JPH09104925A - Method for quenching medium-high carbon-containing steel pipe - Google Patents
Method for quenching medium-high carbon-containing steel pipeInfo
- Publication number
- JPH09104925A JPH09104925A JP26110595A JP26110595A JPH09104925A JP H09104925 A JPH09104925 A JP H09104925A JP 26110595 A JP26110595 A JP 26110595A JP 26110595 A JP26110595 A JP 26110595A JP H09104925 A JPH09104925 A JP H09104925A
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- Prior art keywords
- steel pipe
- quenching
- cooling
- high carbon
- steel
- Prior art date
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Abstract
Description
【発明の属する技術分野】本発明は、中・高炭素含有鋼
管の焼入れ方法に関し、更に詳しくは、従来水焼入れな
どの所謂「急冷焼入れ処理」を施すと焼割れを生じるこ
との多かった中・高炭素含有鋼管の焼割れを防止する焼
入れ方法に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a quenching method for steel pipes containing medium to high carbon content, and more specifically, it often causes quenching cracks when subjected to so-called "quench quenching treatment" such as water quenching. The present invention relates to a quenching method for preventing quench cracking of a high carbon content steel pipe.
【従来の技術】中・高炭素含有鋼は調質処理すなわち焼
入れ焼戻し処理すると優れた強度・靭性を示すので、機
械構造用部材を始めとして多くの用途に使用されてき
た。しかしながら、鋼管形状品を焼入れした場合には、
鋼板形状品や棒・線状品の場合に比べて極めて複雑な応
力状態を呈する。このため、炭素含有量の多い鋼管形状
品に例えば水焼入れのような急冷焼入れを施すと、焼割
れ感受性が著しく高くなって焼割れが多発し、製品歩留
まりが極めて低くなってしまう。従って、中・高炭素含
有鋼管を焼入れ処理する場合には、焼割れを防止して製
品歩留まりを高くするために、水焼入れに比べて冷却能
の小さい油焼入れを行ったり、ミスト冷却による緩冷却
を行ったりして、焼入れ時の冷却速度をコントロールし
ている。しかしながら、前記のような焼入れ手段を採っ
た場合には、充分な量のマルテンサイト組織が得られ
ず、高温で生ずるベイナイトなどがかなり混じった組織
になってしまう。そのため焼入れ焼戻ししても、焼戻し
マルテンサイト組織の優れた強靭性を充分には活用でき
ず、製品である鋼管の強度・靭性レベルが低下してしま
うという問題があった。BACKGROUND OF THE INVENTION Medium and high carbon content steels have excellent strength and toughness when subjected to a tempering treatment, that is, a quenching and tempering treatment, and therefore have been used in many applications including machine structural members. However, when quenching a steel pipe shaped product,
Exhibits extremely complicated stress conditions compared to steel plate-shaped products and rod / line products. For this reason, when a steel pipe-shaped product having a high carbon content is subjected to quenching quenching such as water quenching, the susceptibility to quenching cracks becomes extremely high, quenching cracks frequently occur, and the product yield becomes extremely low. Therefore, when quenching the medium and high carbon content steel pipes, in order to prevent quenching cracks and increase the product yield, oil quenching, which has a smaller cooling capacity than water quenching, or slow cooling by mist cooling is performed. The cooling rate at the time of quenching is controlled. However, when the quenching means as described above is adopted, a sufficient amount of martensite structure cannot be obtained, and a structure in which bainite and the like generated at high temperature are considerably mixed is obtained. Therefore, even if quenching and tempering, the excellent toughness of the tempered martensite structure cannot be fully utilized, and there is a problem that the strength and toughness level of the product steel pipe is lowered.
