Method for improving forming performance of IF steel alloyed galvanized sheet coating

Abstract

The invention provides a method for improving the forming performance of a plating layer of an IF steel alloyed galvanized sheet, and belongs to the field of steel preparation. The method comprises the following steps: carrying out hot-dip galvanizing on a cold hard coil to obtain a first galvanized plate; the first galvanized sheet is subjected to sectional alloying heat treatment and cooling, and a second galvanized sheet is obtained; the second galvanized sheet is subjected to primary finishing with the first set finishing roller surface average roughness and the first set finishing elongation, and a third galvanized sheet is obtained; the third galvanized plate is subjected to secondary finishing with the second set finishing roller surface average roughness and the second set finishing elongation, and a fourth galvanized plate is obtained; the fourth galvanized plate is subjected to oil coating treatment, and a fifth galvanized plate is obtained; and the fifth galvanized sheet is coiled, and the alloyed galvanized sheet is obtained. And on the premise of not additionally coating a coating, the surface friction coefficient of the plating layer is reduced by coordinating parameters of the two-time finishing process in cooperation with alloying heat treatment and control over the oil coating amount, and the forming performance of the plating layer is obviously improved.

Description

Technical Field

[0001] The present application relates to the technical field of steel preparation, and in particular to a method for improving the forming performance of the coating of IF steel alloyed galvanized sheet. Background Art

[0002] Galvannealed steel sheet (GA sheet) is a steel sheet produced by alloying the strip after exiting the zinc pot on a conventional hot-dip galvanizing (GI) production line, resulting in a coated steel sheet containing an iron-zinc layer. The Fe content in the coating is generally between 7% and 15%. Compared to conventional galvanized sheet, GA sheet offers numerous structural and performance advantages, including excellent weldability, coating properties, heat resistance, and corrosion resistance, making it widely used in the automotive industry. The alloyed coating contains Zn-Fe alloy phases such as Γ, Γ1, δ, and ζ phases, which provide advantages in weldability and impact resistance. However, the coating surface is generally composed of columnar ζ phases and granular δ phases, resulting in a hard coating with a high friction coefficient, which affects the material's formability.

[0003] In the prior art, to improve the formability of the alloyed galvanized steel coating and reduce the surface friction coefficient, a commonly used process is pre-lubrication. This involves applying a phosphate-based pre-lubricant to the surface of the steel strip by roller coating or spraying after cooling. This produces a mixture of zinc phosphide crystals and amorphous materials on the coating surface, forming a solid phosphate lubricating film that is beneficial for stamping and reduces the surface friction coefficient of the coating. However, pre-lubrication increases production costs, and improper film thickness control can affect subsequent electrophoresis and coating processes, resulting in surface defects. Other approaches have also proposed electroplating a hard iron-based alloy layer onto the hot-dip galvanized or alloyed hot-dip galvanized layer. While this technique effectively addresses the aforementioned issues, it requires further electroplating after hot-dip galvanizing or hot-dip galvannealing, resulting in complex processes and high production costs. Furthermore, it has been proposed to improve the formability of the steel sheet by controlling the coating composition of the alloyed hot-dip galvanized steel sheet and forming a film containing a complex oxide of Mn and P and a water-soluble P compound on the coating surface. However, even if the technical solution provided by the patent is followed, the surface friction coefficient of the alloyed hot-dip galvanized steel sheet containing a Mn and P composite oxide film obtained is still relatively high, and the fluidity of the steel sheet during processing and forming is still not ideal. Summary of the Invention

[0004] The present application provides a method for improving the coating forming performance of IF steel alloyed galvanized sheet to solve the following technical problem: how to improve the coating forming performance of IF steel alloyed galvanized sheet.

