JPH0613745B2 - Manufacturing method of high toughness low alloy steel - Google Patents
Manufacturing method of high toughness low alloy steelInfo
- Publication number
- JPH0613745B2 JPH0613745B2 JP59254514A JP25451484A JPH0613745B2 JP H0613745 B2 JPH0613745 B2 JP H0613745B2 JP 59254514 A JP59254514 A JP 59254514A JP 25451484 A JP25451484 A JP 25451484A JP H0613745 B2 JPH0613745 B2 JP H0613745B2
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- JP
- Japan
- Prior art keywords
- steel
- quenching
- present
- toughness
- tempering
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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- Heat Treatment Of Articles (AREA)
- Heat Treatment Of Strip Materials And Filament Materials (AREA)
Description
【発明の詳細な説明】 〔産業上の利用分野〕 本発明は産業用車両の走行用、駆動用部品等に用いられ
る高靱性、高強度を有し、かつ焼入れ性、被削性に優れ
た低合金鋼の製造方法に関する。DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention has high toughness and high strength used for parts for driving and driving of industrial vehicles, and has excellent hardenability and machinability. The present invention relates to a method for manufacturing low alloy steel.
産業用車両の走行用、駆動用部品としてトラックリン
ク、クランクシャフト、ステアリングナックル等があ
る。例えば第２図および第３図に示す大型トラックリン
ク１は最小断面が２５mm以上の大断面を有するものであ
って、熱間鍛造によって成形されたのち、切削加工によ
り一対のブッシュ孔２が仕上げられ、この一対のブッシ
ュ孔２にワッシャ３を介してブッシュ４を圧入し、かつ
ブッシュ４にピン５を挿入固定してチェン状となし、つ
いでボルト６およびナット７によってシュー８に取付け
るもので、トラックリンクとシューとは一体的に回転し
産業車両を走行させるものである。There are truck links, crankshafts, steering knuckles, etc. as driving and driving parts for industrial vehicles. For example, the heavy-duty truck link 1 shown in FIGS. 2 and 3 has a large cross-section with a minimum cross section of 25 mm or more. After being formed by hot forging, a pair of bush holes 2 are finished by cutting. , A bush 4 is press-fitted into the pair of bush holes 2 via a washer 3, and a pin 5 is inserted and fixed to the bush 4 to form a chain, and then attached to a shoe 8 by a bolt 6 and a nut 7. The link and the shoe rotate integrally to drive the industrial vehicle.
この車両走行用部品には走行時に高い曲げ応力，捩り，
引張りおよび圧縮繰り返し応力などの負荷が加わるもの
であって、このような走行用，駆動用部品に用いる鋼に
対して高い靱性と強度を有し、かつ大断面を有する前記
部品の芯部まで焼入れ組織とするため優れた焼入れ性を
有していることが要求される。This vehicle running component has high bending stress,
A load such as tensile and compressive repetitive stress is applied, and it has high toughness and strength with respect to the steel used for such running and driving parts, and is quenched to the core of the part having a large cross section. Since it has a structure, it is required to have excellent hardenability.
また、産業用車両は−５０℃以下の寒冷地においても作
業をするものであるから、極低温域においても前記特性
があまり低下することがなく、特に低温靱性に優れてい
ることが要求される。Further, since the industrial vehicle is used even in a cold region of -50 ° C or lower, the above characteristics are not significantly deteriorated even in an extremely low temperature range, and it is particularly required to have excellent low temperature toughness. .
従来、前記のような特性が要求される産業用車両の走行
用，駆動用部品に用いる鋼として、SNCM431などのニッ
ケル・クロム・モリブデン鋼が使用されているが、SNCM
431はNiを1.8％含有することによって低温靱性について
は優れているが、反面1.8％のNiを含有することによっ
て熱間鍛造後の焼なましに長時間を要し、かつ被削性が
劣るとともに、多量のNiを含有することによって高価な
鋼となっていた。Conventionally, nickel-chromium-molybdenum steels such as SNCM431 are used as steels for running and driving parts of industrial vehicles that require the above characteristics.
431 is superior in low temperature toughness because it contains 1.8% Ni, but on the other hand, because it contains 1.8% Ni, it takes a long time to anneal after hot forging and the machinability is poor. At the same time, it became an expensive steel by containing a large amount of Ni.
また、SNCM431などの従来鋼は、焼入れに際してマルテ
ンサイトを主体とする組織となり、焼入れ時に大きな変
態応力、熱応力が加わることによって焼き割れが発生し
易いので、従来は水焼入れを行うことができず、油焼入
れを施していた。しかし、油焼入れにおいては、焼入れ
油の管理を十分に行わないと焼入れ硬さがバラツクとい
う欠点があり、例えば劣化した焼入れ油を使用して焼入
れを行うと、被焼入れ材の各部分において冷却速度が変
化することによって、焼入れ組織がマルテンサイトとベ
イナイトとが不均一に分布した組織となり、焼入れ硬さ
にバラツキが生じるとともに、所望の硬さが得られない
という問題があった。さらに、油焼入れにおいては十分
な焼入れ硬さが得られないため、従来焼入れに際して高
温で焼入れを行い、かつ焼もどしにおいては低温もどし
を施さなければならないため、油焼入れ材は靱性が低い
ものとなり、従来トラックリンクにおいては、使用中に
ブッシュ孔付近に割れが発生するという問題があった。In addition, conventional steels such as SNCM431 have a structure mainly composed of martensite during quenching, and quenching cracks easily occur due to large transformation stress and thermal stress applied during quenching. , It was oil-quenched. However, in oil quenching, there is a drawback that the quenching hardness varies if the quenching oil is not properly managed.For example, if quenching is performed using deteriorated quenching oil, the cooling rate in each part of the material to be quenched Change causes the quenching structure to become a structure in which martensite and bainite are non-uniformly distributed, resulting in variations in quenching hardness and a problem that desired hardness cannot be obtained. Further, in oil quenching, sufficient quenching hardness cannot be obtained, so conventional quenching requires high temperature quenching, and tempering requires low temperature tempering, so the oil-quenched material has low toughness, Conventional track links have a problem that cracks occur near the bush holes during use.
