Zinc-iron coating part and preparation method thereof

Abstract

The invention relates to the technical field of coating part preparation, in particular to a zinc-iron coating part and a preparation method thereof. The preparation method comprises the steps that a part steel base body is annealed, and an annealed base plate is obtained; carrying out hot dipping on the annealed substrate by using a zinc-containing plating solution, and then carrying out alloying treatment to obtain a rough steel plate containing a zinc-iron plating layer; the rough steel plate is subjected to cold stamping forming, and a preformed part is obtained; according to the thickness of the preformed part, the optimal hot stamping processing parameters are determined; and the rough part is subjected to heat treatment through the hot stamping treatment parameters, and the zinc-iron coating part is obtained. The hot stamping treatment parameters comprise austenitizing heating temperature and austenitizing heat preservation time; and the thickness of the preformed part is in positive correlation with the temperature and the time respectively. According to the preparation method, the correlation between the thickness of the preformed part and the austenitizing heating temperature and the austenitizing heat preservation time is defined, so that the content of a brittle gamma phase in a zinc-iron coating is reduced; and further, the liquid metal embrittlement sensitivity of the preformed part in the hot stamping treatment process is reduced.

Description

Technical Field

[0001] The present application relates to the technical field of coating part preparation, and in particular to a zinc-iron coating part and a preparation method thereof. Background Art

[0002] In general, the amount of hot-formed steel used in models known for safety has reached more than 40% of the weight of the body in white. Among these hot-formed steels, the most widely used type is the hot-formed steel plate with Al-Si coating. However, on the one hand, during the application of hot-formed steel with Al-Si coating, its Al-Si coating is easy to form eutectic Al-Si alloy, and a brittle FeAl2O3 alloy will be formed between its inhibition layers. 3 and Fe 2 Al 5 alloy phase, which makes it easy for microcracks to form on the surface of the Al-S coated hot-formed steel. The presence of these microcracks will greatly reduce the fracture strain and cold bending performance of these hot-formed steels. Therefore, these hot-formed steels are not suitable for producing parts with complex shapes. On the other hand, the hot-formed steel plates with Al-Si coating have good corrosion resistance and pitting resistance, but because the electrode potential of the Al-Si coating is basically the same as that of the substrate of the hot-formed steel plate, the Al-Si coating does not have cathodic protection function. In the subsequent edge corrosion process of the hot-formed steel plate, the Al-Si coating cannot provide cathodic protection, which reduces the corrosion resistance of the hot-formed steel plate with Al-Si coating.

[0003] At present, the Zn-Fe alloy coating in hot-formed steel is a pure zinc coating as the surface layer, which does not contain FeAl 3 and Fe 2 Al 5 alloy phase, so the Zn-Fe alloy coating in the Zn-Fe alloy coated hot-formed steel can not only greatly reduce the occurrence of surface microcracks, but also play a cathodic protection performance for the Zn-Fe alloy coated hot-formed steel substrate, and at the same time can well prevent the oxidation peeling and decarburization of the steel during the heating process. Therefore, the Zn-Fe alloy coated hot-formed steel has been widely studied and concerned in recent years.

[0004] However, at present, in order to ensure the excellent performance of Zn-Fe alloy-coated hot-formed steel during hot stamping, a large pressure is used, which leads to the disadvantage of excessive sensitivity to liquid metal embrittlement during the hot stamping process. Summary of the invention

[0005] The present application provides a zinc-iron coated part and a preparation method thereof to solve the following technical problem: how to reduce the sensitivity of Zn-Fe alloy coated hot-formed steel to liquid metal embrittlement during hot stamping.

[0006] In a first aspect, the present application provides a method for preparing a zinc-iron plated part, the preparation method comprising:

[0007] Annealing the steel substrate of the part to obtain an annealed substrate;

[0008] The annealed substrate is hot-dip plated with a zinc-containing plating solution, and then the annealed substrate in the zinc-containing plating solution is alloyed to form an iron-zinc coating on the surface of the annealed substrate to obtain a raw steel plate containing a zinc-iron coating;

[0009] The raw steel plate containing zinc and iron coating is cold stamped to obtain a preformed part;

[0010] Determining the most suitable hot stamping processing parameters according to the thickness of the preformed part; and

[0011] Using the most suitable hot stamping processing parameters to perform hot stamping processing on the preformed part, and then quenching the preformed part after the hot stamping processing to obtain a zinc-iron plated part;

[0012] Wherein, the hot stamping processing parameters include the austenitizing heating temperature and the austenitizing holding time;

[0013] The thickness of the preformed part is positively correlated with the temperature of the austenitizing heating, and the thickness of the preformed part is positively correlated with the austenitizing heat preservation time.

[0014] Optionally, the austenitizing heating temperature is 855° C. to 895° C., and the austenitizing holding time is 150s to 300s.

[0015] Optionally, determining the most suitable hot stamping processing parameters according to the thickness of the preformed part comprises the steps of:

[0016] When the thickness of the preformed part is less than 1.5 mm, the austenitizing heating temperature is 855° C. to 875° C., and the austenitizing holding time is 150 s to 250 s.

[0017] When the thickness of the preformed part is greater than or equal to 1.5 mm and less than 2.0 mm, the austenitizing heating temperature is 865° C. to 885° C., and the austenitizing holding time is 180 s to 280 s;

[0018] When the thickness of the preformed part is greater than or equal to 2.0 mm and less than or equal to 2.5 mm, the temperature of the austenitizing heating is 875° C. to 895° C., and the austenitizing holding time is 200 s to 300 s.

[0019] Optionally, the heating rate of the austenitizing heating is ≥25°C / min, and the dew point temperature of the austenitizing heating is ≤-5°C.

