JP5399000B2 - Heat-resistant cast steel jig material for vacuum carburizing heat treatment - Google Patents
Heat-resistant cast steel jig material for vacuum carburizing heat treatment Download PDFInfo
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Description
本発明は、種々の鋼材に真空浸炭熱処理を施す場合に用いられる真空浸炭熱処理用耐熱鋳鋼ジグ（単に真空浸炭用ジグともいう。）および同様な使用環境下で用いることのできる耐真空浸炭性及び耐熱性を有する鋳鋼（単に耐真空浸炭性耐熱鋳鋼ともいう。）に関する。より詳しくは、真空浸炭熱処理において１０００℃以上の温度水準でアセチレンなどの炭化水素によるガス浸炭雰囲気（真空・減圧状態でかつ強還元性或いは超還元性）で使用する熱処理用ジグ及び同様な使用環境下で用いることのできる耐真空浸炭性耐熱鋳鋼に関する。 The present invention relates to a heat-resistant cast steel jig for vacuum carburizing heat treatment (also simply referred to as a jig for vacuum carburizing) used in the case of subjecting various steel materials to vacuum carburizing heat treatment, and vacuum carburization resistance that can be used in a similar use environment. The present invention relates to cast steel having heat resistance (also simply referred to as vacuum carburization-resistant heat-resistant cast steel). More specifically, a jig for heat treatment and a similar use environment used in a gas carburizing atmosphere with a hydrocarbon such as acetylene at a temperature level of 1000 ° C. or higher in vacuum carburizing heat treatment (in a vacuum / depressurized state and strong or superreducible). The present invention relates to a vacuum carburization-resistant heat-resistant cast steel that can be used below.
従来の耐浸炭性耐熱鋳鋼は総て、“有酸素中での使用”を前提として開発されている。その耐浸炭基本機構は、鋳鋼の表面に生じるクロム酸化層、及びその下に生じるシリコン酸化層（セカンドバリヤー）により炭素浸入を阻止することにあった。提案されている従来の耐熱鋳鋼はこの酸化皮膜層を安定化するために、種々のレアアース（Ｚｒ、Ｙなど）を添加したり、アルミニウムを添加してＡｌ２Ｏ３の効果を期待したりしたものであった（例えば、特許文献１〜４参照）。
しかしながら、提案されている従来の耐浸炭性耐熱鋳鋼は、真空浸炭熱処理において１０００℃以上の温度水準でアセチレンなどの炭化水素によるガス浸炭雰囲気で使用する鋳鋼熱処理ジグ材料として利用するには、以下の問題があり、実用上利用困難であった。 However, the proposed conventional carburization-resistant heat-resistant cast steel can be used as a cast steel heat treatment jig material used in a gas carburizing atmosphere with hydrocarbons such as acetylene at a temperature level of 1000 ° C. or higher in vacuum carburizing heat treatment. There was a problem and practical use was difficult.
第１に、真空浸炭熱処理における雰囲気は、強還元性或いは超還元性ともいうべき雰囲気であり、鋳鋼の表面に酸化物は生成し難い。したがって、Ｓｉ、Ａｌ、Ｚｒ、Ｙなどの添加という構成になっていたため、その効果はほとんど無い。 First, the atmosphere in the vacuum carburizing heat treatment is an atmosphere that should be referred to as strong reducibility or super reducibility, and it is difficult for oxides to be generated on the surface of cast steel. Therefore, since it has a configuration of adding Si, Al, Zr, Y, etc., there is almost no effect.
第２に、セカンドバリアーの効果を期待するあまり、Ｓｉの添加を必要以上に増やし、γマトリックス中のカーバイド（炭化物）の周辺にＳｉの偏析を生じ、この周辺の融点が低下し１０００℃以上の温度域ではクリープラプチャー強度が低下する、という事態が生じる。また、真空浸炭雰囲気に於いてはＳｉの添加は耐浸炭性には何ら寄与しない。何となればＳｉＯ２のセカンドバリアー層が出現しないからである。 Secondly, too much anticipation of the effect of the second barrier, the addition of Si is increased more than necessary, and segregation of Si occurs around the carbide (carbide) in the γ matrix, the melting point of this periphery decreases, and the temperature exceeds 1000 ° C. In the temperature range, the creep rupture strength decreases. Further, in the vacuum carburizing atmosphere, addition of Si does not contribute to carburization resistance. This is because the second barrier layer of SiO 2 does not appear.
上記問題点１、２を回避する為、欧州高級車メーカーは、例えばインコネル７１３Ｃ等Ｎｉ含有量が５０質量％以上の高ニッケル合金を使用している。Ｎｉ内部の炭素拡散速度は緩慢であるから耐浸炭性には有利である。また、Ａｌを大量が含有させて得たγプライム（Ｎｉ３Ａｌ相の炭化物）による高温強度も高い。しかし、Ｎｉ含有量が７５質量％と大量の為、Ｎｉ価格の高い国内では実用性に乏しい。また、１０００℃以上の温度領域になると、γプライムが再固溶して分解しクリープラプチャー強度（以下、クリープ破断強度ともいう。）が極端に低くなる等の欠点があるという構成になっている為、実用化には問題点がある。 In order to avoid the above problems 1 and 2, European luxury car manufacturers use high nickel alloys having a Ni content of 50% by mass or more, such as Inconel 713C. Since the carbon diffusion rate inside Ni is slow, it is advantageous for carburization resistance. Moreover, the high temperature strength by the γ prime (Ni 3 Al phase carbide) obtained by containing a large amount of Al is also high. However, since the Ni content is as large as 75% by mass, it is not practical in the country where Ni prices are high. In addition, when the temperature range is 1000 ° C. or higher, the γ prime is dissolved again and decomposes, and the creep rupture strength (hereinafter also referred to as “creep rupture strength”) is extremely low. Therefore, there is a problem in practical use.
そこで本発明の目的は、真空浸炭熱処理において１０００℃以上の温度水準でアセチレン等の炭化水素によるガス浸炭雰囲気で使用することのできる安価で実用性のある真空浸炭用ジグ及び同様な環境下で用いることのできる耐真空浸炭性耐熱鋳鋼を提供するものである。 Therefore, an object of the present invention is to use an inexpensive and practical vacuum carburizing jig that can be used in a gas carburizing atmosphere with a hydrocarbon such as acetylene at a temperature level of 1000 ° C. or higher in a vacuum carburizing heat treatment and in a similar environment. The present invention provides a heat-resistant cast steel that can withstand vacuum carburization.
