JP2015040315A - Die alloy tool steel having small anisotropy and dimensional change due to heat treatment - Google Patents
Die alloy tool steel having small anisotropy and dimensional change due to heat treatment Download PDFInfo
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本発明は、合金工具鋼、詳しくは焼入焼戻しの際に熱処理による寸法変化（以下、特に断らない限り、単に「寸法変化」という。）の異方性が小さい性質を有する金型用の合金工具鋼に関する。 The present invention relates to an alloy tool steel, and more particularly, an alloy for a mold having a property of small anisotropy of a dimensional change caused by heat treatment during quenching and tempering (hereinafter, simply referred to as “dimensional change” unless otherwise specified). It relates to tool steel.
金型の製作は、焼なまし状態の素材を粗加工し、さらに必要硬さを得るために焼入焼戻し処理を行って製作される。その焼入焼戻しに伴って粗加工された材料中で組織変化が起こり寸法変化が生じる。また、素材の採取方向によって焼入焼戻し後の寸法変化の異方性があると粗加工時のサイズを決め難く、そこで寸法不足を避けるために粗加工時のサイズを大きくせざるを得ず、仕上加工する時に、多くの部分を切削して金型として作製している。そこで金型の製造コストや製造時間を低減するために、焼戻し後の寸法変化が小さく等方的であることが望まれる。 The mold is manufactured by roughly processing an annealed material and performing a quenching and tempering process in order to obtain a required hardness. Along with the quenching and tempering, a structural change occurs in the roughly processed material and a dimensional change occurs. Also, if there is anisotropy of dimensional change after quenching and tempering depending on the material sampling direction, it is difficult to determine the size at the time of rough machining, so in order to avoid lack of dimensions, the size at the time of rough machining must be increased, When finishing, many parts are cut to make a mold. Therefore, in order to reduce the manufacturing cost and manufacturing time of the mold, it is desired that the dimensional change after tempering is small and isotropic.
上記した要望に応えるべく、必要な硬さが得られる温度で、寸法変化の小さい鋼種が発明されている。しかし、一般的には、５００℃程度まで焼戻しされているので、ピーク硬さが得られないだけでなく、その後にＰＶＤなどの表面処理を行う際に、処理時に５００℃以上に加熱されるため、焼戻しが進み、寸法変化が起きる。そのために、一般的にピーク硬さが得られる焼戻温度域（５２０〜５３０℃）における寸法変化が小さく、素材の採取方向による寸法変化の異方性の少ない鋼材が求められる。 In order to meet the above-described demand, a steel type having a small dimensional change has been invented at a temperature at which necessary hardness can be obtained. However, in general, since it is tempered to about 500 ° C., not only the peak hardness is not obtained, but also when performing a surface treatment such as PVD after that, it is heated to 500 ° C. or more during the treatment. Tempering progresses and dimensional changes occur. Therefore, a steel material is generally required that has a small dimensional change in the tempering temperature range (520 to 530 ° C.) in which peak hardness is obtained and has a small anisotropy in dimensional change depending on the material sampling direction.
そこで、このような鋼材として、化学成分およびＣｒ偏析に注目した、炭化物分散による低寸法変化の工具鋼が開発されている（例えば、特許文献１参照。）。しかし、この鋼材は寸法変化が圧延方向のみで、垂直方向への寸法変化は考慮されておらず、垂直方向の線熱膨張率が０．１％以下になるかどうかが判らないので、垂直方向は粗加工をして、仕上加工時に削り取る量を多く設定する必要がある。 Therefore, as such a steel material, a tool steel having a low dimensional change due to carbide dispersion, focusing on chemical components and Cr segregation, has been developed (for example, see Patent Document 1). However, this steel material has a dimensional change only in the rolling direction, the dimensional change in the vertical direction is not considered, and it is not known whether the linear thermal expansion coefficient in the vertical direction is 0.1% or less. For roughing, it is necessary to set a large amount of scraping during finishing.
