JPH05186885A - Production of steel sheet for enameling - Google Patents

Abstract

PURPOSE:To simplify a pretreating process before enameling, to impart suitability to enameling even to an ordinary steel sheet which is difficult to enamel by the conventional method and to attain contribution to qualitative and quantitative extension of enamelware. CONSTITUTION:Oxide scale 2 on the surface of a hot rolled steel sheet 1 is removed with electric arc 3 in vacuum, the surface of the steel sheet 1 is roughened with the arc 3 and enameling is carried out. In the case of a cold rolled steel sheet, the surface of the steel sheet is roughened with electric arc in vacuum and enameling is carried out.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a enamel steel sheet, and provides a method for producing a enamel steel sheet which simplifies the pretreatment process for enamel and enables enamel to be applied even on ordinary steel sheets not for enamel. It is a thing.

[0002]

2. Description of the Related Art The treatment process of a steel sheet enamel, which is produced by applying a vitreous glaze on the surface of a steel sheet and melting it at a high temperature, includes one-time application and two-step application. In the manufacturing process of the one-time enamel, after the steel sheet is molded, degreasing-water washing-pickling-Ni flush-water washing-neutralization-drying pretreatments are performed, and then glaze-drying-firing-cooling. In addition, in the manufacturing process of the enamel which is applied twice, after performing the above-mentioned pretreatment, lower glaze-drying-firing-cooling-upper glaze-drying-firing-cooling. Here, in the degreasing in the pretreatment step, an alkaline degreasing method is usually adopted in order to remove the rust preventive oil applied to the surface of the steel sheet or the lubricating oil used in forming the steel sheet.
For about 5 minutes. Next, pickling is usually carried out in an aqueous solution of about 10% sulfuric acid at 70 ° C. for about 5 minutes. This removes the rust and coating on the surface of the steel sheet, cleans the surface of the steel sheet, and dissolves it moderately to roughen it. Ni flushing is an essential step for uniformly and sparsely adhering Ni to the surface of a steel sheet that has been roughened by pickling to improve enamel adhesion, and is usually performed in a 1.5% Ni sulfate aqueous solution at 70 ° C. It is processed for about 3 minutes.

There is a close relationship between the above-mentioned pickling and Ni flush. It is generally known that an increase in pickling time leads to an increase in pickling loss (weight reduction of steel sheet due to pickling) and an increase in the Ni deposition amount at that time. It is known that these further have a great influence on enamel adhesion and enamel characteristics such as foam. If either or both of the pickling loss and Ni adhesion amount are too small, the enamel adhesion will decrease, and If the amount is too large, enamel defects such as bubbles, pinholes, and black spots are likely to occur, and the enamel adhesion is also adversely affected. For this reason, as treatment conditions that ensure good enamel adhesion and are free of enamel defects, the pickling loss is usually about 20 to 300 g / m ² , and the Ni adhesion is about 0.
It is processed in the range of 5 to ³ g / m ² .

Therefore, pickling and Ni flush in the pretreatment process of enamel are indispensable. For the double-coated enamel, a technique has been developed in which pickling or pickling and Ni flush can be omitted by using non-pickling / Ni-treated glaze or pickling / Ni-free glaze. Is not practical because it is expensive.

As described above, since the pretreatment process for enamel is long and complicated and it is difficult to omit the process, a great deal of labor is required to stably manufacture enamel products. Therefore, there is a drawback that the cost is high. Furthermore, since the pretreatment of the enamel described above is performed by a thermal method, rust is likely to occur on the surface of the steel sheet, and hydrogen is likely to penetrate into the steel sheet during the pickling process. The hydrogen that has penetrated into the steel sheet causes defects such as so-called nail popping in which the enamel layer is peeled in a half-moon shape after firing and cooling of the enamel, and defects caused by hydrogen such as bubbles and pinholes.

