Zinc-plated steel sheet with excellent corrosion resistance, hot-pressed parts, and method for manufacturing the same.

Abstract

The present invention discloses a zinc-plated steel sheet having a zinc-plated layer in which the mass percentage content of Zn is ≥ 50%, the mass percentage content of Al + Mg is < 50%, and the thickness of the zinc-plated layer is 3 to 15 micrometers. Accordingly, the present invention further discloses a hot-pressed part manufactured using the zinc-plated steel sheet, wherein the plating layer of the hot-pressed part comprises a surface layer and a ZnFe alloy layer, wherein the mass percentage content of zinc oxide in the surface layer is 5 to 50%, and the manganese oxide content is less than 5%, wherein the ZnFe alloy layer comprises a first ZnFe alloy phase with a mass percentage content of Fe of 25% or less, and a second ZnFe alloy phase with a mass percentage content of Fe of 50 to 70%, and the mass percentage content of Fe in the plating layer of the hot-pressed part gradually increases from the surface toward the steel substrate. The present invention further discloses a method for manufacturing the zinc-plated steel sheet and the hot-pressed part. The hot-pressed parts manufactured by the above method exhibited excellent corrosion resistance.

Description

Technical Field

[0001] The present invention relates to a steel sheet, a hot press part, and a method for manufacturing the same, and particularly to a plated steel sheet, a hot press part, and a method for manufacturing the same.

Background Art

[0002] Hot press parts have wide applicability due to their excellent mechanical properties and good formability.

[0003] In the production of hot press parts, it is necessary to heat the steel sheet to a temperature above the austenitizing temperature. However, conventional steel sheets cannot meet the usage requirements due to problems such as surface oxidation, decarburization, shot blasting treatment, and poor dimensional accuracy.

[0004] Therefore, one of the current solutions is to adopt an aluminum-silicon plated steel sheet. Although aluminum-silicon plating has excellent high-temperature resistance and oxidation resistance and is applicable to hot press steel, the joint part between the aluminum-silicon plated hot press part and the adjacent material is often difficult to be completely covered during the electrocoating process of the entire vehicle. In the durability test of the entire vehicle, it is confirmed that the edges and cutouts of the aluminum-silicon plated hot press parts tend to corrode first.

[0005] Another solution is to manufacture hot press parts using a zinc-plated steel sheet. This is because metallic zinc exhibits an excellent corrosion protection effect on cutouts due to its chemical properties. However, due to the low melting point of zinc, zinc volatilization, melting, and ultimately LME cracking to the substrate are likely to occur during the hot press forming process, greatly limiting the use of zinc-based hot press steel.

[0006] To address this issue, a Chinese patent document with publication number CN107922988A, published on April 17, 2018, and titled "Method for Non-Contact Cooling of Steel Sheets and Equipment Used in the Method" discloses a hot pressing method and apparatus having a pre-cooling process, wherein the steel sheet undergoes forming transformation hardening at 450-700°C in a transformation delay manner by actively cooling it after heating and before forming.

[0007] Furthermore, a Chinese patent document with publication number CN109070396A, publication date December 21, 2018, and title "Method and Apparatus for Producing Hardened Steel Parts" discloses a method in which zinc is rapidly converted into a stable composite by passing a fluid through it during the pressing process, thereby preventing minute secondary cracks.

[0008] Therefore, since all of the above methods employ an indirect hot pressing method rather than a direct hot pressing method, they have some impact on production efficiency and require special production equipment.

[0009] Based on this, there is a strong demand for a solution that enables the efficient production of corrosion-resistant hot-pressed parts using a direct hot-pressing method. [Overview of the project] [Problems that the invention aims to solve]

[0010] One objective of the present invention is to provide a zinc-plated steel sheet that can be efficiently used in the manufacture of zinc-plated hot-pressed parts, enabling the production of hot-pressed parts with excellent corrosion resistance, and also improving the production efficiency of hot-pressed parts. [Means for solving the problem]

[0011] To achieve the above objective, the present invention provides a zinc-plated steel sheet comprising a steel substrate and a zinc-based plating layer plated on the surface of the steel substrate, wherein the mass percentage content of Zn in the zinc-based plating layer is ≥50%, the mass percentage content of Al+Mg is <50%, and the thickness of the zinc-based plating layer is 3 to 15 micrometers.

