JP4280616B2 - Horticulture blade - Google Patents
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- JP4280616B2 JP4280616B2 JP2003411322A JP2003411322A JP4280616B2 JP 4280616 B2 JP4280616 B2 JP 4280616B2 JP 2003411322 A JP2003411322 A JP 2003411322A JP 2003411322 A JP2003411322 A JP 2003411322A JP 4280616 B2 JP4280616 B2 JP 4280616B2
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- 238000003898 horticulture Methods 0.000 title description 2
- 239000000758 substrate Substances 0.000 claims description 29
- 229910000831 Steel Inorganic materials 0.000 claims description 25
- 239000010959 steel Substances 0.000 claims description 25
- 238000010413 gardening Methods 0.000 claims description 7
- 229910052759 nickel Inorganic materials 0.000 claims description 4
- 239000012535 impurity Substances 0.000 claims description 3
- 239000000203 mixture Substances 0.000 claims description 3
- 229910052758 niobium Inorganic materials 0.000 claims description 2
- 238000005496 tempering Methods 0.000 description 15
- 230000000694 effects Effects 0.000 description 11
- 239000000463 material Substances 0.000 description 9
- 238000010791 quenching Methods 0.000 description 7
- 230000000171 quenching effect Effects 0.000 description 7
- 238000005452 bending Methods 0.000 description 6
- 230000007423 decrease Effects 0.000 description 6
- 229910001566 austenite Inorganic materials 0.000 description 5
- 229910052804 chromium Inorganic materials 0.000 description 5
- 208000019300 CLIPPERS Diseases 0.000 description 4
- 244000269722 Thea sinensis Species 0.000 description 4
- 230000002411 adverse Effects 0.000 description 4
- 208000021930 chronic lymphocytic inflammation with pontine perivascular enhancement responsive to steroids Diseases 0.000 description 4
- 238000005299 abrasion Methods 0.000 description 3
- 229910045601 alloy Inorganic materials 0.000 description 3
- 239000000956 alloy Substances 0.000 description 3
- 229910052748 manganese Inorganic materials 0.000 description 3
- 229910052750 molybdenum Inorganic materials 0.000 description 3
- 150000004767 nitrides Chemical class 0.000 description 3
- 229910052698 phosphorus Inorganic materials 0.000 description 3
- 229910052710 silicon Inorganic materials 0.000 description 3
- 238000009864 tensile test Methods 0.000 description 3
- 229910052720 vanadium Inorganic materials 0.000 description 3
- 244000025254 Cannabis sativa Species 0.000 description 2
- 241000196324 Embryophyta Species 0.000 description 2
- 229910052799 carbon Inorganic materials 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- 238000009863 impact test Methods 0.000 description 2
- 150000001247 metal acetylides Chemical class 0.000 description 2
- 229920006395 saturated elastomer Polymers 0.000 description 2
- 230000004580 weight loss Effects 0.000 description 2
- 229910004298 SiO 2 Inorganic materials 0.000 description 1
- 238000000137 annealing Methods 0.000 description 1
- 229910052785 arsenic Inorganic materials 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 230000003749 cleanliness Effects 0.000 description 1
- 230000001143 conditioned effect Effects 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 238000005098 hot rolling Methods 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 238000011084 recovery Methods 0.000 description 1
- 238000005096 rolling process Methods 0.000 description 1
- 238000002791 soaking Methods 0.000 description 1
- 239000006104 solid solution Substances 0.000 description 1
- 238000009628 steelmaking Methods 0.000 description 1
- 230000008685 targeting Effects 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
- 238000004804 winding Methods 0.000 description 1
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Description
本発明は、ヘッジトリマー，バリカン等の園芸機械に装着され、切れ味，耐久性に優れた刈刃に関する。 The present invention relates to a cutting blade that is mounted on a gardening machine such as a hedge trimmer and a clipper and has excellent sharpness and durability.