On the other hand, the enameled steel sheet has a unique manufacturing method in order to secure good enameling adhesion as well as formability and to impart enameling properties such as generation of bubbles and pinholes. Has been taken. That is, ultra-low carbon steel is required from the viewpoint of ensuring formability and preventing bubble defects, and decarburization annealing is performed in addition to steelmaking decarburization. In addition, in order to prevent nail jumping after enameling firing and cooling, inclusions such as MnS and other precipitates such as carbides are increased in the steel, and voids formed around these inclusions and precipitates are added to the steel. A manufacturing method is adopted that occludes the invading hydrogen and prevents the hydrogen from diffusing at the boundary between the steel plate and the enamel layer. in addition,
Addition of Cu is indispensable to secure the adhesiveness of enamel, and Si, Mn, P, and
A method of increasing the content of Ti, B, Nb, V, W, etc. is also carried out as necessary. Therefore, when a plain steel sheet which is not used for enamel is used, the enamel property is poor even though the formability is secured, and it has not been put to practical use.

[0007] Although such a method for producing an enameled steel sheet has hitherto been considered as a necessary condition, it has also been an essential problem of the enameled steel sheet.

Further, when using a hot-rolled steel sheet, the oxide scale formed on the surface of the steel sheet peels off during forming and causes surface defects, and the oxide scale floats up during enamel firing and deteriorates the appearance of enamel. At the same time, there is an adverse effect such as a decrease in enamel adhesion, so it is necessary to remove it beforehand by a method such as pickling.

Next, as a technique for improving the problems of the above-described enameled steel plate, Japanese Patent Laid-Open No. 1-316470 discloses that the surface of the steel plate is roughened by a method such as shot blasting,
This is followed by a method for producing an extremely thin oxide film. This method is effective only for double enamel, but is not applied to single enamel. Further, a mechanical surface roughening method such as shot blasting has a drawback that since the steel sheet surface layer is strongly processed, distortion is likely to occur during firing in addition to deformation such as warpage and bending.

[0010]

As mentioned above, it is necessary for the steel sheet for enamel to secure formability and enamel property, and all the characteristics are indispensable. Therefore, the manufacturing conditions are severely restricted, which causes a cost increase.
Furthermore, even if the ordinary steel sheet can secure the formability, it cannot secure the enamel characteristics.

An object of the present invention is to provide a technique for solving these manufacturing problems. That is, the present invention relates to the production of a enamel steel plate, and provides a method for producing a enamel steel plate which simplifies the pretreatment process for enamel and enables enamel to be applied even on ordinary steel plates.

[0012]

The gist of the present invention is characterized in that surface oxide scale of a hot rolled steel sheet is removed by an electric arc under vacuum and the steel sheet surface is roughened and then enameled. Manufacturing method of steel plate for enamel, and
A method for producing a steel plate for enamel, characterized in that the surface of a cold-rolled steel plate is roughened by an electric arc under vacuum and then enameled.

[0013]

In general, a enamel steel sheet requires the above-mentioned steel sheet manufacturing method and the enamel pretreatment step. As in the present invention, the surface oxide scale of the hot rolled steel sheet is removed and the enamel pretreatment step is performed to roughen the surface of the steel sheet. Until now, there is no technology to perform surface treatment in the same process. Further, in the case of cold-rolled steel sheets, there has been no method for producing enameled steel sheets capable of omitting not only the roughening but also the step of decarburizing and annealing performed subsequent to cold rolling. Furthermore, there are very few technologies that enable enameling even on ordinary steel plates that are not for enameling.

The present invention will be described in detail below.

The enameled steel sheet is a decarburized steel sheet and steel strip for enameling such as SPP of JIS G 3133, a steel sheet and steel strip for hot-rolled enameling which are not in the JIS standard, rimmed steel for casting, capped steel and aluminum quilted steel. Steel sheet and strip, and continuous cast aluminum quilt steel are hot-rolled and then hot-rolled at high temperature for skin pass, and steel sheet and strip with enamel property added, and P and other alloying elements to secure strength Including P-added steel and low alloy steel.

Ordinary steel sheets are SPHC, SPHD, SP
HE JIS G3131 hot rolled mild steel sheet and strip,
These are steel sheets and steel strips including cold rolled steel sheets and steel strips of SPCC, SPCD and SPE of JIS G3141, and tin plate original sheets such as SPB of JIS G3303.

