JP6270563B2 - Precipitation hardening type stainless steel powder that can obtain high strength after sintering-aging treatment, its production method, and its compact - Google Patents
Precipitation hardening type stainless steel powder that can obtain high strength after sintering-aging treatment, its production method, and its compact Download PDFInfo
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- 239000000843 powder Substances 0.000 title claims description 53
- 238000004881 precipitation hardening Methods 0.000 title claims description 27
- 229910001220 stainless steel Inorganic materials 0.000 title claims description 24
- 239000010935 stainless steel Substances 0.000 title claims description 24
- 238000004519 manufacturing process Methods 0.000 title description 13
- 229910000734 martensite Inorganic materials 0.000 claims description 28
- 229910052757 nitrogen Inorganic materials 0.000 claims description 17
- 229910000831 Steel Inorganic materials 0.000 claims description 10
- 229910052799 carbon Inorganic materials 0.000 claims description 9
- 239000010959 steel Substances 0.000 claims description 9
- 229910052782 aluminium Inorganic materials 0.000 claims description 7
- 229910052758 niobium Inorganic materials 0.000 claims description 5
- 229910052759 nickel Inorganic materials 0.000 claims description 4
- 229910052802 copper Inorganic materials 0.000 claims description 3
- 229910052750 molybdenum Inorganic materials 0.000 claims description 3
- 229910052804 chromium Inorganic materials 0.000 claims description 2
- 239000012535 impurity Substances 0.000 claims description 2
- 229910052748 manganese Inorganic materials 0.000 claims description 2
- 229910052710 silicon Inorganic materials 0.000 claims description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 27
- 238000005245 sintering Methods 0.000 description 27
- 238000000034 method Methods 0.000 description 18
- 229910001566 austenite Inorganic materials 0.000 description 15
- 230000000052 comparative effect Effects 0.000 description 13
- 230000000717 retained effect Effects 0.000 description 13
- 238000003483 aging Methods 0.000 description 11
- 229910000859 α-Fe Inorganic materials 0.000 description 10
- 239000000463 material Substances 0.000 description 9
- 239000000654 additive Substances 0.000 description 8
- 230000000996 additive effect Effects 0.000 description 8
- PXHVJJICTQNCMI-UHFFFAOYSA-N nickel Substances [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 8
- 230000032683 aging Effects 0.000 description 7
- 230000000694 effects Effects 0.000 description 6
- 238000001513 hot isostatic pressing Methods 0.000 description 6
- 229910052751 metal Inorganic materials 0.000 description 6
- 239000002184 metal Substances 0.000 description 6
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 5
- 238000000465 moulding Methods 0.000 description 5
- 238000001556 precipitation Methods 0.000 description 5
- 238000007711 solidification Methods 0.000 description 5
- 230000008023 solidification Effects 0.000 description 5
- 230000007797 corrosion Effects 0.000 description 4
- 238000005260 corrosion Methods 0.000 description 4
- 238000005336 cracking Methods 0.000 description 4
- 230000007423 decrease Effects 0.000 description 4
- 238000001816 cooling Methods 0.000 description 3
- 238000010438 heat treatment Methods 0.000 description 3
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- 239000000243 solution Substances 0.000 description 3
- 239000012298 atmosphere Substances 0.000 description 2
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
- 230000006866 deterioration Effects 0.000 description 2
- 238000010894 electron beam technology Methods 0.000 description 2
- 238000009689 gas atomisation Methods 0.000 description 2
- 238000002844 melting Methods 0.000 description 2
- 230000008018 melting Effects 0.000 description 2
- 239000001301 oxygen Substances 0.000 description 2
- 229910052760 oxygen Inorganic materials 0.000 description 2
- 239000006104 solid solution Substances 0.000 description 2
- 230000009466 transformation Effects 0.000 description 2
- 238000007088 Archimedes method Methods 0.000 description 1
- 230000018199 S phase Effects 0.000 description 1
- 238000002441 X-ray diffraction Methods 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 238000000137 annealing Methods 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 229910001873 dinitrogen Inorganic materials 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- -1 ferrous metals Chemical class 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 239000011261 inert gas Substances 0.000 description 1
- 238000002347 injection Methods 0.000 description 1
- 239000007924 injection Substances 0.000 description 1
- 238000001746 injection moulding Methods 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 238000003475 lamination Methods 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 239000012299 nitrogen atmosphere Substances 0.000 description 1
- 238000010587 phase diagram Methods 0.000 description 1
- 238000004663 powder metallurgy Methods 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 230000000087 stabilizing effect Effects 0.000 description 1
- 238000005728 strengthening Methods 0.000 description 1
- 229910052715 tantalum Inorganic materials 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
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Description
本発明は、焼結体まま時効しても高強度が得られる析出硬化型ステンレス鋼粉末およびその製造方法並びにその成形体に関するものである。 The present invention relates to a precipitation hardening stainless steel powder that can obtain high strength even when aged as it is, and a method for producing the same, and a molded body thereof.
