JP2010144195A - Method for manufacturing high nitrogen-containing stainless steel - Google Patents
Method for manufacturing high nitrogen-containing stainless steel Download PDFInfo
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- JP2010144195A JP2010144195A JP2008319587A JP2008319587A JP2010144195A JP 2010144195 A JP2010144195 A JP 2010144195A JP 2008319587 A JP2008319587 A JP 2008319587A JP 2008319587 A JP2008319587 A JP 2008319587A JP 2010144195 A JP2010144195 A JP 2010144195A
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- 229910001220 stainless steel Inorganic materials 0.000 title claims abstract description 125
- 239000010935 stainless steel Substances 0.000 title claims abstract description 125
- 238000000034 method Methods 0.000 title claims abstract description 20
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 17
- QJGQUHMNIGDVPM-UHFFFAOYSA-N nitrogen group Chemical group [N] QJGQUHMNIGDVPM-UHFFFAOYSA-N 0.000 title claims abstract description 16
- 229910045601 alloy Inorganic materials 0.000 claims abstract description 31
- 239000000956 alloy Substances 0.000 claims abstract description 31
- 239000002893 slag Substances 0.000 claims abstract description 29
- 229910052581 Si3N4 Inorganic materials 0.000 claims abstract description 20
- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 claims abstract description 20
- 229910000831 Steel Inorganic materials 0.000 claims abstract description 15
- 239000010959 steel Substances 0.000 claims abstract description 15
- 238000007670 refining Methods 0.000 claims abstract description 11
- 229910000519 Ferrosilicon Inorganic materials 0.000 claims abstract description 5
- 150000004767 nitrides Chemical class 0.000 claims description 30
- 229910004298 SiO 2 Inorganic materials 0.000 claims description 7
- 229910052799 carbon Inorganic materials 0.000 claims description 6
- 229910052748 manganese Inorganic materials 0.000 claims description 6
- 229910052759 nickel Inorganic materials 0.000 claims description 5
- 239000000155 melt Substances 0.000 claims description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 abstract description 65
- 229910052757 nitrogen Inorganic materials 0.000 abstract description 30
- 238000009835 boiling Methods 0.000 abstract description 16
- 238000005121 nitriding Methods 0.000 abstract description 4
- PXHVJJICTQNCMI-UHFFFAOYSA-N nickel Substances [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 12
- 239000011572 manganese Substances 0.000 description 11
- 239000011651 chromium Substances 0.000 description 7
- 238000002844 melting Methods 0.000 description 7
- 230000008018 melting Effects 0.000 description 7
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 6
- 230000000052 comparative effect Effects 0.000 description 6
- 239000001301 oxygen Substances 0.000 description 6
- 229910052760 oxygen Inorganic materials 0.000 description 6
- 229910001873 dinitrogen Inorganic materials 0.000 description 5
- 229910001566 austenite Inorganic materials 0.000 description 4
- 239000000203 mixture Substances 0.000 description 4
- 239000012071 phase Substances 0.000 description 4
- 230000000087 stabilizing effect Effects 0.000 description 4
- 238000003483 aging Methods 0.000 description 3
- RRZKHZBOZDIQJG-UHFFFAOYSA-N azane;manganese Chemical compound N.[Mn] RRZKHZBOZDIQJG-UHFFFAOYSA-N 0.000 description 3
- 238000005260 corrosion Methods 0.000 description 3
- 230000007797 corrosion Effects 0.000 description 3
- 238000000354 decomposition reaction Methods 0.000 description 3
- 238000004090 dissolution Methods 0.000 description 3
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 2
- 229910000616 Ferromanganese Inorganic materials 0.000 description 2
- CXOWYMLTGOFURZ-UHFFFAOYSA-N azanylidynechromium Chemical compound [Cr]#N CXOWYMLTGOFURZ-UHFFFAOYSA-N 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 238000007664 blowing Methods 0.000 description 2
- 238000005266 casting Methods 0.000 description 2
- 229910052804 chromium Inorganic materials 0.000 description 2
- 238000002474 experimental method Methods 0.000 description 2
- -1 ferromanganese nitride Chemical class 0.000 description 2
- 239000007789 gas Substances 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- 229910052710 silicon Inorganic materials 0.000 description 2
- 238000003756 stirring Methods 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 1
- 229910000604 Ferrochrome Inorganic materials 0.000 description 1
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 1
- 229910000963 austenitic stainless steel Inorganic materials 0.000 description 1
- 238000005452 bending Methods 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 238000009749 continuous casting Methods 0.000 description 1
- 238000005261 decarburization Methods 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 230000006698 induction Effects 0.000 description 1
- 239000007791 liquid phase Substances 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 230000000007 visual effect Effects 0.000 description 1
- 229910000859 α-Fe Inorganic materials 0.000 description 1
Classifications
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
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- Treatment Of Steel In Its Molten State (AREA)
Abstract
Description
本発明は、高窒素含有ステンレス鋼の製造方法に関し、特に、高強度材料として使用される窒素含有量が０．０３質量％以上の高窒素含有ステンレス鋼の製造方法に関する。 The present invention relates to a method for producing high nitrogen-containing stainless steel, and particularly relates to a method for producing high nitrogen-containing stainless steel having a nitrogen content of 0.03% by mass or more used as a high-strength material.