[0005] The present invention provides a method for improving the forming performance of the coating of IF steel alloyed galvannealed sheet, the method comprising:

[0006] Hot-dip galvanizing the chilled coil to obtain a first galvanized sheet;

[0007] The first galvanized sheet is subjected to a segmented alloying heat treatment and cooling to obtain a second galvanized sheet; wherein the segmented alloying heat treatment includes an induction heating section and a soaking and heat preservation section arranged in sequence;

[0008] The second galvanized sheet is subjected to a first pass through a pass through roller having a first set average roughness of the pass through roller surface and a first set pass through elongation, to obtain a third galvanized sheet;

[0009] The third galvanized sheet is subjected to secondary skin pass with a second set skin pass roller surface average roughness and a second set skin pass elongation to obtain a fourth galvanized sheet;

[0010] performing an oiling treatment on the fourth galvanized sheet with a set single-side oiling amount to obtain a fifth galvanized sheet;

[0011] The fifth galvanized sheet is coiled to obtain an alloyed galvanized sheet.

[0012] Optionally, the temperature of the induction heating section is 490° C. to 530° C., the temperature of the soaking and heat preservation section is 460° C. to 510° C., and the total time of the induction heating section and the soaking and heat preservation section is 13s to 22s.

[0013] Optionally, the first set average roughness of the surface of the polishing roller is 2.0 μm to 3.0 μm, and the first set polishing elongation is 0.6% to 1.2%.

[0014] Optionally, the second setting average roughness of the surface of the polishing roller is 0.3 μm to 1.0 μm, and the second setting polishing elongation is 0.2% to 0.6%.

[0015] Optionally, the oil coating amount on one side is set to 1600 mg / m 2 ~2000 mg / m 2 .

[0016] Optionally, the chilled coil is Nb-Ti-IF steel, and the thickness of the chilled coil is 0.6 mm to 0.8 mm.

[0017] Optionally, the temperature of the hot-dip galvanized strip entering the zinc pot is 460°C to 470°C, the temperature of the zinc liquid in the zinc pot is 455°C to 465°C, and the zinc liquid is composed of the following chemical components by mass fraction: aluminum: 0.125% to 0.130%, and the remainder is zinc and unavoidable impurities.

[0018] Optionally, the hot-dip galvanized coating weight is 40 g / m 2 ~60g / m2 .

[0019] Optionally, the Fe content of the coating of the alloyed galvannealed sheet is 11.0-12.0%, and the surface of the coating is composed of δ phase.

[0020] Optionally, the surface smoothing and flattening rate of the coating of the alloyed galvanized sheet is ≥80%, the average roughness Ra is 0.6 μm to 0.8 μm, and the friction coefficient is 0.120 to 0.130.

[0021] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art:

[0022] The embodiment of the present application provides a method for improving the forming performance of the coating of IF steel alloyed galvanized sheet. Without applying an additional coating, the surface friction coefficient of the coating is reduced by coordinating the parameters of the two finishing processes with the alloying heat treatment and the control of the amount of oil applied, thereby significantly improving the forming performance of the coating. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0024] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0025] Figure 1 A schematic flow chart of a method for improving the forming performance of the coating of IF steel alloyed galvannealed sheet provided in an embodiment of the present application;

[0026] Figure 2 This is a low-magnification surface morphology image of the coating of the alloyed galvanized sheet provided in Example 1 of the present application;

[0027] Figure 3 This is a high-magnification surface morphology image of the coating of the alloyed galvanized sheet provided in Example 1 of the present application. DETAILED DESCRIPTION

[0028] To make the purpose, technical solutions, and advantages of the embodiments of this application more clear, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the examples described are part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0029] Various embodiments of the present application may be presented in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity and should not be understood as a hard limitation on the scope of the present application; therefore, the range description should be considered to have specifically disclosed all possible sub-ranges and single numbers within the range. For example, the description of a range from 1 to 6 should be considered to have 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., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, which applies regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0030] In addition, in the description of the specification of this application, the terms "including", "comprising", etc. mean "including but not limited to". In this article, relational terms such as "first" and "second" are merely used 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 article, "and / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. Wherein A and B can be singular or plural. In this article, "at least one" refers to one or more, and "plurality" refers to 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 all represent: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, c can be single or multiple. "Parts" such as parts by weight and parts by mass represent the proportional relationship between the components. In the proportional relationship involved in this article, the parameters that need to be described by proportion should be understood as the first term of the proportional formula in the order of description, and the proportional numbers should be understood as the second term of the proportional formula. For example, if the mass ratio of substance A, substance B, and substance C is 1:2:3, then substance A, substance B, and substance C should correspond one-to-one to the proportional numbers in the proportional formula in the order of description, that is, the mass of substance A: the mass of substance B: the mass of substance C = 1:2:3.

