JPH05255733A - Production of carburized and case hardened steel material having delayed fracture resistance - Google Patents
Production of carburized and case hardened steel material having delayed fracture resistanceInfo
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- JPH05255733A JPH05255733A JP8627292A JP8627292A JPH05255733A JP H05255733 A JPH05255733 A JP H05255733A JP 8627292 A JP8627292 A JP 8627292A JP 8627292 A JP8627292 A JP 8627292A JP H05255733 A JPH05255733 A JP H05255733A
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- carburized
- tempering
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Abstract
Description
【０００１】[0001]
【産業上の利用分野】この発明は、自動車，建設機械等
における“ネジ部が存在する浸炭部品”用として好適な
浸炭肌焼鋼材の製造方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 producing a carburized case-hardened steel material suitable for "carburized parts having a screw portion" in automobiles, construction machines and the like.
【０００２】[0002]
【従来技術とその課題】一般に、自動車，土木建設機
械，産業機械等における摩耗が生じやすい部位には浸炭
処理を施した浸炭肌焼鋼部材が多用されている。この
“浸炭処理”は、例えばＣＯ，Ｎ2 ，Ｈ2 等のガス雰囲
気中で熱処理を施して鋼の表層部に炭素を浸入させ、該
表層部の炭素濃度（炭素含有量）を高めることにより焼
入れ後の硬さを増加させる熱処理で、耐摩耗性，疲労特
性の向上を目的とした処理であることは周知であるが、
一方で、鋼材に浸炭処理を施すと“遅れ破壊”を生じや
すくなると言う事実がある。2. Description of the Related Art Generally, carburized case hardened steel members subjected to carburizing treatment are often used in parts of automobiles, civil engineering construction machines, industrial machines, etc. where wear is likely to occur. This "carburizing treatment" is carried out by, for example, performing heat treatment in a gas atmosphere of CO, N 2 , H 2 or the like to infiltrate carbon into the surface layer portion of the steel to increase the carbon concentration (carbon content) of the surface layer portion It is well known that this is a heat treatment for increasing the hardness after quenching, which is intended to improve wear resistance and fatigue characteristics.
On the other hand, there is a fact that when steel is carburized, "delayed fracture" tends to occur.
【０００３】この“遅れ破壊”は、使用の途中で突然に
脆性破壊を起こす現象で、特に引張応力が生じる場合に
はその傾向は更に著しくなるため、引張応力の発生が避
けられないボルト類（ネジ部を有する部品）では上述の
ような浸炭処理が誘因となる遅れ破壊が大きな問題とな
っている。そのため、ネジ部を有する（締付け時に引張
応力が発生する）浸炭部品においては、ネジ部の浸炭を
防止すべく浸炭防止剤を塗布したり、ネジ部にカバ−を
設けて浸炭防止を図る等の工夫が強いられていた。This "delayed fracture" is a phenomenon in which brittle fracture suddenly occurs during use, and particularly when tensile stress occurs, the tendency becomes more remarkable. Therefore, the occurrence of tensile stress is unavoidable. In the case of parts having a screw portion), delayed fracture caused by the carburizing treatment as described above is a serious problem. Therefore, for carburized parts that have threaded parts (tensile stress is generated during tightening), a carburizing inhibitor should be applied to prevent carburization of the threaded parts, or a cover should be provided on the threaded parts to prevent carburization. It had to be devised.
【０００４】しかしながら、浸炭防止剤をムラ無く塗布
することは実際作業上非常に難しいことであり、またカ
バ−を設けたとしても隙間から浸炭ガスが侵入するのを
完全に防ぐことができないことから、前記工夫を施して
も浸炭を完全に防止することは困難であった。しかも、
これらの手立てを施すことは著しい作業性の低下につな
がるものであったため、より簡易に耐遅れ破壊性を向上
させる手段の開発が切望されていた。However, it is very difficult in practice to apply the carburizing inhibitor evenly, and even if a cover is provided, it is not possible to completely prevent the carburizing gas from entering through the gap. However, it was difficult to completely prevent carburization even with the above measures. Moreover,
Since applying these measures leads to a marked decrease in workability, there has been a strong demand for the development of means for more easily improving delayed fracture resistance.
