A method for manufacturing a galvanized steel strip, a galvanized steel strip and an automobile outer panel

Abstract

The application provides a preparation method of a galvanized strip steel, the galvanized strip steel and an automobile outer plate, and belongs to the field of steel preparation. The method comprises the following steps: cleaning a strip steel under set parameters to obtain a clean strip steel; annealing the clean strip steel and controlling the following parameters of the annealing: a strip steel running speed, a heating section furnace pressure, a furnace H2 content and a furnace O content, to obtain an annealed strip steel; galvanizing the annealed strip steel and controlling the following parameters of the galvanizing: a zinc pot roller vibration amplitude, a zinc pot liquid level and a zinc pot temperature, to obtain a zinc layer strip steel; flattening and oiling the zinc layer strip steel to obtain a galvanized strip steel. The strip steel cleaning quality before annealing is improved by optimizing the cleaning process parameters; the occurrence frequency of strip steel nodulation in the furnace is reduced by strictly controlling the furnace oxygen content and hydrogen content parameters; the surface galvanizing quality effect is ensured by stabilizing the zinc pot roller vibration amplitude, the zinc pot liquid level and the temperature parameters. Therefore, the surface quality of the galvanized automobile outer plate is improved.

Description

Technical Field

[0001] This application relates to the field of steel preparation technology, and in particular to a method for preparing galvanized steel strip, galvanized steel strip, and automotive outer panels. Background Technology

[0002] Automotive sheet metal is the largest raw material used in automobile production, with an average of 600-800 kg used per passenger vehicle. With the rapid development of my country's automotive industry, the demand for galvanized automotive outer sheets has been increasing year by year, and the need for high surface quality continues to grow.

[0003] To obtain high-quality galvanized automotive exterior panels, continuous exploration and optimization of process control are needed in stages such as strip cleaning, annealing, galvanizing, finishing, and quality inspection. Currently, the basic production processes of galvanized automotive sheet production lines both domestically and internationally are largely consistent, mainly including uncoiling, welding, cleaning, annealing, galvanizing, finishing, edge trimming, and coiling, which can meet the production needs of ordinary automotive interior panels. However, current production processes frequently encounter defects such as furnace roller scratches in the annealing furnace, submerged roller marks in the zinc pot area, and zinc ash and dross when producing high-grade galvanized automotive exterior panels, hindering the stable production of high-grade galvanized automotive exterior panels. Therefore, improving the surface quality of galvanized automotive exterior panels is a pressing technical problem that needs to be solved. Summary of the Invention

[0004] This application provides a method for preparing galvanized steel strip, galvanized steel strip, and automotive outer panel to solve the following technical problem: how to improve the surface quality of galvanized automotive outer panel.

[0005] In a first aspect, this application provides a method for preparing galvanized steel strip, the method comprising:

[0006] The strip steel is cleaned under set parameters to obtain clean strip steel;

[0007] The cleaned strip steel is annealed, and the following parameters of the annealing are controlled: strip steel running speed, furnace pressure in the heating section, H2 content in the furnace, and O content in the furnace to obtain annealed strip steel;

[0008] The annealed strip steel is galvanized, and the following parameters of the galvanizing process are controlled: the vibration amplitude of the zinc pot roller, the zinc pot liquid level and the zinc pot temperature, to obtain zinc-coated strip steel.

[0009] The zinc-coated steel strip is flattened and coated with oil to obtain galvanized steel strip.

[0010] Optionally, the step of cleaning the strip steel under set parameters to obtain clean strip steel includes:

[0011] The strip steel is subjected to alkaline washing, electrolytic cleaning, rinsing, and drying to obtain clean strip steel; wherein, the concentration of the alkaline solution in the alkaline washing is ≥35g / L, the concentration of the electrolyte in the electrolytic cleaning is ≥45g / L, and the brush roller currents for the alkaline washing and rinsing satisfy the following relationship:

[0012] I1 > I2 + a,

[0013] In the formula, I1 is the brush roller current, I2 is the memory current, and a is 0.5A to 3A.

[0014] Optionally, the cleanliness of the clean strip meets the requirements of Grade 1 or above, or the reflectivity of the clean strip is maintained above 93%.

