Manufacturing method of hot stamping product

Abstract

Provided is a method for manufacturing a hot-pressed product, whereby adhesion (adhesion) of an aluminum plating layer of an aluminum-plated steel sheet to a mold can be easily and effectively suppressed or prevented in a hot-pressing step. Provided is a method for producing a hot-stamped product from an aluminum-plated steel sheet by a hot-stamping step, in which a non-flammable and non-volatile water-soluble chemical agent is applied to the surface of a mold facing the aluminum-plated steel sheet, and then the product is produced.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a hot stamping product by manufacturing a product (including a component) from a steel plate using a hot stamping (hot pressing) process, and in particular to a method for manufacturing a hot stamping product by which the adhesion (adhesion) of an aluminum coating layer to a hot stamping die can be suppressed or prevented when the product is manufactured from an aluminum-plated steel plate. Background Art

[0002] The hot stamping process is as follows Figure 1 First, prepare Figure 1 The steel plate material 1 shown in (A) is carried into Figure 1 (B) The heating furnace 2 is heated (for example, 900°C) and the mold is pressurized to perform the following steps: Figure 1 (C) is formed and quenched to form a molded product 3, and the molded product 3 is appropriately processed to finally obtain a molded product as shown in FIG. Figure 1 (D) shows the product 4. In this case, an aluminum-plated steel sheet is generally used as the steel sheet material 1 in order to prevent oxidation of the steel material and improve corrosion resistance.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2005-146354

[0006] Patent document 2: WO2011 / 158818

[0007] Patent Document 3: WO2013 / 145229

[0008] Patent Document 4: Japanese Patent Application Publication No. 2022-185340 Summary of the invention

[0009] Technical problem to be solved by the invention

[0010] Here, in the case of using an aluminum-plated steel sheet as a raw material steel sheet, in hot stamping in which the steel sheet is heated to austenite transformation temperature (Ac3 point) or higher and the heated steel sheet is press-formed and quenched, as shown in FIG. Figure 2 As shown in (A), the hot stamping furnace is heated and then transported, and the hot stamping furnace is used as shown in Figure 2 (B) The dies 10 and 11 with concave and convex shapes shown in FIG. 1 are quenched and formed. However, during this forming, the aluminum plating cannot follow the deformation of the raw material (steel), causing the aluminum plating to peel off from the steel plate, and the aluminum plating is firmly attached (adhered) to the die surface. Figure 3 (A) and Figure 3(B) shows the actual state of the aluminum coating attached to the mold. When the aluminum coating is attached to the mold, the attachment will be transferred to the subsequent product, resulting in scratches and other damage. Figure 4 (A) The product dents, or Figure 4 Appearance scratches (scratches) such as the scratches shown in (B) lead to poor product quality. Poor product quality is a fatal problem.

[0011] The deposits (aluminum coating) attached to the mold are very strong and cannot be removed by simple operations such as scraping with hands or wiping with cloth. They must be removed by mechanical operations such as scraping with a grinder. However, when scraping with a grinder, the mold surface and the attached aluminum coating are often scraped off, causing expensive mold wear and deterioration.

[0012] As a countermeasure, a coating (such as DLC (diamond-like carbon), AlCrN, AlCrTi) is usually applied to the mold surface, but the effect of suppressing the adhesion of the aluminum coating to the mold is small, and there is also a problem that the coating is damaged due to molding. Figure 5 In addition, when trying to remove the attached matter using a grinder, etc., the coating may be damaged or peeled off, so the effect of the coating is extremely short-lived.

[0013] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for manufacturing a hot stamped product that can easily and effectively suppress or prevent the aluminum plating layer of an aluminum-plated steel sheet from adhering (sticking) to a die during a hot stamping process.

[0014] Technical solutions adopted to solve technical problems

[0015] The present invention relates to a method for manufacturing a product made of aluminum-plated steel sheets by a hot stamping process. The above-mentioned purpose of the present invention is achieved by the following means, namely, preparing a non-flammable and non-volatile water-soluble agent with a mixing ratio of 1 to 25 parts (weight %) of a high molecular polymer, a mixing ratio of 50 to 98 parts (weight %) of water, and a mixing ratio of 1 to 25 parts (weight %) of a surfactant, and after applying the above-mentioned water-soluble agent on the surface of a mold facing the above-mentioned aluminum-plated steel sheet, manufacturing the above-mentioned product, and suppressing or preventing the aluminum coating from adhering to the above-mentioned mold by applying the above-mentioned water-soluble agent on the surface of the above-mentioned mold. By regularly implementing the above-mentioned coating, the above-mentioned purpose of the present invention can be more effectively achieved.

