JP4094017B2 - Austenitic heat-resistant materials with excellent high-temperature durability, heat-resistant parts, and heat-resistant parts around the engine - Google Patents
Austenitic heat-resistant materials with excellent high-temperature durability, heat-resistant parts, and heat-resistant parts around the engine Download PDFInfo
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Description
本発明は、500〜1000℃の比較的高温域において高温耐久性に優れるとともに、材料の製造性や加工性にも優れるオーステナイト系耐熱材料と、その材料を用いて製造する耐熱部品およびエンジン周り用耐熱部品に関するものである。 The present invention is an austenitic heat-resistant material that is excellent in high-temperature durability in a relatively high temperature range of 500 to 1000 ° C., and also excellent in material manufacturability and workability, heat-resistant parts produced using the material, and engine surroundings It relates to heat-resistant parts.
ガスタービンやエンジン周り等に用いられるバルブやボルト、その他の高温環境で使用される耐熱部品は、高温強度や耐酸化性、耐高温摩擦摩耗特性、組織安定性等の高温耐久性に優れていることが求められる。そのため、従来から、このような用途には、Niを多量に含むオーステナイト系ステンレス鋼やFe基超合金／Ni基超合金などの高価な材料が用いられている。 Valves and bolts used around gas turbines and engines, and other heat-resistant parts used in high-temperature environments are excellent in high-temperature durability such as high-temperature strength, oxidation resistance, high-temperature friction and wear resistance, and tissue stability. Is required. Therefore, conventionally, expensive materials such as austenitic stainless steel and Fe-based superalloy / Ni-based superalloy containing a large amount of Ni have been used for such applications.
高Niの耐熱オーステナイト系ステンレス鋼(材料)としては、例えば、ＳＵＳ３１０Ｓが知られている(例えば、非特許文献１参照)。しかし、この材料は、製造性や加工性(塑性加工性、機械加工性)に劣るため、この材料を用いた部品を工業製品として経済的に製造することが難しいという問題がある。また、この材料は、高温強度や耐酸化性には優れるものの、高温での耐摩擦摩耗性(摩耗粉の発生や粗い摩耗痕の生成)や、金属組織変化による材質変化(高温組織安定性)や寸法変化(寸法安定性)などの点で問題があり、量産化を阻害する要因となっている。加えて、この材料は、Niを20mass％と多量に含有しているため高価であり、より安価な材料が求められている。 As a high Ni heat-resistant austenitic stainless steel (material), for example, SUS310S is known (see, for example, Non-Patent Document 1). However, since this material is inferior in manufacturability and workability (plastic workability, machinability), there is a problem that it is difficult to economically manufacture a part using this material as an industrial product. In addition, this material is excellent in high-temperature strength and oxidation resistance, but it is resistant to friction and wear at high temperatures (generation of wear powder and formation of rough wear marks) and material change due to changes in metal structure (high-temperature structure stability). There is a problem in terms of dimensional change (dimensional stability) and the like, which is a factor that hinders mass production. In addition, this material is expensive because it contains a large amount of Ni at 20 mass%, and a cheaper material is required.
一方、同じオーステナイト系のステンレス鋼であるＳＵＳ３０４などは、ＳＵＳ３１０Ｓと比較してNi含有量が少なく、汎用材として量産されているため安価であり、また、塑性加工性も比較的良好である。しかし、その反面、500〜1000℃の温度域で使用した場合には、焼き付きが発生したり、摺動部に多量の摩耗粉が発生したり、あるいは、耐酸化性が劣るなどの問題がある(例えば、非特許文献１参照)。そのため、ＳＵＳ３０４などのステンレス鋼を、耐熱部品の素材に用いることは難しいのが実状である。
そこで、本発明の目的は、ＳＵＳ３１０Ｓなどの従来の耐熱材料が抱える上記諸問題を解決し、安価で、500〜1000℃の比較的高温域において高温耐久性に優れるとともに、材料の製造性、加工性にも優れるオーステナイト系耐熱材料と、その耐熱材料を用いて製造した耐熱部品やエンジン周り用耐熱部品を提供することにある。 Therefore, the object of the present invention is to solve the above-mentioned problems of conventional heat-resistant materials such as SUS310S, and is inexpensive and excellent in high-temperature durability in a relatively high temperature range of 500 to 1000 ° C. Another object is to provide an austenitic heat-resistant material that is also excellent in heat resistance, a heat-resistant component manufactured using the heat-resistant material, and a heat-resistant component for engine surroundings.
発明者らは、上述した従来技術の諸問題を解決し、安価で、かつ、高温強度や耐酸化性、耐高温摩擦摩耗特性、組織安定性などの高温耐久性に優れるだけでなく、材料の製造性や、塑性加工性、機械加工性等の加工性にも優れる耐熱材料を実現するため、それら諸特性に及ぼす主成分や添加成分の影響について鋭意検討を重ねた。その結果、以下の知見を得た。
（1）安価でかつ高温耐久性に優れた耐熱材料を得るためには、高価なNiの含有量を、ＳＵＳ３１０Ｓに比較して大幅に低下せしめた上で、Crの含有量を狭小な適正範囲に限定するとともに、Cu，Ｎ，Ｃ，Si，Mnを適正量添加することが有効である。
（2）耐高温摩擦摩耗特性を改善するには、Cu，Ｎ，Ca，REMの添加が有効であり、いずれも摩耗粉の発生、粗い摩耗痕の生成を抑制する効果がある。特に、Ca，REMを単独もしくは複合添加した場合には、微量にも拘わらず著しい効果がある。この効果は、上記元素を添加することにより、ペロブスカイト系酸化クロムを主体とする高温酸化保護皮膜が生成するとともに、皮膜と地鉄との境界におけるボイド(空孔)が低減する結果、密着性が向上することによる。
（3）材料の組織安定性を確保するには、従来から知られているＮ添加だけでなく、さらに、Si，Cr，Ni，Cu，Ｃなどの主要成分の含有量を制御し、Ni当量の値を適正範囲に制御する必要がある。
（4）材料の製造性を改善するには、凝固時に生成するδフェライトの量を適正範囲に制御する必要があり、そのためには、δフェライトの予測値δcalが適正範囲となるよう、Si，Cr，Ｃ，Ｎ，Ni，MnおよびCuの含有量を制御することが重要である。
（5）材料の塑性加工性を改善するには、Ｃ，Ｎ量の適正化やCu，Ca，REMの添加だけでなく、Ｃ，Si，Mn，Ni，Cr，CuおよびＮの含有量から予測される硬さＨvを適正範囲に制御することが重要である。
（6）また、本発明材料の優れた特性を、500〜1000℃の温度範囲、特にこの範囲内の高温側で有効に発現させるためには、本発明の耐熱材料を用いて製造した部品の表面に硬質層を設ける表面改質処理を施すことが有効である。
本発明は、上記知見に基づき、開発したものである。
The inventors have solved the above-mentioned problems of the prior art and are not only inexpensive and excellent in high-temperature durability such as high-temperature strength, oxidation resistance, high-temperature friction and wear resistance, and tissue stability, but also In order to realize heat-resistant materials with excellent workability such as manufacturability, plastic workability, and machinability, we conducted extensive studies on the effects of main components and additive components on these properties. As a result, the following knowledge was obtained.
(1) In order to obtain a heat-resistant material that is inexpensive and excellent in high-temperature durability, the content of expensive Ni is greatly reduced as compared to SUS310S, and the Cr content is narrowly in an appropriate range. It is effective to add a proper amount of Cu, N, C, Si, and Mn.
(2) Addition of Cu, N, Ca, and REM is effective in improving the high temperature frictional wear resistance, and all have the effect of suppressing the generation of wear powder and the formation of rough wear marks. In particular, when Ca and REM are added singly or in combination, there is a remarkable effect regardless of the trace amount. This effect is achieved by adding a high-temperature oxidation protective film mainly composed of perovskite-based chromium oxide and reducing voids at the boundary between the film and the ground iron. By improving.
(3) In order to ensure the structural stability of the material, not only the conventionally known N addition, but also the content of main components such as Si, Cr, Ni, Cu, C, etc. is controlled, and the Ni equivalent Must be controlled within the proper range.
(4) In order to improve the manufacturability of the material, it is necessary to control the amount of δ ferrite generated during solidification within an appropriate range. To that end, Si, It is important to control the contents of Cr, C, N, Ni, Mn and Cu.
(5) In order to improve the plastic workability of materials, not only optimization of the amount of C and N and addition of Cu, Ca and REM, but also the content of C, Si, Mn, Ni, Cr, Cu and N It is important to control the predicted hardness Hv within an appropriate range.
(6) Moreover, in order to effectively exhibit the excellent characteristics of the material of the present invention in the temperature range of 500 to 1000 ° C., particularly in the high temperature side within this range, the components manufactured using the heat resistant material of the present invention It is effective to perform a surface modification treatment that provides a hard layer on the surface.
The present invention has been developed based on the above findings.
