JP3783961B2 - Manufacturing method of steel strip for metal belt - Google Patents
Manufacturing method of steel strip for metal belt Download PDFInfo
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- JP3783961B2 JP3783961B2 JP2004058951A JP2004058951A JP3783961B2 JP 3783961 B2 JP3783961 B2 JP 3783961B2 JP 2004058951 A JP2004058951 A JP 2004058951A JP 2004058951 A JP2004058951 A JP 2004058951A JP 3783961 B2 JP3783961 B2 JP 3783961B2
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- 229910000831 Steel Inorganic materials 0.000 title claims description 55
- 239000010959 steel Substances 0.000 title claims description 55
- 239000002184 metal Substances 0.000 title claims description 37
- 229910052751 metal Inorganic materials 0.000 title claims description 37
- 238000004519 manufacturing process Methods 0.000 title claims description 25
- 230000007547 defect Effects 0.000 claims description 36
- 238000005097 cold rolling Methods 0.000 claims description 29
- 238000000034 method Methods 0.000 claims description 20
- 238000005554 pickling Methods 0.000 claims description 17
- 229910000851 Alloy steel Inorganic materials 0.000 claims description 15
- 230000003746 surface roughness Effects 0.000 claims description 14
- 229910001240 Maraging steel Inorganic materials 0.000 claims description 12
- 229910000734 martensite Inorganic materials 0.000 claims description 9
- 238000005096 rolling process Methods 0.000 claims description 9
- 239000000203 mixture Substances 0.000 claims description 8
- 229910052748 manganese Inorganic materials 0.000 claims description 7
- 229910052710 silicon Inorganic materials 0.000 claims description 7
- 239000000126 substance Substances 0.000 claims description 6
- 238000005098 hot rolling Methods 0.000 claims description 5
- 239000002994 raw material Substances 0.000 claims description 5
- 229910052799 carbon Inorganic materials 0.000 claims description 4
- 229910052750 molybdenum Inorganic materials 0.000 claims description 4
- 229910052717 sulfur Inorganic materials 0.000 claims description 4
- 229910052760 oxygen Inorganic materials 0.000 claims description 3
- 229910052759 nickel Inorganic materials 0.000 claims description 2
- 239000000463 material Substances 0.000 description 18
- 206010016256 fatigue Diseases 0.000 description 16
- 230000005540 biological transmission Effects 0.000 description 15
- 239000006061 abrasive grain Substances 0.000 description 11
- 150000004767 nitrides Chemical class 0.000 description 9
- 238000000227 grinding Methods 0.000 description 8
- 238000000137 annealing Methods 0.000 description 7
- 229910045601 alloy Inorganic materials 0.000 description 6
- 239000000956 alloy Substances 0.000 description 6
- 230000000694 effects Effects 0.000 description 6
- 238000001556 precipitation Methods 0.000 description 6
- 229910000765 intermetallic Inorganic materials 0.000 description 5
- 239000000843 powder Substances 0.000 description 5
- 230000032683 aging Effects 0.000 description 4
- 238000005728 strengthening Methods 0.000 description 4
- 238000005520 cutting process Methods 0.000 description 3
- 238000010438 heat treatment Methods 0.000 description 3
- 239000011159 matrix material Substances 0.000 description 3
- 238000002844 melting Methods 0.000 description 3
- 230000008018 melting Effects 0.000 description 3
- 239000000047 product Substances 0.000 description 3
- 239000000243 solution Substances 0.000 description 3
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 2
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 2
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 2
- 238000003483 aging Methods 0.000 description 2
- 239000013078 crystal Substances 0.000 description 2
- 238000005530 etching Methods 0.000 description 2
- 230000006698 induction Effects 0.000 description 2
- 239000011259 mixed solution Substances 0.000 description 2
- 229910017604 nitric acid Inorganic materials 0.000 description 2
- 230000003287 optical effect Effects 0.000 description 2
- 238000007670 refining Methods 0.000 description 2
- 230000035882 stress Effects 0.000 description 2
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 1
- 208000010392 Bone Fractures Diseases 0.000 description 1
- 229910000640 Fe alloy Inorganic materials 0.000 description 1
- 206010017076 Fracture Diseases 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 229910001566 austenite Inorganic materials 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 229910052804 chromium Inorganic materials 0.000 description 1
- 230000006378 damage Effects 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 238000010894 electron beam technology Methods 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 238000005242 forging Methods 0.000 description 1
- 230000014509 gene expression Effects 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 238000005304 joining Methods 0.000 description 1
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- 150000001247 metal acetylides Chemical class 0.000 description 1
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- 238000010313 vacuum arc remelting Methods 0.000 description 1
- 238000005406 washing Methods 0.000 description 1
- 229910052726 zirconium Inorganic materials 0.000 description 1
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- Metal Rolling (AREA)
Description
本発明は、無段変速機用部品の動力伝達用の金属ベルトに用いる金属ベルト用鋼帯の製造方法に関するものである。 The present invention relates to a method for manufacturing a steel strip for a metal belt used for a metal belt for power transmission of a continuously variable transmission component.
無段変速機用部品の動力伝達用の金属ベルトに用いる金属ベルト用鋼帯として、マルエージング鋼や、マルテンサイト系の鋼があり、高い疲労強度が求められている。
高い疲労強度を劣化させる要因の一つに仕上げ冷間圧延後に鋼帯表面に残存する線状のキズや、面状のキズ等の表面欠陥が挙げられる。これら表面欠陥が残存した鋼帯を用いて製造された部材は、表面欠陥を起点として部材の破断が発生する。
このＦｅ基合金でなる鋼帯の表面欠陥を防止する提案としては、例えば特開２００１−４７１０６号（特許文献１参照）として、疲労強度の高い熱延鋼板とその製造方法が提案されている。
As steel strips for metal belts used for power transmission metal belts for continuously variable transmission parts, there are maraging steels and martensitic steels, and high fatigue strength is required.
