The tested alloy NS3105 (/%：0.021C

0.06Si

0.02Mn

0.0007S

0.007P

29. 75Cr

59. 90Ni

9. 88Fe

0.0100N) is melted by 12t vacuum induction furnace and electro-slag remelting to 3t ingot with shielding atmosphere

forged breaking-down to Φ236 mm bloom

hot extrusion to Φ95mmx16mm pierced shell

then cold-rolled to Φ63mmx10mm tube. Effect of the solid-solution treatment of cold-rolled tube at 800〜1140°C for 5~15min on structure of steel has been studied. Results show that as the alloy NS3150 hot-worked tube cold-rolled with 60% deformation

the original equiaxed crystal structure of alloy occur large deformation

the deformed grains in cold-rolled tube start to recover-recrystallize at 800°C and the recrystallization is completed basically at 950°C；with increasing temperature and heating time the recrystallized grains of cold-rolled tube grow continuously

and the grains grow inhomogeneously at 950〜1080°C and the mix-grain and coarse-fine grain structure occur; at 1080~1120°C the grains grow homogeneously; and at more than 1120°C the grains of cold-rolled tube grow obviously and the structure is coarser. The optimum solid-solution treated temperature for cold-rolled tube of alloy NS3105 is 1080~1120°C.