Microstructure, Toughness and Hardness of the Simulated HAZ Area of Steel S1300QL

Abstract

The introduction contains information (found in available reference publications) concerning the weldability of steel S1300QL. The introduction also presents general information concerning the effect of the microstructure and the chemical composition of filler metals used in the welding of high-strength steels on the mechanical properties of weld deposit. The subject of simulation tests (discussed in the article) was structural steel S1300QL having a yield point of more than 900 MPa S1300QL. Simulations involved both single (Tmax = 1250°C) and double welding thermal cycles (Tmax = 1250°C + 600°C, Tmax = 1250°C + 760°C and Tmax = 1250°C + 900°C) as well as cooling times t8/5 = 3 s, 5 s and 10 s. Specimens with simulated HAZ areas were subjected to impact strength tests performed at a temperature of -40°C and +20°C, Vickers hardness tests (HV10) and microscopic metallographic tests involving the use of light microscopy. The test results are presented in related diagrams and photographs. The final part of the article contains a discussion concerning test results and concluding remarks. The tests revealed that, in terms of the test steel, the number of repetitions of thermal cycles having pre-set parameters did not explicitly translated into changes of impact energy values concerning the simulated HAZ areas. The tests also revealed that recommended thermal cycles making it possible to obtain the required combination of the high toughness and hardness of the simulated HAZ area of steel S1300QL (similar to that of the base material) were double thermal cycles of maximum temperature Tmax1 = 1250°C + Tmax2 = 600°C and Tmax1 = 1250°C + Tmax2 = 900°C combined with cooling times t8/5 = 5 s and 10 s and all numbers of repeated thermal cycles.