JPH09206804A - Manufacture of high-strength rail excellent in ductility and toughness - Google Patents
Manufacture of high-strength rail excellent in ductility and toughnessInfo
- Publication number
- JPH09206804A JPH09206804A JP1601696A JP1601696A JPH09206804A JP H09206804 A JPH09206804 A JP H09206804A JP 1601696 A JP1601696 A JP 1601696A JP 1601696 A JP1601696 A JP 1601696A JP H09206804 A JPH09206804 A JP H09206804A
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- Prior art keywords
- toughness
- mns
- rail
- pearlite
- ductility
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Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、レール鋼のパーラ
イト組織を微細化して靭性および延性の向上を図った鉄
道用高強度レールの製造法に関するものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a high-strength rail for a railway, which has a fine pearlite structure of a rail steel to improve toughness and ductility.
【０００２】[0002]
【従来の技術】近年、鉄道輸送は高荷重化、高速化が指
向され、レールに要求される特性がますます厳しくなっ
ている。高荷重鉄道では急曲線区間の摩耗対策、レール
頭部内部疲労損傷対策が要求され、高速鉄道では主とし
て直線区間の表面損傷が課題として挙げられている。こ
れに加えて、寒冷地においては、冬季にレール破断が集
中的に発生する傾向が認められており、寒冷地鉄道での
レール材の靭性改善は、安全な鉄道輸送に欠かせない特
性になっている。2. Description of the Related Art In recent years, railway transportation has been aimed at higher loads and higher speeds, and the characteristics required for rails have become increasingly severe. For heavy-duty railways, measures against wear on sharp curves and internal fatigue damage to rail heads are required. On high-speed railways, surface damage mainly on straight sections is cited as an issue. In addition to this, in cold regions, it is recognized that rail ruptures tend to occur intensively in winter, and improving the toughness of rail materials for cold region railways is an essential property for safe rail transportation. ing.
【０００３】また、鉄道輸送の高効率化のために、高速
化および貨物の重積載化が進められているが、これに伴
ってレール頭部の摩耗や疲労損傷が急速に増加しつつあ
る。このようなレール材の使用環境の過酷化特に摩耗の
増加に対処するために、レール鋼の高強度化のための技
術開発が加速され、国内・外を問わず曲線区間のレール
材はほとんどすべて高強度レールが支配することとなっ
た。Further, in order to improve the efficiency of rail transportation, speeding up and heavy loading of cargo have been promoted, but along with this, wear and fatigue damage of rail heads are rapidly increasing. In order to cope with the harsh environment in which rail materials are used, especially the increase in wear, technological development for increasing the strength of rail steel has been accelerated, and almost all rail materials in curved sections, both in Japan and abroad, are being used. The high-strength rails now dominate.
【０００４】しかし、一方ではレール鋼の耐摩耗性の向
上とともに、本来摩耗によって削り取られるべき疲労ダ
メージ層がレール頭表面、特に車輪フランジ付け根部が
押しつけられるゲージ・コーナー（ＧＣ）表面に残存
し、表面損傷を生成させる傾向が認められるようになっ
た。さらにレール鋼の耐摩耗性の向上は、車輪荷重のレ
ールＧＣ内部での応力集中を一点に固定させることとな
り、レール頭部内部からの疲労損傷を急増させることと
なった。このようなレール頭表面損傷性の改善および内
部疲労損傷に対する抵抗性を改善するためには、レール
材質として靭性および延性を向上させることが重要であ
る。On the other hand, on the other hand, as the wear resistance of the rail steel is improved, a fatigue damage layer that should be scraped off due to wear remains on the rail head surface, particularly on the gauge corner (GC) surface against which the wheel flange root is pressed, A tendency to produce surface damage has become apparent. Further, the improvement of the wear resistance of the rail steel means that the stress concentration inside the rail GC due to the wheel load is fixed at one point, and the fatigue damage from the inside of the rail head rapidly increases. In order to improve such rail head surface damage and resistance to internal fatigue damage, it is important to improve the toughness and ductility of the rail material.
【０００５】高強度レールの靭性および延性改善の方策
としては以下の方法が考えられる。 （１）普通圧延後一旦室温まで冷却したレール頭部を低
温度で再加熱した後加速冷却する方法。 （２）制御圧延によりオーステナイト粒を微細化した後
レール頭部を加速冷却する方法。 （３）制御圧延した後、パーライト変態前で低温度に再
加熱し、その後加速冷却する方法。The following methods are considered as measures for improving the toughness and ductility of the high-strength rail. (1) A method in which a rail head that has been once cooled to room temperature after normal rolling is reheated at a low temperature and then accelerated cooling is performed. (2) A method of accelerating and cooling the rail head after refining austenite grains by controlled rolling. (3) A method in which after controlled rolling, it is reheated to a low temperature before pearlite transformation and then accelerated cooling is performed.
【０００６】[0006]
【発明が解決しようとする課題】上記方法の（１）で
は、大幅な靭性・延性改善のためには特開昭５５−１２
５２３１号公報に記載されているような通常の加熱温度
よりも低い８５０℃以下の低温度に再加熱し、オーステ
ナイト粒度を微細にすることによって靭性および延性を
改善しようとするもので、低温度で加熱してかつレール
頭部内部まで加熱を深めようとすると、投入熱量を下げ
て長時間加熱する必要がある。このため熱処理生産性を
著しく阻害し製造コストを高める難点がある。また、
（２）の方法は特開昭５２−１３８４２７号公報および
特開昭５２−１３８４２８号公報に記載されているよう
に、圧延時のオーステナイト粒の細粒化によって靭性・
延性の向上を図ろうとすると、高温での大圧下が要求さ
れ、レール圧延機の能力あるいはレールの形状制御の観
点からも問題を含んでいる。さらに（３）の方法は、特
公平４−４３７１号公報に記載されているように、８０
０℃以下で５％以上の圧延を実施した後、再度７５０〜
９００℃に加熱することによりオーステナイト粒を微細
にしようとする方法であり、圧延後に低温再加熱のため
の加熱炉を必要とするため作業性、生産性、製造コスト
の観点から問題が多い。In the above method (1), in order to improve the toughness and ductility to a great extent, JP-A-55-12 is used.