さらに、他の鋼材として、Ｎｉ、ＡｌおよびＣｕを添加し金属間化合物の析出を利用して焼戻し時の膨張を抑えている鋼が開発されている（例えば、特許文献２参照。）。しかし、金属間化合物が増えると脆化しやすくなり、金型の廃却要因の一つである大割れが起こりやすくなり、この鋼材では寸法変化が小さいことによる切削コスト低減の効果が限定的になってしまう。 Furthermore, steel which adds Ni, Al, and Cu as another steel material and suppresses expansion at the time of tempering using precipitation of intermetallic compounds has been developed (for example, refer to Patent Document 2). However, as the amount of intermetallic compounds increases, embrittlement easily occurs, and large cracks, which are one of the causes of mold disposal, tend to occur, and this steel material has a limited cutting cost reduction effect due to small dimensional changes. End up.
本発明の課題は、焼入焼戻しの際の寸法変化が小さく、かつ、異方性の小さい性質を有する合金工具鋼を提供することである。 An object of the present invention is to provide an alloy tool steel having a small dimensional change during quenching and tempering and a property of low anisotropy.
上記の課題を解決するための本発明の手段は、質量％で、Ｃ：０．３５〜０．９５％、Ｓｉ：０．６０〜１．２０％、Ｍｎ：０．１〜０．６％、Ｃｒ：７．０〜１３．０％、（Ｍｏ＋Ｗ／２）０．５〜２．０％、Ｖ：１．２％以下からなり、残部がＦｅおよび不可避不純物からなる鋼で、該鋼の焼戻温度５１０〜５３０℃における圧延方向の寸法変化状態を示す値をＡおよび圧延方向に対する垂直方向の寸法変化状態を示す値をＢとするとき、Ａ＝０．３９Ｃ−０．５４Ｓｉ＋０．１７Ｃｒからなり、かつ、Ｂ＝０．３６Ｃ＋０．５４Ｓｉ−０．０５Ｃｒからなり、Ａ：１．１３〜２．１０、かつ、Ｂ：０．０９〜０．４３であり、寸法変化率が−０．０５％〜＋０．０５％であることを特徴とする熱処理による寸法変化が少なく、かつ、寸法変化の異方性の小さな金型用の合金工具鋼である。 The means of the present invention for solving the above-mentioned problems is, in mass%, C: 0.35 to 0.95%, Si: 0.60 to 1.20%, Mn: 0.1 to 0.6% Cr: 7.0 to 13.0%, (Mo + W / 2) 0.5 to 2.0%, V: 1.2% or less, the balance being Fe and inevitable impurities, From A = 0.39C−0.54Si + 0.17Cr, where A is the value indicating the dimensional change state in the rolling direction at a tempering temperature of 510 to 530 ° C. and B is the value indicating the dimensional change state in the direction perpendicular to the rolling direction. And B = 0.36C + 0.54Si-0.05Cr, A: 1.13 to 2.10, and B: 0.09 to 0.43, and the dimensional change rate is -0.05. % To + 0.05%, there is little dimensional change due to heat treatment, and Which is an alloy tool steel for a small mold of the anisotropy of the change.
以上の手段とすることで、本願の金型用の合金工具鋼は、圧延方向とこの方向に対する垂直方向の焼入焼戻しの際の熱処理による寸法変化率が−０．０５％〜＋０．０５％内である異方性の小さな等方的な性質を有しており、したがって、この合金工具鋼を用いて金型を製造するとき、粗加工時の寸法を必要以上に大きく取らずに済むので材料費が節減でき、また仕上げ加工の加工費も低減できるので、寸法精度に優れた金型を低コストで製造できる極めて優れた効果を奏する。 By using the above means, the alloy tool steel for the mold of the present application has a dimensional change rate of -0.05% to + 0.05% due to heat treatment in the rolling direction and in the quenching and tempering direction perpendicular to the rolling direction. Therefore, when manufacturing molds using this alloy tool steel, it is not necessary to take dimensions larger than necessary during rough machining. Since the material cost can be reduced and the finishing processing cost can also be reduced, it is possible to produce a die having excellent dimensional accuracy at a low cost.
