JP2007051341A - Steel with high young's modulus - Google Patents

Steel with high young's modulus Download PDF

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JP2007051341A
JP2007051341A JP2005237728A JP2005237728A JP2007051341A JP 2007051341 A JP2007051341 A JP 2007051341A JP 2005237728 A JP2005237728 A JP 2005237728A JP 2005237728 A JP2005237728 A JP 2005237728A JP 2007051341 A JP2007051341 A JP 2007051341A
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steel
type
modulus
boride
young
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Yoshiori Kono
佳織 河野
Takeshi Yoshino
健 吉野
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Nippon Steel Corp
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Sumitomo Metal Industries Ltd
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Abstract

<P>PROBLEM TO BE SOLVED: To provide a steel with a high Young's modulus which exhibits a high Young's modulus, and simultaneously maintains satisfactory ductility and toughness by a relatively simple means. <P>SOLUTION: As dispersed grains, V<SB>3</SB>B<SB>4</SB>type boride of ≥5 mass% and M(C, N) type carbonitride (M is V and/or Ti) of ≥1.5 mass% are incorporated into a steel, and also, the total content of both is controlled to 8 to 30 mass%. The steel with a high Young's modulus can be produced by subjecting a slab comprising, by mass, 0.1 to 0.8% C, 0.05 to 0.5% Si, 0.2 to 1.5% Mn, 1 to 7% Ti, 4 to 8% V, 2 to 3% B, 0.005 to 0.2% Al, 1 to 7% Cr and 0.001 to 0.01% N, and the balance Fe with impurities to hot working in the temperature range of 850 to 1,200°C at the total reduction of area of ≥70%. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

本発明は、自動車用材料、ロボット用材料、スポーツ用品、機械構造用材料等の、剛性を必要とする部材に好適な、高ヤング率鋼およびその製造方法に関する。   The present invention relates to a high Young's modulus steel suitable for members that require rigidity, such as materials for automobiles, materials for robots, sports equipment, and materials for machine structures, and a method for producing the same.

自動車分野では、燃費向上のため車体の軽量化が進んでいる。軽量化のために素材の求められる性能として、強度とともに剛性が挙げられる。剛性が向上すれば、たわみが抑制され、たわみに起因するフリクションロスが軽減できる上、薄肉化、小軸径化が可能となって部品を小型化できるからである。   In the automobile field, the weight of the vehicle body has been reduced to improve fuel efficiency. The performance required of the material for weight reduction includes rigidity as well as strength. This is because if the rigidity is improved, the deflection is suppressed, the friction loss due to the deflection can be reduced, and the thickness can be reduced and the shaft diameter can be reduced, so that the part can be miniaturized.

鋼の剛性(一般にヤング率で評価される)を向上させる手法として、
・合金元素の添加(Cr,Co,Re,など)、
・集合組織の利用、
・高剛性化合物の分散、
が挙げられる。
As a technique to improve the rigidity (generally evaluated by Young's modulus) of steel,
・ Addition of alloy elements (Cr, Co, Re, etc.),
・ Use of collective organization
・ Dispersion of highly rigid compounds,
Is mentioned.

これらの手法のうち、Cr、Co、Reなどの合金元素の添加では、ヤング率は高々数%しか向上しない。集合組織を利用する場合には、ヤング率の異方性が大きくなり、構造部材への適用には限界がある。それに対し、高いヤング率を有する化合物をFeマトリックスに分散させて複合材料化すると、等方的に高いヤング率を得ることができる。   Of these methods, the addition of alloying elements such as Cr, Co, and Re improves the Young's modulus by only a few percent at most. When texture is used, the Young's modulus anisotropy increases, and there is a limit to application to structural members. In contrast, when a compound having a high Young's modulus is dispersed in an Fe matrix to form a composite material, an isotropically high Young's modulus can be obtained.

上記複合材料のヤング率は、下記非特許文献1に記載されているように、一般に含有化合物の体積率によって決定される。すなわち、鋼中に分散させた含有化合物のヤング率が高いほど、また、その含有量が多いほど、複合材料のヤング率が大きくなる。このヤング率の複合則に従えば、例えば、約15vol%のTiB、約20vol%のTiCのいずれかをFeマトリックス中に含有させることによって、約250GPaのヤング率が得られ、通常の鋼のヤング率:208GPaから約20%も大きくなる。 The Young's modulus of the composite material is generally determined by the volume ratio of the contained compound as described in Non-Patent Document 1 below. That is, the higher the Young's modulus of the contained compound dispersed in the steel and the greater the content, the greater the Young's modulus of the composite material. According to the composite law of Young's modulus, for example, by including either about 15 vol% TiB 2 or about 20 vol% TiC in the Fe matrix, a Young's modulus of about 250 GPa can be obtained. Young's modulus: increases from 208 GPa to about 20%.

しかし、このように多量の高剛性化合物を鋼中に含有させた複合材料型の高ヤング率鋼は、通常の溶製や熱間加工の工程を経て製造することは困難である。そのため、このような高剛性化合物を多量に含有する高ヤング率鋼に関して、下記のような技術がこれまでに提案されている。   However, it is difficult to produce a composite type high Young's modulus steel containing a large amount of a high-rigidity compound in the steel through ordinary melting and hot working processes. Therefore, the following techniques have been proposed so far for high Young's modulus steel containing a large amount of such a highly rigid compound.

(1)メカニカルアロイング法による方法(下記特許文献1);
(2)溶製による方法:(a)鉄または鉄合金中に化合物を構成する元素が完全に溶解する温度以上まで加熱し、冷却、凝固時に高剛性化合物を晶出または析出させる方法(下記特許文献2)および(b)所定の割合で合金原料を配合し、真空中または不活性ガス雰囲気中で完全に溶融させた後、金型またはセラミックス型へ鋳造することにより製造する方法(下記特許文献3)。
特開平5−239504号公報 特開平10−68048号公報 特開2001−59146号公報 日本機械学会編集の「金属材料の弾性係数」(初版発効日:1980年10月31日、発行所:社団法人日本機械学会)
(1) Method by mechanical alloying method (Patent Document 1 below);
(2) Method by melting: (a) Method of heating to a temperature at which the element constituting the compound is completely dissolved in iron or an iron alloy, and crystallizing or precipitating a highly rigid compound during cooling and solidification (the following patent) Documents 2) and (b) A method in which alloy raw materials are blended at a predetermined ratio, completely melted in a vacuum or an inert gas atmosphere, and then cast into a mold or a ceramic mold (the following patent documents) 3).
JP-A-5-239504 JP-A-10-68048 JP 2001-59146 A "Elastic modulus of metallic materials" edited by the Japan Society of Mechanical Engineers (Effective date: October 31, 1980, publisher: Japan Society of Mechanical Engineers)

上記(1)のメカニカルアロイング法は、コストがかさむ上、大型部品の製造ができないという問題がある。上記(2)の溶製法の(a)および(b)の方法では、溶鋼から晶出する粒子が一般的に粗大化しやすく、延性、靱性、疲労強度の低下原因となるという問題がある。   The mechanical alloying method (1) has a problem that the cost is high and a large part cannot be manufactured. In the method (a) and (b) of the melting method (2) described above, there is a problem that particles crystallized from the molten steel are generally easily coarsened, causing a decrease in ductility, toughness and fatigue strength.

本発明は、このような問題点のない高ヤング率鋼とその製造方法を提供することを課題とする。具体的には、メカニカルアロイング法を利用せず、延性や靱性を低下させることなく、高剛性化合物を鋼中に多量に含有させた、複合材料型の高ヤング率鋼とその製造方法を提供することである。   This invention makes it a subject to provide the high Young's modulus steel which does not have such a problem, and its manufacturing method. Specifically, we provide a composite material type high Young's modulus steel that contains a large amount of a high-rigidity compound in steel without using mechanical alloying and without reducing ductility and toughness, and a method for producing the same. It is to be.

