Abstract: The causes and practical effects of macrostructure “bubbles” in WB36 thick wall seamless steel pipe are analyzed and studied by means of scanning electron microscope,magnetic particle and ultrasonic flaw detection and performance test. The results show that the main reasons for the formation of macrostructure bubbles are poor deoxidation,high pouring temperature,and damp of ladle and refractory materials etc,the bubbles are short linear dark stripes at the macro, and circular or elliptical holes in the micro,it is mainly distributed near the inner wall to 1/2 wall thickness of the steel pipe corresponding to ingot head near hot top. Slight bubbles cannot be detected by magnetic particle,penetration and ultrasonic flaw detection,which has little impact on the mechanical properties of the steel pipe at room temperature. With controlling casting temperature of WB36 steel below 1590℃,holding time of VD refining at 67 Pa should not be less than 15 min,and moisture content of heating agent and thermal insulation material less than 0. 1%,the generation of macrostructure bubble defects can be effectively prevented.

Key words: WB36 Seamless Steel Pipe , Macrostructure , Bubble , Performance

摘要： 采用扫描电镜、磁粉和超声探伤以及性能测试等方式对WB36厚壁无缝钢管低倍“气泡”形成的原因和实际影响进行了分析研究。结果表明：低倍组织气泡产生的原因主要有脱氧不良、浇注温度高、钢包和耐火材料受潮等，气泡在宏观下呈短线状暗色条纹，微观下为圆形或椭圆形孔洞，主要分布于对应钢锭头部接近冒口端部的钢管近内壁至1/2壁厚处。轻微的气泡采用磁粉、渗透、超声波探伤均无法检出，对钢管的室温力学性能影响较小。 WB36钢浇注温度控制在1590℃以下，保证VD 精炼67 Pa保持时间不少于15 min、发热剂和保温材料水分含量小 于0.1%能够有效防止低倍组织气泡缺陷产生。

关键词: WB36无缝钢管, 低倍组织, 气泡, 性能