[0015] Optionally, the strip running speed is 90mpm to 130mpm, the furnace pressure in the heating section is 2.0hPa to 4.0hPa, the H2 content in the furnace is 3.0% to 6.0% by mass fraction, and the O content in the furnace is ≤20ppm by parts per million.

[0016] Optionally, the vibration amplitude of the zinc pot roller is ≤3.0mm / s, the zinc pot liquid level is -42mm to -38mm, and the zinc pot temperature is 450℃ to 460℃.

[0017] Optionally, the galvanizing process also includes the following parameters: the dew point of the furnace nose is -10℃ to -30℃, the speed of the zinc ash pump at the furnace nose is 110rpm to 190rpm, and the Al content in the zinc bath is 0.22% to 0.25% by mass fraction.

[0018] Optionally, the cleaning pressure of the finishing process is 80 bar to 150 bar, and the surface roughness of the finishing roller is 1.6 μm to 2.5 μm.

[0019] Optionally, the oiling process includes the following parameters: the heating temperature of the oiling machine body is 55℃~75℃, the temperature detected by the thermocouple at the top of the oiling machine is >60℃, the heat tracing temperature of the oiling machine blade beam is 65℃~75℃, and the voltage of the upper and lower blade beams of the oiling machine is 70kV~85kV.

[0020] Secondly, this application provides a galvanized steel strip prepared by the method described in any embodiment of the first aspect, wherein the galvanized steel strip satisfies at least one of the following properties: the number of black spots on the edge is ≤20 / 100cm. 2 The number of black dots in the middle is ≤15 / 100cm 2 The quality degradation rate is ≤5%.

[0021] Thirdly, this application provides an automotive outer panel, wherein the automotive outer panel is made of galvanized steel strip as described in the second aspect embodiment.

[0022] The technical solutions provided in this application have the following advantages compared with the prior art:

[0023] This application provides a method for preparing galvanized steel strip, comprising: cleaning the steel strip under set parameters to obtain clean steel strip; annealing the clean steel strip and controlling the following parameters of the annealing: steel strip running speed, furnace pressure in the heating section, H2 content in the furnace, and O content in the furnace, to obtain annealed steel strip; galvanizing the annealed steel strip and controlling the following parameters of the galvanizing: vibration amplitude of the zinc pot roller, zinc pot liquid level, and zinc pot temperature, to obtain zinc-coated steel strip; and leveling and oiling the zinc-coated steel strip to obtain galvanized steel strip. By optimizing the cleaning process parameters, the quality of the steel strip cleaning before annealing is improved; by strictly controlling parameters such as oxygen content and hydrogen content in the furnace, the frequency of nodule formation in the steel strip in the furnace is reduced; and by stabilizing the vibration amplitude of the zinc pot roller and stabilizing parameters such as the zinc pot liquid level and temperature, the quality of the surface galvanizing is ensured. This improves the surface quality of galvanized automotive exterior panels. Attached Figure Description

[0024] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0025] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a schematic flowchart illustrating a method for preparing galvanized steel strip, as provided in an embodiment of this application. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0028] Various embodiments of this application may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a hard limitation on the scope of this application; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Furthermore, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the referred range.

[0029] Furthermore, in the description of this application, the terms "comprising," "including," etc., mean "including but not limited to." In this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. In this document, "and / or" describes the relationship between related objects, indicating that three relationships can exist; for example, A and / or B can represent: A alone, A and B simultaneously, or B alone. A and B can be singular or plural. In this document, "at least one" means one or more, and "more than" means two or more. "At least one," "at least one of the following," or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, "at least one of a, b, or c" or "at least one of a, b, and c" can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be a single or multiple.

[0030] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0031] Based on existing processes, this invention mainly focuses on improving cleaning quality, precisely controlling the atmosphere inside the annealing furnace, and continuously exploring new processes for galvanizing. It effectively controls common defects in the galvanizing process, such as furnace roller scratches, submerged roller marks, zinc ash, and zinc slag, to meet high-level quality requirements and create favorable conditions for continuous and stable production.

[0032] Figure 1 This is a schematic flowchart illustrating a method for preparing galvanized steel strip, as provided in an embodiment of this application.