園芸機械には、通常、草木用と小枝，茶葉等用とで刈刃を区別している。草刈刃は比較的柔らかい草木を対象としているので、高速回転するディスク状刈刃が通常使用されている。草木に比べて硬い小枝，茶葉等を対象とする場合、ディスク状刈刃をもつ園芸機械では刃先に過剰な負荷がかかって破損しやすいので、ディスク状刈刃に比較して低速で刈刃を往復動させるヘッジトリマー型，バリカン型等の園芸機械が使用される。 Horticulture machines usually distinguish cutting blades for plants and for twigs, tea leaves and the like. Since the grass cutting blade is intended for relatively soft vegetation, a disk-shaped cutting blade rotating at high speed is usually used. When targeting hard twigs, tea leaves, etc. compared to plants, gardening machines with disk-shaped cutting blades are subject to excessive load on the cutting edge and are likely to break. A gardening machine such as a hedge trimmer type or a hair clipper type that reciprocates is used.
ヘッジトリマーは、公園，道路分離帯，茶畑等における小枝の刈込みに使用され、作業者を起点として刈刃を前後に往復動させるタイプである。バリカンも同様な小枝の刈込みに使用されるが、作業者の左右方向に刈刃が往復動する。小枝の刈込み作業は、刃先の切れ味に作業効率が大きく影響される。この点、草刈刃では４７ＨＲＣ程度の刈刃基板（特許文献１）が使用可能であったが、ヘッジトリマーやバリカンではより硬質の５０ＨＲＣ以上に調質された刈刃基板が必要となる。
小枝の刈込みに際し、コンクリート，壁等の障害物に刈刃が誤って接触すると、刈刃が欠けて飛散する。垣根等の中に紛れ込んでいる針金等も、刈刃を破損，折損させる原因である。ある程度の強度，剛性をもつ刈刃基板に靭性，延性を付与することにより、刈刃の破損，折損を少なくできる。そのため、焼入れで硬質化した刈刃基板を焼き戻すことにより、４７〜５２ＨＲＣ程度の硬さを維持しながら靭性，延性を回復させている。 When cutting a twig, if the cutting blade accidentally contacts an obstacle such as concrete or a wall, the cutting blade is chipped and scattered. Wires and the like mixed in the fences are also a cause of breaking or breaking the cutting blade. By imparting toughness and ductility to a cutting blade substrate having a certain degree of strength and rigidity, it is possible to reduce the damage and breakage of the cutting blade. Therefore, the toughness and ductility are recovered by maintaining the hardness of about 47 to 52 HRC by tempering the cutting blade substrate hardened by quenching.
刈刃基板の折損や破片の飛散は、園芸機械使用者にとって非常に危険な事態である。そのため、刈刃基板の硬さを犠牲にしても靭性，延性の回復に主眼を置きがちである。使用者の安全性を高めるため、刃先の角度を緩くすることにより刃欠けや折損を防止することもある。しかし、刈刃基板の硬度低下は刃物にとって最も重要な切れ味が低下することを意味し、剛性の低下は刈刃基板が使用できなくなる程度に捩れ変形しやすくなる原因である。 Breaking of the cutting blade substrate and scattering of debris are extremely dangerous for gardening machine users. For this reason, even if the hardness of the cutting blade substrate is sacrificed, it tends to focus on the recovery of toughness and ductility. In order to enhance the safety of the user, the chipping or breakage may be prevented by reducing the angle of the blade edge. However, the reduction in the hardness of the cutting blade substrate means that the sharpness that is most important for the blade is reduced, and the reduction in rigidity is a cause that the cutting blade substrate is easily twisted and deformed to such an extent that it cannot be used.
本発明は、このような問題を解消すべく案出されたものであり、刈刃基板に使用する鋼板の成分及び金属組織を適正管理することにより、刈刃に必要な切れ味を維持しながらも、強度，剛性，靭性，延性，耐摩耗性の全てにおいて優れた特性を呈する園芸機械用刈刃を提供することを目的とする。 The present invention has been devised to solve such problems, while maintaining the sharpness necessary for the cutting blade by properly managing the components and metal structure of the steel plate used for the cutting blade substrate. An object of the present invention is to provide a cutting blade for a gardening machine that exhibits excellent properties in all of strength, rigidity, toughness, ductility, and wear resistance.
