JP4598702B2 - Manufacturing method of high Si content grain-oriented electrical steel sheet with excellent magnetic properties - Google Patents
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Description
本発明は、主にトランス等の鉄芯として使用される方向性電磁鋼板を製造する方法に関するものである。 The present invention relates to a method for producing a grain-oriented electrical steel sheet mainly used as an iron core such as a transformer.
方向性電磁鋼板の磁気特性は、鉄損、磁束密度及び磁歪である。鉄損は磁束密度が高い(Goss方位集積度が先鋭だ)と磁区制御技術(特許文献1、特許文献2、特許文献3等)により改善される。磁歪もまた、磁束密度が高いと小さく(良好に)なる。磁束密度が高いと変圧器の励磁電流を小さくできるのでサイズが小さく出来る。すなわち、製造する上で方向性電磁鋼板の最も基本な注目すべき磁気特性は、磁束密度であり、その向上がこの分野での大きな技術開発項目である。本発明の目的は、良好なグラス皮膜を形成させて、高Si含有の方向性電磁鋼板の磁束密度を従来より更に向上させることである。 The magnetic properties of grain-oriented electrical steel sheets are iron loss, magnetic flux density, and magnetostriction. The iron loss is improved by a magnetic domain control technique (Patent Document 1, Patent Document 2, Patent Document 3, etc.) when the magnetic flux density is high (the Goss orientation integration degree is sharp). Magnetostriction also decreases (good) when the magnetic flux density is high. If the magnetic flux density is high, the transformer excitation current can be reduced, so the size can be reduced. In other words, the most notable magnetic characteristic of grain-oriented electrical steel sheets in manufacturing is the magnetic flux density, and its improvement is a major technological development item in this field. An object of the present invention is to form a good glass film and further improve the magnetic flux density of a grain-oriented electrical steel sheet having a high Si content.
ところで、方向性電磁鋼板の製造方法は、二次再結晶を制御するために(一次再結晶)粒成長抑制剤(インヒビター)の造り込みにより完全固溶型と充分析出型に分類され、AlNを二次再結晶の主なインヒビターとする場合は、冶金的には熱間圧延でのスラブ加熱の考え方に加えてインヒビターの補強のための後工程窒化の有無により分類される。それを表1に示す。即ち、1)完全固溶非窒化型、2)充分析出窒化型、3)完全固溶窒化型、4)不完全固溶窒化型である。 By the way, in order to control the secondary recrystallization (primary recrystallization), the method of manufacturing grain-oriented electrical steel sheets is classified into a completely solid solution type and a sufficiently precipitated type by incorporating a grain growth inhibitor (inhibitor). When the main inhibitor for secondary recrystallization is used, it is classified metallurgically by the presence or absence of nitriding in the subsequent step for reinforcing the inhibitor in addition to the concept of slab heating in hot rolling. It is shown in Table 1. That is, 1) complete solid solution non-nitriding type, 2) sufficient precipitation nitriding type, 3) complete solid solution nitriding type, and 4) incomplete solid solution nitriding type.
本発明は、表1の2)の充分析出窒化型において最終冷間圧延前の熱間圧延鋼帯焼鈍は、二段サイクルと一段サイクルが提案されている。前者には、特許文献11、特許文献12、特許文献13等である。また、後者には、特許文献14がある。前者はニ段サイクルであるので本発明とは異なる。後者は、N含有量と冷却速度の関係を示している。本発明は、Al、N、TiのいわゆるフリーなAlと熱間圧延鋼帯焼鈍温度の関係を規定したものでありこれら特許文献に記載された発明とは全く異なるものである。 The present invention proposes a two-stage cycle and a one-stage cycle for hot-rolled steel strip annealing before the final cold rolling in the sufficient precipitation nitriding type of 2) in Table 1. The former includes Patent Document 11, Patent Document 12, Patent Document 13, and the like. Moreover, there exists patent document 14 in the latter. Since the former is a two-stage cycle, it differs from the present invention. The latter shows the relationship between the N content and the cooling rate. The present invention defines the relationship between the so-called free Al of Al, N, and Ti and the hot-rolled steel strip annealing temperature, and is completely different from the inventions described in these patent documents.
従来から、方向性電磁鋼板において、Si含有量を増やすとγ相率確保のためにC量を増やすことが通常行われてきた。これは、主に一次再結晶集合組織を劣化させないためで、Cを増やすことなくγ相率を確保しないと、一次再結晶集合組織が劣化し、二次再結晶のGoss方位集積度が低下する。低温スラブ加熱と窒化を必須とする製造法でもSi含有量を増やすとC含有量をも増やすことは行われていた。2)の製造方法は、スラブ加熱温度が低いためインヒビター物質は充分に析出しており、いわゆる一次インヒビターは完全固溶型に比べるとかなり弱く、脱炭焼鈍後の一次再結晶組織の粒径は完全固溶系より大きいし、その脱炭焼鈍温度依存性も大きい。 Conventionally, in a grain-oriented electrical steel sheet, when the Si content is increased, the C content is usually increased in order to secure the γ phase ratio. This is mainly because the primary recrystallization texture is not deteriorated. If the γ phase ratio is not secured without increasing C, the primary recrystallization texture is deteriorated and the Goss orientation accumulation degree of the secondary recrystallization is lowered. . Even in the manufacturing method in which low-temperature slab heating and nitriding are essential, increasing the Si content has also increased the C content. In the production method of 2), the inhibitor substance is sufficiently precipitated because the slab heating temperature is low. The so-called primary inhibitor is considerably weaker than the complete solid solution type, and the grain size of the primary recrystallized structure after decarburization annealing is It is larger than the complete solid solution system, and its decarburization annealing temperature dependency is also large.
一方、大量脱炭を強制的にさせると粒組織が極端な形になることは公知である。例えば、炭素鋼では、非特許文献1に、Si含有鋼では、非特許文献2に記載されている。これは、表層から脱炭されるのでその方向に粒成長する現象であり柱状晶的様相を示す。この原因は、粒成長を抑制しているのが、脱炭焼鈍温度では変化しない所謂インヒビター(粒成長抑制物質)でなく、炭素含有の変態相であるため、それが脱炭で消滅するとき脱炭が一方向に起こりその方向に原子の再配列が生じるためである。 On the other hand, it is known that when mass decarburization is forced, the grain structure becomes extreme. For example, non-patent document 1 describes carbon steel, and non-patent document 2 describes Si-containing steel. This is a phenomenon of grain growth in that direction because it is decarburized from the surface layer and shows a columnar crystal appearance. The reason for this is that the grain growth is not a so-called inhibitor (grain growth inhibitor) that does not change at the decarburization annealing temperature, but a carbon-containing transformation phase. This is because charcoal occurs in one direction and atomic rearrangement occurs in that direction.
