JP-7854972-B2 - Press forming method

Inventors

• 菅原 稔
• 宮城 隆司
• 中世古 洸
• 石野 泰信

Assignees

• 日本製鉄株式会社
• 豊田鉄工株式会社

Dates

Publication Date

20260507

Application Date

20230823

Claims (4)

1. The intermediate molded product forming process involves pressing a metal sheet to form an intermediate molded product, An additional processing step is performed on the aforementioned intermediate molded product by press working. The process includes a process for identifying a low-pressure portion in which a low pressure is applied to the intermediate molded product during the additional processing step, In the aforementioned additional machining process, the additional machining is performed with the pressure applied to the low-pressure lower portion set to a predetermined pressure or less. A press forming method in which, in the specified step, the portion in which the difference in plastic strain before and after press working on the intermediate molded product without providing a relief portion is 0.02 or less is defined as the low-reduction portion .
2. The press forming method according to claim 1, wherein in the additional processing step, the pressure applied to the low-pressure portion is 100 MPa or less when the additional processing is performed.
3. The press forming method according to claim 1 or 2, wherein the metal plate is a steel plate with a tensile strength of 590 MPa or more.
4. The press molding method according to claim 1 or 2, wherein the intermediate molded product molding step and the additional processing step are steps in which cold press working is performed.

Description

This invention relates to a press molding method. The press forming load when press forming a metal sheet increases with increasing material strength or sheet thickness. Furthermore, the press forming load also increases with larger press-formed products and more complex shapes. However, there is an upper limit to the load that a press machine can apply to a metal sheet. Therefore, depending on the existing press machine, it may not be possible to apply the target load to the metal sheet, making it impossible to manufacture press-formed products of the desired shape. To reduce press load, Patent Document 1 discloses a method for manufacturing press-formed products in which the press-formed shape is arranged to be inclined with respect to the press direction, and the press-formed shape is formed using a cam mechanism. This method converts the load applied in the press direction to the inclined surface, thereby reducing the press-direction load. Furthermore, for example, in a transfer press machine, a metal sheet is subjected to multiple pressing processes to produce a press-formed product. In a pressing process involving multiple pressing processes, areas formed in previous pressing processes may be subjected to repeated pressure. In the following, this repeated pressure on areas formed in previous pressing processes may be referred to as "repeated pressing." As a technique to reduce repeated pressing, for example, Patent Document 2 discloses a press forming method for press forming vehicle body parts from a plate-like material through multiple processes, in which the clearance between the mold and the workpiece is made larger than the plate thickness in the formed portion of the intermediate molded product where the impact on springback in the next process is significant. Japanese Patent Publication No. 2020-75275Japanese Patent Publication No. 2020-163416 This is a flowchart illustrating the flow of a press forming method according to one embodiment of the present invention.This is a model diagram of the molded product in the example.This is a contour diagram showing the dimensional difference between the molded product of Example 1 of the present invention and the molded product of a reference example.This is a contour diagram showing the dimensional difference between the molded product of Example 2 of the present invention and the molded product of the reference example.This is a contour map showing the dimensional difference between the comparative example molded product and the reference example molded product. The embodiments of the present invention will be described below with reference to the drawings. The press forming method according to this embodiment comprises: an intermediate molded product forming step of forming an intermediate molded product by press working a metal sheet; an additional processing step of further processing the intermediate molded product by press working; and a specification step of identifying a low-pressure area in the additional processing step where a low pressure is applied to the intermediate molded product. In the additional processing step, the pressure applied to the low-pressure area is set to a predetermined pressure or less when performing the additional processing. <Intermediate molding process> In the intermediate molded product forming process, an intermediate molded product is formed by press-forming a metal sheet. The metal sheet is not particularly limited, and various metal sheets can be used as the material. Examples of metal sheets include steel sheets, stainless steel sheets, aluminum steel sheets, copper sheets, titanium sheets, etc. However, the higher the strength, the greater the load required for press-forming, and the more pronounced the effects of this embodiment can be obtained. For example, the metal sheet is preferably a steel sheet with a tensile strength of 590 MPa or more, more preferably a steel sheet with a tensile strength of 980 MPa or more, and even more preferably a steel sheet with a tensile strength of 1180 MPa or more, or 1470 MPa or more. The thickness of the metal sheet is not particularly limited, but as the sheet thickness increases, the load required for press working increases, and the effects of this embodiment can be more significantly obtained. Therefore, the sheet thickness of the metal sheet is preferably 1.0 mm or more, more preferably 1.4 mm or more, and even more preferably 1.8 mm or more. The sheet thickness may also be, for example, 3.2 mm or less. The press working in the intermediate molded product forming process is cold press working, and this press working can include, for example, deep drawing, pad drawing, pad bending, stamping, deep drawing, stretching, or bending. <Additional work process> In the additional processing step, the intermediate molded product is further processed by press working. In the additional processing step, the pressure applied to the low-reduced portion, which is specified in the s