JPH03126858A - Carburizing and heat treating method for high-carbon chromium bearing steel - Google Patents
Carburizing and heat treating method for high-carbon chromium bearing steelInfo
- Publication number
- JPH03126858A JPH03126858A JP26574189A JP26574189A JPH03126858A JP H03126858 A JPH03126858 A JP H03126858A JP 26574189 A JP26574189 A JP 26574189A JP 26574189 A JP26574189 A JP 26574189A JP H03126858 A JPH03126858 A JP H03126858A
- Authority
- JP
- Japan
- Prior art keywords
- steel
- carburizing
- decarburized layer
- transformation point
- bearing steel
- 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.)
- Granted
Links
- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 58
- 239000010959 steel Substances 0.000 title claims abstract description 58
- 238000000034 method Methods 0.000 title claims abstract description 46
- 238000005255 carburizing Methods 0.000 title claims description 47
- 229910052799 carbon Inorganic materials 0.000 title abstract description 18
- 229910052804 chromium Inorganic materials 0.000 title abstract description 4
- 239000011651 chromium Substances 0.000 title abstract description 4
- 238000010438 heat treatment Methods 0.000 claims abstract description 29
- 230000009466 transformation Effects 0.000 claims abstract description 22
- 230000008569 process Effects 0.000 claims description 18
- FXNGWBDIVIGISM-UHFFFAOYSA-N methylidynechromium Chemical group [Cr]#[C] FXNGWBDIVIGISM-UHFFFAOYSA-N 0.000 claims description 14
- 238000000137 annealing Methods 0.000 claims description 11
- 238000011282 treatment Methods 0.000 abstract description 20
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 abstract description 13
- 229910001566 austenite Inorganic materials 0.000 abstract description 11
- 229910000859 α-Fe Inorganic materials 0.000 abstract description 10
- 238000001816 cooling Methods 0.000 abstract description 7
- 238000009792 diffusion process Methods 0.000 abstract description 7
- 239000013078 crystal Substances 0.000 abstract description 5
- 239000000463 material Substances 0.000 description 23
- 239000007789 gas Substances 0.000 description 15
- 238000012360 testing method Methods 0.000 description 14
- 238000005096 rolling process Methods 0.000 description 8
- 238000005261 decarburization Methods 0.000 description 6
- 150000001247 metal acetylides Chemical class 0.000 description 6
- 230000000694 effects Effects 0.000 description 4
- 238000005755 formation reaction Methods 0.000 description 4
- 238000004519 manufacturing process Methods 0.000 description 4
- 238000010583 slow cooling Methods 0.000 description 4
- 239000002436 steel type Substances 0.000 description 4
- 230000015572 biosynthetic process Effects 0.000 description 3
- 238000006243 chemical reaction Methods 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- 230000004888 barrier function Effects 0.000 description 2
- 238000000227 grinding Methods 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 239000000523 sample Substances 0.000 description 2
- 239000007787 solid Substances 0.000 description 2
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- 238000005266 casting Methods 0.000 description 1
- 239000000567 combustion gas Substances 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 238000005262 decarbonization Methods 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 238000007542 hardness measurement Methods 0.000 description 1
- 238000005098 hot rolling Methods 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 229910052750 molybdenum Inorganic materials 0.000 description 1
- 238000010899 nucleation Methods 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 239000011347 resin Substances 0.000 description 1
- 229920005989 resin Polymers 0.000 description 1
- 238000004904 shortening Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 229910052721 tungsten Inorganic materials 0.000 description 1
Abstract
Description
【発明の詳細な説明】
（産業上の利用分野）
この発明は、表面に脱炭層の生じた高炭素クロム軸受鋼
の復炭のための熱処理方法、および復炭と球状化焼なま
しとを兼ねた熱処理方法に関する。[Detailed Description of the Invention] (Field of Industrial Application) This invention provides a heat treatment method for decarburizing high carbon chromium bearing steel with a decarburized layer on its surface, and a process of decarburizing and spheroidizing annealing. This invention relates to a heat treatment method that also serves as a heat treatment method.
（従来の技術）
軸受の転動体や軌道幅（レース）あるいはピストンリン
グなどに用いられる材料には局部的に大きな面圧が加わ
り、その繰り返しによる摩耗に対する抵抗性が必要とさ
れるので、均一なＡｌ１１織を有する硬い鋼が使用され
る。このような鋼としては、ＪＩＳ Ｇ ４８０５に規
定される高炭素クロム軸受鋼が代表的なものであり、こ
れは母材の炭素含有量を高め、炭化物を球状化する熱処
理を施すことにより硬い鋼表面と良好な摺動特性を発揮
し、特にころがり軸受用として優れている。(Prior technology) Materials used for bearing rolling elements, raceway widths (races), piston rings, etc. are subject to large localized surface pressures, and they must have resistance to wear caused by repeated exposure. A hard steel with an Al11 weave is used. A typical example of such steel is high carbon chromium bearing steel specified in JIS G 4805, which is made into a hard steel by increasing the carbon content of the base material and applying heat treatment to make the carbides spheroidal. It exhibits good sliding characteristics on the surface and is particularly suitable for rolling bearings.
