WO2018123831A1

WO2018123831A1 - Plated steel sheet for hot pressing, method for manufacturing plated steel sheet for hot pressing, method for manufacturing hot-press-formed article, and method for manufacturing vehicle

Info

Publication number: WO2018123831A1
Application number: PCT/JP2017/046035
Authority: WO
Inventors: 雅寛久保; 嘉明中澤; 鈴木　利哉; 野村　成彦; 宗士藤田; 秀昭入川
Original assignee: 新日鐵住金株式会社
Priority date: 2016-12-28
Filing date: 2017-12-21
Publication date: 2018-07-05
Also published as: RU2710396C1; EP3564409A1; CA3048362A1; CA3048362C; KR20190085137A; CN110114510A; MX2019007700A; BR112019013257A2; JPWO2018123831A1; US20200024748A1; JP6369659B1; EP3564409A4; CN110114510B; KR102037085B1

Abstract

A plated steel sheet for hot pressing, and a method for manufacturing the same, the plated steel sheet for hot pressing having: a plated steel sheet body having a steel sheet and an aluminum plating layer provided on one or both surfaces of the steel sheet; and a zinc-based metal soap coating, the deposited amount of which is 7.1-19.8 g/m² in terms of Zn, the zinc-based metal soap coating being provided on the surface of the aluminum plating layer side of the plated steel sheet body (in the plated steel sheet body, when there is a zinc-oxide coating on the surface of the aluminum plating layer, the total deposited amount of the zinc oxide coating and the zinc-based metal soap coating is 7.1-19.8 g/m² in terms of Zn). A method for manufacturing a hot-press-formed article using the plated steel sheet for hot pressing, and a method for manufacturing a vehicle which uses a press-formed article manufactured by the method for manufacturing a hot-press-formed article.

Description

Hot-pressed plated steel sheet, hot-pressed plated steel sheet manufacturing method, hot-press formed product manufacturing method, and vehicle manufacturing method

The present disclosure relates to a hot-pressed plated steel sheet, a hot-pressed plated steel sheet manufacturing method, a hot-press molded product manufacturing method, and a vehicle manufacturing method.

In recent years, in order to protect the environment and prevent global warming, there is an increasing demand for reducing the consumption of chemical fuels, and this demand has affected various manufacturing industries. For example, an automobile that is indispensable for daily life and activities as a means of transportation is no exception, and there is a demand for improvement in fuel consumption by reducing the weight of the vehicle body. However, in automobiles, it is not permitted in terms of product quality to simply reduce the weight of the vehicle body, and it is necessary to ensure appropriate safety.

Most automobile structures are made of iron, particularly steel plates, and reducing the weight of these steel plates is important for reducing the weight of the vehicle body. However, as described above, it is not permitted to simply reduce the weight of the steel sheet, and it is also required to ensure the mechanical strength of the steel sheet. Requests for such steel sheets are made not only in the automobile manufacturing industry but also in various manufacturing industries. Therefore, research and development have been conducted on steel plates that can maintain or increase the mechanical strength even when they are thinner than the steel plates that have been used before by increasing the mechanical strength of the steel plates.

Generally, a material having a high mechanical strength tends to have a low shape freezing property in a forming process such as a bending process. When processing into a complicated shape, the process itself becomes difficult. As one of means for solving the problem regarding the formability, there is a so-called “hot press method (hot press method, high temperature press method, die quench method)”. In this hot pressing method, a material to be molded is once heated to a high temperature, the material softened by heating is pressed and molded, and then cooled.

According to this hot pressing method, since the material is once heated to a high temperature and softened, the material can be easily pressed. Therefore, a molded product having both good shape freezing property and high mechanical strength can be obtained by this hot pressing. In particular, when the material is steel, the mechanical strength of the press-formed product can be increased due to the quenching effect by cooling after forming.

However, when this hot pressing method is applied to a steel sheet, for example, by heating to a high temperature of 800 ° C. or higher, iron on the surface is oxidized and scale (oxide) is generated. Therefore, after the hot pressing is performed, a step of removing the scale (descaling step) is required, and productivity is lowered. Moreover, in the member etc. which require corrosion resistance, it is necessary to carry out a rust prevention process and metal coating to the member surface after a process, and a surface cleaning process and a surface treatment process are needed, and productivity falls too.

An example of a method for suppressing such a decrease in productivity is a method of coating a steel sheet. In general, various materials such as organic materials and inorganic materials are used as the coating on the steel plate. In particular, zinc-based plated steel sheets that have sacrificial anticorrosive action on steel sheets are widely used for automobile steel sheets and the like from the viewpoint of their anticorrosive performance and steel sheet production technology. The heating temperature in the hot pressing is aimed at a temperature higher than the Ac3 transformation point of steel in order to obtain a quenching effect. That is, the heating temperature is about 700 to 1000 ° C. However, this heating temperature is higher than the decomposition temperature of organic materials, the boiling point of metallic materials such as Zn materials, and the like. For this reason, when heated for hot pressing, the plating layer on the surface evaporates, which may cause significant deterioration of the surface properties.

Therefore, for steel plates that are hot-pressed to be heated to high temperatures, for example, Al-based metal-coated steel plates that have a higher boiling point than organic-based materials or Zn-based metal coatings, so-called aluminum-plated steel plates are used. It is preferable to do.

By applying an Al-based metal coating, it is possible to prevent the scale from adhering to the surface of the steel sheet, and a process such as a descaling process becomes unnecessary, thereby improving productivity. Further, since the Al-based metal coating also has a rust prevention effect, the corrosion resistance after painting is also improved. Patent Document 1 discloses a method in which an aluminum-plated steel sheet in which an Al-based metal coating is applied to steel having a predetermined steel component is used for hot pressing.

However, when an Al-based metal coating is applied, depending on the preheating conditions before the press working in the hot press method, the Al coating is first melted, and then an Al—Fe compound layer is formed by Fe diffusion from the steel plate. . The Al—Fe compound layer may grow and become an Al—Fe compound layer up to the surface of the steel sheet. Hereinafter, this compound layer is referred to as an alloy layer. Since this alloy layer is extremely hard, a processing flaw is formed by contact with a mold during press working.

On the other hand, Patent Document 2 discloses that a wurtzite-type compound film such as a ZnO film is aluminized steel sheet for the purpose of improving chemical treatment and corrosion resistance as well as hot lubricity to prevent the occurrence of processing flaws. A method of forming on the surface is disclosed.

On the other hand, Patent Document 3 discloses that one or more Zn compounds selected from the group consisting of Zn hydroxide, Zn phosphate, and organic acid Zn are used for the purpose of enhancing the adhesion of the ZnO film during press molding. A method for forming a film on the surface of an Al-plated steel sheet is disclosed. In the method of Patent Document 2, a ZnO film is formed by heat when hot-pressing an aluminum-plated steel sheet on which a Zn compound film is formed, and a ZnO film having excellent adhesion is formed. Lubricity, film adhesion, spot weldability, and post-coating corrosion resistance can be improved.

Patent Document 1: Japanese Patent Application Laid-Open No. 2000-38640 Patent Document 2: International Publication No. 2009/131233 Patent Document 3: Japanese Patent Application Laid-Open No. 2014-139350

Here, all of the plated steel sheets of Patent Documents 2 to 3 are excellent in hot lubricity and can suppress the generation of work defects. By the way, in general, when hot press forming is performed using a non-plated material or a plated steel plate, the hot press mold slide on which the plated steel plate slides, such as the vertical wall portion and flange portion of the press-formed product. Wear occurs on the surface. For this reason, in the high surface pressure portion of hot press molding, it is necessary to care for the die as a countermeasure against wear occurring on the sliding surface of the die. Although it was expected that the plating wear was reduced by the plated steel sheets of Patent Documents 2 to 3, even with Patent Documents 2 to 3, the mold wear could not be solved like other non-plated materials and plated steel sheets. It was.