2)の技術については、特にSi含有量を増やして炭素含有量を増やすと上述したことが顕著である。図1に、Si%:3.50%、C:0.070%の材料を、熱間圧延板焼鈍を従来の二段サイクルで行い、855℃で90秒の脱炭・一次再結晶焼鈍を行ったもので、組織は柱状晶的様相を示す。また、一次再結晶粒径の整粒性が極めて劣る結果が得られている。2)の充分固溶窒化型では、C含有量が極端に多くない場合も確率論的に程度の差異はあってもこの現象は多かれ少なかれ生じ、整粒性が劣ると推定される。磁束密度は、2)の製造技術の場合は、1)の完全固溶非窒化型と比べて劣るが、その理由の一つに一次インヒビター強度が弱いため、多かれ少なかれこの柱状晶的粒成長が生じ、結果として一次再結晶組織の整粒性が劣るためと推定している。 Regarding the technique of 2), the above-mentioned is remarkable especially when the Si content is increased and the carbon content is increased. Fig. 1 shows the material of Si%: 3.50%, C: 0.070%, hot-rolled sheet annealing is performed in a conventional two-stage cycle, and decarburization and primary recrystallization annealing at 855 ° C for 90 seconds. What was done, the structure shows a columnar appearance. Moreover, the result in which the primary recrystallized grain size is extremely inferior is obtained. In the case of the sufficiently solid solution nitriding type of 2), even if the C content is not extremely large, this phenomenon occurs more or less even if there is a difference in probability, and it is estimated that the grain sizeability is inferior. The magnetic flux density is inferior to the completely solid solution non-nitrided type of 1) in the case of the manufacturing technique of 2), but one of the reasons is that the strength of the primary inhibitor is weak, so that this columnar grain growth is more or less. As a result, it is presumed that the primary recrystallized structure is inferior in grain size.
そこで、本発明者らは、鋭意検討を重ね、2)の充分析出窒化型の製造法においてスラブ加熱温度を変更せずに、一次インヒビター強度を強化させる方法を見出し、柱状晶的粒成長を抑制し、一次再結晶組織の整粒性を確保し、Goss方位集積度を向上せしめることに成功した。特に、Si含有量が多い場合は、γ相率確保のためにC含有量を増やす必要があるので極めて有効である。 Therefore, the present inventors have made extensive studies and found a method for strengthening the primary inhibitor strength without changing the slab heating temperature in the production method of 2) sufficient precipitation nitriding type, thereby suppressing columnar grain growth. As a result, the grain size of the primary recrystallized structure was ensured and the Goss orientation accumulation degree was improved. In particular, when the Si content is large, it is necessary to increase the C content in order to secure the γ phase ratio, which is extremely effective.
本発明は、AlNを二次再結晶の主なインヒビターとし、スラブ加熱温度が低い充分析出窒化型2)の高Si含有の方向性電磁鋼板の製造において、熱間圧延鋼帯焼鈍条件を一段として一次再結晶粒径の整粒性を確保し、高磁束密度の方向性電磁鋼板を得る製造方法を提案するものである。本発明は以下の構成からなる。 The present invention uses AlN as a main inhibitor of secondary recrystallization, and in the production of a sufficiently precipitated nitriding type 2) high Si content grain-oriented electrical steel sheet having a low slab heating temperature, with the annealing conditions for hot rolled steel strip as one step. The present invention proposes a production method for securing grain sizeability of the primary recrystallized grain size and obtaining a grain-oriented electrical steel sheet having a high magnetic flux density. The present invention has the following configuration.
(1)質量%で、C:0.050〜0.080%、Si:3.2〜4.0%、酸可溶性Al:0.026〜0.035%、N:0.0060〜0.0095%、SとSeをSeq(S当量)=S+0.405Seとして Seq=0.005〜0.013%、Mn:0.06〜0.15%、Ti≦0.005%、残部がFe及び不可避的不純物からなる鋳片を1200℃以下の温度で加熱し、熱間圧延を施して熱間圧延鋼帯とし、この熱延鋼帯を焼鈍し、最終冷間圧延の圧延率を85%〜92%として冷間圧延し、次いで、一次再結晶・脱炭焼鈍温度を810℃〜880℃として一次再結晶・脱炭焼鈍し、一次再結晶粒の円相当の平均粒径(直径)を20μm以上26μm以下とし、ストリップ走行状態下で水素、窒素及びアンモニアの混合ガス中の全窒素含有量を0.015〜0.027質量%とする窒化処理を施し、その後MgOを主成分とする焼鈍分離剤を塗布して最終仕上げ焼鈍を施す方向性電磁鋼板の製造において、冷間圧延前の熱間圧延鋼帯焼鈍条件を、925℃以上1120℃未満の間の下記Tmax.℃およびTmin.℃の式で規定される特定の温度域で、90秒以上300秒以下で焼鈍し、磁束密度(B8(T))が1.88T超となることを特徴とする方向性電磁鋼板の製造方法。ここで温度の上限下限は次の式で与えられる。
Tmax.(上限値)(℃)=15/22×AlNR+1000
Tmin.(下限値)(℃)=15/22×AlNR+900
ここで、AlNR(ppm)=酸可溶性Al−27/14(N−14/48Ti)
(1) By mass%, C: 0.050-0.080%, Si: 3.2-4.0%, acid-soluble Al: 0.026-0.035%, N: 0.0060-0. 0095%, S and Se as Seq (S equivalent) = S + 0.405Se, Seq = 0.005 to 0.013%, Mn: 0.06 to 0.15%, Ti ≦ 0.005%, the balance being Fe and A slab made of inevitable impurities is heated at a temperature of 1200 ° C. or less, hot-rolled to form a hot-rolled steel strip, the hot-rolled steel strip is annealed, and the rolling rate of the final cold rolling is 85% to Cold-rolled to 92%, then primary recrystallization / decarburization annealing at a primary recrystallization / decarburization annealing temperature of 810 ° C. to 880 ° C., and the average particle diameter (diameter) equivalent to the circle of the primary recrystallized grains is 20 μm 26 μm or less, and all of the mixed gas of hydrogen, nitrogen and ammonia under the strip running condition In the manufacture of grain-oriented electrical steel sheets, which are subjected to nitriding treatment with an elemental content of 0.015 to 0.027% by mass, and then subjected to final finish annealing by applying an annealing separator mainly composed of MgO, cold rolling The annealing conditions for the previous hot-rolled steel strip were annealed for 90 seconds to 300 seconds in a specific temperature range defined by the following Tmax. ° C and Tmin. ° C equations between 925 ° C and less than 1120 ° C. magnetic flux density (B8 (T)) are provided methods for producing oriented electrical steel sheets towards you, characterized in that a 1.88T greater. Here, the upper and lower limits of the temperature are given by the following equations.
Tmax. (Upper limit value) (° C.) = 15/22 × AlNR + 1000
Tmin. (Lower limit value) (° C.) = 15/22 × AlNR + 900
Here, AlNR (ppm) = acid-soluble Al-27 / 14 (N-14 / 48Ti)
(2)熱間圧延鋼帯焼鈍後の冷却をTmax.とTmin.の間の温度域から900℃まで空冷し、その後900℃から550℃以下までの冷却速度を15℃/秒以上100℃/秒以下とすることを特徴とする(1)記載の方向性電磁鋼板の製造方法。 (2) Cooling after annealing the hot-rolled steel strip is air-cooled from the temperature range between Tmax. And Tmin. To 900 ° C, and then the cooling rate from 900 ° C to 550 ° C or less is 15 ° C / second or more and 100 ° C / second. characterized by a second or less (1) the method of producing oriented electrical steel sheet towards the description.
