Abstract: The production flowsheet of Φ108 mm x 15 mm tube shell of tested steel TP347H (/% : 0. 08C, 0. 36Si, 1. 27Mn, 0. 020P, 0.0005S, 18.l0Cr, 10.80Ni, 0.78Nb, 0.007Cu) is hot-metal pretreatment- 90 t K-OBM-S melting- VOD-LF-220 mm x220 mm bloom casting- hot-rolled to Φ110 mm tube blank- piercing to tube shell. The batches intermittent and irregular cracks at inner wall of shell occur after pickling. By examination and analysis the inner defects of shell it is defined that inner defects is double layers formed by large-external composite inclusions in base, during conical-extrusion-piercing process, the base metal produces breaking caused by uneven stress led to form inner wall cracks. With prolonging LF soft stirring time and killing time, maintaining liquid in tundish more than 20 t, increasing the quality of submerged nozzle and increasing the baking temperature of nozzle form ≥800℃ to ≥1 000℃, the rating of each type of inclusions is 0 ~ 1.0 and the rate of shell inner defects decreases form 3.41% to less than 0.01%.

摘要： 试验TP347H钢(/%:0.08C,0.36Si,1.27Mn,0.020P,0.000 5S,18.10Cr,10.80Ni,0.78Nb,0.007Cu)Φ108 mm×15 mm荒管的生产流程为:铁水预处理-90 t K-OBM-S熔炼-VOD-LF-220 mm×220 mm方坯连铸-热轧Φ110 mm管坯-穿孔成荒管。对荒管内壁酸洗检验后发现批量间断无规律的裂纹缺陷。经检测确认荒管内壁缺陷是由于外来大型复合夹杂物在基体形成"夹层",在锥形挤压穿孔过程中,基体金属受力不均匀产生破裂,导致形成内壁裂纹。通过延长LF弱搅拌和镇静时间,保持中间包钢水容量20 t,提高浸入式水口质量,水口烘烤温度由≥800℃提高至≥1 000℃,使管坯中各类夹杂物为0～1.0级,荒管内壁缺陷率由3.41%下降至0.01%以下。

关键词: TP347H奥氏体不锈钢, Φ 108 mm X 15 mm荒管, 内壁夹杂物裂纹, 工艺改进