High-corrosion-resistance coated steel plate and manufacturing method thereof

Abstract

The invention discloses a high-corrosion-resistance coated steel plate and a manufacturing method thereof, the high-corrosion-resistance coated steel plate comprises a matrix steel plate and an alloy plating layer coated on the matrix steel plate, and the plating layer comprises the following alloy elements in percentage by weight: 2.0-4.5% of Al, 1.0-3.0% of Mg, 0.5-0.9% of Ti and the balance of Zn; wherein 2.6 < = Al / Ti < = 5.8, and 1.0 < = Al / Mg < = 3.0; the plating layer is composed of a Zn-rich phase, a Zn-MgZn2 binary alloy phase, a Zn-Al-MgZn2 ternary alloy phase and an AlTiZn ternary alloy phase. The coated steel plate is not only high in corrosion resistance, but also good in surface quality.

Description

Technical Field

[0001] The present invention belongs to the technical field of coated steel plates, and particularly relates to a highly corrosion-resistant coated steel plate and a manufacturing method thereof. Background Art

[0002] Hot-dip galvanized steel plates are widely used in industries such as construction, household appliances, and automobiles. In recent years, with the increasing requirement for the corrosion resistance of materials, on the basis of hot-dip galvanized steel plates, GF steel plates with Al elements added to the coating and zinc-aluminum-magnesium steel plates with Al and Mg elements added to the coating have gradually been applied. Although the corrosion resistance of the materials has been increased to a certain extent, there is a problem that the improvement of corrosion resistance brought by Al and Mg cannot be balanced with the control of surface quality, and the corrosion resistance cannot meet the requirements of more severe environments.

[0003] Chinese Patent CN103282533A discloses a hot-dip Zn alloy steel plate with high corrosion resistance and a manufacturing method thereof. The invention provides a hot-dip Zn alloy steel plate with high corrosion resistance, including: a bottom steel plate and a hot-dip Zn alloy coating. The composition of the hot-dip Zn alloy coating includes 1-3 wt% of aluminum (Al), 1.5-4.0 wt% of magnesium (Mg), and the balance of Zn and inevitable impurities, where Al+Mg is in the range of 2.5-7.0 wt% and Al:(Al+Mg) is in the range of 0.38-0.48, and a method for manufacturing a hot-dip Zn alloy steel plate with high corrosion resistance. However, this technology improves the corrosion resistance by spraying an aqueous phosphate solution during the cooling process, increasing the difficulty of surface quality control.

[0004] Chinese Patent CN 116804274 A discloses a zinc-aluminum-magnesium alloy coating, a zinc-aluminum-magnesium alloy coating steel plate and a preparation method thereof. The chemical components inside the coating described in this application include: Mg, Al, and Zn; the chemical components on the surface of the coating include at least one of the following: Ni, Cr, Co; among them, the surface depth of the distribution of Ni, Cr, and Co ≤ 1 μm, and the contents of Ni, Cr, and Co satisfy the following relationship: 0.01 wt% ≤ [Ni]+[Cr]+[Co] ≤ 20 wt%, where [Ni] represents the weight fraction of Ni, [Cr] represents the weight fraction of Cr, and [Co] represents the weight fraction of Co. It mainly solves the technical problem that the surface color of the existing zinc-aluminum-magnesium coated steel plate tends to darken when used in the atmosphere. However, this technology adds alloy elements Ni, Cr, Co by one of vapor deposition, ion implantation, and electroplating, and the implementation difficulty and cost are relatively high.

[0005] Chinese Patent CN 116804274 A discloses a high-corrosion-resistant zinc-aluminum-magnesium coated steel sheet and its preparation method. By adding elements such as Mg, Al, and Si to the zinc-aluminum-magnesium alloy coating, and controlling the mass fraction of Mg element in the coating within 3%-8% and the mass fraction of Al element within 12%-25%, the volume fraction of Mg-Zn compounds on the coating surface does not exceed 2%, and controlling the ratio of the content of Si element to Al element in the coating within 0.05-0.15, thus enabling the provided zinc-aluminum-magnesium coated steel sheet to have good corrosion resistance and excellent surface quality. However, in this application, the highest Al content reaches 25% and the highest Mg content reaches 8%. The oxidation tendency of Al element and Mg element is extremely high, and it is extremely difficult to control the surface quality during production.

