Galvanized steel sheet

Abstract

The present disclosure relates to a galvanized steel sheet comprising at least a substrate layer (1), an oxide layer (2) adjacent to the substrate layer (1), and a zinc plating (4) adjacent to the oxide layer (2), wherein the oxide layer (2) contains grain boundary silicon oxide and / or intracrystalline silicon oxide, the oxide layer (2) has a thickness of 3 μm to 10 μm, and the mass fraction of the grain boundary silicon oxide in the oxide layer (2) is 4% or more.

Description

[Technical Field]

[0001] The present disclosure relates to the technical field of plated steel sheets, and in particular to zinc-plated steel sheets. [Background technology]

[0002] To achieve the required mechanical and surface properties, steel sheets require the addition of several chemical elements or surface treatments, but some of these chemical elements can adversely affect the weldability of the steel sheet. For example, forming a zinc coating on the surface of a steel sheet can prevent oxidation and decarburization of the surface during heating, eliminate the need for a subsequent shot blasting process, and further provide protection as a sacrificial anode, improving the corrosion prevention performance after painting the zinc-coated steel sheet.

[0003] However, during the welding process of galvanized steel sheets, especially during resistance spot welding, the galvanized coating, which has a relatively low melting point, melts at a relatively high welding temperature. Mechanical tensile stresses, which occur when pressure is applied to the steel sheet by the electrodes sandwiched between the steel sheets, or thermal stresses, which occur when the steel sheet expands and contracts, play a role, causing the molten liquid zinc to seep into the grain boundaries of the galvanized steel sheet base material. This embrittles the grain boundaries and causes cracks. Liquid zinc can cause liquid metal embrittlement (LME) cracking, severely limiting the application of galvanized steel sheets.

[0004] It should be noted that the information disclosed in the background art section above is intended merely to aid in understanding the background of the present disclosure and may include information that does not constitute prior art information known to those skilled in the art. Summary of the Invention [Problem to be solved by the invention]

[0005] One or more embodiments of the present disclosure can solve the technical problem that galvanized steel sheets are prone to liquid metal embrittlement cracking defects when they are welded. [Means for solving the problem]

[0006] A galvanized steel sheet provided by an embodiment of the present disclosure includes at least a substrate layer, an oxide layer adjacent to the substrate layer, and a galvanized layer adjacent to the oxide layer, wherein the oxide layer includes grain boundary silicon oxide and / or intracrystalline silicon oxide, the thickness of the oxide layer is 3 μm to 10 μm, and the mass fraction of the grain boundary silicon oxide in the oxide layer is 4% or more. [Brief explanation of the drawings]

[0007] In order to more clearly explain the technical solutions according to the embodiments of the present disclosure, the following briefly introduces the drawings necessary for explaining the embodiments. Obviously, the drawings described below are only some embodiments of the present disclosure, and those skilled in the art can obtain other drawings based on these drawings without inventive steps.

[0008] [Figure 1] FIG. 10 is a schematic diagram showing a cross-sectional configuration of a galvanized steel sheet according to Example 3 of the present disclosure. [Figure 2] 10 is a photograph showing a microscopic structure of a cross section near the zinc plating in a zinc-plated steel sheet according to Example 3 of the present disclosure. [Figure 3] 10 is a photograph showing a microscopic structure of a part of an oxide layer in a galvanized steel sheet according to Example 3 of the present disclosure. [Figure 4] 10 is a photograph showing the distribution of iron in the suppression layer of a galvanized steel sheet according to Example 3 of the present disclosure. [Figure 5] 10 is a photograph showing the distribution of aluminum in the suppression layer of a zinc-plated steel sheet according to Example 3 of the present disclosure. [Figure 6] 1 is a photograph showing a microstructure of a galvanized steel sheet according to Example 3 of the present disclosure. [Figure 7]1 is a photograph showing a microscopic structure of a cross section near the zinc plating in a zinc-plated steel sheet according to Comparative Example 1 of the present disclosure. [Figure 8] 1 is a photograph showing a microscopic structure of a cross section near the zinc plating in a zinc-plated steel sheet according to Comparative Example 2 of the present disclosure. [Figure 9] 1 is a photograph showing a microscopic structure of a part of an oxide layer in a galvanized steel sheet according to Comparative Example 2 of the present disclosure. [Figure 10] 10 is a photograph locally showing a shoulder portion of a cross section of a spot-welded joint in a galvanized steel sheet according to Example 3 of the present disclosure. [Figure 11] 1 is a photograph showing a localized shoulder portion of a cross section of a spot-welded joint in a zinc-plated steel sheet according to Comparative Example 1 of the present disclosure. [Figure 12] 10 is a photograph locally showing a shoulder portion of a cross section of a spot-welded joint in a galvanized steel sheet according to Comparative Example 2 of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0009] In order to clarify the purpose, technical solution and advantages of the embodiments of the present application, the technical solutions of the embodiments of the present application will be described below clearly and completely with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, not all of the embodiments. Based on the embodiments of the present application, any other embodiments that can be obtained by those skilled in the art without inventive steps will also fall within the scope of protection of the present application.

