JP6725191B2 - Ni-containing high C martensitic heat resistant steel - Google Patents
Ni-containing high C martensitic heat resistant steel Download PDFInfo
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この出願の発明は、高温環境において使用されるＮｉ含有高Ｃマルテンサイト系耐熱鋼に関する。 The invention of this application relates to a Ni-containing high-C martensitic heat-resistant steel used in a high temperature environment.
従来、マルテンサイト系耐熱鋼は、高温において使用されるが、冷間加工性が劣るため、通常は、熱間鍛造により、各部材が製造されている。そのため加工時の材料組織および硬さについては、それほど重要視されていなかった。しかしながら、熱間鍛造による製造では、生産性やコストの面で冷間鍛造に比べて劣るという問題があり、近年、これらマルテンサイト系耐熱鋼の冷鍛化の開発が求められている。この場合、冷間鍛造機などの使用により、素材が加工されるため、加工前の素材硬さが少しでも低いことが求められている。 Conventionally, martensitic heat-resistant steel is used at high temperatures, but since cold workability is poor, each member is usually manufactured by hot forging. Therefore, the material structure and hardness during processing were not so important. However, the manufacturing by hot forging has a problem that it is inferior to the cold forging in terms of productivity and cost, and in recent years, development of cold forging of these martensitic heat-resistant steels has been demanded. In this case, since the material is processed by using a cold forging machine or the like, it is required that the material hardness before processing is as low as possible.
一方、マルテンサイト系耐熱鋼であって冷鍛性に優れた耐熱鋼の製造方法に関する発明として、Ｎｉ含有の高Ｃ系マルテンサイト系耐熱鋼が提案されている（例えば、特許文献１参照。）。しかし、この提案の発明は、Ｃの範囲が十分でなく、またＣｒ含有量が低い成分系であり、炭化物の粒界被覆率が靭性に与える影響および耐酸化性に関する記述がない。 On the other hand, a Ni-containing high C martensitic heat resistant steel has been proposed as an invention relating to a method for producing a martensitic heat resistant steel having excellent cold forging properties (see, for example, Patent Document 1). .. However, the proposed invention is a component system in which the range of C is not sufficient and the Cr content is low, and there is no description about the influence of the carbide grain boundary coverage on the toughness and the oxidation resistance.
さらに、高温使用時に硬さの低減などの特性変化を起こし難いマルテンサイト系耐熱鋼に関する発明が提案されている（例えば、特許文献２参照。）。この発明は、Ｃ：０．３５〜０．６０％、Ｓｉ：１．０〜２．５％、Ｍｎ：０．１％以上１．５％未満、およびＣｒ：７．５〜１３．０％に加えて、請求項１では、Ｍｏ＋０．５Ｗ：１．５〜３．０％を加え、請求項２では、さらにＮｂ＋Ｔａを加え、請求項３では、さらにＶを添加したマルテンサイト系耐熱鋼である。しかし、この提案の発明は、本願の発明とは成分系が異なり、また炭化物の粒界被覆率が靭性に与える影響に関する記述がない。 Furthermore, an invention relating to a martensitic heat-resistant steel that is unlikely to cause a change in properties such as a decrease in hardness when used at high temperatures has been proposed (see, for example, Patent Document 2). This invention is C: 0.35-0.60%, Si: 1.0-2.5%, Mn: 0.1% or more and less than 1.5%, and Cr: 7.5-13.0%. In addition, in claim 1, Mo+0.5W: 1.5-3.0% is added, in claim 2, Nb+Ta is further added, and in claim 3, a martensitic heat-resistant steel further containing V is added. is there. However, the composition of the proposed invention is different from that of the invention of the present application, and there is no description about the influence of the grain boundary coverage of carbides on the toughness.
上記のように、従来技術では０．８％程度のＣおよび２％程度のＮｉを含有しているが、高Ｃｒ系である耐熱鋼に関する記述がない上に、靭性が低く製造性が低いことも問題である。 As described above, the prior art contains about 0.8% C and about 2% Ni, but there is no description about heat-resistant steel that is a high Cr system, and the toughness is low and the manufacturability is low. Is also a problem.