[0006] Chinese Patent CN 114846171 A discloses a hot-dip alloy steel with excellent corrosion resistance and its manufacturing method. The hot-dip alloy coating contains: Al: more than 8% to 25%, Mg: more than 4% to 12%, the balance being Zn and other inevitable impurities. The surface X-ray diffraction intensity of the hot-dip alloy coating satisfies the following relational expression 1. [Relational Expression 1] 2000 cps ≤ X-ray diffraction intensity ≤ 20000 cps (wherein, the X-ray diffraction intensity is M-N, M refers to the peak intensity in the range of 2θ = 20.00° to less than 21°, and N refers to the peak intensity at 2θ = 20.00°). However, in this application, the highest Al content reaches 25% and the highest Mg content reaches 12%, and it is extremely difficult to control the surface quality during production.

[0007] Domestic Publication No. CN 117802438 A discloses a zinc-aluminum-magnesium coating, a zinc-aluminum-magnesium coated steel sheet and its preparation method. The chemical composition of the zinc-aluminum-magnesium coating includes: Al, Mg, Mn, and Zn; wherein, the weight content of Mn is 0.5-5%, and the ratio of the weight content of Mn to the weight content of Al is ≥0.5. The Al8Mn5 phase precipitated at the grain boundaries of the zinc-aluminum-magnesium coating and the hexagonal Al0.8Mn phase precipitated simultaneously at the grain boundaries and in the pure zinc phase. The precipitation of these phases makes the tissue structure finer, and the solid solution formed by Mn dissolved in the matrix can reduce the potential difference between the intermetallic compound and the matrix, which can improve the corrosion resistance of the matrix, enabling the zinc-aluminum-magnesium coated steel sheet to have excellent corrosion resistance. This invention controls the structure by adding Mn element, but the Al and Mg contents of this technology are relatively low, and the improvement of corrosion resistance is limited.

[0008] It can be seen that in the prior art, the corrosion resistance of steel plates is mainly improved in the following ways: 1) In a low-Al and low-Mg system, the structure is controlled by adding high-melting-point compounds or increasing equipment, but this method has the problem of too high cost; 2) A medium-Al and low-Mg or medium-Al and medium-Mg system is adopted, but this system has the problem that the surface quality is difficult to control. Summary of the Invention

[0009] To solve the above technical problems, the present invention provides a highly corrosion-resistant coated steel plate and a manufacturing method thereof, achieving a balanced control of the improvement of corrosion resistance and surface quality.

[0010] The technical solutions adopted by the present invention are as follows:

[0011] The present invention provides a highly corrosion-resistant coated steel plate, including a base steel plate and an alloy coating applied on the base steel plate. The alloying elements and their weight percentages in the coating are: Al 2.0 - 4.5%, Mg 1.0 - 3.0%, Ti 0.5 - 0.9%, and the balance is Zn; where 2.6 ≤ Al / Ti ≤ 5.8 and 1.0 ≤ Al / Mg ≤ 3.0.

[0012] The coating is composed of a Zn-rich phase, a Zn-MgZn2 binary alloy phase, a Zn-Al-MgZn2 ternary alloy phase, and an AlTiZn ternary alloy phase.

[0013] The area of the MgZn2 alloy phase in the coating is 60 - 80%, among which, the area of the Zn-Al-MgZn2 ternary alloy phase is 10 - 20%; the area of the AlTiZn ternary alloy phase is 5 - 15%.

[0014] The base steel plate includes the following chemical components by weight percentage: 0.001% ≤ C ≤ 0.25%, 0.02% ≤ Mn ≤ 1.5%, Si ≤ 0.1%, P ≤ 0.02%, S ≤ 0.02%, Ti ≤ 0.2%, Nb ≤ 0.2%, V ≤ 0.2%, Cr ≤ 0.2%, Mo ≤ 0.2%, Cu ≤ 0.2%, and the balance is Fe and inevitable impurities.

[0015] The present invention also provides a manufacturing method of the highly corrosion-resistant coated steel plate, and the manufacturing method includes the following steps:

[0016] (1) Annealing the base steel plate;

[0017] (2) Hot dip plating;

[0018] (3) Post - plating cooling: A three - stage cooling process is adopted. The values of the hot - dip plating temperature T1, the temperature T2 at the end of the first - stage cooling, the cooling rate v1 of the first stage, the Al / Ti ratio A, and the strip thickness t satisfy the following relationship: 0.36 ≤ (t * v1 * lnA) / (T1 - T2) ≤ 3.08;

[0019] (4) Skin - pass.

