JP4937816B2 - Cold rolled steel sheet for enamel processing and method for producing enamel processed product - Google Patents

Description

  The present invention relates to a cold rolled steel sheet for enamel processing in which an enamel layer is provided only on one side and a method for producing an enamel processed product using this cold rolled steel sheet, and in particular, a gas / electric microwave oven, a gas cooker, a stove, etc. The present invention relates to a cold rolled steel sheet for enamel processing suitable as an inner part and a method for producing an enamel processed product.

  An enameled product has a glassy enamel layer formed on the surface of a base material made of a metal material such as steel, cast iron, aluminum, copper and stainless steel. For example, after forming a metal base into a predetermined shape It is manufactured by glazing (frit) the surface and firing at a high temperature. This enameled product is resistant to wrinkles on the surface, can easily remove oil stains, etc., and has excellent heat resistance, acid resistance and alkali resistance, so it can be used in kitchen products, tableware, sanitary containers, buildings. It is used for a wide range of applications such as exterior materials.

  Conventionally, as a method for producing an enamel processed product, generally, a steel sheet formed into a predetermined shape is subjected to pretreatment such as degreasing, pickling, plating treatment of Ni and Co, and the like on both sides (a ) A method of firing by performing so-called single glazing that omits the ground coat, (b) A method of performing firing by performing so-called double glazing to form a cover coat after the ground coat treatment, (c) Ground coating There are three types of methods: glazing and calcination, and further glazing after glazing with a cover coat.

  However, if both sides of the steel plate are glazed as in the method described above, the consumption of enamel increases, and in the case of a spray-type glazing device, the line must be passed twice, resulting in a result. As a result, the manufacturing cost increases. Therefore, recently, double-sided glazing is applied to the outer plate member, but from the viewpoint of improving manufacturing cost and productivity, the steel plate is used as an inner member such as a gas / electric microwave oven, gas cooker and stove. There is an increasing number of cases in which only one surface of the material is glazed and the other surface is not glazed.

  Usually, even when an enamel layer is formed only on one side, the same steel plate as that formed on both sides is used, but conventionally, a hot-rolled steel plate for single-sided enamel has also been proposed (Patent Document 1). reference). The single-sided enamel hot-rolled steel sheet described in Patent Document 1 prevents C, Mn, P, solids in the steel sheet in order to prevent strength reduction due to grain coarsening after firing and to obtain good enamel characteristics. The content of dissolved Al and N, the ratio of dissolved Al and N, and the amount of free N are specified.

JP-A-63-42355

  However, when a conventional cold rolled steel sheet for enamel developed for double-sided glazing is used to produce an enameled product by single-sided glazing, there is a problem that the oxide film formed on the non-glazed surface tends to peel off. . If the adhesion of the oxide film formed on the non-glazed surface is low, the oxide film is peeled off in the assembly process, and this peeled oxide film is mixed into the product or becomes an obstacle to the assembly work, which is not preferable. On the other hand, the hot-rolled steel sheet for single-sided enamel described in Patent Document 1 assumes single-side glazing, but this technique relates to hot-rolled steel sheets, and the same effect cannot be obtained even when applied to cold-rolled steel sheets. . Moreover, in the hot rolled steel sheet for single-sided enamel described in Patent Document 1, an oxide film (scale) has already been formed on the surface in the production process, so an oxide film formed on the non-glazed surface by firing after glazing. Has not been studied.

  In addition, regarding hot-rolled steel sheets, various studies have been made on improving the adhesion of scales formed in the hot rolling process, but the scales in hot-rolled steel sheets are oxide films formed by water vapor, and cold-rolled steel sheets The properties are different from those of the oxide film formed by baking when the enamel treatment is performed. Further, conventionally, in the cold rolled steel sheet for enamel processing, no study has been made on improving the adhesion of the oxide film formed on the non-glazed surface. For these reasons, not only are the enamel characteristics and workability excellent for single-side glazing, but also the adhesion of the oxide film formed on the non-glazed surface is good, and the oxide film peels off in the subsequent steps. There is no need for steel plates.

  The present invention has been devised in view of the above-mentioned problems, and has excellent enamel characteristics and workability, and good enamel adhesion of an oxide film formed on a non-glazed surface in a baking treatment after glazing. It aims at providing the manufacturing method of the cold-rolled steel plate for processing, and an enamel processed product.

  The cold rolled steel sheet for enamel processing according to the present invention is a cold rolled steel sheet for enamel processing in which an enamel layer is provided only on one surface, and is in mass%, C: 0.0001 to 0.040%, Si: 0. 0.0001-0.50%, Mn: 0.001-2.00%, P: 0.0001-0.10%, S: 0.0001-0.060%, Al: 0.0001-0.10 %, N: 0.0001 to 0.015%, O: 0.0001 to 0.070%, Ni: 0.002 to 2.00%, Co: 0.0005 to 2.00%, Selected from the group consisting of Cr: 0.001-2.00%, Cu: 0.002-2.00%, Mo: 0.0001-2.00% and Ti: 0.0005-0.50% Contains one or more elements, the balance being Fe and inevitable impurities, N The content (%) is [Ni], the Co content (%) is [Co], the Cr content (%) is [Cr], the Cu content (%) is [Cu], and the Mo content (%) is When [Mo], Ti content (%) is [Ti], Mn content (%) is [Mn], and S content (%) is [S], the following formulas (1) and (2) It is characterized by satisfying.