Then, the subject of 1 aspect of this indication is providing the plated steel plate for hot press which suppresses generation | occurrence | production of the sliding surface of the metal mold | die for hot press, and its manufacturing method.
Another problem of one aspect of the present disclosure is a method for producing a hot press-formed product that uses the hot-pressed plated steel sheet and suppresses the occurrence of wear on the sliding surface of the hot press die, And it is providing the manufacturing method of the vehicle using the press molding manufactured by the manufacturing method of a hot press molding.

When the inventors examined, the following was found. When a zinc oxide film layer (ZnO film) is formed on the surface of the aluminum plating layer, the surface properties of the aluminum plating layer having a convex portion on the surface are reflected in the surface properties of the zinc oxide film. When the aluminum-plated steel sheet with the zinc oxide film layer formed on the surface and the surface of the hot press mold slide, the local pressure is applied to the convex part of the zinc oxide film, thereby Wear on the sliding surface of the mold. Thus, the inventors have found that if a zinc oxide film with high smoothness can be formed, the occurrence of wear on the sliding surface of the hot press die can be suppressed.

The gist of the present disclosure is as follows.

<1>
A plated steel sheet body having a steel sheet and an aluminum plating layer provided on one or both surfaces of the steel sheet;
A zinc-based metal soap film provided on the surface of the plated steel sheet body on the side of the aluminum plating layer and having an adhesion amount of 7.1 to 19.8 g / m ^{2 in} terms of Zn amount;
A hot-pressed plated steel sheet.
<2>
A plated steel sheet body having a steel sheet, an aluminum plating layer provided on one or both surfaces of the steel sheet, and a zinc oxide film provided on the surface of the aluminum plating layer;
A zinc-based metal soap film provided on the surface of the zinc oxide film of the plated steel sheet body;
With
A hot-pressed plated steel sheet, wherein the total adhesion amount of the zinc oxide film and the zinc-based metal soap film is 7.1 to 19.8 g / m ² in terms of Zn content.
<3>
For hot pressing according to <2>, more than half of the total amount of adhesion of the zinc oxide film and the zinc-based metal soap film is the amount of adhesion of the zinc-based metal soap film Plated steel sheet.
<4>
<1> to <3>, wherein the zinc-based metal soap film is a film of at least one zinc-based metal soap selected from the group consisting of zinc bisoctanoate, zinc octylate, zinc laurate, and zinc stearate. A plated steel sheet for hot pressing as set forth in any one of the above items.
<5>
A plated steel sheet body having a steel sheet and an aluminum plating layer provided on one or both surfaces of the steel sheet;
A zinc oxide film provided on the surface of the plated steel sheet body on the aluminum plating layer side;
Have
A plated steel sheet for hot pressing, wherein the maximum value of the skewness Rsk of the surface roughness curve of the zinc oxide film is less than 0.
<6>
On the surface of the plated steel sheet main body having a steel sheet and an aluminum plated layer provided on one or both sides of the steel sheet, the adhesion amount of the adhesion portion is 7.1 to 19.8 g in terms of Zn amount. method for manufacturing a hot-press coated steel sheet comprising a step of forming a zinc-based metal soap coating so that / m ^2.
<7>
The zinc oxide film on the surface of the zinc oxide film of a plated steel sheet main body having a steel plate, an aluminum plating layer provided on one or both surfaces of the steel plate, and a zinc oxide film provided on the aluminum plating layer Plating for hot press having a step of forming a zinc-based metal soap film so that the total adhesion amount of the adhesion portion with the adhesion amount of the zinc is 7.1 to 19.8 g / m ² in terms of Zn amount A method of manufacturing a steel sheet.
<8>
In the step of forming the zinc-based metal soap film, more than half of the total adhesion amount of the zinc oxide film and the zinc oxide film is defined as the adhesion amount of the adhesion part of the zinc-based metal soap film. The manufacturing method of the plated steel plate for hot press as described in <7>.
<9>
The method for producing a hot-pressed plated steel sheet according to any one of <6> to <8>, further comprising a step of heating the zinc-based metal soap film at 300 ° C. or more to form a zinc oxide film.
<10>
The method for producing a hot-pressed plated steel sheet according to <9>, wherein the maximum value of the skewness Rsk of the surface roughness curve of the zinc oxide film formed by heating the zinc-based metal soap film is less than 0.
<11>
<6> to <10>, wherein the zinc-based metal soap film is a film of at least one zinc-based metal soap selected from the group consisting of zinc bisoctanoate, zinc octylate, zinc laurate, and zinc stearate. The manufacturing method of the plated steel plate for hot press of any one of Claims 1.
<12>
<6>-<11> A process for producing a hot-pressed plated steel sheet by the method for producing a hot-pressed plated steel sheet according to any one of the above items, wherein the zinc-based metal soap film is formed. And forming at least the zinc-based metal soap film on the surface on the aluminum plating layer side of the plated steel sheet body on the surface in contact with the sliding surface of the hot pressing mold in a subsequent hot pressing step. Manufacturing a hot-pressed plated steel sheet,
A hot pressing step for hot press forming the plated steel sheet for hot pressing;
A method for producing a hot press-formed product having
<13>
The manufacturing method of the hot press-formed product which hot-press-forms the hot-pressed plated steel plate manufactured by the manufacturing method of the hot-pressing plated steel plate as described in <10>.
<14>
<12> or <13> The manufacturing method of the vehicle which attaches the press molded product manufactured by the manufacturing method of the hot press molded product as described in <13> toward the outer side of a vehicle with a surface with a zinc oxide film.

According to one aspect of the present disclosure, it is possible to provide a hot-pressed plated steel sheet that suppresses the occurrence of wear on the sliding surface of the hot-press mold and a method for manufacturing the hot-pressed plated steel sheet.
Moreover, according to one aspect of the present disclosure, a method for manufacturing a hot press-formed product that uses the hot-pressed plated steel sheet and suppresses the occurrence of scratches on the sliding surface of the hot press die, and The manufacturing method of the vehicle using the press-molded product manufactured by the manufacturing method of the hot press-formed product can be provided.

It is a schematic sectional drawing which shows an example of the hot-pressed plated steel plate which concerns on this embodiment. It is a schematic sectional drawing which shows a mode that the plated steel plate for hot press concerning this embodiment and the metal mold | die contacted. It is a schematic sectional drawing which shows an example of the conventional plated steel plate for hot presses. It is a schematic sectional drawing which shows a mode that the conventional plated steel plate for hot presses and the metal mold | die contacted. It is process drawing which shows an example of the normal process from manufacture of a plated steel plate to hot press forming. It is a schematic block diagram which shows the evaluation apparatus of hot lubricity.

Next, an embodiment that is an example of the present disclosure will be described in detail.
Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings.
In addition, in this specification and drawing, about the component which has the substantially the same function structure, duplication description may be abbreviate | omitted by attaching | subjecting the same code | symbol.
In addition, a numerical range expressed using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.
In addition, the term “process” is not limited to an independent process, and is included in this term if the intended purpose of the process is achieved even when it cannot be clearly distinguished from other processes.

<Plated steel plate>
A plated steel sheet according to an embodiment of the present disclosure will be described.
The hot-pressed plated steel sheet (hereinafter also referred to as “plated steel sheet”) according to the present embodiment includes a steel sheet and an aluminum plated layer (hereinafter also referred to as “Al plated layer”) provided on one or both surfaces of the steel sheet. And a zinc-based metal soap film provided on the surface of the plated steel sheet on the side of the Al plating layer and having an adhesion amount of 7.1 to 19.8 g / m ^{2 in} terms of Zn amount. Have.
In the plated steel sheet according to the present embodiment, the plated steel sheet body may have a zinc oxide film (hereinafter also referred to as “ZnO film”) provided on the Al plating layer. However, when the plated steel sheet main body has a ZnO film, the adhesion amount of the total adhesion part of the ZnO film and the zinc-based metal soap film is 7.1 to 19.8 g / m ^{2 in} terms of Zn amount.