(3)前記鋳片の成分として、更に、質量%で、Sn、Sb、Pの少なくとも1種を0.02〜0.30含有することを特徴とする(1)または(2)に記載の方向性電磁鋼板の製造方法。 (3) as a component of the cast piece, further, in mass%, Sn, Sb, according to at least one of P, characterized in that it contains 0.02 to 0.30 (1) or (2) manufacturing method of a square oriented electrical steel sheet.
(4)更に、質量%で、Cuを0.05〜0.30%含有することを特徴とする(1)〜(3)のいずれか記載の方向性電磁鋼板の製造方法。 (4) Moreover, in mass%, the Cu characterized by containing from 0.05 to 0.30 percent (1) to (3) any method for producing oriented electrical steel sheet towards the description.
(5)更に、質量%で、Crを0.02〜0.30含有することを特徴とする(1)〜(4)のいずれか記載の方向性電磁鋼板の製造方法。 (5) Moreover, in mass%, Cr and characterized by containing 0.02 to 0.30 (1) to (4) any method for producing oriented electrical steel sheet towards the description.
(6)脱炭焼鈍板圧延方向断面の粒径に関して結晶粒の平均値とその標準偏差の比が0.55以下である整粒性が優れたことを特徴とする(1)〜(5)のいずれか記載の方向性電磁鋼板の製造方法。 (6) The grain size is excellent in that the ratio of the average value of the crystal grains and the standard deviation thereof is 0.55 or less with respect to the grain size in the rolling direction section of the decarburized and annealed plate (1) to (5) method for producing oriented electrical steel sheet towards any one of.
本発明において、充分析出窒化型の方向性電磁鋼板の製造において、熱間圧延板焼鈍条件を成分との関係で規定される温度で一段化することにより、一次インヒビター強度を強化し、一次再結晶粒径の整粒性を確保(標準偏差を極力小さく)してGoss方位集積度を向上させることが可能になった。 In the present invention, in the production of a sufficiently precipitation-nitrided grain-oriented electrical steel sheet, the primary inhibitor strength is enhanced by making the hot-rolled sheet annealing conditions one stage at the temperature defined by the relationship with the components, and the primary recrystallization. It has become possible to improve the Goss orientation accumulation degree by ensuring the grain size control (standard deviation as small as possible).
まず、本発明における鋳片の成分範囲の限定理由について述べる。なお、鋳片の成分は質量%である。 First, the reasons for limiting the component range of the slab in the present invention will be described. In addition, the component of a slab is the mass%.
Cは、Si含有量と対応しておりγ相率確保のためには0.050%以上必要である。これより少ないと、整粒性は良好になるものの一次再結晶集合組織が適切でなくなる。0.08%を超えると本発明の方法を用いても柱状晶的粒成長となり整粒性は極めて悪化する。 C corresponds to the Si content and needs to be 0.050% or more for securing the γ phase ratio. If the amount is less than this, the primary recrystallization texture is not suitable, although the grain size is improved. If it exceeds 0.08%, columnar grain growth occurs even if the method of the present invention is used, and the grain size is extremely deteriorated.
Siは、3.2%より少ないと鉄損の低減が充分でなく、3.2%より低いとγ相率確保のためのC含有量を増やす必要がなく柱状晶的組織形成は極めて少なく、平均粒径とその標準偏差の比は0.55より大きくならないので除く。4.0%を超えると冷延が極めて困難となり工業生産に適していない。 If Si is less than 3.2%, the reduction of iron loss is not sufficient, and if it is less than 3.2%, there is no need to increase the C content for securing the γ phase ratio, and the formation of columnar crystal structure is extremely small. The ratio of the average particle size to its standard deviation is excluded because it does not become larger than 0.55. If it exceeds 4.0%, cold rolling becomes extremely difficult and it is not suitable for industrial production.
酸可溶性AlはNと結合してAlNを形成し、インヒビターとして機能する。このAlNは、窒化前に形成されるものと窒化後高温焼鈍時に形成されるものがある。窒化前のものは、一次インヒビターと言いこれには、AlNの他に上述のMnS,MnSe,Cu-S等がある。一次インヒビター強度により一次再結晶粒径は決定される。二次インヒビターは窒化窒素により主に確保される。このために可溶性Alが0.026%未満では、二次インヒビター効果が小さくGoss集合組織の先鋭性が低下する。まら、0.035%を超えると二次再結晶不良になるし、グラス皮膜形成が劣化する。 Acid-soluble Al combines with N to form AlN and functions as an inhibitor. This AlN includes those formed before nitriding and those formed during high-temperature annealing after nitriding. Those before nitriding are called primary inhibitors, and include AlN, MnS, MnSe, Cu—S and the like described above. The primary recrystallized particle size is determined by the primary inhibitor strength. Secondary inhibitors are mainly secured by nitrogen nitride. For this reason, if soluble Al is less than 0.026%, the secondary inhibitor effect is small and the sharpness of the Goss texture decreases. In addition, if it exceeds 0.035%, secondary recrystallization is poor and glass film formation deteriorates.
Nは、0.0060%未満では一次インヒビター強度が確保されず二次再結晶が不安定になる。0.0095%を超えると一次インヒビター強度が強すぎてGoss方位集積度が劣化するし、膨れと呼ばれる窒素が起因の欠陥が生じる。 If N is less than 0.0060%, the strength of the primary inhibitor is not secured, and secondary recrystallization becomes unstable. If it exceeds 0.0095%, the primary inhibitor strength is too strong, the Goss orientation accumulation degree deteriorates, and a defect caused by nitrogen called blistering occurs.
SおよびSeは、Mnと結合するので基本的に少ない方が望ましいが、あまり少ないと一次インヒビター強度が極端に弱くなる。S当量(S+0.405Se)で0.005%が下限である。また、0.013%を超えると熱延時のスラブ加熱でのインヒビター物質の析出挙動の不均一性を増長させいわゆるスキッドマークが生じるので工業生産では避けなければならない。 Since S and Se are bonded to Mn, it is basically desirable that the amount of S and Se is small. However, if the amount is too small, the strength of the primary inhibitor becomes extremely weak. The lower limit is 0.005% in S equivalent (S + 0.405Se). On the other hand, if it exceeds 0.013%, the non-uniformity of the precipitation behavior of the inhibitor substance during slab heating during hot rolling is increased and so-called skid marks are generated, which must be avoided in industrial production.
Mnは、0.06%より少ない熱延鋼帯では割れが発生しやすく、歩留まりが低下し二次再結晶が安定しない。一方、0.15%を超えるとグラス皮膜が良好に形成されず実工業生産では安定生産に問題が生じる。 Mn tends to crack in a hot-rolled steel strip of less than 0.06%, yield decreases, and secondary recrystallization is not stable. On the other hand, if it exceeds 0.15%, the glass film is not formed well, and there is a problem in stable production in actual industrial production.
