JP2002309302A - Method for manufacturing tool-steel powder with increased nitrogen content - Google Patents
Method for manufacturing tool-steel powder with increased nitrogen contentInfo
- Publication number
- JP2002309302A JP2002309302A JP2001113155A JP2001113155A JP2002309302A JP 2002309302 A JP2002309302 A JP 2002309302A JP 2001113155 A JP2001113155 A JP 2001113155A JP 2001113155 A JP2001113155 A JP 2001113155A JP 2002309302 A JP2002309302 A JP 2002309302A
- Authority
- JP
- Japan
- Prior art keywords
- steel powder
- temperature
- nitriding
- tool steel
- nitrogen
- 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.)
- Withdrawn
Links
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 title claims abstract description 195
- 239000000843 powder Substances 0.000 title claims abstract description 110
- 229910052757 nitrogen Inorganic materials 0.000 title claims abstract description 78
- 229910001315 Tool steel Inorganic materials 0.000 title claims abstract description 61
- 238000000034 method Methods 0.000 title claims abstract description 36
- 230000001965 increasing effect Effects 0.000 title claims abstract description 21
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 11
- 238000005121 nitriding Methods 0.000 claims abstract description 74
- 238000009924 canning Methods 0.000 claims abstract description 8
- 238000007872 degassing Methods 0.000 claims abstract description 6
- 229910000831 Steel Inorganic materials 0.000 claims description 72
- 239000010959 steel Substances 0.000 claims description 72
- 229910001873 dinitrogen Inorganic materials 0.000 claims description 39
- 238000010438 heat treatment Methods 0.000 claims description 16
- 150000002829 nitrogen Chemical class 0.000 claims description 9
- 239000007789 gas Substances 0.000 claims description 8
- 239000000203 mixture Substances 0.000 claims description 2
- 238000002791 soaking Methods 0.000 abstract description 6
- 238000003825 pressing Methods 0.000 abstract 1
- 230000000694 effects Effects 0.000 description 13
- 150000001247 metal acetylides Chemical class 0.000 description 13
- 229910000997 High-speed steel Inorganic materials 0.000 description 12
- 230000000052 comparative effect Effects 0.000 description 7
- 239000011159 matrix material Substances 0.000 description 7
- 238000004663 powder metallurgy Methods 0.000 description 7
- 238000010521 absorption reaction Methods 0.000 description 6
- 238000002347 injection Methods 0.000 description 5
- 239000007924 injection Substances 0.000 description 5
- 238000005496 tempering Methods 0.000 description 5
- 238000007664 blowing Methods 0.000 description 4
- 229910052804 chromium Inorganic materials 0.000 description 4
- 238000005520 cutting process Methods 0.000 description 4
- 230000007423 decrease Effects 0.000 description 4
- 238000005275 alloying Methods 0.000 description 3
- 230000003111 delayed effect Effects 0.000 description 3
- 238000010586 diagram Methods 0.000 description 3
- 150000004767 nitrides Chemical class 0.000 description 3
- 238000010791 quenching Methods 0.000 description 3
- 230000000171 quenching effect Effects 0.000 description 3
- 229910052720 vanadium Inorganic materials 0.000 description 3
- 238000003723 Smelting Methods 0.000 description 2
- 229910052799 carbon Inorganic materials 0.000 description 2
- 239000003795 chemical substances by application Substances 0.000 description 2
- 230000006866 deterioration Effects 0.000 description 2
- 238000001513 hot isostatic pressing Methods 0.000 description 2
- 230000006872 improvement Effects 0.000 description 2
- 239000012535 impurity Substances 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 238000002844 melting Methods 0.000 description 2
- 230000008018 melting Effects 0.000 description 2
- 238000002156 mixing Methods 0.000 description 2
- QJGQUHMNIGDVPM-UHFFFAOYSA-N nitrogen group Chemical group [N] QJGQUHMNIGDVPM-UHFFFAOYSA-N 0.000 description 2
- 238000001556 precipitation Methods 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 1
- 229910000975 Carbon steel Inorganic materials 0.000 description 1
- 229910017313 Mo—Co Inorganic materials 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- 229910052787 antimony Inorganic materials 0.000 description 1
- 229910052785 arsenic Inorganic materials 0.000 description 1
- 229910001566 austenite Inorganic materials 0.000 description 1
- SKKMWRVAJNPLFY-UHFFFAOYSA-N azanylidynevanadium Chemical compound [V]#N SKKMWRVAJNPLFY-UHFFFAOYSA-N 0.000 description 1
- 239000010962 carbon steel Substances 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 230000002708 enhancing effect Effects 0.000 description 1
- 230000001747 exhibiting effect Effects 0.000 description 1
- 238000011049 filling Methods 0.000 description 1
- -1 for example Inorganic materials 0.000 description 1
- 229910052748 manganese Inorganic materials 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 229910052750 molybdenum Inorganic materials 0.000 description 1
- 238000000465 moulding Methods 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 229910052758 niobium Inorganic materials 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 229910052698 phosphorus Inorganic materials 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 230000001737 promoting effect Effects 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 230000000717 retained effect Effects 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
- 239000006104 solid solution Substances 0.000 description 1
- 239000000161 steel melt Substances 0.000 description 1
- 238000005728 strengthening Methods 0.000 description 1
- 229910052717 sulfur Inorganic materials 0.000 description 1
- 229910052721 tungsten Inorganic materials 0.000 description 1
- 238000009423 ventilation Methods 0.000 description 1
Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、粉末冶金法によっ
て切削工具やパンチ、金型などを製造する際の原料とし
て有用な工具鋼粉末の製法に関し、特に、高硬度で長寿
命の工具を与える高窒素含有量で窒素含有量の均一な工
具鋼粉末を製造する有用な方法に関するものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing tool steel powder useful as a raw material for producing cutting tools, punches, dies, and the like by powder metallurgy, and more particularly to providing a tool having a high hardness and a long life. The present invention relates to a useful method for producing a tool steel powder having a high nitrogen content and a uniform nitrogen content.
【０００２】[0002]
【従来の技術】工具鋼、例えば高速度鋼（ハイス）は、
Ｃ，Ｃｒ，Ｗ，Ｍｏ，Ｖ，Ｃｏ等の合金元素を多量に加
えて硬さや耐摩耗性を高めた鋼材であり、エンドミルや
ドリルの如く靭性が要求される切削工具等の素材として
汎用されている。この種の工具鋼には、合金元素として
Ｗを多量に添加したＷ系のもの（Ｗ系ハイス）と、Ｗ系
ハイスにおけるＷの一部をＭｏに置き換えたＭｏ系のも
の（Ｍｏ系ハイス）が知られている。また、上記Ｍｏ系
ハイスに更にＣｏを含有させることによって、高温耐久
性を高めたＭｏ−Ｃｏ系ハイスも開発されている。尚、
上記Ｍｏ系ハイスは、Ｗ系ハイスに比べて優れた靭性を
発揮すると言われているが、これは、Ｍｏ炭化物がＷ炭
化物に比べて球状化され易いためであるとされている。2. Description of the Related Art Tool steel, for example, high-speed steel (high-speed steel),
A steel material with increased hardness and wear resistance by adding a large amount of alloying elements such as C, Cr, W, Mo, V, and Co. It is widely used as a material for cutting tools such as end mills and drills that require toughness. ing. This type of tool steel includes a W-based steel to which a large amount of W is added as an alloying element (W-based high-speed steel) and a Mo-based steel in which part of W in the W-based high-speed steel is replaced with Mo (Mo-based high-speed steel). It has been known. In addition, Mo-Co-based high speed steels having improved high-temperature durability by further containing Co in the Mo-based high speed steels have been developed. still,
The Mo-based high speed steel is said to exhibit superior toughness as compared with the W-type high speed steel. This is because Mo carbides are more likely to be spheroidized than W carbides.
