JPH03219040A - High strength sintered steel and its manufacture - Google Patents
High strength sintered steel and its manufactureInfo
- Publication number
- JPH03219040A JPH03219040A JP1438190A JP1438190A JPH03219040A JP H03219040 A JPH03219040 A JP H03219040A JP 1438190 A JP1438190 A JP 1438190A JP 1438190 A JP1438190 A JP 1438190A JP H03219040 A JPH03219040 A JP H03219040A
- Authority
- JP
- Japan
- Prior art keywords
- powder
- sintered
- carbon
- steel
- sintered 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.)
- Pending
Links
- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 57
- 239000010959 steel Substances 0.000 title claims abstract description 57
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 8
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 34
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims abstract description 25
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 25
- 239000000843 powder Substances 0.000 claims abstract description 21
- 238000005121 nitriding Methods 0.000 claims abstract description 20
- 229910001566 austenite Inorganic materials 0.000 claims abstract description 18
- 238000005245 sintering Methods 0.000 claims abstract description 18
- 230000000717 retained effect Effects 0.000 claims abstract description 15
- 239000002344 surface layer Substances 0.000 claims abstract description 15
- 229910045601 alloy Inorganic materials 0.000 claims abstract description 13
- 239000000956 alloy Substances 0.000 claims abstract description 13
- 239000011812 mixed powder Substances 0.000 claims abstract description 12
- 229910000851 Alloy steel Inorganic materials 0.000 claims abstract description 11
- 238000005256 carbonitriding Methods 0.000 claims abstract description 10
- 229910052759 nickel Inorganic materials 0.000 claims abstract description 10
- 229910052750 molybdenum Inorganic materials 0.000 claims abstract description 9
- 229910052804 chromium Inorganic materials 0.000 claims abstract description 8
- 238000001816 cooling Methods 0.000 claims abstract description 7
- 230000009466 transformation Effects 0.000 claims abstract description 7
- 229910052742 iron Inorganic materials 0.000 claims abstract description 6
- 238000005480 shot peening Methods 0.000 claims abstract description 6
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 4
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 claims description 18
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 claims description 9
- 239000011733 molybdenum Substances 0.000 claims description 9
- 230000001590 oxidative effect Effects 0.000 claims description 9
- 239000011651 chromium Substances 0.000 claims description 8
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 claims description 7
- 238000005496 tempering Methods 0.000 claims description 6
- WPBNNNQJVZRUHP-UHFFFAOYSA-L manganese(2+);methyl n-[[2-(methoxycarbonylcarbamothioylamino)phenyl]carbamothioyl]carbamate;n-[2-(sulfidocarbothioylamino)ethyl]carbamodithioate Chemical compound [Mn+2].[S-]C(=S)NCCNC([S-])=S.COC(=O)NC(=S)NC1=CC=CC=C1NC(=S)NC(=O)OC WPBNNNQJVZRUHP-UHFFFAOYSA-L 0.000 claims description 5
- 238000000034 method Methods 0.000 claims description 5
- 239000000203 mixture Substances 0.000 claims description 5
- 238000000465 moulding Methods 0.000 claims description 5
- 239000012535 impurity Substances 0.000 claims description 4
- 239000010703 silicon Substances 0.000 claims description 3
- 229910001021 Ferroalloy Inorganic materials 0.000 claims description 2
- 125000004433 nitrogen atom Chemical group N* 0.000 claims description 2
- 238000003825 pressing Methods 0.000 claims description 2
- 229910052748 manganese Inorganic materials 0.000 abstract description 5
- 230000015572 biosynthetic process Effects 0.000 abstract description 3
- 229910052757 nitrogen Inorganic materials 0.000 abstract description 2
- 239000011800 void material Substances 0.000 abstract description 2
- 229910002804 graphite Inorganic materials 0.000 abstract 1
- 239000010439 graphite Substances 0.000 abstract 1
- 239000002994 raw material Substances 0.000 abstract 1
- 230000001105 regulatory effect Effects 0.000 abstract 1
- 238000012360 testing method Methods 0.000 description 11
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 8
- 230000000052 comparative effect Effects 0.000 description 8
- 238000010791 quenching Methods 0.000 description 8
- 230000000171 quenching effect Effects 0.000 description 8
- 229910000640 Fe alloy Inorganic materials 0.000 description 5
- 238000005452 bending Methods 0.000 description 5
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 4
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 4
- 229910021529 ammonia Inorganic materials 0.000 description 4
- 239000011572 manganese Substances 0.000 description 4
- 239000010949 copper Substances 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 239000007789 gas Substances 0.000 description 3
