L80-9Cr连铸坯异常坯料分析

Analysis of Abnormality of L80-9Cr Continuous Casting Billet

通过采用连铸坯+热挤压的方式代替传统的锻坯挤压生产9Cr管材,生产出的L80-9Cr连铸坯在锯切中存在切割困难等明显异常情况,经取样分析,发现异常区域的组织除铁素体+碳化物以外,还存在一定量的马氏体组织,异常区域的硬度明显高于正常区域的硬度,但成分与铁素体、珠光体区域无明显差别,分析认为是在退火过程中部分马氏体未完全转变为铁素体+珠光体,马氏体残留较多致使连铸坯局部硬度较高,导致锯切困难,容易切斜,锯切断面处颜色不均。后续延长坯料退火时间,未再发现此类现象。

The 9Cr steel pipe is manufactured by means of the process of CC billet+hot-extrusion.However obvious abnormalities like cutting difficulty are found with the L80-9Cr CC billet during the cutting operation.Relevant analysis is conducted with sample as taken from the abnormal section of the said CC billet,which reveals that in the abnormal area,there exist in the micro structure contents not only ferrite+carbide,but also certain content of the martensite structure,and that the hardness of the abnormal area is remarkably higher than that of the normal area,but the contents are not obviously other than those of the ferrite and pearlite areas.It is regarded via the analysis that during the annealing process,part of the marstenite has not completely transformed into ferrite+pearlite,and thus much more residual marstenite leads to local high hardness of the CC billet,which in turn causes cutting difficulties like frequent oblique cutting,and uneven color of the sawed pipe end face.Accordingly the time for the follow-up annealing of the billet is extended,and then no more abnormalities as above mentioned are found.