一般的な析出硬化ステンレス鋼粉末を金属粉末射出成形（ＭＩＭ）や粉末冶金法、並びに粉末積層による焼結造形（いわゆる三次元造形）等で焼結造形した場合、焼結体を直接時効処理、すなわち、４００〜６００℃と言った低温で保持することで時効硬化を促進する熱処理をしただけでは硬度が例えば、ＪＩＳ Ｇ ４３０３を参照したＳＵＳ６３０の場合にはＨ９００処理（４８０℃、空冷）では硬度４０ＨＲＣ以上を確保することは出来ない。 When a general precipitation hardening stainless steel powder is sintered by metal powder injection molding (MIM), powder metallurgy, and sintering modeling by powder lamination (so-called three-dimensional modeling), the sintered body is directly aged, That is, the hardness is only obtained by heat treatment that promotes age hardening by holding at a low temperature of 400 to 600 ° C. For example, in the case of SUS630 with reference to JIS G 4303, the hardness is H900 treatment (480 ° C., air cooling). It is not possible to secure more than 40 HRC.
ＪＩＳ Ｇ ４３０３に記載の通り、焼結体を１０５０℃付近で固溶化熱処理した後で
、時効処理を施した場合は硬度確保するが、工程増加、高温・急冷の固溶化熱処理による歪の発生が起こること、その歪除去のための再焼鈍や形状修正加工が必要となる等新たな問題が発生するため、実用に際しての課題解決とはなっていない。このように実用に即した、焼結−時効処理のみで高強度が得られる析出硬化型ステンレス鋼粉末が求められているが、要求事項を満たす粉末がないのが現状である。
As described in JIS G 4303, when the sintered body is subjected to solution heat treatment at around 1050 ° C. and then subjected to aging treatment, the hardness is ensured. Since new problems occur, such as the occurrence of re-annealing and the need for shape correction to remove the distortion, it is not a solution for practical use. Thus, there is a need for a precipitation hardening type stainless steel powder that can be obtained with high strength only by sintering-aging treatment, but there is no powder that satisfies the requirements.
一方、焼結造形法としては、例えば特開２０１１−２１２１８号公報（特許文献１）に開示されているように、アルミニウム製の実用的な試作品や製品を直接焼結又は溶融・固化により作製する方法が提案されている。また、特開２００２−２４９８０５号公報（特許文献２）に開示されているように、無機質あるいは有機質の粉末材料に光ビームを照射して溶融層を形成し、この溶融層を積み重ねて所望の三次元形状を有する焼結体を製造する方法が提案されている。 On the other hand, as a sintering modeling method, as disclosed in, for example, Japanese Patent Application Laid-Open No. 2011-21218 (Patent Document 1), a practical prototype or product made of aluminum is directly sintered or melted and solidified. A method has been proposed. Further, as disclosed in Japanese Patent Laid-Open No. 2002-249805 (Patent Document 2), an inorganic or organic powder material is irradiated with a light beam to form a molten layer, and the molten layers are stacked to form a desired tertiary layer. A method of manufacturing a sintered body having an original shape has been proposed.
さらに、特開２００４−１２４２０１号公報（特許文献３）に開示されているように、薄い金属粉末の層をレーザービームで任意の形状に焼結する工程を積み重ねていき、金属製試作部品や射出成形金型等の３次元造形物を作製する金属粉末光造形方法が提案されている。しかし、これら特許文献はいずれも対象が非鉄金属等を対象とするもので、鋼粉末で、特に高強度のステンレス鋼粉末の処理ではない。 Further, as disclosed in Japanese Patent Application Laid-Open No. 2004-124201 (Patent Document 3), a process of sintering a thin metal powder layer into an arbitrary shape with a laser beam is stacked, and a metal prototype part or injection A metal powder stereolithography method for producing a three-dimensional structure such as a molding die has been proposed. However, all of these patent documents are directed to non-ferrous metals and the like, and are not a treatment of steel powder, particularly high-strength stainless steel powder.
上述したような問題を解消するために、その対策として、焼結後に時効硬度が上昇しな
い原因について発明者らは鋭意検討した結果、一般的な析出硬化ステンレス鋼粉末（粉砕、水アトマイズ等）は含有窒素量が高く、低酸素化のための還元処理を施しても窒素量は下がらない。また、焼結中に更なる窒素導入もあり、結果として焼結―冷却後の残留オーステナイト量が増加する。そのことで時効硬化に寄与する低炭素マルテンサイト組織が減少し、時効硬化能が低減していることを解明した。
In order to solve the problems as described above, as a countermeasure, the inventors have intensively studied the reason why the aging hardness does not increase after sintering. The amount of nitrogen contained is high, and the amount of nitrogen does not decrease even when reduction treatment for reducing oxygen is performed. There is also further nitrogen introduction during sintering, resulting in an increase in the amount of retained austenite after sintering-cooling. As a result, it was clarified that the low carbon martensite structure contributing to age hardening decreased and the age hardening ability was reduced.