【０００５】このようなことから、本発明が目的とした
のは、優れた耐遅れ破壊性を示すと共に、機械的特性も
十分に満足できる浸炭肌焼鋼材を簡易に実現し得る手段
を確立することであった。In view of the above, the object of the present invention is to establish means for easily realizing a carburized case-hardened steel material which exhibits excellent delayed fracture resistance and also has sufficient mechanical properties. Was that.
【０００６】[0006]
【課題を解決するための手段】そこで、本発明者等は上
記目的を達成すべく鋭意研究を重ねた結果、次のような
知見を得ることができた。即ち、鋼材に浸炭処理を施す
と、この浸炭処理時に鋼材内部へ水素が浸入し、これが
浸炭肌焼鋼の遅れ破壊を引き起こす原因となる。そし
て、鋼材内部へ浸入した水素は通常の焼戻し（加熱温
度：１７０〜２００℃）を行っても完全に放散されるこ
とはない。もっとも、“２００℃焼戻し”を実施したも
のは焼戻しによって浸入水素量の約６５％まで減少する
ものの、それ以上は時間が経過しても殆ど減少せず、安
定した状態で半永久的に残留する。The inventors of the present invention have made extensive studies in order to achieve the above objects, and as a result, have obtained the following findings. That is, when a steel material is subjected to a carburizing treatment, hydrogen penetrates into the steel material during the carburizing treatment, which causes delayed fracture of the carburized case-hardened steel. The hydrogen that has penetrated into the steel material is not completely released even if ordinary tempering (heating temperature: 170 to 200 ° C.) is performed. However, in the case of performing "200 ° C tempering", the amount of infiltrated hydrogen is reduced to about 65% by tempering, but beyond that, there is almost no reduction over time, and it remains in a stable state semipermanently.
【０００７】しかるに、浸炭後に４００℃以上の高温で
焼戻しを施すと、鋼材内部へ浸入した水素の殆どは放散
してしまい、浸炭処理前の水素含有量レベルにまで低下
させることができる。However, if tempering is performed at a high temperature of 400 ° C. or higher after carburization, most of the hydrogen that has penetrated into the steel material is released, and the hydrogen content level before carburizing can be reduced.
【０００８】焼戻し温度によって水素の放散率が異なる
理由は以下の通りであると考えられる。 1) 浸炭の後直ちに２００℃近傍で焼戻しする場合に
は、焼戻し処理中に浸炭層でχ(カイ)炭化物が極めて微細
に析出する。そして、このχ炭化物と地鉄の界面に水素
がトラップされ、焼戻し処理中に水素が完全に拡散放出
することができなくなる。ここで、χ炭化物とは化学式
Fe2■3Ｃで示される特殊炭化物である。The reason why the hydrogen emission rate differs depending on the tempering temperature is considered as follows. 1) When tempering immediately after carburization at about 200 ° C., χ (kai) carbide is extremely finely precipitated in the carburized layer during the tempering treatment. Then, hydrogen is trapped at the interface between the χ carbide and the base iron, and hydrogen cannot be completely diffused and released during the tempering process. Here, χ carbide is a chemical formula
Fe 2 ■ 3 C is a special carbide.
【０００９】2) 一方、４００℃以上の高温で焼戻しを
行うと、χ炭化物は析出せずにθ炭化物（セメンタイ
ト:Fe3Ｃ）が析出する。このθ炭化物は地鉄との整合性
が良好であり、水素が界面にトラップされることがなく
て容易に拡散放出する。2) On the other hand, when tempering is performed at a high temperature of 400 ° C. or more, θ carbide (cementite: Fe 3 C) does not precipitate but χ carbide precipitates. The θ carbide has good compatibility with the base steel, and hydrogen is easily diffused and released without being trapped at the interface.
【００１０】3) しかし、４００℃以上で焼戻しを実施
すると浸炭層の硬さが低下し、浸炭肌焼鋼本来の目的で
ある耐摩耗性が低下する。また、母材強度が低下し、引
張強度，疲労強度の低下を招く。3) However, when tempering is carried out at 400 ° C. or higher, the hardness of the carburized layer is lowered, and the wear resistance which is the original purpose of the carburized case-hardening steel is lowered. In addition, the strength of the base material is lowered, and the tensile strength and fatigue strength are lowered.
