JP2006045580A - Plated steel sheet to be enameled with adequate adhesiveness to enamel, manufacturing method therefor and enameled product - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a steel sheet to be enameled which has adequate adhesiveness to enamel, even without being pretreated for enameling and using an expensive glaze containing Ni and Co. <P>SOLUTION: The plated steel sheet to be enameled has a composition comprising, by mass%, 0.070% or less C, 0.50% or less Si, 0.010-0.95% Mn, 0.20% or less P, 0.080% or less S, 0.20% or less Al, 0.070% or less N, 0.070% or less O, further one or more elements among 0.051-8.0% Cu, 0.051-8.0% Ni, 0.051-8.0% Co and 0.051-8.0% Mo, and the balance Fe with unavoidable impurities; and further has a plated film that contains one or more elements of Cu, Ni, Co and Mo, has a coating mass of 0.001 to 5.0 g/m<SP>2</SP>, and is preferentially formed on a concentrated part with Cu, Ni, Co and Mo in the surface of the steel sheet, which is formed by controlling a heat history in a process of manufacturing the steel sheet. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an enameled steel sheet for enamel that exhibits enamelability, particularly good enamel adhesion, even though enamel pretreatment is simple.

  In steel plate enamel, the effectiveness of Ni, Co, etc. existing at the interface between the steel plate and the enamel layer is well known in order to more firmly join the metal plate and glass enamel coating. Before applying the glaze to the steel sheet, a technique called Ni flash is used, in which the steel sheet is immersed in a Ni-containing solution and Ni is deposited on the steel sheet surface.

  In order to omit such enamel pre-treatment process, many methods for plating Ni or the like in the steel sheet manufacturing process have been studied, and improvements by annealing after plating, steel sheet roughness, steel sheet oxidation, chemical conversion treatment, etc. have been disclosed. Yes.

  For example, in Patent Document 1, an alloy containing 0.1% or more of nickel or iron and molybdenum or tungsten or a total amount of 5% or more is included on the surface of a steel material prior to plating. Coating to a thickness of 10 μm is disclosed.

  Patent Document 2 discloses that when enamelling a steel material, the surface is roughened by a mechanical or chemical etching method, and then one or more of Co, Ni, and Fe and one of Mo and W are used. Alternatively, an enamel surface treatment method in which an alloy of two kinds is electroplated is disclosed.

  In Patent Document 3, in the manufacture of an enameled steel plate consisting of cold rolling, annealing, temper rolling, degreasing, pickling, nickel plating, glazing and firing, the steel plate is subjected to laser dull processing in the temper rolling step to obtain roughness. A technique for adjusting the above is disclosed.

  Patent Document 4 discloses an enameled coated steel sheet having a 50 to 1100-thick iron oxide layer on a steel sheet having a surface roughness Rmax of 15 to 60 μm. In particular, both sides of ordinary steel sheets such as SPCC and SPCE 1 It has been shown that a hanging enamel is possible.

  Patent Document 5 discloses a treatment method comprising a first stage of amorphous phosphating and a second stage of nickel plating as a ground treatment method for the metal surface of a steel sheet that is directly enameled after pickling. Yes.

  The technology as described above is basically obtained by simply plating a conventional steel plate for enamel, which has not only a small effect of improving adhesion, but also a steel plate for producing enamel products. When the above processing is performed, the plating of the surface is not a little damaged due to deformation of the steel material or contact with the tool, and the targeted effect is reduced in the processed portion. Thick plating is necessary to avoid such damage, and there are drawbacks such as deterioration in productivity of the plating process and very high manufacturing cost, and it has not been put into practical use.

  On the other hand, as a method of optimizing the role of Ni to the ultimate, the present inventor disclosed a technique for concentrating Ni contained in a steel sheet in Patent Document 6 on the surface of the steel sheet in the steel sheet manufacturing process, and then added further improvements. In addition, a patent application has been filed for a technology that incorporates the idea of actively controlling the form of the Cu, Co, and Mo enriched portions. By applying this surface layer concentration technology, it is possible to easily omit the pickling and Ni treatment just before enameling, which is conventionally performed, or without using expensive glazes containing Ni or Co. It became possible to obtain enamel characteristics.

Japanese Examined Patent Publication No. 54-24413 Japanese Patent Publication No.56-32399 Japanese Patent Publication No. 06-68155 Japanese Patent Publication No. 06-60421 JP 09-111474 A Japanese Patent Application No. 2003-17745

  Even with the improvements described above, there is no particular need to improve enamel adhesion, and in the future, the adhesion of the enamel product manufacturer, that is, the enamel steel plate user, can be simplified while further improving adhesion. Steel plate development is required.

  An object of the present invention is to achieve both low-cost manufacturing and securing of enamel adhesion after processing, which cannot be achieved by conventionally known Ni plating, when enamel pretreatment is simply omitted. And

  The present invention has been developed by the inventors of the present invention by performing plating including these further on a steel plate formed by unevenly distributing a concentrated portion containing one or more of Cu, Ni, Co, and Mo on the steel plate surface. Concentration and uneven distribution of the above elements are further remarkably controlled to greatly improve enamel adhesion. The gist of the present invention is as follows.