高窒素含有オーステナイト系ステンレス鋼（以下、「高窒素含有ステンレス鋼」という）は、高強度且つ時効硬化に優れていることから、高強度材料として種々の分野で使用されている。この高窒素含有ステンレス鋼では、強度を高めるため、一般的に窒素含有量が０．０３質量％以上に調整されている。
高窒素含有ステンレス鋼の製造方法としては、ステンレス溶鋼の精錬過程において窒素含有量を高める方法が一般的に知られている。例えば、ＡＯＤ法の場合、多量の窒素ガスを羽口からステンレス溶鋼中に吹き込むことによって窒素含有量を高める方法がある（例えば、特許文献１及び２）。また、ＶＯＤ法の場合、合金中に窒素を約７質量％含有する窒化フェロマンガンや窒化クロム等の窒化合金をステンレス溶鋼に添加することによって窒素含有量を高める方法がある（例えば、特許文献３）。
High nitrogen-containing austenitic stainless steel (hereinafter referred to as “high nitrogen-containing stainless steel”) is used in various fields as a high-strength material because of its high strength and excellent age hardening. In this high nitrogen-containing stainless steel, the nitrogen content is generally adjusted to 0.03% by mass or more in order to increase the strength.
As a method for producing high nitrogen-containing stainless steel, a method for increasing the nitrogen content in the refining process of molten stainless steel is generally known. For example, in the case of the AOD method, there is a method of increasing the nitrogen content by blowing a large amount of nitrogen gas into the molten stainless steel from the tuyere (for example, Patent Documents 1 and 2). In addition, in the case of the VOD method, there is a method of increasing the nitrogen content by adding a nitride alloy such as ferromanganese nitride or chromium nitride containing approximately 7% by mass of nitrogen to the molten stainless steel (for example, Patent Document 3). ).
しかしながら、窒素ガスをステンレス溶鋼中に吹き込む方法では、ステンレス溶鋼中に窒素が迅速且つ効率的に取り込まれ難い。
一方、窒化合金をステンレス溶鋼に添加する方法では、一般的に使用されている窒化合金の融点（例えば、窒化フェロマンガン：約１２５０℃、窒化クロム：約１０８０℃、窒化フェロクロム：約１５２０℃）が、ステンレス溶鋼の溶鋼温度（一般的に１５５０〜１６５０℃）に比べて低すぎるため、ステンレス溶鋼に窒化合金を添加すると、窒化合金の溶解に伴って多くの窒素ガスが急激に生じる。その結果、窒素ガスによってステンレス溶鋼のボイリングや突沸が起こり、窒素ガスが空気中に放出されるため、ステンレス溶鋼中に窒素が迅速且つ効率的に取り込まれ難い。さらに、この方法では、ステンレス溶鋼中に窒素が迅速且つ効率的に取り込まれ難いために、窒化合金をステンレス溶鋼に追加しなければならず、原料コストが上昇する。また、ステンレス溶鋼のボイリングや突沸が沈静化するまで次の操業を停止する必要があり、高窒素含有ステンレス鋼の生産性が低い。特に、連続鋳造を行う場合には、ステンレス溶鋼のボイリングや突沸が沈静化するまで鋳造開始時間を遅らせる必要があり、また２チャージ目のステンレス溶鋼のボイリングや突沸が沈静化するまで１チャージ目の鋳造速度を減速せざるを得ない状況が生じていた。
However, in the method in which nitrogen gas is blown into the molten stainless steel, it is difficult to quickly and efficiently incorporate nitrogen into the molten stainless steel.
