Correlation Between Acoustic Emission and Induced Hydrogen of Shield Metal Arc Welding

This chapter presents a study on detecting acoustic emission (AE) of hydrogen diffusion after shield metal arc welding (SMAW) process. Technique to detect hydrogen which diffused from steel, gas, or other elements is performed. A correlation between occurred AE and induced hydrogen in weldment after welding is determined. In the experiment, a broadband AE sensor and welded specimens were mounted on a wave guide plate which has 250 mm of separate distance for monitoring and recording AE activity of hydrogen diffusion. The specimens are prepared according to the welding standard (JIS Z 3113). The specimen sizes were 25 mm width, 130 mm length, and 12 mm thickness. Four types of electrodes were used for welding to vary hydrogen amount. The welding current was lower than the manufacturer’s specification of 15 amperes. The specimens were quenched in 5 s after welding process. The results showed that the AE technique can be used to detect hydrogen diffusion after weld. The emitted AE signals were analyzed to determine the relation with the amount of hydrogen. The method for measurement of hydrogen referred to the welding standard (JIS Z 3113). The correlation plot between AE and diffused hydrogen amount can be shown as 0.8 of R 2 linearity. The benefit of this study will be applied to monitor the weldment before cold crack occurs.