JPH06212368A - Low alloy sintered steel excellent in fatigue strength and its production - Google Patents
Low alloy sintered steel excellent in fatigue strength and its productionInfo
- Publication number
- JPH06212368A JPH06212368A JP5326304A JP32630493A JPH06212368A JP H06212368 A JPH06212368 A JP H06212368A JP 5326304 A JP5326304 A JP 5326304A JP 32630493 A JP32630493 A JP 32630493A JP H06212368 A JPH06212368 A JP H06212368A
- Authority
- JP
- Japan
- Prior art keywords
- powder
- low alloy
- fatigue strength
- alloy sintered
- 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 58
- 239000010959 steel Substances 0.000 title claims abstract description 58
- 229910045601 alloy Inorganic materials 0.000 title claims abstract description 52
- 239000000956 alloy Substances 0.000 title claims abstract description 52
- 238000004519 manufacturing process Methods 0.000 title claims description 9
- 239000000843 powder Substances 0.000 claims abstract description 74
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 31
- 239000013078 crystal Substances 0.000 claims abstract description 31
- 239000000203 mixture Substances 0.000 claims abstract description 22
- 239000002994 raw material Substances 0.000 claims abstract description 19
- 229910000640 Fe alloy Inorganic materials 0.000 claims abstract description 12
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims abstract description 11
- 229910000734 martensite Inorganic materials 0.000 claims abstract description 11
- 239000011159 matrix material Substances 0.000 claims abstract description 11
- 238000005245 sintering Methods 0.000 claims abstract description 10
- 229910000851 Alloy steel Inorganic materials 0.000 claims abstract description 8
- 239000011812 mixed powder Substances 0.000 claims abstract description 7
- 229910052782 aluminium Inorganic materials 0.000 claims abstract description 5
- 150000001247 metal acetylides Chemical class 0.000 claims abstract description 5
- 229910052758 niobium Inorganic materials 0.000 claims abstract description 5
- 150000004767 nitrides Chemical class 0.000 claims abstract description 5
- 229910052719 titanium Inorganic materials 0.000 claims abstract description 5
- 229910052721 tungsten Inorganic materials 0.000 claims abstract description 5
- 229910052720 vanadium Inorganic materials 0.000 claims abstract description 5
- 238000000034 method Methods 0.000 claims description 26
- 239000002245 particle Substances 0.000 claims description 22
- 229910052799 carbon Inorganic materials 0.000 claims description 19
- 239000012298 atmosphere Substances 0.000 claims description 14
- 229910001566 austenite Inorganic materials 0.000 claims description 10
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 claims description 9
- 229910052796 boron Inorganic materials 0.000 claims description 9
- 239000011148 porous material Substances 0.000 claims description 7
- 239000006104 solid solution Substances 0.000 claims description 7
- 239000010955 niobium Substances 0.000 claims description 6
- 239000010936 titanium Substances 0.000 claims description 6
- 238000000137 annealing Methods 0.000 claims description 5
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 claims description 4
- 239000007787 solid Substances 0.000 claims description 4
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 claims description 4
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 3
- 239000011261 inert gas Substances 0.000 claims description 3
- GUCVJGMIXFAOAE-UHFFFAOYSA-N niobium atom Chemical compound [Nb] GUCVJGMIXFAOAE-UHFFFAOYSA-N 0.000 claims description 3
- 239000010937 tungsten Substances 0.000 claims description 3
- LEONUFNNVUYDNQ-UHFFFAOYSA-N vanadium atom Chemical compound [V] LEONUFNNVUYDNQ-UHFFFAOYSA-N 0.000 claims description 3
- 230000001590 oxidative effect Effects 0.000 claims description 2
- 238000010438 heat treatment Methods 0.000 abstract description 19
- 238000011282 treatment Methods 0.000 abstract description 8
- 229910052742 iron Inorganic materials 0.000 abstract description 3
- 238000010298 pulverizing process Methods 0.000 abstract description 3
- 238000005097 cold rolling Methods 0.000 abstract 1
- 238000009740 moulding (composite fabrication) Methods 0.000 abstract 1
- 239000000463 material Substances 0.000 description 27
- 238000005452 bending Methods 0.000 description 12
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 10
- 230000000694 effects Effects 0.000 description 10
- 238000005242 forging Methods 0.000 description 10
- 238000012360 testing method Methods 0.000 description 10
- 230000000052 comparative effect Effects 0.000 description 9
- 238000009692 water atomization Methods 0.000 description 7
- 229910052750 molybdenum Inorganic materials 0.000 description 6
- 229910017263 Mo—C Inorganic materials 0.000 description 5
- 230000006872 improvement Effects 0.000 description 5
- 238000010791 quenching Methods 0.000 description 5
- 230000000171 quenching effect Effects 0.000 description 5
- 229910000984 420 stainless steel Inorganic materials 0.000 description 4
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 4
- 230000007423 decrease Effects 0.000 description 4
- 238000004663 powder metallurgy Methods 0.000 description 4
- 230000009466 transformation Effects 0.000 description 4
- 238000005275 alloying Methods 0.000 description 3
- 238000005255 carburizing Methods 0.000 description 3
- 229910002804 graphite Inorganic materials 0.000 description 3
- 239000010439 graphite Substances 0.000 description 3
- 238000002844 melting Methods 0.000 description 3
- 230000008018 melting Effects 0.000 description 3
- 239000012299 nitrogen atmosphere Substances 0.000 description 3
- 238000012545 processing Methods 0.000 description 3
- 230000003068 static effect Effects 0.000 description 3
- 238000005728 strengthening Methods 0.000 description 3
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 2
- 229910000975 Carbon steel Inorganic materials 0.000 description 2
- 229910000746 Structural steel Inorganic materials 0.000 description 2
- 239000010962 carbon steel Substances 0.000 description 2
- 230000008859 change Effects 0.000 description 2
- 239000003795 chemical substances by application Substances 0.000 description 2
- 239000011248 coating agent Substances 0.000 description 2
- 238000000576 coating method Methods 0.000 description 2
- 238000009694 cold isostatic pressing Methods 0.000 description 2
- 230000001186 cumulative effect Effects 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 238000001192 hot extrusion Methods 0.000 description 2
- 238000001513 hot isostatic pressing Methods 0.000 description 2
- 229910052757 nitrogen Inorganic materials 0.000 description 2
- 229910000592 Ferroniobium Inorganic materials 0.000 description 1
- 229910000628 Ferrovanadium Inorganic materials 0.000 description 1
- 241000237858 Gastropoda Species 0.000 description 1
- 229910001030 Iron–nickel alloy Inorganic materials 0.000 description 1
- 238000005299 abrasion Methods 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 238000005256 carbonitriding Methods 0.000 description 1
- 238000003763 carbonization Methods 0.000 description 1
- 229910052804 chromium Inorganic materials 0.000 description 1
- PMHQVHHXPFUNSP-UHFFFAOYSA-M copper(1+);methylsulfanylmethane;bromide Chemical compound Br[Cu].CSC PMHQVHHXPFUNSP-UHFFFAOYSA-M 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000002950 deficient Effects 0.000 description 1
- 238000000280 densification Methods 0.000 description 1
- 230000003009 desulfurizing effect Effects 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000007723 die pressing method Methods 0.000 description 1
- 230000000376 effect on fatigue Effects 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 238000009661 fatigue test Methods 0.000 description 1
- 239000010419 fine particle Substances 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 230000006698 induction Effects 0.000 description 1
- ZFGFKQDDQUAJQP-UHFFFAOYSA-N iron niobium Chemical compound [Fe].[Fe].[Nb] ZFGFKQDDQUAJQP-UHFFFAOYSA-N 0.000 description 1
- PNXOJQQRXBVKEX-UHFFFAOYSA-N iron vanadium Chemical compound [V].[Fe] PNXOJQQRXBVKEX-UHFFFAOYSA-N 0.000 description 1
- 229910052748 manganese Inorganic materials 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 238000005121 nitriding Methods 0.000 description 1
- 230000006911 nucleation Effects 0.000 description 1
- 238000010899 nucleation Methods 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 238000005498 polishing Methods 0.000 description 1
- 238000009700 powder processing Methods 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 238000007670 refining Methods 0.000 description 1
- 238000005204 segregation Methods 0.000 description 1
- 238000009628 steelmaking Methods 0.000 description 1
- 238000005496 tempering Methods 0.000 description 1
- 238000003826 uniaxial pressing Methods 0.000 description 1
Landscapes
- Powder Metallurgy (AREA)
Abstract
Description
【0001】[0001]
【産業上の利用分野】本発明は、歯車、軸受けのレース
等の高い疲労強度を要求される機械構造部品に用いられ
る低合金焼結鋼、及びその製造方法に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low alloy sintered steel used for mechanical structural parts such as gears and races of bearings which require high fatigue strength, and a manufacturing method thereof.
