C.
また、溶融亜鉛めっき浴のAl含有量は0.05~0.50%であるのが好ましく、0.10~0.30%であるのがより好ましく、0.12~0.20%であるのがさらに好ましい。めっき浴中に上記の範囲でAlを含有することで、めっき浴中のZnと基材中のFeとが反応して過度に合金化するのを抑制することが可能となる。In addition, the Al content of the hot-dip galvanizing bath is preferably 0.05 to 0.50%, more preferably 0.10 to 0.30%, and even more preferably 0.12 to 0.20%. By including Al in the above range in the plating bath, it is possible to suppress excessive alloying caused by the reaction between the Zn in the plating bath and the Fe in the base material.
亜鉛めっき層中のAl含有量は、鋼板の種類またはめっき条件等により、めっき浴中のAl含有量よりもやや高めとなる。この際、亜鉛めっき層中のAl含有量によってめっき表面のAl酸化物の形成状態が異なってしまうため、本発明ではめっき浴中のAl含有量ではなく、亜鉛めっき層中のAl含有量に応じた研削量の調整が必要となる。亜鉛めっき層中のAl含有量は、質量%で、0.15~0.70%とし、0.15~0.60%とするのが好ましく、0.20~0.50%とするのがより好ましい。The Al content in the zinc plating layer is slightly higher than the Al content in the plating bath, depending on the type of steel sheet or plating conditions. In this case, the state of formation of Al oxide on the plating surface differs depending on the Al content in the zinc plating layer, so in the present invention, it is necessary to adjust the grinding amount according to the Al content in the zinc plating layer, not the Al content in the plating bath. The Al content in the zinc plating layer is 0.15 to 0.70%, preferably 0.15 to 0.60%, and more preferably 0.20 to 0.50%, by mass.
亜鉛めっき層中のAl含有量を測定する方法としては、インラインで測定する場合は蛍光X線分析が用いられる。具体的には、あらかじめ所定のめっき鋼板を用いて、蛍光X線分析によって得られるAl測定値と、亜鉛めっき層を希塩酸で溶解してICP発光分析により測定されるAl含有量との関係を導く。そして、測定対象となるめっき鋼板に蛍光X線を照射してAl測定値を得て、上記の関係からAl含有量を求める。 X-ray fluorescence analysis is used as a method for measuring the Al content in a zinc-plated layer when the measurement is performed in-line. Specifically, a specific plated steel sheet is used in advance, and the relationship between the Al measurement value obtained by X-ray fluorescence analysis and the Al content measured by dissolving the zinc-plated layer in dilute hydrochloric acid and measuring it by ICP optical emission analysis is derived. Then, the plated steel sheet to be measured is irradiated with fluorescent X-rays to obtain the Al measurement value, and the Al content is calculated from the above relationship.
溶融亜鉛めっき浴中には、その他に、Mg、Pb、Si等が含まれていてもよいが、これらの合計含有量は10質量%以下であることが好ましい。The hot-dip galvanizing bath may also contain other elements such as Mg, Pb, Si, etc., but it is preferable that the total content of these elements is 10 mass% or less.
次いで、亜鉛めっき層が付着した基材をめっき浴から引き上げる。本工程において、めっき浴からの鋼板の引き上げ速度、ワイピングのガスの流量、流速を適宜調整することにより、亜鉛めっき層の厚さを調整することが可能になる。ワイピングガスの流速は、例えば、10m/s以上とすることが好ましい。Next, the substrate with the zinc plating layer attached is pulled out of the plating bath. In this process, the thickness of the zinc plating layer can be adjusted by appropriately adjusting the speed at which the steel sheet is pulled out of the plating bath and the flow rate and flow rate of the wiping gas. It is preferable that the flow rate of the wiping gas is, for example, 10 m/s or more.
基材をめっき浴から引き上げ、亜鉛めっき層の厚さを調整し、亜鉛めっき層を形成した後、亜鉛めっき層が凝固するまで冷却する。この際の冷却速度が低いと、上述のように、亜鉛めっき層中における基材との界面付近において、Fe-Al金属間化合物層が厚く形成し、基材からのMnの溶出が著しく阻害される。The substrate is removed from the plating bath, the thickness of the zinc plating layer is adjusted, and the zinc plating layer is formed. After this, the substrate is cooled until the zinc plating layer solidifies. If the cooling rate is low, as mentioned above, a thick Fe-Al intermetallic compound layer forms in the zinc plating layer near the interface with the substrate, significantly inhibiting the elution of Mn from the substrate.
