JP5930210B2 - Tin-plated surface-treated steel sheet and manufacturing method thereof - Google Patents

Description

  The present invention relates to a tin-plated surface-treated steel sheet and a method for producing the same. Specifically, the present invention relates to a tin-plated surface-treated steel sheet having a low glossiness and suitable for use as a base steel sheet for coating, and a method for producing the same. is there.

  “Crimping” defined by JIS G3303, which is obtained by applying tin plating to the surface of a cold-rolled steel sheet, is broadly classified into “heated tinting” and “electroplating tinting”. “Electric plating tinplate”, which has a small basis weight, that is, resource-saving and energy-saving and capable of mass production, has become the mainstream.

  As shown in FIG. 1, the electroplating tin plating is a reflow process in which the surface of a cold-rolled steel sheet is electroplated to deposit metal Sn and then heated to a temperature equal to or higher than the melting point of Sn (232 ° C.). After forming a Fe-Sn alloy layer between the ground iron and the metal Sn layer, a chromic acid cathode treatment or the like was applied to form a chromium hydrated oxide layer on the Sn plating layer In addition to having excellent corrosion resistance, workability, and solder wettability, it is characterized by a beautiful metallic luster.

  Therefore, the above electroplating tinplate is widely used as a material for cans such as food cans, beverage cans, confectionery cans, chemical cans, spray cans, pail cans, 18 liter cans and other miscellaneous cans, and as a material for toys. However, in recent years, it has come to be widely used for building materials, automobile members, etc., in addition to home appliances and electrical / electronic devices.

  For example, Patent Document 1 includes Cr: 0.3 wt% or more, Si: less than 0.1 wt%, and N: less than 0.005 wt%, with the balance being substantially inevitable impurities and Fe. A tin-plated steel sheet for a fuel tank, characterized by being coated with Sn, and Patent Document 2 discloses one or more of Mg and Ca of group IIa (alkaline earth metal) elements in a tin-based plating layer And an IVb group element Si, Sn containing an intermetallic compound composed of at least one element, automotive exterior panels, exhaust system members, gasoline tank materials, roof building walls and other metal building materials, civil engineering materials In addition, a tin-plated surface-treated steel material having excellent corrosion resistance and used for household and industrial electrical equipment is disclosed.

Japanese Patent Laid-Open No. 10-025542 JP 2012-007245 A

  By the way, conventionally, electroplating tinplates are used for applications such as confectionery cans and cosmetic cans that require little corrosion resistance but are highly required to be beautiful after painting and printing. In recent years, in addition to home appliances and electrical / electronic devices, when used for construction materials, automobile members, etc., they are increasingly used after being painted. However, when the coating is directly applied to the surface of the steel plate having a metallic luster, the base may be seen through or the sharpness may be inferior. Therefore, a white coating containing titanium oxide (titanium white) is applied as a base coating, and a main coating is applied thereon.

  However, the above-mentioned base coating has a problem that it causes an increase in work process and an increase in manufacturing cost. Moreover, since the steel sheet surface which performed the reflow process is covered with the soft metal Sn, it is easy to be damaged at the time of handling or processing, and since it is metallic luster, there is also a problem that the included damage is easily noticeable.

  Accordingly, in applications having such problems, a steel plate surface close to white in which the steel plate surface does not have metallic luster has been desired. Specifically, it is often desired that the specular glossiness Gs (60 °) specified in JIS Z8741 is 40 (%) or less. Note that even an electrotin-plated steel sheet can have a semi-glossy surface by so-called “matt finish” that does not undergo reflow treatment after electroplating. However, since the mat finishing material is obtained by simply depositing metal Sn on the surface of the steel sheet, there is a problem that the Sn plating layer is porous and inferior in corrosion resistance and adhesion. Further, the techniques disclosed in Patent Documents 1 and 2 described above do not consider such problems at all.

  The present invention has been made in view of the above-mentioned problems of the prior art, and the object thereof is to provide a tin-plated surface-treated steel sheet having a low glossiness on the steel sheet surface and to propose an advantageous production method thereof. There is.

  In order to solve the above-mentioned problems, the inventors made extensive studies by paying attention to the configuration of the electric Sn plating layer formed on the surface of the cold-rolled steel sheet. As a result, metallic Sn is deposited on the surface of the steel sheet by electroplating, and after Cr is further deposited thereon, a reflow treatment is performed to form a Cr—Sn alloy layer on the surface of the Sn plating layer. Has found that a surface-treated steel sheet having a low thickness can be obtained, and has led to the development of the present invention.

