piercer with three rolls(A derivation of the Mannesmann tube-process has been developed, using a piercer with three rolls, which has greater accuracy and concentricity. 曼内斯曼制管法的进一步发展,开始使用三辊穿孔机,它具有更高的加工精度和同心度。)
cause of hearth burning-through(【技】炉缸烧穿事故不但使生产和设备遭受重大损失,而且可能引起人身事故。炉缸烧穿的原因包括:砖衬质量差、施工质量差、冷却强度低、冷却水管长期未清洗、冷却器长期漏水、炉缸局部碳砖被氧化、缺少必要的设备检查制度、高炉热制度不稳定、出铁口长期过浅等。)