Technical field
[0001]
　The present invention relates to a steel plate and enameled products.
　The present application, to 09 on May 11, 2015, claiming priority based on Japanese Patent Application No. 2015-179722, filed in Japan, the contents of which are incorporated here.
Background technique
[0002]
　Enamel products are those glassy burned onto the surface of the enamel steel sheet for. Enamel products, heat resistance, weather resistance, chemical resistance, because it has a waterproof function, conventionally, pans such, kitchenware sink or the like, and is widely used as a material such as building materials. Such enameled products generally, after processing a steel plate into a predetermined shape, after being assembled to the product shape by welding or the like, is produced by enameling treatment (firing treatment) is performed.
[0003]
　The enameling steel sheet for which is used as the enamel product material, as its properties, seizure forming strain resistance, 耐爪 jump, adhesion, 耐泡-black spot defects, etc. are required. In addition, in the production of enameled products, typically because it is pressing in order to obtain the product shape, good moldability is obtained.
[0004]
　Also, since the improved corrosion resistance in harsh corrosive environment that includes sulfuric acid by performing enamel process, enamel products are spread application range to the energy fields such as power generation equipment. In such areas, there is a need for reliability to fatigue and the like in long-term use, further, for the purpose of weight reduction of parts, high strength of steel sheet used is required. For the reliability of the above fatigue and the like, processing of enamel products - changes in the morphology of the steel sheet in the production process of the enameling process, namely that the intensity variation due to differences in morphology within the steel sheet affects known ing.
[0005]
　Previously, with regard to the changes in tissue morphology caused by enameling process, a technique for preventing 耐爪 jump degradation by coarsening of crystal grain size, for example, described in Patent Document 1. In Patent Document 1, based on the known high oxygen steel, the composition of the inclusions, size, shape, proportion, and at the same time optimizing the number, Ni, Cr, to V, and Mo is added in a small amount, further, needs depending Nb, B, and Ti was added, by optimizing the manufacturing conditions of the steel sheet, even when a enameling process repeatedly, it is described that it is possible to reduce the decrease in 耐爪 jump of ing.
[0006]
　In Patent Document 2, with respect to issues deflection during firing is deteriorated dimensional accuracy caused by strength reduction due to the grain growth in enameling process high oxygen steel Ownership of enameling steel sheet for, namely ferrite and uniform particle size is described to be effective to reduce the particle size distribution. In Patent Document 2, in the steel sheet production process, refinement of the structure of hot-rolled steel sheet, for uniformity of grain growth in annealing is performed addition of Ni and Cr.
[0007]
　However, both Patent Documents 1 and 2, the enamel products was enameling process involving tissue change, although believed to allow certain properties securing, in order to solve the problems related to crystal grain growth in the enameling process, the Ni It is an essential addition. That is, the resolution of the problem, it is necessary to add expensive alloy elements. Also with respect to Patent Document 2, by hardly interfere with the ferrite grain growth by coarsening of the oxide by Cr addition, to improve the uniformity of the particle size of the ferrite by suppressing the abnormal grain growth, it becomes mixed grain It is suppressed. However, the precipitates and inclusions this method not using the suppression of grain growth by pinning, when the temperature in the member during enamel process varies particle size of unevenness generated in not obtaining effect is obtained possibilities may be considered. In this case, strength after enameling treatment can not be obtained stably. In Patent Document 2, an object to suppress the deflection of the member after enameling process, since the study only yield stress before and after the enameling process, changes affecting the tensile strength fatigue properties is unclear.
[0008]
　Thus, an important characteristic of enameling steel sheet for, 耐爪 jump resistance and guidance to become strength properties of the steel sheet reliability, reality is a high-strength steel sheet satisfactory in consideration of the manufacturing process has not been provided , and the for a further improvement in characteristics is remain still problems.
CITATION
Patent Literature
[0009]
Patent Document 1: Japanese Patent 2001-316760 JP
Patent Document 2: Japanese Patent 2000-063985 JP
Summary of the Invention
Problems that the Invention is to Solve
[0010]
