Optimization of Welding Parameters in HSLA Steel Using SAW Process: a Pipeline Manufacturing Approach

Abstract

The HSLA steel API 5L X70 is used to manufacture pipes for transporting hydrocarbons. The construction of pipe of this material involves high amount of welding, where the parameters used affect directly in the metallurgical structure and in the mechanical properties thereof when welded. Thus, to study the impact of the parameters of the submerged arc welding in mechanical strength and hardness of the heat affected zone (HAZ), it was held a central composite design which totaled 17 tests. The input variables were current, voltage and travel speed; as output variables was considered tensile strength and Vickers hardness of the HAZ. For this study it was used the SAW process (Submerged Arc Welding), tensile testing and Vickers hardness testing. The response surface methodology was used for modeling and the optimization was done using genetic algorithms and Pareto front graph. Sixteen combinations of parameters were obtained with the optimization, of which one was chosen to validate the models. With the results it was possible to establish satisfactory empirical mathematical models for the response variables.

Key-words:
Response surface methodology; SAW process; HSLA steel