すなわち、本発明は、Ｃ：0.02〜0.07mass％、Si：0.2〜1.7mass％、Mn：5.0mass％以下、Ni：12.0〜15.0mass％、Cr：22.0〜25.0mass％、Cu：0.5〜4.5mass％、Ｎ：0.05〜0.17mass％、かつ、Ca、REMのうちの１種または２種を0.0005〜0.05mass％含有し、残部がFeおよび不可避的不純物からなり、下記(1)式で定義されるNi当量が30.0以上、下記(2)式で定義されるδcalが0.5〜8.0、下記(3)式で定義されるＨvが120〜160であることを特徴とする高温耐久性に優れるオーステナイト系耐熱材料である。
記
Ni当量＝Ni＋0.65Cr＋1.05Mn＋0.35Si＋0.6Cu＋25.2Ｃ＋12.6Ｎ ・・・ (1)
δcal＝3.2(1.5Si＋Cr)−2.5(30Ｃ＋30Ｎ＋Ni＋0.5Mn＋0.3Cu)−24.7 ・・・ (2)
Ｈv＝87Ｃ＋２Si−1.2Mn−6.7Ni＋2.7Cr−2.6Cu＋690Ｎ＋88 ・・・ (3)
That is, the present invention includes C: 0.02 to 0.07 mass%, Si: 0.2 to 1.7 mass%, Mn: 5.0 mass% or less, Ni: 12.0 to 15.0 mass%, Cr: 22.0 to 25.0 mass%, Cu: 0.5 to 4.5 mass%, N: 0.05 to 0.17 mass%, and one or two of Ca and REM are contained in 0.0005 to 0.05 mass%, with the balance being Fe and inevitable impurities, defined by the following formula (1) Austenite excellent in high temperature durability, characterized in that Ni equivalent is 30.0 or more, δcal defined by the following formula (2) is 0.5 to 8.0, and Hv defined by the following formula (3) is 120 to 160 This is a heat-resistant material.
Record
Ni equivalent = Ni + 0.65Cr + 1.05Mn + 0.35Si + 0.6Cu + 25.2C + 12.6N (1)
δcal = 3.2 (1.5Si + Cr) −2.5 (30C + 30N + Ni + 0.5Mn + 0.3Cu) −24.7 (2)
Hv = 87C + 2Si-1.2Mn-6.7Ni + 2.7Cr-2.6Cu + 690N + 88 (3)
また、本発明は、上記に記載の耐熱材料からなることを特徴とする耐熱部品である。 In addition, the present invention is a heat-resistant component comprising the heat-resistant material described above.
また、本発明は、上記に記載の耐熱材料からなることを特徴とするエンジン周り用耐熱部品である。 Further, the present invention is a heat-resistant component for an engine periphery, characterized by comprising the heat-resistant material described above.
本発明の上記耐熱部品は、部品の表面に硬化層を設けてなることを特徴とする。 The heat-resistant component of the present invention is characterized in that a hardened layer is provided on the surface of the component.
本発明の上記エンジン周り用耐熱部品は、部品の表面に硬化層を設けてなることを特徴とする。 The heat-resistant component for the engine periphery of the present invention is characterized in that a hardened layer is provided on the surface of the component.
本発明によれば、高温強度や耐酸化性、耐高温摩擦摩耗特性、組織安定性などの高温耐久性に優れるだけでなく、材料の製造性や塑性加工性、機械加工性にも優れる耐熱材料を安価に提供することができる。すなわち、本発明によれば、低コスト化と製造性の大幅な改善が図れるだけでなく、ＳＵＳ３１０Ｓと同等もしくはそれ以上の塑性加工性、機械加工性を有し、しかも、ＳＵＳ３１０Ｓと同等もしくはそれ以上の高温における寸法安定性や耐酸化性、高温摩擦摩耗特性、組織安定性を有する耐熱材料を提供することができる。したがって、本発明の材料を用いて製造した耐熱部品は、安価で、しかもＳＵＳ３１０Ｓと同等もしくはそれ以上の高温耐久性を有するので、500〜1000℃の比較的高温度域で使用される各種耐熱部品やエンジン周りに用いられる耐熱部品として好適である。さらに、この温度域の高温側で使用する耐熱部品には、加工後の部品表面を硬質化する改質処理を施すことは、極めて有効である。 According to the present invention, the heat-resistant material not only has excellent high-temperature durability such as high-temperature strength, oxidation resistance, high-temperature friction and wear characteristics, and structural stability, but also excellent material productivity, plastic workability, and machinability. Can be provided at low cost. That is, according to the present invention, not only cost reduction and significant improvement in manufacturability can be achieved, but also plastic workability and machinability equivalent to or higher than SUS310S, and equivalent to or higher than SUS310S. It is possible to provide a heat-resistant material having dimensional stability and oxidation resistance at high temperatures, high-temperature frictional wear characteristics, and structural stability. Therefore, the heat-resistant parts manufactured using the material of the present invention are inexpensive and have high temperature durability equivalent to or higher than SUS310S, so various heat-resistant parts used in a relatively high temperature range of 500 to 1000 ° C. It is suitable as a heat-resistant component used around the engine. Furthermore, it is extremely effective to subject the heat-resistant parts used on the high temperature side of this temperature range to a modification process that hardens the surface of the parts after processing.
本発明の課題は、上述したように、ＳＵＳ３１０Ｓなどの高Ni耐熱ステンレス鋼を一般耐熱部品やエンジン周りの耐熱部品に適用しようとした場合に起こる、材料が高価で、製造性や塑性加工性、機械加工性が劣るという問題点、ならびに、汎用材であるＳＵＳ３０４を適用した場合に起こる、高温耐久性に劣る、即ち、耐高温酸化性や高温摩擦摩耗性が劣り、しかも熱サイクルによる寸法変化を生じやすいという問題点を改善することによって、既存の高Ni耐熱ステンレス鋼に代わることのできる耐熱材料を安価に提供することにある。これらの諸課題は、耐熱材料を構成する主要成分や添加成分の含有量を個々に調整することである程度まで改善することができる。しかし、その効果は十分なものとは言えず、成分全体の組成バランスを考慮することが重要である。以下に、本発明の技術思想、特徴、新知見、原理および機構について具体的に説明する。 As described above, the problem of the present invention is that when high Ni heat resistant stainless steel such as SUS310S is applied to general heat resistant parts and heat resistant parts around the engine, the material is expensive, manufacturability and plastic workability, The problem of inferior machinability, as well as inferior high-temperature durability that occurs when SUS304, a general-purpose material, is applied. By improving the problem of being easily generated, the object is to provide a low-temperature heat-resistant material that can replace the existing high-Ni heat-resistant stainless steel. These problems can be improved to some extent by individually adjusting the contents of main components and additive components constituting the heat-resistant material. However, the effect cannot be said to be sufficient, and it is important to consider the compositional balance of the whole component. The technical idea, features, new knowledge, principles and mechanism of the present invention will be specifically described below.
[１] 高温耐久性
本発明の耐熱材料およびこの材料から製造した耐熱部品にとって、高温耐久性は、極めて重要な特性である。ここで、本発明における上記高温耐久性とは、高温引張特性(引張強度、伸び、寸法安定性)、耐酸化性、耐高温摩擦摩耗特性および組織安定性を総称したものである。
[1] High-temperature durability High-temperature durability is a very important characteristic for the heat-resistant material of the present invention and the heat-resistant parts produced from this material. Here, the high temperature durability in the present invention is a general term for high temperature tensile properties (tensile strength, elongation, dimensional stability), oxidation resistance, high temperature friction and wear properties, and structure stability.
（1）高温引張特性(引張強度、伸び、寸法安定性)
図１は、本発明の耐熱材料(後述する実施例の表１の発明材料Ａ、以下、「本発明材料」とも言う)と現用のＳＵＳ３１０Ｓについて、600〜900℃の温度範囲で引張特性の温度依存性を調査した結果を示したものである。図１から、引張強度の温度依存性は、本発明材料とＳＵＳ３１０Ｓとの間に特段の差はないものの、各温度における強度は、本発明の方が例外なく大きい。他方、伸びの温度依存性と各温度における伸びについては、両材料間には大きな差がある。例えば、800℃では、ＳＵＳ３１０Ｓの伸びは80％にも達するのに対し、本発明材料では30％程度であることがわかる。この伸びの違いは、両材料の高温における粒内変形と粒界変形のバランスが異なるためと推定される。また、この違いは、高温での使用中における寸法安定性とも関係しており、過度に変形し易いＳＵＳ３１０Ｓより、適度に変形する本発明材料のほうが、寸法安定性に優れることを示すものである。言い換えれば、このような巨視的な全伸び(破断伸び)の大きな差は、材料内部の局部的な変形量とその不均一性の発現に関与しており、その程度が本発明材料のほうが少ない。このことが、高温使用時の負荷ならびに熱サイクルによる局部変形とその蓄積を減少し、寸法安定性を向上させることになる。なお、本発明材料は、全伸びが800℃でも30％もあるので、オーステナイト系材料に特有の、冷却過程において生じ易い延性低下高温割れに対しても充分な抵抗性をもつものである。
(1) High temperature tensile properties (tensile strength, elongation, dimensional stability)
FIG. 1 shows the temperature of the tensile properties in the temperature range of 600 to 900 ° C. for the heat-resistant material of the present invention (Inventive material A in Table 1 of Examples described later, hereinafter also referred to as “the present invention material”) and the current SUS310S. The result of investigating the dependency is shown. From FIG. 1, the temperature dependence of the tensile strength is not particularly different between the material of the present invention and SUS310S, but the strength at each temperature is greater in the present invention without exception. On the other hand, there is a large difference between the two materials regarding the temperature dependence of elongation and the elongation at each temperature. For example, at 800 ° C., the elongation of SUS310S reaches as high as 80%, whereas the material of the present invention is about 30%. This difference in elongation is presumed to be because the balance between intragranular deformation and intergranular deformation at high temperatures of both materials is different. This difference is also related to dimensional stability during use at high temperature, and shows that the material of the present invention that is deformed moderately is superior to SUS310S that is easily deformed excessively. . In other words, such a large difference in macroscopic total elongation (breaking elongation) is related to the local deformation amount inside the material and the expression of the non-uniformity, and the degree is less in the material of the present invention. . This reduces local deformation and accumulation due to load and heat cycle during high temperature use, and improves dimensional stability. The material of the present invention has a sufficient elongation resistance against high temperature cracking, which is characteristic of austenitic materials and easily occurs in the cooling process, because the total elongation is as high as 30% even at 800 ° C.