One of the factors that deteriorate the high fatigue strength is surface defects such as linear scratches remaining on the surface of the steel strip after finish cold rolling and planar scratches. In the member manufactured using the steel strip in which the surface defects remain, the member breaks starting from the surface defects.
As a proposal for preventing surface defects of a steel strip made of this Fe-based alloy, for example, Japanese Patent Application Laid-Open No. 2001-47106 (see Patent Document 1) proposes a hot-rolled steel sheet having high fatigue strength and a method for producing the same.
上述した特許文献１に開示される技術は、高い疲労強度を備えた自動車部品に代表される部品を製造する熱間圧延鋼板とその製造方法を提案するものである。
具体的には、鋼中のＣ、Ｓｉ、Ｍｎに関しＣｅｑ．＝Ｃ％＋１／６Ｍｎ％＋１／２４Ｓｉ％で規定する数値が式（１）を満足し、かつ、鋼中のＭｎ、ＳがＳ≦０．０２５％で（２）式を充足し、酸洗後、調質圧延されたコイルの表面において、鋼板の圧延方向および幅方向のそれぞれの平均粗さＲａ（μｍ）及び表面粗さＲｚ（μｍ）が（３）、（４）式を満足するというものである。
この特許文献１に開示されるのは、仕上げ圧延（調質圧延）をダルロールで行い、表面粗さを特定の粗さに調整しようとするものである。
The technique disclosed in Patent Document 1 described above proposes a hot-rolled steel sheet for manufacturing parts typified by automobile parts having high fatigue strength and a manufacturing method thereof.
Specifically, for C, Si and Mn in steel, Ceq. = Numeric value specified by C% + 1 / 6Mn% + 1 / 24Si% satisfies the formula (1), and Mn and S in the steel satisfy the formula (2) when S ≦ 0.025%, and pickling Later, on the surface of the temper rolled coil, the average roughness Ra (μm) and the surface roughness Rz (μm) in the rolling direction and the width direction of the steel sheet satisfy the expressions (3) and (4), respectively. Is.
This patent document 1 discloses that finish rolling (temper rolling) is performed by a dull roll to adjust the surface roughness to a specific roughness.
特許文献１によれば、製品の板厚として２．３１ｍｍの比較的厚めの鋼帯に対して適用しているが、疲労強度が求められる鋼帯を用いた用途の中には金属ベルト用の鋼帯のように０．７ｍｍ以下というような薄帯で、疲労強度が求められるような用途もある。
このような薄帯に対してダルロールを用いての調質圧延は、素材表面に線状欠陥や面状欠陥を故意に形成しようとするものであり、ダルロールで粗らされた表面には部分的に応力集中が発生し易く、薄い金属ベルト用の鋼帯として用いるには不適当である。
本発明の目的は、表面欠陥を低減できる金属ベルト用の鋼帯の製造方法を提供することである。
According to Patent Document 1, it is applied to a relatively thick steel strip having a thickness of 2.31 mm as a product thickness. However, some uses for steel belts that require fatigue strength include metal belts. There are also applications where fatigue strength is required with a thin strip of 0.7 mm or less, such as a steel strip.
The temper rolling using dull roll for such a ribbon is intended to intentionally form a linear defect or a planar defect on the surface of the material, and the surface roughened with the dull roll is partially applied. Stress concentration is likely to occur in the steel, and it is not suitable for use as a steel strip for a thin metal belt.
The objective of this invention is providing the manufacturing method of the steel strip for metal belts which can reduce a surface defect.
本発明は上述した課題を解決するためになされたものである。
即ち本発明は、熱間圧延後のＦｅ基合金鋼帯を素材とし、該素材を用いて冷間圧延を行う金属ベルト用帯鋼の製造方法において、冷間圧延工程中に少なくとも１回以上の酸洗処理を行い、少なくとも仕上げの冷間圧延はロールの表面粗さ（Ｒａ）が０．２μｍ以下のロールを用い、且つ３〜３０％の圧下率とし、Ｆｅ基合金鋼帯の厚さを０．７ｍｍ以下とする金属ベルト用鋼帯の製造方法である。
好ましくは、酸洗処理は２回以上行うことなう金属ベルト用鋼帯の製造方法である。
更に好ましくは、仕上げ冷間圧延後のＦｅ基合金鋼帯の表面において、１００ｍｍ２の範囲内に存在する線状欠陥の深さが５μｍ以下であり、最大長径が１０μｍ以下の面状欠陥が５個以下である金属ベルト用鋼帯の製造方法である。
The present invention has been made to solve the above-described problems.
That is, the present invention uses a Fe-based alloy steel strip after hot rolling as a raw material, and in the method for producing a steel strip for a metal belt that performs cold rolling using the raw material, at least once during the cold rolling step. Pickling treatment is performed, and at least the finish cold rolling uses a roll having a surface roughness (Ra) of 0.2 μm or less and a rolling reduction of 3 to 30%, and the thickness of the Fe-based alloy steel strip It is a manufacturing method of the steel belt for metal belts made into 0.7 mm or less.
Preferably, the pickling treatment is a method for producing a steel strip for a metal belt that is performed twice or more.
More preferably, on the surface of the Fe-based alloy steel strip after the finish cold rolling, a planar defect having a depth of 5 μm or less and a maximum length of 10 μm or less in the range of 100 mm 2 is 5 It is a manufacturing method of the steel belt for metal belts which is below.
