板坯连铸大辊径大压下及低压缩比轧制特厚板

 近年来,国内外科研工作者开发的连铸凝固末端重压下技术在改善连铸坯的疏松、偏析等方面取得了良好效果,但仍存在扇形段小辊径压下厚铸坯时,应变难以渗透到铸坯芯部、不利于中心疏松改善等不足。以高效率、低成本、低能耗获得高质量厚铸坯,并实现低压缩比轧制高质量厚规格产品,仍需要进一步探索。为了更加有效地解决厚铸坯连铸凝固过程产生的中心疏松及偏析问题,提出一种全新的宽厚板坯连铸大辊径大压下(BRHR)技术并研制了BRHR设备,在宽厚板坯连铸生产线上安装、调试并运行两年多,同时配套开发了宽厚板坯连铸工艺过程预测与控制系统、二冷水工艺优化控制技术。结果表明,开发的BRHR装备与技术有利于压下应变渗透到铸坯芯部,在连铸生产线上利用凝固末端或刚完全凝固(固相分数f_s=1.0)形成的大于500 ℃或大于400 ℃的大梯度温度场实施大直径辊大压下,可以显著改善宽厚板坯中心缺陷。生产实践证明,采用BRHR装备与技术使厚度为400 mm的宽厚板连铸坯缩孔、疏松及偏析得到显著改善,结合轧制工艺优化以1.90~2.53的极低压缩比轧制生产出厚度为150~200 mm的高质量特厚板,这对低成本、短流程生产高质量特厚规格产品及节能减排意义重大。

Slab continuous casting by big roll heavy reduction and extra thick plate rolled by low compression ratio

In recent years, the heavy reduction technology at solidification end of continuous casting developed at home and abroad has achieved good effect on reducing porosity and segregation in thick slab, while there are also some deficiencies, for instance, when the thick slab is pressed by the small rolls of segment, the strain is difficult to penetrate into the core of slab, which is not conducive to ameliorate the central porosity. Obtaining high-quality thick slab with high efficiency, low cost as well as low energy consumption and rolling high-quality thick slab with low compression ratio are still the direction of further exploration and development. In order to solve the problems of central porosity and segregation defects in the solidification process of thick slab continuous casting more effectively, a new technical of wide-thick slab continuous casting by big roll heavy reduction(BRHR) was proposed and the BRHR equipment was developed. The BRHR equipment had been installed, commissioned on the wide and thick slab continuous casting line and operated for more than two years. Meanwhile, the process prediction and control system and secondary cooling water process optimization control technology were developed. The research proves that developed BRHR equipment and technology for continuous casting are conducive to make the reduction strain penetrate into the core of slab. Using the large gradient temperature field which is larger than 500 ℃ or 400 ℃ formed at the end of solidification or just complete solidification (f_s=1.0) on the continuous casting line to implement large diameter roll for large reduction can significantly reduce the central defects of wide and thick slab. The production practice proves that shrinkage, porosity and segregation in 400 mm thickness specification wide and thick continuous casting slab have been significantly ameliorated by BRHR equipment and technology. Combined with the optimization of rolling process, the high-quality extra thick slab with thickness of 150-200 mm is produced with very low compression ratio of 1.90-2.53, which has great significance for low cost and short process production of high-quality extra thick products as well as energy conservation and emission reduction.