METHOD FOR MANUFACTURING AN ARTICLE FORMED BY HOT PRESSING AND AN ARTICLE FORMED BY HOT PRESSING

Abstract

This method of manufacturing a hot-pressed formed article includes a heating step of heating an Al-plated steel sheet and a forming step of obtaining a hot-pressed formed article using a die. After the heating step, the Al-plated steel sheet has a base steel sheet, an Al plating layer, and a coating layer. The coating layer is a metal layer containing at least one of the metals Mg, Ca, V, Ti, and Zn, a metal oxide layer containing an oxide of one or more of Mg, Ca, V, Ti, and Zn, or a mixed layer that includes the metal layer and the metal oxide layer. The die has a hard layer on one surface, HVMatriz, which is a surface hardness of the die at a position of the hard layer, being HV1500 or more and HV3800 or less.and a temperature Tm of the aluminum-clad steel sheet at the beginning of forming and an average movement speed V of the die in the forming step satisfy 800 - (HVMatriz / 40) = Tm = 850 - (V / 4) - (HVMatriz / 100).,

Description

[1] The present invention relates to a method of manufacturing an article formed by hot pressing and an article formed by hot pressing. Priority is claimed over Japanese Patent Application No. 2020-074701, filed on April 20, 2020, the contents of which are incorporated herein by reference. Related technique [2] In recent years, there have been calls to eliminate the consumption of chemical fuels for environmental protection and to prevent global warming. Regarding this call, automobiles, which are indispensable for life and daily activities as a means of transportation, are no exception. In response to this call, studies are being conducted on improving fuel efficiency in automobiles by reducing the weight of vehicle bodies or similar components. Since most automobile structures are made of iron, particularly steel sheets, reducing the weight of steel sheets through thinning is significantly effective in reducing the weight of vehicle bodies.However, when the weight of a steel sheet is reduced simply by thinning it, there is concern that the structure's strength may decrease and safety may be compromised. Therefore, when thinning the steel sheet, it is necessary to increase the mechanical strength of the steel sheet used to avoid reducing the structure's strength. Therefore, research and development are underway regarding steel sheets capable of maintaining or increasing mechanical strength despite a thinner thickness compared to the steel sheets used to date by increasing the sheet's mechanical strength. This demand for steel sheets is true not only in the automotive manufacturing industry but also in a variety of other manufacturing industries. [3] In general, materials with high mechanical strength tend to have poor formability in processes such as bending, and when the material is to be processed into a complex shape, the processing itself becomes difficult. As one of the methods to overcome this problem with respect to formability, the so-called hot pressing method (also known as hot stamping, hot pressing, high-temperature pressing, warm pressing, or die tempering) is an illustrative example.In this hot pressing method, a material to be formed is heated once to a high temperature (e.g., 850°C or higher) to austenitize it. The softened material is then formed by pressing, and subsequently, or simultaneously with forming, the material is rapidly cooled with a die to undergo a martensitic transformation. This makes it possible to obtain a high-strength processed product after forming. [4] According to this hot pressing method, since the material is heated once to a high temperature to soften it and pressed in a softened state, the material can be easily pressed. Therefore, this hot pressing makes it possible to obtain a stamped article that has both good shape retention and high mechanical strength.In particular, when the material is steel, it is possible to increase the mechanical strength of a pressed article through the tempering effect of cooling after forming. [5] However, when this hot pressing method is applied to a steel sheet, heating the sheet to, for example, a high temperature of 800°C to 850°C or higher oxidizes the iron or similar material on the surface to form scale (rust). Therefore, a scale removal step (descaling step) is required after hot pressing, which reduces productivity.Furthermore, for a member or similar that requires corrosion resistance, there is a need to perform an anti-rust treatment or metal coating on the surface of the member after processing, and therefore a surface cleaning step and a surface treatment step are required, which also degrades productivity. [6] An example of a method to suppress such productivity degradation is a method in which a coating is applied to a steel sheet. Generally, a variety of materials, such as organic or inorganic materials, are used as coatings for steel sheets. Among these, zinc-based plating, which has a sacrificial protective action, is often applied to steel sheets from the standpoint of corrosion resistance and as a steel sheet production technique. Incidentally, the heating temperature in hot pressing is often higher than the Ac3 transformation temperature of the steel to achieve a quenching effect; the heating temperature is, for example, approximately 800°C to 1000°C.However, this heating temperature is higher than the decomposition temperatures of organic materials or the boiling points of metallic materials such as zinc-based metals. Therefore, if a steel sheet coated with an organic or zinc-based material is heated for hot pressing, there is a possibility that a coating layer will evaporate from the surface of the steel sheet, resulting in a significant deterioration of its surface properties. [7] In order to avoid such deterioration of the surface properties, it is preferable to coat a steel sheet, on which a hot pressing is to be carried out in which the steel sheet is heated to a high temperature, with, for example, an Al-based metal having a higher boiling point than organic material coatings or Zn-based metallic coatings. The use of a steel sheet with an aluminum-based metallic coating, known as aluminum-clad steel sheet, prevents scale from adhering to the surface and eliminates the need for steps such as descaling, thus improving productivity. Furthermore, since the aluminum-based metallic coating also has an anti-corrosive effect, it also enhances corrosion resistance after coating. [8] For example, Patent Document 1 describes a method in which an Al-plated steel sheet including an Al-based metallic coating provided over steel having a predetermined steel component is used for hot pressing. [9] However, when a conventional Al-plated steel sheet is hot-pressed for hot-press forming (a plated steel sheet having Al plating layers on both surfaces of the steel sheet), since an Al alloy plating layer on the surface of the Al plating layer or an oxide (alumina) film that forms on the surface of the Al alloy plating layer is hard, there is a case where the surface of a die wears down and, consequently, in particular, the shape of the die becomes distorted, which is a problem.

[10] With respect to this problem, Patent Document 2 describes a hot-pressed plated steel sheet in which a zinc-based metal soap coating is provided on the surface of the plated steel sheet body on the side of the aluminum plating layer. Patent Document 2 describes that the occurrence of wear on the sliding surface of a hot-press die (die) after hot-press forming is suppressed.

[11] However, in the technique of Patent Document 2, there was a case where a material and the die rubbed against each other during hot forming. Part of the metallic soap coating peeled off, causing die wear. When hot pressing was repeated several times, the surface irregularity of the worn die increased. In this case, there was either a problem of excoriation occurring on the material side after pressing or a problem of impaired sliding ability.

[12] With regard to this problem, in recent years studies have been carried out on improving the wear resistance of a matrix by performing a treatment to form a hard layer such as a nitriding treatment or a PVD treatment on the surface of a matrix material. For example, Patent Document 3 describes a technique in which a hard membrane is provided in a die used for hot pressing zinc-coated steel sheets. Furthermore, Patent Documents 4, 5, and 6 describe a technique in which, for hot pressing an aluminum- or zinc-coated steel sheet, or an aluminum-coated steel sheet having a zinc compound or a metallic zinc layer as the outermost layer over an aluminum coating layer, a die provided with a hard PVD membrane, such as a nitride, is used. Incidentally, press-formed articles used for automobiles and similar applications are also required to have a low gloss and a pleasing external appearance. This is because a high gloss is considered indicative of numerous defects in the formed article, and there is concern that corrosion resistance may be compromised. However, in hot stamping, a vertical wall portion typically rubs against a die, increasing the gloss and degrading the external appearance. In the case of using a technique where a die described in Patent Documents 3 to 6 is provided with a hard membrane, such as a nitriding or PVD coating, on the die surface, the hardness of the die surface presents a problem: a surface defect is likely to develop in the material.In particular, in a case where a hot pressing method such as hot stamping is used, since a material is rapidly pressed to bottom dead center in a high-temperature state, the surface of the material is in a high-temperature softened state, a die-shaped surface defect is more likely to occur, and the external appearance of the surface of a pressed article will deteriorate.

[13] That is, conventionally, when a formed article (hot-pressed formed article) is manufactured by hot-pressing an Al-plated steel sheet, it is difficult to ensure an excellent external surface appearance (low gloss) of the formed article and then suppress die wear. R7R7 ίη / ΖΖΩΖ / Ε / ΥΙΛΙ Previous technique document Patent Document

[14] Patent Document 1: Japanese Patent No. 3931251 Patent Document 2: Japanese Patent No. 6369659 Patent Document 3: Japanese Patent No. 6055324 Patent Document 4: Japanese Patent No. 6477867 Patent Document 5: Japanese Patent No. 6125313 Patent Document 6: International Publication of the PCT No. WO 2019-198728 Description of the invention Problems to be solved by the invention

[15] The present invention has been made with a view to the problem described above. An object of the present invention is to provide a method of manufacturing a hot-pressed article in order to obtain a hot-pressed article having an excellent external surface appearance (external appearance) while suppressing die wear and a hot-pressed article having an excellent external surface appearance. Means to solve the problem

[16] As a result of studies, the inventors hereof discovered that, when an Al-plated steel sheet is hot-pressed using a die having a hard layer formed on the surface to improve the wear resistance of the die, when the temperature of the aluminum-coated steel sheet at the beginning of forming (when the moving die comes into contact with the aluminum-plated steel sheet) is denoted by Tm in the unit of °C, and the average movement speed (hence called forming speed) of the die from the beginning of forming until the arrival of bottom dead center (when the die reaches bottom dead center) is denoted by V in the unit of mm / s, Tm and V satisfy the following formula (1), 800 - (HVMatriz / 4 0) < Tm < 850 - (V / 4) - (HVMatriz / 100) . . . Formula (1) In addition, a metal layer containing at least one of the metals Mg, Ca, V, Ti and Zn, a metal oxide layer containing an oxide of Mg, Ca, V, Ti or Zn, or a mixed layer of the metal layer and the metal oxide layer is formed on the surface of the Al-plated steel sheet that is being formed, so that it is possible to suppress the brightness of a formed article to a low level and obtain a hot-pressed formed article having an excellent external surface appearance. This formula (1) means that, in the event that a hard layer is present that improves wear resistance on the surface of a die, controlling the forming start temperature and the average movement speed of the die according to the hardness of the hard layer is important to obtain a hot-pressed article that has an excellent external surface appearance. The formula Tm 850 - (V / 4) - (HVMatriz / 100), which determines the upper limit of the forming start temperature, means that 1) as the temperature increases, the surface hardness of an aluminum-clad steel sheet gradually softens, making defects more likely. Therefore, it is important to suppress the forming start temperature to a certain temperature or lower; 2) during forming, the aluminum-clad steel sheet comes into contact with a die, removing heat and cooling the sheet. However, when the forming rate is high, heat removal is suppressed. Therefore, even when the forming start temperature is the same, as the forming rate increases, the surface of the aluminum-clad steel sheet is processed in a more softened state, thus necessitating further adjustments. R7R7 ίΠ / ZZΖηZ / E / YΙΛΙ reduce the formation start temperature according to the formation rate, and 3) the degree of ease in generating a defect is affected by the hardness of the hard layer on the surface of the die and therefore as the hardness of the die surface increases, there is a need to reduce the formation start temperature. Furthermore, Formula 800 - (HVMatriz / 40) d Tm, which determines the lower limit of the forming start temperature, means that when the forming start temperature is low, the surface of the aluminum-plated steel sheet hardens, the die side is likely to be damaged, and the die's wear resistance deteriorates. When the die's wear resistance deteriorates, the die surface becomes irregular due to the defect generated in the die, and as a result, the surface of the hot-pressed item is damaged due to the local stress concentration attributed to the die projections, and the external appearance of the surface deteriorates. The coefficients (1 / 4, 1 / 40 and 1 / 100) in Formula (1) are values ​​to convert the influence of Vickers hardness or formation rate derived from the inventors' experiences obtained so far and recently obtained temperature results R7R7 ίη / ΖΖΠΖ / Ε / ΥΙΛΙ experimentally .