本発明は、従来鋼のSNCM431などのニッケル・クロム・
モリブデン鋼に比して、焼入れ硬さ、焼もどし硬さは同
等もしくはそれ以上の硬さを有し、引張り強さ、靱性に
おいては従来鋼より優れた焼もどしマルテンサイトと焼
もどしベイナイト組織とを有する高靱性低合金鋼の方法
を提供しようとするものである。The present invention is based on conventional steel such as SNCM431 nickel-chromium-
Compared with molybdenum steel, it has the same or higher quenching hardness and tempering hardness, and is superior in temper strength and toughness to conventional tempered martensite and tempered bainite microstructure. The present invention seeks to provide a method of high toughness low alloy steel having.
即ち、本発明者らの研究によれば、従来の含Ni鋼におい
て水焼入れを施した場合に焼き割れが発生するのは、該
含Ni鋼はオーステナイト領域が広いため、焼入れ時にほ
ぼマルテンサイト一相の組織となることと、Ｃ量が高い
ことが相俟って、水焼入れ時に大きな変態応力、熱応力
が被焼入れ材に加わることによって発生することを見出
した。そこで本発明においては、従来の含Ｎｉ鋼に比し
てＮｉ含有量を不純物量程度に止め、Ｍｏ含有量を高め
た鋼材を準備し、従来の含Ｎｉ鋼において施される油焼
入れの温度により低い温度の水焼入れを可能とする温度
で焼入れを行い、かつ従来の含Ｎｉ鋼において施される
焼もどしの温度より高温で焼もどしを行うことにより、
焼入れ時にマルテンサイトの析出を抑制して焼入れ組織
をマルテンサイトとベイナイトの混合組織とすることに
より変態応力を緩和し、焼もどしを施して鋼の組織を焼
もどしマルテンサイトと焼もどしベイナイトの混合組織
を有する高靱性低合金鋼を製造する方法を提供するもの
である。本発明によれば、産業用車両の走行用、駆動用
部品に適した、高靱性、高強度を有し、優れた被削性お
よび耐摩耗性を有する低合金鋼を製造することができ
る。That is, according to the research conducted by the present inventors, quench cracking occurs when water quenching is performed in a conventional Ni-containing steel because the Ni-containing steel has a wide austenite region, so that it is almost martensitic during quenching. It has been found that, together with the formation of a phase structure and the high C content, a large amount of transformation stress and thermal stress are applied to the hardened material during water quenching. Therefore, in the present invention, compared with the conventional Ni-containing steel, the Ni content is kept to about the amount of impurities and a steel material having an increased Mo content is prepared, and the temperature of the oil quenching performed in the conventional Ni-containing steel is changed. By quenching at a temperature that enables water quenching at a low temperature, and by performing tempering at a temperature higher than the tempering temperature performed in conventional Ni-containing steel,
By suppressing the precipitation of martensite during quenching, the transformation structure is relaxed by making the quenching structure a mixed structure of martensite and bainite, and tempering is performed to temper the structure of the steel. A mixed structure of martensite and tempered bainite. A method of producing a high toughness low alloy steel having According to the present invention, it is possible to manufacture a low alloy steel having high toughness, high strength, and excellent machinability and wear resistance, which is suitable for running and driving parts of an industrial vehicle.
本発明によれば、鋼材を810〜880℃に加熱し、冷却速度
２５℃／min以上で焼入れする際に、前記鋼材にＭｏを
0.33〜0.50％含有させ、かつＮｉを不純物量程度に止め
たため、マルテンサイトの析出が抑制されて焼入れ組織
をマルテンサイトとベイナイトの混合組織とすることに
より鋼材の変態応力が緩和され、焼割れを防止すること
ができる。ついで行われる540〜580℃での焼もどしの際
に微細な炭化物を生成させて、鋼の組織を焼もどしマル
テンサイトと焼もどしベイナイトの混合組織とし、従来
鋼に比べ同等またはそれ以上の強度と被削性を有し、従
来鋼より優れた靱性および耐摩耗性を有する低合金鋼が
製造される。According to the present invention, when a steel material is heated to 810 to 880 ° C and quenched at a cooling rate of 25 ° C / min or more, Mo is added to the steel material.
Since 0.33 to 0.50% is contained and Ni is kept to an impurity level, precipitation of martensite is suppressed and the quenching structure is a mixed structure of martensite and bainite, whereby the transformation stress of the steel material is relaxed and quench cracking occurs. Can be prevented. During the subsequent tempering at 540 to 580 ° C, fine carbides are generated to change the structure of the steel into a mixed structure of tempered martensite and tempered bainite, with strength equal to or higher than that of conventional steel. A low alloy steel is produced which has machinability and toughness and wear resistance superior to conventional steels.
本発明は、重量比にして、Ｃ：0.32〜0.40％、Ｓｉ：0.
15〜0.65％、Ｍｎ：0.65〜1.20％、Ｃｒ：0.90〜2.00
％、Ｍｏ：0.33〜0.50％を含有し、残部Ｆｅならびに不
純物元素からなる鋼材を、810〜880℃に加熱し、冷却速
度２５℃／min以上で焼入れを施して焼入れ組織をマル
テンサイトとベイナイトの混合組織とし、ついで540〜5
80℃で焼もどしを施すことにより、鋼の組織を焼もどし
マルテンサイトと焼もどしベイナイトの混合組織とする
高靱性低合金鋼の製造方法である。また本発明の前記鋼
材にさらにＶ：0.05〜0.30％、Ｎｂ：0.05〜0.30％の１
種または２種を含有せしめることにより、鋼の結晶粒を
さらに微細化させ、低温靱性のさらに優れた高靱性低合
金を製造することができる。また本発明の前記鋼材にさ
らにＳ：0.035％以下、Ｐｂ：0.15％以下のうち１種な
いし２種を含有せしめることにより、被削性のさらに優
れた高靱性低合金鋼を製造することができる。In the present invention, C: 0.32 to 0.40% and Si: 0.
