High chromium cast iron material 1.4405 GX4CrNiMo 16-5-1 is successfully used in chemical process industry components loaded with hot, highly corrosive and abrasive at high pressures. Overheating test made a discontinuous yielding knee to appear caused probably by dissolution of carbon containing smaller phases but the overall strength and ductility are not affected. Microstructures are studied by optical and SEM microscopy and hardness measurements. This alloy has three main phases appearing as a mixture of rounded and lamellar phases. The work hardening behaviour is studied by analytical composite phase models and 2D FEM models with individual bilinear hardening phase models. The results agreed reasonably. FEM models showed the weak points of the alloy. Fit to test data was better with rounded phase than lamellar phase model. Combination of these tools is useful for innovative special alloy developments.