[0020] The post - plating cooling process adopts a three - stage cooling process, which are respectively: the cooling rate v1 of the first stage is 15 - 25 °C / s, and the temperature T2 at the end of the first - stage cooling is 380 - 400 °C; the cooling rate v2 of the second stage is 25 - 35 °C / s, and the temperature T3 at the end of the second - stage cooling is 335 - 350 °C; the cooling rate v3 of the third stage is 1 - 10 °C / s, and the temperature T4 at the end of the third - stage cooling is 200 - 250 °C.

[0021] The substrate annealing temperature is 680 - 840 °C.

[0022] The hot - dip plating temperature T1 is 440 - 480 °C.

[0023] The roughness of the steel sheet after skin - pass is 1.5 - 2.5 μm.

[0024] After skin - pass, it also includes passivation or oiling treatment.

[0025] The highly corrosion - resistant coated steel sheet provided by the present invention improves the corrosion resistance of the steel sheet by controlling the Al content and Mg content in the coating, and reduces the adverse effects on the surface quality; by controlling the Ti content in the coating, the eutectic structure is refined to improve the corrosion resistance; by controlling Al / Ti and Al / Mg, the formation of coarse zinc - rich phases is inhibited, the proportion of eutectic phases is increased to improve the corrosion resistance, and the generation of zinc slag is inhibited to achieve good control of the surface quality.

[0026] Specifically:

[0027] For the highly corrosion - resistant coated steel sheet provided by the present invention, the control of each component in the coating is as follows:

[0028] Al: When the Al content is too low, the improvement effect of corrosion resistance is not ideal; when the Al content is too high, coarse Al - rich phases are formed, deteriorating the corrosion - resistant performance. Therefore, the present invention preferably controls the Al content to be 2.0 - 4.5%.

[0029] Mg: When the Mg content is too low, the improvement of corrosion resistance is limited; when the Mg content is too high, the plating solution is easily oxidized, generating surface defects. Therefore, the present invention preferably controls the Mg content in the coating to be 1.0 - 3.0%.

[0030] Ti: Adding a certain amount of Ti element can refine the eutectic structure. The dense structure can reduce the possibility of intergranular corrosion. When the Ti content is too low, it not only fails to play a refining role but also is not easy to form the ternary eutectic phase of AlTiZn, thus unable to enhance the corrosion resistance. When the Ti content is too high, it reduces the fluidity of the zinc pot and increases the zinc consumption. Therefore, the present invention preferably controls the Ti content to be 0.5 - 0.9%.

[0031] For the ratio A of Al element to Ti element: When A < 2.6, the Ti element content is relatively high, and binary alloy phases such as TiZn8 and TiZn 16 etc. will be formed, which is unfavorable for the corrosion resistance and processing performance. When A > 5.8, Al and Ti cannot form a ternary alloy phase, and the effect on improving the corrosion resistance is limited. Therefore, the present invention preferably controls 2.6 ≤ A ≤ 5.8.

[0032] For the ratio B of Al element to Mg element: When B < 1.0, not only the formation of zinc slag cannot be inhibited, but also the formation of the Zn-rich phase cannot be inhibited. The potential of the Zn-rich phase is relatively positive compared with the binary and ternary eutectic phases, and it cannot play a role in preferential corrosion protection. When the content is relatively high, the improvement of the corrosion resistance is not obvious. When B > 3.0, it is unfavorable for the formation of the MgZn2 phase and deteriorates the corrosion resistance. Therefore, the present invention preferably controls 1.0 ≤ B ≤ 3.0.

