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JP-7855618-B2 - Hot stamping parts and their manufacturing method

JP7855618B2JP 7855618 B2JP7855618 B2JP 7855618B2JP-7855618-B2

Inventors

  • チャン、ミンホ
  • チャン、クンウ

Assignees

  • ヒュンダイ スチール カンパニー

Dates

Publication Date
20260508
Application Date
20220127
Priority Date
20210630

Claims (10)

  1. Steel plate and Located on the aforementioned steel plate, a plating layer containing Zn, The plated layer includes a surface layer located on the aforementioned plating layer, The aforementioned surface layer is A post-treatment layer containing a Si-based inorganic post-treatment agent, A Zn oxide layer located on the aforementioned plating layer in the same layer as the post-treatment layer, Between the post-treatment layer and the Zn oxide layer and the plating layer, there is an interdiffusion layer located superimposed on the post-treatment layer and the Zn oxide layer, which contains at least one of Si, Mn, O, Fe, Zn, and SiO, The post-treatment layer comprises 20-90 wt% Si, 0-15 wt% Mn, 10-80 wt% O, 0-15 wt% Fe, and 0-15 wt% Zn. The interdiffusion layer comprises 15-35 wt% Si, 0-15 wt% Mn, 35-80 wt% O, 0-15 wt% Fe, and 5-40 wt% Zn. The average Zn content of the interdiffusion layer is greater than the average Zn content of the post-treatment layer, and the average Zn content of the Zn oxide layer is greater than the average Zn content of the interdiffusion layer. The area fraction of the interdiffusion layer is 10% to 80% of the total area fraction of the post-treatment layer. A hot-stamped component having an average thickness of 0.1 μm to 2 μm in the aforementioned interdiffusion layer .
  2. The average thickness of the post-treatment layer is thinner than the average thickness of the Zn oxide layer. The hot stamping part according to claim 1, wherein the average thickness of the post-treatment layer is 5% or more and less than 100% of the average thickness of the Zn oxide layer.
  3. The average thickness of the post-treatment layer is 0.5 μm to 3 μm. The hot stamping part according to claim 2 , wherein the average thickness of the Zn oxide layer is 1 μm to 10 μm.
  4. A heating step in which a steel plate with a Si-based inorganic post-treatment agent applied to a Zn-containing plating layer is placed in a heating furnace and heated, A transfer step of transferring the heated steel plate from the heating furnace to a press die, The molding step involves hot stamping the transferred steel plate to form a molded body, The step includes cooling the molded body, In the aforementioned heating step, The inorganic post-treatment agent and the components of the plating layer are diffused to form an interdiffusion layer, a post-treatment layer, and a Zn oxide layer obtained by oxidizing the plating layer. The interdiffusion layer is located between the post-treatment layer and the Zn oxide layer and the plating layer, superimposed on the post-treatment layer and the Zn oxide layer, and contains at least one of Si, Mn, O, Fe, Zn, and SiO. The post-treatment layer comprises 20-90 wt% Si, 0-15 wt% Mn, 10-80 wt% O, 0-15 wt% Fe, and 0-15 wt% Zn. The interdiffusion layer comprises 15-35 wt% Si, 0-15 wt% Mn, 35-80 wt% O, 0-15 wt% Fe, and 5-40 wt% Zn. The average Zn content of the interdiffusion layer is greater than the average Zn content of the post-treatment layer, and the average Zn content of the Zn oxide layer is greater than the average Zn content of the interdiffusion layer. In the aforementioned heating step, The steel plate is heated in the heating furnace to a target heating temperature having a temperature range of Ac1 to 910°C. The steel plate is heated so that the average heating rate of the steel plate in the section from 700°C to the target heating temperature is 1.5°C/sec to 7°C/sec, thereby forming the interdiffusion layer . The area fraction of the interdiffusion layer is formed to be between 10% and 80% of the total area fraction of the post-treatment layer. A method for manufacturing hot-stamped parts, wherein the average thickness of the interdiffusion layer is formed to be 0.1 μm to 2 μm .
  5. The average thickness of the post-treatment layer is thinner than the average thickness of the Zn oxide layer. The method for manufacturing a hot stamped part according to claim 4 , wherein the average thickness of the post-treatment layer is 5% or more of the average thickness of the Zn oxide layer.
  6. The average thickness of the post-treatment layer is 0.5 μm to 3 μm. The method for manufacturing a hot stamped part according to claim 5 , wherein the average thickness of the Zn oxide layer is formed to be 1 μm to 10 μm.
  7. In the aforementioned heating step, The method for manufacturing a hot stamped part according to claim 4 , wherein the steel plate is heated while remaining in place for 120 to 600 seconds.
  8. Prior to the aforementioned heating step, The method for manufacturing a hot stamped part according to claim 4 , further comprising a post-treatment step of applying the Si-based inorganic post-treatment agent onto the steel sheet on which the plating layer is formed, drying it, and forming a pre-post-treatment layer.
  9. In the aforementioned post-processing step, The method for manufacturing hot stamped parts according to claim 8, wherein the inorganic post-treatment agent is applied to the steel plate to a thickness of 0.5 μm to 3 μm to form the pre-post-treatment layer, and the amount of inorganic post-treatment agent applied is 0.5 g/ m² to 3 g/ m² .
  10. In the aforementioned post-processing step, The method for manufacturing a hot stamped part according to claim 8 , wherein the steel plate to which the inorganic post-treatment agent has been applied is dried at a temperature of 70°C to 150°C for 1 to 10 seconds.