本発明の園芸機械用刈刃は、駆動源からの動力を受けて前後方向又は左右方向に高速往復動する刈刃であり、Ｃ：０.５〜０.７質量％，Ｓｉ：０.５質量％以下，Ｍｎ：０.１〜２.０質量％，Ｐ：０．０２質量％以下，Ｓ：０.０１質量％以下，Ｃｒ：０．１〜１.５質量％以下と、さらに必要に応じてＭｏ：０.５質量％以下，Ｖ：０.５質量％以下，Ｎｉ：０.１〜２.０質量％，Ｔｉ：０.０１〜０.１質量％，Ｎｂ：０.０１〜０.１質量％，Ｂ：０.０００３〜０.０１質量％の１種又は２種以上を含み、残部がＦｅ及び不可避的不純物からなり、かつＸ＝３.５Ｍｎ＋４.２Ｃｒ＋３.３Ｍｏ＋４.８Ｖ＋０.６Ｎｉで定義されるＸ値が３〜８に調整された組成をもち、硬さ：５０ＨＲＣ以上に調質された熱処理鋼板で刈刃基板が作製されていることを特徴とする。 The cutting blade for horticultural machines of the present invention is a cutting blade that reciprocates at high speed in the front-rear direction or the left-right direction by receiving power from a drive source, and C: 0.5 to 0.7 mass%, Si: 0.5. Less than mass%, Mn: 0.1 to 2.0 mass%, P: 0.02 mass% or less, S: 0.01 mass% or less, Cr: 0.1 to 1.5 mass% or less, and further necessary According to the following: Mo: 0.5 mass% or less, V: 0.5 mass% or less, Ni: 0.1-2.0 mass%, Ti: 0.01-0.1 mass%, Nb: 0.01 ~ 0.1% by mass, B: 0.0003 to 0.01% by mass of one or more, the balance being Fe and inevitable impurities, and X = 3.5Mn + 4.2Cr + 3.3Mo + 4.8V + 0 The cutting blade substrate is made of a heat-treated steel sheet having a composition in which the X value defined by .6Ni is adjusted to 3 to 8 and having a hardness of 50 HRC or higher. To.
刈刃基板に従来から使用されているＳＫＳ５，ＳＫＳ５１等の鋼材は、強度（硬さ），耐摩耗性を確保するためＣ含有量を０.７５質量％以上に調節している。熱処理後の強度が同じであっても、Ｃ含有量が低いほど靭性，延性が向上する。しかし、耐摩耗性に有効な炭化物の形成にＣを利用しているので、極端なＣの低下は耐摩耗性の面から好ましくない。耐摩耗性に悪影響を及ぼさないＣ低下は、Ｃ：０.５〜０.７質量％の範囲にある。 Steel materials such as SKS5 and SKS51 conventionally used for cutting blade substrates have their C content adjusted to 0.75% by mass or more in order to ensure strength (hardness) and wear resistance. Even if the strength after heat treatment is the same, the lower the C content, the better the toughness and ductility. However, since C is used for the formation of a carbide effective for wear resistance, an extreme decrease in C is not preferable from the viewpoint of wear resistance. The C decrease that does not adversely affect the wear resistance is in the range of C: 0.5 to 0.7% by mass.
そこで、Ｃ：０.５〜０.７質量％の系を前提に、合金成分，熱処理条件が強度，耐摩耗性，靭性，延性に及ぼす影響を調査した。所望の硬さに調質する焼戻し温度は低Ｃ化に伴って低下するが、過度に低い焼戻し温度ではプレステンパー等の形状修正にとって好ましくない。そこで、適量のＣｒ，Ｍｏ，Ｖ，Ｎｉ等を添加することにより、焼戻し軟化抵抗を高めている。Ｃｒ，Ｍｏ，Ｖ，Ｎｉ等は、Ｍｎと共に鋼材の焼入れ性を改善する上でも有効な成分である。 Therefore, on the premise of a system of C: 0.5 to 0.7% by mass, the effects of alloy components and heat treatment conditions on strength, wear resistance, toughness, and ductility were investigated. Although the tempering temperature for tempering to a desired hardness decreases as the C content decreases, an excessively low tempering temperature is not preferable for shape correction of a press temper or the like. Therefore, the temper softening resistance is increased by adding an appropriate amount of Cr, Mo, V, Ni or the like. Cr, Mo, V, Ni and the like are effective components for improving the hardenability of the steel material together with Mn.
