CN-121992325-A - Galvanized steel sheet suitable for high-speed roll forming process and preparation method thereof

Abstract

The invention relates to the technical field of coated products, in particular to a galvanized steel sheet suitable for a high-speed roll forming process and a preparation method thereof. During preparation, alloy powder is sprayed when the galvanized layer is not solidified, and the alloy powder is subjected to two-stage cooling control, and then is coated with a passivating agent and baked to form a film. According to the invention, through the synergistic effect of surface alloying and composite lubrication passivation, the hardness and wear resistance of a coating are obviously improved, the rolling friction coefficient is reduced, and the steel plate still has excellent corrosion resistance and surface integrity after high-speed forming, thus being suitable for high-efficiency continuous production.

Inventors

• LI CHAO
• LI WEIGANG
• WANG TENG
• SUN LIN
• CHEN HONGYE

Assignees

• 马鞍山钢铁有限公司

Dates

Publication Date

20260508

Application Date

20260126

Claims (10)

1. 1. A galvanized steel sheet suitable for use in a high-speed roll forming process, comprising: A steel substrate; A zinc plating layer formed on the surface of the steel substrate; And a chromium-free passivation layer formed on the surface of the galvanized layer; The surface of the galvanized layer is subjected to alloying treatment by spraying zinc-aluminum alloy powder to form an alloy layer.
2. 2. The galvanized steel sheet according to claim 1, wherein the steel substrate comprises, by mass, not more than 0.1% of C, not more than 0.1% of Mn, not more than 0.1% of Si, not more than 0.02% of P, not more than 0.01% of S, not more than 0.1% of Ti, and the balance Fe and unavoidable impurities, the steel substrate has a thickness of 0.5-2.0 mm, a yield strength of not less than 270MPa, a tensile strength of not less than 350MPa, and the double-sided galvanized layer of the steel substrate has a weight of 80-275 g/m 2 .
3. 3. The galvanized steel sheet according to claim 1, wherein the zinc-aluminum alloy powder comprises 2-10% by mass of aluminum and the balance zinc and unavoidable impurities, the zinc-aluminum alloy powder has a particle size of 15-45 μm for D 10 ≤10μm,D 50 and 70 μm for D 90 , and the alloy layer has a thickness of 2-8 μm.
4. 4. The galvanized steel sheet according to claim 1, wherein the size of the aluminum-rich phase or zinc-rich phase precipitated first in the surface microstructure of the alloy layer is not more than 15 μm, the size of the eutectic phase formed between the aluminum-rich phases or between the zinc-rich phases is not less than 25 μm, the size of the aluminum-rich phase or zinc-rich phase precipitated first in the cross-sectional microstructure of the alloy layer is not more than 20 μm, and the lamellar spacing of the eutectic phase between the aluminum-rich phases or between the zinc-rich phases is not more than 2 μm.
5. 5. The galvanized steel sheet according to claim 1, characterized in that the film weight of the chromium-free passivation layer is 0.9-1.5 g/m 2 , the chromium-free passivation layer is formed by a passivation agent, the passivation agent comprises aqueous epoxy modified acrylic resin, lubricating component polytetrafluoroethylene, molybdenum disulfide and hexagonal boron nitride, and the following solid content mass of each component satisfies the following relationship: relationship one is that a/(a+b+c) is less than or equal to 1.0 and less than or equal to 1.8; Relationship II: c/d is more than or equal to 0.5 and less than or equal to 1.2; relationship III, b/(c+d) is less than or equal to 2.0 and less than or equal to 4.0; Wherein a is the mass percentage of the aqueous epoxy modified acrylic resin, b is the mass percentage of polytetrafluoroethylene, c is the mass percentage of molybdenum disulfide, and d is the mass percentage of hexagonal boron nitride.
6. 6. A method for preparing the galvanized steel sheet suitable for high-speed roll forming process as claimed in any one of claims 1 to 5, characterized by comprising the steps of: s1, providing a steel substrate, performing hot dip galvanizing, and forming a galvanized layer on the surface of the steel substrate; S2, spraying zinc-aluminum alloy powder on the surface of the galvanized layer when the galvanized layer is not solidified, and carrying out surface alloying treatment; and S3, coating a chromium-free passivation agent on the surface of the galvanized layer after alloying treatment, and baking to form the chromium-free passivation layer.
7. 7. The method according to claim 6, wherein in the step S2, the strip steel is cooled to 390-430 ℃ at a primary cooling rate of 2-5 ℃ per second before the zinc-aluminum alloy powder is sprayed, and is cooled to 270-380 ℃ at a secondary cooling rate of 15-25 ℃ per second after the zinc-aluminum alloy powder is sprayed.
8. 8. The method according to claim 6, wherein in step S2, the amount of zinc-aluminum alloy powder sprayed satisfies the following formula: G=B×(ρ/1000)×(251×d+s); Wherein G is the spraying amount of zinc-aluminum alloy powder, the unit G/min, B is the width of the strip steel, the unit mm, ρ is the density of the zinc-aluminum alloy powder, the unit G/cm 3 , d is the thickness of the alloy layer, the unit μm, and s is the running speed of the strip steel, and the unit m/min.
9. 9. The method according to claim 8, wherein the alloy layer thickness d is controlled to be 2-4 μm and the ejection amount G is not less than 5.7G/min when the galvanized layer weight is 80-150G/m 2 , and is controlled to be 5-8 μm and the ejection amount G is not less than 13.8G/min when the galvanized layer weight is 150-275G/m 2 .
10. 10. The method of claim 6, wherein in the step S2, a powder spraying device provided with a straight slit nozzle is adopted for spraying powder, the width of the straight slit is not less than 1500mm, the adjustable range of the opening degree of the straight slit is 0.5-2 mm, the vertical height of the lower end of the powder spraying device from an air knife is not more than 800mm, and the length of the powder spraying device is not less than 1000mm.

