JP5857983B2 - Manufacturing method of grain-oriented electrical steel sheet and MgO for annealing separator - Google Patents
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- 238000000137 annealing Methods 0.000 title claims description 75
- 238000004519 manufacturing process Methods 0.000 title claims description 31
- 229910001224 Grain-oriented electrical steel Inorganic materials 0.000 title claims description 26
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 68
- 238000001953 recrystallisation Methods 0.000 claims description 52
- 229910000831 Steel Inorganic materials 0.000 claims description 39
- 239000010959 steel Substances 0.000 claims description 39
- 229910052757 nitrogen Inorganic materials 0.000 claims description 37
- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Chemical compound OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 claims description 36
- 238000000034 method Methods 0.000 claims description 32
- 238000005121 nitriding Methods 0.000 claims description 31
- 238000010438 heat treatment Methods 0.000 claims description 22
- 230000000694 effects Effects 0.000 claims description 19
- 229910052760 oxygen Inorganic materials 0.000 claims description 7
- 230000008569 process Effects 0.000 claims description 7
- 229910052710 silicon Inorganic materials 0.000 claims description 7
- 229910052717 sulfur Inorganic materials 0.000 claims description 7
- 229910010413 TiO 2 Inorganic materials 0.000 claims description 5
- 229910052711 selenium Inorganic materials 0.000 claims description 5
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 claims description 4
- 239000012535 impurity Substances 0.000 claims description 4
- 229910052748 manganese Inorganic materials 0.000 claims description 4
- 239000000203 mixture Substances 0.000 claims description 4
- OGIDPMRJRNCKJF-UHFFFAOYSA-N titanium oxide Inorganic materials [Ti]=O OGIDPMRJRNCKJF-UHFFFAOYSA-N 0.000 claims description 4
- CPLXHLVBOLITMK-UHFFFAOYSA-N Magnesium oxide Chemical compound [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 description 63
- 239000000395 magnesium oxide Substances 0.000 description 31
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 16
- 239000003112 inhibitor Substances 0.000 description 16
- 239000011248 coating agent Substances 0.000 description 15
- 238000000576 coating method Methods 0.000 description 15
- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 description 14
- 229910052581 Si3N4 Inorganic materials 0.000 description 13
- 238000005097 cold rolling Methods 0.000 description 12
- 238000005261 decarburization Methods 0.000 description 11
- 239000012298 atmosphere Substances 0.000 description 8
- 229910052839 forsterite Inorganic materials 0.000 description 8
- 239000007789 gas Substances 0.000 description 8
- HCWCAKKEBCNQJP-UHFFFAOYSA-N magnesium orthosilicate Chemical compound [Mg+2].[Mg+2].[O-][Si]([O-])([O-])[O-] HCWCAKKEBCNQJP-UHFFFAOYSA-N 0.000 description 8
- 238000005755 formation reaction Methods 0.000 description 7
- 229910052742 iron Inorganic materials 0.000 description 7
- 230000009257 reactivity Effects 0.000 description 6
- 238000005096 rolling process Methods 0.000 description 6
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 6
- 230000015572 biosynthetic process Effects 0.000 description 5
- 238000010304 firing Methods 0.000 description 5
- 230000004907 flux Effects 0.000 description 5
- 238000005098 hot rolling Methods 0.000 description 5
- 150000004767 nitrides Chemical class 0.000 description 5
- 238000001556 precipitation Methods 0.000 description 5
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- 239000002344 surface layer Substances 0.000 description 5
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- 238000011156 evaluation Methods 0.000 description 4
- 229910052739 hydrogen Inorganic materials 0.000 description 4
- 238000005259 measurement Methods 0.000 description 4
- 229910000976 Electrical steel Inorganic materials 0.000 description 3
- 229910019142 PO4 Inorganic materials 0.000 description 3
- 239000001257 hydrogen Substances 0.000 description 3
- 239000010410 layer Substances 0.000 description 3
- 239000011777 magnesium Substances 0.000 description 3
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- 230000003647 oxidation Effects 0.000 description 3
- 238000007254 oxidation reaction Methods 0.000 description 3
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 description 3
- 239000010452 phosphate Substances 0.000 description 3
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- 239000000047 product Substances 0.000 description 3
- 239000002002 slurry Substances 0.000 description 3
- 239000004480 active ingredient Substances 0.000 description 2
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
- 229910052799 carbon Inorganic materials 0.000 description 2
- 229910052802 copper Inorganic materials 0.000 description 2
- 238000009792 diffusion process Methods 0.000 description 2
- 239000006185 dispersion Substances 0.000 description 2
- 238000002149 energy-dispersive X-ray emission spectroscopy Methods 0.000 description 2
- 150000002431 hydrogen Chemical class 0.000 description 2
- 229910052750 molybdenum Inorganic materials 0.000 description 2
- 239000001301 oxygen Substances 0.000 description 2
- 239000002245 particle Substances 0.000 description 2
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- 230000001376 precipitating effect Effects 0.000 description 2
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- 239000007858 starting material Substances 0.000 description 2
- 238000009628 steelmaking Methods 0.000 description 2
- 239000012808 vapor phase Substances 0.000 description 2
- 235000008733 Citrus aurantifolia Nutrition 0.000 description 1
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- 235000011941 Tilia x europaea Nutrition 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- 239000012300 argon atmosphere Substances 0.000 description 1
- 125000004429 atom Chemical group 0.000 description 1
- 230000003416 augmentation Effects 0.000 description 1
- YYXHRUSBEPGBCD-UHFFFAOYSA-N azanylidyneiron Chemical compound [N].[Fe] YYXHRUSBEPGBCD-UHFFFAOYSA-N 0.000 description 1
- 239000010953 base metal Substances 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 239000008119 colloidal silica Substances 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
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- ZLNQQNXFFQJAID-UHFFFAOYSA-L magnesium carbonate Chemical compound [Mg+2].[O-]C([O-])=O ZLNQQNXFFQJAID-UHFFFAOYSA-L 0.000 description 1
- 239000001095 magnesium carbonate Substances 0.000 description 1
- 229910000021 magnesium carbonate Inorganic materials 0.000 description 1
- VTHJTEIRLNZDEV-UHFFFAOYSA-L magnesium dihydroxide Chemical compound [OH-].[OH-].[Mg+2] VTHJTEIRLNZDEV-UHFFFAOYSA-L 0.000 description 1
- 239000000347 magnesium hydroxide Substances 0.000 description 1
- 229910001862 magnesium hydroxide Inorganic materials 0.000 description 1
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- 235000013336 milk Nutrition 0.000 description 1
- 229910052758 niobium Inorganic materials 0.000 description 1
- 150000002829 nitrogen Chemical class 0.000 description 1
- QJGQUHMNIGDVPM-UHFFFAOYSA-N nitrogen group Chemical group [N] QJGQUHMNIGDVPM-UHFFFAOYSA-N 0.000 description 1
- 238000003303 reheating Methods 0.000 description 1
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- Chemical Treatment Of Metals (AREA)
- Manufacturing Of Steel Electrode Plates (AREA)
- Soft Magnetic Materials (AREA)
Description
本発明は、優れた磁気特性を有する方向性電磁鋼板を安価に得ることができる磁気特性に優れた方向性電磁鋼板の製造方法および焼鈍分離剤用MgOに関するものである。 The present invention relates to a method for producing a grain-oriented electrical steel sheet having excellent magnetic properties and an MgO for annealing separator, which can obtain a grain-oriented electrical steel sheet having excellent magnetic properties at low cost.
方向性電磁鋼板は、変圧器や発電機の鉄心材料として用いられる軟磁性材料で、鉄の磁化容易軸である<001>方位が鋼板の圧延方向に高度に揃った結晶組織を有するものである。このような集合組織は、方向性電磁鋼板の製造工程中、二次再結晶焼鈍の際にいわゆるゴス(Goss)方位と称される{110}<001>方位の結晶粒を優先的に巨大成長させる、二次再結晶を通じて形成される。 A grain-oriented electrical steel sheet is a soft magnetic material used as a core material for transformers and generators, and has a crystal structure in which the <001> orientation, which is the easy axis of iron, is highly aligned in the rolling direction of the steel sheet. . Such a texture preferentially grows grains of the {110} <001> orientation called the Goss orientation during secondary recrystallization annealing during the production process of grain-oriented electrical steel sheets. Formed through secondary recrystallization.