【発明が解決しようとする課題】本発明の課題は、水焼
入れなどの所謂「急冷焼入れ処理」を施しても焼割れを
生じることがない、中・高炭素含有鋼管の焼入れ方法を
提供することにある。更には、焼割れの防止によって製
品歩留まりを高めると共に焼入れ後にその鋼管を焼戻し
することで焼戻しマルテンサイト組織の優れた強靭性を
充分に活用し、合金元素の多量添加を行わずとも、製品
鋼管に優れた特性を付与することが可能な中・高炭素含
有鋼管の焼入れ方法を提供することにある。SUMMARY OF THE INVENTION An object of the present invention is to provide a quenching method for medium / high carbon content steel pipes which does not cause quench cracking even when subjected to so-called "quench quenching treatment" such as water quenching. It is in. Furthermore, by increasing the product yield by preventing quenching cracks and by tempering the steel pipe after quenching, the excellent toughness of the tempered martensite structure is fully utilized, and even if a large amount of alloying elements are not added, the product steel pipe An object of the present invention is to provide a quenching method for steel pipes containing medium to high carbon which can impart excellent properties.
【課題を解決するための手段】本発明者は、前記した課
題を解決するために実験、研究を重ねた。その結果、例
えば水焼入れのような急冷処理によっても焼割れを起こ
すことがなく、且つ、ベイナイトなどの高温変態生成物
を抑えて充分なマルテンサイト組織を得るための焼入れ
としては、下記〜に示すいずれかの方法が適切であ
ることを実証した。 焼入れ時の強制冷却を鋼管の内面だけから行う。 焼入れ時の強制冷却を鋼管の内面だけから行い、更に
鋼管を回転させて均一に冷却する。 焼入れ時、鋼管外面冷却速度よりも大きな鋼管内面冷
却速度で鋼管の内外面から強制冷却を行い、更に鋼管を
回転させて均一に冷却する。 上記知見に基づく本発明は下記（１）〜（３）に示す中
・高炭素含有鋼管の焼入れ方法を要旨とする。 （１）重量％で、０．２〜１．２％のＣを含有する鋼管
の焼割れを防止する焼入れ方法であって、焼入れにおい
て冷却を鋼管の内面だけから行うことを特徴とする中・
高炭素含有鋼管の焼入れ方法。 （２）焼入れにおいて冷却を鋼管の内面だけから行うと
共に冷却時にその鋼管を回転させることを特徴とする上
記（１）に記載の中・高炭素含有鋼管の焼入れ方法。 （３）重量％で、０．２〜１．２％のＣを含有する鋼管
の焼割れを防止する焼入れ方法であって、焼入れにおい
て鋼管外面冷却速度よりも大きな鋼管内面冷却速度で冷
却を鋼管の内外面から行うと共に、冷却時にその鋼管を
回転させることを特徴とする中・高炭素含有鋼管の焼入
れ方法。Means for Solving the Problems The present inventors have conducted experiments and research to solve the above-mentioned problems. As a result, as quenching that does not cause quenching cracks even by rapid cooling treatment such as water quenching, and suppresses high temperature transformation products such as bainite to obtain a sufficient martensite structure, the following are shown. Either method proved to be suitable. Forced cooling during quenching is performed only from the inner surface of the steel pipe. Forced cooling at the time of quenching is performed only from the inner surface of the steel pipe, and the steel pipe is further rotated for uniform cooling. During quenching, forced cooling is performed from the inner and outer surfaces of the steel pipe at a steel pipe inner surface cooling rate higher than the steel tube outer surface cooling rate, and the steel tube is further rotated to uniformly cool the steel tube. The gist of the present invention based on the above findings is a quenching method for a medium / high carbon content steel pipe shown in the following (1) to (3). (1) A quenching method for preventing quench cracking of a steel pipe containing 0.2 to 1.2% by weight of C, characterized in that cooling is performed only from the inner surface of the steel pipe during quenching.
Quenching method for high carbon content steel pipe. (2) The quenching method for a medium / high carbon content steel pipe according to the above (1), wherein the quenching is performed only from the inner surface of the steel pipe and the steel pipe is rotated during cooling. (3) A quenching method for preventing quench cracking of a steel pipe containing 0.2 to 1.2% by weight of C, wherein cooling is performed at a steel pipe inner surface cooling rate higher than a steel tube outer surface cooling rate during quenching. A method for quenching medium- and high-carbon-containing steel pipes, characterized in that the steel pipes are rotated from the inner and outer surfaces of the steel, and the steel pipes are rotated during cooling.