【００１１】4) ところが、４００℃以上の高温で焼戻
しを施した場合でも、焼戻し後に再度簡易な高周波焼入
れを実施することで浸炭層の硬さ低下の問題が十分に解
決される上、適用する鋼材のＣ量を高目に調整すること
で所望特性に格別な悪影響を及ぼすことなく強度低下を
も効果的に防止することが可能となる。4) However, even when tempering is performed at a high temperature of 400 ° C. or higher, simple induction hardening is carried out again after tempering, which sufficiently solves the problem of hardness reduction of the carburized layer and is applied. By adjusting the C content of the steel material to a high value, it becomes possible to effectively prevent the strength from decreasing without particularly adversely affecting the desired characteristics.
【００１２】本発明は、上記知見事項等を基にして完成
されたもので、 「Ｃ：0.30〜0.45％（以降、 成分割合を表す％は重量割
合とする), Si：1.00％以下， Mn：2.00％以下， Ni：3.50
％以下， Cr：3.00％以下， Mo：3.00％以下 を含有するか、 或いは更に Nb： 0.050％以下， Ｖ：0.30％以下， Pb：0.
30％以下， Ca：0.0100％以下， Ｂ：0.0005〜0.0050％ の１種以上をも含み、 残部がFe及び不可避的不純物から
成る鋼材を浸炭焼入れした後、 ４００〜６００℃で焼戻
し処理を行い、 次いで高周波焼入れを施して焼戻しによ
って軟化した浸炭層の硬さを復活させることにより、 耐
遅れ破壊性に優れた浸炭肌焼鋼材を簡易かつ安定に製造
し得るようにした点」に大きな特徴を有している。The present invention has been completed based on the above-mentioned findings and the like. "C: 0.30 to 0.45% (hereinafter,% representing a component ratio is a weight ratio), Si: 1.00% or less, Mn : 2.00% or less, Ni: 3.50
% Or less, Cr: 3.00% or less, Mo: 3.00% or less, or Nb: 0.050% or less, V: 0.30% or less, Pb: 0.
30% or less, Ca: 0.0100% or less, B: 0.0005 to 0.0050%, including at least one kind, the balance of which is steel and unavoidable impurities, and after carburizing and quenching, steel is tempered at 400 to 600 ° C. Next, induction hardening is performed and the hardness of the carburized layer softened by tempering is restored to enable easy and stable production of a carburized case-hardened steel material with excellent delayed fracture resistance. is doing.
【００１３】このように、本発明は、焼戻し処理におけ
る“炭化物析出”と“遅れ破壊の原因となる水素の捕
獲”との関連性を究明し、耐遅れ破壊性に優れた浸炭肌
焼鋼材を簡易に実現する方法を提供するものであるが、
次に、本発明法において鋼材の化学成分組成並びに処理
条件を前記の如くに限定した理由をその作用と共に説明
する。As described above, in the present invention, the relationship between "carbide precipitation" and "capture of hydrogen which causes delayed fracture" in the tempering process was investigated, and a carburized case hardened steel material excellent in delayed fracture resistance was obtained. Although it provides a simple method,
Next, the reason why the chemical composition of the steel material and the treatment conditions are limited as described above in the method of the present invention will be explained together with its action.
【００１４】A) 化学成分組成Ｃ Ｃは、鋼に所望の静的強度を付与するのに必要な元素で
ある。特に、本発明では耐遅れ破壊性を向上させるため
に４００℃以上の高い温度で焼戻しを行うが、このよう
な高温焼戻し後にも要求される静的強度を維持させるに
は、0.30％以上のＣ含有量を確保しておく必要がある。
しかしながら、0.45％を超えてＣを含有させると靱性低
下が目立つようになる。従って、Ｃ含有量は0.30〜0.45
％と定めた。A) Chemical Composition C C is an element necessary for imparting desired static strength to steel. In particular, in the present invention, tempering is performed at a high temperature of 400 ° C. or higher in order to improve delayed fracture resistance, but in order to maintain the required static strength even after such high temperature tempering, C of 0.30% or more is required. It is necessary to secure the content.
However, when C is contained in excess of 0.45%, the toughness becomes conspicuous. Therefore, the C content is 0.30 to 0.45.
Defined as%.
