The outer zone is made up of reticular cells, columnar cells and mucous cells;
外区主要由网状上皮细胞、柱状上皮细胞、黏液细胞组成；
2
The results show that:under the no preheating condition, the microstructure of weld metal is columnar austenitic, and brittle martensite exists in the fusion zone and over-heated zone unavoidably.