【発明の実施の形態】以下、本発明について更に詳しく
説明する。なお成分元素量における「％」は「重量％」
を意味する。 （Ａ）化学組成：本発明は、焼き割れ感受性が高い中・
高炭素含有鋼管に関する発明であり、鋼管の化学組成と
してＣ含有量のみを０．２〜１．２％に限定する。これ
は鋼管の場合であってもＣ含有量が０．２％未満では、
例えば水槽に浸漬するような通常の水焼入れによる急冷
焼入れをしても焼割れを生じないからである。一方、Ｃ
含有量が１．２％を超えると、残留するオーステナイト
の量が多くなって焼割れ感受性が小さくなり、やはり焼
割れを生じ難くなるが、焼入れで生ずるマルテンサイト
の量が少ないため、焼戻し後に所望の強靭性が得難くな
る。従って、本発明においては中・高炭素含有鋼管のう
ち、特に０．２〜１．２％のＣを含有する鋼管を対象と
するものである。なお、焼戻しマルテンサイト組織の優
れた強靭性を充分に活用し、合金元素の多量添加を行わ
ずとも製品鋼管に優れた強靭性を付与するためには、鋼
管を常温まで強制冷却した時、そのミクロ組織は８０％
以上のマルテンサイト組織からなるものであることが好
ましい。ここでミクロ組織の量（％）は顕微鏡観察によ
る面積率のことをいう。そして、「ミクロ組織がマルテ
ンサイト８０％以上である」というのは、全組織がマル
テンサイト（マルテンサイト１００％）であっても良
く、２０％未満の他の組織が混在していても良い、とい
う意味である。なお、本発明は水焼入れのような急冷焼
入れを行うものであるから、マルテンサイト以外の組織
とは残留オ−ステナイトと焼入れ加熱時に基地（オ−ス
テナイト地）に固溶しなかった未固溶の炭化物や窒化
物、炭窒化物などを指す。従って、上記の好ましいミク
ロ組織を得るために、本発明の対象とする中・高炭素含
有鋼管のＣ含有量は０．２〜０．９％であることが望ま
しく、更に、０．２〜０．６％のＣ含有量であることが
一層望ましい。残留オ−ステナイトをマルテンサイトに
変態させて好ましいミクロ組織を得るために、焼入れ処
理後にサブゼロ処理を行っても良い。ところで、ミクロ
組織が８０％以上のマルテンサイト組織からなる中・高
炭素含有鋼管を得るための化学組成としてのＣ以外の他
の化学成分については、特別な限定を加える必要はな
い。焼戻しマルテンサイト組織の優れた強靭性を充分に
活用して所望の特性（主として強靭性）を確保できるよ
うな成分組成でありさえすれば良い。具体的には、例え
ば、Ｃ以外の元素としてはＳｉ：０．０１％〜２．０
％、Ｍｎ：０．０１％〜２．０％、Ｃｒ：０〜７％、Ｍ
ｏ：０〜２％、Ｎｉ：０〜２％、Ａｌ：０．００１〜
０．１％、Ｎ ：０〜０．１％、Ｎｂ：０〜０．５％、
Ｔｉ：０〜０．５％、Ｖ：０〜０．８％、Ｃｕ：０〜２
％、Ｃａ：０〜０．０１％、Ｂ：０〜０．０１％を含有
し、残部はＦｅと不可避的不純物からなり、不純物とし
てのＰ：０．１％以下、Ｓ：０．０５％、のものであれ
ば良い。 （Ｂ）焼入れ時の冷却：本発明に係わる中・高炭素含有
鋼管を焼入れして、好ましいミクロ組織（８０％以上の
マルテンサイト組織からなるもの）を得るためには急冷
焼入れすることが重要である。この急冷焼入れ時、８０
０℃から５００℃における平均冷却速度として１０℃／
秒以上の冷却速度を確保することが望ましい。なお、上
記の冷却速度が２０℃／ｓ以上であれば一層好ましい。
又、冷却は冷却設備上の上限の冷却速度で行っても構わ
ない。上記の冷却速度は「最も冷却が遅くなる部位の平
均冷却速度」のことをいう。ここで「最も冷却が遅くな
る部位」には、焼入れにおいて冷却を鋼管の内面だけか
ら行う場合の鋼管肉厚の外表面近傍の部位が、又、冷却
を鋼管の内外面から行う場合の肉厚の中央近傍の部位が
それぞれ該当する。焼入れに際して、少なくともマルテ
ンサイト変態開始温度（Ｍｓ点）までは強制冷却するこ
とが必要である。本発明の方法による強制冷却では焼割
れを生じないので、常温まで強制冷却して冷やしきって
も問題はない。ところで焼入れ前の加熱温度は、亜共析
鋼に対してはＡｃ3 点以上、過共析鋼に対してはＡｃ1
