JP2013072104A - Steel excellent in toughness and wear resistance - Google Patents
Steel excellent in toughness and wear resistance Download PDFInfo
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- JP2013072104A JP2013072104A JP2011210793A JP2011210793A JP2013072104A JP 2013072104 A JP2013072104 A JP 2013072104A JP 2011210793 A JP2011210793 A JP 2011210793A JP 2011210793 A JP2011210793 A JP 2011210793A JP 2013072104 A JP2013072104 A JP 2013072104A
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 56
- 239000010959 steel Substances 0.000 title claims abstract description 56
- 229910052804 chromium Inorganic materials 0.000 claims abstract description 17
- 229910052748 manganese Inorganic materials 0.000 claims abstract description 14
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 14
- 229910001566 austenite Inorganic materials 0.000 claims abstract description 11
- 229910052750 molybdenum Inorganic materials 0.000 claims abstract description 8
- 239000012535 impurity Substances 0.000 claims abstract description 7
- 229910052758 niobium Inorganic materials 0.000 claims abstract description 6
- 229910052757 nitrogen Inorganic materials 0.000 claims abstract description 5
- 229910052760 oxygen Inorganic materials 0.000 claims abstract description 5
- 229910052698 phosphorus Inorganic materials 0.000 claims abstract description 5
- 229910052796 boron Inorganic materials 0.000 claims abstract description 4
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 4
- 229910052717 sulfur Inorganic materials 0.000 claims abstract description 4
- 229910052719 titanium Inorganic materials 0.000 claims abstract description 4
- 239000000203 mixture Substances 0.000 claims description 7
- 238000010791 quenching Methods 0.000 abstract description 21
- 230000000171 quenching effect Effects 0.000 abstract description 21
- 238000005496 tempering Methods 0.000 abstract description 17
- 239000000463 material Substances 0.000 abstract description 9
- 229910052759 nickel Inorganic materials 0.000 abstract description 4
- 238000012360 testing method Methods 0.000 description 12
- 230000000694 effects Effects 0.000 description 8
- 230000000052 comparative effect Effects 0.000 description 5
- 238000009863 impact test Methods 0.000 description 5
- 238000001816 cooling Methods 0.000 description 4
- 238000005336 cracking Methods 0.000 description 4
- 239000002245 particle Substances 0.000 description 4
- 239000002244 precipitate Substances 0.000 description 4
- 238000000034 method Methods 0.000 description 3
- 238000005728 strengthening Methods 0.000 description 3
- 229910052720 vanadium Inorganic materials 0.000 description 3
- 239000002131 composite material Substances 0.000 description 2
- 238000007542 hardness measurement Methods 0.000 description 2
- 230000003287 optical effect Effects 0.000 description 2
- 229920006395 saturated elastomer Polymers 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 1
- 238000005299 abrasion Methods 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 229910000734 martensite Inorganic materials 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 150000001247 metal acetylides Chemical class 0.000 description 1
- 238000005096 rolling process Methods 0.000 description 1
- 238000005204 segregation Methods 0.000 description 1
- 238000009628 steelmaking Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
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Abstract
Description
本発明は自動車や各種産業機械等の部品に用いられる機械構造用鋼の内、靭性および耐磨耗性に優れた鋼に関する。 The present invention relates to steel having excellent toughness and wear resistance among mechanical structural steels used for parts such as automobiles and various industrial machines.
自動車、各種産業機械の部品の内、特に耐磨耗性、疲労特性等を必要とする部品に用いられる鋼は、焼入れ処理によって高硬度化することが一般的である。焼入れ処理によってマルテンサイト組織を主体とした鋼材は、鋼成分中のＣ含有量により硬度が決まり、Ｃ含有量を高めることで鋼材の硬度を上昇させることができる。しかし、高硬度化は反面として靭性を低下させ、衝撃が加えられた場合に割れを生じるため、鋼材には硬度と靭性のバランスが要求される。 In general, steel used for parts that require wear resistance, fatigue characteristics, etc. among parts of automobiles and various industrial machines is generally hardened by quenching treatment. A steel material mainly composed of a martensite structure by quenching treatment has a hardness determined by the C content in the steel component, and the hardness of the steel material can be increased by increasing the C content. However, higher hardness, on the other hand, lowers toughness and causes cracking when an impact is applied, so steel materials are required to have a balance between hardness and toughness.
