WO2013030916A1

WO2013030916A1 - Metal mold for hot pressing

Info

Publication number: WO2013030916A1
Application number: PCT/JP2011/069431
Authority: WO
Inventors: 愼治石井
Original assignee: トヨタ自動車株式会社
Priority date: 2011-08-29
Filing date: 2011-08-29
Publication date: 2013-03-07
Also published as: JPWO2013030916A1; JP5807681B2; DE112011105567T5; US20140190233A1; CN103764311A

Abstract

This metal mold for hot pressing is provided with a fixed mold and a movable mold disposed such that the molding surfaces face each other, sandwiches heated work between the fixed mold and movable mold and carries out press processing thereon, while at the same time cooling the work by keeping the molding surfaces of the fixed mold and movable mold in a state of contact with the surface of the work. At least the portions of the molding surface of the fixed mold where the striking during press processing is strong have formed thereon a layer constituted of a shape memory alloy. According to this metal mold for hot pressing, formation of gaps between the metal mold and work is suppressed, and uniform contact between the metal mold and work can be achieved.

Description

Hot press mold

The present invention relates to a mold structure used for hot press molding in which a heated workpiece is cooled at the same time as being pressed.

Conventionally, a workpiece such as a steel plate heated to a temperature above which the austenite structure appears is subjected to press processing by a press device to which a die composed of an upper die and a lower die is attached, and at the same time, contact between the die and the workpiece. Hot press molding that performs a quenching process using cooling by the above is widely known (see, for example, Patent Document 1).

JP 2009-72801 A

In conventional hot press molds, how to contact the mold and the workpiece in the clamped state due to wrinkles due to the shape of the molded product, mold manufacturing accuracy, mold deflection, press machine deflection, etc. ( Difference in strength of hit). This creates a gap between the mold and the workpiece, and there is a problem that the workpiece cannot be uniformly cooled.
Therefore, the present invention provides a hot press die that can suppress the occurrence of a gap between the die and the workpiece and can realize uniform contact between the die and the workpiece.

The hot press mold of the present invention includes a fixed mold and a movable mold that are arranged so that their molding surfaces face each other. When the heated workpiece is sandwiched between the fixed mold and the movable mold, press working is performed. At the same time, a mold for hot pressing that cools the workpiece by holding the molding surface of the fixed mold and the movable mold in contact with the surface of the workpiece, and among the molding surfaces of the stationary mold, A layer made of a shape memory alloy is formed at least at a site where the hit is strong during the press working.

The product shape of the workpiece has a hat-shaped cross section in the longitudinal direction, and the shape of the fixed mold on the surface corresponding to the flange surface and the top surface of the hat-shaped cross section of the product shape of the workpiece. A memory alloy layer is preferably formed.

The shape memory alloy layer formed on the molding surface of the fixed mold is preferably composed of a superelastic alloy.

According to the hot press die of the present invention, it is possible to suppress the occurrence of a gap between the die and the workpiece, and to realize uniform contact between the die and the workpiece.

It is a figure which shows the metal mold | die for hot press. It is a figure which shows the lower mold | type in which the shape memory alloy was provided in the molding surface. It is a figure which shows the hot press process using the metal mold | die for hot press. It is a figure which shows another embodiment of the lower mold | type in which the shape memory alloy was provided in the molding surface. It is a figure which shows another embodiment of the metal mold | die for hot presses.

The mold 1 is a hot press mold for producing a product by subjecting the work 2 to hot press molding. As shown in FIG. 1, the mold 1 includes a lower mold 10 and an upper mold 20, and the work 2 is sandwiched and pressed between them to form the work 2 into a predetermined product shape.
The workpiece 2 is a steel plate and is put into the mold 1 in a state of being heated to a temperature higher than the temperature at which the austenite structure appears. The workpiece 2 is molded into a product shape in the mold 1 and held for a certain period of time while being sandwiched between the lower mold 10 and the upper mold 20, thereby being quenched and quenched.

The workpiece 2 is formed into a product shape having a hat-shaped cross section in the longitudinal direction. That is, the product shape of the workpiece 2 has a flange surface and a top surface formed as surfaces orthogonal to the pressing direction in the mold 1 and has a wall surface connecting these flange surfaces and the top surface. The wall surface in this product shape is formed as a surface substantially parallel to the pressing direction of the mold 1.
The flange surface and the top surface are not limited to those that are strictly perpendicular to the pressing direction, and may have a certain degree of inclination (for example, a surface having an inclination with respect to the pressing direction of 30 degrees or less). And the product which has a top surface should just be a range generally used as what has a hat-shaped cross section.

The lower mold 10 is configured as a fixed mold and is fixed to a floor surface or the like. The lower mold 10 is formed with a convex portion that protrudes with respect to the upper mold 20, and the lower mold 10 is configured as a convex mold facing upward.
The upper mold 20 is configured as a movable mold. The upper mold 20 is supported by an appropriate press device and is movable with respect to the lower mold 10. The upper mold 20 is formed with a concave portion corresponding to the convex portion of the lower mold 10, and the upper mold 20 is configured as a concave mold.
The mutually opposing surfaces of the lower mold 10 and the upper mold 20 are formed as molding surfaces, and the workpiece 2 is molded according to the shape of the molding surface. In other words, the lower mold 10 and the upper mold 20 have a molding surface corresponding to the product shape of the workpiece 2 and are arranged so that the molding surfaces face each other.

As shown in FIG. 2, a shape memory alloy layer 30 is formed over the entire molding surface of the lower mold 10.
The shape memory alloy layer 30 is an alloy layer formed integrally with the lower die 10 by welding the shape memory alloy to the surface of the lower die 10 by laser welding or the like. The shape memory alloy layer 30 is formed with a thickness that does not affect the moldability of the mold 1.