[17] The present invention is based on the findings described above. The essence of the present invention is as described below. [1] A method of manufacturing a hot-stamped article according to an aspect of the present invention includes a heating step of heating an Al-plated steel sheet to 850°C to 1000°C and a forming step of forming the Al-plated steel sheet using a die to obtain a hot-molded article after the heating step, wherein the Al-plated steel sheet has a base steel sheet, an Al plating layer formed on a surface of the base steel sheet, and a coating layer formed on a surface of the Al coating layer, the coating layer being a metal layer containing at least one of the metals Mg, Ca, V, Ti, and Zn, a metal oxide layer containing an oxide of one or more of Mg, Ca, V, Ti, and Zn, or a mixed layer including the metal layer and the metal oxide layer, the die having a hard layer on a surface,HVMatriz, which is a surface hardness of the die at a position where the hard layer is present, is HV1500 or more and HV3800 or less, and, when a temperature of the Al-plated steel sheet at the beginning of forming is indicated by Tm in a unit of °C, and an average movement speed of the die from the start of forming until the arrival of a bottom dead center is indicated by V in a unit of mm / s, in the forming step, Tm and V satisfy the following formula (1). 800 - (HVMatrlz / 40) < Tm < 850 - (V / 4) - (HVMatrlz / 100) . . . Formula (1) [2] In the method of manufacturing an article formed by hot pressing in accordance with [1], HVMatriz, Tm and V can satisfy the following formula (2). 800 - (HVMatrlz / 40) < Tm < 850 - (V / 2) - (HVMatrlz / 50) . . . Formula (2) [3] In the method of manufacturing an article formed by hot pressing in accordance with [1] or [2], the thickness of the coating layer can be from 0.3 to 10.0 pm. [4] In the method of manufacturing an article formed by hot pressing according to any of [1] to [3], the surface temperature of the die at the beginning of forming can be 5°C or higher and 180°C or lower. [5] An article formed by hot pressing in accordance with another aspect of the present invention is composed of an Al-plated steel sheet having an Al plating layer, wherein Gs60°, which is the brightness regulated by JIS Z 8741: 1997 on a surface, is 30 or less. R7R7 ίη / 77Ω7 / Β / YILI [6] In the article formed by hot pressing in accordance with [5], the Gs60° may be 25 or less. [7] The article formed by hot pressing in accordance with [5] or [6] includes a coating layer over a surface of the Al plating layer, wherein the coating layer may be a metal layer composed of at least one of Mg, Ca, V, Ti and Zn metals, a metal oxide layer composed of an oxide of one or more of Mg, Ca, V, Ti and Zn, or a mixed layer formed by the metal layer and the metal oxide layer. [8] In the article formed by hot pressing in accordance with [7], the thickness of the coating layer can be from 0.3 to 10.0 pm. Effects of the invention

[18] In accordance with the above-described aspects of the present invention, a method of manufacturing a hot-pressed article to obtain a hot-pressed article having an excellent external surface appearance while suppressing die wear and a hot-pressed article having an excellent external surface appearance can be obtained. R7R7 ίη / ΖΖΩΖ / Ε / ΥΙΛΙ Brief description of the drawings

[19] Figure 1 is a schematic view of an Al-plated steel sheet used in a method of manufacturing a hot-pressed article in accordance with the present modality. Figure 2 is a view showing an evaluation device for an external surface appearance of an article formed by hot pressing. Figure 3 is a view showing the external appearances of sliding parts of hot-formed articles tested with the evaluation device of Figure 2 and examples of gloss measurement. Modalities of the invention

[20] A method of manufacturing an article formed by hot pressing according to an embodiment of the present invention (a method of manufacturing an article formed by hot pressing in accordance with the present embodiment) and an article formed by hot pressing in accordance with an embodiment of the present invention (an article formed by hot pressing in accordance with the present embodiment).

[21] Method of manufacturing the article formed by hot pressing The inventors of this invention investigated the cause of plating damage and the resulting increase in brightness of a hot-pressed article in a process where an aluminum-clad steel sheet is heated by a hot-pressing method and immediately formed by pressing. As a result, the following four points were found to be the cause. 1) After heating, a hard Al-Fe based alloy layer that forms on the surface of the Al coating by an alloying reaction between an Al coating layer and a base metal and / or hard aluminum oxide is peeled off because the surface of the aluminum-plated steel sheet and a die rub against each other during pressure forming, the peeled alloy layer and the aluminum oxide act as an abrasive dust, and the plating on the surface of the aluminum-plated steel sheet is severely damaged. 2) On the surface of the die provided with a hard membrane, when the hardness is low, the die wears down; conversely, when the hardness is high, the surface of the aluminum-clad steel sheet rubbed against the die (for example, on a part of the standing wall) is damaged. R7R7 ίΠ / ΖΖηΖ / Ε / ΥΙΛΙ 3) In the case of pressure forming immediately after heating, when the temperature at the beginning of forming is high, the aluminum plating softens and, therefore, the surface of the aluminum-plated steel sheet is likely to be damaged by rubbing against the die. 4) In the case of being formed by pressing, during the formation after the start of the forming process, the temperature of the aluminum-clad steel sheet is removed by heat from the die that came into contact with the aluminum-clad steel sheet, and the temperature of the aluminum-clad steel sheet decreases; however, in a case where the forming speed is fast, the heat removal is suppressed, the die rubs the surface of the aluminum-clad steel sheet in a state in which the temperature of the aluminum-clad steel sheet is maintained even more at a high temperature, and it is more likely that the surface of the aluminum-clad steel sheet will be damaged. Based on these findings, the inventors of the present found that the problem can be solved by covering the surface of the Al coating with a layer of a metal having low hardness or a metal oxide having low hardness and controlling the forming temperature T (°C) and the forming speed V (mm / s) to satisfy a predetermined relationship with respect to the surface hardness HVMatriz of a die.

[22] The method of manufacturing a hot-pressed article according to this modality includes a heating step of heating an aluminum-clad steel sheet to 850°C to 1000°C and a forming step of forming the aluminum-clad steel sheet using a die to obtain a hot-pressed article after the heating step. The forming step is performed, for example, within 30 seconds after the steel sheet is removed from a heating furnace. Furthermore, the Al-plated steel sheet has a base steel sheet, an Al plating layer formed on a surface of the base steel sheet, and a coating layer formed on the surface of the Al plating layer, and the coating layer is a metal layer containing at least one of Mg, Ca, V, Ti, and Zn metals, a metal oxide layer containing an oxide of one or more of Mg, Ca, V, Ti, and Zn, or a mixed layer including the metal layer and the metal oxide layer. In addition, the die has a hard layer on the surface of the die that comes into contact with the Al-plated steel sheet in the forming step, and the HVMatriz, which is the surface hardness of the die at the position of the hard layer, is HV1500 or more and HV3800 or less. Furthermore, when the temperature (forming temperature) of the Al-plated steel sheet at the beginning of forming in the forming step is indicated by Tm in the unit of °C, and the average movement speed (forming speed) of the die from the start of forming to the bottom dead center is indicated by V in the unit of mm / s, Tm and V satisfy the following Formula (1). 800 - (HVMatrlz / 40) < Tm < 850 - (V / 4) - (HVMatrlz / 100) . . . Formula (1)

[23] In press forming, the steel sheet is fed into the die hole and formed. If the edge of the die hole (also known as the die shoulder or R-part) protrudes and curves outward from the die hole, the steel sheet contracts and distorts when fed into the die hole. In the case of draw forming, during flange contraction and distortion, the thickness of the steel sheet increases towards the edge of the die hole (part of the die shoulder). As the thickness of the steel sheet increases, a high contact pressure is applied to it. In the case of bending formation, during the R7R7 ίη / ZZOZ / E / YILI Contraction and distortion of the flange cause wrinkles to form in the steel sheet towards the edge of the die hole (part of the die shoulder). When wrinkles form in the steel sheet, a portion of the sheet that has become wrinkled in the vicinity of the die hole comes into contact with the die, and high contact pressure is applied at the contact site. In the method of manufacturing an article formed by hot pressing according to the present embodiment, in hot pressing, for example, the steel sheet is converted into a blank (stamped), if necessary, and then heated to a high temperature, thereby softening the veneered steel sheet. Furthermore, the softened veneered steel sheet is pressed using a die at a forming temperature Tm°C and a forming speed V mm / s, and then rapidly cooled by removing heat while the steel sheet remains in the die. As described above, in hot pressing, the veneered steel sheet is softened once, thus facilitating subsequent pressing.Furthermore, a press-formed article that has been formed by hot pressing is tempered by heating and cooling and becomes a formed article that has a high hardness of HV400 or more (load 1 kgf (9.8 N)) in terms of Vickers hardness.