On the other hand, in the method of adding a nitride alloy to molten stainless steel, the melting points of commonly used nitride alloys (for example, ferromanganese nitride: about 1250 ° C., chromium nitride: about 1080 ° C., ferrochrome nitride: about 1520 ° C.) Since the temperature of the molten steel is too low compared with the molten steel temperature (generally 1550 to 1650 ° C.), when a nitriding alloy is added to the molten stainless steel, a lot of nitrogen gas is rapidly generated as the nitriding alloy dissolves. As a result, boiling and bumping of the molten stainless steel occurs due to the nitrogen gas, and the nitrogen gas is released into the air. Therefore, it is difficult to quickly and efficiently incorporate nitrogen into the molten stainless steel. Furthermore, in this method, since nitrogen is difficult to be quickly and efficiently taken into the molten stainless steel, a nitride alloy must be added to the molten stainless steel, which increases raw material costs. Further, it is necessary to stop the next operation until the boiling or bumping of the molten stainless steel subsides, and the productivity of the high nitrogen-containing stainless steel is low. In particular, when performing continuous casting, it is necessary to delay the casting start time until the boiling and bumping of molten stainless steel subside, and the first charge until the boiling and bumping of the second molten stainless steel subside. There was a situation where the casting speed had to be reduced.
本発明は、上記のような問題を解決するためになされたものであり、ステンレス溶鋼のボイリングや突沸を抑制してステンレス溶鋼中に窒素を迅速且つ効率的に取り込むことが可能な生産性の高い高窒素含有ステンレス鋼の製造方法を提供することを目的とする。 The present invention has been made to solve the above-described problems, and has high productivity capable of quickly and efficiently incorporating nitrogen into molten stainless steel by suppressing boiling and bumping of molten stainless steel. It aims at providing the manufacturing method of high nitrogen content stainless steel.
そこで、本発明者等は、ステンレス溶鋼のボイリングや突沸が窒化合金の融点が溶鋼温度に比べて低いことに起因していると考え、この問題を解決すべく鋭意研究した結果、溶鋼温度よりも融点が高い窒化合金を用いると共に、この窒化合金を他の成分の補助によってステンレス溶鋼に溶解させることで、窒化合金の溶解速度を緩やかにし、ステンレス溶鋼のボイリングや突沸を抑制してステンレス溶鋼中に窒素を迅速且つ効率的に取り込ませ得ることに想到し、本発明を完成するに至った。
すなわち、本発明は、ステンレス溶鋼の精錬過程において、精錬時の溶鋼温度で溶融するスラグをステンレス溶鋼１トンあたり５ｋｇ以上の割合でステンレス溶鋼中に存在させ、窒化フェロ珪素及び窒化珪素から選択される少なくとも１つの窒化合金をステンレス溶鋼に添加することを特徴とする高窒素含有ステンレス鋼の製造方法である。
Therefore, the present inventors considered that the boiling and bumping of the molten stainless steel was caused by the fact that the melting point of the nitrided alloy was lower than the molten steel temperature, and as a result of earnest research to solve this problem, A nitride alloy with a high melting point is used, and this nitride alloy is dissolved in stainless steel with the aid of other components, thereby slowing the dissolution rate of the nitride alloy and suppressing boiling and bumping of the stainless steel in the stainless steel. The inventors have conceived that nitrogen can be taken in quickly and efficiently, and have completed the present invention.
That is, according to the present invention, in the refining process of molten stainless steel, slag that melts at the molten steel temperature at the time of refining is present in the molten stainless steel at a rate of 5 kg or more per ton of molten stainless steel, and is selected from ferrosilicon nitride and silicon nitride. A method for producing high nitrogen-containing stainless steel, comprising adding at least one nitride alloy to molten stainless steel.
本発明によれば、ステンレス溶鋼のボイリングや突沸を抑制してステンレス溶鋼中に窒素を迅速且つ効率的に取り込むことが可能な生産性の高い高窒素含有ステンレス鋼の製造方法を提供することができる。 ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the high nitrogen content stainless steel with high productivity which can suppress the boiling and bumping of stainless steel molten steel, and can take in nitrogen in stainless steel molten steel quickly and efficiently can be provided. .
本発明の高窒素含有ステンレス鋼の製造方法は、ステンレス溶鋼の精錬過程において、所定のスラグをステンレス溶鋼中に存在させつつ、所定の窒化合金をステンレス溶鋼に添加する。
本発明の高窒素含有ステンレス鋼の製造方法に用いられる窒化合金は、一般的な精錬過程における溶鋼温度（１５５０〜１６５０℃）よりも融点が高い窒化フェロ珪素（融点：約１８９０℃）及び窒化珪素（融点：約１９００℃）であり、これらは単独又は混合して使用することができる。これらの窒化合金は窒素含有量が高く（窒化フェロ珪素：約３０質量％、窒化珪素：約４０質量％）、ステンレス溶鋼に添加する窒化合金の量を少なくすることができるため、原料コストを抑えることも可能となる。
In the method for producing high nitrogen-containing stainless steel according to the present invention, a predetermined nitride alloy is added to the molten stainless steel while the predetermined slag is present in the molten stainless steel in the refining process of the molten stainless steel.