（2）耐酸化性
図２は、本発明の耐熱材料(後述する実施例の表１の発明材料Ａ)と現用のＳＵＳ３１０ＳおよびＳＵＳ３０４を、10vol％水蒸気添加大気雰囲気中で、850℃で30分保持する熱処理を100サイクル行う酸化試験を行ったときの、酸化増量を測定した結果を示したものである。図２から、本発明材料とＳＵＳ３１０Ｓとでは、耐酸化性に差がないことがわかる。これは、図３に示した、酸化試験後の試料のスケール断面をＸ線マイクロアナライザーで分析した結果から明らかなように、本発明材料、ＳＵＳ３１０Ｓともに、表面にペロブスカイト系Cr2Ｏ3を主体とする保護皮膜が生成しており、これによって、酸素が内方へ拡散するのを抑制しているからである。このことのために、本発明では、Cr量を比較的狭い範囲に限定したのである。なお、図４に示した、酸化試験後の試料のスケール断面を光学顕微鏡で観察した結果からわかるように、本発明材料とＳＵＳ３１０Ｓとは、酸化の程度が同等であるが、ＳＵＳ３０４は、著しく酸化が進行しており、耐熱材料として使用できるような耐酸化性を有していないことがわかる。
(2) Oxidation resistance FIG. 2 shows the heat resistant material of the present invention (Inventive material A in Table 1 of Examples described later) and the current SUS310S and SUS304 in an atmosphere of 10 vol% steamed atmosphere at 850 ° C. for 30 minutes. It shows the results of measuring the amount of increase in oxidation when an oxidation test is performed in which the heat treatment to be held is performed 100 cycles. FIG. 2 shows that there is no difference in oxidation resistance between the material of the present invention and SUS310S. As is clear from the result of analyzing the scale cross section of the sample after the oxidation test shown in FIG. 3 with an X-ray microanalyzer, both the material of the present invention and SUS310S are mainly composed of perovskite Cr 2 O 3 on the surface. This is because a protective film is formed, which suppresses the diffusion of oxygen inward. For this reason, in the present invention, the Cr content is limited to a relatively narrow range. As can be seen from the result of observing the scale cross section of the sample after the oxidation test shown in FIG. 4 with an optical microscope, the material of the present invention and SUS310S are equivalent in degree of oxidation, but SUS304 is significantly oxidized. It can be seen that the film does not have oxidation resistance that can be used as a heat-resistant material.
（3）高温摩擦摩耗特性
本発明材料(後述する実施例の表１の発明材料Ａ)とＳＵＳ３１０Ｓについて高温摩擦摩耗試験を行った場合、両者ともに焼き付きの発生はなく、また動摩擦係数にも差はなく、ほぼ同等の摩擦特性をもつが、摩耗に関しては両者間で大きな差がある。例えば、800℃の大気雰囲気中で、ピン、ディスクが同材の組み合わせのピン−オン−ディスク試験を行った場合、本発明材料では、全摩耗粉の発生量が0.0045ｇに過ぎないのに対し、ＳＵＳ３１０Ｓのそれは0.0215ｇで、本発明材料の約５倍にも達する。また、図５に示した、摩耗痕を走査型電子顕微鏡で観察した結果によると、本発明材料は、遅進行性の微動摩耗が生じているのに対し、ＳＵＳ３１０Ｓでは、進行性の微動摩耗が生じている。また、同図中に示した摩耗痕の表面粗さチャートを比較しても、明らかに本発明材料の粗度は小さく、凹凸も小さい。これらの違いの起こる原因は、本発明の耐熱材料には、Ca，REMが添加され、かつ高Ｎ材であることから、表面に生成したペロブスカイト系Cr2Ｏ3を主体とする保護皮膜の母材との密着性が、これらの添加元素およびその化合物の存在によって改善されたためと考えられる。この事実は、本発明材料がＳＵＳ３１０Ｓよりも高温摩耗特性に優れていることを示すものである。
(3) High-temperature friction and wear characteristics When a high-temperature friction and wear test is performed on the material of the present invention (Invention material A in Table 1 of Examples described later) and SUS310S, neither of them shows seizure, and there is no difference in the dynamic friction coefficient. However, there is a large difference between the two in terms of wear. For example, when a pin-on-disk test is performed in the air atmosphere at 800 ° C. where the pin and the disk are the same material combination, the amount of generated wear powder is only 0.0045 g in the material of the present invention. SUS310S is 0.0215 g, which is about 5 times that of the material of the present invention. Further, according to the result of observing the wear scars with a scanning electron microscope shown in FIG. 5, the material of the present invention shows slow progressive wear, whereas SUS310S has progressive fine wear. Has occurred. Further, even when comparing the surface roughness charts of the wear marks shown in the same figure, the roughness of the material of the present invention is clearly small and the unevenness is also small. The cause of these differences is that the heat-resistant material of the present invention includes Ca and REM, and is a high-N material. Therefore, the mother of the protective film mainly composed of perovskite-based Cr 2 O 3 formed on the surface. This is probably because the adhesion to the material was improved by the presence of these additive elements and their compounds. This fact shows that the material of the present invention is superior to SUS310S in high temperature wear characteristics.
（4）高温組織安定性
オーステナイト系材料は、成分組成によっては、高温で長時間使用した場合、σ相の生成による材質劣化や、粒界への炭化物析出(鋭敏化)による脆化、あるいは高温腐食を引き起こすことがある。これらの問題を改善するためには、オーステナイト相の安定度を高めて室温や高温での組織安定性を確保する必要がある。そのためには、従来から知られているオーステナト安定化元素であるＮの添加だけでは不十分で、下記(1)式；
Ni当量＝Ni＋0.65Cr＋1.05Mn＋0.35Si＋0.6Cu＋25.2Ｃ＋12.6Ｎ ・・・（1）
(但し、各元素記号は、材料中の各元素の含有量(mass％)を示す)
で表されるNi当量の値を適正範囲となるよう、Ni，Cr，Mn等主要成分の含有量を制御する必要がある。
(4) High-temperature structure stability Depending on the composition of austenitic materials, when used for a long time at high temperatures, material deterioration due to the formation of σ phase, embrittlement due to carbide precipitation (sensitization) at grain boundaries, or high temperature May cause corrosion. In order to improve these problems, it is necessary to increase the stability of the austenite phase and ensure the structural stability at room temperature and high temperature. For that purpose, the addition of N, which is a conventionally known austenate stabilizing element, is not sufficient, and the following formula (1):
Ni equivalent = Ni + 0.65Cr + 1.05Mn + 0.35Si + 0.6Cu + 25.2C + 12.6N (1)
(However, each element symbol indicates the content (mass%) of each element in the material)
It is necessary to control the content of main components such as Ni, Cr, Mn so that the Ni equivalent value represented by
図６は、上記式で定義されるNi当量を25〜35の間で変化させた試料を、大気雰囲気中において、850℃で800時間保持する長時間の酸化試験を行い、試験後の金属組織を光学顕微鏡で観察してσ相の生成量を測定し、その量から組織安定性を評価した結果である。この図６から、ＳＵＳ３１０Ｓを超える組織安定性を得るためには、Ni当量を30.0以上とする必要があることがわかる。そこで、本発明では、Ni当量を30.0以上とすることとした。 FIG. 6 shows a sample obtained by changing the Ni equivalent defined by the above formula between 25 and 35 in a long-term oxidation test held at 850 ° C. for 800 hours in an air atmosphere. This is a result of measuring the amount of σ phase produced by observing with an optical microscope and evaluating the tissue stability from the amount. From FIG. 6, it can be seen that the Ni equivalent needs to be 30.0 or more in order to obtain the structural stability exceeding SUS310S. Therefore, in the present invention, the Ni equivalent is set to 30.0 or more.
図７は、本発明の耐熱材料(後述する実施例の表１の発明材料Ａ)とＳＵＳ３１０ＳおよびＳＵＳ３０４の試料を、大気雰囲気中で850℃×800時間の長時間熱処理を施してから、試料断面をＫＯＨエッチングし、光学顕微鏡でσ相の生成状況を観察したときの組織写真である。この写真から、本発明の材料は、σ相(Fe‐Cr金属間化合物)の発生量が、ＳＵＳ３１０Ｓよりもはるかに少ないことがわかる。これは、両材料のCrやその他成分の組成の違いによって、本発明材料のσ相の生成自由エネルギーがＳＵＳ３１０Ｓよりも大きくなったためである。この結果は、本発明材料を用いた耐熱部品が、使用中にσ脆化して破損するのではないかという懸念を払拭するものである。なお、ＳＵＳ３０４では、σ相は殆ど認められないが、図２や図４からわかるように、耐酸化性が劣るため耐熱材料としては事実上、使用が難しい。 FIG. 7 shows a cross section of a sample after heat-treating a heat resistant material of the present invention (Inventive material A in Table 1 of Examples described later) and a sample of SUS310S and SUS304 in an air atmosphere for a long time of 850 ° C. × 800 hours. It is a structure | tissue photograph when KOH etching is observed and the production | generation condition of (sigma) phase is observed with the optical microscope. From this photograph, it can be seen that the material of the present invention generates much less σ phase (Fe—Cr intermetallic compound) than SUS310S. This is because the free energy of formation of the σ phase of the material of the present invention is larger than that of SUS310S due to the difference in the composition of Cr and other components of both materials. This result dispels the concern that heat-resistant parts using the material of the present invention may be broken due to σ embrittlement during use. In SUS304, the σ phase is hardly recognized, but as can be seen from FIGS. 2 and 4, since it has poor oxidation resistance, it is practically difficult to use as a heat resistant material.