上記目的を達成する為の本発明は、真空浸炭用ジク鋳鋼材の化学成分組成（質量％）がＣ：０．１５〜０．６０、Ｍｎ：２．００以下、Ｃｒ：１５〜２９、Ｎｉ：１０〜４０、Ｓｉ：１．８以下、Ｎｂ＋Ｔｉ＋（Ｗ／Ｍｏ）：１．８〜２．８である真空浸炭用ジグである。化学成分組成の残部はＦｅおよび不可避の不純物からなるものである。 In order to achieve the above object, the present invention has a chemical component composition (mass%) of vacuum cast carburizing galvanized steel of C: 0.15 to 0.60, Mn: 2.00 or less, Cr: 15 to 29, Ni. : 10 to 40, Si: 1.8 or less, Nb + Ti + (W / Mo): 1.8 to 2.8. The balance of the chemical component composition is composed of Fe and inevitable impurities.
なお、上記真空浸炭用ジグ鋳鋼材の各成分量の単位は、いずれも質量パーセント（質量％）であるため、単位表記を省略している。またＮｂ＋Ｔｉ＋（Ｗ／Ｍｏ）は、Ｎｂかつ、Ｔｉかつ、Ｗおよび／またはＭｏを略記したものである。以下、同様に略記して表すこともある。また、上記化学成分組成は、いずれも化学記号で表示している。 In addition, since the unit of each component amount of the said jig cast steel material for vacuum carburizing is mass percent (mass%), the unit description is abbreviate | omitted. Nb + Ti + (W / Mo) is an abbreviation for Nb, Ti, and W and / or Mo. Hereinafter, it may be abbreviated as well. Moreover, all the said chemical component composition is displayed with the chemical symbol.
本発明によれば、鋼材の化学成分組成については高価なＮｉ量を極力抑えた上で、さらにＳｉ量を１．８質量％以下に制限し、尚且つＮｂ＋Ｔｉ＋（Ｗ／Ｍｏ）を適量添加することで、高耐浸炭性及び高耐熱性を有し安価で実用性のある真空浸炭用ジグを提供することができる。 According to the present invention, with regard to the chemical composition of the steel material, the amount of Si is limited to 1.8% by mass or less while suppressing an expensive amount of Ni as much as possible, and an appropriate amount of Nb + Ti + (W / Mo) is added. Thus, it is possible to provide a jig for vacuum carburization that has high carburization resistance and high heat resistance and is inexpensive and practical.
詳しくは、本発明によれば、真空浸炭熱処理において１０００℃以上の温度水準でアセチレン等の炭化水素によるガス浸炭雰囲気で使用しても、浸炭され難く（浸炭深さが制限され）、高温強度（高いクリープ破断強度）を長期間に安定的に保持できる。そのため、真空浸炭用ジグの耐用期間（寿命）を大幅に延ばすことができる。併せて、同様に優れた耐浸炭性及び耐熱性を備えた安価で実用性のある耐真空浸炭性耐熱鋳鋼を提供することもできる。 Specifically, according to the present invention, even when used in a gas carburizing atmosphere with a hydrocarbon such as acetylene at a temperature level of 1000 ° C. or higher in vacuum carburizing heat treatment, carburization is difficult (the carburizing depth is limited), and high temperature strength ( High creep rupture strength) can be stably maintained over a long period of time. Therefore, the service life (life) of the vacuum carburizing jig can be greatly extended. In addition, an inexpensive and practical vacuum carburization-resistant heat-resistant cast steel having excellent carburization resistance and heat resistance can also be provided.
＜Ｉ＞本発明に係る真空浸炭用ジグについて
本発明に係る真空浸炭用ジグは、該真空浸炭用ジグ鋳鋼材の化学成分組成（質量％）がＣ：０．１５〜０．６０、Ｍｎ：２．００以下、Ｃｒ：１５〜２９、Ｎｉ：１０〜４０、Ｓｉ：１．８以下、Ｎｂ＋Ｔｉ＋（Ｗ／Ｍｏ）：１．８〜２．８であることを特徴とする。なお上記真空浸炭用ジグ鋳鋼材の化学成分組成の残部はＦｅおよび不可避の不純物からなるものである。本発明の真空浸炭用ジグを形成（構成）する鋳鋼材は、Ｆｅと以下に説明するいくつかの添加成分とから構成される鋼材であるが、これら以外の成分（元素）の存在・混入を否定するものではない。したがって、上述した耐真空浸炭性や耐熱性や実用性等の性能・品質・コスト等に影響を与えない限りにおいて、種々の金属・非金属、例えば、Ｃｕ、Ａｓ、Ｓｂ、Ｓｎ、Ｐ、Ｓ、Ｂ、Ｎ、Ｈ、Ｏ等を微量成分として含有していてもよい。例えば、種々の鋼材にＰ、Ｓ等の不可避の不純物（不可避的不純物とも称されている）が微量ながら含まれ得ることは当該分野における周知事項である。
<I> About the vacuum carburizing jig according to the present invention The vacuum carburizing jig according to the present invention has a chemical component composition (mass%) of C: 0.15-0.60, Mn: 2.00 or less, Cr: 15 to 29, Ni: 10 to 40, Si: 1.8 or less, Nb + Ti + (W / Mo): 1.8 to 2.8. The balance of the chemical composition of the vacuum carburizing jig cast steel is composed of Fe and inevitable impurities. The cast steel material forming (constituting) the vacuum carburizing jig of the present invention is a steel material composed of Fe and some additional components described below. There is no denial. Therefore, various metals and non-metals, for example, Cu, As, Sb, Sn, P, S, etc., as long as they do not affect the performance, quality, cost, etc., such as vacuum carburization resistance, heat resistance, and practicality described above. , B, N, H, O, etc. may be contained as trace components. For example, it is a well-known matter in this field that various steel materials can contain unavoidable impurities such as P and S (also referred to as unavoidable impurities) in a small amount.
本発明では、真空浸炭用ジグ鋳鋼材の化学成分組成を上記範囲とすることで、優れた耐真空浸炭性及び耐熱性を発現することができ（詳しくは、後述する実施例の表１の真空下での浸炭深さ及びクリープ破断強度参照）、ジグの耐用期間を大幅に延ばすことができる。加えて、安価で実用性を持たせることもできる。また、鋼材の化学成分組成（特に各成分量の単位）については、特に断らない限り、％は、質量パーセント（質量％）を言うものとする。 In the present invention, by setting the chemical composition of the jig for steel for vacuum carburization within the above range, excellent vacuum carburization resistance and heat resistance can be expressed (for details, refer to the vacuum in Table 1 of Examples described later). (See below carburization depth and creep rupture strength), greatly extending the useful life of the jig. In addition, it is inexpensive and practical. Moreover, about the chemical component composition (especially the unit of each component amount) of steel materials, unless otherwise indicated,% shall mean the mass percentage (mass%).