Hereinafter, the “specific element” in this specification represents “one or more elements of Cu, Ni, Co, or Mo”. By controlling the concentration of the specific elements on the steel sheet surface formed by segregating the specific elements in the steel and the adhesion of the specific elements due to the plating in this way, it is markedly superior to conventional plated steel sheets. Even if the plating amount is small or the steel plate is damaged during processing, the deterioration of enamel adhesion can be minimized.
(1) By mass%, C: 0.070% or less, Si: 0.50% or less, Mn: 0.010 to 0.95%, P: 0.20% or less, S: 0.080% or less, Al: 0.20% or less, N: 0.070% or less, O: 0.070% or less, further Cu: 0.051-8.0%, Ni: 0.051-8.0%, Co: 0.051 to 8.0%, Mo: 0.051 to 8.0%, at least one of Fe, unavoidable impurities, and at least one of Cu, Ni, Co, and Mo A plated steel sheet for enamel having good enamel adhesion, comprising the above and plated with an adhesion amount of 0.001 to 5.0 g / m ² .
(2) In the enameled steel sheet for enamel according to (1), the concentration of at least one element of Cu, Ni, Co, and Mo is not less than 2.5 times the average content in steel in mass%, and the steel sheet thickness. Enamel adhesion characterized in that a concentrated region satisfying at least one of the three conditions of a thickness in the direction of 0.01 μm or more and a steel sheet surface coverage of 5% or more exists on the steel sheet surface Plated steel for enamel with good properties.
(3) In the enameled steel sheet according to (1) or (2), a concentrated region or an independent non-dense of at least one element of independent Cu, Ni, Co, and Mo having a diameter of 0.1 μm or more. The enameled region has a number density of 0.001 piece / μm ² or more, and is a plated steel plate for enamel having good enamel adhesion.
(4) In the enameled steel sheet for enamel according to any one of (1) to (3), the concentrated portion for at least one element of Cu, Ni, Co, and Mo formed by plating is plated. A plated steel sheet for enamel having good enamel adhesion, characterized in that it is preferentially produced over the surface of the enriched portion of at least one element of Cu, Ni, Co, and Mo existing previously.
(5) The enameled steel sheet for enamel according to any one of (1) to (4), wherein the steel sheet has a surface roughness Ra of 0.20 μm or more and a PPI of 50 or more. Plated steel sheet for enamel with good enamel adhesion.
(6) In the enameled steel sheet for enamel according to any one of (2) to (5), the concentrated part containing at least one of Cu, Ni, Co, and Mo present on the surface of the steel sheet. Is a plated steel sheet for enamel having good enamel adhesion, characterized in that is mainly present on the convex portion on the steel sheet surface.
(7) In the enameled steel sheet for enamel according to any one of (2) to (6), the enriched part containing at least one of Cu, Ni, Co, and Mo present on the surface of the steel sheet. An enameled steel plate for enamel having good enamel adhesion, characterized in that the amount of concentration at the convex portion on the steel sheet surface is greater than the amount of concentration at the concave portion.
(8) When manufacturing the enameled steel sheet for enamel according to any one of (1) to (7), the holding time at 1000 to 1200 ° C. in the heat history in hot rolling slab heating is 40 minutes or more. Holding time at 650 ° C. or higher in coil heat history after cold rolling after finish rolling is 30 minutes or more, and holding time at 20 ° C. or higher in dew point of −20 ° C. or higher and 750 ° C. or higher in heat history of coil after cold rolling A method for producing a plated steel sheet for enamel having good enamel adhesion, wherein at least one of the above conditions is satisfied.
(9) The method for producing an enameled steel sheet for enamel having good enamel adhesion according to (8), characterized in that after the cold rolling step, the acid wash loss is performed at 0.01 g / m ² or more.
(10) The method for producing enameled steel sheet for enamel having good enamel adhesion according to (8) or (9), wherein the plating is performed by substitution plating for 5 seconds or more and 5 minutes or less.
(11) The method for producing a plated steel sheet for enamel having good enamel adhesion according to any one of (8) to (10), wherein plating is performed after pickling.
(12) Manufacturing of enameled steel sheet for enamel with good enamel adhesion according to any one of (8) to (11), wherein annealing is performed at 500 ° C. or more and 2 seconds or more after plating. Method.
(13) The enameled steel sheet for enamel according to any one of (1) to (7) is used as a raw material, and Cu, Ni, Co, and Mo are low in all the processes for producing enamel products before applying enamel glaze. An enamel product characterized by being manufactured without undergoing a surface treatment step in an atmosphere containing at least one kind.
(14) The enameled steel sheet according to any one of (1) to (7) is used as a raw material, and it is produced without passing through the pickling process in all the processes for producing enamel products before applying enamel glaze. Enamel product characterized by that.
(15) An enamel product manufactured using the enameled steel sheet for enamel according to any one of (1) to (7) as a raw material without using a glaze containing 5% or more of Ni or Co.

  The steel plate for enamel of the present invention has good workability and further satisfies all of the resistance to squeezing, the adhesion to the enamel and the surface characteristics necessary for the steel plate for enamel. In particular, Ni treatment and pickling performed on ordinary steel plates for enameling can be easily omitted to increase enamel adhesion, thus reducing costs and improving productivity, and waste liquid treatment accompanying Ni treatment and pickling. Can reduce or eliminate environmental pollution problems. In addition, since good adhesion can be obtained without using expensive glazes containing Ni, Co, etc., the double-hanging enamel can be simplified, cost-reduced, and single-time.

  This will be described in detail below. The content of each component element is mass%.

  Conventionally, it is known that the lower the C, the better the workability and foam resistance. However, in the present invention, in order to obtain good aging resistance, workability and enamelability, the content is made 0.070% or less. There is a need. In applications where the enamel surface quality is severe, such as foam, if it is 0.040% or less, more preferably 0.020% or less, the occurrence of foam or the like is suppressed, and the enamel surface quality is improved. In applications where workability is required, the preferred range is 0.0040% or less, more preferably 0.0020% or less, and even more preferably 0.0015% or less. The lower limit is not particularly limited, but a practical lower limit is 0.0003% because lowering the C content increases the steelmaking cost.

  Ni is a very important element in the present invention because it can improve the enamel adhesion and easily omit the enamel pretreatment by leaving a concentrated portion on the steel surface in the same manner as Cu described later. Since the beneficial effect is hardly detected at about 0.05% or less, the content of which is inevitably contained in a normal steel plate for enamel steel, it is necessary to add it positively. It is the same. In order to obtain a beneficial effect, 0.10% or more must be added, preferably 0.30% or more, more preferably 0.50% or more, and 1.0% or more. If the addition is 2.0% or more, the effect tends to be saturated. Excessive addition is not preferable from the viewpoint of alloy cost, but at the same time, the heterogeneity of the reaction between enamel and steel becomes large, and enamel defects such as black spots are likely to occur, and there is an adverse effect on workability. Therefore, the upper limit is set to 8.0%. Preferably, it is 5.0% or less, and even if it is 3.0% or less, a sufficient effect can be obtained.

  In the present invention, Cu is concentrated in the interface between the scale and the steel by appropriately oxidizing the surface of the steel material in the steel plate manufacturing process or enamel product manufacturing process to form an oxide scale, and then pickling. This is an important element in the present invention because one of the main points is to leave a Cu-enriched portion on the steel surface even after a descaling process such as the above. The effect of the present invention is hardly detected when the content is about 0.050% or less, which is contained for improving the enamel adhesion of an ordinary enamel steel plate, and therefore it is necessary to add it beyond the normal level. In order to sufficiently obtain the effects of the invention, addition of 0.11% or more is necessary, preferably 0.31% or more, more preferably 0.51% or more, and 1.01% or more, a remarkable effect can be obtained. . The effect tends to saturate at an addition of 2.01% or more. Excessive addition is not preferable from the viewpoint of alloy cost, but at the same time, the heterogeneity of the reaction between enamel and steel becomes large, and enamel defects such as black spots are likely to occur, and there is an adverse effect on workability. Therefore, the upper limit is set to 8.0%. Preferably, it is 5.0% or less, and even if it is 3.0% or less, a sufficient effect can be obtained.