[24] Warm-up step In the heating step, the aluminum-clad steel sheet is heated to 850°C to 1000°C. When the heating temperature is set to 850°C or higher, which is the Ac3 point of the base steel sheet (the base material portion of the aluminum-clad steel sheet), the aluminum-clad steel sheet becomes austenitized, improving its formability in the subsequent forming step. Furthermore, when the aluminum-clad steel sheet is heated to 850°C or higher, martensitic transformation of the base steel sheet can be induced by rapidly cooling the aluminum-clad steel sheet with a die immediately afterward. This results in a hot-formed article with high tensile strength.When the temperature of the steel sheet drops before it is rapidly cooled in the die, the austenite-to-ferrite transformation occurs, and the desired martensitic transformation cannot be achieved even when the steel sheet is rapidly cooled in the die. Furthermore, heating the aluminum-clad steel sheet to 850°C or higher causes an alloying reaction between the aluminum cladding layer and the base steel sheet, and also contributes to the formation of an Al-Fe-based alloy layer that has favorable surface defect resistance. R7R7 ίη / ZZOZ / E / YILI If the heating temperature is below 850°C, ferritic transformation may begin before cooling in the die, preventing the formation of sufficient hardness in the formed articles. Therefore, the heating temperature is set to 850°C or higher. To maintain a high temperature in the steel sheet even during the forming step, the heating temperature is preferably 890°C or higher, very preferably 910°C or higher, and very preferably 925°C or higher. On the other hand, when the heating temperature exceeds 1000°C, excessive oxidation of the aluminum plating surface occurs, increasing die wear. Furthermore, such a high temperature also leads to high-temperature press forming, softening the plating surface and potentially causing a defect on the die side. Therefore, the heating temperature is set to 1000°C or lower. Ideally, the heating temperature should be 980°C or lower, and very preferably 960°C or lower. As a heating method, in addition to radiant heating with a normal electric oven or a radiant tube oven, a heating method using infrared heating can be adopted. R7R7 iη / ZZOZ / E / YILI activation heating, induction heating, or similar methods. Heating is carried out in atmospheric conditions, a nitrogen atmosphere, or a combustion gas atmosphere, and the dew point of the atmosphere is not particularly limited, but the heating atmosphere preferably contains 10% by volume or more oxygen. When it contains 10% by volume or more oxygen, evaporation of the coating layer onto the surface of the Al plating can be suppressed. Very preferably, the oxygen content is 20% by volume, which is the same as in atmospheric conditions, or higher. The rate of temperature increase by heating is preferably 7.0°C / s slower. In the method of manufacturing a hot-pressed article according to the present embodiment, in the Al-plated steel sheet to be heated, there is a case in which the coating layer formed on the surface of the Al plating layer contains Zn (Chemical Handbook Second Revised Edition, Basic Edition I (Author: The Chemical Society of Japan, Publisher: Maruzen Co., Ltd., Publication Date 1975): boiling point 907°C), Mg (equal: boiling point 1107°C), or Ca (equal: boiling point 1487°C), which is relatively lower than the boiling point of Al (equal: 2467°C). Therefore, evaporation of the coating layer is favored by a rapid increase in temperature, and there is a possibility that the external appearance of a component may deteriorate after pressing.When the temperature rise rate is set to 7.0°C / s or less, the coating layer oxidizes with atmospheric oxygen, suppressing excessive evaporation. Ideally, the temperature rise rate should be set to 6.0°C / s or less. To obtain the rate of temperature rise (°C / s), a type K thermocouple is connected to the steel sheet by spot welding. The sheet's temperature is measured while the heating temperature reaches 850°C from an initial temperature Ts (°C). The temperature rise is then divided by the time t (seconds) it takes for the heating temperature to reach 850°C from the sheet's initial temperature Ts (°C) after the start of heating, thus obtaining the rate of temperature rise. The formula for the rate of temperature rise is (850 Ts) / t.

[25] Aluminum-clad steel sheet The aluminum-clad steel sheet that undergoes the heating step has a base steel sheet, an aluminum cladding layer formed on the surface of the sheet, and a layer of aluminum cladding formed on the surface of the sheet. R7R7 ίη / ZZΖηZ / E / YΙΛΙ base steel and a coating layer formed on the surface of the Al plating layer. This coating layer is a metal layer containing at least one of Mg, Ca, V, Ti and Zn metals, a metal oxide layer containing an oxide of one or more of Mg, Ca, V, Ti and Zn, or a mixed layer including the metal layer and the metal oxide layer. Specifically, for example, as shown in Figure 1, an Al-plated steel sheet 1 includes plating layers of Al 3A and 3B on both surfaces (the top surface and the bottom surface) of a base steel sheet 2 and a coating layer (a metal layer, a metal oxide layer, or a mixed layer thereof) 4A or 4B as the outermost layer over each of the Al 3A and 3B plating layers.

[26] The base steel sheet 2 (steel sheet before plating) is, for example, preferably a steel sheet having high mechanical strength (meaning a variety of properties related to mechanical distortion and fracture, e.g., tensile strength, yield strength, elongation, reduction of area, hardness, impact strength, fatigue strength, creep strength, and the like). In the aluminum-plated steel sheet 1 used in the method of manufacturing a hot-pressed article according to this modality, R7R7 ίη / ZZOZ / E / YILI The chemical composition of the base steel sheet 2 is not limited; however, in the case of achieving high mechanical strength, an example of a preferred chemical composition of the base steel sheet 2 is as described below. Hereafter, the notation % with respect to chemical composition means % by mass unless specifically stated otherwise. That is, the chemical composition of base steel sheet 2 contains, for example, in % by mass, C: 0.18% or more and 0.50% or less, Si: 2.00% or less, Mn: 0.30% or more and 5.00% or less, Cr: 2.00% or less, P: 0.100% or less, S: 0.100% or less, N: 0.0100% or less, Al: 0.500% or less, and B: 0.0002% or more and 0.0100% or less and further contains, if necessary, one or more of W: 3.00% or less, Mo: 3.00% or less, V: 2.00% or less, Ti: 0.500% or less, Nb: 0.500% or less, Ni: 5.00% or less, Cu: 3.00% or less, Co: 3.00% or less, Sn: 0.100% or less, Sb: 0.100% or less, Mg: 0.0050% or less, Ca: 0.0050% or less, REM: 0.0070% or less, and O: 0.0070% or less, and the remainder Fe and an impurity.

[27] The reason why the chemical composition described above is preferred will be described. C: 0.18% or more and 0.50% or less A hot-pressed article obtained by the hot stamping method is required to have a high strength of, for example, 1000 MPa R7R7 ίη / ZZΖΠZ / E / YΙΛΙ or more. In this case, it is required that the structure (metallographic structure) of the hot-formed article be transformed into a structure composed mainly of martensite by rapid cooling after hot stamping. When the carbon (C) content is less than 0.18%, hardenability deteriorates and strength is insufficient. Therefore, the C content is preferably 0.18% or higher. A C content of 0.20% or higher is highly preferable, and even more preferably 0.22% or higher. On the other hand, when the carbon content exceeds 0.50%, the toughness of the steel sheet deteriorates significantly, and its workability is also impaired. Therefore, the carbon content is preferably set at 0.50% or less. A carbon content of 0.40% or less is highly preferable, and even more preferably 0.35% or less.

[28] Yes: 2.00% or less The lower limit for silicon (Si) content is not particularly restricted and can be 0%; however, if the silicon (Si) content is less than 0.01%, the hardenability and fatigue properties are poor. Therefore, the Si content is preferably 0.01% or more. The Si content is very preferably 0.05% or more, very preferably still 0.10% or more, and very preferably still 0.30% or more. On the other hand, since silicon (Si) is more readily oxidized than iron (Fe), when the Si content exceeds 2.00% in a continuous annealing line, a stable Si-based oxide film forms on the surface of the base steel sheet during the annealing process. This affects the adhesion of the hot-dip aluminum plating, and there is a concern that it will not adhere. Therefore, the Si content is preferably set at 2.00% or less. Highly preferable, 1.00% or less; very preferably still, 0.80% or less; and extremely preferable still, 0.70% or less or 0.60% or less.

[29] Mn: 0.30% or more and 5.00% or less Manganese (Mn) is an effective element for improving the hardenability of steel sheets and also for suppressing the hot embrittlement caused by the sulfur that is inevitably incorporated. If the Mn content is less than 0.30%, hardenability deteriorates and strength becomes insufficient. Therefore, the Mn content is preferably 0.30% or higher. The Mn content is very preferably 0.50% or higher, very preferably 0.80% or higher, and very preferably 1.00% or higher. On the other hand, if the Mn content exceeds 5.00%, the impact characteristics after rapid cooling deteriorate. Therefore, the Mn content is preferably adjusted to 5.00% or less. The Mn content is very preferably 4.00% or less, very preferably still 3.00% or less, and very preferably still 2.50% or less or 2.00% or less.

[30] Cr: 2.00% or less The lower limit for chromium (Cr) content is not particularly restricted and can be 0%, but chromium (Cr) is an element that improves the hardenability of steel sheets. If the Cr content is less than 0.001%, the hardenability improvement described above cannot be achieved, and the strength is insufficient. Therefore, the Cr content is preferably 0.001% or higher. A Cr content of 0.05% or higher is very preferably preferred, and 0.10% or higher is even more highly preferred. On the other hand, since chromium (Cr) oxidizes more readily than iron (Fe), if the Cr content exceeds 2.00%, a stable Cr-based oxide film forms on the surface of the base steel sheet during annealing. This affects the adhesion of the hot-dip aluminum plating, and there is a concern that it will not adhere properly. Therefore, the Cr content is preferably set at 2.00% or less. Very preferably, the Cr content is 1.60% or less, very preferably still 1.40% or less, and very preferably still 1.00% or less.

[31] B: 0.0002% or more and 0.0100% or less Boron (B) is a useful element from a hardenability standpoint, and when it contains 0.0002% or more, hardenability is improved. Therefore, the B content is preferably adjusted to 0.0002% or more. The B content is very preferably 0.0005% or more, and very preferably still 0.0010% or more. On the other hand, when the B content exceeds 0.0100%, the hardenability-enhancing effect described above becomes saturated, and manufacturability deteriorates due to the generation of casting defects or cracks during hot rolling. Therefore, the B content is preferably set at 0.0100% or less. The B content is very preferably 0.0080% or less, very preferably still 0.0070% or less, and very preferably still 0.0060% or less.

[32] Al: 0.500% or less Aluminum (Al) is contained in steel as a deoxidizing agent. Since Al is more readily oxidized than Fe, if the Al content exceeds 0.500%, a stable Al-based oxide film forms on the surface of the base steel sheet during annealing. This impairs the adhesion of the hot-dip aluminum plating and can lead to non-plating. Therefore, the Al content is preferably adjusted to 0.500% or less. Highly preferable, 0.200% or less; even more preferably, 0.100% or less; and most preferably still, 0.080% or less. On the other hand, the lower limit for Al content is not particularly restricted and can be 0%, but adjusting the Al content to less than 0.001% is not economical given the refining limitations. Therefore, the Al content can be adjusted to 0.001% or higher.

[33] P: 0.100% or less Phosphorus (P) is an impurity. It is also a solid solution strengthening agent and can increase the strength of steel sheets at a relatively low cost. However, if the P content exceeds 0.100%, a significant adverse effect, such as reduced toughness, occurs. Therefore, the P content is preferably kept to 0.100% or less. A P content of 0.050% or less is highly preferable, and even more preferably 0.020% or less. On the other hand, the lower limit for P content is not particularly restricted and can be 0%, but adjusting the P content to less than 0.001% is not economical given the refining limits. Therefore, the P content can be adjusted to 0.001% or higher.

[34] S: 0.100% or less Sulfur (S) is an element present as an impurity in steel, where it forms inclusions such as MnS. If the S content exceeds 0.100%, MnS acts as a starting point for fracture, impairing ductility, toughness, and workability. Therefore, the S content is preferably kept to 0.100% or less. Very preferably, the S content is 0.050% or less, very preferably 0.010% or less, and very preferably still 0.005% or less. Furthermore, since sulfur (S) is not required in the aluminum-clad steel sheet according to this modality, the lower limit of the S content is not particularly restricted and can be 0%; however, adjusting the S content to less than 0.0001% is not economical in view of refining limitations. Therefore, the S content can be adjusted to 0.0001% or more.

[35] N: 0.0100% or less Nitrogen (N) is an element present as an impurity and is preferably fixed (converted into a compound) using Ti, Nb, Al, and similar elements to stabilize the product's characteristics. As the N content increases, the amount of elements required to fix N becomes large, leading to increased costs. Therefore, the N content is preferably 0.0100% or less. The N content is very preferably 0.0080% or less. The N content is preferably as small as possible and can be 0%, but adjusting the N content to less than 0.0010% is not economical given the refining limitations. Therefore, the N content can be adjusted to 0.0010% or more.