以下、本発明の真空浸炭用ジグ鋳鋼材の各化学成分ごとに、上記に規定する含有量に限定することによる作用効果につき説明する。 Hereinafter, the effect by limiting to the content prescribed | regulated above for each chemical component of the jig cast steel material for vacuum carburizing of this invention is demonstrated.
（１）Ｓｉ含有量：１．８％以下について
本発明の真空浸炭用ジグ鋳鋼材においては、溶湯の湯流れを良好にして鋳造性を確保する為、Ｓｉを最低限添加量に抑えて、耐浸炭のために添加した元素の粒界の高温強度を確保し、クリープラプチャー強度を高くしたものである。
(1) About Si content: 1.8% or less In the jig steel product for vacuum carburizing of the present invention, in order to ensure the castability by improving the flow of molten metal, Si is suppressed to the minimum addition amount, The high temperature strength of the grain boundaries of the elements added for carburization resistance is ensured, and the creep rupture strength is increased.
Ｓｉの添加を必要以上に増やすと、具体的には１．８％を超えると、γマトリックス中のカーバイドの周辺にＳｉの偏析を生じ、この周辺の融点が低下し１０００℃以上の温度域ではクリープラプチャー強度が低下する。かかる観点から好ましくは１．６％以下が望ましい。一方、Ｓｉの下限量については特に制限されるものではない。ただし、鋳造に際して、湯流れを良好にし鋳造性を良好にすることができるなど、真空浸炭用ジグ鋳鋼材の生産性（製造性）を高めることができる観点から、実操業上はＳｉを１．０％以上含有することが望ましい。従って、Ｓｉ量は、１．８％以下、好ましくは１．０％以上、１．８％以下、より望ましくは１．０％以上、１．６％以下である。 When the addition of Si is increased more than necessary, specifically, if it exceeds 1.8%, segregation of Si occurs around the carbide in the γ matrix, the melting point of this periphery decreases, and in the temperature range of 1000 ° C. or higher. Creep rupture strength decreases. From this viewpoint, it is preferably 1.6% or less. On the other hand, the lower limit amount of Si is not particularly limited. However, from the viewpoint of improving the productivity (manufacturability) of the jig steel product for vacuum carburization, such as a good flow of hot water and good castability during casting, Si is 1. It is desirable to contain 0% or more. Therefore, the Si content is 1.8% or less, preferably 1.0% or more and 1.8% or less, more preferably 1.0% or more and 1.6% or less.
（２）Ｃ含有量：０．１５〜０．６０％について
Ｃは、基地であるＦｅに固溶するほか、Ｃｒ、Ｗ、Ｍｏ、Ｎｂ、Ｔｉ等と炭化物を形成し得る主要成分であり、鋼の高温強度、例えば後述する実施例に示すようなクリープ破壊強度を向上させ得る成分である。而して、Ｃは、０．１５％未満ではＮｂ又はＮｂ、Ｔｉによる炭化物形成に消費されて熱間強度の低下とフェライト相の増加による高温長期間使用中の脆化が著しい。一方、０．６０％を超えると使用中のＣｒの二次炭化物の析出が著しく、熱衝撃割れに敏感になるので０．１５〜０．６０％に限定したものである。フェライト面積率、二次炭化物の析出量を考慮すると、より望ましくは０．２０〜０．５０％である。
(2) About C content: 0.15 to 0.60% C is a main component capable of forming a carbide with Cr, W, Mo, Nb, Ti, etc., in addition to solid solution in Fe as a base, It is a component that can improve the high temperature strength of steel, for example, the creep rupture strength as shown in the examples described later. Thus, if C is less than 0.15%, it is consumed for carbide formation by Nb, Nb, or Ti, and brittleness during use at high temperatures and for a long time due to a decrease in hot strength and an increase in ferrite phase is significant. On the other hand, if it exceeds 0.60%, precipitation of Cr secondary carbide in use becomes remarkable and becomes sensitive to thermal shock cracking, so it is limited to 0.15 to 0.60%. Considering the ferrite area ratio and the amount of precipitation of secondary carbide, it is more preferably 0.20 to 0.50%.
（３）Ｍｎ含有量：２．００％以下について
Ｍｎは鋳造性を高め、脱酸剤として有効であるが、耐酸化性、高温強度を低下させるために２．００％以下に限定したものである。Ｍｎの下限量については、特に制限されるものではない。ただし、溶湯の湯流れを良好にして鋳造性を確保して真空浸炭用ジグ鋳鋼材の生産性（製造性）を高め、尚且つ脱酸剤として有効に寄与することができる観点から、０．５％以上が望ましい。したがって、Ｍｎ含有量は、２．００％以下、より望ましくは０．５％以上２．００％以下である。
(3) About Mn content: 2.00% or less Mn is effective as a deoxidizer for enhancing castability, but is limited to 2.00% or less in order to reduce oxidation resistance and high-temperature strength. is there. The lower limit amount of Mn is not particularly limited. However, from the viewpoint of improving the productivity (manufacturability) of the jig steel material for vacuum carburization by improving the flow of the molten metal and ensuring the castability, it is possible to contribute effectively as a deoxidizer. 5% or more is desirable. Therefore, the Mn content is 2.00% or less, more desirably 0.5% or more and 2.00% or less.
（４）Ｃｒ含有量：１５〜２９％について
Ｃｒは、基地に固溶するほか、Ｃと結合して炭化物を形成する主要成分である。而して、その炭化物が結晶粒界に析出して粒界を強化することにより、鋼の高温強度が向上する。よって、Ｃｒ含有量が１５％未満では高温強度が不足し、２９％を超えると靭性の低下が著しくなるので、１５〜２９％に限定したものである。高温強度とオーステナィトの安定性、炭化物の析出、成長の抑制から、より望ましくは２０〜２８％の範囲である。
(4) About Cr content: 15-29% Cr is a main component which forms a carbide | carbonized_material by couple | bonding with C besides solid solution in a base. Thus, the carbides precipitate at the grain boundaries and strengthen the grain boundaries, thereby improving the high-temperature strength of the steel. Therefore, if the Cr content is less than 15%, the high-temperature strength is insufficient, and if it exceeds 29%, the toughness is remarkably lowered, so the content is limited to 15 to 29%. From the viewpoint of high temperature strength and austenite stability, carbide precipitation, and growth suppression, the range of 20 to 28% is more desirable.