従来、このような方向性電磁鋼板は、4.5mass%以下程度のSiと、MnS,MnSeおよびAlNなどのインヒビター成分を含有するスラブを、1300℃以上に加熱し、インヒビター成分を一旦固溶させたのち、熱間圧延し、必要に応じて熱延板焼鈍を施して、1回または中間焼鈍を挟む2回以上の冷間圧延によって最終板厚とし、ついで湿潤水素雰囲気中で一次再結晶焼純を施して、一次再結晶および脱炭を行い、ついでマグネシア(MgO)を主剤とする焼鈍分離剤を塗布してから、二次再結晶およびインヒビター成分の純化のために、1200℃で5h程度の最終仕上焼鈍を行うことによって製造されてきた(例えば、特許文献1、特許文献2および特許文献3)。 Conventionally, such a grain-oriented electrical steel sheet is heated to 1300 ° C or higher by heating a slab containing about 4.5 mass% or less of Si and an inhibitor component such as MnS, MnSe, and AlN to once dissolve the inhibitor component. After that, it is hot-rolled and subjected to hot-rolled sheet annealing as necessary, to obtain the final sheet thickness by one or more cold rollings sandwiching intermediate annealing, followed by primary recrystallization annealing in a wet hydrogen atmosphere After performing primary recrystallization and decarburization, and then applying an annealing separator mainly composed of magnesia (MgO), the secondary recrystallization and the inhibitor component are purified at 1200 ° C. for about 5 hours. It has been manufactured by performing final finish annealing (for example, Patent Document 1, Patent Document 2, and Patent Document 3).
上述したとおり、従来の方向性電磁鋼板の製造に際しては、MnS,MnSe,AlNなどの析出物(インヒビター成分)をスラブ段階で含有させて、1300℃を超える高温のスラブ加熱をすることにより、これらのインヒビター成分を一旦固溶させ、後工程で微細析出させることによって二次再結晶を発現させるという工程が採用されてきた。 As described above, when producing conventional grain-oriented electrical steel sheets, precipitates (inhibitor components) such as MnS, MnSe, and AlN are included in the slab stage, and these are heated at a high temperature exceeding 1300 ° C. The step of causing secondary recrystallization by once dissolving the inhibitor component of this compound and then precipitating it finely in a subsequent step has been adopted.
このように、従来の方向性電磁鋼板の製造工程では、1300℃を超える高温でのスラブ加熱が必要であったため、その製造コストは極めて高いものとならざるを得ず、近年の製造コスト低減の要求に応えることができないというところに問題を残していた。 As described above, in the manufacturing process of conventional grain-oriented electrical steel sheets, slab heating at a high temperature exceeding 1300 ° C. is necessary, so the manufacturing cost has to be extremely high, and in recent years the manufacturing cost has been reduced. He left a problem where he was unable to meet the demand.
こうした問題を解決するために、例えば、特許文献4では、酸可溶性Al(sol.Al)を0.010〜0.060%含有させ、スラブ加熱を低温に抑えて脱炭焼鈍工程で適正な窒化雰囲気を用いて窒化を行なうことにより、二次再結晶時に(Al,Si)Nを析出させインヒビターとして用いる方法が提案されている。(Al,Si)Nは鋼中に微細分散することで有効なインヒビターとして機能するが、Alの含有量によってインヒビター強度が決まるために、製鋼でのAl的中精度が不十分な場合は、十分な粒成長抑制力が得られない場合があった。このような途中工程で窒化処理を行ない、(Al,Si)NあるいはAlNをインヒビターとして利用する方法が数多く提案されているが、最近では、スラブ加熱温度が1300℃を超える製造方法等も開示されている。 In order to solve such a problem, for example, in Patent Document 4, 0.010 to 0.060% of acid-soluble Al (sol. Al) is contained, slab heating is suppressed to a low temperature, and an appropriate nitriding atmosphere is used in the decarburization annealing process. A method has been proposed in which (Al, Si) N is precipitated during secondary recrystallization by nitriding and used as an inhibitor. (Al, Si) N functions as an effective inhibitor by being finely dispersed in the steel, but since the inhibitor strength is determined by the Al content, it is sufficient if the accuracy of Al in steelmaking is insufficient. In some cases, it was not possible to obtain a sufficient grain growth inhibiting force. Many methods have been proposed in which nitriding treatment is performed in the middle of the process and (Al, Si) N or AlN is used as an inhibitor. Recently, however, a manufacturing method in which the slab heating temperature exceeds 1300 ° C has been disclosed. ing.
一方、そもそもスラブにインヒビター成分を含有させずに二次再結晶を発現させる技術については、特許文献5に、インヒビター成分を含有させなくとも二次再結晶ができる技術(インヒビターレス法)が開示されている。
ここに、インヒビターレス法は、より高純度化した鋼を利用し、テクスチャー(集合組織の制御)によって二次再結晶を発現させる技術である。しかしながら、インヒビターレス法では、高温のスラブ加熱が不要であって、低コストでの方向性電磁鋼板の製造が可能であるものの、インヒビターを有しないが故に、製造工程中での温度ばらつきなどの影響を受けて、製品での磁気特性にバラつきが生じやすいといった不利があった。
On the other hand, as a technique for causing secondary recrystallization without including an inhibitor component in the slab, Patent Document 5 discloses a technique (inhibitorless method) capable of performing secondary recrystallization without containing an inhibitor component. ing.
Here, the inhibitorless method is a technique in which secondary recrystallization is manifested by texture (control of texture) using higher-purity steel. However, the inhibitorless method does not require high-temperature slab heating and enables production of grain-oriented electrical steel sheets at a low cost. As a result, there is a disadvantage that the magnetic characteristics of the product are likely to vary.
また、集合組織の制御は、磁気特性に対して重要な要素であるため、集合組織制御を行う温間圧延などには、多くの条件が提案されている。こうした集合組織制御が十分に行なえない場合は、インヒビターを用いる技術に比べると、二次再結晶後のゴス方位({110}<001>)への集積度が低く、磁束密度も低くなる傾向になる。 In addition, since texture control is an important factor for magnetic properties, many conditions have been proposed for warm rolling and the like in which texture control is performed. If this texture control cannot be performed sufficiently, the degree of integration in the Goss orientation ({110} <001>) after secondary recrystallization will be lower and the magnetic flux density will tend to be lower than in the technique using inhibitors. Become.
上述したとおり、これまで提案されてきた方向性電磁鋼板の製造方法では、良好な磁気特性を安定的に実現することが難しい場合が多かった。
これに対し、発明者らは、Alを100ppm未満に抑制したインヒビターレス成分に準じた成分を用いて、高温スラブ加熱を回避しつつ、窒素増量を適用することで、AlNではなく窒化珪素を析出させ、この窒化珪素を正常粒成長の抑制力として機能させることで、磁気特性のバラつきを大幅に低減し、工業的に安定して良好な特性を有する方向性電磁鋼板の製造方法に想到した。
As described above, it has often been difficult to stably achieve good magnetic properties in the method of manufacturing grain-oriented electrical steel sheets that has been proposed so far.
On the other hand, the inventors deposited silicon nitride instead of AlN by applying nitrogen augmentation while avoiding high-temperature slab heating using a component according to the inhibitorless component in which Al was suppressed to less than 100 ppm. Thus, by making this silicon nitride function as a suppressive force for normal grain growth, the inventors have come up with a method for producing grain-oriented electrical steel sheets that have significantly reduced variations in magnetic properties and have industrially stable and good properties.
しかしながら、上記方法は、追加インヒビターとして、窒化珪素を形成する目的で二次再結晶前の鋼板に窒素を加えることが必要になる一方、二次再結晶後には、この窒素は不要となる。従って、焼鈍終了までに鋼中から除去しなければならない窒素量が多くなることで、従来の方法では除去しきれない窒素が存在し、鉄損がかえって増加するという、新たな問題が露見した。 However, in the above method, as an additional inhibitor, it is necessary to add nitrogen to the steel sheet before the secondary recrystallization for the purpose of forming silicon nitride, but this nitrogen is unnecessary after the secondary recrystallization. Therefore, a new problem has been revealed that the amount of nitrogen that must be removed from the steel by the end of annealing increases, so that there is nitrogen that cannot be removed by the conventional method and the iron loss increases.
本発明は、上記の現状に鑑み開発されたもので、窒化珪素を形成する目的で二次再結晶前の鋼板に窒素を加える方向性電磁鋼板の製造方法であっても、効率的に窒素を除去し、工業的に安定して良好な磁気特性を有する方向性電磁鋼板の製造方法を提供することを目的とする。 The present invention has been developed in view of the above situation, and even in a method for producing a grain-oriented electrical steel sheet in which nitrogen is added to a steel sheet before secondary recrystallization for the purpose of forming silicon nitride, nitrogen is efficiently used. An object of the present invention is to provide a method for producing a grain-oriented electrical steel sheet having good magnetic properties which is removed and industrially stable.