[0020] Optionally, the hot stamping treatment further comprises cooling in the form of mold pressure-maintaining and shape-correcting cooling and / or aerosol cooling, and the initial cooling temperature is 650° C. to 780° C.; and / or

[0021] In the case where the cooling includes mold pressure-maintaining and shape-correcting cooling, the pressure of the mold pressure-maintaining and shape-correcting cooling is ≥160t, the time of the mold pressure-maintaining and shape-correcting cooling is 10-15s, and the cooling rate of the mold pressure-maintaining and shape-correcting cooling is ≥30°C / s;

[0022] In the case where the cooling includes aerosol cooling, the pressure of the aerosol cooling is ≥ 0.5 MPa, and the cooling rate of the aerosol cooling is ≥ 30° C. / s.

[0023] Optionally, the chemical composition of the zinc-containing plating solution satisfies, by mass fraction: Al: 0.10% to 0.25%, Fe: 0.01% to 0.03%, and the remainder is Zn and unavoidable impurities; and / or

[0024] The temperature of the zinc-containing plating solution is 420° C. to 480° C., and the time of the hot-dip plating is 2s to 8s.

[0025] Optionally, the temperature of the alloying treatment is 470° C. to 530° C., and the time of the alloying treatment is 10s to 20s.

[0026] Optionally, the thickness of the zinc-iron coating in the crude steel plate containing the zinc-iron coating is 9 μm to 15 μm; and / or

[0027] The temperature of the annealing substrate is 410° C. to 470° C.; and / or

[0028] The temperature of the quenching treatment is 650° C. to 780° C., and the time of the quenching treatment is 10s to 15s.

[0029] In the second aspect, the present application provides a zinc-iron coated part, which is prepared by the preparation method described in the first aspect, and the zinc-iron coated part includes a steel substrate, an inhibition layer and a zinc-iron coating from the inside to the outside, and the thickness h1 of the zinc-iron coating, the thickness h2 of the inhibition layer and the thickness h3 of the steel substrate satisfy the relationship: h1:h2:h3=(15~25):2:(700~2500).

[0030] Optionally, the chemical composition of the steel matrix satisfies, by mass fraction: C: 0.05% to 0.30%, Si: 0.05% to 0.2%, Mn: 0.6% to 2.2%, Cr≤0.35%, Mo≤0.22%, Ti: 0.01% to 0.02%, Nb≤0.02%, V≤0.02%, B: 0.002% to 0.008%, P≤0.005%, S≤0.005%, Al: 0.02% to 0.10%, and the rest is Fe and unavoidable impurities; and / or

[0031] Calculated by mass fraction, the chemical composition of the zinc-iron coating satisfies: Al: 0.10% to 0.25%, Fe: 7% to 16%, and the remaining elements are Zn and unavoidable impurities.

[0032] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art:

[0033] A method for preparing a zinc-iron coated part is provided in an embodiment of the present application. The method clarifies that the thickness of a rough preformed part containing a zinc-iron coating is positively correlated with the temperature of austenitizing heating and the time of austenitizing insulation in hot stamping treatment. The two parameters of the temperature of austenitizing heating and the time of austenitizing insulation in hot stamping treatment can be adjusted according to the thickness of the preformed part to reduce the diffusion rate of the iron element of the steel matrix of the preformed part to the zinc-iron coating in the preformed part during the hot stamping process, thereby controlling the growth thickness of the Γ-FeZn phase in the zinc-iron coating of the preformed part and reducing the content of the brittle Γ phase in the zinc-iron coating. The zinc-iron coating with a low Γ phase content can avoid the zinc-iron coating from being broken during the hot stamping process, thereby reducing the sensitivity of the preformed part to liquid metal embrittlement during the hot stamping process, so as to finally obtain a zinc-iron coated part product with expected performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] 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.

[0035] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0036] Figure 1 A schematic diagram of a process for preparing a zinc-iron plated part provided in an embodiment of the present application;

[0037] Figure 2A detailed schematic diagram of a method for preparing a zinc-iron plated part provided in an embodiment of the present application;

[0038] Figure 3 A schematic diagram of the microstructure of a zinc-iron coating in a zinc-iron coating part provided in Example 1 of the present application;

[0039] Figure 4 A schematic diagram of a roller hearth furnace model in a method for preparing a zinc-iron coated part provided in an embodiment of the present application, wherein 1-a rough part after cold stamping pre-forming, 2-a rough part after alloying treatment, 3-a zinc-iron coated part after quenching treatment;

[0040] Figure 5 A schematic diagram of the microstructure of a zinc-iron plated part provided in Examples 1 to 3 of the present application and Comparative Example 1;

[0041] Figure 6 A schematic diagram of the microstructure and microhardness of a zinc-iron plated part provided in Examples 1 to 3 of the present application and Comparative Example 1. DETAILED DESCRIPTION

[0042] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0043] 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 rigid limitation on the scope of the present application; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within the range; for example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., 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 in this document, it is meant to include any cited numbers (fractions or integers) within the indicated range.