また、図８は、本発明の耐熱材料(後述する実施例の表１の発明材料Ａ)とＳＵＳ３１０ＳおよびＳＵＳ３０４の試料を、10vol％水蒸気添加大気雰囲気中で、850℃で30分間保持する熱処理を100サイクル行う酸化試験を行った後、該試料を蓚酸電解エッチングして、Cr炭化物の粒界析出状況を比較した結果を示したものである。これから、本発明材料は、ＳＵＳ３１０Ｓに比べてCr炭化物の粒界析出が少なく、鋭敏化の程度が小さいことがわかる。これは、本発明材料では、Cu，Caなどの粒界偏析元素の添加によって、Cr炭化物の粒界析出が抑制されるのに対して、ＳＵＳ３１０Ｓでは、そのような効果が得られないためと推察される。なお、ＳＵＳ３０４の鋭敏化度は小さいが、前述したように、耐酸化性に乏しく耐熱材料として使用することは難しい。 FIG. 8 shows a heat treatment in which the heat-resistant material of the present invention (Inventive material A in Table 1 of Examples described later) and SUS310S and SUS304 samples are held at 850 ° C. for 30 minutes in a 10 vol% steam-added air atmosphere. FIG. 5 shows the result of comparison of the grain boundary precipitation state of Cr carbide after performing an oxidation test for 100 cycles and then subjecting the sample to oxalic acid electrolytic etching. From this, it can be seen that the inventive material has less grain boundary precipitation of Cr carbide and less sensitization than SUS310S. This is presumed that in the material of the present invention, grain boundary precipitation of Cr carbide is suppressed by the addition of grain boundary segregation elements such as Cu and Ca, whereas SUS310S cannot provide such an effect. Is done. In addition, although the degree of sensitization of SUS304 is small, as described above, it is difficult to use as a heat-resistant material due to poor oxidation resistance.
（5）表面改質処理
本発明の耐熱材料およびそれから製造した耐熱部品は、上記のように、現用のＳＵＳ３１０Ｓと比較しても優れた高温耐久性を有する。しかし、その使用条件や使用環境に応じて、耐熱部品に加工した後、表面改質処理を施して表面に硬質層を形成してから、単品としてあるいは組立品として使用するのが好ましい。特に、本発明の耐熱材料が想定している使用温度範囲(500〜1000℃)の上限近傍の温度で使用する耐熱部品に、表面を硬質化する改質処理を施すことは、極めて有効である。上記表面改質の方法としては、従来公知の方法を用いることができ、例えば、浸炭処理(真空浸炭、プラズマ浸炭、低温浸炭)、浸窒処理(軟窒化を含む)、塩浴処理、拡散浸透処理、物理／化学蒸着、イオンプレーティング、ＴＤ処理、ＤＬＣ処理等、いずれの方法でもよく、耐熱部品に求められる仕様や使用条件、使用環境、製造コストなどを考慮して決定することが好ましい。
(5) Surface modification treatment As described above, the heat-resistant material of the present invention and the heat-resistant parts produced therefrom have excellent high-temperature durability as compared with the current SUS310S. However, it is preferable to use as a single product or as an assembly after processing into a heat-resistant component and then subjecting it to a surface modification treatment to form a hard layer on the surface, depending on the usage conditions and usage environment. In particular, it is extremely effective to subject the heat resistant component used at a temperature near the upper limit of the working temperature range (500 to 1000 ° C.) assumed by the heat resistant material of the present invention to harden the surface. . As the surface modification method, a conventionally known method can be used.For example, carburizing treatment (vacuum carburizing, plasma carburizing, low temperature carburizing), nitrocarburizing treatment (including soft nitriding), salt bath treatment, diffusion infiltration. Any method such as treatment, physical / chemical vapor deposition, ion plating, TD treatment, DLC treatment, etc. may be used, and it is preferable to determine in consideration of specifications, use conditions, use environment, production cost, etc. required for heat-resistant parts.
[２] プロセス技術
上記[１]で述べた、優れた高温特性を有する新しい耐熱材料の開発に当たって考慮すべき重要なことは、材料の製造性と加工性(塑性加工性、機械加工性)である。前者は、材料の製造コストや安定供給性に関係し、後者は、種々の一般耐熱部品やエンジン周り用耐熱部品の製造性に関係するからである。以下、これらの点について具体的に説明する。
[2] Process technology The important points to consider in the development of new heat-resistant materials with excellent high-temperature characteristics described in [1] above are the manufacturability and workability (plastic workability, machinability) of materials. is there. This is because the former is related to the production cost and stable supply of the material, and the latter is related to the productivity of various general heat-resistant parts and heat-resistant parts around the engine. Hereinafter, these points will be specifically described.
（1）材料の製造性
500〜1000℃程度の比較的高温度域で使用される耐熱材料ＳＵＳ３１０Ｓは、希少金属で高価なNiを多量に含有しているため、高コストで、世界経済情勢の影響を受けやすいという問題を抱えている。また、製造性にも問題があり、熱間圧延時に割れを起こし易いため、工程負荷の増大や歩留り低下を招いて、さらなる製造コストの上昇原因となっている。そこで、本発明では、Ni含有量を大幅に削減して原料コストを低減するとともに、凝固組織中に生成し、製造性に大きな影響を及ぼすδフェライトの量に着目し、このδフェライトの生成量を適正範囲に制御することにより、製造性の改善を図っている。
(1) Manufacturability of materials
The heat-resistant material SUS310S used in a relatively high temperature range of about 500 to 1000 ° C contains a large amount of rare metal and expensive Ni, so it is costly and easily affected by the world economic situation. I have it. In addition, there is a problem in manufacturability, and cracking is likely to occur during hot rolling, which causes an increase in process load and a decrease in yield, which further increases manufacturing costs. Therefore, in the present invention, the Ni content is greatly reduced to reduce raw material costs, and attention is paid to the amount of δ ferrite that is produced in the solidified structure and greatly affects manufacturability. Is controlled within an appropriate range to improve manufacturability.
上記δフェライトの生成量は、材料の成分組成から、下記(2)式；
δcal＝3.2(1.5Si＋Cr)−2.5(30Ｃ＋30Ｎ＋Ni＋0.5Mn＋0.3Cu)−24.7 ・・・（2）
(但し、各元素記号は、材料中の各元素の含有量(mass％)を示す)
で予測することができる。
発明者らは、このδcalと製造性(ここでは、熱間圧延材の表面欠陥(割れ)の発生率を採用)との関係を調査した結果、図９に示すように、δcalが0.5〜8.0の範囲で、製造性が良好となり、δcalを上記適正範囲となるよう、オーステナイト相生成元素であるNi，Cu，Ｃ，Ｎ、およびフェライト相生成元素であるCr，Sｉの組成を制御することによって、現用のＳＵＳ３１０Ｓに比べて大幅な製造性の改善が実現できることを見出した。
The amount of δ ferrite produced is expressed by the following formula (2) from the component composition of the material:
δcal = 3.2 (1.5Si + Cr) −2.5 (30C + 30N + Ni + 0.5Mn + 0.3Cu) −24.7 (2)
(However, each element symbol indicates the content (mass%) of each element in the material)
Can be predicted.
As a result of investigating the relationship between this δcal and manufacturability (here, the occurrence rate of surface defects (cracks) in the hot rolled material is adopted), as shown in FIG. 9, δcal is 0.5 to 8.0. By controlling the composition of Ni, Cu, C, N, which are austenite phase forming elements, and Cr, Si, which are ferrite phase forming elements, so that manufacturability is good and δcal is within the above-described range. The present inventors have found that a significant improvement in manufacturability can be realized as compared with the current SUS310S.
上記δcalと製造性との関係について、発明者らは以下のように考えている。
現用のＳＵＳ３１０Ｓが製造性に劣る理由は、鋳造後の凝固組織が、δフェライト相の生成しないオーステナイト(γ)単相組織であり、δフェライト相に優先的に固溶する不純物元素がγ相中に残存し、Ｐ，Ｓの粒界偏析が著しくなる結果、凝固割れや熱間加工時の割れの発生頻度が、凝固組織が(δフェライト＋γ)相となる材料よりも高くなるためである。したがって、鋳造時における凝固割れや熱間加工時の割れを防止し、優れた製造性を確保するためには、凝固組織中に、ある程度の、つまりδcalが0.5以上で実現しうるδフェライト相の存在する(δフェライト＋γ)二相組織とする必要がある。
The inventors consider the relationship between δcal and manufacturability as follows.
The reason why the current SUS310S is inferior in manufacturability is that the solidified structure after casting is an austenite (γ) single-phase structure in which no δ ferrite phase is formed, and an impurity element preferentially dissolved in the δ ferrite phase is contained in the γ phase. This is because the grain boundary segregation of P and S becomes remarkable, and as a result, the frequency of occurrence of solidification cracks and cracks during hot working becomes higher than that of a material whose solidification structure is a (δ ferrite + γ) phase. Therefore, in order to prevent solidification cracking during casting and cracking during hot working and ensure excellent manufacturability, a certain amount of δ ferrite phase can be realized in the solidified structure, that is, δcal is 0.5 or more. The existing (δ ferrite + γ) two-phase structure is required.
しかし、δフェライトの生成量が増加して、(2)式のδcalの値が8.0を超えるようになると、δ相を過度に有する(γ＋δフェライト)の純然たる二相組織となってしまい、硬質相と軟質相が混在して圧延時の負荷に対して応力の不均一分布が生じるため、却って割れが起きやすくなり、製造性が劣化する。また、δフェライト相が多くなって、特性上δフェライトと全く同等の、低温におけるαフェライト相(即ち、両相は、材料学上の慣用的な呼称の違いに過ぎない)が製品まで残存するようになると、高温強度が低下したり、また、αフェライトとオーステナイトの両相の熱膨張差およびその温度依存性の違いにより、使用中に寸法変化を起こしたりする原因となるため好ましくない。従って、凝固後に生成するδフェライトの生成量は、δcalを0.5〜8.0の適正範囲となるよう制御する必要がある。 However, if the amount of δ ferrite produced increases and the value of δcal in equation (2) exceeds 8.0, it becomes a pure two-phase structure of (γ + δ ferrite) that has an excessively δ phase, and is hard. Since a phase and a soft phase coexist and a non-uniform distribution of stress occurs with respect to the load during rolling, cracks tend to occur on the contrary, and the manufacturability deteriorates. In addition, the amount of δ ferrite phase is increased, and the α ferrite phase at low temperature (that is, both phases are just a difference in conventional names in material science), which is exactly equivalent to δ ferrite, remains in the product. If this is the case, it is not preferable because the high-temperature strength is reduced, and a change in the thermal expansion between the α ferrite and austenite phases and the difference in temperature dependence thereof cause a dimensional change during use. Therefore, the amount of δ ferrite generated after solidification needs to be controlled so that δcal is in an appropriate range of 0.5 to 8.0.
