JP6209991B2 - Blank material manufacturing method, hot stamp molded product manufacturing method, blank material, and hot stamp molded product - Google Patents

Description

  The present invention is suitable for use in forming a plurality of metal plates whose plate surfaces are bonded to each other by a hot stamping process.

  Conventionally, a hot stamp molded product is manufactured by a hot stamp process. Under the present circumstances, the intensity | strength and rigidity of a hot stamping molded article are also performed by using for the hot stamp process the blank material manufactured by joining the plate surfaces of several steel plates. In this case, in the area of the main steel plate, the area where the strength and rigidity are reduced compared to other areas when it becomes a hot stamped product, or the area where higher strength and rigidity are required than other areas. On the other hand, one or a plurality of steel plates are joined. As an application of a hot stamp molded product using such a blank material, for example, there are a front side member, a center pillar, and the like which are components of a monocoque body (unit construction body).

  In Patent Document 1, a reinforcing steel plate is arranged so that the plate surfaces face each other at least with respect to a region that becomes a ridge line portion of a hot stamped molded product in a region of a main steel plate, and becomes the ridge line portion. A technique is disclosed in which plate surfaces of a main steel plate and a reinforcing steel plate are joined to each other by spot welding in a region.

In Patent Document 2, a brazing material (hard solder; the same applies hereinafter) is disposed between the main steel plate and the reinforcing steel plate, and the steel plate and the brazing material are temporarily fixed by welding. A technique is disclosed in which a steel plate is heated to a temperature higher than the forming temperature to perform hot press forming, and then the formed steel plate is cooled in a mold to solidify the brazing material.
In Patent Document 3, a brazing material having a solidus temperature of 1050 ° C. or lower and a liquidus temperature of 700 ° C. or higher is sandwiched between a main steel plate and a plate surface of a reinforcing steel plate, and this is used as a heating furnace. And heating at 900 ° C. to 1050 ° C., followed by quenching and press molding (hot stamping).
In Patent Document 4, a main steel plate coated with a brazing material on a plate surface is heated for quenching and the brazing material is melted. A technique for joining a plate surface of a steel plate and then performing quenching and press forming (hot stamping) is disclosed.

International Publication No. 2012/36261 JP 2002-178069 A JP 2004-141913 A JP 2011-88484 A

  However, in the technique described in Patent Document 1, the main steel plate and the reinforcing steel plate are joined by welding. For this reason, there exists a possibility that a clearance gap may remain between steel plates. Further, even in the techniques described in Patent Documents 2 to 4, there is a possibility that a portion where the brazing material is not filled between the steel plates is generated, and there is a possibility that a gap remains between the steel plates. Therefore, in the techniques described in Patent Documents 1 to 4, it is not easy to sufficiently improve the strength and rigidity of the hot stamped product.

  In view of this, the present inventors, in Japanese Patent Application No. 2013-082003, sandwiched a brazing material between the heating process for hot stamping or the transition from the heating process to the hot stamping process. A method to pressurize multiple metal plates in the thickness direction was proposed. According to this method, it is possible to prevent a gap from remaining between the steel plates as in the techniques described in Patent Documents 1 to 4.

  However, in the method described in Japanese Patent Application No. 2013-082003, it is necessary to make a major change to the hot stamping process in order to melt the brazing material during the heating process for quenching. Therefore, there is a possibility that a large capital investment may be required and a man-hour may be significantly increased. Further, since the brazing material is melted together with the heating for quenching, the brazing management is not easy, and there is a possibility that the brazing conditions may be restricted depending on the heating conditions of the hot stamped steel sheet. Further, when the liquidus temperature of the brazing material is higher than the heating temperature for quenching, liquid metal embrittlement cracking may occur. In this case, the press molding temperature may need to be managed.

  The present invention has been made in view of the above problems, and the strength and rigidity of a hot stamp molded product manufactured from a blank material in which plate surfaces of a plurality of metal plates are joined to each other are greatly increased in the hot stamping process. The goal is to improve without any changes.