（５）Ｎｉ含有量：１０〜４０％について
Ｎｉは１０％未満では組織が不安定となりフェライトの晶出面積が大きくなり、組織の安定化・靭性の維持には多い程有効である。しかしながら、４０％を超えても、経済上のデメリット（国内での実用性に乏しい点）を解消し得る程の更なる効果はなく４０％を限度とし、１０〜４０％に限定したものである。経済性（実用性）の面から、より望ましくは１０〜３５％の範囲である。
(5) About Ni content: 10 to 40% When Ni is less than 10%, the structure becomes unstable and the crystallization area of ferrite increases, and the more effective the structure is stabilized and the toughness is maintained. However, even if it exceeds 40%, there is no further effect that can eliminate economic disadvantages (poor point of practicability in Japan), and the limit is 40%, limited to 10-40%. . From the viewpoint of economy (practicality), it is more preferably in the range of 10 to 35%.
また、本発明では、更に主要な添加重金属として、Ｎｂ＋Ｔｉ＋（Ｗ／Ｍｏ）の総量を１．８％以上、２．８％以下の範囲に制限してなることを特徴とするものである。すなわち、１．８％≦（Ｎｂ＋Ｔｉ＋Ｗ＋Ｍｏ）≦２．８％、または１．８％≦（Ｎｂ＋Ｔｉ＋Ｗ）≦２．８％、または１．８％≦（Ｎｂ＋Ｔｉ＋Ｍｏ）≦２．８％である。 In addition, the present invention is characterized in that as a main additive heavy metal, the total amount of Nb + Ti + (W / Mo) is limited to a range of 1.8% or more and 2.8% or less. That is, 1.8% ≦ (Nb + Ti + W + Mo) ≦ 2.8%, or 1.8% ≦ (Nb + Ti + W) ≦ 2.8%, or 1.8% ≦ (Nb + Ti + Mo) ≦ 2.8%.
Ｎｂ＋Ｔｉ＋（Ｗ／Ｍｏ）の更なる添加により、γ粒界に炭化物が多く析出し、炭素の進入を防ぐため、耐浸炭性が向上する。よって、これらの効果を有効に発現させるためには、Ｎｂ＋Ｔｉ＋（Ｗ／Ｍｏ）の総量は、１．８％以上が必要となる。一方、上記Ｎｂ＋Ｔｉ＋（Ｗ／Ｍｏ）の総量が２．８％を超えると、γマトリックス中の固溶炭素量が枯渇して、マトリックスに微細炭化物の析出が無くなる。これは、クリープラプチャー強度を減じて、実用性が無くなる。上記した効果が顕著に得られることから、上記Ｎｂ＋Ｔｉ＋（Ｗ／Ｍｏ）の総量は、２．４％以上、２．８％以下がより望ましい。即ち、かかる好適な範囲とすることで、γ粒界に炭化物が多く析出し、炭素の進入を防ぐため、耐浸炭性を顕著に高めることができる。更に、γマトリックス中の固溶炭素量が枯渇することなくマトリックスに微細炭化物を効果的に析出し、クリープラプチャー強度を高めることもできる。 By further addition of Nb + Ti + (W / Mo), a large amount of carbide precipitates at the γ grain boundary and prevents the ingress of carbon, so that the carburization resistance is improved. Therefore, in order to effectively express these effects, the total amount of Nb + Ti + (W / Mo) needs to be 1.8% or more. On the other hand, when the total amount of Nb + Ti + (W / Mo) exceeds 2.8%, the amount of dissolved carbon in the γ matrix is depleted and fine carbides are not precipitated in the matrix. This reduces the creep rupture strength and makes it less practical. Since the above-described effects can be obtained remarkably, the total amount of Nb + Ti + (W / Mo) is more preferably 2.4% or more and 2.8% or less. That is, by setting it as this suitable range, since many carbide | carbonized_material precipitates in a (gamma) grain boundary and prevents the approach of carbon, carburization resistance can be improved notably. Furthermore, fine carbides can be effectively precipitated in the matrix without depleting the amount of dissolved carbon in the γ matrix, and the creep rupture strength can be increased.
また、ＷとＭｏについては、両方を添加してもよいし、いずれか一方を添加させるだけでもよい。これは、後述するように、Ｗは、Ｍｏと同様にＣｒとの間で炭化物を形成してクリープ破断強度（高温引張強度）の向上に寄与し、また、耐浸炭性を高めることにも寄与し得るためである。加えて、ＷとＭｏは時の経済事情によってメタル価格が乱高下しやすい。本発明では、安価な方を適時選択することができることから、購入決定に柔軟性が出てより実用性が高くなる点でも優れている。 Moreover, about W and Mo, both may be added and only one may be added. As will be described later, W contributes to the improvement of creep rupture strength (high temperature tensile strength) by forming a carbide with Cr as well as Mo, and also contributes to improving carburization resistance. Because it can. In addition, the metal price of W and Mo is likely to fluctuate depending on the economic situation. In the present invention, since the cheaper one can be selected in a timely manner, the present invention is excellent in that the purchase decision is flexible and the practicality becomes higher.
また、本発明では、Ｎｂ＋Ｔｉ＋（Ｗ／Ｍｏ）の総量に加えて、更にこれら主要な添加金属の各成分の含有量についても、下記の通り限定するのが望ましい。 In the present invention, in addition to the total amount of Nb + Ti + (W / Mo), the content of each component of these main additive metals is preferably limited as follows.
（ａ）Ｎｂ含有量：０．３〜２．８％について
Ｎｂはクリープ破断強度、耐浸炭性を高める。０．３％未満ではその効果が不足するが、多量に添加すると、生成するＮｂＣ炭化物の粗大化、および合金中のＣ量の減少に起因して、高温強度が低下するので、２．８％を限度としたものである。生成するＮｂＣ炭化物の粗大化及び高温強度の低下の抑制から望ましくは１．５％以下とするのがよい。
(A) Nb content: 0.3 to 2.8% Nb increases creep rupture strength and carburization resistance. If the amount is less than 0.3%, the effect is insufficient. However, if added in a large amount, the high temperature strength decreases due to the coarsening of the NbC carbide produced and the decrease in the amount of C in the alloy. Is the limit. Desirably, the NbC carbide content is set to 1.5% or less in view of coarsening of the NbC carbide to be generated and suppression of reduction in high-temperature strength.
