Abstract
Various welding methods are widely applied in large fabrication of high strength steel. However, commonly the problem occurs where a coarse grain is formed near fusion zone causing reduce the impact toughness due to the weld joint become brittle. Ductility and toughness in a coarse grain heat affected zone (CGHAZ) is low due to the formation of coarsening grain size. The objective of this research is to investigate the microstructure evolution, impact toughness and fracture appearance at sub-zero temperatures of the high strength steel arc welded. The steel that used in this experiment is a HY-80 steel welded by gas metal arc welding (GMAW) with a mixture of argon and carbon dioxide (90%Ar and 10%CO2) and ER100S solid wire. Microstructure observation and Charpy V-notch (CVN) tests were performed on the weld joint which consist of base metal (BM), heat affected zone (HAZ), and weld metal (WM). The CVN tests on the HY-80 steel plate at various temperatures (20, -20, -60 and -80 °C) show impact toughness decrease when the test temperature decrease. The CVN tests on the HY-80 weld joint at a temperature of 80 °C show the lowest impact toughness was measured at WM (61 J) and followed fusion line-FL (101 J) with brittle fracture appearance.
Highlights
HY-80 is a high strength steel with minimum yield strength of 80 ksi and it was developed in the 1960s for submarine and naval ship construction
This paper describes microstructure evolution and impact toughness of HY-80 steel weld joint
3.1 Microstructure analysis A macro photograph of HY-80 weldment has indicated that no crack or other welding defect found in the weldment
Summary
HY-80 is a high strength steel with minimum yield strength of 80 ksi and it was developed in the 1960s for submarine and naval ship construction. This steel is produced in quenched and tempered condition where the microstructure shows tempered bainite martensite [1,2,3]. The mechanical properties (i.e. strength, ductility and toughness) of weld joint change drastically. The problem found in the HAZ near fusion zone due to coarsening grain size formed and degrade the properties of the weld joint [5,9,10]. The CGHAZ affect to deteriorate impact toughness due to presence of coarsening grain size and
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