本発明者らは、低コストで製造可能な溶製を前提として、溶製時に十分な量の高剛性化合物を鋼中に微細分散させることにより、延性、靱性および疲労強度の低下を防止することに着目し、鋼中に微細分散可能な高剛性化合物を見出すべく検討を重ねた。   Based on the premise of melting that can be manufactured at low cost, the present inventors prevent a decrease in ductility, toughness and fatigue strength by finely dispersing a sufficient amount of high-rigidity compound in the steel during melting. Focusing on the above, research was repeated to find a highly rigid compound that can be finely dispersed in steel.

そして、所定の割合で合金原料を配合し、通常の溶製・凝固過程でMB型硼化物およびMB型硼化物を晶出させることにより、靭性の防止が可能となる高剛性鋼とその製造方法の発明を、特願2003−154879号として出願した。 Then, alloy raw materials are blended at a predetermined ratio, and MB 2 type boride and MB type boride are crystallized in a normal melting and solidification process, thereby making it possible to prevent toughness and its production. The invention of the method was filed as Japanese Patent Application No. 2003-154879.

本発明者らは、さらに検討を重ねた結果、C、B、V、Crを含む鋼では、晶出または析出しうる化合物は下記に示す硼化物、炭窒化物、または炭硼化物であることを明らかにした。かっこ内に各化合物のヤング率の測定値を示す。   As a result of further studies, the present inventors have found that in steels containing C, B, V, and Cr, the compounds that can be crystallized or precipitated are borides, carbonitrides, or carbon borides shown below. Was revealed. The measured value of Young's modulus of each compound is shown in parentheses.

VB型硼化物(ヤング率:547GPa)、
型硼化物(ヤング率:620GPa)、
M(C,N)型炭窒化物(MはV及び/またはTi)(ヤング率:460GPa)、
FeB型硼化物(ヤング率:200GPa以下)。
VB type 2 boride (Young's modulus: 547 GPa),
V 3 B type 4 boride (Young's modulus: 620 GPa),
M (C, N) type carbonitride (M is V and / or Ti) (Young's modulus: 460 GPa),
FeB type boride (Young's modulus: 200 GPa or less).

23(C,B)型炭硼化物(ヤング率:200以下)
上記の化合物の中で、鋼のヤング率向上に寄与する可能性があるのは、ヤング率の高いVB型硼化物、V型硼化物、およびM(C,N)型炭窒化物である。VB型硼化物は高融点化合物であり、凝固過程でFeマトリックスとの共晶により晶出する。一方、V型硼化物はVB型硼化物より低融点であるので、通常の凝固や析出過程では生成しない。しかし、VB型硼化物が晶出した鋼片に熱間加工を加えると、VB型硼化物が相分離することによりV型硼化物が形成されることが判明した。
M 23 (C, B) Type 6 boride (Young's modulus: 200 or less)
Among the above-mentioned compounds, VB 2 type boride, V 3 B 4 type boride, and M (C, N) type carbonitride having high Young's modulus may contribute to the improvement of Young's modulus of steel. It is a thing. VB type 2 boride is a high melting point compound and crystallizes out by eutectic with the Fe matrix during the solidification process. On the other hand, since V 3 B 4 type boride has a lower melting point than VB 2 type boride, it does not form during normal solidification and precipitation processes. However, it has been found that when hot working is applied to a steel piece from which VB 2 type boride has crystallized, V 3 B 4 type boride is formed due to phase separation of VB 2 type boride.

型硼化物の形成過程は次の通りであると考えられる:
(i)凝固過程でVB型硼化物がFeマトリックスとの共晶により晶出する;
(ii)(i)の共晶組織に熱間加工を加えることによりVB型硼化物が塑性変形する;
(iii)塑性変形によりVB→VB+V→V+(Fe,V)Bなる相分離が生じ、V型硼化物が形成される。
The formation process of the V 3 B 4 type boride is believed to be as follows:
(I) VB type 2 boride is crystallized by eutectic with Fe matrix during solidification process;
(Ii) VB type 2 boride is plastically deformed by hot working the eutectic structure of (i);
(Iii) Due to plastic deformation, phase separation of VB 2 → VB 2 + V 3 B 4 → V 3 B 4 + (Fe, V) B occurs, and a V 3 B 4 type boride is formed.

こうして塑性変形の過程で形成されたV型硼化物の形態は、VB型硼化物に比べて微細で、かつ形状が球状であり、鋼中に均一に分散する。一方、共晶により晶出したVB型硼化物はFeマトリックスとのラメラ組織を示し、球状のV型硼化物よりずっと粗大である。 The form of the V 3 B 4 type boride formed in the process of plastic deformation in this manner is finer and spherical in shape than the VB 2 type boride, and is uniformly dispersed in the steel. On the other hand, the VB type 2 boride crystallized by eutectic shows a lamellar structure with the Fe matrix and is much coarser than the spherical type V 3 B 4 type boride.

そのため、VB型硼化物を多く含有する鋼は、この硼化物の高いヤング率のために高ヤング率を示すことができるものの、この硼化物の層状のラメラ組織のため、引張試験における延性が低く、耐力、伸び、抗折力が悪化する。一方、高ヤング率のV型硼化物を含有する鋼は、この硼化物が微細な球状であるため、耐力、伸び、抗折力を高水準に保持したまま高ヤング率を与えることができ、従って鋼の高ヤング率化に最適であることが判明した。 Therefore, a steel containing a large amount of VB type 2 boride can exhibit a high Young's modulus because of the high Young's modulus of this boride, but due to the lamellar lamellar structure of this boride, the ductility in the tensile test is low. Low, yield strength, elongation and bending strength deteriorate. On the other hand, a steel containing a high Young's modulus V 3 B 4 type boride provides a high Young's modulus while maintaining a high level of proof stress, elongation, and bending strength because the boride is fine spherical. Therefore, it was found that it is optimal for increasing the Young's modulus of steel.

型硼化物が生成可能な鋼の組成範囲は、質量%で、C:0.1%以上、0.8%以下;Si:0.05%以上、0.5%以下;Mn:0.2%以上、1.5%以下;Ti:1%以上、7%以下;V:4%以上、8%以下;B:2%以上、3%以下;Al:0.005%以上、0.2%以下;Cr:1%以上、7%以下;N:0.001%以上、0.01%以下を含む組成であることも明らかとなった。 The composition range of steel in which V 3 B 4 type boride can be produced is, by mass, C: 0.1% or more, 0.8% or less; Si: 0.05% or more, 0.5% or less; Mn : 0.2% or more, 1.5% or less; Ti: 1% or more, 7% or less; V: 4% or more, 8% or less; B: 2% or more, 3% or less; Al: 0.005% or more 0.2% or less; Cr: 1% or more, 7% or less; N: 0.001% or more and 0.01% or less.

また、熱間加工中の塑性変形によりVB型硼化物からV型硼化物に相変化させるには、850℃〜1200℃の加工温度範囲で総減面率70%以上の加工を加える熱間加工を付与すればよいこともわかった。 Also, in order to change the phase from VB 2 type boride to V 3 B 4 type boride by plastic deformation during hot working, machining with a total area reduction of 70% or more in the working temperature range of 850 ° C. to 1200 ° C. It has also been found that it is only necessary to provide additional hot working.

一方、鋼の高強度化の面ではV型硼化物の寄与は小さい。したがって、別に強度の向上策が必要である。上述した析出物の中で、M(C,N)型炭窒化物[MはVおよび/またはTi]はVと競合しないため、析出強化粒子として好適である。 On the other hand, the contribution of V 3 B 4 type boride is small in terms of increasing the strength of steel. Therefore, another measure to improve the strength is necessary. Among the above-mentioned precipitates, M (C, N) type carbonitride [M is V and / or Ti] does not compete with V 3 B 4 and is therefore suitable as precipitation strengthening particles.

