Surface-treated steel material and method for producing surface-treated steel material

Abstract

This surface-treated steel material includes a plating layer disposed on a surface of a steel material, the plating layer having an average chemical composition comprising, in terms of mass%, 10.0-40.0%, excluding 10.0%, Al, 4.0-15.0%, excluding 4.0%, Mg, and the remainder comprising 40% or more Zn and impurities, and further includes a zinc phosphate crystal layer including Zn3(PO4)2·4H2O formed on the surface of the plating layer. The zinc phosphate crystal layer contains Mg in a concentration of 1.5 mass% or higher and Al in a concentration of 1.0 mass% or higher.

Description

Surface-treated steel material and method for manufacturing the surface-treated steel material

[0001] The present invention relates to a surface-treated steel material and a method for manufacturing the surface-treated steel material. This application claims priority to Japanese Patent Application No. 2024-014240, filed on February 1, 2024, the contents of which are incorporated herein by reference.

[0002] Hot-dip galvanized steel sheets used in the fields of building materials, civil engineering, home appliances, and automobiles are generally produced by removing grease and oxide films from the surface of the steel sheet, immersing the steel sheet in a hot-dip galvanizing bath, withdrawing it, immediately controlling the coating weight to a predetermined amount by gas wiping, and then cooling it by air cooling, water cooling, or air-water cooling. Hot-dip galvanized steel sheets produced in this manner have a glossy surface of the coating layer, but this gloss may make them unsuitable for some applications. For example, in the field of building materials, when hot-dip galvanized steel sheets are used unpainted for road guardrails, roofing and wall materials for buildings, back panels for home appliances, etc., glare caused by reflected light from the sun or lighting can be a problem from the perspectives of discomfort and safety. For this reason, surface-treated steel sheets with reduced glare have been developed.

[0003] For example, Patent Document 1 proposes a hot-dip galvanized steel sheet having excellent antiglare properties, in which the crystal grain size on the surface of the hot-dip galvanized layer is 50 μm or less and the average roughness Ra of the surface is 0.4 to 1.0 μm.

[0004] Furthermore, Patent Document 2 also describes that, although not intended for anti-glare properties, it is possible to obtain a hot-dip galvanized steel sheet in which "glare," i.e., the reflected light from the surface of the plating layer is suppressed from being so intense as to be uncomfortable, by setting the arithmetic mean roughness Ra of the zinc plating film to 0.50 μm or more and 1.50 μm or less and the mean peak spacing Sm to 40 μm or more and 100 μm or less.

[0005] However, there is a demand for hot-dip galvanized steel products with sufficient antiglare properties for practical use, and a method for relatively easily and stably producing such products.In addition, in recent years, there has been a demand for color tones that are closer to black.

[0006] Japanese Patent No. 3148542 Japanese Patent Application Laid-Open No. 2004-27263

[0007] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a surface-treated steel material that is excellent in workability and can further reduce gloss, and a method for manufacturing the same.

[0008] In order to solve the above problems, the present invention employs the following configuration: [1] A steel material and a plating layer disposed on a surface of the steel material, wherein the plating layer has an average chemical composition, in mass%, of Al: more than 10.0% and not more than 40.0%, Mg: more than 4.0% and not more than 15.0%, Si: 0% to 1.0%, Sn: 0% to 0.7%, Bi: 0% to 0.3%, In: 0% to 0.3%, total amount ΣX of Sn, Bi, and In: 0% to 0.7%, Ca: 0% to 0.6%, Y: 0% to 0.3%, La: 0% to 0.3%, Ce: 0% to 0.3%, Sr: 0% to 0.3%, Li: 0% to 0.3%. Total amount of Ca, Y, La, Ce, Sr, and Li, ΣYa: 0% or more, 0.6% or less, Cr: 0% or more, 3.0% or less, Ni: 0% or more, 1.0% or less, Mo: 0% or more, 0.25% or less, Cu: 0% or more, 1.0% or less, Ag: 0% or more, 0.25% or less, Sb: 0% or more, 0.25% or less, Pb: 0% or more, 0.25% or less, Total amount of Cr, Ni, Mo, Cu, Ag, Sb, and Pb, ΣYb: 0% or more, 3.0% or less, B: 0% or more, 0.5% or less, P: 0% or more, 0.5% or less, Total amount of B and P, ΣYc: 0% or more, 0.5% or less, Ti: 0% or more, 0.25% or less, Co: 0% or more and 0.25% or less, V: 0% or more and 0.25% or less, Nb: 0% or more and 0.25% or less, Mn: 0% or more and 0.25% or less, Zr: 0% or more and 0.25% or less, W: 0% or more and 0.25% or less, total amount ΣZ of Ti, Co, V, Nb, Mn, Zr and W: 0% or more and 0.25% or less, Fe: 0% or more and 5.0% or less, balance: 40% or more of Zn and impurities, and Zn is deposited on the surface of the plating layer. ３ (P.O. ４ ) ２ ・4H ２[2] A surface-treated steel material having a zinc phosphate crystal layer containing O laminated thereon, the zinc phosphate crystal layer containing Mg at a concentration of 1.5 mass % or more and Al at a concentration of 1.0 mass % or more. ２[3] The surface-treated steel material according to [1] or [2], in which the 60-degree specular gloss Gs(60°) measured from the zinc phosphate crystal layer side is less than 25.0. [4] The surface-treated steel material according to [1] or [2], in which the Munsell value N measured from the zinc phosphate crystal layer side is 3.5 or less. [5] A method for producing a surface-treated steel material, which comprises forming a zinc phosphate crystal layer on a surface of a plated steel material comprising a steel material and a plating layer disposed on the surface of the steel material, wherein the plating layer has an average chemical composition, in mass%, of Al: more than 10.0% and not more than 40.0%, Mg: more than 4.0% and not more than 15.0%, Si: 0% or more and not more than 1.0%, Sn: 0% or more and not more than 0.7%, Bi: 0% or more and not more than 0.3%, In: 0% or more and not more than 0.3%, total amount of Sn, Bi, and In ΣX: 0% or more and not more than 0.7%, Ca: 0% or more and not more than 0.6%, Y: 0% or more and not more than 0.3%, La: 0% or more and not more than 0.3%, Ce: 0% or more and not more than 0.3%, Sr: 0% or more and not more than 0.3%, Li: 0% or more and not more than 0.3%. Total amount of Ca, Y, La, Ce, Sr, and Li, ΣYa: 0% or more, 0.6% or less, Cr: 0% or more, 3.0% or less, Ni: 0% or more, 1.0% or less, Mo: 0% or more, 0.25% or less, Cu: 0% or more, 1.0% or less, Ag: 0% or more, 0.25% or less, Sb: 0% or more, 0.25% or less, Pb: 0% or more, 0.25% or less, Total amount of Cr, Ni, Mo, Cu, Ag, Sb, and Pb, ΣYb: 0% or more, 3.0% or less, B: 0% or more, 0.5% or less, P: 0% or more, 0.5% or less, Total amount of B and P, ΣYc: 0% or more, 0.5% or less, Ti: 0% or more, 0.25% or less, Co: 0% or more and 0.25% or less, V: 0% or more and 0.25% or less, Nb: 0% or more and 0.25% or less, Mn: 0% or more and 0.25% or less, Zr: 0% or more and 0.25% or less, W: 0% or more and 0.25% or less, total amount ΣZ of Ti, Co, V, Nb, Mn, Zr and W: 0% or more and 0.25% or less, Fe: 0% or more and 5.0% or less, balance: 40% or more of Zn and impurities, and by applying a zinc phosphate solution of pH 5.0 or less to the surface of the plating layer, Zn is ３ (P.O. ４ ) ２ ・4H２ 1. A method for manufacturing a surface-treated steel material, comprising forming a zinc phosphate crystal layer containing O, Mg at a concentration of 1.5 mass % or more, and Al at a concentration of 1.0 mass % or more.