Tiについて、0.005%を超えて含有すると、NはTiNとなって実質的に低N含有鋼となり、インヒビター強度が確保されず二次再結晶不良が生じる。 When Ti is contained in excess of 0.005%, N becomes TiN and becomes a low N-containing steel substantially, and the inhibitor strength is not secured, resulting in secondary recrystallization failure.
また、Sn、Sb、Pは一次再結晶集合組織の改善に有効である。これらの元素の含有量が0.02%より少ないと改善効果が少なく、また、0.30%を超えると安定したフォルステライト皮膜(一次皮膜、グラス皮膜)形成が困難となる。さらに、Sn,Sb、Pは粒界偏析元素であり二次再結晶を安定化ならしめる効果があることは周知である。 Sn, Sb, and P are effective in improving the primary recrystallization texture. If the content of these elements is less than 0.02%, the improvement effect is small, and if it exceeds 0.30%, it becomes difficult to form a stable forsterite film (primary film, glass film). Furthermore, it is well known that Sn, Sb, and P are grain boundary segregation elements and have the effect of stabilizing secondary recrystallization.
Cuは、SとCu-Sを形成する。これは、固溶温度が低いので一次インヒビターとして有用であり、その強化に効果的である。このため、0.05〜0.30%の範囲で添加することが望ましい。0.3%を超えると上記効果が飽和するとともに、熱延時に「カッパーヘゲ」なる表面疵の原因になる。 Cu forms S and Cu-S. This is useful as a primary inhibitor because of its low solid solution temperature, and is effective in strengthening it. For this reason, it is desirable to add in the range of 0.05 to 0.30%. If it exceeds 0.3%, the above effect is saturated, and it causes surface flaws such as “copper lashes” during hot rolling.
また、Crはフォルステライト皮膜(一次皮膜、グラス皮膜)形成に有効で、0.02〜0.30%含むことが望まれる。0.03%未満では酸素が確保されにくく、0.30%を超えると皮膜が形成されない。 Further, Cr is effective for forming a forsterite film (primary film, glass film), and is desirably contained in an amount of 0.02 to 0.30%. If it is less than 0.03%, it is difficult to ensure oxygen, and if it exceeds 0.30%, no film is formed.
その他、Ni、Mo,Cdについては、添加することを妨げない。また電気炉溶製の場合は必然的に混入するものでもある。Niは一次、二次インヒビターとしての析出物の均一分散に著しい効果があるので、Niを添加すると磁気特性は更に良好且つ安定する。0.02%より少ないと効果が無く、0.3%を超えると、脱炭焼鈍後の酸素の富化し難くくになりフォルステライト皮膜形成が困難になる。Mo、Cdは硫化物もしくはセレン化物を形成しインヒビターの強化に資する。0.008%未満では効果が無く、0.3%を超えると析出物が粗大化してインヒビターの機能を得られず、磁気特性が安定しない。 In addition, Ni, Mo, and Cd are not prevented from being added. Moreover, in the case of electric furnace melting, it is inevitably mixed. Since Ni has a remarkable effect on the uniform dispersion of precipitates as primary and secondary inhibitors, the magnetic properties are further improved and stabilized when Ni is added. If it is less than 0.02%, there is no effect, and if it exceeds 0.3%, it becomes difficult to enrich oxygen after decarburization annealing and it becomes difficult to form a forsterite film. Mo and Cd form sulfides or selenides and contribute to strengthening of the inhibitor. If it is less than 0.008%, there is no effect, and if it exceeds 0.3%, precipitates are coarsened and the function of the inhibitor cannot be obtained, and the magnetic properties are not stable.
次に、本発明におけるその他製造工程条件の限定理由について述べる。
熱間圧延での鋳片(スラブ)の再加熱条件については、1200℃を超えるとインヒビター物質が局所的に固溶し不均一分不となるため、二次再結晶性が変動してスキッドマークが生じ工業生産できない。温度が低い方は特に規定しないが、実際の熱間圧延では1050℃が限界である。
Next, the reasons for limiting other manufacturing process conditions in the present invention will be described.
Regarding reheating conditions for slabs in hot rolling, if the temperature exceeds 1200 ° C, the inhibitor substance locally dissolves and becomes inhomogeneous, resulting in variations in secondary recrystallization and skid marks. Industrial production is not possible. The lower temperature is not particularly defined, but 1050 ° C. is the limit in actual hot rolling.
冷間圧延率は、85%未満ではGoss方位集積度が劣り、92%を超えるとGoss核が極端に減り二次再結晶が困難になる。 If the cold rolling rate is less than 85%, the Goss orientation accumulation degree is inferior, and if it exceeds 92%, Goss nuclei are extremely reduced and secondary recrystallization becomes difficult.
脱炭焼鈍完了後の一次再結晶粒の平均粒径が、20μm未満であるとGoss方位集積度が大きく劣化し、26μmを超えると二次再結晶が不安定になる。 If the average grain size of primary recrystallized grains after completion of decarburization annealing is less than 20 μm, the Goss orientation accumulation degree is greatly deteriorated, and if it exceeds 26 μm, secondary recrystallization becomes unstable.
窒化後の総窒素含有量は、0.015%未満であると二次再結晶が不安定になり、0.027%を超えると二次再結晶が過安定となりGoss方位集積度が劣化する。 If the total nitrogen content after nitriding is less than 0.015%, secondary recrystallization becomes unstable, and if it exceeds 0.027%, secondary recrystallization becomes overstable and the Goss orientation accumulation degree deteriorates.
本発明において最も重要な熱間圧延鋼帯の焼鈍条件について述べる。まず、本発明では、高磁束密度方向性電磁鋼板の製造を規定するものであるので最終冷間圧延前の熱処理は不可欠である。この処理で一次インヒビターの強度を制御して脱炭焼鈍時の柱状晶的組織の形成を防止するのである。このため、熱間圧延の焼鈍温度の上下限は、
AlNR(ppm)(有効酸可溶性Al=酸可溶性Al−27/14(N−14/48Ti)により、
Tmax.(上限値)(℃)=15/22×AlR+1000:(1120℃未満)
Tmin.(下限値)(℃)=15/22×AlR+900:(925℃以上)、
で規定する。この上限値より高いと一次再結晶粒径は20μmより小さくなり、Goss方位集積度は劣化する。また、下限値より低いと、一次再結晶粒径は26μmを超えニ次再結晶が不安定になる。焼鈍時間は、90秒より短いと析出処理が充分でなく、また組織が均一されないので二次再結晶が不安定になる。300秒を超えることは冶金的には問題はないが、生産性が低下するので避けることが望ましい。
The most important condition for annealing a hot-rolled steel strip in the present invention will be described. First, in the present invention, since the production of a high magnetic flux density grain-oriented electrical steel sheet is specified, the heat treatment before the final cold rolling is indispensable. This treatment controls the strength of the primary inhibitor to prevent the formation of a columnar crystal structure during decarburization annealing. For this reason, the upper and lower limits of the annealing temperature for hot rolling are:
AlNR (ppm) (effective acid-soluble Al = acid-soluble Al-27 / 14 (N-14 / 48Ti)
Tmax. (Upper limit value) (° C.) = 15/22 × AlR + 1000: (less than 1120 ° C.)