Reheating to a low temperature of 850 ° C. or lower, which is lower than the normal heating temperature as described in Japanese Patent No. 5231, attempts to improve toughness and ductility by making the austenite grain size fine. When heating and deepening the heating to the inside of the rail head, it is necessary to lower the amount of heat input and heat for a long time. Therefore, there is a problem that heat treatment productivity is significantly impaired and manufacturing cost is increased. Also,
As described in JP-A-52-138427 and JP-A-52-138428, the method (2) is toughness due to austenite grain refinement during rolling.
In order to improve the ductility, a large reduction at high temperature is required, which causes a problem from the viewpoint of rail rolling mill capacity or rail shape control. Furthermore, the method (3) is described in Japanese Patent Publication No.
After rolling 5% or more at 0 ° C. or less, 750 to 750 again
This is a method in which the austenite grains are made fine by heating at 900 ° C., and since a heating furnace for low-temperature reheating after rolling is required, there are many problems from the viewpoint of workability, productivity, and manufacturing cost.
【０００７】[0007]
【課題を解決するための手段】本発明は上記問題点を解
消しようとするものであり、重量％で、 Ｃ ：０．５５〜０．８５％、 Ｓｉ：０．２０〜１．２０％、 Ｍｎ：０．５０〜１．５０％、 Ｓ ：０．００２〜０．０３５％ を含有し、さらに必要に応じて、 Ｃｒ：０．１〜１．０％、 Ｎｉ：０．１〜４．０％、 Ｍｏ：０．１０〜０．５０％、 Ｔｉ：０．００１〜０．０５０％、 Ｖ ：０．０２〜０．２０％の１種または２種以上 を含有し残部が鉄および不可避的不純物からなる１３０
０℃以上に加熱した鋼片、または溶鋼から製造された鋼
片を直接３℃／ｓ以上で９００℃以上の熱間圧延開始温
度まで冷却し、引き続き熱間圧延を施しＭｎＳから直接
パーライト変態を生成させることを特徴とする延性およ
び靭性に優れた高強度レールの製造法である。DISCLOSURE OF THE INVENTION The present invention is intended to solve the above problems, and in weight%, C: 0.55 to 0.85%, Si: 0.20 to 1.20%, Mn: 0.50 to 1.50%, S: 0.002 to 0.035%, and if necessary, Cr: 0.1 to 1.0%, Ni: 0.1 to 4. 0%, Mo: 0.10 to 0.50%, Ti: 0.001 to 0.050%, V: 0.02 to 0.20%, and one or more of them is contained, and the balance is iron and unavoidable. Consisting of specific impurities
A steel slab heated to 0 ° C. or higher or a steel slab manufactured from molten steel is directly cooled at a temperature of 3 ° C./s or more to a hot rolling start temperature of 900 ° C. or higher, and then hot rolled to directly transform pearlite from MnS. It is a method for producing a high-strength rail having excellent ductility and toughness, which is characterized by being produced.
【０００８】本発明では、従来オーステナイト粒界のみ
からしか生成しないといわれていたパーライト変態を、
オーステナイト粒内のＭｎＳからもパーライト変態の核
の役割を担わせ、オーステナイト粒内からもパーライト
変態を生成させることを特徴としており、１３００℃以
上に鋼片を加熱し、あるいは溶鋼から直接鋼片を介して
熱間圧延を行い、ＭｎＳの少なくとも一部溶解後、Ｍｎ
Ｓの再析出あるいは凝集時にＭｎＳの境界部に生じるＭ
ｎ希薄帯の形成によるパーライト変態核生成を誘起させ
ることに立脚している。In the present invention, the pearlite transformation, which was conventionally said to be generated only from the austenite grain boundaries,
MnS in the austenite grains also plays a role of nuclei for pearlite transformation, and pearlite transformation is generated also in the austenite grains. The steel slab is heated to 1300 ° C. or higher, or the steel slab is directly melted. Hot-rolling is performed to dissolve MnS at least partially, and then MnS is melted.
M generated at the boundary of MnS during reprecipitation or aggregation of S
It is based on inducing pearlite transformation nucleation by forming n-dilute bands.
【０００９】すなわち、本発明者等の詳細な実験・解析
結果からＭｎＳの溶解・再析出時には、拡散速度の遅い
ＭｎがＭｎＳと鋼素地のγ鉄の境界部にＭｎ濃度の低い
領域を生成させその後の冷却域でパーライト組織のフェ
ライトの芽が誘起され、このフェライトの芽から吐き出
された炭素がパーライト組織のセメンタイト板を生成さ
せ、これらの繰り返しによりパーライト変態がＭｎＳか
ら生成することを見いだした。このようにして、パーラ
イト組織生成核であるＭｎＳをオーステナイト粒内に微
細に分散させ、粒内から効率良く生成したパーライトに
よって著しく組織が微細化し、これにともなって大幅な
靭性および延性の改善を図ることができる。That is, from the detailed experiments and analysis results of the present inventors, when MnS is dissolved and reprecipitated, Mn having a slow diffusion rate causes a region having a low Mn concentration to form at the boundary between MnS and γ-iron in the steel base. In the subsequent cooling zone, ferrite buds of pearlite structure were induced, and the carbon discharged from the ferrite buds formed a cementite plate of pearlite structure, and it was found that pearlite transformation was generated from MnS by repeating these. In this way, MnS, which is a pearlite structure forming nucleus, is finely dispersed in the austenite grains, and the structure is remarkably refined by the pearlite efficiently generated from within the grains, and accordingly, the toughness and ductility are greatly improved. be able to.