[0009] According to the present invention, it is possible to provide a surface-treated steel material and a method for manufacturing the same that have good powdering resistance, excellent processability, particularly bending processability, and the ability to further reduce gloss and impart anti-glare properties. According to the present invention, it is possible to provide a surface-treated steel material that has excellent anti-glare properties and is particularly used in building materials, civil engineering, home appliances, automobiles, etc. In this way, the present invention can contribute to the development of industry by providing a material that has excellent anti-glare properties, is inexpensive, and has excellent aesthetic appeal.

[0010] FIG. 1 is a cross-sectional schematic view showing a surface-treated steel material according to an embodiment of the present invention.

[0011] The present inventors have conducted extensive research into means for imparting antiglare properties to hot-dip plated steel materials and for imparting a black appearance over a long period of time.

[0012] Phosphate treatment is sometimes used to impart anti-glare properties to zinc plating layers. Phosphate treatment precipitates phosphate as a crystalline phase on the surface of the plating layer, imparting a black compound to the metal surface. In public works projects, etc., there are cases where the delivery of zinc-plated steel sheets with specified Munsell values ​​is required for aesthetic reasons. However, while phosphate treatment can impart anti-glare properties, further improvements in anti-glare properties have been sought.

[0013] The present inventors have investigated means for improving antiglare properties by making the external color of a phosphate-treated zinc-based plating layer closer to black. The Munsell value N of a phosphate-treated zinc-plated steel sheet is often about 4.0 to 5.0. The present inventors have discovered that the Munsell value N of the plating layer after phosphate treatment can be reduced to a lower value, specifically to 3.5 or less, by incorporating small amounts of Mg and Al into the zinc phosphate layer during formation of the zinc phosphate layer.

[0014] In order to achieve a low Munsell value N by incorporating Mg and Al into a zinc phosphate layer, it is necessary to incorporate Al and Mg at a certain concentration or higher into the plating layer to be phosphate-treated. It has also been found that controlling the pH of the phosphate treatment solution during phosphate treatment is effective in incorporating Mg and Al into the zinc phosphate layer. Furthermore, it has been found that incorporating metals such as Sn, Bi, and In at a certain concentration or higher can further lower the Munsell value N. This is thought to be because incorporating metals such as Sn, Bi, and In at a certain concentration or higher can destroy the strong oxide film that can form on the surface of a plating layer that contains relatively large amounts of Al and Mg.

[0015] Hereinafter, a surface-treated steel material according to an embodiment of the present invention will be described.

[0016] The surface-treated steel material of this embodiment includes a steel material and a plating layer disposed on the surface of the steel material, and the plating layer has an average chemical composition, in mass%, of Al: more than 10.0% and not more than 40.0%, Mg: more than 4.0% and not more than 15.0%, Si: 0% or more and not more than 1.0%, Sn: 0% or more and not more than 0.7%, Bi: 0% or more and not more than 0.3%, In: 0% or more and not more than 0.3%, and a total amount ΣX of Sn, Bi, and In: 0% or more and not more than 0.7%. or less, Ca: 0% or more, 0.6% or less, Y: 0% or more, 0.3% or less, La: 0% or more, 0.3% or less, Ce: 0% or more, 0.3% or less, Sr: 0% or more, 0.3% or less, Li: 0% or more, 0.3% or less, total amount of Ca, Y, La, Ce, Sr and Li ΣYa: 0% or more, 0.6% or less, Cr: 0% or more, 3.0% or less, Ni: 0% or more, 1.0% or less, Mo: 0% or more, 0.25% or less, C u: 0% or more, 1.0% or less, Ag: 0% or more, 0.25% or less, Sb: 0% or more, 0.25% or less, Pb: 0% or more, 0.25% or less, total amount of Cr, Ni, Mo, Cu, Ag, Sb and Pb ΣYb: 0% or more, 3.0% or less, B: 0% or more, 0.5% or less, P: 0% or more, 0.5% or less, total amount of B and P ΣYc: 0% or more, 0.5% or less, Ti: 0% or more, 0.25% or less, Co: 0% or more and 0.25% or less, V: 0% or more and 0.25% or less, Nb: 0% or more and 0.25% or less, Mn: 0% or more and 0.25% or less, Zr: 0% or more and 0.25% or less, W: 0% or more and 0.25% or less, total amount ΣZ of Ti, Co, V, Nb, Mn, Zr and W: 0% or more and 0.25% or less, Fe: 0% or more and 5.0% or less, balance: 40% or more of Zn and impurities, and ３ (P.O. ４ ) ２ ・4H ２ The surface-treated steel material of this embodiment has a zinc phosphate crystal layer containing O laminated thereon, and the zinc phosphate crystal layer contains Mg at a concentration of 1.5 mass % or more and Al at a concentration of 1.0 mass % or more. ２Preferably, the surface-treated steel material of this embodiment has a 60° gloss measured from the zinc phosphate crystal layer side of less than 25.0. Preferably, the surface-treated steel material of this embodiment has a Munsell value N measured from the zinc phosphate crystal layer side of 3.5 or less.

[0017] In this embodiment, excellent antiglare properties means that the 60-degree specular gloss Gs(60°) measured from the zinc phosphate crystal layer side is less than 25.0.

[0018] In the following description, the "%" used to indicate the content of each element in the chemical composition means "mass %." A numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits. When the numerical values ​​before and after "to" are followed by "greater than" or "less than," the numerical range does not include these numerical values ​​as the lower or upper limit.

[0019] As shown in FIG. 1 , the surface-treated steel material 1 of this embodiment is composed of a steel material 11, a plating layer 12 disposed on the surface of the steel material 11, and a zinc phosphate crystal layer 13 laminated on the plating layer 12.

[0020] The steel material 11 to be plated will now be described. The steel material 11 is, for example, mainly a steel plate, but there are no particular restrictions on its size. The steel material 11 may be any steel material that can be used in a normal hot-dip galvanizing process. Specifically, this applies to steel plates that can be used in processes such as continuous hot-dip galvanizing lines (CGLs) where the steel is immersed in molten metal and solidified. The size of the steel material 11 may be, for example, a plate thickness of 10 mm or less and a plate width of 2000 mm or less, but the size of the steel material 11 is not limited to this. The steel plate shape also includes checkered steel plates that have macroscopic surface irregularities previously applied.