このような刈刃基板の要求特性を考慮し、Ｘ＝３.５Ｍｎ＋４.２Ｃｒ＋３.３Ｍｏ＋４.８Ｖ＋０.６Ｎｉと定義されるＸ値を３〜８の範囲に調節した成分設計を採用すると、調質硬さを５０ＨＲＣ以上に高めても、従来材と同等以上の靭性，延性が確保されることがわかった。しかも、耐摩耗性に優れているので、良好な切れ味が長期間にわたって維持される園芸機械用刈刃が得られる。関係式：Ｘ＝３.５Ｍｎ＋４.２Ｃｒ＋３.３Ｍｏ＋４.８Ｖ＋０.６Ｎｉは、本発明者等による多数の実験結果から見出され、刈刃基板の要求特性を満足する合金設計の重要な指標である。
以下、刈刃基板に使用される鋼材の成分，含有量等を説明する。
Considering the required characteristics of the cutting blade substrate, adopting a component design in which the X value defined as X = 3.5Mn + 4.2Cr + 3.3Mo + 4.8V + 0.6Ni is adjusted within the range of 3-8, It has been found that even if the thickness is increased to 50 HRC or more, toughness and ductility equal to or higher than those of conventional materials are secured. And since it is excellent in abrasion resistance, the cutting blade for garden machines in which favorable sharpness is maintained over a long period of time is obtained. The relational expression: X = 3.5Mn + 4.2Cr + 3.3Mo + 4.8V + 0.6Ni is found from many experimental results by the present inventors and is an important index of alloy design satisfying the required characteristics of the cutting blade substrate.
Hereinafter, the components, contents, and the like of the steel material used for the cutting blade substrate will be described.
Ｃ：０.５〜０.７質量％
園芸機械用刈刃に必要な強度，耐摩耗性を確保し、切れ味を持続させるため０.５質量％以上が必要であるが、Ｃ含有量の増加に伴い靭性，延性が低下するので０.７質量％に上限を設定した。
Ｓｉ：０.５質量％以下
製鋼段階で溶鋼の脱酸剤として添加される成分であり、焼戻しによる軟化を抑制する作用も呈する。しかし、過剰添加すると脱酸生成物ＳｉＯ2が鋼中に残存し、鋼の清浄度，靭性を低下させるので０.５質量％を上限とした。
C: 0.5-0.7 mass%
0.5% by mass or more is necessary to ensure the strength and wear resistance necessary for the cutting blade for horticultural machinery and to maintain the sharpness. However, since the toughness and ductility decrease as the C content increases, the amount is decreased. The upper limit was set to 7% by mass.
Si: 0.5% by mass or less Si is a component added as a deoxidizer for molten steel in the steelmaking stage, and also exhibits an effect of suppressing softening due to tempering. However, if it is excessively added, the deoxidation product SiO 2 remains in the steel and lowers the cleanliness and toughness of the steel, so the upper limit was made 0.5 mass%.
Ｍｎ：０.１〜２.０質量％
焼入れ性の向上に有効な成分であり、０.１質量％以上でＭｎの添加効果がみられる。しかし、過剰添加は延性，靭性を低下させるので、２.０質量％を上限とした。
Ｐ：０.０２質量％以下
焼入れ時にオーステナイト粒界に偏析して靭性，延性を低下させる有害成分であり、可能な限りＰ含有量を下げることが好ましいが、上限を０.０２質量％とすることによりＰ起因の悪影響が抑制される。
Mn: 0.1 to 2.0% by mass
It is an effective component for improving hardenability, and the effect of adding Mn is observed at 0.1% by mass or more. However, excessive addition reduces ductility and toughness, so 2.0 mass% was made the upper limit.
