JP5155141B2 - Method for refining Ni-base alloy with excellent hot workability - Google Patents
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本発明は、熱間加工性に優れたNi基合金の精錬方法に係り、特にAl含有量の高いNi基合金の二次精錬方法に特徴を有する精錬方法を提案する。 The present invention relates to a refining method for a Ni-based alloy having excellent hot workability, and particularly proposes a refining method characterized by a secondary refining method for a Ni-based alloy having a high Al content.
一般に、Ni基合金は、電気炉で一次精錬した後、ＡＯＤやＶＯＤ等の二次精錬設備で脱炭などの酸化処理を行い、その後、還元もしくは脱酸処理する二次仕上げ精錬を施して精錬する方法、あるいは全工程を真空誘導炉で処理する方法などで溶製されている。 Generally, Ni-based alloys are refined by primary refining in an electric furnace, followed by oxidation treatment such as decarburization in secondary refining equipment such as AOD and VOD, and then secondary finishing refining for reduction or deoxidation treatment. Or a method in which all steps are processed in a vacuum induction furnace.
従来、かかるNi基合金の中には、従来、Mgを0.005〜0.04 mass％含有させることにより、熱間加工後の表面品質を向上させようとする技術がある（特許文献１、２）。これらの従来技術は、そのMgの濃度を制御する方法として、溶融合金中にMgを添加することとしている。しかしながら、Mgは、蒸気圧が高く、作業上も安全面で問題があり、また、このMgは活性であるため、添加方式では濃度管理ならびに歩留りの点で問題があった。しかも、これら従来技術の場合、添加の歩留りが悪いので、高価なMgを大量に使用する必要が生じ、経済的でないという問題があった。
Conventionally, in such Ni-based alloys, there is a technique for improving the surface quality after hot working by containing 0.005 to 0.04 mass% of Mg (
これに対し、上述した問題点のないNi含有合金の例として、例えば、高Al含有ステンレス鋼があるが、特許文献３として示す従来技術の場合、凝固時のMgガス放出により、健全な鋼塊が得られないことが指摘されており、また、特許文献４として示すものでは、真空処理時のMgガス放出により処理時間が長くかかるという問題点が指摘されている。ただし、これらの従来技術では、Mgのピックアップ対策の１つとして、スラグ中のCaＯ／Al2Ｏ3比を制御する方法を提案しているものの、Mgを不純物元素として、それの低下を目指す技術である。
その他、特許文献５として示す方法では精錬容器内張りレンガ材質のアルミナを95％以上とすることにより、スラグへのMgＯの混入を抑え、溶鋼中Mgピックアップを防止することが開示されているが、この材質は特殊材であることから、チャンスフリーで溶製することはできず、高価であるため、コストアップの原因となっていた。
On the other hand, as an example of the Ni-containing alloy that does not have the above-mentioned problems, for example, there is a high Al-containing stainless steel, but in the case of the prior art shown as Patent Document 3, a healthy steel ingot is obtained by releasing Mg gas during solidification. Further, it is pointed out that the processing time is long due to the release of Mg gas during vacuum processing in the case shown in Patent Document 4. However, although these conventional technologies have proposed a method of controlling the CaO / Al 2 O 3 ratio in slag as one of the measures for picking up Mg, a technology that aims to lower it by using Mg as an impurity element. It is.
In addition, in the method shown in Patent Document 5, it is disclosed that the alumina of the smelting vessel lining brick material is 95% or more, thereby suppressing the mixing of MgO into the slag and preventing Mg pickup in the molten steel. Since the material is a special material, it cannot be melted in a chance-free manner, and is expensive, leading to an increase in cost.
本発明の目的は、表面品質の良好なNi基合金を得ること、そのために必要な熱間加工性の良好なNi基合金を有利に製造する技術を確立すること、そしてそのために、合金中のMg濃度、Ca濃度、酸素濃度およびＳ濃度を精度良く制御するための精錬方法を提案することにある。 An object of the present invention is to obtain a Ni-base alloy having a good surface quality, to establish a technique for advantageously producing a Ni-base alloy having a good hot workability necessary for that purpose, and to this end, in the alloy The object is to propose a refining method for accurately controlling Mg concentration, Ca concentration, oxygen concentration and S concentration.
