中碳钢连铸方坯内部角裂机制研究与优化

 分别选取西钢某厂实际生产中易发生内部角裂缺陷的40Cr和45钢连铸坯为研究对象，通过对缺陷采用热酸浸低倍试验、金相法和探针能谱分析，发现缺陷处不存在明显的组织异常和质点沉淀。运用ANSYS软件对连铸结晶器凝固过程进行热模拟。研究结果表明，缺陷形成于结晶器内的凝固过程，根本原因是铸坯在结晶器中凝固传热不均导致出现铸坯偏角区热节区效应，从而诱导产生热应力，致使沿柱状晶晶间铁素体开裂，并伴随一定量的铸坯鼓肚现象。通过重新设定结晶器铜管圆角半径和优化生产部分工艺后，最终使连铸坯内部角裂评级在10级以上的比例下降到1042%。

Mechanism of Internal Corner Crack for Continuous Casting Billet of Medium Carbon Steel

In order to investigated the internal corner crack for continuous casting billet of 40Cr and 45 steel in Xining Special Steel Co Ltd.,macroscopic test eroded by hot hydrochloric acid,metallographical test,electron probe and energy spectrum analysis were used to research the defects.However,there was no obvious abnormal microstructure and particle precipitation around defect.The solidification process of billet was simulated by ANSYS software.The results show that the defects are formed in mold during the solidification process.The mechanism of internal corner crack is inferred as follows: firstly,the hot spot region formed as the off-corner of billet is caused by uneven heat flow in the mold;and then,the thermal stress is evoked subsequently,which results in ferrite cracks between two adjacent columnar crystal and bulging of the billet.After re-setting fillet of mold and optimization process of continuous casting,the proportion of the internal corner crack greater than 1.0 of billet is reduced to 10.42%.