本発明は、高ＣでかつＮｉを含有する高Ｃｒ系の耐熱鋼に係る発明であり、炭化物の粒界被覆率が靭性に影響を与えることを発見したことから着想を得たものであり、さらに、使用環境を考慮して耐酸化性に関しても検討したＮｉ含有高Ｃマルテンサイト系耐熱鋼を提供することである。 The present invention is an invention relating to a high-Cr heat-resisting steel containing high C and Ni, and was conceived from the discovery that the grain boundary coverage of carbides affects toughness, Another object of the present invention is to provide a Ni-containing high C martensitic heat-resistant steel whose oxidation resistance is also considered in consideration of the use environment.
上記の課題を解決するための手段では、開発鋼１の手段は、質量％で、Ｃ：０．４０〜０．８５％、Ｓｉ：０．５０〜２．００％、Ｍｎ：０．１０〜２．００％、Ｐ：≦０．０３０％、Ｎｉ：０．１０〜２．００％、Ｃｒ：１６．００〜２３．５０％、Ｏ：≦０．００８０％、Ｎ：≦０．０６００％を有し、およびＦｅ並びに不可避不純物を有し、シャルピー衝撃値による靱性：５．０Ｊ／ｃｍ2 以上、粒界被覆率指数Ｗ値の１６．３［％Ｃ］＋１５．４×［％Ｎｉ］＋３．３×［％Ｃｒ］：≦１０４であることを特徴とするＮｉ含有高Ｃマルテンサイト系耐熱鋼である。 In the means for solving the above problems, the means of the developed steel 1 is, by mass%, C: 0.40 to 0.85%, Si: 0.50 to 2.00%, Mn: 0.10 to 2.00%, P: ≤ 0.030%, Ni: 0.10 to 2.00%, Cr: 16.00 to 23.50%, O: ≤ 0.0080%, N: ≤ 0.0600%. And Fe and unavoidable impurities, toughness according to Charpy impact value: 5.0 J/cm 2 or more , grain boundary coverage index W value of 16.3 [% C]+15.4×[% Ni] +3.3×[% Cr]:≦104 is a Ni-containing high-C martensitic heat-resistant steel.
開発鋼２の手段は、質量％で、Ｃ：０．４０〜０．８５％、Ｓｉ：０．５０〜２．００％、Ｍｎ：０．１０〜２．００％、Ｐ：≦０．０３０％、Ｎｉ：０．１０〜２．００％、Ｃｒ：１６．００〜２３．５０％、Ｏ：≦０．００８０％、Ｎ：≦０．０６００％を有し、さらに、Ｍｏ：≦１．００％、Ｔｉ：≦０．２０％、Ｖ：≦０．３０％、Ｎｂ≦０．５０％、Ｗ：≦１．００％、Ｂ：≦０．０２００％のいずれか１種または２種以上を含有し、さらにＦｅおよび不可避不純物を有し、シャルピー衝撃値による靱性：５．０Ｊ／ｃｍ2 以上、粒界被覆率指数Ｗ値の１６．３［％Ｃ］＋１５．４×［％Ｎｉ］＋３．３×［％Ｃｒ］：≦１０４、さらにＡ値の［％Ｍｏ］＋１／２×［％Ｗ］：≦１．０、およびＢ値の５×［％Ｔｉ］＋２×［％Ｎｂ］：≦１．５であることを特徴とする開発鋼１の手段のＮｉ含有高Ｃマルテンサイト系耐熱鋼である。 The means of the developed steel 2 is, by mass%, C: 0.40 to 0.85%, Si: 0.50 to 2.00%, Mn: 0.10 to 2.00%, P: ≤ 0.030. %, Ni: 0.10 to 2.00%, Cr: 16.0 to 23.50%, O: ≤ 0.0080%, N: ≤ 0.0600%, and Mo: ≤ 1. 00%, Ti: ≤ 0.20%, V: ≤ 0.30%, Nb ≤ 0.50%, W: ≤ 1.00%, B: ≤ 0.0200%, one or more of them. In addition, Fe and unavoidable impurities, toughness according to Charpy impact value: 5.0 J/cm 2 or more , grain boundary coverage index W value of 16.3 [% C]+15.4×[% Ni] +3.3×[%Cr]:≦104, A value of [%Mo]+1/2×[%W]:≦1.0, and B value of 5×[%Ti]+2×[%Nb] : Ni-containing high C martensitic heat resistant steel as a means of the developed steel 1 characterized in that: ≦1.5.
