Influence of Mn on microstructure and properties of vertically welded joint with pulse combustion welding rod

Q235 steel was welded by manual high-temperature synthesis (SHS) vertical welding process with pulse combustion welding rod,and the influence of Mn content on the microstructure and properties of the resultant joints were studied. The results show that,without adding Mn in the pulse combustion welding rod,massive pores appeared in the weld without forming effective weld pool at the starting position of welding. When the Mn content was less than 5.9 wt%,the higher the Mn content was,the better the weld was shaped,and the pores reduced rapidly. Fe-rich phases dominated in the weld with the proportion increasing with the increase of Mn content,and the mechanical properties of the joints also increased. When the Mn content was 5.9wt%,the mechanical properties of the joints reached the optimum with tensile strength of 421 MPa and microhardness of 1 578.8 MPa. When the Mn content exceeded 5.9wt%,the increase of Mn content resulted in the weld pool flowing downward seriously and forming welding beading or even burning through the substrate. The resulting weld mainly comprised Cu-rich phases with lots of cracks,which deteriorated the mechanical properties of the joint.