[0021] There are no particular limitations on the material of the steel material 11. For example, the steel material 11 can be general steel, pre-plated steel thinly plated with various metals, Al-killed steel, ultra-low carbon steel, high carbon steel, various high-tensile steels, and some high alloy steels (steels containing elements that strengthen corrosion resistance, such as Ni and Cr).

[0022] In addition, the manufacturing process for steel material 11 includes common processes such as iron and steel making processes using a blast furnace or electric furnace, hot rolling processes, pickling processes, cold rolling processes, and heat treatment processes, but the steel material 11 of this embodiment may have undergone any of these processes, and the processing conditions for each process are not limited.

[0023] Next, the plating layer 12 will be described. The plating layer 12 according to this embodiment includes a Zn—Al—Mg alloy layer. The reason for adopting such a plating layer 12 is that, when the plating layer 12 is phosphate treated, a dark black zinc phosphate layer having a Munsell value of N=3.5 or less is formed.

[0024] The Zn—Al—Mg alloy layer is made of a Zn—Al—Mg alloy. The Zn—Al—Mg alloy refers to a ternary alloy whose main elements are Zn, Al, and Mg, and which is allowed to contain optional elements. The main elements refer to elements other than Fe that constitute the plating layer 12, and refer to elements that account for a total of 95% or more of the total.

[0025] The Al—Fe-based interfacial alloy layer is an interfacial alloy layer between the steel material 11 and the Zn—Al—Mg-based alloy layer, and is in contact with the surface of the steel material 11 .

[0026] That is, the plating layer 12 may have a single-layer structure of a Zn—Al—Mg alloy layer, or a laminated structure including a Zn—Al—Mg alloy layer and an Al—Fe interfacial alloy layer. In the case of a laminated structure, the Zn—Al—Mg alloy layer is preferably a layer that constitutes the surface of the plating layer 12.

[0027] The overall thickness of the plating layer 12 is affected by the plating conditions, and therefore there are no particular limitations on the upper and lower limits of the overall thickness of the plating layer 12. That is, in a typical hot-dip plating method, the overall thickness of the plating layer 12 is affected by the viscosity and specific gravity of the plating bath. It is also affected by the withdrawal speed of the steel material 11 from the plating bath and the wiping conditions. Since the maximum thickness of the plating layer 12 formed on a steel wire material or steel wire by a typical hot-dip plating method is often 100 μm or less, the plating thickness of the hot-dip plated steel material 1 of this embodiment may be, for example, 100 μm or less.

[0028] In the Zn-Al-Mg alloy layer, a very small amount of the plating layer 12 dissolves during phosphate treatment, and the metal ions of the dissolved plating layer 12 react with phosphoric acid, so from the viewpoint of ensuring corrosion resistance, it is preferable that the plating layer 12 have a certain thickness or more. Therefore, the thickness of the plating layer 12 is preferably 5 μm or more.

[0029] Next, the average chemical composition of the plating layer 12 will be described. When the plating layer 12 has a single-layer structure of a Zn—Al—Mg alloy layer, the average chemical composition of the entire plating layer 12 is the average chemical composition of the Zn—Al—Mg alloy layer. When the plating layer 12 has a laminate structure of an Al—Fe interface alloy layer and a Zn—Al—Mg alloy layer, the average chemical composition is the combined average chemical composition of the Al—Fe interface alloy layer and the Zn—Al—Mg alloy layer. In the plating layer 12 defined in the present invention, the thickness of the Al—Fe interface alloy layer is preferably small, 10% or less of the overall thickness of the plating layer 12, and therefore the Fe concentration of the plating layer 12 is often within 5%. Therefore, the average chemical composition of the plating layer 12 can be safely considered to be roughly the composition of the Zn—Al—Mg alloy layer. Furthermore, traces of the original plating sheet are unlikely to remain as chemical components of the plating layer 12. Therefore, the average chemical composition of the plating layer 12 can be considered to be approximately equivalent to the components of the plating bath used in its production.

[0030] The chemical composition of the plating layer 12 determines the hardness of the plating layer 12. That is, the plating layer 12 produced on a normal plating production line is often completed in a short time (up to 60 seconds or less) from hot dip plating to reaching the top roll, and is ultimately phosphate treated, so there is no need to impose any particular conditions on the solidification state of these metal layers.

[0031] The average chemical composition of the plating layer 12 is, in mass%, Al: more than 10.0% and 40.0% or less, Mg: more than 4.0% and 15.0% or less, Si: 0% or more and 1.0% or less, a total amount ΣX of Sn, Bi, and In: 0.03% or more and 0.7% or less, a total amount ΣYa of Ca, Y, La, Ce, Sr, and Li: 0% or more and 0.6% or less, a total amount ΣYb of Cr, Ni, Mo, Cu, Ag, Sb, and Pb: 0% or more and 3.0% or less, a total amount ΣYc of B and P: 0% or more and 0.5% or less, a total amount ΣZ of Ti, Co, V, Nb, Mn, Zr, and W: 0% or more and 0.25% or less, Fe: 0% or more and 5.0% or less, and the balance including 40% or more of Zn and less than 0.05% of impurities. That is, Zn, Al, and Mg are the main elements in the plating layer 12, and the total of these elements accounts for 95% or more.

[0032] The content of each element will be explained below.

[0033] Al: More than 10.0% and 40.0% or less. Al is the main constituent element of the plating layer 12 and contributes to improving flat surface corrosion resistance and sacrificial corrosion protection. Furthermore, to reduce the Munsell value of the zinc phosphate crystal layer 13, it is necessary to dissolve a portion of the plating layer 12 during phosphate treatment to incorporate Al into the zinc phosphate crystal layer 13. If the Al concentration in the plating layer 12 is low, it may be impossible to incorporate Al into the zinc phosphate crystal layer 13. Therefore, the Al concentration is set to be more than 10.0%. The Al concentration may be set to 11.0% or more, 12.0% or more, or 15.0% or more. On the other hand, if the Al concentration is excessive, the Mg concentration and Zn concentration will be relatively reduced, resulting in deterioration of sacrificial corrosion protection. Therefore, the Al concentration is set to be 40.0% or less. The Al concentration may be set to 35.0% or less, 30.0% or less, or 25.0% or less. In particular, in order to incorporate Al and Mg into the zinc phosphate crystal layer 13, the Al concentration is preferably 15.0% or more and 35.0% or less, and more preferably 19.0% or more and 30.0% or less.

[0034] Mg: More than 4.0% and 15.0% or Less Like Zn, Mg is an element that mainly constitutes the plating layer 12. Mg contributes to improving flat surface corrosion resistance and sacrificial corrosion protection. Furthermore, to reduce the Munsell value of the zinc phosphate crystal layer 13, it is necessary to dissolve a portion of the plating layer 12 during phosphate treatment to incorporate Mg into the zinc phosphate crystal layer 13. If the Mg concentration in the plating layer 12 is low, it may be impossible to incorporate Mg into the zinc phosphate crystal layer 13. Therefore, the Mg concentration is set to more than 4.0%. The Mg concentration may be set to 4.5% or more, 5.0% or more, or 6.0% or more. On the other hand, excessive Mg concentration may deteriorate workability, particularly powdering resistance, and further deteriorate flat surface corrosion resistance. Therefore, the Mg concentration is set to 15.0% or less. The Mg concentration may also be set to 12.0% or less, 10.0% or less, or 8.0% or less. In particular, in order to include Al and Mg in the zinc phosphate crystal layer 13, the Mg concentration is preferably 5.0% or more and 8.0% or less, and more preferably 6.0% or more and 7.0% or less.

