# US 2018/0021829 A1 · Formed metal item including tubular part with slit, method for producing the same, and producing device and die assembly used in method for producing the same > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2018/0021829 A1 - Document ID: US20180021829A1 - Status: Published application - Kind: A1 - Application number: 15/550,813 - Filed: 2016-02-25 - Published: 2018-01-25 - Earliest claimed: 2015-02-25 - Assignees: Nippon Steel & Sumitomo Metal Corporation - Applicants: Nippon Steel & Sumitomo Metal Corporation - Inventors: Masahiko SATO; Tohru YOSHIDA - Web page: https://patentgrep.com/patent/US20180021829A1 ## CPC - B21D 5/015: {for making tubes} - B21C 37/0815: {without continuous longitudinal movement of the sheet during the bending operation} - B21D 5/10: for making tubes - B21D: WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL (working or processing of wire B21F) - B21C: MANUFACTURE OF METAL SHEETS, WIRE, RODS, TUBES, PROFILES OR LIKE SEMI-MANUFACTURED PRODUCTS OTHERWISE THAN BY ROLLING; AUXILIARY OPERATIONS USED IN CONNECTION WITH METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL ## Abstract A producing method to be disclosed is a producing method for producing a formed metal item that includes a tubular part with a slit. This producing method includes a step (i) of forming U-shaped part having a U-shaped cross section by deforming a metal plate, and a step (ii) of forming the tubular part with the slit by deforming the U-shaped part using a die assembly with a protruding part in such a manner that two end parts of the U-shaped part clamp the protruding part. In step (ii), a cross-section peripheral length LH of the tubular part is made shorter than a cross-section length LU of the U-shaped part. ## Claims ### Claim 1 A producing method for producing a formed metal item that includes a tubular part with a slit, the producing method comprising: (i) a step of forming a U-shaped part having a U-shaped cross section by deforming a metal plate; and (ii) a step of forming the tubular part with the slit by deforming the U-shaped part using a die assembly provided with a protruding part in such a manner that two end parts of the U-shaped part clamp the protruding part, wherein in the step (ii), the cross-section peripheral length LH of the tubular part is made shorter than the cross-section length LU of the U-shaped part. ### Claim 2 (depends on 1) The producing method according to claim 1, wherein the cross-section length LU of the U-shaped part and the cross-section peripheral length LH of the tubular part satisfy an expression of 0.2≦100×(LU−LH)/LU<1. ### Claim 3 (depends on 1) The producing method according to claim 1, wherein the step (ii) includes: (ii-1) a step of forming a cylindrical-shape portion by deforming the U-shaped part using the die assembly in such a manner that the two end parts of the U-shaped part clamp the protruding part, the cylindrical-shape portion being to be the tubular part; and (ii-2) a step of pressing an outer peripheral surface of the cylindrical-shape portion while the two end parts are clamping the protruding part, whereby the cross-section peripheral length LT of the cylindrical-shape portion is shortened. ### Claim 4 (depends on 3) The producing method according to claim 3, wherein the die assembly includes a first die including the protruding part, and includes a second die, the first and second dies include first and second pressing surface, respectively, the first and second pressing surface being configured to deform the U-shaped part to form the cylindrical-shape portion, at least one die selected from the first die and the second die is separable into a plurality of die members, in the step (ii-1), the cylindrical-shape portion is formed by deforming the U-shaped part using the die assembly while the plurality of die members are separated, and in the step (ii-2), the outer peripheral surface of the cylindrical-shape portion is pressed by bringing the plurality of die members close to each other, whereby the cross-section peripheral length LT of the cylindrical-shape portion is shortened. ### Claim 5 (depends on 1) The producing method according to claim 1, wherein the die assembly includes a pressing surface that corresponds to an outer peripheral surface of the tubular part, and a cross-section peripheral length of the pressing surface is shorter than the cross-section length LU of the U-shaped part. ### Claim 6 (depends on 3) The producing method according to claim 3, wherein the die assembly includes a first die including the protruding part, and includes a second die, the first and second dies include first and second pressing surface, respectively, the first and second pressing surface being configured to deform the U-shaped part to form the cylindrical-shape portion, at least one die selected from the first die and the second die includes a body part and a movable part that is movable relative to the body part, in the step (ii-1), the cylindrical-shape portion is formed by deforming the U-shaped part using the die assembly while a pressing surface of the movable part does not project from a pressing surface of the body part, and in the step (ii-2), the outer peripheral surface of the cylindrical-shape portion is pressed by causing the pressing surface of the movable part to project from the pressing surface of the body part, whereby the cross-section peripheral length LT of the cylindrical-shape portion is shortened. ### Claim 7 A formed metal item that includes a tubular part with a slit, wherein when a variation S in Vickers hardness in a thickness direction of a cross section of the tubular part is expressed by a following expression, an average value of variations S in a circumferential direction is less than 0.4, S=(Bmax−Bmin)/Bmax where Bmin is a minimum value of Vickers hardnesses in a thickness direction of the cross section, and Bmax is a maximum value of Vickers hardnesses in the thickness direction of the cross section. ### Claim 8 A producing device for producing a formed metal item that includes a tubular part with a slit, the producing device comprising a die assembly and a movement mechanism for moving the die assembly, wherein the die assembly includes a first die including a protruding part for forming the slit, and includes a second die, the first and second dies include first and second pressing surfaces, respectively, the first and second pressing surfaces being configured to deform a U-shaped part having a U-shaped cross section to form a cylindrical-shape portion with a gap, the gap being to be the slit, and the die assembly has a configuration to press an outer peripheral surface of the cylindrical-shape portion so that a cross-section peripheral length of the cylindrical-shape portion is made short. ### Claim 9 (depends on 8) The producing device according to claim 8, wherein at least one die selected from the first die and the second die is separable into a plurality of die members, and the movement mechanism includes: a first movement mechanism to bring the first die and the second die close to each other while the plurality of die members are separated; and a second movement mechanism to bring the plurality of die members being separated close to each other. ### Claim 10 (depends on 8) The producing device according to claim 8, wherein at least one die selected from the first die and the second die includes a body part and a movable part that is movable relative to the body part, and the movement mechanism includes: a first movement mechanism to bring the first die and the second die close to each other, while the movable part is not projecting from the first and second pressing surfaces; and a second movement mechanism to move the movable part so that the movable part projects from the pressing surface. ### Claim 11 A die assembly for producing a formed metal item that includes a tubular part with a slit, the die assembly comprising a first die that includes a protruding part for forming the slit, and includes a second die, wherein the first and second dies include first and second pressing surfaces, respectively, the first and second pressing surfaces being configured to deform a U-shaped part having a U-shaped cross section to form a cylindrical-shape portion with a gap, the gap being to be the slit, and the die assembly includes a configuration to press an outer peripheral surface of the cylindrical-shape portion so that a cross-section peripheral length of the cylindrical-shape portion is shortened. ### Claim 12 (depends on 11) The die assembly according to claim 11, wherein at least one die selected from the first die and the second die is separable into a plurality of die members. ### Claim 13 (depends on 12) The die assembly according to claim 12, wherein the first die is separable into a first die member and a second die member, and the protruding part is configured by a first protruding part included in the first die member and a second protruding part included in the second die member. ### Claim 14 (depends on 11) The die assembly according to claim 11, wherein at least one die selected from the first die and the second die includes a body part and a movable part that is movable relative to the body part. ### Claim 15 (depends on 11) The die assembly according to claim 11, wherein the protruding part is replaceable.