PULSED CURRENT NARROW GAP GAS METAL ARC WELDING OF THICK HSLA STEEL PLATE

Abstract

The welding of high strength low alloy (HSLA) steels largely dominates their use in fabrication of various components of modern applications starting from manufacturing of automobile vehicles dealing with sheet metal to heavy engineering employing thick sections. According to their chemical compositions often these steels maintain good weldability due to low carbon and alloying content (3-5 Wt. %). However, because of its comparatively complex weld thermal behaviour the multi-pass welding of thick sections of HSLA steel becomes critical in order to satisfy desired joint properties. Welding of thick sections of HSLA steels are generally carried out largely by consumable electrode welding processes such as shielded metal are welding (SMAW) and gas metal are welding (GMAW). They influence severity of weld thermal cycle in different manner primarily depending upon amount of weld deposit, welding parameters and shielding environment. The amount of weld deposition can be considerably reduced by using narrow gap welding technique. However preparation of narrow groove weld joints by SMAW requiring appropriate manipulation of electrode at a low angle of attack can be done only by a skilled welder and as such the process automation practically not become feasible. SMAW has further limitation with respect to slag entrapment. The limitations of SMAW processes can be well addressed by the merits of GMAW process considering its advantage of producing relatively fast, long, clean and continuous weld at any position and introducing automation.