JP2019077910A - Manufacturing method of boron-containing stainless steel - Google Patents
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本発明は、少なくともＡｌ２Ｏ３を含むスラグ及び消耗電極を用いた二次溶解法によるボロン含有ステンレス鋼の製造方法に関し、特に、ＢＮ（ボロンナイトライド）の微細粒子による高温機械強度の向上を与え得るボロン含有ステンレス鋼の製造方法に関する。 The present invention relates to a method of producing a boron-containing stainless steel by secondary melting method using a slag containing at least Al 2 O 3 and a consumable electrode, and in particular, an improvement of high temperature mechanical strength by fine particles of BN (boron nitride) The present invention relates to a method of producing a boron-containing stainless steel that can be provided.
スラグと消耗電極を用いたＥＳＲ（Electro-Slag Remelting）法による鋼の二次溶解法において、消耗電極の下端で生成した滴はスラグ中を落下して、メタルプールを経て凝固し鋼塊を形成する。つまり、スラグ中でのメタル−スラグ反応を制御することで鋼塊の成分組成を調整することができる。 In the secondary melting method of steel by ESR (Electro-Slag Remelting) method using slag and consumable electrode, the droplets formed at the lower end of the consumable electrode fall in the slag and solidify through the metal pool to form steel ingot Do. That is, the component composition of the steel ingot can be adjusted by controlling the metal-slag reaction in the slag.
例えば、特許文献１では、Ｔｉ及びＡｌを含有する耐熱鋼のＥＳＲ法による製造方法において、スラグの成分組成を調整することでＴｉ及びＡｌの成分変動を抑え、成分偏析の少ないインゴットを得ようとする製造方法を開示している。スラグは、Ａｌ２Ｏ３−ＣａＯ（生石灰）−ＣａＦ２（ホタル石）系であって、ＣａＦ２に、質量％で、５％≦Ａｌ２Ｏ３≦３０％、ＣａＯ≦１５％を与え、更に、１％≦ＴｉＯ２≦１５％を与えた組成を有している。これにより、消耗電極中のＴｉ及びＡｌと、スラグ中のＴｉＯ２及びＡｌ２Ｏ３のバランスを制御できる。なお、対象とする鋼は、質量％で０．５％≦Ｔｉ≦５．０％、０．１％≦Ａｌ≦２．０％を含む成分組成である。 For example, in Patent Document 1, in the production method of a heat-resistant steel containing Ti and Al according to the ESR method, the component composition of the slag is adjusted to suppress the component fluctuation of Ti and Al and obtain an ingot with less component segregation. Discloses a manufacturing method. The slag is an Al 2 O 3 -CaO (quick lime) -CaF 2 (fluorite) system, which gives 5% ≦ Al 2 O 3 ≦ 30%, CaO ≦ 15% by mass% to CaF 2 , Furthermore, it has a composition giving 1% ≦ TiO 2 ≦ 15%. This makes it possible to control the balance between Ti and Al in the consumable electrode and TiO 2 and Al 2 O 3 in the slag. In addition, the target steel is a component composition including 0.5% ≦ Ti ≦ 5.0% and 0.1% ≦ Al ≦ 2.0% by mass.
同様に、Ｂを含有する鋼のＥＳＲ法による製造方法においても、スラグの成分組成を調整することが提案されている。 Similarly, in the method of producing B-containing steel by the ESR method, it is proposed to adjust the composition of the slag.