15 to 0.65%, Mn: 0.65 to 1.20%, Cr: 0.90 to 2.00
%, Mo: 0.33 to 0.50%, and a steel material containing the balance Fe and impurity elements, heated to 810 to 880 ° C., and quenched at a cooling rate of 25 ° C./min or more to obtain a quenched structure of martensite and bainite. Mixed tissue, then 540-5
It is a method for producing a high toughness low alloy steel in which the structure of the steel is tempered at 80 ° C to obtain a mixed structure of martensite and tempered bainite. Further, in the steel material of the present invention, V: 0.05 to 0.30%, Nb: 0.05 to 0.30% 1
By containing one or two kinds, it is possible to further refine the crystal grains of steel and manufacture a high toughness and low alloy having further excellent low temperature toughness. Further, by adding one or two kinds of S: 0.035% or less and Pb: 0.15% or less to the steel material of the present invention, it is possible to manufacture a high toughness low alloy steel having further excellent machinability. .
以下に本発明の製造方法において準備する鋼材の成分限
定理由について説明する。Ｃは、産業用車両の走行用，
駆動用部品として要求される強度を確保するに必要な元
素であって、所望の硬さを得るためには少なくとも0.32
％以上のＣを含有させる必要があり、下限を0.32％とし
た。しかし0.40％を超えて含有させると、靱性が低下す
るとともに熱処理によって歪が発生し易くなるので上限
を0.40％とした。The reasons for limiting the components of the steel material prepared in the manufacturing method of the present invention will be described below. C is for driving industrial vehicles,
It is an element necessary to secure the strength required as a drive component, and at least 0.32 to obtain the desired hardness.
% Or more C must be contained, and the lower limit was made 0.32%. However, if the content exceeds 0.40%, the toughness deteriorates and the strain easily occurs by heat treatment, so the upper limit was made 0.40%.
Siは、脱酸作用を有するとともに地質に固溶して素地の
強度を向上し、さらに焼もどし軟化抵抗を有する元素で
あって、これらの効果を得るには0.15％以上含有させる
必要があり下限を0.15％とした。しかし必要以上にSiを
含有させると被削性が損なわれるので上限を0.65％とし
た。Si is an element that has a deoxidizing effect, forms a solid solution with the geology to improve the strength of the base material, and further has resistance to temper softening. It is necessary to contain 0.15% or more to obtain these effects. Was set to 0.15%. However, if Si is contained more than necessary, machinability is impaired, so the upper limit was made 0.65%.
MnはSiと同様に脱酸剤として用いられ、かつ焼入性を向
上させる元素であって、大型トラックリンクのような大
断面を有する走行用部品においても芯部まで焼入れ組織
とするためには0.65％以上含有させる必要があり、下限
を0.65％とした。しかし必要以上に含有させると水焼入
れ等により冷却速度を２５℃／min以上としたときにお
いて割れが発生し易くなるので、上限を1.20％とした。Mn is an element that is used as a deoxidizer like Si and improves the hardenability, and even in the case of running parts having a large cross section such as large truck links, it is necessary to have a hardened structure up to the core. It is necessary to contain 0.65% or more, and the lower limit was made 0.65%. However, if it is contained more than necessary, cracking tends to occur at a cooling rate of 25 ° C./min or more due to water quenching, etc., so the upper limit was made 1.20%.
Crは、Mnと同様じ焼入性を高め、かつ炭化物を形成して
耐摩耗性を向上させる元素であって、走行用部品として
必要な焼入れ性と耐摩耗性を得るには0.90％以上含有さ
せる必要があり、下限を0.90％とした。しかし多く含有
させると炭化物が粗大化し、かつ硬い炭化物が生成し、
かえって焼入性とを耐摩耗性を損うので、上限を2.0％
とした。Cr is an element that enhances hardenability similarly to Mn and also forms carbides to improve wear resistance. 0.90% or more is contained in order to obtain hardenability and wear resistance required for running parts. Therefore, the lower limit was set to 0.90%. However, if a large amount is included, the carbide becomes coarse and hard carbide is generated,
On the contrary, hardenability and wear resistance are impaired, so the upper limit is 2.0%.
And
Moは、本発明鋼の変態応力を緩和し、水焼入れを可能と
する優れた焼入れ性と、靱性および焼もどし軟化抵抗を
高め、さらに微細な炭化物を生成して耐摩耗性を向上さ
せる。本発明においては最も重要な元素であって、これ
らの効果を得るには少なくとも0.33％以上含有させる必
要があり、下限を0.33％とした。しかし必要以上に多く
含有させるとベイナイトノーズが後退し、水焼入れ時に
焼割れが発生し易くなり、かつMoは高価な元素であるの
で、上限を0.50％とした。Mo relaxes the transformation stress of the steel of the present invention, has excellent hardenability that enables water quenching, enhances toughness and temper softening resistance, and further produces fine carbides to improve wear resistance. It is the most important element in the present invention, and it is necessary to contain at least 0.33% or more in order to obtain these effects, and the lower limit was made 0.33%. However, if it is contained in a larger amount than necessary, the bainite nose will recede, quench cracks will easily occur during water quenching, and Mo is an expensive element, so the upper limit was made 0.50%.
ＶおよびNbは、炭窒化物を生成するとともに結晶粒を微
細化し、強度と靱性を向上させる元素であって、これら
の効果を得るには0.05％以上含有させる必要があり下限
を0.05％とした。しかし、ＶおよびNbはともに0.30％を
超えて含有させても効果の向上が小さいので、上限を0.
30％とした。V and Nb are elements that generate carbonitrides, refine the crystal grains, and improve strength and toughness. To obtain these effects, it is necessary to contain 0.05% or more, and the lower limit is 0.05%. . However, since the improvement of the effect is small even if V and Nb are contained in excess of 0.30%, the upper limit is set to 0.
30%.
Ｓは、MnSを生成して被削性を改善する元素であって、P
bは、鋼中において単独あるいは化合物を形成し、切削
時に切欠き効果と、潤滑作用により切削抵抗を減少させ
て工具寿命、切屑の破砕性を著しく改善する元素であ
る。しかし、ＳおよびPbは、その含有量が多くなると機
械的性質を損うものであるから、Ｓは0.035％、Pbは0.1
5％とその上限を規制した。S is an element that produces MnS to improve machinability, and P
b is an element that forms a single or compound in the steel and significantly improves the tool life and chip crushability by reducing the notch effect during cutting and the cutting resistance due to the lubricating action. However, since S and Pb impair mechanical properties when their contents increase, S is 0.035% and Pb is 0.1%.