上記の高炭素クロム軸受鋼は、母材の炭素含有量が高い
ため、高温に加熱すると、炉内雰囲気を特別に制御しな
い限り、その表面が脱炭してしまう、このような鋼材は
、通常、溶製−鋳造−分塊圧延の工程でビレットにされ
、その後、熱間圧延によって棒、線、管（継目無管）な
どに加工されるのであるが、分塊圧延および次の熱間圧
延前のビレット加熱は、１１５０’Ｃを超える高い温度
で行われるため、数曲程度の深い脱炭層が生しる。この
脱炭が起こらないように、鋼材表面付近の雰囲気を制御
するのは、実際の製造現場では極めて困難なことである
０分塊圧延の際およびビレット加熱の際に生じた脱炭層
は、ビレット加熱後の圧延時の圧下比にもよるが、圧延
製品（棒、線、管）の表面に残存することが多く、この
ような素材から製造される軸受等はう面硬度の低下や摺
動性の劣化を招く、従って、このような場合、通常は研
削などの手段で脱炭層を除去することも行われているが
、これは工数の増加、歩留りの低下などにより製造コス
トを大きく増加させてしまう。The high carbon chromium bearing steel mentioned above has a high carbon content in the base material, so when heated to high temperatures, its surface will decarburize unless the furnace atmosphere is specially controlled. It is made into a billet through the process of melting, casting, and blooming, and then processed into bars, wires, pipes (seamless pipes), etc. by hot rolling. The previous billet heating is performed at a high temperature exceeding 1150'C, resulting in a deep decarburization layer of several degrees. In actual manufacturing sites, it is extremely difficult to control the atmosphere near the steel surface to prevent this decarburization. Although it depends on the rolling reduction ratio during rolling after heating, it often remains on the surface of rolled products (rods, wires, tubes), and bearings made from such materials may suffer from a decrease in surface hardness or sliding problems. Therefore, in such cases, the decarburized layer is usually removed by means such as grinding, but this greatly increases manufacturing costs due to increased man-hours and decreased yield. It ends up.
特公昭６２−４７６０５号公報には、上記の問題に関す
る一つの対策が開示されている。これは、脱炭層の生じ
た鋼材に浸炭処理を施して復炭させ、脱炭層をなくする
というのであり、研削除去のような方法に較べてはるか
に優れた方法である。しかし、特公昭６２−４７６０５
号公報に示される方法は、復炭処理を８００〜９５０℃
という高温度で、しかも２４時間というような長時間行
うものであり、後述するような材質劣化を招くだけでな
く、エネルギーコストの削減、工程の短縮という昨今の
要請に応えられない。Japanese Patent Publication No. 62-47605 discloses one solution to the above problem. This is a method that is far superior to methods such as grinding and removing, as the steel material with a decarburized layer is carburized and reincarburized to eliminate the decarburized layer. However, special public service No. 62-47605
In the method shown in the publication, the decarbonization treatment is carried out at 800 to 950°C.
This process is carried out at such high temperatures and for a long period of time, such as 24 hours, which not only causes material deterioration as described below, but also fails to meet the recent demands for reducing energy costs and shortening processes.
さて、高炭素クロム軸受鋼の熱処理のうち比較的長時間
にわたり鋼を加熱する熱処理に、球状化焼なましがある
０球状化焼鈍は炭化物を球状化するための必須の処理で
あるが、その方法には、■Ａ１変態点の直下で長時間保
持する方法、■Ａ１変態点の直上と直下で繰り返し加熱
する方法、■Ａ１変態点の直上で加熱したのち徐冷する
方法、などがある、いずれの方法でも、炉の雰囲気を制
御することで鋼表面を保護し熱処理中に脱炭を生しさせ
ない処置が取られているが、既に存在する脱炭層に復炭
させるような処置は講しられていない、その理由は、球
状化焼なまし前の素材は場合により数百μ■もの深い脱
炭層が存在すること、上記■〜■のような熱処理パター
ンでは、仮に雰囲気を浸炭雰囲気にしても浸炭の程度が
不十分で脱炭層を完全に復炭することは困難であると考
えられていたこと、にある。Now, among the heat treatments for high carbon chromium bearing steel, spheroidizing annealing is a heat treatment that heats the steel for a relatively long period of time.Spheroidizing annealing is an essential treatment for spheroidizing carbides. Methods include: ■ Holding the temperature just below the A1 transformation point for a long time; ■ Repeating heating just above and below the A1 transformation point; ■ Heating just above the A1 transformation point and then slow cooling. In both methods, measures are taken to protect the steel surface and prevent decarburization during heat treatment by controlling the furnace atmosphere, but no measures are taken to reincarnate the already existing decarburized layer. The reason for this is that the material before spheroidizing annealing has a decarburized layer as deep as several hundred micrometers in some cases. However, it was thought that the degree of carburization was insufficient and it would be difficult to completely recarburize the decarburized layer.