　The present invention is to develop a technology of enameling steel sheet for the aforementioned, aging resistance and moldability, and, after enameling treatment, by excellent enameling characteristics (耐爪 jump, adhesion, appearance) and strength properties (enameling process It does not cause a decrease in tensile strength, or properties of tensile strength degradation can be stably suppressed) and to provide a steel sheet is obtained. Further, the present invention aims to provide a superior enamel products enameling characteristics with the steel plate.
Means for Solving the Problems
[0011]
　The present invention was obtained by conducted various studies in order to overcome the problems of the conventional enameling steel sheet for, in particular,耐爪jump of the steel sheet after the enameling process, the reduction in strength such as suppressing, chemical composition, based on the study as a result of the knowledge obtained the influence of manufacturing conditions.
　That is, the present invention is based on the finding of the following 1) to 4).
1)耐爪jump resistance controls the steel during precipitation by optimizing the steel ingredients, by trapping steel in hydrogen which causes the pawl skipping can be improved. In particular, oxides of 1.0μm ultra ~ 10 [mu] m is present in the steel, the diameter of the oxide, the number it is possible to ensure耐爪jump properties by optimizing the.
2) Nb is a rare metal, it is not used is advantageous in environmental. However, if the Nb is not contained, the strength reduction after enameling process is increased. This heating of Nb is enameling process when Nb is contained, inhibits the grain growth during the heat insulation is in the case of not containing an Nb is due to the inability to achieve this effect.
3) even without containing Nb, the steel sheet before enameling process, i.e. steel components of the original sheet, the crystal grain size, as well as by optimizing the diameter and number of the steel oxide, the strength after enameling process, it is possible to stably secure (i.e., can suppress the strength reduction due to enamel process). In particular, in order to suppress grain growth during enameling process is a major factor of reduction in strength due to enameling process, it is effective to optimize the number density of oxide of 0.1 ~ 1.0 .mu.m.
4) by controlling the steelmaking conditions, to control the size of the oxide, the hot rolling conditions, cold rolling conditions, by appropriately controlling the annealing conditions and temper rolling conditions, the precipitate forms in the final product it is possible to control.
[0012]
　The present invention has been completed based on these findings, the gist of the invention is as follows.
(1) steel sheet according to one embodiment of the present invention, in mass%, C: 0.0060% or less, Si: 0.0010 ~ 0.050%, Mn: 0.05 ~ 0.50%, P: 0 .005 ~ 0.100%, S: 0.0030 ~ 0.0500%, Al: 0.0010 ~ 0.010%, Cu: 0.010 ~ 0.045%, O: 0.0250 ~ 0.0700 %, N: 0.0010 ~ 0.0045% , the balance: Fe and impurities, tissue containing ferrite average crystal grain size of the ferrite in the 1/4 position in the plate thickness in the thickness direction from the surface There is less 20.0 .mu.m, contains an oxide containing Fe and Mn, of the oxide, the number density of diameter greater 10μm or less of the oxide than 1.0 .mu.m, 1.0 × 10 3 cells / mm 2 or more, 5.0 × 10 4 cells / mm 2 or less, or Diameter number density of the oxide of 0.1 ~ 1.0 .mu.m is 5.0 × 10 3 cells / mm 2 at least.
(2) a steel sheet according to (1), in the impurity, by mass%, B, Cr, Ni, As, Ti, Se, Ta, W, Mo, Sn, Sb, La, Ce, Ca, Mg one or more of the total of: may be limited to 0.100% or less.
(3) a steel sheet according to (1) or (2), in the impurity, by mass%, Nb: may be limited to 0.010% or less.
(4) a steel sheet according to any one of the above (1) to (3) may be a cold-rolled steel sheet.
(5) steel sheet according to any one of the above (1) to (4) may be enameling steel sheet for.
(6) enamel product according to another aspect of the present invention comprises a steel sheet according to any one of the above (1) to (5).
Effect of the invention
[0013]
　Steel sheet according to this aspect of the present invention, formability, excellent strength after enamel treatment and耐爪jump resistance. Moreover, aging resistance, enamel adhesiveness, excellent in appearance after enameling process. Therefore, it is preferable kitchenware, building materials, as enameling steel sheet for a base material of enamel products that are applied to the energy field and the like.
　Furthermore, enamel products according to the aspect of the present invention is excellent in enameling properties. Therefore, it is suitable to kitchen utensils, building materials, etc. energy field of application.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014]
[1] diameter of a photograph showing an example of an oxide of 0.1 ~ 1.0 .mu.m.
[Figure 2] diameter of a photograph showing an example of the following oxide greater than 1.0 .mu.m 10 [mu] m.
DESCRIPTION OF THE INVENTION
[0015]
　Steel sheet according to an embodiment of the present invention (hereinafter, the steel sheet according to the present embodiment) will be described in detail. Steel sheet according to the present embodiment is suitably used as a substrate for enamel products (enamel steel plate).
[0016]