そこで、一般的に言われるシェフラーの状態図を参考にしつつ、窒素量の制御とＮｉ−ｂａｌ制御により、上述したＭＩＭ、粉末焼結および積層造形といった焼結法で製造された造形体の残留オーステナイト量を低く抑えることが出来、結果として高い時効硬化能をもたせる低炭素マルテンサイト組織を９０％以上に制御することが可能となった。特に、積層造形法では電子ビームやレーザー光といった高エネルギー源を使用し、極微小領域の粉末を溶融急速凝固させることを繰返すため、本発明粉末が焼結造形物の時効硬化能を持たせることに最適であることが分かった。 Therefore, with reference to Schaeffler's phase diagram, which is generally referred to, residual austenite of a shaped body manufactured by a sintering method such as MIM, powder sintering, and additive manufacturing described above by controlling the amount of nitrogen and controlling Ni-bal. The amount could be kept low, and as a result, it became possible to control the low carbon martensite structure having high age-hardening ability to 90% or more. In particular, the additive manufacturing method uses a high energy source such as an electron beam or a laser beam, and repeats melting and rapidly solidifying the powder in a very small area, so that the powder of the present invention has the age hardening ability of the sintered structure. It turned out to be optimal.
その発明の要旨とするところは、
（１）質量％で、Ｃ：≦０．０５％、Ｓｉ：≦１．０％、Ｍｎ：≦１．５％、Ｎｉ：３．０〜８．５％、Ｃｒ：１２．０〜２０．０％、Ｍｏ：０．１〜２．５％、Ｃｕ：１．０〜５．０％、Ｎｂ＋Ｔａ≧５Ｃ、残部Ｆｅおよび不可避的不純物からなり、かつ下記式（１）のＮｉ−ｂａｌ．が−４以上である析出硬化ステンレス鋼からなる粉末であって、該鋼粉末からなる焼結体に含有されるマルテンサイト組織が９０％以上であることを特徴とする析出硬化型ステンレス鋼粉末。
Ｎｉ−ｂａｌ．＝Ｎｉ＋２７Ｃ＋２３Ｎ＋０．２Ｍｎ＋０．３Ｃｕ−１．２（Ｃｒ＋Ｍｏ）−０．５Ｓｉ−０．３Ｎｂ＋１０ … （１）
The gist of the invention is that
(1) By mass%, C: ≦ 0.05%, Si: ≦ 1.0%, Mn: ≦ 1.5%, Ni: 3.0 to 8.5%, Cr: 12.0 to 20. 0%, Mo: 0.1-2.5%, Cu: 1.0-5.0%, Nb + Ta ≧ 5C, the balance Fe and unavoidable impurities, and Ni-bal. Precipitation hardening type stainless steel powder characterized in that it is a powder made of precipitation hardening stainless steel having a -4 or more and the martensite structure contained in the sintered body made of the steel powder is 90% or more.
Ni-bal. = Ni + 27C + 23N + 0.2Mn + 0.3Cu-1.2 (Cr + Mo) -0.5Si-0.3Nb + 10 (1)
（２）前記（１）に記載の鋼に加えて、ＴｉまたはＡｌの１種または２種を１．０〜５．０％含有させたことを特徴とする析出硬化型ステンレス鋼粉末。
（３）前記（１）に記載のＣｕに代え、ＴｉまたはＡｌの１種または２種を１．０〜５．０％含有させたことを特徴とする析出硬化型ステンレス鋼粉末。
(2) A precipitation hardening stainless steel powder containing 1.0 to 5.0% of Ti or Al in addition to the steel described in (1).
(3) A precipitation hardening stainless steel powder characterized by containing 1.0 to 5.0% of Ti or Al in place of Cu described in (1).
（４）前記（１）〜（３）のいずれか１に記載の鋼粉末を真空溶解し不活性ガスアトマイズ法にて製造することにより窒素量と原料粉末の結晶粒度を制御し、球状度に優れる粉末を得ることを特徴とする析出硬化型ステンレス鋼粉末の製造方法。
（５）前記（１）〜（３）のいずれか１に記載の鋼粉末を焼結し成形してなる成形体にある。
(4) The steel powder according to any one of the above (1) to (3) is vacuum-dissolved and manufactured by an inert gas atomization method, thereby controlling the amount of nitrogen and the crystal grain size of the raw material powder, and being excellent in sphericity. A method for producing a precipitation hardening stainless steel powder, characterized by obtaining a powder.
(5) A molded body obtained by sintering and molding the steel powder according to any one of (1) to (3).
本発明は、上述したように、成分組成の析出硬化ステンレス鋼粉末の窒素量を３５０ｐｐｍ以下とすることで焼結後のマルテンサイト組織を９０％以上となる析出硬化型ステンレス鋼粉末を得ることを可能とした。 As described above, the present invention provides a precipitation hardening stainless steel powder having a martensite structure after sintering of 90% or more by setting the nitrogen content of the precipitation hardening stainless steel powder of the component composition to 350 ppm or less. It was possible.