これらに対処する従来の技術として、鋼成分中にＳｉ、Ｎｂ、Ｃr、Ｍｏ、Ｖを含むことを特徴とし、特定の圧延、熱処理により、使用中にＶを核とするＣr、Ｍｏ、Ｖの複合析出物を形成せしめた、優れた耐磨耗性と靭性を兼ね備える鋼が提案されている（例えば、特許文献１参照）。さらに、焼入れ後の焼戻し過程で、Ｍｎ、Ｎｉ、Ｃｒ等の合金成分が含まれるとＭｎ、Ｎｉ、Ｃｒ等の炭化物が旧オーステナイト粒界に析出し粒界破壊の原因となることに対し、Ｍｏを添加するとＭｏの炭化物が旧オーステナイト粒内にある転位を核として析出するため、析出物は旧オーステナイト粒内に微細に分散析出し粒界破壊の原因とはならないとした、耐衝撃性耐磨耗性に優れた鋼が提案されている（例えば、特許文献２参照）。また、低Ｐ、低Ｓ化による粒界偏析の軽減、低Ｍｎ化による粒界強化、Ｍｏの増量とＮｂ添加による細粒化によって靭性向上を図り、さらに、Ｎｂ、Ｃｒ、Ｍｏの複合添加は鋼の焼戻し軟化抵抗を著しく高めるため、高い焼戻し温度を採用することによる靭性向上を図った高強度かつ靭性および耐磨耗性が良好な高強度高靭性耐磨耗用鋼が提案されている（例えば、特許文献３参照）。 As a conventional technique for dealing with these, the steel component is characterized by containing Si, Nb, Cr, Mo, V, and Cr, Mo, V having V as a core during use by specific rolling and heat treatment. Steels having excellent wear resistance and toughness in which composite precipitates are formed have been proposed (see, for example, Patent Document 1). Furthermore, in the tempering process after quenching, if alloy components such as Mn, Ni, and Cr are included, carbides such as Mn, Ni, and Cr are precipitated at the prior austenite grain boundaries, causing intergranular fracture. When Mo is added, the carbide of Mo precipitates with the dislocations in the prior austenite grains as nuclei. Steel with excellent wear resistance has been proposed (see, for example, Patent Document 2). Moreover, grain boundary segregation is reduced by lowering P and lowering S, grain boundary strengthening by lowering Mn, increasing toughness by increasing the amount of Mo and making finer by adding Nb, and further adding Nb, Cr, and Mo In order to remarkably increase the temper softening resistance of steel, a high strength, high toughness and wear resistant steel with improved toughness and good toughness and wear resistance by adopting a high tempering temperature has been proposed ( For example, see Patent Document 3).
しかし、上記の先行技術文献における、Ｃｒ、Ｍｏ、Ｖの複合析出物を形成するには、焼戻し温度を２００〜５５０℃で行う必要があるため、所定の硬度が得られない可能性がある。また、Ｍｏ添加による靭性向上は高温焼戻し条件下でのことであり、硬度確保のため低温焼戻しを行う場合には、その効果は明確ではない。さらに、低Ｐ化は製鋼段階での脱リン操業を通常操業より過剰に行う必要があるため、製造性、コストアップの問題がある。つまり、高硬度かつ高靭性であることが従来技術では達成できていない。 However, in order to form the composite precipitates of Cr, Mo, and V in the above-described prior art documents, it is necessary to perform the tempering temperature at 200 to 550 ° C., so that the predetermined hardness may not be obtained. Moreover, the toughness improvement by addition of Mo is under high temperature tempering conditions, and the effect is not clear when performing low temperature tempering to ensure hardness. Further, the reduction in P requires the dephosphorization operation at the steel making stage to be performed more excessively than the normal operation. That is, high hardness and high toughness cannot be achieved by the prior art.