【0002】[0002]
【従来の技術】粉末冶金法によって製造される低合金焼
結鋼からなる焼結機械部品は経済性に優れるという点か
ら、例えば自動車部品、事務機器、家電製品、農機具等
に広く利用されており、その需要は年々増加している。
この需要の増加に伴って、低合金焼結鋼に要求される特
性も次第に厳しくなってきている。2. Description of the Related Art Sintered machine parts made of low alloy sintered steel produced by powder metallurgy are widely used, for example, for automobile parts, office equipment, home electric appliances, agricultural machinery, etc. because of their excellent economical efficiency. , Its demand is increasing year by year.
With this increase in demand, the properties required for low alloy sintered steel have become increasingly severe.
【0003】この要求を満たすため各種の研究が行わ
れ、例えば低合金焼結鋼の組成では古くからのFe−N
i−C系やFe−Cu−C系ばかりでなく、Fe−Ni
−Mo−C系、Fe−Ni−Cu−Mo−C系、Fe−
Cr−Mn−Mo−C系等の低合金焼結鋼が開発されて
いる。又、原料粉末の点では、従来の還元粉末から高密
度が得やすいアトマイズ粉末が主流となりつつある。Various studies have been carried out to meet this requirement. For example, in the composition of low alloy sintered steel, Fe-N has long been used.
Fe-Ni as well as i-C and Fe-Cu-C
-Mo-C system, Fe-Ni-Cu-Mo-C system, Fe-
Low alloy sintered steels such as Cr-Mn-Mo-C series have been developed. In terms of raw material powder, atomized powder, which is easy to obtain high density from conventional reduced powder, is becoming the mainstream.
【0004】これらの技術開発により低合金焼結鋼の強
度は大幅に改善され、その引張強度に代表される静的な
特性は、溶解・鍛造法によって作製された一般の機械構
造用鋼に匹敵するレベルに達するようになった。しかし
ながら、靭性や疲労強度等に代表される動的な特性は未
だ充分ではなく、特性改善の要求を満たし更に用途を拡
大するためには動的な特性の改善向上が不可欠である。With the development of these technologies, the strength of low alloy sintered steel has been greatly improved, and the static characteristics represented by the tensile strength thereof are comparable to those of general mechanical structural steel produced by the melting / forging method. I have reached the level to do. However, the dynamic properties represented by toughness and fatigue strength are not sufficient, and it is essential to improve and improve the dynamic properties in order to meet the demand for property improvement and further expand the applications.
【0005】粉末冶金法によって製造される低合金焼結
鋼の動的特性を改善するための最も有効な方法は、その
密度を上げ、内部に残留する空孔を減らすことにある。
焼結鋼の密度を上げる一つの方法として、粉末鍛造法が
古くから知られている。しかしながら、粉末鍛造法によ
り製造された低合金鋼は、同一組成の溶解・鍛造法によ
り製造された一般の機械構造用鋼のレベルを上回ること
はできなかった。The most effective way to improve the dynamic properties of low alloy sintered steels produced by powder metallurgy is to increase their density and reduce the voids that remain inside.
The powder forging method has long been known as one method of increasing the density of sintered steel. However, the low alloy steel produced by the powder forging method could not exceed the level of general mechanical structural steel produced by the melting / forging method having the same composition.
【0006】その原因として、鋼粉末表面の酸化物被膜
が焼結の進行を妨げたり合金元素の偏析を招くこと、非
金属介在物が存在し且つ製鋼技術の差に起因して非金属
介在物レベルに差があること、鍛造体表層等に空孔が残
存すること等があげられる。特公昭57−8841号公
報には、鋼粉末表面の酸化物被膜を機械的粉砕により剥
離除去する方法が記載されているが、この方法では粉末
表面の酸化物被膜を除去するに止まり、鋼粉末粒子の内
部にも存在する非金属介在物を除去するには至っていな
い。[0006] The cause is that the oxide film on the surface of the steel powder hinders the progress of sintering or causes segregation of alloying elements, non-metallic inclusions are present, and non-metallic inclusions are caused by the difference in steelmaking technology. There are differences in level, and holes are left on the surface of the forged body. Japanese Patent Publication No. 57-8841 describes a method of peeling and removing the oxide coating on the surface of the steel powder by mechanical pulverization. However, this method only removes the oxide coating on the surface of the steel powder. It has not been possible to remove non-metallic inclusions existing inside the particles.
【0007】[0007]
【発明が解決しようとする課題】本発明は、かかる従来
の事情に鑑み、優れた静的特性に加えて、疲労強度を主
とする動的特性を大幅に改善向上させた低合金焼結鋼、
及びその製造方法を提供することを目的とする。SUMMARY OF THE INVENTION In view of such conventional circumstances, the present invention is a low alloy sintered steel in which, in addition to excellent static properties, dynamic properties mainly including fatigue strength are greatly improved. ,
And its manufacturing method.
【0008】[0008]
【課題を解決するための手段】上記目的を達成するた
め、本発明の疲労強度に優れた低合金焼結鋼は、0.1
5重量%以上0.8重量%未満の炭素を含む低合金焼結
鋼において、そのマトリックスが旧γ結晶粒の平均粒径
が15μm以下の焼戻しマルテンサイトであり、該マト
リックス中に含まれる空孔又は非金属介在物の最大径が
50μm以下であって、密度が理論密度の96%以上で
あることを特徴とする。To achieve the above object, the low alloy sintered steel excellent in fatigue strength of the present invention is 0.1
In a low alloy sintered steel containing carbon in an amount of 5% by weight or more and less than 0.8% by weight, the matrix is tempered martensite having an average grain size of old γ crystal grains of 15 μm or less, and pores contained in the matrix. Alternatively, the maximum diameter of the non-metallic inclusion is 50 μm or less, and the density is 96% or more of the theoretical density.
【0009】本発明における疲労強度に優れた低合金焼
結鋼の製造方法は、アトマイズ法により製造された鉄粉
末又は鉄合金粉末若しくはこれらを含む低合金鋼の原料
粉末を、不活性ガス雰囲気中又は大気中において乾式ミ
ルで処理することにより、原料粉末に転位を導入すると
共に非金属介在物を最大径50μm以下に粉砕し、その
後この処理粉末を軟化焼鈍し、最終組成での炭素が0.
15重量%以上0.8重量%未満となるように炭素粉末
を添加混合した後、この混合粉末を冷間成形し、焼結又
は熱間塑性加工により理論密度の96%以上に緻密化
し、更に熱処理してマトリックスを焼戻しマルテンサイ
トとすることを特徴とする。The method for producing a low alloy sintered steel excellent in fatigue strength according to the present invention is a method in which an iron powder produced by an atomizing method, an iron alloy powder, or a raw material powder of a low alloy steel containing these is used in an inert gas atmosphere. Alternatively, by treating with a dry mill in the air, dislocations are introduced into the raw material powder and the non-metallic inclusions are pulverized to a maximum diameter of 50 μm or less, and then the treated powder is softened and annealed so that carbon in the final composition is 0.
After carbon powder is added and mixed so as to be 15% by weight or more and less than 0.8% by weight, the mixed powder is cold-formed and densified to 96% or more of the theoretical density by sintering or hot plastic working. It is characterized in that the matrix is heat treated to be tempered martensite.
【0010】ここで、低合金焼結鋼とは、従来から知ら
れている鉄と炭素からなる炭素鋼及び鉄と炭素と他の合
金元素からなる低合金鋼であって、原料粉末の焼結によ
り得られたものを意味する。又、旧γ結晶粒は、低合金
焼結鋼中の結晶粒で且つ焼入れ加熱時のオーステナイト
域においてγ結晶粒であったものを意味し、一般に焼入
れ鋼の結晶粒径の比較はこの旧γ結晶粒の粒径の比較に
より行われている。Here, the low alloy sintered steel is a conventionally known carbon steel composed of iron and carbon and a low alloy steel composed of iron, carbon and other alloying elements, and a raw material powder is sintered. Means that obtained by. The old γ crystal grains mean those in the low alloy sintered steel and the γ crystal grains in the austenite region during quenching and heating. It is performed by comparing the grain sizes of crystal grains.
