TWI704237B

TWI704237B - Steel sheet and enameled product

Info

Publication number: TWI704237B
Application number: TW108117118A
Authority: TW
Inventors: 楠見和久; 福里哲次
Original assignee: 日商日本製鐵股份有限公司
Priority date: 2018-05-17
Filing date: 2019-05-17
Publication date: 2020-09-11
Also published as: TW201947043A; CN112119174A; JPWO2019221286A1; WO2019221286A1; CN112119174B; KR102504491B1; JP6683294B1; KR20210002639A

Abstract

This steel sheet include a predetermined chemical composition, wherein Ti > (N-0.0003) × 3.43, and C > 0.25 × Ti +0.129 × Nb +0.235 × V + 0.132 × Zr + 0.125 × Mo + 0.0652 × W + 0.0040 are satisfied, a microstructure includes, ferrite and one or two selected from cementite in crystal grains of the ferrite and either or both of cementite and pearlite in a crystal grain boundary of the ferrite, in the crystal grain of the ferrite, the cementite having a grain diameter is 0.3 to 1.5 μm, and in which a number density thereof is 1.00 × 10^-1 /μm² or less, is present, in the crystal grain boundary of the ferrite, either of both of cementite and pearlite having an average length of a major axis is 0.5 to 1.5 μm, and in which a number density thereof is 5.00 × 10^-4 /μm² to 1.00 × 10^-1 /μm² , is present, and a relationship between [N as BN], which is a N content included in BN, and a B content included in the steel satisfies [N as BN] / (1.27 × B) > 0.95.

Description

鋼板及琺瑯製品Steel plate and enamel products

發明領域本發明有關一種鋼板及琺瑯製品。本案係依據已於2018年5月17日於日本提申之日本特願2018-095190號主張優先權，並於此援引其內容。Invention field The invention relates to a steel plate and enamel products. This case is based on Japanese Special Application No. 2018-095190 that was filed in Japan on May 17, 2018, and its content is cited here.

發明背景琺瑯製品係在鋼板表面燒附有玻璃質之物。琺瑯製品具有耐熱性、耐候性、耐化學性及耐水性之機能，故以往係被廣泛利用來作為鍋具類、流理台等廚房用品及建材等的材料。如上述之琺瑯製品一般係透過將鋼板加工成預定形狀後，藉由熔接等來組裝成製品形狀，然後施以琺瑯處理(燒成處理)而製出。Background of the invention Enamel products are burnt with glass on the surface of the steel plate. Enamel products have the functions of heat resistance, weather resistance, chemical resistance, and water resistance, so they have been widely used in the past as materials for kitchen utensils such as pots and pans, countertops, and building materials. The enamel products mentioned above are generally manufactured by processing a steel plate into a predetermined shape, then assembling it into a product shape by welding or the like, and then applying an enamel treatment (firing treatment).

對於用來作為琺瑯製品的胚料之鋼板(琺瑯用鋼板)，作為其特性，係要求有抗燒成應變性、琺瑯處理後之抗鱗狀破面性、琺瑯密著性及琺瑯處理後之抗氣泡及黑點缺陷性等。除此之外，在琺瑯製品之製造中，通常會為了得到製品形狀而進行壓製加工，故對琺瑯用鋼板會要求良好的成形性。For steel plates used as blanks for enamel products (steel plates for enamel), as its characteristics, it is required to have resistance to firing strain, resistance to scaly fracture after enamel treatment, adhesion of enamel and after enamel treatment Anti-bubble and black spot defects etc. In addition, in the manufacture of enamel products, pressing is usually performed in order to obtain the shape of the product. Therefore, the steel plate for enamel is required to have good formability.

另，由於透過施行琺瑯處理可提升在含硫酸等的嚴苛腐蝕環境下之耐蝕性，故琺瑯製品在發電設備等的能源領域中，應用範圍亦逐漸擴大。在上述領域中，有著對於對歷年使用之疲勞等之可靠性的需求，並且以零件之輕量化為目的，也會要求所使用之鋼板的高強度化。對於上述之對疲勞等之可靠性，已知強度變化會帶來影響，該強度變化係因在將鋼板加工成製品形狀後再進行琺瑯處理為止的製造步驟中，鋼板組織形態的變化、亦即在鋼板內之組織形態的差異所造成。In addition, because the enamel treatment can improve the corrosion resistance in harsh corrosive environments containing sulfuric acid, etc., the application range of enamel products in the energy field of power generation equipment is gradually expanding. In the above-mentioned fields, there is a demand for the reliability of fatigue and other factors used over the years, and for the purpose of reducing the weight of parts, there is also a demand for higher strength of the steel plates used. Regarding the reliability of fatigue and the like mentioned above, it is known that the strength change will have an impact. The strength change is due to the change in the structure of the steel plate during the manufacturing steps until the steel plate is processed into the product shape and then subjected to the enamel treatment. Caused by the difference in the structure of the steel plate.

截至目前，關於琺瑯處理所伴隨的鋼板組織形態的變化，已有一種防止因結晶粒徑之粗大化所致之抗鱗狀破面性劣化的手法記載於例如專利文獻1中。專利文獻1中記載：以周知的高氧鋼為基底，將夾雜物的組成、大小、形狀、比率及個數最佳化，同時微量添加Ni、Cr、V及Mo，並且視需要添加Nb、B及Ti，並將鋼板的製造條件最佳化，藉此就算進行了重複的琺瑯處理時，仍能將抗鱗狀破面性降低的情形減緩。Up to now, regarding the change in the structure of the steel sheet accompanying the enamel treatment, there has been a method for preventing the deterioration of the scaly fracture resistance due to the coarsening of the crystal grain size, which is described in Patent Document 1, for example. Patent Document 1 describes that the composition, size, shape, ratio, and number of inclusions are optimized based on well-known high-oxygen steel, and Ni, Cr, V, and Mo are added in small amounts, and Nb, B and Ti, and optimize the manufacturing conditions of the steel plate, so that even if the enamel treatment is repeated, the deterioration of the scaly crack resistance can still be slowed down.

另，專利文獻2中記載：對於因高氧鋼之琺瑯處理中之晶粒成長所伴隨之強度降低，導致發生燒成中的撓變而尺寸精度劣化之課題，使琺瑯用鋼板之組織形態、亦即使肥粒鐵粒徑均一化來縮小粒度分布之作法係有效的。專利文獻2中，為了鋼板之製造步驟中之熱軋鋼板組織的微細化、及退火中之晶粒成長的均一化，添加了Ni及Cr。In addition, Patent Document 2 describes that the structure of the steel sheet for enamel has been improved with respect to the problem of deflection during firing and deterioration of dimensional accuracy due to the decrease in strength associated with the growth of crystal grains in the enamel treatment of high-oxygen steel. Even if the size of the fertilizer particles is uniformized to reduce the particle size distribution, it is effective. In Patent Document 2, Ni and Cr are added in order to refine the structure of the hot-rolled steel sheet in the manufacturing step of the steel sheet and to uniformize the grain growth during annealing.

此外，專利文獻3中，為了抑制高氧鋼之琺瑯處理中之軟化，而規定了氧化物之析出狀態。專利文獻3中，係使微細氧化物殘留下來，透過釘扎效果抑制琺瑯燒成步驟中之晶粒成長，並抑制軟化。In addition, in Patent Document 3, in order to suppress the softening in the enamel treatment of high-oxygen steel, the precipitation state of oxides is specified. In Patent Document 3, fine oxides are left, and the pinning effect suppresses the growth of crystal grains in the enamel firing step and suppresses softening.

就進行了伴有組織變化之琺瑯處理的琺瑯製品，專利文獻1與2可確保一定的特性。然而，若為專利文獻1與2，則必須添加Ni，以解決與琺瑯處理中之晶粒成長相關的課題。亦即，為了解決課題，必須添加高價的合金元素。另外，關於專利文獻2，係透過添加Cr使氧化物粗大化，以使其難以妨礙肥粒鐵晶粒成長，藉此提升肥粒鐵粒徑之均一性，抑制異常晶粒成長而抑制成為混粒。然而，若為未利用析出物或夾雜物之釘扎所行之抑制晶粒成長之此方法，當琺瑯處理中，構件中的溫度有所變動時，便會產生粒徑之不均一，也可能無法獲得所求效果。在此情況下，無法穩定獲得琺瑯處理後之強度。For enamel products that have undergone an enamel treatment with structural changes, Patent Documents 1 and 2 can ensure certain characteristics. However, in the case of Patent Documents 1 and 2, Ni must be added to solve the problems related to crystal grain growth in enamel processing. That is, in order to solve the problem, it is necessary to add expensive alloying elements. In addition, with regard to Patent Document 2, the oxide is coarsened by adding Cr to make it difficult to hinder the growth of ferrite grains, thereby enhancing the uniformity of ferrite grains, suppressing abnormal grain growth and suppressing mixing. grain. However, if the method of suppressing the growth of crystal grains without using the pinning of precipitates or inclusions, when the temperature in the component changes during the enamel treatment, uneven particle size will occur, or it may be Unable to obtain the desired effect. In this case, the strength after enamel treatment cannot be obtained stably.

另，有關專利文獻3，除含有高濃度的氧外，還控制製鋼步驟中之製造條件，藉此生成微細氧化物，利用該氧化物之釘扎力來抑制琺瑯燒成時的晶粒成長。吾等認為以上所述本身即為優異技術。根本而言，專利文獻3中將含氧量提高的理由係為了保證屬琺瑯用鋼板之重要特性之抗鱗狀破面性。In addition, in Patent Document 3, in addition to containing a high concentration of oxygen, the manufacturing conditions in the steel making step are controlled to generate fine oxides, and the pinning force of the oxides is used to suppress the growth of crystal grains during enamel firing. We believe that the above is an excellent technology in itself. Fundamentally, the reason for increasing the oxygen content in Patent Document 3 is to ensure the scaly fracture resistance, which is an important characteristic of steel sheets for enamels.

在提升抗鱗狀破面性的目的下使含氧量增加，以形成氫的陷阱位置之方法，另於專利文獻4、專利文獻5中亦有記載。然而，使含氧量增加的方法有時會發生脫屑等起因於氧化物的瑕疵，且有製鋼成本變高的問題。於是，期望開發一種除活用氧化物以外之可抑制晶粒成長而能確保抗鱗狀破面性之技術。For the purpose of improving the resistance to scaly cracking, a method of increasing the oxygen content to form a hydrogen trap site is also described in Patent Document 4 and Patent Document 5. However, the method of increasing the oxygen content may cause defects caused by oxides such as desquamation, and there is a problem that the steel production cost becomes high. Therefore, it is desired to develop a technology that can suppress the growth of crystal grains and ensure the resistance to scaly cracking in addition to the active oxide.

作為除活用氧化物以外之確保抗鱗狀破面性之技術，專利文獻4與專利文獻5中揭示了活用BN作為陷阱位置之方法，專利文獻6中則揭示了活用TiS作為氫的陷阱位置之方法。然而，使用TiS和BN的方法中會大量添加S、B及N等元素，故會生成大量析出物。在此情況下，除可認為延性會降低外，添加元素亦會招致製鋼成本增加。此外，活用BN時，使用高氧的成分的情況亦多，而留有使用高氧鋼時的問題。As a technique for ensuring the resistance to scaly fractures in addition to using oxides, Patent Document 4 and Patent Document 5 disclose a method of using BN as a trap site, and Patent Document 6 discloses using TiS as one of the trap sites for hydrogen. method. However, in the method using TiS and BN, elements such as S, B, and N are added in large amounts, so a large amount of precipitates are generated. In this case, in addition to the reduction in ductility, the addition of elements will also increase the cost of steel making. In addition, when using BN, there are many cases where high-oxygen components are used, and there remains a problem when using high-oxygen steel.

作為不使用高氧鋼亦不活用BN和TiS之可保證抗鱗狀破面性之技術，專利文獻7中記載了一種使用低碳鋁脫氧鋼，並藉由粗大MnS與施行脫碳退火而產生的點作為陷阱位置加以活用之技術。專利文獻7之技術中係採用低碳鋁脫氧鋼，故製鋼成本低，但因施行脫碳退火，而有變成高成本的問題。As a technology that can ensure the resistance to scaly cracking without using high-oxygen steel or using BN and TiS, Patent Document 7 describes the use of low-carbon aluminum deoxidized steel, which is produced by coarsening MnS and performing decarburization annealing. The point is used as a trap position. The technique of Patent Document 7 uses low-carbon aluminum deoxidized steel, so the steel production cost is low, but there is a problem of high cost due to decarburization annealing.

