| 摘要 |
<p>Provided is a method for producing a seamless tube, in which after a starting material to be extruded has been heated to a heating temperature T [°C] satisfying the relationship of Formula (1) or Formula (2) depending on the outside diameter do [mm] thereof, the starting material is hot-extruded by providing a solid lubricating glass between the starting material to be extruded and a die, whereby a transverse flaw on the outer surface in the top portion of tube can be prevented when hot-extrusion is performed by using a starting material for extrusion having low deformability at high temperatures. When d 0 <200, T ‰¤ 1250+1.1487xA-7.838×ln(t 0 /t)-10.135×ln(d 0 /d) ... (1); when d 0 ‰¥200, T ‰¤ 1219+1.1487xA-7.838×ln(t 0 /t)-10.135×ln(d 0 /d) ... (2), where A = L/V av × 1000 [msec], V av = (V 0 + V 0 ×Á)/2 [mm/sec], p = (t 0 ×(d 0 -t 0 ))/(t×(d-t)), t 0 : wall thickness of starting material to be extruded [mm], d: outside diameter of extruded tube [mm], t: wall thickness thereof [mm], L: length of approach portion of die along extrusion direction [mm], and V 0 : ram speed [mm/sec].</p> |