[0010] The application range of steel sheets is extremely wide. For example, in the automobile manufacturing industry, reducing the weight of automobiles is an effective way to reduce the fuel consumption rate of automobiles and achieve the goal of reducing automobile carbon emissions.

[0011] In order to meet the automobile safety regulations and achieve the goal of reducing the weight of automobiles, the application and development of steel sheets for automobile bodies has attracted much attention in the industry. For example, to ensure the normal use of automobiles in corrosive environments, zinc plating is applied to the surface of steel sheets to improve the corrosion resistance of the steel sheets.

[0012] When manufacturing an automobile body using steel sheets, assembly can be performed using a welding process. Resistance spot welding is a commonly used welding process in the assembly of automobile bodies. However, the relatively high temperatures generated during resistance spot welding cause the zinc in the galvanized coating, which has a relatively low melting point, to melt at high temperatures. Mechanical tensile stresses generated when electrodes sandwiching the steel sheet apply pressure to the steel sheet, or thermal stresses generated by the steel sheet's expansion and contraction, can cause the molten liquid zinc to seep into the grain boundaries of the galvanized steel sheet. This can embrittle the grain boundaries and cause cracks. Liquid zinc can also cause liquid metal embrittlement (LME) cracking, severely limiting the application of galvanized steel.

[0013] To address the problem that galvanized steel sheets according to related art are prone to liquid metal embrittlement cracking defects caused by liquid zinc, the present disclosure provides a galvanized steel sheet according to an embodiment. As shown in Figure 1, this galvanized steel sheet according to an embodiment 3 of the present disclosure includes at least a substrate layer, an oxide layer adjacent to the substrate layer, and a zinc coating adjacent to the oxide layer, and the oxide layer includes grain boundary silicon oxide and / or intracrystalline silicon oxide.

[0014] It should be noted that in this disclosure, silicon and the chemical symbol Si are interchangeable and have the same meaning.

[0015] In some embodiments of the present disclosure, an oxide layer is provided on a galvanized steel sheet, and the oxide layer contains grain boundary silicon oxide and / or intracrystalline silicon oxide. That is, silicon oxide is concentrated in the oxide layer. The silicon oxide can prevent liquid zinc from penetrating into the substrate layer to some extent, thereby solving the technical problem of liquid metal embrittlement cracking defects to some extent.

[0016] During the welding process, the grain boundary silicon oxide and / or intracrystalline silicon oxide in the oxide layer can prevent liquid zinc from penetrating into the substrate layer, and to some extent can prevent defects such as liquid metal embrittlement cracking caused by liquid zinc.

[0017] In some examples, as shown in Figures 2 and 3, Figure 2 is a photograph showing the microstructure of a cross section near the zinc coating in a galvanized steel sheet according to Example 3 of the present disclosure, and Figure 3 is a photograph showing the microstructure of a portion of the oxide layer in a galvanized steel sheet according to Example 3 of the present disclosure. As can be seen from Figures 2 and 3, the oxide layer is adjacent to the substrate layer and is located on the surface of the substrate layer.

[0018] In some embodiments, the oxide layer may include only intercrystalline silicon oxide. In some other embodiments, the oxide layer may include only intracrystalline silicon oxide. In some other embodiments, the oxide layer may include both intercrystalline silicon oxide and intracrystalline silicon oxide.

[0019] In some embodiments, the silicon oxide may be any one or more selected from SiO, SiO2, and Si2O6.

[0020] In a preferred embodiment, the thickness of the oxide layer is 3 μm to 10 μm.

[0021] In some embodiments, by controlling the thickness of the oxide layer to 3 μm to 10 μm, it is possible to effectively prevent liquid zinc from penetrating into the substrate layer, thereby effectively suppressing the occurrence of LME cracking without significantly affecting the material properties of the substrate layer.