以上の知見に基づいて完成した本発明は、
(a)V型硼化物5質量%以上と、(b)M(C,N)型炭窒化物(MはV及び/またはTi)1.5質量%以上とを含有し、(a)と(b)の合計量が8〜30質量%であることを特徴とする、高ヤング率鋼、
である。
The present invention completed based on the above findings,
(A) V 3 B 4 type boride 5% by mass or more and (b) M (C, N) type carbonitride (M is V and / or Ti) 1.5% by mass or more, high Young's modulus steel, characterized in that the total amount of a) and (b) is 8-30% by mass,
It is.

本発明の高ヤング率鋼は、VB型硼化物を全く含有しないことが好ましい。本発明の高ヤング率鋼の化学組成は、質量%で、
C:0.1%以上、0.8%以下; Si:0.05%以上、0.5%以下;
Mn:0.2%以上、1.5%以下; Ti:1%以上、7%以下;
V:4%以上、8%以下; B:2%以上、3%以下;
Al:0.005%以上、0.2%以下; Cr:1%以上、7%以下;
N:0.001%以上、0.01%以下
を含有し、残部はFeおよび不純物からなるものであることが好ましい。
The high Young's modulus steel of the present invention preferably contains no VB 2 type boride. The chemical composition of the high Young's modulus steel of the present invention is mass%,
C: 0.1% to 0.8%; Si: 0.05% to 0.5%;
Mn: 0.2% to 1.5%; Ti: 1% to 7%;
V: 4% to 8%; B: 2% to 3%;
Al: 0.005% to 0.2%; Cr: 1% to 7%;
N: It is preferable to contain 0.001% or more and 0.01% or less, and the remainder consists of Fe and impurities.

本発明はまた、質量%で、
C:0.1%以上、0.8%以下; Si:0.05%以上、0.5%以下;
Mn:0.2%以上、1.5%以下; Ti:1%以上、7%以下;
V:4%以上、8%以下; B:2%以上、3%以下;
Al:0.005%以上、0.2%以下; Cr:1%以上、7%以下;
N:0.001%以上、0.01%以下
を含有し、残部はFeおよび不純物からなる鋼片に、850℃〜1200℃の温度範囲で、総減面率70%以上の熱間加工を施すことを特徴とする、高ヤング率鋼の製造方法、
にも関する。
The present invention is also in weight percent,
C: 0.1% to 0.8%; Si: 0.05% to 0.5%;
Mn: 0.2% to 1.5%; Ti: 1% to 7%;
V: 4% to 8%; B: 2% to 3%;
Al: 0.005% to 0.2%; Cr: 1% to 7%;
N: 0.001% or more and 0.01% or less, and the remainder is hot-worked with a total area reduction of 70% or more in a temperature range of 850 ° C. to 1200 ° C. in a steel piece made of Fe and impurities. A method for producing a high Young's modulus steel, characterized by:
Also related.

本発明により、鋼中に分散した高剛性化合物を多量に含みながら、なおかつ良好な延性と靱性を保持した高ヤング率鋼が、比較的簡便な手段により得られる。それにより、例えば、自動車用材料、ロボット用材料、スポーツ用品、機械構造用材料等、剛性を必要とする部材に好適な高ヤング率鋼を比較的安価に安定して供給することが可能となる。   According to the present invention, a high Young's modulus steel containing a large amount of a high-rigidity compound dispersed in the steel and having good ductility and toughness can be obtained by a relatively simple means. Thereby, for example, high Young's modulus steel suitable for members that require rigidity, such as materials for automobiles, materials for robots, sports equipment, and materials for machine structures, can be stably supplied at a relatively low cost. .

以下、本発明についてより詳しく説明する。以下の説明において、鋼の化学成分に関する%(鋼中の分散化合物の含有量も含む)はいずれも質量%である。
[高剛性化合物の含有量]
本発明に係る高ヤング率鋼は、高剛性化合物として、(a)5%以上のV型硼化物と、(b)1.5%以上のM(C,N)型炭窒化物(MはV及び/またはTiを意味する)という2種類の化合物を含有し、(a)と(b)の合計量は8〜30%とする。Vのヤング率は620GPa、M(C,N)のヤング率は460GPaである。前者は特に鋼の高ヤング率化に寄与し、後者は鋼の高強度化に寄与する。前述したように、V型硼化物は、溶製過程で析出させることはできないため、VB型硼化物が晶出した鋼片に熱間加工を加えることによって、VB型硼化物の相分離により鋼中で生成させる。
Hereinafter, the present invention will be described in more detail. In the following description, all the percentages (including the content of dispersed compounds in steel) relating to the chemical components of steel are mass%.
[Content of highly rigid compound]
The high Young's modulus steel according to the present invention comprises (a) 5% or more of V 3 B 4 type boride and (b) 1.5% or more of M (C, N) type carbonitride as high rigidity compounds. (M represents V and / or Ti). The total amount of (a) and (b) is 8-30%. The Young's modulus of V 3 B 4 is 620 GPa, and the Young's modulus of M (C, N) is 460 GPa. The former particularly contributes to increasing the Young's modulus of steel, and the latter contributes to increasing the strength of steel. As described above, V 3 B 4 type boride, since it is impossible to deposit in melting process, by adding hot working the billet VB 2 type boride crystallized out, VB 2 type borides It is produced in steel by phase separation.

これらの高剛性化合物を鉄マトリックス中に含有させて鋼の高剛性化を図る場合、V型硼化物の含有量が5%未満では所望のヤング率が得られない。一方、M(C,N)型炭窒化物の析出量が1.5%未満では強度が低下する。さらに、V型硼化物とM(C,N)型炭窒化物の総含有量が8%未満では、ヤング率と強度が両立しない。一方、V型硼化物とM(C,N)型炭窒化物の総含有量の上限は溶製鋼で可能な30質量%である。 When these high-rigidity compounds are contained in the iron matrix to increase the rigidity of the steel, the desired Young's modulus cannot be obtained if the content of the V 3 B 4 type boride is less than 5%. On the other hand, if the amount of M (C, N) carbonitride deposited is less than 1.5%, the strength decreases. Furthermore, if the total content of the V 3 B 4 type boride and the M (C, N) type carbonitride is less than 8%, the Young's modulus and the strength are not compatible. On the other hand, the upper limit of the total content of the V 3 B 4 type boride and the M (C, N) type carbonitride is 30% by mass that is possible with molten steel.

これらの化合物の量の好ましい範囲は、V型硼化物10%以上、M(C,N)型炭窒化物が2.0%以上、両者の合計が12〜20%である。その他の化合物として、FeB型硼化物、M23(C,B)(MはVおよび/またはTi)型炭硼化物、等が析出する場合があるが、その析出総量は7.5%未満とするのが望ましい。前述した通り、VBからVを生ずる塑性変形によって(Fe,V)B型硼化物が副生するので、この硼化物も鋼中に含有される。 The preferable range of the amount of these compounds is 10% or more of V 3 B 4 type boride, 2.0% or more of M (C, N) type carbonitride, and the total of both is 12 to 20%. As other compounds, FeB type boride, M 23 (C, B) 6 (M is V and / or Ti) type carbon boride, and the like may precipitate, but the total precipitation amount is less than 7.5%. Is desirable. As described above, (Fe, V) by plastic deformation from VB 2 results in V 3 B 4 since B-type boride is produced as a by-product, the borides are also contained in the steel.

VBからVへの塑性変形は完全に熱間加工中に完全に進行させることが好ましい。この塑性変形が不完全で、鋼組織にVB型硼化物が残留していると、溶製時に晶出したVB型硼化物およびM(C,N)型炭窒化物からなる粗大なラメラ組織が残留し、鋼の延性が低下して、伸びや抗折力が低下する。したがって、本発明の鋼はVB型硼化物を含有していないことが好ましい。しかし、1%以下程度の残留は許容される。 Plastic deformation from VB 2 to V 3 B 4 is preferably allowed to proceed fully into the completely hot worked. If this plastic deformation is incomplete and VB 2 type boride remains in the steel structure, a coarse lamella composed of VB 2 type boride and M (C, N) type carbonitride crystallized during melting. The structure remains, the ductility of the steel decreases, and the elongation and bending strength decrease. Therefore, it is preferable that the steel of the present invention does not contain VB type 2 boride. However, a residue of about 1% or less is allowed.