従来、浸炭処理は鋼のオーステナイ１−（ｒ）域で行う
のが常識である０例えば、第３版「鉄鋼便覧ＶＩＪ（丸
善、昭和５７年５月３１日発行）の５６３頁には「浸炭
は、オーステナイト中に炭素を固溶させる反応」と定義
されており、改定３版「金属便覧Ｊ（丸善、昭和４６年
１２月１０日発行）の１６８７頁の図１４・１６にある
ように浸炭温度は８５０〜１ｏｏｏ’ｃとオーステナイ
ト域になっている。このように、従来は、ガス浸炭であ
れ固体浸炭であれ、浸炭処理は温度の高いオーステナイ
ト域で炭素を拡散浸透させるのが常識であった。温度の
低いところで浸炭した場合には、拡散した炭素は結晶粒
界に塊状炭化物を生威し、これが拡散障壁となるため十
分な深さの浸炭層は得られないと信しられていたのであ
る。Conventionally, it is common knowledge that carburizing treatment is carried out in the austeni 1-(r) range of steel.For example, on page 563 of the 3rd edition "Steel Handbook VIJ" (Maruzen, published on May 31, 1980), there is a "Carburizing treatment" Carburizing is defined as a reaction to solidly dissolve carbon in austenite, and as shown in Figures 14 and 16 on page 1687 of the revised 3rd edition, Metal Handbook J (Maruzen, published December 10, 1970), carburization The temperature is 850~1ooo'c, which is in the austenite range.As shown above, conventionally, whether it is gas carburizing or solid carburizing, it is common sense that carbon is diffused and penetrated in the high-temperature austenite range. It was believed that if carburization was carried out at low temperatures, the diffused carbon would form massive carbides at the grain boundaries, and this would act as a diffusion barrier, making it impossible to obtain a sufficiently deep carburized layer. It is.
（発明が解決しようとする課１！り
本発明の目的は、脱炭層を持つ高炭素クロム軸受鋼の復
炭をできるだけ低温で短時間に行うことのできる技術を
提（」（すること、さらに、ｌｊ状化焼なまし処理と同
時に脱炭層の復炭を行うことができる技術を提（」（す
ること、にある。(Issue 1 to be solved by the invention!) The purpose of the present invention is to provide a technology that can decarburize high carbon chromium bearing steel having a decarburized layer at as low a temperature as possible in a short time. , we present a technology that can perform recarburization of the decarburized layer simultaneously with lj-forming annealing treatment.
（課題を解決するための手段）
浸炭層深さは、種々の要因により決まるが、般には炭化
物の生成挙動ならびに固溶炭素の母材中の拡散に大きく
依存し、温度が高く、処理時間が長い程浸炭層は深くな
ると考えられている。同じ浸炭層深さを得るには、高温
で処理するほど短時間ですむというのが常識である。前
述のごとく、従来、鋼の浸炭処理が高温のｒｆＪ域で行
われていたのはこの理由による。しかし、従来の高温域
で長時間加熱する浸炭処理には、特に球状化処理を行わ
なければならない高炭素クロム軸受鋼では、次のような
問題がある。即ち、Ｔ域で鋼を長時間加熱すると、オー
ステナイト結晶粒がＩｎ大化してしまい、引き続く熱処
理によっても均一に分１１（シた球状炭化物が得られな
い、仮に、Ｔ域での浸炭処理によって、脱炭層の復炭が
できても、次の球状化処理で所望の＆ｎ織が得られなけ
れば軸受鋼としての特性が発渾できない、さらに、浸炭
処理であれ、球状化処理であれ、適切な雰囲気に保った
炉内に被処理材を通して連続的に処理するのが望ましい
のであるが、従来のような高温での長時間処理では設備
的にも連続処理は難しい。(Means for solving the problem) The depth of the carburized layer is determined by various factors, but in general, it largely depends on the formation behavior of carbides and the diffusion of solute carbon in the base material, and it depends on It is believed that the longer the carburized layer, the deeper the carburized layer. It is common knowledge that to obtain the same carburized layer depth, the higher the temperature, the shorter the time required. As mentioned above, this is the reason why carburizing of steel has conventionally been carried out at high temperatures in the rfJ range. However, the conventional carburizing treatment that involves heating in a high-temperature range for a long time has the following problems, especially for high-carbon chromium bearing steels that must be spheroidized. In other words, if steel is heated for a long time in the T region, the austenite crystal grains will become large and the subsequent heat treatment will not uniformly produce spheroidal carbides. Even if the decarburized layer is recarburized, the properties as a bearing steel cannot be developed unless the desired &n texture is obtained in the next spheroidizing treatment. Although it is desirable to continuously process the material by passing it through a furnace maintained in an atmosphere, continuous processing is difficult due to the equipment required for conventional long-term processing at high temperatures.
上記のような問題点を解決する最良の方ｌ去は、浸炭（
脱炭層の復炭）をできるだけ低い温度でしかも短時間に
行うことである。さらに、この処理を、球状化熱処理と
兼ねて行うことができれば、生産効率の向上効果は計り
知れない。本発明者は、このような観点から、鋼の浸炭
挙動を改めて訂細に検討した。The best way to solve the above problems is carburizing (
The aim is to carry out the recarburization of the decarburized layer at the lowest possible temperature and in a short time. Furthermore, if this treatment can be performed concurrently with the spheroidization heat treatment, the effect of improving production efficiency is immeasurable. From this point of view, the inventors have once again examined the carburizing behavior of steel in detail.