Regulated 5% and its upper limit.
また、本発明において加熱温度を８１０〜８８０℃と限
定したのは、それぞれ８１０℃未満では不完全焼入れと
なり所望の硬さが得られず、また８８０℃を超えると結
晶粒が粗大化し靱性が低下するためであり、かつ焼入れ
時の冷却速度を２５℃／min以上としたのは、２５℃／m
in未満では十分な焼入れ硬さが得られないためである。
また、焼もどし温度を５４０〜５８０℃と限定したの
は、それぞれ５４０℃未満では十分な靱性が得られず、
かつ５８０℃を超えると硬さが低下しすぎるためであ
る。In the present invention, the heating temperature is limited to 810 to 880 ° C. The reason is that if the temperature is less than 810 ° C., incomplete quenching does not result in desired hardness, and if it exceeds 880 ° C., the crystal grains become coarse and the toughness decreases. The reason for this is that the cooling rate during quenching was set to 25 ° C / min or more because
This is because if it is less than in, sufficient quenching hardness cannot be obtained.
Further, the reason for limiting the tempering temperature to 540 to 580 ° C is that sufficient toughness cannot be obtained at temperatures below 540 ° C,
Moreover, if the temperature exceeds 580 ° C., the hardness becomes too low.
製造方法の実施例を用いた供試鋼Ａ〜Ｊ（以下単に本発
明鋼という）の化学成分を、本発明方法の焼入れ、焼も
どしの特長を比較により明らかにするために用いた供試
鋼Ｗ〜Ｚ（以下単に比較鋼という）の化学成分とともに
記載した表である。なお前記比較鋼のう ち、Ｗ鋼はSNCM431に基く従来鋼、Ｘ鋼は、本発明にお
いて準備される鋼材の成分と比べてＭｏ量の低いＳＣＭ
430に基く比較鋼、Ｙ鋼は、前記本発明において準備さ
れる鋼材の成分と比べてＣ量およびＭｏ量を低くした比
較鋼、Ｚ鋼は、前記本発明において準備される鋼材の成
分と比べてＭｎ量およびＭｏ量を低くした比較鋼であ
る。The test steels used to clarify the chemical composition of the test steels A to J (hereinafter simply referred to as the present invention steels) using the examples of the manufacturing method by comparing the characteristics of quenching and tempering of the present invention method by comparison. It is the table described together with the chemical composition of W to Z (hereinafter simply referred to as comparative steel). In addition, the comparative steel The W steel is a conventional steel based on SNCM431, and the X steel is an SCM having a lower Mo content than the components of the steel material prepared in the present invention.
Comparative steel based on 430, Y steel is a comparative steel in which the C content and Mo content are lower than the components of the steel material prepared in the present invention, and Z steel is compared with the components of the steel material prepared in the present invention. It is a comparative steel in which the amount of Mn and the amount of Mo are lowered.
なお、本発明鋼のＡ〜Ｊ鋼および比較鋼のＸ〜Ｚ鋼の欄
に記載のＮｉ量は、通常電気炉溶解において不純物とし
て含有されるＮｉ量を示したものである。The amounts of Ni described in the columns of A to J steels of the present invention steel and X to Z steels of comparative steels are the amounts of Ni contained as impurities in the electric furnace melting in general.
上記第１表に記載の化学成分を有する鋼を鋳造後、圧延
比５０以上で直径５０mmに熱間圧延を施して供試鋼と
し、これに焼入れ、焼もどし処理を行い、焼入れ時、焼
もどし時の硬さ、引張り強さ、伸び、絞り、シャルピー
衝撃値などの機械的性質を測定した。その結果を第２表
に示す。前記焼入れ、焼もどし温度は、比較鋼中従来鋼
であるＷ鋼については、従来技術に基いて８８０℃に加
熱して油焼入れを行い、次いで４８０℃で焼もどし処理
を行い、本発明鋼および残りの比較鋼については、８５
０℃に加熱して水焼入れを行い、次いで５６０℃で焼も
どし処理を行った。なお、本発明鋼および比較鋼中のＸ
鋼、Ｙ鋼およびＺ鋼の焼入れ時の冷却速度は２９℃／mi
n、Ｗ鋼の焼入れ時の冷却速度は５℃／minであった。ま
た引張り強さ、 伸び、絞りについては、JIS４号試験片を用いて測定
し、衝撃値はJIS３号試験片を用いて測定した。After casting the steel having the chemical composition shown in Table 1 above, it is hot-rolled to a diameter of 50 mm with a rolling ratio of 50 or more to obtain a sample steel, which is then subjected to quenching and tempering treatment, and at the time of quenching, tempering Mechanical properties such as hardness, tensile strength, elongation, drawing, and Charpy impact value were measured. The results are shown in Table 2. Regarding the quenching and tempering temperatures, for the W steel, which is a conventional steel among comparative steels, according to the conventional technique, it is heated to 880 ° C. for oil quenching, and then tempered at 480 ° C. 85 for the remaining comparative steels
Water quenching was performed by heating to 0 ° C., and then tempering treatment was performed at 560 ° C. In addition, X in the present invention steel and comparative steel
Cooling rate during quenching of steel, Y steel and Z steel is 29 ℃ / mi
The cooling rate during quenching of n and W steel was 5 ° C / min. Also tensile strength, The elongation and the drawing were measured using JIS No. 4 test pieces, and the impact values were measured using JIS No. 3 test pieces.
