Cai Qingwu

Q345 Ultra-Heavy Plate Rolled with Temperature Gradient

It seems to be generally acceptable that recrystallization-controlled rolling is used to produce ultra-heavy plate. However, due to large thickness of the slab, it is difficult to make enough plastic deformation, occurred in central layer. This leads to coarse grain in the center and heterogeneity of property along thickness direction. In this study, the effect of temperature gradient on the strain and austenite grain recrystallization was investigated during ultra-heavy plate rolling by means of FEM and experiments. Results indicate that gradient temperature rolling is better for increasing strain and enhancing austenite recrystallization in the center of ultra-heavy plate.

Nb‐Ti‐Mo Ferrite Matrix Micro‐Alloy Steel With NanoMetersized Precipitates for Refuge Alternative Plate

Three kinds of Nb-Ti-Mo ferrite matrix micro-alloyed steels with three different Ti contents were designed. With optical microcopy, transmission electron microcopy, energy spectrum analysis and tensile test, the microstructures, precipitate particles as well as mechanical properties of three steels were studied. The strength and toughness of steel with0.092% Ti content were verified to adequate for Q600 grade refuge alternative plates. The results show that there were two kinds of particles with obvious different size in ferrite micro-alloy steels. The dominating precipitates are compound carbonitrides of Nb, Ti and Mo, which are less than 10nm and precipitated in chains or dispersed in the interior of grain. Another kind of particles are titanium carbonitrides with size about 200–300 nm. By the method of tensile tests at room temperature and at 500°C, the Nb-Ti-Mo ferrite matrix micro-alloyed steels have excellent mechanical properties. In addition, the samples with 0.092% Ti content have yield strength at 500°C exceeding400MPa, which are suitable as refuge alternation-plates.