先前技術文獻專利文獻專利文獻1：日本特開2001-316760號公報專利文獻2：日本特開2000-063985號公報專利文獻3：日本專利第6115691號公報專利文獻4：日本特開平8-27522號公報專利文獻5：日本特開平7-242997號公報專利文獻6：日本特開平2-104640號公報專利文獻7：日本特開平6-192727號公報Prior art literature Patent literature Patent Document 1: Japanese Patent Application Publication No. 2001-316760 Patent Document 2: Japanese Patent Application Publication No. 2000-063985 Patent Document 3: Japanese Patent No. 6115691 Patent Document 4: Japanese Patent Application Laid-Open No. 8-27522 Patent Document 5: Japanese Patent Application Publication No. 7-242997 Patent Document 6: Japanese Patent Application Laid-Open No. 2-104640 Patent Document 7: Japanese Patent Laid-Open No. 6-192727

發明概要發明欲解決之課題本發明之課題在於發展前述鋼板之技術，以提供一種鋼板與琺瑯製品，該鋼板具優異成形性、琺瑯處理後之抗鱗狀破面性、琺瑯處理後之強度特性及琺瑯處理後之外觀(已抑制氣泡、黑點的生成)。Summary of the invention Problems to be solved by the invention The subject of the present invention is to develop the technology of the aforementioned steel plate to provide a steel plate and enamel product which has excellent formability, resistance to scaly fracture after enamel treatment, strength characteristics after enamel treatment, and appearance after enamel treatment ( The generation of bubbles and black spots has been suppressed).

用以解決課題之手段本發明係為解決上述課題而作成者，該發明之主旨如下。Means to solve the problem The present invention was made to solve the above-mentioned problems, and the gist of the invention is as follows.

[1]本發明一態樣之鋼板為以下鋼板：化學組成以質量%計含有C：0.0050~0.0700%、Si：0.0010~0.0500%、Mn：0.0500~1.0000%、P：0.0050~0.1000%、S：0.0010~0.0500%、Al：0.007~0.100%、O：0.0005~0.0100%、B：0.0003~0.0100%、N：0.0010~0.0100%、Ti：0~0.0100%、Nb、Zr、V、Mo及W中之1種或2種以上：合計0.0020~0.0300%、Cu：0~0.045%、Cr、Ni之1種或2種：合計0~1.000%、As、Se、Ta、Sn、Sb、Ca、Mg、Y及REM中之1種或2種以上：合計0~0.1000%，且剩餘部分由Fe及不純物所構成，並且滿足式(1)及式(2)；前述鋼板之金屬組織含有：肥粒鐵；位於前述肥粒鐵晶粒內之雪明碳鐵；以及，位於前述肥粒鐵晶界之雪明碳鐵及波來鐵之1種或2種；於前述肥粒鐵之前述晶粒內，粒徑0.3~1.5μm之雪明碳鐵係以個數密度為1.00×10^-1 個/μm² 以下之範圍存在；於前述肥粒鐵之前述晶界存在有雪明碳鐵及波來鐵之1種或2種，且其等之長徑之平均值為0.5~15μm、個數密度為5.00×10^-4 ~1.00×10^-1 個/μm² ；並且BN中含有之N含量即[N as BN]與鋼中含有之B含量之關係滿足式(3)。 Ti>(N-0.0003)×3.43 ・・・式(1) C>0.25×Ti+0.129×Nb+0.235×V+0.132×Zr+0.125×Mo+0.0652×W+0.0040 ・・・式(2) [N as BN]/(1.27×B)>0.95 ・・・式(3) 惟，式(1)~(3)中之元素符號表示該元素以質量%計之含量，式(3)中之[N as BN]則表示BN中含有之以質量%計之N含量。 [2]如上述[1]之鋼板中，以質量%計亦可含有Cu：0.010~0.045%。 [3]如上述[1]或[2]之鋼板中，以質量%計亦可含有合計0.005~1.000%之Cr、Ni之1種或2種。 [4]如上述[1]~[3]中任一項之鋼板中，亦可含有以下中之1種或2種以上元素且以質量%計含有合計0.0005~0.1000%：As、Se、Ta、Sn、Sb、Ca、Mg、Y及REM。 [5]如上述[1]~[4]中任一項之鋼板中，前述鋼板亦可為冷軋鋼板。 [6]如上述[1]~[5]中任一項之鋼板中，前述鋼板亦可為琺瑯用鋼板。 [7]本發明另一態樣之琺瑯製品具備如上述[1]~[4]中任一項之鋼板。[1] The steel sheet of one aspect of the present invention is the following steel sheet: the chemical composition contains C: 0.0050~0.0700%, Si: 0.0010~0.0500%, Mn: 0.0500~1.0000%, P: 0.0050~0.1000%, S : 0.0010~0.0500%, Al: 0.007~0.100%, O: 0.0005~0.0100%, B: 0.0003~0.0100%, N: 0.0010~0.0100%, Ti: 0~0.0100%, Nb, Zr, V, Mo and W One or more of two types: 0.0020~0.0300% in total, Cu: 0~0.045%, one or two of Cr, Ni: 0~1.000% in total, As, Se, Ta, Sn, Sb, Ca, One or more of Mg, Y and REM: 0~0.1000% in total, and the remainder is composed of Fe and impurities, and satisfies formula (1) and formula (2); the metal structure of the aforementioned steel plate contains: fertilizer Nitrate iron; Xueming carbon iron located in the aforementioned fertile iron grains; and, one or two types of Xueming carbon iron and bolly iron located at the aforementioned fertile iron grain boundaries; in the aforementioned crystals of the aforementioned fertile iron In the grains, Xueming carbon iron with a particle diameter of 0.3~1.5μm exists in the range of number density of 1.00×10 ^-1 pieces/μm ² or less; there are Xueming carbon iron and One or two kinds of Polly Iron, and the average long diameter of the same is 0.5~15μm, the number density is 5.00×10 ^-4 ~1.00×10 ^-1 pieces/μm ² ; and the N contained in BN The content, that is, the relationship between [N as BN] and the B content in the steel satisfies formula (3). Ti>(N-0.0003)×3.43 ・・・ Formula (1) C>0.25×Ti+0.129×Nb+0.235×V+0.132×Zr+0.125×Mo+0.0652×W+0.0040 ・・・ Formula (2) [N as BN]/(1.27×B)>0.95 ・・・Formula (3) However, the element symbols in formulas (1)~(3) indicate the content of the element in mass%, and in formula (3) [N as BN] means the N content in mass% contained in BN. [2] As in the steel sheet of [1] above, Cu may be contained in mass %: 0.010 to 0.045%. [3] The steel sheet described in [1] or [2] may also contain one or two of Cr and Ni in a total of 0.005 to 1.000% by mass%. [4] The steel sheet of any one of [1] to [3] above may also contain one or more of the following elements and the total content is 0.0005 to 0.1000% by mass: As, Se, Ta , Sn, Sb, Ca, Mg, Y and REM. [5] In the steel sheet according to any one of [1] to [4] above, the steel sheet may be a cold rolled steel sheet. [6] In the steel plate of any one of [1] to [5] above, the steel plate may be a steel plate for enamel. [7] An enamel product of another aspect of the present invention includes the steel plate of any one of [1] to [4] above.

發明效果本發明上述態樣之鋼板具優異成形性、琺瑯處理後之抗鱗狀破面性及琺瑯處理後之強度。並且還具優異琺瑯密著性及琺瑯處理後之外觀。因此，其適合作為琺瑯製品之基材之鋼板(琺瑯用鋼板)，該琺瑯製品係應用於廚房用品、建材及能源領域等。Invention effect The steel sheet of the above aspect of the present invention has excellent formability, scaly fracture resistance after enamel treatment, and strength after enamel treatment. It also has excellent enamel adhesion and appearance after enamel treatment. Therefore, it is suitable as a steel plate (steel plate for enamel) as the base material of enamel products, which are used in kitchenware, building materials, and energy fields.

用以實施發明之形態本實施形態之鋼板係為了克服以往鋼板之課題經反覆進行各種研討而得者，並且係根據針對鋼板之成形性、琺瑯處理後之抗鱗狀破面性及琺瑯處理後之強度特性，研討了化學組成與製造條件之影響而得之結果所得出之知識見解。亦即，係根據以下1)~4)之知識見解。The form used to implement the invention The steel plate of this embodiment is obtained through various studies to overcome the problems of the previous steel plate, and is based on the formability of the steel plate, the resistance to scaly fracture after enamel treatment, and the strength characteristics after enamel treatment. Knowledge and insights derived from the effects of chemical composition and manufacturing conditions. That is, it is based on the knowledge insights 1) to 4) below.

1)針對琺瑯處理後之強度，透過含有一定量以上的C來活用固溶C及鐵碳化物，藉此可抑制琺瑯處理時之晶粒成長，並抑制強度降低。尤其，對於施加有輕加工時之應變誘發晶粒成長，固溶C及鐵碳化物的影響大，故藉由活用固溶C及鐵碳化物，可抑制琺瑯處理後之強度降低。其機制雖尚不明確，但吾等認為係如下述。在琺瑯處理時，因碳化物之熔解而存在固溶C。當有固溶C存在時，可能會產生抑制晶界移動之效果、及於琺瑯處理時變態成沃斯田鐵，將肥粒鐵晶界釘扎而抑制晶粒成長之效果。另外，當亦殘留有鐵碳化物時，會有透過釘扎效果而抑制晶粒成長之效果。另外，藉由含有Nb、V、Zr、Mo及W之碳化物形成元素，可透過生成之碳化物的釘扎效果來抑制晶粒成長，並抑制強度降低。而，琺瑯處理後之強度降低情形小時，亦可抑制疲勞強度降低。1) Regarding the strength after enamel treatment, solid solution C and iron carbide are used by containing more than a certain amount of C, thereby suppressing the growth of crystal grains during enamel treatment and suppressing the decrease in strength. In particular, solid solution C and iron carbide have a great influence on strain-induced grain growth when light processing is applied. Therefore, by using solid solution C and iron carbide, the strength reduction after enamel treatment can be suppressed. Although the mechanism is not clear, we believe it is as follows. During enamel treatment, solid solution C exists due to the melting of carbides. When solid solution C is present, it may have the effect of inhibiting the movement of grain boundaries, and the effect of metamorphosing into austenitic iron during enamel processing, pinning the grain boundaries of fertilizer grains and inhibiting grain growth. In addition, when iron carbides still remain, there is an effect of suppressing grain growth through the pinning effect. In addition, by containing carbide forming elements of Nb, V, Zr, Mo, and W, the pinning effect of the generated carbides can suppress the growth of crystal grains and suppress the decrease in strength. However, if the strength decrease after enamel treatment is small, the fatigue strength decrease can also be suppressed.

2)又，藉由含有C，會生成雪明碳鐵及波來鐵。其等係作為氫的陷阱位置發揮作用，故即使將高氧鋼中的鐵系氧化物、TiS及BN之析出量限制在某個程度，仍可確保充分抗鱗狀破面性。具體而言，藉由控制雪明碳鐵之尺寸及個數，可獲得充分的抗鱗狀破面性。2) In addition, by containing C, Xueming Carbon Iron and Bora Iron are produced. These systems function as trap sites for hydrogen, so even if the precipitation amount of iron-based oxides, TiS, and BN in the high-oxygen steel is limited to a certain level, sufficient resistance to scaly cracking can be ensured. Specifically, by controlling the size and number of Xueming carbon iron, sufficient resistance to scaly cracking can be obtained.

3)上述析出物之中，BN作為氫的陷阱位置之機能高，因此若限制Ti含量，減低以TiN之形態析出之N量，以使BN殘留下來，抗鱗狀破面性便會提升。3) Among the above-mentioned precipitates, BN has a high function as a trap site for hydrogen. Therefore, if the Ti content is limited, the amount of N precipitated in the form of TiN is reduced so that BN remains, and the resistance to scaly cracking will be improved.

4)針對成形性，藉由適量含有屬會對鐵碳化物之形成造成影響的元素之C、屬固溶強化元素之Si、Mn及P、屬有助於析出強化的元素之Nb、Zr、V、Mo及W、以及會影響夾雜物之生成之O，便能透過抑制強度過度上升來確保延性。4) Regarding the formability, by appropriately including C, which is an element that affects the formation of iron carbides, Si, Mn, and P, which are solid solution strengthening elements, and Nb, Zr, and P, which are elements that contribute to precipitation strengthening. V, Mo, W, and O, which affect the formation of inclusions, can ensure ductility by suppressing excessive rise in strength.

以下，詳細說明本實施形態之鋼板。本實施形態之鋼板可適合用來作為琺瑯製品之基材。Hereinafter, the steel sheet of this embodiment will be described in detail. The steel plate of this embodiment can be suitably used as a base material for enamel products.