Tmin. (Lower limit value) (° C.) = 15/22 × AlR + 900: (925 ° C. or higher),
Stipulated in If it is higher than this upper limit value, the primary recrystallized grain size becomes smaller than 20 μm, and the Goss orientation integration degree deteriorates. On the other hand, if the value is lower than the lower limit, the primary recrystallization grain size exceeds 26 μm and the secondary recrystallization becomes unstable. If the annealing time is shorter than 90 seconds, the precipitation process is not sufficient, and the structure is not uniform, and secondary recrystallization becomes unstable. Exceeding 300 seconds is not a problem in terms of metallurgy, but it is preferable to avoid it because productivity decreases.
この場合は、所謂一段サイクルである。従来の二段サイクルでは、750〜900℃程度の保定がありここで析出させているので一次再結晶粒の整粒性は向上するものの、一次再結晶粒の成長性が良く一次再結晶焼鈍温度が810℃以下で26μmを容易に越える。更に一次再結晶焼鈍温度を下げることは粒径の観点からは可能であるが、良好なグラス皮膜形成と脱炭のためには温度下げることは避けねばならず、810℃〜880℃とすべきである。また、他の対策として、酸可溶性Al含有量を下げることが可能であり、一次再結晶粒の成長性は低下し26μm以下が得られ、二次再結晶性は改善されるものの磁気特性、特に磁束密度(B8(T))が1.88T以下となるので本発明には含まれない。本発明では、二段サイクルの保定を取らずに、一次インヒビター強度を確保して一次再結晶・脱炭焼鈍温度を810℃〜880℃として整粒性を確保する技術である。 In this case, it is a so-called one-stage cycle. In the conventional two-stage cycle, there is a holding of about 750 to 900 ° C., and precipitation is performed here, so that the primary recrystallized grains are improved in grain size, but the primary recrystallized grains have good growth properties and the primary recrystallization annealing temperature. Easily exceeds 26 μm at 810 ° C. or lower. Further, it is possible to lower the primary recrystallization annealing temperature from the viewpoint of particle size, but for good glass film formation and decarburization, the temperature should be avoided and should be 810 ° C to 880 ° C. It is. As another countermeasure, it is possible to reduce the content of acid-soluble Al. The primary recrystallized grain growth is reduced to 26 μm or less, and the secondary recrystallization is improved. Since the magnetic flux density (B8 (T)) is 1.88T or less, it is not included in the present invention. In the present invention, the primary inhibitor strength is secured without taking the two-stage cycle, and the primary recrystallization / decarburization annealing temperature is set to 810 ° C. to 880 ° C. to secure the grain size.
次に脱炭焼鈍板の整粒性について述べる。まず評価方法について述べる。この整粒性は、円相当の平均粒径を測定してその標準偏差を求める。測定方法は、圧延方向の断面とし、測定粒数は400粒以上が望ましい。この根拠は、400粒数未満ならば統計的誤差大きくなり信頼性が低下するためである。また、平均粒径が大きくなると当然、その標準偏差も大きくなるので、標準偏差を平均値で除した値を用いて整粒性を評価する普遍的なパラメーター(整粒性評価値)とする。この値が小さいほど整粒性が良好なのである。また、実際にはこの場合の粒径二次元的評価であり、実際の粒は3次元的に存在するのであるので、実際の平均粒径より小さくなる。 Next, the sizing properties of the decarburized annealing plate will be described. First, the evaluation method is described. The grain size is determined by measuring the average grain size equivalent to a circle and obtaining its standard deviation. The measuring method is a cross section in the rolling direction, and the number of measured grains is preferably 400 or more. The reason for this is that if the number is less than 400 grains, the statistical error increases and the reliability decreases. Moreover, since the standard deviation naturally increases as the average particle size increases, the value obtained by dividing the standard deviation by the average value is used as a universal parameter for evaluating the particle sizeability (particle size evaluation value). The smaller this value is, the better the particle size is. Moreover, in actuality, this is a two-dimensional evaluation of the particle diameter in this case, and since the actual grains exist three-dimensionally, they are smaller than the actual average particle diameter.
本発明者らは、この整粒性評価値が大きくなると磁気特性、特に磁束密度が低下することを見出した。これは、大きな粒は必ずしもGoss方位粒ではないものの、この粒が優先的に二次再結晶する確率が大きくなりGoss方位集積度が低下して磁束密度が低くなるためと考えられる。また極端な場合は、二次再結晶が均一には起こらず不良が生じる。この値が0.55を超えると磁束密度が低下しはじめ、0.60以上では二次再結晶が不良になることを見出した。この様に、0.55以下に確保するためには、本発明の所謂、一段均熱により一次インヒビターを強化することが効果的であることを見出した。 The inventors of the present invention have found that the magnetic properties, particularly the magnetic flux density, decrease as the particle size evaluation value increases. This is presumably because large grains are not necessarily Goss orientation grains, but the probability that these grains preferentially recrystallize secondarily increases, the Goss orientation integration degree decreases, and the magnetic flux density decreases. In extreme cases, secondary recrystallization does not occur uniformly and a defect occurs. It has been found that when this value exceeds 0.55, the magnetic flux density starts to decrease, and when it is 0.60 or more, secondary recrystallization becomes defective. Thus, in order to secure 0.55 or less, it has been found that it is effective to strengthen the primary inhibitor by the so-called one-step soaking of the present invention.
焼鈍後の焼鈍温度(≧925℃)から900℃までの冷却は、析出量を確保するためには空冷が望ましい。900℃から550℃までの冷却は、15℃/秒より遅いと炭化物が析出し一次再結晶集合組織が劣り、100℃/秒を超えると一次インヒビター物質が微細に析出するため一次インヒビター強度が強くなり過ぎ、その二次インヒビター効果が弱まり二次再結晶が不安定になる。下限温度の550℃は、これ以下の温度では、インヒビターの析出及び変態相の形態が変わらず効果がないためで工業生産での生産性・設備制約で規定される。 The cooling from the annealing temperature after annealing (≧ 925 ° C.) to 900 ° C. is preferably air cooling in order to secure the precipitation amount. When cooling from 900 ° C. to 550 ° C. is slower than 15 ° C./second, carbide precipitates and the primary recrystallization texture is inferior, and when it exceeds 100 ° C./second, the primary inhibitor substance precipitates finely, so the strength of the primary inhibitor is strong. As a result, the secondary inhibitor effect becomes weak and secondary recrystallization becomes unstable. The lower limit temperature of 550 ° C. is regulated by productivity and equipment restrictions in industrial production because the inhibitor precipitation and the transformation phase do not change and the effect is not effective at temperatures below this temperature.