[0035] Si: 0% or more, 1.0% or less. The Si concentration may be 0%, but when Si is contained in the coating layer 12, it forms intermetallic compounds in the coating layer 12. The coating composition in this embodiment has a high melting point, and therefore, the operating temperature during hot-dip coating is approximately 500°C. At such an operating temperature, when the steel material 11 is immersed in the coating bath, Al and Zn undergo active interdiffusion with Fe to form Fe-based intermetallic compounds, but Si suppresses this excessive reaction. Therefore, when Si is contained, if it is 0.01% or more, the Fe diffusion reaction is significantly suppressed, making it easier to control the formation of Fe-based intermetallic compounds contained in the coating layer 12. On the other hand, if the Si content is excessive, the effect saturates, so the Si content is set to 1.0% or less. The Si content is preferably 0.05% or more or 0.25% or more. Furthermore, the Si content is preferably 0.75% or less.

[0036] Element Group X Sn: 0% or more, 0.7% or less Bi: 0% or more, 0.3% or less In: 0% or more, 0.3% or less Total amount ΣX of Sn, Bi, and In: 0% or more, 0.7% or less Each element of element group X (Sn, Bi, In) can be optionally contained, and therefore the content of each is set to 0% or more. However, when each element of element group X is contained in the plating layer 12, it improves the sacrificial corrosion protection effect of the plating layer 12. Furthermore, each element of element group X has the effect of promoting the dissolution of Mg during phosphate treatment and reducing the Munsell value of the zinc phosphate crystal layer 13. Therefore, each element of element group X (Sn, Bi, In) is preferably set to 0.03% or more or 0.05% or more. On the other hand, excessive content of each element of element group X deteriorates planar corrosion resistance. Therefore, Sn is set to 0.7% or less, and Bi and In are each set to 0.3% or less. For the same reason, the total amount ΣX of these elements is set to 0% or more and 0.7% or less.

[0037] Note that optional added elements other than element X may form intermetallic compounds that are more noble than Zn in the plating layer 12, and therefore are not involved in the growth of zinc phosphate crystals.

[0038] Element Group Ya Ca: 0% or more, 0.6% or less Y: 0% or more, 0.3% or less La: 0% or more, 0.3% or less Ce: 0% or more, 0.3% or less Sr: 0% or more, 0.3% or less Li: 0% or more, 0.3% or less Total amount ΣYa of Ca, Y, La, Ce, Sr, and Li: 0% or more, 0.6% or less Each element in the element group Ya is an optional element, and its content may be 0% or less. Ca, one of the elements in the element group Ya, is an element that can adjust the optimal amount of Mg elution to impart planar corrosion resistance. When Ca is contained, it may be 0.01% or more or 0.02% or more. On the other hand, excessive Ca concentration deteriorates planar corrosion resistance. Furthermore, various floating dross is formed in the coating bath, increasing coating defects and significantly deteriorating the appearance of the coating layer 12. Therefore, the Ca concentration is set to 0.6% or less. The Ca concentration may be 0.5% or less or 0.3% or less.

[0039] The elements of the element group Ya other than Ca (Y, La, Ce, Sr, and Li) can be added as a substitute for Ca because they have effects similar to those of Ca. When these elements are added, they may each be 0.01% or more or 0.02% or more. Furthermore, the content of each of these elements Y, La, Ce, Sr, and Li is 0.3% or less. If the content of each element exceeds 0.3%, the plane corrosion resistance decreases. Preferably, it is 0.2% or less or 0.1% or less.

[0040] The total amount ΣYa of the element group Ya is set to the range of 0 to 0.6% in order to improve the plane corrosion resistance.

[0041] Element group Yb Cr: 0% or more, 3.0% or less Ni: 0% or more, 1.0% or less Mo: 0% or more, 0.25% or less Cu: 0% or more, 1.0% or less Ag: 0% or more, 0.25% or less Sb: 0% or more, 0.25% or less Pb: 0% or more, 0.25% or less Total amount ΣYb of Cr, Ni, Mo, Cu, Ag, Sb, and Pb: 0% or more, 3.0% or less Each element of the element group Yb (Cr, Ni, Mo, Cu, Ag, Sb, and Pb) is an optional added element, so their respective contents may be 0%. On the other hand, each element of the element group Yb has properties similar to Zn and can be contained in a relatively large amount. When these elements are contained within the above concentration ranges, corrosion resistance is improved. Therefore, when these elements are contained, the content may be 0.01% or more, or 0.02% or more. On the other hand, if the concentration of each element in the element group Yb is excessive, the effect saturates. Therefore, the content of each element in the element group Yb is set to Cr: 3.0% or less, Ni and Cu: 1.0% or less, and Mo, Ag, Sb, and Pb: 0.25% or less.

[0042] The total amount ΣYb of the element group Yb is set to the range of 0 to 3.0% in order to improve the sacrificial corrosion resistance.

[0043] Element group Yc B: 0% or more, 0.5% or less P: 0% or more, 0.5% or less Total amount of B and P ΣYc: 0% or more, 0.5% or less Since each element (B, P) of the element group Yc is an optional added element, the content of each may be 0%. On the other hand, each element of the element group Yc contributes to improving the corrosion resistance of the flat portion. Therefore, the concentration of each element of the element group Yc may be 0.01% or more or 0.02% or more. On the other hand, if the concentration of each element of the element group Yc is excessive, the effect will saturate. Therefore, the concentration of each element of the element group Yc is set to 0.5% or less. The concentration of each element of the element group Yc may be 0.4% or less or 0.3% or less.

[0044] The total amount ΣYc of the element group Yc is set to the range of 0 to 0.5% in order to improve the corrosion resistance of the flat surface portion.

[0045] Element Group Z Ti: 0% or more, 0.25% or less Co: 0% or more, 0.25% or less V: 0% or more, 0.25% or less Nb: 0% or more, 0.25% or less Mn: 0% or more, 0.25% or less Zr: 0% or more, 0.25% or less W: 0% or more, 0.25% or less Total amount ΣZ of Ti, Co, V, Nb, Mn, Zr, and W: 0% or more, 0.25% or less Each element of element group Z (Ti, Co, V, Nb, Mn, Zr, and W) is an optional element, so their respective contents may be 0% or less. On the other hand, each element of element group Z contributes to improving flat corrosion resistance. Therefore, the concentration of each element of element group Z may be 0.01% or more or 0.02% or more. On the other hand, if the concentration of each element of element group Z is excessive, the effect saturates. Therefore, the concentration of each element in element group Z is set to 0.25% or less. The concentration of each element in element group Z may also be set to 0.20% or less, or 0.10% or less, respectively.

[0046] The total amount ΣZ of the element group Z is set to the range of 0 to 0.25% in order to improve the corrosion resistance of the flat surface portion.