（2）塑性加工性の改善
本発明の耐熱材料を用いて耐熱部品を製造する場合には、材料に何らかの塑性加工を加える必要がある。塑性加工の方法は、変形モードによって種々に分類されるが、本発明が対象とする耐熱部品の場合には、主に、伸びフランジ成形、縮みフランジ成形や分離加工(打抜加工)等が多く行われている。このうち、前２者の加工性については、Ｃ，Ｎ量の制御および結晶粒組織の調整のほかに、Cuの適正量(0.5〜4.5mass％)の添加、Ｈvの上限値規制が有効であり、これによって、ＳＵＳ３１０Ｓなどのオーステナイト系ステンレス鋼と同等の加工性が得られる。Cu添加によって塑性加工性が改善される理由は、Cuが積層欠陥エネルギー(面欠陥生成エネルギー)を増大する元素であるためと考えられる。
(2) Improvement of plastic workability When manufacturing a heat-resistant component using the heat-resistant material of the present invention, it is necessary to add some plastic working to the material. Plastic processing methods are classified into various types depending on the deformation mode, but in the case of heat-resistant parts that are the subject of the present invention, there are mainly stretch flange molding, shrink flange molding, separation processing (punching processing), etc. Has been done. Among these, for the workability of the former two, in addition to the control of the C and N amount and the adjustment of the crystal grain structure, the addition of an appropriate amount of Cu (0.5 to 4.5 mass%) and the upper limit regulation of Hv are effective. With this, workability equivalent to that of austenitic stainless steel such as SUS310S can be obtained. The reason why the plastic workability is improved by the addition of Cu is considered to be because Cu is an element that increases the stacking fault energy (surface defect generation energy).
また、Ｈvの上限規制により塑性加工性が改善する理由は、材料の軟質化により、塑性変形時の変形低抗が低減し、変形しやすくなるためである。ここで、上記Ｈvは、下記(３)式；
Ｈv＝87Ｃ＋２Si−1.2Mn−6.7Ni＋2.7Cr−2.6Cu＋690Ｎ＋88 ・・・（３）
（但し、各元素の記号は、材料中の含有量(mass％）を示す)によって、材料の成分組成から計算される値である。
なお、打抜加工性については、Ni低減による粘性低下、Caおよび／またはREMの添加が有効であるが、Ｈvの制御も重要であり、特に、切断面のダレの発生を抑制し、加工後の手入れ省略あるいは簡素化を実現するためには、ある程度の硬さが必要であり、また、切断面のバリの発生を抑制し、加工後の手入れを簡略化するには、硬さが小さい方が望ましいから、上限値および下限値の双方を規制する必要がある。
The reason why the plastic workability is improved by the upper limit of Hv is that the deformation resistance at the time of plastic deformation is reduced and the material is easily deformed by softening the material. Here, the above Hv is the following formula (3);
Hv = 87C + 2Si-1.2Mn-6.7Ni + 2.7Cr-2.6Cu + 690N + 88 (3)
(However, the symbol of each element indicates a content (mass%) in the material), which is a value calculated from the component composition of the material.
For punching workability, it is effective to reduce the viscosity by reducing Ni, and to add Ca and / or REM. However, control of Hv is also important. To achieve omission or simplification of maintenance, a certain degree of hardness is required. Also, to reduce the occurrence of burrs on the cut surface and to simplify the maintenance after processing, the one with low hardness Therefore, it is necessary to regulate both the upper limit value and the lower limit value.
図１０は、Ｈvを90〜190の間で変化させた耐熱材料の冷延板に対して、伸びフランジ成形と打ち抜き加工を行い、図１１に示したような形状、寸法の耐熱部品を製造し、この時の成形部品の割れ発生率と打ち抜き品の剪断面におけるだれの発生状況を評価した結果を示したものである。この図１０から、塑性加工性と打ち抜き性の両特性に優れるためには、Ｈvを120〜160の範囲に制御する必要があることがわかる。 FIG. 10 shows a heat-resistant material having a shape and dimensions as shown in FIG. 11 by performing stretch flange molding and punching on a cold-rolled sheet of heat-resistant material with Hv varied between 90 and 190. The results of evaluating the crack occurrence rate of molded parts at this time and the state of occurrence of dripping on the sheared surface of the punched product are shown. From FIG. 10, it is understood that Hv needs to be controlled in the range of 120 to 160 in order to be excellent in both the plastic workability and the punchability.
（3）機械加工性の改善
一方、機械加工性(主に、切削加工性)の改善については、Caおよび／またはREMの添加が有効である。その理由は、Caおよび／またはREMの添加によって非金属介在物の形態制御がなされること、これらの微量酸化物の生成によって切削工具の先端に形成される構成刃先の出現が抑制されることによって、平面切削性や、ドリル穴あけ、ホーニング加工などの研削性や研摩性が改善されるためである。
(3) Improvement of machinability On the other hand, addition of Ca and / or REM is effective for improving machinability (mainly, machinability). The reason for this is that the addition of Ca and / or REM controls the morphology of non-metallic inclusions, and the generation of these trace amounts of oxide suppresses the appearance of component cutting edges formed at the tip of the cutting tool. This is because surface machinability, grindability such as drilling and honing, and abrasiveness are improved.
[３] 本発明材料の成分組成
本発明材料において、[１]の高温特性および[２]のプロセス技術において述べた新規な現象、知見を発現させるために必要な成分組成と各種パラメータについて説明する。
（1）成分組成の限定理由
Ｃ：0.02〜0.07mass％
Ｃは、オーステナイト組織を安定化する元素であり、高温強度を確保するためにも必要な元素である。それらの効果を得るためには、少なくとも0.02mass％の添加が必要である。しかし、0.07mass％を超えて添加すると、硬さの増加による塑性加工性の劣化や炭化物析出による組織の不安定化を招くので、0.07mass％以下とする。
[3] Component composition of the material of the present invention In the material of the present invention, the component composition and various parameters necessary for expressing the high temperature characteristics of [1] and the new phenomenon and knowledge described in the process technology of [2] will be described. .
(1) Reason for limitation of component composition C: 0.02 to 0.07 mass%
C is an element that stabilizes the austenite structure, and is also an element necessary for ensuring high-temperature strength. In order to obtain these effects, it is necessary to add at least 0.02 mass%. However, if added over 0.07 mass%, it causes deterioration of plastic workability due to increase in hardness and instability of the structure due to carbide precipitation, so 0.07 mass% or less.
Si：0.2〜1.7mass％
Siは、脱酸に必要な元素であり、さらに耐酸化性を向上させる元素である。それらの効果を得るためには、少なくとも0.2mass％の添加が必要である。しかし、1.7mass％を超えて添加すると、連続鋳造時に割れが発生しやすくなる他、σ相の生成を促進したり、高温耐久性をも阻害したりする懸念があるため、上限は1.7mass％とする。
Si: 0.2-1.7mass%
Si is an element necessary for deoxidation, and further improves the oxidation resistance. In order to obtain these effects, it is necessary to add at least 0.2 mass%. However, if added over 1.7 mass%, cracking is likely to occur during continuous casting, and there is a concern of promoting the formation of the σ phase and inhibiting high temperature durability, so the upper limit is 1.7 mass% And
Mn：5.0mass％以下
Mnは、Siと同様、脱酸に必要な元素である。しかし、5.0mass％を超えて添加すると、耐酸化性の劣化を招く。よって、Mnの上限は5.0mass％とする。
Mn: 5.0 mass% or less
Mn is an element necessary for deoxidation like Si. However, if it exceeds 5.0 mass%, the oxidation resistance is deteriorated. Therefore, the upper limit of Mn is 5.0 mass%.
Ni：12.0〜15.0mass％
Niは、オーステナイトを生成させるために添加する元素であり、本発明のオーステナイト系耐熱材料においては必須の重要な元素である。Ni含有量が12.0mass％未満では、高温での組織安定性が劣化する。一方、15.0mass％を超えると、材料の製造性の劣化を招く他、原料コストの上昇を招く。よって、Niの含有量は、12.0〜15.0mass％とする。
Ni: 12.0 to 15.0 mass%
Ni is an element added to generate austenite, and is an essential element essential in the austenitic heat-resistant material of the present invention. When the Ni content is less than 12.0 mass%, the structure stability at high temperatures deteriorates. On the other hand, if it exceeds 15.0 mass%, the manufacturability of the material is deteriorated and the raw material cost is increased. Therefore, the Ni content is 12.0 to 15.0 mass%.