発明者らは、Ni基合金中のMg濃度に及ぼす影響を知るために種々の実験を行った。この実験の１つは、アルゴン雰囲気に調整された容器内に、10ｋｇ容量のMgＯ製るつぼを設置した高周波誘導加熱炉を使用し、前記るつぼ内に電解Niを収容して溶解し、得られた合金溶湯に種々の組成のCaＯ−Al2Ｏ3−MgＯ−Ｆ系スラグ゛を添加し、その後金属Alを添加した。Al濃度は0.01〜５％の範囲内で、調整した。得られた合金の成分分析を行った。その後、旋盤加工して８mmΦの引張り試験片を作製して、熱間圧延を想定した高温引張り実験を行った。 The inventors conducted various experiments in order to know the effect on the Mg concentration in the Ni-based alloy. One of the experiments was obtained by using a high-frequency induction heating furnace in which a 10 kg capacity MgO crucible was installed in a container adjusted to an argon atmosphere, and containing electrolytic Ni in the crucible and melting. CaO—Al 2 O 3 —MgO—F-based slag having various compositions was added to the molten alloy, and then metal Al was added. The Al concentration was adjusted within the range of 0.01 to 5%. The components of the obtained alloy were analyzed. Thereafter, a lathe was processed to produce a tensile test piece of 8 mmΦ, and a high temperature tensile experiment was performed assuming hot rolling.
その結果、合金の化学成分は、Mg濃度が0.005〜0.04mass％、Ca濃度が0.0005〜0.04mass％、酸素濃度が３〜50massppm、Ｓ濃度が0.0006mass％以下の時に、優れた熱間加工性を有することが確かめられた。また、この時のスラグの組成について、サンプリングして調べたところ、スラグ組成がCaＯ／Al2Ｏ3質量濃度比が1.30〜1.95、マグネシア濃度が1〜18mass％の時に、上記したMg濃度、Ca濃度、酸素濃度、Ｓ濃度の範囲を満足することができることを見出し、本発明を完成させるに至った。 As a result, the chemical composition of the alloy has excellent hot workability when the Mg concentration is 0.005 to 0.04 mass%, the Ca concentration is 0.0005 to 0.04 mass%, the oxygen concentration is 3 to 50 massppm, and the S concentration is 0.0006 mass% or less. It was confirmed to have Further, when the composition of the slag at this time was sampled and examined, when the slag composition was CaO / Al 2 O 3 mass concentration ratio of 1.30 to 1.95 and the magnesia concentration was 1 to 18 mass%, the above-mentioned Mg concentration, Ca The inventors have found that the ranges of concentration, oxygen concentration, and S concentration can be satisfied, and have completed the present invention.
即ち、本発明は、Ｃ：0.3mass％以下、Si：0.5mass％以下、Mn：２mass％以下、Cr：３mass％以下、Cu：40mass％以下、Fe：３mass％以下、Ti：２mass％以下、Mg：0.005〜0.04mass％、Ca：0.0005〜0.04mass％、酸素：3〜50ppm、Ｓ：0.0006mass％以下、Al：0.01〜５mass％、残部Niおよび不可避的不純物からなるNi基合金の精錬に当たり、原料をまず電気炉等で溶解した後、MgＯ系耐火物を用いた二次精錬用容器に出鋼して除滓し、続く二次仕上げ精錬においては、酸素吹精したのちAlを添加して脱酸する過程において、石灰石、螢石、アルミナ、マグネシアのうち１種または２種以上からなるスラグ成分を添加して、生成する二次精錬スラグの組成を、CaＯとAl2Ｏ3の質量濃度比（CaＯ／Al2Ｏ3）を1.30〜1.95、マグネシア濃度を1〜18mass％としたCaO−Al2Ｏ3−MgO系スラグもしくはCaＯ−Al2Ｏ3−MgO−Ｆ系スラグに調整して脱硫することにより、Ｓ含有量が0.0006mass％以下の合金となるようにすることを特徴とする、熱間加工性に優れたNi基合金の精錬方法を提案するものである。
That is, the present invention is C: 0.3 mass% or less, Si: 0.5 mass% or less, Mn: 2 mass% or less, Cr: 3 mass% or less, Cu: 40 mass% or less, Fe: 3 mass% or less, Ti: 2 mass% or less, Mg: 0.005 to 0.04 mass%, Ca: 0.0005 to 0.04 mass%, Oxygen: 3 to 50 ppm, S: 0.0006 mass% or less, Al: 0.01 to 5 mass%, balance Ni and refining Ni-based alloy consisting of inevitable impurities First, the raw materials are first melted in an electric furnace, etc., then removed into a secondary refining vessel using MgO-based refractories and removed, and in the subsequent secondary finishing refining, Al is added after oxygen blowing. In the process of deoxidizing, the composition of the secondary refining slag produced by adding one or more slag components of limestone, meteorite, alumina, magnesia to the mass of CaO and Al 2 O 3 concentration ratio (CaO / Al 2 O 3) and from 1.30 to 1.95, a