[0047] Fe: 0% or more, 5.0% or less The Fe concentration may be 0%. However, because the coating layer 12 of the surface-treated steel material 1 of this embodiment is produced by a hot-dip galvanizing method, Fe may diffuse from the steel material 11 to the coating layer 12 during production. Therefore, the coating layer 12 may contain 0.01% or more Fe. The Fe concentration may be, for example, 0.05% or more, 0.1% or more, 0.5% or more, or 1.0% or more. On the other hand, it has been confirmed that an Fe concentration of 5.0% or less does not adversely affect the performance of the coating layer 12. The Fe concentration may be, for example, 2.0% or less or 1.0% or less.

[0048] Balance: Zn and impurities The balance preferably contains Zn. In the plating layer 12 according to this embodiment, Zn is the element contained in the largest amount. Zn is an element that provides flat surface corrosion resistance and sacrificial corrosion protection to the plating layer 12, so the Zn concentration needs to be 40% or more.

[0049] Impurities refer to components contained in raw materials or components mixed in during the manufacturing process, but not intentionally added. For example, trace amounts of components other than Fe may be mixed into the plating layer 12 as impurities due to mutual atomic diffusion between the steel material 11 (base steel) and the plating bath. Furthermore, since metals with 3N purity are typically used to manufacture plating alloys, the total concentration of impurities may be approximately 0.03% or less.

[0050] To identify the average chemical composition of the plating layer 12, an acid solution is obtained by stripping and dissolving the plating layer 12 with an acid containing an inhibitor that suppresses corrosion of the base steel (steel material 11). The chemical composition can then be determined by measuring the resulting acid solution using ICP atomic emission spectroscopy or ICP-MS. There are no particular limitations on the type of acid, as long as it can dissolve the plating layer 12.

[0051] Next, the zinc phosphate crystal layer 13 formed on the surface of the plating layer 12 will be described. The zinc phosphate crystal layer 13 is formed by phosphate treatment of the plating layer 12. By performing phosphate treatment on the plating layer 12 containing 40% or more Zn using a treatment solution containing zinc phosphate, crystalline zinc phosphate tetrahydrate (Zn phosphate tetrahydrate), known as hopite, is formed. ３(P.O. ４ ) ２ ・4H ２ O) is formed. ３ (P.O. ４ ) ２ ・4H ２ The O content is 95% by mass or more, preferably 98% by mass or more.

[0052] The zinc phosphate crystal layer 13 also contains Mg at a concentration of 1.5 mass % or more and Al at a concentration of 1.0 mass % or more. The Mg and Al contained in the zinc phosphate crystal layer 13 originate from the plating layer 12. That is, during the phosphate treatment, the pH of the phosphate treatment solution is adjusted to slightly dissolve the surface of the plating layer 12, promoting the elution of Al and Mg, and the eluted Al ions and Mg ions are captured in the zinc phosphate crystal layer 13.

[0053] By containing Mg at a concentration of 1.5 mass% or more and Al at a concentration of 1.0 mass% or more in the zinc phosphate crystal layer 13, the zinc phosphate crystal layer 13 appears black, thereby reducing the intensity of reflected light and improving antiglare properties. Specifically, the Munsell value N of the zinc phosphate crystal layer 13 becomes 3.5 or less. If the zinc phosphate crystal layer 13 does not contain Mg and Al, the Munsell value N is about 4.0, but if the zinc phosphate crystal layer 13 contains Mg and Al, the Munsell value N becomes 3.5 or less, and the zinc phosphate crystal layer 13 becomes increasingly black. If the Mg concentration in the zinc phosphate crystal layer 13 is less than 1.5% or the Al concentration is less than 1.0%, the Munsell value of the zinc phosphate crystal layer 13 cannot be sufficiently increased. The reason why the Munsell value decreases when a small amount of Mg and Al is contained in the zinc phosphate crystal layer 13 is unknown, but it is presumed that this is due to a change in the crystal structure of the zinc phosphate crystals or the formation of an oxygen-deficient oxide film on the surface of the plating layer 12.

[0054] The amount of zinc phosphate crystal layer 13 deposited on the surface of the plating layer 12 is 1.0 g / m ２ It is preferable that the content is 1.5 g / m or more, and more preferably 1.5 g / m ２ The coating weight of the zinc phosphate crystal layer 13 is preferably 1.0 g / m or more.２ If the amount is 10.0 g / m or more, sufficient antiglare properties can be ensured. ２ The following is good:

[0055] The Mg concentration and Al concentration in the zinc phosphate crystal layer 13 are measured as follows. A scanning electron microscope equipped with an energy dispersive elemental analyzer is used as the measuring device. The surface of the zinc phosphate crystal layer 13 is observed with the scanning electron microscope. The conditions for the scanning electron microscope are an electron gun acceleration voltage of 15 kV, an observation magnification of 1000 to 3000 times, and an observation region of 40 × 30 μm. Ten observation regions are arbitrarily selected. Quantitative elemental analysis is performed on each observation region with the energy dispersive elemental analyzer. The deposition weight of the zinc phosphate crystal layer 13 is 1.0 g / m ２ It has been confirmed that if the deposition amount is equal to or greater than this, characteristic X-rays from the underlying plating layer 12 will not be detected when the acceleration voltage of the electron gun is set to 15 kV. The elements targeted for quantitative analysis are C, O, Mg, Al, Si, P, Mn, Ni, and Zn. When the total amount of the target elements is taken as 100 mass%, the Mg content (mass%) and Al content (mass%) are determined for each observation region, and the average values ​​are taken as the Mg concentration and Al concentration in the zinc phosphate crystal layer 13.

[0056] In addition, the zinc phosphate crystal layer 13 contains zinc phosphate tetrahydrate (Zn ３ (P.O. ４ ) ２ ・4H ２ Whether or not ZnO is contained is confirmed by X-ray diffraction measurement. X-ray diffraction measurement is performed over a range of 0 to 180 degrees using a Cu X-ray tube, an X-ray output of 40 kV, 100 mA, and a scan speed of 5 degrees / min, to obtain the X-ray diffraction results. ３ (P.O. ４ ) ２ ・4H ２ The presence of O diffraction peaks is confirmed.

[0057] The amount of the zinc phosphate crystal layer 13 attached is measured by immersing the surface-treated steel material 1 in a 20% aqueous solution of chromium (VI) oxide at room temperature (e.g., 25°C) to dissolve the zinc phosphate crystal layer 13. The amount of attachment can then be measured from the change in weight before and after immersion in the 20% aqueous solution of chromium (VI) oxide.

[0058] The surface-treated steel material 1 of this embodiment has a 60-degree specular gloss Gs(60°) of less than 25.0, measured from the zinc phosphate crystal layer 13 side, and has excellent antiglare properties. The 60-degree specular gloss Gs(60°) is measured using a glossmeter according to the method specified in JIS Z 8741, and the 60-degree gloss (%) of the surface of the zinc phosphate crystal layer 13 is measured.