[鋼の化学組成]
本発明の高ヤング率鋼において高ヤング率化に主要な役割を果たすV型硼化物を熱間加工による塑性変形によって生成させるため、鋼の化学組成を、C:0.1%以上、0.8%以下;Si:0.05%以上、0.5%以下;Mn:0.2%以上、1.5%以下;Ti:1%以上、7%以下;V:4%以上、8%以下;B:2%以上、3%以下;Al:0.005%以上、0.2%以下;Cr:1%以上、7%以下;N:0.001%以上、0.01%以下を含む組成(残部はFeおよび不純物)とする。
[Chemical composition of steel]
In order to produce V 3 B 4 type boride which plays a major role in increasing the Young's modulus in the high Young's modulus steel of the present invention by plastic deformation by hot working, the chemical composition of the steel is C: 0.1% or more 0.8% or less; Si: 0.05% or more, 0.5% or less; Mn: 0.2% or more, 1.5% or less; Ti: 1% or more, 7% or less; V: 4% or more 8% or less; B: 2% or more, 3% or less; Al: 0.005% or more, 0.2% or less; Cr: 1% or more, 7% or less; N: 0.001% or more, 0.01 % Of the composition (the balance is Fe and impurities).

C:0.1%以上、0.8%以下
Cは、鋼の強度を効果的に上げるとともに、マトリックスの組織を制御する重要な元素である。さらに、凝固時にVC、TiCなどの炭化物を晶出させ、やはり凝固時に晶出するV硼化物やTi硼化物の粗大化を抑制する。しかし、その含有量が0.1%未満の場合には上記の効果が得られない。一方、その含有量が0.8%を越えると、粗大でヤング率の低いM23(C,B)型炭硼化物が生成しやすくなるため、熱間加工性、延性、靱性に悪影響を及ぼし、また鋼のヤング率を低下させる。望ましいCの含有量は0.3%以上、0.5%以下である。
C: 0.1% or more and 0.8% or less C is an important element that effectively increases the strength of the steel and controls the matrix structure. Further, carbides such as VC and TiC are crystallized at the time of solidification, and the coarsening of V boride and Ti boride that is also crystallized at the time of solidification is suppressed. However, when the content is less than 0.1%, the above effect cannot be obtained. On the other hand, if the content exceeds 0.8%, a coarse and low Young's modulus M 23 (C, B) 6- type carbonitride is likely to be produced, which adversely affects hot workability, ductility, and toughness. And lowers the Young's modulus of the steel. Desirable C content is 0.3% or more and 0.5% or less.

Si:0.05%以上、0.5%以下
Siは脱酸に有効な元素であるが、その含有量が0.05%未満ではこの効果が得がたい。一方、0.5%を越えると、靱性に悪影響を及ぼすラーベス相が形成しやすくなる。
Si: 0.05% or more, 0.5% or less Si is an element effective for deoxidation, but if its content is less than 0.05%, this effect is difficult to obtain. On the other hand, if it exceeds 0.5%, a Laves phase that adversely affects toughness is likely to be formed.

Mn:0.2%以上、1.5%以下
Mnは、鋼の不純物を固定して熱間割れを抑制する。しかし、Mnの含有量が0.2%未満では上記の効果が得られない。一方、その含有量が1.5%を越えると、かえって、粒界を弱化させ、靱性や延性に悪影響を及ぼす。
Mn: 0.2% or more, 1.5% or less Mn fixes impurities in steel and suppresses hot cracking. However, if the Mn content is less than 0.2%, the above effect cannot be obtained. On the other hand, if the content exceeds 1.5%, the grain boundaries are weakened and the toughness and ductility are adversely affected.

Ti:1%以上、7%以下
Tiは凝固過程で酸化物、窒化物、炭化物、硼化物、等を形成し、凝固組織の微細化に有効である。さらに、溶融温度を高めるため、熱間加工温度範囲を高める作用がある。しかし、その含有量が1%未満では上記の効果が得られない。一方、その含有量が7%を越えると、粗大なTi炭窒化物やTi硼化物を形成し、熱間加工性、延性、靱性に悪影響を及ぼす。望ましいTiの含有量は3%以上、6%以下である。
Ti: 1% or more and 7% or less Ti forms oxides, nitrides, carbides, borides, and the like during the solidification process, and is effective in refining the solidified structure. Furthermore, in order to raise melting temperature, there exists an effect | action which raises the hot working temperature range. However, if the content is less than 1%, the above effect cannot be obtained. On the other hand, if the content exceeds 7%, coarse Ti carbonitrides and Ti borides are formed, which adversely affects hot workability, ductility and toughness. Desirable Ti content is 3% or more and 6% or less.

V:4%以上、8%以下
VはV型硼化物を形成し、鋼のヤング率を高めるのに有効な元素である。さらに、析出強化粒子であるV(C,N)型炭窒化物を生成する。しかし、その含有量が4%未満では上記の効果が得られない。一方、その含有量が8%を越えると粗大なV硼化物や炭窒化物を形成し、熱間加工性、延性、靱性に悪影響を及ぼす。望ましいVの含有量は5%以上、7%以下である。
V: 4% or more, 8% or less V is an element that forms a V 3 B 4 type boride and is effective in increasing the Young's modulus of steel. Furthermore, V (C, N) type carbonitrides which are precipitation strengthening particles are generated. However, if the content is less than 4%, the above effect cannot be obtained. On the other hand, if the content exceeds 8%, coarse V borides and carbonitrides are formed, which adversely affects hot workability, ductility and toughness. Desirable V content is 5% or more and 7% or less.

B:2%以上、3%以下
BはV型硼化物を形成する重要な元素である。しかし、その含有量が2%未満の場合には、形成する硼化物の量が少なく、所望のヤング率(240GPa)以上が得られない。一方、その含有量が3%を越えると、硼化物が粗大化し、熱間加工性、延性、靱性に悪影響を及ぼす。
B: 2% or more and 3% or less B is an important element for forming a V 3 B 4 type boride. However, when the content is less than 2%, the amount of boride to be formed is small, and a desired Young's modulus (240 GPa) or more cannot be obtained. On the other hand, if the content exceeds 3%, the boride becomes coarse and adversely affects hot workability, ductility, and toughness.

sol Al:0.005%以上、0.2%以下
Alは脱酸の観点から添加する。また、凝固組織を微細化する効果もある。しかし、その含有量が0.005%未満ではこれらの効果はない。一方、0.2%を超えると、粗大な酸化物が生成し易くなる。好ましいAlの含有量は0.05%以上、0.2%以下である。
sol Al: 0.005% to 0.2% Al is added from the viewpoint of deoxidation. It also has the effect of miniaturizing the solidified structure. However, if the content is less than 0.005%, these effects are not obtained. On the other hand, when it exceeds 0.2%, a coarse oxide is easily generated. A preferable Al content is 0.05% or more and 0.2% or less.

Cr:1%以上、7%以下
CrはV型硼化物の安定化と微細化に寄与する。しかし、1%未満ではその効果はない。一方、7%を超えると、V型硼化物が安定して生成しなくなり、熱間加工性、延性、靱性に悪影響を及ぼす。望ましいCrの含有量は4%以上、6%以下である。
Cr: 1% or more and 7% or less Cr contributes to stabilization and refinement of the V 3 B 4 type boride. However, less than 1% has no effect. On the other hand, when it exceeds 7%, the V 3 B 4 type boride is not generated stably, which adversely affects hot workability, ductility, and toughness. Desirable Cr content is 4% or more and 6% or less.