The composition range of the enameled steel plate and the ordinary steel plate is determined according to the above-mentioned JIS standard. Further, Cu is 0.08% or less, Al is 0.08% or less, and T
i is 0.12% or less, and B and N are 0.02% or less. The reason for setting Cu to 0.08% or less is that Cu is added to improve enamel adhesion, but if it exceeds 0.08%, the effect is saturated, and surface defects due to Cu easily occur. , And high cost. Further, the reason for setting Al to 0.08% or less is that the content of Al is unavoidable by deoxidizing Al, and the upper limit is 0.08 so that enamel adhesion is good and enamel defects do not occur. % And Al is 0.
If it exceeds 08%, it is excessive and the cost becomes high. Ti
The content of 0.12% or less is that Ti is added as a deoxidizing agent like Al and forms nitrides and carbides to improve the non-aging property and workability of the steel sheet, and to improve the nitrides, carbides and sulfides. This is because the effect of preventing nail popping is improved by forming an object. Although it is effective up to 0.12%, if it exceeds 0.12%, there are adverse effects such as poor weldability, resulting in high cost. The reason for setting B to 0.02% or less is to add nitrides and carbides to form the same effect as Ti, so as to have the same effect as Ti, but if it exceeds 0.02%, the workability deteriorates. This is because there is an adverse effect of. In addition, N forms the above-mentioned nitride and is added to obtain predetermined characteristics.
If it exceeds 0.02%, the effect is saturated and there is an adverse effect such as deterioration of workability, so the content was made 0.02% or less.

Next, the adhesion mechanism between the enamel and the steel plate in the manufacturing process of enamel is generally considered as follows.
During the firing after the glaze, which is performed after the above-described enameling pretreatment, the surface of the steel sheet is first oxidized to form an oxide film.
Next, the enamel glaze melts (softens), iron oxide is dissolved in the glaze until the firing is completed, and the enamel and the steel plate adhere to each other. Here, when the iron oxide is excessive, it is not sufficiently dissolved in the enamel glaze and the adhesion of the enamel is deteriorated, and the undissolved iron oxide floats on the surface, causing surface defects. Oxide scale generated on the surface when manufacturing a hot rolled steel sheet is usually 2 to 10
Since it is extremely thick as μm and does not dissolve in enameled glaze,
Usually, it is necessary to remove it beforehand by a method such as pickling.

In the present invention, first, regarding the hot rolled steel sheet,
As shown in FIG. 1, the oxide scale 2 is treated with an electric arc 3 under vacuum to remove the oxide scale 2 and roughen the surface of the steel sheet 1 at the same time. As a result, there is no need to remove the oxide scale by pickling or the like and then apply rust preventive oil, and the degreasing-water washing-pickling-water washing steps in the enamel pretreatment step can be omitted.
Further, after removing the oxide scale and roughening the surface of the steel sheet with an electric arc under vacuum, Ni flash is subjected to vapor phase plating treatment such as an ion vapor deposition method to produce a pretreated steel sheet. Further, although the conventional method is sufficient for the glaze, by performing baking-cooling after performing dry coating such as electrostatic coating, it becomes possible to manufacture enamel from a conventional warm process to a dry process. ..

Next, for the cold rolled steel sheet, the surface of the steel sheet is roughened by an electric arc under vacuum after cold rolling. Further, the production of the pretreated steel sheet and the conventional glazing-drying-firing or enamel treatment steps are all carried out by a dry method by omitting the enamel pretreatment step and Ni flash by vapor phase plating treatment.

Further, after the surface of the steel sheet is roughened, a very thin oxide film may be formed on the surface of the steel sheet and Ni may be attached thereto.

In the present invention, in order to roughen the surface of the steel sheet with an electric arc in a vacuum, the steel sheet is used as a cathode and the electrode facing the steel sheet is used as an anode to generate an electric arc between both electrodes. The electric arc generation condition is to select a vacuum degree, a voltage, and a current in accordance with the thickness of the surface oxide scale of the steel sheet to be used, the surface roughness, and the plate passing speed to ensure a predetermined surface roughness.
If necessary, the surface roughness and the processing speed may be changed by changing the number of electrodes and the current density.

