阅读说明：本技术 一种耐黑变锌铝镁镀层钢板及其制备方法 (blackening-resistant zinc-aluminum-magnesium coated steel plate and preparation method thereof ) 是由 商婷 蒋光锐 刘广会 滕华湘 李飞 邱婉凌 于 2019-10-22 设计创作，主要内容包括：本发明涉及一种耐黑变锌铝镁镀层钢板及其制备方法,属于轧钢技术领域,该耐黑变锌铝镁镀层钢板,所述锌铝镁镀层钢板包括钢基体和锌铝镁镀层,按重量百分比计,所述锌铝镁镀层的化学成分为：0.2-1.5％Mg,其余为Zn、Al和不可避免的杂质元素,所述锌铝镁镀层表面含有以氢氧根形式存在的氧原子,和/或以碳酸根形式存在的碳原子,本发明实施例提供的耐黑变锌铝镁镀层钢板,只需要控制镀层中Mg含量,最终效果不受锌、铝含量的影响,且耐黑变性强。(The invention relates to blackening-resistant zinc-aluminum-magnesium coated steel plates and a preparation method thereof, belonging to the technical field of steel rolling, wherein the blackening-resistant zinc-aluminum-magnesium coated steel plate comprises a steel substrate and a zinc-aluminum-magnesium coating, the chemical components of the zinc-aluminum-magnesium coating comprise 0.2-1.5% of Mg, and the balance of Zn, Al and inevitable impurity elements in percentage by weight, and the surface of the zinc-aluminum-magnesium coating contains oxygen atoms existing in the form of hydroxyl and/or carbon atoms existing in the form of carbonate.)

The blackening-resistant zinc-aluminum-magnesium coated steel sheet is characterized by comprising a steel substrate and a zinc-aluminum-magnesium coating, wherein the zinc-aluminum-magnesium coating comprises the chemical components of 0.2-1.5 wt% of Mg, and the balance of Zn, Al and inevitable impurity elements, and the surface of the zinc-aluminum-magnesium coating contains oxygen atoms in the form of hydroxyl and/or carbon atoms in the form of carbonate.

2. The kinds of blackening resistant Zn-Al-Mg coated steel sheet of claim 1, wherein the maximum height of the roughness profile of the surface of said steel substrate is less than or equal to the thickness of one side of said Zn-Al-Mg coating.

3. The kinds of blackening resistant zinc-aluminum-magnesium plated steel sheet according to claim 2, wherein said single-sided thickness is 4-50 um.

4. The kinds of blackening resistant zinc-aluminum-magnesium coated steel sheet of claim 1, wherein the sum of the contents of impurity elements is 0.01% or less, and the impurity elements include at least kinds of lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, yttrium, scandium, beryllium, calcium, strontium, barium, lithium, sodium, gallium, and indium.

5. The kinds of blackening resistant zinc-aluminum-magnesium coated steel sheet of claim 1, wherein the magnesium element is contained in an amount of 0.4 to 1.0% by mass.

6. The kinds of blackening resistant zinc-aluminum-magnesium coated steel sheet of claim 1, wherein the content of said oxygen atoms in the form of hydroxyl groups is 50% or more by mass.

7. The kinds of blackening resistant zinc-aluminum-magnesium coated steel sheet of claim 1, wherein the carbon atoms present in the form of carbonate are contained in an amount of not less than 40% by mass.

8, A method for producing a blackening resistant zinc aluminium magnesium plated steel sheet as claimed in any of claims 1 to 7 and , wherein said zinc aluminium magnesium plated steel sheet is obtained by subjecting said steel substrate to hot dip coating, rolling, surface treatment and coiling in this order;

the chemical components of the plating solution for hot dip plating comprise magnesium element, and the mass percentage content of the magnesium element is 0.2-1.5%:

in the rolling process, the elongation of the steel plate is 0.3-2.0%, and the average height Ra of the roughness of the roller surface is 0.8-6.0 um.

9. The method of claim 8, wherein the surface treatment comprises immersing the steel sheet in an alkaline solution having a pH of 8.0-10.0 to perform the surface treatment.