  Co can be added in the present invention because Co enrichment sites remain on the steel surface in the same manner as Ni and Cu, so that enamel adhesion can be improved and enamel pretreatment can be simplified. Since the beneficial effect is hardly detected at about 0.05% or less, the content of which is inevitably contained in a normal steel plate for enamel steel, it is necessary to add it positively. It is the same. In order to obtain a beneficial effect, 0.10% or more must be added, preferably 0.30% or more, more preferably 0.50% or more, and 1.0% or more. If the addition is 2.0% or more, the effect tends to be saturated. Excessive addition is not preferable from the viewpoint of alloy cost, but at the same time, the heterogeneity of the reaction between enamel and steel becomes large, and enamel defects such as black spots are likely to occur, and there is an adverse effect on workability. Therefore, the upper limit is set to 8.0%. Preferably, it is 5.0% or less, and even if it is 3.0% or less, a sufficient effect can be obtained.

  Mo can be added in the present invention because Mo enrichment sites remain on the steel surface, as with Ni, Cu and Co, so that enamel adhesion can be improved and the enamel pretreatment can be simplified. . Since the beneficial effect is hardly detected at about 0.05% or less, the content of which is inevitably contained in a normal steel plate for enamel steel, it is necessary to add it positively. It is the same. In order to obtain a beneficial effect, 0.10% or more must be added, preferably 0.30% or more, more preferably 0.50% or more, and 1.0% or more. If the addition is 2.0% or more, the effect tends to be saturated. Excessive addition is not preferable from the viewpoint of alloy cost, but at the same time, the heterogeneity of the reaction between enamel and steel becomes large, and enamel defects such as black spots are likely to occur, and there is an adverse effect on workability. Therefore, the upper limit is set to 8.0%. Preferably, it is 5.0% or less, and even if it is 3.0% or less, a sufficient effect can be obtained.

  The effect of improving the enamel adhesion by Ni, Cu, Co, and Mo (hereinafter referred to as “specific element” in the present invention), which is the object of the present invention, is particularly easy to omit the pickling and Ni treatment immediately before enameling that is usually performed. It becomes noticeable if you do. In other words, if the pickling and Ni treatment just before enameling are performed as usual, the necessary enamel adhesion can be obtained without intentionally containing a high concentration of specific elements according to the present invention. However, it goes without saying that the steel according to the present invention can be applied in the case of carrying out a normal pretreatment in order to obtain much better enamel adhesion than the present state. In addition, the steel of the present invention contains little or no content of Ni or Co when an expensive glaze added with Ni or Co is used to obtain good enamel adhesion even if the enamel pretreatment is simplified. It is also very effective when trying to obtain good enamel adhesion by applying an inexpensive glaze that does not. Such expensive glazes containing Ni and Co are usually used as a double glaze enamel to ensure the adhesion between the steel sheet and the enamel.

  The specific element is concentrated at the interface between the scale and the steel material mainly with the formation of the oxide scale in the manufacturing process of the steel sheet, and then remains on the surface of the steel material and affects the enamel adhesion. However, it is necessary to pay attention, especially when the content of only Cu is high, because the surface defects of the steel sheet may be increased to increase enamel bubble defects and black spots. The cause of this is not clear, but when utilizing the concentration phenomenon associated with scale generation as in the present invention, the Cu concentrated portion melts and the difference between the grain boundary portion of the steel material and the portion that is not the grain boundary becomes noticeable and excessive. It seems that the dark and light shade is formed until it causes surface defects, and the Cu concentration portion covers the entire surface of the interface between the scale and the steel, thereby reducing the wettability of the enamel. However, in the case of Cu containing about 0.5% or less, there is almost no adverse effect as described above, and even when the concentration is higher, it can be avoided by controlling the manufacturing conditions as described later.

  Further, when a considerable amount of Ni, Co or Mo is contained, the adverse effect of the abnormal Cu concentration is hardly observed, and at the same time, a combined concentration form of Cu and Ni, Co or Mo is obtained and has a favorable effect.

  The cause of the effect of coexistence of Cu and Ni, Co, or Mo is not clear, but is considered as follows. When Cu and Ni, Co, or Mo coexist, both elements are similarly concentrated at the interface between the scale and the steel, and the steel surface is covered with islands at appropriate intervals without being covered with a single element. Depending on the type and amount, the reaction between the molten glass and steel during the enamel firing will be different, forming a small local battery and improving the adhesion by forming fine irregularities at the interface between the enamel and the steel plate It seems to be.

  As described above, the local non-uniformity of the concentrated part due to the variation in the type and amount of the concentrated element causes the above-mentioned non-uniform reaction between the molten glass and the steel due to the non-uniformity in the in-plane direction. In addition to forming minute irregularities at the glass-steel interface, it also causes fluctuations in element species and concentration in the depth direction and exhibits the function of so-called gradient materials. It seems to have the effect of solidifying the joint. Of course, the effect of the present invention is not completely lost even if such non-uniformity of the element species and amount is not formed and a homogeneously concentrated portion is formed.

  In the present invention, a specified amount of at least one of Cu, Ni, Co, and Mo is contained. However, considering the functions related to the bonding of glass and steel, Cu and Mo have a similar effect, and Ni and Co tend to have a similar effect. By analogy with general knowledge, Cu and Mo tend to contribute to the improvement of adhesion by being mainly present on the steel side of the glass-steel interface, and Ni and Co are mainly present on the glass side of the glass-steel interface. It exists in the tendency which contributes to adhesiveness improvement by existing. This means that when two elements are contained, it is advantageous from the viewpoint of the effect that one of Cu or Mo and one of Ni or Co are selectively contained. The effect of the invention is not lost by the detailed difference in the combination and the existence form of each element. The detailed mechanism of these elements has not been clarified in general steel plates for enamel, and further elucidation is awaited.

  Since Si hinders the enamel property, it is not necessary to add it intentionally. The smaller the amount, the better. However, it is possible to add the upper limit to 0.5% in order to compensate for the increase in strength. In order to ensure the enamel property above the normal level, it is 0.050% or less, more preferably 0.010% or less.

  Mn is a component that affects the enamel property in relation to oxygen and S content. At the same time, it is an element for preventing hot brittleness caused by S during hot rolling, and in the present invention containing a large amount of oxygen, the content is made 0.01% or more. On the other hand, if the amount of Mn increases, the enamel adhesion deteriorates and bubbles and black spots are likely to be generated. Therefore, the upper limit is made 0.95%. Preferably it is 0.6% or less, More preferably, it is 0.39% or less.