例えば、特許文献２では、Ｂを含有する耐熱鋼のＥＳＲ法による製造方法において、消耗電極のＳｉとＢの成分量に合わせてスラグ中のＳｉＯ２とＢ２Ｏ３の成分量を調整することで、溶鋼の成分組成中のＢの成分量を制御する耐熱鋼の製造方法を開示している。かかる製造方法において用いられるスラグは、Ａｌ２Ｏ３−ＣａＯ−ＣａＦ２にフラックスとしてＳｉＯ２とともにＢ２Ｏ３を与えたものである。ここで、溶鋼成分とスラグ成分との間では、
３（ＳｉＯ２）＋４Ｂ＝２（Ｂ２Ｏ３）＋３Ｓｉ
の反応が生じるため、ＳｉＯ２の存在下ではＢが酸化されて成分偏析や目標成分値からの逸脱を生じさせるとしている。そこで、スラグ中のＳｉＯ２とＢ２Ｏ３の成分量を所定の式を満たすように調整することで、上記反応式の両辺のバランスを制御し溶鋼中でのＢの成分量を制御している。
For example, in Patent Document 2, in the method of manufacturing B-containing heat-resistant steel according to the ESR method, adjusting the amounts of SiO 2 and B 2 O 3 in the slag according to the amounts of Si and B of the consumable electrode. Thus, a method for producing a heat-resistant steel is disclosed, which controls the amount of B in the component composition of molten steel. The slag used in this production method is one obtained by adding B 2 O 3 together with SiO 2 as a flux to Al 2 O 3 -CaO-CaF 2 . Here, between the molten steel component and the slag component,
3 (SiO 2) + 4B = 2 (B 2 O 3) + 3Si
In the presence of SiO 2 , B is oxidized to cause component segregation and deviation from the target component value. Therefore, by adjusting the amount of components of SiO 2 and B 2 O 3 in the slag to satisfy a predetermined equation, the balance of both sides of the above reaction formula is controlled, and the amount of component of B in molten steel is controlled. There is.
ＢＮの微細粒子を利用してクリープなどの高温機械強度の向上を与えたＢを含有する耐熱鋼が知られている。かかる耐熱鋼では、上記したようなＡｌ２Ｏ３−ＣａＯ−ＣａＦ２系スラグを用いたメタル−スラグ反応において、Ｂの酸化物だけでなく、窒化物についても考慮する必要がある。ここで、特に、Ａｌも酸化物だけでなく窒化物を形成するため、ＢＮの微細粒子の析出状態を変化させ、高温機械強度にも影響を与え得る。そこで、特に、Ａｌ量を減じた耐熱鋼が提案され、これに合わせてスラグ中のＡｌ２Ｏ３を減じることが考慮される。しかしながら、スラグ中のＡｌ２Ｏ３量が低減されることでスラグの比抵抗が小さくなり、二次溶解法における電力消費量が増加し、また、消耗電極の溶解が難しくなる場合もある。かかる状況は、大型鋼塊を得ようとする場合に特に問題となり得る。 A heat-resistant steel containing B is known which has been improved in high temperature mechanical strength such as creep using fine particles of BN. In such a heat-resistant steel, it is necessary to consider not only oxides of B but also nitrides in the metal-slag reaction using the Al 2 O 3 -CaO-CaF 2 -based slag as described above. Here, in particular, Al forms not only oxides but also nitrides, so that the precipitation state of BN fine particles can be changed, and high-temperature mechanical strength can also be affected. Therefore, in particular, a heat resistant steel with a reduced amount of Al is proposed, and it is considered to reduce the amount of Al 2 O 3 in the slag according to this. However, as the amount of Al 2 O 3 in the slag is reduced, the specific resistance of the slag may be reduced, the power consumption in the secondary melting method may be increased, and it may be difficult to melt the consumable electrode. Such a situation can be particularly problematic when trying to obtain large steel ingots.
本発明はかかる状況に鑑みてなされたものであって、その目的とするところは、比抵抗の低下を抑制すべくＡｌ２Ｏ３を含むスラグと消耗電極を用いた二次溶解によるボロン含有ステンレス鋼の製造方法において、ＢＮ粒子の析出に影響を与えるスラグ成分を考慮し高温機械強度の向上を与え得るボロン含有ステンレス鋼の製造方法を提供することにある。 The present invention has been made in view of such circumstances, and the object of the present invention is to use boron-containing stainless steel by secondary melting using a slag containing Al 2 O 3 and a consumable electrode to suppress a decrease in specific resistance. It is an object of the present invention to provide a method for producing a boron-containing stainless steel capable of providing an improvement in high-temperature mechanical strength in consideration of a slag component which affects precipitation of BN particles in a method of producing steel.