[0033] Please see Figure 1This application provides a method for preparing galvanized steel strip, the method comprising:

[0034] S1. Clean the strip steel under set parameters to obtain clean strip steel;

[0035] In some embodiments, the step of cleaning the strip steel under set parameters to obtain clean strip steel includes:

[0036] The strip steel is subjected to alkaline washing, electrolytic cleaning, rinsing, and drying to obtain clean strip steel; wherein, the concentration of the alkaline solution in the alkaline washing is ≥35g / L, the concentration of the electrolyte in the electrolytic cleaning is ≥45g / L, and the brush roller currents for the alkaline washing and rinsing satisfy the following relationship:

[0037] I1 > I2 + a,

[0038] In the formula, I1 is the brush roller current, I2 is the memory current, and a is 0.5A to 3A.

[0039] In the above embodiments, by controlling the cleaning parameters, it is possible to ensure the effective removal of residual oil and iron from cold-hardened coiled steel, thereby improving cleaning quality and ensuring that the cleanliness meets the requirements of the outer sheet. For example, the concentration of the alkaline solution for alkaline washing can be 35g / L, 36g / L, 37g / L, 40g / L, 45g / L, 50g / L, etc., and the concentration of the electrolyte for electrolytic cleaning can be 45g / L, 48g / L, 50g / L, 52g / L, 55g / L, 60g / L, etc.

[0040] In some embodiments, the alkaline solution temperature is 65℃~85℃, the rinsing water conductivity is <30μs / cm, the brush roller pressing amount is ≤100mm, and the drying machine temperature is 90℃~130℃.

[0041] In some embodiments, the cleanliness of the clean strip meets the requirements of Grade 1 or above, or the reflectivity of the clean strip is maintained above 93%.

[0042] S2. Anneal the cleaned strip steel and control the following parameters of the annealing: strip steel running speed, furnace pressure in the heating section, H2 content in the furnace, and O content in the furnace to obtain annealed strip steel;

[0043] In some embodiments, the strip running speed is 90mpm to 130mpm, the furnace pressure in the heating section is 2.0hPa to 4.0hPa, the H2 content in the furnace is 3.0% to 6.0% by mass fraction, and the O content in the furnace is ≤20ppm by parts per million.

[0044] In the above embodiments, the strip running speed in the furnace area is not allowed to be increased or decreased during the production of the outer plate, and the furnace atmosphere is kept within a stable control range to avoid quality defects such as nodules and color differences in the strip. This ensures the stability of the annealed surface. For example, the strip running speed can be 90mpm, 100mpm, 110mpm, 120mpm, 130mpm, etc., and the furnace pressure in the heating section can be 2.0hPa, 2.5hPa, 3.0hPa, 3.5hPa, 4.0hPa, etc. The H2 content in the furnace is 3.0%, 4.0%, 4.5%, 5.0%, 6.0%, etc. by mass fraction, and the O content in the furnace is 5ppm, 8ppm, 10ppm, 12ppm, 15ppm, 18ppm, 20ppm, etc. by parts per million.

[0045] S3. The annealed strip steel is galvanized, and the following parameters of the galvanizing are controlled: vibration amplitude of the zinc pot roller, zinc pot liquid level and zinc pot temperature, to obtain zinc-coated strip steel.

[0046] In some embodiments, the vibration amplitude of the zinc pot roller is ≤3.0mm / s, the zinc pot liquid level is -42mm to -38mm, and the zinc pot temperature is 450℃ to 460℃.

[0047] In the above embodiment, the zinc pot needs to undergo zinc pot roller vibration measurement. The three rollers of the zinc pot are measured once per shift, and the measurement must be completed within 2 hours after the start of each shift. If the vibration value reaches 1.5-3.0 mm / s, the vibration measurement frequency is increased to once every 4 hours. If the vibration value is ≥3.0 mm / s, the production of the outer plate is stopped.

[0048] In some embodiments, the galvanizing also includes the following parameters: the dew point of the furnace nose is -10℃ to -30℃, the speed of the furnace nose zinc ash pump is 110rpm to 190rpm, and the Al content in the zinc pot liquid is 0.22% to 0.25% by mass fraction.