[0044] In this document, the terms including "including" and "including" mean "including but not limited to". Relational terms such as "first" and "second" are only 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. "And / or" describes the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone; where A and B can be singular or plural. "At least one" means one or more, and "plurality" means two or more; "at least one", "at least one of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items; for example, "at least one of a, b, or c", or "at least one of a, b, and c" can all mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple. Unless otherwise specified, various raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0045] Figure 1 The schematic diagram of the process of preparing a zinc-iron plated part provided in an embodiment of the present application is exemplarily shown;

[0046] like Figure 1 As shown, the embodiment of the present application provides a method for preparing a zinc-iron plated part, the preparation method comprising:

[0047] S1. Annealing the steel substrate of the part to obtain an annealed substrate;

[0048] S2. The annealed substrate is hot-dip plated using a zinc-containing plating solution, and then the annealed substrate in the zinc-containing plating solution is alloyed to form an iron-zinc coating on the surface of the annealed substrate to obtain a rough steel plate containing zinc and iron coating;

[0049] S3. The rough steel plate containing zinc and iron is cold stamped to obtain a preformed part;

[0050] S4. Determine the optimum hot stamping processing parameters according to the thickness of the preformed part; and

[0051] S5. Using the most suitable hot stamping processing parameters to hot stamp the preformed part, and then quenching the preformed part after the hot stamping to obtain a zinc-iron coated part;

[0052] Wherein, the hot stamping processing parameters include the austenitizing heating temperature and the austenitizing holding time;

[0053] The thickness of the preformed part is positively correlated with the temperature of the austenitizing heating, and the thickness of the preformed part is positively correlated with the austenitizing heat preservation time.

[0054] It should be noted that the hot stamping process generally includes the trimming process of the preformed parts. In addition, the hot stamping process includes processes such as austenitizing heating and austenitizing insulation to promote the transformation of the zinc-containing plating solution into a mold. After austenitizing heating and insulation, the hot-pressed rough parts can be transferred to the original cold stamping preforming mold by manual or mechanical devices for subsequent mold pressure-holding and shape-correcting cooling or aerosol cooling.

[0055] It should be noted that the deformation amount of the cold stamping forming is 90% to 95% of the total deformation amount of the preformed part.

[0056] Figure 4 The schematic diagram of the roller hearth furnace model in the method for preparing zinc-iron coated parts provided in the embodiment of the present application is exemplarily shown;

[0057] It should be noted that the austenitizing heating method can use a roller hearth furnace or a box furnace; when a roller hearth furnace is used, Figure 4 As shown, the plane of the working interface of the roller hearth furnace can be set to a circle, which ultimately promotes the transformation of the structure in the preformed part to an austenitic structure.

[0058] It should be noted that the mold used for the cold stamping preforming can also be used for hot stamping treatment and mold pressure holding and shape correction cooling processes to recycle the mold and save the processing cost of alloying hot pressing treatment.

[0059] In some optional embodiments, the austenitizing heating temperature is 855°C to 895°C, and the austenitizing holding time is 150s to 300s;

[0060] In these embodiments, the austenitizing heating temperature can be 855°C to 895°C, and the austenitizing holding time can be 150s to 300s, which can ensure that the hot stamping process has sufficient temperature and austenitizing holding time to promote the microstructure phase transformation of the zinc-iron coating in the preformed part and the steel matrix in the preformed part into a martensitic structure during the hot stamping process, and at the same time reduce the content of the brittle Γ phase in the zinc-iron coating in the preformed part, thereby reducing the sensitivity of the preformed part to liquid metal embrittlement during the hot stamping process, so as to ultimately obtain a zinc-iron coated part product with expected performance.

[0061] The temperature of the austenitizing heating may be 855°C, 860°C, 865°C, 870°C, 875°C, 880°C, 885°C, 890°C or 895°C.

[0062] The austenitizing holding time may be 150s, 160s, 170s, 180s, 190s, 200s, 210s, 220s, 230s, 240s, 250s, 260s, 270s, 280s, 290s or 300s.

[0063] Figure 2 The detailed process diagram of a method for preparing a zinc-iron plated part provided in an embodiment of the present application is exemplarily shown;

[0064] In some optional embodiments, such as Figure 2 As shown, the method of determining the most suitable alloying hot pressing treatment parameters according to the thickness of the preformed part comprises the steps of:

[0065] S401. When the thickness of the preformed part is less than 1.5 mm, the austenitizing heating temperature is 855°C to 875°C, and the austenitizing holding time is 150s to 250s;

[0066] S402. When the thickness of the preformed part is greater than or equal to 1.5 mm and less than 2.0 mm, the austenitizing heating temperature is 865° C. to 885° C., and the austenitizing holding time is 180 s to 280 s;

[0067] S403. When the thickness of the preformed part is greater than or equal to 2.0 mm and less than or equal to 2.5 mm, the austenitizing heating temperature is 875° C. to 895° C., and the austenitizing holding time is 200 s to 300 s;

[0068] In these embodiments, the thickness of the preformed part is divided into three different sections according to 1.5 mm, 2.0 mm and 2.5 mm as critical points, and the corresponding austenitizing heating temperature and austenitizing holding time are matched according to the thickness of the preformed part. For example, for a preformed part with a thickness of less than 1.5 mm, the designed austenitizing heating temperature can be 855° C. to 875° C. and the austenitizing holding time can be 150s to 250s; for a preformed part with a thickness greater than or equal to 1.5 mm and less than 2.0 mm, the designed austenitizing heating temperature can be 865° C. to 885° C. and the austenitizing holding time can be 180s to 280s; and for a preformed part with a thickness greater than or equal to 1.5 mm and less than 2.0 mm, the designed austenitizing heating temperature can be 865° C. to 885° C. and the austenitizing holding time can be 180s to 280s; For preformed parts with a thickness greater than or equal to 2.0 mm and less than or equal to 2.5 mm, the designed austenitizing heating temperature can be 875°C to 895°C and the austenitizing holding time can be 200s to 300s. The appropriate austenitizing heating temperature and austenitizing holding time can be adopted according to the actual thickness of the preformed parts to promote the microstructure phase transformation of the zinc-iron coating and the steel matrix in the preformed parts during the hot stamping process to the martensitic structure. At the same time, the content of the brittle Γ phase in the zinc-iron coating in the preformed parts can also be reduced, thereby reducing the sensitivity of the preformed parts to liquid metal embrittlement during the hot stamping process, so as to finally obtain a zinc-iron coated part product with expected performance.