N:0.001%以上、0.01%以下
Nは凝固過程で窒化物を生成し、凝固組織の微細化に寄与する。しかし、その含有量が0.001%未満ではこの効果はない。一方、0.01%を超えて含有させると粗大な窒化物が形成し、熱間加工性、靱性、延性に悪影響を及ぼす。
N: 0.001% or more and 0.01% or less N generates nitrides in the solidification process and contributes to the refinement of the solidified structure. However, this effect is not obtained when the content is less than 0.001%. On the other hand, if the content exceeds 0.01%, coarse nitrides are formed, which adversely affects hot workability, toughness, and ductility.

本発明の高ヤング率鋼は、本質的に上記成分と残部のFeおよび不純物からなるものであることが好ましい。しかし、5%以上のV型硼化物と、1.5%以上のM(C,N)型炭窒化物(MはV及び/またはTiを意味する)とを含有し、かつこれら2種類の化合物の合計量が8〜30%であれば、鋼の化学組成は上記と異なるものであってもよい。例えば、上記以外の合金元素として、Cu,Ni,Mo等の硼化物を形成しない合金元素をさらに含有することもできる。 The high Young's modulus steel of the present invention is preferably essentially composed of the above components, the remaining Fe and impurities. However, it contains 5% or more of V 3 B 4 type boride and 1.5% or more of M (C, N) type carbonitride (M means V and / or Ti), and these If the total amount of the two kinds of compounds is 8 to 30%, the chemical composition of the steel may be different from the above. For example, as an alloy element other than the above, an alloy element that does not form borides such as Cu, Ni, and Mo can be further contained.

[製造方法]
本発明に係る高ヤング率鋼は、上記の化学組成を有する鋼片を、850℃〜1200℃の温度において総減面率70%以上で熱間加工を行うことを特徴とする方法により製造することができる。鋼片は通常の溶製法により製造したものでよい。
[Production method]
The high Young's modulus steel according to the present invention is manufactured by a method characterized by hot working a steel slab having the above chemical composition at a temperature of 850 ° C. to 1200 ° C. with a total area reduction of 70% or more. be able to. The steel piece may be manufactured by a normal melting method.

熱間加工温度範囲:850℃〜1200℃
本発明の骨子は、熱間加工を与えることにより鋼中に晶出したVB型硼化物を塑性変形させ、塑性変形したVB型硼化物がV型硼化物に相分離する現象を活用して、鋼中に高ヤング率化の効果が高いV型硼化物を多量に均一分散させることである。
Hot working temperature range: 850 ° C to 1200 ° C
Gist of the present invention, the VB 2 type boride issued in the steel crystallization by providing the hot working is plastically deformed, a phenomenon VB 2 type boride was plastic deformation phase separation V 3 B 4 type boride Is used to uniformly disperse a large amount of V 3 B 4 type boride, which has a high Young's modulus, in steel.

この現象について種々の熱間加工温度で調査した結果、熱間加工温度が850℃未満ではVB型硼化物が十分に塑性変形せず、VB型硼化物からV型硼化物の相変化が生じないことが明らかとなった。また、熱間加工温度が低いと変形能が不充分なため、割れが発生しやすくなる。一方、熱間加工温度が1200℃を超えると、FeBなどの低融点化合物が溶解して、熱間加工の阻害要因となる。したがって、熱間加工温度範囲は850℃以上、1200℃以下とする。好ましい熱間加工温度範囲は870〜1100℃である。 As a result of investigating this phenomenon at various hot working temperatures, when the hot working temperature is less than 850 ° C., the VB 2 type boride is not sufficiently plastically deformed, and from the VB 2 type boride to the V 3 B 4 type boride. It became clear that no phase change occurred. Moreover, since the deformability is insufficient when the hot working temperature is low, cracking is likely to occur. On the other hand, when the hot working temperature exceeds 1200 ° C., a low-melting point compound such as FeB is dissolved, which becomes an impediment to hot working. Therefore, the hot working temperature range is 850 ° C. or more and 1200 ° C. or less. The preferred hot working temperature range is 870-1100 ° C.

熱間加工量:総減面率で70%以上
850〜1200℃の温度範囲での熱間加工による加工率が総減面率で70%未満であると、V型硼化物の生成量が少ないうえに、均一に分散しないため、延性、靱性に悪影響を及ぼす。したがって、上記温度範囲での熱間加工率は、総減面率で70%以上とする。この総減面率は好ましくは80%以上である。
Amount of hot work: 70% or more in total area reduction rate When the work rate by hot working in the temperature range of 850 to 1200 ° C. is less than 70% in total area reduction, V 3 B 4 type boride is formed. In addition to its small amount, it does not disperse uniformly, which adversely affects ductility and toughness. Therefore, the hot working rate in the above temperature range is 70% or more in terms of the total area reduction. This total area reduction is preferably 80% or more.

熱間加工の種類は特に制限されるものではないが、鍛造、圧延、抽伸、等が可能である。本発明の高ヤング率鋼は、板材、管材、棒材、型材など、多様な形状で提供しうる。   The type of hot working is not particularly limited, but forging, rolling, drawing, etc. are possible. The high Young's modulus steel of the present invention can be provided in various shapes such as a plate material, a pipe material, a bar material, and a mold material.

本例では、表1に示す化学成分を有する鋼A〜Lを、その合金成分のうちTiおよびB以外の元素を真空中でFeに溶解した後、Bを含有する合金鉄(フェロボロン)およびTi/Bを含有する合金鉄をこの順に添加して完全に溶解することにより、50Kgの鋼塊を得た。鋼HはB含有合金鉄のみを添加した。鋼塊のサイズは、上側直径が180mm、下側直径が130mm、高さが310mmであった。   In this example, steels A to L having the chemical components shown in Table 1 were dissolved in Fe in the alloy components other than Ti and B in Fe, and then alloy iron (ferroboron) containing B and Ti The alloy iron containing / B was added in this order and completely dissolved to obtain a 50 kg steel ingot. For steel H, only B-containing alloy iron was added. As for the size of the steel ingot, the upper diameter was 180 mm, the lower diameter was 130 mm, and the height was 310 mm.

鋼Aの一部は、こうして得られた鋳造材のままで評価試験を行った(試験番号1)。
上記以外は、表2に示す温度に加熱した後、表2に示す温度範囲、パス回数および総減面率で熱間鍛造を行い、棒状に加工した。熱間加工中に温度が低下した場合には、再加熱を行って、熱間鍛造温度が所定の範囲に入るようにした。熱間鍛造後の冷却は空冷であった。
A part of Steel A was subjected to an evaluation test with the cast material thus obtained (Test No. 1).
Except for the above, after heating to the temperature shown in Table 2, hot forging was performed in the temperature range shown in Table 2, the number of passes, and the total area reduction rate, and processed into a rod shape. When the temperature decreased during hot working, reheating was performed so that the hot forging temperature was within a predetermined range. Cooling after hot forging was air cooling.

このようにして得られた棒鋼の中心部から試験片を採取し、晶出物・析出物の同定、ヤング率の測定、引張特性および抗折力の測定を実施した。これらの試験結果を表2に併記する。また、一部の棒鋼については、試験片の断面SEM観察により析出化合物の形状を判定した。   A test piece was collected from the central portion of the steel bar thus obtained, and crystallized substances / precipitates were identified, Young's modulus was measured, tensile properties, and bending strength were measured. These test results are also shown in Table 2. Moreover, about some bar steel, the shape of the precipitation compound was determined by cross-sectional SEM observation of the test piece.

晶出物・析出物の同定は、10%アセチルアセトン−1%テトラメチルアンモニウムクロライド−メタノール系電解液で得られた残渣のX線回折により行った。
晶出物・析出物の含有量は、そのX線回折のピーク強度から換算して求めた。
The crystallized substance / precipitate was identified by X-ray diffraction of the residue obtained with 10% acetylacetone-1% tetramethylammonium chloride-methanol electrolyte.
The content of the crystallized product / precipitate was calculated from the peak intensity of the X-ray diffraction.