[36] The base steel sheet 2 of the steel sheet clad with Ά1 1 may have a chemical composition containing the elements described above and the remainder consisting of Fe and an impurity. However, to further improve the characteristics, the base steel sheet 2 may also contain the elements described below (optional elements), and the lower limits of the quantities of the optional elements of the base steel sheet 2 described below are all 0%.

[37] W and Mo: every 3.00% or less The lower limits for tungsten (W) and molybdenum (Mo) content are not particularly restricted and can be 0%, but W and Mo are useful elements from a hardenability standpoint and have an effect on hardenability improvement when their contents are 0.01% or higher. If this effect is desired, the W and Mo content are adjusted accordingly. R7R7 ίΠ / ZZΖηZ / E / YΙΛΙ preferably at 0.01% or more. The W content and the Mo content are each very preferably 0.05% or more. On the other hand, if the W and Mo content each exceeds 3.00%, the effect described above becomes saturated and the cost also increases. Therefore, the W and Mo content should preferably be 3.00% or less. Ideally, the W and Mo content should each be 1.00% or less.

[38] V: 2.00% or less The lower limit for vanadium (V) content is not particularly restricted and can be 0%, but V is a useful element from a hardenability standpoint and shows an effect on improving hardenability when its content is 0.01% or higher. Therefore, if this effect is desired, the V content is preferably adjusted to 0.01% or higher. A V content of 0.05% or higher is highly preferable. On the other hand, if the V content exceeds 2.00%, the effect described above becomes saturated and the cost also increases. Therefore, the V content should preferably be adjusted to 2.00% or less. Ideally, the V content should be 1.00% or less.

[39] Ti: 0.500% or less The lower limit for titanium (Ti) content is not particularly restricted and can be 0%, but Ti is an effective nitrogen-fixing element and may be present. If this effect is desired, it is preferable that the Ti content be approximately 3.4 times or more the nitrogen content by mass percent. Since the nitrogen content is typically around 10 ppm (0.001%) even when attempts are made to reduce it, the Ti content is preferably 0.005% or higher. A Ti content of 0.010% or higher is highly preferable. On the other hand, when the Ti content becomes excessive, hardenability deteriorates and strength decreases. This deterioration in hardenability and strength becomes significant when the Ti content exceeds 0.500%. Therefore, the Ti content is preferably adjusted to 0.500% or less. Ideally, the Ti content should be 0.100% or less.

[40] Nb: 0.500% or less The lower limit for niobium (Nb) content is not particularly restricted and can be 0%, but Nb is an effective nitrogen fixer and may be present. To achieve this effect, it is preferable to contain approximately 6.6 times or more the N content by mass percent. Since the N content is typically around 10 ppm (0.001%) even when attempts are made to reduce it, the Nb content is preferably 0.006% or higher. A Nb content of 0.010% or higher is highly preferable. On the other hand, when the Nb content becomes excessive, hardenability deteriorates and strength decreases. Since this deterioration of hardenability and strength becomes significant when the Nb content exceeds 0.500%, the Nb content is preferably adjusted to 0.500% or less. The Nb content is highly preferable to be 0.100% or less.

[41] Furthermore, even when the chemical composition of the base steel sheet 2 contains Ni, Cu, Co, Sn, Sb, Mg, Ca, REM, O and the like, the effects in the present form are not affected as long as the contents are within upper or lower limit ranges as described below.

[42] Ni: 5.00% or less The lower limit for nickel (Ni) content is not particularly restricted and can be 0%, but Ni is a useful element for improving low-temperature toughness, leading to improved impact resistance and hardenability. To achieve the aforementioned effect, the Ni content is preferably adjusted to 0.01% or higher. On the other hand, when the Ni content exceeds 5.00%, the effect described above becomes saturated and the cost increases. Therefore, the Ni content is preferably adjusted to 5.00% or less.

[43] Cu and Co: 3.00% or less The lower limit for the amount of each copper (Cu) and cobalt (Co) is not particularly restricted and can be 0%, but both Cu and Co are useful elements for improving toughness as well as hardenability. If this effect is desired, the Cu and Co content is preferably adjusted to 0.01% or more. On the other hand, when the amount of Cu and Co exceeds 3.00%, the effect described above becomes saturated and the cost increases. Furthermore, when present in excessive amounts, both Cu and Co cause deterioration of the casting's properties or the generation of cracks or defects during hot rolling. Therefore, the Cu and Co content is preferably adjusted to 3.00% or less.

[44] Sn and Sb: 0.100% or less The lower limits for tin (Sn) and antimony (Sb) content are not particularly restricted and can be 0% each, but Sn and Sb are effective elements for improving the wettability and adhesion of the coating. To achieve this effect, 0.001% or more of at least one of Sn and Sb is preferably included. Furthermore, if the content exceeds 0.100% of either Sn or Sb, a manufacturing defect or reduced toughness is likely. Therefore, the Sn and Sb content should preferably be 0.100% or less.

[45] Mg and Ca: 0.0050% or less Both magnesium (Mg) and calcium (Ca) are present as impurities, and the lower limits for their content are not particularly restricted and can be set to 0%. When present, both Mg and Ca can suppress inclusions in the base metal in some cases and can be contained, but they can act as the starting point for fracture when present in large quantities. Therefore, the Mg and Ca content should preferably be 0.0050% or less each.

[46] REM and O: 0.0070% or less Reactive oxygen species (RES) and oxygen (O) are not essential elements and are present, for example, in steel as impurities. REM and O contribute to the deterioration of steel sheet properties by forming an oxide and acting as a point of origin for fracture. Furthermore, there is a case where an oxide present near the surface of the steel sheet causes a surface defect and impairs the quality of its appearance. Therefore, the REM and O content should preferably be as low as possible. In particular, when the REM and O content exceed 0.0070%, the properties deteriorate significantly; therefore, the REM and O content should each preferably be 0.0070% or less. The lower limits for REM and O content are not particularly restricted and can be 0%, but the upper limits are 0%.0.0005% in the actual operation considering the refining and therefore the substantial lower limits of the REM content and the O content are each 0.0005%. R7R7 ίη / ΖΖηΖ / Ε / ΥΙΛΙ

[47] Regarding other components Other components are not specifically regulated, but there is a case where elements such as Zr and As are incorporated from scrap. However, provided the quantity of incorporated elements is within a normal range, the characteristics (mechanical strength and the like) of the base steel sheet 2 in accordance with this modality are not affected. The remainder of the chemical composition of the base steel sheet 2 is Fe and an impurity. Impurity means a component that is incorporated from a raw material such as an ore or scrap, or by a variety of causes in the manufacturing steps during the industrial production of a steel material, and is permitted to be contained provided that the impurity does not adversely affect the Al-clad steel sheet 1 in accordance with this modality.

[48] ​​Al plating layer In the Al plated steel sheet 1 used in the method of manufacturing a hot-pressed article according to this modality, the Al plated layers 3A and 3B are plated layers containing, by mass percent, 50% or more Al in their composition. Elements other than Al are not particularly restricted, but Si may be present for the following reasons.

[49] When Si is contained in the Al plating layers 3A and 3B, Al-Fe-Si alloy layers form at the interfaces between the Al plating layers 3A and 3B and the base steel sheet 2 (base metal), thus suppressing the formation of a brittle Al-Fe alloy layer that occurs during hot-dip plating. If the Si content is less than 3% by mass, the Al-Fe alloy layer thickens during the plating process, promoting cracking of the plating layers during processing, and potentially negatively impacting corrosion resistance. On the other hand, if the Si content exceeds 15% by mass, the volume percentage of the Si-containing layers increases, raising concerns that the workability and corrosion resistance of the coating layers may deteriorate. Therefore, the Si content in the Al plating layer is preferably kept between 3% and 15%. As a method of manufacturing an Al-plated steel sheet by treating the Al plating on the base steel sheet, a method in which a plate containing a chemical composition adjusted by normal pig iron manufacturing and steelmaking is subjected to normal hot rolling, pickling and cold rolling and is subjected to Sendzimir-type continuous annealing, immersion in a hot-dip Al plating bath and adjusting the thicknesses of the Al plating layers by rubbing, thereby manufacturing an Al-plated steel sheet is an illustrative example.

[50] The Al 3A and 3B plating layers prevent corrosion of the steel sheet when used as a vehicle component. Furthermore, even when the aluminum-plated steel sheet 1 is heated to a high temperature during hot pressing, the aluminum 3A and 3B plating layers do not produce any scale (iron oxide) on the surface of the base metal. Because the Al 3A and 3B plating layers prevent scale formation, scale removal, surface cleaning, and surface treatment steps can be omitted, thus improving the productivity of the hot-pressed product. Iron oxide, which is a scale, becomes hard and rough when heated and therefore also causes die wear.Furthermore, the Al 3A and 3B plating layers have higher boiling and melting points than coating layers composed of other metal-based materials (e.g., Zn-based materials). Therefore, when the Al-plated steel sheet is formed by hot pressing, the Al plating layers are less likely to evaporate, making high-temperature hot pressing possible. This further improves formability in hot pressing, and the Al-plated steel sheet can be easily formed.

[51] In general, there is a case where an Al oxide coating with a thickness of 0.01 to 0.1 pm is present on the surface of the Al plating layer of the Al-coated steel sheet 1. There is a case where the thickness of this Al oxide coating increases to 0.01 to 0.5 pm after hot pressing.The reason the thickness of the aluminum oxide coating increases after hot pressing is that the aluminum oxide coating oxidizes with oxygen or water vapor in the atmosphere after the hot pressing process. The formation of this Al oxide coating and the increase in thickness are suppressed by the formation of a metal layer or a metal oxide layer on the surface of the Al plating layer. However, in the case where coating layers 4A and 4B, which include a metal layer or a metal oxide layer, are present on the Al plating layers 3A and 3B, as in the Al-plated steel sheet 1 according to the present modality, the formation of an Al oxide coating is suppressed on the outermost surface side. However, there is a case where a reaction occurs at the interfaces between the metal layer and / or the metal oxide layer and the Al plating layers, and an Al-containing metal oxide is formed on the metal oxide layer after hot pressing.

[52] The aluminum in aluminum plating layers can be alloyed with iron in the steel sheet by heating during hot-dip plating and hot-press forming. Therefore, it is not always true that the aluminum plating layer forms as a single layer with a constant composition, and the aluminum plating layer includes a partially alloyed layer (alloy layer). The alloy layer is hard and brittle and thus causes die wear during hot forming. However, when a metal layer or a metal oxide layer forms on the surface, it is possible to prevent this alloy layer from contacting the die and causing die wear. Furthermore, a defect that arises in the alloy layer of the die is suppressed, and the deterioration of the external appearance is prevented.