[0069] When the thickness of the preformed part is less than 1.5 mm, the austenitizing heating temperature may be 855°C, 860°C, 865°C, 870°C or 875°C, and the austenitizing holding time may be 150s, 160s, 170s, 180s, 190s, 200s, 210s, 220s, 230s, 240s or 250s.

[0070] When the thickness of the preformed part is greater than or equal to 1.5 mm and less than 2.0 mm, the austenitizing heating temperature can be 865°C, 870°C, 875°C, 880°C or 885°C, and the austenitizing holding time can be 150s, 160s, 170s, 180s, 190s, 200s, 210s, 220s, 230s, 240s or 250s.

[0071] When the thickness of the preformed part is greater than or equal to 2.0 mm and less than or equal to 2.5 mm, the austenitizing heating temperature can be 875°C, 880°C, 885°C, 890°C or 895°C, and the austenitizing holding time can be 200s, 210s, 220s, 230s, 240s, 250s, 260s, 270s, 280s, 290s or 300s.

[0072] In some optional embodiments, the heating rate of the austenitizing heating is ≥25°C / min, and the dew point temperature of the hot stamping treatment is ≤-5°C;

[0073] In these embodiments, the heating rate of austenitizing heating can be ≥25°C / min, and the dew point temperature of austenitizing heating can be ≤-5°C, the zinc-iron coating in the rough parts containing the zinc-iron coating and the part steel matrix in the rough parts are transformed into a martensitic structure, and the content of the brittle Γ phase in the zinc-iron coating in the rough parts can be reduced, thereby further reducing the sensitivity of the rough parts to liquid metal embrittlement during the alloying hot pressing process, so as to finally obtain a zinc-iron coated part product with expected performance.

[0074] In some optional embodiments, the hot stamping process further comprises cooling by mold pressure-maintaining and shape-correcting cooling and / or aerosol cooling, and the initial cooling temperature is 650° C. to 780° C.; and / or

[0075] In the case where the cooling includes mold pressure-maintaining and shape-correcting cooling, the pressure of the mold pressure-maintaining and shape-correcting cooling is ≥160t, the time of the mold pressure-maintaining and shape-correcting cooling is 10s-15s, and the cooling rate of the mold pressure-maintaining and shape-correcting cooling is ≥30°C / s;

[0076] In the case where the cooling includes aerosol cooling, the pressure of the aerosol cooling is ≥ 0.5 MPa, and the cooling rate of the aerosol cooling is ≥ 30°C / s;

[0077] In these embodiments, the hot stamping treatment may also include cooling by mold pressure-holding and shaping cooling and / or aerosol cooling, and the initial cooling temperature may be 650°C to 780°C. In addition, when the cooling includes mold pressure-holding and shaping cooling, the pressure of the mold pressure-holding and shaping cooling may be ≥160t, and the cooling rate of the mold pressure-holding and shaping cooling may be ≥30°C / s; in addition, when the cooling includes aerosol cooling, the pressure of the volume aerosol cooling may be ≥0.5MPa, and the cooling rate of the aerosol cooling may be ≥30°C / s. The mold pressure-holding and shaping cooling and aerosol cooling may be used to promote the microstructure phase transformation of the zinc-iron coating in the preformed parts and the steel matrix of the preformed parts during the alloying hot pressing process to form a martensitic structure. At the same time, the content of the brittle Γ phase in the zinc-iron coating in the preformed parts may be reduced, thereby reducing the sensitivity of the preformed parts to liquid metal embrittlement during the hot stamping process, so as to ultimately obtain a zinc-iron coating part product with expected performance.

[0078] The initial temperature of the mold pressure-maintaining shape cooling or aerosol cooling can be 650°C, 660°C, 670°C, 680°C, 690°C, 700°C, 710°C, 720°C, 730°C, 740°C, 750°C, 760°C, 770°C or 780°C.

[0079] In some optional embodiments, the chemical composition of the zinc-containing plating solution satisfies, by mass fraction: Al: 0.10% to 0.25%, Fe: 0.01% to 0.03%, and the remainder is Zn and unavoidable impurities; and / or

[0080] The temperature of the zinc-containing plating solution is 420° C. to 480° C., and the hot-dip plating time is 2s to 8s;

[0081] In these embodiments, the chemical composition of the zinc-containing plating solution can meet the following conditions: Al: 0.10% to 0.25%, Fe: 0.01% to 0.03%, and the temperature of the plating solution used for hot-dip plating can be 420°C to 480°C, and the hot-dip plating time can be 2s to 8s, which can prompt the plating solution to form a zinc-containing coating of sufficient thickness on the surface of the annealed substrate to facilitate the smooth progress of the organizational phase transformation process of the subsequent alloying treatment to generate a zinc-iron coating.

[0082] The chemical composition of the zinc-containing plating solution satisfies: the mass fraction of Al can be 0.10%, 0.15%, 0.20% or 0.25%; and the mass fraction of Fe can be 0.01%, 0.02% or 0.03%.

[0083] The temperature of the zinc-containing plating solution may be 420°C, 430°C, 440°C, 450°C, 460°C, 470°C or 480°C.

[0084] The hot dipping time can be 2s, 3s, 4s, 5s, 6s, 7s or 8s.