Fe-Al金属間化合物層の形成を抑制するため、亜鉛めっき層を形成してから、亜鉛めっき層の表面の温度が400℃まで冷却する間の平均冷却速度を10℃/s以上とする。上記平均冷却速度は15℃/s以上であるのが好ましく、20℃/s以上であるのがより好ましい。平均冷却速度に上限を設ける必要はない。めっき後の冷却速度は、冷却ガスまたはミストの吹き付けを行うことで調整されることが多い。この際の吹き付け速度が過剰であると、外観のムラなどの原因となる。そのため、めっき後の冷却速度は、30℃/s以下であるのが好ましく、25℃/s以下であるのがより好ましい。 To suppress the formation of an Fe-Al intermetallic compound layer, the average cooling rate from the formation of the zinc plating layer until the surface temperature of the zinc plating layer cools to 400°C is 10°C/s or more. The above average cooling rate is preferably 15°C/s or more, and more preferably 20°C/s or more. There is no need to set an upper limit to the average cooling rate. The cooling rate after plating is often adjusted by spraying cooling gas or mist. If the spraying rate is excessive, it can cause unevenness in the appearance. Therefore, the cooling rate after plating is preferably 30°C/s or less, and more preferably 25°C/s or less.
基材表面に形成される亜鉛めっき層のめっき付着量は、Zn含有量において、65~150g/m2とする。厚目付とすることで、優れた耐食性を有するホットスタンプ成形体を製造することができる。 The plating weight of the zinc plating layer formed on the substrate surface is set to 65 to 150 g/ m2 in terms of Zn content. By setting the plating weight thickly, it is possible to produce a hot stamped product having excellent corrosion resistance.
加えて、蜘蛛の巣状の表面欠陥は、厚目付であるほど生じやすい。そのため、亜鉛めっき層のめっき付着量が、Zn含有量において、65g/m2以上である場合において、本発明の効果が顕著に発揮される。一方、亜鉛めっき層のめっき付着量が、Zn含有量において、150g/m2を超えると、ホットスタンプ時の加熱によって生じるめっき液相の流動を抑制するのが極めて困難になる。亜鉛めっき層のめっき付着量は、Zn含有量において、100g/m2超であるのが好ましく、110g/m2以上であるのがより好ましく、130g/m2以下であるのが好ましい。 In addition, the thicker the coating weight, the more likely the spider web-like surface defects are to occur. Therefore, when the coating weight of the zinc plating layer is 65 g/ m2 or more in terms of the Zn content, the effect of the present invention is remarkable. On the other hand, when the coating weight of the zinc plating layer is more than 150 g/ m2 in terms of the Zn content, it becomes very difficult to suppress the flow of the plating liquid phase caused by heating during hot stamping. The coating weight of the zinc plating layer is preferably more than 100 g/ m2 in terms of the Zn content, more preferably 110 g/ m2 or more, and preferably 130 g/ m2 or less.
なお、蜘蛛の巣状の表面欠陥の問題は、めっき後に合金化させずに凝固させた溶融亜鉛めっき鋼板に対して、ホットスタンプを施すことで発生する。溶融亜鉛めっき処理後にさらに合金化を施した合金化溶融亜鉛めっき鋼板ではこのような問題は生じないため、本実施形態の対象とはならない。すなわち、本実施形態における溶融亜鉛めっき処理工程では、合金化処理は行わない。The problem of spider web-like surface defects occurs when hot stamping is performed on hot-dip galvanized steel sheets that have been solidified after plating without being alloyed. Such problems do not occur with alloyed hot-dip galvanized steel sheets that have been further alloyed after hot-dip galvanizing, and therefore are not subject to this embodiment. In other words, no alloying treatment is performed in the hot-dip galvanizing treatment process in this embodiment.
[表面研削工程]
表面研削工程では、亜鉛めっき層が形成されためっき鋼板に対して、表面研削を施す。これにより、亜鉛めっき層の表面に形成された薄いAlを含む酸化物層の一部を除去し、残存部分についても細かく破砕する。
[Surface grinding process]
In the surface grinding process, the plated steel sheet on which the zinc plating layer is formed is subjected to surface grinding, thereby removing a part of the thin oxide layer containing Al formed on the surface of the zinc plating layer, and crushing the remaining part into small pieces.
