Charpy value (CVN), grain size and microstructure produced in the HSLA 450 steel HAZ, welded under a SMAW process

In this paper several features of the HAZ between the weld metal and the parent metal, after the heat cycle produced by a SMAW process in 450 N/mm exp 2 HSLA steels are analysed, taking into consideration the temperatures reached in the HAZ as from Rosenthal's equation. The aspects under examination are: grain morphology by means of micrographs obtained with the Scanning Electron Microscopy to check the bands that control the grain size due to the microalloyings of the designed steel, taking into account the temperatures reached and the cooling rate in each of the HAZ regions; fracture toughness, checked by means of CTOD testing; hardness grain size determined by the Ashby and Esterling procedure, and based on the values obtained with the Heyn method, ratio between stable growth and heat input; CTOD values which are found to be satisfactory under the welding conditions with a heat input of 1.6 Kj/mm.