P: 0.02 mass% or less It is a harmful component that segregates at the austenite grain boundaries during quenching and lowers toughness and ductility. It is preferable to lower the P content as much as possible, but the upper limit is set to 0.02 mass% As a result, adverse effects caused by P are suppressed.
Ｓ：０.０１質量％以下
亀裂の起点となるＭｎＳを鋼中に生成して靭性，延性を低下させる有害成分であるが、上限を０.０１質量％とすることにより実質的な悪影響がなくなる。
Ｃｒ：０．１〜１.５質量％
Ｍｎと同様に焼入れ性の向上に有効な成分であり、耐摩耗性改善効果もある。焼入れ性の改善には０.１質量％以上のＣｒとする。しかし、過剰添加は未溶解炭化物が多量生成する原因であり、未溶解炭化物を起点とする亀裂が生じやすく、靭性，延性に悪影響を及ぼすので、Ｃｒ含有量の上限を１.５質量％に設定した。
S: not more than 0.01% by mass MnS, which is the starting point of cracking, is a harmful component that lowers toughness and ductility in steel, but there is no substantial adverse effect by setting the upper limit to 0.01% by mass. .
Cr: 0.1 to 1.5% by mass
Like Mn, it is an effective component for improving hardenability and also has an effect of improving wear resistance. To improve hardenability, 0.1 mass% or more Cr is used . However, excessive addition causes a large amount of undissolved carbides, and cracks originating from the undissolved carbides are likely to occur, adversely affecting toughness and ductility. Therefore, the upper limit of Cr content is set to 1.5% by mass. did.
Ｍｏ：０.５質量％以下
焼入れ性，焼戻し軟化抵抗に有効な成分であり、Ｍｎ，Ｃｒの過剰添加に起因する靭性低下を抑制するために補助的に添加される。しかし、高価な元素であり、過剰添加は鋼材コストの上昇を招くので、上限を０.５質量％とした。
Ｖ：０.５質量％以下
焼入れ時に結晶粒を微細化し、刈刃基板の靭性を向上させるが、過剰添加は鋼材コストの上昇を招くので、上限を０.５質量％とした。
Mo: 0.5% by mass or less Mo is an effective component for hardenability and temper softening resistance, and is supplementarily added to suppress a decrease in toughness due to excessive addition of Mn and Cr. However, since it is an expensive element and excessive addition causes an increase in steel material cost, the upper limit is set to 0.5 mass%.
V: 0.5% by mass or less The crystal grains are refined at the time of quenching to improve the toughness of the cutting blade substrate. However, excessive addition causes an increase in steel material cost, so the upper limit was made 0.5% by mass.
Ｎｉ：０.１〜２.０質量％
必要に応じて添加される成分であり、焼入れ性，靭性の向上に有効である。Ｎｉの添加効果は０.１質量％以上でみられるが、２.０質量％で飽和し、それ以上添加しても鋼材コストが上昇するだけである。
Ｔｉ：０.０１〜０.１質量％
必要に応じて添加される成分であり、Ｎと結合して窒化物を形成し、焼入れ時にオーステナイト粒の粗粒化を抑え、焼入れ性向上に有効な固溶Ｂが窒化物として消費されることを防止する。Ｔｉの添加効果は０.０１質量％以上でみられるが、旧オーステナイト粒の微細化には０.１質量％で十分である。
Ni: 0.1-2.0 mass%
It is a component added as necessary, and is effective in improving hardenability and toughness. The effect of addition of Ni is seen at 0.1% by mass or more, but it is saturated at 2.0% by mass, and adding more will only increase the cost of the steel material.