【００１０】[0010]
【発明の実施の形態】以下に本発明について詳細に説明
する。本発明において１３００℃以上に加熱もしくは、
溶鋼から製造された鋼片を用いるのはＭｎＳの溶解を目
的としており、その後３℃／ｓ以上の冷却速度で９００
℃以上の熱間圧延開始温度まで冷却する目的は、γ中の
加速冷却によってＭｎＳを微細分散させるパーライト変
態核を確保すると同時に、溶解・再析出したＭｎＳ境界
のＭｎの拡散を抑制して、Ｍｎ希薄帯を低温まで維持さ
せるところにある。このとき、１３００℃以下ではＭｎ
Ｓの溶解が不十分であり、３℃／ｓ以下の冷却速度で９
００℃以下に冷却するとＭｎＳが粗大化、粗分散化して
しまうと同時に、ＭｎＳの再析出にともなうＭｎ希薄帯
が拡散によって消滅してしまうため、１３００℃以上の
温度から３℃／ｓ以上の冷却速度で９００℃以上の熱間
圧延開始温度まで冷却し、引き続き熱間圧延を施す必要
がある。BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below. In the present invention, heating to 1300 ° C. or higher, or
The purpose of using the steel billet produced from molten steel is to melt MnS, and then 900 at a cooling rate of 3 ° C / s or more.
The purpose of cooling to the hot rolling start temperature of ℃ or more is to secure the pearlite transformation nuclei that finely disperse MnS by accelerated cooling in γ, and at the same time suppress the diffusion of Mn at the boundary of dissolved and re-precipitated MnS. This is where the thin strip is maintained at a low temperature. At this time, at 1300 ° C. or lower, Mn
The dissolution of S is insufficient and it is 9 at a cooling rate of 3 ° C / s or less.
When cooled to 00 ° C. or lower, MnS coarsens and coarsely disperses, and at the same time, the Mn diluted zone disappears due to diffusion upon reprecipitation of MnS. Therefore, cooling from 1300 ° C. or higher to 3 ° C./s or higher It is necessary to cool to a hot rolling start temperature of 900 ° C. or higher at a speed and then perform hot rolling.
【００１１】なお、通常のレール圧延においては鋼片を
１３００℃以上のできるだけ高温に加熱することによっ
て、ＭｎＳを十分に溶解させ、再析出量を確保する必要
があるが、炭素含有量の高いパーライト鋼は融点が低い
ため、１３５０℃以上ではγ粒界が溶融して、引き続く
圧延で液膜脆化を生成させるため９００℃以上のできる
だけ低温まで冷却し、熱間圧延を開始することが望まし
い。また、溶鋼を鋼片にした後直接熱間圧延を行う場合
においては、鋼片は最終形状であるレールの断面形状に
近い状態から、かつ９００℃以上の熱間圧延開始温度か
ら熱間圧延を施されるが、この間においてもＭｎＳ境界
のＭｎ希薄帯は維持されることが実験的に確認されてお
り、その後の冷却中にγ粒界のみならずγ粒内のＭｎＳ
境界の希薄帯からもパーライト変態が生成して、微細な
パーライト組織を得ることができる。In ordinary rail rolling, it is necessary to sufficiently dissolve MnS and secure a reprecipitation amount by heating a steel slab to a temperature as high as 1300 ° C. or higher, but pearlite having a high carbon content is required. Since the melting point of steel is low, the γ grain boundary melts at 1350 ° C. or higher, and it is desirable to cool to as low as 900 ° C. or higher to start hot rolling in order to generate liquid film embrittlement in the subsequent rolling. In the case of directly performing hot rolling after forming molten steel into billets, hot rolling is performed from a state where the billets are close to the cross-sectional shape of the rail, which is the final shape, and from the hot rolling start temperature of 900 ° C or higher. Although it is applied, it is experimentally confirmed that the Mn diluted zone at the MnS boundary is maintained even during this period, and not only the γ grain boundary but also the MnS in the γ grain during the subsequent cooling.
The fine pearlite structure can be obtained by the pearlite transformation also generated from the thin strip at the boundary.
【００１２】次に、鋼片の化学成分を前記のように限定
した理由について述べる。 Ｃ：Ｃは高強度化およびパーライト組織生成のための必
須元素であり、また耐摩耗性に対しても一義的に効果を
示す元素であるが０．５５％未満ではオーステナイト粒
界に耐摩耗性および耐損傷性に好ましくない初析フェラ
イトが多量に生成し、また０．８５％を超えるとオース
テナイト粒界を脆化させる有害な初析セメンタイトを生
成させるばかりか、レール頭部熱処理層や溶接部の微小
偏析部にマルテンサイトが生成し、靭性・延性を著しく
損なうため０．５５〜０．８５％に限定した。Next, the reason for limiting the chemical composition of the steel bill as described above will be described. C: C is an essential element for increasing the strength and generating a pearlite structure, and is an element that also has a unique effect on wear resistance, but if it is less than 0.55%, wear resistance at austenite grain boundaries In addition, a large amount of proeutectoid ferrite, which is unfavorable to damage resistance, is generated, and when it exceeds 0.85%, not only harmful harmful proeutectoid cementite that embrittles the austenite grain boundary is generated, but also a rail head heat treatment layer or welded portion. Since martensite is generated in the finely segregated part and markedly impairs toughness and ductility, the content is limited to 0.55 to 0.85%.