以下、本発明鋼についての成分を限定した理由について説明する。
Ｃ：≦０．０５％
Ｃは、析出硬化ステンレス鋼では固溶化状態での加工性改善と焼結体での残留オーステナイト量を低減し、低Ｃマルテンサイト組織とするため低く抑える必要がある。好ましくは０．０３％以下とする。また、多くなると固溶化状態での硬さが増加し、加工性が劣化する。本発明では焼結時、凝固開始時にδフェライト相が多くなるため焼結時の割れやすさも増加する。したがって、上限を０．０５％とした。
Hereinafter, the reason which limited the component about this invention steel is demonstrated.
C: ≦ 0.05%
In precipitation hardened stainless steel, C needs to be kept low because it improves the workability in a solid solution state and reduces the amount of retained austenite in the sintered body, resulting in a low C martensite structure. Preferably it is 0.03% or less. Moreover, when it increases, the hardness in a solution state will increase and workability will deteriorate. In the present invention, since the δ ferrite phase increases at the start of solidification during sintering, the susceptibility to cracking during sintering also increases. Therefore, the upper limit was made 0.05%.
Ｓｉ：≦１．０％
Ｓｉは、脱酸材として有効並びに硬度向上にも有効である元素である。しかし、硬度向上のため焼結時の割れやすさが増大、また耐孔食性も劣化させるため、その上限を１．０％とした。
Ｍｎ：≦１．５％
Ｍｎは、強度と靭性を向上させるのに有効な元素であるが、しかし、１．５％を超えると焼結体でのマルテンサイト組織量が減少し、時効硬化硬さが不足するため、その上限を１．５％とした。
Si: ≦ 1.0%
Si is an element that is effective as a deoxidizer and also effective in improving hardness. However, the upper limit is set to 1.0% because the susceptibility to cracking during sintering increases and the pitting corrosion resistance deteriorates due to the improvement in hardness.
Mn: ≦ 1.5%
Mn is an element effective for improving the strength and toughness. However, if it exceeds 1.5%, the amount of martensite structure in the sintered body decreases and the age hardening hardness is insufficient. The upper limit was 1.5%.
Ｎｉ：３．０〜８．５％
Ｎｉは、全体の組織調整および、δフェライトの生成を抑制し、かつ析出硬化に必要不可欠な元素である。しかし、３．０％未満ではその効果が得られないことから３．０％以上とした。一方、多すぎると残留オーステナイトが増加し、焼結体の析出硬化能が確保できないため、上限を８．５％とした。
Ni: 3.0-8.5%
Ni is an element indispensable for the overall structure adjustment and the formation of δ ferrite and for precipitation hardening. However, if it is less than 3.0%, the effect cannot be obtained. On the other hand, if the amount is too large, the retained austenite increases and the precipitation hardening ability of the sintered body cannot be secured, so the upper limit was made 8.5%.
Ｃｒ：１２．０〜２０．０％
Ｃｒは、ステンレス鋼として耐食性を確保するためには１２．０％以上必要である。しかし、２０．０％を超えると単に耐食性増加にはいいものの、焼結時に低炭素マルテンサイト組織とならず、また残留オーステナイト組織ともならず、フェライト組織となり析出硬化能や素材の靭性が劣化することから、その上限を２０．０％とした。
Cr: 12.0 to 20.0%
Cr as a stainless steel needs to be 12.0% or more in order to ensure corrosion resistance. However, if it exceeds 20.0%, it is only good for increasing the corrosion resistance, but it does not become a low carbon martensite structure during sintering, it does not become a retained austenite structure, it becomes a ferrite structure, and the precipitation hardening ability and the toughness of the material deteriorate. Therefore, the upper limit was made 20.0%.
Ｍｏ：０．１〜２．５％
Ｍｏは、耐食性を確保するために必要な元素である。しかし、添加しすぎるとＮｉバランスがマイナス方向になるため焼結時に低炭素マルテンサイト組織とならず、また残留オーステナイト組織ともならず、フェライト組織となり析出硬化能や素材の靭性が劣化する。したがって、その範囲を０．１〜２．５％とした。
Mo: 0.1-2.5%
Mo is an element necessary for ensuring corrosion resistance. However, if it is added too much, the Ni balance becomes negative, so that it does not become a low carbon martensite structure during sintering, does not become a retained austenite structure, and becomes a ferrite structure, which deteriorates the precipitation hardening ability and the toughness of the material. Therefore, the range was made 0.1 to 2.5%.
Ｃｕ：１．０〜５．０％
Ｃｕは、析出硬化能を確保するための元素である。しかし、１．０％未満ではその効果が得られず、その下限を１．０％とした。好ましくは３％の添加が必要である。しかし、５％を超えると靭性、さらに本発明用途では問題とならない場合が多いが、焼結体の熱間加工性も劣化するため、上限を５％とした。
Cu: 1.0-5.0%
Cu is an element for ensuring precipitation hardening ability. However, if it is less than 1.0%, the effect cannot be obtained, and the lower limit is set to 1.0%. Preferably 3% addition is required. However, if it exceeds 5%, toughness is not a problem in the present invention in many cases, but the hot workability of the sintered body also deteriorates, so the upper limit was made 5%.