上述のＦｅ基合金鋼帯がマルエージング鋼またはマルテンサイト系合金鋼であり、前述のマルエージング鋼の好ましい化学組成は、質量％でＴｉ：０．２〜３．０％、Ｃ：０．０１％以下、Ｎｉ：８．０〜２２．０％、Ｃｏ：２．０〜２０．０％、Ｍｏ：２．０〜９．０％、Ａｌ：１．７％以下、Ｐ：０．０２％以下、Ｓ：０．０２％以下、Ｍｎ：０．５％以下、Ｓｉ：０．５％以下、Ｏ：３０ｐｐｍ以下、Ｎ：３０ｐｐｍ以下、残部は実質的にＦｅからなる金属ベルト用鋼帯の製造方法である。
また、上記の化学組成に加え、更にＭｇ：１〜１００ｐｐｍを含有する金属ベルト用鋼帯の製造方法である。
なお、本発明の動力伝達用マルエージング鋼帯には、必要に応じて結晶粒を微細化するのに有効なＢを靱性が劣化させない程度の０．０１％以下の範囲で含有させても良いし、靭性や延性の改善効果があるとされるＣａを０．１％以下の範囲で含有させても良い。
The above-described Fe-based alloy steel strip is maraging steel or martensitic alloy steel, and the preferred chemical composition of the above-mentioned maraging steel is Ti: 0.2-3.0% by mass%, C: 0.01 %: Ni: 8.0-22.0%, Co: 2.0-20.0%, Mo: 2.0-9.0%, Al: 1.7% or less, P: 0.02% Hereinafter, S: 0.02% or less, Mn: 0.5% or less, Si: 0.5% or less, O: 30ppm or less, N: 30ppm or less, and the balance of the steel strip for metal belt substantially made of Fe It is a manufacturing method.
Moreover, it is a manufacturing method of the steel strip for metal belts which contains Mg: 1-100ppm in addition to said chemical composition.
In addition, in the maraging steel strip for power transmission of the present invention, B that is effective for refining crystal grains as necessary may be contained in a range of 0.01% or less to the extent that the toughness does not deteriorate. However, Ca, which is said to have an effect of improving toughness and ductility, may be contained in a range of 0.1% or less.
本発明の金属ベルト用鋼帯の製造方法を適用すれば疲労強度を低下させる表面欠陥を著しく低減でき、自動車エンジンの無段変速機用部品の動力伝達用の金属ベルトとして最適とすることができる。 By applying the method for producing a steel strip for a metal belt according to the present invention, surface defects that reduce fatigue strength can be remarkably reduced, and it can be optimized as a power transmission metal belt for a continuously variable transmission component of an automobile engine. .
先ず、本発明では、熱間圧延後のＦｅ基合金鋼帯を素材とし、該素材を冷間圧延を行う金属ベルト用帯鋼の製造方法において、冷間圧延工程中に少なくとも１回以上の酸洗処理を行う。
自動車エンジンの無段変速機用部品の動力伝達用の金属ベルトにおいては、１０７回以上の高サイクル領域において鋼中の介在物に代表される異物を起点として疲労破壊が生じるため、疲労破壊の起点となる異物（砥粒）の混入を防ぐことが必要となる。また、低サイクル領域においては表面欠陥を起点とした疲労破壊を生じるため、表面への異物の噛み込みやキズなどの表面欠陥を防止することも必要となる。
First, in the present invention, in a method for producing a steel strip for a metal belt in which a raw material is a Fe-based alloy steel strip after hot rolling, and the material is cold-rolled, at least one acid is generated during the cold rolling step. Washing is performed.
In the metal belt for power transmission of the continuously variable component transmission of an automobile engine, because the fatigue fracture occurs foreign matters typified by inclusions in the steel in the high cycle range above 10 7 times as a starting point of fatigue fracture It is necessary to prevent the entry of foreign substances (abrasive grains) as starting points. Further, in the low cycle region, fatigue failure starting from surface defects occurs, so it is also necessary to prevent surface defects such as biting of foreign matter and scratches on the surface.
冷間圧延工程の初期段階（例えば板厚が２ｍｍ前後）においては、その後の冷間圧延に備えて軟化焼鈍（溶体化処理ともいわれることもある）を行い、冷間圧延材料の表面清浄化とある程度の平坦度の付与や板厚寸法を調整するためにグラインダ研削を行う場合が多い。特に例えばＴｉやＡｌを必須で含有するマルエージング鋼では軟化焼鈍後の冷間圧延材表面には酸化被膜が形成されるため、グラインダ研削によって酸化膜を除去するのが効果的である。
この時に、グラインダ研削によって素材に打ち込まれた研削の砥粒の除去や研削粉の除去を最大の目的として酸洗処理を行う。酸洗処理した冷間圧延材の表面からグラインダ研削によって打ち込まれた砥粒や切削粉、冷間圧延工程前の段階（例えば熱間圧延段階）でグラインダ研削されて残留した砥粒が除去され、酸化スケールも除去される。
なお、この時のグラインダ研削−酸洗処理は冷間圧延材を移動させながら連続で処理すると生産性の点から好ましく、勿論、砥粒の打ち込みを完全に防止するために酸洗処理のみとしても良い。
In the initial stage of the cold rolling process (for example, the plate thickness is around 2 mm), softening annealing (sometimes referred to as solution treatment) is performed in preparation for the subsequent cold rolling, and the surface of the cold rolled material is cleaned. In many cases, grinder grinding is performed in order to give a certain degree of flatness and adjust the thickness of the plate. Particularly, for example, in maraging steel that essentially contains Ti or Al, an oxide film is formed on the surface of the cold-rolled material after soft annealing, and therefore it is effective to remove the oxide film by grinder grinding.
