RELATED APPLICATIONS

The present application is a National Phase of International Application Number PCT/JP2017/023702, filed Jun. 28, 2017.

TECHNICAL FIELD

The present invention relates to a method for cutting a metal plate, a method for manufacturing a metal product, and the metal product.

BACKGROUND ART

In general, a blanking process is known as a method for shearing a metal plate by using a press to obtain a product (see, for example, Patent Literature 1).

The blanking process described in Patent Literature 1 is a fine blanking process and can highly accurately punch out a product from a work piece. For example, in the fine blanking process, a cutting punch punches out part corresponding to a product with a removal target part of a metal plate being firmly held by a die and a plate holding die and the part corresponding to the product being applied with counter pressure by a counter punch. In this way, the product is punched out from the metal plate by shear force.

Here, a product punched out by a common blanking process has an end surface as shown inFIG. 4. As shown inFIG. 4, the end surface of the product has a sag61, a sheared surface62, and a fracture surface63which are formed in order from one edge portion toward the other edge portion in a thickness direction of the product, and a burr64is formed at the other edge portion.

In contrast, in the case of the fine blanking process, an end surface of a product has a sag, a sheared surface, fracture surface, and a burr formed in the same manner as the common blanking process, but the sheared surface has a large ratio, and the fine blanking process can thus produce precision products.

CITATION LIST

Patent Literature

Patent Literature 1: JP 2006-255740 A

Here, when excessive external force is applied such a product, a crack may extend to cause destruction. For example, if an edge portion of the product has a finely uneven portion such as a burr, a crack is likely to be formed from this edge portion.

In this regard, the fine blanking process enables precise processing, but a fracture surface and/or a burr are formed at the edge portion in a similar manner to a general punching process, and therefore, a crack is likely to be formed at the edge portion when external force of a predetermined value or more is applied. Thus, even with the fine blanking process, it is impossible to increase the strength of a product to a certain level or higher.

On the other hand, you may think that the strength of a product would be improved by performing a shaving process on a cut surface of the product to scrape off a burr formed at an edge portion of the product to finish the cut surface.

Performing the shaving process, however, makes the cut surface of the product smooth in appearance, but a burr is formed newly at the edge portion due to the shaving process, and therefore, it is not possible to improve the strength of the product.

SUMMARY OF INVENTION

In view of the foregoing, it is an object of the present invention to provide a method for cutting a metal plate which enables the formation of cracks in a product to be suppressed even with application of external force and enables strength of the product to be increased, a method for manufacturing a metal product, and the metal product.

A method of one aspect according to the present invention is a method for cutting a metal plate and includes a crushing step of crushing a removal target part of the metal plate in a thickness direction of the metal plate by applying, to the removal target part, force from both sides in the thickness direction so as to deform the removal target part into a thin-walled part, and a separation step of separating, after the crushing step, the thin-walled part from a body of the metal plate.

A method of one aspect according to the present invention is a method for manufacturing a metal product by cutting off a removal target part from a metal plate and includes crushing the removal target part in a thickness direction of the metal plate by applying, to the removal target part, force from both sides in the thickness direction so as to deform the removal target part into a thin-walled part, and a separation step of separating, after the crushing step, the thin-walled part from a body of the metal plate to obtain the metal product.

A metal product of one aspect according to the present invention includes an end surface having a fracture surface which is, in a thickness direction of the metal product, shorter than a thickness of the metal product, the fracture surface being at a middle location in the thickness direction of the metal product.

