TWI Industrial Member Report Summary 943/2010
There are occasions when it would be beneficial to know whether there has been a problem with hydrogen control when welding a thick section steel before completion of the weld. It may be that a source of hydrogen is introduced during welding (from inadequate cleaning or a region of damp flux, for example), and that if early detection and immediate action can be taken to avoid hydrogen cracking in the component, the requirement for repair and the related costs could be avoided. Such action may be increasing the interpass time to allow additional hydrogen diffusion prior to welding the next pass, or maintaining a postheat on completion of welding to allow hydrogen diffusion before the weld cools.
Using a hydrogen effusion rate monitoring probe, the hydrogen effusion at various stages of welding could be used on procedure qualification pieces to establish baseline levels of hydrogen effusion rate. If, during welding, the hydrogen effusion rate exceeds the values determined during procedure qualification, remedial action could be taken.
In a previous report, the proof of this concept was explained, considering the application of the probe to the workpiece and modelling of hydrogen effusion accounting for the falling temperature. The current report covers additional work carried out to demonstrate the effects of hydrogen effusion on the remaining hydrogen content in the weld and the prevention of cracking in a weld that has experienced a deviation to the intended welding procedure.
Demonstrate the use of the Hydrosteel TM for real welds, both in terms of actual hydrogen content and in terms of avoidance of cracking.