また、本発明は、Ｃ：２mass％以下、Si：１mass％以下、Mn：２mass％以下、Ｐ：0.03mass％以下、Cr：30mass％以下、Cu：１mass％以下、Ti：２mass％以下、Fe：20mass％以下、Mg：0.005〜0.04mass％、Ca：0.0005〜0.04mass％、酸素：3〜50ppm、Ｓ：0.0006mass％以下、Al：0.01〜５mass％、残部Niおよび不可避的不純物からなるNi基合金の精錬に当たり、原料をまず電気炉等で溶解した後、MgＯ系耐火物を用いた二次精錬用容器に出鋼して除滓し、続く二次仕上げ精錬においては、酸素吹精したのちAlを添加して脱酸する過程において、石灰石、螢石、アルミナ、マグネシアのうち１種または２種以上からなるスラグ成分を添加して、生成する二次精錬スラグの組成を、CaＯとAl2Ｏ3の質量濃度比（CaＯ／Al2Ｏ3）を1.30〜1.95、マグネシア濃度を1〜18mass％としたCaO−Al2Ｏ3−MgO系スラグもしくはCaＯ−Al2Ｏ3−MgO−Ｆ系スラグに調整して脱硫することにより、Ｓ含有量が0.0006mass％以下の合金となるようにすることを特徴とする、熱間加工性に優れたNi基合金の精錬方法を提案するものである。
Moreover, this invention is C: 2 mass% or less, Si: 1 mass% or less, Mn: 2 mass% or less, P: 0.03 mass% or less, Cr: 30 mass% or less, Cu: 1 mass% or less, Ti: 2 mass% or less, Fe : 20 mass% or less, Mg: 0.005 to 0.04 mass%, Ca: 0.0005 to 0.04 mass%, oxygen: 3 to 50 ppm, S: 0.0006 mass% or less, Al: 0.01 to 5 mass%, the balance Ni and Ni consisting of inevitable impurities In refining the base alloy, the raw materials were first melted in an electric furnace, etc., then removed into a secondary refining vessel using MgO-based refractories and removed, and in the subsequent secondary finishing refining, oxygen blowing was performed. Later, in the process of deoxidizing by adding Al, the composition of the secondary refining slag produced by adding one or more slag components of limestone, aragonite, alumina, magnesia to CaO and Al mass concentration ratio of 2 O 3 (CaO / Al 2 O 3) and 1.30 ~ 1.95, CaO-Al 2 O 3 in which the
以上説明したように、本発明に係る精錬方法によれば、Alを含有するNi基合金の熱間加工性を改善するために必要なMgおよびCa濃度の制御を、二次仕上げ精錬のスラグ成分の制御により簡便に行うことができるから、従来の方法よりも精度よく、かつ低コストで行うことが可能である。 As described above, according to the refining method according to the present invention, the control of Mg and Ca concentration necessary for improving the hot workability of the Ni-based alloy containing Al, the slag component of secondary finishing refining Therefore, it can be performed with higher accuracy and at a lower cost than the conventional method.
本発明の精錬方法では、まず、電気炉にて、純金属ニッケルやスクラップ、銅、フェロクロム、金属クロムなどを溶解してNi基合金の粗溶湯を得る。その後、このNi基合金の粗溶湯を、MgＯ系耐火物を用いた二次精錬用容器内に出鋼して望ましくは除滓を行う。その後、前記二次精錬用容器を用いるＶＯＤまたはＡＯＤあるいはその両方での二次仕上げ精錬において、Ｃを除去するための酸素吹精（酸化精錬）を行い、その後、脱酸と成分調整（Al添加を含む）などを目的とした精錬を行うと共に、Al含有量の調整（Al添加）を行う。
なお、本発明において用いる上記二次精錬用容器のMgＯ含有耐火物とは、ドロマイト、マグネシアカーボン、マグネシアアルミナカーボン、マグネシアクロム煉瓦などのライニングをいう。
In the refining method of the present invention, first, pure metal nickel, scrap, copper, ferrochrome, metal chromium, etc. are melted in an electric furnace to obtain a Ni-base alloy crude molten metal. Thereafter, the Ni-based alloy crude molten steel is steeled in a secondary refining vessel using MgO-based refractory, and is preferably removed. Then, in secondary finishing refining using VOD and / or AOD using the secondary refining vessel, oxygen blowing (oxidative refining) to remove C is performed, and then deoxidation and component adjustment (Al addition) Refining for the purpose of adjusting the Al content (adding Al).
The MgO-containing refractory used in the secondary refining vessel used in the present invention refers to a lining of dolomite, magnesia carbon, magnesia alumina carbon, magnesia chrome brick or the like.