本発明によるボロン含有ステンレス鋼の製造方法は、質量％で、Ｃ：０．０８〜０．４０％、Ｃｒ：８〜１４％を少なくとも含み、ＢＮ微細粒子を析出させ得るよう、Ｂ：０．００１０〜０．０３００％を含む一方でとともに、Ａｌを０．０１％以下に抑制した成分組成のボロン含有ステンレス鋼を得るための少なくともＡｌ２Ｏ３を含むスラグ及び消耗電極を用いた二次溶解法による製造方法であって、前記スラグは、質量％で、ＣａＯ：２０〜４０％、Ａｌ２Ｏ３：２０〜４０、ＳｉＯ２：６〜１５％を含むとともに、添加物としてＢ２Ｏ３を２％以下で含み得て、残部ＣａＦ２及び不可避的不純物からなることを特徴とする。 The method for producing a boron-containing stainless steel according to the present invention contains at least by mass: C: 0.08 to 0.40%, Cr: 8 to 14%, and B: 0. B so that BN fine particles can be precipitated. Secondary dissolution using a slag and a consumable electrode containing at least Al 2 O 3 to obtain a boron-containing stainless steel having a component composition in which Al is suppressed to 0.01% or less while containing 0010 to 0.0300% The slag includes CaO: 20 to 40%, Al 2 O 3 : 20 to 40, SiO 2 : 6 to 15% by mass, and B 2 O 3 as an additive. May be contained at 2% or less, and the balance is characterized by consisting of the balance CaF 2 and unavoidable impurities.
かかる発明によれば、比抵抗の低下を抑制するようにＡｌ２Ｏ３を一定量含むＡｌ２Ｏ３−ＣａＯ−ＣａＦ２系スラグでありながら、ＢＮと窒化において競合し得る鋼中のＡｌ量を抑制させてＢＮを形成し得るＢ量を適正化できて、ＢＮ微細粒子を析出させて高温機械強度を向上させ得るボロン含有ステンレス鋼を与えるのである。 According to the invention, while being Al 2 O 3 -CaO-CaF 2 slag containing Al 2 O 3 a certain amount so as to suppress a decrease in specific resistance, Al content in steel which may compete in BN nitride It is possible to optimize the amount of B capable of forming BN by suppressing B, and to provide a boron-containing stainless steel capable of precipitating BN fine particles and improving high-temperature mechanical strength.
上記した発明において、前記消耗電極は、質量％で、Ｃ：０．０８〜０．４０％、Ｃｒ：８〜１４％、Ｎｉ：２．５％以下、Ｖ：０．１〜０．３％、Ｃｏ：０．５〜３．５％、Ｎｂ：０．０３〜０．１０％、Ｂ：０．００１０〜０．０３００％、及び、Ｎ：０．０１００〜０．０５００％、を含み、残部Ｆｅ及び不可避的不純物とするとともに、Ａｌ及びＳｉの含有量をそれぞれ０．０１０％以下及び０．１０％以下に抑制した成分組成を有することを特徴としてもよい。かかる発明によれば、上記したスラグ成分の範囲内でＢ量を適正化できて、結果として降温機械強度を向上させ得るボロン含有ステンレス鋼を確実に与えるのである。 In the above invention, the consumable electrode is, by mass%, C: 0.08 to 0.40%, Cr: 8 to 14%, Ni: 2.5% or less, V: 0.1 to 0.3% , Co: 0.5 to 3.5%, Nb: 0.03 to 0.10%, B: 0.0010 to 0.0300%, and N: 0.0100 to 0.0500%. It may be characterized by having a component composition in which the content of Al and Si is suppressed to 0.010% or less and 0.10% or less, respectively, as the balance Fe and the inevitable impurities. According to this invention, the amount of B can be optimized within the range of the above-mentioned slag component, and as a result, the boron-containing stainless steel which can improve the temperature-falling mechanical strength is surely given.
上記した発明において、前記消耗電極中の成分Ｍの質量％を［％Ｍ］、前記スラグ中の含有物Ｑのモル分率を｛ｍｆＱ｝として、前記スラグは、Ｙ＝ｌｏｇ（［％Ｂ］４／［％Ｓｉ］３） Ｘ＝ｌｏｇ（｛ｍｆＢ２Ｏ３｝２／｛ｍｆＳｉＯ２｝３）とすると、−５．１≦Ｙ−Ｘ≦−４．６の範囲内となる成分組成を有することを特徴としてもよい。かかる発明によれば、得られるＢ量をより適正化し、高温機械強度を向上させ得るボロン含有ステンレス鋼を確実に与えるのである。 In the above-described invention, assuming that the mass% of the component M in the consumable electrode is [% M] and the molar fraction of the inclusion Q in the slag is {mf Q}, the slag has Y = log ([% B] Assuming that 4 / [% Si] 3 ) X = log ({mfB 2 O 3 } 2 / {mfSiO 2 } 3 ), the component composition within the range of −5.1 ≦ Y−X ≦ −4.6 It may be characterized by having. According to this invention, the boron content stainless steel which can make the amount of B obtained more appropriate and can improve high temperature mechanical strength is certainly given.