【００１５】Si Siは鋼の脱酸に必要な元素であると共に、鋼に所定の静
的強度を付与する作用を有している。しかし、1.00％を
超えて含有させると粒界脆化を生じて靱性が低下するこ
とから、Si含有量は1.00％以下と定めた。 Si Si is an element necessary for deoxidizing steel, and has an effect of imparting a predetermined static strength to steel. However, if the content exceeds 1.00%, intergranular embrittlement occurs and the toughness decreases, so the Si content was defined as 1.00% or less.
【００１６】Mn MnもSiと同様に鋼の脱酸処理に必要な元素であるが、同
時に焼入れ性を付与する上でも必要な元素と言える。し
かしながら、2.00％を超えて含有させると、Siの場合と
同様、粒界脆化を生じて靱性の低下を招く。従って、Mn
含有量は2.00％以下と定めた。 Mn Mn is an element necessary for deoxidizing steel, similar to Si, but at the same time can be said to be an element necessary for imparting hardenability. However, if the content exceeds 2.00%, grain boundary embrittlement occurs and the toughness is reduced, as in the case of Si. Therefore, Mn
The content was determined to be 2.00% or less.
【００１７】Ni Niは鋼の焼入れ性を改善して静的強度及び靱性を向上さ
せるのに有効な元素であることから、これらの特性改善
のために添加される成分であるが、3.50％を超えて含有
させてもその効果が飽和し、経済性を損なうことになる
ので、Ni含有量は3.50％以下と定めた。 Ni Ni is an element effective for improving the hardenability of steel and improving the static strength and toughness, so it is a component added for improving these properties, but 3.50% The Ni content was set to 3.50% or less because the effect is saturated and the economical efficiency is impaired even if it is contained in excess.
【００１８】Cr Crも鋼に焼入れ性を付与する作用を有しており、また浸
炭性向上のために肌焼鋼に添加されることが多い元素で
もある。しかしながら、Cr含有量が3.00％を超えるとCr
酸化物が生成して逆に浸炭性を低下させるようになる。
従って、Cr含有量は3.00％以下と定めた。 Cr Cr also has the effect of imparting hardenability to steel, and is also an element often added to case-hardening steel to improve carburization. However, when the Cr content exceeds 3.00%, Cr
On the contrary, an oxide is formed to lower the carburizing property.
Therefore, the Cr content is set to 3.00% or less.
【００１９】Mo Moも、Niと同様、鋼の焼入れ性を改善して静的強度及び
靱性を向上させるのに有効な元素である。しかし、3.00
％を超えて添加してもその効果は飽和し、経済性を損な
うようになることから、Mo含有量は3.00％以下と定め
た。 Mo Mo, like Ni, is also an element effective in improving the hardenability of steel and improving the static strength and toughness. But 3.00
Even if added in excess of%, the effect will be saturated and the economic efficiency will be impaired, so the Mo content was defined as 3.00% or less.
【００２０】Nb，Ｖ，Pb，Ca及びＢ これらは、各々、浸炭肌焼鋼の所望特性を更に改善する
作用を有しているので１種又は２種以上添加するのが好
ましい成分であるが、以下にそれぞれの成分の添加量を
限定した理由を説明する。 Nb, V, Pb, Ca and B each have an effect of further improving the desired characteristics of the carburized case-hardening steel, and therefore it is preferable to add one or more of them. The reason why the addition amount of each component is limited will be described below.
【００２１】a) Nb Nbには鋼の粒界脆化を抑制する作用があるので、靱性を
向上し耐遅れ破壊性を改善するために添加するのが好ま
しい成分であるが、 0.050％を超えて含有させると結晶
粒が粗大化して靱性低下を招くことから、Nb含有量は
0.050％以下と定めた。A) Nb Since Nb has an action of suppressing grain boundary embrittlement of steel, it is a preferable component to be added in order to improve toughness and delayed fracture resistance, but more than 0.050% Content of Nb causes coarsening of the crystal grains and a decrease in toughness.
It was defined as 0.050% or less.
【００２２】b) Ｖ Ｖは、鋼中で炭窒化物を生成して鋼の高温強度を高める
作用を有している。しかし、0.30％を超えて含有させて
もその効果は飽和してしまい、経済性を損なうようにな
ることから、Ｖ含有量は0.30％以下と定めた。B) V V has the effect of forming carbonitrides in the steel to increase the high temperature strength of the steel. However, even if the content of V exceeds 0.30%, the effect is saturated and the economy is impaired. Therefore, the V content is set to 0.30% or less.