At this time, the pickling process is performed for the maximum purpose of removing abrasive grains and grinding powder driven into the material by grinder grinding. Abrasive grains and cutting powder driven by grinder grinding from the surface of the cold-rolled cold-rolled material, the abrasive grains remaining after grinder grinding in the stage before the cold rolling process (for example, hot rolling stage) are removed, Oxide scale is also removed.
In addition, it is preferable from the viewpoint of productivity that the grinder grinding-pickling process at this time is continuously processed while moving the cold-rolled material. Of course, only the pickling process may be used in order to completely prevent the abrasive grains from being driven. good.
そして、冷間圧延工程の中間段階或いは更に最終段階においては冷間圧延で硬化した冷間圧延材の軟化焼鈍を行うが、材料の材質、厚さに応じてグラインダ研削−酸洗処理の工程か、酸洗処理のみの工程を施すとよい。
この時の酸洗処理により、殆どの砥粒や切削粉を除去でき、実質的に異物の噛み込みを起因とした疲労破壊の危険性を殆どなくすことができることから、冷間圧延工程中には２回以上の酸洗処理を行うのが好ましく、この時の酸洗処理は冷間圧延材を移動させながら連続で処理すると生産性の点から好ましい。
なお、本発明においてＦｅ基合金鋼帯の材質は、自動車エンジンの無段変速機用部品の動力伝達用の金属ベルトに用いるに必要な引張強度として、１２００ＭＰａ以上が得られるものを用いると良く、好ましい材質、組成に付いては後述する。
In the intermediate stage or further final stage of the cold rolling process, the soft rolled annealing of the cold rolled material hardened by the cold rolling is performed. Depending on the material and thickness of the material, the grinder grinding-pickling process It is preferable to perform only the pickling process.
By pickling at this time, most of the abrasive grains and cutting powder can be removed, and the risk of fatigue failure due to the biting of foreign matter can be substantially eliminated, so during the cold rolling process It is preferable to carry out pickling treatment twice or more, and pickling treatment at this time is preferable from the viewpoint of productivity if the cold-rolled material is continuously processed while being moved.
In the present invention, the material of the Fe-based alloy steel strip is preferably a material that can obtain 1200 MPa or more as a tensile strength necessary for use in a metal belt for power transmission of a continuously variable transmission part of an automobile engine. A preferable material and composition will be described later.
そして、少なくとも仕上げの冷間圧延に用いるロールには表面粗さ（Ｒａ）が０．２μｍ以下のロールを用いる。
これは、表面粗さ（Ｒａ）が０．２μｍを超えると、鋼帯表面の部分的な応力集中が起き易くなること、鋼帯表面の線状欠陥や面状欠陥が残存し易く、鋼帯表面の欠陥を起因とする破断の危険性が高まるということと、板厚方向の寸法精度が低くなる場合があるためである。そのため、本発明では冷間圧延に用いるロールの表面粗さを（Ｒａ）が０．２μｍ以下とする。好ましくは０．０２〜０．１の範囲である。
なお、冷間圧延工程で用いるロールの表面粗さ（Ｒａ）が０．２μｍ以下のロールを用いることが望ましい。
And the roll whose surface roughness (Ra) is 0.2 micrometer or less is used for the roll used for the cold rolling of finish at least.
This is because when the surface roughness (Ra) exceeds 0.2 μm, partial stress concentration on the surface of the steel strip is likely to occur, and linear defects or planar defects on the surface of the steel strip are likely to remain. This is because the risk of fracture due to surface defects is increased and the dimensional accuracy in the thickness direction may be lowered. Therefore, in the present invention, the surface roughness of the roll used for cold rolling is (Ra) 0.2 μm or less. Preferably it is the range of 0.02-0.1.
In addition, it is desirable to use a roll having a surface roughness (Ra) of 0.2 μm or less used in the cold rolling process.
そして、仕上げの冷間圧延で鋼帯の厚さを０．７ｍｍ以下とする。
この時の圧下率は３〜３０％とする。これは、鋼帯組織の微細化と鋼帯の平坦度（寸法精度）を得るためである。そして、鋼帯の厚みを０．７ｍｍ以下とするが、これは、その後に行われる、鋼帯を適当な長さに切断し、両端を接合してリングとして、最終の自動車エンジンの無段変速機用部品の動力伝達用の金属ベルトにするための素材とするためである。
よって、本発明の仕上げ圧延後の厚さは０．７ｍｍ以下とするが、下限はおおよそ０．２ｍｍ程度となる。
And the thickness of a steel strip shall be 0.7 mm or less by finish cold rolling.
The rolling reduction at this time is 3 to 30%. This is for obtaining a refined steel strip structure and flatness (dimensional accuracy) of the steel strip. The thickness of the steel strip is set to 0.7 mm or less. This is performed after that by cutting the steel strip to an appropriate length and joining both ends as a ring to make a continuously variable transmission of the final automobile engine. This is because it is a material for forming a metal belt for power transmission of machine parts.
Therefore, the thickness after finish rolling of the present invention is 0.7 mm or less, but the lower limit is about 0.2 mm.
