基于高温蠕变理论的连铸坯弯曲矫直机理研究

During the steel continuous casting production,using the plastic deformation of the slab to realize the bending and straightening results in the craks easily which will affect the quality of slab. At the same time, the height and construction cost of continous caster are very high. In order to improve the quality of the slab and ruduce the height of the continuous caster, a new mechanism to realize the slab bending and straightening and a new theory of designing the continuous caster model curves will be put forward in this study. In this theory the traditional bending and straightening mechanism which uses the plastic deformation of the slab is improved into the mechanism which uses high-temperature slab creep deformation. For this purpose, the characteristics of high-temperature creep of the slab was studied firstly, the high temperature creep theory is applied to the designing of bending and straightening of the slab and the creep deformation was used to achieve the whole liquid high-temperature continuous bending and straightening of the slab before the solidified shell of the slab into the plastic state. The study is useful for reducing the level of stress and strain in the solidified shell and the height of continuous caster significantly, decreasing bulge deformation of the slab and the rejection rate, avoiding bending and straightening cracks, increasing the added value of the products, saving the construction cost of casting machine and the workshop, and improving the slab quality and productivity. This study has theoretical and practical significance to improve the level of continuous casting technology, to promote the development of the efficient continuous casting technology and to the technological progress of the steel manufacturing industry,and can be apllied widely.

目前，连铸生产中利用塑性变形原理进行连铸坯弯曲矫直存在铸坯容易产生裂纹、铸机高度大、建设成本高等缺点。为提高铸坯质量，降低铸机高度，本研究拟改变传统的利用铸坯塑性变形进行弯曲矫直的机理，探索利用铸坯的高温蠕变变形完成弯曲矫直的新机理，提出确定连续弯曲矫直曲线及机型曲线的新理论。为此从铸坯的高温蠕变特性研究入手，将钢的高温蠕变理论应用到连铸坯的弯曲矫直设计中，改变目前连铸机机型，使铸坯坯壳在未进入到塑性状态的情况下，完全利用蠕变变形实现连铸坯连续弯曲和连续矫直，达到降低坯壳内的应力应变水平、降低铸机高度、减小鼓肚变形量、避免弯曲矫直裂纹、降低废品率、增加产品附加值、减少铸机和厂房的建设成本及提高生产率的目的。本研究对提高连铸技术水平、推动高效连铸技术的发展和钢铁制造业的技术进步具有重要的理论、实际意义和广阔的应用前景。

针对当前连铸生产中连铸坯在弯曲矫直变形过程中容易产生裂纹，并且连铸机机型设计利用塑性变形原理导致铸机高度大、建设成本高等缺点，本研究提出利用铸坯的高温蠕变变形完成弯曲矫直的新机理，提出确定连续弯曲矫直曲线及机型曲线的新理论。为此，本项目首先从材料的高温蠕变特性入手，采用试验的方法确定了四个常用钢种的高温蠕变方程；其次，通过对连铸坯在结晶器和二冷区的凝固传热的研究，确定了连铸坯的凝固位置和二冷区的温度分布，依据温度场的参数得到铸坯在弯曲矫直变形的蠕变性能，确定利用坯壳高温蠕变变形实现连续弯曲和连续矫直的曲线形式及其构造方法；然后，本研究提出了三种连续弯曲矫直曲线，通过延长弯曲段和矫直段曲线的长度，增加蠕变变形的时间，设计了四种符合铸坯高温蠕变特性的连铸机机型曲线，并且利用三维动态热-力耦合数值模拟分析计算了每种机型下铸坯弯曲矫直变形的应力、应变等参数；最后，在实验室连铸坯弯曲矫直实验设备上进行模拟实验研究，进一步验证了高温蠕变弯曲矫直机理和机型曲线设计理论的正确性和优越性。本研究从铸坯的高温蠕变特性研究入手，将钢的高温蠕变理论应用到连铸坯的弯曲矫直设计中，改变目前连铸机机型，使铸坯坯壳在未进入到塑性状态的情况下，完全利用蠕变变形实现连铸坯连续弯曲和连续矫直，达到降低坯壳内的应力应变水平、避免弯曲矫直裂纹、降低铸机高度、减小鼓肚变形量、降低废品率、增加产品附加值及提高生产率的目的。本研究对提高连铸技术水平、推动高效连铸技术的发展和钢铁制造业的技术进步具有重要的理论、实际意义和广阔的应用前景。