本発明者は、炭素の拡散の遅速は母材の結晶構造に大き
く依存し、通常はＴ相よりもα相の方が拡散が早い点に
着目し、温度の低いフェライト（α）相領域で浸炭が可
能かどうかを調べた。その結果、従来の常識に反し、温
度の低いα相領域でも充分に浸炭することが明らかにな
った。もちろん、同し結晶構造であれば、温度の高い方
が拡散速度は大きいのであるが、炭素のに敗は、高ｌＨ
のＴ相よりも、低温のα相の方、が格段に早いのである
。しかも、浸炭深さは炭素の拡散に大きく依存し、炭化
物生成反応の影響は浸炭に関しては小さく、比較的低温
で浸炭しても、結晶粒界には塊状の炭化物は顕著には生
成せず、拡１１父の障壁とはならないという新しい知見
が得られた。このことは、同し浸炭（復炭）深さを得る
場合には、α相領域で処理した方がＴ相領域で処理する
よりも短時間ですむということを意味する。The present inventors focused on the fact that the slow rate of carbon diffusion largely depends on the crystal structure of the base material, and that diffusion is usually faster in the α phase than in the T phase. We investigated whether carburizing is possible. As a result, it was revealed that, contrary to conventional wisdom, sufficient carburization occurs even in the low-temperature α phase region. Of course, if the crystal structure is the same, the higher the temperature, the faster the diffusion rate, but carbon's failure is due to the high lH
The low-temperature α phase is much faster than the T phase. Furthermore, the carburization depth largely depends on carbon diffusion, and the influence of carbide formation reactions is small on carburization. Even when carburizing at a relatively low temperature, lumpy carbides do not form noticeably at grain boundaries. New knowledge has been obtained that it is not a barrier to the expansion of the 11th generation. This means that in order to obtain the same carburization (recarburization) depth, processing in the α phase region takes less time than processing in the T phase region.
上記の知見に基づく本発明は、下記（１）および（２）
を要旨とするものである。The present invention based on the above knowledge provides the following (1) and (2)
The main points are as follows.
（１）前工程で表面に脱炭層の生じた高炭素り〔１ム軸
受鋼に、その鋼のＡ、変態点以下の温度で浸炭処理を施
して脱炭層に復炭させることを特徴とする高炭素クロム
軸受鋼のガス浸炭方法。(1) A high-carbon bearing steel with a decarburized layer formed on its surface in the previous process [characterized by carburizing the 1-mu bearing steel at a temperature below the A, transformation point of the steel to recarburize the decarburized layer. Gas carburizing method for high carbon chromium bearing steel.
（２）前工程で表面に脱炭層の生じた高炭素りｌコム軸
受鋼を球状化焼なましする際に、その鋼がＡ、変態点以
下の温度域にあるときにＪＪＩＩ熱雰囲気を浸炭雰囲気
とし、球状化と脱炭層の復炭とを同時に行うことを特徴
とする高炭素クロム軸受鋼の熱処理方法。(2) When spheroidizing and annealing high-carbon comb bearing steel with a decarburized layer on its surface in the previous process, the JJII thermal atmosphere is used to carburize the steel when it is in the temperature range below the A transformation point. A heat treatment method for high carbon chromium bearing steel characterized by simultaneously performing spheroidization and decarburization of a decarburized layer in an atmosphere.
本発明の対象となる高炭素クロム軸受鋼とは、例えば、
ＪＩＳ Ｇ４８０５のＳＵＪ Ｉ〜５に代表される炭素
が０．９５〜１．ｌＯ％程度、クロムが０．９０〜１．
６０％程度含有される鋼で、この外にＭｏ、 Ｗ、■等
を必要に応じて含有する改良鋼種も対象になる。The high carbon chromium bearing steel that is the subject of the present invention is, for example,
The carbon content represented by SUJ I-5 of JIS G4805 is 0.95-1. About 1O%, chromium is 0.90 to 1.
Improved steel types that contain about 60% of C and also include Mo, W, ■, etc., as necessary, are also targeted.
処理される時の形態は、通常、圧延のまま、または圧延
後に脱スケールされた棒、線、管などであるが、その外
、歯車や軸受の転動体、レース等のような部品の形態に
なっているものでもよい。The processed forms are usually rods, wires, tubes, etc., either as rolled or descaled after rolling, but also in the form of parts such as gears, rolling elements of bearings, races, etc. It may be something that is.
浸炭処理は、ガス浸炭、液体浸炭、固体浸炭、のいずれ
でもよいが、工業的にはガス浸炭が好ましい、特に、所
定温度に保った炉中に被処理材を連続的に通して復炭、
あるいは復炭と球状化処理を兼ねて行うには、雰囲気調
整の容易なガス浸炭法が望ましい。The carburizing treatment may be gas carburizing, liquid carburizing, or solid carburizing, but gas carburizing is preferred industrially.In particular, carburizing is carried out by continuously passing the material to be treated through a furnace kept at a predetermined temperature.