本発明の実施の形態について、表および図を参照して説明する。先ず、最初に本発明に係る鋼の化学成分の成分範囲を限定した理由およびこれらの化学成分の組合せからなる式であるＡおよびＢの値を限定した理由について説明する。なお、これらにおいて、％は質量％を示すものとする。 Embodiments of the present invention will be described with reference to tables and drawings. First, the reason for limiting the component range of the chemical components of the steel according to the present invention and the reason for limiting the values of A and B, which are formulas composed of combinations of these chemical components, will be described. In these, “%” represents mass%.
Ｃ：０．３５〜０．９５％
Ｃは、寸法変化に影響するセメンタイトの析出反応、残留オーステナイトのマルテンサイト化や二次炭化物の析出反応に対して寄与する元素である。また、固溶強化による硬さを向上させるとともに焼入性を高める元素である。その効果を得るためには、Ｃは０．３５％以上必要である。一方、Ｃは０．９５％より多く含有されると粗大な１次炭化物を形成し、寸法変化の異方性が大きくなる。そこで、Ｃは０．３５〜０．９５％とする。
C: 0.35-0.95%
C is an element that contributes to the precipitation reaction of cementite that affects the dimensional change, martensite formation of residual austenite, and precipitation reaction of secondary carbides. Moreover, it is an element which improves the hardenability while improving the hardness by solid solution strengthening. In order to acquire the effect, C needs to be 0.35% or more. On the other hand, when C is contained in an amount of more than 0.95%, coarse primary carbides are formed, and the anisotropy of dimensional change increases. Therefore, C is set to 0.35 to 0.95%.
Ｓｉ：０．６０〜１．２０％
Ｓｉは、寸法変化に影響するセメンタイトの析出反応、および、二次炭化物の析出反応に対して寄与する元素である。また、焼入性および基地の硬さを得るために必要な元素である。その効果を得るためには、Ｓｉは０．６０％以上必要である。一方、Ｓｉは１．２０％より多く含有されると靱性および加工性が悪化する。そこで、Ｓｉは０．６０〜１．２０％とする。
Si: 0.60 to 1.20%
Si is an element that contributes to the precipitation reaction of cementite and the precipitation reaction of secondary carbides that affect the dimensional change. Further, it is an element necessary for obtaining hardenability and hardness of the base. In order to obtain the effect, Si needs to be 0.60% or more. On the other hand, when Si is contained more than 1.20%, toughness and workability deteriorate. Therefore, Si is made 0.60 to 1.20%.
Ｍｎ：０．１〜０．６％
Ｍｎは、脱酸剤として必要な元素で、また焼入性を得るために必要な元素である。その効果を得るためには、Ｍｎは０．１％以上必要である。しかし、Ｍｎは０．６％より多すぎると、マトリックスを脆化させ、靱性を悪化する。そこで、Ｍｎは０．６％以下とする。
Mn: 0.1 to 0.6%
Mn is an element necessary as a deoxidizer and an element necessary for obtaining hardenability. In order to obtain the effect, Mn needs to be 0.1% or more. However, if Mn is more than 0.6%, the matrix becomes brittle and toughness deteriorates. Therefore, Mn is set to 0.6% or less.
Ｃｒ：７．０〜１３．０％
Ｃｒは、寸法変化に影響するセメンタイトの析出反応、および、残留オーステナイトのマルテンサイト化や二次炭化物の析出反応に対して寄与する元素である。また、焼入性を高めるとともに、炭化物を形成するのに必要な元素である。その効果を得るためには、Ｃｒは７．０％以上必要である。一方、Ｃｒは１３．０％より多く含有されると、粗大な炭化物を形成して偏析し、寸法変化の異方性が大きくなる。そこで、Ｃｒは７．０〜１３．０％とする。
Cr: 7.0 to 13.0%
Cr is an element that contributes to the precipitation reaction of cementite that affects the dimensional change, the martensite formation of retained austenite, and the precipitation reaction of secondary carbides. Further, it is an element necessary for improving hardenability and forming carbides. In order to obtain the effect, Cr needs to be 7.0% or more. On the other hand, when Cr is contained in an amount of more than 13.0%, coarse carbides are formed and segregated, and the anisotropy of dimensional change increases. Therefore, Cr is set to 7.0 to 13.0%.