>化學成分> 本實施形態之鋼板，以質量%計含有C：0.0050~0.0700%、Si：0.0010~0.0500%、Mn：0.0500~1.0000%、P：0.0050~0.1000%、S：0.0010~0.0500%、Al：0.007~0.100%、O：0.0005~0.0100%、B：0.0003~0.0100%、N：0.0010~0.0100%、Ti：0~0.0100%、Nb、Zr、V、Mo及W中之1種或2種以上：合計0.002~0.0300%、Cu：0~0.045%、Cr、Ni之1種或2種：合計0~1.000%、及As、Se、Ta、Sn、Sb、Ca、Mg、Y及REM中之1種或2種以上：合計0~0.1000%，且剩餘部分由Fe及不純物所構成，並且滿足下述式(1)及式(2)。並且，本實施形態之鋼板中，BN中含有之N含量即[N as BN]與鋼中含有之B含量之關係滿足式(3)。>Chemical composition> The steel sheet of this embodiment contains C: 0.0050~0.0700%, Si: 0.0010~0.0500%, Mn: 0.0500~1.0000%, P: 0.0050~0.1000%, S: 0.0010~0.0500%, Al: 0.007~ 0.100%, O: 0.0005~0.0100%, B: 0.0003~0.0100%, N: 0.0010~0.0100%, Ti: 0~0.0100%, one or more of Nb, Zr, V, Mo and W: total 0.002~0.0300%, Cu: 0~0.045%, 1 or 2 of Cr, Ni: 0~1.000% in total, and 1 of As, Se, Ta, Sn, Sb, Ca, Mg, Y, and REM Or 2 or more types: 0~0.1000% in total, and the remainder is composed of Fe and impurities, and satisfies the following formulas (1) and (2). Furthermore, in the steel sheet of the present embodiment, the relationship between the content of N contained in BN, that is, [N as BN] and the content of B contained in the steel, satisfies the formula (3).

Ti>(N-0.0003)×3.43 ・・・式(1) C>0.25×Ti+0.129×Nb+0.235×V+0.132×Zr+0.125×Mo+0.0652×W+0.0040 ・・・式(2) [N as BN]/(1.27×B)>0.95 ・・・式(3) 惟，式(1)~式(3)中之元素符號表示該元素之含量(質量%)，式(3)中之[N as BN]則表示BN中含有之N量(質量%)。Ti>(N-0.0003)×3.43 ・・・ formula (1) C>0.25×Ti+0.129×Nb+0.235×V+0.132×Zr+0.125×Mo+0.0652×W+0.0040 ・・・ Equation (2) [N as BN]/(1.27×B)>0.95 ・・・Equation (3) However, the element symbol in formula (1) ~ formula (3) indicates the content (mass%) of the element, and [N as BN] in formula (3) indicates the amount of N contained in BN (mass%).

另，本實施形態之鋼板以質量%計，亦可含有Cu：0.010~0.045%。另，本實施形態之鋼板以質量%計，亦可含有合計0.005~1.000%之Cr、Ni之1種或2種。另，本實施形態之鋼板亦可更含有以下中之1種或2種以上元素，且以質量%計含有合計0.0005~0.1000%以下：As、Se、Ta、Sn、Sb、Ca、Mg、Y及REM。In addition, the steel sheet of this embodiment may contain Cu: 0.010 to 0.045% in terms of mass %. In addition, the steel sheet of this embodiment may contain one or two of Cr and Ni in a total of 0.005 to 1.000% in terms of mass%. In addition, the steel sheet of this embodiment may further contain one or two or more of the following elements, and the total content is 0.0005 to 0.1000% or less in mass%: As, Se, Ta, Sn, Sb, Ca, Mg, Y And REM.

以下，闡明限定鋼板之化學成分的理由。在此，符號「%」意指質量%。Below, the reasons for limiting the chemical composition of the steel sheet will be explained. Here, the symbol "%" means mass%.

C：0.0050～0.0700% C含量越少，雪明碳鐵與波來鐵形成量就越變少，故抗鱗狀破面性降低，並且抑制琺瑯處理時之晶粒成長的效果也會消失，而發生強度降低。另外，若C含量大於0.0700%，就變得容易產生氣泡缺陷之針孔。並且會大量生成雪明碳鐵或波來鐵，因而導致延性降低。因此，係將C含量設為0.0050~0.0700%。較佳為0.0100~0.0300%之範圍。C: 0.0050～0.0700% The less the C content, the less the formation of Xueming carbon iron and pleite, so the resistance to scaly cracking is reduced, and the effect of inhibiting the growth of crystal grains during enamel treatment is also lost, and the strength is reduced. In addition, if the C content is greater than 0.0700%, it becomes easy to produce pinholes with bubble defects. In addition, a large amount of snow carbon iron or pyrite iron is generated, which causes a decrease in ductility. Therefore, the C content is set to 0.0050 to 0.0700%. It is preferably in the range of 0.0100 to 0.0300%.

Si：0.0010～0.0500% Si為固溶強化元素，亦為具有抑制琺瑯處理所致之強度降低的效果的元素。但，若Si含量過多，除會導致延性降低外，製造成本也會增加。因此，係將Si含量設為0.0010~0.0500%。較佳為0.0040~0.0300%之範圍。Si: 0.0010～0.0500% Si is a solid solution strengthening element and an element that has the effect of suppressing the decrease in strength caused by the enamel treatment. However, if the Si content is too large, in addition to reducing ductility, manufacturing costs will also increase. Therefore, the Si content is set to 0.0010 to 0.0500%. It is preferably in the range of 0.0040 to 0.0300%.

Mn：0.0500～1.0000% Mn係會影響生成可用來作為BN之析出位置之MnS的重要成分，該BN可對琺瑯用鋼板之抗鱗狀破面性發揮效果。並且MnS本身亦具有提升抗鱗狀破面性的效果。此外，Mn還係可防止熱軋延時因S所致之熱脆性的元素。為了獲得上述效果，係將Mn含量設為0.0500%以上。然而，若Mn含量變得過多，延性便會劣化。因此，係將Mn含量上限設為1.0000%以下。較佳為0.0800~0.5000%之範圍。Mn: 0.0500～1.0000% The Mn system affects the formation of an important component of MnS that can be used as the precipitation site of BN, and this BN can exert an effect on the anti-scaly cracking property of the steel sheet for enamel. And MnS itself also has the effect of improving the resistance to scaly cracking. In addition, Mn is also an element that can prevent hot embrittlement caused by S due to hot rolling delay. In order to obtain the above effect, the Mn content is set to 0.0500% or more. However, if the Mn content becomes too much, the ductility will deteriorate. Therefore, the upper limit of the Mn content is set to 1.0000% or less. It is preferably in the range of 0.0800 to 0.5000%.

P：0.0050～0.1000% P係對鋼板之高強度化有效之元素。並且，P亦為具有抑制琺瑯處理所致之強度降低的效果的元素。為了獲得上述效果，係將P含量設為0.0050%以上。另一方面，若P含量變得過多，在琺瑯處理時P會在鋼板的晶界中高濃度地偏析，有時會成為造成氣泡及黑點等的主要原因。並且，有時亦會導致延性降低。因此，係將P含量設為0.1000%以下。較佳係在0.0500%以下。P: 0.0050～0.1000% P is an element that is effective in increasing the strength of the steel plate. In addition, P is also an element that has the effect of suppressing the decrease in strength caused by enamel treatment. In order to obtain the above effect, the P content is set to 0.0050% or more. On the other hand, if the P content becomes too large, P will segregate in a high concentration in the grain boundaries of the steel sheet during the enamel treatment, which may cause bubbles, black spots, and the like. In addition, sometimes the ductility is reduced. Therefore, the P content is set to 0.1000% or less. Preferably it is 0.0500% or less.

S：0.0010～0.0500% S係可形成MnS的元素。該硫化物可作為BN之析出位置發揮作用，有助於提升抗鱗狀破面性。並且MnS本身亦具有提升抗鱗狀破面性的效果。為了獲得上述效果，係將S含量設為0.0010%以上。且較理想係在0.0030%以上。然而，若S含量變得過多，有時會產生因MnS所致之瑕疵。因此，係將S含量設為0.0500%以下。較佳係設為0.0300%以下。S: 0.0010～0.0500% S is an element that can form MnS. The sulfide can act as the precipitation location of BN and help improve the resistance to scaly cracking. And MnS itself also has the effect of improving the resistance to scaly cracking. In order to obtain the above effect, the S content is set to 0.0010% or more. And the ideal system is above 0.0030%. However, if the S content becomes too much, defects due to MnS may sometimes occur. Therefore, the S content is set to 0.0500% or less. Preferably, it is set to 0.0300% or less.

Al：0.007~0.100% Al係可作為脫氧元素發揮作用之元素。當Al含量少時，脫氧效果就低，而會導致夾雜物量增加。因此，係將Al含量設為0.007%以上。另一方面，若Al含量過多，延性便會降低。因此，係將Al含量設為0.100%以下。較佳為0.010~0.060%之範圍。Al: 0.007~0.100% Al is an element that functions as a deoxidizing element. When the Al content is small, the deoxidation effect is low, and the amount of inclusions increases. Therefore, the Al content is set to 0.007% or more. On the other hand, if the Al content is too large, the ductility will decrease. Therefore, the Al content is set to 0.100% or less. It is preferably in the range of 0.010 to 0.060%.

O：0.0005～0.0100% 若O含量變多，便會大量生成鐵氧化物而成為延性降低的原因，並且會成為脫屑的原因。就此觀點而言，O含量宜盡可能減低。然而，若過度使O含量降低，製造成本便會增加。因此，O含量設為0.0005~0.0100%。較佳為0.0010~0.0070%之範圍。O: 0.0005～0.0100% If the O content is increased, a large amount of iron oxides will be produced, which will cause the ductility to decrease, and will also cause the chipping. From this point of view, the O content should be as low as possible. However, if the O content is excessively reduced, the manufacturing cost will increase. Therefore, the O content is set to 0.0005 to 0.0100%. It is preferably in the range of 0.0010% to 0.0070%.

B：0.0003~0.0100% B係為了生成BN而含有，該BN具有提升琺瑯用鋼板之抗鱗狀破面性的效果。並且，未成為BN之B會以固溶B之形態存在，而可抑制琺瑯處理中之晶粒成長。為了獲得上述效果，必須使B含量在0.0003%以上。且較佳係在0.0005%以上。另一方面，當B含量變得過多時，晶粒成長會明顯受到抑制，而導致延性降低。因此，係將B含量設為0.0100%以下。較佳係在0.0030%以下。B: 0.0003~0.0100% B is contained in order to generate BN, and this BN has the effect of improving the scaly crack resistance of the steel sheet for enamel. In addition, B that has not become BN will exist in the form of solid solution B, which can inhibit the growth of crystal grains during enamel processing. In order to obtain the above effects, the B content must be 0.0003% or more. And it is preferably 0.0005% or more. On the other hand, when the B content becomes excessive, the growth of crystal grains is significantly suppressed, resulting in a decrease in ductility. Therefore, the B content is set to 0.0100% or less. It is preferably less than 0.0030%.

N：0.0010～0.0100% N係用以生成BN之必要元素，該BN具有提升琺瑯用鋼板之抗鱗狀破面性的效果。為了獲得該效果，係將N含量設為0.0010%以上。另一方面，若N含量變得過多，延性便會降低。因此，係將N含量設為0.0100%以下。較佳係在0.0070%以下。N: 0.0010～0.0100% N is an essential element for generating BN, which has the effect of improving the resistance of enamel steel plate to scaly cracking. In order to obtain this effect, the N content is set to 0.0010% or more. On the other hand, if the N content becomes too much, the ductility will decrease. Therefore, the N content is set to 0.0100% or less. It is preferably less than 0.0070%.

Ti：0~0.0100% Ti係可輕易形成氮化物的元素，且係會阻礙生成可對抗鱗狀破面性發揮效果之BN的元素。因此，以極力不含有其為佳。於是，係將Ti含量設為0~0.0100%之範圍。而較佳係在0.0050%以下。但，要使Ti含量在0.0003%以下的話，製造成本有可能會增加。因此，實際製造之下限值亦可設為0.0003%。Ti: 0~0.0100% Ti is an element that can easily form nitrides, and is an element that hinders the generation of BN, which is effective against scaly cracking. Therefore, it is better not to contain it as much as possible. Therefore, the Ti content is set in the range of 0 to 0.0100%. It is preferably less than 0.0050%. However, if the Ti content is less than 0.0003%, the manufacturing cost may increase. Therefore, the actual manufacturing lower limit can also be set to 0.0003%.

Nb、Zr、V、Mo及W中之1種或2種以上之合計：0.0020~0.0300% 該等元素係會形成微細碳化物，而抑制晶粒成長之元素。透過含有該等元素，琺瑯處理時之晶粒成長會被抑制，而可抑制強度降低。但，若過度含有該等元素，延性便會降低。因此，該等元素之1種或2種以上之合計含量設為0.0020~0.0300%。且較佳為0.0030~0.0200%。One or more of Nb, Zr, V, Mo and W in total: 0.0020~0.0300% These elements form fine carbides and inhibit the growth of crystal grains. By containing these elements, the growth of crystal grains during enamel processing can be suppressed, and the decrease in strength can be suppressed. However, if these elements are contained excessively, ductility will decrease. Therefore, the total content of one or more of these elements is set to 0.0020 to 0.0300%. And it is preferably 0.0030 to 0.0200%.

本實施形態中，除上述元素以外，可視需要含有下述元素。並且，因亦可不含該等元素，故下限為0%。In this embodiment, in addition to the above-mentioned elements, the following elements may be contained as necessary. In addition, since these elements may not be included, the lower limit is 0%.