- 238000010438 heat treatment Methods 0.000 description 3
- 239000003921 oil Substances 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- 239000000654 additive Substances 0.000 description 2
- 230000000996 additive effect Effects 0.000 description 2
- 238000005255 carburizing Methods 0.000 description 2
- 229910052802 copper Inorganic materials 0.000 description 2
- 238000000354 decomposition reaction Methods 0.000 description 2
- 230000007423 decrease Effects 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 238000009661 fatigue test Methods 0.000 description 2
- 239000010410 layer Substances 0.000 description 2
- 239000000314 lubricant Substances 0.000 description 2
- 150000004767 nitrides Chemical class 0.000 description 2
- 238000010587 phase diagram Methods 0.000 description 2
- 238000004513 sizing Methods 0.000 description 2
- 229910001339 C alloy Inorganic materials 0.000 description 1
- 229910000881 Cu alloy Inorganic materials 0.000 description 1
- 229910017263 Mo—C Inorganic materials 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 238000012937 correction Methods 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000002050 diffraction method Methods 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 210000004709 eyebrow Anatomy 0.000 description 1
- 238000005242 forging Methods 0.000 description 1
- 238000011835 investigation Methods 0.000 description 1
- AMWRITDGCCNYAT-UHFFFAOYSA-L manganese oxide Inorganic materials [Mn].O[Mn]=O.O[Mn]=O AMWRITDGCCNYAT-UHFFFAOYSA-L 0.000 description 1
- PPNAOCWZXJOHFK-UHFFFAOYSA-N manganese(2+);oxygen(2-) Chemical class [O-2].[Mn+2] PPNAOCWZXJOHFK-UHFFFAOYSA-N 0.000 description 1
- 229910000476 molybdenum oxide Inorganic materials 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 230000002040 relaxant effect Effects 0.000 description 1
- 230000002269 spontaneous effect Effects 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000003466 welding Methods 0.000 description 1
Landscapes
- Powder Metallurgy (AREA)
Abstract
Description
【発明の詳細な説明】
〔産業上の利用分野〕
本発明は、機械特性の回転曲げ、衝撃値などの疲労限を
向上させた高強度焼結鋼に関し、かつ高強度焼結鋼の製
造方法に関する。[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a high-strength sintered steel with improved fatigue limits such as rotary bending mechanical properties and impact values, and a method for manufacturing the high-strength sintered steel. Regarding.
一般に高強度、高靭性を要求される機械部品の高強度焼
結鋼には、焼入性を向上させる添加元素として炭素、ニ
ッケル、モリブデン、クロム、マンガンおよび銅などを
適当量種り組合せた合金銅または合金鉄の粉末、および
Fe−Mn−Cr門o−C系合金鋼(4100系)、F
e−Mn−Cr−Mo−C系合金金鋼(4600系)な
どの粉末が使用され、これらの粉末を高密度に成形加圧
し、1200〜1300“Cの温度範囲で焼結させ、焼
入れ焼戻し、または浸炭焼入れ焼戻しなどの熱処理を施
して合金鋼焼結体の機械的強化が行われている。High-strength sintered steel for mechanical parts that generally require high strength and high toughness is an alloy containing appropriate amounts of carbon, nickel, molybdenum, chromium, manganese, copper, etc. as additive elements to improve hardenability. Copper or iron alloy powder, and Fe-Mn-Cr o-C alloy steel (4100 series), F
Powders such as e-Mn-Cr-Mo-C alloy steel (4600 series) are used, and these powders are compacted and pressed to a high density, sintered at a temperature range of 1200 to 1300"C, and then quenched and tempered. Alternatively, the alloy steel sintered body is mechanically strengthened by heat treatment such as carburizing, quenching, and tempering.
しかし、これらの高強度焼結鋼では、その表面層での空
隙に切欠きが存在するため、焼入れ時にマイクロクラン
クが発生して疲労限強度を低下させる。そのため、焼結
鋼の表面層を改質させるために、該焼結鋼にショットピ
ーニングを施して疲労限強度が低下しない手段がとられ
ている。However, in these high-strength sintered steels, since notches exist in the voids in the surface layer, microcranks occur during quenching, reducing the fatigue limit strength. Therefore, in order to modify the surface layer of sintered steel, shot peening is applied to the sintered steel so that the fatigue limit strength does not decrease.
これらの高強度焼結鋼は、ショットピーニングを施した
り、また、製造技術の改善によって引張り強さが90〜
200kg/mm2とかなり高められているが、焼結鋼
空隙部への応力の集中に伴って起る疲労限、すなわち回
転曲げ値が30〜35kg/ mm 2、衝撃値が1〜
2 kg−m/cI!程度であるため、より高強度を要
求される歯車部分などへの適用には制限されるという問
題点がある。These high-strength sintered steels have a tensile strength of 90~90 through shot peening and improvements in manufacturing technology.
Although it is quite high at 200 kg/mm2, the fatigue limit that occurs due to the concentration of stress in the sintered steel voids, that is, the rotational bending value is 30-35 kg/mm2, and the impact value is 1-35 kg/mm2.
2 kg-m/cI! Therefore, there is a problem in that it is limited in its application to gear parts that require higher strength.
そこで、疲労限強度を更に向上させるため、再加圧再焼
結、鍛造などによって空隙を減少させで焼結鋼の高密度
化をはかる手段が必要となる。このためコスト高になる
という問題点がある。Therefore, in order to further improve the fatigue limit strength, there is a need for a means of increasing the density of sintered steel by reducing the voids by repressurization, resintering, forging, or the like. Therefore, there is a problem that the cost is high.