（Ｍｏ＋Ｗ／２）：０．５〜２．０％、
Ｍｏの質量とＷの半分の質量の合計量、つまり（Ｍｏ＋Ｗ／２）は、硬質炭化物を形成し、硬さ、耐摩耗性を向上させるとともに、焼入性および焼戻し軟化抵抗性を高める元素である。その効果を得るためには、（Ｍｏ＋Ｗ／２）は０．５％以上必要である。一方、（Ｍｏ＋Ｗ／２）は粗大な炭化物および炭化物偏析を形成し寸法変化の異方性が大きくなる。そこで、（Ｍｏ＋Ｗ／２）は０．５〜２．０％とする。
(Mo + W / 2): 0.5 to 2.0%,
The total mass of Mo and half the mass of W, that is, (Mo + W / 2) is an element that forms hard carbides, improves hardness and wear resistance, and improves hardenability and temper softening resistance. is there. In order to obtain the effect, (Mo + W / 2) needs to be 0.5% or more. On the other hand, (Mo + W / 2) forms coarse carbides and carbide segregation and increases the anisotropy of dimensional change. Therefore, (Mo + W / 2) is set to 0.5 to 2.0%.
Ｖ：１．２％以下
Ｖは、鋼材中に炭化バナジウムとして微細に分散して析出し、この微細に分散して析出した炭化バナジウムが他の炭化物の析出起点となり、炭化物偏析を抑制する働きを有する元素であるため添加しても良い。しかし、Ｖは１．２％より多く含有されると、炭化バナジウム自体が粗大な炭化物および炭化物偏析を形成して、寸法変化の異方性が大きくなる。そこで、Ｖは１．２％以下とする。
V: 1.2% or less V is finely dispersed and precipitated as vanadium carbide in the steel material, and the finely dispersed and precipitated vanadium carbide serves as a precipitation starting point for other carbides and functions to suppress carbide segregation. Since it is an element having, it may be added. However, when V is contained in an amount of more than 1.2%, vanadium carbide itself forms coarse carbides and carbide segregation, and the anisotropy of dimensional change increases. Therefore, V is set to 1.2% or less.
Ａ：１．１３〜２．１０、ただし、Ａ＝０．３９Ｃ−０．５４Ｓｉ＋０．１７Ｃｒ（以下、この式を「Ａ式」という。）とする。
Ａは、焼戻温度の５１０〜５３０℃における圧延方向の寸法変化状態を表す値である。図１に示すように、焼戻温度５１０℃〜５３０℃は、膨張傾向となる温度域であり、かつピーク硬さが得られる温度域である。すなわち５１０℃および５３０℃での寸法変化率が共に寸法変化率が−０．０５〜＋０．０５％の範囲内に入る必要がある。この温度域での寸法変化は、焼戻し時に起こるセメンタイトの析出反応、および、残留オーステナイトのマルテンサイト化や二次炭化物の析出反応が足し合わされたものである。Ｃは、焼入れ時および残留オーステナイトのマルテンサイト化時に結晶格子を広げて膨張を起こし、またセメンタイトの析出反応や二次炭化物の析出反応を促進する。Ｓｉは、セメンタイト析出の抑制および二次炭化物析出の抑制をする。Ｃｒはセメンタイト析出を抑制し、残留オーステナイトのマルテンサイト化や二次炭化物の析出反応を促進する。これら成分の影響に加え、垂直方向の膨張や収縮が圧延方向の寸法変化に影響する。これら成分の影響と垂直方向の寸法変化の影響を考慮すると、圧延方向の寸法変化状態はＡで表すことが出来、Ａが１．１３未満であると、焼戻温度が５１０℃のときの圧延方向の寸法変化率は−０．０５％よりさらに−側へ大きな数値の％となる。一方、Ａが２．１０を超えると、焼戻温度が５３０℃のときの圧延方向の寸法変化率は＋０．０５％よりさらに＋側へ大きな数値の％となる。そこで、圧延方向の寸法変化率を−０．０５〜＋０．０５％とするために、Ａは１．１３〜２．１０とする。
A: 1.13 to 2.10, where A = 0.39C−0.54Si + 0.17Cr (hereinafter, this equation is referred to as “A equation”).