That is, the present invention has an Sn plating layer on the surface of the cold-rolled steel sheet after cold rolling and annealing, and the amount of Cr deposited on the surface layer of the Sn plating layer is 100 to 200 mg / m ² (per one side). A tin-plated surface-treated steel sheet having a Cr—Sn alloy layer and having a specular gloss on the steel sheet surface of 40% or less in terms of Gs (60 °) defined in JIS Z8741.

The Sn plating layer in the tin-plated surface-treated steel sheet of the present invention is characterized in that the Sn adhesion amount is 0.3 g / m ² or more (per one side).

Moreover, this invention is a manufacturing method of the tin plating system surface treatment steel plate in any one of said, Comprising: After cold-rolling, the surface of the cold-rolled steel plate which annealed is electroplated, and Sn plating layer is formed. After forming and depositing 100 to 200 mg / m ² (per side) of metal Cr on the Sn plating layer, reflow treatment is performed at a temperature not lower than the melting point of Sn and not higher than 252 ° C. A method for producing a tin-plated surface-treated steel sheet, characterized in that a Cr—Sn alloy layer is formed on the surface layer and the specular gloss is 40% or less in terms of Gs (60 °) as defined in JIS Z8741. .

  Further, in the method for producing a tin-plated surface-treated steel sheet according to the present invention, the method for depositing the Cr on the Sn plating layer is any one or more of coating, spraying, electrolytic treatment, and vapor deposition. And

  According to the present invention, it is possible to provide a steel sheet having a low glossiness without having a metallic luster, so that titanium white in a base coating in a coated steel sheet that requires sharpness after coating is reduced, It is possible to omit the painting itself. In addition, the steel sheet of the present invention can be suitably used as a material for electronic devices, home appliances, and the like that are required to be beautiful because surface scratches are not noticeable even without coating.

It is a figure explaining Sn plating layer sectional structure of the conventional electroplating tinplate. It is a figure which illustrates typically the plating layer section structure of the tin plating system surface treatment steel plate of the present invention. It is a Cr-Sn binary system phase diagram.

Embodiments of the present invention will be described below.
As shown in FIG. 2, the tin-plated surface-treated steel sheet of the present invention has an Sn plating layer formed on the surface of the material steel sheet by electroplating, and Cr is further formed on the surface of the Sn plating layer. A Cr—Sn alloy layer made of Sn and Sn is formed.

  Here, the steel plate used as the material of the tin-plated surface-treated steel plate of the present invention is not particularly limited as long as it is a steel plate that can be electroplated with Sn, but the surface beauty, shape, workability, etc. of the steel plate are not limited. From this point of view, it is desirable that after cold rolling, recrystallization annealing is performed, and further, skin pass rolling (temper rolling) and double rolling (DR) are performed as necessary.

  Further, the tin-plated surface-treated steel sheet of the present invention does not have a metallic luster like a conventional tinplate by forming a Cr-Sn alloy layer on the surface of the Sn plating layer, specifically, The glossiness Gs (60 °) specified in JIS Z8741; 1997 is preferably 40% or less. If the glossiness exceeds 130, it will have a metallic luster, so when using it on a coated steel sheet, it is necessary to have a base coat, or it is easy to get scratches during processing, etc. This is because the appearance quality is impaired. Preferably it is 35 (%) or less, More preferably, it is 30 (%) or less.

  Here, the reason why the metallic luster is not exhibited by forming the Cr—Sn alloy layer on the surface of the Sn plating layer as described above has not been clarified yet, but Cr is a body-centered cubic lattice. , Sn is a body-centered tetragonal lattice. When Cr is deposited on the Sn plating layer and reflow treatment is performed, as shown in FIG. 3, Cr—Sn solid solution and metal Sn coexist at room temperature. This is because the crystal grains become finer and diffusely reflect light.

Next, the manufacturing method of the said tin plating type surface treatment steel plate of this invention is demonstrated.
In the tin-plated surface-treated steel sheet of the present invention, after cold rolling, the surface of the annealed cold-rolled steel sheet is electroplated to form a Sn plating layer, and then metal Cr is adhered on the Sn plating layer. Then, a reflow process is performed to produce a Cr—Sn alloy layer on the surface of the Sn plating layer.