鋼中から窒素を除去(純化)する方法としては、高温でフォルステライト被膜が形成する前に焼鈍雰囲気中へ窒素を放出する方法(気相放出)と、フォルステライト被膜形成後に窒化物として被膜中に窒素を固定する方法があることが知られている。 Nitrogen is removed (purified) from the steel by releasing nitrogen into the annealing atmosphere before the forsterite film is formed at high temperature (gas phase emission), and after forming the forsterite film in the film as a nitride. It is known that there is a method of fixing nitrogen.
本製造方法では、いわゆる窒素増量を行うため、純化が必要となる窒素量が多くなって被膜中に固定できる窒素量を超えてしまう。そのため、発明者らは、フォルステライト被膜の形成を遅くすることで窒素の気相放出を促し、窒素を純化する方法を鋭意研究した。その結果、被膜形成を遅くしつつ、気相放出後の被膜形成速度を上げること、すなわち低温での被膜形成反応を抑制しつつ、高温での被膜形成反応を促進することによって、窒素気相放出時間を確保すると共に、二次再結晶焼鈍後の被膜外観を良好に保つ方法を見出し、本発明を完成させた。 In this manufacturing method, since so-called nitrogen increase is performed, the amount of nitrogen that needs to be purified increases and exceeds the amount of nitrogen that can be fixed in the coating. Therefore, the inventors diligently studied a method for purifying nitrogen by promoting the vapor phase release of nitrogen by slowing the formation of the forsterite film. As a result, it is possible to increase the film formation rate after vapor phase release while slowing the film formation, that is, by suppressing the film formation reaction at low temperature and promoting the film formation reaction at high temperature, The present invention was completed by finding a method for maintaining a good coating appearance after secondary recrystallization annealing while securing time.
本発明の要旨構成は次のとおりである。
1.質量%で、C:0.08%以下、Si:2.0〜4.5%およびMn:0.5%以下を含有すると共に、S、SeおよびOをそれぞれ50質量ppm未満、sol.Alを100質量ppm未満に抑制し、さらにNを〔酸可溶性Al(sol.Al)質量ppm/26.98〕×14.00≦N≦80質量ppmの範囲に制御し、残部はFeおよび不可避的不純物の組成になる鋼スラブを、再加熱することなくあるいは再加熱後、熱間圧延を施して熱延板としたのち、焼鈍および圧延によって最終板厚の冷間圧延板とし、二次再結晶焼鈍前までに、800℃以下または800℃超30秒以下で、かつ窒素増量が50質量ppm以上1000質量ppm以下となる窒化処理を施した後、焼鈍分離剤を塗布し、二次再結晶焼鈍の昇温過程において300℃〜800℃間の滞留時間を5時間以上150時間以下とする一連の方向性電磁鋼板の製造において、
上記焼鈍分離剤として、MgOを50mass%以上含有し、該MgOのクエン酸活性度が60秒≦CAA30≦90秒で、かつ150秒≦CAA70≦250秒を満たすものを使用することを特徴とする方向性電磁鋼板の製造方法。
The gist of the present invention is as follows.
1. In addition to containing C: 0.08% or less, Si: 2.0 to 4.5%, and Mn: 0.5% or less, S, Se, and O are each suppressed to less than 50 ppm by mass, and sol.Al is suppressed to less than 100 ppm by mass. Further, N is controlled in the range of [acid-soluble Al (sol.Al) mass ppm / 26.98] × 14.00 ≦ N ≦ 80 mass ppm, and the remainder is reheated to a steel slab having a composition of Fe and inevitable impurities. Without re-heating or after re-heating, hot rolled to make a hot rolled sheet, then annealed and rolled to a cold rolled sheet with the final thickness, and before secondary recrystallization annealing , below 800 ° C or above 800 ° C After performing nitriding treatment for 30 seconds or less and increasing the nitrogen amount to 50 mass ppm or more and 1000 mass ppm or less, an annealing separator is applied, and during the temperature increase process of secondary recrystallization annealing, the temperature is increased between 300 ° C and 800 ° C. In the production of a series of grain-oriented electrical steel sheets with a residence time of 5 hours or more and 150 hours or less,
The annealing separator contains MgO in an amount of 50 mass% or more, and the MgO has a citric acid activity of 60 seconds ≦ CAA30 ≦ 90 seconds and 150 seconds ≦ CAA70 ≦ 250 seconds. A method for producing grain-oriented electrical steel sheets.
2.焼鈍分離剤として、さらにチタン酸化物をTiO2換算で、焼鈍分離剤100質量部に対し、5質量部以上20質量部以下含むことを特徴とする前記1に記載の方向性電磁鋼板の製造方法。 2. 2. The method for producing a grain-oriented electrical steel sheet according to 1 above, further comprising, as an annealing separator, titanium oxide in terms of TiO 2 in an amount of 5 parts by mass to 20 parts by mass with respect to 100 parts by mass of the annealing separator. .
3.さらに、前記鋼スラブが、質量%で、
Ni:0.005〜1.50%、
Sn:0.01〜0.50%、
Sb:0.005〜0.50%、
Cu:0.01〜0.50%、
Cr:0.01〜1.50%、
P:0.0050〜0.50%、
Mo:0.01〜0.50%および
Nb:0.0005〜0.0100%
のうちから選んだ1種または2種以上を含有することを特徴とする前記1または2に記載の方向性電磁鋼板の製造方法。
3. Furthermore, the said steel slab is mass%,
Ni: 0.005-1.50%,
Sn: 0.01 to 0.50%,
Sb: 0.005-0.50%,
Cu: 0.01 to 0.50%,
Cr: 0.01 to 1.50%,
P: 0.0050 to 0.50%,
Mo: 0.01-0.50% and
Nb: 0.0005-0.0100%
The method for producing a grain-oriented electrical steel sheet according to 1 or 2 above, comprising one or more selected from among the above.
4.前記1乃至3のいずれかに記載の方向性電磁鋼板の製造方法に用いる、クエン酸活性度が60秒≦CAA30≦90秒で、かつ150秒≦CAA70≦250秒を満たす焼鈍分離剤用MgO。 4). MgO for annealing separator used in the method for producing a grain-oriented electrical steel sheet according to any one of 1 to 3 above, wherein the citric acid activity satisfies 60 seconds ≦ CAA30 ≦ 90 seconds and 150 seconds ≦ CAA70 ≦ 250 seconds.
本発明によれば、高温スラブ加熱を施さずとも、磁気特性のバラつきが大幅に低減され、工業的に安定して良好な特性を有する方向性電磁鋼板を得ることができる。 According to the present invention, even if high temperature slab heating is not performed, the magnetic property variation is greatly reduced, and a grain-oriented electrical steel sheet having industrially stable and good characteristics can be obtained.
以下、本発明を具体的に説明する。
まず、本発明において、鋼スラブの成分組成の限定理由について説明する。なお、成分に関する「%」および「ppm」表示は特に断らない限り、それぞれ質量%および質量ppmを意味するものとする。
C:0.08%以下
Cは、一次再結晶集合組織を改善する上で有用な元素であるが、含有量が0.08%を超えると、かえって一次再結晶集合組織の劣化を招くので、本発明では0.08%以下に限定した。磁気特性の観点から望ましい添加量は、0.01〜0.06%の範囲である。なお、要求される磁気特性のレベルがさほど高くない場合には、一次再結晶焼鈍における脱炭を省略あるいは簡略化するために、Cを0.01%以下としてもよい。
Hereinafter, the present invention will be specifically described.
First, the reason for limiting the component composition of the steel slab in the present invention will be described. Unless otherwise specified, “%” and “ppm” in relation to ingredients mean mass% and mass ppm, respectively.
C: 0.08% or less C is an element useful for improving the primary recrystallization texture. However, if the content exceeds 0.08%, the primary recrystallization texture is deteriorated. % Or less. A desirable addition amount from the viewpoint of magnetic properties is in the range of 0.01 to 0.06%. If the required magnetic property level is not so high, C may be set to 0.01% or less in order to omit or simplify the decarburization in the primary recrystallization annealing.
Si:2.0〜4.5%
Siは、電気抵抗を高めることによって鉄損を改善する有用元素であるが、含有量が4.5%を超えると、冷間圧延性が著しく劣化するので、Siは4.5%以下に限定した。また本発明では、Siを窒化物形成元素として機能させる必要があるため、2.0%以上含有させることが重要である。なお、鉄損の観点からの望ましい添加量は、2.0〜4.5%の範囲である。
Si: 2.0-4.5%
Si is a useful element that improves iron loss by increasing electric resistance. However, if the content exceeds 4.5%, the cold rolling property deteriorates remarkably, so Si is limited to 4.5% or less. In the present invention, Si needs to function as a nitride-forming element, so it is important to contain 2.0% or more. In addition, the desirable addition amount from the viewpoint of iron loss is in the range of 2.0 to 4.5%.
