无缝钢管分层缺陷的鉴定

Evaluation of Lamination Defect of Seamless Steel Pipe

连铸圆管坯轧制无缝钢管出现的分层缺陷,是钢管壁厚中间区域和靠近内表面区域存在着异常夹杂物所致,这些异常夹杂物是钢液在冶炼和浇注过程中的脱氧产物,以及卷入钢液中的熔渣、被浸蚀的耐火材料及保护渣。使用超声波测厚仪或超声波探伤仪可以发现这种缺陷;在有分层缺陷的钢管内表面,往往伴有许多鼓包和翘皮;连铸圆管坯生产厂家应该保证连铸圆管坯轧制的无缝钢管无冶炼和浇铸因素引起的分层缺陷。

It is identified that the lamination defect of the seamless steel tube produced with the continuously-cast round billet is in fact abnormal inclusions existing in the tube wall middle area and near inside surface area. Such inclusions includes matters as deoxidation products of liquid steel formed during the melting and casting processes, and molten slag trapped in the hot metal, eroded refractory and protective slag which failed to float up to be skimmed and thus remained in the steel. The lamination defect can be identified by means of the ultrasonic thickness gauge or the ultrasonic detector. It is always the case that there exist lots of bulges and fins on the inner surface of a steel pipe bearing lamination defects. Producers for CC rounds as prepared for tube rolling are obligated to make sure that seamless steel tubes as rolled from their products will be free of lamination defects as originated during the steel melting and casting processes.