The blank material manufacturing method of the present invention is a blank material that is formed and quenched by a hot stamping process, and is a method for manufacturing a blank material that includes a plurality of metal plates and a brazing material. Of the plurality of metal plates whose plate surfaces oppose each other, a brazing material constituting a plate set in which the brazing material is arranged in a predetermined region between the plate surfaces of two metal plates adjacent to each other An arrangement step, a brazing material heating step for heating the plate set constituted by the brazing material arrangement step, and a brazing material cooling step for cooling the plate set heated by the brazing material heating step, The solidus temperature of the brazing material is higher than the heating temperature in the heating process for quenching in the hot stamping process and lower than the solidus temperature of the metal plate. Above the liquidus temperature of And heating the plate assembly at a temperature lower than the solidus temperature of the metal plate, and the brazing material cooling step is performed until the temperature of the brazing material is lower than the solidus temperature of the brazing material. The set is cooled.
The manufacturing method of the hot stamping molded product of the present invention heats the blank material manufactured by the blank material manufacturing process and the blank material manufacturing process for manufacturing the blank material by the blank material manufacturing method for quenching. It has a heating process for hot stamping, and a hot stamping process for forming and quenching the blank material heated by the heating process for hot stamping.

The blank material of the present invention is a blank material that is molded and quenched by a hot stamping process, and a plurality of metal plates that are stacked so that plate surfaces face each other, and the plurality of metal plates A brazing material that joins the two metal plates between the plate surfaces of the two adjacent metal plates, and the solidus temperature of the brazing material is determined by the hot stamping process. The temperature is higher than the heating temperature in the heating step for quenching in the steel, and lower than the solidus temperature of the metal plate.
The hot stamp molded product of the present invention is formed by molding and quenching the blank material by a hot stamp process.

  According to the present invention, a plurality of metal plates are brazed with a brazing material having a solidus temperature higher than the heating temperature in the heating step for quenching in the hot stamping process and lower than the solidus temperature of the metal plate. After performing the above, a hot stamp process is performed. Therefore, the strength and rigidity of the hot stamp molded product manufactured by the hot stamping process can be improved without adding a significant change to the hot stamping process.

It is a figure which shows an example of the external appearance structure of a molded component. It is a figure which shows an example of a structure of a blank material. It is a figure explaining an example of the pressurization method with respect to a board assembly. It is a figure which shows the structure of the blank material of an Example. It is a figure which shows the structure of a molded component. It is a figure which shows the structure of the blank material of a comparative example. It is a figure explaining a three-point bending test. It is a figure which shows the result of a three-point bending test. It is a figure (photograph) which shows the cross section of a junction part.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
In this embodiment, a case where a molded part used for a front side member, a center pillar, or the like of an automobile is manufactured will be described as an example. However, the molded part is not limited to this.

(Outline of molded parts)
First, an example of the molded part of this embodiment will be described. FIG. 1 is a diagram illustrating an example of an external configuration of a molded part 100. The XYZ coordinates shown in each figure indicate the relationship of directions in each figure, and the origin of the coordinates is common in each figure.
In FIG. 1, the molded part 100 includes a hat-shaped member 110 and a closing plate 120.

The hat-shaped member 110 is an example of a hot stamp molded product, and includes a main member 111 and a reinforcing member 112. The main member 111 and the reinforcing member 112 are each made of a single metal plate.
The shape of the cross section of the main member 111 is a hat shape. The shape of the cross section of the reinforcing member 112 is a U-shape that matches the shape and size of the inner surface of the convex portion of the main member 111. The outer surface of the reinforcing member 112 and the inner surface of the convex portion of the main member 111 are joined by brazing. Thereby, the region including the ridge line on the inner surface of the convex portion of the main member 111 is covered with the reinforcing member 112. Details of brazing will be described later.

The closing plate 120 is made of a single metal plate (flat plate). The lower surface of the flange portion of the main member 111 and the upper surface of the closing plate 120 are joined by performing welding such as spot welding.
The thickness of the main member 111, the reinforcing member 112, and the closing plate 120 may be the same or different.

(Manufacturing process)
Next, an example of a manufacturing process of a molded part will be described. The manufacturing process of a molded part includes a blank material manufacturing process and a hot stamping process. The process order is the order of the blank material manufacturing process and the hot stamping process.
[Blank material manufacturing process]
A blank material manufacturing process is a process of manufacturing a blank material. In this embodiment, a blank material for forming the hat-shaped member 110 is manufactured in the blank material manufacturing process.
<Configuration of Blank Material 200>
FIG. 2 is a diagram illustrating an example of the configuration of the blank material 200. Specifically, FIG. 2A is a diagram showing a cross section of the blank material. FIG. 2B is a diagram illustrating a region where the brazing material 230 is disposed, and is a diagram of the blank material 200 viewed from above the metal plate 220. In FIG.2 (b), the area | region where the brazing material 230 is arrange | positioned is shown with a dashed-dotted line (perspectively).