Here, it is preferable that the Sn adhesion amount of electroplating applied to the steel plate surface is 0.3 g / m ² (per one side; the same applies hereinafter). This is because if the Sn adhesion amount is less than 0.3 g / m ² , the entire surface of the steel sheet cannot be covered with Sn. In addition, in addition to low glossiness, when corrosion resistance is required, it is preferably 1.7 g / m ² or more, and more preferably 2.8 g / m ² or more. On the other hand, the upper limit of the Sn adhesion amount is not particularly required from the viewpoint of glossiness, but from the viewpoint of corrosion resistance, the improvement effect is not only saturated even if it exceeds 15 g / m ² , It only causes a decrease in the productivity of the plating line and an increase in Sn cost. Therefore, the upper limit is preferably about 15 g / m ² . Moreover, from a viewpoint of corrosion resistance and manufacturing cost, 11.2 g / m < ² > or less is preferable, and it is more preferable to set it as 8.4 g / m < ² > or less.

The amount of Cr deposited on the Sn plating layer is preferably in the range of 10 to 200 mg / m ² (per one side; the same applies hereinafter). If the adhesion amount of Cr is less than 10 mg / m ² , the effect of reducing the glossiness cannot be obtained sufficiently. On the other hand, when the adhesion amount of Cr exceeds 200 mg / m ² , the melting point of the Cr—Sn solid solution formed by the reflow process rapidly increases (see FIG. 3), so that it becomes difficult to alloy by the reflow process. On the other hand, if it exceeds 200 mg / m ² , the amount of Cr deposited on “Tin-Free Steel” specified in JIS G3315 will increase, making it difficult to manufacture on an industrial scale with good productivity. More preferably 5 to 50 mg / ^{m 2,} more preferably in the range of 10 to 30 mg / ^{m 2.}

The method for depositing Cr on the Sn plating layer may be any method as long as Cr can be uniformly deposited and the amount of deposition can be controlled. For example, Cr ₂ O ₃ or Cr ₂ O A method of applying or spraying a chemical solution containing ₇ etc. on the surface of a steel plate, a method of attaching metal Cr, chromium hydrated oxide, etc. by electrolytic chromic acid treatment (electrolytic treatment) like tin-free steel There is a method of attaching metal Cr by physical vapor deposition (PVD), chemical vapor deposition (CVD), or the like. Any method may be used, and two or more methods may be used in combination. Furthermore, it goes without saying that other methods such as electroless plating may be used.

  In the present invention, Cr is used as an element for forming an alloy layer to be formed on the surface of the Sn plating layer, but the low gloss technology of the present invention is not limited to the above Cr, for example, Ni, Zr, Ti, and the like can also be used because they have the same effect as Cr.

  The steel plate with Cr deposited on the Sn plating layer is then subjected to a reflow treatment that is heated to a temperature equal to or higher than the melting point of Sn to melt the Sn plating layer on the surface of the steel plate, and Cr atoms are contained in the molten Sn. A Cr—Sn alloy layer is formed by diffusing. Although there is no restriction | limiting in particular about the method of heating a steel plate by the said reflow process, If it is the induction heating method and the resistance heating method (electric current heating method) generally used for manufacture of an electroplating tinplate, it will use suitably. be able to. Note that the formation of an alloy layer of Cr and Sn in the reflow process can be easily confirmed by measuring the distribution of Cr and Sn in the depth direction with a glow discharge emission spectrometer GDS.

  In the reflow process, an Fe—Sn alloy layer is formed between the Sn plating layer and the underlying steel plate. Since this Fe—Sn alloy layer is located inside the Cr—Sn alloy layer, Has little effect on glossiness.

  The temperature at which the steel sheet is heated by the reflow treatment is preferably not less than the melting point of Sn (melting point of Sn + 50 ° C.) and not more. An alloy layer is not formed below the melting point of Sn (232 ° C.). On the other hand, the upper limit of the heating temperature is not limited in forming the Cr—Sn alloy layer, but if it is higher than the melting point of Sn + 50 ° C. (282 ° C.), the equipment for heating and cooling the steel plate becomes long, This is not preferable because the energy required for heating increases.