（ｂ）Ｔｉ含有量：０．０４〜０．５％について
Ｔｉは炭化物等を形成して高温強度、耐熱衝撃性等、耐浸炭性を高める。このために０．０４％以上を必要とするが、多量の添加はＴｉＣ（チタンカーバイド）析出物の粗大化を招き、かえって強度低下をみるので、０．５％を上限としたものである。特に０．２％を超えると大気溶解鋳造の場合、鋳込時に溶湯中のＴｉが鋳型表面と反応を起こしＴｉ酸化物を生じ、表面欠陥となる場合がある。従って、大気溶解鋳造の場合には、０．１５％以下とするのがよい。
(B) About Ti content: 0.04 to 0.5% Ti forms carbides and the like to enhance carburization resistance such as high temperature strength and thermal shock resistance. For this reason, 0.04% or more is required. However, addition of a large amount leads to coarsening of TiC (titanium carbide) precipitates, and on the contrary, a decrease in strength is observed, so the upper limit is 0.5%. In particular, if it exceeds 0.2%, in the case of atmospheric melting casting, Ti in the molten metal reacts with the mold surface during casting to produce Ti oxide, which may cause surface defects. Therefore, in the case of atmospheric melting casting, it is good to be 0.15% or less.
（ｃ）Ｗ含有量：０．５〜２．８％について
Ｗはマトリックスに固溶すると共に、Ｃｒ−Ｗ系炭化物を形成してクリープ破断強度（高温引張強度）の向上に寄与する。また、耐浸炭性を高める。Ｗが０．５％に満たないと、その効果が不足する。一方、多量に含むと合金の延靱性の低下を招くので、２．８％を上限とし、好ましくは、２．０％以下である。
(C) About W content: 0.5 to 2.8% W is solid-dissolved in the matrix and forms Cr—W-based carbides, contributing to the improvement of creep rupture strength (high temperature tensile strength). It also increases carburization resistance. If W is less than 0.5%, the effect is insufficient. On the other hand, if contained in a large amount, the ductility of the alloy is lowered, so the upper limit is 2.8%, and preferably 2.0% or less.
（ｄ）Ｍｏ含有量：０．２〜２．８％について
Ｍｏは、オーステナイト基地の固溶強化と、Ｃｒ−Ｍｏ系炭化物の形成による粒界強化の作用によりクリープ破断強度（高温引張強度）を高める。また、耐浸炭性を高める。その効果を確保するために、少なくとも０．２％を要するが、多量の添加は合金の延靱性を損なうので、２．８％を上限とし、好ましくは、１．５％以下である。
(D) Mo content: about 0.2 to 2.8% Mo has a creep rupture strength (high temperature tensile strength) due to solid solution strengthening of austenite base and grain boundary strengthening due to formation of Cr-Mo carbide. Increase. It also increases carburization resistance. In order to ensure the effect, at least 0.2% is required. However, addition of a large amount impairs the toughness of the alloy, so the upper limit is 2.8%, and preferably 1.5% or less.
［本発明の真空浸炭用ジグ鋳鋼材及び本発明の耐真空浸炭性耐熱鋳鋼材の化学成分組成の判定基準］
本発明の真空浸炭用ジグ鋳鋼材及び本発明の耐真空浸炭性耐熱鋳鋼材の化学成分組成は、ジグ形成（鋳造）時から浸炭処理に繰り返し使用するにつれ、その炭素含有率が経時的に変化していく。そのため、上述した真空浸炭用ジグ鋳鋼材及び本発明の耐真空浸炭性耐熱鋳鋼材の化学成分組成は、あくまでジグ形成（鋳造）時あるいはジグ形成時と実質的に同じ鋳造ままの炭素比率を維持している部位の化学成分組成をいうものとする。言い換えれば、浸炭処理に繰り返し使用して炭素含有率がジグ形成（鋳造）時とは異なってしまった部位を除く趣旨である。ジグ形成時と実質的に同じ鋳造ままの炭素比率を維持している部位としては、例えば、度重なる真空浸炭処理によっても鋳造ままの炭素比率が実質的に変動しないジグ壁面の深層部分が該当し得る。
[Criteria for determination of chemical composition of jig and steel for vacuum carburization of the present invention and heat resistant cast steel for vacuum carburization resistance of the present invention]
The chemical composition of the vacuum carburized jig cast steel of the present invention and the vacuum carburized heat resistant cast steel of the present invention changes over time as the carbon content changes as it is repeatedly used for carburizing treatment from the time of jig formation (casting). I will do it. Therefore, the chemical composition of the above-described vacuum carburized jig cast steel and the vacuum carburized heat-resistant cast steel of the present invention is maintained at the same as-cast carbon ratio at the time of jig formation (casting) or jig formation. It shall refer to the chemical composition of the part that is being used. In other words, it is intended to exclude parts that have been repeatedly used for carburizing treatment and have a carbon content different from that during jig formation (casting). Examples of the part that maintains the as-cast carbon ratio that is substantially the same as when forming the jig include, for example, the deep part of the jig wall surface where the as-cast carbon ratio does not vary substantially even with repeated vacuum carburization. obtain.
［本発明の真空浸炭用ジグの製造方法］
本発明の真空浸炭用ジグは、耐真空浸炭性耐熱鋳鋼材の原料を下の実施例に説明するような鋳造（鋳鋼生産）技術を用いて製造してもよいし、耐真空浸炭性耐熱鋳鋼の鋼材を切削加工（切断・溶接など）による組立技術などを用いて製造してもよい。あるいはこれらを組み合わせてもよいなど、特に制限されるものではなく、従来公知のジグ製造技術を適用し得るものである。鋳造技術を用いた大量生産方法としては、例えば、「高圧高速自動造型機による砂型鋳造法」、「ロストワックス法」、「シェルモールド法」など模型に金型を使用した製造法がよい。
[Method for producing jig for vacuum carburizing according to the present invention]
The jig for vacuum carburizing according to the present invention may be manufactured by using a casting (cast steel production) technique as described in the examples below, or a vacuum carburizing resistant heat resistant cast steel. These steel materials may be manufactured using an assembly technique by cutting (cutting, welding, etc.). Or they may be combined, and are not particularly limited, and conventionally known jig manufacturing techniques can be applied. As a mass production method using a casting technique, for example, a manufacturing method using a mold for a model such as “sand mold casting method using a high-pressure high-speed automatic molding machine”, “lost wax method”, “shell mold method” is preferable.
［本発明の真空浸炭用ジグの適用範囲］
本発明の真空浸炭用ジグは、種々の鋼材に真空浸炭処理を施す場合に用いられるジグであればよく、例えば、歯車やデファレンシャルギア等の被処理材を真空浸炭炉内で保持するための形状複雑なスケルトンタイプ・フィクスチャーやトレイなどが挙げられる。
[Applicable range of vacuum carburizing jig of the present invention]
The vacuum carburizing jig of the present invention may be a jig used when vacuum carburizing treatment is performed on various steel materials. For example, a shape for holding a workpiece such as a gear or a differential gear in a vacuum carburizing furnace. Complex skeleton type fixtures and trays.