また、焼結鋼をより高強度化すれば、従来から焼結鋼部
分の寸法修正に使用されるサイジング、コイニングなど
において部品の硬度と金型寿命の関係から通用できなく
なるという問題点がある。Further, if the strength of sintered steel is increased, there is a problem that it cannot be used in sizing, coining, etc., which have been conventionally used to correct the dimensions of sintered steel parts, due to the relationship between the hardness of the part and the life of the mold.
本発明は上記に鑑みてなされたもので、焼入性を向上さ
せる元素として炭素、ニッケル、モリブデン、クロム、
マンガンなどの添加元素を低含有量の範囲で、種々組合
せた炭素を含む合金鋼粉末、または炭素を含まない合金
鉄粉末を用いて、寸法精度が良好で、空隙欠陥を改善し
、かつ高強度、高靭性を有する焼結機械部品が容易に得
られるようにするとともにその製造方法を提供すること
を目的とするものである。The present invention has been made in view of the above, and includes carbon, nickel, molybdenum, chromium, and other elements that improve hardenability.
By using carbon-containing alloy steel powder or carbon-free alloy iron powder containing various combinations of additive elements such as manganese in a low content range, we can produce products with good dimensional accuracy, improved void defects, and high strength. The object of the present invention is to easily obtain sintered mechanical parts having high toughness and to provide a method for manufacturing the same.
本発明者らは上記の課題を解決するために種々検討した
結果、疲労に影響を与える因子として焼結体の空隙部に
集中する応力を緩和すれば、疲労限強度が向上できるこ
とに注目した。さらに焼結体表面層に多量の残留オース
テナイト組織を浸窒または浸炭浸窒処理によって残留さ
せると、焼結体の疲労限強度が向上できることを見出し
て本発明を完成させたものである。As a result of various studies to solve the above problems, the present inventors noticed that the fatigue limit strength can be improved by relaxing the stress concentrated in the voids of the sintered body, which is a factor that affects fatigue. Furthermore, the present invention was completed based on the discovery that the fatigue limit strength of the sintered body can be improved by leaving a large amount of retained austenite structure in the surface layer of the sintered body by nitriding or carbonitriding.
本発明の高強度焼結鋼は、炭素を含む合金鋼粉末、およ
び/または炭素を含まない合金鉄粉末と黒鉛粉との混合
粉末を所定形状に成形加圧し、高温の非酸化雰囲気中で
焼結し、焼結後、600 ’C以上の温度で浸窒または
浸炭浸窒処理して、焼結体中に窒素原子を拡散し、次い
でA1変態線以上の温度からの急冷によって焼結体表面
層および空隙部に容積比で30〜95volχ範囲の残
留オーステナイl−&11織を形成させたことを特徴と
するものである。The high-strength sintered steel of the present invention is produced by molding and pressing a mixed powder of carbon-containing alloy steel powder and/or carbon-free alloy iron powder and graphite powder into a predetermined shape, and then sintering it in a high-temperature non-oxidizing atmosphere. After sintering, nitrogen atoms are diffused into the sintered body by nitriding or carbonitriding at a temperature of 600'C or higher, and then the surface of the sintered body is improved by rapid cooling from a temperature higher than the A1 transformation line. It is characterized in that a retained austenite l-&11 weave having a volume ratio of 30 to 95 vol.chi. is formed in the layers and the voids.
また、炭素を含む合金銅粉末および/または炭素を含ま
ない合金鉄粉末と黒鉛粉末との混合粉末を成形加圧する
工程、
成形加圧された成形体を非酸化雰囲気中で焼結させる工
程、または前記、非酸化雰囲気中で焼結させる工程後に
焼結鋼を再圧縮成形して非酸化雰囲気中で焼結させる工
程、
600℃以上の温度で焼結鋼を浸窒または浸炭浸窒する
工程および
A1変態線以上の温度から焼結鋼を急冷し、焼戻しする
工程
を有することを特徴とする高強度焼結鋼の製造方法を提
案するものである。Further, a step of molding and pressurizing a mixed powder of a carbon-containing alloy copper powder and/or a carbon-free alloy iron powder and graphite powder, a step of sintering the molded and pressurized compact in a non-oxidizing atmosphere, or After the step of sintering in a non-oxidizing atmosphere, the sintered steel is recompressed and sintered in a non-oxidizing atmosphere, the sintered steel is nitrided or carbo-nitrided at a temperature of 600° C. or higher, and The present invention proposes a method for producing high-strength sintered steel, which includes a step of rapidly cooling sintered steel from a temperature equal to or higher than the A1 transformation line and tempering it.
次に、本発明の構成について更に説明する。Next, the configuration of the present invention will be further explained.
本発明で使用する炭素を含む合金鋼粉末とは、0.05
〜1.5wt!ケイ素、0.5〜1.owtχクロム、
0.5〜5.0wt%ニッケル、0.1〜1.owtχ
モリブデン、0.1〜2.0wt%マンガン分のうちの
1種または2種以上を含有し、残部が鉄および不可避不
純物ならびに炭素を有する組成粉であり、炭素を含まな
い合金鉄粉末と黒鉛粉との混合粉とは0.1〜1.0w
t炭素に加えて、前記合金成分および残部が鉄および不
可避不純物を有する組成粉である。The carbon-containing alloy steel powder used in the present invention is 0.05
~1.5wt! Silicon, 0.5-1. owtχ chromium,
0.5-5.0 wt% nickel, 0.1-1. owtχ
It is a composition powder containing one or more of molybdenum and 0.1 to 2.0 wt% manganese, and the balance is iron, unavoidable impurities, and carbon, and contains iron alloy powder and graphite powder that do not contain carbon. Mixed powder with 0.1-1.0w
In addition to t-carbon, the above-mentioned alloy components and the balance are a powder composition containing iron and unavoidable impurities.
