A method for preparing continuously hot-dip galvanized steel strip

Abstract

This invention relates to the field of metallurgical technology and proposes a method for preparing continuously hot-dip galvanized steel strip, comprising the following steps: molten iron pretreatment, smelting, refining, hot rolling, and cold rolling to obtain a steel strip substrate; electrolytic cleaning of the steel strip substrate, annealing followed by hot-dip galvanizing treatment, cooling, and post-treatment to obtain hot-dip galvanized steel strip; the steel strip substrate is composed of the following components by mass percentage: C 0.09%~0.12%, Mn 0.9%~1.15%, Al 0.03%~0.05%, B 0.004%~0.005%, Nb 0.02%~0.04%, Si≤0.01%, Ca 0.003%~0.005%, Yb 0.001%~0.003%, with the balance being Fe and other unavoidable impurities. This technical solution solves the problem of poor corrosion resistance and mechanical properties of existing galvanized steel strips.

Description

Technical Field

[0001] This invention relates to the field of metallurgical technology, specifically to a method for preparing continuously hot-dip galvanized strip steel. Background Technology

[0002] With the rapid development of my country's industrialization, galvanized steel strip, due to its superior corrosion resistance, weldability, oxidation resistance, and machinability, is widely used in important fields such as construction, transportation, metallurgy, automobile manufacturing, electrical appliance manufacturing, and shipbuilding. This industrial development places increasingly stringent demands on the quality of the galvanized coating. Controlling the thickness and uniformity of the galvanized coating directly affects product quality, and controlling the sheet shape in each hot-dip galvanizing process is a key issue that needs to be addressed to ensure the quality of the galvanized coating. However, due to limitations in processes, some defects are unavoidable on the surface of galvanized steel strip. These defects affect the corrosion resistance and mechanical properties of the product to varying degrees. Therefore, minimizing defects in the galvanized coating, ensuring its quality, and improving the corrosion resistance and mechanical properties of the galvanized steel strip are of great significance for its application. Summary of the Invention

[0003] This invention proposes a method for preparing continuously hot-dip galvanized steel strip, which solves the problem of poor corrosion resistance and mechanical properties of galvanized steel strip in related technologies.

[0004] The technical solution of the present invention is as follows:

[0005] This invention proposes a method for preparing continuously hot-dip galvanized steel strip, comprising the following steps:

[0006] S1. Hot iron pretreatment, smelting, refining, hot rolling, cold rolling to obtain strip steel substrate;

[0007] S2. The strip substrate is electrolytically cleaned and annealed to obtain a pretreated substrate.

[0008] S3. The pretreated substrate is hot-dip galvanized and cooled to obtain a hot-dip galvanized substrate.

[0009] S4. The hot-dip galvanized substrate is post-processed to obtain hot-dip galvanized strip steel.

[0010] The strip substrate is composed of the following components by mass percentage: C 0.09%~0.12%, Mn 0.9%~1.15%, Al 0.03%~0.05%, B 0.004%~0.005%, Nb 0.02%~0.04%, Si≤0.01%, Ca 0.003%~0.005%, Yb 0.001%~0.003%, with the balance being Fe and other unavoidable impurities.

[0011] As a further technical solution, the temperature during hot rolling in step S1 is 850~930℃.

[0012] As a further technical solution, in step S2, the temperature during electrolytic cleaning is 85~90℃, the volume concentration of the alkaline solution is 5%~8%, and the conductivity is 50~55ms / cm.

[0013] As a further technical solution, in step S2, the annealing is carried out under a protective gas condition, wherein the mass content of hydrogen in the protective gas is 8%~10% and the residual oxygen is 5~10ppm.

[0014] As a further technical solution, in step S2, the heating rate of the preheating section of the annealing is 30-40℃ / s, and the uniform heating temperature is 650-700℃.