[0022] In some embodiments, if the oxide layer is too thick, it can affect the material properties of the substrate layer to some extent, while if the oxide layer is too thin, it can affect the oxide layer's ability to suppress LME cracking to some extent. Preferably, the oxide layer thickness can be any thickness value in the range of 3 μm to 10 μm, such as 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, or 10 μm.

[0023] In a preferred embodiment, the mass fraction of grain boundary silicon oxide in the oxide layer is 4% or more.

[0024] In some embodiments, the oxide layer may have a grain boundary silicon oxide mass fraction of 4% or more, so that the silicon oxide present along the grain boundaries blocks the penetration paths of liquid zinc and inhibits penetration of liquid zinc into the substrate layer. If the oxide layer has too low a content of silicon oxide at the grain boundaries, it may become difficult to effectively block the penetration paths of liquid zinc, resulting in a decrease in the effectiveness of blocking liquid zinc penetration.

[0025] In some embodiments, the mass fraction of grain boundary silicon oxide in the oxide layer may be 4%, 4.5%, 5%, 5.5%, 6%, and the like.

[0026] In a preferred embodiment, the mass fraction of grain boundary silicon oxide in the oxide layer is 5.0% to 6.4%.

[0027] In a preferred embodiment, the mass fraction of intracrystalline silicon oxide in the oxide layer is 1% or more, and the ratio of the mass fraction of intracrystalline silicon oxide in the oxide layer to the mass fraction of grain boundary silicon oxide in the oxide layer is less than 1:2.

[0028] In some embodiments, the mass fraction of intracrystalline silicon oxide in the oxide layer is controlled so that the mass fraction of intracrystalline silicon oxide in the oxide layer is 1% or more, and the ratio of the mass fraction of intracrystalline silicon oxide in the oxide layer to the mass fraction of grain boundary silicon oxide in the oxide layer is less than 1:2. This allows the silicon oxide in the crystal to reduce the wettability of liquid zinc and inhibit the penetration of liquid zinc into the substrate layer. If the mass fraction of intracrystalline silicon oxide in the oxide layer is too low, the effect of the intracrystalline silicon oxide in reducing the wettability of liquid zinc is reduced, and the effect of inhibiting the penetration of liquid zinc into the substrate layer is not apparent. If the ratio of the mass fraction of intracrystalline silicon oxide in the oxide layer to the mass fraction of grain boundary silicon oxide in the oxide layer is too large, the role of the intracrystalline silicon oxide in reducing the wettability of liquid zinc will have a certain impact on the production and quality of the zinc coating, resulting in the risk of plating defects on the zinc coating surface.

[0029] In some embodiments, the mass fraction of intracrystalline silicon oxide in the oxide layer may be 1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 2%, etc., and the ratio between the mass fraction of intracrystalline silicon oxide in the oxide layer and the mass fraction of grain boundary silicon oxide in the oxide layer may be 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:5, etc.

[0030] In a preferred embodiment, the mass fraction of intracrystalline silicon oxide in the oxide layer is 1.0 to 2.0%.

[0031] In some embodiments, the grain boundary silicon oxide and intracrystalline silicon oxide contents in the oxide layer may be measured using an energy dispersive spectrometer (EDS) in conjunction with a scanning electron microscope (SEM). For example, the oxide layer shown in FIG. 3 after measurement has a grain boundary silicon oxide mass fraction of 5.0% to 6.4% and an intracrystalline silicon oxide mass fraction of 1.0% to 2.0%.

[0032] It should be noted that in the embodiments of the present disclosure, the mass fraction of grain boundary silicon oxides refers to the percentage of the total mass of grain boundary silicon oxides in the oxide layer relative to the total mass of the oxide layer, and the mass fraction of intracrystalline silicon oxides refers to the percentage of the total mass of intracrystalline silicon oxides in the oxide layer relative to the total mass of the oxide layer.

[0033] In a preferred embodiment, the galvanized steel sheet may further include an inhibition layer adjacent to the oxide layer and the galvanized layer, the inhibition layer having a thickness of 2 μm or less.

[0034] In some embodiments, the galvanized steel sheet further includes an inhibitor layer, which is located between the oxide layer and the galvanized layer and has a thickness of 2 μm or less. The inhibitor layer can suppress the occurrence of defects such as liquid metal embrittlement cracking without increasing the difficulty and cost of manufacturing. Furthermore, the thickness of the inhibitor layer does not need to be too large. If the inhibitor layer is too thick, it not only increases the difficulty and cost of manufacturing the galvanized steel sheet to some extent, but also fails to significantly improve the effectiveness of suppressing defects such as liquid metal embrittlement cracking.

