Abstract: Effects of different heat treatment processes on microstructure and room temperature mechanical properties of Fe-12Cr-1.5W-0.2V-0.15Ta F/M steel cladding pipes were studied by normalizing at 980-1150 ℃ and tempering at 600-730 ℃. The results show that, after normalizing at different temperatures, the microstructure of F/M steel cladding pipes is lath martensite, while with the increase of normalizing temperature, the coarse carbide particles will gradually dissolved into the matrix, and the grain size of the prior austenite coarsens from 40 μm at 1050 ℃ to 80 μm at 1150 ℃. After tempering at different temperatures, fine carbide nanoparticles precipitate in the martensite matrix, and the amount of carbide particles increases significantly with the increase of tempering temperature, but the size of carbide particles does not change obviously. After normalizing at 1100 ℃ for 60 min and tempering at 650 ℃ for 90 min, the cladding pipes have good microstructure and mechanical properties, original austenite grains do not grow obviously, and the average grain size of martensite laths is about 6.0 μm, the ratio of small angle grain boundary is 59.6%, the nano-phase precipitate along the original austenite grain boundary, and a large number of nano-phases precipitate at the interface of intragranular martensite, at this time, the pipes show good strong plastic matching, the tensile strength is 1024 MPa, the yield strength is 849 MPa and the elongation is 17.3%.

Key words: F/M steel, heat treatment, microstructure, carbide particles, mechanical properties