[0016] Effects of the Invention

[0017] According to the manufacturing method of hot stamping products of the present invention, by coating a water-soluble agent composed of a high molecular polymer, water and a surfactant on the surface of the hot stamping die of the aluminum-plated steel plate, it is possible to inhibit or prevent the aluminum coating from adhering (sticking) to the die, thereby improving the quality of the product, and eliminating the need for a grinding machine or other process for removing the attachments, thereby reducing the wear and degradation of the expensive die. Therefore, the economic benefits of product manufacturing are very large.

[0018] In order to inhibit or prevent the aluminum plating from adhering to the mold, a water-soluble agent can be applied to the entire surface of the mold using a sprayer or by hand, and a very simple operation can produce a good effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a schematic flow chart of an example of a hot stamping process.

[0020] Figure 2 This is a schematic flow chart showing the heating and quenching conditions of an aluminum-plated steel plate.

[0021] Figure 3 This is an image showing an example of aluminum plating attached to a mold.

[0022] Figure 4 This is an example of an image of a mold attachment being transferred onto a product.

[0023] Figure 5 This is an image diagram showing an example of peeling of the mold coating.

[0024] Figure 6 It is a schematic diagram of the concept that forms the premise of the present invention.

[0025] Figure 7 It is a schematic flow chart for explaining the principle of the present invention.

[0026] Figure 8 This is an appearance diagram of a square head drawing die used to demonstrate the effect of the present invention.

[0027] Fig. 9 This is an appearance diagram of a component that demonstrates the effects of the present invention.

[0028] Fig.10 This is a conceptual diagram for explaining the composition of the water-soluble drug of the present invention. DETAILED DESCRIPTION

[0029] The inventors of the present invention speculate that the main reason why the aluminum plating layer is attached (adhered) to the mold is that aluminum (Al) is hydrophilic and iron (Fe) as the material of the mold is also hydrophilic (see Figure 6 (A)), due to Figure 6(B) The aluminum coating adheres to the iron due to the hydrogen bonding effect shown in Figure 2. Based on this assumption, in order to inhibit or prevent the aluminum coating from adhering to the mold, after repeated experiments, it was found that as long as the Figure 6 (B) The hydrogen bond shown is sufficient.

[0030] Therefore, the inventors speculate that as long as a layer of a water-soluble substance is provided on the surface of the mold, the above-mentioned hydrogen bond can be hindered or prevented. By making a water-soluble agent as a water-soluble substance and conducting an experiment, it is found that a significant effect can be produced. The water-soluble agent is formed by mixing a high molecular polymer, water and a surfactant, which is non-flammable and non-volatile, has a lubricity with a low friction coefficient for the aluminum coating, and has good residue film retention. Surfactants include anionic surfactants (anions), cationic surfactants (cations), amphoteric surfactants (amphoteric), nonionic surfactants (nonionic), etc., and any of them can be used. Stamping oil is generally used in cold forming, but stamping oil is highly flammable and produces hot air, so it is a necessary condition that the water-soluble agent of the present invention is a particularly non-flammable water-soluble agent.

[0031] The water-soluble drug of the present invention is produced according to the following mixing ratio.

[0032] High molecular weight polymer: 1-25 parts (weight %)

[0033] Water: 50-98 parts (weight %)

[0034] Surfactant: 1-25 parts (weight %)

[0035] By mixing and stirring in the above-mentioned ratio, the water-soluble agent of the present invention can be manufactured. If it is not adjusted within this range, the film quality, film thickness, and lubrication effect are affected, resulting in the ability to inhibit or prevent the aluminum plating layer from adhering (adhering) to the mold, as well as the weldability and degreasing performance being impaired.

[0036] In the present invention, Figure 7 As shown in (A), a water-soluble agent is uniformly applied to the entire surface of the mold 30 using a sprayer or the like, and then, as shown in Figure 7 As shown in (A), a steel plate material 20 consisting of a plate (steel plate) 21 and an aluminum coating 22 heated to a high temperature is conveyed to a mold 30 coated with a water-soluble agent in a heating furnace. From the perspective of work efficiency, the water-soluble agent is preferably applied by spraying with a sprayer, but it can also be applied manually using a brush or the like.