[0012] In the present invention, the composition of the zinc-based plating layer may include, in addition to Zn, one or more of Al, Mg, Si, etc. Therefore, the composition of the zinc-based plating layer according to the present invention may be a Zn-containing binary or multi-component alloy, and may include, but is not limited to, Zn-Al, Zn-Al-Mg, or Zn-Al-Mg-Si.

[0013] Furthermore, in the zinc-plated steel sheet according to the present invention, the zinc-plated layer further contains Si. Preferably, the mass percentage content of Si is ≤10%, and more preferably ≤5%.

[0014] In some embodiments, the mass percentage content of Zn in the zinc-based plating layer is 50 to 99.9%.

[0015] In some embodiments, the mass percentage content of Al+Mg is ≤45%. In some embodiments, the mass percentage content of Al+Mg is 0.1 to 45%. In some embodiments, the mass percentage content of Al+Mg is 1 to 45%.

[0016] Furthermore, in the zinc-plated steel sheet according to the present invention, the thickness of the zinc-plated layer is 3 to 10 micrometers or 5 to 10 micrometers.

[0017] Furthermore, in the zinc-plated steel sheet according to the present invention, the steel substrate may be any known steel material that can be used in the art for manufacturing zinc-plated hot-pressed parts. The mass percentage content of the chemical elements in an example steel substrate is C: 0.05~0.5%, Si: 0.01~2.0%, Mn: 0.3~3.0%, Al: 0.005~0.3%, Ti≦0.1%, B≦0.1%, Cr≦0.5%, Nb≦0.1%, V≦0.1%, Ni≦0.5%, Mo≦0.5%, with the remainder being Fe and unavoidable impurities.

[0018] Furthermore, in the zinc-plated steel sheet according to the present invention, the unavoidable impurities in the steel substrate are P ≤ 0.3% and S ≤ 0.1%.

[0019] It is necessary to explain that in some other embodiments, steel substrates having other component content formulations are also available.

[0020] In some embodiments, the thickness of the steel substrate is 1.0 to 2.5 millimeters.

[0021] Another objective of the present invention is to provide hot-pressed parts that have excellent corrosion resistance, good strength, and high production efficiency.

[0022] In accordance with the above-described objectives of the invention, the present invention further provides a hot-pressed part comprising a steel substrate and a plating layer plated on the surface of the steel substrate, wherein the plating layer comprises a surface layer and a ZnFe alloy layer, wherein the mass percentage content of zinc oxide in the surface layer is 5 to 50% and the manganese oxide content is less than 5%, wherein the ZnFe alloy layer comprises a first ZnFe alloy phase with a mass percentage content of Fe of 25% or less and a second ZnFe alloy phase with a mass percentage content of Fe of 50 to 70%, and the mass percentage content of Fe in the plating layer of the hot-pressed part gradually increases from the surface toward the steel substrate. Preferably, the steel substrate is one described in any embodiment of the present invention. Preferably, the plating layer is a zinc-based plating layer described in any embodiment of the present invention.

[0023] In some embodiments, in the surface layer, the mass percentage content of aluminum oxide is 1% to 50%, and the mass percentage content of magnesium oxide is 0.5% to 10%.

[0024] In some embodiments, the area of the first ZnFe alloy phase occupies 5% to 50% of the plating layer region, and the area of the second ZnFe alloy phase occupies 40% to 90% of the plating layer region.

[0025] One of the core improvements of the present invention is to set the content of zinc oxide in the surface layer of the plating layer of the hot press part to 5% to 50% and the content of manganese oxide to less than 5%, thereby imparting excellent weldability, paintability, and corrosion resistance to the part. In addition, the first ZnFe alloy phase with an Fe content of 25% or less in the alloy layer imparts excellent corrosion resistance to the part, and the second ZnFe alloy phase with an Fe content of 50% to 70% can suppress the generation and expansion of cracks in the plating layer.

[0026] Furthermore, the microstructure of the hot press part according to the present invention has at least one of martensite, bainite, and ferrite. In some embodiments, the microstructure of the hot press part has martensite or bainite, and optionally pearlite or ferrite.