[53] The thicknesses of the Al 3A and 3B plating layers are preferably 10 µm or more and 60 µm or less. When the thicknesses of the Al 3A and 3B plating layers are less than 10 µm, iron inclusions form in the base steel sheet 2 and die wear is favored. The thicknesses of the Al 3A and 3B plating layers are very preferably 12 µm or more and very preferably still 15 µm or more. On the other hand, when the adhesion of the 3A and 3B layers of the Al veneer exceeds 60 µm, the coating is subjected to high shear stress, and a significant amount of the Al veneer exfoliates. In this case, the matrix is ​​damaged, and matrix wear is accelerated. The thicknesses of the 3A and 3B Al veneer layers are preferably 55 µm or less, and ideally 50 µm or less.

[54] The thicknesses of the Al 3A and 3B plating layers can be obtained by collecting a sample so that a cross-section can be observed in the thickness direction, polishing the cross-section and then observing the R7R7 ίΠ / ZZΖηZ / E / YΙΛΙ cross section with an optical microscope with a magnification of 1000 times.

[55] Coating layer In the aluminum-clad steel sheet 1 used in the method of manufacturing a hot-pressed article in accordance with this modality, layers of metal, layers of metal oxide, or mixed layers thereof are provided over the aluminum cladding layers 3A and 3B as the coating layers 4A and 4B as the outermost layers. These coating layers 4A and 4B are extremely important to suppress die wear and obtain a beautiful external appearance of a hot-pressed item. As described above, in a case where the Al 1-plated steel sheet is hot-pressed, one of the reasons the plating is damaged is the presence of a hard layer of Al-Fe alloy and aluminum oxide that forms on the surface of the Al plating during heating for hot stamping. Therefore, in the method of manufacturing a hot-stamped article according to the present modality, metal layers containing at least one of the metals Mg, Ca, V, Ti, and Zn, metal oxide layers containing one or more of the oxides Mg, Ca, V, Ti, and Zn, or mixed layers including the metal layer and the metal oxide layer are formed on the surfaces of the Al 3A and 3B plating layers to cover the surfaces of the Al 3A and 3B plating layers. The reason why the metal layer or the metal oxide layer is effective is not clear, but it is conceivable that a substance with a low Morse hardness (Chemical Handbook Basic Edition p475, Maruzen Co., Ltd., published in 1966) may be effective. For example, Mg (Morse hardness 2.0), Ca (1.5), and Zn (2.5) are all lower than Al (2.9). Furthermore, MgO (Morse hardness 5.5 to 6), CaCO3 (3), ZnO (4.5 to 5), and TiC2 (Morse hardness 5.5 to 7) are all lower.5) are lower than that of Al oxide (the same 9). However, it is not always true that wear is solved by this alone, and it is conceivable that, for example, in the case of a metal, the melting point may have an influence, and, in the case of an oxide, size or similar factors may also have an influence. The metal oxide contained in the coating layer, referred to herein, includes not only oxides of the metals described above but also hydroxides and carbon oxides of the metals described above. This is because most hydroxides and carbon oxides are considered to convert to oxides after heating in a furnace. R7R7 ίΠ / ΖΖηΖ / Ε / ΥΙΛΙ warming up. Since the metal and metal oxide that make up the metal layer and the metal oxide layer included in the coating layer, metallic Zn, metallic Mg, ZnO or MgO are preferable from the point of view of cost and ease of obtaining. Incidentally, from the point of view of suppressing evaporation of the coating layer during the heating stage of hot pressing, a coating layer other than a layer of Zn or ZnO alone, having a relatively low boiling point and including any metal layer containing at least one of Mg, Ca, V and Ti metals, is preferable to a metal oxide layer containing an oxide of one or more of Mg, Ca, V and Ti, or a mixed layer thereof. In the present embodiment, the metal layer, the metal oxide layer, or the mixed layer which includes the metal layer and the metal oxide layer refers to a layer in which a total of 8% by mass or more of at least one of the elements Mg, Ca, V, Ti, and Zn is contained. The coating layer can be a composite layer of a metal layer and a metal oxide layer, where a portion of the metal layer has been oxidized. Alternatively, the metal layer or metal oxide layer can be composed of the metal or metal oxide described above, or it can be a mixture of a metal or metal oxide and a resin. Since the resin acts as a binder, its mixture strongly bonds the metal layer or metal oxide layer to the aluminum plating surface. The resin referred to here means a compound consisting primarily of carbon, or a compound containing hydrogen, oxygen, nitrogen, and sulfur, and consisting primarily of carbon.Even when the resin is mixed, since the resin burns easily in a heating oven and is released as carbon dioxide and disappears from the coating layer after pressing, the resin has little influence on the characteristics of the metal layer or metal oxide layer.

[56] In the heating step during hot pressing, the Al-plated steel sheet is heated in an atmosphere containing oxygen or water vapor. Therefore, when the Al-plated steel sheet is removed from the heating furnace and then hot-pressed, and after the Al-plated steel sheet has been hot-pressed (when the Al-plated steel sheet has become a hot-pressed article), some or all of the metal that was not an oxide before hot pressing oxidizes, and the metal layer becomes a mixed layer of metal and metal oxide, or a metal oxide layer. For example, a metallic Zn layer becomes wholly or partially a ZnO layer.

[57] A method of forming coating layers 4A and 4B is not particularly limited and, for example, when the coating layer is a metal layer, it can be formed on the Al-plated steel sheet by precipitation using an electrolytic plating method or by vapor deposition using a physical vapor deposition method. When the coating layer is a metal oxide layer, for example, it can be formed by a method in which the metal layer formed on the Al-plated steel sheet is heated in air for a short period of time to oxidize, or it can also be formed, for example, by dispersing a commercially available metal oxide sol in water, applying the water dispersion liquid to the Al-plated steel sheet, and drying the moisture to form a membrane.At this time, it is also possible to mix a resin with the water dispersion liquid.

[58] When the thicknesses of coating layers 4A and 4B are adjusted to 0.3 pm or more, die wear is suppressed, and a pleasing external appearance can be achieved on a hot-formed article after hot forming (a low gloss can be obtained). Therefore, the thicknesses of coating layers 4A and 4B are preferably adjusted to 0.3 pm or more. The thicknesses are R7R7 ίΠ / ZZΖηZ / E / YΙΛΙ very preferably 0.4 pm or more and very preferably still 0.5 pm or more. On the other hand, when the coating thickness exceeds 10.0 pm, there are instances where the metal layer or the metal oxide layer itself detracts from the external appearance. Therefore, the coating thickness is preferably set at 10.0 pm or less. A coating thickness of 7.0 pm or less is highly preferable, and even more preferably 5.0 pm or less. The thicknesses of coating layers 4A and 4B (the metal layers and / or the metal oxide layers) can be measured by embedding the sample in a resin, polishing the sample, and observing the cross-sections in the thickness direction using a scanning electron microscope (SEM) at a magnification of 1000x to 30000x. Coating layers 4A and 4B, which are the metal layers, metal oxide layers, or mixed layers including both the metal and metal oxide layers, refer to layers in which the content ratio of at least one element from Mg, Ca, V, Ti, and Zn is 8% or more by mass, and the content ratio is obtained by analyzing the cross-section with an electron probe microanalyzer (ERMA). If necessary, the surface of the material can be observed after it has been deposited with gold before embedding the material to clarify the boundary between the coating layer and the embedding resin. R7R7 ίΠ / ΖΖηΖ / Ε / ΥΙΛΙ

[59] Training step In the forming step, the heated Al 1 coated steel sheet is formed using a die after completing the heating step, thus obtaining an article formed by hot pressing. When the time elapsed from the end of the heating step to the start of forming exceeds 30 seconds, the base metal of the heat-austenitized steel sheet undergoes a ferritic transformation, making it impossible to obtain a high-strength martensitic structure after pressing. Therefore, the time elapsed from the end of the heating step to the start of forming is preferably set to 30 seconds or less. Since aluminum-clad steel sheet is preferably formed as quickly as possible, it is not necessary to limit the lower limit; however, when considering facility constraints such as the conveying speed from the heating furnace to a press and the descent speed of a press die, the time can be set to 3 seconds or more.However, the time that elapses until formation is controlled in order to ensure the temperature of the Al-plated steel sheet.

[60] Matrix As a die used for forming, it is not necessary to use a die that is particularly limited by its application. Tool steel in general, represented by JIS SKD11 and SKD61 (JIS G 4404: 2015), high-speed steel, and similar materials are illustrative examples. However, the die used in the present embodiment has a hard layer on the surface of the die that comes into contact with the Al-plated steel sheet. Furthermore, HVMatriz, which is the surface hardness of the die at the location of the hard layer, is HV1500 or higher and HV3800 or lower. This hard layer is extremely important to suppress die wear and to obtain a beautiful external appearance of an item formed by hot pressing. To further suppress wear, the hard layer is preferably formed with a thickness of 1.0 pm or more. The upper limit of the hard layer thickness is preferably 20 pm or less to suppress excessive increases in internal stress or deterioration of the hard layer's toughness. In the method of manufacturing an article formed by hot pressing in accordance with this In this pressing method, the upper and lower dies of the die move relatively in a constant direction, and the steel sheet installed between the upper and lower dies is drawn into the die hole and formed by this movement. In this pressing method, a die surface in a direction parallel to the direction in which the die (the upper and lower dies) moves relatively (generally, the vertical direction) comes into contact with the steel sheet to be processed and slides.On the surface in the direction parallel to the direction of relative motion, for example, the surface of the R portion of the die is in contact with the vertical wall portion of the hot-pressed article, and additional examples include the surface of a wrinkle-suppressing flange portion of the die, in the case of a flanged die, the surface of the upper portion of the flange head, and the like. When the matrix hardness (HVMatriz) of the hardened layer within the die is HV1500 or higher, wear of the sliding surface (the surface that slides in contact with the steel sheet) of the die during hot forming is suppressed. With a hardness lower than HV1500, the die wears. For example, SKD11 or SKD61 material is typically HV500 to HV1000. However, after nitriding, the hardness is HV600 to HV1400, and the die wears. Therefore, HVMatriz is set to HV1500 or higher. HVMatriz is preferably HV2000 or higher, and very preferably HV2500 or higher. No upper limit for surface hardness is specified, but the hardened layer becomes brittle if it is excessively hard, and a phenomenon occurs in which the hardened layer and the base metal of the die exfoliate. Furthermore, the matrix damages the surface of the Al-plated steel sheet during hot pressing and degrades the external appearance.Therefore, HVMatriz is set to HV3800 or lower. HVMatriz is preferably HV3600 or lower, and very preferably HV3400 or lower. The matrix hardness (HVMatrix) is the hardness measured with a test load of 10 gf to 25 gf (0.098 N to 0.245 N) using the Vickers hardness test method specified by JIS Z 2244:2009. The HM-211 micro Vickers tester, manufactured by Mitutoyo Corporation, can be used for this hardness measurement. The micro Vickers indenter is used to make indentations at two or more points separated by 30 pm or more, and the diagonal length of the indentation is measured using SEM to determine the hardness.