上記二次仕上げ精錬において、Alを添加して脱酸する過程において、石灰石、螢石、アルミナ、マグネシアのうちの１種または２種以上からなるスラグ成分を添加し、後述するようなスラグ組成の調整を行う。なお、この場合において、マグネシア源をスラグ成分として用いない場合でも、MgＯ含有耐火物中のマグネシアがCaＯ-Al2Ｏ3系スラグあるいはCaＯ-Al2Ｏ3-Ｆ系スラグ中に溶解することで、CaＯ-Al2Ｏ3-MgＯ系スラグあるいはCaＯ-Al2Ｏ3-MgＯ-Ｆ系スラグが形成される。もちろん、マグネシア源としてMgＯを積極的に添加しても構わない。このようにして、スラグ中に添加されたMgＯが、下記の（１）式の反応式によって還元され、該溶融合金中に供給されるものと考えられる。
３MgＯ（スラグ）+２Al（メタル）=Al2Ｏ3（スラグ）+３Mg（メタル）…(1)
In the secondary finishing refining, in the process of adding and deoxidizing Al, a slag component consisting of one or more of limestone, meteorite, alumina and magnesia is added, and the slag composition as described later is added. Make adjustments. In this case, even when the magnesia source is not used as the slag component, the magnesia in the MgO-containing refractory dissolves in the CaO—Al 2 O 3 slag or CaO—Al 2 O 3 —F slag. CaO—Al 2 O 3 —MgO slag or CaO—Al 2 O 3 —MgO—F slag is formed. Of course, MgO may be positively added as a magnesia source. Thus, it is considered that MgO added to the slag is reduced by the following reaction formula (1) and supplied into the molten alloy.
3MgO (slag) + 2Al (metal) = Al 2 O 3 (slag) + 3Mg (metal) ... (1)
上記（１）式からわかるように、スラグからのMgの供給を制御するには、スラグ中のアルミナの活量とマグネシアの活量を適正な値に制御することが必要である。図１にCaＯ-Al2Ｏ3系スラグにおけるアルミナの1600℃における活量を示す。この図より、スラグ中のアルミナ濃度の増加に伴い、アルミナの活量が増加していくことがわかる。図２は、2.5mass％のAlを含有する溶融Ni基合金において、Mgをスラグから還元反応により添加した実験の結果を示す。ここで、スラグ中のMgＯ濃度は10mass％とし、溶鋼温度は1550℃として実験した。なお、この図は、反応30分後の分析値をプロットした図であるが、この図により、CaＯ／Al2Ｏ3比の増加に伴い、すなわち、スラグ中のアルミナ濃度の減少に伴い、溶融Ni基合金中のMgが（１）式に従い増加することがわかる。
以上のことから、Alを含有する溶融Ni基合金において、Mg濃度を制御するためには、MgＯを含有するスラグのCaＯ／Al2Ｏ3比を制御すればよいことがわかった。
As can be seen from the above equation (1), in order to control the supply of Mg from the slag, it is necessary to control the activity of alumina and the activity of magnesia in the slag to appropriate values. FIG. 1 shows the activity at 1600 ° C. of alumina in CaO—Al 2 O 3 slag. From this figure, it can be seen that the alumina activity increases as the concentration of alumina in the slag increases. FIG. 2 shows the result of an experiment in which Mg was added from slag by a reduction reaction in a molten Ni-based alloy containing 2.5 mass% Al. Here, the MgO concentration in the slag was set to 10 mass%, and the molten steel temperature was set to 1550 ° C. In addition, this figure is a figure in which the analysis values after 30 minutes of reaction are plotted, but according to this figure, as the CaO / Al 2 O 3 ratio increases, that is, as the alumina concentration in the slag decreases, It can be seen that Mg in the Ni-based alloy increases according to the formula (1).
From the above, it was found that in the molten Ni-based alloy containing Al, in order to control the Mg concentration, the CaO / Al 2 O 3 ratio of the slag containing MgO may be controlled.
次に、スラグ中のCaＯについてもまた、上述したと同様に、下記（２）式の反応に従い還元され、該溶融Ni基合金中に供給される。
３CaＯ（スラグ）+2Al（メタル）=Al2Ｏ3（スラグ）+３Ca（メタル）…(2)
Next, CaO in the slag is also reduced according to the reaction of the following formula (2) and supplied into the molten Ni-based alloy, as described above.
3CaO (slag) + 2Al (metal) = Al 2 O 3 (slag) + 3Ca (metal) ... (2)
上記（２）式に示したCaＯの還元反応についても、MgＯの還元反応と同様に、スラグ中のCaＯの活量とアルミナの活量を制御することで、溶融合金中に供給するCa濃度を制御でき、そして図３に示すとおり、CaＯ／Al2Ｏ3比が1.30〜1.95、Ca濃度を0.0005〜0.04mass％、好ましくは0.0005〜0.02mass％に制御可能であることがわかる。 As for the reduction reaction of CaO shown in the above formula (2), similarly to the reduction reaction of MgO, the Ca concentration supplied into the molten alloy is controlled by controlling the activity of CaO in the slag and the activity of alumina. As shown in FIG. 3, it can be seen that the CaO / Al 2 O 3 ratio can be controlled to 1.30 to 1.95 , and the Ca concentration can be controlled to 0.0005 to 0.04 mass%, preferably 0.0005 to 0.02 mass%.