[0085] In some optional embodiments, the temperature of the alloying treatment is 470° C. to 530° C., and the time of the alloying treatment is 10s to 20s;

[0086] In these embodiments, the temperature of the alloying treatment may be 470° C. to 530° C., and the time of the alloying treatment may be 10 s to 20 s. The alloying treatment causes the zinc-containing coating formed in the coating forming section to be transformed into a zinc-iron coating. In addition, a layer having a chemical composition of Fe is formed between the formed zinc-iron coating and the interface of the annealed substrate. 2 Al 5 An inhibition layer is formed to reduce the content of brittle Γ phase in the zinc-iron coating in the rough parts, so as to further reduce the sensitivity of the rough parts to liquid metal embrittlement during the alloying hot pressing treatment, so as to finally obtain a zinc-iron coated parts product with expected performance.

[0087] The temperature of the coating alloying treatment may be 470°C, 480°C, 490°C, 500°C, 510°C, 520°C or 530°C.

[0088] The coating alloying treatment time can be 10s, 11s, 12s, 13s, 14s, 15s, 16s, 17s, 18s, 19s or 20s.

[0089] In some optional embodiments, the thickness of the zinc-iron coating in the rough part containing the zinc-iron coating is 9 μm to 15 μm; and / or

[0090] The temperature of the annealing substrate is 410° C. to 470° C.; and / or

[0091] The quenching treatment temperature is 650°C to 780°C, and the quenching treatment time is 10s to 15s;

[0092] In these embodiments, the thickness of the zinc-iron coating in the raw steel plate containing the zinc-iron coating can be 9 μm to 15 μm, which can enable the raw steel plate containing the zinc-iron coating to have a zinc-iron coating of sufficient thickness, so that the final zinc-iron coated parts have a zinc-iron coating of sufficient thickness; in addition, the temperature of the annealing substrate can be 410°C to 470°C, which can enable the annealing substrate to have sufficient heat, and the annealing substrate with sufficient heat can enable hot dip plating to be fully carried out, so that the final zinc-iron coated parts have a zinc-iron coating of sufficient thickness; in addition, the temperature of the quenching treatment can be 650°C to 780°C, and the time of the quenching treatment can be 10s to 15s. After the quenching treatment, the microstructure phase transformation between the zinc-iron coating and the steel matrix can be complete, thereby improving the performance of the zinc-iron coated parts.

[0093] The thickness of the zinc-iron coating in the zinc-iron coating rough part may be 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm or 15 μm.

[0094] The temperature of the annealing substrate may be 410°C, 420°C, 430°C, 440°C, 450°C, 460°C, or 470°C.

[0095] Figure 3 A schematic diagram of the microstructure of a zinc-iron coating in a zinc-iron coating part provided in Example 1 of the present application is shown by way of example;

[0096] Based on a general inventive concept, such as Figure 3As shown, the present application provides a zinc-iron coated part, which is prepared by the preparation method, and the zinc-iron coated part includes a steel substrate, an inhibition layer and a zinc-iron coating from the inside to the outside, and the thickness h1 of the zinc-iron coating, the thickness h2 of the inhibition layer and the thickness h3 of the steel substrate satisfy the relationship: h1:h2:h3=(15~25):2:(700~2500).

[0097] The zinc-iron plated part is obtained based on the above-mentioned preparation method. The specific steps of the preparation method can refer to the above-mentioned embodiment. Since the zinc-iron plated part adopts part or all of the technical solutions of the above-mentioned embodiment, it has at least all the beneficial effects brought by the technical solutions of the above-mentioned embodiment, which will not be described one by one here.

[0098] It should be noted that the thickness h1 of the zinc-iron coating, the thickness h2 of the inhibition layer and the thickness h3 of the steel substrate can satisfy the relationship: h1:h2:h3=(15~25):2:(700~2500), which can enable the zinc-iron coated parts to have zinc-iron coating, inhibition layer and steel substrate of sufficient thickness. The zinc-iron coating, inhibition layer and steel substrate can improve the corrosion resistance and ultimate bending performance of the zinc-iron coated parts.

[0099] The thickness h1 of the zinc-iron coating, the thickness h2 of the inhibition layer and the thickness h3 of the steel substrate may satisfy the relationship: h1:h2:h3=15:2:700, 15:2:1000, 15:2:1500, 15:2:2000, 15:2:2500, 20:2:700, 20:2:2000, 20:2:1500, 20:2:2000, 20:2:2500, 25:2:700, 25:2:1000, 25:2:2500, 25:2:2000 or 25:2:2500.

[0100] In some optional embodiments, the chemical composition of the steel matrix satisfies, by mass fraction: C: 0.05% to 0.30%, Si: 0.05% to 0.2%, Mn: 0.6% to 2.2%, Cr≤0.35%, Mo≤0.22%, Ti: 0.01% to 0.02%, Nb≤0.02%, V≤0.02%, B: 0.002% to 0.008%, P≤0.005%, S≤0.005%, Al: 0.02% to 0.10%, and the rest is Fe and unavoidable impurities; and / or

[0101] In terms of mass fraction, the chemical composition of the zinc-iron coating satisfies: Al: 0.10% to 0.25%, Fe: 7% to 16%, and the remaining elements are Zn and unavoidable impurities; in these embodiments, the chemical composition of the steel substrate may satisfy: C: 0.05% to 0.30%, Si: 0.05% to 0.2%, Mn: 0.6% to 2.2%, Cr≤0.35%, Mo≤0.22%, Ti: 0.01% to 0.02%, Nb≤0.02%, V≤0.02%, B: 0.002% ~0.008%, P≤0.005%, S≤0.005%, Al: 0.02%~0.10%, which can make the steel matrix have good corrosion resistance and high mechanical properties to meet the needs of alloy heat treatment; in addition, the chemical composition of the zinc-iron coating can meet: Al: 0.10%~0.25%, Fe: 7%~16%, which can make the zinc-iron coating form an inhibition layer on the surface of the steel substrate, thereby improving the corrosion resistance and ultimate bending performance of the zinc-iron coated parts through the zinc-iron coating, the inhibition layer and the steel substrate.