Ｔｉ、Ａｌ：１．０〜５．０％
ＴｉおよびＡｌは、Ｃｕと複合もしくは単独添加で析出硬化能を発揮する元素である。そのため、最低でも１％の添加が必要である。しかし、５％を超えると靭性劣化およびδフェライト生成傾向が高くなりすぎ焼結時に低炭素マルテンサイト組織とならず、また残留オーステナイト組織にもならないため５％を上限とする。
Ti, Al: 1.0-5.0%
Ti and Al are elements that exhibit precipitation hardening ability when combined with Cu or added alone. Therefore, it is necessary to add at least 1%. However, if it exceeds 5%, the toughness deterioration and the tendency to form δ ferrite become so high that it does not become a low-carbon martensite structure during sintering, nor does it become a retained austenite structure, so 5% is made the upper limit.
Ｎｂ＋Ｔａ≧５Ｃ
Ｎｂ＋Ｔａは、Ｃの安定化と析出硬化度を向上させるのに必要不可欠な元素である。その量は５Ｃより多く必要である。具体的には０．１％以上を確保するのが望ましい。５Ｃを超えるにつれ析出硬化能を向上させる効果がある。但し、靭性劣化傾向もあるがＭｏが複合添加されている場合は焼戻脆化に伴う靭性劣化が抑制できる。したがって、Ｎｂ＋Ｔａ≧５Ｃとした。
Nb + Ta ≧ 5C
Nb + Ta is an indispensable element for stabilizing C and improving the precipitation hardening degree. The amount needs more than 5C. Specifically, it is desirable to secure 0.1% or more. As it exceeds 5C, there is an effect of improving the precipitation hardening ability. However, although there is also a tendency to deteriorate toughness, when Mo is added in combination, toughness deterioration accompanying temper embrittlement can be suppressed. Therefore, Nb + Ta ≧ 5C.
Ｎ≦３５０ｐｐｍ
Ｎは、本発明の析出硬化ステンレス鋼ではＮ量の制御とＮｉ−ｂａｌ制御により、ＭＩＭ、粉末焼結および積層造形といった焼結法で製造された造形体の残留オーステナイト量を低く抑えることが出来、結果として高い時効硬化能をもたせることを可能とする役目がある。特に、積層造形法では電子ビームやレーザー光といった高エネルギー源を使用し、極微小領域の粉末を溶融急速凝固させることを繰返すため、本発明粉末が焼結造形物の時効硬化能を持たせることができる。好ましくは２７５ｐｐｍ以下とした。
N ≦ 350ppm
N is a precipitation hardened stainless steel of the present invention, and the amount of retained austenite of a shaped body produced by a sintering method such as MIM, powder sintering, and additive manufacturing can be kept low by controlling the amount of N and controlling Ni-bal. As a result, there is a role that makes it possible to have a high age hardening ability. In particular, the additive manufacturing method uses a high energy source such as an electron beam or a laser beam, and repeats melting and rapidly solidifying the powder in a very small area, so that the powder of the present invention has the age hardening ability of the sintered structure. Can do. Preferably it was 275 ppm or less.
また、鋼粉末の窒素量を３５０ｐｐｍ以下とすることで、焼結し冷却後された焼結体に含有されるマルテンサイト組織が９０％以上とした。マルテンサイト組織を９０％以上とした理由は、析出硬化ステンレス鋼粉末（粉砕、水アトマイズ等）は含有窒素量が高く、低酸素化のための還元処理を施しても窒素量は下がらないこと。また、焼結造形中に更なる窒素導入もあり、結果として残留オーステナイト量が増加すること。これらのことで時効硬化に寄与する低炭素マルテンサイト組織が減るため、時効硬化能が低減するため、残留オーステナイト量を抑え、マルテンサイト組織化する必要がある。そのマルテンサイト組織が９０％以上となることで、目的とする時効処理後の硬さ３９０ＨＶ以上を得ることを可能とするものである。しかし、マルテンサイト組織が９０％未満ではその効果が得られない。したがって、マルテンサイト組織を９０％以上とした。 Moreover, the martensite structure | tissue contained in the sintered compact after sintering and cooling was made into 90% or more because the nitrogen content of steel powder shall be 350 ppm or less. The reason why the martensite structure is 90% or more is that the precipitation hardened stainless steel powder (pulverized, water atomized, etc.) has a high nitrogen content, and the nitrogen content does not decrease even when reduction treatment for reducing oxygen is performed. In addition, there is further introduction of nitrogen during sintering molding, resulting in an increase in the amount of retained austenite. Since the low carbon martensite structure which contributes to age hardening decreases by these things, since age hardening ability reduces, it is necessary to suppress a retained austenite amount and to make a martensite structure. When the martensite structure is 90% or more, it is possible to obtain a target hardness of 390 HV or more after aging treatment. However, if the martensite structure is less than 90%, the effect cannot be obtained. Therefore, the martensite structure is 90% or more.