The nitride alloy used in the method for producing high nitrogen-containing stainless steel of the present invention includes ferrosilicon nitride (melting point: about 1890 ° C.) and silicon nitride having a melting point higher than the molten steel temperature (1550 to 1650 ° C.) in a general refining process. (Melting point: about 1900 ° C.), and these can be used alone or in combination. These nitride alloys have a high nitrogen content (ferrosilicon nitride: about 30% by mass, silicon nitride: about 40% by mass), and the amount of nitride alloy added to the molten stainless steel can be reduced, thereby reducing raw material costs. It is also possible.
ここで、溶鋼温度が１６００℃のステンレス溶鋼に窒化合金を添加した場合の反応機構について、窒化合金として窒化珪素を用いた場合を例にして説明する。
１６００℃における窒化珪素の分解反応の標準生成自由エネルギー（ΔＧ０）は、下記式（１）に示されるように正の値であるため、ステンレス溶鋼に窒化珪素を添加しただけでは窒化珪素は分解反応せず、ステンレス溶鋼に窒素が取り込まれない。
Ｓｉ３Ｎ４＝３［Ｓｉ］＋４［Ｎ］ ΔＧ０＝３３０ＫＪ／ｍｏｌ ・・・（１）
ところが、１６００℃における窒化珪素の分解反応に酸素を加えると、標準生成自由エネルギー（ΔＧ０）は、下記式（２）で示されるように負の値となり、１６００℃でも窒化珪素は分解し、ステンレス溶鋼に窒素が取り込まれる。
Ｓｉ３Ｎ４＋６［Ｏ］＝３（ＳｉＯ２）＋４［Ｎ］ ΔＧ０＝−２０６ＫＪ／ｍｏｌ ・・・（２）
従って、窒化珪素等の窒化合金をステンレス溶鋼に添加して溶解させるためには、ステンレス溶鋼中に酸素源が存在している必要がある。
Here, the reaction mechanism when a nitride alloy is added to a molten stainless steel having a molten steel temperature of 1600 ° C. will be described by taking an example of using silicon nitride as the nitride alloy.
Since the standard free energy of formation (ΔG 0 ) of the decomposition reaction of silicon nitride at 1600 ° C. is a positive value as shown in the following formula (1), silicon nitride is decomposed only by adding silicon nitride to stainless steel molten steel. It does not react and nitrogen is not taken into the molten stainless steel.
Si 3 N 4 = 3 [Si] +4 [N] ΔG 0 = 330 KJ / mol (1)
However, when oxygen is added to the decomposition reaction of silicon nitride at 1600 ° C., the standard free energy of formation (ΔG 0 ) becomes a negative value as shown by the following formula (2), and silicon nitride decomposes even at 1600 ° C. Nitrogen is taken into the molten stainless steel.
Si 3 N 4 +6 [O] = 3 (SiO 2 ) +4 [N] ΔG 0 = −206 KJ / mol (2)
Therefore, in order to add and dissolve a nitride alloy such as silicon nitride in molten stainless steel, it is necessary that an oxygen source be present in the molten stainless steel.
窒化合金の添加量は、ステンレス溶鋼の組成や量、窒化合金の種類、目標とする窒素含有量等に応じて適宜設定すればよく特に限定されることはない。 The addition amount of the nitride alloy is not particularly limited as long as it is appropriately set according to the composition and amount of molten stainless steel, the type of nitride alloy, the target nitrogen content, and the like.
