| 摘要 |
PROBLEM TO BE SOLVED: To provide a steel tube free from any inner surface flaws without preworking a difficult-to-work material, in particular, a stock material inferior in the inner quality of the as-cast stock material by providing a back pressure applying means to push the stock material by the pressure until it is stably bit while applying the back pressure to the stock material. SOLUTION: The pusher preferably has a forward speed changing means to change the forward speed of the pusher according to the rolling condition, and a back pressure changing means to change the back pressure of the pusher. When a stock material 2 is carried before a pusher 10 at the retracted position, a sensor 5 detects the stock material 2, and the high-speed advancement to a drive control part of the pusher 10, and the pusher 10 carries the stock material 2 to a roll 3 side at high speed. When a sensor 4 provided immediately before the roll 3 detects the stock material 2, the sensor commands the low- speed advancement to the drive control part of the pusher 10, and the pusher 10 allows the stock material 2 to be bitten by the roll 3 at a low speed. The specified back pressure is applied to the stock material 2 until the biting is completed, and then, the pusher 10 is retracted.
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