【００１３】Ｓｉ：Ｓｉはパーライト組織中のフェライ
ト相への固溶体硬化による高強度化に寄与するばかり
か、わずかながらレール鋼の靭性・延性改善にも貢献す
る。またＳｉはＭｎとともにＭｎＳの核となるマンガン
シリケート系酸化物を構成する重要な元素であり、適正
な脱酸方法を行うことにより有効な微細酸化物を生成さ
せることができる。Ｓｉは、０．２％以下ではその効果
が期待できずさらにＳｉは脱酸元素として０．２％以上
の添加が必要であり、１．２％を超えると脆化をもたら
し溶接接合性も減ずるので、０．２０〜１．２０％に限
定した。Si: Si contributes not only to the strengthening of the ferrite phase in the pearlite structure by solid solution hardening but also to a slight improvement in the toughness and ductility of the rail steel. In addition, Si is an important element that constitutes a manganese silicate-based oxide that becomes the core of MnS together with Mn, and an effective fine oxide can be generated by performing an appropriate deoxidizing method. If Si is 0.2% or less, the effect cannot be expected, and Si needs to be added as a deoxidizing element in an amount of 0.2% or more. If it exceeds 1.2%, embrittlement occurs and weld bondability is reduced. Therefore, it was limited to 0.20 to 1.20%.
【００１４】Ｍｎ：ＭｎはＣ同様にパーライト変態温度
を低下させ、焼入性を高めることによって高強度化に寄
与する元素であり、さらにＳｉ同様にＭｎＳの核として
マンガンシリケートの構成元素として、および脱酸元素
としても欠かせない元素であり、適正な脱酸を行うこと
によりいっそう酸化物の微細化が達成されＭｎＳの微細
析出の誘導および引き続くパーライトの核生成に効果を
発揮する。しかし、０．５％未満ではその効果が小さく
また１．５０％を超えると偏析部にマルテンサイト組織
を生成させ易くするため０．５０〜１．５０％に限定し
た。Mn: Mn is an element which, like C, lowers the pearlite transformation temperature and contributes to strengthening by increasing the hardenability. Further, like Mn, it acts as the core of MnS and as a constituent element of manganese silicate, and It is an element that is also essential as a deoxidizing element, and by performing appropriate deoxidation, further miniaturization of the oxide is achieved, and it is effective in inducing fine precipitation of MnS and in subsequent nucleation of pearlite. However, if it is less than 0.5%, its effect is small, and if it exceeds 1.50%, the content is limited to 0.50 to 1.50% so that a martensite structure is easily generated in the segregated portion.
【００１５】Ｓ：Ｓは一般に有害元素として知られてい
るが、本発明においてはオーステナイト粒内のマンガン
シリケートなどの酸化物を核とするＭｎＳを変態核とす
るパーライト組成が生成するため欠かせない元素であ
る。しかし、０．００２％未満ではパーライト変態核と
してのＭｎＳ量が減じてしまい、パーライト粒内変態を
確保できなくする。また０．０３５％以上ではＭｎＳが
多量に生成し靭性・延性を著しく低下させるため０．０
０２〜０．０３５％に限定した。S: S is generally known as a harmful element, but it is indispensable in the present invention because a pearlite composition having MnS whose core is an oxide such as manganese silicate in austenite grains is a transformation core is generated. It is an element. However, if it is less than 0.002%, the amount of MnS as pearlite transformation nuclei is reduced, and pearlite intragranular transformation cannot be secured. On the other hand, if it is more than 0.035%, a large amount of MnS is formed and the toughness and ductility are remarkably deteriorated.
It was limited to 02 to 0.035%.
【００１６】さらに本発明においては、上記成分の他に
必要に応じて１種または２種以上のＣｒ，Ｎｉ，Ｍｏ，
Ｔｉ，Ｖの添加によってパーライト地の靭性改善、冷却
後の強度の確保、およびＭｎＳ上にＴｉ，Ｖなどの炭窒
化物を析出させることによりいっそうのパーライト組織
の微細化を達成することができる。これらの化学成分を
限定した理由を以下に説明する。 Ｃｒ：Ｃｒはパーライト変態を低下させることによって
高強度化に寄与すると同時に、パーライト組織中のセメ
ンタイト相を強化することによっても耐摩耗性向上に貢
献するが、一方ではセメンタイトの衝撃靭性を低下させ
る作用も有している。しかし、Ｃｒのセメンタイト強化
作用は無視しがたく、さらに溶接継手部軟化防止の観点
からも微量のＣｒの添加も望ましい。そこで強度確保に
一定の寄与が期待されかつ靭性・延性を損なわない範囲
内で０．１〜１．０％に限定した。Further, in the present invention, in addition to the above-mentioned components, one or more kinds of Cr, Ni, Mo, and
By adding Ti and V, it is possible to improve the toughness of the pearlite material, to secure the strength after cooling, and to further refine the pearlite structure by precipitating carbonitrides such as Ti and V on MnS. The reason for limiting these chemical components will be described below. Cr: Cr contributes to the increase in strength by reducing the pearlite transformation, and at the same time contributes to the improvement of wear resistance by strengthening the cementite phase in the pearlite structure. On the other hand, the action of reducing the impact toughness of cementite. I also have. However, the cementite strengthening effect of Cr cannot be ignored, and it is also desirable to add a trace amount of Cr from the viewpoint of preventing softening of the welded joint. Therefore, it is limited to 0.1 to 1.0% within a range in which a certain contribution is expected to secure the strength and the toughness and ductility are not impaired.