この際、亜鉛めっき層中のAl含有量が高いほど、そして、亜鉛めっき層のめっき付着量が大きいほど、酸化物層をより厚く除去し、かつより微細に破砕する必要がある。そのため、研削量G(g/m2)が、下記(i)式で定義されるLとの関係において、下記(ii)式を満足する条件で表面研削を施す。ここで、(i)式中のMは亜鉛めっき層のZn含有量換算でのめっき付着量(g/m2)、Aは亜鉛めっき層中のAl含有量(質量%)である。
L=0.0048×A×M+0.138 ・・・(i)
L≦G≦10L ・・・(ii)
In this case, the higher the Al content in the zinc-plated layer and the greater the coating weight of the zinc-plated layer, the thicker the oxide layer must be removed and the finer the crushing must be. Therefore, surface grinding is performed under conditions where the grinding amount G (g/ m2 ) satisfies the following formula (ii) in relation to L defined by the following formula (i): M in formula (i) is the coating weight (g/ m2 ) of the zinc-plated layer converted to the Zn content, and A is the Al content (mass%) in the zinc-plated layer.
L = 0.0048 × A × M + 0.138 ... (i)
L≦G≦10L (ii)
なお、研削量が大きすぎると、酸化物層が完全に除去され、ホットスタンプ工程での加熱時にZn酸化膜が成長しすぎて塗装密着性が悪化する。そのため、研削量Gは、10L以下とし、好ましくは5L以下とする。If the grinding amount is too large, the oxide layer is completely removed, and the Zn oxide film grows too much during heating in the hot stamping process, causing deterioration of paint adhesion. Therefore, the grinding amount G is set to 10L or less, and preferably 5L or less.
なお、研削量は、所定のサイズの鋼板の研削前後の重量変化で求めることができる。また、研削量は、研削に用いるブラシの種類、回転速度、鋼板への押し付け力、鋼板との対向速度差等を変化させることで、制御することができる。具体的には、研削に用いるブラシと鋼板との対向速度差は50mpm以上とすることが好ましい。The amount of grinding can be determined from the change in weight before and after grinding a steel plate of a given size. The amount of grinding can also be controlled by changing the type of brush used for grinding, the rotational speed, the pressing force against the steel plate, the opposing speed difference with the steel plate, etc. Specifically, it is preferable that the opposing speed difference between the brush used for grinding and the steel plate is 50 mpm or more.
研削ブラシには様々なものを用いることができるが、酸化物層をより細かく破砕するには、鋼製の芯に対して、セラミックスなどの砥粒を含有した硬質プラスチック線を生やしたブラシ等が好適である。その際の砥粒の粒径としては直径1mm以下のものが好適である。 Various grinding brushes can be used, but to break down the oxide layer more finely, a brush with a steel core and hard plastic wire containing ceramic or other abrasive grains is suitable. The abrasive grain diameter should be 1 mm or less.
(B)ホットスタンプ成形体の製造方法
本発明の一実施形態に係るホットスタンプ成形体の製造方法は、上述の溶融亜鉛めっき処理工程および表面研削工程に加えて、ホットスタンプ工程をさらに備える。以下、ホットスタンプ工程について詳しく説明する。
(B) Manufacturing Method of Hot Stamped Steel The manufacturing method of the hot stamped steel according to one embodiment of the present invention further includes a hot stamping step in addition to the above-mentioned hot-dip galvanizing step and surface grinding step. The hot stamping step will be described in detail below.
[ホットスタンプ工程]
ホットスタンプ工程では、表面研削を施した後のめっき鋼板を加熱し、その後に、成形および焼入れを同時に行う。ホットスタンプ工程での加熱条件については、特に制限はない。加熱する際の最高到達温度は、例えば、Ac3点~950℃とすることができる。最高到達温度をAc3点以上とすることで、加熱時に基材がオーステナイト化し、十分な焼入れ効果が得られる。
[Hot stamping process]
In the hot stamping process, the plated steel sheet after surface grinding is heated, and then formed and quenched at the same time. There are no particular limitations on the heating conditions in the hot stamping process. The maximum temperature reached during heating can be, for example, Ac 3 to 950°C. By setting the maximum temperature reached at Ac 3 or higher, the base material is austenitized during heating, and a sufficient quenching effect can be obtained.