Here, the surface roughness of the steel sheet for obtaining the enamel characteristics aimed at by the present invention has a surface roughness R _{max of 5} to 80 μm.
m, the center line average roughness _Ra is 0.3 to 10 μm, and the peak number PPI per inch is required to be 15 to 500. That is, when R _max is less than 5 μm, the surface of the steel sheet is unnecessarily smoothed, resulting in lower enamel adhesion and higher cost. On the contrary, if R _max exceeds 80 μm, the surface quality of the enamel product is deteriorated and the appearance is deteriorated. Desirably R
20 to 50 μm for _max , 0.5 to 5 μm for _Ra , PPI
To 200-350.

In this method, when an oxide scale is present on the surface of a steel sheet such as a hot rolled steel sheet, an oxide having a small work function is preferentially removed by an electric arc.
There is an advantage that scale removal and roughening of the steel sheet surface can be continuously and simultaneously performed. On the other hand, in cold-rolled steel sheets, there is no thick oxide scale on the surface of the steel sheet unlike in hot-rolled steel sheets, so it is sufficient to roughen the surface of the steel sheet. As a result, it is possible to obtain surface characteristics equal to or higher than those of the steel sheet after pickling in the pretreatment process for enamel. In addition, when the surface of the steel sheet is roughened, decarburization is performed when the outermost surface layer is once melted by an electric arc, so that conventional decarburization treatment can be reduced.

Furthermore, the method of the present invention is capable of providing good enamel properties in which the occurrence of enamel defects such as nail pops and bubbles is extremely small in the enamel steel plate as compared with the conventional method, and a large number of steps can be omitted. Not only is it possible, but there is a great advantage that enamel can be applied to ordinary steel plates that are not for enamel. That is, the ordinary steel sheet could not be used because enamel defects due to hydrogen such as nail pops and bubbles are generated after enamel firing and cooling. Therefore, steel plates for enamel are mainly made by a method of forming inclusions, precipitates, etc. in the steel plate and occluding hydrogen that has penetrated into the steel in the voids formed around these, which is It was an essential manufacturing problem. The method of the present invention is based on a method in which hydrogen, which is the main cause of these enamel defects, is not allowed to penetrate into the steel sheet, in particular, avoiding penetration of hydrogen in the pickling step, and firing by a dry process. It was obtained by preventing the invasion of hydrogen due to water in the heating atmosphere at that time, and it is not necessary to form inclusions or precipitates in the steel sheet to prevent nail popping and bubbles. In other words, this is an epoch-making technology that can obtain sufficiently good enameling properties even for ordinary steel sheets not for enameling. As a result, enamel can be applied to a steel sheet having excellent formability as compared with the conventional steel sheet for enamel.

Further, in the case of the enamel which is applied twice, after the pretreatment, the lower glaze-drying-baking-cooling-the upper glaze-
Drying-firing-cooling is performed, but in the method of the present invention,
The (drying) -firing-cooling step after the lower glaze may be omitted, as in the case of the lower glaze- (drying) -upper glaze-drying-firing-cooling.

The enamel products produced by the method of the present invention are used for stoves, stoves, bathtubs, pots, sinks, panels and the like which are excellent in corrosion resistance, heat resistance, chemical resistance, abrasion resistance and color resistance. ..

[0028]

Example 1 With respect to the hot-rolled steel sheet having the thickness of 2.0 mm and the components shown in Table 1, the oxide scale was removed by an electric arc in a vacuum of 10 Pa, and the surface roughness of the steel sheet was R _max 20 to 50.
After roughening to μm, Ni was added to 2.0 g /
m ^{2 was} attached, and enamel was applied once. In addition,
As a comparative example, the same steel sheet was heated to 70 ° C. and 6%.
After removing the oxide scale in a hydrochloric acid aqueous solution, rust preventive oil was applied, and enamel was applied once in the conventional pretreatment process for enamel. In both cases, the thickness of enamel is about 100
μm, and firing was performed in air at 830 ° C. for 6 minutes and 40 seconds.

[0029]

[Table 1]

As a result, in the case where the enamel was applied once according to the method of the present invention, enamel defects such as nail pops and bubbles did not occur, and the enamel adhesion was improved. In particular, the enamel properties of ordinary steel sheets were significantly improved. On the other hand, in the comparative example, nail skipping occurred frequently, there were many bubble defects, and the enamel adhesion was poor. The results are shown in Table 2.