　describe the reason for limiting the chemical components of the steel sheet according to the first embodiment (chemical composition). "%" For component means mass% unless otherwise specified.
[0017]

　C ductile becomes better the content is low. Also, C content tends to occur foam defects exceeds 0.0060%. Therefore, the C content, and 0.0060% or less. To ductility improvement, C content is preferably lower. However, since the increase is the steelmaking cost lower the C content, C content is preferably 0.0015% or more.
[0018]
Si is an element having an effect of controlling the composition of the oxide. To obtain this effect, the Si content is 0.0010% or more. Meanwhile containing excessive Si in may Inhibition of enameling properties to multimeric form a Si oxide in hot rolling at the same time, reducing the耐爪jump resistance. Therefore, the Si content to 0.050% or less. 耐泡improves the like耐黒point, yet from the viewpoint of obtaining a surface property after good enameling process, preferably not more than 0.0080%.
[0019]

　Mn, in conjunction with the O content, affect the composition of the oxide to exert an effect on耐爪jump of the steel sheet for porcelain enameling, high strength of the steel sheet at the same time it is an important component which contributes to reduction. The Mn is an element to prevent hot shortness caused by S during hot rolling. To obtain these effects, the Mn content is 0.05% or more. Usually, enamel adhesiveness is deteriorated when the Mn content is higher, but bubbles and black spots are likely to occur, when present in steel as an oxide, the deterioration of these properties is small. However, ductility is deteriorated when the Mn content is excessive. Therefore, 0.50% of the upper limit of the Mn content.
[0020]

　P is an effective element for high strength of a steel sheet. Also, P is also an effect of suppressing the strength reduction due to enameling process. To obtain these effects, the P content is 0.005% or more. Also, P is by raising the recrystallization temperature, an element effective against grain growth inhibition during enameling process. To obtain this effect, the P content is preferably set to 0.015% or more. On the other hand if the P content is excessive, P is segregated at a high concentration in the grain boundaries of the steel sheet during the enameling process, it may become a factor, such as foam-black spots. Therefore, to the P content 0.100% or less. Preferably not more than 0.075%.
[0021]

　S is an element which forms a Mn sulfides. The sulfides may be composite deposited on oxide, it is possible to further improve the耐爪jump resistance when complexed precipitated. To obtain this effect, it may contain a S. To obtain the above effect, it is desirable to the S content 0.0030% or more. More preferably 0.0100% or more, more preferably not less than 0.0150%. However, when the S content is excessive, it may decrease the effect of Mn required for controlling the oxides in the steel. Therefore, to 0.0500% the upper limit of the S content. Preferably is less than or equal to 0.0300%.
[0022]
Al is a strong deoxidizing element. Therefore it is necessary to carefully control. If Al content exceeds 0.010%, it becomes difficult to keep the O amount required in the steel, the control of oxides becomes effective耐爪jump resistance becomes difficult. Therefore, the Al content is 0.010% or less. On the other hand, when the Al content is less than 0.0010%, casting foaming defects are likely to occur in pieces, large load is applied to the finishing line is the steelmaking process since more than usual slab in steelmaking steps. Therefore the lower limit of Al content is 0.0010%.
[0023]
Cu controls the reaction between the glassy and steel during enamel process, is an element that improves the adhesion of the enamel. In order to obtain the effect, the Cu content is set to 0.010% or more. Meanwhile, Cu is sometimes its the content is excessive, not only inhibits the reaction between the glassy and the steel and degrades the ductility. To avoid such adverse effect, the Cu content to 0.045% or less. Preferably 0.029% or less, more preferably not more than 0.019%.
[0024]