[61] The material or method of forming the hard layer that forms in the matrix is ​​not limited as long as the hard layer satisfies HVMatriz or HV1500. Examples of these include a hard coating layer (deposited film) by the physical vapor deposition method (PVD method), and specific examples R7R7 ίη / 77Ω7 / Β / YILI include a nitride film, a carbide film and a carbonitride film, containing one or more selected Ti, Cr and Al as main components, a diamond-like carbon (DLC) film and the like. Among these, the film deposited as a hard coating layer is preferably one containing Ti or Cr, or a combination thereof. For example, the deposited film is preferably one in which the metallic component is a nitride, carbide, or carbonitride containing one or more of Ti, Cr, and Al as the main components. Furthermore, the deposited film is very preferably one in which the metallic component is a nitride, carbide, or carbonitride containing Ti or Cr as the main component. The HVmatrix hardness of the PVD coating in which the metallic component contains Ti, Cr, or Al is between 2000 and 4000. In the case of using diamond-like carbon, the HVmatrix hardness of the PVD coating is between 5000 and 8000.

[62] In the present embodiment, a method of forming a film deposited by physical vapor deposition is an illustrative example of a method for hard layer formation on the matrix. The type of physical vapor deposition method is not particularly limited. For example, an arc ion coating method and a sputtering method are desirable as physical vapor deposition methods. In addition, a chemical vapor deposition (CVD) method can also be used. For example, a variety of metallic targets and reaction gases (N2 gas, CH4 gas and the like) are used as the sources of evaporation of the metallic components, and the temperature and pressure of the gas are adjusted to apply a polarizing voltage, so that a PVD film can be formed on the surface of the base metal of the matrix. Before the hard coating layer (deposited film) is formed on the matrix by the physical vapor deposition (PVD) method, a nitriding layer is preferably formed, acting as an underlying layer (a surface hardening treatment using diffusion, called nitriding). Here, the nitriding layer is generally less than HV1500 and is not included in the hard matrix layer required for wear resistance in this configuration. The nitriding layer is formed by performing, for example, an ion nitriding treatment, i.e., performing an ion nitriding treatment by adjusting the temperature in an atmosphere of N2 and H2 gas that has a predetermined concentration in the matrix base metal. At this time, the composite layer, such as the nitriding layer called the white layer that forms due to the nitriding treatment, causes deterioration of adhesion and, therefore, it is desirable to avoid the formation of the composite layer by controlling the treatment conditions or removing the composite layer by polishing or similar means.

[63] In the method of manufacturing an article formed by hot pressing in accordance with the present modality, in the hot pressing forming, when the temperature of the Al 1 coated steel sheet at the beginning of forming is indicated by Tm in the unit of °C, and the average movement speed of the die from the beginning of forming to the bottom dead center is indicated by V in the unit of mm / s, the forming is carried out in such a way that Tm and V satisfy the following formula (1) in accordance with HVMatriz. 800 - (HVMatrix / 4 0 ) < Tm < 850 - (V / 4) - (HVMatrlz / 100) . . . Formula (1) This formula (1) is extremely important to suppress die wear and obtain a beautiful external appearance of a hot-pressed item. The temperature (forming temperature: Tm) (°C) of the aluminum-clad steel sheet 1 at the start of forming must be ((850 - V / 4) - (HVMatriz / 100)) or lower. When the forming temperature is higher than ((850 - V / 4) - (HVMatriz / 100)), the surfaces of the cladding layers of The Al 3A and 3B on the surface of the Al 1-plated steel sheet soften and rub against the die, making it likely that a defect will occur and degrading the external appearance of a hot-pressed article after forming (the quality of the external appearance deteriorates). The average movement speed (forming speed: V) of the die from the start of forming until reaching bottom dead center can be obtained from a relationship of V = S / t using a time t (seconds) taken for the movement of both the aluminum 1-plated steel sheet and the die to stop from the start of forming (generally also called bottom dead center) and a movement distance S (mm) of the die while the movement of both the aluminum plated steel sheet and the die comes to a stop from the start of forming.The reason the external appearance of a hot-pressed article depends on the average movement speed V (forming speed) of the die during forming is that, as the forming speed increases, heat removal from the steel sheet by contact with the die is further suppressed. This makes the steel sheet more likely to be impacted by the high-temperature die, resulting in a defect and a more likely deterioration of the external appearance. Here, the start of forming refers to the moment when the moving die makes contact with the aluminum-clad steel sheet. Furthermore, since the appropriate temperature to suppress damage on the material side (Al-plated steel sheet) is also affected by the surface hardness of the matrix, Tm and V preferably satisfy Formula (2). 800 - (HVwatriz / 40) < Tm < 850 - (V / 2) - (HVMatrlz / 50) . . . Formula (2) In other words, the forming temperature (Tm) (°C) of the Al-plated steel sheet at the start of forming is preferably ((850 - V / 2) - (HVMatriz / 50)) or lower. This is because the surface of a press-formed article is more likely to be damaged when the HVMatriz hardness of the die surface is high, and therefore a more aesthetically pleasing hot-pressed article can be obtained by further suppressing the forming temperature according to HVMatriz. On the other hand, when the forming temperature Tm (°C) is lower than (800 - (HVMatriz / 40)), the surface of the steel sheet becomes hard, and therefore the die and the steel sheet rub together intensely during pressing, causing the die to wear out. Therefore, the forming temperature (°C) is adjusted to (800 - (HVMatriz / 40)) or higher. R7R7 ίη / ΖΖΩΖ / Ε / ΥΙΛΙ The formation temperature Tm (°C) is preferably (805 (HVMatriz / 40)) or higher and very preferably (810 (HVMatriz / 40)) or higher. The average movement speed V (mm / s) of the die from the start of forming to bottom dead center is not particularly limited as long as Formulas (1) and (2) are satisfied. Heat from the formed article is removed by contact with the die; however, when the average movement speed is adjusted to be slow, the amount of heat removed becomes large, and the formed article comes into contact with the die at a lower temperature. This reduces surface damage and decreases gloss. Therefore, in terms of external appearance, the average movement speed (forming speed) is preferably 95 mm / s slower and very preferably 85 mm / s slower.However, when the average movement speed is too slow, excessive heat is extracted from the formed article, promoting die wear due to the deterioration of the material's martensitic transformation and surface hardening. Therefore, the average movement speed (forming speed) is preferably 15 mm / s faster and very preferably 25 mm / s faster. The average movement speed V (mm / s) is obtained by dividing the die movement distance (mm) by the time (seconds) taken from the start of forming (when the die starts) to bottom dead center (when the die movement and the formed article stop). As a method of measuring the temperature (forming temperature: Tm) (°C) of the Al-plated steel sheet 1 at the start of forming, the temperature can be measured with a radiation thermometer or by connecting a thermocouple to the Al-plated steel sheet 1. Generally, in the case of connecting a thermocouple, the part to which the thermocouple is connected becomes convex and hinders hot pressing forming, and therefore, a method in which the thermocouple is connected to the side surface of the end of the Al-plated steel sheet (a surface perpendicular to the surface where the Al plating layer is present) can be used.The forming temperature Tm (°C) is not particularly limited as long as Formula (1) and Formula (2) are satisfied, but it is preferably 550°C or higher, very preferably 600°C or higher, and very preferably still 650°C or higher from the point of view of increasing the mechanical strength of the pressed article by causing the material to undergo a martensitic transformation during hot pressing. On the other hand, from the point of view... R7R7 ίη / 77Ω7 / Β / YILI to ensure the movement time from the heating oven to the pressing formation, the forming temperature Tm (°C) is preferably 850°C or lower, very preferably 830°C or lower, and very preferably still 810°C or lower.

[64] The die surface temperature at the start of forming is preferably 180°C or lower. When the die side is damaged, irregularities form, damage to the material side increases, and the external appearance deteriorates; however, when the die surface temperature is set at 180°C or lower, die damage can be suppressed more reliably. The die surface temperature at the start of forming is very preferably 170°C or lower, and very preferably still 160°C or lower. The lower limit of the die surface temperature is not specifically determined, but is preferably 5°C or higher.Furthermore, the die temperature increases due to contact with the heated aluminum-clad steel sheet during forming, or, when forming is done continuously, heat is stored in the die and the die temperature gradually increases, so the lower limit is very preferably 20°C or higher and very preferably still 50°C or higher. The surface temperature of the matrix can R7R7 ίΠ / ZZΖηZ / E / YΙΛΙ measure by connecting a thermocouple to the die by spot welding.

[65] The die travel distance is preferably 150 mm or less. The travel distance referred to here means the distance the die travels in the direction in which the die (the upper and lower dies) moves relative to each other while the die and the Al-plated steel sheet first come into contact and the die's descent stops at the end of forming (generally also referred to as bottom dead center) during hot pressing. As the die travel distance increases, the distance the aluminum-plated steel sheet and the die rub against and slide against each other also increases. As the sliding distance increases, the Al-Fe alloy or Al oxide layer in the exfoliated coating begins to act as an abrasive, and the external appearance gradually deteriorates.When the movement distance exceeds 150 mm, the external appearance deteriorates significantly. The die movement distance is highly preferable to be 130 mm or less, and even more preferably 110 mm or less.

[66] The metallic material of the die base metal is not specifically defined, and well-known metallic materials can be used, for example, cold-formed die steel, hot-formed die steel, high-speed steel, cemented carbide, and the like. In this regard, improved metal types that have been proposed as a type of steel suitable for use in conventional dies, including standard metal types (steel types) by JIS or similar standards, can also be applied. R7R7 ίη / ΖΖΠΖ / Ε / ΥΙΛΙ

[67] Article formed by hot pressing The article formed by hot pressing in accordance with the present modality is a hot-pressed article consisting of an Al-plated steel sheet having an Al-plated layer, wherein the brightness (Gs60°) regulated by JIS Z 8741: 1997 on the surface is 30 or less. The hot-pressed article according to this embodiment can be obtained by the manufacturing method described above from a hot-pressed article according to this embodiment. In this embodiment, the hot-pressed article does not necessarily refer only to a hot-pressed article that accompanies the distortion of the shape of an aluminum-clad steel sheet and also includes aluminum-clad steel sheets that have been slipped after heating or aluminum-clad steel sheets that have been inserted by the die after heating and subjected to pressure. The article formed by hot pressing in accordance with the present modality is obtained by forming an Al-plated steel sheet that includes a metal layer composed of at least one metal of Mg, Ca, V, Ti and Zn, a metal oxide layer composed of an oxide of Mg, Ca, V, Ti and Zn, or a mixed layer formed by the metal layer and the metal oxide layer formed on the surface of the sliding surface that comes into contact with the die at least during hot pressing. Therefore, on the surface of the article formed by hot pressing in accordance with this specification, the gloss (Gs60°) regulated in JIS Z 8741: 1997 is 30 or less, and the external appearance of the surface is excellent. The gloss is preferably 25 or less. The gloss can be measured on the vertical wall part (sliding part) where the external appearance is most likely to deteriorate.