Alternatively, in order to perform both recarburization and spheroidization treatment, a gas carburizing method that allows easy atmosphere adjustment is desirable.
八、変態点というのは、低温から加熱していく場合には
Ａｃｔ変熊点を意味し、高温から冷却していく場合には
Ａｒｌ変態点を意味する。8. Transformation point means the Act transformation point when heating starts from a low temperature, and means the Arl transformation point when cooling from a high temperature.
（２）の方法における球状化処理は、前記■〜■の方法
、その他いずれの方法でもよい。■の方法であれば、球
状化処理中の仕置の時間に雰囲気を浸炭雰囲気にして実
施する。■の方法でも、少ｉｉ くとも鋼がＡ、変態点
以下の温度にあるときに浸炭雰囲気にして迅速な復炭を
行わせることができる。The spheroidizing treatment in method (2) may be performed by any of the methods (1) to (4) above, or any other method. In the case of method (2), the atmosphere is set to be a carburizing atmosphere during the finishing time during the spheroidization process. Even in the method (2), it is possible to carry out rapid reincarburization by creating a carburizing atmosphere when the steel is at least at a temperature below the transformation point A.
■の方法では、徐冷中のＡｔ ｉ態点以下の温度域にあ
るときに浸炭雰囲気にする。なお、■および■の場合に
、Ａ１変態点直上にあるときにも浸炭雰囲気とすること
は何ら差し支えない。In method (2), a carburizing atmosphere is created when the temperature is below the At i state during slow cooling. In addition, in the cases of (1) and (2), there is no problem in creating a carburizing atmosphere even when the temperature is directly above the A1 transformation point.
（作用）
前述のように数百μ国もの脱炭層のある鋼を種度処理に
よって復炭させるためには、炭素の拡１１りをフェライ
ト相で行わせる必要がある。そのため、浸炭処理を綱の
＾、変態点以下で行う。この低温浸炭処理であれば、数
’ｄ’ ｕ ｍの深さまで脱炭している鋼でも前δＧの
オーステナイト結晶粒の過大成長などの弊害なしに復炭
させることができる。しかも、従来の球状化焼なましの
条件で、同特に−１分に復炭させることができる。(Function) As mentioned above, in order to recarburize steel with a decarburized layer of several hundred μm in diameter through a seeding treatment, it is necessary to cause the expansion of carbon to occur in the ferrite phase. Therefore, the carburizing treatment is carried out below the transformation point of the steel. With this low-temperature carburizing treatment, even steel that has been decarburized to a depth of several d' um can be recarburized without problems such as excessive growth of austenite crystal grains with pre-δG. Furthermore, under the conventional conditions of spheroidizing annealing, it is possible to recarburize the steel to -1 minute.
球状化焼鈍を徐冷法（前記■の方法）で行う場合には、
鋼の冷却速度を８０°Ｃ／ｈｒ以下に抑えるのがよい、
これは８０°Ｃ／ｈｒよりも連い冷却速度だと浸炭の時
間が短くなり、フェライト相で浸炭しても必要な復炭が
達成されないことがあるからであ以下、実施例によって
本発明を更に具体的に説明する。When performing spheroidization annealing using the slow cooling method (method ① above),
It is best to keep the cooling rate of steel below 80°C/hr.
This is because if the cooling rate is higher than 80°C/hr, the carburizing time will be shortened, and even if carburized in the ferrite phase, the necessary reincarburization may not be achieved. This will be explained more specifically.
〔実施例１、復炭処理の例〕 第１表に示す化学組成の素材を使用した。[Example 1, example of recharging treatment] Materials having the chemical composition shown in Table 1 were used.
試験片は、マンネスマン方式で製管された５０．８φＸ
７ ｔ （ｍｍ）の圧延のままの素管から採取し、試
験に供した。試験片形状を第１図に示す。The test piece was a 50.8φX pipe made using the Mannesmann method.
A sample was taken from a 7 t (mm) unrolled pipe and used for testing. The shape of the test piece is shown in Figure 1.
素管は、分塊圧延、ビレット加熱、穿孔圧延等のプロセ
スを経て来ているため、管外表面には約５００〜７５０
μ−の脱炭層が存在していた。試験片の一部のものにつ
いては、鋼表面を切削し、脱炭層を完全に除去したもの
も準備した。以降の浸炭挙動の検討には主として管外表
面を用いている。The raw pipe has gone through processes such as blooming rolling, billet heating, and piercing rolling, so the outer surface of the pipe has about 500 to 750
A μ− decarburized layer was present. Some test specimens were prepared by cutting the steel surface and completely removing the decarburized layer. In the subsequent study of carburization behavior, the outer surface of the tube was mainly used.