そこで、本発明が解決しようとする課題は、硬度を高く保つため焼入れ後、低温焼戻しを施した条件下において、高硬度と高靭性を両立し、耐磨耗性に優れた鋼材を提供することである。 Therefore, the problem to be solved by the present invention is to provide a steel material having both high hardness and high toughness and excellent wear resistance under the conditions of low temperature tempering after quenching in order to keep the hardness high. It is.
上記の課題を解決するための本発明の手段は、請求項１の手段では、質量％で、Ｃ：０．３０〜０．６５％、Ｓｉ：０．２０〜１．００％、Ｍｎ：０．２０〜０．６０％、Ｐ：０．０３０％以下、Ｓ：０．０３０％以下、Ｃｒ：１．００〜３．００％、Ａｌ：０．００５〜０．２００％、Ｎ：０．０２００％以下、Ｏ：０．００３０％以下を含有し、残部がＦｅおよび不可避不純物からなる鋼である。しかも、該鋼は上記組成のＳｉ、Ｍｎ、Ｃｒの含有量から算出される４Ｓｉ＋３Ｃｒ−Ｍｎの値が６．００％以上を満足し、かつ、旧オーステナイト粒径を８．０μｍ以下とした、高硬度、高靭性で耐磨耗性に優れた鋼である。 The means of the present invention for solving the above problem is that in the means of claim 1, C: 0.30 to 0.65%, Si: 0.20 to 1.00%, Mn: 0 in mass%. 20 to 0.60%, P: 0.030% or less, S: 0.030% or less, Cr: 1.00 to 3.00%, Al: 0.005 to 0.200%, N: 0.00. This steel contains 0200% or less, O: 0.0030% or less, with the balance being Fe and inevitable impurities. Moreover, the steel has a value of 4Si + 3Cr-Mn calculated from the contents of Si, Mn, and Cr of the above composition satisfying 6.00% or more, and the prior austenite grain size is 8.0 μm or less. Steel with high hardness, high toughness and excellent wear resistance.
請求項２の手段では、質量％で、Ｃ：０．３０〜０．６５％、Ｓｉ：０．２０〜１．００％、Ｍｎ：０．２０〜０．６０％、Ｐ：０．０３０％以下、Ｓ：０．０３０％以下、Ｃｒ：１．００〜３．００％、Ａｌ：０．００５〜０．２００％、Ｎ：０．０２００％以下、Ｏ：０．００３０％以下を含有し、さらにＮｉ：０．５０〜２．００％、Ｍｏ：０．０５〜１．００％、Ｂ：０．０００５〜０．００５０％、Ｔｉ：０．０１０〜０．２００％、Ｎｂ：０．０１０〜０．１００％のうち１種または２種以上を含有し、残部がＦｅおよび不可避不純物からなる鋼である。しかも、該鋼は上記組成のＳｉ、Ｍｎ、Ｃｒの含有量から算出される４Ｓｉ＋３Ｃｒ−Ｍｎの値が６．００％以上を満足し、かつ、旧オーステナイト粒径を８．０μｍ以下とした、高硬度、高靭性で耐磨耗性に優れた鋼である。
In the means of
本発明における鋼の化学成分の限定理由を以下に説明する。なお、以下において％は質量％を示す。 The reason for limiting the chemical composition of steel in the present invention will be described below. In the following, “%” represents mass%.
Ｃ:０．３０〜０．６５％
Ｃは、必要な強度および焼入れ硬さを確保するために必要な元素である。したがって、耐磨耗性の支配因子である硬さを確保するために０．３０％以上が必要である。一方、０．６５％を超えると靭性が低下するとともに素材の硬さが上昇するため加工性、被削性の劣化は避けられない。そこで、Ｃは０．３０〜０．６５％ とし、望ましくは０．３５〜０．５０％とする。
C: 0.30 to 0.65%
C is an element necessary for ensuring necessary strength and quenching hardness. Therefore, 0.30% or more is necessary in order to ensure the hardness which is the controlling factor of wear resistance. On the other hand, if it exceeds 0.65%, the toughness is lowered and the hardness of the material is increased, so that deterioration of workability and machinability is inevitable. Therefore, C is 0.30 to 0.65%, preferably 0.35 to 0.50%.