Ti: 0.01-0.1 mass%
It is a component that is added as necessary, and forms nitrides by combining with N, suppresses coarsening of austenite grains during quenching, and solid solution B effective for improving hardenability is consumed as nitrides To prevent. The effect of addition of Ti is observed at 0.01% by mass or more, but 0.1% by mass is sufficient for refinement of prior austenite grains.
Ｎｂ：０.０１〜０.１質量％
必要に応じて添加される成分であり、炭窒化物を形成して焼入れ時にオーステナイト粒の粗粒化を抑え、焼入れ性向上に有効な固溶Ｂが窒化物として消費されることを防止する。Ｎｂの添加効果は０.０１質量％以上でみられるが、旧オーステナイト粒の微細化には０.１質量％で十分である。
Ｂ：０.０００３〜０.０１質量％
必要に応じて添加される成分であり、焼入れ性，靭性の向上に有効な成分であり、０.０００３質量％以上でＢの添加効果がみられる。しかし、多量添加しても効果が飽和するので、Ｂ含有量の上限を０.０１質量％に設定した。
Nb: 0.01 to 0.1% by mass
It is a component added as necessary, and forms carbonitrides to suppress coarsening of austenite grains during quenching, and prevents solute B effective for improving hardenability from being consumed as nitrides. The effect of Nb addition is observed at 0.01% by mass or more, but 0.1% by mass is sufficient for refinement of prior austenite grains.
B: 0.0003-0.01 mass%
It is a component added as necessary, is an effective component for improving hardenability and toughness, and the effect of adding B is observed at 0.0003 mass% or more. However, even if a large amount is added, the effect is saturated, so the upper limit of the B content was set to 0.01% by mass.
Ｘ値（Ｘ=３.５Ｍｎ+４.２Ｃｒ+３.３Ｍｏ+４.８Ｖ+０.６Ｎｉ）：３〜８
焼入れ性，焼戻し軟化抵抗に合金成分が及ぼす影響を表し指標であり、Ｘ値を３〜８の範囲に調整することにより刈刃基板の要求特性を満足する鋼材が得られる。３未満のＸ値では、焼入れ性が十分でなく、しかも所望の硬さに調質した場合に焼戻し温度が低くなってプレステンパーによる形状修正が困難になる。すなわち、園芸機械用刈刃は焼戻しと同時にプレステンパーによって形状修正するが、３未満のＸ値ではプレステンパー後に良好な形状が得られがたい。逆に８を超えるＸ値では、靭性，延性が低下する。
X value (X = 3.5Mn + 4.2Cr + 3.3Mo + 4.8V + 0.6Ni): 3-8
It is an index representing the influence of alloy components on hardenability and temper softening resistance, and by adjusting the X value in the range of 3 to 8, a steel material satisfying the required characteristics of the cutting blade substrate can be obtained. When the X value is less than 3, the hardenability is not sufficient, and the tempering temperature is lowered when the tempering is performed to a desired hardness, making it difficult to correct the shape with a press temper. That is, the shape of the gardening machine blade is corrected by press tempering at the same time as tempering. However, when the X value is less than 3, it is difficult to obtain a good shape after press tempering. Conversely, if the X value exceeds 8, the toughness and ductility are reduced.
表１に示す鋼材を溶製し、仕上げ温度：８５０℃，巻取り温度：５７０℃の熱延で板厚２.５ｍｍの熱延板を製造した。熱延板に７３０℃×２０時間の焼鈍を施した後、８００〜８５０℃×均熱５分→水焼入れで焼き入れし、３０分の焼戻しで硬さを調質した。硬さは、焼戻し温度を２５０〜４５０℃の温度範囲で変更することにより調整した。 The steel materials shown in Table 1 were melted, and hot rolled sheets with a thickness of 2.5 mm were manufactured by hot rolling at a finishing temperature of 850 ° C. and a winding temperature of 570 ° C. After subjecting the hot-rolled sheet to annealing at 730 ° C. for 20 hours, it was quenched by 800-850 ° C. × soaking for 5 minutes → water quenching and tempered by tempering for 30 minutes. The hardness was adjusted by changing the tempering temperature in a temperature range of 250 to 450 ° C.