  This enameled cold-rolled steel sheet is, in mass%, C: 0.0001 to 0.0040%, Si: 0.0001 to 0.10%, Mn: 0.001 to 1.00%, P: 0.00. 0001 to 0.050%, S: 0.0005 to 0.060%, Al: 0.0001 to 0.010%, N: 0.0001 to 0.0040%, O: 0.0010 to 0.050% Ni: 0.005 to 1.00%, Co: 0.001 to 1.00%, Cr: 0.005 to 1.00%, Cu: 0.005 to 1.00%, Mo Containing one or more elements selected from the group consisting of: 0.0005 to 1.00% and Ti: 0.0005 to 0.10%, with the balance consisting of Fe and inevitable impurities [ Ni] + [Co] + ([Cr] / 2) + [Cu] + [Mo] + [Ti] is 0. It is preferable that the 20-4.0.

  Or, in mass%, C: 0.0001 to 0.0040%, Si: 0.0001 to 0.10%, Mn: 0.001 to 1.00%, P: 0.0001 to 0.050%, S: 0.0005 to 0.060%, Al: 0.0001 to 0.010%, N: 0.0001 to 0.0040%, O: 0.0010 to 0.050%, Ti: 0.001 It is preferable that the composition contains 0.050%, and the balance is composed of Fe and inevitable impurities.

  Another cold rolled steel sheet for enamel processing according to the present invention is a cold rolled steel sheet for enamel processing in which an enamel layer is provided only on one surface, and is in mass%, C: 0.0001 to 0.040%, Si : 0.0001 to 0.50%, Mn: 0.001 to 2.00%, P: 0.0001 to 0.10%, S: 0.0001 to 0.060%, Al: 0.0001 to 0 .10%, N: 0.0001 to 0.015%, O: 0.0001 to 0.070%, Ni: 0.002 to 2.00%, Co: 0.0005 to 2.00%, Cr: One selected from the group consisting of 0.001 to 2.00%, Cu: 0.002 to 2.00%, Mo: 0.0001 to 2.00% and Ti: 0.0005 to 0.50% Or two or more elements, and Nb: 0.0005 to 1.00% and B: 0.0002 to 1 or 2 elements selected from the group consisting of 0.0500%, the balance being Fe and inevitable impurities, Ni content (%) [Ni], Co content (%) [ Co], Cr content (%) [Cr], Cu content (%) [Cu], Mo content (%) [Mo], Nb content (%) [Nb], Ti content (%) Is [Ti], B content (%) is [B], Mn content (%) is [Mn], and S content (%) is [S]. The above mathematical formula (2) is satisfied.

  This enameled cold-rolled steel sheet is, in mass%, C: 0.0001 to 0.0040%, Si: 0.0001 to 0.10%, Mn: 0.001 to 1.00%, P: 0.00. 0001 to 0.050%, S: 0.0005 to 0.060%, Al: 0.0001 to 0.010%, N: 0.0001 to 0.0040%, O: 0.0010 to 0.050% , Ni: 0.005 to 1.00%, Co: 0.001 to 1.00%, Cr: 0.005 to 1.00%, Cu: 0.005 to 1.00%, Mo: 0.0005 ~ 1.00% and Ti: 0.0005 to 0.10%, one or more elements selected from the group consisting of Nb: 0.003 to 0.20% and B: 0.0010 Contains one or two elements selected from the group consisting of ~ 0.0100%, the balance being Fe [Ni] + [Co] + ([Cr] / 2) + [Cu] + [Mo] + [Nb] + [Ti] + 10 × [B] is 0.020-4. 0 is preferred.

  Or, in mass%, C: 0.0001 to 0.0040%, Si: 0.0001 to 0.10%, Mn: 0.001 to 1.00%, P: 0.0001 to 0.050%, S: 0.0005 to 0.060%, Al: 0.0001 to 0.010%, N: 0.0001 to 0.0040%, O: 0.0010 to 0.050%, Ti: 0.001 It contains 0.050% and contains one or two elements selected from the group consisting of Nb: 0.003-0.15% and B: 0.0010-0.0050%, with the balance being It consists of Fe and inevitable impurities, and [Nb] + 10 × [B] is preferably 0.020 to 0.2.

  These enameled cold-rolled steel sheets are, in mass%, preferably S: 0.005 to 0.050%, and more preferably S: 0.0075 to 0.030%.

  Moreover, it is preferable that ratio ([Mn] / [S]) of Mn content ([Mn]) and S content ([S]) is 10-30.

The manufacturing method of the enamel processed product according to the present invention is that, after enamelling 30-50 μm of enamel only on one surface of the cold rolled steel sheet for enamel processing described above, in the atmosphere at a temperature of 650-850 ° C., Baking treatment is performed for 1 to 20 minutes.

  In this method for producing an enamel processed product, a top coating enamel may be further applied by 30 to 500 μm on the enamel, followed by firing treatment.

Alternatively, after the baking treatment, 30 to 500 μm of an overcoated enamel can be applied onto the enamel and the baking treatment can be carried out in the atmosphere at a temperature of 650 to 850 ° C. for 1 to 20 minutes.

  According to the present invention, the steel composition, particularly the S content, is optimized within a range in which an oxide film having excellent adhesion is formed in the baking treatment after glazing, so that the enamel characteristics and workability are excellent, and the glazing A cold-rolled steel sheet for enamel processing and an enamel processed product with good adhesion of the oxide film formed on the non-glazed surface in the subsequent firing treatment are obtained.