[0035] In some embodiments, the thickness of the containment layer may be less than or equal to 2 μm, such as 2 μm, 1.8 μm, 1.6 μm, and 1.4 μm.

[0036] In a preferred embodiment, the suppression layer contains at least iron and zinc, and may further contain aluminum.

[0037] In some embodiments, the iron and aluminum in the inhibition layer can form iron-aluminum (Fe-Al) compounds, which can generally inhibit the alloying reaction between the zinc coating and the substrate layer, thereby inhibiting the occurrence of liquid metal embrittlement cracking defects.

[0038] In some embodiments, the distribution of elements in the inhibit layer can be measured using an electron probe micro-analyzer (EPMA). As shown in Figures 4 and 5, Figure 4 is an EPMA photograph showing the distribution of iron in the inhibit layer of a galvanized steel sheet according to Example 3 of the present disclosure, and Figure 5 is an EPMA photograph showing the distribution of aluminum in the inhibit layer of a galvanized steel sheet according to Example 3 of the present disclosure.

[0039] In a preferred embodiment, the zinc plating includes pure zinc plating and / or zinc alloy plating, the zinc alloy plating includes zinc, and the zinc alloy plating further includes at least one of iron, aluminum, magnesium, and nickel, and the contents of iron, aluminum, magnesium, nickel, and zinc contained in the zinc alloy plating are, when calculated in mass fraction, The iron content is 0.0 to 15.0%; The aluminum content is 0.0 to 60.0%. The magnesium content is 0.0 to 4.0%, The nickel content is 0.0 to 20.0%, and The remainder is the zinc content.

[0040] In some embodiments, the role of galvanization is primarily to protect the steel sheet and prevent corrosion, thereby ensuring that the equipment incorporating the galvanized steel sheet can be used normally in a corrosive environment, such as in an automobile, where the galvanization can ensure that the automobile can be used normally in a corrosive environment with a certain humidity, thereby extending the service life of the automobile.

[0041] In some embodiments, the galvanized steel sheet may be continuously annealed and galvanized with pure zinc to form a pure zinc coating.

[0042] In some implementations, the galvanized steel sheet may be continuously annealed and galvanized with a zinc-containing alloy to form a zinc alloy coating, which may include not only zinc but also at least one of iron, aluminum, magnesium, and nickel.

[0043] In some implementations, the zinc plating may further include both pure zinc plating and zinc alloy plating at the same time.

[0044] In some embodiments, the zinc plating may have a thickness of 5 μm to 15 μm, such as 5 μm, 6 μm, 7 μm, 9 μm, 11 μm, 12 μm, 13 μm, 14 μm, and 15 μm.

[0045] In some embodiments, when pure zinc plating is used as the zinc plating, an inhibitor layer may be provided between the pure zinc plating and the oxide layer. The inhibitor layer can inhibit the alloying reaction between the pure zinc plating and the ferroalloy (both the oxide layer and / or the substrate layer may be considered as the ferroalloy) at high temperatures, thereby suppressing the occurrence of liquid metal embrittlement cracking defects.

[0046] In a preferred embodiment, the contents of iron, aluminum, magnesium, nickel, and zinc contained in the zinc alloy plating are, when calculated in mass fraction, as follows: The iron content is 5.0% to 15.0%. The aluminum content is 1.0% to 60.0%. The magnesium content is 0.5% to 4.0%. The nickel content is 8.0% to 20.0%; and The remainder is zinc and unavoidable impurities.

[0047] In a preferred embodiment, the substrate layer includes iron, carbon, manganese, and silicon, and the substrate layer further includes at least one of aluminum, chromium, molybdenum, niobium, titanium, and boron, and the contents of iron, carbon, manganese, silicon, aluminum, chromium, molybdenum, niobium, titanium, and boron contained in the substrate layer are, calculated as mass fractions, The carbon content is 0.05% to 1.00%. The manganese content is 1.20% to 3.00%. The silicon content is 0.10% to 3.00%. The aluminum content is 0.00 to 1.00%. The chromium content is 0.00 to 0.60%. The molybdenum content is 0.00 to 0.60%, The niobium content is 0.00 to 0.10%, The titanium content is 0.00 to 0.10%; The boron content is 0.0000 to 0.0025%, and The rest is iron and unavoidable impurities.

