| 摘要 |
PROBLEM TO BE SOLVED: To provide a seamless steel tube excellent in inner face quality.SOLUTION: A method for production of a seamless steel tube is provided in which a steel tube material is subjected to piercing rolling using a piercing rolling tool having an oxidized scale film on a surface by scaling heat treatment. The method includes coating at least a part of the surface of the piercing rolling tool with a lubricant just after the scaling heat treatment and before the piercing rolling, and performing multiple piercing rolling using the above piercing rolling tool. The lubricant has a composition containing by mass% based on total amount of the lubricant, 3-20% Li-containing compound in terms of LiO, 30-80% Si-containing compound in terms of SiO, and 0.01% or more but less than 20% of iron oxide-containing substance in terms of FeO, or further regulatory substances blended in the composition. The lubricant may be a coating material blended in water or a solvent prepared by mixing water and alcohols. A molten material having extremely high fluidity is formed on a tool surface at piercing rolling, and the occurrence of flaw on the inner face of the tube is prevented. As a result, the seamless steel tube excellent in inner face quality is produced with high productivity.SELECTED DRAWING: Figure 1 |