【０００３】ところで、上記の様な工具鋼は溶製法によ
って製造されていたが、溶製法によって得られる工具鋼
は、粗大炭化物が生成したり合金元素が偏析するという
問題があるので、最近では、溶製法に代わり粉末冶金法
を適用した粉末工具鋼も多く用いられている。[0003] By the way, tool steels as described above have been manufactured by a smelting method. However, tool steels obtained by the smelting method have problems in that coarse carbides are formed and alloy elements are segregated. Powder tool steel to which powder metallurgy is applied instead of the melting method is also often used.
【０００４】即ち粉末冶金法で製造される工具鋼は、工
具鋼溶湯をアトマイズ法により急冷凝固粉末とし、この
粉末を熱間静水圧加圧（ＨＩＰ）等の粉末冶金法によっ
て成形されるので、通常の溶製法では製造し難い成分系
でも製造可能で組織も均一となり、靭性および切削性に
優れた工具が得られ易いからである。そして該粉末冶金
法であれば、粉末状態で窒化処理することによって窒素
含有量を様々に変えることができ、それにより析出物を
微細化して靭性を高め得るばかりでなく、耐焼付き性も
向上する。[0004] That is, the tool steel produced by the powder metallurgy method is formed by quenching the tool steel melt into a rapidly solidified powder by an atomizing method, and molding the powder by a powder metallurgy method such as hot isostatic pressing (HIP). This is because a component system that is difficult to produce by a normal melting method can be produced, the structure becomes uniform, and a tool excellent in toughness and machinability is easily obtained. In the case of the powder metallurgy method, the nitrogen content can be variously changed by performing a nitriding treatment in a powder state, whereby not only a precipitate can be refined to increase toughness, but also seizure resistance is improved. .
【０００５】この様なことから、粉末冶金法を利用し窒
素含有量を種々変えた工具鋼が提案されているが、窒化
方法については、特開昭５０−４９１０８号公報や特公
昭５６−４４９４３号公報に見られる様な方法を除いて
殆ど言及されていない。[0005] For these reasons, a tool steel in which the nitrogen content is variously changed by using powder metallurgy has been proposed. Regarding the nitriding method, JP-A-50-49108 and JP-B-56-44943. Almost no mention is made except for the method found in the publication.
【０００６】そして上記特開昭５０−４９１０８号公報
には、キャニング工程の前または後に鋼粉を窒素含有ガ
ス雰囲気中で加熱して窒化する方法を開示している。し
かしこの公報に実施例として示された方法は、窒素含有
ガスとしてアンモニアガスを使用する方法であり、高温
での取扱いが難しい。また特公昭５６−４４９４３号公
報に開示された方法の場合、キャニング後に窒化処理す
る方法では鋼粉末の通気抵抗によって容器開口側と底部
側で窒化量に差異が生じることに鑑み、キャニング前に
粉末を窒化し全体として所望の窒素含有量となる様に窒
化鋼粉と未窒化鋼粉を均一にブレンドする方法を採用し
ている。しかしこの方法には、ブレンド作業が付加され
るという作業上の難点がある。Japanese Patent Laid-Open Publication No. 50-49108 discloses a method in which steel powder is heated and nitrided in a nitrogen-containing gas atmosphere before or after the canning step. However, the method disclosed as an example in this publication uses ammonia gas as the nitrogen-containing gas, and is difficult to handle at high temperatures. In the case of the method disclosed in Japanese Patent Publication No. 56-44943, in the method of nitriding after canning, the nitriding amount is different between the container opening side and the bottom side due to the ventilation resistance of the steel powder. And a method of uniformly blending the nitrided steel powder and the unnitrided steel powder so as to obtain a desired nitrogen content as a whole. However, this method has an operational disadvantage that a blending operation is added.
【０００７】[0007]
【発明が解決しようとする課題】本発明者らは上記の様
な状況の下で、特に窒素含有量の高められた鋼粉の製造
技術についてかねてより研究を進めており、粉末工具鋼
を対象とし高窒素含有量で且つ窒素含有量の均一な工具
鋼粉末を提供すべく検討を重ねてきた。Under the above-mentioned circumstances, the present inventors have been studying, in particular, a technique for producing a steel powder having an increased nitrogen content. The study has been repeated to provide a tool steel powder having a high nitrogen content and a uniform nitrogen content.
【０００８】従って本発明の目的は、高窒素含有量で且
つ全体に亘って窒素含有量の均一な工具鋼粉末を製造す
ることのできる有用な方法を提供することにある。Accordingly, it is an object of the present invention to provide a useful method capable of producing a tool steel powder having a high nitrogen content and a uniform nitrogen content throughout.
【０００９】[0009]
【課題を解決するための手段】上記課題を解決すること
のできた本発明の製法とは、工具鋼粉末をキャニング
し、脱ガス後キャン内に窒素ガスを供給しつつ加熱して
窒化することにより窒素含有量の高められた工具鋼粉末
を製造するに際し、(1)キャン内に窒素ガスを圧入して
から昇温し、炉内雰囲気温度を６００℃以上、工具鋼粉
末のオーステナイト化温度未満の温度に保って均熱した
後、炉内雰囲気温度を該工具鋼粉末のオーステナイト化
温度以上に高めて窒化し、(2)キャン内に加熱された窒
素ガスを圧入しつつ、炉内雰囲気温度を前記工具鋼粉末
のオーステナイト化温度以上に高めて窒化し、あるいは
(3)キャン内に窒素ガスを圧入してから昇温し、キャン
内温度を６００℃以上、工具鋼粉末のオーステナイト化
温度未満の温度に保って均熱した後、キャン内に加熱さ
れた窒素ガスを圧入しつつ、炉内雰囲気温度を前記工具
鋼粉末のオーステナイト化温度以上に高めて窒化すると
ころに要旨を有している。Means for Solving the Problems The manufacturing method of the present invention which can solve the above-mentioned problems is to carry out canning of tool steel powder, and after degassing, heating and nitriding while supplying nitrogen gas into the can. When producing tool steel powder with increased nitrogen content, (1) Nitrogen gas was injected into the can and then the temperature was raised, and the furnace atmosphere temperature was 600 ° C or higher and lower than the austenitizing temperature of the tool steel powder. After maintaining the temperature and equalizing the temperature, the furnace atmosphere temperature was raised to the austenitizing temperature of the tool steel powder or higher and nitriding was performed. (2) The furnace atmosphere temperature was reduced while pressurized nitrogen gas was injected into the can. Nitriding by raising the temperature above the austenitizing temperature of the tool steel powder, or
(3) Nitrogen gas was injected into the can and then the temperature was raised. The temperature in the can was maintained at 600 ° C. or higher and lower than the austenitizing temperature of the tool steel powder, and the temperature was uniformed. The gist is that the furnace atmosphere temperature is raised to the austenitizing temperature of the tool steel powder or more while the gas is injected, and nitriding is performed.
【００１０】本発明が適用される上記工具鋼粉末の種類
は特に制限されないが、本発明の窒化処理による靭性や
耐摩耗性などの改善効果を有効に発揮させる上で特に好
ましいのは、工具鋼粉末が、Ｃ：０．５質量％以上、Ｃ
ｒ：３〜５質量％、Ｖ：２．５質量％以上を含有すると
共に、Ｗ及び／又はＭｏ：（Ｗ＋２Ｍｏ）で８．５質量
％以上を含み、あるいは更に他の元素としてＣｏ：２０
質量％以下（０％を含まない）む高速度鋼粉末であり、
これらの鋼粉末中の窒素含有量を上記窒化処理によって
０．２質量％以上、飽和窒素量未満、より好ましくは
０．２５質量％以上、０．７質量％以下に高めたもの
は、卓越した性能の高速度鋼工具を与えるので好まし
い。Although the type of the tool steel powder to which the present invention is applied is not particularly limited, tool steel is particularly preferable for effectively exhibiting the effect of improving the toughness and wear resistance by the nitriding treatment of the present invention. When the powder is C: 0.5% by mass or more, C
r: 3 to 5% by mass, V: 2.5% by mass or more, and W and / or Mo: 8.5% by mass or more in (W + 2Mo), or Co: 20 as another element
High-speed steel powder containing less than 0% by mass (not including 0%)
Those in which the nitrogen content in these steel powders was increased to 0.2% by mass or more and less than the saturated nitrogen amount, more preferably 0.25% by mass or more and 0.7% by mass or less by the above-mentioned nitriding treatment were excellent. Preferred because it gives a high speed steel tool of high performance.
