| 摘要 |
<p>A method of using a Cr-plated mandrel bar repeatedly used in mandrel mill rolling in Mannesmann pipe making process, which comprises carrying out either regeneration when the surface flaw occurring by use in mandrel mill rolling is 1.5 mm or more in opening width (H) and is from 0.3 mm to less than 2.0 mm in depth (D) so as to enable reuse as a tool of the same dimension, or downsizing when the surface flaw occurring by use in mandrel mill rolling is 2.0 mm or more in depth (D) so as to enable reuse as a tool of small diameter dimension. By the regeneration or downsizing in accordance with the property or configuration of the surface flaw followed by repeated use in mandrel mill rolling, there can be attained prolongation of the service life of mandrel bar and enhancement of specific productivity.</p> |