[0049] In some embodiments, the slag removal requirements are as follows: slag removal can only be performed on the slag removal roll, with one slag removal roll arranged for every five rolls of outer plates. During slag removal, all floating slag on both the upper and lower surfaces must be cleaned. Before slag removal, it must be confirmed whether there are ingots on the DS side to ensure that there are ingots on the DS side at all times during slag removal, thus ensuring a stable liquid level.

[0050] In some embodiments, the slag removal requirements for galvanizing are as follows: slag must be removed from the weld seam, ensuring that the slag is removed at least 50cm from the center of the strip and at least 15cm from the edge. Slag removal should be carried out towards the four corners of the zinc pot. During the outer plate production process, it is not permitted to push zinc slag from the sides to the upper surface. The zinc slag around the zinc ash pump and the level gauge detection point should be thoroughly cleaned.

[0051] In some embodiments, the online fluctuation range of the zinc plating thickness is +5 g / m.2 To meet order requirements, the distance between the upper and lower air knives is 12mm to 30mm, and the air knife height is ≤200mm.

[0052] By controlling the galvanizing process parameters, the zinc pot process can be kept within the required range over a long period, avoiding defects such as zinc ash carryover and submerged roller marks. For example, the vibration amplitude of the zinc pot roller can be 1.0 mm / s, 1.5 mm / s, 2.0 mm / s, 2.5 mm / s, 3.0 mm / s, etc.; the zinc pot liquid level can be -42 mm, -41 mm, -40 mm, -39 mm, -38 mm, etc.; and the zinc pot temperature can be 450℃, 452℃, 454℃, 456℃, 458℃, 460℃, etc. The dew point of the furnace nose can be -10℃, -15℃, -20℃, -25℃, -30℃, etc., and the speed of the zinc ash pump of the furnace nose can be 110rpm, 120rpm, 130rpm, 140rpm, 160rpm, 180rpm, 190rpm, etc., and the Al content in the zinc pot liquid is 0.22%, 0.23%, 0.24%, 0.25%, etc. by mass fraction.

[0053] S4. The zinc-coated strip is flattened and oiled to obtain galvanized strip.

[0054] In some embodiments, the cleaning pressure of the finishing process is 80 bar to 150 bar, and the surface roughness of the finishing roller is 1.6 μm to 2.5 μm.

[0055] In some embodiments, the finishing elongation rate of the leveling machine is executed at ±0.1% of the planned value. During the production of the outer plate, the maximum tension at the IF steel finishing inlet and outlet does not exceed 10% of the secondary value, and is adjusted appropriately by the operator according to the plate shape. If raw material inclusions and peeling defects are encountered, the leveling machine should be opened to the middle position in advance, and high-pressure cleaning should be performed to ensure normal operation. When finishing bright spot defects occur, it is forbidden to rinse a fixed point or a fixed section of the roller surface for a long time to prevent color difference defects.

[0056] In the above embodiments, by controlling the flattening parameters, the strip shape is ensured while meeting the required elongation rate. For example, the cleaning pressure for finishing can be 80 bar, 90 bar, 100 bar, 110 bar, 120 bar, 130 bar, 140 bar, 150 bar, etc., and the surface roughness of the finishing roller can be 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2.1 μm, 2.4 μm, 2.5 μm, etc.

[0057] In some embodiments, the oiling process includes the following parameters: the heating temperature of the oiling machine body is 55℃~75℃, the temperature detected by the thermocouple at the top of the oiling machine is >60℃, the heat tracing temperature of the oiling machine blade beam is 65℃~75℃, and the voltage of the upper and lower blade beams of the oiling machine is 70kV~85kV.

[0058] In some embodiments, the oiling machine is turned on and preheated 5 hours in advance.

[0059] In the above embodiments, the uniformity and adhesion of the oil coating are ensured by controlling the process parameters of the oil coating. For example, the heating temperature of the oil coating machine body can be 55℃, 60℃, 65℃, 70℃, 75℃, etc.; the temperature detected by the thermocouple on the top of the oil coating machine can be 61℃, 65℃, 68℃, 70℃, 75℃, etc.; the heat tracing temperature of the oil coating machine blade beam can be 65℃, 67℃, 69℃, 70℃, 72℃, 74℃, 75℃, etc.; and the voltage of the upper and lower blade beams of the oil coating machine can be 70kV, 72kV, 75kV, 78kV, 82kV, 85kV, etc.