一方、めっき鋼板を加熱する際の最高到達温度が高すぎると、蜘蛛の巣状の欠陥を抑制することが困難になる場合がある。そのため、最高到達温度は950℃以下とし、900℃以下とすることが好ましく、890℃以下とすることがより好ましく、870℃以下とすることがさらに好ましい。On the other hand, if the maximum temperature reached when heating the plated steel sheet is too high, it may be difficult to suppress spider web defects. Therefore, the maximum temperature reached is set to 950°C or less, preferably 900°C or less, more preferably 890°C or less, and even more preferably 870°C or less.
また、加熱速度についても特に制限はなく、製造コスト低減の観点からは急速加熱することが望まれる。しかし、加熱時にMnの溶出・拡散をさらに促進する観点からは、加熱速度を低くすることが好ましく、具体的には、20℃/s未満の平均加熱速度とすることが好ましく、18℃/s以下の平均加熱速度とすることがより好ましい。There is no particular restriction on the heating rate, and rapid heating is desirable from the viewpoint of reducing manufacturing costs. However, from the viewpoint of further promoting the dissolution and diffusion of Mn during heating, it is preferable to lower the heating rate. Specifically, it is preferable to set the average heating rate to less than 20°C/s, and more preferably to set the average heating rate to 18°C/s or less.
鋼板の加熱方法については特に制限はなく、ガス炉または電気炉内で加熱する方法が一般的であるが、通電加熱または誘導加熱等の方法を採用してもよい。There are no particular restrictions on the method for heating the steel plate; heating in a gas furnace or electric furnace is common, but methods such as electrical heating or induction heating may also be used.
また、本発明において、上述する温度は鋼板の表面温度を意味する。鋼板の表面温度を測定する方法としては、材料に熱電対を取り付けて測定する方法が最も正確に測定できる。しかしながら、量産材では熱電対を取り付けた跡が残るため好ましくない。In addition, in the present invention, the above-mentioned temperature refers to the surface temperature of the steel plate. The most accurate method for measuring the surface temperature of the steel plate is to attach a thermocouple to the material. However, this is not preferable for mass-produced materials because it leaves traces of the thermocouple attachment.
そこで、事前に部品形状、板厚およびめっき目付毎に熱電対を付けたダミー材でヒートパターンを測定して、本発明に適するヒートパターンを再現できるように炉の加熱条件を設定しておき、その一定条件で量産することで、本発明に適した条件で加熱することができる。Therefore, the heat pattern is measured in advance using dummy material with a thermocouple attached for each part shape, plate thickness, and plating weight, and the furnace heating conditions are set so that the heat pattern suitable for this invention can be reproduced. Mass production is then carried out under these constant conditions, allowing heating under conditions suitable for this invention.
さらに、熱電対を用いる以外の方法としては、炉内に放射温度計を設置して事前に条件出しをして、放射率を規定した放射温度計で測定することもできる。放射率は厳密には材料表面の状態で変化するが、本材料の場合は、0.5程度に設定しておけば今回の発明の効果が得られる温度測定は可能である。 As an alternative to using a thermocouple, a radiation thermometer can be installed inside the furnace, the conditions can be set in advance, and measurements can be taken with a radiation thermometer with a specified emissivity. Strictly speaking, emissivity changes depending on the condition of the material surface, but in the case of this material, setting it to around 0.5 makes it possible to measure the temperature and obtain the effects of this invention.
次に、加熱された亜鉛めっき鋼板を、金型を用いてプレス成形する。このプレス成形と同時に、金型によって鋼板を焼入れする。金型内には冷却媒体(例えば水)が循環しており、金型が亜鉛めっき鋼板の抜熱を促して、焼入れがなされる。以上の工程により、成形体を製造することができる。Next, the heated galvanized steel sheet is press-formed using a die. At the same time as this press-forming, the steel sheet is hardened by the die. A cooling medium (e.g. water) circulates inside the die, and the die promotes heat removal from the galvanized steel sheet, thereby hardening it. Through these steps, a formed body can be manufactured.