[0048] In some embodiments, the substrate layer comprises components with mass fractions as follows: The carbon content is 0.15% to 0.25%. The manganese content is 1.70% to 2.80%. The silicon content is 1.0% to 2.00%, and The rest is iron and unavoidable impurities.

[0049] In a preferred embodiment, the substrate layer contains iron, carbon, manganese, silicon, aluminum, chromium, molybdenum, niobium, titanium, and boron in an amount calculated as a mass fraction of: The carbon content is 0.05% to 1.00%. The manganese content is 1.20% to 3.00%. The silicon content is 0.10% to 3.00%. The aluminum content is 0.02% to 1.00%. The chromium content is 0.10% to 0.60%. The molybdenum content is 0.05% to 0.60%. The niobium content is 0.01% to 0.10%; The titanium content is 0.01% to 0.10%. The boron content is 0.0001% to 0.0025%, and The rest is iron and unavoidable impurities.

[0050] In a preferred embodiment, the microstructure of the substrate layer comprises retained austenite.

[0051] In some embodiments, the substrate layer contains retained austenite, and the plasticity of the substrate layer can be increased to meet the elongation requirement by utilizing the principle that the retained austenite transforms into martensite during deformation.

[0052] In a preferred embodiment, the microstructure of the substrate layer comprises ferrite, and the microstructure of the substrate layer further comprises at least one of pearlite, bainite, and martensite.

[0053] In some embodiments, the ferrous element of the substrate layer can increase the plasticity of the substrate layer to meet elongation requirements.

[0054] In some embodiments, pearlite, bainite, and martensite in the substrate layer can increase the strength of the substrate layer to meet strength requirements.

[0055] In some implementations of the present disclosure, the tensile strength of the galvanized steel sheet is 500 MPa or greater.

[0056] Preferably, the tensile strength of the galvanized steel sheet is 800 MPa or more, the yield strength of the galvanized steel sheet is 600 MPa or more, and the elongation is 15% or more, so that the strength and elongation of the galvanized steel sheet can meet the requirements of the structural parts of the automobile to which the galvanized steel sheet is applied.

[0057] For example, referring to FIG. 6, FIG. 6 is a photograph showing the microstructure of a galvanized steel sheet according to Example 3 of the present disclosure. After inspection, the galvanized steel sheet according to Example 3 has a yield strength of ≧650 MPa, a tensile strength of ≧1000 MPa, and an elongation of ≧16%.

[0058] It should be noted that high temperatures in reference to the embodiments of the present disclosure refer to temperatures that melt zinc and the range of temperatures above that melt zinc.

[0059] Based on the same inventive idea, the present disclosure further provides a method for manufacturing the above-mentioned galvanized steel sheet, which includes the steps of sequentially performing continuous annealing and galvanizing on a full hard cold-rolled steel sheet to obtain a galvanized steel sheet, wherein the continuous annealing includes an initial oxidation stage, a heating stage, and a soaking stage.

[0060] In some embodiments, the continuous annealing treatment can form an oxide layer on the surface of the substrate layer and simultaneously improve the surface condition of the oxide layer, so that when a subsequent zinc plating treatment is performed, a zinc plating with good adhesion can be obtained.

[0061] In a preferred embodiment, before the process of continuous annealing the full hard cold-rolled steel plate, the process may further include a smelting step, a continuous casting step, a hot rolling step, a pickling step, and a cold rolling step to obtain the cold-rolled steel plate.

[0062] In a preferred embodiment, the continuous annealing process may further include a cooling step after the soaking step.

[0063] In a preferred embodiment, the dew point temperature in the initial oxidation stage is 0°C to 20°C.

[0064] In some embodiments, controlling the dew point temperature of the initial oxidation stage to be in the range of 0°C to 20°C can form an iron oxide layer on the surface of the substrate layer, and silicon can be oxidized to collect at grain boundaries and inside crystals near the surface of the substrate layer, forming an oxide layer near the surface of the substrate layer, which may be considered as a part of the substrate layer adjacent to the surface.

