| 摘要 |
PURPOSE: To provide a mandrel bar by which lubricity can be improved at the time of producing a hot rolled seamless pipe. CONSTITUTION: A mandrel bar for a hot rolled seamless pipe with a Cr-plated film having 1.0 to 4.0μm center line average roughness (Ra) in the axial direction on its surface is provided. Even for the rolling of a high alloy steel pipe made of 13Cr steel, etc., excellent wear characteristic and pipe making service life are secured and a large effect is secured for the improvement in the quality of the inside surface of the seamless pipe.
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