また、上記Ni基合金溶湯は、その後、普通造塊あるいは連続鋳造により凝固させて鋼片とするが、このとき、熱間加工性に有害となるＳついては、該溶融Ni基合金中のMgあるいはCaと（３）、（４）式のように反応し、硫化物として固着される。このように、熱間加工性に有害なＳを無害な硫化物の形態に制御することで、熱間加工性が改善できる。
Ca（メタル）+Ｓ（メタル）＝CaＳ（硫化物） …(3)
Mg（メタル）+Ｓ（メタル）＝MgＳ（硫化物） …(4)
The Ni-based alloy molten metal is then solidified by normal ingot or continuous casting to form a steel slab. At this time, S that is detrimental to hot workability is either Mg or Mg in the molten Ni-based alloy. It reacts with Ca as shown in formulas (3) and (4) and is fixed as sulfide. Thus, hot workability can be improved by controlling S, which is harmful to hot workability, to a harmless sulfide form.
Ca (metal) + S (metal) = CaS (sulfide) (3)
Mg (metal) + S (metal) = MgS (sulfide) (4)
以下に、本発明に係る精錬方法について詳細に説明する。
一般に、MgはNi基合金の熱間加工性を阻害するSと結合し、MgＳを形成し、Ｓを無害化する作用のある元素である。その作用効果は、0.005mass％以上としたときに発揮される。一方、このMgを0.04mass％を超えて過剰に添加してもＳの無害化効果が飽和するため、経済的でない上に、MgNi2のような低融点の金属間化合物を生成して、逆に熱間加工性を悪化させる。そのため、Ni基合金中のMgの含有量は0.005〜0.04mass％とする。好ましくは0.007〜0.035mass％、より好ましくは、0.01mass％〜0.03mass％とする。
The refining method according to the present invention will be described in detail below.
In general, Mg is an element that has an action of detoxifying S by combining with S that inhibits hot workability of a Ni-based alloy to form MgS. The effect is demonstrated when it is 0.005 mass% or more. On the other hand, even if this Mg is added in excess of 0.04 mass%, the detoxification effect of S is saturated, so that it is not economical and a low melting point intermetallic compound such as MgNi 2 is formed, and the reverse Deteriorates hot workability. Therefore, the content of Mg in the Ni-based alloy is set to 0.005 to 0.04 mass%. Preferably it is 0.007-0.035 mass%, More preferably, you may be 0.01 mass%-0.03 mass%.
Ni基合金中のCaもMg同様に、熱間加工性を阻害するＳと結合し、CaＳを形成して、Ｓを無害化する元素である。その効果は、0.0005mass％以上の含有量のとき顕著である。一方、このCa量が0.04mass％を超えて過剰に添加してもＳ無害化の効果が少なく、経済的でない上に、溶接性を悪化させる。そのため、Caは0.0005mass％〜0.04mass％とする。好ましくは0.0007mass％〜0.03mass％、より好ましくは0.001mass％〜0.02mass％とする。 Similarly to Mg, Ca in the Ni-based alloy is an element that binds to S that inhibits hot workability, forms CaS, and renders S harmless. The effect is remarkable when the content is 0.0005 mass% or more. On the other hand, even if this Ca content exceeds 0.04 mass% and is added excessively, the effect of detoxifying S is small, which is not economical and deteriorates weldability. Therefore, Ca shall be 0.0005 mass%-0.04 mass%. Preferably it is 0.0007 mass%-0.03 mass%, More preferably, it is 0.001 mass%-0.02 mass%.
Ni基合金中のＳは、0.0006mass％を超えると粒界への硫化物の析出によって、熱間加工性を悪化させ、熱間加工後に、表面に割れなどの欠陥が発生し、表面品質を悪くして、歩留り低下させる。そのため、Ni基合金中のＳは0.0006mass％以下とする。 If the content of S in the Ni-base alloy exceeds 0.0006 mass%, the hot workability deteriorates due to precipitation of sulfides at the grain boundaries, and defects such as cracks occur on the surface after hot working, improving the surface quality. To make it worse, decrease the yield. Therefore, S in the Ni-based alloy is set to 0.0006 mass% or less.
