Taguchi Optimization of X70 Carbon Steel Heat Treatment: A Study on Hardness, Thickness and Phase Analysis

The application of carbon steel fiber metal laminate (CFML) has been increasing in engineering industries such as aerospace, automotive and processing industries. In fabricating CFML, the surface quality is a fundamental criterion as its stability is the key to avoiding delamination and corrosion. Delamination and corrosion can be prevented by growing a fresh and stable oxide layer with good mechanical properties via heat treatment on carbon steel. In this paper, the influence of heat treatment parameters namely temperature (400, 600 and 800 ⁰C), heating time (60, 90 and 120 min), heating rate (10, 15 and 20 ⁰C/min) and substrate roughness (P80, P240 and P800) on the X70 carbon steel oxide phase formation, thickness and hardness properties were investigated. Using Taguchi’s method, a total of 9 experiments were performed based on the L9 orthogonal array. The signal-to-noise ratio (S/N) and contribution percentage of the analysis of variance (ANOVA) of each parameter on the responses were studied. The optimal conditions for thickness were obtained at temperature 800 ⁰C, heating time 120mins, heating rate 10 ⁰C/min and sample prepared with P80 sandpaper grit. Meanwhile, optimal conditions for hardness were obtained at temperature 800 ⁰C, heating time 120mins, heating rate 10 ⁰C/min and sample prepared with P80 sandpaper grit.