【００１１】[0011]
【発明の実施の形態】本発明者らは前述した様な課題の
下で、工具鋼粉末をキャニングしてから窒化処理する際
に、キャン内部の鋼粉の存在位置によって窒素含有量に
著しいバラツキが生じる原因を追求した結果、次の様な
事実が確認された。DESCRIPTION OF THE PREFERRED EMBODIMENTS Under the above-mentioned problems, the present inventors have found that when nitriding a tool steel powder after canning, the nitrogen content varies significantly depending on the position of the steel powder inside the can. As a result of pursuing the cause of the occurrence, the following facts were confirmed.
【００１２】即ち鋼粉をキャニングしてから窒化処理を
行なう通常の方法では、例えば図１に示す如く円筒状の
キャン１内に鋼粉Ｈを充填し、脱ガスしてから加熱炉２
内へ装入し、キャン１内に窒素ガスを圧入すると共にキ
ャン１を外面側から所定温度（例えば８５０℃程度以
上）に加熱することによって窒化処理が行われる。とこ
ろが、該窒化処理時におけるキャン１内の鋼粉Ｈの存在
位置や窒素ガス吹込み位置によって窒化の進行状態は著
しく変わり、これが窒素含有量のバラツキになって表わ
れることが確認された。That is, in a usual method of carrying out nitriding treatment after canning of steel powder, for example, as shown in FIG. 1, a cylindrical can 1 is filled with steel powder H, degassed, and then heated furnace 2
The nitriding treatment is performed by charging the inside of the can 1 and pressurizing nitrogen gas into the can 1 and heating the can 1 to a predetermined temperature (for example, about 850 ° C. or higher) from the outer surface side. However, it was confirmed that the progress of nitridation was significantly changed depending on the position of the steel powder H in the can 1 and the position of the nitrogen gas injection during the nitriding treatment, and this was manifested as a variation in the nitrogen content.
【００１３】尚、キャン内の鋼粉を窒化する際に、該鋼
粉を窒化処理条件（窒素圧力や温度）によって決定され
る飽和窒素量にまで高めるのであれば、最終的にキャン
内を当該窒化処理条件で一定時間以上保持することで、
窒化速度の如何を問わずキャン内全体の鋼粉の窒素含有
量は当該飽和窒素量で一定になる。しかし鋼粉の種類や
窒化処理条件にもよるが、通常の工具鋼粉末を一般的な
窒化処理条件で窒化する際の飽和窒素量は１質量％前後
であり、この様に窒素含有量が多くなり過ぎると炭窒化
物量が過大となり工具鋼としての性能が低下する。従っ
て、窒化処理により工具鋼を改質する際の一般的な窒素
含有量は０．７質量％程度までに抑えられている。この
様に、飽和窒素量に満たない窒素含有量を前述の様な窒
化処理によって得るには、飽和窒素量に至るまでの途中
段階で窒化を止めねばならないので、窒化処理時間を適
正にコントロールすると共に、被窒化鋼粉の窒化を全体
に亘って均等に進めることが重要となる。When nitriding the steel powder in the can, if the steel powder is increased to a saturated nitrogen amount determined by the nitriding conditions (nitrogen pressure and temperature), the inside of the can is finally changed to the saturated nitrogen amount. By holding for a certain period of time under nitriding conditions,
Regardless of the nitriding rate, the nitrogen content of the steel powder in the entire can in the can becomes constant at the saturated nitrogen amount. However, depending on the type of the steel powder and the nitriding conditions, the amount of saturated nitrogen when nitriding ordinary tool steel powder under general nitriding conditions is about 1% by mass. If it becomes too much, the amount of carbonitride becomes excessive and the performance as a tool steel decreases. Therefore, the typical nitrogen content when modifying tool steel by nitriding is suppressed to about 0.7% by mass. As described above, in order to obtain the nitrogen content less than the saturated nitrogen amount by the nitriding treatment as described above, the nitriding must be stopped in the middle stage until the saturated nitrogen amount is reached, so that the nitriding treatment time is appropriately controlled. At the same time, it is important to promote the nitriding of the steel powder to be nitrided uniformly over the whole.
【００１４】ところがキャン内に充填された鋼粉を窒化
処理する際に、キャン内の外面側（加熱炉の内面側）に
位置する鋼粉は、外面側からの加熱によって早期に昇温
されるのに対し、キャンの中心部に存在する鋼粉への熱
伝達は相対的に遅れるため、外面側から中心方向に温度
が低くなる温度勾配ができる。窒化速度は温度によって
著しく変わるため、窒化処理時に上記の様な温度勾配が
できると、キャン外面側に位置する鋼粉の窒化は速やか
に進行するのに対し、中心部に位置する鋼粉の窒化は相
対的に遅れることになる。その結果、キャン外面側の鋼
粉の窒素含有量は相対的に高く、中心側に位置する鋼粉
の窒素含有量は低くなる。However, when the steel powder filled in the can is subjected to nitriding treatment, the temperature of the steel powder located on the outer surface side (the inner surface side of the heating furnace) in the can is raised early by heating from the outer surface side. On the other hand, the heat transfer to the steel powder present in the center of the can is relatively delayed, so that there is a temperature gradient in which the temperature decreases from the outer surface toward the center. Since the nitriding rate changes significantly with temperature, if the temperature gradient as described above occurs during nitriding, the nitriding of the steel powder located on the outer surface of the can progresses rapidly, whereas the nitriding of the steel powder located in the center part proceeds. Will be relatively late. As a result, the nitrogen content of the steel powder on the outer surface side of the can is relatively high, and the nitrogen content of the steel powder located on the center side is low.
【００１５】他方、キャン内の窒素ガス吹込み口側（図
１の例では上方側）に存在する鋼粉は、早期に窒素ガス
と接触するため、窒素ガスの熱吸収により温度が低下す
る。そのため、窒素吹込み側位置に存在する鋼粉の窒化
速度は遅れることになり、その結果、図１の窒素吹込み
側に存在する鋼粉の窒素含有量は、底部側に存在する鋼
粉の窒素含有量よりも低くなる。On the other hand, since the steel powder present on the nitrogen gas inlet side (upper side in the example of FIG. 1) in the can comes into contact with the nitrogen gas at an early stage, the temperature decreases due to the heat absorption of the nitrogen gas. Therefore, the nitriding speed of the steel powder present at the nitrogen injection side position is delayed, and as a result, the nitrogen content of the steel powder existing at the nitrogen injection side in FIG. Lower than the nitrogen content.
【００１６】従って、キャン内の鋼粉を全体に万遍なく
均一に窒化するには、上記の様な温度勾配の違いによる
窒化速度のアンバランスを無くすことが重要となる。Therefore, in order to uniformly and uniformly nitride the steel powder in the can, it is important to eliminate the imbalance in the nitriding rate due to the difference in temperature gradient as described above.
