The electro-slag cladding process: application, main metallurgical and testing issues in the fabrication of reactors in large thickness 2¼Cr–1Mo–¼V

Abstract

In the fabrication of reactors (made of Cr–Mo steel modified with vanadium) operating in high hydrogen pressure and high-temperature service, internal cladding in austenitic stainless steel (typically made of AISI 347) is required in order to guarantee satisfactory corrosion resistance against the process fluids desulphurized hydrocarbons. Application of an electro-slag strip cladding (ESSC) process for internal weld overlay and clad restoring on heads, barrels and nozzles of 2¼Cr–1Mo–¼V reactors (with single-layer or double-layer technique) is described in the paper. The first part of the paper is focused on metallurgical aspects, cracking phenomena (hydrogen cracking, solidification cracking, under-clad cracking and hydrogen-induced disbonding) and cladding residual stresses referable to ESSC process. The second part of the paper is focused on operating aspects of the ESSC process and UT examination of weld overlay and clad restoring, optimized for the detection of planar defects under cladding.