添加スるクロム、ニッケル、モリブデン、マンガン量の
下限値は焼結体の焼入性を考慮するもので、クロムおよ
びモリブデンの添加の上限値はコスト的な観点から制限
するものである。ニッケルおよびマンガンの添加は残留
オーステナイト相の形成に寄与させるが、マンガンは酸
化されやすいため影響のない上限値とし、ニッケルはコ
スト的な観点と焼結鋼の強度との関係がら低ニツケル基
としている。ここで、炭素を含まない合金鉄と黒鉛粉を
混合することは、成形性がよく、かつ、焼結体の炭素含
有量を自由に調整できるので好ましい。また、添加する
炭素は、焼結鋼の硬さを高め、強度化させる成分である
が、添加量が0.1wt″A未満では強度化に欠け、逆
に、1.0iytχを超えると焼結鋼の靭性が低下する
ので好ましくない。好ましい範囲は0.1〜1.0−L
χである。The lower limits of the amounts of chromium, nickel, molybdenum, and manganese to be added are determined by taking into account the hardenability of the sintered body, and the upper limits of the amounts of chromium and molybdenum are determined from the viewpoint of cost. The addition of nickel and manganese contributes to the formation of a retained austenite phase, but since manganese is easily oxidized, the upper limit is set so that it has no effect, and nickel is set to a low nickel base from a cost perspective and in relation to the strength of sintered steel. . Here, it is preferable to mix carbon-free ferroalloy and graphite powder because the moldability is good and the carbon content of the sintered body can be freely adjusted. Carbon added is a component that increases the hardness and strength of sintered steel, but if the amount added is less than 0.1wt''A, it lacks strength, and on the other hand, if it exceeds 1.0iytχ, sintering will occur. It is not preferable because the toughness of the steel decreases.The preferable range is 0.1 to 1.0-L.
It is χ.
本発明の構成で、高温の非酸化雰囲気中で焼結しとある
のは、使用する合金鋼または鉄粉末中に、−モリブデン
、マンガンなどを添加しているので、モリブデンおよび
マンガンの酸化物が存在すると焼結中、粒間の拡散を妨
げる。そのため1O−2torr以下の真空雰囲気で焼
結条件として1200〜1300℃×60〜120分の
範囲で行うのが好ましい。In the structure of the present invention, sintering is performed in a high-temperature non-oxidizing atmosphere because molybdenum, manganese, etc. are added to the alloy steel or iron powder used, so molybdenum and manganese oxides are Its presence impedes intergranular diffusion during sintering. Therefore, it is preferable to perform the sintering in a vacuum atmosphere of 10-2 torr or less at 1200 to 1300° C. for 60 to 120 minutes.
本発明の構成で、600℃以上の温度で浸窒しまたは浸
炭浸窒処理して、とあるのは、窒化のように通常550
〜570″C程度で熱処理すると、粒子表面に窒化物が
生成して、焼結鋼の強度が低下する。浸窒処理は窒化と
異なり、本発明の必須条件であって、600℃以上の温
度と定めた理由は、特に、浸窒処理する時にγ、8層な
どの窒化物が表面層に析出(白眉と呼ばれるもの)し難
い温度とするものである。浸窒処理は、アンモニヤ分解
ガス雰囲気中(残留アンモニヤ濃度5〜15%) 、8
00〜900″Cの温度範囲で行うのが好ましい。浸窒
処理のみをするのは、原則的に炭素を含む合金鋼粉から
焼結鋼を得る場合で、浸炭浸窒処理は炭素を含まない合
金鉄粉と黒鉛粉の混合粉から焼結鋼を得る場合には、常
法に従って先ず、浸炭処理を行った後、引続いて浸窒処
理を行い、焼結体中に窒素を拡散させる。In the structure of the present invention, the nitriding or carbonitriding treatment is performed at a temperature of 600°C or higher, and the term nitriding is usually 550°C, as in nitriding.
When heat treated at about ~570"C, nitrides are generated on the particle surface and the strength of the sintered steel is reduced. Nitriding treatment is different from nitriding and is an essential condition of the present invention, and a temperature of 600"C or higher is required. The reason for this is to set the temperature at which nitrides such as γ and 8 layers are difficult to precipitate on the surface layer (referred to as white eyebrows) during nitriding treatment.Nitriding treatment is performed in an ammonia decomposition gas atmosphere. Medium (residual ammonia concentration 5-15%), 8
It is preferable to carry out the process at a temperature range of 00 to 900"C. In principle, only nitriding is performed when obtaining sintered steel from alloyed steel powder containing carbon, and carbo-nitriding is performed only when sintered steel is obtained from alloyed steel powder containing carbon. When obtaining sintered steel from a mixed powder of alloyed iron powder and graphite powder, the steel is first carburized according to a conventional method, and then nitrided to diffuse nitrogen into the sintered body.