開発鋼３の手段は、質量％で、Ｃ：０．４０〜０．８５％、Ｓｉ：０．５０〜２．００％、Ｍｎ：０．１０〜２．００％、Ｐ：≦０．０３０％、Ｎｉ：０．１０〜２．００％、Ｃｒ：１６．００〜２３．５０％、Ｏ：≦０．００８０％、Ｎ：≦０．０６００％を有し、さらに、Ｍｏ：≦１．００％、Ｔｉ：≦０．２０％、Ｖ：≦０．３０％、Ｎｂ≦０．５０％、Ｗ：≦１．００％、Ｂ：≦０．０２００％のいずれか１種または２種以上を含有し、さらに、Ｓ：０より大きく０．１５０％以下であり、さらにＦｅおよび不可避不純物を有し、シャルピー衝撃値による靱性：５．０Ｊ／ｃｍ2 以上、粒界被覆率指数Ｗ値の１６．３［％Ｃ］＋１５．４×［％Ｎｉ］＋３．３×［％Ｃｒ］：≦１０４、さらにＡ値の［％Ｍｏ］＋１／２×［％Ｗ］：≦１．０、およびＢ値の５×［％Ｔｉ］＋２×［％Ｎｂ］：≦１．５であることを特徴とする開発鋼１または２の手段のＮｉ含有高Ｃマルテンサイト系耐熱鋼である。 The means of the developed steel 3 is, by mass%, C: 0.40 to 0.85%, Si: 0.50 to 2.00%, Mn: 0.10 to 2.00%, P: ≤ 0.030. %, Ni: 0.10 to 2.00%, Cr: 16.0 to 23.50%, O: ≤ 0.0080%, N: ≤ 0.0600%, and Mo: ≤ 1. 00%, Ti: ≤ 0.20%, V: ≤ 0.30%, Nb ≤ 0.50%, W: ≤ 1.00%, B: ≤ 0.0200%, one or more of them. In addition, S: more than 0.1 and not more than 0.150%, Fe and inevitable impurities, toughness according to Charpy impact value: 5.0 J/cm 2 or more , grain boundary coverage index W value of 16.3 [% C] + 15.4 x [% Ni] + 3.3 x [% Cr]: ≤ 104, A value [% Mo] + 1/2 x [% W]: ≤ 1.0, and The B value is 5×[%Ti]+2×[%Nb]:≦1.5, which is the Ni-containing high C martensitic heat resistant steel of the means of the developed steel 1 or 2.
本願発明は、Ｎｉ含有高Ｃマルテンサイト系耐熱鋼であり、Ｃの範囲が０．４０〜０．８５％と広く、Ｃｒ含有量も１６．００〜２３．５０％と高いものの、炭化物の粒界被覆率が５０％以下と低いので、靱性が高く確保される等の効果を有する。 INDUSTRIAL APPLICABILITY The present invention is a Ni-containing high-C martensitic heat-resisting steel, which has a wide C range of 0.40 to 0.85% and a high Cr content of 16.00 to 23.50%, but has carbide grains. Since the boundary coverage is as low as 50% or less, it has an effect of ensuring high toughness.