Mn:0.5%以下
Mnは、製造時における熱間加工性を向上させる効果があるが、含有量が0.5%を超えた場合には、一次再結晶集合組織が悪化して磁気特性の劣化を招くので、Mnは0.5%以下に限定した。なお、Mnの下限値は特に定めないが、0.01%程度が好ましい。
Mn: 0.5% or less
Mn has the effect of improving hot workability during production, but if the content exceeds 0.5%, the primary recrystallized texture deteriorates and causes deterioration of magnetic properties, so Mn is 0.5 % Or less. The lower limit of Mn is not particularly defined, but is preferably about 0.01%.
S,SeおよびO:それぞれ50ppm未満
S,SeおよびO量がそれぞれ50ppm以上になると、所望の二次再結晶を得ることが困難となる。この理由は、粗大な酸化物や、スラブ加熱によって粗大化したMnS,MnSeが一次再結晶組織を不均一にするためである。従って、S,SeおよびOはいずれも、50ppm未満に抑制するものとした。
S, Se, and O: less than 50 ppm each When the amount of S, Se, and O is 50 ppm or more, it becomes difficult to obtain a desired secondary recrystallization. This is because coarse oxides and MnS and MnSe coarsened by slab heating make the primary recrystallized structure non-uniform. Accordingly, S, Se, and O are all suppressed to less than 50 ppm.
sol.Al:100ppm未満
Alは、表面に緻密な酸化膜を形成し、窒化の際にその窒化量の制御を困難にしたり、脱炭を阻害したりすることがあるため、Alはsol.Al量で100ppm未満に抑制した。但し、酸素親和力の高いAlは、製鋼で微量添加することによって鋼中の溶存酸素量を低減し、鋼板の特性劣化につながる酸化物系介在物の低減などを見込めるため、100ppm未満の範囲で添加することにより磁性劣化を抑制することができる。
sol.Al: less than 100ppm
Al forms a dense oxide film on the surface, which may make it difficult to control the amount of nitridation during nitridation or inhibit decarburization. Therefore, Al is suppressed to less than 100 ppm in terms of sol.Al. did. However, Al with high oxygen affinity can be added in a range of less than 100ppm because it can be added in a small amount in steelmaking to reduce the amount of dissolved oxygen in the steel and reduce oxide inclusions that lead to deterioration of the steel sheet properties. By doing so, magnetic deterioration can be suppressed.
N:(sol.Al/26.98)×14.00ppm≦N≦80ppm
本発明は、窒化後、鋼板組織に窒化珪素を析出させることが特徴であるため、含有するAl量に対して、AlNとして析出するN以上のNを事前に含有させておくことが肝要である。すなわちAlNは、原子それぞれが1:1で結合しているため、(sol.Al)量×〔N原子量(14.00)/Al原子量(26.98)〕以上のNを含有させておくことで、鋼中に含まれる微量Alを窒化処理前に析出させておくことができる。一方で、スラブ加熱時の「フクレ」などの欠陥の原因となることもあるため、80ppm以下に抑制する必要がある。また望ましくは60ppm以下である。
N: (sol.Al/26.98)×14.00 ppm ≦ N ≦ 80 ppm
Since the present invention is characterized by precipitating silicon nitride in the steel sheet structure after nitriding, it is important to previously contain N equal to or more than N that precipitates as AlN with respect to the amount of Al contained. . That is, since each atom of AlN is bonded at a ratio of 1: 1, it is possible to add N in the amount of (sol.Al) × [N atomic weight (14.00) / Al atomic weight (26.98)] in the steel. A small amount of Al contained in can be deposited before nitriding. On the other hand, since it may cause defects such as “swelling” at the time of slab heating, it must be suppressed to 80 ppm or less. Further, it is desirably 60 ppm or less.
以上、必須成分について説明したが、本発明では、工業的により安定して磁気特性を改善する成分として、以下の元素を適宜含有させることができる。なお、残部は、Feおよび不可避的不純物である。
Ni:0.005〜1.5%
Niは、熱延板組織の均一性を高めることにより、磁気特性を改善する働きがあって、そのためには0.005%以上含有させることが好ましいが、含有量が1.5%を超えると所望の二次再結晶を得ることが困難となり、磁気特性が劣化するので、Niは0.005〜1.5%の範囲で含有させることが望ましい。
The essential components have been described above. In the present invention, the following elements can be appropriately contained as components that improve the magnetic properties more stably industrially. The balance is Fe and inevitable impurities.
Ni: 0.005-1.5%
Ni works to improve the magnetic properties by increasing the uniformity of the hot-rolled sheet structure. For this purpose, it is preferable to contain 0.005% or more, but if the content exceeds 1.5%, the desired secondary Since it becomes difficult to obtain recrystallization and the magnetic properties deteriorate, it is desirable to contain Ni in the range of 0.005 to 1.5%.
Sn:0.01〜0.50%
Snは、二次再結晶焼鈍中の鋼板の窒化や酸化を抑制し、良好な結晶方位を有する結晶粒の二次再結晶を促進して磁気特性を向上させる有用元素であり、そのためには0.01%以上含有させることが好ましいが、0.50%を超えて含有されると冷間圧延性が劣化するので、Snは0.01〜0.50%の範囲で含有させることが望ましい。
Sn: 0.01-0.50%
Sn is a useful element that suppresses nitriding and oxidation of steel sheets during secondary recrystallization annealing and promotes secondary recrystallization of grains having good crystal orientation to improve magnetic properties. However, if it exceeds 0.50%, the cold rolling property deteriorates, so it is desirable to contain Sn in the range of 0.01 to 0.50%.
Sb:0.005〜0.50%
Sbは、二次再結晶焼鈍中の鋼板の窒化や酸化を抑制し、良好な結晶方位を有する結晶粒の二次再結晶を促進して磁気特性を効果的に向上させる有用元素であり、その目的のためには0.005%以上含有させることが好ましいが、0.50%を超えて含有されると冷間圧延性が劣化するので、Sbは0.005〜0.50%の範囲で含有させることが望ましい。
Sb: 0.005-0.50%
Sb is a useful element that effectively suppresses nitridation and oxidation of steel sheets during secondary recrystallization annealing, promotes secondary recrystallization of grains with good crystal orientation, and effectively improves magnetic properties. For the purpose, it is preferable to contain 0.005% or more, but if it exceeds 0.50%, the cold rolling property deteriorates, so Sb is preferably contained in the range of 0.005 to 0.50%.
Cu:0.01〜0.50%
Cuは、二次再結晶焼鈍中の鋼板の酸化を抑制し、良好な結晶方位を有する結晶粒の二次再結晶を促進して磁気特性を効果的に向上させる働きがあり、そのためには0.01%以上含有させることが好ましいが、0.50%を超えて含有されると熱間圧延性の劣化を招くので、Cuは0.01〜0.50%の範囲で含有させることが望ましい。
Cu: 0.01-0.50%
Cu suppresses oxidation of the steel sheet during secondary recrystallization annealing, promotes secondary recrystallization of grains having a good crystal orientation, and effectively improves magnetic properties. However, if it exceeds 0.50%, the hot rolling property is deteriorated, so it is desirable to contain Cu in the range of 0.01 to 0.50%.
Cr:0.01〜1.50%
Crは、フォルステライト被膜の形成を安定化させる働きがあり、そのためには0.01%以上含有させることが好ましいが、一方でその含有量が1.50%を超えると所望の二次再結晶を得ることが困難となり、磁気特性が劣化するので、Crは0.01〜1.50%の範囲で含有させることが望ましい。
Cr: 0.01 to 1.50%
Cr has a function of stabilizing the formation of the forsterite film, and for that purpose, it is preferable to contain 0.01% or more, but when the content exceeds 1.50%, a desired secondary recrystallization can be obtained. Since it becomes difficult and the magnetic properties deteriorate, it is desirable to contain Cr in the range of 0.01 to 1.50%.
P:0.0050〜0.50%
Pは、フォルステライト被膜の形成を安定化させる働きがあり、そのためには0.0050%以上含有させることが好ましいが、含有量が0.50%を超えると冷間圧延性が劣化するので、Pは0.0050〜0.50%の範囲で含有させることが望ましい。
P: 0.0050 ~ 0.50%
P has a function of stabilizing the formation of the forsterite film. For that purpose, P is preferably contained in an amount of 0.0050% or more. However, if the content exceeds 0.50%, the cold rolling property deteriorates, so P is 0.0050 to It is desirable to make it contain in 0.50% of range.