なお、表面研削工程とホットスタンプ工程との間で鋼板表面に厚い酸化皮膜が新たに形成されると、基材からのMnの溶出・拡散が阻害されるため、蜘蛛の巣模様の発生を抑制できなくなる。そのため、本実施形態に係るホットスタンプ用めっき鋼板の製造方法およびホットスタンプ成形体の製造方法においては、表面研削工程の後に、自然酸化による酸化皮膜は形成し得るが、意図的に酸化皮膜を形成する工程を含まない。If a new thick oxide film is formed on the steel sheet surface between the surface grinding process and the hot stamping process, the dissolution and diffusion of Mn from the base material is hindered, making it impossible to suppress the occurrence of spider web patterns. Therefore, in the manufacturing method of plated steel sheet for hot stamping and the manufacturing method of hot stamped formed body according to this embodiment, although an oxide film may be formed by natural oxidation after the surface grinding process, no process is included for intentionally forming an oxide film.
(C)ホットスタンプ成形体
次に、上述の方法で製造されるホットスタンプ成形体について説明する。本発明の一実施形態に係るホットスタンプ成形体は、基材の表面に厚さ1μm以上の亜鉛めっき層を有する。そして、亜鉛めっき層の表面から深さ1μmまでの表層領域における化学組成が、下記(iii)式を満足する。
Mn/Al≧5.0 ・・・(iii)
但し、上記式中の元素記号は、亜鉛めっき層の表層領域中における各元素の含有量(質量%)を表す。
(C) Hot-stamped product Next, the hot-stamped product produced by the above-mentioned method will be described. The hot-stamped product according to one embodiment of the present invention has a zinc-plated layer having a thickness of 1 μm or more on the surface of the substrate. The chemical composition of the surface region of the zinc-plated layer to a depth of 1 μm from the surface satisfies the following formula (iii).
Mn/Al≧5.0 (iii)
In the above formula, the element symbols represent the content (mass %) of each element in the surface region of the zinc plating layer.
上述のように、基材からのMnの溶出・拡散が促進され、亜鉛めっき層の表面に均一に濃化し、その結果、表層領域における化学組成が上記(iii)式を満足することで、蜘蛛の巣状の色むらが抑制される。蜘蛛の巣状の色むらをより確実に抑制するためには、上記(iii)式の左辺値は12.0以上であるのが好ましい。なお、上記(iii)式の左辺値に上限を設ける必要はないが、基材中のMn含有量が3.0%以下である場合には、20.0が実質的な上限となる。As described above, the dissolution and diffusion of Mn from the base material is promoted, and the zinc plating layer is uniformly concentrated on the surface thereof. As a result, the chemical composition in the surface region satisfies the above formula (iii), and spider web-like color unevenness is suppressed. In order to more reliably suppress spider web-like color unevenness, the value on the left side of the above formula (iii) is preferably 12.0 or more. It is not necessary to set an upper limit on the value on the left side of the above formula (iii), but when the Mn content in the base material is 3.0% or less, 20.0 is the practical upper limit.
なお、本実施形態において、ホットスタンプ加熱後の亜鉛めっき層の厚さは通常10μm以上となる。亜鉛めっき層の厚さは16μm以上であるのが好ましく、18μm以上または20μm以上であるのがより好ましい。また、亜鉛めっき層の厚さは37μm以下であるのが好ましく、35μm以下または32μm以下であるのがより好ましい。In this embodiment, the thickness of the zinc plating layer after hot stamp heating is usually 10 μm or more. The thickness of the zinc plating layer is preferably 16 μm or more, more preferably 18 μm or more or 20 μm or more. The thickness of the zinc plating layer is preferably 37 μm or less, more preferably 35 μm or less or 32 μm or less.
亜鉛めっき層の表層領域における化学組成および亜鉛めっき層の厚さは、高周波グロー放電発光表面分析装置(GDS)によって測定することが可能である。具体的には以下の手順により測定を行う。The chemical composition of the surface region of the zinc plating layer and the thickness of the zinc plating layer can be measured using a high-frequency glow discharge optical emission surface analyzer (GDS). Specifically, the measurement is performed according to the following procedure.
ホットスタンプ成形体の表面のうち、任意の10点の測定位置を決定する。各測定点において、亜鉛めっき層の表面から深さ1μmまでの表層領域においてスパッタリングしながら、0.01μmピッチで、Fe、Mn、Zn、Si、Al、O、Crの各元素濃度を測定し、深さ1μmまでのMnおよびAlの平均含有量(質量%)を求める。全ての測定点(10点)で求めたMn含有量およびAl含有量の平均を求め、表層領域中の各元素の含有量とする。 Ten arbitrary measurement positions are determined on the surface of the hot stamped body. At each measurement point, the elemental concentrations of Fe, Mn, Zn, Si, Al, O, and Cr are measured at 0.01 μm pitches while sputtering in the surface region from the surface of the zinc plating layer to a depth of 1 μm, and the average Mn and Al contents (mass %) up to a depth of 1 μm are calculated. The Mn and Al contents determined at all measurement points (10 points) are averaged to determine the content of each element in the surface region.