  Hereinafter, the best mode for carrying out the present invention will be described in detail. In the following description, mass% in the composition of the steel sheet is simply described as%.

  The present inventor has investigated the adhesion of an oxide film obtained by oxidizing steel sheets having different compositions and punishing the steel sheet. When the S content in the steel is appropriate, the steel sheet and the oxide film are formed at high temperatures. It has been found that a molten phase of FeO-FeS is formed at the interface with the. Further, the present inventor can preferably control the unevenness of the interface between the steel sheet and the oxide film by making the structure of the oxide film in an appropriate state, and further, when Nb and / or B is present in the steel sheet. It has been found that the unevenness of this interface becomes more preferable. And this inventor came to this invention based on these knowledge.

  First, an enameled cold-rolled steel sheet (hereinafter also simply referred to as a cold-rolled steel sheet) according to a first embodiment of the present invention will be described. The cold-rolled steel sheet of the present embodiment is an enameled steel sheet provided with an enamel layer only on one side, C: 0.0001 to 0.040%, Si: 0.0001 to 0.50%, Mn: 0.001-2.00%, P: 0.0001-0.10%, S: 0.0001-0.060%, Al: 0.0001-0.10%, N: 0.0001-0. 015% and O: 0.0001 to 0.070%, Ni: 0.002 to 2.00%, Co: 0.0005 to 2.00%, Cr: 0.001 to 2.00% Cu, 0.002 to 2.00%, Mo: 0.0001 to 2.00%, and Ti: 0.0005 to 0.50%, containing one or more elements selected from the group And the balance consists of Fe and inevitable impurities, and further, the following formula (4) and formula ( ) It is intended to meet the. In the following formula (4), [Ni] is Ni content (%), [Co] is Co content, [Cr] is Cr content (%), [Cu] is Cu content (%), [ Mo] is the Mo content (%), and [Ti] is the Ti content (%). In the following mathematical formula (5), [Mn] is the Mn content (%), and [S] is the S content (%).

  Hereinafter, the reason for adding each steel component constituting the cold-rolled steel sheet of the present embodiment and the reason for limiting the numerical value will be described.

C: 0.0001 to 0.040%
The lower the C, the better the workability, so the lower limit of the C content does not need to be specifically limited. However, reducing the amount of C in the steel increases the steelmaking cost. The content is preferably 0.0001% or more. When the C content exceeds 0.040%, good workability cannot be obtained. Therefore, the C content is set to 0.0001 to 0.040%. Note that the C content is preferably 0.0040% or less, and more preferably 0.0015% or less. Thereby, since elongation and r value of a cold-rolled steel plate become high, workability can be improved more.

Si: 0.0001 to 0.50%
Although the composition of the oxide can be controlled by adding Si, the effect cannot be obtained when the Si content is less than 0.0001%. On the other hand, when Si is added excessively, specifically, when the Si content exceeds 0.50%, not only the enamel characteristics are inhibited, but also a large amount of Si oxide having poor ductility in hot rolling. As a result, the resistance to picking is reduced. Therefore, the Si content is set to 0.0001 to 0.50%. In addition, it is preferable that Si content shall be 0.10% or less, and, thereby, it can improve a tear resistance more.

Mn: 0.001 to 2.00%
Mn is an essential component for avoiding hot brittleness, but if the Mn content is less than 0.001%, the effect cannot be obtained. On the other hand, when Mn is added excessively, specifically, when the Mn content exceeds 2.00%, the above-described formation of FeO-FeS is inhibited, so that the effect of improving the adhesion of the oxide film is obtained. In addition, the enamelability is impaired and the press workability is lowered. Therefore, the Mn content is set to 0.001 to 2.00%. In addition, it is preferable that Mn content shall be 1.00% or less, and this can improve the adhesiveness of an oxide film more.

P: 0.0001 to 0.10%
P is an element contained in steel as an unavoidable impurity. When the content thereof increases, specifically, when the P content exceeds 0.10%, glass and steel are used during firing after glazing. In particular, P segregates at a high concentration at the grain boundaries of the steel sheet, causing bubbles, black spots, and the like, deteriorating the enamel appearance. On the other hand, if the amount of P in the steel is reduced, the steelmaking cost increases. Therefore, considering practicality, the P content is preferably 0.0001% or more. Therefore, the P content is set to 0.0001 to 0.10%. In addition, it is preferable that P content shall be 0.050% or less, and, thereby, an enamel characteristic can be improved further.

S: 0.0001 to 0.060%
S is an element effective for improving the tightness of the oxide film because it has the effect of improving the resistance to squeezing and promotes the formation of the aforementioned FeO-FeS. However, when S is added excessively, specifically, when the S content exceeds 0.060%, the influence on hot brittleness becomes obvious, and enamel inhibition and press workability decrease are caused. . On the other hand, if the amount of S in the steel is reduced, the steelmaking cost increases. Therefore, considering practicality, the S content is preferably 0.0001% or more. Therefore, the S content is set to 0.0001 to 0.060%. In addition, it is preferable that S content is 0.005-0.050%, More preferably, it is 0.0075-0.030%. Thereby, the adhesiveness of an oxide film and hot brittleness reduction can be highly balanced.