[0031] 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.

[0032] Figure 1A schematic flow chart of a method for improving the forming performance of the coating of IF steel alloyed galvanized sheet provided in an embodiment of the present application.

[0033] like Figure 1 As shown, the embodiment of the present application provides a method for improving the forming performance of the coating of IF steel alloyed galvannealed sheet, the method comprising:

[0034] S1, hot-dip galvanizing the chilled coil to obtain a first galvanized sheet;

[0035] In some embodiments, the chilled coil is Nb-Ti-IF steel, and the thickness of the chilled coil is 0.6 mm to 0.8 mm.

[0036] It should be noted that Nb-Ti-IF steel is made on the basis of ultra-low carbon steel. By adding a certain amount of niobium (Nb) and titanium (Ti), the carbon (C) and nitrogen (N) atoms in the steel are fixed into carbides and nitrides, so that there are no interstitial atoms in the steel. Therefore, it is called interstitial-free steel (IF steel).

[0037] In some embodiments, the temperature of the hot-dip galvanized steel strip entering the zinc pot is 460°C to 470°C, the temperature of the zinc liquid in the zinc pot is 455°C to 465°C, and the zinc liquid is composed of the following chemical components by mass fraction: aluminum: 0.125% to 0.130%, and the balance is zinc and unavoidable impurities.

[0038] It should be noted that Zn is an essential element, and the specific content / content range of Zn can be obtained by the upper and lower limit formula of the components, that is, the sum of the percentages of the contents of each component in a composition should be equal to 100%, and the content ranges of several components should meet the following conditions: the upper limit value of a component + the lower limit value of other components ≤ 100; the lower limit value of a component + the upper limit value of other components ≥ 100.

[0039] The higher the temperature of the steel strip entering the zinc pot, the more intense the reaction with the Al and Zn in the zinc pot, and the thicker the resulting alloy layer. Increasing the zinc pot temperature also produces the same effect. The presence of a thick alloy layer is detrimental to the subsequent alloying reaction. Therefore, relatively low hot-dip temperatures are generally used in the production of alloyed galvanized sheet. For example, the temperature of the steel strip entering the zinc pot for hot-dip galvanizing can be 460°C, 462°C, 464°C, 466°C, 468°C, 470°C, etc., and the temperature of the zinc liquid in the zinc pot can be 455°C, 456°C, 458°C, 460°C, 462°C, 464°C, 465°C, etc.

[0040] The Al content of the zinc solution in the zinc pot directly determines the formation of the alloy layer after the strip enters the zinc solution. When the Al content is low, the inhibition layer formed on the surface of the strip after entering the zinc pot is thin or discontinuous, resulting in a violent Fe-Zn reaction and easy formation of explosive structure, causing unevenness on the surface of the alloyed galvanized sheet. When the Al content is high, the inhibition layer is thick, which seriously hinders the occurrence of the Fe-Zn reaction and delays the alloying process. When the alloying reaction is accelerated by increasing the alloying temperature or extending the alloying time, the local Fe-Al alloy layer will be destroyed, forming explosive structure, affecting the coating performance. For example, the mass fraction of aluminum in the zinc solution can be 0.125%, 0.126%, 0.127%, 0.128%, 0.129%, 0.130%, etc.

[0041] In some embodiments, the hot-dip galvanized coating weight is 40 g / m 2 ~60g / m 2 .

[0042] Select the air knife control process parameters and the corresponding air knife equipment to ensure that the coating thickness is uniform in both the rolling direction and the transverse direction, and the coating weight is controlled at 40g / m 2 ~60g / m 2 The coating weight of hot-dip galvanizing is limited to 40g / m 2 ~60g / m 2 , can provide sufficient anti-corrosion barrier for steel, effectively resisting the erosion of corrosive media such as oxygen, moisture, salt, etc. in the environment. For example, the coating weight of hot-dip galvanizing is 40g / m 2 , 42g / m 2 , 45g / m 2 , 50g / m 2 , 52g / m 2 , 56g / m 2 , 60g / m 2 wait.