さらに、上記の各測定点において、深さ方向に化学組成の測定を行い、Zn含有量が15%以下となるまでの深さを求める。そして、各測定点での深さの平均を求め、その平均値を亜鉛めっき層の厚さとする。Furthermore, at each of the above measurement points, the chemical composition is measured in the depth direction to determine the depth to which the Zn content is 15% or less. The depths at each measurement point are then averaged, and this average value is regarded as the thickness of the zinc plating layer.
GDSの測定装置としては、例えば、LECOジャパン社製のGDS850Aの装置を用い、測定条件は30W、1000V、アルゴン圧0.27MPa、測定径4mmφとすることができる。 As a GDS measuring device, for example, a GDS850A device manufactured by LECO Japan can be used, and the measurement conditions can be 30 W, 1000 V, argon pressure 0.27 MPa, and measurement diameter 4 mmφ.
以下、実施例によって本発明をより具体的に説明するが、本発明はこれらの実施例に限定されるものではない。The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples.
厚さ1.0mmであり、Mn含有量が、質量%で、1.3%、1.5%、または2.0%の3種の冷延鋼板を用意した。これらの冷延鋼板のMn含有量以外の化学組成はいずれも、C:0.21%、Si:0.2%、P:0.01%、S:0.007%、Cr:0.2%、Ti:0.02%、B:0.003%、残部:Feおよび不純物とした。なお、上記の冷延鋼板のAc3点は、加熱速度およびMn含有量にも依存するが、いずれも810~840℃程度の範囲内であった。 Three types of cold-rolled steel sheets were prepared, each having a thickness of 1.0 mm and a Mn content of 1.3%, 1.5%, or 2.0% by mass. The chemical compositions of these cold-rolled steel sheets other than the Mn content were C: 0.21%, Si: 0.2%, P: 0.01%, S: 0.007%, Cr: 0.2%, Ti: 0.02%, B: 0.003%, and the balance: Fe and impurities. The Ac 3 points of the above cold-rolled steel sheets were all within the range of about 810 to 840 ° C., depending on the heating rate and Mn content.
上記の冷延鋼板に対して、連続溶融亜鉛めっきラインにより焼鈍を施し、続けて、表1に示す条件でめっきを施し、めっき鋼板とした。なお、めっき浴組成はAl含有量:0.13質量%、残部:Znであり、めっき浴温度は460℃とした。めっき後、ワイピングガスおよび冷却ガスを噴射する距離、流量を調整して、亜鉛めっき層の表面の温度が400℃となるまでの平均冷却速度を種々に調整した。The above cold-rolled steel sheet was annealed in a continuous hot-dip galvanizing line and then plated under the conditions shown in Table 1 to obtain a plated steel sheet. The plating bath composition was Al content: 0.13 mass%, balance: Zn, and the plating bath temperature was 460°C. After plating, the average cooling rate was adjusted to various levels until the surface temperature of the zinc plating layer reached 400°C by adjusting the distance and flow rate of the wiping gas and cooling gas.
得られためっき鋼板に対して、さらに表1に示す条件で表面研削を施した。その後、各試験例のめっき鋼板について、100mm角のサイズに切り出した後、大気雰囲気の通電加熱炉を用いて表1に示す平均加熱速度で900℃まで加熱した後、速やかに水冷配管を内蔵した平板プレスに挟んで急冷してホットスタンプ成形体を得た。The resulting plated steel sheets were further subjected to surface grinding under the conditions shown in Table 1. After that, the plated steel sheets of each test example were cut into a size of 100 mm square, and then heated to 900°C at the average heating rate shown in Table 1 using an electric heating furnace in an atmospheric air environment, and then quickly clamped between a flat press equipped with built-in water cooling piping to rapidly cool, thereby obtaining hot stamped bodies.
得られた成形体について、亜鉛めっき層の表層領域における化学組成を上述の方法により測定し、Mn/Alの値を算出した。なお、亜鉛めっき層の厚さはいずれも10μm以上であった。The chemical composition of the surface region of the zinc-plated layer of the obtained molded bodies was measured by the above-mentioned method, and the Mn/Al value was calculated. The thickness of the zinc-plated layer was 10 μm or more in all cases.