【００２３】c) Pb Pbは、鋼の切削性を向上させる作用を有しているので必
要により添加するのが好ましい成分であるが、0.30％を
超えて含有させると静的強度，疲労強度を著しく低下す
ることから、Pb含有量は0.30％以下と定めた。C) Pb Pb has the action of improving the machinability of steel, so it is a preferable component to be added if necessary. However, if it is contained in excess of 0.30%, the static strength and fatigue strength are improved. The Pb content was determined to be 0.30% or less, because it markedly decreases.
【００２４】d) Ca Caも鋼の切削性を向上させる作用を有しているので必要
により添加するのが好ましい成分であるが、0.0100％を
超えて含有させると靱性が著しく低下することから、Ca
含有量は0.0100％以下と定めた。D) Ca Since Ca also has an action of improving the machinability of steel, it is a preferable component to be added if necessary, but if it is contained in excess of 0.0100%, the toughness is remarkably reduced. Ca
The content was set to 0.0100% or less.
【００２５】e) Ｂ Ｂは、鋼の焼入れ性を向上させて静的強度を上昇させる
のに有効な元素であるが、その含有量が0.0005％未満で
は十分な効果が現れず、一方、0.0050％を超えて含有さ
せると鋼の結晶粒が粗大化して靱性の低下を招くように
なる。従って、Ｂ含有量は0.0005〜0.0050％と定めた。E) BB B is an element effective in improving the hardenability of steel and increasing the static strength, but if its content is less than 0.0005%, no sufficient effect appears, while 0.0050 If it is contained in excess of%, the crystal grains of the steel become coarse and the toughness is lowered. Therefore, the B content is set to 0.0005 to 0.0050%.
【００２６】B) 浸炭焼入れ後の焼戻し温度 浸炭焼入れ後の焼戻し温度（加熱温度）が４００℃未満
であると、浸炭時に鋼中へ浸入した水素が完全に放散さ
れずに所望の耐遅れ破壊性を確保することができない。
一方、上記焼戻し温度が６００℃を超えると母材（鋼の
内層部）の硬さが低下し、引張強度，疲労強度が著しく
低下する。従って、浸炭焼入れ後の焼戻し温度範囲は４
００〜６００℃と定めた。B) Tempering temperature after carburizing and quenching When the tempering temperature (heating temperature) after carburizing and quenching is less than 400 ° C., hydrogen that has penetrated into the steel during carburizing is not completely released and desired delayed fracture resistance is obtained. Cannot be secured.
On the other hand, if the tempering temperature exceeds 600 ° C., the hardness of the base material (inner layer of steel) decreases, and the tensile strength and fatigue strength decrease significantly. Therefore, the tempering temperature range after carburizing and quenching is 4
It was set at 00 to 600 ° C.
【００２７】C) 焼戻し後の高周波焼入れ 高温の焼戻しにより軟化した浸炭層の硬さを復活させて
所望の表面硬さを確保するためには、焼戻し後に高周波
焼入れを施す必要がある。この高周波焼入れ条件は格別
に規制されるものではなく、通常の高周波焼入れ条件で
十分であるが、浸炭層に十分な焼きが入るよう加熱温度
や加熱時間に注意を要する。C) Induction hardening after tempering In order to restore the hardness of the carburized layer softened by high temperature tempering and to secure a desired surface hardness, it is necessary to carry out induction hardening after tempering. The induction hardening conditions are not particularly restricted, and ordinary induction hardening conditions are sufficient, but the heating temperature and the heating time must be careful so that the carburized layer is sufficiently hardened.
【００２８】続いて、本発明の効果を実施例により具体
的に説明する。Next, the effects of the present invention will be specifically described by way of examples.
【実施例】まず、１５０kg真空溶解炉により表１に示す
如き化学成分組成の鋼を溶製した後、得られた鋼塊を１
２５０℃に１時間加熱し、３０mmφに鍛伸した。そし
て、更に９２５℃×１hrの焼ならし処理を施して供試材
とした。EXAMPLES First, a steel having a chemical composition as shown in Table 1 was melted in a 150 kg vacuum melting furnace, and the obtained steel ingot was
It was heated to 250 ° C. for 1 hour and forged to 30 mmφ. Then, a normalizing treatment of 925 ° C. × 1 hr was further performed to obtain a test material.