[0027] In some embodiments, in the hot press part according to the present invention, the content of manganese oxide is 0% to 4.8%.

[0028] In some embodiments, in the first ZnFe alloy phase of the hot press part according to the present invention, the mass percentage of Fe is 10% to 25%, for example 15% to 25%.

[0029] Preferably, the hot press part is directly obtained by hot pressing using the zinc-based plated steel sheet described in any of the embodiments of the present text. Preferably, the hot press part is manufactured by the manufacturing method of the hot press part described in any of the embodiments of the present text.

[0030] The specific microstructure is related to the composition of the steel substrate and the cooling rate during the hot pressing process.

[0031] Another object of the present invention is to provide a method for manufacturing zinc-plated steel sheets, which includes the steps of steelmaking, hot rolling, cold rolling, annealing and hot-dip galvanizing, and leveling, wherein in the hot rolling step the coiling temperature is controlled to 500-700°C, and in the annealing and hot-dip galvanizing step the annealing temperature is controlled to 700-810°C, the plating solution temperature is controlled to 400-600°C, and the cooling rate after removing the steel sheet from the zinc pot is controlled to 5-30°C / s.

[0032] In some embodiments, based on the total weight of the plating solution, the composition of the plating solution is 0.0001 to 50% Al, 0.0001 to 10% Mg, and 0 to 5% Si, where the mass ratio of Al to Mg (Al / Mg) is in the range of 1 to 10000, and the remainder is Zn and unavoidable impurities.

[0033] It needs to be explained that the hot winding temperature can be adjusted within the range of 500 to 700°C depending on the plate thickness. When the plate thickness is large, the winding temperature may be adjusted appropriately to a lower temperature within this range, and when the plate thickness is small, the winding temperature may be adjusted appropriately to a higher temperature within this range. The first purpose of this is to improve the coil shape of the hot-rolled coil, the second purpose is to improve the characteristics of internal and external oxidation on the surface of the hot-rolled plate, thereby affecting the variation in Fe content in the ZnFe alloy phase in the alloy layer of the hot-pressed part, and the third purpose is to control the dimensional accuracy of the steel plate and prevent variations in thickness.

[0034] After pickling the hot-pressed sheet to remove surface oxide scale, cold rolling deformation is performed to obtain the required thickness specifications. The amount of cold rolling deformation is controlled to 10-70%. If the deformation amount is less than 10%, non-uniformity exists in the microstructure of the cold-rolled steel sheet, affecting the toughness stability of the hot-pressed part. However, if the deformation amount exceeds 70%, the difficulty of cold rolling increases.

[0035] Furthermore, in the method for manufacturing zinc-plated steel sheets according to the present invention, the amount of cold rolling deformation is controlled to 10-70% during the cold rolling process.

[0036] A further object of the present invention is to provide a method for manufacturing hot-pressed parts, which includes the following steps.

[0037] To manufacture the aforementioned zinc-plated steel sheet; The zinc-plated steel sheet is subjected to a first-stage heating process, where the heating temperature for the first stage is 350-750°C and the heating time for the first stage is 10-600 seconds. A second stage of heating is performed on the zinc-plated steel sheet, provided that the heating temperature in the second stage is 760-950°C and the heating time in the second stage is adjusted according to the thickness of the zinc-plated steel sheet; The zinc-plated steel sheet is transferred to the mold, and cooling and pressing are performed simultaneously.

[0038] A further core improvement of the present invention is that, according to the above process, a special plating layer structure can be achieved in hot-pressed parts, namely, the mass percentage content of zinc oxide in the surface layer is 5-50%, the manganese oxide content is less than 5%, the aluminum oxide content is 1-50%, and the magnesium oxide content is 0.5-10%, provided that the ZnFe alloy layer comprises a first ZnFe alloy phase with a mass percentage content of Fe of 25% or less and a second ZnFe alloy phase with a mass percentage content of Fe of 50-70%, the area of ​​the first ZnFe alloy phase occupies 5-50% of the plating layer region, and the area of ​​the second ZnFe alloy phase occupies 40-90% of the plating layer region, thereby achieving a gradual increase in the mass percentage content of Fe in the plating layer of hot-pressed parts from the surface toward the steel substrate, thereby achieving excellent corrosion resistance, particularly excellent protection against corrosion of notched areas.