【００１７】Ｎｉ：Ｎｉはパーライト組織中のフェライ
ト中に固溶しフェライトの靭性を向上させるのに有効な
元素であり、０．１％未満の場合はその硬化が極めて少
なく、また４．０％を超えて含有してもその硬化は飽和
する。したがって靭性向上の観点から０．１〜４．０％
の範囲に限定した。 Ｍｏ：Ｍｏはパーライト変態速度を抑制し、パーライト
変態を低温に誘導することによってパーライト組織を微
細化することから、靭性向上に有効な元素である。さら
に、Ｍｏは加速冷却時にレール内部において、表面層の
パーライト変態にともなう発熱に連動した高温での変態
誘起を防止し、レール内部の高強度化に寄与し、レール
頭部の硬化伸度を高める。しかし、Ｍｏの０．１％未満
の含有では上記の効果は少なく、また０．５０％を超え
る含有ではパーライト変態速度を極端に低下させ、パー
ライト組織中にベイナイト組織やマルテンサイト組織な
どの有害組織を生成させ靭性を極度に低下させる。した
がってＭｏ含有量を０．１０〜０．５０％の範囲に限定
した。Ni: Ni is an element effective as a solid solution in the ferrite in the pearlite structure to improve the toughness of the ferrite. If it is less than 0.1%, its hardening is extremely small, and 4.0%. Even if it is contained in excess of, the curing will be saturated. Therefore, from the viewpoint of improving toughness, 0.1 to 4.0%
Limited to the range. Mo: Mo is an element effective in improving toughness because it suppresses the pearlite transformation rate and induces pearlite transformation to a low temperature to refine the pearlite structure. Further, Mo prevents transformation induction at high temperature in conjunction with heat generation due to pearlite transformation of the surface layer inside the rail during accelerated cooling, contributes to higher strength inside the rail, and enhances hardening elongation of the rail head. . However, if the content of Mo is less than 0.1%, the above effect is small, and if it exceeds 0.50%, the pearlite transformation rate is extremely decreased, and a harmful structure such as bainite structure or martensite structure is contained in the pearlite structure. To reduce the toughness extremely. Therefore, the Mo content is limited to the range of 0.10 to 0.50%.
【００１８】Ｔｉ：Ｔｉを炭窒化物としてＭｎＳ上に析
出させることによって、ＭｎＳからのパーライト変態を
加速させる効果を有する。しかし、０．００１％未満で
は十分に炭窒化物を生成させることができず、また、
０．０５０％を超えて含有させると、Ｔｉ炭窒化物が粗
大化してレール頭部内部から生成する疲労き裂の起点と
して有害となることから、その範囲を０．００１〜０．
０５０％とした。 Ｖ：ＶはＴｉ同様にＭｎＳ上に析出して効果的にＭｎＳ
からのパーライト変態を促進する元素である。しかし、
０．０２％以下ではその効果が期待できず、また０．２
０％以上添加してもその効果が飽和するために、添加量
範囲を０．０２〜０．２０％に限定した。不可避的不純
物元素であるＰは、レール鋼の靭性を向上させるために
はできるだけ低減させることが望ましい。Ti: Precipitating Ti as carbonitride on MnS has the effect of accelerating the pearlite transformation from MnS. However, if it is less than 0.001%, carbonitride cannot be sufficiently generated, and
If it is contained in an amount of more than 0.050%, the Ti carbonitride is coarsened and becomes harmful as a starting point of a fatigue crack generated from the inside of the rail head.
It was set to 050%. V: V precipitates on MnS as well as Ti, effectively MnS
It is an element that promotes the pearlite transformation from. But,
If 0.02% or less, the effect cannot be expected, and 0.2
Since the effect is saturated even if 0% or more is added, the addition amount range is limited to 0.02 to 0.20%. It is desirable to reduce P, which is an unavoidable impurity element, as much as possible in order to improve the toughness of the rail steel.
【００１９】前記のような成分組成で構成されるレール
鋼は、転炉、電気炉などの通常使用される溶解炉で溶製
を行い、この溶鋼を造塊・分塊法あるいは連続鋳造法に
より鋼片とし、これを直接熱間圧延するかもしくは、鋼
片を１３００℃以上に加熱した後、熱間圧延を経て製造
する。熱間圧延を終えたレールは、冷却中においてオー
ステナイト粒内のＭｎＳから直接的に、あるいはＭｎＳ
上に析出させたＴｉ炭窒化物もしくはＶ炭窒化物からも
パーライト変態が生成し、オーステナイト粒界から生成
するパーライトと共に微細なパーライト粒を構成する。
その結果、圧延ままで靭性の優れた高強度レールを製造
することができる。The rail steel having the above-described composition is melted in a commonly used melting furnace such as a converter or an electric furnace, and this molten steel is melted by the ingot-casting method or the continuous casting method. A steel slab is directly hot-rolled, or the slab is heated to 1300 ° C. or higher and then hot-rolled. The rails that have been hot-rolled are cooled directly from MnS in the austenite grains or MnS during cooling.