本発明の構成で、残留オーステナイト組織を容量比で3
0〜95νolχとするのは、焼結鋼に適切な疲労限強
度と靭性を付与させるためであって、30vo lχ未
満では空隙部に集中する応力を緩和させるには不十分で
ある。なお、浸炭処理のみで焼入して30νolχ近い
残留オーステナイト相が得られるが、疲労限強度と靭性
を向上させることができない。With the configuration of the present invention, the retained austenite structure has a capacity ratio of 3
The reason for setting it to 0 to 95 volχ is to impart appropriate fatigue limit strength and toughness to the sintered steel, and less than 30 volχ is insufficient to relieve stress concentrated in the voids. Note that although a retained austenite phase of nearly 30 νolχ can be obtained by quenching with only carburizing treatment, fatigue limit strength and toughness cannot be improved.
逆に、95νo1χを超えるときは、例えば、歯車など
局部力たりが高いものでは、残留オーステナイト相が比
較的に軟質なものであるため、歯車形状がへたる恐れが
ある。しかしl00volXになっても、疲労限強度、
衝撃値については特性が大きく劣化しないので、使用目
的、用途によっては100vol′A残留オーステナイ
ト相を形成させてもよい。On the other hand, when it exceeds 95νo1χ, the retained austenite phase is relatively soft in items such as gears where the local force is high, so there is a risk that the shape of the gear will collapse. However, even if it becomes 100volX, the fatigue limit strength,
As for the impact value, since the properties do not deteriorate significantly, a 100 vol'A retained austenite phase may be formed depending on the purpose and application.
本発明の構成で、A1変態線以上の温度から急冷とある
のは、C−Fe状態図に示されるA1変態線であって、
その温度は721℃である。共析焼結鋼(C:0.85
wtχ)では740℃から急冷できる。In the configuration of the present invention, quenching from a temperature above the A1 transformation line refers to the A1 transformation line shown in the C-Fe phase diagram,
Its temperature is 721°C. Eutectoid sintered steel (C: 0.85
wtχ) allows rapid cooling from 740°C.
0.85wtχ炭素を含む共析焼結銅以外の焼結鋼では
、C−Fe合金状態図から理解されるように、その炭素
含有量に応じて液相線以上の温度から急冷してオーステ
ナイトの状態をそっくり、そのまま常温において形成さ
せる。In sintered steels other than eutectoid sintered copper containing 0.85wtχ carbon, as understood from the C-Fe alloy phase diagram, austenite is formed by rapid cooling from a temperature above the liquidus depending on the carbon content. The condition is exactly the same, and it is formed as it is at room temperature.
〔作 用]
本発明は、特に焼結体表面層および空隙部に多量の残留
オーステナイト組織を浸窒または浸炭浸窒処理によって
残留させるので、焼結鋼の疲労限強度が著しく向上でき
、且つ靭性が高められる。また、表面層および空隙部に
多層の残留オーステナイト相を残留させることにより、
焼結体表面に露出する空隙切欠および表面近傍下に存在
する空隙切欠から発生しやすいマイクロクラックを未然
に防止するのに大きな効果がある。更に、残留オーステ
ナイト相を形成させる焼入れ焼戻しの熱処理後、焼結体
の表面層をショットピーニングすることによって、表面
層により著しい圧縮の残留応力が形成され、かつ表面層
に僅かに残存する空隙部の目潰しによって切欠による疲
労の影響を低減させ、より高い疲労限強度を有する焼結
鋼が得られ、また、残留オーステナイト相を多量に残留
させると、表面層の硬さが従来のものより軟質化できる
ので、焼結鋼の変形抵抗が低減でき寸法修正のサイジン
グがより容易になる。[Function] The present invention leaves a large amount of retained austenite structure in the surface layer and voids of the sintered body through nitriding or carbonitriding treatment, so that the fatigue limit strength of the sintered steel can be significantly improved, and the toughness can be improved. is enhanced. In addition, by leaving a multilayered retained austenite phase in the surface layer and voids,
It is highly effective in preventing microcracks that are likely to occur from the gap cutouts exposed on the surface of the sintered body and the gap cutouts that exist near the surface. Furthermore, by shot peening the surface layer of the sintered body after the heat treatment of quenching and tempering to form a retained austenite phase, significant compressive residual stress is formed in the surface layer, and the voids slightly remaining in the surface layer are removed. Crushing reduces the effects of fatigue due to notches, resulting in a sintered steel with higher fatigue limit strength.Also, by leaving a large amount of retained austenite phase, the hardness of the surface layer can be made softer than that of conventional steel. Therefore, the deformation resistance of the sintered steel can be reduced, making sizing easier to correct.