The plated steel sheet according to the present embodiment suppresses the occurrence of wear on the sliding surface of a hot press die (hereinafter also referred to as “die”) when hot press-molded by the above configuration. And the plated steel plate which concerns on this embodiment was discovered by the knowledge shown below.

First, analysis of a press-formed product and a mold obtained by hot press-molding a plated steel sheet (a plated steel sheet having a ZnO film formed on an Al plating layer) of Patent Document 2 confirmed the following. In the plated steel sheet of Patent Document 2, the ZnO film had convex portions along the surface properties of the Al plating layer (see FIG. 2A: in FIG. 2A, 12 is a steel sheet, 14 is an Al plating layer, and 16 is a ZnO film. Show.) When the plated steel sheet is hot press-molded, a local surface pressure is applied to the convex part of the ZnO film from the sliding surface that slides with the mold, so that the top of the convex part of the ZnO film peels off, and Al The plating layer was exposed. In addition, a mold-derived substance adhered in the vicinity of the exposed Al plating layer. From this, it was found that Al in the exposed Al plating layer reacts with Fe of the mold to generate an intermetallic compound, and wears the sliding surface of the mold.
In other words, the following was found. 1) In the plated steel sheet of Patent Document 2, since the thin ZnO film is formed on the Al plating layer, the maximum value of the skewness Rsk of the surface roughness curve exceeds 0, and a protruding portion protruding to the surface is formed. That. 2) The protruding part protruding from the surface should be in point contact with the mold. 3) When the press pressure of hot press forming increases, high surface pressure is generated at the convex portions on the surface, and the sliding surface of the mold is worn (see FIG. 2B: in FIG. 2B, 12 is a steel plate, 14 is Al plating layer, 16 is a ZnO film, and 26 is a mold).

Therefore, the inventors have found that the following is effective in suppressing wear of the sliding surface of the mold. 1) Applying a lubricant to improve the smoothness of the ZnO film. 2) Use zinc-based metal soap containing Zn as a lubricant in consideration of chemical conversion properties after hot press molding and corrosion resistance. Specifically, the inventors have found the following.

Zinc-based metal soap is used in lubricant applications, so if the amount of adhesion is increased, the surface of the underlying plated steel sheet body (Al-plated layer or ZnO film) is hardly affected, and the zinc-based metal has high smoothness. A soap film can be formed (see FIG. 1A: in FIG. 1A, 10 indicates a plated steel sheet, 10A indicates a plated steel sheet body, 12 indicates a steel sheet, 14 indicates an Al plating layer, 16 indicates a ZnO film, and 18 indicates a zinc-based metal soap film. .) This zinc-based metal soap film becomes a ZnO film as a result of the oxidation of zinc and the decomposition of organic substances other than zinc (fatty acids, etc.) by heating before pressing in hot press molding. That is, at the time of hot press forming, a ZnO film having high smoothness (for example, a ZnO film having a maximum skewness Rsk of the surface roughness curve of less than 0) is formed on the surface of the plated steel sheet. In addition, it is good also as a ZnO film | membrane by heating a zinc type metal soap film | membrane before hot press molding.

Since the ZnO film on the outermost surface of the plated steel sheet is smooth, the surface pressure applied to the ZnO film from the sliding surface that slides on the mold is reduced when the plated steel sheet is hot press formed. That is, the ZnO film of the plated steel sheet and the sliding surface of the mold come into surface contact with each other, the real contact area between the ZnO film of the plated steel sheet and the sliding surface of the mold increases, and the contact surface pressure is reduced. For this reason, peeling of the ZnO film is suppressed (see FIG. 1B: in FIG. 1B, 10 is a plated steel sheet, 10A is a plated steel sheet body, 12 is a steel sheet, 14 is an Al plating layer, 16 is a ZnO film, and 18A is a zinc-based metal. ZnO film formed from a soap film, 26 indicates a mold). Since the exfoliation of the ZnO film is suppressed, it is possible to prevent the metal mold and the Al plating layer from contacting and reacting to generate an intermetallic compound. As a result, since the production | generation of the metal tube compound which causes abrasion of a metal mold | die is suppressed, abrasion of the sliding surface of the metal mold | die which a plated steel plate slides is suppressed.

Based on the above knowledge, the inventors have found that the plated steel sheet according to the present embodiment suppresses the occurrence of wear on the sliding surface of the hot press die when hot press-molded by the above configuration. .
The inventors have also found the following. In the plated steel sheet according to the present embodiment, a ZnO film formed from a zinc-based metal soap film is difficult to peel off during and after hot press molding, and wear of the mold hardly occurs. Therefore, a molded product having high mass productivity, high chemical conversion property, excellent adhesion between the Al plating layer after molding and the ZnO film, and high corrosion resistance (that is, corrosion resistance after coating) can be obtained.

Hereinafter, details of the plated steel sheet according to the present embodiment will be described.

<Plated steel plate body>
The plated steel sheet body includes a steel sheet and an Al plating layer provided on one or both surfaces of the steel sheet. And the plated steel plate body may have a ZnO film provided on the Al plating layer.

(steel sheet)
As a steel plate (steel plate before plating), for example, mechanical deformation such as high mechanical strength (for example, tensile strength, yield point, elongation, drawing, hardness, impact value, fatigue strength, creep strength, and the like) It is preferable to use a steel sheet formed so as to have various properties related to fracture. An example of the steel plate (steel plate before plating) that realizes high mechanical strength used in the plated steel plate according to this embodiment is as follows. In addition, the description of% means the mass% unless there is particular notice.

The steel sheet is, by mass%, C: 0.1 to 0.6%, Si: 0.01 to 0.6%, Mn: 0.5 to 3%, Ti: 0.01 to 0.1%, and B: preferably contains at least one of 0.0001 to 0.1%, and consists of the remainder Fe and impurities.

C is included to ensure the desired mechanical strength. When C is less than 0.1%, sufficient mechanical strength cannot be improved, and the effect of containing C becomes poor. On the other hand, when C exceeds 0.6%, the steel sheet can be further hardened, but melt cracking tends to occur. Therefore, the C content is preferably 0.1% or more and 0.6% or less.

Si is one of the strength improving elements for improving the mechanical strength, and is contained in the same manner as C to ensure the desired mechanical strength. When Si is less than 0.01%, it is difficult to exert the effect of improving the strength and sufficient mechanical strength cannot be improved. On the other hand, Si is also an easily oxidizable element. Therefore, when Si exceeds 0.6%, wettability is lowered when hot-dip aluminum plating is performed, and non-plating may occur. Therefore, the Si content is preferably 0.01% or more and 0.6% or less.

Mn is one of the strengthening elements that strengthens steel and is also one of the elements that enhances hardenability. Further, Mn is effective in preventing hot brittleness due to S which is one of impurities. When Mn is less than 0.5%, these effects cannot be obtained, and the above effects are exhibited when 0.5% or more. On the other hand, when Mn exceeds 3%, there is a possibility that the residual γ phase becomes excessive and the strength is lowered. Therefore, the Mn content is preferably 0.5% or more and 3% or less.

Ti is one of strength-enhancing elements and is an element that improves the heat resistance of the Al plating layer. When Ti is less than 0.01%, the effect of improving the strength and the effect of improving the oxidation resistance cannot be obtained, and these effects are exhibited when the content is 0.01% or more. On the other hand, if Ti is contained too much, for example, carbide or nitride may be formed to soften the steel. In particular, when Ti exceeds 0.1%, there is a high possibility that the target mechanical strength cannot be obtained. Therefore, the Ti content is preferably 0.01% or more and 0.1% or less.

B has the effect of increasing the strength by acting during quenching. When B is less than 0.0001%, such an effect of improving the strength is low. On the other hand, when B exceeds 0.1%, inclusions are formed and become brittle, which may reduce the fatigue strength. Therefore, the B content is preferably 0.0001% or more and 0.1% or less.