The pearlite transformation is also generated from the Ti carbonitride or V carbonitride deposited on the top, and constitutes fine pearlite grains together with the pearlite generated from the austenite grain boundaries.
As a result, a high-strength rail having excellent toughness can be manufactured as rolled.
【００２０】さらに高強度とともに高靭性が要求される
場合には、圧延終了後あるいは、一度室温に冷却され熱
処理する目的で再加熱されたオーステナイト域温度から
７００〜５００℃間を１〜５℃/secで加熱冷却されたレ
ール鋼では、一層の高靭性が得られる。すなわち、パー
ライト組織鋼の特徴として、加速冷却することによって
低温でパーライト変態を生じさせ、このことによりパー
ライト変態核の生成速度が向上し結果的にパーライト粒
を微細にすることができるからである。従ってＭｎＳか
ら直接的に、あるいはＭｎＳ上に析出させたＴｉ／Ｖ炭
窒化物からのパーライト組織のオーステナイト粒内変態
と、加速冷却によるオーステナイト粒界からのパーライ
ト変態が重畳して一層のレール鋼の靭性向上を達成する
ことができる。この際冷却媒体は、空気あるいはミスト
などの気液混合物を用い、レール頭部もしくは底部の強
度が１１００MPa 以上とすることが望ましい。When high strength and high toughness are required, 1 to 5 ° C./700 to 500 ° C. from the reheated austenite region temperature for the purpose of heat treatment after completion of rolling or once cooled to room temperature. Rail steel that has been heated and cooled for sec can achieve even higher toughness. That is, as a characteristic of the pearlite structure steel, pearlite transformation is caused at a low temperature by accelerated cooling, whereby the generation rate of pearlite transformation nuclei is improved, and as a result, pearlite grains can be made fine. Therefore, the austenite intragranular transformation of the pearlite structure from Ti / V carbonitride deposited directly on MnS or on MnS and the pearlite transformation from the austenite grain boundaries due to accelerated cooling are superposed on each other to form a more rail steel. Improved toughness can be achieved. At this time, it is desirable that the cooling medium is a gas-liquid mixture such as air or mist, and the strength of the rail head or bottom is 1100 MPa or more.
【００２１】レール鋼の靭性評価法としては、ロシアの
ＧＯＳＴ規格によって定められた２mmU ノッチシャルピ
ー試験における＋２０℃での衝撃吸収エネルギーがあ
り、同規格によれば高強度熱処理レールの＋２０℃での
衝撃吸収エネルギーは０．２５MJ/m2 以上が必要とされ
ている。上述したオーステナイト粒内のＭｎＳに析出さ
せたＴｉ炭窒化物をパーライト変態核として活用するこ
とによって、本発明のレール鋼ではパーライト粒が微細
化し、０．２５MJ/m2 以上の衝撃吸収エネルギーを得る
ことができる。As a method for evaluating the toughness of rail steel, there is the impact absorbed energy at + 20 ° C. in the 2 mm U notch Charpy test specified by the Russian GOST standard. According to the standard, the impact of high strength heat treated rails at + 20 ° C. Absorbed energy is required to be 0.25 MJ / m 2 or more. By utilizing the Ti carbonitrides precipitated in MnS in the austenite grains as pearlite transformation nuclei, the pearlite grains are refined in the rail steel of the present invention, and impact absorption energy of 0.25 MJ / m 2 or more is obtained. be able to.
【００２２】レールの延性はレール頭部の疲労損傷の生
成に影響を与え、中国における高強度レールの延性要求
は、レール頭部ＧＣ内部１０mm深さ位置から採取した平
行部径６mm、平行部長さ３０mmの引張試験において１２
％以上の伸び値が必要であるとしている。このような材
質要求に対して本発明のオーステナイト粒内に生成させ
たＭｎＳからパーライト変態を生成させることにより、
微細なパーライト組織を生成せしめ靭性同様にレール鋼
の延性も大幅に改善することができた。The ductility of the rail affects the generation of fatigue damage to the rail head, and the ductility requirement of the high strength rail in China is that the diameter of the parallel portion is 6 mm and the length of the parallel portion is 10 mm inside the rail head GC. 12 in a 30 mm tensile test
It is said that an elongation value of at least% is required. In response to such material requirements, by generating a pearlite transformation from MnS generated in the austenite grains of the present invention,
The ductility of the rail steel as well as the toughness due to the formation of the fine pearlite structure could be greatly improved.
【００２３】[0023]
【実施例】次に本発明により製造した高靭性を有する高
強度レールの製造実施例について述べる。表１には供試
鋼の化学成分を示す。また１３００℃以下の加熱およ
び、１３００℃以上の加熱ならびに溶鋼から製造された
鋼片を直接熱間圧延した場合の、冷却後の組織中にＭｎ
Ｓを核とするパーライト粒内変態が含まれているかどう
かを観察した結果を表２に示す。１３００℃以上に加熱
された鋼片および溶鋼から製造された鋼片から製造され
たレールには、所定の量の微細なＭｎＳの生成が確認さ
れ、さらにＶおよびＴｉ添加した本発明鋼では明らかに
オーステナイト粒内からのＭｎＳを核としたＶ／Ｔｉ炭
窒化物を生成起点としたパーライト組織の生成が確認さ
れた。EXAMPLES Next, examples of production of high strength rails having high toughness produced according to the present invention will be described. Table 1 shows the chemical composition of the test steel. In addition, when heating at 1300 ° C. or lower, heating at 1300 ° C. or higher, and direct hot rolling of a steel slab produced from molten steel, Mn is contained in the microstructure after cooling.