Nb:0.0005〜0.0100%、Mo:0.01〜0.50%
NbおよびMoは、スラブ加熱時の温度変化による割れの抑制等を介して、熱延後のヘゲを抑制する効果を有している。これらの元素は、少なくともどちらか一方を、上記下限値以上含有させなければヘゲ抑制の効果は小さく、一方、どちらかが上記上限を超えると、炭化物や窒化物を形成するなどして最終製品まで残留した際、鉄損劣化を引き起こすため、上述した範囲とすることが望ましい。
Nb: 0.0005-0.0100%, Mo: 0.01-0.50%
Nb and Mo have an effect of suppressing sag after hot rolling through suppression of cracking due to temperature change during slab heating. If these elements do not contain at least one of the above lower limit value or more, the effect of suppressing heges is small. On the other hand, if either of these elements exceeds the above upper limit, carbide or nitride is formed, and the final product. In order to cause deterioration of the iron loss when remaining up to, it is desirable to be in the above range.
次に、本発明の製造方法について説明する。
上記の好適成分組成範囲に調整した鋼スラブを、再加熱することなくあるいは再加熱したのち、熱間圧延に供する。なお、スラブを再加熱する場合には、再加熱温度は、1000℃以上1300℃以下程度とすることが望ましい。というのは、1300℃を超えるスラブ加熱は、スラブの段階で鋼中にインヒビターをほとんど含まない本発明にとって無意味であり、コストアップの要因となるだけである。一方、1000℃未満のスラブ加熱では、熱間圧延時の圧延荷重が高くなって、圧延することが困難になるからである。
Next, the manufacturing method of this invention is demonstrated.
The steel slab adjusted to the above preferable component composition range is subjected to hot rolling without being reheated or after being reheated. When the slab is reheated, the reheating temperature is preferably about 1000 ° C. or higher and 1300 ° C. or lower. This is because slab heating above 1300 ° C is meaningless for the present invention, which contains almost no inhibitor in the steel at the slab stage, and only increases costs. On the other hand, when the slab is heated at a temperature lower than 1000 ° C., the rolling load at the time of hot rolling becomes high and it becomes difficult to perform rolling.
ついで、熱延板に、焼鈍および圧延を施すことによって最終板厚の冷間圧延板とする。具体的には、必要に応じて熱延板焼鈍を施したのち、1回の冷間圧延あるいは中間焼鈍を挟む2回以上の冷間圧延を施して、最終冷延板とする。この冷間圧延は、常温で行ってもよいし、常温より高い温度たとえば250℃程度に鋼板温度を上げて圧延する温間圧延としてもよい。 Next, the hot-rolled sheet is annealed and rolled to obtain a cold-rolled sheet having a final thickness. Specifically, after performing hot-rolled sheet annealing as necessary, it is subjected to one or more cold rollings or two or more cold rollings sandwiching intermediate annealing to obtain a final cold-rolled sheet. This cold rolling may be performed at normal temperature, or may be warm rolling in which the steel sheet temperature is raised to a temperature higher than normal temperature, for example, about 250 ° C.
引続き、最終冷間圧延板に一次再結晶焼鈍を施す。この一次再結晶焼鈍の目的は、圧延組織を有する冷間圧延板を一次再結晶させて、二次再結晶に最適な一次再結晶粒径に調整することである。そのためには、一次再結晶焼鈍の焼鈍温度を800℃以上950℃未満程度とすることが望ましい。なお、この時の焼鈍雰囲気を、湿水素窒素あるいは湿水素アルゴン雰囲気とし、脱炭焼鈍を兼ねても良い。 Subsequently, primary recrystallization annealing is applied to the final cold rolled sheet. The purpose of this primary recrystallization annealing is to adjust the primary recrystallization grain size optimal for secondary recrystallization by primary recrystallization of a cold rolled sheet having a rolled structure. For that purpose, it is desirable to set the annealing temperature of the primary recrystallization annealing to about 800 ° C. or more and less than 950 ° C. Note that the annealing atmosphere at this time may be wet hydrogen nitrogen or wet hydrogen argon atmosphere, and may also serve as decarburization annealing.
本発明における窒素増量のための窒化処理は、冷間圧延後から一次再結晶焼鈍後に焼鈍分離剤を塗布する前、の間で施す。窒化の手法は、増量する窒化量を制御できれば、特に限定しないが、過去に実施されている、例えば、コイル形態のままNH3雰囲気ガスを用いてガス窒化を行う手法や、走行するストリップに対して連続的に窒化を行う手法を採ることができる。また、ガス窒化に比べて窒化能の高い塩浴窒化を利用することも好ましい。 The nitriding treatment for increasing the amount of nitrogen in the present invention is performed after the cold rolling and before the application of the annealing separator after the primary recrystallization annealing. The nitriding method is not particularly limited as long as the amount of nitriding to be increased can be controlled. For example, the nitriding method has been implemented in the past, for example, a method of performing gas nitriding using NH 3 atmosphere gas in a coil form, Thus, it is possible to adopt a method of continuously nitriding. It is also preferable to use salt bath nitriding, which has a higher nitriding ability than gas nitriding.
上記窒化処理の際、重要な点は表層に窒化物層を形成することである。特に、鋼中への拡散を抑制するために800℃以下の温度で窒化を行なうことが望ましいが、時間を短時間(例えば30秒程度)とすることで、高温であっても表面へ窒化物層を形成させることが可能となる。また、窒化による窒素増量は50ppm以上1000ppm以下とするのが肝要である。なお、当該窒素濃度は、たとえ鋼板の一部に濃化していたとしても、鋼板の厚み方向の平均に均した値である。
窒素増量が50ppm未満では、その効果は十分に得られず、一方、1000ppmを超えると窒化珪素の析出量が過多となって二次再結晶が生じないからである。望ましくは200ppm以上1000ppm以下である。
In the nitriding process, an important point is to form a nitride layer on the surface layer. In particular, it is desirable to perform nitriding at a temperature of 800 ° C. or lower in order to suppress diffusion into the steel, but by reducing the time to a short time (for example, about 30 seconds), the nitride is applied to the surface even at high temperatures. A layer can be formed. In addition, it is important that the nitrogen increase by nitriding is 50 ppm or more and 1000 ppm or less. Note that the nitrogen concentration is a value averaged to the average in the thickness direction of the steel plate even if it is concentrated in a part of the steel plate.
This is because if the nitrogen increase is less than 50 ppm, the effect cannot be obtained sufficiently, while if it exceeds 1000 ppm, the amount of silicon nitride deposited becomes excessive and secondary recrystallization does not occur. Desirably, it is 200 ppm or more and 1000 ppm or less.
窒化処理後、鋼板表面には、焼鈍分離剤を塗布するが、その焼鈍分離剤は、二次再結晶焼鈍後の鋼板表面にフォルステライト被膜を形成するために、焼鈍分離剤中の50質量%以上をMgOとする。また、本発明では、さらにチタン酸化物をTiO2換算で、焼鈍分離剤100質量部に対し、5質量部以上20質量部以下含むことができる。チタン酸化物をかかる含有量に制御することで、被膜外観が向上したり、被膜の密着性が向上したりするという利点があるからである。 After the nitriding treatment, an annealing separator is applied to the surface of the steel sheet. The annealing separator is 50% by mass in the annealing separator to form a forsterite film on the steel sheet surface after the secondary recrystallization annealing. The above is MgO. In the present invention, titanium oxide can be further contained in an amount of 5 parts by mass or more and 20 parts by mass or less in terms of TiO 2 with respect to 100 parts by mass of the annealing separator. This is because by controlling the titanium oxide to such a content, there is an advantage that the appearance of the coating is improved or the adhesion of the coating is improved.
さらに、本発明では、二次再結晶後に不要となった窒素を気相に純化するために、フォルステライト被膜の低温反応性を抑制する必要があり、そのためには、MgOのクエン酸活性度は、60秒≦CAA30≦90秒とする必要がある。また、窒素純化後のフォルステライト被膜の反応性を促進するためには、MgOのクエン酸活性度が、150秒≦CAA70≦250秒に調整される必要がある。
そして、かかるMgOを用いることで、以下に示すように、窒素の純化と良好な被膜外観を、効果的に両立させることができる。
Furthermore, in the present invention, it is necessary to suppress the low-temperature reactivity of the forsterite coating in order to purify nitrogen that has become unnecessary after the secondary recrystallization into the gas phase, and for this purpose, the citric acid activity of MgO is 60 seconds ≦ CAA30 ≦ 90 seconds. In order to promote the reactivity of the forsterite film after nitrogen purification, the citric acid activity of MgO needs to be adjusted to 150 seconds ≦ CAA70 ≦ 250 seconds.