  P can be increased in strength by increasing the content, but is preferably lower in order to suppress defects such as bubbles and black spots during enamel. When the content exceeds 0.20%, the material is remarkably embrittled and it becomes difficult to manufacture. Preferably, it is 0.05% or less, and in order to ensure good enamel performance, it is preferably 0.019% or less, more preferably 0.015% or less, and still more preferably 0.009% or less.

  S increases the amount of smut during pickling in the enamel pretreatment and easily generates bubbles and black spots. Therefore, the content is set to 0.080% or less, preferably 0.030% or less. However, if the amount is too low, the amount of smut becomes too small and the enamel adhesion may deteriorate. Therefore, it is preferably 0.011% or more, more preferably 0.015% or more, and more preferably 0.020% or more. .

  If too much Al is contained, O in the steel, which has a very favorable effect on the resistance to twisting, cannot be controlled within the preferred range. In addition, Al nitride reacts with moisture during enamel firing, generating gas and causing bubble defects, which is not preferable. For this reason, the content is 0.20% or less, more preferably 0.10% or less, more preferably 0.02% or less, more preferably 0.0099% or less, further preferably 0.0049% or less, more preferably It is limited to 0.0039% or less. The lower limit is not particularly limited and may be 0, but 0.0002% or more is contained in a normal production method, and 0.0009% or more is unavoidably contained unless cost is particularly required.

  O is very preferable for improving the toughness, and at the same time affects the enamel adhesion and the bubble resistance / spot resistance in relation to the amount of Mn. In order to exhibit these effects, 0.002%, preferably 0.005% is necessary. On the other hand, if the amount of O becomes excessively high, productivity at the time of steelmaking is lowered and workability of the steel sheet is deteriorated, so the upper limit is specified as 0.070%, more preferably 0.055%. A preferred range is 0.010 to 0.044%, and a more preferred range is 0.021 to 0.034%. O may be 0.002% or less when the toughness is not particularly problematic, or when other carbides, nitrides, sulfides, or composite precipitates thereof exhibit the same effects as oxides.

  N is preferably as small as possible from the viewpoints of workability, aging properties, bubble resistance / spot resistance, but the harm can be reduced by adding an appropriate nitride-forming element. If it is 0.0700% or more, even if a nitride is formed, good characteristics cannot be obtained, so this is the upper limit. In the case where molten steel is produced with normal equipment and solidified to obtain a steel slab, 0.0200% or less is preferable from the quality and operability of the steel slab. More preferably, it is 0.0049% or less, More preferably, it is 0.0039% or less, More preferably, it is 0.0034% or less. On the other hand, excessively lowering not only increases costs but also has a small effect, so it is preferably 0.0006% or more, more preferably 0.0011% or more, and still more preferably 0.0016% or more.

  Nb, V, Ti, Cr, and B are elements that are oxide-forming elements that greatly affect enamelability from the viewpoint of oxide form control, and that can be expected to improve aging and workability with carbonitride-forming elements. is there. These elements do not have any influence on the surface concentration of the specific element, which is a feature of the present invention, and may not be contained at all, or may be contained in an amount inevitable from ores and scraps. Although it is added for improving aging property, workability, etc., Nb: 0.80% or less, preferably 0.2% or less, more preferably 0. 1% or less, more preferably 0.08% or less, V: 0.40% or less, preferably 0.1% or less, more preferably 0.08% or less, more preferably 0.05% or less, Ti: 0 .49% or less, preferably 0.19% or less, more preferably 0.049% or less, more preferably 0.019% or less, further preferably 0.009% or less, more preferably 0.005% or less, Preferably it is 0.003% or less, B: 0.0099% or less, preferably 0.0049% or less, more preferably 0.0029% or less, more preferably 0.0014% or less, more preferably 0.0010% or less, and more preferably less 0.0006%.

  In particular, with regard to Ti, if the content is high, it is difficult to maintain O in the steel having a very favorable effect on the resistance to sticking in the preferred range, so it is preferable to keep the content in a low range of 0.049% or less. As for Cr, in the present invention using the oxide scale, not only the oxidation is remarkably suppressed and the effect of the present invention is not easily exhibited, but the descaling property of the oxide scale is reduced, and the occurrence of enamel defects such as bubbles and black spots is remarkable. It is necessary to avoid excessive addition. The upper limit is 10.0%, preferably 5% or less, more preferably 3% or less, and further 1% or less, and if it is about 0.1% or less, which is usually unavoidably included due to scrap mixing, etc., the effect of the present invention is achieved. No negative effects are seen.

  Further, the addition of trace elements for various purposes in addition to the amount inevitably contained from ore and scrap does not impair the effects of the present invention. Also in this case, at least one of W, Sn, Sb, Mg, Ca, and Ce is made 0.2% or less in total in consideration of cost and enamelability.

  What is important as a factor to be controlled in the present invention is the concentration of a specific element formed on the surface of the steel sheet by the steel sheet manufacturing process including the plating process. In the present invention, the “concentrated portion” of a specific element refers to an element that exists on the surface of a steel sheet before or after plating. The concentrated part of a specific element should generally be said to be a part whose concentration is higher than the average content of the specific element in steel.In the present invention, however, the specific element is specified in consideration of the effect on enamel adhesion and measurement variation. A portion where the concentration in the concentrated portion is 2.5 times or more the concentration in steel with respect to the total of the elements is defined as a concentrated portion of the specific element required in the present invention.

  In the present invention, there may be a case where the specific element species that exists as an additive element in steel and is concentrated on the surface of the steel plate without plating is different from the specific element species formed by plating. Even in such a case, as described later, there is a specific relationship between the positions where these concentrated portions exist, but in consideration of the case where the element types are different, the present invention uses the total concentration of the specific elements. Defines the thickening part. This concentration can be sufficiently observed with the latest analysis equipment such as electron microscope, X-ray analysis, electron beam analysis, ion analysis and the like. Of course, identification is possible by other methods such as chemical analysis.

  Needless to say, when examining measurement data, it is necessary to determine the concentration of a specific element in consideration of not only the area of the measurement region but also the depth of the measurement region when analyzing from the surface. For example, if a film with a specific element of 100% is formed on the surface, but it is very thin, if the component analysis is performed from the surface with an analytical instrument using an electron beam or X-ray, the film will be transmitted. This is a case where a low quantitative value is obtained as the content of the specific element because the components in the region including the base material portion are detected. In the present invention, analysis limited to a spatially sufficiently small region is necessary. Of course, even in a quantitative value obtained by averaging a wide region including a region where the specific element is not concentrated as in the above example, the quantitative value defined in the present invention, for example, the concentration of the specific element is 2 of the average content in steel. If it satisfies .5 times or more, it is not a problem to adopt the data.