[0031]

[Table 2]

[0032]

Example 2 With respect to the hot-rolled steel sheet having a thickness of 2 mm and having the components shown in Table 1, oxide scale was removed by an electric arc in a vacuum of 10 Pa, and the surface roughness of the steel sheet was roughened to R _{max of} 20 to 50 μm. Ni was attached at 2.0 g / m ² by an ion vapor deposition method, and enamel was applied twice. As a comparative example,
The conventional enamel was applied twice. Here, the thickness of each of the lower glaze and the upper glaze is about 100 μm, and the firing of the lower glaze is 8 μm.
The baking of the glaze was carried out at 70 ° C. for 7 minutes and at 830 ° C. for 6 minutes and 40 seconds in the atmosphere. Furthermore, removal of oxide scale and roughening of the steel sheet surface by the method of the present invention, Ni
About the adhered steel plate Lower glaze-Upper glaze-Dry-
Firing-cooling was also carried out at the same time without the lower glaze firing step.

As a result, the enamel which has been subjected to double enamel by the method of the present invention has good enamel properties, and in particular, enamel adhesion is good even on ordinary steel plates, and enamel defects such as nail pops and bubbles occur. There wasn't. On the other hand, in the comparative example, enamel defects such as nail pops and bubbles were generated, and the enamel adhesion was poor. The results are shown in Table 3.

[0034]

[Table 3]

[0035]

Example 3 The surface of a cold-rolled steel sheet having a thickness of 0.8 mm and having the components shown in Table 1 was subjected to an electric arc in a vacuum of a pressure of 10 Pa to obtain a roughness R.
After roughening to a _{maximum of} 20 to 40 μm, N by the ion deposition method
i was applied at 2.0 g / m ^{2 and} enamel was applied once. In addition, as a comparative example, the same steel sheet was subjected to the conventional method of single-step enamel. Here, each enamel thickness was about 100 μm, and baking was performed in the air at 830 ° C. for 2 minutes and 40 seconds.

As a result, the enamel which was applied once by the method of the present invention had good enamel adhesiveness and did not cause enamel defects such as nail pops and bubbles. Especially, in the case of ordinary steel plate, the above-mentioned enameled properties were significantly improved. On the other hand, in the comparative example, the nail skips frequently occurred and the enamel adhesion was poor. The results are shown in Table 4.

[0037]

[Table 4]

[0038]

[Example 4] The surface of a cold-rolled steel sheet having a thickness of 0.8 mm and having the components shown in Table 1 was subjected to an electric arc in a vacuum of a pressure of 10 Pa to obtain a roughness R.
After roughening to a _{maximum of} 20 to 40 μm, N by the ion deposition method
i was applied at 2.0 g / m ^{2 and} enamel was applied twice. In addition, after the treatment up to Ni adhesion was carried out by the same method, a double enamel which omitted the lower glaze firing step was also carried out. As a comparative example, the conventional enamel was applied once. Here, the thickness of the enamel is about 100 μm, and 8
Baking was performed in the air at 30 ° C. for 2 minutes and 40 seconds.

As a result, the enamel which was applied twice by the method of the present invention had good enamel adhesion, and
No enamel defects such as nail pops and bubbles occurred. on the other hand,
In the comparative example, enamel adhesion was low, and enamel defects such as fingernails and bubbles frequently occurred. The results are shown in Table 5.

[0040]

[Table 5]

[0041]

INDUSTRIAL APPLICABILITY The present invention simplifies the pretreatment process for enamel, and imparts extremely excellent enamel properties even to ordinary steel sheets which have been difficult to enamel. This makes it possible to produce enamel products having excellent enamel properties and contributes to the qualitative and quantitative expansion of enamel products.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing removal of oxidized scale and roughening of the surface of a hot rolled steel sheet by an electric arc under vacuum.