【0011】[0011]
【作用】一般に、鋼の疲労強度は硬さの増加と共に向上
するものの、硬さがある水準に達すると疲労強度はほぼ
一定になるか、若しくは低下する傾向を示す。この原因
として非金属介在物の存在が挙げられ、硬さが向上する
に連れて低硬度では起点となり得なかった小さな介在物
が疲労クラックの起点となるため、疲労強度が向上しな
くなるものと考えられている。従って、介在物のない材
料が得られれば、その疲労強度を大幅に向上せしめるこ
とができると予想されるものの、工業的にその様な材料
を得ることは困難である。In general, although the fatigue strength of steel improves with an increase in hardness, when the hardness reaches a certain level, the fatigue strength tends to become almost constant or decrease. The cause of this is the presence of non-metallic inclusions, and as the hardness improves, small inclusions that could not be the starting point at low hardness become the starting points of fatigue cracks, so it is thought that the fatigue strength will not improve. Has been. Therefore, it is expected that if a material without inclusions can be obtained, the fatigue strength thereof can be greatly improved, but it is difficult to industrially obtain such a material.
【0012】又、疲労強度の向上が頭打ちになる高硬度
の水準では、疲労寿命はクラックの進展速度に依存する
ことが知られている。ところが、クラックの進展速度は
結晶粒界の近傍で大幅に低下する。従って、結晶粒界が
多数存在する構造が達成されれば、疲労強度の向上を達
成し得るものと考えられる。本発明はこの様な観点か
ら、空孔を減らして高密度にすると同時に、マトリック
スを特に微細な焼戻しマルテンサイトとして結晶粒界を
増加させ、更に空孔や非金属介在物の大きさを出来るだ
け小さくして、低合金焼結鋼の疲労強度その他の動的特
性を改善向上させたものである。It is known that the fatigue life depends on the crack growth rate at a high hardness level where improvement in fatigue strength reaches a ceiling. However, the crack growth rate is significantly reduced near the grain boundaries. Therefore, it is considered that improvement in fatigue strength can be achieved if a structure having a large number of crystal grain boundaries is achieved. From this point of view, the present invention reduces the number of vacancies to increase the density and at the same time increases the grain boundaries by using the matrix as a particularly fine tempered martensite to further increase the size of vacancies and non-metallic inclusions. By making it smaller, the fatigue strength and other dynamic characteristics of the low alloy sintered steel are improved and improved.
【0013】本発明では、低合金焼結鋼のマトリックス
を旧γ結晶粒の平均粒径が15μm以下の微細マルテン
サイトとするが、この様な特に微細なマルテンサイトを
得るためには、焼入れ加熱時のオーステナイトを微細に
する必要がある。その方法としては、溶解・鍛造法によ
る一般低合金鋼ではオースフォーミング等の加工熱処理
法があるが、粉末冶金法による本発明では不活性ガス雰
囲気中又は大気中において原料粉末をボールミル、振動
ミル、アトライター等の乾式ミルを用いて長時間処理
し、予め原料粉末に多量の転位を導入しておくことが最
も有効な手段であることが判った。即ち、この様にして
多量の転位を導入した原料粉末を用いることで、焼入れ
加熱時のオーステナイトが微細になり、その結果微細な
焼戻しマルテンサイトが得られる。In the present invention, the matrix of the low alloy sintered steel is fine martensite having an average grain size of the former γ crystal grains of 15 μm or less. In order to obtain such particularly fine martensite, quenching heating is performed. It is necessary to refine the austenite in time. As the method, there is a work heat treatment method such as ausforming in a general low alloy steel by a melting / forging method, but in the present invention by a powder metallurgy method, a raw material powder is ball milled in an inert gas atmosphere or in the air, a vibration mill, It has been found that the most effective means is to preliminarily introduce a large amount of dislocations into the raw material powder by treating for a long time with a dry mill such as an attritor. That is, by using the raw material powder in which a large amount of dislocations are introduced in this way, austenite during quenching and heating becomes fine, and as a result, fine tempered martensite is obtained.
【0014】又、この乾式ミルを用いた原料粉末の処理
によって、原料粉末に多量の転位を導入すると同時に、
原料粉末中に含まれる非金属介在物を粉砕して微細化
し、疲労強度に有害な大きな介在物を低減させることが
可能である。即ち、非金属介在物の最大径を50μm以
下、好ましくは25μm以下にすることによって、低合
金焼結鋼の疲労強度に与える影響を大幅に減少させ得る
ことが判明した。By processing the raw material powder using this dry mill, a large amount of dislocations are introduced into the raw material powder, and at the same time,
It is possible to reduce non-metallic inclusions contained in the raw material powder by pulverizing them to reduce large inclusions harmful to fatigue strength. That is, it was found that the influence on the fatigue strength of the low alloy sintered steel can be significantly reduced by setting the maximum diameter of the non-metallic inclusions to 50 μm or less, preferably 25 μm or less.
【0015】乾式ミルで処理された処理粉末は、転位の
多量の導入により硬さが上昇しているため、そのままで
は冷間成形が困難であるから、歪みとり焼鈍により軟化
させて冷間成形性を増加させる必要がある。焼鈍は真空
中又は非酸化性雰囲気中において600〜1000℃の
温度で実施することが望ましい。焼鈍温度が600℃未
満では加工歪みの除去が不十分で、粉末の軟化が少なく
成形性を改善することができず、又1000℃を越える
と粉末間に焼結が進行し、再度破砕処理を行わなければ
冷間成形ができなくなる。Since the hardness of the treated powder processed by the dry mill increases due to the introduction of a large amount of dislocations, it is difficult to perform cold forming as it is. Therefore, it is softened by strain relief annealing to form cold formability. Need to be increased. Annealing is preferably performed at a temperature of 600 to 1000 ° C. in a vacuum or a non-oxidizing atmosphere. If the annealing temperature is less than 600 ° C, the removal of work strain is insufficient, the softening of the powder is small and the formability cannot be improved, and if it exceeds 1000 ° C, the sintering progresses between the powders and the crushing treatment is performed again. Otherwise, cold forming will not be possible.
【0016】かくして得られた処理粉末には、黒鉛等の
炭素粉末を混合して炭素量を調整する。炭素は鋼の特性
を支配する重要な合金元素であり、炭素量が増加するに
従って、強度及び硬さは増加するが延性は低下する。炭
素量が0.15重量%未満では熱処理後に良好な硬さを
得ることができず、又0.8重量%以上含有しても硬さ
の改善効果は少なく、むしろ残留γ結晶の増加や焼入れ
性の著しい低下によって疲労強度の低下を招くので、本
発明では炭素量を0.15重量%以上0.8重量%未満と
する。The treated powder thus obtained is mixed with a carbon powder such as graphite to adjust the amount of carbon. Carbon is an important alloying element that controls the properties of steel, and as the amount of carbon increases, the strength and hardness increase, but the ductility decreases. If the amount of carbon is less than 0.15% by weight, good hardness cannot be obtained after heat treatment, and if the amount of carbon is more than 0.8% by weight, the effect of improving the hardness is small, rather the increase of residual γ crystals and quenching In the present invention, the carbon content is set to be 0.15% by weight or more and less than 0.8% by weight because the fatigue strength is lowered due to the remarkable deterioration of the properties.
【0017】処理粉末に炭素粉末を添加混合した混合粉
末は、金型を用いた1軸プレスや冷間静水圧成形(CI
P)等により冷間成形した後、A3変態以上の温度にお
ける焼結又は熱間鍛造、熱間押出、熱間等方静水圧成形
(HIP)等の熱間塑性加工によって、理論密度の96
%以上に緻密化される。必要に応じて、残留する空孔を
消失させるため、焼結後に再加圧、熱間鍛造、熱間押
出、HIP等を施すことが望ましい。空孔は疲労強度に
大きな影響を及ぼし、非金属介在物と同等に見なすこと
ができるので、その最大径は50μm以下、好ましくは
25μm以下とする必要があり、その残存量は4体積%
以下が望ましい。The mixed powder obtained by adding and mixing carbon powder to the treated powder can be used for uniaxial pressing using a die or cold isostatic pressing (CI).
After cold forming by P) or the like, a theoretical density of 96 is obtained by sintering at a temperature of A3 transformation or higher or hot plastic working such as hot forging, hot extrusion, hot isostatic pressing (HIP).
It is densified to more than%. It is desirable to perform re-pressurization, hot forging, hot extrusion, HIP, or the like after the sintering in order to eliminate the remaining pores, if necessary. Voids have a large effect on fatigue strength and can be regarded as equivalent to non-metallic inclusions, so their maximum diameter must be 50 μm or less, preferably 25 μm or less, and the remaining amount is 4% by volume.
The following is desirable.
【0018】尚、乾式ミルにより多量の転位を導入され
た処理粉末は、焼結や熱間塑性加工等の緻密化工程で高
温にさらされると結晶粒の粗大化が進行しやすいが、こ
れを防ぐためには微細な粒子を均一に分散させて粒界の
移動をピン止めする方法が有効である。かかる分散粒子
としては、高温のオーステナイト域でマトリックスに固
溶しないか又は固溶度の低い酸化物、窒化物又は炭化
物、例えばアルミナや窒化アルミニウム等が有効であ
る。The treated powder in which a large amount of dislocations have been introduced by a dry mill is apt to undergo coarsening of crystal grains when exposed to high temperature in a densification step such as sintering or hot plastic working. In order to prevent this, a method of uniformly dispersing fine particles and pinning the movement of grain boundaries is effective. As such dispersed particles, oxides, nitrides or carbides that do not form a solid solution or have a low solid solubility in the matrix in the high temperature austenite region, such as alumina and aluminum nitride, are effective.