ヤング率は、厚さが1.5mm、幅が10mm、長さが60mmのヤング率測定用サンプルを用いて、通常の横共振法で共振周波数を測定することにより求めた。
引張特性は、平行部の直径6mm、平行部長さ40mmの丸棒引張試験片を用い、10mm/分の引張速度により、耐力、引張強さ、破断伸びを求めた。
The Young's modulus was obtained by measuring the resonance frequency by a normal lateral resonance method using a Young's modulus measurement sample having a thickness of 1.5 mm, a width of 10 mm, and a length of 60 mm.
Tensile properties were determined by using a round bar tensile test piece having a parallel part diameter of 6 mm and a parallel part length of 40 mm at a tensile speed of 10 mm / min and yield strength, tensile strength, and elongation at break.

抗折力は、直径5mm、長さ70mmの抗折力測定用サンプルを用い、支点間距離50mm、曲げ速度1mm/分で荷重を加え、破断するまでの荷重(抗折荷重)を求めた。
抗折荷重P[N]の時、抗折力σ[MPa]は下式で与えられる。
The bending strength was determined by using a sample for measuring the bending strength having a diameter of 5 mm and a length of 70 mm, applying a load at a fulcrum distance of 50 mm and a bending speed of 1 mm / min to obtain a load (breaking load) until breaking.
When the bending load P [N], the bending force σ [MPa] is given by the following equation.

抗折力σ=8P・L/π・d
L:支点間距離、
d:サンプルの直径。
Folding force σ = 8P · L / π · d 3
L: Distance between fulcrums,
d: Sample diameter.

Figure 2007051341
Figure 2007051341

Figure 2007051341
Figure 2007051341

表2において、試験番号1〜5は、本発明に適した特定範囲内の同一の化学組成を有するが、加工履歴がそれぞれ異なる鋼の例を示す。   In Table 2, test numbers 1 to 5 show examples of steels having the same chemical composition within a specific range suitable for the present invention but having different processing histories.

試験番号1は、鋳造ままの鋳造材である。X線回折と断面SEM観察の結果、VB型硼化物およびM(C,N)型炭窒化物が層状(ラメラ組織として)に生成していた。V型硼化物は検出されなかった。したがって、ヤング率は高い値を示すものの、引張試験による延性が低く、抗折力も低かった。 Test number 1 is a cast material as cast. As a result of X-ray diffraction and cross-sectional SEM observation, VB type 2 boride and M (C, N) type carbonitride were produced in a layered form (as a lamellar structure). V 3 B type 4 boride was not detected. Therefore, although the Young's modulus was high, the ductility by the tensile test was low and the bending strength was also low.

試験番号2は、本発明にしたがった適切な熱間加工を施した鋼である。熱間加工により5%以上のV型硼化物が生成しており、VB型硼化物は検出されなかった。生成したV型硼化物は球状化した微細粒子であり、断面SEM観察により粒子の平均アスペクト比が1に近いことが認められた。その結果、この鋼は、高ヤング率でありながら、引張強度>600MPa、伸び>10%、抗折力>2500MPa以上の性能を示した。 Test No. 2 is a steel that has been subjected to appropriate hot working according to the present invention. 5% or more of V 3 B 4 boride was generated by hot working, and no VB 2 boride was detected. The generated V 3 B 4 type boride was fine particles that were spheroidized, and the average aspect ratio of the particles was found to be close to 1 by cross-sectional SEM observation. As a result, this steel exhibited performances of tensile strength> 600 MPa, elongation> 10%, and bending strength> 2,500 MPa or more while having a high Young's modulus.

図1に試験番号1および2の鋼について検出された化合物のX線回折パターンを示す。バナジウム硼化物の回折ピークとして、試験番号1ではVBに帰属するピークのみが、試験番号2ではVに帰属するピークのみが観測されている。したがって、試験番号2で実施した熱間加工による塑性変形によって、VBからのVへの相分離が完全に起こったことがわかる。 FIG. 1 shows the X-ray diffraction patterns of the compounds detected for the steels of test numbers 1 and 2. As a diffraction peak of vanadium boride, only a peak attributed to VB 2 is observed in Test No. 1 and only a peak attributed to V 3 B 4 is observed in Test No. 2. Therefore, it can be seen that the phase separation from VB 2 to V 3 B 4 occurred completely due to the plastic deformation by the hot working performed in Test No. 2.

図2は、試験番号1および2の鋼の断面SEM像を示す。試験番号1では、分散化合物が偏平ないし層状のラメラ組織であるのに対し、その2倍の倍率で示す試験番号2では、分散化合物が球形(平均アスペクト比が1)に近く、ずっと微細で均一に分散しており、ラメラ組織は全く見当たらない。この図からも、適切な熱間加工を加えることによるVBからのVへの相分離が完全に起こることがわかる。 FIG. 2 shows cross-sectional SEM images of the steels of test numbers 1 and 2. In Test No. 1, the dispersed compound is a flat or lamellar lamellar structure, whereas in Test No. 2, which shows a magnification twice that of the dispersed compound, the dispersed compound is nearly spherical (average aspect ratio is 1), much finer and uniform. The lamellar tissue is not found at all. Also from this figure, it can be seen that phase separation from VB 2 to V 3 B 4 occurs completely by applying appropriate hot working.

図3は、試験番号2の鋼である鋼種Bについて、試験番号2と同じ温度範囲で減面率を変えた場合のTEM像を示す。図3(a)は減面率50%の場合のTEM像であり、図3(b)は減面率80%の場合のTEM像である。減面率50%では、VB+Vの粒子が認められ、VB→Vへの相分離が不完全であり、粒子は粗大であった。一方、減面率80%では、VBからのVへの相分離が完全に起こり、VBは消失して、Vの微細で球状の粒子と(Fe,V)Bの粒子が観察された。この図から、バナジウム硼化物については、熱間加工の過程でVB→VB+V→V+(Fe,V)Bなる相変化が生ずることがわかる。 FIG. 3 shows a TEM image of the steel type B, which is the steel of test number 2, when the reduction in area is changed in the same temperature range as that of test number 2. FIG. 3A is a TEM image when the area reduction rate is 50%, and FIG. 3B is a TEM image when the area reduction rate is 80%. At an area reduction of 50%, VB 2 + V 3 B 4 particles were observed, the phase separation from VB 2 → V 3 B 4 was incomplete, and the particles were coarse. On the other hand, at an area reduction rate of 80%, phase separation from VB 2 to V 3 B 4 occurs completely, VB 2 disappears, and fine spherical particles of V 3 B 4 and (Fe, V) B Of particles were observed. From this figure, it can be seen that vanadium boride undergoes a phase change of VB 2 → VB 2 + V 3 B 4 → V 4 B 5 + (Fe, V) B during the hot working process.

試験番号3では、熱間鍛造温度が高すぎたために、熱間加工中に割れが生じ、評価用サンプルが得られなかった。
試験番号4では、熱間加工温度は適切であったが、総減面率が46.2%と加工量が少なすぎたため、V型硼化物の生成量が不十分で、多量のVB型硼化物が残っていた。断面SEM観察では、このVB型硼化物およびM(C,N)型炭窒化物の層状組織が残っていた。その結果、伸び、抗折力とも不芳であった。
In test number 3, since the hot forging temperature was too high, cracking occurred during hot working, and an evaluation sample could not be obtained.
In test No. 4, the hot working temperature was appropriate, but the total area reduction rate was 46.2%, and the amount of processing was too small. Therefore, the amount of V 3 B 4 type boride was insufficient, VB type 2 boride remained. In the cross-sectional SEM observation, the VB 2 type borides and M (C, N) had remained layered tissue type carbonitrides. As a result, the elongation and bending strength were unsatisfactory.

試験番号5では、熱間鍛造温度が低すぎたため、熱間加工中に割れが生じ、評価用サンプルが得られなかった。
試験番号6および7も、本発明に適した同一の化学組成を有するが、加工履歴の異なる鋼の例を示す。
In test number 5, since the hot forging temperature was too low, cracks occurred during hot working, and no sample for evaluation was obtained.
Test numbers 6 and 7 also show examples of steels having the same chemical composition suitable for the present invention, but with different processing histories.