　O is耐爪jump resistance, and at the same time directly affects the ductility, is an element that forms an oxide, influence the耐爪jump resistance associated with Mn content to. To obtain excellent ductility, the耐爪jumping property, the O content is set to 0.0250% or more. Preferably, at least 0.0400%. On the other hand, if the O content is excessively high, the ductility deteriorates, an increase in Mn content for forming an oxide of the amount required, the alloy cost increases. Therefore, the O content is set to less 0.0700%.
　In this embodiment, O content, according to JIS G1239, by the oxygen of the steel in a sample of about 0.5g is reacted with the graphite crucible, to quantify the concentration of the generated CO as measured by infrared absorption method Measure.
[0025]

　N is an interstitial solid solution element, ductility is deteriorated when the content in a large amount. Also, when the N content is high, aging resistance is deteriorated. Therefore, the upper limit of the N content to 0.0045%. The lower limit is not particularly necessary to limit, in the state of the art because it takes considerably expensive to melting below 0.0010%, the lower limit of the N content is 0.0010%.
[0026]
　Steel sheet according to the present embodiment includes the above elements, and the balance basically in that it consists of Fe and impurities. The impurities, in producing the steel industrially, from raw materials such as ores or scraps, or a component mixed by various factors of the manufacturing process, does not adversely affect the steel sheet according to the embodiment It means what is allowed in the range.
　In the steel sheet according to the present embodiment, the elements contained as impurities is preferably limited to a range to be described later the content thereof.
[0027]
　Cr, Ni, B, As, Ti, Se, Ta, W, Mo, Sn, Sb, La, Ce, Ca, Mg: 0.100% in total less
　Cr, Ni, B, As, Ti, Se, Ta , W, Mo, Sn, Sb , La, Ce, Ca, Mg is an element that need not be contained positively, which is an impurity inevitably mixed. These elements generally be incorporated alone is small, for example, is often mixed with 2 or more elements as in Cr and Ni.
　When these elements excessively contained, the reaction of the oxide-forming elements can not be ignored, it is preferred to limit the total content to 0.100% or less since becomes difficult desired oxide control. More preferably 0.050% is less, further preferably 0.010% or less.
　Further, these elements in the case of acting as a deoxidizing element may affect the value of the free oxygen is adjusted free oxygen becomes difficult. Therefore, it is preferable upper limit of each element to be in a range not affected the value of the free oxygen in the casting stage.
[0028]
　Nb: 0.010% or less
　Nb is a rare metal, it is advantageous for those who are environmentally not used. Therefore, the steel sheet according to the present embodiment, without the addition of Nb. Nb is also there be incorporated as an impurity, an element influencing the inclusions number, it is preferred to limit the Nb content to 0.010% or less.
[0029]

