Review potential processes for mechanised three layer (intermediate buffer layer) welding of CRA clad components.
Carry out trials using pure Fe and pure Ni wires and shortlisted processes. Carry out inspection and metallurgical evaluation including mechanical strength testing as per DNV OS F101:2007.
Compare techno-commercially the approach of welding the entire joint using CRA weld metal vis--vis the three-layer approach.
Experimental trials will be carried out to evaluate the option of three layered girth welds in piping and establish the key parameters for achieving a weld that is fit-for-purpose. Feedback from the use of such welding procedures in stainless steel clad components suggests that the weldability of the buffer layer is very different to that of both high Nickel and carbon steel consumables, and that the weld pool is difficult to control (highly fluid). Quality control issues can arise with the use of three different consumables in the same joint, with the buffer layer having reduced mechanical properties compared to the high Nickel and carbon steel consumables and the base materials. Additionally, the interface of three consumables with two base materials and the different properties and characteristics of each, increases the likelihood of weld defects to occur. With so many interfaces, the resultant metallurgical microstructure analysis can be difficult to determine and control and the non-destructive examination of such welds will also become increasingly difficult. The use of such a three-layered weld might preclude the necessity for PWHT, which will also be reviewed as a part of the program. However, successful resolution of the above issues will provide improved fabrication options for future developments involving clad systems, particularly if PWHT can be avoided.
Relevant Industry Sectors
Oil and Gas, Power, Nuclear
Technical and Economic Benefits
Improved fabrication options for future developments involving clad systems.
Industrial Member Report
Access the Industrial Member Report resulting from this programme: Welding of CRA Clad Materials - Three Layer (Buffer Layer) Approach