上述の製造方法で得られた仕上げ冷間圧延後の鋼帯は、鋼帯の表面において１００ｍｍ２の範囲内に存在する線状欠陥の深さが５μｍ以下であり、最大長径が１０μｍ以上の面状欠陥が５個以下とすることができる。線状欠陥の深さが５μｍ以下、最大長径が１０μｍ以上の面状欠陥が５個以下であれば、鋼帯表面の欠陥を起因とする破断の危険性を回避することが十分に可能である。
なお、本発明で１００ｍｍ２の範囲としたのは、本来であれば表面全体を観察するのが良いが、それは現実的ではなく、従来からの経験として１００ｍｍ２の範囲とすれば１００ｍｍ２を超える範囲の観察結果と比して、表面欠陥不良発生の頻度に差異は無いため、１００ｍｍ２の範囲とした。
そして、本発明で言う線状欠陥とは、長手方向に１μｍ以上の幅をもって伸びたものを言い、面状欠陥とはエッチングによるピット状のキズや打痕、或いは研削粉や砥粒の噛み込み跡のようなものを言い、その欠陥部が最大長径が１０μｍ以上の領域を持ったものを言う。これらの欠陥の有無、深さの測定は例えば光学顕微鏡で測定すれば良い。
The steel strip after finish cold rolling obtained by the above-described manufacturing method has a surface where the depth of linear defects existing in the range of 100 mm 2 on the surface of the steel strip is 5 μm or less and the maximum major axis is 10 μm or more. The number of shape defects can be 5 or less. If the depth of the linear defect is 5 μm or less and the number of the planar defects whose maximum major axis is 10 μm or more is 5 or less, it is possible to avoid the risk of breakage caused by defects on the surface of the steel strip. .
In the present invention, the range of 100 mm 2 should be originally observed if the entire surface is observed, but this is not realistic, and if it is a range of 100 mm 2 as a conventional experience, it exceeds 100 mm 2 . Since there is no difference in the occurrence frequency of surface defects compared to the observation results of the range, the range was set to 100 mm 2 .
The linear defect referred to in the present invention means one extending in the longitudinal direction with a width of 1 μm or more, and the planar defect is a pit-like scratch or dent caused by etching, or biting of grinding powder or abrasive grains. A mark having a maximum major axis of 10 μm or more is said to be a mark. The presence / absence and depth of these defects may be measured, for example, with an optical microscope.
ところで、本発明で用いるＦｅ基合金にはマルエージング鋼またはマルテンサイト系合金鋼であるのが好ましい。これらの合金は熱処理や加工によって強度が約１３００ＭＰａ以上が得られるためである。
なお、本発明で言うマルエージング鋼とは、マルテンサイト組織にエージング（時効硬化処理）を施すことで１３００Ｍｐａ以上（好ましくは２０００ＭＰａ前後）の非常に高い強度と優れた延性が得られる合金であり、Ｎｉを８〜２５％含む時効硬化型の超強力鋼を言う。
マルテンサイト系合金鋼とは、加工誘起型や熱処理によって金属組織がマルテンサイト相を体積％で５０％以上となるものを言い、好ましい化学組成は質量％で、Ｃ：０．０１〜０．１０％、Ｓｉ：３．０％以下、Ｍｎ：５．０％を越え１０．０％以下、Ｎｉ：１．０〜１２．０％、Ｃｒ：４〜１８％、ＭｏまたはＷの１種または２種が、Ｍｏ＋１・２Ｗで０．１〜４．０％、Ｃｕ：５．０％以下（０％を含む）、Ｎ：０．１５％以下（０％を含む）、Ａｌ：０．１０％以下、Ｏ：０．００５％以下、残部が実質的にＦｅの合金である。
By the way, the Fe-based alloy used in the present invention is preferably maraging steel or martensitic alloy steel. This is because these alloys can obtain a strength of about 1300 MPa or more by heat treatment or processing.
In addition, the maraging steel referred to in the present invention is an alloy in which a very high strength of 1300 Mpa or more (preferably around 2000 MPa) and excellent ductility can be obtained by performing aging (age hardening treatment) on the martensite structure. An age-hardening type super strong steel containing 8 to 25% of Ni.
The martensitic alloy steel means that the metal structure has a martensite phase of 50% or more by volume% due to work induction type or heat treatment, and a preferable chemical composition is mass%, and C: 0.01 to 0.10. %, Si: 3.0% or less, Mn: more than 5.0% and 10.0% or less, Ni: 1.0 to 12.0%, Cr: 4 to 18%, one or two of Mo or W The seeds are 0.1 to 4.0% in Mo + 1 · 2W, Cu: 5.0% or less (including 0%), N: 0.15% or less (including 0%), Al: 0.10% Hereinafter, O: 0.005% or less, the balance being substantially an Fe alloy.
次に、上述のマルエージング鋼の好ましい組成について説明する。各元素の含有量は質量％として示す。
Ｔｉ：０．２〜３．０％
Ｔｉは時効処理により微細な金属間化合物を形成し、析出することによって強化に寄与するマルエージング鋼において必要不可欠な元素であり０．２％以上含有させるが、その含有量が３．０％を越えて含有させると延性、靱性が劣化するため、Ｔｉの含有量を０．２〜３．０％とした。好ましくは、０．３〜２．０％の範囲である。
Ｃ：０．０１％以下
Ｃは炭化物を形成し、金属間化合物の析出量を減少させて疲労強度を低下させるため本発明ではＣの上限を０．０１％以下とした。なお、下限については、今現在の技術的な限界としては１０ｐｐｍとするのがせいぜいである。
Ｎｉ：８．０〜２２．０％
Ｎｉは靱性の高い母相組織を形成させるためには不可欠の元素であるが、８．０％未満では靱性が劣化する。一方、２２％を越えるとオーステナイトが安定化し、マルテンサイト組織を形成し難くなることから、Ｎｉは８．０〜２２．０％とした。
Next, the preferable composition of the above-mentioned maraging steel will be described. The content of each element is shown as mass%.
Ti: 0.2-3.0%
Ti is an indispensable element in maraging steel that contributes to strengthening by forming fine intermetallic compounds by aging treatment, and is contained in an amount of 0.2% or more, but its content is 3.0%. If the content exceeds this, ductility and toughness deteriorate, so the Ti content is set to 0.2 to 3.0%. Preferably, it is 0.3 to 2.0% of range.
