Cleaness of the First Pipeline Steel Slab along with Casting Direction

Abstract

To improve the quality controlling of pipeline steel and to avoid mis-down grade, the cleaness including content of non-metallic inclusions, total oxygen and nitrogen of the first continuous casting slags of X70 pipeline steel were investigated. Results showed that, content of total oxygen, nitrogen, large non-metallic inclusions and inclusions areal density decrease with casting length increasing gradually. But at casting length of about 5.0 m which is just during the drastic changeing period of casting speed approaching to stead casting state, the content of large non-metallic inclusions and inclusions areal density increases abruptly induced by the entrapment of mold powders. Thus, to decrease the degradation rate of pipeline slab, the increasing rate of casting speed should be adjusted more evenly.