［本発明の真空浸炭用ジグの使用環境］
本発明の真空浸炭用ジグは、真空浸炭熱処理において、長期間安定して使用できるものである。真空浸炭熱処理としては、特に制限されるものではないが、１０００℃以上の温度水準、典型的には１０００〜１１００℃（例えば、ターゲット温度１０５０℃）で、アセチレン等の炭化水素によるガス浸炭雰囲気（真空・減圧状態でかつ強還元性或いは超還元性）で行われるものが挙げられる。ただし、本発明は、これらに何ら制限されるものではなく、各種の改良・改善が施された真空浸炭熱処理法に幅広く適用可能なばかりではなく、後述するようなプラズマ浸炭処理法などにも十分に適用可能である。
[Usage environment of the jig for vacuum carburizing of the present invention]
The jig for vacuum carburizing according to the present invention can be used stably for a long time in vacuum carburizing heat treatment. The vacuum carburizing heat treatment is not particularly limited, but a gas carburizing atmosphere with a hydrocarbon such as acetylene at a temperature level of 1000 ° C. or higher, typically 1000 to 1100 ° C. (for example, a target temperature of 1050 ° C.) Examples thereof include those carried out in a vacuum / depressurized state with strong or super-reducing properties. However, the present invention is not limited to these, and is not only widely applicable to vacuum carburizing heat treatment methods with various improvements and improvements, but is also sufficient for plasma carburizing treatment methods as described later. It is applicable to.
＜ＩＩ＞本発明に係る耐真空浸炭性耐熱鋳鋼について
本発明に係る耐真空浸炭性耐熱鋳鋼は、化学成分組成（質量％）が、Ｃ：０．１５〜０．６０、Ｍｎ：２．００以下、Ｃｒ：１５〜２９、Ｎｉ：１０〜４０、Ｓｉ：１．８以下、Ｎｂ＋Ｔｉ＋（Ｗ／Ｍｏ）：１．８〜２．８であることを特徴とする。なお上記耐真空浸炭性耐熱鋳鋼材の化学成分組成の残部はＦｅおよび不可避の不純物からなるものである。耐真空浸炭性耐熱鋳鋼の化学成分組成を上記範囲とすることで、上記真空浸炭用ジグで説明したと同様の使用環境下で優れた耐真空浸炭性及び耐熱性を発現することができる（詳しくは、後述する実施例の表１の真空下での浸炭深さ及びクリープ破断強度参照）。
<II> About vacuum carburization-resistant heat-resistant cast steel according to the present invention The vacuum carburization-resistant heat-resistant cast steel according to the present invention has a chemical composition (mass%) of C: 0.15 to 0.60, Mn: 2.00. Hereinafter, Cr: 15 to 29, Ni: 10 to 40, Si: 1.8 or less, and Nb + Ti + (W / Mo): 1.8 to 2.8. The balance of the chemical composition of the vacuum carburized heat-resistant cast steel is composed of Fe and inevitable impurities. By setting the chemical composition of the vacuum carburization-resistant heat-resistant cast steel within the above range, it is possible to develop excellent vacuum carburization resistance and heat resistance under the same usage environment as described for the vacuum carburization jig (details). (See the carburizing depth and creep rupture strength under vacuum in Table 1 of Examples described later).
［本発明の耐真空浸炭性耐熱鋳鋼の各合金化学成分含有量］
本発明の耐真空浸炭性耐熱鋳鋼の各合金化学成分の含有量の説明に関しては、上記した本発明の真空浸炭用ジグ鋳鋼材の各合金化学成分の含有量の説明と同様である為、ここでは重複説明を避けるため省略する。
[Chemical component content of each alloy of vacuum carburization-resistant heat-resistant cast steel of the present invention]
The explanation of the content of each alloy chemical component of the vacuum carburization-resistant heat-resistant cast steel of the present invention is the same as the explanation of the content of each alloy chemical component of the vacuum carburizing jig cast steel of the present invention described above. Then, in order to avoid duplication description, it abbreviate | omits.
［本発明の耐真空浸炭性耐熱鋳鋼の利用用途（応用範囲）］
本発明の耐真空浸炭性耐熱鋳鋼は、真空浸炭用ジグ鋳鋼材として有効に利用することができるほか、同様の環境下（１０００℃以上の温度水準でアセチレンなどの炭化水素によるガス浸炭雰囲気）で使用されている各種用途に利用することができる。例えば、上記真空浸炭熱処理に用いられる真空浸炭炉の内張り材や該真空浸炭熱処理に供せられる製品のワーク材などに有効に活用できる。さらに、これよりも比較的温度条件が低いプラズマ浸炭に用いられるプラズマ浸炭用ジグ、プラズマ浸炭炉の内張り材や該プラズマ浸炭処理に供せられる製品のワーク材などにも有効に利用できる。ただし、本発明の耐真空浸炭性耐熱鋳鋼の利用用途は、これらに何ら制限されるものではなく、当該耐真空浸炭性耐熱鋳鋼の持つ優れた耐真空浸炭性ないし耐熱性を有効に利用できる技術分野で幅広く活用できることはいうまでもない。
[Application of vacuum carburized heat-resistant cast steel of the present invention (application range)]
The vacuum carburization-resistant heat-resistant cast steel of the present invention can be effectively used as a jig cast steel material for vacuum carburization, and in a similar environment (gas carburizing atmosphere with hydrocarbons such as acetylene at a temperature level of 1000 ° C. or higher). It can be used for various uses. For example, it can be effectively used for a lining material of a vacuum carburizing furnace used for the vacuum carburizing heat treatment or a workpiece material of a product used for the vacuum carburizing heat treatment. Furthermore, the present invention can be effectively used for plasma carburizing jigs used for plasma carburizing, which have relatively lower temperature conditions than this, lining materials for plasma carburizing furnaces, and work materials for products used for the plasma carburizing treatment. However, the use application of the vacuum carburization-resistant heat-resistant cast steel of the present invention is not limited to these, and the technology that can effectively use the excellent vacuum carburization-resistant or heat resistance of the vacuum carburization-resistant heat-resistant cast steel. Needless to say, it can be widely used in various fields.
［本発明の耐真空浸炭性耐熱鋳鋼の製造履歴］
本発明の耐真空浸炭性耐熱鋳鋼は、各種造型プロセスの砂型、シェルモールド、ロストワックス等で鋳造した鋳鋼製品が挙げられるが、特に製造プロセスに制限されるものではない。
[Production history of vacuum carburization-resistant heat-resistant cast steel of the present invention]
Examples of the vacuum carburization-resistant heat-resistant cast steel of the present invention include cast steel products cast with sand molds, shell molds, lost waxes and the like of various molding processes, but are not particularly limited to the production process.