本発明の高窒素含有ステンレス鋼の製造方法に用いられる酸素源はスラグである。スラグは、窒化合金の溶解を促進させるため、酸素源としての機能を発揮できるように精錬時の溶鋼温度で溶融している必要がある。なお、スラグは、ステンレス溶鋼中に完全に溶融（すなわち、液相率が１００％）している必要はなく、目視観察において湯面上に固体で浮遊している場合であっても、５０％以上溶融していれば窒化合金の分解反応に供する酸素源として十分な量である。
このようなスラグとしては、ＣａＯ−ＳｉＯ２系、ＣａＯ−ＳｉＯ２−Ａｌ２Ｏ３系、ＣａＯ−Ａｌ２Ｏ３系等が挙げられ、これらは単独又は混合して用いることができる。
スラグをステンレス溶鋼に存在させる方法としては、特に限定されることはなく、スラグをステンレス溶鋼に添加したり、所定の成分を添加することによってステンレス鋼中で所望のスラグを生成させればよい。
The oxygen source used in the method for producing high nitrogen-containing stainless steel of the present invention is slag. In order to promote the melting of the nitride alloy, the slag needs to be melted at the molten steel temperature at the time of refining so that the function as an oxygen source can be exhibited. Note that the slag does not need to be completely melted in the molten stainless steel (that is, the liquid phase ratio is 100%), and even if the slag floats as a solid on the molten metal surface by visual observation, 50% If it is melted as described above, the amount is sufficient as an oxygen source for the decomposition reaction of the nitride alloy.
Examples of such slag include CaO—SiO 2 , CaO—SiO 2 —Al 2 O 3 , and CaO—Al 2 O 3 , which can be used alone or in combination.
The method for causing the slag to exist in the molten stainless steel is not particularly limited, and a desired slag may be generated in the stainless steel by adding the slag to the molten stainless steel or by adding predetermined components.
ステンレス溶鋼におけるスラグの存在量は、ステンレス溶鋼１トンあたり５ｋｇ以上である。スラグの存在量が５ｋｇ未満であると、窒化合金の溶解速度が極めて遅くなり、所望の生産性が得られない。また、スラグの存在量の上限は、特に限定されることはないが、必要以上にスラグを存在させると、精錬の際に取鍋又は坩堝からスラグやステンレス溶鋼がオーバーフローしてしまうことがある。そのため、取鍋や坩堝、ステンレス溶鋼の量等に応じて適宜設定する必要があるが、一般に、ステンレス溶鋼１トンあたり１００ｋｇ以下である。 The amount of slag present in the molten stainless steel is 5 kg or more per ton of molten stainless steel. If the amount of slag present is less than 5 kg, the dissolution rate of the nitride alloy becomes extremely slow, and the desired productivity cannot be obtained. Moreover, the upper limit of the amount of slag is not particularly limited, but if slag is present more than necessary, slag and stainless steel may overflow from the ladle or crucible during refining. Therefore, although it is necessary to set suitably according to the ladle, the crucible, the amount of molten stainless steel, etc., it is generally 100 kg or less per 1 ton of molten stainless steel.
本発明の高窒素含有ステンレス鋼の製造方法に用いられるステンレス溶鋼は、Ｃ（炭素）、Ｓｉ（珪素）、Ｍｎ（マンガン）、Ｎｉ（ニッケル）及びＣｒ（クロム）を含有する。
＜Ｃ：０．００５〜０．２質量％＞
Ｃは、オーステナイト相安定化元素であり、侵入型元素であるため、ステンレス鋼の強度の向上に寄与する。そのため、ステンレス溶鋼は、少なくとも０．００５質量％のＣを含有する必要がある。ただし、Ｃ含有量が多すぎると耐食性及び溶接性が低下するため、Ｃ含有量の上限は０．２質量％とする必要がある。
Stainless steel molten steel used in the method for producing high nitrogen-containing stainless steel of the present invention contains C (carbon), Si (silicon), Mn (manganese), Ni (nickel), and Cr (chromium).
<C: 0.005 to 0.2% by mass>
C is an austenite phase stabilizing element and is an interstitial element, and thus contributes to an improvement in the strength of stainless steel. For this reason, the molten stainless steel needs to contain at least 0.005% by mass of C. However, since corrosion resistance and weldability will fall when there is too much C content, the upper limit of C content needs to be 0.2 mass%.
＜Ｓｉ：４．０質量％以下＞
Ｓｉは、ステンレス鋼に必要な硬度を与えるために必要な元素である。Ｓｉ含有量の増加と共に時効硬化特性が向上するものの、Ｓｉ含有量が多すぎると熱間加工性が低下する。そのため、Ｓｉ含有量の上限は４．０質量％とする必要がある。
＜Ｍｎ：０．２〜２５．０質量％＞
Ｍｎは、Ｃと同様にオーステナイト相安定化元素であり、ステンレス鋼の所望の強度を得るため、ステンレス溶鋼は、少なくとも０．２質量％のＭｎを含有する必要がある。ただし、Ｍｎ含有量が多すぎるとステンレス鋼の曲げ加工性が低下するため、Ｍｎ含有量の上限は２５．０質量％とする必要がある。
<Si: 4.0 mass% or less>
Si is an element necessary for imparting the necessary hardness to stainless steel. Although age hardening characteristics improve with an increase in Si content, hot workability decreases when the Si content is too high. Therefore, the upper limit of Si content needs to be 4.0 mass%.