本発明による１つの実施例であるボロン含有ステンレス鋼の製造方法について、図１を用いて詳細を説明する。 A method of manufacturing a boron-containing stainless steel according to an embodiment of the present invention will be described in detail with reference to FIG.
本実施例において、得ようとするボロン含有ステンレス鋼は、質量％で、Ｃ：０．０８〜０．４０％、Ｃｒ：８〜１４％を少なくとも含む。また、Ｂを０．００１０〜０．０３００％で含有させるとともにＡｌを０．０１％以下に抑制したことで、鋼塊にＢを分布させ、その後の処理においてＢＮ微細粒子を粒界に析出させ得るようにして、耐クリープ特性などの高温機械強度に優れるようにすることを意図している。 In the present embodiment, the boron-containing stainless steel to be obtained at least contains at least C: 0.08 to 0.40% and Cr: 8 to 14% by mass. In addition, B is contained in 0.0010 to 0.0300% and Al is suppressed to 0.01% or less, whereby B is distributed to the steel ingot and BN fine particles are precipitated in grain boundaries in the subsequent processing. It is intended to obtain excellent high-temperature mechanical strength such as creep resistance.
このような鋼は、消耗電極とスラグを用いたＥＳＲ（エレクトロスラグ再溶解）などの二次溶解法によって製造することができる。なお、二次溶解は、不活性ガスもしくは真空をベースに、アルゴンや窒素などを調整した雰囲気中で行われることが好ましい。 Such steels can be manufactured by secondary melting methods such as ESR (electroslag remelting) using consumable electrodes and slag. In addition, it is preferable that secondary melting is performed in the atmosphere which adjusted argon, nitrogen, etc. based on inert gas or a vacuum.
ここで、図１に示すように、消耗電極の材料としては、例えば鋼種Ａ〜Ｄの４種類の成分組成を有する鋼を用い得る。なお、本実施例において用い得る消耗電極の材料となる鋼の成分組成としては、質量％で、Ｃ：０．０８〜０．４０％、Ｎｉ：２．５％以下、Ｃｒ：８〜１４％、Ｖ：０．１〜０．３％、Ｃｏ：０．５〜３．５％、Ｎｂ：０．０３〜０．１０％、Ｂ：０．００１０〜０．０３００％、Ｎ：０．０１００〜０．０５００％として含み、Ａｌの含有量を０．０１％以下、Ｓｉの含有量を０．１０％以下にそれぞれ制御したものが好ましい。また、これらの鋼においては、不可避的不純物として、Ｐ、Ｓ、Ｃｕ、Ｐｂ、Ａｓ、Ｓｎ、Ｓｂ、Ｔｉ、Ｏ、Ｈなどを含み得る。 Here, as shown in FIG. 1, as a material of the consumable electrode, for example, steel having four kinds of component compositions of steel types A to D can be used. In addition, as a component composition of the steel used as a material of the consumable electrode which can be used in a present Example, C: 0.08-0.40%, Ni: 2.5% or less, Cr: 8-14% by mass% , V: 0.1 to 0.3%, Co: 0.5 to 3.5%, Nb: 0.03 to 0.10%, B: 0.0010 to 0.0300%, N: 0.0100 It is preferable to control the content of Al as 0.01% or less and the content of Si as 0.10% or less. Moreover, in these steels, P, S, Cu, Pb, As, Sn, Sb, Ti, O, H etc. may be included as unavoidable impurities.
