关键词: P92, 无缝钢管, 斜轧穿孔, 内表面裂纹, 高温δ-铁素体

Abstract: During the production of large-sized P92 ferrite heat-resistant seamless steel pipe by rotary piercing process,the inner surface of the steel pipe is prone to produce small cracks. Through metallographic analysis,high-temperature phase transformation calculation and high-temperature heating test, the studies show that because of the higher heating temperature and the longer heating time,which increases the surface oxidation and decarburization,during the heating process of the P92 billet with a through hole in the center make a large number of high temperature δ ferrite phases near the inner wall and then the cracks generate and propagate around the δ Ferrite phases at the subsequent process of rotary piercing. According to the mechanism of internal surface cracks,through the control of the Cr＜13%,Ni_eq＜4% for P92 pipe chemical composition, the lowering of the billet heating temperature from 1220-1250 ℃ to 1190-1220℃,and the improvement parameters of roll speed,roll distance and the piercing point,the problem of cracks on the internal surface of large-diameter P92 seamless steel pipe is effectively solved,and the yield and production efficiency of P92 seamless steel pipe are improved.

Key words: P92, Seamless Steel Pipe, Rotary Piercing, Inner Surface Cracks, High Temperature δ Ferrite