[0015] As a further technical solution, in step S3, the zinc bath during hot-dip galvanizing is composed of the following components by mass percentage: Ni 0.1%~0.15%, Fe 0.001%~0.01%, Al 0.05%~0.15%, rare earth elements 0.04%~0.08%, with the balance being Zn and other unavoidable impurities.

[0016] As a further technical solution, the rare earth elements are Yb and Dy.

[0017] As a further technical solution, the mass ratio of Yb to Dy is 1:1.

[0018] As a further technical solution, in step S3, the temperature during hot-dip galvanizing is 455~465℃.

[0019] As a further technical solution, in step S3, the post-processing includes finishing and edge trimming.

[0020] The working principle and beneficial effects of this invention are as follows:

[0021] 1. In this invention, by adjusting the mass percentage of each component in the strip steel substrate, the mass percentages of B, Nb, and Yb are controlled within 0.004%~0.005%, 0.02%~0.04%, and 0.001%~0.003%, respectively. This is beneficial to increasing the strength of the strip steel substrate and the plating availability during hot-dip galvanizing, ensuring the quality of the coating after hot-dip galvanizing, and significantly improving the mechanical properties and corrosion resistance of the hot-dip galvanized strip steel.

[0022] 2. In this invention, by introducing rare earth elements Yb and Dy into the zinc bath for hot-dip galvanizing, and adjusting the content of rare earth elements and Ni, Fe, and Al in the composition, the surface tension of the hot-dip galvanized layer is reduced, the wettability of the zinc bath on the surface of the strip steel is improved, the hot-dip galvanized coating is made more uniform, and thus the corrosion resistance of the hot-dip galvanized strip steel is improved. Detailed Implementation

[0023] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0024] Example 1

[0025] A method for preparing continuously hot-dip galvanized steel strip includes the following steps:

[0026] S1. Hot iron pretreatment, smelting, refining, hot rolling at 850℃, cold rolling to obtain strip steel substrate;

[0027] S2. After electrolytic cleaning of the steel strip substrate at a temperature of 85℃, an alkaline solution volume concentration of 8%, and a conductivity of 50ms / cm, it is annealed in a protective gas with a hydrogen mass content of 8% and a residual oxygen content of 10ppm to obtain a pretreated substrate. During annealing, the heating rate of the preheating section is 30℃ / s, and the soaking temperature is 650℃.

[0028] S3. The pretreated substrate is hot-dip galvanized at 455°C and then cooled to obtain a hot-dip galvanized substrate.

[0029] S4. The hot-dip galvanized substrate is smoothed and trimmed to obtain hot-dip galvanized strip steel;

[0030] The steel strip substrate is composed of the following components by mass percentage: C 0.09%, Mn 0.9%, Al 0.03%, B 0.004%, Nb 0.02%, Si 0.005%, Ca 0.003%, Yb 0.001%, with the balance being Fe and other unavoidable impurities;

[0031] The zinc bath used in hot-dip galvanizing consists of the following components by mass percentage: Ni 0.1%, Fe 0.001%, Al 0.05%, Yb 0.04%, with the balance being Zn and other unavoidable impurities.

[0032] Example 2

[0033] A method for preparing continuously hot-dip galvanized steel strip includes the following steps:

[0034] S1. Hot iron pretreatment, smelting, refining, hot rolling at 930℃, cold rolling to obtain strip steel substrate;

[0035] S2. After electrolytic cleaning of the steel strip substrate at a temperature of 90℃, an alkaline solution volume concentration of 5%, and an electrical conductivity of 55ms / cm, it is annealed in a protective gas with a hydrogen mass content of 10% and a residual oxygen content of 5ppm to obtain a pretreated substrate. During annealing, the heating rate of the preheating section is 40℃ / s, and the soaking temperature is 700℃.

[0036] S3. The pretreated substrate is hot-dip galvanized at 465°C and then cooled to obtain a hot-dip galvanized substrate.