【００２９】[0029]
【表１】 [Table 1]
【００３０】次に、上記供試材を用いて鋼材中の水素含
有量を測定すると共に、 「遅れ破壊試験」, 「引張試験」,
「シャルピ−衝撃試験」 及び 「浸炭層の硬さ測定」 を実
施した。なお、「水素含有量の測定」は、直径６mmφ，
長さ１２mmの試験片を作成し、これを図１に示すヒ−ト
パタ−ンで浸炭焼入れした後、２００〜７００℃の範囲
で１時間の焼戻しを行ったものについて実施した。Next, the hydrogen content in the steel material was measured using the above test material, and the "delayed fracture test", "tensile test",
"Charpy impact test" and "hardness measurement of carburized layer" were carried out. In addition, "measurement of hydrogen content" is a diameter of 6mmφ,
A test piece having a length of 12 mm was prepared, carburized and quenched by the heat pattern shown in FIG. 1, and then tempered at 200 to 700 ° C. for 1 hour.
【００３１】また、「遅れ破壊試験」は、前記供試材を
図２に示す試験片に加工後、水素含有量測定の場合と同
じく図１に示す条件にて浸炭焼入れと焼戻しを行い、更
に下記に示す条件で高周波焼入れを施し、この処理済試
験片につき定荷重引張試験機を用いて負荷応力σ／σN
＝0.8 で実施した（σ：負荷応力，σN ：切欠引張応
力）。遅れ破壊試験時間は１０００時間までとし、破断
が生じなくても該時間で試験を中止した。 〔高周波焼入れ条件〕 周波数： ２００ｋHz， 加熱方法： 移動焼入れ， 冷却方法： 水冷（スプレ−式）， 加熱温度： ９５０℃， 移動速度： １０mm/s 。In the "delayed fracture test", after the test material is processed into the test piece shown in FIG. 2, carburizing and tempering are performed under the conditions shown in FIG. 1 as in the case of measuring the hydrogen content. Induction hardening was performed under the conditions shown below, and the load stress σ / σ N of this treated test piece was measured using a constant load tensile tester.
= 0.8 (σ: load stress, σ N : notch tensile stress). The delayed fracture test time was up to 1000 hours, and the test was stopped at that time even if no fracture occurred. [Induction hardening conditions] Frequency: 200 kHz, heating method: moving hardening, cooling method: water cooling (spray type), heating temperature: 950 ° C, moving speed: 10 mm / s.
【００３２】「引張試験」は、遅れ破壊試験片と同一形
状の試験片を用い、これに遅れ破壊試験の場合と同じ条
件で浸炭焼入れ，焼戻し及び高周波焼入れ処理を施して
試験に供した。In the "tensile test", a test piece having the same shape as the delayed fracture test piece was used, and this was subjected to carburizing quenching, tempering and induction hardening treatment under the same conditions as in the delayed fracture test.
【００３３】「シャルピ−衝撃試験」では、前記供試材
をＪＩＳ３号試験片に加工後、図１に示す条件の浸炭焼
入れと７００℃×１hrの焼戻し処理を施し、更に遅れ破
壊試験の場合と同一条件の高周波焼入れを行った後、こ
の処理済試験片をシャルピ−衝撃試験機にかけて衝撃特
性を調査した。更に、「浸炭層の硬さ測定」はこの残材
を用いて実施した。これらの結果を表２乃至５に示す。In the "Charpy impact test", after the test material was processed into a JIS No. 3 test piece, carburizing and quenching under the conditions shown in FIG. 1 and a tempering treatment at 700 ° C. × 1 hr were performed, and the delayed fracture test was performed. After induction hardening under the same conditions, the treated test piece was subjected to a Charpy impact tester to investigate impact properties. Furthermore, "hardness measurement of carburized layer" was carried out using this residual material. The results are shown in Tables 2 to 5.