発明を実施するための形態の記載に先立って、本願発明の鋼の化学成分の限定理由を記載する。 Before describing the modes for carrying out the invention, the reasons for limiting the chemical composition of the steel of the present invention will be described.
Ｃ：０．４０〜０．８５％
Ｃは、強度や耐摩耗性を確保するために必要な元素であり、十分な強度や耐摩耗性を得るためには０．４０％添加する必要がある。しかし、０．４０％より少ないと鋼の焼入焼戻し硬さを低下し、一方、０．８５％より多いと鋼の焼なまし硬さを大きくして熱間加工性を悪化する。そこで、Ｃは０．４０〜０．８５％とする。好ましくは、０．５５〜０．８０％とする。
C: 0.40 to 0.85%
C is an element necessary for securing strength and wear resistance, and it is necessary to add 0.40% to obtain sufficient strength and wear resistance. However, if it is less than 0.40%, the quenching and tempering hardness of the steel is lowered, while if it is more than 0.85%, the annealing hardness of the steel is increased and the hot workability is deteriorated. Therefore, C is set to 0.40 to 0.85%. Preferably, it is 0.55 to 0.80%.
Ｓｉ：０．５０〜２．００％
Ｓｉは、脱酸剤として必要な元素である。しかし、Ｓｉは０．５０％より少ないと鋼の酸化減量を大きくし、一方、２．００％より多いと鋼の靱性を悪化し、冷鍛性が得られない。そこで、Ｓｉは０．５０〜２．００％とし、好ましくは、１．００〜２．００％とする。
Si: 0.50 to 2.00%
Si is an element required as a deoxidizer. However, if Si is less than 0.50%, the oxidation loss of the steel is increased, while if it is more than 2.00%, the toughness of the steel is deteriorated and cold forgeability cannot be obtained. Therefore, Si is set to 0.50 to 2.00%, preferably 1.00 to 2.00%.
Ｍｎ：０．１０〜２．００％
Ｍｎは、脱酸剤、脱硫剤として必要な元素である。しかし、Ｍｎは０．１０％より少ないと鋼の靱性を悪化する。一方、Ｍｎは２．００％より多いと鋼の熱間加工性を悪化する。そこで、Ｍｎは０．１０〜２．００％とし、好ましくは、０．３０〜１．００％とする。
Mn: 0.10 to 2.00%
Mn is an element required as a deoxidizing agent and a desulfurizing agent. However, if Mn is less than 0.10%, the toughness of steel deteriorates. On the other hand, if Mn is more than 2.00%, the hot workability of steel deteriorates. Therefore, Mn is set to 0.10 to 2.00%, preferably 0.30 to 1.00%.
Ｐ：≦０．０３０％
Ｐは、不可避不純物元素であるが、０．０３０％より多いと鋼の熱間加工性を悪化する。そこで、Ｐ≦０．０３０％とし、好ましくは、０．０２０％以下とする。
P: ≤0.030%
P is an unavoidable impurity element, but if it is more than 0.030%, the hot workability of steel deteriorates. Therefore, P≦0.030%, and preferably 0.020% or less.
Ｎｉ：０．１０〜２．００％
Ｎｉは、焼入性の向上、強度の向上に有効である。しかし、Ｎｉは０．１０％より少ないと鋼の酸化減量を大きくする。一方、Ｎｉは２．００％より多いと鋼の焼なまし硬さを大きくし、かつコストアップも招く。そこで、Ｎｉは０．１０〜２．００％とし、好ましくは、０．５０〜１．７０％とする。
Ni: 0.10 to 2.00%
Ni is effective in improving hardenability and strength. However, if Ni is less than 0.10%, the oxidation weight loss of steel is increased. On the other hand, when Ni is more than 2.00%, the annealing hardness of steel is increased and the cost is increased. Therefore, the Ni content is 0.10 to 2.00%, preferably 0.50 to 1.70%.