試験番号6では、本発明にしたがって熱間加工により、5%以上のV型硼化物が生成していた。このV型硼化物は、試験番号2と同様に球状化した微細粒子で均一に分散していることが断面SEM観察から確認された。これにより、高ヤング率の鋼でありながら、引張強度>600MPa、伸び>10%、抗折力>2500MPa以上の性能を示した。 In test number 6, 5% or more V 3 B 4 type boride was generated by hot working according to the present invention. It was confirmed from cross-sectional SEM observation that the V 3 B 4 type boride was uniformly dispersed with spherical fine particles as in Test No. 2. Thereby, although it was steel with high Young's modulus, the performance of tensile strength> 600 MPa, elongation> 10%, and bending strength> 2,500 MPa or more was exhibited.

試験番号7では、熱間加工温度は適切であったが、加工量が少なすぎたため、V型硼化物の生成量が不十分で、VB型硼化物およびM(C,N)型炭窒化物からなる層状組織が残っていた。その結果、伸び、抗折力が不芳であった。 In test number 7, the hot working temperature was appropriate, but the amount of processing was too small, so the amount of V 3 B 4 type boride produced was insufficient, and VB 2 type boride and M (C, N) A layered structure made of type carbonitride remained. As a result, elongation and bending strength were unsatisfactory.

試験番号8〜10はいずれも、化学組成と熱間加工条件がいずれも適切な、本発明にしたがった鋼を例示する。化学組成は互いに異なるものの、適切な熱間加工により5%以上のV型硼化物が生成した。このV型硼化物はいずれも、試験番号2と同様の球状化した微細粒子で鋼中に均一に分散していること、が断面SEM観察から確認された。そのため、高ヤング率の鋼でありながら、引張強度>600MPa、伸び>10%、抗折力>2500MPa以上の性能を示す。 Test numbers 8-10 all illustrate steel according to the present invention in which both chemical composition and hot working conditions are appropriate. Although the chemical compositions were different from each other, 5% or more of V 3 B 4 type boride was formed by appropriate hot working. It was confirmed from cross-sectional SEM observation that all of these V 3 B 4 type borides were uniformly dispersed in steel with the same spherical fine particles as in Test No. 2. Therefore, although it is a steel having a high Young's modulus, it exhibits performances of tensile strength> 600 MPa, elongation> 10%, and bending strength> 2500 MPa.

試験番号11は、C量が多すぎる例である。そのため、熱間加工条件は適切であったにもかかわらず、鋼中のV型硼化物の量が本発明における下限の5%に達しなかった。これは、C量が多いため、大量のM23(C,B)型炭硼化物が生成したためであると考えられる。この鋼のヤング率は240GPaに達せず、伸び、抗折力も不芳であった。これは、多量の析出したM23(C,B)型炭硼化物のヤング率が200GPa以下と低いためであり、これを多く含む鋼はヤング率が低くなる。 Test number 11 is an example in which the amount of C is too large. Therefore, although the hot working conditions were appropriate, the amount of V 3 B 4 type boride in the steel did not reach the lower limit of 5% in the present invention. This is thought to be because a large amount of M 23 (C, B) 6 type carbon boride was generated because of the large amount of C. The Young's modulus of this steel did not reach 240 GPa, and the elongation and bending strength were poor. This is because the Young's modulus of a large amount of precipitated M 23 (C, B) 6 type carbon boride is as low as 200 GPa or less, and the steel containing a large amount thereof has a low Young's modulus.

試験番号12は、C量が少なすぎ、Crを含まない例である。熱間加工条件は適切であったにもかかわらず、V型硼化物の生成量が不十分で、VB型硼化物とM(C,N)型炭窒化物からなる層状組織が残った。また、C量が少ないため、M(C,N)型炭窒化物の量が少なすぎ、V型硼化物とM(C,N)型炭窒化物の合計量が本発明における下限である8%に達しなかった。その結果、引張強度、伸び、抗折力のいずれも不芳であった。 Test number 12 is an example in which the amount of C is too small and Cr is not included. Although the hot working conditions were appropriate, the amount of V 3 B 4 type boride produced was insufficient, and a layered structure consisting of VB 2 type boride and M (C, N) type carbonitride was obtained. The remaining. Further, since the amount of C is small, the amount of M (C, N) type carbonitride is too small, and the total amount of V 3 B 4 type boride and M (C, N) type carbonitride is the lower limit in the present invention. It did not reach 8%. As a result, all of tensile strength, elongation, and bending strength were unsatisfactory.

試験番号13は、Tiを含有せず、N量が多すぎる例である。熱間加工可能な温度範囲が狭いため、熱間鍛造中に割れを生じ、評価用サンプルが得られなかった。
試験番号14は、Ti量が多すぎ、V量が少なすぎる例である。この鋼は、多量のTiB型硼化物(ヤング率:約550GPa)を含有するため、ヤング率は高くなかったが、V型硼化物が全く生成しないので、靱性や延性は不芳であった。
Test No. 13 is an example that does not contain Ti and the amount of N is too large. Since the temperature range in which hot working can be performed is narrow, cracking occurred during hot forging, and an evaluation sample could not be obtained.
Test number 14 is an example in which the Ti amount is too large and the V amount is too small. Since this steel contains a large amount of TiB 2 type boride (Young's modulus: about 550 GPa), the Young's modulus was not high, but V 3 B 4 type boride was not formed at all, so the toughness and ductility were poor. Met.

試験番号15は、Cr量、V量、B量がいずれも多すぎる例である。多量の化合物が析出したが、適切な熱間加工によりVB型硼化物を全て相分離させることができ、多量のV型硼化物が生成した。そのため、ヤング率は非常に高くなった。しかし、溶製時に多量の硼化物が析出したため、M(C,N)型炭窒化物の析出量が不足し、引張強度が低くなった。また、延性、抗折力も不芳であったが、その原因は析出物が凝集粗大化していたためと考えられる。 Test number 15 is an example in which there are too many Cr, V, and B amounts. Although a large amount of the compound was precipitated, all the VB 2 type borides could be phase-separated by appropriate hot working, and a large amount of V 3 B 4 type borides were formed. Therefore, Young's modulus became very high. However, since a large amount of boride was precipitated during melting, the amount of M (C, N) carbonitride deposited was insufficient, and the tensile strength was low. Moreover, although ductility and bending strength were also unsatisfactory, the cause is thought to be because the precipitates were agglomerated and coarsened.

試験番号16は、Ti量、V量、B量がいずれも少なすぎる例である。鋼中の高剛性化合物の量が少ないため、所望のヤング率が得られなかった。
試験番号17はいずれも、化学組成と熱間加工条件がいずれも適切な、本発明にしたがった鋼を例示する。化学組成は互いに異なるものの、適切な熱間加工により5%以上のV型硼化物が生成した。このV型硼化物はいずれも、試験番号2と同様の球状化した微細粒子で鋼中に均一に分散していること、が断面SEM観察から確認された。そのため、高ヤング率の鋼でありながら、引張強度>600MPa、伸び>10%、抗折力>2500MPa以上の性能を示す。
Test number 16 is an example in which the Ti amount, V amount, and B amount are all too small. The desired Young's modulus could not be obtained due to the small amount of high rigidity compound in the steel.
Test number 17 exemplifies steel according to the present invention where both chemical composition and hot working conditions are appropriate. Although the chemical compositions were different from each other, 5% or more of V 3 B 4 type boride was formed by appropriate hot working. It was confirmed from cross-sectional SEM observation that all of these V 3 B 4 type borides were uniformly dispersed in steel with the same spherical fine particles as in Test No. 2. Therefore, although it is a steel having a high Young's modulus, it exhibits performances of tensile strength> 600 MPa, elongation> 10%, and bending strength> 2500 MPa.