<Mn: 0.2 to 25.0 mass%>
Mn is an austenite phase stabilizing element like C, and in order to obtain a desired strength of stainless steel, the molten stainless steel needs to contain at least 0.2 mass% of Mn. However, if the Mn content is too large, the bending workability of the stainless steel is lowered, so the upper limit of the Mn content needs to be 25.0% by mass.
＜Ｎｉ：０．１〜１８．０質量％＞
Ｎｉは、ＣやＭｎと同様にオーステナイト相安定化元素であり、ステンレス鋼の所望の強度を得るため、ステンレス溶鋼は、少なくとも０．１質量％のＮｉを含有する必要がある。ただし、Ｎｉは高価な元素であるため、必要以上の添加は無駄なコスト上昇を招くので、Ｎｉ含有量の上限は１８．０質量％とする必要がある。
＜Ｃｒ：１２．０〜３０．０質量％＞
Ｃｒは、ステンレス鋼に要求される耐食性を得るために必須の元素であり、ステンレス鋼の所望の耐食性を得るため、ステンレス溶鋼は、少なくとも１２．０質量％のＣｒを含有する必要がある。ただし、Ｎｉを過剰添加するとデルタフェライトが多量に生成して熱間加工性を低下させることがあるので、Ｃｒ含有量の上限は３０．０質量％とする必要がある。
<Ni: 0.1 to 18.0% by mass>
Ni is an austenite phase stabilizing element like C and Mn, and in order to obtain the desired strength of stainless steel, the molten stainless steel needs to contain at least 0.1% by mass of Ni. However, since Ni is an expensive element, excessive addition causes unnecessary cost increase, so the upper limit of Ni content needs to be 18.0% by mass.
<Cr: 12.0 to 30.0 mass%>
Cr is an essential element for obtaining the corrosion resistance required for stainless steel. In order to obtain the desired corrosion resistance of stainless steel, the molten stainless steel needs to contain at least 12.0% by mass of Cr. However, since excessive addition of Ni may generate a large amount of delta ferrite and reduce hot workability, the upper limit of the Cr content needs to be 30.0% by mass.
上記の元素を含有するステンレス溶鋼を用い、上記の方法にて製造されるステンレス鋼は、ステンレス溶鋼のボイリングや突沸を抑制してステンレス溶鋼中に窒素を迅速且つ効率的に取り込むことが可能であるため、高濃度の窒素を含有する。
窒素は、Ｃ、Ｍｎ及びＮｉと同様にオーステナイト相安定化元素であり、ステンレス鋼に必要な硬度及び優れた時効硬化特性を得るために必要な元素である。そのため、ステンレス鋼は、少なくとも０．０３質量％を含有している必要がある。窒素含有量の上限は、ＭｎやＮｉ等の含有量に応じて飽和する濃度まで添加してもよいが、好ましくは１．３質量％である。
また、ステンレス鋼における他の元素の含有量は、スラグに含有されるＳｉ等の元素によって、ステンレス溶鋼の組成に比べてＳｉ等の元素の含有量が僅かに高くなるものの、Ｓｉ等の元素のほとんどはスラグ中に残存するので、ステンレス鋼における他の元素の含有量は、ステンレス溶鋼における他の元素の含有量と実質的に同じである。
The stainless steel produced by the above method using the above-mentioned molten stainless steel containing the elements is capable of quickly and efficiently incorporating nitrogen into the molten stainless steel while suppressing boiling and bumping of the molten stainless steel. Therefore, it contains a high concentration of nitrogen.
Nitrogen is an austenite phase stabilizing element like C, Mn, and Ni, and is an element necessary for obtaining the hardness necessary for stainless steel and excellent age hardening characteristics. Therefore, the stainless steel needs to contain at least 0.03% by mass. The upper limit of the nitrogen content may be added up to a concentration that saturates depending on the content of Mn, Ni or the like, but is preferably 1.3% by mass.
The content of other elements in the stainless steel is slightly higher than the composition of the molten stainless steel due to the elements such as Si contained in the slag, but the elements such as Si Since most of it remains in the slag, the content of other elements in the stainless steel is substantially the same as the content of other elements in the molten stainless steel.