まず、第１表のｔｊ４Ｉｌ１２の素管を使用し、復炭の
試験を行った。熱処理には第２図に示すヒートノ＜ター
ンを用いた。炉の雰囲気は第２図に矢印で示した領域だ
け浸炭性ガスを流し、その他の区間は鋼と雰囲気ガス（
燃焼ガス）との反応を避けるためｈガスを通気した。浸
炭性ガスとしては、炭素活量の高いｄ合ガス（ＣＯ：２
５ｖｏ１．％、Ｈｚ： ３０ｖｏ１．％、ＣＯＩ： ０
．２ｖｏ１０％、ｂａｌ、Ｎｔ）を用いた。浸炭性ガス
を通気する温度範囲を第２図中の１〜Ｖのように変化さ
せ浸炭時の鋼の相状態を区分した。なお、供試鋼のＡ１
変悪意はいずれも加熱昇温時（Ａｃ、変態点）は約７６
０°Ｃであり、降温時（Ａｒ、変態点〉は約７２０°Ｃ
である。従って、第２図の熱処理範囲の１および■はオ
ーステナイト領域、■および■はフェライト領域で、■
はオーステナイトとフェライトの二つの相の領域で浸炭
反応を行ったことになる。First, a recarbonization test was conducted using the tj4Il12 raw tube shown in Table 1. For the heat treatment, a heat no<turn shown in FIG. 2 was used. The atmosphere in the furnace is such that carburizing gas is flowed only in the area indicated by the arrow in Figure 2, and the other areas are filled with steel and atmospheric gas (
h gas was vented to avoid reaction with combustion gas). As the carburizing gas, d gas with high carbon activity (CO:2
5vo1. %, Hz: 30vo1. %, COI: 0
．． 2vo10%, bal, Nt) was used. The phase state of the steel during carburization was classified by changing the temperature range in which the carburizing gas was passed as shown in 1 to V in FIG. 2. In addition, A1 of the test steel
The transformation temperature is approximately 76 when heated and heated (Ac, transformation point).
0°C, and when the temperature is lowered (Ar, transformation point) is approximately 720°C
It is. Therefore, 1 and ■ in the heat treatment range in Fig. 2 are austenite regions, ■ and ■ are ferrite regions, and ■
This means that the carburizing reaction took place in the two-phase region of austenite and ferrite.
熱処理後は、試験片の外表面の断面をミツ１１組織試験
用に樹脂に埋め込んで研磨し、ＪＩＳ Ｇ ０５５７．
０５５８で規定される全硬化層もしくは全脱炭層を測定
した。After heat treatment, the cross section of the outer surface of the test piece was embedded in resin for Mitsu 11 microstructure testing, and polished to JIS G 0557.
The total hardened layer or total decarburized layer defined by 0558 was measured.
測定結果を第２表に示す、第２表には素管の管外表面の
脱炭層を切削除去したものを健全な素材とし、脱炭層の
深さが５００μ園と７５０μ−のイ」（試材についての
結果を示した。なお、全硬化層（浸炭Ｉりを＋、全脱炭
層を−で記した。The measurement results are shown in Table 2. In Table 2, the decarburized layer on the outer surface of the raw pipe was removed and used as a sound material, and the decarburized layer depth was 500μ and 750μ. The results are shown for the materials.The total hardened layer (carburized layer is marked with +, and the total decarburized layer is marked with -).
第２表に明らかなように、オーステナイト領域（Ｉおよ
び■）で浸炭させたものは、フェライト領域（Ｅｌｌお
よび■）で浸炭させたものに比し、脱炭層のない健全な
素材でも浸炭層は極く浅い、もともと５００ｐ■、７５
０μ−の脱炭層を有する材料では、第２図に示す■およ
び■のオーステナイト域だけで浸炭させても完全には復
炭していない、しかし、第２図の■、■、■における浸
炭処理のように、少なくとも浸炭処理の一部がフェライ
ト域でなされた場合には、十分に復炭している。なお、
復炭が完了した上さらに浸炭が進んでいるものもあるが
、浸炭層の形成は軸受鋼の特性に悪影響は及ぼさない０
本発明方法は、この浸炭層の形成も自在に調整できると
いう利点も有する。As is clear from Table 2, those carburized in the austenite region (I and ■) are more carburized than those carburized in the ferrite region (Ell and ■), even if the material is sound and has no decarburized layer. Extremely shallow, originally 500p■, 75
For materials with a decarburized layer of 0 μ-, carburization is not complete even if the austenitic regions of ■ and ■ shown in Figure 2 are carburized, but the carburizing treatment of ■, ■, and ■ in Figure 2 If at least a part of the carburizing treatment is performed in the ferrite region, as in the case shown in FIG. In addition,
In some cases, carburization has progressed even after recarburization has been completed, but the formation of a carburized layer does not have a negative effect on the properties of the bearing steel.
The method of the present invention also has the advantage that the formation of this carburized layer can be freely adjusted.
第３表は、第１表に示したＪＩＳ Ｇ ４８０５（７）
ＳＵＪＩ 〜５を含む各種の高炭素クロム軸受鋼を、第
２図の■の領域で浸炭処理した場合の結果である。熱処
理前の素材は約５００μｍ程度脱戻していたが、第３表
に示すように、フェライト相領域で浸炭させることによ
って素材で認められた脱炭層は鋼種によらずいずれも完
全に復炭していた。Table 3 shows JIS G 4805 (7) shown in Table 1.