Cr：22.0〜25.0mass％
Crは、Niと同様、本発明のオーステナイト系耐熱材料における必須の重要な元素であり、耐酸化性向上および組織安定性を改善するために添加する。しかし、Cr含有量が22.0mass％未満となると、基本特性として必須の耐酸化性が劣化するばかりでなく、動摩擦係数の上昇によって焼き付きが生じ易くなり、高温摩擦摩耗特性が劣化するので好ましくない。一方、Cr含有量が25.0mass％を超えると、σ相の生成が容易となり、組織安定性が劣化してしまう。よって、Crの含有量は22.0〜25.0mass％の範囲とする。
Cr: 22.0-25.0 mass%
Cr, like Ni, is an essential and important element in the austenitic heat-resistant material of the present invention, and is added to improve oxidation resistance and improve structure stability. However, if the Cr content is less than 22.0 mass%, not only the oxidation resistance, which is essential as a basic characteristic, is deteriorated but also seizure is likely to occur due to an increase in the dynamic friction coefficient, and the high temperature frictional wear characteristic is deteriorated. On the other hand, when the Cr content exceeds 25.0 mass%, the generation of the σ phase becomes easy, and the structure stability deteriorates. Therefore, the Cr content is in the range of 22.0 to 25.0 mass%.
Cu：0.5〜4.5mass％
Cuは、主として組織安定性を向上することによって高温耐久性を改善するとともに、材料の積層欠陥エネルギーを増加させて、転位の交差すべりを容易にするため、硬さを低減して塑性加工性を向上する元素である。これらの効果を得るためには、少なくとも0.5mass％を添加する必要がある。しかし、4.5mass％を超えて添加すると、耐酸化性の劣化が顕著となる。よって、Cuの添加量は0.5〜4.5mass％の範囲とする。好ましくは、0.5〜2.0mass％の範囲である。
Cu: 0.5-4.5mass%
Cu improves the high-temperature durability mainly by improving the structural stability and increases the stacking fault energy of the material to facilitate the cross-slip of dislocations, thus reducing the hardness and improving the plastic workability. It is an element that improves. In order to obtain these effects, it is necessary to add at least 0.5 mass%. However, when it is added exceeding 4.5 mass%, the deterioration of oxidation resistance becomes remarkable. Therefore, the amount of Cu added is in the range of 0.5 to 4.5 mass%. Preferably, it is in the range of 0.5 to 2.0 mass%.
Ｎ：0.05〜0.17mass％
Ｎは、オーステナイト相を安定化するとともに、酸化皮膜の密着性を向上し、摩耗粉の発生を抑制するので、高温耐久性を向上させる効果を有する元素である。さらに、高温強度を高めるため、高温での変形を抑えて、寸法変化を小さくする効果もある。これらの効果を得るためには、少なくとも0.05mass％を含有させることが必要である。しかし、0.17mass％を超えて添加すると、硬さが上昇し過ぎて塑性加工性に対して悪影響を及ぼすようになる。そのため、Ｎの含有量は0.05〜0.17mass％とする。好ましくは0.05〜0.14mass％である。
N: 0.05-0.17mass%
N stabilizes the austenite phase, improves the adhesion of the oxide film, and suppresses the generation of wear powder, so is an element that has the effect of improving high-temperature durability. Further, in order to increase the high temperature strength, there is an effect of suppressing deformation at a high temperature and reducing the dimensional change. In order to obtain these effects, it is necessary to contain at least 0.05 mass%. However, when it exceeds 0.17 mass%, hardness will rise too much and will have a bad influence on plastic workability. Therefore, the N content is 0.05 to 0.17 mass%. Preferably it is 0.05-0.14 mass%.
CaおよびREMのうちの１種または２種：0.0005〜0.05mass％
CaおよびREMは、酸化皮膜の密着性を向上させて摩耗粉の発生を抑制することで、高温耐久性を向上させる。また、機械加工性を向上させる元素でもある。これらの効果は、CaおよびREMの単独添加、複合添加のいずれの場合でも得られが、CaおよびREMの合計で少なくとも0.0005mass％添加する必要がある。しかし、0.05mass％を超えて添加しても、その効果は飽和してしまい、添加量に見合った効果は得られない。よって、CaおよびREMの添加量は、合計で0.0005〜0.05mass％とする。好ましくは0.0005〜0.01mass％である。
One or two of Ca and REM: 0.0005 to 0.05 mass%
Ca and REM improve the high-temperature durability by improving the adhesion of the oxide film and suppressing the generation of wear powder. It is also an element that improves machinability. These effects can be obtained in both cases where Ca and REM are added alone or in combination, but it is necessary to add at least 0.0005 mass% in total of Ca and REM. However, even if added over 0.05 mass%, the effect is saturated and an effect commensurate with the amount added cannot be obtained. Therefore, the total amount of Ca and REM added is 0.0005 to 0.05 mass%. Preferably it is 0.0005-0.01 mass%.
（2）定式パラメータの限定理由
次に、本発明のオーステナイト系耐熱材料において、組織安定性の指標となるNi当量、製造性の指標となるδcalおよび加工性の指標となるＨvを、上記範囲に制限する理由について説明する。
(2) Reason for limitation of formula parameters Next, in the austenitic heat-resistant material of the present invention, Ni equivalent as an index of structure stability, δcal as an index of manufacturability, and Hv as an index of workability fall within the above ranges. The reason for the restriction will be described.
Ni当量≧30.0
Ni当量は、上述したように、室温、高温でのオーステナイト相の安定性に及ぼす成分組成の影響を示す式であり、下記(1)式；
Ni当量＝Ni＋0.65Cr＋1.05Mn＋0.35Si＋0.6Cu＋25.2Ｃ＋12.6Ｎ ・・・（1）
(但し、各元素記号は、材料中の各元素の含有量(mass％)を示す)
で表される。この値が30.0を下回ると組織安定性が低下するため高温耐久性に問題が生じるようになるので、Ni当量は30.0以上とする。オーステナイト相の安定性をより向上させる観点からは、Ni当量は、36以上がより好ましい。
Ni equivalent ≥ 30.0
Ni equivalent is a formula showing the influence of the component composition on the stability of the austenite phase at room temperature and high temperature, as described above, and the following formula (1);
Ni equivalent = Ni + 0.65Cr + 1.05Mn + 0.35Si + 0.6Cu + 25.2C + 12.6N (1)
(However, each element symbol indicates the content (mass%) of each element in the material)
It is represented by If this value is less than 30.0, the stability of the structure deteriorates and high temperature durability becomes problematic, so the Ni equivalent is set to 30.0 or more. From the viewpoint of further improving the stability of the austenite phase, the Ni equivalent is more preferably 36 or more.
δcal：0.5〜8.0
δcalは、先に述べたように、本発明の耐熱材料の製造性に及ぼす成分組成の影響を示す指標であり、下記(2)式；
δcal＝3.2(1.5Si＋Cr)−2.5(30Ｃ＋30Ｎ＋Ni＋0.5Mn＋0.3Cu)−24.7 ・・・（2）
(但し、各元素記号は、材料中の各元素の含有量(mass％)を示す)
で表される。このδcalの値が0.5を下回ると、連続鋳造時の凝固組織が、ほぼオーステナイト(γ)単相組織となり、Ｐ，Ｓなどの不純物元素の粒界偏析が著しくなるため、材料自体が脆弱となり、凝固収縮時や熱間圧延時に割れを生じて、製造性を損ねることとなる。一方、δcalの値が8.0を超えると、(γ＋δ)の二相組織となり、硬質相と軟質相が混在するようになり、圧延時の負荷に対し、応力の不均一分布が生じるため、却って製造性を劣化させる。さらに、加工部品にまで、金属組織としてはδフェライト相と同質のαフェライト相（［００２７］参照）が残存して、高温強度の低下を招く。よって、δcalの値は、0.5〜8.0の範囲とするのが好ましい。より好ましくは、δcalは1.0〜6.0の範囲である。
δcal: 0.5 to 8.0
δcal is an index indicating the influence of the component composition on the manufacturability of the heat-resistant material of the present invention, as described above, and the following formula (2):
δcal = 3.2 (1.5Si + Cr) −2.5 (30C + 30N + Ni + 0.5Mn + 0.3Cu) −24.7 (2)
(However, each element symbol indicates the content (mass%) of each element in the material)
It is represented by If the value of δcal is less than 0.5, the solidified structure during continuous casting is almost an austenite (γ) single-phase structure, and grain boundary segregation of impurity elements such as P and S becomes significant. Cracks occur during solidification shrinkage and hot rolling, thereby impairing manufacturability. On the other hand, when the value of δcal exceeds 8.0, a two-phase structure of (γ + δ) is formed, and a hard phase and a soft phase are mixed, resulting in a non-uniform distribution of stress against the load during rolling. Deteriorate the sex. Furthermore, the α ferrite phase (see [0027]) of the same quality as the δ ferrite phase remains as a metal structure in the processed part, resulting in a decrease in high temperature strength. Therefore, the value of δcal is preferably in the range of 0.5 to 8.0. More preferably, δcal is in the range of 1.0 to 6.0.
Ｈv：120〜160
良好な塑性加工性を確保するためには、材料が適切な硬さを有する必要がある。材料の硬さ(ビッカース硬度Ｈv)は、成分組成との間で、下記(3)式；
Ｈv＝87Ｃ＋２Si−1.2Mn−6.7Ni＋2.7Cr−2.6Cu＋690Ｎ＋88 ・・・（3）
(但し、各元素記号は、材料中の各元素の含有量(mass％)を示す)
で推定され、良好な塑性加工性を得るためには、上記Ｈvが160以下であることが好ましい。Ｈvが160を上回る硬さでは、安定した塑性加工、例えばプレス加工、打ち抜き加工、冷間鍛造などを行うことが難しくなる。一方、Ｈvが120を下回ると、逆に軟質となりすぎ、切断面のだれが大きくなったり(機械加工性の劣化)、寸法精度や形状凍結性が悪化したりする。よって、Ｈvは、120〜160の範囲であることが好ましい。より好ましくは、120〜150の範囲である。
Hv: 120-160
In order to ensure good plastic workability, the material needs to have an appropriate hardness. The hardness of the material (Vickers hardness Hv) depends on the composition of the following formula (3):
Hv = 87C + 2Si-1.2Mn-6.7Ni + 2.7Cr-2.6Cu + 690N + 88 (3)
(However, each element symbol indicates the content (mass%) of each element in the material)
In order to obtain good plastic workability, the Hv is preferably 160 or less. When the hardness is higher than 160, it becomes difficult to perform stable plastic processing, for example, press processing, punching processing, cold forging, and the like. On the other hand, if the Hv is less than 120, on the other hand, it becomes too soft and the cut surface becomes large (deterioration of machinability), and the dimensional accuracy and shape freezing property deteriorate. Therefore, Hv is preferably in the range of 120 to 160. More preferably, it is the range of 120-150.