[0033] The coating of the high-corrosion-resistant coated steel plate provided by the present invention has a coating structure of Zn-rich phase, Zn-MgZn2 binary alloy phase, Zn-Al-MgZn2 ternary alloy phase, and AlTiZn ternary alloy phase to achieve the improvement of the corrosion resistance. Among them, the sum of the proportions of the binary eutectic structure Zn-MgZn2 containing the MgZn2 phase and the ternary eutectic structure Zn-Al-MgZn2 is 60 - 80%, forming a dense corrosion product in the cathode area on the steel plate surface, having a barrier effect to inhibit the penetration of corrosion factors (O2, Cl - ) and thus improving the corrosion resistance. The area of the fine Zn-Al-MgZn2 ternary alloy phase is 10 - 20%, and the area of the AlTiZn ternary alloy phase is 5 - 15%. Such a coating composition ensures the corrosion resistance of the steel plate and reduces the risk of surface color difference. Specifically:

[0034] MgZn2 alloy phase: MgZn2 has a relatively low corrosion potential and can be preferentially dissolved to improve the corrosion resistance, having a sacrificial protection effect. When the area is too small, the improvement effect is not obvious. When the area is too large, since the MgZn2 phase is a brittle phase, even for simple deformation, large cracks will appear in the coating, and in actual applications, corrosion factors will enter the substrate through the large cracks, resulting in a decrease in the corrosion resistance of the coating. The present invention preferably controls the area of the alloy phase containing MgZn2 to be 60 - 80%.

[0035] Zn-Al-MgZn2 ternary alloy phase and AlTiZn ternary alloy phase: The Zn-Al-MgZn2 ternary eutectic phase and AlTiZn ternary alloy phase are relatively fine, which not only improves the corrosion resistance but also can enhance the processing performance. When the content is low, the effect is not obvious; when the content is high, the reflection interference of light is large, and color difference defects are likely to occur. Therefore, in the present invention, the area of the Zn-Al-MgZn2 ternary alloy phase is controlled to be 10-20%, and the area of the AlTiZn ternary alloy phase is 5-15%.

[0036] In the manufacturing method of the highly corrosion-resistant coated steel sheet provided by the present invention, by controlling the annealing temperature, hot-dip plating temperature, and post-plating cooling process, the highly corrosion-resistant coated steel sheet has good surface quality, specifically:

[0037] Annealing temperature: When the annealing temperature is low, the steel sheet is in an unrecrystallized state, which is not conducive to the control of the forming performance; when the annealing temperature is high, the core heat of the steel sheet is high. Especially for thick steel sheets with a thickness of more than 2.0 mm, it is difficult to cool, and the surface quality control is difficult. Therefore, in the present invention, the annealing temperature is preferably controlled to be 680-840 °C.

[0038] Hot-dip plating temperature: When the hot-dip plating temperature is low, it is not conducive to the formation of the AlTiZn ternary eutectic phase; when the hot-dip plating temperature is high, more dross is generated, the surface quality is poor, and the corrosion of the equipment in the pot is increased. Therefore, in the present invention, the hot-dip plating temperature is preferably controlled to be 440-480 °C.

[0039] Cooling process: The post-plating cooling process adopts a three-stage cooling process to cooperate with the composition to control the type and proportion of the coating structure. First, the cooling rate v1 of the first stage is preferably controlled to be 15-25 °C / s, the end temperature T2 of the first stage of cooling is 380-400 °C, and the values of the hot-dip plating temperature T1, the end temperature T2 of the first stage of cooling, the cooling rate v1 of the first stage, the A1 / Ti ratio A, and the strip thickness t satisfy the following relationship: 0.36 ≤ (t * v1 * lnA) / (T1 - T2) ≤ 3.08, so as to form the AlTiZn ternary eutectic phase in the coating and inhibit the generation of zinc dross; secondly, the cooling rate v2 of the second stage is controlled to be 25-35 °C / s, and the end temperature T3 of the second stage of cooling is 335-350 °C, so as to form a eutectic phase containing MgZn2 in the coating; finally, the cooling rate v3 of the third stage is controlled to be 1-10 °C / s, and the end temperature T4 of the third stage of cooling is 200-250 °C to promote the growth of the eutectic phase.

[0040] The present invention also controls the surface roughness of the coating through a finishing process. When the roughness is small, the surface area in contact with the surface treatment agent is small, and the effect of the surface treatment agent in improving corrosion resistance is weak; when the roughness is large, the surface appearance is poor. Therefore, the present invention preferably controls the roughness of the steel plate after finishing to be 1.5 - 2.5 μm.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] By controlling the content and ratio of Al, Mg, and Ti elements in the coating, and coordinating the control of the hot-dip plating process, post-plating cooling process, etc., the coating structure is a certain proportion of Zn-rich phase, Zn-MgZn2 binary alloy phase, Zn-Al-MgZn2 ternary alloy phase, and AlTiZn ternary alloy phase, which not only improves the corrosion resistance of the coated steel plate but also has good surface quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 It is a cross-sectional SEM diagram of the coated steel plate in Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0044] A highly corrosion-resistant coated steel plate provided by the present invention includes a base steel plate and an alloy coating coated on the base steel plate. The alloy elements and their weight percentages in the coating are: Al 2.0 - 4.5%, Mg 1.0 - 3.0%, Ti 0.5 - 0.9%, and the balance is Zn; where 2.6 ≤ Al / Ti ≤ 5.8 and 1.0 ≤ Al / Mg ≤ 3.0.