These are the results when various high carbon chromium bearing steels including SUJI ~5 were carburized in the area marked with ■ in FIG. 2. The material before heat treatment had decarburized by approximately 500 μm, but as shown in Table 3, the decarburized layer observed in the material by carburizing in the ferrite phase region was completely decarburized regardless of the steel type. Ta.
〔実施例２、球状化と復炭の例〕
第１表の鋼種２の試験片を用いて、徐冷法による球状化
焼なましを実施した。その際、冷却過程で鋼がフェライ
ト相となる領域（第３図に太線で示す７２０℃と６７０
℃の間）で鋼を浸炭性ガス雰囲気（実施例１と同組成）
と接触させ、ガス浸炭させた。[Example 2, Example of spheroidization and reincarburization] Spheroidization annealing was carried out using a slow cooling method using a test piece of steel type 2 in Table 1. At that time, the region where the steel becomes a ferrite phase during the cooling process (720°C and 670°C shown as thick lines in Figure 3)
℃) in a carburizing gas atmosphere (same composition as Example 1)
was brought into contact with gas carburizing.
熱処理のヒートパターンを第３図に示す、このとき、冷
却速度を５°Ｃ／ｈｒ〜９０’ｃ ／ｈｒの間で種々変
化させ、復炭の状況を調査した。素材としては、約７５
０μ−の脱炭層のあるものを使用した。The heat pattern of the heat treatment is shown in FIG. 3. At this time, the cooling rate was variously varied between 5°C/hr and 90'c/hr, and the state of recoburization was investigated. The material is approximately 75
A material with a 0 μ- decarburized layer was used.
試験結果を第４表に示す、降温速度が８０°Ｃ／ｈｒ以
下の場合には、供試材に見られた脱炭層は完全に復炭し
、良好な鋼表面性状が得られた。また、第４表に示す表
面から３００μ−の深さにおりる硬度の測定結果をみれ
ば、球状化も充分に行われていることがわかる。The test results are shown in Table 4. When the cooling rate was 80°C/hr or less, the decarburized layer observed in the sample material was completely recarburized, and good steel surface properties were obtained. Further, from the measurement results of the hardness at a depth of 300 μm from the surface shown in Table 4, it can be seen that spheroidization is also sufficiently performed.
〔実施例３、球状化と復炭の例〕
第１表の鋼種２の試験片を用いて、繰り返し法による球
状化焼なましを実施した。ヒートパターンを第４図に示
す。[Example 3, Example of Spheroidization and Recarburization] Spheroidization annealing was carried out by a repeated method using a test piece of steel type 2 in Table 1. The heat pattern is shown in FIG.
１回目のオーステナイト域加熱と２回目のオーステナイ
ト域加熱の間のフェライト相領域（図のヒートパターン
の太線の部分）でガス浸炭を行った。ガス組成は実施例
１と同しである。浸炭時間を３０分〜１時間の間で変化
させて、素材の復炭状況を観察した。素材としては約７
５０／／Ｉｍの脱炭層のあるものを用いた。拭験結果を
第５表に示す。Gas carburization was performed in the ferrite phase region (the thick line part of the heat pattern in the figure) between the first austenite region heating and the second austenite region heating. The gas composition is the same as in Example 1. The carburizing time was varied between 30 minutes and 1 hour, and the recarburization status of the material was observed. The material is about 7
A material with a decarburized layer of 50//Im was used. The wiping test results are shown in Table 5.
また、処理後の表面から３００μ錫の深さの位置での硬
度測定結果を併記する。In addition, hardness measurement results at a depth of 300 μm from the surface after treatment are also shown.
第４図に示すこの実施例のヒートパターンでは、α相領
域での浸炭時間を３０分より長くすれば、完全に復炭し
、かつＦｉＥ状化した良好な鋼が得られることがわかる
。In the heat pattern of this example shown in FIG. 4, it can be seen that if the carburizing time in the α phase region is made longer than 30 minutes, a good steel that is completely reincarburized and becomes FiE-like can be obtained.
（以下、余白）
第
表
（以下、余白）
第
表
（以下、余白）
第
３
表
（以下、余白）
第
表
第
表
（以下、余白）
（発明の効果）
本発明は、鋼の浸炭がＴ相領域よりもα相領域で迅速に
進行するという従来の常識に反する匁に基づいてなされ
たものである０本発明方法にれば、脱炭層の復炭処理を
従来よりも低温で実することができ、高温での浸炭処理
に伴う多く問題が一挙に解決できる。この方法では短時
間で深い浸炭層が得られるため、連続処理にも適してお
り、特に、高炭素クロム軸受鋼の製造に必須の工程であ
る球状化処理の際に脱炭層の復炭処理日時に行うことが
できるから、工程合理化の効が極めて大きい。(hereinafter referred to as margin) Table 1 (hereinafter referred to as margin) Table 3 (hereinafter referred to as margin) Table 3 (hereinafter referred to as margin) Table 1 (hereinafter referred to as margin) (Effect of the invention) The present invention shows that carburizing of steel is This method was based on the conventional wisdom that decarburization proceeds more quickly in the α-phase region than in the α-phase region. According to the method of the present invention, the decarburization process of the decarburized layer can be carried out at a lower temperature than before. This allows many problems associated with high-temperature carburizing treatment to be solved at once. Since this method can obtain a deep carburized layer in a short time, it is also suitable for continuous processing.In particular, during the spheroidizing process, which is an essential process in the production of high carbon chromium bearing steel, the decarburized layer is recarburized. Since it can be carried out in a number of steps, it is extremely effective in streamlining the process.
