熱間継目無鋼管圧延の潤滑特性に及ぼす炭素鋼スケールの影響と硼砂散布の効果

抄録

It is empirically known that an iron oxide layer formed on a surface of work piece plays an important role of lubricating properties in hot rolling. However, very few works on the influence of iron oxide layer on lubrication properties have been reported. Therefore, we investigated the influence of thick iron oxide scale layer on lubricity in the case of carbon steel hot rolling by means of a simulation test of seamless pipe hot rolling. Furthermore, based on the result, we found the effectiveness of borax application on the surface of the work piece in terms of lubricity improvement.
A carbon steel work piece, which has a controlled thickness of an oxide layer by heating up to the set elevated temperature followed by exposing to ambient atmosphere for the set duration, was rolled between a cylindrical roll and a flat tool lubricated with graphite-based lubricant.
Summaries of the results are shown below.
① In case of high rolling reduction, the iron oxide was embedded into the substrate in rolling, which caused high friction coefficient when hard iron oxide layer generated thickly.
② It is effective to soften the iron oxide by, for instance, applying bolax on the work piece surface in order to prevent the iron oxide from being embedded into the substrate and from increasing the friction coefficient when the hard iron oxide scale layer generated thickly.