Ｓｉ:０．２０〜１．００％
Ｓｉは、鋼の脱酸に有効な元素であり、鋼に必要な焼入性を付与し強度を高めるために添加する。さらに、Ｓｉは焼戻し軟化抵抗を向上させる。すなわち焼戻し処理および使用時の摩擦熱による耐軟化性を向上させる元素である。したがって、０．２０％以上が必要である。一方、１．００％を超えると靭性が低下するとともに素材の硬さが上昇して加工性が劣化する。そこで、Ｓｉは０．２０〜１．００％とし、望ましくは０．４０〜０．８０％とする。
Si: 0.20 to 1.00%
Si is an element effective for deoxidation of steel, and is added to impart necessary hardenability to the steel and increase strength. Furthermore, Si improves the temper softening resistance. That is, it is an element that improves the softening resistance due to frictional heat during tempering and use. Therefore, 0.20% or more is necessary. On the other hand, if it exceeds 1.00%, the toughness is lowered and the hardness of the material is increased to deteriorate the workability. Therefore, Si is 0.20 to 1.00%, preferably 0.40 to 0.80%.
Ｍｎ：０．２０〜０．６０％
Ｍｎは、鋼の脱酸に有効な元素である。さらに、鋼に必要な焼入性を付与し強度を高めるために添加する。しかし、多量に添加すると靭性を低下させ、さらに、Ｓと結合してＭｎＳの介在物を形成するため割れの起点となる。そこで、Ｍｎは０．２０〜０．６０％とし、望ましくは０．３０〜０．５０％とする。
Mn: 0.20 to 0.60%
Mn is an element effective for deoxidation of steel. Furthermore, it is added to impart the necessary hardenability to the steel and increase the strength. However, if added in a large amount, the toughness is lowered, and further, it combines with S to form inclusions of MnS, which becomes the starting point of cracking. Therefore, Mn is 0.20 to 0.60%, preferably 0.30 to 0.50%.
Ｐ：０．０３０％以下
Ｐは、不可避不純物として粒界に偏析し、０．０３０％を超えると靭性を低下させる。そこで、Ｐは０．０３０％以下とする。
P: 0.030% or less P segregates at grain boundaries as an inevitable impurity, and if it exceeds 0.030%, toughness is reduced. Therefore, P is set to 0.030% or less.
Ｓ：０．０３０％以下
Ｓは、不可避不純物としてＭｎＳの介在物を形成して靭性を低下させる。そこで、Ｓは０．０３０％以下とする。
S: 0.030% or less S lowers toughness by forming inclusions of MnS as inevitable impurities. Therefore, S is set to 0.030% or less.
Ｃｒ：１．００〜３．００％
Ｃｒは、鋼に必要な焼入性を付与し強度を高めるために添加する。さらに、Ｃｒは焼戻し軟化抵抗を向上させるため、焼戻し処理および使用時の摩擦熱による耐軟化性を向上させる元素である。したがって、１．００％以上が必要である。一方、３．００％を超えると靭性が低下するとともに素材の硬さが上昇して加工性が劣化する。そこで、Ｃｒは１．００〜３．００％とし、望ましくは１．２０〜２．２０％とする。
Cr: 1.00 to 3.00%
Cr is added to impart the necessary hardenability to the steel and increase the strength. Furthermore, Cr is an element that improves the softening resistance due to frictional heat during tempering and use in order to improve temper softening resistance. Therefore, 1.00% or more is necessary. On the other hand, if it exceeds 3.00%, the toughness is lowered and the hardness of the material is increased to deteriorate the workability. Therefore, Cr is 1.00 to 3.00%, preferably 1.20 to 2.20%.