[0060] In some embodiments, the method further includes: performing quality inspection on the galvanized steel strip, as proper quality inspection is essential for ensuring the quality of the outer panel.

[0061] In some embodiments, during the production of outer sheets, the production line must use a stroboscope to inspect the quality of each coil of outer sheets in the intermediate quality inspection room, focusing on defects such as sunken roller marks, short line scratches, and furnace scratches. Among these defects, sunken roller marks visible under side light on the lower tower strip are not allowed to exceed 100mm from the edge; if they do, the production process must be adjusted or the coiled strip must be pulled up immediately.

[0062] In some embodiments, black spot inspection must be performed during the production of the outer panel, once per large roll. Before counting the black spots, the panel must be cleaned with a special wiping cloth. Black spots need to be counted on both the upper and lower surfaces. The number of black spots on the edges should be ≤20 per 100cm. 2 The number of black dots in the middle is ≤15 / 100cm 2 .

[0063] In some embodiments, a stamping inspection must be performed during the production of the outer sheet, normally once every three large rolls. After a speed increase or decrease in the furnace zone, the first roll of the final product must be stamped. The stamping depth is set at 80mm. Judgment criteria: After stamping, the convex surface is polished (the concave surface is not polished). No more than two high points on the concave surface caused by zinc slag or zinc ash are allowed (not caused by mold problems).

[0064] In some embodiments, vertical inspection must be performed during outer sheet production: vertical grinding is performed every 3 large rolls. Defects that cannot be confirmed by vertical grinding must be reconfirmed by offline grinding of export sample sheets. The first roll after changing rolls must be vertically ground, with the direction perpendicular to the rolling direction, and the grinding length must be guaranteed to be 2m.

[0065] In some embodiments, during the production of the outer sheet, a rewinding process must be arranged to produce one sample roll, and the strip within a 50m range and in the middle of the strip must be polished at least once to check for the presence of periodic defects.

[0066] Based on a general inventive concept, this application provides a galvanized steel strip prepared by the method described in any embodiment of the first aspect, wherein the galvanized steel strip satisfies at least one of the following properties: the number of black spots on the edge is ≤20 / 100cm. 2 The number of black dots in the middle is ≤15 / 100cm 2 The quality degradation rate is ≤5%.

[0067] The galvanized steel strip is made based on the above-described method for preparing galvanized steel strip. The specific steps of the method for preparing galvanized steel strip can be referred to the above embodiments. Since the galvanized steel strip adopts some or all of the technical solutions of the above embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be elaborated here.

[0068] Based on a general inventive concept, this application provides an automotive outer panel, wherein the automotive outer panel is made of galvanized steel strip as described in the second aspect embodiment.

[0069] The present application is further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the application. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to industry standards. If there is no corresponding industry standard, then common international standards, conventional conditions, or conditions recommended by the manufacturer are followed.

[0070] This embodiment provides a method for preparing galvanized steel strip, the method comprising:

[0071] S11. Clean the strip steel under the set parameters to obtain clean strip steel;

[0072] S21. Anneal the cleaned strip steel and control the following parameters of the annealing: strip steel running speed, furnace pressure in the heating section, H2 content in the furnace, and O content in the furnace to obtain annealed strip steel;

[0073] S31. The annealed strip steel is galvanized, and the following parameters of the galvanizing are controlled: the vibration amplitude of the zinc pot roller, the zinc pot liquid level and the zinc pot temperature, to obtain zinc-coated strip steel.

[0074] S41. The zinc-coated strip is leveled and oiled to obtain galvanized strip. For the parameters of the preparation method of galvanized strip, please refer to Tables 1 to 3.

[0075] Table 1. Parameters of the cleaning and annealing processes in the preparation of galvanized steel strip.

[0076]

[0077]

[0078] Table 2. Parameters of the galvanizing and finishing processes in the preparation of galvanized steel strip.

[0079]

[0080] Table 3. Parameters of the oiling process in the preparation of galvanized steel strip.