Ni基合金中のＯは、50massppmを超えると、該合金中の介在物量が多くなり、表面品質に悪影響を及ぼす。また、脱酸が不充分になってしまうので、スラグメタル間において起こる脱硫反応も十分に進行せず、Ｓ含有量が0.0006mass％を超えて熱間加工性の低下を招き、割れが発生するおそれがある。一方、Ｏが3massppmより低いと、脱酸が効きすぎた状態となるために、スラグ中のMgＯの還元反応が進行しすぎてしまい、Mgが0.04mass％を超えてしまうため、熱間加工性が悪化する。同様に、スラグ中のCaＯの還元反応も進行しすぎてしまい、Caが0.04mass％を越えてしまうため、溶接性が悪化してしまう。そのためにＯは、3〜50massppmとする。好ましくは、4〜45massppmが好適であり、より好ましくは5〜40massppmである。 If O in the Ni-based alloy exceeds 50 massppm, the amount of inclusions in the alloy increases, which adversely affects the surface quality. In addition, since deoxidation becomes insufficient, the desulfurization reaction that occurs between slag metals does not proceed sufficiently, and the S content exceeds 0.0006 mass%, leading to a decrease in hot workability and cracking. There is a fear. On the other hand, if O is lower than 3 massppm, deoxidation becomes too effective, and the reduction reaction of MgO in the slag proceeds too much, and Mg exceeds 0.04 mass%, so hot workability. Gets worse. Similarly, the reduction reaction of CaO in the slag also proceeds excessively, and Ca exceeds 0.04 mass%, so that the weldability is deteriorated. Therefore, O is 3-50 massppm. Preferably, 4-45 massppm is suitable, More preferably, it is 5-40 massppm.
Ni基合金中のAlは、Ni基合金の耐酸化性を向上したり、ガンマプライム相を析出して、合金の硬度を上げるために必要な元素である。場合によっては、脱酸元素としても必要となる。本発明では、これらの特性を満足させるために、Ni基合金中のAl濃度の範囲を0.01〜5mass％とする。 Al in the Ni-base alloy is an element necessary for improving the oxidation resistance of the Ni-base alloy and for increasing the hardness of the alloy by depositing a gamma prime phase. In some cases, it is also required as a deoxidizing element. In the present invention, in order to satisfy these characteristics, the range of Al concentration in the Ni-based alloy is set to 0.01 to 5 mass%.
上述したNi基合金の二次仕上げ精錬過程において、上述した組成のNi基合金を得るためには、Alの添加を伴う脱酸時、またその後に生成する二次精錬スラグのCaＯ／Al2Ｏ3比を、上述したように1.30〜1.95に、調整するが、これは合金中のMgおよびCa濃度を制御する上で極めて重要な作業である。それはもし、この二次精錬スラグのCaＯ／Al2Ｏ3質量濃度比が1.95を超えると、スラグ中のAl2Ｏ3の活量が低下し、またMgＯの活量が高くなって、上記（１）式に従い溶融合金中にMgが過剰に還元さる結果、Mg濃度が高くなって、熱間加工性が悪化するためである。 In the secondary finishing refining process of the Ni-based alloy described above, in order to obtain the Ni-based alloy having the above-described composition, the CaO / Al 2 O of the secondary refining slag generated during and after deoxidation with the addition of Al. The 3 ratio is adjusted to 1.30 to 1.95 as described above, which is a very important task in controlling the Mg and Ca concentrations in the alloy. If the CaO / Al 2 O 3 mass concentration ratio of this secondary refining slag exceeds 1.95 , the activity of Al 2 O 3 in the slag will decrease, and the activity of MgO will increase. This is because as a result of excessive reduction of Mg in the molten alloy according to the formula 1), the Mg concentration increases and hot workability deteriorates.
一方、CaＯ／Al2Ｏ3質量濃度比が1.30より低いとMgの還元が不十分となるだけででなく、スラグの脱硫能が低下して、脱硫不足となり、溶融合金中のＳ濃度が0.0006mass％以下にならず、熱間加工性が悪くなる。また、同様にCaＯ／Al2Ｏ3比が1.95を超えると、Caが過剰に供給されて、溶接性が悪化する。一方、CaＯ／Al2Ｏ3質量濃度比が1.30より低いと、Caの還元が十分に行われないばかりか、スラグの脱硫能が低下して、脱硫不足となり、合金中のＳ濃度が0.0006mass％以下に低下せず、熱間加工性が悪くなる。 On the other hand, if the CaO / Al 2 O 3 mass concentration ratio is lower than 1.30 , not only the reduction of Mg becomes insufficient, but also the desulfurization ability of the slag decreases, the desulfurization becomes insufficient, and the S concentration in the molten alloy becomes 0.0006. Not less than mass%, hot workability deteriorates. Similarly, if the CaO / Al 2 O 3 ratio exceeds 1.95 , Ca is excessively supplied and the weldability deteriorates. On the other hand, when the CaO / Al 2 O 3 mass concentration ratio is lower than 1.30, not only Ca is not sufficiently reduced, but also the desulfurization ability of the slag is lowered, resulting in insufficient desulfurization, and the S concentration in the alloy is 0.0006 mass. %, The hot workability deteriorates .