Ａｌ：０．００５〜０．２００％
Ａｌは、鋼の脱酸に有効な元素であり、さらにＮと結合しＡｌＮを生成するため、結晶粒粗大化の抑制に有効である。したがって、０．００５％以上が必要である。しかし、Ａｌは多量に添加すると非金属介在物を生成して割れの起点となる。そこで、Ａｌは０．００５〜０．２００％とし、望ましくは０．０１５〜０．１５０％とする。
Al: 0.005 to 0.200%
Al is an element effective for deoxidation of steel, and further binds to N to produce AlN, so that it is effective for suppressing grain coarsening. Therefore, 0.005% or more is necessary. However, if Al is added in a large amount, non-metallic inclusions are generated and become the starting point of cracking. Therefore, Al is made 0.005 to 0.200%, preferably 0.015 to 0.150%.
Ｎ：０．０２００％以下
Ｎは、Ａｌと結合してＡｌＮを生成するため結晶粒粗大化の抑制に有効である。しかし、Ｎは多すぎても、その効果が飽和するため、Ｎは０．０２００％以下とする。
N: 0.0200% or less N is effective in suppressing grain coarsening because it combines with Al to produce AlN. However, even if there is too much N, the effect is saturated, so N is made 0.0200% or less.
Ｏ：０．００３０％以下
Ｏは、０．００３０％を超えて含有すると、割れの起点となる酸化物系介在物を生成する。そこで、酸化物系介在物の生成を抑制するために、Ｏは０．００３０％以下とする。
O: 0.0030% or less If O is contained in excess of 0.0030%, an oxide-based inclusion serving as a starting point of cracking is generated. Therefore, in order to suppress the formation of oxide inclusions, O is made 0.0030% or less.
以上は本発明における鋼の基本成分であるが、さらに本発明では上記成分の他にＮｉ、Ｍｏ、Ｂ、Ｔｉ、Ｎｂのうち１種または２種以上を添加することができる。 The above are the basic components of steel in the present invention. In the present invention, one or more of Ni, Mo, B, Ti, and Nb can be added in addition to the above components.
Ｎｉ：０．５０〜２．００％
Ｎｉは、焼入性と靭性を向上させるために有効な元素である。その効果を発揮するため０．５０％以上が必要であるが、Ｎｉはコストを上昇させる元素であるため、Ｎｉは０．５０〜２．００％とする。
Ni: 0.50 to 2.00%
Ni is an element effective for improving hardenability and toughness. In order to exhibit the effect, 0.50% or more is necessary. However, since Ni is an element that increases the cost, Ni is set to 0.50 to 2.00%.
Ｍｏ：０．０５〜１．００％
Ｍｏは、焼入性と靭性を向上させるために有効な元素である。その効果を発揮するため０．０５％以上が必要であるが、Ｍｏはコストを上昇させる元素であるため、Ｍｏは０．０５〜１．００％とする。
Mo: 0.05-1.00%
Mo is an effective element for improving hardenability and toughness. In order to exhibit the effect, 0.05% or more is necessary. However, since Mo is an element that increases the cost, Mo is set to 0.05 to 1.00%.
Ｂ：０．０００５〜０．００５０％
Ｂは、微量の添加で焼入性を向上させ、さらに、粒界を強化し靭性向上に有効な元素である。したがって、０．０００５％以上が必要であるが、０．００５０％を超えるとその効果は飽和するため、Ｂは０．０００５〜０．００５０％とする。
B: 0.0005 to 0.0050%
B is an element effective for improving hardenability by addition of a small amount, further strengthening grain boundaries and improving toughness. Therefore, 0.0005% or more is necessary, but if it exceeds 0.0050%, the effect is saturated, so B is made 0.0005 to 0.0050%.