  Also, depending on the degree of concentration, for example, even if the concentrated part can be confirmed before cold rolling, depending on the cold rolling rate, etc., the concentrated part will be stretched very thin together with the steel material, which is difficult to detect with ordinary analytical equipment. It is also assumed that For this reason, in the present invention, not only the steel plate just before applying enamel glaze, but also the concentration of specific elements in semi-finished products, such as hot-rolled steel sheets before and after pickling and slabs during hot-rolled slab heating, throughout the entire steel plate manufacturing process Restrictions also apply to the parts.

  In the present invention, the concentrated portion of the specific element has a component by mass% and is 2.5 times or more of the average content in steel, the thickness in the steel plate thickness direction is 0.01 μm or more, and the coverage of the steel plate surface is 5% or more It is assumed that at least one of the three conditions is satisfied. It goes without saying that satisfying two of these conditions at the same time makes the effects of the invention more remarkable, more preferably satisfying all of the conditions. The coverage is determined by quantifying the concentration of the specific element having a sufficiently small area, and the measurement data of 1000 points or more is defined by the area ratio of the concentrated portion of the specific element that satisfies the provisions of the present invention. In particular, in a normal enamel cold-rolled steel sheet or enameled hot-rolled steel sheet, it is convenient to define the effect of the present invention to detect this concentrated portion after pickling.

  As for a more preferable form of the concentrated portion of the specific element, the component is 3% by mass of the average content in the steel, more preferably 4 times or more, and the thickness in the steel plate thickness direction is 0.05 μm or more, more preferably. It is 0.1 μm or more and the steel sheet surface coverage is 20% or more, more preferably 40% or more. Of these, the component may be 100% of a specific element. Usually, Fe is mainly detected in addition to the specific element. However, in addition to the specific element, elements such as Si, P, Al, and Mn are contained in steel. This does not impair the effects of the present invention. As described above, the thickness may be very thin depending on the steel plate manufacturing process as described above, and it may be difficult to detect the thickness. However, if the thickness is not 0, the effect of the present invention can be obtained in principle.

  The concentration of the specific element described above is preferably localized and the concentration is finely dispersed, rather than covering the entire large surface. In other words, it is preferable that a certain fine element is uniformly dispersed rather than a coarse element sparsely dispersed as a form of the concentrated portion of the specific element existing on the surface of the steel plate. However, too fine ones are difficult to measure and cause a large measurement error, so those with a diameter of 0.10 μm or more are targeted. The diameter of the thickened portion preferable for the enamel adhesion is 0.2 to 30 μm, more preferably 0.5 to 20 μm, still more preferably 1 to 15 μm, and further preferably 1.5 to 10 μm.

In the present invention, the number density on the surface of the steel sheet is limited with respect to the independent concentrated area or the independent non-concentrated area on the steel sheet surface. In the present invention, the claim range is limited by a numerical value having a higher number density among the concentrated region and the non-concentrated region. It is considered that the higher the numerical value, the finer the non-uniformity of the steel sheet surface is. In the present invention, the number density is 0.001 piece / μm ² or more. Preferably it is 0.003 piece / μm ² or more, more preferably 0.010 piece / μm ² or more, more preferably 0.030 piece / μm ² or more, more preferably 0.10 piece / μm ² or more, more preferably 0. 30 pieces / μm ² or more, more preferably 1.0 pieces / μm ² or more, and further preferably 3.0 pieces / μm ² or more.

  The area ratio and number density in the present invention described above can be schematically represented as shown in FIGS. There is an appropriate region in the coverage of the steel plate surface of the concentrated portion of the specific element having such a form. The upper limit of the coverage may be 100%, but if a too thick concentrated layer covers the entire surface, the wettability of the enamel glaze may be reduced and the adhesion may be impaired. Even in the case of 100%, the concentrated layer is unevenly distributed, That is, it is preferable that the thickness of the concentrated layer is not uniform and the concentration of the concentrated element varies. Preferably, the non-concentrated part of the specific element partially exists, and the surface coverage of the concentrated part is preferably 95% or less, and more preferably 80% or less.

  Further, one of the features of the present invention is that the enriched portion of the specific element is related to the unevenness of the steel sheet surface. The present invention has a great feature in controlling the existence form of the above-described concentrated portion in relation to the roughness of the steel plate surface, and basically the concentrated portion is formed on the convex and concave portions of the steel plate surface. To control. This is indicated by the ratio of the number of concentrated parts existing in the convex part, by checking whether the existence position of the concentrated part of a sufficiently large number of specific elements is a convex part or a concave part of the steel plate base material. . Preferably it is 70% or more, More preferably, it is 80% or more, More preferably, it is 90% or more. Alternatively, the number of thickening parts present for each of convex parts and concave parts existing within a certain area, the size of the thickening part of the specific element and the concentration of the specific element, and the thickening amount at the convex part and the concave part It can also be shown that the amount of concentration at the convex portion is larger than the amount of concentration at the concave portion.

  The correspondence between the convex portion and the concentrated portion of the specific element first occurs during slab heating. When the specific element is formed under the scale, the oxidation of the portion is suppressed, and the scale becomes a convex portion after peeling off the scale. In hot-rolled steel sheets, the concentration of specific elements at the time of pickling is such that if normal pickling is performed, the concentrated portion remains undissolved and remains to form protrusions. This also contributes to the fact that the smut contained in the concentration tends to adhere to the convex portion, and the correspondence between the convex portion and the concentrated portion of the specific element is very good. Moreover, also in a cold-rolled steel sheet, the concentrated part which exists in the convex part formed at the time of pickling of a hot-rolled sheet also tends to become a convex part after cold rolling and annealing. Although the cause of this is not clear, it seems that the concentrated portion of the specific element is harder than the base steel plate steel, so that it is easy to form a convex portion after cold rolling.

  However, the correspondence between the convex portion and the concentrated portion of the specific element tends to be unclear as compared with that after pickling of the hot-rolled sheet. One effective way to improve this is to pickle the steel sheet after cold rolling. If this pickling is after the cold rolling process, it may be before or after annealing, but if the skin pass is performed after pickling, the unevenness synchronized with the thickening portion is likely to disappear, so the pickling is performed after the skin pass, When skin pass is performed after pickling, the skin pass cold rolling rate is preferably 5% or less. Preferably it is 2% or less. Needless to say, the irregularities on the surface of the steel sheet to be controlled in the present invention must be synchronized with the specific element concentrating portion, for example, a normal obtained only by transferring the roll roughness of skin pass rolling. The objective cannot be achieved with steel sheet roughness.