[0065] In some implementations, if the dew point temperature in the initial oxidation stage is too high, the thickness of the silicon layer collected near the surface of the substrate layer will increase to a certain extent, i.e., the thickness of the oxide layer formed through the heating and soaking stages will increase, thereby affecting the mechanical properties of the galvanized steel sheet.If the dew point temperature in the initial oxidation stage is too low, the formation of the iron oxide layer on the surface of the substrate layer in the initial oxidation stage will be affected to a certain extent, and will not be useful for forming an inhibitor layer in the later stage.

[0066] In some embodiments, the dew point temperature of the initial oxidation stage may be 0°C, 4°C, 8°C, 12°C, 16°C, 20°C, etc. Preferably, the dew point temperature of the initial oxidation stage may be 5°C to 10°C.

[0067] In a preferred embodiment, the dew point temperature in the heating step is -32°C to -25°C, and the dew point temperature in the soaking step is -32°C to -25°C.

[0068] In some embodiments, controlling the dew point temperatures during the heating and soaking steps so that both are within the range of −32°C to −25°C can reduce iron oxides formed on the surface of the substrate layer and form a relatively thick iron-reduced layer on the surface of the substrate layer. The iron-reduced layer can be considered a portion located on the surface of the substrate layer. This iron-reduced layer can improve the platability of the surface of the substrate layer and enhance the adhesion of zinc plating. At the same time, silicon is an oxygen-philic element during the heating and soaking steps, and silicon concentrated near the surface of the substrate layer, both at the grain boundaries and within the crystals, is continuously oxidized, forming an oxide layer that meets the silicon oxide content requirements. Furthermore, the iron-reduced layer located on the surface of the substrate layer forms an inhibitor layer of iron-aluminum compounds with aluminum, etc., in the zinc plating process, thereby ensuring the quality of the zinc plating and enhancing its adhesion.

[0069] In some embodiments, if the dew point temperature of the heating or soaking step is too high, the iron oxide layer formed in the initial oxidation step may not be reduced to a certain extent, which may affect the quality of the zinc coating.If the dew point temperature of the heating or soaking step is too low, the progress of silicon oxidation during the heating or soaking step may be affected to a certain extent, which may make it difficult to form an oxide layer that blocks the penetration of liquid zinc.

[0070] In some embodiments, the dew point temperature for the heating stage may be -32°C, -31°C, -29°C, -27°C, -25°C, etc., and the dew point temperature for the soaking stage may be -32°C, -31°C, -29°C, -27°C, -25°C, etc.

[0071] The manufacturing method of a galvanized steel sheet according to the embodiments of the present disclosure is for manufacturing the above-mentioned galvanized steel sheet, and the configuration of the galvanized steel sheet may refer to the above-mentioned embodiments. The manufacturing method of the galvanized steel sheet employs some or all of the technical solutions in the above-mentioned embodiments, and therefore has at least all the beneficial effects of the technical solutions in the above-mentioned embodiments, and the description thereof will not be repeated here.

[0072] The present application will be further described with reference to specific examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present application. In the following examples, for test methods that do not specify specific conditions, measurements should generally be made in accordance with national standards. If there is no corresponding national standard, measurements should be made in accordance with general international standards, common conditions, or conditions recommended by manufacturers or manufacturers.

[0073] An embodiment of the present disclosure provides a galvanized steel sheet. The galvanized steel sheet includes a substrate layer, an oxide layer, an inhibition layer, and a galvanized coating, which are successively adjacent to each other, and the oxide layer includes grain boundary silicon oxide and / or intracrystalline silicon oxide. The chemical composition of the substrate layer is shown in Table 1, and the surface characteristic parameters of the galvanized steel sheet are shown in Table 2.

[0074] JPEG2025538068000002.jpg34170

[0075] JPEG2025538068000003.jpg37170

[0076] In some examples, the distribution of grain boundary silicon oxides and intracrystalline silicon oxides in a galvanized steel sheet can be measured using an EDS energy dispersive X-ray analyzer in combination with a scanning electron microscope (SEM). Fig. 3 is a photograph showing the microscopic structure of a portion of the oxide layer in a galvanized steel sheet according to Example 3 of the present disclosure, and Fig. 9 is a photograph showing the microscopic structure of a portion of the oxide layer in a galvanized steel sheet according to Comparative Example 2 of the present disclosure. The distributions of grain boundary silicon oxides and intracrystalline silicon oxides in Example 3 and Comparative Example 2 measured using the combined EDS energy dispersive X-ray analyzer are shown in Table 3.