(発明の効果]
したがって、本発明の高強度焼結鋼は、該焼結体の表面
層の空隙部に多量の残留オーステナイト組織を浸窒また
は浸炭浸窒処理によって残留させているので、従来の焼
結鋼に比べて疲労限強度が大きくでき、大きな衝撃にも
強い靭性を有する焼結鋼が安価に得られるので、エンジ
ン、油接、連接、自動車などに使用される歯車類の高強
度部品への適用が可能になる。(Effects of the Invention) Therefore, the high-strength sintered steel of the present invention has a large amount of retained austenite structure remaining in the voids of the surface layer of the sintered body by nitriding or carbonitriding treatment. Sintered steel has a higher fatigue limit strength than sintered steel and has toughness that can withstand large impacts. Sintered steel can be obtained at low cost, making it suitable for high-strength parts of gears used in engines, oil welding, connections, automobiles, etc. It becomes possible to apply to
以下、本発明の実施例を比較例と対比しつつ説明する。 Examples of the present invention will be described below in comparison with comparative examples.
第1表は本発明の実施に使用する合金鉄粉の化学組成を
示す。Table 1 shows the chemical composition of the iron alloy powder used in the practice of the present invention.
第 1 表
実施例1
第1表のNo、 lの合金鉄粉(神鋼アトメル4600
)に0.3wtχの黒鉛粉(ロンザ社製KS6)と0.
5wtχのアクラワンクス(潤滑剤)を添加した混合粉
を金型に入れ、6L/c+flの加圧で成形し、1O−
2Lorr以下の真空雰囲気中で、1250℃×60分
の焼結条件で焼結した。得られた焼結鋼をJI32号の
回転曲げ疲労試験片の形状に機械加工を施した後、試験
片の表面カーボンポテンシャルが0.8wtχ炭素にな
るように、930℃X5時間の熱処理条件で浸炭した後
、更に10% アンモニヤ分解ガス雰囲気中、850℃
X4時間の条件で浸窒処理を行い、直接80℃の油中で
焼入れし、試験片を150℃X3時間の焼戻し処理して
本発明の焼結鋼試験片(1)を得た。上記同様にして得
た試験片(1ンの表面層にショットピーニングを施した
試験片(2)を作成した。比較例として浸窒処理を施さ
ないほかは、上記実施例と同一条件で油中に焼入れした
後、150℃X3時間の焼戻し処理を施して焼結鋼試験
片を得た。得られた試験片(1)、(2)と比較例のそ
れぞれについて、回転曲げ疲労限、衝撃値および残留オ
ーステナイトffiなどを調べた結果を第2表に示す。Table 1 Example 1 Alloy iron powder No. 1 in Table 1 (Shinko Atmel 4600
) with 0.3wtχ graphite powder (KS6 manufactured by Lonza) and 0.3wtχ graphite powder (KS6 manufactured by Lonza).
A mixed powder to which 5wtχ of Akrawanx (lubricant) was added was put into a mold, molded under a pressure of 6L/c+fl, and 1O-
Sintering was carried out at 1250° C. for 60 minutes in a vacuum atmosphere of 2 Lorr or less. The obtained sintered steel was machined into the shape of a JI32 rotary bending fatigue test piece, and then carburized under heat treatment conditions of 930°C for 5 hours so that the surface carbon potential of the test piece became 0.8wtχ carbon. After that, further 10% ammonia decomposition gas atmosphere at 850℃
A nitriding treatment was carried out under the conditions of x4 hours, quenching was performed directly in oil at 80°C, and the test piece was tempered at 150°C for 3 hours to obtain a sintered steel test piece (1) of the present invention. A test piece (2) was prepared in which the surface layer of the test piece (1) obtained in the same manner as above was subjected to shot peening. After quenching, a sintered steel test piece was obtained by tempering at 150°C for 3 hours.The rotating bending fatigue limit and impact value were determined for each of the obtained test pieces (1) and (2) and the comparative example. Table 2 shows the results of the investigation of residual austenite ffi, etc.
残留オーステナイl−量の測定は顕微鏡による観察とX
線回折法によって求めた。The amount of residual austenite is measured by observation using a microscope and
Obtained by line diffraction method.
第 2 表
結果から、本発明に係わる焼結鋼は比較例と対比して疲
労限強度、衝撃値が著しく向上している。また、ショト
ピーニングを施すと疲労限強度が約10%向上できる。From the results in Table 2, the fatigue limit strength and impact value of the sintered steel according to the present invention are significantly improved compared to the comparative example. Further, by applying short peening, the fatigue limit strength can be improved by about 10%.
実施例2
第1表のNo、 1〜4配合の合金鉄粉を6t/c+I
lの加圧力で成型し、10−”torr以下の真空雰囲
気中、850℃X60分の条件で焼結した後、更に焼結
体をプレスで6t/allの加圧力で再圧縮成型し、1
0−2torr以下の真空雰囲気中、1250℃×60
分の焼結条件で焼結した。得られた焼結鋼を実施例1と
同一条件で浸炭、浸窒処理を施して本発明の焼結鋼試験
片(3) 、 (4) 、 (5) 、 (6)を得た
。Example 2 6t/c+I of No. 1 to 4 alloyed iron powder in Table 1
After sintering at 850°C for 60 minutes in a vacuum atmosphere of 10-''torr or less, the sintered body was further compressed and molded with a press at a pressure of 6t/all.
In a vacuum atmosphere of 0-2 torr or less, 1250℃ x 60
It was sintered under the same sintering conditions. The obtained sintered steel was carburized and nitrided under the same conditions as in Example 1 to obtain sintered steel test pieces (3), (4), (5), and (6) of the present invention.