In addition, this steel plate may contain impurities that are mixed in in other manufacturing processes.

A steel plate formed of such chemical components is quenched by heating by a hot press method or the like, and can have a mechanical strength of about 1500 MPa or more. Although it is a steel plate having such a high mechanical strength, since it can be hot-pressed in a state softened by heating, it can be easily formed if it is processed by a hot pressing method. Further, the steel sheet can realize high mechanical strength, and can maintain or improve the mechanical strength even if it is thinned for weight reduction.

(Al plating layer)
The Al plating layer is formed on one side or both sides of the steel plate before plating. The Al plating layer is formed on one or both surfaces of a steel plate by, for example, a hot dipping method, but the forming method is not limited to this.

The component composition of the Al plating layer may contain 50% or more of Al. Elements other than Al are not particularly limited, but Si may be positively contained for the following reasons.

When Si is contained, an Al—Fe—Si alloy layer is formed at the interface between the plating and the base iron, and the formation of a brittle Al—Fe alloy layer generated during hot dipping can be suppressed. When Si is less than 3%, the Al—Fe alloy layer grows thick at the stage of applying aluminum plating, which may promote cracking of the plating layer during processing and may adversely affect the corrosion resistance. On the other hand, when Si exceeds 15%, on the contrary, the volume ratio of the layer containing Si may increase, and the workability and corrosion resistance of the plating layer may be reduced. Therefore, the Si content in the Al plating layer is preferably 3 to 15%.

¡Al plating layer prevents corrosion of steel sheet. Further, when the plated aluminum sheet is processed by a hot press method, the Al plating layer does not generate scale (iron oxide) due to oxidation of the surface even when heated to a high temperature. By preventing the generation of scale in the Al plating layer, the scale removal process, the surface cleaning process, the surface treatment process, and the like can be omitted, and the productivity of the molded product is improved. Moreover, the Al plating layer has a boiling point and a melting point higher than those of a plating layer made of an organic material or a plating layer made of another metal material (for example, a Zn material). Therefore, when forming by hot press forming, the plating layer does not evaporate, so hot press forming at a high temperature is possible. Therefore, the moldability in the hot press molding can be further enhanced and molding can be easily performed.

The Al plating layer can be alloyed with Fe in the steel sheet by heating at the time of hot dipping and hot pressing. Therefore, the Al plating layer is not necessarily formed of a single layer having a constant component composition, and includes a partially alloyed layer (alloy layer).

(ZnO film)
A ZnO film (film containing ZnO) is formed on the surface of the Al plating layer of the plated steel sheet body as necessary. In particular, when the zinc-based metal soap film is formed on a part of the surface on the Al plating layer side of the plated steel sheet body, the ZnO film is preferably formed on the entire surface of the Al plated layer of the plated steel sheet body. In the region where the ZnO film is the outermost surface layer of the plated steel sheet, the ZnO film imparts hot lubricity, chemical conversion property, and corrosion resistance to the plated steel sheet.

The formation method of the ZnO film is not particularly limited, and can be formed on the Al plating layer by the methods described in

Patent Documents

1 and 2, for example.

The adhesion amount of the adhesion portion of the ZnO film (hereinafter also simply referred to as “adhesion amount”) is preferably 0.5 to 7 g / m ^{2 in} terms of Zn amount per one side of the steel sheet. When the ZnO film adhesion amount is 0.5 g / m ² or more in terms of Zn amount, the lubrication improving effect can be effectively exhibited in a region in contact with other than the sliding surface of the mold in hot press molding. it can. On the other hand, when the adhesion amount of the ZnO film exceeds 7 g / m _{2 in} terms of Zn amount, the thickness of the Al plating layer and the ZnO film becomes too thick, and the weldability and paint adhesion may deteriorate.
The adhesion amount of the ZnO film is particularly preferably about 1 to 4 g / m ^{2 in} terms of Zn amount per one surface of the steel sheet, and lubrication during hot pressing is performed in a region in contact with other than the sliding surface of the mold in hot press forming. In addition, the weldability and paint adhesion can be improved.
In addition, as a measuring method of the adhesion amount of a ZnO film | membrane, a fluorescent X ray method is utilized. Specifically, a calibration curve is created using several types of standard samples with a known amount of ZnO film deposited (in terms of Zn content) by the fluorescent X-ray method, and the Zn intensity of the sample to be measured is measured using the ZnO film. In terms of the adhesion amount, the adhesion amount of the ZnO film is obtained.

<Zinc-based metal soap film>
A zinc-based metal soap film (a film containing a zinc-based metal soap) is provided on the surface of the plated steel sheet on the Al plating layer side. Specifically, when the ZnO film is not provided on the Al plating layer of the plated steel sheet body, the zinc-based metal soap film is provided on the surface (entire surface) of the Al plating layer. On the other hand, when the ZnO film is provided on the Al plating layer of the plated steel sheet body, the zinc-based metal soap film is provided on at least a part of the surface of the ZnO film.

The metal soap of the zinc-based metal soap film includes a metal salt (fatty acid zinc salt) of a fatty acid (for example, a fatty acid having 7 to 20 carbon atoms) and zinc. The fatty acid may be either a saturated fatty acid or an unsaturated fatty acid.
In particular, from the viewpoint of forming a zinc-based metal soap film with high smoothness, the metal soap of the zinc-based metal soap film is preferably a liquid metal soap at room temperature (25 ° C.).
Specific examples of the zinc-based metal soap film include at least one zinc-based metal soap film selected from the group consisting of zinc bisoctanoate, zinc octylate, zinc laurate, and zinc stearate. .

Since the zinc-based metal soap film is formed using a zinc-based metal soap for lubricants, it is a highly smooth film. On the other hand, the zinc-based metal soap film, for example, is oxidized by heating at 300 ° C. or higher (heating before hot press molding, or prior heating before hot press molding), and other than zinc. Organic substances (such as fatty acids) are decomposed to form a ZnO film. That is, the area | region in which the zinc-type metal soap film | membrane of the plated steel plate main body was provided turns into an area | region coat | covered with the ZnO film | membrane derived from a zinc-type metal soap film | membrane by heating.

Then, by heating the zinc-based metal soap film having high smoothness, a ZnO film having high smoothness (for example, a ZnO film in which the maximum value of the skewness Rsk of the surface roughness curve satisfies Rsk <0) can be formed. . When the plated steel sheet is hot-press formed by this highly smooth ZnO film, wear of the sliding surface of the mold on which the plated steel sheet slides is suppressed.

Here, when the plated steel sheet body does not have a ZnO film (that is, when a zinc-based metal soap film is formed on the surface of the Al plating layer of the plated steel sheet body), Even if it is too little or too much, it is affected by the surface properties of the base plated steel sheet body (Al plating layer), and the smoothness of the zinc-based metal soap film as well as the ZnO film formed from the zinc-based metal soap film. Smoothness decreases. Accordingly, the adhesion amount of the adhesion part of the zinc-based metal soap film (hereinafter also simply referred to as “adhesion amount”) is 7.1 to 19.8 g / m ^{2 in} terms of Zn amount, preferably 8.82 to 16. 3 g / m ² . Further, the adhesion amount is in the range of 8.9 to 19.8 g / m ² , 9.2 to 19.8 g / m ² , or 9.5 to 19.8 g / m ² in terms of Zn amount. There may be.

On the other hand, when the plated steel sheet body has a ZnO film (that is, when a zinc-based metal soap film is formed on the surface of the ZnO film of the plated steel sheet body), the amount of zinc-based metal soap film deposited is It is necessary to consider that the surface of the ZnO film is smooth in both the ZnO film and the ZnO film formed from the zinc-based metal soap film. Therefore, the total adhesion amount of the zinc-based metal soap film to the adhesion amount of the ZnO film on the plated steel sheet body (the total adhesion amount of the ZnO film and the zinc-based metal soap film on the plating steel sheet body) is 7. 1 to 19.8 g / m ² , preferably 8.82 to 16.3 g / m ² . Further, the adhesion amount is in the range of 8.9 to 16.3 g / m ² , 9.2 to 16.3 g / m ² , or 9.5 to 16.3 g / m ² in terms of Zn amount. There may be.