Ｔｉ：０．０１０〜０．２００％
Ｔｉは、Ｎと結合してＴｉＮを生成するため、Ｎを固定して、焼入性向上に寄与する有効Ｂを確保する。さらに、ＴｉはＣと結合しＴｉＣを生成するため、ピンニング効果による結晶粒粗大化の抑制および耐磨耗性の向上に有効である。したがって、０．０１０％以上を添加する。一方、０．２００％を越えると靭性および加工性が低下する。そこで、Ｔｉは０．０１０〜０．２００％とする。
Ti: 0.010 to 0.200%
Since Ti combines with N to generate TiN, N is fixed to ensure effective B that contributes to improving hardenability. Furthermore, since Ti combines with C to produce TiC, it is effective for suppressing grain coarsening due to the pinning effect and improving wear resistance. Therefore, 0.010% or more is added. On the other hand, if it exceeds 0.200%, the toughness and workability deteriorate. Therefore, Ti is set to 0.010 to 0.200%.
Ｎｂ：０．０１０〜０．１００％
Ｎｂは、Ｎｂ炭窒化物を生成するので、Ｎｂ炭窒化物のピンニング効果による結晶粒粗大化の抑制に有効である。このためには、Ｎｂを０．０１０％以上添加する必要がある。一方、Ｎｂは０．１００％を超えると粗大なＮｂ析出物が生じて靭性が低下する。そこで、Ｎｂは０．０１０〜０．１００％とする。
Nb: 0.010 to 0.100%
Since Nb produces Nb carbonitride, it is effective for suppressing grain coarsening due to the pinning effect of Nb carbonitride. For this purpose, it is necessary to add 0.010% or more of Nb. On the other hand, if Nb exceeds 0.100%, coarse Nb precipitates are produced and the toughness is lowered. Therefore, Nb is made 0.010 to 0.100%.
Ｓｉ、Ｍｎ、Ｃｒの含有量から算出される４Ｓｉ＋３Ｃｒ−Ｍｎの値：≧６．００％
本発明における鋼は、上記組成のＳｉ、Ｍｎ、Ｃｒの含有量から算出される４Ｓｉ＋３Ｃｒ−Ｍｎの値が６．００％以上を満足する鋼である。上述の通り、Ｓｉ、Ｃｒは焼戻し軟化抵抗を向上させる元素であるため、使用時の摩擦熱による軟化を抑制し磨耗量の低減に有効である。さらに、高Ｓｉ、高Ｃｒの成分設計にすると粒界強化の作用がある。一方、Ｍｎは鋼を脆化させる元素であるため、添加量は最小限とする必要がある。そこで、Ｓｉ、Ｍｎ、Ｃｒの含有量から算出される４Ｓｉ＋３Ｃｒ−Ｍｎの値を６．００％以上とする。
Value of 4Si + 3Cr-Mn calculated from the contents of Si, Mn, and Cr: ≧ 6.00%
The steel in the present invention is a steel in which the value of 4Si + 3Cr-Mn calculated from the contents of Si, Mn, and Cr having the above composition satisfies 6.00% or more. As described above, since Si and Cr are elements that improve temper softening resistance, softening due to frictional heat during use is suppressed and effective in reducing the amount of wear. Furthermore, the design of high Si and high Cr components has the effect of strengthening grain boundaries. On the other hand, since Mn is an element that embrittles steel, the addition amount must be minimized. Therefore, the value of 4Si + 3Cr-Mn calculated from the contents of Si, Mn, and Cr is set to 6.00% or more.
上記した本発明の手段とすることで、硬度を高く保つため焼入れ後、低温焼戻しを施した条件下において、高硬度と高靭性を両立した鋼材を得ることができる。 By using the above-described means of the present invention, a steel material having both high hardness and high toughness can be obtained under the conditions of low temperature tempering after quenching in order to keep the hardness high.
表１に示す化学組成の鋼を１００ｋｇ真空溶解炉で溶製し、得られた鋼を１２００℃で熱間鍛造し、４０ｍｍ×４０ｍｍの角鋼および径３２ｍｍの丸棒鋼に製造し、これらの角鋼および丸棒鋼を８７０℃に６０分間保持し空冷して焼ならし処理を行った。なお、表１における網掛け部は本発明の請求項から外れることを示している。 Steel having the chemical composition shown in Table 1 was melted in a 100 kg vacuum melting furnace, and the obtained steel was hot forged at 1200 ° C. to produce 40 mm × 40 mm square bar and 32 mm diameter round bar steel. The round steel bar was kept at 870 ° C. for 60 minutes, air cooled, and subjected to a normalizing treatment. It should be noted that the shaded portions in Table 1 are outside the claims of the present invention.