  As described above, the unevenness of the surface which is important in the state of the steel sheet surface is defined by the roughness in the present invention, and Ra is preferably 0.20 μm or more and PPI is preferably 50 or more. Here, PPI uses a value with a cutoff value of 50 μm. Ra is preferably 0.30 μm or more, more preferably 0.50 μm or more, still more preferably 0.80 μm or more, and even more preferably 1.5 μm or more. However, if Ra is too large, bubbles are easily generated during enameling. Therefore, it should be 5 μm or less. The PPI is preferably 70 or more, more preferably 100 or more, further preferably 150 or more, more preferably 200 or more, further preferably 250 or more, and more preferably 300 or more.

  Ra and PPI can be controlled in consideration of the conditions of pickling (acid type, concentration, temperature, time) and the like, as well as skin pass conditions. However, it is impossible to limit the conditions in general because it largely depends on the steel composition and the production history so far. However, those skilled in the art with ordinary technology can use the application and enamel characteristics after an appropriate number of trials. It is not so difficult to control within an appropriate range considering the user's request.

  The technically important point in the uneven distribution of the concentrated portion of the specific element described above is that the concentrated portion formed by plating is formed at a position related to the concentrated portion existing before plating. In general, when different metal phases come into contact with the surface of steel during plating, it is thought that they are generated from some nucleus, but if there is no nucleus that promotes preferential generation, the plating layer is formed uniformly. It is not preferable for obtaining the effects of the present invention sufficiently.

  In the steel of the present invention, the enriched portion of the specific element generated by plating is generated in relation to the segregation of the specific element existing before plating. That is, in the steel of the present invention, a plating phase is preferentially generated in the concentrated portion of the specific element that existed before plating. As described later, in the steel of the present invention, as described later, it is possible to generate a concentrated portion of a specific element unevenly distributed on the surface of the steel plate before plating, and the plating phase containing the specific element has its concentrated portion as a nucleus. Generate preferentially on top. Further, the preferential nucleus for forming the plating phase is a convex portion as the form of the steel plate surface. This is because, as will be described later, in the steel of the present invention, the concentrated portion of the specific element is preferentially formed on the convex portion of the steel sheet surface through the scale generation and pickling steps in the manufacturing process.

  Various plating methods for improving enamel adhesion have been technically disclosed so far. In the present invention, as described above, the surface roughness formed by the concentrated portion of the specific element or mainly pickling, or in addition to these, In addition, it is characterized in that the concentrated portion of the specific element is formed by plating, and this makes it possible to obtain exceptional good enamel adhesion that has never been considered before. In particular, the effect on the enamel adhesion deterioration at the steel sheet processing site is exceptional.

  The effect of the present invention can be obtained as long as the type of plating includes Ni, Cu, Co or Mo. In particular, since the plated metal is present on the outermost surface of the steel plate and is in direct contact with the glass, glass-steel Ni or Co, which is an element that exists mainly on the glass side at the interface and improves enamel adhesion, is preferably included.

  The reason why such a characteristic plating effect appears in the steel of the present invention is not clear, but in the steel of the present invention, the plating metal adheres to the steel plate surface through the concentrated portion formed by segregation from the steel plate. It is estimated that the chemical component change from the steel sheet to the glass film is continuous and firmly adhered, and fine irregularities at the interface formed by the local cell action during firing are effectively formed. In detail, the type of the element of the concentration site before plating and the element of the plating metal is a problem. In the case of the same type, it is expected that these elements are formed at the same position. It seems that it is easy to form at the same position because of its similar corrosion resistance and the like.

  The steel containing the above components is melted in a converter in the same manner as a normal enamel steel plate, made into a slab by continuous casting, and then manufactured by processes such as hot rolling, pickling, cold rolling, and annealing. The effects of the present invention are not impaired at all by going through a decarburization step or the like among these steps. Moreover, there is no problem even if it is manufactured by a process such as a thin slab CC which omits the hot rolling process instead of the normal process.

  Formation of the concentrated portion of the specific element characterized in the present invention on the surface of the steel sheet can be achieved through the following thermal history. However, what should be controlled in the present invention is basically the concentration of a specific element formed at the interface between the scale and the base iron generated during heat treatment. Even if the thermal history is the same, the scale generation situation differs depending on the steel composition and atmosphere. Naturally, there is a difference in the concentration of specific elements. Basically, if the temperature is high and the time is long, the amount of scale generation is large and the concentration of the specific element becomes remarkable, but due to various factors, the concentration of the specific element may occur sufficiently even at low temperature and short time. It should be noted that the thermal history is only a guide.

  In this process of manufacturing a product plate, the heat history in hot-rolled slab heating should be kept at 1000 to 1200 ° C. for 40 minutes or longer, and the coil heat history after hot-rolling finish rolling and before cold rolling should be controlled on this premise. Satisfies at least one of the following conditions: holding time at 650 ° C. or higher for 30 minutes or longer, and thermal history of coil after cold rolling at a dew point of −20 ° C. or higher and holding time at 750 ° C. or higher for 20 seconds or longer. It is to be. Basically, thickening is achieved by forming many scales at high temperature, long time, and high dew point, but when the temperature is too high, long time, and high dew point, concentration becomes abnormal and adversely affects enamel characteristics. There is a need to be careful. Also, especially when the dew point is low, new scale generation does not occur, so even if surface enrichment existed before that, the concentrated element diffuses unilaterally into the steel plate and the effect of surface enrichment disappears. Sometimes.

  For optimum control, it is important to consider the steel composition, etc., and the required properties vary depending on the application and user, so it cannot be determined unconditionally. However, those skilled in the art having ordinary skills can make an appropriate number of trials. Thereafter, it is easy to control within an appropriate manufacturing range.

  In the case of cold rolled steel sheets for enamel, this process is usually the final heat treatment, but if this process is held at a high dew point and high temperature for a long time, it is convenient for surface concentration of specific elements, but the scale thickness May become too thick and cause appearance problems when used as a product. When the processed member is pickled immediately before enameling, this problem is almost solved. However, when the processed member is not pickled, the steel plate after the heat treatment can be pickled lightly. This pickling not only removes the scale formed in the final heat treatment, but also has the effect of enhancing the surface concentration of the specific element and improving the enamel adhesion.

  In particular, with respect to the steps after hot rolling, the steps of the present invention can obtain a sufficient effect by hot rolling, pickling, cold rolling, annealing, skin pass, plating (or plating, skin pass). However, it becomes possible to obtain a more remarkable effect by using a characteristic process sequence particularly for pickling, annealing, and plating.

