| 摘要 |
PROBLEM TO BE SOLVED: To obtain an excellent inner surface property even in the case of rolling with a large rolling reduction by specifying the transfer speed of a plug and feeding a powdery lubricant consisting of the mixture of powder of oxide, a hydroxide or a hydroxide contg. water of crystallization with prescribed constituent and graphite powder into the tube stock. SOLUTION: In the plug mill rolling method of a seamless metal tube capable of rolling tube stock consisting of the ferrous alloy containing 4.5 weight% or more Cr with a large wall thickness rolling reduction, the plug is transferred at the speed of >=2.0 mm/sec in the rolling advancing direction of the tube or in the inverse direction of the rolling advancing direction. Besides, the powdery lubricant consisting of the mixture of one kind or two kinds or more of powder selected from the oxide, the hydroxide or the hydroxide contg. water of crystallization consisting of each element or plural elements of, as main constituent, aluminum, silicon, calcium, titanium, iron, boron and sodium and graphite powder is fed into the tube stock. |