[0045] In the coating, the area of the MgZn2 alloy phase is 60 - 80%, the area of the Zn-Al-MgZn2 ternary alloy phase is 10 - 20%, and the area of the AlTiZn ternary alloy phase is 5 - 15%.

[0046] The base steel plate includes the following chemical components by weight percentage: 0.001 ≤ C ≤ 0.25, 0.02 ≤ Mn ≤ 1.5, Si ≤ 0.1, P ≤ 0.02, S ≤ 0.02, Ti ≤ 0.2, Nb ≤ 0.2, V ≤ 0.2, Cr ≤ 0.2, Mo ≤ 0.2, Cu ≤ 0.2, and the balance is Fe and unavoidable impurities.

[0047] A manufacturing method of the highly corrosion-resistant coated steel plate provided by the present invention includes the following steps:

[0048] (1) Annealing of the base steel plate: The annealing temperature is 680 - 840 °C

[0049] (2) Hot-dip plating: The dipping temperature T1 is 440 - 480 °C

[0050] (3) Post - plating cooling: A three - stage cooling process is adopted, specifically: the cooling rate v1 in the first stage is 15 - 25 °C / s, and the end - temperature T2 of the first - stage cooling is 380 - 400 °C; the cooling rate v2 in the second stage is 25 - 35 °C / s, and the end - temperature T3 of the second - stage cooling is 335 - 350 °C; the cooling rate v3 in the third stage is 1 - 10 °C / s, and the end - temperature T4 of the third - stage cooling is 200 - 250 °C.

[0051] The values of the hot - dip plating temperature T1, the end - temperature T2 of the first - stage cooling, the cooling rate v1 of the first stage, the Al / Ti ratio A, and the strip thickness t satisfy the following relationship: 0.36 ≤ (t * v1 * lnA) / (T1 - T2) ≤ 3.08;

[0052] Skin - pass rolling: The surface roughness of the steel plate after skin - pass rolling is 1.5 - 2.5 μm.

[0053] The present invention will be described in detail below in conjunction with the embodiments.

[0054] For the coated steel plates in each of the embodiments and comparative examples, the same substrate is used, and its composition and weight percentages satisfy: 0.001% ≤ C ≤ 0.25%, 0.02% ≤ Mn ≤ 1.5%, Si ≤ 0.1%, P ≤ 0.02%, S ≤ 0.02%, Ti ≤ 0.2%, Nb ≤ 0.2%, V ≤ 0.2%, Cr ≤ 0.2%, Mo ≤ 0.2%, Cu ≤ 0.2%, and the balance is Fe and inevitable impurities.

[0055] For the coated steel plates in each of the embodiments and comparative examples, the alloying elements and their weight percentages in the coating are shown in Table 1, and the balance is Zn.

[0056] Table 1

[0057]

[0058] The manufacturing process parameters of the coated steel plates in each of the embodiments and comparative examples are shown in Table 2.

[0059] Table 2 Process control

[0060]

[0061]

[0062]

[0063] The coating structure, corrosion resistance, and surface quality of the coated steel plates in each of the embodiments and comparative examples, and the implementation effects of the high - corrosion - resistant coated steel plates of the present invention are shown in Table 2.

[0064] Corrosion resistance test: The test was carried out according to GB 10125, and at the same time as the pure zinc product with the same coating weight. The multiple of the time to 5% red rust appearance in the examples and comparative examples compared with the pure zinc coating is R. When 2 ≤ R < 3, it is recorded as "Level 1"; when 3 ≤ R < 5, it is recorded as "Level 2"; when 5 ≤ R < 7, it is recorded as "Level 3"; when 7 ≤ R < 9, it is recorded as "Level 4"; when 9 ≤ R < 11, it is recorded as "Level 5".