一方、スラグは、比抵抗の低下を抑制すべく少なくともＡｌ２Ｏ３を含むスラグであって、質量％で、ＣａＯ：２０〜４０％、Ａｌ２Ｏ３：２０〜４０％、ＳｉＯ２：６〜１５％、残部ＣａＦ２とした組成を有するＡｌ２Ｏ３−ＣａＯ−ＣａＦ２系スラグである。このような組成範囲とすることで、二次溶解において電気抵抗値の低下を抑制するとともに、消耗電極からの溶湯とスラグとのメタル−スラグ反応をバランスさせて、メタルプール中のＡｌ量を抑制できる。Ａｌ量を抑制することで、得られた鋼塊においてＡｌ窒化物の生成が抑制され、Ａｌ窒化物以外の窒化物を生成するようＮを残存させ、結果として、ＢＮの形成を促進させるのである。上記したように、Ａｌ２Ｏ３を減じることでスラグの比抵抗が低下してしまうため、比抵抗の低下を抑制すべく所定量のＡｌ２Ｏ３を含むスラグを用いる。このようなスラグは、特に、１０トン以上の大型鋼塊を得る場合などにおいて好ましい。 On the other hand, the slag is a slag containing at least Al 2 O 3 in order to suppress a decrease in specific resistance, and by mass%, CaO: 20 to 40%, Al 2 O 3 : 20 to 40%, SiO 2 : 6 15%, an Al 2 O 3 -CaO-CaF 2 slag having a composition with the remainder CaF 2. By setting it as such a composition range, while suppressing the fall of an electrical resistance value in secondary melting, the metal-slag reaction of the molten metal and slag from a consumable electrode is balanced, and the amount of Al in a metal pool is suppressed. it can. By suppressing the amount of Al, the formation of Al nitride is suppressed in the obtained steel ingot, N is left to form nitrides other than Al nitride, and as a result, the formation of BN is promoted. . As described above, because the lowered specific resistance of slag by reducing the Al 2 O 3, using a slag containing Al 2 O 3 of a predetermined amount so as to suppress a decrease in specific resistance. Such a slag is preferable particularly when obtaining a large steel ingot of 10 tons or more.
また、スラグには、添加物として２質量％以下でＢ２Ｏ３を更に含んでもよい。ここで、消耗電極中の成分Ｍの質量％を［％Ｍ］、スラグ中の含有物Ｑのモル分率を｛ｍｆＱ｝として、
Ｙ＝ｌｏｇ（［％Ｂ］４／［％Ｓｉ］３） （式１）
Ｘ＝ｌｏｇ（｛ｍｆＢ２Ｏ３｝２／｛ｍｆＳｉＯ２｝３） （式２）
とすると、−５．１≦Ｙ−Ｘ≦−４．６の範囲内とすることが好ましい。これによって、得られる鋼塊内におけるＡｌの含有量を抑えることが容易となる。
In addition, the slag may further contain B 2 O 3 at 2 % by mass or less as an additive. Here, the% by mass of the component M in the consumable electrode is [% M], and the molar fraction of the inclusion Q in the slag is {mf Q},
Y = log ([% B] 4 / [% Si] 3 ) (Equation 1)
X = log ({mfB 2 O 3 } 2 / {mfSiO 2 } 3 ) (Equation 2)
Then, it is preferable to set in the range of −5.1 ≦ Y−X ≦ −4.6. This makes it easy to reduce the content of Al in the obtained steel ingot.
かかるメタル−スラグ反応は、下記平衡式によって制御され得る。ここで、［ ］はメタル中の成分、｛ ｝はスラグ中の成分である。
平衡の式ａ：４［Ａｌ］＋３｛ＳｉＯ２｝⇔２｛Ａｌ２Ｏ３｝＋３［Ｓｉ］
平衡の式ｂ：３［Ｓｉ］＋２｛Ｂ２Ｏ３｝⇔３｛ＳｉＯ２｝＋４［Ｂ］
平衡の式ｃ：２［Ａｌ］＋｛Ｂ２Ｏ３｝⇔｛Ａｌ２Ｏ３｝＋２［Ｂ］
Such metal-slag reaction can be controlled by the following equilibrium equation. Here, [] is a component in metal and {} is a component in slag.