Al: 0.0001 to 0.10%
Al is an oxide-forming element, and it is desirable that oxygen in the steel be present in the steel sheet in an appropriate amount as an oxide in order to improve the resistance to engraving as an enamel characteristic. However, this effect cannot be obtained when the Al content is less than 0.0001%. On the other hand, since Al is also a strong deoxidizing element, when it is contained in a large amount, specifically, when the Al content exceeds 0.10%, the amount of oxygen required in the present invention may be retained in the steel. Along with this, a large amount of Al oxide having poor ductility in hot rolling is formed, and the resistance to fatigue is lowered. Therefore, the Al content is 0.0001 to 0.10%. In addition, it is preferable that Al content is 0.010% or less, and, thereby, it can improve a tear resistance more.

N: 0.0001 to 0.015%
N is an interstitial solid solution element like C, and when it is contained in a large amount, specifically, when the N content exceeds 0.015%, a nitride-forming element such as Ti, Nb, and B described later Even if it adds, workability will deteriorate and it will become difficult to manufacture a non-aging steel plate. On the other hand, the lower limit of the N content is not particularly limited, but reducing the N content in the steel increases the steelmaking cost. Therefore, considering practicality, the N content should be 0.0001% or more. Is desirable. Therefore, the N content is set to 0.0001 to 0.015%. In addition, it is preferable that N content shall be 0.0040% or less, and thereby workability can be improved more.

O: 0.0001 to 0.070%
The cause of worsening enamelability such as picking is caused by hydrogen that penetrates into the steel plate during enamel firing, and according to the technique of the present application, oxides are dispersedly formed in the steel plate and around the oxides generated by rolling. O is an important element because it can trap hydrogen in the voids. In other words, it is an element necessary for oxide formation and directly affects the resistance to workability and workability, and also affects the resistance to resistance in relation to the contents of Mn, Al, Nb, etc., and is essential in the present invention. Elements. However, if the O content is less than 0.0001%, the effect of improving the resistance to squeezing and workability cannot be obtained. On the other hand, when the O content increases, specifically, when the O content exceeds 0.070%, the workability deteriorates, and the cost of steelmaking refractory increases. Therefore, the O content is set to 0.0001 to 0.070%. In addition, it is preferable to make O content into 0.050% or less, and, thereby, it can improve a tear resistance and workability more. Moreover, it is preferable that O content shall be 0.0010% or more, and, thereby, it can improve a tear-proof property markedly.

One or more of Ni, Co, Cr, Cu, Mo and Ti. These elements are contained in the oxide in a complex manner, and are elements that affect oxide formation. For example, it is unevenly distributed in the oxide, and the ductility and hardness are locally changed to improve the dispersion state of the oxide and to generate a large number of voids generated by rolling.

  However, the Ni content is less than 0.002%, the Co content is less than 0.0005%, the Cr content is less than 0.001%, the Cu content is less than 0.002%, and the Mo content is 0.0001%. If the Ti content is less than 0.0005%, the above-described effects cannot be obtained. On the other hand, when the Ni content exceeds 2.00%, the Co content exceeds 2.00%, the Cr content exceeds 2.00%, or the Ti content exceeds 0.50%, The homogenization of the physical properties of the oxide is promoted, and the characteristic and effective effect of the present invention is reduced. In addition, the manufacturing cost increases. Further, if the Cu content exceeds 2.00%, not only the reaction between glass and steel is inhibited, but also the workability deteriorates. Furthermore, if the Mo content exceeds 2.00%, the corrosion resistance effect is saturated and the manufacturing cost is increased. Therefore, in the cold-rolled steel sheet of the present embodiment, Ni: 0.002-2.00%, Co: 0.0005-2.00%, Cr: 0.001-2.00%, Cu: 0.002- One or more elements selected from the group consisting of 2.00%, Mo: 0.0001-2.00% and Ti: 0.0005-0.50% are included.

  The Ni content is 0.005 to 1.00%, Co: 0.001 to 1.00%, the Cr content is 0.005 to 1.00%, and the Cu content is 0.005 to 1.00. %, The Mo content is preferably 0.0005 to 1.00%, and the Ti content is preferably 0.0005 to 0.10%, so that the enamel characteristics can be further improved.

[Ni] + [Co] + ([Cr] / 2) + [Cu] + [Mo] + [Ti]: 0.010 to 8.0
The effects of adding Ni, Co, and Cr and the effects of adding Cu, Mo, and Ti are added and act. Specifically, when [Ni] + [Co] + ([Cr] / 2) + [Cu] + [Mo] + [Ti] is less than 0.010, the effect of improving enamel characteristics can be enjoyed. Moreover, when it exceeds 8.0, the homogenization of the physical property of an oxide is accelerated | stimulated and the fall of the characteristic effective effect of this invention is caused. Therefore, in the cold-rolled steel sheet of the present embodiment, the steel composition is in the above-described range, and the contents of Ni, Co, C, Cu, Mo, and Ti satisfy the above formula (4). [Ni] + [Co] + ([Cr] / 2) + [Cu] + [Mo] + [Ti] is preferably 0.020 to 4.0, which further enhances the enamel characteristics. It can be in a good state.

[Mn] / [S]: 5-40
The ratio between the Mn content and the S content affects the adhesion and hot brittleness of the oxide film. In FIG. 1, the horizontal axis represents the ratio of Mn content ([Mn]) to S content ([S]), and the vertical axis represents the adhesion and annual brittleness of the oxide film. It is a graph which shows the relationship between ratio ([Mn] / [S]) and the adhesiveness of an oxide film, and hot brittleness. As shown in FIG. 1, when [Mn] / [S] is less than 5, the adhesion of the oxide film is lowered, and when [Mn] / [S] exceeds 40, hot brittleness is lowered. Therefore, in the cold rolled steel sheet of the present embodiment, in addition to the above-described conditions, the Mn content and the S content satisfy the above formula (5). In addition, it is preferable that [Mn] / [S] is 10-30. Thereby, the adhesiveness and hot brittleness of an oxide film can be improved more.