[0039] Furthermore, the hot pressing method described above ensures that the ZnFe alloying change in the plating layer is optimized, and that within the alloy layer, the ZnFe alloy phase with an Fe content of 7-25% is preferentially formed on the surface, while the ZnFe alloy phase with an Fe content of 50-70% is present on the steel substrate side. This two-layer structure effectively prevents the expansion of cracks on the surface of the component.

[0040] Furthermore, the heating process employed in the heating settings of the present invention allows for the control of the rate at which zinc oxide and manganese oxide are formed on the surface and their content on the surface, thereby ensuring the corrosion resistance, weldability, and paintability of the parts.

[0041] Furthermore, the first-stage heating temperature can be a constant temperature within the range of 350 to 750°C, or a set of multiple (e.g., one, two, three, four, or five) varying temperatures. The heating temperature may be increased gradually, or it may be raised and lowered in a stepwise manner at set temperature intervals, or it may be raised first, then lowered, and then raised again. For example, the temperature intervals may be 20 to 150°C each, and one, two, three, or four temperature intervals may be set.

[0042] Furthermore, the heating temperature in the second stage can be a constant temperature within the range of 760 to 950°C, or a set of multiple (e.g., one, two, three, four, or five) varying temperatures. The heating temperature may be increased gradually, or it may be raised and lowered in a stepwise manner at set temperature intervals, or it may be raised first, then lowered, and then raised again. For example, the temperature intervals may be 30 to 150°C each, and one, two, three, or four temperature intervals may be set.

[0043] Furthermore, in the method for manufacturing hot-pressed parts according to the present invention, the heating time in the second stage is controlled to t = a + 150(d - 0.8), where d represents the thickness of the zinc-plated steel sheet, its unit parameter is mm, a represents the time correction value, its range is 50 to 120, and the unit parameter of t is s.

[0044] Furthermore, in the method for manufacturing hot-pressed parts according to the present invention, the heating temperature in the first stage is set to 450 to 650°C.

[0045] Furthermore, in the method for manufacturing hot-pressed parts according to the present invention, during the cooling and pressing process, the mold clamping speed is controlled to 20-300 mm / s and the cooling speed is controlled to 15-100 °C / s from the moment the mold and the galvanized steel sheet are in close contact until the end of pressing.

[0046] Furthermore, in the method for manufacturing hot-pressed parts according to the present invention, the zinc-plated steel sheet is manufactured by the processes of steelmaking, hot rolling, cold rolling, annealing and hot-dip galvanizing, and leveling, wherein in the hot rolling process the coiling temperature is controlled to 500-700°C, and in the annealing and hot-dip galvanizing processes the annealing temperature is controlled to 700-810°C, the plating solution temperature is controlled to 400-600°C, and the cooling rate after removing the steel sheet from the zinc pot is controlled to 5-30°C / s.

[0047] Furthermore, in the method for manufacturing hot-pressed parts according to the present invention, the amount of cold-rolling deformation is controlled to 10-70% during the cold-rolling process. [Effects of the Invention]

[0048] The zinc-plated steel sheet, hot-pressed parts, and their manufacturing methods according to the present invention have the following advantages and beneficial effects: (1) Compared with conventional zinc-plated steel sheets, the zinc-plated steel sheet according to the present invention can be used directly for hot press forming. For complex molded parts, it is not necessary to first partially form the plated steel sheet by cold pressing before hot pressing, thus significantly improving production efficiency and reducing production costs. (2) Compared to conventional hot pressing methods, the pressing method according to the present invention makes it possible to perform heating, cooling, and molding continuously, and since there is no need to pre-cool the blank before molding, good moldability of the blank can be ensured; (3) The hot-pressed part according to the present invention comprises a surface layer and a ZnFe alloy layer in the plating layer, with a zinc oxide content of 5-50% in the surface layer and a manganese oxide content of less than 5%, thereby providing the hot-pressed part with excellent weldability, paintability, and corrosion resistance; (4) In the hot-pressed part according to the present invention, the ZnFe alloy layer of the plating layer comprises a first ZnFe alloy phase with an Fe content of 25% or less and a second ZnFe alloy phase with an Fe content of 50-70%, thereby providing the hot-pressed part with excellent corrosion resistance and suppressing the occurrence and expansion of cracks in the plating layer; (5) The hot-pressed parts according to the present invention have excellent corrosion resistance, and in particular, excellent corrosion protection of the notched portion. [Brief explanation of the drawing]