Equilibrium equation a: 4 [Al] + 3 {SiO 2 } ⇔ 2 {Al 2 O 3 } + 3 [Si]
Equation of equilibrium b: 3 [Si] + 2 {B 2 O 3 } ⇔ 3 {SiO 2 } + 4 [B]
Equilibrium equation c: 2 [Al] + {B 2 O 3 } ⇔ {Al 2 O 3 } + 2 [B]
これらの平衡の式において、本実施例では、スラグの組成成分を制御することでメタル中でのＡｌの含有量を抑制するとともに必要なＢの含有量を確保するようにバランスさせる。例えば、ＳｉＯ２を多くすることで平衡の式ａは右辺に進行しやすくなり、メタル中のＡｌの含有量を抑えることができる。 In these equations of equilibrium, in the present embodiment, by controlling the composition component of the slag, the content of Al in the metal is suppressed, and the necessary content of B is secured. For example, by increasing the amount of SiO 2 , the equilibrium expression a can easily progress to the right side, and the content of Al in the metal can be suppressed.
以上のようなボロン含有ステンレス鋼の製造方法によって、鋼塊にＢを分布させて、ＢＮの微細粒子を析出させ得るようにして、高温機械強度の向上を可能とする。すなわち、ＢＮと窒化において競合するＡｌ量を抑制させるよう、スラグ組成を調整するのである。 By the method of manufacturing a boron-containing stainless steel as described above, B can be distributed in a steel ingot so that fine particles of BN can be precipitated, and high temperature mechanical strength can be improved. That is, the slag composition is adjusted so as to suppress the amount of Al competing with BN in nitriding.
［実施例］
以下、上記した消耗電極及びスラグを用いた二次溶解法によるボロン含有ステンレス鋼の製造方法によって鋼塊を製造した結果について、図１乃至図４を用いて説明する。
[Example]
Hereinafter, the result of producing a steel ingot by the method for producing a boron-containing stainless steel by the secondary melting method using the consumable electrode and the slag described above will be described using FIGS. 1 to 4.
ここでは、図１に示すように、代表成分である鋼種Ａ〜Ｄを消耗電極の材料として用いた。 Here, as shown in FIG. 1, steel types A to D, which are representative components, were used as the material of the consumable electrode.
図２に示すように、各鋼種Ａ〜Ｄによる消耗電極と、各スラグ組成を有するスラグとを用いた実施例１〜５、比較例１及び２によって、それぞれ二次溶解法で鋼塊を製造した。 As shown in FIG. 2, steel ingots are produced by the secondary melting method in each of Examples 1 to 5 and Comparative Examples 1 and 2 using consumable electrodes of each steel type A to D and slag having each slag composition. did.
図３には鋼塊を製造した結果として、製造に用いた電極及びスラグの組成に関する上記した式１によるＸの値、式２によるＹの値、及び、Ｙ−Ｘの値と、得られた鋼塊中におけるＢのばらつき及びＡｌの含有量を示した。Ｂのばらつきについては、鋼塊のＴｏｐ側、中央、Ｂｏｔｔｏｍ側からそれぞれサンプルを切り出してＢの含有量を定量し、それらの最大値から最小値を減じてこれを平均値で除した上で、百分率で示した。 In FIG. 3, as a result of producing a steel ingot, the value of X according to the equation 1 described above, the value of Y according to the equation 2 and the value of Y-X with respect to the composition of the electrode and slag used for production were obtained The variation of B and the content of Al in the steel ingot are shown. Samples are cut from the top side, center, and bottom side of the steel ingot to determine the B variation, the B content is quantified, the minimum value is subtracted from the maximum value, and this is divided by the average value, It is shown as a percentage.
実施例１〜５で得られた鋼塊において、Ａｌの含有量は０.００２％と少なかった。つまり、スラグの成分組成を制御することで、得られる鋼塊のＡｌの含有量を抑制できている。 In the steel ingots obtained in Examples 1 to 5, the content of Al was as low as 0.002%. That is, by controlling the component composition of the slag, the content of Al in the steel ingot obtained can be suppressed.