[0077] JPEG2025538068000004.jpg54170

[0078] A method for manufacturing a galvanized steel sheet provided by an embodiment of the present disclosure includes the following steps. In step S11, the cold-rolled steel sheet is subjected to continuous annealing and galvanization to obtain a galvanized steel sheet. The continuous annealing includes an initial oxidation stage, a heating stage, and a soaking stage. The dew point temperatures in the initial oxidation stage, the heating stage, and the soaking stage are shown in Table 4, and the mechanical properties of the resulting galvanized steel sheet are shown in Table 5.

[0079] JPEG2025538068000005.jpg39170

[0080] JPEG2025538068000006.jpg35170

[0081] To demonstrate the effectiveness of the embodiments of the present disclosure in reducing LME cracking caused by resistance spot welding, the conditions under which LME cracking occurred in the resistance spot welded joints of Examples 1 to 3 and Comparative Examples 1 and 2 were analyzed, and the galvanized steel sheets of Examples 1 to 3 and Comparative Examples 1 and 2 were welded by resistance spot welding according to the welding process parameters for measuring LME cracking in galvanized steel sheets shown in Table 6. The welding tests were conducted in accordance with the SEP1220-2 resistance spot welding standard, and the upper limit current close to the expulsion current of each material was selected for welding. The results of measuring LME cracking in welded galvanized steel sheets are shown in Table 7.

[0082] JPEG2025538068000007.jpg44170

[0083] JPEG2025538068000008.jpg35170

[0084] FIG. 7 is a photograph showing the microstructure of a cross section near the zinc plating in a zinc-plated steel sheet according to Comparative Example 1 of the present disclosure.

[0085] Fig. 8 is a photograph showing the microstructure of a cross section near the zinc plating in a zinc-plated steel sheet according to Comparative Example 2 of the present disclosure. Fig. 9 is a photograph showing the microstructure of a part of the oxide layer in a zinc-plated steel sheet according to Comparative Example 2 of the present disclosure. As shown in Figs. 7 to 9, the oxide layers in Comparative Examples 1 and 2 are different from the oxide layer in Example 3.

[0086] Fig. 10 is a photograph locally showing the shoulder of a cross section of a spot-welded joint according to Example 3 of the present disclosure, Fig. 11 is a photograph locally showing the shoulder of a cross section of a spot-welded joint according to Comparative Example 1 of the present disclosure, and Fig. 12 is a photograph locally showing the shoulder of a cross section of a spot-welded joint according to Comparative Example 2 of the present disclosure. As shown in Figs. 10 to 12, the shoulder of the cross section of the spot-welded joint according to Example 3 of the present disclosure does not show any obvious LME cracks, but the shoulders of the cross sections of the spot-welded joints according to Comparative Examples 1 and 2 both show obvious LME cracks. As can be seen, when a manufacturing method different from that of the examples of the present disclosure is used, a galvanized steel sheet manufactured using a different manufacturing method and having a different oxide layer configuration from that of the examples of the present disclosure has mechanical performance similar to that of the examples of the present disclosure, but clearly exhibits LME crack defects, posing a safety risk.

[0087] In contrast to the comparative examples, the galvanized steel sheets according to the examples of the present disclosure have an oxide layer on the galvanized steel sheet, and the oxide layer contains grain boundary silicon oxide and / or intracrystalline silicon oxide. In addition, the silicon oxide is concentrated in the oxide layer, and the silicon oxide can prevent liquid zinc from penetrating into the substrate layer to some extent, and thus can solve the technical problem of liquid metal embrittlement cracking defects to some extent.

[0088] During the welding process, the grain boundary silicon oxide and / or intracrystalline silicon oxide in the oxide layer can prevent the liquid zinc from penetrating into the substrate layer, and to some extent can avoid the appearance of defects caused by liquid metal embrittlement cracking caused by liquid zinc.

[0089] At the same time, the galvanized steel sheet may further be provided with an inhibitor layer, which can enhance the effect of inhibiting liquid metal embrittlement cracking defects to a certain extent.

[0090] Various embodiments in this application may be presented in a range format. It should be understood that the description in a range format is provided for convenience and brevity, and should not be construed as mechanically limiting the scope of the present application. Thus, the description of a range should be construed as specifically disclosing subranges and every possible single numerical value within that range. For example, a description of a range of 1 to 6 should be construed as specifically disclosing subranges, e.g., 1 to 3, 1 to 4, 1 to 5, 2 to 4, 2 to 6, 3 to 6, etc., and as disclosing single numbers within that range, e.g., 1, 2, 3, 4, 5, and 6, and any applicable range. Furthermore, whenever a range of numerical values ​​is described herein, it is intended to include any numbers (fractional or integer) that are referenced within the range.