A is a value representing a dimensional change state in the rolling direction at a tempering temperature of 510 to 530 ° C. As shown in FIG. 1, a tempering temperature of 510 ° C. to 530 ° C. is a temperature range that tends to expand and a temperature range where peak hardness is obtained. That is, the dimensional change rate at 510 ° C. and 530 ° C. must be within the range of −0.05 to + 0.05%. The dimensional change in this temperature range is a combination of cementite precipitation reaction that occurs during tempering, martensite formation of retained austenite and secondary carbide precipitation reaction. C expands by expanding the crystal lattice during quenching and when martensite is retained austenite, and promotes the precipitation reaction of cementite and the precipitation reaction of secondary carbides. Si suppresses cementite precipitation and secondary carbide precipitation. Cr suppresses cementite precipitation and promotes martensite formation of residual austenite and precipitation reaction of secondary carbides. In addition to the influence of these components, vertical expansion and contraction affect the dimensional change in the rolling direction. Considering the influence of these components and the influence of the dimensional change in the vertical direction, the dimensional change state in the rolling direction can be represented by A, and when A is less than 1.13, the rolling is performed when the tempering temperature is 510 ° C. The dimensional change rate in the direction is a larger numerical value% from -0.05% to the-side. On the other hand, when A exceeds 2.10, the dimensional change rate in the rolling direction when the tempering temperature is 530 ° C. is a larger numerical value% to the + side than + 0.05%. Therefore, A is set to 1.13 to 2.10 in order to set the dimensional change rate in the rolling direction to -0.05 to + 0.05%.
Ｂ：０．０９〜０．４３、ただし、Ｂ＝０．３６Ｃ＋０．５４Ｓｉ−０．０５Ｃｒ（以下、この式を「Ｂ式」という。）とする。
Ｂは、Ａと同様に、焼戻し時に起こるセメンタイトの析出反応、および、残留オーステナイトのマルテンサイト化や二次炭化物の析出反応へのＣ、Ｓｉ、Ｃｒの影響と圧延方向への膨張収縮からの影響を考慮した、焼戻温度５１０℃〜５３０℃における垂直方向の寸法変化状態を表した値であり、Ｂが０．０９未満であると、焼戻温度が５３０℃のときの垂直方向の寸法変化率は＋０．０５％よりさらに＋側への大きな数値の％となる。一方、Ｂが０．４３を超えると、焼戻温度が５１０℃のときの垂直方向の寸法変化率は−０．０５％よりさらに−側への大きな数値の％となる。そこで、垂直方向の寸法変化率を−０．０５〜＋０．０５％とするために、Ｂは０．０９〜０．４３とする。
B: 0.09 to 0.43, provided that B = 0.36C + 0.54Si−0.05Cr (hereinafter, this formula is referred to as “B formula”).
B, like A, affects cementite precipitation that occurs during tempering, and the effects of C, Si, and Cr on the martensite and secondary carbide precipitation reactions of retained austenite and the expansion and contraction in the rolling direction. Is a value that represents the dimensional change state in the vertical direction at a tempering temperature of 510 ° C. to 530 ° C., and when B is less than 0.09, the dimensional change in the vertical direction when the tempering temperature is 530 ° C. The rate is a large numerical value% from + 0.05% to the + side. On the other hand, when B exceeds 0.43, the dimensional change rate in the vertical direction when the tempering temperature is 510 ° C. becomes a larger numerical value% toward −side than −0.05%. Therefore, B is set to 0.09 to 0.43 in order to set the dimensional change rate in the vertical direction to -0.05 to + 0.05%.
焼入焼戻しの際の寸法変化の挙動の原理図を図１として示す。 FIG. 1 shows a principle diagram of the behavior of dimensional change during quenching and tempering.