[Explanation of symbols]

 1 Steel plate 2 Oxide scale 3 Electric arc

[Procedure amendment]

[Submission date] February 26, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0011

[Correction method] Change

[Correction content]

An object of the present invention is to provide a technique for solving these manufacturing problems. That is, the present invention relates to the production of a enamel steel plate, and provides a method for producing a enamel steel plate that simplifies the pretreatment process for enamel and enables ordinary enameled steel plates that are not for enamel.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0015

[Correction method] Change

[Correction content]

[0015] The enameling steel plate, enameling for decarburization sheet and steel strip SPP etc. JISG3133, between not the JIS standard hot rolled enameling for steel sheet and strip, the mold casting rimmed steel, capped steel and Arumikiru de Steel mild steel plate and steel strip, subjected to skin pass in hot rolling after hot coiling the Arumikiru de steel continuous casting, some steel plates and strip imparted with enamel properties, the P other alloying elements for ensuring the strength additive Including P-added steel and low alloy steel.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0016

[Correction method] Change

[Correction content]

Ordinary steel sheets are SPHC, SPHD, SP
HE JIS G3131 hot rolled mild steel sheet and strip,
JISG3141 of SPCC, SPCD, cold rolled steel sheets and steel strip SP C E, a steel sheet and strip containing tin original sheet or the like of the SPB etc. JISG3303.

[Procedure amendment 4]

[Document name to be amended] Statement

[Name of item to be corrected] 0032

[Correction method] Change

[Correction content]

[0032]

Example 2 With respect to the hot-rolled steel sheet having a thickness of 2.0 mm having the components shown in Table 1, the oxide scale was removed by an electric arc in a vacuum of 10 Pa, and the surface roughness of the steel sheet was roughened to R _{max of} 20 to 50 μm. After conversion, Ni was deposited at 2.0 g / m ² by an ion vapor deposition method, and enamel was applied twice. As a comparative example, conventional enamel was applied twice. Here, the thickness of each of the lower glaze and the upper glaze was about 100 μm, the firing of the lower glaze was 870 ° C. for 7 minutes, and the firing of the upper glaze was 830 ° C. for 6 minutes 40.
Each was performed in the atmosphere for 2 seconds. Furthermore, removal of oxide scale and roughening of the steel sheet surface by the method of the present invention, N
i The glazed glazed-upper glazed glazed-drying-firing-cooling of the adhered steel sheet was also carried out at the same time with the lower glaze firing step omitted.

[Procedure Amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0035

[Correction method] Change

[Correction content]

[0035]

Example 3 The surface of a cold-rolled steel sheet having a thickness of 0.8 mm and having the components shown in Table 1 was subjected to an electric arc in a vacuum of a pressure of 10 Pa to obtain a roughness R.
After roughening to a _{maximum of} 10 to 40 μm, N by an ion deposition method
i was applied at 2.0 g / m ^{2 and} enamel was applied once. In addition, as a comparative example, the same steel sheet was subjected to the conventional method of single-step enamel. Here, each enamel thickness was about 100 μm, and baking was performed in the air at 830 ° C. for 2 minutes and 40 seconds.

[Procedure correction 6]

[Document name to be amended] Statement

[Correction target item name] 0038

[Correction method] Change

[Correction content]

[0038]

[Example 4] The surface of a cold-rolled steel sheet having a thickness of 0.8 mm and having the components shown in Table 1 was subjected to an electric arc in a vacuum of a pressure of 10 Pa to obtain a roughness R.
After roughening to a _{max of} 10 to 40 μm, N by ion vapor deposition
i was applied at 2.0 g / m ^{2 and} enamel was applied twice. In addition, after the treatment up to Ni adhesion was carried out by the same method, a double enamel which omitted the lower glaze firing step was also carried out. As a comparative example, it was performed twice hooking enamel according to the conventional method. Here, the thickness of the enamel is the same as the lower glaze and the upper glaze.
And respectively about 100 [mu] m, Shita釉the Oyo 3 minutes at 850 ° C.
Each of the glazes was baked at 830 ° C. for 2 minutes and 40 seconds in the atmosphere.

Claims (2)

[Claims] 1. A method for producing a steel plate for enamel, which comprises removing surface oxide scale of a hot-rolled steel plate with an electric arc under vacuum and roughening the surface of the steel plate and then performing enamel lapping. 2. A method for producing a steel sheet for enamel, which comprises roughening the surface of a cold rolled steel sheet with an electric arc under vacuum and then performing enamel plating.