Toughness Behaviour in Armour Steel Welds

Abstract

The process of welding armor steel is a complex process not only due to high percentage of carbon in the base metal, but also because of possible welding faults, appearing in the weld metal zone in the form of cracks and pores. Austenitic filler material is traditionally used for welding armor steels, thus avoiding the negative effect of hydrogen content due to slow diffusion towards the sensitive fusion line. For heavy structural engineering such as armored military vehicles, which are frequently under the effect of impact and dynamic load, it is important to know the dynamic properties of the most sensitive area of welded joints, the weld metal zone. Instrumented impact testing was made on Charpy V specimens. The impact energy results were 56 J and 29 J for crack initiation and propagation, respectively. Due to a significant interest in quantification of material resistance to crack initiation and propagation, the fatigue crack growth rate was measured in the welded metal zone, while the resistance to crack growth in the weld metal was tested by the amount of austenite transformed into martensite. Accordingly, the threshold stress concentration factor was 10 MPa m1/2. XRD spectral analysis revealed direct transformation of γ - austenite into α’ - martensite.

Keywords

• armor steel
• austenitic stainless steel and martensitic transformation
• fatigue crack growth
• instrumented Charpy tests