First, pickling is preferably performed once after cold rolling separately from pickling before cold rolling. This is because pickling is effective for the formation of the concentrated portion existing before plating, which is one of the features of the present invention. The plating is preferably performed in a step immediately after pickling. This is due to the fact that plating is performed in a clear state, which is one of the characteristics of the present invention, in order to form the concentrated portion at a preferred position by plating. Moreover, it is preferable to perform annealing after plating as conventionally known. This is because, as is well known, the concentration change is moderated by the diffusion of the plated metal to improve the adhesion between the plating and the base steel plate. Taking these into account, examples of preferable steps after hot rolling include the following.
(A) Hot Rolling-Pickling-Cold Rolling-Annealing-Skin Pass-Pickling-Plating (b) Hot Rolling-Pickling-Plating-Cold Rolling-Annealing-Skin Pass Of course, plating and annealing are not limited to one time. Multiple productions are possible if the production cost allows. Further, in the steel of the present invention in which the enrichment part of the specific element including plating is controlled, it is possible to remarkably enhance the enamel adhesion by performing some treatment on the surface of the enrichment part of the specific element. As a surface treatment having such an effect, for example, there is a phosphoric acid treatment (bonding treatment) applied to a steel plate for automobiles in order to improve paint adhesion and corrosion resistance. It is sufficient to apply the conditions of the phosphoric acid treatment as they are applied to a normal automobile steel sheet. The steps after hot rolling in the case of performing such a process are, for example, (c) hot rolling, pickling, cold rolling, annealing, skin pass, pickling, plating, phosphoric acid treatment (d) hot rolling, pickling, cold rolling, It is like annealing-skin pass-pickling-phosphating-plating.

In the pickling step, the kind, concentration, temperature and the like of the pickling solution are not particularly limited, and a known method can be applied. Particularly, the pickling weight loss should be controlled. In order to sufficiently obtain the effects of the invention, the pickling weight loss is 0.01 g / m ² or more. Preferably it is 0.1 g / m ² or more, more preferably 1 g / m ² or more. Depending on the subsequent process, when pickling after cold rolling, the concentration of specific elements formed by pickling becomes excessive, or the smut adhering to the steel sheet surface during pickling becomes excessive, resulting in improved enamel characteristics. Excess pickling should be avoided, as it can be adversely affected. Preferably it is 200 g / m ² or less, more preferably 150 g / m ² or less. A preferred range is 5 to 100 g / m ² , more preferably 10 to 50 g / m ² . In the case of pickling before cold rolling, no problem occurs even if the amount of pickling is large, and it is possible to make the pickling loss higher than the above value in order to peel off the thick scale formed by hot rolling.

  The plating method and conditions are not particularly limited, and a known plating method can be applied. As the Ni plating method for enamel steel plates, electroplating is mainly known. However, the substitution plating method, which has a simple plating facility and is advantageous in terms of cost, is characteristic in the present invention. This is one of the particularly preferred methods for the preferential generation action at a specific position on the surface of the steel plate of the phase. The plating time is set to 5 seconds or more and 5 minutes or less in consideration of the adhesion effect of the plating phase by plating, the manufacturing cost, the influence on the state of the steel plate surface adjusted before plating, and the like. Preferably, it is 10 seconds to 2 minutes.

If the amount of plating is excessive, not only will the cost increase, but the plating layer will become thick, and the effect of the present invention for controlling the formation of the plating layer in relation to the surface of the underlying steel sheet tends to be unclear. According to the present invention, a sufficient effect can be obtained without performing a large amount of plating, so that the upper limit is 5.0 g / m ² is sufficient. To recognize the effect of plating, 0.001 g / m ² is necessary. Preferably it is 0.01-4.0 g / m < ² >, More preferably, it is 0.05-3.0 g / m < ² >, More preferably, it is 0.1-2.0 g / m < ² >, More preferably, it is 0.2-1. 0 g / m ² . The effect of the present invention can be sufficiently obtained even at 0.9 g / m ² or less, further 0.8 g / m ² or less, further 0.7 g / m ² or less, and further 0.6 g / m ² or less.

  In order to obtain the effect of improving the enamel adhesion by reducing the damage due to the processing before applying the enamel by smoothing the concentration fluctuation of the specific element from the plating layer to the iron bar by annealing after the plating, and 2 It is necessary to make the condition more than second. It is preferably 600 ° C. or higher, more preferably 700 ° C. or higher, and 750 ° C. or higher if the workability of the steel sheet is to be improved by combining with recrystallization and grain growth after cold rolling. However, if the temperature is too high for a long time, the concentration of the concentrated layer of the specific element may decrease due to the diffusion of the element, and the effect of the invention may become unclear. Therefore, holding at 900 ° C. or higher should not be performed for 5 minutes or longer. . Of course, if this excessive heat treatment is performed after some steps including the enamel baking step, it is not a problem because it is performed after the improvement of enamel adhesion according to the present invention.

  The steel of the present invention is intended to avoid pickling, Ni treatment (Ni flash), and expensive glazes containing a large amount of Ni, Co and the like in conventional enamel pretreatment by the application. From preferably, the steel sheet of the present invention is used as a raw material, and it is manufactured without any surface treatment process or pickling process in an atmosphere containing one or more of specific elements in all processes of manufacturing enamel products before applying enamel glaze. It is preferable not to use expensive glazes containing a large amount of Ni, Co or the like. Of course, it is possible to obtain the same enamel adhesion even if the pre-treatment is the same as before or an expensive glaze is used. Pre-treatment such as shortening the pickling time and reducing the concentration of the treatment liquid is possible. Even when simplified or an inexpensive glaze is used, the use of the steel of the present invention can provide a significant improvement in enamel adhesion.

  If an expensive glaze containing Ni or Co is currently used, even if this is changed to an inexpensive glaze with a reduced content of Ni or Co, equivalent adhesion can be ensured. In the steel of the present invention, a glaze containing no Ni or Co is used unless there is any necessity other than the enamel adhesion, and the Ni or Co content in the glaze is 5% or less, preferably 2% or less, It is preferably 1% or less, and it is possible to obtain very good adhesion even if it is not contained at all. Furthermore, the above-described expensive glaze containing Ni or Co used in the so-called double enamel can be completely omitted, and the enamel can be encased once with only the glaze not containing Ni or Co.

  In the present invention, especially when the Cu content is as high as about 1.5% or more, depending on the Cu content and the thermal history, a considerable amount of Cu in the steel precipitates in the steel as a metallic Cu phase called ε-Cu. There is a case. Care must be taken because if this is too coarse, the workability may be degraded. Further, as disclosed in the prior art, it is not necessary to impair the effect of the present invention by finely depositing it in steel to increase the strength.

  The use is not particularly limited, and it is applicable to all uses in which enamel products such as building materials and chemical industrial products are used in addition to ordinary enamel uses such as kitchenware and sanitary products.

  In addition, the steel sheet that is the subject of the present invention can obtain the effect regardless of the manufacturing method not specified in the present invention, such as the thickness, hot-rolled steel sheet, cold-rolled steel sheet, and the surface necessary for some purpose. It is also possible to perform processing or the like.