Cu：0～0.045% 亦可含有Cu，以控制琺瑯處理時之玻璃質與鋼之反應。要獲得上述效果時，宜將Cu含量設為0.010%以上。Cu亦可為0%。另一方面，若Cu含量變得過多，不僅玻璃質與鋼之反應會受到阻礙，加工性有時亦會劣化。因此，要避免如上述之不良影響的話，宜使Cu含量在0.045%以下。Cu: 0～0.045% It can also contain Cu to control the reaction of glass and steel during enamel processing. To obtain the above effects, the Cu content should be set to 0.010% or more. Cu may also be 0%. On the other hand, if the Cu content becomes too large, not only the reaction between glass and steel will be hindered, but workability may also be deteriorated. Therefore, to avoid the above-mentioned adverse effects, the Cu content should be less than 0.045%.

Cr、Ni之1種以上：合計0~1.000% Cr、Ni具有可提升鋼板與琺瑯層之密著性的效果，故可含有其等。Cr、Ni之合計含量在0.005%以上時，提升與琺瑯層之密著性的效果會變得明顯，故較佳。且更佳為0.010%以上。另一方面，Cr、Ni之合計含量若大於1.000%，提升密著性的效果會達飽和，機械特性亦會降低。當含有Cr與Ni時，就算含有0.500%以下，仍可預期有某種程度之效果。因此，當含有Cr與Ni時，係使其含量合計在0.005~1.000%。且較佳為0.010~0.500%。More than one of Cr and Ni: 0~1.000% in total Cr and Ni have the effect of improving the adhesion between the steel plate and the enamel layer, so they may be contained. When the total content of Cr and Ni is more than 0.005%, the effect of improving the adhesion to the enamel layer becomes obvious, so it is better. And more preferably, it is 0.010% or more. On the other hand, if the total content of Cr and Ni is greater than 1.000%, the effect of improving the adhesion will be saturated and the mechanical properties will also be reduced. When Cr and Ni are contained, even if the content is less than 0.500%, a certain degree of effect can be expected. Therefore, when Cr and Ni are contained, the total content is 0.005 to 1.000%. And preferably it is 0.010~0.500%.

As、Se、Ta、Sn、Sb、Ca、Mg、Y及REM之1種以上：合計0~0.1000% 透過微量含有該等元素以形成氧化物，而可具有提升抗鱗狀破面性的效果。惟，過度含有時，會大量析出氧化物。由於該氧化物在變形時會成為斷裂的起點，而使延性降低。因此，該等元素之1種以上之含量宜設為合計0~0.1000%。且較佳為0.0005~0.1000%。更佳為0.0025~0.0500%。REM係指週期表中原子序號57~71之鑭系元素之1種或2種以上。One or more of As, Se, Ta, Sn, Sb, Ca, Mg, Y and REM: 0~0.1000% in total By containing these elements in a small amount to form oxides, it has the effect of improving the anti-scaly cracking property. However, when it is contained excessively, a large amount of oxides will be precipitated. Since the oxide becomes the starting point of fracture during deformation, the ductility is reduced. Therefore, the content of one or more of these elements should be set to 0~0.1000% in total. And it is preferably 0.0005 to 0.1000%. More preferably, it is 0.0025~0.0500%. REM refers to one or more of the lanthanides with atomic numbers 57 to 71 in the periodic table.

另，透過滿足下述式(1)~(3)，可更提升抗鱗狀破面性，並且可更抑制琺瑯處理時之強度降低。 Ti>(N-0.0003)×3.43 ・・・式(1) 如前所述，Ti係可輕易形成氮化物的元素，當含有Ti時，亦須使N殘留下來，該N係用以形成可提升抗鱗狀破面性之BN。因此，將Ti含量限定於式(1)之範圍。In addition, by satisfying the following formulas (1) to (3), the scaly fracture resistance can be improved, and the strength reduction during enamel treatment can be further suppressed. Ti>(N-0.0003)×3.43 ・・・ formula (1) As mentioned above, Ti is an element that can easily form nitrides. When Ti is contained, N must be left. The N is used to form BN that can improve the resistance to scaly cracking. Therefore, the Ti content is limited to the range of formula (1).

C>0.25×Ti+0.129×Nb+0.235×V+0.132×Zr+0.125×Mo+0.0652×W+0.0040 ・・・式(2) 為了抑制琺瑯處理時之強度降低，如上所述必須使固溶C存在，或者須有鐵碳化物存在。要獲得上述效果的話，當形成有Ti、Nb、V、Zr、Mo及W之合金碳化物時，仍須殘留固溶狀態的C。因此，將C含量限定於式(2)之範圍。C>0.25×Ti+0.129×Nb+0.235×V+0.132×Zr+0.125×Mo+0.0652×W+0.0040 ・・・ Equation (2) In order to suppress the decrease in strength during enamel treatment, the solid solution C must be present as described above, or iron carbide must be present. To achieve the above effects, when alloy carbides of Ti, Nb, V, Zr, Mo, and W are formed, C in a solid solution state must remain. Therefore, the C content is limited to the range of formula (2).

[N as BN]/(1.27×B)>0.95 ・・・式(3) B係為了形成BN以提升抗鱗狀破面性而含有，然而當殘留有固溶B時，會抑制琺瑯處理時之晶粒成長，而產生抑制強度降低的效果。因此，要使所含之B不會全部析出為BN。表示BN中含有之N含量之[N as BN]可透過化學分析來定量，故係使用該值規定BN之生成狀態，以將可有效抑制晶粒成長之BN析出量的範圍規定為式(3)。[N as BN]可利用鋼之萃取殘渣(溴甲醇法)求算。[N as BN]/(1.27×B)>0.95 ・・・ formula (3) B is contained in order to form BN to improve the resistance to scaly cracking. However, when solid solution B remains, it will inhibit the growth of crystal grains during the enamel treatment and produce the effect of inhibiting the decrease in strength. Therefore, it is necessary to prevent all the contained B from being precipitated as BN. [N as BN], which represents the content of N contained in BN, can be quantified by chemical analysis, so this value is used to specify the state of BN production, and the range of the amount of BN precipitation that can effectively inhibit crystal grain growth is specified as formula (3 ). [N as BN] can be calculated using the extraction residue of steel (bromo methanol method).

>金屬組織> 本實施形態之鋼板之金屬組織含有肥粒鐵、雪明碳鐵及/或波來鐵，且肥粒鐵為主體組織。更具體而言，本實施形態之鋼板之金屬組織含有：肥粒鐵；位於肥粒鐵晶粒內之雪明碳鐵；以及，位於肥粒鐵晶界之雪明碳鐵及/或波來鐵。並且，亦可更含有雪明碳鐵以外之碳化物、氮化物及氧化物中之1種以上。肥粒鐵之延性優異，故本實施形態之鋼板係以肥粒鐵為主相，藉此可實現優異加工性。另外，若金屬組織中存在雪明碳鐵及波來鐵，屬琺瑯用鋼板之必要特性之抗鱗狀破面性便會提升。可認為這係由於琺瑯處理中生成之氫被捕捉在肥粒鐵與雪明碳鐵之界面所致。另一方面，還可認為若存在雪明碳鐵及波來鐵，於琺瑯處理中生成之氫便會以碳化氫氣體之形態釋放到鋼板外。此時，亦會成為氣泡缺陷的原因。因此，必須限制所含雪明碳鐵、波來鐵之尺寸與個數密度。>Metal Structure> The metal structure of the steel sheet of the present embodiment contains fertile iron, snow carbon iron and/or polished iron, and the fertile iron is the main structure. More specifically, the metal structure of the steel sheet of the present embodiment contains: Fertilizer iron; Xueming carbon iron located in the fertilizer grain iron grains; and Xueming carbon iron and/or wavelet iron located in the grain boundaries of the fertilizer grain iron iron. In addition, it may further contain one or more of carbides, nitrides, and oxides other than Xueming Carbon. Fertile iron is excellent in ductility, so the steel plate of the present embodiment is mainly composed of ferrous iron, thereby achieving excellent workability. In addition, if Xueming Carbon Iron and Bory Iron are present in the metal structure, the scaly fracture resistance, which is a necessary characteristic of steel plates for enamel, will be improved. It can be considered that this is due to the hydrogen generated in the enamel treatment being trapped at the interface between the ferrite iron and the snow carbon iron. On the other hand, it is also believed that if Xueming Carbon Iron and Bory Iron are present, the hydrogen generated in the enamel treatment will be released out of the steel plate in the form of hydrocarbon gas. At this time, it will also become a cause of bubble defects. Therefore, it is necessary to limit the size and number density of Xueming Carbon Iron and Bory Iron contained.

首先，針對肥粒鐵晶粒內之雪明碳鐵，係將粒徑0.3~1.5μm之雪明碳鐵的個數密度設為1.00×10^-1 個/μm² 以下。於肥粒鐵晶粒內微細析出之雪明碳鐵會在琺瑯處理中熔解，並以一氧化碳或二氧化碳氣體之形態釋放出來，而產生氣泡缺陷。因此，必須將位於肥粒鐵晶粒內之微細的晶粒內碳化物的個數限制在1.00×10^-1 個/μm² 以下。而粒徑大於1.5μm之晶粒內雪明碳鐵係無害的，故不特別加以規定。另，粒徑小於0.3μm之雪明碳鐵即便產生氣泡缺陷，其對於抗鱗狀破面性所造成的影響仍微小。因此，係測定粒徑為0.3~1.5μm之晶粒內雪明碳鐵，以評估個數密度。而，一個雪明碳鐵的粒徑係設為長徑與短徑的平均。First of all, for the Xueming carbon iron in the ferrous iron grains, the number density of Xueming carbon iron with a particle size of 0.3 to 1.5 μm is set to 1.00×10 ^-1 pieces/μm ² or less. The finely precipitated Xueming carbon iron in the ferrite grains will be melted during the enamel treatment and released in the form of carbon monoxide or carbon dioxide gas, resulting in bubble defects. Therefore, the number of fine intra-grain carbides located in the ferrous iron grains must be limited to 1.00×10 ^-1 /μm ² or less. However, the Xueming carbon-iron system in the crystal grains with a particle size greater than 1.5μm is harmless, so it is not specifically specified. In addition, even if the Xueming carbon iron with a particle size of less than 0.3 μm produces bubble defects, its effect on the resistance to scaly cracking is still small. Therefore, the determination of the number density in the crystal grains with a particle size of 0.3~1.5μm is performed. On the other hand, the particle size of one Xueming carbon iron is the average of the long axis and the short axis.

接著，存在於肥粒鐵晶界上之雪明碳鐵及/或波來鐵，因係存在於琺瑯處理時氫的擴散路徑上，故會捕捉氫而具有提升抗鱗狀破面性之效果。將該等雪明碳鐵及/或波來鐵之長徑平均值限制在0.5~15μm，並且將雪明碳鐵、波來鐵的個數密度限制在5.00×10^-4 ~1.00×10^-1 個/μm² 。雪明碳鐵、波來鐵之長徑平均值小於0.5μm時，提升抗鱗狀破面性的效果較少。並且，會變得容易於琺瑯處理中熔解，並以一氧化碳或二氧化碳氣體之形態釋放出來，故會成為氣泡缺陷的原因。另一方面，長徑平均值大於15μm時，會成為加工時的破壞之起點，導致延性降低。因此，係將長徑平均值設為0.5~15μm。另外，當個數密度小於5.00×10^-4 個/μm² 時，無法觀察到提升抗鱗狀破面性的效果，而個數密度大於1.00×10^-1 個/μm² 時，會成為變形時的破壞之起點，導致延性降低。因此，係將存在於肥粒鐵晶界上之雪明碳鐵及/或波來鐵的個數密度設為5.00×10^-4 ~1.00×10^-1 個/μm² 。雪明碳鐵及波來鐵有一者存在即可，亦可存在兩者。又，此處所謂的雪明碳鐵係與含於波來鐵中之層狀雪明碳鐵有所區別，且係指不被含於波來鐵組織中之雪明碳鐵。Next, the Xueming Carbon Iron and/or Polly Iron, which exist on the grain boundaries of the fertilized iron, are present in the diffusion path of hydrogen during the enamel treatment, so they will capture hydrogen and have the effect of improving the resistance to scaly cracking. . The iron and carbon and the like Xueming / or pearlite limit of the average long diameter of 0.5 ~ 15μm, and the iron-carbon clear snow, the number density of pearlite limit ^{5.00 × 10 -4 ~ 1.00 × 10} - ¹ piece/μm ² . When the average value of the long diameter of Xueming carbon iron and pleite is less than 0.5μm, the effect of improving the resistance to scaly cracking is less. In addition, it becomes easy to dissolve in the enamel treatment and is released in the form of carbon monoxide or carbon dioxide gas, which can cause bubble defects. On the other hand, when the average value of the major axis is larger than 15 μm, it becomes the starting point of failure during processing, resulting in a decrease in ductility. Therefore, the average value of the major axis is set to 0.5 to 15 μm. In addition, when the number density is less than 5.00×10 ^-4 pieces/μm ² , the effect of improving the resistance to scaly cracking cannot be observed, and when the number density is greater than 1.00×10 ^-1 pieces/μm ² , it will become deformed The starting point of destruction at time, leading to reduced ductility. Therefore, the number density of Xueming carbon iron and/or poriferous iron present on the grain boundaries of fertilizer grains is set to 5.00×10 ^-4 to 1.00×10 ^-1 pieces/μm ² . Only one of Xueming carbon iron and plastered iron can exist, or both can exist. In addition, the so-called Xueming carbon iron system is different from the layered Xueming carbon iron contained in the Bory iron, and refers to the snow Ming carbon iron that is not contained in the Bory iron structure.