点以上とすれば良いが、結晶粒を粗大化させず、しかも
好ましいミクロ組織を得るために、亜共析鋼に対しては
８００〜１０５０℃、過共析鋼に対しては７５０〜１１
００℃とすることが望ましい。更に、焼入れの加熱温度
は亜共析鋼に対しては８００〜９５０℃、過共析鋼に対
しては７５０〜１０００℃とすることが一層望ましい。
焼入れプロセスとしては、所謂オフラインの焼入れだけ
でなく、熱間での製管後に素材の保有する熱を利用し
て、あるいはライン中で再加熱して、そのまま焼入れを
実施するところの所謂「直接焼入れ」によっても良い。 （Ｄ）冷却方法：本発明に係わる中・高炭素含有鋼管を
従来法によって急冷焼入れすると、マルテンサイト変態
する時の体積膨張によって鋼管の外面に大きな引張り応
力が作用するため、焼き割れを回避することが困難であ
った。すなわち、従来法では外面の冷却速度が内面のそ
れに比べて極めて大きいために、内面側のマルテンサイ
ト変態が遅れる。そのため、内面側の変態に伴う体積膨
張で外面に大きな引張り応力が働き、既に変態を終えた
外面の変形能の小さなマルテンサイトに割れを生じるこ
とになってしまう。しかしながら、中・高炭素含有鋼管
を焼入れするに際して、鋼管の内面だけから冷却す
る、鋼管を回転させながら内面だけから冷却する、
鋼管外面冷却速度よりも大きな鋼管内面冷却速度で、鋼
管を回転させながら内外面から冷却する、のいずれかの
方法を採れば熱応力と変態応力とがうまくバランスす
る。すなわち上記の本発明の方法で焼入れすれば、鋼管
の内面側のマルテンサイト変態が先行する。そのため外
面側には圧縮応力が働き、一方、内面側の引張り応力は
著しく低減するので後述の実施例で示すように、水焼入
れのような急冷焼入れ処理でも焼割れを生じない。なお
内面から鋼管を冷却する方法は特定されるものではな
く、ノズル孔を設けたパイプを鋼管の内面に挿入しそこ
から冷却媒体を吹き付ける方法や、鋼管の内面に冷却媒
体のジェット流を走らせる方法など適当な方法を用いれ
ば良い。又、内外面から鋼管を冷却する方法も特定され
るものではなく、鋼管の内外面にノズルから冷却媒体を
吹き付ける方法や、鋼管を冷却媒体の浴に浸漬して外面
を冷却し内面は上記した内面冷却方法で冷却するなど適
当な方法を用いれば良い。なお内面だけから鋼管を冷却
する場合、鋼管の回転は必ずしも必要ではないが、鋼管
を回転させれば一層均一な冷却条件となり特性が安定す
る。とりわけ１０回／分以上の回転数で鋼管を回転させ
れば、一層安定した特性を製品鋼管に付与することがで
きる。又、鋼管を回転させながら内外面から冷却する際
の鋼管の回転条件も同様に、回転数を１０回／分以上と
することが好ましい。なおこの場合、鋼管内面冷却速度
と鋼管外面冷却速度はそれぞれ冷却媒体の内面流量と外
面流量にほぼ比例するので、冷却媒体の鋼管内面におけ
る流量を鋼管外面における流量より多くしておけば、鋼
管外面冷却速度よりも大きな鋼管内面冷却速度が得られ
る。冷却媒体の種類にもよるが、少なくとも鋼管内面流
量を鋼管外面流量よりも０．２ｍ3 ／分以上大きくすれ
ば安定した特性が得られる。上記した〜の３方法の
うちどれを選択するかは、鋼管の肉厚、素材鋼の焼入れ
性、更には焼入れ装置の制約によって適宜選択して良
い。本発明の方法によって焼入れされた中・高炭素含有
鋼管は、その後Ａｃ1 点以下の温度で焼戻しされて所望
の特性を付与されて製品となる。あるいはＡｃ1 点以下
の温度で焼戻しされた後に、切断、機械加工、熱処理と
いった所謂「２、３次加工」されて最終の製品となる。BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. In addition, "%" in the component element amounts is "% by weight"
Means (A) Chemical composition: The present invention has high susceptibility to quench cracking.
