Study on Prevention of Brittle Fracture in Weld Bond for High Tensile Steel (Report 3)

Effect of Alloying Elements on Brittle Fracture Characteristics of Submerged-Arc Welded Joint

Abstract

Continuing study was made on the effect of alloying elements on brttle fracture characteristics of submerged-arc welded joint.
Small amount of titanium is strongly effective improving the weld bond fracture characteristics.
A favorable effect of titanium could be clearly recogrized in a static bend test of Vee-notched Charpy specimen, thus showing the strain rate dependency of this phenomenon. And the favorable effect of titanium was also recognized in lower nitrogen steel.
Favorable effect of titanium is presumed to be due to the formation of titanium nitride, decrease of free nitrogen and increase of hardness in the weld heat-affected zone. This was also concluded from the results of chemical analyses of aluminium, titanium and nitrogen in acid-soluble and insoluble state and that of nitrogen as aluminium nitride in the duplicated weld heat-affected zone.
A suitable composition of high tensile steel for high heat input welding is proposed based on the aobve experimental results.