  In addition, the components other than the above in the cold-rolled steel sheet of the present embodiment, that is, the remainder are Fe and inevitable impurities. Inevitable impurities in steel may adversely affect the material characteristics and enamel characteristics of cold-rolled steel sheets, so it is desirable to reduce the amount thereof.

  In the cold-rolled steel sheet of the present embodiment, C: 0.0001 to 0.0040%, Si: 0.0001 to 0.10%, Mn: 0.001 to 1.00%, P: 0.0001 ~ 0.050%, S: 0.0005 to 0.060%, Al: 0.0001 to 0.010%, N: 0.0001 to 0.0040%, O: 0.0010 to 0.050% Ni: 0.005 to 1.00%, Co: 0.001 to 1.00%, Cr: 0.005 to 1.00%, Cu: 0.005 to 1.00%, Mo: It contains one or more elements selected from the group consisting of 0.0005 to 1.00% and Ti: 0.0005 to 0.10%, and the balance is composed of Fe and inevitable impurities. In this case, [Ni] + [Co] + ([Cr] / 2) + [ u] + [Mo] + [Ti] it is preferably set to 0.020 to 4.0. With such a composition, the balance of each component is improved, so that all the characteristics of enamel characteristics, oxide film adhesion, hot brittleness, and press workability can be improved in a balanced manner.

  Alternatively, C: 0.0001 to 0.0040%, Si: 0.0001 to 0.10%, Mn: 0.001 to 1.00%, P: 0.0001 to 0.050%, S: 0.00. 0005 to 0.060%, Al: 0.0001 to 0.010%, N: 0.0001 to 0.0040%, O: 0.0010 to 0.050%, Ti: 0.001 to 0.050% And the balance may be composed of Fe and inevitable impurities. By setting it as such a composition, since especially Ti can be made into the optimal range, the balance of workability and an enamel characteristic can be improved.

  As described above, in the cold-rolled steel sheet of the present embodiment, the steel composition, particularly the S content, is optimized, so that the adhesion of the oxide film formed on the non-glazed surface by the firing treatment can be improved. As a result, the enamel characteristics and workability are excellent, and even with single-side glazing, the adhesion of the oxide film formed on the non-glazed surface in the subsequent firing treatment is good, and the oxide film does not peel off during assembly. A cold-rolled steel sheet for processing is obtained.

  Next, a method for manufacturing a cold-rolled steel sheet according to the second embodiment of the present invention will be described. The cold-rolled steel sheet of this embodiment is obtained by adding Nb and / or B to the composition of the cold-rolled steel sheet of the first embodiment described above. Specifically, the cold-rolled steel sheet of this embodiment is a cold-rolled steel sheet for enamel processing in which an enamel layer is provided only on one surface, and is in mass%, C: 0.0001 to 0.040%, Si : 0.0001 to 0.50%, Mn: 0.001 to 2.00%, P: 0.0001 to 0.10%, S: 0.0001 to 0.060%, Al: 0.0001 to 0 .10%, N: 0.0001 to 0.015%, O: 0.0001 to 0.070%, Ni: 0.002 to 2.00%, Co: 0.0005 to 2.00%, Cr: One selected from the group consisting of 0.001 to 2.00%, Cu: 0.002 to 2.00%, Mo: 0.0001 to 2.00% and Ti: 0.0005 to 0.50% Or two or more elements, and Nb: 0.0005 to 1.00% and B: 0.0002 to 0.0 Contain one or two elements selected from the group consisting of 100%, the balance being Fe and unavoidable impurities, and further, satisfies the following formula (6) and the equation (5). In the following formula (6), [Nb] is the Nb content (%), and [B] is the B content (%).

Nb: 0.0005 to 1.00%
Nb and B segregate at the interface between the steel sheet and the oxide film, as with Mn, and form fine irregularities at this interface during firing after glazing. In addition, an oxide containing Ti, K, Na and B derived from the glaze is precipitated on the fine irregularities of the interface, and is an important element having an effect of improving the adhesion between the steel plate and the enamel layer. . Furthermore, Nb fixes C and N, improves deep drawability, improves the workability by non-aging, and forms an oxide by combining with oxygen in the steel, thereby preventing tripping. There is also an effect that works effectively. However, when the Nb content is less than 0.0005%, these effects cannot be obtained. Moreover, when Nb content exceeds 1.00%, it will deoxidize at the time of Nb addition, and it will become difficult to retain an oxide in steel, and bubble resistance and black spot property will deteriorate. Therefore, when adding Nb, it is set as 0.0005 to 1.00%. In addition, it is preferable that Nb content shall be 0.003-0.20%, More preferably, it is 0.003-0.15%. Thereby, the balance of the adhesion and enamelability of the oxide film can be improved.