また、上記二次精錬スラグ中のMgＯ濃度も、Ni基合金中のMg濃度を制御する上で重要な支配因子である。このスラグ中MgＯ濃度が18mass％を超えて高くなると、溶融合金中にMgが過剰に還元し、Mgのピックアップが起こり、熱間加工性が著しく低下する。しかも、スラグの融点の上昇を通じてスラグ流動不足を招き、脱硫能が低下することに伴うＳ起因の熱間加工性の悪化を招く。
スラグ中のMgＯ濃度が１％よりも低いと、MgをNi基合金中に0.005mass％以上供給することができなくなる。そのため、二次精錬スラグ中のMgＯ濃度は、１mass％〜18mass％とする。好ましくは３mass％〜15mass％、より好ましくは、４mass％〜13mass％とする。
Further, the MgO concentration in the secondary refining slag is also an important controlling factor in controlling the Mg concentration in the Ni-based alloy. If the MgO concentration in the slag is higher than 18 mass%, Mg is excessively reduced in the molten alloy, Mg pick-up occurs, and hot workability is significantly reduced. In addition, slag flow is insufficient due to an increase in the melting point of slag, and hot workability due to S accompanying deterioration in desulfurization ability is caused.
If the MgO concentration in the slag is lower than 1%, Mg cannot be supplied to the Ni-based alloy in an amount of 0.005 mass% or more. Therefore, the MgO density | concentration in secondary refining slag shall be 1 mass%-18 mass%. Preferably it is 3 mass%-15 mass%, More preferably, you may be 4 mass%-13 mass%.
なお、本発明に係る精錬方法によって製造されるNi基合金は、Niを30mass％以上、とくに60mass％以上含有する合金の製造に適用すると有効である。特にモネル合金やインコネル６０１の製造方法として有効である。例えば、モネル合金の化学成分は、Ｃ：0.3mass％以下、Si：0.5mass％以下、Mn：２mass％以下、Cr：３mass％以下、Cu：40mass％以下、Fe：３mass％以下、Ti：２mass％以下、残部Niおよび不可避的不純物からなるもの、例えば、代表組成が30mass％Cu-0.03mass％Al-0.01mass％Mg-Niであるモネル４００（ＪＩＳ鋼種名：ＮＷ４４００）や、代表組成が30mass％Cu-３mass％Al-0.5mass％Ti−0.02mass％Mg-NiであるモネルＫ−５００（ＪＩＳ鋼種名：ＮＷ５５００）などが対象なる。この場合において、上記インコネル６０１（ＪＩＳ鋼種名：ＮＣＦ６０１）の化学成分は、Ｃ：２mass％以下、Si：１mass％以下、Mn：２mass％以下、Ｐ：0.03mass％以下、Cr：30mass％以下、Cu：１mass％以下、Ti：２mass％以下、Fe：20mass％以下、残部Niおよび不可避的不純物からなり、代表組成は23mass％Cr-15mass％Fe-1.5mass％Al-0.01mass％Mg-Niおよび不可避的不純物からなるNi基合金の溶製技術として有効である。 The Ni-based alloy produced by the refining method according to the present invention is effective when applied to the production of an alloy containing Ni of 30 mass% or more, particularly 60 mass% or more. In particular, it is effective as a method for producing a Monel alloy or Inconel 601. For example, the chemical composition of the Monel alloy is C: 0.3 mass% or less, Si: 0.5 mass% or less, Mn: 2 mass% or less, Cr: 3 mass% or less, Cu: 40 mass% or less, Fe: 3 mass% or less, Ti: 2 mass % Or less, the balance Ni and inevitable impurities, for example, Monel 400 (JIS steel type name: NW4400) whose representative composition is 30 mass% Cu-0.03 mass% Al-0.01 mass% Mg-Ni, and the representative composition is 30 mass Monel K-500 (JIS steel type name: NW5500) which is% Cu-3mass% Al-0.5mass% Ti-0.02mass% Mg-Ni is targeted. In this case, the chemical components of Inconel 601 (JIS steel type name: NCF601) are C: 2 mass% or less, Si: 1 mass% or less, Mn: 2 mass% or less, P: 0.03 mass% or less, Cr: 30 mass% or less, Cu: 1 mass% or less, Ti: 2 mass% or less, Fe: 20 mass% or less, balance Ni and inevitable impurities, representative composition is 23 mass% Cr-15 mass% Fe-1.5 mass% Al-0.01 mass% Mg-Ni and It is effective as a melting technique for Ni-based alloys composed of inevitable impurities.