【0019】これら分散粒子の平均粒径は5μm未満と
すべきであり、好ましくは0.5μm以下、更に好まし
くは0.1μm以下である。分散粒径の平均粒径が0.5
μmを越えると疲労強度が低下し、特に平均粒径が5μ
m以上では分散粒子が欠陥として作用するからである。
又、これら分散粒子の添加量が増えると延性の低下をも
たらすので、処理粉末に対して0.5〜5体積%程度が
適当である。The average particle size of these dispersed particles should be less than 5 μm, preferably 0.5 μm or less, and more preferably 0.1 μm or less. Average particle size of dispersed particle size is 0.5
If it exceeds μm, the fatigue strength will decrease, especially if the average particle size is 5μ.
This is because dispersed particles act as defects when m or more.
Further, if the addition amount of these dispersed particles is increased, the ductility is lowered, so about 0.5 to 5% by volume relative to the treated powder is suitable.
【0020】この様にして得られた焼結体ないし熱間塑
性加工体は、通常のごとく熱処理によりオーステナイト
からマルテンサイトへの変態を経て強化され、本発明の
微細な焼戻しマルテンサイトの低合金焼結鋼となる。具
体的な熱処理としては、オーステナイト域まで加熱保持
し、油焼入れした後、焼戻しを行うが、これらの熱処理
と組み合わせた浸炭処理、浸炭窒化処理、窒化処理、誘
導加熱による表面焼入れ等も有効である。The thus obtained sintered body or hot-plastic worked body is strengthened by a usual heat treatment through transformation from austenite to martensite, and the fine alloy tempered martensite of the present invention is low alloy fired. Becomes steel. As a specific heat treatment, heating and holding to an austenite region, oil quenching, and then tempering are carried out, but carburizing treatment, carbonitriding treatment, nitriding treatment, surface hardening by induction heating, etc. combined with these heat treatments are also effective. .
【0021】本発明の低合金焼結鋼の組成は、前記のご
とく公知の炭素鋼や低合金鋼の組成であって良い。しか
し、粉末冶金法による本発明では、そのプロセス的制約
から好ましい合金組成が存在する。その一例として、F
e−Ni−Mo−C系、及びFe−Cr−Mo−Mn−
C系等がある。Fe−Cr−Mo−Mn−C系の低合金
焼結鋼は、Fe−Ni−Mo−C系よりも焼入れ性に優
れるという特徴を有する反面、CrやMn等の酸化され
やすい金属元素を含むため、焼結や鍛造等の際の加熱雰
囲気に敏感である。従って、粉末処理や加熱時における
雰囲気の選択並びに制御が重要となる。The composition of the low alloy sintered steel of the present invention may be the composition of known carbon steel or low alloy steel as described above. However, in the present invention by the powder metallurgy method, a preferable alloy composition exists due to the process restriction. As an example, F
e-Ni-Mo-C system, and Fe-Cr-Mo-Mn-
There are C series etc. Fe-Cr-Mo-Mn-C-based low alloy sintered steel is characterized by being superior in hardenability than Fe-Ni-Mo-C-based steel, but contains easily oxidizable metallic elements such as Cr and Mn. Therefore, it is sensitive to the heating atmosphere during sintering or forging. Therefore, it is important to select and control the atmosphere during powder processing and heating.
【0022】上記の合金組成において、Niは焼入れ性
を大幅に改善するが0.5重量%未満ではその効果がな
く、3重量%を越えると粉末の冷間成形が困難になるば
かりでなく、熱処理後の残留γ結晶が増えるため疲労強
度特性に有害となる。Moは少量の添加により焼入れ性
を改善し、又炭素と炭化物を形成して耐摩耗性及び耐熱
性を改善する。しかし、Moが0.1重量%未満ではそ
の効果がなく、1.5重量%を越えると固溶強化により
成形性を劣化させる。In the above alloy composition, Ni greatly improves the hardenability, but if it is less than 0.5% by weight, its effect is not exhibited, and if it exceeds 3% by weight, cold forming of powder becomes difficult, and The residual γ crystals after heat treatment increase, which is harmful to the fatigue strength characteristics. Mo improves the hardenability by adding a small amount, and forms carbon and carbide to improve wear resistance and heat resistance. However, if Mo is less than 0.1% by weight, the effect is not obtained, and if it exceeds 1.5% by weight, solid solution strengthening deteriorates moldability.
【0023】又、Crは焼入れ性を大幅に改善すると共
に、焼戻し軟化抵抗を増加させる作用を有する。しか
し、Crが0.5重量%未満では焼入れ性改善の効果が
なく、3重量%を越えると固溶強化により成形性が低下
する。Mnは焼入れ性を改善すると共に、粉末製造の際
には脱酸剤、脱硫剤として作用して粉末の酸素量を低下
させる。しかし、0.2重量%未満では焼入れ性の改善
効果がなく、1.6重量%を越えると固溶強化により成
形性が劣化する。Further, Cr has the functions of significantly improving the hardenability and increasing the temper softening resistance. However, if Cr is less than 0.5% by weight, the effect of improving hardenability is not provided, and if it exceeds 3% by weight, formability is deteriorated due to solid solution strengthening. Mn improves the hardenability and also acts as a deoxidizing agent and a desulfurizing agent during powder production to reduce the oxygen content of the powder. However, if it is less than 0.2% by weight, there is no improvement effect on the hardenability, and if it exceeds 1.6% by weight, the formability deteriorates due to solid solution strengthening.
【0024】高温での粒成長の抑制に分散粒子によるピ
ン止め効果が有効であることは前記したが、同様にオー
ステナイト域で固溶度の低い炭化物や窒化物を形成する
元素を原料の合金粉末に添加することも有効である。こ
の方法によればオーステナイト化時の結晶粒の成長を抑
制できるので、旧γ結晶粒の粒径を一層微細化すること
が可能である。この種の元素としては、ニオブ、バナジ
ウム、チタン、タングステン、又はアルミニウムが有望
であり、その添加量は合計で0.05〜3.0重量%が好
ましい。その理由は、0.05重量%未満では結晶粒の
成長抑制の効果がなく、3.0重量%を越えて添加して
ももはや結晶粒は細かくならず、むしろ固溶硬化により
粉末の成形性が低下するからである。As described above, the pinning effect of dispersed particles is effective in suppressing grain growth at high temperatures, but similarly, alloy powders made of raw materials containing elements that form carbides and nitrides with low solid solubility in the austenite region It is also effective to add to. According to this method, the growth of crystal grains during austenitization can be suppressed, so that the grain size of old γ crystal grains can be further refined. As this kind of element, niobium, vanadium, titanium, tungsten, or aluminum is promising, and the total addition amount thereof is preferably 0.05 to 3.0% by weight. The reason is that if it is less than 0.05% by weight, there is no effect of suppressing the growth of crystal grains, and if it is added in excess of 3.0% by weight, the crystal grains will no longer become finer, but rather the solid solution hardening will make the powder formable. Is reduced.
【0025】本発明の低合金焼結鋼の場合、結晶粒を非
常に小さくすることにより結晶粒界を増加させてあるの
で、変態の核となる部分が増えてγ→α+Fe3Cの変
態が促進され、その結果焼入れ性が劣化しやすいという
問題がある。ところが、ホウ素はオーステナイト粒界に
偏析して結晶粒界のエネルギーを下げることにより、結
晶粒界の核生成サイトとしての機能を低下させることが
できるので、微量の添加で焼入れ性を向上させる効果が
ある。この効果を得る為にはホウ素を重量分率で10p
pm以上添加する必要があるが、300ppmを越えて
も焼き入れ性の向上がもはや見られないばかりか、結晶
粒界の強度が弱くなって脆化するので好ましくない。In the case of the low alloy sintered steel of the present invention, the crystal grain boundaries are increased by making the crystal grains very small, so that the core of the transformation is increased and the transformation of γ → α + Fe 3 C occurs. However, there is a problem that the hardenability is likely to deteriorate as a result. However, boron segregates at the austenite grain boundaries and lowers the energy of the crystal grain boundaries, so that the function of the crystal grain boundaries as a nucleation site can be reduced, so the addition of a trace amount has the effect of improving hardenability. is there. To obtain this effect, boron is used in a weight fraction of 10 p
It is necessary to add more than pm, but even if it exceeds 300 ppm, not only the improvement of the hardenability is no longer observed, but also the strength of the crystal grain boundary becomes weak and it becomes brittle, which is not preferable.
