直接轧制高强带肋钢筋晶粒细化机理分析及控制

Analysis and control of grain refinement mechanism of high strength ribbed bar in free-heating direct rolling

为了推动棒线材免加热直接轧制生产工艺装备技术的发展,分析了在铸坯断面大温差条件下免加热直接轧制轧件晶粒细化的机理及其特点,亦即低温直接轧制时铸坯表面温度较低,心部温度较高,同一截面心表温差约166℃,铸坯心部变形抗力远小于表面,轧件易产生单鼓形不均匀变形;另外,开轧时轧制速度较低,轧制力有足够的时间渗透到轧件心部,使心部铸态组织被破碎和充分再结晶,形成细小晶粒组织,同时还可消除心部孔隙和疏松等铸造缺陷,可以极大地改善轧件组织,提高产品的性能和质量。同时,提出了用轧件中部、边部晶粒度的比值,即晶粒度中边比作为轧件晶粒细化的指标,阐述了实际应用中生产控制的关键点以及对装备的要求。以期为棒线材直接轧制改造的新设计及改造提供依据,为免加热直接轧制高强带肋钢筋生产质量控制提供参考。

In order to promote the development of the production process and equipment technology of free-heating direct rolling,the mechanism and characteristics of grain refinement infree-heating direct rolling under the condition of large temperature difference of billet section were analyzed,that is,the surface temperature of the billet is low,the core temperature is high,the temperature difference between the core and surface of the same section is about 166℃,and the deformation resistance of the core of the billet is much smaller than that of the surface,and the piece is easy to produce single drum uneven deformation;In addition,the rolling speed is low when rolling,and the rolling force has enough time to penetrate into the core of the piece,so that the billet structure of the core is broken and fully recrystallized to form a fine grain structure,and at the same time,the casting defects such as the pore and porosity of the core can be eliminated,which can greatly improve the piece structure and improve the performance and quality of the product.At the same time,the ratio of grain size in the center and edge of the rolled piece and the ratio of grain size in the middle and edge of the rolled piece are put forward to measure the grain refinement of the piece,and the key points of production control in practical application and the requirements for equipment are expounded.In order to provide a basis for the new design and transformation of free-heating direct rolling for rod and wire,and to provide a reference for the quality control of production of high strength ribbed bar.