次に実施例を提示して本発明の構成および作用効果をより明らかにするが、本発明は以下の実施例にのみ限定されるものではない。
電気炉で純Ni、ステンレス屑、フェロニッケル、銅、場合によっては、フェロクロム、金属Crなどを溶解した後、溶湯をMgＯ系耐火物（ドロマイトまたはマグネシアクロム質レンガ）を用いた二次精錬用容器内に出鋼した後、除滓した。その後、前記二次精錬用容器内Ni基合金の一次精錬溶湯をＶＯＤによる二次仕上げ精錬段階において、Ｃを除去する目的で酸素吹精して酸化精錬を行った。その後、脱酸と合金成分の添加を目的としてAlを投入し、引続き石灰石、螢石、アルミナあるいはマグネシア源としてマグネシアあるいはドロマイトレンガ屑の一種又は２種以上を添加して、スラグ成分を調整して、脱硫を行った。さらに、Al、Ｃ、Si、Mnなどの成分元素を厳密に調整し、最終的に普通造塊あるいは、連続鋳造機を用いて鋼片を得た。普通造塊の場合には、熱間鍛造を行い、スラブとした。その後、いずれの場合のスラブも表面を研削し、さらに、熱間圧延を実施し合金板を製造した。
Next, examples will be presented to clarify the configuration and operational effects of the present invention. However, the present invention is not limited to the following examples.
Pure Ni, stainless scrap in an electric furnace, ferronickel, copper, optionally, ferrochromium, was dissolved such as metal Cr, the melt MgO-based refractory container secondary refining using (dolomite or magnesia chrome bricks) After steeling out, the steel was removed. Thereafter, the primary refining melt of the Ni-based alloy in the secondary refining vessel was subjected to oxidation refining by blowing oxygen for the purpose of removing C in the secondary finishing refining stage by VOD. Then, Al is added for the purpose of deoxidation and addition of alloy components, and then one or more kinds of magnesia or dolomite brick scraps are added as limestone, meteorite, alumina or magnesia source, and the slag component is adjusted. Desulfurization was performed. Furthermore, component elements such as Al, C, Si, and Mn were strictly adjusted, and finally a steel slab was obtained using a normal ingot or a continuous casting machine. In the case of ordinary ingots, hot forging was performed to form a slab. Thereafter, the surface of each slab was ground and further hot-rolled to produce an alloy plate.
表１に、得られたNi基合金（モネル合金）の化学成分、二次仕上げ精錬時のスラグの組成を示す。表２には、他のNi基合金（インコネル６０１合金）の化学成分、二次仕上げ精錬時のスラグ組成を示す。そして、表１記載の合金（モネル合金）のスラブ表面性状および圧延後の割れの状況について評価した結果を、表３にまとめて示す。また、表４は、表２記載のNi基合金（インコネル６０１合金）のスラブ表面性状および圧延後の割れの状況について評価した結果を示している。
合金の化学成分および二次仕上げ精錬時のスラグ組成は、蛍光X線分析装置を用いて定量分析を行い、合金の酸素濃度は不活性ガスインパルス融解赤外線吸収法で定量分析を行った。スラブ表面の割れの有無は、スラブ表面を研削した後に、浸透探傷試験（ＰＴ）を行い評価した。圧延後の割れの有無は、表面のスケールを除去した後に、目視により確認したものである。
Table 1 shows the chemical composition of the obtained Ni-based alloy (monel alloy) and the slag composition during secondary finishing refining. Table 2 shows chemical components of other Ni-based alloys (Inconel 601 alloy) and slag compositions during secondary finishing refining. And the result evaluated about the slab surface property of the alloy (Monel alloy) of Table 1, and the condition of the crack after rolling is put together in Table 3, and is shown. Table 4 shows the results of evaluating the slab surface properties of the Ni-based alloy (Inconel 601 alloy) listed in Table 2 and the cracking after rolling.
The chemical composition of the alloy and the slag composition during secondary finishing refining were quantitatively analyzed using a fluorescent X-ray analyzer, and the oxygen concentration of the alloy was quantitatively analyzed by an inert gas impulse melting infrared absorption method. The presence or absence of cracks on the slab surface was evaluated by conducting a penetration flaw test (PT) after grinding the slab surface. The presence or absence of cracks after rolling was confirmed by visual observation after removing the scale on the surface.
表１〜４に示す結果からわかるように、本発明の範囲を外れる条件で製造した比較例の合金は、スラブ表面で割れが観察されたり、あるいはその後の熱間圧延において割れが発生し、その割れ部はトリミングができないほど大きいため屑化になった。 As can be seen from the results shown in Tables 1 to 4, in the comparative alloy manufactured under conditions outside the scope of the present invention, cracks were observed on the slab surface, or cracks occurred in the subsequent hot rolling. Since the cracked part was so large that it could not be trimmed, it was scrapped.
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