  In FIG. 2, the blank material 200 includes metal plates 210 and 220 and a brazing material 230. The metal plate 210 becomes the main member 111, and the metal plate 220 becomes the reinforcing member 112. The brazing material 230 is disposed between the plate surfaces of the metal plates 210 and 220. As shown in FIG. 2B, the brazing material 230 is disposed in a predetermined region excluding the edge portion of the plate surface of the plate surface region of the metal plate 220. The brazing material 230 may be disposed on the entire surface of the metal plate 220.

<Configuration of metal plates 210 and 220>
The material and thickness of the metal plates 210 and 220 are not particularly limited. The molded part 100 manufactured in the present embodiment is required to have high strength and high rigidity. Therefore, the metal plates 210 and 220 are, for example, high-strength steel plates, and it is preferable that the chemical composition and other designs are made so as to obtain the strength and rigidity required for the molded part. In the hot stamping process, quenching is performed during molding (in the mold). Therefore, it is preferable that the hardenability of the metal plates 210 and 220 is high. That is, it is preferable that the metal plates 210 and 220 contain elements that enhance strength, rigidity, and hardenability. Further, the metal plates 210 and 220 may be plated steel plates. The plated steel sheet is, for example, a known zinc-based plated steel sheet or an aluminum-based plated steel sheet. The same applies to the metal plate constituting the closing plate 120.

<Configuration of brazing material 230>
As the brazing material 230, a brazing material having a solidus temperature higher than the heating temperature in the hot stamp heating step described later and lower than the solidus temperature of the metal plates 210 and 220 is used. In the heating process for hot stamping, the brazing material 230 is prevented from entering a liquid phase state or a solid-liquid coexistence state (a state where a solid phase and a liquid phase coexist), and the metal plate 210 is used during brazing as described below. , 220 is prevented from entering a liquid phase state or a solid-liquid coexistence state.

  Generally, when performing hot stamping, a blank material is heated by a heating furnace. In this case, the brazing filler metal 230 having a solidus temperature exceeding the furnace temperature of the heating furnace (atmosphere temperature in the furnace) is used. Since the furnace temperature of such a heating furnace is usually at least Ac3 point (temperature at which the steel sheet is austenitized), assuming such a heating furnace, the solidus temperature at least higher than the Ac3 point is assumed. A brazing material 230 having the following must be used. Examples of the brazing material 230 that satisfies such conditions include a copper brazing material (Cu, Cu-Zn, Cu-Sn, etc.), a nickel brazing material (Ni, Ni-Cr-B-Si, Ni-B-Si, etc.), gold-based brazing materials (Au, Au-Cu, Au-Cu-Ni, Au-Pd-Ni, etc.), palladium brazing materials (Pd-Ag, Pd-Cu, Pd-Ag-) Cu etc.).

The blank material manufacturing process includes a brazing material arrangement process, a brazing material heating process, and a brazing material cooling process. The order of the process is the order of the brazing material arrangement process, the brazing material heating process, and the brazing material cooling process. Below, the content of each process is demonstrated.
<Brazing material placement process>
When the blank material 200 is manufactured, first, the brazing material 230 is arranged so that the brazing material 230 is disposed in a predetermined region of the plate surface area of the metal plate 220 excluding the edge portion of the plate surface. The plate surfaces of the metal plates 210 and 220 are overlapped with each other. At this time, the metal plates 210 and 220 are aligned so that a desired positional relationship between the main member 111 and the reinforcing member 112 is obtained and the position is suitable for brazing.

The brazing material 230 may be in the form of powder, paste, or solid.
When the paste-like brazing material 230 is used, for example, after applying the brazing material 230 to the above-described region (region excluding the edge) of the plate surface of the metal plate 220, the plate surface of the metal plate 220 (the brazing material 230 is formed). The applied surface) and the plate surface of the metal plate 210 are overlapped by performing the alignment described above.
On the other hand, when the powdery and solid brazing material 230 is used, for example, the brazing material 230 is disposed in the above-described region (region excluding the edge) between the plate surfaces of the metal plates 210 and 220. Thus, the metal plates 210 and 220 are overlapped with the brazing material 230 interposed therebetween.

Here, the thickness of the brazing material 230 is not particularly limited. For example, the thickness of the brazing material 230 can be set to 30 μm to 200 μm from the viewpoint that the metal plates 210 and 220 can be bonded.
In the following description, the metal plates 210 and 220 that are superposed with the brazing material 230 interposed therebetween as described above are referred to as “plate assemblies” as necessary.