Ｎｉ−ｂａｌは著名なシェフラーが提唱したニッケルバランスを基本とし、本発明では従来より得られてきた実測値から多重解析により求めたものである。またシェフラーの式にはＣｕとＮｂの項がないので、これらの項についても加えたものである。
さらに、Ｎｉ−ｂａｌの値を−４にした理由は、Ｎｉ−ｂａｌを大きくずらしたものは残留オーステナイト量が増加した影響、並びに凝固や焼結初期時にδフェライト量が増加する影響で（残留オーステナイト相はＦＣＣ、他はＢＣＣと熱膨張係数が異なるため）、焼結体表面にクラックが入りやすい傾向が認められた。しかし、Ｎｉ−ｂａｌの値を−４以上とすることでクラックの発生が見られなかった。したがって、健全な焼結体を得るためにＮｉ−ｂａｌの値を−４以上とした。
Ni-bal is based on a nickel balance proposed by a prominent Schaeffler, and in the present invention, it is obtained by multiple analysis from actual measurement values obtained conventionally. Since the Schaeffler equation does not have Cu and Nb terms, these terms are also added.
Further, the reason why the value of Ni-bal is set to -4 is that the Ni-bal is greatly shifted due to the effect of increasing the amount of retained austenite and the effect of increasing the amount of δ ferrite at the initial stage of solidification and sintering (residual austenite). Since the phase is FCC and the others are different in thermal expansion coefficient from BCC), the surface of the sintered body tends to crack. However, no crack was observed when the Ni-bal value was −4 or more. Therefore, in order to obtain a sound sintered body, the value of Ni-bal is set to -4 or more.
以下、本発明について実施例によって具体的に説明する。
表１に示す本発明鋼の成分組成について、真空溶解した溶湯よりガスアトマイズ法にて低窒素の球状粉末を作製した。特に窒素量は３５０ｐｐｍ以下、好ましくは２７５ｐｐｍ以下とした粉末を篩目５３μｍの網を用いて５３μｍ以下に分級した。また、比較材として上記方法と同一で本発明範囲外の球状粉末を作製すると共にＮｏ．３０には市販のＪＩＳ Ｇ ４３０３ ＳＵＳ６３０相当成分となる粉末を用いた。これら本発明による粉末と比較材粉末をそれぞれ粉末焼結法、ＨＩＰによる固化法、または積層造形法で焼結し、焼結体を得た。
Hereinafter, the present invention will be specifically described with reference to examples.
About the component composition of this invention steel shown in Table 1, the spherical powder of low nitrogen was produced by the gas atomizing method from the molten metal melt | dissolved in vacuum. In particular, a powder having a nitrogen content of 350 ppm or less, preferably 275 ppm or less was classified to 53 μm or less using a mesh having a mesh size of 53 μm. Further, as a comparative material, a spherical powder which is the same as the above method and is outside the scope of the present invention is prepared, and No. 2 is prepared. For 30, a powder that is a commercially available component of JIS G 4303 SUS630 was used. The powder according to the present invention and the comparative material powder were sintered by a powder sintering method, a solidification method by HIP, or an additive manufacturing method, respectively, to obtain a sintered body.
粉末焼結法では粉末を角１５ｍｍ、長さ４０ｍｍの金型に入れ、常温で成形圧力１２Ｍ
Ｐａにて仮成形を施し、この仮成形体を真空炉にて１２００℃、１時間加熱、保持後、加圧窒素ガスにて急冷して角１０ｍｍ、長さ３５ｍｍを確保できる焼結体を得た。ＨＩＰによる固化法では、粉末をφ４０ｍｍ、長さ４５ｍｍの鉄製容器に充填し、蓋を溶接後、中を真空脱気する。その後、真空脱気した容器を１１５０℃、１４７ＭＰａにてＨＩＰ（熱間静水圧プレス）を施し、φ３５ｍｍ、長さ３５ｍｍを確保できる１００％密度の焼結体を得た。
In the powder sintering method, the powder is put into a mold with a square of 15 mm and a length of 40 mm, and a molding pressure of 12 M at room temperature.
Temporary molding is performed at Pa, and after heating and holding the temporary molded body at 1200 ° C. for 1 hour in a vacuum furnace, the sintered compact is rapidly cooled with pressurized nitrogen gas to obtain a sintered body that can secure a 10 mm square and a length of 35 mm. It was. In the solidification method using HIP, powder is filled into an iron container having a diameter of 40 mm and a length of 45 mm, the lid is welded, and the inside is vacuum degassed. Thereafter, the vacuum degassed container was subjected to HIP (hot isostatic pressing) at 1150 ° C. and 147 MPa to obtain a 100% density sintered body capable of securing φ35 mm and length of 35 mm.