Table 2 shows the results of observation as to whether or not the pearlite intragranular transformation having S as a nucleus is included. It was confirmed that a predetermined amount of fine MnS was generated in the rail manufactured from the steel slab heated to 1300 ° C. or higher and the steel slab manufactured from the molten steel, and it was apparent in the steel of the present invention in which V and Ti were added. It was confirmed that a pearlite structure starting from the generation origin of V / Ti carbonitride having MnS as a nucleus was generated from austenite grains.
【００２４】表３には圧延まま、および強度を一定とす
るために化学成分毎にオーステナイト域温度から７００
〜５００℃間を冷却速度１〜５℃／ｓの範囲で変化させ
た加速冷却後のレール鋼の引張試験強度、伸びおよび２
mmU ノッチシャルピー試験における＋２０℃での衝撃吸
収エネルギー測定結果を示す。引張試験はレール頭部Ｇ
Ｃ内部１０mm深さ位置から採取した平行部径６mm、平行
部長さ３０mmの試験片で行った。衝撃試験はレール頭部
１mm下より採取した。この試験条件は熱処理レールにお
ける靭性を規定したロシアのＧＯＳＴ規格に基づくもの
で、同規格によれば高強度熱処理レールの＋２０℃での
衝撃吸収エネルギーは０．２５MJ/m2 以上が必要とされ
ている。In Table 3, as-rolled and 700-700 from the austenite range temperature for each chemical component in order to keep the strength constant.
Tensile strength, elongation and 2 of the rail steel after accelerated cooling in which the cooling rate was changed in the range of 1 to 5 ° C / s in the range of 500 ° C to 500 ° C.
The measurement result of the impact absorption energy at + 20 ° C. in the mmU notch Charpy test is shown. Tensile test for rail head G
A test piece having a parallel part diameter of 6 mm and a parallel part length of 30 mm was sampled from a depth position of 10 mm inside C. The impact test was taken from 1 mm below the rail head. This test condition is based on the Russian GOST standard that regulates the toughness of heat treated rails. According to this standard, the impact absorption energy at + 20 ° C of high strength heat treated rails must be 0.25 MJ / m 2 or more. There is.
【００２５】[0025]
【表１】 [Table 1]
【００２６】[0026]
【表２】 [Table 2]
【００２７】[0027]
【表３】 [Table 3]
【００２８】[0028]
【発明の効果】上記表３に示す結果からも明らかのよう
に、本発明鋼は、比較鋼に比べて十分にパーライト微細
組織の効果としての改善が認められる。また、本発明は
適正な脱酸を行うことによってオーステナイト粒内から
もパーライト変態を生成させた微細パーライト組織鋼と
なり、いずれもＧＯＳＴ規格に定められたシャルピー吸
収エネルギーを十分に満たしている。As is clear from the results shown in Table 3 above, the steel of the present invention is sufficiently improved as the effect of the pearlite microstructure as compared with the comparative steel. Further, the present invention provides a fine pearlite structure steel in which pearlite transformation is generated from inside austenite grains by performing appropriate deoxidation, and all of them sufficiently satisfy Charpy absorbed energy specified in the GOST standard.
───────────────────────────────────────────────────── フロントページの続き (51)Int.Cl.6 識別記号 庁内整理番号 ＦＩ 技術表示箇所 Ｅ０１Ｂ 5/02 Ｅ０１Ｂ 5/02 ─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. 6 Identification code Internal reference number FI Technical display location E01B 5/02 E01B 5/02
Claims (3)
よび不可避的不純物からなる１３００℃以上に加熱した
鋼片または溶鋼から製造された鋼片を３℃／ｓ以上で９
００℃以上の熱間圧延開始温度まで冷却し、引き続き熱
間圧延を施しＭｎＳから直接パーライト変態を生成させ
ることを特徴とする延性および靭性に優れた高強度レー
ルの製造法。1. In mass%, C: 0.55 to 0.85%, Si: 0.20 to 1.20%, Mn: 0.50 to 1.50%, S: 0.002 to 0. A steel slab containing 035% and the balance consisting of iron and unavoidable impurities heated to 1300 ° C. or higher or a steel slab manufactured from molten steel at 9 ° C./s or higher
A method for producing a high-strength rail excellent in ductility and toughness, which comprises cooling to a hot rolling start temperature of 00 ° C. or higher and subsequently hot rolling to directly generate pearlite transformation from MnS.
含有し残部が鉄および不可避的不純物からなる１３００
℃以上に加熱した鋼片または溶鋼から製造された鋼片を
３℃／ｓ以上で９００℃以上の熱間圧延開始温度まで冷
却し、引き続き熱間圧延を施しＭｎＳから直接パーライ
ト変態を生成させることを特徴とする延性および靭性に
優れた高強度レールの製造法。2. In mass%, C: 0.55 to 0.85%, Si: 0.20 to 1.20%, Mn: 0.50 to 1.50%, S: 0.002 to 0. It contains 035%, further Cr: 0.1-1.0%, Ni: 0.1-4.0%, Mo: 0.10-0.50%, Ti: 0.001-0.050. %, V: 0.02 to 0.20%, 1300 or more, and the balance consists of iron and inevitable impurities 1300
To cool a steel slab heated to ℃ or more or a steel slab manufactured from molten steel to a hot rolling start temperature of 900 ℃ or more at 3 ℃ / s or more, and then perform hot rolling to directly generate pearlite transformation from MnS. A method for manufacturing a high-strength rail with excellent ductility and toughness.