以下、実施例により本発明を詳細に説明するが、これらによって本発明が限定されるものではない。
（実施例１）
０．０１５質量％のＣ、２．０質量％のＳｉ、３．０質量％のＭｎ、８．０質量％のＮｉ、１８．０質量％のＣｒを含有するステンレス鋼３０ｋｇを、Ａｒガス雰囲気下にてＭｇＯ坩堝内で高周波誘導加熱炉を用いて溶融させた。なお、ステンレス溶鋼中のＮ含有量は、０．００５質量％以下であった。このステンレス溶鋼を１６００℃に温度調整した後、ＣａＯ−ＳｉＯ２系のスラグをステンレス溶鋼１ｋｇあたり５ｇの割合で添加し、底吹ガスによってステンレス溶鋼とスラグとを十分に撹拌してスラグをステンレス溶鋼に溶融させた。次に、１８５ｇの窒化珪素（Ｎ含有量は７４ｇ）をステンレス溶鋼に添加して十分に撹拌したところ、窒化珪素の溶解が２分程度で完了した。ここで、窒化珪素を溶解させる段階及び窒化珪素の溶解後の段階のいずれにおいてもステンレス溶鋼のボイリングや突沸が生じることはなかった。窒化珪素を添加してから３分後にステンレス溶鋼をサンプリングしたところ、窒素の含有量は０．１８３質量％であった。
EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited by these.
Example 1
30 kg of stainless steel containing 0.015 mass% C, 2.0 mass% Si, 3.0 mass% Mn, 8.0 mass% Ni, 18.0 mass% Cr, Ar gas atmosphere Below, it melted in a MgO crucible using a high frequency induction heating furnace. In addition, N content in stainless steel molten steel was 0.005 mass% or less. After adjusting the temperature of this molten stainless steel to 1600 ° C., CaO—SiO 2 slag is added at a rate of 5 g per kg of molten stainless steel, and the molten stainless steel and slag are sufficiently stirred by the bottom blowing gas to slag the molten stainless steel. To melt. Next, when 185 g of silicon nitride (N content is 74 g) was added to the molten stainless steel and stirred sufficiently, the dissolution of silicon nitride was completed in about 2 minutes. Here, neither boiling nor bumping of the molten stainless steel occurred in any of the steps of dissolving silicon nitride and the step after dissolving silicon nitride. When the molten stainless steel was sampled 3 minutes after adding silicon nitride, the nitrogen content was 0.183% by mass.
（比較例１）
比較例１では、ＣａＯ−ＳｉＯ２系スラグをステンレス溶鋼に添加しないこと以外は実施例１と同様にして実験を行った。その結果、窒化珪素を添加してから３０分を経過しても窒化珪素はステンレス溶鋼に溶解せず、ステンレス溶鋼の窒素の含有量は０．００６質量％であった。この結果は、比較例１では、酸素源が不足しているために窒化珪素がステンレス溶鋼中にほとんど溶解しなかったことに起因しているものと考えられる。
(Comparative Example 1)
In Comparative Example 1, the experiment was performed in the same manner as in Example 1 except that CaO—SiO 2 slag was not added to the molten stainless steel. As a result, even after 30 minutes had passed since silicon nitride was added, silicon nitride did not dissolve in the molten stainless steel, and the content of nitrogen in the molten stainless steel was 0.006% by mass. This result is considered to be due to the fact that silicon nitride was hardly dissolved in the molten stainless steel in Comparative Example 1 because the oxygen source was insufficient.
（実施例２：サンプルＮｏ．１〜１２）
電気炉でスクラップを溶解し、転炉で粗脱炭した表１に示す組成を有するステンレス溶鋼８０トンをＶＯＤ法にて脱炭を行った。この脱炭時に生成したＳｉＯに見合うＣａＯを、ステンレス溶鋼１トンあたり１０〜９５ｋｇの割合のＣａＯ−ＳｉＯ２系スラグとなるように添加し、ステンレス溶鋼とスラグとを十分に撹拌してスラグをステンレス溶鋼に溶融させた。次に、所定量の窒化合金をステンレス溶鋼に添加して撹拌した後、窒化合金を添加してから５分後にステンレス溶鋼をサンプリングして各元素の含有量を調べた。その結果を表２に示す。
(Example 2: Sample Nos. 1-12)
80 tons of molten stainless steel having the composition shown in Table 1 was melted by an electric furnace and roughly decarburized by a converter, and then decarburized by the VOD method. Add CaO commensurate with SiO generated during decarburization so that it becomes CaO-SiO 2 slag at a rate of 10 to 95 kg per ton of molten stainless steel, and thoroughly stir the molten stainless steel and slag to remove the slag from stainless steel. Molten into molten steel. Next, after adding a predetermined amount of nitrided alloy to the molten stainless steel and stirring, the molten stainless steel was sampled 5 minutes after the addition of the nitrided alloy, and the content of each element was examined. The results are shown in Table 2.
