表层细晶化Q235中厚板轧制工艺的研究

SPECIAL ROLLING PROCESS OF Q235 PLATE FOR SURFACE LAYER FERRITE GRAIN REFINEMENT

采用 Q2 35成分的连铸板坯 ,在首钢中厚板厂 330 0 m m轧机上进行了中板表层组织细晶化的工业轧制实验 ,研究了轧制温度、轧制变形量分配、待温期间冷却方式对板材组织和性能的影响。结果表明 ,在奥氏体低温区增加精轧总变形量可以实现 2 0 m m成品板材的表层组织细化 ,屈服强度达到 30 0 MPa左右 ,铁素体晶粒达到 8.5级 ,增加待温期间中间坯的水幕冷却有利于整个板材厚度截面的组织细化 ,屈服强度达到 330MPa左右 ,铁素体晶粒达到 9级 ,材料的强度接近 Q345同规格板材的水平 。

Industrial experiments for grain refinement of Q235 plates were carried out with continuous casting slabs on the 3300 mm rolling mill in the Shougang Plate Rolling Plant. The effects of deformation temperature, deformation amount of passes, cooling modes between rough rolling and finish rolling on the microstructure and mechanical properties of the plates were studied. The results show that with the increase of total deformation amount during the finish rolling period at low temperature in austenite zone, the surface layer ferrite grains are effectively refined for the 20 mm Q235 plate and the yield strength goes up to 300 MPa with ASTM 8.5 ferrite grade; it is beneficial for ferrite grain refinement along the thickness direction to adopt the water curtain cooling between the rough and finish rolling and the yield strength is not less than 330 MPa with ASTM 9 ferrite grade and in this case, the 20 mm plates possess satisfying elongation and good toughness.