[0049] [Figure 1] Figure 1 shows the cross-sectional plating layer structure of a hot-pressed part according to Embodiment 6 of the present invention. [Modes for carrying out the invention]

[0050] The following interpretation and explanation will be based on the drawings and specific embodiments, and will further describe the zinc-plated steel sheet, hot-pressed parts, and manufacturing methods thereof according to the present invention. However, this interpretation and explanation will not unduly limit the technical solutions of the present invention.

[0051] In each embodiment of the present invention, hot-pressed parts were manufactured by the following process: (1) Zinc-plated steel sheets were manufactured by steelmaking, hot rolling, cold rolling, annealing, hot-dip galvanizing, and leveling. The zinc-plated steel sheets consisted of a steel substrate and a zinc-plated layer plated on the surface of the steel substrate, wherein the mass percentage content of Zn in the zinc-plated layer was ≥50%, the mass percentage content of Al+Mg was <50%, and the thickness of the zinc-plated layer was 3 to 15 micrometers. The composition and thickness of the zinc-plated layer for each example are shown in Table 1. The mass percentage composition of each chemical element in the steel substrate of the zinc-plated steel sheets for each example is shown in Table 2.

[0052] However, in the hot rolling process, the coiling temperature was controlled to 500-700°C, and in the annealing and hot-dip galvanizing processes, the annealing temperature was controlled to 700-810°C and the galvanizing solution temperature to 400-600°C. The galvanizing solution composition was Al: 0.0001-50%, Mg: 0.0001-10%, Si: 0-5%, Al / Mg: 1-10000, with the remainder being Zn and unavoidable impurities (see Table 2). The cooling rate after removing the steel sheet from the zinc pot was controlled to 5-30°C / s.

[0053] In some examples, the amount of cold rolling deformation was controlled to 10-70% during the cold rolling process.

[0054] (2) A zinc-plated steel sheet is subjected to two heating stages, wherein the heating temperature of the first stage is 350 to 750°C, and the heating temperature of the first stage can be a constant temperature within the range of 350 to 750°C, or a range of variable temperatures, and the heating temperature may be increased in stages, or raised in steps at set temperature intervals, or raised first, then lowered, and then raised again, the heating time of the first stage is 10 to 600 s, and the heating temperature of the second stage is 760 to 950°C, and the heating time t of the second stage is related to the thickness of the sheet, and in some embodiments t = a + 150(d - 0.8), where d represents the thickness of the zinc-plated steel sheet and its unit parameter is mm, a represents the time correction value and its range is 50 to 120, and the unit parameter of t is s.

[0055] (3) The zinc-plated steel sheet was transferred to the mold, and cooling and pressing were performed simultaneously. However, from the moment the mold and the zinc-plated steel sheet were in close contact until the end of pressing, the mold clamping speed was controlled to 20-300 mm / s and the cooling speed was controlled to 15-100 °C / s.

[0056] The structural parameters of the zinc-plated steel sheets used in Examples 1 to 6 are shown in Table 1.

[0057] [Table 1]

[0058] [Table 2]

[0059] The mass percentage composition of each chemical element in the steel substrate of the zinc-plated steel sheets used in Examples 1 to 6 is shown in Table 3.

[0060] [Table 3]

[0061] The manufacturing process parameters for zinc-plated steel sheets in Examples 1 to 6 are shown in Table 4.

[0062] [Table 4]

[0063] The manufacturing process parameters for the hot-pressed parts in Examples 1 to 6 are shown in Table 5.

[0064] [Table 5]

[0065] Accordingly, samples were taken from the hot-pressed parts of the finished products manufactured in Examples 1 to 6, and their microstructures were detected. The relevant detection results are shown in Table 6 below. However, the zinc oxide and manganese oxide content in the surface layer was obtained by XRD or EDS analysis, and the Fe content in the first ZnFe alloy phase and the second ZnFe alloy phase in the ZnFe alloy layer was obtained by EDS analysis.