10. The method for manufacturing kinds of blackening resistant zinc-aluminum-magnesium coated steel sheets according to claim 9, wherein the alkaline solution contains carbonate ions, and the carbonate ions are contained in an amount of 0.5-10.0% by mass.

Technical Field

The invention belongs to the technical field of steel rolling, and particularly relates to blackening-resistant zinc-aluminum-magnesium coated steel plates and a preparation method thereof.

Background

The Zn-Al-Mg coated steel sheet is widely used for manufacturing automobiles, buildings, household electrical appliances and the like by , however, the Al and Mg elements in the coating are easy to be oxidized in the air to form an oxide film, the oxide film easily causes the surface of the coating to be dark, if the thickness of the oxide film is uneven, the degree of the dark surface of the coating is different, so that the color of the surface of the coating cannot meet the use requirement, and the coating has a blackening defect.

The patent with application number CN 200810041723 provides anti-blackening electrogalvanized steel sheets and a manufacturing method thereof, the invention puts the electrogalvanized steel sheets into an acid solution containing Ni2+ to be soaked for more than 1 second, and then coats the surfaces with oil, the method can not provide a preparation method and products of an anti-blackening zinc aluminum magnesium coating, and Ni2+ has environmental toxicity.

Patent application No. CN 201380081069 provides a galvanized steel sheet having excellent blackening resistance and corrosion resistance, in which a Zn-Al-Mg-Si alloy plating layer is formed on the surface of the galvanized steel sheet, and a coating film containing Al is formed on the plating layer, the coating film containing Al being composed of an insulating material containing scale-like Al particles, and a method for manufacturing the same. The surface of the product of the invention is coated with an insulating substance, so that the product is difficult to be used in the field of automobiles which need surface electrophoresis treatment.

The invention is similar to the technology of CN 200810041723, and meanwhile, the addition of Ni can lead to the formation of Ni-Al and Ni-Mg phases in the coating, thus deteriorating the corrosion resistance of the coating.

The patent with the application number of CN 201610166546 provides hot-dip galvanized steels and a manufacturing method thereof, and the aim of avoiding blackening defects of a plating layer is achieved by adding Ca and/or Ba and Li elements in the plating layer.

Disclosure of Invention

In view of the above problems, the present invention has been made to provide blackening resistant zinc-aluminum-magnesium plated steel sheet and a method for manufacturing the same, which overcome or at least partially solve the above problems.

The embodiment of the invention provides blackening-resistant zinc-aluminum-magnesium coated steel plates, which comprise a steel substrate and a zinc-aluminum-magnesium coating, wherein the zinc-aluminum-magnesium coating comprises the chemical components of 0.2-1.5% of Mg, and the balance of Zn, Al and inevitable impurity elements in percentage by weight, and the surface of the zinc-aluminum-magnesium coating contains oxygen atoms in the form of hydroxyl and/or carbon atoms in the form of carbonate.

, the maximum height of the roughness profile of the surface of the steel matrix is less than or equal to the single-side thickness of the zinc-aluminum-magnesium coating.

And , the thickness of the single face is 4-50 um.

, the total content of the impurity elements is less than or equal to 0.01% by mass, and the impurity elements comprise at least of lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, yttrium, scandium, beryllium, calcium, strontium, barium, lithium, sodium, gallium and indium.

, the content of magnesium element is 0.4-1.0% by weight.

, the content of oxygen atoms in the form of hydroxyl groups is greater than or equal to 50% by mass.

, the carbon atoms are present in the form of carbonate in an amount of at least 40% by mass.

Based on the same inventive concept, the embodiment of the invention also provides a preparation method of blackening resistant zinc-aluminum-magnesium coated steel plates, which comprises the steps of sequentially carrying out hot dip coating, rolling, surface treatment and coiling on a steel substrate to obtain the zinc-aluminum-magnesium coated steel plates;

the chemical components of the plating solution for hot dipping comprise magnesium element, and the mass percentage content of the magnesium element is 0.2-1.5%;

in the rolling process, the elongation of the steel plate is 0.3-2.0%, and the average height Ra of the roughness of the roller surface is 0.8-6.0 um.

, the surface treatment comprises immersing the steel plate in an alkaline solution to perform the surface treatment, wherein the pH value of the alkaline solution is 8.0-10.0.