その後、上記の４０ｍｍ×４０ｍｍの角鋼を、図１に示す２ｍｍ−Ｕノッチシャルピー衝撃試験片の粗形に加工し、１回焼入れを行う場合は８５０℃で２０分保持し油焼入れを施した後１８０℃で９０分保持し空冷する焼戻し処理を行い、また、２回焼入れを行う場合は８５０℃で２０分保持し油焼入れを施した後５５０℃で９０分保持し水冷する焼戻しを行った。これらの１回焼入れ〜２回焼入れに続いて、さらに８５０℃で２０分保持して油焼入れを施した後、１８０℃で９０分保持し空冷する焼戻し行って、繰り返し焼入れ焼戻し処理を行った。その後、さらに、この粗形を仕上げ加工して、図１に示す２ｍｍ−Ｕノッチシャルピー衝撃試験片とした。この２ｍｍ−Ｕノッチシャルピー衝撃試験片を用いてシャルピー衝撃試験を行った。さらに、上記の試験片を用いて、硬さ測定ならびに光学顕微鏡観察を行うことにより旧オーステナイト粒径を求めた。 After that, after the above 40 mm × 40 mm square steel is processed into a rough shape of a 2 mm-U notch Charpy impact test piece shown in FIG. 1, after quenching for 20 minutes at 850 ° C., oil quenching is performed. Tempering was carried out by holding at 180 ° C. for 90 minutes and air cooling, and in the case of twice quenching, holding at 850 ° C. for 20 minutes followed by oil quenching followed by holding at 550 ° C. for 90 minutes and water cooling. Subsequent to these quenching and quenching twice, oil quenching was further performed at 850 ° C. for 20 minutes, followed by tempering by holding at 180 ° C. for 90 minutes and air cooling, and repeated quenching and tempering treatment. Thereafter, the rough shape was further processed into a 2 mm-U notch Charpy impact test piece shown in FIG. A Charpy impact test was performed using the 2 mm-U notch Charpy impact test piece. Furthermore, the prior austenite particle size was calculated | required by performing hardness measurement and optical microscope observation using said test piece.
上記した１回焼入れおよび２回焼入れについては、旧オーステナイト粒径を８．０μｍ以下に制御するために使い分けた。 About the above-mentioned 1 time quenching and 2 times quenching, in order to control the prior austenite particle size to 8.0 micrometers or less, it used properly.
また、上記の径３２ｍｍの丸棒鋼を、図２に示すローラーピッチング試験の粗形に加工し、１回焼入れを行う場合は、８５０℃で２０分保持し油焼入れを施した後、１８０℃で９０分保持し空冷する焼戻し処理を行った。また、２回焼入れを行う場合は、８５０℃で２０分保持し油焼入れを施した後、５５０℃で９０分保持し水冷する焼戻し処理を行った。さらに、８５０℃で２０分保持し油焼入れを施した後、１８０℃で９０分保持し空冷する焼戻しを行なって、繰り返し焼入れ焼戻し処理を行った。その後、さらに、この粗形を仕上げ加工して、図２に示すローラーピッチング試験片とした。このローラーピッチング試験片を用い、面圧３．３ＧＰａ、すべり率−４０％の条件でローラーピッチング試験を行い、５×１０6サイクルに到達後、ローラーピッチング試験を中止し、試験片のすべり接触部の磨耗量を測定した。 In addition, when the above round bar steel having a diameter of 32 mm is processed into a rough shape of the roller pitching test shown in FIG. A tempering process was performed for 90 minutes. Moreover, when performing quenching twice, after holding at 850 degreeC for 20 minutes and performing oil hardening, the tempering process which hold | maintains at 550 degreeC for 90 minutes and water-cools was performed. Furthermore, after performing oil quenching by holding at 850 ° C. for 20 minutes, tempering by holding at 180 ° C. for 90 minutes and air cooling was performed, and repeated quenching and tempering treatment was performed. Thereafter, this rough shape was further processed into a roller pitching test piece shown in FIG. Using this roller pitching test piece, a roller pitching test was conducted under conditions of a surface pressure of 3.3 GPa and a slip rate of −40%. After reaching 5 × 10 6 cycles, the roller pitching test was stopped, and the sliding contact portion of the test piece The amount of wear was measured.