Description

This invention relates to hot stamping parts and a method for manufacturing the same. High-strength steel is used in automotive parts for weight reduction and stability. However, while high-strength steel can achieve high strength relative to its weight, the increased strength reduces press formability, leading to material fracture or springback during processing, making it difficult to form complex and precise shapes. One solution to address these problems is the hot stamping method, and interest in it is growing, along with active research into materials for hot stamping. For example, as disclosed in Korean Patent Publication No. 10-2017-0076009, the hot stamping method is a forming technique that manufactures high-strength parts by heating a hot stamping steel sheet to a high temperature, then rapidly cooling it simultaneously with forming it in a press die. Related technologies include Korean Patent Publication No. 10-2018-0095757 (Title of Invention: Method for Manufacturing Hot Stamped Parts). On the other hand, hot-stamping steel sheets have a problem in that the surface of the steel sheet oxidizes during heating, generating scale. This reduces the surface properties and paintability of the product, and the corrosion resistance is inferior to that of plated materials. Therefore, a separate process such as shot blasting or shot peening is required after product formation to remove the scale. Alternatively, to prevent the aforementioned problems, a method has been used in which an Al-based plating layer is used to suppress the oxidation reaction on the surface of the steel sheet and induce the formation of an Al passive film, thereby increasing the corrosion resistance of the steel sheet. However, in the case of such Al-plated materials, while the heat resistance is excellent, the corrosion resistance is inferior to that of Zn-plated materials, and there is a problem of increased manufacturing costs. However, Zn-based hot-stamped steel sheets are susceptible to significant deterioration in paint adhesion and appearance due to the oxidation of Zn that occurs during the hot-stamping heat treatment. While post-treatment processes such as shot peening have been introduced to address this, they introduce additional costs and processes, leading to decreased productivity. This is a flowchart illustrating a method for manufacturing hot-stamped parts according to one embodiment of the present invention.This is a TEM (transmission electron microscope) image showing a portion of the material before the hot stamping process according to one embodiment of the present invention.This is a TEM image showing a part of a component after the hot stamping process according to one embodiment of the present invention.This is a cross-sectional view showing a part after a hot stamping process according to one embodiment of the present invention.Figure 2 is a magnified TEM image of a portion of the part after the hot stamping process.This drawing compares the adhesion evaluation of a hot stamped part according to a comparative example and a hot stamped part according to one embodiment of the present invention. The present invention can have various embodiments through diverse modifications; specific embodiments are illustrated in the drawings and described in detail in the detailed description. The effects and features of the present invention, and the methods for achieving them, will become clear when referred to the embodiments described in detail below, along with the drawings. However, such inventions are not limited to the embodiments disclosed below and can be embodied in a variety of forms. In the following embodiments, terms such as "first," "second," etc., are used not in a restrictive sense, but to distinguish one component from another. In the following examples, the singular expression includes plural expressions unless the context clearly indicates otherwise. In the following embodiments, terms such as "includes" or "has" mean that the features or components described in the specification are present, and do not preclude the possibility of adding one or more other features or components. In the following embodiments, when a part such as a film, region, or component is located on or above another part, this includes not only cases where it is directly above the other part, but also cases where another film, region, or component is interposed between them. In drawings, the size of components may be exaggerated or reduced for illustrative purposes. For example, the size and thickness of each component shown in the drawings are arbitrarily shown for illustrative purposes, and the present invention is not necessarily limited to what is shown. If a particular embodiment can be manifested in a different way, a specific sequence of steps may be performed in a different order than that described. For example, two steps described consecutively may be performed substantially simultaneously and in reverse order of the descrip