【００３４】[0034]
【表２】 [Table 2]
【００３５】[0035]
【表３】 [Table 3]
【００３６】[0036]
【表４】 [Table 4]
【００３７】[0037]
【表５】 [Table 5]
【００３８】さて、表２乃至５に示される結果からも明
らかなように、本発明で規定する条件通りに製造された
浸炭肌焼鋼材は何れも水素含有量が十分に低く、優れた
耐遅れ破壊性を示すと共に、引張強度，衝撃特性，浸炭
層硬度の何れについても十分な要求レベルを満たしてい
ることが分かる。As is clear from the results shown in Tables 2 to 5, all of the carburized case-hardened steel products manufactured under the conditions specified in the present invention have a sufficiently low hydrogen content and excellent lag resistance. It can be seen that, while exhibiting destructiveness, the tensile strength, impact properties, and carburized layer hardness all satisfy sufficient required levels.
【００３９】なお、表２に示される結果からは、「浸炭
時に浸入した水素を十分に低下させるためには焼戻し温
度を４００℃以上にする必要がある」ことを確認でき
る。また、表３に示される結果からは、「焼戻しを４０
０℃以上で実施すると遅れ破壊特性も著しく向上する」
ことが確認できる。From the results shown in Table 2, it can be confirmed that "the tempering temperature must be 400 ° C. or higher in order to sufficiently reduce the hydrogen that has entered during carburization". In addition, from the results shown in Table 3, "tempering 40
If it is carried out at 0 ° C or higher, delayed fracture characteristics will also be significantly improved.
You can confirm that.
【００４０】しかし、表４に示される結果からは、「Ｃ
含有量が本発明の下限値から外れた鋼を用いた場合に４
００℃以上で焼戻しを行うと、 強度が不足して本来の浸
炭肌焼鋼の特性を満足しなくなる」ことが分かる。そし
て、表５に示される結果は、「Ｃ，Si，Mnが本発明の上
限値から外れた鋼を用いた場合には衝撃値が劣る」こと
や、「Crが本発明の上限値から外れた鋼を用いた場合に
は浸炭特性が低下して浸炭層の硬さが要求レベルを満た
さない」ことを示している。However, from the results shown in Table 4, "C
When using a steel whose content deviates from the lower limit of the present invention, 4
If tempered at a temperature of 00 ° C or higher, the strength will be insufficient and the original characteristics of the carburized case-hardened steel will not be satisfied. ” The results shown in Table 5 indicate that the impact value is inferior when using steel in which C, Si, and Mn deviate from the upper limits of the present invention, and "Cr deviates from the upper limits of the present invention." However, the hardness of the carburized layer does not meet the required level when the steel is used.
【００４１】[0041]
【効果の総括】以上に説明した如く、この発明によれ
ば、浸炭肌焼鋼材に要求される諸特性が十分に確保さ
れ、しかも著しく優れた耐遅れ破壊性を備えた浸炭肌焼
鋼材を簡易に提供できるなど、産業上極めて有用な効果
がもたらされる。[Summary of Effects] As described above, according to the present invention, it is possible to easily obtain a carburized case hardened steel material that sufficiently secures various characteristics required for the carburized case hardened steel material and that has extremely excellent delayed fracture resistance. It is possible to provide a very useful effect in the industry, such as being provided to
【図１】浸炭ヒ−トパタ−ン及び焼戻しパタ−ンを示す
線図である。FIG. 1 is a diagram showing a carburizing heat pattern and a tempering pattern.
【図２】遅れ破壊試験片の形状を説明した概略図であ
る。FIG. 2 is a schematic diagram illustrating the shape of a delayed fracture test piece.
───────────────────────────────────────────────────── フロントページの続き (51)Int.Cl.5 識別記号 庁内整理番号 ＦＩ 技術表示箇所 Ｃ２２Ｃ 38/60 ─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. 5 Identification code Office reference number FI technical display location C22C 38/60
Claims (2)
00％以下， Ni：3.50％以下， Cr：3.00％以下， Mo：3.
00％以下 を含み、残部がFe及び不可避的不純物から成る鋼材を浸
炭焼入れした後、４００〜６００℃で焼戻し処理を行
い、次いで高周波焼入れを施して焼戻しによって軟化し
た浸炭層の硬さを復活させることを特徴とする、耐遅れ
破壊性に優れた浸炭肌焼鋼材の製造方法。1. By weight ratio, C: 0.30 to 0.45%, Si: 1.00% or less, Mn: 2.
