IMPACT PRESS-FORMED METAL TUBE BODY

To provide an impact press-formed metal tube body in which a region with large surface roughness along a circumferential direction is formed on an outer peripheral surface of a tubular part, called a shock line uniquely generated by impact press forming and an uneven thickness is suppressed.SOLUTION: In the impact press-formed metal tube body, at least one condition of a condition (1), a condition (2) and a condition (3) is satisfied. In the condition (1), ratios (Rz1/Rz2) of surface roughness Rz1 of an outer peripheral surface of a bottom part to surface roughness Rz2 of an outer peripheral surface of a center part in a shaft direction of a tubular part are in a range of 2 or more and 4000 or less. In the condition (2), Vickers hardness HV1 of the outer peripheral surface of the bottom part is smaller by a range of 5HV or more and 27HV or less than Vickers hardness HV1 of the outer peripheral surface of the center part in the shaft direction of the tubular part. In the condition (3), an average crystal grain diameter D1 on the outer peripheral surface of the bottom part is larger by a range of 50 μm or more and 999.9 μm or less than an average crystal grain diameter D2 of the outer peripheral surface of the center part in the shaft direction of the tubular part.SELECTED DRAWING: Figure 1 【課題】インパクトプレス加工で特有に発生するショックラインと呼ばれる、筒状部の外周面に、周方向に沿った表面粗度の大きな領域の発生と共に、偏肉が抑制されているインパクトプレス加工金属筒体を提供すること。【解決手段】条件（１）と条件（２）及び条件（３）の少なくとも一方の条件と、を満たすインパクトプレス加工金属筒体。条件（１）底部の外周面の表面粗さＲｚ１と、筒状部の軸方向中央部の外周面の表面粗さＲｚ２と、の比（Ｒｚ１／Ｒｚ２）が、２以上４０００以下の範囲である。条件（２）底部の外周面のビッカース硬度ＨＶ１が、筒状部の軸方向中央部の外周面のビッカース硬度ＨＶ１に比べ５ＨＶ以上２７ＨＶ以下の範囲で小さい。条件（３）底部の外周面の平均結晶粒径Ｄ１が、筒状部の軸方向中央部の外周面の平均結晶粒径Ｄ２に比べ５０μｍ以上９９９.９μｍ以下の範囲で大きい。【選択図】図１