[0066] [Table 6]

[0067] As can be seen from Table 6 above, the microstructure of the hot-rolled part according to the present invention may be one or more of martensite, bainite, ferrite, and pearlite, and its specific composition is related to the chemical elemental composition of the steel substrate and the cooling rate in Table 5.

[0068] As can be further seen from Table 6, the plating layer of the hot-pressed parts in each example included a surface layer and a ZnFe alloy layer, however, the mass percentage content of zinc oxide in the surface layer was 5-50%, and the manganese oxide content was less than 5%. The ZnFe alloy layer included a first ZnFe alloy phase with a mass percentage content of Fe of 25% or less, and a second ZnFe alloy phase with a mass percentage content of Fe of 50-70%. The second ZnFe alloy phase was located closer to the steel substrate than the first ZnFe alloy phase, and the mass percentage content of Fe in the plating layer of the hot-pressed parts gradually increased from the surface toward the steel substrate. Also, as detected by the same method, the mass percentage content of aluminum oxide in the surface layer of the hot-pressed parts in each example was 1-50%, and the mass percentage content of magnesium oxide was 0.5-10%.

[0069] Furthermore, the inventors sampled from each embodiment and further measured the corrosion resistance, adhesion, and weldability of the hot-pressed parts according to each embodiment. The measurement results are shown in Table 7. However, Corrosion resistance evaluation is performed after 30 cycles according to Volkswagen's standard PV1210 method, and levels are assigned based on the depth and width of corrosion, with level 5 indicating the best and level 1 indicating the worst.

[0070] Paint adhesion is evaluated according to GB / T9286-1998, using a visual inspection with a grid method to assess the degree of paint film peeling. Adhesion decreases progressively from level 0 to 5, with level 5 being the worst.

[0071] Weldability evaluation will be conducted in accordance with GM Motorsman's standard GWS-5:2011, with the presence or absence of weld spatter as the evaluation criterion.

[0072] [Table 7]

[0073] As can be seen from Table 7, the hot-pressed parts according to each embodiment of the present invention all have excellent corrosion resistance, as well as excellent paint adhesion and excellent weldability.

[0074] Furthermore, Figure 1 shows a photograph of the cross-sectional plating layer of a hot-pressed part according to Embodiment 6 of the present invention.

[0075] As can be seen from Figure 1, the plating layer of the hot-pressed part in question consisted of a first ZnFe alloy phase with an Fe content of 25% or less and a second ZnFe alloy phase with an Fe content of 50-70%. The second ZnFe alloy phase was located on the steel substrate side, was complete and continuous, and the plating layer was also complete and continuous.

[0076] Furthermore, the combinations of technical features in this application are not limited to the combinations described in the claims or the specific embodiments, and all technical features described in this application can be freely combined or combined in any form, as long as they do not contradict each other.

[0077] Furthermore, it should be noted that the embodiments described above are merely specific examples of the present invention. The present invention is not limited to the above embodiments, and it is clear that any similar changes or modifications that a person skilled in the art can directly derive from the disclosure of the present invention or readily conceive are also covered within the scope of the present invention.

Claims

1. A zinc-plated steel sheet having excellent corrosion resistance, comprising a steel substrate and a zinc-plated layer plated on the surface of the steel substrate, wherein the mass percentage content of Zn in the zinc-plated layer is ≥ 50%, the mass percentage content of Al + Mg is < 50%, and the thickness of the zinc-plated layer is 3 to 15 micrometers.

2. The zinc-plated steel sheet according to claim 1, characterized in that the zinc-plated layer further contains Si, and / or the thickness of the zinc-plated layer is 5 to 10 micrometers.

3. The zinc-plated steel sheet according to claim 1, characterized in that the mass percentage content of the chemical elements in the steel substrate is C: 0.05-0.5%, Si: 0.01-2.0%, Mn: 0.3-3.0%, Al: 0.005-0.3%, Ti ≤ 0.1%, B ≤ 0.1%, Cr ≤ 0.5%, Nb ≤ 0.1%, V ≤ 0.1%, Ni ≤ 0.5%, Mo ≤ 0.5%, with the remainder being Fe and unavoidable impurities.