  The steel sheet subjected to the above reflow treatment is then subjected to a chromate treatment to form a chromate treatment film, or a chemical conversion treatment of Zr, P, Ti, etc. for the purpose of chromate-free, in the same manner as normal electroplating tinplate. It may be applied.

C: 0.040 mass%, Si: 0.02 mass%, Mn: 0.25 mass%, P: 0.010 mass%, S: 0.012 mass%, Al: 0.037 mass%, N: 0.0035 mass%, balance A steel material having a composition comprising Fe and inevitable impurities is hot-rolled, cold-rolled, continuously annealed, temper-rolled, and plate thickness: 0.32 mm × sheet width: 800 mm SPTE-T -3 CA-class cold rolled steel sheet.
Next, the cold-rolled steel sheet was passed through an electric tin plating line (ETL), and as shown in Table 1, the Sn basis weight was applied in the range of 0 to 15.1 g / m ² , After passing through an electrolytic chromic acid treatment line and depositing Cr on the Sn plating layer so as to have an adhesion amount shown in Table 1, reflow treatment was performed at the same temperature as shown in Table 1. In addition, the method of making Cr adhere is performed by three methods of electrolytic treatment, application | coating, and spraying, and the resistance heating method was used as a heating means of reflow processing.

The surface of the steel sheet thus obtained was measured for specular gloss and the presence or absence of color unevenness, and the results are also shown in Table 1.
As for the specular gloss, the specular gloss Gs (60 °) was measured by a method defined in JIS Z8741; 1997 using a multi-angle gloss meter (manufactured by Suga Test Instruments Co., Ltd .; GS-1K).
In addition, the presence or absence of color unevenness was measured by measuring the area where gloss unevenness occurred due to abnormality of the Sn electrodeposition pattern generated within a range of 1 m ² using a laser type surface defect detection device, and the following formula:
Gloss unevenness area ratio (%) = Gloss unevenness occurrence area (m ² ) / steel plate surface area (1 m ² ) × 100
The gloss non-uniformity area ratio defined in (1) was measured, and those having a value of 5% or less were evaluated as “non-glossy”, and those exceeding 5% were evaluated as “existing”. Also, the presence / absence of gloss unevenness was visually evaluated, and those evaluated as “present” by any of the above methods were rejected.
From the results shown in Table 1, all the steel sheets that meet the conditions of the present invention have Gs (60 °) of 40 (%) or less, no color unevenness, and suitable characteristics as a material for coated steel sheets. You can see that

  In the above description, it is assumed that the steel sheet material used for painting is used for applications that are easily scratched or noticeable, such as electronic equipment and electrical products, but the use of the steel sheet of the present invention is limited to the above range. Rather than being used, for example, it is also suitable for use in decorations such as trays, home appliances such as lighting equipment, office equipment and furniture members, and building and building materials such as wall materials and roofing materials. Can do.

Claims (4)

After cold rolling and the cold-rolled steel sheet after annealing has an Sn plating layer, and a Cr-Sn alloy layer of the Sn Cr deposition amount on the surface of the plated layer is 100 to 200 mg / ^{m 2} (per one side) a tin plating based surface-treated steel sheet, wherein the specular glossiness of the steel sheet surface is 40% or lower Gs defined in JIS Z8741 (60 °). ^2. The tin-plated surface-treated steel sheet according to claim 1, wherein the Sn plating layer has an Sn adhesion amount of 0.3 g / m ² or more (per one side). It is a manufacturing method of the tin plating system surface treatment steel plate according to claim 1 or 2 ,
After cold rolling, the surface of the annealed cold rolled steel sheet is electroplated to form a Sn plating layer,
After depositing 100 to 200 mg / m ² (per one side) of metal Cr on the Sn plating layer, a reflow treatment is performed at a temperature not lower than the melting point of Sn and not higher than 252 ° C., whereby Cr is applied to the surface layer of the Sn plating layer. A method for producing a tin-plated surface-treated steel sheet, wherein a Sn alloy layer is formed, and the specular gloss is 40% or less in terms of Gs (60 °) defined in JIS Z8741 . The tin-plated surface-treated steel sheet according to claim 3 , wherein the Cr is deposited on the Sn plating layer by any one or more of coating, spraying, electrolytic treatment, and vapor deposition. Manufacturing method.

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