既に述べたように、本発明は、2)の充分析出窒化型であり、脱炭焼鈍後二次再結晶開始前に鋼板に窒化処理を施すことは本発明では必須である。その方法は、高温焼鈍時の焼鈍分離剤に窒化物(CrN,MnN等)を混合させる方法と、脱炭焼鈍後にストリップを走行させた状態下でアンモニアを含んだ雰囲気で窒化させる方法がある。どちらの方法を採用しても良いが、後者の方が工業生産で現実的であり本発明では後者に限定する。この窒化時の温度は、一次再結晶粒をさらに成長させないために脱炭・一次再結晶焼鈍温度より低いことが求められる。 As already described, the present invention is of the sufficiently precipitated nitriding type of 2), and it is essential in the present invention that the steel sheet is subjected to nitriding treatment after decarburization annealing and before the start of secondary recrystallization. The method includes a method of mixing a nitride (CrN, MnN, etc.) with an annealing separator at the time of high-temperature annealing, and a method of nitriding in an atmosphere containing ammonia in a state where the strip is run after decarburization annealing. Either method may be adopted, but the latter is more practical in industrial production and is limited to the latter in the present invention. The temperature at the time of nitriding is required to be lower than the decarburization / primary recrystallization annealing temperature in order to prevent further growth of primary recrystallized grains.
鋳片(スラブ)を得るための鋳造は、従来の連続鋳造でよい。さらに鋳片の加熱を容易にするために分塊法を適用することは構わない。具体的には、公知の連続鋳造法により初期の厚みが150mmから300mmの範囲、好ましくは200mmから250mmの範囲の鋳片を製造する。この代わりに、鋳片は初期の厚みが約30mmから70mmの範囲のいわゆる薄鋳片であってもよい。これらの場合は、熱延鋼帯を製造する際、中間厚みに粗加工をする必要がないとの利点がある。また、鋼帯鋳造により鋳片又は鋼帯を事前に製造しておけば、一層薄い初期厚みの鋳片または鋼帯を用いて本発明方法により方向性電磁鋼板を製造することもできるが、均一析出状態を得るためには操業を精密に制御することが強く望まれる。 Casting for obtaining a slab (slab) may be conventional continuous casting. Furthermore, it is possible to apply the lump method in order to facilitate heating of the slab. Specifically, a slab having an initial thickness in the range of 150 mm to 300 mm, preferably in the range of 200 mm to 250 mm, is manufactured by a known continuous casting method. Alternatively, the slab may be a so-called thin slab with an initial thickness in the range of about 30 mm to 70 mm. In these cases, when manufacturing a hot-rolled steel strip, there is an advantage that it is not necessary to perform rough processing to an intermediate thickness. In addition, if a slab or steel strip is manufactured in advance by steel strip casting, a grain-oriented electrical steel sheet can be manufactured by the method of the present invention using a slab or steel strip having a thinner initial thickness. In order to obtain the precipitation state, it is strongly desired to precisely control the operation.
最終冷間圧延は常温で実施してもよいが、少なくとも1パスを100〜300℃の温度範囲に1分以上保つリバース圧延機での圧延では一次再結晶集合組織が改善され磁気特性が極めて良好になる。 The final cold rolling may be performed at room temperature, but the primary recrystallized texture is improved and the magnetic properties are extremely good in rolling with a reverse rolling mill that keeps at least one pass in the temperature range of 100 to 300 ° C. for 1 minute or longer. become.
脱炭燒鈍における室温から650〜850℃までの加熱速度を100℃/sec以上とすると、一次再結晶集合組織が改善され磁気特性が良好になる。加熱速度を確保するためには種々な方法が考えられる。即ち、抵抗加熱、誘導加熱、直接エネルギー付与加熱等がある。加熱速度を早くすると一次再結晶集合組織においてGoss方位が多くなり二次再結晶粒径が小さくなることは特許文献15等で公知でありこの方法の適用を妨げない。
When the heating rate from room temperature to 650 to 850 ° C. in decarburization annealing is set to 100 ° C./sec or more, the primary recrystallization texture is improved and the magnetic properties are improved. Various methods are conceivable for securing the heating rate. That is, there are resistance heating, induction heating, direct energy application heating, and the like. It is known in
その他の工程条件は、方向性電磁鋼板の製造において公知・既知である条件を適用する。即ち、湿気水素窒素混合ガス条件の810℃から880℃間で板厚により異なる時間で一次再結晶・脱炭焼鈍し、その後アンモニア含有雰囲気で連続的に窒化し、MgOを主成分とする焼鈍分離剤を鋼板表面に塗布し、箱型の炉で二次再結晶焼鈍を施す。その後、連続炉にて平坦化熱処理を行い、表面に絶縁皮膜を塗布して製造される。 Other process conditions are known and known in the production of grain-oriented electrical steel sheets. That is, primary recrystallization and decarburization annealing is performed at different times depending on the plate thickness between 810 ° C and 880 ° C under the condition of wet hydrogen-nitrogen mixed gas, and then nitriding continuously in an ammonia-containing atmosphere and annealing separation with MgO as the main component The agent is applied to the surface of the steel sheet and subjected to secondary recrystallization annealing in a box-type furnace. Thereafter, planarization heat treatment is performed in a continuous furnace, and an insulating film is applied to the surface to manufacture.
<実施例1>
表2に示す通常の方法で溶製した250mm厚の鋳片を1145℃〜1155℃で再加熱後2.6mm厚の熱間圧延鋼帯とした。この鋼帯を次の条件で熱処理した。表2に示す条件で熱間圧延板焼鈍後酸洗し、240℃3回の時効処理を含んでリバース冷間圧延で0.285mm厚とした。なお、熱延圧延板焼鈍後の900℃から550℃までの冷却は20℃/秒〜30℃/秒とした。その後、150秒の湿水素雰囲気で脱炭・一次再結晶焼鈍を行った。この材料を窒化後総窒素含有量が約0.021%Nとなるように窒化して、MgOを主成分とする焼鈍分離剤を表面に塗布し二次再結晶焼鈍を施した。その条件は、N2 :25%、H2 :75%の雰囲気として10〜20℃/時間で1200℃まで昇温した。その後、1200℃の温度で20時間以上、H2 :100%で純化処理を行った。その後、通常用いられる絶縁張力コーティングの塗布と平坦化処理を行った。表2に示す様に本発明を適用すれば磁気特性が優れる。
<Example 1>
A 250 mm thick slab melted by the usual method shown in Table 2 was reheated at 1145 ° C. to 1155 ° C. to obtain a 2.6 mm thick hot rolled steel strip. This steel strip was heat-treated under the following conditions. It was pickled after hot-rolled sheet annealing under the conditions shown in Table 2, and the thickness was 0.285 mm by reverse cold rolling, including an aging treatment at 240 ° C. three times. The cooling from 900 ° C. to 550 ° C. after the hot-rolled sheet annealing was performed at 20 ° C./second to 30 ° C./second. Thereafter, decarburization and primary recrystallization annealing were performed in a wet hydrogen atmosphere for 150 seconds. This material was nitrided so that the total nitrogen content was about 0.021% N after nitriding, and an annealing separator containing MgO as a main component was applied to the surface and subjected to secondary recrystallization annealing. The temperature was raised to 1200 ° C. at 10 to 20 ° C./hour in an atmosphere of N 2 : 25% and H 2 : 75%. Thereafter, a purification treatment was performed at a temperature of 1200 ° C. for 20 hours or more and H 2 : 100%. Thereafter, a generally used insulating tension coating was applied and planarized. As shown in Table 2, when the present invention is applied, the magnetic properties are excellent.