なお、第1表のNo、 1の合金鉄粉を用いて浸窒処理
を施さないほかは、同一の条件で処理したものを比較例
とした。A comparative example was prepared using the iron alloy powder No. 1 in Table 1 and treated under the same conditions except that the nitriding treatment was not performed.
得られた試験片と比較例について、第2表と同様な特性
値を調べた結果を第3表に示す。Table 3 shows the results of examining the same characteristic values as in Table 2 for the obtained test pieces and comparative examples.
第 3
表
結果から、焼結工程で再圧縮成型再焼結を行うと、比較
例とくらべて同一焼結混合粉であっても著しく疲労限強
度、衝撃値のいずれもの値が向上できることがわかる。From the results in Table 3, it can be seen that by performing recompression molding and resintering in the sintering process, both the fatigue limit strength and impact value can be significantly improved compared to the comparative example even with the same sintered mixed powder. .
比較例では、残留オーステナイトの生成が少なく、疲労
限の向上がみられない。In the comparative example, the formation of retained austenite is small and no improvement in fatigue limit is observed.
実施例3
第1表のNolの合金鉄粉(神鋼アトメル4600)に
0.8wtχの黒鉛粉(ロンザ社製KS6)と0.5w
Lχのアクラワックス(潤滑剤)を添加した混合粉を金
型に入れ、実施例1と同一条件で焼結した。Example 3 0.8wtx graphite powder (KS6 manufactured by Lonza) and 0.5w were added to Nol alloy iron powder (Shinko Atmel 4600) in Table 1.
A mixed powder to which Lχ Acra wax (lubricant) was added was placed in a mold and sintered under the same conditions as in Example 1.
得られた焼結鋼を機械加工してJI32号の回転曲げ疲
労試験片とし、10%アンモニヤ分解ガス雰囲気中、8
00℃X4時間の条件で浸窒処理のみを行い、直接13
0℃の油中で焼入れし、400’CX 3時間の焼戻し
処理をして焼結鋼試験片(7)を得た。The obtained sintered steel was machined into a JI No. 32 rotating bending fatigue test piece, and was subjected to a 10% ammonia cracking gas atmosphere.
Only nitriding treatment was performed under the conditions of 00°C x 4 hours, and directly 13
A sintered steel test piece (7) was obtained by quenching in oil at 0°C and tempering at 400'CX for 3 hours.
前記処理条件中、浸窒処理を行わないものを比較例とし
た。Among the above treatment conditions, a sample without nitriding treatment was used as a comparative example.
得られた試験片について、第2表と同様な特性値を調べ
た結果を第4表に示す。Table 4 shows the results of examining the same characteristic values as in Table 2 for the obtained test pieces.
第4表 手 続 1、事件の表示 2、発明の名称 3、補正をする者 事件との関係 住 所(居所) 氏 名(名称) 4、代理人 住 所 特願平2−14381号 高強度焼結鋼およびその製造方法 大阪市西区新町1丁目4番21号 ネ市 正 書(自発)Table 4 hand Continued 1.Display of the incident 2. Name of the invention 3. Person who makes corrections Relationship with the incident Residence (residence) Full name (name) 4. Agent address Patent Application No. 14381 Hei 2-14381 High strength sintered steel and its manufacturing method 1-4-21 Shinmachi, Nishi-ku, Osaka Ne city official book (spontaneous)
Claims (1)
い合金鉄粉末と黒鉛粉との混合粉末を所定形状に成形加
圧し、高温の非酸化雰囲気で焼結する高強度焼結鋼にお
いて、 焼結後、600℃以上の温度で浸窒または浸炭浸窒処理
して焼結体中に窒素原子を拡散し、次いでA_1変態線
以上の温度からの急冷によって焼結体表面層および空隙
部に容積比で30〜95vol%範囲の残留オーステナ
イト組織を形成させたことを特徴とする高強度焼結鋼。 2 高強度焼結鋼の表面層にショットピーニングによる
圧縮残留応力を形成させた請求項1に記載の高強度焼結
鋼。 3 炭素を含む合金鋼粉末および/または炭素を含まな
い合金鉄粉末と黒鉛粉末との混合粉末を成形加圧する工
程、 成形加圧された成形体を非酸化雰囲気中で焼結させる工
程、または前記、非酸化雰囲気中で焼結させる工程後に
焼結鋼を再圧縮成形して非酸化雰囲気中で焼結させる工
程、 600℃以上の温度で焼結鋼を浸窒または浸炭浸窒する
工程および A_1変態線以上の温度から焼結鋼を急冷し、焼戻しす
る工程 を有することを特徴とする高強度焼結鋼の製造方法。 4 前記炭素を含む合金鋼粉末が、0.05〜1.5w
t%ケイ素、0.5〜2.0wt%クロム、0.5〜5
.0wt%ニッケル、0.1〜1.0wt%モリブデン
、0.1〜2.0wt%マンガン分のうちの1種または
2種以上を含有し、残部が鉄および不可避不純物ならび
に炭素を有する組成である請求項1または3に記載のも
の。 5 前記炭素を含まない合金鉄粉末と黒鉛粉との混合粉
末が、0.1〜1.0wt%炭素に加えて0.05〜1
.5wt%ケイ素、0.5〜2.0wt%クロム、0.