　present in the steel sheet according to the following present embodiment, Fe, explaining the reasons for limitation regarding oxide containing Mn.
　The steel sheet of the steel structure according to the present embodiment, Fe as an element of the deoxidation products, include oxide containing Mn. The steel sheet according to the present embodiment, since no addition of Nb, not included Nb as an element for deoxidation product oxide. Further, the oxide is preferably free Al, Cr, also Si or the like. This is for the above elements is accomplished by the addition so as not to affect the limiting the content, or an oxide composition. However, there is a case Al as a deoxidizer when molten steel composition adjustment, Cr, even without the addition of Si or the like, the Al degree 6% or less when the oxide analysis, Cr, Si or the like is detected from the oxide. These are included as an impurity element Al, Cr, since Si or the like is considered to have been incorporated into the oxide, about 15% or less, preferably component in oxide is contained more than about 6% deoxidation It does not count as an element of the product.
That is, it oxides steel sheet according to the present embodiment includes substantially Fe, Mn, O composed only (unavoidably Al, Cr, even Si is not contained, the total is more than 15% of the content of in which) it is preferable. However, it may also be combined precipitates and sulfides such as MnS. Oxides, if they do not contain Nb, Al, Cr, and Si, etc. as elements for deoxidation product, the oxide can be finely dispersed by adjusting the free oxygen during casting. On the other hand if the element deoxidation product containing Al, Nb, Cr, and Si, etc., by free oxygen adjustment in the present casting process, by controlling the number and size and the oxide in the desired range It becomes difficult.
　The steel sheet according to the present embodiment, among the oxide, the number density of diameter greater 10μm or less of the oxide than 1.0 .mu.m, 1.0 × 10 3 cells / mm 2 or more, 5.0 × 10 4 pieces / mm 2 or less and a diameter of the number density of the oxide of ~ 1.0 .mu.m 5.0 0.1 × 10 3 cells / mm 2 is required to be higher.
[0030]
　Oxides diameter exceeds 1.0μm improves耐爪jump resistance. Small oxide than this range, the effect of improving the耐爪jump resistance decreases. From the viewpoint of耐爪jump effect of improving need not be particularly the upper limit of the diameter. However, although depending on the oxygen content, reduced number density of coarse oxides are many becomes oxides, hydrogen permeation inhibiting effect is reduced. Further, coarse oxides are easily become a starting point of cracking during working, reducing the ductility. Therefore, the diameter of the oxide utilized for耐爪jump improvement is, 10 [mu] m or less, more preferably to 5μm or less. That is, to improve the耐爪jumping property, to control the oxide having a diameter of 1.0 super ~ 10 [mu] m.
　In order to improve the耐爪jump property, an oxide containing Fe and Mn diameter 1.0 super ~ 10 [mu] m, 1.0 × 10 3 cells / mm 2 is necessary to be contained above. It can not ensure good耐爪jump resistance when this than the number density is small. On the other hand, the oxide is 5.0 × 10 4 cells / mm 2 when present at greater than a number occurs more than necessary air gap in the interface of the oxide and the plate matrix during processing, strength after enameling process is reduced . Therefore, the upper limit of the number density 5.0 × 10 4 cells / mm 2 and. Preferably 1.0 × 10 4 cells / mm 2 or less. Oxides diameter exceeds 1.0μm, as shown in FIG. 2, it is often a round shape.

　By
mass%, C: 0.0060% or
less,
Si: 0.0010
~ 0.050%, Mn: 0.05 ~ 0.50%, P: 0.005
~ 0.100%, S: 0.0500 % or
less,
Al:
0.0010 ~ 0.010%, Cu: 0.010 ~
0.045%, O: 0.0250 ~ 0.0700%, N: 0.0010 ~ 0.0045%,
the balance: Fe and consists impurities,
　tissue containing ferrite average crystal grain size of the ferrite in the 1/4 position of the sheet thickness from the surface in the thickness direction is not more than 20.0 .mu.m,
　an oxide containing Fe and Mn contain, among the oxides, the number density of the oxide is less larger than 1.0 .mu.m 10 [mu] m in diameter, 1.0 × 10 3 cells / mm 2 or more, 5.0 × 10 4 cells / mm 2 or less , and the and the oxidation of diameter 0.1 ~ 1.0 .mu.m The number density of the object is 5.0 × 10 3 cells / mm 2 is more than
the steel plate, characterized in that.
[Claim 2]
　In the impurity, by
　mass%, B, Cr, Ni, As, Ti, Se, Ta, W, Mo, Sn, Sb, La, Ce, Ca, 1 or more of the total of Mg: 0.100% or less
in the steel sheet according to claim 1, characterized in that restrict.
[Claim 3]
　In the impurity, by
　mass%, Nb: 0.010% or less,
the steel sheet according to claim 1, characterized in that to limit the.
[Claim 4]
　Steel sheet according to claim 1 or 2, characterized in that a cold-rolled steel sheet.
[Claim 5]
　Steel sheet according to claim 1 or 2, characterized in that the enameling steel sheet for.
[Claim 6]
　Enamel products with the steel sheet according to any one of claims 1 to 3.