B: 0.0002 to 0.0500%
On the other hand, when the B content is less than 0.0002%, the above-described addition effect cannot be obtained, and when the B content exceeds 0.0500%, the castability deteriorates. In addition, when the Nb content is relatively high, the recrystallization temperature rises remarkably due to the addition of B. Therefore, in order to obtain good workability after cold rolling / annealing, annealing at an extremely high temperature is required. , Annealing productivity may decrease. For this reason, although depending on Nb content, when adding both Nb and B, it is preferable to make B content into 0.0100% or less, and it is more preferable to set it as 0.0050% or less. In addition, it is preferable to make B content into 0.0010% or more, and this can improve the balance of the adhesiveness and enamelability of an oxide film.

[Ni] + [Co] + ([Cr] / 2) + [Cu] + [Mo] + [Nb] + [Ti] + 10 × [B]: 0.010 to 8.0
The effect of adding Nb and B acts in addition to the effect of adding Cu, Mo, and Ti. As the magnitude of its contribution, B has an effect 10 times that of Nb. Therefore, if [Ni] + [Co] + ([Cr] / 2) + [Cu] + [Mo] + [Nb] + [Ti] + 10 × [B] is less than 0.010, enamel characteristics The improvement effect cannot be enjoyed, and if it exceeds 8.0, homogenization of the physical properties of the oxide is promoted, and the characteristic and effective effect of the present invention is lowered. Therefore, in the cold-rolled steel sheet of this embodiment, when adding Nb and B, it is necessary to satisfy the above formula (6) in addition to the above-described conditions. [Ni] + [Co] + ([Cr] / 2) + [Cu] + [Mo] + [Nb] + [Ti] + 10 × [B] should be 0.020 to 4.0. Preferably, this can make the enamel characteristics even better.

  The reasons for limiting the numerical values other than the above in the cold rolled steel sheet of the present embodiment are the same as those of the cold rolled steel sheet of the first embodiment described above.

  In the cold-rolled steel sheet of the present embodiment, C: 0.0001 to 0.0040%, Si: 0.0001 to 0.10%, Mn: 0.001 to 1.00%, P: 0.0001 ~ 0.050%, S: 0.0005 to 0.060%, Al: 0.0001 to 0.010%, N: 0.0001 to 0.0040%, O: 0.0010 to 0.050%, Ni: 0.005-1.00%, Co: 0.001-1.00%, Cr: 0.005-1.00%, Cu: 0.005-1.00%, Mo: 0.0005 One or more elements selected from the group consisting of 1.00% and Ti: 0.0005 to 0.10%, and Nb: 0.003 to 0.20% and B: 0.0010 Contains one or two elements selected from the group consisting of 0.0100%, the balance being Fe and A composition comprising inevitable impurities is preferable. In that case, [Ni] + [Co] + ([Cr] / 2) + [Cu] + [Mo] + [Nb] + [Ti] + 10 × [B ] Is preferably 0.020 to 4.0. By using such a composition, the effect of improving the adhesion of the oxide film by Nb and B can be enjoyed, so that the adhesion of the oxide film can be particularly improved in addition to the enamel characteristics and press workability.

  Alternatively, C: 0.0001 to 0.0040%, Si: 0.0001 to 0.10%, Mn: 0.001 to 1.00%, P: 0.0001 to 0.050%, S: 0.00. 0005 to 0.060%, Al: 0.0001 to 0.010%, N: 0.0001 to 0.0040%, O: 0.0010 to 0.050%, Ti: 0.001 to 0.050% And Nb: 0.003 to 0.15% and B: 0.0010 to 0.0050%, and one or two elements selected from the group consisting of 0.0010 to 0.0050%, the balance being Fe and inevitable A composition composed of impurities is preferable. At this time, since the addition effect of Nb and B acts as an addition, these addition effects can be further improved by adding these elements in combination. On the other hand, if Nb and B are added in combination, the recrystallization temperature of the steel sheet will rise significantly, so if ([Nb] + 10 × [B]) exceeds 0.2, the steel sheet will not be sufficiently recrystallized and processed. May decrease. In addition, when ([Nb] + 10 × [B]) is less than 0.020, the combined effect may not be sufficiently obtained. Therefore, when the steel composition is within the above range, it is desirable that [Nb] + 10 × [B] is 0.020 to 0.2 in addition to the above-described conditions. This further improves the balance between the adhesion of the oxide film and the enamel characteristics.

  As described above, in the cold-rolled steel sheet of the present embodiment, the steel composition, particularly the S content, is optimized, so that the adhesion of the oxide film formed on the non-glazed surface by the firing treatment can be improved. As a result, the enamel characteristics and workability are excellent, and even with single-side glazing, the adhesion of the oxide film formed on the non-glazed surface in the subsequent firing treatment is good, and the oxide film does not peel off during assembly. A cold-rolled steel sheet for processing is obtained.

  Next, as a third embodiment of the present invention, a method for manufacturing an enamel processed product using the cold-rolled steel sheets of the first to third embodiments described above will be described. In the method for manufacturing an enamel processed product according to this embodiment, after enamelling 30-50 μm of enamel only on one surface of the cold-rolled steel sheets of the first to third embodiments described above, in the atmosphere or in a weakly oxidizing atmosphere. Then, baking is performed at a temperature of 650 to 850 ° C. for 1 to 20 minutes. Thereby, an enamel layer is formed on one surface (glazed surface) of the cold-rolled steel sheet, and an oxide film having a thickness of, for example, 20 to 500 μm is formed on the other surface (non-glazed surface).

