Prevention of cold cracking in ultra-high strength steel Weldox 1300

The cold cracking process in MAG welding, microstructure and mechanical properties of ultra-high strength steel Weldox 1300 were investigated. It has been shown that the microstructure of the Weldox 1300 steel is composed of tempered martensite and inside the lathes the minor precipitations mainly V(CN) and molybdenum carbide Mo2C were observed. A Tekken cold cracking test was used to assess the weldability of steel at two different net heat input and different preheating temperatures in the range of 20–200 °C. The experimental results showed that the heat input and preheating temperature decided of tendency to cold cracking and the optimal preheating temperature was 100 °C. Additionally the results revealed that the analytical formulas of calculating the preheating temperature are not useful for this kind of steel.