Description

Galvanized steel sheet suitable for high-speed roll forming process and preparation method thereof Technical Field The invention relates to the technical field of coated products, in particular to a galvanized steel sheet suitable for a high-speed roll forming process and a preparation method thereof. Background The hot dip galvanized steel sheet has good corrosion resistance and good aesthetic quality, and the galvanized steel sheet pipe is widely applied in the fields of building, heating ventilation, automobiles and household appliances. Compared with the traditional single pipe, the high-speed rolling pipe manufacturing process (the linear speed is 150-200 m/min) has the advantages of high production efficiency, high yield, good dimensional accuracy, good flexibility and the like, and the traditional process is replaced to be the main processing mode of the galvanized steel sheet pipe manufacturing industry. However, the chromium-free passivated galvanized steel sheet also has a plurality of problems in the continuous high-speed rolling production process, such as scratches on the surface zinc layer after tube making and serious falling of the passivation film, so that large-area white rust and even local red rust are extremely easy to occur in the use process of the tube, the service life is greatly reduced, and the like. Aiming at improving the surface property of the galvanized steel sheet, many researches and improvements exist in the prior art. For example, chinese patent application No. CN108467649a discloses a process for preparing wear-resistant corrosion-resistant high-strength galvanized sheet. According to the technical scheme, firstly, a steel plate is annealed and cleaned, then silane coupling agent modifying liquid is applied to the surface of the steel substrate in a closed heating chamber in an atomization spraying mode for modifying treatment, the treatment time is about 1-1.5 hours, the modifying liquid comprises the silane coupling agent, a solvent, water and a catalyst, and the dosage of the modifying liquid is 0.5-0.7% of the weight of the steel substrate. After surface modification, the surface is treated with a zinc plating solution to form a zinc plating coating, which also takes 1 to 1.5 hours. The invention aims to solve the problems of low coating density, low adhesive force, poor water resistance and the like of the water-based zinc-chromium coating after being dipped, brushed or sprayed on the surface of a steel part. However, the technology has obvious limitations that firstly, chromium is contained in the treatment liquid, the technology does not accord with the current development trend of environmental protection and chromium free, secondly, the technological process needs to carry out surface treatment (modification and galvanization) twice, the treatment time and the subsequent baking time are longer, the overall production efficiency is lower, the technology cannot be matched with the rhythm of a modern rolling production line which is continuous at high speed, thirdly, the technology is designed to be focused on improving the adhesive force and corrosion resistance of a coating in a static or conventional environment, and is not optimized for the rolling forming dynamic working condition of high speed, high pressure and high friction, and particularly, the technology does not relate to the remarkable improvement of the surface hardness of a coating and the construction of a long-acting lubrication mechanism under the extreme friction condition. Therefore, although the prior art provides a solution in terms of improving the adhesion and corrosion resistance of the plating layer, it has disadvantages in terms of environmental protection, production efficiency and applicability to a specific working condition of high-speed rolling. Development of a chromium-free environment-friendly galvanized steel sheet which has excellent corrosion resistance, high surface hardness and good lubricity and can be suitable for high-speed continuous roll forming production has become a technical problem to be solved in the field. Disclosure of Invention In order to solve the problems in the prior art, the invention aims to provide a galvanized steel sheet suitable for a high-speed roll forming process and a preparation method thereof, and the galvanized steel sheet still has good corrosion resistance after roll forming by reasonably designing a steel substrate, a plating layer and a chromium-free passivation layer of the chromium-free passivation galvanized steel sheet, so that the requirements of high-efficiency production of clients are met. In order to achieve the above purpose, the present invention is realized by the following technical scheme: in a first aspect, the present invention provides a galvanized steel sheet suitable for a high-speed roll forming process, comprising: A steel substrate; A zinc plating layer formed on the surface of the steel substrate; And a chromium-free p