When the plated steel sheet body has a ZnO film (that is, when a zinc-based metal soap film is formed on the surface of the ZnO film of the plated steel sheet body), the surface smoothness of the ZnO film formed from the zinc-based metal soap film is increased. From the viewpoint, it is preferable that more than half of the total adhesion amount of the ZnO film and the zinc oxide film is the adhesion amount of the zinc-based metal soap film.

In addition, as a measuring method of the adhesion amount of the zinc-based metal soap film, for example, a fluorescent X-ray method is used. Specifically, a calibration curve is created using several types of standard samples with known amounts of zinc-based metal soap film deposited (in terms of Zn content) by the fluorescent X-ray method, and the Zn intensity of the sample to be measured is determined. In terms of the amount of zinc-based metal soap film, the amount of zinc-based metal soap film is determined.

Here, the zinc-based metal soap film is preferably formed at least on the surface on the Al plating layer side of the plated steel sheet body on the surface that contacts the sliding surface of the hot press mold.
Specifically, for example, when a ZnO film is formed on the Al plating layer of the plated steel sheet body, the zinc-based metal soap film is obtained when the plated steel sheet is hot press-molded with a hot pressing die. It is good to be formed at least on the surface of the plated steel sheet (Al plated layer or ZnO film of the plated steel sheet main body) to be the vertical wall part and the flange part of the press-formed product. The surface of the plated steel sheet in the vertical wall and flange part of the press-formed product is a mold (for example, “a holder part and a shoulder part for holding a steel sheet” in the upper mold, and “a holder part for holding a steel sheet in the lower mold”) And the shoulder portion ”) (see FIG. 3 (8)), and therefore, the mold is likely to be worn.
On the other hand, when the ZnO film is not formed on the Al plating layer of the plated steel sheet body, the zinc-based metal soap film is preferably formed on the entire surface of the Al plating layer.

The plated steel sheet according to the present embodiment described above is used for hot press forming in a state having a zinc-based metal soap film, but hot press-forming in a state in which the zinc-based metal soap film is preheated to form a ZnO film. May be used for
That is, the plated steel sheet according to the present embodiment is a plated steel sheet body having a steel sheet and an Al plated layer provided on one or both sides of the steel sheet, and ZnO provided on the surface of the plated steel sheet body on the Al plated layer side. As a plated steel sheet for hot pressing in which the maximum value of the skewness Rsk of the surface roughness curve of the ZnO film is less than 0, the film may be used for hot press forming.

Here, the skewness Rsk of the roughness curve is measured according to JIS B 0601 (2001). Specifically, the skewness Rsk of the roughness curve is measured under the following measurement conditions according to IS B 0601 (2001).

-Measurement condition-
Measuring device: Mitutoyo Co., Ltd. “Surface Roughness / Contour Shape Measuring Machine Form Tracer”
Measurement length L: 9.6 mm
Cut-off wavelength λc: 0.8 mm
Tip shape of stylus: tip angle 60 ° conical stylus tip radius: 2 μm
Measurement speed: 1mm / sec

Here, the skewness Rsk of the roughness curve is defined in JIS B 0601 (2001), and is an index representing the symmetry of the peak and valley with respect to the average line of the roughness curve. When this Rsk is positive (0 <Rsk), it indicates a state in which the peaks and valleys are unevenly distributed below the average line of the roughness curve. On the other hand, when this Rsk is negative (Rsk <0), it indicates a state in which peaks and valleys are unevenly distributed above the average line of the roughness curve. That is, when Rsk is negative (Rsk <0), there are few peaks protruding on the surface, indicating a state of high smoothness.
And if the value of Rsk is positive even partly, there will be a protruding part protruding on part of the surface of the hot-pressed plated steel sheet. That is, the surface pressure between the convex portion on the surface and the sliding surface of the mold becomes relatively high, and wear of the sliding surface of the mold is likely to occur. Therefore, the maximum value of Rsk on the surface of the ZnO film is preferably less than 0. By making the maximum value of Rsk on the surface of the ZnO film less than 0, a uniform contact between the surface of the ZnO film and the sliding surface of the mold can be realized, and the effective surface pressure when the mold slides can be reduced. The wear of the sliding surface of the mold is suppressed.

<Method for producing hot-pressed plated steel sheet>
The manufacturing method of the plated steel plate which concerns on this embodiment has the process of forming a zinc type metal soap film | membrane on the surface at the side of the Al plating layer of a plated steel plate main body.
Specifically, for example, when the ZnO film is not provided on the Al plating layer of the plated steel sheet body, the method for manufacturing the plated steel sheet includes a step of forming a zinc-based metal soap film on the surface of the Al plating layer. On the other hand, when the ZnO film is provided on the Al plating layer of the plated steel sheet body, the method for producing the plated steel sheet includes a step of forming a zinc-based metal soap film on at least a part of the surface of the ZnO film.

When the plated steel sheet body does not have a ZnO film (that is, when a zinc-based metal soap film is formed on the surface of the Al plating layer of the plated steel sheet body), the adhesion amount of the zinc-based metal soap film is 7 in terms of Zn amount. 0.1 to 19.8 g / m ² , preferably 8.82 to 16.3 g / m ² .
On the other hand, when the plated steel sheet body has a ZnO film (that is, when a zinc-based metal soap film is formed on the surface of the ZnO film of the plated steel sheet body), the total zinc system combined with the ZnO film adhesion amount of the plated steel sheet body The adhesion amount of the metal soap film (total adhesion amount of the ZnO film and the zinc-based metal soap film on the plated steel sheet body) is 7.1 to 19.8 g / m ^{2 in} terms of Zn amount, preferably 8.82 to 16 .3 g / m ² . However, from the viewpoint of enhancing the smoothness of the surface of the ZnO film formed from the zinc-based metal soap film, more than half of the total adhesion amount of the ZnO film and the zinc oxide film is the adhesion amount of the zinc-based metal soap film. It is preferable to do.

In the step of forming the zinc-based metal soap film, the zinc-based metal soap film is formed by applying the zinc-based metal soap itself using a known coating device such as a spray coater, a roll coater, or a die coater. In addition, a zinc-based metal soap film may be formed using a sponge, an electrostatic oiling device, or the like. At the time of application, the viscosity of the zinc-based metal soap may be adjusted with an organic solvent. And after apply | coating zinc-based metal soap, a zinc-based metal soap film is formed as needed, for example by drying the coating film of zinc-based metal soap 300 degreeC or more for 2 minutes or more.

Here, in the step of forming the zinc-based metal soap film, the type of zinc-based metal soap and the formation area of the zinc-based metal soap film are as described above.

The method for manufacturing a plated steel sheet according to the present embodiment may include a step of heating the zinc-based metal soap film at 300 ° C. or higher to obtain a ZnO film. In other words, by heating, the zinc-based metal soap film is oxidized with zinc, and organic substances other than zinc (fatty acid, etc.) are decomposed to form a ZnO film (for example, a surface roughness curve skewness Rsk satisfying Rsk <0). ), The obtained plated steel sheet may be used for hot press forming.
In addition, it is preferable to perform the heating which uses a zinc-type metal soap film | membrane as a ZnO film | membrane on the conditions of 300 degreeC or more and 2 minutes or more.

<Method of manufacturing a hot press-formed product>
The method for manufacturing a hot press-formed product according to the present embodiment is a method for manufacturing a formed product by hot press-forming the plated steel sheet according to the present embodiment.