<Brazing material heating process>
Next, the plate assembly is set in a jig for maintaining its position at a position suitable for brazing.
Next, the plate assembly set in the jig is so adjusted that the temperature of the brazing material 230 is higher than the liquidus temperature of the brazing material 230 and lower than the solidus temperature of the metal plates 210 and 220. Heat. The heating here is heating for brazing, and has a different purpose from the heating for quenching in the heating process described later.

The heating means may be any method as long as it is a heating means (arc, laser, gas, etc.) capable of melting the brazing filler metal 230, for example, furnace heating, electric heating, high frequency heating (induction heating), or the like. Can be used.
In-furnace heating refers to heating the brazing material 230 by charging a plate set set in a jig into the heating furnace. When the metal plates 210 and 220 are not plated, the atmosphere in the heating furnace is preferably a reducing atmosphere or a vacuum atmosphere for the metal plates 210 and 220 and the brazing material 230. When the metal plates 210 and 220 are plated, it is preferable that the atmosphere in the heating furnace is a reducing atmosphere for the brazing material 230. When heating in the furnace, a heating furnace different from the heating furnace for quenching described later is used.

  As described above, the solidus temperature of the brazing material 230 is higher than the heating temperature of the blank material 200 in the heating process described later. Therefore, even if the atmosphere of the heating furnace for quenching is a non-reducing atmosphere for the brazing material, the brazing material can be used. That is, in the heating process for hot stamp described later, even if the brazing material is exposed to a non-reducing atmosphere, the brazing material does not enter a liquid phase state or a solid-liquid coexistence state. It is possible to prevent the brazing itself from becoming impossible.

The energization heating refers to heating the brazing material 230 by attaching an electrode to the metal plates 210 and 220 constituting the plate set set on the jig and energizing between the metal plates 210 and 220.
In the high-frequency heating, the brazing material 230 is heated by passing a current through the metal plates 210 and 220 by the action of electromagnetic induction by passing a plate set set in a jig through a coil through which a high-frequency current is passed. That means.
These energization heating and high frequency heating are preferably performed in a vacuum or in an inert gas atmosphere.

  Moreover, you may pressurize to the plate | board thickness direction of the metal plates 210 and 220 with respect to the board set during heating. By applying pressure in this manner, it is possible to suppress the formation of a gap between the metal plates 210 and 220 and the brazing material 230, and the metal plates 210 and 220 and the brazing material 230 can be made as much as possible. Can be adhered to.

There are various methods for pressing the plate assembly. FIG. 3 is a diagram illustrating an example of a pressing method for the plate assembly.
As shown in FIG. 3, the support plate 310 is disposed on the entire lower surface of the metal plate 210. A pressing plate 320 is disposed on the entire top surface of the metal plate 220. Then, the plate assembly sandwiched between the pressing plate 320 and the support plate 310 is heated as described above. At this time, the plate assembly is pressurized with the pressure P by the weight of the pressing plate 320. By this pressurization, the deformation of the metal plates 210 and 220 in the plate set is restrained. Therefore, it is possible to suppress the formation of a gap between the metal plates 210 and 220 and the brazing material 230 in the plate assembly after heating, and the metal plates 210 and 220 and the brazing material 230 are made as much as possible. It can be adhered.

The support plate 310 and the pressing plate 320 are not particularly limited in material as long as they have sufficient strength and / or thickness to suppress deformation of the metal plates 210 and 220 being heated. The preferable average load with respect to the metal plates 210 and 220 at the time of pressurization is 1.0 × 10 ^{−3 to} 1.0 MPa. Therefore, it is preferable that the holding plate 320 has a weight that can apply this average load to the plate assembly (metal plates 210 and 220).

  When the plate assembly is heated using the support plate 310 and the press plate 320, the support plate 310 and the press plate 320 shield the heat, and thus the temperature of the plate set may be difficult to increase. Therefore, the support plate 310 and the pressing plate 320 can be reduced in thickness or have a lattice-like or net-like structure within a range in which the strength enough to prevent the metal plates 210 and 220 from being deformed during heating can be secured. .

<Brass cooling process>
Next, the plate assembly heated as described above is cooled until the temperature of the brazing material 230 falls below the solidus temperature of the brazing material 230. At this time, in order to suppress the coarsening (growth) of crystal grains of the metal plates 210 and 220, the plate assembly is cooled until the temperature of the metal plates 210 and 220 becomes a temperature lower than the Ac1 point of the metal plates 210 and 220. In order to facilitate handling of the plate assembly, it is even more preferable to cool the plate assembly until the temperature of the plate assembly reaches room temperature.
There are various methods for cooling the plate assembly. For example, the cooled metal material can be brought into contact with the lower surface of the metal plate 210 and the upper surface of the metal plate 220 (the surface of the metal plates 210 and 220 that is not in contact with the brazing material 230). For example, an internal water-cooled metal material (for example, a metal material having a water-cooled pipe formed therein) can be used. In addition, it may cool.