【0026】[0026]
【実施例】実施例1 水アトマイズ法により製造されたAISI 4600組
成(Fe−1.8重量%Ni−0.5重量%Mo)を有す
る市販の鉄合金粉末を、高エネルギー乾式ミルを用いて
Ar雰囲気中で、処理時間を2、3、4、20、40、
80時間と変えて処理した。得られた各処理粉末を、窒
素雰囲気中にて800℃で1時間加熱して焼鈍軟化さ
せ、最終組成で炭素量が0.25重量%となるように黒
鉛粉末を添加混合した後、成形密度6.9g/cm3(密
度比0.878)となるように金型プレスによりそれぞ
れ冷間成形した。得られた各成形体を、窒素中において
1150℃で1時間焼結し、更にその温度で鍛造して、
密度比0.99以上の鍛造体を得た。 Example 1 A commercially available iron alloy powder having an AISI 4600 composition (Fe-1.8 wt% Ni-0.5 wt% Mo) produced by a water atomizing method was prepared using a high energy dry mill. In Ar atmosphere, the processing time is 2, 3, 4, 20, 40,
It was treated for 80 hours. Each of the obtained treated powders was annealed and softened by heating at 800 ° C for 1 hour in a nitrogen atmosphere, and graphite powder was added and mixed so that the carbon content in the final composition would be 0.25% by weight. Each was cold-molded by a die press so as to have a density of 6.9 g / cm 3 (density ratio 0.878). Each of the obtained compacts was sintered in nitrogen at 1150 ° C. for 1 hour and further forged at that temperature,
A forged body having a density ratio of 0.99 or more was obtained.
【0027】各鍛造体を、有効浸炭深さ1mmとなるよ
うに910℃で浸炭を行い、続いて850℃に保持した
後、油中に焼入れし、200℃で90分の焼戻しを行っ
た。このようにして得られた各低合金焼結鋼について、
旧γ結晶粒の平均粒径、400mm2中の空孔及び最も
大きな非金属介在物の最大径、抗折強度、及び疲労強度
を測定し、表1の結果を得た。尚、疲労強度は平滑試験
片を用いた回転曲げ疲労試験により、抗折強度は4×9
×45mmの平滑試験片を用いて求めた。Each forged body was carburized at 910 ° C. so as to have an effective carburizing depth of 1 mm, then kept at 850 ° C., then quenched in oil and tempered at 200 ° C. for 90 minutes. For each low alloy sintered steel thus obtained,
The average particle size of the old γ crystal grains, the maximum diameter of the pores and the largest non-metallic inclusions in 400 mm 2 , the bending strength, and the fatigue strength were measured, and the results in Table 1 were obtained. The fatigue strength was 4 × 9 as determined by a rotary bending fatigue test using a smooth test piece.
It was determined using a smooth test piece of × 45 mm.
【0028】[0028]
【表1】 処理時間 旧γ粒径 介在物最大径 抗折強度 疲労強度試料 (hr) (μm) (μm) (kg/mm2) (kg/mm2) 1 2 18.7 186 220 80 2 3 15.0 48 230 85 3 4 12.6 47 244 90 4 20 10.4 33 261 95 5 40 8.8 25 277 100 6 80 8.2 27 273 100[Table 1] Treatment time Old γ grain size Maximum inclusion size Bending strength Fatigue strength Sample (hr) (μm) (μm) (kg / mm 2 ) (kg / mm 2 ) 1 2 18.7 186 220 80 2 3 15.0 48 230 85 3 4 12.6 47 244 90 4 20 10.4 33 261 95 5 40 8.8 25 277 100 6 80 8.2 27 273 100
【0029】表1の結果から、乾式ミルによる原料粉末
の処理時間が増すにつれて、旧γ結晶粒の平均粒径及び
最大介在物の大きさが小さくなること、及びそれに伴い
低合金焼結鋼の特性が改善され、特に疲労強度が大幅に
増加することが判る。From the results shown in Table 1, the average grain size of the old γ crystal grains and the size of the maximum inclusions become smaller as the treatment time of the raw material powder in the dry mill increases, and accordingly, the low alloy sintered steel It can be seen that the characteristics are improved, and especially the fatigue strength is greatly increased.
【0030】実施例2 水アトマイズ法により製造されたAISI 4600組
成(Fe−1.8重量%Ni−0.5重量%Mo)を有す
る市販の鉄合金粉末を、高エネルギー乾式ミルを用いて
Ar雰囲気中で40時間処理した。得られた処理粉末
を、窒素雰囲気中にて800℃で1時間加熱して焼鈍軟
化させた後、最終組成で炭素量が0.25重量%となる
ようにグラファイトを添加混合した。この混合粉末を成
形密度6.9g/cm3(密度比0.878)となるよう
に金型プレスにより冷間成形し、窒素中において115
0℃で1時間焼結し、更にその温度で鍛造して、鍛造後
の密度比をそれぞれ0.92〜0.99の範囲で変化させ
た。[0030]Example 2 AISI 4600 set manufactured by water atomization method
Composition (Fe-1.8 wt% Ni-0.5 wt% Mo)
Using a high energy dry mill, a commercially available iron alloy powder
It processed in Ar atmosphere for 40 hours. The resulting treated powder
Is annealed and softened by heating at 800 ° C for 1 hour in a nitrogen atmosphere.
After carbonization, the final composition has a carbon content of 0.25% by weight.
Graphite was added and mixed in this manner. Form this mixed powder
Shape density 6.9 g / cm3(Density ratio 0.878)
Cold-molded in a die press to 115 in nitrogen
Sinter at 0 ° C for 1 hour, forge at that temperature, and then forge
Change the density ratio of each in the range of 0.92 to 0.99.
It was
【0031】得られた密度比の異なる各鍛造体を実施例
1と同様に熱処理し、得られた各低合金焼結鋼につい
て、旧γ結晶粒の平均粒径、抗折強度、衝撃値、及び疲
労強度を測定し、表2の結果を得た。尚、各低合金焼結
鋼中に存在する空孔及び最大の介在物の最大径は、いず
れも50μm以下であった。比較のために、乾式ミルに
よる原料粉末の処理を行わない以外、上記と同様にして
低合金焼結鋼を製造し、この比較材についても同じ評価
を行い、その結果を表2に併せて示した。Each of the obtained forged bodies having different density ratios was heat treated in the same manner as in Example 1, and the obtained low alloy sintered steels had the same average grain size of the former γ crystal grains, bending strength, impact value, and The fatigue strength was measured and the results shown in Table 2 were obtained. The maximum diameters of pores and maximum inclusions present in each low alloy sintered steel were 50 μm or less. For comparison, a low alloy sintered steel was produced in the same manner as above except that the raw material powder was not treated with a dry mill, and the same evaluation was performed on this comparative material. The results are also shown in Table 2. It was
【0032】[0032]
【表2】 旧γ粒径 抗折強度 衝 撃 値 疲労強度試料 密度比 (μm) (kg/mm2) (kgf・m/cm2) (kg/mm2) 7 0.92 8.8 202 0.66 70 8 0.94 8.9 221 0.92 75 9 0.96 8.8 248 1.4 85 10 0.99 8.7 277 3.2 100 比較材 0.99 22.4 210 1.72 75[Table 2] Old γ particle size Bending strength Impact value Fatigue strength Sample density ratio (μm) (kg / mm 2 ) (kgf ・ m / cm 2 ) (kg / mm 2 ) 7 0.92 8.8 202 0.66 70 8 0.94 8.9 221 0.92 75 9 0.96 8.8 248 1.4 85 10 0.99 8.7 277 3.2 100 Comparative material 0.99 22.4 210 1.72 75
【0033】表2の結果から、密度比が上がるに連れ
て、低合金焼結鋼の強度、靭性、疲労強度のいずれも増
加することが判る。しかし、原料粉末を乾式ミルで処理
していない比較材においては、旧γ結晶粒の平均粒径が
大きいため、高密度にしても強度、靭性、疲労強度のい
ずれもが本発明の試料より劣っている。From the results shown in Table 2, it can be seen that the strength, toughness, and fatigue strength of the low alloy sintered steel also increase as the density ratio increases. However, in the comparative material in which the raw material powder is not processed by the dry mill, the average grain size of the old γ crystal grains is large, so that even if the density is high, the strength, toughness, and fatigue strength are inferior to those of the sample of the present invention. ing.