Specifically, for example, the method for manufacturing a hot press-formed product is a step of forming a zinc-based metal soap film in the method for manufacturing a plated steel sheet according to the present embodiment, and the surface on the Al plating layer side of the plated steel sheet body. Among the above, at least a zinc-based metal soap film is formed on the surface that contacts the sliding surface of the hot press mold, and then the manufactured hot press plated steel sheet is hot press formed. In this case, after the zinc-based metal soap film of the plated steel sheet becomes a ZnO film by heating before pressing, the plated steel sheet is pressed.

Further, for example, in the method for producing a hot press-formed product, in the method for producing a plated steel sheet according to the present embodiment, the zinc-based metal soap film is heated at 300 ° C. or higher, and the skewness Rsk of the surface roughness curve is 0 < You may hot press-mold the plated steel plate manufactured through the process of setting it as the ZnO membrane | film | coat which satisfy | fills Rsk.

In the method of manufacturing a hot press-formed product according to the present embodiment, in the hot press-forming method, for example, blanking (punching) is performed as necessary, and then heated to a high temperature to soften the plated steel sheet. And using the metal mold | die, the softened plated steel plate is pressed and shape | molded, and it cools after that. Thus, in hot press forming, subsequent plating can be easily performed by once softening the plated steel sheet. Moreover, the hot-pressed press-molded product is quenched by heating and cooling, and becomes a molded product having a high tensile strength of about 1500 MPa or more.

As a heating method for hot press forming, it is possible to adopt a heating method by infrared heating, electric heating, induction heating, etc. in addition to a normal electric furnace and radiant tube furnace.

The Al plating layer of the plated steel sheet melts when heated to a temperature higher than the melting point, and at the same time, the Al phase changes into an Al—Fe alloy phase and an Al—Fe—Si alloy phase due to mutual diffusion with Fe. The melting points of the Al—Fe alloy phase and the Al—Fe—Si alloy phase are high and are about 1150 ° C. There are a plurality of types of intermetallic compounds contained in the Al—Fe alloy phase and the Al—Fe—Si alloy phase, and the alloy phase changes to a higher Fe concentration when heated at high temperature or for a long time.

The preferable state of the Al plating layer as a press-formed product is a state in which the surface is alloyed and the Fe concentration in the alloy phase is not high. If Al which is not alloyed remains, only this portion is rapidly corroded, the corrosion resistance after coating is deteriorated, and the coating film bulges very easily, which is not preferable. On the other hand, if the Fe concentration in the alloy phase becomes too high, the corrosion resistance of the alloy phase itself decreases, the corrosion resistance after coating deteriorates, and the coating film tends to swell. That is, the corrosion resistance of the alloy phase depends on the Al concentration in the alloy phase. Therefore, in order to improve the corrosion resistance after painting, the alloying state is controlled by the amount of Al deposited and the heating conditions.

In the heating method for hot press forming, it is preferable to set the average rate of temperature increase in the temperature range from 50 ° C. to 10 ° C. lower than the highest plate temperature to 10 to 300 ° C./second. The average temperature increase rate affects the productivity in hot press forming of the plated steel sheet. If the average heating rate is less than 10 ° C./second, it takes time to soften the hot-pressed plated steel sheet. On the other hand, if it exceeds 300 ° C., softening is rapid, but alloying of the Al plating layer may cause powdering significantly. A general average temperature increase rate is about 5 ° C./second in the case of atmospheric heating. An average temperature increase rate of 100 ° C./second or more can be achieved by energization heating or high frequency induction heating.

On the other hand, the maximum temperature reached is usually about 900 to 950 ° C. because it is necessary to perform hot press molding in the austenite single phase region. In hot press molding, the maximum temperature reached is not particularly limited, but if it is less than 850 ° C., it is not preferable because sufficient quenching hardness cannot be obtained. Also, the Al plating layer needs to be an Al—Fe alloy phase. From these viewpoints, the maximum temperature reached is preferably 850 ° C. or higher. On the other hand, when the maximum temperature exceeds 1000 ° C., alloying proceeds too much, and the Fe concentration in the Al—Fe alloy phase increases, which may lead to a decrease in corrosion resistance after coating. From these viewpoints, the upper limit of the maximum attainable temperature depends on the rate of temperature rise and the amount of Al deposited. .

And in hot press forming, a plated steel plate heated to a high temperature is press-formed with a mold. Then, the press-molded product of the target shape is obtained by cooling.

Here, an example of the normal process from manufacture of a plated steel plate to hot press forming is as follows.
First, an Al plating layer is formed on one side or both sides of a steel plate (FIG. 3 (1): 12 in FIG. 3 indicates a steel plate) (FIG. 3 (2): 14 in FIG. 3 indicates an Al plating layer).
Next, a ZnO film is formed on the surface of the Al plating layer (FIG. 3 (3): 16 in FIG. 3 indicates the ZnO film).
Next, the obtained plated steel sheet is wound up in a coil shape (FIG. 3 (4): 20 in FIG. 3 indicates a plated steel sheet (plated steel sheet body in this embodiment) wound in a coil shape).
Next, the plated steel sheet wound in a coil shape is pulled out and blanked (punched) (FIGS. 3 (5) to 3 (6): 22 in FIG. 3 indicates a blank).
Next, the blank is heated in a heating furnace (FIG. 3 (7): 24 in FIG. 3 indicates a heating furnace).
Next, the heated blank is breathed by a pair of upper and lower molds, and molded and quenched (FIG. 3 (8): 26A in FIG. 3 indicates the upper mold, and 26B indicates the lower mold).
And the target press-molded product is obtained by removing from a metal mold | die (FIG. 3 (9): 28 in FIG. 3 shows a press-molded product).

On the other hand, in the normal process from the production of the plated steel sheet to the hot press forming, the zinc-based metal soap film is formed between the Al plating layer and after each process or between the processes until the plated steel sheet (blank material) is heated. Form with. Specifically, the zinc-based metal soap film is formed on the surface of the Al plating layer of the plated steel sheet body (blank after blanking, etc.) after the formation of the Al plating layer (in addition, the entire surface of the Al plating layer) When a zinc-based metal soap film is formed on the ZnO film, the formation of the ZnO film may be omitted.) Or 2) After the formation of the ZnO film, the ZnO film of the plated steel sheet body (blank after blanking, etc.) A zinc-based metal soap film is formed on the surface.

The formation location of the zinc-based metal soap film is preferably on the entire surface of the Al plating layer or ZnO film, but may be on the surface that contacts the sliding surface of the hot press mold. The surface on which the plated steel plate comes into contact with the sliding surface of the hot pressing die is, for example, a plated steel plate (Al plating layer or ZnO film of the plated steel plate body) that becomes the vertical wall portion and flange portion of the obtained press-formed product. The surface. Specifically, for example, the surface on which the plated steel plate comes into contact with the sliding surface of the hot press die is the “holder and shoulder for holding the steel plate” in the upper die, and the “holder for holding the steel plate” in the lower die. The surface of the plated steel sheet (plated steel sheet body) in contact with the “part and shoulder” (see FIG. 3 (8): 26A1 in FIG. 3 is an upper mold holder, 26A2 is an upper mold shoulder, and 26B1 is a lower mold. The holder part 26B2 shows the lower shoulder part.)

It should be noted that heating of the plated steel sheet before pressing may be performed while the zinc-based metal soap film is used, or after the zinc-based metal soap film is changed to a ZnO film.

<Vehicle manufacturing method>
In the hot press forming method according to the present embodiment, various press-formed products can be manufactured. In the manufactured press-molded product, the surface on which the ZnO film is formed is particularly excellent in corrosion resistance (that is, coating corrosion resistance). For this reason, when a press-formed product for a vehicle is manufactured, it is preferable to manufacture the vehicle by attaching the manufactured press-formed product with the surface with the ZnO film facing the outside of the vehicle.