【００１７】他方本発明者らが別途確認したところによ
ると、鋼粉の窒化速度は温度によって著しく変わる。例
えば図２は、供試鋼粉として0.97％Ｃ−４％Ｃｒ−６％
Ｍｏ−６％W−3.5％Ｖ−５％Ｃｏよりなるガスアトマイ
ズ鋼粉（粒度構成は６０メッシュ以下）を使用し、これ
をキャン内に充填し脱ガスののち常温で窒素ガス置換し
た後、窒素ガス圧力を＋８００mmH2Oに保って加熱した
時の温度と窒素吸収量の関係を示したグラフである。こ
のグラフからも明らかな様に、７００℃未満の低温域に
おける窒素吸収量はごく僅かであるのに対し、温度が７
５０℃を超えると窒素吸収量は大幅に増大している。そ
して該窒素吸収量が急増する温度は、鋼粉のオーステナ
イト化温度にほぼ対応していることが分かった。On the other hand, the present inventors have separately confirmed that the nitriding rate of the steel powder varies significantly with temperature. For example, FIG. 2 shows 0.97% C-4% Cr-6% as test steel powder.
A gas atomized steel powder of Mo-6% W-3.5% V-5% Co (particle size of 60 mesh or less) was used, filled in a can, degassed, replaced with nitrogen gas at room temperature, and then nitrogen. it is a graph showing the relationship between the temperature and nitrogen uptake when heated by keeping the gas pressure in the + 800mmH 2 O. As is clear from this graph, the nitrogen absorption in the low temperature range below 700 ° C. is very small, while
Above 50 ° C., the amount of nitrogen absorption increases significantly. And it turned out that the temperature at which the nitrogen absorption amount rapidly increased substantially corresponds to the austenitizing temperature of the steel powder.
【００１８】そこでこうした現象を活かし、キャン内に
充填された鋼粉の窒化を全体に亘って均等に進めること
のできる方法を確立すべく研究を重ねた結果、まず第一
に、キャン内に充填された鋼粉を窒化する際に、炉内雰
囲気温度を窒素吸収が殆ど起こらない略６００℃程度に
まで高め、この温度でキャン内の鋼粉全体を均熱してお
き、しかる後にオーステナイト化温度以上に昇温してや
れば、キャン内における外面側から中心部方向への温度
勾配が少なくなり、その結果として、キャン内の外面側
と中心部側で鋼粉の窒化がほぼ均等に進行し、得られる
鋼粉の窒素含有量のバラツキが可及的に抑えられること
を知った。[0018] Accordingly, as a result of repeated studies to establish a method capable of uniformly promoting the nitriding of the steel powder filled in the can by utilizing such a phenomenon, first of all, the filling of the can in the can was carried out. At the time of nitriding the steel powder, the atmosphere temperature in the furnace is raised to about 600 ° C. at which nitrogen absorption hardly occurs. At this temperature, the entire steel powder in the can is uniformly heated. , The temperature gradient from the outer surface side to the central portion in the can is reduced, and as a result, the nitriding of the steel powder proceeds almost uniformly on the outer surface side and the central portion side in the can, and is obtained. I learned that the variation in the nitrogen content of steel powder can be suppressed as much as possible.
【００１９】また、前記図１に示した様に、キャン内に
充填された鋼粉を予熱しておき、これに窒素ガス吹込み
口から窒素ガスを吹込む際にも、炉内雰囲気温度が略６
００℃までの低温域で窒素ガスを吹込んでキャン内全体
に窒素ガスを万遍なく行き渡らせておき、その後に全体
を鋼粉のオーステナイト化温度以上に高めてやれば、そ
れによっても全体の窒化を均等に進めることができ、窒
素含有量のバラツキを可及的に少なくすることができ
る。As shown in FIG. 1, the steel powder filled in the can is preheated, and when the nitrogen gas is blown into the steel powder from the nitrogen gas inlet, the atmosphere temperature in the furnace is also reduced. About 6
Nitrogen gas is blown all over the inside of the can by blowing nitrogen gas in the low temperature range up to 00 ° C, and then the whole is raised to the austenitizing temperature of the steel powder or more, so that nitriding of the whole And the variation of the nitrogen content can be reduced as much as possible.
【００２０】但し、均熱後昇温して窒化が進行すると、
それに伴って窒素ガス圧力は低下してくるので、窒素ガ
スの補給が必要となる。この時、昇温したキャン内に室
温の窒素ガスを補給すると、窒素ガス吹込み口側の鋼粉
が該窒素ガスによって冷却され、その部分の窒化が遅れ
る現象が生じてくる。そこで、こうした窒素ガス吹込み
口付近の温度低下を抑えて当該部分の窒化不足を解消す
べく検討を行なった結果、補給する窒素ガスを予め高め
てから吹込めば、上記の様な吹込み窒素ガスによる温度
降下も起こらず、窒素吹込み口付近の窒化不足も解消さ
れ、全体に渡ってほぼ均一に窒化を進め得ることが確認
された。However, if the temperature rises after soaking and the nitriding proceeds,
Accordingly, the nitrogen gas pressure decreases, so that it is necessary to supply nitrogen gas. At this time, if nitrogen gas at room temperature is replenished into the heated can, the steel powder on the nitrogen gas injection port side is cooled by the nitrogen gas, and a phenomenon occurs in which nitriding of the portion is delayed. Therefore, as a result of studying to suppress the temperature drop near the nitrogen gas inlet and to eliminate the insufficient nitriding of the portion, if the nitrogen gas to be replenished is increased beforehand and then injected, the above-described nitrogen gas is blown. It was confirmed that the temperature did not drop due to the gas, the lack of nitridation near the nitrogen injection port was resolved, and the nitriding could be proceeded almost uniformly over the entirety.
【００２１】従って本発明の第二の構成では、キャン内
に補給される窒素ガスを予め昇温させておくところに特
徴を有している。窒素ガスの加熱手段は特に制限されな
いが、好ましいのは、窒素吹込みラインを加熱炉内もし
くはこれに接して設けておき、窒化処理のための加熱源
を利用して該ライン内の窒素を加熱する方法であり、こ
の方法であれば、補給される窒素ガスを窒化処理温度と
ほぼ等しい温度に予熱することができるので実用的であ
る。但し、補給される窒素ガスの加熱はこうした方法に
限定されるわけではなく、別途設けた任意の加熱手段で
加熱することも勿論可能である。Therefore, the second configuration of the present invention is characterized in that the temperature of the nitrogen gas supplied into the can is raised in advance. The means for heating the nitrogen gas is not particularly limited, but preferably, a nitrogen blowing line is provided in or in contact with the heating furnace, and the nitrogen in the line is heated using a heating source for nitriding treatment. This method is practical because the replenished nitrogen gas can be preheated to a temperature substantially equal to the nitriding temperature. However, the heating of the replenished nitrogen gas is not limited to such a method, and it is of course possible to heat it with an optional heating means provided separately.
【００２２】上記の様に本発明では、第一の構成とし
て、キャンの外面側から中心方向に生じる温度勾配によ
る窒化速度の不均一を解消し窒化速度を均一化するた
め、６００℃以上、工具鋼粉末のオーステナイト化温度
未満の温度で均熱した後、該工具鋼粉末のオーステナイ
ト化温度以上に高めて窒化を行なう方法を採用し、或は
第二の構成として、窒素吹込み口側の補給窒素による降
温とそれに伴う窒素吸収量の低減による窒素含有量のバ
ラツキを無くすための補給窒素の加熱吹込みを採用する
ところに特徴を有している。As described above, in the present invention, as a first configuration, a tool having a temperature of 600 ° C. or more is used to eliminate the non-uniformity of the nitriding rate due to the temperature gradient generated from the outer surface side of the can to the center and to make the nitriding rate uniform. After soaking at a temperature lower than the austenitizing temperature of the steel powder, a method is adopted in which the temperature is raised to a temperature equal to or higher than the austenitizing temperature of the tool steel powder to perform nitriding. It is characterized by adopting a heating and blowing of supplementary nitrogen to eliminate the variation in the nitrogen content due to the temperature drop by nitrogen and the accompanying reduction in the amount of nitrogen absorption.