Ｃｒ：１６．００〜２３．５０％
Ｃｒは、耐酸化性の向上に有効である。しかし、Ｃｒは１６．００％より少ないと鋼の酸化減量を大きくし、一方、２３．５０％より多いと鋼の焼入焼戻し硬さが低下し、かつ靱性が悪化する。そこで、Ｃｒは１６．００〜２３．５０％とし、好ましくは、１８．００〜２１．５０％とする。
Cr: 16.0-23.50%
Cr is effective in improving the oxidation resistance. However, if Cr is less than 16.00%, the oxidation loss of the steel is increased, while if it is more than 23.50%, the quenching and tempering hardness of the steel decreases and the toughness deteriorates. Therefore, Cr is set to 16.00 to 23.50%, and preferably 18.0 to 21.50%.
Ｏ：≦０．００８０％
Ｏは、不可避不純物元素であるが、０．００８０％より多くなると、耐酸化性に有効なＳｉやＣｒを奪うため、酸化減量が増大する。そこで、Ｏ≦０．００８０％とし、好ましくは、０．００５５％以下とする。
O: ≤ 0.0080%
O is an unavoidable impurity element, but if it exceeds 0.0080%, Si and Cr, which are effective for oxidation resistance, are deprived, so the oxidation weight loss increases. Therefore, O≦0.0080%, and preferably 0.0055% or less.
Ｎ：≦０．０６００％
Ｎは、不可避不純物元素であるが、０．０６００％より多くなると、熱間加工性を悪化し、粒界被覆率指数のＷ値の増大に伴う靱性を悪化する。そこで、Ｎ：≦０．０６００％とし、好ましくは、０．０５００％以下とする。
N: ≤0.0600%
N is an unavoidable impurity element, but if it is more than 0.0600%, the hot workability deteriorates, and the toughness deteriorates as the W value of the grain boundary coverage index increases. Therefore, N: ≤ 0.0600%, preferably 0.0500% or less.
Ｍｏ：≦１．００％
Ｍｏは、焼入性を高める他に、焼戻し軟化抵抗を向上させ、Ａ1点を高くする元素であり、焼戻し時にＭ7Ｃ3やＭ2Ｃなどの炭化物を形成して、高温強度を増大させる。Ｍｏは多量に添加すると焼なまし硬さを大とし、靱性を劣化し、その上にＭｏは高価な元素である。そこで、Ｍｏ≦１．００％とし、好ましくは、０．８５％以下とする。
Mo: ≤1.00%
Mo is an element that not only enhances hardenability but also improves temper softening resistance and raises A 1 point, and forms carbides such as M 7 C 3 and M 2 C during tempering to increase high temperature strength. Let Addition of a large amount of Mo increases the annealing hardness and deteriorates the toughness, and on top of that, Mo is an expensive element. Therefore, Mo≦1.00%, and preferably 0.85% or less.
Ｔｉ：≦０．２０％
Ｔｉは、Ｂに比べてＮとの親和力が極めて強い元素である。ＴｉＮの形成によってＢＮ
の析出を抑制し、炭化物の粗大化を抑制するＢの効果を高めるために、Ｔｉを０．００５％以上添加することが好ましい。一方Ｔｉを過剰に添加すると、粗大なＴｉＣが析出または晶出し、靱性を低下するため、Ｔｉを０．２０％以下とし、好ましくは、０．１５％以下とする。
Ti: ≤ 0.20%
Ti is an element having an extremely strong affinity with N as compared with B. BN by forming TiN
In order to suppress the precipitation of Al and enhance the effect of B that suppresses the coarsening of carbides, it is preferable to add 0.005% or more of Ti. On the other hand, if Ti is excessively added, coarse TiC is precipitated or crystallized to lower the toughness. Therefore, the Ti content is 0.20% or less, preferably 0.15% or less.