以下、実施例を用いて本発明を詳細に説明する。 Hereinafter, the present invention will be described in detail using examples.
実施例１〜２及び比較例１〜４
（実験方法）
先ず、実施例１〜２及び比較例１〜４のそれぞれについて、表１に示す合金化学成分組成となるように所定の原料を配合し、高周波誘導加熱炉にてかかる配合物を加熱・溶解した。次いで、かかる溶融物を所定の鋳型に注入することによって、各合金化学成分組成のＪＩＳ Ｇ ０３０７Ａ号試験材（いわゆるＹブロック）を鋳造した。
Examples 1-2 and Comparative Examples 1-4
(experimental method)
First, about each of Examples 1-2 and Comparative Examples 1-4, a predetermined raw material was blended so as to have an alloy chemical component composition shown in Table 1, and the blended material was heated and dissolved in a high-frequency induction heating furnace. . Next, by injecting the melt into a predetermined mold, JIS G 0307A test material (so-called Y block) having a chemical composition of each alloy was cast.
次に、実施例１〜２及び比較例１〜４のそれぞれについて、上記作製したＹブロックから所定の形状の鋼材（試験片）を切り出して、耐浸炭性を調べた。すなわち、各合金化学成分組成のＹブロックからそれぞれ円柱状鋼材（径２０ｍｍ、長さ６０ｍｍ）を切り出した。その鋼材を所定の真空浸炭炉に入れて、炉内温度を１０５０℃（即ち、鋼材が１０５０℃になる）に設定し、浸炭用ガス（アセチレンガス）を所定の流量（ｍ３／ｓ）で供給しながら、炉内圧力を９００Ｐａになるように調整して３００分、真空浸炭熱処理を行った。かかる処理を終了した後、各鋼材の表面を約０．２０ｍｍ間隔で切粉を採取した。そして採取した切粉のＣ量を分析し、表面から深さ方向のＣ量プロファイルを作成し、Ｃ量が鋳放しまま（鋳造まま；ａｓ ｃａｓｔ）材と同量％となる位置を浸炭深さとした。而して、浸炭深さの測定結果を表１に示す。 Next, for each of Examples 1-2 and Comparative Examples 1-4, a steel material (test piece) having a predetermined shape was cut out from the produced Y block, and carburization resistance was examined. That is, a cylindrical steel material (diameter 20 mm, length 60 mm) was cut out from the Y block of each alloy chemical composition. The steel material is put into a predetermined vacuum carburizing furnace, the furnace temperature is set to 1050 ° C. (that is, the steel material becomes 1050 ° C.), and the carburizing gas (acetylene gas) is set at a predetermined flow rate (m 3 / s). While supplying, vacuum carburizing heat treatment was performed for 300 minutes by adjusting the pressure in the furnace to 900 Pa. After finishing this treatment, chips were collected from the surface of each steel material at intervals of about 0.20 mm. Then, the C amount of the collected chips is analyzed, a C amount profile in the depth direction is created from the surface, and the position where the C amount is the same as the as-cast material is determined as the carburization depth. did. Thus, Table 1 shows the measurement results of the carburization depth.
次に、実施例１〜２及び比較例１〜４のそれぞれについて、上記作製したＹブロックから所定の形状の鋼材（試験片）を切り出し、クリープ破断試験による高温強度の評価を行った。すなわち、各合金化学成分組成のＹブロックからそれぞれ円柱状（平行部直径６ｍｍ、ゲージ部長さ２５ｍｍ）の鋼材を切り出した。そして得られた各鋼材に１０５０℃の大気雰囲気中にて、０．４〜３．０Ｋｇ／ｍｍ２の間で９水準の引張応力を付加し、クリープ破断時間（破断寿命）を測定した。得られた結果から求めた１００００時間の破断強度を表１に示す。 Next, about each of Examples 1-2 and Comparative Examples 1-4, the steel material (test piece) of a predetermined shape was cut out from the produced said Y block, and the high temperature strength was evaluated by the creep rupture test. That is, a steel material having a columnar shape (parallel portion diameter 6 mm, gauge portion length 25 mm) was cut out from the Y block of each alloy chemical component composition. Then, 9 levels of tensile stress was applied between 0.4 to 3.0 Kg / mm 2 in the air atmosphere at 1050 ° C., and the creep rupture time (rupture life) was measured. Table 1 shows the breaking strength for 10,000 hours obtained from the obtained results.
注）上記表１中の合金化学成分（質量％）は、鋳造して得られた試験材（鋳鋼材）の化学成分組成を表すものであり、残部は、表中には記載していないが、いずれの実施例及び比較例についても、Ｆｅおよび不可避の不純物からなるものである。 Note) The chemical composition (mass%) of the alloy in Table 1 above represents the chemical composition of the test material (cast steel) obtained by casting, and the remainder is not described in the table. Each of the examples and comparative examples is composed of Fe and inevitable impurities.
（考察）
上記実験結果（表１参照）に基づく、実施例１〜２及び比較例１〜４それぞれの考察を以下に示す。
(Discussion)
Consideration of each of Examples 1-2 and Comparative Examples 1-4 based on the above experimental results (see Table 1) is shown below.
実施例１
本実施例の合金化学成分組成は、Ｓｉ＝１．３４％（１．０％以上１．６％の範囲）、Ｎｂ＋Ｔｉ＋Ｗ＝２．５７％（１．８％以上、２．８％以下の範囲）であり、真空浸炭性、クリープ破断強度（高温強度、耐熱性）とも良好であることが確認できた。
Example 1
The alloy chemical composition of this example is as follows: Si = 1.34% (1.0% to 1.6% range), Nb + Ti + W = 2.57% (1.8% to 2.8% range) It was confirmed that the vacuum carburization property and the creep rupture strength (high temperature strength, heat resistance) were good.
実施例２
本実施例の合金化学成分組成は、Ｓｉ＝１．３８％（１．０％以上１．６％の範囲）、Ｎｂ＋Ｔｉ＋Ｍｏ＝２．６２％（１．８％以上、２．８％以下の範囲）であり、耐真空浸炭性、クリープ破断強度（高温強度、耐熱性）とも良好であることが確認できた。
Example 2
The alloy chemical composition of this example is as follows: Si = 1.38% (1.0% to 1.6% range), Nb + Ti + Mo = 2.62% (1.8% to 2.8% range) It was confirmed that the vacuum carburization resistance and the creep rupture strength (high temperature strength, heat resistance) were also good.