第２表から明らかなように、本発明鋼の場合は、電気炉
等の熱処理炉内で850℃に加熱し、冷却速度２９℃／min
で水焼入れを施し、560℃で焼もどしを施した結果、焼
入れ硬さがHB475〜525、焼もどし硬さがHB363〜３９９
の範囲内に、引張り強さが１１５〜１３８kg・ｆ／mm2
の範囲内に、伸びが11.3〜15.8の範囲内に、絞りが40.3
〜46.3の範囲内に、シャルピー衝撃値が7.4〜10.1kg・
ｆ−ｍ／cm2の範囲内にあるのに対し、従来鋼のＷ鋼（S
NCM431）は８８０℃で焼入れ、４８０℃で焼もどしとい
う高温焼入れ、低温焼もどしを施した結果、焼入れ硬さ
はHB485、焼もどし硬さはHB370であり、引張り強さは１
１９kg・ｆ／mm2と強度については優れているが、シャ
ルピー衝撃値については6.9kg・ｆ−ｍ／cm2と靱性につ
いては低い。As is clear from Table 2, in the case of the steel of the present invention, the steel was heated to 850 ° C in a heat treatment furnace such as an electric furnace and the cooling rate was 29 ° C / min.
As a result of water quenching at 560 ℃, quenching hardness HB475 ~ 525, tempering hardness HB363 ~ 399
Within the range, the tensile strength is 115 to 138 kg · f / mm 2
Within the range of, elongation is within the range of 11.3 to 15.8, the aperture is 40.3
Charpy impact value is 7.4 to 10.1kg within the range of to 46.3
While it is within the range of fm / cm 2 , the conventional steel W steel (S
NCM431) is tempered at 880 ℃, tempered at 480 ℃, and tempered at low temperature. As a result, the quenching hardness is HB485, the tempering hardness is HB370, and the tensile strength is 1
The strength is excellent at 19 kg · f / mm 2 , but the Charpy impact value is low at 6.9 kg · fm−cm 2 and the toughness is low.
また、比較鋼中の従来鋼であるＸ鋼（SCM430）およびそ
の他の比較鋼であるＹ鋼およびＺ鋼は８５０℃で水焼
入、５６０℃で焼もどしを施した結果、焼入硬さはHB38
5〜446、焼もどし硬さＨＢ２９７〜３４２とＷ鋼に比べ
て低く、かつ、引張り強さについても７２〜１０１kg・
ｆ／mm2とＷ鋼に比べて低く、前記Ｗ鋼や本発明鋼の場
合に比べて強度が劣っている。Further, among the comparative steels, the conventional steel X steel (SCM430) and the other comparative steels Y steel and Z steel were water-quenched at 850 ° C and tempered at 560 ° C. HB38
5-446, tempering hardness HB297-342, which is lower than that of W steel, and tensile strength is 72-101 kg.
The f / mm 2 is lower than that of the W steel, and the strength is inferior to that of the W steel and the steel of the present invention.
前記の従来鋼、比較鋼に対して本発明鋼であるＡ〜Ｊ鋼
はいずれも８５０℃という低い温度で水焼入し、かつ５
６０℃という高い温度で焼もどしを施しても焼入硬さは
HB475〜525、焼もどし硬さはHB363〜399と、1.8％ものN
iを含有する従来鋼であるＷ鋼と同等もしくはそれ以上
の硬さを有するものであり、かつ引張り強さについても
１１５〜１３８kg・ｆ／mm2とＷ鋼以上の優れた強度を
有するものである。さらに本発明鋼の場合は高温もどし
を施したことによりシャルピー衝撃値が7.4〜10.1kg・
ｆ−ｍ／cm2と靱性についてもＷ鋼に比べて大巾に優れ
ており、本発明によれば、高強度と高靱性とを有する低
合金鋼を製造することができる方法を提供するものであ
るということができる。In contrast to the conventional steel and the comparative steel, the A to J steels of the present invention were all water-quenched at a low temperature of 850 ° C. and 5
Even if tempered at a high temperature of 60 ° C, the quenching hardness is
HB475 ~ 525, temper hardness HB363 ~ 399, 1.8% N
It has a hardness equal to or higher than that of W steel, which is a conventional steel containing i, and has a tensile strength of 115 to 138 kg · f / mm 2, which is superior to W steel. is there. Further, in the case of the steel of the present invention, the Charpy impact value is 7.4 to 10.1 kg
The fm / cm 2 and toughness are far superior to those of W steel, and the present invention provides a method capable of producing a low alloy steel having high strength and high toughness. It can be said that
第３表は、第１表に示した供試鋼の焼入れ性について測
定をした結果を示す。これらの測定値は前記熱間圧延片
からジョミニー試験片を作製し、 焼入れ端から1.5mm，３mm，５mm，８mm，１１mm，１３m
m，１５mm，２５mmの各距離の部分の硬さを測定したも
のである。Table 3 shows the results of measuring the hardenability of the test steels shown in Table 1. These measured values were produced from the hot rolled piece to a Jominy test piece, 1.5mm, 3mm, 5mm, 8mm, 11mm, 13m from the quenched edge
The hardness is measured at each distance of m, 15 mm, and 25 mm.
第３表から明らかなように、従来鋼であるＸ鋼および比
較鋼であるＹ鋼、Ｚ鋼が、従来鋼Ｗに比して焼入れ硬さ
が低いのに対して、本発明鋼であるＡ〜Ｊ鋼の場合はＷ
鋼と同等あるいはそれ以上の硬さを有することが明あか
であり、本発明鋼は焼入れ性についても優れていること
がわかる。As is clear from Table 3, the conventional steel X steel and the comparative steels Y steel and Z steel have lower quenching hardness than the conventional steel W, whereas the invention steel A ~ W for J steel
It is clear that the steel of the present invention has hardness equal to or higher than that of steel, and it is clear that the steel of the present invention is also excellent in hardenability.
次に第１図に本発明鋼中のＢ鋼およびＦ鋼に焼入れ、焼
もどしを施した後の低温靱性を、従来鋼のＷ鋼とともに
測定した結果を比較して示す。低温靱性はJIS４号試験
片を作製し、２０℃〜−80℃の低温域で供試鋼のシャル
ピー衝撃値を測定したものである。Next, FIG. 1 shows a comparison of the results of measuring the low temperature toughness after quenching and tempering the B steel and F steel in the steels of the present invention together with the W steel of the conventional steel. The low temperature toughness is obtained by preparing a JIS No. 4 test piece and measuring the Charpy impact value of the sample steel in the low temperature range of 20 ° C to -80 ° C.
