Abstract: To ensure the melting of groove sidewall, especially the root thereof, is the key to realizing narrow gap welding. The arc heating area can be controlled effectively by using arc constricted by flux strips, which helps to solve the problem of poor fusion of sidewall in narrow gap welding. With 5 mm “I” groove and metal arc protected by Ar, flux strips of special composition are successively sent into the arc zone along the groove sidewall, flux strips are melted successively by the arc heat while restricting the arc, thus being able to realize ultra-narrow gap welding At different welding voltages, different restriction effects of flux strips on arc and corresponding weld morphologies are obtained by varying the feed velocity of flux strips in carrying out ultra-narrow gap welding.The range of voltage and feed velocity of flux strips that can restrict the arc and ensure good fusion of sidewall are found out.

Key words: Constricted arc by flux strips, Fusion of sidewall, Ultra-narrow gap welding