表１に示すＡ〜Ｌの１２種の成分組成を有する材料を、電気炉＋ＡＯＤ炉を用いて溶製し、連続鋳造して150mm厚×1000mm幅×6000mm長さのスラブとした。このスラブを、1100〜1300℃に加熱し、1000〜1300℃の所定の温度で熱間圧延して板厚が６mmの熱延板とし、この熱延板を、焼鈍・酸洗し、冷間圧延して厚さ３mmの冷延板とし、次いで、1100〜1300℃の範囲内の所定温度で焼鈍して冷延焼鈍板とした。また、参考例として、規格鋼であるＳＵＳ３０４、ＳＵＳ３１０Ｓのスラブからも、上記と同じプロセスで熱延板および冷延焼鈍板を製作した。 The materials having 12 kinds of component compositions A to L shown in Table 1 were melted using an electric furnace + AOD furnace, and continuously cast into a slab of 150 mm thickness × 1000 mm width × 6000 mm length. This slab is heated to 1100-1300 ° C and hot-rolled at a predetermined temperature of 1000-1300 ° C to form a hot-rolled sheet with a thickness of 6 mm. The hot-rolled sheet is annealed, pickled, and cold-rolled. It was rolled into a cold-rolled sheet having a thickness of 3 mm, and then annealed at a predetermined temperature within a range of 1100 to 1300 ° C. to obtain a cold-rolled annealed sheet. As a reference example, hot-rolled sheets and cold-rolled annealed sheets were manufactured from slabs of standard steels SUS304 and SUS310S by the same process as described above.
上記Ａ〜Ｌの材料および参考材料について、製造性を下記要領で評価するとともに、それら材料から製作した熱延焼鈍板および冷延焼鈍板を用いて、下記の評価試験を行った。
＜高温引張試験＞
高温引張試験は、６mm厚の熱延焼鈍板から、平行部が15mm幅×50mm長さの板状試験片(ピン式)を採取し、800℃の大気雰囲気下で、ＪＩＳ Ｇ ０５６７に準拠して、引張強さおよび破断までの伸び(全伸び)を測定した。
＜寸法安定性試験＞
後述する塑性加工性評価のために加工した部品(図１１参照)に対し、大気雰囲気中で、850℃×30分保持する熱処理を100サイクル行い、熱処理前後の寸法変化量を測定し、寸法安定性を評価した。測定は、内径を２ヶ所、それぞれが直角となるように行い、この内径の変化が、熱処理前の内径に対して２％未満であれば良(○)、それ以上であれば不良(×)とする２段階で評価した。
＜酸化試験＞
酸化試験は、ＪＩＳ Ｚ ２２８１に準拠し、10vol％水蒸気添加大気雰囲気中で、850℃で100時間保持する連続酸化試験と、ＪＩＳ Ｚ ２２８２に準拠し、10vol％水蒸気添加大気雰囲気中で、850℃×30分の熱処理を100サイクル行う繰り返し酸化試験を行い、試験後の酸化増量で耐酸化性を評価した。
＜高温摩擦摩耗試験＞
高温摩擦摩耗特性は、一定圧力でピンをディスクに押しつけながら一定時間回転させる、いわゆるピン−オン−ディスク法を用いて評価した。評価試験は、800℃に設定された大気雰囲気中で、2.8mmφのピンを、６mmｔ×50φのディスク上に、荷重49Ｎで押し付けながら、ディスクを周速３m/minで１分間回転させる条件で行った。ディスク中心からピン位置までの距離は、20mmである。耐摩擦摩耗性の評価は、試験中におけるトルクの経時変化から求められる動摩擦係数と、試験終了後の焼付き発生の有無、摩耗粉、摩耗痕の発生状況などから行った。なお、試験に用いたピンおよびディスクは、ピン、ディスクともに上記冷延板、熱延板から採取したものを用いる場合と、ピンにはＳＵＨ６６０(Fe基超合金)製のものを用い、ディスクには上記熱延板から採取したものを用いる場合の２つの組み合わせで行った。因みに、両組み合わせの試験結果は、ほぼ同様であった。
＜表面改質＞
材料Ａから作製した上記ピンおよびディスクの一部については、さらにその試料の表面に硬質層を形成する改質処理を施し、上記と同様の方法の高温摩擦摩耗試験を行い、その有効性を評価した。なお、試験片に施した表面改質処理は、浸炭処理、浸窒処理もしくはクロム拡散浸透処理のいずれかであり、処理後の表面硬度Ｈvは、それぞれ、浸炭処理が850、浸窒処理が800、クロム拡散浸透処理が1200であった。
＜組織安定性＞
組織安定性は、後述する塑性加工性評価のために加工した部品(図１１参照)と、これを大気中で850℃×800時間の長時間熱処理した後の部品と、同じく、塑性加工性評価のために加工した部品に対して、さらに10vol％水蒸気添加大気雰囲気中で、850℃で30分保持する熱処理を100サイクル行う繰り返し酸化試験を行った後の部品について、それぞれの断面をＫＯＨもしくは蓚酸電解エッチングしてから光学顕微鏡でミクロ組織を観察し、αフェライトの残留の有無、σ相の析出の程度およびCr炭窒化物の粒界への析出量すなわち鋭敏化の度合いを調べることにより評価した。
＜製造性＞
製造性は、熱間圧延コイルの表面品質で評価した。すなわち、熱間圧延コイルを焼鈍・酸洗し、その後、このコイルのトップからサンプルを採取して、鋼板表面に発生したスリーバー、ヘゲなどの有害欠陥の個数を目視で測定し、１m2当たり６個以下を良(○)、７個以上を不良(×)と評価した。
＜塑性加工性＞
塑性加工性については、上記冷延焼鈍板から、3.0mmt×200mm×200mmの試験片を採取し、これに伸びフランジ成形と打ち抜き加工を行って、図１１に示した形状の部品を製造し、製品1000個当たりの割れ発生個数、だれによる不良発生個数を調べて、それぞれ６個以下を良(○)、７個以上を劣(×)とする判断基準によって評価した。
＜機械加工性＞
機械加工性は、平面切削性と穴あけ性によって評価した。平面切削性は、試験材として６mm厚の熱延焼鈍板を用い、これを切削工具として超硬合金のバイトを用いて、シェーパーで、切り込み深さ：1.5mm、切削速度：100m/min、切削長さ：200mm/回の平面切削を行い、１本のバイトで切削できる回数を測定し、600回以上を良(○)、200〜600回未満をやや不良(△)および200回未満を不良(×)とする３段階評価によった。また、穴あけ性は、ボール盤で、高速度鋼製ドリルを用いて、水溶性切削油で潤滑しつつ、回転数：1600rpm、送り速度：100mm/minの条件で、試験材(冷延焼鈍板)に３mmφの貫通穴を連続して開け、１本のドリルで加工できた穴数を測定し、600穴数以上を良(○)、200〜600未満の穴数をやや不良(△)、200穴数未満を不良(×)とする３段階評価によった。
Regarding the materials A to L and the reference materials, the manufacturability was evaluated in the following manner, and the following evaluation tests were performed using hot-rolled and cold-rolled annealed plates manufactured from these materials.
<High temperature tensile test>
In the high-temperature tensile test, a plate-shaped test piece (pin type) with a parallel portion of 15 mm width x 50 mm length is taken from a 6 mm thick hot-rolled annealed plate and conforms to JIS G 0567 in an air atmosphere at 800 ° C. The tensile strength and the elongation to break (total elongation) were measured.
<Dimensional stability test>
Parts processed for plastic workability evaluation (see Fig. 11), which will be described later, are subjected to 100 cycles of heat treatment that is held at 850 ° C for 30 minutes in the atmosphere, and the amount of dimensional change before and after the heat treatment is measured. Sex was evaluated. Measurement is performed at two inner diameters at right angles. If the change in the inner diameter is less than 2% of the inner diameter before heat treatment, it is good (○), and if it is more than that, it is bad (×). It was evaluated in two stages.
<Oxidation test>
The oxidation test conforms to JIS Z 2281 and is conducted in a 10 vol% steamed air atmosphere at 100 ° C. for 100 hours, and in accordance with
<High temperature friction wear test>
The high-temperature friction and wear characteristics were evaluated using a so-called pin-on-disk method in which a pin is rotated for a certain time while being pressed against the disk at a constant pressure. The evaluation test is performed in an air atmosphere set at 800 ° C. under the condition that the disk is rotated at a peripheral speed of 3 m / min for 1 minute while pressing a 2.8 mmφ pin onto a 6 mm × 50φ disk with a load of 49 N. It was. The distance from the disk center to the pin position is 20 mm. The evaluation of the friction and wear resistance was performed from the dynamic friction coefficient obtained from the change with time of the torque during the test, the presence or absence of seizure after the test, the occurrence of wear powder, and wear marks. In addition, the pin and the disk used for the test are the case where both the pin and the disk are taken from the cold-rolled plate and the hot-rolled plate, and the pin is made of SUH660 (Fe-base superalloy). Was carried out in two combinations when using a sample taken from the hot-rolled sheet. Incidentally, the test results of both combinations were almost the same.
