SJ301 is a kind of silicon-calcium-type sintered flux,mesh 10-40(2.0-0.45mm) and basicity--1.0-1.1.Either alternating or direct cur rent can be used,but welding wires must be connected with the positive electrode when direct current is used.The welding technology has good performace,fine detachability and fine appearance od weld.The flux is fit for the sumerge-arc welding of low-cabon steel,as well as the fast single-way and double-surface welding of thin steel sheet.And it is usually used for submerge-arc welding of liquefied gas storage tanks,gas bottle and pipeline steel.