積層造形法の場合はレーザー光源を用いた積層造形機を用い、純Ａｒガス雰囲気および
純Ｎ2 雰囲気で単純な角形状造形（角１０ｍｍ、長さ５５ｍｍ）を行い、当該寸法の焼結体を得た。焼結体は４８０℃で２時間保持後空冷する条件で時効処理を施し、アルキメデス法やビッカース硬度計にて相対密度と硬度を確認した。また、焼結性評価として、焼結材表面に入った割れ数を目視してカウントし評価した。またＸ線回折法のＦＣＣとＢＣＣピーク積分値比較により、焼結材の残留オーステナイト量を測定した。
In the case of additive manufacturing, an additive manufacturing machine using a laser light source is used to perform simple rectangular shape modeling (10 mm square, 55 mm length) in a pure Ar gas atmosphere and a pure N 2 atmosphere, and a sintered body having the dimensions is obtained. Obtained. The sintered body was aged at a temperature of 480 ° C. for 2 hours and then air-cooled, and the relative density and hardness were confirmed by Archimedes method or Vickers hardness tester. Further, as a sinterability evaluation, the number of cracks that entered the surface of the sintered material was visually counted and evaluated. Further, the amount of retained austenite of the sintered material was measured by comparing the FCC and BCC peak integral values of the X-ray diffraction method.
表１に示す比較例Ｎｏ．２１は、Ｃ、Ｎ含有量が高いため、焼結体のマルテンサイト組織の含有量が低くなり、時効時の硬度が低くなった。比較例Ｎｏ．２２は、Ｓｉの含有量が高いため、焼結体のマルテンサイト組織の含有量は低いものの高硬度が得られるが、Ｓｉ固溶強化による基地硬さが向上したためであり、Ｎｉ−ｂａｌの値も低いために、焼結体には割れが発生し、実用的な焼結体が得られない。比較例Ｎｏ．２３は、Ｍｎの含有量が高いため、焼結体のマルテンサイト組織の含有量が低くなり、かつＮｂ＋Ｔａの含有量が低く、十分な析出硬化能が得られなくなることと、ＣがＮｂおよびＴａで固定されていないため、Ｃｒ炭化物が析出しやすくなったため、割れが発生した。 Comparative Example No. 1 shown in Table 1 No. 21 had a high C and N content, so the martensite structure content of the sintered body was low, and the hardness at the time of aging was low. Comparative Example No. No. 22 has a high Si content, so that a high hardness is obtained although the content of the martensite structure of the sintered body is low. However, the base hardness is improved by Si solid solution strengthening, and the value of Ni-bal Therefore, the sintered body is cracked and a practical sintered body cannot be obtained. Comparative Example No. 23, since the content of Mn is high, the content of the martensite structure of the sintered body is low, and the content of Nb + Ta is low, so that sufficient precipitation hardening ability cannot be obtained, and C is Nb and Ta. Since it was not fixed by Cr, it became easy for Cr carbide to precipitate, and cracking occurred.
比較例Ｎｏ．２４は、Ｎｉ、Ｎ含有量が高く、Ｎｂ＋Ｔａを添加しても焼結体のマルテンサイト組織の含有量が低くなり、時効時の硬度が低くなった。比較例Ｎｏ．２５は、Ｃｒ含有量が高く、Ｎｉ−ｂａｌの値も低いために主としてマルテンサイト変態が起こらないフェライト組織が多くなることで、焼結体のマルテンサイト組織が相対的に低下、硬度が得られない。また、フェライト組織を起点として焼結体には割れが発生したため、実用的な焼結体が得られない。比較例Ｎｏ．２６は、Ｍｏ、Ｎ含有量が高いことで、焼結体のマルテンサイト組織が相対的に低下、硬度が得られない。 Comparative Example No. No. 24 had a high Ni and N content, and even when Nb + Ta was added, the content of the martensite structure of the sintered body was low, and the hardness at aging was low. Comparative Example No. No. 25 has a high Cr content and a low Ni-bal value, so that the number of ferrite structures that do not cause martensitic transformation mainly increases, so that the martensitic structure of the sintered body is relatively lowered and hardness is obtained. Absent. Moreover, since a crack occurred in the sintered body starting from the ferrite structure, a practical sintered body cannot be obtained. Comparative Example No. No. 26 has a high Mo and N content, so that the martensitic structure of the sintered body is relatively lowered and hardness cannot be obtained.
比較例Ｎｏ．２７は、Ｃｕ含有量が高いため、硬さは確保できるものの焼結時の脆化のため焼結体に割れが発生した。比較例Ｎｏ．２８は、Ｔｉ、Ｎｂ＋Ｔａの含有量が低く、Ｎ含有量が高いため、焼結体のマルテンサイト組織量より残留オーステナイト組織量が多くなることで、析出硬化能はほとんど無くなった。結果として時効時の硬度が低くなった。比較例Ｎｏ．２９は、Ａｌの含有量が高いため、Ｎｉ−ｂａｌの値も低くなり、主としてマルテンサイト変態が起こらないフェライト組織が多くなることで、焼結体のマルテンサイト組織が相対的に低下、硬度が得られない。また、フェライト組織を起点として焼結体には割れが発生したため、実用的な焼結体が得られない。 Comparative Example No. No. 27 had a high Cu content, so that the hardness could be secured, but cracking occurred in the sintered body due to embrittlement during sintering. Comparative Example No. No. 28 has a low content of Ti and Nb + Ta and a high N content, so that the retained austenite structure amount is larger than the martensite structure amount of the sintered body, so that the precipitation hardening ability is almost lost. As a result, the aging hardness was low. Comparative Example No. No. 29 has a high Al content, so the value of Ni-bal is also low, and the ferrite structure in which martensite transformation does not occur mainly increases, so that the martensitic structure of the sintered body is relatively lowered and the hardness is low. I can't get it. Moreover, since a crack occurred in the sintered body starting from the ferrite structure, a practical sintered body cannot be obtained.