The present invention relates to a high carbon content steel pipe, and limits only the C content to 0.2 to 1.2% as the chemical composition of the steel pipe. Even if this is a steel pipe, if the C content is less than 0.2%,
This is because quench cracking does not occur even when quenching and quenching by normal water quenching, such as immersion in a water tank. On the other hand, C
If the content exceeds 1.2%, the amount of retained austenite increases and the quench cracking susceptibility decreases, and quench cracking does not occur easily. However, since the amount of martensite produced during quenching is small, it is desirable after tempering. It becomes difficult to obtain the toughness of. Therefore, in the present invention, among steel pipes containing medium to high carbon, steel pipes containing 0.2 to 1.2% of C are particularly targeted. In addition, in order to impart excellent toughness to the product steel pipe without sufficiently adding the alloying elements in order to fully utilize the excellent toughness of the tempered martensite structure, when the steel pipe is forcibly cooled to room temperature, its 80% microstructure
It is preferably composed of the above martensite structure. Here, the amount (%) of the microstructure refers to the area ratio by microscopic observation. And, "the microstructure is 80% or more of martensite" means that the whole structure may be martensite (martensite 100%), or other structures of less than 20% may be mixed. It means that. Since the present invention is to perform quenching quenching such as water quenching, the structure other than martensite does not form solid solution with the retained austenite and the undissolved solid solution in the matrix (austenite base) during quenching and heating. Refers to carbides, nitrides, carbonitrides, etc. Therefore, in order to obtain the above preferable microstructure, the C content of the medium-high carbon content steel pipe targeted by the present invention is preferably 0.2 to 0.9%, and further 0.2 to 0. It is more desirable that the C content be 0.6%. In order to transform the retained austenite into martensite and obtain a preferable microstructure, a subzero treatment may be performed after the quenching treatment. By the way, it is not necessary to add a special limitation to chemical components other than C as a chemical composition for obtaining a steel pipe having a medium / high carbon content having a microstructure of a martensite structure of 80% or more. It suffices if the composition is such that the desired properties (mainly toughness) can be secured by fully utilizing the excellent toughness of the tempered martensite structure. Specifically, for example, as an element other than C, Si: 0.01% to 2.0
%, Mn: 0.01% to 2.0%, Cr: 0 to 7%, M
o: 0 to 2%, Ni: 0 to 2%, Al: 0.001 to
0.1%, N: 0 to 0.1%, Nb: 0 to 0.5%,
Ti: 0 to 0.5%, V: 0 to 0.8%, Cu: 0 to 2
%, Ca: 0 to 0.01%, B: 0 to 0.01%, the balance consisting of Fe and unavoidable impurities, P as an impurity: 0.1% or less, S: 0.05% Anything is acceptable. (B) Cooling during quenching: Quenching quenching is important for quenching the medium-high carbon content steel pipe according to the present invention to obtain a preferable microstructure (those having a martensite structure of 80% or more). is there. During this quenching and quenching, 80
10 ° C / as an average cooling rate from 0 ° C to 500 ° C
It is desirable to secure a cooling rate of at least 2 seconds. It is more preferable that the cooling rate is 20 ° C./s or more.