[0102] In the chemical composition of the steel matrix, the mass fraction of C may be 0.05%, 0.10%, 0.15%, 0.20%, 0.25% or 0.30%.

[0103] The mass fraction of Si may be 0.05%, 0.10%, 0.15% or 0.20%.

[0104] The mass fraction of Mn may be 0.6%, 0.8%, 1.0%, 1.2%, 1.4%, 1.6%, 1.8%, 2.0% or 2.2%.

[0105] The mass fraction of Ti may be 0.01%, 0.011%, 0.012%, 0.013%, 0.014%, 0.015%, 0.016%, 0.017%, 0.018%, 0.019%, or 0.020%.

[0106] The mass fraction of B may be 0.002%, 0.004%, 0.006% or 0.008%.

[0107] The mass fraction of Al may be 0.02%, 0.04%, 0.06%, 0.08% or 0.10%.

[0108] In the chemical composition of the plating solution used for the zinc-iron plating layer, the mass fraction of Al is 0.10%, 0.15%, 0.20% or 0.25%.

[0109] The mass fraction of Fe may be 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15% or 16%.

[0110] The present application is further described below in conjunction with specific examples. The experimental methods in the following examples that do not specify specific conditions are usually measured according to industry standards; if there are no corresponding industry standards, they are carried out according to common international standards, conventional conditions, or conditions recommended by the manufacturer.

[0111] Example 1

[0112] Select 1.2mm annealed substrate to prepare zinc-iron plated parts. The specific process includes:

[0113] S1. Annealing the steel substrate of the part to obtain an annealed substrate;

[0114] S2. hot-dip plating the annealed substrate using a zinc-containing plating solution, and then alloying the annealed substrate in the zinc-containing plating solution to form an iron-zinc coating on the surface of the annealed substrate to obtain a rough steel plate containing zinc and iron;

[0115] S3. The zinc-iron-coated rough steel plate is cold stamped to obtain a preformed part;

[0116] S4. Determine the most suitable hot stamping processing parameters according to the thickness of the preformed part; and

[0117] S5. hot stamping the preformed part using the most suitable hot stamping processing parameters, and then quenching and cooling to obtain a zinc-iron coated part;

[0118] Determine the most suitable hot stamping process parameters according to the thickness of the preformed part, including the following steps:

[0119] When the thickness of the preformed part is less than 1.5 mm, the austenitizing heating temperature is 860 ° C and the austenitizing holding time is 180 s;

[0120] The heating rate of austenitizing heating is 25°C / min, and the dew point temperature of austenitizing heating is -5°C.

[0121] The hot stamping process also includes cooling in the form of die pressure-maintaining and shape-correcting cooling, with the initial cooling temperature being 750°C;

[0122] When cooling includes mold pressure-holding and shape-correcting cooling, the pressure of mold pressure-holding and shape-correcting cooling is 160t, the time of mold pressure-holding and shape-correcting cooling is 10s, and the cooling rate of mold pressure-holding and shape-correcting cooling is ≥30℃ / s;

[0123] The chemical composition of the zinc-containing plating solution meets the following requirements: Al: 0.16%, Fe: 0.01%, and the rest is Zn and unavoidable impurities

[0124] The temperature of the zinc-containing plating solution is 465°C and the hot-dip plating time is 8s.

[0125] The alloying treatment temperature is 490°C and the alloying treatment time is 8s.

[0126] The temperature of the annealing substrate was 460°C.

[0127] A zinc-iron coated part is prepared by a preparation method. The zinc-iron coated part comprises a steel substrate, an inhibition layer and a zinc-iron coating from the inside to the outside. The thickness h1 of the zinc-iron coating, the thickness h2 of the inhibition layer and the thickness h3 of the steel substrate satisfy the relationship: h1:h2:h3=11.49:2:1200.

[0128] The chemical composition of the steel matrix satisfies, by mass fraction, the following: C: 0.21%, Si: 0.18%, Mn: 1.10%, Cr: 0.21%, Mo: 0.002%, Ti: 0.02%, Nb: 0.01%, V≤0.02%, B: 0.003%, P: 0.004%, S: 0.002%, Al: 0.05%, and the rest is Fe and unavoidable impurities;

[0129] The chemical composition of the zinc-iron coating satisfies: Al: 0.16%, Fe: 9.2%, and the remaining elements are Zn and unavoidable impurities.

[0130] Example 2

[0131] Based on the contents disclosed in Example 1, the following modifications are further made:

[0132] When the thickness of the preformed part is less than 1.5 mm, the austenitizing heating temperature is 860° C., and the austenitizing holding time is 240 s.

[0133] The pressure of the mold pressure-holding and shape-correcting cooling is 160t, the time of the mold pressure-holding and shape-correcting cooling is 12s, and the cooling rate of the mold pressure-holding and shape-correcting cooling is ≥30℃ / s.

[0134] Example 3

[0135] Based on the contents disclosed in Example 1, the following modifications are further made:

[0136] A 1.6 mm annealed substrate was selected.

[0137] When the thickness of the preformed part is greater than or equal to 1.5 mm and less than 2.0 mm, the austenitizing heating temperature is 880° C. and the austenitizing holding time is 240 s.

[0138] The pressure of mold pressure-holding and shape-correcting cooling is 160t, the holding time is 10s, and the cooling speed of mold pressure-holding and shape-correcting cooling is

[0139] ≥30℃ / s.