  In the brazing material heating step described above, when pressure is applied to the plate assembly, the support plate 310 and the holding plate 320 are moved until the temperature of the brazing material 230 falls below the solidus temperature of the brazing material 230. It is preferable to be in a state of being attached to a set. In this way, it is possible to reliably suppress the formation of a gap between the metal plates 210 and 220 and the brazing material 230.

  On the other hand, if no pressure is applied to the plate assembly in the brazing material heating step, the metal plate 210, 220 is pressurized in the thickness direction of the plate assembly in the brazing material cooling step. Is preferred. In this case, for example, before the temperature of the brazing material 230 falls below the liquidus temperature, the plate assembly is cooled while pressurizing the plate assembly in the thickness direction of the metal plates 210 and 220. For example, the metal plates 210 and 220 constituting the plate assembly can be sandwiched and cooled from above and below with an internal water-cooled flat plate press.

  Further, in order to suppress the coarsening of crystal grains, if a precipitate forming element such as Ti, Nb, Al or the like is added to the inside of the metal plates 210, 220, in this brazing material cooling step, the brazing material It is only necessary to cool the plate assembly until the temperature of 230 is lower than the solidus temperature of the brazing material 230, and the crystal grains of the metal plates 210 and 220 can be coarsened without cooling to a lower temperature. Can be suppressed. Further, even when the crystal grains are coarse, there is no effect on the quality. Similarly, in the brazing filler metal cooling process, the plate assembly is used until the temperature of the brazing filler metal 230 falls below the solidus temperature of the brazing filler metal 230. As long as it is cooled.

[Hot stamp process]
A hot stamp process is a process of shape | molding and quenching with respect to the blank material manufactured at the blank material manufacturing process. The hot stamping process includes a hot stamping heating process, a hot stamping process, and a shot blasting process. The order of the processes is the order of the heating process for hot stamping, the hot stamping process, and the shot blasting process. Below, the content of each process is demonstrated.
<Hot stamp heating process>
The blank material 200 manufactured as described above is heated to a temperature necessary for hot stamping. The minimum of a preferable heating temperature is Ac3 point of the metal plates 210 and 220, and the upper limit of a preferable heating temperature is 1000 degreeC. As described above, the solidus temperature of the brazing material 230 is set to be higher than the heating temperature for hot stamping. In the brazing material cooling step, the brazing material 230 is in a solid phase. Therefore, it is possible to suppress the brazing material 230 from becoming a liquid phase in the hot stamp heating step.
There are various heating methods in the heating process for hot stamping. Generally, a walking beam type or batch type heating furnace is used. The kind of heating furnace is not particularly limited, and may be an electric furnace or a gas furnace. In addition to the heating furnace, electric heating or high-frequency heating can be used.

<Hot stamp molding process>
The blank material 200 heated in the heating process for hot stamping is placed in a mold in the hot stamping apparatus. And hot stamp molding is implemented with respect to the blank material 200, and the hat-shaped member 110 (hot stamp molded product) is manufactured. The temperature of the blank 200 when starting hot stamping is equal to or higher than the Ms point of the metal plates 210 and 220 and lower than the solidus temperature of the brazing material 230. Molding and quenching are performed by this hot stamping process.

<Shot blasting process>
The hat-shaped member 110 (hot stamp molded product) manufactured in the hot stamping heating process is subjected to shot plus and processing to remove the scale formed on the surface of the hat-shaped member 110 (metal plates 210 and 220). .
As described above, the hat-shaped member 110 is manufactured. Then, the molded part 100 is manufactured by joining the flange portion of the hat-shaped member 110 and the closing plate 120 by, for example, spot welding.
The hot stamp heating process, the hot stamp molding process, and the shot blasting process can be realized by a general hot stamp process.

(Example)
Next, examples of the present invention will be described.
<Test member>
First, the same kind of cold-rolled steel plates were used one by one as the metal plates forming the main member and the reinforcing member. The size of the metal plate forming the main member (hereinafter referred to as main steel plate) is length 600 mm × width 225 mm × thickness 1.2 mm.
On the other hand, the size of a metal plate (hereinafter referred to as a reinforcing steel plate) forming the reinforcing member is 600 mm long × 170 mm wide × 1.4 mm thick.