【００２３】しかし本発明で最も好ましいのは、第三の
構成として上記第一と第二の構成を組合わせて実施する
方法であり、この方法によれば、キャン内の外面側から
中心方向に生じる温度勾配による窒化速度の不均一が解
消されると共に、補給窒素の加熱吹込みにより、窒素吹
込み口側の補給窒素による降温とそれに伴う窒素吸収量
の低減による窒素含有量のバラツキも無くすことがで
き、キャン内に充填された鋼粉の全てを万遍なく均等に
窒化することができる。However, the most preferred embodiment of the present invention is a method in which the above-mentioned first and second configurations are combined as the third configuration. According to this method, from the outer surface side inside the can to the center direction. In addition to eliminating the non-uniformity of the nitriding rate due to the resulting temperature gradient, the heating and blowing of make-up nitrogen also eliminates the variation in the nitrogen content due to the temperature drop due to the make-up nitrogen at the nitrogen inlet and the accompanying reduction in the amount of nitrogen absorbed. Thus, all of the steel powder filled in the can can be uniformly and uniformly nitrided.
【００２４】尚本発明によって工具鋼粉に導入される窒
素量は、工具鋼の用途に応じて求められる特性、特に耐
摩耗性と靭性のバランスを考慮して適宜選定すればよい
が、窒化処理による耐摩耗性向上効果をより有効に発揮
させる上で好ましいのは、窒素含有量で０．２質量％以
上、より好ましくは０．２５質量%以上で、飽和窒素含
有量未満である。The amount of nitrogen introduced into the tool steel powder according to the present invention may be appropriately selected in consideration of the characteristics required in accordance with the use of the tool steel, particularly the balance between wear resistance and toughness. In order to more effectively exert the effect of improving the wear resistance by the above, the nitrogen content is preferably 0.2% by mass or more, more preferably 0.25% by mass or more, and less than the saturated nitrogen content.
【００２５】かくして得られる窒化鋼粉を使用し、通常
の粉末冶金法に準じてＨＩＰ処理などにより任意の形状
に固化成形すると、窒素含有量の高められた高性能の工
具鋼を得ることができる。尚、該固化成形した状態で
は、マトリックス内に窒化物、炭化物および炭窒化物が
形成される。この成形体に適切な温度で焼入れ処理を施
し、例えば５５０〜６００℃程度で複数回（通常２〜４
回）の焼戻し処理を施すことにより、マトリックス組
織、炭化物・窒化物・炭窒化物が適切な状態に形成さ
れ、耐摩耗性に優れた工具を得ることができる。When the nitrided steel powder thus obtained is solidified and formed into an arbitrary shape by HIP treatment or the like according to a usual powder metallurgy method, a high-performance tool steel with an increased nitrogen content can be obtained. . In the solidified state, nitrides, carbides and carbonitrides are formed in the matrix. This molded body is subjected to a quenching treatment at an appropriate temperature, for example, several times at about 550 to 600 ° C. (usually 2 to 4 times).
By performing the tempering process of (1), a matrix structure, carbides / nitrides / carbonitrides are formed in an appropriate state, and a tool having excellent wear resistance can be obtained.
【００２６】なお、本発明で窒化処理に付される工具鋼
粉末は格別特殊なものではなく、一般に工具鋼に分類さ
れる鋼種が全て包含されるが、代表的なのはＣ、Ｃｒ及
びＶを必須的に含有すると共に、Ｍｏ及び／又はＷを含
み、或は更にＣｏを含有する高速度鋼粉であり、それら
各元素の好ましい含有率は下記の通りである。The tool steel powder to be subjected to the nitriding treatment in the present invention is not particularly special, and includes all types of steel generally classified as tool steel, but typical ones are C, Cr and V. It is a high-speed steel powder that contains Mo and / or W and further contains Co, and the preferred content of each of these elements is as follows.
【００２７】Ｃ：０．５％（化学成分の場合は質量％を
意味する、以下同じ）以上 Ｃは、マトリックス中に溶け込んでマトリックスの強化
に寄与する元素であり、またＣｒ，Ｖ，Ｗ，Ｍｏ等と結
合して炭化物を形成して粉末工具鋼の耐摩耗性を向上さ
せるのに有用な元素で、他の合金元素の含有率にもよる
が、０．５％以上含有させることが望ましい。Ｃのより
好ましい含有率は０．６％以上、３％以下の範囲であ
る。C: not less than 0.5% (mean% by mass in the case of chemical components, the same applies hereinafter) C is an element that dissolves into the matrix and contributes to the strengthening of the matrix, and Cr, V, W, It is an element useful for improving the wear resistance of powdered tool steel by forming carbides by combining with Mo and the like, and it is desirable to contain 0.5% or more, depending on the content of other alloying elements. . A more preferable content of C is in a range of 0.6% or more and 3% or less.
【００２８】即ち上記Ｃの効果は、０．５％以上含有さ
せることによって有効に発揮されるが、３％を超えて含
有量が多くなり過ぎると、鋼が硬質化し過ぎて靭性が劣
化し工具寿命を却って劣化させるばかりでなく、焼入れ
焼戻し後の金属組織中の残留オーステナイト量が多くな
ってミクロ組織が不均一になるからである。Ｃ含有量の
より好ましい上限は２．５％である。That is, the above-mentioned effect of C is effectively exhibited by containing 0.5% or more. However, if the content exceeds 3%, the content becomes too large, the steel becomes too hard, and the toughness is deteriorated. This is because not only does the life deteriorate, but also the amount of retained austenite in the metal structure after quenching and tempering increases, and the microstructure becomes uneven. A more preferred upper limit of the C content is 2.5%.
【００２９】Ｃｒ：３〜６％ Ｃｒは、鋼の焼入れ性を高めて焼戻し硬さや高温硬さを
確保し、且つ熱処理時の耐酸化性を高め、更には炭化物
を形成して鋼の耐摩耗性を高める上でも有用な元素であ
る。これらの効果を有効に発揮させるには、３％以上含
有させることが望ましい。しかし、含有量が多過ぎても
その効果が飽和するばかりか、却って靭性を劣化させる
原因になるので、６％以下に抑えるのがよい。Ｃｒ含有
量のより好ましい下限は３．５％、より好ましい上限は
５％である。Cr: 3 to 6% Cr enhances the hardenability of the steel to ensure tempering hardness and high-temperature hardness, and also enhances the oxidation resistance during heat treatment, and furthermore, forms carbides to reduce the wear resistance of the steel. It is an element that is also useful for enhancing the properties. In order to exhibit these effects effectively, it is desirable to contain 3% or more. However, if the content is too large, not only the effect is saturated, but also the toughness is rather deteriorated. Therefore, the content is preferably suppressed to 6% or less. A more preferred lower limit of the Cr content is 3.5%, and a more preferred upper limit is 5%.
【００３０】Ｖ：２．５％以上 Ｖは、粉末工具鋼における主要元素であり、Ｃと結合し
て微細な炭化物を形成すると共に、バナジウム窒化物お
よび炭窒化物の生成源となって耐摩耗性の向上に寄与す
る。こうした効果を有効に発揮させるには、２．５％以
上含有させるのがよい。しかし多過ぎると靭性に悪影響
を及ぼすので、７％以下に抑えるべきである。Ｖのより
好ましい下限は３％、より好ましい上限は６％である。V: 2.5% or more V is a main element in powder tool steel and combines with C to form fine carbides, and also serves as a source of vanadium nitride and carbonitride to provide wear resistance. It contributes to the improvement of performance. In order to effectively exhibit such effects, it is preferable to contain 2.5% or more. However, if the content is too large, the toughness is adversely affected. A more preferred lower limit of V is 3%, and a more preferred upper limit is 6%.