Specifically, for example, by the hot press molding method according to the present embodiment, a press molded product (for example, a center pillar outer, a door outer, a roof rail outer, a side panel, a fender, etc.) exposed when attached to a vehicle is manufactured. To do. When these press-molded products are attached to the vehicle, the press-molded product is attached to the vehicle so that the “surface on which the ZnO film is formed” faces the outside of the vehicle (for example, is exposed from the vehicle).

Next, the present disclosure will be further described with reference to examples. Note that the present disclosure is not limited to the following examples.

<Comparative Examples 1 to 4>
Cold-rolled steel sheets having the thicknesses shown in Table 1 (in mass%, C: 0.21%, Si: 0.12%, Mn: 1.21%, P: 0.02%, S: 0.012%, Ti: 0.02%, B: 0.03%, Al: 0.04%, balance: Fe and impurities) were plated with Al by the Sendzimer method. The annealing temperature was about 800 ° C., the Al plating bath contained 9% Si, and contained Fe eluted from the cold-rolled steel sheet. The Al basis weight after plating was adjusted by a gas wiping method to obtain an Al basis weight per side shown in Table 1, and then cooled. Then, on the formed Al plating layer, a chemical solution (Nanotek slurry, manufactured by C-I Kasei Co., Ltd., particle size of zinc oxide particles = 70 nm) was applied with a roll coater and baked at about 80 ° C., and the adhesion amount shown in Table 1 A ZnO film was formed. In this way, a specimen for a plated steel sheet was obtained.

<Examples 1 to 4, Comparative Examples 5 to 6>
Cold-rolled steel sheets having the thicknesses shown in Table 1 (in mass%, C: 0.21%, Si: 0.12%, Mn: 1.21%, P: 0.02%, S: 0.012%, Ti: 0.02%, B: 0.03%, Al: 0.04%, balance: Fe and impurities) were plated with Al by the Sendzimer method. The annealing temperature was about 800 ° C., the Al plating bath contained 9% Si, and contained Fe eluted from the cold-rolled steel sheet. The Al basis weight after plating was adjusted by a gas wiping method to obtain an Al basis weight per side shown in Table 1, and then cooled. Then, on the formed Al plating layer, a chemical solution (Nanotek slurry, manufactured by C-I Kasei Co., Ltd., particle size of zinc oxide particles = 70 nm) was applied with a roll coater and baked at about 80 ° C., and the adhesion amount shown in Table 1 A ZnO film of (Zn amount conversion) was formed. Next, zinc bisoctanoate (“Zn-OCTOATE 22% non-solvent” manufactured by DIC) as a zinc-based metal soap is applied on the ZnO film with a roll coater to form a zinc-based metal soap film with the adhesion amount shown in Table 1. did. In this way, a specimen for a plated steel sheet was obtained.

<Examples 5 to 8, Comparative Examples 7 to 8>
Cold-rolled steel sheets having the thicknesses shown in Table 1 (in mass%, C: 0.21%, Si: 0.12%, Mn: 1.21%, P: 0.02%, S: 0.012%, Ti: 0.02%, B: 0.03%, Al: 0.04%, balance: Fe and impurities) were plated with Al by the Sendzimer method. The annealing temperature was about 800 ° C., the Al plating bath contained 9% Si, and contained Fe eluted from the cold-rolled steel sheet. The Al basis weight after plating was adjusted by a gas wiping method to obtain an Al basis weight per side shown in Table 1, and then cooled. Thereafter, zinc bisoctanoate (“Zn-OCTOATE 22% non-solvent” manufactured by DIC) was applied as a zinc-based metal soap on the formed Al plating layer with a roll coater, and the zinc-based metal soap film having the adhesion amount shown in Table 1 was applied. Formed. In this way, a specimen for a plated steel sheet was obtained.

<Evaluation>
The characteristics of the specimens of the plated steel sheets produced as described above were evaluated by the following methods. In addition, the average temperature increase rate at the time of heating to 920 ° C. was set to 7.5 ° C./second.

(1) Hot lubricity Using the hot lubricity evaluation apparatus shown in FIG. 4, the hot lubricity of the specimen of the plated steel sheet was evaluated. The hot lubricity evaluation apparatus shown in FIG. 4 includes a near-infrared heating furnace 100 and a mold including an upper mold 102A and a lower mold 102B. The upper mold 102A and the lower mold 102B have a convex part with a width of 10 mm extending in a direction orthogonal to the drawing direction of the plated steel sheet, and a predetermined test piece is sandwiched between the top surfaces of the convex parts. Apply a pressing load. The hot lubricity evaluation apparatus is also provided with a plated steel sheet heated in the near-infrared heating furnace 100 and a thermocouple (not shown) for measuring the temperature of the plated steel sheet when sandwiched between molds. Yes. In addition, in FIG. 4, 10 shows the test material of a plated steel plate.
Using a hot lubricity evaluation apparatus shown in FIG. 4, a 30 mm × 500 mm specimen was heated at 920 ° C. in a near-infrared heating furnace 100 in a nitrogen atmosphere. Then, while applying a pressing load of 3 kN with a mold composed of the upper mold 102A and the lower mold 102B (that is, sliding the test material on the mold), the extraction load was measured. The drawing length was 100 mm and the drawing speed was 40 mm / s. Then, the hot friction coefficient (= (pull-out load) / (pressing load)) was obtained.

(2) Mold wear amount The mold wear amount was measured by analyzing the surface shape difference of (1) “die of hot lubricity measuring device” before and after the hot lubricity evaluation test. Specifically, the amount of wear of the mold was measured by measuring the profile of the mold surface at the sliding part before and after sliding using a contact-type shape measuring machine. The die wear amount was an average value of the upper die wear amount and the lower die wear amount.

(3) Surface properties of the test material (1) The maximum value of the skewness Rsk of the roughness curve was evaluated positively or negatively for the surface properties of the test material (its ZnO film) after the evaluation test of hot lubricity. The skewness Rsk of the roughness curve was measured for each of two cross sections in the rolling direction and the perpendicular direction of rolling of the material by the method described above. The maximum value among them was used as the evaluation value. In the table, the notation “+” indicates “0 <Rsk”, and the notation “−” indicates “Rsk <0”.

(4) Adhesion amount of ZnO film of test material (1) Adhesion amount (Zn amount conversion) of ZnO film on the surface of the test material after the evaluation test of hot lubricity was measured by the method described above.

Table 1 below shows a list of details of Examples 1 to 8 and Comparative Examples 1 to 8.
In Table 1, the total amount in terms of Zn content of the surface deposit indicates “adhesion amount of ZnO film and zinc-based metal soap film (Zn amount conversion)”.

From Table 1, in Examples 1 to 8, by forming an appropriate amount of the zinc-based metal soap film, a highly smooth ZnO film was formed from the zinc-based metal soap film. It was confirmed that the wear of the sliding surface can be reduced.
In Examples 1 to 8, it was confirmed that after the hot lubricity evaluation test, the ZnO film was not peeled off on the surface of the test material, and the chemical conversion treatment property and corrosion resistance of the obtained molded product could be improved. .
In Examples 2, 3, 6, and 7, the total adhesion amount of the zinc-based metal soap film together with the adhesion amount of the ZnO film is larger than 8.8 g / m ^{2 in} terms of Zn amount (including 8.8). In the case of 16.3 g / m ² or less, die wear is suppressed and the hot friction coefficient is 0.4 or less. As a result, it was confirmed that the moldability of the material in hot press molding (hot press) can be improved.

<Examples 9 to 16, Comparative Example 9, Reference Example 1>
The object (time) and conditions (formation method, adhesion amount, zinc-based metal soap film) for forming the zinc-based metal soap film from the production of the plated steel sheet to hot press forming (hot press) (see Fig. 3) The presence or absence of the heating step for forming the ZnO film and the formation site) were changed as shown in Table 2 to produce press-formed products (dish-shaped products). However, when the object for forming the zinc-based metal soap film was the surface of the Al plating layer, the ZnO film was not formed.
In hot press forming (hot press), the plated steel sheet was heated to 900 ° C. and then pressed under the conditions of 700 ° C. and 3 kN pressing load, as in the hot lubricity evaluation test.
Moreover, the kind of steel plate, the conditions for forming the Al plating layer, the condition for forming the ZnO film, and the kind of zinc-based metal soap were the same as those in Example 1.