4. The zinc-plated steel sheet according to claim 3, characterized in that the unavoidable impurities in the steel substrate are P ≤ 0.3% and S ≤ 0.1%.

5. A hot-pressed part comprising a steel substrate and a plating layer plated on the surface of the steel substrate, wherein the plating layer comprises a surface layer and a ZnFe alloy layer, wherein the mass percentage content of zinc oxide in the surface layer is 5 to 50% and the manganese oxide content is less than 5%, wherein the ZnFe alloy layer comprises a first ZnFe alloy phase with a mass percentage content of Fe of 25% or less and a second ZnFe alloy phase with a mass percentage content of Fe of 50 to 70%, and the mass percentage content of Fe in the plating layer of the hot-pressed part gradually increases from the surface toward the steel substrate.

6. The hot-pressed part according to claim 5, characterized in that the surface layer contains 1 to 50% by mass of aluminum oxide, 0.5 to 10% by mass of magnesium oxide, and / or the area of ​​the first ZnFe alloy phase occupies 5 to 50% of the plating layer region, and the area of ​​the second ZnFe alloy phase occupies 40 to 90% of the plating layer region.

7. The hot-pressed part according to claim 5, characterized in that it is obtained by directly hot-pressing a zinc-plated steel sheet according to any one of claims 1 to 4.

8. The hot-pressed part according to any one of claims 5 to 7, characterized in that its microstructure has at least one of martensite, bainite, ferrite, and pearlite.

9. A method for manufacturing a zinc-plated steel sheet according to any one of claims 1 to 4, comprising the steps of steelmaking, hot rolling, cold rolling, annealing and hot-dip galvanizing, and leveling, wherein in the hot rolling step the coiling temperature is controlled to 500 to 700°C, in the annealing and hot-dip galvanizing step the annealing temperature is controlled to 700 to 810°C, the plating solution temperature is controlled to 400 to 600°C, and the cooling rate after removing the steel sheet from the zinc pot is controlled to 5 to 30°C / s.

10. The method for producing a zinc-plated steel sheet according to claim 9, characterized in that, in the cold rolling process, the amount of cold rolling deformation is controlled to 10 to 70%, and / or, based on the total weight of the plating solution, the composition of the plating solution is 0.0001 to 50% Al, 0.0001 to 10% Mg, 0 to 5% Si, with the remainder being Zn and unavoidable impurities, provided that the mass ratio of Al to Mg (Al / Mg) is in the range of 1 to 10000.

11. A method for manufacturing a hot-pressed part according to claim 9 or 10, characterized by including the following steps. To manufacture the aforementioned zinc-plated steel sheet; A zinc-plated steel sheet is subjected to a first-stage heating process, wherein the heating temperature for the first stage is 350 to 750°C, and the heating time for the first stage is 10 to 600 seconds. A second stage of heating is performed on the zinc-plated steel sheet, provided that the heating temperature in the second stage is 760 to 950°C, and the heating time in the second stage is adjusted according to the thickness of the zinc-plated steel sheet; The zinc-plated steel sheet is transferred to the mold, and cooling and pressing are performed simultaneously.

12. The method for manufacturing a hot-pressed part according to claim 11, characterized in that the heating time in the second stage is controlled to t = a + 150(d - 0.8), where d represents the thickness of the zinc-plated steel sheet and its unit parameter is mm, a represents the time correction value and its range is 50 to 120, and the unit parameter of t is s.

13. The method for manufacturing hot-pressed parts according to claim 11, characterized in that the heating temperature in the first stage is 450 to 650°C.

14. The method for manufacturing hot-pressed parts according to claim 11, characterized in that, during the cooling and pressing process, the mold clamping speed is controlled to 20 to 300 mm / s and the cooling rate is controlled to 15 to 100°C / s from the time when the mold and the galvanized steel sheet are in close contact until the end of pressing.

15. The method for manufacturing a hot-pressed part according to claim 11, characterized in that the zinc-plated steel sheet is manufactured by the method described in claim 9 or 10.

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