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Insitute of Energetics , Ljubljana , Slovenia
Faculty of metallurgy, University of Zagreb , Zagreb , Croatia
Faculty of Natural Sciences and Engineering , University of Ljubljana , Ljubljana , Slovenia
Faculty of Natural Sciences and Engineering , University of Ljubljana , Ljubljana , Slovenia
Faculty of Natural Sciences and Engineering , University of Ljubljana , Ljubljana , Slovenia
High strength low alloy (HSLA) steels represents a group of low carbon steels that utilise small
amaunts of alloying elements, such as Mo, Ti, V and Nb, to attain yield strengths in excess of 275
MPa in the as rolled condition. The main properties of HSLA steels that make them for wide variety of
applications are: strength and toughness, corrosion resistance, weldability and cost effectiveness.
The high strength low alloyed (HSLA) structural steel Niomol 490K, produced in steelwork ACRONI,
Jesenice, Slovenia with the microstructure of dispersion of cementite particles in ferrite, with linear
grain size of aproximately 2.5 m and the yield stress of 490 MPa has been investigated.
Heat treatment of the steel Niomol 490K consisted from austenitisation at 920 oC for 10 minutes and
reheating up to 1250 oC for 5 seconds. After austenitization the quenching was carried out in both
water (temperature of 70 oC) and lead bath up to 400 oC following cooling on air. It was found that
Charpy impact energy is higher and the transition temperature is lower for transformation of
austenite to bainite than to martensite microstructure. Experimantal results showed that different
fracture surface observed.
The authors want to thank professor Franc Vodopivec (Institute of Metals and Technology), professor Anton Smolej (University of Ljubljana), and professor Ladislav Kosec (University of Ljubljana) for mentorship at study HSLA steels, Mrs. Nika Breskvar (University of Ljubljana) for SEM analysis, and Mr. Boris Arzenšek (Institute of Metals and Technology) for mechanical testing
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