As the main steel plate and the reinforcing steel plate, those having a tensile strength of about 600 MPa to 700 MPa before hot stamping and a tensile strength of 1500 MPa class after hot stamping were used.
As the brazing material, a (solid) brass brazing material having Cu of 64 mass% to 68 mass% and the balance of Zn was used. The brass wax has a solidus temperature of 903 ° C. and a liquidus temperature of 930 ° C.
FIG. 4 is a diagram illustrating a configuration of the blank member 400 of the present embodiment. Specifically, FIG. 4A is a view in which the main steel plate 410 is the upper side, the reinforcing steel plate 420 (see FIG. 4B) is the lower side, and the blank 400 is viewed from the upper side. The place where is arranged is shown through with a dashed-dotted line. FIG. 4B is a cross-sectional view (II ′ cross-sectional view) of the blank 400 shown in FIG. In FIGS. 4A and 4B, the numbers shown beside the dimension lines indicate the dimensions, and the unit is mm.

A plate assembly is formed by sandwiching the brazing material 430 between the main steel plate 410 and the reinforcing steel plate 420 so that such a blank material 400 is formed, and these positions are maintained at positions suitable for brazing. After setting the plate assembly to the jig as described above, heating in the furnace was performed on the plate assembly. The furnace temperature was 950 ° C., the residence time (joining time) in the furnace was 5 minutes, and the atmosphere in the furnace was a reducing atmosphere. Further, in this example, the plate assembly was not pressurized during heating in the furnace.
After carrying out the brazing material heating step under the above conditions, the main steel plate 410 and the reinforcing steel plate 420 constituting the plate assembly are sandwiched from above and below with an internal water-cooled flat plate press, and the temperature of the main steel plate 410 and the reinforcing steel plate 420 However, the temperature (50 ° C.) plate assembly that cooled below the Ac1 point of the main steel plate 410 and the reinforcing steel plate 420 and became easy to handle was cooled.

  The heating process for hot stamping was implemented with respect to the blank material manufactured as mentioned above. At this time, the furnace temperature was 890 ° C. The residence time in the furnace was 5 min, and the atmosphere in the furnace was a reducing atmosphere. Thereafter, hot stamping was performed on the blank 400 with an internal water-cooled press to produce a hat-shaped member 510 as shown in FIG. Then, as shown in FIG. 5, a hat-shaped member 510 (a flange portion thereof) and a closing plate 520 were joined by spot welding to manufacture a molded part 500. The closing plate 520 is a single 780 MPa grade cold-rolled steel sheet having a length of 600 mm, a width of 150 mm, and a thickness of 1.8 mm.

Here, the temperature of the blank 400 when starting hot stamping was set to 750 ° C., which is equal to or higher than the Ms point of the main steel plate 410 and the reinforcing steel plate 420 and lower than the solidus temperature of the brazing material 430. Further, spot welding was performed between the hat-shaped member 510 (the flange portion thereof) and the closing plate 520 with a pressing force of 400 kgf, a welding current of 8.3 kA, an energization cycle of 16 cycles, a holding time of 10 cycles, and a welding interval of 40 mm. .
FIG. 5 is a diagram (front view) showing an example of the configuration of the molded part 500. In FIG. 5, the numbers shown beside the dimension lines indicate the dimensions, and the unit is mm. The length of the molded part 500 in the longitudinal direction (Y-axis direction) is 600 mm (see the length in the Y-axis direction in FIG. 4A).
Here, the shot blasting process that does not affect the result of the bending load is omitted.

  As the molded part 500 as described above, three types of molded parts 500 in which the thickness of the brazing material 430 was 50 μm, 100 μm, and 150 μm were manufactured as examples of the present invention (thickness of the brazing material 430 was 50 μm, 100 μm, and 150 μm). Are referred to as Invention Examples 1, 2, and 3, respectively).

Further, a molded part manufactured under the same conditions as the molded part 500 described above was manufactured as a comparative example except that the main steel plate and the reinforcing steel plate were joined by spot welding instead of the brazing material 430.
FIG. 6 is a diagram illustrating a configuration of a blank material 600 of a comparative example. FIG. 6 is a diagram corresponding to FIG. In addition, the number shown beside a dimension line in FIG. 6 shows a dimension, and a unit is mm. A broken-line circle in FIG. 6 indicates a spot-welded portion.
Here, spot welding was performed between the main steel plate and the reinforcing steel plate with a pressing force of 400 kgf, a welding current of 7.9 kA, an energization cycle of 24 cycles, and a holding time of 10 cycles.