[0043] S2. Performing a segmented alloying heat treatment and cooling on the first galvanized sheet to obtain a second galvanized sheet; wherein the segmented alloying heat treatment includes an induction heating segment and a soaking and heat preservation segment arranged in sequence;

[0044] In some embodiments, the temperature of the induction heating section is 490° C. to 530° C., the temperature of the soaking and heat preservation section is 460° C. to 510° C., and the total time of the induction heating section and the soaking and heat preservation section is 13s to 22s.

[0045] Alloying heat treatment is completed by induction heating section and soaking and holding section. If the alloying temperature is too low or the alloying time is too short, the Fe content of the coating will be too low and there is a risk of under-alloying. At the same time, the coating surface contains a large amount of columnar ζ phase with a certain direction, which reduces the friction coefficient and affects the forming performance. If the alloying temperature is too high or the alloying time is too long, the Fe content of the coating will be too high and there is a risk of over-alloying. The coating's anti-powdering performance is reduced, and the coating is prone to powdering or peeling during the forming process. For example, the temperature of the induction heating section can be 490℃, 500℃, 510℃, 520℃, 530℃, etc., the temperature of the soaking and holding section can be 460℃, 470℃, 480℃, 490℃, 500℃, 510℃, etc., and the total time of the induction heating section and the soaking and holding section can be 13s, 15s, 17s, 19s, 20s, 22s, etc.

[0046] In some embodiments, induction heating causes the strip to quickly heat up to 500°C to 520°C, and then enters the soaking section and is slowly cooled to 480°C to 500°C by resistance band heating. The time it takes for the strip to pass through the heating section and the soaking section is 15s to 18s.

[0047] S3, performing a first skin pass on the second galvanized sheet with a first set skin pass roller surface average roughness and a first set skin pass elongation to obtain a third galvanized sheet;

[0048] S4, performing secondary skin pass on the third galvanized sheet with a second set skin pass roller surface average roughness and a second set skin pass elongation to obtain a fourth galvanized sheet; and

[0049] In some embodiments, the first set average roughness of the surface of the skin-pass roller is 2.0 μm to 3.0 μm, and the first set skin-pass elongation is 0.6% to 1.2%.

[0050] In some embodiments, the second set average roughness of the surface of the skin-pass roller is 0.3 μm to 1.0 μm, and the second set skin-pass elongation is 0.2% to 0.6%.

[0051] In continuous hot-dip galvanizing units, the role of skin finishing is usually reflected in two main aspects. One is the adjustment of mechanical properties. The yield platform can be eliminated through skin finishing. For IF steel, which does not have a yield platform, skin finishing can also fine-tune the yield strength to reach the appropriate range. The other role is to optimize the surface quality of the strip. For pure hot-dip galvanized products, since the surface is pure zinc and does not contain other phases, the initial roughness is very low. Skin finishing is required to give a certain roughness to improve the subsequent adhesion of the coating. It can also improve oil storage and cover some small surface defects. However, for alloyed hot-dip galvanized products, due to the presence of Fe-Zn alloy phase on the surface, the initial roughness is often above 3.0μm. Therefore, skin finishing is required to reduce the surface roughness, improve the surface morphology and reduce the friction coefficient.

[0052] In the embodiment of the present application, a slightly larger polishing roller roughness and polishing elongation are used in the first pass, which can mainly reduce the surface roughness of the coating and form a certain proportion of polishing flattening area. In the second pass, a smaller polishing roller roughness and polishing elongation are used to further increase the proportion of the polishing flattening area, reduce the friction coefficient, and at the same time ensure a certain roughness. Furthermore, because the alloyed coating is relatively hard and brittle with poor ductility, it is easy to break when subjected to large rolling. The method of two small pass-throughs and step-by-step rolling can also reduce the amount of coating breakage, which is conducive to improving the surface quality. For example, the average roughness Ra of the first pass roller surface can be 2.0μm, 2.2μm, 2.4μm, 2.6μm, 2.8μm, 3.0μm, etc., and the polishing elongation can be 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, etc. The average roughness Ra of the secondary skin-passing roller surface can be 0.3μm, 0.4μm, 0.6μm, 0.8μm, 1.0μm, etc., and the skin-passing elongation can be 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, etc.

