DEVELOPMENT OF HIGH STRENGTH SMAW CONSUMABLES FOR SBD APPLICATIONS

摘要

Strain based design of pipelines for seismic environments using high strength materials is a relatively recent approach in the world of line-pipe installation. The development of suitable welding consumables for these applications has also been lagging. This paper outlines the efforts of a consumable manufacturer to fill that gap and design SMAW consumables for strain based applications. The main challenge in this exercise lies in achieving a high enough strength level while at the same time maintaining adequate toughness levels. A microstructure-optimization approach was followed in the design process to achieve the optimum combination of properties. Since the balance of strength and toughness is pivotal to the application, the welding procedure becomes a critical component of the design process. This paper highlights the importance of maintaining a tight control on the welding process in order to achieve consistently acceptable mechanical properties. Due to the high strength levels involved, a low hydrogen system was used as the design basis. Testing was done with both an uphill and downhill welding electrode slag system. Since the choice between these two types of low hydrogen SMAW electrodes is largely a matter of contractor preference and/or a function of the availability of skilled welders, it was considered important to have a choice of both types of strain-based electrodes.