[0059] The Munsell value is measured using a spectrophotometer or a color difference meter. The measured Munsell value is used to determine the degree of blackness of the surface of the surface-treated steel material 1. As an example, the Munsell value N is measured using a spectrophotometer (CM-26dG, manufactured by Konica Minolta) in accordance with JIS Z 8722. Here, N means achromatic color.

[0060] Next, a description will be given of a method for manufacturing the surface-treated steel material 1 of this embodiment. The surface-treated steel material 1 of this embodiment is manufactured by manufacturing a plated steel material including a steel material 11 and a plating layer 12 disposed on the surface of the steel material 11, and then forming a zinc phosphate crystal layer 13 on the surface of the plating layer 12 of the plated steel material.

[0061] First, a method for producing a plated steel material will be described. The plated steel material is preferably produced by a continuous hot-dip galvanizing method. However, due to size restrictions of the steel material 11, it may also be produced by a batch-type hot-dip galvanizing method, if necessary.

[0062] Specifically, the steel material 11 is annealed in a reducing atmosphere, and the temperature of the annealed steel material 11 is set to about (the coating bath temperature ±30)°C, and then the steel material 11 is immersed in a hot-dip coating bath and pulled out of the hot-dip coating bath, thereby forming a coating layer 12 on the surface of the steel material 11. For annealing in a reducing atmosphere, for example, the reducing atmosphere is a nitrogen atmosphere containing 5% by volume of hydrogen, and the steel material 11 is heated and held at a temperature of around 800°C for about 1 minute to sufficiently reduce the surface of the steel material 11. When the steel material 11 is immersed in the coating bath, N ２ Gas cooling is used to prevent fluctuations in the plating bath temperature during the manufacturing process.

[0063] Next, the steel material 11 whose surface has been sufficiently reduced is immersed in a reduced state in a coating bath. The chemical composition of the coating bath may be adjusted as appropriate so as to obtain the chemical composition of the coating layer 12 described above. The temperature of the coating bath is also not particularly limited, and any temperature at which hot-dip coating can be performed may be selected as appropriate. For example, the coating bath temperature may be set to a value approximately 20°C or more higher than the melting point of the coating bath. The immersion time of the steel material 11 in the coating bath may be, for example, in the range of 1 to 5 seconds.

[0064] After immersion in the plating bath, the thickness of the plating layer 12 is adjusted by wiping immediately. After wiping is completed, the plating layer 12 is cooled. There are no particular restrictions on the cooling conditions. In this manner, a plated steel material is produced.

[0065] Next, the plated steel is subjected to a phosphate treatment. In the phosphate treatment, the surface of the plating layer 12 is degreased and then rinsed with water. Next, if necessary, the surface of the plating layer 12 is subjected to a surface conditioning treatment. Next, the plated steel is immersed in a phosphate treatment solution, or the phosphate treatment solution is applied or sprayed onto the surface of the plating layer 12, thereby adhering the phosphate treatment solution to the surface of the plating layer 12. Thereafter, the phosphate treatment solution is removed from the surface of the plating layer 12 by rinsing with water or the like.

[0066] The specific procedure for the degreasing treatment is not particularly limited. For example, a degreasing bath prepared by adding an alkaline degreasing agent (trade name: Fine Cleaner (FD-E6408)) manufactured by Nihon Parkerizing Co., Ltd. to water is used, the temperature of the degreasing bath is adjusted to a range of 55 to 65°C, and the plated steel material is immersed in the degreasing bath for about 5 to 15 minutes.

[0067] The water rinse after the degreasing treatment may be carried out by immersing the plated steel material in a water bath filled with water, or by spraying water onto the plated steel material.

[0068] After rinsing with water, a surface conditioning treatment may be performed to increase the surface reactivity of the plating layer 12. The surface conditioning treatment is performed by immersing the plated steel material in a conditioning bath containing a surface conditioner immediately before treatment with a phosphate treatment solution, or by applying or spraying the conditioning bath onto the plating layer 12. As the surface conditioner, for example, a surface treatment agent (product name: Preparen X) manufactured by Nihon Parkerizing Co., Ltd. can be used. The temperature of the conditioning bath is set to room temperature (e.g., 10°C) to 40°C, and the immersion time, if any, is set to about 30 to 60 seconds.

[0069] The phosphate treatment is performed by immersing the plated steel in a bath of the phosphate treatment solution, or by applying or spraying the phosphate treatment solution onto the plating layer 12. The phosphate treatment solution is an aqueous solution containing zinc phosphate (zinc phosphate solution) adjusted to a pH of 5.0 or less. The pH of the phosphate treatment solution is preferably 3.0 to 4.0. A low pH increases the time required for zinc phosphate treatment, so a pH of 3.0 or higher is preferable. Making the phosphate treatment solution acidic promotes dissolution of the plating layer 12 and promotes the elution of Al and Mg from the plating layer 12. The phosphate treatment solution may contain other additives as long as they do not inhibit the phosphate treatment. Examples of phosphate treatment solutions that can be used include the phosphate treatment solution manufactured by Nippon Parkerizing Co., Ltd. (product name: Palbond (PB-SX35)). The temperature of the phosphate treatment solution is set to 33 to 37°C, and the immersion time is set to about 1.5 to 2.0 minutes.

[0070] After the phosphate treatment, the substrate may be washed with warm water at 70° C. or higher and then dried, thereby obtaining a zinc phosphate crystal layer 13 containing Mg and Al.

[0071] In this embodiment, the surface of the plating layer 12 is phosphate-treated using a phosphate treatment solution adjusted to a pH of 5.0 or less, whereby a portion of the plating layer 12 dissolves in the phosphate treatment solution containing phosphoric acid, and the dissolved constituent elements of the plating layer 12 undergo a chemical reaction with the phosphoric acid, resulting in the precipitation of phosphate (zinc phosphate) on the plating layer 12. It is presumed that the Al and Mg constituent elements of the plating layer 12 are incorporated into the zinc phosphate during this process. The zinc phosphate crystal layer 13 containing Al and Mg exhibits an appearance close to black and has a Munsell value N of 3.5 or less.

[0072] Furthermore, one or more organic resin coating layers may be formed on the zinc phosphate crystal layer 13 directly on the plating layer 12. The organic resin is not limited to a specific type, and examples thereof include polyester resin, polyurethane resin, epoxy resin, acrylic resin, polyolefin resin, and modified versions of these resins. Here, the modified version refers to a resin obtained by reacting a reactive functional group contained in the structure of these resins with another compound (such as a monomer or a crosslinking agent) containing a functional group capable of reacting with the functional group contained in the structure of the resin.

[0073] Such organic resins may be a mixture of one or more unmodified organic resins, or a mixture of one or more organic resins obtained by modifying at least one other organic resin in the presence of at least one organic resin. The organic resin film may also contain any coloring pigment or anti-rust pigment. Water-based organic resins obtained by dissolving or dispersing them in water may also be used.

[0074] Examples of the present invention will be described below. However, the conditions in the examples are merely examples adopted to confirm the feasibility and effects of the present invention. The present invention is not limited to these examples. Various conditions may be adopted in the present invention as long as they do not deviate from the gist of the present invention and the object of the present invention is achieved.