C: 0.01% or less C forms carbides and decreases the precipitation amount of intermetallic compounds to reduce fatigue strength. Therefore, in the present invention, the upper limit of C is set to 0.01% or less. The lower limit is at most 10 ppm as the current technical limit.
Ni: 8.0 to 22.0%
Ni is an indispensable element for forming a matrix structure with high toughness, but if it is less than 8.0%, the toughness deteriorates. On the other hand, if it exceeds 22%, austenite is stabilized and it becomes difficult to form a martensite structure. Therefore, Ni is set to 8.0 to 22.0%.
Ｃｏ：２．０〜２０．０％
Ｃｏはマトリックスであるマルテンサイト組織を安定性に大きく影響することなく、Ｍｏの固溶度を低下させることによってＭｏが微細な金属間化合物を形成して析出するのを促進することによって析出強化に寄与するが、その含有量が２．０％未満では必ずしも十分効果が得られず、また２０．０％を越えると脆化する傾向がみられることから、Ｃｏの含有量は２．０〜２０．０％にした。なお、引張強度を２０００ＭＰａ前後まで高めるには、Ｃｏの範囲を５．０〜２０．０％とすれば良い。
Ｍｏ：２．０〜９．０％
Ｍｏは時効処理により、微細な金属間化合物を形成し、マトリックスに析出することによって強化に寄与する元素であるが、その含有量が２．０％未満の場合その効果が少なく、また９．０％を越えて含有すると延性、靱性を劣化させるＦｅ，Ｍｏを主要元素とする粗大析出物を形成しやすくなるため、Ｍｏの含有量を２．０〜９．０％とした。
Ａｌ：１．７％以下
Ａｌは、時効析出した強化に寄与するだけでなく、脱酸作用を持っているが、１．７％を越えて含有させると靱性が劣化することから、その含有量を１．７％以下とした。好ましい下限は０．０２％とすれば良い。
Co: 2.0-20.0%
Co does not greatly affect the stability of the martensite structure that is the matrix, but reduces precipitation of Mo to promote precipitation of Mo by forming fine intermetallic compounds and thereby strengthening precipitation. However, if the content is less than 2.0%, a sufficient effect is not necessarily obtained. If the content exceeds 20.0%, embrittlement tends to occur, so the Co content is 2.0 to 20%. 0.0%. In addition, what is necessary is just to make the range of Co 5.0 to 20.0% in order to raise tensile strength to about 2000 MPa.
Mo: 2.0-9.0%
Mo is an element that contributes to strengthening by forming a fine intermetallic compound by aging treatment and precipitating in the matrix. However, when its content is less than 2.0%, its effect is small, and 9.0 If the content exceeds 50%, it becomes easy to form coarse precipitates containing Fe and Mo as main elements which deteriorate ductility and toughness. Therefore, the Mo content is set to 2.0 to 9.0%.
Al: 1.7% or less Al not only contributes to strengthening by aging precipitation, but also has a deoxidizing action, but if it exceeds 1.7%, the toughness deteriorates, so its content Was made 1.7% or less. A preferable lower limit may be 0.02%.
Ｐ：０．０２％以下、Ｓ：０．０２％以下
Ｐ、Ｓは粒界脆化させたり、介在物を形成して疲労強度を低下させるので、０．０２％以下とすると良く、好ましくは０．０１％以下であり、無添加レベル以下でも良い。
Ｍｎ：０．５％以下、Ｓｉ：０．５％以下
Ｓｉ、Ｍｎは脆化をもたらす粗大な金属間化合物の析出を促進して延性、靭性を低下させたり、介在物を形成して疲労強度を低下させるので、Ｓｉ、Ｍｎ共に０．５％以下にした。好ましくは０．２％未満、更に好ましくは０．０１％以下とすれば良く、無添加レベル以下でも良い。
Ｏ：３０ｐｐｍ以下
Ｏは酸化物系介在物を形成するため、３０ｐｐｍ以下に制限する。Ｏが３０ｐｐｍを超えて含有すると疲労強度が著しく低下するため、その含有量を３０ｐｐｍ以下にした。好ましくは２０ｐｐｍ以下である。なお、下限については、今現在の技術的な限界としては１ｐｐｍとするのがせいぜいである。
P: 0.02% or less, S: 0.02% or less Since P and S cause grain boundary embrittlement or formation of inclusions to reduce fatigue strength, the content is preferably 0.02% or less, preferably It may be 0.01% or less and may be an additive-free level or less.
Mn: 0.5% or less, Si: 0.5% or less Si and Mn promote the precipitation of coarse intermetallic compounds that cause embrittlement, reduce ductility and toughness, and form inclusions to increase fatigue strength. Therefore, both Si and Mn were made 0.5% or less. Preferably, it may be less than 0.2%, more preferably 0.01% or less, and it may be the additive-free level or less.
O: 30 ppm or less O is limited to 30 ppm or less because it forms oxide inclusions. When the O content exceeds 30 ppm, the fatigue strength is remarkably reduced, so the content was made 30 ppm or less. Preferably it is 20 ppm or less. The lower limit is at most 1 ppm as the current technical limit.
Ｎ：３０ｐｐｍ以下
Ｎは窒化物や炭窒化物系介在物を形成するため、３０ｐｐｍ以下に制限する。Ｎが３０ｐｐｍを超えて含有すると疲労強度が著しく低下するため、その含有量を３０ｐｐｍにした。好ましくは２０ｐｐｍ以下である。なお、下限については、今現在の技術的な限界としては２ｐｐｍとするのがせいぜいである。
残部は実質的にＦｅ
本発明では上述した元素以外は実質的にＦｅとしているが、例えばＢは結晶粒を微細化するのに有効な元素であるため、靱性が劣化させない程度の０．０１％以下の範囲で含有させても良い。Ｃａ、Ｚｒは靭性や延性の改善効果があるため、０．１％以下の範囲で含有させてもよい。また、不可避的に含有する不純物元素は含有されるものである。
N: 30 ppm or less N is limited to 30 ppm or less in order to form nitrides and carbonitride inclusions. When N exceeds 30 ppm, the fatigue strength is remarkably lowered, so the content was made 30 ppm. Preferably it is 20 ppm or less. The lower limit is at most 2 ppm as the current technical limit.