第１図から明らかなように、従来鋼であるＷ鋼の−40℃
におけるシャルピー衝撃値が5.2kg・ｆ−ｍ／cm2である
のに対し、本発明鋼であるＢ鋼、Ｆ鋼の場合は7.3〜7.8
kg・ｆ−ｍ／cm2であって、Ｗ鋼に比して大幅に高くな
っており、本発明鋼の場合は低温靱性についても優れて
いることがわかる。As is clear from Fig. 1, the W steel, which is a conventional steel, has a temperature of -40 ° C.
While the Charpy impact value at 5.2 kg · fm / cm 2 is 7.3 to 7.8 for steels B and F, which are the steels of the present invention.
It is kg · fm / cm 2 , which is significantly higher than that of W steel, and it is understood that the steel of the present invention is also excellent in low temperature toughness.
次に本発明の製造方法により得られた鋼の被削性を本発
明鋼についてはＢ鋼、Ｈ鋼、Ｉ鋼およびＪ鋼を選び、比
較鋼については従来鋼であるＷ鋼を選んで、対比する。
この対比試験は、前記各供試鋼について焼入れ、焼もど
し処理を施したものから、直径４０mm、長さ１０mmの素
材を用意し、これを定盤上に固定し、直径５mmのSKH9ス
トレートドリルを用いて、回転数1140rpm、推力３０kg
（重錘自由落下法）により、ドリル穿孔性を測定したも
のである。なお第４表には従来鋼であるＷ鋼のドリル穿
孔性を１００とした指数で示した。Next, regarding the machinability of the steel obtained by the production method of the present invention, B steel, H steel, I steel and J steel are selected for the present invention steel, and W steel which is a conventional steel is selected for the comparative steel, To contrast.
In this comparison test, a material with a diameter of 40 mm and a length of 10 mm is prepared from the above-mentioned steels that have been quenched and tempered, fixed on a surface plate, and a SKH9 straight drill with a diameter of 5 mm is prepared. Using, rotation speed 1140rpm, thrust 30kg
The drill piercing property was measured by the (weight free fall method). In Table 4, the index is shown with the drillability of W steel, which is a conventional steel, as 100.
第４表により明らかなように、本発明鋼の場合はいずれ
も従来鋼であるＷ鋼に比して優れた被削性を有してお
り、特に快削性元素であるＳ，Pbを含有せしめたＨ鋼、
Ｉ鋼およびＪ鋼は、Ｗ鋼に比して大幅に被削性を改善し
たものとなっている。 As is clear from Table 4, in the case of the steels of the present invention, each has excellent machinability as compared with the conventional steel W steel, and particularly contains the free-cutting elements S and Pb. Aged H steel,
The I steel and J steel have significantly improved machinability compared to the W steel.
本発明は産業車両の走行用，駆動用部品等に用いられる
高靱性低合金鋼の製造方法において、焼入れ、焼もどし
を施す鋼材として、Ｃを、要求強度を確保するため、お
よび靱性を低下させずかつ熱処理による歪の発生を阻止
する範囲の0.32〜0.40％、Siを、素地の強度を向上し、
かつ焼もどし軟化抵抗を有せしめるため、および被削性
を損わない範囲の0.15〜0.65％、Mnを、大断面を有する
鍛造部品の芯部まで焼入れ組織とするため、および焼入
れにあたり割れの発生を阻止する範囲の0.65〜1.20％、
Crを、大断面を有する鍛造部品の焼入れ性を得るととも
に微細な炭化物を形成して耐摩耗性を得るため、および
前記炭化物を粗大化せしめない範囲の0.90〜2.0％を含
有させるとともに、Moを、変態応力を緩和し、水焼入れ
を可能とする焼入れ性と、靱性および焼もどし軟化抵抗
を高め、さらに微細な炭化物を生成して耐摩耗性を向上
するため、およびベイナイトノーズが後退して水焼入れ
時に焼き割れが発生しない範囲の0.33〜0.50％を含有さ
せ、高い量のＣの存在下において水焼入れ時に大きな変
態応力、熱応力を被焼入れ材に加えるNiを積極的に添加
することなく、不純物量程度に止めた鋼材を準備し、こ
の鋼材を、従来産業車両の走行用，駆動用部品に用いら
れていたSNCM431に比して低い８１０〜８８０℃の温度
い加熱し、この温度から冷却速度２５℃／min以上で焼
入れし、次いで５４０〜５８０℃という高い温度で焼も
どしを施すことにより、従来鋼と同等もしくはそれ以上
の硬さおよび機械的性質を有し、特に靱性については大
幅に優れている高靱性低合金鋼を製造することができ
る。INDUSTRIAL APPLICABILITY The present invention relates to a method for producing a high toughness low alloy steel used for running and driving parts of an industrial vehicle, wherein C is used as a steel material to be quenched and tempered in order to secure required strength and to reduce toughness. Of 0.32 to 0.40% of Si, which prevents the generation of strain due to heat treatment, improves the strength of the base material,
In addition, in order to have tempering and softening resistance, and to make 0.15 to 0.65%, Mn of the range that does not impair machinability, Mn a hardened structure up to the core of a forged part with a large cross section, and cracking during hardening. 0.65 to 1.20% of the range to prevent
Cr, in order to obtain the hardenability of a forged part having a large cross section and to obtain wear resistance by forming fine carbide, and containing 0.90 to 2.0% of the range that does not coarsen the carbide, Mo In order to alleviate the transformation stress and enhance the hardenability that enables water quenching, toughness and temper softening resistance, and to generate fine carbides to improve wear resistance, and bainite nose recedes into water. 0.33 to 0.50% of the range where quench cracking does not occur at the time of quenching is contained, and in the presence of a high amount of C, large transformation stress and thermal stress are added to the material to be quenched during water quenching without actively adding Ni, Prepare a steel material containing only a small amount of impurities, heat this steel material to a temperature of 810 to 880 ° C, which is lower than that of SNCM431, which has been used for running and driving parts of conventional industrial vehicles, and then cool from this temperature. Speed By quenching at a temperature of 25 ° C / min or more and then tempering at a high temperature of 540 to 580 ° C, it has hardness and mechanical properties equal to or higher than conventional steel, and in particular toughness Excellent high toughness low alloy steel can be produced.