  Moreover, in the manufacturing method of the enamel processed goods of this embodiment, after carrying out 30-500 micrometers glazing of the top-coated enamel on the previously glazed enamel, baking processing may be performed on the conditions mentioned above. Or, first, after forming the enamel layer to be the above-described method ground coat, the top coat enamel is applied 30 to 500 μm, and in the atmosphere or in a weakly oxidizing atmosphere at a temperature of 650 to 850 ° C., An enamel layer to be a cover coat may be formed by baking for 1 to 20 minutes.

  In the manufacturing method of the enamel processed product of this embodiment, since the cold-rolled steel sheet of the first to third embodiments described above is used, the adhesion of the oxide film on the non-glazed surface is excellent, and at the time of assembly The oxide film does not peel off, and the enamel characteristics and workability are excellent.

  Hereinafter, the effects of the present invention will be specifically described with reference to examples of the present invention and comparative examples that are out of the scope of the present invention. First, as Example 1 of the present invention, a steel having the composition shown in Table 1 below is melted in a vacuum melting furnace, cast into an ingot, subjected to hot rolling and cold rolling, and then subjected to annealing skin pass rolling. A cold-rolled steel sheet having a thickness of 0.8 mm was produced. And after enamelling 150 μm of enamel on only one surface of each cold-rolled steel sheet, it was fired at 820 ° C. for 6 minutes to obtain enameled products of Examples and Comparative Examples. The balance of the steel composition shown in Table 1 below is Fe and inevitable impurities. In Table 1 below, conditions outside the scope of the present invention are underlined.

  Next, for each enamel processed product of Examples and Comparative Examples prepared by the above-described method, enamel characteristics (slip resistance, foam / spot characteristics), adhesion of oxide film on non-glazed surface, hot brittleness and press Processability was evaluated.

  The resistance to pickling was judged by the state of occurrence of picking in the enamel layer of each enameled product by holding each enameled product at 200 ° C. for 20 minutes and then performing a thermal shock test in which it was cooled in water for 3 cycles. ◎ if there was no occurrence of flickering, ○ if it was over 0% and 0.5% or less, △ if it was over 0.5% and 5.0% or less, and 5.0% What exceeded was set as x.

  In the evaluation of foam / spot characteristics, each enamel processed product was kept in a thermostatic bath at 0 ° C. for 2 hours, and then the occurrence of bubbles / spots in the enamel layer of each enamel processed product was visually confirmed. As a result, the case where no bubble / spot was generated was ○, the case where it was more than 0% and 0.5% or less was ◯, the case where it was more than 0.5% and 5.0% or less was Δ, A value exceeding 0.0% was evaluated as x.

The adhesion of the oxide film was evaluated by measuring the adhesion area ratio when a 5 mm # type score line was put on a 100 mm square sample, a cellophane tape was applied and peeled off. As a result, the adhesion rate was 80% or more, ◎, 60% or more and less than 80%, ○, 40% or more and less than 60%, Δ, or less than 40%. X.
(Cello tape is a registered trademark, so it was a cellophane tape.)

  Hot brittleness was evaluated by performing a greeble test at 900 to 1450 ° C. using a round bar taken from an ingot before rolling. As a result, the cross-sectional drawing ratio was 60% or more, ％, 40% or more and less than 60% ○, 30% or more and less than 40% △, less than 30%. What was there was marked as x.

  The workability was evaluated based on the r value by preparing a JIS No. 5 test piece from each enameled product and conducting a tensile test. As a result, those having an r value of 2.0 or more are ◎, those having an r value of 1.8 or more and less than 2.0 are ○, those having an r value of 1.5 or more and less than 1.8 △ and r value of less than 1.5% were marked with ×. The above evaluation results are summarized in Table 2 below.

  As shown in Table 2 above, Examples 1 to 20 of the present invention have evaluations of 、, ○, and Δ for enamel characteristics, oxide film adhesion, hot brittleness, and press workability, and correspond to evaluation of ×. There was nothing. On the other hand, in Comparative Examples 21 to 32 that deviate from the scope of the present invention, one having an evaluation of x among enamel characteristics, oxide film adhesion, hot brittleness, and press workability was present. For this reason, in any evaluation item, it can be said that it is necessary to adopt the configuration of the example of the present invention in order to prevent the evaluation of x.

Taking the ratio of the Mn content ([Mn]) and the S content ([S]) on the horizontal axis and the adhesion and annual brittleness on the vertical axis, the Mn content and the S content It is a graph which shows the relationship between ratio ([Mn] / [S]), the adhesiveness of an oxide film, and hot brittleness.

Claims (12)

A cold-rolled steel sheet for enamel processing in which an enamel layer is provided only on one side,
% By mass
C: 0.0001 to 0.040%,
Si: 0.0001 to 0.50%,
Mn: 0.001 to 2.00%,
P: 0.0001 to 0.10%,
S: 0.0001 to 0.060%,
Al: 0.0001 to 0.10%,
N: 0.0001 to 0.015%,
O: containing 0.0001-0.070%,
Ni: 0.002-2.00%, Co: 0.0005-2.00%, Cr: 0.001-2.00%, Cu: 0.002-2.00%, Mo: 0.0001- Containing one or more elements selected from the group consisting of 2.00% and Ti: 0.0005-0.50%,
The balance consists of Fe and inevitable impurities,
Ni content (%) is [Ni], Co content (%) is [Co], Cr content (%) is [Cr], Cu content (%) is [Cu], Mo content (%) Is [Mo], Ti content (%) is [Ti], Mn content (%) is [Mn], and S content (%) is [S], the following formulas (A) and (B A cold rolled steel sheet for enamel processing.