[0065] Surface quality: Visual observation was adopted. When the surface quality is good, it is recorded as "◎", and when there are defects such as black spots, tooth marks, zinc dross, color difference, etc. on the surface, it is recorded as "×".

[0066] Table 2 Coating structure, surface quality and corrosion resistance

[0067]

[0068]

[0069] It can be seen from the above content that for the high corrosion-resistant coated steel sheet in the examples implemented according to the technical solution of the present invention, the area of the MgZn2 alloy phase in the coating is 60 - 80%, the area of the Zn-Al-MgZn2 ternary alloy phase is 10 - 20%, and the area of the AlTiZn ternary alloy phase is 5 - 15%. The coated steel sheet has excellent corrosion resistance and good surface quality. In the comparative examples, due to the failure to control according to the requirements of the technical solution of the present invention, the above requirements cannot be fully met.

[0070] The above detailed description of a high corrosion-resistant coated steel sheet and its manufacturing method with reference to the examples is illustrative rather than restrictive. Several examples can be listed within the defined scope. Therefore, changes and modifications without departing from the general concept of the present invention should fall within the protection scope of the present invention.

Claims

1. A highly corrosion-resistant coated steel sheet, comprising a base steel sheet and an alloy coating applied on the base steel sheet, characterized in that, The alloying elements and their weight percentages in the coating are as follows: Al 2.0 - 4.5%, Mg 1.0 - 3.0%, Ti 0.5 - 0.9%, and the balance is Zn; where 2.6 ≤ Al / Ti ≤ 5.8 and 1.0 ≤ Al / Mg ≤ 3.

0.

2. The highly corrosion-resistant coated steel sheet according to claim 1, wherein The coating consists of a Zn-rich phase, a Zn-MgZn2 binary alloy phase, a Zn-Al-MgZn2 ternary alloy phase, and an AlTiZn ternary alloy phase.

3. The highly corrosion-resistant coated steel sheet according to claim 1, wherein The area of the MgZn2 alloy phase in the coating is 60 - 80%, among which, the area of the Zn-Al-MgZn2 ternary alloy phase is 10 - 20%; the area of the AlTiZn ternary alloy phase is 5 - 15%.

4. The highly corrosion-resistant coated steel sheet according to claim 1, wherein, The substrate steel plate includes the following chemical components by weight percentage: 0.001% ≤ C ≤ 0.25%, 0.02% ≤ Mn ≤ 1.5%, Si ≤ 0.1%, P ≤ 0.02%, S ≤ 0.02%, Ti ≤ 0.2%, Nb ≤ 0.2%, V ≤ 0.2%, Cr ≤ 0.2%, Mo ≤ 0.2%, Cu ≤ 0.2%, and the balance is Fe and unavoidable impurities.

5. The manufacturing method of the highly corrosion-resistant coated steel sheet according to any one of claims 1-4, characterized in that, The manufacturing method includes the following steps: (1) Annealing of the substrate steel plate; (2) Hot dip coating; (3) Post-plating cooling: A three-stage cooling process is adopted, and the values of the hot dip coating temperature T1, the end temperature T2 of the first-stage cooling, the first-stage cooling rate v1, the Al / Ti ratio A, and the strip thickness t satisfy the following relational expression: 0.36 ≤ (t * v1 * lnA) / (T1 - T2) ≤ 3.08; (4) Skin pass.

6. The manufacturing method according to claim 5, characterized in that, The post-plating cooling process adopts a three-stage cooling process, which are respectively: the first-stage cooling rate v1 is 15 - 25 °C / s, and the end temperature T2 of the first-stage cooling is 380 - 400 °C; the second-stage cooling rate v2 is 25 - 35 °C / s, and the end temperature T3 of the second-stage cooling is 335 - 350 °C; the third-stage cooling rate v3 is 1 - 10 °C / s, and the end temperature T4 of the third-stage cooling is 200 - 250 °C.

7. The manufacturing method according to claim 5, characterized in that, The annealing temperature of the substrate is 680 - 840 °C.

8. The manufacturing method according to claim 5, characterized in that, The hot dip coating temperature T1 is 440 - 480 °C.

9. The manufacturing method according to claim 5, characterized in that, The roughness of the steel plate after skin pass is 1.5 - 2.5 μm.

10. The manufacturing method according to claim 5, characterized in that, After skin pass, it also includes passivation or oiling treatment.

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