た後、７００〜５００℃間を１〜５℃/secで加速冷却す
ることを特徴とする請求項１および２に記載の延性およ
び靭性に優れた高強度レールの製造法。3. The ductility according to claim 1, wherein the steel slab according to claim 1 or 2 is hot-rolled and then accelerated cooling is performed at 700 to 500 ° C. at 1 to 5 ° C./sec. And a method of manufacturing high strength rails with excellent toughness.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1601696A JPH09206804A (en) | 1996-01-31 | 1996-01-31 | Manufacture of high-strength rail excellent in ductility and toughness |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1601696A JPH09206804A (en) | 1996-01-31 | 1996-01-31 | Manufacture of high-strength rail excellent in ductility and toughness |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH09206804A true JPH09206804A (en) | 1997-08-12 |
Family
ID=11904785
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP1601696A Withdrawn JPH09206804A (en) | 1996-01-31 | 1996-01-31 | Manufacture of high-strength rail excellent in ductility and toughness |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH09206804A (en) |
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|---|---|---|---|---|
| EP1241277A2 (en) * | 2001-03-05 | 2002-09-18 | AMSTED Industries Incorporated | Railway wheel alloy |
| WO2007111285A1 (en) * | 2006-03-16 | 2007-10-04 | Jfe Steel Corporation | High-strength pearlite rail with excellent delayed-fracture resistance |
| JP2007277716A (en) * | 2006-03-16 | 2007-10-25 | Jfe Steel Kk | High-strength perlitic rail with excellent delayed-fracture resistance |
| JP2013224471A (en) * | 2012-04-23 | 2013-10-31 | Nippon Steel & Sumitomo Metal Corp | Rail excellent in delayed-fracture resistance characteristics |
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| CN104480390A (en) * | 2015-01-07 | 2015-04-01 | 攀钢集团攀枝花钢铁研究院有限公司 | High-impact-toughness steel rail and production method thereof |
| CN105238917A (en) * | 2015-11-06 | 2016-01-13 | 攀钢集团攀枝花钢铁研究院有限公司 | Method for improving low-temperature fracture toughness of steel rail and obtained steel rail and application thereof |
| CN112410663A (en) * | 2020-11-04 | 2021-02-26 | 武汉钢铁有限公司 | Low-resistivity wear-resistant steel for guide steel rail and preparation method thereof |
| CN113621881A (en) * | 2021-08-09 | 2021-11-09 | 攀钢集团攀枝花钢铁研究院有限公司 | Method for improving low-temperature toughness of medium-carbon steel rail welded joint |
-
1996
- 1996-01-31 JP JP1601696A patent/JPH09206804A/en not_active Withdrawn
Cited By (16)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP1241277A3 (en) * | 2001-03-05 | 2003-03-19 | AMSTED Industries Incorporated | Railway wheel alloy |
| CZ303508B6 (en) * | 2001-03-05 | 2012-10-31 | Amsted Industries Incorporated | Alloy for railway vehicle wheels |
| EP1241277A2 (en) * | 2001-03-05 | 2002-09-18 | AMSTED Industries Incorporated | Railway wheel alloy |
| EP2006406A4 (en) * | 2006-03-16 | 2015-08-12 | Jfe Steel Corp | High-strength pearlite rail with excellent delayed-fracture resistance |
| WO2007111285A1 (en) * | 2006-03-16 | 2007-10-04 | Jfe Steel Corporation | High-strength pearlite rail with excellent delayed-fracture resistance |
| JP2007277716A (en) * | 2006-03-16 | 2007-10-25 | Jfe Steel Kk | High-strength perlitic rail with excellent delayed-fracture resistance |
| AU2007230254B2 (en) * | 2006-03-16 | 2010-12-02 | Jfe Steel Corporation | High-strength pearlitic steel rail having excellent delayed fracture properties |
| US8361382B2 (en) | 2006-03-16 | 2013-01-29 | Jfe Steel Corporation | High-strength pearlitic steel rail having excellent delayed fracture properties |
| US8404178B2 (en) | 2006-03-16 | 2013-03-26 | Jfe Steel Corporation | High-strength pearlitic steel rail having excellent delayed fracture properties |
| JP2013224471A (en) * | 2012-04-23 | 2013-10-31 | Nippon Steel & Sumitomo Metal Corp | Rail excellent in delayed-fracture resistance characteristics |
| CN104018095A (en) * | 2013-12-13 | 2014-09-03 | 无锡透平叶片有限公司 | Special mold steel material for high-energy spiral pressure machine |
| CN104480390A (en) * | 2015-01-07 | 2015-04-01 | 攀钢集团攀枝花钢铁研究院有限公司 | High-impact-toughness steel rail and production method thereof |
| CN105238917A (en) * | 2015-11-06 | 2016-01-13 | 攀钢集团攀枝花钢铁研究院有限公司 | Method for improving low-temperature fracture toughness of steel rail and obtained steel rail and application thereof |
| CN112410663A (en) * | 2020-11-04 | 2021-02-26 | 武汉钢铁有限公司 | Low-resistivity wear-resistant steel for guide steel rail and preparation method thereof |
| CN112410663B (en) * | 2020-11-04 | 2022-02-01 | 武汉钢铁有限公司 | Low-resistivity wear-resistant steel for guide steel rail and preparation method thereof |
| CN113621881A (en) * | 2021-08-09 | 2021-11-09 | 攀钢集团攀枝花钢铁研究院有限公司 | Method for improving low-temperature toughness of medium-carbon steel rail welded joint |
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