Investigation of the Evolution of Central Defects in Ultra-Heavy Plate Rolled Using Gradient Temperature Process

To eliminate flaws, such as shrinkage, porosity, and micro-cracks, in heavy plates, the slab or ingot needs to be subjected to a sufficiently large cumulative reduction in central area. Traditionally, a large slab size is considered to be necessary for thick plate rolling. The evolution of central cracks in heavy plate was investigated by finite element modeling using two different rolling processes: gradient temperature rolling (GTR) with 1073 K (800 °C) on the surface and 1373 K (1100 °C) in the core, and uniform temperature rolling (UTR). The results of simulation were confirmed by clad rolling experiments. Results reveal that, using GTR, the central crack closes easily because of increased central strain and stress. Clad plate produced by GTR has a good bonding interface and fine microstructure. Ferrite grains in GTR plate are refined to 22 µm and the quarter- and half thickness impact energies are increased by 25.8 and 50.1 pct, respectively, compared with UTR plate, the properties of central layer decrease slightly, compared with those of the base materials.