[0081]

[0082] It should be noted that in the actual production process, the furnace pressure in the heating section, H2 content, O content in the furnace, zinc pot liquid level, zinc liquid temperature, and zinc pot roller vibration fluctuate within a certain range, rather than specific values. Therefore, the range values ​​in Tables 1 to 3 correspond to the range of fluctuations.

[0083] A statistical comparative analysis was conducted on the quality degradation rate of approximately 1000 tons of products produced using the processes of Examples 1-5 and Comparative Examples 1-3. By utilizing the aforementioned reasonable process control methods, the defect incidence rate was reduced, thereby improving the surface quality of the strip steel. The quality degradation rate of Comparative Examples 1-3 was approximately 10%, while the quality degradation rate was reduced to below 5% after applying the method of this application. The results are shown in Table 4.

[0084] Table 4 Quality downgrade rate and number of black spots in high-grade automotive steel galvanizing production line

[0085]

[0086] Furthermore, one or more technical solutions in the embodiments of the present invention have at least the following technical effects or advantages:

[0087] In this embodiment of the invention, the cleaning quality of the strip steel before annealing is improved by optimizing the cleaning process parameters. Stricter control over parameters such as oxygen and hydrogen content in the furnace reduces the frequency of nodule formation on the strip steel. Stabilizing the vibration amplitude of the zinc pot rollers and parameters such as the zinc pot liquid level and temperature ensures the quality of the galvanized surface, achieving the ideal surface quality requirements for automotive exterior panels. The number of black spots on the edge of the galvanized strip steel is ≤20 per 100cm. 2 The number of black dots in the middle is ≤15 / 100cm 2 The quality degradation rate is ≤5%.

[0088] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for preparing galvanized steel strip, characterized in that, The method includes: The strip steel is cleaned under set parameters to obtain clean strip steel; The cleaned strip steel is annealed, and the following parameters of the annealing are controlled: strip steel running speed, furnace pressure in the heating section, H2 content in the furnace, and O content in the furnace to obtain annealed strip steel; The annealed strip steel is galvanized, and the following parameters of the galvanizing process are controlled: the vibration amplitude of the zinc pot roller, the zinc pot liquid level and the zinc pot temperature, to obtain zinc-coated strip steel. The zinc-coated steel strip is then smoothed and oiled to obtain galvanized steel strip. The step of cleaning the strip steel under set parameters to obtain clean strip steel includes: The strip steel is subjected to alkaline washing, electrolytic cleaning, rinsing, and drying to obtain clean strip steel; wherein the concentration of the alkaline solution for alkaline washing is 35 g / L, the concentration of the electrolyte for electrolytic cleaning is 45 g / L, and the brush roller currents for alkaline washing and rinsing satisfy the following relationship: I1 > I2 + a, In the formula, I1 is the brush roller current, I2 is the memory current, and a is 0.5A~3A; The strip running speed is 105 mpm, the furnace pressure in the heating section is 2.0 hPa to 2.6 hPa, the H2 content in the furnace is 5.2% to 5.4% by mass fraction, and the O content in the furnace is 5 ppm to 8 ppm by parts per million. The vibration amplitude of the zinc pot roller is ≤2.2mm / s, the zinc pot liquid level is -40.0mm to -41.5mm, and the zinc pot temperature is 454.3℃ to 455.7℃. The cleaning pressure for finishing is 100 bar, and the surface roughness of the finishing roller is 1.8 μm. The oiling process includes the following parameters: the heating temperature of the oiling machine body is 55℃, the temperature detected by the thermocouple at the top of the oiling machine is 65℃, the heat tracing temperature of the oiling machine blade beam is 77℃, and the voltage of the upper and lower blade beams of the oiling machine is 80kV.

2. The method according to claim 1, characterized in that, The galvanizing process also includes the following parameters: the dew point of the furnace nose is -10℃ to -30℃, the speed of the zinc ash pump at the furnace nose is 110rpm to 190rpm, and the Al content in the zinc pot liquid is 0.22% to 0.25% by mass fraction.

3. A galvanized steel strip prepared by the method as described in claim 1 or 2.

4. A car exterior panel, characterized in that, The vehicle exterior panel is made of galvanized steel strip as described in claim 3.

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