% By mass
C: 0.0001 to 0.0040%,
Si: 0.0001 to 0.10%,
Mn: 0.001 to 1.00%,
P: 0.0001 to 0.050%,
S: 0.0005 to 0.060%,
Al: 0.0001 to 0.010%,
N: 0.0001 to 0.0040%,
O: containing 0.0010 to 0.050%,
Ni: 0.005-1.00%, Co: 0.001-1.00%, Cr: 0.005-1.00%, Cu: 0.005-1.00%, Mo: 0.0005 Containing one or more elements selected from the group consisting of 1.00% and Ti: 0.0005-0.10%,
The balance consists of Fe and inevitable impurities,
The enamel treatment according to claim 1, wherein [Ni] + [Co] + ([Cr] / 2) + [Cu] + [Mo] + [Ti] is 0.020 to 4.0. Cold rolled steel sheet. % By mass
C: 0.0001 to 0.0040%,
Si: 0.0001 to 0.10%,
Mn: 0.001 to 1.00%,
P: 0.0001 to 0.050%,
S: 0.0005 to 0.060%,
Al: 0.0001 to 0.010%,
N: 0.0001 to 0.0040%,
O: 0.0010 to 0.050%
Ti: 0.001 to 0.050% is contained,
2. The cold rolled steel sheet for enamel processing according to claim 1, wherein the balance is made of Fe and inevitable impurities. A cold-rolled steel sheet for enamel processing in which an enamel layer is provided only on one side,
% By mass
C: 0.0001 to 0.040%,
Si: 0.0001 to 0.50%,
Mn: 0.001 to 2.00%,
P: 0.0001 to 0.10%,
S: 0.0001 to 0.060%,
Al: 0.0001 to 0.10%,
N: 0.0001 to 0.015%,
O: 0.0001 to 0.070%,
Ni: 0.002-2.00%, Co: 0.0005-2.00%, Cr: 0.001-2.00%, Cu: 0.002-2.00%, Mo: 0.0001- One or more elements selected from the group consisting of 2.00% and Ti: 0.0005 to 0.50%, and
Containing one or two elements selected from the group consisting of Nb: 0.0005-1.00% and B: 0.0002-0.0500%,
The balance consists of Fe and inevitable impurities,
Ni content (%) is [Ni], Co content (%) is [Co], Cr content (%) is [Cr], Cu content (%) is [Cu], Mo content (%) [Mo], Nb content (%) [Nb], Ti content (%) [Ti], B content (%) [B], Mn content (%) [Mn], S An enameled cold-rolled steel sheet characterized by satisfying the following formula (C) and formula (D) when the content (%) is [S].

% By mass
C: 0.0001 to 0.0040%,
Si: 0.0001 to 0.10%,
Mn: 0.001 to 1.00%,
P: 0.0001 to 0.050%,
S: 0.0005 to 0.060%,
Al: 0.0001 to 0.010%,
N: 0.0001 to 0.0040%,
O: 0.0010 to 0.050%
Ni: 0.005-1.00%, Co: 0.001-1.00%, Cr: 0.005-1.00%, Cu: 0.005-1.00%, Mo: 0.0005 One or more elements selected from the group consisting of 1.00% and Ti: 0.0005-0.10%, and Nb: 0.003-0.20% and B: 0.0010-0 Containing one or two elements selected from the group consisting of .0100%,
The balance consists of Fe and inevitable impurities,
[Ni] + [Co] + ([Cr] / 2) + [Cu] + [Mo] + [Nb] + [Ti] + 10 × [B] is 0.020 to 4.0, The cold rolled steel sheet for enamel processing according to claim 4. % By mass
C: 0.0001 to 0.0040%,
Si: 0.0001 to 0.10%,
Mn: 0.001 to 1.00%,
P: 0.0001 to 0.050%,
S: 0.0005 to 0.060%,
Al: 0.0001 to 0.010%,
N: 0.0001 to 0.0040%,
O: 0.0010 to 0.050%
Ti: 0.001 to 0.050% containing,
Containing one or two elements selected from the group consisting of Nb: 0.003-0.15% and B: 0.0010-0.0050%,
The balance consists of Fe and inevitable impurities,
The cold rolled steel sheet for enamel treatment according to claim 4, wherein [Nb] + 10 x [B] is 0.020 to 0.2.   The cold rolled steel sheet for enamel treatment according to any one of claims 1 to 6, wherein S is 0.005 to 0.050% by mass.   The cold rolled steel sheet for enamel treatment according to claim 7, wherein the mass ratio is S: 0.0075 to 0.030%.   9. The ratio ([Mn] / [S]) of the Mn content ([Mn]) and the S content ([S]) is 10 to 30. Cold rolled steel sheet for enamel processing as described in 1. On one surface of the enameling process for cold-rolled steel sheet according to any one of claims 1 to 9 only after 30~50μm glazed with enamel, in air, at a temperature of 650 to 850 ° C., 1 A method for producing a processed enamel product, characterized by firing for 20 minutes.
  The method for producing an enamel processed product according to claim 10, further comprising applying an overcoated enamel 30 to 500 μm on the enamel and then performing a baking treatment. The calcining treatment is further performed by applying 30 to 500 µm of a top-coated enamel on the enamel and firing in the atmosphere at a temperature of 650 to 850 ° C for 1 to 20 minutes. A method for producing an enamel processed product according to 1.

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