比較例１
本比較例の合金化学成分組成は、Ｓｉ＝２．１％＞１．６％のためにＳｉが偏析し、この周辺の融点が低下するため、クリープ破断強度（高温強度、耐熱性）が悪化することが確認できた。また、耐真空浸炭性についても実施例１、２に比して３割程度低くなることが確認できた。
Comparative Example 1
In this comparative example, the chemical composition of the alloy is such that Si segregates due to Si = 2.1%> 1.6%, and the melting point around this decreases, so that the creep rupture strength (high temperature strength, heat resistance) deteriorates. I was able to confirm. It was also confirmed that the vacuum carburization resistance was lower by about 30% compared to Examples 1 and 2.
比較例２
本比較例の合金化学成分組成は、Ｎｂ＋Ｔｉ＋Ｍｏ＝３．０２％＞２．８％のために、γ粒界炭化物が析出することにより耐真空浸炭性は向上するが、γマトリックス中の固溶炭素量が枯渇によりクリープ破断強度（高温強度、耐熱性）が悪化することが確認できた。
Comparative Example 2
Since the alloy chemical composition of this comparative example is Nb + Ti + Mo = 3.02%> 2.8%, the vacuum carburization resistance is improved by precipitation of γ grain boundary carbide, but the solid solution carbon in the γ matrix. It was confirmed that the creep rupture strength (high temperature strength, heat resistance) deteriorated due to the depletion of the amount.
比較例３
本比較例の鋼材には開発ベース材（ＳＣＨ２４＝従来鋼と同様の合金化学成分組成）を作製したものである。その合金化学成分組成は、Ｎｂ＋Ｔｉ＋（Ｗ／Ｍｏ）＝０％＜１８％のために、浸炭深さが８００μｍとなり耐真空浸炭性が大幅に低下し、またクリープ破断強度（高温強度、耐熱性）も実施例１、２に比して低く十分でないことが確認できた。
Comparative Example 3
A developed base material (SCH24 = alloy chemical composition similar to that of conventional steel) is prepared for the steel material of this comparative example. Since the chemical composition of the alloy is Nb + Ti + (W / Mo) = 0% <18%, the carburization depth is 800 μm, and the vacuum carburization resistance is greatly reduced, and the creep rupture strength (high temperature strength, heat resistance). It was also confirmed that it was not sufficiently low compared to Examples 1 and 2.
比較例４
本比較例の鋼材にはＳＣＨ２４改良材と同様の合金化学成分組成としたものである。その合金化学成分組成は、Ｎｂ＋Ｔｉ＝０％のままであるが、Ｗ＝１．５％添加により、比較例３に比して若干耐真空浸炭性・クリープ破断強度向上する。しかしながら、浸炭深さは５２０μｍもあり、実施例１、２に比して、耐真空浸炭性が大幅に低く十分でないことが確認できた。また、クリープ破断強度（高温強度、耐熱性）も実施例１、２に比して１割程度低いことも確認できた。
Comparative Example 4
The steel material of this comparative example has an alloy chemical composition similar to that of the SCH24 improving material. The alloy chemical composition remains Nb + Ti = 0%, but the addition of W = 1.5% slightly improves the vacuum carburization resistance and creep rupture strength as compared with Comparative Example 3. However, the carburization depth was 520 μm, and it was confirmed that the vacuum carburization resistance was significantly low and not sufficient as compared with Examples 1 and 2. It was also confirmed that the creep rupture strength (high temperature strength, heat resistance) was about 10% lower than those of Examples 1 and 2.
Claims (4)
Ｃ：０．１５〜０．６０％、
Ｍｎ：２．００％以下、
Ｃｒ：１５〜２９％、
Ｎｉ：１０〜４０％、
Ｓｉ：１．８％以下で、更に
Ｎｂ：０．３〜１．５％、Ｔｉ：０．０４〜０．５％、Ｗ：０．５〜１．１２％の範囲で、尚且つＮｂかつＴｉかつＷの総量が１．８〜２．８％であるか、またはＮｂ：０．３〜１．５％、Ｔｉ：０．０４〜０．５％、Ｍｏ：０．２〜１．５％の範囲で、尚且つＮｂかつＴｉかつＭｏの総量が１．８〜２．８％であり、
残部がＦｅおよび不可避の不純物からなることを特徴とする真空浸炭用ジグ。 In jig casting steel for vacuum carburizing, the chemical composition of the steel is a mass percent,
C: 0.15-0.60%,
Mn: 2.00% or less,
Cr: 15-29%,
Ni: 10 to 40%,
Si: 1.8% or less, and
Nb: 0.3 to 1.5%, Ti: 0.04 to 0.5%, W: 0.5 to 1.12%, and the total amount of Nb, Ti and W is 1.8 to 2.8% , or Nb: 0.3 to 1.5%, Ti: 0.04 to 0.5%, Mo: 0.2 to 1.5%, Nb and Ti And the total amount of Mo is 1.8-2.8%,
A vacuum carburizing jig characterized in that the balance consists of Fe and inevitable impurities.
Ｃ：０．１５〜０．６０％、
Ｍｎ：２．００％以下、
Ｃｒ：１５〜２９％、
Ｎｉ：１０〜４０％、
Ｓｉ：１．８％以下で、更に
Ｎｂ：０．３〜１．５％、Ｔｉ：０．０４〜０．５％、Ｗ：０．５〜１．１２％の範囲で、尚且つＮｂかつＴｉかつＷの総量が１．８〜２．８％であるか、またはＮｂ：０．３〜１．５％、Ｔｉ：０．０４〜０．５％、Ｍｏ：０．２〜１．５％の範囲で、尚且つＮｂかつＴｉかつＭｏの総量が１．８〜２．８％であり、
残部がＦｅおよび不可避の不純物からなることを特徴とする耐真空浸炭性耐熱鋳鋼。 The chemical composition of steel is mass percent,
C: 0.15-0.60%,
Mn: 2.00% or less,
Cr: 15-29%,
Ni: 10 to 40%,
Si: 1.8% or less, and
Nb: 0.3 to 1.5%, Ti: 0.04 to 0.5%, W: 0.5 to 1.12%, and the total amount of Nb, Ti and W is 1.8 to 2.8% , or Nb: 0.3 to 1.5%, Ti: 0.04 to 0.5%, Mo: 0.2 to 1.5%, Nb and Ti And the total amount of Mo is 1.8-2.8%,
A vacuum carburization-resistant heat-resistant cast steel characterized in that the balance consists of Fe and inevitable impurities.
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