By using such MgO, it is possible to effectively achieve both nitrogen purification and good coating appearance as described below.
ここで、クエン酸活性度CAA30とは、0.4Nのクエン酸と30%のMgOが30℃で反応するまでの時間のことで、CAA70は、同じく0.4Nのクエン酸と70%のMgOが30℃で反応するまでに時間のことをいう。クエン酸活性度によるMgO反応性を規定することは特段珍しいことではなく、例えば、特許3650525号公報には、CAA70%が250〜1000秒で、CAA70%/CAA40%の値が1.5〜6.0で、さらに粒径20%値が1.2μm以下、BET値が20.5〜35であるマグネシアが提案されている。
また、特公昭57−45472号公報にはCaO、SO3およびB等の不純物濃度や比表面積、粒径、クエン酸活性度の分布を所定の範囲に収めることによって良好な被膜を形成する技術が提案されている。
しかしながら、窒素を増量して窒化珪素を利用した本発明の方向性電磁鋼板の製造に適するMgOについては、なんら示唆されるものがなく、加えて、公知の技術を用いたMgOでは、窒素の純化と良好な被膜外観を両立させることができないことが確認された。
Here, citric acid activity CAA30 is the time required for 0.4N citric acid and 30% MgO to react at 30 ° C. CAA70 is also 0.4N citric acid and 70% MgO 30 Time to react at ℃. It is not particularly unusual to define MgO reactivity by citric acid activity. For example, in Patent 3650525, CAA 70% is 250 to 1000 seconds, CAA 70% / CAA 40% is 1.5 to 6.0, Further, magnesia having a particle size 20% value of 1.2 μm or less and a BET value of 20.5 to 35 has been proposed.
Japanese Examined Patent Publication No. 57-45472 discloses a technique for forming a good film by keeping the concentration of impurities such as CaO, SO 3 and B, the specific surface area, the particle diameter, and the distribution of citric acid activity within a predetermined range. Proposed.
However, there is no suggestion about MgO suitable for the production of the grain-oriented electrical steel sheet of the present invention using silicon nitride by increasing the amount of nitrogen. In addition, MgO using a known technique does not purify nitrogen. It was confirmed that a good film appearance could not be achieved.
そこで、本発明では、低温反応性、すなわち高活性成分の指標としてCAA30を用いたのである。すなわち、CAA20では、評価する活性度が高すぎるために、窒素の純化に最適な値を得ることができない。また、従来から多く採用されているCAA40では、活性度が低すぎて、たとえ後述のCAA70を制御したとしても、良好な被膜が得られるための最適な値を安定して得ることができない。そこで、本発明では、CAA30を規定することとした。 Therefore, in the present invention, CAA30 is used as an index of low-temperature reactivity, that is, a highly active ingredient. That is, in CAA20, since the activity to be evaluated is too high, an optimal value for purifying nitrogen cannot be obtained. In addition, the CAA 40 that has been widely used in the past has too low activity, and even if the CAA 70 described later is controlled, the optimum value for obtaining a good coating cannot be stably obtained. Therefore, in the present invention, CAA30 is defined.
一方、CAA30の1点評価は、窒素の純化に最適な値の範囲を得ることができるものの、やはり良好な被膜を安定して得ることができなかった。そこで、高温反応性に係る指標、すなわちMgOの低活性成分の指標としてCAA70を併せて制御することにより、良好な被膜を安定的に得ることに成功した。なお、CAA80、CAA90などでは評価する反応性が低すぎるためいずれの値を調整しても良好な被膜を得ることができない。 On the other hand, one-point evaluation of CAA30 was able to obtain a range of values optimal for nitrogen purification, but still could not stably obtain a good film. Therefore, by controlling CAA70 as an index related to high temperature reactivity, that is, an index of a low active ingredient of MgO, it has succeeded in stably obtaining a good film. In addition, since the reactivity evaluated by CAA80, CAA90, etc. is too low, a favorable film cannot be obtained even if any value is adjusted.
ここで、本発明に用いるMgOの製造方法の一例を示す。
出発原料としては、主に苦汁(主成分MgCl2)や、海水などが挙げられる。この出発原料と石灰乳(Ca(OH)2)を反応させてMg(OH)2を得る。得られたMg(OH)2をロータリーキルンやマッフル炉を用い、700℃から1000℃程度の温度で焼成することで、各種活性度を持ったMgOを製造することができる。この際、低温かつ短時間、例えば700℃、30minで焼成することによってCAA値が小さい(すなわち活性度が高い)MgOを得ることができる。一方、高温かつ長時間、例えば1000℃、1hで焼成することによってCAA値が大きい(すなわち活性度が低い)MgOを得ることができる。
Here, an example of the manufacturing method of MgO used for this invention is shown.
Starting materials include mainly bitter juice (main component MgCl 2 ) and seawater. This starting material is reacted with lime milk (Ca (OH) 2 ) to obtain Mg (OH) 2 . MgO having various activities can be produced by firing the obtained Mg (OH) 2 at a temperature of about 700 ° C. to 1000 ° C. using a rotary kiln or a muffle furnace. At this time, MgO having a small CAA value (that is, high activity) can be obtained by firing at a low temperature for a short time, for example, 700 ° C. for 30 minutes. On the other hand, MgO having a large CAA value (ie, low activity) can be obtained by baking at a high temperature for a long time, for example, 1000 ° C. for 1 hour.
また、MgOの純度を向上させる目的や製造のばらつきを抑えるなどの目的で、一度得られた上記MgOを、再度水と反応させてMg(OH)2の形に戻し(再水和)、再度ロータリーキルンやマッフル炉で焼成する方法もある。このようにして得られたMgOを、その製造ロットごとにCAA値を測定し、異なるCAA値を持つロットを混合することで、本発明に適したMgOを容易に得ることができる。特に、マッフル炉で焼成したものは、焼きむらができやすいため、製造ロットによっては、他のロットと混合することなく本発明に適したMgOを得ることもできる。
その他、炭酸マグネシウムを焼成する方法や、MgCl2を直接焼成することでMgOを得る方法などがあるが、いずれの方法を用いたとしても、MgOのクエン酸活性度が60秒≦CAA30≦90秒で、かつ150秒≦CAA70≦250秒を満たす条件を選択することが肝要である。
In addition, for the purpose of improving the purity of MgO and suppressing the dispersion of production, the MgO obtained once is reacted with water again to return to the form of Mg (OH) 2 (rehydration), and again. There are also methods of firing in a rotary kiln or muffle furnace. MgO suitable for the present invention can be easily obtained by measuring the CAA value for each production lot and mixing lots having different CAA values. In particular, those fired in a muffle furnace are susceptible to uneven baking, and depending on the production lot, MgO suitable for the present invention can be obtained without mixing with other lots.
In addition, there are a method of baking magnesium carbonate, a method of obtaining MgO by directly baking MgCl 2 , etc. Even if any method is used, the citric acid activity of MgO is 60 seconds ≦ CAA 30 ≦ 90 seconds It is important to select a condition that satisfies 150 seconds ≦ CAA70 ≦ 250 seconds.
焼鈍分離剤塗布に引続き二次再結晶焼鈍を行なう。本発明における二次再結晶焼鈍では、300〜800℃間の滞留時間を5時間以上150時間以下とする必要がある。この間に表層の窒化物層は分解して、Nが鋼中へ拡散する。特に、AlNを形成することができるAlが残存しない本成分系では、粒界偏析元素であるNは、粒界を拡散経路として、鋼中へ拡散する。窒化珪素は、鋼とのmisfit率が大きいために、その析出速度は極めて遅い。ここで、窒化珪素の析出は、正常粒成長の抑制が目的であるため、正常粒成長が進行する800℃の段階では十分な量が粒界上に選択的に析出している必要がある。 Following the application of the annealing separator, secondary recrystallization annealing is performed. In the secondary recrystallization annealing in the present invention, the residence time between 300 and 800 ° C. needs to be 5 hours or more and 150 hours or less. During this time, the surface nitride layer decomposes and N diffuses into the steel. In particular, in this component system in which Al that can form AlN does not remain, N which is a grain boundary segregation element diffuses into steel using the grain boundary as a diffusion path. Since silicon nitride has a high misfit rate with steel, its precipitation rate is extremely slow. Here, since precipitation of silicon nitride is intended to suppress normal grain growth, a sufficient amount needs to be selectively deposited on the grain boundary at the stage of 800 ° C. where normal grain growth proceeds.