The balance is substantially Fe
In the present invention, elements other than the above-described elements are substantially Fe. For example, B is an element effective for refining crystal grains, so that it is contained in a range of 0.01% or less to the extent that toughness does not deteriorate. May be. Since Ca and Zr have an effect of improving toughness and ductility, they may be contained within a range of 0.1% or less. Moreover, the impurity element contained unavoidable is contained.
本発明においてはＭｇ：１〜１００ｐｐｍを含有することができる。
Ｍｇを１〜１００ｐｐｍ含有させることで、インゴットの酸素濃度を安定して下げることができ、酸化物の組成がＡｌ２Ｏ３に代表されるＡｌを主成分とする酸化物に代わり、金属元素としてＭｇを主要成分とする酸化物となり、更にそのサイズも微細化するため、必要に応じて添加する。また、Ｍｇを添加して真空二重溶解を適用すれば、窒化物系介在物の大きさも微細にすることができる。
このＭｇの効果を得るには１ｐｐｍ未満では前述の効果が得にくく、１００ｐｐｍを超えると靭性が劣化するので、Ｍｇを添加する場合には１〜１００ｐｐｍの範囲とするのが良い。好ましくは２〜７０ｐｐｍの範囲である。
なお、Ｍｇを添加することにより冷間圧延工程前の素材状態で酸化物系介在物であれば２０μｍ以下に、窒化物系介在物であれば１２μｍ以下に微細化することができ、冷間圧延工程終了後においては、酸化物系介在物は１５μｍ以下とすることができる。
In the present invention, Mg: 1 to 100 ppm can be contained.
By containing 1 to 100 ppm of Mg, the oxygen concentration of the ingot can be stably lowered, and the oxide composition is used as a metal element instead of an oxide mainly composed of Al typified by Al 2 O 3. In order to become an oxide containing Mg as a main component and further reduce its size, it is added as necessary. In addition, if Mg is added and vacuum double melting is applied, the size of the nitride inclusions can be reduced.
In order to obtain the effect of Mg, it is difficult to obtain the above-described effect if it is less than 1 ppm, and the toughness deteriorates if it exceeds 100 ppm. Therefore, when Mg is added, the content is preferably in the range of 1 to 100 ppm. Preferably it is the range of 2-70 ppm.
In addition, by adding Mg, it can be refined to 20 μm or less if it is an oxide-based inclusion in the material state before the cold rolling step, and to 12 μm or less if it is a nitride-based inclusion. After the process is completed, the oxide inclusions can be 15 μm or less.
以下、実施例として更に詳しく本発明を説明する。
真空誘導溶解で電極を製造し、真空アーク再溶解を行い鋼塊を得た。鋼塊を１２５０℃でソーキングを行なった後、熱間鍛造を行なって熱間鍛造品とし、熱間鍛造品を熱間圧延し、熱間圧延後の帯状のＦｅ基合金に形成された酸化スケールは酸洗処理にて除去し、厚み２ｍｍの冷間圧延用の素材とした。
今回のＦｅ基合金鋼帯の素材は２０００ＭＰａ前後の引張強度を得ることができるマルエージング鋼とした。化学組成を表１に示す。
Hereinafter, the present invention will be described in more detail as examples.
An electrode was manufactured by vacuum induction melting, and vacuum arc remelting was performed to obtain a steel ingot. After the steel ingot is soaked at 1250 ° C., hot forging is performed to form a hot forged product, the hot forged product is hot rolled, and the oxide scale formed on the strip-shaped Fe-based alloy after hot rolling Was removed by pickling treatment and used as a material for cold rolling with a thickness of 2 mm.
The material of the present Fe-based alloy steel strip was maraging steel capable of obtaining a tensile strength of around 2000 MPa. The chemical composition is shown in Table 1.
次に、上記の帯状のＦｅ基合金を用いて、溶体化処理と冷間圧延を繰り返し、厚み０．５ｍｍのマルエージング鋼製の金属ベルト用鋼帯を製造した。仕上げの冷間圧延に用いたロール及び冷間圧延工程で用いたロールの表面粗さは工程Ｎｏ．１及びＮｏ．３〜６までを（Ｒａ）０．０４５μｍとした。工程Ｎｏ．２のロール粗さは（Ｒａ）０．２５μｍとし、冷間圧延と軟化焼鈍を繰返し行った。
なお、酸洗処理に用いた溶液は硫酸及び硝酸の混合液であり、グラインダ→酸洗処理工程、酸洗処理工程及びグラインダ工程は何れも連続で処理した。軟化焼鈍は９００℃として連続熱処理とした。
軟化焼鈍は冷間圧延工程中に２回実施し、軟化焼鈍後の表面処理方法と仕上げ圧延率を表２に示す。
Next, solution treatment and cold rolling were repeated using the above-described belt-shaped Fe-based alloy, and a steel belt for metal belt made of maraging steel having a thickness of 0.5 mm was manufactured. The surface roughness of the roll used in the finish cold rolling and the roll used in the cold rolling process is the process No. 1 and no. The range from 3 to 6 was (Ra) 0.045 μm. Step No. The roll roughness of No. 2 was (Ra) 0.25 μm, and cold rolling and softening annealing were repeated.