次に、上記の成形体の表面を観察し、蜘蛛の巣状の欠陥が無いかどうか評価した。評価基準は、蜘蛛の巣状の欠陥が成形体の表面に非常にくっきり見えている場合をF、薄く見えており化成電着後も見える場合はC、わずかに見えるが化成電着後は見えない場合はB、化成電着する前の状態でも見えない場合はAとした。本実施例ではC以上を合格とした。Next, the surface of the molded body was observed and evaluated for the presence or absence of spider web-like defects. The evaluation criteria were as follows: F if the spider web-like defects were very clearly visible on the surface of the molded body, C if they were faintly visible even after electrochemical deposition, B if they were slightly visible but not visible after electrochemical deposition, and A if they were not visible even before electrochemical deposition. In this example, a grade of C or above was considered a pass.
また、耐食性は、温塩水浸漬による塗膜密着性試験で評価した。ホットスタンプ加熱後の供試材に日本パーカライジング株式会社製PBL-3080で通常の化成処理条件により燐酸亜鉛処理を行った後、関西ペイント製電着塗料GT-10を電圧200Vのスロープ通電で電着塗装し、焼き付け温度150℃で20分焼き付け塗装した。塗膜厚みは20μmであった。そのサンプルを5%50℃のNaCl水溶液中に500時間浸積した後、塗装にテープ剥離試験を行い、5%以上の剥離が発生した場合は耐食性不良としてF、1%以上5%未満をC、0%を超えて1%未満の場合をB、0%の場合をAとした。本実施例ではB以上を合格とした。 Corrosion resistance was evaluated by a coating adhesion test using immersion in warm salt water. After hot stamp heating, the test material was zinc phosphate treated using PBL-3080 manufactured by Nihon Parkerizing Co., Ltd. under normal chemical conversion treatment conditions, and then electrodeposition coating was performed using Kansai Paint's electrodeposition paint GT-10 with a slope current of 200V, followed by baking at a baking temperature of 150°C for 20 minutes. The coating thickness was 20μm. The sample was immersed in a 5% NaCl aqueous solution at 50°C for 500 hours, after which a tape peeling test was performed on the coating. If peeling of 5% or more occurred, the corrosion resistance was deemed poor and rated F, if peeling occurred between 1% and less than 5%, C, if peeling occurred between 0% and less than 1%, B, and if peeling occurred at 0%, A. In this example, B or higher was deemed a pass.
以上の評価結果を表1に併せて示す。 The above evaluation results are shown in Table 1.
以上のように、本発明に係る製造方法よれば、Al含有Znめっきを用いた場合において、ホットスタンプ成形体を製造する際に、蜘蛛の巣状の表面欠陥を抑制することが可能となる。As described above, the manufacturing method of the present invention makes it possible to suppress spider web-like surface defects when manufacturing hot stamped bodies using Al-containing Zn plating.
Claims (7)
前記めっき鋼板に対して表面研削を施す表面研削工程と、を備え、
前記溶融亜鉛めっき処理工程では、
前記亜鉛めっき層を形成してから、前記亜鉛めっき層の表面の温度が400℃まで冷却する間の平均冷却速度を10℃/s以上とし、
前記亜鉛めっき層のめっき付着量を、Zn含有量において、65~150g/m2とし、かつ、前記亜鉛めっき層中のAl含有量を、質量%で、0.15~0.70%とし、
前記表面研削工程では、前記亜鉛めっき層のZn含有量換算でのめっき付着量をM、前記亜鉛めっき層中のAl含有量をAとした時に、研削量G(g/m2)が、下記(i)式で定義されるLとの関係において、下記(ii)式を満足する条件で表面研削を施す、
ホットスタンプ用めっき鋼板の製造方法。
L=0.0048×A×M+0.138 ・・・(i)
L≦G≦10L ・・・(ii) a hot-dip galvanizing process for forming a zinc-plated layer on the surface of the substrate to obtain a plated steel sheet;
A surface grinding step of grinding the surface of the plated steel sheet,
In the hot dip galvanizing treatment step,
The average cooling rate during the period from the formation of the zinc-plated layer to the temperature of the surface of the zinc-plated layer being cooled to 400° C. is set to 10° C./s or more;
The coating weight of the zinc-plated layer is 65 to 150 g/ m2 in terms of Zn content, and the Al content in the zinc-plated layer is 0.15 to 0.70% in terms of mass%,
In the surface grinding step, when the coating weight of the zinc-plated layer in terms of Zn content is M and the Al content in the zinc-plated layer is A, the surface grinding is performed under conditions such that the grinding amount G (g/m 2 ) satisfies the following formula (ii) in relation to L defined by the following formula (i):
A manufacturing method of plated steel sheet for hot stamping.