<Third-turn bending test>
A three-point bending test was performed on the molded parts of the inventive examples 1 to 3 and the comparative example manufactured as described above. FIG. 7 is a diagram for explaining a three-point bending test. In addition, the number shown beside a dimension line in FIG. 7 shows a dimension, and a unit is mm.
In FIG. 7, a molded part is disposed between the impactor 710 and a pair of support members (support points) 720. At this time, the convex portion of the hat-shaped member 510 was in contact with the impactor 710, and the closing plate 520 joined to the flange portion was in contact with the pair of support members 720 and 730.

The impactor 710 was lowered at a crushing speed of 0.25 mm / sec, and the load (kN) applied to the hat-shaped member 510 was measured. The maximum stroke amount of the impactor 710 was 50 mm.
FIG. 8 shows the stroke amount (mm) of the impactor 710 and the load (kN) applied to the hat-shaped member 510 in the molded parts of the inventive examples 1 to 3 and the comparative example obtained by the three-point bending test. It is a figure which shows a relationship.
8, the curve 810 is the result of the three-point bending test of Example 1 of the present invention, the curve 820 is the result of the three-point bending test of Example 2 of the present invention, and the curve 830 is the result of the three-point bending test of Example 3 of the present invention. Reference numeral 840 indicates the result of the three-point bending test of the comparative example.

As shown in FIG. 8, in the inventive examples 1 to 3, the maximum load exceeded 80 kN. On the other hand, in the comparative example, the maximum load was about 60 kN.
Further, an increase in load (inclinations of curves 810, 820, 830, and 840 in this region) in a range where the stroke amount of the three-point bending test is 0 to 5 mm (that is, during elastic deformation) is the bending rigidity of each hat-shaped member 510. Index. As shown in FIG. 8, the inclination of this example 1-3 of this invention in this area | region is larger than the inclination of a comparative example. Therefore, it can be seen that the hat-shaped member 510 of the present invention has superior rigidity compared to the hat-shaped member 510 of the comparative example.
The present inventors confirmed that the same results as those shown in FIG. 8 were obtained with the above-described brazing filler metals other than brass brazing.

<Cross-section observation test>
Further, the thickness of the brazing material 430 (solidus temperature: 903 ° C., liquidus temperature: 930 ° C.) is set to 30 μm, and the main steel plate 410, the reinforcing steel plate 420, and the brazing material 430 described above are used, and the same Three plate assemblies were formed under conditions. Each plate assembly was heated at a furnace temperature of 1000 ° C. and a residence time in the furnace of 5 min, and then subjected to bending press and cooling with a curvature radius of the bending portion of 3 mm. For one of the three plate assemblies, bending press is performed when the temperature is 880 ° C., and for the other one, bending press is performed when the temperature is 920 ° C., and the remaining one As for, bending press was performed when the temperature was 950 ° C. The temperature was measured using an R-type thermocouple.

FIG. 9 is a diagram (photograph) showing a cross section of the joint. FIG. 9A shows the result of bending press when the temperature is 880 ° C., and FIG. 9B shows the result of bending press when the temperature is 920 ° C. ) Shows the result of bending press when the temperature is 950 ° C.
As described above, the brazing filler metal 430 has a solidus temperature of 903 ° C. and a liquidus temperature of 930 ° C. Therefore, FIG. 9A shows the result of bending press with the brazing material 430 in a solid state, and FIG. 9B shows the state in which the brazing material 430 coexists with the solid phase and the liquid phase (solid-liquid). The result of bending press in the coexistence state) is shown, and FIG. 9C shows the result of bending press with the brazing material 430 in the liquid phase.
As shown in FIGS. 9B and 9C, when the brazing material 430 is subjected to bending press (that is, hot stamping process) in a solid-liquid coexistence state or a liquid phase state, liquid metal embrittlement cracking occurs. . In contrast, as shown in FIG. 9A, when the brazing material 430 is subjected to a bending press (that is, a hot stamping process) in a solid state, it can be seen that liquid metal embrittlement cracking does not occur.

(Summary)
As described above, in the present embodiment, the metal plates 210 and 220 are made of the brazing material 230 that has a solidus temperature that is higher than the heating temperature in the heating process for hot stamping and lower than the solidus temperature of the metal plates 210 and 220. The blank material 200 was manufactured by brazing. Therefore, it is possible to manufacture the blank material 200 having a high bending load while suppressing changes in the hot stamp process as much as possible. Moreover, since brazing is performed in a process different from heating for hot pressing, brazing management is facilitated, and restrictions on brazing conditions can be suppressed. Furthermore, since the brazing filler metal 230 having a solidus temperature lower than the solidus temperature of the metal plates 210 and 220 is used, the occurrence of liquid metal embrittlement cracking can be suppressed. Therefore, it is possible to improve the strength and rigidity of the molded part 100 manufactured by the hot stamping process without significantly changing the hot stamping process (hot stamping heating process, hot stamping molding process, shot blasting process). it can.