比較例Ｎｏ．３０は、Ｎの含有量が高いことにより、焼結体のマルテンサイト組織の含有量が低くなり、時効時の硬度が低くなった。これに対し、本発明例Ｎｏ．１〜２０は、いずれも本発明の条件を満たしていることから、粉末焼結法、ＨＩＰによる固化法、または積層造形法の全ての焼結製法において本発明材はすべて３９０ＨＶ以上を確保でき、かつ割れのない高硬度材を得ることが出来た。特に積層造形のＡｒ雰囲気で造形したものは４２５ＨＶ以上を確保できた。 Comparative Example No. No. 30 had a high content of N, so that the content of the martensite structure of the sintered body was low, and the hardness at the time of aging was low. On the other hand, the present invention example No. Since 1 to 20 all satisfy the conditions of the present invention, all of the present invention materials can ensure 390 HV or more in the powder sintering method, the solidification method by HIP, or all the sintering methods of the additive manufacturing method, In addition, a high hardness material without cracks could be obtained. Especially 425 HV or more was ensured in the layered modeling Ar atmosphere.
以上述べたように、本発明による析出硬化ステンレス鋼粉末の成分組成とＮｉ−ｂａｌと窒素量を制御することで析出硬化ステンレス鋼の範囲を制限し、造形のままで残留オーステナイトがなく、しかもマルテンサイト組織とすることで、時効硬化能を十分に発揮した高強度の優れた割れのない析出硬化型ステンレス鋼粉末およびその成形体を提供するものである。
特許出願人 山陽特殊製鋼株式会社
代理人 弁理士 椎 名 彊
As described above, the composition of the precipitation hardened stainless steel powder according to the present invention, the Ni-bal and the nitrogen content are controlled to limit the range of the precipitation hardened stainless steel, and there is no retained austenite as it is shaped. By providing a site structure, the present invention provides a high-strength, excellent crack-free precipitation-hardening stainless steel powder that sufficiently exhibits age-hardening ability and a molded body thereof.
Patent Applicant Sanyo Special Steel Co., Ltd.
Attorney: Attorney Shiina
Claims (4)
Ｃ：≦０．０５％、
Ｓｉ：≦１．０％、
Ｍｎ：≦１．５％、
Ｎｉ：３．０〜８．５％、
Ｃｒ：１２．０〜２０．０％、
Ｍｏ：０．１〜２．５％、
Ｃｕ：１．０〜５．０％、
Ｎｂ＋Ｔａ≧５Ｃ、
Ｎ≦３５０ｐｐｍ
残部Ｆｅおよび不可避的不純物からなり、かつ下記式（１）のＮｉ−ｂａｌ．が−４以上であること、を特徴とする析出硬化型ステンレス鋼粉末。
Ｎｉ−ｂａｌ．＝Ｎｉ＋２７Ｃ＋２３Ｎ＋０．２Ｍｎ＋０．３Ｃｕ−１．２（Ｃｒ＋Ｍｏ）−０．５Ｓｉ−０．３Ｎｂ＋１０ ・・・（１）
但し、（１）式中のＮｉ，Ｃ，Ｎ，Ｍｎ，Ｃｕ，Ｃｒ，Ｍｏ，Ｓｉ，Ｎｂは上記各元素の質量含有率（質量％）の数値を示す。 % By mass
C: ≦ 0.05%
Si: ≦ 1.0%,
Mn: ≦ 1.5%
Ni: 3.0 to 8.5%,
Cr: 12.0-20.0%,
Mo: 0.1 to 2.5%,
Cu: 1.0-5.0%,
Nb + Ta ≧ 5C,
N ≦ 350ppm
Ni-bal. Of the following formula (1) consisting of the balance Fe and inevitable impurities. Is a precipitation hardening stainless steel powder , characterized in that it is -4 or more.
Ni-bal. = Ni + 27C + 23N + 0.2Mn + 0.3Cu-1.2 (Cr + Mo) -0.5Si-0.3Nb + 10 (1)
However, Ni, C, N, Mn, Cu, Cr, Mo, Si, and Nb in the formula (1) indicate numerical values of mass contents (% by mass) of the respective elements.
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| TWI522192B (en) * | 2012-07-31 | 2016-02-21 | 台耀科技股份有限公司 | Method of producing pressed-and-sintered workpiece and workpiece thereof |
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