A method for producing a corrosion-resistant connection of tubes

摘要

Production of a hot gas corrosion resistant joint (20) between pipes (10), which have a corrosion protective thermally sprayed layer (12), involves weld depositing a corrosion resistant material onto one of the pipes in its butt end region (14) adjacent the other pipe prior to thermal spraying. Alternatively, a pipe piece, made of or coated with corrosion resistant material, is welded to the pipes (10) prior to thermal spraying. Preferably, the corrosion resistant layer (22) is applied to a width (b) of 0.5-150 (preferably 2-50, especially 5-30) mm on both sides of the pipe joint plane (E) and has a thickness (e) of 0.5-10 (preferably 1-5) mm. When a coated pipe piece insert is used, the corrosion resistant coating is preferably applied by thermal spraying or weld deposition. Preferably, the butt ends (14) of the pipes (10) are welded together by a root weld layer of boiler-plate steel and a top layer of corrosion resistant alloy, this top layer optionally being located in the weld deposited corrosion resistant layer (22). A Ni, Ni-Cr, Co, Fe or Fe-Cr alloy is preferably used as weld additive material for weld depositing the corrosion resistant layer (22) at the joint plane (E) or on the pipe piece, the layer (22) being produced by plasma powder weld deposition, autogenous welding or arc welding. The thermally sprayed layer (12) may be a sprayed and melted layer of a self-fluxing alloy, such as a self-fluxing Ni-Cr-B-Si, Ni-B-Si or Co alloy, or a sprayed layer of non-melted Ni, Ni-Cr, Fe or Co alloy and may be applied by autogenous flame spraying, high velocity flame spraying (HVOF) or plasma spraying.