The solution used for the pickling treatment was a mixed solution of sulfuric acid and nitric acid, and the grinder → the pickling treatment step, the pickling treatment step, and the grinder step were all treated continuously. Soft annealing was performed at 900 ° C. for continuous heat treatment.
Softening annealing was performed twice during the cold rolling process, and Table 2 shows the surface treatment method and finish rolling rate after softening annealing.
仕上げ冷間圧延後の金属ベルト用鋼帯の表面粗さ、表面欠陥及び砥粒の残存状況を断面から調査した。
金属ベルト用鋼帯の表面粗さは表面粗さ計を用いて測定した。また、表面欠陥は、１００ｍｍ２の範囲内に見られた線状欠陥のうち、最も深いものを表３に示し、最大長径が１０μｍ以上の面状欠陥の個数も測定し、併せて表３に示した。
なお、線状欠陥や面状欠陥の有無、深さの測定は光学顕微鏡及び表面粗さ計で測定し、面状欠陥の場合、最大長径が１０μｍ以上の領域を持ったエッチングによるピット状のキズや打痕、或いは研削粉や砥粒の噛み込み跡が確認できた物をカウントした。この時、表面欠陥としてグラインダ砥粒の残存状況も併せて観察した。
The surface roughness, surface defects, and remaining state of abrasive grains of the steel strip for metal belt after finish cold rolling were investigated from the cross section.
The surface roughness of the metal belt steel strip was measured using a surface roughness meter. In addition, the surface defects are the deepest of the line defects found within the range of 100 mm 2 are shown in Table 3, and the number of planar defects having a maximum major axis of 10 μm or more was also measured. Indicated.
The presence or absence of linear defects and planar defects, and the depth are measured with an optical microscope and a surface roughness meter. In the case of planar defects, pit-like scratches due to etching having an area with a maximum major axis of 10 μm or more are measured. The number of dents, dents, or traces of grinding powder or abrasive grains could be confirmed. At this time, the remaining state of the grinder abrasive grains as a surface defect was also observed.
表３に示すように、本発明の製造方法を適用した金属ベルト用鋼帯では、表面の欠陥が極めて少ないことが分かる。また、砥粒の残存も無く表面欠陥を起因とした破壊の危険性が著しく低減されることが分かる。また、本発明の方法を適用した金属ベルト用鋼帯の表面粗さも良好であることが分かる。
そして、工程Ｎｏ．１及び４の金属ベルト用鋼帯を用いて、介在物測定用のサンプルを採取し、介在物の最大長さを測定した。窒化物系介在物は硝酸と塩酸の混合溶液で試料を溶解後、フィルターでろ過し、フィルター上の窒化物系介在物の残渣を電子顕微鏡で観察を行い、サイズを調査した。酸化物系介在物は、エレクトロンビーム溶解で試料を溶解させ、浮上してきた酸化物系介在物について、電子顕微鏡で観察を行い、サイズを調査した。
As shown in Table 3, it can be seen that the metal belt steel strip to which the production method of the present invention is applied has very few surface defects. It can also be seen that there is no residual abrasive grains and the risk of destruction due to surface defects is significantly reduced. Moreover, it turns out that the surface roughness of the steel strip for metal belts which applied the method of this invention is also favorable.
And process no. Using the steel belts 1 and 4 for the metal belt, a sample for inclusion measurement was taken, and the maximum length of the inclusion was measured. The nitride inclusions were dissolved in a mixed solution of nitric acid and hydrochloric acid, filtered through a filter, and the residue of nitride inclusions on the filter was observed with an electron microscope to investigate the size. For the oxide inclusions, the sample was dissolved by electron beam melting, and the oxide inclusions that floated were observed with an electron microscope and the size was investigated.
この時、窒化系介在物の大きさは、窒化物系介在物は矩形形状であるため、長辺ａと短辺ｂを測定し、面積ａ×ｂに相当する円の直径をその最大長さとし、酸化物系介在物は、酸化物系介在物に外接する円の直径を非金属介在物の最大長さとした。その結果、Ｎｏ．１では窒化物系介在物が８．５μｍ、酸化物系介在物が１３μｍであり、この程度の大きさであれば、１０７回以上の高サイクル領域において優れた疲労強度が得られるレベルであった。また、Ｎｏ．４では窒化物系介在物が６．５μｍ、酸化物系介在物が１０μｍであり、この程度の大きさであれば、１０８回以上の高サイクル領域において優れた疲労強度が得られるレベルであった。
以上、説明する通り、本発明の製造方法を適用すれば、無段変速機用部品の動力伝達用の金属ベルトに用いる金属ベルト用鋼帯として最適となる。
At this time, since the nitride inclusions have a rectangular shape, the nitride inclusions have a rectangular shape. Therefore, the long side a and the short side b are measured, and the diameter of the circle corresponding to the area a × b is the maximum length. For the oxide inclusions, the diameter of the circle circumscribing the oxide inclusions was the maximum length of the nonmetallic inclusions. As a result, no. In No. 1, the nitride inclusions are 8.5 μm and the oxide inclusions are 13 μm. With this size, excellent fatigue strength can be obtained in a high cycle region of 10 7 times or more. It was. No. In No. 4, the nitride inclusions are 6.5 μm and the oxide inclusions are 10 μm. With this size, excellent fatigue strength can be obtained in a high cycle region of 10 8 times or more. It was.
As described above, when the manufacturing method of the present invention is applied, it is optimal as a steel belt for a metal belt used for a metal belt for power transmission of a continuously variable transmission component.
本発明の製造方法では、表面欠陥が問題となる用途への適用に好適である。 The production method of the present invention is suitable for application to applications where surface defects are a problem.
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