[0140] Example 4

[0141] Based on the contents disclosed in Example 1, the following modifications are further made:

[0142] A 1.6 mm annealed substrate was selected.

[0143] When the thickness of the rough part is greater than or equal to 1.5 mm and less than 2.0 mm, the austenitizing heating temperature is 890° C. and the austenitizing holding time is 180 s.

[0144] The pressure of mold pressure holding and shaping cooling is 160t, the holding time is 12s, and the cooling speed of mold pressure holding and shaping cooling is

[0145] ≥30℃ / s;

[0146] Comparative Example 1

[0147] Based on the contents disclosed in Example 1, the following modifications are further made:

[0148] The austenitizing heating temperature and the austenitizing holding time are not adjusted according to the thickness of the preformed parts, and the treatment is directly carried out according to the conventional heating temperature of 840°C and the austenitizing holding time of 180s.

[0149] The pressure of the mold pressure-holding and shape-correcting cooling is 160t, the time of the mold pressure-holding and shape-correcting cooling is 12s, and the cooling rate of the mold pressure-holding and shape-correcting cooling is ≥30℃ / s.

[0150] Comparative Example 2

[0151] Based on the contents disclosed in Example 3, the following modifications are further made:

[0152] When the thickness of the preformed part is greater than or equal to 1.5 mm and less than 2.0 mm, the austenitizing heating temperature is 900° C. and the austenitizing holding time is 300 s.

[0153] The pressure of the mold pressure-holding and shape-correcting cooling is 160t, the time of the mold pressure-holding and shape-correcting cooling is 12s, and the cooling rate of the mold pressure-holding and shape-correcting cooling is ≥30℃ / s.

[0154] Related experiments and effect data:

[0155] The zinc-iron plated parts obtained in Example 1 and Comparative Example 2 were observed by scanning electron microscope. Figure 3 As shown, in the BED mode of SEM, the α-Fe(Zn) phase is gray and the Г-FeZn phase is white. Figure 3 The volume proportion of the Г-FeZn phase is only ≤10%.

[0156] This is mainly due to the use of a lower austenitizing heating temperature and a shorter austenitizing holding time in the alloy heat treatment, which can reduce the diffusion rate of iron into the zinc-iron coating, which is conducive to the formation of zinc-rich Г-FeZn phase. In addition, this organizational process can prevent the growth thickness of the Γ-FeZn phase from being too large, so that the risk of zinc-iron coated parts being broken due to the bending of a large number of brittle Γ phases during the subsequent stamping process of the alloy heat treatment can be reduced.

[0157] The zinc-iron plated parts obtained in the embodiment and the comparative example were subjected to microstructure inspection and performance testing, and the results are shown in Table 1.

[0158] Table 1 Microstructure distribution and performance results of zinc-iron coated parts in various embodiments and comparative examples

[0159]

[0160]

[0161] In Table 1, the results of the ultimate bending strain are based on the ultimate bending strain detection device and the ultimate bending strain detection method described in CN202111088877.7. The ultimate bending strain of the part is measured locally, and the result evaluation is divided into three levels: when the measured ultimate fracture strain value is greater than 0.5, the rating of the sample is marked as A; when the measured ultimate fracture strain is greater than or equal to 0.25 and less than or equal to 0.5, the rating of the sample is marked as B; when the measured ultimate fracture strain is less than 0.25, the rating of the sample is marked as C. Among them, when the measured ultimate strain level is A or B, it indicates that the part is qualified; when the measured ultimate strain level is C, the sampling is repeated twice for measurement. If the results of both times are A or B, the final evaluation of the part is qualified, otherwise the final evaluation of the part is unqualified.

[0162] The zinc-iron plated parts obtained in Examples 1 to 3 and Comparative Example 1 were examined by scanning electron microscopy. The results are as follows: Figure 4 and Figure 5 As shown, combined Figure 4 , Figure 5As shown in Table 1, the microstructures of the parts all include a large amount of martensite using four different alloy heat treatment processes. However, Example 1 uses a lower austenitizing heating temperature of 860°C and a shorter austenitizing holding time of 180s. The microstructure of the zinc-iron coated parts obtained also includes some ferrite. However, the performance of the zinc-iron coated parts of Example 1 finally meets the target value. In addition, the data from Examples 1 to 3 show that the thickness of the zinc-iron coating increases by more than one time after the alloying heat treatment, which indicates that the alloying heat treatment The process increases the mutual penetration rate of zinc and iron elements between the zinc-iron coating and the steel matrix in the rough parts to improve the alloying rate of the two, thereby achieving a rapid and uniform advancement of the zinc-iron alloying process, and ultimately increasing the thickness of the coating; in addition, the alloying heat treatment with increased rate retains only a small amount of zinc-rich Г-FeZn phase in the zinc-iron coating, thereby causing the zinc-iron coating to be mainly composed of α-Fe (Zn) phase, which can reduce the sensitivity of the rough parts to liquid metal embrittlement during the alloying hot pressing process, so as to ultimately obtain a zinc-iron coated parts product with performance that meets expectations.

[0163] In addition, although comparative example 1 obtained a zinc-iron plated component product with expected performance, it used too high a temperature and too long a holding time, which increased the production cost and also caused other performances of the product to deteriorate.

[0164] In summary, the embodiment of the present application provides a method for preparing a zinc-iron coated part, which clarifies that the thickness of the preformed part is positively correlated with the temperature of austenitizing heating and the time of austenitizing insulation during hot stamping. The growth thickness of the Γ-FeZn phase in the zinc-iron coating in the preformed part can be controlled, and the content of the brittle Γ phase in the zinc-iron coating can be reduced, thereby reducing the sensitivity of the preformed part to liquid metal embrittlement during the hot stamping process, so as to ultimately obtain a zinc-iron coated part product with expected performance.

