Bi-metal composite pipe and corrosion-resistant alloy prefabricated inner-filled steel pipe have been widely used in oilfields due to their excellent corrosion resistance and performance-free joint characteristics. Especially the corrosionresistant alloy prefabricated inner-filled steel pipe is relatively inexpensive. In recent years

the cost has been promoted in a large area of high-corrosion ground pipelines in domestic oil fields

and has achieved very good results. Due to the differences in the chemical composition

microstructure

and physical properties of the inner and outer layers of the bimetal composite pipe

the commonly used butt welding process has the problems of complex procedures

difficult operation

high construction costs

and strict requirements for welder skills

which can easily cause composition segregation

dilution of corrosion-resistant alloy components

poor internal bead forming

false welding

carbon migration

and structural changes in the fusion zone caused by heat input. This article starts from the factors that affect the quality of bimetal welds

and takes the horizontal fixed butt welding of stainless steel composite pipes as the research object.Research and experiments have been carried out from the bevel form

the pairing method

the welding method of the corrosion-resistant alloy underlayer and the bimetal transition welding layer

and new process methods such as internal sealing of composite pipes

U-shaped groove free-space group pairing

back protection of the molten pool

unfilled fusion welding bottoming and unfilled fusion welding transition have been proposed.Through X-ray inspection and welding process evaluation

combined with microstructure analysis

comprehensively evalu-ated the welding process and concluded.