[0075] The following plated steel sheets were prepared as plated steel materials to which zinc phosphate treatment was applied. For the plated steel sheets, a hot-dip galvanizing simulator manufactured by Rhesca was used to prepare alloys by mixing predetermined amounts of pure metals and other ingredients, and then the alloys were melted and hot-dipped.

[0076] The base sheet for plating was 200 × 100 × 1.2 mm (cold-rolled steel sheet SPCC JIS G3141). A hot-rolled checkered steel sheet was used for some of the substrates for plating.

[0077] Before plating, ２ -H ２ (95% by volume N ２ , 5 vol% H ２ The steel sheet surface was kept at 800°C for 1 minute in a 5% by volume atmosphere (dew point -40°C) to be fully reduced, and then immersed in a plating bath at a bath temperature of +30°C for 3 seconds and pulled out. ２ Gas wiping was applied to the plated material to a thickness of 25 μm. Immediately after wiping, the plated material was cooled to room temperature at an average cooling rate of 10° C. / sec.

[0078] The produced plated steel sheets were skin-pass rolled at a steel sheet thickness reduction rate of 1% or less so that the surface roughness was within the range of Ra 0.1 to 1.8 μm. If the surface roughness of the plated steel sheet is within the range of Ra 0.8 to 1.5 μm, it is possible to reduce the gloss (Gs) without impairing the load on the roll during temper rolling (zinc wrapping) and press formability. Ra refers to the arithmetic mean roughness, and was measured in accordance with JIS B 0601:2013.

[0079] Next, a phosphate treatment was carried out. First, the surface of the plating layer was degreased. For the degreasing treatment, a degreasing bath containing an alkaline degreaser (product name: Fine Cleaner (FD-E6408)) manufactured by Nihon Parkerizing Co., Ltd. added to water was used, and the temperature of the degreasing bath was set to a range of 55 to 65°C, and the plated steel sheet was immersed in the degreasing bath for approximately 5 to 15 minutes.

[0080] Next, as a water rinse after the degreasing treatment, the plated steel sheet was immersed in a water bath filled with water to perform water rinse.

[0081] After rinsing with water, the surface of the plating layer was subjected to a surface conditioning treatment. The surface conditioning treatment was performed by immersing the plated steel sheet in an adjusting bath containing a surface conditioner. The surface conditioner used was a surface treatment agent (product name: Preparen X) manufactured by Nihon Parkerizing Co., Ltd. The temperature of the adjusting bath was set to room temperature (e.g., 10°C) to 40°C, and the immersion time was set to 30 to 60 seconds.

[0082] Next, the plated steel material was immersed in a bath of phosphate treatment solution to form a zinc phosphate crystal layer. The phosphate treatment solution used was a phosphate treatment solution (product name: Palbond (PB-SX35)) manufactured by Nihon Parkerizing Co., Ltd., and the pH of the phosphate treatment solution was adjusted to a range of 3.0 to 4.0. The temperature of the phosphate treatment solution was 33 to 37°C, and the immersion time was 1.5 to 2.0 minutes.

[0083] After the phosphate treatment, the steel was washed with warm water at 70°C or higher and dried with hot air at 100°C using a hot air blower. Washing with warm water at 70°C or higher (suppresses or removes the formation of phosphate crystals with low Al and Mg concentrations that form after removal from the treatment solution) allows the Al concentration in the zinc phosphate crystals to be 1.0% or higher and the Mg concentration to be 1.5% or higher. Drying with warm air at 100°C using a hot air blower suppresses color unevenness and reduces the Munsell value to 3.5 or lower. Surface-treated steel products Nos. 1 to 39 were produced in this manner. Nos. 40 to 41 were washed with water at room temperature, and No. 41 was further dried for 5 minutes in an electric furnace set at 100°C.

[0084] The average chemical compositions of the plating layers were as shown in Tables 1A to 1E. Among the manufacturing conditions, the pH of the phosphate treatment solution was as shown in Table 2. The gloss and Munsell values ​​of the surface-treated steel materials were also measured, and the results are shown in Table 2.

[0085] To identify the average chemical composition of the plating layer, the surface-treated steel material is immersed in a 20% aqueous solution of chromium (VI) oxide at room temperature (e.g., 25°C) to dissolve the zinc phosphate crystal layer 13, and then the plating layer is stripped and dissolved with an acid containing an inhibitor that suppresses corrosion of the base steel (steel material) to obtain an acid solution, and the resulting acid solution is measured using ICP atomic emission spectroscopy and ICP-MS to determine the chemical composition. The acid containing an inhibitor that suppresses corrosion of the base steel (steel material) may be, for example, an acid solution prepared by adding 0.01% propargyl alcohol to a 5% aqueous solution of hydrochloric acid.

[0086] The Mg concentration and Al concentration in the zinc phosphate crystal layer were measured as follows. A scanning electron microscope equipped with an energy dispersive elemental analyzer was used as the measurement device. The surface of the zinc phosphate crystal layer was observed using the scanning electron microscope. The conditions for the scanning electron microscope were an electron gun acceleration voltage of 15 kV, an observation magnification of 1000 to 3000 times, and an observation area of ​​40 × 30 μm. Ten observation areas were arbitrarily selected. Quantitative elemental analysis was performed on each observation area using the energy dispersive elemental analyzer. The elements targeted for quantitative analysis were C, O, Mg, Al, Si, P, Mn, Ni, and Zn. The Mg content (mass%) and Al content (mass%) were determined for each observation area, assuming the total amount of the target elements to be 100 mass%, and the average values ​​were used as the Mg concentration and Al concentration in the zinc phosphate crystal layer.

[0087] In addition, zinc phosphate tetrahydrate (Zn ３ (P.O. ４ ) ２ ・4H ２ Whether or not ZnO is contained was confirmed by X-ray diffraction measurement. X-ray diffraction measurement was performed over a range of 0 to 180 degrees using a Cu X-ray tube, an X-ray output of 40 kV, 100 mA, and a scan speed of 5 degrees / min, to obtain the X-ray diffraction results. ３ (P.O. ４ ) ２ ・4H ２ The presence of O diffraction peaks was confirmed.

[0088] The amount of zinc phosphate crystal layer deposited was measured by immersing the surface-treated steel material in a 20% aqueous solution of chromium (VI) oxide at 25° C. to dissolve the zinc phosphate crystal layer. The amount of deposition was then determined from the change in weight before and after immersion in the 20% aqueous solution of chromium (VI) oxide.

[0089] The gloss of the surface-treated steel material was measured using a glossmeter with 60-degree specular gloss Gs (60°) as an index, as a 60° gloss (%) according to the method specified in JIS Z 8741. A 60° gloss (%) of less than 25.0 was deemed to be acceptable.

[0090] The Munsell value N was measured using a spectrophotometer (CM-26dG manufactured by Konica Minolta). Here, N means achromatic color. The evaluation criteria for the Munsell value are shown below. A Munsell value N of 3.5 or less was considered to be acceptable. The results are shown in the table.