[0053] In some embodiments, the first set average roughness of the surface of the skin-pass roller is 2.0 μm to 2.5 μm, and the first set skin-pass elongation is 0.8% to 1.0%.

[0054] In some embodiments, the second set average roughness of the surface of the skin-pass roller is 0.5 μm to 0.8 μm, and the second set skin-pass elongation is 0.3% to 0.5%.

[0055] S5, applying oil to the fourth galvanized sheet with a set amount of oil applied on one side to obtain a fifth galvanized sheet;

[0056] In some embodiments, the set single-side oil coating amount is 1600 mg / m 2 ~2000 mg / m 2 .

[0057] The strip surface is evenly coated with rolling oil, with the oil coating amount on one side being 1600mg / m 2 ~2000 mg / m 2 Since the alloyed galvanized sheet has good oil storage, increasing the amount of oil applied can significantly improve the surface lubricity, which is beneficial to the improvement of the overall forming performance. For example, the amount of oil applied on one side can be 1600mg / m 2 , 1700mg / m 2 , 1800mg / m 2 , 1900mg / m 2 , 2000mg / m 2 wait.

[0058] S6. Coil the fifth galvanized sheet to obtain an alloyed galvanized sheet.

[0059] In some embodiments, the Fe content of the coating of the alloyed galvannealed sheet is 11.0-12.0%, and the surface of the coating is composed of δ phase.

[0060] In some embodiments, the surface smoothing and flattening rate of the coating of the alloyed galvannealed sheet is ≥80%, the average roughness Ra is 0.6 μm to 0.8 μm, and the friction coefficient is 0.120 to 0.130.

[0061] It should be noted that the surface finishing flattening rate is the ratio of the surface area of ​​the coating flattened by the finishing roller to the total surface area.

[0062] It can be seen that the method provided by the present invention for improving the forming performance of the coating of IF steel alloyed galvanized sheet, without additional coating, adjusts the surface phase composition and physical morphology of the alloyed coating plate by coordinating the two finishing process parameters with the alloying heat treatment and the control of the oil coating amount, reduces the surface friction coefficient of the coating, and significantly improves the forming performance of the coating.

[0063] In summary, the method for improving the forming performance of the coating of IF steel alloyed galvannealed sheet provided in this application has the following advantages:

[0064] (1) Optimizing alloying heat treatment: Through segmented alloying heat treatment and cooling, the temperature and time of the induction heating section and the soaking section are precisely controlled to avoid the risks of under-alloying and over-alloying, ensure the appropriate range of Fe content in the coating, and at the same time ensure the coating's anti-powdering performance, laying the foundation for good forming performance.

[0065] (2) Precision finishing process: By adopting two finishing processes and setting different average roughness and finishing elongation of the finishing roller, the surface roughness of the coating is effectively reduced, the surface finishing flattening rate is increased, the surface morphology is improved, and the friction coefficient is reduced, thereby improving the forming performance of the coating. At the same time, the two-step finishing method of step-by-step rolling reduces the amount of coating breakage, which is conducive to improving the surface quality.

[0066] (3) Reasonable oiling amount control: By setting the oiling amount on one side to 1600mg / m 2 ~2000 mg / m 2 , making full use of the good oil storage capacity of alloyed galvanized sheet, improving surface lubricity and further promoting the improvement of forming performance.

[0067] (4) Optimized coating properties: The resulting alloyed galvannealed sheet coating has a moderate Fe content (11.0-12.0%), and the coating surface is composed entirely of δ phase, without ζ phase, exhibiting excellent physical and chemical properties. The coating surface has a high smoothing flatness, a moderate average roughness (0.6μm-0.8μm), and a low friction coefficient (0.120-0.130). These properties work together to improve the coating's formability.

[0068] (5) Process innovation: This method improves the forming performance of the coating by coordinating the parameters of the two finishing processes, alloying heat treatment, and controlling the amount of oil coating without applying additional coatings. It is innovative and practical.

[0069] (6) Environmental protection and energy saving: Compared with traditional surface coating treatment methods, this method avoids additional coating materials and energy consumption, which is in line with the development trend of environmental protection and energy saving.