これに対し、比較鋼であるＸ鋼、Ｙ鋼およびＺ鋼は、Ｎ
ｉを不純物量程度しか含有しないが、本発明において準
備する鋼材の化学成分と比べて、Ｘ鋼はＭｏ量が低く、
Ｙ鋼はＣ量およびＭｏ量が低く、Ｚ鋼はＭｚ量およびＭ
ｏ量が低く、その結果焼入れ、焼もどし後の強度および
硬さにおいて、従来鋼であるＷ鋼（ＳＮＣＭ431）より
著しく劣っている。In contrast, the comparative steels X steel, Y steel and Z steel are N
Although i contains only about the amount of impurities, compared with the chemical composition of the steel material prepared in the present invention, X steel has a low Mo content,
Y steel has low C content and Mo content, and Z steel has Mz content and M content.
The amount of o is low, and as a result, the strength and hardness after quenching and tempering are significantly inferior to the conventional steel W steel (SNCM431).
従って本発明により製造された低合金鋼は、従来鋼であ
るＷ鋼（ＳＮＣＭ431）と同等またはそれ以上の強度を
保持しながら、より優れた靱性を有する鋼であるといえ
る。Therefore, it can be said that the low alloy steel produced according to the present invention is steel having more excellent toughness while maintaining strength equal to or higher than that of the conventional W steel (SNCM431).
また本発明の製造方法においては、準備される前記鋼材
にさらにＶ：0.05〜0.30％、Ｎｂ：0.05〜0.30％の１種
または２種を含有させるとにより、製造される低合金鋼
中に炭窒化物を生成させるとともに結晶粒を微細化さ
せ、これにより低温靱性のさらに向上した高靱性低合金
鋼を製造することができる。Further, in the production method of the present invention, by adding one or two of V: 0.05 to 0.30% and Nb: 0.05 to 0.30% to the prepared steel material, carbon is added to the produced low alloy steel. It is possible to produce a nitride and refine the crystal grains, thereby producing a high toughness low alloy steel with further improved low temperature toughness.
本発明によれば、焼入れ焼もどしを施す鋼材に含有させ
るＣ、Ｓｉ、Ｍｎ、ＣｒおよびＭｏを前記数値範囲に規
定し、Ｎｉを不純物量程度に止めたことにより、従来の
産業車両の走行用、駆動用部品に用いられていた含Ｎｉ
合金に比べ、810〜880℃の温度から２５℃／min以上の
冷却速度での低温焼入れを施し、高いＣ量にも拘らず適
量のＭｏの存在により、マルテンサイトの析出を抑制し
て焼入れ組織をマルテンサイトとベイナイトの混合組織
とすることにより焼入れ時の変態応力を緩和し、次いで
540〜580℃という高い温度で焼もどしを施すことによ
り、鋼の組織を焼もどしマルテンサイトと焼もどしベイ
ナイトの混合組織とすることができ、大断面を有する鋳
造部品においても焼き割れを発生させることなく芯まで
焼入れ焼もどし組織とすることができ、硬さおよび強度
が大であって被削性および耐摩耗性に優れた高靱性低合
金鋼を製造することができる。According to the present invention, C, Si, Mn, Cr, and Mo contained in the steel material to be quenched and tempered are regulated within the above numerical range, and Ni is kept to an amount of impurities, so that the conventional industrial vehicle can be run. , Ni-containing used for drive parts
Compared with alloys, low temperature quenching is performed at a cooling rate of 25 ° C / min or higher from a temperature of 810 to 880 ° C, and despite the high C content, the presence of an appropriate amount of Mo suppresses the precipitation of martensite and quenches the microstructure. Is a mixed structure of martensite and bainite to relax the transformation stress during quenching, and then
By tempering at a high temperature of 540 to 580 ° C, the structure of steel can be made into a mixed structure of tempered martensite and tempered bainite, and quench cracking can occur even in cast parts with large cross sections. It is possible to manufacture a high-toughness low-alloy steel that has a high hardness and strength, and has excellent machinability and wear resistance, since it can have a quenched and tempered structure up to the core.
第１図は本発明の実施例の鋼と比較鋼の低温靱性を示す
試験温度とシャルピー衝撃値との関係の線図、第２図は
本発明鋼の用途として適したトラックリンクの分解図、
第３図はその組立図を示す。 なお図中１はトラックリンク、２はブッシュ孔、４はブ
ッシュ、５はピン、８はシュー、をそれぞれ示すもので
ある。FIG. 1 is a diagram showing the relationship between the test temperature and the Charpy impact value showing the low temperature toughness of the steel of the example of the present invention and the comparative steel, and FIG. 2 is an exploded view of a track link suitable for use as the steel of the present invention.
FIG. 3 shows the assembly drawing. In the figure, 1 is a track link, 2 is a bush hole, 4 is a bush, 5 is a pin, and 8 is a shoe.
───────────────────────────────────────────────────── フロントページの続き (72)発明者 渡辺 武司 茨城県水海道市豊岡町丁1354の１ (56)参考文献 特開 昭58−93857（ＪＰ，Ａ) ＪＩＳ Ｇ 4105（1979） クロム モ リブデン鉄鋼材（ＳＣＭ430〜822化学成分 および熱処理) ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Takeshi Watanabe 1354-1354, Toyooka-cho, Mizukaido-shi, Ibaraki (56) References JP 58-93857 (JP, A) JIS G 4105 (1979) Chromium Molybden Steel Material (SCM430-822 chemical composition and heat treatment)
Claims (3)
0.15〜0.65％、Ｍｎ：0.65〜1.20％、Ｃｒ：0.90〜2.00
％、Ｍｏ：0.33〜0.50％を含有し、残部Ｆｅならびに不
純物元素からなる鋼材を810〜880℃に加熱し、冷却速度
２５℃／min以上で焼入れを施して焼入れ組織をマルテ
ンサイトとベイナイトの混合組織とし、ついで540〜580
℃で焼もどしを施し、鋼の組織を焼もどしマルテンサイ
トと焼もどしベイナイトの混合組織としたことを特徴と
する高靱性低合金鋼の製造方法。1. A weight ratio of C: 0.32 to 0.40%, Si:
0.15 to 0.65%, Mn: 0.65 to 1.20%, Cr: 0.90 to 2.00
%, Mo: 0.33 to 0.50%, the steel material consisting of the balance Fe and impurity elements is heated to 810 to 880 ° C., and is quenched at a cooling rate of 25 ° C./min or more to obtain a mixed structure of martensite and bainite. Organization and then 540-580
A method for producing a high-toughness low-alloy steel, characterized in that tempering is performed at ℃, and the structure of the steel is tempered to have a mixed structure of martensite and tempered bainite.
