Method for improving inner quality of continuous casting billet with thick and large section

Abstract

The invention relates to the filed of the manufacture of continuous casting billets, in particular to a method for improving inner quality of a continuous casting billet with a thick and large section, which can solve the problems of the centerline shrinkage, porosity and segregation of the continuous casting billet with the thick and large section in the prior art. In the invention, through controlling degree of purity of molten steel and degree of superheat of pouring, and cooperatively adopting the micro-region oscillation technology and the solidification self-feeding technology, the inner quality of the continuous casting billet can be improved. The micro-region oscillation technology can effectively eliminate the defects of segregation in the continuous casting billet, can also effectively reduce solidification tissues, and decreases the centerline shrinkageand porosity; and the solidification self-feeding technology can realize simultaneous solidification and plastic movement of solid metal in the subsequent solidification shrinkage process, so that the purpose of radial self-feeding of high-temperature deformable metal can be achieved, further, the centerline shrinkage in the continuous casting billet can be eliminated, and the porosity in the continuous casting billet can be remarkably improved and is even eliminated. The invention is suitable for carbon steel, alloy steel and nonferrous metal casting billets with the thick and large sections, particularly for continuous casting sheet billets with the thickness being over 300mm, square billets, and round casting billets with the section phi being over 500mm.

Description

technical field [0001] The invention relates to the field of thick and large-section continuous casting round billets, square billets and slabs, in particular to a method for improving the internal quality of thick and large-section continuous casting billets, eliminating central shrinkage cavities, and reducing porosity and macrosegregation . Background technique [0002] my country has dozens of wide and heavy plate rolling production lines, including Anshan Iron and Steel's 5000mm and 5500mm rolling mills, Baosteel's 5000mm rolling mills, etc., with a new capacity of more than 20 million tons. A large number of continuously cast slabs with a thickness greater than 300mm are required. At the same time, my country has dozens of continuous casting round billet production lines with a diameter of Φ500mm or more, which are used to produce high-quality steel such as bearing steel, pipeline steel, and rack steel. Slabs with a thickness of more than 300mm and round billets with...

AI Technical Summary

Problems solved by technology

However, the riser ratio of thick and large cross-section continuous casting slabs is very small, and the aspect ratio is greater than 4, so the axial gravity feeding of the slab cannot be realized

Using traditional feeding technology, it is difficult to completely eliminate the shrinkage cavity and porosity defects inside the thick and large section continuous casting slab

To suppress the macro-segregation defects inside the continuous casting slab, external field control methods such as electromagnetic stirring, light reduction and forced cooling are often used to increase the solidification speed; for thick and large-section continuous casting slabs, the electromagnetic field attenuation is serious and it is difficult to act on the entire slab section, and the casting slab If the shell thickness is large, the light reduction technology is helpless, and the solidification rate cannot be effectively increased due to the heat transfer of the billet shell

Therefore, conventional external field methods cannot effectively eliminate macro-segregation defects inside thick and large-section continuous casting slabs

[0004] To sum up, shrinkage porosity and macro-segregation inside thick and large section continuous casting slabs are the technical bottlenecks that restrict the development of casting slabs to larger section sizes

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