雪明碳鐵及波來鐵係在將鋼板之軋延方向截面加以研磨後，以苦味酸蝕劑進行腐蝕，並且在以光學顯微鏡觀察時顯現為黑色對比。作為鋼板組織之代表點，係觀察從表面起沿板厚方向1/4板厚t的位置(1/4t)之部位。並且，藉由調整苦味酸蝕劑腐蝕的程度，亦可使肥粒鐵晶界顯現，故能判定雪明碳鐵、波來鐵之觀察位置與晶界之關係。觀察係以400~1000倍之倍率來進行即可。於晶界析出之雪明碳鐵在晶界三接點連接時，係測定於各晶界之邊析出之雪明碳鐵的長度並加以合計。若為波來鐵，有時會被多個肥粒鐵晶粒包圍，在此情況下亦視為存在於肥粒鐵晶界來測定個數。於圖1中示出測定例之示意圖。上述記載之雪明碳鐵與波來鐵的個數密度係將觀察到的個數除以觀察面積而得之值，令其單位為個/μm² 。Xueming Carbon Iron and Borai Iron are polished on the cross section of the steel sheet in the rolling direction and then corroded with a bitter acid etchant, and they appear as black contrast when observed with an optical microscope. As a representative point of the steel plate structure, the position (1/4t) of the 1/4 plate thickness t in the plate thickness direction from the surface is observed. In addition, by adjusting the degree of corrosion by the bitter acid, the grain boundaries of the ferrite grains can also be revealed, so the relationship between the observation position of the Xueming carbon iron and the porphyrite and the grain boundaries can be determined. The observation system can be performed at a magnification of 400 to 1000 times. When the Xueming carbon iron precipitated at the grain boundary is connected at the three junctions of the grain boundary, the length of the Xueming carbon iron precipitated on the sides of each grain boundary is measured and totaled. In the case of pleite, it is sometimes surrounded by multiple ferrite grains. In this case, it is also considered to be present in the ferrite grain boundary to determine the number. The schematic diagram of the measurement example is shown in FIG. The number density of Xueming carbon iron and pleite described above is the value obtained by dividing the observed number by the observation area, and the unit is unit/μm ² .

例如，在圖1中，雪明碳鐵a存在於位於2個肥粒鐵晶粒之間的1個晶界上，並且以沿著晶界之長度La為長徑。雪明碳鐵b係沿著由3個肥粒鐵晶粒所形成的2個晶界存在，而以沿著各晶界之長度Lb1與Lb2之合計(Lb1+Lb2)為長徑。雪明碳鐵c係沿著由4個肥粒鐵晶粒所形成的3個晶界存在，而以沿著各晶界之長度Lc1~Lc3之合計(Lc1+Lc2+Lc3)為長徑。雪明碳鐵d係沿著由3個肥粒鐵晶粒所形成的3個晶界存在，而以沿著各晶界之長度Ld1~Ld3之合計(Ld1+Ld2+Ld3)為長徑。波來鐵e~i則分別以最大長徑Le~Li為長徑。For example, in Fig. 1, Xueming carbon iron a exists on a grain boundary located between two ferrite grains, and the length La along the grain boundary is taken as the major axis. Xueming carbon iron b exists along two grain boundaries formed by three ferrous iron grains, and the total length of Lb1 and Lb2 (Lb1+Lb2) along each grain boundary is taken as the major axis. Xueming carbon iron c exists along three grain boundaries formed by four ferrous iron grains, and the total length of Lc1~Lc3 along each grain boundary (Lc1+Lc2+Lc3) is taken as the major axis. Xueming carbon iron d exists along three grain boundaries formed by three ferrous iron grains, and the total length of Ld1~Ld3 along each grain boundary (Ld1+Ld2+Ld3) is taken as the major axis. The longest diameters Le~Li are taken as the longest diameters of Pollyite e~i.

另外，琺瑯處理前之鋼板組織中肥粒鐵之平均結晶粒徑，在從表面起沿板厚方向1/4板厚t的位置(1/4t)上為30.0μm以下即可。藉由使平均結晶粒徑在30.0μm以下，可謀求鋼板之高強度化。並且較佳係在20.0μm以下，更佳係在15.0μm以下。雖然在謀求高強度化上係以平均結晶粒徑小較為理想，但隨著平均結晶粒徑變小，加工性會劣化。因此，必須決定對所欲製品形狀而言最佳之結晶粒徑。In addition, the average crystal grain size of the ferrous iron in the steel plate structure before the enamel treatment may be 30.0 μm or less at the position (1/4t) of the 1/4 plate thickness t in the plate thickness direction from the surface. By setting the average crystal grain size to 30.0 μm or less, it is possible to increase the strength of the steel sheet. And it is preferably 20.0 μm or less, more preferably 15.0 μm or less. Although it is preferable that the average crystal grain size is small in order to achieve high strength, as the average crystal grain size becomes smaller, the workability deteriorates. Therefore, it is necessary to determine the optimum crystal grain size for the desired product shape.

肥粒鐵之平均結晶粒徑，係以JIS G0551：2013附錄B中記載之使用方形試驗線之方法，求算1個晶粒之平均結晶面積，算出為等效圓直徑。亦即，若令平均結晶面積為a，則平均結晶粒徑d係以下述式(4)表示。The average crystal grain size of ferrous iron is calculated by the method of using a square test line as described in JIS G0551:2013 Appendix B to calculate the average crystal area of one crystal grain and calculate it as the equivalent circle diameter. That is, if the average crystal area is a, the average crystal grain size d is represented by the following formula (4).

d＝2√(a/π) ・・・式(4)d=2√(a/π) ・・・Equation (4)

>製造方法> 說明本實施形態鋼板之較佳製造方法。本實施形態之鋼板係歷經熔解、鑄造、熱軋延、冷軋延、退火及調質軋延之步驟，而可製得。各步驟除以下所示條件以外，只要根據常規方法來設定便可。>Manufacturing Method> The preferred manufacturing method of the steel plate of this embodiment is described. The steel sheet of this embodiment can be manufactured through the steps of melting, casting, hot rolling, cold rolling, annealing, and tempering rolling. In addition to the conditions shown below, each step can be set according to a conventional method.

在製造本實施形態之鋼板上的重點在於：控制鋼板之雪明碳鐵及波來鐵的析出狀態、及控制BN的析出狀態。如上述所說明，限制於肥粒鐵晶粒內析出之微細雪明碳鐵的個數密度，另一方面並控制於肥粒鐵晶界生成之雪明碳鐵、波來鐵之尺寸與個數密度，藉此可提升抗鱗狀破面性，還可抑制氣泡缺陷。另外，控制BN之析出狀態，在使BN析出的同時亦使固溶B殘留下來，藉此可提升抗鱗狀破面性，並且還可抑制琺瑯處理時之晶粒成長，而能抑制強度降低。The key points in the manufacture of the steel sheet of this embodiment are to control the precipitation state of snow carbon iron and polished iron in the steel sheet, and control the precipitation state of BN. As explained above, the number density of the fine snow carbon iron precipitated in the ferrite grains is limited, and on the other hand, the size and the size and the size of the snow carbon iron and the pyrite iron formed at the grain boundaries of the ferrite iron are controlled. The number density can improve the resistance to scaly cracking, and can also suppress bubble defects. In addition, by controlling the precipitation state of BN, the solid solution B remains while precipitating BN, which can improve the resistance to scaly cracking, and can also inhibit the growth of crystal grains during enamel processing, thereby suppressing the decrease in strength .

熱軋延之鋼胚加熱溫度宜為1000~1300℃，熱軋延之精加工溫度宜為Ar3~1000℃，Ar3+100℃以下之軋縮率宜大於25%，軋延結束溫度宜在Ar3℃以上，而捲取溫度宜為500~800℃。The heating temperature of the hot-rolled steel billet should be 1000~1300℃, the finishing temperature of the hot-rolling should be Ar3~1000℃, the rolling shrinkage rate below Ar3+100℃ should be greater than 25%, and the rolling end temperature should be Ar3 ℃ above, and the coiling temperature should be 500~800℃.

在低於1000℃下加熱了鋼胚時，BN變得容易生成，而有以固溶B之形態殘留之B含量降低之疑慮。鋼胚加熱溫度之上限並無特別規定，但因經濟面的理由而以設為1300℃左右為理想。When the steel billet is heated below 1000°C, BN becomes easy to form, and there is a concern that the B content remaining in the form of solid solution B will decrease. The upper limit of the steel billet heating temperature is not specifically defined, but for economic reasons, it is ideal to set it to about 1300°C.

熱軋延之精加工溫度低於Ar3℃時，在軋延中會生成肥粒鐵而在軋延後的冷卻中不會發生變態，故該部位有時會成為粗大晶粒，造成晶粒產生不均一的情形。另，當精加工溫度高於1000℃時，至捲取溫度為止的溫度降低幅度大，不符經濟效益，故精加工溫度宜為Ar3~1000℃之範圍。在進行精整軋延時，Ar3係利用以下式(a)所示根據鋼成分之預測式來推定。並且根據以該方法預測而得的Ar3設定軋延條件。 Ar3(℃)＝901-325×C-92×Mn+33×Si+287×P+40×Al-30 (a) 惟，式(a)中之元素符號(C、Mn、Si、P及Al)表示該元素之含量(質量%)。另外，實際上精整軋延溫度是否低於Ar3℃，可在實際作業中改變精加工溫度來進行熱軋延，並且觀察軋延板之微觀組織，依據有無產生粗大晶粒來加以確認。粗大晶粒會產生在精加工溫度低於Ar3℃之部位，主要會產生在鋼板端部及表層。其平均粒徑會係板寬中心且板厚中心之平均粒徑的1.5倍以上。When the finishing temperature of hot rolling is lower than Ar3℃, ferrous iron will be formed during rolling and will not be deformed during cooling after rolling. Therefore, the part may become coarse grains, causing grains to occur. Uneven situation. In addition, when the finishing temperature is higher than 1000°C, the temperature drop from the coiling temperature is large, which is not economical, so the finishing temperature should be in the range of Ar3~1000°C. When the finishing rolling delay is performed, the Ar3 system is estimated using the prediction formula based on the steel composition shown in the following formula (a). And the rolling conditions are set based on the Ar3 predicted by this method. Ar3(℃)=901-325×C-92×Mn+33×Si+287×P+40×Al-30 (a) However, the element symbols (C, Mn, Si, P and Al) in formula (a) indicate the content (mass%) of the element. In addition, whether the finishing temperature is actually lower than Ar3°C, you can change the finishing temperature to perform hot rolling in actual operation, and observe the microstructure of the rolled plate to confirm whether or not coarse grains are generated. Coarse grains will be generated in the parts where the finishing temperature is lower than Ar3℃, mainly at the end and surface of the steel plate. The average particle size will be more than 1.5 times the average particle size at the center of the plate width and the center of the plate thickness.

捲取溫度並無特別限制，但當捲取溫度低於500℃時，於熱軋延時生成之雪明碳鐵及波來鐵的尺寸會變小，而可能對冷軋退火後之碳化物造成影響。因此，在500℃以上較理想。此外，後續步驟之連續退火中無過時效步驟的情況下，捲取溫度宜在550℃以上。另，捲取溫度高於800℃時，於表面生成之鏽皮會變厚，導致後續步驟之酸洗中的成本增加。因此，在800℃以下較理想。The coiling temperature is not particularly limited, but when the coiling temperature is lower than 500°C, the size of the snow-minded carbon iron and the corundum produced during the hot rolling delay will become smaller, which may cause the carbides after the cold rolling and annealing influences. Therefore, 500°C or higher is preferable. In addition, if there is no over-aging step in the subsequent step of continuous annealing, the coiling temperature should be above 550°C. In addition, when the coiling temperature is higher than 800°C, the scale formed on the surface will become thicker, which will increase the cost of pickling in the subsequent steps. Therefore, the temperature below 800°C is ideal.