以上からわかる通り、本発明に従った量のV型硼化物およびM(C,N)型炭窒化物を含有する鋼は、240GPa以上の高いヤング率(剛性)を示すと同時に、延性と靱性も高く、引張強度>600MPa、伸び>10%、抗折力>2500MPa以上の性能を示す。 As can be seen from the above, V 3 B 4 type boride in an amount in accordance with the present invention and M (C, N) type steel containing carbonitride is simultaneously shown above high Young's modulus 240GPa a (rigid), The ductility and toughness are also high, and the tensile strength> 600 MPa, the elongation> 10%, and the bending strength> 2,500 MPa or more are exhibited.

本発明の高ヤング率鋼は、適切な化学成分の鋼に適切な条件で熱間加工を施すことにより製造することができる。化学成分が適切であっても熱間加工条件が不適切であるか、逆に熱間加工条件が適切であっても鋼の化学成分が不適切であると、本発明にしたがった量のV型硼化物およびM(C,N)型炭窒化物を含有する高ヤング率鋼を得ることはできない。 The high Young's modulus steel of the present invention can be produced by subjecting steel having an appropriate chemical composition to hot working under appropriate conditions. Even if the chemical composition is appropriate, the hot working conditions are inadequate, or conversely, if the hot working conditions are appropriate, the steel chemical composition is inadequate. High Young's modulus steel containing 3 B type 4 boride and M (C, N) type carbonitride cannot be obtained.

鋼の化学組成が同一の鋳造材(試験番号1)および鍛造材(試験番号2)から採取した抽出残渣のX線回折図を示す。The X-ray diffraction pattern of the extraction residue extract | collected from the cast material (test number 1) and forging material (test number 2) with the same chemical composition of steel is shown. 鋼の化学組成が同一の鋳造材(試験番号1)および鍛造材(試験番号2)の断面SEM像を示す。The cross-sectional SEM image of the cast material (test number 1) and forging material (test number 2) with the same chemical composition of steel is shown. 鋼種Bについて減面率を変えて熱間加工した時の、V型硼化物の生成過程を示すTEM像である。When hot working by changing the reduction rate for steel type B, and a TEM image showing a process of generating V 3 B 4 type boride.

Claims (4)

(a)V型硼化物5質量%以上と、(b)M(C,N)型炭窒化物(MはV及び/またはTi)1.5質量%以上とを含有し、(a)と(b)の合計量が8〜30質量%であることを特徴とする、高ヤング率鋼。 (A) V 3 B 4 type boride 5% by mass or more and (b) M (C, N) type carbonitride (M is V and / or Ti) 1.5% by mass or more, A high Young's modulus steel characterized in that the total amount of a) and (b) is 8 to 30% by mass. VB型硼化物を含有しない、請求項1記載の高ヤング率鋼。 The high Young's modulus steel according to claim 1, which does not contain VB type 2 boride. 質量%で、
C:0.1%以上、0.8%以下; Si:0.05%以上、0.5%以下;
Mn:0.2%以上、1.5%以下; Ti:1%以上、7%以下;
V:4%以上、8%以下; B:2%以上、3%以下;
Al:0.005%以上、0.2%以下; Cr:1%以上、7%以下;
N:0.001%以上、0.01%以下
を含有し、残部はFeおよび不純物からなる、請求項1または2記載の高ヤング率鋼。
% By mass
C: 0.1% to 0.8%; Si: 0.05% to 0.5%;
Mn: 0.2% to 1.5%; Ti: 1% to 7%;
V: 4% to 8%; B: 2% to 3%;
Al: 0.005% to 0.2%; Cr: 1% to 7%;
N: The high Young's modulus steel of Claim 1 or 2 containing 0.001% or more and 0.01% or less, and remainder consists of Fe and an impurity.
質量%で、
C:0.1%以上、0.8%以下; Si:0.05%以上、0.5%以下;
Mn:0.2%以上、1.5%以下; Ti:1%以上、7%以下;
V:4%以上、8%以下; B:2%以上、3%以下;
Al:0.005%以上、0.2%以下;Cr:1%以上、7%以下;
N:0.001%以上、0.01%以下
を含有し、残部はFeおよび不純物からなる鋼片に、850℃〜1200℃の温度範囲で、総減面率70%以上の熱間加工を施すことを特徴とする、高ヤング率鋼の製造方法。
% By mass
C: 0.1% to 0.8%; Si: 0.05% to 0.5%;
Mn: 0.2% to 1.5%; Ti: 1% to 7%;
V: 4% to 8%; B: 2% to 3%;
Al: 0.005% to 0.2%; Cr: 1% to 7%;
N: 0.001% or more and 0.01% or less, and the remainder is hot-worked with a total area reduction of 70% or more in a temperature range of 850 ° C. to 1200 ° C. in a steel piece made of Fe and impurities. A method for producing a high Young's modulus steel, characterized by comprising:
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Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2013050397A1 (en) 2011-10-04 2013-04-11 Tata Steel Nederland Technology Bv Steel product with improved e-modulus and method for producing said product
WO2013171231A1 (en) 2012-05-14 2013-11-21 Tata Steel Nederland Technology Bv High strength steel with increased e-modulus and method for producing said steel
EP2703509A1 (en) 2012-08-28 2014-03-05 Tata Steel Nederland Technology B.V. TiC- and TiB2-Particles reinforced high strength and low density steel with improved E-modulus and method for producing said steel
EP2703510A1 (en) 2012-08-28 2014-03-05 Tata Steel Nederland Technology B.V. Particle-reinforced steel with improved E-modulus and method for producing said steel
WO2014040783A1 (en) 2012-09-14 2014-03-20 Tata Steel Nederland Technology Bv TiC-PARTICLE-REINFORCED HIGH STRENGTH AND LOW DENSITY STEEL PRODUCTS WITH IMPROVED E-MODULUS AND METHOD FOR PRODUCING SAID PRODUCT
US9315883B2 (en) 2012-09-14 2016-04-19 Tata Steel Nederland Technology Bv High strength and low density particle-reinforced steel with improved E-modulus and method for producing said steel

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2004035948A (en) * 2002-07-03 2004-02-05 Sumitomo Metal Ind Ltd High-strength high-stiffness steel and manufacturing method therefor
JP2004353063A (en) * 2003-05-30 2004-12-16 Sumitomo Metal Ind Ltd High rigidity steel having excellent toughness, and its production method
JP2005082831A (en) * 2003-09-05 2005-03-31 Sumitomo Metal Ind Ltd Smelted high-rigidity steel

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2004035948A (en) * 2002-07-03 2004-02-05 Sumitomo Metal Ind Ltd High-strength high-stiffness steel and manufacturing method therefor
JP2004353063A (en) * 2003-05-30 2004-12-16 Sumitomo Metal Ind Ltd High rigidity steel having excellent toughness, and its production method
JP2005082831A (en) * 2003-09-05 2005-03-31 Sumitomo Metal Ind Ltd Smelted high-rigidity steel

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2013050397A1 (en) 2011-10-04 2013-04-11 Tata Steel Nederland Technology Bv Steel product with improved e-modulus and method for producing said product
WO2013171231A1 (en) 2012-05-14 2013-11-21 Tata Steel Nederland Technology Bv High strength steel with increased e-modulus and method for producing said steel
EP2703509A1 (en) 2012-08-28 2014-03-05 Tata Steel Nederland Technology B.V. TiC- and TiB2-Particles reinforced high strength and low density steel with improved E-modulus and method for producing said steel
EP2703510A1 (en) 2012-08-28 2014-03-05 Tata Steel Nederland Technology B.V. Particle-reinforced steel with improved E-modulus and method for producing said steel
WO2014040783A1 (en) 2012-09-14 2014-03-20 Tata Steel Nederland Technology Bv TiC-PARTICLE-REINFORCED HIGH STRENGTH AND LOW DENSITY STEEL PRODUCTS WITH IMPROVED E-MODULUS AND METHOD FOR PRODUCING SAID PRODUCT
US9315883B2 (en) 2012-09-14 2016-04-19 Tata Steel Nederland Technology Bv High strength and low density particle-reinforced steel with improved E-modulus and method for producing said steel

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