【００３１】Ｗ及び／又はＭｏ：（Ｗ＋２Ｍｏ）として
８．５％以上 Ｗは、高速度工具鋼として基本的な特性を付与する重要
な元素であり、炭化物を形成すると共に、その一部はマ
トリックス中に溶け込んで耐摩耗性や焼戻し硬さ、高温
硬さ等を高め、工具等の切削性能を改善する作用を発揮
する。こうした効果を有効に発揮させるには、３％以上
含有させることが望ましい。しかし多過ぎると、炭化物
の析出量が多くなると共に析出する炭化物サイズも大き
くなり、靭性劣化を招く原因になるので、１５％程度以
下、より好ましくは１３％程度以下に抑えることが望ま
しい。W and / or Mo: 8.5% or more as (W + 2Mo) W is an important element that imparts basic properties as a high-speed tool steel, forms carbides, and partially forms a matrix. It dissolves into the inside to increase wear resistance, tempering hardness, high-temperature hardness, etc., and exerts the effect of improving the cutting performance of tools and the like. In order to exhibit such effects effectively, it is desirable to contain 3% or more. However, if it is too large, the amount of carbide precipitation increases and the size of the precipitated carbide also increases, which causes deterioration in toughness. Therefore, it is desirable to suppress the amount to about 15% or less, more preferably to about 13% or less.
【００３２】またＭｏも、上記Ｗと同様に炭化物を形成
して耐摩耗性、焼戻し硬さ、高温硬さ等を高め、切削性
能の向上に寄与する。こうしたＭｏの作用は、上記Ｗの
１／２量にほぼ対応している。従って、Ｗの一部をＭｏ
に置き換えて含有させることが可能であり、両者を併用
する時の好ましい含有率は「Ｗ＋２Ｍｏ」として８．５
質量％以上、より好ましくは１１％以上である。しかし
Ｍｏの含有量が多過ぎると、炭化物が粗大化し加工性を
低下させる原因になるので、Ｍｏとしての含有量は１０
％以下が好ましい。Mo also forms carbides as in the case of the above-mentioned W, thereby increasing wear resistance, tempering hardness, high-temperature hardness, etc., and contributing to the improvement of cutting performance. Such an action of Mo substantially corresponds to the half amount of W described above. Therefore, a part of W is
It is possible to replace the content with the above, and when both are used in combination, a preferable content rate is 8.5 as “W + 2Mo”.
% Or more, more preferably 11% or more. However, if the content of Mo is too large, carbides become coarse and cause deterioration of workability.
% Or less is preferable.
【００３３】Ｃｏ：２０％以下 Ｃｏはマトリックス中に固溶して耐熱性を向上させ、高
温硬さを高めるのに有効な元素である。また、炭化物の
析出を促進するがそれ自体は炭化物を生成しないので、
マトリックスを高質化するうえで有効に作用する。こう
した作用は、Ｃｏの含有量を増すにつれて大きくなる
が、２０％を超えて過度に含有させてもそれ以上の効果
は得られず不経済であるので、２０％程度以下、より好
ましくは１５％程度以下に抑えるのがよい。Co: 20% or less Co is a solid solution in the matrix to improve heat resistance and is an element effective for increasing high-temperature hardness. Also, it promotes the precipitation of carbides but does not itself produce carbides,
Effectively works to improve the quality of the matrix. Such an effect increases as the content of Co increases, but if the content exceeds 20%, an excessive effect cannot be obtained, and it is uneconomical. Therefore, about 20% or less, more preferably 15% or less. It is better to keep it below.
【００３４】本発明で使用する工具鋼の基本成分は上記
の通りであるが、この他、一般的に含有される代表的な
元素としてＳｉおよびＭｎが挙げられ、これらの作用と
好ましい含有率は下記の通りである。The basic components of the tool steel used in the present invention are as described above. In addition, typical elements generally contained include Si and Mn. It is as follows.
【００３５】Ｓｉ：３％以下 Ｓｉは通常脱酸剤として含まれているが、粉末工具鋼の
硬さを向上させる上でも有効に作用する。こうした効果
はＳｉ含量が増すにつれて大きくなるが、多過ぎると粉
末工具鋼の靭性を劣化させる原因になるので、好ましく
は３％以下、より好ましくは１．０％以下に抑えること
が望ましい。Si: 3% or less Si is usually contained as a deoxidizing agent, but effectively acts to improve the hardness of powdered tool steel. Such an effect increases as the Si content increases. However, if the Si content is too large, the toughness of the powder tool steel is deteriorated. Therefore, the effect is preferably suppressed to 3% or less, more preferably 1.0% or less.
【００３６】Ｍｎ：３％以下 ＭｎもＳｉと同様に脱酸剤として含まれることが多く、
また焼入れ性の向上にも有効に作用する。しかし多過ぎ
ると、粉末工具鋼としての靭性を劣化させる原因になる
ので、好ましくは３％以下、より好ましくは１．０％以
下に抑えるのがよい。Mn: 3% or less Mn is often contained as a deoxidizing agent similarly to Si.
It also effectively works to improve hardenability. However, if it is too large, it may cause the toughness of the powdered tool steel to deteriorate, so it is preferable to keep the content at 3% or less, more preferably at 1.0% or less.
【００３７】本発明に係る粉末工具鋼の好ましい化学成
分組成は上記の通りであり、残部は実質的にＦｅからな
るものであるが、本発明においては、上記各成分以外に
もその特性を阻害しない程度の微量成分を含むものであ
ってもよく、それらも本発明の技術的範囲に含まれる。
かかる微量成分としては、Ｎｉ，Ｎｂ等の許容成分や、
Ｐ，Ｓ，Ｃｕ，Ａｓ，Ｓｂ等の不純物、或は不可避的不
純物が挙げられる。The preferred chemical composition of the powdered tool steel according to the present invention is as described above, and the balance is substantially composed of Fe. It may contain trace components to such an extent that they do not, and they are also included in the technical scope of the present invention.
As such trace components, allowable components such as Ni and Nb,
Impurities such as P, S, Cu, As, and Sb, or unavoidable impurities are included.
【００３８】[0038]
【実施例】以下、実施例、比較例によって本発明の構成
及び作用効果をより具体的に説明するが、本発明はもと
より下記実施例によって制限を受けるものではなく、前
・後記の趣旨に適合し得る範囲で適当に変更を加えて実
施することも可能であり、それらは何れも本発明の技術
的範囲に包含される。EXAMPLES Hereinafter, the structure and operation and effect of the present invention will be described in more detail with reference to Examples and Comparative Examples. However, the present invention is not limited to the following Examples, and conforms to the preceding and following points. It is also possible to carry out the present invention with appropriate modifications within a possible range, and all of them are included in the technical scope of the present invention.
【００３９】比較例１ 供試鋼粉末として0.97％Ｃ−４％Ｃｒ−６％Ｍｏ−６％
W−3.5％Ｖ−５％Ｃｏ（オーステナイト化温度：約８０
０℃）よりなるガスアトマイズ鋼粉（６０メッシュ以
下）を使用し、これを図１に示した如くキャン１（炭素
鋼製、内径３２０ｍｍ×高さ６００ｍｍ）内に充填して
脱気装置にセットし、弁Ｖ3を閉じ、弁Ｖ1，Ｖ2を開放
して脱気処理を３００℃で実施する。Comparative Example 1 0.97% C-4% Cr-6% Mo-6% as test steel powder
W-3.5% V-5% Co (Austenitizing temperature: about 80
0 ° C.), filled in a can 1 (made of carbon steel, inner diameter 320 mm × height 600 mm) as shown in FIG. 1 and set in a deaerator. , closing valve V 3, to open the valve V 1, V 2 carried degassing treatment at 300 ° C..