The cooling may be performed at the upper limit cooling rate on the cooling equipment. The above cooling rate refers to "the average cooling rate of the site where cooling is slowest". Here, "the part where cooling is slowest" means the part near the outer surface of the steel pipe wall thickness when cooling is performed only from the inner surface of the steel pipe during quenching, and the wall thickness when cooling is performed from the inner and outer surface of the steel pipe. The parts near the center of are corresponding respectively. At the time of quenching, it is necessary to perform forced cooling at least up to the martensitic transformation start temperature (Ms point). Since forced cracking by the method of the present invention does not cause quench cracking, there is no problem even if forced cooling to room temperature and cooling is completed. By the way, the heating temperature before quenching is Ac 3 points or more for hypoeutectoid steel and Ac 1 for hypereutectoid steel.
Although it may be set to a point or more, in order to prevent coarsening of crystal grains and obtain a preferable microstructure, 800-1050 ° C. for hypoeutectoid steel and 750-11 for hypereutectoid steel.
Desirably, the temperature is set to 00 ° C. Further, the heating temperature for quenching is more preferably 800 to 950 ° C for hypoeutectoid steel and 750 to 1000 ° C for hypereutectoid steel.
As the quenching process, not only so-called offline quenching but also so-called "direct quenching" in which the quenching is carried out by utilizing the heat of the material after hot pipe making or by reheating in the line Is also good. (D) Cooling method: When the medium / high carbon content steel pipe according to the present invention is quenched and quenched by the conventional method, a large tensile stress acts on the outer surface of the steel pipe due to volume expansion during the martensitic transformation, so that quench cracking is avoided. Was difficult. That is, in the conventional method, since the cooling rate of the outer surface is extremely higher than that of the inner surface, the martensitic transformation on the inner surface side is delayed. Therefore, a large tensile stress acts on the outer surface due to the volume expansion accompanying the transformation on the inner surface side, and a crack occurs in martensite having a small deformability on the outer surface which has already been transformed. However, when quenching a medium / high carbon content steel pipe, only the inner surface of the steel pipe is cooled, while the steel pipe is rotated, only the inner surface is cooled.
If either method of cooling the steel pipe from the inner and outer surfaces while rotating the steel pipe at a steel tube inner surface cooling rate higher than the steel tube outer surface cooling rate, thermal stress and transformation stress are well balanced. That is, if quenching is performed by the above-described method of the present invention, martensitic transformation on the inner surface side of the steel pipe precedes. Therefore, compressive stress acts on the outer surface side, while tensile stress on the inner surface side is significantly reduced, so that quench cracking does not occur even with rapid quenching treatment such as water quenching, as will be shown in Examples described later. The method of cooling the steel pipe from the inner surface is not specified, but a method of inserting a pipe with nozzle holes into the inner surface of the steel pipe and blowing a cooling medium from it, or running a jet of cooling medium on the inner surface of the steel pipe. A suitable method such as a method may be used. Also, the method of cooling the steel pipe from the inner and outer surfaces is not specified, and the method of spraying a cooling medium from the nozzle to the inner and outer surfaces of the steel pipe, or the steel pipe being immersed in a bath of the cooling medium to cool the outer surface and the inner surface is as described above. A suitable method such as cooling by the inner surface cooling method may be used. When cooling the steel pipe only from the inner surface, it is not always necessary to rotate the steel pipe, but if the steel pipe is rotated, more uniform cooling conditions will be obtained and the characteristics will be stable. Particularly, if the steel pipe is rotated at a rotation speed of 10 times / minute or more, more stable characteristics can be imparted to the product steel pipe. Similarly, the rotation condition of the steel pipe when cooling the steel pipe from the inner and outer surfaces while rotating the steel pipe is preferably 10 times / minute or more. In this case, since the cooling rate on the inner surface of the steel pipe and the cooling rate on the outer surface of the steel tube are approximately proportional to the inner surface flow rate and the outer surface flow rate of the cooling medium, respectively, if the flow rate of the cooling medium on the steel pipe inner surface is larger than that on the steel pipe outer surface, A cooling rate on the inner surface of the steel pipe that is higher than the cooling rate can be obtained. Depending on the type of cooling medium, stable characteristics can be obtained if at least the inner surface flow rate of the steel pipe is set to be 0.2 m 3 / min or more higher than the outer surface flow rate of the steel pipe. Which of the above three methods is selected may be appropriately selected depending on the wall thickness of the steel pipe, the hardenability of the material steel, and the restrictions of the quenching device. The medium-high carbon content steel pipe quenched by the method of the present invention is then tempered at a temperature of Ac 1 point or lower to give desired properties to be a product. Alternatively, after being tempered at a temperature of Ac 1 point or less, so-called "second and third processing" such as cutting, machining and heat treatment is performed to obtain a final product.