As the shape memory alloy constituting the shape memory alloy layer 30, a commonly used alloy such as a Ni—Ti alloy or an iron-based shape memory alloy can be used. However, the shape memory alloy constituting the shape memory alloy layer 30 needs to reach the transformation point and exhibit superelastic characteristics at least when the workpiece 2 is hot pressed by the mold 1.
Here, as a property of the shape memory alloy constituting the shape memory alloy layer 30, a composition that can easily reach the shape recovery temperature by heat transfer from the workpiece 2 in a state where the mold 1 is clamped (for example, after several seconds). Preferably, it is a superelastic alloy in which the normal temperature (about 20 ° C.) or lower is set as the shape recovery temperature.

The function of the shape memory alloy layer 30 when the workpiece 2 is hot-pressed using the mold 1 will be described with reference to FIG.

As shown in FIG. 3, press work of the work 2 is started by moving the upper mold 20 with respect to the lower mold 10 with the work 2 set. And the upper mold | type 20 is moved further and it hold | maintains for the predetermined time in the state which reached | attained the bottom dead center.
At this time, the shape memory alloy layer 30 formed on the molding surface of the lower mold 10 can be superelastically deformed by heat transfer from the workpiece 2 or by setting its shape recovery temperature. For this reason, in a portion where the upper die 20 is strongly hit (a portion corresponding to a surface orthogonal to the pressing direction, such as a flange surface or a top surface in the product), superelastic deformation is performed according to the pressing force received from the upper die 20 and the workpiece 2 To do. The shape memory alloy layer 30 is superelastically deformed and strokes at a strong hit portion, and further flows from a strong hit portion toward a weak portion, thereby increasing the thickness of the weak hit portion and applying a press load. it can.

As described above, the gap between the workpiece 2 and the lower mold 10 can be absorbed by the superelastic deformation of the shape memory alloy layer 30. Furthermore, when the molding surface of the lower mold 10 is deformed by the shape memory alloy layer 30, the manner in which the lower mold 10 and the work 2 are brought into contact changes, and the contact between the work 2 and the upper mold 20 is also improved. Thereby, it is difficult for a gap to be generated between the workpiece 2 and the upper mold 20. That is, by providing the shape memory alloy layer 30 on the molding surface of the lower mold 10, it is possible to suppress the generation of a gap between the mold 1 and the work 2.
In particular, when the product shape of the workpiece 2 has a hat-shaped cross section as in the present embodiment, it is known that wrinkles are likely to occur at a portion where the bending amount is large (such as a corner portion), a shrinkage flange, or the like. Even when wrinkles occur in this way, the shape memory alloy layer 30 is superelastically deformed, so that a part of the molding surface of the lower mold 10 enters the wrinkles, so that the workpiece 2 and the mold 1 are evenly contacted. Can be realized. Moreover, since the contact with the wall surface part contained in the product shape of the workpiece 2 can be increased, the time required for cooling the workpiece 2 can be shortened. Therefore, when hot pressing the workpiece 2 using the mold 1, the cycle time can be shortened while ensuring the quality.

After the hot press with the mold 1 is completed, the press load by the upper mold 20 is released. The shape memory alloy layer 30 returns to its original shape due to the superelastic characteristics.

As shown in FIG. 4, the shape memory alloy layer 30 provided on the lower mold 10 may be partially disposed instead of being disposed on the entire molding surface of the lower mold 10. Specifically, the shape memory alloy layer 30 is disposed at a portion corresponding to the flange surface and top surface of the product shape of the workpiece 2, which is a portion where the upper die 20 is strongly hit on the molding surface of the lower die 10. As a result, the shape memory alloy layer 30 is superelastically deformed at a portion where the upper die 20 is strongly hit, and the upper die 20 is stroked, and the hit against the wall portion which is a weakly hit portion becomes stronger. That is, the contact with the workpiece 2 in the mold 1 can be made uniform.
As described above, by disposing the shape memory alloy layer 30 at least on the molding surface of the lower mold 10 (part orthogonal to the pressing direction), the contact between the mold 1 and the workpiece 2 can be improved.

As shown in FIG. 5, the shape memory alloy layer 30 may be formed on the molding surface of the upper mold 20 in addition to the molding surface of the lower mold 10. By providing the shape memory alloy layer 30 on the molding surface of the upper mold 20, the contact between the mold 1 and the workpiece 2 can be further improved.

The present invention can be used for a mold used for hot press molding in which a heated workpiece is cooled at the same time as being pressed.

1: Mold (hot press mold) 2: Workpiece 10: Lower mold 20: Upper mold 30: Shape memory alloy layer

Claims

The fixed mold and the movable mold are arranged so that their molding surfaces face each other, and the heated workpiece is sandwiched between the fixed mold and the movable mold and pressed, and at the same time, the fixed mold is placed on the surface of the workpiece. And a mold for hot pressing that cools the workpiece by holding the movable mold in contact with the molding surface,
A mold for hot pressing in which a layer made of a shape memory alloy is formed at least on a portion of the molding surface of the fixed die that is strong at the time of pressing.
The product shape of the workpiece has a hat-shaped cross section in the longitudinal direction,
2. The hot press mold according to claim 1, wherein the shape memory alloy layer is formed in a portion corresponding to a flange surface and a top surface of a hat-shaped cross section in the product shape of the workpiece on the molding surface of the fixed mold.
The hot press mold according to claim 1 or 2, wherein the shape memory alloy layer formed on the molding surface of the fixed mold is made of a superelastic alloy.