【0034】実施例3 水アトマイズ法により製造されたAISI 4600組
成(Fe−1.8重量%Ni−0.5重量%Mo)を有す
る市販の鉄合金粉末に、平均粒径0.05μmのアルミ
ナ粉末を体積分率が0.5%、1.0%、2.0%、5.0
%となるように各々配合して混合した後、高エネルギー
乾式ミルを用いてAr雰囲気中で40時間処理した。得
られた各処理粉末を、実施例1と同一条件で、焼鈍軟
化、黒鉛粉末の混合、冷間成形、焼結、密度比0.99
以上となる鍛造、及び熱処理を行って低合金焼結鋼を製
造した。 Example 3 A commercially available iron alloy powder having an AISI 4600 composition (Fe-1.8 wt% Ni-0.5 wt% Mo) produced by the water atomizing method was added to alumina having an average particle size of 0.05 μm. The powder has a volume fraction of 0.5%, 1.0%, 2.0%, 5.0.
%, And then mixed and then treated in an Ar atmosphere for 40 hours using a high energy dry mill. Each of the obtained treated powders was annealed and softened, graphite powder was mixed, cold compacted, sintered, and the density ratio was 0.99 under the same conditions as in Example 1.
The above forging and heat treatment were performed to manufacture a low alloy sintered steel.
【0035】得られた各低合金焼結鋼について、旧γ結
晶粒の平均粒径と共に、抗折強度、衝撃値、疲労強度を
測定し、その結果を表3に示した。尚、各低合金焼結鋼
中に存在する空孔及び介在物の最大径は、いずれも50
μm以下であった。下記表3の結果から、アルミナの添
加により旧γ結晶粒が微細化されることが判るが、その
添加量が5体積%を越えると微細化の効果は頭打ちにな
り、衝撃値も低下傾向になることが判る。With respect to each of the obtained low alloy sintered steels, bending strength, impact value and fatigue strength were measured together with the average grain size of the old γ crystal grains, and the results are shown in Table 3. The maximum diameters of pores and inclusions present in each low alloy sintered steel are 50
It was less than μm. From the results shown in Table 3 below, it can be seen that the old γ crystal grains are refined by the addition of alumina, but if the amount of addition exceeds 5% by volume, the effect of refining reaches a ceiling and the impact value tends to decrease. I see.
【0036】[0036]
【表3】 Al2O3含量 旧γ粒径 抗折強度 衝 撃 値 疲労強度試料 (vol%) (μm) (kg/mm2) (kgf・m/cm2) (kg/mm2) 11 0.5 7.8 279 3.4 100 12 1.0 4.8 330 6.1 120 13 2.0 2.9 338 6.7 120 14 5.0 2.5 342 5.9 120[Table 3] Al 2 O 3 content Old γ grain size Bending strength Impact strength Fatigue strength Sample (vol%) (μm) (kg / mm 2 ) (kgf ・ m / cm 2 ) (kg / mm 2 ) 11 0.5 7.8 279 3.4 100 12 1.0 4.8 330 6.1 120 13 2.0 2.9 338 6.7 120 14 5.0 2.5 342 5.9 120
【0037】実施例4 水アトマイズ法により製造されたAISI 4600組
成(Fe−1.8重量%Ni−0.5重量%Mo)を有す
る市販の鉄合金粉末に、平均粒径が0.05μm、0.1
μm、0.5μm、5μm、15μm、及び24μmの
各アルミナ粉末を体積分率が1.0%となるように各々
配合して混合した後、高エネルギー乾式ミルを用いてA
r雰囲気中で40時間処理した。得られた各処理粉末
を、実施例1と同一条件で、焼鈍軟化、黒鉛粉末の混
合、冷間成形、焼結、密度比0.99以上となる鍛造、
及び熱処理を行って低合金焼結鋼を製造した。 Example 4 A commercially available iron alloy powder having an AISI 4600 composition (Fe-1.8 wt% Ni-0.5 wt% Mo) produced by a water atomizing method was used, and the average particle size was 0.05 μm. 0.1
Alumina powders of μm, 0.5 μm, 5 μm, 15 μm, and 24 μm were mixed and mixed so that the volume fraction was 1.0%, and then A using a high energy dry mill.
It was treated for 40 hours in an atmosphere of r. Each of the obtained treated powders was annealed and softened, graphite powder was mixed, cold compacted, sintered, and forged to have a density ratio of 0.99 or more, under the same conditions as in Example 1.
And heat treatment was performed to produce a low alloy sintered steel.
【0038】得られた各低合金焼結鋼について、旧γ結
晶粒の平均粒径と共に、抗折強度、衝撃値、疲労強度を
測定し、その結果を表4に示した。下記表4の結果か
ら、添加するアルミナ粉末の平均粒径が小さくなるほど
低合金焼結鋼中の旧γ結晶粒は微細化されるが、アルミ
ナ粉末の平均粒径が5μm以上ではアルミナはむしろ欠
陥として作用し、強度や靭性を低下させることが判る。With respect to each of the obtained low alloy sintered steels, the bending strength, impact value and fatigue strength were measured together with the average grain size of the old γ crystal grains, and the results are shown in Table 4. From the results shown in Table 4 below, as the average particle size of the alumina powder to be added becomes smaller, the old γ crystal grains in the low alloy sintered steel become finer, but if the average particle size of the alumina powder is 5 μm or more, the alumina is rather defective. It can be seen that it acts as an alloy and reduces strength and toughness.
【0039】[0039]
【表4】 Al2O3粒径 旧γ粒径 抗折強度 衝 撃 値 疲労強度試料 (μm) (μm) (kg/mm2) (kgf・m/cm2) (kg/mm2) 15 0.05 4.8 330 6.1 120 16 0.1 6.2 315 4.4 120 17 0.5 10.8 272 3.2 115 18 5 14.2 232 2.0 80 19 15 17.3 218 1.8 78 20 24 22.2 212 1.6 75[Table 4] Al 2 O 3 grain size Old γ grain size Bending strength Impact strength Fatigue strength Sample (μm) (μm) (kg / mm 2 ) (kgf · m / cm 2 ) (kg / mm 2 ) 15 0.05 4.8 330 6.1 120 16 0.1 6.2 315 4.4 120 17 0.5 10.8 272 3.2 115 18 5 14.2 232 2.0 80 19 15 17.3 218 1.8 78 20 24 22.2 212 1.6 75
【0040】実施例5 水アトマイズ法により製造されたAISI 4100組
成(Fe−0.8重量%Mn−1.0重量%Cr−0.2
5重量%Mo)を有する市販の鉄合金粉末、及びこの鉄
合金粉末にNb源、Ti源、V源、W源、及びAl源と
してそれぞれフェロニオブ粉末、チタン粉末、フェロバ
ナジウム粉末、タングステン粉末、及びフェロアルミニ
ウム粉末を、最終組成で上記添加元素の含有量が0.5
重量%になるように添加混合した各粉末を、高エネルギ
ー乾式ミルを用いてAr雰囲気中で40時間処理した。 Example 5 Composition of AISI 4100 manufactured by water atomization method (Fe-0.8 wt% Mn-1.0 wt% Cr-0.2
A commercially available iron alloy powder having 5 wt% Mo), and ferroniobium powder, titanium powder, ferrovanadium powder, tungsten powder as Nb source, Ti source, V source, W source, and Al source, respectively, to the iron alloy powder. Ferroaluminum powder was added to the final composition, and the content of the above-mentioned additional elements was 0.5
Each powder added and mixed so as to have a weight percentage was treated for 40 hours in an Ar atmosphere using a high energy dry mill.
【0041】得られた各処理粉末を、窒素雰囲気中にて
800℃で1時間加熱して焼鈍軟化させた後、最終組成
で炭素量が0.2重量%となるようにグラファイトをそ
れぞれ添加混合した。これらの混合粉末を、実施例1と
同様に冷間成形、焼結、及び鍛造して、鍛造後の密度比
0.99以上の鍛造体を得た。各鍛造体を有効浸炭深さ
が1mmになるようにガス浸炭した後、850℃で加熱
し、油中に焼入れした後、200℃で90分の焼戻しを
行った。Each of the obtained treated powders was heated in a nitrogen atmosphere at 800 ° C. for 1 hour to be annealed and softened, and then graphite was added and mixed so that the final composition had a carbon content of 0.2% by weight. did. These mixed powders were cold-formed, sintered and forged in the same manner as in Example 1 to obtain a forged body having a density ratio of 0.99 or more after forging. Each forged body was gas carburized so that the effective carburizing depth was 1 mm, heated at 850 ° C., quenched in oil, and then tempered at 200 ° C. for 90 minutes.