[0037] When the high temperature steel plate raw material 20 is transported to the mold 30, the water-soluble agent coated on the surface of the mold 30 evaporates only the water due to the high temperature steel plate material 20 approaching, and the high molecular polymer and the surfactant remain as residues, such as Figure 7As shown in (C), the residue films 40 and 41 are formed. The residue film 40 physically blocks the aluminum plating layer 22 and the mold 30 to form hydrogen bonds, thereby suppressing or preventing the aluminum plating layer 22 from being attached to the mold 30.

[0038] If the retention of the residue film 40 is good, the quality of the hot stamping product can be maintained for a long time, which is economical, so the retention of the residue film 40 of the water-soluble agent is very important. If the retention is poor, the water-soluble agent must be applied frequently. Even if the retention is good, in order to achieve uniformity of the coating surface, appropriate coating amount, and maintenance of the residue film, it is necessary to apply the water-soluble agent regularly.

[0039] Figure 8 An example of a square head drawing die for evaluating the adhesion of aluminum plating is shown. A die coated with the water-soluble agent of the present invention and a die not coated with the water-soluble agent are used. After 12 hot stamping steps, the adhesion (convex part) is measured using a three-dimensional measuring instrument for comparison. The results are as follows. Fig. 9 As shown in the figure, the remarkable effect of the present invention was confirmed. That is, when the water-soluble agent was not applied, the aluminum plating layer was already attached to the mold at the 12th hot pressing after application, while when the aqueous solution agent was applied, even if the hot pressing was repeated 12 times after application, no aluminum plating layer was confirmed to be attached to the mold.

[0040] The water-soluble agent of the present invention, which exerts the above effects, inhibits or prevents the aluminum plating from adhering to the mold, but the effect on spot weldability needs to be considered. Spot welding (or resistance spot welding) is a method of connecting metals together using the electrical resistance of metals, but if the concentration of high molecular weight polymers is high, Fig.10 As shown in (A), the amount of residue carried out of the molded product increases, the current resistance becomes larger, and spattering occurs, resulting in poor weldability. Therefore, in order to ensure spot weldability, the present invention increases the mixing ratio of water to polymer, and produces a water-soluble agent that does not impair spot weldability and can prevent spattering. That is, if the concentration of the polymer is low, Fig.10 As shown in (B), the amount of residue carried out of the molded product is reduced, the resistance to current conduction is also reduced, and splashing is not caused. Therefore, the balance between the polymer and the spray frequency is important.

[0041] If the spray frequency is high, the retention of the residue film will increase, and the amount of reagent used (cost) will also increase. The concentration of the polymer affects the weldability and the retention of the residue film. In the case of low concentration, the weldability and the retention of the residue film deteriorate. In the case of using a low concentration to ensure weldability, the retention of the residue film will decrease, so it is necessary to increase the spray frequency. In this way, the balance between the spray frequency and the reagent concentration becomes a compromise between weldability and reagent cost, and there is a standard for weldability.

[0042] In addition, for example, water repellency in the vehicle body painting process has a trend of water repellency → poor degreasing → poor film adhesion → reduced corrosion resistance of the actual vehicle → corrosion → reduced strength → reduced safety, which will reduce the safety of the vehicle body. Therefore, as the agent is applied, it is necessary to determine whether water repellency as a characteristic exists. By using a water-soluble high molecular polymer, the residue attached to the molded product is degreased in the film coating process, which can suppress the deterioration of the film coating. As compounds that can be added to the agent, compounds such as fluorine and silicon tend to show water repellency, but fluorine compounds and silicon compounds with high water repellency are difficult to degrease, so they are not included in the water-soluble agent of the present invention.

[0043] Explanation of symbols

[0044] 1,20 Steel Plate Raw Materials

[0045] 2Heating furnace

[0046] 3Molding products

[0047] 4 products

[0048] 10, 11, 30, 31 molds

[0049] 40, 41 residue film.

Claims

1. A method for manufacturing a hot stamping product, which is a method for manufacturing a product from an aluminum-plated steel sheet by a hot stamping process, wherein: A nonflammable and nonvolatile water-soluble agent is prepared, wherein the mixing ratio of the polymer is 1 to 25 parts (weight %), the mixing ratio of water is 50 to 98 parts (weight %), and the mixing ratio of the surfactant is 1 to 25 parts (weight %), After applying the water-soluble agent on the surface of the mold facing the aluminum-plated steel plate, the product is manufactured. The water-soluble agent is applied to the surface of the mold to inhibit or prevent the aluminum plating layer from adhering to the mold.

2. The method for manufacturing a hot stamped product according to claim 1, wherein: The coating is performed periodically.

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