DOMOVCOVÁ Lucia ŽP Research and Development Centre

Spoluautoři FUJDA Martin, PARILÁK Ľudovít

The steel grade X10CrMoVNb9-1 is a creep-resistant steel, alloyed with Cr, Mo, V and Nb, respectively. It is aimed towards applications demanding ultrasupercritical conditions (temperature up to 650 °C, pressureup to 30 MPa). In this paper we introduce the chemical and structural concepts along with our experience in tempering of this particular steel grade. The transformation temperatures were estimated using four different chemical compositions. The values obtained were (830 ÷ 860) °C for Ac1 and (870 ÷ 890) °C for Ac3, respectively. Based on our results we can conclude that the transformation temperatures are strongly dependent on chemical composition.The heat treatment was performed at various temperature intervals; in particular, the experimental tempering took place at (730 ÷ 860) °C. For temperature range of (750 ÷ 800) °C there was a homogeneous precipitation of carbides in martensitic matrix. For temperatures over Ac1 the dual-phase structure was observed, increasing the mechanical properties.The final microstructure after tempering consisted of a tempered martensite. During microstructure analysis the presence of M23C6 carbides as well as MX-type carbonitrides was clearly observed. The ultimate goal of this experiment was to optimize the production and heat treatment processes for seamless steel tubes in Železiarne Podbrezová.