[0091] S: Munsell value is 2.0 or less AA: Munsell value is over 2.0 to 2.5 or less A: Munsell value is over 2.5 to 3.0 or less B: Munsell value is over 3.0 to 3.5 or less C: Munsell value is over 3.5

[0092] As shown in Tables 1A to 2, Nos. 9, 11 to 33 had an average chemical composition of the plating layer, and an Al concentration and an Mg concentration of the zinc phosphate crystal layer that satisfied the ranges of the present invention. As a result, the 60-degree specular gloss Gs (60°) was less than 25.0, and the Munsell value was 3.5 or less, improving anti-glare properties. In addition, the zinc phosphate crystal layer contained zinc phosphate tetrahydrate (Zn ３ (P.O. ４ ) ２ ・4H ２ O) was contained.

[0093] In Nos. 1 to 8, 10, 35 to 37, and 41, the amount of Mg in the plating layer was insufficient. In addition, in Nos. 1 to 4, 38, and 41, the amount of Al in the plating layer was insufficient. Furthermore, in No. 39, the amount of Al was excessive. Therefore, zinc phosphate tetrahydrate (Zn ３ (P.O. ４ ) ２ ・4H ２Although No. 34 contained zinc phosphate crystal layer containing ZnO, the Al concentration in the zinc phosphate crystal layer was less than 1.0% or the Mg concentration was less than 1.5%, resulting in a 60-degree specular gloss Gs(60°) of 25.0 or more and a Munsell value of over 3.5, resulting in poor anti-glare properties. No. 34 had relatively good Munsell values ​​and gloss. However, because the Mg content in the plating layer was excessive, bending significantly deteriorated the processability, particularly powdering, resulting in an unsatisfactory product. No. 40 was manufactured using a manufacturing method outside the preferred ranges of the present invention, resulting in the Al concentration and Mg concentration in the zinc phosphate crystal layer being outside the ranges of the present invention, resulting in a 60-degree specular gloss Gs(60°) of 25.0 or more and a Munsell value of over 3.5, resulting in poor anti-glare properties.

[0094]

[0095]

[0096]

[0097]

[0098]

[0099]

[0100]

[0101]

[0102] The surface-treated steel material and the manufacturing method thereof disclosed herein have excellent processability and are capable of further reducing gloss, and therefore have high industrial applicability.

[0103] 1... surface-treated steel material, 11... steel material, 12... plating layer, 13... zinc phosphate crystal layer

Claims

1. A steel material comprising a steel material and a plating layer disposed on a surface of the steel material, wherein the plating layer has an average chemical composition, in mass%, of Al: more than 10.0% and not more than 40.0%, Mg: more than 4.0% and not more than 15.0%, Si: 0% to 1.0%, Sn: 0% to 0.7%, Bi: 0% to 0.3%, In: 0% to 0.3%, total amount of Sn, Bi, and In ΣX: 0% to 0.7%, Ca: 0% to 0.6%, Y: 0% to 0.3%, La: 0% to 0.3%, Ce: 0% to 0.3%, Sr: 0% to 0.3%, Li: 0% to 0.3%, Total amount of Ca, Y, La, Ce, Sr, and Li, ΣYa: 0% or more, 0.6% or less, Cr: 0% or more, 3.0% or less, Ni: 0% or more, 1.0% or less, Mo: 0% or more, 0.25% or less, Cu: 0% or more, 1.0% or less, Ag: 0% or more, 0.25% or less, Sb: 0% or more, 0.25% or less, Pb: 0% or more, 0.25% or less, Total amount of Cr, Ni, Mo, Cu, Ag, Sb, and Pb, ΣYb: 0% or more, 3.0% or less, B: 0% or more, 0.5% or less, P: 0% or more, 0.5% or less, Total amount of B and P, ΣYc: 0% or more, 0.5% or less, Ti: 0% or more, 0.25% or less, Co: 0% or more and 0.25% or less, V: 0% or more and 0.25% or less, Nb: 0% or more and 0.25% or less, Mn: 0% or more and 0.25% or less, Zr: 0% or more and 0.25% or less, W: 0% or more and 0.25% or less, total amount ΣZ of Ti, Co, V, Nb, Mn, Zr and W: 0% or more and 0.25% or less, Fe: 0% or more and 5.0% or less, balance: 40% or more of Zn and impurities, and Zn is deposited on the surface of the plating layer. ３ (P.O. ４ ) ２ ・4H ２ 1. A surface-treated steel material comprising a zinc phosphate crystal layer containing O, the zinc phosphate crystal layer containing Mg at a concentration of 1.5 mass % or more and Al at a concentration of 1.0 mass % or more.

2. The coating weight of the zinc phosphate crystal layer on the surface of the plating layer is 1.0 g / m ２ The surface-treated steel material according to claim 1 .

3. A surface-treated steel material according to claim 1 or 2, wherein the 60-degree specular gloss Gs(60°) measured from the zinc phosphate crystal layer side is less than 25.

0.

4. A surface-treated steel material according to claim 1 or 2, wherein the Munsell value N measured from the zinc phosphate crystal layer side is 3.5 or less.

5. A method for producing a surface-treated steel product, which comprises a steel product and a plating layer disposed on the surface of the steel product, and forms a zinc phosphate crystal layer on the surface of the plated steel product, wherein the plating layer has an average chemical composition, in mass%, of Al: more than 10.0% and not more than 40.0%, Mg: more than 4.0% and not more than 15.0%, Si: 0% to 1.0%, Sn: 0% to 0.7%, Bi: 0% to 0.3%, In: 0% to 0.3%, total amount of Sn, Bi, and In ΣX: 0% to 0.7%, Ca: 0% to 0.6%, Y: 0% to 0.3%, La: 0% to 0.3%, Ce: 0% to 0.3%, Sr: 0% to 0.3%, Li: 0% to 0.3%. Total amount of Ca, Y, La, Ce, Sr, and Li, ΣYa: 0% or more, 0.6% or less, Cr: 0% or more, 3.0% or less, Ni: 0% or more, 1.0% or less, Mo: 0% or more, 0.25% or less, Cu: 0% or more, 1.0% or less, Ag: 0% or more, 0.25% or less, Sb: 0% or more, 0.25% or less, Pb: 0% or more, 0.25% or less, Total amount of Cr, Ni, Mo, Cu, Ag, Sb, and Pb, ΣYb: 0% or more, 3.0% or less, B: 0% or more, 0.5% or less, P: 0% or more, 0.5% or less, Total amount of B and P, ΣYc: 0% or more, 0.5% or less, Ti: 0% or more, 0.25% or less, Co: 0% or more and 0.25% or less, V: 0% or more and 0.25% or less, Nb: 0% or more and 0.25% or less, Mn: 0% or more and 0.25% or less, Zr: 0% or more and 0.25% or less, W: 0% or more and 0.25% or less, total amount ΣZ of Ti, Co, V, Nb, Mn, Zr and W: 0% or more and 0.25% or less, Fe: 0% or more and 5.0% or less, balance: 40% or more of Zn and impurities, and by applying a zinc phosphate solution of pH 5.0 or less to the surface of the plating layer, Zn is ３ (P.O. ４ ) ２ ・4H ２ 1. A method for manufacturing a surface-treated steel material, comprising forming a zinc phosphate crystal layer containing O, Mg at a concentration of 1.5 mass % or more, and Al at a concentration of 1.0 mass % or more.

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