And the following evaluation was implemented.
1) The test material of the plated steel plate of the same conditions as the obtained molded article was produced, and the said hot lubricity evaluation was implemented using this test material.
2) In the same manner as the above-described evaluation of the wear amount of the mold, the wear of the mold (“the holder and the shoulder for holding the steel plate” in the upper die, “the holder and the shoulder for holding the steel plate” in the lower die)) The amount was measured.
3) The surface property of the molded product (vertical wall portion and flange portion) was evaluated in the same manner as the evaluation of the surface property of the test material.

The details of Examples 9 to 16, Comparative Example 9, and Reference Example 1 are listed below in Table 2.
In Table 2, the column for the amount of zinc-based aliphatic metal soap film attached (in terms of Zn content) is “Zinc-based” in Example 9 where a zinc-based aliphatic metal soap film is formed on the surface of the Al plating layer. In Examples 10 to 16 in which the adhesion amount (in terms of Zn amount) of the aliphatic metal soap film itself is shown and the zinc-based aliphatic metal soap film is formed on the surface of the ZnO film, “ZnO film and zinc-based aliphatic metal soap” The total adhesion amount (in terms of Zn amount) of the film is shown.

From Table 2, as shown in Examples 9 to 16, a zinc-based metal soap film is formed on the surface of the Al plating layer or the ZnO film between the production of the plated steel sheet and before the press of hot press forming (hot press). It has been confirmed that the formation of can improve the hot lubricity and reduce the wear on the sliding surface of the mold.
As shown in Examples 9 to 10, it has been confirmed that even when a zinc-based metal soap film is heated to a ZnO film, the hot lubricity can be improved and the wear of the sliding surface of the mold can be reduced. did.
As shown in Examples 14 to 16, at least a zinc-based metal soap film is formed on the surface of the plated steel sheet (the Al plated layer or ZnO film of the plated steel sheet body) that becomes the vertical wall portion and the flange portion of the molded product. It was confirmed that the wear on the sliding surface of the mold can be reduced.
In Examples 9 to 16, no peeling of the ZnO film on the surface of the molded product was observed, and it was confirmed that the chemical conversion treatment property and corrosion resistance of the obtained molded product could be improved.

In addition, as shown in Comparative Example 9, even if a zinc-based metal soap film is formed on the surface of the mold (the upper mold and the lower mold shoulder and holder) on which the plated steel sheet slides during breathing, It was confirmed that there was no improvement in inter-lubricity and no wear reduction on the sliding surface of the mold.
However, as shown in Reference Example 1, by continuously supplying metal soap so as not to cause film breakage, improvement in hot lubricity and reduction in wear on the sliding surface of the mold were observed. .

As mentioned above, although preferred embodiment of this indication was described in detail, referring an accompanying drawing, it cannot be overemphasized that this indication is not limited to this example. It is obvious that a person having ordinary knowledge in the technical field to which the present disclosure belongs can come up with various changes or modifications within the scope of the technical idea described in the claims. Of course, it is understood that these also belong to the technical scope of the present disclosure.

The entire disclosure of Japanese Patent Application No. 2016-256016 is incorporated herein by reference.
All documents, patent applications, and technical standards mentioned in this specification are to the same extent as if each individual document, patent application, and technical standard were specifically and individually described to be incorporated by reference, Incorporated herein by reference.

Claims

A plated steel sheet body having a steel sheet and an aluminum plating layer provided on one or both surfaces of the steel sheet;
A zinc-based metal soap film provided on the surface of the plated steel sheet body on the side of the aluminum plating layer and having an adhesion amount of 7.1 to 19.8 g / m 2 in terms of Zn amount;
A hot-pressed plated steel sheet.
A plated steel sheet body having a steel sheet, an aluminum plating layer provided on one or both surfaces of the steel sheet, and a zinc oxide film provided on the surface of the aluminum plating layer;
A zinc-based metal soap film provided on the surface of the zinc oxide film of the plated steel sheet body;
With
A hot-pressed plated steel sheet, wherein the total adhesion amount of the zinc oxide film and the zinc-based metal soap film is 7.1 to 19.8 g / m 2 in terms of Zn content.
3. For hot pressing according to claim 2, wherein more than half of the total adhesion amount of the zinc oxide film and the zinc-based metal soap film is the adhesion amount of the zinc-based metal soap film. Plated steel sheet.
The zinc-based metal soap film is at least one zinc-based metal soap film selected from the group consisting of zinc bisoctanoate, zinc octylate, zinc laurate, and zinc stearate. A plated steel sheet for hot pressing as set forth in any one of the above items.
A plated steel sheet body having a steel sheet and an aluminum plating layer provided on one or both surfaces of the steel sheet;
A zinc oxide film provided on the surface of the plated steel sheet body on the aluminum plating layer side;
Have
A plated steel sheet for hot pressing, wherein the maximum value of the skewness Rsk of the surface roughness curve of the zinc oxide film is less than 0.
On the surface of the plated steel sheet main body having a steel sheet and an aluminum plated layer provided on one or both sides of the steel sheet, the adhesion amount of the adhesion portion is 7.1 to 19.8 g in terms of Zn amount. method for manufacturing a hot-press coated steel sheet comprising a step of forming a zinc-based metal soap coating so that / m 2.
The zinc oxide film on the surface of the zinc oxide film of a plated steel sheet main body having a steel plate, an aluminum plating layer provided on one or both surfaces of the steel plate, and a zinc oxide film provided on the aluminum plating layer Plating for hot press having a step of forming a zinc-based metal soap film so that the total adhesion amount of the adhesion portion with the adhesion amount of the zinc is 7.1 to 19.8 g / m 2 in terms of Zn amount A method of manufacturing a steel sheet.
In the step of forming the zinc-based metal soap film, more than half of the total adhesion amount of the zinc oxide film and the zinc oxide film is defined as the adhesion amount of the adhesion part of the zinc-based metal soap film. The manufacturing method of the plated steel plate for hot presses of Claim 7.
The method for producing a plated steel sheet for hot pressing according to any one of claims 6 to 8, further comprising a step of heating the zinc-based metal soap film at 300 ° C or higher to form a zinc oxide film.
The method for producing a hot-pressed plated steel sheet according to claim 9, wherein the maximum value of the skewness Rsk of the surface roughness curve of the zinc oxide film formed by heating the zinc-based metal soap film is less than 0.
11. The zinc-based metal soap film is at least one zinc-based metal soap film selected from the group consisting of zinc bisoctanoate, zinc octylate, zinc laurate, and zinc stearate. The manufacturing method of the plated steel plate for hot press of any one of Claims 1.
A process for producing a hot-pressed plated steel sheet by the method for producing a hot-pressed plated steel sheet according to any one of claims 6 to 11, wherein the zinc-based metal soap film is formed. And forming at least the zinc-based metal soap film on the surface on the aluminum plating layer side of the plated steel sheet body on the surface in contact with the sliding surface of the hot pressing mold in a subsequent hot pressing step. Manufacturing a hot-pressed plated steel sheet,
A hot pressing step for hot press forming the plated steel sheet for hot pressing;
A method for producing a hot press-formed product having
A method for producing a hot press-formed product, wherein the hot-pressed plated steel plate produced by the method for producing a hot-pressed plated steel plate according to claim 10 is hot-press formed.
A vehicle manufacturing method in which a press-formed product manufactured by the method for manufacturing a hot press-formed product according to claim 12 or 13 is attached with a surface having a zinc oxide film facing the outside of the vehicle.