, the alkaline solution contains carbonate ions, and the mass percentage content of the carbonate ions is 0.5-10.0%.

or more technical solutions in the embodiment of the present invention have at least the following technical effects or advantages:

1. the blackening-resistant zinc-aluminum-magnesium plated steel plate provided by the embodiment of the invention only needs to control the Mg content in the plating layer, and the final effect is not influenced by the contents of zinc and aluminum.

2. The blackening resistant zinc-aluminum-magnesium coated steel plate provided by the embodiment of the invention has strong blackening resistance.

Detailed Description

The present invention will be described in detail below with reference to specific embodiments and examples, and the advantages and various effects of the present invention will be more clearly apparent therefrom. It will be understood by those skilled in the art that these specific embodiments and examples are for the purpose of illustrating the invention and are not to be construed as limiting the invention.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs .

Unless otherwise specifically stated, various raw materials, reagents, instruments, equipment and the like used in the present invention are commercially available or can be prepared by existing methods.

In order to solve the technical problems, the general idea of the embodiment of the application is as follows:

the invention relates to a blackening-resistant zinc-aluminum-magnesium coated steel plate which comprises a steel substrate and a zinc-aluminum-magnesium coating formed on the surface of the steel substrate.

The steel substrate is not particularly limited, and ordinary steel sheets such as hot-rolled steel sheets and cold-rolled steel sheets can be used, and the steel type is not particularly limited, and for example, aluminum-killed steel, ultra-low carbon steel, high-strength steel, and the like can be used.

Since oxides cover the surface of the zinc-aluminum-magnesium plating layer and cause blackening, it is necessary to specify that the content of active impurity elements (lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, yttrium, scandium, beryllium, calcium, strontium, barium, lithium, sodium, gallium, indium, etc.) in the plating layer should not exceed 0.01%, and the total of all elements should not exceed 0.1%. The main reason why the zinc-aluminum-magnesium coating blackens in the atmospheric environment is that a thin liquid film is formed on the surface of the zinc-aluminum-magnesium coating in the atmosphere, an electrochemical reaction occurs between a magnesium-rich phase and a zinc-rich phase in the coating, and the magnesium-rich phase is preferentially dissolved to release magnesium ions. Magnesium ions are oxidized in the thin liquid film to magnesium oxide. Because the thin liquid film is insufficient in dissolved oxygen, vacancies exist at oxygen atom positions in the oxide, so that the oxide has an absorption effect on visible light and is represented as gray black. Therefore, the magnesium element in the coating is strictly required, and the magnesium content in the coating is required to be not more than 1.5%. However, if the magnesium content in the coating is less than 0.2%, the corrosion resistance of the zinc-aluminum-magnesium coating is impaired. The invention thus requires that the magnesium content of the coating be in the range of 0.2-1.5%, preferably in the range of 0.4-1.0%. The maximum value Rz of the surface roughness height of the substrate is too large, so that the coating is locally obviously thinned, even the coating cannot completely cover the roughness appearance, magnesium and aluminum in the coating are obviously enriched to the surface, and in addition, the surface color can be darkened due to the scattering of visible light caused by the rougher surface. Therefore, the maximum value Rz of the roughness height of the surface of the steel substrate does not exceed the single-sided thickness of the zinc-aluminum-magnesium plating layer. The Gibbs free energy (-3160kJ/mol, room temperature-100 ℃) of the hydrozincite is far lower than that of MgCO₃(1100 kJ/mol at room temperature to 100 ℃), which indicates that hydrozincite [ Zn ] is preferentially formed on the surface of the coating₅(OH)₆(CO₃)₂And hydrozincite [ Zn ]₅(OH)₈Cl₂·H₂O. The hydrozincite and the hydrozincite chloride can be used as a protective barrier for preventing blackening, and the hydrozincite becomes stable at a pH value of 8.0-10.0, so that the invention requires a surface treatment mode of immersing the steel plateInto an alkaline solution, and the pH value of the alkaline solution is in the range of 8.0-10.0, preferably in the range of 8.5-9.5.

The blackening resistant zinc-aluminum-magnesium plated steel sheet and the method for manufacturing the same according to the present application will be described in detail with reference to specific examples.