[0091] In this specification, the relational relationship "and / or" indicating related objects can indicate the existence of three relationships. For example, A and / or B can indicate that A exists singly, A and B exist simultaneously, and B exists singly. A and B may be singular or plural. In this specification, "at least one" means one or plural, and "plurality" means two or more. "At least one," "hereinafter, at least one," or similar expressions refer to any combination of these items, and any combination of these items includes any combination of a single item or multiple items. For example, "at least one of a, b, or c" or "at least one of a, b, and c" can each be a, b, c, a-b (i.e., a and b), a-c, b-c, or a-b-c, where a, b, and c can each be singular or plural.

[0092] Unless otherwise specified, the various raw materials, reagents, instruments, and devices used in the present application can all be obtained commercially or produced by conventional techniques.

[0093] The above description is merely a specific embodiment of the present application, intended to enable those skilled in the art to understand and implement the present application. Modifications to these embodiments will be apparent to those skilled in the art. The general principles defined herein may be implemented in other embodiments without departing from the spirit and scope of the present application. Therefore, the present application is not limited to the embodiments described herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein. [Explanation of symbols]

[0094] 1. Substrate Layer 2. Oxide layer 3 Inhibition layer 4. Zinc plating

Claims

1. The steel sheet includes at least a substrate layer, an oxide layer adjacent to the substrate layer, and a zinc plating layer adjacent to the oxide layer; the oxide layer contains grain boundary silicon oxide and / or intracrystalline silicon oxide, and the thickness of the oxide layer is 3 μm to 10 μm; The oxide layer has a mass fraction of grain boundary silicon oxide of 4% or more.

2. 2. The galvanized steel sheet according to claim 1, wherein the oxide layer has a grain boundary silicon oxide mass fraction of 5.0% to 6.4%.

3. the oxide layer has an intracrystalline silicon oxide mass fraction of 1% or more; 2. The galvanized steel sheet according to claim 1, wherein a ratio of a mass fraction of intracrystalline silicon oxide in the oxide layer to a mass fraction of grain boundary silicon oxide in the oxide layer is smaller than 1:

2.

4. 4. The galvanized steel sheet according to claim 3, wherein the oxide layer has an intracrystalline silicon oxide mass fraction of 1.0 to 2.0%.

5. further comprising an inhibition layer adjacent to the oxide layer and the zinc plating; 2. The galvanized steel sheet according to claim 1, wherein the thickness of the suppression layer is 2 μm or less.

6. The galvanized steel sheet according to claim 5 , wherein the inhibiting layer contains at least iron and zinc.

7. The galvanized steel sheet according to claim 5 , wherein the inhibiting layer further contains aluminum.

8. The zinc plating includes pure zinc plating and / or zinc alloy plating, The zinc alloy plating contains zinc, The zinc alloy plating further contains at least one of iron, aluminum, magnesium, and nickel, The contents of iron, aluminum, magnesium, nickel, and zinc contained in the zinc alloy plating are, when calculated in mass fraction, as follows: The iron content is 0.0 to 15.0%, The aluminum content is 0.0 to 60.0%, The magnesium content is 0.0 to 4.0%, The nickel content is 0.0 to 20.0%, and The galvanized steel sheet according to any one of claims 1 to 7, characterized in that the remainder is zinc.

9. the substrate layer comprises iron, carbon, manganese, and silicon; the substrate layer further comprises at least one of aluminum, chromium, molybdenum, niobium, titanium, and boron; The contents of iron, carbon, manganese, silicon, aluminum, chromium, molybdenum, niobium, titanium, and boron contained in the substrate layer are, calculated as mass fractions, as follows: The carbon content is 0.05% to 1.00%; The manganese content is 1.20% to 3.00%; The silicon content is 0.10% to 3.00%; The aluminum content is 0.00 to 1.00%, The chromium content is 0.00 to 0.60%, The molybdenum content is 0.00 to 0.60%, The niobium content is 0.00 to 0.10%, The titanium content is 0.00 to 0.10%, The boron content is 0.0000 to 0.0025%, and 9. The galvanized steel sheet according to claim 8, wherein the remainder is iron and unavoidable impurities.

10. 10. The galvanized steel sheet of claim 9, wherein the microstructure of the substrate layer comprises retained austenite.

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