Patent ID: 8245552

Claim:
A process for producing a high-alloy seamless tube, wherein a starting material to be extruded made of a high alloy comprising, in mass %, Cr: 20 to 30% and Ni: more than 22% and 60% or less is heated to a temperature predetermined according to the contents of Mo and W and subjected to a hot-extrusion process by the Ugine-Sejournet tube-making method, the heating temperature (T) satisfying a relationship of Formula (1), (2), or (3) as below, which is expressed in terms of the average cross-sectional area (A) of the starting material to be extruded, the extrusion ratio (EL), and the extrusion speed (V), the extrusion process being carried out with an average extrusion speed from start to finish being in the range of 80 mm/s or more to 200 mm/s or less, while with the extrusion ratio being 10 or less: when 0%≦Mo+0.5W<4%, T≦ 1343−0.001322 ×A− 1.059 ×EL− 0.129 ×V (1); when 4%≦Mo+0.5W<7%, T≦ 1316−0.001322 ×A− 1.059 ×EL− 0.129 ×V (2); and when 7%≦Mo+0.5W, T≦ 1289−0.001322× A− 1.059 ×EL× 0.129 ×V (3), where A and EL in Formulae (1) to (3) are determined by the following Formulae (4) and (5): A=π×t 0 ×( d 0 −t 0 ) (4); and EL=L 1 /L 0 (5), given that each symbol in the above Formulae (1) to (5) means the following quantity: Mo: Mo content in the starting material to be extruded (mass %), W: W content in the starting material to be extruded (mass %), T: Heating temperature of the starting material to be extruded (° C.), A: Average cross-sectional area of the starting material to be extruded (mm 2 ), EL: Extrusion ratio (−), V: Extrusion speed (mm/s), d 0 : Average outside diameter of the starting material to be extruded (mm), t 0 : Average wall thickness of the starting material to be extruded (mm), L 0 : Length of the starting material to be extruded (mm), and L 1 : Length of the extruded tube (mm).