Heat Treatment and Austenitization Temperature Effect on Microstructure and Impact Toughness of an Ultra-High Strength Steel

Heat treatment parameters were varied to determine the effect of normalizing and austenitizing temperature on the properties of an ultra-high strength wrought steel. Normalizing temperature did not have a significant effect on strength and ductility. Higher normalizing temperatures led to an increase in final prior austenite grain size and a slight loss in toughness. Austenitizing temperature of 825 degrees C was insufficient to produce a fully austenitic structure prior to quenching and led to sub-par impact behavior. The best properties were obtained after austenitizing at 915 degrees C followed by water quenching; the resulting quasi static properties were shown to be a yield strength of 1380 MPa with an ultimate tensile strength of 1670 MPa and 12.5% total ductility. Charpy V-notch impact properties as high as 52 J at -40 degrees C and 75 J at 25 degrees C and the behavior were achieved using higher austenitizing temperatures as well.

Automated summary

The research found that the normalizing temperature of wrought steel has little effect on strength and ductility, but higher normalizing temperatures can lead to an increase in grain size and a slight decrease in toughness. Lower austenitizing temperatures may result in incomplete austenitic structure formation before quenching, affecting impact behavior. The best properties were obtained after austenitizing at 915 degrees C followed by water quenching.