これに対し、比較例１及び２では、いずれもスラグのＳｉＯ２の含有量を０．４％と少なくしており、得られた鋼塊のＡｌの含有量がそれぞれ０．００８質量％及び０．０１１質量％として実施例１〜５に比べて多くなった。上記した平衡の式ａにより、ＳｉＯ２の含有量を少なくすることでメタル中のＡｌの含有量を多くしやすく、そのため得られた鋼塊においてもＡｌの含有量を多くしてしまったものと考えられる。 On the other hand, in Comparative Examples 1 and 2, the content of SiO 2 in the slag is reduced to 0.4%, and the content of Al in the obtained steel ingot is 0.008% by mass and 0, respectively. .011% by mass was increased as compared with Examples 1 to 5. The content of Al in the metal can be easily increased by decreasing the content of SiO 2 according to the above-mentioned equation of equilibrium a, and therefore the content of Al in the obtained steel ingot is also increased. Conceivable.
ここで、図４を併せて参照すると、実施例１〜５、比較例１及び２のそれぞれについて（Ｘ，Ｙ）をグラフにプロットした。得られた鋼塊におけるＡｌの含有量の少ない実施例１〜５では上記したＹ−Ｘの値が−５．１以上かつ−４．６以下の範囲内となった。これに対し、Ａｌの含有量の多い比較例１及び２では、Ｙ−Ｘの値がその範囲外となった。つまり、消耗電極の合金及びスラグの組成は、上記した式１及び式２に基づいて−５．１≦Ｙ−Ｘ≦−４．６となるように調整されることが好ましく、これによって得られる鋼塊中のＡｌの含有量を少なくすることを容易とするのである。 Here, referring to FIG. 4 together, (X, Y) was plotted on a graph for each of Examples 1 to 5 and Comparative Examples 1 and 2. In Examples 1 to 5 in which the content of Al in the obtained steel ingot is small, the value of Y-X described above is in the range of -5.1 or more and -4.6 or less. On the other hand, in Comparative Examples 1 and 2 in which the content of Al is large, the value of Y-X was out of the range. That is, it is preferable that the composition of the alloy and the slag of the consumable electrode be adjusted to satisfy −5.1 ≦ Y−X ≦ −4.6 based on the equation 1 and the equation 2 described above. It is easy to reduce the content of Al in the steel ingot.
なお、消耗電極に用いた鋼種Ａ〜Ｄは、それぞれ成分組成に差異を有するが、得られる鋼塊中のＡｌの含有量に関しては同等の成分組成を有している。例えば、鋼種Ｄは比較例１にのみ用いられているが、消耗電極の鋼種の成分組成から算出されるＹの値を他の鋼種Ａ〜Ｃと同等としている。つまり、比較例１においてＡｌの含有量を多くした主な原因は、消耗電極の成分組成ではなくスラグの組成にあると言える。 The steel types A to D used for the consumable electrode have differences in component compositions, but have similar component compositions as to the content of Al in the steel ingot obtained. For example, steel type D is used only in comparative example 1, but the value of Y calculated from the component composition of the steel type of the consumable electrode is made equal to the other steel types A to C. That is, it can be said that the main reason for increasing the content of Al in Comparative Example 1 is not the component composition of the consumable electrode but the composition of slag.
ところで、上記したボロン含有ステンレス鋼の製造方法に用いられるスラグの組成範囲は以下のように定められる。 By the way, the composition range of the slag used for the manufacturing method of the above-mentioned boron containing stainless steel is defined as follows.
ＣａＯは、精錬能の確保のために２０質量％以上とし、鋼塊肌を良好に保ち歩留まりの悪化を防ぐために４０質量％以下とした。 CaO is 20% by mass or more to secure the refining ability, and 40% by mass or less to keep the steel ingot surface well and prevent the deterioration of the yield.
Ａｌ２Ｏ３は、Ａｌ２Ｏ３−ＣａＯ−ＣａＦ２系スラグにおける比抵抗の低下を抑制するために２０質量％以上とし、鋼塊肌を良好に保ち歩留まりの悪化を防ぐために４０質量％以下とした。 Al 2 O 3 is 20% by mass or more in order to suppress a decrease in specific resistance in Al 2 O 3 -CaO-CaF 2 type slag, and 40% by mass or less in order to keep steel ingot surface well and prevent deterioration of yield And
ＳｉＯ２は、Ａｌの増加による窒素のピックアップを抑制するため６質量％以上とし、ＳｉＯ２の量によって添加すべき量の増加するＢ２Ｏ３を少なくしてコストの悪化を避けるように１５質量％以下とした。 The amount of SiO 2 is 6% by mass or more in order to suppress the pickup of nitrogen due to the increase of Al, and the amount of B 2 O 3 to be added according to the amount of SiO 2 is reduced to avoid the deterioration of cost by 15%. % Or less.