本発明における金型用の合金工具鋼は、焼入れ後には、マルテンサイトに残留オーステナイトが混じった組織となる。この合金工具鋼では、主体となっているマルテンサイト組織中に固溶するＣによって、結晶格子が押し広げられて膨張する。そこで、焼戻温度を上げてゆくと、縦軸に焼入れ直前の寸法を標準とした寸法変化率をとり、横軸に焼戻温度をとってグラフを図１に示す。この図１のグラフにおいて、横軸の（Ａ）域では、セメンタイトが析出して鋼の寸法変化が収縮する傾向となって、グラフは焼戻温度の上昇に連れて右下がりになっている。一方、横軸の（Ｂ）域では、焼入れ時に発生していた残留オーステナイトのマルテンサイト化する量が焼戻温度の上昇に連れて多くなり、また二次炭化物の析出も生じることで、膨張傾向が発生して、グラフは温度上昇に連れて急激な右上がりとなっている。 The alloy tool steel for a mold in the present invention has a structure in which retained austenite is mixed with martensite after quenching. In this alloy tool steel, the crystal lattice is expanded and expanded by C dissolved in the main martensite structure. Therefore, when the tempering temperature is increased, the dimensional change rate with the dimension immediately before quenching as a standard is taken on the vertical axis, and the tempering temperature is taken on the horizontal axis, and the graph is shown in FIG. In the graph of FIG. 1, in the region (A) on the horizontal axis, cementite precipitates and the dimensional change of the steel tends to shrink, and the graph decreases to the right as the tempering temperature increases. On the other hand, in the region (B) on the horizontal axis, the amount of retained austenite generated during quenching becomes martensitic as the tempering temperature rises, and secondary carbide precipitates. The graph shows a sharp rise to the right as the temperature rises.
ところで、これらのグラフに見られる鋼の反応としては、（Ａ）域ではＳｉおよびＣｒによってセメンタイトの析出が抑制され、（Ｂ）域ではＣ、ＳｉおよびＣｒによって残留オーステナイトのマルテンサイト化および二次炭化物の析出が促進されることが定性的に知られている。本発明における５１０℃〜５３０℃の寸法変化は、焼入れ時のマルテンサイト化による膨張も含め、（Ａ）域および（Ｂ）域での反応が足し合わされた状態となって生じている。また、これらの反応による寸法変化量は、鋼素材中の炭化物に影響される。炭化物が一方向に偏って存在すると、炭化物は寸法変化を殆ど起こさないため、その方向への膨張や収縮が抑制される。そのため、鋼素材の圧延方向あるいは垂直方向による寸法変化の異方性が生じる。 By the way, the steel reactions shown in these graphs are as follows. In the (A) region, precipitation of cementite is suppressed by Si and Cr, and in the (B) region, the retained austenite is martensified and secondary by C, Si and Cr. It is qualitatively known that the precipitation of carbides is promoted. The dimensional change of 510 ° C. to 530 ° C. in the present invention occurs in a state where the reactions in the (A) region and (B) region are added, including expansion due to martensite formation during quenching. Moreover, the dimensional change amount by these reaction is influenced by the carbide | carbonized_material in a steel raw material. If the carbide is present in a biased direction, the carbide hardly undergoes a dimensional change, and thus expansion and contraction in that direction are suppressed. Therefore, the anisotropy of the dimensional change by the rolling direction of a steel material or a perpendicular direction arises.
そこで、発明者は寸法変化に及ぼす諸因子の影響を詳細に調査して考究した結果、本発明の請求項に示す合金成分範囲内の鋼材であれば、鋼中のＣ、Ｓｉ、Ｃｒの含有量により寸法変化を制御できることを発見した。また、鋼素材中の炭化物の分布は、主に炭化物形成元素であるＣ、Ｃｒの含有量の影響を受けており、これらの元素の含有量により寸法変化の異方性が制御できることを発見した。これらの知見を基にして鋭意開発を進めた結果、本発明の請求項に示す合金成分および式Ａおよび式Ｂを満たすことで、鋼素材の向きに関係なく、５１０℃〜５３０℃における寸法変化を小さく抑えられることを見出した。 Therefore, as a result of investigating and studying the influence of various factors on the dimensional change in detail, the inventor, if steel material within the alloy composition range shown in the claims of the present invention, the inclusion of C, Si, Cr in the steel It was discovered that dimensional change can be controlled by quantity. Moreover, the distribution of carbides in the steel material is mainly influenced by the contents of C and Cr, which are carbide forming elements, and it has been discovered that the anisotropy of dimensional change can be controlled by the contents of these elements. . As a result of diligent development based on these findings, dimensional changes at 510 ° C. to 530 ° C. are satisfied regardless of the orientation of the steel material by satisfying the alloy components and the formulas A and B shown in the claims of the present invention. Has been found to be small.