【0042】得られた各低合金焼結鋼について、旧γ結
晶粒の平均粒径、抗折強度、衝撃値及び疲労強度を測定
し、表5の結果を得た。尚、各鋼中に存在する空孔及び
介在物の最大径は、いずれも50μm以下であった。表
5の結果から、Nb、Ti、V、W又はAlの添加によ
って旧γ結晶粒の微細化が促進され、これらの元素を添
加しない場合に比べて強度や靭性が一層改善されること
が判る。With respect to each of the obtained low alloy sintered steels, the average grain size of the old γ crystal grains, the bending strength, the impact value and the fatigue strength were measured, and the results in Table 5 were obtained. The maximum diameters of pores and inclusions present in each steel were 50 μm or less. From the results in Table 5, it can be seen that the addition of Nb, Ti, V, W or Al promotes the refinement of the former γ crystal grains and further improves the strength and toughness as compared with the case where these elements are not added. .
【0043】[0043]
【表5】 旧γ粒径 抗折強度 衝 撃 値 疲労強度試料 添加元素 (μm) (kg/mm2) (kgf・m/cm2) (kg/mm2) 21 なし 8.8 277 3.2 100 22 Nb 6.2 321 4.9 120 23 Ti 7.7 318 4.9 115 24 V 6.5 310 4.8 120 25 W 7.2 316 5.1 120 26 Al 6.3 319 5.0 118[Table 5] Old γ grain size Bending strength Impact value Fatigue strength Sample addition element (μm) (kg / mm 2 ) (kgf ・ m / cm 2 ) (kg / mm 2 ) 21 None 8.8 277 3.2 100 22 Nb 6.2 321 4.9 120 23 Ti 7.7 318 4.9 115 24 V 6.5 310 4.8 120 25 W 7.2 316 5.1 120 26 Al 6.3 319 5.0 118
【0044】実施例6 水アトマイズ法により製造されたAISI 4600組
成(Fe−1.8重量%Ni−0.5重量%Mo)を有す
る市販の鉄合金粉末に、平均粒径0.05μmのアルミ
ナ粉末を1.0体積%混合した後、高エネルギー乾式ミ
ルを用いてAr雰囲気中で40時間処理した。得られた
処理粉末を、実施例1と同一条件で焼鈍軟化させた後、
最終組成で炭素が0.25重量%及びホウ素が30pp
mとなるように黒鉛粉末とフェロボロン粉末を混合し
た。この混合粉末を、実施例1と同様に冷間成形、焼
結、及び鍛造して、密度比0.99以上の鍛造体を得
た。 Example 6 A commercially available iron alloy powder having an AISI 4600 composition (Fe-1.8 wt% Ni-0.5 wt% Mo) produced by a water atomizing method was added to alumina having an average particle size of 0.05 μm. The powder was mixed in an amount of 1.0% by volume, and then treated in a high energy dry mill in an Ar atmosphere for 40 hours. After the obtained treated powder is annealed and softened under the same conditions as in Example 1,
0.25 wt% carbon and 30 pp boron in final composition
Graphite powder and ferroboron powder were mixed so as to obtain m. This mixed powder was cold-formed, sintered, and forged in the same manner as in Example 1 to obtain a forged body having a density ratio of 0.99 or more.
【0045】得られた鍛造体から直径25.4mm×長
さ101.6mm(1×4インチ)の丸棒を削り出し、
その焼入れ性を評価するためにジョミニー試験を行っ
た。比較のため、実施例3で作製した1.0体積%のア
ルミナを含有し且つホウ素を含まない鍛造体(試料12
=B無添加本発明材)、及びSCM 420鋼材から同
一形状の丸棒を削り出し、これらについても焼入れ性を
比較評価した。その結果を図1に示す。図1から、B無
添加本発明材(試料12)では旧γ結晶粒の微細化によ
り焼入れ性は低下するが、これにホウ素を添加した本実
施例のB添加本発明材では焼入れ性は大幅に改善され、
SCM 420鋼材とほぼ同等レベルになることが判
る。From the obtained forged body, a round bar having a diameter of 25.4 mm and a length of 101.6 mm (1 × 4 inches) was carved out,
A Jominy test was conducted to evaluate the hardenability. For comparison, the forged body produced in Example 3 containing 1.0 vol% alumina and containing no boron (Sample 12).
= B additive-free present invention material) and a SCM 420 steel material, a round bar having the same shape was machined, and the hardenability of these was also comparatively evaluated. The result is shown in FIG. From FIG. 1, it can be seen that in the B-free invention material (Sample 12), the hardenability is deteriorated due to the refinement of the old γ crystal grains, but in the B-added invention material of the present example in which boron is added, the hardenability is significantly increased. Improved to
It turns out that it is almost the same level as SCM 420 steel.
【0046】実施例7 水アトマイズ法により製造されたAISI 4600組
成(Fe−1.8重量%Ni−0.5重量%Mo)を有す
る市販の鉄合金粉末に、平均粒径0.05μmのアルミ
ナ粉末を1.0体積%混合した後、高エネルギー乾式ミ
ルを用いてAr雰囲気中で40時間処理した。得られた
処理粉末を、真空中において1000℃で1時間焼鈍軟
化させた後、最終組成で炭素が0.25重量%となるよ
うに黒鉛粉末を混合し、実施例1と同様に冷間成形し
て、一方向クラッチの部品形状の成形体を作製した。 Example 7 A commercially available iron alloy powder having an AISI 4600 composition (Fe-1.8% by weight Ni-0.5% by weight) produced by a water atomizing method was added to alumina having an average particle size of 0.05 μm. The powder was mixed in an amount of 1.0% by volume, and then treated in a high energy dry mill in an Ar atmosphere for 40 hours. The treated powder thus obtained was annealed and softened at 1000 ° C. for 1 hour in vacuum, and then graphite powder was mixed so that the final composition of carbon was 0.25% by weight, followed by cold forming in the same manner as in Example 1. Then, a molded product having a component shape of the one-way clutch was produced.
【0047】成形体は実施例1と同様に焼結、鍛造、及
び熱処理した後、研磨等の加工を施して自動車用オート
マチックトランスミッションに用いる一方向クラッチの
外輪、及びスプラッグとした。比較のために、同様に熱
処理したSCM 420から同じ外輪及びスプラッグを
作製した。これらの本発明材と比較材の外輪及びスプラ
ッグを用いてクラッチを組み立て、ストローキング耐久
試験を行った。試験条件は下記表6の通りである。The molded body was sintered, forged, and heat-treated in the same manner as in Example 1, and then subjected to processing such as polishing to give an outer ring and a slug of a one-way clutch used for an automatic transmission for automobiles. For comparison, the same outer ring and slugs were made from similarly heat treated SCM 420. A stroking durability test was conducted by assembling a clutch using the outer ring and the sprags of the present invention material and the comparative material. The test conditions are as shown in Table 6 below.
【0048】[0048]
【表6】 [Table 6]
【0049】上記耐久試験の結果として、本発明材と比
較材の外輪についての剥離等による累積破損確率を図2
に示す。この図2から、本発明材は比較材である従来の
SCM 420浸炭鋼材よりも、剥離等に対する寿命に
優れていることが判る。又、上記耐久試験で、揺動数が
104、105、106の時点における各外輪とスプラッ
グの摩耗量を測定して図3に示す結果を得た。この図3
より、本発明材は比較材である従来のSCM 420浸
炭鋼材よりも、耐摩耗性に優れていることが判る。As a result of the above durability test, the cumulative damage probability due to peeling etc. of the outer ring of the material of the present invention and the comparative material is shown in FIG.
Shown in. From this FIG. 2, it is understood that the material of the present invention has a longer life against peeling and the like than the conventional SCM 420 carburized steel material which is a comparative material. Further, in the above durability test, the wear amount of each outer ring and the slug at the time of rocking numbers of 10 4 , 10 5 , and 10 6 was measured, and the results shown in FIG. 3 were obtained. This Figure 3
From the above, it is understood that the material of the present invention is superior in wear resistance to the conventional SCM 420 carburized steel material which is the comparative material.
【0050】[0050]
【発明の効果】本発明によれば、抗折強度等の静的特性
のみならず、疲労強度や靭性等の動的特性にも優れた低
合金焼結鋼を提供することができる。よって、本発明の
低合金焼結鋼は、歯車やクラッチ部品等の高い疲労強度
を要求される機械構造部品として特に有用であるほか、
従来この種の低合金焼結鋼が使用されていなかった分野
にも用途を開拓できるものと期待される。According to the present invention, it is possible to provide a low alloy sintered steel which is excellent not only in static characteristics such as bending strength but also in dynamic characteristics such as fatigue strength and toughness. Therefore, the low alloy sintered steel of the present invention is particularly useful as a mechanical structural part requiring high fatigue strength such as gears and clutch parts,
It is expected that it will be possible to develop applications in fields where this type of low alloy sintered steel has not been used in the past.
