Fracture mechanic and charpy impact properties of a crack in weld metal, HAZ and base metal of welded armor steel

Abstract

Welding of armored steel is complicated by the high percentage of carbon in the base metal, the presence of defects in the form of cracks and pores that occur in the weld metal and heat affected zone (HAZ) during the welding process. For heavy structural engineering such as military armored vehicles that are frequently under the influence of impact loads, it is important to know the fracture toughness in all zones of the welded joint. The crack formed in base metal or HAZ, due to dynamic or impact loads, can easily continue to propagate to the fusion line, after which its accelerated growth may occur. The fracture mechanics testing was applied to SEN (B) test specimens, which investigated cracks initiation and certain fracture mechanics parameters. Due to the significant interest in quantifying the resistance of material to initiation and propagation of cracks, the impact energy was measured with instrumented pendulum in the zone of base metal, weld metal and HAZ, at temperatures of -40 °C, -20 °C, 0 °C and 20 °C , while the fracture mechanics parameters in these zones were tested at room temperature. The impact energy tests showed high energy for initiation as well as crack propagation in weld metal and HAZ zones, while the lowest energy was in the base metal. The fracture toughness in the base metal is 86.1 MPa*m<sup>1/2</sup>, while in HAZ and weld metal zones is 286 MPa*m<sup>1/2 </sup>and 355 MPa*m<sup>1/2</sup>, respectively.