熱軋延時之Ar3+100℃以下之軋縮率(累積軋縮率)設為大於25%。Ar3+100℃以下之溫度區中的軋延率若為25%以下，累積應變的效果會變小，成為在精整軋延後產生的肥粒鐵變態或肥粒鐵波來鐵變態之成核部位之γ晶界變少，導致雪明碳鐵或波來鐵之生成密度變疏且粗大化。若使用如上述之熱軋鋼板，可認為冷軋退火後之晶界的雪明碳鐵及/或波來鐵之析出密度會降低。並且，Ar3+100℃以下之軋縮率若為25%以下，可認為熱軋鋼板之粒徑會變得粗大，而r值降低。為了保證壓製成形性，冷軋延及退火後之軋延方向之r值、或軋延方向與相對於軋延方向為正交之方向(之後，記載為正交方向)之r值兩者宜成為0.8以上，為了達成上述，必須使Ar3+100℃以下之軋縮率大於25%。熱軋延後，會實施酸洗等以去除於表面生成之鏽皮，而其方法及條件不特別規定。The reduction ratio (cumulative reduction ratio) of Ar3+100°C or less after the hot rolling delay is set to be greater than 25%. If the rolling rate in the temperature range below Ar3+100°C is 25% or less, the effect of cumulative strain will be reduced, and it will be the result of the fat iron deformation or the fat iron deformation after finishing rolling. The γ grain boundary in the core part becomes less, which leads to the sparse and coarser production density of Xueming carbon iron or porphyrite. If the above-mentioned hot-rolled steel sheet is used, it is considered that the precipitation density of snow-minded carbon iron and/or boryliron at the grain boundary after cold rolling and annealing will decrease. In addition, if the rolling shrinkage ratio of Ar3+100°C or less is 25% or less, it can be considered that the grain size of the hot-rolled steel sheet becomes coarse and the r value decreases. In order to ensure the press formability, the r value of the rolling direction after cold rolling and annealing, or the r value of the rolling direction and the direction orthogonal to the rolling direction (hereinafter referred to as the orthogonal direction) is suitable To be 0.8 or more, in order to achieve the above, the reduction ratio of Ar3+100°C or less must be greater than 25%. After the hot rolling, pickling etc. will be implemented to remove the scale formed on the surface, and the method and conditions are not specifically specified.

對熱軋延後的熱軋鋼板會進行冷軋延。冷軋延之軋縮率(冷軋率)並未特別規定，只要以適合各個冷軋延機之條件來進行軋延即可。通常，軋縮率宜為50~90%。The hot-rolled steel sheet after hot rolling is cold-rolled. The reduction ratio (cold rolling ratio) of the cold rolling is not particularly specified, as long as the rolling is performed under conditions suitable for each cold rolling mill. Generally, the reduction ratio should be 50~90%.

對冷軋延後之冷軋鋼板進行連續退火。連續退火步驟係會對鐵碳化物之形成造成影響之重要步驟。就退火溫度，係以700~850℃之範圍較為理想。若在700℃以上之溫度下進行退火，晶粒內的微細雪明碳鐵量便會熔解而減少，而可控制成不產生氣泡缺陷的程度之析出量。若退火溫度低於700℃，雪明碳鐵之熔解便不充分。另一方面，若在高於850℃下進行退火，鐵碳化物就會過度熔解，導致對抗鱗狀破面性具有效果之大小的雪明碳鐵及波來鐵變得難以殘留。有關升溫速度，從會發生鐵碳化物之熔解之650℃起至退火溫度為止之升溫速度若過快，鐵碳化物之熔解就少，而殘留許多微細之晶粒內碳化物，故容易產生氣泡缺陷。因此，從650℃起至退火溫度為止之升溫速度在50℃/s以下較為理想。關於連續退火，琺瑯用鋼板之製造法中有時亦會進行脫碳退火，該脫碳退火係採用OCA(鬆捲退火；Open Coil Anneling)並提高氣體環境中之露點，而本實施形態中並不進行脫碳退火。其理由係因一旦施行脫碳退火，鋼中的碳濃度便會降低並且碳化物會消失，而無法確保本實施形態之鋼板設為目標之碳化物狀態。此情況下，便無法抑制肥粒鐵之晶粒成長，有時無法獲得充分強度。而在例如含體積濃度3%之氫、剩餘部分為氮且露點為-40℃之氣體環境下進行退火。Continuous annealing is performed on the cold rolled steel sheet after the cold rolling. The continuous annealing step is an important step that affects the formation of iron carbides. As for the annealing temperature, the range of 700~850℃ is ideal. If annealing is performed at a temperature above 700°C, the amount of fine snow carbon iron in the crystal grains will be melted and reduced, and the amount of precipitation can be controlled to a level that does not produce bubble defects. If the annealing temperature is lower than 700°C, the melting of Xueming carbon iron will be insufficient. On the other hand, if the annealing is performed at a temperature higher than 850°C, the iron carbides will be excessively melted, which makes it difficult to retain the scaly carbon iron and the scaly iron, which are effective in resisting scale fracture. Regarding the heating rate, if the heating rate from 650°C where the melting of iron carbides occurs to the annealing temperature is too fast, the melting of iron carbides will be less, and many fine intra-grain carbides will remain, so bubbles are likely to be generated defect. Therefore, the heating rate from 650°C to the annealing temperature is preferably 50°C/s or less. Regarding continuous annealing, decarburization annealing is sometimes performed in the manufacturing method of steel sheets for enamel. The decarburization annealing system adopts OCA (Open Coil Anneling) and increases the dew point in the gas environment. However, this embodiment does not No decarburization annealing is performed. The reason is that once the decarburization annealing is performed, the carbon concentration in the steel will decrease and the carbides will disappear, and it is impossible to ensure that the steel sheet of this embodiment is set to the target carbide state. In this case, the grain growth of fat iron cannot be suppressed, and sometimes sufficient strength cannot be obtained. For example, annealing is performed in a gas environment containing 3% hydrogen by volume, nitrogen as the remainder, and a dew point of -40°C.

於連續退火後進行過時效處理時，宜在200℃~500℃之溫度區下維持20s(秒)以上。在此情況下，位於肥粒鐵之晶粒的晶界之雪明碳鐵會成長，而可獲得抗鱗狀破面性之提升。在要進行過時效處理的情況下，熱軋延時之捲取溫度係如前所述以500℃以上為宜。當過時效處理溫度低於200℃時，位於晶界之雪明碳鐵之成長效果不充分，若高於500℃，則晶界之雪明碳鐵會大幅成長，導致晶界之雪明碳鐵變得過大。當不進行過時效處理時，宜將熱軋延時之捲取溫度設為550℃以上。When the aging treatment is performed after continuous annealing, it should be maintained at a temperature range of 200℃~500℃ for more than 20s (seconds). In this case, the Xueming carbon iron located at the grain boundary of the fertilized iron grains will grow, and the resistance to scaly cracking can be improved. In the case of aging treatment, the coiling temperature of the hot rolling delay is preferably 500℃ or more as mentioned above. When the over-aging treatment temperature is lower than 200℃, the growth effect of the Xueming carbon iron at the grain boundary is not sufficient. If it is higher than 500℃, the Xueming carbon iron at the grain boundary will grow substantially, resulting in the Xueming carbon iron at the grain boundary. Become too big. When the aging treatment is not carried out, the coiling temperature of the hot rolling delay should be set to 550℃ or higher.

之後，以控制形狀為主要目的而施行調質軋延。在調質軋延中，在控制形狀的同時，還利用調質軋延率在鋼板中導入應變。此時，若調質軋延率變大，亦即導入鋼板中之應變量變多，則會助長熔接或琺瑯處理時之異常晶粒成長。因此，調質軋延率係以可控制形狀之軋延率為上限，不宜賦予所需以上之應變。從控制形狀的觀點看來，調質軋延之軋延率宜在2%以下。After that, temper rolling is performed for the main purpose of shape control. In temper rolling, while controlling the shape, the temper rolling rate is also used to introduce strain into the steel sheet. At this time, if the quenching and tempering rolling rate becomes larger, that is, the amount of strain introduced into the steel plate becomes larger, it will promote abnormal grain growth during welding or enamel processing. Therefore, the tempering rolling rate is the upper limit of the rolling rate of the controllable shape, and it is not suitable to impart more than the required strain. From the point of view of shape control, the rolling rate of quenched and tempered rolling should be less than 2%.

藉由以上，便能製得具有所欲特性之冷軋鋼板。而所得鋼板可作為琺瑯製品之基材之琺瑯用鋼板來加以使用。Through the above, a cold rolled steel sheet with desired characteristics can be obtained. The obtained steel plate can be used as a steel plate for enamel as the base material of enamel products.

另外，本實施形態之鋼板係在加工成預定形狀後，藉由熔接等組裝成製品形狀，並且施以琺瑯處理(燒成處理)，藉此製成琺瑯製品。關於琺瑯處理，只要例如將塗佈有釉藥之鋼板加熱至預定溫度，並維持預定時間，藉此使釉藥之玻璃質與鋼板密著即可。就本實施形態之鋼板之較佳燒成處理條件，係以譬如燒成溫度750~900℃、燒成時間1.5~10分鐘(在爐)之範圍為佳。並且，為了2次塗工及補修，亦可重複數次燒成。藉由在上述條件下進行燒成處理，會變得可利用固溶C及鐵碳化物來抑制琺瑯處理中之晶粒成長，而可抑制強度降低。此處所示燒成處理之條件僅為例示，並非用以限定本實施形態之鋼板之琺瑯處理條件者。In addition, the steel plate of the present embodiment is processed into a predetermined shape, assembled into a product shape by welding or the like, and subjected to an enamel treatment (firing treatment) to produce an enamel product. Regarding the enamel treatment, for example, the steel plate coated with the glaze is heated to a predetermined temperature and maintained for a predetermined time, thereby making the glass of the glaze adhere to the steel plate. As for the preferable firing treatment conditions of the steel plate of this embodiment, for example, the firing temperature is 750 to 900° C., and the firing time is 1.5 to 10 minutes (in the furnace). In addition, the firing can be repeated several times for two coats and repairs. By performing the firing treatment under the above-mentioned conditions, solid solution C and iron carbide can be used to suppress the growth of crystal grains in the enamel treatment, and the decrease in strength can be suppressed. The conditions of the firing treatment shown here are only examples, and are not intended to limit the enamel treatment conditions of the steel sheet of this embodiment.

實施例以轉爐熔製表1-1A~表1-3B及表1-4A~表1-4B所示化學組成(剩餘部分為Fe及不純物)之鋼，並藉由連續鑄造製成鋼胚。並且以表2所記載之條件將該等鋼胚製成鋼板。亦即，在加熱鋼胚後，進行粗軋延及精整軋延，並進行捲取而製出熱軋鋼板。然後，在酸洗熱軋鋼板後，改變冷軋延之軋延率以製成冷軋鋼板，並進一步在含體積濃度3%之氫、剩餘部分為氮且露點為-40℃之氣體環境下施行連續退火後，施行調質軋延，製成板厚0.8mm之鋼板。為了使調質軋延後之板厚一定，相對於冷軋延之軋延率改變了熱軋鋼板之板厚。針對一部分的鋼板，於退火後進行了過時效處理。另，Ar3係以上述式(a)計算，使用該值設定了Ar3+100℃以下(Ar3以上)之軋縮率。製法No.C1~C13中，Ar3+100℃以下之軋縮率之目標設為30%以上，而製法No.C14中，軋縮率之目標設為25%。而實際上係成為如表3-1~表3-4所示軋縮率。另外，透過觀察熱軋鋼板之微觀組織，根據有無產生粗大晶粒來確認了與Ａr3點之關係。具體而言，係將平均粒徑成為板寬中心且板厚中心之平均粒徑的1.5倍以上之晶粒判斷為粗大晶粒。可認為表2所示製法No.C1~C14之熱軋延精加工溫度皆在Ar3~1000℃之範圍內。另，表2中之加熱速度為650℃~退火溫度為止之加熱速度。Example The steel with the chemical composition shown in Table 1-1A~Table 1-3B and Table 1-4A~Table 1-4B (the remaining part is Fe and impurities) is melted by a converter, and the steel blank is made by continuous casting. The steel blanks were made into steel sheets under the conditions described in Table 2. That is, after heating the steel billet, rough rolling and finishing rolling are performed, and coiling is performed to produce a hot-rolled steel sheet. Then, after pickling the hot-rolled steel sheet, the elongation rate of the cold-rolled steel sheet is changed to make the cold-rolled steel sheet, and further under a gas environment containing 3% hydrogen by volume concentration, nitrogen as the remainder and a dew point of -40°C After continuous annealing, quenched and tempered rolling is performed to produce a steel plate with a thickness of 0.8mm. In order to make the thickness of the hot-rolled steel sheet constant, the thickness of the hot-rolled steel sheet is changed from that of the cold-rolled rolling. For some steel plates, over-aging treatment is carried out after annealing. In addition, Ar3 is calculated by the above-mentioned formula (a), and the reduction ratio of Ar3+100°C or less (Ar3 or more) is set using this value. In production method No. C1 to C13, the target reduction ratio of Ar3+100°C or less is set to 30% or more, while in production method No. C14, the target reduction ratio is set to 25%. In fact, the reduction ratio is as shown in Table 3-1 to Table 3-4. In addition, by observing the microstructure of the hot-rolled steel sheet, the relationship with the Ar3 point was confirmed based on the presence or absence of coarse grains. Specifically, a crystal grain having an average particle size at the center of the plate width and 1.5 times or more the average particle diameter of the center of the plate thickness is judged to be coarse crystal grains. It can be considered that the hot rolling finishing temperature of No. C1~C14 shown in Table 2 is in the range of Ar3~1000℃. In addition, the heating rate in Table 2 is the heating rate from 650°C to the annealing temperature.