そして、当該温度領域の滞留時間を5時間以上とすることで、窒化珪素は、粒内で析出することはできないものの、粒界を拡散して来たNと結びつき、粒界上に選択的に析出させることができる。上限については必ずしも設ける必要はないが、150時間を超える焼鈍を行なっても焼鈍に要するエネルギーばかりが必要になるだけなので、150時間以下の時間で行なうこととする。また焼鈍雰囲気としては、N2、Ar、H2あるいはこれらの混合ガスのいずれもが適合する。 And by setting the residence time in the temperature region to 5 hours or more, silicon nitride cannot be precipitated in the grains, but is connected to N that has diffused through the grain boundaries, and selectively on the grain boundaries. It can be deposited. Although it is not always necessary to set an upper limit, even if annealing is performed for more than 150 hours, only the energy required for annealing is required. As the annealing atmosphere, any of N 2 , Ar, H 2 or a mixed gas thereof is suitable.
こうしたAl量が抑制され、AlN析出に対して過剰なNを有しつつ、他のMnS、MnSe等に代表されるインヒビター成分をほとんど含有しないスラブに対して、上述した本発明に従う工程を経て製造された方向性電磁鋼板では、二次再結晶焼鈍昇温過程および二次再結晶開始までの段階において、従来インヒビターに比べて粗大なサイズ(100nm以上)の窒化珪素を粒界に選択的に形成することができる。 Produced through the process according to the present invention described above for slabs in which the amount of Al is suppressed and slabs that contain excess N with respect to AlN precipitation and hardly contain other inhibitor components typified by MnS, MnSe, etc. In the oriented grain-oriented electrical steel sheet, silicon nitride of coarser size (100 nm or more) is selectively formed at grain boundaries compared to conventional inhibitors in the secondary recrystallization annealing temperature raising process and the stage until the start of secondary recrystallization. can do.
図1は、脱炭焼鈍を行なった後、100ppmおよび500ppmの窒化増量が得られるよう窒化処理を行ない300℃〜800℃の滞留時間が8時間となる昇温速度で800℃まで昇温した後、直ちに水冷し、その組織を電子顕微鏡により観察、同定したものである。同図から明らかなように、従来利用されてきた微細析出物(<100nm)とは異なり、最小のものであっても100nmを超える粗大な窒化珪素が粒界上に析出している様子が確認される。 1 shows that after decarburization annealing, nitriding treatment is performed so that nitriding increase of 100 ppm and 500 ppm can be obtained, and the temperature is raised to 800 ° C. at a heating rate of 300 ° C. to 800 ° C. for a residence time of 8 hours. Immediately cooled with water, the structure was observed and identified with an electron microscope. As is clear from the figure, it is confirmed that coarse silicon nitride exceeding 100 nm is precipitated on the grain boundaries even if it is the smallest, unlike the fine precipitates (<100 nm) used conventionally. Is done.
製造上、窒化珪素の析出には、二次再結晶昇温過程を利用するのがエネルギー効率の観点から、最も有効であることは明白であるが、同様のヒートサイクルを利用すれば窒化珪素の粒界選択析出は可能であるため、長時間の二次再結晶焼鈍の前に、窒化珪素分散焼鈍として、別途の熱処理を実施することも可能である。 From the viewpoint of energy efficiency, it is clear that the secondary recrystallization heating process is most effective for precipitation of silicon nitride in terms of production. However, if a similar heat cycle is used, Since grain boundary selective precipitation is possible, a separate heat treatment can be performed as silicon nitride dispersion annealing before the long-time secondary recrystallization annealing.
上記の二次再結晶焼鈍後、鋼板表面に、さらに絶縁被膜を塗布、焼き付けることもできる。かかる絶縁被膜の種類については、特に限定されず、従来公知のあらゆる絶縁被膜が適合する。例えば、特開昭50−79442号公報や特開昭48−39338号公報に記載されているリン酸塩−クロム酸塩−コロイダルシリカを含有する塗布液を鋼板に塗布し、800℃程度で焼付ける方法が好適である。
また、平坦化焼鈍により、鋼板の形状を整えることも可能であり、さらにこの平坦化焼鈍を、絶縁被膜の焼付け処理と兼ねることもできる。
After the secondary recrystallization annealing, an insulating film can be further applied and baked on the steel sheet surface. The type of the insulating coating is not particularly limited, and any conventionally known insulating coating is suitable. For example, a coating solution containing phosphate-chromate-colloidal silica described in JP-A-50-79442 and JP-A-48-39338 is applied to a steel plate and baked at about 800 ° C. The attaching method is suitable.
Further, the shape of the steel sheet can be adjusted by flattening annealing, and this flattening annealing can also be combined with the baking treatment of the insulating film.
(実施例1)
質量%で、Si:3.3%、C:0.06%、Mn:0.08%、S:0.001%、Al:0.002%、N:0.002%、Cu:0.05%およびSb:0.01%を含有する珪素鋼板スラブを、1100℃、30分加熱後、熱間圧延して2.2mmの板厚の熱延板とし、1000℃、1分間の焼鈍を施した後、冷間圧延により0.23mmの最終板厚とし、得られた冷間圧延コイルの中央部から、100mm×400mmサイズの試料を採取し、ラボにて一次再結晶焼鈍と脱炭および窒化(連続窒化処理)を兼ねた焼鈍をおこなった。窒化処理はH2-NH3混合ガスによるガス窒化処理を750℃、20秒行った。窒素量は、全厚を対象としたもので300ppm、表層(両面)各3μmをサンドペーパーで削り、表層を除いた状態で25ppmであった。引き続き95%MgO、5%TiO2の割合で混合した焼鈍分離剤を、水スラリ状にしてから塗布、乾燥した。この際、MgOとして表1に記載のCAA値に調整したものを用いた。MgOは水酸化マグネシウムを焼成することで作成し、その焼成温度を変更したMgOを混合することによって調整した。この鋼板に対し、300℃から800℃間を100時間かけて昇温させた後、1200℃まで50℃/hで昇温させ、1200℃で5時間焼鈍する最終仕上げ焼鈍を行った。
続いてリン酸塩系の絶縁張力コーティングの塗布焼付け、磁化力800A/mでの磁束密度(B8,T)、1.7T、50Hz励磁での鉄損(W17/50,W/kg)を測定し、被膜外観、被膜剥離後の地鉄窒素量を評価した。なお、被膜外観は、目視による被膜被覆率が99%以上で、かつ外観の色調が均一のものを良好とした。
測定および評価結果を表1に併記する。
Example 1
A silicon steel plate slab containing, in mass%, Si: 3.3%, C: 0.06%, Mn: 0.08%, S: 0.001%, Al: 0.002%, N: 0.002%, Cu: 0.05% and Sb: 0.01% After heating at 1100 ° C for 30 minutes, hot rolled to a hot rolled sheet with a thickness of 2.2 mm, after annealing at 1000 ° C for 1 minute, it was cold rolled to a final thickness of 0.23 mm, A sample having a size of 100 mm × 400 mm was taken from the center of the obtained cold rolled coil and subjected to primary recrystallization annealing, decarburization and nitriding (continuous nitriding treatment) in a laboratory. Nitriding treatment was performed by gas nitriding treatment with H 2 —NH 3 mixed gas at 750 ° C. for 20 seconds. The amount of nitrogen was 300 ppm for the total thickness, and 25 ppm when the surface layer (both sides) was 3 μm each shaved with sandpaper and the surface layer was removed. Subsequently, an annealing separator mixed at a ratio of 95% MgO and 5% TiO 2 was applied to a water slurry, and then applied and dried. At this time, MgO adjusted to the CAA value described in Table 1 was used. MgO was prepared by firing magnesium hydroxide and adjusted by mixing MgO whose firing temperature was changed. The steel sheet was heated from 300 ° C. to 800 ° C. over 100 hours, then heated to 1200 ° C. at 50 ° C./h and subjected to final finish annealing at 1200 ° C. for 5 hours.
Subsequently applying baking of the insulating tension coating Phosphate, magnetic flux density at a magnetizing force 800A / m (B 8, T ), 1.7T, iron loss at 50Hz excited (W 17/50, W / kg) Measurements were made to evaluate the appearance of the film and the amount of nitrogen in the base metal after the film was peeled off. The appearance of the film was determined to be good when the film coverage by visual observation was 99% or more and the color tone of the appearance was uniform.
The measurement and evaluation results are also shown in Table 1.
同表に記載のとおり、本発明に従う発明例では、被膜特性、窒素純化が良好である。 As described in the table, in the invention examples according to the present invention, the film properties and nitrogen purification are good.
