小口径锅炉管生产技术开发

Development of Production Technologies for Small-diameter Boiler Tube

内蒙古包钢特种钢管有限公司围绕集团公司“突围打样提升产品质量”的要求,通过创新工艺设计,设计开发小口径锅炉管,并提高锅炉管的质量指标。机组原设计使用Φ150 mm连铸坯料轧制外径范围为51~114.3 mm、壁厚范围为3.5~12 mm的无缝钢管。锅炉管行业对于外径38~48 mm、壁厚3.5~8 mm的小口径锅炉管有较大的需求量。研究开发连轧机组大减径率技术,利用Φ150 mm连铸坯料生产外径范围为38~48 mm的无缝钢管,实现使用同一直径坯料生产两组外径范围无缝钢管,钢管的壁厚精度为-7.14%~9.14%。轧制材质为25MnG、15CrMoG和12Cr1MoVG小口径锅炉管时,在钢管的内表面出现了“内直道”缺陷,外表面出现了“青线”缺陷和“皮下裂纹”缺陷,结合变形工艺和材质特性分析了这些缺陷产生的原因,制定解决措施,产品超声探伤合格率由86.82%提高到91.32%。制定了材质为15CrMoG和12Cr1MoVG小口径锅炉管热处理制度,在该工艺制度下,产品的机械性能稳定,能够满足GB/T 5310—2017标准要求。

The small-diameter boiler tube is designed and developed through innovating process design as well as its quality indexes are improved by Inner Mongolia Baotou Steel Special Steel Pipe Co.,Ltd.based on the requirements of group company,“break through and improve product quality”.The seamless steel pipe with outer diameter of 51~114.3 mm and wall thickness of 3.5~12 mm is rolled by continuous casting billet ofΦ150 mm in the original design of the unit.The demand of small-diameter boiler tube with outer diameter of 38~48 mm and wall thickness of 3.5~8 mm in the boiler tube industry is greater.The seamless steel pipes of two groups of outer diameter produced with the billets of the same diameter is realized and their wall thickness accuracy is-7.14%~9.14%through researching and developing the technology of large tube reducing rate for continuous mill unit as well as producing the seamless steel pipe with outer diameter of 38~48 mm by continuous casting billet ofΦ150 mm.When rolling small-diameter boiler tubes made of materials of 25MnG,15CrMoG and 12Cr1MoVG,there are defects of“straight fold”on inner surface as well as“linear indentation”and“subsurface cracks”on outer surface of steel tube.Their causes are analyzed combining with the deformation process and material characteristics as well as the solutions are formulated so that qualified rate of ultrasonic flaw detection of product is increased from 86.82%to 91.32%.The heat-treatment schedule for small-diameter boiler tubes made of materials of 15CrMoG and 12Cr1MoVG is formulated as well as the mechanical properties of products are stable under this process schedule,which could meet the requirements of GB/T 5310-2017 standard.