また、二段焼鈍で一次再結晶粒径が所定の範囲に入り磁束密度が良好なものがあるが、一次再結晶焼鈍温度が低くグラス皮膜形成が悪かった。 In addition, there are those in which the primary recrystallization grain size is in a predetermined range and the magnetic flux density is good in the two-stage annealing, but the primary recrystallization annealing temperature is low and the glass film formation is poor.
表3に示す通常の方法で溶製した250mm厚の鋳片を1145℃〜1150℃で再加熱後2.0mm厚の熱間圧延鋼帯とした。この鋼帯を次の条件で熱処理した。表3に示す条件で熱間圧延板焼鈍後に酸洗し、240℃で3回の時効処理を含んでリバース冷間圧延で0.22mm厚とした。なお、熱延圧延板焼鈍後の900℃から550℃までの冷却は20℃/秒〜30℃/秒とした。その後110秒の湿水素雰囲気で脱炭・一次再結晶焼鈍を行った。
A 250 mm thick slab melted by the usual method shown in Table 3 was reheated at 1145 ° C. to 1150 ° C. to obtain a 2.0 mm thick hot rolled steel strip. This steel strip was heat-treated under the following conditions. It pickled after hot-rolled sheet annealing on the conditions shown in Table 3, and it was 0.22 mm thickness by reverse cold rolling including aging treatment three times at 240 ° C. The cooling from 900 ° C. to 550 ° C. after the hot-rolled sheet annealing was performed at 20 ° C./second to 30 ° C./second. Thereafter, decarburization and primary recrystallization annealing were performed in a wet hydrogen atmosphere for 110 seconds.
この材料を窒化後総窒素含有量が約0.021%Nとなるように窒化して、MgOを主成分とする焼鈍分離剤を表面に塗布し二次再結晶焼鈍を施した。その条件は、N2 :25%、H2 :75%の雰囲気として10〜20℃/時間で1200℃まで昇温した。その後、1200℃の温度で20時間以上、H2 :100%で純化処理を行った。その後、通常用いられる絶縁張力コーティングの塗布と平坦化処理を行った。表3に示す様に本発明を適用すれば磁気特性が優れる。 This material was nitrided so that the total nitrogen content was about 0.021% N after nitriding, and an annealing separator containing MgO as a main component was applied to the surface and subjected to secondary recrystallization annealing. The temperature was raised to 1200 ° C. at 10 to 20 ° C./hour in an atmosphere of N 2 : 25% and H 2 : 75%. Thereafter, a purification treatment was performed at a temperature of 1200 ° C. for 20 hours or more and H 2 : 100%. Thereafter, a generally used insulating tension coating was applied and planarized. As shown in Table 3, when the present invention is applied, the magnetic properties are excellent.
また、二段焼鈍で一次再結晶粒径が所定の範囲に入り磁束密度が良好なものがあるが、一次再結晶焼鈍温度が低くグラス皮膜形成が悪かった。
<実施例3>
表4に示す通常の方法で溶製した250mm厚の鋳片を1140℃〜1150℃で再加熱後2.2mm厚の熱間圧延鋼帯とした。この鋼帯を次の条件で熱処理した。表4に示す条件で熱間圧延板焼鈍後酸洗し、200℃で3回の時効処理を含んで冷間圧延で0.285mm厚とした。なお、熱延圧延板焼鈍後の900℃から550℃までの冷却は20℃/秒〜30℃/秒とした。その後、150秒の湿水素雰囲気で脱炭・一次再結晶焼鈍を行った。この材料を約0.022%Nとなるように窒化して、MgOを主成分とする焼鈍分離剤を表面に塗布し二次再結晶焼鈍を施した。その条件は、N2 :25%、H2 :75%の雰囲気として10〜20℃/時間で1200℃まで昇温した。その後、1200℃の温度で20時間以上、H2 :100%で純化処理を行った。その後、通常用いられる絶縁張力コーティングの塗布と平坦化処理を行った。磁気特性を表4に示す。
<Example 3>
A 250 mm thick slab melted by the usual method shown in Table 4 was reheated at 1140 ° C. to 1150 ° C. to obtain a hot rolled steel strip having a thickness of 2.2 mm. This steel strip was heat-treated under the following conditions. It pickled after hot-rolled sheet annealing on the conditions shown in Table 4, and it was made into 0.285 mm thickness by cold rolling including the aging treatment 3 times at 200 degreeC. The cooling from 900 ° C. to 550 ° C. after the hot-rolled sheet annealing was performed at 20 ° C./second to 30 ° C./second. Thereafter, decarburization and primary recrystallization annealing were performed in a wet hydrogen atmosphere for 150 seconds. This material was nitrided to about 0.022% N, and an annealing separator mainly composed of MgO was applied to the surface to perform secondary recrystallization annealing. The temperature was raised to 1200 ° C. at 10 to 20 ° C./hour in an atmosphere of N 2 : 25% and H 2 : 75%. Thereafter, a purification treatment was performed at a temperature of 1200 ° C. for 20 hours or more and H 2 : 100%. Thereafter, a generally used insulating tension coating was applied and planarized. Table 4 shows the magnetic characteristics.
また、二段焼鈍で一次再結晶粒径が所定の範囲に入り磁束密度が良好なものがあるが、一次再結晶焼鈍温度が低く脱炭不良(C含有量が0.0040%以上)が生じると共にグラス皮膜形成が悪かった。
<実施例4>
実施例3で得られた熱間圧延材について、一段サイクルで1040℃で160秒間の焼鈍後の900℃〜550℃までの冷却速度を、i)大気中冷により10℃/秒,ii)ブロアーによる冷却により20℃/秒、iii)100℃沸騰水中への焼入れで30℃/秒、iv)0℃氷水中への焼入れで110℃/秒の条件で冷却した。その後、酸洗し、200℃で3回の時効処理を含んで冷間圧延で0.285mm厚とした。その後、840℃と850℃で150秒の湿水素雰囲気で脱炭・一次再結晶焼鈍を行った。この材料を約0.021%Nとなるように窒化して、MgOを主成分とする焼鈍分離剤を表面に塗布し二次再結晶焼鈍を施した。その条件は、N2 :25%、H2 :75%の雰囲気として10〜20℃/時間で1200℃まで昇温した。その後、1200℃の温度で20時間以上、H2 :100%で純化処理を行った。その後、通常用いられる絶縁張力コーティングの塗布と平坦化処理を行った。得られた磁気特性を表5に示す。
<Example 4>
About the hot-rolled material obtained in Example 3, the cooling rate from 900 ° C. to 550 ° C. after annealing at 1040 ° C. for 160 seconds in a single cycle, i) 10 ° C./second by air cooling, and ii) blower Cooling was carried out under the conditions of 20 ° C./second by cooling with iii) 30 ° C./second by quenching in 100 ° C. boiling water, and iv) 110 ° C./second by quenching in 0 ° C. ice water. Thereafter, pickling was performed, and the thickness was 0.285 mm by cold rolling including aging treatment at 200 ° C. three times. Thereafter, decarburization and primary recrystallization annealing were performed at 840 ° C. and 850 ° C. in a wet hydrogen atmosphere for 150 seconds. This material was nitrided to about 0.021% N, and an annealing separator mainly composed of MgO was applied to the surface to perform secondary recrystallization annealing. The temperature was raised to 1200 ° C. at 10 to 20 ° C./hour in an atmosphere of N 2 : 25% and H 2 : 75%. Thereafter, a purification treatment was performed at a temperature of 1200 ° C. for 20 hours or more and H 2 : 100%. Thereafter, a generally used insulating tension coating was applied and planarized. Table 5 shows the obtained magnetic properties.