(実施例2)
表2に示す成分を含有する珪素鋼板スラブを、1200℃で20分の加熱後、熱間圧延して2.0mmの板厚の熱延板とし、1000℃、1分の焼鈍を施した後、冷間圧延により板厚:1.5mmまでの冷間圧延後、1100℃、2分の中間焼鈍を施し、以下に示す冷間圧延により0.27mmの最終板厚としてから、PH2O/PH2=0.3の雰囲気下、焼鈍温度:820℃となる条件で2分間保持し脱炭焼鈍を行なった。その後、一部コイルに対してバッチ処理で窒化処理(NH3雰囲気下)を行ない、鋼中N量を550ppm増量させた後、表2に記載されたCAAを持つMgOを主成分とし、TiO2を10%添加した焼鈍分離剤を水と混ぜてスラリ状としたものを塗布して後、コイルに巻き取り、300〜800℃の間の滞留時間が30時間となる昇温速度で最終仕上げ焼鈍を行い、続いてリン酸塩系の絶縁張力コーティングの塗布焼付けと鋼帯の平坦化を目的とする平坦化焼鈍を施して製品とした。
かようにして得られた製品コイルからエプスタイン試験片を採取して、磁束密度(B8)を測定した結果および、被膜外観、被膜剥離後の地鉄窒素量を評価した。
測定および評価結果を表2に併記する。
(Example 2)
After heating the silicon steel plate slab containing the components shown in Table 2 at 1200 ° C. for 20 minutes, hot rolling to a hot-rolled sheet having a thickness of 2.0 mm, annealing at 1000 ° C. for 1 minute, Thickness by cold rolling: Cold rolling to 1.5mm, intermediate annealing at 1100 ° C for 2 minutes, and final rolling thickness of 0.27mm by cold rolling shown below, PH 2 O / PH 2 = In an atmosphere of 0.3, decarburization annealing was performed by maintaining the annealing temperature at 820 ° C. for 2 minutes. Thereafter, nitriding treatment (under NH 3 atmosphere) is performed on some coils by batch treatment to increase the amount of N in the steel by 550 ppm, and then MgO having CAA listed in Table 2 is the main component, and TiO 2 After applying a slurry of 10% annealing separator mixed with water, it is wound into a coil, and the final finish annealing is performed at a temperature increase rate of 30 hours between 300 and 800 ° C. Subsequently, the product was subjected to flattening annealing for the purpose of applying and baking a phosphate-based insulating tension coating and flattening the steel strip.
The Epstein test piece was collected from the product coil thus obtained, the magnetic flux density (B 8 ) was measured, and the appearance of the coating and the amount of ground nitrogen after stripping were evaluated.
The measurement and evaluation results are also shown in Table 2.
同表に記載のとおり、本発明に従う発明例では高磁束密度が得られ、かつ被膜外観、地鉄窒素純化が良好であることが分かる。 As shown in the table, it can be seen that in the inventive examples according to the present invention, a high magnetic flux density is obtained, and the appearance of the coating film and the purification of the ground iron nitrogen are good.
(実施例3)
質量%で、Si:3.3%、C:0.06%、Mn:0.08%、S:0.001%、Al:0.002%、N:0.002%、Cu:0.05%およびSb:0.01%を含有する珪素鋼板スラブを、1100℃、30分加熱後、熱間圧延して2.2mmの板厚の熱延板とし、1000℃、1分間の焼鈍を施した後、冷間圧延により0.23mmの最終板厚とし、得られた冷間圧延コイルの中央部から、100mm×400mmサイズの試料を採取し、ラボにて一次再結晶と脱炭を兼ねた焼鈍を行なった。一部試料については一次再結晶焼鈍と脱炭を兼ねた焼鈍をおこなった。その後、表3に示す条件で窒化処理(バッチ処理)をおこない、鋼中窒素量を増加させた。窒素は全厚を対象としたものと、表層(両面)各3μmをサンドペーパーで削り、表層を除いた試料を対象としたものと、それぞれを化学分析によって定量した。同一条件の鋼板は一条件につき21枚作製し、CAA30が70秒、CAA70が210秒のMgOを焼鈍分離剤として水スラリ状にしてから塗布乾燥し鋼板上に焼き付けた。うち20枚は表3に記載の条件で最終仕上げ焼鈍を行い、続いてリン酸塩系の絶縁張力コーティングの塗布焼付け、磁化力800A/mでの磁束密度(B8,T)や、1.7T、50Hz励磁での鉄損(W17/50,W/kg)を評価した。磁気特性は、各条件20枚の平均値でそれぞれ評価した。
測定および評価結果を表3に併記する。
(Example 3)
A silicon steel plate slab containing, in mass%, Si: 3.3%, C: 0.06%, Mn: 0.08%, S: 0.001%, Al: 0.002%, N: 0.002%, Cu: 0.05% and Sb: 0.01% After heating at 1100 ° C for 30 minutes, hot-rolled to a hot-rolled sheet with a thickness of 2.2 mm, annealed at 1000 ° C for 1 minute, and then cold-rolled to a final thickness of 0.23 mm. A sample with a size of 100 mm × 400 mm was taken from the center of the cold-rolled coil and annealed for both primary recrystallization and decarburization in a laboratory. Some samples were subjected to primary recrystallization annealing and decarburization annealing. Thereafter, nitriding treatment (batch treatment) was performed under the conditions shown in Table 3 to increase the amount of nitrogen in the steel. Nitrogen was quantified by chemical analysis for the total thickness and for the surface layer (both sides) 3 μm each with sandpaper and the sample excluding the surface layer. 21 steel plates with the same conditions were prepared for each condition, and MgO with CAA30 of 70 seconds and CAA70 of 210 seconds was formed into a water slurry using an annealing separator, and then applied, dried, and baked on the steel plate. Twenty of them were subjected to final finish annealing under the conditions shown in Table 3, followed by application and baking of a phosphate-based insulating tension coating, magnetic flux density (B 8 , T) at a magnetizing force of 800 A / m, 1.7 T The iron loss (W 17/50 , W / kg) at 50 Hz excitation was evaluated. The magnetic characteristics were evaluated by the average value of 20 sheets for each condition.
The measurement and evaluation results are also shown in Table 3.
同表に記載のとおり、本発明に従う発明例では、磁気特性、被膜特性とも良好な結果を示している。
As shown in the table, the inventive examples according to the present invention show good results in both magnetic properties and film properties.
Claims (4)
上記焼鈍分離剤として、MgOを50mass%以上含有し、該MgOのクエン酸活性度が60秒≦CAA30≦90秒で、かつ150秒≦CAA70≦250秒を満たすものを使用することを特徴とする方向性電磁鋼板の製造方法。 In addition to containing C: 0.08% or less, Si: 2.0 to 4.5%, and Mn: 0.5% or less, S, Se, and O are each suppressed to less than 50 ppm by mass, and sol.Al is suppressed to less than 100 ppm by mass. Further, N is controlled in the range of [acid-soluble Al (sol.Al) mass ppm / 26.98] × 14.00 ≦ N ≦ 80 mass ppm, and the remainder is reheated to a steel slab having a composition of Fe and inevitable impurities. Without re-heating or after re-heating, hot rolled to make a hot rolled sheet, then annealed and rolled to a cold rolled sheet with the final thickness, and before secondary recrystallization annealing , below 800 ° C or above 800 ° C After performing nitriding treatment for 30 seconds or less and increasing the nitrogen amount to 50 mass ppm or more and 1000 mass ppm or less, an annealing separator is applied, and during the temperature increase process of secondary recrystallization annealing, the temperature is increased between 300 ° C and 800 ° C. In the production of a series of grain-oriented electrical steel sheets with a residence time of 5 hours or more and 150 hours or less,
The annealing separator contains MgO in an amount of 50 mass% or more, and the MgO has a citric acid activity of 60 seconds ≦ CAA30 ≦ 90 seconds and 150 seconds ≦ CAA70 ≦ 250 seconds. A method for producing grain-oriented electrical steel sheets.
Ni:0.005〜1.50%、
Sn:0.01〜0.50%、
Sb:0.005〜0.50%、
Cu:0.01〜0.50%、
Cr:0.01〜1.50%、
P:0.0050〜0.50%、
Mo:0.01〜0.50%および
Nb:0.0005〜0.0100%
のうちから選んだ1種または2種以上を含有することを特徴とする請求項1または2に記載の方向性電磁鋼板の製造方法。 Furthermore, the said steel slab is mass%,
Ni: 0.005-1.50%,
Sn: 0.01 to 0.50%,
Sb: 0.005-0.50%,
Cu: 0.01 to 0.50%,
Cr: 0.01 to 1.50%,
P: 0.0050 to 0.50%,
Mo: 0.01-0.50% and
Nb: 0.0005-0.0100%
The method for producing a grain-oriented electrical steel sheet according to claim 1, comprising one or more selected from among the above.
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