以上のシャルピー衝撃試験、硬さ測定、光学顕微鏡観察、ローラーピッチング試験の結果として、粒径、硬さ、衝撃値、磨耗量について表２に記載する。 Table 2 shows the particle size, hardness, impact value, and wear amount as a result of the Charpy impact test, hardness measurement, optical microscope observation, and roller pitching test.
表２において、比較鋼のＮｏ．１６〜Ｎｏ．２７の網掛けをしている部分は、粒径が８．０μｍより大きいもの、衝撃値が５０Ｊ／ｃｍ2に満たないもの、および磨耗量が１５μｍより多いものである。一方、発明鋼のＮｏ．１〜Ｎｏ．１５は、衝撃値が５０Ｊ／ｃｍ2以上のもの、および磨耗量が１５μｍ以下のものであるため、優れた靭性と耐磨耗性を有している。 In Table 2, No. of the comparative steel. 16-No. The shaded portion 27 has a particle size larger than 8.0 μm, an impact value of less than 50 J / cm 2 , and a wear amount larger than 15 μm. On the other hand, No. of invention steel. 1-No. Since No. 15 has an impact value of 50 J / cm 2 or more and an abrasion amount of 15 μm or less, it has excellent toughness and wear resistance.
また、硬さと衝撃値および硬さと磨耗量の関係を図３および図４に記載している。発明鋼のＮｏ．１〜Ｎｏ．１５は、比較鋼のＮｏ．１６〜Ｎｏ．２７よりも同一硬さにおける衝撃値および磨耗量が優れていることがわかる。 Further, the relationship between hardness and impact value, and hardness and wear amount is shown in FIGS. No. of invention steel. 1-No. No. 15 is a comparative steel No. 15. 16-No. It can be seen that the impact value and the wear amount at the same hardness are superior to 27.
なお、発明鋼のＮｏ．２と比較鋼のＮｏ．２５、発明鋼のＮｏ．１１と比較鋼のＮｏ．２６、発明鋼のＮｏ．１４と比較鋼のＮｏ．２７は同じ成分である。発明鋼のＮｏ．２、Ｎｏ．１１、Ｎｏ．１４は２回焼入れを施したことにより旧オーステナイト粒径が８．０μｍ以下となり優れた靭性を示したが、比較鋼のＮｏ．２５、Ｎｏ．２６、Ｎｏ．２７は１回焼入れのため旧オーステナイト粒径が８．０μｍより大きくなり発明鋼のＮｏ．２、Ｎｏ．１１、Ｎｏ．１４と比較して靭性が低下した。 In addition, No. of invention steel. No. 2 and No. of comparative steel. 25, No. of invention steel. 11 and No. of comparative steel. 26, No. 26 of invention steel. No. 14 and No. of comparative steel. 27 is the same component. No. of invention steel. 2, No. 11, no. No. 14 exhibited excellent toughness with a prior austenite grain size of 8.0 μm or less as a result of being quenched twice. 25, no. 26, no. No. 27 is a one-time quenching, so that the prior austenite grain size becomes larger than 8.0 μm, and the steel No. 2, No. 11, no. Compared to 14, toughness decreased.
１ ２ｍｍ−Ｕノッチシャルピー試験片
１ａ ノッチ部
２ ローラーピッチング試験片
1 2 mm-U notch
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| JP2018123411A (en) * | 2017-02-03 | 2018-08-09 | Ｊｆｅスチール株式会社 | Abrasion resistant steel sheet, and method for producing the same |
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