Development of a fracture toughness quality system tool applicable for steel producers and steel users of heavy plates, profiles and weldments

The major aim of the performed research was to develop a procedure for a simple but effective assessment of fracture toughness from charpy tests. Results shall help steel producers and end-users to assess their production result in terms of fracture toughness from correlation with charpy tests. It can be practically used in cases where fracture toughness is not available e.g. for fitness analysis. The work covers both, base metal and weldments. An experimental study concentrating on fracture and charpy toughness testing was performed on selected structural steels with strength level from 355 to 890 MPA. The steels selected were of normalised and quenched and tempered type. Different thick plates up to 60 mm were selected. For two grades (S355 and P690 both in 30 mm) weldments have been produced and tested. Three different models have been developed from which two were based on an exponential function which needs a limitation in the upper shelf and therefore are better to be used in the lower shelf and the transition area. The other model is based on the Tanhyp function and covers the full transition curve. Beside others the three major achievements of the project are: 1. mean value description of charpy transition curve plus scatter on the tanh base and for lower part of the transition curve based on exponential function; 2. calculation method to derive T 27J temperature from incomplete data sets; 3. transferability of results also to weldments and to FITNET fitness for purpose procedure.