表１に示す、化学成分を含有し、残部Ｆｅおよび不可避不純物からなり、さらに式Ａおよび式Ｂの値を有する、Ｎｏ．Ａ〜Ｊの１０種の発明鋼およびＮｏ．Ｋ〜Ｖの１２種の比較鋼である、各合金工具鋼の１００ｋｇを真空誘導溶解炉で溶製し、得られた鋼を１０００℃〜１２００℃の圧延温度で圧延して径６０ｍｍの鋼材とした後に焼なました。なお、表１において、各成分の値は質量％で示し、網かけで示す成分は本願の請求項における成分範囲を外れていることを示す。 No. 1 containing the chemical components shown in Table 1, consisting of the balance Fe and inevitable impurities, and having the values of Formula A and Formula B. 10 types of invention steels A to J and No. 100 kg of each alloy tool steel, which is 12 kinds of comparative steels K to V, is melted in a vacuum induction melting furnace, and the obtained steel is rolled at a rolling temperature of 1000 ° C. to 1200 ° C. And then baked. In Table 1, the value of each component is indicated by mass%, and the component indicated by shading indicates that it is outside the component range in the claims of this application.
次いで、上記の圧延して焼なましを行った、発明鋼のＮｏ．Ａ〜Ｊの１０種および比較鋼のＮｏ．Ｋ〜Ｖの１２種のそれぞれの鋼からなる径６０ｍｍの鋼材を５０ｍｍの長さで切り出して、熱処理前の圧延方向およびその垂直方向の寸法をマイクロメーターで測定した。この測定した長さを試験片の寸法変化を求めるための基準値とした。これらの試験片を１０３０℃で１時間加熱した後、窒素ガスによる冷却を行って焼入処理を行った。さらに、これらの試験片を５１０℃に１．５時間加熱して焼戻した後に空冷する熱処理、または５３０℃に１．５時間加熱して焼戻した後に空冷する熱処理の１回ずつ計２回の焼戻処理を行った。なお、これらの熱処理は試験片が酸化しないように真空熱処理炉を用いて行った。さらに、上記の熱処理後の試験片の圧延方向および垂直方向の長さをマイクロメーターで測定して、基準値に対する長さの変化割合である寸法変化率を求めた。 Next, No. of the invention steel that was rolled and annealed as described above. No. 10 of AJ and comparative steel No. A steel material having a diameter of 60 mm made of each of 12 types of steels K to V was cut out to a length of 50 mm, and the rolling direction before heat treatment and the dimensions in the vertical direction were measured with a micrometer. This measured length was used as a reference value for determining the dimensional change of the test piece. These test pieces were heated at 1030 ° C. for 1 hour and then cooled with nitrogen gas for quenching treatment. Furthermore, these test pieces were heated to 510 ° C. for 1.5 hours and then tempered and then air-cooled, or heated to 530 ° C. for 1.5 hours and then tempered and then air-cooled, and then twice. Return processing was performed. These heat treatments were performed using a vacuum heat treatment furnace so that the test pieces were not oxidized. Further, the length in the rolling direction and the vertical direction of the test piece after the heat treatment was measured with a micrometer, and the dimensional change rate, which is the change rate of the length with respect to the reference value, was obtained.
寸法変化率は、次式により求めた。すなわち、寸法変化率＝｛（Ｌ1−Ｌ0）×１００／Ｌ0｝（％）、ただし、Ｌ0は焼入れ前の基準寸法、Ｌ1は焼戻し後の寸法を示す。表２に、これらの寸法変化率による評価結果を示す。 The dimensional change rate was obtained by the following equation. That is, the dimensional change rate = {(L 1 −L 0 ) × 100 / L 0 } (%), where L 0 represents a reference dimension before quenching and L 1 represents a dimension after tempering. Table 2 shows the evaluation results based on these dimensional change rates.