5〜5.0wt%ニッケル、0.1〜1.0wt%モリ
ブデン、0.1〜2.0wt%マンガン分のうちの1種
または2種以上を含有し、残部が鉄および不可避不純物
を有する組成である請求項1または3に記載のもの。[Claims] 1. A high-strength sintering method in which a mixed powder of carbon-containing alloy steel powder and/or carbon-free alloy iron powder and graphite powder is molded and pressed into a predetermined shape and sintered in a high-temperature non-oxidizing atmosphere. In sintered steel, after sintering, nitrogen atoms are diffused into the sintered body by nitriding or carbonitriding at a temperature of 600°C or higher, and then the surface layer of the sintered body is formed by rapid cooling from a temperature higher than the A_1 transformation line. and a high-strength sintered steel characterized in that a retained austenite structure with a volume ratio of 30 to 95 vol% is formed in the voids. 2. The high-strength sintered steel according to claim 1, wherein compressive residual stress is formed in the surface layer of the high-strength sintered steel by shot peening. 3. A step of molding and pressing a mixed powder of a carbon-containing alloy steel powder and/or a carbon-free carbon-free alloy iron powder and graphite powder, a step of sintering the molded and pressurized compact in a non-oxidizing atmosphere, or the above-mentioned step. , a step of recompression molding the sintered steel after the step of sintering in a non-oxidizing atmosphere and sintering it in a non-oxidizing atmosphere, a step of nitriding or carbonitriding the sintered steel at a temperature of 600°C or higher, and A_1 A method for producing high-strength sintered steel, comprising the steps of rapidly cooling sintered steel from a temperature above its transformation line and tempering it. 4 The carbon-containing alloy steel powder is 0.05 to 1.5w
t% silicon, 0.5-2.0wt% chromium, 0.5-5
.. It has a composition containing one or more of 0 wt% nickel, 0.1 to 1.0 wt% molybdenum, and 0.1 to 2.0 wt% manganese, with the balance being iron, inevitable impurities, and carbon. The product according to claim 1 or 3. 5 The mixed powder of carbon-free ferroalloy powder and graphite powder contains 0.1 to 1.0 wt% carbon and 0.05 to 1
.. 5wt% silicon, 0.5-2.0wt% chromium, 0.
A composition containing one or more of 5 to 5.0 wt% nickel, 0.1 to 1.0 wt% molybdenum, and 0.1 to 2.0 wt% manganese, with the remainder containing iron and unavoidable impurities. The product according to claim 1 or 3.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP1438190A JPH03219040A (en) | 1990-01-24 | 1990-01-24 | High strength sintered steel and its manufacture |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP1438190A JPH03219040A (en) | 1990-01-24 | 1990-01-24 | High strength sintered steel and its manufacture |
Publications (1)
Publication Number | Publication Date |
---|---|
JPH03219040A true JPH03219040A (en) | 1991-09-26 |
Family
ID=11859469
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
JP1438190A Pending JPH03219040A (en) | 1990-01-24 | 1990-01-24 | High strength sintered steel and its manufacture |
Country Status (1)
Country | Link |
---|---|
JP (1) | JPH03219040A (en) |
Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2006037979A (en) * | 2004-07-22 | 2006-02-09 | Aisin Seiki Co Ltd | Gear and its manufacturing method |
US7622197B2 (en) * | 2006-11-20 | 2009-11-24 | Ferroxy-Aled, Llc | Seasoned ferrous cookware |
WO2011115255A1 (en) * | 2010-03-18 | 2011-09-22 | 日本発條株式会社 | Spring steel and surface treatment method for steel material |
WO2019093480A1 (en) * | 2017-11-10 | 2019-05-16 | 日立化成株式会社 | Iron-based sintered alloy material and production method therefor |
-
1990
- 1990-01-24 JP JP1438190A patent/JPH03219040A/en active Pending
Cited By (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2006037979A (en) * | 2004-07-22 | 2006-02-09 | Aisin Seiki Co Ltd | Gear and its manufacturing method |
JP4501573B2 (en) * | 2004-07-22 | 2010-07-14 | アイシン精機株式会社 | Gear and gear manufacturing method |
US7622197B2 (en) * | 2006-11-20 | 2009-11-24 | Ferroxy-Aled, Llc | Seasoned ferrous cookware |
WO2011115255A1 (en) * | 2010-03-18 | 2011-09-22 | 日本発條株式会社 | Spring steel and surface treatment method for steel material |
US9469895B2 (en) | 2010-03-18 | 2016-10-18 | Nhk Spring Co., Ltd. | Spring steel and surface treatment method for steel material |
WO2019093480A1 (en) * | 2017-11-10 | 2019-05-16 | 日立化成株式会社 | Iron-based sintered alloy material and production method therefor |
JP2019085634A (en) * | 2017-11-10 | 2019-06-06 | 日立化成株式会社 | Iron-based sintered alloy material, and production method therefor |
CN115595530A (en) * | 2017-11-10 | 2023-01-13 | 昭和电工材料株式会社(Jp) | Surface hardening material of iron-based sintered alloy material, and sprocket, gear and shaft comprising same |
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