硬线钢拉拔断裂机理及连铸工艺优化

 硬线钢除了要求良好的力学性能,还要求良好的加工性能,但硬线钢盘条在拉拔过程中常发生断丝,给加工的连续性带来巨大危害。为了减少硬线钢的拉拔断丝,对其拉拔断裂机理进行了研究,并开展了相应的连铸工艺优化。首先对82B硬线钢拉拔断丝试样进行了分析,通过对断裂试样的断口和纵剖面分析,结合对应的连铸坯内部质量检测,得出连铸坯中心缺陷及偏析对硬线钢拉拔断裂的影响机制为促进了盘条中心渗碳体膜的生成,导致了裂纹的产生和扩展。然后通过施加电流为350 A、频率为6.0 Hz的连铸凝固末端电磁搅拌,降低浇铸时钢水过热度至30 ℃以下等措施,82B硬线钢连铸坯中心缩孔和中心偏析度分别降低至0.5级和1.08以下,82B硬线钢拉拔断丝率由优化前的10~15 次/百t显著下降到4~5 次/百t。

Mechanism of drawing fracture of hard wire steel and optimization of continuous casting process

Hard wire steel requires not only good mechanical properties,but also good processing properties. However,wire breakage often occurs in the drawing process of the wire rod of hard wire steel,which brings great harm to the continuity of processing. In order to reduce the wire breakage during the drawing of hard wire steel,the drawing fracture mechanism was studied,and the optimization of the corresponding continuous casting process was carried out. The drawing fractured wire sample of 82B hard wire steel was analyzed firstly. Through the analysis on the fractograph and longitudinal section of the fracture specimen,combined with the internal quality inspection of corresponding continuous casting billet,the influence mechanism of central defects and segregation of billet on drawing fracture of hard wire steel was obtained,which promoted the formation of cementite film in the center of wire rod and led to the generation and propagation of cracks. Then,by applying final electromagnetic stirring (F-EMS) at the solidification end of continuous casting with current of 350 A and frequency of 6.0 Hz,and reducing the superheat of molten steel to below 30 ℃,the central shrinkage and central segregation of 82B hard wire steel billet were reduced to 0.5 and 1.08, respectively,and the wire breaking rate of 82B hard wire steel was significantly reduced from 10-15 times per 100 tons before optimization to 4-5 times per 100 tons.