【００４０】その後、弁Ｖ1，Ｖ2を閉じた後、弁Ｖ3,Ｖ
2を開放して窒素ガスをキャン１内へ導入し、キャン1内
の窒素圧力を大気圧よりも加圧状態としてから、弁Ｖ3,
Ｖ2を閉じる。その後、窒化炉２内にキャン１を装入
し、弁Ｖ1を開放し、弁Ｖ2を開いてキャン１内を所定圧
力(大気圧＋８００mmH2O)となる様に調整する。Then, after closing the valves V 1 and V 2 , the valves V 3 and V 2
2 an open by introducing nitrogen gas into the can 1, the nitrogen pressure in the can 1 after also pressurized state above atmospheric pressure, valve V 3,
Close the V 2. Then, charged with the can 1 into the nitriding furnace 2, opening valve V 1, to adjust the inside the can 1 by opening the valve V 2 so as a predetermined pressure (atmospheric pressure + 800mmH 2 O).
【００４１】上記圧力調整が終わった段階で昇温工程に
入り、キャン内を＋８００mmH2Oに維持しつつ、図３に
示す如く６時間かけて８５０℃まで昇温し、同温度で５
時間保持することによって窒化処理を行なう。その後、
室温まで冷却する炉内に冷却空気を導入して室温まで降
温する。At the stage when the above pressure adjustment is completed, a temperature raising step is started. While maintaining the inside of the can at +800 mmH 2 O, the temperature is raised to 850 ° C. over 6 hours as shown in FIG.
The nitriding process is performed by holding for a time. afterwards,
Cooling air is introduced into a furnace that cools to room temperature, and the temperature is lowered to room temperature.
【００４２】この方法で窒化処理された鋼粉のキャン内
位置（即ち、キャン内の中心方向位置と上下方向位置）
における窒素含有量を調べたところ、図４および図５に
示す結果が得られた。The position in the can of the steel powder nitrided by this method (ie, the center position and the vertical position in the can)
When the nitrogen content in was measured, the results shown in FIGS. 4 and 5 were obtained.
【００４３】図４，５からも明らかな様に、この比較例
で窒化された鋼粉は、キャンの中心方向位置および上下
方向位置（トップからの深さ位置）の何れにおいても窒
素量のバラツキが大きく、鋼粉全体として窒素含有量の
均一性を欠いている。As is clear from FIGS. 4 and 5, the steel powder nitrided in this comparative example shows a variation in the amount of nitrogen at both the center position of the can and the vertical position (depth position from the top). And the nitrogen content of the steel powder as a whole lacks uniformity.
【００４４】実施例１ 上記比較例１において、キャン内を＋８００mmH2Oに維
持しつつ、図６に示す如く６５０℃にまで昇温して３時
間保持して均熱化し、その後２時間かけて８５０℃にま
で昇温し同温度で５時間保持した以外は前記実施例１と
同様にして窒化処理を行なった。Example 1 In Comparative Example 1, while maintaining the inside of the can at +800 mmH 2 O, the temperature was raised to 650 ° C. as shown in FIG. The nitriding treatment was performed in the same manner as in Example 1 except that the temperature was raised to 850 ° C. and the temperature was maintained at the same temperature for 5 hours.
【００４５】この方法で窒化処理された鋼粉のキャン内
位置（キャン内の中心方向位置と上下方向位置）と窒素
含有量を調べたところ、図７および図８に示す結果が得
られた。When the position in the can (the center position and the vertical position in the can) and the nitrogen content of the steel powder nitrided by this method were examined, the results shown in FIGS. 7 and 8 were obtained.
【００４６】これらの図からも明らかな様に、この実施
例で窒化された鋼粉は、８５０℃での窒化に先立って６
５０℃での均熱処理を施したことで、キャン内中心方向
に位置する鋼粉の窒素量のバラツキが大幅に小さくなっ
ている。但し本例では、キャン頂部側から常温の窒素ガ
スを補給したため、キャン頂部側１００ｍｍまでの位置
で補給窒素ガスによる温度降下により窒素含有量の低下
が見られる。従って該鋼粉を使用するに当たっては、キ
ャン頂部側の鋼粉を除外することにより、窒素含有量の
バラツキを少なく抑えることができる。As can be seen from these figures, the steel powder nitrided in this example was subjected to 6% prior to nitriding at 850 ° C.
By performing the soaking treatment at 50 ° C., the variation in the amount of nitrogen of the steel powder located in the center direction in the can is significantly reduced. However, in this example, since nitrogen gas at room temperature was supplied from the top of the can, normal nitrogen gas was reduced at a position up to 100 mm on the top of the can due to a temperature drop by the supplied nitrogen gas. Therefore, when using the steel powder, by excluding the steel powder on the top side of the can, the variation in the nitrogen content can be reduced.
【００４７】実施例２ 上記実施例１において、キャン内を＋８００mmH2Oに維
持しつつ、図９に示す如くまず６５０℃にまで昇温して
３時間保持して均熱化し、その後２時間かけて８５０℃
にまで昇温して同温度で５時間保持し、この間補給用と
して窒化加熱のライン内で予熱した窒素ガスを供給する
ことによりキャン内を＋８００mmH2Oに維持した以外
は、実施例１と同様にして窒化処理を行なった。Example 2 In Example 1, while maintaining the inside of the can at +800 mmH 2 O, the temperature was first raised to 650 ° C. as shown in FIG. 850 ℃
, And maintained at the same temperature for 5 hours. During this period, the inside of the can was maintained at +800 mmH 2 O by supplying nitrogen gas preheated in a nitriding heating line for replenishment, and the same as in Example 1 was performed. And a nitriding treatment was performed.
【００４８】この方法で窒化処理された鋼粉のキャン内
位置（キャン内の中心方向位置と上下方向位置）におけ
る窒素含有量を調べたところ、図１０および図１１に示
す結果が得られた。When the nitrogen content of the steel powder nitrided by this method at the position inside the can (the center position and the vertical position within the can) was examined, the results shown in FIGS. 10 and 11 were obtained.
【００４９】これらの図からも明らかな様に、この実施
例で窒化された鋼粉は、８５０℃での窒化に先立って６
５０℃での均熱処理を施すと共に、補給用の窒素ガスを
予熱しておくことで、キャン内中心方向およびキャン内
上下方向に位置する鋼粉の窒素量のバラツキが共に小さ
くなり、全体に亘ってほぼ均一な窒素含有量が得られて
いる。As can be seen from these figures, the steel powder nitrided in this example was subjected to 6% prior to nitriding at 850 ° C.
By performing the soaking at 50 ° C. and preheating the replenishing nitrogen gas, the variation in the amount of nitrogen in the steel powder located both in the center direction in the can and in the vertical direction in the can is reduced, and the entirety is reduced. Thus, a substantially uniform nitrogen content is obtained.
【００５０】[0050]
【発明の効果】本発明は以上の様に構成されており、工
具鋼をキャニングして窒化処理を行なう際に、キャン内
を窒素ガス置換した後、1)キャン内温度を６００℃以
上、工具鋼粉末のオーステナイト化温度未満の温度に保
って均熱した後、オーステナイト化温度以上に高めて窒
化することにより、キャン内中心方向の窒化速度のバラ
ツキを抑え、或は2)キャン内に補給される窒素ガスを予
熱しておくことによって、キャン内上下方向の窒化速度
のバラツキを抑え、あるいは更に、3)上記1)、2)を組合
わせて実施することによって、キャン内中心方向および
上下方向の窒化速度のバラツキを共に抑え、窒素含有量
の均一な工具鋼粉末を提供し得ることになった。The present invention is constituted as described above. When the tool steel is canned and subjected to nitriding treatment, the inside of the can is replaced with nitrogen gas. After soaking at a temperature lower than the austenitizing temperature of the steel powder and then nitriding by raising it to a temperature higher than the austenitizing temperature, the variation in the nitriding rate in the center direction in the can is suppressed, or 2) replenished in the can. By preheating nitrogen gas, the variation in the nitriding rate in the vertical direction inside the can is suppressed, or 3) the above 1) and 2) are combined to implement Thus, it is possible to provide a tool steel powder having a uniform nitrogen content while suppressing variations in the nitriding rate of the steel.
