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

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.

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.