本願の発明鋼を構成する元素が、表１において、化学成分の成分範囲が請求項で規定する範囲内のものであっても、式Ａまたは式Ｂの値が請求項で規定する限定範囲から外れている比較鋼のＮｏ．のものは、寸法変化率が−０．０５％〜０．０５％の範囲から外れている。例えば、表１の比較鋼のＮｏ．Ｎは、化学成分は全て請求項の範囲内のものであるが、式Ａの値は１．０４であり、この値は請求項で規定する式Ａの下限値の１．１３よりも小さく、さらに式Ｂの値は０．４４であり、この値は請求項で規定する式Ｂの上限値の０．４３よりも大きく、これらの値は請求項で規定する値の範囲外である。したがって、表２において、Ｎｏ．Ｎは、５１０℃焼戻しでは、圧延方向で寸法変化率が−０．０６％で、垂直方向で寸法変化率が−０．０６％であり、これらの５１０℃焼戻しの値は請求項で規定する寸法変化率の範囲から外れている。しかし、５３０℃焼戻しでは、圧延方向で寸法変化率が−０．０４％で、垂直方向で寸法変化率が−０．０２％であり、これらの５３０℃焼戻しの値は請求項で規定する寸法変化率の範囲内である。 Even if the elements constituting the invention steel of the present application are in Table 1, the component range of the chemical component is within the range specified in the claims, the value of Formula A or Formula B is from the limited range specified in the claims. The comparative steel No. In those, the dimensional change rate is out of the range of -0.05% to 0.05%. For example, the comparative steel No. N has all chemical components within the scope of the claims, but the value of the formula A is 1.04, which is smaller than the lower limit value 1.13 of the formula A defined in the claims, Further, the value of the formula B is 0.44, which is larger than the upper limit value 0.43 of the formula B specified in the claims, and these values are outside the range of the values specified in the claims. Therefore, in Table 2, no. N has a dimensional change rate of -0.06% in the rolling direction and a dimensional change rate of -0.06% in the rolling direction in tempering at 510 ° C, and these 510 ° C tempering values are defined in the claims. Out of range of dimensional change rate. However, in tempering at 530 ° C., the dimensional change rate is −0.04% in the rolling direction and the dimensional change rate is −0.02% in the vertical direction, and these 530 ° C. temper values are the dimensions specified in the claims. Within the range of rate of change.
一方、本願の発明鋼を構成する元素が、表１における化学成分の成分範囲が請求項で規定する成分範囲から外れる比較鋼のＮｏ．のものは、表２における寸法変化率が−０．０５％〜０．０５％の範囲から大きく外れている。また、比較鋼のＮｏ．Ｕ、Ｎｏ．Ｖに関しては、表１において、式Ａの値および式Ｂの値は請求項の範囲内の１．１３≦Ａ≦２．１０を満足する１．２６、０．１８であり、さらに０．０９≦Ｂ≦０．４３を満足する０．２４、０．２７でありながら、５３０℃焼戻しにおいて、圧延方向の−０．０１、−０．０２から垂直方向の０．０８、０．０７となっており、したがって異方性が大きくなっている。 On the other hand, the elements constituting the inventive steel of the present application are No. of comparative steels in which the component ranges of chemical components in Table 1 deviate from the component ranges specified in the claims. The dimensional change rate in Table 2 deviates significantly from the range of -0.05% to 0.05%. Moreover, No. of comparative steel. U, No. Regarding V, in Table 1, the values of Formula A and Formula B are 1.26, 0.18 satisfying 1.13 ≦ A ≦ 2.10 within the scope of the claims, and further 0.09 ≦ B ≦ 0.43 satisfying 0.24 and 0.27, but in tempering at 530 ° C., from −0.01 and −0.02 in the rolling direction to 0.08 and 0.07 in the vertical direction. Therefore, the anisotropy is large.
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