Solidification behavior and characteristics of molten pool of high manganese austenitic steel for cryogenic application

The weld metal of high manganese austenitic steel was prepared by submerged arc welding process with the main composition (wt.%) range of 0.30-0.50 C, 22.00-25.00 Mn, 3.50-5.50 Cr. The segregation behavior of alloying elements and the solidification characteristics of the molten pool of high manganese austenitic steel were studied by OM, EBSD, EPMA and other analysis methods. The analysis of microstructure and chemical composition shows that there are inhomogeneous mixed zone and partially melted zone (PMZ) in the fusion zone of high manganese austenitic steel welded joints prepared with the same composition system. The alloy element segregation zone of C, Mn and Cr produced by hot rolling in the test steel resulted in partial melting of the PMZ in the fusion zone of the welded joint, and further increases its degree of elemental segregation. The inhomogeneous mixed zone co-crystallizes in the PMZ in the form of cellular crystals, and the distribution of the alloy elements continues the distribution in the PMZ. The molten pool co-crystallizes in the form of cellular crystals on the protruding solid phase peninsula on the PMZ. The width of the initial cytosolic crystals correlates is intrinsically related to the spacing of the hot-rolled segregation bands of the base metal, which is produced by the segregation of alloying elements in the hot rolled strip in the partially melted zone and the concave solid-liquid interface formed by its partial melting.