In the present embodiment, the case where the number of metal plates to be surface bonded is two has been described as an example. However, the number of metal plates to be surface bonded may be three or more. In this case, the brazing material is arranged between each of the two metal plates facing each other. Moreover, in this embodiment, the case where all the metal plates to be surface bonded were steel plates was described as an example. However, this is not always necessary. For example, a steel plate and at least one metal plate having a solidus temperature higher than the Ac3 point of iron may be used for surface bonding. When two or more metal plates having a solidus temperature higher than the Ac3 point of iron are used, the metal plates may be different types of metal plates or the same type of metal plates.
Moreover, in this embodiment, the factory which performs a blank material manufacturing process (a brazing material arrangement | positioning process, a brazing material heating process, and a brazing material cooling process), and a hot stamp process (a heating process for hot stamping, a hot stamping process, shot blasting) The explanation was given assuming that the factory performing the process is a factory on the same site. However, the blank is in a brazed state and can be transported over a long distance. Therefore, these factories may be independent factories that are not on the same site. For example, a form in which a manufacturer that manufactures a blank material sells the blank material to a manufacturer that performs hot stamping may be used.

  It should be noted that the embodiments of the present invention described above are merely examples of implementation in carrying out the present invention, and the technical scope of the present invention should not be construed as being limited thereto. Is. That is, the present invention can be implemented in various forms without departing from the technical idea or the main features thereof.

  100: molded part, 110: hat-shaped member, 111: main member, 112: reinforcing member, 120: closing plate, 200: blank material, 210: metal plate, 220: metal plate, 230: brazing material, 310: support Plate, 320: pressing plate, 400: blank, 410: main steel plate, 420: reinforcing steel plate, 430: brazing material, 500: molded part, 510: hat-shaped member, 520: closing plate

Claims (7)

It is a blank material that is molded and quenched by a hot stamp process, and is a method of manufacturing a blank material that is configured by using a plurality of metal plates and a brazing material,
Among the plurality of metal plates whose plate surfaces oppose each other, a brazing material arrangement constituting a plate set in which the brazing material is arranged in a predetermined region between the plate surfaces of two metal plates adjacent to each other Process,
A brazing filler metal heating step for heating the plate assembly constituted by the brazing filler metal placement step;
A brazing filler metal cooling step for cooling the plate assembly heated by the brazing filler metal heating step;
Have
The brazing filler metal solidus temperature is higher than the heating temperature in the heating step for quenching in the hot stamping process, and lower than the solidus temperature of the metal plate,
In the brazing material heating step, the plate assembly is heated at a temperature above the liquidus temperature of the brazing material and below the solidus temperature of the metal plate,
The said brazing material cooling process cools the said board assembly until the temperature of the said brazing material falls below the solidus temperature of the said brazing material, The manufacturing method of the blank material characterized by the above-mentioned.   The said brazing material cooling process cools the said board set until the temperature of the said metal plate becomes temperature lower than Ac1 point of the said metal plate, The manufacturing method of the blank material of Claim 1 characterized by the above-mentioned.   The said heating process heats the said board set, pressing the said board set in the plate | board thickness direction of the said metal plate, The manufacturing method of the blank material of Claim 1 or 2 characterized by the above-mentioned.   The said brazing material cooling process cools the said board set, pressurizing the said board set in the plate | board thickness direction of the said metal plate, The manufacturing method of the blank material of Claim 1 or 2 characterized by the above-mentioned. The blank material manufacturing process which manufactures a blank material with the manufacturing method of the blank material of any one of Claims 1-4,
A heating step for hot stamping for heating the blank material manufactured by the blank material manufacturing step for quenching;
A hot stamping process for molding and quenching the blank material heated by the hot stamping heating process;
A method for producing a hot stamping molded product, comprising: A blank material that is molded and quenched by a hot stamping process,
A plurality of metal plates stacked such that the plate surfaces face each other;
A brazing material that joins the two metal plates between the plate surfaces of the two metal plates adjacent to each other among the plurality of metal plates;
The blank material, wherein a solidus temperature of the brazing material is higher than a heating temperature in a heating process for quenching in the hot stamping process and lower than a solidus temperature of the metal plate.   A hot stamping molded product, which is formed by molding and quenching the blank material according to claim 6 by a hot stamping process.