Ｂ２Ｏ３は、Ｂの歩留まりを確保するために２質量％以下で添加してもよい。 B 2 O 3 may be added at 2% by mass or less in order to secure the yield of B.
ＣａＦは、上記した他の成分の残部としてスラグに配合されるが、粘性の増大を避けて操業の安定性を確保するため３０質量％以上とすることが好ましい。 CaF is blended into the slag as the balance of the other components described above, but it is preferably 30% by mass or more in order to avoid the increase in viscosity and ensure the stability of operation.
ここまで本発明による代表的実施例及びこれに基づく改変例について説明したが、本発明は必ずしもこれらに限定されるものではない。当業者であれば、添付した特許請求の範囲を逸脱することなく、種々の代替実施例を見出すことができるであろう。
Although the representative embodiments according to the present invention and the modifications based thereon are described above, the present invention is not necessarily limited thereto. Those skilled in the art will be able to find various alternative embodiments without departing from the scope of the appended claims.
Claims (3)
前記スラグは、質量％で、ＣａＯ：２０〜４０％、Ａｌ２Ｏ３：２０〜４０％、ＳｉＯ２：６〜１５％を含むとともに、添加物としてＢ２Ｏ３を２％以下で含み得て、残部ＣａＦ２及び不可避的不純物からなることを特徴とするボロン含有ステンレス鋼の製造方法。 C: 0.08 to 0.40%, Cr: 8 to 14% at least, B: 0.0010 to 0.0300% so as to precipitate BN fine particles, Al is included A manufacturing method by a secondary melting method using a slag including at least Al 2 O 3 and a consumable electrode for obtaining a boron-containing stainless steel having a component composition suppressed to 0.01% or less,
The slag may contain, by mass%, 20 to 40% of CaO, 20 to 40% of Al 2 O 3 , 6 to 15% of SiO 2 and may contain 2% or less of B 2 O 3 as an additive. And a balance of CaF 2 and inevitable impurities.
Ｃ：０．０８〜０．４０％、
Ｃｒ：８〜１４％、
Ｎｉ：２．５％以下、
Ｖ：０．１〜０．３％、
Ｃｏ：０．５〜３．５％、
Ｎｂ：０．０３〜０．１０％、
Ｂ：０．００１０〜０．０３００％、及び、
Ｎ：０．０１００〜０．０５００％、を含み、残部Ｆｅ及び不可避的不純物とするとともに、Ａｌ及びＳｉの含有量をそれぞれ０．０１０％以下及び０．１０％以下に抑制した成分組成を有することを特徴とする請求項１記載のボロン含有ステンレス鋼の製造方法。 The consumable electrode is in mass%,
C: 0.08 to 0.40%,
Cr: 8 to 14%,
Ni: 2.5% or less,
V: 0.1 to 0.3%,
Co: 0.5 to 3.5%,
Nb: 0.03 to 0.10%,
B: 0.0010 to 0.0300%, and
N: contains 0.0100 to 0.0500%, has the balance Fe and inevitable impurities, and has a component composition in which the content of Al and Si is suppressed to 0.010% or less and 0.10% or less, respectively The method for producing a boron-containing stainless steel according to claim 1, characterized in that:
前記スラグは、
Ｙ＝ｌｏｇ（［％Ｂ］４／［％Ｓｉ］３）
Ｘ＝ｌｏｇ（｛ｍｆＢ２Ｏ３｝２／｛ｍｆＳｉＯ２｝３）とすると、
−５．１≦Ｙ−Ｘ≦−４．６
の範囲内となる成分組成を有することを特徴とする請求項１記載のボロン含有ステンレス鋼の製造方法。 The% by mass of the component M in the consumable electrode is [% M], and the molar fraction of the inclusion Q in the slag is {mf Q},
The slag is
Y = log ([% B] 4 / [% Si] 3 )
Assuming that X = log ({mfB 2 O 3 } 2 / {mfSiO 2 } 3 ),
−5.1 ≦ Y−X ≦ −4.6
The method for producing a boron-containing stainless steel according to claim 1, having a component composition within the range of
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