Weldability of Ferritic Stainless Steel

Abstract

The ferritic stainless steels are generally considered less weldable than austenitic stainless steels. In case of welding of first-generation ferritic stainless steels, rapid grain growth of ferrite takes place in both the fusion zone and heat-affected zone. These coarse grains have very low ductility and toughness. Excessive grain growth can be avoided by using lower welding heat input and or certain types of additives. They are lower in cost and have better resistance to stress corrosion cracking than austenitic stainless steels. They are used in a variety of applications where corrosion resistance, rather than mechanical properties is the primary service requirement. The ferritic stainless steels are generally used in automotive applications such as exhaust system. Recently, global warming and air pollution have become very important factors in selection of any material and process. In case of automotive exhaust system design, the environment can be protected in a better way by increasing the exhaust gas temperature approximately to 900 °C and by reducing the weight of the parts. Excellent heat-resistant properties, especially thermal fatigue resistance, are the required properties of these parts. The conventional manifolds are made of cast iron, which has a poor heat resistance and is relatively heavy in weight. Certain grades of ferritic stainless steel are considered good alternatives of cast iron for this purpose. In the present paper, weldability of ferritic stainless steels was investigated and proper recommendations were made.