  In addition, the application of the present invention does not adversely affect the characteristics, for example, the workability, which are preferably included in the enamel steel plate not described in the present invention.

  A continuous cast slab having various chemical compositions shown in Table 1 is hot-rolled, cold-rolled, and annealed under the conditions shown in Table 2, subjected to temper rolling with a reduction ratio of 1%, and a plate thickness of 1.2 mm A steel plate was obtained. Some of the materials were pickled after annealing, and passed through Ni sulfate, followed by displacement plating. However, the steel number 14 was electroplated according to a technique known in Patent Document 1 or the like. For steel No. 8, heat treatment was further performed at 750 ° C. for 1 minute after substitution plating, and the effect of diffusion of the specific element in the concentrated portion of the specific element into the steel plate base material was examined. While measuring the surface state of the obtained steel plate, only degreasing was performed and enameling was performed to evaluate enamelability. The glazes were all the same and did not contain Ni or Co, and those usually used once for enamel.

  The enamel adhesion is generally performed by P.I. E. I. In the adhesion test method (ASTM C313-59), it is difficult to make a difference in adhesion, so the weight of a 2 kg ball head is dropped three times from the height of 0.5 m to the same site, and the enamel peeling state of the deformed portion is changed to 169 pieces. It measured with the palpation needle and evaluated by the area ratio of the unpeeled part. This peeling condition is comparatively strict, and even on the premise that enamel pretreatment is performed, it is about 30% for a normal material and about 50% even for a material with good adhesion. is there. In addition, there were no particular problems with all materials regarding the sunspots and spikes that are normally evaluated as enamel characteristics.

  Various characteristics are shown in Table 2. As is apparent from the results in the table, the present invention can provide an enamel steel plate for enamel that has enormous improvement in enamel adhesion and good enamel capability. Steel No. 14 was used as a comparative example because it has good enamel characteristics, but the manufacturing cost is very high and impractical. Moreover, the effect that the heat treatment after plating improves the adhesion after processing is clear from Steel No. 8.

It is a figure which shows the calculation method of the area ratio and number density of a concentration area | region. It is a figure which shows the calculation method of the area ratio and number density of a non-concentrated area | region.

Claims (15)

In mass%, C: 0.070% or less, Si: 0.50% or less, Mn: 0.010 to 0.95%, P: 0.20% or less, S: 0.080% or less, Al: 0 20% or less, N: 0.070% or less, O: 0.070% or less, further Cu: 0.051 to 8.0%, Ni: 0.051 to 8.0%, Co: 0 0.051 to 8.0%, Mo: at least one of 0.051 to 8.0%, consisting of Fe and unavoidable impurities, including at least one of Cu, Ni, Co, and Mo And the plating steel plate for enamels with favorable enamel adhesion characterized by having plated with 0.001-5.0 g / m < ² > of adhesion amount.   The plated steel sheet for enamel according to claim 1, wherein the concentration of at least one element of Cu, Ni, Co, and Mo is 2.5% or more of the average content in steel by mass%, and the thickness in the thickness direction of the steel sheet. Good enamel adhesion, characterized in that a concentrated region that satisfies at least one of the three conditions of 0.01 μm or more and a steel sheet surface coverage of 5% or more exists on the steel sheet surface Plated steel plate for enamel. In the enameled steel sheet for enamel according to claim 1 or 2, the number of the enriched region or the independent non-concentrated region of at least one element of independent Cu, Ni, Co, Mo having a diameter of 0.1 μm or more. A plated steel sheet for enamel having good enamel adhesion, characterized in that the density is 0.001 piece / μm ² or more.   The enameled steel sheet for enamel according to any one of claims 1 to 3, wherein the enriched portion for at least one element of Cu, Ni, Co, and Mo formed by plating is present before plating. A plated steel sheet for enamel having good enamel adhesion, wherein the enamel is preferentially formed on the surface of the enriched portion of at least one element of Ni, Co, and Mo.   The enameled steel sheet for enamel according to any one of claims 1 to 4, wherein the surface roughness of the steel sheet is 0.20 µm or more in Ra and 50 or more in PPI. Plated steel plate for enamel.   The enameled steel sheet according to any one of claims 2 to 5, wherein the enriched portion containing at least one of Cu, Ni, Co, and Mo present on the surface of the steel sheet is mainly on the steel sheet surface. An enameled steel sheet for enamel having good enamel adhesion, characterized in that it is present on a convex part.   The enameled steel sheet for enamel according to any one of claims 2 to 6, wherein the convexity on the surface of the steel sheet is related to the concentrated portion containing at least one of Cu, Ni, Co, and Mo present on the surface of the steel sheet. An enameled steel sheet for enamel having good enamel adhesion, characterized in that the concentration at the part is greater than the concentration at the recess.   When manufacturing the enameled steel sheet for enamel according to any one of claims 1 to 7, the holding time at 1000 to 1200 ° C in the heat history in hot rolling slab heating is 40 minutes or more, and cold rolling after hot rolling finish rolling. Among the conditions that the holding time at 650 ° C. or higher in the previous coil thermal history is 30 minutes or longer, and the holding time at 20 ° C. or higher and dew point of −20 ° C. or higher and 750 ° C. or higher is in the thermal history of the coil after cold rolling A method for producing a plated steel sheet for enamel having good enamel adhesion, characterized by satisfying at least one. The method for producing a plated steel sheet for enamel having good enamel adhesion according to claim 8, wherein after the cold rolling step, the acid wash loss is performed at 0.01 g / m ² or more.   The method for producing a plated steel sheet for enamel with good enamel adhesion according to claim 8 or 9, wherein the plating is performed by substitution plating for 5 seconds or more and 5 minutes or less.   Plating is performed after pickling, The manufacturing method of the enameled steel plate for enamel with good enamel adhesion as described in any one of Claims 8-10 characterized by the above-mentioned.   The method for producing enameled steel plate for enamel having good enamel adhesion according to any one of claims 8 to 11, wherein annealing is performed at 500 ° C or more and 2 seconds or more after plating.   The plated steel plate for enamel according to any one of claims 1 to 7 is used as a raw material, and at least one or more of Cu, Ni, Co, and Mo are used in all steps of producing enamel products before applying enamel glaze. An enamel product, which is manufactured without undergoing a surface treatment step in a contained atmosphere.   The plated steel sheet for enamel according to any one of claims 1 to 7 is used as a raw material, and it is produced without passing through a pickling process in all processes for producing enamel products before applying enamel glaze. Enamel products.   An enamel product produced by using the enameled steel sheet for enamel according to any one of claims 1 to 7 without using a glaze containing 5% or more of Ni or Co.

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