[68] Furthermore, the hot-pressed article produced according to this embodiment preferably has a coating layer consisting of a metallic layer of at least one of Ca, V, Ti, and Zn, a metal oxide layer of at least one of Mg, Ca, V, Ti, and Zn, or a mixed layer of the metallic layer and the metal oxide layer on the surface of the Al plating layer to achieve the brightness described above. Furthermore, the thickness of the coating layer is preferably from 0.3 to 10.0 µm. Examples

[69] Example 1 The aluminum plating was applied by the Sendzimir method to both surfaces of a cold-rolled steel sheet with a chemical composition (unit: % by mass, remainder: Fe and an impurity) shown in Table 1 and a sheet thickness of 1.4 mm. The annealing temperature prior to immersion in an electroplating bath was set to approximately 750°C. The aluminum plating bath contained 9.5% Si by mass and also contained Fe eluted from the cold-rolled steel sheet; the remainder was aluminum. The thickness (weight per unit area) of an aluminum plating layer after coating was adjusted by a gas cleaning method, and the thicknesses (weight per unit area) of the aluminum plating layers formed on both surfaces of the cold-rolled steel sheet were both adjusted to 20 µm, after which quenching was performed. After that, an operation whereby the Al plating layers on both surfaces were partially coated with each of Zn oxide, Ti oxide, V oxide, Mg oxide and / or Ca oxide from chemicals (manufactured by Sigma-Aldrich Japan, CI Kasei Co., Ltd., Taki The aluminum oxide coatings were applied to both surfaces using a roller coating machine and baked at approximately 80°C. In some of the aluminum plated layers, the same mass percentage of a polyurethane resin was mixed with the zinc oxide, and the aluminum plated layers were coated and baked, thus forming coatings. In all coating layers, the total mass ratio of at least one element from the aluminum oxides was 8% or more. The aluminum-clad steel sheets Al to A35 shown in Table 3-1 to Table 3-4 were obtained as described above. R7R7 ίΠ / ΖΖηΖ / Ε / ΥΙΛΙ

[70] Example 2 The aluminum plating was applied by the Sendzimir method to both surfaces of a cold-rolled steel sheet with a chemical composition (unit: mass %, remainder: Fe and an impurity) shown in Table 2 and a sheet thickness of 1.4 mm. The annealing temperature prior to immersion in a plating bath was set to approximately 750°C. The aluminum plating bath contained 9.5 mass percent Si and also contained Fe eluted from the cold-rolled steel sheet, with the remainder being aluminum. The thickness (weight per unit area) of an aluminum plating layer after plating was adjusted by a gas cleaning method. The thicknesses (weight per unit area) of the aluminum plating layers formed on both surfaces of the cold-rolled steel sheet were both adjusted to 30 µm, and then the aluminum plating layers were cooled.Furthermore, on both surfaces of the Al plating layers, metal layers of Mg, Ca, V, Ti, and Zn were formed, as well as metal layers in which Zn and Mg were mixed, and metal layers in which Zn and V were mixed, using an ion plating method. Additionally, on some of the Al plating layers, the metal layers were formed on both surfaces in the same manner and then heated in air to 700°C for 4 minutes, thereby oxidizing some of the metal layers to form mixed layers of an oxide layer and a metal oxide layer over the Al plating layers. In all plating layers, the total content of at least one of the elements Mg, Ca, V, Ti, and Zn was 8% by mass or more. The A36 to A49 aluminum-clad steel sheets shown in Table 3-1 to Table 3-4 were obtained as described above. At the same time, Al A50 and A51 coated steel sheets were also prepared in which neither a metal layer nor a metal oxide layer was provided over the Al coating layer. Table 1

[71] (7th by mass) (the rest: Fe and impurity) c Si Mn PS Al Cr Ti BN 0.22 0.27 1.23 0.017 0.003 0.029 0.19 0.024 0.0023 0.0030 R7R7 ίΠ / ΖΖηΖ / Ε / ΥΙΛΙ

[72] Table 2 (% by mass) (the remainder: Fe and impurity) c Si Mn PS Al Cr Ti BN Ni Cu Nb Sn Ca REM 0 0.23 0.25 1.19 0.015 0.003 0.022 0.21 0.025 0.0030 0.0030 0.20 0.20 0.013 0.010 0.0022 0.0012 0.0025

[73] A slip test was performed on the Al-plated steel sheets (Al to A51) obtained as described above using a die. This test simulated slippage between the die and the aluminum-plated steel sheet on a surface parallel to the direction in which the die moved during hot pressing. In the slip test, a device shown in Figure 2 was used. The Al-plated steel sheets were heated to the heating temperatures shown in Tables 3-1 through 3-4, then placed in a die at a pressure of 3 kN and slid a distance of 100 mm at the forming temperatures Tm (°C) and forming speeds V (mm / s) shown in Tables 3-1 through 3-4, thus forming the Al-plated steel sheets. The times taken from the end of heating to the beginning of forming were set at 3 to 30 seconds.The atmosphere during warming adjusted to the atmospheric environment. R7R7 ίη / ΖΖΠΖ / Ε / ΥΙΛΙ In addition, the matrix used for the slip test was prepared as described below.

[74] Matrix Production The steel corresponding to SKD61 (JIS G 4404: 2015) was prepared as tool steel, machined approximately into a shape approximated by a die shown by 6A and 6B in Figure 2 in an annealed condition, heated and held at 1180°C in a vacuum, quenched by nitrogen gas quenching, and then thermally refined by tempering at 540°C to 580°C such that the hardness became HV600. After that, finishing processing was carried out, thus obtaining substrates for a plurality of dies. On some of the substrates, an ion nitriding treatment was performed under the conditions described below. Specifically, the ion nitriding treatment was carried out in an atmosphere with a flow rate of 5% N2 (the remainder being H2) while maintaining the substrate at 500°C for 5 hours. Afterward, each of the test surfaces was polished to form a nitrided layer. The surface hardness after the nitriding layer was HV1200. In addition, on some of the substrates, a hard layer formed at a site where the nitriding layer formed. The hard layer was a PVD film, and plasma cleaning was performed with a thermal filament by applying a polarizing voltage in an Ar atmosphere using an arc ion coating device. Following this, a PVD film was formed at a polarizing voltage using a variety of metal targets, which were the sources of evaporation of the metal components, N2 gas as the base, and CH4 gas, if required, as reaction gases. The surface hardness of the die after PVD film formation was prepared to HV2500, HV3200, or HV7000.

[75] Tables 3-1 through 3-4 show the individual forming conditions, the surface hardness of the dies used, and the surface temperatures at the start of forming.

[76] Regarding the Al-coated steel sheets after the slip test, the external appearances were evaluated. In some examples, in one case where a metal layer was provided on the surface, the metal layer oxidized when the hot-pressed article was heated, and an oxide layer formed. R7R7 ίη / 77Ω7 / Β / YILI

[77] Evaluation of external appearance after training A position was cut by cutting at a sliding distance of 50 mm and the brightness (Gs60°) regulated in JIS Z 8741: 1997 was measured using a brightness meter. A brightness of 25 or less was rated as VG (Very Good), a brightness of more than 25 and 30 or less was rated as G (Good), and a brightness of more than 30 was rated as NG (Not Good). R7R7 ίη / ΖΖΩΖ / Ε / ΥΙΛΙ

[78] Evaluation of wear resistance In addition, the wear resistance of the dies was evaluated. Specifically, for the matrix surface shape profile after formation, the arithmetic mean roughness Ra was measured using a contact-type roughness gauge (Kosaka Laboratory Ltd. SE700, measuring probe diameter R: 2 pm) in accordance with JIS B 0601: 2013. The differences between the Ra of a non-sliding portion and the Ra of a sliding portion were compared; a case where the Ra of the sliding portion was 5 pm or more above the Ra of a non-sliding portion was rated as NG (not good), and a case where the difference was less than 5 pm was rated as G (good). The results are shown in Table 3-1 to Table 3-4.

[79] Table 3-1 Test No. Coating Layer Slip Test Test Conditions Metal Layer Metal Oxide Layer Thickness Heating Temperature Temperature Rise Rate Formation Temperature Determination 1 (Comparison of lower limit of Tm) Determination 2 (Comparison of upper limit of Tm) Determination 3 (Comparison of upper limit of Tm 2) [µm] rcj rc / s] Tm [°C] 800 HV_Matrix / 40 850 - (V / 4) HV_Matrix / 100 850 - (V / 2) HV.Matrix / 50 Example of the invention A1 ZnO 1.0 930 6 750 738 OK 815 OK 780 OK Example of the invention A2 ZnO 1.0 950 6 750 738 OK 815 OK 780 OK Comparative example A3 ZnO 1.0 SDQ 4 6_00 738 NG 815 OK 780 OK Comparative example A4 ZnO 1.0 1150 10 750 738 OK 815 OK 780 OK Example of the invention A5 ZnO 1.0 930 6 770 738 OK 815 OK 780 OK Example of the invention A6 ZnO 1.0 930 6 800 738 OK 815 OK 780 NG Comparative example A7 ZnO 1.0 930 6 600 738 NG 815 OK 780 OK Comparative example A8 ZnO 1.Example of invention A9 ZnO 1.0 930 6 850 738 OK 815 NG 780 NG Example of invention A10 ZnO 1.0 930 6 750 738 OK 805 OK 760 OK Example of invention A10 ZnO 1.0 930 6 750 738 OK 803 OK 755 OK Example of invention A12 ZnO 1.0 930 6 750 738 OK 798 OK 745 NG Example of invention A12 ZnO 1.0 930 6 750 738 OK 775 OK 700 NG Comparative example A13 ZnO 1.0 930 6 738 OK 795 NG 740 NG Comparative example A14 ZnO 1.0 930 6 800 738 OK 775 NG 700 NG Comparative Example A15 ZnO 1.0 930 6 75_0 785 NG 834 OK 818 OK Comparative Example A16 ZnO 1.0 930 6 750 770 NG 828 OK 806 OK Comparative Example A17 ZnO 1.0 930 6 800 785 OK 834 OK 818 OK Comparative Example A18 ZnO 1.0 930 6 800 770 OK 828 OK 806 OK Example of the Invention A19 ZnO 1.0 930 6 750 720 OK 808 OK 766 OK Example of the Invention A20 ZnO 1.0 930 6 800 720 OK 808 OK 766 NG Comparative example A21 ZnO 1.0 930 6 800 625 OK 770 NG 690 NG Example of the invention A22 ZnO 0.2 930 6 750 738 OK 815 OK 780 OK Example of the invention A23 ZnO 0.5 930 6 750 738 OK 815 OK 780 OK Example of the invention A24 ZnO 3.0 930 6 750 738 OK 815 OK 780 OK Example of the invention A25 ZnO 6.0 930 6 750 738 OK 815 OK 780 OK Example of the invention A26 ZnO 12.0 930 6 750 738 OK 815 OK 780 OK.