【実施例】以下実施例によって、本発明の効果を説明す
る。表１に示す化学組成の中・高炭素含有鋼を溶製し、
通常の方法によって表２及び表３に示す直径と肉厚の鋼
管に熱間製管した。上記の各鋼管から長さ１ｍの試験鋼
管を切り出し、表２及び表３に示す各条件で２０本ずつ
焼入れを実施した。焼入れ後の試験鋼管は目視で焼割れ
の有無を判定した。焼割れ判定結果を表２及び表３に併
せて示す。試験番号１〜２１に示すように、本発明の方
法で焼入れを行うと、水焼入れしたにも拘らず焼割れは
皆無である。一方、試験番号２２〜２４の油浸漬、又は
水浸漬による従来の鋼管の焼入れ方法では焼割れが発生
した。特に、試験番号２３の従来法によって水焼入れし
た場合には９５％の試験鋼管に焼割れが生じ、歩留まり
が極めて低くなることが明らかである。一方、試験番号
２５、２６に示すように、本発明の方法から外れた外面
だけからの冷却では、鋼管を回転させてもさせなくても
焼割れが発生する。更に、試験番号２７に示すように、
鋼管内面冷却速度を鋼管外面冷却速度より高めても、鋼
管を回転させなければ焼割れが発生する。試験番号２８
では鋼管内面冷却速度が鋼管外面冷却速度に比べて小さ
いので、鋼管を回転させても焼割れが発生している。EXAMPLES The effects of the present invention will be described with reference to the following examples. Steel with medium and high carbon content of chemical composition shown in Table 1,
Hot pipes were formed into steel pipes having diameters and wall thicknesses shown in Tables 2 and 3 by a usual method. A test steel pipe having a length of 1 m was cut out from each of the above-mentioned steel pipes, and each 20 pipes were quenched under the conditions shown in Tables 2 and 3. After the quenching, the test steel pipe was visually evaluated for the presence of quench cracks. The results of the quench cracking judgment are shown in Table 2 and Table 3 together. As shown in Test Nos. 1 to 21, when quenching is performed by the method of the present invention, no quenching cracks are present despite water quenching. On the other hand, quench cracking occurred in the conventional quenching method for steel pipes by immersion in oil or water in test numbers 22 to 24. In particular, it is clear that when water quenching is performed by the conventional method of Test No. 23, 95% of the test steel pipes undergo quenching cracks and the yield is extremely low. On the other hand, as shown in Test Nos. 25 and 26, cooling only from the outer surface deviated from the method of the present invention causes quench cracking whether the steel pipe is rotated or not. Furthermore, as shown in test number 27,
Even if the cooling rate on the inner surface of the steel pipe is higher than the cooling rate on the outer surface of the steel pipe, quench cracking occurs unless the steel pipe is rotated. Test number 28
However, since the cooling rate of the inner surface of the steel pipe is lower than the cooling rate of the outer surface of the steel pipe, quench cracking occurs even when the steel tube is rotated.
【表１】 [Table 1]
【表２】 [Table 2]
【表３】 [Table 3]
【発明の効果】本発明によれば、中・高炭素含有鋼管を
焼割れを生じることなく得ることができる。このため、
製品歩留まりが高まると共に焼入れ後にその鋼管を焼戻
しすることで焼戻しマルテンサイト組織の優れた強靭性
を充分に活用し、合金元素の多量添加を行わずとも、製
品鋼管に優れた特性を付与することが可能となる。従っ
て、産業上の効果は極めて大きい。EFFECTS OF THE INVENTION According to the present invention, it is possible to obtain steel pipes containing medium to high carbon without quenching cracks. For this reason,
By increasing the product yield and tempering the steel pipe after quenching, it is possible to fully utilize the excellent toughness of the tempered martensite structure and to impart excellent properties to the product steel pipe without adding a large amount of alloying elements. It will be possible. Therefore, the industrial effect is extremely large.