【図1】ホウ素を含有する本発明材と、ホウ素を含まな
い本発明材と、SCM 420鋼材とについて、ジョミ
ニー試験により得られた水冷端からの距離に対応する硬
さ(ロックウエルC硬度)の変化を示したグラフであ
る。FIG. 1 shows the hardness (Rockwell C hardness) corresponding to the distance from the water-cooled end obtained by the Jominy test for the present invention material containing boron, the present invention material not containing boron, and the SCM 420 steel material. It is a graph which showed change.
【図2】クラッチのストローキング耐久試験において、
本発明材とSCM 420鋼材の比較材とで作製した外
輪の剥離等に対する寿命を示す累積破損確率のグラフで
ある。[Fig. 2] In the stroking durability test of the clutch,
It is a graph of the cumulative damage probability showing the life of the outer ring produced by the material of the present invention and the comparative material of SCM 420 steel with respect to peeling and the like.
【図3】クラッチのストローキング耐久試験において、
本発明材で作製した外輪及びスプラッグと、SCM 4
20鋼材の比較材で作製した外輪及びスプラッグの耐摩
耗性を示すグラフである。[Fig. 3] In the stroking durability test of the clutch,
Outer ring and sprag made from the material of the present invention, and SCM 4
It is a graph which shows the abrasion resistance of the outer ring and the slug which were produced with the comparative material of 20 steel materials.
Claims (8)
素を含む低合金焼結鋼において、そのマトリックスが旧
γ結晶粒の平均粒径が15μm以下の焼戻しマルテンサ
イトであり、該マトリックス中に含まれる空孔又は非金
属介在物の最大径が50μm以下であって、密度が理論
密度の96%以上であることを特徴とする疲労強度に優
れた低合金焼結鋼。1. A low alloy sintered steel containing carbon in an amount of 0.15% by weight or more and less than 0.8% by weight, the matrix of which is tempered martensite having an average grain size of old γ crystal grains of 15 μm or less, A low alloy sintered steel excellent in fatigue strength, characterized in that the pores or non-metallic inclusions contained in the matrix have a maximum diameter of 50 μm or less and a density of 96% or more of the theoretical density.
固溶しないか又は固溶度の低い酸化物、窒化物及び炭化
物から選ばれた少なくとも1種からなる、平均粒径0.
5μm以下の粒子が均一に分散していることを特徴とす
る、請求項1に記載の疲労強度に優れた低合金焼結鋼。2. An average particle size of at least one selected from oxides, nitrides and carbides which do not form a solid solution in the austenite region or have a low solid solubility in the matrix.
The low alloy sintered steel excellent in fatigue strength according to claim 1, wherein particles of 5 μm or less are uniformly dispersed.
含有することを特徴とする、請求項1又は2に記載の疲
労強度に優れた低合金焼結鋼。3. Boron in a weight fraction of 10 to 300 ppm
The low alloy sintered steel excellent in fatigue strength according to claim 1 or 2, characterized in that it is contained.
テン、及びアルミニウムから選ばれた少なくとも1種
を、合計で0.05〜3重量%含有することを特徴とす
る、請求項1ないし3のいずれかに記載の疲労強度に優
れた低合金焼結鋼。4. At least one selected from niobium, vanadium, titanium, tungsten and aluminum is contained in a total amount of 0.05 to 3% by weight, according to any one of claims 1 to 3. Low alloy sintered steel with excellent fatigue strength as described.
は鉄合金粉末若しくはこれらを含む低合金鋼の原料粉末
を、不活性ガス雰囲気中又は大気中において乾式ミルで
処理することにより、原料粉末に転位を導入すると共に
非金属介在物を最大径50μm以下に粉砕し、その後こ
の処理粉末を軟化焼鈍し、最終組成での炭素が0.15
重量%以上0.8重量%未満となるように炭素粉末を添
加混合した後、この混合粉末を冷間成形し、焼結又は熱
間塑性加工により理論密度の96%以上に緻密化し、更
に熱処理してマトリックスを焼戻しマルテンサイトとす
ることを特徴とする疲労強度に優れた低合金焼結鋼の製
造方法。5. Iron powder or iron alloy powder produced by an atomizing method, or a raw material powder of low alloy steel containing the same is treated with a dry mill in an inert gas atmosphere or in the air to transfer to the raw material powder. And the non-metallic inclusions are crushed to a maximum diameter of 50 μm or less, and then the treated powder is softened and annealed so that carbon in the final composition is 0.15.
After carbon powder is added and mixed so as to be not less than 0.8% by weight, the mixed powder is cold-formed, densified to 96% or more of theoretical density by sintering or hot plastic working, and further heat treated. And a tempered martensite matrix is used to produce a low alloy sintered steel having excellent fatigue strength.
含む低合金鋼の原料粉末に、オーステナイト域で固溶し
ないか又は固溶度の低い酸化物、窒化物及び炭化物から
選ばれた少なくとも1種からなる平均粒径0.5μm以
下の粒子を混合し、及び/又はニオブ、バナジウム、チ
タン、タングステン及びアルミニウムから選ばれた少な
くとも1種を合計で0.05〜3重量%となるように混
合した後、これを乾式ミルで処理することを特徴とす
る、請求項5に記載の疲労強度に優れた低合金焼結鋼の
製造方法。6. At least one selected from oxides, nitrides and carbides which do not form a solid solution or have a low solid solubility in iron powder or iron alloy powder or a raw material powder of a low alloy steel containing the same in the austenite region. Particles having an average particle size of 0.5 μm or less and / or at least one selected from niobium, vanadium, titanium, tungsten and aluminum were mixed so that the total amount was 0.05 to 3% by weight. After that, this is processed with a dry mill, The manufacturing method of the low alloy sintered steel excellent in the fatigue strength of Claim 5 characterized by the above-mentioned.
を、真空中又は非酸化性雰囲気中にて600〜1000
℃の温度で行うことを特徴とする、請求項5又は6に記
載の疲労強度に優れた低合金焼結鋼の製造方法。7. The softening annealing of the treated powder treated with a dry mill is performed in vacuum or in a non-oxidizing atmosphere at 600 to 1000.
The method for producing a low alloy sintered steel having excellent fatigue strength according to claim 5 or 6, wherein the method is performed at a temperature of ° C.
分率で10〜300ppmとなるようにフェロボロン粉
末を添加混合することを特徴とする、請求項5ないし7
のいずれかに記載の疲労強度に優れた低合金焼結鋼の製
造方法。8. The ferroboron powder is added and mixed to the treated powder after softening and annealing so that the weight fraction of boron is 10 to 300 ppm.
A method for producing a low alloy sintered steel having excellent fatigue strength according to any one of 1.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP5326304A JPH06212368A (en) | 1992-11-30 | 1993-11-30 | Low alloy sintered steel excellent in fatigue strength and its production |
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP34314592 | 1992-11-30 | ||
JP4-343145 | 1992-11-30 | ||
JP5326304A JPH06212368A (en) | 1992-11-30 | 1993-11-30 | Low alloy sintered steel excellent in fatigue strength and its production |
Publications (1)
Publication Number | Publication Date |
---|---|
JPH06212368A true JPH06212368A (en) | 1994-08-02 |
Family
ID=26572145
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
JP5326304A Pending JPH06212368A (en) | 1992-11-30 | 1993-11-30 | Low alloy sintered steel excellent in fatigue strength and its production |
Country Status (1)
Country | Link |
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JP (1) | JPH06212368A (en) |
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1993
- 1993-11-30 JP JP5326304A patent/JPH06212368A/en active Pending
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JP2006501421A (en) * | 2002-10-01 | 2006-01-12 | シンタースタール コーポレイション−パワートレイン | Powder metal clutch race for one-way clutch and manufacturing method thereof |
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JP2007132518A (en) * | 2006-12-15 | 2007-05-31 | Ntn Corp | Pulley unit with built-in clutch |
WO2014030480A1 (en) * | 2012-08-23 | 2014-02-27 | Ntn株式会社 | Machine part and process for producing same |
JP2014040646A (en) * | 2012-08-23 | 2014-03-06 | Ntn Corp | Machine component and method for manufacturing the same |
CN104540973A (en) * | 2012-08-23 | 2015-04-22 | Ntn株式会社 | Machine part and process for producing same |
CN104540973B (en) * | 2012-08-23 | 2018-01-12 | Ntn株式会社 | Mechanical part and its manufacture method |
WO2019021935A1 (en) * | 2017-07-26 | 2019-01-31 | 住友電気工業株式会社 | Sintered member |
JPWO2019021935A1 (en) * | 2017-07-26 | 2020-05-28 | 住友電気工業株式会社 | Sintered member |
JP2022174140A (en) * | 2017-07-26 | 2022-11-22 | 住友電気工業株式会社 | Sinter member |
CN115367813A (en) * | 2022-08-16 | 2022-11-22 | 矿冶科技集团有限公司 | Spinel type nickel-zinc ferrite and preparation method and application thereof |
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