[80] Table 3-2 Test No. Slip Test Article formed by hot pressing after the slip test Die wear resistance Test conditions Die Forming speed Hardness Surface temperature External appearance of the formed article (gloss) Coating layer over Al plating V [mm / s] Hv.Diet [°C] Gs [60°] Type Thickness [mm] Example of the invention Al 40 2500 20 VG ZnO 1.0 G Example of the invention A2 40 2500 20 VG ZnO 1.0 G Comparative example A3 40 2500 20 NG ZnO 1.0 G Comparative example A4 40 2500 20 NG ZnO 1.0 G Example of the invention A5 40 2500 20 VG ZnO 1.0 G Example of the invention A6 40 2500 20 G ZnO 1.0 G Comparative example A7 40 2500 20 NG ZnO 1.0 NG Comparative example A8 40 2500 20 NG ZnO 1.0 G Example of the invention A9 80 2500 20 VG ZnO 1.0 G Example of the invention AID 90 2500 20 VG ZnO 1.0 G Example of the invention All 110 2500 20 G ZnO 1.0 G Example of the invention A12 200 2500 20 G ZnO 1.0 G Comparative Example Al 3 120 2500 20 NG ZnO 1.0 G Comparative Example A14 200 2500 20 NG ZnO 1.0 G Comparative Example Al 5 40 600 20 NG ZnO 1.0 NG Comparative Example Aló 40 1200 20 NG ZnO 1.0 NG Comparative Example A17 40 600 20 NG ZnO 1.0 NG Comparative Example A18 40 1200 20 NG ZnO 1.0 NG Example of the Invention Al 9 40 3200 20 VG ZnO 1.0 G Example of the Invention A20 40 3200 20 G ZnO 1.0 G Comparative Example A21 40 7000 20 NG ZnO 1.0 G Example of the invention A22 40 2500 20 G ZnO 0.2 G Example of the invention A23 40 2500 20 VG ZnO 0.5 G Example of the invention A24 40 2500 20 VG ZnO 3.0 G Example of the invention A25 40 2500 20 VG ZnO 6.0 G Example of the invention A26 40 2500 20 G ZnO 12.0 G.

[81] Table 3-3 Test No. Coating Layer Slip Test Test Conditions Metal Layer Metal Oxide Layer Thickness Heating Temperature Rate of Temperature Rise Formation Temperature Determination 1 (Comparison of lower limit of Tm) Determination 2 (Comparison of upper limit of Tm) Determination 3 (Comparison of upper limit of Tm 2) M reí rc / si Tm ['C] 800 HV_Matrix / 40 850 - (V / 4) HV.Matrix / 100 850 - (V / 2) HV.Matrix / 50 Example of the invention A27 ZnO 1.0 930 6 750 720 OK 808 OK 766 OK Example of the invention A28 ZnO 1.0 930 6 750 720 OK 808 OK 766 OK Example of the invention A29 ZnO 1.0 930 6 750 720 OK 808 OK 766 OK Example of invention A30 MgO 0.5 930 6 750 720 OK 808 OK 766 OK Example of invention A31 CaO 0.5 930 6 750 720 OK 808 OK 766 OK Example of invention A32 Ti Os 0.5 930 6 750 720 OK 808 OK 766 OK Example of invention A33 VsOs + TiO2 0.5 930 6 750 720 OK 808 OK 766 OK Example of invention A34 MgO + ZnO 0.Example of Invention A35 ZnO + resin 1.0 5 930 6 750 720 OK 808 OK 766 OK Example of Invention A36 Zn 0.5 930 6 750 720 OK 808 OK 766 OK Example of Invention A37 Mg 0.5 930 6 750 720 OK 808 OK 766 OK Example of Invention A38 Zn 0.5 930 8 750 720 OK 808 OK 766 OK Example of Invention A39 Mg 0.5 930 10 750 720 OK 808 OK 766 OK Example of Invention A40 Ca 0.5 930 6 750 720 OK 808 OK 766 OK Example of Invention A41 Ti 0.5 930 or 750 720 OK 808 OK 766 OK Example of Invention A42 V 0.5 930 6 750 720 OK 808 OK 766 OK Example of Invention A43 Zn + Mg 0.5 930 6 750 720 OK 808 OK 766 OK Example of Invention A44 Zn + V 0.5 930 6 750 720 OK 808 OK 766 OK Example of Invention A45 Zn + ZnO 2.0 930 6 750 720 OK 808 OK 766 OK Example of Invention A46 Mg + MgO 2.0 930 6 750 720 OK 808 OK 766 OK Example of the invention A47 Ca + CaO 2.0 930 6 750 720 OK 808 OK 766 OK Example of the invention A48 Ti + TiO2 2.0 930 6 750 720 OK 808 OK 766 OK Example of the invention A49 V + V2O5 2.0 930 6 750 720 OK 808 OK 766 OK Comparative example A5D None None 930 6 750 720 OK 808 OK 766 OK Comparative example A51 None None 930 or 750 785 NO 834 OK 818 OK.

[82] Table 3-4 Test No. Slip Test Article formed by hot pressing after the slip test Die wear resistance Test condition Die Forming speed Hardness Surface temperature External appearance of the formed article (gloss) Coating layer over Al plating V [mm / s] Hv.Diet [°C] Gs [60°] Type Thickness [g] Example of the invention A27 40 3200 50 VG ZnO 1.0 G Example of the invention A28 40 3200 100 VG ZnO 1.0 G Example of the invention A29 40 3200 200 G ZnO 1.0 G Example of the invention A30 40 3200 20 VG MgO 0.5 G Example of the invention A31 40 3200 20 VG CaO 0.5 G Example of the invention A32 40 3200 20 VG TiO2 0.5 G Example of the invention A33 40 3200 20 VG V2O5 + TiO2 0.5 G Example of the invention A34 40 3200 20 VG MgO + ZnO 0.5 G Example of the invention A35 40 3200 20 VG ZnO 0.5 G Example of the invention A36 40 3200 20 VG ZnO 0.7 G Example of the invention A37 40 3200 20 VG MgO 0.Example of Invention A38: 40 3200 20 G ZnO 0.7 G; Example of Invention A39: 40 3200 20 G MgO 0.7 G; Example of Invention A40: 40 3200 20 VG CaO 0.7 G; Example of Invention A41: 40 3200 20 VG TiO2 0.7 G; Example of Invention A42: 40 3200 20 VG V2O5 0.7 G; Example of Invention A43: 40 3200 20 VG ZnO + MgO 0.7 G; Example of Invention A44: 40 3200 20 VG ZnO + V2O5 0.7 G; Example of Invention A45: 40 3200 20 VG Zn + ZnO 2.5 G; Example of Invention A46 40 3200 20 VG Mg + MgO 2.5 G Example of the invention A47 40 3200 20 VG Ca + CaO 2.5 G Example of the invention A48 40 3200 20 VG Ti + TiO2 2.5 G Example of the invention A49 40 3200 20 VG V + V2O5 2.5 G Comparative example A50 40 3200 20 NG None - G Comparative example A51 40 600 20 NG None - NG.

[83] As is clear from Table 3-1 to Table 3-4, in accordance with the present invention, it is possible to obtain a component in which the sliding part of a hot-pressed article is beautiful (the brightness Gs60° is 30 or less) while improving the wear resistance of a die. In comparative examples, the heating temperature was too low for A3. Furthermore, the heating temperature was too high for A4. Therefore, a defect was generated in the aluminum-clad steel sheet after hot pressing; the brightness increased to over 30, and the external appearance deteriorated. In A7, the forming temperature was too low. In A8, A13, and A14, the forming temperatures were too high. Consequently, the external appearance of the aluminum-coated steel sheets deteriorated after hot pressing. In A7, the forming temperature was too low, and therefore the die also wore down. Furthermore, in A15 to A18, the surface hardness of the dies was too low, and in A15 and A16, the forming temperatures were too low. Therefore, the dies were worn, and the external appearance of the aluminum-coated steel sheets after pressing was poor. R7R7 ίη / 77Ω7 / Β / ΥΙΛΙ hot also deteriorated. In A21, the surface hardness of the die was too high. Therefore, a defect developed in the aluminum-clad steel sheet after hot pressing, and the external appearance deteriorated. In A50 and A51, because neither a metal layer nor a metal oxide layer was provided on the Al plating, a surface defect developed on the Al-plated steel sheet after hot pressing, and the external appearance deteriorated. In A51, the die hardness was also low, resulting in die wear. R7R7 ίη / 77Ω7 / Β / YILI Industrial applicability

[84] According to the present invention, a method of manufacturing a hot-stamped article to obtain a hot-stamped article that has an excellent external appearance from the wear of a die and one that has an external appearance can be obtained. surface while removing hot stamped item from the excellent surface Brief description of the reference symbols

[85] 1 steel sheet clad with Al base steel sheet 3A Aluminum plating layer (top surface side) 3B Aluminum plating layer (bottom surface side) 4A Coating layer (upper surface side) 4B Coating layer (lower surface side) Heating oven for aluminum-coated steel sheet 6A Matrix (upper matrix that comes into contact with the upper surface of the aluminum-clad steel sheet) 6B Die (lower die that comes into contact with the lower surface of the aluminum-clad steel sheet)

Claims

1. A method of manufacturing a hot-stamped article, comprising: heating an Al-plated steel sheet from 850°C to 1000°C; and forming the Al-plated steel sheet using a die to obtain a hot-pressed article after heating, wherein the Al-plated steel sheet has a base steel sheet, an Al plating layer formed on a surface of the base steel sheet, and a coating layer formed on a surface of the Al plating layer, the coating layer being a metal layer containing at least one of Mg, Ca, V, Ti, and Zn metals, a metal oxide layer containing an oxide of one or more of Mg, Ca, V, Ti, and Zn, or a mixed layer including the metal layer and the metal oxide layer, the die having a hard layer on a surface, HVMatriz, which is a surface hardness of the die at a position where the hard layer is present, is HV1500 or more and HV3800 or less.and when the temperature of the aluminum-clad steel sheet at the beginning of forming is indicated by Tm in a unit of °C, and the average movement speed of the die from the beginning of forming until reaching the bottom dead center is indicated by V in a unit of mm / s, in forming, Tm and V satisfy the following Formula (1), 800 - (HVMatriz / 4 0) < Tm < 850 - (V / 4) - (HVMatriz / 100) . . . Formula (1)., 2. The method of manufacturing a hot-stamped article according to claim 1, wherein HVMatriz, Tm and V satisfy the following Formula (2), 800 - (HVMatriz / 40) < Tm < 850 - (V / 2) - (HVMatriz / 50) . . . Formula (2) .

3. The method of manufacturing a hot-stamped article according to claim 1 or 2, wherein the thickness of the coating layer is from 0.3 to 10.0 pm.

4. The method of manufacturing an article formed by hot pressing according to claim 1 or 2, wherein the surface temperature of the die at the start of forming is 5°C or higher and 180°C or lower. R7R7 iP / ZZΖ / E / YILI 5. The method of manufacturing an article formed by hot pressing according to claim 3, wherein the surface temperature of the die at the beginning of forming is 5°C or higher and 180°C or lower.

6. A hot-pressed article consisting of an Al-plated steel sheet having an Al plating layer, wherein Gs60°, which is the brightness regulated by JIS Z 8741: 1997 on a surface, is 30 or less.

7. The article formed by hot pressing according to claim 6, wherein Gs60° is 25 or less.

8. The article formed by hot pressing according to claim 6 or 7, comprising: a coating layer on a surface of the Al plating layer, wherein the coating layer is a metal layer composed of at least one of the metals Mg, Ca, V, Ti and Zn, a metal oxide layer composed of an oxide of one or more of Mg, Ca, V, Ti and Zn, or a mixed layer formed by the metal layer and the metal oxide layer.

9. The article formed by hot pressing according to claim 8, wherein the thickness of the coating layer is from 0.3 to 10.0 pm.