對上述中製得之鋼板，以下述所示各種方法實施了特性之評估。The properties of the steel plates prepared in the above were evaluated by various methods shown below.

>機械特性> 機械特性係依據JIS Z2241：2011，使用JIS5號試驗片進行拉伸試驗，測定拉伸強度(Rm)及致斷延伸率(A)。從強度的觀點看來，係將拉伸強度在300MPa以上者判斷為具有充分強度，而從成形性的觀點看來，係將致斷延伸率在30%以上者判斷為成形性優異。另外，依據JIS Z2254：2008測定了r值(塑性應變比)，該r值係以與軋延方向成平行、及與軋延方向成直角的方式採取了試驗片時之值。測定之結果，除了後述d38之外，軋延方向與正交方向之r值兩者皆在0.8以上。>Mechanical Characteristics> The mechanical properties are based on JIS Z2241: 2011, and a JIS No. 5 test piece is used for a tensile test to measure the tensile strength (Rm) and elongation at break (A). From the standpoint of strength, those with a tensile strength of 300 MPa or more are judged to have sufficient strength, and from the standpoint of formability, those with a breaking elongation of 30% or more are judged to be excellent in formability. In addition, the r value (plastic strain ratio) was measured in accordance with JIS Z2254:2008, and the r value is a value when a test piece is taken so as to be parallel to the rolling direction and at right angles to the rolling direction. As a result of the measurement, except for d38 described later, the r values in both the rolling direction and the orthogonal direction were 0.8 or more.

>金屬組織(肥粒鐵、雪明碳鐵、波來鐵)之觀察> 鋼中之析出物係藉由在研磨與冷軋延方向成平行之截面後，以苦味酸蝕劑進行腐蝕，並以光學顯微鏡進行觀察，以針對存在於肥粒鐵晶粒內之雪明碳鐵、與存在於晶界之雪明碳鐵及/或波來鐵進行測定。亦即，在研磨鋼板之軋延方向截面後，以苦味酸蝕劑進行了腐蝕。作為鋼板組織(金屬組織)之代表點，觀察了從表面起在板厚方向上1/4板厚t的位置(1/4t)之部位。雪明碳鐵及波來鐵在以光學顯微鏡觀察時係顯現為黑色對比。並且，藉由調整苦味酸蝕劑腐蝕的程度，使肥粒鐵晶界顯現，以判定雪明碳鐵、波來鐵之觀察位置與晶界之關係。觀察係以400~1000倍之倍率進行。於晶界析出之雪明碳鐵在晶界三接點連接時，係測定於各晶界之邊析出之雪明碳鐵的長度並加以合計。若為波來鐵，有時會被多個肥粒鐵晶粒包圍，在此情況下亦視為存在於肥粒鐵晶界而測定個數。於圖1示出測定例之示意圖。雪明碳鐵和波來鐵之個數密度係將所觀察到的個數除以觀察面積而得之值，其單位定為個/μm² 。 D1~D89、d1~d46皆為作為金屬組織係含有肥粒鐵、位於肥粒鐵晶粒內之雪明碳鐵、位於肥粒鐵晶界之雪明碳鐵及/或波來鐵之例。>Observation of metal structure (ferrite iron, snow carbon iron, pleite iron)> The precipitation in steel is corroded by bitter acid after grinding a section parallel to the cold rolling direction, and Observation was carried out with an optical microscope, and the determination was carried out for the Xueming carbon iron existing in the ferrite grains, and the Xueming carbon iron and/or boring iron existing in the grain boundaries. That is, after grinding the cross section in the rolling direction of the steel sheet, it was corroded with a bitter etching agent. As a representative point of the steel plate structure (metal structure), the position (1/4t) of the 1/4 plate thickness t in the plate thickness direction from the surface was observed. Snow carbon iron and pleite appear as black contrast when observed with an optical microscope. In addition, by adjusting the degree of corrosion of the bitter acid, the grain boundaries of the ferrite grains are displayed, so as to determine the relationship between the observation positions of the Xueming carbon iron and the porphyrite and the grain boundaries. The observation system is performed at a magnification of 400 to 1000 times. When the Xueming carbon iron precipitated at the grain boundary is connected at the three junctions of the grain boundary, the length of the Xueming carbon iron precipitated on the sides of each grain boundary is measured and totaled. In the case of pleite, it is sometimes surrounded by multiple ferrite grains. In this case, it is considered to be present at the ferrite grain boundary and the number is measured. The schematic diagram of the measurement example is shown in FIG. The number density of Xueming Carbon Iron and Polly Iron is the value obtained by dividing the observed number by the observation area, and the unit is set as pieces/μm ² . D1~D89, d1~d46 are all examples of metal structure containing ferrous iron, snow carbon iron located in the grains of the fertilizer iron, snow carbon iron and/or bolly iron located in the grain boundaries of the fertilizer iron .

肥粒鐵之平均結晶粒徑，係以JIS G0551：2013附錄B中記載之使用方形試驗線之方法，求算1個晶粒之平均結晶面積，算出為等效圓直徑。亦即，若令平均結晶面積為a，則平均結晶粒徑d設為以下述式(5)所示之值。The average crystal grain size of ferrous iron is calculated by the method of using a square test line as described in JIS G0551:2013 Appendix B to calculate the average crystal area of one crystal grain and calculate it as the equivalent circle diameter. That is, if the average crystal area is a, the average crystal grain size d is set to a value represented by the following formula (5).

d=2√(a/π) ・・・式(5)d=2√(a/π) ・・・Equation (5)

>琺瑯處理後之強度特性> 另外，評估了琺瑯處理後之晶粒成長所致之強度降低情形。具體而言，係將鋼板在爐溫830℃下施行4分鐘之模擬了琺瑯處理之熱處理，並且與上述同樣藉由拉伸試驗求算拉伸強度，而求出相對於熱處理前強度之熱處理後強度的比率，該鋼板係經施行軋縮率10%之冷軋延以模擬壓製加工。當琺瑯處理後之拉伸強度為琺瑯處理前之拉伸強度的0.85(85%)以上時，即判斷為已抑制琺瑯處理後之強度降低。>Strength characteristics after enamel treatment> In addition, the strength reduction caused by the grain growth after the enamel treatment was evaluated. Specifically, the steel plate is subjected to a heat treatment that simulates enamel treatment at a furnace temperature of 830°C for 4 minutes, and the tensile strength is calculated by the tensile test in the same manner as above, and the heat treatment is calculated relative to the strength before the heat treatment. In terms of strength ratio, the steel plate is subjected to cold rolling with a reduction ratio of 10% to simulate pressing. When the tensile strength after enamel treatment is 0.85 (85%) or more of the tensile strength before enamel treatment, it is judged that the strength decrease after enamel treatment has been suppressed.

另外，琺瑯特性係以下述方式進行調查。 >抗鱗狀破面性> 抗鱗狀破面性係對以下之物實施評估：使用100×150mm尺寸之鋼板，利用粉體靜電塗裝法以乾式塗佈100μm之釉藥後，於大氣中在爐溫830℃下進行5分鐘的燒成而成者。將琺瑯處理後之鋼板放入160℃的恆溫槽中10小時，進行鱗狀破面促進試驗，並且利用目視以以下4階段判定鱗狀破面發生狀況：A：優異、B：稍優、C：普通、及D：有問題，若為A、B及C便判斷為已確保了預定抗鱗狀破面性，並且以D評價時為不合格。具體而言，A係完全無發生鱗狀破面的情況，B係發生1~5個鱗狀破面的情況，C係發生6~15個鱗狀破面的情況，D則係發生15個以上鱗狀破面的情況。In addition, the enamel properties were investigated in the following manner. >Anti-scaly broken surface> Anti-scaly cracking performance is evaluated for the following: use a steel plate with a size of 100×150mm, dry coating a 100μm glaze by a powder electrostatic coating method, and perform 5 in the atmosphere at a furnace temperature of 830℃ Burned in minutes. Place the enamel-treated steel plate in a constant temperature bath at 160°C for 10 hours to conduct a scale fracture promotion test, and visually determine the occurrence of scale fracture in the following four stages: A: excellent, B: slightly excellent, C : Normal, and D: There is a problem. If it is A, B, and C, it is judged that the predetermined anti-scaly cracking property has been ensured, and when it is evaluated as D, it is unqualified. Specifically, there were no scaly fractures in line A, 1-5 scaly fractures in line B, 6-15 scaly fractures in line C, and 15 scaly fractures in line D. The above scaly broken face.

>琺瑯密著性> 琺瑯密著性因經與上述同樣進行琺瑯處理後之鋼板在一般進行之P.E.I.密著試驗方法(ASTM C313-59)下於密著性並無差異，故係從1m的高度使2kg之球頭重物落下3次後，以169根觸診針測量變形部之琺瑯剝離狀態，並且以未剝離部之面積率進行評估。只要未剝離部之面積率在40%以上，便判斷為具有充分之琺瑯密著性。>Enamel adhesion> Enamel Adhesion Since the steel plate subjected to the same enamel treatment as above has no difference in adhesion under the general PEI adhesion test method (ASTM C313-59), the ball head weighs 2kg from a height of 1m. After the object was dropped 3 times, the enamel peeling state of the deformed part was measured with 169 palpation needles, and the area ratio of the unpeeled part was evaluated. As long as the area ratio of the unpeeled part is more than 40%, it is judged to have sufficient enamel adhesion.

>外觀> 琺瑯處理後之外觀係將經與上述同樣進行琺瑯處理後之鋼板進行目視觀察，觀察氣泡及黑點的狀況，並以A：非常優異、B：優異、C：一般、D：稍差及E：非常差之5個階段來評估，若為A、B、C及D便判斷為已獲得預定外觀，並以評估為非常差之E時為不合格。>Appearance> The appearance after the enamel treatment is to visually observe the steel plate after the same enamel treatment as above to observe the condition of bubbles and black spots. A: very excellent, B: excellent, C: fair, D: slightly poor and E : Very poor evaluation in 5 stages, if it is A, B, C, and D, it is judged that the predetermined appearance has been obtained, and the evaluation is very bad E as unqualified.

評估結果顯示於表3-1～3-4。No.D1~D89中，鋼成分、碳化物之析出狀態及BN之析出狀態在本發明範圍內，而顯示出良好特性。The evaluation results are shown in Tables 3-1 to 3-4. In Nos. D1 to D89, the steel composition, the precipitation state of carbides, and the precipitation state of BN are within the scope of the present invention, and they show good characteristics.

No.d1因鋼板之C含量少，另No.d2因C含量過多，故機械特性差。 No.d3因鋼板之Si含量少，另No.d4因Si含量過多，故機械特性差。 No.d5因鋼板之Mn含量少，故抗鱗狀破面性降低。 No.d6因鋼板之Mn含量過多，故機械特性差。 No.d7因鋼板之P含量少，另No.d8因P含量過多，故機械特性差。 No.d9因鋼板之S含量少，故抗鱗狀破面性降低。 No.d10因鋼板之Al含量少，另No.d11因Al含量過多，故機械特性差。 No.d12因鋼板之B含量少，故抗鱗狀破面性降低。另，No.d13因B含量過多，故機械特性差。 No.d14因鋼板之N含量少，故抗鱗狀破面性降低。 No.d15因鋼板之N含量過多，故機械特性差。 No.d16因鋼板之Ti含量過多，故抗鱗狀破面性降低。 No.d17~d20因A群元素(Nb、Zr、V、Mo、W)之含量未滿足發明範圍，另d21因鋼板之B群元素(Cr、Ni)之含量未滿足發明範圍，故機械特性差。 No.d22及d23因鋼板之化學成分未滿足(1)式，故抗鱗狀破面性降低。 No.d24及d25因鋼板之化學成分未滿足(2)式，故機械特性差。No. d1 has less C content in the steel plate, and No. d2 has too much C content, so the mechanical properties are poor. No. d3 has low Si content in the steel plate, and No. d4 has too much Si content, so the mechanical properties are poor. No. d5 has a low Mn content in the steel plate, so the scaly crack resistance is reduced. No. d6 has too much Mn content in the steel sheet, so its mechanical properties are poor. No. d7 has low P content in the steel plate, and No. d8 has too much P content, so the mechanical properties are poor. No. d9 has a low S content in the steel plate, so the resistance to scaly cracking is reduced. No. d10 has a small Al content in the steel plate, and No. d11 has too much Al content, so the mechanical properties are poor. No. d12 has a low B content in the steel plate, so the resistance to scaly cracking is reduced. In addition, No. d13 had too much B content, so its mechanical properties were poor. No. d14 has low N content in the steel plate, so the resistance to scaly cracking is reduced. No. d15 has too much N content in the steel sheet, so its mechanical properties are poor. No. d16 has too much Ti content in the steel plate, so the scaly crack resistance is reduced. No. d17~d20 because the content of group A elements (Nb, Zr, V, Mo, W) does not meet the scope of the invention, and d21 because the content of group B elements (Cr, Ni) of the steel plate does not meet the scope of the invention, mechanical properties difference. In No. d22 and d23, the chemical composition of the steel sheet did not satisfy the formula (1), so the resistance to scaly cracking was reduced. No. d24 and d25 have poor mechanical properties because the chemical composition of the steel sheet does not satisfy the formula (2).