Claims (3)
る鋼管の焼割れを防止する焼入れ方法であって、焼入れ
において冷却を鋼管の内面だけから行うことを特徴とす
る中・高炭素含有鋼管の焼入れ方法。1. A quenching method for preventing quench cracking of a steel pipe containing 0.2 to 1.2% by weight of C, characterized in that in quenching, cooling is performed only from the inner surface of the steel pipe. Quenching method for medium and high carbon content steel pipes.
行うと共に冷却時にその鋼管を回転させることを特徴と
する請求項１に記載の中・高炭素含有鋼管の焼入れ方
法。2. The method for quenching a medium / high carbon content steel pipe according to claim 1, wherein cooling is performed only from the inner surface of the steel pipe during quenching and the steel pipe is rotated during cooling.
る鋼管の焼割れを防止する焼入れ方法であって、焼入れ
において鋼管外面冷却速度よりも大きな鋼管内面冷却速
度で冷却を鋼管の内外面から行うと共に、冷却時にその
鋼管を回転させることを特徴とする中・高炭素含有鋼管
の焼入れ方法。3. A quenching method for preventing quench cracking of a steel pipe containing 0.2 to 1.2% by weight of C, wherein the quenching is performed at a cooling rate on the inner surface of the steel pipe which is higher than a cooling rate on the outer surface of the steel pipe. The method for quenching steel pipes containing medium to high carbon content is characterized in that the steel pipe is rotated from inside and outside of the steel pipe during cooling.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP26110595A JP3873306B2 (en) | 1995-10-09 | 1995-10-09 | Quenching method to prevent quench cracking of medium and high carbon content steel pipes |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP26110595A JP3873306B2 (en) | 1995-10-09 | 1995-10-09 | Quenching method to prevent quench cracking of medium and high carbon content steel pipes |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH09104925A true JPH09104925A (en) | 1997-04-22 |
| JP3873306B2 JP3873306B2 (en) | 2007-01-24 |
Family
ID=17357160
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP26110595A Expired - Fee Related JP3873306B2 (en) | 1995-10-09 | 1995-10-09 | Quenching method to prevent quench cracking of medium and high carbon content steel pipes |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3873306B2 (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1999019522A1 (en) * | 1997-10-08 | 1999-04-22 | Mannesmann Ag | Method for preventing quenching cracks from forming on the inner surface of a cylindrical hollow body |
| JP2006046621A (en) * | 2004-07-08 | 2006-02-16 | Nsk Warner Kk | Clutch housing and its manufacturing method |
| WO2012127811A1 (en) | 2011-03-18 | 2012-09-27 | 住友金属工業株式会社 | Steel pipe quenching method |
-
1995
- 1995-10-09 JP JP26110595A patent/JP3873306B2/en not_active Expired - Fee Related
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1999019522A1 (en) * | 1997-10-08 | 1999-04-22 | Mannesmann Ag | Method for preventing quenching cracks from forming on the inner surface of a cylindrical hollow body |
| JP2006046621A (en) * | 2004-07-08 | 2006-02-16 | Nsk Warner Kk | Clutch housing and its manufacturing method |
| JP4533039B2 (en) * | 2004-07-08 | 2010-08-25 | Ｎｓｋワーナー株式会社 | Clutch housing and manufacturing method thereof |
| WO2012127811A1 (en) | 2011-03-18 | 2012-09-27 | 住友金属工業株式会社 | Steel pipe quenching method |
| US9546408B2 (en) | 2011-03-18 | 2017-01-17 | Nippon Steel & Sumitomo Metal Corporation | Quenching method for steel pipe |
Also Published As
| Publication number | Publication date |
|---|---|
| JP3873306B2 (en) | 2007-01-24 |
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