控制冷却工艺对Ti微合金化中碳钢板组织和性能的影响

采用控制轧制-控制冷却-淬火-回火工艺制备20 mm 厚的Ti微合金化中碳钢板,研究了控制冷却工艺(冷却速度)对该钢有效晶粒尺寸和析出相的影响,并探讨了其强韧化机理。结果表明:冷却速度越快,有效晶粒尺寸越小,马氏体板条宽度越窄,含Ti析出相越细小,使其兼具高强度和良好的塑性韧性。主要是由于快速冷却保留了轧制时获得的晶体缺陷和形变能,使再加热奥氏体细化,而且快速冷却抑制了Ti在冷却过程中析出,使Ti处于过饱和状态,再加热过程中逐渐析出细小的含Ti析出相,能更有效地阻止奥氏体晶粒长大。有效晶粒细化以及纳米级含Ti析出相使该钢板具有良好的力学性能。

Effect of controlled cooling process on microstructure and properties of Ti-microalloyed medium carbon steel plate

Ti-microalloyed medium carbon steel plate of 20 mm thickness was prepared by controlled rolling-controlled cooling-quenching-tempering processes. The effect of controlled cooling process (cooling rate) on effective grain size and precipitates of the steel was studied, and the strengthening and toughening mechanisms were also discussed. The results show that the faster the cooling rate, the smaller the effective grain size is, the narrower the martensite lath width is, and the finer the Ti-containing precipitates are, so that the steel has both high strength, good ductility and toughness. This is mainly because the rapid cooling can retain the crystal defects and deformation energy obtained during rolling, making the austenite refined during reheating. Moreover, the rapid cooling inhibits the precipitation of Ti in the cooling process, making Ti in the super-saturated state. In the reheating process, fine Ti-containing precipitates gradually precipitate, which can effectively prevent the growth of austenite grains. Effective grain refinement and nano Ti precipitates make the steel plate having good mechanical properties.