熱間圧延板焼鈍後の冷却条件を10℃/秒の緩和冷却(表5の1,5)二次再結晶は良好なるも、磁気特性があまり優れない。また、100℃/秒を超える急冷(表5の4,5)二次再結晶が不安定なったりしている。本発明の範囲(表5の2,3,6,7)では良好な磁気特性が得られている。
<実施例5> <Example 5>
C:0.065%、Si:3.47%、Mn:0.99%、P:0.025%、S:0.0067%、Cr:0.15%、酸可溶性Al:0.0295%、N:0.0083%、Sn:0.06%、Ti:0.0017%、残部Feおよび不可避的不純物からなる溶鋼を鋳造し250mm厚の鋳片を得、この鋳片を1145℃〜1150℃で再加熱後2.0mm厚の熱間圧延鋼帯とした。この鋼帯を、i)二段サイクル:前段1120℃の後段900℃で750℃から水冷、一段サイクル、ii)970℃、iii)1050℃、iv)1120℃でそれぞれ180秒の焼鈍後900℃から水冷の熱間圧延鋼帯焼鈍を行い、酸洗後、3回の230℃保定の時効処理を含む冷間圧延で0.22mm厚とした。なお、熱間圧延鋼板焼鈍時の冷却速度は、i)25℃/秒、ii)、iii)、iv)は30℃〜35℃/秒であった。その後、810℃から870℃の範囲で15℃の間隔で、110秒の湿水素雰囲気で脱炭・一次再結晶焼鈍を行った。この材料を窒化後総窒素含有量が約0.021%Nとなるように窒化して、MgOを主成分とする焼鈍分離剤を表面に塗布し二次再結晶焼鈍を施した。その条件は、N2 :25%、H2 :75%の雰囲気として10〜20℃/時間で1200℃まで昇温した。その後、1200℃の温度で20時間以上、H2 :100%で純化処理を行った。その後、通常用いられる絶縁張力コーティングの塗布と平坦化処理を行った。この場合のTmax.:1099℃、Tmin.:999℃である。この場合の脱炭焼鈍後の平均粒径及び整粒性評価値並びに二次再結晶後の磁束密度を調査した結果を図2に示す。 C: 0.065%, Si: 3.47%, Mn: 0.99%, P: 0.025%, S: 0.0067%, Cr: 0.15%, acid-soluble Al: 0.0295% , N: 0.0083%, Sn: 0.06%, Ti: 0.0017%, the molten steel composed of the balance Fe and inevitable impurities is cast to obtain a 250 mm thick slab, and this slab is obtained at 1145 ° C to 1150 ° C. After reheating at ° C., a 2.0 mm thick hot rolled steel strip was obtained. The steel strip is subjected to i) two-stage cycle: front stage 1120 ° C. after 900 ° C. from 750 ° C. to water cooling, one-stage cycle, ii) 970 ° C., iii) 1050 ° C., iv) 1120 ° C. after annealing for 180 seconds, respectively From this, water-cooled hot-rolled steel strip annealing was performed, and after pickling, the thickness was 0.22 mm by cold rolling including aging treatment of 230 ° C. holding three times. In addition, the cooling rate at the time of hot-rolled steel sheet annealing was i) 25 ° C./second, ii), iii), and iv) were 30 ° C. to 35 ° C./second. Thereafter, decarburization and primary recrystallization annealing were performed in a wet hydrogen atmosphere for 110 seconds at intervals of 15 ° C. in the range of 810 ° C. to 870 ° C. This material was nitrided so that the total nitrogen content was about 0.021% N after nitriding, and an annealing separator containing MgO as a main component was applied to the surface and subjected to secondary recrystallization annealing. The temperature was raised to 1200 ° C. at 10 to 20 ° C./hour in an atmosphere of N 2 : 25% and H 2 : 75%. Thereafter, a purification treatment was performed at a temperature of 1200 ° C. for 20 hours or more and H 2 : 100%. Thereafter, a generally used insulating tension coating was applied and planarized. In this case, Tmax .: 1099 ° C. and Tmin .: 999 ° C. FIG. 2 shows the results of investigating the average particle size and grain size evaluation value after decarburization annealing and the magnetic flux density after secondary recrystallization in this case.
Claims (6)
ここで温度の上限、下限は次の式で与えられる。
Tmax.(上限値)(℃)=15/22×AlNR+1000 Tmin.(下限値)(℃)=15/22×AlNR+900 ここで、AlNR(ppm)=酸可溶性Al−27/14(N−14/48Ti) In mass%, C: 0.050 to 0.080%, Si: 3.2 to 4.0%, acid-soluble Al: 0.026 to 0.035%, N: 0.0060 to 0.0095%, Seq is Seq (S equivalent) = S + 0.405Se, Seq = 0.005 to 0.013%, Mn: 0.06 to 0.15%, Ti ≦ 0.005%, the balance being Fe and inevitable impurities The cast slab is heated at a temperature of 1200 ° C. or less, hot-rolled to obtain a hot-rolled steel strip, the hot-rolled steel strip is annealed, and the rolling rate of the final cold rolling is 85% to 92%. Cold-rolled, then primary recrystallization / decarburization annealing at a primary recrystallization / decarburization annealing temperature of 810 ° C. to 880 ° C., and the average particle diameter (diameter) corresponding to the circle of the primary recrystallized grains is 20 μm or more and 26 μm or less In a mixed gas of hydrogen, nitrogen and ammonia under strip running conditions. In the production of a grain-oriented electrical steel sheet that is subjected to nitriding treatment with an amount of 0.015 to 0.027% by mass, and then applied with an annealing separator mainly composed of MgO and subjected to final finish annealing, before cold rolling. Annealing is performed for 90 seconds to 300 seconds in a specific temperature range defined by the following Tmax. ° C. and Tmin. ° C. equations between 925 ° C. and less than 1120 ° C. (B8 (T)) are provided methods for producing oriented electrical steel sheets towards you, characterized in that a 1.88T greater.
Here, the upper limit and the lower limit of the temperature are given by the following equations.
Tmax. (Upper limit value) (° C.) = 15/22 × AlNR + 1000 Tmin. (Lower limit value) (° C.) = 15/22 × AlNR + 900 where AlNR (ppm) = acid-soluble Al-27 / 14 (N-14 / 48Ti)
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