No.d26~d37為：雖鋼成分在本發明範圍內，但製造條件超出較佳範圍外，故碳化物之析出狀態及BN之析出狀態成為超出本發明範圍外，而無法獲得良好機械特性及琺瑯特性之示例。 No.d26、d29之鋼胚加熱溫度低，導致變得容易生成BN，且以固溶B之形態殘留之B含量降低，而(3)式不成立，機械特性差。 No.d27、d30之熱軋延後之捲取溫度低，於熱軋延時生成之雪明碳鐵及波來鐵的尺寸變小，導致肥粒鐵晶粒內之雪明碳鐵個數密度過高，而外觀差。 No.d28之過時效溫度高，使得晶界之雪明碳鐵大幅成長，晶界之雪明碳鐵變得過大，因此造成肥粒鐵晶界之雪明碳鐵及波來鐵之個數密度不足，抗鱗狀破面性降低。 No.d31因退火時之加熱速度超過上限，另d32因退火溫度過低，故肥粒鐵晶粒內之雪明碳鐵個數密度過高，而外觀差。 No.d33、d36因捲取溫度高，另d34因退火溫度過高，故肥粒鐵晶界之雪明碳鐵及波來鐵的個數密度不足，抗鱗狀破面性降低。 No.d35之捲取溫度低，於熱軋延時生成之雪明碳鐵及波來鐵的尺寸變小，導致肥粒鐵晶粒內之雪明碳鐵個數密度過高，而外觀差。 No.d37因過時效溫度落在低位而晶界之雪明碳鐵不會成長，導致規定範圍之雪明碳鐵及波來鐵的個數密度在下限以下，而抗鱗狀破面性差。 No.d38因從(Ar3+100)℃至Ar3之溫度範圍中之軋縮率並不充分，故雪明碳鐵及波來鐵之晶界個數密度變小。並且軋延方向之r值小於0.8，而落在低位。No. d26~d37 are: Although the steel composition is within the scope of the present invention, but the manufacturing conditions are outside the preferred range, the precipitation state of carbides and the precipitation state of BN are outside the scope of the present invention, and good mechanical properties and cannot be obtained. Examples of enamel properties. The steel billets of No. d26 and d29 have low heating temperature, which makes it easy to produce BN, and the content of B remaining in the form of solid solution B is reduced. However, the formula (3) does not hold and the mechanical properties are poor. The coiling temperature of No.d27 and d30 after hot rolling is low, and the size of Xueming carbon iron and plastered iron produced during the hot rolling delay time become smaller, resulting in the number density of Xueming carbon iron in the ferrite grains. Too high and poor appearance. The high over-aging temperature of No.d28 makes the Xueming carbon iron at the grain boundary grow significantly, and the Xueming carbon iron at the grain boundary becomes too large, which results in the number of Xueming carbon iron and bolite iron at the grain boundary of the fertilizer grain. Insufficient density and reduced resistance to scaly cracking. No. d31 is because the heating rate during annealing exceeds the upper limit, and d32 is because the annealing temperature is too low, so the number density of Xueming carbon iron in the ferrite grain is too high, and the appearance is poor. Due to the high coiling temperature of No. d33 and d36, and the high annealing temperature of d34, the number density of snow carbon iron and plastered iron at the grain boundary of the fertile iron is insufficient, and the resistance to scaly cracking is reduced. The coiling temperature of No.d35 is low, and the size of the Xueming Carbon Iron and Bory Iron that are formed after the hot rolling delay becomes smaller, resulting in the high number density of Xueming Carbon Iron in the ferrite grains and poor appearance. No. d37 due to the low temperature of the over-aging temperature and the crystal boundary of the Xueming carbon iron will not grow, resulting in the specified range of Xueming carbon iron and plastered iron number density below the lower limit, and poor resistance to scale fracture. No. d38 has insufficient rolling shrinkage in the temperature range from (Ar3+100)°C to Ar3, so the number density of the grain boundary of Xueming Carbon Iron and Bory Iron is reduced. And the value of r in the rolling direction is less than 0.8, which is low.

另外，No.d39~d46因C群元素(As、Se、Ta、Sn、Sb、Ca、Mg、Y及REM)之含量未滿足發明範圍，故機械特性差。In addition, No. d39 to d46 have poor mechanical properties because the content of C group elements (As, Se, Ta, Sn, Sb, Ca, Mg, Y, and REM) does not meet the invention range.

根據表3-1~表3-4之結果，可確認到以本發明鋼之範圍可提供一種琺瑯用鋼板，其琺瑯密著性、產生氣泡等之外觀及抗鱗狀破面性優異，並且可抑制琺瑯處理所致之後續之拉伸強度降低的情形。According to the results of Table 3-1 to Table 3-4, it can be confirmed that a steel sheet for enamel can be provided within the scope of the steel of the present invention, which has excellent enamel adhesion, appearance such as bubbles, and resistance to scaly cracking, and It can suppress the subsequent decrease in tensile strength caused by the enamel treatment.

[表1-1A]

[Table 1-1A]

[表1-1B]

[Table 1-1B]

[表1-2A]

[Table 1-2A]

[表1-2B]

[Table 1-2B]

[表1-3A]

[Table 1-3A]

[表1-3B]

[Table 1-3B]

[表1-4A]

[Table 1-4A]

[表1-4B]

[Table 1-4B]

[表2]

[Table 2]

[表3-1]

[Table 3-1]

[表3-2]

[Table 3-2]

[表3-3]

[Table 3-3]

[表3-4]

[Table 3-4]

產業上之可利用性本發明上述態樣之鋼板於琺瑯處理後，在應用於廚房用品、建材及能源領域等時，具優異成形性、琺瑯處理後之抗鱗狀破面性及強度特性。因此，其適合作為琺瑯用鋼板，產業上之可利用性高。Industrial availability The steel sheet of the above aspect of the present invention has excellent formability, anti-scaly cracking properties and strength characteristics after enamel treatment when it is applied to kitchenware, building materials and energy fields. Therefore, it is suitable as a steel sheet for enamel and has high industrial applicability.

圖1係示出存在於晶界上之雪明碳鐵及波來鐵之長徑之測定例的圖。Fig. 1 is a diagram showing a measurement example of the long axis of the snow carbon iron and the plasterite present on the grain boundary.

Claims

一種鋼板，其特徵在於：其化學組成以質量%計含有以下元素：C：0.0050~0.0700%、Si：0.0010~0.0500%、Mn：0.0500~1.0000%、P：0.0050~0.1000%、S：0.0010~0.0500%、Al：0.007~0.100%、O：0.0005~0.0100%、B：0.0003~0.0100%、N：0.0010~0.0100%、Ti：0~0.0100%、Nb、Zr、V、Mo及W中之1種或2種以上：合計0.0020~0.0300%、Cu：0~0.045%、Cr、Ni之1種或2種：合計0~1.000%、及As、Se、Ta、Sn、Sb、Ca、Mg、Y及REM中之1種或2種以上：合計0~0.1000%，且剩餘部分由Fe及不純物所構成，並且滿足式(1)及式(2)；前述鋼板之金屬組織含有：肥粒鐵；位於前述肥粒鐵晶粒內之雪明碳鐵；以及，位於前述肥粒鐵晶界之雪明碳鐵及波來鐵之1種或2種；於前述肥粒鐵之前述晶粒內，粒徑0.3~1.5μm之雪明碳鐵係以個數密度為1.00×10^-1個/μm²以下之範圍存在；於前述肥粒鐵之前述晶界，存在有雪明碳鐵及波來鐵之1種或2種，且其等之長徑之平均值為0.5~15μm、個數密度為5.00×10^-4~1.00×10^-1個/μm²；並且BN中含有之N含量即[N as BN]與鋼中含有之B含量之關係滿足式(3)；Ti<(N-0.0003)×3.43‧‧‧式(1) C>0.25×Ti+0.129×Nb+0.235×V+0.132×Zr+0.125×Mo+0.0652×W+0.0040‧‧‧式(2) [N as BN]/(1.27×B)<0.95‧‧‧式(3)惟，式(1)~(3)中之元素符號表示該元素以質量%計之含量，式(3)中之[N as BN]則表示BN中含有之以質量%計之N含量。 A steel plate characterized in that its chemical composition contains the following elements in mass %: C: 0.0050~0.0700%, Si: 0.0010~0.0500%, Mn: 0.0500~1.0000%, P: 0.0050~0.1000%, S: 0.0010~ 0.0500%, Al: 0.007~0.100%, O: 0.0005~0.0100%, B: 0.0003~0.0100%, N: 0.0010~0.0100%, Ti: 0~0.0100%, 1 of Nb, Zr, V, Mo and W One or two or more types: 0.0020~0.0300% in total, Cu: 0~0.045%, one or two of Cr, Ni: 0~1.000% in total, and As, Se, Ta, Sn, Sb, Ca, Mg, One or more of Y and REM: 0~0.1000% in total, and the remainder is composed of Fe and impurities, and satisfies formula (1) and formula (2); the metal structure of the aforementioned steel plate contains: Fertilizer iron ; Xueming carbon iron located in the aforementioned fertile iron grains; and, one or two types of Xueming carbon iron and polished iron located in the aforementioned fertile iron grain boundaries; in the aforementioned grains of the aforementioned fertilizer iron , Xueming carbon iron with a particle size of 0.3~1.5μm exists in the range of number density of 1.00×10 ^-1 pieces/μm ² or less; in the aforementioned grain boundaries of the fertilizer grain iron, there are Xueming carbon iron and wave One or two kinds of iron, and the average value of its major diameter is 0.5~15μm, the number density is 5.00×10 ^-4 ~1.00×10 ^-1 pieces/μm ² ; and the N content contained in BN That is, the relationship between [N as BN] and the B content in steel satisfies formula (3); Ti<(N-0.0003)×3.43‧‧‧ formula (1) C>0.25×Ti+0.129×Nb+0.235×V +0.132×Zr+0.125×Mo+0.0652×W+0.0040‧‧‧ formula (2) [N as BN]/(1.27×B)<0.95‧‧‧ formula (3) However, formulas (1)~(3 The element symbol in) represents the content of the element in mass%, and the [N as BN] in formula (3) represents the N content in mass% in BN.

如請求項1之鋼板，其以質量%計含有Cu：0.010~0.045%。 Such as the steel plate of claim 1, which contains Cu in mass %: 0.010~0.045%.

如請求項1或2之鋼板，其以質量%計含有合計0.005~1.000%之Cr、Ni之1種或2種。 For example, the steel plate of claim 1 or 2 contains one or two types of Cr and Ni in a total of 0.005 to 1.000% by mass%.

如請求項1或2之鋼板，其含有以下中之1種或2種以上元素且以質量%計含有合計0.0005~0.1000%：As、Se、Ta、Sn、Sb、Ca、Mg、Y及REM。 For example, the steel plate of claim 1 or 2, which contains one or more of the following elements and a total of 0.0005~0.1000% by mass: As, Se, Ta, Sn, Sb, Ca, Mg, Y and REM .

如請求項1或2之鋼板，其中前述鋼板為冷軋鋼板。 Such as the steel sheet of claim 1 or 2, wherein the aforementioned steel sheet is a cold rolled steel sheet.

如請求項1或2之鋼板，其中前述鋼板為琺瑯用鋼板。 Such as the steel plate of claim 1 or 2, wherein the aforementioned steel plate is a steel plate for enamel.

如請求項3之鋼板，其含有以下中之1種或2種以上元素且以質量%計含有合計0.0005~0.1000%：As、Se、Ta、Sn、Sb、Ca、Mg、Y及REM。 For example, the steel plate of claim 3, which contains one or more of the following elements and a total of 0.0005 to 0.1000% by mass%: As, Se, Ta, Sn, Sb, Ca, Mg, Y, and REM.

如請求項3之鋼板，其中前述鋼板為冷軋鋼板。 Such as the steel sheet of claim 3, wherein the aforementioned steel sheet is a cold rolled steel sheet.

如請求項3之鋼板，其中前述鋼板為琺瑯用鋼板。 Such as the steel plate of claim 3, wherein the aforementioned steel plate is a steel plate for enamel.

一種琺瑯製品，具備有如請求項1至請求項9中任一項之鋼板。 An enamel product with a steel plate as in any one of claim 1 to claim 9.