00% or less, Ni: 3.50% or less, Cr: 3.00% or less, Mo: 3.
A steel material containing 00% or less and the balance consisting of Fe and unavoidable impurities is carburized and quenched, then tempered at 400 to 600 ° C, and then induction hardened to restore the hardness of the carburized layer softened by tempering. A method for producing a carburized case-hardened steel material having excellent delayed fracture resistance, which is characterized by the following.
00％以下， Ni：3.50％以下， Cr：3.00％以下， Mo：3.
00％以下 を含有すると共に、 Nb： 0.050％以下， Ｖ：0.30％以下， Pb：0.
30％以下， Ca：0.0100％以下， Ｂ：0.0005〜0.0050％ の１種以上をも含み、残部がFe及び不可避的不純物から
成る鋼材を浸炭焼入れした後、４００〜６００℃で焼戻
し処理を行い、次いで高周波焼入れを施して焼戻しによ
って軟化した浸炭層の硬さを復活させることを特徴とす
る、耐遅れ破壊性に優れた浸炭肌焼鋼材の製造方法。2. By weight ratio, C: 0.30 to 0.45%, Si: 1.00% or less, Mn: 2.
00% or less, Ni: 3.50% or less, Cr: 3.00% or less, Mo: 3.
In addition to containing less than 00%, Nb: 0.050% or less, V: 0.30% or less, Pb: 0.
30% or less, Ca: 0.0100% or less, B: 0.0005 to 0.0050%, including at least one type, the balance of which is Fe and unavoidable impurities, and is then carburized and quenched, and then tempered at 400 to 600 ° C. Then, induction hardening is performed to restore the hardness of the carburized layer that has been softened by tempering, and a method for producing a carburized case-hardened steel material having excellent delayed fracture resistance.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP8627292A JPH05255733A (en) | 1992-03-10 | 1992-03-10 | Production of carburized and case hardened steel material having delayed fracture resistance |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP8627292A JPH05255733A (en) | 1992-03-10 | 1992-03-10 | Production of carburized and case hardened steel material having delayed fracture resistance |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH05255733A true JPH05255733A (en) | 1993-10-05 |
Family
ID=13882191
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP8627292A Pending JPH05255733A (en) | 1992-03-10 | 1992-03-10 | Production of carburized and case hardened steel material having delayed fracture resistance |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH05255733A (en) |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR100605723B1 (en) * | 2004-11-24 | 2006-08-01 | 주식회사 포스코 | High strength steel having excellent delayed fracture resistance and method for producing the same |
| EP1980630A1 (en) | 2007-04-09 | 2008-10-15 | Daido Tokushuko Kabushiki Kaisha | Carburized and high-frequency hardened part having high strength |
| US8123873B2 (en) | 2008-10-08 | 2012-02-28 | Aisin Aw Co., Ltd. | Method for manufacturing carburized part, and steel part |
| US10774413B2 (en) | 2015-11-11 | 2020-09-15 | Honeywell International Inc. | Low pressure induction carburization |
| JP7052976B1 (en) * | 2021-03-29 | 2022-04-12 | 國友熱工株式会社 | Manufacturing method of rod-shaped fastener |
-
1992
- 1992-03-10 JP JP8627292A patent/JPH05255733A/en active Pending
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR100605723B1 (en) * | 2004-11-24 | 2006-08-01 | 주식회사 포스코 | High strength steel having excellent delayed fracture resistance and method for producing the same |
| EP1980630A1 (en) | 2007-04-09 | 2008-10-15 | Daido Tokushuko Kabushiki Kaisha | Carburized and high-frequency hardened part having high strength |
| US8894778B2 (en) | 2007-04-09 | 2014-11-25 | Daido Tokushuko Kabushiki Kaisha | Carburized and high-frequency hardened part having high strength |
| US8123873B2 (en) | 2008-10-08 | 2012-02-28 | Aisin Aw Co., Ltd. | Method for manufacturing carburized part, and steel part |
| US10774413B2 (en) | 2015-11-11 | 2020-09-15 | Honeywell International Inc. | Low pressure induction carburization |
| JP7052976B1 (en) * | 2021-03-29 | 2022-04-12 | 國友熱工株式会社 | Manufacturing method of rod-shaped fastener |
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