（比較例２：サンプルＮｏ．１３〜１８）
比較例２では、ステンレス溶鋼の組成、添加するＣａＯの量（すなわち、ステンレス溶鋼中に生成させるスラグの量）、及び窒化合金の種類を変えたこと以外は実施例２と同様にして実験を行った。その結果を表２に示す。
(Comparative Example 2: Sample Nos. 13-18)
In Comparative Example 2, the experiment was performed in the same manner as in Example 2 except that the composition of the molten stainless steel, the amount of CaO to be added (that is, the amount of slag generated in the molten stainless steel), and the type of the nitride alloy were changed. It was. The results are shown in Table 2.
本発明例（サンプルＮｏ．１〜１２）では、窒化合金を添加してから５分後には既に目標とする窒素含有量にステンレス溶鋼のボイリングや突沸が生じることなく到達した。
これに対して、比較例（サンプルＮｏ．１３〜１８）では、窒化合金を添加してから５分経過しても目標とする窒素含有量に到達しなかった。特に、窒化合金として窒化マンガンを用いたサンプルＮｏ．１６〜１８では、窒化マンガンを添加した後にステンレス溶鋼のボイリングや突沸が生じると共に、目標とする窒素含有量に到達するまでに長時間を要した（Ｎｏ．１６では６０分、Ｎｏ．１７では３５分、Ｎｏ．１８では９０分）。また、また、サンプルＮｏ．１６〜１８では、窒化マンガンを分けて添加した場合であっても、その都度ボイリングや突沸が生じ、ステンレス溶鋼が沈静化するまでに合計約３０分〜８０分の長時間を要した。
以上の結果からわかるように、本発明の高窒素含有ステンレス鋼の製造方法は、ステンレス溶鋼のボイリングや突沸を抑制してステンレス溶鋼中に窒素を迅速且つ効率的に取り込むことができ、非常に生産性が高い。
In the present invention examples (Sample Nos. 1 to 12), the target nitrogen content was already reached without causing boiling or bumping of the molten stainless steel 5 minutes after the addition of the nitride alloy.
On the other hand, in the comparative examples (sample Nos. 13 to 18), the target nitrogen content was not reached even after 5 minutes had elapsed since the addition of the nitride alloy. In particular, Sample No. using manganese nitride as the nitride alloy. In Nos. 16 to 18, boiling and bumping of molten stainless steel occurred after adding manganese nitride, and it took a long time to reach the target nitrogen content (60 minutes for No. 16 and 35 for No. 17). Minutes, 90 minutes for No. 18). In addition, Sample No. In Nos. 16 to 18, even when manganese nitride was added separately, boiling and bumping occurred each time, and it took a total of about 30 minutes to 80 minutes for the molten stainless steel to settle down.
As can be seen from the above results, the method for producing high nitrogen content stainless steel of the present invention can rapidly and efficiently incorporate nitrogen into the molten stainless steel by suppressing the boiling and bumping of the molten stainless steel, which is extremely productive. High nature.
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| CN105463230A (en) * | 2015-11-26 | 2016-04-06 | 北京科技大学 | Method for producing low-carbon low-melting-point silicon-nitrogen alloy |
| CN107955857A (en) * | 2017-10-23 | 2018-04-24 | 邢台钢铁有限责任公司 | A kind of control nitrogen method during AOD smelting stainless steels |
| CN114734044A (en) * | 2022-04-02 | 2022-07-12 | 广州纳联材料科技有限公司 | High-nitrogen nickel-free stainless steel powder and preparation method and application thereof |
| CN115401216A (en) * | 2022-09-21 | 2022-11-29 | 华北理工大学 | Method for preparing high-nitrogen stainless steel by selective laser melting of alloy over-mixed powder |
| CN115418429A (en) * | 2022-08-24 | 2022-12-02 | 广西北港新材料有限公司 | Method for smelting 200-series stainless steel in AOD furnace |
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| CN115401216B (en) * | 2022-09-21 | 2024-03-05 | 华北理工大学 | Method for preparing high-nitrogen stainless steel by alloy powder passing through selective laser melting |
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