第１図は、熱処理の試験に供した試験片の形を、示す図
、第２図は、浸炭処理を行うヒートパーンを示す図、第
３図および第４図は、浸炭と軟化処理を同時に行うヒー
トパターンを示す図である。Figure 1 shows the shape of the test piece used in the heat treatment test, Figure 2 shows the heat burner that performs the carburizing process, and Figures 3 and 4 show the carburizing and softening processes performed simultaneously. It is a figure showing a heat pattern.
Claims (2)
鋼に、その鋼のＡ＿１変態点以下の温度で浸炭処理を施
して脱炭層に復炭させることを特徴とする高炭素クロム
軸受鋼の浸炭・熱処理方法。(1) A high carbon chromium bearing characterized by carburizing high carbon chromium bearing steel, which has a decarburized layer on its surface in a previous process, at a temperature below the A_1 transformation point of the steel to reincarburize the decarburized layer. Carburizing and heat treatment methods for steel.
鋼を球状化焼なましする際に、その鋼がＡ＿１変態点以
下の温度域にあるときに加熱雰囲気を浸炭雰囲気とし、
球状化と脱炭層の復炭とを同時に行うことを特徴とする
高炭素クロム軸受鋼の浸炭・熱処理方法。(2) When spheroidizing and annealing high carbon chromium bearing steel with a decarburized layer on its surface in the previous process, the heating atmosphere is set to a carburizing atmosphere when the steel is in the temperature range below the A_1 transformation point,
A method for carburizing and heat treating high carbon chromium bearing steel, which is characterized by simultaneously performing spheroidization and reincarburization of a decarburized layer.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP26574189A JPH0730438B2 (en) | 1989-10-12 | 1989-10-12 | Carburizing and heat treatment method for high carbon chrome bearing steel |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP26574189A JPH0730438B2 (en) | 1989-10-12 | 1989-10-12 | Carburizing and heat treatment method for high carbon chrome bearing steel |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH03126858A true JPH03126858A (en) | 1991-05-30 |
| JPH0730438B2 JPH0730438B2 (en) | 1995-04-05 |
Family
ID=17421352
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP26574189A Expired - Fee Related JPH0730438B2 (en) | 1989-10-12 | 1989-10-12 | Carburizing and heat treatment method for high carbon chrome bearing steel |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH0730438B2 (en) |
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| JP2009019639A (en) * | 2003-02-28 | 2009-01-29 | Ntn Corp | Manufacturing process of roller cam follower for engine |
| WO2012081229A1 (en) | 2010-12-13 | 2012-06-21 | 住友金属工業株式会社 | High-carbon chromium bearing steel, and process for production thereof |
| JP2015218349A (en) * | 2014-05-15 | 2015-12-07 | 新日鐵住金株式会社 | Heat treatment method for steel pipe and manufacturing method for bearing steel pipe using the same |
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| JP5786764B2 (en) * | 2012-03-06 | 2015-09-30 | 新日鐵住金株式会社 | Manufacturing method of high carbon chromium bearing steel |
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1989
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2009019639A (en) * | 2003-02-28 | 2009-01-29 | Ntn Corp | Manufacturing process of roller cam follower for engine |
| JP2007297672A (en) * | 2006-04-28 | 2007-11-15 | Ntn Corp | Method for manufacturing rolling parts, and bearing ring and bearing |
| JP4712603B2 (en) * | 2006-04-28 | 2011-06-29 | Ｎｔｎ株式会社 | Rolling part manufacturing method, race ring and bearing |
| WO2012081229A1 (en) | 2010-12-13 | 2012-06-21 | 住友金属工業株式会社 | High-carbon chromium bearing steel, and process for production thereof |
| JP5093410B2 (en) * | 2010-12-13 | 2012-12-12 | 住友金属工業株式会社 | High carbon chromium bearing steel and manufacturing method thereof |
| US8808470B2 (en) | 2010-12-13 | 2014-08-19 | Nippon Steel & Sumitomo Metal Corporation | High-carbon chromium bearing steel and production method of the same |
| JP2015218349A (en) * | 2014-05-15 | 2015-12-07 | 新日鐵住金株式会社 | Heat treatment method for steel pipe and manufacturing method for bearing steel pipe using the same |
| CN108950154A (en) * | 2018-08-09 | 2018-12-07 | 洛阳Lyc轴承有限公司 | A kind of annealing process of bearing parts |
Also Published As
| Publication number | Publication date |
|---|---|
| JPH0730438B2 (en) | 1995-04-05 |
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