Rudder horn, in ship structures, is typically attached on the shell plate by welding. It is an important part of steering systems and has possibilities of fatigue crack due to various fluctuating loads. In this study, therefore, fatigue strength assessment for casting weld joint is carried out by making fillet weld joint specimens with cast steel and carbon steel in order to evaluate the fatigue behavior of a rudder horn. The specimens were fabricated and tested for three different conditions such as pre-heating effect, shape of weld joint effect and welding position effect. Test results of each case are represented in terms of S-N curves and are compared for evaluating the effect of fatigue strength improvement.
Cast steel has a similar chemical composition with that of rolled steel or forged steel which are commonly used. Also cast steel is widely used in ships, railway cars and tools because it has excellent strength and damping compared to cast iron or other castings. The welding process is important for constructing structures with steel castings. It is used in two ways:
in fabricating structures either by welding castings together (cast weld construction) or by welding steel castings to wrought steel products (composite fabrication), and
in the correction of casting irregularities which may occur in the course of manufacture.
Steel castings, as a component of weldments, are widely used because of possible cost savings. The use of steel castings is advantageous in regard to quality production, useful properties, and simplified design [1]. In ship structures, rudder horn is typically attached on the bottom shell plate by welding. It is made from steel castings to fix and support the rudder as an important steering system of a ship. And rudder structures in a ship are exposed to fatigue failure due to various cyclic loads such as hydrodynamic force and propeller force.