[0070] The present application will be further described below in conjunction with specific examples. It should be understood that these examples are intended to illustrate the present application only and are not intended to limit the scope of the present application. The experimental methods in the following examples where specific conditions are not specified are generally measured according to industry standards. If there are no corresponding industry standards, then the methods are carried out according to general international standards, conventional conditions, or the conditions recommended by the manufacturer.

[0071] The embodiment provides a method for improving the forming performance of the coating of IF steel alloyed galvannealed sheet, the method comprising:

[0072] The chilled coil substrates of the compositions listed in Table 1 were produced through the process of molten iron pretreatment → converter smelting → alloy fine-tuning → refining → continuous casting → hot rolling → pickling → cold rolling → electrolytic cleaning → continuous annealing. Then, each chilled coil substrate was subjected to the process of hot-dip galvanizing → alloying → cooling → primary leveling → secondary leveling and controlled according to the parameters in Table 2 to prepare IF steel alloyed galvanized steel sheets.

[0073] Table 1 Chemical composition of each chilled coil substrate in the examples and comparative examples (wt%)

[0074] sample C Si Mn P S Alt Nb Ti Example 1 0.0015 0.010 0.115 0.008 0.010 0.035 0.011 0.022 Example 2 0.0015 0.010 0.115 0.008 0.010 0.035 0.011 0.022 Example 3 0.0013 0.009 0.117 0.009 0.008 0.040 0.013 0.025 Example 4 0.0013 0.009 0.117 0.009 0.008 0.040 0.013 0.025 Example 5 0.0013 0.009 0.117 0.009 0.008 0.040 0.013 0.025 Comparative Example 1 0.0012 0.010 0.121 0.007 0.008 0.045 0.010 0.026 Comparative Example 2 0.0012 0.010 0.121 0.007 0.008 0.045 0.010 0.026 Comparative Example 3 0.0012 0.013 0.121 0.007 0.008 0.045 0.010 0.026 Comparative Example 4 0.0017 0.013 0.105 0.008 0.010 0.040 0.014 0.021 Comparative Example 5 0.0017 0.013 0.105 0.008 0.010 0.040 0.014 0.021

[0075] Table 2 Main process parameters of each embodiment and comparative example

[0076]

[0077]

[0078] The specifications of the examples and comparative examples in Table 1 and Table 2 are all 0.7×1200 mm, and the thickness of the zinc layer is 45 g / m on one side. 2 Table 3 shows the main performance index values ​​of the coatings of the embodiment and the comparative example.

[0079] Table 3 Main performance index values ​​of coatings in Examples and Comparative Examples

[0080] sample <![CDATA[Single-sided zinc weight / g·m 2 > Fe content of coating / % Roughness / μm Friction coefficient Example 1 46 11.3 0.69 0.121 Example 2 46 11.0 0.71 0.120 Example 3 47 11.3 0.73 0.122 Example 4 46 11.5 0.70 0.123 Example 5 47 11.0 0.74 0.121 Comparative Example 1 47 10.8 0.82 0.145 Comparative Example 2 48 11.0 0.88 0.136 Comparative Example 3 47 10.5 0.90 0.141 Comparative Example 4 46 10.3 0.93 0.115 Comparative Example 5 46 10.5 0.91 0.118

[0081] As can be seen from Table 3, the alloyed hot-dip galvanized steel sheet examples 1 to 5 produced by the method of the present invention have a coating Fe content of 11.0% to 11.5%, a roughness of 0.6μm to 0.8μm, and a friction coefficient of 0.120 to 0.125. The friction coefficient is measured using a flat plate sliding method under the following conditions: a pressure of 3000N, a sliding speed of 200mm / min, and a sliding distance of 100mm. Under the same test conditions, the friction coefficient is lower than that of the conventional process examples 1 to 3, which is about 0.02 lower on average. The friction coefficient of the comparative examples 4 and 5, which are close to the pre-lubrication treatment, is only about 0.005 higher on average. It can be seen that the forming performance of the alloyed galvanized sheet prepared by the present invention is significantly improved compared to the conventional process.

[0082] Figure 2 This is a low-magnification surface morphology image of the coating of the alloyed galvanized sheet provided in Example 1 of the present application; Figure 3 This is a high-magnification surface morphology image of the coating of the alloyed galvanized sheet provided in Example 1 of the present application.

