Microalloying effects on microstructure and mechanical properties of 18Cr–2Mo ferritic stainless steel heavy plates

• We focus on Nb–V stabilized 18Cr–2Mo ferritic stainless steel with/without Ti.
• We compare microstructures and mechanical properties of steels using several methods.
• Modification of microstructure that Ti induces reduces toughness of FSS heavy plates.
• Properties improvement Nb–V steel brings is important for application of FSS plates.

The microstructure, including grain size and precipitation, tensile strength and Charpy impact toughness of (Nb + V) 18Cr–2Mo ferritic stainless steel heavy plates with/without Ti were investigated by means of optical microscopy, scanning electron microscopy, transmission electron microscopy, X-ray diffraction and standard tensile strength and Charpy impact toughness testing. It was found that for 18Cr–2Mo heavy plate, a good combination of Nb–V stabilized method without Ti induces refinement of grain sizes due to the precipitation of amounts of fine Nb carbonitrides and V nitrides. Meanwhile, the mechanical testing results indicate that optimal transformation of grain size, precipitation that Nb–V composition system brings to 18Cr–2Mo heavy plate is beneficial to improvement of strength and impact toughness.