Ｖ：≦０．３０％
Ｖは、過剰に添加すると粗大なＶＣを析出または晶出して靱性を悪化するため、また、Ｖは高価な元素であるので、Ｖは０．３０％以下とし、好ましくは、０．２０％以下する。
V: ≤ 0.30%
If V is added excessively, coarse VC is precipitated or crystallized to deteriorate the toughness. Further, since V is an expensive element, V is set to 0.30% or less, preferably 0.20% or less. To do.
Ｎｂ：≦０．５０％
Ｎｂは、過剰に添加すると粗大なＮｂＣを析出または晶出して靱性を悪化し、焼入れ硬さを低下させる。そこで、Ｎｂは０．５０％以下とし、好ましくは、０．３０％以下とする。
Nb: ≤0.50%
When Nb is added excessively, coarse NbC is precipitated or crystallized to deteriorate the toughness and reduce the quenching hardness. Therefore, Nb is 0.50% or less, and preferably 0.30% or less.
Ｗ：≦１．００％
Ｗは、過剰に添加すると粗大な炭化物を析出して靱性を悪化し、焼入れ硬さを低下させかつＷは高価な元素である。そこで、Ｗは１．００％以下とし、好ましくは、０．５０％以下とする。
W: ≤1.00%
When W is added excessively, coarse carbides are precipitated to deteriorate toughness, quenching hardness is lowered, and W is an expensive element. Therefore, W is 1.00% or less, and preferably 0.50% or less.
Ｓ：≦０．１５０％
Ｓは、不可避不純物元素であるが、０．１５０％より多いと鋼の熱間加工性を悪化する。そこで、Ｓ≦０．１５０％とし、好ましくは、０．１００％以下とする。
S: ≤0.150%
S is an unavoidable impurity element, but if it exceeds 0.150%, the hot workability of steel deteriorates. Therefore, S≦0.150%, and preferably 0.100% or less.
靱性としてのシャルピー衝撃値：５．０Ｊ／ｃｍ2以上
シャルピー衝撃値が、５．０Ｊ／ｃｍ2未満であると靱性が低く製造性が低下する。そこで、靱性としてのシャルピー衝撃値は５．０Ｊ／ｃｍ2以上とする。
Charpy impact value as toughness: 5.0 J/cm 2 or more If the Charpy impact value is less than 5.0 J/cm 2 , toughness is low and manufacturability is reduced. Therefore, the Charpy impact value as toughness is set to 5.0 J/cm 2 or more.
粒界被覆率指数Ｗ値：１６．３［％Ｃ］＋１５．４×［％Ｎｉ］＋３．３×［％Ｃｒ］≦１０４
粒界被覆率指数Ｗ値は、１０４より大きくなると、炭化物の粒界被覆率が増加し、靱性が確保できなくなる。そこで、粒界被覆率指数Ｗ値の１６．３［％Ｃ］＋１５．４×［％Ｎｉ］＋３．３×［％Ｃｒ］は、１０４以下とする。
Grain boundary coverage index W value: 16.3 [%C]+15.4×[%Ni]+3.3×[%Cr]≦104
If the grain boundary coverage index W value is larger than 104, the grain boundary coverage of carbides increases and it becomes impossible to secure toughness. Therefore, the grain boundary coverage index W value of 16.3[%C]+15.4×[%Ni]+3.3×[%Cr] is set to 104 or less.
Ａ値：［％Ｍｏ］＋１／２×［％Ｗ］
Ａ値は、１.０より大きくなると本願開発鋼の請求項２の靱性を悪化する。そこで、Ａ値の［％Ｍｏ］＋１／２×［％Ｗ］は、１．０以下とする。
A value: [%Mo]+1/2×[%W]
When the A value exceeds 1.0, the toughness of claim 2 of the developed steel of the present application deteriorates. Therefore, the A value [%Mo]+1/2×[%W] is set to 1.0 or less.