[0037] S4. The hot-dip galvanized substrate is smoothed and trimmed to obtain hot-dip galvanized strip steel;

[0038] The steel strip substrate is composed of the following components by mass percentage: C 0.12%, Mn 1.15%, Al 0.05%, B 0.005%, Nb 0.04%, Si 0.01%, Ca 0.005%, Yb 0.003%, with the balance being Fe and other unavoidable impurities;

[0039] The zinc bath used in hot-dip galvanizing consists of the following components by mass percentage: Ni 0.15%, Fe 0.01%, Al 0.15%, Yb 0.08%, with the balance being Zn and other unavoidable impurities.

[0040] Example 3

[0041] A method for preparing continuously hot-dip galvanized steel strip includes the following steps:

[0042] S1. Hot iron pretreatment, smelting, refining, hot rolling at 900℃, cold rolling to obtain strip steel substrate;

[0043] S2. After electrolytic cleaning of the steel strip substrate at a temperature of 90℃, an alkaline solution volume concentration of 6%, and a conductivity of 55ms / cm, it is annealed in a protective gas with a hydrogen mass content of 9% and a residual oxygen content of 7ppm to obtain a pretreated substrate. During annealing, the heating rate of the preheating section is 40℃ / s, and the soaking temperature is 650℃.

[0044] S3. The pretreated substrate is hot-dip galvanized at 460°C and then cooled to obtain a hot-dip galvanized substrate.

[0045] S4. The hot-dip galvanized substrate is smoothed and trimmed to obtain hot-dip galvanized strip steel;

[0046] The steel strip substrate is composed of the following components by mass percentage: C 0.01%, Mn 1.1%, Al 0.04%, B 0.004%, Nb 0.03%, Si 0.003%, Ca 0.004%, Yb 0.002%, with the balance being Fe and other unavoidable impurities;

[0047] The zinc bath used in hot-dip galvanizing consists of the following components by mass percentage: Ni 0.13%, Fe 0.007%, Al 0.01%, Yb 0.06%, with the balance being Zn and other unavoidable impurities.

[0048] Example 4

[0049] The difference between this embodiment and Embodiment 3 lies only in the zinc bath used for hot-dip galvanizing, which is composed of the following components by mass percentage: Ni 0.13%, Fe 0.007%, Al 0.01%, Dy 0.06%, with the balance being Zn and other unavoidable impurities.

[0050] Example 5

[0051] The difference between this embodiment and Embodiment 4 lies only in the zinc bath used for hot-dip galvanizing, which is composed of the following components by mass percentage: Ni 0.13%, Fe 0.007%, Al 0.01%, Yb 0.03%, Dy 0.03%, with the balance being Zn and other unavoidable impurities.

[0052] Comparative Example 1

[0053] The only difference between this comparative example and Example 3 is that the steel strip substrate is composed of the following components by mass percentage: C 0.01%, Mn 1.1%, Al 0.04%, B 0.006%, Nb 0.03%, Si 0.003%, Ca 0.004%, with the balance being Fe and other unavoidable impurities.

[0054] Comparative Example 2

[0055] The only difference between this comparative example and Example 3 is that the steel strip substrate is composed of the following components by mass percentage: C 0.01%, Mn 1.1%, Al 0.04%, Nb 0.03%, Si 0.003%, Ca 0.004%, Yb 0.006%, with the balance being Fe and other unavoidable impurities.

[0056] Comparative Example 3

[0057] The only difference between this comparative example and Example 3 is that the steel strip substrate is composed of the following components by mass percentage: C 0.01%, Mn 1.1%, Al 0.04%, Nb 0.036%, Si 0.003%, Ca 0.004%, with the balance being Fe and other unavoidable impurities;

[0058] The tensile strength of the hot-dip galvanized steel strips prepared in Examples 1-5 and Comparative Examples 1-3 were tested according to the standard GB / T 228.1-2021 "Metallic materials - Tensile testing - Part 1: Test method at room temperature". The tensile test specimens were prepared in the longitudinal direction.