[0165] In addition, a zinc-iron coated part provided in an embodiment of the present application can improve the corrosion resistance of the zinc-iron coated part during service by redesigning the composition of the steel substrate and the zinc-iron coating, thereby greatly increasing the service life of the zinc-iron coated part.

[0166] The above is only a specific implementation of the present application, so that those skilled in the art can understand or implement the present application. It will be apparent to those skilled in the art that various modifications to these embodiments are possible, and the general principles defined in the present application can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown in the present application, but will conform to the widest scope consistent with the principles and novel features applied for by the present application.

Claims

1. A method for preparing a zinc-iron plated part, characterized in that: The preparation method comprises: Annealing the steel substrate of the part to obtain an annealed substrate; The annealed substrate is hot-dip plated with a zinc-containing plating solution, and then the annealed substrate in the zinc-containing plating solution is alloyed to form an iron-zinc coating on the surface of the annealed substrate to obtain a raw steel plate containing a zinc-iron coating; The raw steel plate containing zinc and iron coating is cold stamped to obtain a preformed part; Determining the most suitable hot stamping processing parameters according to the thickness of the preformed part; and Using the most suitable hot stamping processing parameters to perform hot stamping processing on the preformed part, and then quenching the preformed part after the hot stamping processing to obtain a zinc-iron plated part; Wherein, the hot stamping processing parameters include the austenitizing heating temperature and the austenitizing holding time; The thickness of the preformed part is positively correlated with the temperature of the austenitizing heating, and the thickness of the preformed part is positively correlated with the austenitizing heat preservation time.

2. The preparation method according to claim 1, characterized in that: The austenitizing heating temperature is 855° C. to 895° C., and the austenitizing heat preservation time is 150s to 300s.

3. The preparation method according to claim 1 or 2, characterized in that: Determining the most suitable hot stamping processing parameters according to the thickness of the preformed part comprises the steps of: When the thickness of the preformed part is less than 1.5 mm, the austenitizing heating temperature is 855° C. to 875° C., and the austenitizing holding time is 150 s to 250 s. When the thickness of the preformed part is greater than or equal to 1.5 mm and less than 2.0 mm, the austenitizing heating temperature is 865° C. to 885° C., and the austenitizing holding time is 180 s to 280 s; When the thickness of the preformed part is greater than or equal to 2.0 mm and less than or equal to 2.5 mm, the temperature of the austenitizing heating is 875° C. to 895° C., and the austenitizing holding time is 200 s to 300 s.

4. The preparation method according to claim 1, characterized in that: The austenitizing heating heating rate is ≥25°C / min, and the dew point temperature of the austenitizing heating is ≤-5°C.

5. The preparation method according to claim 1, characterized in that: The hot stamping treatment further comprises cooling by means of die pressure keeping and shaping and / or aerosol cooling, wherein the initial temperature of the cooling is 650° C. to 780° C.; and / or In the case where the cooling includes mold pressure-maintaining and shape-correcting cooling, the pressure of the mold pressure-maintaining and shape-correcting cooling is ≥160t, the time of the mold pressure-maintaining and shape-correcting cooling is 10s-15s, and the cooling rate of the mold pressure-maintaining and shape-correcting cooling is ≥30°C / s; In the case where the cooling includes aerosol cooling, the pressure of the aerosol cooling is ≥ 0.5 MPa, and the cooling rate of the aerosol cooling is ≥ 30° C. / s.

6. The preparation method according to claim 1, characterized in that: The chemical composition of the zinc-containing plating solution, measured by mass fraction, satisfies the following: Al: 0.10% to 0.25%, Fe: 0.01% to 0.03%, and the remainder is Zn and unavoidable impurities; and / or The temperature of the zinc-containing plating solution is 420° C. to 480° C., and the time of the hot-dip plating is 2s to 8s.

7. The preparation method according to claim 1, characterized in that: The temperature of the alloying treatment is 470° C. to 530° C., and the time of the alloying treatment is 10s to 20s.

8. The preparation method according to claim 1, characterized in that: The thickness of the zinc-iron coating in the crude steel plate containing the zinc-iron coating is 9 μm to 15 μm; and / or The temperature of the annealing substrate is 410° C. to 470° C.; and / or The temperature of the quenching treatment is 650° C. to 780° C., and the time of the quenching treatment is 10s to 15s.

9. A zinc-iron coated part, characterized in that: The zinc-iron coated part is prepared by the preparation method described in any one of claims 1 to 8, and the zinc-iron coated part comprises a steel substrate, an inhibition layer and a zinc-iron coating from the inside to the outside, and the thickness h1 of the zinc-iron coating, the thickness h2 of the inhibition layer and the thickness h3 of the steel substrate satisfy the relationship: h1:h2:h3=(15-25):2:(700-2500).

10. The zinc-iron coated part according to claim 9, characterized in that: The chemical composition of the steel matrix satisfies, by mass fraction, the following: C: 0.05% to 0.30%, Si: 0.05% to 0.2%, Mn: 0.6% to 2.2%, Cr≤0.35%, Mo≤0.22%, Ti: 0.01% to 0.02%, Nb≤0.02%, V≤0.02%, B: 0.002% to 0.008%, P≤0.005%, S≤0.005%, Al: 0.02% to 0.10%, and the rest is Fe and unavoidable impurities; and / or Calculated by mass fraction, the chemical composition of the zinc-iron coating satisfies: Al: 0.10% to 0.25%, Fe: 7% to 16%, and the remaining elements are Zn and unavoidable impurities.

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