【図１】キャニング状態での窒化処理法を例示する概略
説明図である。FIG. 1 is a schematic explanatory view illustrating a nitriding treatment method in a canning state.
【図２】窒化処理時の温度と窒素吸収量の関係を示すグ
ラフである。FIG. 2 is a graph showing the relationship between the temperature during nitriding and the amount of nitrogen absorbed.
【図３】比較例１で採用した窒化処理時のヒートパター
ンを示す図である。FIG. 3 is a view showing a heat pattern at the time of nitriding treatment employed in Comparative Example 1.
【図４】比較例１で得た窒化鋼粉のキャン内位置と窒素
量を示す図である。FIG. 4 is a view showing the position in a can and the amount of nitrogen of the nitrided steel powder obtained in Comparative Example 1.
【図５】比較例１で得た窒化鋼粉のキャン内位置と窒素
量を示すグラフである。FIG. 5 is a graph showing the position in a can and the amount of nitrogen of the nitrided steel powder obtained in Comparative Example 1.
【図６】実施例例１で採用した窒化処理時のヒートパタ
ーンを示す図である。FIG. 6 is a diagram showing a heat pattern at the time of nitriding treatment employed in Example 1.
【図７】実施例１で得た窒化鋼粉のキャン内位置と窒素
量を示す図である。FIG. 7 is a diagram showing the position in a can and the amount of nitrogen of the nitrided steel powder obtained in Example 1.
【図８】実施例１で得た窒化鋼粉のキャン内位置と窒素
量を示すグラフである。FIG. 8 is a graph showing the in-can position and the amount of nitrogen of the nitrided steel powder obtained in Example 1.
【図９】実施例２で採用した窒化処理時のヒートパター
ンを示す図である。FIG. 9 is a view showing a heat pattern at the time of nitriding treatment employed in Example 2.
【図１０】実施例２で得た窒化鋼粉のキャン内位置と窒
素量を示す図である。FIG. 10 is a diagram showing the position in a can and the amount of nitrogen of the nitrided steel powder obtained in Example 2.
【図１１】実施例２で得た窒化鋼粉のキャン内位置と窒
素量を示すグラフである。FIG. 11 is a graph showing the position in a can and the amount of nitrogen of the nitrided steel powder obtained in Example 2.
───────────────────────────────────────────────────── フロントページの続き (72)発明者 吉田 正知 兵庫県高砂市荒井町新浜２丁目３番１号 株式会社神戸製鋼所高砂製作所内 Ｆターム(参考） 4K018 AA32 BA15 BC01 BD08 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Masatomo Yoshida 2-3-1, Shinhama, Arai-machi, Takasago-shi, Hyogo F-term in Kobe Steel, Ltd. Takasago Mfg. Co., Ltd. 4K018 AA32 BA15 BC01 BD08
Claims (6)
ャン内に窒素ガスを供給しつつ加熱して窒化することに
より窒素含有量の高められた工具鋼粉末を製造するに際
し、キャン内に窒素ガスを圧入してから昇温し、炉内雰
囲気温度を６００℃以上、工具鋼粉末のオーステナイト
化温度未満の温度に保って均熱した後、炉内雰囲気温度
を該工具鋼粉末のオーステナイト化温度以上に高めて窒
化することを特徴とする窒素含有量の高められた工具鋼
粉末の製法。When producing tool steel powder having an increased nitrogen content by canning tool steel powder, degassing, and heating and nitriding while supplying nitrogen gas into the can, nitrogen is contained in the can. After the gas was injected, the temperature was raised and the furnace was kept at an ambient temperature of at least 600 ° C. and less than the austenitizing temperature of the tool steel powder. A method for producing a tool steel powder having an increased nitrogen content, characterized in that the above is increased and nitrided.
ャン内に窒素ガスを供給しつつ加熱して窒化することに
より窒素含有量の高められた工具鋼粉末を製造するに際
し、キャン内に加熱された窒素ガスを圧入しつつ、炉内
雰囲気温度を前記工具鋼粉末のオーステナイト化温度以
上に高めて窒化することを特徴とする窒素含有量の高め
られた工具鋼粉末の製法。2. A method for producing tool steel powder having an increased nitrogen content by heating the tool steel powder and nitriding it while supplying nitrogen gas into the can after degassing the tool steel powder. A method for producing a tool steel powder having an increased nitrogen content, characterized in that the furnace atmosphere temperature is raised to a temperature equal to or higher than the austenitizing temperature of the tool steel powder and nitriding is performed while pressurized nitrogen gas is injected.
ャン内に窒素ガスを供給しつつ加熱して窒化することに
より窒素含有量の高められた工具鋼粉末を製造するに際
し、キャン内に窒素ガスを圧入してから昇温し、炉内雰
囲気温度を６００℃以上、工具鋼粉末のオーステナイト
化温度未満の温度に保って均熱した後、キャン内に加熱
された窒素ガスを圧入しつつ、炉内雰囲気温度を前記工
具鋼粉末のオーステナイト化温度以上に高めて窒化する
ことを特徴とする窒素含有量の高められた工具鋼粉末の
製法。3. A method for producing tool steel powder having an increased nitrogen content by heating the tool steel powder and nitriding it while supplying nitrogen gas into the can after degassing the tool steel powder. After the gas was injected, the temperature was raised, the furnace atmosphere temperature was maintained at 600 ° C. or higher, and the temperature was maintained at a temperature lower than the austenitizing temperature of the tool steel powder, and then the heated nitrogen gas was injected into the can. A method for producing a tool steel powder having an increased nitrogen content, wherein the furnace atmosphere temperature is increased to a temperature higher than the austenitizing temperature of the tool steel powder and nitriding is performed.
Ｃｒ：３〜５質量％、Ｖ：２．５質量％以上を含有する
と共に、Ｗ及び／又はＭｏ：（Ｗ＋２Ｍｏ）で８．５質
量％以上を含むものである請求項１〜３のいずれかに記
載の製法。4. A tool steel powder comprising: C: 0.5% by mass or more;
4. The steel according to claim 1, which contains Cr: 3 to 5% by mass, V: 2.5% by mass or more and W and / or Mo: (W + 2Mo) by 8.5% by mass or more. Recipe.
０質量％以下（０％を含まない）を含むものである請求
項４に記載の製法。5. The tool steel powder contains Co: 2 as another element.
5. The method according to claim 4, wherein the composition contains 0% by mass or less (excluding 0%).
％以上、飽和窒素含有量未満に高める請求項１〜５のい
ずれかに記載の製法。6. The method according to claim 1, wherein the nitrogen content is increased to 0.2% by mass or more and less than the saturated nitrogen content by nitriding.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2001113155A JP2002309302A (en) | 2001-04-11 | 2001-04-11 | Method for manufacturing tool-steel powder with increased nitrogen content |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2001113155A JP2002309302A (en) | 2001-04-11 | 2001-04-11 | Method for manufacturing tool-steel powder with increased nitrogen content |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JP2002309302A true JP2002309302A (en) | 2002-10-23 |
Family
ID=18964425
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP2001113155A Withdrawn JP2002309302A (en) | 2001-04-11 | 2001-04-11 | Method for manufacturing tool-steel powder with increased nitrogen content |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2002309302A (en) |
-
2001
- 2001-04-11 JP JP2001113155A patent/JP2002309302A/en not_active Withdrawn
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