Ｂ値：５×［％Ｔｉ］＋２×［％Ｎｂ］
Ｂ値は、１.５より大きくなると本願開発鋼の請求項２の靱性を悪化する。そこで、Ｂ
値の５×［％Ｔｉ］＋２×［％Ｎｂ］は、１．５以下とする。
B value: 5×[%Ti]+2×[%Nb]
If the B value exceeds 1.5, the toughness of claim 2 of the developed steel of the present application deteriorates. So B
The value 5×[%Ti]+2×[%Nb] is 1.5 or less.
ここで、本願の発明を実施するための形態について説明する。表１に示す本願発明の開発鋼の各成分の各Ｎｏ．の鋼、および表２に示す各比較鋼の各成分の各Ｎｏ．の鋼のそれぞれを、１００ｋｇＶＩＭにて溶解してインゴットに鋳造した。 Here, modes for carrying out the invention of the present application will be described. Each No. of each component of the developed steel of the present invention shown in Table 1 is as follows. No. of each component of each of the comparative steels shown in Table 2 and No. Each of the steels was melted with 100 kg VIM and cast into an ingot.
これらのインゴットを、第１グループでは径６５ｍｍ丸棒の鍛伸材に鍛伸し、第２グループでは４５ｍｍＨ×９５ｍｍＷに鍛伸し、これらグループのそれぞれを８５０〜９５０℃にて焼なまして素材とした。それぞれのサイズに調整した素材から、以下の試験をそれぞれ実施した。試験結果は、表３に本願発明の開発鋼の値を示し、表４に比較項の値を示した。また、熱間加工性に関しては鍛伸時の割れ発生状況から判断し、割れが発生しないものを○、割れが発生したものを×として評価した。 These ingots were forged into a forged material of a round bar with a diameter of 65 mm in the first group, 45 mmH×95 mmW in the second group, and each of these groups was annealed at 850 to 950° C. did. The following tests were carried out from the materials adjusted to the respective sizes. As for the test results, Table 3 shows the values of the developed steel of the present invention, and Table 4 shows the values of the comparative items. Further, the hot workability was judged from the crack occurrence state during forging, and the case where the crack did not occur was evaluated as ◯, and the case where the crack occurred was evaluated as x.
第１グループの評価は、径６５ｍｍの丸棒の鍛伸材を径６０ｍｍに調整した後、焼なまし硬さの測定、焼入焼戻し硬さの測定、炭化物の粒界被覆率の測定を実施し、表３に本願発明鋼の値を示し、表４に比較鋼の値を示した。 For the evaluation of the first group, after adjusting the diameter of the forged material of the round bar having a diameter of 65 mm to the diameter of 60 mm, the annealing hardness, the quenching and tempering hardness, and the grain boundary coverage of the carbide were measured. Then, Table 3 shows the values of the present invention steels, and Table 4 shows the values of the comparative steels.
焼なまし硬さ（表３および表４でＡ硬さと表示）は、供試材の長手方向と垂直な面の中周にて、ＨＲＣスケールでの硬さを測定して実施した。表３の本願発明鋼および表４の比較鋼には、それぞれ５点平均の値を示した。 The annealing hardness (indicated as A hardness in Tables 3 and 4) was measured by measuring the hardness on the HRC scale in the middle circumference of the surface perpendicular to the longitudinal direction of the test material. The present invention steels in Table 3 and the comparative steels in Table 4 each show an average value of 5 points.
焼入焼戻し硬さ（表３および表４でＱＴ硬さと表示）は、供試材に１０００〜１１５０℃で焼入、その後５５０〜６５０℃で焼戻しを実施した。焼なまし硬さと同様に測定して、それぞれ５点平均の値を示した。 Regarding the quenching and tempering hardness (indicated as QT hardness in Tables 3 and 4), the test material was quenched at 1000 to 1150°C, and then tempered at 550 to 650°C. The measurement was performed in the same manner as the annealing hardness, and the average value of 5 points was shown for each.