<Surface modification>
For some of the pins and discs made from material A, the sample is further subjected to a modification treatment to form a hard layer on the surface of the sample, and a high-temperature friction and wear test in the same manner as described above is performed to evaluate its effectiveness. did. The surface modification treatment applied to the test piece is any one of carburizing treatment, nitrocarburizing treatment, and chrome diffusion penetrating treatment, and the surface hardness Hv after the treatment is 850 for carburizing treatment and 800 for nitriding treatment, respectively. The chromium diffusion penetration treatment was 1200.
<Organizational stability>
The stability of the structure is the same as the part processed for the plastic workability evaluation described later (see FIG. 11) and the part after heat treatment in the atmosphere for a long time of 850 ° C. × 800 hours. For the parts after repeated oxidation tests for 100 cycles of heat treatment held at 850 ° C. for 30 minutes in a 10 vol% steam-added air atmosphere, the cross-section of each part was KOH or oxalic acid. It was evaluated by observing the microstructure with an optical microscope after electrolytic etching and examining the presence or absence of α-ferrite, the degree of precipitation of σ phase, and the amount of Cr carbonitride deposited on grain boundaries, that is, the degree of sensitization. .
<Manufacturability>
Manufacturability was evaluated by the surface quality of the hot rolled coil. That is, the hot rolled coil was annealed, pickled, then samples were taken from the top of the coil, Suriba generated on the surface of the steel sheet, the number of harmful defects such as scab was determined visually, 1 m 2 per Six or less were evaluated as good (◯), and seven or more were evaluated as bad (×).
<Plastic workability>
For plastic workability, a 3.0 mmt × 200 mm × 200 mm test piece was sampled from the cold-rolled annealed plate, and subjected to stretch flange molding and punching to produce a part having the shape shown in FIG. The number of cracks generated per 1000 products and the number of defects generated by the sabotage were examined, and evaluation was made according to the judgment criterion that 6 or less was good (◯) and 7 or more was poor (×).
<Machinability>
Machinability was evaluated by plane cutting ability and drilling ability. Planar cutting performance uses a 6mm-thick hot-rolled annealed plate as a test material, using a cemented carbide tool as a cutting tool, with a shaper, cutting depth: 1.5mm, cutting speed: 100m / min, cutting Length: Performs plane cutting at 200mm / time, measures the number of times that can be cut with a single tool, 600 times or more is good (○), 200 to less than 600 times is slightly bad (△), and less than 200 times is bad It was based on a three-step evaluation with (×). In addition, the drillability is a test material (cold-rolled annealed plate) with a drilling machine, using a high-speed steel drill and lubricated with water-soluble cutting oil, at a rotation speed of 1600 rpm and a feed rate of 100 mm / min. 3mmφ through-holes are continuously drilled on the surface, and the number of holes that can be processed with one drill is measured. If the number of holes is 600 or more, good (○), and the number of holes less than 200 to 600 is slightly bad (△), 200 The evaluation was based on a three-level evaluation in which less than the number of holes was regarded as defective (x).
上記各試験の結果を、表２および表３に示した。
これらの結果から、本発明の条件を満たす発明材料(Ａ〜Ｅ)は、高温耐久性に優れていることがわかる。また、これらの材料は、上述した(1)〜(3)式を同時に満たしているので、組織安定性、製造性および加工性(塑性加工性、機械加工性)のいずれにも優れたものとなっている。さらに、本発明材料のＡの冷延焼鈍板に、浸炭処理、浸窒処理あるいはクロム拡散浸透処理のいずれかの改質処理を施し、表面に硬化層を設けた材料についても高温摩擦摩耗性を評価したが、いずれも耐摩耗性は良好であることが確認された(Ａａ，Ａｂ，Ａｃ)。
これに対して、高温耐久性を改善する元素であるCu，Ca，REMを含有していない比較材料Ｆ，Ｈは、酸化試験による酸化増量が多く、摩擦摩耗試験における摩耗粉の発生量が多くて摩耗痕も粗く、しかも鋭敏化の程度も大きく、高温で使用する摺動部品に用いるには適切でない。また、Ｎ含有量が本発明範囲より高い比較材料Ｇは、材料の製造性は良好で、高温強度も高く、高温耐久性は良好であるものの、材料自体が硬質で塑性加工性に劣るため、図１１に示した部品に加工することができなかった。また、Cr含有量が本発明範囲より少ない比較材料Ｉは、摩擦摩耗試験で焼き付きが発生しており、これも高温での使用には難がある。材料の製造性の指標であるδcalが本発明範囲より大きい比較材料Ｊは、高温での摩耗粉の発生、焼き付きの発生はなく良好であるが、熱延板に表面欠陥が発生し、しかも、図１１に示した部品に加工した後でもαフェライト相が残存するため、高温強度、組織安定性がともに劣っている。組織安定性の指標であるNi当量が本発明範囲より低い比較材料Ｋは、組織安定性に難がある。Ｈvが本発明範囲より高い比較材料Ｌは、Ｊと同様、塑性加工性および機械加工性に難があることがわかった。
また、参考例として調査したＳＵＳ３０４は、高温摩擦摩耗試験では焼付きが発生し、酸化試験でも激しい酸化が生じており、耐熱部品としての使用は難しい。同じく参考例として調査したＳＵＳ３１０Ｓは、製造過程でスラブ割れや表面欠陥が発生し、製造性が良好とは言えず、また、高温摩擦摩耗試験では、動摩擦係数が本発明材料と同等で、焼付きは発生しないものの摩耗粉が発生しており、組立品の駆動部分に適用した場合には、摩耗により不具合を発生するおそれが大きく、耐熱部品としての使用はやはり難しい。加えて、これらの参考材料はいずれも、塑性加工性、機械加工性(主に切削性)が良好とはいえない。
The results of the above tests are shown in Tables 2 and 3.
From these results, it can be seen that the inventive materials (A to E) satisfying the conditions of the present invention are excellent in high-temperature durability. In addition, these materials satisfy the above formulas (1) to (3) at the same time, so that they are excellent in all of the structural stability, manufacturability and workability (plastic workability, machinability). It has become. Furthermore, the cold-rolled annealed sheet A of the material of the present invention is subjected to any modification treatment of carburizing treatment, nitriding treatment or chromium diffusion penetration treatment, and a material having a hardened layer on the surface has high-temperature frictional wear resistance. Although it evaluated, it was confirmed that all have favorable abrasion resistance (Aa, Ab, Ac).
In contrast, comparative materials F and H that do not contain Cu, Ca, and REM, which are elements that improve high-temperature durability, have a large amount of oxidation increase by the oxidation test, and a large amount of wear powder is generated in the friction wear test. In addition, the wear scar is rough and the degree of sensitization is large, and it is not suitable for use in sliding parts used at high temperatures. Further, the comparative material G having a higher N content than the scope of the present invention has good material manufacturability, high temperature strength, and good high temperature durability, but the material itself is hard and inferior in plastic workability. The parts shown in FIG. 11 could not be processed. Further, the comparative material I having a Cr content less than the range of the present invention is seized in the frictional wear test, which is also difficult to use at high temperatures. Comparative material J having an index of material manufacturability, which is larger than the range of the present invention, is good without generation of wear powder and seizure at high temperatures, but surface defects occur in the hot-rolled sheet, Even after processing the part shown in FIG. 11, the α-ferrite phase remains, so both the high-temperature strength and the structural stability are inferior. The comparative material K having a Ni equivalent, which is an index of tissue stability, is lower than the range of the present invention has difficulty in tissue stability. It was found that the comparative material L having a Hv higher than the range of the present invention has difficulty in plastic workability and machinability as in the case of J.
In addition, SUS304 investigated as a reference example shows seizure in the high-temperature frictional wear test and severe oxidation in the oxidation test, which makes it difficult to use as a heat-resistant component. SUS310S, which was also investigated as a reference example, produced slab cracks and surface defects in the manufacturing process, and it could not be said that the manufacturability was good. In the high-temperature friction and wear test, the dynamic friction coefficient was the same as that of the material of the present invention and seizure. However, when it is applied to the drive part of an assembly, there is a high risk of occurrence of problems due to wear, and it is still difficult to use as a heat-resistant component. In addition, none of these reference materials has good plastic workability and machinability (mainly machinability).
Claims (5)
記
Ni当量＝Ni＋0.65Cr＋1.05Mn＋0.35Si＋0.6Cu＋25.2Ｃ＋12.6Ｎ ・・・ (1)
δcal＝3.2(1.5Si＋Cr)−2.5(30Ｃ＋30Ｎ＋Ni＋0.5Mn＋0.3Cu)−24.7 ・・・ (2)
Ｈv＝87Ｃ＋２Si−1.2Mn−6.7Ni＋2.7Cr−2.6Cu＋690Ｎ＋88 ・・・ (3) C: 0.02 to 0.07 mass%, Si: 0.2 to 1.7 mass%, Mn: 5.0 mass% or less, Ni: 12.0 to 15.0 mass%, Cr: 22.0 to 25.0 mass%, Cu: 0.5 to 4.5 mass%, N: 0.05 ~ 0.17mass%, and one or two of Ca and REM are contained in 0.0005 ~ 0.05mass%, the balance consists of Fe and inevitable impurities, Ni equivalent defined by the following formula (1) is 30.0 As described above, an austenitic heat-resistant material excellent in high-temperature durability, wherein δcal defined by the following formula (2) is 0.5 to 8.0 and Hv defined by the following formula (3) is 120 to 160.
Record
Ni equivalent = Ni + 0.65Cr + 1.05Mn + 0.35Si + 0.6Cu + 25.2C + 12.6N (1)
δcal = 3.2 (1.5Si + Cr) −2.5 (30C + 30N + Ni + 0.5Mn + 0.3Cu) −24.7 (2)
Hv = 87C + 2Si-1.2Mn-6.7Ni + 2.7Cr-2.6Cu + 690N + 88 (3)
The heat-resistant component for an engine periphery according to claim 3, wherein a hardened layer is provided on the surface of the component.
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