0.15〜0.65％、Ｍｎ：0.65〜1.20％、Ｃｒ：0.90〜2.00
％、Ｍｏ：0.33〜0.50％と、さらにＶ：0.05〜0.30％、
Ｎｂ：0.05〜0.30％のうち１種ないし２種を含有し、残
部Ｆｅならびに不純物元素からなる鋼材を、810〜880℃
に加熱し、冷却速度２５℃／min以上で焼入れを施して
焼入れ組織をマルテンサイトとベイナイトの混合組織と
し、ついで540〜580℃で焼もどしを施し、鋼の組織を焼
もどしマルテンサイトと焼もどしベイナイトの混合組織
としたことを特徴とする高靱性低合金鋼の製造方法。2. A weight ratio of C: 0.32 to 0.40%, Si:
0.15 to 0.65%, Mn: 0.65 to 1.20%, Cr: 0.90 to 2.00
%, Mo: 0.33 to 0.50%, V: 0.05 to 0.30%,
Nb: A steel material containing 1 to 2 of 0.05 to 0.30% and the balance Fe and impurity elements at 810 to 880 ° C.
To a mixed structure of martensite and bainite by quenching at a cooling rate of 25 ° C / min or more, and then tempering at 540 to 580 ° C to temper the steel structure and martensite. A method for producing a high-toughness low-alloy steel, which has a mixed structure of bainite.
0.15〜0.65％、Ｍｎ：0.65〜1.20％、Ｃｒ：0.90〜2.00
％、Ｍｏ：0.33〜0.50％と、さらにＳ：0.035％以下、
Ｐｂ：0.15％以下のうち１種ないし２種を含有し、残部
Ｆｅならびに不純物元素からなる鋼材を、810〜880℃に
加熱し、冷却速度２５℃／min以上で焼入れを施して焼
入れ組織をマルテンサイトとベイナイトの混合組織と
し、ついで540〜580℃で焼もどしを施し、鋼の組織を焼
もどしマルテンサイトと焼もどしベイナイトの混合組織
としたことを特徴とする高靱性低合金鋼の製造方法。3. A weight ratio of C: 0.32 to 0.40%, Si:
0.15 to 0.65%, Mn: 0.65 to 1.20%, Cr: 0.90 to 2.00
%, Mo: 0.33 to 0.50%, and S: 0.035% or less,
Pb: A steel material containing one or two of 0.15% or less and the balance Fe and impurity elements is heated to 810 to 880 ° C. and quenched at a cooling rate of 25 ° C./min or more to obtain a quenched structure. A method for producing a high toughness low alloy steel, characterized in that a mixed structure of site and bainite is obtained, and then tempering is performed at 540 to 580 ° C, and the structure of steel is a mixed structure of tempered martensite and tempered bainite.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP59254514A JPH0613745B2 (en) | 1984-12-01 | 1984-12-01 | Manufacturing method of high toughness low alloy steel |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP59254514A JPH0613745B2 (en) | 1984-12-01 | 1984-12-01 | Manufacturing method of high toughness low alloy steel |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS61133364A JPS61133364A (en) | 1986-06-20 |
| JPH0613745B2 true JPH0613745B2 (en) | 1994-02-23 |
Family
ID=17266102
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP59254514A Expired - Lifetime JPH0613745B2 (en) | 1984-12-01 | 1984-12-01 | Manufacturing method of high toughness low alloy steel |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH0613745B2 (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP4495106B2 (en) * | 2006-03-28 | 2010-06-30 | 新日本製鐵株式会社 | Steel pipe for machine structure excellent in machinability and manufacturing method thereof |
| CN109338226B (en) * | 2018-11-20 | 2020-09-25 | 中铁工程装备集团隧道设备制造有限公司 | Material for high-performance TBM cutter head scraper plate and preparation method thereof |
Family Cites Families (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5779116A (en) * | 1980-10-31 | 1982-05-18 | Nippon Steel Corp | Production of high tensile steel having superior toughness |
| US4354882A (en) * | 1981-05-08 | 1982-10-19 | Lone Star Steel Company | High performance tubulars for critical oil country applications and process for their preparation |
| JPS5819438A (en) * | 1981-07-28 | 1983-02-04 | Sumitomo Metal Ind Ltd | Production of steel pipe having high strength and high toughness |
| JPS5893857A (en) * | 1981-11-30 | 1983-06-03 | Sumitomo Metal Ind Ltd | Railway wheel with superior heat check resistance and breaking resistance |
| JPS58171554A (en) * | 1982-03-31 | 1983-10-08 | Daido Steel Co Ltd | Parts for machine structure |
| JPS59104426A (en) * | 1982-12-03 | 1984-06-16 | Daido Steel Co Ltd | Preparation of steel for high frequency hardening |
| JPS59153868A (en) * | 1983-02-22 | 1984-09-01 | Nisshin Steel Co Ltd | Shaft for golf club |
| JPS59159969A (en) * | 1983-03-03 | 1984-09-10 | Sumitomo Metal Ind Ltd | Steel material for chain with high strength and toughness |
| JPS60169544A (en) * | 1984-02-14 | 1985-09-03 | Daido Steel Co Ltd | Machine structural parts of high strength and manufacture thereof |
-
1984
- 1984-12-01 JP JP59254514A patent/JPH0613745B2/en not_active Expired - Lifetime
Non-Patent Citations (1)
| Title |
|---|
| ＪＩＳＧ４１０５（１９７９）クロムモリブデン鉄鋼材（ＳＣＭ４３０〜８２２化学成分および熱処理） |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS61133364A (en) | 1986-06-20 |
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