L = 0.0048 × A × M + 0.138 ... (i)
L≦G≦10L (ii)
請求項1に記載のホットスタンプ用めっき鋼板の製造方法。 The Mn content in the base material is, in mass%, more than 1.3%;
The method for producing the plated steel sheet for hot stamping according to claim 1.
前記めっき鋼板に対して表面研削を施す表面研削工程と、
前記表面研削を施した後の前記めっき鋼板を加熱し、その後に、成形および焼入れを同時に行うホットスタンプ工程と、を備え、
前記溶融亜鉛めっき処理工程では、
前記亜鉛めっき層を形成してから、前記亜鉛めっき層の表面の温度が400℃まで冷却する間の平均冷却速度を10℃/s以上とし、
前記亜鉛めっき層のめっき付着量を、Zn含有量において、65~150g/m2とし、かつ、前記亜鉛めっき層中のAl含有量を、質量%で、0.15~0.70%とし、
前記表面研削工程では、前記亜鉛めっき層のZn含有量換算でのめっき付着量をM、前記亜鉛めっき層中のAl含有量をAとした時に、研削量G(g/m2)が、下記(i)式で定義されるLとの関係において、下記(ii)式を満足する条件で表面研削を施す、
ホットスタンプ成形体の製造方法。
L=0.0048×A×M+0.138 ・・・(i)
L≦G≦10L ・・・(ii) a hot-dip galvanizing process for forming a zinc-plated layer on the surface of the substrate to obtain a plated steel sheet;
a surface grinding step of grinding the surface of the plated steel sheet;
a hot stamping process in which the plated steel sheet after the surface grinding is heated and then formed and quenched at the same time,
In the hot dip galvanizing treatment step,
The average cooling rate during the period from the formation of the zinc-plated layer to the temperature of the surface of the zinc-plated layer being cooled to 400° C. is set to 10° C./s or more;
The coating weight of the zinc-plated layer is 65 to 150 g/ m2 in terms of Zn content, and the Al content in the zinc-plated layer is 0.15 to 0.70% in terms of mass%,
In the surface grinding step, when the coating weight of the zinc-plated layer in terms of Zn content is M and the Al content in the zinc-plated layer is A, the surface grinding is performed under conditions such that the grinding amount G (g/m 2 ) satisfies the following formula (ii) in relation to L defined by the following formula (i):
A method for producing a hot stamped product.
L = 0.0048 × A × M + 0.138 ... (i)
L≦G≦10L (ii)
請求項3に記載のホットスタンプ成形体の製造方法。 The Mn content in the base material is, in mass%, more than 1.3%;
The method for producing the hot stamped product according to claim 3.
請求項3または請求項4に記載のホットスタンプ成形体の製造方法。 In the hot stamping process, heating is performed to a temperature range of Ac 3 to 950 ° C. at an average heating rate of less than 20 ° C./s.
The method for producing a hot stamped product according to claim 3 or 4.
前記亜鉛めっき層中のAl含有量が、質量%で、0.15~0.70%であり、
前記亜鉛めっき層の表面から深さ1μmまでの表層領域における化学組成が、下記(iii)式を満足する、
ホットスタンプ成形体。
Mn/Al≧5.0 ・・・(iii)
但し、上記式中の元素記号は、前記表層領域中における各元素の含有量(質量%)を表す。 A zinc plating layer having a thickness of 1 μm or more is provided on the surface of the base material,
The Al content in the zinc plating layer is, in mass%, 0.15 to 0.70%;
The chemical composition of a surface region of the zinc plating layer from the surface to a depth of 1 μm satisfies the following formula (iii):
Hot stamped compact.
Mn/Al≧5.0 (iii)
In the above formula, the element symbols represent the content (mass %) of each element in the surface layer region.
請求項6に記載のホットスタンプ成形体。 The Mn content in the base material is, in mass%, more than 1.3%;
The hot stamped product according to claim 6.
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