[0059] Salt spray resistance test: The YWST-86 salt spray test apparatus was used for the experiment. The experimental procedure was set as follows: spraying for 15 minutes every 15 minutes, the spray medium was a 10% (mass fraction) NaCl solution, and the temperature inside the salt spray chamber was (35±2)℃. After the set experimental cycle, a section of each type of sample was taken out, and the corrosion of the sample surface was observed. The time when corrosion began to appear on the sample surface was recorded. The test results are shown in the table below.

[0060]

[0061] By comparing the data of Examples 1-5 and Comparative Examples 1-3, it was found that the hot-dip galvanized steel strips prepared in Examples 1-5 had higher tensile strength and longer salt spray resistance time compared with Comparative Examples 1-3. This indicates that by adjusting the mass percentage of each component in the steel strip substrate, the mechanical properties and corrosion resistance of the hot-dip galvanized steel strip can be significantly improved.

[0062] By comparing the data from Examples 3 to 5, it was found that the hot-dip galvanized steel strip prepared in Example 5 had a longer salt spray resistance time compared with Examples 3 to 4. This indicates that by introducing rare earth elements Yb and Dy into the zinc bath of hot-dip galvanizing and adjusting the content of rare earth elements and other elements in the composition, the corrosion resistance of hot-dip galvanized steel strip can be improved.

[0063] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for producing a continuously hot dip galvanized steel strip, characterized in that, It includes the following steps: S1. Molten iron pretreatment, smelting, refining, hot rolling, and cold rolling to obtain a strip substrate; S2. Electrochemically cleaning and annealing the strip substrate to obtain a pretreated substrate; S3. Hot-dip galvanizing the pretreated substrate and cooling to obtain a hot-dip galvanized substrate; S4. Post-treating the hot-dip galvanized substrate to obtain a hot-dip galvanized strip; The strip substrate consists of the following components by mass percentage: C 0.09% - 0.12%, Mn 0.9% - 1.15%, Al 0.03% - 0.05%, B 0.004% - 0.005%, Nb 0.02% - 0.04%, Si ≤ 0.01%, Ca 0.003% - 0.005%, Yb 0.001% - 0.003%, and the balance is Fe and other inevitable impurities; In step S3, the zinc bath for hot-dip galvanizing consists of the following components by mass percentage: Ni 0.1% - 0.15%, Fe 0.001% - 0.01%, Al 0.05% - 0.15%, rare earth elements 0.04% - 0.08%, and the balance is Zn and other inevitable impurities; The rare earth elements consist of Yb and Dy with a mass ratio of 1:

1.

2. The method of producing a continuous hot dip galvanized steel sheet according to claim 1, characterized by, The temperature during hot rolling in step S1 is 850 - 930°C.

3. The method of producing a continuous hot dip galvanized steel sheet according to claim 1, characterized by, In step S2, the temperature during electrochemical cleaning is 85 - 90°C, the volume concentration of the alkali solution is 5% - 8%, and the conductivity is 50 - 55 ms / cm.

4. The method of producing a continuous hot dip galvanized steel sheet according to claim 1, characterized by, In step S2, the annealing is carried out under the condition of a protective gas. The mass content of hydrogen in the protective gas is 8% - 10%, and the residual oxygen is 5 - 10 ppm.

5. The method of producing a continuous hot dip galvanized steel sheet according to claim 1, wherein In step S2, the heating rate in the preheating section of the annealing is 30 - 40°C / s, and the soaking temperature is 650 - 700°C.

6. The method of producing a continuous hot dip galvanized steel sheet according to claim 1, wherein In step S3, the temperature during hot-dip galvanizing is 455 - 465°C.

7. The method of producing a continuous hot dip galvanized steel sheet according to claim 1, wherein In step S3, the post-treatment includes skin pass rolling and trimming.

Images