熱処理後の鋼材（板厚：２.５ｍｍ）から試験片を切り出し、曲げ試験，引張試験，衝撃試験，摩耗試験，プレステンパー試験に供した。
曲げ試験では、圧延方向に直交する方向に沿って採取した幅３０ｍｍ，長さ２００ｍｍの試験片を用い、Ｖブロック上に載置した試験片にポンチを押し当てて９０度曲げした。ポンチの先端半径によって試験片の曲げ半径を変え、ｎ＝５枚で割れなければ限界曲げ半径として評価した。そして、先端曲げ半径が７ｔ以下（ｔ：試験片の板厚）を割れのない刈刃基板と判定した。
A test piece was cut out from the heat-treated steel (plate thickness: 2.5 mm) and subjected to a bending test, a tensile test, an impact test, an abrasion test, and a press temper test.
In the bending test, a test piece with a width of 30 mm and a length of 200 mm collected along the direction perpendicular to the rolling direction was used, and a punch was pressed against the test piece placed on the V block and bent 90 degrees. The bending radius of the test piece was changed depending on the tip radius of the punch, and if it was not broken at n = 5, it was evaluated as a limit bending radius. A tip bending radius of 7 t or less (t: thickness of the test piece) was determined as a cutting blade substrate without cracks.
引張試験では、Ｌ方向に沿って採取したJIS 13号B試験片を用い、JIS Z2241に準拠した引張試験で０.２％耐力を測定した。０.２％耐力の測定値を剛性の指標とし、０.２％耐力：１４５０Ｎ／ｍｍ2以上を剛性の高い刈刃基板と判定した。
衝撃試験では、Ｃ方向に沿って採取した２ｍｍＶノッチ試験片をJIS Z2242に準拠して衝撃値を測定した。衝撃値が２０Ｊ／ｃｍ2以上を靭性の高い刈刃基板と判定した。
In the tensile test, a 0.2% proof stress was measured by a tensile test based on JIS Z2241, using JIS No. 13 B specimens taken along the L direction. The measured value of 0.2% proof stress was used as an index of rigidity, and 0.2% proof stress: 1450 N / mm 2 or more was determined to be a highly rigid cutting blade substrate.
In the impact test, the impact value was measured in accordance with JIS Z2242 for a 2 mmV notch test piece collected along the C direction. An impact value of 20 J / cm 2 or more was determined as a cutting blade substrate having high toughness.
摩耗試験では、幅６０ｍｍ，長さ１００ｍｍの試験片を回転軸に装着し、径３ｍｍ，６５ＨＲＣのショットグリットを充填したドラム中に埋没させ、３００ｒｐｍの速度で回転させた。回転を２００時間継続した後、ドラムから取り出した試験片を重量測定した。試験前後の重量から試験片の摩耗減量を質量比として算出し、摩耗減量２.０質量％以下を耐摩耗性に優れた刈刃基板と判定した。
プレステンパー試験では、幅３０ｍｍ，長さ２００ｍｍの曲げ試験片を定盤で挟み、熱処理された試験片の平坦度をディプスゲージで測定した。試験片長さ２００ｍｍについて測定した高低差をもって平坦度とし、１.０ｍｍ以下の平坦度をプレステンパーによる形状修正が良好な刈刃基板と判定した。
In the wear test, a test piece having a width of 60 mm and a length of 100 mm was mounted on a rotating shaft, embedded in a drum filled with shot grit having a diameter of 3 mm and 65 HRC, and rotated at a speed of 300 rpm. After the rotation was continued for 200 hours, the test piece taken out from the drum was weighed. From the weight before and after the test, the weight loss of the test piece was calculated as a mass ratio, and the weight loss of 2.0% by mass or less was determined to be a cutting blade substrate having excellent wear resistance.
In the press temper test, a bending test piece having a width of 30 mm and a length of 200 mm was sandwiched between surface plates, and the flatness of the heat-treated test piece was measured with a depth gauge. The difference in height measured for a test piece length of 200 mm was defined as flatness, and a flatness of 1.0 mm or less was determined to be a cutting blade substrate with good shape correction by a press temper.
