| 摘要 |
The present invention provides a seamless tube piercing/rolling plug and a seamless tube producing method in which piercing/rolling is performed with an inclined rotary piercing mill while the seamless tube piercing/rolling plug is used as a piercing tool. The seamless tube piercing/rolling plug is used while a front part and a rear part of the split plug are held as an integral plug, at least the front part is made of low alloy steel, and oxide films are formed on surfaces of the front part and rear part. The present invention also provides a seamless tube piercing/rolling apparatus and a seamless tube producing method in which the front part and/or rear part is replaceable in a tube making process line using the seamless tube piercing/rolling apparatus. In the seamless tube piercing/rolling apparatus, the front part and rear part are held as the integral plug, the front part and/or rear part is removably mounted, a mandrel bar holding the plug goes through the rear part, and the mandrel bar is coupled with the front part. It is preferable that a thickness of the oxide film formed in the front part be set to 200 mum or more while the oxide film formed in the front part is thicker than the oxide film formed in the rear part. Even if a hard working material is pierced/rolled, a seam defect and inside surface defects are eliminated, and excellent life-time of plug and excellent plug cost per production quantity can be achieved.
|