粒界被覆率は、大角（度）粒界上の析出物長さの総和を大角（度）粒界長さの総和で除した値であり、完全に被覆されている場合は１００％となり、全く被覆していない場合を０％と判断するパラメータである。
炭化物の粒界被覆率は、焼なましの状態で、供試材の長手方向にて組織観察を実施し、粒界被覆率を測定した。粒界被覆率は、まず１万倍の電子顕微鏡観察により、大角（度）粒界上に析出した粒子を、エネルギー分散型Ｘ線分光分析（ＥＤＸ）または同じく１万倍の薄膜透過型電子顕微鏡解析における透過型電子回折パターン解析によってＭ23Ｃ6型炭化物またはＭ7Ｃ3型炭化物と判断できる析出物を特定する。その粒子が大角（度）粒界を被覆する長さを測定し、当該測定を少なくとも１試料あたり５視野、１合金あたり５個以上の試験片を採取して行ない、合計２５試料以上のその場観察、または電子顕微鏡の解析によって求めることができる。
The grain boundary coverage is a value obtained by dividing the sum of precipitate lengths on the large angle (degree) grain boundary by the sum of the large angle (degree) grain boundary lengths, and 100% when completely covered, This is a parameter for determining 0% when there is no coating.
The grain boundary coverage of the carbide was measured by observing the structure in the longitudinal direction of the test material in the annealed state and measuring the grain boundary coverage. Grain boundary coverage is first measured by an electron microscope with a magnification of 10,000, and then the particles deposited on large-angle (degree) grain boundaries are analyzed by energy dispersive X-ray spectroscopy (EDX) or a thin film transmission electron microscope with a magnification of 10,000. Precipitates that can be judged to be M 23 C 6 type carbides or M 7 C 3 type carbides are specified by transmission electron diffraction pattern analysis in the analysis. The length of the particle covering a large angle (degree) grain boundary is measured, and the measurement is performed by collecting at least 5 fields of view per sample and 5 or more test pieces per alloy, and a total of 25 or more samples in situ. It can be determined by observation or analysis with an electron microscope.
第２グループの評価は、上記で作製した４５ｍｍＨ×９５ｍｍＷの素材を連続酸化試験し、焼入焼戻し状態のシャルピー衝撃試験を実施し、表３に本願発明鋼の結果を示し、表４に比較鋼の結果を示した。 In the evaluation of the second group, the 45 mmH×95 mmW material produced above was subjected to a continuous oxidation test and a Charpy impact test in a quenched and tempered state. Table 3 shows the results of the invention steels, and Table 4 shows comparative steels. The results of
すなわち、連続酸化試験は、上記で作製した４５ｍｍ高さ×９５ｍｍ幅の素材を径１２ｍｍ長さ２１ｍｍに調整した後、１１００℃で１００ｈｒの連続酸化実験を実施した。さらに、ショットブラストにて脱スケールを施し、酸化減量の値を測定した。 That is, in the continuous oxidation test, after adjusting the material of 45 mm height×95 mm width prepared above to a diameter of 12 mm and a length of 21 mm, a continuous oxidation experiment was carried out at 1100° C. for 100 hours. Furthermore, descaling was performed by shot blasting, and the value of weight loss on oxidation was measured.
シャルピー衝撃試験は、供試材を１０００〜１１５０℃で焼入れし、その後５５０〜６５０℃で焼戻しを実施し、角１０×５５ｍｍの標準試験片に調整した後、ＪＩＳ Ｚ ２２４２に則って２ｍｍＵノッチのシャルピー衝撃試験を実施し、３回平均の値を、それぞれ表３に本願開発鋼の靱性をシャルピー衝撃値で示し、表４に比較鋼の靱性をシャルピー衝撃値で示した。 In the Charpy impact test, the test material was quenched at 1000 to 1150° C., then tempered at 550 to 650° C., adjusted to a standard test piece having a corner of 10×55 mm, and then subjected to a 2 mm U notch according to JIS Z 2242. A Charpy impact test was carried out, and the average value of three times was shown in Table 3 showing the toughness of the developed steel in Charpy impact value, and in Table 4 showing the toughness of the comparative steel in Charpy impact value.
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