The effect of weld bead heat input on the mechanical properties of 3CR12 stainless steel

3CR12 is a low cost special stainless steel containing 12% chromium. It is widely used in material handling, road transport, rail transport, power generation and petrochemical applications due to its favourable corrosion performance. 3CR12 is an easy to weld material. However, challenges such as low ductility and poor toughness of 3CR12 stainless steel welds, unfavourable microstructure characteristics of the weld bead section because of weld heat input and the rate of heat transfer and susceptibility to cracking caused by poor welding techniques negate the positive attributes of the 3CR12 in welded joints. Welding-ability of 3CR12 stainless steel can be characterised by the hardness of the high-temperature heat affected zone (HT HAZ) and the cold cracking vulnerability of the welds. When stainless steel is welded, non-uniform heating and cooling in the weld metal and in base metal generate harder Heat Affected Zone (HAZ), cold crack vulnerability and residual stresses in weld beads. Welding procedures for 3CR12 recommend the use of minimum heat input to avoid weld defects and unfavourable material properties. However, there are methods that could potentially mitigate these problems. One approach is weld bead heat input tempering. Varying the heat input into the proceeding weld bead may improve mechanical performance of the overall welded joint. This paper reports on the effect of varying weld bead heat input on the mechanical properties of 3CR12 welds. The focus is on micro hardness and microstructural changes. Heat input was varied by altering the welding parameters such as the welding voltage 20V -29V, welding current 90A-150A, and feed rate of 1.77 m/min. The results show that it is possible to alter the weld bead mechanical properties by fine-tuning the welding parameters and hence the weld bead heat input.