表２の試験結果にみられるように、本発明で規定した成分条件を満足する鋼Ｄ，Ｇ，Ｇ-2，Ｎ，Ｏ，Ｑから作製された刈刃基板は、５０ＨＲＣ以上の硬さでありながら何れも剛性，平坦度，靭性，延性が良好で、刃物として最も重要な特性である耐摩耗性にも極めて優れている。したがって、長期にわたって良好な切れ味を維持する園芸機械用刈刃として使用されることが判る。 As seen in the test results in Table 2, a cutting blade substrate made of steel D, G, G-2, N, O, Q that satisfies the component conditions defined in the present invention has a hardness of 50 HRC or more. However, they all have excellent rigidity, flatness, toughness, and ductility, and are extremely excellent in wear resistance, which is the most important characteristic of a blade. Therefore, it turns out that it is used as a cutting blade for horticultural machines that maintains a good sharpness over a long period of time.
これに対し、Ｃ量の低い鋼Ａから作製した刈刃基板は、強度，靭性，延性が良好であるものの、平坦度が悪く、耐摩耗性にも劣っていた。Ｘ値が低い鋼Ｂ，Ｋから作製した刈刃基板は、焼き入れ不良で調質硬さを確保できず、強度，剛性が不足し、耐摩耗性，平坦度にも劣っていた。また、鋼Ｋ-2では、調質硬さを確保するため低温で焼き戻した結果、平坦度が非常に悪化していた。Ｐ，Ｓ，Ｓｉを過剰に含む鋼Ｃ，Ｐ，Ｌから作製された刈刃基板は、鋼中介在物に起因して靭性，延性に劣っていた。Ｃ，Ｓｉ，Ｍｎ，Ｃｒ，Ｍｏ等の過剰量を添加した鋼Ｅ，Ｆ，Ｈ，Ｉ，Ｌ，Ｍは、調質後の硬さが高いものの靭性，延性に劣っていた。Ｘ値が高すぎる鋼Ｊから作製された刈刃基板も、靭性，延性に劣っていた。調質硬さが低い鋼Ｇ-3，Ｌ-2から作製した刈刃基板は、強度，剛性が不足し、耐摩耗性にも劣っていた。 On the other hand, although the cutting blade substrate produced from steel A having a low C amount has good strength, toughness, and ductility, it has poor flatness and poor wear resistance. Cutting blade substrates produced from steels B and K having a low X value could not ensure tempered hardness due to poor quenching, lacked strength and rigidity, and were inferior in wear resistance and flatness. Moreover, as a result of tempering steel K-2 at a low temperature to ensure tempered hardness, the flatness was very deteriorated. Cutting blade substrates produced from steels C, P, and L containing excessive amounts of P, S, and Si were inferior in toughness and ductility due to inclusions in the steel. Steels E, F, H, I, L, and M added with excess amounts of C, Si, Mn, Cr, Mo, etc. were inferior in toughness and ductility although their hardness after tempering was high. The cutting blade substrate produced from steel J having an X value that is too high was also inferior in toughness and ductility. Cutting blade substrates produced from steels G-3 and L-2 with low tempering hardness were insufficient in strength and rigidity and inferior in wear resistance.
以上に説明したように、本発明の園芸機械用刈刃は、５０ＨＲＣ以上の高硬度であるにも拘らず、靭性，延性に優れているため、使用中の破損やチッピングが抑制される。耐摩耗性にも優れているので長期にわたり良好な切れ味が維持され、小枝，茶葉等の刈込みが高い作業効率でしかも安全に行われる。 As described above, the cutting blade for horticultural machinery according to the present invention is excellent in toughness and ductility despite being high hardness of 50 HRC or higher, so that breakage and chipping during use are suppressed. Excellent abrasion resistance maintains good sharpness over a long period of time, and cutting of twigs, tea leaves, etc. is performed with high work efficiency and safety.
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