[0083] Depend on Figure 2 and Figure 3 It can be seen that the surface of the coating of the sample in Example 1 is mainly composed of granular δ phase, and the skin-smoothing and flattening area accounts for more than 80%, which is beneficial to the improvement of the overall forming performance of the coating.

[0084] In addition, one or more technical solutions in the embodiments of the present application have at least the following technical effects or advantages:

[0085] In the embodiment of the present application, without applying an additional coating, by coordinating the two finishing process parameters with the alloying heat treatment and the control of the oiling amount, the surface phase composition and physical morphology of the alloyed coating plate are adjusted, the surface friction coefficient of the coating is reduced, and the coating forming performance is significantly improved.

[0086] In the embodiment of the present application, the obtained IF steel alloyed galvannealed sheet has a coating Fe content maintained at 11.0% to 12.0%, the coating surface is entirely composed of δ phase and does not contain ζ phase, and the surface smoothing and flattening rate (the proportion of the coating surface flattened by the smoothing roller to the total area) is ≥80%, the average roughness Ra is 0.6μm to 0.8μm, and the friction coefficient is 0.120 to 0.130.

[0087] The foregoing is merely a list of specific embodiments of the present application, intended to enable those skilled in the art to understand or implement the present 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 the present application. Therefore, the present application is not limited to the embodiments shown herein, but is intended to conform to the broadest scope consistent with the principles and novel features of the present application.

Claims

1. A method for improving the forming performance of the coating of IF steel alloyed galvannealed sheet, the method comprising: Hot-dip galvanizing the chilled coil to obtain a first galvanized sheet; The first galvanized sheet is subjected to a segmented alloying heat treatment and cooling to obtain a second galvanized sheet; wherein the segmented alloying heat treatment includes an induction heating section and a soaking and heat preservation section arranged in sequence; The second galvanized sheet is subjected to a first pass through a pass through roller having a first set average roughness of the pass through roller surface and a first set pass through elongation, to obtain a third galvanized sheet; The third galvanized sheet is subjected to secondary skin pass with a second set skin pass roller surface average roughness and a second set skin pass elongation to obtain a fourth galvanized sheet; performing an oiling treatment on the fourth galvanized sheet with a set single-side oiling amount to obtain a fifth galvanized sheet; The fifth galvanized sheet is coiled to obtain an alloyed galvanized sheet.

2. The method according to claim 1, characterized in that The temperature of the induction heating section is 490° C. to 530° C., the temperature of the soaking and heat preservation section is 460° C. to 510° C., and the total time of the induction heating section and the soaking and heat preservation section is 13s to 22s.

3. The method according to claim 1, characterized in that The first set average roughness of the surface of the skin-pass roller is 2.0 μm to 3.0 μm, and the first set skin-pass elongation is 0.6% to 1.2%.

4. The method according to claim 1, wherein The second set average roughness of the surface of the skin-pass roller is 0.3 μm to 1.0 μm, and the second set skin-pass elongation is 0.2% to 0.6%.

5. The method according to claim 1, wherein The set single-side oil coating amount is 1600 mg / m 2 ~2000 mg / m 2 .

6. The method according to claim 1, characterized in that The chilled coil is made of Nb-Ti-IF steel, and the thickness of the chilled coil is 0.6 mm to 0.8 mm.

7. The method according to claim 1, characterized in that The temperature of the hot-dip galvanized steel strip entering the zinc pot is 460° C. to 470° C., and the temperature of the zinc liquid in the zinc pot is 455° C. to 465° C. The zinc liquid is composed of the following chemical components by mass fraction: aluminum: 0.125% to 0.130%, and the balance is zinc and unavoidable impurities.

8. The method according to claim 7, characterized in that The hot-dip galvanized coating weight is 40 g / m 2 ~60g / m 2 .

9. The method according to claim 1, characterized in that The Fe content of the coating of the alloyed galvanized sheet is 11.0-12.0%, and the surface of the coating is composed of delta phase.

10. The method according to claim 9, characterized in that The surface smoothing and flattening rate of the coating of the alloyed galvanized sheet is ≥80%, the average roughness Ra is 0.6 μm to 0.8 μm, and the friction coefficient is 0.120 to 0.130.

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