Nonmetallic Inclusions in HSLA Steel Weldments

The U.S. Navy is currently funding a program for certification of HSLA steels to replace the HY series of high strength steels for structural fabrication. Integral to this program is the certification of welding consumables for use with these steels. The size, distribution and composition of nonmetallic inclusions in HSLA steel weld metal has been shown to play a key role in the final strength and toughness of the deposited weld. The purpose of this study was to develop a procedure for analysis of nonmetallic inclusions in HSLA steel multipass weldments utilizing optical microscopy and examination and EDX analysis in a SEM. The results of the study suggest that the mean diameter of inclusions in the final pass of a GMAW weldment in a 2.0 inch HSLA-100 plate is larger than the mean diameter of those in the root pass. Additionally the material in the final pass contains a greater amount of Si and Ti deoxidation products than that in the root pass. The larger size, composition and complex structure of the inclusions in the final pass suggest that they contain deoxidation products from previous welding passes which have been released through remelting and coalesced into larger inclusions. Theses.